A Study of 

Global Sand Seas

Edwin D. McKee, Editor

GEOLOGICAL SURVEY PROFESSIONAL PAPER 1052

Prepared in cooperation with the

National Aeronautics and Space Administration

UNITED STATES GOVERNMENT PRINTING OFFICE, WASHINGTON : 1979
COMPLEX LINEAR RIDGE with reversing and star dunes superimposed; broad interdunes 

on each side. Aerial photograph, taken southwest of the Kuiseb River, Namib Desert, SouthWest Africa, by E. Tad Nichols. (Frontispiece.)
A STUDY OF

GLOBAL SAND SEAS
STAR DUNE WITH CURVING ARMS, south of Kuiseb River, Namib Desert, South-West 

Africa. Photograph by E. Tad Nichols. (Cover.)
UNITED STATES DEPARTMENT OF THE INTERIOR 

CECIL D. ANDRUS, Secretary

GEOLOGICAL SURVEY 

H. William Menard, Director

Library of Congress Cataloging in Publication Data

Main entry under title: A study of global sand seas.

(Geological Survey Professional Paper 1052)

Bibliography.

Includes index.

1. Sand. 2. Sand dunes. I. McKee, Edwin D., 1906. II. United States National Aeronautics and

Space Administration. III. Series: United States Geological Survey Professional Paper 1052. 

QE471.2.S88 553'.62 79-1452

For sale by the Superintendent of Documents, U.S. Government Printing Office

Washington, D.C. 20402 

Stock Number 024-001-03202-3
FOREWORD

NE HUNDRED YEARS AGO, the U.S. Geological Survey had its inception in Washington, D.C., when Congress established a unified 

geological survey under the Department of the Interior, combining the 

duties of and replacing four earlier government surveys. The Survey's 

program included "classification of the public land, and examination of 

the geological structure, mineral resources, and products of the national 

domain." It seems entirely appropriate, therefore, that a professional 

paper summarizing the progress of investigations and synthesizing our 

present state of knowledge in the important field of eolian deposition be 

one of those issued to commemorate the Geological Survey's 100th anniversary.

Early descriptions and considerations of the characteristics of modern 

eolian sand deposits, mostly in the great sand seas of the world, date back 

to the 1880's and 1890's, when pioneer geologists and explorers, including 

Walther, von Zittel, and Sven Hedin, wrote their classic papers on desert 

dunes. One or two decades later, interest in eolian processes greatly increased when wind-formed deposits were recognized in ancient 

sandstones in many parts of the world and in rocks of many ages.

Throughout the 20th century, as the science of geology has expanded 

and the programs of the U.S. Geological Survey have proliferated to keep 

pace, dune studies have had a similar growth. Work was initially concentrated mostly on the description of dune forms or morphology and on 

analysis of textural features; by midcentury, however, major contributions had been made to the physics of eolian sand, as exemplified by the 

classic work of Bagnold, by detailed studies and interpretations of minor 

eolian structures, by statistical analyses of cross-strata dip directions, and 

by the development of systems for dune classification. Most recently, interest has been renewed in detailed grain studies, in the study of crossstrata, and in interpretation of dune patterns by means of aerial photographs and Landsat imagery.

A major feature of this report on global sand seas is the compilation and 

comparison of available data based on many different methods of investigation. Evidence at one extreme is obtained from the detailed studies 

of minute particles and from analysis of individual grains. At the opposite 

extreme is evidence obtained from remote sensing, in which dune patterns, recorded from approximately 500 miles in space, are compared from 

one sand sea to another. Furthermore, comparisons are made between ancient and modern deposits with respect to textures, structures, and other 

characteristics. Criteria for recognizing the eolian origin of various ancient deposits are discussed. The application of these studies to economic 

problems, which is described in one chapter, clearly illustrates the importance of eolian deposits to our present culture and to human welfare.

H. William Menard 

Director, U.S. Geological Survey

VII

Contents

[For convenience in cross-referencing, each chapter of this publication has a letter designation]

Page 

A. Introduction to a study of global sand seas, by Edwin D. McKee .................... 1

B. Textural parameters of eolian deposits, by Thomas S. Ahlbrandt ..................... 21

C. Differentiation of eolian deposits by discriminant analysis, by R. J. Moiola and A. B.

Spencer ..................................................................... 53

D. Red color in dune sand, by Theodore R. Walker ................................... 61

E. Sedimentary structures in dunes, by Edwin D. McKee, with two sections on the Lagoa

dune field, Brazil, by joao J. Bigarella ........................................... 83

F. Dune forms and wind regime, by Steven G. Fryberger, assisted by Gary Dean ......... 137

G. Laboratory studies of sand patterns resulting from current movements, by Theodore F.

Tyler ....................................................................... 171

H. Ancient sandstones considered to be eolian, by Edwin D. McKee, with sections by Joao J.

Bigarella .................................................................... 187

I. Sediments of ancient eolian environments Reservoir inhomogeneity, by Robert Lupe

and Thomas S. Ahlbrandt ..................................................... 241

J. Morphology and distribution of dunes in sand seas observed by remote sensing, by Carol

S. Breed and Teresa Grow ..................................................... 253

K. Regional studies of sand seas using Landsat (ERTS) imagery, by Carol S. Breed, Steven C

Fryberger, Sarah Andrews, Camilla McCauley, Frances Lennartz, Dana Gebel, and Kevin

Horstman ................................................................... 305

Glossary, prepared by Marguerite Glenn .............................................. 399

Selected references ................................................................. 409

Index ............................................................................. 423

IX

A STUDY OF GLOBAL SAND SEAS

INTRODUCTION TO 

A STUDY OF GLOBAL SAND SEAS

Chapter A

By EDWIN D. McKEE

Contents

Subject matter .................... ................

Facets of dune study .... ........ ...............

Dune classification .............................

Sand-texture studies ............................

Physical processes involved .....................

Statistical studies of mean current directions ......

Preservation of surface structures, tracks, and trails

Analysis of cross-strata ........................

Application of remote sensing (ERTS) ....

Data from Skylab 4 ......................

Studies of dune color .........................

Page

3 Wind regimes .........................

3 Types of dunes ........................

4 Basis for classifying ................

4 Basic (simple) dune types ...........

4 Compound dune types ....

5 Complex dune types ...............

5 Varieties of dunes ..................

5 Interpretation of ancient eolian sandstones

6 Terminology and geographic names .......

6 Systems of measurement .............

7 Acknowledgments ......................

Page 

8 

8 

8 

8

13 

13 

13 

15 

15 

17 

17
A STUDY OF GLOBAL SAND SEAS

Illustrations

Page 

FIGURE 1. Index map of principal deserts ......................................... 7

2. Photograph of star dune, showing slipfaces and arms, Namib Desert, SouthWest Africa ........... ...... .... ....................... 9

3 -5. Block diagrams of dune types:

3. Barchan ........... ................... ...................... 11

4. Barchanoid ridge .. ........ ........ ...................... H

5. Transverse ............................... .......... ........ . 11

6. Diagram of sequence of dune types with diminishing sand supply and unidirectional wind .... ........ ........................................ 12

7 -12. Block diagrams of dune types:

7. Dome...... ............................ ................... 12

8. Blowout ............. .......... ........ .................... 12

9. Parabolic .... ................................................ 12

10. Linear.......................................................... 13

11. Star .......... ...... ........ .......................... 13

12. Reversing.................................. ...... ....... 13

13. Drawings showing examples of compound dunes ...................... 14

14. Drawings showing examples of complex dunes .................. ...... 15

15. Sketches of some distinctive dune varieties .............................. ie

Table

Page 

TABLE 1. Terminology of basic (simple) dune types ............................... 10
INTRODUCTION

Subject Matter

HE BIRTH of the idea that led to this publication on "Global Sand Seas" dates back to the 

late 1920's. At that time I was engaged in a study of 

the Coconino Sandstone of Arizona's Grand Canyon. Considerable controversy existed then as to 

whether this sandstone was a subaqueous deposit 

or was composed of wind-formed dunes. It became 

apparent that definitive literature was sparse or 

lacking on types of dunes, global distribution of 

these types, the mechanics of their development, 

the precise nature of their internal structure of 

cross-stratificiation, and the relation of wind 

systems to these sand forms. Especially lacking 

were data on criteria that could confidently be used 

in the recognition of ancient dunes.

The common denominator in this publication is 

eolian sand bodies. Although the book is concerned 

primarily with desert sand seas, the subject matter 

is not restricted to deserts; it includes many 

references to deposits of coastal sand and to sand 

bodies in humid climates. Nor does the book deal 

exclusively with dunes, which, according to most 

definitions, involve mounds or hills. Many 

references are made to sand sheets, sand stringers, 

and other types of sand deposits that have no prominent topographic expression. All sand bodies accumulated by the action of wind are discussed.

Chapters A-J of this publication are primarily 

topical. Chapters cover the grain texture, the color, 

and the structure of modern dunes and other eolian 

sands. Special treatment is given to the relation of 

wind data to dune interpretation, the evolution of 

form in current-deposited sand bodies as determined from experimental studies, and the discriminant analysis technique for differentiating between 

coastal and inland desert sands. This topical part of 

the publication also includes an analysis of criteria 

used in ancient deposits to interpret their eolian 

genesis and a consideration of economic application 

of the principles described, including a discussion 

of potentials and problems associated with eolian 

hydrocarbon reservoirs. The final chapters present 

a discussion of the morphology and distribution of 

dunes as determined largely from Landsat images.

Chapter K of the publication is devoted to 

descriptions of major sand seas based largely on 

thematic maps derived from Landsat (ERTS)

mosaics. Although inclusion herein of the actual 

mosaics proved to be impractical, the maps derived 

from them do show the distribution and abundance 

of various dune types and the relations of these 

types to certain associated features, such as 

bedrock, water bodies, and juxtaposed dunes. Furthermore, sand roses included with each of these 

maps enable the user to draw conclusions on the 

probable relations of wind strength and direction to 

dune type in a particular area.

Regional studies (chapter K) were a team effort. 

Analysis of the Landsat (ERTS) mosaics and mapping boundaries of individual dune types were by 

Carol Breed. Synthesis of the rather voluminous 

literature and preparation of abstracts covering it 

was by Camilla MacCauley. Actual preparation of 

maps was by Franci Lennartz and later by Sarah 

Andrews. The gathering of data on wind, the 

calculation of wind roses, and the interpretation of 

their relations to sand bodies were by Steven Fryberger, assisted by Gary Dean.

Facets of Dune Study

DURING THE COURSE of several decades, 

eolian dune studies have been made in ever-increasing numbers and from many different approaches. As might be expected most of the early 

studies were largely descriptive, with observations 

focused especially on external form and movement 

of sand bodies. Attempts to classify dune types advanced slowly, but basic forms were early recognized in relation to such factors as wind regime and 

physical barriers.

Principal approaches to dune study in the United 

States, and probably elsewhere to a considerable 

extent, have been as follows: (1) Classification of 

dune forms and sand patterns, first from ground 

studies, later from aerial photography, and finally 

from remote sensing; (2) textural studies involving 

characteristics of grain surfaces and shapes and 

comparisons with sand textures representing other 

environments; (3) studies of the physical processes 

involved in wind transport and deposition of sand;

(4) statistical studies of cross-strata attitudes or dip 

directions and determination of resultant vectors;

(5) investigations, both in the laboratory and in the 

field, of environments favorable to the preservation 

of surface structures and animal tracks or trails in
A STUDY OF GLOBAL SAND SEAS

sand; (6) analysis in three dimensions of eolian 

cross-strata including statistical studies of basic 

types; (7) quantitative morphology studies made 

from products of remote sensing in which constant 

scale allows direct comparisons between sand seas; 

and (8) studies, based primarily on the scanning 

electron microscope, of the factors controlling the 

red color that is characteristic of many dunes.

Dune Classification

Most geologists involved in the study of sand 

bodies have been faced with the problem of 

describing the type or types of dunes in one area 

and of assigning a name either formalized from 

local terminology, adapted from some other sand 

sea, or newly designated. Thus, for the most part, 

local terminologies have proliferated, but formal 

classifications that apply to many regions have 

been neglected. Lack of means to make direct comparisons, at scale, between dunes of different 

regions has been a major deterrent in this field.

In North America two principal attempts both 

in the 1940's were made to classify dune types. 

"A Tentative Classification of Sand Dunes: Its Application to Dune History in the Southern High 

Plains," by Melton (1940), distinguished into 

classes those dunes on bare surfaces or loose sand 

and those formed in conflict with vegetation. 

"Dunes of the Western Navajo Country," by Hack 

(1941), indicated three basic controls in development; wind regime, available sand, and plant 

growth. The present publication describes a general 

classification with two variants, one based on 

ground observation of dune forms and internal 

structures, the other based largely on dune patterns 

recognized on images from remote sensing.

Sand-Texture Studies

The texture of eolian sand grains has received 

the attention of investigators for a very long time 

(Udden, 1898; Dake, 1921; Ries and Conant, 1931; 

Wentworth, 1932). Interest in textures came about 

partly because, on theoretical grounds, windabraded sand grains were believed to show certain 

features that are rare or absent among waterborne 

sand grains and partly because laboratory experiments disclosed major differences, especially in the 

rate of developing certain textures. Further 

knowledge of textures resulted from studies comparing modern sands of dune, marine, and fluvial 

types, which differ markedly in various textural 

features.

The principal attributes that are involved in textural considerations are grain size (mean diameter), 

sorting, sphericity, roundness, pitting, and frosting. 

Numerous scales and techniques for measuring and 

recording these properties have been developed 

through the years, ranging from rough visual estimates to highly sophisticated measurements and 

from simple tabulations to elaborate histograms and 

curves.

Despite all the studies that have been made and 

the voluminous literature on the subject, results 

from the textural approach in recognizing and 

defining eolian deposits have remained highly 

debatable for two inherent reasons. First, the grain 

properties that can be described are primarily the 

results of transportation, not deposition. They may 

represent the effects of intensive movement by 

water, although deposition was by wind, or the 

reverse. Second, the grains of a particular wind 

deposit may be and commonly are the product of a 

second or third generation, reflecting the properties 

inherited from some earlier sediment. Furthermore, 

some surface features, such as frosting, may not be 

primary; rather, they are the result of diagenesis 

and, therefore, unrelated to the origin of the 

deposit.

The application of textural parameters to eolian 

sands is discussed in chapter B by Ahlbrandt. Discriminant analysis, which is used to differentiate 

beach, river, and eolian sands, is described by 

Moiola and Spencer (chapter C).

Physical Processes Involved

Sand physics, focusing especially on the movement of sand in air, is critical to an understanding 

of the growth and movement of dunes. This field of 

investigation, which necessarily involves both observational data from active dunes and the results 

of wind-tunnel experiments on sand transport, was 

the subject of a classic study by Bagnold (1941) entitled "The Physics of Blown Sand." Bagnold's 

treatise clarified many features of the mechanics of 

dune development and gave much impetus to the 

general study of sand seas.

The investigations of Bagnold constituted primarily a study of the behavior of sand grains in a
INTRODUCTION

stream of wind and consisted of "precise measurement and experimental verification." The resulting 

information explained qualitatively many dune 

forms and, with relatively few modifications, has 

stood the test of checking since publication. Additional important contributions to our knowledge of 

the interaction between wind and sand have subsequently been described by Sharp (1963, 1966).

Statistical Studies of 

Mean Current Directions

The value of measuring cross-strata dip directions in order to determine regional trends in dune 

movement has been recognized since before the 

start of the 20th century. This approach has been 

used in studies both of modern dunes and of ancient sandstones believed to be eolian in origin. A 

model for eolian paleocurrents has been described 

by Selley (1968, p. 103).

Results of directional vector measurements commonly have been presented in either of two forms: 

(1) a circular histogram or rose diagram, as illustrated by the early work of Knight (1929) on the 

Casper Formation of Wyoming, U.S.A., and by 

Shotton (1937) on the Bunter Mottled Sandstone of 

England; and (2) a stereonet as introduced by 

Reiche (1938) for analysis of the Coconino 

Sandstone in Arizona.

Both methods of illustrating vectors serve well to 

illustrate the spread in wind current directions and 

to focus attention on mean or dominant azimuth 

directions. The stereonet has the added advantage 

of showing the degree of dip, which is useful in 

differentiating between dune slipfaces and windward-side deposits and in indicating the weight to 

be given various readings. Many statistical investigations of this type, in both modern and ancient eolian cross-strata, have been made within recent years; they not only help in determining the 

direction or directions of sand transport but also, in 

some situations, indicate the type of dune involved.

Preservation of Surface Structures, 

Tracks, and Trails

The environmental conditions necessary for the 

preservation of various markings in eolian sand 

deposits have been investigated in considerable

detail by numerous geologists. These markings consist of primary sedimentary structures, varieties of 

contorted bedding, and the tracks and trails of 

animals. Such studies are especially important in 

the recognition of ancient eolian sands because 

they furnish some compelling evidence of genesis.

Minor sedimentary structures that are moderately common and that have distinctive features 

when formed in windblown sand include ripple 

marks, rain pits, and slump markings. These structures have been studied both in the field and 

through laboratory experiments during and after 

the 1940's (McKee 1945; Poole, 1962; Tanner, 1966) 

and compared with corresponding structures 

formed under aqueous conditions.

Studies of penecontemporaneous folding (contorted bedding) in eolian sands were conducted in 

the laboratory (McKee, Douglass, and Rittenhouse,

1971) and later in the field (McKee and Bigarella,

1972). A principal result of these studies is a means 

of distinguishing in ancient eolian sandstones 

whether they were formed in wet sand, saturated 

sand, damp crusty sand, or dry sand. Also, the 

studies supplied a means for distinguishing between sand accumulated in the zone of tension (upper slope) and sand in the compressional zone at 

the base of foresets. Other structural features 

served to differentiate between the products of 

different processes, such as avalanching, loading, 

and surface dragging (McKee, Reynolds, and Baker, 

1962a, b).

Investigations of the conditions under which the 

tracks and trails of various animals were formed 

and preserved were made during the 1940's, both in 

the laboratory (McKee, 1944, 1947) and through 

field observations (Peabody, 1940). These studies 

established criteria for determining the degree of 

cohesiveness of track-bearing sand at the time 

prints were made and for explaining selective 

orientation of tracks as commonly observed in 

eolian cross-strata.

Analysis of Cross-Strata

In the United States the method of using a direct 

approach in determing structure in various types of 

dunes started with the trenching of a double 

barchan dune near Leupp, Ariz., in the summer of 

1951 (McKee, 1957). The dune selected was about
A STUDY OF GLOBAL SAND SEAS

270 feet (80 m) high; dips on the windward slope 

ranged from 5° to 7°, but most dips on the lee side 

were slightly more than 30°. The method used was 

to wet the dune by pouring water into it near the 

crest, allowing the water to spread outward and 

downward along cross-strata planes, and then to 

section the dune in selected places by digging 

trenches and pits with a shovel. The result recorded 

in three dimensions the structure within the dune. 

Methods used in the experiment at Leupp, 

though primitive, proved so successful that, with 

minor modifications, they have been used in many 

places, and by many geologists since, and a considerable fund of information on dune structure has 

resulted. During trenching near Sabha, Libya, in 

1961, a pump was available for lifting water to the 

dune crest (McKee and Tibbitts, 1964); this was far 

easier than the earlier method of transporting water 

in buckets. At White Sands National Monument, 

New Mexico, U. S. A., in 1964 -65 trenches were 

dug by bulldozer a tremendous improvement 

over handshovel work as done elsewhere (McKee, 

1966). However, in most places, it has been necessary to use whatever equipment was already on 

hand at the scene.

Many important results from the trenching of 

coastal dunes in Brazil have been obtained in recent 

years by Bigarella and associates (Bigarella, Becker, 

and Duarte, 1969; Bigarella, 1972,1975a, b). In these 

dunes internal moisture resulting from the humid 

climate has made digging possible without first 

pouring water. Likewise, at Killpecker dune field in 

Wyoming, U.S.A., the moisture within some dunes 

was sufficient to permit trenching at various places 

(Ahlbrandt, 1973).

Following exposure of the cross-strata pattern, a 

record normally is made by photography or by 

measuring and sketching. The most exact and most 

permanent method of recording details of structure, 

however, has been to make peels with latex or 

some other material.

Application of Remote Sensing (ERTS)

With the launching on July 27, 1972, of the unmanned Earth Resources Technology Satellite 

(ERTS-1), later renamed Landsat-1, a new and 

important approach to the investigation of sand 

seas became available. In an 18-day earth-orbiting 

cycle, images were obtained from an altitude of

about 570 miles (915 km) by a multispectral scanner 

(MSS) aboard the satellite. These images cover 

broad bands or swaths around the globe between lat 

80° N. and lat 80° S.

A project designated as "The Morphology, Provenance, and Movement of Desert Sand Seas" was 

developed with the acquisition of ERTS imagery 

that covered 15 major desert areas around the globe 

(fig. 1). These images, though representing widely 

spaced regions, were all at the same scale, thus permitting direct comparisons of dune patterns and 

meaningful descriptions of form and distribution. 

The principal investigator on this project was E. D. 

McKee and the coinvestigator was Carol Breed. 

Four to six persons assisted in the program at 

various stages.

Work was done originally using single-band 

black-and-white positive transparencies and paper 

prints at a scale of 1:1,000,000; subsequently, falsecolor ERTS images at the same scale became available and proved to have many advantages. These 

false-color images were assembled into mosiacs of, 

selected sand seas and formed the base for thematic 

maps portraying patterns of dune types and their 

regional distribution. Through use of these maps, 

surface morphologies could be directly compared.

The study of sand seas from false-color Landsat 

(ERTS) imagery has contributed to an interpretation 

of the depositional environment, to an understanding of dune movement, and to the prediction of 

future sand sea development. Advances were made 

through the description and comparison of surface 

morphologies. For a complete understanding of the 

sand bodies, however, ground-based studies of climate, field studies of structures determined 

through trenching, and laboratory studies of texture 

were also necessary. The structural and textural 

studies contributed to an analysis of factors too 

small to establish from space; the meteorological 

data, especially wind vectors when superimposed 

on images, helped in understanding the complex 

relations between dune forms and wind activity.

Data from Skylab 4

During the winter and spring of 1974 when 

Skylab 4 was in orbit a considerable number of 

photographs were taken with a handheld camera, 

by request, of desert features in the major areas 

being studied on this project. These photographs
INTRODUCTION

30° 0° 30° 60° 90° 120° 150°

WESTERN

NORTH

AMERICA

PACIFIC 

OCEAN

ATLANTIC 

OCEAN

INDIAN 

OCEAN

TROPIC OF CAPRICORN

Arid and extremely arid desert 

regions (from Meigs, 1951)

Areas mapped from Landsat 

(ERTS-1) images, this paper

Areas covered by Landsat

(ERTS-1) mosaics, but not mapped

PRINCIPAL DESERT AND SEMIDESERT REGIONS and selected 

test areas: 1, Western Sahara, Mauritania and Senegal; 2, Northern Sahara (Grand Erg Occidental and Grand Erg Oriental), 

Algeria; 3, Northern Sahara, Libya; 4, Southern Sahara and 

Sahel, Mauritania, Mali, and Niger; 5, Namib Desert, SouthWest Africa; 6, Kalahari Desert, South-West Africa, Botswana, 

and South Africa; 7, Rub' al Khali, Saudi Arabia, United Arab

were taken from distances much closer than those 

of the ERTS images and showed more detail in 

many places. Also, they had the advantage of being 

produced in true color. Sites chosen for taking these 

photographs were northern Africa, southern 

Africa, Saudi Arabia, India, China, U. S. S. R., and 

Australia.

Studies of Dune Color

A distinctive feature of most sand seas is the 

brilliant coloring of the sand largely red with 

various degrees of intensity. Color has long been

Emirates, Oman, and Yemen; 8, Peski Karakumy and Peski 

Kyzylkum, U.S.S.R.; 9, Thar Desert, India and Pakistan; 10, 

Takla Makan, People's Republic of China; 11, Ala Shan Desert, 

People's Republic of China; 12, Great Sandy Desert, Australia; 

13, Great Victoria Desert, Australia; 14, Simpson Desert, 

Australia; 15, Algodones Desert and Gran Desierto, U.S.A. and 

Mexico. (Fig. 1.)

recognized as a function of iron oxide pigments 

associated with individual grains of sand and in 

various stages of oxidation, but how and when the 

iron has been introduced and when the oxidation 

has taken place are controversial problems with no 

single, simple answer.

Recent detailed studies of the red coloring in 

dune sands were made by T. R. Walker, using a 

scanning electron microscope, as well as a 

petrographic microscope, for analysis. Chapter D 

describes some of his results, Especially significant 

is the conclusion that at least seven separate and independent factors control the degree (variations in
A STUDY OF GLOBAL SAND SEAS

intensity) of redness in a sand deposit. This illustrates the complexity of the problem.

Colors as determined from satellite observation 

and handheld cameras and from false-color images 

of Landsat (ERTS) are useful in locating areas of 

color difference within a region and in showing the 

global distribution of various shades and intensities 

of particular colors.

Wind Regimes

BECAUSE EOLIAN SAND accumulation and 

dune migration are functions of wind regime, a 

study of available meteorological data for each sand 

sea was considered to be a necessary part of the 

global program as designed for ERTS imagery. A 

comparison of wind regimes with dune types was 

made for various localities around the world and is 

included in the parts of this Professional Paper 

dealing with regional analyses.

A type of sand rose, as described by Fryberger in 

chapter F was developed to show from accumulated wind data the direction and relative amount 

of sand drift at a given locality. By use of a "weighting equation" the relatively much greater ability of 

winds of high velocity to cause sand drift is taken 

into account. Resulting sand roses have been 

superimposed on the various regional maps in this 

publication to allow direct comparison with associated dune types as mapped.

Types of Dunes

A PRINCIPAL AIM of this investigation has been 

to construct an objective and descriptive classification which segregates into types the various distinctive dune forms and relates these types to 

specific environments of deposition. Two innovations in methods of study contributed substantially 

to the construction of this classification.

The first factor in establishing a sound basis for 

classifying eolian sand bodies is improved 

knowledge of process of construction, obtained 

from direct observation of their structure in pits 

and trenches. The second factor is availability of 

data from remote sensing programs, especially in 

the form of Landsat (ERTS) imagery, in which a 

uniform scale permits direct comparisons between 

various parts of the world. These two approaches

have greatly stimulated efforts to better describe 

and classify dune forms.

Basis for Classifying

In the investigation of eolian sands, the 

classification recommended is based on two 

descriptive attributes the shape or form of the 

sand body and the position and number of slipfaces 

(steep lee-side surfaces) (fig. 2; table 1). Generally, 

these two attributes constitute recognizable 

features both in closeup ground views and at the 

great distances represented by ERTS images. Exceptions are those sand features that are too small 

to be identified on the Landsat (ERTS) images.

Two slightly different terminologies are used in 

the classification system for this publication. One 

version (table 1, col. 3) is derived primarily from an 

analysis of dune structures and so constitutes both 

a description of the sand dune forms and a partial 

record of their genesis. The other version (table 1, 

col. 6) of the classification is developed largely 

from the patterns of Landsat (ERTS) imagery and is 

used both in the thematic maps prepared from the 

ERTS mosaics of the principal sand seas and in 

ERTS-based studies of distribution and 

morphology. One version of the classification 

stresses factors that record the growth and development of individual dune bodies; the other version 

emphasizes the gross features of dune patterns 

where details cannot be observed.

An examination of sand seas from various approaches including studies of Landsat (ERTS) 

images, air photos, ground records, and other 

material suggests that the number of basic or 

simple dune forms is fairly limited (table 1). 

However, a large number of combinations of dune 

types and an almost infinite number of varieties occur. Dune combinations are of two categories: (1) 

compound dunes made up of two or more dunes of 

the same type, coalescing or overlapping, and (2) 

complex dunes in which two different basic types 

are combined or superimposed.

Basic (Simple) Dune Types

The simple dune types, because they are 

classified partly on overall form and partly on number of slipfaces, generally reflect factors of the 

depositional environments in which they devel-
STAR DUNES, showing three curving arms with steep slipfaces oriented in various directions. Tsondab Vlei, northeastern part of Namib Desert, South-West Africa. Photograph by 

E. Tad Nichols. (Fig. 2.)

oped, especially the wind (strength and direction), 

the sand supply, vegetation, physical barriers (rock 

outcrops and water bodies), and distance from 

source. Various combinations of these factors are 

responsible for each distinctive dune type and permit some generalizations concerning their genesis.

Probably the best known and commonest basic 

dune forms result from winds having a single dominant direction and are oriented with their axes at 

right angles to wind direction. Such dunes range 

from the small crescent-shaped type commonly 

known as barchan (fig. 3), through parallel rows of 

coalesced barchans, here referred to as barchanoid 

ridges (fig. 4), to essentially parallel straight ridges 

known as transverse dunes (fig. 5). All three types, 

which may occur in gradational sequence, are 

referred to as "crescentic" on the regional sandseas maps presented in this publication. Most 

barchan types are too small to be recognized on 

Landsat (ERTS) images, and at that scale the 

transverse dunes are difficult to distinguish from 

some of the smaller barchanoid ridges and from 

many linear dunes.

The genetic relationship between the three dune 

types previously referred to seems to be reasonably 

well established through the observations of many 

geologists and has been described in numerous 

papers. These dunes are all characterized by slipfaces in one direction and therefore represent 

unidirectional wind movement. The three types 

commonly occur in a definite sequence (fig. 6) 

downwind as a result of diminishing sand supply. 

In general, the type represented in a particular area 

seems to be a function of the amount of available 

sand. Barchan dunes clearly result from sparse sand 

and in many areas are scattered over bare rock surfaces. Transverse dunes, the other extreme, 

develop where sand is abundant, and they attain 

maximum height where there is a balance between 

strength of wind and available sand.

Because most barchanoid-type dunes 

barchans, barchanoid ridges, and transverse 

dunes form patterns of parallel wavy lines on 

ERTS images, they were referred to collectively as 

"parallel wavy dunes" in the classification of dune 

patterns used during ERTS studies (McKee and 

Breed, 1974a, b).
10 A STUDY OF GLOBAL SAND SEAS

TABLE 1. Terminology of basic dune types and other eolian deposits

[Examples may show simple or compound dunes; however, they are designated by basic dune type only]

Form

Sheetlike 

with broad, 

flat surface

Thin, elongate 

strip

Circular or 

elliptical mound

Crescent in 

plan view

Row of connected 

crescents in 

plan view

Asymmetrical 

ridge

Circular rim 

of depression

"U" shape in 

plan view

Symmetrical 

ridge

Asymmetrical 

ridge

Central peak 

with 3 or 

more arms

Number of 

slipfaces

None

None

None 2

1

1

1

1 or more

1 or more

2

2

3 or more

Name used in ground 

study of form, slipface, 

and internal structure

Sheet

Stringer

Dome

Barchan

Barchanoid ridge

Transverse ridge

Blowout4

Parabolic4

Linear (seif)

Reversing

Star

Block diagram 

figure numbers 

(Chapter A)

None, flat 

surface

None, flat 

surface

For detail 

see fig. 7

For detail 

see fig. 3

For detail 

see fig. 4

For detail 

see fig. 5

For detail 

see fig. 8

For detail 

see fig. 9

For detail 

36 fig. 10

For detail 

see fig. 12

For detail 

see fig. 11

Name used in space-imagery and 

air-photo study of pattern and 

morphology (Chapters J, K)

Sheet 1

Streak1

Dome-shaped

Barchan

_o 

c

0) 

U

£ Barchanoid ridge

0

Not recognized

Parabolic

Linear

Reversing

Star

Examples from 

Landsat imagery

9 MILES 1 P

0 ] KILOMETRES 25

'^V

w

- mT^

( 3 )

( 3 >

^UfeU

J*J<ffS *~i». C" 

*"» $ iJ ^*-i i •*>-•

A* '< t "

•*• Sr-»

H

( 3 )

 1

%

*~#* *

ji - j -Vv 

'£ ?"#^yA

f

*4r %^ -

'i».*r i * -% «. *" ^ "j* *' * % -

&^r^ i v-Srv* «*-.*-;%* ^^S^

iMay include mounds and other features too small to appear on Landsat imagery.

^Internal structures may show embryo barchan-type with one slipface

SBecause of their small size, dome dunes, blowout dunes and individual barchan dunes are difficult to distinguish on Landsat imagery.

iDunes controlled by vegetation.
INTRODUCTION 11

BARCHAN DUNES. Arrow shows prevailing wind direction. 

(Fig. 3.)

BARCHANOID RIDGE. Arrow shows prevailing wind direction. 

(Fig. 4.)

TRANSVERSE DUNE. Arrow shows prevailing wind direction. 

(Fig. 5.)

Some sand bodies display no slipfaces. These 

bodies are commonly referred to as sheets and 

stringers, using the geologic terminology usually 

applied to bodies of rock or sediment having such 

forms. These sand bodies are not considered to be 

dunes, because the term "dune," according to most 

definitions, refers to a mound or ridge. A stringer 

may be considered to be a variety of sand sheet 

having a stringlike shape, and, commonly, though 

not exclusively, it develops along the margins or at 

the downwind extremity of a sheet. The term 

"streak" is used instead of "stringer" on thematic 

maps in this publication. Streaks identified on the 

basis of Landsat (ERTS) mosaics may, therefore, include barchans and other small dunes which are 

not visible on the image.

Dome dunes (fig. 7), which probably consist of 

more than one type (as discussed in chapter E on 

dune structure), normally show no external slipfaces and are circular or elliptical in plan view. 

However, some dunes of this type internally disclose slipfaces dipping in one direction, suggesting 

that they began development as barchans, and implying that the dome form is the result of strong 

winds that truncated the top and flattened the lee 

slopes of a barchan. Many dome dunes of coastal 

areas probably have their shapes controlled more 

by moisture and vegetation than by strength of 

wind, as described later.

A class of dunes in which the forms apparently 

are controlled more by partial stabilization from 

vegetation or moisture or both, than by wind 

strength and direction, is represented by the 

blowout (fig. 8) and the parabolic dunes (fig. 9). 

Such dunes may have slipfaces sloping in one or 

many directions depending on what parts of their 

rims are free to migrate. They are, to a considerable 

extent, features of deflation by wind, but deposition 

occurs wherever margins are free to migrate as on 

other dunes. The blowout type is normally a circular bowl, whereas the parabolic develops a U-shape 

or V-shape from arms that are anchored and nose 

that migrates downwind. A coastal dune of ridge 

form which reflects control by vegetation is referred to by some authors as a retention ridge; it may 

have small blowouts developed on it.

Perhaps the most controversial type of dune is 

the linear dune (fig. 10) commonly known as the
12 A STUDY OF GLOBAL SAND SEAS

•••<*» -••-, ).#••

\

SEQUENCE OF DUNE TYPES with unidirectional wind and (from left to right) diminishing sand supply; transverse, 

barchanoid ridge, and barchan. Arrow shows prevailing wind direction. (Fig. 6.)

self dune in Africa and Saudi Arabia and as the from nearly opposite directions are balanced with 

longitudinal dune in many other regions. Whatever respect to strength and duration. Such dunes may 

the mechanics of its genesis and number of wind have the general form of transverse ridges, but a 

directions involved, it is, in general, a straight ridge 

with slipfaces on both sides; groups of these ridges, 

as seen in ERTS images or air photos, appear as 

parallel straight lines.

Dunes of multiple slipfaces are the result of 

winds from several directions; they commonly 

have a high central peak and three or more arms extending radially. Such forms are called star dunes 

(fig. 11) and have an infinite variety of shapes. 

They mostly grow vertically, rather than migrating 

laterally.

Intermediate in character between the star dune 

and the transverse ridge is the reversing dune (fig. 

12). It characteristically forms where two winds BLOWOUT DUNES. (Fig. 8.)

DOME DUNES. (Fig. 7.)

PARABOLIC DUNES. Arrow shows prevailing wind direction. 

(Fig. 9.)
INTRODUCTION 13

second slipface, oriented in a direction nearly opposite that of the primary slipface, develops 

periodically.

LINEAR DUNES. Arrows show probable dominant winds. 

(Fig. 10.)

STAR DUNES. Arrows show effective wind directions. (Fig. 11.)

REVERSING DUNES. Arrows show wind directions. (Fig. 12.)

Compound Dune Types

In addition to the basic or simple dune forms just 

described, compound forms are abundant in most 

sand seas. These consist of two or more of the same 

type combined by overlapping or by being superimposed (fig. 13) on one another. Examples of compound dunes are (1) barchanoid ridges coalescing, 

(2) star dunes coalescing to form an intricate pattern of arms and peaks, (3) little barchan dunes on 

the windward flanks of large ones, (4) small 

parabolic dunes between the arms of a larger one, 

and (5) major ridges covered by many smaller 

linear dunes.

Complex Dune Types

Complex dunes in which two different basic 

types have coalesced or grown together are represented in most sand seas by various combinations 

(fig. 14). These combinations include linear dunes 

in parallel rows with star dunes on their crests; 

these are called "chains of stars" and are well 

developed in several major sand seas. Complex 

dunes also are illustrated by small barchan dunes in 

the corridors of linear dunes, by blowout dunes on 

transverse dunes, and by large star dunes with 

superimposed barchanoid dunes.

Varieties of Dunes

For all dune types simple, compound, and 

complex an almost infinite number of varieties 

occurs. The varieties are too numerous to describe 

or even classify by name herein, for they probably 

represent transitions from one basic type to another 

and result from differences in the direction and 

strength of wind, the amount of available sand, the 

physical obstructions, and other factors that control 

dune types. Some varieties that are especially conspicuous and have been much discussed in the 

literature are barchans with one horn greatly extended, linear dunes with many branches diverging 

from one end suggesting the name feather dunes, 

and parabolic dunes that are V-shaped rather than 

U-shaped (fig. 15).
14 A STUDY OF GLOBAL SAND SEAS

c

COMPOUND DUNES: A, Barchanoid ridges coalescing. B, Star 

dunes coalescing. C, Small barchans on large barchan. D, 

Parabolic dunes within a large parabolic dune. E, Linear dunes 

on large linear ridge. (Fig. 13.)
INTRODUCTION

Interpretation of Ancient 

Eolian Sandstones

A MAJOR EFFORT of this investigation was to 

establish criteria for the recognition of ancient 

eolian-type sandstones (chapter H). Recognition of 

wind-deposited sand in ancient sandstones was 

recorded nearly 100 years ago by Walther (1888, p. 

253) when he stated that a detailed study of the Nubian Sandstone in Sinai and adjacent parts of the 

Arabian Desert "has led me to the conviction that 

these sandstone deposits are an eolian dune 

development * * * and that North Africa contained 

deserts of Paleozoic and Mesozoic age."

Subsequently, the eolian origin of certain sandstones in the Southwestern United States was 

postulated by Huntington (1907, p. 380) because of 

textural and structural features "frequently seen 

among modern sand dunes of Persia, Transcaspia, 

and Chinese Turkestan." Other early references to 

sandstones believed to have been wind-deposited 

are Fourtau (1902), Sherzer and Grabau (1909), 

Twenhofel (1926, p. 174, 557), and Cuvillier (1930). 

In general, however, compelling evidence for the 

recognition of eolian sandstones had to await the 

fairly sophisticated analyses of cross-strata characteristics and direction vectors, studies of minor 

structures and their preservation, and other approaches that were introduced about 1937 and later, 

as described in chapter E on modern dune structures.

Terminology and Geographic 

Names

TERMS USED in this professional paper are 

defined in the glossary. Most definitions are from 

"A Desert Glossary," by R. O. Stone (1967), and 

from "Glossary of Geology," published by the 

American Geological Institute (1972), although 

various other glossaries were also consulted. A few 

terms introduced for the first time in this paper are 

also defined.

The names of geographic localities outside the 

United States are according to the gazetteer for each 

of the countries concerned. The spellings have been 

approved by the U. S. Board on Geographic Names

15

•^L, 1 ^-

COMPLEX DUNES: A, Star dunes on linear dune. B, Linear dunes 

with barchans in interdunes. C, Blowouts on transverse dune. 

(Fig. 14.)
16 A STUDY OF GLOBAL SAND SEAS

BABCHAN

^^^Sy^f^.^y^': ^..^-i-..

-• ,~- :v^5«s£^' -^ r~.~ jjt /^^ &%-'Si%i<&.^%^ "t??SS'"j>-.?:'f %;" ir'^---- i '•--j'3: '*$- ySlSff^"-S'^1$fff''"":

^i?jW5a=a!p^^}t<cs8ajKS£?«wsg«ww*--- r'' 'HiBBiiii| '"T ^:ri 'T'

r,^« v:.;MW*-^-e*5*5».- st **. «

^^"^TawsHawiBrt^

•GSSsv^* 5?^ •' --, *- f& ,-• -,-«, •^ ^-^'^:2^.:

^'''^--A^^ff^'''^ * *

'^^^S^2*

J6»«^.%

SOME DISTINCTIVE VARIETIES of basic dune types. (Fig. 15.)
INTRODUCTION 17

and the U. S. Department of Defense, Defense Mapping Agency. International boundaries and geographic names and their spellings do not 

necessarily reflect recognition of political status of 

an area.

Systems of Measurement

THIS TREATMENT OF SAND SEAS on a global 

scale includes measurements of many kinds and 

from many sources. Resulting figures should 

preserve as nearly as possible the original measurements as derived, but at the same time should be 

readily visualized by people of various backgrounds 

and training. Thus, where an original measurement 

was made in terms of the metric system, it is expressed in that system, but for the convenience of 

some readers, its converted equivalent in the 

English system follows in parentheses. Likewise, 

where an object was measured in inches, feet, or 

miles, that measurement as recorded is presented in 

the text, succeeded by its metric equivalent in 

parentheses.

The following English-metric conversion scales 

are given for the convenience of the reader. They 

are for visual comparison only and do not represent 

actual units of measurement. Abbreviations shown 

in parentheses are those used in this publication.

0.5 3 Inches (in)

0 0.5 1

1———— 

6 Centimetres (cm)

10 Feet (ft)

-r1 

3 Metres (m)

0 10 20 30 40 Miles 

-J (mi)

0 5 10 20 30 40 Kilometres (km)

Comparative English and metric scales of distance.

Most of the conversions from one system to the 

other were made by Patricia Melrose of the U.S. 

Geological Survey, using a conversion calculator. 

Except where a high degree of precision was available and required by a particular situation, 

references throughout the text were converted only 

approximately.

Acknowledgments

A VERY LARGE NUMBER of organizations and 

individuals have contributed ideas, facts, and 

materials, as well as time and effort, to assist in the 

preparation of this treatise. To all of these we extend our gratitude. Contributions that pertain to 

particular chapters are, for the most part, 

acknowledged within the appropriate chapters; 

contributions that affect numerous chapters or the 

entire Professional Paper are acknowledged here.

Geologic and Geographic Data

For assistance in interpreting local features of 

various sand seas:

Dr. G. Lennis Berlin, Northern Arizona University, Flagstaff, Arizona, U. S. A.

Dr. Arthur L. Bowsher, Arabian American Oil 

Co., Dhahran, Saudi Arabia.

Dr. I. H. Hamrabaev, Institute of Geology and 

Geophysics, Tashkent, U. S. S. R.

Mr. Donald Holm, formerly with Arabian 

American Oil Co., Saudi Arabia.

Mr. Brad Musick, Office of Arid Lands Studies, 

Tucson, Arizona, U. S. A.

Dr. Shumil E. Roy, Indian Agricultural 

Research Institute, New Delhi, India.

Dr. M. K. Seely, Desert Ecological Research Institute, Walvis Bay, South-West Africa.

Remote Sensing Program

For guidance, support, and assistance in those 

phases of sand sea study based on remote sensing 

programs, we are indebeted to the following people 

in the United States:

National Aeronautics and Space Administration (NASA):

G. Richard Stonesifer, Technical Monitor. 

Paul D. Lowman, Scientific Monitor.

EROS Program, Office of U.S. Geological 

Survey;

J.M. DeNoyer, Director. 

Richard S. Williams, Jr., Geologist. 

W. Douglas Carter, Geologist. 

Priscilla Woll. EROS Technical Publications Office.
18 A STUDY OF GLOBAL SAND SEAS

Landsat (ERTS) Office of U.S. Geological 

Survey:

W. R. Hemphill, Chief, Resources Working Group. 

Lawrence C. Rowan, Staff Geologist and

Coordinator for Remote Sensing. 

Allan N. Kover, Staff Geologist, Remote

Sensing. 

Robert D. Regan, Staff Geologist, Remote

Sensing. 

Skylab, NASA:

V. R. Wilmarth, Program Scientist. 

John Kaltenbach, Project Scientist. 

Michael McEwen, Geologist.

Wind Record and Other Climate Data

The following persons and institutions assisted in 

the gathering and interpreting of meteorologic 

records used in compiling wind roses;

Arabian American Oil Co., Dhahran, Saudi 

Arabia — Mr. J. P. Mandaville.

Central Arid Zone Research Institute, India — 

Dr. H. S. Mann.

Desert Ecological Research Institute, Walvis 

Bay, South-West Africa — Dr. M. K. Seely.

Indian Meteorological Department, Poona, India — Dr. K. Krishnamurthy.

Meteorological Department, Ministry of Communications, Tripoli, Libyan Arab Republic — Mr. M. M. Sasy.

National Climatic Center, Ashville, N. C., 

U.S.A. — Dr. Harold L. Crutcher.

Manuscript Review

For helpful suggestions and criticism, after their 

technical review of drafts for various chapters we 

thank the following:

John Dingier, University of California at San

Diego, California U. S. A. 

Gerald Friedman, Rensselaer Polytechnic Institute, Troy, New York, U. S. A. 

Dr. A. S. Goudie, Oxford University, England. 

Dr. R. L. Maby and colleagues, Arabian

American Oil Co., Dhahran, Saudi Arabia. 

Dr. John Rogers, University of Cape Town,

Rondebosch, South Africa. 

Dr. D. B. Thompson, Manchester University, 

England.

Volunteer Assistance for Work on 

Landsat (ERTS-1) Program

Many phases of the remote sensing program for 

Sand Seas Analysis, conducted at Flagstaff, 

Arizona, U. S. A., were made possible by the volunteer services of geology students, mostly from the 

Northern Arizona University. The following persons are given special thanks for their contributions 

to this program:

Marion Blancett: photographic work. 

Dana Gebel: Cataloguing imagery acquisitions, 

work on chart of dune terminology, rough 

draft maps.

Kevin Horstman: Measuring dune and interdune areas with density slicer. 

Katherine Nation: Preparing mosaics from

ERTS imagery.

Iris Sanchez: Vegetation studies, dune 

measurement studies.

Photographic and Other Illustrative 

Materials

Photographs for use in illustrating sand bodies of 

various types and localities were kindly furnished 

by the following in the United States:

Dr. Stanley Froden, NASA, Ames Research

Laboratory, Iowa. 

George Morrison, National Park Service, White

Sands National Monument, New Mexico. 

E. Tad Nichols, Tucson, Arizona. 

J. Philip Schafer, Flagstaff, Arizona. 

Joseph F. Schreiber, University of Arizona,

Tucson, Arizona. 

John Shelton, La Jolla, California. 

H. T. U. Smith (now deceased), Department of

Geology, University of Massachusetts,

Amherst, Massachusetts.

Editing and Preparation of Text and 

Illustrations

Because of the considerable size and numerous 

ramifications involved in this publication, far more 

than normal time and effort was required by some 

people of the U.S. Geological Survey to bring the 

text and illustrations to their final form. As editors, 

Patricia Melrose, and Shirley Person did much
INTRODUCTION 19

valuable work on preliminary drafts of the 

manuscript. For work on the completed text during 

early stages, much credit is due Priscilla Patton; for 

later painstaking review and for seeing the 

manuscript to completion, credit is due Diane 

Schnabel; and an excellent job of illustration editing was done by Sigrid Asher-Bolinder. Final editing and preparation for printing was by Carol Hurr; 

graphics are by Arthur Isom.

Library and Literature Review Research

The extensive program of literature review that 

was required in support of the ERTS program was

greatly facilitated by the help of the following 

librarians and reference-service personnel here in 

the United States:

Katharine Bartlett, Museum of Northern

Arizona library, Flagstaff, Arizona. 

Elizabeth Behrendt and Helen King, U. S.

Geological Survey, Denver, Colorado. 

Mary Haymes and Pamela Noaecker, National

Center for Atmospheric Research, Boulder,

Colorado. 

James Nation, U.S. Geological Survey,

Flagstaff, Arizona. 

Patricia Paylore, University of Arizona library,

Tucson, Arizona.

^- '.;•'.• ' '. ' t^ .' JrfS??'"" •'-;•:"''•""- " • ' :'-r'$8y-'f?*"'-;"~.. '• '•-.'•'.•'.'!'':'•"• •'•'-..'

A STUDY OF GLOBAL SAND SEAS

TEXTURAL PARAMETERS OF EOLIAN DEPOSITS

Chapter B

By THOMAS S. AHLBRANDT

Contents

Page 

Summary of conclusions ............................ 23

Introduction ...................................... 23

Acknowledgments ................................. 24

Textural parameters of coastal dune, inland dune, and interdune and serir deposits ........................ 24

Recognition of depositional environments ............ 27

Porosity and permeability relationship to textural

parameters ...................................... 32

21
22 A STUDY OF GLOBAL SAND SEAS

Illustrations

Page 

FIGURE 16. Map showing general locations of the 506 eolian sand samples studied .... 25

17. Photograph of dune and interdune deposits, Namib Desert, South-West Africa 27

18. Histograms of graphical measures for 191 eolian sand samples ............. 28

19-21. Plots of graphical measures of:

19. 291 coastal dune sand samples ...... .......................... 29

20. 175 inland dune sand samples ................................. 30

21. 40 interdune and serir sand samples ............................ 30

22. Histograms showing textural contrasts among dune and interdune sand .... 31

23. Photograph showing large, complex linear dunes which derive sand from

coastal deposits, Namib Desert, South-West Africa ..................... 32

24. Diagram showing relationship between initial porosity and sorting ......... 32

25. Diagram showing the interrelationship of mean grain size and sorting on initial

permeability for wet, packed sand .................................... 33

26. Map and columnar sections of cores and plug samples taken for porosity and 

permeability determinations, White Sands National Monument, New Mexico, U.S.A. ......................................................... 34

27. Diagram showing porosity-permeability distribution of dune and interdune

sediments, White Sands National Monument, New Mexico, U.S.A. ....... 35

Tables

Page 

TABLE 2. Comparison of textural parameters for selected dune fields ................ 26

3. Porosity and permeability measurements in alluvial, littoral, and coastal dune

sand .............................................................. 33

4. Porosity and permeability measurements in eolian subenvironments: Coastal

dune, inland dune, and interdune sand ............................... 33

5. Graphical measures of sand samples from coastal dunes used as a data base 36

6. Graphical measures of sand samples from inland dunes used as a data base. 44

7. Graphical measures of sand samples from interdune and serir deposits used as

a data base ........................................................ 50
TEXTURAL PARAMETERS OF EOLIAN DEPOSITS 23

Summary of Conclusions

SUITE OF 506 eolian sand samples was 

divided into 291 coastal dune samples, 175 inland dune samples, and 40 interdune and serir samples. Textural parameters for each sample are 

listed. These three subenvironments of eolian 

deposits have different textural parameters: (1) 

well-sorted to very well sorted fine coastal dune 

sand. (2) moderately sorted to well-sorted fine to 

medium inland dune sand, and (3) poorly sorted interdune and serir sand. The dune-sand samples, including those from coastal and inland dunes, range 

in mean grain size from -0.68 0 (1.6 millimetres) to 

3.4 0 (0.1 millimetres). Most interdune and serir 

samples are bimodal in the sand fraction and also 

have higher silt and clay contents compared with 

adjacent dune-sand samples. Textural contrasts occur among samples from different positions on a 

given dune type, and among samples from dunes 

formed under different wind regimes.

In the absence of sedimentary structures as primary evidence of eolian deposits, textural criteria 

become important. Alluvial, littoral, and eolian 

sands differ in their porosity and permeability, 

which are functions of mean grain size, sorting, and 

packing arrangements. Impermeable or low permeability deposits, such as interdune or fluvial 

deposits adjacent to more permeable deposits, particularly well-sorted coastal dune sand, may form a 

barrier to fluid migration — oil or water. Therefore, 

differentiation of depositional environments in 

eolianites can enhance fluid recovery operations. 

Skewness and kurtosis values for eolian deposits 

are highly variable and were not found to be diagnostic. Sophisticated approaches, such as discriminant analysis or moment measures, rather than 

graphical measures of textural parameters may be a 

means to differentiate alluvial, littoral, and eolian 

sands on a textural basis as discussed by Moiola and 

Spencer (chapter C, this paper).

Introduction

THE DEGREE to which textural parameters may 

be used to identify eolian deposits is highly controversial. Folk and Ward (1957), Mason and Folk 

(1958), Friedman (1961), Folk (1962), Mabesoone 

(1963), Visher (1971), and others believe that textural parameters, such as excellent sorting, positive 

skewness, mean grain size, or rounded and frosted 

grains uniquely define eolian deposits. In contrast, 

Udden (1914), Shepard and Young (1961), Schlee, 

Uchupi, and Trumbull (1964), Moiola and Weiser 

(1968), Bigarella (1972), Ahlbrandt (1974b), and 

others consider these parameters to be considerably 

less diagnostic of eolian deposits.

In this chapter and in chapter C, particle-size 

diameter is measured in the phi (</>) grade scale 

followed by the equivalent in millimetres (mm) 

(Wentworth grade scale). The progression is as 

follows:

. . . —2 <f> =4 mm 

—1 <f> = 2 mm 

00=1 mm 

10 =0.5 mm

2 <f> =0.25 mm

3 0 =0.125 mm 

40= 0.0625 mm . . .

Grains of sand size -1.0 to 4.0 0 (2.0-0.062 mm) 

compose most sand sea deposits (Cooke and Warren, 1973, p. 255-267); thus, the sand fraction of 

eolian deposits is discussed in this chapter. Eolian 

silts (loess), eolian clays, clay coatings on grains 

(Walker, chapter D, this paper) and sand size aggregates of silt and clay are not discussed.

Deficiencies of certain sizes of clastic material 

are considered to be eolian indicators by Udden 

(1914) and Kuenen (1960). Deficiencies of eolian 

material larger than 0.0 0 (1 mm) and smaller than 

3.3 0 (0.1 mm) were noted by Kuenen (1960), and 

deficiencies of elastics smaller than 4.3 0 (0.05 mm) 

were observed by Bagnold (1941). In general, deficiencies of clastic particles in the very coarse sand 

to granule range, 0.0 to -2.0 0 (1-4 mm), and the 

very fine sand to silt range, 3.0 to 4.0 0 (0.125 -0.062 

mm), have been observed in a number of depositional environments (Shea, 1974). On the basis of 

analyses of 11,212 samples, Shea (1974) concluded 

that these clastic deficiencies do not exist. 

Although clastic particles larger than very coarse 

sand, < -0.68 0 (1.6 mm), and smaller than very fine 

sand, >3.4 0 (0.1 mm), are absent in the dune-sand 

samples used in this study, the interdune samples 

from the sample suite contain material that ranges 

in size from granule to clay. Because of the 

problems with the deficiencies concept discussed 

by Shea (1974) and the variety of material that oc-
24 A STUDY OF GLOBAL SAND SEAS

curs in the interdune and serir samples, this chapter 

will focus on the clastic material in the samples.

Several other types of textural studies will be 

briefly discussed. Upturned plates of quartz 

(chevrons) formed during the frosting process can 

be detected with the scanning electron microscope 

and, thus, is a potential indicator of eolian processes (Kuenen, 1960; Margolis and Krinsley, 1971; 

Rogers and Tankard, 1974). In indurated rocks, 

defrosting by the diagenetic effects of pressure 

solution and grain alteration reduce the reliability 

of this indicator (Kuenen and Perdok, 1962; 

Margolis and Krinsley, 1971). Despite these 

problems, Le Ribault (1974) suggested that original 

surficial textures may persist in the geologic record.

Differential settling velocities of light and heavy 

minerals have been used to document eolianites 

and their traction, saltation, and suspension components (Friedman, 1961; Hand, 1967; Steidtmann, 

1974). Provided that all grain sizes are available and 

stable heavy minerals are used, this technique 

should be diagnostic because the relative sizes of 

hydraulically equivalent light and heavy grains 

deposited in air are different from those deposited 

in water.

The purpose of this discussion is to present and 

synthesize data for a broad-based collection of 

eolian deposits throughout the world and the 

graphical measures of their textural parameters, 

and to provide impetus for future textural studies 

of eolian deposits. Data used in this chapter are not 

the result of systematic worldwide sampling networks to prove or disprove a particular hypothesis, 

such as I. G. Wilson's (1973) hypothesis of granulometric control of eolian bedforms. There are few 

systematic textural studies of entire dune fields; 

however, the overall large and varied nature of the 

population studied in this report (506 samples) may 

lead to significant conclusions. This population 

comprises 191 sand samples primarily from inland 

dune fields and 315 samples mostly from coastal 

dunes in Brazil (fig. 16). The forms sampled include 

star, seif, dome, transverse, barchan, parabolic, 

hanging (falling), climbing, produne, and coastal 

dunes. Moreover, the samples came from various 

positions on the dunes, such as the crest, windward 

and leeward or slipface, from ripples, sand ridges, 

interdune and serir deposits. The composition of 

the samples includes carbonate sands (Bahama Islands) and clastic sands; the latter including gypsum (White Sands National Monument, New Mexico), olivene (Hawaii), quartzose and feldspathic 

sands.

The textural parameters, derived from quarter 

phi sieve data, of mean grain size (Mz), inclusive 

graphic standard deviation (o-j), inclusive graphic 

skewness (Skj), and transgraphic kurtosis (K'G) as 

defined by Folk (1968b) will be used in this chapter.

Acknowledgments

SAMPLES WERE SIEVED on quarter phi intervals by R. J. Moiola and A. B. Spencer, both of 

Mobil Research and Development Corp., Dallas, 

Texas, and their data are at the end of this chapter. 

Edwin D. McKee of the U.S. Geological Survey provided 191 sand samples for this study. J. J. Bigarella 

of the Geological Institute, Federal University of 

Parana, Brazil, and L. R. Martins of the Ceco-Instituto de Geaciencias-UFRGS, Porto Alegre, Brazil, 

provided the data for 315 samples from Brazilian 

coastal dunes. Textural data from the literature 

were obtained by Camilla McCauley of the U.S. 

Geological Survey. I thank them all.

Textural Parameters of Costal

Dune; Inland Dune, and 

Interdune and Serir Deposits

A COMPARISON of published information of 

mean grain size and sorting values for selected 

dune sands (as opposed to interdune) from five 

continents indicates that the dune sands are 

generally in the fine sand range (0.125-0.25 mm) 

and are moderately well sorted (o-j values from 

0.50-0.71, Trask values from 1.4-2.0). (See table 

2.) These data represent a variable number of samples, a multitude of sampling and laboratory techniques, many different dune types, and different 

locations of samples on the dunes. Because of the 

general confusion in the literature regarding textures of eolian deposits, generalizations based upon 

textures as discussed in the literature seem inappropriate. The textural parameters for the 506 sand 

samples used in this chapter and by Moiola and 

Spencer (chapter C, this paper) were all derived 

from quarter phi sieve data, thus allowing textural 

comparisons.
TEXTURAL PARAMETERS OF EOLIAN DEPOSITS 25

180°

GENERAL LOCATIONS of the 506 eolian sand samples studied, (fig. 16.)

The majority of the 191 samples collected by Edwin D. McKee throughout the world represent inland dune and interdune environments (fig. 17 and 

frontispiece), and demonstrate the maximum range 

of textural parameters for eolian deposits. The 

dominant mean grain sizes for these samples are in 

the medium and fine sand ranges (fig. 18). Sorting 

values show a wide range with a considerable portion occurring in the poor sorting category (fig. 18). 

The histogram of the skewness values shows that 

the majority of the samples are positively skewed, 

although at least 20 percent of the samples are 

negatively skewed (fig. 18). The kurtosis histogram 

shows considerable scatter (fig. 18).

Data for another 315 samples, mostly from 

Brazilian coastal dunes, were combined with 

McKee's data and then divided into three major 

categories (where n is number of samples): (1) 

coastal dune sand (n=291), (2) inland dune sand 

(n=175), and (3) interdune and serir sand (n=40). 

The data at the end of this chapter (tables 5-7) are 

presented according to these categories and are 

grouped alphabetically by geographic area within

these categories. The statistical differentiation, 

using discriminant analysis, of coastal dune sand 

samples from inland dune samples, and of inland 

dune sand samples from interdune samples is presented by Moiola and Spencer (chapter C, this 

paper). The textural contrasts among coastal, inland, and interdune samples are illustrated by plots 

of their textural parameters.

Comparison of 291 coastal dune sand samples 

with 175 inland dune sand samples shows several 

differences. The coastal dunes are composed almost 

totally of very well sorted fine sand (fig. 19). 

Furthermore, they are symmetrical to positively 

(fine) skewed and are platykurtic to mesokurtic 

(fig. 19). Inland dune sand samples, by contrast, 

show a much greater range in mean grain size and 

sorting values (fig. 20). Skewness values show wide 

scatter, from positive to negative, and the kurtosis 

values tend to be mostly platykurtic (fig. 20).

The most significant textural differences occur 

between dune sands and interdune and serir sands. 

The mean grain size of 40 interdune and serir sand 

samples is highly variable, due to their poor sorting
26 A STUDY OF GLOBAL SAND SEAS

TABLE 2. — Comparison of textural parameters of sand from selected dune fields and sand seas

[Leaders (...) indicate no data]

Selected area Mean grain size 

(millimetres)

Sorting Reference

Trask2

Africa

Grand Erg Occidental, Grand Erg 30.10 - 0.30

Oriental, Algeria.

Mauritania, Mali ................ 30.25- 0.40

Libya, Niger, Chad ............... 0.20

...... do ....................... 0.34

Kalahari Desert, South Africa ..... 0.21

Namib Desert, South-West Africa .. 0.23

0.55

Wilson (1973, p. 104).

Tricart and Brochu (1955, p.

161).

Warren (1972, p. 42). 

Hoque (1975, p. 395). 

Goudie, Allchin, and Hedge

(1973, p. 248). 

Do.

Asia

Ala Shan Desert, China .... 

Takla Makan Desert, China 

Thar Desert, India ........

Rub' al Khali ...........

Saudi Arabia (Oman) ... 

Peski Kyzylkum, U.S.S.R.

40.19 

*0.17 

"O.IO- 0.15

0.25 

0.19 

30.13- 0.25

0.66 

30.22-0.54

Yu and others (1962, p. 276). 

Chu and others (1962, p. 23). 

Goudie, Allchin, and Hedge

(1973, p. 248). 

Ahlbrandt (this chapter). 

Glennie (1970, p. 82). 

Yakubov and Bespalova (1961,

p. 654).

North America and South America

Algodones dunes, California, 

U.S.A.

Great Sand Dunes National 

Monument, Colorado, U.S.A.

Killpecker dunes, Wyoming, 

U.S.A.

Navajo Indian Reservation, 

Arizona, U.S.A.

White Sands National Monument, 

New Mexico, U.S.A.

Gran Desierto, Mexico 

Coastal dunes, Brazil ..

0.28

0.23

30.09-0.30

50.73 (reversing dunes6) 

3 0.24-1.51 3Q.15-1.25 

30.13- 0.43 (transverse

dunes6) ............ 3o.i8-0.93

«0.20 50.52

3 0.15-1.10 3 0.35-0.96 

0.25—0.55 (transverse 

dunes6) ............ 0.55

3 1.22 -3.47 

1.13

3o.i3- o.25 

3o.i5- o.24

1.27

30.25-0.49

Beheiry (1967, p. 29). 

Norris (1966, p. 298). 

Van de Kamp (1973, p. 846).

Ahlbrandt (this chapter).

Ahlbrandt (1974b, p. 43). 

Ahlbrandt (this chapter).

Do.

McKee and Moiola (1975, p.

61); Ahlbrandt (this

chapter).

Merriam (1969, p. 531). 

Bigarella, Alessi, Becker, and

Duarte (1969, p. 75-76).

Australia 

Great Sandy Desert ... 0.53

Great Victoria Desert . 

Simpson Desert ......

0.28 (sheet deposits8 )

0.53 (parabolic dunes6)

0.50 (crests6) 

3 0.26-0.30

0.16 

3 0.14-0.19

1.40

0.43 (crests6) 

0.57 (flanks6)

Bettenay (1962, p. 15).

Do. 

Wopfner and Twidale (1967,

p. 132).

Folk (1971a, p. 27). 

Do.

1 Textural parameters as defined by Folk and Ward (1957).

2 Textural parameters as defined by Trask (1931).

3 Range of values for this parameter.

4 Values calculated from data in original manuscript.

5 Average of values for this parameter.

6 Details of sample location or dune type(s) sampled, when known.

(fig. 21). The bimodality of interdune and serir 

sands accounts for the poor sorting values of these 

deposits (fig. 22), as has been noted by authors in 

deserts around the world (Beheiry, 1967; Folk, 

1968a; Warren, 1972; Cooke and Warren, 1973). 

Skewness values generally show a tendency

toward negative skewness with decreasing grain 

size (fig. 21), a phenomenon also observed in inland 

dunes of Wyoming, using settling tube data 

(Ahlbrandt, 1974b). Kurtosis values show considerable scatter but are predominantly platykurtic 

(fig. 21).
TEXTURAL PARAMETERS OF EOLIAN DEPOSITS 27

Recognition of Depositional 

Environments

Traditionally, three depositional environments 

have been differentiated on a textural basis — 

alluvial, littoral, and eolian. Their delineation based 

solely on graphical measures of textural parameters 

has not been satisfactory, as summarized by Friedman (1973, p. 626, 627): "Hence after many years of 

empirical measurements, experimentation and 

compilation of statistical parameters based on sizefrequency distribution, textural parameters as clues 

to depositional environment have been a source of 

disenchantment.''

Although the three eolian subenvironments, 

coastal dune, inland dune, and interdune and serir,

have widely differing textural parameters, they 

reflect their source which is usually alluvial or littoral sand.

Inland dunes have variable mean grain size and 

sorting values, because their source materials are 

normally from alluvial fan, glaciofluviatile, 

fluviatile, lacustrine, or playa deposits.

The textural contrasts among inland dunes are illustrated by comparing samples from different 

dune types and by comparing samples from the 

base and crest of a given dune type (fig. 22). Textural contrasts occur both among dunes formed in 

different wind regimes (fig. 22) and among dunes 

formed in a given wind regime. For example, in inland dune fields with predominantly unidirectional 

wind regimes, both McKee (1966) and Ahlbrandt 

(1974b, 1975) observed improved sorting and finer

DUNE AND INTERDUNE DEPOSITS in the northwestern Namib Desert, South-West Africa. The star dune in the background is approximately 300 feet (100 m) high. Photograph by E. Tad Nichols. (Fig. 17.)
28 A STUDY OF GLOBAL SAND SEAS

50

I- 40

Z

a- 30

Z

20

LL 10

-1.0 0.0 1.0 2.0 3.0 4.0 0.0 0.4 0.8 1.2 1.6 2.0

Very 

coarse 

sand

Coarse 

sand

Medium 

sand

c- Fine Very 

well

GRAPHIC MEAN (MZ) 

Finest 3.13 Mean 1.83 

Coarsest -0.68 o-Mean 0.67 

Median 1.93

Poor

SORTING (o-,)

Best a-/ 0.11 Mean 0.73 

Poorest a/ 1.68 Median 0.64

50

I- 40

a-30

20

-0.8 -0.4 0.0 0.4 0.8

Strongly

coarse

skewed

03 "D 

CO 0)

CD 5

8%U CO

0

03

E

E

£/)

T3 

0) 0)

c $

LI «

CO

Strongly

fine

skewed

SKEWNESS (SKi) 

Most positively skewed 0.73 

Most negatively skewed -0.76

Mean 0.13 

o-Mean 0.29 

Median 0.13

TRANSGRAPHIC KURTOSIS (K'a) 

Most peaked 0.73 Mean 0.49 

Least peaked 0.33 o- Mean 0.07 

Median 0.50

GRAPHICAL MEASURES for 191 eolian sand samples. (Fig. 18.;

mean grain size downwind from the source of sand 

in a sequence of dome, transverse, barchan, and 

parabolic dunes, respectively. Dome dunes, which 

occur on the upwind margins of dune fields, are 

noticeably coarser grained and more poorly sorted 

than are downwind dune types in the dunes at

White Sands National Monument, New Mexico, 

and also in the Killpecker dune field in southwestern Wyoming. The textural differences among 

dune types are apparently not related to compositional differences as gypsum sand composes the 

dunes at White Sands National Monument (McKee,
TEXTURAL PARAMETERS OF EOLIAN DEPOSITS 29

«0

1.600 

Poor

1.200

Moderate 0 800

Moderately well

Well 0.400

Very well

——————————— 0.000

Strongly 1 -400 

fine

SkeW6d 0.800

Fine skewed 0.200

Symmetrical

Coarse skewed

Strongly -°-400 

coarse 

skewed

—————— — 1 nnn

I I I I

- ' -

- '-..''"". . —

• . ".:i^r_i:

I I I ~ ^"'l

I I I I

— .•.:"". .—.*.£££.. . — ;• . • ••-" —

.:'. ..

I I I I

(K'G) TRANSGRAPHIC KURTOSIS 

——————————— 0.750 —————————— ———————————————

Leptokurtic

0.650

Mesokurtic o.550

Platykurtic Q.450

Very 0.350 

platykurtic

——————————— 0.250

-1

2

•'•• • "\:z=zOd> 0.0 1.0 2.0 3.0 4 

Omm 1.0 0.50 0.25 0.125 0

Verv Very 

coarse Coars,e Medium Fine fjney

sand sand sand sand sand

MEAN GRAIN SIZE, MZ

GRAPHICAL MEASURES of 291 coastal dune sand samples. (Fig. 19.)

1966), whereas quartzose and feldspathic sand 

compose the Killpecker dunes (Ahlbrandt, 1974b). 

In reversing and multidirectional wind regimes, 

sand accumulates in dunes that may have little net 

lateral migration. Reversing dunes and star dunes 

are examples of dunes that grow vertically rather 

than migrate laterally. (See fig. 17.) The clastic 

material within these dunes represents a combination of available source material rather than the 

segregation and winnowing of source material 

downwind observed in dunes formed under 

unidirectional wind regimes. (Compare figs. 22C 

and D with fig. 22 A.) For example, the Great Sand 

Dunes in Colorado have reversing wind flow —

that is, winds flow from nearly opposite directions 

at different times of the year (Merk, 1960). Streams 

emerge from the Sangre de Cristo Range onto 

alluvial fans east of the dune field providing poorly 

sorted coarse sand to the dunes. Periodically, wind 

flow reverses and unconsolidated alluvial and 

lacustrine or playa sediments in the San Luis Valley 

to the west of the dune field provide well-sorted 

fine sand (E. D. McKee, oral commun., 1975). The 

resultant eolian deposits are a combination of the 

two sands (fig. 22 Q.

Thus, considering the textural heterogeneity of 

inland dune sands, it is understandable why few 

textural studies using graphical measures can uni-
30 A STUDY OF GLOBAL SAND SEAS

1.600 

Poor

1.200

Moderate 0800

Moderately well

Well 0.400

Very well

———————— o.ooo

——————————— 2.000

Strongly 1 40° 

fine

s ewe o.soo

Fine skewed 0.200

Symmetrical

Coarse skewed

Strongly -° 400 

coarse 

skewed

1 nnn

I I I

...r •*....-.-!

* "**.**....••• .

- :~ •• • •: .. •.-... _

I I ' I I

I

. ..•: .T. ..\ru.~i." ... :

(K'o) TRANSGRAPHIC KURTOSIS Leptokurtic

0.650

Mesokurtic 0.550

Platykurtic 0.450

Very 0.350 

platykurtic

—————————— 0.250

-1 

2

-

0<4 0 

Omm 1 

Very 

coarse 

sand

•

0 1 

0 0

Coarse 

sand

.?.*.£• 'n

0 2 

50 0

Medium 

sand

?W-: '

0 3 

25 0

Fine 

sand

.

0 4 

125 0 

Very 

fine 

sand

0 

063

MEAN GRAIN SIZE, MZ

GRAPHICAL MEASURES of 175 inland dune sand samples. 

(Fig. 20.)

quely differentiate inland dune sand from its 

source (Moiola and Weiser, 1968). The compositional similarity of eolian sand and its fluvial sand 

source, the Colorado River delta, in the northwestern part of the Sonoran Desert has been shown 

by Merriam (1969). However, Friedman (1973, p. 

627) suggested that moment measures may be more 

discriminative, such as the use of sorting of inland 

dune and river sand versus swash-zone sand or 

mean cubed deviation of inland dune versus river 

sand.

Coastal dunes are generally composed of wellsorted fine sand derived from beach deposits (fig.

SORTING SKEWNESS (SKi) i)(<T

1.600 

Poor

1.200

Moderate 0800

Moderately well

Well 0.400

Very well

1 1 1 1 

——————— o.ooo —————————————— 1 1 1 1 — ——

—————————— 2.000 ————————————————————————————————————

Strongly 1 40° 

fine

SkeW6d 0.800

Fine skewed 0.200

Symmetrical

Coarse skewed

Strongly -° 400 

coarse 

skewed

i nnn 1 1 1 1

(K'c> TRANSGRAPHIC KURTOSIS Leptokurtic

Mesokurtic

Platykurtic

Very 

platykurtic

0.650

0.550

0.450

0.350

1 1 • 1 1 

1 1 1 1

-1.00 0.0

2.0mm 1.0

Very 

coarse 

sand

Coarse 

sand

1.0 2.0

0.50 0.25

Medium 

sand

Fine 

sand

3.0

0.125

Very 

fine 

sand

4.0

0.063

MEAN GRAIN SIZE, MZ

GRAPHICAL MEASURES of 40 interdune and serir sand samples. 

(Fig. 21.)

23). Much recent detailed work with graphical 

measures of textural parameters attempting to 

differentiate coastal dune sand from littoral sand 

has met with limited success (Bigarella, Alessi, 

Decker, and Duarte, 1969; Bigarella, 1972; Friedman, 

1966,1973; Martins, 1967). Bigarella, Alessf, Becker, 

and Duarte (1969, p. 16) found that beach and dune 

sands in Brazil could not be distinguished using 

mean grain size and sorting when the source is a 

fine sand; however, medium- to coarse-grained 

sources showed dune sands to be better sorted and 

finer grained than beach deposits. Bigarella (1972, 

p. 14) questioned the significance of positive skew-
TEXTURAL PARAMETERS OF EOLIAN DEPOSITS 31

-2

A

(D

Crest

Base

-Base

54.0 PERCENT

n^•Crest

-101 23

BARCHAN DUNE

White Sands National

Monument, N. Mex.

Crest 657 (1072)

Base 656 (1071)

LINEAR DUNE

Libya

Crest 626 (717) 

Base 590 (725)

DUNE DEPOSITS

-2-10 1 2 3 

C REVERSING DUNE 

Great Sand Dunes, Colo. 

Crest 609 (645) 

Base 563 (643)

-2 -1 

D

0123 

STAR DUNE 

Saudi Arabia 

Crest 601 (984) 

Base 648 (987)

20

15

10

5

-2-1 01 23 

£ INTERDUNE

White Sands National

Monument, N. Mex.

4137 (828)

2-1 01 23 

p INTERDUNE 

Libya

-

2-101234 

3 SERIR 

Algeria

1

L

519 (745) 4018 (26) 

INTERDUNE OR SERIR DEPOSITS

-2-10123 

H INTERDUNE

Tunisia 

1621 (693)

HISTOGRAMS SHOWING TEXTURAL CONTRASTS among dune and interdune samples. Values along abscissa are in whole phi; 

histogram class intervals are quarter phi. Numbers below each histogram are the computer index number (outside parentheses) and 

McKee index number (inside parentheses) of samples listed in tables 5-7. Silt- and clay-size fraction to the right of 4 <A (Fig. 22.)

ness as an eolian indicator because some dune 

sands have negative skewness values. Although 

dune sand is usually more rounded than beach 

sand, Bigarella (1972, p. 14) found the most dependable eolian indicator to be light- and heavymineral separations.

In the absence of sedimentary structures as primary evidence of eolian deposits, other criteria must 

be used. Discriminant analysis (Moiola and 

Spencer, chapter C), certain moment measures, and 

perhaps light- and heavy-mineral separations may 

be able to differentiate eolian sands from alluvial

and littoral sands. Frosted grains, as viewed with 

the scanning electron microscope, have also been 

used as an eolian indicator; however, that technique may be limited by the degree of diagenesis 

grains have undergone. Graphical measures are 

certainly less discriminating and of more limited 

use than these latter techniques. Sorting and mean 

grain size values do have application as will be 

shown. The application of skewness and kurtosis 

are, at best, tenuous because they show wide scatter in eolian deposits (figs. 18-21) and because 

skewness is dependent on mean grain size 

(Ahlbrandt, 1975; this chapter, fig. 21).
LARGE COMPLEX LINEAR DUNES which derive sand from adjacent coastal deposits. Slipfaces on the dunes face inland at the time 

the photograph was taken. Sandfisch Bay, western part of Namib Desert, South-West Africa. Photograph by E Tad Nichols (Fig 

23.)

Porosity and Permeability

Relationship to Textural

Parameters

THE MEAN GRAIN SIZE, sorting, and packing 

arrangement of grains affect porosity and permeability in alluvial, littoral, and eolian sands. 

Porosity in modern sediments decreases with 

progressively more poorly sorted material regardless of grain size (fig. 24). Figure 24 indicates that 

the initial porosity (from 28 to 43 percent) is as 

much as 15 percent lower in very poorly sorted 

sand than in extremely well sorted sand. The corresponding pore-volume loss for a given grain-size 

range is 35 percent. This range of values demonstrates the difference between very well sorted

45

40

- 35

30

25

I I T

J_______I_______I_______L

Extremely 

well

Very 

well

Well Moderate Poor Very 

poor

SORTING, TRASK SYSTEM

RELATIONSHIP BETWEEN initial porosity and sorting. The curve 

was drawn for wet, packed sand from data by Beard and Weyl 

(1973). (Fig. 24.)
TEXTURAL PARAMETERS OF EOLIAN DEPOSITS 33

1000

Extremely 

well

SORTING, TRASK SYSTEM

INTERRELATIONSHIP OF MEAN GRAIN SIZE (in millimetres) 

and sorting on initial permeability for wet, packed sand from 

data by Beard and Weyl (1973). (fig. 25.)

dune sand and poorly to very poorly sorted interdune and serir sands. Permeability decreases with 

poorer sorting and finer mean grain size (fig. 25) 

but is also affected by packing arrangements (Rittenhouse, 1971; Pryor 1973). Less symmetric packing — for example, orthorhombic packing (rotated 

30°) — results in greater porosity loss due to solution than do cubicly packed grains (Rittenhouse, 

1971, p. 82.) Porosity loss due to solution is maximized in very poorly sorted, extremely well sorted 

or very angular sand and minimized in very well 

rounded, well-sorted sand (Rittenhouse, 1971, p. 

86). The well-rounded and well-sorted character of 

many eolian deposits favor them to have higher initial and diagenetically altered porosities (considering solution only) than do alluvial, and perhaps littoral, deposits.

Pryor (1973, p. 162) found that within a dune 

sand body there is little variability in porosity and 

permeability, whereas river bar and beach sands

have directional permeabilities that are parallel to 

the long dimension of the deposit. The heterogeneity of sediments and more irregular packing arrangement of grains in the river bar sand "packets" 

(Pryor, 1973, p. 187) resulted in lower effective permeabilities for them as compared with beach and 

dune sands (table 3). Effective permeability 

measures the flow across bedding units or 

"packets" of contrasting permeability.

TABLE 3. — Porosity and permeability measurements in 

alluvial, littoral, and coastal dune sand

[Modified from Pryor, 1973, p. 162. n, number of samples; D, darcies; mD, 

millidarcies]

Type of sand

Alluvial 

(point bar) 

(n=348) (n=480)

Littoral Coastal dune

(n = 164)

Average porosity .. (percent).. 41 

Range of porosity ..(percent).. 17-52 

Average permeability ........ 93 D

Range of permeability ....... 4 mD -

500 D

49 49 

39-56 42-54 

68 D 54 D 

3.6- 5-104D 

166 D

The contrast in textures among well-sorted to 

very well sorted coastal dune sands, moderately 

sorted to well-sorted inland dune sands, and poorly 

sorted interdune and serir sands should show 

progressively lower porosity and permeability. In 

order to test the inland dune-interdune porosity 

and permeability relationship, cores from four drill 

holes in the White Sands National Monument, New 

Mexico, U.S.A., were studied. The differences in 

sorting for the dune and interdune environments at 

White Sands and elsewhere are shown in figure 22.

The cores penetrate dune and interdune deposits, 

both of which are weakly cemented owing to the 

gypsiferous composition of the sand. The 14 samples taken for porosity and permeability analyses 

(fig. 26) show a general reduction in permeability 

for the interdune deposits (fig. 27). The high 

porosity yet low permeability of the interdune

TABLE 4. — Porosity and permeability measurements in 

eolian subenvironments; Coastal dune, inland dune, and interdune sand

[n, number of samples; D, darcies; mD, millidarcies]

Type of sand

Coastal dune Inland dune Interdune

(n= 164)i (n = 6)

Average porosity . . (percent). 

Range of porosity . . (percent). 

Average permeability ........

Range of permeability .......

49 

. 42-54 

54 D

5-104D

26 

23-30 

137 mD 28-

450 mD

31 

25-38 

120 mD 33 —

270 mD

1 Pryor, 1973, p. 162.
34 A STUDY OF GLOBAL SAND SEAS

DRILLING SITE NUMBER 

1234

LU 

LU 

U_

Z

I

Q.

LU

Q

r

5-

10-

1 <J

-

25-

-

*J\J

35- 

40-

rrf\

• -.'i'

F^

E?£

i^^_

rEI-

— —

r —

-* -

-

-

-* .,

-

-

::: ' -

~ —— •

I^

'_~~~ ...:

^

. — . _ _— —

TD 51.0 TD 51 

EXPLANATION

wv.;:;;:-: :

-

-* -

-

-

-

-* -

•* -

-

-

-

-

.0

Dune Interdi 

deposits depos

Fluvial 

deposits

No 

ecovery

::

me -

its -

^r^r^

Playa 

deposits

— •

^ru:

r^

3£E

^:

^^^

^i

^H

-

_

-

-* -

*

-

-

-

-

'•'•• '•'''••: •

:".•.-;'.•;•:•:•.•

E?£

g

^3^

^^^

TD 59

TD 65.0 

TD

Total 

depth

106°15'

Plug taken for porosity and 

permeability determination

National \

Park

Service

Headquarters

. Location of 

drilling site

EXPLANATION 

Sand \ ^~ "| Playa N Mountain 

base

LOCATIONS OF CORES and depth of plug samples taken for porosity and permeability determinations, White Sands National 

Monument, New Mexico, U.S.A. Core descriptions and modified index map from McKee and Moiola (1975, p. 60, 65). (Fig. 26.)
TEXTURAL PARAMETERS OF EOLIAN DEPOSITS 35

1000

2 100

10

20 22 24 26 28 30 32 34 

POROSITY, IN PERCENT

36 38 40

POROSITY-PERMEABILITY DISTRIBUTION of dune and interdune sediments from cores, White Sands National Monument, 

New Mexico, U.S.A. Analyses by Core Laboratories, Inc., 

Denver, Colorado, U.S.A. Location and description of cores are 

shown in figure 26. (fig. 27.)

deposits suggests that much of the porosity is ineffective and probably is incorporated into the finegrained matrix.

It appears that the textural differences in eolian 

subenvironments also bear significantly on initial 

porosity and permeability (table 4).

The more poorly sorted interdune deposits may 

form effective permeability barriers after burial 

owing to greater grain-to-grain contacts which increase porosity loss by pressure solution and cementation. Tightly cemented, poorly sorted interdune deposits separate porous well-sorted dune 

sandstones in the Tensleep and Weber Sandstones 

(Pennsylvanian and Permian) in the Wertz and 

Brady oil fields, Wyoming, U.S.A., forming local 

barriers to oil migration. The porosity and permeability contrasts in the two deposits must relate 

in part to the textural differences of the dune-interdune sediments that compose part of the Tensleep 

and Weber Sandstones (chapter I).
Locality 

Computer McKee's

Mean grain size

Principal county Specific area Index No. Index No. <£ 

or area

531

1619

Brazil ............ Garopaba Sirin (State of Santa 1510

Catarina).

1511

1512

1513

1514

1515

1516 

1517 

Brazil ............ Island of Santa Catarina .......... 772

773 

774

775 

776 

777

778

779 

780

781

782

783

784

785

786

787

788

789

790

791

792

793

794

795

796

797

580 

580

586 

22 

402

403

404

405

406

407

408 

409 

7 

6 

5

4 

3 

2

1

4 

4

4

3

3

3

2

2

2

1

1

1

8

9

10

11

12

13

14

1. 

1.

1. 

2. 

2.

2.

2.

2.

2.

2.

2. 

2. 

1. 

2. 

1.

1. 

2. 

2.

2.

2. 

2.

2.

2.

2.

2.

2.

2.

2.

2.

2.

2.

2.

2.

2.

2.

2.

2.

2.

916 

186

710 

360 

630

550

440

480

330

240

660 

630 

800 

200 

900

920 

050 

100

060

190 

100

020

120

100

100

290

250

300

200

200

200

200

300

250

300

280

250

300

Median grain 

size

mm <f>

0. 

0.

0. 

0. 

0.

0.

0.

0.

0.

0.

0. 

0. 

0. 

0. 

0.

0. 

0. 

0.

0.

0. 

0.

0.

0.

0.

0.

0.

0.

0.

0.

0.

0.

0.

0.

0.

0.

0.

0.

0.

2661 

4383

3057 

1948 

1615

1708

1843

1792

1989

2117

1582 

1615 

2872 

2176 

2679

2643 

2415 

2333

2398

2192 

2333

2466

2300

2333

2333

2045

2102

2031

2176

2176

2176

2176

2031

2102

2031

2059

2102

2031

1.870 

1.200

1.800 

2.280 

2.610

2.550

2.400

2.480

2.270

2.120

2.650 

2.609 

1.810 

2.203 

1.920

1.926 

2.076 

2.140

2.096

2.203 

2.130

2.030

2.173

2.133

2.126

2.296

2.276

2.310

2.230

2.216

2.210

2.230

2.220

2.210

2.210

2.200

2.210

2.250

mm

0.2736 

0.4353

0.2872 

0.2059 

0.1639

0.1708

0.1895

0.1792

0.2073

0.2300

0.1593 

0.1649 

0.2852 

0.2172 

0.2643

0.2632 

0.2372 

0.2269

0.2339

0.2172 

0.2285

0.2449

0.2217

0.2280

0.2291

0.2036

0.2065

0.2017

0.2132

0.2152

0.2161

0.2132

0.2146

0.2161

0.2161

0.2176

0.2161

0.2102

Sor

in

0.49

0.42

0.7

0.5

0.2

0.2

0.3

0.3

0.3

0.3

0.2

0.3

0.2

0.3

0.3

0.2

0.2

0.2

0.1

0.2

0.2

0.1

0.1

0.2

0.2

0.1

0.2

0.2

0.1

0.1

0.1

0.1

0.1

0.1

0.1

0.1

0.1

0.1
Brazil Laguna (State of Santa Catarina)

Brazil Morro Conventos (late Clube)

Brazil Planicie Costeira (State of Rio 

Grande do Sol).

798

799

1500

1501

1502

1503

1504

1505

1506

1507

1508

1509

1538

1539

1540

1541

1542

1543

1544

1545

1546

1548

663

664

665

666

667

668

669

670

671

672

673

674

675

676

677

678

679

680

681

682

683

15

16

241

242

243

244

245

246

247

248

249

250

434

435

436

437

438

439

440

441

442

444

1

3

4

8

10

11

14

15

16

17

18

9

19

20

21

24

26

28

30

34

36

2.290

2.300

2.620

2.590

2.450

2.520

2.640

2.530

2.800

2.660

2.670

2.600

2.320

2.550

2.530

2.600

2.540

2.520

2.540

2.550

2.490

2.440

2.800

2.900

2.600

2.760

2.800

2.890

2.600

2.500

2.590

2.500

1.590

2.800

2.560

2.600

2.570

2.550

2.600

2.500

2.580

2.500

2.320

0.2045

0.2031

0.1627

0.1661

0.1830

0.1743

0.1604

0.1731

0.1436

0.1582

0.1571

0.1649

0.2003

0.1708

0.1731

0.1649

0.1719

0.1743

0.1719

0.1708

0.1780

0.1843

0.1436

0.1340

0.1649

0.1476

0.1436

0.1350

0.1649

0.1768

0.1661

0.1768

0.3322

0.1436

0.1696

0.1649

0.1684

0.1708

0.1649

0.1768

0.1672

0.1768

0.2003

2.250

2.210

2.700

2.600

2.450

2.550

2.700

2.580

2.800

2.700

2.700

2.610

2.400

2.550

2.500

2.590

2.530

2.500

2.540

2.490

2.450

2.450

2.833

2.903

2.603

2.770

2.886

2.840

2.603

2.500

2.593

2.526

1.596

2.806

2.580

2.600

2.570

2.550

2.610

2.513

2.580

2.513

2.360

0.2102

0.2161

0.1539

0.1649

0.1830

0.1708

0.1539

0.1672

0.1436

0.1539

0.1539

0.1638

0.1895

0.1708

0.1768

0.1661

0.1731

0.1768

0.1719

0.1780

0.1830

0.1830

0.1406

0.1340

0.1649

0.1466

0.1350

0.1397

0.1649

0.1768

0.1661

0.1731

0.3299

0.1426

0.1672

0.1649

0.1684

0.1708

0.1638

0.1756

0.1672

0.1756

0.1948

0.1

0.1

0.2

0.1

0.3

0.2

0.2

0.2

0.2

0.2

0.2

0.2

0.3

0.3

0.3

0.2

0.2

0.2

0.3

0.3

0.3

0.3

0.2

0.1

0.2

0.2

0.3

0.2

0.1

0.2

0.1

0.1

0.2

0.2

0.2

0.0

0.1

0.7

0.1

0.1

0.1

0.2

0.2
Locality 

Computer McKee's

Mean grain size

Principal county Specific area Index No. Index No. 0 

or area

Brazil — Con. Planicie Costeira (State, of Rio 684

Grande do Sol) — Con. 685

686

687

688

689

690

691

692

693

694

695 

696 

697 

698

699 

700

701 

702 

703

704

705

706

707

708

709

710

711

712

713

714

715

716

717

718

38

39

40

41

42

43

45

46

44

47

48

49 

50 

51 

53

57 

59

62 

63 

65

67

70

71

72

73

78

79

80

81

83

87

89

93

97

99

2.

2.

1.

2.

2.

2.

2.

2.

2.

2.

2.

2. 

2. 

2. 

2.

2. 

2.

2. 

2. 

2.

2.

2.

2.

2.

2.

2.

2.

2.

2.

2.

2.

2.

2.

2.

2.

700

250

050

390

570

480

520

750

500

720

500

510 

480 

600 

500

490 

480

580 

460 

500

580

490

410

600

690

510

520

400

390

410

370

600

390

520

500

Median grain 

size

mm <j)

0. 1539

0.2102

0.4841

0.

0.

0.

0.

0.

0.

0.

0.

0. 

0. 

0. 

0.

0. 

0.

0. 

0. 

0.

0.

0.

0.

0.

0.

0.

0.

0.

0.

0.

0.

0.

0.

0.

0.

1908

1684

1792

1743

1487

1768

1518

1768

1756 

1792 

1649 

1768

1780 

1792

1672 

1817 

1768

1672

1780

1882

1649

1550

1756

1743

1895

1908

1882

1934

1649

1908

1743

1768

2.680

2.253

1.093

2.413

2.590

2.486

2.530

2.750

2.510

2.760

2.516

2.530 

2.476 

2.636 

2.503

2.506 

2.466

2.596 

2.483 

2.530

2.530

2.503

2.420

2.600

2.636

2.503

2.533

2.420

2.403

2.453

2.391

2.610

2.393

2.546

2.520

mm

0.1560

0.2102

0.4697

0.1882

0.1661

0.1780

0.1731

0.1487

0.1736

0.1476

0.1743

0.1731 

0.1792 

0.1604 

0.1768

0.1756 

0.1805

0.1649 

0.1792 

0.1731

0.1731

0.1768

0.1869

0.1649

0.1604

0.1768

0.1731

0.1869

0.1895

0.1830

0.1908

0.1638

0.1908

0.1708

0.1743

Sor

"l

0.18

0.14

0.47

0.27

0.21

0.25

0.25

0.20

0.25

0.19

0.24

0.23

0.23

0.29

0.30

0.28

0.29

0.17

0.28

0.24

0.29

0.23

0.27

0.20

0.2

0.27

0.19

0.24

0.24

0.27

0.29

0.2

0.2

0.2

0.2
TEXTURAL PARAMETERS OF EOLIAN DEPOSITS 39

O O ON CM ON 

CM in O sf NO

m «* m m «*

ooooo

-a* r^ -a* in ON 

m — i CM m vo

•— i -^ O CO CM

ooooo

NO CO O •— i 00 

NO NO "^J" NO in 

CM CM CM CM CM

OOOOO 

vO r^* "-a* in ON

in ^H co r** in 

r^ O ON ON O

OOOOO

NO NO NO CO CO 

O O NO sf 00 in co co co CM

CM CM CM CM CM

CM NO 00 l~« ON 

ON -^ O •— i m 

r~« —i ON O O 

•— t CM — 1 CM CM

OOOOO

ooooo

CO CM CJN -* 00 

-3- CM CO CO CM

CM CM CM CM CM

CM ON CM CO ^T

ON O -^ CM CO 

-* CM CM CM CM

r** o co 

oo vo m

O O O

CM Sf ON

CM —* O

o o o

o o o

m oo m

o o o

CM CM CM

ON 00 00 

00 ON ON

O O O

o o o CM NO ON

CM CM CM

CM CM CM

ON CO 

m ON

0 0

CM m

CM CO

0 O

o o

ON 00

O 0 

O CO

CM CM

NO CO

r^ O

o o

0 0 

—* CM

CM CM

CM CM

o\

o

CO 

CM

o

o

o

CO

CM

<y\

o

0

o

CM

CM

oo m NO co 

m o ON r~« 

m m m -^

o o o o

<y\ co -* •* •* CM -* ON

o o o o

o o o o

o o o o

O NO NO O

CM CM CM CM

ON 00 ON 00

0 0 O O

O O O O 

O O O O

CM CM CM CM

CO CO CO CO

CM CO r-i O ON

m m NO m ^

ooooo

*a* NO in ^f r^* 

ON in ^* CO ^*

ooooo

O »— ( vD C*") ON 

^ CM CM CM CM

OOOOO

CO ON vD ON vD 

ON ^3" ON vD in

OOOOO 

O vO vO O vO

m o vo CM co

CM CM CM CM CM

00 ON ON in CM 

CO *a* ^ ON 00 

vD vD vD 00 00

OOOOO

OOOOO 

-* O O O —* 

vO vO vO •^ ^f

CM CM CM CM CM

00 O -^ CM CO

CO CO CO CO CO

m •— i o •— i •— i 

o m -^ vo oo 

m m ^r m ^r

ooooo

co m CM oo co 

m CM vo oo CM

ooooo

ON —I ON —i vD 

CM CM r~« CM CM

OOOOO

CM m m m co 

ON ON CO ON ^

OOOOO 

00 O vO O CM

CM CM —i CM CM

o m o m oo

CO ON ON ON vD 

CO CO O OO t^-

OOOOO 

OOOOO

m o ON o o 

<r ^r CM ^r m

CM CM •— I CM CM

^f in r** ON co

ON O ^ CM CO

^ r^ oo oo ^ 

m m m vo m

ooooo

OO CJN -* CM O

m -^ ON m ^3"

O O CM CM CM

OOOOO

^•x vD »— ( ^ 00 

^" 00 "^ ^ ^

OOOOO

^ 00 ON "^ ^ 

CM ON CO O CM

OOOOO

CO vO CO vO vO 

CM vD O ^T CM

CM CM CM CM CM

00 00 O m ON 

CO ON in »••( *^

ooooo 

ooooo •— i vD ON CO O

CM CM CM CM CM

m m m m m

^r m vo r-» oo

o m 

co oo 

vo m

o o 

sf m

<-> CM

O O

r~- oo 

CM m

O O

Oi ^

m co 

m r^

O O

CO vD cy> co 

vo m

CM CM

ON vD

m m 

m r^

0 0 

O O

ON -*

vo m

CM CM

O -* 

vD vO

CJN O

^r m

—* ^ CM

in *^ NO

o o o

o m ^r

CM CM ^

o o o 

o co m

o o o

O CO *sj"

in ^* NO

o o o

O O vO

oo CM r^

CM CM CM

CO CM CM ON ON r^. 

in ^* vo

O O 0 

0 O 0

m oo oo 

vo ^f in

CM CM CM

CM co ^r

^ CM CO

m m m

•— i -^ vo o m 

m m m vo m

ooooo

»— 4 CO »— ( vD vD 

CM O CM —I —1

ooooo

C*l ON ON CM •— i

ooooo

ON st vD O 00 r-i co in oo vo

ooooo

CO vO vD NO O

>d" r^ .— i ON O 

m m m sf m

CM CM CM CM CM

vD CM 00 O 00

OOOOO

OOOOO 

<-> 00 O ON O 

m m m ^ m

CM CM CM CM CM

in vD t"» 00 ON

^ in NO ^ oo 

m m m m m

ON oo m o m

00 st O O -* ^3- m m m m

ooooo

ON vO 00 NO O 

vO vO CM 00 NO 

O —< -^ O CM

OOOOO 

—i ON in CM O

oo oo CM ^ ^r

ooooo

in ^ NO ON •— < 

O CM ON <f" CO

OOOOO

O NO NO NO CO

r~» CM NO O co ^ NO in NO in

CM CM CM CM CM

O 00 00 ON O

oo co o ^r oo

ooooo 

ooooo

ON —i m O ON

CM CM CM CM CM

o -^ CM co ^r

ON O ^H CM CO
TABLE 5. — GraphicaJ measures of sand sampJes from coastal dunes used as a data base — Continued

Locality 

Computer

Principal county Specific area Index No. 

or area

Brazil — Con. Planicie Costeira (State, of Rio 764

Grande do Sol) —Con. 765

766

767

768

769

770

771

1567

1568

1569

1570

1571

1572

1573

1574

1575

1576

1577

1578

1579

1580

1581

1582

1583

1584

1585

1586

1587

1588

1589

1590

1591

1592

1593

McKee's 

Index No.

175

176

177

178

179

180

181

182

280

310

311

311

312

313

315

316

317

318

320

321

322

324

341

342

343

344

345

346

347

348

350

351

352

353

356

Mean grain size

2.

2.

2.

2.

2.

2.

2.

2.

2.

2.

2.

2.

2.

2.

2.

2.

2.

2.

2.

2.

2.

2.

2.

2.

2.

2.

2.

2.

2.

2.

2.

2.

2.

2.

2.

0

600

600

600

550

600

500

510

550

693

693

506

640

493

616

660

643

706

573

693

500

710

496

696

700

706

753

623

640

606

500

573

553

653

636

450

mm

0.1649

0.1649

0.1649

0.1708

0.1649

0.1768

0.1756

0.1708

0.1550

0.1550

0.1768

0.1604

0.1780

0.1638

0.1582

0.1604

0.1539

0.1684

0.1550

0.1768

0.1528

0.1780

0.1550

0.1539

0.1539

0.1487

0.1627

0.1604

0.1649

0.1768

0.1684

0.1708

0.1593

0.1615

0.1830

Median grain 

size

<*»

2.636

2.626

2.630

2.556

2.633

2.513

2.567

2.570

2.700

2.690

2.600

2.610

2.510

2.600

2.650

2.630

2.700

2.550

2.690

2.500

2.700

2.430

2.700

2.700

2.700

2.750

2.600

2.620

2.600

2.500

2.550

2.550

2.680

2.640

2.450

0.

0.

0.

0.

0.

0.

0.

0.

0.

0.

0.

0.

0.

0.

0.

0.

0.

0.

0.

0.

0.

0.

0.

0.

0.

0.

0.

0.

0.

0.

0.

0.

0.

0.

0.

mm

1615

1627

1615

1708

1615

1756

1696

1684

1539

1550

1649

1638

1756

1649

1593

1615

1539

1708

1550

1768

1539

1856

1539

1539

1539

1487

1649

1627

1649

1768

1708

1708

1560

1604

1830

So

0.22

0.25

0.23

0.23

0.20

0.22

0.2

0.2

0.20

0.2

0.2

0.2

0.2

0.3

0.2

0.2

0.2

0.2

0.2

0.3

0.3

0.2

0.2

0.2

0.1

0.1

0.2

0.1

0.2

0.2

0.3

0.2

0.2

0.1

0.2
TEXTURAL PARAMETERS OF EOLIAN DEPOSITS 41

"^ ^ !£ 2 !£? r2 ~* "^ ^ ^ f^^ooon^-^-oor^ poin-Hinin m ^H ^ ^ ^ oo (N o> o o — i «M m o «M o oo o> o> o> "i -J °° « ^> vo-H-Hinoo — i<Npn-HPMo<Nr^mo> <N o> o o o — i -* o o> oo r-^ o> oo -* PO vor-^o>vom ir> oo -H oo ir> ir> ir> ir> vo ir> ir> vo vo •* ir> r-^inininin^ir,^.^.^. ,* ,* ir> ir> ir> inininin-j- •* •* ir> ir> vo vo -*•*•*•* •^••^•oOinin

OOOOO OOOOO OOOOOOOOOO OOOOO O O O O O OOOOO OOOOO C3OC3C3C3

<N-*voino> oovoooo-n o>o>>*>*a>iri-H-H (N -HPO-*-HO ^--Hino<N r-^-^-oo-H >*r^>*oooo o>r^or^-* .J^H^^HVD -HOO>O-H -Hpo-Hoovo^Hr-^oo •* inr^a>mu-i oor-^-j-voo ooo>vovooo >*>*OO<N(N r-^inm-H«M

PO-HmcM-H (NOiriO-H -HOO-HO^HOfOQfO COOO-HO OO-HOm OO-HOO <NO(NOO O-H-HO-H

OOOOO OOOOO OOOOOooO^O C3C3C3C3C3 C3C3C3C3O C3C3C3C3C3 C3C3C3C3C3 OOOOO

oooomoovo OPOLTIOOO CTNOoootiri^Hvooor^vo cor^r^ovo inrovo-HOt m m ^H in «M (Notf^oto VO-HPOOOVO a>a>in-H-a- ^H~HO~HVO -Hiri(N<N'-H^HO-His*r^ OLTIVO<N>* -H-HOOVOPO iriina>oooo OOOOO<NO O>«M<N-HVO

-H-H(N<N(N (N<N<N(N(N (NtMtMfNltMcMfNlPOfNlfM PO<N<N<N<N (N<N-HPO<N <N(NPO>*<N >*PO«MPOPO (N«MPO<N-H

OOOOO OOOOO OOOOOOOOOO OOOOO OOOOO OOOOO OOOOO OOOOO

SiSSJSlT; SSSJ'S 0 oroomooo>ro(Noo-H r^o>o>-H(N oovooor-^ roo>vooo> o>vooO(N>* o>o>a>invo POPOPOPO(N (NPOPOvOvD LTia>vD^HVO.J-a>r^vDvD OtmrOr^OO vOLT|<NvO<N a>POO>PO>* >*a>OOOOO •*POvO-HPO in-a-ininvo ininiriinin Lriininvor^voirivDr^at >*iniriiniri iniri-j-r^vD ininvooovo VDVOI^LTIVO VOLTIOOVO-*

OOOOO OOOOO OOOC3C3C3C3C3C3C3 OOOOO OOOOO OOOOO OOOOO OOOOO

2222° OOOOO OOOOOOOOOO OOOOO OOOOO OOOOO OOOOO OOOOO

OOOOCM -HOOOOOO ^LTiOOrOOoOOOOi/"! >*OOIs*vD 00^-HO<N inOvDiOO OvOtrivOf^ OO<Nf)O r^oor^r^vo r^r^r^vovO vOvOvOvOtrivof^vDLripo r^r^r^vovo VOVOOOLTIVO vor^LTi-^^o voiriinvoin vor^-^vooo

(N<N«M<N(N <N<N<N<N<N <N<N<N(N<N(N(N(N(N(N (NCN(NP^(N pgp^(N<N<N (N<N<N«MCM (N<N«M<NCM (N<NCN<N<N

r^vo-*oo(N o>o>ooo> a>po-HpovOoopo>*ooiri -Hoor^otM oo^oooo -noor^OLn «M-*O>(N<N r^oopo-^-vo ^POO-HOO popovovoro PO^r^^inpo^oovD^ I^CMOVDOO inirioovo I^-HCMOO-H r^oo-^-oor^ <N-H-^O<N

-*-*voiniri ininininin LTiinininr^voirivor^oo LnLni^Lniri inin-^-r^iri iriinvor^vo vovovoirivo VOLTIOOVO-*

OOOOO OOOOO OOOOOC3C3C3C3C3 C3C3C3C3C3 OOOOO OOOOO OOOOO OOOOO

OvDPOvOO OPOPOvOvO POrOvDvOOvDOvDOO OOOOO OOOOO OOOOO OOOOO OOOOO >*O-*<NVO ooooooo otrir^iri-H-Hor^oo I^-HPOOOVD atatPOirioo r^cMtMotPO oor^ovooo «M<N-*>*-H

f^oovor^vO r^r^vOvor^ f^vovovOLrivDr^iriLri^ vor^r^vovo vo^oooinvO vor^vo-a-vo mLTivOvOtri vot^^vooo

(N<N<N<N(N (N(N<NCNCN <N<N<N<N<N(N(N<N<N<N (N<NCN<N(N (N<N<N<N<N (N<N<N(N<N (N«M<N<N<N <N«M<N<N<N

(N-^LTivDr^ OOOO^O-H vOf^OO^O-HCMPOOO^ PO-J-LTivDr^ 00^-*LnvO r^OOCTNO-H (NPO'J'LrivO I^OO^O-H

vOvOvOvOvO vOvDvOr^r^ OOOOOOOOO>CTNCTNCTNO><Ti OOOOO OO-H-H-H -H-H-HCMCN (N<N<N<N<N (NfMSMPOPO

oto-HCMm -a-irivor^ooato^tNPO -a-irivor^oo o>oooo>o ^H «M en •* 10

^OOOO OOOOOO-H-H-H-H (NCN<N<N<N (NPO-H-H<N (N<N(N<N<N invovOvovo vovDvovDvovOvovovDvo VOVOVDVDVD vo^OLTii/iin Lninininiri
TABLE 5. — Graphical measures of sand samples from coastal dunes used as a data base — Continued

Locality 

Computer

Principal county Specific area Index No. 

or area

1536

1537

501

502

503

504

505

506

507

508

509

510

511

512

513

514

515

516

517

518

533

534

535

536

537

538

539

540

541

542

543

544

545

546

547

548

552

McKee's 

Index No.

432

433

14 

23

17

28

34

19

21

15

18

16

20

30

10

8

3

11

4

9

1

51

56

42

41

43

46

45

50

49

47

39

44

26

24

36

586

38

Mean grain size

2,

2

2, 

2

2

2

2

2

2

2

1

2

2

2

2

2

2

2

2

2

2

2

2

2

2

2

2

2

2

2

2

2

2

2

2

2

1

2

0

.410

.450

.603 

.556

.526

.513

.513

.580

.570

.500

.596

.593

.600

.580

.886

.770

.903

.840

.600

.806

.833

.636

.403

.590

.413

.486

.750

.530

.476

.530

.760

.530

.510

.610

.550

,360

.393

.680

mm

0.1882

0.1830

0.1649 

0.1696

0.1731

0.1756

0.1756

0.1672

0.1684

0.1708

0.3299

0.1661

0.1649

0.1672

0.1350

0.1466

0.1340

0.1397

0.1649

0.1426

0.1406

0.1604

0.1895

0.1661

0.1882

0.1780

0.1487

0.1731

0.1792

0.1731

0.1476

0.1731

0.1756

0.1638

0.1708

0.1948

0.3896

0.1560

2.

2.

2. 

2.

2.

2.

2.

2.

2.

2.

1.

2.

2.

2.

2.

2.

2.

2.

2.

2.

2.

2.

2.

2.

2.

2.

2.

2.

2.

2.

2.

2.

2.

2.

2.

2.

1.

2.

Median grain 

size

*

420

420

600 

550

500

500

500

560

570

500

590

590

600

580

800

760

900

890

603

800

800

600

400

570

390

480

750

520

480

510

720

250

500

600

550

320

310

700

mm

0.1869

0.1869

0.1649 

0.1708

0.1708

0.1708

0.1708

0.1696

0.1684

0.1708

0.3322

0.1661

0.1649

0.1672

0.1436

0.1476

0.1340

0.1350

0.1649

0.1436

0.1436

0.1649

0.1895

0.1684

0.1908

0.1792

0.1487

0.1743

0.1792

0.1756

0.1518

0.2102

0.1768

0.1649

0.1708

0.2003

0.4033

0.1539

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0
California (U.S.A.)

Libya .............

New Jersey (U.S.A.)

P"i Q1TIO R^flr*Vl *. m. rn.rn.rn.. s^n

635

..... 1620

..... 569

..... 1560

.... 1565

610

522

613

548

548

fcO t

f. OQ

31

659

658

659

660

3.353

2.730

O OOO

1 ft9 ^

i jm

1.586

1.680

1.613

1.560

0.0981

0.1507 0

9107

O OQ'lO 0 9ft 1 T

0.3345

0.3121

0.3276

0.3392

3

ocrj

2.710

o onn

i fton

1.800

1.600

1.680

1.680

1.530

0.

0.

0.

0.

0.

0.

0.

0.

0.

0981

1528

O 1 "7£

OQOO

0077

3299

3121

3121

3463
TABLE 6. — Graphical measures of sand samples from inland dunes used as a data base

[Localities are listed alphabetically by country, and specific area where known. The computer index number and M

are also listed. Specific sampling information relating to dune type or position on a dune is listed under "rem

no data]

Locality

Principal country or Specific area Computer 

area Index No.

Mean grain

McKee's 

Index 

No.

phi

size

mm

Median grain 

size

phi mm

Sorting

rho I

Skewness

Ski

Inland dunes

Texas (U.S.A.) .... Padre Island ......................

Algeria .......... Bou Saada ............. 4019

Ouargla ............... 1558

Arizona (U.S. A. ) .. Coal Mountain ......... 1559

566 

Grand Falls ........... 4028

Hotevilla ............. 605

1552

1553 

4010 

4011

1554 

1555

Page . ...... ........ 558

628 962 

627 965 

629 967

27 

28

29 

1134 

566 

566

37 

570 

9

10

11 

12 

13

14 

16

569 

568

2.026 

2.190

1.563 

3.012 

3.056 

2.703

1.195 

1.900 

2.686

2.296

2.403 

2.457 

2.402

2.233 

2.336

2.670 

2.036

0. 

0.

0. 

0. 

0. 

0.

0. 

0. 

0.

0.

0. 

0. 

0.

0. 

0.

0. 

0.

2 

2 

2

2455 

2192

1240 

1207 

1539

4368 

2679 

1560

2045

1895 

1821 

1892

2132 

1989

1571 

2432

.480 0 

.690 0 

.350 0

ND 

2.100

1.500 

ND 

3.210 

2.690

ND 

1.900 

2.700

2.250

2.380 

ND 

ND

2.200 

2.280

2.610 

1.980

.1792 2 

.1550 2 

.1961 2

ND 

0.2333

0.3536 

ND 

0.1081 

0.1550

ND 

0.2679 

0.1539

0.2102

0.1921 

ND 

ND

0.2176 

0.2059

0.1638 

0.2535

.800 0. 

.680 0. 

.360 0.

0.549 

0.504

0.409 

0.474 

0.613 

0.545

0.638 

0.366 

0.530

0.427

0.516 

0.516 

0.573

0.608 

0.433

0.480 

0.611

.1436 0 

1560 0 

1948 0

0.247 

0.311

0.321 

0.116 

0.357 

0.131

0.291 

ND 

0.020

0.220

0.136 

0.091 

0.023

0.090 

0.193

0.230 

0.156
TEXTURAL PARAMETERS OF EOLIAN DEPOSITS 45

4-1 

O 

4J

CD cd •

0 4J cd •> w si

4-1 Q) 4-1 00 

PU C 1 -H 

• -H 3 O Q)

O i-H T3 CM si 

O CO

CM CM sO

CO -H -H

sr m m

do d

4-1 *O 

° • %cd

4J 01 >

CO (3 *O 01 3 C

M -O -H

O 5

r-. m

CM ^H

sr m

d d

4-1 

O 4-1 

O 

0) • 

Pu Q) 4J 

O (2 CO i— 1 3 CU

co -a M 

o

00 

CO

sr

d

a>

a

3 •

•o o

Q

O r-» 

CM CM

m sr

0 0

CUC 

-o

4-1

•H 

0) 

CO

CM

m 

m

o

poo Q a a

CO -H CM -H -H r-« 

m m m

ooo

0 0

O ON m -H 

sr m

o o

A

a)

3

-o

4-1

o o o o a)

Q Q Q Q CO

O O ON r-. -H 

so O r-» m co 

in m in m m

ooooo

a> o

CO O 

M CO J

• a) e

4J > «T

co to 01 j: 

cy a a M cd 3 i

O M T3 4 

H

sr CM 

o o 

m so

o o

a)

34-10

>o o cd

H 4-1 

3 Q) Pu 

CO iH j cd .-i •

-1 ,0 CO O

Q

CO 

sO

m

d

ans verseme,

M -O 

H

CO

m

d

0) tO 

0 00 13 

cd (3 -H 

4-1 -H • CO 

d, ,0 01 l-l < 

•H S C Q) I

, 1 _j *4 »^ |

*• 1~1 ^ ^ (

CO <-{ T3 Q) ^

O 04

o m 

m sr

d d

.* % « 

oo y co

00 -H TM 00 cd •S^S'S'0

• CO " "*J CO • 

U M Q) ^j M Q) 

3 0) C W Q) C 3 > 3 C > 3

3 0) T3 O Q) T3

04 04

CO CM m r-»

d d

CM O 

O O

O O

sO 

O 

O

so so o sr

m o\ oo so

O CM O CO

er> CM a\ CM r*»

CJ\ CTi in CM sO

CM -H CO St CM

co oo r-« sr co

oo -H -H co sr

CO O CO -^ CM

ooo ooooo ooooo

-H O

00 O

O CM

d d

so ty> a\ o

-H O

co sr m

CO CO CO

o -H o

co m m -H 

r-. so

• • 

o o

CM -H

O CO

-^ O

CM CM

• •

O O

-H sr

so m

a\ so

• •

o o

sO

CM CM SO 

sO O CO

sr oo o a\ o

r-» -H m -H sr

m m sr -H m

o oo sr sr sr

m co r-» so m

sr r-. sr CM co

o\ co

sr oo

CM CM

CM

d

CM CO

0\ O

-H CM • •

o o

O O O -H O

a a a a a

ooooo

CO

Q Q Q Q O

a a a a <N

o o

CO CM

sr r-»

00 00

-H CM

d d

CO O\ O r-»

co sr

d d

00 O

CM CM

o o

SO 

SO

m

sr

sO 

CO CO

d

o o

m o

CM CO

o 

o

CM

o o

00 O Q

co co a a a a a a

o

Q O

a co

o o

sr o

sr oo

o o

r-» co

-H CM

O 

O 

00

o

mCM

co in

r- sr

o o

CM CM

d d

sO 

sO

m

CO

o

CM

sO 

CO 

sO

sr

m

o oo sr

oo sr -H

r-» o\ CM -H -H CM

-H 00 CO -H CM O cj\ m oo cj\

<r so -H o\ oo

CM -H CO CM -H

sr co r-« co in

r-« CM co -^ r-. CM -H m r-. o\

CO CM CM CM -H

sO CM m m

oo oo

ooo ooooo ooooo

CM CO

m o

00 O

CM CM

d d

oo 

o 

so

CM

CO CO

r-. o\

CM CM

CM CM

00 

CTi 

SO

o co m

o\ so r-» sr co -H

oo oo m so CM

m m so sr o

o m so r-« sr

-H SO O\ CM O

-H co r-» oo sr

sO CM CJ\ 00 CO

CO CO

CO -H

sr oo

o o

-H CM

00 CO

CMCMCM CMCM-H-HCM

oo sr

so m 

m so

o

CO

sr

CO

m so o\

CO CO ON 

sO

m so r-« oo ty>

CM CM CM CM CM

sO sO sO sO sO

O -H CM CO 00 O SO

co co co co ON CM m

sO sO sO sO sO sO in

SO CO m m

m so

r*- sr

-H 00

so m

CM -H m

CM SO CM

o m o

sr -H sr

so CM -o -H -H so o r-»

o in •» o

sr -H -i sr

-H CM co sr m 

sr sr sr sr sr 

ooooo 

sr sr sr sr sr

so r-« oo ON oo

sr sr sr sr r-»

o o o o m

sr sr sr sr

o oo

sO sO

m m

oo CM CM so

m m

so m

o -H

-H sO O

sr sr

so

cd

a

CO -o .

a 4-j cd a

CO 01

e

Q) 2 M i!cd

o C *£

COcd PQ

cd M)

CU -o

0) O

4J ^H

CO ^H

o cd

^5 PM

a w cd a

co a)

cd a a> o

O

3 O

 rl «W 

60 i-l

•H ^H 

0) CO
TABLE 6. — Graphical measures of sand samples from inland dunes used as a data base — Continued 

Locality

Principal country Specific area 

or area

Colorado (U.S. A.) —

Con.

Egypt ............

India ............

T & TT Sk 0 1

Hawaii (U.S. A.) ...

Libya ............

Great Sand Dunes National

Monument. — Con.

Ayn Amur, El Kharea ....

Al Wahat al Kharijah ..

Ayn Amur, El Kharea ...

Uadi Aou Arta, Sinai ..

A 1 U.Q y

Tel Aviv ..............

Computer McKee 

Index No. Index N

563

593

609

4176

4177

4097

4178

4179

4180

4181

4182

4183

1557

4131

4132

4133

4129

1566

577

651

652

653

4162

633

4128

607

641

581

636

643

644

645

1211

1212

723

1213

1214

1215

1216

1217

1218

24

768

769

770

766

692

696

1020

21

1022

1065

686

765

17

714

715

716

Mean grain size 

's

O. <fr

-0.586

0.833

2.090

2.000

1.977

1.455

1.892

2.038

1.917

0.453

ND

0.872

1.460

2.040

-0.112

0.609

2.085

1.403

0 OftO 

J. i.\JJ

3.000

3.200

3.380

3.011

2.503

1.434

1.530

2.320

1.260

2.420

mm

1.5052

0.5625

0.2339

0.2500

0.2540

0.3648

0.2694

0.2435

0.2648

0.7305

1.0000

0.5464

0.3635

0.2432

1.0807

0.6557

0.2357

0.3789

0.1088

0.1233

0.1073

0.0954

0.1241

0.1768

0.3701

0.3463

0.2003

0.4176

0.1869

Median grain 

size

*

0.600

0.800

2.100

ND

ND

ND

ND

ND

ND

ND

ND

ND

1.400

ND

ND

ND

ND

1 380

3*200

3.020

3.220

3.390

ND

2.500

ND

1.620

2.320

1.000

2.340

mm

1.5157

0.5743

0.2333

ND

ND

ND

ND

ND

ND

ND

ND

ND

0.3789

ND

ND

ND

ND

0.3842

0.1088

0.1250

0.1088

0.0960

ND

0.1768

ND

0.3253

0.2003

0.5000

0.1975

SortP I

0.146

0.246

0.262

0.484

0.433

1.077

0.498

0.507

0.443

1.029

0.484

1.028

0.706

1.148

0.769

0.934

0.444

0.569

0.395

0.290

0.388

0.550

0.396

0.260

0.599

0.489

0.400

0.630

0.520

Skewness

Ski

1.485

0.212

0.050

-0.157

0.043

-0.072

-0.025

-0.006

-0.009

0.535

0.292

-0.106

0.199

-0.090

0.493

0.584

0.040

0.108

0.047

0.798

0.079

0.155

0.048

0.056

0.206

0.143

0.003

0.613

0.223

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0
TEXTURAL PARAMETERS OF EOLIAN DEPOSITS 47

« 00 

CD a)

c u

3 O 

X) W

M-l J3 P. 

4-1 00 i-l

1-1 in 1-1 rH

CD «* J3 CO

m

*

o

^T

« 00

CD i-l

C J3

•^J 4J

4-1

4-1

... iH in

O O O CD «*

Q Q Q CO

•H CO O^ *H

co co r^ CM m m »d" vo

.... 

oooo

m <r o -H

f— •* ^5 ^O CM m CM CM — <

0 0 0 O

<f <f 0 <*

ff} Q^ if) fs|

lO PO "^ P"**

O O CO O

CT» oo in co

vO vO CT» in CM r-. oo CM

CM — < ^H CM

o o o o

oooo

<r o o in — < m <r — <

CM CM CM CM

o\ oo co P^

00 vO O O

o\ r^» co CM

— ( — ( CM CM

CO 0 O O

O O O ^O

co o CM r^

co m co -4

CM CM CM CM

—< CM CO 00

-4 -4 -4 "4

r^ CM oo oo

oo co — < oo

in ^o vo in

4-1 •

0 CD

O

CD cd

rH 4-1

XJ iH

B co o o o o

Q Q Q Q

csi ro ON r**- O •— * ON oo

oooo

«-H vO PO O

CM C^ ^H PO

CM vO O O

OOOO

r**- co ^3 co

O O O 00

oo -H r^ oo

O -I O O

oo r^ m

r^ o -<

CO CM £3. ^f

CO CM Z CM

0 O O

o o o

o oo Q m f* -i Z O

—< CM CM

oo cyi r^ CM

r^- CT» co oo

O O CO CO

CO CO CM CM

oooo

vo PO r-- O

vO CT» O O

_l _l (X| CM

a\ o —< — <

-H CM CM CM

o\ co ^f P^

00 CM Oi — ( m m o vo

oooo

Q Q Q Q

CM <Ti <Ti <Ti -H r^ -H m 

m <r m m

oooo

vo <r co vo

•— ( CTi O CO

— ( <-l CO -H

OOOO

00 0 vO vO

m m <r co

oooo

00 CO CM

00 Is* O

CM CM Z CM

O O O

o o o

m m Q m

CT> r*- 55 CM

— ( — ( CM

00 CM CO <Ti

oo m <r m

m oo co o

CM CM CO CM

OOOO

O O — ( O

m — < oo oo ai oo m CM

-H — ( — ( CM

CM <r <r — <

CM CM CM O

m oo ai m — < co <TI m

ooo

Q Q Q

vo m m -H CO CM m *3" »J

ooo

o\ oo o\

vO CO CM

O -< O

ooo

CM O O

CTi «3" CTi m !"*• — <

ooo

O -I

O CM Q m a\

Z CM -1

CO CO

o o

Q O oo

Z O co

CM CM

m CM oo

CT» CO ^"

^- ^- Q«^

CM CM — (

ooo

CO O O

O O CO

CM CM CM

00 <Ti O

O 0 -(

O O — <

oo <r CM CO vO vO

^r

» 00

CD -H

tf .*"{

3•d w

4-1 LM •H m

CD <JCO

__,

5

o

vO

^O

CM

O

i— (

vO

oo

O

CO

CO

CO

CM

O

O

O

I— (

CM

ooo\

CO

CM

O

o

vO

O

CM

mCM

r~- 

o

a\

in

.

0)

4-1 O

o cd

4-1

CD CX

CO -r-i

43 CO O O O O

Q Q Q Q

oo -H in in

^f ^f ^> ^f

oooo

CM in -H i--

•— i r^- CM cr*

O O CO ^3"

O O O — (

c^ o\ m in — < r^ CM co

oo oo oo cr*

oooo

in CTI CM

_< ^ r**

Q >* CM 00

3 CM CO CM

OOO

ooo Q m o o

3 O vO OO

CM — 1 — (

vO CO CM CM

CM CO CO O-

\O CO CT* OO

CM CM CM CO

OOOO

O\ CO *«O CO

CM O vO 00

O\ — ( I-. CO

•—( CM •—*•—<

in vo *3" in

CM CM O O

r~4 C?\ CO CM

o — < oo o

— * vo in vo

A

•> 00

CD -H

3

73 *J

4-1

<4-l

o o o <u <r

Q Q Q CO

o\ f-^ in CM

oo CM <r <r

oooo

<r c* co -.

ro 10 r**- o

C^ CM «TM^ 0*4

oooo

O ^3" CO CT* r^ CM in -*

CM o r^ oo

— ( — ( O O

o ^0 in CM

co m \o o

r~. r^ co — <

<r — < CM CM

oooo

oooo

oo "4 oo m

o m o CM

-4 CM CM CM

m in oo in r*» *3* oo oo — < o in CM

-* CM CM CM

OOOO

O O CO CO ^o CT* in co

CM CM CTi — (

-H CM — ( CM

\o r^ co co

O O O CM

o O r-* — <

CM l~» vO CM

vo in in in

rH CD 

rH O

•H cd «

4-14-1 CD

a c

« -H 3

CD rH T3

rH CO cd IH S C -H

CO O CD

CO

r^ — <

<r CM 

<r m

o o

CM vO

r~- oo

O 0

0 0

1

r^ o

r^ <r

O CO

-^ O

&

CTi

Q CM

.

O

O

Q 0

<Z vO

i— (

oo co

<r in

vO CM

CO CO

o o

in o

m CM

<r vo

i— < i— <

CO CM

CM v£)

r~- -4

C^ *H

CO ^iD

. *

CD CD T)

0 C I-l cd 3 cd M-l T) U

a -o

•H M-l C

CO CD &

CO

r^

-H

m

0

oo

oo

CM

O

r~.

m

CO

o

CMm

oo

CM

O

o

I— (

00

—4

r-4

vO

vO

CM

O

O

i— 4

^

i— (

CO

vO

vO

O

vO

A 

J2

* 00

(1) vH

C J2

• 3

CD T3 *J

(X 4-1

O i*-l

co CD r^

CO

vO

m

0

o

<r

m.

o

o

CM

OO

0

in

ooin

CO

•

o

o

oo

<r

—4

CM

CO

oo

CM

CO

o

CM

00

•— (

m•-O

o

CM

t— t

>£>

A

CD

C

• 3

W T)

CO

CD 4-1

0 CD

CO

oo 

m

. 

o

^*m

•^

o

mco

vO

o

^

o

r^

o

o

o

m

o

00

CTi

m

vO

o

o

CT» m.

o

v£>

vO

v£)

a^

r~

m

.

cu

§

. T)

CD

CO 4-1 Cd i-l

Z> CD

CO

00

vO

O

^.

oo

CO

CO

^.

^"

CO

—4

vO

CO^"

^H

o

o

o

oo

CM

i— (

CM

CT» i— (

O

CO

oo

CO

CM

oo

vO

vO

a\

CM

m
TABLE 6. — Graphical measures of sand samples from inland dunes used as a data base — Continued 

Locality 

Computer

Principal country Specific area Index No. 

or area

Sedales ............... 608

614 

Three Mountains ....... 4065

Marshall Islands . Mejatto Islet ......... 582

Mexico ........... Chihuahua ............. 1550

Missouri(U.S.A.) . Waverly ............... 4004

New Mexico (U.S. A.) Santa Rosa ............ 4003

White Sands National 4023

Monument .

586 

574

623 

527 

565

575

532

603

549

658

659

550

660

661

645

644

643

592

591

642

637

McKee's 

Index No.

673

674 

679 

519 

6

5 

4 

32

825 

826

827 

829 

837

849

850

851

971

971

972

972

973

974

975

976

977

977

979

979

980

Mean grain size

+

2.

1. 

2. 

1. 

2.

3. 

1. 

1.

1. 

1.

1. 

1. 

1.

1.

1.

1.

1.

1.

2.

2.

1.

1.

1.

1.

2.

1.

1.

2.

1.

070

930 

566 

980 

593

134 

357 

047

636 

763

570 

263 

536

663

400

610

270

220

120

163

330

910

100

603

700

490

766

820

606

mm

0.2382

0.2624 

0.1689 

0.2535 

0.1661

0.1139 

0.3904 

0.4840

0.3209 

0.2952

0.3368 

0.4175 

0.3439

0.3164

0.3789

0.3276

0.4147

0.4147

0.2238

0.2238

0.3869

0.2643

0.4665

0.3299

0.1539

0.3560

0.2932

0.1416

0.3276

Median grain 

size

*

2.000

1.900 

ND 

1.980 

2.570

ND 

ND 

ND

1.600 

1.700

1.500 

1.150 

1.540

1.600

1.400

1.600

1.220

1.270

2.163

2.120

1.370

1.920

1.000

1.580

2.650

1.320

1.720

1.760

1.480

mm

0.2500

0.2679 

ND 

0.2535 

0.1684

ND 

ND 

ND

0.3299 

0.3078

0.3536 

0.4506 

0.3439

0.3299

0.3789

0.3299

0.4293

0.4293

0.2300

0.2300

0.3978

0.2661

0.5000

0.3345

0.1593

0.4005

0.3035

0.2952

0.3585

Sorting

0.890

0.576 

0.560 

0.318 

0.365

0.403 

0.832 

0.301

0.308 

0.495

0.409 

0.765 

0.467

0.442

0.930

0.900

0.083

0.830

0.777

0.777

0.823

0.677

0.780

0.890

0.720

0.944

0.515

0.440

0.590

Skewness

Skj

0.281

0.142 

0.019 

0.071 

0.074

-0.031 

0.234 

0.001

0.187 

0.262

0.380 

0.332 

0.025

0.268

0.038

0.041

0.008

0.008

0.093

0.093

0.102

0.506

0.240

0.076

0.130

0.326

0.306

0.420

0.420

0

0

0

0

0

0

0

0

0
Texas (U.S. A.) .... Midland ..............

Mr* n fi V* fi n c

OT*JITIO^ A. ^ ^ . ^ .A

Signal Peak ..........

Tunisia .......... Bir Sultan ...........

662

654

655

656

657

4168

1623

557

4187

4188

4189

4190

1564

630

4185

4033

4184

601

649

646

647

648

650

600

4006

4174

4001

551

1549

554

4175

4186

981

1069

1070

1071

1072

1099

1100

0

0

0

0

0

652

652

1226

249

1224

984

988

985

986

987

989

993

8

1156

1

3

3

693

1180

1234

1.700

1.310

1.400

1.630

1.720

1.719

1.566

1.663

1.462

2.255

2.278

2.005

2.966

2.870

2.133

-0.667

1.314

2.670

2.130

1.430

2.040

1.170

2.330

-0.376

2.583

2.115

1.584

2.640

2.083

3.386

1.650

1.629

0.2952

0.3938

0.3711

0.4118

0.2932

0.3038

0.3392

0.3164

0.3630

0.2095

0.2062

0.2491

0.1285

0.1368

0.2280

1.5878

0.4022

0.1571

0.2285

0.3711

0.2432

0.4444

0.1989

1.3014

0.1669

0.2308

0.3336

0.1604

0.2365

0.0954

0.3186

0.3233

1.760

1.330

1.430

1.280

1.770

ND

1.520

1.680

ND

ND

ND

ND

3.000

2.900

ND

ND

ND

2.680

1.910

1.040

1.950

1.120

2.300

0.910

ND

ND

ND

2.650

2.030

3.360

ND

ND

0.3078

0.4033

0.3789

0.3231

0.3035

ND

0.3487

0.3121

ND

ND

ND

ND

0.1250

0.1340

ND

ND

ND

0.1560

0.2661

0.4863

0.2588

0.4601

0.2031

1.8790

ND

ND

ND

0.1593

0.2449

0.0974

ND

ND

0.292

0.255

0.350

0.470

0.350

0.482

0.429

0.633

0.495

0.870

0.858

0.717

0.452

0.380

0.524

0.153

0.645

0.320

0.800

1.180

0.660

0.670

0.540

0.495

0.533

0.271

0.511

0.193

0.448

0.225

0.422

0.471

0.039

0.190

0.221

0.294

0.310

0.315

0.221

0.055

0.427

0.164

0.180

0.170

0.088

0.005

0.054

0.585

0.398

0.051

0.450

0.450

0.266

0.141

0.555

1.144

0.203

-0.008

-0.096

0.057

0.190

0.226

0.116

0.141
TABLE 6. — Graphical measures of sand samples from inland dunes used as a

Locality 

Comouti

Principal country Specific area Index N< 

or area

Kanab ................. 624

631 

571

625 

Lund .................. 1614

1615

Mount Carmel Junction . 1618

583 

San Rafael Swell ...... 4170

4171

er McKee' 

o. Index N

846 

847

848

848 

243 

245

1106 

571

571 

1101

1102

Mean grain size 

s

0. </)

2.420 

2.590

2.476

1.440 

3.276 

2.976

2.533 

2.316

1.993 

2.394

2.390

0. 

0.

0.

0. 

0. 

0.

0. 

0.

0. 

0.

0.

mm

1869 

1661

1792

3686 

1037 

1276

1728 

2017

2517 

1903

1908

data base

Median grain 

size

<t>

2.400 

2.560

2.390

1.390 

3.280 

2.980

ND 

2.250

1.950 

ND

ND

mm

0.1895 

0.1696

0.1908

0.3816 

0.1029 

0.1267

ND 

0.2102

0.2588 

ND

ND

— Continued

SortP i

0.240 

0.390

0.356

0.287 

0.468 

0.492

0.727 

0.555

0.283 

0.644

0.650

Skewness

Skj

0.193 

0.202

0.400

0.332 

0.019 

0.019

-0.035 

0.238

0.272 

0.444

0.476

0

0

0

0

0

0

0

0

0

0

0

Interdune and serir sands

TABLE 7. — Graphical measures of sand samples from interdune and serir deposits used as a data base

[Localities are listed alphabetically by country, and specific area where known. The computer index number and Mc

are also listed. ND indicates no data]

Principal country 

area

A 1 oo T""f £>

Egypt ............

Locality

or Specific area

Mean grain size

Computer 

Index No.

4018

4130

594

McKee's 

Index

No.

26 

767 

685

phi

1.935 

-0.683 

1.403

mm

0.2615 

1.6055 

0.3789

Median grain 

size

phi

ND 

ND 

1.200

mm

ND 

ND 

0.4353

Sorting

rho 

1.5

0.1

1.1
Lybia Fezzan

Ghat . 

Sabha

Sedales ........

Three Mountains

New Mexico(U.S.A.) White Sands National Monument

Peru ............. Pampe Corre Viento, Lomitas ..

Tunisia .......... Bir Sultan ...................

622

639

556

616

4106

4107

595

4109

597

4111

561

573

585 

4115 

523 

4117 

564

524 

598 

4121 

4122 

4123

4124

599 

519 

576

559

553 

525 

4061

596

526

4137

4191

4031

4032

1621

702

703

727

728

729

729

730

730

731

731

732

733

734 

734 

735 

735 

736

737 

738 

739 

739 

740

743

744 

745 

746

675

664 

667 

672

680

681

828

0

247

248

693

2.190

2.350

2.370

1.570

1.754

1.578

2.333

2.279

2.213

1.684

2.003

1.839

1.450 

1.155 

2.886 

2.412 

1.563

2.670 

1.230 

2.468 

2.044 

1.677

0.961

1.560 

2.450 

2.000

2.006

1.553 

2.300 

1.769

2.236

2.210

2.047

2.702

-0.093

0.787

2.416

0.2192

0.1961

0.1934

0.3368

0.2965

0.3349

0.1989

0.2060

0.2161

0.3112

0.2500

0.2793

0.3660 

0.4491 

0.1350 

0.1879 

0.3392

0.1571 

0.4263 

0.1807 

0.2425 

0.3127

0.5137

0.3392 

0.1830 

0.2500

0.2483

0.3415 

0.2031 

0.2934

0.2117

0.2161

0.2420

0.1537

1.0666

0.5795

0.1882

2.200

2.490

2.350

1.290

ND

ND

3.000

ND

2.000

ND

1.700

1.400

0.700 

ND 

3.680 

ND 

1.400

3.400 

0.350 

ND 

ND 

ND

ND

0.800 

2.850 

1.900

2.620

1.550 

2.950 

ND

2.000

2.150

ND

ND

ND

ND

2.350

0.2176

0.1780

0.1961

0.4090

ND

ND

0.1250

ND

0.2500

ND

0.3078

0.3789

0.6156 

ND 

0.1560 

ND 

0.3789

0.0947 

0.7846 

ND 

ND 

ND

ND

0.5743 

0.1387 

0.2679

0.1627

0.3415 

0.1294 

ND

0.2500

0.2253

ND

ND

ND

ND

0.1961

0.

0.

0.9

1.

0.

0.

1.

1.5

1.

1.3

1.

1.2

1.3

1.

1.3

1.4

0.8

1.3

1.6

1.3

1.4

1.5

1.4

1.6

1.3

1.4

1.6

0.9

1.5

1.4

1.1

1.1

1.0

0.8

0.6

1.4

0.9

:mf --:-^-^-:-^/^

A STUDY OF GLOBAL SAND SEAS

DIFFERENTIATION OF EOLIAN

DEPOSITS BY DISCRIMINANT

ANALYSIS

Chapter C

By R. J. MOIOLAi and A. B. SPENCER1

Contents

Summary of conclusions 

Introduction ..........

Discriminant analysis ... 

Application ..........

Results ..............

55

55

55

55

57

1 Mobil Research and Development Corp., P.O. Box 900, Dallas, Texas 75221.

53
54 A STUDY OF GLOBAL SAND SEAS

Illustrations

Page 

FIGURE 28. Discriminant frequency plots and cumulative distribution curves of beach,

river, coastal dune, and inland dune samples .......................... 56

29. Discriminant frequency plot of 152 inland dune and 291 coastal dune samples 57

30. Discriminant frequency plot of 31 interdune and 38 inland dune samples ... 58
DIFFERENTIATION OF EOLIAN DEPOSITS BY DISCRIMINANT ANALYSIS 55

Summary of Conclusions

LTHOUGH IT WAS NECESSARY to use textural parameters (mean, standard deviation, 

skewness, kurtosis) -which in themselves are an 

abridgment of the grain-size distribution — as input 

variables, inland and coastal eolian deposits were 

effectively differentiated by discriminant analysis. 

Previous studies have demonstrated that the weight 

fractions of quarter phi grain-size analyses are the 

preferred input for discriminant analysis (Moiola, 

Spencer, and Weiser, 1974). Therefore, if quarter 

phi data were available, even better separation of 

these deposits could be expected. This conclusion is 

supported by the excellent separation obtained for 

the inland dune and interdune deposits of Fezzan, 

Libya, using quarter phi grain-size data.

These results confirm the contention of Moiola, 

Spencer, and McKee (1973) and Moiola, Spencer, 

and Weiser (1974) that discriminant analysis is 

perhaps the most effective method for differentiating modern eolian sands by their textural characteristics.

Introduction

VARIOUS GRAIN-SIZE TECHNIQUES are 

available for differentiating sand bodies (PettiJohn, 

Potter, and Siever, 1972). These techniques are primarily attempts to classify and assign sets of 

unknown samples to one of two or more populations. Mathematically, they have become progressively more sophisticated, beginning with simple 

visual comparison of histograms, to plotting textural parameters, to graphical analysis of cumulative curves, and finally to such techniques as discriminant analysis.

Perhaps the most popular approach to date has 

been the use of textural parameters plotted as 

variables on a two-dimensional coordinate system 

(Mason and Folk, 1958; Friedman, 1961, 1967). Unfortunately, this use of textural parameters has met 

with only partial success (Shepard and Young, 

1961; Schlee, Uchupi, and Trumbull, 1964; Gees, 

1965; Sevon, 1966; Moiola and Weiser, 1968). For 

example, Moiola and Weiser (1968) demonstrated 

that certain combinations of textural parameters, 

such as mean diameter and skewness, can be used 

to differentiate certain sand deposits, but textural

parameters could not differentiate beach and 

coastal dune sands and could only poorly differentiate river and inland dune sands.

Recent studies by Sahu (1964), Sevon (1966), 

Greenwood (1969), Tillman (1971), Moiola, 

Spencer, and McKee (1973), and Moiola, Spencer, 

and Weiser (1974) suggest that discriminant 

analysis is probably the most effective grain-size 

technique for differentiating modern sand bodies. 

In this study, the discriminant technique is used to 

differentiate inland dune, coastal dune, and interdune deposits.

Discriminant Analysis

DISCRIMINANT ANALYSIS is a classifying 

technique that differentiates distinct populations 

by using a number of independent attributes. It was 

developed by Fisher (1936) to solve a taxonomic 

problem. The method uses a classifying function to 

assign samples individually to one of two or more 

populations. A priori knowledge that the populations differ is a prerequisite for its use. The technique defines the coefficients of a function, which 

allows samples described by a number of independent variables to be projected onto a line so that the 

distance between projected populations is maximized relative to the scatter within each projected 

population.

The detailed mathematical treatment of the technique is not presented here but can be found in a 

number of standard references, such as Wilks 

(1962), Miller and Kahn (1962), and Krumbein and 

Graybill (1965). Its application to grain-size data 

has been amplified by Moiola, Spencer, and Weiser 

(1974). The independent variables can be the 

weight fractions of each size class, textural 

parameters, or other measurable attributes. Both 

weight fractions of quarter phi grain-size analyses 

and textural parameters calculated from sieve data 

according to the scheme of Folk and Ward (1957) 

are used in this study.

Application

THE EFFECTIVENESS of linear discriminant 

analysis for differentiating modern beach, river, inland dune, and coastal dune sands has been 

demonstrated by Moiola, Spencer, and Weiser
56 A STUDY OF GLOBAL SAND SEAS

too

T

0 20 40 60 80 IOO 120 

CUMULATIVE DISTRIBUTION CURVE

Beach mean -^

40 80 I20

^-Inland dune mean 

FREQUENCY PLOT FROM WHOLE PHI DATA

A

0 20 40 60 80 IOO 120 

CUMULATIVE DISTRIBUTION CURVE

40 80 120

Tl I 11 ll infill !• ii ii I

^— f*r\aotal Coastal rli dune ino rv\ mean

FREQUENCY PLOT FROM WHOLE PHI DATA

B

IOO 

80 

60 

40 - 

20 

0

^Maximum 

separation ' 

93 percent

20 40 60 80 100 

CUMULATIVE DISTRIBUTION CURVE

120

Beach mean

120

-River mean 

FREQUENCY PLOT FROM WHOLE PHI DATA

c

IOO

80 -

i?: 60 -

40 -

20 -

0 20 40 60 80 IOO I20 

CUMULATIVE DISTRIBUTION CURVE

Inland dune mean 

mi

4O 80 120

*— Coastal dune mean 

FREQUENCY PLOT FROM WHOLE PHI DATA

D

IOO

80 - 

60 - 

40 - 

20 -

I"""/—Maximum 

K separation 

92 percent i —— i —— i —— r — i —— i —— r 

0 20 40 60 80 IOO 120

CUMULATIVE DISTRIBUTION CURVE

I pniv

!•!! I !!• L

River mean

40 80 120

Inland dune mean

FREQUENCY PLOT FROM WHOLE PHI DATA

Maximum 

separation 

92 percent

0 20 40 60 80 IOO 120 

CUMULATIVE DISTRIBUTION CURVE

mean 

.. .1.

40 80 120

itTF

Coastal dune meanFREQUENCY PLOT FROM WHOLE PHI DATA

DISCRIMINANT FREQUENCY plots and cumulative distribution curves of beach, river, coastal dune, and inland dune 

samples (modified from Moiola, Spencer, and Weiser, 1974). Scale of 0 -120 is arbitrary. (Fig. 28.)
DIFFERENTIATION OF EOLIAN DEPOSITS BY DISCRIMINANT ANALYSIS 57

(1974). In their study, using whole phi analyses of 

sets of 30 samples from each environment, the 

differentiation obtained between pairs of sets was 

no less than 87 percent (fig. 28). They also 

demonstrated that linear discriminant analysis 

using whole phi data is at least as effective as the 

best combination of textural parameters based on 

quarter phi data in differentiating sands from these 

environments. In addition, the technique successfully differentiated beach and coastal sands, as 

well as river and inland dune sands, whereas textural parameter plots did not.

In this study various eolian deposits are differentiated. A selected suite of 152 inland dune, 291 

coastal dune, and 38 interdune samples, compiled 

by Ahlbrandt (chapter B), is the data base. The discriminant function used is of the following form:

Z = CiXi + + . . . CnXn + b,

where z is the transformed sample value; c lf c 2 . . . 

cn are the coefficients of the discriminant function; 

x ls x 2 . . . xn are the descriptive variables; and b provides scaling so that the means of the two projected 

populations fall at 40 and 80 on an arbitrarily 

chosen scale of 0 -120.

Because weight fractions of each size class, 

which are ordinarily used, were not available for 

the set of coastal dunes, it was necessary to find 

alternative variables for discriminant analysis. Textural parameters were selected. A sub-set of eolian

samples from Fezzan, Libya, for which quarter phi 

weight fractions were available, was used to determine whether associated inland dune and interdune deposits could be differentiated.

Results

BIVARIANT TEXTURAL PARAMETER plots 

have not proven particularly effective in separating 

environments in general. The parameters themselves, when used as descriptive variables in discriminant analysis, have been found to be sensitive 

descriptors (Sevon, 1966). Results of the present 

study support this contention.

Using Folk and Ward's (1957) approximations of 

the mean, standard deviation, skewness, and kurtosis of the grain-size distribution as input for linear 

discriminant analysis, sets of inland dune and 

coastal dune samples can be easily differentiated 

(fig. 29). The population of projected coastal dune 

samples tightly clusters around its mean at 80 on 

the arbitrarily chosen scale of 0—120. Although the 

population of projected inland dunes is loosely dispersed about its mean at 40, maximum separation 

(91 percent) occurs at approximately 69 on the 

scale, with only 24 coastal dune samples and 13 inland dune samples from the total population of 443 

falling outside their fields. Comparison of the relative dispersions of the coastal and inland dune 

populations suggests that the textural character of

Maximum separation 

of 91 percent

C

r 

0

i

I

OASTAL DUNE .

,lhll I, I i,i

10 20 30 40 50 60 70 80 90 100 110 120

MLAND DUNE

ll|l 1 Illl

DISCRIMINANT FREQUENCY plot of 152 inland dune and 291 coastal dune samples. Inland dune samples indicated below 

abscissa; coastal dune samples indicated above abscissa. Maximum separation of 91 percent occurs at 69 on the arbitrarily chosen 

scale of 0-120.(Fig. 29.)
58 A STUDY OF GLOBAL SAND SEAS

INLAND DUNE

Maximum separation 

of 97 percent

I 

10

separation i

>ercent .1 I ,

• ill .llll i l.l.li. I

0

I I I I

20 30 i H'("'( 40 

++

50 60 70 .i—ri—Hr

80

i i

90

i

100

I I I I I I

110

i i i

120

INTERDUNE

DISCRIMINANT FREQUENCY plot of 31 interdune and 38 inland dune samples. Interdune samples indicated below abscissa; inland 

dune samples indicated above abscissa. Maximum separation of 97 percent occurs at 65 on the arbitrarily chosen scale of 0 -120. 

(Fig. 30.)

inland dune sands is more variable than that of 

coastal dunes. (See Ahlbrandt, chapter B). This 

may reflect the more varied source of inland eolian 

deposits.

The effectiveness of the linear discriminant technique in differentiating the intimately associated 

eolian subenvironments, such as dune and interdune, is shown in figure 30. Of the 69 samples in 

the combined set of dune and interdune samples 

from Fezzan, Libya, only one interdune sample out 

of 31 and one dune sample out of 38 fall outside 

their respective fields. Thus, 97 percent of the samples are successfully differentiated with maximum 

separation occuring at 65 on the scale.


A STUDY OF GLOBAL SAND SEAS

RED COLOR IN DUNE SAND

Chapter D

By THEODORE R. WALKER2

Contents

	Page 

Summary of conclusions ............................ 63

Introduction ...................................... 63

Acknowledgments ............................. 64

Regional setting .................................... 65

Moisture ...................................... 65

Winds and eolian transport ..................... 65

Bedrock ...................................... 65

Soils.......................................... 65

Distribution of red sands ....................... 67

Characteristics of the pigment .. .................... 68

Sources of iron .......................... ......... 69

Origin of clay coatings on eolian sand grains .......... 69

Conditions favoring formation of iron oxide pigment... 78

Factors affecting regional and local variations in redness 79

2 University of Colorado, Boulder, Colorado 80309.

61
62 A STUDY OF GLOBAL SAND SEAS

Illustrations

Page

FIGURE 31. Gemini XI space photograph of Libya ...................................... 64

32. Generalized geologic map of northwestern Libya ............................ 66

33. SEM photomicrographs of quartz grain coated by film of reddish-yellow pigment,

and X-ray traces showing elemental composition of analyzed areas ......... 70

34. SEM photomicrographs of quartz grain with red pigment concentrated in indentations, and X-ray traces showing elemental composition of analyzed areas .... 71

35. Photograph of etched hornblende grain from modern dune .................. 72

36. Photograph of etched augite grain from modern dune ....................... 72

37. SEM photomicrographs of matrix-rich sand from weakly stabilized reddish dune, 

northern coastal region, Libya, and X-ray traces showing elemental composition 

of matrix clay ........................................................ 74

38. SEM photomicrographs of quartz grain with reddish-brown pigment in indentations, and X-ray traces showing elemental composition of pigmenting material 75

39. SEM photomicrographs of quartz grain collected from pink modern dune, and Xray traces showing elemental composition of the pigmental material in fine and 

very fine sand ........................................................ 76

40. SEM photomicrographs of quartz grain collected from red dune, and X-ray traces 

showing elemental composition of pigmenting material of surface clay and iron 

oxide ................................................................ 77

Table

Page 

TABLE 8. Clay mineral analyses .................................................... 67
RED COLOR IN DUNE SAND 63

Summary of Conclusions

€

OLIAN DEPOSITS in western Libya provide 

an outstanding example of modern dune 

sands that have reddened with age and with distance of transport. The pigment in the dunes is 

chemically precipitated iron oxide, which is 

derived in part from alteration of ferromagnesian 

silicate minerals and in part from iron-bearing clay 

minerals that adhere to the surfaces of sand grains. 

The clay minerals of the surface coatings are 

derived mainly from airborne dust mechanically infiltrated into the dunes and into other surficial 

deposits from which the dune sands are derived.

To the extent that iron-bearing minerals are not 

in equilibrium with meteoric water, they react with 

dew, rain, and interstitial water, and release iron, 

which, owing to the oxidizing and alkaline chemical environment, precipitates on the surfaces of the 

sand grains as yellowish ferric hydrate (limonite). 

Subsequently, as these grains are abraded during 

eolian transport, the limonite and limonite-stained 

clay are removed from exposed surfaces of coarser 

grains, but these materials are retained in indentations where they are protected from abrasion. The 

fine grains are abraded much more slowly than the 

coarse ones and therefore tend to have more indentations in which to preserve the pigment. Thus, the 

finer grains usually are more heavily stained than 

are the coarser grains. Conditions that favor the acquisition of additional iron oxide and clay coatings 

on the surface of grains are likely to occur 

whenever the grains are at rest.

The light-yellow ferric hydrate is metastable, 

and, upon aging under the chemical conditions existing in this desert region, it ultimately converts to 

hematite. The aging of ferric hydrate is accompanied by reddening; hence, the sands become redder with increasing age and distance of transport. 

Although aging is prerequisite to the reddening of 

the dune sands, the time interval involved is also 

affected by such factors as the amount of moisture 

available, availability of iron, and amount and type 

of clay minerals retained on grains. The effects of 

these factors are regionally variable; therefore, 

although the dunes redden with increasing age, the 

intensity of redness is not a reliable measure of the 

age of the deposits, and it is not a reliable criterion 

for correlation.

Each step in the sequence of events leading to the 

accumulation of the stain and its gradual reddening 

can be documented in deposits that are forming in 

the desert today. This important fact indicates that 

the reddening is a product of the modern desert environment, not the product of an alleged earlier 

moist climate.

Introduction

A COMMONLY OBSERVED feature of deserts is 

that dune sands have a reddish hue and become increasingly redder with distance of transport and 

with increasing age (Norris, 1969). The origin and 

climatic significance of the pigment in such dunes 

has been a subject of considerable controversy 

among geologists for many decades. What is the 

nature of the pigmenting material and how and 

when is it accumulated on the grains? Does the pigment reflect the reworking of sands which 

developed their color during earlier, much more 

moist climates than those existing now (as for example, during Pleistocene pluvial intervals), or is it 

the product of processes that are going on at present 

in deserts? Is the intensity of redness a reliable 

measure of the age of dunes, or are factors other 

than age equally important in the reddening? 

Hopefully, the evidence presented in this chapter 

will help to answer these questions.

Excellent examples of dune sands that show reddening in the direction of transport are the Sahra' 

Awbari" and Sahra' Marzuq of western Libya (fig. 

31). In the author's opinion, these and other dune 

sands in Libya convincingly document successive 

stages in the development of red pigment, and they 

are believed to form models that illustrate the processes of dune-reddening active today in hot desert 

regions throughout the world.

The evidence presented here supports the conclusions of Norris (1969) that much of the iron in 

the pigment is derived internally from the dunes 

and that processes leading to the reddening are active in modern deserts. The evidence also supports 

the conclusion of Folk (1969) that airborne dust 

plays an important role in the reddening of dunes. 

The dunes studied by Folk, in the Simpson Desert 

of Australia, however, are considered by him to 

have attained redness from dust that initially was 

red and was derived from red lateritic soils
64 A STUDY OF GLOBAL SAND SEAS

GEMINI XI SPACE PHOTOGRAPH of Libya. Northeastward view from above eastern Algeria. Prevailing wind is from northeast (upper right). Note marked increase in redness of Sahra' AwbarTand Sahra' Marzuq in direction of sand transport. (Fig. 31.)

developed under a former, more humid climate. In 

contrast, evidence presented here indicates that 

dust involved in the reddening of dunes in the 

Sahara initially was not red, but has become red in 

the existing arid climate.

Acknowledgments

This research was supported by National Science 

Foundation Grant GA -20738 and the University of
RED COLOR IN DUNE SAND 65

Colorado Council on Research and Creative Work. 

John C. Harms (Marathon Oil Co.) and James R. 

Steidtmann (University of Wyoming) critically 

reviewed the manuscript. A. J. Crone provided 

valuable laboratory assistance. All of this aid is 

gratefully acknowledged.

Regional Setting

Moisture

WITH THE EXCEPTION of a narrow belt of arid 

steppe climate along the Mediterranean coast, 

western Libya is mostly a region of severe desert 

(fig. 32). Average annual rainfall along the coast 

westward from the Gulf of Sidra is about 200 mm (8 

in.), and the amount diminishes markedly within a 

short distance inland. Along the southern margin of 

the Gulf of Sidra the desert begins almost at the 

coastline (fig. 32). The central part of the country 

lies in the driest part of the Sahara, where, at times 

several years may pass with no rainfall whatever. 

However, nearly all areas— even those in the 

driest parts of the desert — receive some rainfall 

(Fiirst, 1970), and even seemingly negligible 

amounts become important geologically because 

over long periods they can provide enough 

moisture to cause mineral alterations that result in 

reddening. In addition, diurnal temperature 

changes commonly are extreme in the Sahara, and 

they lead to frequent occurrences of heavy dew. 

Although apparently insignificant, such small 

amounts of moisture, when replenished over and 

over again, may play an important role in the reddening processes described herein. The importance 

of dew as an agent of mineral alteration in deserts 

has been stressed by many previous writers (among 

them, Engel and Sharp, 1958; Kuenen and Perdok, 

1962; Margolis and Krinsley, 1971).

Winds and Eolian Transport

Throughout most of Libya prevailing winds blow 

from the northeast except near the coast, where 

westerlies prevail during the winter months. The 

major direction of eolian transport into the interior 

of the desert, therefore, is south westward. Accordingly, the major sand seas that dominate the landscape in southwestern Libya (§ahra' AwbarT and

Sahra' Marzuq) are composed of sand derived principally from sources lying northeastward toward 

the Gulf of Sidra and in northeastern Libya (figs. 31, 

32). In addition, the §ahra' AwbarT, particularly its 

northern arm, probably receives a significant contribution of sand blown southwestward from the 

coastal steppe region across the Al ^amadahal 

Hamra plateau (figs. 31, 32).

O

Bedrock

Bedrock throughout Libya consists dominantly of 

non-red sedimentary rocks of Paleozoic to Tertiary 

age overlain locally by Tertiary volcanic rocks (fig. 

32). All geologic periods are represented by the 

sedimentary rocks, but those rocks of Cretaceous 

and Tertiary age are the most important insofar as 

the present discussion is concerned. They are 

areally dominant, and they provide the major 

bedrock sources of the eolian deposits. The Cretaceous and Tertiary sedimentary rocks consist 

mainly of marine limestones and shales but locally 

contain interbedded continental deposits of 

sandstone and shale (Conant and Goudarzi, 1964).

The Cretaceous and Tertiary sandstones are 

mostly orthoquartzites and probably provide a major source of the quartz sand which dominates the 

dunes. Cretaceous and Tertiary limestone, shales, 

and volcanic rocks provide sources of sand-size 

rock fragments, but grains of these lithologies in 

most places constitute only a very small percentage 

of the dune sands.

Tertiary volcanic rocks are the probable major 

sources of unstable ferromagnesian silicate 

minerals, such as augite, hornblende, and epidote, 

which occur in the heavy-mineral fractions of dune 

sands at all the sampled localities. In addition, 

shales, sandstones, and, to a lesser degree, 

limestones are the ultimate sources of airborne 

dust, which, as will be shown in the subsequent 

discussion, is a significant factor in the development of red pigment in the dune sands. The 

bedrock formations include some red beds of 

Mesozoic age, but these beds are of limited occurrence and are relatively unimportant as sources of 

pigment in the dune sands.

Soils

In most places bedrock is overlain by a veneer of 

surficial deposits, which are mainly light red eolian
66 A STUDY OF GLOBAL SAND SEAS

7(Ma)

KaU8b(S> MEDITERRANEAN

Qaryat Abii Nujaym

SAtfRA' 

AW8ARJ

EXPLANATION

Geology 

Quaternary surficial deposits

Tertiary sedimentary rocks 

Tertiary volcanic rocks 

Mesozoic sedimentary rocks 

fts .N Paleozoic sedimentary rocks 

SAHRA; pCr I Precambrian crystalline rocks

MAttZUQ

25° —

GENERALIZED GEOLOGIC MAP of western Libya, showing sample localities. Geology generalized from Conant and Goudarzi 

(1964). (Fig. 32.)

sands. Where migration of these deposits has been 

temporarily halted either by vegetation, as in many 

places in the coastal region, or by the development 

of protective gravel pavements, as on deflation surfaces in the interior of the desert, and on the upland 

surfaces of dissected alluvial fans, weakly 

developed but strikingly reddish (2.5 YR to 5 YR, 

Munsell Soil Color Chart, Munsell Color Co., 1954) 

soils have been formed. These soils belong to the

great soil group known as "Red Desert Soils" and, 

as evidenced by the following characteristics, they 

attest to long-term regional aridity.

The soils are calcareous throughout their 

profiles, and in places near the coast they contain 

prominent concentrations of carbonate deposits 

(caliches) which commonly are a metre (3 ft) or 

more thick. Somewhat farther inland, where aridity 

is greater (as in the area beginning about 75 km (47
RED COLOR IN DUNE SAND 67

mi) south of Misratah and extending to Qaryat Abu 

Nujaym), caliche zones are composed mainly of 

gypsum. Gypsum caliches also occur nearby in the 

desert regions of Tunisia (Page, 1972). In most 

places the soils also contain sand- and pebble-sized 

rock fragments of limestone, and in the coastal 

region they typically contain grains of carbonate 

shell debris.

The occurrence of carbonate and gypsum caliche, 

and the presence of carbonate clasts, imply an absence of significant leaching during soil formation. 

Moreover, soils in the more arid regions commonly 

contain palygorskite as a major constituent of the 

clay fraction (table 8). This clay mineral requires an 

alkaline environment for development and survival. The importance of all these characteristics 

can hardly be over-emphasized because they indicate that the soils formed under nonleaching, 

alkaline conditions. The nature of the soils provides 

evidence that for at least as long as the age of these 

soils, which presumably extends from early 

Pleistocene to Holocene, the climate in this part of 

the desert has not been significantly more moist 

than it is at present. Accordingly, the characteristics of the soils provide strong evidence that 

the associated reddish pigment, is the product of an 

arid climate.

TABLE 8. — Clay minerals identified in samples analyzed for 

this study

[Sample localities are shown in figure 31. Clay minerals are listed in order of 

decreasing abundance. Capital letter symbols indicate major constituent; lowercase letter symbols indicate minor constituent; parentheses, trace amount. K, 

kaolinite; I, illite; ML-IM mixed-layer illite montmorillonite; P, palygorskite]

TABLE 8 — Continued

Sample Clay minerals Age and rock type

Bedrock

1

2

10

11

26

53

58

67

68

72

73

74

78

85

104

I, ml-im

K, I, ml-im

I, K, ML-IM

K, I, ml-im

ML-IM, I, K

I, K, ml-im

K, ML-IM, i

K, i, ml-im

K, P, I, ml-im

K, ml-im

K, I, ml-im

K, I, ml-im

K, i, ml-im

K, i

I, K, ml-im

Triassic shale

Cretaceous shale

Do.

Do.

Miocene shale

Tertiary clay

Cretaceous shale

Cretaceous sandstone

Tertiary sandstone

Cretaceous claystone

Cretaceous sandstone

Cretaceous shale

Cretaceous sandstone

Cretaceous conglomerate

Tertiary (?) mudstone

Sample Clay mineral || Sample Clay mineral

Soils

5

6

9

13

18b

22

23

28

29

30

35

37

38

52

59

61

62

I, K, ml-im

I, K, ml-im

I, K, ml-im

I, K, ml-im

I, K, ml-im

I, K, ml-im

I, K, ml-im

I, K, ml-im, p

P, K, i, ml-im

P, K, i, ml-im

P, I, K, ml-im

P, I, K, ml-im

P, K, I, ml-im

I, K, ml-im

I, K, ml-im, (p\

I, K, ml-im, (p)

I, K, ml-im

63

65

76

77

80

81

82

88

89

92

95

97

99

107

112

113

P, K, i

P, K, I, ml-im

K, I, ml-im

K, I, ml-im

I, K, ml-im

P, K, i, ml-im

P, K, i, ml-im

K, P, i, ml-im

I, K, ml-im

I, K, ml-im

I, K, ml-im

I, K, ml-im

I, K, ml-im

I, K, ml-im

I, K, ml-im

I, K, ml-im

Modern alluvium

4

7

17

18a

20

21

25

31

32

36

41

I, K, ml-im

I, K, ml-im

I, K, ml-im

I, K, ml-im

I, K, ml-im

I, K, ml-im

I, K, ml-im

I, K, ml-im, p

I, K, ml-im

I, K, ml-im, (p)

I, K, ml-im

49

50

51

54

57

66

86

87

93

94

98

P, I, K, ml-im

I K, ML-IM

I K, ML-IM

I K, ml-im

I K, ML-IM

I K, ml-im

K, I, ml-im

I, K, ML-IM

ML-IM, I, K

I, K, ML-IM

I, K, ML-IM

Modern dune sand

8

33

44

55

71

K, I, ml-im

I, P, K, ml-im

I, K, ml-im

I, K, ml-im

K, i, ml-im, (p)

100

105

106

672

674

I, K, ml-im

K, I, ml-im

K, I, ml-im

K, I, ML-IM

K, I, ML-IM

Quaternary(?) dune sand

15

19

69

I, K, ml-im

I, K, ml-im

P, K, I, ML-IM

111

114

I, K, ml-im

I, K, ml-im

Quaternary(?) alluvium

27

83

K, I, p, ml-im

K, I, ML-IM

84

101

K, I, ml-im

I, K, ml-im

Distribution of Red Sands

Eolian sands that show pronounced reddening in 

the direction of transport occur in two parts of 

western Libya. One is in the belt of arid steppe climate that extends inland for several tens of 

kilometres along the Mediterranean coast, west of 

the Gulf of Sidra (fig. 32). Here, sand is blown landward from the beach and piled into dunes which, 

through time, migrate further inland. The beach
68 A STUDY OF GLOBAL SAND SEAS

sands and dunes adjacent to the beach are not even 

slightly red, but the dunes become progressively 

redder inland, and within a few kilometres of the 

coast they have reddish hues ranging from 5YR to a 

maximum redness of about 2.SYR, values from 5 to 

7, and chromas from 4 to 8, as determined by comparisons with the Munsell Soil Color Chart (Munsell Color Co., 1954). The most commonly occurring 

colors are designated as "reddish yellow" and 

"yellowish red" on that chart.

A second region of red dunes is that occupied by 

the sand seas called Sajira1 AwbarT and Sahra' 

Marzuq in the intensely arid interior of the desert 

(figs. 31, 32). Most of the sand in these two dune 

fields has been transported from sources that lie 

several hundred kilometres to the northeast in the 

very arid coastal region south of the Gulf of Sidra. 

These sands, like those in the northern coastal 

region of western Libya, redden progressively in 

the direction of transport, but, because of the 

greater aridity of this region, the distance of 

transport required to achieve a comparable degree 

of redness is much greater here.

The full range of color change in the interior 

deposits was not studied because those sands were 

not traced to their source area. However, in the area 

between Waddan and Sabha (figs. 31, 32), which 

lies at the upwind end of the sampled area, the color of the sands range from about 8YR 7/4 (pink) to 

about 6.5YR 6/6 (reddish yellow), whereas near Al 

'Uwaynat, which lies near the downwind end of the 

southern arm of the §ahra AwbarT (fig. 32) the color 

is about 4YR 5/8 (yellowish red). The distance 

across which this amount of reddening occurs is 

nearly 700 km (435 mi), or about 10 times the distance necessary to achieve approximately the same 

degree of redness in the northern coastal region of 

western Libya.

Characteristics of the Pigment

WHEN SAMPLES of the stained dune sands 

rom both of the regions studied are examined 

under a binocular microscope, the pigment is seen 

to occur, in part, as extremely thin films which 

generally form complete coatings on grains and in 

part as thicker concentrations which lie within indentations on grains, where the material has been 

protected from abrasion. The latter material characteristically is the reddest. Moreover, fine and very 

fine grains commonly are more heavily stained and 

redder than are coarser grains.

The mineralogy, texture, and chemical composition of both the thin films and thicker concentrations of pigment were determined by combining Xray-diffraction techniques with scanning electron 

microscope (SEM) and energy-dispersive X-ray 

analysis. Representative samples of dunes showing 

different degrees of redness were treated in the 

following manner. Between 10 and 20 grams of 

sand were split from the bulk sample, and this portion was washed and treated in an ultrasonic 

cleaner until enough of the pigmenting material 

was available for X-ray analysis. Untreated portions of the bulk sample were examined under a 

binocular microscope; several grains which showed 

typical staining characteristics were selected from 

each sample, and the grains were mounted on SEM 

stubs.

After mounting the grains on stubs — but prior to 

coating them with a conductive film of gold and 

paladium — each grain was again examined under 

the binocular microscope, and a sketch was drawn, 

showing the distribution of concentrations of the 

pigmenting material. These sketches were used 

during the SEM examination as maps for locating 

areas on the grains that would be particularly suitable for detailed study. All of the mounted grains 

from each sample were then examined using a 

Cambridge Stereoscan SEM.3 One or more representative grains from each was photographed at 

magnifications ranging from about x 200 to about x 

11,000. Finally, using a Kevex X-ray energy 

spectrometer attached to the SEM, semiquantitative 

chemical analyses of the pigmenting material were 

made at locations that could be identified on the 

photomicrographs. Representative results are illustrated in figures 33 and 34 and 37 - 40.

Pigment in the thin films apparently is composed 

of amorphous ferric hydrate ("limonite") because, 

although energy-dispersive X-ray analyses show 

that they contain iron (fig. 33, trace 2), they show 

no evidence of crystallinity when viewed under the 

SEM at magnifications of x 50,000 and higher.

3 Trade names and company names are included for the benefit of the reader 

and do not imply endorsement of the product or company by the U.S. Geological 

Survey.
RED COLOR IN DUNE SAND 69

Moreover, few X-ray-diffraction analyses of concentrates of the pigmenting material reveal the presence of crystalline iron oxide minerals. Some of 

the red material concentrated in indentations on 

grains is composed entirely of essentially pure iron 

oxide (fig. 34), but most commonly it is composed 

of iron oxide stained platelets of clay minerals, the 

composition of which is confirmed by energy-dispersive X-ray analyses. Such analyses reveal that 

most of the platelets are aluminum silicates (figs. 

38 — 40), although some platelets are composed of 

pure silica (fig. 33). The clay-mineral and silicaplatelets occur in aggregates that have clastic textures similar to those displayed by clay 

mechanically infiltrated into sand (Crone, 1974, 

1975; Walker and Crone, 1974; Walker, 1976). For 

reasons explained later, such platelets are interpreted by the author to be dominantly of that 

origin.

X-ray analyses of concentrates of clayey material, removed from grains by using an ultrasonic 

cleaner, show that throughout Libya the clay 

minerals in the coatings are mixtures of dominantly 

kaolinite and illite, with subordinate amounts of 

mixed-layer illite-montmorillonite (table 8). X-ray 

analyses also show that only the reddest dune 

sands, such as those occurring near Al 'Uwaynat, at 

the downwind end of the Sahra' Awbaff (samples 

672 and 674), contain detectable hematite in the 

grain coatings. In the author's opinion this hematite 

represents iron oxide, which initially was precipitated as ferric hydrate and which upon aging either 

in place or during transport has converted to 

hematite in the manner discussed by Berner (1969) 

and by Langmuir (1971).

Sources of Iron

THE SOURCE OF IRON in the pigment cannot 

be determined unequivocally from available data. 

However, the fact that the redness of the dunes increases with age and distance of transport, coupled 

with the likelihood that source areas of the sands 

have not changed, suggests that the iron is derived 

internally from the dunes. Two likely sources are 

the iron-bearing accessory minerals within the 

sands and the clay minerals in the clay coatings.

Studies of heavy-mineral concentrates show that 

grains of iron-bearing minerals, such as augite, 

hornblende, epidote, ilmenite, and magnetite, are 

present in dunes throughout the area examined. 

Because these minerals are not in equilibrium with

meteoric water, they provide potentially important 

sources of iron in the pigment. That at least some of 

the more unstable of these minerals, such as augite 

and hornblende, have undergone alteration is indicated by the fact that grains of these materials commonly show evidence of pitting by dissolution (fig. 

35), and they commonly display cockscomblike terminations blunted by abrasion (fig. 36).

Regional comparisons of the heavy-mineral fractions show a noticeable increase in the degree of 

alteration of both augite and hornblende with distance of travel. For example, near the upwind end 

of the gahra' AwbarT, augite — the more unstable 

of these two silicates — typically is only weakly 

etched, and hornblende is essentially unaltered. In 

contrast, near Al 'Uwaynat, at the downwind end 

of that sand sea where dunes are the reddest, augite 

is nearly absent in the sands, and hornblende has 

become noticeably etched (fig. 35). These relationships support Morris' (1969) contention that grains 

of detrital iron-bearing minerals are important 

sources of iron for staining dune sands, even in 

very dry deserts.

Energy-dispersive X-ray analyses of clay coatings on representative sand grains in samples collected from dunes throughout the region, show that 

the clays characteristically are iron-bearing. Some 

of the iron occurs as limonitic coatings on the clay, 

but some also occurs within the lattices of the clay 

minerals because energy-dispersive X-ray analyses 

show that iron is present in unstained clay. Inasmuch as these clays are not authigenic, they 

probably are not in complete chemical equilibrium 

with meteoric water, and, hence, upon being 

repeatedly moistened by surface and interstitial 

waters, they likely release additional iron. The importance of iron-bearing clay minerals as potential 

sources of iron for iron oxide pigment in other 

desert sediments has been stressed previously 

(Walker and Honea, 1969; Walker, 1976).

Origin of Clay Coatings on 

EolianSand Grains

INASMUCH AS RED pigment commonly is 

associated with clay that partially coats desert sand 

grains, the origin of the coatings and the circumstances that allow them to be preserved on grains
70 A STUDY OF GLOBAL SAND SEAS

SCANNING ELECTRON MICROSCOPE (SEM) photomicrographs (A-Q of a coarse rounded quartz grain which, 

when viewed under the binocular microscope, was completely 

coated by a film of reddish-yellow pigment (5YR6/6 on Munsell 

Soil Color Chart, Munsell Color Co., 1954); however, the grain 

showed no discernible evidence of concentrations of pigment 

in indentations on the surface. Rectangle in A is area of B; that in 

B is area of C D, Energy-dispersive X-ray traces showing the elemental composition of the analyzed areas outlined in C (traces 1 

and 2). The photomicrographs reveal that the shallow indentation on the grain contains scattered platelets that were not visible under the binocular microscope. The elemental data indicate that the platelets are composed of silica and a small amount 

of iron (trace 1 in Q The platelets that have a clastic texture and 

appear to be sitting on the surface of the grain (for example, the 

analyzed platelet) are interpreted to be silica dust acquired during transport and derived from eolian abrasion of quartz sand 

grains. Some of the more firmly attached platelets may be chips 

which are spalling from the surface as proposed by Margolis and 

Krinsley (1971). The iron is interpreted to be iron oxide which 

coats the entire surface of the grain (trace 2 in Q, including the 

platelets (trace 1 in Q. Gold and paladium recorded in the 

traces are contained in the conductive coating applied for SEM 

examination. (Fig. 33.)

1

Al?-

Sample 674

D
RED COLOR IN DUNE SAND 71

SCANNING ELECTRON MICROSCOPE (SEM) photomicrographs (A-Q of a medium-sized subangular quartz grain 

which contains abundant red (4YR 5/6 on Munsell Soil Color 

Chart, Munsell Color Co., 1954) pigment concentrated in indentations on the grain surface. Rectangle in A is area of B; that in B 

is area of C D, Energy-dispersive X-ray traces showing the elemental composition of the pigmenting material in the analyzed 

area outlined within rectangle in C The photomicrographs 

reveal that the pigmenting material is composed of anhedral 

particles that are oriented parallel to the grain surface. The elemental data indicate that the particles are composed almost entirely of iron oxide. The particles are interpreted to be a poorly 

crystalline iron oxide mineral, possibly hematite. Gold and 

paladium recorded in the traces are contained in the conductive 

coating applied for SEM examination. (Fig. 34.)

Sample 674

D
72 A STUDY OF GLOBAL SAND SEAS

100

Sample 672

ETCHED HORNBLENDE GRAIN from 

modern dune near Al 'Uwaynat, Libya. (Fig. 

35.)

100 im

Sample 33

ETCHED AUGITE GRAIN from modern 

dune near As Saddadah, Libya. (Fig. 36.)

despite long distances of eolian transport needs explanation. In part, the coatings may be inherited 

from matrix clays in sandstones and other bedrock 

lithologies from which the sand grains are derived. 

However, three lines of evidence, when considered 

together, indicate that clay coatings commonly consist of airborne dust emplaced on sand grains by 

mechanical infiltration of dust particles into the 

dunes or into other surficial deposits from which 

sand grains of the dunes are derived. This method 

of acquiring clay coatings is similar to that proposed 

by Folk (1969) to account for the formation of clay 

coatings on sand grains in Australian dunes. 

The types of evidence are as follows:

1. Clay coatings are not present on sand grains of 

the beach from which coastal dune sands are 

derived, but they are common on grains in 

the dunes located a short distance inland 

from the beach. Thus, clay coatings must be 

acquired as the sand migrates inland.

2. Clay coatings on sand grains of dunes throughout the region characteristically are composed of aggregates of tiny platelets (figs. 

37-40) which display clastic textures that are 

similar to those produced experimentally by 

infiltrating clay-bearing water into sand 

(Crone, 1974, 1975). These textures, in turn, 

are similar to those produced naturally by 

clay which has been infiltrated into sand by 

influent seepage of surface water (Walker 

and Crone, 1974; Crone, 1975; Walker, 1976). 

Such similarities indicate that the clay is 

composed of mechanically infiltrated particles, and influent rainwater is the most logical agent to accomplish the infiltration.

3. The mineralogy of the clay in the coatings is 

similar to that expected of the airborne dust, 

suggesting that dust is the probable source of 

the clay. This latter point needs further explanation.

Time limitations precluded the establishment of 

stations in Libya for the systematic collection of airborne dust samples. The mineralogical composition 

of airborne dust was predicted, however, by analyzing the clay fraction of representative samples of 

the major types of potential source materials. The 

types and number of samples analyzed were 

bedrock (15), Quaternary (?) alluvium (4), Quaternary (?) dune sand (5), soils (33), modern alluvium
RED COLOR IN DUNE SAND 73

(22). These are compared with the clay in coatings 

on sand grains in the modern dunes.

The locations of analyzed samples are shown in 

figure 32. Results of these analyses (table 8) show 

that essentially all types of materials which are exposed to the wind and which could provide sources 

of clay contain the same varieties of clay minerals 

in roughly the same proportions. In all types of 

source materials — if palygorskite, a likely 

authigenic clay, is exluded — kaolinite and illite are 

the predominant clay minerals, almost without exception, and mixed-layer illite-montmorillonite is 

the principal subordinate clay mineral. The same 

varieties of clay minerals in roughly the same proportions occur in the coatings on sand grains in the 

modern dunes (table 8). These mineralogical 

similarities and the clastic texture of the clay 

strongly suggest that the clay coatings are composed of infiltrated dust derived ultimately from 

the bedrock.

To what extent clay minerals, other than 

palygorskite, have formed by processes of surface 

weathering is not known, but in view of the striking 

similarities between the clay mineralogy of the 

soils and that of the bedrock (table 8), it seems 

likely that clays in the soils also are derived mainly 

from the bedrock, not from weathering. Indeed, all 

available evidence leads to the conclusion that 

there has been no significant authigenesis of clay 

minerals except for the palygorskite.

The preceding interpretation readily explains the 

origin of kaolinite which occurs as a dominant clay 

mineral in the alkaline desert soils, as it cannot 

reasonably be expected to have formed in place 

there. Furthermore, SEM studies of the soils show 

that clay in the argilic "B" horizons characteristically has a clastic texture similar to that 

shown in figure 37, and this texture is indicative of 

mechanically infiltrated material. The importance 

of infiltrated dust on the formation of desert soils 

has been stressed previously by Yaalon and Ganor 

(1973). The conclusion is reached therefore, that all 

the clay in all types of the surficial deposits has 

been mechanically infiltrated into the sediments. 

This may have been accomplished either by infiltration of airborne dust by occasional rain, as 

with dunes and soils, or by infiltration of clay suspended in the water of intermittent influent 

streams, as with alluvial deposits.

Presumably, part of the clay-size platelets of 

silica that occur on some sand grains (fig. 33) also 

are derived from airborne dust, but they consist of 

particles which have been abraded from quartz 

grains during eolian transport, rather than eroded 

from the bedrock. Some of the silica platelets may 

also represent chips that are in the process of spalling from the surface of the grains (fig. 33C) in the 

manner proposed by Margolis and Krinsley (1971, 

p. 3397).

The mechanism for producing clay coatings on 

sand grains by mechanical infiltration probably 

operates throughout the desert, but it is most effective in areas where rainfall is greatest because, in 

such areas, water penetrates more frequently and 

deeper into the deposits. Consequently, the amount 

of clay infiltrated into the surficial deposits is 

greatest and the rate of formation of clay coatings 

on the included sand grains is most rapid in the 

region of relatively high rainfall near the coast. The 

characteristic occurrence of mechanically infiltrated clay matrix in the soils and temporarily 

stabilized dunes in the coastal region (fig. 37) supports this interpretation.

Although the prevailing winds are onshore from 

the Mediterranean Sea, the airborne dust even in 

the coastal region is derived principally from North 

African sources, not from sources across the sea. 

The winter westerlies and other winds that diverge 

from the prevailing direction have ample energy to 

erode dust from local sources. The transportation of 

dust from the central Sahara northward into Europe 

and east-northeastward into the Middle East is well 

documented (Yaalon and Ganor, 1973).

The infiltrated clayey matrix tends to bind 

together the framework grains of initially unconsolidated surficial deposits; thus, the clay helps, at 

least temporarily, to anchor the deposits. However, 

owing in part to the friable nature of the surficial 

deposits and in part to the paucity of vegetation to 

anchor them, their stabilization in this dry climate 

is only temporary. Subsequent erosion releases the 

clay-coated sand grains to eolian transport.

As clay-coated grains are blown about by the 

wind, the clay is removed from exposed surfaces of 

the grains by abrasion, but it tends to remain in indentations, where it is protected from abrasion. 

Such clay-coated indentations are common on 

grains of all sizes but are most abundant on small
74 A STUDY OF GLOBAL SAND SEAS

SCANNING ELECTRON MICROSCOPE (SEM) photomicrographs (A-Q of matrix-rich sand collected 2 metres 

below the surface of a weakly stabilized red dune in the northern coastal region near Mi^ratah. The color of the clay as determined under a binocular microscope is reddish yellow (SYR 6/6 

on Munsell Soil Color Chart, Munsell Color Co., 1954). Rectangle in A is area of B; that in B is area of C D, Energy-dispersive 

X-ray traces showing the elemental composition of the matrix 

clay in the analyzed area outlined within rectangle in C The 

photomicrographs reveal that the matrix is composed of an aggregate of clay-size platelets (Q. The elemental data indicate 

that the platelets are composed mainly of aluminum silicates 

(clay minerals) and iron. The matrix is interpreted to be composed of airborne dust that has been mechanically infiltrated 

into the dune sand and has become reddened by iron oxide 

stain subsequent to infiltration. Gold and paladium recorded in 

the trace are contained in the conductive coating applied for 

SEM examination. (Fig. 37)

Sample 114

D
RED COLOR IN DUNE SAND 75

SCANNING ELECTRON MICROSCOPE (SEM) photomicrographs (A— Q of a fine-grained subrounded quartz grain 

which contains abundant light-reddish-brown (SYR 6/4 on 

Munsell Soil Color Chart, Munsell Color Co., 1954) pigment 

concentrated in indentations. Rectangle in A is area of 6; that in 

6 is area of C D, Energy-dispersive X-ray traces showing the elemental composition of the pigmenting material in the analyzed 

area within rectangle C The photomicrographs reveal that the 

pigment is composed of aggregates of clay-size particles. The 

elemental data indicate that the particles are composed mainly 

of aluminum silicates (clay minerals) and iron. The sample from 

which this grain was selected was collected from the surface of 

a modern red dune about 100 km (62 mi) inland from the coast 

near Tripoli. The grain is typical of clay-coated sand grains 

which comprise a major portion of the dune. The sand in the 

dune has been reworked from nearby matrix-rich soils and dune 

sands that have characteristics similar to those shown in figure 

37. The pigmenting material illustrated here is interpreted as 

mechanically infiltrated matrix clay which is analogous to but 

coarser than that shown in figure 37 and which during eolian 

transport has been retained in indentations on grains where it is 

protected from abrasion. Gold and paladium recorded in the 

trace are contained in the conductive coating applied for SEM 

examination. (Fig. 38.)

Sample 8

D
76 A STUDY OF GLOBAL SAND SEAS

SCANNING ELECTRON MICROSCOPE (SEM) photomicrographs (A—Q of a fine-grained subangular quartz grain 

collected from a pink (8YR 7/4 on Munsell Soil Color Chart, 

Munsell Color Co., 1954) modern dune near Qaryat Abu Nujaym. Rectangle in A is area of B; that in B is area of C D, Energydispersive X-ray traces showing the elemental composition of 

the pigmenting material in the analyzed area within rectangle in 

C. This grain is typical of fine and very fine sand in dunes 

throughout the interior of the desert. Note low degree of roundness and abundance of protected indentations containing concentrations of clay platelets analogous to those illustrated in 

figure 38. Gold and paladium recorded in the trace are contained in the conductive coating applied for SEM examination. 

(Fig. 39.)

Sample 44
RED COLOR IN DUNE SAND 77

SCANNING ELECTRON MICROSCOPE (SEM) photomicrographs (A-Q of a medium-grained rounded quartz grain 

collected from a red (SYR 5/6 on Munsell Soil Color Chart, Munsell Color Co., 1954) dune near Al 'Uwaynat. Rectangle in A is 

area of 6; that in 6 is area of C D, Energy-dispersive X-ray trace 

showing the elemental composition of the pigmenting material 

in the analyzed area within rectangle C The photomicrographs, 

coupled with the elemental data, show that despite the rounded 

character of the grain, iron oxide stained clay platelets are abundant in shallow indentations. Such concentrations of clay and 

iron oxide are common on the surfaces of rounded and wellrounded sand grains throughout the desert. Gold and paladium 

recorded in the trace are contained in the conductive coating 

applied for SEM examination (Fig. 40.)

Sample 674

D
78 A STUDY OF GLOBAL SAND SEAS

grains, such as those in the fine and very fine sand 

sizes. These small grains show little evidence of 

abrasion despite long distances of eolian transport. 

Characteristically, they tend to have angular to 

subangular shapes and to retain their original surface irregularities. Such observations support the 

experimental data of Kuenen (1960), who found 

that eolian abrasion decreases rapidly with 

decrease in grain size and becomes insignificant for 

sizes below 150 yum. A typical grain of fine sand is 

shown in figure 39. A typical coarser grain 

(medium sand) is shown in figure 40.

The development of coatings of infiltrated clay 

on sand grains of the Libyan dunes seems to be particularly favored by the readily available source of 

clay in the sedimentary rocks that dominate the 

bedrock source areas. Erosion of these rocks by 

wind, rain, and ephemeral streams provides an 

unending source of clay for airborne dust. In addition, the developing of the coatings is enhanced by 

prolonged residence of the sand grains in surficial 

deposits in the coastal steppe area, where conditions are especially favorable for the mechanical infiltration of clay. Sand grains that bypass this zone 

or migrate across it quickly are likely to reach the 

desert interior without having acquired the clay 

coatings, and acquisition of the coatings is much 

slower once the grains reach the very arid interior.

Unstained grains occur in all of the active dunes 

that were investigated in this study, both in the 

coastal region and in the interior of the desert, but 

in both regions they are progressively less common 

with increased distance of transport. This distribution suggests that the coatings are acquired during 

migration of the dunes, even in the intensely arid 

regions.

The mechanisms proposed by Folk (1969) to explain the acquisition of clay coating on sand grains 

in the Simpson Desert seems thoroughly adequate 

to accomplish the task here. That is, during calm 

periods between wind storms, airborne dust settles 

onto the dune surfaces where it adheres to sand 

grains, particularly if moisture from dew or rain is 

present. Moreover, during periods of rainfall additional dust is washed from the atmosphere and carried into the dunes by influent rain, where 

ultimately it also settles onto the surfaces of sand 

grains.

The processes that introduce clay presumably 

operate over and over again as the eolian sands 

migrate and the dune fields accumulate. Therefore, 

deep infiltration of the dust into the deposit is not 

required for the formation of coatings, and the coatings are acquired even where rainfall is negligible.

Conditions Favoring

Formation of Iron Oxide

Pigment

NO DATA ARE AVAILABLE concerning 

chemistry of the water in contact with the sand 

grains (for example, dew at the ground surface, 

pellicular films of water on grains within the 

vadose zone, and ground water below the water table), but the water can be assumed with confidence 

to be oxidizing and alkaline and, therefore, to lie in 

the Eh-pH stability field of ferric hydrates and 

hematite (Garrels and Christ, 1965, fig. 7.6). The 

paucity of vegetation — indeed, the complete lack 

of it throughout most of the desert —and the lack of 

any other reducing agents provide assurance that 

meteoric water, upon infiltration into the sand, retains dissolved oxygen obtained from the atmosphere. Accordingly, an oxidizing environment 

seems a certainty.

Moreover, the widespread occurrence of carbonate, gypsum, and palygorskite in surficial deposits 

of the desert indicates an alkaline weathering environment. Therefore, iron released by alteration of 

any of the above-mentioned iron-bearing minerals, 

including the clay minerals in clay coatings, precipitates as iron oxide, probably initially as 

amorphous ferric hydrate and (or) finely crystalline 

goethite, both of which are metastable and convert 

to hematite upon aging (Berner, 1969; Langmuir, 

1971).

Stated another way, hot desert climates, such as 

those in north Africa, are ideally suited for the formation and preservation of iron oxide pigments. Indeed, precursor oxides of hematite and, ultimately, 

hematite should be expected to occur as stains in 

desert deposits wherever and whenever moisture, 

even in seemingly negligible amounts, comes into
RED COLOR IN DUNE SAND 79

contact with any kind of iron-bearing minerals that 

are not in equilibrium with the water.

Factors Affecting Regional and 

Local Variations in Redness

REDDENING ACCOMPANIES aging of the initially precipitated precursor oxides of hematite; 

consequently, dunes tend to redden with increasing 

age and distance of transport. If aging of the ferric 

hydrates were the only factor involved in reddening, the intensity of redness of dunes would be a 

measure of their age, and their color probably could 

be used as a basis for correlation. The evidence that 

has been presented in this chapter, however, shows 

that redness also is affected by a variety of other 

factors which are not uniform everywhere. Consequently, local or regional variations in numerous 

environmental factors can be expected to cause 

variations in the color of the dunes. Following is a 

list summarizing these factors, many of them interrelated, and their effects on the color.

1. Availability of unstable iron-bearing 

minerals in source rocks.—Unstable iron-bearing 

minerals, particularly ferromagnesian silicates, 

such as augite and hornblende, are perhaps the 

most important sources of iron for pigment in dune 

sands. If other conditions are equal, dune sands 

derived from source rocks rich in these minerals 

probably will redden faster than sands derived from 

rocks deficient in these minerals. This point was 

stressed by Norris (1969).

The effect of differences in source-rock 

mineralogy may explain why the §ahra' AwbarT 

and §a^r£f Marzuq are strikingly redder than the 

Sahra" Rabyanah and Sartr Tibasti (fig. 31), despite 

the fact that sand in the Sajira" Rabyanah and SarTr 

Tibasti has travelled at least as far as that in the 

other deposits. The §a|ira' Awbari and §ahra 

Marzuq lie downwind from volcanic rocks exposed 

in the highlands of Al Haruj al Asway and Jabal as 

Sawda' (figs. 31, 32), and both deposits almost certainly receive contributions of sand from these 

rocks. The ^ajira' Rabyanah and SarTr Tibasti, on 

the other hand, have no comparable source of 

unstable iron-bearing minerals exposed upwind.

2. Amount of clay retained on sand grains. —

Inasmuch as pigment in the dunes is carried in part 

by clay coatings on sand grains, dunes tend to 

become redder with the increase in the amount of 

clay that is acquired and retained on individual 

grains. Hence, a significant factor in determining 

the redness of dunes is the percentage of sand 

grains that have clay coatings, and also the percentage of the surface area of these grains that is 

coated.

The modern dune from which the sand grain in 

figure 38 was collected is strikingly red because it is 

composed mostly of grains which, like the one in 

the photograph, retain extensive coatings of stained 

clay. Sand in this dune was derived, in part, from 

nearby red soils of the desert type described earlier, 

and in part from older weakly stabilized red dunes, 

both of which contain abundant infiltrated clay 

matrix similar to that in the example shown in 

figure 37. Owing to the relatively short distance of 

transport, a large amount of clay is retained on the 

grains. Analogous red dunes of modern or nearmodern age are common in the coastal region of 

northern Libya.

3. Amount of moisture available.—Water 

plays several important roles that enhance the reddening process: (a) It provides the medium for 

chemical hydrolysis of iron-bearing minerals (for 

example, ferromagnesian silicates and clay 

minerals in the grain coatings) and is responsible 

for the release of iron, which precipiates as oxide 

stain; (b) it provides a mechanism for mechanical 

infiltration of airborne clay into dune sands and 

into other surficial deposits from which dune sands 

are derived, thereby increasing the amount of clay 

available for coating and staining sand grains; (c) it 

assists in the growth of vegetation, which in turn 

tends to stabilize dunes and helps protect the desert 

soils from erosion, thus keeping grains longer in the 

environment where conditions are most favorable 

for reddening. Reddening of dune sands is much 

faster in the coastal region than in the interior of 

the desert because of the increased amount of 

moisture along the coast. The moisture may be rain, 

dew, or ground water.

4. Time.—Time is required for the alteration of 

both the ferromagnesian silicate minerals and the 

clay minerals in grain coatings. Together, they pro-
80 A STUDY OF GLOBAL SAND SEAS

vide the major sources of iron in the pigment. 

Because these alterations are continuous and 

because reddening normally accompanies aging of 

iron oxides, dunes throughout western Libya have 

tended to become increasingly red with age. The 

time required to achieve a specific degree of redness, however, is decreased where the amount of 

moisture is increased, so reddening is faster in the 

steppe region along the coast than in the intensely 

arid interior of the desert.

5. Grain size and grain shape.—During eolian 

transport coarse grains are abraded at a faster rate 

and to a greater degree than are fine grains; hence, 

they become more rounded and the indentations 

caused by original irregularities in grain shape tend 

to be reduced in size and number. The coatings of 

iron oxide and iron oxide stained clay, which can 

persist only if protected from abrasion, are 

therefore less common on the surfaces of coarse 

sand than on fine sand. The finer grains, on the 

other hand, because they abrade very slowly, or not 

at all (Kuenen, 1960), tend to retain original irregularities, and iron oxide stain once acquired 

tends to persist. Fine sand grains in dunes, 

therefore, normally are coated with more clay, contain more pigment, and are redder than are the 

coarse grains.

The effect of grain size on color is striking in 

places where modern dunes show two distinctly 

different colors of sand. As an illustration, dunes 

located near As Saddadah (fig. 32) were examined 

by the author after a day of particularly strong 

winds. Surfaces of the slipfaces on the dunes were 

covered by a veneer of dominantly medium sand 

which had a color of pink to reddish yellow (7.5YR 

7/5, Munsell Soil Color Chart, Munsell Color Co., 

1954) and had been deposited by the strong winds 

of the previous day. Exposed in places on these 

slipfaces, beneath the veneer of medium sand, were 

distinctly redder (4YR 6/8), fine to very fine sands 

that had been deposited earlier by winds of lesser 

velocity. A likely analogous example has been illustrated by Furst (1970, pi. 5) in a color photograph 

that clearly shows the dual color of the sand in 

some dunes in the Sahra" AwbarT. However, the 

two different colors are attributed by Furst to 

different ages of the sands rather than to different 

grains sizes. Other analogous relationships between 

color and grain size in dune sands have been recognized by Folk (1976), in the Simpson Desert in 

Australia.

6. Distance of transport.—This factor has the 

same effect as time. Increased distance of travel 

normally increases the time available for alterations that cause reddening; hence, reddening increases with distance of travel. One might expect 

the pigment to be removed from sand grains by erosion during prolonged eolian transport, but this is 

not the case, as demonstrated by the evidence presented already.

Two opposing and unequal processes act upon 

grains during their transport: (1) abrasion when the 

grains are in transit, and (2) accumulation of pigment when the grains are at rest. Abrasion is much 

more effective with coarse grains than with fine, 

because coarse grains, owing to greater mass, 

abrade more rapidly. Nevertheless, pigment characteristically is preserved even on coarse grains in 

pits, where it is protected from abrasion, and it 

commonly occurs as films that envelop coarse 

grains. Accumulation of pigment, on the other 

hand, is the dominant process with finer grains 

because, owing to their small mass, they abrade 

slowly, if at all.

Fine and very fine grains, which are the predominant sizes in the dunes studied in this investigation, 

tend to accumulate more pigment on their surfaces 

when they are at rest than they lose by abrasion 

when they are in transit. The accumulation of pigment in this manner, coupled with the fact that it 

reddens upon aging, causes the dunes to become increasingly redder with distance of transport. As is 

true of time, the distance required to achieve a 

specific degree of redness is shorter if the amount 

of moisture is increased. Consequently, in the intensely arid interior of the desert, the distance required to achieve a certain degree of redness is 

many times greater than it is in the moister coastal 

region.

7. Types of clay minerals contained in coatings on sand grains.—Iron is carried by clay 

minerals as a constituent of the clay-mineral lattice, 

as well as in coatings of iron oxides on the surfaces 

of clay particles (Carroll, 1958). Such iron can be 

released by weathering processes if the clay 

minerals are not in equilibrium with the meteoric 

water with which they come in contact. Because 

the Eh and pH of interstitial moisture are high in 

the desert environment, iron released by such 

weathering should precipitate almost immediately 

and increase the amount of iron oxide on the surface of clay particles. The amount of iron released
RED COLOR IN DUNE SAND 81

by such weathering depends in part on the type of 

clay minerals that are present in the coatings, 

because clays are not equally capable of carrying 

iron as a constituent of the crystal lattice (Carroll, 

1958, table 1).

Among the clays occurring as coatings on sand 

grains in the dunes of western Libya, iron is likely 

to be more abundant in illite and mixed-layer illitemontmorillonite than in kaolinite. Grains with 

coatings containing high percentages of illite and 

(or) mixed-layer illite-montmorillonite, therefore, 

probably have greater potential for increasing redness faster than do those with low percentages of 

these minerals. The effect of such differences, 

however, may be insignificant in the sands studied 

in this investigation because the mixtures of clay 

minerals in the coatings are virtually the same 

throughout the region. In other parts of the Sahara 

or in other deserts, differences in the types of clay 

minerals occurring in clay coatings might conceivably make significant differences in the rate at 

which reddening occurs.

8. Percentage of sand grains derived from 

older red beds.—Red beds of Mesozoic age crop out 

locally in western Libya and red sand grains that 

apparently have been reworked from these deposits 

commonly can be identified in the dunes. These 

grains, in places, contribute in a minor way to the 

color of the dunes, but the author saw no red dunes 

in Libya that obviously owed their color mainly to

concentrations of such grains. If such dunes occur 

there, they have only local significance. Grains of 

sand which have been reworked from the Mesozoic 

red beds usually can be distinguished readily from 

grains which have developed red pigment in the 

manner described earlier. For example, the 

reworked grains normally are much redder than the 

pigments forming today. They have hues ranging 

from 10R to 7.5R on the Munsell Soil Color Chart 

(Munsell Color Co., 1954) compared with hues of 

only 5YR to about 3YR in the younger pigments.

Most reworked sand includes rock fragments of 

red sandstone, red siltstone, and (or) red shale, all 

of which contain matrix with dark-red color, which 

attests to the derivation of the grains from red beds. 

Moreover, the red pigment in reworked quartz 

grains commonly penetrates the interior of the 

grains along incipient fractures and, hence, cannot 

easily be removed completely when the grains are 

treated with reducing agents. In contrast, pigments 

that are forming today are limited to the surfaces of 

grains, and they are easily and quickly removed by 

reducing agents. Although they are considered 

unimportant here, red sands that are reworked 

from older red beds may play important roles, at 

least locally, in producing red dunes elsewhere. 

Such dunes, in contrast to those discussed here, 

should show a decrease in redness with distance of 

transport away from the source of the sand because 

of dilution by non-red sands from other sources.

A STUDY OF GLOBAL SAND SEAS

SEDIMENTARY STRUCTURES IN DUNES

Chapter E

By EDWIN D. McKEE

With sections on THE LAGOA DUNE FIELD, BRAZIL

By JOAO J. BIGARELLA 4

•"Geological Institute, Federal University of Parana, Brazil

Contents

Summary of conclusions 

Introduction ..........

Page 

87

87

Sedimentary structures common to most dunes ..... 39

Sedimentary structures characteristic of certain dune

types ....................................... 89

Barchan and barchanoid ridge ................. 89

Transverse ................................... 93

Blowout ................. ................... 94

Parabolic..................................... 94

Retention ridges ............................... 96

Dome ........................................ 98

Linear ........................................ 102

Reversing ............................ ...... 103

Star .......................................... 106

Sedimentary structures of interdune areas ... ...... 107

Deformational structures in dunes ................... in

Structural features at Lagoa dune field, Brazil,

by Joab J. Bigarella ........................ 114

Parabolic dunes ............................ , 114

Method of study .. .......... ............. 114

Cross-stratification ........ ........... 114

Nose area ............................ .... 114

Crest area .......................... .... 118

Arms ..................... ............... 119

Deformation ............................. 121

Interdune areas among parabolic dunes ......... a22

Interdune areas among reversing dunes ........... 123

Dissipation of dunes, Lagoa, Brazil, by Joao ]. Bigarella I 24 

General features and environment of dune dissipation .............................. ........ 124

Processes, structures, and soil formation .......... 127

Dunes .................................... 127

Interdune areas ............................ 130

Deformation results of dune dissipation .......... 130

83
84 A STUDY OF GLOBAL SAND SEAS

Illustrations

Page 

FIGURE 41. Photographs of sand avalanching down dune slipface, White Sands National

Monument, New Mexico, U.S.A. ..................................... 88

42. Cross sections of barchan dune showing structure ....................... 90

43-45. White Sands National Monument, New Mexico, U.S.A.:

43. Photograph showing series of steeply dipping cross-strata forming

tabular-planar sets in barchanoid ridge ......................... 91

44. Cross sections of barchanoid ridge dune ......................... 91

45. Photograph showing beveled remnant of barchan dunes in interdune

area ....................................................... 91

46. Cross sections and plan view of barchanoid ridge dune, Killpecker dune field,

Wyoming, U.S.A. ................................................... 92

47. Photograph showing barchanoid ridge dunes and interdunes, White Sands National Monument, New Mexico, U.S.A. ................................ 92

48. Cross sections of two transverse dunes in the United States ............... 93

49. Photographs of blowout dunes on shore of Lake Michigan and in California,

U.S.A. ............................................................ 94

50. Photographs showing parabolic dunes, White Sands National Monument, New

Mexico, U.S.A. ..................................................... 95

51. Sketched sections through a parabolic dune, White Sands National Monument,

New Mexico, U.S.A. ................................................ 96

52. Sketch of trench wall on nose of parabolic dune, Killpecker dune field, Wyoming, U.S.A. ........................................................ 97

53. Cross sections of retention dune showing details of stratification, Jardim Sao

Pedro, Praia do Leste, Parana, Brazil................................... 98

54. Stereonets for three sections showing angle and direction of dip on foresets of

retention ridge, Guairamar, Parana, Brazil .............................. 98

55. Photograph showing trench through dome dune, White Sands National Monument, New Mexico, U.S.A. ........................................... 99

56. Cross section of dome dune, White Sands National Monument, New Mexico,

U.S.A. ............................................................. 100

57. Cross sections of dome dune, Killpecker dune field, Wyoming, U.S.A. ...... 101

58. Cross sections of coastal dome dune showing characteristic stratification, Praia

do Leste, Parana, Brazil .............................................. 102

59. Aerial photograph of seif or linear dunes, north of Sebha, Libya ............ 102

60. Sketch of hypothetical section, showing structure of seif dune ............. 103

61. Cross section of seif dune near Sebha, Libya, based on series of test pits .... 104

62. Aerial photographs of reversing dunes, Great Sand Dunes National Monument,

Colorado, U.S.A. ................................................... 105

63. Drawing showing structure in reversing dune, Great Sand Dunes National

Monument, Colorado, U.S.A. ........................................ 105

64. Photograph of trench in dune parallel to dominant wind direction, White Sands 

National Monument, New Mexico, U.S.A., illustrating effects of wind reversal 

during winter season ................................................ 106

65. Aerial photograph of star dunes, southeast of Zalim, Saudi Arabia .......... 107

66. Photograph showing steeply dipping cross-strata in trench at crest of high star

dune, southeast of Zalim, Saudi Arabia ................................ 107

67. Photograph showing star dunes along ridges of linear dunes, Gobabeb, SouthWest Africa ........................................................ 108

68- 72. Photographs at White Sands National Monument, New Mexico, U.S.A., showing:

68. Interdune area ............................................... 1°9

69. Beveled windward surface of transverse dune with truncation of leeside foresets ................................................ 110

70. Beveled remnant of barchan dunes in interdune area .............. HO

71. Beveled remnant of transverse dune in interdune area ............. HO

72. Horizontal and irregularly bedded strata in interdune area between

barchanoid ridges ........................................... Ill
SEDIMENTARY STRUCTURES IN DUNES 85

Page

FIGURE 73. Block diagrams and photograph of interdune structures between seif dunes,

northeast of Sebha, Libya ............................................ m

74. Photograph showing interdune surface among star dunes, Namib Desert,

South-West Africa .................................................. 112

75. Sketches showing principal types of deformation structures in avalanche

deposits of dunes .................................................. H3

76. Map showing location of Lagoa dune field, llha de Santa Catarina, Brazil .... 115 

77-86. Parabolic dune, Lagoa dune field, llha de Santa Catarina, Brazil:

77. Cross sections, plan view, and profiles ........................... 116

78. Rose diagrams of cross-strata dip directions representing principal parts

of parabolic dune and interdune area .......................... 119

79. Rose diagrams of attitude of cross-strata deposited in an earlier dune

crest and in the nose of a parabolic dune ...................... 123

80. Outcropping laminae exposed on beveled surface in interior of

parabolic dune .............................................. 124

81. Deformational structures observed in eastern arm of dune ......... 125

82. Photographs of internal structures ............................... 126

83. Diagrams showing stratification in pits along east-west line in interdune area between arms of dune ............................. 128

84. Diagrams showing stratification in pits along north-south line of interdune area between arms of dune ............................. 129

85. Photographs showing structures of interdune area between arms of

large dune .................................................. 129

86. Rose diagram showing cross-strata dip directions, interdune area ... 130

87. Diagrams showing reversing dune and interdune structures, Lagoa dune field,

llha de Santa Catarina, Brazil ......................................... 131

88. Map showing dissipation ramp leading down from Joaquina Hill to Lagoa dune

field, llha de Santa Catarina, Brazil .................................... 132

89. Sketches showing contorted wavy pattern separating individual sand-flow

layers developed during dissipation processes ......................... 133

90. Schematic cross sections illustrating features resulting from dissipation conditions .............................................................. 134

Tables

Page 

TABLE 9. Classification of principal dune types according to number of slipfaces and to

form .............................................................. 89

10-13. Various data for a parabolic dune, Lagoa dune field, Brazil:

10. Frequency of dip-direction intervals for cross-strata ............... 120

11. Directions and degree of dip for cross-strata ...................... 120

12. Attitude of cross-strata sets in trench F .......................... 121

13. Attitude of cross-strata sets in trench G .......................... 122

SEDIMENTARY STRUCTURES IN DUNES 87

Summary of Conclusions

I

EDIMENTARY STRUCTURES in dunes con 

sist of cross-stratification and of minor surface 

features, such as ripple marks and rain pits. Penecontemporaneous deformational features, including slump marks, also are present in a wide variety 

of forms. Interdune deposits differ from dunes in 

composition and texture, as well as in structure. 

This chapter is devoted largely to the description 

and analysis of the cross-strata that are characteristic of the various dune types. These structures 

provide the record of dune development, the means 

of recognizing and identifying dune types in the 

subsurface and in ancient rocks, and important controls of fluid migration and accumulation.

The study of dune cross-strata is still in a pioneer 

state and much more work must be done before 

meaningful generalizations can be made for many 

varieties of dunes. Most of the work done so far has 

consisted of a direct approach in which trenches or 

pits have been dug in dunes, exposing three-dimensional views of cross-strata. Additional studies 

have consisted of making statistical analyses of 

foreset dip directions, the vectors of which furnish 

information on the direction or directions of sand 

transport and the type of dune represented.

A structural classification based in part on the 

number of slipfaces, as represented by the principal 

directions of high-angle foreset planes, is useful. 

Thus, dunes having slipfaces inclined in one direction, two directions, or many directions are recognized, in addition to sheet sands and stringers and 

interdune deposits that have no slipfaces. Interdune 

deposits typically have flat or irregular stratification.

Descriptions of dune cross-strata are concerned 

primarily with the bounding surfaces of sets and 

the foreset planes within these sets. The crossstrata are mostly of two basic types — tabular 

planar and wedge planar. Trough-type cross-strata 

are rare in those dunes that have been examined internally. Although there are many exceptions, 

high-angle and large-scale foreset planes are typical 

of dune structures in general. The spread and pattern of dip directions of foresets give valuble information on dune types. Some types of dunes also can 

be differentiated by such features as the upward or

downward concavity of laminae, the abundance of 

scour troughs, and the horizontality of apparent 

dips normal to wind direction.

Introduction

THE PRINCIPAL FACTORS that control dune 

development and are therefore responsible for dune 

form are an adequate source of sand and wind of 

sufficient strength and duration to transport and 

deposit it. The geomorphic form assumed by an accumulating sand mass is determined primarily by 

the direction and strength of the responsible wind 

but may be influenced locally by barriers or deflecting factors, such as bedrock, vegetation, water, or 

other sand masses. The internal structure or crossstratification within each dune is a record of its 

depositional history.

Development of dune structures, as described by 

Bagnold (1941, p. 37), involves two principal processes: (1) transport of sand particles up the gentle 

windward (stoss) slope of the dune by saltation, or 

bouncing, of grains; and (2) avalanching of sand 

down the slipface on the steep lee side (fig. 41) 

either by slumping (mass movement) or by grain 

flowage. Where wind is strong, some sand commonly is carried outward from the dune crest and 

settles directly from suspension.

Sedimentary structures in eolian dunes commonly consist of sets of medium- to large-scale 

foresets that dip downwind and are separated by 

bounding surfaces that are horizontal or inclined at 

low angles. An exception to this basic pattern of 

cross-stratification develops where the available 

sand load exceeds the amount of sand that the wind 

can move up a dune slope, thereby causing deposition of low-angle strata dipping to windward. Other 

exceptions develop when the wind is unusually 

strong or changes direction, thus introducing partial 

erosion of earlier deposits to form either troughs or 

beveled surfaces that are subsequently buried and 

form part of the dune record.

Distinctive dune forms have been correlated with 

genetic factors by many students of sand seas, and 

numerous classifications of dune patterns (chapter 

J, tables 26 -32) have resulted. A common method 

of subdividing dune forms is to recognize the 

characteristic shapes attributed to the direction or
88 A STUDY OF GLOBAL SAND SEAS

AVALANCHINC SAND BY SLUMPING and grain flowage down 

slipface of dunes, White Sands National Monument, New Mexico, U.S.A. A, Small blocks of weakly cohesive sand formed 

from damp crust in upper part of slump masses. Length of base 

of ripple is 6 inches (15 cm). B, Curving crest of barchanoid

dune delineated by top of avalanching sand. Ripple length in 

lower left is 4 inches (10 cm). C, Series of slumps partially burying ripple-marked slipface. Knife handle is 6 inches (15 cm) 

long. D, Scoop surface where slump mass broke loose near top 

of slipface on transverse dune. (Fig. 41.)

directions of the dominant wind or winds involved 

(table 9). Those dunes that are formed by a prevailing wind (or a single dominant wind) include types 

commonly referred to as barchan, barchanoid ridge, 

transverse, dome-shaped, and some parabolic. 

Dunes attributed to bidirectional winds may form 

linear ridges, locally known as longitudinal dunes 

or seif dunes, where the winds converge at low 

angles, or they may form reversing dunes if winds 

blow from nearly opposite directions. Where winds 

are shifting around the compass they form star

dunes with three, four, or more arms extending outward from a central high point.

Although all eolian dunes are primarily controlled by wind activity and therefore share many 

structural features, some distinctive and probably 

unique structures characterize each type. The value 

of recognizing such distinguishing features should 

be apparent, for they make possible the interpretation of genesis and an understanding of subsurface 

trends in various sand bodies. Whether the sand 

has advanced in a constant direction to form a sheet
SEDIMENTARY STRUCTURES IN DUNES 89

TABLE 9. — Classification of principal dune types according to form and to number of

slipfaces

Number of slipfaces

None 

(no mound)

Sheet. 

Stringer. 

Climbing. 

Falling.

None 

(mound)

Dome.1

One

Barchan. 

Barchan ridge. 

Transverse ridge. 

Retention ridge.

Two

Linear (seif or 

longitudinal). 

Reversing.

Multiple

Star. 

Blowout. 

Parabolic.2

1 Internal structure may show buried foresets.

2 May have only one slipface developed.

DUNE TYPES

Simple: Dunes in the forms shown above.

Varieties: Dunes having differences in details of topographic form. 

Compound: Dunes in which two or more of the same type are superimposed. 

Complex: Dunes having two or more types combined.

or has built mostly vertically into a thick lens; 

whether it has advanced in one or in more than one 

direction; and whether the accretion of additional 

sediment has been rapid or slow, therefore resulting in relatively pure sand or in much-contaminated sand — these are questions that may be 

answered by structural analysis.

Dunes that have been studied in detail from the 

standpoint of structure are relatively few, but 

trenching and dissection have been undertaken in 

the United States at White Sands National Monument in New Mexico, at Great Sand Dunes National 

Monument in Colorado, and at Killpecker dune 

field in Wyoming. Similar studies have been made 

in Libya, in Saudi Arabia, and at several localities in 

Brazil. Some investigations have been made in solitary dunes, others in selected parts of large composite dunes, where extrapolation was necessary to 

reveal the complete structure. Many more studies 

of certain dune types in various geographical situations are needed before generalizations can be 

made with complete confidence, but some features 

seem very definitely established already.

Sedimentary Structures 

Common to Most Dunes

THE FOLLOWING STRUCTURES, on the basis

of our limited present knowledge, are considered to

be common to most types of eolian dunes:

1. Sets of medium- to large-scale cross-strata that

typically consist of foresets dipping leeward

at high angles (not uncommonly 30° -34°) and 

represent original angles of repose.

2. Sets of tabular-planar cross-strata that in vertical sequences in high dunes tend to be 

progressively thinned from the base upward; 

sloping laminae within these sets tend to 

repeat the pattern of foresets displayed in the 

thick basal set, but the angle of dip may be 

lower (figs. 43, 46, 48).

3. Bounding planes between individual sets of 

cross-strata that mostly are horizontal or dip 

leeward at low angles; in high dunes additional bounding surfaces commonly form in 

downwind parts, with dips at moderately 

high angles (20°-28°), and these planes truncate foresets that dip at still higher angles 

(28°-34°; fig. 48).

Various other structures apparently are characteristic of only one or two dune types. Such 

features will be discussed in the following pages 

under each of the principal dune types in which 

they occur.

Sedimentary Structures

Characteristic of 

Certain Dune Types

Barchan and Barchanoid Ridge

THE BARCHAN DUNE, one of the best known 

and most elemental forms, is also probably the best-
90 A STUDY OF GLOBAL SAND SEAS

B

D

Wind direction

*——124ft——— 

(38m)

CROSS SECTIONS OF BARCHAN DUNE near Leupp, Coconino 

County, Arizona, U.S.A., taken through crest in direction of 

dominant wind. Modified from McKee (1957). A, 12 feet (3.7m) 

from base, 72 feet (22m) from crest; 8, 24 feet (7.3m) from base, 

60 feet (18.3m) from crest; C, 36 feet (11.0m) from base, 48 feet 

(14.6m) from crest; D, 48 feet (14.6m) from base, 36 feet 

(11.0m) from crest; £, crest, on east side. 100 feet =30.5 metres. 

Scale of sections /\-D=1 x2 feet. (Fig. 42.)

recorded dune in terms of sedimentary structure. 

The typical crescent shape, with horns pointing 

downwind, commonly develops as a single, isolated 

sand deposit; groups of barchans that coalesce to 

form barchanoid ridges in a parallel wavy pattern 

are also common.

A small isolated barchan dune located a few 

miles north of Leupp Trading Post, in eastern 

Coconino County, Arizona, was dissected and its 

structures were studied in detail in 1951 (McKee, 

1957, p. 1721). The dune was a double crescent with 

a height of about 11 feet (8 m) and a width of 270 

feet (80 m). Five test pits — three located from base 

to crest on the windward side and one on the forward part of each horn — provided good insight 

into the structure of a typical barchan.

Laminae in the middle part of the Arizona dune 

consisted of long, even layers dipping consistently 

31° -32° downwind. In the lower part of the windward slope, the truncated tops of these laminae

were covered by a veneer of laminae dipping upwind at angles of 5°-7° (fig. 42). On the wings, 

variations from the normal trend of stratification 

occurred as changes in direction and amount of dip. 

The wings contained strata dipping with relatively 

low angles, resulting from growth in locations of 

low wind stability and at extremities of the slipface 

surface.

At White Sands National Monument, New Mexico, one segment of a barchanoid ridge dune was 

trenched and analyzed (McKee, 1966, p. 39). The 

crescent-shaped mound studied was about 170 feet 

(50 m) long, 290 feet (90 m) wide, and approximately 27 feet (9 m) high. Trenching by a 

bulldozer, in directions both parallel to and normal 

to the prevailing wind, exposed to view crosslamination of the dune in three dimensions.

The pattern of the barchanoid ridge structure as 

recorded in the main trench consisted upwind of a 

series of nearly flat-lying tabular-planar sets of 

cross-strata, each about 3 or 4 feet (p.9 -1.2 m) thick 

and containing foresets that dipped downwind at 

26° -34° (figs. 43, 44). In the downwind part of the 

trench, the bounding surfaces of each set changed 

from nearly horizontal to steeply dipping (20° -28°) 

and the foresets between them attained dips up to 

34° and lengths of 40 feet (12 m). A few low-angle 

(2° ^5°) windward-dipping laminae capped the 

dune, probably formed as windward-side deposits 

at times when the wind was not competent to carry 

its entire load over the crest. Shallow, small-scale 

lenses of sand, scattered among sets of windwarddipping cross-strata, apparently represent scourand-fill deposits of shifting winds.

Crossbedding, as seen in the walls of the trench, 

at right angles to wind direction (fig. 44B), was 

materially different from that exposed in the main 

trench. A section cut straight across the crescent 

exposed, near its middle, crossbed sets and their 

bounding planes that appear nearly horizontal. On 

the flanks both cross-strata and bounding surfaces 

dip outward at low angles as a result of curvature of 

the horns or wings; individual cross-strata sets form 

wedges that taper toward dune margins, and 

foresets show apparent dips of 12°-23°. Small 

trough structures, probably formed as blowouts 

during fluctuations of wind regime as the dune was 

forming, were conspicuous near the dune center.

Horizontal sections cut above the barchan dune 

floor showed the curving lines formed by trunca-
SEDIMENTARY STRUCTURES IN DUNES 91

*&****

I V,

- \ ,T. •

SERIES OF STEEPLY DIPPING CROSS-STRATA forming tabularplanar sets in barchanoid ridge dune. Strata tangential with basal 

bounding planes. White Sands National Monument, New Mexico, U.S.A. Photograph by E. Tad Nichols. (Fig. 43.)

"•*>Z*t-^-.. *•;

BEVELED REMNANT OF BARCHAN DUNES in interdune area, 

White Sands National Monument, New Mexico, U.S.A. From 

McKee (1966). (Fig. 45.)

NE

METRES FEET

6 -

Poor 2 -

exposures

Base of dune

0-J-O

(- 20

-15

-10

— 5

NW 30 FEET

EXPLANATION

Bounding surface of cross-strata set 

Selected cross-stratum SE 

Apparent dip, in degrees

Base of dune

CROSS-STRATA IN BARCHANOID RIDGE DUNE, White Sands National Monument, New Mexico, U.S.A. A, Section parallel to 

dominant wind direction; B, section normal to dominant wind direction. Modified from McKee (1966). Lines queried where structure was obscure in field. (Fig. 44.)

tion of laminae that had formed on the slipfaces of 

the dune. The overall pattern was one of festoons, 

with one arc or crescent overlapping another (fig. 

45).

Barchanoid ridge dunes of the Killpecker field in 

western Wyoming (Ahlbrandt, 1973, p. 38) showed

virtually the same sedimentary structures (fig. 46) 

as those at White Sands. A trench on the lee side 

revealed foresets dipping at high angles (26° -34°) 

to lee and a bounding surface dipping 4° in the same 

direction. Deformational structures consisted of 

fadeout laminae and overthrusts.
92 A STUDY OF GLOBAL SAND SEAS

FEET

EXPLANATION 

Type of sand

-Trench 1

22

Fine 

Coarse 

Red oxidized 

Magnetite rich

Apparent dip, 

in degrees

BARCHANOID RIDGE DUNE, showing stratification to dominant wind direction (arrow), Killpecker dune field, Wyoming, 

U.S.A. A, Cross section of lee side, trench 1; B, cross section of 

upwind side, trench 2; C, plan view showing trench locations. 

Modified from Ahlbrandt (1973), 1 foot=0.3 m. (Fig. 46.)

A second trench in the Killpecker barchanoid 

ridge, dug on the upwind side, exposed four sets of 

cross-strata, all dipping leeward. In two sets the 

dips were high angle (34°), in a third they were 

medium angle (18°-22°), and, in a thin but persistent unit, they were low angle (8°) at one end but 

steepened downwind to the angle of repose. The 

low-angle strata contained small lenses with scourand-fill structures.

One feature of the barchanoid ridge in the 

Killpecker dune field, not recorded in other 

barchans, was an alternation of coarse and fine 

laminae and a filling of lenses with relative coarse

BARCHANOID RIDGE DUNES and interdunes, White Sands 

National Monument, New Mexico, U.S.A. Photograph by Holloman Air Force Base. (Fig. 47.)

sand. Such contrasts in texture apparently resulted 

from poor sorting in the source sand and the proximity of this source. In terms of textural parameters 

(chapter B), interior desert dunes commonly are 

more poorly sorted than coastal dunes because of 

normal differences in source material.
SEDIMENTARY STRUCTURES IN DUNES 93

sw

—Windward edge of dune at 440 feet; 

no topsets at 340 feet

10 20 30 FEET MAIN TRENCH, NORTH WALL

Base of dune

NW

,Margin of main trench

SIDE TRENCH, EAST WALL 

W

SE FEET 

15

-10

-5

-0

EXPLANATION 

Type of sand

B

32

Bounding 

surface

Selected 

crossstratum

Apparent dip, 

in degrees

0 1

D

4 

FEET

CROSS SECTIONS OF TWO TRANSVERSE DUNES in the United States. A, B, 

White Sands National Monument, New Mexico. From McKee (1966, fig. 7). C, D, 

Killpecker dune field, Wyoming. Modified from Ahlbrandt (1973). A, Parallel to 

dominant wind direction. B, Normal to dominant wind direction. C, Parallel to 

dominant wind direction on windward side. D, Parallel to dominant wind direction on lee side. 1 foot=0.3 metre. (Fig. 48.)

Transverse

Transverse dunes resemble barchan dunes in 

being a product of unidirectional winds, with steep 

slipfaces oriented normal to wind direction. The 

transverse dune apparently evolves into the 

barchan downwind with an intervening intermediate form, here referred to as a barchanoid ridge. 

The barchanoid ridges consist of parallel rows of 

crescents or barchanlike forms that have combined 

to form parallel wavy sand ridges (fig. 47). Interdune areas, forming long corridors, occur between 

pairs of ridges. The barchanoid ridge and transverse 

types of dunes, although similar in general form, 

differ in internal structure.

Transverse dunes at White Sands National 

Monument, New Mexico, are the highest dunes in 

the area and form long parallel ridges, upwind from

the smaller, much more irregular barchanoid types. 

A typical example selected for sectioning and study 

was about 40 feet (12 m) high, 400 feet (120 m) 

thick, and had a nearly straight crest extending for 

more than 800 feet (240 m) at right angles to the 

wind direction. The general straightness of this 

crestline was the feature that especially distinguished this dune type from adjacent barchanoid 

ridges and was reflected in the internal structures 

of transverse dunes.

Crossbedding in the main trench at the White 

Sands transverse dune, cut parallel to the dominant 

wind direction (fig. 48), consisted largely of tabular-planar sets of steeply dipping (30° -34°) strata 

within bounding planes that ranged from nearly 

horizontal to moderately high angle (20°-26°) 

downwind. Foresets in the lower part of the dune 

were very large, some strata extending for 55 feet
94 A STUDY OF GLOBAL SAND SEAS

(16 m) downdip and terminating as tangential 

curves at the dune base. Crossbed sets in the upper 

part were relatively thin, mostly 2-3 feet (0.6—1.0 

m) thick, with nearly parallel bounding planes.

Perhaps the most diagnostic feature of the 

transverse dune structure was the great extent of 

horizontal, or nearly horizontal, parallel laminae 

formed by the apparent dip of strata as seen in cross 

sections cut normal to wind direction (fig. 48). 

Some cross-strata in these sections dipped at low 

angles, and a few sets appeared as cut-and-fill (festoon) structures with axes parallel to wind direction, but high-angle foresets were absent.

A transverse dune at Killpecker dune field, 

Wyoming (fig. 48), which was trenched and 

analyzed by Ahlbrandt (1973, p. 36), showed most 

of the same features. Like the White Sands dunes, it 

was located downwind from dome dunes and to 

windward of barchans. It was formed largely of 

tabular sets of strata dipping steeply (29°-34°) 

downwind and bounding surfaces, that is, slipfaces, 

dipping as much as 21°. Water saturation in parts of 

the dune had made the sand cohesive, and overthrusts had developed. In dry areas fadeout laminae 

were abundant. Another feature of the dune was 

the presence of lenticular zones of coarse sand 

among laminae of fine sand, probably the result of 

scouring and later infilling among strata with lowangle dips on the windward side.

Blowout

In many coastal areas and others where sand 

becomes stabilized by vegetation cover, moisture 

content, or both, a common dune form is referred to 

as the "blowout" and, in general, appears like a 

crater (fig. 49). Blowouts differ widely in size and 

shape partly because their rims are anchored in so 

many places that even in regions of a dominant 

wind direction, prevailing winds are deflected in 

many directions, and local sand resistance to deflation and transport is extremely variable.

A circular blowout dune may evolve into a Ushaped parabolic form where a prevailing wind can 

cause the advance of an unstable section of the rim. 

In this manner, the nose of a parabolic dune may 

develop and migration of this dune type can be initiated. The internal structure of parabolic dunes 

has been examined and is described on succeeding 

pages, but the stratification of normal blowouts

does not seem to have been recorded as yet. Judging 

from the characteristic shapes and distribution of 

blowouts, one might expect a series of scour-andfill structures to develop; however, this is yet to be 

determined by trenching techniques.

BLOWOUT DUNES in the United States. A, South shore of Lake 

Michigan; photograph by R. L. Gutschick. B, East of Salton Sea, 

California; photograph by John S. Shelton. (Fig. 49.)

Parabolic

A parabolic dune is U-shaped or V-shaped and 

represents a type of blowout in which the middle 

part has moved forward with respect to the sides, or 

arms (fig. 50). This kind of dune occurs in many 

parts of the world but is especially prevalent in 

coastal areas and along margins of desert regions 

where vegetation has obtained a foothold. A distinctive feature is the anchoring of the dune arms 

by plant growth, which causes the entire dune to be 

relatively stable. The middle, or blowout, part of
SEDIMENTARY STRUCTURES IN DUNES 95

AERIAL VIEWS OF PARABOLIC DUNES at White Sands National Monument, New Mexico, U.S.A. A, Compare prevailing southwest 

winds (in knots) shown by wind rose with orientation of dunes. Photograph by Holloman Air Force Base. B, Vegetation anchoring 

arms of dunes. Orientation of dunes same as in A. Individual dunes, including the dragging arms, average about 700 feet (215 m) 

long in this area. (Fig. 50.)

the sand mass commonly migrates slowly, forming 

a rounded nose that points downwind.

Parabolic dunes vary greatly in size. In the Thar 

Desert of India and Pakistan, they commonly are 

very large, individual dunes extending several 

miles downwind, the U-shapes readily discernible 

in Landsat (ERTS) images. Elsewhere, for example, 

at Cabo Frio, on the Brazilian coast (McKee and 

Bigarella, 1972, p. 672), parabolic dunes are only a 

few hundred feet long, and among the Indiana 

dunes on the shore of Lake Michigan, they range in 

length "from a few tens of feet to several 

hundreds" (Cressey, 1928, p. 6).

Because parabolic dunes are largely the product 

of unidirectional winds, although secondary movements may be to both sides, their structures include 

many features common to all dunes that are dominated by one major wind direction. Their steep 

depositional faces (slipfaces), which form on the 

dune nose, have foresets consistently dipping 

downwind; however, strata in the arms dip normal 

to the dune axis, both right and left. Various combinations of parabolic dunes occur, such as series 

with one dune inserted inside another (common 

among dunes of the Thar Desert, India-Pakistan) 

and reversing types as at Lagoa, Brazil (McKee and

Bigarella, 1972, p. 672); these compound dunes are 

very complicated structurally.

A parabolic dune was trenched at White Sands 

National Monument, New Mexico (fig. 51). In its 

lower part this dune shows cross-strata with highangle foresets as in barchanoid ridge and other 

dune types of the area, but in the upper part, 

especially on the upwind side, many of the strata 

are very low angle or are nearly horizontal and in 

thin sets. Deposition extended from a nearly flat 

top, over the crest, and down the slipface. Its dipping laminae, except near the top, are in sets mostly 

2 -5 feet (1 -2 m) thick of tabular-planar or wedgeplanar form. A few scattered sets of symmetrically 

filled trough cross-strata — about 25 -30 feet (7 -9 

m) wide and 3 -A feet (1 m) deep — also occur near 

the top.

The White Sands parabolic dunes exhibit two 

structural features seemingly unique to this dune 

type: (1) many foresets are concave downward (fig. 

51), probably resulting from cross winds that undercut and oversteepened the bases of foresets on the 

dune nose, and (2) organic accumulations that 

locally warped strata, result from root growth, 

especially along the bedding surfaces.

The parabolic dune examined at White Sands 

showed an unusually wide directional spread of
96 A STUDY OF GLOBAL SAND SEAS

ea illustrated

SW NE

Approximate 

/ top of dune

B

EXPLANATION

Bounding surface

Selected crossstratum

22 Apparent dip, 

in degrees

NW

VARIOUSLY ORIENTED SECTIONS through a parabolic dune, 

White Sands National Monument, New Mexico, U.S.A. 

Modified from McKee (1966, fig. 9). A, Parallel to dominant 

wind; 8, C, parallel to wind direction, showing high-angle 

foresets; D, normal to dominant wind. All measurements are in 

feet. 1 foot =0.3 metre. (Fig. 51.)

crossbedding dips (McKee, 1966, table IV) — a distinctive feature of this dune type. Seventy-three 

readings of true dip in foresets showed a spread of 

200°, and 161 readings of truncated foresets in adjacent interdune areas showed a spread of 210°. 

Barchanoid ridge, transverse, and other dunes upwind at White Sands showed much smaller 

spreads, ranging from 60° to 140°.

Structures of parabolic dunes on the coastal plain 

of Brazil at Cabo Frio (McKee and Bigarella, 1972, p. 

672, fig. 4d) resemble those at White Sands. Recent 

extensive trenching, by Bigarella, of a large 

parabolic dune with smaller ones inside at the

Lagoa dune field in Santa Catarina, Brazil, has disclosed many additional features discussed later in 

this chapter.

Parabolic dunes, whether inland or coastal, seem 

to characteristically migrate very slowly (McKee 

and Douglass, 1971, p. D113). In most places they 

are anchored by vegetation and in coastal areas, 

especially, they are partly stabilized by moisture. In 

Brazilian retention dunes, which are in a similar 

coastal environment, "the supply of sand from the 

source area [beach] seems to be large enough to 

overcharge the gentle slope of the dune's surface 

* * * but the winds are not so intense nor the sand 

so dry that the complete removal of the previously 

deposited beds can be accomplished * * * [so] a new 

set of strata just barely covers the former one" 

(Bigarella, Becker, and Duarte, 1969, p. 38).

The partly stabilized coastal dunes of Brazil also 

show virtually concordant attitudes between slipface sets. The difference in angle between strata of 

various sets is small despite disturbances from 

slumping along slipface surfaces, according to 

Bigarella, Becker, and Duarte (1969, p. 38).

Dunes of normal parabolic shape are well 

developed at the high altitude and under the cool 

dry climatic conditions of western Wyoming. Their 

structures have been examined by Ahlbrandt (1973, 

p. 39-41). One dune of this type is described as 

having foresets dipping 24°-34°, commonly 

26° -30°. Internal structures are disturbed by plant 

roots, and laminae of the dune nose exhibit minor 

folding. A bulging of the dune nose is reflected in 

the convex-upward form of the laminae as seen in 

the test trench (fig. 52). Thus, the Wyoming dune 

displays the same principal structures observed at 

White Sands and in the Brazilian coastal dunes.

Retention Ridges

Retention ridges, common features of many 

coastal dune areas, characteristically form long narrow dunes parallel to the shore on the landward 

margins of backshore beach deposits. They develop 

where dune sand accumulates against vegetation 

barriers, forming a nearly stabilized type of dune 

that may gradually be enveloped by trees and other 

plants. This type of dune ridge is common along the 

west coast of the United States and in that area has 

been referred to by Cooper (1958, p. 55; 1967, p. 22) 

as "precipitation ridge."
SEDIMENTARY STRUCTURES IN DUNES 97

Plant

250 FEET

NORTH WALL OF A TRENCH on the nose of parabolic dune, 

Killpecker dune field, Wyoming, U.S.A. Strata are concave 

downward in lower two sets. From Ahlbrandt (1975, figs. 8,14). 

Measurements in feet. 1 foot = 0.3 metre. (Fig. 52.)

Primary structures in retention ridges of Brazil 

were studied in detail by Bigarella, Becker, and 

Duarte (1969, p. 28 -29) and by Bigarella (1972, p. 

20—21). Trenches were dug and cross sections examined at Jardim Sao Pedro (fig. 53), Guairamar, 

and Porto Novo on the coast of Parana in Brazil. 

These dune ridges formed under conditions of high 

humidity and considerable vegetation and included 

many "blowout" features. They apparently advanced very slowly and contained most of the

structural characteristics of parabolic dunes. "Convex-upward strata * * * are rather frequent in the 

dunes studied," and distinctive types of distortion 

on many of the slipface surfaces were common 

features (Bigarella, Becker, and Duarte, 1969, p. 

37, 45).

A distinctive feature of Brazilian ridge dunes 

(beach dune ridges) with high moisture content is 

that "both the topset and foreset are made up by the 

same continuous set of strata, and not by different 

truncated sets" (Bigarella, Becker, and Duarte, 1969, 

p. 36). Probably the abundance of sand supply and 

the slow rate of movement (because of internal 

dampness) are responsible for this feature, suggesting that it results from the humid climate, rather 

than the type of wind. Sinuous sand layers, of 

medium scale, that occur in lower parts of the 

Brazilian retention ridges (fig. 53C) are similar to 

strata in small dome dunes that commonly occur to 

seaward. Above the wavy basal beds in the ridges 

examined were tabular-planar sets of cross-strata. 

In some of these sets the bounding surfaces dipped 

at low angles, and in others, at moderate to high 

angles (fig. 53). The tabular-planar sets included 

both nonerosional (simple) and erosional types; 

few trough-type cross-strata were associated.

Some cross-strata in the retention ridge dunes of 

Brazil dip downwind at very high angles (34° -39°) 

probably owing to high humidity at the time of 

deposition (Bigarella, 1972, p. 21). In sections normal to prevailing wind direction, however, most of 

the stratification is horizontal or nearly horizontal, 

except across protuberances in which strata dip at 

low angles toward the outer margins, giving a 

strongly curving appearance in section. Sets of 

cross-strata tended to be realtively thick (some 

more than 3 feet (1 m)) and to have relatively high 

angles of dip near the dune base, but in the upper 

part they were thinner (0.32 -0.98 foot (0.1 -0.3 m)) 

and had lower angles of dip.

The degree and direction of dip from several 

dune sections of the Guairamar dune are illustrated 

by stereonets (fig. 54). The spread of high-angle 

(>30°) foreset dip directions at Jardim Sao Pedro is 

more than 170° (Bigarella, Becker, and Duarte, 

1969) which is very much greater than the spread of 

barchanoid and transverse dunes at White Sands, 

New Mexico, in the United States.
98 A STUDY OF GLOBAL SAND SEAS

2 -

SCALE

FOR

A.B.C

\ 1

) 1 2

I

3 METRES

RETENTION DUNE CROSS SECTIONS showing details of stratification, Jardim Sab Pedro, Praia do Leste, Parana, Brazil. A, Section 

parallel to prevailing wind; B, section normal to prevailing wind at linguoid protuberance where crest and slipface are curved; C, 

section normal to prevailing wind at middle part of dune. Modified from Bigarella, Becker, and Duarte (1969). 1 metre= 3.28 feet. 

(Fig. 53.)

Dome

Dome dunes develop in the upwind parts of some 

dune fields, where winds are sufficiently strong to 

bevel and, thus, effectively retard a normal upward 

growth of dune crests. Three localities where dunes 

of this type are characteristically developed and 

where they have been trenched in order to determine the primary structure pattern are (1) White 

Sands National Monument, New Mexico, U.S.A., a 

desert environment, (2) the Killpecker dune field, 

Wyoming, U.S.A., a high-altitude, cold climate, and 

(3) along the southern coast of Brazil, a warm, 

humid environment.

The dome dunes at White Sands National Monument, New Mexico (described in detail by McKee, 

1966, p. 26, 27), are round or oval in ground plan, 

have rounded tops, and do not display steep 

avalanche faces on their lee sides. One dune — 490 

feet (150 m) wide, 460 feet (140 m) long, and 20 feet 

(6 m) high — considered to be typical of that area, 

was selected for trenching and study. Its texture 

showed poorer sorting and a higher percentage of

STEREONETS FOR THREE SECTIONS showing angle (distance 

from center) and direction (azimuth) of dip on foresets of retention ridge, Guairamar, Parana, Brazil. Modified from Bigarella, 

Becker, and Duarte (1969). (Fig. 54.)
SEDIMENTARY STRUCTURES IN DUNES 99

TRENCH THROUGH DOME DUNE, White Sands National 

Monument, New Mexico, U.S.A. Section parallel to dominant 

wind from left. Scale is in inches. 1 inch = 2.54 centimetres. (Fig. 

55.)

coarse grains than did the other types of dunes located farther downwind.

Structures in the upwind part of the White Sands 

dome dune consisted largely of tabular-planar 

cross-strata (fig. 55) with foresets dipping downwind at high angles (28°-33°). In the downwind 

part, foresets dipped somewhat less (14°-27°), 

perhaps because much of the sand there had been 

deposited from suspension rather than mainly from 

slumping (fig. 56A). In a trench normal to the dominant wind direction, most of the stratification appeared to be horizontal or to have very low dip 

toward the dune margins (fig. 56B). Thus, in basic 

structure, this dune type resembles other unidirectional wind deposits at White Sands. The dome 

dunes probably began as isolated barchans, if shape 

and structure can be used as criteria.

Two features of the dome dune seem to be distinctive and are either absent or not well developed 

in other types of dunes in the area. First, cut-andfill structures — probably the result of troughforming deflation by strong, unchecked winds, 

followed by sand deposition under weaker 

winds — formed a series of sand-filled scours 

parallel to wind direction. Second, in the same section a layer of horizontal or nearly horizontal

laminae, capping the rounded dune top, formed 

topset beds that connected with dipping foresets 

downwind. Both features distinguish dome dune 

structures from those of other dune types in the 

area.

Dome dunes in the Killpecker dune field of 

western Wyoming, like those at White Sands, occur 

farthest upwind of all dunes, and are developed 

under the full force of approaching sand storms. 

Three trenches dug by Ahlbrandt (1973, p. 32) in a 

Killpecker dune revealed structures generally similar to those at White Sands. In sections parallel to 

wind movement, strata dipped consistently downwind at the angle of repose (about 34°) to form 

tabular-planar cross-strata, except on the lee side, 

where fractures (fig. 57) were developed from 

incipient slipface movement. These fractures 

defined slump blocks which locally were responsible for great oversteepening of beds, some of which 

dipped as much as 55°. The steepness of dips on 

such beds is attributed to the accumulation of snow 

layers within the deposit with subsequent melting 

and collapse of overlying cross-strata.

Other features of the dissected dome dune in the 

Killpecker field were (1) beds dipping i°-4° to 

windward in the upper 1.5 feet (0.5 m) on the upwind side, apparently resulting from an overabundance of sand supply, and (2) slump structures on 

the downwind side consisting of many normal 

faults and a few fadeout laminae, typical of 

avalanches in many dune sands (McKee, Douglass, 

and Rittenhouse, 1971, p. 370-372).

Dome dunes on the coasts of Parana and Santa 

Catarina in Brazil occur as miniature foredunes, 

seaward of retention ridges that parallel the coast. 

They resemble dome dunes of the desert areas of 

the Western United States in that they also form in 

unobstructed upwind locations and develop with 

oval or circular shapes and with relatively flat tops. 

They differ from the desert dome dunes in their 

smaller size — typically less than 1 metre (3 ft) 

high and 12 -14 m (40 -45 ft) in diameter — and in 

the type of structures and large spread of dip directions of their stratification. The differences probably result mainly from contrasts in depositional environment. In coastal Brazil, the domes are formed 

under humid conditions and on a surface 

roughened by many grasses and small shrubs.

Structures in Brazilian dome dunes have been examined and described by Bigarella and Popp (1966, 

p. 143 -148) at Barra do Sul, by Bigarella, Becker,
MAIN TRENCH, NORTH WALL Projection of side trench walls on main trench wall 

Dune crest

Base of trench

10 20 30 40 50 60 70 90 100 110 120 130 140 150 160 170 180 190 Concealed FEET

FEET 

15-

10- 

5-

0-

,Lee surface

Small swale on 

dune surface

.Lee surface

A, continued

Common megaripples in addition to regular 

size ripples on dune surface

SIDE TRENCH, WEST WALL Lower 4 feet of wall contains

numerous horizontal and wavy,

locally discordant laminae

Base of trench

390 400 FEET

J______L

N

FEET 

r-15

- 5

0 FEET

B

a a

P

O 

aenen W

Bounding surface

EXPLANATION

Selected cross-stratum 21 Apparent dip, in degrees

CROSS SECTIONS OF DOME DUNE, White Sands National Monument, New Mexico, U.S.A., (A) parallel to dominant wind direction and (B) normal to dominant 

wind direction. Modified from McKee (1966, fig. 6). All measurements are in feet. 100 feet=30.5 metres. Lines are queried where structure is obscure 

(Fig. 56.)
SEDIMENTARY STRUCTURES IN DUNES

E

EXPLANATION 

Selected cross-strata in fine sand

Medium sand

Interlayered medium and fine sand

Fracture

Erosion surface

Surface of planation

Selected cross-strata

DOME DUNE, Killpecker dune field, Wyoming, U.S.A. A, Stratification on steep lee side in section parallel to wind direction. Note 

fractures defining slump blocks caused by snowmelt and collapse of strata. B, Section near crest showing lee-dipping strata overlain 

by horizontal strata. C, Section upwind, showing low-angle capping beds dipping upwind. D, Ground plan of dome dune, showing 

location of sections A, B, and C Modified from Ahlbrandt (1973). 1 foot=0.3 metre. (Fig. 57.)

and Duarte (1969, p. 17) at Praia do Leste, and by 

Bigarella (1972, p. 24 -25) at Barra do Sul. They consist, in general, of numerous sets of superimposed, 

curving strata in which bounding planes and many 

laminae are convex upward (fig. 58). Uniformly 

dipping, high-angle foresets, such as form the cores

and lower parts of desert domes, are lacking, and 

the characteristic sets of low-angle strata, dipping 

in many directions, apparently represent windward-side deposits, topsets, and also foresets; few 

avalanche deposits are recognized. In brief, the 

domes consist of blanket deposits resulting from a
102 A STUDY OF GLOBAL SAND SEAS

NW

0.5-

EXPLANATION 

Bounding surface 

Selected cross-strata

SW

0.5-

u B

CROSS SECTIONS OF COASTAL DOME DUNE, Praia do Leste, Parana, Brazil, showing (A) stratification in section parallel to dominant wind direction, and (B, Q stratification in sections normal to dominant wind directions. Modified from Bigarella (1972) All 

measurements are in metres. 1 metre=3.28 feet. (Fig. 58.)

large source of material and a wide spread of winds 

that alternately deposit and erode sand on an irregular surface.

Brazilian coastal dome dunes are characterized 

by strata with "dip directions * * * distributed completely around the compass" (Bigarella, 1972, p. 25). 

This is partly the result of surface irregularities 

from vegetation and partly from retarding effects of 

moisture. Both upwind dips and nearly horizontal 

topset beds are also developed in domes of desert 

sands, but on a larger scale. They occur as blankets 

above normal foresets of tabular-planar sets. In 

both coastal and desert environments a large sand 

source is available, but in the humid environment 

with abundant vegetation, accumulation of sand is 

irregular, in time and direction, and associated 

blowout features are common.

Linear

One of the most common but least understood 

types of desert dune is the long straight ridge herein 

called a linear dune (fig. 59). It is commonly referred to as a seif dune in North Africa and Saudi 

Arabia, as a sand ridge in Australia, and as a 

longitudinal dune in many other places; its pattern, 

as observed on Landsat (ERTS) images (McKee and 

Breed, 1976, p. 81) has been termed "parallel 

straight." At least three subtypes of this dune form

AERIAL VIEW OF SEIF, or linear, dunes, north of Sebha, Libya. 

Dune ridges are about 50 feet (15 m) high Distance between 

dunes ranges from 1/« to fy mile (0.4 to 0.8 km). (Fig. 59.)

may be distinguished, according to Price (1950, p. 

462), which doubtless is one reason for the current 

confusion regarding its genesis. Differences in 

details of shape likewise occur in various sand seas, 

and many varieties are recorded, including the 

feather-type in Saudi Arabia, the zigzag type in 

Libya, and the converging, nonparallel type with 

junctures in Australia.

An environment favorable to development of 

linear dunes seems to be one in which there is high 

wind velocity (Glennie, 1970, p. 95; Bagnold, 1941,
SEDIMENTARY STRUCTURES IN DUNES 103

p. 171; Twidale, 1972, p. 82). As pointed out by Bagnold (1941, p. 178), "a strong sand-laden wind with 

uniform drift over a uniform rough surface has 

transverse instability so sand tends to deposit in 

longitudinal strips." According to Glennie (1970, p. 

95), "The higher wind velocity, the larger the seif 

dune and the greater the interdune spacing."

The origin of linear dunes has long been a matter 

of controversy; many geologists (Bagnold, 1941, p. 

223; McKee and Tibbits, 1964; Twidale, 1972, p. 103; 

and others) believe them to be the product of twodirectional winds, but others attribute them to a 

unidirectional or prevailing wind (Dubief, 1952; 

Glennie, 1970). Even among the geologists who 

adhere to one or the other concept of directional 

control by wind, there are many differences in the 

mechanisms by which this dune form is attained.

Some linear dunes are explained as forming from 

the trailing arms of parabolic dunes that have 

become separated from dune noses (Dubief, 1952; 

Capot-Rey, 1943; King, 1960; and others); other 

linear dunes are shown to have formed by elongation of one horn of a barchan by winds oblique to 

the prevailing transport direction (Bagnold, 1941, p. 

223). An explanation that calls for the development 

of wind cells in interdune areas through pressure 

gradients along the dune sides was proposed by 

Glennie (1970, p. 90), and experiments with running a roller across a layer of grease suggested to 

Folk (1971b, p. 3464) a theory of helicoidal air flow. 

Recent work on Australian dunes led Twidale 

(1972, p. 103) to the conclusion that "longitudinal 

dunes are being initiated from leeside mounds bordering playas and alluvial plains" and that "these 

mounds cause changes in the airflow in a bi-directional regime."

Regardless of the mechanism by which linear 

dunes are formed, their structures make a distinctive pattern very different from those of barchan - 

oid-type dunes. In linear dunes that have been examined thus far, slipfaces develop on both sides of 

the crest, and foreset dip directions form two 

clusters of points in nearly opposite directions, 

rather than a single grouping. Unfortunately, few 

detailed studies based on trenching have yet been 

made of these dunes, so examples in different sand 

seas that appear similar in size and form may not 

actually be alike structurally.

Probably the first reconstruction of linear dune 

structure was that by Bagnold (1941, p. 242) in 

which he showed a nearly symmetrical, hypothetical section based on "the few tests already made by 

the author." This section (fig. 60) shows the "arrangement of accretion and encroachment 

deposits," with the middle and upper parts of the 

dune composed of avalanched sand, and the low 

outer margins, or plinth, on both sides, formed of 

accretion deposits. The section shows growth of a 

perfectly regular type, but, as Bagnold pointed out, 

successive stages in nature doubtless are very irregular. In any event, deposition probably alternates from side to side by avalanching down the 

steep slipfaces.

Crest

EXPLANATION 

Avalanche deposit Accretion deposit

HYPOTHETICAL SECTION, showing structure of seif dune. 

Modified from Bagnold (1941, fig. 83). Note foreset dips in opposite directions. (Fig. 60.)

Confirmation of the validity of the basic structure 

pattern as determined by Bagnold is found in a 

series of trenches made by McKee and Tibbits 

(1964, p. 17) across a "seif dune" near Sabha, Libya, 

and by laboratory experiments conducted in 

Denver, Colorado, U.S.A., in which a small linear 

dune was developed. In the section across the Libyan dune (fig. 61), high-angle cross-strata 

(26°-34°), presumably slipfaces, show at many 

places in the upper half of the dune and on both 

sides; low-angle (4° —14°) cross-strata occur on the 

lower flanks of the dune and probably represent accretion beds.

Reversing

The existence in central Asia of dunes formed as 

a result of reversing winds was noted by Sven 

Hedin in 1896 (p. 267-268). Likewise, dunes of this 

type were described and discussed by Cornish in 

1897 (p. 286). Neither man had examined or
104 A STUDY OF GLOBAL SAND SEAS

FEET

45-

30-

15-

0 J

77-23

EXPLANATION

Structureless sand Near-vertifcal laminae 

between slip planes

Apparent dip, 

in degrees

CROSS SECTION OF SEIF DUNE near Sebha, Libya, based on series of test pits. From McKee and Tibbitts (1964, p. 17). All measurements are in feet. 1 foot=0.3 metre. (Fig. 61.)

analyzed the internal structures of the dunes, but 

Cornish's sketches (1897, fig. 7) clearly indicate 

that steep slipfaces had developed on opposite sides 

of a sand hill with re-forming of the dune top during a wing reversal. Another early reference to 

reversing dunes is by Bagnold (1941, p. 242), who 

stated, in discussing dunes in North Africa: 

"Reverse slip-faces formed during bouts of wind 

from opposite directions can be distinguished at 

once by direction of the sloping shear-planes."

Reversing dunes at Great Sand Dunes National 

Monument in southern Colorado in the United 

States were examined by Merk (1960, p. 127) with 

regard to internal structures. From excavation of a 

few test pits, Merk showed that the bases and lower 

parts of the large dunes indicated deposition by a 

prevailing southwesterly wind, whereas the upper 

parts commonly re-formed with steep slipfaces 

toward the southwest, during periods of easterly 

storm winds. Thus, in a single dune of barchanoid 

or transverse type (fig. 62), two groups of steeply 

dipping foresets, facing nearly opposite directions, 

were developed (fig. 63). Further, in many large

dunes, a considerable number of low-angle laminae 

that probably formed as windward-slope deposits, 

have been buried in the lower parts during reversals of wind direction. Contorted structures commonly result from slumping during the frequent 

reversals.

Reversing dunes about 30 feet (9 m) high occur in 

Antarctica, where approximately 30 barchans of 

reversing type were reported from Victoria Valley 

by Lindsay (1973, p. 1799). His descriptions of these 

dunes indicate that they are much like reversing 

dunes elsewhere; however, they have frozen cores. 

Slopes developed on windward sides are said to dip 

an average of about 6° in their basal parts, but are 

much steeper (approximately 15°) in the upper 

parts; the zone of change apparently coinciding 

with the lower limit of surface moisture. Avalanche 

slopes are reported to range from 29.5° to 33°, which 

is normal for most dunes elsewhere; this steepness 

readily differentiates the slipfaces from other surfaces. Below the slipfaces are relatively low-angle 

(14°-16°) slopes referred to as "aprons."
SEDIMENTARY STRUCTURES IN DUNES 105

REVERSING DUNES, Great Sand Dunes National Monument, 

near Alamosa, Colorado, U.S.A. Higher dunes are as much as 

700 feet (210 m). Aerial photographs by J. S. Shelton. (Fig. 62.)

The attitude of the cross-strata and the structure 

patterns of the reversing dunes in the Kelso dune 

field, California, U.S.A., as determined by Sharp 

(1966, p. 1062) illustrate several distinctive 

features: (1) High-angle foresets of lee-side 

deposits are relatively scarce, suggesting that the 

"steeply dipping (>30°) slipface deposits are rarely 

preserved within these dunes." (2) Lee-side bedding which underlies a "veneer of windward 

deposits" dipped leeward 10°-15° in many pits, indicating that most of these strata are from the lower 

part of foresets. (3) "Bedding relationships are more 

complex and thickness of units greater in the 

crestal areas" presumably because of frequent 

reversals in asymmetry and "back-and-forth movement of the crest."

At Lagoa, Ilha de Santa Catarina, on the southern 

coast of Brazil, a large reversing dune, caused by

Primary wind- 

———— Reversing wind

STRUCTURE IN REVERSING DUNE, parallel to dominant wind, 

Great Sand Dunes National Monument, Colorado, U.S.A. Based 

on photograph by Merk (1960). Primary wind from left to right; 

reversing wind from right to left. Set A, A', primary dune foreset 

laminae; set B, modified dune windward laminae; set C, primary 

dune foreset laminae; set D, modified dune windward laminae. 

(Fig. 63.)

seasonal shifts in wind direction, was dissected and 

examined by McKee and Bigarella (1972, p. 677). In 

this dune, steep foresets, formed on slipfaces that 

dip in two nearly opposite directions, are conspicuous. Both stairstep folds and thrusts, characteristic of avalanches in wet, strongly cohesive 

sand, are abundant (McKee and Bigarella, 1972, fig. 

3).

The elongate ridges of the Kelso dunes in the Mojave Desert of California probably have received 

more detailed study than any other reversing 

dunes. They lie in a valley nearly surrounded by 

desert ranges but are exposed on the northwest 

side, from which additional windblown sand is introduced. During an interval of 15 years, measurements were made and data kept at 10 stations 

(Sharp, 1966); sand movements were recorded, and 

changes both in dune form and in the facing direction of dunes were documented. Although no 

trenching was done, dune movements were 

measured precisely with respect to 10 series of fixed poles, and the nature of dune structures was 

determined by digging a large number of pits, 4 -5 

feet (1.0-1.5 m) deep, at various locations.

The most frequent winds in the Kelso dune field 

are from the west, but winds from other quadrants
106 A STUDY OF GLOBAL SAND SEAS

are believed (Sharp, 1966, p. 1049) to have higher 

velocity and, therefore, to be nearly equal in sandmoving capacity. In any event, a summary of many 

measurements shows that the dune ridges moved 

northeast at the slow rate of only 12 feet (3.6 m) in 

12 years but that during that time "the crest shifted 

back and forth within a zone about 30 feet (9 m) 

wide." Thus, "scouring and truncation of dune 

crests occur when a sharp crest is subjected to a 

powerful reverse wind" (Sharp, 1966, p. 1050).

At White Sands National Monument, New Mexico, U.S.A., where dunes are mostly the result of 

unidirectional winds, cross-strata resulting from 

reversal in wind direction were preserved in some 

cross sections (fig. 64) parallel to the dominant 

wind direction (McKee and Douglass, 1971, p. D114, 

fig. 3). Weather records show that in this area the 

principal wind direction normally shifts from 

southwest to north for a short period each winter 

season, and this shift is recorded in the dune structure.

To summarize the relatively scant data available, 

reversing dunes are characteristically developed 

under many different climatic regimes. They occur 

in arid, low-altitude areas (Kelso dune fields, 

California, U.S.A.); in humid, low-altitude areas 

(Santa Catarina, Brazil); cold, high-altitude areas 

(Great Sand Dunes National Monument, Colorado, 

U.S.A.); and cold, low-altitude areas (Antarctica). 

Because their development seems to be basically a 

function of contrasting wind directions, regardless 

of other environmental factors, the topographic

control (especially mountain ranges) of wind 

movements seems to dictate the type of dune pattern developed. In brief, most, if not all, of the 

reversing dunes cited are in areas where the wind 

pattern is locally but strongly affected by physical 

barriers.

Star

Star dunes (fig. 65), apparently the result of wind 

from several directions, are among the most complex of dunes, from the standpoint of primary structure. Two representative examples of such dunes, 

100 feet (30 m) and 35 feet (11 m) high, in central 

Saudi Arabia, near Zalim, were examined and 

described (McKee, 1966, p. 65).

The larger star dune (fig. 65), with four arms or 

ridges extending out from a high central crest, indicates by its structure a shifting in the direction of 

wind movement. Each arm has a slipface on one 

side, with characteristic high-angle dips (31° -33°) 

and a more gentle slope (17° -21°) on the other (fig. 

66). Thus, a seasonal rotating wind direction probably was necessary to initially establish the positions 

of these arms. Confirmation of a shift in direction of 

wind was found in cross sections exposed in 

trenches at the dune crest. These sections showed 

cross-laminae dipping at high angles in three principal directions which coincided with directions of 

seasonal wind movement in the area.

The smaller star dune that was trenched and 

studied near Zalim, Saudi Arabia, had three arms

SECTION IN A TRENCH parallel to dominant wind direction, White Sands National Monument, New Mexico, U.S.A., illustrating 

effects of wind reversal during winter season. Scale is in inches. 1 inch = 2.54 centimeters. (Fig. 64.)
SEDIMENTARY STRUCTURES IN DUNES 107

nr * *?

STAR DUNES, southeast of Zalim, Saudi Arabia. Crests are 

70-100 feet (20-30 m) high. Aerial photograph by E. Tad 

Nichols. (Fig. 65.)

TRENCH AT CREST of 100-foot-high (30.5-m-high) star dune, 

southeast of Zalim, Saudi Arabia. Wedge-planar cross-strata dip 

steeply in three directions. Scale is in inches. 1 inch = 2.54 centimetres. Photograph by E. Tad Nichols. (Fig. 66.)

and was structurally more complex and difficult to 

explain genetically than the large one. However, it 

also showed a complicated mixture of structures 

dipping in several directions (McKee, 1966, p. 68) 

and almost certainly was the result of alternation 

among several wind regimes.

Star dunes occur in many parts of the world and 

under a variety of conditions. They are especially 

numerous in the Rub' al Khali of Saudi Arabia and 

in the Grand Erg Oriental of Algeria but also are 

well developed in the Gran Desierto of Sonora, 

Mexico. In most places they appear as individual or 

separate mounds randomly scattered across a sand 

surface, but in other places two or more seem to 

have coalesced to form compound dunes. In several 

sand deserts (fig. 67), they are distributed along the 

crests of linear dunes, forming parallel rows of 

stars, sometimes referred to as "strings of beads." 

These are complex dunes, composed of two distinctive types.

So far as is known, neither complex nor compound star dunes have ever been trenched for 

structure analysis. Observations on the orientation 

of slipfaces suggest, however, that, as the product 

of multiwind development, their structures are 

complicated and show a wide spread in dip directions. Furthermore, the great heights attained by 

many star dunes indicate a dominant vertical, 

rather than horizontal, growth.

The rows of compound dunes suggest two 

generations of growth — the earlier one with a 

bimodal-wind environment, the later one with 

multiple-wind environment. The overall structure 

pattern represented in sand deserts of this type can 

only be determined with certainty when direct observations from trenching have been made. Entirely unrecorded are the structural characteristics 

of interdune areas either in fields of scattered star 

dunes or between parallel ridges of compound 

linear-star dunes.

Sedimentary Structures 

of Interdune Areas

INTERDUNE AREAS, which are the spaces between dunes, differ greatly in size and shape, depending largely on the types of dune that are separ-
STAR DUNES ALONG RIDGES of linear dunes, Namib Desert, 6 miles (10 km) south of Kuiseb River at Gobabeb, South-West 

Africa. Photograph by E. Tad Nichols. (Fig. 67.)

ated by them. Study of deposits that accumulate 

within interdune areas of barchanoid types show 

the sediment to be mostly (1) dust or silt-size particles that settle out of the atmosphere, (2) organic 

matter largely derived from vegetation, and (3) 

limited amounts of sand that have strayed from adjacent dunes (fig. 68). In the White Sands area that 

has been studied in detail these deposits are very 

thin, ranging in thickness from 1 to 4 feet (0.3 to 1.3 

m), depending largely on how long the surface has 

been exposed before burial by advancing dune forsets.

When dunes migrate across a dune field with a 

unidirectional wind, the sand surface of the dune 

ahead of each interdune is constantly being beveled 

through truncation of its cross-strata (fig. 69), and, 

at the same time, the windward side of the interdune is being buried and preserved. If dune migration is very rapid, interdune deposits will be 

especially thin or even lacking. If migration is very 

slow, an appreciable amount of sediment may accumulate on the interdune surface before burial.

Regardless of the migration rate, the proportion of 

clean, well-sorted eolian sand to the impure, contaminated sediment of the interdunes is great, and 

the result is thick sand layers of crossbedded sets, 

separated by thin parting beds of mixed sediment 

with flat-lying or irregular strata. Such relations 

have been established through a drilling program 

for the White Sands dune field, New Mexico 

(McKee and Moiola, 1975), where three or four sequences of dune sand are separated by a corresponding number of interdune deposits.

In some dune fields — for example, in parts of 

Algeria and Australia — the sand supply is sparse 

and forms isolated dunes on a bedrock or other nonsand surface. In southern Algeria, sand dunes rest 

on a pediplane cutting Precambrian metamorphic 

rocks. Under such circumstances, sand is very transient and migrates until some sediment trap causes 

it to accumulate as a large body. In areas of considerable sand accumulation, the interdune surface 

may show beveled tops of earlier dunes that have 

recently been planed off. Such surfaces define on
SEDIMENTARY STRUCTURES IN DUNES 109

INTERDUNE AREA showing miniature stringers and sheets of 

flat-bedded sand (wind-shadow deposits) advancing across interdune. White Sands National Monument, New Mexico, U.S.A. 

From McKee and Moiola (1975, fig. 6). (Fig. 68.)

horizontal planes the curving arcs of barchans (fig. 

70), the long, relatively straight crest lines of 

transverse ridge dunes (fig. 71), or other patterns 

representing stages in dune migration. Where these 

interdune surfaces have been exposed for an appreciable time, the relict structures are obliterated 

by accumulating sediment.

Interdune deposits at White Sands National 

Monument, New Mexico, U.S.A., were examined in 

vertical sections by trenching in areas contiguous 

both to barchanoid ridges and to transverse dunes 

(McKee and Moiola, 1975, p. 61). Structures in 

these sections consisted of thin, flat or irregular 

beds of silts and sands with scattered fragments of 

plants and with laminae contorted by root growth 

(fig. 72). The interdune deposits examined at the 

surface, and also in cores, range in thickness from 1 

to 4 feet (0.3 to 1.3 m). A few kilometres upwind in

the same dune field, where sand movement is 

much more rapid, the thickness probably is proportionately less. Interdune surfaces in many such 

places are represented merely by horizontal bedding planes.

The Killpecker dune field in Wyoming, also 

formed mainly by unidirectional winds, has been 

examined through trenching, and the nature of interdune structures has been determined 

(Ahlbrandt, 1973, p. 41, figs. 20, 66, 67). Trenches in 

this field showed mostly horizontal laminae disrupted in places by root tubules and consisting in 

part of marl developed in interdunal ponds. The 

deposits examined were formed in the upwind part 

of the field under the influence of very strong 

winds; the sand included some of the coarsest and 

most poorly sorted detritus in the entire dune field.

Structures of interdune areas among the coastal 

dunes of Brazil, like the just-described North 

American desert types, consist mostly of horizontal 

laminae that rest upon truncated cross-strata like 

those of nearby active dunes (Bigarella, 1972, p. 27). 

The beveled foresets are the remnants of earlier 

dunes that migrated across the area; they formed an 

overlapping pattern as "the result either of changes 

in wind direction or of irregular superposition of 

the curved foreset strata." Coastal-type interdunes 

in Brazil are further discussed by Bigarella later in 

this chapter.

Interdune surfaces in areas of parallel-straight or 

linear dunes, commonly referred to as seif or 

longitudinal, represent a depositional environment 

very different from that among transverse-type 

dunes. Between linear-type dunes, the interdune 

surfaces commonly are many times wider than the 

sand ridges that enclose them (fig. 59). Furthermore, these surfaces between the long, straight 

dunes extend in a direction generally parallel to the 

prevailing wind or winds. They have an open accessway upwind and few, if any, barriers downwind.

Detailed studies of a well-developed interdune 

deposit between linear (seif) dunes in the Fezzan of 

Libya were made in 1962 (McKee and Tibbits, 1964, 

p. 13). These studies indicated that effective winds 

moving down the length of a flat interdune surface 

deposited sand as flat-lying laminae to a thickness 

of at least 4 feet (1 m), as shown in test pits (fig. 73). 

No cross-strata were noted. The sand as determined 

by analysis was poorly sorted, ranging in size from
110 A STUDY OF GLOBAL SAND SEAS

BEVELED WINDWARD SURFACE of transverse dune showing truncation of lee-side foresets, White Sands National Monument, 

New Mexico, U.S.A. From McKee and Moiola (1975, fig. 66). (Fig. 69.)

^V 5s« B?j^-^rv-«« '£^'-9* T. - —.< A " --T*. ',' £it"-~~ \x^, -*-••- ar.i« '--^%,

•-W. ^ • <^ij JM^S^H^V^-r^^ ^'^S$M

>S BEVELED REMNANT OF TRANSVERSE DUNE in interdune area, 

rf White Sands National Monument, New Mexico, U.S.A. From

BEVELED REMNANT OF BARCHAN DUNES in interdune area, McKee (1966)- ( Fl& 7r) 

White Sands National Monument, New Mexico, U.S.A. Three 

truncated sets of cross-strata are visible. (Fig. 70.)
SEDIMENTARY STRUCTURES IN DUNES 111

HORIZONTAL AND IRREGULARLY BEDDED STRATA in trench, 

interdune area between barchanoid ridges, White Sands National Monument, New Mexico, U.S.A. Scale is in inches. 1 inch 

= 2.54 centimetres. From McKee and Moiola (1975, fig. 6). (Fig. 

72.)

very fine to coarse, in contrast to well-sorted sand 

in nearby dunes. Along the margins of the linear 

dunes, which have slipfaces on both sides dipping 

at high angles (as much as 35°), interdune deposits 

consisted partly of low-angle strata (10°-13°), dipping toward the dunes, and partly of very fine 

structureless sand. No information is available on 

the thickness of these interdune deposits.

The nature of interdune deposits between star 

dunes (fig. 74), which are the product of multidirectional wind regimes, has not been investigated, to 

the author's knowledge. Such dunes mainly build 

vertically, rather than migrating laterally. After attaining a maximum peak height permitted by the 

threshold velocity, they must spread outward from 

the base, so it seems probable that the interdunes 

develop few of the features characteristic of 

troughs (sediment traps) associated with the active 

migration of transverse-type dunes. The structural 

character of interdunes in fields of star dunes is yet 

to be determined.

Deformational 

Structures in Dunes

IN ADDITION TO sedimentary structures 

formed by deposition, numerous penecontemporaneous structures, caused by deformation of 

strata during or immediately following deposition, 

are characteristic of various dune types. Principal

Sandy clay 

Lag gravels

White 

sandy clay

EXPLANATION

B

BLOCK DIAGRAMS (A, B) OF INTERDUNE STRUCTURES and 

photograph of test pit between seif dunes, northeast of Sebha, 

Libya. A, pit 14; B, pit 12. From McKee and Tibbitts (1964, fig. 8a, 

c). C, Test pit in center of interdune area, shows horizontal 

stratification. Steel tape extends 4 feet (1 m) down. Photograph 

by Gordon C. Tibbitts, Jr. (Fig. 73.)
INTERDUNE SURFACE AMONG STAR DUNES near Tsondab Vlei, Namib Desert, South-West Africa. Photograph by E. Tad Nichols. 

(Fig. 74.)

forms of deformation in dune cross-stratification 

are folds, faults, and brecciated strata of which 

there are many varieties.

Penecontemporaneous deformation is caused in 

dunes primarily by avalanching, either through 

slumping (mass movement) or by grain flowage; 

less frequently it results from loading, plant 

growth, scour-and-fill processes, and sand drag. 

Virtually all forms are considered to be contorted 

bedding, and most are very irregular, especially 

when compared to similar-appearing structures 

formed in competent rock masses.

A classification of deformational structures in 

dunes, with suggested terminology for various 

forms that have been recognized, was proposed by 

McKee, Douglass, and Rittenhouse (1971). This

classification was based partly on experimental 

work in the U.S. Geological Survey Sedimentary 

Structures Laboratory in Denver, Colorado, and 

partly on field investigations at White Sands National Monument, New Mexico. Subsequent field 

studies, testing the validity of this classification on 

coastal dunes of Brazil, were made by McKee and 

Bigarella (1972).

Principal types of deformation structures formed 

in avalanche deposits are referred to as rotated 

structures, warps or gentle folds, drag folds and 

flames, high-angle asymmetrical folds, overturned 

folds, overthrusts, break-aparts, breccias, and 

fadeout laminae (fig. 75). Some of these structures 

are characteristic of tensional stresses, common 

near the tops of dune slipfaces; others are principally the result of compressional forces that
SEDIMENTARY STRUCTURES IN DUNES 113

develop near the bottoms of dune foresets. Some 

are common in dry sand, others develop mostly in 

wetted sand, saturated sand, or sand with damp 

crusts.

Moisture greatly affects the type of contorted 

structure developed within a sand body because it 

largely controls the degree of cohesion of sand particles. In sand that is dry, cohesion of grains is 

slight, and the chief deformational structures are 

fadeout laminae, drag folds and flames, and warps 

or gentle folds. In sand that has been wetted, considerable cohesion develops, and common deformational structures are break-aparts and breccias, rotated plates and blocks, and high-angle asymmetrical folds. An analysis of these trends as determined 

in laboratory experiments and in a comparison of 

desert sands in New Mexico and coastal sands in 

Brazil was tabulated by McKee, Douglass, and Rittenhouse (1971, table 5).

In many dune sands, both coastal and desert, 

moisture may form wet crusts, as from early morning dew. In such deposits, certain layers have been 

dampened or wetted shortly after deposition, so 

wet and dry layers alternate.

"**»•..

B

Nl

» .

^"Vs

• "\

'

D

X., ^'-x """xv

**•. '^ '•."

"""'

•~:*X!-* -• ••*..'•*' •"" .••' .r"

G H I

PRINCIPAL TYPES OF DEFORMATIONAL STRUCTURES in avalanche deposits of dunes: A, Rotated structures; B, warps or gentle 

folds; C, flame structure; D, drag fold; E, high-angle asymmetrical folds; F, overturned folds; G, overthrust; H, break-aparts; /, breccias. 

Each block represents an area approximately 6x4 inches (15x10 cm). (Fig. 75.)
114 A STUDY OF GLOBAL SAND SEAS

Structural Features at 

Lagoa Dune Field, Brazil

By JOAO J. BIGARELLA

Parabolic Dunes

THE LAGOA DUNE FIELD is in the east-central 

part of Ilha de Santa Catarina (State of Santa 

Catarina, Brazil). The dune field is bounded on the 

east by crystalline hills (mostly granite), on the 

south by the Campeche Beach (locally referred to as 

Joaquina or Lagoa Beach), and on the west and 

north by the Lagoa da Conceicao lagoon (fig. 76).

Prevailing winds in this area blow from the 

northeast, but short-term storm winds come from 

the south. The influence of the prevailing winds on 

the dune field is decreased considerably by granitic 

rock hills located upwind. The prevailing winds are 

deflected by the mountains to the west of the Lagoa 

da Conceicao and reach the dune area as northerly 

winds. Because the dune field is located in a 

shadow area, protected from the northeasterly prevailing winds, the deflected northerly winds cannot 

counteract the action of sand transport from the 

southern short-term storm winds. Thus, the main 

eolian sand movement is to the north (Bigarella, 

1972).

The Joaquina Beach constitutes a main source of 

eolian sand. However, the amount of dry sand 

available for eolian transport on the beach is too 

small to counteract the deflation caused by the 

strength of the southern storm winds in the 

southern part of the dune field. Therefore great 

numbers of blowout features, including parabolic 

dunes, are well developed. In the northern part of 

the dune field, a series of reversing dunes has 

formed from the interaction of opposing winds. 

They are slowly moving northward.

Method of Study

The present study is of a compound parabolic 

dune located in the southern part of the Lagoa dune 

field about 480 metres (1,575 ft) from the beach. 

Most of the internal structures to be recorded and 

analyzed were exposed by digging a series of 

trenches and pits, and by cleaning two erosion 

scarps cut by deflation near the dune nose (fig. 77). 

Trenches C, D, I, and H are located in the most active part of the parabolic dune, trench I on the slipface, trench H on the windward side behind the 

crest, and trenches C and D oriented oblique to the 

wind direction. Trench E and pits Elf E,, and E3 are 

alined roughly parallel to the wind direction and 

constitute a southern continuation of scarp B, extending down the windward slope into the interdune area. Trenches F and G, and pits 1 -7 are 

oriented normal both to the dune's arms and to the 

dominant wind direction. These pits are located in 

the interdune area and dissect some of the small 

satellite parabolic dunes.

Cross-Stratification

Cross-strata in the parabolic dune are medium 

scale in the crest area but large scale in the nose and 

the arms. Many laminae dip at high angles 

(29° -34°) in the nose and also in the arms where 

they are normal to the dominant wind direction and 

to the dune axis. Both along the crest and in some 

parts of the arms, the bounding surfaces between 

sets of cross-strata are nearly horizontal. 

Elsewhere, as in the nose and parts of the arms, 

they dip at angles ranging from low to high. As 

verified for other dune types (McKee, 1966; 

Bigarella, Becker, and Duarte, 1969), individual sets 

of cross-strata tend to be thinner and the laminae 

flatter near the top than at the bottom of the dune 

(fig. 77).

Cross-strata measurements for all trenches, 

scarps, and pits in the various parts of the dune are 

summarized in tables 10 and 11, and in figure 78. 

Measurements in each part are controlled by its 

local morphological conditions (fig. 77).

Nose Area

In the nose, high-angle foresets are characteristic 

features in the walls of trenches C and I. These 

trenches were oriented oblique and parallel, respectively, to the southern storm winds (fig. 77). Trench 

C, excavated in the slipface, was oriented N. 52° W. 

at an angle of about 46° to the direction of the 

southern storm winds, but approximately in the 

average cross-strata dip direction as calculated 

from nine measurements. In trench I, excavated 

parallel to the direction of the storm winds, five 

measurements of cross-strata were made, and their 

dips were N. 2° -15° W. The average dip, N. 6° W., 

coincides with the main direction of the southern
SEDIMENTARY STRUCTURES IN DUNES 115

LAGOA 

DUNE 

FIELD

Sand

Parabolic dunes 40 metres (131 ft) high

Parabolic dunes 20 metres (65 ft) high

Sandy ramps—Developed by dissipation of eolian 

sands from earlier dunes

Low plain—Mostly sandy with few swampy areas 

Precambrian crystalline basement—Mostly granite 

Boundary—Dashed where approximated

LOCATION OF LAGOA DUNE FIELD, llha de Santa Catarina, State of Santa Catarina, Brazil. Modified from Bigarella (I975b, fig. 1). 

(Fig. 76.)
116 A STUDY OF GLOBAL SAND SEAS

EXPLANATION

Forward edge of dune slipface 

Dune crest

Cross-strata (thin lines) bounded by 

erosion surface (heavy line)

0123

Tnnch H

Tnnch G

CROSS SECTIONS AND PLAN VIEW of parabolic dunes studied in the Lagoa dune field, llha de Santa Catarina, Brazil, showing 

A—A', 8—8', and C—C show surface profiles across dune and interdune areas with locations of pits and trenches. All measure-
SEDIMENTARY STRUCTURES IN DUNES 117

SSE

scarps, trenches, and pits. Groups of lines numbered 1-5 are approximate locations of outcropping laminae. Cross sections 

ments in metres. 1 metre=3.28 feet Modified from Bigarella (1975b, figs. 4, 5). (Fig. 77.)
118 A STUDY OF GLOBAL SAND SEAS

storm winds (S. 6° E.) and with the axis orientation 

of blowout dunes inside the Lagoa dune field. In 

trench I, the average cross-strata dip direction coincides with the dip direction of the slipface surface. 

The rose diagrams of figure 79 illustrate crossstrata dip directions from various trenches dug in 

the slipface and crest areas. The slipface and the 

crest just behind it have a similar cross-strata attitude, but differ in the average of the cross-strata 

dip angles, which are 10° -13° less in the crest beds.

Crest Area

In the present crest area, trenches D and H constitute southward continuations of trenches C and I 

in the slipface area (fig. 77). In trenches D and H, 

internal structures consist of two main parts: (1) a 

thick set of cross-strata with high-angle foresets, 

deposited as the nose of this parabolic dune at an 

earlier stage, and (2) thinner cross-strata sets with 

low- to moderate-angle dips deposited on the crest 

(fig. 77).

An erosion surface truncates the lower set in 

both trenches. On the west side of trench D (fig. 

77), an early set of crest-strata dipping 6°-11° 

toward N. 37° W. is overlain by high-angle foresets, 

mostly dipping 29° -35° (average 28°) to N. 58° W. 

This succession suggests a former slipface on the 

western flank of the nose approximately where 

trench C is located (fig. 77). The truncated slipface 

is overlain by a sequence of strata dipping at low 

angles (1° -11°) toward the eastern quadrant N. 55° 

E. -S. 52° E.

High-angle cross-strata in the lower part of 

trench H (fig. 77) dip N. 13° E., whereas those from 

the upper part (crest beds) dip N. 27° E. (four 

measurements). These cross-strata of the crest continue northward to form strata of the slipface. In 

the area of transition between the crest and the 

slipface, strata are convex upward. Both parts of 

trench H have dip directions which diverge by 

19°-33°, indicating that the former slipface dip 

direction was more north-northeastward than the 

slipface of trench I, which is alined with the wind 

direction.

Structures representing an earlier position of the 

crest are exposed scarps A and B. The former crests 

were cut in half by a deflation corridor and a new 

crest was built downwind. In the erosion scarps,5 

about 2.5 metres (8.2 ft) of sand sequences were exposed— both windward strata and downwind 

strata (fig. 77). Sets of cross-strata are prominent in 

erosion scarps A and B, and bounding surfaces dip 

slightly to moderately windward. Some sets of 

strata dip downwind at low angles, other sets are 

approximately horizontal.

The whole crest seems to result from the coalescence of several low mounds of sand. Rose 

diagrams in figure 79 illustrate the peripherally dipping attitudes of cross-strata deposited in the windward and downwind parts of the former dune crest. 

High-angle dips (15°-30°) occur among lee-side 

sets of cross-strata on the west side of erosion scarp 

A (fig. 77). On this scarp, the average dip of crossstrata is 12.8°; many angles of dip are between 

3° -11°. The resultant southeasterly vector and the 

low-angle strata indicate a predominance of windward-deposited strata (fig. 77), although about 20 

percent of the strata dip peripherally in all directions around the compass, suggesting a very gentle 

dome structure.

Erosion scarp B, on the opposite side of the deflation corridor from scarp A, exposed strata dipping 

mostly less than 10° and averaging 8.4°. The strata 

dip consistently south west ward, suggesting that 

this part of the former crest of the parabolic dune 

had a dome shape.

Trench E extends southward from erosion scarp 

B (fig. 77) and has in its upper part strata that dip 

south and belong to the former dome-shaped crest. 

Internal structures indicate the presence of cresttype cross-strata, of which the average dip is 12.9°. 

The lower part of the trench is composed of lowangle strata dipping downwind 8° -16°, whereas the 

upper part is composed of windward-dipping strata 

with dips of 16° -18°. The sequence of erosion scarp 

B overlies strata of trench E. Trench E strata, in 

turn, overlie sets of high-angle cross-strata exposed 

in pits Elt E2 , and E3 in the present interdune area. 

The high-angle (25°-33°) strata in these pits are 

lower parts of slipface deposits of a parabolic dune 

nose which migrated northward and was truncated 

by deflation. A new crest was later developed 

(lower part of trench E deposits) but was eroded on 

its windward side, which formed the deposit downwind represented in the erosion scarp B sequence.

The crossbedding pattern exposed at the surface, 

upwind from the crest, at the transitional edge of 

the interdune area, is illustrated in figure 80 (outcropping laminae in fig. 77). The trace of high-angle
SEDIMENTARY STRUCTURES IN DUNES 119

cross-strata represents deposits from the nose and 

lower parts of the arms of this parabolic dune. 

Cross-stratification is periodically exposed by 

deflation in this area. The three main sets of nose 

deposits downwind suggest the way in which the 

crest and nose split and develop as wide and very 

low moundlike features.

Rose diagrams (fig. 78) show the attitude of 

cross-strata that are exposed behind (upwind of) 

the crest. Measurements were made on both the left 

(west) and right (east) sides of the dune axis. The

average dip direction for both sides is within a 

spread of 33°. The resultant vector N. 13° E., is 18° 

to the east of the main direction of the southern 

storm winds.

Arms

Basic structures in the arms of the parabolic dune 

are illustrated in trenches F and G, which are nor5 Erosion scarps refer to surfaces along the sides of deflated or "blowout" areas 

which have been smoothed by machete. Trench walls refer to elongate excavations of much longer dimensions than the pits.

ENTIRE DUNE

SCARP A; 

TRENCHES C, D

SCARPS (NOSE 

AND CREST) A, B; 

TRENCHES C, D, E

SCARP B; 

TRENCH E

TRENCH F COMPOSITE OF PITS 

0-7, E v E2 , E3 (INTERDUNE)

TRENCH G

ROSE DIAGRAMS OF CROSS-STRATA DIP DIRECTIONS recorded for scarps, trenches, and pits representing principal parts of 

parabolic dune and interdune area. Values are in percent. Modified from Bigarella (1975b, fig. 6). (Fig. 78.)
TABLE 10. — Frequency of dip-direction intervals for cross-strata in trenches, scarps, pits, and surface of a parabolic dune, Lag

field, Brazil 

[Modified from Bigarella (1975b, fig. 6). Locations shown in fig. 77]

Interval 

(degrees)

0-30 

30-60 

60-90 

90-120

120-150 

150-180 

180-210 

210-240

240-270 

270-300 

300-330 

330-360

Scarps and trenches

A

1 

2 

1 

1

6 

10 

3

1

1 

1

1

B

3

10

1

c

2 

7

D

1

1 

2

6

11 

2

E

1

2

1 

6

F

1 

1

1 

3

4 

10 

4 

1

G

1 

25 

12

5 

9 

2

Total

2 

4 

27 

15

9 

13 

5 

4

20 

29 

25 

10

Pits

1

1 

4

1 

1

1

4 

5 

1

2

5

2 

1 

5

3

2 

1

1

3 

5

4

1

2 

1

1

1

5

2 

5

7

1

6

1

1

2 

1

7

1

2 

4 

2

EI

1

2 

2

E2

1

1 

3 

2

E3

2 

1 

5

Total

13 

12 

16 

2

2 

1

1

7 

11 

18 

15

Surface

West

27 

4

8

21

East

19 

22 

1

1 

2

TABLE 11. — Direction and degree of dip for cross-strata in trenches, scarps, pits, and surface of a parabolic dune, Lago

field, Brazil 

[Modified from Bigarella (1975b, fig. 6). Locations shown in fig. 77]

Locality

Scarps A, B, trenches C, D, E .........

Trpnrh F

Trench G ...........................

Total .........................

Total pits .....................

Surface — East side .................

Surface — West side .................

Total .........................

Entire dune ...................

Number of Mean dip 

measurements direction1

H4

25

54

163

98

45

60

.... 105

.... 366

N. 83° W. 

N. 75° W. 

N. 74° E.

N. 53° W.

N. 5°W.

N. 31° E. 

N. 3°W.

N. 13° E.

N. 5°W.

277° 

285° 

74°

307°

355°

31° 

357°

13°

355°

Consistency 

ratio2

0.32 

.51 

.43

.13

0.15

0.95 

.84

0.44

0.42

Maximum 

dip

35° 

28° 

34°

35°

37°

34° 

34°

34°

37°

Avera

dip

16.1

14.1

22.2

17.8

17.4

25.5

23.6

24.4

19.6

1 The frequency of dip-direction data from which the mean dip direction was derived are shown in table 10.

2 Consistency ratio is obtained by dividing the length of the vector resultant of all observations at a given locality by the sum of the lengths of individual v

is a weighted measure of degree of grouping of vectors. It ranges from 1 to 0.
SEDIMENTARY STRUCTURES IN DUNES 121

mal to the direction of the southern storm winds 

(fig. 77). The cross-strata sets dip toward both the 

eastern and the western quadrants, almost at right 

angles, or oblique to those on the dune nose.

The profile across the arms of the parabolic dune 

may be divided into two parts — the inner and the 

outer. The inner side, less steep than the outer, 

commonly is an area of deflation. The steeper, 

outer profile has a slipface and is an area of deposition.

In trench G, on the right arm of the parabolic 

dune, the lower part of the sequence on the left side 

of the trench is composed of westerly dipping strata 

averaging 15.2° (fig. 77). The highest dips are 

19° -22° and the lowest, 9° -13°, similar to the middle part of trench F below the crest, where dip 

angles are also 9°-13° (fig. 77). These cross-strata 

are not typical slipface deposits like those shown on 

the right (eastern) side of trench G (fig. 77). The 

left (western) part of trench G may represent a 

former outer part of the left arm of an earlier 

migrating parabolic dune, subsequently truncated 

by the present dune.

On the east side of trench G (fig. 77), foresets are 

mostly medium- to large-scale. The cross-strata dip 

eastward. Forty percent of them have high-angle 

dips (30° -34°); most of the others dip only 21° -29°. 

Bounding surfaces also have moderate dip angles. 

The average dip of cross-strata in trench G is 22.2°. 

High-angle strata from the outer part of the arm 

dissected by trench G seem to overlie low-angle interdune cross-strata, enriched with humate compounds. In some places, an incipient paleo A 

horizon is developed (nearly vertical lines, on east 

edge of trench G fig. 77).

The internal structure of trench F is far more 

complex than that of trench G. The right (east) side 

of trench F (fig 77) is composed in the lower part of 

truncated cross-strata dipping westward at moderate angles (18° -25°). They represent deposits of the 

left arm of a former parabolic dune which migrated 

across the area. Between this sequence and the one 

forming the crest are nearly flat lying strata (3° -5°) 

which probably represent interdune deposits. 

Above these interdune strata, the structures of the 

arm can be traced across a series of erosion surfaces, each series truncating slipface strata, up to 

the present position of the crest. Bounding surfaces 

in trench F dip moderately westward.

Low-angle cross-strata commonly are deposited 

on the windward sides of dunes, but in the arm of 

this parabolic dune some of the low-angle dipping 

strata seem to have been deposited on the inner 

side of the arm at almost right angles to the wind 

direction.

The opposing attitudes of cross-strata in trenches 

F and G are illustrated in a rose diagram (fig. 78; 

tables 12, 13).

TABLE 12. — Attitudes of 25 cross-strata sets in trench F of 

parabolic dune, Lagoa dune field, Brazil

[Modified from Bigarella (1975b, table 1)]

Set

No.

1

2

3

4

5

6

7

8

9

10

11

12

13

Dip 

direction (°)

290

310

312

332

315

295

111

98

6

136

165

172

165

Amount 

of dip (e)

25

20

18

12

25

12

18

3

5

25

10

11

8

Set

No.

14

15

16

17

18

19

20

21

22

23

24

25

Dip 

direction (°)

270

305

310

325

310

302

302

276

280

279

310

285

Amount 

of dip (°)

6

14

8

16

9

12

13

11

13

16

15

28

Dip direction: For true north, subtract 12°.

Deformation

Penecontemporaneous deformation, caused by 

slumping of steep foresets, is common in most 

coastal dune structures (fig. 81). This gravity 

slumping occurs during or soon after deposition.

Deformational structures also occur in 

moderately to gently dipping strata. Deformed 

laminae may occur between undeformed beds (fig. 

82A) or may affect adjoining sets of strata. The 

structures produced by deformation seem to be 

chaotic — folds, faults, and breccias which consist 

of broken, rolled, and crinkled masses of sand (fig. 

81). Some contorted structures result from the activities of organisms (fig. 82C).

The response to stresses and the type of structures produced during deformation are controlled 

largely by the amount of moisture present in the 

sand (McKee, Douglass, and Rittenhouse, 1971; 

Bigarella, Becker, and Duarte, 1969; McKee and 

Bigarella, 1972).
122 A STUDY OF GLOBAL SAND SEAS

TABLE 13. — Attitudes of 54 cross-strata sets in trench G of 

parabolic dune, Lagoa dune field, Brazil

[Modified from Bigarella (1975b, table 2)]

Set 

No.

1

2

3

4

5

6

7

8

9

10

11

12

13

14

15

16

17

18

19

20

21

22

23

24

25

26

27

Dip 

direction (°)

274

331

290

291

310

278

305

332

288

284

296

279

283

275

286

279

77

99

110

64

91

91

89

85

91

88

102

Amount 

of dip (°)

20

9

22

14

10

17

14

12

18

20

15

16

19

14

13

10

22

23

3

12

21

27

16

26

31

25

18

Set 

No.

28

29

30

31

32

33

34

35

36

37

38

39

40

41

42

43

44

45

46

47

48

49

50

51

52

53

54

Dip 

direction (°)

95

94

102

95

87

95

95

107

97

103

103

110

106

108

97

97

102

108

97

100

97

96

102

92

99

75

84

Amount 

of dip (°)

27

21

21

27

23

30

31

29

32

34

32

27

37

30

34

33

32

28

32

29

30

27

33

20

8

12

16

Dip direction: For true north, subtract 12°

Interdune Areas Among Parabolic 

Dunes

In an interdune area, between the arms of a surveyed parabolic dune (fig. 77), two lines of pits 

were dug. The east-west line (pits 1 -7) provided 

information concerning the interdune area between 

the trenches G and F on the trailing arms of the 

parabolic dune. The north-south line (pits E1 -E3 ) 

forms a southward continuation of trench E. The 

pits are rectangular in cross section with sides approximately 1 -2 metres (3 -6 ft) long and depths of 

1 -2 metres (3 -6 ft; figs. 83, 84).

Characteristic of the interdune area are the apparently structureless sands, enriched with humic 

compounds derived from incipient soil formation. 

In some places, paleosol A horizons alternate with 

stratified sand (pit 6, fig. 83).

The interdune area frequently becomes wet, 

sometimes swampy, after rains, and small ponds

may form in low parts when the phreatic water 

level rises. A typical vegetation cover of grasses 

and shrubs grows in the interdune environment 

when the sand is wet, and many small plants, 

especially Gramineae and Cyperaceae germinate 

there. Humic compounds that originate from decay 

of the organic material stain the sandy substratum 

and are responsible for the brown color of both 

ground water and surface water.

The buried upper surface of the brown structureless sand is irregular. Above this surface are sequences of cross-stratified eolian sand deposited 

either by migration of the main parabolic dune or 

by growth of small satellite parabolic dunes (fig. 

85).

The attitudes of 98 cross-strata were measured in 

the 10 pits. About 42 percent had dip angles greater 

than 20°, whereas 58 percent had dip angles less 

than 15°. The maximum dip recorded was 37°, and 

the average dip was 17°. The crossbedding pattern 

from the interdune area documents the migration 

or movement of former dune bodies across this 

area. The traces of several parabolic dunes, both 

nose and arms, can be recognized. A rose diagram 

(fig. 86) shows most strata in this area dipping 

toward the northern quadrants, with an average dip 

direction of N. 5° W.

Substantial changes in dune morphology along 

the Brazilian coast have been caused by climatic 

change (Bigarella, 1965,1972). Recent action of concentrated rainfall has greatly modified the original 

sand body at Lagoa — the eolian sands were spread 

by floodwaters like a blanket, decreasing in thickness downstream.

Climatic changes in the past provided conditions 

under which extensive dune development alternated with dune modification. Early deposits of 

eolian sands have become mixed with colluvial 

material producing an unsorted sandy, muddy sediment. Mixing took place during colluvium movement caused by climatic change.

The dunes subjected to heavy rainfall became 

saturated with water. This rainfall caused wet sliding, sand flows, gullying, and the formation of 

many alluvial fans that coalesced to form dissipation ramps (fig. 76). Many faults were developed in 

the sand during avalanching. Sand-flow and rainwash deposits mostly form wavy or lens-shaped 

layers, and many of them are imbricated. Some
SEDIMENTARY STRUCTURES IN DUNES 123

deposits are largely derived from alteration of the 

dunes; others are mixtures of colluvium and 

modified eolian sands. In some places, clay was 

deposited in ephemeral interdune ponds. Times of 

soil formation alternated with times of erosion. In 

the same manner, dissipation deposits are intercalated with deposits having normal dune crossstratification.

Interdune Areas Among Reversing 

Dunes

At Lagoa dune field the depositional environment of interdune areas among reversing dunes is

much drier than the corresponding areas among 

parabolic dunes. Some ephemeral ponds are present, but most of the area is covered with Gramineae 

and Cyperaceae, and some parts of it consist of sand 

plains without vegetation. In the unvegetated area, 

four pits and two trenches were dug to expose the 

internal structures of an interdune (fig. 87). Trench 

VII shows a sequence of northward-dipping truncated foresets deposited by short-term storm winds 

from the south. In trenches VIII, XVII, XVIII, and 

XIX, high-angle foresets are covered by flat-lying 

beds, dipping less than 1°. Where these strata approach the slipface of the next dune upwind, 

however, the dip is as much as 10°. In trench IX the

TRENCHES

Number of measurements (nm), dip direction (dd), consistency 

ratio (cr), and average dip (ad) data for trenches and scarps

SCARPS

A, B

C, I

Trench

Scarp

C

D

I

H

E

A

B

nm

__ __ Q

—— 23

—— 5

— — 6

—— 10

-— 28

—— 14

dd

N. 55° W.

N. 46° W.

N. 07° W.

N. 22° E.

N. 22° W.

S. 25° E.

S. 74° W.

cr

0.99

.66

1.00

.99

.61

.57

.98

ad 

(degrees)

32.6

19.8

29.8

19.5

12.9

12.8

8.4

CROSS SECTION

ROSE DIAGRAMS OF ATTITUDES of cross-strata deposited in an earlier dune crest (trenches D, H, E, and scarps A, B) and in the 

nose (trenches C, I) of a parabolic dune (fig. 77), Lagoa dune field, Brazil. Values are in percent. Generalized cross section through 

dune is parallel to dominant wind direction and shows location of trenches and scarps. Table gives statistical data. Modified from 

Bigarella (1975b, fig. 7). (Fig. 79.)
124 A STUDY OF GLOBAL SAND SEAS

OUTCROPPING LAMINAE EXPOSED on beveled surface in interior of parabolic dune. Units 1-5 show details of traces of laminae 

as exposed by natural truncation in interdune area (fig. 77). Direction of strike and dip shown by symbols. Scale is approximate. 

Modified from Bigarella (1975b, fig. 6). (Fig. 80.)

high-angle foresets are covered by interdune 

deposits which range in dip from low angle to 

almost horizontal, and above these is another set of 

high-angle dune foresets.

Dissipation of Dunes, 

Lagoa, Brazil

By JOAO J. BIGARELLA

General Features and Environment of 

Dune Dissipation

ALONG THE BRAZILIAN coastal plain flash 

floods have changed both internal pattern and 

morphology of the original dunes and beach-ridge 

deposits. This reworking (by dissipation) modifies 

or destroys original dune structures, and it concentrates colloidal materials in a wavy, irregular 

pattern known as dissipation structure.

In an area within the Lagoa dune field on the Ilha 

de Santa Catarina, Brazil (fig. 76), dissipation structures in parabolic dunes were studied. Flash flooding in this area forms the large sandy ramps and the 

small-scale structures that interrupt normal dune

bedding patterns. The processes seem to be cyclic 

and occur only under certain environmental conditions; accordingly, dissipation layers alternate with 

dune bedding and are recurrent in the stratigraphic 

section. The older dunes in the dune field have lost 

their original shape by dissipation. Some still show 

either a hummocky morphology or a rounded 

topography. Others have been changed to tongueshaped layers that are not intercalated among other 

dune deposits.

Four principal sequences of eolian sands separated by paleosols (A horizons) occur as a dissipation ramp on the slopes of the granite hill (Joaquina 

Hill) just east of the dune field (fig. 88; study area 

in fig. 76). The contacts between the various sand 

sequences are irregular, owing to either erosion or 

the hilly topography of the dunes.

The oldest sequence, which is reddish brown, 

rests on a clayey lag deposit, composed of granite 

and quartz pebbles, which, in turn, overlies 

weathered granite. The eolian sand above the 

gravel pavement originally consisted of fine 

windblown grains. This sand subsequently became 

mixed with granules (primarily quartz and 

feldspar), clays, and silts from the weathered granitic mantle.
SEDIMENTARY STRUCTURES IN DUNES 125

SCARP A TRENCH F

0 10

0 25

TRENCH G

DEFORMATIONAL STRUCTURES OBSERVED in parabolic dune, Lagoa dune field, Brazil. All measurements are in centimetres. 1 

centimetre =0.39 inch. (Fig. 81.)
126 A STUDY OF GLOBAL SAND SEAS

STRUCTURES IN A PARABOLIC DUNE, Lagoa dune field, llha 

de Santa Catarina, Brazil. A-D, Structures in trench G, eastern 

arm of parabolic dune. A, Contorted bedding in strata dipping 

toward the interdune area between the arms. B, Strata in trench 

showing a shift of the dune arm. The lower set dips toward the 

interdune area between the dune arms, and the upper set dips 

outward. C, Collapse structure caused by sand flow filling nearby burrowing crab tube. Strata are dipping eastward in trench.

D, High-angle strata set dipping eastward in trench showing 

string-and-nail grid for recording structures. E, F, Structures in 

eastern arm of parabolic dune, f, Former crest area exposed by 

erosion (deflation), showing downwind strata dipping to the 

left, upwind strata dipping to the right and horizontal to 

subhorizontal strata corresponding to crest deposits. F, Former 

crest area showing transition from crest-area strata into foreset 

strata. (Fig. 82.)
SEDIMENTARY STRUCTURES IN DUNES 127

Textural changes are numerous among the dissipation sands at Joaquina Hill. A mixing of textures occurred when the dune sands slid 

downslope, destroying original structures. Moving 

sands contributed detrital material from the underlying weathered mantle. Mud and sand flows 

containing granules, from upslope, mixed with and 

covered sliding eolian sands. This formed the final 

sediment layer of an unsorted light red sandy granule deposit.

An erosional unconformity, with local paleosol 

(A horizon) development, separates each sequence 

of eolian sand. Former dunes in the two intermediate sequences also underwent mass movement, 

causing structural and compositional changes similar to those previously discussed. As a result, each 

successive sequence has fewer granules.

Processes, Structures, and Soil 

Formation

Dunes

The original eolian deposits of the Lagoa dune 

field consist of reversing parabolic and captation 

dunes, such as stringers and hanging dunes. Sedimentary structures differentiate dune sands from 

beach sands of the neighboring source area and the 

patterns of eolian cross-strata allow differentiation 

of dune types.

At times large parts of dunes or entire dunes undergo subsequent structural changes, causing disappearance of the characteristic eolian cross-strata 

patterns. The original structures are replaced by 

much less clearly defined patterns or by structureless deposits — that is, dissipation structures.

Structures produced by reworking of eolian 

sands are not as easily visible as those of original 

dunes, but they constitute new sedimentary structures — that is, dissipation structures. Most of these 

structures resemble contorted bedding, but they are 

produced by heavy density flow or by loading. 

Some resemble cut-and-fill structures; others 

follow shearing planes and small intraformational 

faults produced by sand flowage. Tube-shaped 

features, reflecting root growth or the burrowing of 

animals, such as crabs, also occur in these deposits. 

Small circular or irregular patches may suggest 

root growth.

The new internal structure commonly is characterized by an irregular, wavy pattern accented by 

differences in concentrations of colloidal material 

composed predominantly of clays, hydrous iron oxides, and humic compounds (fig. 89). Previously 

these features generally were ascribed to soil-forming processes; now, they are known to be the result 

of reworking by dissipation processes. The wavy 

features are especially prominent because they are 

outlined with colloidal material along preferential 

lines. The concentration of colloidal material 

follows irregular directions that do not correspond 

to any previous stratification planes or dune structures. At Joaquina Hill, the colloidal material is 

composed predominantly of clay minerals and hydrous iron oxides, as well as minor amounts of 

humic compounds. Apparently, colloidal material 

tends to concentrate preferentially along structural 

patterns that developed during the dissipation of 

former dunes.

Flash floods cause the mineral colloidal material, 

such as from a weathered granitic mantle, to mix 

with the eolian sands. The amount of mineral matter reinforcing the structures is variable — in most 

places, less than 5 or 10 percent. After every sand 

flow, the colloidal material either concentrates at 

the uppermost section of the sedimentary layer as a 

"peel" or filters down into lower layers. In the 

lower layers, colloidal material tends to settle along 

structural lines, which makes the strata more 

readily visible. Structures later become vague as the 

colloidal enrichment progresses. With an increasing 

content of colloidal material, the structures lose 

identity, and the sediments develop a uniform, 

brown color.

Close to the source of weathered granite mantle, 

the usually thin colloidal peel increases in thickness and becomes a colluvial layer. Such layers 

alternate with reworked eolian sands. The development of a colluvial layer over a reworked eolian 

sand produces an irregular surface with tongues 

and other features that indicate inclusion of the 

sand in the colluvial layer. The overlying colluvial 

layer produces contorted structures in the underlying sediments.

In surface accumulations deposition of colloidal 

material may be contemporaneous with deposition 

of sand layers. Downward migration of colloidal 

material is a penecontemporaneous feature. The in-
128 A STUDY OF GLOBAL SAND SEAS

Set Dip0 Strike"

Set

1

2

3

4

5

6

7

8

9

10

11

12

Dip0

14

7

14

8

9

9

15

20

13

10

11

25

Strike0

354

349

344

334

351

49

39

327

133

6

30

328

l/\——I

50cm[J__I

Set Dip" Strike0

EXPLANATION

Structureless sand impregnated with humic compounds; 

locally includes incipient paleosol (A horizon)

Paleosol (A horizon)

STRATIFICATION IN PITS 1-7 along east-west line in the interdune area between the arms of a parabolic dune in the Lagoa dune 

field, llha de Santa Catarina, Brazil. Dip and strike are given for each numbered cross-strata set within a pit. Pit locations are shown 

in figure 77. Modified from Bigarella (1975b, figs. 14-16). (Fig. 83.)
SEDIMENTARY STRUCTURES IN DUNES 129

Set Dip0 Strike" 

332

01 

356

21 

335

Set Dip0 Strike0 

1 15 286 

25 327

23 340

24

31

11

13

331

342

346

43

STRATIFICATION IN PITS E,, E2, and E3 along north-south line 

of the interdune area between the arms of a parabolic dune, 

Lagoa dune field, llha de Santa Catarina, Brazil. Dip and strike 

are given for each numbered cross-strata set within a pit. Light 

stippled areas are nonstratified sand. Pit locations shown in 

figure 77. Modified from Bigarella (1975b, fig. 17). (Fig. 84.)

STRUCTURES OF INTERDUNE AREA between the arms of large 

parabolic dune at Lagoa dune field, llha de Santa Catarina, 

Brazil. A, Collapse structure of sand filling tube of burrowing 

animal; 6, set of high-angle cross-strata of earlier dune between 

sets of interdune subhorizontal strata; C, high-angle faults in 

foresets of earlier dune preserved in interdune area. (Fig. 85.)
130 A STUDY OF GLOBAL SAND SEAS

10%

ROSE DIAGRAM OF CROSS-STRATA DIP DIRECTIONS, based 

on 98 measurements; interdune area, Lagoa dune field, llha de 

Santa Catarina, Brazil. (Fig. 86.)

troduced material follows and reinforces the primary structures developed by reworking of the eolian 

sands (dissipation of former dunes). In this way, 

the apparently structureless pattern that originated 

during the dissipation process becomes more evident.

In addition to the dissipation action of water, 

these dunes are subjected to soil-forming processes 

that create soil horizons. The red and brown colors 

of the apparently structureless eolian sands are 

generally attributed to soil formation; however, at 

the Lagoa dune field, most dunes investigated 

showed little red color to have been developed in 

situ by such processes. The amount of heavy 

minerals present in the dunes is not sufficient to 

provide the colloidal materials (clay and iron compounds) for staining the quartz grains under normal 

soil-forming conditions.

A surficial soil profile is not well developed on 

the dunes. Thus, the red and brown materials are 

not commonly a result of downward migration of 

colloidal material from soil formation. Large 

amounts of foreign materials, mostly colluvial, 

have been introduced in the dune field by mud and 

(or) sand flows, which probably originated during 

drier climates at times of regionally concentrated 

rainfall.

Foreign material obviously was introduced into 

the dune field, and the migration of this material 

definitely results from the action of percolating 

waters and soil formation. Evidences of migration

are locally very clear in some of the trenches 

studied.

The highest concentration of organic matter is 

found in paleosol (A horizon). Humic compounds 

derived from the organic soil horizon and from the 

decay of plant debris migrate downward through 

the sand profile into the zone of saturation below 

the water table, causing the sand to become brown. 

In migrating, the humic compounds tend to impregnate first on the shear planes and sedimentary 

structures produced by the dissipation processes; 

the resulting near-black stain makes the structures 

easily visible. As the impregnation progresses 

laterally, the structures tend to be less visible and 

disappear into a dark-brown sandy area. In turn, 

the fluctuation of the phreatic water level, rich in 

humic colloids, is responsible for additional impregnation of the organically cemented dark-brown 

crusts of layers.

Interdune Areas

In the eastern part of the Lagoa dune field, not far 

from the granite hill, several trenches were dug in 

an area of parabolic dunes. The sediment in these 

trenches contained dissipation structures representing drier climate episodes, during which there 

was a regional loss of vegetation and only sporadic 

but intense rainfall. Flash floods had washed 

weathered material both from the side of the granite hill and from the dune into the interdune area. 

In the trench wall, sand- and granule-size stream 

deposits and thin clayey beds deposited in small 

ponds were exposed. These deposits alternate with 

sets of well-stratified dune sand. Thus, the dissipation structures represent times when the flash 

floods dominated in the development of dunes.

Deformation Results of Dune 

Dissipation

The response to stresses and the types of structure produced during deformation depend on the 

amount of moisture present in the sand (McKee, 

Douglass, and Rittenhouse, 1971). The cyclic sequences at the Lagoa dune field were developed 

under varying moisture conditions. Some units consist of typical eolian dune sediments; others are 

water-reworked dune deposits; some are mixed
SEDIMENTARY STRUCTURES IN DUNES 131

0 4 8 12 METRES

Interdune area Interdune area

REVERSING DUNE AND INTERDUNE STRUCTURES, Lagoa dune field, llha de Santa Catarina, Brazil. A, Dune profile 

showing locations of trenches; 8, trenches in reversing dunes; C, trenches in interdune areas. Dip of cross-strata is shown 

in degrees; no vertical exaggeration. Modified from Bigarella (1975b, fig. 13). (Fig. 87.)
132 A STUDY OF GLOBAL SAND SEAS

: :: ' --^V"V"V'V'*,X 'V'V'* s ' Dissipation ' : \\" ' V ' x * /" N / *'% > *"s ' '] 

: ramp.: v» :.;. .: ^// V - V ' V> ;• ^ ,s I> ^

Sand

Dissipation ramp

EXPLANATION

Stabilized parabolic dune

Surveyed parabolic dune

Precambrian crystalline 

basement; mostly granite

Boundary; dashed 

where approximate

DISSIPATION RAMP LEADING DOWN from Joaquina Hill to Lagoa dune field, llha de Santa Catarina, Brazil. Hachures indicate inward slope. Map is study area of figure 76. Modified from Bigarella (1975b, fig. 2). (Fig. 88.)
SEDIMENTARY STRUCTURES IN DUNES 133

5 cm

0 5cm

CONTORTED WAVY PATTERN IN DUNE SAND formed by colloidal material, mostly clay, separating individual sand-flow 

layers developed during dissipation processes. Cross-sections 

of dune normal to dip at Lagoa dune field, llha de Santa 

Catarina, Brazil. (Fig. 89.)

with sediments derived from the reworking of colluvial material from the nearby granite hills.

Under conditions normally present in an arid climate, the coastal dunes of Lagoa would have 

formed primarily by the accumulation of sands that 

avalanched down the steep lee faces. The most 

common structures from such avalanching, besides 

cross-stratification, are shear planes, thrust faults, 

high-angle asymmetrical folds, overturned folds, 

breccias, normal faults, fadeout laminae, and intertonguing sand lenses (McKee and Bigarella, 1972, p.

674). Dissipation conditions at Lagoa, however, 

were established by an increased amount of water. 

Periodic mass movements in these dunes (fig. 90), 

such as "wet avalanches," develop faults connected 

with systems of shear planes, brecciated sand 

masses, and folds. Downward movement of the 

saturated sediments differs from normal avalanching of dry or damp sand. In a more advanced stage, 

the action of sand flow and rainwash may spread 

across the whole sand body producing its dissipation, and the resulting structures display a wavy 

and lenticular pattern.

The avalanching of sand on the lee side of a dune 

produces shear planes in which heavy minerals are 

concentrated by downward migration through the 

voids between grains. Locally, avalanches in wet 

reworked dune sand resulted in wavy and lensshaped structures. This movement may have been 

started in wet sand by undercutting at the base of 

the deposit. The avalanching of wet sand is a mass 

movement that develops more than one shear plane 

(fault) parallel or subparallel to the main movement. A secondary system of shear planes commonly forms roughly perpendicular to the main 

faults.

Normal faults and breccias are common to 

avalanching in wet sand (McKee and Bigarella, 

1972, p. 674). The faulting due to avalanching is 

caused by heavy rainfall that soaks the dune. 

Associated interdune sediments indicate the presence of small ephemeral streams that may undercut the dune base to start sand movement.

Scour-and-fill structures may form as part of a 

single process in which the troughs are scoured by 

flowing water and subsequently filled with sand. 

Scouring and filling seem to be related to rainfall 

patterns and to the sediment carried in small 

ephemeral streams that flow in interdunal areas 

during the dissipation process.
134 A STUDY OF GLOBAL SAND SEAS

SCHEMATIC CROSS SECTIONS illustrating features such as shearing planes, faults, breccia-bed sands, wavy dissipation structures, 

and coarse sand layers that result from dissipation conditions. Black dots, colluvium pellets; f, fault; ws, white sand; gws, graywhitish sand; bs, brown sand; psA, paleosol A, enriched with organic matter. Hachures indicate predune surface. Modified from 

Bigarella (1975b, fig. 20). 1 centimetre =0.39 inch. (Fig. 90.)


A STUDY OF GLOBAL SAND SEAS

DUNE FORMS AND WIND REGIME

Chapter F

By STEVEN G. FRYBERGER, 

assisted by GARY DEAN

Contents

	Page

Summary of conclusions ......... ................ 141

Introduction . ........ .......................... 142

Acknowledgments ........................... 142

Methods of study .................................. 143

Types of available wind data .................. 143

Limitations of wind data ....................... 143

Evaluation of wind data ....................... 145

Selection of a weighting equation ........... 145

Calculation of drift potentials ...... ........ 146

Calculation and plotting of sand roses ...... 147

Additional computations .......... ........ 148

Classification of wind environments ...... ........ 148

Direction of surface winds ................. 148

Energy of surface winds ........................ 150

Page

Dune forms and associated wind environments ....... 150

Summary of observed wind environments of the 

various dune types ............... ........ 150

Barchanoid (transverse) dunes ....... ........... 151

Subtypes and size of barchanoid dunes studied 151 

Summary of observed wind environments of 

barchanoid dunes ........................ 152

Examples of wind environments of barchanoid 

dunes .................... ........ .... 152

White Sands National Monument, New 

Mexico, U.S.A. ....... ............... 152

Namib Desert, South-West Africa ....... 153

Cherchen Desert, China ................ 154

Ala Shan Desert, China ................. 155

137
138 A STUDY OF GLOBAL SAND SEAS

Page Pa«e 

Dune forms and associated wind environments— Continued Dune forms and associated wind environments— Continued

Linear dunes .................................. 155 Linear dunes— Continued

Summary of observed wind environments of Examples of wind environments—Continued

linear dunes ............................. 155 £ rg Hammami region, Mauritania, and Erg

	Bilma region, Niger................... 164

Examples of wind environments of linear dunes 156 Star dunes .................................... 165

Southwest Kalahari Desert, South Africa .. 156 Summary of observed wind environments of star

Western Simpson Desert, Australia .. .... 157 dunes .................................. 165

Ramlat Zallaf sand sea, Libya ............ 161 Examples of wind environments of star dunes . 165

Northwestern Kalahari Desert, South-West Eastern Grand Erg Oriental, Algeria-Libya . 165

Africa, and Great Victoria Desert, Grand Erg Occidental, Algeria ........... 165

Australia ............................ 163 Western Grand Erg Oriental, Algeria ......' 166

Illustrations

Page 

FIGURE 91. Photographic copies of N summaries of surface winds from which estimates of

relative sand drift were made .................................... 144

92. Graph showing sand transport rate versus shear velocity of air motion ...... 145

93. Sketch showing sand rose used in this chapter........................... 147

94. Graph showing drift potential versus rate of sand drift for two threshold drag

velocities ........................................................ 148

95. Wind rose for Juraid Island, Arabia, showing relative numbers of wind observations from 360° of the compass .................................... 149

96. Sand roses showing five commonly occurring directional distributions of effective wind regimes ................................................ 149

97. Sand roses depicting typical high-energy wind regimes of three basic dune

types ............................................................ 151

98. Graph showing drift potential versus RDP/DP for 14 weather stations near

barchanoid dunes ................................................ 152

99. Landsat imagery of barchanoid and parabolic dunes at White Sands National 

Monument, New Mexico, U.S.A., and sand roses for Holloman Air Force 

Base downwind of the dune field .................................. 154

100. Landsat imagery of barchanoid dunes along the coast of northern Namib

Desert, South-West Africa ...... ................................. 155

101. Landsat imagery of barchanoid dunes in the eastern Cherchen Desert, China,

and sand roses for Charkhlik (Nochiang), China ..................... 156

102. Wind rose for maximum winds and table of average maximum monthly winds

at Charkhlik (Nochiang), China, 1956-61 ...... ..................... 156

103. Landsat imagery of barchanoid dunes in the western Ala Shan Desert near MaoMu (Ting-hsin), China, and sand roses for Mao-Mu ................... 157

104. Graph showing drift potential versus RDP/DP for 13 weather stations near linear

dunes .............................................. ............ 158

105. Landsat false-color imagery of linear dunes and sand streaks in the southwestern Kalahari Desert near Upington, South Africa, and sand roses for 

Upington ........................................................ 159

106. Wind rose for maximum winds and table of average maximum monthly winds

at Upington, South Africa, 1956-67 ........... ..................... 160

107. Landsat imagery of linear dunes in the southwestern Simpson Desert near Oodnadatta, Australia, and sand roses for Oodnadatta .................... 160

108. Landsat imagery of linear dunes in the Ramlat Zallaf sand sea near-Sabha, Libya,

and sand roses for Sabha .................. ....................... 162

109. Wind rose for maximum winds and table of average maximum monthly winds

at Sabha, Libya, 1949 and 1961 -63 ................................. 162

110. Landsat imagery of presumed linear dunes in the Peski Karakumy near Ekidze,

U.S.S.R., and annual sand rose for Ekidze ............................ 163
DUNE FORMS AND WIND REGIME 139

FIGURE 111- Landsat imagery of linear dunes in the northwestern Kalahari Desert near

Mariental, South-West Africa, and annual sand rose for Mariental ...... 164

112. Landsat imagery of linear dunes in the Great Victoria Desert near Giles,

Australia, and annual sand rose for Giles ............................ 164

113. Wind rose for maximum winds and table of average maximum monthly winds

at Mariental, South-West Africa, 1960-67 ............................ 165

114. Landsat imagery of linear dunes in the Erg Hammami region, northern

Mauritania ....................................................... 165

115. Landsat imagery of linear dunes in the Erg Bilma near Bilma, Niger, and sand

roses for Bilma ................................................... 166

116. Graph showing drift potential versus RDP/DPfor five weather stations near star

dunes ........................................................... 167

117. Landsat imagery of isolated star dunes in the Grand Erg Oriental near

Ghudamis, Libya, and sand roses for Ghudamis ...................... 167

118. Landsat imagery of star dunes along an escarpment in the Grand Erg Occidental

near Beni Abbes, Algeria, and sand roses for Beni Abbes .............. 168

119. Landsat imagery of alined star dunes in the Grand Erg Oriental near Hassi

Messaoud, Algeria, and sand roses for Hassi Messaoud ............... 168

Tables

Page

TABLE 14. Derivation of weighting factors for relative rate of sand transport by substitution of average wind velocities into the generalized Lettau equation .... 147

15. Computation, from N summary, of vector unit total from the west-northwest,

Yuma, Arizona, U.S.A. ............................................. 147

16. Average monthly and annual drift potentials for 13 desert regions, based on

data from selected stations ........................................ 150

17. Localities used to evaluate the wind environments of barchanoid dunes .... 153

18. Localities used to evaluate the wind environments of linear dunes ......... 158

19. Localities used to evaluate the wind environments of star dunes ........... 167

DUNE FORMS AND WIND REGIME 141

Summary of Conclusions

HE COMPARISON OF WIND REGIMES to 

dune forms on a worldwide basis has become 

possible through two types of data. The first is recently available Landsat imagery for deserts of the 

entire world, some parts of which are very difficult 

of access. The second is reliable surface wind information for these regions, available from the National Climatic Center, Asheville, North Carolina, 

U.S.A. In this report the morphologies of dunes 

both from well-studied and from relatively less 

studied parts of the world were compared with 

local and regional winds. Characteristic wind environments were discerned for barchanoid, linear, 

and star dunes.

By making several simplifying assumptions, surface winds were analyzed for direction and relative 

amount of sand migration (drift), using the Lettau6 

equation for sand drift:

q-g/C"p=V* 2 (V*-X*). 

This formula was modified to:

Qoc V 2 (V-M).t,

Where Q is a proportionate amount of sand drift, V 

is average wind velocity at 10-metre (33-ft) height, 

Vt is impact threshold wind velocity, and t is time 

wind blew, expressed as a percentage in a wind 

summary.

Values derived from this formula by substitution 

reflect the sand-moving capacity of the wind for the 

time period of the wind summary and are herein 

known as drift potentials (DP), which are 

numerically expressed in vector units (VU). The 

direction and magnitude of the vector resultants of 

drift potentials from the 16 compass directions are 

herein known as the resultant drift direction (RDD) 

and the resultant drift potential (RDP), respectively. An index of the directional variability of the 

wind is the ratio of the resultant drift potential to 

the drift potential, herein known as RDP/DP. The 

greater the directional variability of the effective 

winds at a station, the lower its associated RDP/DP 

will be.

6 K. and H. Lettau, Meteorology Department, University of Wisconsin, 

Madison, Wisconsin: unpublished data, 1975. Equation reproduced by permission 

of the authors.

The average annual amount of wind energy in 

the deserts studied ranges from approximately 80 to 

489 VU. On the basis of rough groupings of deserts 

in terms of wind energy, the wind energy of desert 

environments is classified as follows: low energy, 

DP less than 200 VU; intermediate energy, DP, 

200-399 VU; high energy, DP, 400 VUor greater.

Sand roses are circular histograms representing 

the potential effects of winds from the directions of 

the compass, as evaluated from the modified Lettau 

equation. Effective (sand-moving) winds tend to 

occur in directional groupings or modes, which are 

reflected in sand roses. The directional classification of effective wind regimes as represented on 

sand roses is based on the relationships of modes 

and includes the categories herein designated as 

"narrow unimodal," "wide unimodal," "acute 

bimodal," "obtuse bimodal," and "complex."

Barchanoid dunes, including barchans, domes, 

and transverse ridge dunes, have similar wind environments. Wind distributions associated with 

these dunes generally are narrow unimodal or wide 

unimodal but may be acute bimodal if one mode is 

much stronger than the other. Barchanoid dunes in 

environments with high drift potentials seem to be 

associated with a higher RDP/DP than those in environments with low drift potentials.

Barchanoid dunes are observed in present-day 

wind environments of low, intermediate, and high 

energy (drift potential). Large fields of barchanoid 

dunes occur in continental settings and in restricted 

high-energy settings along coasts. Of all the dune 

types observed, barchanoid dunes are associated 

with the least variability in effective wind direction 

for a given drift potential.

Linear dunes are associated with a variety of 

effective wind environments — from low to high 

energy. Effective wind distributions range from 

wide unimodal through complex. The wind environments of most linear dunes have a greater 

directional variability of effective winds than do 

those of barchanoid dunes for a given drift potential. Simple linear dunes are a nearly exclusive type 

over wide regions of the Peski Karakumy and the 

Kalahari, Simpson, Great Sandy, and Great Victoria 

Deserts. The unvegetated dunes in the southwest 

Kalahari and Simpson Deserts are associated with 

intermediate to high-energy bimodal or wide 

unimodal wind regimes. Partially vegetated dunes
142 A STUDY OF GLOBAL SAND SEAS

in the northwest Kalahari and Great Victoria 

Deserts are associated with low-energy bimodal or 

complex wind regimes.

Simple linear dunes can occur in the same highenergy wind environment as compound linear 

dunes. This suggests that factors other than wind, 

such as available sand and the age of the dunes, 

may determine the type of linear dune observed at 

a particular high-energy locality. Compound linear 

dunes are most frequently observed in intermediate- to high-energy wind environments, with wide 

unimodal or bimodal distributions of effective 

winds.

Star dunes have been observed in complex wind 

regimes of low, intermediate, and high energy. The 

complex wind regimes associated with star dunes 

can differ in several respects from those associated 

with linear dunes. Unlike linear dunes, star dunes 

have been observed in a complex wind environment of high drift potential, in which complex wind 

distributions prevail during the windiest months, 

and in which the dominant modes are directly opposed.

Star dunes in a high-energy wind regime near 

Ghudamis, Libya, are isolated mounds, whereas 

star dunes in a low-energy wind regime near Beni 

Abbes, Algeria, seem to be connected by sinuous 

arms. Some star dunes are developed in linear patterns atop "sand sheets," linear dunes, or possibly 

crescentic dunes. Wind regimes associated with 

alined star dunes in the two examples available 

have characteristics intermediate between dune 

types in terms of RDP/DP.

Introduction

The following conclusions are theoretical 

because the author was not able to visit many of the 

localities studied from Landsat imagery during the 

course of the investigation. Early in the study, 

however, it was observed that a single dune type 

commonly occurred throughout wide stretches of 

desert. For example, barchanoid dunes characterize 

the eastern Takla Makan Desert of China; linear 

dunes, the Erg Makteir of Mauritania; and star 

dunes, the Grand Erg Oriental of Algeria. Thus, if 

the winds of the various regions could be defined, it 

seemed possible to obtain insight into the wind 

regimes responsible for creating major dune types.

Following the suggestion of Bagnold (1941, p. 184), 

winds were evaluated and defined in terms of their 

potential sand-moving effectiveness through the 

use of a suitable weighting equation applied to a 

standardized set of data.

Parts of this chapter on barchanoid, linear, and 

star dunes are designed to give a summary of the 

author's observations, based on the included tables 

and on material in chapter K. In addition, examples 

are given of observed wind environments of certain 

dune types. These examples were chosen first to illustrate the most common wind environments in 

which the representative dune types were observed, and second to illustrate problems requiring 

further research. Finally, examples were chosen, 

where possible, to compare the wind environments 

of similar dune types in different regions. Examples 

were selected from localities where the author had 

most confidence that the winds measured at nearby 

meteorological stations were representative of the 

regional wind environment.

The classification of effective wind environments used in this paper will enable the reader to 

compare one effective wind environment with 

another but is not intended to be a formal system. 

Although the sand rose concept (discussed later) 

seems useful in delimiting the gross directional and 

energy properties of effective wind regimes, the 

more important problem of the effect on 

morphology of rare, high-speed winds versus winds 

of intermediate strength remains to be solved.

An important caution should be kept in mind by 

the reader in regard to the observations in this 

report. Although the available surface wind data 

provide a good picture of present-day effective 

winds, the maximum period of record seldom exceeds 15 years. In contrast, many of the observed 

dunes are very large and, therefore, possibly are 

very old. Thus, some of the large dunes observed, 

particularly in regions of low or intermediate drift 

potential, may in part have developed in response 

to older, different wind regimes. The most reliable 

comparisons, therefore, are between dunes and 

wind environments with high drift potentials.

Acknowledgments

Technical assistance and criticism for this 

chapter were generously given by Robert P. Sharp, 

California Institute of Technology; Heinz Lettau,
DUNE FORMS AND WIND REGIME 143

University of Wisconsin; Douglas L. Inman, Scripps 

Institute of Oceanography; Harold L. Crutcher, National Climatic Center; Harry Van Loon, National 

Center for Atmospheric Research; and Errol L. 

Montgomery, Northern Arizona University.

Methods of Study

Types of Wind Data Available

SAND DRIFT REFERS to the process of sand 

movement across the desert as a result of surface 

winds. Most estimates of sand drift given in this 

report were made from surface wind tabulations 

known as "N summaries." These were prepared by 

the Environmental Technical Applications Center 

of the U.S. Air Force. They are stored at the National Climatic Center, Asheville, North Carolina, 

U.S.A., and are available by station name or by 

World Meteorological Organization (W.M.O.) number. Each W.M.O. station summary normally contains both monthly and annual data. Wind speed is 

recorded in knots to the nearest 10° of direction at 

3- to 6-hour intervals. The period of record for stations used in this chapter averages 10 years.

Two N summary formats are available (fig. 91). 

The first format (fig. 91 A) is more useful because 

wind velocities are divided into 9 or 11 categories, 

whereas the second format (fig. 91B) has only 5 

velocity categories. About 100 summaries using the 

first format were analyzed. The linear-regression 

technique was used to estimate relative sand drift 

from 34 summaries in the second format.

Detailed wind data, other than the N summaries, 

were also obtained from some government offices, 

desert research organizations, corporations, and 

libraries. These data were reduced to a form similar 

to that shown in figure 91 A, then evaluated by the 

same methods.

Limitations of Wind Data

The surface-wind data used in this report 

generally was of good quality. However, methods 

of gathering data and summarization processes both 

introduced some systematic inaccuracies.

Inaccuracies introduced during data gathering 

occur primarily in two ways. The first, known as

observer bias (Ratner, 1950, p. 185), is the tendency 

for weather observers to record wind occurrences 

from the prime directions rather than from intermediate directions of the compass. For example, 

when an observer is uncertain, he commonly 

records wind as coming from the northeast rather 

than from the east-northeast.

A second type of inaccuracy occurs during data 

gathering because of deviations from standard observing conditions as specified in the W.M.O. 

"Guide to Meteorological Practices." One common 

occurrence is the mounting of an anemometer at a 

height other than the standard 10 m (33 ft) specified 

by the World Meteorological Organization. For example, the anemometer height at El Golea, Algeria, 

was 4 m (13 ft) during 1949-56, 22 m (72 ft) during 

1956-60, and 7 m (23 ft) from 1960-73. Additionally, a station may be sheltered from the wind 

by nearby trees, buildings, or high ground.

The mounting of anemometers at nonstandard 

heights may have slightly affected some calculations of drift potential, because threshold drag 

velocity assumed in calculations is based on wind 

velocity at a 10-m height. If anemometers are 

mounted lower than the standard 10 m, calculated 

drift potential will be slightly less than the true drift 

potential which would result from calculations 

based on a 10-m height. This is because wind 

velocities are lower near the ground; thus, the 

theoretical threshold velocity will be exceeded less 

often.

Inaccuracy also arises during summarization of 

data, and it usually develops in two principal ways. 

First, inaccuracy enters a summary when data is 

condensed from 36 to 16 compass directions. This is 

known as procedure error (Wallington, 1968, p. 

293). The result is to create an apparent increase in 

observations from the prime compass directions at 

the expense of the intermediate directions. Second, 

summarizing of observations results in a coarsening 

of the resolution of the data in terms of velocity, 

direction, and percent occurrence. Most percentages on N summaries are expressed to the nearest 

0.1 percent (fig. 91 A). Depending on the number of 

observations, however, single occurrences may be 

represented in a summary as more than 0.1 percent. 

For example, an easterly maximum wind of 17 

knots was recorded during October at T'ieh-kan-lik'o, China, for which period only 137 observations
144 A STUDY OF GLOBAL SAND SEAS

DATA PROCESSING DIVISION PERCENTAGE FREQUENCY OF WIND SURFACE WINDS 

ETAC/USAF DIRECTION AND SPEED

MR WEATHER SERVICE/MAC (FRQM HQURLY OBSER VAT|ONS) 

23195 YUMA ARIZONA IAP 48-71 ALL

STATION

SPEED

(KNTS) 

OIR.

N

NNE

NE

ENE

E

ESE

SE

SSE

S

SSW

SW

WSW

W

WNW

NW

NNW

VARBL

CALM

1 • 3

1.0

1.0

.8

.5

.7

.4

.6

.5

.8

.6

.8

.6

.7

.6

.6

.6

^x^

10.8

STATION NAME YEARS MONTH 

ALL WEATHER ALL

CLASS

CONDITION

4- 6

3.4

3.4

2.1

1.1

1.0

.8

1.4

1.9

2.6

1.7

2.6

2.6

3.0

2.5

1.8

1.7

^xC^

33.8

7 • 10

3.1

2.6

1.1

.4

.3

.4

1.9

3.0

3.2

1.8

1.9

2.1

2.5

2.2

1.3

1.8

^xi

29.6

11 • 16

1.8

.7

.2

.1

.1

.1

1.6

2.6

1.6

.7

.3

.4

.9

1 3

.5

.9

^xd

13.8

17 • 21

.4

.1

.0

.0

.0

.0

.3

.4

.1

.0

.0

.0

.2

.3

.1

.1

^XC^

2.1

22 • 27

.1

.0

.0

.0

.0

.0

.0

.0

.0

.0

.0

.0

.1

.1

.0

.0

^x^

.3

28 • 33

.0

.0

.0

.0

.0

.0

.0

.0

.0

.0

.0

^x^

.0

34 • 40

.0

^x^

.0

41 • 47

.0

^x^

.0

48 • 55

X

>56

X

HOURS (L.S.T.)

%

9.7

7.7

4.3

2.2

2.2

1.7

5.8

8.5

8.4

4.9

5.6

5.7

7.3

6.9

4.3

5.1

9.6

100.0

MEAN 

WIND 

SPEED

8.0

6.6

5.8

5.7

5.3

5.8

8.9

9.5

7.8

7.1

6.2

6.5

7.5

8.2

6.9

7.8

6.7

TOTAL NUMBER OF OBSERVATIONS

AIR WEATHER SERVICE 

CLIMATIC CENTER 

DATA PROCESSING DIVISION 

YEARS 49,50,51 ,52,54,55,56,57,58,59,60,61 ,62,63

DIRECTION

N

NNE

NE

ENE

E

ESE

SE

SSE

S

SSW

SW

WSW

W

WNW

NW

NNW

VARIABLE

CALM

TOTALS

PERCENTAGE FREQUENCY OF SURFACE WINDS 

62002 NALUT LIBYA 

31 52 N 010 59 E 2036 FT

WIND SPEED GROUPS IN KNOTS

01-06

5.8

2.6

2.1

.6

.4

.2

.2

.6

2.4

1.0

1.1

2.1

4.3

1.4

1.3

1.0

27.3

07-16

10.9

3.8

3.2

.9

.5

.2

.8

1.2

5.1

2.2

3.6

3.6

4.6

1.3

1.3

2.0

45.2

1 7-27 28-40 GTR 40

2.1 .0

1.0

1.1

.1

.4 .1

.1 .1

.3 .2

1.4 .3

4.0 .6 .1

1.2 .3 .0

1.9 .4 .2

.9 .2 .0

1.8 .0

.1

.1

.1

16.5 2.4 .4

TOTAL

%

18.8

7.4

6.5

1.6

1.4

.5

1.5

3.6

12.2

4.8

7.3

6.9

10.7

2.9

2.7

3.1

8.2

100.0

N SUMMARY #1 

MAR

TOTAL

DBS

468

184

160

40

35

13

37

87

303

118

180

170

265

71

66

78

203

2478

MAXIMUM WIND SW

MEAN WIND

SPEED/KTS

10.2

10.0

10.5

9.0

13.7

15.8

16.6

16.5

15.2

14.2

15.4

11.3

10.2

7.9

8.0

9.2

10.8

50 KTS

B

TWO TYPES OF N SUMMARIES containing surface wind data from which estimates of relative 

sand drift were made. A, 16 directional categories and 11 velocity categories. B, 16 directional 

categories and 5 velocity categories. (Fig. 91.)
DUNE FORMS AND WIND REGIME 145

are available. This single observation is represented 

as 0.7 percent of all observations. It is questionable 

whether this occurrence represents a group of 

winds which blew 0.7 percent of the time, or 5.2 

hours of the 744 hours, in October.

Corrections were not made for the limitations 

just described because it was not known when and 

where they occurred. Furthermore, techniques 

available for correcting observer bias and procedure 

error (Wallington, 1968, p. 296; Ratner, 1950, p. 186) 

could not be applied uniformly to the different 

types of wind summaries used in this study. More 

detailed future work involving the collection and 

summarization of surface-wind data would be improved by taking the factors previously discussed 

into account. However, these factors probably did 

not affect the data enough to detract from the 

general conclusions of this study.

Evaluation of Wind Data 

Selection of a Weighting Equation

A number of equations are available to compute 

rates of sand drift if the shear velocities are known. 

The most useful formulas, including those of Bagnold (1941), Kawamura (1951), and Zingg (1953) 

were tested by Belly (1964, p. 3-5) with data from 

his wind-tunnel studies. All formulas were found 

by Belly to describe the data well when suitably 

evaluated. A formula recently suggested by K. and 

H. Lettau (written commun., 1975) produces a 

theoretical curve that agrees very well with Belly's 

work for 0.44-mm-diameter sand (fig. 92). For this 

reason, the Lettau equation for the rate of sand drift 

was chosen in this study as the basis for the weighting equation for sand movement, although other 

formulas probably would have given similar 

results. Lettau's equation is as follows:

Additionally,

C"p (v* - va, (1)

where

q = rate of sand drift;

g = gravitational constant;

C" = empirical constant based on grain size;

p = density of air;

V* = shear velocity; and

V* = impact threshold shear velocity, or the

minimum shear velocity required to

keep sand in saltation.

C" =C' (8/8*)",

where

C' = universal constant for sand (about 6.7), 

8 = grain diameter of sand moved, 

8* = 0.25 mm (standard diameter), and 

n = empirical constant -0.5.

All units are c.g.s. (centimetre-gram-second).

s

1.00

0.75

0.50

O 0.25

LETTAU 

qg/p=6.S V*2

800

700

600

500

400

300

200

100

25 30 35 40 45 50 55 60 

SHEAR VELOCITY,*/*, IN CM/SEC

RATE OF SAND TRANSPORT (grams moving per second across 

a crosswind distance of 1 cm (0.40 in.)), q, versus shear velocity, 

V*, of air motion, according to theoretical curves by Bagnold 

(1941), Kawamura (1951), and Heinz Lettau (1975, unpublished 

data) in comparison with wind tunnel measurements (circles) 

by Belly (1964, p. 17). Reproduced by permission of the 

authors, K. and H. Lettau, Meteorology Department, University 

of Wisconsin, Madison, Wisconsin, U.S.A. (fig. 92.)

Surface conditions, in addition to shear velocity, 

control the rate of sand drift. Four important factors 

are mean grain diameter of the sand (Bagnold, 1941, 

p. 67; Belly, 1964, p. 13), the degree of surface 

roughness (Chepil and Woodruff, 1963, p. 240; Bagnold, 1941, p. 71), the amount and kind of vegetative cover (Chepil and Woodruff, 1963, p. 221), and 

the amount of moisture in the sand (Belly, 1964, p. 

Ill 21). These parameters could not be evaluated for 

many of the localities studied. For this reason, 

localities were compared using relative quantities 

of potential sand drift.
146 A STUDY OF GLOBAL SAND SEAS

The Lettau equation for the rate of sand transport 

was generalized as follows:

qoc -v,*) •

(2)

Drag velocity is proportional to wind velocity for 

a given height (Belly, 1964, p. 18). Therefore, as a 

first approximation, wind velocities at a 10-m (33- 

ft) height (the standard W.M.O. anemometer 

height) may be substituted for drag velocities. The 

Lettau equation then becomes:

qcc V2 (V-Vt), (3)

where 

V wind velocity of at 10-m (33-ft) height,

and 

impact threshold wind velocity at 10 m

(33 ft) (minimum velocity at 10 m (33

ft) to keep sand in saltation).

This relationship produces a number which expresses the relative amount of sand potentially 

moved by the wind during the time it is presumed 

to blow. When the factor of time is added to equation 3 (thereby creating equation 5), the resulting 

number is here referred to as the drift potential 

(DP) and is a measure of the relative amount of potential sand drift at a station for a stated period of 

time. For convenience, the units of drift potential 

are here called vector units (VL7) because wind 

velocities are treated as vectors. The detailed 

method of computation of drift potentials is 

described next.

Calculation of Drift Potentials

Assumptions Required to Apply the Weighting 

Equation

In order to use a weighting equation to determine 

the effects of surface wind, the condition of the surface over which the wind blows must be assumed. 

For our purposes, this surface is assumed to consist 

of loose quartz sand grains with an average 

diameter of 0.25-0.30 mm. The surface is further 

assumed to be without bedforms larger than ripples, to be dry, and to be without vegetation. Similar surfaces have been used for most wind tunnel 

studies of sand drift, and 0.25-0.30 mm is the

average diameter of many desert dune sands 

(Ahlbrandt, chapter B, fig. 21). The assumed surface might not serve to predict actual rates of sand 

drift in areas with very large dunes, but it is useful 

when comparing one area to another in terms of 

available wind energy.

A threshold wind velocity must be determined in 

order to use a weighting formula. For a sand surface 

of 0.30-mm average diameter quartz sand, the surface roughness factor (Z') as determined by Belly 

(1964, p. 11 -12) during sand driving was 0.3048 cm 

(0.118 in.). The threshold wind velocity at height Z' 

(V{) was 274 cm/s (107 in./s) and V* was 16 cm/s (6 

in./s). V[ may be extrapolated to a 10-m (33-ft) 

height (the height at which most of the wind data 

were collected) using the equation (Bagnold, 1941, 

p. 104):

V, m) = 5.75 v; log J- + v; (4)

When this is done, a value of 11.6 knots is obtained 

for Vt.

This value indicates that for the conditions 

described, threshold wind velocity as measured at a 

10-m (33-ft) height should be within the 11 -16 knot 

velocity category on N summaries, such as that 

shown in figure 91 A. For this study a value of 12 

knots was chosen for Vt(10m) .

The assumption was made that a wind speed and 

direction component occurred in nature for an 

amount of time proportional to its percentage in the 

summary. With a few exceptions, such as that previously described for T'ieh-kan-li-k'o, China, this 

assumption seems reasonable because periods of 

record are long, observations are taken at different 

times of day and night, and each annual summary 

averages more than 1,000 observations.

Derivation of Weighting Factors 

and Application to Wind Data

Weighting factors as used here are numbers 

which represent the relative rates at which winds 

of differing average velocities can move sand. 

These numbers are derived by substitution of 

values for wind velocity (average wind speed of a 

velocity category) into the weighting equation of 

Lettau (equation 3) as shown in table 14.
DUNE FORMS AND WIND REGIME 147

TABLE 14. — Derivation of weighting factors for relative rate 

of sand transport by substitution of average wind velocities 

into the generalized Lettau equation (equation 3 in textj

[The value of V (V - V() is divided by 100 to reduce weighting factors to smaller 

sizes for convenience in plotting sand roses, as described in text. Velocities exceeding 40 knots are rare and are not computed]

N summary Mean velocity 

velocity of winds in 

category (knots) category V V

11-16 ...

17-21 ...

22-27 ...

28-33 ...

34-40 . . .

13.5

19.0

24.5

30.5

37.0

182.3

361.0

600.3

930.3

1,369.0

(V V,)

1.5

7.0

12.5

18.5

25.0

Weighting 

factor 

V*(V Vt)/100

2.7

25.3

75.0

172.1

342.3

The weighting factors represent rates of sand 

transport, and the percentages of wind occurrence 

in the summaries represent the length of time during which the winds blew. Therefore,

Qoc V2 (V-Vt)t,

or Q oc (weighting factor) t, (5)

where

Q

= time wind blew, expressed as a percentage on N summary; and 

= annual rate of sand drift.

To evaluate the relative amount of sand drift 

which potentially occurs at a station, the weighting 

factor derived from equation 3 for each velocity 

category is multiplied by the percentage occurrence 

of wind in that category for all 16 directions of the 

summary, and the results are totaled. This computation is shown for a single direction in table 15. 

Calculations of this sort are tedious; therefore, a 

programmable calculator was used for much of the 

work. The most convenient method of expression 

of the results is the sand rose, construction of which 

is described later.

TABLE 15. — Computation, from N summary, of vector unit 

total from the west-northwest, Yuma, Arizona, U.S.A.

[The drift potential at the station is the sum of the vector unit totals computed in 

the same manner from each of the 16 compass directions. Total vector units 

from west-northwest equals 18.6. Wind data shown in figure 91 A]

Velocity category (knots)

11-16 17-21 22-27 28-33 34 40

Weighting factor 

Percent

occurrence . . . Vector units ....

2.7

1.3

3.5

25.3

.3

7.6

75.0

.1

7.5

172.0

0

0

342.3

0

0

Calculation and Plotting of Sand Roses

A sand rose is a circular histogram which represents potential sand drift from the 16 directions of 

the compass (fig. 93). The arms of a sand rose are 

proportional in length to the potential sand drift 

from a given direction as computed in vector units. 

Thus, a sand rose expresses graphically both the 

amount of potential sand drift (drift potential) and 

its directional variability.

These diagrams differ from paleocurrent roses 

constructed from crossbedding dip directions, 

because the arms point toward the direction from 

which sediment moved, that is "into the wind." 

Sand roses are based on surface wind only and thus 

reflect only potential sand transport. The pattern 

suggested by the sand rose may be considerably 

modified by local conditions.

Arm

Reduction factor

(not shown on

monthly sand

roses)

ROD

TYPE OF SAND ROSE USED in this chapter. Components are as 

follows: Arm (vector-unit totals, plotted in millimetres), proportional in length to potential amount of sand drift from a given 

direction toward center circle. Reduction factor, number by 

which vector-unit total of each sand rose arm was divided so 

the longest arm would plot at <50 mm (2 in.). DP (drift potential, in vector units), measure of relative sand-moving capability 

of wind; derived from reduction of surface-wind data through a 

weighting equation (equation 3 in text). ROD (resultant drift 

direction, in vector units), net trend of sand drift. Station, name 

of meteorological station at which wind data was recorded. (Fig. 

93.)

Sand roses are plotted with a Hewlett-Packard 

9810 A calculator and 9862 A plotter.7 The vector 

unit totals from each direction are plotted in 

millimetres. When the vector unit total for any 

direction exceeds 50, all arms of that sand rose are 

divided by two until the longest arm of the sand 

rose plots at less than 50 mm (2 in.) in length. The 

number by which the arms are divided is known as

7 Use of a specific brand name does not necessarily constitute endorsement of 

the product by the U.S. Geological Survey.
148 A STUDY OF GLOBAL SAND SEAS

the reduction factor and is shown in the center circle of the sand rose (fig. 93).

Vector unit totals from the different directions 

may be vectorially resolved to a single resultant. 

The direction of this computed resultant is herein 

referred to as the resultant drift direction (ROD), as 

shown on figure 93. The RDD expresses the net 

trend of sand drift, or the direction in which sand 

would tend to drift under the influence of winds 

from the different directions. The magnitude of the 

resultant drift direction may be found from the 

same data, using the Pythagorean theorem, and is 

herein referred to as the resultant drift potential 

(RDP). The RDP expresses, in vector units, the net 

sand transport potential when winds from various 

directions interact.

Additional Computations

Drift potentials were estimated for a number of 

stations in India, Libya, and China, for which only 

those N summaries in the less detailed format (fig. 

91B) were available. Percentages in each velocity 

category of the figure 91B summary were apportioned into two smaller velocity categories of the 

figure 91A summary, based on the ratios of adjacent percentages established by linear regression 

analysis, using data from 36 randomly selected

50

40

30

20

10

100 200 300 400 500 

DRIFT POTENTIAL, IN VECTOR UNITS

600

DRIFT POTENTIAL (ANNUAL) VERSUS rate of sand drift (m 3/yr) 

across a 1-metre (3.3-ft) section normal to the drift direction for 

two threshold drag velocities, according to the Lettau equation 

(equation 1 in text) in which VJ* = impact threshold shear 

velocity. Line A, V^ = 16 cm/s (0.5 ft/s) (Belly, 1964, p. 11); line B, 

V? = 19 cm/s (0.58 ft/s) (Bagnold, 1941, p. 60). (Fig. 94.) •

detailed (fig. 91 A) summaries for each computation.

The ratio of the resultant drift potential to the 

drift potential — the RDP/DP — was computed for 

all stations in the study. The RDP/DP is an index of 

the directional variability of the wind. Where the 

wind usually comes from the same direction, the 

RDP/DP approaches unity. In contrast, where the 

wind comes from many directions, the RDP/DP approaches zero because the resultant drift potential 

is very low.

Although this study required only qualitative 

estimates of rate of sand drift, quantitative rates 

can be predicted using equation 1. The relationship 

of drift potential to annual rate of sand drift predicted by this equation for two presumed threshold 

drag velocities is shown in figure 94.

Classification of Wind 

Environments

Direction of Surface Winds

MOST SETS OF SURFACE WIND observations, 

such as those used in this study, exhibit groupings, 

or distributions, in terms of both direction and 

speed (for example, fig. 91 A, B). Some sets of surface-wind-direction distributions may be described 

as elliptical, or may be complicated because of mixed land and sea breezes, through mixtures of 

seasonal flows, or for other reasons (Crutcher and 

Baer, 1962, p. 522). For example, the 360-point 

directional wind rose for Juraid Island, Arabia, (fig. 

95) suggests four groups of winds; a group from the 

west, northwest, northeast, and southeast. 

However, most directional observations at Juraid 

Island are encompassed within groups of winds 

from the west and northeast which make an obtuse 

angle with each other. Sand roses plotted from surface wind data reflect such directional groupings. 

Although surface wind distributions, such as that 

for Juraid Island, can be very complex in detail, experience indicates that, as a first approximation, 

five relationships of directional distributions occur 

frequently. These relationships form the basis for 

the classification of directional charcteristics of 

effective winds in terms of sand roses shown in 

figure 96. This scheme was adopted in order to 

simplify the discussion of wind regimes and associated dune forms that follows.
DUNE FORMS AND WIND REGIME 149

330° 30°

300° 60°

W 270° 90° E

240° 120°

210° 150°

WIND ROSE FOR JURAID ISLAND, ARABIA (lat 27°12'03" N., 

long 49°57'23" E.), showing relative numbers of wind observations for 360° of the compass. Lengths of arms of the rose are 

proportional to the number of times wind came from a given 

direction. Winds from the west and northeast constitute the 

dominant groups. Based on wind records during March 

lO^April 10, 1971, observations taken at 15-minute intervals. 

(Data from Arabian American Oil Co.). (Fig. 95.)

The five commonly occurring wind regimes (fig.

96) are:

1. Narrow unimodal. — 90 percent or more of the 

drift potential at a station falls within two adjacent directional categories, or within a 45° 

arc of the compass.

2. Wide unimodal. — any other directional distribution with a single peak or mode.

3. Acute bimodal. — a distribution with two 

modes, in which the peak directions of the 

distributions (longest arms on the sand rose) 

of the two modes form an acute angle (here 

arbitrarily including also the right angle, 90°).

4. Obtuse bimodal. — a distribution with two 

modes, in which the peak directions of the 

two modes form an obtuse angle.

5. Complex. — any distribution with more than 

two modes, or with poorly defined modes. 

The 16 point wind-direction data commonly 

will not clearly show more than three modes.

Modes observed on sand roses are not considered 

to be significant for purposes of classifying a wind 

regime if the modal direction and the two adjacent 

categories constitute less than about 15 percent of 

the drift potential at the station. This simplifies the 

classification of wind regimes by focusing on the 

dominant modes that are controlled by large 

pressure systems. All sand roses tend to reflect procedure and observer bias. Extreme bias results in a 

"sawtooth" pattern of arms (example, fig. 111B). 

This pattern can sometimes make unimodal or 

bimodal wind regimes seem complex.

The RDP/DP which is a measure of the directional variability of the wind, is arbitrarily 

classified as follows: 0.0 to less than 0.3, low; 0.3 to 

less than 0.8, intermediate; 0.8 or greater, high. 

Many low ratios (RDP/DP) are associated with 

complex or obtuse bimodal wind regimes, intermediate ratios with obtuse bimodal or acute bimoArea ........... Walvisbaai, South- Bahrain, Arabia

West Africa 

DP....... ........... 518 540

RDP ................ 448 435

RDP/DP ................ 0.86 0.81

Badanah, Arabia

528

327

0.62

Timimoun, Algeria

245

46

0.19

Ghudamis, Libya

658

46

0.07

FIVE COMMONLY OCCURING RELATIONSHIPS of modes on sand roses. A, Narrow unimodal; 6, wide unimodal; C, acute bimodal, D, obtuse bimodal, (a special example in which the modes are almost exactly opposed); and E, complex. DP (drift potential) and 

RDP (resultant drift potential), in vector units. Arrows indicate resultant drift direction (RDD). (Fig. 96.)
150 A STUDY OF GLOBAL SAND SEAS

dal wind regimes, and high ratios with wide and 

narrow unimodal wind regimes.

Energy of Surface Winds

Drift potentials, which are measures of the 

energy of surface winds in terms of sand movement, are classified according to rough groupings of 

average annual drift potential for the desert regions 

shown in table 16. The deserts in China (127 VL/; 81 

VU) and India (82 VU) and the Kalahari Desert of 

South-West Africa (191 VU) constitute a lowenergy group. The northern Saudi Arabian (489 

VU) and Libyan (431 VU) deserts are a high-energy 

group. All other deserts studied are in the intermediate-energy group. On the basis of this classification, low-energy wind environments have drift 

potentials less than 200 VU; intermediate-energy 

wind environments have drift potentials of 

200-399 VU; and high-energy wind environments 

have drift potentials of at least 400 VU. This grouping of regions by wind energy in terms of potential 

sand movement applies only to the generally arid 

regions surveyed during this study. Other regions 

probably have different average drift potentials 

(perhaps very much higher than desert regions, 

many of which are known to be relatively calm). 

However, within the regions studied, the 

differences in relative sand-moving power of wind 

are related to specific weather patterns. Aspects of

the wind-energy structure of various desert 

regions, with regard to sand movement only, are 

discussed in detail in chapter K.

Further, the relative wind energies (in terms of 

sand movement) shown in table 16 are rough approximations. In fact, most desert regions are 

strongly zoned in terms of wind energy. For example, high drift potentials occur in Northern 

Mauritania; intermediate to low DP's occur farther 

south toward the Senegal River. (See chapter K, fig. 

197).

Dune Forms and Associated 

Wind Environments

Summary of Observed Wind

Environments of the Various Dune

Types

THE METHODS OF EVALUATING wind 

regimes discussed under "Methods of Study" in 

this chapter were used to compare wind environments with different dune types as observed on 

Landsat imagery and on aerial photographs. The 

dunes and associated wind regimes will be discussed in order of presumed increasing complexity 

of dune type — that is, barchanoid, linear and star. 

A synthesis of the more detailed discussions of

TABLE 16. — Average monthly and annual drift potentials for 13 desert regions, based on data from selected stations

[*, drift potentials estimated; leaders (...), no data]

Number 

of 

Desert region stations Jan. Feb. Mar. Apr. May June July Aug. Sept. Oct. Nov.

Annual 

drift 

Dec. potential

High -energy wind environments

Saudi Arabia and Kuwait (An 

Nafud, north) ...............

Libya (central, west)* ..........

10

7

35 

40

39 52 

42 48

54 51 

64 51

66

41

49 

20

33 

18

20

24

18

24

16

22

25 489 

37 431

Intermediate-energy wind environments

Australia (Simpson, south) .....

Mauritania ...................

U.S.S.R. (Peski Karakumy, Peski 

Kyzylkum) ................. « i • ' Algeria ......................

South-West Africa (Namib) .... 

Saudi Arabia (Rub1 al Khali, 

north) ......................

1 

10

15 

21 

5

1

43 

45

39 

21 

8

23

40 27 

49 45

41 43 

27 37 

2 6

28 53

17 13 

38 33

43 33 

48 32 

17 13

32 20

10 

40

25 

27 

50

30

18 

26

22 

18 

19

26 

19

21 

13 

22

52 

20

23 

15 

27

56 

20

23 

16

44

1

46 

19

24 

16 

17

7

43 391 

30 384

29 366 

23 293 

12 237

7 201

Low-energy wind environments

South-West Africa (Kalahari) . . . Mali (Sahel, Niger River) .......

China (Gobi)* ................

India (Rajasthan, Thar)* .......

China (Takla Makan)* .........

7 

8 

5 

7 

11

14 

9 

9 

2 

3

11 8 

12 14 

11 16 

2 5 

2 9

10 9 

12 19 

23 20 

5 10 

16 16

11 

22 

11 

21 

9

18 

15 

7 

19 

9

24 

9 

5 

9 

5

26 

10

5 

5 

4

26 

5 

5 

2 

5

17 

5 

7 

1 

2

18 191 

7 139 

8 127 

1 82 

1 81
DUNE FORMS AND WIND REGIME 151

each dune type and wind regime is given in figure 

97 for comparative purposes. Figure 97 demonstrates the greater directional variability of effective winds associated with star dunes in contrast to 

the less variable wind regimes commonly associated with barchanoid dunes (in high-energy wind 

environments).

Narrow unimodal to wide unimodal winds are 

associated with transverse dunes, such as 

barchanoid ridges. Bimodal winds are commonly 

associated with linear dunes, and complex wind 

distributions, with star dunes.

Barchanoid (Transverse Dunes)

Subtypes and Sizes of Barchanoid Dunes 

Studied

Dunes referred to as crescentic in the 

morphological classification used for Landsat imagery (chapter J), including the barchan, barchanoid 

ridge, and transverse ridge of the structural 

classification (chapter A) are included in the 

following discussion. Unique wind environments 

for each of the subtypes, as defined in chapter A, 

could not be distinguished with the regional data 

available. These dunes commonly occur in the 

same dune field (McKee, 1966, p. 4, fig. 1; 

Ahlbrandt, 1975, p. 61). Dome dunes and parabolic 

dunes may be found in association with barchans, 

barchanoid, and other transverse-type ridges. 

Dome dunes of the type studied by McKee at 

White Sands National Monument, New Mexico, 

U.S.A. (1966, p. 26), are not discussed in this 

chapter because they could not be identified by the 

author on Landsat imagery.

Small barchanoid dunes occur both singly and in 

environments where star dunes (Glennie, 1970, p. 

87, figs. 70, 71) or linear dunes (Glennie, 1970, p. 94,

£>P=518 

ANNUAL

DP=9 

FEB.

DP=30 

APR.

DP=39 

JUNE

DP=62 

AUG.

DP= 123 

OCT.

£>P=661 

ANNUAL

DP=QQ 

FEB. APR.

£>P=59 

JUNE

DP=46 

AUG.

DP=42 

OCT.

DP=52 

DEC.

£>P=662 

ANNUAL

£>P=39 

DEC.

TYPICAL HIGH-ENERGY WIND REGIMES of three basic dune types. Annual and bimonthly sand roses depict distribution of effective winds at each station. A, Narrow unimodal; barchanoid dunes near Pelican Point, South-West Africa. B, Bimodal; linear dunes 

near Fort-Gouraud, Mauritania. C, Complex; star dunes near Ghudamis, Libya. Number in center circle of each rose is reduction factor. DP (drift potential, in vector units) is given for each rose. Arrows indicate resultant drift direction (ROD). (Fig. 97.)
152 A STUDY OF GLOBAL SAND SEAS

fig. 75) are the dominant type. In the latter places 

they apparently develop in response to a seasonal 

component of a wind regime (Glennie, 1970, p. 92). 

Often, relatively small dunes, such as those 

developed in response to a seasonal wind, are not 

visible on Landsat imagery. With a few exceptions 

(for which adequate field observations are available), dunes discussed in this paper are large enough 

to be clearly defined from Landsat imagery. These 

dunes apparently have developed in response to the 

annual wind regime, of which the annual sand rose 

is an approximate measure.

Summary of Observed Wind Environments of 

Barchanoid Dunes

The wind environments of barchanoid dunes are 

evaluated with data from the 14 stations listed in table 17, and from regional analyses in chapter K. 

Drift potentials range from low (51 VU, Pa-Ch'u, 

China) to extremely high (estimated 2,823 VU, 

Pomona, South-West Africa). The data in table 17 

indicate that the barchanoid dune type is not 

restricted to either a low- or high-energy wind environment, assuming that dunes observed on the 

Landsat imagery are adjusted to present-day wind 

regimes. Active8 barchanoid dunes seen on Landsat 

imagery seldom occur in a wind environment with 

an RDP/DP lower than 0.50 (fig. 98). They are 

associated with less directional variability of effective winds where they occur in environments of 

high energy (fig. 98). Barchanoid dunes develop in 

wind regimes with less directional variability than 

those of linear dunes or star dunes for a given 

energy environment. (Compare fig. 98 with figs. 

104 and 116.) Annual wind regimes associated with 

barchanoid dunes may be unimodal or bimodal, 

although in bimodal regimes, one mode normally is 

much stronger than the other. Extensive fields of 

barchanoid dunes occur along coastlines swept by 

oceanic tradewinds or by monsoon winds, in both 

high- and low-energy settings. In addition, 

barchanoid dunes are the,dominant type in some 

continental regions such as the Takla Makan and 

Ala Shan Deserts in China.

z

D

DC

O

bLLI

>

Z

_r

F 

z

LLI 1-

2

t

DC 

0

ouuu

2500

2000

1500

*\

1000

800

600

400

£.\J\J 7flfl

n

I I I I I I I I I

-

_

_ _

^

_ _

•

-

— —

•

High

Intermediate

Low • • 9

I i I I f • I *t I i

0.1 0.2 0.3 0.4 0.5 0.6 

RDP/DP

0.7 0.8 0.9 1.0

8Dunes observed on Landsat imagery are considered to be active where they occur in regions of less than 100 mm (3.93 in.) average annual rainfall, if vegetation 

(which appears red on false-color imagery) is not apparent, if they have distinct 

slipfaces and sharp outlines, or if evidence of movement is available from aerial 

photographs or published reports.

DRIFT POTENTIAL (DP) VERSUS RDP/DP for 14 stations near 

barchanoid dunes, which are represented by dots in the figure. 

All dunes except those near El Centre, California, U.S.A., and 

Pomona, South-West Africa, were large enough to be observed 

on Landsat imagery. Although based on few stations, the distribution of points indicates that barchanoid (transverse) dunes 

occur in wind environments with less directional variability 

than those of linear or star dunes. (Compare with figs. 104 and 

116.) Barchanoid dunes in environments with high drift potentials ( >399 VU) are associated with higher RDP/DPs (less directional variability) than are barchanoid dunes in environments 

with low drift potentials ( <200 VU). Based on data from table 

17. (Fig. 98.)

Examples of Wind Environments of

Barchanoid Dunes 

White Sands National Monument, New Mexico, U.S.A.

Barchanoid dunes, dome dunes, and parabolic 

dunes can develop in low-energy wind environments having considerable directional variability of 

effective winds. These three types of dunes occur 

at White Sands National Monument, New Mexico 

(McKee, 1966, p. 4). The annual sand rose for 

Holloman Air Force Base, located downwind from 

the dunes at White Sands, has an obtuse bimodal 

wind distribution (fig. 99). Effective winds from the 

north-northwest and from the southeast occur during much of the year. However, these winds have 

less potential effect than do the southwesterly 

winds, which are strongest during April (fig. 99C). 

The drift potential at Holloman Air Force Base is 

149 VU — a low value compared with most other 

desert regions around the world (table 16).
DUNE FORMS AND WIND REGIME 153

The alinement of parabolic dunes visible in 

figures 99A and 99B is parallel to the resultant drift 

direction at Holloman Air Force Base. The gross 

alinement of barchanoid dunes shown in figures 

99A and 99B is roughly at right angles to the resultant drift direction. Individual slipfaces within the 

dune field may be oriented in various directions 

during the year (McKee, 1966, p. 14) in response to 

the effective winds from several directions (fig. 

99 C).

Namib Desert Coast, South-West Africa

Some barchanoid dunes occur in wind environments with a high drift potential and a narrow 

unimodal wind distribution. For example, 

transverse ridge, barchanoid ridge, and barchan 

dunes occur in such an environment along the coast

of the Namib Desert, South-West Africa, near 

Pelican Point (figs. 97A, 100). Although barchan 

dunes at this locality are not visible on Landsat 

(ERTS) imagery, they were observed along the 

coast by M. K. Seely (oral commun., 1975). This 

coastal region is swept by onshore winds derived 

from the southeast tradewinds of the South Atlantic Ocean, which are strongest during October in 

the region of Pelican Point. Although the energy of 

effective wind — and, thus, the drift potential 

along the coastline — varies greatly during the year 

(chapter K, fig. 232), effective winds in the region 

as shown in figure 97 A are mostly from the south or 

southwest and result in a narrow unimodal wind 

distribution. Barchanoid dunes occur in other 

coastal settings as well, particularly along shores 

swept by oceanic tradewinds or by monsoonal

TABLE 17. — Localities used to evaluate the wind environments o/ barchanoid dunes

[DP, drift potential; RDP, resultant drift potential]

Dune form(s)

Barchan, barchanoid ridge, 

parabolic. 

Barchanoid ridge, barchan

Compound and simple 

barchanoid ridges. 

Compound barchanoid ridge, 

and barchanoid ridge. 

Compound barchanoid ridge . .

Small barchanoid ridges, also 

linear dunes.

Dune coordinates 

(lat, long)'

31°50'N., 

115°50' W. 

Near station ....

38°20' N., 

85°30' E. 

37°10' N., 

79°30' E. 

39°00' N., 

87°30' E. 

38°00' N., 

78°00' E. 

39°30' N., 

79°00' E. 

28W N., 

41°40' E.

.. .do ..........

40°20' N., 

87°30' E. 

40°15'N.,100°- 

100°30' E. 

18°50' N., 

11°30' W.

Nearest representative Station 

station coordinates Other 

(distance from dunes in km) (lat, long) data2

El Centra, California, U.S.A. 

(40).

(5-10). 

Cherchen (Charchan), China 

(22). 

Khotan, China (56) ...........

Charkhlik (Nochiang) , China5 

(40). 

So-ch'e (Yarkand), China (50).

Pa-ch'u, China (30) ...........

Ha'il, Arabia (40) .............

Mexico, U.S. A.5 (5).

(0). 

T'ieh-kan-li-k'o, China (20) ....

Mao-mu (Ting-hsin), China5 

(15). 

Tidjikdja, Mauritania (30) ......

. . Bilma, Niger (5 -10) ..........

32°49' N., 

115°40' W. 

27°09' S., 

15°15'E. 

38°08' N., 

85°32' E. 

37°07' N., 

79°55' E.4 

38°40' N., 

88°03' E. 

38°25' N. 

77°15' E.4 

39°46' N., 

78°20' E.4 

27°30' N., 

41°40' E.4 

32°18' N., 

106°55' E. 

22°53' S., 

14°26' E. 

. 40°39' N., 

87°42' E. 

40°20' N., 

99°45' E. 

18°33' N., 

11°26' W. 

18°41'N., 

12°55' E.

Yes

No 

No 

No 

No 

No 

No 

No 

Yes 

Yes 

Yes 

No 

No 

No

DP RDP/DP

525 

32,823 

85 

33 

185 

42 

51

n

149 

518 

50 

140 

133 

948

0.75 

.97 

.60 

.70 

.79 

.69 

.51 

.78 

.37 

.86 

.54 

.57 

.64 

.74

Wind regime 

classification, 

using 

sand rose

Narrow unimodal. 

Do. 

Wide unimodal. 

Do. 

Do. 

Unclassified.6 

Obtuse bimodal. 

Wide unimodal. 

Obtuse bimodal. 

Narrow unimodal. 

Wide unimodal. 

Obtuse bimodal. 

Wide unimodal. 

Narrow unimodal.

1 10-km-radius circle centered on this point.

2 "Yes" indicates airphoto or other data used to confirm identification of dune type.

3 Estimated from Beaufort data, one year of record by John Rogers (written commun., 1975).

4 Coordinates approximate.

5 Discussed as example in text.

6 Annual wind summary not available.

7 Not computed.
154 A STUDY OF GLOBAL SAND SEAS

106°30' 106°00'

DP=149 

ANNUAL FEB

DP=6 

OCT.

DP=8 

DEC.

LANDSAT IMAGERY OF WHITE SANDS National Monument, 

New Mexico, U.S.A. (A, B), and sand roses for Holloman Air 

Force Base, New Mexico, near the downwind end of the dune 

field (C). A, Produced from computer-compatible tape at the 

Center of Astrogeology, Flagstaff, Arizona; scale approximately 

1:290,000. Parabolic and barchanoid dunes are clearly visible. 8, 

Produced by bulk-processing facility at Sioux Falls, South 

Dakota. At this scale (1:1,000,000) barchanoid dunes are barely 

visible, but parabolic dunes can still be clearly seen. A and Bare

winds, such as the Wahiba Sands of Arabia and the 

sands of the Thar Desert of eastern Pakistan and 

western India. The associated environments can 

have either high or low drift potentials.

Cherchen Desert, China

Several groups of barchanoid dunes may occur 

within a single dune field, each group characterized 

by a different size and orientation. In the eastern 

Cherchen Desert, China, three sets of barchanoid 

dunes have orientations differing from 45 to 90 

degrees, depending on locality (fig. 101 A). Effective 

surface winds in the Cherchen Desert, and in the 

eastern Takla Makan basin tend to be weak but 

very steady in direction (chapter K, fig. 206).

included for comparative purposes to illustrate the resolution of 

the bulk-processed Landsat imagery used in this study. C, Annual sand rose and six monthly sand roses for Holloman Air 

Force Base, illustrating the directional variability of effective 

winds near the dunes. Annual wind regime is obtuse bimodal. 

Principal effective winds occur in April (DP = 30 VU) from the 

southwest. Number in center circle of rose is reduction factor. 

DP (drift potential, in vector units) is given for each rose. Arrows 

indicate resultant drift direction (ROD). (Fig. 99.)

Most effective winds at Charkhlik (Nochiang), 

about 40 km (25 mi) southeast of the dunes shown 

in figure 101 A, are weak (estimated DP at Nochiang 

is 185 VU) but very steady in direction during the 

year (fig. 101 B). Thus, they do not provide a ready 

explanation for the different orientations of the 

transverse dunes. Possibly one set of dunes is older 

than the other and is inactive; however, no indications were noted from Landsat imagery, such as 

vegetation, that any of the dunes are stabilized. 

Another possible explanation for several orientations is that the dunes which are alined approximately north-northeast to south-southwest have 

developed transverse to the very strongest winds 

that occur at the station. These winds are from the
DUNE FORMS AND WIND REGIME 155

LANDSAT IMAGERY OF THE NORTHERN PART of the Namib 

Desert, South-West Africa, showing barchanoid dunes along the 

coastal margin of the desert. The wind regime which has produced the dunes is probably restricted to the coastal region. 

This assumption is based on the distribution of the dunes and 

other evidence (chapter K). Large linear dunes occur inland. 

Streaks north of the Kuiseb River, oriented northeast-southwest, 

are alined roughly with the resultant drift directions at the inland 

stations of Zwartbank, Rooi Bank, and Gobabeb during June 

and July, the windiest months at these stations. Sand roses for 

Pelican Point are shown in figure 97 A (Fig. 100.)

east-northeast for 8 months of the year (figs. 101 A, 

102).

Occasional extreme gusts or winds, not sustained 

long, may have important morphological effects in 

such regions as the Cherchen Desert, where winds 

of intermediate strength occur infrequently and 

where the region as a whole has a low drift potential. A more detailed analysis of this problem with 

respect to the Cherchen Desert region, shown in 

figure 101 A, is precluded because of limitations in 

available wind data. This example is presented, 

however, to illustrate the development in the same 

field of very large transverse dunes with orientations differing as much as 90°.

Ala Shan Desert, China

Barchanoid dunes of the western Ala Shan 

Desert of China (fig. 103A) differ greatly in

morphology from those of the Cherchen Desert to 

the west. In the Ala Shan region smaller transverse 

dunes grade westward into larger compound 

barchanoid ridge dunes. In contrast, the transverse 

dunes of the Cherchen Desert have developed as 

continuous ridges with relatively continuous slipfaces (fig. 101 A). Large discontinuous slipfaces occur on the compound dunes of the Ala Shan region. 

These slipfaces are arranged to form a secondary 

alinement at an angle of approximately 22° to the 

annual resultant drift direction at Mao-Mu (Tinghsin), the closest available wind station. Surface 

wind data are not presently available for the interior of the Ala Shan Desert. Regional analysis 

(chapter K) suggests that winds in the Ala Shan 

Desert are more variable in direction than those in 

the Takla Makan Desert. A spring sand-moving 

season occurs at both Charkhlik (Nochiang) and 

Mao-Mu (Ting-hsin). But winds during April, 

which is the month of highest drift potential at both 

stations, are about twice as effective at Charkhlik 

(Nochiang) as they are at Mao-Mu (Ting-hsin). The 

winds at Charkhlik (Nochiang) are also more directionally steady during this time (compare April 

sand roses for Charkhlik (Nochiang), fig. 101B, and 

Mao-Mu (Ting-hsin), fig. 103B).

Simple barchanoid ridge dunes near the station of 

Mao-Mu (Ting-hsin) occur in a wind environment 

similar to that of White Sands National Monument, 

New Mexico, U.S.A., previously described. The 

sand roses for each station are similar (compare annual sand roses, figs. 99C, 103B), and the estimated 

drift potential at Mao-Mu (Ting-hsin) (140 VU) is 

close to the drift potential at White Sands (Holloman Air Force Base, 149 VU).

Linear Dunes

Summary of Observed Wind Environments of 

Linear Dunes

The active linear dunes observed on Landsat imagery occupy a wide range of wind environments in 

terms of both energy and directional variability. 

Drift potentials associated with linear dunes range 

from 45 VU (estimated) in an interdune corridor at 

Narabeb, South-West Africa, to 948 VU at Bilma, 

Niger (table 18). The wind environment of a linear 

dune seems to have a greater directional variability 

of effective winds (lower RDP/DP) than does the 

wind environment of a barchanoid dune, for a
156 A STUDY OF GLOBAL SAND SEAS

87W 87°30' LANDSAT IMAGERY OF THE EASTERN CHERCHEN DESERT, 

China showing (A) dune field with three sets of transverse 

dunes. Two large sets of approximately equal size strike roughly 

northeast and northwest; a smaller set also strikes northwest. 

One set of dunes may be oriented transverse to strongest winds 

in the region indicated by arrow, and other sets may be 

transverse to more frequently occurring winds of lesser strength. 

Resultant of latter winds corresponds roughly to estimated annual resultant drift direction (ROD, indicated by arrow) at 

Nochiang. B, Annual and six monthly sand roses for Charkhlik 

(Nochiang), China, show that most of the effective winds at the 

station, and in the eastern Cherchen Desert, are from the northeast quadrant throughout the year. Number in center circle of 

rose is reduction factor. DP (drift potential, in vector units) is 

given for each rose. Arrows indicate resultant drift direction 

(ROD). (Fig. 101.)

a

ANNUAL

given drift potential (fig. 104). Also, a linear dune 

may require less directional variability of effective 

winds with increasing energy of wind environment 

(fig. 104). Wind distributions associated with active 

linear dunes range from wide unimodal through 

complex. Linear dunes are usually alined parallel to 

the resultant drift direction of effective winds in 

the surrounding environment. This is true whether 

the associated wind distribution is wide unimodal, 

bimodal, or complex. The alinement is closest at 

localities where wind data are most reliable and 

dunes most clearly active, as at Fort-Gouraud, 

Mauritania; Upington, South Africa; and Sabha, 

Libya. Junctures ("tuning fork" or "Y") are a common feature of linear dunes and were observed at 

most localities. The junctures usually open into the 

effective wind (against the resultant drift direction) 

and are most common at localities with low-energy

OCT. DEC.

complex wind regimes. Junctures are least common 

at localities with high-energy wide unimodal wind 

regimes.

Examples of Wind Environments of Linear 

Dunes

Southwest Kalahari Desert, South Africa

Simple linear dunes are the nearly exclusive type 

visible on Landsat imagery of the Kalahari Desert of 

South Africa (chapter K). Active linear dunes and 

sand sheets occur near Upington, in the southwestern part of the Kalahari Desert (fig. 105A). The 

linear dunes and the sand sheets are alined with the 

resultant drift direction of a high-energy obtuse 

bimodal wind regime (fig. 105B). Both the northwesterly and southwesterly components of the 

wind regime are persistent throughout the year.

Direction from which 

maximum winds came

Jan. Feb. Mar. Apr. May June July Aug. Sept. Oct. Nov. Dec. 

ENE. ENE. WSW. ENE. NNE. W. ENE. ENE. ENE. NE. ENE. ENE.

Speed (knots) 35 27 27 35 35 31 27 31 31 31 27 19

WIND ROSE FOR MAXIMUM WINDS and table of average maximum monthly winds at Charkhlik (Nochiang), China, for 1956-61. 

Each tick mark on a wind-rose arm represents a maximum gust from the direction indicated by the arm. (Fig. 102.)
99°30'

DUNE FORMS AND WIND REGIME

ioo°3o;

157

ioroo'

40°30

4rj°oo

D/>=140 

ANNUAL

MOSAIC OF TWO LANDSAT IMAGES (A) of the western Ala 

Shan Desert, China. Small barchanoid ridge dunes grade eastward from the region of Mao-Mu (Ting-hsin) into larger compound barchanoid ridge dunes. Barchanoid dunes in this sand 

sea are peaked, unlike those in the Cherchen Desert (fig. 101 A). 

Arrow on mosaic, and those on roses indicate resultant drift

The distribution in occurrence of maximum winds 

follows closely the pattern of effective winds of all 

velocities suggested by the annual sand rose (fig. 

106). At this locality the resultant drift direction 

varies little throughout the year (fig. 105B).

Western Simpson Desert near Oodnadatta, Australia

Simple linear dunes are an exclusive type 

throughout much of the Simpson, Great Victoria, 

and Great Sandy Deserts of Australia. The driest 

and windiest region of the Simpson Desert may be 

characterized by a markedly different wind regime 

from that of the southwestern Kalahari Desert just 

discussed, although the dunes in both regions are of 

the same type (fig. 107A). The wind regime at Oodnadatta, Australia (located approximately 110 km 

(68 mi) from the dunes shown in fig. 107A), has a

AUG. DEC.

direction (ROD). B, Annual and six monthly sand roses for MaoMu (Ting-hsin), China, illustrating directional variability of lowenergy effective winds near the westernmost part of the Ala 

Shan Desert. Number in center circle of rose is reduction factor. 

DP (drift potential, in vector units) is shown for each rose. (Fig. 

103.)

wide unimodal distribution of effective winds and 

an intermediate drift potential (fig. 107B). The 

northerly group (mode) of effective winds is here 

neglected; it has 12 percent of the total DP at the 

station and occurs during the period of weakest 

winds.

Instead of two distinct and relatively persistent 

components of the wind regime as at Upington, 

several components exist at Oodnadatta. These 

components change in relative intensity during the 

year, resulting in the wide unimodal annual distribution dominated by effective winds from the 

south. The systematic shift of effective winds from 

roughly southerly to southeasterly in January, to 

southwesterly in July, and back during the rest of 

the year results in a gradual swing of the resultant 

drift direction. It moves from a northwestward-
158 A STUDY OF GLOBAL SAND SEAS

TABLE 18. — Localities used to evaluate the wind environments of linear dunes 

[DP, drift potential; RDP, resultant drift potential]

Dune coordinates 

Dune form(s) (lat, long)1

Compound and simple linear.

Simple linear; also linear "sand 

sheets." 

Compound linear; also linear 

"sand sheets."

24°37' S., 

18°10' E. 

25°14' S., 

128°13' E. 

27°33' S., 

135° 27' E. 

Same as static

Near station . 

Near station .

22°30' N., 

1216' W. 

20°50' N., 

13°30' W. 

19°30' N., 

14°10' W. 

Same as static

Near station ,

28°20' S., 

21°26' E. 

Near station ,

Nearest representative 

station 

(distance from dunes in km)

Mariental, South- West Africa3 

(25). 

Giles, Australia3 (25) .........

Oodnadatta, Australia3 (110) . . 

n Ekidze, U.S.S.R.3 (0) .........

. Sabha, Libya3 (5) ............

' mf \ 1

. Bilma, Niger3 (5) .............

Fort-Gouraud, Mauritania3 

(40-50).

n Narabeb, South-West Africa (in 

interdune corridor) (0). 

, . El Golea, Algeria (0) .........

Upington, South Africa3 

(10-25). 

. . Ash Shariqah (Sharjah), Arabia 

(5-10).

Station 

coordinates 

(lat, long)

24°37' S., 

17°58' E. 

25°02' S., 

128°18' E. 

27°33' S., 

135°27' E. 

41°02' N., 

57°46' E.4 

27°01' N., 

14°26' E. 

18°41' N., 

12°55' E. 

22°41' N., 

12°42' W. 

20°31' N., 

13°04' W. 

19°45' N., 

14°22' W. 

23°52' S., 

14°52' E.4 

30°30' N., 

02°52' E. 

28°24' S., 

21 To li. 

25°21' N., 

55°23' E.

Other 

data2

Yes

No 

No 

No 

Yes 

No 

No 

No 

No 

Yes 

No 

No 

No

DP

50 

101 

388 

111 

268 

948 

661 

443 

352 

45 

270 

520 

280

Wind regime 

classification, 

using 

RDP/DP sand rose

0.32 

.23 

.46 

.19 

.20 

.74 

.67 

.64 

.68 

.24 

.26 

.66 

.60

Complex. 

Do. 

Wide unimodal. 

Complex. 

Do. 

Wide unimodal. 

Acute bimodal. 

Wide unimodal. 

Do. 

Unclassified.5 

Complex. 

Obtuse bimodal. 

Acute bimodal.

1 10-km-radius circle centered on this point.

2 "Yes" indicates airphoto or other data used to confirm identification of dune type.

3 Discussed as example in text.

4 Coordinates approximate.

5 Annual wind summary not available.

DRIFT POTENTIAL (DP) VERSUS RDP/DP for 13 stations near 

linear dunes visible on Landsat imagery. Linear dunes represented by triangles. Data from figure 98 also shown, barchanoid 

dunes represented by dots. Dot within triangle denotes a 

locality near which both dune types are well developed. The 

distribution of points indicates that wind environments of linear 

dunes have greater directional variability than do wind environments of barchanoid dunes for a particular drift potential. Linear 

dunes in wind environments with high drift potentials are 

associated with less directional variability of effective winds 

than are linear dunes in wind environments with low drift potentials. (Fig. 104.)

3UUU 

2500

Z 2000

EC

0 1500

<J -\ ill

^ 1000

_r

g 600 

a.

t 400 

cc 

a

200

n

1 1 II.

-

^ x^

A

A 

* • •

A 

A A 

A A *

AA . • .

, A ,A , n • 1 > 1 1

0.1 0.2 0.3 0.4 0.5 0.6 

RDP/DP

0.7 0.8 0.9 1.0
20°00'

DUNE FORMS AND WIND REGIME

20°30' 21°00 r

159

ANNUAL

DP=2B 

APR.

DP=40 

JUNE

DP=80 

AUG.

DP=45 

OCT.

DP=48 

DEC.

LANDSAT FALSE-COLOR IMAGERY (A) of part of the southwestern Kalahari Desert near Upington, South Africa. Red sand 

is yellow on Landsat false-color imagery. Linear dunes with 

sharp crests are visible near Upington and farther east near the 

Orange River (upper right corner of image). Wider linear streaks 

which lie across drainages and hills are marked by lines parallel 

to streaks. Although linear in gross aspect, they may contain 

transverse bedforms too small to be seen on Landsat imagery. 

(Similar streaks are visible on Landsat imagery of northern 

Arizona north of the Little Colorado River near Cameron, 

Arizona, in the United States and were examined in the field by

the author. These streaks were extended sandy areas with 

barchanoid dunes.) Green vegetation along the Orange River 

shows as red on Landsat false-color imagery. Clouds are white. 

Arrow indicates annual resultant drift direction (ROD) at 

Upington. 8, Annual and six monthly sand roses for Upington, 

South Africa, illustrating an obtuse bimodal wind regime. The 

resultant drift direction (arrows) remains steady and approximately parallel to the orientation of linear dunes in the region 

throughout the year. Number shown in center circle of rose is 

reduction factor. DP (drift potential, in vector units) is given for 

each rose (Fig. 105.)
160 A STUDY OF GLOBAL SAND SEAS

/

Direction from which 

maximum winds came

Jan. Feb. Mar. Apr. May June July Aug. Sept. Oct. Nov. Dec. 

NNW. NW. N. WSW. WSW. N. N. N. NNE. WSW. NNE. W.

Speed (knots) 33 40 35 31 32 29 36 37 52 35 33 37

WIND ROSE FOR MAXIMUM WINDS and table of average max- Upington closely reflect the obtuse bimodal distribution of all 

imum monthly winds at Upington, South Africa, for 1956- 67. effective winds shown in the annual sand rose in figure 105B. 

Each tick mark on a wind rose arm represents a maximum gust (Fig. 106.) 

from the direction indicated by the arm. Strongest winds at

136°30' 137°00' 137°30'

LANDSAT IMAGERY OF SOUTHWESTERN SIMPSON DESERT, 

Australia (A). Straight simple linear dunes are the only type visible on Landsat imagery throughout much of this desert and 

along its margins. B, Annual and twelve monthly sand roses for 

Oodnadatta, Australia, approximately 110 km (68 mi) from the 

dunes in A. Wide unimodal wind distribution of effective winds

displayed by annual sand rose results from interaction of winds 

between the southwest and southeast during the year. Arrows 

indicate resultant drift direction. Number in center circle of rose 

is reduction factor. DP (drift potential, in vector units) is given 

for each rose. (Fig. 107.)
DUNE FORMS AND WIND REGIME 161

_^ ^

M Tir

DP=17 

APR.

DP=13 

MAY

DP=10 

JUNE

D/>=388 

ANNUAL

D/>=18 

JULY

DP=26 

AUG.

DP=52 

SEPT.

DP=56 

OCT.

DP=46 

NOV.

DP=43 

DEC.

directed HDD in January, to an east-northeastwarddirected HDD in July, and back. Another region 

characterized by a regular swing of resultant drift 

direction back and forth is western Mauritania 

(chapter K). This region is also characterized by 

linear dunes, although both wind regimes and 

dunes differ in detail from those near Oodnadatta.

Ramlat Zallaf sand sea near Sabha, Libya, and 

Peski Karakumy, U. S. S. R.

Some simple linear dunes occur in regions of 

complex wind distributions of low or intermediate 

energy. Long, relatively narrow linear dunes, 

which are very gently curving on Landsat imagery 

(fig. 108A), occur west of Sabha, Libya, in a complex intermediate-energy wind regime (fig. 108B). 

These dunes, in fact, have a zigzag pattern in plan 

when viewed from the ground or on aerial photographs (McKee and Tibbitts, 1964, p. 14-15, plates 

I, II). Wind regimes from month to month are complex, with the exception of May through August 

when easterly effective winds are most important. 

The occurrence of maximum winds suggests a complex pattern (fig. 109). The trend of the dunes near 

Sabha is exactly parallel to the annual resultant 

drift direction at the station (fig. 108B).

The parallelism of dune trend and effective wind 

direction at Sabha suggests that each component of 

a complex wind regime may have a proportionate 

effect on the growth of dunes and their resulting 

orientation. On the other hand, the orientation of 

the dunes is also parallel to the resultant drift direction during May, the month of highest drift potential at the station. Therefore, it seems equally possible that most of the growth of the dunes occurs 

from May until September, the time of relatively 

steady easterly winds. Complex monthly wind 

regimes during the remainder of the year might be 

incapable of obliterating the linear form of the 

dunes established during the May to September 

season.

An example of linear dunes, probably active, in a 

complex wind regime of low energy occurs in the 

northern Peski Karakumy in the region of Ekidze, 

U.S.S.R. (fig. 110A). Near Ekidze, features that 

seem to be linear dunes — because they exhibit the
162 A STUDY OF GLOBAL SAND SEAS

14°00' 14°30' LANDSAT IMAGERY OF THE RAMLAT ZALLAF SAND SEA near 

Sabha, Libya (A). Linear dunes are gently curving, thin streaks 

extending from west-northwest to east-southeast across the image. B, Annual and twelve monthly sand roses for Sabha, Libya, 

illustrating the complex pattern of effective surface winds. 

Dunes shown in A are alined with the annual resultant drift 

direction at the station and with the monthly resultant drift 

direction during May, when the highest drift potentials occur. 

Winds are relatively steady from May through August, during 

which about 35 percent of the average annual drift potential occurs. Number inside center circle is reduction factor. Arrows are 

resultant drift direction (ROD). DP (drift potential, in vector 

units) is given for each rose. (Fig. 108.)

DP=n 

JAN. MAY

DP=26 

JUNE

DP=268 

ANNUAL

B

DP=8 

JULY

DP=7 

AUG. SEPT.

DP=2G 

NOV. DEC.

IN

t Direction from which 

maximum winds came

Jan. Feb. Mar. Apr. May June July Aug. Sept. Oct. Nov. Dec. 

NNW. NNW. SW. ESE. SE. S. W. NE. WNW. S. SSW. SE.

Speed (knots) 24 24 27 24 30 22 25 19 26 31 24 23

WIND ROSE FOR MAXIMUM WINDS and table of average maximum monthly winds at Sabha, Libya, for 1949 and 1961 -63. Each 

tick mark on a wind rose arm represents a maximum gust from the direction indicated by the arm. Strongest winds at Sabha reflect 

the complex distribution of all effective winds shown on the annual sand rose in figure 1086. (Fig. 109.)
DUNE FORMS AND WIND REGIME 163

EKIDZE

20 KM

10 Ml

RDP= 21 

RDP/DP=0.-\9

LANDSAT IMAGERY OF PRESUMED LINEAR DUNES (A) in the 

Peski Karakumy near Ekidze, U.S.S.R. Linear dunes have sharp 

crests and junctures which open upwind (against the resultant 

drift direction, ROD, indicated by arrow). B, Annual sand rose for 

Ekidze, illustrating a complex wind regime dominated by a 

mode from the east and a mode from the west. Linear dunes 

near Ekidze are alined with the annual ROD (arrow) at the station but exhibit more waviness in plan than do linear dunes 

near Upington, South Africa, and Oodnadatta, Australia, which 

have higher energy, bimodal effective wind distributions. DP, 

drift potential; RDP, resultant drift potential; both in vector units. 

(Fig. 110.)

windward-facing tuning-fork junctures characteristic of linear dunes — are perfectly alined with 

the resultant drift direction at Ekidze (arrows, figs. 

110A,B). The complex wind regime at the station is 

dominated by two opposing modes of effective 

wind from roughly the west and the east.

Northwestern Kalahari Desert, South-West Africa, 

and Great Victoria Desert, Australia

Simple linear dunes are partially vegetated in 

wide regions of the Kalahari, Great Victoria, and 

Great Sandy Deserts. Near Mariental, South-West 

Africa (fig. Ill A), and Giles, Australia (fig. 112 A), 

partially vegetated linear dunes are associated with 

low-energy wind regimes (figs. lllB, 112JB) compatible with the observed dune types.

The sand rose for Mariental reflects a high degree 

of observer or procedure bias. Nevertheless, as does

the distribution of maximum winds (fig. 113), this 

sand rose suggests a wide unimodal or perhaps 

acute bimodal distribution of effective winds. The 

wind regime at Giles is complex but composed primarily of wide modes from the north-northeast and 

south.

The degree to which the observed morphologies 

are a result of present day winds is difficult to 

determine from available data. For example, 

vegetation on dunes in the Sahel and southwestern 

Mauritania seems to be associated with climatic 

change which has led to the immobilization of the 

dunes (chapter K), although not all the observed 

dunes in these regions are out of adjustment, or 

alinement, with present-day winds.

In addition to vegetation, which tends to reduce 

sand movement, the wind regimes at Mariental and 

Giles have low drift potentials. For example, the 

drift potential of 50 VU at Mariental indicates 

negligible sand drift if the impact threshold shear 

velocity (Vf) is assumed to be 19 cm/s (0.58 ft/s) in 

figure 94. On the other hand, dunes near Mariental 

and possibly near Giles are only partially vegetated, 

indicating that they may be at least partly active.

The compatibility of the wind regimes with dune 

types at Giles and Mariental, and the continuity of 

dune trends from partially vegetated to unvegetated areas across considerable distances in both the 

Kalahari and Simpson Deserts (chapter K) indicate 

that the dune morphologies are at least partially the 

result of present-day winds. In addition, the degree 

of waviness in dune plan in the unvegetated and 

the vegetated regions of the Kalahari Desert and in 

the Australian deserts corresponds roughly to the 

directional variability of the wind regimes (compare dunes near Giles and Ekidze with those near 

Oodnadatta and Upington).

Even if present-day low-energy wind regimes 

have not created the dunes near Mariental and 

Giles, they may still serve to maintain the form of 

the dunes or have insufficient strength to obliterate 

them. More specific knowledge of the degree to 

which the dunes observed near Mariental and Giles 

are the product of present-day winds would facilitate interpretation of the paleoclimate of these 

regions.
164 A STUDY OF GLOBAL SAND SEAS

lfi°30'

0^=50 

/?DP=15 

RDP/DP=Q3Q

LANDSAT IMAGERY OF THE NORTHWESTERN KALAHARI 

DESERT (A) near Mariental, South-West Africa. Partially vegetated, straight linear dunes with junctures opening upwind, or 

against the resultant drift direction. Resultant drift direction at 

Mariental indicated by arrow. B, Annual sand rose for Mariental 

shows extreme observer or procedure bias (few observations 

between the prime points of the compass) but suggests wide 

unimodal, or perhaps acute bimodal, wind distribution. DP, drift 

potential; RDP, resultant drift potential; both in vector units. Arrow indicates resultant drift direction (ROD). (Fig. 111.)

Erg Hammami Region, Mauritania, and Erg Bilma 

Region, Niger

Both compound and simple linear dunes occur in 

regions characterized by acute bimodal, or wide 

unimodal wind distributions and a high drift potential. Much of Mauritania northwest of a line from 

Akjoujt through Atar is characterized by acute 

bimodal winds, and by compound and simple linear 

dunes which extend subparallel to the resultant 

drift direction of present-day winds (fig. 114).

The long, straight, very large linear dunes near 

Fort-Gouraud, Mauritania (fig. 114), seem to have 

developed in an acute bimodal high-energy wind 

regime in which the two major components are 

mainly in different seasons (fig. 97B). The more 

dominant group of winds, from north through 

northeast, is active from spring through fall. This 

group results from anticyclonic tradewind circulation from the North Atlantic high-pressure cell,

= 101

B

LANDSAT IMAGERY OF LINEAR DUNES IN THE GREAT VICTORIA DESERT (A) near Giles, Australia. These dunes are more 

wavy in plan than those near Mariental, South-West Africa (fig. 

111A). B, Annual sand rose for Giles illustrates not only the 

complex nature of effective winds but also the difficulties of 

classifying directional characteristics of effective wind regimes. 

The subsidiary groups of the distribution (from approximately 

the northwest and east-southeast, as bracketed) each comprise 

more than 15 percent of the annual drift potential at the station. 

Most of the effective winds at the station, however, occur in 

groups from the north-northwest and south. In this example, 

because maximum wind data are unavailable, the classification 

may be either complex or obtuse bimodal. The sand rose illustrates well, however, the greater directional variability of effective winds at Giles than at Mariental (fig. 1118). DP, drift potential, in vector units. Arrow indicates resultant drift direction 

(RDD). (Fig. 112.)

which is strongest in midsummer (chapter K). The 

group of winds from the southwest may represent 

the effect of anticyclonic circulation from a wintertime high-pressure ridge over the northern Sahara.

Simple linear dunes and compound linear dunes, 

similar in appearance to those near Fort-Gouraud 

occur near Bilma, Niger (fig. 115A), in a region 

characterized by a wide unimodal high-energy 

wind regime (fig. 115B). In this region, simple 

linear dunes and compound linear dunes occur in
DUNE FORMS AND WIND REGIME 165

l\t Direction from which 

maximum winds came

Jan. Feb. Mar. Apr. May June July Aug. Sept. Oct. Nov. Dec. 

NW. NE. N. SE. NW. N. NE. N. N. N. NW. E.

Speed (knots) 25 35 20 25 23 23 23 25 30 30 25 25

WIND ROSE FOR MAXIMUM WINDS and table of average monthly maximum winds at Mariental, South-West Africa, for 1960-67. 

Each tick mark on a wind rose arm represents a maximum gust from the direction indicated by the arm. Strongest winds at Mariental 

support the classification of effective winds in figure 1116 as either wide unimodal or acute bimodal. (Fig. 113.)

12°3D' 12°00'

LANDSAT IMAGERY OF LINEAR DUNES in the Erg Hammami 

region, northern Mauritania. Long, large compound linear dunes 

in this region have developed in an acute bimodal high-energy 

wind regime (fig. 976). (Fig. 114.)

two different areas. This evidence indicates that 

both simple linear and compound linear dunes can 

develop in high-energy wind regimes. Perhaps 

available sand supply and age of the dunes, as well 

as wind regime, may be important factors that 

determine whether simple linear or compound 

linear dunes will form at a given locality.

Star Dunes

Summary of Observed Wind Environments of 

Star Dunes

Star dunes observed in this study are in areas

with complex wind regimes (table 19). Drift potentials range from low (73 VU at Illizi, Algeria) to 

high (658 VUat Ghudamis, Libya), and RDP/DFs 

range from intermediate to low. Isolated star dunes 

are associated with RDP/DP of less than 0.20, and 

star dunes in chains or atop linear features are 

associated with higher RDP/DP (fig. 116).

Examples of Wind Environments of Star 

Dunes

Eastern Grand Erg Oriental, Algeria-Libya

Isolated star dunes occur in the Grand Erg Oriental near Ghudamis, Libya (fig. 117) in a high-energy 

complex wind regime (fig. 97C). This association 

supports the suggestion of McKee (1966, p. 68) that 

star dunes develop as a result of effective winds 

from several directions.

The complex wind regime at Ghudamis differs 

from the complex wind regime associated with 

linear sand dunes at Sabha (fig. 108B) in several significant ways. First, the drift potential at Ghudamis 

is 2.5 times as great as at Sabha; second, complex 

wind distributions prevail during the months of 

highest drift potential at Ghudamis and become 

relatively narrow only during the seasons of low 

drift potential from December through February. At 

Sabha, the reverse situation occurs. Finally, 

although two dominant modes may be recognized 

in the annual sand roses for both Ghudamis and 

Sabha, the dominant modes are perfectly opposed 

at Ghudamis but are at approximately a right angle 

at Sahba.

Grand Erg Occidental, Algeria

Some star dunes occur in low-energy complex 

wind regimes. Star dunes occur in such an environ-
166 A STUDY OF GLOBAL SAND SEAS

ment along and atop an escarpment near Beni 

Abbes, Algeria (fig. 118A). The drift potential at 

Beni Abbes is low (185 VL7), and effective winds 

during the month of highest drift potential are complex, as at Ghudamis, Libya (fig. 118B). Star dunes 

near Beni Abbes, visible in an aerial photograph 

(Alimen and others, 1957, plate III), seem to be

composed of sinuous ridges rather than having 

formed isolated mounds, as at Ghudamis.

Western Grand Erg Oriental, Algeria

Star dunes have been observed on Landsat imagery atop other sand features, many of which have a 

linear aspect in plan view. These linear features on

13°30' 14°00'

B DP=948 

ANNUAL

LANDSAT IMAGERY OF LINEAR DUNES (A) in the Erg Bilma. Both simple and compound linear dunes occur near Bilma in the 

same regional wind environment. B, Annual and six monthly sand roses for Bilma, Niger, illustrate a wide unimodal high-energy 

wind regime near the dunes. Arrow indicates resultant drift direction (ROD). Number in center circle of rose is reduction factor. DP 

(drift potential, in vector units) is given for each rose. (Fig. 115.)
DUNE FORMS AND WIND REGIME 167

TABLE 19. — Localities used to evaluate the wind environments of star dunes

[DP, drift potential; RDP, resultant drift potential]

Dune form(s)

Dune coordinates 

(lat, long) 1

Nearest representative 

station 

(distance from dunes in km)

Station 

coordinates 

(lat, long)

Other 

data2

Wind regime 

classification, 

using 

DP RDP/ DP sand rose

Star Near station .. Ghudamis, Libya3 (=5) . 

Do. ...... Beni Abbes, Algeria3 (0)

Do. ...... Illizi, Algeria (0) .......

Star dunes in chains or on

linear "sheets." 

Star dunes atop linear or

barchanoid features.

26°22' S., Aus, South-West Africa (23) . .

16°14' E. 

31°34' N., Hassi Messaoud, Algeria3 (20) .

06°15' E.

Near station .. Bordj Omar Driss (Fort 

___________Flatters), Algeria (0).

30°08' N.,

09°30' E. 

SOW N.,

02°10' W. 

26°30' N.,

08°29' E. 

26°42' S.,

16°14' E." 

31°40' N.,

06°09' E. 

28°08' N.,

06°50' E.

Yes 658 0.09 Complex.

Yes 184 .11 Do.

No 73 .07 Do.

No (5) (5) Wind rose only.

No 200 .31 Complex.

No 112 .35 Do.

1 10-km-radius circle centered on this point.

2 "Yes" indicates airphoto or other data used to confirm identification of 

dune types.

3 Discussed as example in text.

4 Station coordinates approximate.

5 Drift potential unknown.

JUUU

2500

^ 2000

D

0 1500 d ^

> 1000

Z

< 800 lLLI r5 60°

Q_

1 «°° 

o

200

o

III II

_

^

A

-

* A 

A A * " High

A A Hassi Messaoud A Intermediate

,k ^ Bordj Omar Driss «a

AA >){• • • LoW

* I A ,A , . • ^ % , |

Q 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1

RDPIDP

DRIFT POTENTIAL (DP) versus RDPIDP tot five stations near star 

dunes, which are represented by stars. Data from figures 98 and 

104 also shown; barchanoid dunes represented by dots, linear 

dunes represented by triangles. Dot within triangle indicates 

locality near which both barchanoid and linear types are well 

developed, Isolated star dunes were observed only in wind environments with low RDPIDP. Star dunes on broadly linear sand 

"sheets," or atop other linear features were observed in intermediate environments in terms of RDPIDP. Examples in Algeria 

are dunes near Hassi Messaoud and Bordj Omar Driss (Fort Flatters). (Fig. 116.)

which the star dunes have developed may, in some 

places, represent older barchanoid or linear dunes, 

or extended linear "sand sheets." Star dunes near 

Hassi Messaoud, Algeria, have developed in chains 

atop extended linear sand features of indeterminate 

identity (fig. 119A). The annual effective wind 

regime at Hassi Messaoud is difficult to classify but 

is either obtuse bimodal or complex. Effective wind

30°30' 9°orj'

30° 

00'

Ghudamis

o

20 KM •>.

LANDSAT IMAGERY OF ISOLATED STAR DUNES in the Grand 

Erg Oriental near Ghudamis, Libya. Annual and six monthly 

sand roses for Ghudamis illustrating complex high-energy wind 

regime are shown in figure 97C (Fig. 117.)
168 A STUDY OF GLOBAL SAND SEAS

02°00' LANDSAT IMAGERY OF STAR DUNES (A) that occur along and 

atop an escarpment at the southern margin of the Grand Erg Occidental near Beni Abbes, Algeria. These star dunes are not as 

large as those near Ghudamis, Libya. B, Annual and six monthly 

sand roses for Beni Abbes. Annual effective wind regime is complex, low energy. Effective wind regime is complex during April, 

the month of highest drift potential. Arrows indicate resultant 

drift direction (ROD). Number in center circle of rose is reduction factor. DP (drift potential, in vector units) is given for each 

rose. (Fig. 118.)

DP=185 

ANNUAL

DP=5 

AUG.

DP=7 

OCT.

LANDSAT IMAGERY OF ALINED STAR DUNES (A) atop linear 

sand sheets near Hassi Messaoud, Grand Erg Oriental, Algeria. 

Exact nature of the sheets is unknown. B, Annual and six 

monthly sand roses for Hassi Messaoud, Algeria, illustrating 

complex (or possibly obtuse bimodal) intermediate-energy 

effective wind regime at the station. The present-day wind environment of the region seems intermediate between those of 

star and linear dunes (figs. 104, 116). The dune pattern may 

have developed from present-day winds or may represent the 

result of two or more stages of development involving different 

wind regimes. Arrows indicate resultant drift direction (ROD), in 

vector units. Number in center circle of rose is reduction factor. 

DP (drift potential, in vector units) is given for each rose. 

(Fig. 119.)

\

DP=23 

FEB. APR.
DUNE FORMS AND WIND REGIME 169

distributions from month to month tend to be bimodal or complex (fig. 119B). This wind regime differs 

from other wind regimes associated with star dunes 

because the resultant drift direction at the station is 

relatively steady (toward the southeast) during the 

year. This wind environment seems to be intermediate between that associated with linear dunes 

and that with star dunes, in terms of RDP/DP (fig. 

116).

An anomaly is presented by dunes in the region 

of Erg Irarrarene near Bordj Omar Driss (Fort Flatters), Algeria. There, star dunes are atop what seem 

from Landsat imagery (chapter K) to be barchanoid 

dunes. If the sand bodies upon which the star dunes 

have developed were originally barchanoid dunes, 

a climatic change is indicated because the observed 

environments of star and barchanoid dune types 

differ widely (fig. 116). Present-day winds at Bordj 

Omar Driss are intermediate between those forming linear dunes and those forming star dunes, in 

terms of RDP/DP.

A STUDY OF GLOBAL SAND SEAS

LABORATORY STUDIES OF SAND

PATTERNS RESULTING FROM

CURRENT MOVEMENTS

Chapter G

By THEODORE F. TYLER

Contents

Page Page

Summary of conclusions ............................ 173 Present study— Continued

Introduction ..................................... 173 Wave-tank experiments — Continued

Background information ...................... .. 173 Experiment 1 ............................... 177

Hierarchy of bed roughness ...... ............ 173 Experiments 2 and 3 ........................ 180

Oscillation ripple ........................ .... 173 Ripple development patterns ........ ........ 182

Present study .............. ................. .... 174 Comparison of aqueous wave ripples (aqueous dunes)

Equipment and procedure ..................... 174 and eolian dunes ........................... 182

Wave-tank experiments ......................... 177 Effects of barriers on ripple development ........ 183

171
172

Illustrations Page

FIGURE 120. Sketch of generalized ripple profile, showing gently sloping stoss side and

steeply sloping lee side ............................................ 174

121. Sketches of bedform patterns of large-scale ripples (aqueous dunes) near the

Bahama Islands .................................................. 175

122. Generalized diagram of wave tank used in laboratory experiments.......... 176

123. Graph showing starting sand profile in wave tank, experiments 1, 2, and 3 .. 176

124. Sketch showing plan view of ripple patterns for experiment 1 after 10, 30, and

50 minutes of wave action ........................................ 178

125. Sketch of plan view of ripple crests, showing process of ripple branching ... 178

126. Graphs showing ripple height and wavelength after 10 and 50 minutes of wave

action ........................................................... 179

127. Graphs showing stoss- and lee-side horizontal dimensions after 10 and 50

minutes of wave action ........................................... 179

128-131. Sketches showing:

128. Plan view of ripple patterns for experiment 2 after 10 and 50 minutes of

wave action . ................... .......................... 180

129. Plan view of ripple patterns for experiment 3 after 10 and 50 minutes of

wave action ................................................ 181

130. Sequence of small-scale ripples changing with time and increase in flow

velocity and (or) water depth ................................. 182

128-131. Sketches —Continued

131. Sequence of small-scale ripples changing with increase in flow velocity

and (or) water depth ........................................ 182

132. Photographs, Landsat imagery, and sketches comparing plan views of aqueous

and eolian bedforms .............................................. 184

133. Sequential photographs showing the effects of a barrier on ripple development

134. Sequential photographs showing bedforms developed in a wind-tunnel experiment ...... ................... ................................. 184

135. Landsat imagery of questionable barchan dunes developing into barchanoid

ridges, Arabian Peninsula .......................................... 185

136. Landsat imagery of development of dunes across a geomorphically controlled

area, Arabian Peninsula ............................................ 185

Tables Page

TABLE 20. Ripple dimensions and ripple symmetry index for experiment 1 after 10, 30 and

50 minutes ...................................................... 177

21. Ripple dimensions and ripple symmetry index for experiment 2 after 10 and 50

minutes ......................................................... 181

22. Ripple dimensions and ripple symmetry index for experiment 3 after 10 and 50

minutes ....................................................... 182

23. Bedforms oriented transverse to wave or wind direction .................. 183
LABORATORY STUDIES OF SAND PATTERNS RESULTING FROM CURRENT MOVEMENTS 173

Summary of Conclusions

HIS STUDY IS A COMPARISON of laboratory-generated small-scale aqueous ripples, 

natural large-scale ripples (aqueous dunes), and 

eolian dunes to show similarities in their developmental sequences and resulting bedform patterns. 

Small-scale aqueous ripple development on smooth 

sloping sand beds and ripple development in the lee 

of barriers placed on smooth-leveled sand beds 

were studied in a laboratory wave channel by 

means of tracings and still photography. These tracings and photographs were compared with oblique 

aerial photographs and Landsat (ERTS) imagery to 

determine similarities between aqueous and eolian 

bedform patterns. The various bedforms show 

remarkable similarities although developed under 

different environmental conditions.

Bedforms can be categorized on the basis of their 

developmental sequences, as follows: (1) Isolated 

crescentic forms (isolated barchan), (2) coalescing 

crescentic form (coalescing barchan), (3) parallelsinuous form (barchanoid ridge), and (4) parallelstraight form (transverse ridge).

Introduction

THIS STUDY WAS UNDERTAKEN in the U.S. 

Geological Survey sedimentary structures laboratory to determine the transition patterns of smallscale oscillation ripples on gently sloping surfaces, 

and on level surfaces when barriers were present to 

disrupt the normal wave motion. Tracings were 

made as the ripples developed under normal wave 

action, and a tracing was made every 10 minutes for 

a 50- to 60-minute period. Then the ripples were 

classified according to crest shape. Comparisons 

were made between the bedforms of these smallscale aqueous ripples and those of the large-scale 

ripples (aqueous dunes) developed under natural 

conditions. The aqueous forms were then compared with large-scale eolian dunes, by using aerial 

photographs and Landsat (ERTS) imagery. 

Emphasis was placed on the similarities between 

their plan views and transition patterns.

The following discussion falls into four categories: (1) hierarchy of bed roughness, (2) the wave

tank and procedures used for this study, (3) ripple 

patterns developed during three laboratory experiments and a comparison of aqueous dunes with 

eolian dune development, and (4) effects of barriers 

on bedform development in both aqueous and 

eolian environments as evidenced by use of photographs of laboratory experiments, oblique aerial 

photographs, and Landsat (ERTS) imagery.

Background Information

BEDFORMS OCCUR on the surface of noncohesive sediments in response to fluid motion. It is 

extremely difficult to determine the various 

parameters and mechanisms and the intricate interrelations which control bedform development in a 

natural situation. Under laboratory conditions one 

parameter at a time may be varied to study its effect 

on bedform development and to provide insight 

into this parameter's effect on bedform patterns observed in the field.

Hierarchy of Bed Roughness

A critical, or threshold, velocity, which is a function of grain size, must be reached to initiate motion 

in noncohesive sands. Before onset of grain motion 

on a flat bed, only grains themselves contribute to 

bed roughness. A second-order, and possibly a 

third-order, of bed roughness may develop once 

grain movement starts. This hierarchy of bed 

roughness is: (1) individual grains, (2) small-scale 

ripples, and (3) dunes. In general, the individual 

grain is the basic building block for this hierarchy 

of bed roughness, and for the development of a 

sedimentary structure. Bedform development is 

also dependent on other factors, such as the 

availability of sand, the water or wind velocity, 

water depth, and time.

Oscillation Ripple

A ripple is defined as any deviation from a flat 

bed that resembles or suggests a ripple of water and 

that is formed on the bedding surface of a sedimentary deposit. Aqueous ripples vary considerably in 

size and shape. Figure 120 shows a ripple profile at 

right angles to wave propagation and gives the
174 A STUDY OF GLOBAL SAND SEAS

DIRECTION OF WAVE PROROGATION

GENERALIZED RIPPLE PROFILE, showing gently sloping stoss 

side and steeply sloping lee side. (Fig. 120.)

terms commonly used to describe a ripple. In 

general, a ripple whose crest becomes more planar 

than those shown in figure 120 is defined as having 

a platform crest. Two ratios are useful in characterizing a ripple:

1. Ripple symmetry index (RSI):

DOT _ Horizontal projection of stoss side 

Horizontal projection of lee side

For a symmetrical ripple formed under 

oscillatory flow conditions (wave ripple), this 

ratio should be equal to 1.0; for asymmetrical 

wave ripples this ratio ranges from 1.1 to 3.8 

(Reineck and Singh, 1973, p. 25).

2. Ripple index (RI):

R7 _ Wavelength 

Height

For both symmetrical and asymmetrical wave 

ripples the ripple index ranges from 5 to infinity, with most wavelengths being 6-8 

(Dingier, 1975, p. 95; Reineck and Singh, 1973, 

p. 25). For unidirectional current ripples, the 

RJ is always more than 5, with most values 

falling between 8-15 (Reineck and Singh, 

1973, p. 29).

Small-scale oscillation ripples are defined as having wavelengths ranging from 0.4 to 78.8 inches (1 

to 200 cm) and heights from 0.1 to 9.1 inches (0.3 to 

23 cm) (Reineck and Singh, 1973, p. 24- 25). Smallscale unidirectional current ripples are defined as 

having wavelengths of 1.6 to 23.6 inches (4 to 60 

cm) and heights of 0.1 to 2.4 inches (0.3 to 6 cm) 

(Reineck and Singh, 1973, p. 29).

Large-scale ripples (aqueous dunes) are not as 

well described in the literature as are small-scale 

ripples, but some good examples can be found. A 

development of bedform patterns at the southeastern edge of the Tongue of the Ocean, Bahama 

Islands, in water 3-4 fathoms (5.5- 7.3 m) deep is 

shown by Newell and Rigby (1957, pi. 10, fig. 1). 

Crescentic (barchanoid) forms occur as solitary 

forms which coalesce and eventually form parallelsinuous and parallel-straight forms (fig. 121 A). The 

horns of the simple crescentic forms are 50 - 200 

feet (15-61 m) wide, and they coalesce to form 

great ripples (aqueous dunes) with wavelengths of 

10-30 feet (3-9 m). Parallel-straight to parallelsinuous transverse ripples (dunes) are developed in 

the vicinity of the Northwest Channel Light, 

Bahama Islands (fig. 121B). These forms have 

wavelengths of approximately 300 feet (91 m).

Oscillation megaripples and certain eolian dunes 

show similarities in their external profile and 

developmental patterns when viewed in plan. 

Thus, figure 120 and the associated terms can also 

be used to describe an eolian dune oriented 

transverse to the wind direction. The lee- and stossside dimensions and height of an eolian dune range 

from a few feet to tens of feet in magnitude, very 

similar to the megaripples (aqueous dunes) at the 

Tongue of the Ocean previously described.

Present Study

A DESCRIPTION FOLLOWS of the wave tank 

and of the procedures used for experiments conducted in the laboratory. Ripple development on 

gently sloping surfaces and the transition patterns 

of these ripples are compared for three experiments.

Equipment and Procedure

A 46-foot-long by 2-foot-deep by 1.5-foot-wide 

(14-m-long by 0.6-m-deep by 0.5-m-wide) wave 

tank was used for all experiments (fig. 122). Distances along the wave tank were measured from 

the down wave end of the tank. The tank has a 

piston-type paddle at the upwave end and a silica 

sand beach with a median grain size of 0.319 mm at 

the down wave end. The study area was the interval 

between 15 and 30 feet (4.6 and 9.1 m). This area in-
LABORATORY STUDIES OF SAND PATTERNS RESULTING FROM CURRENT MOVEMENTS 175

•'^^^•^^^^

„. • -'-!-^fe>^« ^ .^&^fe«%^^^^^«1»S5i. 

v>s- 3--,''£ wefttw;

BEDFORM PATTERNS OF LARGE-SCALE RIPPLES (aqueous dunes) in the Bahama Islands. Sketched from photographs in Newell 

and Rigby (1957, pi. 10, fig. 1, and fig. 2) A, Southeastern edge of the Tongue of the Ocean. The water is 3 - 4 fathoms (5.5 - 7.3 m) 

deep in the area. B, Vicinity of the Northwest Channel Light. (Fig. 121.)
176 A STUDY OF GLOBAL SAND SEAS

DIRECTION OF WAVE PROROGATION

Up wave Back of tank Downwave

46

GENERALIZED DIAGRAM OF THE WAVE TANK used in the laboratory experiments. Dimensions of the tank are in feet (1 

foot =0.31 metres). (Fig. 122.)

eluded the sand bed from the breaker-related bar 

zone upwave to a point where the sand was about 

0.4 inch (1.0 cm) thick. From 15 to 0 feet (4.6 to 0.0 

m) the sand-water interphase was affected by the 

borelike motion of the water, which occurs after the 

wave breaks, and the interval was therefore excluded from this study.

The following parameters were held constant for 

the first three experiments: The grain size of the 

sand, D, was 0.319 mm; the water depth, h, at the 

30-foot location (9.1 m) was 8.6 inches (21.8 cm); 

and wave period, T, was 2.5 seconds. Differences in 

these parameters, between experiments, reflected 

the initial variations in the sand thickness (fig. 123).

Another series of experiments were conducted to 

study the effect barriers had on ripple development. 

The sand in the tank from the first experiments was 

leveled, and the barrier was placed on this leveled 

sand surface.

The following procedures were used for the experiments: 

A. Sloping sand bed without barriers:

1. The sand was leveled to a predetermined 

profile.

2. Waves were generated for a total time of 

50-60 minutes per experiment.

3. Wave generation was stopped at the end of 

each 10-minute interval, and tracings 

were made of the bottom (plan view).

4. Ripple height was measured directly, using 

a metre stick.

DIRECTION OF WAVE PROROGATION 

Upwave

Water level

Downwave

25 20 15 10 

LENGTH OF BED, IN FEET

STARTING SAND PROFILE IN WAVE TANK, experiments 1, 2, 

and 3. 1 inch =2.54 centimetres; 1 foot =0.31 metres. 

Measurements for study stop at X's. (Fig. 123.)

5. Potassium permanganate dye was injected 

into the water to permit visualization of 

the flow conditions.

6. Magnetite grains were allowed to settle onto 

the sediment at various times to indicate 

surface changes as a function of time.

7. The horizontal projections of the lee- and 

stoss-side dimensions were measured 

from the ripple tracings.

8. The rate of ripple migration was calculated 

when possible by following the movement of specific ripples over a predetermined time interval.

9. The ripple symmetry index (RSI) and the 

ripple index (RI) were calculated for 

groups of ripples with similar crest 

shapes.

10. Photographs of ripple development were 

taken and used for comparative purposes.
LABORATORY STUDIES OF SAND PATTERNS RESULTING FROM CURRENT MOVEMENTS 177

B. Flat sand bed with barriers:

1. The sand was leveled and a barrier was 

placed on it.

2. Waves were generated until ripple development began to propagate downwave in a 

uniform pattern.

3. Photographs of ripple development were 

taken and used for comparative purposes.

Wave-Tank Experiments

To avoid repetition, ripple development is discussed in detail for experiment 1 and only briefly 

for experiments 2 and 3. Illustrations, tables, and 

graphs are used to examine ripple growth from a 

gently sloping sand bed and their developmental 

sequences.

Experiment 1

Oscillatory waves were generated for 60 minutes 

during experiment 1. The initial sand profile is 

shown in figure 123, and the bed in plan at given 

time intervals is shown in figure 124. The wave 

height, H, ranged from 5 inches (12.7 cm) at 17 feet 

(5.2 m) to 3.2 inches (8.1 cm) at 24 feet (7.3 m). 

Assuming a horizontal bottom at 24 feet (7.3 m) and 

using a linear wave theory (Airy, 1845), the maximum near-bottom fluid velocity, Um, is calculated 

to be 10.6 in./s (27 cm/s), where:

Um =7rH/Tsinh(Wi),

k =2 TT/L is the wave number, and

L, which is the wavelength, is a function of h and T.

Initial ripple development took place during the 

first 5 minutes of wave action. Parallel-straight to 

slightly parallel-sinuous ripples developed between 

15.5 and 16 feet (4.7 and 4.9 m) while nonuniformly 

spaced crescentic and coalescing crescentic ripples 

developed between 16 and 19.5 feet (4.9 and 5.9 m). 

After 10 minutes (fig. 124) bar development was located at 15.2 feet (4.6 m), and branching ripples and 

ripples that terminate in mid-tank formed between 

15.2 and 18.5 feet (4.6 and 5.6 m). Parallel-sinuous 

ripples developed from 18.5 to 20.0 feet (5.6 to 6.1 

m), and ripples which terminated in mid-tank 

developed between 20 and 21 feet (6.1 and 6.4 m) 

(fig. 124).

Branching ripple development took place early in 

the experiment, when ripples either joined (fig. 

125, sets A, D) or separated to form individual ripples (fig. 125, sets B, C, E, F). Those ripples which 

did not completely cross the tank (ripple crest 3 of 

set B) seemed to initiate this branching process. 

The segment of the ripple that separated from the 

branching bedform migrated downwave and joined 

with the next ripple. This process could be repeated 

with the newly branched bedform acting as the 

nucleus.

The average ripple wavelength, height, stossand lee-side horizontal dimensions, and ripple symmetry index (RSI) were calculated for groups of 

similar ripple patterns (table 20).

After 30 minutes of wave action the bar zone was 

located at 15.3 feet (4.7 m) (fig. 124). Parallelstraight to slightly parallel-sinuous ripples were 

distinct crests developed throughout the wave tank 

(fig. 124).

One ripple in group E and one in group F were 

followed for 20 minutes more (fig. 124) to study 

rates of ripple migration. The ripple in group E 

migrated 0.74 foot (0.23 m) and the ripple in group F 

migrated 0.65 foot (0.20 m). This corresponds to 

rates of 0.43 inch (1.1 cm) per minute and 0.39 inch 

(1.0 cm) per minute, respectively.

The bar was located at 15.6 feet (4.8 m) after 50 

minutes of wave action. Parallel-sinuous ripples occurred from 15.6 to 16.4 feet (4.8 to 5 m). Between 

16.4 and 17.3 feet (5 and 5.3 m), the ripples did not 

extend across the full width of the tank. Instead, 

they terminated approximately 5.9 inches (15 cm) 

from the front side of the tank (fig. 124). These ripples still had a slightly parallel-sinuous pattern 

with platform crests and filled troughs. Crests loTABLE 20. — Summary of ripple dimensions fin centimetres) 

and ripple symmetry index for experiment 1 after 10, 30, and 50

minutes 

[Letters designating ripple groups correspond to those in figure 124]

Ripple 

group

A......

B ......

C ......

D ......

E ......

F ......

G ......

H......

I.......

Average 

wavelength

8.8

8.6

6.7

9.1

. 11.0

8.8

9.9

. 10.9

. 10.1

Average Average 

height stoss

After 10 minutes

1.5 5.0

1.5 5.1

.9 4.1

After 30 minutes

1.4 6.3

1.7 8.3

1.4 6.6

1.5 7.0

After 50 minutes

1.7 7.4

1.8 7.0

Average 

lee

3.8

3.6

2.6

3.0

2.7

2.8

2.8

3.5

3.1

Ripple 

symmetry 

index (RSI)

1.3

1.4

1.6

2.1

3.1

2.3

2.5

2.2

2.3
178 A STUDY OF GLOBAL SAND SEAS

DIRECTION OF WAVE PROROGATION

C B

5.8 

METRES

PLAN VIEW OF RIPPLE PATTERNS for experiment 1 after 10, 30, and 50 minutes of wave action. Trough lines dashed. Slanting lines 

connecting the same ripple demonstrated ripple migration (distance indicated on line). Letters A -1 indicate groups of ripples listed 

in table 20. (Fig. 124.)

cated between 17.3 and 19.0 feet (5.3 and 5.8 m) 

were platform and had a parallel-straight to slightly 

parallel-sinuous pattern. Parallel-straight ripples 

with distinct crests developed from 19.0 to 20.0 feet 

(5.8 to 6.1 m). Crests from 20.0 to 21.5 feet (6.1 to 6.6 

m) were platform. Between 21.7 and 23.5 feet (6.6 

and 7.2 m), the ripples did not completely cross the 

tank and, therefore, were not included in figure 124 

beyond 20.2 feet (6.2 m).

Figures 126 and 127 illustrate the manner in 

which the ripple parameters change as a function of 

time. In figures 126A and B, the RI values of 5, 6,

DIRECTION OF WAVE PROROGATION

2345 12345 12345 12345 12345

1 ;

1

1 1 :

i i :

1

!

l :

r

i-i 1 •

D

PROCESS OF RIPPLE BRANCHING. Plan view of ripple crests, 

sets A (earliest time) through F (latest time). (Fig. 125.)
2.5

2.0

1.5

fE 1.0

0.5

LABORATORY STUDIES OF SAND PATTERNS RESULTING FROM CURRENT MOVEMENTS 179

I i 9

/W=6

8

S 4

SE 2-5

10 12 14 16

2.0

1.5

1.0

0.5

/?/=5

/W=6

/W=8

POSmON IN TANK 

• Front 

D Middle 

x Back

B

6 8 10 12 14 

WAVELENGTH, IN CENTIMETRES

16

GRAPHS SHOWING RIPPLE HEIGHT AND WAVELENGTH after 

(A) 10 minutes and (B) 50 minutes of wave action. Ripple index 

lines (Rl = wavelength/height) plotted to reflect their relation to 

the 5-8 range of asymmetrical wave ripples. As shown in A, 74 

percent of the ripples are in the 5 to 8 range, and in B, 86 percent 

are in the 5 to 8 range. Ripple height and wavelength measured 

approximately 10 cm from front and back of wave tank. 1 centimetre = 0.394 inch. (Fig. 126.)

GRAPHS OF STOSS- AND LEE-SIDE horizontal dimensions after 

(A) 10 minutes and (B) 50 minutes of wave action. Ripple symmetry index lines (RSI = Horizontal projection of stoss 

side/Horizontal projection of lee side) plotted to reflect their 

relation to the 1.1 -3.8 range of asymmetrical wave ripples. As 

shown in A, 80 percent of the ripples are in the 1.1 -3.8 range, 

and in B, 97 percent are in the 1.1 -3.8 range. Stoss- and lee-side 

measurements were made approximately 10 cm from the front 

and back of the tank; measurements were made in the middle 

of the tank when they could not be made along the front and 

back. 1 centimetre =0.394 inch. (Fig. 127.)

I POSITION IN TANK 

• Front

/?S/=1.0

POSITION IN TANK 

• Front

a Middle 

x Back

B

12345678 

HORIZONTAL LEE-SIDE DIMENSIONS, IN CENTIMETRES
180 A STUDY OF GLOBAL SAND SEAS

and 8 are indicated by solid lines. After 10 minutes, 

74 percent of the ripples fell within the 5-8 range, 

and after 50 minutes 86 percent fell within that 

range. Lines of constant RSI (RSI = 1.1, 3.8) are 

drawn in figures 127A and B to correspond to the 

reported RSI range for asymmetrical wave ripples. 

After 10 and 50 minutes, 80 and 97 percent of the 

ripples, respectively, fell within this range. Ripples 

which plot outside the indicated ranges fall into one 

of four categories: (1) Ripples that are influenced 

by their position near the bar zone, (2) branching 

ripples, (3) washed-out ripples, and (4) ripples at 

the upwave end of the sand bed. The ripples in 

category 4 are not considered to be fully developed.

Experiments 2 and 3

The starting sand profiles for experiments 2 and 3 

are shown in figure 125. For experiment 2, wave 

break was located at 17 feet (5.2 m), the wave 

height, H, was 4.1 inches (10.4 cm) at 19 feet (5.8 m) 

and 3.7 inches (9.4 cm) at 23 feet (7 m) (fig. 128). 

For experiment 3, wave break was located at 17 feet 

(5.2 m), wave height, H, was 3.9 inches (10 cm) at 

19 feet (5.8 m) (fig. 129).

In experiment 2, irregular crescentic ripples 

developed throughout the wave tank after approximately 3 minutes with the best development occurring at about 23 feet (7 m). Parallel-straight to 

slightly parallel-sinuous ripples with a uniform pattern developed after 10 minutes of wave action (fig. 

128; table 21).

In experiment 3, irregular crescentic ripples 

developed after 2 minutes of continuous wave action. Isolated crescentic ripples coalesced to four 

large crescentic ripples after 5 minutes at approximately 23 feet (7 m). Parallel-straight, branching 

bedforms, parallel-sinuous, and irregular crescentic 

ripples developed after 10 minutes of wave action 

(fig. 129; table 22).

After 50 minutes, ripple development was less 

distinct in experiments 2 and 3 (figs. 128,129; tables 

21, 22). The ripples were washed out between approximately 17 and 19 feet (5.2 and 5.8 m) with 

crests becoming more platform and troughs filling, 

causing the bottom profile to become more planar.

The RI values calculated for experiments 2 and 3 

show that after 10 minutes 90 and 77 percent, 

respectively, fell within the 5-8 range and that

B

DIRECTION OF WAVE PROROGATION

(/ (\

\ II \\ 

\ |\\ If

D

Scoured 

1 area

23 22 21 20 19 

FEET

18 17 16 15

7.0 6.7 6.4 6.1 5.8 

METRES

5.5 5.2 4.9 4.6

PLAN VIEW OF RIPPLE PATTERNS for experiment 2 after 10 and 50 minutes of wave action. Trough line dashed. Letters A-£ indicate groups of ripples listed in table 21. (Fig. 128.)
LABORATORY STUDIES OF SAND PATTERNS RESULTING FROM CURRENT MOVEMENTS 181

DIRECTION OF WAVE PROROGATION

D

22 21 20 19 

FEET

l

18 17 16

6.7 6.4 6.1 5.8 

METRES

5.5 5.2 4.9

PLAN VIEW OF RIPPLE PATTERNS for experiment 3 after 10 and 50 minutes of wave action. Trough lines dashed. Letters A-F indicate groups of ripples listed in table 22. (Fig. 129.)

TABLE 21. — Summary of ripple dimensions fin centimetres^ 

and ripple symmetry index for experiment 2 after 10 and 50

minutes

[Letters designating ripple groups correspond to those in figure 128]

Ripple 

group

Average 

wavelength

Average 

height

Average 

stoss

Average 

lee

Ripple 

symmetry 

index (RSI)

After 10 minutes

A......

B ......

6.7 

. 10.9

1.0 

1.5

4.0 

6.8

3.2 

3.3

1.3 

2.0

After 50 minutes

C ......

D ......

E ......

12.1 

13.2 

. 11.5

2.1 

1.5 

1.8

7.5 

8.3 

7.6

4.5 

4.9 

3.9

1.7 

1.7 

2.0

after 50 minutes 88 percent of the HI values for both 

experiments fell within this range. RSI values 

calculated for experiments 2 and 3 show that after 

10 minutes 95 and 100 percent, respectively, fell 

within the 1.1-3.8 range cited for asymmetrical 

wave ripples and after 50 minutes 90 and 82 perTABLE 22. — Summary of ripple dimensions fin centimetres^ 

and ripple symmetry index for experiment 3 after 10 and 50

minutes

[Letters designating ripple groups correspond to those in figure 129]

Ripple 

group

Average 

wavelength

Average 

height

Average 

stoss

Average 

lee

Ripple 

symmetry 

index (RSI)

After 10 minutes

A......

B ......

9.7 

. 10.8

1.5 

1.8

6.4

7.2

3.4 

3.7

1.9 

2.0

After 50 minutes

c ......

D ......

E ......

F

10.2 

18.5 

18.3 

8.1

1.4 

2.5 

1.7 

1.4

6.1 

11.0

7.5 

5.4

4.1 

7.6 

4.8 

2.7

1.4 

1.5 

1.6 

2.0

cent, respectively, fell within these limits. The 

decrease in the RSI percentages appears to be 

caused by ripples that are being washed out in the 

area between 17 and 19 feet (5.2 and 5.8 m) (figs. 

128, 129). This washing out resulted in crests 

becoming platform and in troughs filling.
182 A STUDY OF GLOBAL SAND SEAS

Ripple Development Patterns

Figure 130 shows the transition from one form to 

another that oscillatory ripples make with time. 

This change in pattern seems to develop as (1) a 

function of the flow velocity of the water and (or) 

water depth and (2) time. Ripples during experiments 1, 2, and 3 appeared to develop in the following manner: Sand movement was dominantly by 

traction and saltation in a downwave direction 

when the ripples first started to develop. When one 

ripple became more distinct by its height increasing, sand movement was affected by the vortex or 

eddy developed in the lee of the ripple. The circular 

action of the eddy churned up the sediment on the 

lee surface and in the trough in front of the ripple, 

and this churning put the finer sand in suspension. 

The finer material was held in suspension and 

moved in both a downwave and an upwave direction due to the oscillation of the passing wave. The 

coarser material dropped out of suspension and 

caused avalanching on the lee surface of the ripple.

DECREASING DEPTH

INCREASING VELOCITY

1234 56

SEQUENCE OF SMALL-SCALE RIPPLES (plan 

view), changing with time and with an increase 

in flow velocity and (or) water depth. Forms 

are (1) isolated crescentic, (2) coalescing crescentic, (3) parallel-sinuous, (4) parallel-straight, 

(5) irregular pattern, and (6) bar zone (zone of 

ripple destruction). (Fig. 130.)

_____DECREASING DEPTH ^ 

INCREASING VELOCITY ^

SEQUENCE OF SMALL-SCALE RIPPLES (plan view) 

changing with an increase in flow velocity and (or) 

water depth. Sketched and modified from J. R. L. 

Alien (1968, fig. 4.61a). Forms are (1) parallelstraight, (2) parallel-sinuous, and (3) linguoidal. 

(Fig. 131.)

Therefore, sand movement was by traction and 

saltation on the stoss side and dominantly by 

suspension and avalanching on the lee side of the 

ripple. With time, this process of sand movement 

could change an isolated crescentic ripple into a 

coalescing crescentic ripple and a coalescing crescentic ripple into a parallel-sinuous or parallelstraight ripple. If Um (the maximum near-bottom 

fluid velocity) increased above a certain critical 

velocity, sheet flow instead of oscillatory wave motion would occur near the bottom. With this change 

in Um toward sheet-flow conditions, ripples become 

washed out, and eventually a planar surface devoid 

of ripples develops.

Unidirectional current ripples undergo a somewhat similar change in ripple patterns as a function 

of flow velocity and (or) water depth (Alien, 1968, 

p. 93) (fig. 131).

Comparison of Aqueous Wave

Ripples (Aqueous Dunes) and

Eolian Dunes

The similarity in crestal patterns of aqueous ripples (dunes) and eolian dunes is striking (table 23; 

fig. 132). In an aqueous environment having limited 

sand supply, crescentic ripples develop (fig. 132, 

aqueous forms; fig. 121). In an eolian environment 

barchan dunes occur under the same sand-supply 

conditions. When sufficient sand is available, 

parallel-straight and branching aqueous ripples 

develop, and they appear to be very similar to 

eolian barchanoid and transverse ridges.

TABLE 23. — Bed/orms oriented transverse to wave or 

wind direction

Oscillatory wave ripples

Crescentic solitary form

Coalescing crescentic form 

(parallel -sinuous form)

Parallel -straight and 

branching form

Eolian dunes

Barchan form (solitary)

Barchanoid ridge 

(coalescing barchanoid 

form)

Transverse ridge
LABORATORY STUDIES OF SAND PATTERNS RESULTING FROM CURRENT MOVEMENTS 183

AQUEOUS BEDFORMS—Laboratory 

wave tank examples

1. Crescentic 2. Coalescing crescentic 

solitary (parallel-sinuous)

EOLIAN BEDFORMS—Sketch and

ERTS examples 

1. Barchanoid solitary

2 Barchanoid ridge 

(coalescing barchanoid)

3. Parallel-straight and branching

E1183-06194 

3. Transverse ridge

E1128-04253

COMPARISON OF AQUEOUS AND EOLIAN BEDFORMS (plan views). Direction of wave 

propogation and of wind is from left to right. White in aqueous bedforms 1 and 2 is bottom 

of wave tank exposed by erosion due to limited sand supply. Numbers next to round 

photographs refer to Landsat (ERTS) imagery from which examples were taken. (Fig. 132.)

Effects of Barriers on Ripple 

Development

Experiments were conducted to study the effects 

of barriers on wave ripple development. Barriers 

were placed on a flat sand surface to disrupt the 

wave motion, and photographs were taken of the 

resultant ripple development. The barriers used 

were a steel ball 3.5 inches (9.0 cm) in diameter and 

clay bricks of various dimensions. Figure 133 illustrates the ball's effect on ripple development. 

Scour occurred around the edges of the ball, and, 

with time, crescentic, coalescing crescentic, and

transverse ripples propagated in a down wave direction from the ball. The asymmetry of the wavegenerated flow prevented upwave ripple formation 

from the ball during this experiment. Initial smallscale ripple development is similar in an eolian environment (fig. 134). Comparisons of bedforms can 

also be made on a much larger scale, as evident on 

Landsat (ERTS) imagery of eolian dunes in the An 

Nafud Desert, Arabian Peninsula (figs. 135, 136). 

The images show questionable barchan dunes 

developing into barchanoid ridges, and the development of dunes across a geomorphically controlled 

area.
184 A STUDY OF GLOBAL SAND SEAS

SEQUENTIAL PHOTOGRAPHS SHOWING EFFECTS of a barrier 

on ripple development in a wave tank. Steel ball 3.5 inches (9 

cm) in diameter. Direction of wave propogation is left to right. 

A, Scour occurring around the edges of the ball after 2 minutes,

and, 6, after 5 minutes. C, Isolated crescentic form developing 

after 82 minutes. D, Isolated and coalescing crescentic forms 

developing after 107 minutes, f, Coalescing crescentic and 

parallel-straight forms developing after 114 minutes. (Fig. 133.)

SEQUENTIAL PHOTOGRAPHS OF BEDFORMS (1-6) 

developed in a wind-tunnel experiment. Wind direction is from 

left to right. Crater is approximately 7 inches (18 cm) in 

diameter, modeled in loose sand and placed in the wind tunnel. 

Wind velocity is 160 inches per second (420 cm/s). Slight rippling of sand in photographs 4—6 is effect of tunnel wall. 

Photographs from Greeley and others (1974, p. 487). (Fig. 134.)
LABORATORY STUDIES OF SAND PATTERNS RESULTING FROM CURRENT MOVEMENTS 185

QUESTIONABLE BARCHAN DUNES developing into 

barchanoid ridges, An Nafud Desert, Arabian Peninsula. General 

wind direction from west-northwest. From Landsat (ERTS) imagery E-1171-06530-7 01. (Fig. 135.)

DEVELOPMENT OF DUNES across a geomorphically controlled area, An Nafud Desert, Arabian Peninsula. General 

wind direction from northwest. From Landsat (ERTS) imagery 

E-1226-06593-7 01. (Fig. 136.)

A STUDY OF GLOBAL SAND SEAS

ANCIENT SANDSTONES 

CONSIDERED TO BE EOLIAN

Chapter H

By EDWIN D. McKEE 

With sections by JOAO J. BIGARELLA9

Contents

	Page

Summary of conclusions ............................ 189

Introduction ....... ...... ...... .... 189

Distribution and age .. ............................ 189

Characteristics of eolian sandstones ................. 191

Characteristics of interdune record ................... 193

Recognition of dune types ...... ................... 194

Facies associated with dunes .... ...... ...... 196

Selected examples of eolian sandstones .............. 196

Coconino Sandstone (Permian), U.S.A. .... .......... 197

De Chelly Sandstone (Permian), U.S.A. .... .......... 204

Navajo Sandstone (Triassic? and Jurassic), U.S.A. ...... 209

Page

Lyons Sandstone (Permian), U.S.A. ..... .. .. 217

Casper Formation (Pennsylvanian and Permian), U.S.A. . 221 

Rotliegendes of northwestern Europe (Permian) ....... 225

Lower Mottled Sandstone (Permian?), England ........ 227

Frodsham Member of so-called Keuper Sandstone Formation of England (Triassic) .................. ..... 228

Barun Coyot Formation (Upper Cretaceous), Mongolia 230 

Botucatu and Sambaiba Sandstones of South America 

(Jurassic and Cretaceous), by Joao J. Bigarella .... 233

Cave Sandstone and similar sandstones of southern Africa 

(Triassic), by Joao J. Bigarella ...................... 236

187
188

Illustrations

Page

FIGURE 137. Block diagrams of basic forms of cross-strata in eolian-type sandstones 1^2

138. Photograph of ripple marks in eolian-type Coconino Sandstone showing

rounded crests and high indices .............................. 193

139. Selected stereonets showing distribution of cross-strata dip directions in

typical eolian-type sandstones ................................ 195

140-145. Photographs taken in Grand Canyon National Park, Arizona, U.S.A.:

140. Permian Coconino Sandstone forming cliff on west side of Hermit Basin .......................................... 198

141. Permian Coconino Sandstone showing sets of high-angle 

cross-strata and tangential bases of foresets, Dripping 

Springs Trail ....................................... 198

142. Wedge-planar cross-strata in Permian Coconino Sandstone,

Kaibab Trail ....................................... 199

143. Ripple marks on foreset surface of cross-strata Coconino

Sandstone, Kaibab Trail ...... ................... 200

144. Slump marks on slipface of cross-strata, Coconino Sandstone,

Grandview Trail ..... .............................. 201

145. Miniature terrace-and-cliff structure formed on foreset surface

of Coconino Sandstone, Bunker Trail ............... 201

146—151. Photographs showing:

146. Contorted bedding in large-scale cross-strata of Coconino

Sandstone near Flagstaff, Arizona .................... 202

147. Footprints of probable reptile preserved on dip slope of 

crossbedded Coconino Sandstone, Grand Canyon National Park, Arizona ................................. 202

148. Uphill tracks of chuckwalla lizard made on foreset slopes of

fine-grained dune sand ......... ........ ........ 203

149. Trails of millipedes ...................................... 204

150. Large- and medium-scale cross-strata of tabular-planar type in

Permian De Chelly Sandstone, Canyon De Chelly, Arizona 207

151. Interdune deposit between cross-strata sets of eolian dune

type, De Chelly Sandstone, Canyon De Chelly, Arizona 208 

152. Isopach-lithofacies map and cross-section showing distribution and

thickness of Navajo, Kayenta, and correlative units .............. 210

153-156. Photographs showing:

153. Cross-strata in Navajo Sandstone north of Kanab, Utah ..... 212

154. Contorted structures in Navajo Sandstone, Kanab Creek area,

Utah ........ .......... ........ ........ ...... 213

155. Navajo Sandstone, showing large-scale wedge-planar crossstrata between tabular-planar cross-strata, Zion National 

Park, Utah ......................................... 216

156. Pits of raindrops in modern sand of Lyons texture .......... 219

157. Block diagram of festoon cross-lamination from sandstone of Casper Formation, Wyoming .......................................... 222

158. Aerial photograph of blowout dunes along south shore of Lake Michigan 223

159. Outcropping areas in South America of the Mesozoic Sambaiba and

Botucatu Sandstone ........................................ 234

Table Page

TABLE 24. Age, thickness, composition, and postulated environments of units forming Lower "Keuper" and underlying sandstones, England ........ 229
ANCIENT SANDSTONES CONSIDERED TO BE EOLIAN 189

Summary of Conclusions

INCIENT SANDSTONES of many ages and in 

,many parts of the world have been attributed 

to an eolian origin. They are generally recognized by 

their primary structures, especially cross-strata 

which characteristically are on a large scale and dip 

at high angles. Other diagnostic structures are ripple 

marks with distinctive orientation and indices, 

unique forms of slump marks, and contorted bedding of types characteristic of dry sand. Commonly, 

the sand is well sorted and fine to medium grained, 

and has surficial markings, such as frosting and pitting. Sharply defined animal tracks and trails are 

also distinctive features of eolian sandstones; 

associated units of interdune deposits containing 

nonmarine faunas occur within sequences. Thus, 

although the genesis of some sandstones of this 

type is open to question, the origin of most seems 

sufficiently definite to merit calling them eoliantype sandstones.

As in modern sand seas, the dominant wind or 

winds were largely responsible for development of 

individual dune forms preserved in each eoliantype sandstone. Because wind direction commonly 

can be determined from orientation of slipfaces, dip 

directions of cross-strata in ancient eolian-type 

sandstones normally will reveal both the course of 

the wind and the type of dune represented. 

Unidirectional, bidirectional, and possibly multidirectional winds can be identified in many ancient 

sandstones by the clustering and spread of dipdirectional measurements in cross-strata. The type 

of resulting dune — barchan, linear, or star — can 

also be recognized by the dip-direction spread and 

by certain other features of the cross-strata. Coastal 

dunes can be distinguished from interior desert 

dunes in part by the geometry or shape of the sand 

body and in part by their intertonguing or other 

close association with bordering marine deposits.

Introduction

LONG SWEEPING CROSS-STRATA of evengrained sandstone that form the sheer walls of 

many canyons in southwestern Utah led Huntington in 1907 (p. 381) to ascribe an eolian origin to 

these rocks (Navajo Sandstone) of Jurassic and

Triassic(?) age. Subsequently, many other 

sandstones of that region, having similar textural 

and structural characteristics, have been attributed 

to the accumulation of dune sand. Additional kinds 

of evidence have been recognized in some of these 

formations, which make their eolian genesis 

reasonably certain, but in others the origin has remained debatable and subject to different interpretations.

For the most part, the eolian-type sandstones of 

the Western United States, over which controversy 

regarding genesis has continued, are mixtures of 

two or more facies in which intertonguing relations 

exist or one rock type grades into another. Where 

either fluviatile and eolian facies or marine and 

eolian facies abut, or overlie one another, the diagnostic features of one environment frequently have 

been used in interpreting both. Furthermore, the 

surfaces and deposits of interdune areas that normally occur intercalated between sets of dune 

sands commonly have not been recognized for what 

they are and have confused interpretations by their 

noneolian features.

Major advances in understanding the eolian 

development of certain sandstone bodies resulted 

from several basic pioneer investigations. Statistical 

studies on the orientation of cross-strata and their 

relations to current (wind) directions were initiated 

in the United States by Knight (1929) in the Casper 

Formation of Wyoming and by Reiche (1938) in the 

Coconino Sandstone of Arizona. Analysis of crossstrata patterns and of cross-strata surfaces of erosion and deposition in migrating dunes of the 

barchanoid and transverse types were elucidated 

by Shotton (1937) for rocks referred to as the 

"Lower Bunter Sandstones" in England. Shotton's 

study served to explain basic relations between 

wind direction, availability of sand, and dune structure. Still later, work of Bagnold (1941) on sand 

movement and dune processes in modern deserts 

clarified many features of wind activity, greatly 

stimulating the study of eolian deposits in general 

and providing a better understanding of their 

development.

Distribution and Age

SANDSTONES OF PROBABLE eolian origin are 

widespread in both time and space throughout the
190 A STUDY OF GLOBAL SAND SEAS

world. Cross-strata attributed to deposition by wind 

have been reported from rocks of the Precambrian, 

Paleozoic, Mesozoic, and Cenozoic Eras; they are 

described from North America, South America, 

Europe, Asia, Africa, and Australia. Not all these 

assignments to eolian genesis have stood the test of 

critical analysis, but, in general, more sandstones 

are interpreted as dune deposits today than were a 

few decades ago. In brief, the well-sorted finegrained sandstones with large-scale cross-strata 

that commonly are attributed to eolian processes 

are numerous in rocks of various ages, and they 

constitute a considerable amount of the geologic 

column.

Eolian-type sandstones are especially numerous 

and widely distributed throughout the Western and 

Southwestern United States in rocks of late 

Paleozoic and early to middle Mesozoic age. They 

have been extensively studied by many geologists, 

although genesis remains unsolved in a number of 

formations. A summary of these sandstones of 

probable eolian origin has been made for the Colorado Plateau by Poole (1962). He grouped them by 

age and recognized a total of 15 lithic units in 4 major age categories. Some of these sandstones comprise entire formations; some consist of tongues 

that extend into other lithologically dissimilar formations; others are merely parts or facies of a formation associated with one or more other 

lithofacies.

The principal eolian-type formations of the Colorado Plateau listed by Poole are as follows:

Late Jurassic time

Entrada Sandstone

Cow Springs Sandstone 

Jurassic and Triassic(?) time

Navajo Sandstone

Aztec Sandstone 

Jurassic (?) and Triassic(?) time

Nugget Sandstone 

Triassic time

Wingate Sandstone

Moenkopi Formation 

Permian time

Coconino Sandstone

White Rim Sandstone Member of the Cutler 

Formation

De Chelly Sandstone 

Permian and Pennsylvanian time

Weber Sandstone

Of the just-listed sandstones in the Western 

United States, some clearly represent extensive 

dune deposits of interior deserts, as evidenced not 

only by the great lateral extent of the sandstone 

bodies but also by distinctive features of primary 

structure and by faunal traces. To illustrate desert 

dune deposits, the Coconino Sandstone and the 

Navajo Sandstone are selected for detailed discussion later in this chapter. In contrast, coastal-plain 

sand accumulations are illustrated by the Lyons 

Sandstone (Permian) and the Casper Formation 

(Permian and Pennsylvanian), which contain structures typical of a coastal dune environment and intertongue with marine strata. The De Chelly 

Sandstone seems to be in a position intermediate 

between the Coconino and various noneolian 

depositional environments.

Extensive eolianlike deposits are represented in 

South America (Brazil) by the Botucatu and Sambaiba Sandstones of Mesozoic age and in Africa by 

the Cave and time-equivalent sandstones which are 

also of Mesozoic age. Texturally and structurally 

these formations resemble sandstones of the 

Western United states and are described by 

Bigarella later in this chapter. In Africa also are 

"feldspathic arenites" of Zambia said to be of EoCambrian [late Precambrian] age and attributed by 

Garlick (1969, p. 114) to an eolian origin. In 

Australia the Chatsworth Limestone of Cambrian 

age, with a thickness of 12 m (36 ft) has been attributed to eolian deposition on the basis of structural features (Shergold and others, 1976, p. 10, 

33-34).

In northwestern Europe the Rotliegendes of Permian age has generally been interpreted as a desert 

deposit that includes considerable eolian sand. 

Because of its petroleum potential, it has been extensively studied in England, the Netherlands, Germany, and elsewhere. In England, the "so-called 

Lower 'Bunter' Sandstone or Lower Bunter Mottled 

Sandstone, probably Permian in age" and also the 

"Yellow Sands of Durham and parts of the Keuper 

Sandstone of probable Permian and Triassic Age" 

are believed to be eolian (D. B. Thompson, written 

commun., 1976). For comparative purposes, these 

stratigraphic units are briefly described in this 

chapter.

The Barun Goyot Formation of Late Cretaceous 

age in central Asia probably represents deposits of a 

great interior desert. Exceptionally thick and
ANCIENT SANDSTONES CONSIDERED TO BE EOLIAN 191

widespread interdune sediments occur between 

sets of large-scale cross-stratified sandstones considered to be eolian. The interdune sediments probably were accumulated both by intermittent 

streams and in temporary ponds and lakes. Unique 

in these deposits — both dune and interdune — is 

their extensive fauna of vertebrate animals.

The Precambrian Makgabeng Formation of the 

Waterberg Supergroup (northern Transvaal) is considered (Meinster and Tickell, 1976, p. 191) "of 

aeolian origin and shows many of the characteristics of transverse dunes."

Characteristics of Eolian 

Sandstones

ANCIENT SANDSTONES believed to be of 

eolian origin are mostly light colored (white, buff, 

yellow, and pale red), highly cross-stratified, even 

grained, and cliff-forming. The criteria by which 

their eolian genesis may be determined are of two 

types: (1) features that are distinctive of modern 

eolian deposits and therefore may be considered 

diagnostic, or (2) features that are compatible with 

an eolian environment but furnish no proof of wind 

deposition.

The geometry of dune sandstone bodies probably 

depends largely on the general environment of 

deposition — whether an inland desert basin or a 

coastal strip. Some ancient sand bodies that are 

very extensive, such as the Wingate, Navajo, and 

Coconino Sandstones of western North America, 

are either tabular- or wedge-shaped on a huge scale 

and definitely represent sinking basins. Others, 

such as the Lyons Sandstone and the Casper Formation, farther east, occur as relatively narrow 

sheets that apparently bordered strandlines and 

Developed along the margins of regressing seas.

Boundaries of eolian sandstones mostly are 

abrupt, for these sandstones normally interfinger 

with, rather than grade into, adjacent facies. Examples are numerous of contacts either with marine 

deposits or with fluviatile and lacustrine deposits. 

Contrasts in lithology usually make the contacts 

easily recognizable.

Most ancient dune-type sandstones are composed almost entirely of quartz grains, and many 

are classed as orthoquartzitic. Some, like the De 

Chelly, Lyons, and Casper, contain small percentages of feldspar (much authigenic), and others

contain chert grains. Cross-stratified gypsum sands, 

believed to be wind deposited, occur locally in the 

Triassic Moenkopi Formation of Arizona (McKee, 

1954, pi. 3B).

Textures in the ancient eolianlike sandstones 

resemble, in most respects, those in modern dune 

fields; however, many of the same characteristics 

are also found in modern beach deposits and some 

other deposits. The sand is typically very fine to 

medium, well sorted, rounded, and frosted. In many 

sandstones, these grains represent reworked 

material (second or third generation); hence, the 

textural properties may represent inherited 

features and bear little relation to length or manner 

of transport in the present regime. Furthermore, 

frosting may be the result of postdepositional 

chemical alteration.

In some ancient eolian sandstones the texture 

has been greatly modified by quartz overgrowths or 

by iron oxide coatings on the grains, or both. Commonly, there is intergranular silica, calciie, or iron 

oxide, but matrix is rare because silt and finer particles forming dust were winnowed out by the wind 

at the time of deposition. Coarse grains, except 

those developed as lag on the horizontal interdune 

deposits, are also lacking. Most lag deposits that 

have been described, as in the Lyons and Casper 

Formations, are coarse-grained sandstones, but granules may occur on some interdune surfaces, 

especially near the margins of a dune field.

Whereas composition reflects the source of a 

sediment and texture is largely a function of 

transportation, primary structures furnish the 

record of manner of deposition. The most common 

and most distinctive structure of eolian deposits is 

cross-stratification. Other characteristic structures 

preserved in some eolian-type sandstones are ripple 

marks, rain pits, and slump marks. All these are 

diagnostic features of dune deposits, especially 

when used as part of a critical evaluation of all 

available data (Selley, 1970, p. 52).

Cross-strata of dune-type sandstones are characteristically, though not entirely, large to medium 

scale and high angled. They commonly attain 

lengths of more than 100 feet (30 m) and dip 

20°-30°. These dips are somewhat less than the 

angle of repose for modern dune-sand slipfaces, 

which is commonly 33° or 34°, but the difference is 

attributed to subsequent compaction (Glennie,
192 A STUDY OF GLOBAL SAND SEAS

1972, p. 1058; Walker and Harms, 1972, p. 280) or to 

differential preservation with higher, steeper parts 

removed (Poole, 1962, p. 148). Low-angle crossstrata typical of windward-side deposition are occasionally preserved on modern dunes and have been 

recognized in ancient sandstones by their dip-direcB

BASIC FORMS OF CROSS-STRATA recognized 

in eolian-type sandstones. A, Tabular-planar, 

abundant; B, wedge-planar, abundant; C, 

trough type, rare. (Fig. 137.)

tion vector opposite that of the regional current 

direction. (See description under Coconino 

Sandstone in this chapter.)

Cross-stratification is mostly of two basic 

types — tabular planar and wedge planar (fig. 137). 

In the tabular-planar type, lower bounding surfaces 

are believed to represent interdune deposits or erosion surfaces; dipping foresets above form tangents 

at their bases as in most modern barchanoid dunes. 

In the wedge-planar type, abutting sets of crossstrata probably reflect shifting winds within a 

single dune sequence. Simple lenticular types are 

recorded, but the trough type is rare, with the notable exception of the remarkable "festoon structures" in sandstone of the Casper Formation. These 

structures have not been established unequivocally 

as eolian but may represent "blowout" dunes.

Ripple marks, not uncommonly preserved in 

many of the eolian-type sandstones, are distinctive 

(McKee, 1945, p. 318). They invariably have high 

ripple indices (above 15, mostly far above), in contrast to the low indices of water-formed ripple 

marks (Tanner, 1966). In addition, most of them are 

oriented with their parallel troughs and crests passing up and down the steeply dipping foresets of 

cross-strata— a feature not recorded for ripple 

marks under water — and their crests generally are 

well rounded (fig. 138).

Adhesion ripples, formed where dry sand is 

blown onto moist surfaces and fixed by surface tension, are recorded (Glennie, 1972, p. 1061) at many 

horizons in the Rotliegendes of northwest Europe 

and are viewed as evidence of interdune surfaces.

Raindrop craters with raised rims and reoriented 

basins formed on the dip slopes of high-angle crossstrata have been recorded from the Coconino 

Sandstone (McKee, 1934b, p. 102) and the Lyons 

Sandstone (Walker and Harms, 1972, p. 282). These 

pits are typical of modern raindrop craters in dry 

sand and are considered to be good evidence of 

eolian deposition.

Various forms of avalanche or slump marks are 

preserved on cross-strata surfaces in several eolian 

type sandstones (McKee, 1945, p. 321), and contorted strata are locally prominent, although, in 

general, such structures are surprisingly uncommon. In the Coconino Sandstone the "miniature 

step" variety seems to be good evidence of slumping at the angle of repose when the sand was wet 

(Reiche, 1938, p. 918), and other varieties suggest
ANCIENT SANDSTONES CONSIDERED TO BE EOLIAN 193

dry sand movement (McKee, Douglass, and Rittenhouse, 1971, p. 368).

RIPPLE MARKS with high ripple indices and rounded crests in 

slab of eolian-type sandstone, Coconino Sandstone, Kaibab 

Trail, Grand Canyon National Park, Arizona, U.S.A. (Fig. 138.)

Some of the most conclusive evidence of eolian 

origin for cross-stratified sandstones is the presence 

of clearly preserved footprints of four-footed 

animals on steep dip slopes. Experimental work has 

shown that tracks with such excellent preservation 

and with orientation uphill only must have been 

formed on dry sand at or near the angle of repose. 

These tracks could not have been formed under 

water (Peabody, in McKee, 1947, p. 27) or in either 

wet or damp-crust sand (McKee, 1947, p. 25). 

Tracks of this type are common and widespread in 

the Coconino Sandstone and are also present in the 

De Chelly and Lyons Sandstones.

Selective preservation of certain parts of dune 

sands doubtless is responsible for absence in the 

geologic record of many features that occur in 

modern dunes. Upwind features, for instance, are 

mostly destroyed by erosion on that side of a dune, 

and the steeply dipping cross-strata at the top of 

each set commonly are nearly or entirely removed 

by planation prior to deposition of the overlying set. 

Thus, the normally abundant, horizontally oriented 

ripple marks, as well as many tracks and trails on 

low-angle surfaces, are very rarely preserved in 

eolian sandstones.

Vertebrate fossil remains are rarely found in the 

highly permeable cross-stratified sand of eolian 

deposits, presumably because conditions for preservation were poor. In the Navajo Sandstone, two articulated skeletons of dinosaurs have been discovered, showing clearly that the sand in the area 

was continental (Brady, 1935; Camp, 1936). Many 

dinosaur eggs and some dinosaur skeletons have 

been found in dune-type cross-strata of the Barun 

Goyot Formation in Mongolia (Gradzinski and 

Jerzykiewicz, 1974b, p. 140).

Characteristics of 

Interdune Record

COMPARED TO THE AMOUNT of attention 

that has been given dune deposits, the record of interdunes has been largely neglected and is as yet 

only poorly understood. Interdune areas differ 

greatly from place to place in modern dune fields — 

ranging from long narrow corridors between 

barchanoid ridges to small rounded or elliptical 

depressions in "blowout" areas and from very 

wide, flat surfaces between linear dunes to the typical radially sloping surfaces within parabolic dunes.

In the geologic record some interdune deposits 

can be recognized by texture and structure, but 

many interdunes are recorded merely as erosion 

surfaces within vertical sequences of dune sands. 

Whether or not characteristic sediments are accumulated and preserved seems to be at least partly a 

function of time for detritus to accumulate before 

being buried by migrating dunes. The process involved in the preservation of interdunes has been 

described for barchanoid and transverse ridges of 

the White Sands dune field, New Mexico (McKee 

and Moiola, 1975).

Some interdune areas within major sand seas 

develop in an environment controlled by standing 

bodies of water, either at the surface or as ground 

water directly below. The term "interdune 

sabkhas" was applied to such environments by 

Glennie (1972, p. 1061); he described the deposits 

that accumulate in them as consisting of "small, irregular, and more or less horizontally bedded adhesion ripples" of sand grains that "range from fine to 

coarse and generally are poorly sorted." Sediments 

with similar textures and structures, preserved in 

the Permian Rotliegendes of northwest Europe, 

were interpreted by Glennie as interdune deposits. 

"Steeply dipping eolian sandstones," separated by 9 

inches of nearly horizontal adhesion-rippled 

sandstone are shown (Glennie, 1972, fig. 14) in a 

drill-core photograph.
194 A STUDY OF GLOBAL SAND SEAS

Excellent examples of strata believed to have 

been formed as interdune deposits, without adhesion ripples, are preserved in the type De Chelly 

Sandstone of Canyon De Chelly, Arizona, where 

sets of high-angle large-scale cross-strata of eolian 

type are separated by extensive thin units of 

horizontal strata composed of poorly sorted redbrown silt and sand (McKee, 1934a).

In many eolian-type sandstones, interdunes are 

represented by few or no deposits. However, their 

positions in vertical sections are marked by surfaces of beveling that form the nearly horizontal 

bounding planes of adjoining cross-strata sets. 

Many such surfaces are developed in the Coconino, 

Navajo, and similar sandstones of the Southwestern 

United States. They are prominent planes and are 

more irregular than the diagonal erosion surfaces 

that separate wedge cross sets, probably because 

they represent greater time spans. In some 

sandstones, such as the Lyons Sandstone and the 

Casper Formation, the truncation planes are gently 

curving, rather than flat, and have coarse grains interpreted as lag scattered on their surfaces. Injection structures in some deposits, like the Lyons 

Sandstone, have been recorded.

In various ancient eolian-type sandstones, the 

bounding surfaces overlying large-scale cross-strata 

commonly preserve the truncated upper traces of 

those strata. The resulting dune pattern may then 

etch out on weathering to show on a horizontal 

plane the character of cross-strata sets. Such structures are observed on many modern interdune surfaces before their burial by fresh sand (chapter E, 

figs. 45, 70, 71). Likewise, cross-strata sets have 

been recorded in ancient eolian-type sandstones, 

including the Lyons Sandstone of Colorado (Walker 

and Harms, 1972, p. 284) and the Navajo and 

Coconino Sandstones of Arizona.

Coarse sand or granules formed as lag are introduced in interdune areas by the process of creep 

resulting from saltation (Bagnold, 1941, p. 102). 

Probably, they are largely restricted to upwind 

areas (McKee and Tibbitts, 1964, p. 13) or to interdunes near source materials as along coasts because 

of the slow particle movement involved. Most examples in ancient dune sandstones containing lag 

seem to be from coastal dune areas.

Recognition 

of Dune Types

THE RECOGNITION OF various basic types of 

dunes in ancient sandstones is possible where certain diagnostic features are well developed and accessible for study. Those differences that result 

from changes in wind direction, amount of available sand, and the presence or absence of moisture in 

the sand at the time of deposition are commonly 

reflected in the form of distinctive structures in the 

sandstones.

Amount of spread and distribution of cross-strata 

dip directions are perhaps the most satisfactory 

features for differentiating types of dunes in ancient rocks. Study of structures in modern analogs 

has furnished some useful and reliable generalizations. For example, unidirectional winds that are 

responsible for barchans, barchanoid ridges, and 

transverse ridges normally have cross-strata dip 

directions restricted to a single small arc, about one 

quadrant or less (fig. 139). This type of distribution 

(A, B) is illustrated by rose diagrams or stereonets 

for the Navajo Sandstone, Coconino Sandstone, and 

numerous others in the Colorado Plateau of the 

Southwestern United States.

In linear dunes, commonly called seif or 

longitudinal, the distribution of cross-strata dip 

directions (chapter E, fig. 61) is very different from 

that in transverse dunes. Even though no general 

agreement on exact cause of linear dunes has yet 

been reached, their pattern of cross-strata was predicted (Shotton, 1956, p. 460) and has been recorded 

in trenches (McKee and Tibbitts, 1964, fig. 6). It is 

represented on a stereonet by two separate clusters 

of dip attitudes almost opposite one another (Glennie, 1972, fig. 13b). Ancient eolian sandstones 

representing linear (seif) dunes have been recognized in the Permian Rotliegendes of the North Sea 

area by Glennie (1972, p. 1061) and probably occur 

in many other formations.

A third distinctive pattern represented by the 

spread in cross-strata dip directions is that of 

parabolic and other "blowout"-type dunes. These 

dunes occur wherever vegetation or moisture, or 

both, tend to stabilize or anchor the sand but are
ANCIENT SANDSTONES CONSIDERED TO BE EOLIAN 195

especially characteristic of coastal areas. The 

feature of the spread in dip directions is its width, 

encompassing an arc of 180° or more, some being as 

great as 270°, as shown by Bigarella (chapter E, figs. 

78, 79; tables 10, 11). Among ancient rocks, the 

Casper Formation of Wyoming (Knight, 1929, p. 65, 

66; this chapter, fig. 139) and the Lyons Sandstone 

of Colorado (Walker and Harms, 1972, p. 281) show

the characteristic spread of cross-strata orientation 

(fig. 139).

Reversing dunes, in which nearly opposite wind 

directions periodically affect the sand body in alternate direction and so develop two opposed slipfaces, form distinctive patterns of dip directions. 

Such dunes occur in various modern sand seas 

(among them, Great Sand Dunes National Monu60. 60

A s

PERMIAN COCONINO SANDSTONE TRIASSIC(?) AND JURASSIC NAVAJO SANDSTONE, MIDDLE UNIT

60, 60

60

60

E W

60

60

60.

E W

PENNSYLVANIAN AND PERMIAN CASPER FORMATION PERMIAN DE CHELLY SANDSTONE

SELECTED STEREONETS, SHOWING DISTRIBUTION OF CROSS-STRATA dip directions (dots) in typical eolian-type sandstones, 

Western United States. Azimuth of dot represents direction of dip; distance of dot from center indicates degree of dip. Dashed line 

enclosing dots represents foreset direction considered the result of downwind-current deposition. A, Bunker Trail, Grand Canyon 

National Park, Arizona (Reiche, 1938). 8, Central Buckhorn Wash, Utah. B', San Rafael River, Utah (Kiersch, 1950). C, Red Buttes 

area, Wyoming. C, Sand Creek area, Wyoming (adapted from histograms by Knight, 1929). D, White House Trail, Canyon DeChelly, 

Arizona (Reiche, 1938). (Fig. 139.)
196 A STUDY OF GLOBAL SAND SEAS

ment, Colorado, U.S.A., and Florinopolis, Brazil) 

and should be expected in ancient eolian 

sandstones but as yet have not been recognized or 

recorded.

Additional structures that may be helpful in 

determining the type of dune represented by an ancient eolian deposit are the uncommon low-angle 

dips that sometimes are formed on upwind surfaces 

of transverse ridge dunes and that contrast with 

normal high-angle cross-strata of the lee side. 

These structures were recorded in the Lower Mottled Sandstone by Shotton (1937, fig. 2) and in the 

Coconino by Reiche (1938, fig. 1, p. 909). Concave 

downward foresets are distinctive features of many 

parabolic dunes, formed on the foresets of the dune 

nose which is vulnerable to undercutting and 

steepening near its base by crosswinds (McKee, 

1966, p. 51; Ahlbrandt, 1973, p. 39).

Other features distinctive of different dune 

types, discussed elsewhere in this chapter, are the 

slump marks of wet and dry sand, the contrasts in 

typical contorted structures, and differences in 

associated interdune surfaces.

Facies Associated With Dunes

A major difficulty in the recognition of ancient 

eolian deposits in the geologic record is their intimate association with rocks of other facies and the 

temptation to use the criteria preserved in one for 

interpreting the other. Interdune deposits that commonly involve features of an aqueous environment 

have been discussed, but in addition, all eolian 

deposits must have on their borders various facies 

that are fluviatile, lacustrine, or marine and that intertongue with and, under some conditions, grade 

into them.

Fluviatile deposits in desert areas can generally 

be categorized as river channel, flood plain, or 

alluvial fan. The river channels in desert areas 

commonly are dry streambeds, referred to as arroyos or washes in the Southwestern United States 

and as wadis in north Africa; their deposits consist 

primarily of high-energy sediments but may be intermixed with eolian or ponded materials. The 

flood-plain sediments are mostly overbank deposits 

and are largely low-energy varieties that contrast 

with those of the channels. Alluvial fans containing 

much coarse detritus are common on the margins of 

most dune areas that are bordered by mountainous 

terrain.

Deposits of desert lakes and playas, which 

characteristically are shallow and ephemeral, contain low-energy textures and structures except 

where they border high-relief areas that contribute 

alluvial sediments. Most desert lakes and ponds accumulate salt and clay in horizontal beds, various 

amounts of windblown sand and, in some places, 

anhydrite or other salts. They typically develop 

mudcracks and mud curls during dry times when 

water is absent. Sandstone dikes commonly are 

associated with these deposits. In inland sebkhas or 

sinking basins, where the water table rises and 

periodically reaches the interdune surface, characteristic sedimentary features are adhesion ripples 

and irregular or horizontal beds, commonly accompanied by crusts of salt or gypsum (Glennie, 1972, 

p. 1053).

Many dune fields in both humid and arid regions 

form adjacent to the sea and so are a part of the 

coastal environment. Whether the wind is offshore 

or onshore, the beach, bar, or shallow-water marine 

sands may intertongue with dune sands and provide a complex of environments containing typical 

dune structures proximate to marine deposits. The 

Permian Lyons Sandstone of Colorado and the Permian and Pennsylvanian Casper Formation of 

Wyoming are probable examples of coastal dune 

deposits that are adjacent to marine sediments.

Selected Examples of Eolian 

Sandstones

This discussion of ancient eolian sandstones 

seeks to describe the characteristics of sandstones 

believed to have been formed by wind action, to indicate those attributes considered evidence of 

eolian origin, and to show methods of distinguishing between the different basic dune types. Examples of formations thought to have been formed by 

wind activity are also given. From 30 or more 

sandstones known to qualify as dunelike types, 12 

examples were chosen for analysis.

The sandstones discussed herein (1) are formations that have been studied in detail, (2) represent 

principal types of deposition and illustrate distinctive features of various dune forms, and (3) are 

geographically widely distributed. Because the data 

used came from many different sources and represent various degrees of detailed research, the conclusions presented here differ considerably from 

area to area in both scope and dependability.
ANCIENT SANDSTONES CONSIDERED TO BE EOLIAN 197

The sandstone formations believed to be examples of interior desert dune-field deposits that were 

selected for analysis are the Coconino Sandstone of 

Arizona, U.S.A., of Permian age, and the Lower 

Mottled Sandstone of England of Permian (?) age; 

the Navajo Sandstone of Arizona and Utah, U.S.A., 

the Botucatii Sandstone of Brazil, and the Cave 

Sandstone of southern Africa, all of Mesozoic age. 

Sandstones illustrating a coastal dune environment 

are the Lyons Sandstone of Colorado and the 

Casper Formation (eolian origin uncertain) of 

Wyoming, both in the United States and of late 

Paleozoic age.

The Frodsham Member of the so-called Keuper 

Sandstone of the Permian-Triassic Cheshire Basin 

in England, though very limited in extent, illustrates the dome type of dune, and the discussion 

presents a method of recognizing it through structural characteristics. The De Chelly Sandstone of 

Arizona typically shows well-developed interdune 

deposits between sands interpreted as transverse 

dunes, and it illustrates complex relations along its 

margins between dune and other continental facies. 

Finally, evidence from the Rotliegendes of the 

North Sea area is reviewed because it is believed to 

include examples of seif dunes as well as transverse 

types and because typical sebkha structures are 

recognized in its interdune strata.

Coconino Sandstone 

(Permian), U.S.A.

THE PERMIAN COCONINO SANDSTONE of 

northern Arizona is considered by many geologists 

to represent the deposits of a large sand sea. It consists of large-scale cross-stratified quartz sandstone 

(fig. 140), flat-bedded interdune deposits are sparse. 

The general lack of interdunes, with only horizontal bedding planes occurring between sets 

of cross-strata, suggests an abundant sand source 

with resulting rapid dune migration and burial of 

interdune spaces. The large scale of the foresets 

suggests the growth of high dunes.

The Coconino Sandstone forms a conspicuous 

cliff in the upper walls of Grand Canyon, along the 

Mogollon Rim to the south and east, and in many 

other parts of the region, where it occurs as a prominent white to buff layer, commonly several 

hundred feet thick. The Coconino is a uniformly

fine grained, nearly pure quartz sandstone with 

siliceous cement, has a massive appearance, and is 

cross-stratified on a large scale. Cross-strata mostly 

dip at high angles (fig. 141). Commonly, crossbed 

sets form large truncated wedges, and numerous individual beds extend as much as 60 or 80 feet (18 or 

24 m), curving to form a tangent with the underlying bounding plane.

Although the Coconino characteristically is 

white, it locally has a brownish cast, as in Marble 

Canyon, or is bright red, as near Flagstaff. Most of 

the sloping bedding surfaces are extremely smooth 

and even, but some contain abundant ripple marks, 

clearly impressed fossil footprints, and other minor 

structures. A general uniformity of texture and 

structure is characteristic.

Distribution and Thickness

The Coconino Sandstone forms a great sedimentary wedge across most of northern Arizona. Along 

the entire Arizona-Utah boundary, it is either very 

thin or absent, ranging in thickness from 40 feet (12 

m) at Lees Ferry to 60 feet (18 m) at Hacks Canyon, 

farther west, and 50 feet (15 m) at Grand Gulch 

mine, near the Nevada State line. To the south 100 

miles (160 km) or more, it is more than 500 feet (150 

m) thick along the Mogollon Rim of central Arizona 

and attains a maximum thickness of more than 

1,000 feet (300 m) near the town of Pine. The 

Coconino Sandstone covers about 32,000 square 

miles (51,500 km2).

Formation Boundaries

The white sandstone of the Coconino rests upon 

a flat surface of red mudstone of the Hermit Shale 

across nearly its entire area of deposition. 

Generally, the contact is sharp and even, but in 

some places the surface of the red Hermit is 

trenched with large shrinkage cracks, probably the 

result of desiccation, which are filled with white 

sandstone of Coconino type that apparently filtered 

down from above.

The upper boundary of the Coconino in Grand 

Canyon sections is marked by sandstone of the 

Toroweap Formation (Rawson and Turner, 1974). 

Steeply dipping crossbeds directly below are truncated everywhere to form a flat surface at the contact. Quartz grains probably derived from the 

Coconino form the basal unit of the Toroweap and 

suggest that the sand of the Coconino had not yet
198 A STUDY OF GLOBAL SAND SEAS

PERMIAN COCONINO SANDSTONE, forming cliff on west side of Hermit Basin, Grand Canyon National Park, 

Arizona, U.S.A. Large-scale tabular-planar cross-strata are prominently displayed. (Fig. 140.)

PERMIAN COCONINO SANDSTONE, showing sets of high-angle cross-strata and tangential bases (arrow) of foresets, 

Dripping Springs Trail, Grand Canyon National Park, Arizona, U.S.A. (Fig. 141.)
ANCIENT SANDSTONES CONSIDERED TO BE EOLIAN 199

consolidated when the formation's top surface was 

beveled and quartz sand began to cover it.

Texture

The Coconino Sandstone is composed dominantly of well-sorted fine-grained (0.125-0.25 

mm) sandstone. Nearly all the grains are rounded to 

subangular, and many are pitted or frosted. The 

sandstone consists of white quartz with a few scattered feldspar grains and traces of heavy minerals 

(McKee, 1934b, p. 91). As evident from the pale color, the grains are free of iron oxides in most 

localities.

Uniformity of grain size and various textural 

features of the Coconino sand grains have been 

described in detail by McKee (1934b p. 90-96). 

Because sorting and texture are functions of 

transportation rather than deposition, and, further, 

may reflect processes of an earlier generation, they 

cannot be considered to be proof of eolian origin. 

Grain characteristics of the Coconino are, however, 

typical in all respects of many modern dune sands.

Primary Structures 

Stratification

The most conspicuous primary structure 

preserved in the Coconino Sandstone is the largescale cross-stratification. It is composed of long 

sweeping layers, many of them 30-40 feet (9-12 

m) long, and some of them as long as 80 feet (24 m). 

They dip mostly at 25° - 30°, but a few reach a maximum of about 34° (McKee, 1940, p. 823). In general, 

the dip is southward, but the spread of readings is 

relatively great, ranging between SW. and SE. 

(Reiche, 1938, p. 908).

Cross-stratification of the Coconino is uniform 

throughout wide areas, forming large irregular 

wedges truncated by overlying layers (fig. 142). 

Thin laminae form parallel curves, concave upward, that are tangential with underlying bounding 

planes (McKee, 1934b, p. 98). Contrasting with the 

common high-angle cross-strata are some lowangle (< 15°) cross-strata that dip in the opposite 

direction. They occur in limited numbers in a few 

localities (McKee, 1940, p. 823). Horizontal laminae 

constitute the basal 3-6 feet (1 - 2 m) of the formation at many localities.

A stereographic polar net for representation of 

crossbedding attitudes was first used by Reiche 

(1938) in connection with analyses of Coconino 

cross-strata. His analyses yielded weighted average

|TV . £-

WEDGE-PLANAR CROSS-STRATA, a common structure of the 

Permian Coconino Sandstone, Kaibab Trail, Grand Canyon National Park, Arizona, U.S.A. (Fig. 142.)

directions of dip and expressed numerically 

measures of the consistency in direction of individual dips. This study was the earliest in 

America to employ a rigid statistical approach and 

has been followed by numerous similar investigations made to determine mean current directions 

within various sedimentary environments. This 

quantitative and statistical method of study has 

become an important tool for the analysis of crossstrata.

A distinctive feature of the stratification in both 

dipping and horizontal strata of the Coconino 

Sandstone is a characteristic splitting to form flat 

bedding surfaces. The detachment of one laminae 

from another in sandstone of such uniform composition suggests either marked differences in grain 

size or differences in cohesion between individual 

laminae probably resulting from variations in wetness or dryness of the sand surface at time of burial. 

Because analyses show few differences in grain size 

between laminae, the easy detachment along 

planes of stratification seems to reflect a lack of 

cohesion in the original deposit (McKee, 1934b, p. 

100).

Ripple Marks

Although not abundant throughout the formation, ripple marks are locally numerous and distinctive (fig. 143). They all seem to be of one general 

form — low, wide, and asymmetrical with ripple 

indexes (ratio of wavelength to amplitude) greater 

than 15 (McKee, 1934b, p. 101). Most crests and 

troughs are oriented parallel to the direction of dip 

of the foreset slopes.
200 A STUDY OF GLOBAL SAND SEAS

RIPPLE MARKS ON FORESET SURFACE of cross-strata, 

Coconino Sandstone, Kaibab Trail, Grand Canyon National 

Park, Arizona, U.S.A. (Fig. 143.)

A detailed analysis made in 1945 of ripple marks 

in the Coconino, in which about 50 sets were examined, shows compelling evidence, on the basis of 

five characteristics, that the ripple marks were 

wind formed (McKee, 1945, p. 317- 320). The diagnostic features are as follows:

1. Large ripple index (lowest was 17; most were 

considerably higher).

2. Ripple crests were definitely rounded in all 

specimens.

3. A concentration of coarser sand grains occurred 

on or about the crests in most specimens.

4. All specimens in situ had crests trending up and 

down surfaces of sloping laminae; none was 

normal to dip.

5. Crests and troughs were straight and parallel, 

with little change in direction where exposed 

for distances of 3 feet or more. 

The apparent discrepancy between the abundance of ripple marks on modern dunes and the 

general scarcity and localized distribution of this 

structure in the Coconino may be attributed to two 

factors related to preservation. First, a large majority of ripple marks in modern dunes are formed 

on the gentle windward slopes of saltation, but in 

ancient dunes, because of differential preservation, 

most windward-side deposits have not been 

preserved. The steep slipfaces of lee sides, where 

few ripple marks form because deposition is by

avalanching, constitute nearly all the sediment 

preserved in ancient dune sandstones. In barchan 

dunes or barchanoid ridges, lee-side ripple marks 

are largely restricted to the sides or wings where 

crosswinds are effective (McKee, 1934b, p. 101). 

Second, most ripple marks formed in dry sand are 

unlikely to be preserved on any surface unless the 

sand later develops cohesion through moisture 

received as dew or light rain. These special conditions required for the preservation of ripple marks 

in dune sand place a strong limitation on the places 

and times favorable for permanent preservation 

(McKee, 1945, p. 315-316).

Raindrop Impressions

Raindrop impressions in sand form small craterlike pits, some of which have been recognized in 

the Coconino Sandstone at several localities 

(McKee, 1934b, p. 102). These pits are especially 

significant in interpreting genesis, for they give 

positive evidence of subaerial deposition. They 

differ in several respects from rain pits in mud, 

such as have frequently been recorded in the 

literature.

Rain pits in fine sand form thin, detached layers, 

or shells, roughly circular but with irregular 

margins resulting from cohesion of grains by the introduction of moisture. These detached shells of 

sand, when formed on sloping surfaces like those of 

the Coconino, have become reoriented with respect 

to the lamination plane, and each circular pit tends 

to face upward, or vertically, thus raising the 

downslope rim (McKee, 1945, p. 323).

Rain pits on sloping surfaces of fine dry sand are 

readily reproduced in the laboratory; they are very 

distinctive and are not likely to be confused with 

craters having other origin. "Only brief showers 

can leave such a record, for on the surface of a dune 

that is thoroughly wetted, the shells lose 

coherence" (McKee, 1945, p. 324, fig. 7). This structure therefore may be considered an additional indication of dry-sand origin.

Slump Marks

Slump marks indicate mass movement or 

avalanching. In sand dunes they are commonly 

formed when lee-side slopes near the angle of 

repose are oversteepened. One form, as described 

by Bagnold (1937, p. 433), is the result of "sue-
ANCIENT SANDSTONES CONSIDERED TO BE EOLIAN 201

cessive discontinuous jerks with miniature land- f 

slides." Another (McKee, 1945, p. 321) is a series of 

variable and irregular lines roughly parallel to the 

direction of slope and marking the border of the 

sand mass that has slumped (fig. 144). These and 

other types of dry-sand slump marks have been 

recognized on surfaces of the Coconino (McKee, 

1945, figs. 5, 6).

SLUMP MARKS ON SLIPPAGE of cross-strata, Coconino 

Sandstone, Crandview Trail, Grand Canyon National Park, 

Arizona, U.S.A. Scale in inches; 1 inch equals 2.54 cm. (Fig. 144.)

The nature of slump marks and the differences 

between those formed in dry sand, damp sand, and 

wetted sand have been studied extensively, both in 

the laboratory and in the field (McKee, 1945, p. 320; 

McKee, Douglass, and Rittenhouse, 1971, p. 

363-375; McKee and Bigarella, 1972, p. 673-677). 

Those described from the Coconino Sandstone 

seem to give further strong evidence of the formation's eolian origin.

Miscellaneous

A minor structure of the Coconino, referred to as 

"miniature terrace-and-cliff structure" (fig. 145), 

was said by Reiche (1938, p. 918) to have "ready explanation as a dune feature, but * * * [to be] scarce-

"MINIATURE TERRACE-AND-CLIFF STRUCTURE" (Reiche, 

1938, p. 918) or "stair-step fault structure" (McKee, Douglass, 

and Rittenhouse, 1971, fig. 8b) formed on foreset surface of 

Coconino Sandstone, Bunker Trail, Grand Canyon National 

Park, Arizona, U.S.A. White scale is 6 inches (15 cm) long. (Fig. 

145.)

ly understandable otherwise." This structure consists of "a succession of abrupt rises or steps of 

about one-tenth inch each, ascending the slope" 

(McKee, 1934b, p. 103); otherwise, the surface of 

the slab is smooth and regular. The genesis of this 

feature is attributed by Reiche to the local disruption and breaking down, with rapid uphill recession, of successive layers of recently wetted sand 

on the lee side of a dune. This structure has been 

noted in the Frodsham Member of the so-called 

Keuper Sandstone Formation in England (D. B. 

Thompson, written commun., 1975) and has been 

reproduced experimentally in the U.S. Geological 

Survey sedimentary structures laboratory in 

Denver (McKee, Douglass, and Rittenhouse, 1971, 

fig. 8b).

Contorted Bedding

Penecontemporaneously deformed cross-strata 

are not common in the Coconino Sandstone, 

although they occur in a few places on a large scale. 

A spectacular example is near Doney Crater, northeast of Flagstaff, Arizona (fig. 146), where dipping 

foresets many feet in length have been folded 

locally, but the cross-strata above and below are 

undisturbed. The sand apparently had some 

coherence at the time of contortion, but whether 

the strata were wet or dry is not clear, for this type
202 A STUDY OF GLOBAL SAND SEAS

CONTORTED BEDDING IN LARGE-SCALE CROSS-STRATA of 

Coconino Sandstone about 2 miles (3.2 km) northeast of Doney 

Crater, near Flagstaff, Arizona, U.S.A. (Fig. 146.)

of fold has been developed under both conditions 

(McKee, Douglass, and Rittenhouse, 1971, p. 372).

Tracks and Trails

The fauna of the Coconino Sandstone consists 

exclusively of the "footprints of vertebrate animals 

and the trails of worms and other invertebrates" 

(McKee, 1934b, p. 106). The invertebrates were not 

classified by Gilmore (1926, p. 33), but they were 

compared by Brady (1939, p. 32) with modern 

arthropods. All the vertebrate tracks were formed 

by quadrupeds (fig. 147); however, they vary 

widely in size and character. Fifteen genera and 22 

species were named and described by Gilmore 

(1926, 1927, 1928).

No skeletal parts of the vertebrate animals 

responsible for Coconino footprints have yet been 

found. According to Schuchert (1918, p. 350), this 

lack of organic remains is "probably due to the 

originally loose and repeatedly reworked sands, a 

most unfavorable habitat for animals."

The tracks have sharp definition, even margins, 

and general excellence of preservation. The significance of these features in interpreting the environment of deposition was clearly stated by Matthes 

(in McKee, 1934b, p. 99), as follows: "the footprints 

have not the soft, vague outlines which tracks made 

in loose sand under water commonly have * * * 

even the deep impressions made by the claws of the 

animals being well preserved."

FOOTPRINTS OF VERTEBRATE animal, probably reptile, 

preserved on dip slope (about 30°) of crossbedded Coconino 

Sandstone. Tracks point uphill. Grand Canyon National Park, 

Arizona, U.S.A. Photograph by U.S. National Park Service. About 

one-fourth natural size. (Fig. 147.)

An additional attribute of the Coconino 

footprints, important to their interpretation, is the 

fact that these trackways "with only three exceptions out of many hundreds examined, were all 

leading uphill" (McKee, 1944, p. 62). Explanation of 

this distinctive feature was obtained through a 

series of controlled experiments made in 1943 by 

the writer (McKee, 1944, 1947). On loose sand 

derived from the Coconino and deposited at high 

angles (25° -28°) comparable to that in crossbedding of the Coconino, a chuckwalla lizard was enticed to walk both up and down the surfaces of dry 

loose sand, damp (sprayed) sand with a crust, and
ANCIENT SANDSTONES CONSIDERED TO BE EOLIAN 203

UPHILL TRACKS OF CHUCKWALLA LIZARD made on foreset slopes at 28° of fine dune sand. A, Dry sand. B, Damp sand with 

crust. C, Wet sand. Experiments made in laboratory, Museum of Northern Arizona, Flagstaff, Arizona, U.S.A. (Fig. 148.)

wet sand (fig. 148). Only in dry sand, uphill, could 

footprints be formed similar in size and clarity to 

those of the Coconino. Damp and wet sands gave 

very different results, and tracks made downhill 

were consistently destroyed by avalanching.

Experiments made with modern millipedes lend 

further support to the belief that the Coconino was 

deposited as dry sand (McKee, 1944, p. 70). The 

trails formed by these invertebrates consist of 

either two or three small furrows between low 

parallel ridges when made on low-angle slopes (less 

than 12°) of dry sand (fig. 149). The uphill trails 

contained two furrows, and the downhill, three. 

These animals were too light to leave trails in wet 

or damp sand and were unable to effectively climb 

slopes steeper than about 20°. The similarity is 

strong between millipede trails formed under experimental conditions and invertebrate markings in 

certain low-angle beds of the Coconino.

Environment of Deposition

The Coconino Sandstone is believed to have 

been deposited largely as dry sand in the form of

dunes. Structures are typical of barchan or 

barchanoid-ridge and transverse types. In some 

places, the curving shapes of small barchan types 

are recognizable, but mostly the cross-stratification 

is on a very large scale with individual lamination 

planes extending downdip for 50-150 feet (15- 30 

m) or more. The planes have sweeping curves in 

their lower parts to form tangents with the underlying bounding surfaces (figs. 141,142). They clearly 

are the result of unidirectional winds, as shown by 

crossbedding vector analyses (fig. 139).

Although most of the minor structures and all 

the animal tracks and trails probably were formed 

in dry sand, their permanent preservation required, 

first, prompt surface dampening by dew or other 

moisture. Dune surfaces with sand crusts apparently formed in this manner are recorded from 

many desert areas of today and explain cohesion of 

surface grains that preserve surface structures 

(McKee, 1934b, p. 100; Glennie, 1972, p. 1049).

Selective preservation of lee-slope deposits is a 

second controlling factor in the protection of surface features in dunes. Mostly, the gentle wind-
204 A STUDY OF GLOBAL SAND SEAS

TRAILS OF MILLIPEDES. A, In Coconino Sandstone, low-angle foresets near base, Grand Canyon National Park. B, In 

modern dry dune sand on 18° slope. Trails made in experimental trough at Museum of Northern Arizona, Flagstaff, 

Arizona, U.S.A. Scale in inches; 1 inch equals 2.54 cm. (Fig. 149.)

ward slopes of dunes are continually eroded, but 

downwind sides are constantly being buried by 

avalanching sand and protected. Thus, ripple marks 

and other structures upwind are seldom preserved, 

yet the relatively rare ripple marks on the slipfaces 

and the tracks of animals on such slopes have, if 

buried promptly, a good chance of permanent 

preservation.

Summary of Criteria for Eolian Origin

The basis for considering the Coconino 

Sandstone to be of eolian origin involves numerous 

criteria, some of which are distinctive of an eolian 

environment and others merely compatible with 

but not diagnostic of it. No single type of evidence 

seems entirely conclusive, but, together, the 

various features present very strong evidence. The 

principal criteria of dune deposition are as follows:

1. The extent and homogeneity of the sand body.

2. The tabular-planar and wedge-planar type and 

large scale of cross-stratification. The common 

high-angle deposits are interpreted as slipfaces 

on the lee sides of dunes, and the relatively 

rare low-angle cross-strata that dip toward the 

opposite quadrant apparently represent 

deposits of windward slopes.

3. Slump marks of several varieties preserved on 

the steeply dipping surfaces of lee-side 

deposits. These are distinctive of dry sand 

avalanching.

4. Ripple marks which are common on surfaces of 

high-angle crossbedding suggest eolian deposition both by their high indexes (above 15) and 

by their orientation with axes parallel to dip 

slopes.

5. The local preservation of a distinctive type of 

rain pit. Such pits illustrate the cohesion of 

sand grains with added moisture and a reorientation of the crater axes with respect to bedding slopes.

6. Successions of miniature rises or steps ascending 

dip slopes of crossbeds.

7. The preservation in fine sand of reptile 

footprints and probable millipede trails with 

sharp definition and clear impression.

8. The consistent orientation of reptilian tracks up 

(not down) the steep foreset slopes.

De Chelly Sandstone 

(Permian), U.S.A.

THE DE CHELLY SANDSTONE of northeastern 

Arizona is generally considered to be the lateral 

equivalent of the Coconino Sandstone to the west 

(McKee, 1934a, p. 231; Reiche, 1938, p. 924; Peirce, 

1963, p. 137), although Baars (1962) showed it as 

older in his correlations. Like the Coconino, the De 

Chelly is believed to be an eolian deposit, at least in 

part, but is much more complex and includes 

several distinctive noneolian members and facies.
ANCIENT SANDSTONES CONSIDERED TO BE EOLIAN 205

Contrasts in sedimentary structures, grain-size distribution, and composition distinguish these other 

facies and indicate various noneolian depositional 

environments.

Although the contrasting facies just referred to 

have been recognized as discrete parts of the De 

Chelly by most geologists (among them, Read, 1951; 

Alien and Balk, 1954; Peirce, 1963) who have 

studied them, the following discussion concentrates 

on the two facies that are considered to be eolian. 

Facies that occupy the eastern margin of the formation almost certainly represent various subaqueous 

environments. Farther west in the type locality at 

Canyon De Chelly, most of the sandstone consists 

of alternating units believed to be dune and interdune deposits. To the south and the northwest, 

pure sandstone considered to be eolian closely 

resembles the Coconino and may indeed be an 

eastern extension of the main body of that formation.

Distribution and Thickness

Rocks commonly assigned to the De Chelly 

Sandstone form a relatively narrow belt extending 

about 125 miles (200 km) from north to south in 

northeastern Arizona. The formation is about 800 

feet (240 m) thick at its type locality at Canyon De 

Chelly but is progressively thinner both north and 

south. At Bonito Canyon, Hunter's Point, and Oak 

Springs Cliffs, between 25 and 40 miles (40 and 65 

km) to the southeast, its thickness ranges from 640 

feet (200 m) to less than 500 feet (150 m). It thins to 

approximately 250 feet (75 m) at the south end of 

the Defiance Plateau (Peirce, 1963, p. 16). Northward from Canyon De Chelly, it terminates in the 

subsurface, probably somewhere near the ArizonaUtah border.

The eastern margin of the De Chelly is obscure 

both because of facies complications and because of 

the lack of surface exposures. In a westward direction, the De Chelly is represented by a facies with 

large-scale cross-strata essentially identical to those 

of the Coconino.

A facies consisting of alternating sets of horizontal beds and of large-scale cross-strata is, so far as is 

known, limited to the upper, or major, cliff member 

(570 ft (175 m) thick) of the De Chelly in Canyon 

De Chelly and its environs. The area of outcrop is 

about 20 miles (30 km) square, but, as suggested by

Peirce (1963, p. 59), this facies may be represented 

in neighboring localities, such as Nazlini and Bonito 

Canyons, although largely lacking the characteristic sets of horizontal beds. If all areas mentioned are included in this facies, it has a northsouth extent of 60 miles (95 km) and definitely 

merges into normal Coconino-like deposits across a 

wide belt.

Composition

Compositionally, the De Chelly Sandstone 

ranges from nearly pure quartz sandstone or orthoquartzite to beds containing enough feldspar to be 

classified as subarkoses. Specks of what seem to be 

kaolin are common throughout parts of the formation and may have been developed by the breakdown of feldspars. They are characteristic of the 

crossbedded sandstones in Canyon De Chelly and 

canyons to the south (McKee, 1934a, p. 224), and in 

subsurface samples from the Four Corners area to 

the north (McKee, Oriel, and others, 1967).

Most of the quartz grains are white, but sparse 

red quartz grains characteristically are scattered 

through much of the formation (Gregory, 1917, p. 

33; McKee, 1934a, p. 225). They probably result 

from ferric material that coats the grains or fills surface irregularities. Thin-section study revealed that 

they have developed partly before and partly after 

quartz overgrowths (Peirce, 1963, p. 115).

In the thin flat-bedded silty sandstones of probably subaqueous or interdune origin, mica is 

widespread, but it seems to be rare or absent in the 

large-scale cross-stratified sandstones. Heavy 

minerals are rare in all these strata.

Texture

Analyses of 125 samples showed the De Chelly 

(Peirce, 1963, p. 93) to consist principally of fine 

sand with a modal size between 0.125 and 0.177 

mm, a median diameter of 0.164 mm, and a sorting 

coefficient (Trask) of 1.25 mm. Therefore, the formation as a whole is considered to be a rather 

uniform "well-sorted fine-grained sandstone."

Although the size analyses of the De Chelly, as 

averaged for all its sandstone facies, reveal a 

general overall similarity, perhaps more significant 

are comparisons made by Peirce (1963, p. 94) of 

grains from each of the various structural types 

(facies) of sandstone. In the upper, or main, 

sandstone member in Canyon De Chelly, sand
206 A STUDY OF GLOBAL SAND SEAS

grains of the large-scale cross-strata that are 

believed to be dune sands "average 0.170 mm in 

median diameter, [which is] slightly coarser than 

those of the formation as a whole" (Peirce, 1963, 

fig. 8, D). Horizontally stratified silty sandstones, 

here interpreted as interdune deposits, that form 

thin zones repeated throughout this member, have 

a wider range in grain size, with more coarse grains, 

as well as a higher silt-clay content (Peirce, 1963, 

figs. 10B, 10E).

A comparison of sand from the large-scale 

(eolian) cross-strata of the upper member at Canyon De Chelly with sand from the corresponding 

unit at six localities to the south and southeast 

shows similar size properties in all sections (Peirce, 

1963, table 2), as follows:

Coarse sand: Very little or none. 

Silt and clay: Less than 10 percent. 

Median grain

size (mm): 0.149-0.186. 

Sorting index (Trask): 1.19-1.32.

Comparing the eolian-type sandstone of the upper member with sandstones that Peirce (1963, table 2) considered of aqueous origin in the lower 

member at Bonito Canyon to the southeast discloses 

the contrast shown in the following unnumbered 

table.

Coarse

sand Silt-clay 

(percent) (percent)

Median Sorting

grain size index

(mm) (Trask)

Canyon De

Chelly ..... 

Bonito Canyon

Trace 

0.4

0.170

.126

1.21

1.50

Sand grains in the De Chelly, regardless of facies, 

are nearly all rounded or subrounded. Commonly, 

they are pitted or grooved, and many are frosted. 

This frosting, however, is caused by "the light scattering effect of myriads of minute quartz crystals, 

or incipient silicification" (Peirce, 1963, p. 98).

Primary Structures 

Stratification

The upper unit or member of the De Chelly 

Sandstone in Canyon De Chelly contains two alternating and contrasting types of stratification that 

together distinguish it from all other facies in the 

formation. These cross-strata consist of (1) a largescale high-angle type, interpreted as eolian, and (2) 

a thin, virtually horizontal type believed to represent interdune deposits. The large-scale cross-strata 

constitute a major part of the total deposit and occur in thick layers, in terms of feet or metres, 

whereas the horizontal strata form thin sets, a few 

of which are more than 3 feet (more than 1 m) thick 

and which laterally may be represented by bedding 

(parting) planes. These units of alternating 

crossbeds and horizontal beds were noted by 

McKee (1934a, p. 222, 224) and described in detail 

by Peirce (1963, p. 51-67).

The large-scale cross-stratified sandstones that 

form the main cliff of De Chelly Sandstone in Canyon De Chelly, similar in structure to the Coconino 

Sandstone and to the Coconino-like sandstones 

near Ganado to the south and in Monument Valley 

to the northwest, have been considered extensions 

(facies) of the De Chelly (Gregory, 1917; Baker, 

1936). The large-scale cross-stratified sandstones 

form two principal structural types— tabular 

planar and wedge planar. In the tabular-planar 

type, bounding planes both above and below the 

foresets are nearly horizontal and truncate the underlying crossbeds (fig. 150).

In the wedge-planar type, oblique erosion surfaces separate sets of cross-strata. The tabularplanar type is interpreted as representing an interdune surface on which no deposits accumulated 

(McKee and Moiola, 1975); the wedge-planar type 

is developed within a migrating dune of barchanoid 

or transverse type and is common in the dunes at 

White Sands National Monument, New Mexico 

(McKee, 1966, p. 59).

The thin horizontal silty sandstone beds that 

characteristically alternate with large cross-strata 

rest on flat erosion surfaces that truncate crossstrata sets (fig. 151). Followed laterally, some of the 

horizontal beds are seen to thin and wedge out, but 

the underlying erosion surface continues as a 

bounding plane between sets of cross-strata above 

and below. A detailed description of these structures (Peirce, 1963, p. 56-59) suggests that 

although the flat-bedded silty deposits occupy only 

restricted areas on truncation planes, they occur as 

sedimentary structural features throughout an area 

of many square miles.

The distribution, composition, and structure of 

the thin lensing flat beds that occur between largescale cross strata, strongly resemble the interdune 

deposits now developing in the dune field at White
ANCIENT SANDSTONES CONSIDERED TO BE EOLIAN 207

LARGE-SCALE AND MEDIUM-SCALE CROSS-STRATA of tabular-planar type in Permian DeChelly Sandstone, Canyon 

De Chelly, Arizona, U.S.A. (Fig. 150.)

Sands National Monument, New Mexico (McKee 

and Moiola, 1975). If the White Sands analog is 

valid, the thickness of a flat-bedded deposit (interdune) may be considered a function of the time of 

exposure before the next dune migrates over and 

buries it. Likewise, the horizontal bedding planes 

lacking deposits are the record of surfaces that were 

buried rapidly by advancing dunes.

Ripple Marks

Ripple marks in several parts of the Monument 

Valley area are preserved on cross-stratified 

sandstones assigned to the De Chelly (Peirce, 1963, 

pis. 25, 26). They are described as "having axes 

aligned up and down dip" and are therefore considered to be wind-formed. They resemble closely 

the abundant ripple marks described from the 

Coconino Sandstone of Grand Canyon and give 

further indication that the sandstone containing

them constitutes an eastern extension of the 

Coconino or at least a recurrence of its eolian facies.

Tracks and Trails

Footprints of several species of vertebrate 

animals and trails of invertebrates, similar to forms 

represented in the Coconino Sandstone of Grand 

Canyon, occur in the large-scale cross-stratified 

sandstone member of the De Chelly at Nazlini Canyon (McKee, 1934a, p. 227) and at Kinlichee 

(McKee, 1934a, p. 232) south of Canyon De Chelly. 

They are also reported from western Monument 

Valley in crossbedded sandstone assigned to the De 

Chelly (Peirce, 1963, p. 26). All these tracks and 

trails lead up the steep dip slopes of the cross-strata, 

as do those in the Grand Canyon.

The significance of these footprints in the history 

of the sandstone is threefold. First, they suggest a 

direct correlation between the Coconino Sandstone
208 A STUDY OF GLOBAL SAND SEAS

HORIZONTALLY BEDDED SILTY SANDSTONE, interdune deposit (arrow) between cross-strata sets of eolian dune 

type. Permian De Chelly Sandstone, Canyon De Chelly, Arizona, U.S.A. (Fig. 151.)

and the De Chelly Sandstone and furnish evidence 

of similar environments of deposition. Second, the 

sharpness of the imprints and the general manner 

of preservation indicate that the imprints were 

formed in dry sand. Third, their preferred orientation, up the bedding slope only (never down), is 

evidence of having been formed in dune sand near 

the angle of repose. (See the preceding discussion 

of the Coconino Sandstone.)

Environment of Deposition

Of the three members that form the De Chelly 

Sandstone in its type locality, only the upper is considered to be dominantly of eolian origin. It forms 

the major cliff in the walls of Canyon De Chelly 

where it is nearly 600 feet (180 m) thick. The largescale cross-strata in this unit show a persistent 

southwestward dip and are interpreted as indicating a prevailing wind that caused dunes to migrate

in that direction. Between cross-bedding sets, in 

many places, are thin sets of horizontal beds 

believed to have developed as interdune deposits. 

The other two members in Canyon De Chelly are 

probably of subaqueous origin. The thin (45 ft, 

14m) middle member, composed of micaceous 

siltstone and silty sandstone, is considered to represent a relatively low-energy deposit and may have 

formed on the margin of saline basins to the south. 

The lower member, formed of cross-stratified sand, 

is believed by Peirce (1963, p. 145) to be "a high 

energy fluvial" deposit accumulated on "an aggrading delta."

Two additional members (or facies) in the De 

Chelly Sandstone occur in the eastern part of the 

Defiance uplift (Peirce, 1963). These members underlie the cliff-forming upper member and are considered by Peirce (1963, p 148-149) to be lowenergy lagoon or tidal flat deposits overlying "near-
ANCIENT SANDSTONES CONSIDERED TO BE EOLIAN 209

shore marine deposits," together with some crossstratified sandstone, possibly eolian.

The foregoing interpretations suggest that in the 

western part of the region the De Chelly Sandstone 

represents stream deposits followed by extensive 

dune deposits but that, in a parallel belt to the east, 

near-shore marine deposits preceded the development of eolian strata.

Summary of Criteria for Eolian Origin

Those facies of the De Chelly Sandstone believed 

to be composed of windblown deposits are of two 

principal types. One f acies resembles the Coconino 

in its uniformity of grain size and structure and in 

large-scale high-angle cross-stratification. Characteristics of the cross-strata indicate deposition as 

barchans or barchanoid ridges. The orientation of 

ripple marks and the state of preservation of reptilian tracks are further evidence of eolian origin; 

these features are common to both the Coconino 

and the western part of the De Chelly.

The second facies of probable eolian origin in 

the De Chelly consists of an alternation of (1) 

large-scale high-angle cross-strata forming tabularplanar and wedge-planar sets and (2) very thin 

sets of horizontally bedded silty sandstone. From 

the standpoint of both texture and structure, these 

two types of sandstone compare well with the 

alternating dune and interdune deposits of a 

modern dune field developed under conditions of a 

prevailing wind.

Navajo Sandstone (Triassic? 

and Jurassic), U.S.A.

THE NAVAJO SANDSTONE has been selected 

to illustrate eolian-type sandstone because of its 

broad geographic extent and great thickness and 

because of the large-scale and excellent development of its primary structures, permitting it to be 

analyzed across a wide area and observed in relation to other facies. Preservation in the Navajo 

Sandstone of small dinosaurs and other forms of 

continental life makes it unlikely that this sandstone represents accumulations of sand waves in 

deep marine waters of the North Sea type, at least 

in areas where those animals are present. Various 

features of associated facies indicate development

in a regional environment of aridity. In brief, considerable evidence is available to suggest that the 

Navajo represents an extensive sand sea of a great 

interior desert, mostly or entirely Lower Jurassic 

(Lias) time.

Obviously, making generalizations concerning 

the character and genesis of this huge sand body is 

difficult. Observations made in one area may not 

apply entirely to another area, yet many of the distinctive features are common to most parts. The 

local exceptions, doubtless related to subenvironments, have prompted Various different interpretations. The really remarkable feature of the Navajo 

is the high degree of uniformity of the sandstone 

and its general consistency throughout the region.

Distribution and Thickness

The Navajo Sandstone as currently recognized 

(McKee, Oriel, Swanson, and others, 1956, table 1) 

extends across much of Utah, northeastern 

Arizona, and southwestern Colorado. It is correlated with, and almost certainly is a continuation of, 

the Aztec Sandstone (Triassic? and Jurassic) to the 

west in southern Nevada and California, and of the 

Nugget Sandstone (Triassic? and Jurassic?) to the 

north and east in northern Utah, southwestern 

Wyoming, southeastern Idaho, and northwestern 

Colorado (Baker and others, 1936). As shown by 

isopachs in figure 152, this great cross-stratified 

sandstone body extends approximately 600 miles 

(965 km) from north to south and at least 250 miles 

(400 km) from east to west. These measurements 

approximate the present extent of the sandstone; 

the original sand sea doubtless extended much 

farther but has been removed by Cenozoic erosion, 

as in northwestern Arizona and eastern Nevada.

The Navajo Sandstone is more than 1,000 feet 

(300 m) thick in parts of northeastern Arizona and 

more than 2,000 feet (600 m) thick in southwestern 

Utah (fig. 152); its correlative, the Aztec Sandstone, 

is 3,000 feet (900 m) thick in the Mohave Desert of 

California. Along its eastern and southeastern 

margins in Colorado and northern Arizona the 

Navajo forms a wedge and thins to a vanishing 

point; elsewhere its margins are less definite.

Along the southern margins of the Navajo 

Sandstone, prominent tongues of large-scale crossstratified sandstone extend southward and south-
210 A STUDY OF GLOBAL SAND SEAS

116° 114° 112° 110° 108°

• - :

. •••:-:-:-:/::::^::-

38°

36°

ISOPACH-LITHOFACIES MAP AND CROSS-SECTION showing distribution and thickness of Triassic(?) and Jurassic Navajo 

Sandstone, Triassic(?) Kayenta Formation, and correlative units. (Modified from McKee, Oriel, and others, 1956, pi. 4). 100 feet 

equals 30.5 metres. (Fig. 152.)
ANCIENT SANDSTONES CONSIDERED TO BE EOLIAN 211

Navajo, Kayenta, and correlative sandstones

Dashes indicate areas of some shale

Area where Navajo, Kayenta, and correlative sandstones absent within the region of their distribution

.2000

Outcrop or well where Navajo, Kayenta, and correlative

sandstones are present

Thickness, in feet

Outcrop or well where Navajo, Kayenta, and correlative

sandstones are absent

Older rocks are overlain by younger Jurassic, Cretaceous, or (locally) 

Tertiary rocks

Isopach in areas of good control 

Thickness, in feet

—— — — — — 5OO—?— — -----

Isopach in areas of poor control

Thickness, in feet; queried where especially questionable.

Dotted where inferred

— -—- — - — 50O-- — - — - —

Isopach showing inferred former thickness of Navajo, 

Kayenta, and correlative sandstones where they are known 

to be eroded

Thickness, in feet

Crossbedded A' ~

Horizontal scale x 1.5 

Vertical scale exaggerated

-e

100 MILES

I ' I

0 200 KILOMETRES

SECTION OF NAVAJO, KAYENTA, AND CORRELATIVE 

SANDSTONES ALONG LINE A-A'

(Fig. 152. — Continued.)

westward into the dominantly flat-bedded sandstones, siltstones, and limestones of the Kayenta 

Formation (Harshbarger and others, 1957, p. 22; R. 

F. Wilson, 1958, p. 116). Some of these tongues have 

appreciable thickness and have been named by 

workers in various parts of the region — for example, the Triassic (?) Lamb Point (R. F. Wilson, 1958) 

and Shurtz Sandstone Tongues of the Navajo 

(Averitt and others, 1955). A correlation of named 

tongues of the Navajo is included in table 1 of 

Hatchell (1967, p. 25).

The Kayenta Formation consists of sedimentary 

rocks believed to be fluvial and probably represents 

the deposits of southwestward-flowing streams. 

Thus, the tongues of the Navajo are interpreted 

(Harshbarger and others, 1957, p. 1) as windblown 

sands from the north or northwest that "gradually 

overwhelmed" the streambeds.

Composition and Texture

Studies in several widely separated areas indicate that nearly everywhere the Navajo Sandstone 

consists largely of fine-grained quartz sand, with 

very minor amounts of feldspar and a few other accessory minerals. It apparently is homogeneous and 

well sorted throughout, and in central Utah the 

Navajo is described as "monotonously uniform" in 

texture (Kiersch, 1950, p. 927). The quartz particles 

have been reported as medium- to fine-grained 

with an average diameter of 0.21 mm in northeastern Arizona (Harshbarger and others, 1957, p. 

19) but as fine-grained to very fine grained near 

Navajo Mountain on the Utah-Arizona border 

(Hatchell, 1967, p. 30). Sand grains are uniformly 

about 0.2 mm in diameter (fine grained) in the 

northern part of the San Rafael Swell area, Utah 

(Kiersch, 1950, p. 927).

In the Navajo Sandstone, most quartz grains are 

rounded or subrounded, and relatively few particles are subangular or angular (Kiersch, 1950, 

p. 927; Harshbarger and others, 1957, p. 22; 

Hatchell, 1967, p. 30). Among samples from the 

northeastern Arizona area examined by 

Harshbarger, Repenning, and Irwin, about 25 percent were determined to be rounded. Frosting has 

been noted on quartz grains in many areas, and 

angular overgrowths of silica, forming orthoquartzite, are reported (Kiersch, 1950, p. 927). Cement is mainly silica but locally iron oxide or 

calcite (Hatchell, 1967, p. 30; Kiersch, 1950, p. 927).
212 A STUDY OF GLOBAL SAND SEAS

Horizontally interbedded units locally among the 

massive cosets of sandstone throughout the region 

are thin layers and lenses of aphanitic limestone 

and siltstone (Baker and others, 1936, p. 52; 

Harshbarger and others, 1957, p. 19), that probably 

represent interdune deposits. Wind-faceted pebbles, ranging in diameter up to more than 2 inches 

(5 cm), locally occur between units of crossstratified sandstone in the San Rafael Swell and 

Green River Desert areas of east-central Utah 

(Baker and others, 1936, pis. 13, 14). Small pebbles 

and coarse sand grains of quartz and chalcedony occur along some planes of cross-strata in Buckhorn 

Wash in east-central Utah (Kiersch, 1950, p. 927).

Primary Structures 

Stratification

Primary structures of the Navajo Sandstone of 

southern Utah consist "of large wedge-shaped 

planar sets of large-scale, high-angle, tangential 

cross-strata. The bounding surfaces of individual 

sets of cross-strata are planar sets that dip gently in 

a direction opposite to that of the steeply dipping 

cross-strata" (R. F. Wilson, 1958, p. 112, 141, 145). 

The formation contains both tabular-planar and 

wedge-planar cross-strata. These structures are 

characteristic of the formation in the Zion Canyon 

area and in the Kanab area farther east (fig. 153).

In the Navajo of northeastern Arizona, a dominance of large-scale wedge-planar and tabularplanar cross-strata has been recorded both by 

Harshbarger, Repenning, and Irwin (1957, p. 19) 

and by Hatchell (1967, p. 30). Simple wedge structures (without beveled tops) have also been 

recorded there by Hatchell and in east-central Utah 

by Kiersch (1950, p. 930). An absence of troughtype cross-strata was noted by R. F. Wilson (1958, 

p. 147) and by Hatchell (1967, p. 32), although, according to Wilson, trough structures — some of 

them large scale — are common in sandstones of 

the underlying Kayenta Formation of probable 

fluviatile origin.

In southwestern Utah much of the Navajo crossstratification is large scale, commonly exceeding 50 

feet (15 m) in length and forming sweeping arcs, 

concave upward. The thickness of sets in eastcentral Utah is as much as 15 feet (4.5 m) (Kiersch, 

1950, p. 930) and in the Navajo Mountain area of 

Utah and Arizona is up to 100 feet (33 m) (Hatchell,

1967, p. 30). The prevalence of high-angle dips, 

greater than 20°, in most areas, is noted by many 

geologists, among them R. F. Wilson, (1958, p. 148, 

table 6).

Ripple Marks

Ripple marks, though uncommon in the Navajo 

Sandstone, occur locally in widely scattered parts 

of the formation. They have been recorded from the 

east-central Utah area by Kiersch (1950, p. 935) and 

from the Arizona-Utah border by Hatchell (1967, 

p. 31), both of whom considered them to be windformed types because of orientation with crests 

parallel to the dip slopes of crossbeds. Ripple marks 

have also been reported from southwestern Utah 

and classified as eolian on the basis of ripple indices 

(Tanner, 1964, p. 432).

CROSS-STRATA IN NAVAJO SANDSTONE, north of Kanab, 

Utah, U.S.A. A, Wedge-planar type. 8, Tabular-planar type. 

Photographs by E. Tad Nichols. (Fig. 153.)
ANCIENT SANDSTONES CONSIDERED TO BE EOLIAN 213

The relative scarcity of ripple marks in the Navajo, as compared with their great abundance in most 

modern dune fields, is probably a function of selective preservation, as in the Coconino (McKee, 

1934b, p. 101). Only the relatively few ripple marks 

that form from crosswinds on the lee-side slipface 

have a chance of burial and preservation. Furthermore, even though wind ripples form in dry sand, 

permanent preservation requires some degree of 

cohesion, usually contributed by dew or light rain, a 

requirement further limiting the chances of ripplemark survival (McKee, 1945, p. 324).

Contorted Bedding

Zones of contorted bedding in which irregularly 

folded strata occur between sets of undisturbed 

strata are fairly numerous in various parts of the 

Navajo Sandstone (fig. 154). They have been referred to by most authors as slump structures. In eastcentral Utah contorted zones have been described 

by Kiersch (1950, p. 941) as 35-50 feet (10-15 m) 

thick, occurring at many widely scattered localities 

in the upper middle part of the formation. In southwestern Utah, zones of contorted strata (R. F. 

Wilson, 1958, p. 142) range in thickness from a few 

feet to 20 feet (6 m) and extend laterally as much as 

100 feet (30 m). In northeastern Arizona, they occur 

in foresets "in many places" (Harshbarger and 

others, 1957; Hatchell, 1967, p. 31).

Irregular folds, some of them recumbent, in the 

contorted zones of the Navajo have generally been 

attributed to oversteepening on the lee sides of 

dunes or to the weight of overlying sediment (R. F. 

Wilson, 1958, p. 142). These processes can be distinguished by the type of fold that has developed 

(McKee, Reynolds, and Baker, 1962a); however, the 

environmental implications which are recognized

CONTORTED STRUCTURES IN NAVAJO SANDSTONE, Kanab Creek area, Utah, U.S.A. Photograph by E. Tad 

Nichols, (Fig. 154.)
214 A STUDY OF GLOBAL SAND SEAS

by the degree of sharpness or "fuzziness" in resulting fold structures are more important. These 

features are largely a function of the cohesiveness 

of the sand at the time of deformation and serve to 

differentiate between saturated, wet, damp, and 

dry sand (McKee, Douglass, and Rittenhouse, 1971, 

table 1). Folds resembling many in the Navajo 

Sandstone are recorded in modern dune deposits, 

especially where the sand has been wetted (McKee 

and Bigarella, 1972, p. 674).

Interdune Deposits

Although the term "interdune" has not been 

mentioned in any of the many publications dealing 

with the Navajo Sandstone, probably many of the 

references to thin horizontal beds, silts tone or 

limestone lenses, and other distinctive deposits 

among the massive units of cross-stratified 

sandstones actually refer to interdune deposits. If 

so, then interdune deposits are well represented in 

the Navajo by a variety of sedimentary bodies having in common thinness, limited lateral extent, and 

either horizontal or uneven stratification.

In the Lamb Point Tongue of the Navajo in 

central southern Utah are "scattered thin lenses of 

flat-bedded to laminated, pale reddish brown 

siltstone and claystone" (R. F. Wilson, 1958, p. 141). 

The lenses are not more than 2 or 3 feet (0.5 -1 m) 

thick and they pinch out along strike. Farther west 

in Zion Canyon, Utah, R. F. Wilson (1958, p. 150) 

referred to Navajo cross-strata that alternate with 

flat-lying beds or with beds that have low-angle 

dips. The claystone and siltstone lenticular bodies 

probably formed as interdunes, according to 

modern analogs (McKee and Moiola, 1975).

Locally, Navajo interbeds include extensive 

lenses of thin-bedded limestone, presumably 

formed in ephemeral ponds. Among the sandstones 

of east-central Utah are "limy and argillaceous 

beds" (Kiersch, 1950, p. 927). In northeastern 

Arizona, many lenticular beds of cherty limestone 

occur within the Navajo (Harshbarger and others, 

1957, p. 19), and thin discontinuous beds of gray 

limestone, calcareous siltstone, sandstone, and 

limestone conglomerate form platy or flaggy units 

between sandstones (Hatchell, 1967, p. 2).

Numerous distinctive structures and other 

features in the Navajo of eastern Utah probably are 

attributable (Baker and others, 1936, p. 12, 52) to interdune deposits: "sand-filled desiccation cracks in 

limestone," "a bed of nodular-weathering silty red 

sandstone," "The occurrence of excellent dreikanter," and "local thin lenses of dense unfossiliferous gray limestone from a few feet to 

several miles in diameter" interpreted as the product of "ephemeral water-filled basins" and 

"formed through algal or purely chemical actions." 

The limestones contain mud cracks.

Fauna

Fossils are uncommon in the Navajo Sandstone, 

the total recorded forms consisting of two small 

bipedal dinosaurs (Brady, 1935; Camp, 1936), some 

dinosaur tracks, a few ostracodes, and some other 

crustaceans (Harshbarger and others, 1957, p. 1). 

These animals probably inhabited interdune areas, 

as evidenced by the dinosaur tracks near Navajo 

Canyon, Arizona (Gregory, 1917), that are preserved in thin lenses of limestone probably precipitated in ponds by chemical processes. The 

ostracodes likewise are from limestone lenses 

(Harshbarger and others, 1957) and presumably 

lived in shallow ephemeral water bodies between 

dunes.

Probably more important as evidence of the 

sandstone genesis than the animals themselves is 

their manner of preservation. For example, the 

skeleton of the small dinosaur recorded by Camp 

(1936, p. 39) from northern Arizona was buried on a 

surface parallel to the dipping "planes of crossbedding of the Navajo sandstone at that point" with the 

axis of the body horizontal and the right hind foot 

pressed into the sand. The creature seems to have 

been covered "by shifting sand before death, or 

soon after" (Camp, 1936, p. 41).

The uniform sand that constitutes the Navajo, 

Nugget, and Aztec Sandstones across a vast area is 

generally interpreted as an eolian accumulation 

with a source to the north or northwest 

(Harshbarger and others, 1957, p. 3). Studies of 

wind directions as determined from cross-strata 

dips in these sandstones have been made by 

numerous geologists in many parts of the region 

(for example, Poole, 1962, fig. 163.1). Cross-strata 

orientations, indicated by arrows on Poole's map, 

show dominant north and northeast winds for the 

Nugget and Navajo Sandstones in northeastern 

Utah and northwestern Colorado and for the Aztec
ANCIENT SANDSTONES CONSIDERED TO BE EOLIAN 215

Sandstone in southern Nevada, but show northwest 

winds for the Navajo Sandstone in most of 

southeastern Utah and adjacent Arizona. "The consistency of cross-strata dip bearings in a southerly 

direction suggests [for that period] a broad belt of 

strong and persistent northerly winds * * *." (Poole, 

1962, p. D150).

The sources of the sand have been postulated by 

various geologists; but no one source sufficiently 

great to have furnished the entire volume represented by these sandstones can readily be 

visualized. A major source in western Nevada 

where mountain uplift probably occurred at that 

time is suggested by conglomerates in the adjacent 

region (Harshbarger and others, 1957, p. 3). In 

northeastern Arizona, where sands of the Navajo 

apparently advanced eastward and eventually 

covered the fluvial Kayenta Formation, "Kayenta 

streams [are believed to have been] the primary 

source of material for the Navajo dunes * * *." 

(Harshbarger and others, 1957, p. 25). A source far 

to the north, certainly for the Nugget sandstone, 

also has been suggested.

The depositional environment of the Navajo and 

its correlative sandstones has generally been recognized as a great interior desert basin that sank gradually as the several thousand feet of sand accumulated. Aridity is evident from such features as the 

wind-faceted pebbles in east-central Utah and 

desiccation cracks in limestone beds of interdune 

deposits, and it can readily be inferred from the 

great size and thickness of the sand sea. That some 

dunes were very high is shown by the large scale of 

individual foresets and by the thickness of some 

cross-strata sets.

Dunes of the Navajo Sandstone are believed to 

have been transverse or barchanoid types, according to analyses of the cross-strata (R. F. Wilson, 

1958, p. 150) and the orientation and average dips of 

cross-strata. The cross-strata show a very small arc 

of spread, especially when compared with the 

spread of underlying fluvial deposits (R. F. Wilson, 

1958, p. 148, table 6). Between sets of dune sands in 

many places are thin beds or lenses thought to be 

interdune deposits that consist of flat-bedded 

siltstones, claystones, and limestones (R. F. Wilson, 

1958, p. 141) and probably made up the desert floor.

While the Navajo Sandstone was forming in the 

southern part of the region, the Carmel Sea probably was beginning to transgress across it from the 

north. This is indicated at the upper contact of the 

Navajo in east-central Utah, where inundation by 

the sea is evidenced by reworking of the sand, leaving "swash marks, beach cusps and other water 

marks" (Kiersch, 1950, p. 927). The gradational 

sediments locally at the Navajo-Carmel contact indicate that there was no appreciable hiatus but virtually continuous, uninterrupted sedimentation.

Not all geologists agree with the concept of an 

eolian origin of the Navajo Sandstone. Largely from 

examination of a thin stratigraphic section near 

Woodside, Utah, and textural analyses of six sand 

samples, Visher (1971, p. 1423) postulated a marine 

high-energy channel sequence. From field measurements and textural studies at seven sections in 

southern Utah, Marzolf (1969) postulated a 

marginal marine environment, rather than an arid 

interior desert.

Summary of Criteria for Eolian Origin

A synthesis of criteria for considering the Navajo 

Sandstone to be eolian was prepared 40 years ago 

by Baker, Dane, and Reeside (1936, p. 52) when 

they suggested five kinds of evidence — three positive and two negative. Positive evidence consisted 

of (1) the abundance and "gigantic scale" of the 

cross-strata, (2) the well-rounded grains, mostly 

well sorted, but with coarse grains scattered locally 

along bedding planes, and (3) the truncation of 

cross-strata sets by other sets, dipping "at all angles 

without system," that is, tangential foresets. Negative evidence was (1) a lack of numerous regular 

(horizontal) bedding planes and (2) the general 

scarcity of silt, ripple marks, mudcracks, mudpellet conglomerates, and other evidences of water 

action.

As indicated elsewhere in this chapter, textural 

features and the various types of negative evidence, 

though compatible with a dune environment, cannot be considered incontrovertible proof. However, 

the discovery of wind-faceted quartz pebbles in 

what may be considered interdune deposits of the 

Navajo in San Rafael Swell and Green River Desert 

(Baker and others, 1936, pis. 13, 14) probably constitutes important additional evidence. Still other 

evidence has been accumulated in support of an 

eolian genesis during later years.
216 A STUDY OF GLOBAL SAND SEAS

Detailed analysis by R. F. Wilson (1958, p. 143) of 

cross-strata in both the Navajo Sandstone and the 

Lamb Point Tongue of the Navajo in southern Utah 

clarified several points concerning their structure. 

After comparison with analogs in modern barchanand transverse-type dunes, the following features 

seem to be common to both modern and ancient:

1. Type of cross-strata — largely tabular and wedge 

planar, no large trough types (fig. 155).

2. Numerous large-scale foresets, 50 feet or more 

(15 m) long.

3. High-angle (>20°) dips of foresets.

4. Cross-strata dip directions with consistent orientation and narrow range of vectors.

5. Cross-strata largely tangential and concave upward.

The numerous zones of penecontemporaneous 

contorted bedding with sharp outlines and irregular 

fold patterns in the Navajo are considered evidence 

of sand that has become wet but not saturated, and 

those zones are comparable to structures in some 

modern dune fields.

NAVAJO SANDSTONE, showing large-scale wedge-planar cross-strata (middle) between tabular-planar cross-strata (above and 

below), Zion National Park, Utah, U.S.A. Photograph by E. Tad Nichols. (Fig. 155.)
ANCIENT SANDSTONES CONSIDERED TO BE EOLIAN 217

The vast extent and considerable thickness of 

well sorted fine sand with uniform character 

throughout rarely occur except in eolian environments. A possible exception is in areas of large submarine sand waves that are said (Jordan, 1962, 

p. 840) to resemble desert dunes in general form; 

however, nothing is yet known of their internal 

structure. In any event, the association of articulated skeletons of terrestrial dinosaurs in some parts 

of the Navajo precludes the possibility of those 

parts having formed under marine conditions.

Eolian-type ripple marks in the Navajo seem 

good evidence of a dune environment. Numerous 

lenses and thin beds of limestone and siltstone between sets of cross-strata in the Navajo are believed 

to represent deposits of interdunes.

Lyons Sandstone (Permian), 

U.S.A.

THE LYONS SANDSTONE of Permian age in 

Colorado was selected for description in this 

chapter for two principal reasons. First, outcrops at 

its type locality near Lyons, Colorado, offer excellent opportunities for detailed examination and 

careful analysis (Walker and Harms, 1972). Second, 

it apparently represents deposits of a coastal dune 

area in relation to other facies for which considerable environmental data are available.

In many respects, the Lyons Sandstone closely 

resembles the Coconino Sandstone of Arizona and 

many of the features considered to be evidence of 

the Coconino's eolian origin also occur in the 

Lyons. The nature of cross-strata, the uniformity of 

fine sand, the presence of high-index ripple marks, 

rain pits, and distinctive kinds of slump marks, and 

the presence of nearly identical tracks of vertebrate 

animals show a generally similar depositional environment for both formations. In certain other 

features, the two differ markedly — the size and 

geometry of the entire cross-stratified sand body, 

the character of erosion planes considered to be interdunal surfaces, and the abundance and distribution pattern of relatively coarse sand concentrates.

The question presented here is not whether the 

Lyons Sandstone of the type locality is eolian — 

this seems to be established on rather firm grounds 

— rather, what type of dune is represented and 

why was its depositional environment somewhat 

different from that of the Coconino.

Distribution and Thickness

The Lyons Sandstone forms a narrow foothills 

belt, extending about 160 miles (250 km) from its 

northernmost outcrop near the Wyoming — Colorado line to its southernmost outcrop, south of 

Colorado Springs (Hubert, 1960, p. 35), Colorado. Its 

thickness, as determined in a series of measured 

sections along the outcrop belt between Boulder 

and Colorado Springs, ranges from 150 to 680 feet 

(45- 200 m) (Hubert, 1960, p. 25). At its north end, 

the formation wedges out between tongues of the 

Permian Satanka Formation. To the south, it 

wedges out between red Paleozoic sandstones and 

siltstones (W. O. Thompson, 1949).

Eastward in the subsurface of eastern Colorado, 

the Lyons is represented by various facies, probably 

marine, of sandstone, siltstone and evaporites, as 

shown on subsurface maps by Maher (1954) and 

Broin (1957). East of Colorado Springs, the Lyons 

seems to maintain its identity for nearly 40 miles 

(65 km) before grading into other facies (Maher, 

1954).

The following discussion of the Lyons Sandstone 

concerns mainly that part which consists of largescale high-angle cross-strata, believed to be of 

eolian origin, at the type locality and in a few other 

limited areas along the outcrop belt. Intimately related noneolian facies of the formation are of interest primarily because they furnished supporting 

evidence concerning the depositional environment 

and paleogeographic setting. The eolian-type 

deposits in this formation are only known over a 

relatively few miles along the north-south belt and 

are very different in extent from other windformed sandstones, such as the Coconino and the 

Navajo.

Composition and Texture

Along its outcrop belt the Lyons Sandstone consists of two principal rock types— "arkoses (24 

percent) and feldspathic quartzites (75 percent)" 

(Hubert, 1960, p. 13, 100). The arkoses are mainly 

conglomerates and pebbly sandstones; intraformational conglomerates, lenticular dolomitic quartzites, and micaceous siltstone and shales constitute 

about 1 percent. The arkoses and many of the 

feldspathic quartzites indicate by their textures, 

structures, and other features noneolian depositional environments. The eolian facies consist of a
218 A STUDY OF GLOBAL SAND SEAS

relatively uniform fine-grained feldspathic sandstone which has conveniently been delimited by 

Walker and Harms (1972, p. 279) as the "flagstone 

beds."

Texturally, sandstones of the high-angle largescale cross-strata in the Lyons Sandstone, as represented at the type locality, are characteristically 

fine grained and well sorted. Pebbles, granules and 

beds of fine detritus, such as silt and clay, are absent (Walker and Harms, 1972, p. 284). The grains 

include both quartz and feldspar which mostly are 

tightly cemented by quartz; much of the feldspar 

has been altered by replacement.

Sand grains of medium or coarse size are concentrated on erosion surfaces that truncate sets of 

cross-strata throughout the formation. Relatively 

coarse grains uniformly scattered over these surfaces are interpreted as lag deposits of interdunes 

(Walker and Harms, 1972, p. 284). Such lag deposits 

occur on serirs and interdune surfaces of various 

modern dune fields (McKee and Tibbitts, 1964, pi. 

IB).

The relatively clay-free clean sand that composes the dune-type sandstone of the Lyons has 

been called variously a first-generation and a second-generation sand. Its relative purity has been attributed to the abrasion and winnowing of arkosic 

material shed from the ancestral Front Range highland (Maher, 1954, p. 2237), and to accumulation 

along a "Permian strand by waves and currents that 

carried in clean sands probably derived from previously existing sediments" (W. O. Thompson, 

1954).

Primary Structures 

Stratification

The Lyons Sandstone, as exposed at the type 

locality near Lyons, Colorado, is characterized by 

large-scale high-angle cross-strata. These crossstrata are mostly of the tabular-planar type with individual sets as much as 42 feet (13 m) thick and 

with bounding planes described as "scoop-like erosional surfaces" (Walker and Harms, 1972, p. 279, 

281). Many sets of strata extend laterally "for 

hundreds of yards" with little change in character; 

laminae within them are straight or gently curved 

in cross section.

The presence of relatively small subsets of crossstrata within the major sets of high-angle crossstrata is indicated by the traces of laminae exposed 

on the truncated surfaces that form bounding 

planes between sets. The nature of these subsets 

was recorded and analyzed in detail by Walker and 

Harms (1972, p. 281), who believed them to represent a record of nonuniform accretion along a 

planar surface resulting from wind drift. Such 

lateral shifting of cross-strata to form subsets apparently is common in many modern dunes of 

various types, and can be seen both on the floors of 

dune trenches and on interdune surfaces before 

burial (McKee, 1966, pi. VIIA). Shifts in wind direction also result in wedge-planar sets in many dunes. 

(See chapter E, "Sedimentary Structures in 

Dunes.")

Cross-strata in the Lyons, as described, resemble 

structures in many modern dunes but are duplicated in relatively few other environments. The 

maximum dip angles of the foresets are commonly 

4° - 5° less than the angles of repose or maximum 

dips (33° - 34°) of many modern dunes. In ancient 

dune deposits, a maximum angle of dip consistently 

lower than in modern dry sand has been attributed 

to compaction (Glennie, 1972, p. 1061; Walker and 

Harms, 1972, p. 280) and to removal of unstable 

grains by intrastratal alteration (Walker and Harms, 

1972, p. 280). An alternative explanation is 

differential preservation in cross-strata sets, where 

the upper parts of foresets that are relatively higher 

angled commonly are removed by erosion and 

planation (Poole, 1962, p. D148; Walker and Harms, 

1972, p. 280).

Miscellaneous

Several minor structures occur in many places in 

the ubiquitous cross-stratification of the eoliantype facies of the Lyons Sandstone (Walker and 

Harms, 1972, p. 279). These structures include 

asymmetrical ripple marks invariably oriented up 

and down the dip surfaces of foresets and with very 

low crests that are parallel and straight for long distances. These ripple marks have the high indices of 

wind ripples. Other structures are raindrop pits 

with typical ring shapes and raised rims (fig. 156) 

and slump marks (called avalanche structures by 

Walker and Harms), including the distinctive "step 

type" that is characteristic of many slipface
ANCIENT SANDSTONES CONSIDERED TO BE EOLIAN 219

PITS OF RAINDROPS in modern sand of Lyons Sandstone texture. One inch equals 2.54 cm. (Fig. 156.)

avalanches, where the surface is slightly cohesive 

(McKee, Douglass, and Rittenhouse, 1971, p. 369). 

These minor structures seem to be similar in all 

essential respects to the ripple marks, raindrop 

pits, and slump marks that are recorded from the 

Coconino, De Chelly, and some other eolian-type 

sandstones. Their probable modes of preservation 

and their interpretation were discussed in the section entitled "Coconino Sandstone." It is sufficient 

to say that these structures all give strong supporting evidence for deposition in an eolian environment.

Tracks and Trails

The footprints of vertebrate animals, probably 

reptilian, and the tracks of scorpionlike invertebrates preserved on the steeply dipping foresets of 

the Lyons Sandstone were described many years 

ago (Henderson, 1924). These clear and sharp 

tracks, which preserve delicate details, including 

the claw marks of the reptiles, probably are identical to forms reported from the Coconino and De 

Chelly Sandstones. The manner of their preservation and the conditions under which they apparently were preserved indicate deposition in dry 

dune sand.

The validity of the preceding conclusions is indicated by the following:

1. Experiments with living reptiles on steep slopes 

of fine sand indicate that such tracks could 

readily be formed in dry sand but not in wet or 

damp sand (McKee, 1944, p. 68; 1947, p. 27).

2. Experiments on the forming of tracks by living 

salamanders showed the virtual impossibility 

for such animals to leave diagnostic trackways 

on a sand surface under water (Peabody, in 

McKee, 1947, p. 27).

3. In extensive observations of modern amphibian 

trackways on mudflats, no examples of the 

clear outlines of individual footprints 

preserved under water were found, even 

where some trackway patterns remained 

(Peabody, in McKee, 1947, p. 27). 

The environmental conditions under which 

tracks in dry sand might be permanently preserved 

were discussed under "Coconino Sandstone."

Environment of Deposition

Two aspects of the regional environment in 

which the Lyons Sandstone was formed are 

generally agreed upon. First, the formation was 

deposited in a long narrow coastal area extending 

from north to south with a seaway to the east. Second, it was flanked to the west by a granitic terrane 

referred to as the ancestral Front Range highlands, 

and this upland contributed arkosic detritus to the 

formation. Details concerning the subenvironments 

in which various facies of the formation developed 

have been interpreted in many ways and ideas 

about their genesis have differed greatly.

Various investigators have attributed the sedimentary deposits that compose the Lyons Sandstone to accumulation (1) by streams, (2) on 

beaches and bars, (3) by the wind, and (4) through 

combinations of these factors. Deposition by 

streams, at least in part, is advocated by Maher 

(1954), Vail (1917), W. O. Thompson (1949), and 

Weimer and Land (1972). Littoral sedimentation, 

primarily beach and bar accumulation, is referred 

to by W. O. Thompson (1949), Maher (1954), and 

Hubert (1960). Eolian deposition, involving the 

highly cross-stratified facies, is advocated by Vail 

(1917), Tieje (1923), and Walker and Harms (1972). 

Most of the early workers gave little specific evidence to support their conclusions, seemingly 

reached largely on the basis of paleogeographic and
220 A STUDY OF GLOBAL SAND SEAS

other general considerations. Eolian deposition 

now seems well established for major parts of the 

Lyons, but numerous other facies, both coastal and 

alluvial, probably occur in the formation.

The kind of dune that is represented by the 

large-scale cross-strata of the Lyons Sandstone at 

and near its type locality has caused much 

speculation. Several types of pertinent evidence 

have been discussed, including analysis of crossstrata dip directions, descriptive information on 

the nature and extent of interdune surfaces, and 

conclusions based on paleogeographic and environmental considerations.

Systematic directional data based on dip readings 

have not been obtained for the eolian-type unit of 

the Lyons Sandstone. The sets of large-scale crossstrata at its type locality were reported by Walker 

and Harms (1972, p. 281) "to dip in a broad arc from 

southeast to west." As further stated by them, "the 

highly variable local dip directions show that accretion occurred along [rock] faces of diverse orientation." Statistically sound data are needed to firmly 

establish the amount of spread; nevertheless, at 

least suggestive is the considerable width of spread 

in dip directions. This spread, as described, forms a 

pattern similar to that of coastal parabolic dunes in 

Brazil determined by Bigarella (this chapter). The 

pattern in the Lyons seems very different from that 

shown to be typical of barchanoid and transverse 

dunes (Glennie, 1972, p. 1061) with their narrow 

spread (clustering of points). It contrasts even more 

with the nearly opposite double clusters of points 

on linear (seif, longitudinal) dunes illustrated by 

Glennie (1972, fig. 13) and by McKee and Tibbitts 

(1964, fig. 6).

Compelling evidence suggests that the winddeposited sands of the Lyons represent parabolic 

dunes, not barchanoid- or linear-type dunes. Interdune surfaces between sets of high-angle crossstrata are "scoop-like erosional surfaces" that "intersect along gently curved nicklines" (Walker and 

Harms, 1972, p. 281). These surfaces are broadly 

curved and exposed the beveled tops of earlier 

cross-strata sets, as is typical of most modern interdunes (McKee and Moiola, 1975). They represent a 

blowout phenomenon, which marks an early stage 

of coastal parabolic dunes, and differ from interdunes among barchans and transverse ridges in that 

they are relatively small and have curving surfaces.

They differ even more from the very broad, flat interdunes between linear (seif) dunes, which commonly have horizontal strata (McKee and Tibbitts, 

1964, fig. 8) accumulated on their surfaces. (See 

section entitled "Characteristics of Interdune 

Record," this chapter.)

Another aspect of the Lyons dune deposits, lending support to interpretation of their origin as 

parabolic types, is their geographic position. 

General agreement among concerned geologists, 

based on a considerable amount of evidence, indicates that the Lyons Sandstone was formed in a 

coastal environment, so a variety of coastal dune is 

inferred. If such an inference is correct, then the 

evidence already cited — blowout-type interdunes, 

divergent wind directions, large-scale cross-strata, 

and common wind ripple marks — all seem compatible with the parabolic dune interpretation.

Summary of Criteria for Eolian Origin

The following features indicate the eolian origin 

of the highly cross-stratified sandstone facies of the 

Lyons Sandstone:

1. A composition of clean fine quartzose and 

feldspathic sand, well sorted, subangular to 

well rounded, and commonly frosted. Such 

features, although not incontrovertible proof 

of genesis, are compatible with the texture of 

many modern dune deposits.

2. Thin layers of scattered but rather uniformly 

spaced, coarse grains resting on surfaces of 

truncation within fine cross-stratified sand. 

The coarse detritus is interpreted as lag 

material.

3. Major primary structures consist of large-scale 

high-angle cross-strata in tabular-planar sets. 

Such structures are typical of most dunes 

formed under conditions of unidirectional 

winds but rarely occur in other environments.

4. Curving scoop-shaped surfaces, exposing the 

beveled tops of cross-strata that represent sets 

of earlier development, are characteristic 

features of interdunes developing in a 

parabolic-dune environment.

5. Numerous asymmetrical ripple marks oriented 

parallel to the dip directions of foresets which 

have high ripple indices characteristic of windformed ripple marks.
ANCIENT SANDSTONES CONSIDERED TO BE EOLIAN 221

6. Surfaces of some strata have slump features, 

both the small steplike variety and the 

dendritic type that are commonly formed from 

avalanching of damp, cohesive sand. Surfaces 

also have raindrop pits.

7. Locally, the sharp, well-preserved footprints of 

four-footed animals, probably reptiles, occur 

on the steep foresets. This type of preservation, characteristic of a dry-sand environment, 

is not possible under water.

Casper Formation

(Pennsylvanian and Permian),

U.S.A.

THE GENESIS OF the cross-stratified sandstone 

of the Casper Formation in the southern part of the 

Laramie Basin, Wyoming, has long been a subject of 

dispute. Whether this formation is marine or eolian 

has been difficult to demonstrate largely because 

composition and texture of the sandstone could 

represent either environment, and the size and type 

of cross-strata and contorted beds that are its most 

distinctive structures have not yet been demonstrated to occur in any modern deposits.

Fortunately, for the understanding of the origin 

of the sandstone facies in the Casper, an excellent 

detailed description and analysis of its structure 

was made many years ago by Knight (1929). This 

pioneer work, a model for much subsequent work 

in the study of cross-stratification, called attention 

to the remarkable and baffling type of structure 

which Knight termed "festoon cross-lamination." 

(See discussion of "Festoon Structures" later in this 

section on the Casper Formation.) Today, it is commonly referred to as large-scale trough crossstratification.

Festoon structures that are extensive and large, 

like those in the trough-type cross-strata of the 

Casper, do not seem to have good analogs in any 

modern sand deposits that have been examined by 

trenching; nevertheless, the Casper is believed by 

many geologists to represent a dune environment, 

on the basis of other data. Accordingly, the Casper, 

as a unique form, is described herein. Trough structures of festoon type in some modern noneolian 

deposits are described, and certain dune environments which may produce large festoons are discussed on following pages.

Distribution and Thickness

The Casper Formation, including both limestones and sandstones, bounds much of the southern part of the Laramie Basin and flanks the 

Laramie Range in southern Wyoming, an area 75 

miles (120 km) wide and 100 miles (160 km) long. 

The cross-stratified sandstones, believed to be 

eolian, occupy the entire thickness of the formation 

on its southeastern margin encompassing at least 

1,000 square miles (1,600 km2) (Knight, 1929, p. 56).

The Casper is more than 700 feet (200 m) thick 

east of the Laramie Range; near the center of the 

Laramie Basin about 550 feet (165 km) thick, and in 

the Sand Creek area to the south (where the crossstratified sandstones have been most studied) 120 

feet (36 m) thick (Steidtmann, 1974). Its facies apparently are lateral extensions of still other and 

very different facies represented in the Permian 

and Pennsylvanian Tensleep Sandstone to the 

northwest. It may also be at least partly contemporaneous with the Permian and Pennsylvanian 

arkosic Fountain Formation to the south, which is 

considered to be formed largely of coalescing 

alluvial fans (Hubert, 1960).

Composition and Texture

The cross-stratified sandstone of the Casper is 

fine grained and well sorted. Exceptions to this 

uniformity are laminae at the bottoms of crossstrata troughs that commonly contain evenly distributed, scattered coarse grains of quartz and 

feldspar. These grains may be lag material (Steidtmann, 1974, p. 1838); if so, the laminae probably 

represent interdune surfaces developed in an environment of blowout dunes.

Sandstone of the Casper is classed as calcareous 

subarkose or orthoquartzite, according to Steidtmann (1974, p. 1836). In some areas it is interstratified with beds of marine aphanitic limestone 

that attain a maximum total thickness of 210 feet 

(64 m) on the west flank of the Laramie Range. 

Limestones are absent in the southern part of the 

area (Knight, 1929, p. 53).
222 A STUDY OF GLOBAL SAND SEAS

Primary Structures 

Stratification

The sandstone facies of the Casper Formation 

throughout a broad area characteristically consists 

of large trough cross-stratification, commonly 

termed "festoon lamination." This type of crossstrata consists of a repetition of two elements — 

erosion surfaces that form plunging troughs and 

thin concave-upward laminae that fill the troughs 

and conform largely to the shape of the trough 

floors (fig. 157).

The erosion troughs in the Casper differ greatly 

in size, ranging in width from 5 to 1,000 feet (1.5 to 

300 m), in length from 25 feet to a few thousand 

feet (8 m to a few hundred metres), and in depth 

from a few feet to 100 feet (30 m) (Knight, 1929, 

p. 59). The surface of each trough is cut across at 

one end by one or more overlying troughs, and so 

each trough has "the general shape of a long, 

shallow, scoop-like depression." The average inclination of trough surfaces is 10° -15°.

Most of the laminae that fill the erosion troughs 

form symmetrical sets, only a few being asymmetrical. The angles of inclination of the strata as determined by Knight (1929, p. 64) from about 800 readings were 15°-25° and averaged approximately 20°. 

Very few sets dipped toward the northeast quadrant; nearly all dip directions fell within the 220° 

arc from N. 35° W. southwestward to S. 75° E. 

(Knight, 1929, fig. 30).

FESTOON CROSS-LAMINATION, as described by Knight 

(1929), from sandstone of Casper Formation, Wyoming, U.S.A. 

This structure consists of overlapping, symmetrically filled 

troughs. (Fig. 157.)

Festoon Structures

The term "festoon cross-lamination" as originally used by Knight (1929) for cross-strata of the 

Permian and Pennsylvanian Casper Formation was 

applied to a type of trough cross-stratification filled 

either symmetrically or asymmetrically and having 

a large range in size.

The term "festoon-type cross-bedding" has been 

used by Tanner (1965, p. 564; 1966) for a structure 

apparently very different from the original "festoon 

lamination" of Knight. Tanner probably referred to 

the wedge-planar sets in the Jurassic Entrada 

Sandstone, which he stated "form additional evidence * * * of a wind origin." These sediment-filled 

troughs are superimposed one above another and 

overlap to form the characteristic festoon pattern. 

The genesis of this structure was attributed by 

Knight to marine processes. His evidence did not 

consist of characteristics of the cross-strata, 

however, and his chief reason was the close association of sandstones of the Casper with other 

facies that were of undoubted marine origin. Since 

that pioneer study, several geologists have contended that an eolian origin better explained 

various features of the sandstone, especially the 

minor structures.

Today, the origin of the festoon-type crossstratification in the Casper still remains an enigma. 

Probably the greatest deterrent to a widespread acceptance of the eolian origin has been the fact that 

no modern analogs displaying all the Casper's 

characteristics have been recorded. Point bars in 

major river systems seem to be the closest modern 

analog.

Festoon structures in river point bars were first 

reported and illustrated by Frazier and Osanik 

(1961) from the Mississippi River Delta. Sections 

transverse to current direction revealed welldeveloped festoons forming superimposed semicircular troughs filled with concave-upward strata 

comparable to those of the Casper. Principal 

differences were lenses of gravel and other coarse 

detritus, local accumulations of plant debris, and a 

lack of any very large channels (up to 1,000 ft (300 

m) wide and 100 ft (30 m) deep), such as occur in 

the Casper. Other examples of festoon structures in 

river sediments were recorded by Hamblin (1961), 

Harms, MacKenzie, and McCubbin (1963), Harms 

and Fahnestock (1965), and Williams (1968), an in-
ANCIENT SANDSTONES CONSIDERED TO BE EOLIAN 223

dication that they are fairly common in a fluvial environment.

How fluviatile large-scale trough cross-strata 

formed — by a single process of scour-and-fill related to large sand waves, or by two stages involving the filling through megaripples of previously 

cut troughs — has been controversial. Whatever the 

process, the resulting structures differ from the 

Casper-type structures in being considerably smaller, shallower, and less symmetrically filled. Trough 

structures preserved in dry river channels in South 

Australia are described (Williams, 1968, p. 138) as 

having relatively coarse texture — that is, coarse to 

very coarse sand with some granules and pebbles; 

locally, they include concentrations of sticks and 

leaves.

In modern eolian dune deposits, large trough 

structures seem to be rare, and those that are 

recorded are mostly shallow and not sufficiently 

overlapping to form festoon structures. Scattered 

channels were found at White Sands National 

Monument, New Mexico, in trenches parallel to the 

dune crest of a transverse dune (McKee, 1966, fig. 

7), but few were found in other types of dunes in 

that area. Similarly, in the coastal dune ridges of 

Brazil examined by Bigarella, Decker, and Duarte 

(1969) uncommon trough structures are shallow 

and lack well-developed festoon patterns.

In modern dune areas, festoon structure 

analogous to that of the Casper is most likely 

among coastal dunes where "blowouts" are abundant. Trenching, followed by detailed analysis of 

structures, apparently has not been attempted in 

this environment, but the shape, abundance, and 

size of blowouts in some regions (fig. 158) may account for large festoon structures.

Contorted Bedding

Numerous sets of trough cross-strata in the 

Casper Sandstone are crumpled and contorted on a 

huge scale, with folds having amplitudes up to 25 

feet (8 m) locally. This contortion of bedding apparently developed during or immediately after 

deposition of the sand; examples are numerous of 

highly deformed strata in one set that is directly adjacent to or overlying uncontorted sets (Knight, 

1929, p. 74).

The deformation of strata within the Casper 

troughs, resulting in large, locally developed folds 

oriented in many directions, was attributed by

BLOWOUT DUNES ALONG SOUTH SHORE of Lake Michigan, 

U.S.A. Photograph by R. C. Gutschick. (Fig. 158.)

Knight (1929, p. 27) to asymmetrical filling with 

sand. This process forms slopes above the angle of 

repose with a resulting creep down the oversteepened side and a tendency toward overturning 

the compressional folds. This process was believed 

by Knight to have required saturated sand; dry sand 

dune deposits were not considered favorable.

Recent experiments on contorted bedding 

(McKee, Douglass, and Rittenhouse, 1971, p. 373) 

showed, however, that a high degree of cohesion is 

necessary in forming structures of this type and 

that such cohesion occurs only in wetted sand 

(such as occurs in dunes that have been exposed to 

considerable rainfall or other moisture) and not in 

saturated sand. Coastal dunes of Brazil have been 

found to contain many contorted structures 

(Bigarella, Becker, and Duarte, 1969; McKee and 

Bigarella, 1972, p. 673), although most of these are 

much smaller than those of the Casper Formation.

Ripple Marks

Low wide ripple marks with parallel crests and 

troughs, oriented up and down the dip slopes of 

cross-strata, are relatively numerous in the Casper. 

These ripple marks are basically like those in the 

Coconino Sandstone of Arizona which were 

studied many years ago and described by the author 

(McKee, 1934b, p. 100; McKee, 1945, p. 323). Similar 

ripple marks have since been recorded from the De 

Chelly Sandstone, the Lyons Sandstone, and 

various others thought to be of eolian origin and 

discussed in this chapter.

Low-amplitude ripple marks in the Casper Formation were described by Steidtmann (1974, p.
224 A STUDY OF GLOBAL SAND SEAS

1837), as follows: "The ripple crests are relatively 

straight, parallel, slightly asymmetric, and spaced 

5.5 to 9.0 cm apart. Their heights are from 1.5 to 3 

mm; therefore, the ripple indices are 36 to 30." Both 

orientation of the ripples and the ripple indices are 

typical of eolian forms.

The ancient ripple marks just described resemble 

structures developed on the lee faces of various 

kinds of modern dunes formed when winds normal 

to the prevailing wind are active. Modern lee-side 

ripple marks have been observed on both 

barchanoid ridge and transverse ridge dunes at 

White Sands National Monument, New Mexico, 

(Chapter E, figs. 41C, 4lD), on reversing dunes at 

Great Sand Dunes, Colorado, on transverse dunes 

at Padre Island, Texas, and many others.

Interdune Deposits

Thin lenticular limestones that occur "along lowrelief truncation surfaces within the sandstone 

units" of the Casper Formation were reported by 

Hanley and Steidtmann (1973). These limestones, 

of local distribution, do not contain any marine 

macrofossils, are described as "ostracodal, peloidal, 

microsparites" and contain shrinkage cracks, gas 

cavities, and burrow traces.

From the description, these limestone lenses are 

interpreted herein as interdune deposits, rather 

than as tongues of normal marine or of lagoonal 

limestone. They are believed (Hanley and 

Steidtmann, 1973, p. 428) to have been "precipitated in small, shallow ponds in which environmental conditions were harsh because of fluctuation in water temperature, depth, and salinity."

Trace Fossils

Two varieties of trace fossils in the Casper Formation have been recorded (Hanley and others, 

1971). One variety consists of ribbonlike trails on 

the upper bounding surfaces of cross-strata that fill 

troughs of the Casper; the narrow trails intersect 

one another but do not branch. The second variety 

consists of tubular internal traces. Animals responsible for the first variety of trail have variously 

been assumed to be insects ("beetles"), arthropods, 

and annelids (Hanley and others, 1971, p. 1067); 

however, the main importance of these trails is that 

they indicate the probable depositional environment of the enclosing trough-type structures. Their

preservation could scarcely have occurred either in 

saturated sand or in dry loose sand (Hanley and 

others, 1971, p. 1067); a moist cohesive sand, possibly in a coastal environment, would have been 

most favorable. Development and burial of these 

trails probably were like those attributed to the invertebrate tracks of the Coconino (McKee, 1934b, p. 

108, pi. 13a).

Environment of Deposition

The broad regional environment in which the 

Casper Formation was deposited is readily determined. Criteria that seem convincing are available 

to permit an interpretation, and geologists have 

reached general agreement on paleogeographic 

controls (Knight, 1929; Steidtmann, 1974). Apparently, a mountain mass of some relief — the ancestral Front Range — extended from northwest to 

southeast across south-central Wyoming. Parallel to 

and northeast of those highlands was the margin of 

a seaway. Between the mountains and the sea was a 

broad coastal plain across which rivers transported 

much arkosic sediment. Evidence for the sea is furnished by limestones of the Casper containing 

many kinds of marine fossils (Miller and Thomas, 

1936; Thompson and Thomas, 1953).

The environment of deposition of the troughtype cross-stratified sandstones in the Casper 

clearly is related to the environment of the interbedded or closely associated marine limestones. 

Whether the sandstone is marine or eolian remains 

uncertain, mainly because no known analog in 

modern sediments completely matches the sedimentary structures observed in the Casper. Despite 

some evidence of dune deposition, an interpretation of the remarkably large-scale trough structure 

cannot be considered to be secure until a modern 

analog is found.

Summary of Criteria for Eolian Origin

Probably the most compelling evidence that 

sandstones of the Casper were formed through 

deposition by the wind is found in the relatively 

numerous eolian-type ripple marks with crests 

oriented parallel to the dip of foresets and with high 

ripple indices.

Further suggestion of eolian origin is furnished 

by surfaces of scattered coarse sand at the bottoms
ANCIENT SANDSTONES CONSIDERED TO BE EOLIAN 225

of cross-strata troughs. These deposits are interpreted as lag sand of interdune areas; thus, the 

troughs may be considered blowout phenomena, 

such as are common in many coastal dune fields 

and the fillings are blowout-type dunes. Supporting 

this concept is the very wide spread of cross-strata 

dip directions, characteristic of some coastal dune 

areas, such as the Lagoa dune field, Brazil (chapter E).

Results of experiments on settling velocities of 

light and heavy minerals made by Steidtmann 

(1974, p. 1840) are presented by him as corroborative evidence of an eolian deposition.

The presence of lenticular limestone beds locally 

distributed along truncation surfaces of crossstratified sandstones, their ostracodal peloidal texture, and their associated shrinkage cracks, gas 

cavities, and burrow traces strongly suggest an interdunal origin. Trace fossils, consisting of ribbonlike trails on upper bounding surfaces of crossstrata, indicate by their clear preservation that the 

sand was neither dry nor saturated at the time of 

burial but probably was moist and cohesive.

Various features of texture and structure are 

compatible with the concept of an eolian origin, but 

a conclusive test of genesis involving dissection of 

dune types on a modern coastal area, where troughtype structures are exposed, has not yet been made.

Rotliegendes of Northwestern 

Europe (Permian)

THE PERMIAN RED-BED sequence of northwestern Europe, normally referred to in Germany 

as the Rotliegendes, represents a great desert area 

of the past, and so merits discussion here. A careful 

analysis of these strata and a comparison with 

deposits of some modern desert areas were made by 

Glennie (1972, p. 1048). The following brief discussion is largely a synthesis of his work as it pertains 

to those sandstones in the Rotliegendes believed to 

be eolian. Additional information on the 

Rotliegendes and its environment of deposition is 

derived from Falke (1972) for central and western 

Europe and from Wills (1948, 1956) for England.

Distribution and Facies

Sedimentary rocks of the Rotliegendes extend 

over a wide area from Poland to France and

western Germany, from Scotland and southern 

Norway, across England and the Netherlands to 

central Germany (Kent and Walmsley, 1970). This 

Permian desert probably approached "in scale the 

area of the present Sahara, especially if one considers its possible former extension into North 

America," according to Glennie (1972, p. 1069), 

who has suggested that it may originally have been 

"between the paleolatitudes of roughly 10° N. and 

30° S.," as indicated by paleomagnetic data. Since 

then, the landmass containing this low-latitude 

paleodesert apparently has migrated by continental 

drift to its present position.

The thickness of the Rotliegendes is about 750 

feet (225 m) along its southern margin (Gill, 1967; 

Kent and Walmsley, 1970) and more than 5,000 feet 

(1,500 m) in the central part of the depositional 

basin in northern Germany (Kent and Walmsley, 

1970). These figures for distribution and thickness 

refer to the entire formation or desert environment 

and include several noneolian facies. The major environments or facies as classified by Glennie (1972, 

fig. 17) are dune, wadi, sebkha, and desert lake. 

Sandstones in the southern North Sea area that are 

attributed to a dune-sand origin have a thickness up 

to 600 feet (180 m) (Glennie, 1972, p. 1048).

Texture

Quartz grains in those sandstones of the 

Rotliegendes that are considered to be eolian 

generally range in size from fine to medium; locally 

some coarse grains occur. The finer grains are 

mostly subangular, whereas the coarser ones tend 

to be subrounded to rounded. "Impact fractures 

typical of those found in modern aeolian sands 

have been recognized during electron-microscope 

investigation of the lower Permian Penrith 

Sandstone" (D. B. Smith, 1972, p. 13). The cements 

are principally hematite and authigenic clay, and 

locally dolomite or anhydrite. Argillaceous matrix 

is lacking (Glennie, 1972, p. 1058).

Interbedded detrital sediments that comprise 

thin, roughly horizontal sets between crossbedded 

units of dune type are interpreted by Glennie (1972, 

p. 1061) as interdune sebkha deposits that are composed largely of fine to coarse sand. As in many 

modern interdune deposits, such horizontal beds 

are characteristically poorly sorted and are silty. 

They commonly contain many small irregular
226 A STUDY OF GLOBAL SAND SEAS

adhesion ripples but very little argillaceous 

material.

Primary Structures 

Stratification

Cross-stratified sandstones, interpreted as eolian, 

typically occur as large-scale planar types with 

steeply dipping (20° - 27°) foresets. Dip directions 

of laminae are relatively uniform, dips tend to increase upward, and truncated tops of sets are overlain by subhorizontal finely laminated sandstones 

(Glennie, 1972, p. 1058). In many places these dunetype laminae overlie other sand sequences that are 

considered to represent a wadi environment. Stereographic polar nets prepared by Glennie (1970, 

fig. 68) strongly suggest that both barchanoid 

(transverse) and linear (seif, longitudinal) dunes are 

represented in the sandstones believed to be eolian. 

Within barchanoid-type dunes, the dip attitudes of 

foresets are characteristically concentrated in a 

single, limited area which is in line with the 

predominant wind direction. In linear-type dunes, 

however, foreset dip directions are concentrated in 

two widely separated, nearly opposite directions 

(McKee and Tibbitts, 1964, p. 12). Borehole data 

plotted for the basal Permian "Yellow Sands of 

Durham," of Great Britain, show a form that, according to Smith and Francis (1967, p. 97-98, fig. 

18) "strikingly resembles" a seif dune, such as that 

developed under two alternating wind regimes 

postulated by Bagnold (1941).

The trend and pattern of cross-strata "in several 

basins of central and western Britain have shown 

that the sand [was] accumulated in those places in 

barchans" under easterly winds as described by D. 

B. Smith (1972, p. 13), but he further states that in 

northeastern England "east-north-east trending 

longitudinal dunes were present." Cross-strata dip 

directions in the Rotliegendes, according to Glennie 

(1972, p. 1061), suggest that seif dunes predominated in Britain and West Germany and that the 

barchanoid-type was prevalent in other areas (that 

is, away from the Variscan Mountains).

Adhesion Ripples

Interdune deposits on the Rotliegendes are thin 

zones primarily consisting of "small, irregular, and 

more or less horizontally-bedded adhesion ripples" 

(Glennie, 1972, p. 1061). Adhesion ripples are

defined as small irregular mounds or ridges formed 

where dry sand is blown onto a nearly horizontal 

humid surface and fixed there by surface tension. 

Laminae are concave upward.

Summary of Criteria for Eolian Origin

Large sequences of cross-stratified sandstone in 

the Rotliegendes have long been attributed to accumulations of sand by eolian processes, because 

their textural and structural properties are similar 

to those of modern dune deposits and because they 

are closely related to surrounding and interbedded 

deposits recognized as desert facies. These facies 

include wadis, desert lakes, and sebkhas. Few, if 

any, of the properties described for the 

Rotliegendes can individually be considered proof 

of a dune origin, yet in aggregate they present 

strong evidence. On the other hand, recent 

petrographic studies led Pry or (1971 a, b) to question this origin for some of the sandstones and to 

postulate a genesis in "a shallow marine environment" where sand was reworked by the sea and 

transported south westward.

Most eolian sands are characterized by dominantly subrounded frosted well-sorted grains and 

by lack of argillaceous matter. Such textural 

features are common in the Rotliegendes. Structures including well-laminated high-angle crossstrata are typical, but not indisputable, evidence. 

More compelling as evidence are the individual sequences that show upward progressions from 

subhorizontal to steeply inclined laminae and a 

record of interdunes shown by intraformational unconformities and by horizontally bedded adhesion 

ripples. Additional strong evidence furnished by 

cross-strata is their common occurrence as largescale planar types.

Statistical studies of dip directions on crossstrata, indicating a small spread in trends of depositional currents, offer evidence of eolian origin and 

also a means of differentiating between the lineartype dunes (with two nearly opposite clusters of 

readings) and the barchanoid-types (with a single, 

larger grouping of directional points).

Strongly suggesting a desert dune genesis is the 

association of large-scale dune-type cross-strata 

with evaporite basin deposits of anhydrite, halite, 

and red clay above and with probable wadi deposits 

of conglomerate, mudcracked clays, and flat-bedded sands below.
ANCIENT SANDSTONES CONSIDERED TO BE EOLIAN 227

Lower Mottled Sandstone 

(Permian?), England

ONE OF THE FIRST detailed studies of eoliantype sandstones, critically analyzed and studied in 

detail, was Shotton's 1937 investigation of the 

"Lower Bunter Sandstone," now commonly referred to as Lower Mottled Sandstone, of the Birmingham area in England. His work, which formed 

a model for many later studies, not only presented 

evidence for ascribing an eolian origin but also 

developed criteria for interpreting the type of dune, 

believed to be barchan. His report was a penetrating 

analysis of the manner in which dune structures 

are developed and the effect of various factors involved. His statistical study of cross-strata dip 

directions and discussion of their significance in 

terms of regional wind currents and dune migration 

paved the way for an understanding of the environment and history of eolian deposits in many other 

regions. The classic study by Shotton was 

published almost simultaneously with Reiche's 

pioneer work (1938) along similar lines — analysis 

of the Coconino Sandstone of Arizona.

Both because of its historic significance and 

because of the excellence of deductive reasoning 

with regard to a basic dune type, here classed as the 

barchanoid dune ridge, Shotton's work qualifies the 

"Bunter" for discussion in this publication. Nearly 

all data used herein are derived from Shotton's 

classic paper; additional important references are 

Wills (1948; 1956, figs. 2416) and Shotton (1956).

Distribution and Thickness

The Lower "Bunter" Mottled sandstone (Shotton, 1937, p. 535) "consists of nothing but sand," 

with no clay beds and no pebbles in the four areas 

of outcrop, west and northwest of Birmingham, 

England, where it was studied. These outcrops extended along a belt roughly 25 miles (40 km) northsouth and 10 miles (15 km) wide. A maximum 

thickness of 850 feet (260 m) for the formation is 

reported (Shotton, 1937, p. 536) from a borehole in 

the area studied. In other parts of the southern 

Cheshire basin, the same formation is known to be 

650 feet (217 m) thick.

Composition and Texture

The Lower "Bunter" Mottled Sandstone is 

formed almost entirely of quartz sand grains but includes some scattered feldspar grains (Shotton, 

1937, p. 535). The dull-red coloring of the rock is attributed to thin grain coatings of iron oxide, which 

is believed to be "the only cementation." The 

sandstone has "extraordinary uniformity," as confirmed by analyses of samples from 476 exposures. 

The average grain size was determined to be 0.2 

mm, with the median diameter ranging from 0.129 

to 0.410 mm; no particles are smaller than 0.05 mm 

or larger than 1 mm (Shotton, 1937, p. 552). The 

fineness of grain and high degree of sorting characterize the entire sandstone throughout the area examined.

Primary Structures 

Stratification

A systematic investigation of cross-stratification 

in the "Lower Bunter Sandstone," undertaken by 

Shotton and others, enabled Shotton (1937) to make 

a detailed description and careful analysis of its 

structures. Cross-strata in the formation are 

recorded as dominantly high angle, ranging between 20° and 30°, and are mostly large scale, forming tabular-planar sets up to nearly 100 feet (30 m) 

thick. Individual foresets are steepest in their upper 

parts and are truncated by low-angle erosion surfaces at their tops; they are tangential with the underlying bounding planes. Between sets of crossstrata low-angle erosion surfaces dip in a direction 

opposite that of the cross-strata. These low-angle 

planes are interpreted as windward-side dune surfaces.

Statistical measurements of cross-strata dip 

directions made at 476 exposures and consisting of 

1,142 readings furnished data for determining both 

current-direction vectors and the amount of spread 

involved in dip directions of each outcrop area 

studied. Using the mean direction of dip as representing the dominant wind direction, a regional 

wind from the east was determined. Calculating the 

size of arc represented by all readings in a particular area disclosed a considerable curvature in dune 

ridges to be typical. Hence, a barchanoid ridge, 

rather than a straight transverse-type ridge, is 

postulated for this formation.

Environment of Deposition

The sand desert with inferred barchanoid-type 

dunes of the "Bunter" Mottled Sandstone is interpreted by Shotton (1937, p. 550) as occupying an 

elongate strip west of a highland formed during the
228 A STUDY OF GLOBAL SAND SEAS

Hercynian orogeny. This highland "fulfilled the 

double function of abstracting moisture from the 

prevailing east wind, and of providing the material 

to build up the sand sea."

Between the postulated highlands to the east and 

the dune-type cross-strata of the "Bunter" are pebble and sand beds, interpreted as weathering 

deposits derived from the uplands and spread by intermittent streams across the lower slopes of the 

hills to the edges of the desert. These alluvial 

deposits, therefore, are considered the principal 

source of the dune sands. Despite some uncertainty 

in correlation of the fluviatile deposits with eolian 

strata (Shotton, 1937, p. 352) because no transition 

zone now exists, much evidence supports the relationship.

Summary of Criteria for Eolian Origin

Textural features of the Lower "Bunter" Mottled 

Sandstone (Shotton, 1937, p. 538) are comparable in 

all respects with the textures of sands in most 

modern dunes but show marked differences from 

the textures developed in many other depositional 

environments. Distinctive textural features are the 

fineness of grain, the high degree of sorting, and the 

absence of both coarse detritus and silt-clay particles.

Most compelling evidences of eolian origin are 

the size and type of cross-strata represented in the 

formation — high-angle large-scale tabular-planar, 

with long curving surfaces tangential to the bounding planes at their bases. The frequency distribution of the cross-strata dips suggests that the dunes 

were of the barchanoid-ridge type, migrating in a 

constant direction and accumulating one set upon 

another.

Frodsham Member of 

So-Called Keuper Sandstone 

Formation (Triassic), England

ONE OF THE MOST SUCCESSFUL attempts to 

interpret ancient deposits of probable eolian origin 

in terms of specific dune types, is D. B. Thompson's 

(1969) study of the Frodsham Member of the socalled Keuper Sandstone Formation (Triassic). For 

his investigation, cross-strata patterns recorded in 

sandstone of the Frodsham Member in West

Cheshire, England, were compared with structures 

exposed by trenching in modern dunes of New 

Mexico in the United States (McKee, 1966).

The sandstone study by Thompson represents a 

detailed description of a relatively small but distinctive eolian-type sandstone and presents a rather 

convincing case, through cross-strata analysis, for 

the presence of dome-shaped dunes that had not 

previously been recognized in ancient rocks. The 

method of tracing major bounding erosion surfaces, 

formed at the base and top of dunes, and of recording the patterns of cross-strata sets between these 

surfaces, is an effective means of establishing the 

diagnostic structural features of various dune types 

(D. B. Thompson, 1969). Furthermore, the relationship of these dune sands to other closely associated 

sedimentary facies illustrates a complex set of 

depositional environments.

The Frodsham Member of the so-called Keuper 

Sandstone Formation, as discussed here, is a 

relatively thin (as great as 55 m or 170 ft) member 

of red fine-grained sandstone which forms the upper part of a sequence that contains medium- to 

coarse-grained sandstones and conglomeratic 

sandstones interbedded with other members composed of soft fine-grained sandstone (table 24; D. B. 

Thompson, 1970a, b). The Frodsham Member is 

present in about 2,000 km2 (1,240 mi2) of the 

Cheshire and East Irish Sea Basins, but the 

Frodsham [facies (sensu stricto)] with domeshaped and transverse dunes apparently is 

restricted to a small area near Frodsham and Runcorn in northwest Cheshire, where D. B. Thompson 

(1969) made his detailed studies.

Composition and Texture

The eolian-type sandstone of the Frodsham 

Member (D. B. Thompson, 1969, p. 272) consists 

dominantly of quartz sand with sparse grains of 

feldspar and little or no mica. The electron 

microscope enabled the identification of authigenic 

feldspar (B. Waugh, oral commun. to D. B. 

Thompson, 1975). In associated beds believed to be 

fluviatile and lacustrine, feldspars are much more 

numerous and mica flakes are common; clay 

minerals are illite and kaolinite.

The roundness of quartz grains in the "Frodsham 

facies" is described as "subangular to subrounded" 

and grain-size analyses show (D. B. Thompson,
ANCIENT SANDSTONES CONSIDERED TO BE EOLIAN 229

TABLE 24 — Age, thickness, composition, and postulated depositionoJ environments of units forming Lower "Keuper" and underlying sandstones in West Cheshire, England

[Prepared by D. B. Thompson, University of Keele, 1975]

Age Informal formations

Scythian "Keuper"

?Anisian Waterstones

Scythian <

Lower "Keuper"

Sandstone

(as much as

220 m thick)

Defined members

Frodsham Soft Sandstone Member

Delamere Pebbly Sandstone Member

Thurstaston Soft Sandstone Member

Maximum 

thickness 

(metres)

55

85

45

Depositional 

environment

Intertidal and ?fluvial.

Eolian: Sand sea rather

than coastal dunes.

Fluvial low sinuosity.

Eolian and fluvial.

Scythian

?Scythian

Buriter

Upper Mottled 

Sandstone

Bunter 

Pebble beds

Alderley Conglomerate Member

Possible unconformity

34 (not Fluvial low sinuosity, 

always 

present)

950 Eolian and fluvial;

fluvial mostly near base.

1969, table 3) that in most sections the sand is dominantly fine grained, and in some, mostly medium 

grained. Very few grains in any sections are above 

or below these size grades, thus attesting to the high 

degree of sorting in the sandstone. Most grains have 

coatings of diagenetic red ferric oxide, deposited 

presumably by circulating ground waters (D. B. 

Thompson, 1969, p. 272).

The attributes of composition and texture just 

described are all consistent with an eolian origin, 

but they reflect genesis and transportation rather 

than deposition. The presence of lenses and other 

concentrations of "millet seed" sand has been 

viewed by various geologists as evidence of wind 

deposition; however, according to D. B. Thompson 

(1969, p. 270) some entire beds in the so-called 

"Keuper Sandstone Formation," dominated by such 

sand, also include large pebbles and clay galls.

Primary Structures 

Stratification

The "Frodsham facies" — the probable eolian 

part of the "Keuper Sandstone Formation," as 

described by D. B. Thompson (1969, p. 273, 285) — 

consists mostly of large sets of cross-strata with 

very long laminated foresets, some of which extend 

downward and laterally into flat-bedded and ripple-bedded bottomsets of siltstone and mudstone. 

Major bounding planes of erosion mark tops and

bottoms of cosets that may include numerous tabular-planar and wedge-planar sets. "Shallow trough 

structures are present * * * but form only a small 

proportion of the structures present;" most of them 

occur directly below major erosion surfaces.

From the cross-stratification patterns analyzed, 

D. B. Thompson (1969, p. 284) recognized "at least 

eight vertically and laterally overlapping eolian 

dunes," six of which were of the dome-shaped type 

with a tendency toward the transverse type. The 

beveled tops of cross-strata sets and other structural 

features as described for dome-shaped dunes at 

White Sands (McKee, 1966) suggest that the 

degradation of the transverse dunes by very strong 

winds is responsible for features described in the 

"Keuper" dome-shaped dunes.

Penecontemporaneous contorted structures are 

not uncommon in tabular-planar and wedge-planar 

sets of cross-strata in the "Frodsham facies of the 

Keuper Sandstone." "Simple concentrically folded 

laminae," several feet thick and overlain by undisturbed strata, closely resemble the sand-drag 

type (McKee, Reynolds, and Baker, 1962b). Other 

varieties, which are numerous, apparently are like 

types attributed to dry and to damp sand (D. B. 

Thompson, 1969, p. 285).

Dip-direction vectors, indicating paleocurrent 

summaries for 10 dunes analyzed in the "Frodsham 

facies," were determined by D. B. Thompson (1969,
230 A STUDY OF GLOBAL SAND SEAS

p. 278). The resulting wind roses show a general 

westerly wind movement and a spread expectable 

for dunes, such as dome-shaped and transverse 

type, formed under a unidirectional wind regime.

Environment of Deposition

The eolian-type sandstone, referred to as the 

"Frodsham facies" by D. B. Thompson (1969, p. 

286), was interpreted by him — largely on the basis 

of cross-strata analysis — to consist principally of 

dome-shaped dunes, attributed to strong winds, 

and, to a lesser extent, of transverse ridge dunes 

from more moderate breezes. Both dune types 

result from unidirectional paleowinds that, as 

determined from cross-strata dips, came from the 

east. Fluctuating crosswinds were largely from the 

southeast and southwest.

Various lithofacies associated with the "Frodsham facies" were recognized and interpreted by 

D. B. Thompson (1969, p. 267): interbedded red 

mudstones, red-brown shaly mudstones and 

siltstones, all considered to be of fluvial and 

lacustrine origin and possibly formed between 

dunes as interdune ponded deposits. Other 

deposits, with clay galls, mica concentrates, and 

argillaceous units, are also undoubtedly of subaqueous origin. Brown shaly flat-bedded and ripplebedded strata among the cross-stratified sandstones 

resemble modern interdune deposits recorded 

elsewhere.

The "Keuper" waterstones immediately above 

the Frodsham Member are partly intertidal, suggesting that the dome-shaped transverse dunes 

might represent a coastal sand belt. The negative 

skew of the grain-size distribution of some of the 

samples suggests derivation from a beach. On the 

other hand, the basinwide areal extent and geometry of the Frodsham Member suggests the existence 

of a sand sea followed by a basinwide transgression.

Summary of Criteria for Eolian Origin

The part of the "Keuper Sandstone Formation" 

called the "Frodsham facies," which is believed to 

be composed dominantly of dome-shaped and 

transverse dunes, is intimately associated with 

facies representing contrasting depositional environments. The closeness of several distinct facies 

may lead to misinterpretations and confusion 

where differentiation is not carefully made.

To separate eolian and noneolian deposits, D. B. 

Thompson (1969, p. 271) used five criteria, which, 

"when taken as a whole rule out the possibility of 

fluvial or other environmental interpretations": (1) 

the recognition of groups and arrangements of sedimentary structures of specific dune types; (2) the 

presence of very large sets (up to 13 m) of finegrained cross-stratified sandstone; (3) uniformly 

fine grained texture of the sandstone; (4) a general 

absence or virtual absence of feldspar and mica, 

even though these minerals are common in the 

associated fluvial lithofacies; and (5) accompanying 

concentrations of "millet seed" sand.

The first two and the fourth of Thompson's criteria seem to be compelling positive evidence of 

eolian deposition; the third and fifth, although compatible, may also occur in some other environments. Important additional evidence of dune environment is the recognition in the stratification of 

bounding surfaces of erosion, formed through interdune processes. Furthermore, the interbedding of 

eolian- and fluviatile-types is strongly suggestive of 

blown sands overwhelming the surfaces of river 

flood plains or of ponded (sebkha) areas.

Barun Goyot Formation

(Upper Cretaceous),

Mongolia

UPPER CRETACEOUS STRATA called the 

Barun Goyot Formation, formerly the Upper 

Nemegt Beds, in the northern part of the Gobi 

Desert of Mongolia, are reviewed herein because 

they include exceptionally extensive interdune 

deposits and contain a large and varied nonmarine 

fauna for a paleodesert environment. The 

sandstone of this formation is considered to be 

eolian not only because of characteristic features of 

structure and texture attributed to wind deposition 

in many other deposits but also because of its 

associated facies and its abundant nonmarine 

fauna.

Continental deposits of Late Cretaceous age in 

central Asia have been known for many years and 

have received considerable fame because of the 

dinosaur and mammalian remains obtained from 

them during a series of paleontological expeditions 

by American, Soviet, and Polish-Mongolian groups 

in the 1920's, 1940's, and 1960's, respectively. The
ANCIENT SANDSTONES CONSIDERED TO BE EOLIAN 231

data on sedimentology reviewed in the following 

synthesis of the Barun Goyot Formation are largely 

from the descriptions and interpretations by 

Gradzinski and Jerzykiewicz (1972,1974a, b).

Distribution and Thickness

Dune-type deposits of the Barun Goyot Formation are widely exposed in the Nemegt Basin, an 

east-trending graben in the Gobi and adjoining 

areas of central Asia. The formation has been 

studied in detail in two main places — the Nemegt 

locality, to the west, and the Khulsan locality, to the 

east, covering an area of "about 100 sq. km [260 

mi2]" (Gradzinski and Jerzykiewicz, 1974b, p. 113).

The total thickness of the Barun Goyot Formation has been given by Gradzinski and Jerzykiewicz 

(1974a, p. 252) as "about 100 meters" (300 ft) and 

described as grading upward into "fluvial deposits" 

of the Nemegt Formation "about 400 m [1,200 feet] 

thick." The Barun Goyot Formation, however, is 

composed only in part of large-scale cross-strata, 

considered to be eolian, and much of its thickness 

comprises interdune deposits of other facies.

Composition and Texture

The results of grain-size distribution studies by 

Gradzinski and Jerzykiewicz (1974a, p. 263; 1974b, 

p. 122, table 1, fig. 5) are summarized in their table 

of statistical parameters and in histograms. From 

these analyses, sand of the eolian-type cross-strata 

is shown to be mainly fine- or medium-grained, 

moderately sorted and slightly skewed on the positive side.

Studies of sphericity, roundness, and surface texture were also made of sand grains from each principal facies. Subrounded and rounded grains predominated in most samples, although some 

subangular and some well-rounded grains were 

noted (Gradzinski and Jerzykiewicz, 1974a, p. 257). 

Mean values for sphericity ranged from 0.66 to 0.72. 

Surface frosting was recorded for 21 - 45 percent of 

the grains, and both ridges and pitting were not uncommon on sands of the large-scale cross-strata.

Composition of the sandstone, calculated from 

eight analyses, was 69-82 percent quartz, 18-28 

percent feldspar, and 1 — 4 percent other minerals, 

including mica and heavy minerals, principally 

epidote. The feldspar is mostly fresh but locally 

weathered, and in some samples fresh and

weathered are mixed together (Gradzinski and 

Jerzykiewicz, 1974a, p. 253).

Primary Structures 

Stratification

In the Barun Goyot Formation, five sediment 

types, based on differences in both lithology and 

primary structures, were recognized by Gradzinski 

and Jerzykiewicz (1974b). Of these types, the 

"mega cross-stratified units" and possibly the 

"massive, 'structureless sandstone' " are probably 

of eolian origin. The "flat-bedded sandstones," 

"diversely stratified sandstones," and "alternating 

claystones and sandstones" probably are mostly or 

entirely interdune deposits.

The "mega cross-stratified sandstone," as 

described (Gradzinski and Jerzykiewicz, 1974a, p. 

259), seems to correspond in all essential structural 

features to the large-scale high-angled cross-strata 

of other sandstones considered to be of eolian-type 

that are discussed in this chapter. Its cross-strata 

dip at high angles (generally 25°-30°, maximum 

36°). They are mostly tabular planar, less commonly wedge planar, and rarely trough shaped. 

Bounding planes between sets of cross-strata are 

mostly even and horizontal for long distances and 

form sets of cross-strata 3-10 m (9-30 ft) thick, 

mostly greater than 5 m (15 ft). The length of individual cross-strata commonly is considerable — 

several tens of metres (90 ft or more). Dip directions are relatively constant, with variations less 

than 20°.

Because the "mega cross-stratified sandstones" 

grade both laterally and vertically into "massive, 

'structureless' sandstones," some of the latter may 

also represent wind-deposited sand, but internal 

structures in them have largely been destroyed. 

"Indistinct traces of internal structures are visible 

in some beds * * * [including] horizontal lamination 

and deformational structures of overturned folds" 

(Gradzinski and Jerzkiewicz, 1974b, p. 134). Thus, 

slumping or other types of contortion may have 

contributed to eradication of primary structure.

Contorted Bedding

Within sets of large-scale cross-strata — between 

sets that are undeformed — are overturned folds 

and other varieties of contorted and disrupted bedding indicating a penecontemporaneous origin of
232 A STUDY OF GLOBAL SAND SEAS

the structures (Gradzinski and Jerzykiewicz, 1974a, 

p. 263, fig. lla). Deformational structures also are 

reported from the "structureless" sandstone facies 

suggesting that processes of contortion may be 

responsible for the partial or complete obliteration 

of primary structures in parts of the Barun Goyot 

Formation (Gradzinski and Jerzykiewicz, 1974a, p. 

274; 1974b, p. 134).

Detailed descriptions of the "contorted and disrupted" cross-strata in the Barun Goyot Formation 

are not available; thus, it cannot yet be determined 

whether they are structures resulting from loading 

in loose sand, of the types described from Brazil 

(McKee and Bigarella, 1972, fig. 4), or whether they 

were formed by avalanching of sand deposits, as 

demonstrated in laboratory experiments (McKee, 

Douglass, and Rittenhouse, 1971, p. 372). If the 

Barun Goyot sands include overturned folds or 

overthrusts, the noncohesive or cohesive nature of 

the sand at the time of deformation might be determined, and, from this information, inferences could 

be made concerning the dryness or wetness of the 

environment.

Interdune Deposits

Strata interpreted as interdune deposits are 

abundantly represented in the Barun Goyot Formation. They consist of facies referred to by 

Gradzinski and Jerzykiewicz (1974b, p. 136) as 

"diversely stratified sandstones" and "alternating 

clays tones and sandstones." The first of these types 

occurs almost exclusively in the lower part of the 

formation, where it fills erosion channels as much 

as 3 m (9 or 10 ft) wide, scoured in the large-scale 

cross-strata of eolian type. The "alternating 

claystones and sandstones," in contrast, are mostly 

sheetlike, horizontal or wavy strata that interfinger 

with the eolian-type large-scale cross-strata and, 

therefore, were formed contemporaneously with 

them.

Textural and structural characteristics of the 

"diversely stratified sandstones" are (1) the common inclusion of small, locally derived pebbles, (2) 

the incorporation of a few large foreign pebbles and 

cobbles and numerous skeletal remains of vertebrate animals, (3) poorly sorted sandstones, (4) 

common trough-type cross-strata, (5) wedging of 

bedding units within short distances, (6) large 

variation in the dip directions of cross-strata, and 

(7) the filling of erosion pockets and scoured surfaces (Gradzinski and Jerzykiewicz, 1974b, p. 134). 

All these features suggest deposition by stream currents.

The facies described as "alternating claystones 

and sandstones" consists of "quiet water" deposits 

as indicated by bedding that is commonly flat or 

wavy, a scarcity of crossbedding, truncation of underlying eolian-type cross-strata, strong deformation of mud layers, and deformational features in 

sand, such as load casts, disrupted sandstone beds, 

and isolated sandstone blocks.

An additional facies of the Barun Goyot Formation, referred to as "flat bedded sandstone" by 

Gradzinski and Jerzykiewicz (1974b, p. 125), occurs 

mostly in the upper part of the formation and probably represents a major change or shift in environment following eolian deposition. It consists of 

units a few metres thick composed mostly of 

sandstone, with some siltstone and sandy 

clays tone. Bedding is largely horizontal or low 

angle (2°-5°). The low-angle beds occur between 

horizontal sets and commonly flatten laterally. Erosion channels are rare. This facies is interpreted as 

playa type (Gradzinski and Jerzykiewicz, 1974b, p. 

129-140).

Fauna

No other eolian-type sandstone has produced so 

rich and varied a fauna as has the Barun Goyot of 

central Asia. From the sandstones of this formation 

"several specimens of dinosaurs, very numerous 

dinosaur eggs, a few crocodiles, several tortoises, a 

pterosaur, about 80 specimens of lizards, about 50 

specimens of mammals .* * * were found within a 

few weeks in the Khulsan and Nemegt localities" 

(Gradzinski and Jerzykiewicz, 1974b, p. 140).

Most of these fossils were found in nondune 

facies — that is, in deposits believed to be interdune consisting of various water-deposited sediments, especially those attributed to intermittent 

streams and lakes. However, in the large-scale 

cross-strata of dune-type sandstone, a few dinosaur 

skeletons and numerous dinosaur eggs have been 

found. Furthermore, in the massive "structureless" 

sandstones "in the immediate neighborhood of 

mega cross-stratified units," nearly complete 

dinosaur skeletons and many intact dinosaur eggs 

were found. The distribution of these fossils clearly 

seems to have been controlled by ecological considerations — the wet or moist vegetated interdune
ANCIENT SANDSTONES CONSIDERED TO BE EOLIAN 233

areas being far more favorable, both for the living 

fauna and for its preservaiton than the bare dune 

environment (Gradzinski and Jerzykiewicz, 1974b, 

p. 141).

Environment of Deposition

Interpretation of the depositional environments 

represented in the Barun Goyot Formation, supported by a considerable amount of evidence, was 

presented by Gradzinski and Jerzykiewicz (1974a, 

p. 272). The thick units of large-scale cross-strata 

(termed "mega cross-stratified units") are considered, principally on the basis of texture and 

structure, to have formed as wind-deposited dunes. 

Furthermore, from the direction and narrow spread 

of cross-strata dip directions, they are believed to 

have resulted from unidirectional, westerly winds 

and to have been primarily of the transverse-ridge 

dune type.

Interdune deposits of at least two varieties are interspersed within the windblown sands. Some of 

these interdune deposits apparently represent a 

fluvial variety, formed by flooding of interdune 

areas; they include both "upper flow regime" sands 

(largely horizontal beds) and. "lower flow regime" 

types. These deposits— the "diversely stratified 

sandstones" of Gradzinski and Jerzykiewicz (1974b, 

p. 139) — include many gravels, channel-fill sediments, wavy laminae, trough bedding, and other indicators of current action.

A second variety of interdune deposits consists 

of alternating claystones and noncrossbedded 

sandstones. These strata, deposited synchronously 

with the eolian sandstones, probably formed in intermittent lakes (Gradzinski and Jerzykiewicz, 

1974b, p. 136, 138).

The relatively great thickness, 2-4 m (6-12 ft), 

of both fluvial-and lacustrine-type interdune units, 

suggests either that dune migration and burial of interdunes was slow or that interdune sedimentation 

was much more rapid than for other ancient eolian 

sandstones described herein. The clear evidence of 

ponding and the abundance of fossil vertebrate remains suggest considerable vegetation in the interdune area.

Summary of Criteria for Eolian Origin

Evidence that large-scale high-angle cross-strata 

("mega cross-stratified units") of the Barun Goyot

Formation were wind deposited was summarized 

by Gradzinski and Jerzykiewicz (1974a, p. 272; 

1974b, p. 137) — the considerable thickness of individual sets, the high-angle dips of most crossstrata, the tabular-planar form that predominates 

among crossbedding sets, and the wide, even form 

of major bounding surfaces. Furthermore, the 

relatively constant dip direction of cross-strata and 

the lateral continuity of sets strongly suggest that 

the sandstone is formed of dunes of the transverse 

ridge type developed under the influence of 

unidirectional winds.

Textural features — fine- to medium-grain size, 

moderate sorting (good to fair on the Payne scale), 

and common grain-surface features including frosting and pitting— are all characteristic of most 

modern dune deposits.

Additional data bearing on the environment of 

deposition are the associated and intertonguing 

deposits of flat-bedded and wavy-bedded sands and 

muds, the thin conglomerate beds, the abundant 

nonmarine fauna (including dinosaur skeletons and 

eggs), and other features of interdune deposits that 

are interspersed among typical dune-type 

sandstones.

Botucatu and Sambaiba

Sandstones of South America

(Jurassic and Cretaceous)

By JOAO J. BIGARELLA

THE BOTUCATU SANDSTONE of Brazil constitutes one of the world's largest and most 

widespread sequences of sandstone of probable 

eolian origin (fig. 159) —an extent of more than 1.3 

million km2 (800,000 mi2). This sandstone not only 

occurs throughout the Parana Basin (States of Sao 

Paulo and Parana), but also extends beyond this 

basin's present edge into the States of Mato Grosso 

and Minas Gerais. Probably, the Botucatu 

Sandstone originally connected with similar 

sandstones of the Parnaiba Basin in northern Brazil 

(States of Maranhao and Piaui). The present distribution of these sandstones is shown in figure 159.

In northern Brazil, the Sambaiba Formation of 

the Parnaiba Basin is considered to be equivalent to 

the Botucatu sequence. This formation is composed 

of large-scale crossbedded sandstones, alternating 

with probable subaqueous deposits.
234 A STUDY OF GLOBAL SAND SEAS

INDEX MAP SHOWING OUTLINES OF AREAS 

A AND B

48° 44°

600 KILOMETRES

0 300 MILES 

Scale is approximate

30°

34°

OUTCROPPING AREAS OF SELECTED MESOZOIC eolian sandstones (dark stipple) in South America: A, Sambaiba Sandstone; B, 

Botucatu Sandstone. (Fig. 159.)

The Botucatu Sandstone, first described by 

Gonzaga de Campos (1889), includes all large-scale 

cross-stratified sandstone units intercalated with or 

underlying the Serra Geral basaltic lava flows. 

Another sequence of large-scale cross-stratified 

sandstones of probable eolian origin overlies 

basaltic flows in the States of Mato Grosso, Sao 

Paulo, and Parang (fig. 159). Some authors have

designated it as the Caiua Sandstone (Washburne, 

1930; Maack, 1941), but others (Almeida, 1954) consider it to be a continuation of the Botucatu 

Sandstone.

The thickness of the Botucatu Sandstone is 

generally 10- 20 m (30-65 ft) but is locally more 

than 30 m (100 ft).
ANCIENT SANDSTONES CONSIDERED TO BE EOLIAN 235

The Botucatu Sandstone was long considered to 

be Triassic-Jurassic in age. However, radiometric 

age determinations of the associated and intercalated basaltic rocks indicate an average age of 

120-130 m.y. for the lava flows (Cordani and Vandoros, 1967), and so its age is now considered to be 

Late Jurassic -Early Cretaceous.

Facies

The sandstone facies of the Botucatu, with largescale cross-stratification considered to be eolian, is 

in some places interbedded with another facies, the 

Piramboia, believed to be fluviatile (Pacheco, 1913). 

This fluviatile facies generally occurs stratigraphically below eolian sandstones and probably represents intermittent stream deposition in small basins 

without outlet.

Another supposed fluviolacustrine or playa-lake 

sequence, which is interbedded with the large-scale 

crossbedded eolian sandstones of the Botucatu, has 

been called Santana facies (Almeida and Barbosa, 

1953, p. 64). "The Santana facies contains a Conchostraca (branchiopod) assemblage consisting of 

Bairdestheria barbosai; Palaeoiimnadia petrii; 

Euestheria mendesi; Pachecoia acuminata; P. 

rodriguesi; Candonopsis pyriformis candona?; 

Estherieila sp."

Sandstones of probable fluviatile origin occur in 

the lowermost part of the Botucatd sequence and 

are interbedded with the large-scale cross-stratified 

sandstones of probable eolian origin. They crop out 

in many places in the States of Parana, Sao Paulo, 

and Minas Gerais.

The equivalent of the Botucatu Sandstone is 

known in Uruguay as the Tacuarembo Sandstone 

and in Paraguay as the Misiones Formation. 

However, not all the strata mapped as Misiones 

Formation (Eckel, 1959) are actually equivalent to 

the Botucatu Sandstone.

Texture

In the Parana Basin of Brazil, for a distance of 

2,500 km (1,550 mi) along the eastern belt of outcrops, 99 samples of eolian-type Botucatu 

Sandstone were collected for textural studies. 

Because most samples contained tails of finegrained material (silt and clay) introduced by 

weathering or by postdepositional impregnation, 

grain-size distribution was recalculated, based on 

quartz grains, to be 0.062 mm. The recalculated

samples contain three or four textural classes with 

more than 1 percent frequency. In the Botucatu 

Sandstone three classes predominate in much of the 

formation, but close to source areas in the 

crystalline shield many of the samples include four 

textural classes. Sandstones — supposedly 

fluviatile but intercalated in the dune sequence — 

contain as many as seven textural classes.

In the Botucatu paleodesert, the modal class, according to recalculated analyses, is mostly finegrained sand (0.125—0.25 mm) and includes some 

medium-grained sand (0.25—0.5 mm). The 

medium-grained sand is mainly near the crystalline 

shield source area; only in a few places is it downwind, toward the central part of the paleodesert.

The average mean diameter of recalculated samples of large-scale cross-stratified Botucatu 

Sandstone decreases southward from 0.209 mm in 

Minas Gerais, to 0.183 mm in Sa*o Paulo and to 0.178 

mm in Parana; it also decreases northward from 

0.233 mm in Rio Grande do Sul to 0.215 mm in Santa Catarina. In both series grain size decreases 

downwind from crystalline areas. The sandstones 

of the northern area of the Botucatu paleodesert are 

generally finer grained (0.186 mm) than those in 

the southern area (0.218 mm). The northern and 

southern areas were under the influence of 

different paleowind regimes. The wind in the 

southern area was stronger, as revealed by larger 

cross-strata, larger sand grains, and larger average 

mean grain-size diameter.

The Botucatu Sandstone is dominantly moderately to well sorted. Sorting mostly is progressively 

better downwind — that is, away from the 

crystalline shield areas. Trask sorting coefficients 

(So) decrease from Minas Gerais (So = 1.44) to Sao 

Paulo (So =1.33) and Parana (So =1.32). They 

decrease also from Rio Grande do Sul (So =1.46) to 

Santa Catarina (So =1.39). The samples from the 

northern area of the Botucatu paleodesert are 

slightly better sorted than are those from the 

southern area. As the mean grain-size diameter increases, the sorting coefficient becomes poorer.

Ventifacts are scattered along some zones of the 

Botucatu Sandstone.

Primary Structures 

Stratification

Cross-stratification typical of eolian slipface 

deposits is the outstanding sedimentary structure of
236 A STUDY OF GLOBAL SAND SEAS

the Botucatu Sandstone and is abundant in almost 

all outcrops. The size of sets may range from small 

to large in the same section. Large sets of crossstrata with lengths of dipping beds of 30 m (100 ft) 

or more and heights of about 12-15 m (40- 50 ft) 

occur in many localities.

Environment of Deposition

Paleowind circulation in the Botucatu paleodesert was investigated by Almeida (1953, 1954), 

Bigarella and Salamuni (1961), and Bigarella and 

Oliveira (1966). Measurements in the correlative 

Sambaiba Formation of northern Brazil were made 

by Bigarella, Montenegro, and Coutinho (unpub. 

data).

Crossbedding dip directions in the southern part 

of the Botucatu paleodesert (Santa Catarina and Rio 

Grande do Sul in Brazil, and Uruguay) indicate that 

paleowinds blew from the west and west-southwest. These winds were deflected toward the north 

in southern Paraguay. In the northern part of the 

Botucatu paleodesert (Mato Grosso, Goias, Minas 

Gerais, Sao Paulo, and Parana in Brazil, and part of 

Paraguay), crossbedding measurements indicate 

mean paleowind trends from the north or northnortheast, representing return tradewinds. In 

Parana, these northerly paleowinds were then 

deflected toward the west.

In the Botucatu paleodesert, southern air masses 

moved northward, leaving their traces mainly in 

Parana and Sao Paulo, and, less frequently, the 

northern air masses penetrated the southern areas; 

so, cold air masses and warmer ones probably conflicted. Rainfall was therefore probably greatest 

north of Santa Catarina. This postulate is supported 

by deposits in that region of the Piramboia and Santana facies, which seem to represent subaqueous 

environments. Such deposits, which are at the base 

of, and interbedded with, supposed eolian deposits, 

are common in Parana and Sao Paulo but decrease 

in abundance northward. Waterlaid deposits are 

rare in the southern part of the Botucatu 

paleodesert (Bigarella and Salamuni, 1961).

Crossbedding measurements in Parana have a 

very low consistency ratio, probably mostly the 

result of the conflict between opposing wind directions, westerly and northerly. The area of conflict 

between these winds extends westward into 

Paraguay.

Crossbedding measurements of the Sambaiba 

Formation, which is the Botucatu Sandstone 

equivalent in northern Brazil, indicates that prevailing winds responsible for sand movement were 

the southeasterly tradewinds. The Botucatu and 

Sambaiba eolian sandstones were deposited in a 

low-latitude paleodesert.

Summary of Criteria for Eolian Origin

Criteria responsible for considering major parts 

of the Botucatu and Sambaiba Sandstones to be of 

eolian origin consist of sedimentary structures and 

grain textures. The most compelling structural evidences are the very large scale and the high angles 

common to much of the wedge-planar and tabularplanar cross-stratification. Textural features are entirely compatible with this interpretation. 

Throughout a large part of Brazil, the great extent 

of moderately sorted to well-sorted sand, which is 

dominantly of fine to medium size, can be explained by few environments other than eolian. 

Additional evidence of genesis is furnished by scattered ventifacts.

Cave Sandstone and

Similar Sandstones of

Southern Africa (Triassic)

By JOAO J. BIGARELLA

THE SUCCESSION OF GONDWANA BEDS in 

southern Africa is known as the Karroo System. 

The basal beds, named the Dwyka Group, are interpreted as glacial and periglacial deposits. The 

uppermost sedimentary beds are believed to have 

been deposited under arid or semiarid conditions, 

although much of the sand was deposited in subaqueous environments. These uppermost strata are 

known by various names — Cave Sandstone in the 

Republic of South Africa, Botswana, Lesotho, and 

Swaziland; the Bush veld Sandstone in the central 

Transvaal; Etjo Sandstone in South-West Africa; 

and the Forest and Nyamandlovu Sandstones in 

Rhodesia. They are mostly Triassic in age but probably represent a range of about 75 m.y.

These sandstones are conformably overlain by or 

intercalated in their upper parts with lavas of 

various compositions. Sedimentation continued
ANCIENT SANDSTONES CONSIDERED TO BE EOLIAN 237

after the first outpourings of lava. The comparatively thin layers of sandstone between flows 

indicate the absence of a major unconformity. In 

places, as in northern Transvaal, the prelava 

sandstone surface is very uneven, possibly reflecting an uneven dune topography or contemporaneous erosion by running water. The main outcrops of the sandstone in Lesotho were studied by 

Beukes (1970), who divided the sequence into three 

parts: lower and middle massive to thick-bedded 

sandstones, and an upper sandstone containing 

large-scale cross-stratification. In Rhodesia the upper part is called the Nyamandlovu Sandstone, and 

its cross-strata are generally considered to be of 

eolian origin.

Distribution and Thickness

The Cave Sandstone and equivalents in the 

Republic of South Africa, Lesotho, and Rhodesia 

conformably overlie a succession of red and purple 

mudstones, shales, and sandstones. The Cave 

Sandstone attains a maximum thickness of about 

350 m (1,150 ft) in the Orange Free State and in 

northern Transvaal, but in most other places, it is 

less than half this thickness. In Rhodesia it is 

relatively thin; in South-West Africa it generally is 

60-150 m (200- 500 ft) thick and attains about 600 

m (2,000 ft) in maximum thickness.

Composition and Texture

The composition of the Cave Sandstone differs 

considerably from place to place. In the upper 

cross-stratified part, detrital grains include 60-73 

percent quartz and 1.0-9.3 percent feldspar. 

Miscellaneous matrix ranges from 10 to 21 percent 

(Beukes, 1970). The remainder of the rock consists 

of rock fragments, silica cement, and heavy 

minerals.

The mean grain size of the cross-stratified 

sandstones ranges from 0.170 mm on the northwestern side of Lesotho to 0.080 mm on the 

southeastern side.

Primary Structures 

Stratification

Along the Huab Valley in South-West Africa, 

and also in parts of northern Transvaal, dunelike 

structures are very prominent in the Cave

Sandstone. However, in most localities in Lesotho, 

Orange Free State, and along the Lebombo Mountains of eastern South Africa and Swaziland, this 

sandstone is not clearly stratified. The unstratified 

layers may represent deposition by flash floods that 

originated in a semiarid climate. Judged by texture, 

these layers probably consist of either mudflows or 

sand flows.

Probably the Cave Sandstone from Lesotho and 

the Lebombo Mountains should be renamed 

because it and the Bushveld Sandstone are much 

older than either the well-cross-stratified eolian 

sandstone of northern Transvaal near the border 

with Botswana or the Etjo Sandstone of the Huab 

Valley.

The Etjo and Cave Sandstones are characterized 

by eolian-type cross-stratification, mostly large to 

medium wedge-shaped sets, interpreted as products 

of transverse and barchan dunes. Some convex-upward strata may be related to parabolic dunes or 

other types of eolian bedforms which produce convex-upward structures (that is, retention dunes, 

protuberances on transverse dunes).

Within the same section, the size of the crossstrata sets ranges from small to large. Cross-strata 

consist of the wedge-planar and tabular-planar 

types. Dips of the strata very seldom exceed 33°; the 

maximum dip recorded is 40°. The average dips are:

Cave Sandstone (around Lesotho) ..... 16.1° 

Cave Sandstone (northern Transvaal) .. 21.9° 

Etjo Sandstone ....................... 21.9°

Fauna

Remains of reptiles, crustaceans, fish, insects, 

and plants indicate an age of Late Triassic or older 

for the Cave Sandstone in South Africa and 

Rhodesia (Haughton, 1969, p. 398). The remains of 

charred trees just below the first lava flow occur in 

the Orange Free State and reptilian tracks are fairly 

common in South-West Africa, Lesotho, and the 

Orange Free State. Sharp, clear tracks of at least 

five different types of reptiles were recently discovered in the northern Transvaal on dune crossstrata (foresets) having dips of about 27°. At the 

Kariba Dam in Rhodesia, reptilian remains occur in 

sandstone intercalated in lava.
238 A STUDY OF GLOBAL SAND SEAS

Environment of Deposition

Although the climate probably varied considerably, the main bulk of the sandstone apparently was 

not deposited under extreme desert conditions. In 

many places, the presence of water is indicated by 

current ripple marks, erosion channels, and lenses 

of shale probably deposited in old depressions.

Summary of Criteria for Eolian Origin

Although sandstones that developed in different 

environments may show similar structural features,

the Cave Sandstone interpretation as eolian depends not only on its characteristic cross-strata pattern but also on associated environmental features. 

As in most eolian sandstones, its sorting is better 

than for subaqueous sandstones. The Cave is 

neither associated nor intercalated with sequences 

of siltstone and claystone, and it does not include 

gravel beds.

Convex-upward cross-strata are believed to be 

typical eolian features developed in some types of 

dunes. Similar types of cross-strata rarely occur in 

subaqueous sandstones.


A STUDY OF GLOBAL SAND SEAS

SEDIMENTS OF THE ANCIENT EOLIAN

ENVIRONMENT—RESERVOIR

INHOMOGENEITY

Chapter I

By ROBERT LUPE and THOMAS S. AHLBRANDT

Contents

Page Page

Summary of conclusions ........................... 243 The model .......................... ............. 245

Introduction ...................................... 243 The model and the subsurface situation .............. 245

Acknowledgments ................................. 245 Application ....................................... 247

Illustrations

Page

FIGURE 160. Schematic diagram and cross section of typical distribution of dune, interdune, and extradune deposits ........................................ 244

161. Graph showing porosity-permeability distribution of dune and interdune sediments from cores, White Sands National Monument, New Mexico, U.S.A. 245

162. Graph of porosity versus permeability, showing delineation of three environments of deposition ................................................ 246

163. Electric logs showing eolian sedimentary structures and depositional environments ............................................................. 248

164. Cross section of depositional environments interpreted from cores of the

Tensleep Sandstone ................................................ 250

165. Diagram of core permeability and porosity and environment of deposition in

the Weber Sandstone ............................................... 251

241

SEDIMENTS OF THE ANCIENT EOLIAN ENVIRONMENT—RESERVOIR INHOMOGENEITY 243

Summary of Conclusions

PPER PALEOZOIC TO MESOZOIC eolian 

blanket sandstones of the Colorado Plateau 

and the Rocky Mountains of Colorado and southern 

Wyoming are texturally complex. As petroleum 

reservoirs, they commonly have poor performance 

histories because they represent a depositional 

system comprised of three closely associated 

subenvironments — dune, interdune, and extradune. Sediments of each subenvironment have 

different textural properties which have resulted 

from different depositional processes. Compared 

with interdune and extradune sediments, dune 

sediments are generally more porous and permeable and may be better quality reservoirs. Extradune 

sediments (a new term) include all deposits adjacent to a dune field and are mainly subaqueous 

deposits. Interdune sediments are here restricted to 

those nondune sediments deposited in the 

relatively flat areas between dunes. A conceptual 

model is proposed, in which dune sediments may 

be enveloped by extradune sediments as the 

depositional system evolves, resulting in a texturally inhomogeneous reservoir that has poor fluid 

migration properties.

This model of textural inhomogeneity in eolian 

blanket sandstones was applied to the Weber 

Sandstone in the Brady field and its equivalent, the 

Tensleep Sandstone, in the Wertz and Lost Soldier 

fields, Sweet water County, Wyoming, U.S.A. Data 

were obtained from both outcrop and subsurface 

and included environmental interpretation, textural analysis, and plotting of the distribution of 

depositional subenvironments. As expected from 

the model, dune sediments in Brady field were 

markedly different in texture from interdune and 

extradune sediments. The predicted geometric distribution of subenvironments was confirmed in 

Lost Soldier and Wertz fields. However, in these 

two fields, secondary cementation and fracturing 

has obscured the original porosity and permeability 

contrasts. The distribution of porosity and permeability, a characteristic depending partly on 

depositional processes, could impede fluid migration in the reservoir and significantly reduce recovery of hydrocarbons.

Introduction

MANY OF THE UPPER PALEOZOIC to 

Mesozoic blanket sandstones of the Colorado 

Plateau and the Rocky Mountains of Colorado and 

southern Wyoming were deposited in eolian and 

closely associated noneolian environments. They 

are the reservoir rocks in many oil and gas fields. 

These sandstone units are widespread and of 

uniform thickness and seem texturally 

homogeneous. There are, however, complex textural variations within the units that may affect 

porosity and permeability and be detrimental to 

their performance as reservoir rocks. These textural differences are related to environments of 

deposition, and a conceptual model is proposed to 

explain them. The model will aid the geologist in 

evaluating porosity and permeability problems and 

result in significant savings in time and money.

The eolian depositional system contains three 

subenvironments which are related both in time 

and by source: dune, interdune, and extradune. The 

term "dune" is applied in the classic geomorphic 

sense of Bagnold (1941). The term "interdune" is 

restricted to the description of the relatively flat 

area between the dunes of a dune complex. The 

new term "extradune" describes the area extending 

beyond the dune field, including some areas previously referred to as interdune. Interdune sediments probably were originally deposited by the 

same wind activity that built the dune (McKee and 

Moiola, 1975) and are commonly reworked by 

water or wind (Glennie, 1970). They are commonly 

preserved as the flat-lying sediments at the base of 

the crossbed sets of a dune sequence (fig. 160). Extradune sediments were probably deposited by 

processes independent of the dune-building process 

and involve sediments of diverse environments, 

such as alluvial fan, wadi, serir, stream, sebkha, 

playa, lake, beach, and tidal flat.

The new term "extradune" fulfills two purposes: 

(1) It specifically describes a geomorphic area 

which has often been incorrectly termed "interdune," and (2) it serves as a general term which 

could include a variety of subenvironments. The 

term can be used in general reference to various 

subenvironments or used when the identification of
244 A STUDY OF GLOBAL SAND SEAS

Boundary of extradune area

A'

DEPOSITS

Dune Interdune 

surface

Alluvial fan Nearshore Fluvial Playa and sebkha

SCHEMATIC DIAGRAM AND CROSS SECTION of dune, interdune, and extradune deposits. A, Plan view of typical distribution of 

dune, interdune, and extradune deposits. B, Cross section illustrating evolution of a dune-extradune system, ending with the 

geographic configuration of A. Subenvironments of the system migrate laterally as well as vertically, resulting in isolation of more 

porous and permeable dune sediments. (Fig. 160.)
SEDIMENTS OF THE ANCIENT EOLIAN ENVIRONMENT—RESERVOIR INHOMOGENEITY 245

specific subenvironments is uncertain but the 

stratigraphic relation to dune sediments is clear.

Acknowledgments

WE PARTICULARLY THANK Amoco Production Co. for their support and gracious granting of 

time and expense. We also thank Champlin 

Petroleum Co., operator of Brady field, and Mountain Fuel Supply Co. and Exxon U.S.A., the other 

Brady field partners; and Milliard Oil and Gas Co. 

for permission to publish data in this report. Pasco, 

Inc., provided data for the Lost Soldier-Wertz field 

studies.

The Model

THE DEGREE OF TEXTURAL contrast in dune, 

interdune, and extradune sediments reflects 

source-material texture, depositional processes, 

and the spatial relations of subenvironments within 

the depositional system.

Dune sediments are relatively better sorted, better rounded, and more compositionally mature than 

are sediments of most other depositional environments (Bagnold, 1941; Twenhofel, 1945; Kuenen, 

1960; Kukal, 1971; Ahlbrandt, chapter B, this 

paper). And, because porosity and permeability in 

modern sediments are largely functions of particle 

size, shape, and sorting (Griffiths, 1967), dune sand 

is generally more porous and more permeable than 

are the source, interdune, or extradune sediments.

Extradune sediments are predominantly subaqueous and, therefore, are usually more poorly 

sorted and less porous and permeable than are dune 

sediments. Additionally, porosity and permeability 

in these sediments could be further reduced 

because the topographically lower interdune and 

extradune areas are commonly the sites of early cementation (Glennie, 1972). Figure 161 shows thp 

distribution of porosity and permeability in modern 

dune-interdune sediments; figure 162 illustrates the 

distribution of porosity and permeability for ancient dune-extradune sediments.

Dune and extradune sediments abut laterally, 

and successive dune-extradune depositional 

systems may overlie one another, with dune sands 

in vertical contact either with other dune sands or 

with extradune sediments (fig. 160). Dune sand 

bodies may become isolated from one another, with

1000

44500

£100

I

ui 50H

tc.

o DUNE

-*- INTERDUNE -

24 28 32 36 

POROSITY, IN PERCENT

40 44

DISTRIBUTION OF POROSITY and permeability in dune and 

interdune sediments from cores, White Sands National Monument, New Mexico, U.S.A. (Fig. 161.)

the degree of isolation depending on the original 

distance between dune complexes and on the way 

in which succeeding depositional systems overlie 

one another. Movement of fluid would be affected. 

Furthermore, the porosity and permeability contrast may be enhanced by the effects of burial (Rittenhouse, 1971).

The Model and the Subsurface 

Situation

EXTENDING THE DUNE-EXTRADUNE model 

for eolian blanket sands to the subsurface has potentially valuable results for the petroleum industry. Two preliminary steps are required — first, 

recognition of sedimentary environments from conventional well-bore data, and, second, recognition 

of the relations between depositional environments 

and the distribution of porosity and permeability, as 

just described. Then, the size and distribution of 

various subenvironments must be determined. In 

some places the spatial relations of subenvironments can only be approximated from outcrop and 

(or) subsurface information. Outcrop data may not 

resemble the actual subsurface situation, and subsurface data may not be geographically dense 

enough to give a complete picture.
246 A STUDY OF GLOBAL SAND SEAS

100-

INTERDUNE AND EXTRADUNE 

(EXCEPT SHOREFACE)

0.01-

8 10 

CORE POROSITY, IN PERCENT

18

GRAPH OF POROSITY VERSUS PERMEABILITY, showing delineation of three known environments of deposition. Values were obtained each foot from 630 feet (192 m) of core of the Weber Sandstone from three wells in the Brady field, T. 16 N., R. 101 W., 

Sweetwater County, Wyoming, U.S.A. A grid was superimposed over the plotted data, and the number of points within each square 

was counted and assigned to the center of each square. Those points are data points for contours (Fig. 162.)

Conversely, subsurface information can provide 

accurate quantitative data for the model. Routine 

log analyses include porosity and, commonly, permeability determinations. Cores can provide not 

only porosity and permeability data but also information on depositional environments. Electric logs, 

if periodically calibrated with core data, can also 

provide information on depositional environment.

Figure 163 is an example in which conventional 

logs were used to interpret environments of deposition. The dipmeter is the most effective tool for 

describing sedimentary environments (Gilreath 

and Maricelli, 1964; Campbell, 1968), but the 

resistivity curve of modern electric logs may also 

provide the same data. In figure 163 the dipmeter 

log accurately recorded the high-angle dune

crossbed sets and the flat-lying interdune and extrad une beds. The resistivity curve of the dual induction laterolog also responded to the same sedimentary structures. The resistivity curve responded inversely to porosity differences — the 

lower the porosity, the higher the resistivity. In this 

example, the porosity contrast resulted from 

porosity differences of sediments deposited in 

different sedimentary environments — that is, 

more porous dune sediments versus less porous interdune and extradune sediments. Hence, the most 

basic suite of logs may not only provide the quantitative data for the construction of a model but also 

discriminate subenvironments in blanket eolian 

sandstones, if secondary cementation has not 

obscured the original porosity distribution. The 

savings of time and money could be significant.
SEDIMENTS OF THE ANCIENT EOLIAN ENVIRONMENT—RESERVOIR INHOMOGENEITY 247

Application

A STUDY OF THE PERMIAN and Pennsylvanian Weber Sandstone in the Brady field and its 

correlative 90 miles (150 km) to the northeast, the 

Tensleep Sandstone in Lost Soldier and Wertz 

fields, Sweetwater County, Wyoming, tested the 

application of the dune-extradune model to the prediction of reservoir complexities. The Weber and 

the Tensleep were selected for three reasons: (1) 

They were considered to be an eolian blanket 

sandstone. (2) They had a history elsewhere of requiring an unpredictably large number of closely 

spaced wells to drain a field. For example, at 

Rangely field, Colorado, Chevron Oil Co. is 

developing the field on only 10-acre spacing 

because of poor fluid migration (Western Oil 

Reporter, December 10, 1973). The cause of the 

poor fluid migration was unknown. The 10-acre 

spacing required to adequately develop the 

Tensleep of Little Buffalo basin field, northwest 

Wyoming, described by Emmett, Beaver, and McCaleb (1972), was attributed to reservoir 

heterogeneity. The possibility of similar poor fluid 

migration reservoir performance in the Weber 

Sandstone in the Brady field or other deep fields, 

where drilling is costly, made the question an 

economic one. (3) The active exploration underway 

in 1975 in the Weber in the Brady field and 

elsewhere permits further testing of the dune-extradune model and resultant porosity and permeability problems.

The study of the Brady, Lost Soldier, and Wertz 

fields was based largely on core examination. Four 

thousand five hundred feet of core from 45 wells in 

Lost Soldier and Wertz fields was described in 

detail, and depositional environments were 

differentiated by Reynolds, Ahlbrandt, Fox, and 

Lambert (1975, 1976) and by Reynolds and Fox 

(1976). Six hundred fifty feet of core from three 

wells in Brady field was examined by Lupe. In addition, core porosity and permeability were measured 

in the cores, and Weber Sandstone outcrops in the 

Uinta Mountains, 175 miles (280 km) southwest of 

Brady field, were examined.

Depositional environments were interpreted 

from cores of selected wells in these fields. The 

Weber or Tensleep Sandstone is a dune-extradune 

system composed of mixed nearshore marine and 

eolian sediments (fig. 164). Dune sandstones were

preserved only in Wertz and Brady fields, where 

they are isolated by foreshore, shoreface, tidal flat, 

supratidal, or sebkha extradune sediments, and to a 

lesser degree, interdune deposits. Furthermore, 

dune sandstone was preserved in upward-thinning 

transgressive and regressive depositional cycles, 

which are normally bounded by intraformational 

unconformities.

Dune sandstones were recognized by their thick 

bedding, their even and relatively continuous 

parallel laminae, which commonly dip at high 

angles, and their lack of holes from burrowing 

animals. They are very fine grained to fine-grained, 

well-sorted to very well sorted sandstones containing frosted grains. Interdune deposits separate dune 

sandstones and are relatively thin (less than 10 ft (3 

m)) and horizontally bedded. They contain poorly 

sorted bimodal sandstones with frosted grains and 

evaporite cements, commonly anhydrite. Flaser 

bedding and adhesions ripples were observed in 

some interdune sediments.

The general criteria used to differentiate extradune subenvironments included many described 

by Campbell (1971). Supratidal and sebkha deposits 

contain rip-up clasts, flaser bedding, adhesion ripples, abundant precipitates (such as anhydrite and 

dolomite), birdseye structures, and desiccation 

features. Tital flat deposits have discontinuous 

wavy nonparallel laminae and algal structures, all 

of which are horizontally bedded and commonly 

burrowed. Foreshore sandstones contain relatively 

discontinuous, even-parallel to wavy-parallel 

laminations, which dip less than 10° and contain 

rare burrows and scour-and-fill structures. They 

are moderately to well sorted. Shoreface deposits 

are extensively burrowed and contain contorted, 

slumped, and discontinuous wavy nonparallel to 

parallel relict laminae with maximum dips of 20°. 

Symmetrical wave ripples were occasionally observed in the relict laminae. The shoreface deposits 

are also distinctly finer grained than juxtaposed 

foreshore deposits.

Although the original environments of deposition and textures of the Weber and Tensleep 

Sandstones in the Brady and Lost Soldier—Wertz 

fields were virtually identical, the present porosity 

and permeability of the two areas are significantly 

different. The Tensleep in the Lost Soldier-Wertz 

fields has been tightly cemented to an average intergranular porosity of 5 percent, and production is
248 A STUDY OF GLOBAL SAND SEAS

DUAL INDUCTION LATEROLOG

DIPMETER READING

Degrees of dip 

0 20 40 60 80

4300

-Tail shows

direction

of dip

4400

4500

4600

-5.2

4

4700

4800

4900

'**

5100

5400 -

RECOGNITION OF SEDIMENTARY STRUCTURES and depositional environments from electric logs (Milliard Oil and Gas Co., Joyce 

dual induction laterolog distinguish between dune, interdune, and extradune sediments. Note correlation of porosity with
SEDIMENTS OF THE ANCIENT EOLIAN ENVIRONMENT—RESERVOIR INHOMOGENEITY 249

SEDIMENTARY STRUCTURE ORIENTATION 

DERIVED FROM DIPMETER READING

Borehole position

SONIC LOG POROSITY, 

IN PERCENT

10 15 20

ENVIRONMENTS OF DEPOSITION

Data incc nclusive

Not dune-related

Not dune-related

Not dune-related

Dune

Extradune

Extradune.

Not dune-related

Data inconclusive

Dune 

Iriterdune"

5 Dune

Dune

Data inconclusive Data inconclusive

Dtine

Dune

;0urie;

Data inc( nclusive

ilnterdune

Dune

Extradune

Extradune

Data inconclusive

Not dune-related c

ft*

Creek 1, SEV4NW1/4 sec. 8, T. 15 N., R. 103 W., Sweetwater County, Wyoming, U.S.A.). Both the dipmeter and resistivity curve of 

sedimentary structures — that is, with depositional environment. (Fig. 163.)
250 A STUDY OF GLOBAL SAND SEAS

WEST

LOST SOLDIER OIL FIELD

EAST

WERTZ OIL FIELD 

42B 46ABCE

0

1 ——0

1

I

I 

.5

2

I

1 MILE

AMSDEN FORMATION (PENNSYLVANIAN)

2 KILOMETRES

27ABC

GOOSE EGG FORMATION

TENSLEEP SS. (PERMIAN AND

METRES 

75-!

50-

25-

0-1-0

FEET

-200

-100

FREMONT CO 

SWUTWATER CO"

1 MILE

EXPLANATION

Dune Interdune Supratidal

and 

sebkha

R. 89 W.

Core—Dashed where 

not available

CROSS SECTION OF DEPOSITIONAL ENVIRONMENTS interpreted from cores of the Tensleep Sandstone in the Lost Soldier and 

Wertz oil fields, Sweetwater County, Wyoming, U.S.A. From Reynolds, Ahlbrandt, Fox, and Lambert (1975,1976) and Reynolds 

and Fox (1976). The top of the Amsden Formation is used as a horizontal datum. (Fig. 164.)
SEDIMENTS OF THE ANCIENT EOLIAN ENVIRONMENT—RESERVOIR INHOMOGENEITY 251

t iz

S ffi PERMEABILITY, POROSITY, ENVIRONMENT 

BELOW IN IN OF 

SURFACE MILLIOARCIES PERCENT DEPOSITION 

,n,wJ0010 1.0 0.11510 5 0 A B C

10 ocn

4200

4210 

13,900-

4220

1 *3 QCfl —

4230

4240 

14,000-

4250 

14,050 -

4260

4270

14,100-

I

< 

^2

^

__ ~=L ———— S~

^

^^^j^

^ ————————— ————*

^J

_5

-5

^-•"

^^

I ~1 — H^3

r

^

j

^

5

_ 

1^?,

i — -

i — i

Shoreface

Lower foreshore

Foreshore

= Intertidal 

Supratidal

I Foreshore? 

Tidal flat

Dune

Shoreface

- Shoreface 

Intertidal

Upper shoreface

_ Shoreface

Shoreface

Intertidal

Shoreface

Intertidal

Dune 

-- - Intertidal-

\Dune

Dune 

Intertidal 

/Dune

/Foreshore 

/Supratidal 

"/Intertidal 

/Dune 

"V^lntertidal-

-\ Dune 

Supratidal

Dune

=^ Interdune

. „. Interdune A Dune

B Shoreface 

C Interdune and 

other extradune

from complexly fractured strata. In Brady field, 

however, much original porosity and permeability 

remains in the Weber; production is from strata 

having intergranular porosity of a maximum 15-20 

percent.

The combination of the studies of the two fields 

creates a nearly complete picture of dune-extradune geometry, of the original distribution of 

porosity and permeability, and of its potential influence on fluid migration. The close control in Lost 

Soldier -Wertz (fig. 164), combined with the 

porosity-permeability contrasts resulting from the 

same depositional processes which are preserved in 

the Brady field (fig. 165), provides a subsurface example of the dune-extradune model. Relatively 

more porous and permeable dune sand is isolated 

by generally less porous and permeable extradune 

sediment at Brady field, so fluid migration may be 

influenced.

From the study of the Weber Sandstone and examination of the Nugget Sandstone in southern 

Wyoming and its correlative, the Navajo Sandstone 

in the Colorado Plateau, we conclude that dune-extradune systems, such as the Weber and Tensleep 

Sandstones, present greater reservoir problems 

than dune-interdune types, such as the Nugget. 

Dune-interdune systems present less of a problem 

because (1) interdune sediments are usually thinner than extradune sediments and are therefore 

less of a porosity and permeability barrier; and (2) 

interdune sediments are commonly lenticular, a 

condition which would allow communication between dune bodies. Furthermore, judged from production histories, porosity-permeability problems 

in dune-interdune reservoirs apparently are not 

common.

Effective fluid movement between well bores is 

influenced by the complex permeability barriers 

that resulted from dune-extradune depositional 

processes. Where fluid movement between well 

bores is critical, as in retrograde reservoirs where 

reservoir pressure must be maintained, the efficient 

recovery of hydrocarbons requires knowledge of 

the distribution of depositional environments and 

the resultant porosity and permeability characteristics.

DIAGRAM OF CORE PERMEABILITY and porosity and environment of deposition in the Weber Sandstone, Champlin 

Petroleum Co. Brady Unit 2, NE1ANEi/4 sec. 2,T. 16 N., R. 101 W., 

Sweetwater County, Wyoming, U.S.A. (Fig. 165.)

A STUDY OF GLOBAL SAND SEAS

MORPHOLOGY AND DISTRIBUTION OF

DUNES IN SAND SEAS OBSERVED BY

REMOTE SENSING

Chapter J

By CAROL S. BREED and TERESA GROW

Contents

Summary of conclusions ............................

Introduction ............... . . ....

Classification of eolian sand features based on Landsat

imagery ...... ............................

Genetic and local terms ......................

Terms based on remote sensing ........ ....

Occurrence in sand seas ........................

Page

257

257

257

257

258

260

Linear dunes . ,, ,. ................

Crescentic dunes ....................

Star dunes . . .....................

Parabolic dunes . . . . .......

Dome-shaped dunes . .... .......

Sand sheets and streaks ...............

Interdune areas ......................

Page

........ ... 261

,,,........... 265

275

277

278

281

282

253
254 A STUDY OF GLOBAL SAND SEAS

Illustrations

Page

FIGURE 166. Sketches showing methods of measuring length, width (or diameter), ana 

wavelength of dunes on Landsat imagery and on Skylab and aerial photographs ............................................................. 258

167. Aerial photographs of common varieties of simple linear dunes ... ........ 262

168. Aerial and space photographs of common varieties of complex linear dunes 264

169. Landsat imagery sample areas on which linear dune width, length, and

wavelength were measured .......................................... 265

170. Histograms showing frequency distribution of dune width, length, and

wavelength in simple linear dunes .................................... 266

171. Histograms showing frequency distribution of dune wavelength in compound

and complex linear dunes ........................................... 267

172. Scatter diagram showing correlation of mean wavelength and mean width in

linear dunes in relation to dune form ................................. 268

173. Aerial photographs of simple crescentic dunes ............... ........... 268

174. Aerial and space photographs of compound and complex crescentic dunes . 270

175. Landsat imagery sample areas on which compound and complex crescentic

dune ridge widths, lengths, and wavelengths were measured ........... 272

176. Histograms showing frequency distribution of wavelengths in small crescentic

dune ridges ........................................................ 272

177. Histograms showing frequency distribution of widths, lengths, and

wavelengths in compound crescentic dune ridges ...................... 273

178. Scatter diagrams showing relation of values of crescentic dunes........... 274

179. Aerial photographs of simple, compound, and complex star dunes ......... 276

180. Landsat imagery sample areas of star dunes, Arabia and western North America 278

181. Histograms showing frequency distribution of diameters and wavelengths of

star dunes ........... ........................................... 279

182. Scatter diagram showing relation of mean dune diameter to mean dune

wavelength in star dunes ............................................ 279

183. Landsat imagery sample areas of parabolic dunes, Thar Desert, India and

Pakistan, and Colombia-Venezuela border ............................. 280

184. Aerial photograph of complex domes in the Nafud ath Thuwayrat, northern

Saudi Arabia .................................. .......... ........ 280

185. Landsat imagery sample areas of dome-shaped dunes............ ........ 281

186. Histograms showing frequency distribution of diameters and wavelengths of

dome-shaped dunes ................................................ 281

187. Landsat imagery showing sand sheets and streaks associated with linear dunes,

Sahara, Mauritania .................................................. 282

Tables

Page

TABLE 25. Examples of types and forms of dunes, using classification based on remote

sensing ........................................................... 259

26- 30. Chronological lists of terms considered equivalent to classification based on 

Landsat imagery:

26. Linear dunes ... ............................................ 284

27. Crescentic dunes ............................. ........ .... 285

28. Star dunes .................................................. 288

29. Parabolic dunes .............................................. 289

30. Dome-shaped dunes .......................................... 290
MORPHOLOGY AND DISTRIBUTION OF DUNES IN SAND SEAS OBSERVED BY REMOTE SENSING 255

Page 

TABLE 31 - 35. Chronological lists of local terms for:

31. Complex dunes of all types .................................... 290

32. Sand seas .................................................... 291

33. Patterns of eolian sand deposits in sand seas ..................... 292

34. Sand sheets and streaks ........................................ 293

35. Interdune areas ............................................... 295

36. Morphometry of linear dunes in sand seas .............................. 296

37. Similarity of linear dune varieties in widely distant sand seas, shown by comparison of ratios derived from measurements .......................... 297

38. Morphometry of crescentic dunes in sand seas .......................... 297

39. Similarity of compound crescentic dunes in widely distant sand seas, shown by

comparison of ratios derived from measurements ...................... 298

40. Morphometry of star dunes in sand seas ................................ 299

41. Similarity of star dunes in widely distant sand seas, shown by comparison of

ratios derived from measurements .................................... 300

42. Morphometry of dome and dome-shaped dunes ......................... 302

43. Similarity of giant domes and dome-shaped dunes in widely distant sand seas,

shown by comparison of ratios derived from measurements ............. 302

MORPHOLOGY AND DISTRIBUTION OF DUNES IN SAND SEAS OBSERVED BY REMOTE SENSING 257

Summary of Conclusions

UNES OF SAND SEAS are classified in this 

chapter according to their external shapes and 

slipface orientations as observed in planimetric 

view on Landsat imagery and on Skylab and aerial 

photographs. Types observed (in order of their relative abundance) are linear, crescentic, star, 

parabolic, and dome-shaped dunes. Within dune 

types, different stages of slipface development are 

used in this chapter to distinguish simple, compound, and complex forms. Measurements of dune 

length, width (or diameter), and wavelength have 

been made on imagery and photographs of sand 

seas where dune type and form are uniform.

Dune patterns in sand seas seem regular because 

the measured values for dune length, width, and 

wavelength are fairly evenly distributed about 

mean values that are characteristic of each sand 

sea. Patterns made by dunes of the same type are 

similar, despite their occurrence in widely distant 

sand seas, because the relationships of mean length, 

width (or diameter), and wavelength are similar 

among dunes of each type, regardless of differences 

in size, form, or geographic location. Progression in 

dune form, from simple to compound or complex, is 

commonly associated with growth to larger size.

Within dune types and forms, varieties are distinguished in this study by assessing degrees of 

similarity as shown by correspondence of scale 

ratios derived from their measured mean lengths, 

widths (or diameters), and wavelengths.

Introduction

SATELLITE IMAGES OF UNIFORM 1:1,000,000 

scale and worldwide coverage provide a base for 

quantitative and qualitative studies of large-scale 

eolian landforms in widely distributed sand seas. 

Desert surfaces recorded on Landsat imagery of 

Africa, Asia, Australia, and North and South 

America were examined for evidence of eolian 

sand. Large-scale eolian landforms, mainly dunes, 

were measured on approximately 110 selected sample areas on Landsat imagery. Some small dunes, 

mostly in minor sand seas of North America, were 

measured in sample areas on aerial and Skylab 

photographs. Identification numbers for all images

and photographs used for sample measurements, 

and latitude and longitude of the sample areas, are 

given in the tables at the end of this chapter.

Dune lengths, widths or diameters, and wavelengths (crest-to-crest distances) were measured 

with an optical comparator on 1:1,000,000 scale 

bulk-processed Landsat transparencies, according 

to the conventions illustrated in figure 166. The 

lower limit of resolution for measurement of sand 

features was 100 metres (328 ft). Dunes measured 

on Landsat imagery commonly are as much as 3,000 

m (3 km, or about 2 mi) wide. Some individual 

linear dunes are more than 50 km (30 mi) long and, 

thus, extend beyond the sample areas. The size of 

most Landsat sample areas is 2,500 km2 (1,550 mi2).

Data resulting from the measurements are 

arithmetic means of various distance measurements and are two-dimensional. Measured values 

are analyzed and compared to show distribution of 

dune sizes and spacing of dune types in various 

sand seas, and to distinguish varieties among dunes 

of the same general type. Associations are shown 

among variables of length, width (or diameter), and 

spacing (wavelength) of dunes of certain types, 

regardless of their size and geographic location.

Classification of Eolian Sand

Features Based on Landsat

Imagery

Genetic and Local Terms

MOST CLASSIFICATIONS OF DUNES are 

based on local descriptions or on terms which carry 

genetic implications, such as "longitudinal" or 

"transverse." (See note by E. D. McKee, editor.10) 

The genetic terms imply a certain mode of origin 

based on slipface orientation relative to the dune 

body, for many dunes generally move and (or)

10 NOTE — the term "transverse" is perhaps an unfortunate one, for it suggests 

a genetic connotation and has been used by some geologists to imply a dune with 

crest transverse to wind direction. However, it has long been used to designate a 

sand ridge with slip face on one side only, and, therefore, it is related to barchans 

and barchanoid ridges, differing only in overall shape and some features of structure. In this publication "transverse" is not used in a genetic sense, but the term is 

retained because of tradition and long usage for a specific type.

E. D. McKee, editor.
258 A STUDY OF GLOBAL SAND SEAS

grow in the direction of avalanching. However, in 

space imagery where relationships of wind regimes 

to dune types in a given locality are not yet proved, 

assumptions that certain dune forms are "longitudinal" or "transverse," in a genetic sense, seem to 

the authors of this chapter inappropriate. Nevertheless, a few well-established local terms such as 

"barchans" and "seifs," are retained to describe distinctive types of dunes recognized in most sand 

seas.

Tables 26-30 list, in chronologic order, terms 

used by previous authors for dunes classified in this 

chapter as linear, crescentic, parabolic, star, or 

dome-shaped. Tables 31-35 provide a similar 

chronological listing, by author, of local terms for 

eolian landforms herein classified as complex 

dunes of all types, sand seas, patterns of eolian sand 

deposits in sand seas, sand sheets and streaks, and 

interdune areas. Each entry in tables 26-35 shows 

the desert region to which the term applies. These 

tables are at the end of this chapter.

The similarity in name of very large dunes, such 

as the dome-shaped dunes, compound barchans, 

and compound linear dunes observed in this study 

of Landsat imagery, with smaller dunes of comparable shape (simple dome, barchan, and seif or

^~^\

barchanoid ridge) does not imply that all of the 

forms within each type category have similar internal structures. The classification based on threedimensional internal dune structures is given in 

Chapter A (table 1).

Terms Based on Remote Sensing

Eolian sand features recognized on Landsat imagery, locally supplemented by Skylab or aerial 

photographs, are dunes, irregularly shaped sand 

sheets, and elongate sand streaks. A morphological 

description of eolian sand bodies is primarily a 

classification of dune types and forms. The term 

"dune" is used here for all well-defined eolian sand 

mounds or ridges that exist independently of surrounding topography (Bagnold, 1941, p. 7), whether 

slipfaces are visible or not. The classification suggested here is based on remote sensing and recognizes types, forms, and varieties of dunes (table 25). 

(See note by E. D. McKee, editor.11 )

Dune Types

Types of dunes as defined here are based on the 

external shape of the dune and the arrangement of 

its slipfaces, if any, relative to its shape in plan 

view.

Linear dunes are straight or slightly sinuous, 

longitudinally symmetrical sand ridges, much 

longer than they are wide, that are bounded on both 

sides by opposite-facing slipfaces. Linear dunes are 

features commonly referred to as "longitudinal" 

dunes, "seifs," and "sandridges" (table 26).

Crescentic dunes are mounds or ridges of sand 

that are crescent-shaped or composed of crescentshaped segments, each generally as wide or wider 

than it is long, and each mound or segment 

bounded on its concave side by a slipface. The 

category includes sand bodies that are referred to 

by many geologists as "barchan" and as 

"transverse" dunes (table 27). In planimetric view 

on space imagery, even large-scale "transverse" 

dunes that seem in ground view to be straight

METHODS OF MEASURING ON LANDSAT IMAGERY, Skylab

1 NOTE — The classification used here and in the following regional descriptions (chapter K) is derived largely from studies of Landsat imagery supplemented

and aerial photographs, the length (I), width (W),or diameter locally by a few Skylab and aerial photographs, and represents an essentially two-

(D) and wavelength (X) of the following dune types: A, Linear; dimensional classification. It differs in certain basic respects from the classifiesv " o \ / " • tion based on three-dimensional studies (chapter A), especially structural, used

B, crescentic; C, star; D, parabolic compound form; £, dome- by other authors of this professionai paper.

Shaped. (Fig. 166). E. D. McKee, editor.
MORPHOLOGY AND DISTRIBUTION OF DUNES IN SAND SEAS OBSERVED BY REMOTE SENSING 259

TABLE 25. — Examples of types and forms of dunes, using classification in this chapter, based on remote sensing

[ERTS (E) and Skylab (SL) numbers are below photographs. NR indicates not recognized on Landsat imagery. Photograph scales 1:1,000,000. Crescentic 

type includes transverse type as used by other authors in this publication ]

Type

Form

Simple Compound Complex

Linear

E-1179-00593 E-1167-06310 E-1187-06433 E-1117-06551 SL3-RL28 E-1111-09435

Crescentic

E-1128-04253 E-1227-08501 E-1183-061 94 E-1183-06194 E-1183-06194 E-1424-03262

E-1183-06203 E-1109-09322 E-1183-06194

Star NR

E-1111-09435 E-1183-06194

Parabolic NR

E-1189-17102 E-1177-14255

Dome-like NR

E-1 155-07040 E-1077-04420

ridges appear to curve slightly in crescent-shaped 

segments, though each segment may be a kilometre 

or more wide from horn to horn.

Star dunes are radially symmetrical, pyramidal 

sand mounds with slipfaces on arms that radiate 

from the high center part of the mound. They include sand bodies known locally as "oghurd" 

dunes, pyramidal dunes, and dune "massifs," summarized in table 28. Parabolic dunes are U -shaped 

or V-shaped mounds of sand, trailed by elongated 

arms, having slipfaces on the outer, convex sides 

(table 29), and are typically associated with
260 A STUDY OF GLOBAL SAND SEAS

vegetation. Dome-shaped dunes are semicircular 

mounds of sand that generally lack surface slipfaces (table 30).

Dune Forms

Forms of dunes are defined by the stage of slipface development and, thus, to some extent by size. 

Simple dune forms are mounds or ridges with slipfaces, all of which are similar in size or character. 

Simple linear dunes are the main sand features of 

the Simpson, Great Sandy, and Great Victoria 

Deserts in Australia, and of the Kalahari Desert in 

South Africa. Simple barchans, barchanoid ridges, 

and simple linear and star dunes are the main dune 

forms of most North American deserts, but they are 

minor, inconspicuous components of most major 

sand seas observed on Landsat imagery.

Many dunes in sand seas of Asia and northern 

Africa are extremely large and are characterized by 

extensive development of secondary sets of slipfaces of lesser size than those which define the 

main mound or ridge. If secondary slipfaces are of 

the same kind as those that define the main ridge or 

mound, the dune is a compound form; if they are of 

a different kind, the dune is a complex form.

Compound dunes are mounds or ridges of sand 

on which smaller dunes of similar type and slipface 

orientation are superimposed. For example, a compound crescentic dune consists of a sand mound or 

ridge having similar but smaller secondary crescent-shaped dunes on its gentle slopes. The arrangement of slipfaces, of similar appearance, gives 

some dunes of compound form a typically broad, 

"two-storied" aspect (Kadar, 1966, p. 447). Subsidiary slipfaces on compound crescentic dunes are 

seldom clearly visible on Landsat imagery, but they 

can be identified by inspection of aerial or Skylab 

photographs, or from descriptions based on field 

observations.

Complex dunes are combinations of two or more 

dune types. The most common complex forms observed on Landsat imagery are linear or crescentic 

ridges with superimposed dunes of some other 

type, such as star dunes, developed along their 

crests. Generally, complex forms consist of a main 

dune type and a secondary dune type and can be 

classed as mainly linear, mainly crescentic, and so 

forth. However, some complex dunes have approximately equal components of different dune types; 

where no one dune type is dominant, the dunes are 

here considered to be complex unclassified.

Dune Varieties

Within the basic classes of type and form are 

numerous dune varieties. Varieties of simple and 

compound forms of most dune types have been observed in many sand seas. They are compared by 

applying a method developed by Strahler (1958, p. 

292-294) for assessing similarity of fluvially produced landforms. According to this method of 

dimensional analysis, landforms are considered to 

be similar when dimensionless numbers formed by 

the ratios of their measured values are closely similar (Strahler, 1958, p. 279). Certain varieties of simple and compound dunes are shown by this method 

to be common to many widely distant sand seas. 

Common names for these dunes are given in tables 

26-30. Varieties of complex dunes, however, tend 

to be unique to specific localities, so their names 

usually only have local application. Those names 

are listed in table 31.

Occurrence in Sand Seas

Large areas of eolian sand constitute sand seas, 

so-called because the dunes in them tend to be 

repeated in orderly sequences rather than occurring 

as scattered solitary features. Sand seas occur from 

above the Arctic Circle in Alaska to below the Antarctic Circle in Antarctica, and at all latitudes between. Most major sand seas, however, lie within a 

belt between lats 40° N. and 30° S., in Africa, Asia, 

and Australia. General distribution of the world's 

sand seas is discussed by I. G. Wilson (1971b, 1973). 

Local names for many sand seas are summarized in 

table 32. Descriptive terms used by various workers 

to identify orderly patterns of eolian sand deposits 

in sand seas are summarized in table 33.

In the following parts of this chapter, dunes are 

described according to type, in order of their relative abundance, as observed on Landsat imagery of 

major sand seas. Linear dunes are the main dune 

type in the Southern Hemisphere deserts of 

Australia and southern Africa. They occupy about 

half the area of the Rub' al Khali in southwestern 

Saudi Arabia, and they occur in several sand seas of 

the Sahara of northern Africa. Crescentic dunes are 

more common than linear dunes in the Northern 

Hemisphere. They occupy large areas of the eastern 

Rub' al Khali in southeastern Saudi Arabia, several 

sand seas in the Sahara, and most sand seas in 

northern China, eastern U.S.S.R., western Argentina, and western North America.
MORPHOLOGY AND DISTRIBUTION OF DUNES IN SAND SEAS OBSERVED BY REMOTE SENSING 261

Star dunes occupy far less area within sand seas 

than do either linear or crescentic dunes but, like 

them, are widely distributed. Major occurrences of 

star dunes are in sand seas of the northern Sahara 

in Algeria and Libya, the Gran Desierto of Mexico, 

and around the margins of sand seas in northern 

China, the Arabian Peninsula, and the Namib 

Desert of South-West Africa.

Parabolic dunes of a size visible on Landsat imagery are rare. Observations on these images are 

mostly limited to the Thar Desert of India and 

Pakistan, and to low-lying areas along the Colombia-Venezuela border near Buenavista, small dune 

fields in the Kalahari Desert of South Africa, and 

White Sands in western North America. Also rare 

on Landsat imagery are domes or dome-shaped 

dunes; they are observed in sand seas of the northern Arabian Peninsula, northern China, and the 

Sahara of northwestern Algeria.

Sand sheets and streaks (termed "stringers" by 

many authors) are abundant in most major sand 

seas, but these features have no common geometric 

characteristics on Landsat imagery by which they 

can be compared from desert to desert. Some of 

them are known to contain small dunes that are 

below the resolution of Landsat imagery. Common 

terms for them are given in table 34.

Linear Dunes

General Distribution

SIMPLE, COMPOUND, AND COMPLEX linear 

dunes are observed on Landsat imagery and on 

Skylab and aerial photographs (figs. 167,168). Simple linear dunes are single or bifurcated ridges with 

narrow crests that may be sharp or subdued but 

which do not have slipfaces of secondary dunes 

developed upon them (fig. 167). Compound linear 

dunes are generally much broader linear ridges that 

have relatively smaller linear ridges, each with its 

own slipfaces, on their tops. In the "feathered" 

variety of compound linear dunes, subsidiary ridges 

intersect or spread obliquely from the main ridge. 

Linear dunes of compound form in Arabian sand 

seas are shown on aerial photographs by Glennie 

(1970, fig. 74) and by Holm (1960, fig. 7). Complex 

linear dunes may be narrow or broad linear ridges 

that have other dune types, such as star, domeshaped, and barchan (crescentic) dunes, superimposed upon them (fig. 168).

Some linear dunes occur as solitary features 

(chapter K, fig. 193) but mostly they form parallel 

ridges separated by sandy, gravelly, or rocky interdune corridors in sand seas. Linear dunes, apparently of simple form, cover most of the 

Australian deserts and the Kalahari Desert of South 

Africa, but in many other sand seas linear dunes 

are mostly compound or complex.

The largest solitary linear dune measured on 

Landsat imagery is a 100-km-long (26-mi-long), 1- 

km-wide (0.62-mi-wide), complex dune between 

Atar and Akjoujt, Mauritania, in the northwest 

Sahara (chapter K, fig. 193). The largest linear 

dunes forming parallel ridges in a sand sea are in 

the Qa'amiyat region of the southwestern Rub' al 

Khali, Saudi Arabia, where individual dunes can be 

traced for 190 km (118 mi) and range in width from 

0.30 to 2.7 km (0.2 to 1.7 mi).

Morphometry

Dune width, length, and wavelength were 

measured on sixty-seven 2,500-kmz (1,550-mi2) 

sample areas of Landsat imagery showing linear 

dunes of simple, compound, and complex form in 

northern Africa, southern Africa, Australia, and the 

Arabian Peninsula. Measurements of linear dunes 

of simple form on the Navajo Indian Reservation, 

northern Arizona, U.S.A., were made from highaltitude aerial photographs (fig. 167B). Some sample areas on other continents are shown in figure 

169. Histograms (figs. 170,171) show distribution of 

the measured values in sample areas of various 

sand seas. In general, measured values for dune 

width, length, and wavelength (crest-to-crest distance) tend to be grouped about characteristic 

means (summarized in table 36) that give a regular 

pattern to each sand sea.

Measured values of dune wavelength for simple 

linear dunes in sampled areas of the Simpson, Great 

Sandy, and Kalahari Deserts, and Arizona sand seas 

are distributed lognormally, unlike the distribution 

of measured values for simple linear dune 

wavelength in the sampled area of the Rub* al Khali 

(fig. 170), and linear dunes of compound and complex forms (fig. 171). The greatly skewed distributions of wavelength12 indicate that spacing of most

12 Transformations of the data, for statistical treatment, are considered unnecessary because the sample mean of such distributions is considered to be 

"more than 90 percent efficient" as an estimate of the population mean, "provided 

that the coefficient of variation is less than 1.2, corresponding to a variance of the 

logarithms of about 0.9" (Koch and Link, 1970, p. 219-220). No coefficients of 

variations (C) shown in figure 170 exceed the allowable figure.
262 A STUDY OF GLOBAL SAND SEAS

simple linear dunes of the variety common to the 

Kalahari and to Australian and Arizona deserts is 

fairly even and ranges about a mean value characteristic of each area, but that extremely wide spacing of a few individual dunes is common.

Measured values for widths and lengths of the 

linear dunes are normally distributed, except in the 

sampled Kalahari and Arizona localities, for 

reasons that are not yet clear.

Size and spacing relationships of linear dunes 

sampled in different sand seas were examined to 

see whether relationships of these variables are 

constant regardless of differences in dune size and 

geographic location. A scatter diagram (fig. 172) 

shows a linear arithmetic relationship between 

mean dune width and spacing in groups of linear 

dunes of all forms and varieties, in 12 sand seas of 

Africa, Asia, Australia, and North America. Sizes of 

dunes represented in figure 172 range from an 

average of 43 m (141 ft) wide, on the Navajo Indian 

Reservation, Arizona, U.S.A., to an average of 1,480 

m (4,860 ft) wide, at the western end of the Rub' al 

Khali, Saudi Arabia (table 36).

Regression analysis indicates that wavelength, 

which is presumed to be an independent variable, 

tends to be about twice the mean width of linear 

dunes, regardless of their size. The relationship also 

indicates a progression of dune form, from simple 

to compound or complex, with increasing size. Increasing size of linear dunes thus seems to be 

associated with development of subsidiary dunes, 

which may have slipfaces of the same or different 

orientations than the slipfaces of the main dune. 

Growth to great size is believed to be a function of 

time (I. G. Wilson, 1971a, p. 182-183), as well as of 

sand supply and effective winds.

Relation to Topographic Barriers and 

Wind Regimes

In sand seas such as the Australian deserts, the 

southwest Kalahari Desert of South Africa, and the 

Qa'amiyat region of the western Rub' al Khali, 

Saudi Arabia (chapter K), groups of linear dunes 

extend for hundreds of kilometres. Large groups of 

linear dunes in the Sahara, on the Arabian Peninsula, in southern Africa, and in Australia generally 

are alined parallel or subparallel to the resultant 

direction of effective winds (chapters F and K).

Tests were made of measurements within these 

deserts to determine whether statistically significant differences in mean dune width, W, mean 

dune spacing, X (crest-to-crest distance), and mean 

frequency, F~(number of dunes per kilometre), are 

associated with relative distances downwind or 

with positions in the open parts of sand seas, as opposed to positions near topographic barriers. 

Several different methods were tried.

First, mean wavelengths of dunes in samples 

measured near hills, playas, and streambeds in the 

Australian and Kalahari sand seas were compared 

with mean wavelengths of dunes in samples 

measured in open areas without such topograhic 

barriers. Differences significant at the 0.098 level 

for the Simpson Desert, 0.047 level for the Great 

Sandy Desert, and 0.010 level for the Kalahari 

Desert show that mean spacing of dunes in these 

sampled areas is significantly wider near

COMMON VARIETIES OF SIMPLE LINEAR DUNES (above and 

facing page). A, Bifurcating but straight dunes in the northwest 

Simpson Desert, Australia. Mean width of the dunes is 0.22 km 

(0.14 mi). Aerial photograph by E. Tad Nichols. B, Linear dunes 

on the Navajo Indian Reservation, Arizona, U.S.A. Aerial photograph by National Aeronautics and Space Administration (JSC 

236 28 0073). (Fig. 167.)
MORPHOLOGY AND DISTRIBUTION OF DUNES IN SAND SEAS OBSERVED BY REMOTE SENSING 263

11H5'

35°55

(Fig. 167 —Continued.)

topographic barriers than where such barriers are 

absent.

Second, regularity of dune spacing (represented 

by dispersion of wavelength measurements) relative to distance downwind in a sand sea was tested 

by plotting the coefficient of variation, C (the ratio

of the standard deviation to the mean of each sample), versus distance downwind in the Rub' al Khali 

and the Kalahari, Simpson, and Great Sandy 

Deserts. No correlation was found.

Third, the numbers of dunes in six sample areas 

of the Simpson Desert were counted to see whether
264 A STUDY OF GLOBAL SAND SEAS

AERIAL AND SPACE PHOTOGRAPHS OF COMPLEX LINEAR 

DUNES. A, Subsidiary star dunes and crescentic dunes on the 

crests of complex linear ridges in the central Namib Desert, 

South-West Africa. Dunes average 2.2 km (1.4 mi) from crest to 

crest. Photograph by H. T. U. Smith. B, Skylab EREP (Earth 

Resources Experiment Package) photograph showing linear 

dunes with barchanoid ridges on their crests in the northwest 

Sahara, Algeria, northern Africa. Photograph by National Aeronautics and Space Administration (SL 3 28 365). (Fig. 168.)

significant changes in dune numbers occur with 

distance downwind (measured in a direction 

parallel to resultant wind direction). No significant 

difference in dune numbers was found either between adjacent samples or between extreme upwind (southeast) and downwind (northwest) samples in the Simpson Desert.

The negative results of these tests suggest that 

simple distance from the upwind end of a sand sea 

(and, presumably, distance from the sand supply) is 

not an important factor in determining the distribution patterns of linear dunes.

Identification of Varieties

Ratios ^derived from measurements of the mean 

widths (W), lengths (L), and wavelengths (X) of 

dunes in each sample area define the geometric 

characteristics of the sampled dunes in each sand 

sea (table 36). The degree of similarity of simple 

linear dunes in different sand seas is shown by the 

degree of correspondence of their ratios (table 37).

At least two varieties of simple linear dunes can 

be distinguished by the degree of similarity of the 

sampled dunes:

1. Long narrow linear dunes of the Australia 

"sandridge" variety, common to the Simpson 

and Great Sandy Deserts, show excellent to 

good correspondence to linear dunes of similar size in the Kalahari Desert and good to fair 

correspondence to much smaller linear dunes 

on the Navajo Indian Reservation in Arizona.

2. Short linear dunes of the "seif" variety in the 

Rub' al Khali sand sea of Saudi Arabia, east of 

Al 'Ubaylah (chapter K, fig. 241) show very 

poor to good correspondence to the linear 

dunes in the Navajo Indian Reservation of 

Arizona in the United States, in southern 

Africa (fig. 169.A), and in parts of Australia 

(fig. 169B). Comparison of ratios, derived 

from measurements, thus seems to support 

the suggestion by Price (1950, p. 462-463) 

that two varieties of linear dunes have been 

described as seifs — one by Bagnold (1941, p. 

222-229) in the Sahara of Libya, and the 

other, called sandridges, by Madigan (1946, p. 

45-63) in the Australian deserts. 

Comparisons of dimensionless ratios for linear

dunes of compound and complex forms are not
MORPHOLOGY AND DISTRIBUTION OF DUNES IN SAND SEAS OBSERVED BY REMOTE SENSING 265

18°30

8°30' 15°00' 4T30'

2V3D'—

10 20 30 40 KM

20 Ml

LANDSAT IMAGERY SAMPLE AREAS on which measurements of linear width, length, and wavelength were made. 

Numbers in parentheses refer to the regions listed in table 36. Each sample is an area 50 km by 50 km, or 2,500 km2 

(1,550 mi 2 ) in a sand sea. A, Kalahari Desert, southern Africa; simple dunes (4). B, Great Sandy Desert, Australia; simple dunes (3). C, Southwestern Rub' al Khali, Saudi Arabia; compound dunes (8). D, Southwestern Sahara; compound dunes (6). f, Namib Desert, South-West Africa; complex dunes (9). F, Western Rub' al Khali, Saudi Arabia; 

complex dunes (12). (Fig. 169.)

given because, as indicated in table 36, lengths of 

these dunes commonly are greater than the sample 

lengths.

Crescentic Dunes

General Distribution

ON THE BASIS OF SLIPPAGE DEVELOPMENT, three basic forms of crescentic dunes — 

whether mounds or ridges — can be discerned on 

Landsat imagery and on aerial and Skylab photographs. Simple crescentic dunes are crescentshaped mounds, commonly referred to as barchan 

dunes. Crescentic ridges, commonly known either 

as barchanoid ridges or as transverse ridges, have a 

single slipface on each arc. In most places they are 

relatively small (fig. 173). Curvature of the segments of some crescentic ridges is extreme, and the 

term "barchanoid" has been used (Cooper, 1967, p. 

28) to distinguish this variety from the very slightly 

curved variety of ridge commonly called transverse 

on the basis of structure (table 27).
266 A STUDY OF GLOBAL SAND SEAS

1=3.65 

S=1.83 - 

C=0.50

WIDTH LENGTH WAVELENGTH

180

160

140

120

100

80

60

40

- r~i 100

80

60

40

20

W=0.29 

5=0.12 

C=0.43

o«-. cMco^incqi*; 

oooooooo

WIDTH

60

40

20

WAVELENGTH

.

5=12.36 

C=1.0

T-o>^inco»— o>^in 

•- CM co ^ ^ in co

20

0

LENGTH

E W=0.38 5=0.12 - 

C=0.32

^

11

"

1 _

1

1 = 14.34 

5=5.86 

h C=0.41 "

^ "

—— I

I

X=1.41 

5=0.58 - 

C=0.41

~ -~

__ .. 1 —— I

1 [

WIDTH

•- CM 

LENGTH

O r- .- CM CM

WAVELENGTH

HISTOGRAMS SHOWING FREQUENCY DISTRIBUTION (f) of 

dune widths (W), dune lengths (L), and dune wavelengths (X), 

in kilometres, in sample areas of linear dunes of simple form,

200

180 -

20 -

100

80

60

20

WAVELENGTH 

60

X=0.70 

5=0.46 

C=0.65

*— m o> co ^ *— in o>

o •- «-

WAVELENGTH

«- CM n * 

LENGTH

measured_on aerial photographsJ^A) and Landsat transparencies 

(B -f); W, mean dune width; L, mean dune length, X, mean 

dune wavelength; 5, standard deviation; C, coefficient of variation. Values along abscissa are in kilometres. Numbers in 

parentheses refer to regions listed in table 36. A, Navajo Indian 

Reservation, Arizona, U.S.A. Area sampled is 625 km2 (390 mi2 ) 

(1). 8, Simpson Desert, Australia. Area sampled is 30,000 km2 

(18,640 mi 2 ), (2). C, Great Sandy Desert, Australia. Area sampled 

is 35,000 km2 (21,740 mi2 ) (3). D, Kalahari Desert, South Africa. 

Area sampled is 15,000 km2 (9,320 mi2 ), (4). f, Northern Rub' al 

Khali, Saudi Arabia. Area sampled is 2,500 km2 (1,550 mi2 ) (5). 

(Fig. 170.)
MORPHOLOGY AND DISTRIBUTION OF DUNES IN SAND SEAS OBSERVED BY REMOTE SENSING 267

20

10

0

X=3.17

S=0.50 -

C=0.16

- -

——— i

j

2.0 2.5 3.0 3.5 4.0 4.5 

A

X=2.20 

- S=0.38 

C=0.17

X=1.93 

S=0.31 

C=0.16

1.0 1.5 2.0 2.5 3.0 

B

1.0 1.5 2.0 2.5 3.0

c

1.0 1.5 2.0 2.5 3.0 3.5 4.0 4.5 5.0 5.5

X=3.28 

5=0.88 

C=0.27

HISTOGRAMS SHOWING FREQUENCY DISTRIBUTION 

(f) of dune wavelengths (X), in kilometres, in compound 

and complex Jmear dunes measured on Landsat 

transparencies: X, mean dune wavelength; 5, standard 

deviation; C, coefficient of variation. Numbers in 

parentheses refer to regions listed in table 36. Values 

along abscissa are in kilometres. A, Western Rub' al Khali, 

Saudi Arabia; complex dunes. Area sampled is 2,500 km2 

(1,550 mi 2 ) (12). B, Namib Desert, South-West Africa;

Compound crescentic dunes (the "megabarchans" of Norris, 1966, p. 292-296) are generally 

much larger than simple crescentic dunes and are 

characterized by the presence of numerous subsidiary crescentic dunes with slipfaces oriented the 

same as the main slipfaces but developed secondarily on the gentle slope of each major dune 

mound or ridge. Several examples are shown on 

aerial photographs in figure 174. Compound crescentic mounds are typified by the Pur-pur dune of 

Peru (Simons, 1956), which is a large solitary 

barchan, 0.75-0.85 km (0.46-0.52 mi) wide and 2.1 

km (1.3 mi) long, with a major slipface forming its 

steep slope; numerous minor crescents, each with a 

slipface on its lee side, occur on the windward 

slope.

Compound crescentic dune ridges are more common than large solitary barchans and are typified 

by the Nebraska Sand Hills, described by H. T. U. 

Smith (1965, p. 564) as "transverse, and probably 

* * * of the compound variety, with minor second1.0 1.5 2.0 2.5 3.0 3.5 4.0 4.5 5.0

F

complex dunes. Area sampled is 2,500 km2 (1,550 mi 2 ) 

(9). C, Southwestern Sahara, Mauritania; compound 

dunes. Area sampled is 2,500 km2 (1,550 mi 2 ) (6). D, 

Northern Sahara, Algeria; complex dunes. Area sampled is 

2,500 km2 (1,550 mi 2 ) (10). f, Southern Sahara, Niger; 

compound dunes. Area sampled is 7,500 km2 (4,660 mi 2 ) 

(7). F, Southern Sahara, Niger; complex dunes. Area 

sampled is 2,500 km2 (1,550 mi 2 ) (11). (Fig. 171.)

ary transverse ridges on the windward slope, which 

appears to be typical where the basic dune form 

reaches large size." Similar features are shown on 

an aerial photograph of the Algodones Dunes, 

California (fig. 174D), in a close view of that area 

by Norris and Norris (1961, pi. 3, fig. 1) and in the 

Peski Karakumy, U.S.S.R., illustrated by Suslov 

(1961, fig. 14-3). In Saudi Arabia, compound crescentic dune ridges showing pronounced curvature 

of the segments (fig. 174>\) have been described 

(Holm, 1960, p. 1372) as "giant crescentic massifs" 

(table 27).

Very large compound crescentic dune ridges 

were observed on Landsat imagery of sand seas at 

relatively high latitudes, in the Peski Karakumy 

(U.S.S.R.), Takla Makan and Ala Shan Deserts 

(northern China), and in the Nebraska Sand Hills 

(U.S.A.). Lower latitude sand seas of large compound crescentic dunes occur in the eastern Rub* al 

Khali (Saudi Arabia), several parts of the Sahara 

(northern Africa), and in the Algodones and Gran
268 A STUDY OF GLOBAL SAND SEAS

3.4 

3.2 

3.0 

2.8 

2.6 

2.4 

2.2 

2.0 

1.8 

1.6 

1.4 

1.2 

1.0 

0.8 

0.6 

0.4 

0.2 

0

®8

®6 ®7

LINEAR DUNES

• Simple

® Compound

O Complex

I I I I I I I

0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1.0 1.1 1.2 1.3 1.4 1.5

SCATTER DIAGRAM SHOWING CORRELATION of mean dune 

wavelength (X) and mean dune width ( W) in linear dunes, in relation to dune form. Measurements in kilometres. The correlation coefficient (r) =0.93, shows excellent correlation. Numbers beside points refer to regions listed in table 36. (Fig. 172.)

W

Ar

f*4

f&rryfij L */>A** f<A^a A{*>YI ^ Arf ^

,-»"- *vLAt*~-*<&& - -m - A^W Jl «•<-•- *. si*7 ^- aWi

500 METRES 

1500 FEET

600 FEET

Comb Ridge, near the Arizona-Utah border, U.S.A., at lat 36°51' 

N., long 110° W. Photograph from Denny, Warren, Dow, and 

Dale (1968, p. 14, fig. Ariz. 3). fi, Barchanoid ridges, White 

Sands, New Mexico, U.S.A. (near lat 32°48' N., long 106°16' 

W.). Photograph used by permission of Holloman Air Force 

Base. C, Transverse ridges grading southward into barchanoid 

ridges and barchans in the Sahara (near lat 20° N., long 11 ° W.).

AERIAL PHOTOGRAPHS OF SIMPLE CRESCENTIC DUNES. A, Photograph from Monod (1958, pi. XXVII, p. 173, used by perTransverse ridges with slightly crescentic segments north of mission of the author). (Fig. 173.)
MORPHOLOGY AND DISTRIBUTION OF DUNES IN SAND SEAS OBSERVED BY REMOTE SENSING 269

Desierto regions of California and Mexico, respectively. The largest dunes of crescentic type that 

have been noted on images are in the Takla Makan 

Desert of China (chapter K), where mean width 

(horn-to-horn) of the segments is 3.24 km (about 2 

mi). Large crescentic dunes, in general, are oriented 

transverse to resultant directions of effective 

winds, but present winds in the regions of these 

large dunes mostly are of relatively low energies 

(chapter F), compared with energies of present 

winds in many other desert regions.

Complex crescentic dunes include both large and 

small mounds or ridges on which subsidiary dunes 

of a different type and orientation — most commonly star dunes — have formed. Some crescentic 

dunes, typified by ridges in the Great Sand Dunes 

National Monument, Colorado (McKee, 1966, p. 61, 

pi. E; Denny and others, 1968, fig. 10B) are included 

in this discussion as a variety of complex crescentic 

dunes because they seem to be combinations of 

both crescentic and star dune types. Some dunes in 

the Namib Desert believed to be of the complex 

crescentic variety are shown on a Skylab photograph in figure 174C.

Groups of relatively small crescentic mounds 

seen on Landsat images occur mainly in the 

southern Sahara and Libyan deserts of northern 

Africa and in the southeastern Rub' al Khali, Saudi 

Arabia. These barchanlike dunes are 0.20-1.5 km 

(0.12-0.93 mi) wide and 0.25-1.1 km (0.15-1.7 mi) 

long; most are probably compound barchans rather 

than simple barchans. A typical field of these dunes 

in the western Sahara of Mali is shown on a sample 

of Landsat imagery (fig. 175>\).

Small crescentic dune ridges are characteristic of 

many dune areas bordering the sea, such as the 

coastal part of the Namib Desert (chapter K, figs. 

222, 223), the Persian Gulf coasjt (eastern Qatar and 

the area around Sebkhat Mati) and the southern 

coast of Mauritania near the Senegal River (figs. 

188, 191). Small crescentic dune ridges also occur 

inland, where they commonly override much larger 

dunes of crescentic type, as in the Al Jiwa' area of 

the eastern Rub* al Khali (chapter K, fig. 240) and 

on the eastern edge of the Takla Makan sand sea 

near T'ieh-kan-li-k'o (chapter K, fig. 261 A). Size of 

the small dunes, however, precludes making 

measurements on Landsat imagery, except for 

wavelength, so apparent similarities cannot be 

tested by comparisons of their scale ratios. Small

coastal crescentic dunes commonly are oriented 

transverse to resultant directions of fairly strong 

present-day winds (chapters F and K).

Morphometry

Dune width (horn-to-horn distance of each crescent or crescentic segment), dune length (distance 

from base of windward slope to base of slipface), 

and dune wavelength (crest-to-crest distance) were 

measured (fig. 166) on forty-five 2,500-km2 (1,500- 

mi2) sample areas of Landsat imagery, representing 

large, compound crescentic dunes in both northern 

and southern Africa, the Arabian Peninsula, 

Pakistan and India, U.S.S.R., northern China, and 

western North America. Wavelengths of smaller, 

possibly simple crescentic ridges were measured on 

numerous Landsat imagery samples of the Arabian 

Peninsula, Pakistan, China, and South-West Africa. 

Some sample areas of Landsat imagery for most of 

these regions are shown in figure 175. Simple crescentic (barchanoid) dunes at White Sands, New 

Mexico, and compound crescentic dunes in the 

Gran Desierto, Mexico, and in the Algodones 

Dunes, California, were measured on aerial and 

Skylab photographs.

Measurements in each sampled sand sea are 

summarized in table 38, and the frequency distributions of measured values are shown by histograms 

in figures 176 and 177. Measurements of individual 

dunes show a wide range in many sand seas, but as 

a group, measurements in each sampled area tend 

to be distributed close to the mean values. Fairly 

uniform distribution of dune lengths, widths, and 

wavelengths defines the apparent regularity of 

dune patterns in each sand sea.

Size and spacing relationships of crescentic dune 

ridges sampled in different sand seas were examined to determine whether these relationships 

are constant despite differences in dune sizes and 

geographic locations. Sizes of dunes represented in 

figure 178 range from crescentic segments with a 

mean width of 111 m (365 ft) at White Sands, New 

Mexico (fig. 173B), to segments with a mean width 

of 3.24 km (2 mi) in the Takla Makan Desert of 

northern China (fig. 175D). Scatter diagrams (fig. 

178) show linear arithmetic relationships between 

the mean widths of crescentic dune segments and 

their mean wavelengths, between the mean widths 

of crescentic dune segments and their mean 

lengths, and between the mean lengths of crescen-
270 A STUDY OF GLOBAL SAND SEAS

*** -^ff'^^t^ :-;^v^2C»,-'»>

*F

'S^S*' "^^^fite*? ;**v$v »OT •*~s&vjr*r~f^"#' '/;•£•** \^^^^fcjS^»

CSBk. .**•*!£••>"«^!*^ • „ ,^^0^^^^^ "v

-^^ -Jj^^:«-

AERIAL AND SPACE PHOTOGRAPHS OF COMPOUND and 

complex crescentic dunes (above and facing page): A, Compound crescentic ridges in the eastern Rub' al Khali (Al'Uruq al 

Mu'taridah), Saudi Arabia, at approximately lat 23° N., long 54° 

E. One giant crescentic segment is outlined to show relation to 

much smaller, simple barchans that cross the interdune areas 

between the ridges. Segments of these ridges average 2.76 km 

(about 1.75 mi) from horn to horn and are about 3.1 km (0.3 mi) 

long, from the base of the gentle slope to base of the main slipface. Photograph by the U.S. Department of Defense. 6, Complex crescentic dune ridges in the southeastern Rub' al Khali, 

Saudi Arabia, at approximately lat 21 °45' N., long 54°30' E. Star 

dunes have formed on the crests of the ridges. Photograph by 

the U.S. Department of Defense. C, Complex crescentic dunes 

along the valley of the Tschaubrivier, South-West Africa. The

i A *

.»

1

i A** - '. '*

dunes nearest the river are about 300 m (1,000 ft) high (Barnard, 

1973, p. 2, 5). Photograph by National Aeronautics and Space 

Administration (SL 4-207-8073). D, Compound crescentic 

dune ridges in the Algodones Dunes, California, U.S.A. Major 

slipfaces are on the south-facing lee slopes, and numerous subsidiary slipfaces are on the gentler slopes. Photograph by National Aeronautics and Space Administration. (Fig. 174.)
MORPHOLOGY AND DISTRIBUTION OF DUNES IN SAND SEAS OBSERVED BY REMOTE SENSING 271

115W

tic dune ridges and their mean wavelengths. The 

latter association is particularly pronounced (correlation coefficient = 0.90), and this suggests that 

spacing of crescentic dunes varies directly with 

dune length, regardless of the size, form, or location 

of the dunes. Correlation of mean widths of crescentic dune segments with their mean lengths is 

also strong (r = 0.81) in dunes of all sizes, forms, 

and locations, which indicates that the correlation 

of width and length of crescentic mounds 

(barchans), as recorded by Finkel (1959, p. 628), 

seems to apply also to segments of crescentic 

ridges. As in linear dunes (fig. 172) progression in 

form from simple to compound or complex in crescentic dunes seems to be associated with growth to 

larger size (fig. 178).

Identification of Varieties

Planimetric similarity among crescentic dune 

ridges of compound form is shown by correspondence of scale ratios derived from their measurements (table 39). Differences in degrees of correspondence of the ratios indicate that two extreme

varieties of compound crescentic dune ridges can 

be distinguished:

1. Crescentic ridges whose segments are much 

wider than they are long, and which are not 

markedly curved; these include the Aoukar 

dunes of the southwestern Sahara in 

Mauritania and the Nebraska Sand Hills, 

U.S.A. (figs. 175F, E). These ridges are known 

by most geologists as "transverse" dunes and 

are referred to by that name in structural 

studies in this publication.

2. Crescentic ridges whose segments are as wide 

or slightly wider than they are long and 

which are markedly curved; these include the 

compound crescentic dunes of the eastern 

Rub* al Khali, Saudi Arabia, the Takla Makan 

and Ala Shan Deserts, China, (figs. 174A 

175B, D, Q and the Thai Desert near Sukkur, 

Pakistan (chapter K, fig. 256B). 

Dunes of the compound crescentic variety show 

very good to excellent correspondence to each 

others' scale ratios but mostly poor to fair correspondence to the ratios of dunes of the variety com-
272

01°30'

A STUDY OF GLOBAL SAND SEAS

mmm~ __________°00'

22°30l

LANDSAT IMAGERY SAMPLE AREAS ON WHICH COMPOUND 

crescentic dune width, length, and wavelength were measured. 

Each sample area is 2,500 km2 (1,500 mi2 ). Numbers in 

parentheses refer to regions listed in table 38. A, Large crescentic 

dunes, probably compound barchans, in the western Sahara, 

Mali (8). 6, Compound crescentic dunes in the eastern Rub' al 

Khali, Saudi Arabia (14); these are the dunes seen in closer view

20 Ml

in figure 174A C, Large barchanoid variety of compound crescentic dunes in the central Ala Shan Desert, China (20). D, Compound crescentic dunes in the northeast Takla Makan Desert, 

China (15). f, Compound crescentic dunes in the Nebraska 

Sand Hills, U.S.A. (19). F, Compound crescentic dunes in the 

Aoukar sand sea, western Sahara, Mauritania (21). (Fig. 175.)

10

A X=0.112 

5=0.036

£=€ 32

D

( ____

|

A— I

s=c 

c=o =^=,

1.90

.13

.22

C

x=o

S fl

\* V

————

628 

16

0.04 0.08 0.12 0.16 0.20 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1.0 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1.0

--10

0

D

-

X=0.87

u.zo

i ——— *i

1 1 1

£

5=0.35

C=0.59

• —— i ___

III I I

0.2 0.4 0.6 0.8 1.0 1.2 1.4 1.6 1.8 2.0

F

"!*' :A

'5;

X=0.89 

S=0.19

C=0.21

0.2 0.4 0.6 0.8 1.0 1.2 1.4 1.6 1.8 2.0 0.5 0.7 0.9 1.1 1.3 1-5

HISTOGRAMS SHOWING FREQUENCY DISTRIBUTION (/) of 

wavelengths (\), in kilometres, in small crescentic dune ridges 

measured on aerial photographs and Landsat imagery. Numbers 

in parentheses refer to regions listed in table 38. \, mean 

wavelength, in kilometres; 5, standard deviation; C, coefficient 

of variation. A, White Sands, New Mexico, U.S.A. (1). B, Thar

Desert north of Umarkot, Pakistan (3). C, Rub' al Khali, Al Jiwa' 

area, Saudi Arabia, (5). D, Coastal Namib Desert between Meob 

Bay and Sandfisch Bay, South-West Africa (4). f, Coastal Arabian 

peninsula along Persian Gulf between Qatar and Sebkhat Mali, 

Saudi Arabia (2). F, Eastern Takla Makan Desert near T'ieh-kan-lik'o, China (6). (Fig. 176.)
MORPHOLOGY AND DISTRIBUTION OF DUNES IN SAND SEAS OBSERVED BY REMOTE SENSING 273

3U

40

30 

20 

10 

0

A 1=2.09 

5=0.48 

C=0.23

-

!*V.v.-.

.: ;»

-

• ] .>*-• ' ~

•~

—

-

-

»;: ;"

;::f

W=2.76

5=0.56 

C=0.20

.?'. \8?"

~

-

-

"

—

-

• -...;:-.-. 

-"-•:->

:-:•..

;;:; ';

-1 :

X=2.56

5=0.50 

C=0.20

-

rv?~n

1.2 1.6 2.0 2.4 2.8 3.2 3.6 1.4 1.8 2.2 2.6 3.0 3.4 3.8 4.2 1.4 1.8 2.2 2.6 3.0 3.4 3.8 4.2

20

B

———— j.,,,,,..,-:,,..

, '«,".

1=2.20 

5=0.54 

C=0.24 ~

SSE=J ———— ,

-

: ' •' ' f '" " -

W=3.24 

5=0.85 

C=0.26

' "•••• •••••- •••••|---------- -^j- :" J:" |-'-——- y. ———

*,$%%? '• ' — .............

« =

111

X=3.0 

5=0.71 

C=0.24

"""""""\ ——— f22323

1.0 1.4 1.8 2.2 2.6 3.0 3.4 1.9 2.3 2.7 3.1 3.5 3.9 4.3 4.7 5.1 5.5 1.9 2.3 2.7 3.1 3.5 3.9 4.3 4.7 5.1 5.5

20 

10 

0

C

i :-;.

1=0.65

M;\

i-0.26

C=0.39

• —— , ———————— 1 ———

-

W=1.43 

5=0.67 

C=0.47

A;: r 1 •,/"

=*=*

-

;;-;

X=1.24 

5=0.33 

C=0.27 ~

::"";-:;:" 

";£•::

0.2 0.4 0.6 0.8 1.0 1.2 1.4 1.6 0.3 0.7 1.1 1.5 1.9 2.3 2.7 3.1 0.3 0.7 1.1 1.5 1.9 2.3

20

10 -

D

Il5=

1.31 

0.29 

0.22 - -

|

~, •';

5=

W

2.22

0.81 

0.36

-

X=2 

5=0 

C=0

.27 

.50 

.22 ;f

-

0.6 0.8 1.0 1.2 1.4 1.6 1.8 2.0 0.9 13 1.7 2.1 2.5 2.9 3.3 3.7 0.6 1.0 1.4 1.8 2.2 2.6 3.0 3.4

20 E I=1'6 

fc 5=0.40

C=0.25 -

; .v

10=3.14 

5=1.03 

C-0.33 -

'!.: — pH

-'-

X=1.7 

5=0.41 

C=0.24 -

—— —|ii — —

0.7 1.1 1.5 1.9 2.3 1.4 2.2 3.0 3.8 4.6 5.4 0.8 1.2 1.6 2.0 2.4 2.8

^U

10 

0

F

1=0.66 

5-0.27 

C=0.41

— —— H=i —

-

5=0.'39 

C=0.37

—— | ——— [ —— | ••••••-••; ;

X=1.38 

5=0.55 

C=0.40

—————— , ———

0.2 0.4 0.6 0.8 1.0 1.2 1.4 1.6 0.4 0.6 0.8 1.0 1.2 1.4 1.6 1.8 2.0 0.4 0.8 1.2 1.6 2.0 2.4 2.8

20

s, 10 -

n 1=0.88 

0 5=0.36

:;;;::.:

::: :::::-':;-.

I

-

W=1.61 

5=0.76

C=0.47

• ••• J | ;•; |

~VA :

X=1.07 

5=0.44

/•> n AI —

0.4 0.6 0.8 1.0 1.2 1.4 1.6 1.8 2.0 2.2 0.4 0.8 1.2 1.6 2.0 2.4 2.8 3.2 3.6 0.3 0.7 1.1 1.5 1.9 2.3 

LENGTH WIDTH WAVELENGTH

HISTOGRAMS SHOWING FREQUENCY DISTRIBUTION (f) of 

compound crescentic dune widths (W), lengths (L), and 

wavelengths (X),in kilometres, measured on Landsat imagery 

and Skylab photographs. W, mean dune width; L, mean dune 

length; X, mean dune wavelength; S, standard deviation; C, 

coefficient of variation. Numbers in parentheses refer to regions 

listed in table 38. A, Eastern Rub' al Khali, Saudi Arabia. Area 

sampled is 10,000 km2 (6,200 mi2 ) (14). B, Takla Makan Desert,

China. Area sampled is 5,000 km2 (3,100 mi 2 ) (15). C, Northern 

Sahara, Algeria and Tunisia. Area sampled is 5,000 km2 (3,100 

mi2 ) (10). D, Peski Karakumy near Gory Bukantau, U.S.S.R. Area 

sampled is 2,500 km2 (1,550 mi 2 ) (16). E, Nebraska Sand Hills, 

U.S.A. Area sampled is 3,000 km2 (1,860 mi 2 ) (19). F, Gran 

Desierto, Sonora, Mexico. Area sampled is 650 km2 (400 mi 2 ) 

(12). G, Algodones Dunes, U.S.A. Area sampled is 500 km2 (310 

mi2 ) (13). (Fig. 177.)
274 A STUDY OF GLOBAL SAND SEAS

3.2 

3.0 

2.8 

2.6 

2.4 

2.2 

2.0 

1.8

Kl.6

1.4 

1.2 

1.0 

0.8 

0.6 

0.4 

0.2 

0.0

OOOOOOOOOO«-«- «- «- «- «-«-

W

I I I I I I I I I I I I I I I I I I I I I I

OOOO«-«- «-«-t-t-t-«-«-«-CM«MCMCM

z

SCATTER DIAGRAMS SHOWING RELATION OF VALUES of bers near dots refer to regions listed injable 38. r, correlacrescentic dunes in sand seas measured on Landsat imagery and tion coefficient. A, Mean dune width (W) versus mean dune 

Skylab and aerial photographs. Circled dots represent dunes wavelength (X); B, mean dune length (I) versus mean dune 

identified from aerial photographs and field reports as com- width (W); _C, mean dune length (I) versus mean dune 

pound ridges. Solid dots represent small simple(?) crescentic wavelength (X). (Fig. 178.) 

ridges and large barchans. Measurements in kilometres. Nummonly referred to as "transverse." Some compound 

crescentic dunes included in the study, such as 

those of the Algodones Dunes of California, U.S.A. 

(fig. 174D), the Peski Karakumy near Mary and 

Gory Bukantau, U.S.S.R., and in the Gran Desierto,

Sonora, Mexico, seem to be intermediate in shape 

between the extremely curved and extremely 

straight varieties, for their correspondence to each 

other and to dunes of the two main varieties ranges 

from very poor to very good, but they are not suffi-
MORPHOLOGY AND DISTRIBUTION OF DUNES IN SAND SEAS OBSERVED BY REMOTE SENSING 275

ciently distinct from the others to be identified with 

separate names.

Only compound dunes, among the crescentic 

forms, were compared by dimensional analysis. 

Crescentic dune ridges in several sand seas that are 

suspected to be compound cannot be definitely 

classed as such because of poor resolution on Landsat imagery and lack of aerial photographs. Such 

regions include the An Nafud in Saudi Arabia and 

parts of the northeastern Sahara of Algeria and 

Tunisia. Dunes of equivalent size in the Gran 

Desierto, Sonora, Mexico, have been determined 

from Skylab photographs to be compound.

Star Dunes

General Distribution

SIMPLE, COMPOUND, AND COMPLEX star 

dunes were examined on Landsat imagery and on 

Skylab and aerial photographs. Simple star dunes 

have three or four arms, all with slipfaces of about 

the same size (fig. 179^. Compound star dunes 

have both large primary arms and small subsidiary 

arms with slipfaces (fig. 179B). Complex star dunes 

are combinations of star and other dune types, in 

which the star element predominates. Examples are 

star dunes with crescentic curvatures, recorded in 

the southeast Rub' al Khali, Saudi Arabia (fig. 

179Q, and Gran Desierto, Mexico (fig. 179D), as 

well as star dunes in linear chains in the Gran 

Desierto, Mexico, and the Grand Erg Oriental, 

Algeria (fig. 180A D).

Star dunes in simple, compound, and complex 

forms are the dominant dunes of the Grand Erg 

Oriental, (fig. 180B), but elsewhere they are limited 

to rather small areas. In the Ala Shan Desert, China, 

and the Namib Desert, South-West Africa (chapter 

K, figs. 264B, 224), star dunes occur around the 

margins of sand seas, typically near topographic 

barriers. In southeast Saudi Arabia, Yemen, and 

Oman, small star dunes occur near the mouths of 

dry washes along the southeastern edge of the Rub' 

al Khali, and they grade northward and westward 

into much larger star dunes (fig. 179Q, which in 

turn merge with very large southward-migrating 

crescentic dune ridges that have star dunes on their 

crests (fig. 174B). In the Gran Desierto, Mexico, 

simple and compound star dunes occur around the 

Sierra del Rosario (fig. 180^. To the east (toward 

Cerro Pinacate), star dunes grade into complex

dunes that are crescentic in shape but have star 

dunes on their crests (fig. 179D). Toward the south 

(Gulf of California), star dunes coalesce in eastwest linear chains. The largest star dunes observed 

in this study are in the Grand Erg Oriental, Algeria 

(chapter K, fig. 210B).

Analysis of the distribution of star dunes in relationship to distribution of effective winds (chapters 

F and K) suggests that star dunes occur where 

effective winds blow with moderate strength from 

several directions.

Morphometry

Histograms (fig. 181) show frequency distributions of star dune diameters and wavelengths in the 

sampled sand seas. Measurements in ten 2,500-km2 

(1,550-mi2) sample areas, and four smaller areas of 

Landsat imagery and Skylab photographs are summarized in table 40. As in sand seas of other types 

of dunes, star dune measurements tend to be 

grouped about characteristic mean values, thus 

defining the regular pattern for each sand sea. 

However, the scatter diagram (fig. 182) shows only 

a very weak association between mean diameters 

of star dunes and their mean wavelengths in the 

sampled sand seas. The weak correlation (r = 0.52) 

indicates that spacing of star dunes, unlike that of 

linear and crescentic dunes (figs. 172,178) does not 

vary directly with their size. Differences in the relationship of dune spacing to dune size in different 

types of dunes may reflect differences in processes 

of growth. Star dunes, unlike linear and crescentic 

dunes, grow upward, rather than forward or 

laterally, in response to effective winds.

Identification of Varieties

Ratios derived from measurements of mean 

diameters and mean wavelengths of star dunes in 

sampled sand seas (table 40) are compared in table 

41. Reliability of the comparisons is limited by the 

weak association of diameter and wavelength 

among star dunes (fig. 182). Also, differences in 

degrees of correspondence of scale ratios support 

the suggestion, based on aerial photographs, that 

three apparently different varieties of star dunes 

exist:

1. Sharp-pointed radiating pyramidal dunes are 

typical of parts of the Gran Desierto, Mexico, 

the Ala Shan Desert, China, parts of the 

southern Sahara in Niger, and much of the
276 A STUDY OF GLOBAL SAND SEAS

D

,Star dures

\

115°00' 32°00'

10 KM

Compound

crescsntic

duries
MORPHOLOGY AND DISTRIBUTION OF DUNES IN SAND SEAS OBSERVED BY REMOTE SENSING 277

AERIAL PHOTOGRAPHS OF SIMPLE, COMPOUND, and complex star dunes (facing page). A, Simple star dunes, Gran Desierto, at approximately lat 32° N., long 115° W. Arms of these 

dunes are generally less than 100 m (330 ft) long. Photograph by 

E. Tad Nichols. B, Compound star dunes, Gran Desierto, Sonora, 

Mexico, at approximately lat 32° N., long 114°30' W. Diameter 

of these dunes averages 700 m (2,300 ft). One dune is outlined 

for contrast with smaller, simple star dunes. C, Complex star 

dunes, eastern Rub' al Khali, Saudi Arabia, at approximately lat 

20°45' N., long 54°45' E. Photograph by the U.S. Department of 

Defense. D, Star dunes in the Gran Desierto, Sonora, Mexico, 

grade eastward into complex crescentic dunes with stars on 

their crests, and these grade into compound crescentic dunes 

near the southern Cerro Pinacate. Photography by National 

Aeronautics and Space Administration (SL 4-92-358). 

(Fig. 179.)

Grand Erg Oriental in Algeria. Similarities of 

dunes in Mexico and in Algeria are illustrated 

in low-altitude aerial photographs of a part of 

the Gran Desierto (fig. 179B) and a part of the 

Grand Erg Oriental (Capot-Rey and CapotRey, 1948, pi. 2).

2. Rounded compact star dunes with arms that do 

not project far from the main mass of each 

dune (H. T. U. Smith, 1963, p. 45) are typical 

of the southern margin of the Grand Erg 

Oriental, Algeria (chapter K, fig. 210B). Correspondence of the southern rounded variety 

to the sharp-pointed variety of star dunes 

farther north in the Grand Erg Oriental is 

very poor to fair (table 41).

3. Sharp-crested dunes with arms greatly elongated in a preferred direction may be a third 

variety. Such dunes are observed in the 

Namib Desert (chapter K, fig. 224), where 

they grade into complex reversing dunes, in 

the eastern Rub' al Khali, where they also are 

associated with complex dunes (fig. 179 Q, 

and in the northern Grand Erg Oriental, 

Algeria. These dunes show excellent correspondence to each other but very poor to fair 

correspondence with dunes of the first two 

varieties.

Star dunes described by McKee (1966, p. 65-68) 

in the 'Irq as Subay1 , Saudi Arabia, are different 

from all these varieties, for they have extremely 

long arms that radiate far from the main body of 

each dune. These dunes are not compared with 

other star dunes in table 41.

Parabolic Dunes

General Distribution

TWO FORMS OF PARABOLIC DUNES are 

recognized on Landsat imagery and on aerial photographs. Simple parabolic dunes are U-shaped or 

V -shaped and consist of a convex mound with two 

long trailing arms. Dunes of this kind at White 

Sands National Monument, New Mexico, U.S.A. 

(McKee, 1966, p. 25, 50-51) are shown on an aerial 

photograph (chapter E, fig. 50).

Compound parabolic dunes are U-shaped, 

V-shaped, or rake-shaped and have numerous secondary trailing arms. In the Thar Desert (India and 

Pakistan, chapter K) rakelike clusters of parabolic 

dunes cover about 100,000 km2 (62,000 mi2). Their 

planimetric aspect was sketched (Verstappen, 

1968a, fig. 3; A. S. Goudie, written commun. to 

McKee, 1974) from aerial photographs and maps 

(chapter K, fig. 254). Their aspect on Landsat imagery is shown in figure 183A. The largest parabolic 

dunes observed on Landsat imagery are near the 

Colombia-Venezuela border at about lat 6° 30' N., 

long 69° W. (fig. 183B). These dunes are U-shaped 

or V-shaped rather than rakelike and have 

numerous trailing arms as much as 12 km (7 mi) 

long.

Parabolic dunes are described from the Midwestern United States (Melton, 1940, p. 126-128; H. 

T. U. Smith, 1946; Ahlbrandt, 1974b, p. 45), coastal 

Oregon and California (Cooper, 1967, p. 22-25), 

White Sands National Monument, New Mexico 

(McKee, 1966, p. 50-51), localities in coastal Brazil 

(chapter E) and Europe (Kadar, 1966, p. 446). 

Parabolic dunes in the Thar Desert and at White 

Sands are alined parallel to the resultant direction 

of effective winds from the southwest (dune noses 

point to the northeast) (McKee, Breed, and others, 

1974, figs. 25, 5; this publication, chapters F and K 

and figs. 252, 253).

Morphometry

Compound parabolic dunes in the sampled part 

of the Thar Desert (fig. 183A) have an average of 

seven arms, mean lengths of 2.6 km (1.6 mi), and a 

mean width of 2.4 km (1.5 mi). Their length-width 

ratio is 1.1. Compound parabolic dunes in South 

America (fig. 183B) have a length-width ratio of 3.7,
278 A STUDY OF GLOBAL SAND SEAS

114°30'

32°00'

08W' LANDSAT IMAGERY SAMPLE AREAS OF STAR DUNES in Arabia 

and western North America. Each area is 2,500 km2 (1,550 mi 2 ). 

Numbers in parentheses refer to regions listed in table 40. A, 

Simple, compound, and complex star dunes, Gran Desierto, 

Sonora, Mexico, including the arrays shown in figures 179/4 and 

B (1). 6, Compound star dunes in the southern Grand Erg Oriental, Algeria (7). C, Compound and complex star dunes, 

southeastern Rub' al Khali, Saudi Arabia (5). Dunes in the northern part of this area are shown in detail in figure 179C D, Complex star dunes (chain variety), Grand Erg Occidental, Algeria. 

(Fig. 180).

53°30'

identical to the 3.7 length-width ratio of much 

smaller parabolic dunes at the southeast end of the 

White Sands dune field, New Mexico, U.S.A. 

(chapter E, fig. 50).

Dome-shaped Dunes

General Distribution

MOUNDS OF SAND that generally lack external 

slipfaces have been described as dome dunes in the 

Western United States localities, such as White
MORPHOLOGY AND DISTRIBUTION OF DUNES IN SAND SEAS OBSERVED BY REMOTE SENSING 279

40 

30

--20

10

0

Z5=0.84 

5=0.24 - 

C=0.28

30° 

20 

10

1.4 0.6 0.8 1.0 1.2 1.4 1.6 0.5 1.0 1.5 2.0 2.5 3.0 3.5

Z5=0.70 

5=0.24 -\ 

C=0.35

„ 0.2 0.4 0.6 0.8 1.0 1.2 20 '—————————|Z5=0.74 

5=0.21 

C=0.28

-

- —r~

X=1.19 

5=0.88 - 

r— n ->A

-

0.0 0.4 0.8 1.2 1.6 2.0 2.4 2.8 3.2 

X=1.37

30

20

10

0.3 0.5 0.7 0.9 1.1 0.1 0.5 0.9 1.3 1.7 2.1 2.5 2.9 3.3

Z5=0.61 

5=0.27 -\ 

C=0.44

0.1 0.3 0.5 0.7 0.9 1.1 1.3 

DIAMETER

-

X=1.0 

5=0.54 - 

C=0.54

-~Tn ,—

0.0 0.4 0.8 1.2 1.6 2.0 2.4 2.8 3.2 

WAVELENGTH

0.2 0.4 0.6 0.8 1.0 1.2 1.4 1.6 1.8 2.0 2.2 2.4 2.6 2.8 3.0 

DIAMETER

ou

50

40

*- 30

20

10

n

E

<-

-

-

-

-— r^

.,,.,,.,.

X=2.07

S=1.05 

C=0.51

—

-

I —— |

- ~^^-___ rl • i — i r-i r—

20

»-: «-T-'csiccsi cscsicor 

WAVELENGTH

*- 10 -

F

—— j

0=1

s=c 

c=c

.65 

).44_ 

.26

0.6 1.0 1.4 1.8 2.2 2.6 3.0 

DIAMETER

1.4 1.8 2.2 2.6 3.0 3.4 

WAVELENGTH

100

90

80

70

60

50

40

30

20

10 

n

G

-

_

—

~

-

-

-

~

X=2.04 

S=0.81

C=0.40

on

*•" C~071

. ,n —— 5=0.23.

C=0.33

n ....... ....... ...... .... .1 -

0.3 0.5 0.7 0.9 1.1 1.3

DIAMETER

-

-

-

....... —— | —— , , ——

0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0 4.5 5.0 5.5 6.0 6.5 7.0 

WAVELENGTH

HISTOGRAMS SHOWING FREQUENCY DISTRIBUTION (f) of 

diameters (D), and wavelengths (X), in kilometres, of star dunes 

measured on Landsat imagery and Skylab photographs. D, mean 

dune diameter; X, mean dune wavelength; 5, standard deviation; and C, coefficient of variation. Numbers in parentheses 

refer to regions listed in table 40. A, Southeastern Rub' al Khali, 

Saudi Arabia. Area sampled is 12,500 km2 (7,770 mj2) (5). B, 

Gran Desierto, Sonora, Mexico. Area sampled is 1,000 km2 (620 

mi2 ) (1). C, Ala Shan Desert, China. Area sampled is 2,000 km2 

(1,240 mi2 ) (4). D, Southern Sahara, Niger. Area sampled is 1,000 

km2 (620 mi2 ) (3). f, Entire Grand Erg Oriental, Algeria. Area 

sampled is 10,000 km2 (6,200 mi2 ) (6). F, Southern margin of the 

Grand Erg Oriental, Algeria. Area sampled is 2,500 km2 (1,550 

mi 2 ) (7). G, Northern part of the Grand Erg Oriental, Algeria. 

Area sampled is 7,500 km 2 (4,660 mi2 ) (8). (Fig. 181.)

2.6 

2.4 

2.2 

2.0 

1.8 

1.6 

1.4 

1.2

1.0

i I I I I I I

0.6 0.7 0.8 0.9 1.0 1.1 1.2 1.3 1.4 1.5 1.6 1.7

SCATTER DIAGRAM SHOWING RELATIONSHIP of mean dune 

diameter (D) to mean dune wavelength (X) in star dunes 

sampled on Landsat imagery and Skylab photographs. All dunes 

are believed to be compound or complex forms. All measurements are in kilometres, r, correlation coefficient. Numbers in 

parentheses refer to regions listed in table 40. (Fig. 182.)
280 A STUDY OF GLOBAL SAND SEAS

69°00'

07°00'

10 15 Ml

LANDSAT IMAGERY SAMPLE AREAS OF 

PARABOLIC DUNES of the (A) Thar 

Desert, India and Pakistan, and (6) Colombia-Venezuela border region. (Fig. 183.)

Sands National Monument, New Mexico (McKee, 

1966, p. 26-27), and the Killpecker dunes, Wyoming (Ahlbrandt, 1974b, p. 45). Terminology for 

dome-shaped dunes is summarized in table 30. 

Small dome-shaped dunes are not visible on Landsat imagery or on space photographs, but a few 

groups of very large dome-shaped dunes have been 

observed. In the northern sand seas of Saudi 

Arabia, such large features are described (Holm, 

1953) as giant domes.

On aerial photographs (fig. 184), the Arabian 

dome-shaped dunes are interpreted as complex for 

their rounded crests are covered by rows of crescentic dune ridges. Adjacent domes are separated 

by low ridges of indeterminate character. The 

nature of these dome-shaped dunes on Landsat imagery is shown in chapter K, figure 244. Dunes of

\

COMPLEX, GIANT DOMES IN THE NAFUD ATM THUWAYRAT, 

northern Saudi Arabia, east of Buraydah at about long 44°30' E., 

lat 26°45' N. Dark spots in the interdune areas are oases. 

Diameters of dome-shaped dunes in this sand sea average 

about 1 km (0.6 mi). The appearance of these dunes on Landsat 

imagery is shown in chapter K, fig. 244. Aerial photograph by 

the U.S. Department of Defense. (Fig. 184.)

similar dome-shaped appearance on Landsat imagery, which have not been studied on aerial photographs nor described in previous work, are observed in the northern Grand Erg Occidental, 

Algeria (fig. 185A), and in the northern Takla 

Makan Desert, China (fig. 185B).

In each of the three geographic regions just referred to, large dome-shaped dunes are located at the 

far upwind margins of sand seas. Small dome dunes 

are located at the upwind end of both the White 

Sands dune field (McKee, 1966, p. 26-27) and the 

Killpecker, Wyoming, dune field (Ahlbrandt, 

1974b, p. 45). Locations of dome dunes in both these 

fields may be related to the presence of fairly strong 

and unidirectional effective winds, as suggested by 

analysis of wind patterns (chapters F, K) and by internal structure.
MORPHOLOGY AND DISTRIBUTION OF DUNES IN SAND SEAS OBSERVED BY REMOTE SENSING 281

LANDSAT IMAGERY SAMPLE AREAS 

SHOWING DOME-SHAPED DUNES. A, 

Giant domes(?) in the northern part of the 

Grand Erg Occidental, Algeria, north of El 

Golea. B, Giant domes(?) in the northern 

Takla Makan Desert, China. Some of these 

features have linear "tails" 0.9-7.0 km 

(0.6-4.3 mi) long. (Fig. 185.)

Morphometry

Measurements of domes and dome-shaped dunes 

were made for five sample areas of Landsat imagery, partly shown in figure 185 and summarized in 

table 42. Histograms (fig. 186) show that diameters 

and wavelengths of dome-shaped dunes are 

broadly distributed about characteristic mean 

values in each sand sea. Samples are too few, 

however, to test relationships of mean diameter 

and mean wavelength between dome-shaped dunes 

of different sizes and in different geographic locations. Comparisons of dimensionless ratios (table

Z5=1.12 

S=0.25 - 

C=0.22

X=3.34 

S=1.18 - 

C=0.35

R0.4 0.6 0.8 1.0 1.2 1.4 1.6 1.8 0.5 1.5 2.5 3.5 4.5 5.5 6.5 7.5 8.5 

DIAMETER WAVELENGTH

40

30

20

10

25=1.21 

S=0.28 

C=0.23

X=2.18 

S=0.69 

C=0.32

0.6 0.8 1.0 1.2 1.4 1.6 1.8 

DIAMETER

0.8 1.2 1.6 2.0 2.4 2.8 3.2 3.6 4.0 4.4 

WAVELENGTH

20

10

25=1.51 

S=0.29 

C=0.19

X=3.42 

5=0.83 

C=0.24

0.8 1.2 1.6 2.0 

DIAMETER

1.5 2.0 2.5 3.0 3.5 4.0 4.5 5.0 

WAVELENGTH

HISTOGRAMS SHOWING FREQUENCY DISTRIBUTION (f) of 

diameters (D) and wavelengths (X), in kilometres, of domeshaped dunes measured on Landsat transparencies. D, mean 

dune diameter; X, mean dune wavelength; 5, standard deviation; C, coefficient of variation. Numbers in parentheses refer to 

regions listed in table 42. A, Takla Makan Desert, China. Area 

sampled is 2,500 km2 (1,550 mi 2 ) (1). B, Sand seas, northern 

Saudi Arabia. Area sampled is 3,000 km2 (1,860 mi 2 ) (3). C, 

Sahara, Algeria. Area sampled is 2,500 km 2 (1,550 mi 2 ) (2). (Fig. 

186.)

43) of all observed dome-shaped dunes show close 

similarity of these features.

Sand Sheets and Streaks

General Distribution

IRREGULAR PATCHES OF EOLIAN SAND 

with external shapes definable on Landsat imagery 

in terms of the bounding topography, and without 

discernible slipfaces, are herein termed "sand 

sheets." Elongate patches with sharply defined 

edges as seen on Landsat imagery are herein termed 

"streaks." (These are the sand stringers mentioned 

by other geologists in this publication). Other 

authors' terms for these features are shown in table 

34.

Sand sheets are ubiquitous to nearly all sand seas 

studied, but sand streaks are less common and seem 

to be associated mainly with sand seas of linear 

dunes. Figure 187 shows large eolian sand streaks 

in the northwest Sahara of Mauritania. Figure 167B 

shows smaller streaks on the Navajo Indian Reser-
282 A STUDY OF GLOBAL SAND SEAS

13W

LANDSAT IMAGERY SHOWING SAND SHEETS and streaks 

(stringers) associated with linear dunes in the northwestern 

Sahara, Mauritania. The area shown is about 34,000 km2 (31,100 

mi 2 ). Effective winds in this region are from the northeast. (Fig. 

187.)

vation in northern Arizona, U.S.A. Other areas 

where streaks are conspicuous are the southern 

Sahara (chapter K, fig. 201) and the northern part of 

the Arabian Peninsula (chapter K, fig. 200). 

Analysis of effective winds in these regions (chapters F and K) suggests that sand streaks are associated with strong, dominantly unimodal effective 

winds. No measurements were made of sand sheets 

or streaks.

Sand streaks (stringers) were noted on orbital 

photographs by Verstappen and van Zuidam (1970, 

p. 41). Ground investigations were made by S. G. 

Fryberger of such sand bodies in an area northeast 

of the Little Colorado River, Arizona, U.S.A. Sandstreak surfaces there had numerous small

barchanoid dunes, some of which are discernible on 

high-altitude aerial photographs.

Interdune Areas

General Distribution

DUNES IN SAND SEAS are commonly separated 

from each other by interdune areas whose welldefined shapes are associated with dunes of certain 

types, regardless of scale of the dunes or their 

geographic location. For example, interdune areas 

in sand seas of linear dune type are generally open 

corridors called "couloirs" in the formerly 

"French" Sahara, "straate" in the Kalahari and 

Namib Deserts of southern Africa, and "sandy 

lanes" in Australia. Some local names distinguish 

sand-covered interdune corridors from those that 

are bedrock.

Names for interdune areas in sand areas of crescentic dunes generally reflect the degree of closure 

of the segments of these dunes and, thus, suggest 

the ease or difficulty of travel through the sand sea. 

An early name applied by geographers to fully 

enclosed interdune areas in sand seas of crescentic 

dune type are "bajirs." Hedin (1905a), used this 

term to describe large flat-floored basins between 

dunes in the eastern Takla Makan Desert of China 

(fig. 175D). Equivalent terms in the Arabian and 

Sahara sand seas are "fuljes" and "feidjs." The 

term "fulje" was applied (Melton, 1940; and H. T. 

U. Smith, 1946) to interdune hollows in the Midwestern United States.

Examples of small-scale interdune areas of the 

fulje type are shown in aerial photographs of White 

Sands and northwest Sahara (figs. 173B, Q; largescale interdune areas of the same type are shown 

on figures 174A and 175 B of the eastern Rub' al 

Khali, Saudi Arabia. Various local names for interdune areas are listed in table 35.

A density slicer with planimeter can be used to 

measure relative areas of dune and interdune surfaces in some sand seas, such as the Grand Erg 

Oriental, Algeria, where Landsat transparences 

show extreme photographic contrast between dune 

and interdune surfaces. The technique is only 

locally successful, however (chapter K), so comparisons from desert to desert have not been made.
Tables 26-39

These tables give chronological lists of local terms for various types of dunes and the morphometry of such dunes 

derived from measurements of sample areas on Landsat imagery and Skylab and aerial photographs.
284 A STUDY OF GLOBAL SAND SEAS

TABLE 26. — Chronological list of terms considered equivalent to dunes classified as linear, based on Landsat imagery

Terms (reference page, figure, plate, and table numbers in parentheses)

Author

(and region)

Simple ridge Compound ridge

lied in, Sven

(Takla Makan Desert, China).

1905a Thresholds (235-236).

Ordinary ridges (323; fig. 267).

[Some] dune accumulations (354-355). 

Dune-range (357).

Aufrere, Leon

(Formerly "French" Sahara, 

North Africa).

1928 Les dunes longitudinales (833). 

1930 do. (220, 227, 229).

1932

1934

Oblique dunes (42, 44).

Dunes de conjonction, dunes d'incidence (132, 138).

[Some] chaines de sable (833).

Chaines longitudinales (833).

Draa or bras (220).

(Some] chaines de sable (220, 230).

No term.

Chaines avec vagues longitudinal (slassels) (137; fig. 2).

[Some] chaines avec vagues obliques (137; fig. 2).

Chaines diagonales (139).

[Some] dunes de conjonction et dunes d'incidence (132).

Bagnold, R. A.

(Libyan desert, North Africa).

1933 Single seif dunes (107-112, 122).

Single line or range of seifs (122) . 

1941 Longitudinal dune, seif (189, 222-225).

Seif dune chain (224-225) .

Whaleback ridge (107, 125). 

Belts of seif dunes (108, 109). 

Whalebacks (230-231; pi. 13a).

Madigan, C. L.

(Simpson Desert, Australia).

1936 Sandridges (206, 210-227).

Longitudinal ridges (224-227). 

1938 Sandridges (513-515).

Longitudinal ridges (513) . 

1946 Sandridges (45-63; pi. 5-8).

Straight and parallel Sandridges (57). 

Seif (pi. siouf) (50). 

Crest or seif (61).

No term. 

Do.

[Some] giant sandridges and whaleback Sandridges 

(figs. 1, 2; pi. 8).

Seif ridges crossing sand ridges at a small angle en 

echelon (50).

Melton, F. A.

(Midwestern United States),

1940 Longitudinal dunes (113, 121; fig. 9, 10). 

[Some] wind-shadow dunes (120). 

[Some] windrift dunes (129-130). 

[Some] source-bordering lee dunes (122; fig. 10, 13).

[Some] longitudinal dunes (121-122).

Oblique windrift dunes(?) (129, fig. 19, 23).

Oblique longitudinal dunes (fig. 27).

Hack, J. T.

(Navajo Indian Reservation, 

U.S.A.).

1941 Longitudinal dune (240-243). No term.

Capot-Rey, Robert

(Formerly "French" Sahara, 

North Africa).

Capot-Rey, Robert, and 

Capot-Rey, Francoise 

(Formerly "French" Sahara,

North Africa). 

Capot-Rey, Robert

(Formerly "French" Sahara, 

North Africa).

1945 Sand ridge (400) .

Longitudinal forms, dune longitudinale (401).

1947b No term.

1948 Longitudinal forms, dune longitudinale (67). 

Sif (pi., siouf) (63, 66-73). 

Elb (pi., aleb) (73) .

1953 No term.

Dunes of quadrature (parallel sif) (401). 

Dune chain with suif (403; fig. 10). 

Dunes of incidence (oblique sif) (401). 

Cordons (87). 

Files de siouf allonges (89).

Do.

Dos de baleine (whalebacks) (63-70). 

[Some] diouf, bras, or draa (72, 75).

Do. (145).

Smith, H. T. U.

(Nebraska, U.S.A.;

Sahara, North Africa).

1946 Longitudinal dunes (197). 

1963 do. (1, 17-18).

Lee dune ridges (34; fig. 6). 

1965 Longitudinal dunes (566-568; pi. 3, 4A).

Linear ridges (557). 

1968 Longitudinal dunes; seif dunes (43).

No term.

Fishbone pattern of longitudinal dune ridges (18), 

Compound longitudinal dunes (20, 41, fig. 13). 

No term.

Do.

Holm, D. A.

(Saudi Arabian deserts).

1953 No. term.

1957 [Some] sigmoidal dunes (1746).

1960 do. (1371; fig. 4).

Linear ridges (1371). 

1968 do. (978).

[Some] sigmoidal dunes (978).

Uruq (112) .

Anastomosing linear complexes (1746).

Linear complexes (1373).

Uruq (1373, 1377; fig. 7).

Linear complexes (978).

McKee, E. D.

(White Sands, U.S.A.; 

Libyan and Saudi Arabian 

deserts).

1957 Longitudinal dune (1720-1721). 

1966 do. (16; pi. IIB) .

Seif dunes (3, 10, 16, 61; pi. IIB).

No term. 

Do.

Cooper, W. S.

(West coast, North America).

1958 Longitudinal dunes (7, 49, 60-64).

Seif, seif chain (61). 

[Some] oblique ridge dunes (7, 49, 59). 

1967 do. (109-110).

Longitudinal elements (26).

[Some] oblique ridge dunes with basal plinth 

and active crests (49).

Grove, A. T.

(Southern Sahara, North Africa; 

Kalahari Desert, South 

Africa).

1958 Linear dunes (526).

Longitudinal dunes (526-530). 

1960b do. (203) 

1969 do. (195-202, 211; fig. 3).

Linear dunes (195) .

Sand ridges (195-202, 211; fig. 3).

No term.

[Some] alab dunes (203).

Do. (195-201, 208). 

[Some] qoz (195).

Monod, Theodore

(Formerly "French" Sahara, 

North Africa).

1958 Le silk (pi., slouk) (25, 142, 147-150; figs. 10(2),

33).

La famille longitudinale; le silk, les cordons vifs 

(slouk) et 1'elb (pi., alab) (141, 147-150).

Les alab longitudinale (89).

Alab: cordons majeures et de slouk superimposes

(71-72; fig. 33). 

Slouk oblique sur elb (141, 148).

Brown, G. F.

(Arabian deserts).

1960 Longitudinal or seif dunes (156-157) . No term.
MORPHOLOGY AND DISTRIBUTION OF DUNES IN SAND SEAS OBSERVED BY REMOTE SENSING 285

TABLE 26. — Chronological list of terms considered equivalent to dunes classified as linear, based on Landsat imagery — 

_________________________________Continued__________________________

Reference Terms (reference page, figure, plate, and table numbers in parentheses)

Author

(and region)

Simple ridge Compound ridge

Norris, R. M., and Norris, K. S. 

(Algodones Dunes, California

and Mexico). 

Norris, R. M.

(Algodones Dunes, California 

and Mexico).

Linear ridges (618; fig. 1; pi. 1).

Sand streamers (294-295, 305). 

Seif dunes (304).

Powers, R. W., and others 

(Saudi Arabian deserts) .

Mabbutt, J. A. 

(Australia) .

Petrov, M. P. 

(U.S.S.R.).

Stone, R. 0. 

(All deserts) .

Glennie, K. W. 

(Saudi Arabian deserts) .

Goudie, A. S. 

(Southern Africa) .

Goudie, A. S., Allchin, Bridget, 

and Hedge, K. T. M. 

(Thar Desert, India).

Wilson, I. G. 

(Algerian Ergs) .

Cooke, R. U., and Warren, Andrew 

(All deserts).

Breed, C. S., and McKee, E. D. 

(All deserts) . 

McKee, E. D., and Breed, C. S. 

(All deserts) .

McKee, E. D., and others 

(All deserts) . 

McKee, E. D., and Breed, C. S. 

(All deserts) .

1966

1967 

1968

1967

1967

1970

1970 

1973

1971b 

1972

1973

1973

1973

1974a 

1974b

1974 

1976

[Some] uruq; sand, ridges and dune chains; sayf dunes 

(D100) .

Longitudinal dunes (149). 

do. (143). 

[Some] parallel ridges (141). 

Single-crested longitudinal ridges (144) . 

Short dunes (144-146) .

Linear barkhans and ridges (301; fig. 102(2)).

Longitudinal dune, ridge, linear dune (232), 

Self or sif (246) .

Linear dunes or self dunes (89-95) .

Linear forms (94) . 

Longitudinal dunes (245-246, 248).

Longitudinal dunes (196). 

Self dunes, seif dune chains (186-187; fig. 4). 

do. (182-183; pi. Ill B, C) . 

Longitudinal dunes (193, 201; pi. Ill C) . 

Elemental longitudinal dunes (193; pi. Ill C) . 

Seif dunes, seif dune chains (84, 103; fig. 21).

Longitudinal dunes (295, 301, 304, 312). 

Oblique dunes (295, 301, 304, 309). 

Seif dunes (301-304, 309, 317, 327).

Linear dunes (160-171).

do. (9-3; figs. 9-3, 9-4) . 

Parallel straight or linear dunes (665, 668, 674; 

fig. 3). 

do. (3, 17, 52-55, 62, 64, 84; figs. 2, 9, 13, 

17, 20-22; table 1) . 

Parallel straight or linear dunes (81; fig. 55).

[Some] uruq (D100) .

No term.

[Some] parallel ridges with oblique crests (141). 

Oblique crestal dunes (143) . 

Climax dune type (147) .

No term.

Sand levee (245) . 

Whaleback (253) .

Pleistocene seif, the Wahiba sands (90-93; fig. 74).

Alab ridges (94) . 

Composite forms (95) . 

Clustered dendritic ridges (97; fig. 2a) . 

No term.

Draas (182, 191, 198). 

Compound (seif) dune ridge (208).

No term.

Draa (50, 231-232) .

No term.

Do. 

Linear and feathered linear megadunes (674; fig. 3, 7).

Do. (3, 17, 23, 47, 62, 84; figs. 2, 7, 13, 17, 20; 

table 1) . 

No term.

TABLE 27. — Chronological list of terms considered equivalent to dunes classified as crescentic, based on Landsat imagery

[Crescentic, as used here, includes barchan, barchanoid ridge, and transverse dunes of other geologists in this publication]

Terms (reference page, figure, plate, and table number in parentheses)

Author

(and region) Simple mound Simple ridge Compound mound Compound ridge

Bedin, Sven 

(Takla Makan

Desert, China) .

1905a Ideal crescents (323; fig. 268).

Individual dunes (351; fig. 

293).

Crescentic individual dunes 

(404) .

Fused dunes, dune triplets

(351-352; figs. 294, 295). 

Transverse thresholds (316-320,

361-363) . 

Barkhans or sandridges (227,

324, 329, 412) . 

Crescentic dunes (270). 

Chains of dunes in festoons

(320). 

Chains of connected dunes (351;

fig. 296). 

Compound dune length (357-358;

figs. 302-303). 

Chains of dunes in festoons

(403). 

Chains of coalescing dunes

(416).

Composite dune (271-273; 

figs; 238-244) .

Dunes d'incidence normal (132). 

Les dunes en vague (136) .

[Some] dune accumulations 

(352-354; figs. 296- 

298).

Aufrere, Leon

(Formerly "French"

Sahara, North

Africa) .

1928

1930

1932

1934

Sif (pi. siouf) or barchans

(833-835).

Barchans (224, 226).

No term.

do.

Les vagues de sable (833) .

No term.

Les vagues de sable (42) .

do. (134, 137; fig. 2).

No term.

do.

do.

Zemlah (pi. zemoul)(?)

(133).

No term.

Do.

Do.

Chaines transversales

(139).
286 A STUDY OF GLOBAL SAND SEAS

TABLE 27. — Chronological list of terms considered equivalent to dunes classified as crescentic, based on Landsat imagery • Continued

Reference

Author 

(and region)

Bagnold. R. A. 

(Libyan desert, 

North Africa) .

Madigan, C. L. 

(Simpson Desert, 

Australia) .

Melton, F. A. 

(Midwestern United 

States).

Hack, J. T. 

(Navajo Indian 

Reservation, 

U.S.A.).

Capot-Rey, Robert 

(Formerly "French" 

Sahara, North 

Africa) .

Capot-Rey, Robert and 

Capot-Rey Francoise 

(Formerly "French 

Sahara, North 

Africa) .

Smith H. T. U. 

(Nebraska, U.S.A.: 

Sahara, North 

Africa).

Holm, D. A. 

(Saudi Arabian 

deserts).

McKee, E. D. 

(White Sands, 

Navajo Indian 

Reservation, 

U.S.A.; Libyan 

desert, North 

Africa).

Cooper, W. S. 

(West coast, North 

America) .

Grove, A. T. 

(Southern Sahara, 

North Africa; 

Kalahari Desert, 

southern Africa) .

Monod, Theodore 

(Formerly "French" 

Sahara, North 

Africa) .

Year

1933 

1941

1936

1938 

1946

1940

1941

1945

194 7b 

1953 

1948

1946 

1953 

1956

1963 

1965

1968

1953 

1960

1968

1957 

1966

1958 

1967

1958 

1960b 

1969

1958

Terms

Simple mound

Barchan dune (106, 109-112). 

do. (189, 208-221).

Barchans, crescentic dunes 

(223). 

Transverse dunes (223-225) . 

Barchans, crescentic dunes 

(514) . 

do. (50, 56-58).

Barcan dune (113-117, 140; 

figs. 1-5, 24, 26).

Barchans (241, 250).

No term.

Barkhanes (96-97). 

do. (144). 

do. (63, 66-69, 71-72).

Qord (71)

Barchans (197). 

do. (102). 

No term.

Barchans (1, 30; fig. 2). 

No term.

do.

Barkhan dunes (106). 

Barchan dunes (1371). 

Crescentic dunes (1373).

Crescentic dunes (975). 

Barchan dunes (975, 978).

Barchan (1720-1725). 

do. (9-15, 17, 25, 39-40, 

50, 59-60; pi. He). 

Barchan crescent (9).

Barchans (27-28). 

Compressed isodiametric 

transverse ridge (28).

No term.

No term. 

Barchans (195, 205; fig. 10).

Barkhanes (100-141).

(reference page, figure, plate,

Simple ridge

No term. 

Colony or chain of dunes (188)

Transverse sand waves (223- 

224). 

Transverse ridges (227). 

do. (513).

No term.

Peak and fulje (fig. 25).

117-118; fig. 7). 

Isolated transverse dune 

ridges (119; fig. 8).

Transverse dunes (241, 250). 

Sand waves (241, 257). 

Climbing dunes (241).

Elb (392). 

Sif (suif) (400-401).

No term. 

Sif (suif) (144). 

Dunes transversales (73).

Transverse dune ridges (177). 

Transverse dunes (102). 

No term.

Transverse ridges (1, 16-17, 

36; fig. 8). 

No term.

do.

[Some] zibarr (110). 

[Some] zibar (1372).

Barchans in transverse ridge 

(compound dunes) (977). 

Transverse ridges (978).

No term. 

Barchanoid forms, gradations 

from barchans to transverse 

dunes (9, 17; pi. IID) .

Undulating dune ridge (7). 

Transverse ridges (25, 27-34, 

58). 

Transverse waves (33-34, 43). 

do. (35). 

Transverse ridges (21, 31, 

109). 

Barchanoid form (28; fig. 1; 

pl. 4).

Transverse ridges (526-531). 

Mreyye or mereie (202). 

Curved- dunes (199).

Elements transverses mineurs, 

undulations du type Myreyye 

(25, 68, 143, 145, 170; fig. 

10; pl. 5) .

and table number in parentheses)

Compound mound

No term. 

. Complex barchans (212). 

Rounded mounds (217) .

No term.

do. 

do.

No term.

No term.

Demkha, amygdaloidal dune 

massif, mastodon (395; 

fig. 6). 

No term, 

do. 

Demkha, amygdaloidal dune, 

massif, mastodon (73; pl. 

II. 1).

No term, 

do. 

do.

Compound transverse dunes (19, 

40, fig. 12). 

do. (557, 564). 

Compound barchans and barchanoid forms (563; pl. 2A) . 

Compound transverse dunes 

35, fig. 3-3).

No term, 

do. 

Giant crescents (1371).

Crescentic hollows(?) (1370, 

1373; fig. 3). 

No term.

No term, 

do.

Huge barchan with system of 

anastomosing transverse 

ridges on [its] back (28).

No term.

No term, 

do. 

do.

Elements transverses 

majeures-les pseudo-alab 

(25, 68, 141-142; fig. 

10(2)).

Compound ridge

No term. 

Do.

No term.

Do. 

Do.

Intersecting transverse

dune series (fig. 26).

No term.

No term.

Do. 

Do. 

Do.

No term. 

Do. 

Giant composite barchans 

(1735). 

Compound barchans 16, 

19, 39; fig. 11). 

No term.

Composite barchans (39).

No term. 

Do. 

Giant crescents, giant 

crescentic massifs 

(1371-1372). 

Giant crescentic dune 

complex (1375; fig. 5). 

No term.

No term. 

Do.

No term. 

Do.

No term. 

Do. 

Do.

Bourrelets monumentaux(?) 

(141).

Serie de bourrelets

transversaux (145). 

Bourrelets geants (147) . 

Les akles typiques (92-94, 141;

figs. 15-18) .

Le ghord individuel (141) .

Les individues ghordiques, 

engages dans une serie de 

vagues transversales (143) .
MORPHOLOGY AND DISTRIBUTION OF DUNES IN SAND SEAS OBSERVED BY REMOTE SENSING 287

TABLE 27. — Chronological list of terms considered equivalent to dunes classified as crescentic, based on Landsat imagery —

Continued

Reference

Author 

, . . , Year (and region)

Norris, R. M., and 1961 

Norris, K. S. 

(Algodones Dunes , 

California and 

Mexico) . 

Norris, R. M. 1966 

(Algondones Dunes, 

California and 

Mexico) .

Kadar, Laslo 1966 

(Central Europe) .

Powers, R. W., and 1966 

others 

(Saudi Arabian 

deserts) .

Petrov, M. P. 1967 

(U.S.S.R.)

Stone, R. 0. 1967 

(All deserts) .

(Kalahari Desert, 

southern Africa;

Australia) .

Goudie, A. S. 1970 

(Southern Africa). 

Goudie, A. S., 1973 

Allchin, Bridget, 

and Hedge, K. T. M. 

(Thar Desert, India).

Glennie, K. W. 1970 

(Saudi Arabian 

deserts) .

Wilson, I. G. 1971b 

(Algerian Ergs) . 1972

1973

Cooke, R. U., and 1973 

Warren, Andrew 

(All deserts) .

Breed, C. S., and 1973 

McKee, E. D. 

(All deserts) . 

McKee, E. D., and 1974b 

Breed, C. S. 

(All deserts) .

McKee, E. D. and 1974 

others . 

(All deserts) .

McKee, E. D., and 1976 

Breed, C. S., 

(All deserts) .

Terms

Simple mound

Barchan dunes (605) .

Barchan dunes (292, 306). 

Crescentic dunes (292) .

No term.

Simple barchan dunes (D100) .

Solitary barkhans (295, 300-301; 

fig. 102(1) ; table 36) .

Barchan; also, barcan, barchane, 

barkan, barkhan (215) . 

Crescentic dune (220).

Barchans (94-95) . 

No term.

Barchan dune or barchan (82-88).

Barcban dunes (185-186; fig. 4). 

do. (181, 192, 208) .

Barchan dunes (83) .

Barchans (282, 290, 292-295, 

297, 300-301, 304, 306, 310; 

figs. 4.31, 4.32).

Barchan (163) . 

No term.

Barchan (28, 61, 63, 69-71, 

81; fig. 28).

No term.

(reference page, figure, plate, a

Simple ridge

Transverse dunes (605) . 

No term.

Crescent dunes or barchans, 

Twin barchans, transversal 

dunes (438, 447; fig. 28) .

Compound barchan dunes, or 

simple rounded transverse 

ridge (D100) .

Barkhan chains (300-301; fig. 

102(3) ; table 36) .

Ridge-barchan form (307).

Climbing dune (220) . 

Transverse dune (251).

T ' 1' k

transverse elements crescentic transverse elements,

or ridges (143-144) .

No term.

Transverse dunes (245-246, 

249) .

Barchanoid forms (84) . 

Transverse dunes (95-99) .

Transverse dunes (196). 

Crescentic barchanoid or 

transverse sandy ridge 

(180-181) . 

Transverse ridges (182, 185, 

190, 199-202).

No term.

Transverse dune ridges (280, 

283, 291, 304, 309) .

Barchanoid and lingoid 

transverse ridge (288-290, 

297, 311 T 312) . 

[Some] zibar (309, 327) .

Crescentic dunes (162).

Parallel wavy or crescentic 

dunes (665, 668; figs. 9, 

10).

do. (3, 24, 62, 64; figs. 

17, 25; table 8).

Barchanoid dune, fishscale 

type, peak and fulje, 

topography (24, 47, 82, 84; 

figs. 3, 9, 10, 12, 13, 15,

17, 25) . 

Transverse dune (fig. 28) . 

Akle (21, 81, 84).

[Some] parallel wavy or crescentic dunes of the simple 

basic type (81-82) .

nd table number in parentheses)

Compound mound

Complex barchans (605, 617) .

Very large, overlapping 

barchans (617) .

Giant barchans megabarchans 

(292-296).

Two-storied barchans (447) .

Complex barchans, giant 

barchans, (D100) .

No term.

Megabarchan (232) .

No term, 

do.

No term.

Draas (182, 191, 198) . 

Transverse draas (191) .

Barchanoid draas (178-179; 

pi. IID, E).

do. (100; fig. 17) .

Draa-sized barchans (282- 

283) .

Mega-barchans (297).

No term.

Crescentic megadunes, giant 

crescents , or megabarchans 

(668; fig. 4, 7) .

Crescentic megadunes, giant 

crescents, or megabarchans 

(3, 24, 69, 74, 83; figs. 

3, 7, 12, 15, 19; table 1) .

Megabarchans or giant 

crescents (82) .

Compound ridge

Complex barchans (605, 

617). 

Very large overlapping 

barchans (617) .

Giant barchans , 

megabarchans (292, 

296).

No term.

Complex barchans giant 

barchans (D100) .

Complex barchan ridges 

or "davana" (295, 298, 

300; fig. 101). 

Alveolar davanas or 

alveolar barkhan sands 

(298, 300; table 36) .

No term.

No term. 

Do.

Giant barchan complex 

(88; fig. 72) . 

Barchan-like complexes 

(98-99; fig. 78) .

Draas (182, 191, 198). 

Transverse draas (191) .

Barchanoid draas (178- 

179); pi. IID, E). 

Giant composite dunes 

[draas] (181). 

Barchanoid draas (100; 

(fig- 17).

Draa-sized barchans 

(282-283) .

Mega-barchans (297) .

No term.

Crescentic megadunes, 

giant crescents or 

or megabarchans (668; 

(figs. 4, 7, 10). 

Crescentic megadunes, 

giant crescents or 

megabarchans (3, 24, 69, 

74, 83; figs. 3, 7, 12, 

14, 15, 19) . 

Dune complexes or draa 

(28, 69-70, 82) .

Crescentic, fishscale 

(fig. 25). 

Transverse, parallel wavy 

(62). 

[Some] parallel-wavy or 

crescentic dune complexes including [some] 

fishscale type and giant 

crescent or megabarchan 

type (82; fig. 56).
288 A STUDY OF GLOBAL SAND SEAS

TABLE 28. — Chronological list of terms considered equivalent to dunes classified as star, based on Landsat imagery

Reference

Author 

(and region)

Hedin, Sven 

(Takla Makan Desert, China).

Aufrere, Leon 

(Formerly "French" Sahara, 

North Africa) .

Capot-Rey, Robert 

(Sahara, North Africa).

Capot-Rey, Robert, and 

Capot-Rey, Francoise 

(Sahara, North Africa) .

Smith, H. T. U. 

(Nebraska, U.S.A.; 

Sahara, North Africa) .

Holm, D. A. 

(Saudi Arabian deserts) .

Monod, Theodore 

(Formerly "French" Sahara, 

North Africa) .

Brown, G. F. 

(Saudi Arabian deserts) .

Powers, R. W., and others 

(Saudi Arabian deserts) .

McKee, E. D. 

(Irq as Subay', Saudi Arabia).

Petrov, M. P. 

(U.S.S.R.) .

Stone, R. 0. 

(All deserts) .

Glennie, K. W. 

(Saudi Arabian deserts) .

Wilson, I. G. 

(Algerian Ergs) .

Cooke, R. U. , and Warren, Andrew 

(All deserts) .

Breed, C. S., and McKee, E. D. 

(All deserts) . 

McKee, E. D., and Breed, C. S. 

(All deserts) . 

McKee, E. D., and others 

(All deserts) .

McKee, E. D., and Breed, C. S.

Year

1905a

1930 

1932 

1934

1945 

1947a 

1953 

1948

1946 

1963

1953 

1960 

1968

1958

1960

1966

1966

1967

1967

1970

1971a 

1972 

1973

1973

1973

1974a 

1974b 

1974

1976

Terms (reference page, figure, plate,

Simple star

Pyramidal dunes (330, 363).

No term. 

[Some] rhourds simples (44) . 

Collines de sable (rhourds) (137, 

139-140; figs. 2, 4(3)) . 

[Some] rhourds degages (139) .

[Some] khurds, guerns (393, 397; fig. 7). 

Oghroud, mastodonte, iguidi (86, 89). 

No term.

Qord, ghourd (72-73; pi. 113).

Rhourd (198) . 

Embryonic forms of peaked dunes (21, 44; 

fig. 16).

Sand peaks or star dunes (112) . 

Pyramidal dunes (1371-1373). 

No term.

[Some] ghords (141) .

Star dunes (159) .

[Some] sand mountains (D100) .

Star dune (3, 10, 62-68; pi. VIII A, B) .

Conical dunes (295, 300-301; figs. lOlc, 

102(4); table 36).

Rhourd (242) . 

Star dune (249) .

No term.

[Some] star-shaped pyramids, rhourds 

(270).

No term, 

do.

[Some] sand mountains or rhourds (304).

Star or radial dunes (162; fig. 9).

Star dunes (9-3) . 

Star or radial dunes (665, 668). 

do. (3, 17, 83-85; figs. 4, 8; 

table 1) .

Star or radial dunes (81).

and table numbers in parentheses)

Compound star

No term.

Oghroud (223) . 

Les grands rhourds polypyramides (45) . 

Rhourd polypyr amide (141) .

[Some] khurds (397; fig. 7). 

Pyr amides aux sommets pointus (89) . 

Do. (145). 

Les grandes pyramides (oghroud) 73, 77) . 

Oghroud (pi. II, 2, no. 3).

No term. 

Peaked complexes (21, 43; fig. 15). 

Domal dune complexes (22, 45; fig. 17).

No term. 

Pyramidal dunes (1373) . 

Do. (977).

[Some] ghords (141) . 

[Some] chaines ghordiques (20) .

No term.

Giant sigmoidal and pyramidal sand peaks 

(D100) .

No term.

No term.

Dune massif (225) . 

Guern (230) . 

Rhourd (242) . 

Star dune (249) .

Stellate dunes (86-88; figs. 70-71).

Draa peaks, rhourds (268).

Star-shaped pyramids, rhourds (270). 

Stellate rosettes (178-179; pi. II C) . 

Draa peaks (oghourds) (188) . 

Oghourds or star dunes (190-191) . 

Draa peaks, rhourds (99; fig. 16).

[Some] sand mountains or rhourds (304).

Radial (star) megadunes (162; figs. 3, 

9). 

Star dunes (9-3; figs. 9-1, 9-2). 

Star or radial megadunes (668; fig. 5). 

Do. (3, 17, 24, 47, 83-85, figs. 4, 

8, 10, 12, 17, 19; table 1). 

Dune complexes or draa (28, 82). 

Star or radial megadunes (82) .

(All deserts).
MORPHOLOGY AND DISTRIBUTION OF DUNES IN SAND SEAS OBSERVED BY REMOTE SENSING 289

TABLE 29. — Chronological list of terms considered equivalent to dunes classified as parabolic, based on Landsat imagery

Reference

Author 

(and region)

Hedin, Sven 

(Takla Makan Desert, China).

Aufrere, Leon 

(Formerly "French" Sahara, 

North Africa) .

Madigan, C. L. 

(Simpson Desert, Australia).

Capot-Rey, Robert, and 

Capot-Rey, Francoise 

(Formerly "French" Sahara, 

North Africa) .

McKee, E. D. 

(White Sands, U.S.A.) .

Grove, A. T. 

(Southern Sahara, North 

Africa; Kalahari Desert, 

Southern Africa) .

Cooper, W. S. 

(West coast, North America).

Stone, R. 0. 

(All deserts) .

Year

1905a

1928

1930 

1934

1936 

1946

1948

1957 

1966

1958 

1969

1967

1967

Terms (reference page, figure, plate,

Simple U-shaped dunes

Spoon-shaped dunes(?) (331; fig. 270).

Les dunes paraboliques et les dunes en U 

(834-835) . 

Dunes de mousson, dunes en rateau (228). 

Les dunes paraboliques et les dunes en U 

(134).

U-shaped dune, fulje-type dunes (224). 

Blowouts (57) . 

Parabolic bowouts or fuljes (61) .

Dunes paraboliques (75).

Parabolic dune (1720-1721) . 

Blowouts (1725) . 

do. (9-10). 

Parabolic dune (3, 9-11, 15, 25, 50-51). 

U-shaped or V-shaped dune (9) .

Parabolic dunes (529) . 

Blowouts (199) .

Parabola dunes (22-25, 111). 

[Some] giant parabolas (24).

Blowout (217) . 

Chevron dune (219) . 

Elongate blowout dune (226) . 

Hairpin dune (230). 

Parabolic dune (236) . 

U-shaped dune (251) . 

Upsiloidal dune (252) .

and table numbers in parentheses)

Compound U-shaped dunes

No term.

No term.

Do. 

Les Chaines bouclees (134) .

No term. 

Do.

No term.

No term. 

Do.

No term. 

Do.

Compound parabola (31). 

[Some] giant parabolas (111) .

No term.

Melton, F. A. 1940 Blowout or parabolic dunes (133, 126-127). "Nested" elongate-blowout dune series 

(Midwestern United States). (128).

Elongate-blowout dunes (127-128; figs. 

17, 18).

Hack, J. T.

(Navajo Indian Reservation, 

U.S.A.).

1941 Parabolic dunes of deflation and 

accumulation (240, 242-243).

No term.

Smith, H. T. U.

(Nebraska, U.S.A.;

Sahara, North Africa).

1946 Upsiloidal dune (197-199).

1953 Phytogenic dunes (102).

1965 Blowouts (557, 569-570).

1968 do. (33).

No term.

Do.

Do.

Elongate U-shaped dunes and subparallel 

ridges (44) .

Goudie, A., Allchin, Bridget, 

and Hedge, K. T. M. 

(Thar Desert, India).

1973 Parabolic dunes (248). No term.

Cooke, R. U., and Warren, Andrew 1973 

(All deserts).

Blowouts, parabolic dune, lunettes (318). Nested parabolic system (318).

Ahlbrandt, T. S.

(Wyoming, U.S.A.).

1974b Parabolic dunes (45).

McKee, E. D., and Breed, C. S. 1974b

(All deserts) . 

McKee, E. D., and others 1974

(All deserts) . 

McKee, E. D., and Breed, C. S. 1976

(All deserts) .

Parabolic or U-shaped dunes (665, 668; 

figs. 6, 9).

do. (3, 24, 53, 61-62, 83, 85; 

figs. 5, 9; table 1).

do. (81-82).

Parabolic dune array, Thar Desert 

(668; fig. 6).

Do. (24, 62; figs. 5, 18, 25). 

Dune complexes or draa (28, 82). 

Parabolic dunes, India (fig. 58).
290 A STUDY OF GLOBAL SAND SEAS

TABLE 30. — Chronological list of terms considered equivalent 

to dunes classified as dome-shaped, based on Landsat imagery

Author

(and region)

Terms (reference page, figure, plate, and 

table numbers in parentheses)

Bagnold, R. A. 1941 Rounded mounds (?) (217). 

(Libyan desert, North Africa).

Holm, D. A.

(Saudi Arabian deserts).

1953 Dome-shaped dunes (106-112; figs. 2-8).

McKee, E. D.

(White Sands, U.S.A.).

1966 Dome-shaped dunes (10, 15, 25-27).

Dwers, R. W., and others 

(Saudi Arabian deserts).

1966 Giant oval sand mounds (D100).

Ahlbrandt, T. S. 

(Wyoming, U.S.A.).

1974b Dome dunes (45).

TABLE 31. — Chronological list of local terms for dunes considered equivalent to those classified as complex, based on Landsat

imagery

Reference

Author

(and region)

Terms (reference page, figure, plate, and table numbers in parentheses)

Year

Hedin, Sven

(Takla Makan Desert, China)

1905a [Some] dune-sccumulations (400).

Aufrere, Leon

(Formerly "French" Sahara, 

North Africa).

1930 [Some] draas, bras, or fluk (220, 223).

Slassels or draa with oghounds (223, 226). 

1932 Chains with rhourds (44). 

1934 Les dunes complexes (133).

ChMnes avec vagues obliques et pitons (draas) (fig. 2).

Rhourds engages (1939) .

Madigan, C. L.

(Simpson Desert, Australia)

1936 Sandridges with minor crescentic dunes on top (212) .

1938 Do. (514).

1946 [Some] plinths with varieties of crest formations (49-51)

Melton, F. A.

(Midwestern United States)

1940 Complex dune forms (fig. 28).

Capot-Rey, Robert

(Formerly "French" Sahara,

North Africa). 

Capot-Rey, Robert, and 

Capot-Rey Francoise 

(Formerly "French" Sahara, 

North Africa).

1945 Dunes of conjonction (sif normal to axis of chain) (401).

[Some] braas or draa (404; fig. 11). 

1947a Do. (88-89). 

1948 Demkhas (73; PI. II 1).

Holm, D. A. 

(Saudi Arabian deserts) .

McKee, E. D. 

(Great Sand Dunes National 

Monument, U.S.A.).

Monod, Theodore 

(Formerly "French" Sahara, 

North Africa) .

Smith, H. T. U. 

(Nebraska, U.S.A.: 

Sahara, North Africa).

Powers, R. W. , and others 

(Saudi Arabian deserts) .

Petrov, M. P. 

(China, U.S.S.R.) .

Stone, R. 0. 

(All deserts) .

1957 

1960 

1968

1966

1958

1963 

1968

1966

1967

1967

Linear belts with V-shaped chevrons; dune complexes; [some] sigmoidal 

dunes (1746) . 

Hooked dunes (1371-1372). 

Linear complexes(?) (1373). 

Complex dunes, dune complexes (977) .

Reversing dune (10, 61, pi. II E) .

Grands bnaig du dhra (83) . 

Dunes en rateau, modele transverse sur 'elb; [some] famille des akles; 

systeme complex (141).

Complex longitudinal dunes (20-21; figs. 10, 14). 

Ridged dune complex (22; fig. 18) . 

Do. (36).

[Some] sand mountains [D100] .

Alveolar barkhan sands with conical tops (323) . 

Longitudinal-transverse and interf erentional dune forms (297; fig. 100).

Fish hook or hooked dune (228) . 

Sigmoidal dune (249) .
MORPHOLOGY AND DISTRIBUTION OF DUNES IN SAND SEAS OBSERVED BY REMOTE SENSING 291

TABLE 31. — Chronological list of local terms for dunes considered equivalent to those classified as complex, based on Landsat

imagery — Continued

Reference

Author

(and region)

Terms (reference page, figure, plate, and table numbers in parentheses)

Year

Mabbutt, J. A. 

(Australia).

1968 [Some] ridges with multiple or braiding crests (143; PI. VI). 

[Some] dune networks with intersecting trends (146). 

Reticulate dunes (148) .

Grove, A. T.

(Namib Desert, South-West 

Africa).

1969 [Some] alab dunes (195-201; pi. Villa).

Glennie, K. W.

(Saudi Arabian deserts).

1970 Seif dunes with barchan-like slipfaces (94-95; fig. 75). 

[Some] dunes of the Uruq al Mu'taridah (96-98; fig. 76).

Wilson, I. G.

(Algerian Ergs, North Africa)

1971b [Some] draas (182, 191, 198).

Lingoid networks with rhomboidal or hexagonal cells (182) 

Giant draa ridges (pi. IIIA, F).

Cooke, R. U., and Warren, Andrew 

(All deserts).

1973 [Some] draa (231-232; fig. 4.27). 

[Some] draa ridges (235, 296-297). 

Oblique draa patterns (300).

Breed, C. S., and McKee, E. D. 

(Namib Desert).

1973 Linear megadunes (fig. 7)

McKee, E. D., and Breed, C. S, 

(All deserts).

McKee, E. D., and others 

(All deserts).

1974a

1974b, 

1974

McKee, E. D., and Breed, C. S. 1976 

(All deserts).

Linear chains of star dunes (9-3; figs. 9-1, 9-2).

Do. (668; fig. 5). 

Chevron or basketweave dunes (668; fig. 4).

Star dunes in chains (19; figs. 4, 8; table 1). 

Linear type (fig. 7).

Chevron or basketweave dunes (81; fig. 3; table 1). 

Reversing dunes (fig. 10).

Chains of star dunes (82; fig. 54).

TABLE 32. — Chronological list of local terms for various sand seas

Reference

Author 

(and region)

Hedin, Sven 

(Takla Makan Desert, China).

Aufrere, Leon

(Formerly "French" Sahara, 

North Africa.

Bagnold, R. A. 

(Libyan desert, North Africa).

Madigan, C. L. 

(Simpson Desert, Australia).

Capot-Rey, Robert

(Formerly "French" Sahara, 

North Africa) .

Capot-Rey, Robert and 

Capot, Rey, Francois, 

(Formerly "French" Sahara, 

North Africa) .

Holm, D. A. 

(Saudi Arabian deserts) .

Year

1905a

1928

1930 

1934

1933

1936

1946

1945

1947a 

1953

1948

1953 

1960

Terms (reference, page, figure, plate, and

table numbers in parentheses)

"Sea" of sand (234) .

Pasage dunaire, la mer de sable (834).

Erg (225). 

Un champ de dunes (132) . 

La mer de sable (134, 138-139).

Sand sea (110) . 

Dunefield (108) .

Mer de sable (224) . 

Sandridge desert (206, 208, 215; fig. 2).

Do. (56).

Erg (391).

Sea of sand, la mer de sable (393). 

Houle de sable (88) . 

La mer de sable (145) .

Akle (145-146) . 

Houle de sable (79).

Nefud (106-112; figs. 2-8). 

Nafud (1369-1374) .

Reference

Author 

(and region)

Norris, R. M., and Norris, K. S. 

(Algodones Dunes, California

and Mexico) .

Smith, H. T. U. 

(Nebraska, U.S.A.: 

'Sahara, North Africa).

McKee, E. D. 

(White Sands, Navajo Indian

Reservation, U.S.A.; Libyan 

desert; Arabian deserts).

Powers, R. W. , and others

(Saudi Arabian deserts) .

Stone, R. 0. 

(All deserts) .

Goudie, A. S. 

(Southern Africa) . 

Goudie, A. S., Allchin, Bridget, 

and Hedge, K. T. M. 

(Southern Africa; Thar Desert) .

Glennie, K. W. 

(Saudi Arabian deserts) .

Year

1961

1963 

1968

1966

1966

1967

1969 

1973

1970

- Terms (reference, page, figure, plate, and

table numbers in parentheses)

Dune mass (617) .

Dune field (36, 43; figs. 8, 15). 

Do. (29).

Dunefield (10) .

Nafud (D100).

Erg (227). 

Sand sea (245)

Dune country (404) .

Ergs (245; table 1). 

Dune fields (247, 249) .

Dunefield (84) .

Mabbutt, J. A.

(Kalahari Desert, southern 

Africa; Simpson Desert 

Australia).

1955 Sandveld (24, 26).

1967 Sandridge deserts (145). 

Dunefields (173).

1968 Do. (140).

Wilson, I. G. 1971a 

(Algerian Ergs, North Africa). 1971b 

1972

Cooper, W. S.

(West coast, North America).

1958 Erg (61).

1967 Body of dunes (39).

Dune complex (42, 44-47, 57-58; fig. 1; 

pi. 8-10, 13). ____

Erg, sand-sea (264-267).

Erg, 180, 184, 190-198; fig. 3).

Do. (187-188). 

Sand-ridge deserts (187). 

Erg (77-105). 

Draa ergs, dune ergs (91).

Cooke, R. U., and Warren, Andrew 1973 

(All deserts).

Grove, A. T.

(Southern Sahara, North 

Africa).

Erg (526-533). 

Qoz (531).

Sand sea (50, 229).

Erg (229. 300, 306, 312, 322-327).

Dunefield (311-315, 322).

Monod, Theodore

(Formerly "French'1 Sahara, 

North Africa).

Erg (22, 55, 63).

Breed, C. S., and McKee, E. D. 1973

(All deserts). 

McKee, E. D., and others 1974

(All deserts). 

McKee, E. D., and Breed, C. S. 1976

(All deserts).

Sand sea, erg (1960).

Sand sea (3-85).

Desert sand seas (81-82).
292 A STUDY OF GLOBAL SAND SEAS

TABLE 33. — Chronological list of local terms for patterns of eolian sand deposits in sand seas

References

Author

(and region)

———————————— Terms (reference page, figure, plate, and table numbers in parentheses) 

Year

Hedin, Sven

(Takla Makan Desert, China)

1905a Network of dunes, bajirs, and thresholds (360, 365; figs. 301-303, 

317; pi. 52).

Aufrere, Leon 1928

(Formerly "French" Sahara, 1932

North Africa). 1934

Les sable en colonne ou en monome (834) . 

Zemloul (44-45).

Dunes espacees et les dunes serrees (133). 

Vagues entrecroisees ou reticulees (138-139).

Bagnold, R. A.

(Libyan desert, North Africa)

1933 Sand sea of parallel self dune lines (110).

Belt of barchans (106, 123-124; fig. 3). 

1941 Belt of barchans (218-221).

Multiple seif chains (231-235) .

Madigan, C. L.

(Simpson Desert, Australia)

1936 Sand-ridge grid, grid of parallel ridges (211, 218; fig. 11).

Melton, F. A.

(Midwestern United States, 

U.S.A.)

1940 Array of dunes (118-119).

Peak and fulje topography; intersecting transverse dune series

(131-132; fig. 25, 26). 

Trains of barchan dunes (figs. 2, 3).

Smith, H. T. U.

(Nebraska, U.S.A.;

Sahara, North Africa).

1963 Barchan field (30; fig. 2).

Trains of barchans (16).

Random pattern (43; fig. 15).

Parallel, subparallel, divergent, reticulate group patterns (17-18) 

1965 Pronounced parallelism like waves of the sea (563) .

Ridge and furrow topography (566) .

Capot-Rey, Robert

(Formerly "French" Sahara, 

North Africa).

Capot-Rey, Robert, and 

Capot-Rey, Francoise. 

(Formerly "French Sahara, 

North Africa).

1947a ChMnons dunaires (88).

Les grandes massifs dunaires (94).

Essaims [swarms] de barkhanes (97). 

1953 Do. (144).

1948 Train [of barchans] (66).

Massif d'un aspect alveole (73).

Cooper, W. S.

(West coast, North America)

1958

1967

Reticulate pattern with rhomboidal meshes (31). 

Oblique ridge pattern (25, 49-60, 62; fig. 2; pi. 11). 

Longitudinal-ridge pattern (62). 

Transverse-ridge pattern (25, 27 

Dune belts (23; figs. 2, 3; pi.

58, 64; fig. 1; pi. 7, 11) 

9).

Dune sheets (33-40, 58-60; figs. 1, 2; pi. 8).

Norris, R. M., and Norris, K. S. 1961 

(Algodones Dunes, California 

and Mexico).

Norris, R. M. 1966 

(Algodones Dunes, California 

and Mexico).

Peak and hollow topography (608) . 

Chains of dunes, chiflones (617). 

Barchan chains (618) .

Barchan swarms (294-295). 

Dune cluster (292) .

Mabbutt, J. A.

(Kalahari Desert, southern 

Africa; Simpson Desert, 

Australia).

1967 Parallel ridges (58, pi. 18c).

1968 Do. (141-143, 146; pi. 1). 

Barchan trains (114)

Widely-spaced parallel ridges (143, 145; pi. 6). 

Convergence and deflection of dune ridges (145, 148; pi. 7) 

Alined short dunes (146) . 

Braided, forked, arcuate crests (146). 

Arcuate belts of dunes (144) . 

Dune networks (145-146; pi. 8). 

Branching patterns (147) .

Monod, Theodore

(Formerly "French" Sahara, 

North Africa.

1958 Regime alab-slouk, regime longitudinal typique (59). 

Regime alat. ay6un (20, 77, 80, 141).

Systemes transverses et systemes longitudinaux (143) . 

Barchans gregaires (141).

Les akles (58, 92-94, 129, 141, 173; pi. 32). 

Un akle reticule (143). 

Erg en rateau ou en peine (145) .
MORPHOLOGY AND DISTRIBUTION OF DUNES IN SAND SEAS OBSERVED BY REMOTE SENSING 293

TABLE 33. — Chronological list of local terms for patterns of eolian sand deposits in sand seas — Continued

References

Author

(and region)

Terms (reference page, figure, plate, and table numbers in parentheses)

Grove. A. T.

(Southern Sahara, North Africa, 

Kalahari Desert, South 

Africa).

1958 Ridges and hollows (526-531) 

Dunefield (527) .

Petrov, M. P. 

(U.S.S.R.).

1967 Crisscrossing barkhan chains (300; table 36).

Stone, R. 0. 

(All deserts).

1967 Complex dunes, peak and depression (fulji) topography (220-221)

Holm, D. A.

(Saudi Arabian deserts).

1968 Dune complex, dune terrains, dune belts (976). 

Waves of dunes (978) .

Goudie, A. S. 1969

(Southern Africa). 

Goudie, A. S., Alchin, Bridget, 1973

and Hedge, K. T. M.

(Thar Desert, India).

Dune network (404) .

Dendritic, reticulate, and parallel ridges (93, 97, 100; fig. 2) 

Clustered dendritic ridges (97) .

Glennie, K. W.

(Saudi Arabian deserts).

1970 Dune pattern (101).

Wilson, I. G.

(Algerian Ergs, North 

Africa).

1971a Network of draa ridges (268).

Complex dune nets (270) . 

1971b Two-trend dune networks (186-187; fig. 4).

Bedform patterns (182-183).

1972 Do. (173-192, 195-204) .

Lunate network, linguoid network with rhomboidal or hexagonal cells (182) 

[Some] self dune ridge varieties (194, fig. 4). 

Gridiron, fishsrale, and braided patterns (207-208).

1973 Bedform patterns (78, 97).

Barchan dunes in belts (84).

Gridiron, fishscale, and braided patterns (100; fig. 17).

Oblique left-handed, en echelon chain (102).

1973 Akle (285, 298, 311; fig. 435). 

Erg patterns (322-327). 

Transverse patterns (295) .

Rectangular reticules; complex patterns (296). 

Dune patterns (229, 283-287, 322-327; figs. 4.25, 4.26). 

Draa patterns (297; fig. 4.34). _________________

Cooke, R. U., and Warren, Andrew 

(all deserts).

McKee, E. D., and others 1974 

(All deserts).

McKee, E. D., and Breed, C. S. 1976 

(All deserts) .

Parallel straight or wavy dune complexes (17, 24, 47, 53, 62, 68;

figs. 1, 2, 17, 19, 25; table 1). 

Dune patterns (68) . 

Parabolic dune arrays (fig. 5).

Parallel straight or wavy dune complexes (81-82; figs. 55, 56).

TABLE 34. — Chronological list of local terms /or sand sheets and streaks (stringers^

[Streaks are considered equivalent to deposits termed "stringers" in preceding chapters of this pu cation]

Reference

Author 

(and region)

Bagnold, R. A. 

(Libyan Desert, North Africa).

Madigan, C. L. 

(Simpson Desert, Australia).

Year

1933 

1941

1938 

1946

Terms

Sand-sheets 

Sand sheets

Sandy plain 

Sand sheets

(reference page,

Sand sheets

(105, 111) . 

(243-245) .

(514 

(58).

figure, plate, and table numbers in parentheses)

Sand streaks

Sand shadows and sand drifts (121; 

fig. D. 

Do. (189-195) .

No term. 

Do.

Melton, F. A.

(Midwestern, United States)

1940 No term. Umbracer or wind shadow dunes 

(113, 120).
294 A STUDY OF GLOBAL SAND SEAS

TABLE 34. — ChronoJogicaJ Jist of local terms /or sand sheets and streaks — Continued

[Streaks are considered equivalent to deposits termed "stringers" in preceding chapters of this publication]

Reference

Author 

(and region)

Hack, J. T. 

(Navajo Indian Reservation, 

U.S.A.) .

Smith, H. T. U. 

(Nebraska, U.S.A.: 

Sahara, North Africa).

Capot-Rey, Robert and 

Capot-Rey, Francoise 

(Formerly "French" Sahara, 

North Africa) .

Holm, D. A. 

(Saudi Arabian deserts) .

Mabbutt, J. A. 

(Kalahari, Desert, southern 

Africa) .

Cooper, W. S. 

(West coast, North America).

Grove, A. T. 

(Southern Sahara, North Africa; 

Kalahari Desert, southern 

Africa) .

Norris, R. M. 

(Algodones Dunes, California 

and Mexico) .

Powers, R. W. and others 

(Saudi Arabian deserts) .

Stone, R. 0. 

(All deserts) .

Glennie, K. W. 

(Saudi Arabian deserts) .

Goudie, A. S. 

(Southern Africa). 

Goudie, A. S., Allchin, Bridget, 

and Hedge, K. T. M. 

(Thar Desert, India).

Wilson, I. G. 

(Algerian Ergs, North Africa).

Cooke, R. U. , and Warren, Andrew 

(All deserts) .

Sagan, Carl, and others 

(On the planet, Mars).

Year

1941

1946 

1963

1948

1953 

1960

1955 

1967 

1968

1958 

1967

1958

1966

1966

1967

1970

1970 

1973

1971a 

1972 

1973

1973

1973

Terms (reference page, figure, plate,

Sand sheets

No term.

No term, 

do.

Nappes de sable, tenere, reg (63) .

[Some] zibarr (110) . 

[Some] zibar (1372) .

Flat sand spread (27) . 

Sand plain (149) . 

do. (139-140, 145; pi. 1.5).

[Some] dune sheets (33-34, 64). 

do. (Fig. 1; pi. 11) .

Sandy drift (526-529) .

No term.

No term.

Sand sheet (245)

Sheet sands (106-109; figs. 89-90).

Topographically-induced sand sheets 

(95). 

do. (246). 

Sand drifts, windward drifts (246, 249).

Sand plain (264) . 

No term. 

Sand-sheet (103-104; fig. 21). 

Sand patches (78) . 

Ripple ergs (91) . 

Coarse-sand ergs (104).

No term.

No term.

and table numbers in parentheses)

Sand streaks

Falling dunes (241) .

Wind-shadow dunes (197) . 

Do. (35; fig. 7). 

Sand streamers (32, fig. 4). 

Sand drifts (33, fig. 5) . 

Climbing dunes, falling dunes, sand 

glaciers (14-15) .

No term.

No term. 

Do.

No term. 

Do. 

Do.

No term. 

Do.

No term.

Sand streamers (294-295, 305).

Giant elongate sound mounds (D100) .

Windrift dune, windshadow dune (253). 

Falling dune (228) . 

Sand drift, sand glacier 245). 

Source — bordering lee dune (249) . 

Umbrafon dune (252) .

No term.

No term.

Lee drifts (249) . 

Wind drifts (244, 248-249).

No term. 

Drifts downwind of scarps (191) . 

No term.

Lee dunes, trailing dunes, trailing 

sand patches (314-315) .

Streaks (179-215) .

MrKee, E. D., and Breed, C. S. 1974h

(All deserts). 

MrKee, E. D., and others 1974

(All deserts) .

McKee, E. D., and Breed, C. S. 1976 

(Al1 deserts).

Sand sheets (665, 668).

do. (3, 52, 61, 73, 85; figs. 17, 

19; table ]).

Sand sheets (81-82; fig. 59).

Stringers (665, 668).

Do. (49, 61; fig. 20) . 

Streaks (3, 52, 55, 61, 85; figs. 6,

17; table 1) . 

Stringers, stringer dunes (81-82;

fig. 59).
MORPHOLOGY AND DISTRIBUTION OF DUNES IN SAND SEAS OBSERVED BY REMOTE SENSING 295

TABLE 35. — Chronological iist of local terms for interdune areas

Reference

Terms (reference page, figure, plate, and table numbers in parentheses)

Author

(and region)

Year

Hedin, Sven

(Takla Makan Desert, China).

1905a Bajirs or depressions (234-251, 311-369).

Aufrere, Leon

(Formerly "French" Sahara, 

North Africa).

1928 Feidjs [sandy] or gassis [bare]; bahirs (834). 

1930 Do. (220).

Vallees eoliennes (222) .

Intervalle"es interdunaires (226, 230).

Les sillons interdunaires (220, 225). 

1934 Couloirs (136, 138).

Haouds (138) .

Madigan, C. L.

(Simpson Desert, Australia).

Melton, F. A.

(Midwestern United States, 

U.S.A.).

1936 Gibber or clay flats (214).

Inter-ridge areas (223).

1938 Inter-ridge spaces; long, narrow clay pans or gibber plains, flats (514) 

1946 Sandy lanes (43, 49).

Transverse hollows (52).

1940 Fuljes or enclosed basins (131).

Bagnold, R. A.

(Libyan desert, North Africa).

1941 Fuljis or interdune hollows (214).

Hack, J. T.

(Navajo Indian Reservation, 

U.S.A.).

1941 Narrow areas that separate waves of sand (241).

Capot-Rey, Robert

(Formerly "French" Sahara,

North Africa) .

Capot-Rey, Robert and

Capot-Rey, Francois

(Formerly "French Sahara,

North Africa) .

Smith, H. T. U.

(Nebraska, U.S.A.;

Sahara, North Africa).

Holm, D. A.

(Saudi Arabian deserts) .

Monod, Theodore

(Formerly "French" Sahara,

North Africa) .

Grove, A. T.

(Southern Sahara, North Africa,

Kalahari Desert, southern

Africa) .

1945

1947a

1953

1948

1946

1963

1965

1968

1969

1953

1960

1958

1958

1969

Gassi: interdune trough without sand; f ei j , sand-covered interdune

trough (395, 401; fig. 4.5).

Sebkhas (392).

Interdune passages, couloirs, aftout (404).

Do. (89).

Cuvettes, une serie d'alveoles (145).

Do. (89-90; pi. III.l).

Interdune passages, couloirs, aftout (73).

Fulji (198).

Inter-dune basins (40; fig. 12).

Interdune basins, troughs, areas (562).

Narrow grooves, network of corridors, broad flats, depressions (32).

Interdune depressions (17, fig. 14).

Interdune valleys (105).

Deflation hollows (109).

Interdune areas (1372) .

Les interdunes (25; fig. 10(2)).

Interdunes sableux et interdunes rocheux (142; fig. 33).

Ayn (pi., ayoun) , tSySret (pi., tyar) (81).

Hollows (526, 529) .

Interdune depressions, interdunal corridors, strate (straat) (199).

Norris, R. M., and Norris, K. S. 

(Algodones Dunes, California

and Mexico). 

Norris, R. M.

(Algodones Dunes, California 

and Mexico).

1961 Large, flat-floored, sand-free depressions (605, 608-610; figs. 1, 2; 

Pi. 2, 3).

1966 Intradune hollows, depressions (292-297, 305).

McKee, E. D.

(White Sands, Navajo Indian 

Reservation, U.S.A.; 

Libyan desert; Irq as SubayV 

Saudi Arabia).

1966 Interdune surfaces or areas (10, 51-56, 61).
296 A STUDY OF GLOBAL SAND SEAS

TABLE 35 — Chronological list of local terms for interdune areas — Continued

Reference

Author

(and region)

Terms (reference page, figure, plate, and table numbers in parentheses)

Year

Cooper, W. S.

(West coast, North America)

1967 Linear series of hallows between dune waves (34).

Petrov, M. P. 

(U.S.S.R.).

1967 Interbarkhan depressions (304). 

Interridge depressions (307).

Stone, R. 0. 

(All deserts).

1967 Dune valley (225) .

Fulji, or Fulje, depression between barchan dunes (228).

Mabbutt, J. A.

(Kalahari Desert, southern 

Africa; Simpson Desert, 

Australia).

1968 Fuljes, interdune corridors (143).

Enclosed or partly enclosed depressions in dune networks (146).

Glennie, K. W.

(Saudi Arabian deserts).

1970 Inland interdune sebkhas, interdune sebkhas, (60-61, 97-98; fig. 77) 

Interdune deflation plane (77). 

Sand-covered inter-dune areas (78). 

Interdune areas (90, 107-108). 

Feidjes (101).

Goudie, A. S.

(Southern Africa).

1970 Inter-dune corridors (95) . 

Inter-cluster corridors, straats (97).

Wilson, I. G.

(Algerian Ergs, North Africa)

1971a Troughs (264)

Sand-free hollows (267).

Dune hollows (270). 

1973 Do. (92).

Cooke, R. U., and Warren, Andrew 

(All deserts).

1973 Interdune corridors (322). 

Interdraa corridors (327).

Breed, C. S., and McKee, E. D. 1973

(All deserts). 

McKee, E. D., and others 1974

(All deserts). 

McKee, E. D., and Breed, C. S. 1976

(All deserts).

Intradune corridors (162) . 

Interdune surfaces or areas (70-71).

Interdune areas (81) .

TABLE 36. — Morphometry of linear dunes in sand seas

[W, mean width; L, mean length (*, some or all dunes extend beyond edge of image); X, mean wavelength (crest-to-crest distance); 

F, mean frequency (number of dunes per kilometre) across sample, normal to trend of dunes. All measurements in kilometres]

Region 1 Latitude , longitude

Area

Desert or sand sea area sampled W

(km 2 )

L I L/W W/X L/X F Figure

No.

Simple (?) linear dunes

1

2 

3 

4 

5

35°30'-36'LN

19°30'-23°30 

23°30'-25°45 

20°30'-21°30

. , lll'-lll-lS 1 W.

., 137 0 -140 0 30' E. 

' S., 122°30'-128°30' E.

1 N. , 52°-52°30' E.

Navajo Indian Reservation (northern

Northeastern Rub' al Khali (Saudi Arabia) -

625 

30,000 

35,000 

15,000 

2,500

0.043 

.22 

.29 

.29 

.38

3.65 

24.0 

22.7 

26.0 

14.34

0.15 

.90 

.90 

.70 

1.41

84. 

109. 

78. 

89. 

37.

.9 

.1 

.3 

.7 

.7

0.29 

.24 

.32 

.41 

.27

24. 

26. 

25. 

37. 

10.

.3 

.67 

.22 

14 

17

4.92 

1.44 

1.06 

1.26 

.64

168B 

None. 

169B 

169A 

241

Compound linear dunes

6 

7 

8

16°30'-19°15

08°-10° W. 

13°-14°30' E. 

1 N. , 45°30'-50° E. Southwestern Rub' al Khali (Saudi Arabia) -

2,500 

7,500 

20,000

0.94 

1.06 

1.21

>100.00* 

>40.* 

>83.*

1.93 

1.90 

2.18

106. 

37. 

68.

.4* 

.7* 

.6*

0.49 

.56 

.55

51. 

21. 

38.

.81* 

.05*

0.48 

.29 

.48

169D 

None. 

169C

Complex linear dunes

24°-24°45' S., 14 0 45'-15°30' 

26°30'-28° N., 00°30'-02°30' 

19°-19°30' N., 15°-15°30' E. 

18°45'-19°30' N., 45°15'-46°

Namib Desert (South-West Africa)———————— 2,500 0.88

Northern Sahara (Algeria)————————————— 2,500 1.09

Southern Sahara (Niger)——————————————— 2,500 1.28

Western Rub' al Khali (Saudi Arabia)———— 2,500 1.48

27 2.20 30.7 0.40 12.27 0.47 169E

30.75 3.24 28.2 .34 9."9 .33 168B

65 3.28 50.8 .39 19.81 .30 None.

73 3.17 49.3 .47 23.03 .21 169F

'sources of data—(1) Aerial photographs. National Aeronautics and Space Administration: 236-28-0071, 236-28-0072.

Following are numbered Landsat images: (2) E1315-00140, E1227-00264, E1224-00100, E1369-00135, E1369-00141, E1133-00040, E1296-00090, E1367-0025, 

E1224-00093;(3) E1344-01160, E1127-01111, E1377-00585, E1127-01113, E1415-01091, EllOO-01045, E1124-00535, E1180-01051, E1125-00591, E1124-00542, 

E1344-01165, E1413-00584, E1344-01162;(4) E1147-08160, E1416-08085, E1416-08091, E1145-08052; (5) E1184-06255; (6) E1119-10324; (7) E1192-Q8553; 

E1193-09012; (8) E1107-06433, E1132-06380, E1187-06435, E1170-06493; (9) E1383-00270; (10) E1115-10074; (11) E1192-08553; (12) E1189-06550.
MORPHOLOGY AND DISTRIBUTION OF DUNES IN SAND SEAS OBSERVED BY REMOTE SENSING 297

TABLE 37. — Similarity of linear dune varieties in widely distant sand seqs_shown by comparison of ratios derived from 

measurements of mean lengths, L, mean width W, and mean wavelength, X

[Subscript following name of sand sea indicates first or second of the pair. Subscripts to L, W, and X indicate first or second of sand sea pair]

Pairs of sand seas 1

Northern Arizona —— _____

Northern Arizona. --------

Northern Arizona - ———— -

Northern Rub 1 al Khali —

Northern Arizona. — —— ——

Northern Rub 1 al Khali —

Northern Rub 1 al Khali —

Northern Rub 1 al Khali. —

L H/L24.

3.

3.

3.

14

3.

14.

14.

14.

0

6.58

65

6.22

65

7.12

.65

.34

3.93

.65

1.15

1.08

1.06

1.67

34

1.58 

.34

1.81 

.34

W Wi/"2

0.22

5.12

.043

6.74

.043

6.74

.043

.38

8.84

.043

1.0

1.32

.76

.58

.38

.76 

.38

.76 

.38

X A 1 /X 2 LI/WI L 2 /W2 L1 /X 1 L2 /X 2 W1 /X 1 W2 /X 2 cor^gspondence 2

0.90

6.0 109.1 84.9 26.67 24.3 0.24 0.29 Fair.

.15

6.0 78.3 84.9 25.22 24.3 .32 .29 Good.

.15

4.67 89.7 84.9 37.14 24.3 .41 .29 Very poor.

.15

1.41

9.4 37.7 84.9 10.17 24.3 .27 .29 very poor.

.15

.78 89.7 78.3 37.14 25.22 .41 .32 Excellent.

.78 89.7 109.1 37.14 26.67 .41 .24 Good.

1.0 109.1 78.3 26.67 25.22 .24 .32 Excellent.

.64 109.1 37.7 26.67 10.17 .24 .27 Fair.

1.41

.64 78.3 37.7 25.22 10.17 .32 .27 Good.

1.41

.50 89.7 37.7 37.14 10.17 .41 .27 Fair. 

1.41

Geographic location of sand seas; Simpson and Great Sandy Deserts, Australia; northern Arizona, U.S.A.; Kalahari Desert, 

Rub 1 al Khali, Saudi Arabia.

2 Standard for degree of correspondence, based on maximum difference in scale ratios: 0.01-0.50 = Excellent; 0.51-1.0 = 

Good; 1.01-1.50 = Fair; 1.51-2.0 = Poor; 2.10 or more = Very poor.

southern Africa;

TABLE 38. — Morphometry of crescentic dunes in sand seas

[L, mean length; W, mean width; \, mean wavelength. All measurements in kilometres. Leaders (——), not determined. Crescentic type includes transverse

type as used by other authors in this publication]

Region 1 Latitude, 

longitude

1 32°45' N. , 

106°15' W. 

2 22°-25° N.,

3 26°-26°45' N.,

4 23°30'-24°30' S. ,

5 23°15'-23°30' N. , 

53° 54°30 f E

6 40°15'N.,

87°15'-88° E.

7 39°45' N.,

79°30"-80° E.

Area Range of Range of Range of 

Desert or sand sea area sampled dune L dune W dune X L/W W/X L/X Figure 

(km2 ) length width wavelength No.

Simple and probable simple crescentic dune ridges

White Sands (U.S.A.) —————— 7.5 0.03-0.185 0.072 0.06-0.215 0.1112 0.06-0.198 0.1115 0.65 1.0 0.65 173B 

Persian Gulf (United Arab

Thar Desert (near Umarkot,

Namib coast (South-West

Al Jiwa, Rub 1 al Khali

Eastern Takla Makan (China)- 2,000 0.5 -1.2 .80 0.5 -1.5 .94 0.6 -1.2 .89 .85 1.06 .90 261A

Western Takla Makan (China)- 2,500 0.6 -1.5 .84 1.0 -3.0 1.66 0.7 -1.5 1.1 .51 1.51 .76 None.

Probable compound crescentic dunes (mounds and ridges)

01°30'-02° W. 

9 20°30' N.,

55°15'-56° E.

10 32°20'-30° N.,

08°30'-09°30" E.

11 27°30'-29° N., 

39°-40° E.

Southeastern Rub 1 al Khali

(Saudi Arabia)——————— 2,500 0.3 -1.1 .67 0.85-2.2 1.43 0.5 -3.2 1.76 .47 0.81 0.38 None

Northeastern Sahara

(Algeria and Tunisia)——— 5,000 0.3 -1.5 .65 0.5 -3.0 1.43 0.5 -2.0 1.24 .45 1.15 .52 2104 

An Nafud (northern

Saudi Arabia)—————————— 5,000 0.5 -2.0 .80 0.6 -2.7 1.41 0.8 -3.3 1.84 .57 .77 .43 None.
298 A STUDY OF GLOBAL SAND SEAS

TABLE 38 — Morphometry of crescentic dunes in sand seas — Continued

[L, mean length; W, mean width; \, mean wavelength. All measurements in kilometres. Leaders (——), not determined. Crescentic type includes transverse

type as used by other authors in this publication]

Region 1 Latitude , 

longitude

Area Range of Range of Range of 

Desert or sand sea area sampled dune L dune W dune X 

(km2 ) length width wavelength

L/W W/X L/X Figure 

No.

Compound crescentic dune ridges

12

13

14

15

16

17

18

19

20

21

31°45'-32°N.,

32°45'-33°10' N.,

21°23' N., 

53°30'-55° E.

39°30'-40 0 30' N.,

37°-37°45' N.,

42"30'-43°30' N. ,

26°30'-27°30 1 N. ,

41°30'-42°30' N.,

101°-102° W.

40°-40°30' N.,

17°30'-19 0 N. ,

09°-13° W.

Gran Desierto (Son or a,

Algodones (California,

Al 'Urug al Mu 1 taridah, 

eastern Rub' al Khali

Cherchen sand sea, Takla

Peski Karakumy (near Mary,

Peski Karakumy (near

Western Thar Desert (near

Nebraska Sand Hills (U.S.A.) 3,000 0.8 -2.3 1.65 1.5 -5.0 3.14 1.0 -2.5 1.73

Pa-tan-chi-lin Sha-mo, Ala

Aoukar sand sea, southwestern Sahara (Mauritania) 5,000 1.2 -2.1 1.59 2.2 -9.6 4.10 1.0 -2.5 1.71

.52 1.81 .95 175E

.39 2.40 .93 175F

1 Sources of data—(1) Aerial photograph: Holloman Air Force Base. Following 

are all numbered Landsat images: (2) E1131-06303, E1131-06310; (3) E1191-05211; 

(4) E1383-08270; (5) E1148-06251; (6) E1146-04251; (7) E1115-04C41; (8) E1115-10083; 

(9) E1182-06141; (10) E1109-09313; (11) E1231-07270, E1231-07272; (14) E1183-06194; 

(15) E1146-04251, E1146-04254; (16) E1126-05581; (17) E1126-05563, E1127-0621; 

(18) E1192-05267, E1120-05267; (19) E1026-17012; (20) E1117-03222; (21) E1227-10335, 

E1229-10445. SKYLAB photographs: (12) SL4-76-085; (13) SL4-76-083.

TABLE 39. — Similarity of compound crescentic dunes in widely distant sand seas, shown by comparison of ratios derived from 

measurements of mean length, L, mean width, W, and mean wavelength, X

[Subscript following name of sand sea indicates first or second of the pair. Subscripts to L, W, and X indicate first or second of sand sea pair]

Pair of sand seas 1

Ala Shan - -———--————

Eastern Rub 1 al Khali — -

Takla Makan — — —— — ———

1

Eastern Rub' al Khali — -

Takla Makan - ———————— —

1

Ala Shan —— — ___________

Bukantau ————— _________

Mary2 —————————————

Ala Shan ——————————— —

1

Mary 2 —————— ————— ———

Takla Makan. ——— ——— - ——

Mary2 —————————————

Ala Shan. ————— —————— —

-mar.--—— -————-——-——

Takla Makan -------------

1

Bukantau — ——————— —— —

Thar — — ————— ——— - ——— -

Gran Desierto ——————— --

Takla Makan — —— —— ——— -

1

Gran Desierto ————— —— —

L

2.16

2.09

2.20

2.09

2.20

2.16

1.31

1.16

2.16

1.16

2.20

1.16

2.16

1.30

2.20

1.31

1.30

.66

2.20

.66

L1/L2 W W1 /W2

2.88

1.03 1.04

2.76

3.24

1.05 1.18

2.74

3.24

1.02 1.13

2.88

2.22

1.13 1.13

1.96

2.88

1.86 1.47

1.96

3.24

1.90 1.65

1.96

2.88

1.66 1.92

1.50

3.24

1.68 1.46

2.22

1.50

1.97 1.44

1.04

3.24

3.33 3.12

1.04

A

2.92

2.56

3.0

2.56

3.0

2.92

2.27

1.76

2.92

1.76

3.0

1.76

2.92

1.44

3.0

2.27

1.44

1.38

3.0

1.38

"A W V=2 'A *A *A EA «S-_-_.=

1.14 0.75 0.76 0.99 1.08 0.74 0.82 Excellent.

1.17 .68 .76 1.08 1.08 .73 .82 Excellent.

1.03 .68 .75 1.08 .99 .73 .74 Excellent.

1.29 .59 .59 .98 1.11 .58 .66 Excellent.

1.66 .75 .59 .99 1.11 -74 .66 Very good.

1.70 .68 .59 1.08 1.11 .73 .66 Very good.

2.03 .75 .87 .99 1.04 .74 .90 Very good.

1.32 .68 .59 1.08 .98 .73 .58 Very good.

1.04 .87 .63 1.04 .75 .94 .48 Poor.

2.17 .68 .63 1.08 .75 .73 .48 Very poor.
MORPHOLOGY AND DISTRIBUTION OF DUNES IN SAND SEAS OBSERVED BY REMOTE SENSING 299

TABLE 39 — Similarity of compound crescentic dunes in widely distant sand seas, shown by comparison of ratios 

derived from measurements of mean length, L, mean width, W, and mean wavelength, X — Continued

[Subscript following name of sand sea indicates first or second of the pair. Subscripts to L, W, and X indicate first or second of sand sea pair]

Pair of sand seas 1

Algodones. ——— —— —— ———

Gran Desierto- — ——— ———

Takla Makan — ----- ——— —

Algodones —————————

Eastern Rub' al Khali^ ——

Algodones_ —— ——— ——— ——

Nebraska Sand Hills.. — ——

Algodones- ---------------

Mary ————————————

Algodones ————————

Ala Shan ——————————

Nebraska Sand Hills — ——

Ala Shan — ——— ———— ————

Algodones- —————————

Thar ————————————

Algodones- —————————

Eastern Rub 1 al Khali ——

Nebraska Sand Hills ———

Eastern Rub 1 al Khali. ——

Aoukar ——————————

Aoukar ———————————

Nebraska Sand Hills- ———

E

.88

.66

2.20

.88

2.09

.88

1.65

.88

1.16

.88

2.16

1.65

2.16

.88

1.30

.88

2.09

1.65

2.09

1.59

1.59

1.65

V4 "

1. 

1.33

1.

3.

2.5

1.

2.

2.37

1.

3.

1.88

1.

1.

1.32

1.

2.

1.31

3.

2.

2.46

1.

1.

1.48

1.

2.

1.27

3.

2.

1.31

4.

4.

.96

3.

*A

61 

1.55

04

24

2.01

61

76

1.71

61

14

2.71

16

96

1.22

61

88

.92

14

88

1.79

61

50

.93

61

76

.88

14

76

.67

10

10

1.31

14

X X /X L /W L,/iL Wn /X n W0 /X0 L,/J L./JL Degree of 

1 2 11 2' 2 11 2' 2 11 22 correspondence

1.07 

.78 .55 .63 1.50 .75 .82 .48 Fair.

1.38

3.0

2.8 .68 .55 1.08 1.50 .73 .82 Fair.

1.07

2.56

2.39 .76 .55 1.08 1.50 .82 .82 Fair

1.07

1.73

1.62 .52 .55 1.81 1.50 .95 .82 Very poor.

1.07

1.76

1.64 .59 .55 1.11 1.50 .66 .82 Very good.

1.07

2.92

1.69 .75 .52 .99 1.81 .74 .95 Fair.

1.73

2.92

2.73 .75 .55 .99 1.50 .74 .82 Poor.

1.07

1.44

1.35 .87 .55 1.04 1.50 .90 .82 Good.

1.07

2.56

1.48 .76 .52 1.08 1.81 .82 .95 Fair

1.73

2.56

1.50 .76 .39 1.08 2.40 .82 .93 Poor.

1.71

1.71

.99 .39 .52 2.40 1.81 .93 .95 Very good

1.73

'Geographic location of sand seas: Ala Shan Desert, China; Rub 1 al Khali, Saudi Arabia; Takla Makan Desert, China; Peski Karakumy, near 

Bukantau and Mary, O.S.S.R.; Gran Desierto, Mexico; Thar Desert, India and Pakistan; Algodones Desert and Nebraska Sand Hills, U.S.A.; 

Aoukar, Maruitania.

2 Standard for degree of correspondence, based on maximum difference in scale ratios: 0.01-0.20 = Excellent; 0.21-0.39 = Very good; 

0.40-0.59 = Good; 0.60-0.79 = Fair; 0.80-0.99 = Poor; 1.00 or more = Very poor.

TABLE 40. — Morphometry of star dunes in sand seas

[D, mean diameter; X, mean wavelength. All measurements in kilometres]

Region 1

A I9 0|;n

Latitude,

'-an0 N. . qq

longitude

° in '-im "in 1 R

Desert or sand sea area

Area

sampled

(km2 )

. ——— 9 nnn

Range of

dune

diameter

n A -1 n

Range of

D

in

dune

wavelenc

n t -1

jth

7

X

1 .17

D/X

_S4

Figure

No.

264B

5 19°-20°30' N., 53°30'-54°30 1 E. Southeastern Rub 1 al Khali (Saudi Arabia)—— 12,500 0.5 -1.3 .84 0.97-2.86 2.06 .41 180C

6 29°30 1 -32° N., 007°30 1 -009° E. Entire Grand Erg Oriental (Algeria)——————— 10,000 0.4 -3.0 .95 0.8 -6.7 2.07 .46 210B

7 29°30 1 -30°15 1 N., 007°30 § -008°15• E. Southern margin, Grand Erg Oriental (Algeria) 2,500 0.7 -3.0 1.65 1.5 -3.1 2.17 .76 180B

8 30°30 1 -32° N., 007°30'-009° E. Northern Grand Erg Oriental (Algeria)—————— 7,500 0.4 -1.3 .71 0.8 -6.7 2.04 .35 210B

'Sources of data are numbered Landsat images: (1) E1159-17451; (2) E1382-08214; (3) E1209-08494; (4) E1209-03340; (5) E1417-06191, E1147-06202,

E1183-06200, E1183-06203; (6) E1109-09320, E1109-09322, E1110-09374; (7) E1109-09322; (8) E1109-09320, E1110-09374.
300 A STUDY OF GLOBAL SAND SEAS

TABLE 41. — Similarity of star dunes in widely distant sand seas, shown by comparison of ratios derived from measurements of

mean diameter, D, and mean wavelength, X

[Subscript following name_of sand sea indicates first or second of the pair. 

Subscripts to 5 and A indicate first or second of sand sea pair]

Pairs of sand seas

Gran Desierto ———————— - —— ———

1

Namib — — ——— ——————— _________

2

Ala Shan ——————————————

Gran Desierto — — ______________

Eastern Rub 1 al Khali --———-—

Gran Desierto — ————— ————— ____

2

Grand Erg Oriental ——— —— — — —

Gran Desierto- — — ———— - -------

Southern Grand Erg Oriental, ----

Gran Desierto ————————————

Northern Grand Erg Oriental, — --

Gran Desierto- — ----------------

Gran Desierto.. — ————————— —— —

Southern Sahara- ————— _________

2

Eastern Rub' al Khali, --————

Ala Shan — — - ——————— -- -------

2

Grand Erg Oriental — ———————— -

Ala Shan- — ——————————— — ———

Grand Erg Oriental — — - ------

Eastern Rub 1 al Khali — — — — —

Ala Shan. — —————————————————

1

Southern Sahara- ——————————

Eastern Rub 1 al Khali, — ——— ———

Northern Grand Erg Oriental- — —

Southern Grand Erg Oriental — —

Eastern Rub" al Khali- ——— ——— —

D D /D

0.70

1.03

.68

.74

1.06

.70

.84

1.2

.70

.95

1.36

.70

1.65

2.36

.70

.71

1.01

.70

.70

1.15

.61

.84

1.14

.74

.95

1.28

.74

.95

1.13

.84

.74

1.21

.61

.84

1.18

.71

1.65

1.96

.84

I I /I ~ /\ n /I Degree of 

12 11 22 correspondence

1.19

0.54 0.59 0.31 Fair.

2.21

1.37

1.15 .54 .59 Excellent.

1.19

2.06

1.73 .41 .59 Fair.

1.19

2.07

1.74 .46 .59 Good.

1.19

2.17

1.82 .76 .59 Fair.

1.19

2.04

1.71 .35 .59 Poor.

1.19

1.19

1.19 .59 .61 Excellent.

1.0

2.06

1.50 .41 .54 Good.

1.37

2.07

1.51 .46 .54 Very good.

1.37

2.07

1.0 .46 .41 Excellent.

2.06

1.37

1.37 .54 .61 Very good.

1.0

2.06

1.01 .41 .35 Very good.

2.04

2.17

1.05 .76 .41 Very poor.

2.06
MORPHOLOGY AND DISTRIBUTION OF DUNES IN SAND SEAS OBSERVED BY REMOTE SENSING 301

TABLE 41. — Similarity of star dunes in widely distant sand seas, shown by comparison of ratios derived from measurements of

mean diameter, D, and mean wavelength, X — Continued

[Subscript following name_of sand sea indicates first or second of the pair. 

Subscripts to 5 and X indicate first or second of sand sea pair]

Pairs of sand seas 1 5 Dn /5_ X X_/X_ D_/X_ D_/X_ egree o

12 12 11 22 correspondence

Southern Grand Erg Oriental——— 1.65 2.17

2.23 1.58 .76 .54 Poor.

Alan Shan ————————————————— .74 1.37

Southern Grand Erg Oriental——— 1.65 2.17

2.43 .98 .76 .31 Very poor.

Namib2 ————————————————————— .68 2.21

Eastern Rub 1 al Khali,———————— .84 2.06

1.24 .93 .41 .31 Good.

Namib2 ————————————————————— .68 2.21

Grand Erg Oriental —————————— .95 2.07

1.4 .94 .46 .31 Fair.

Namib2 ————————————————————— .68 2.21

Grand Erg Oriental ——————————— .95 2.07

1.56 2.07 .46 .61 Fair.

Southern Sahara ————————————— .61 1.0

Eastern Rub 1 al Khali ———————— .84 2.06

1.38 2.06 .41 .61 Poor.

Southern Sahara ————————————— .61 1.0

Namib————————————————————— .68 2.21

1.11 2.21 .31 .61 Very poor.

Southern Sahara ————————————— .61 1.0

Northern Grand Erg Oriental——— .71 2.04

1.16 2.04 .35 .61 Very poor.

Southern Sahara2 ————————————— .61 1.0

Geographic location of sand seas: Gran Desierto, Mexico; Namib Desert, South-West Africa; 

Ala Shan Desert, China; Rub 1 al Khali, Saudi Arabia; Grand Erg Oriental, Algeria; Southern 

Sahara, Niger.

2 Standard for degree of correspondence, based on maximum difference in scale ratios: 

0.01-0.15 = Excellent; 0.16-0.30 - Very good; 0.31-0.45 = Good; 0.46-0.60 = Fair; 0.61-0.75 = 

Poor; 0.76 or more = Very poor. More stringent criteria are set than for dunes of linear and 

crescentic types because fewer ratios are compared for dunes of star type.
302 A STUDY OF GLOBAL SAND SEAS

TABLE 42. — Morphometry of dome and dome-shaped dunes

[D, mean diameter; X, mean wavelength; *, approximate. All measurements in kilometres]

Region ' Latitude

2 32°-32°30' N. ,

, longtitude

0 0

002°-002°30' E.

Desert or sand sea area

Northern Grand Erg Occidental (Algeria) ---------

Area

sampled

(km 2 )

1,000*

Range of

dune D

diameter

0,.9-2.0 1.51

Range of

dune

wavelength

1.6-5.0

X

3.42

D/X

.44 185.3

'Sources of data are numbered Landsat images: (1) E1131-04424; (2) E1186-10003; (3) E1137-07043.

TABLE 43. — Similarity of domes and dome-shaped dunes injyidely distant sand seas, shown by comparison of ratios derived

from mean diameter, D, and mean wavelength, X

[Subscript following name of sand sea indicates first or second of the pair. 

Subscripts to D and X indicate first or second of sand sea pair]

Pairs of sand seas 1

Northern Takla Makan —--—--——

Northern Grand Erg Occidental — 

Northern Takla Makan --—————

Northern Grand Erg Occidental — 

Nafuds — ---———— ————————

D D /D_

1.21 

1.08 

1.12

1.51 

1.35 

1.12

1.51 

1.25 

1.21

*

2.

3.

3. 

3.

3.

2.

T /T ^ /T - /T Degree of A., /A D /A, D /A,, ^ , 2 12 11 22 correspondence

i P

0.65 0.56 0.33 Good. 

34

42 

1.02 .44 .33 Good. 

34

42 

1.57 .44 .55 Good.

1 Q

Geographic location of sand seas: Nafuds, Saudi Arabia; Takla Makan Desert, China; 

Grand Erg Occidental, Algera.

Standard for degree of correspondence, based on maximum difference in scale ratios: 

0.01-0.15 = Excellent; 0.16-0.30 = Very good; 0.31-0.45 = Good; 0.46-0.60 = Fair; 0.61- 

0.75 = Poor; 0.76 or more = Very poor. More stringent criteria are set than for dunes of 

linear and crescentic types because fewer ratios are compared for dunes of dome type.


A STUDY OF GLOBAL SAND SEAS

REGIONAL STUDIES OF SAND SEAS, 

USING LANDSAT (ERTS) IMAGERY

Chapter K

By CAROL S. BREED, STEVEN G. FRYBERGER, SARAH ANDREWS, CAMILLA McCAULEY 

FRANCES LENNARTZ, DANA GEBEL, and KEVIN HORSTMAN

Contents

Method of study 

Definitions .....

Page 

309 

309

Summary of conclusions, review of previous work, interpretation of Landsat imagery, surface 

wind flow and precipitation, and potential sand drift for sand seas in eight desert 

regions: 

Western Sahara of Mauritania, Senegal, Mali, and Spanish Sahara .................... 310

Sahel and southern Sahara of Mauritania, Mali, and Niger ........................... 317

Northern Sahara of Algeria, western Libya, and Tunisia ............................. 326

Namib Desert of South-West Africa .............................................. 346

Kalahari Desert of South-West Africa, South Africa, and Botswana ................... 355

Arabian sand seas of Saudi Arabia, Oman, Yemen, and adjacent States ............... 362

Thar Desert of India and Pakistan ................................................ 375

Takla Makan and Ala Shan Deserts of the Peoples Republic of China ................. 381

305
306 A STUDY OF GLOBAL SAND SEAS

Illustrations

Page

FIGURE 188. Distribution and morphology of eolian sand, western Sahara .............. 311

189. Diagram of sand rose used in this chapter ............................... 312

190. Skylab photograph of elongate sand seas, northwest Sahara and Spanish Sahara 312

191. Landsat false-color imagery showing vegetated, large linear dunes in relation to

precipitation, southern Mauritania .................................. 314

192. Landsat imagery showing compound linear dunes, Makteir sand sea,

Mauritania ....................................................... 315

193. Landsat false-color imagery of a solitary linear dune between Atar and Akjoujt,

Mauritania ....................................................... 316

194. Landsat imagery showing compound crescentic dunes, Aoukar sand sea,

Mauritania ....................................................... 317

195. Map of sea-level mean-pressure contours, Sahara and adjacent regions ..... 318

196. Graph of variation of rainfall during year, Rosso, Akjoujt, and Fort-Gouraud,

Mauritania ....................................................... 319

197. Map of resultant drift directions, drift potentials, and resultant drift potentials at

weather stations in Mauritania . ................................... 320

198. Sand roses for 6 months for Nouakchott, Mauritania ...................... 321

199. Sand roses for 12 months for Boutilimit, Mauritania ...................... 322

200. Graph of drift potential during the year at Boutilimit, Mauritania ........... 323

201. Map showing distribution and morphology of eolian sand, Sahel and southern

Sahara ........................................................... 324

202. Landsat imagery showing compound linear dunes of the Azaouad sand sea

near Timbuktu ................................................... 326

203. Monthly sand roses for Nioro du Sahel, Mali............................. 328

204. Graph of variability of rainfall during the year at Gao and Nioro du Sahel, Mali 328

205. Graph of drift potential during the year at representative stations in the Sahel 329

206. Map showing distribution and morphology of eolian sand in Algeria and

southern Tunisia ................................................. 330

207. Map showing distribution and morphology of eolian sand in northwestern

Libya and southeastern Algeria ..................................... 332

208. Landsat imagery showing the southwestern margin of the Grand Erg Occidental, Algeria ....................................................... 334

209. Landsat imagery showing subparallel complex dunes of linear and star types of

the 'Erg Chech, Algeria ............................................ 336

210. Landsat false-color imagery showing northeastern part of the Grand Erg Oriental, Algeria and Tunisia ............................................ 337

211. Skylab photograph showing star dunes in linear chains, southwestern end of

the Grand Erg Oriental, Algeria .............................._....... 339

212. Landsat imagery of the central and western parts of the Sahra'Awbari, Libya . 340

213. Skylab photograph of dunes at the west edge of the ^ahra'Marzuq, Libya ... 342

214. Weather maps of two meteorological events which produce southwesterly and

northwesterly winds over the northern Sahara ....................... 343

215. Sand roses for 6 months for Laghouat, Algeria ........................... 344

216. Sand roses for 4 months for Ghardaia, Algeria ............................ 344

217. Sand roses for 6 months for Ouargla, Algeria ............................ 345

218. Sand roses for 6 months for Qabis, Tunisia .............................. 345

219. Sand roses for 6 months for l-n-Salah, Algeria ............................ 346

220. Graph showing yearly drift potential, Laghouat and Ouargla, Algeria ........ 346

221. Graph showing yearly drift potential, Ghardaia and l-n-Salah, Algeria ....... 347

222. Map showing distribution and morphology of eolian sand, central Namib

Desert, southern Africa ............................................ 348

223. Landsat imagery of western parts of the main sand sea, central Namib Desert 350

224. Landsat false-color imagery of northeastern parts of main sand sea, central

Namib Desert .................................................... 351

225. Photograph of red sand dunes and tan playa sediments along the interior

margin of the Namib Desert at the Sossus Vlei ....................... 353
REGIONAL STUDIES OF SAND SEAS, USING LANDSAT (ERTS) IMAGERY 307

Page 

FIGURE 226. Maps of mean sea level isobars and isobars of the 850-millibar-pressure surface,

southern Africa ................................................... 354

227. Wind roses from central Namib Desert at Luderitz, South-West Africa ...... 354

228. Graph showing drift potential from the northeast quadrant during June and

July, north-central Namib Desert ................................... 354

229. Sand roses for 11 months for Gobabeb, South-West Africa ................ 355

230. Sand roses for 8 months for Rooi Bank, South-West Africa ................ 356

231. Wind rose for Aus, South-West Africa ................................... 356

232. Graph showing drift potential at Pelican Point, Gobabeb, and Narabeb, SouthWest Africa ...................................................... 357

233. Map showing distribution and morphology of eolian sand, western Kalahari

Desert, southern Africa ............................................ 353

234. Landsat false-color imagery of large linear sand features, invasive sand sheets, 

and abandoned drainages of the Molopo River and Kurumanrivier, 

southern Kalahari Desert .......................................... 359

235. Sand roses for 12 months for Ghanzi, Botswana, northeast Kalahari Desert . . 360

236. Graph showing average monthly rainfall versus average monthly drift potential,

Upington, South-West Africa ....................................... 361

237. Graph showing drift potential at four stations in the Kalahari Desert ........ 361

238. Graph showing distribution and morphology of eolian sand in Saudi Arabia,

Oman, Yemen, and adjacent States of the southern Arabian Peninsula .. 364

239. Skylab oblique photograph showing red linear dunes, western Rub' al Kahli . 366

240. Landsat imagery of crescentic dune ridges, northeastern Rub' al Khali ....... 367

241. Landsat imagery of the north-central part of the Rub' al Khali .............. 367

242. Landsat imagery showing the southern part of the Wahiba Sands, Oman .... 368

243. Outline map, with sand roses, of the northern Arabian Peninsula .......... 369

244. Landsat false-color imagery of Ad Dahna, Saudi Arabia .................... 370

245. Map of sea-level mean-pressure contours on the Arabian Peninsula and adjacent regions ..................................................... 372

246. Sand roses for 6 months for Badanah, Saudi Arabia ....................... 373

247. Sand roses for 12 months for Dhahran, Saudi Arabia ...................... 373

248. Sand roses for 6 months for Ash Slwiqah, Saudi Arabia ................... 374

249. Sand roses for 9 months for Al 'Ubaylah, Saudi Arabia .................... 374

250. Graph showing drift potential during the year at Badanah, Al Qaysumah, and

Dhahran, Saudi Arabia ............................................ 375

251. Graph showing drift potential during the year at Ash Shariqah and Al 'Ubaylah,

Saudi Arabia ..................................................... 375

252. Map showing distribution and morphology of eolian sand in the Thar Desert of

India and Pakistan ................................................ 378

253. Landsat imagery of compound parabolic dune clusters along the southern

margin of the Thar Desert ......................................... 379

254. Sketch showing rakelike arrangement of crests of parabolic dune arms comprising compound forms near Jodhpur, India ........................... 380

255. Landsat imagery of vegetated parabolic and linear dunes in the southwestern

part of the Thar Desert ............................................ 380

256. Landsat imagery of linear and crescentic dunes in the western part of the Thar

Desert ........................................................... 382

257. Graph showing relation of rainfall patterns to effective winds, Jaisalmer and

Barmer, Thar Desert ............................................... 383

258. Outline map of the Thar Desert and resultant drift directions for June and January .......................................................... 383

259. Graph showing drift potential at Bhuj and Barmer, Thar Desert ............ 383

260. Map showing distribution and morphology of eolian sand in the Takla Makan

Desert, Peoples Republic of China .................................. 384

261. Landsat imagery showing compound crescentic dunes and closed elongate interdune areas in the Cherchen Desert, northern Takla Makan Desert, south 

of the Tarim River, Peoples Republic of China ....................... 337
308 A STUDY OF GLOBAL SAND SEAS

Page

FIGURE 262. Landsat imagery of the dunes along the Ho-t'ien Ho, western Takla Makan

Desert........................................................... 388

263. Map showing distribution and morphology of eolian sand in the Ala Shan

Desert, Peoples Republic of China .................................. 390

264. Landsat imagery of the main mass of sand, Pa-tan-chi-lin Sha-mo, Ala Shan

Desert, Peoples Republic of China .................................. 392

265. Landsat imagery of dune fields, eastern Ala Shan Desert................... 394

266. Maps showing mean sea level pressure distribution over the Takla Makan and

Ala Shan Deserts ................................................. 395

267. Sand roses for 6 months for Khotan, southwestern Takla Makan Desert, Peoples

Republic of China ................................................ 396

268. Sand roses for 6 months for Chi-lan-t'ai, eastern Ala Shan Desert, Peoples

Republic of China ................................................ 396

269. Sand roses for 6 months for Kucha, north-central Tarim Basin, Peoples Republic

of China ......................................................... 396

270. Graph showing variation of drift potential during the year at representative stations within the Takla Makan Desert ................................ 397

271. Graph of drift potential at Chi-lan-t'ai and Mao-mu, Ala Shan Desert, Peoples

Republic of China ................................................ 397

Table

Page

TABLE 44. Planimetric similarity of linear dunes of the Wahiba Sands, Oman, and linear 

dunes of the Namib Desert, South-West Africa, shown by comparison of 

their scale ratios .................................................. 369
REGIONAL STUDIES OF SAND SEAS, USING LANDSAT (ERTS) IMAGERY 309

Method of Study Niger; (3) northern Sahara of Algeria, western 

Libya, and Tunisia; (4) Namib Desert of SouthHIS CHAPTER IS A SERIES of regional West Africa; (5) Kalahari Desert of South-West 

studies of selected sand seas and is based on Africa and Botswana; (6) Arabian sand seas of 

available literature, surface wind summaries, and Saudi Arabia, Oman, Yemen, and adjacent States; 

data obtained through remote sensing. Studies of 8 (7) Thar Desert of India and Pakistan; and (8) Takla 

desert regions include sand seas in parts of 17 coun- Makan and Ala Shan Deserts of the Peoples 

tries. Mosaics were prepared from Landsat (ERTS) Republic of China, 

imagery covering each of the regions, and, from 

each mosaic, a map was made of sand bodies and 

other features and their distribution. Supplementary information about dunes of each region was The following list of foreign terms used on maps 

obtained from Skylab and aerial photographs, and in this chapter are given English definitions. All 

from the ground studies of other workers. definitions are adapted from gazetteers prepared by

The Landsat imagery used to map dunes are at a

scale of 1:1,000,000. Many features of relatively ______________________________ 

small dunes, including details of dune shape and Term____Definition________Map on which used____ 

Slipface development commonly used in dune Adrar ....Mountains........... Sahara (western).

classifications by field geologists, are not visible at Berg ...... Mountains........... Namib, Kalahari.

this scale. For this reason, a classification some- CaP •••••• Cape, point .......... Sahara (western).

what different from that used in the ground studies Dhar • • • • • Plateau .............. Sahara (western).

and low-altitude aerial photograph studies treated Djebel ''' Hills •••••••••••••••• Sahara (northern).

in Chapters A - I Was found to be expedient here. Erg ....... Dunes, desertsand Sahara (northern).

For example, the term crescentic dune is here region*.

used to include all dune types that are generally Hamada .. Plateau, stony plain ... Sahara (northern).

referred to as barchans, barchanoid ridges, or Ho ....... stream, river ......... Takla Makan, Ala Shan.

transverse dunes. Hu ••••••• Lake ................ Takla Makan, Ala Shan.

Classification of principal dune types according Jabal ' '' Hills •••••••••••••••• R"b' ^ Khali.

to form and to number of slipfaces is given in Kum ..... Sand area ............ Takla Makan, Ala Shan.

chapter E, table 9. We developed an expanded ver- Lac ....... Lake ................ Sahara, Sahel.

sion of this classification (chapter J) for our studies Massif.... Mountains ........... Sahara.

because dunes seen on Landsat imagery may not be Oued • • • • • Wadi •••••••.••...... Sahara, Sahel.

directly comparable to those that have been studied Pan '••••• Playa •••••••••••••• Kalahari.

on the ground. A comparison of the general ter- plato plateau Kalahari

mmology for dune classification based on observa- Po ....... Lake ................ Takla Makan, Ala Shan.

tions of Landsat imagery and that based on field Puts ...... Well, spring .......... Kalahari.

studies is given in chapter A, table 1. Rann • • • • • Marsh ............... Thar.

Originally, plans for this study were to include Sebkha • • • plava' alkali flat* • • • • • Sahara.

large desert regions in Australia, southern U.S.S.R., 

and the Sonoran Desert of the United States and 

Mexico. Although Landsat imagery was obtained shatt ..... Sebkha .............. Sahara (northern).

and mosaics were prepared for these regions, time Tassili.... Mountains........... Sahara (northern).

limitations precluded compilation of data for use in

this chapter. 'Uruq ..... Sand dunes, dune area . Rub' al Khali.

Vallee .... Wadi ................ Sahel.

The areas selected for this study, using Landsat viei_...... Pan ................. Namib.

imagery, are as follows: (1) Western Sahara of Wadi • • • • • Intermittent or dry Sahara, Rub' al Khali.

Mauritania, Senegal, Mali, and Spanish Sahara; (2) stream, stream valley, 

Sahel and southern Sahara of Mauritania, Mali, and _______°asis "
310 A STUDY OF GLOBAL SAND SEAS

the U.S. Board on Geographic Names. Those definitions marked by an asterisk (*) are adapted from 

Webster's New International Dictionary of the 

English Language, Second Edition, unabridged, 

1960, C & G Merriam Co., Publishers.

Western Sahara of Mauritania,

Senegal, Mali, and Spanish

Sahara

Summary of Conclusions

Dunes of the western Sahara are limited to two 

main types — linear and crescentic — distributed 

throughout wide areas. Linear dunes are the most 

common type, extending to the coast in both 

parallel and en echelon forms from hundreds of 

kilometres inland. Compound and simple linear 

dunes are the most common forms in northern 

Mauritania. Heavily vegetated compound linear 

dunes of proportions similar to those in northern 

Mauritania occur in southern Mauritania, near 

Mederdra and Boutilimit. Crescentic dunes are 

common in the southern part of the desert (Aoukar 

sand sea), and in smaller fields along the Atlantic 

coast. Sand sheets, generally associated with linear 

dunes, occur throughout Mauritania, western Mali, 

Spanish Sahara, and northern Senegal.

Rainfall in the western Sahara ranges from less 

than 100 mm (4 in.) in the northern regions near 

Fort-Gouraud to more than 300 mm (12 in.) in the 

southern regions near Rosso. Effective winds in the 

western Sahara are mostly from the north and 

northeast and result mainly from anticyclonic circulation from the Sahara and Azores high-pressure 

cells.

Relatively unvegetated linear dunes and sand 

sheets in sand seas of northern Mauritania are in a 

high-energy wind environment. These sand seas 

typically are elongate and are alined subparallel to 

the resultant drift direction of present-day winds. 

In some places, however, linear dunes are alined 

oblique to trends of sand seas but parallel to directions of some effective winds. Vegetated, or partially vegetated, linear and crescentic dunes in 

southern Mauritania are in present-day intermediate- or low-energy wind environments with considerable rainfall. Large crescentic dunes in the 

Aoukar sand seas generally occur downwind of 

escarpments or other topographic barriers.

Introduction

Several long, sharply defined sand seas (known 

as ergs in northern Africa), extend southwestward 

from Algeria across the western Sahara. The 

morphology of the dunes and the extent of the sand 

seas, as determined from Landsat imagery, is 

shown in figure 188. Sand roses representing the 

potential sand-moving effect of present-day surface 

winds, and isohyets (lines of equal precipitation) 

show present climatic factors in relation to sand 

distribution (figs. 188, 189). A regional view of the 

sand seas is provided by a Skylab photograph 

(fig. 190).

Few of the eolian sand areas shown in figure 188 

are described in published reports. Sand seas along 

the east margin have been described by Monod 

(1958). Reconnaissance studies of dune areas near 

the Senegal River and northward to about lat 17° N. 

have been made by Tricart and Brochu (1955), 

Leprun (1971), Boulet, Guichard, and Vieillefon 

(1971), and by others. Grove and Warren (1968) 

briefly summarized work in the eastern and 

southern parts of the region. Useful maps of the 

region are the U.S. Department of Commerce, U.S. 

Air Force Operational Navigation Charts H-l, J-l, 

K-l, and J-2; and the U.S. Army Map Service 

Series 1301, sheets NE 29, NF 29, NF 28, and NE 28; 

all maps are at a scale of 1:1,000,000. A regional 

landform map by Raisz (1952) is at a scale of 1 inch 

equals 60 miles (1:3,801,600).

Review of Previous Work

Dunes in the area bounded by Boutilimit, SaintLouis, and Louga (fig. 188) are described (Tricart 

and Brochu, 1955, p. 148-149) as belonging to a 

zone of old red parallel dunes, 40-50 km (25-30 

mi) long, about 1 km (0.6 mi) wide, and 10-20 m 

(33-66 ft) high. Near the coast, interdune corridors 

are reported to be about 2 km (1 mi) wide and dune 

ridges are 20-30 m (66-99 ft) high. Along the 

Aftout'es Saheli (fig. 188), old red dunes have been 

truncated by marine erosion and are overlain by recent brown or yellow crescentic coastal dunes (Tricart and Brochu, 1955, p. 148, 150). Sand depths of 

20-50 m (60-165 ft) are reported near Mederdra 

and Saint-Louis by Tricart and Brochu (1955, p. 

146-147).

The mean diameter of dune sand in the southern 

area is reported to range from 0.25 to 0.40 mm —
REGIONAL STUDIES OF SAND SEAS, USING LANDSAT (ERTS) IMAGERY 311

EXPLANATION

LINEAR DUNES 

Mostly simple, some compound

Feathered compound

CRESCENTIC DUNES 

Simple barchanoid ridges

Compound barchanoid ridges with 

long, straight segments

Complex crescentic ridges with 

linear elements superimposed

SHEET AND STREAKS

Compound sheets and streaks with

linear elements 

BEDROCK OUTCROPS OR BARRIERS

ROCK AND GRAVEL DESERT PLAINS

WITH NO LARGE DUNES 

PLAYAS AND COASTAL SEBKHAS

VEGETATED PLAIN

— 500— ISOHYET—Average annual rainfall,

in millimetres 

BOUNDARY OF SAND SEA

MAP LOCATION

200 KILOMETRES

1

100 MILES

DISTRIBUTION AND MORPHOLOGY OF EOLIAN SAND of the western Sahara of northern Africa Map based on Landsat imagery. 

Isohyets from Griffiths and Soliman (1972). (Fig. 188.)
312 A STUDY OF GLOBAL SAND SEAS

—Arm

Resultant drift potential (RDP)

Drift potential (DP)

16°00'

Reduction factor

Resultant drift direction (ROD)

TYPE OF SAND ROSE used in this chapter. See chapter F, figure 

93 and caption for explanation of parts of rose. (Fig. 189.)

that is, fine to medium grains (Tricart and Brochu, 

1955, p. 156-162). Sands of recent active dunes 

along the coast and elsewhere are reported to have 

a maximum diameter of 0.29 mm. Sand of the older 

red dunes is generally better sorted than that of the 

recent dunes and ranges in diameter from 0.46 to 

0.56 mm (mostly medium grained).

Three groups of immobile dunes are described 

(Leprun, 1971) in the Ferlo region of northwest 

Senegal, south of Dagena (fig. 188). Differentiation 

among the three groups of dunes is on the basis of 

soil development, texture, color, and vegetative 

cover.

The sequence of development of dunes in 

southern Mauritania and northern Senegal, based 

on paleontologic and pedologic studies, may be 

summarized as follows:

1. The large red simple to compound linear dunes 

trending east-northeast in southwestern 

Mauritania and northern Senegal are believed 

to have formed during an arid period when 

sea level was at least 50 m (165 ft) lower than 

it is at present, about 18,000 years before the 

present (Grove and Warren, 1968, p. 196; 

Boulet and others, 1971, p. 104, 113).

2. Reddening of the dune soils and gullying 

reportedly took place during a pluvial period, 

when the Senegal and other rivers cut channels through the linear dune fields to the 

Atlantic Ocean (Grove and Warren, 1968, p. 

196).

3. Sea level rose during the Nouakchottian 

transgression (5,500 to 5,000 years before the 

present) and the lower Senegal River valley 

was flooded as far as Bogue, 250 km (155 mi) 

inland. Beaches between the great linear 

dunes were formed at an elevation 4—6 m 

(13—18 ft) above the present sea level (Grove 

and Warren, 1968, p. 196).

ELONGATE SAND SEAS IN THE NORTHWEST SAHARA of 

Mauritania and Spanish Sahara. Skylab photograph 

SL4-138-3756. Bright pink areas are interpreted as sand seas; 

grayish-pink areas are gravelly, sandy, and rocky plains without 

large dunes; and dark areas include bedrock outcrops and 

coastal sebkhas. (Fig. 190.)
REGIONAL STUDIES OF SAND SEAS, USING LANDSAT (ERTS) IMAGERY 313

4. The sea regressed, and sand from the beaches 

was blown by winds into the coastal "dunes 

jaunes" of Tricart and Brochu (1955, p. 148).

5. Gullying of old red dunes in the southern part 

of the Aoukar sand sea (fig. 188) is continuing 

at present (Daveau, 1965). Gullying of dunes 

in the coastal region is interpreted (Tricart 

and Brochu, 1955, p. 153 ) as evidence of a 

transition zone between the arid northern environment and the more humid southern environment.

Interpretation of Landsat Imagery

Analysis of Landsat imagery shows that two 

main dune types — linear and crescentic — dominate the western Sahara. No dunes of star, dome, or 

parabolic type were recognized on Landsat imagery 

of this region. Complex dunes are relatively rare. 

The simple and compound forms of linear and crescentic dunes are similar to those in other sand seas 

that have been examined on Landsat imagery 

(chapter J). Sand sheets and streaks are conspicuous features of the western Sahara, especially 

in northern Mauritania.

Linear dunes of simple to compound form occur 

in elongate sand seas that extend from northwestern Mali to the coast of Mauritania (figs. 188, 

190, 191). The largest single linear dune seen on 

Landsat imagery is in central Mauritania.

Measurements of linear dunes near Mederdra 

and Boutilimit (fig. 191), made on Landsat imagery, 

yield an average dune width of 0.66 km (0.41 mi). 

Spacing (wavelength, measured crest to crest) in 

this area varies widely, but averages 1.58 km (0.98 

mi). In some areas, linear dunes as much as 20 km 

(12 mi) long are alined en echelon, oblique to- the 

trend of the elongate sand seas. Near Atar, at about 

lat 21°N., long 14°W. (fig. 193), trends of the elongate sand seas are N. 50°E., but linear dunes are 

oriented N. 40°E.

Compound linear dunes measured on Landsat 

images of the Makteir sand sea, northeastern 

Mauritania (fig. 192) commonly are more than 50 

km (30 mi) long, have an average width of 0.97 km 

(0.60 mi), and are very evenly spaced about 1.4 km 

(0.86 mi) from crest to crest.

A solitary linear dune extends from a gap in an 

escarpment south of Atar and crosses a sandy plain

westward to the base of bedrock outcrops near Akjoujt (fig. 193). The dune (Dra' Malichigdane) is 100 

km (62 mi) long and about 1 km (0.6 mi) wide and is 

oriented parallel to the resultant drift direction at 

Atar, as indicated by a sand rose on the map (fig. 

188). Near Akjoujt, the dune has small crescentic 

elements which give it a complex form. Other 

linear features in the same vicinity resemble the 

solitary linear dune in size and orientation but are 

composed of single rows of en echelon short linear 

dunes.

The Aoukar sand sea of southern Mauritania and 

Mali (fig. 194) consists mainly of crescentic dune 

ridges. Dunes in the western part of this sand sea 

are compound crescentic. Measurements of simple 

crescentic dunes were made on images of the 

Aoukar sand sea southeast of Tidjikdja. Boundaries 

of fields of crescentic dunes in the Aoukar sand sea 

characteristically match the spurs and reentrants of 

plateau escarpments.

Small fields of minor, probably simple crescentic 

dunes occur along the Atlantic coast near the 

Senegal River (fig. 188) and among bedrock outcrops south and east of Atar.

Sand sheets dominate the sand seas in the northern part of the western Sahara to a much greater extent than in any other deserts observed on Landsat 

imagery. North and west of Atar and south of FortGouraud are numerous prominent sand sheets 

associated with rock outcrops and escarpments 

(chapter J, fig. 187). Linear dunes occur on many of 

these sheets, and some sheets have small groups of 

crescentic dunes. Some sheets are 100 km (62 mi) 

long, or longer (figs. 190,194).

Sandstorms which blow south westward, parallel 

to the trend of the sand seas, have been observed on 

Landsat imagery of northern Mauritania, a region 

characterized by strong winds, sand sheets, and 

linear dunes.

Surface Wind Flow and Precipitation

Surface wind circulation in the western Sahara 

(between lat 14° N. and 26° N., and long 6° W. to 19° 

W.) is controlled by the Azores and Sahara highpressure cells, and the Intertropical Convergence 

Zone (I.T.C.Z.). During winter, the Azores high is 

nearest the African coast, and the Saharan high is 

strongest (fig. 195A). Outward flow from these
314 A STUDY OF GLOBAL SAND SEAS

15°30'

VEGETATED LARGE LINEAR DUNES shown in relation to precipitation isohyets (in millimetres per year) in southern Mauritania. 

Landsat false-color imagery E1069-10554. Green vegetation appears red, and red dune sands appear yellow on false-color imagery. 

(Fig. 191.)

pressure systems results in winds from the northeast or east over much of the western Sahara.

By June the Sahara high has been replaced by a 

thermal low in the central Sahara (fig. 195B). At 

this time the Azores high is strongest and is centered farthest from the coast at approximately lat 

30°00' N., long 32°30' W., resulting in more northerly wind flow at most stations. Some southern stations near the coast (from Boutilimit westward) experience northwesterly winds during this season. 

During July-September, when the I.T.C.Z. has

moved farthest north, stations south of lat 18° N. 

experience southwesterly monsoonal winds.

Rainfall in the western Sahara ranges from less 

than 50 mm/yr (2 in./yr) at Bir Mogrein (Fort-Trinquet) in the north to more than 300 mm/yr (12 

in./yr) at Rosso, in the south (fig. 188). Rain 

showers and thunderstorms during summer are 

associated with the I.T.C.Z., which moves northward to about lat 16° N. Thus, rainfall and associated southwest winds begin earlier and end later at 

southern stations than at northern stations (fig.
REGIONAL STUDIES OF SAND SEAS, USING LANDSAT (ERTS) IMAGERY 315

COMPOUND LINEAR DUNES IN THE MAKTE'lR SAND SEA north of the Er Richat structural dome, Mauritania. Landsat imagery 

E1103-10434. A basin filled with eolian sand is bounded on the west by hogback ridges. Numerous sand streaks and small linear 

dunes extend downwind (southwestward) from the hogbacks. (Fig. 192.)

196). Areas of active sand as seen on Landsat imagery (fig. 193) are mostly north of the 200-mm (8-in.) 

isohyet shown in figure 188. Considerable vegetation is visible on imagery of dunes south of this line 

(fig. 191).

Direction and Amount of Sand Drift

Annual resultant directions of sand drift (HDD's) 

at most stations in Mauritania are toward the southwest or south (fig. 188). Annual sand roses for these 

stations indicate considerable directional variability 

of wind during the year (fig. 188). This variability is 

cyclic and is reflected in seasonal shifts in resultant 

drift directions at all stations in the region. These 

shifts follow trends in the surface wind circulation 

just described; they produce resultant drift directions generally toward the west and the southwest 

in the winter (fig. 197A) and toward the southsouthwest, south, or southeast during the summer 

(fig. 197 B).

The cyclic swing of resultant drift directions during the year occurs most strongly in the southwestern, heavily vegetated part of the region (fig. 

198). Stations south of approximately 18° N. experience reversals in resultant drift directions during July—September that may be caused by the 

southwest monsoon (fig. 199), but the reversal is 

usually not of sufficient strength or duration to 

have much effect on potential sand movement. 

Moreover, the reversal occurs during the time of 

maximum rainfall in the south, which tends to 

further reduce its effect.
316 A STUDY OF GLOBAL SAND SEAS

SOLITARY LINEAR DUNE (DRA' MALICHIGDANE) between Atar and Akjoujt, Mauritania. Landsat false-color imagery 

E1140-10500. Relatively small elongate fields of crescentic dunes occur south of the linear dune. The intense yellow in the falsecolor imagery indicates that the sand is bright red and lacks vegetative cover (which appears red on false-color imagery); contrast 

with vegetated (red) linear dunes in figure 191 in southern Mauritania. (Fig. 193.)

Average drift potential of nine stations in the 

region (excluding Port-Etienne, which has an 

anomalously high drift potential) is 394 VU (vector 

units, chapter F), an intermediate value compared 

to other deserts of the world (chapter F, table 16). If 

Port-Etienne (2,232 VU) is included in the computations, the average drift potential is 569 VU, and 

the region as a whole is considered to be a highenergy desert. Total drift potentials and ratios of 

the resultant drift potential (RDP) to the total drift 

potential (DP) are highest in the northern areas and 

lowest in the southern areas (fig. 188). RDP/DP 

decreases regularly toward the southwestern part 

of Mauritania, as a result of the greater directional 

variability of the wind in this region. The strongest 

potential sand-moving season at some stations, 

such as Port-Etienne and Bir Mogrei'n (Fort-Trinquet), occurs in June, when the western Sahara lies 

in the zone of strong winds between the Azores 

high and the thermal low over the Sahara (fig. 195,

200). A second potential sand-moving season in 

Mauritania occurs at some stations during winter 

(January and February), when anticyclonicity in 

north Africa is most strongly developed (fig. 200). 

Distribution of the elongate sand seas and linear 

dunes of the western Sahara agrees in general with 

the annual resultant drift direction of sand computed from records of present-day winds. The 

agreement suggests that major changes in wind 

directions have not occurred since emplacement of 

the sand seas, thought to be about 18,000 years 

before the present (Grove and Warren, 1968, p. 

196). The anomalous trends of some linear dunes 

(oblique to the trends of the sand seas in which 

they occur) may result from the action of certain 

effective components within the general wind 

regime, in the manner described by I. G. Wilson 

(1973, p. 97) and by Warren (1970, 1972) for alinements of dunes in northern and southern parts of 

the Sahara.
REGIONAL STUDIES OF SAND SEAS, USING LANDSAT (ERTS) IMAGERY 317

Sahel and Southern Sahara of 

Mauritania, Mali, and Niger

Summary of Conclusions

LINEAR DUNES, CRESCENTIC DUNES, and 

elongate sand sheets occur in the Sahel and 

southern Sahara of northern Africa. Most of these 

features are at least partially vegetated. Two sets of 

dunes, with different orientations, occur along the 

Niger River near Timbuktu. One set of closely 

spaced, narrow linear dunes with sharp crests is 

alined at N. 67° E., in approximate agreement with 

the resultant drift direction of the northeast trade 

winds. More widely spaced, eroded ridges of indeterminate type form a second set in the same 

region and are oriented approximately east-west.

Compound crescentic dunes in the Aoukar sand 

sea have unusually straight segments with slipfaces 

toward the west-southwest. Very large barchans 

with slipfaces toward the southwest or west occur 

in the Valle'e de 1'Azaouk in the eastern part of the

region. Crescentic ridges there, however, have slipfaces toward the northwest. Broad sand "streaks" 

extend from east-northeast to west-southwest 

across the entire middle Niger region, approximately parallel to the resultant drift direction computed from present-day winds.

Most of the region studied averages more than 

100 mm (4 in.) of rainfall per year. Isohyets show 

that much of the region lies in the Sahelian climatic 

zone, where average yearly rainfall may be as much 

as 600 mm (24 in.) per year; the rest of the region 

lies in the sub-Saharan zone, where average annual 

rainfall ranges from 100 to 250 mm (4 to 10 in.) per 

year (Hills, 1966, fig. 15, table 15).

Present-day effective winds come mainly from 

the northeast or southwest throughout the Sahel. 

Drift potentials vary widely from station to station 

but are generally lowest in the south. Highest drift 

potentials at most stations occur in June, but some 

stations also have a winter sand-moving season. 

Eolian landform dimensions, orientation, degree of 

weathering and erosion, and relationship to un14°00'

COMPOUND CRESCENTIC DUNES IN THE AOUKAR SAND SEA, Mauritania. Landsat imagery E1140-10502. This field is directly 

south of the area shown in figure 193. (Fig. 194.)
318 A STUDY OF GLOBAL SAND SEAS

30°

SEA-LEVEL MEAN-PRESSURE CONTOURS, in millibars, of the Sahara and adjacent regions in (A) January and (6) June Average seasonal trends in surface wind flow indicated by arrows. Region of western 

Mauritania included in this study is shown by dark pattern. The position of Intertropical Convergence 

Zone (I.T.C.Z.) indicated by pattern is modified from Crutcher and Meserve (1970). (Fig. 195.)
REGIONAL STUDIES OF SAND SEAS, USING LANDSAT (ERTS) IMAGERY 319

M A M J J A S 

MONTHS OF THE YEAR

VARIATION IN RAINFALL DURING THE YEAR at Rosso, Akjoujt, and Fort-Gouraud, Mauritania. Rainfall is greater and begins 

earlier in the summer at the more southern stations. (Fig. 196.)

derlying topography — as observed on Landsat imagery of the sand seas north of the inland delta of 

the Middle Niger River and in the Vallee de 

1'Azaouk area — are interpreted as evidence of 

more than one episode of aridity and eolian activity.

Introduction

Landsat imagery has been used to map and interpret, with the aid of Skylab photographs, the distribution and morphology of eolian sand along the 

southern border of the Sahara (fig. 201). Severe 

drought and encroachment of eolian sand in that 

region are thought by some workers to be caused by 

poor agricultural and grazing practices but are attributed by others to changing climate.

Published reports (in French) of eolian features 

in the region are by Urvoy (1935, 1942), Monod

(1958), Tricart (1959, 1965), Dresch and Rougerie 

(I960), Daveau (1965), Boulet, Guichard, and 

Vieillefon (1971), Leprun (1971), and others. Other 

papers (in English) are by Grove (1958), Prescott 

and White (1960), Grove and Warren (1968), and 

White (1971). A report on eolian landforms observed on Skylab photographs includes a discussion 

of the Middle Niger River region (McKee and 

Breed, 1977). Useful maps of the region are U.S. 

Department of Commerce, U.S. Air Force Operational Navigation Charts J-2, J-3, K-l, and K-2; 

and U.S. Army Map Service, Series 1301, NF 30, NE 

30, and NE 31; all maps are at a scale of 1:1,000,000.

Review of Previous Work

The Aoukar sand sea ("Awkar" of Monod, 1958) 

is an area of compound crescentic dunes in 

southern Mauritania (the western part was described earlier in this chapter). (See also fig. 188.) 

Dunes in the eastern part of the Aoukar sand sea 

are described (Grove and Warren, 1968, p. 197-198) 

as a sea of "massed barchans," "unusually rectilinear transverse ridges" 40-50 m (130-165 ft) 

high, oriented north-north west to south-southeast 

(with slipfaces toward the southwest) and covered 

with bushes, grasses, and trees. Soil development 

and intermittent gullying of the Aoukar dunes is interpreted (Daveau, 1965; Grove and Warren, 1968, 

p. 198) as evidence of climatic oscillations in the 

Sahel.

Dunes in the inland delta region east of the 

Aoukar sand sea, near Timbuktu (fig. 201), are 

described by Tricart (1959, 1965), by Boulet, 

Guichard, and Vieillefon (1971, p. 110-111), and by 

Grove and Warren (1968, p. 198-200). The oldest 

described set of dunes consists of ridges 10 -20 m 

(about 32-65 ft) high and several kilometres long 

(Grove and Warren, 1968, p. 199) which formed 

locally by eolian winnowing of Niger River sands 

(Tricart, 1959, p. 335; 1965, p. 180-181) during a dry 

period, probably 20,000-15,000 years before the 

present (Boulet and others, 1971, p. Ill -112). Reddening of the upper 2-3 m (7-10 ft) of the dune 

sands, and their erosion by the Niger River, occurred during a more humid period 5,500-5,000 years 

before the present (Grove and Warren, 1968, p. 

199). Formation of "grey-brown and yellow dunes 

which are lower and much less continuous but 

sharper than the older ones" (Grove and Warren,
320 A STUDY OF GLOBAL SAND SEAS

15°

SPANISH SAHARA

I -Fort-Gouraud 

>/54 

58

36

38 

I/ 46 MAURITANIA

- 

18

Boutilimit

19

48

SENEGAL V I

15°-

r

200 MILES

400 KILOMETRES

I

400 KILOMETRES

~ 

200 MILES

RESULTANT DRIFT DIRECTIONS (arrows), drift potentials (denominators), and resultant drift potentials (numerators) at weather 

stations in Mauritania during (A) February and (8) July. Terms are defined in chapter F. During February, resultant drift directions are 

toward the west or southwest over most of the region. During July, resultant drift directions are more toward the south and are 

roughly toward the southeast in the southern, vegetated parts of the sand sea near Rosso, Nouakchott, and Boutilimit. (Fig. 197.)

1968, p. 199) occurred later, during an arid period.

Early maps of sand seas in the Middle Niger 

River region between Mopti and Timbuktu (Urvoy, 

1942, p. 48; Monod, 1958, p. 27; Grove and Warren, 

1968, p. 199) do not distinguish between two dune 

sets subsequently recognized on Skylab photographs (McKee and Breed, 1977). Relationships observed on space photographs and Landsat imagery 

are thus difficult to reconcile with work of previous 

authors.

Crescentic dunes described as "great swellings" 

several hundred metres wide are reported in the 

Vallee de 1'Azaouk, an abandoned river valley incised into lateritic plateau surfaces east of the great 

middle bend of the Niger River, near Menaka (fig. 

201). These dunes are assigned to a "preNouakchottian eolian episode," about 7,000-6,500 

years befor the present (Boulet and others, 1971, p. 

112-113). Other sets of dunes in the area between 

Tillabery and Bourem are mainly compound linear 

dunes (Prescott and White, 1960, p. 200-201). 

Encroaching eolian sand sheets in the Vallee de 

1'Azaouk area are described as flat, featureless 

plains of drift sand from the Sahara that have filled 

and blocked most river channels (White, 1971, p. 

70).
REGIONAL STUDIES OF SAND SEAS, USING LANDSAT (ERTS) IMAGERY 321

JUNE

DP=& 

OCT.

DP=9 

DEC.

SAND ROSES FOR 6 MONTHS FOR NOUAKCHOTT, 

Mauritania (fig. 188). Resultant drift direction (arrow) swings 

cyclically toward the southwest in February, toward the eastsoutheast in August, and then back. Southwest winds of the 

monsoon season do not have much effect at this station 

(note August sand roses) because Nouakchott is too far 

north (lat 18°07' N.). Drift potential, in vector units (chapter 

F), given for each month. (Fig. 198.)

Interpretation of Landsat Imagery

Measurements of Landsat transparencies of compound crescentic dune ridges in the Aoukar sand 

sea of Mauritania show that these dunes are composed of slightly crescentic segments that range in 

horn-to-horn width from 2.2 to 9.6 km (1.4-5.9 mi) 

(average, 4.1 km or 2.5 mi). The dune ridges are 

spaced an average 1.71 km (1 mi) apart (crest-tocrest). The Aoukar dunes have the straightest segments of any ridges of crescentic (transverse) type 

observed on Landsat imagery of the world's sand 

seas (chapter J, tables 38,39). The Aouk§r dunes are 

red (yellow on false-color imagery). Seasonal

changes of color on Landsat imagery indicate that 

these dunes are vegetated.

East of the Aoukar sand sea, between Mopti and 

Timbuktu (fig. 201), is a field of much eroded dune 

ridges of indeterminate type (which appear grayish-pink on imagery) that are oriented nearly eastwest across the course of the Niger River. Braided 

river courses are adjusted to the pattern of these 

parallel dune ridges, thus forming a trellislike arrangement in which numerous tributary streams 

and narrow lakes occupy interdune spaces (fig. 202 

B).

In contrast to the set of eroded dune ridges are 

fields of much narrower, sharper, brighter hued, 

and differently oriented linear dunes. The narrow 

dunes can be traced on imagery (fig. 202) from compound linear dunes in the Azaouad sand sea, which 

occupies the southern Sahara north, west, and east 

of Timbuktu (Monod, 1958), southward into the Lac 

Niangay area. These narrower dunes strike westsouthwest across parts of the other dunes near Lac 

Niangay and also across some of the trellis-patterned drainage (fig. 202B). Superposition of the 

narrow dunes over the east-west set, to which the 

Niger River had become adjusted is interpreted as 

evidence of more than one episode of large-scale 

eolian activity.

East of Bourem and Gao in the Vallee de 

1'Azaouk region (fig. 201, 202) are numerous individual crescentic dunes, probably barchans, commonly 1 km (0.15 mi) or more from horn to horn, 

which are clearly visible against the dark laterite 

plateau surfaces recorded on Landsat transparencies. These are among the largest individual dunes 

of crescentic type that the authors have observed 

on Landsat imagery and are probably compound 

barchans (chapter J). To the south and west in the 

Vallee de 1'Azaouk region are fields of compound 

crescentic dune ridges similar in form to those of 

the Aoukar sand sea farther west but with slipfaces 

to the northwest, rather than to the southwest.

Broad sheets of pale-red sand strike west-southwest across the entire Middle Niger region (McKee 

and Breed, 1977) from at least long 5° E. to long 10° 

W. (fig. 201). Numerous sand-free spaces between 

the sand "streaks" expose underlying topography, 

including remnants of abandoned drainages. 

Triangular-shaped lakes, such as Lac Faguibine and 

Lac Niangay, occupy depressions in some of the
322 A STUDY OF GLOBAL SAND SEAS

OP=33 

JAN.

OP=32 

MAR.

N

Ji

OP=26 

JUNE

DP=17 

JULY

OP=13 

AUG.

OCT.

SAND ROSES FOR 12 MONTHS FOR BOUTILIMIT, Mauritania. This station experiences a cyclic swing of the resultant drift direction (arrow) during the year. It also experiences a reversal in effective wind directions during summer. The reversal is a result of 

westerly through southwesterly winds which occur when the Intertropical Covergance Zone has moved farthest north. Sand roses 

for Fort-Gouraud, which exemplify the pattern of winds in regions farther north, are shown in chapter F, figure 976. Drift potential, 

in vector units (chapter F), is given for each month. (Fig. 199.)

sand-free areas. The sand sheets, like the narrow 

linear dunes associated with them, extend into and 

across some of the old eroded dune ridges near the 

Niger River (fig. 202B).

Surface Wind Flow and Precipitation

Climatic zones of the Sahel and southern Sahel in 

southern Mauritania, Senegal, Upper Volta, Mali, 

Niger, and Chad (Hills, 1966, fig. 15-1) are influenced by circulation from the Sahara and Azores 

highs to the north and equatorial trough (I.T.C.Z.)

to the south. As in the western Sahara (fig. 195), anticyclonic circulation from the Sahara and Azores 

highs results in flow of surface tradewinds from 

northeast to southwest across much of the region 

during winter, but surface wind flow during summer may be from the northeast or southwest. 

Winds from the southwest (southwest monsoon), 

resulting from cyclonic circulation associated with 

the Intertropical Convergence Zone (I.T.C.Z.), are 

strongest during June through August. Because the 

monsoon advances from south to north, stations 

along the southern margin of the Sahara are 

affected most by the southwest winds. Greater fre-
REGIONAL STUDIES OF SAND SEAS, USING LANDSAT (ERTS) IMAGERY 323

quency of the southwest winds at the more 

southern stations is apparent from the annual sand 

roses shown on figure 201.

Annual wind distributions at most stations are 

complex, reflecting the interaction of the pressure 

systems just described. During winter, when the 

region is dominated by anticyclonic flow from the 

northeast and east, wind distributions are narrowed, and winds are steadiest (fig. 203A). During 

summer, however, interaction of the southwest 

monsoon and the northeast winds results in complex wind distributions at most stations (fig. 203 B). 

All of the Sahel and southern Sahara region, by 

definition (Hills, 1966, table 15), receives more than 

100 mm (4 in.) of rainfall per year, as illustrated by 

isohyets (fig. 201). Most of this rain occurs during 

June —September, the period of the southwest monsoon (fig. 204). Rainfall increases from north to 

south, reflecting the greater influence of the monsoon at the more southern stations. Effects of the 

increased rainfall are evident on Landsat imagery, 

which show an increasing amount of vegetation

120

100

so

60

40

20

PORT-ETIENNE

600

500

400

300

200

100

M M O N D J F M 

MONTHS OF THE YEAR

M N D

VARIATION IN DRIFT POTENTIAL during the year (A) at Boutilimit, Atar, and Bir Mogre'i'n (Fort Trinquet) and (B) at Port-Etienne, 

Mauritania. Bir Mogre'i'n and Port-'Etienne experience strong sand-moving seasons in June, when the northern part of the region is in 

the zone between the Azores high and the thermal low in the Sahara. Some stations in the north, such as Atar, may, in addition, experience a sand-moving season in January-February, when anticyclonicity is strongest over the central Sahara (Sahara high). (Fig. 

200.)
324 A STUDY OF GLOBAL SAND SEAS

100 150 200 250 300 KILOMETRES

I I 1 I I I I I

0 25 50 75 100 125 150 175 MILES

DISTRIBUTION AND MORPHOLOGY OF EOLIAN SAND in the Sahel and southern Sahara of northern Africa (above and facing 

page). Map based on Landsat imagery. Isohyets from Griffiths and Soliman (1972) and U.S. Naval Weather Service (1968). (Fig. 201.)

southward from areas near the 100-mm (4-in.) 

isohyet toward the areas of greater rainfall.

Direction and Amount of Sand Drift

Annual resultant drift directions13 across most of 

the region shown in figure 201 are generally westward. Dunes and sand sheets observed on Landsat 

imagery are alined with resultant drift directions at 

several stations; for example, Kidal (off the map to 

the north), Tillabery, Mopti, Nioro du Sahel, and 

Nema. Near other stations, such as Timbuktu and 

Gao, resultant drift directions are neither alined 

with nor transverse to the dunes. The discrepancy 

may result from the unusual conditions for observation at these stations. An unusually low drift potential at Timbuktu, for example (fig. 201), suggests 

that the station may be sheltered from the northeast

winds (chapter F, under methods of study, wind 

data available and limitations). Sand roses are not 

adjusted for varying effects of vegetation at 

different stations or for presumed dampening 

effects of rainfall on sand movement. Potentially 

effective winds from the southwest, shown on the 

sand roses for Timbuktu and Gao (fig. 201), blow 

across heavily vegetated areas and are commonly 

associated with rainfall. Thus, the true sand-moving effectiveness of the southwest winds, relative 

to effectiveness of the northeast winds (which blow 

across the barren Sahara), is probably less than implied by those sand roses.

Compound crescentic dune ridges with northwest-facing slipfaces, in the eastern part of the

13 New terms are defined in chapter F and in the glossary.
REGIONAL STUDIES OF SAND SEAS, USING LANDSAT (ERTS) IMAGERY 325

EXPLANATION 

LINEAR DUNES

MAP LOCATION

Simple, short 

Compound 

CRESCENTIC DUNES 

Simple barchanoid ridges 

Compound 

Barchanoid ridges 

Barchans

SAND SHEETS AND STREAKS 

BEDROCK OUTCROP OR BARRIER

ROCK OR GRAVEL DESERT PLAIN 

WITH NO LARGE SAND DUNES 

VEGETATED FLOODPLAIN OR MARSH

ISOHYET—Average annual rainfall, in millimetres 

—— BOUNDARY OF SAND SEA

(Fig. 201.—Continued.)

region, may be in agreement with the northward 

resultant drift directions suggested by the sand 

roses for Menaka and Gao (fig. 201). The closely 

spaced linear dunes north of Timbuktu, oriented N. 

67° E. (fig. 202), are in approximate alinement with 

modern desert tradewinds (northeast winds), the 

effects of which are reflected in the sand roses for 

NtJina and 'Ayoun el 'Atrous farther west.

Drift potentials within the region studied vary 

widely possibly because vegetation in some 

localities may shelter stations from sand-moving 

winds. Some stations north of lat 16° N. record 

moderate or high drift potentials, for example 

'Ayoun el 'Atrous, (382 VU), Nema (803 VU), and 

Gao (388 VU). Drift potentials may be higher in 

regions north of lat 16° N. than in more southern
326 A STUDY OF GLOBAL SAND SEAS

COMPOUND LINEAR DUNES OF THE AZAOUAD SAND SEA (A) near Timbuktu (above). Landsat imagery E1096-10043. The 

Niger River runs from west to east. B, Two sets of dunes north of Mopli and south of Timbuktu, directly south of the area shown in 

A (facing page). Landsat imagery E1132-10052. The Niger River system is adjusted to the presence of large east-west dunes and is 

overridden on the east by sets of narrow linear dunes and sand sheets oriented like those to the north in A. Spaces between the 

large east-west dunes and some sand-free areas between the sand sheets are occupied by lakes. (Fig. 202.)

regions because the former are exposed longer to 

strong northeast winds than to the relatively weak 

southwest winds, or because more northern regions 

are less vegetated. Most stations studied have a potential sand-moving season in June, as shown in 

figure 205. Some stations also have a potentially 

strong winter sand-moving season; for example, 

'Ayoun el 'Atrous (fig. 205). Portions of the Sahel 

and southern Sahara, like the Thar Desert of India 

and Pakistan, generally are exposed to highest drift 

potentials prior to the onset of the rainy season and 

after an extended period of dryness.

Northern Sahara of Algeria, 

Tunisia, and Libya

Summary of Conclusions

SAND SEAS CONTAINING distinctive dune 

types extend across large parts of the northern

Sahara. These sand seas consist mostly of large 

compound and complex star and crescentic dunes, 

as in the Grand Erg Occidental, the Grand Erg 

Oriental of Algeria, and the Sahra' Marzuq of Libya. 

They are mostly confined to basins separated by 

plateaus and low mountain ranges. Sand seas of 

linear dunes, such as the Er Raoui, Erg-Iguidi, and 

'Erg Chech, commonly extend for long distances 

across rock and gravel plains.

Large isolated star dunes are a common type in 

the northern Sahara. In the central and southern 

parts of the Grand Erg Occidental, star dunes have 

mean diameters which range from 0.7 to 1.7 km (0.4 

to 1.1 mi) and on the downwind margin of the 

Grand Erg Oriental they have maximum diameters 

of 2.4 km (1.5 mi). Large star dunes also occur along 

the southern margin of the Grand Erg Occidental 

and grade northward into compound crescentic 

dunes in the interior of the sand sea. Star dunes in 

the Sahra' Awbari, Libya, and the Grand Erg Orien-
REGIONAL STUDIES OF SAND SEAS, USING LANDSAT (ERTS) IMAGERY

03°00'

327

(Fig. 202. —Continued.)

tal, Algeria, are arranged in linear trends which 

cross.

Widely spaced (5.7 km, or 3.5 mi) compound 

linear dunes in the Er Raoui, Erg-Iguidi, and 'Erg 

Chech extend south-southwestward into northern 

Mali and Mauritania. Barchanoid ridge dunes form 

a network pattern in the northeastern part of the 

Grand Erg Occidental, mostly in Tunisia along the 

border with Algeria and Libya.

Sand seas in the Ramlat Zallaf and Sahra' Awbarf > »

of Libya include crescentic dunes, star dunes, and 

linear dunes. Large crescentic dunes, and isolated 

star dunes with an average horn-to-horn width 

(and spacing) of 2 km (3 mi) occur in the Sahra' 

Marzuq, to the south in Libya. Fields of barchans 

extend in trains from the Sahra' Marzuq southwestward across the Plateau du Mangueni to the Great 

Erg of Bilma in Niger.

Most of the northern Sahara receives less than 

100 mm (4 in.) average annual rainfall. Complex intermediate- to high-energy wind regimes characterize the Grand Erg Occidental and the Grand Erg 

Oriental of Algeria. Very large star dunes occupy 

hundreds of square kilometres in these deserts.

These complex wind regimes reflect the interaction 

of winter westerlies, summer northeasterlies, and 

the southwesterly and northwesterly winds which 

result from cyclonic circulation and frontal 

passages. Annual resultant drift directions are 

toward the southeast at most stations in the Grand 

Erg Oriental.

Unimodal or bimodal high-energy wind regimes 

occur in southern Tunisia, a region characterized 

by a network pattern of barchanoid ridges.

Wind regimes southwards from lat 30° N. in 

western Algeria are generally unimodal or bimodal. 

Linear and crescentic dunes are common types in 

this region. Resultant drift directions are generally 

toward the southwest in the southern part of the 

Grand Erg Occidental and the 'Erg Chech.

Complex wind regimes occur in the Ramlat 

Zallaf and Sahra' Awbarl of western Libya. Near 

Ghudamis and Nalut in northwest Libya, annual 

resultant drift directions are toward the northeast. 

To the southeast near Sabha, and farther south near 

Bordj Omar Driss (Fort Flatters), annual resultant 

drift directions are toward the west or southwest.
328 A STUDY OF GLOBAL SAND SEAS

n

JUNE

MONTHLY SAND ROSES FOR NIORO DU SAHEL, MALI, for 

(A) February, during the winter season of steady east-to-northeast winds, and for (8) June, when the southwest monsoon interacts with east-to-northeast circulation to produce a complex 

wind distribution. Arrowed vector represents resultant drift 

direction, in vector units. (Fig. 203.)

On the average, intermediate drift potentials occur in the deserts of Algeria, whereas high drift potentials occur in the deserts of northwest Libya. 

Highest drift potentials occur in March or April at 

most places in the northern part of the area 

described but occur in June at some southern stations.

Introduction

Landsat imagery has been used to map and 

describe the distribution and morphology of eolian 

sand in several main sand seas of the northern 

Sahara. The main sand seas in Algeria, Tunisia (fig. 

206), and western Libya (fig. 207) are in structural 

and topographic basins, separated by plateaus and 

low mountain ranges. Meteorological data were obtained from numerous weather stations in and 

around the sand seas. Sand roses on the maps (fig. 

206, 207) show potential sand-moving power of surface winds, and isohyets are shown for areas that 

receive 100 mm (4 in.) or more rainfall per year.

260

240 -

M A M J J A S 

MONTHS OF THE YEAR

VARIATION IN RAINFALL DURING AN ENTIRE YEAR at Cao, 

Mali, lat 16°15' N. (dashed line) and Nioro du Sahel, Mali,lat 

15°14' N. (solid line). The southwest monsoon is farthest north 

in August, resulting in greatest rainfall at that time. Most 

southern stations receive greater rainfall than stations in the 

north because they are subject to the southwest monsoon for a 

longer period. (Fig. 204.)

The main geologic studies of the sand seas in 

Algeria and northwestern Libya are by Alimen 

Doudoux-Fenet, Ferrere, and Palau-Caddoux 

(1957), Alimen (1965), Capot-Rey (1943, 1945, 

1947a, b), and I. G. Wilson (1971a, 1972, 1973). 

Quaternary stratigraphy of a region that includes
REGIONAL STUDIES OF SAND SEAS, USING LANDSAT (ERTS) IMAGERY 329

100

80

60

20

JFMAMJJASOND 

MONTHS OF THE YEAR

VARIATION IN DRIFT POTENTIAL during the year at representative stations in the Sahel. All stations have a sand-moving 

season in June; 'Ayoun el 'Atrous has a sand-moving season in 

February (winter). (Fig. 205.)

the Grand Erg Occidental is summarized by 

Chavaillon (1964).

French and Arabic terms for various eolian landforms are shown in tables 26-35 in chapter J. Direct 

translation of Capot-Rey's nomenclature is complicated by his usage of the tern "sif" as a curved slipface on a dune of any type (Capot-Rey, 1945, p. 

392-394, 400, fig. 1; Capot-Rey and Capot-Rey, 

1948, pi. 1 (3)), whereas to most authors it means a 

linear dune.

Studies of dune forms and processes in central 

and southern Libya (Bagnold, 1933, 1941) have 

largely been in the Sarir Kalanshiyu, at Ramll al 

Kabir and Sahra' Rabyanah in the Libyan desert, 

and in the Great Western Desert of Egypt east of the 

region studied for this chapter. References to dunes

and sand sheets in the northern Sahra' Awban and 

Sahra1 Marzuq are mostly limited to reconnaissance 

papers (Capot-Rey, 1947b) and brief sections within 

reports on the geology or hydrogeology of the 

region (Conant and Goudarzi, 1967, p. 721-728; 

Jones, 1971).

Field studies of linear dunes in the Ramlat Zallaf 

are reported by McKee and Tibbitts (1964). 

Features of Libyan sand seas observed on Gemini 

space photographs are described by Pesce (1968). A 

physiographic map of northern Africa by Raisz 

(1952) shows the sand features at a scale of 1 inch 

equals 60 miles (1:3,801,600). Other useful maps of 

the northern Sahara are the U.S. Department of 

Commerce, U.S. Air Force Operational Navigation 

Charts H-2, H-3, H-4, G-l, G-2, J-3, and J-4; 

U.S. Army Map Service, Series 1301, NH 30, NG 29, 

NH 31, NG 31, NG 30, NF 31, NH 32, NH 33, NG 32, 

NG 33; and U.S. Department of Commerce, U.S. Air 

Force World Aeronautical Chart 541. All maps are 

at a scale of 1:1,000,000.

The Grand Erg Occidental and the 'Erg 

Chech, Algeria

Review of Previous Work

South of the foothills of the Atlas Saharien and 

north of the Plateau du Tademait (fig. 206) is a 

topographic basin containing the Grand Erg Occidental. The sand sea, which covers about 103,000 

km2 (64,000 mi2) (Wilson, 1973, p. 86) is bounded on 

the west by the Oued Saoura, a large intermittent 

stream. The sand sea is partly separated from the 

'Erg Chech (to the southwest) by low mountains, 

and separated from the Grand Erg Oriental (to the 

east) by plateaus.

Thirty-two samples of sand from large compound 

star dunes along the west margin of the sand sea, 

between Taghit and Kerzaz (fig. 206) were 

analyzed for grain-size distribution (Alimen and 

others, 1957). In the large star dunes grain size is 

unimodal, ranging from 0.20 to 0.22 mm. Sands of 

minor dunes, sand sheets, and interdune surfaces in 

the central part of the sand sea are bimodal, with a 

range in size from 0.18 to 0.26 mm. All dunes of the 

Grand Erg Occidental, according to Alimen, 

Doudoux-Fenet, Ferrere, and Palau-Caddoux (1957, 

p. 108-109, 112, 135-136, 167-169) and Alimen 

(1965, p. 282), were formed by eolian reworking of
330 A STUDY OF GLOBAL SAND SEAS

3°

"^hr 7&-

Laghouat

0 25 50 75 MILES

DISTRIBUTION AND MORPHOLOGY OF EOLIAN SAND in Algeria and western Tunisia. Map based on Landsat imagery. Isohyets from 

Dubief(1952). (Fig. 206.)
REGIONAL STUDIES OF SAND SEAS, USING LANDSAT (ERTS) IMAGERY

6°

331

10° 11° ^r-^^^n SeQ <r?^-—

*. . , ;f ,V:, «K .*; TM*C **s, -; -^.^.^..i^/^ab''

-- ' X ' * «'*^sv >5»/fll '-Y ' ^:'-l^^ , ^ ?/ *•- :s- A * \ ••

, ' * ; *•' \ »,\ Af

" • \: *i \ • ^

LINEAR DUNES 

Simple, short

Compound

Feathered 

Complex with

Crescentic dunes superimposed 

Star dunes superimposed

CRESCENTIC DUNES 

Simple barchanoid ridges

Compound 

Megabarchans

Barchanoid ridges 

Discontinuous barchanoid ridges

Barchanoid ridges with closed interdunes (fishscale pattern)

Complex crescentic ridges with 

Linear elements superimposed

Dome-shaped dunes superimposed 

STAR DUNES 

Simple, and some compound

Compound, in linear chains

DOME-SHAPED DUNES

Simple and compound

(Fig. 206. —Continued.)

Compound, in linear chains 

UNDIFFERENTIATED COMPLEX DUNES 

SIMPLE SHEETS AND STREAKS

COMPOUND SHEETS AND STREAKS WITH

LINEAR ELEMENTS 

BEDROCK OUTCROP OR BARRIER

ROCK OR GRAVEL DESERT PLAIN WITH

NO LARGE SAND DUNES 

PLAYA

VEGETATED MARSH

—— 100 —— ISOHYET— Average annual rainfall, in 

millimetres

—————— BOUNDARY OF SAND SEA

— INTERMITTENT DRAINAGE— Showing 

direction of flow
332 A STUDY OF GLOBAL SAND SEAS

28°

MAP LOCATION

DISTRIBUTION AND MORPHOLOGY OF EOLIAN SAND in sand seas of northwestern Libya and southeastern Algeria. Map based 

on Landsat imagery. Absence of isohyets indicates that the entire region receives less than 100 mm annual precipitation (Fig. 207.)
REGIONAL STUDIES OF SAND SEAS, USING LANDSAT (ERTS) IMAGERY 333

\K

\> ———— ________LIBYA 

' NIGER

EXPLANATION

LINEAR DUNES 

Simple, short

Mostly simple, some compound 

Compound 

Feathered

Two sets superimposed

Complex with star dunes superimposed 

CRESCENTIC DUNES 

Simple barchanoid ridges 

Compound 

Barchanoid ridges

Discontinuous barchanoid ridges

Barchans 

Complex 

Reversing ridges

Ridges with star dunes superimposed

Ridges with linear elements superimposed 

STAR DUNES 

Simple, and some compound

Compound in sinuous chains 

SHEETS AND STREAKS 

BEDROCK OUTCROP OR BARRIER

ROCK OR GRAVEL DESERT PLAIN WITH NO 

LARGE SAND DUNES

PLAYA

BOUNDARY OF SAND SEA

INTERMITTENT DRAINAGE—Showing 

direction of flow

(Fig. 207 — Continued.)
334 A STUDY OF GLOBAL SAND SEAS

basal early Quaternary (Mazzerien) sediments, 

mainly alluvium, and she suggested that sand in the 

big star dunes along the western margin has undergone more eolian reworking than has the sand of 

the interior. Suggested sources of sand in the 

Quaternary sediments are outcrops of MiocenePliocene sandstones (Alimen and others, 1957, p. 

38-40).

Sand of the Grand Erg Occidental is said to be 

composed almost exclusively of quartz with sparse 

tourmaline and zircon. This pure composition was 

interpreted by Capot-Rey (1945, p. 393) as indicating a long sedimentary history. A similar conclusion is reached by Alimen, Doudoux-Fenet, Ferrere, and Palau-Caddoux (1957) on the basis of 

grain-size distribution of sand and on the variety of 

sizes, colors, and orientations represented.

Interdune surfaces commonly are silicocalcareous crusts developed on sands similar to those 

of the dunes but lacking red color (Capot-Rey, 

1945). Remnants of Neolithic bog soils, composed of

white calcareous silt and containing gastropod 

shells, commonly overlie the interdune crusts 

(Capot-Rey, 1945, p. 398).

Sand of major dunes in the Grand Erg Occidental 

appears a uniform ocher (Alimen and others, 1957, 

p. 173-174) but in bright sunlight appears as 

various shades of red. Recent minor dunes in the 

sand sea and on Quaternary terraces of the Oued 

Saoura are yellow (Alimen and others, 1957, p. 

173—174). Distinct color differences of various 

groups of dunes are interpreted (Alimen and 

others, 1957, p. 175-177, figs. 83, 89) as evidence of 

dune formation under various climatic conditons 

and at different times.

Interpretation of Landsat Imagery

Imagery of the western part of the Grand Erg Occidental (fig. 208) shows very large compound star 

dunes along their downwind (western) margins 

between Taghit and Kerzaz. Toward the interior of

GRAND ERG OCCIDENTAL

Ml

SOUTHWESTERN MARGIN OF THE GRAND ERG OCCIDENTAL, Algeria. A, Complex crescentic and star dunes of the interior of 

the sand sea grading westward into large compound star dunes along the Oued Saoura. Landsat imagery E1116-10123. B, Southern 

boundary of the Grand Erg Occidental at Kerzaz and large linear dunes of the Erg er Raoui. Landsat imagery E1115-10071. The area 

shown in B is just southeast of the area in A. (Fig. 208.)
REGIONAL STUDIES OF SAND SEAS, USING LANDSAT (ERTS) IMAGERY 335

the sand sea, star dunes grade into complex dunes, 

crescentic and star (fig. 206). Measurements of 

Landsat transparencies of star dunes along 50 km 

(30 mi) of the Oued Saoura, north of Kerzaz, show 

that the star dunes have a mean diameter of 0.9 km 

(0.5 mi) and are spaced an average of 1.3 km (0.8 

mi) apart. Among this group of dunes is the Great 

Dune at Kerzaz, illustrated by Alimen, DoudouxFenet, Ferrere, and Palau-Caddoux (1957, pi. V, 1), 

which is more than 200 m (650 ft) high.

The western margin of the Grand Erg Occidental 

matches the contours of folded mountain ranges 

(fig. 208), which although of relatively low relief, 

exert profound topographic control on the downwind boundary of the sand sea.

Beyond the ranges to the southwest are complex 

linear and star dunes of the Erg er Raoui (fig. 208B). 

The linear dunes, which have star dunes on their 

crests, extend south westward across plains and 

through gaps in the low-lying ranges to the 'Erg 

Chech (fig. 209) and Erg Iguidi. The 'Erg Chech 

consists of very large southwest-trending compound linear and complex linear and star dunes

widely spaced on rock and gravel plains. Dunes 

measured on Landsat imagery (fig. 209) have a 

mean width of 1.0 km (0.6 mi) and are spaced an 

average 5.7 km (3.5 mi) apart. Their wide spacing is 

unusual, compared with that of linear dunes in 

other deserts (chapter J, table 36). Dunes of the 'Erg 

Chech, which are yellow on false-color imagery are 

actually red (chapter J, fig. 168B).

Linear dunes of the 'Erg Chech can be traced on 

imagery (partly shown in fig. 209) southwestward 

into sand seas of northwestern Mali and northeastern Mauritania. Extension of the sand several 

hundred kilometres southwestward, in the form of 

linear dunes, seems to support I. G. Wilson's (1971a, 

p. 196) contention that dunes such as these are 

"sand-passing" dunes that transport sand great distances from basin to basin across the Sahara.

The Grand Erg Oriental, Algeria and

Tunisia 

Review of Previous Work

East of Ghardaia and El Golea and north of the 

Hamada de Tinrhert lies the Grand Erg Oriental of

GRAND ERG OCCIDENTAL

(Fig. 208. —Continued.)
336 A STUDY OF GLOBAL SAND SEAS

02°30'

40 KM

,20 Ml

\

SUBPARALLEL COMPLEX DUNES of linear and star types of the 

'Erg Chech, Algeria. Landsat imagery E1116-10135. Widely 

spaced dunes extend south westward across gravel and rock 

plains toward the sand seas of Mali and Mauritania. Outline indicates part of image on which measurements of dune length, 

width, and wavelength were made. (Fig. 209.)

southeastern Algeria and western Tunisia. The 

Grand Erg Oriental includes an area of about 

192,000 km2 (119,000 mi2), and is about 70 percent 

sand-covered (I. G. Wilson, 1973, p. 91-92). The 

sand, if spread out, would have a mean thickness of 

26 m (85 ft). The mean height of dune ridges in the 

Grand Erg Oriental is 117 m (385 ft), and they are 

spaced an average of 1.6 km (1 mi) apart (I. G. 

Wilson, 1973, p. 91 and fig. 7, p. 88). The center of 

the Grand Erg Oriental, with about 90 percent sandcover, is continuous over about 80,000 km2 (50,000 

mi2) (I. G. Wilson, 1973, p. 92). The rock and gravel 

basement is nowhere more than a few metres 

beneath the dunes of the Grand Erg Oriental, even 

where sand covers 90 percent of the surface (I. G. 

Wilson, 1973, p. 92). Perennial grass (Aristida sp.) 

and shrubs grow on dune slopes and in interdune 

areas (Capot-Rey, 1947b, p. 185).

Fieldwork in the Grand Erg Oriental has not been 

extensive. A ground traverse across the Erg by I. G. 

Wilson (1971 a) provided sand samples and field observations for that author's (1973) geomorphic 

analysis, based primarily on aerial photographs and 

analysis of topographic maps. The regions of high 

dunes, which I. G. Wilson (1973, p. 104) called 

"draas," contain mixed sand sizes; the rest of the 

sand sea, according to him, is composed of sand 

having a modal size of about 0.16 mm (fine sand).

Whether I. G. Wilson's figures are entirely based 

on the 620 sand samples collected in the northern 

part of the Algerian ergs (I. G. Wilson, 1971a, p. 

185) or were derived from formulae based on 

postulated relationships between size, type, and 

grain-size distribution of dune and draa (I. G. 

Wilson, 1973, p. 94-97,101, figs. 18,19) is not clear. 

Wilson stated (1973, p. 105) that "in the absence of 

direct data, the variations of grain size in the ergs 

can be roughly inferred from the patterns of draa 

size and orientation, and from aerial photographs 

by variations in sand color and the distribution of 

slipfaces on the dunes." Thus, some workers 

believe that coarse sands develop dunes of size and 

orientation different from those of fine sands for a 

given area, presumably because sand of each grainsize is acted upon in various ways by different components of the wind regime (I. G. Wilson, 1973, p. 

95-96; Warren, 1972).

Sand in the Grand Erg Oriental is believed (I. G. 

Wilson, 1973, p. 84-85) to be derived from deflation 

of alluvium in basins upwind of the sand sea. Estimated mean deflation rates for the bajada surface 

near Biskra, beyond the northern margin of the 

Grand Erg Oriental (fig. 206, 219) is 1 -4 m (3 -13 ft) 

in 2,000 years (I. G. Wilson, 1971a, p. 188). Estimated age of the Grand Erg Oriental is 1,350,000 

years, based on an average annual net flow into the 

area (by wind) of 6 million tons of sand (I. G. 

Wilson, 1971a, p. 197).

Interpretation of Landsat Imagery

Landsat imagery of the Grand Erg Oriental (fig. 

210) shows that the lowest part of the area is occupied by a large salt playa, the Shatt al Jarid. The 

Grand Erg Oriental lies downwind of the playa, and 

is bounded on the south by slopes that rise toward 

the Hamada de Tinrhert and Plateau du Tademait
REGIONAL STUDIES OF SAND SEAS, USING LANDSAT (ERTS) IMAGERY 337

(fig. 206). The abrupt southern boundary of the 

sand sea seems to be topographically controlled, for 

its margin matches the 306-m (1,000-ft) contours of 

the plateau slope (fig. 210). The Grand Erg Oriental 

tapers off to the north into sand sheets, south of the 

Shatt al Jand. To the east, in Tunisia, large dunes 

end in a distinct rampartlike ridge of sand (fig. 210).

Dunes south of the Shatt al Jand and along the 

border between Algeria and Tunisia are barchanoid 

and compound barchanoid ridges in a network pattern (Monod, 1958; Cooke and Warren, 1973; 

chapter J, table 33). Segmented sand ridges (yellow) 

enclose interdune hollows, which appear bluish- or 

greenish-gray on the false-color image. Elements of

09°00'

33°00'-

Barchanoid 

ridges

V?1

Star 

dunes

40 KM

20 Ml

NORTHEASTERN PART OF THE GRAND ERG ORIENTAL, 

Algeria and Tunisia. Landsat false-color imagery E1109-09313. 

Size of crescentic ridges gradually increases southward. To the

pattern of barchanoid ridge dunes (yellow) and fully enclosed 

interdune areas (bluish- and greenish-gray) merges with a pattern of isolated star dunes. The dark blue area at the top left of

east the dunes, which appear yellow, end in a high, curved the image is a playa, the Shatt al Jarid. Red spots are vegetated 

boundary ridge of sand. To the south and west, the network oases. (Fig. 210.)
338 A STUDY OF GLOBAL SAND SEAS

the pattern are progressively larger toward the 

south and west (downwind) margins of the sand 

sea (fig. 210), where the dune ridges are replaced by 

star dunes.

The central part of the sand sea and its southern 

margin west of Ghudamis consist of isolated star 

dunes with a distinctive pattern. These star dunes 

are not distributed at random, but form at the nodes 

of crossing dune trends, according to I. G. Wilson 

(197lb, p. 268; 1973, p. 99, fig. 16). The association 

of star dunes with crossing dune trends can be 

traced westward into the western part of the Grand 

Erg Oriental, where the star dunes merge into 

linear dunes to make complex forms resembling 

chains (fig. 211).

Measurements of the isolated star dunes in the 

Grand Erg Oriental were made on Landsat imagery 

(chapter J, fig. 180B, tables 40, 41). Mean diameter 

of the dunes ranges from 0.7 km (0.4 mi) at the 

northern (upwind) end of the Grand Erg Oriental at 

about lat 32° N., long 8° E., to 1.7 km (1 mi) at the 

southern margin (fig. 211). Mean wavelength 

(crest-to-crest distance) ranges from 0.8-6.7 km 

(0.5-4.1 mi) at the northern end to 1.5-3.1 km 

(0.9-1.9 mi) at the southern end. I. G. Wilson (1973, 

p. 92, 98) has computed the cross-sectional areas of 

relatively small star dunes at the north end of the 

field (about lat 32°30' N., long 7°30' E.) to be as 

much as 10,000 m2 (33,000 ft2) for each dune.

Measurements of the star dune chains in the 

western part of the Grand Erg Oriental (fig. 211) 

were made on three sample areas of Landsat imagery. The measurements show that differences in 

dune size and spacing occur in a downwind direction in the sand sea. At the north (upwind) end of 

the field, the dune chains are spaced an average of 

3.1 km (2 mi) apart and are composed of star dunes 

with a mean diameter of 0.9 km (0.5 mi). At the 

southern (downwind) end of the field, the chains 

are spaced an average 6.3 km (4 mi) apart and are 

composed of star dunes with a mean diameter of 1.6 

km (1 mi). Relative areas of dune/interdune surfaces were measured by Kevin Horstman on Landsat transparencies, using a density-slicer to exploit 

the color contrast between the two kinds of surfaces. Ratio of dune/interdune areas at the north 

end of the field is 80/20 and at the south end of the 

field is 40/60.

Differences in dune size, spacing, and relative 

area from north to south in the Grand Erg Oriental

are measured in a direction parallel to the resultant 

drift direction in this part of the Sahara. The 

differences may have resulted from changes in the 

structure of wind regime with distance across the 

sand sea.

The Sahra' Awbari and Ramlat Zallaf,

• ••_ Libya

Review of Previous Work

South of the Al Hamadah al Hamra' and east of 

the border with Algeria is the Sahra' Awbari and its 

eastern extension, the Ramlat Zallaf. Sand in the 

Ramlat Zallaf is composed mainly of rounded 

grains with coatings of red or yellow iron oxide 

(McKee and Tibbitts, 1964, p. 5). Sand samples 

were taken from linear dunes, interdune areas, and 

sand and gravel plains near Sabha (fig. 207), and 

each type of sand deposit has a distinctive texture 

(McKee and Tibbitts, 1964, p. 8-10). Depth of sand 

is not well known, although, for an area in the 

southern Sahra' Awbari, Glennie (1970, enclosure 

4) showed 120 m (395 ft) of unconsolidated sand 

overlying Cretaceous rocks. Farther east McKee 

and Tibbitts (1964, p. 5) recorded well samples of 

eolian sand more than 1,000 ft (305 m) thick.

Linear dunes in the Sahra' Awban are described 

by Glennie (1970, p. 95) as about 100 m (330 ft) high 

and 100 km (62 mi) or more long, with surfaces 

covered by small barchanlike dunes. The latter 

represent eolian activity related to present winds, 

whereas the large linear dunes were probably 

formed by stronger winds of the past, according to 

Glennie, (1970, p. 95).

Interpretation of Landsat Imagery

Landsat imagery of the eastern, central, and 

western Sahra' Awbari (fig. 212) show a definite 

relation between topography, sand distribution, and 

dune type. Crossing trends of large dune ridges are 

evident on the southern margins of the sand sea 

(fig. 212); in the center of the field, the ridges merge 

into a field of star dunes. Star dunes also occur 

around the edge of the Hamadat Zegher (fig. 212). 

Margins of the sand sea coincide approximately 

with contours of the surrounding plateaus. Elevation of the Hamadat Zegher, although slight (500 m, 

or 1,650 ft; fig. 207) apparently is sufficient to prevent the large dunes to the east at lat 27°30' N., long 

13° E., which have an elevation of 300 m (985 ft), 

from invading it.
REGIONAL STUDIES OF SAND SEAS, USING LANDSAT (ERTS) IMAGERY 339

The Sahra' Marzuq, Libya and Niger

w O

Review of Previous Work

The Sahra' Marzuq (fig. 207) occupies 58,000 km2 

(36,000 mi2) in a structural and topographic basin 

bounded on the north, west and southwest by the 

Hammadat Marzuq, a 1,450-km-long (900-mi-long) 

cuesta of post-Tasillian-Nubian continental rocks, 

mainly sandstones (Capot-Rey, 1947a, p. 71, 81; Conant and Goudarzi, 1967, p. 721-728). Unconsolidated sands 1,200 m (3,940 ft) thick are reported to 

overlie Paleozoic rocks in the Sahra' Marzuq (Glennie, 1970, enclosure 4).

Sand of the Sahra' Marzuq is mainly quartz, and, 

according to Capot-Rey (1947a, p. 85), the median 

size of the grains is considerably greater than that

of dune sand from the Grand Erg Occidental and 

the Grand Erg Oriental of Algeria. Samples show 

bimodal distribution of grain sizes, with most of the 

sand grains larger than 0.35 mm (coarse or larger), 

although sand less than 0.10 mm (very fine) also occurs. The bimodal character of the Sahra' Marzuq 

sand diminishes from east to west across the sand 

sea, and at the western margin the sands have a 

high proportion of fine grains (Capot-Rey, 1947a, p. 

85).

A relationship between grain size of the sand and 

two basic forms of sand topography in the Sahra' 

Marzuq is recorded by Capot-Rey (1947a, p. 86-87). 

Low, rolling, nearly fixed dunes of the southern 

part of the sand sea are composed of coarse sands; 

these are the basal, residual sands of the erg. Above

SOUTHWESTERN END OF THE GRAND ERG ORIENTAL, Algeria, showing 200-km-long (120-mi-long) field of star dunes in linear 

chains. Skylab photograph SL4-138-3885. Southern boundary of the field corresponds approximately to the 400-m (1,300-ft) contour of the Hamada de Tinrhert and Plateau du Tademait (fig. 206). Height of large star dunes above the rock- and gravel-covered 

interdune surfaces at the southern margin is about 230 m (750 ft). (Fig. 211.)
340 A STUDY OF GLOBAL SAND SEAS

the coarse sands — especially in the northern and 

western parts of the basin — are finer sands which 

comprise active high dunes with steep slipfaces.

Interdune surfaces in the Sahra 1 Marzuq commonly have calcareous crusts. No trees are reported 

from the interdune areas, but grasses and shrubs 

(Aristida sp., CaJJigonum sp., CornuJaca sp.) are 

common (Capot-Rey, 1947a, p. 100-103).

Two main types of dunes were recognized during 

a ground traverse by Capot-Rey (1947a, p. 87-89). 

In the area north of Marzuq (fig. 207), compound 

linear dunes are dominant. These are composed, according to CapotrRey, of dune ridges alined one 

beside the other, either parallel or oblique to the 

main axis of the chain. A second main type is the 

compound crescentic dune ridge associated with 

isolated large barchans, reported to be as much as 

180 m (600 ft) high (Capot-Rey, 1947a, p. 88-89).

Interpretation of Landsat Imagery

A Skylab photograph (fig. 213) shows major dune 

forms and their distribution at the west end of the 

Sahra' Marzuq. Along the northwestern part of this 

s'and sea, at about lat 25°30' N., long 12°15' E., are 

numerous isolated large complex dunes, which 

have a mean horn-to-horn width of 2.0 km (1.3 mi) 

and a mean length of 1.5 km (1 mi) and are spaced 

an average 2.0 km (1.3 mi) apart. To the south and 

east, the isolated dunes merge into compound crescentic dune ridges. Southwest-trending linear elements are part of the dune pattern at the south end 

of the basin.

Still farther south, fields of barchans extend 

across escarpments of the Plateau du Mangueni, 

and sand is apparently being blown southwestward 

(fig. 213). The crescentic dunes can be traced on 

Landsat imagery several hundred kilometres south13°00'

>"40Kfe

-i±~^
REGIONAL STUDIES OF SAND SEAS, USING LANDSAT (ERTS) IMAGERY 341

westward, from the edge of the Sahra' Marzug to 

the Great Erg of Bilma in Niger.

Surface Wind Flow and Precipitation

Surface wind flow in the northern Sahara, including Algeria and Libya, is controlled by several 

major pressure systems, as shown in figure 195. 

During the winter, westerly winds prevail in northern Algeria, Tunisia, and northern Libya north of 

approximately lat 30° N. to the Mediterranean 

coast. South of this latitude, outward flow from the 

Azores and Sahara highs results in north to northeast winds. During the summer, a thermal low is 

centered at approximately lat 26 N. and long 03° E., 

and the Sahara high has been replaced by a ridge of 

high pressure extending northwestward into the 

Mediterranean Sea. Outward flow of air from the 

Azores high, which is strongest in June, and from 

high pressure over the Mediterranean Sea into the 

thermal low results in northeast to east tradewinds 

over the deserts of Algeria and Libya.

Another important element of surface wind circulation results from the passage of cyclones (lowpressure cells) from east to west along the Mediterranean Sea and from the passage across the desert 

of cold fronts (fig. 214). Both events result in strong 

winds from the west and southwest across wide 

regions of the desert. Northwest winds sometimes 

occur behind a cold front (fig. 214B). Winter, spring, 

or late autumn are the principal seasons of cyclonic

storms and frontal passages (U.S. Weather Bureau, 

and U.S. Army Air Forces, 1944, p. 7), and these 

mainly affect the northern Sahara. Winds resulting 

from the presumed effects of cyclones and frontal 

passages are shown by dashed arrows in figure 195. 

Except in the highlands and on the northern 

coast, the northern Sahara receives less than 100 

mm (0.4 in.) of rain per year (figs. 206, 207). 

Average annual rainfall variability for most stations is extreme (Griffiths and Soliman, 1972, p. 

97-98). Rainfall over most of the region is insufficient to support vegetation recognizable on Landsat 

imagery.

Direction of Sand Drift

Stations in Algeria from lat 30°N. to the coast (including El Golea, Ouargla, and Ghardaia) are 

characterized by complex wind regimes (fig. 206). 

These regimes result from the interaction of the 

westerly effective winds of winter, the northeasterly effective winds of summer, and the southwesterly effective winds resulting from cyclones 

and cold fronts. Seasonal changes in resultant drift 

directions occur in the northern Sahara in Algeria 

at Laghouat (fig. 215), Gharda'ia (fig. 216), and 

Ouargla (fig. 217). The complex effective wind distributions that characterize northern Algeria may 

account for the occurrence of star dunes, isolated 

and in linear chains, throughout the Grand Erg 

Oriental and parts of the Grand Erg Occidental (fig.

27030'

CENTRAL(A) AND_ WESTERN(B) PARTS OF 

THE SAHRA' AWBARI, Libya. Landsat imagery 

E1105-09101; E1106-09160. A, South-trending ridges in the north, southwest-trending 

ridges in the east, west-trending ridges in the 

south, and star dunes in the center of the sand 

sea. B, Star dunes surrounding the dune-free 

Hamadat Zegher. (Fig. 212.)
1

\
REGIONAL STUDIES OF SAND SEAS, USING LANDSAT (ERTS) IMAGERY 343

DUNES AT THE WEST EDGE OF THE SAHRA' MARZUQ, Libya 

(facing page). Skylab photograph. Red eolian sand fills 

topographically low areas and extends southwestward through 

gaps in the Hammadat Marzuq. Line surrounds a field of isolated combinations of star and crescentic complex dunes. (Fig. 

213.)

206). Star dunes are commonly found in areas with 

complex wind regimes.

Despite complex effective wind distributions, 

many stations north of lat 30° N. in eastern Algeria 

have annual resultant drift directions generally 

toward the southeast (fig. 206). Bechar and 'Am 

Sefra, in western Algeria, along the northwest 

margins of the Grand Erg Occidental (fig. 206) have 

annual resultant drift directions to the north and

5° Op 5°

northeast, probably due to influence of the nearby 

Atlas Saharien on local winds. Annual resultant 

drift directions at the east margin of the Grand Erg 

Oriental near Qabis, Tunisia, are mostly toward the 

northeast (fig. 206, 218). However, weak northeasterly effective winds prevail in this region during the summer, producing a resultant drift direction toward the southwest during that season (figs. 

218, 197).

Wind regimes from lat 30° N. southward in 

western Algeria (including I-n-Salah, Reggane, and 

Timimoun) are generally not complex (fig. 206). 

Dune types in the central and southern parts of the 

Grand Erg Occidental are mostly linear and crescentic ridges, which are associated with less

5° 0° 5°

20°

25°

5° 20° 0° 10° 10° 5° 20° 0° 5° 10°

EXPLANATION

H Center of high-pressure cell 

L Center of low-pressure cell 

© Calm

Leading edge of cold front

TWO METEOROLOGICAL EVENTS which produce southwesterly and northwesterly winds over large areas of the northern Sahara. A, Passage of a low-pressure system (cyclone) 

from west to east to the north of the desert. Counterclockwise circulation around the low results in southwest 

winds from Tamanrasset to Nalut, Libya, and in southeast winds 

at Biskra, northern Algeria. From National Oceanographic and

—————— Isobar

o Weather station

J Points into wind—large barb, 10 

knots; small barb, 3-5 knots

$ Direction of sand drift

Atmospheric Administration synoptic chart of Northern 

Hemisphere, April 3, 1971, 1200 G.M.T. B, Passage of a cold 

front from west to east across the northern desert. Winds in advance of the front are from the southwest, and those behind the 

front, from the northwest. From National Oceanographic and 

Atmospheric Administration synoptic chart of the Northern 

Hemisphere, January 17, 1972, 1200 G.M.T. (Fig. 214.)
344 A STUDY OF GLOBAL SAND SEAS

DP=29 

DEC.

SAND ROSES FOR 6 MONTHS FOR LAGHOUAT, north of the 

Grand Erg Occidental, Algeria. Westerly effective winds in 

winter (from December to February) result in east-southeastward resultant drift direction. By June, northwest winds have 

been partially replaced by northeast winds, and resultant drift 

direction is toward the west-southwest. Southwest winds are 

most prevalent in August. Drift potential, in vector units, is 

given for each month. (Fig. 215.)

variability of wind direction than are star dunes. 

Resultant drift directions at I-n-Salah, Timimoun, 

and Reggane (fig. 206) are toward the southwest, 

approximately parallel to the trend of linear dunes 

in that region (fig. 209). Monthly resultant drift 

directions at I-n-Salah are uniformly to the southwest throughout the year (fig. 219) because I-nSalah is south of the zone of winter westerlies and 

because frontal and cyclonic activity is greatest in 

regions farther north.

Annual resultant drift directions are toward the 

west-north west at Sabha in the eastern Sahra'

SAND ROSES FOR 4 MONTHS FOR GHARDAIA, Algeria, between the Grand Erg Occidental and the Grand Erg Oriental (fig. 

206). The season of winter westerly winds ends earlier at Ghardaia than at Laghouat. The sand-moving potential of winds 

(drift potential) is much greater at this station in the spring at 

161 VU (vector units) than in winter (December, 44 VU; February, 51 VU). (Fig. 216.)

Awbari (lat 27°01' N., long 14°06' E.) (chapter F, fig. 

115B) and south-south westward beyond the map 

region at lat 29°08' N., long 15°57' E. Surface wind 

flow in western Libyan sand seas approximates that 

shown in figure 195, but data are few (fig. 207). Annual sand roses for Bordj Omar Driss (Fort Flatters, 

lat 28°08' N., long 06°50' E.), Illizi (lat 26°30' N., long 

08°38' E.), and Djanet (lat 24°33' N., long 09°38' E.), 

Algeria (fig. 207), indicate complex wind regimes. 

All three stations are situated near mountainous 

terrain which may locally affect wind regimes.

Amount of Sand Drift

The average drift potential of 21 stations around 

the Algerian sand seas is 239 VU (vector units, 

chapter F, table 16), and of 7 stations around the 

Libyan sand seas is 431 VU. These are intermediate 

and high values, respectively, compared to those of 

other desert regions around the world (chapter F, 

table 16). As in other regions, however, a wide 

range of values occurs at individual stations, from 

51 VUat Djanet (fig. 207), to 571 VU at Biskra (fig. 

206). In general, northeastern Algeria, southern
REGIONAL STUDIES OF SAND SEAS, USING LANDSAT (ERTS) IMAGERY 345

FEB.

DP=23 

APR.

DP=3 

AUG.

^

JUNE

DP=B 

AUG.

DP=25 

DEC.

SAND ROSES FOR 6 MONTHS FOR OUARGLA, Algeria, at the 

northwest edge of the Grand Erg Oriental, illustrating complexity of the wind regime in that sand sea throughout the year. The 

complexity results from the interaction of the three dominant 

components of northern Sahara wind regimes; winter 

westerlies, summer northeasterlies, and the southwesterlies 

resulting from frontal passages and cyclones. Despite the variation of resultant drift direction during the year at Laghouat (fig. 

215), Ghardaia (fig. 216), and Ouargla, annual resultant drift 

directions at all of these stations are toward the southeast, approximately parallel to the long dimensions of the chains of star 

dunes southeast of Hassi Messaoud. (Fig. 217.)

Tunisia, and adjacent northwest Libya are in a 

region of intermediate to high drift potentials (fig. 

206). Western Algeria, including the Grand Erg Occidental and areas to the south of the Plateau du

OCT.

SAND ROSES FOR 6 MONTHS FOR QABIS, Tunisia, near the 

northeast margin of the Grand Erg Oriental. Winter westerlies at 

this Mediterranean coastal station are from the southwest rather 

than the northwest, as in the Sahara at Ghardaia (fig. 216) or 

Ouargla (fig. 217), and are stronger than spring winds. Summer 

north westerlies are weaker in this region than at stations farther 

west, such as Ghardaia and Ouargla. Thus, annual resultant drift 

directions at this station and at nearby Remadah, Ghudamis (in 

the region of very large isolated star dunes), and Nalut (fig. 206) 

are toward the northeast. (Fig. 218.)

Tademait and Hamada de Tinrhert have intermediate to low drift potentials. Exceptions to this pattern 

occur at I-n-Salah (541 VU) and Reggane (555 VU). 

In Libya, drift potentials decrease southward and 

eastward toward Jalu (132 VU) and Al Kufrah (81 

VU), which are located at long 21°34' E. and long 

23°20' E., respectively, near the center of the Sahara 

high-pressure cell (fig. 195).

The season of highest drift potentials in northern 

Algeria, Tunisia, and northern Libya usually occurs 

in March or April (fig. 220). Many stations in the 

north also have strong winter sand-moving seasons 

(fig. 220). The range of drift potential at many 

northern stations, such as Ghardaia and Biskra, 

Algeria, and Ghudamis, Libya, may be extreme (fig. 

221). Farther sound towards I-n-Salah and Djanet, 

Algeria, highest drift potentials can occur in June 

and July.
346

DP=27 

JUNE

A STUDY OF GLOBAL SAND SEAS 

60

DP=22 

DEC.

SAND ROSES FOR 6 MONTHS FOR I-N-SALAH, Algeria, south 

of the Grand Erg Occidental and east of the 'Erg Chech, illustrating the steadiness of easterly to northeasterly effective winds 

and resultant drift direction toward the west-southwest and to 

the southwest. This wind regime, in a region of sand sheets, 

contrasts markedly with some more complex wind regimes 

farther north in Algeria in a region of star and complex dunes. 

(See figs. 216-218.) (Fig. 219.)

Namib Desert of South-West 

Africa

Summary of Conclusions

CRESCENTIC, LINEAR, AND STAR DUNES occur in the Namib Desert in three elongate zones 

parallel to the Atlantic coast. Crescentic dunes with 

an average wavelength of 0.9 km (0.6 mi) occupy a 

belt 5-30 km (3.1 -18.6 mi) wide along the Atlantic 

coast between Swakopmund and Liideritz. Compound linear dunes occupy much of the central portion of the desert, from Liideritz northward to the 

Kuiseb River. These linear dunes average 2.2 km 

(1.4 mi) in wavelength and 27 km (16.8 mi) in 

length. Isolated fields of star dunes, reversing 

dunes, and complex dunes of indeterminate type 

occur along the east margin of the Namib Desert. 

The star dunes have a mean diameter of 0.7 km (0.4 

mi) and are spaced an average of 2.2 km (1.4 mi) 

apart. In general, redness of the dune sands seems 

to increase inland from the coast.

AMJJASON D 

MONTHS OF THE YEAR

VARIATION IN DRIFT POTENTIAL during the year at Laghouat 

(solid line) and Ouargla (dashed line), Algeria. These stations 

typify much of the northern Sahara, including southern Tunisia 

and northwestern Libya. Laghouat experiences high drift potentials in the winter and spring. Ouargla, which is closer to the interior, experiences highest drift potentials in the spring but is too 

far south to have equally high drift potentials in the winter. (Fig. 

220.)

Average annual rainfall is less than 100 mm (3.9 

in.) throughout the Namib Desert, except in some of 

its extreme eastern parts. Heavy dew along the 

coast may be the equivalent of as much as 25 mm (1 

in.) of annual rainfall. High-energy unimodal 

winds from the southwest or south occur along the 

Atlantic coast in a zone which corresponds roughly 

to the region of crescentic dunes. An intermediateto low-energy bimodal wind regime may occur in 

the central zone of linear dunes; a complex lowenergy wind regime prevails near the star dunes of 

the eastern Namib Desert. The observed presentday wind regimes of the Namib Desert are roughly 

compatible with the observed dune types in the 

several zones. The rapid decrease in wind energy 

inland from the coast, however, suggests that linear 

and star dunes in the interior are considerably less 

active than are crescentic dunes along the coast.

Introduction

The main sand sea of the central Namib Desert, 

South-West Africa, is bounded on the north by the 

Kuiseb River, on the west by the Atlantic Ocean, on 

the east by the Great Escarpment (Goudie, 1972, p.
REGIONAL STUDIES OF SAND SEAS, USING LANDSAT (ERTS) IMAGERY 347

MONTHS OF THE YEAR

VARIATION IN DRIFT POTENTIAL during the year at Ghardai'a 

and l-n-Salah, Algeria, illustrating the extreme variation in drift 

potential which may occur at some stations. Hassi Messaoud, 

Algeria, and Ghuda'mis, Libya, also exhibit this variable pattern. 

l-n-Salah is far enough south to reflect the summer high in drift 

potentials which occurs at southern stations. (Fig. 221.)

15); it ends at the south in sandy plains north of 

Luderitz and Aus. The sand sea area is about 34,000 

km2 (21,000 mi2) (Barnard, 1973, p. 2). It rests upon 

the Namib platform, a Tertiary erosional surface 

cut on schists, quartzites, and granite intrusives. 

Regional slope of the Namib platform is about 2.3 

m/km (65 ft/mi) from the base of the escarpment to 

the Atlantic Ocean. Numerous intermittent streams 

flow from the escarpment into playas among the 

dunes, and rock outliers protrude through the sand 

as inselbergs.

Landsat imagery has been used to map eolian 

sand distribution and morphology in the main sand 

sea of the central Namib Desert (fig. 222). Interpretations were made with the aid of Skylab 

photographs.

Principal published reports (in German) about 

the Namib sand sea are by Range (1927) and Besler 

(1972). A major work (in Afrikaans) on dunes of 

the central Namib is by Barnard (1973). Reports (in 

English) include a descriptive geomorphic paper by 

Gevers (1936), general geographic treatises by 

Wellington (1955) and by Logan (1960), and two 

papers by Goudie (1970, 1972) that give descriptions of the dunes near Gobabeb. Relationship of 

dunes to the Tsondab River and Tschaubrivier is 

described by Seely and Sandelowsky (1974).

Comprehensive aerial photography of the Namib 

Desert is unavailable and maps of the sand sea, U.S. 

Department of Commerce, U.S. Air Force, Operational Navigation Charts P-3, P-4, and Q-4, state 

that "relief data are unavailable."

Review of Previous Work

Sand of the Namib Desert is thought by most 

workers (J. Rogers, in Seely and Sandelowsky, 

1974, p. 61) to be derived mainly from fluvial sediments transported to the Namib platform by the 

perennial Orange River, in an area off the map (fig. 

222) at about lat 28° S., long 17° E. Some sand is also 

brought in by intermittent streams from the Great 

Escarpment (fig. 222). Some of the sand near the 

coast may be of marine origin (Gevers, 1936. p. 71). 

The sand sea may be as old as Miocene according to 

Barnard (1973, p. 2). Recent active sands in the 

Namib are believed to be derived mostly from 

reworking of Tertiary dunes (Martin, in Seely and 

Sandelowsky, 1974, p. 61).

Field data from the Namib sand sea consist 

mainly of descriptions of dune areas near the coast 

or accessible from Gobabeb (fig. 222). Sand forms 

near Gobabeb are at the downwind end of the sand 

sea near topographic barriers and thus, may not be 

representative of those to the south in the main part 

of the sand sea. Linear ridges near Gobabeb are 

described by Goudie (1970, p. 94-95) as "composite 

forms made up of as many as five subparallel and 

sinuous segments which sometimes isolate deep 

hollows within the dune." Interdune valleys near 

Gobabeb are largely sand free corridors containing 

a few small barchans (Goudie, 1970, p. 95).
348 A STUDY OF GLOBAL SAND SEAS

EXPLANATION 

LINEAR DUNES 

Simple, short

Mostly simple, some compound 

Complex with star dunes superimposed

CRESCENTIC DUNES 

Simple barchanoid ridges

Reversing ridges

STAR DUNES 

Simple, and some compound

Complex with reversing dunes 

superimposed

SHEETS AND STREAKS

BEDROCK OUTCROP OR BARRIER

ROCK OR GRAVEL DESERT PLAIN

WITH NO LARGE SAND DUNES

•200— I SOHYET—Average annual rainfall, 

in millimetres

BOUNDARY OF SAND SEA

•.'•*"•• '• ;£,*• •••'• '•••( v,^ ^S.

:. !-. I •• p^;'-'-".-tr y:J>^^^) 

«:. -./. ^:A'SS^^^^^^%:

••- ?-: ,>\i : '" \^ \ :• \ V^-'\\V^: 'AAV^;

^feft\k^-p^m

J^SiUni^v^

^S^iSt^^^V^

150 KILOMETRES

J

MAP LOCATIOW 75 MILES
REGIONAL STUDIES OF SAND SEAS, USING LANDSAT (ERTS) IMAGERY 349

DISTRIBUTION AND MORPHOLOGY OF EOLIAN SAND in the 

central Namib Desert of South-West Africa. Map based on 

Landsat imagery. Sand roses for Zwartbank, Rooi Bank, and 

Gobabeb are each for the month during which highest drift potential occurs and are not directly comparable to annual sand 

roses (annual sand roses for these stations are not available). 

Drift potentials, resultant drift potentials, and resultant drift 

directions for Zwartbank and Rooi Bank were estimated from 

December-to-August, and December-to-july data, respectively. 

An annual sand rose is shown for Pelican Point. Isohyets are 

from Grove (1969). (Fig. 222.)

Dune ridges of the central Namib are described 

by Logan (1960, p. 136) as having a chaotic and disorderly pattern, the result of disruption of their 

crests by "blowouts," and partial closure of their interdune troughs by "transverse" dunes. A threefold 

division of dunes is recognized by Barnard (1973, p. 

2) in the sand sea of the central Namib. It consists of 

(1) "a littoral belt of closely packed transverse 

dunes," (2) an interior zone of "longitudinal" dunes 

which he believed to have formed by deflation, and 

(3) an eastern zone of "multicyclic" complex dunes.

Some reported dune heights are as follows: 65 m 

(210 ft) for dunes in the coastal belt between 

Sandfisch Bay and Zwartbank (Stapff, 1887, in 

Goudie, 1970, p. 94); 80-100 m (260-380 ft) for 

"basically linear dunes" at Gobabeb (Goudie, 1970, 

p. 94; 1972, p. 24) and 300 m (nearly 1,000 ft) for 

"high, sharply crested dunes" near the Sossus Vlei 

along the interior margin of the sand sea (Barnard, 

1973, p. 2,5).

Sand of the Namib Desert is generally described 

as brown (Goudie, 1970, p. 94) or red (Logan, 1960, 

p. 136). Inland dunes were said by Logan (1960, p. 

136) to be "brick red," whereas dunes near the coast 

are recorded as "yellow-white." He stated that 

"This difference in coloration [between coastal and 

inland dunes] is believed to be the result of the 

greater age of the inland dunes which has allowed 

greater oxidation of the iron components within the 

sand" (Logan, 1960, p. 136).

The Namib Desert sand is reported to be 90 percent quartz and of uniform size, except that deviations in median diameter and sorting occur near the 

coast (Barnard, 1973, p. 2). Textures of Namib sand 

from dunes near Gobabeb and from "sand glaciers" 

(sand sheets, including climbing dunes) near Rossing Mountain, east of Swakopmund and north of 

the Swakop River, have been reported by Goudie 

(1970, p. 96; 1972, p. 24-25, fig. 16).

The main vegetation among the dunes near 

Gobabeb consists of sparse clumps of Stipagrostis 

sabulicola (Goudie, 1970, p. 94). Interdune areas 

support periodic growth of grass following infrequent precipitation (M. K. Seely, oral commun., 

1975).

Fresh or brackish water that occurs beneath 

dunes near the coast, about 85 km (50 mi) west of 

the playa at the end of the Tsondab River (figs. 222, 

223), is interpreted as evidence that the Tsondab 

River, the Tschaubrivier (fig. 224), and probably 

other intermittent streams that flow from the Great 

Escarpment at one time reached the Atlantic but 

that their courses have been truncated by the northward movement of dunes (Seely and Sandelowsky, 

1974). A late Pleistocene age for the earliest occupation by man of the area near Narabeb, west of 

the Tsondab Vlei (figs. 222, 223), is based on the occurence of Early Stone Age tools, estimated to be 

40,000-60,000 years old, in an interdune valley 

(Seely and Sandelowsky, 1974, p. 64).

Interpretation of Landsat Imagery

Dune types are distributed in three distinct zones 

across the sand sea — a coastal zone of crescentic 

dunes, a central zone of compound linear dunes, 

and an interior zone of star dunes and reversing 

dunes. Local variations of dune patterns within the 

zones occur especially near inselbergs and valleys 

of intermittent streams.

Closely spaced crescentic dune ridges occupy a 

belt 5-30 km (3-18 mi) wide along the Atlantic 

coast between Swakopmund and Liideritz (figs. 

222, 223). Measurements of dune width (horn to 

horn), length, and wavelength (spacing) were made 

on Landsat imagery (fig. 223, sample area 2) at 10- 

km (6-mi) intervals between Sandfisch Bay and 

Meob Bay. Mean dune width is 1.12 km (0.69 mi), 

mean length is 0.68 km (0.42 mi) and mean dune 

wavelength, 0.87 km (0.54 mi). These dunes are 

comparable to crescentic dunes in other areas observed on Landsat imagery (chapter J, table 38).

Compound linear dunes and complex dunes, 

mainly linear dune ridges with small star dunes and 

reversing dunes developed along their crests 

(chapter J, fig. 168), extend from the middle of the 

desert east of Liideritz to an abrupt boundary at the 

south bank of the Kuiseb River (figs. 222, 223).
350 A STUDY OF GLOBAL SAND SEAS

24°00'

WESTERN PARTS OF THE MAIN SAND SEA in the central Namib Desert. Landsat imagery F1383-08264; 

E1383-08270. Outlined areas are samples of imagery on which (1) complex linear dunes with superimposed star 

dunes were measured and (2) crescentic dune ridges were measured. (Fig. 223.)

The linear dunes of the central zone occur in distinct parallel straight patterns (figs. 222, 223, 224). 

Disruptions of individual dune crests and interdune 

troughs seem to the authors to create a complexity 

of dune forms but not a "chaos" as described by 

Logan (1960, p. 136). Variations from the generally

straight pattern of dunes alined N. 9° E. (fig. 223) 

are most pronounced near valleys of the Tsondab 

River and Tschaubrivier (figs. 223, 224).

Measurement of the linear dunes in a 2,500 km2 

(1,550 mi2) sample area in the center of the sand sea 

(fig. 223, sample area 1) yields the following mean
REGIONAL STUDIES OF SAND SEAS, USING LANDSAT (ERTS) IMAGERY 351

V

2A°30 •

20 Ml

Reversing and 

star dunes

40 KM 

_l

NORTHEAST MARGIN OF THE MAIN SAND SEA near inselbergs of the Great Escarpment (to the east) in the Namib Desert, Landsat 

false-color imagery E1202- 08222. Disruption of the dune pattern around the Sossus Vlei (playa) is shown. (Fig. 224.)

values: dune width, 0.83 km (0.51 mi); dune length, 

27 km (16 mi); dune wavelength 2.20 km (1.36 mi). 

The Namib dunes are compared with other dunes 

of linear type in chapter J (tables 36, 37).

Fields of star dunes, reversing dunes, and dunes 

of indeterminate (complex?) type occur along the 

eastern margin of the sand sea, near pediplains and 

inselbergs of the Great Escarpment (fig. 224). The 

sharply delineated boundaries of dune fields (fig. 

224) coincide approximately with the 1,200-m 

(4,000-ft) contour line shown on a map of the area 

(U.S. Department of Commerce, U.S. Air Force 

Operational Navigation Chart Q-4). Varieties of

dunes in the interior marginal area contrast greatly 

with the simple crescentic dunes of the coastal belt 

but merge into the linear dunes of the middle zone 

(figs. 222, 223, 224).

Star dunes north of Aus (fig. 222) range in 

diameter from 0.4 km (0.2 mi) to 1 km (0.6 mi), 

mean diameter, 0.7 km (0.4 mi), and are spaced an 

average 2.2 km (1.4 mi) apart. The Namib star 

dunes are of medium size, compared with those of 

other deserts (chapter J, tables 40, 41). They have a 

preferred east-west orientation (large arms oriented 

N. 48° W.).
352 A STUDY OF GLOBAL SAND SEAS

Landsat imagery shows dune-free surfaces on 

pediments around outliers of the Great Escarpment 

and in valleys of intermittent streams (fig. 224). 

Such dune-free areas around topographic barriers 

may result from sheetwash by occasional torrential 

rains along the escarpment. The escarpment is 

generally parallel to the 100-mm precipitation 

isohyet on the map (fig. 222). The eastern margin of 

the sand sea is marked by a high rampartlike ridge 

of sand (fig. 224), described by Logan (1960, p. 136) 

and similar in aspect on Landsat imagery to boundaries of sand seas in Tunisia, as described earlier 

(fig. 210).

Figure 225 shows dunes in the interior zone at 

the Sossus Vlei. Interbedding of white and tan 

playa sediments with the red sand of the dunes is 

common at the ends of the intermittent streams (M. 

K. Seely, written commun., 1975). Reddish hues of 

eolian sand translate on Landsat false-color imagery as shades of yellow (fig. 224), and the deeper 

the red of the sand, the more intense its yellow tone 

on the false-color imagery. In general, observations 

made from Landsat imagery (fig. 224), Skylab 

photographs (McKee and Breed, 1977), and ground 

photographs (fig. 225) confirm Logan's (1960, p. 

136) statement that dunes farthest inland are also 

the reddest. In general, also, large linear dunes in 

the central zone of the Namib sand sea are redder 

than are crescentic dunes both to the west and east 

of them. Reddest of all are the star dunes and other 

eolian sand features, mainly complex dunes and 

sand sheets, around inselbergs near the eastern 

margin (fig. 224). Relative degrees of redness cannot be attributed simply to age differences, or to 

different lengths of time in a subaerial environment 

because numerous factors other than time can also 

control the degree of redness (Walker, chapter D).

Climatic Regime 14

Southern Africa lies within a belt of high atmospheric pressure centered at approximately lat 

30° S. (Schulze, 1972, p. 503). Surface wind circulation over the Namib Desert during the winter is 

controlled by the South Atlantic high, the Indian 

Ocean high, and high pressure over the interior

" Principal sources of meteorological data are National Climatic Center, 

Asheville, North Carolina, U.S.A., and Desert Ecological Research Unit, 

Walvisbaai, South-West Africa.

plateau (fig. 226). Counterclockwise circulation 

around the South Atlantic high during the winter 

season results in southerly winds along the Atlantic 

coast. These winds may be deflected inland by the 

heating of the desert sands and thus become southwesterly winds, particularly near the coast (Harry 

Van Loon, oral commun., 1974). Strong easterly 

winds also occur in the Namib Desert during the 

winter and are locally referred to as the "Berg 

Winds." They may be initiated when coastal lows 

appear on the west coast during the summer or 

winter and move around to the south coast 

(Schulze, 1972, p. 506), promoting winds across the 

adjacent desert. During the summer, a thermal low 

develops in the interior plateau and promotes landward circulation throughout southern Africa (fig. 

226). Onshore (southwest) winds in the Namib 

Desert are strongest during spring and summer.

The Namib Desert receives less than 100 mm (4 

in.) of rain per year, as shown by the isohyets in 

figure 222, and the variability of this rainfall may be 

as much as 80 percent from year to year (Schulze, 

1972, p. 512, 514). An important source of moisture 

along the coast is the heavy dew associated with 

frequent fogs. This moisture may amount to as 

much as 2.5 cm (1 in.) of equivalent rainfall in a 

year (Royal Navy and South African Air Force, 

1944, p. 37).

Direction and Amount of Sand Drift

Annual resultant drift directions along the Namib 

coast, and as far as 50 km (31 mi) inland, are toward 

the north or northeast as shown by annual sand 

rose and wind roses from Alexander Bay (south of 

the mapped area), Liideritz (fig. 227), and Pelican 

Point, South Africa (fig. 222). This northward and 

northeastward direction of sand drift along the 

coast is steady throughout the year, with the exception of May-June, when the east winds ("Berg 

Winds") increase in strength. (See monthly sand 

roses for Pelican Point, chapter F, fig. 97A). Resultant drift directions at stations farther inland along 

the Kuiseb River, at the north end of the sand sea 

(fig. 222) seem to be toward the southwest. This apparent change in direction of potential sand movement may result from a decrease in the strength of 

the southwest wind from the coast inland, and a 

corresponding increase in the strength of the 

easterly winds ("Berg Winds") in the same direction
REGIONAL STUDIES OF SAND SEAS, USING LANDSAT (ERTS) IMAGERY 353

RED SAND DUNES AND TAN PLAYA SEDIMENTS along the interior margin of the Namib Desert. Ground photograph; view at the 

Sossus Vlei. Photograph by M. K. Seely. (Fig. 225.)

Two lines of evidence suggest that at inland stations the potential sand-moving effect of the east 

winds is greater than that of southwest winds. First, 

during June and July, which is the season of east 

winds, the drift potential of winds from the northeast quadrant (encompasses the "Berg Winds") is 

highest at inland stations (fig. 228). Second, the 

high energy of the sea breeze, or southwest wind, 

seems to diminish rapidly inland, as shown by the 

decrease in drift potentials from Pelican Point eastward to Gobabeb (fig. 222). At Gobabeb, the southwest wind is an important sand-moving wind only 

during October (fig. 229). At Rooi Bank, only 30 km 

(19 mi) from the coast, the "Berg Wind" is also a 

very important sand-moving wind (fig. 230).

Available data from stations along the Kuiseb 

River suggest that the resultant drift direction along 

the northern interior margin of the sand sea is 

roughly southwestward but wind data from 

Narabeb, a station within the sand sea, suggest a 

northeastward resultant drift direction (fig. 222). 

All the stations except those at the coast may to
354

10°

10° 20° 30°

A STUDY OF GLOBAL SAND SEAS 

40°- 50° 100r

MEAN SEA LEVEL ISOBARS (solid lines) and isobars of the 850- 

millibar-pressure surface (dashed lines) at 1200 G.M.T. Arrows 

indicate general wind directions. A, June (winter in Southern 

Hemisphere); B, January (summer in Southern Hemisphere). 

Modified from Schulze (1972, p. 504). (Fig. 226.)

ANNUAL 

EVENING

ANNUAL 

MORNING

WIND ROSES SHOWING STRONG SOUTHERLY WIND 

REGIME at the south end of the sand sea in the central Namib 

Desert at Liideritz. Number in centers of circles equal percent 

calm; white, 14-27 knots (25-50 km/hr); black, 28-40 knots 

(51-75 km/hr). (Fig. 227.)

Pelican Point 

WEST

Rooi Bank Zwartbank 

————— STATIONS ——————

Gobabeb 

->• EAST

MONTHLY DRIFT POTENTIAL, in vector units, of winds from 

the northeast quadrant ("Berg Winds") during June and July at 

four stations from west to east across the northern part of the 

Namib Desert. During June, the "Berg Wind" increases in 

strength between Gobabeb and Rooi Bank, then decreases 

rapidly between Rooi Bank and Pelican Point (fig. 222). Southwest resultant drift directions at Rooi Bank and Zwartbank during June (fig. 222) aline with sand streaks north of the Kuiseb 

River, partly shown in figure 223. Asterisks indicate drift potential of southwest wind at Pelican Point during June and July, for 

comparison. (Fig. 228.)

some degree be sheltered from effective winds by 

high dunes nearby. All wind regimes, however, 

reflect both the southwest and east winds to some 

degree and suggest that in the central part of the 

desert, wind regimes may be roughly bimodal, with 

the two modes approximately equal in effectiveness. A bimodal wind regime is compatible with 

linear dunes (chapter F).

A comparison of the low drift potentials at most 

inland stations with those at stations on the coast 

suggests that the dunes in the center and along the 

interior margins of the sand sea are much less active than those near the coast. Wind data from Aus 

(fig. 231) suggests that some areas along the eastern 

margin of the Namib Desert may have complex 

wind regimes. Aus is about 80 km (48 mi) from 

fields of star dunes, which are generally in areas 

that have variable wind directions (chapter F, fig. 

116).

The average drift potential of the Namib Desert is 

237 VU, which places it in a moderate-energy range 

when compared to other deserts of the world 

(chapter F, table 15). The coastal stations of Alex-
REGIONAL STUDIES OF SAND SEAS, USING LANDSAT (ERTS) IMAGERY 355

O

DP=0 

FEB.

DP=6 

MAY

QP=21 

JUNE

AUG.

DP=2 

SEPT.

£V>=4 

OCT.

DP=0 

NOV.

SAND ROSES FOR 11 MONTHS FOR GOBABEB, South-West 

Africa (location shown in figs. 222, 223). The southwest wind is 

strongest during October and is reflected in the long southwest 

arm of the sand rose. East ("Berg") wind is strongest in June, 

July, and August. December sand rose is unavailable. Drift potential is given for each month. (Fig. 229.)

ander Bay and Pelican Point experience a wide 

range in drift potential, with highest values occurring at Pelican Point (122 VV) during the spring 

(fig. 232). Maximum drift potentials at inland stations may occur in June or September (fig. 232).

Kalahari Desert of South-West

Africa, South Africa, and

Botswana

Summary of Conclusions

Linear dunes are the most common sand features 

of the western Kalahari Desert. Partially vegetated, 

mostly simple linear dunes trend northwestsoutheast and cover about 100,000 km2 (62,000 mi2).

These linear dunes average 0.3 km (0.2 mi) in width 

and 26.0 km (16 mi) in length, but many individual 

dunes are much longer. A second type of feature 

consists of long narrow sand bodies (which may be 

very large linear dunes or elongate sand sheets) 

that trend east-west in a region of about 15,000 km2 

(9,300 mi2 ) between the Blydeverwachterplato and 

the Molopo River valley. These sand features have 

an average width of 2.3 km (1.5 mi), and some extend more than 100 km (62 mi) across hills and 

valleys. They swing southward at the Molopo River 

and merge with the sand sea of linear dunes to the 

east.

Annual rainfall in the southwestern Kalahari 

Desert is less than 200 mm (8 in.) in most places but 

increases northward and eastward — from regions 

of little vegetation into regions of much greater 

vegetation. At present, the Kalahari Desert as a 

whole has little wind energy available for sand 

movement, but drift potentials vary widely within 

the desert. High drift potentials occur in the lessvegetated, southernmost part of the study area. 

Low drift potentials occur in the northern parts of 

the study area in regions of partially vegetated simple linear dunes. The linear dunes and (or) sand 

sheets in the southwestern Kalahari Desert are 

alined with the resultant drift directions of presentday winds.

Introduction

The Kalahari physiographic province 

(Wellington, 1955, p. 52) includes about 1,613,800 

km2 (1,002,800 mi2 ) of lowland sandy desert, but 

only the southwestern part — in South Africa, 

Botswana, and South-West Africa — has dunes 

recognizable on Landsat imagery. The sand sea of 

the southwestern Kalahari Desert is in a basin of internal drainage centered at Abiekwasputs on the 

Molopo River (fig. 233). The lower parts of this 

river and its tributaries (the Auob, Nossob, and 

others) are abandoned drainages that have been 

choked with eolian sand for at least 1,000 years 

(Lewis, 1936, p. 30, fig. 6). They are thus cut off 

from the perennial Orange River, which marks the 

southern boundary of the Kalahari dune country 

and drains surrounding territories.

Published reports of the Kalahari region include 

reconnaissance work (A. W. Rogers, 1934, 1936), 

field observations of dunes (Lewis, 1936), a general 

geographic treatise (Wellington, 1955), accounts of 

geology and geomorphology in the southwestern
356 A STUDY OF GLOBAL SAND SEAS

DP=0 

FEB. MAR.

MAY

DP=98 

JUNE

DP=20 

JULY

DP=7 

DEC.

SAND ROSES FOR 8 MONTHS FOR ROOI BANK, South-West 

Africa, approximately 30 km (18 mi) from the coast. Although 

this station is very near the coast, the "Berg Wind" (at this station a northeast wind) is the most important sand-moving wind

NW NE

SW SE

WIND ROSE FOR AUS, South-West Africa, near fields of star 

dunes in the interior of the Namib Desert. Data were insufficient 

for computation of sand roses but indicate sand-moving winds 

from several directions. 1 cm equals 10 percent occurrence. 

Light areas, winds 14-27 knots (25-50 km/hr); dark areas, 

winds 28 -40 knots (51 -75 km/hr). Source of wind data is Royal 

Navy and South African Air Force (1944). (Fig. 231.)

Kalahari (Mabbutt, 1955) and Botswana (McConnell, 1959; Boocock and van Straten, 1962), a paper 

describing landforms in relation to climatic change 

(Grove, 1969), and two papers describing dune

during much of the year. Data for for August-November are 

unavailable. Compare with sand roses for Pelican Point for the 

same months, chapter F., figure 97A Drift potential is given for 

each month. (Fig. 230.)

morphology and distribution (Goudie, 1969, 1970). 

Useful maps are the U.S. Department of Commerce, 

U.S. Air Force Operational Navigation Charts P-4 

and Q-4.

Landsat imagery supplemented by the Skylab 

photographs have been used to map and interpret 

eolian sand morphology and distribution in the 

southwestern Kalahari Desert. Data from 

meteorological stations in southern Africa were 

used to show relationships of the sand bodies to 

present wind regimes and precipitation patterns 

(fig. 233).

Review of Previous Work

About 200 sand samples obtained from dune 

crests, slopes, and interdune areas near the Aoub 

and Nossob Rivers, and Kurumanrivier in the 

southern part of the sand sea are reported (Lewis, 

1936) to be composed of partially rounded sand 

grains that have a composition of 90 percent quartz 

with accessory zircon, garnet, feldspar, ilmenite, 

and tourmaline. Samples from dune crests include 

fine to medium sand, whereas samples from inter-
REGIONAL STUDIES OF SAND SEAS, USING LANDSAT (ERTS) IMAGERY 357

130

M A M J J A S 

MONTHS OF THE YEAR

VARIATION IN DRIFT POTENTIAL (DP), in vector units, at 

Pelican P-'nt Gobabeb, and Narabeb in the Namib Desert, 

South-West Atnca. All stations experience a sand-moving 

season in June, a result of the east ("Berg") wind. Pelican Point 

experiences highest drift potentials during October, when the 

southwest wind is strongest. (Fig. 232.)

dune areas include very fine to very coarse sand 

(Lewis, 1936, p. 22-23, 26-28). A "few dozen" 

samples obtained between Gobabis and the Molopo 

River in the northwestern part of the sand sea contained moderately rounded sand (A. W. Rogers, 

1934, p. 11).

Eolian and fluviatile sediments of the Kalahari 

Beds of Tertiary-Pleistocene age occur throughout 

most of the Kalahari Desert (Boocock and van 

Straten, 1962, p. 151-154). Suggested sources for 

some of the younger sands of the Kalahari Beds are 

the eolian Triassic Cave Sandstone and its 

equivalents, which crop out in several parts of the 

region (Boocock and van Straten, 1962, p. 154). 

Eolian sands of the Upper Kalahari Beds of late Tertiary-Pleistocene age are also known as red sands, 

Plateau Sands, and Kalahari Sands (Mabbutt, 1955, 

p. 20, 25-27; table 1), and as sands of Kalahari type 

(Boocock and van Straten, 1962, p. 151-154).

Samples of some of the near-surface eolian sand 

in the Kalahari sand sea contain detrital kyanite, 

epidote, and staurolite, decreasing in amount to the 

southeast (A. W. Rogers, 1934, p. 11; Poldervaart, 

1955, p. 106). This has led several workers to conclude that the latest redistribution of eolian sand of 

Kalahari type in Botswana has been from the northwest (Boocock and van Straten, 1962, p. 154).

Dune sand in the Kalahari Desert is described 

(Grove, 1969, p. 199) as yellowish red (5 YR/5/6 to 

2.5 YR/4/8; Goddard and others, 1948) without 

regular differences in hue from dune crests to interdune troughs. Observations in Botswana (Boocock 

and van Straten, 1962, p. 153) have indicated that 

sands of Kalahari type occur both as dark-reddishbrown consolidated sand with considerable 

amounts of clay and silt, and as belts of grayishwhite less consolidated sand.

Unconsolidated eolian sand in the Kalahari 

Desert ranges in thickness from 3 to 33 m (10 to 100 

ft) (Grove, 1969, p. 195), but the entire sequence of 

Tertiary-Pleistocene Kalahari Beds composed of 

eolian and fluviatile sediments is 100 m (300 ft) or 

more thick, with maximum thicknesses where 

these sediments have filled in old drainage channels (Boocock and van Straten, 1962, p. 152,154). At 

Sekutani (beyond the map area, in the southeastern 

part of the basin at about lat 25°40' S., long 24°20f 

E.) a borehole through a buried channel penetrated 

157 m (515 ft) of Kalahari Beds (Boocock and van 

Straten, 1962, p. 152), and at Mafeking (east of 

Tsabong at approximately lat 26^ S., long 25°40' E.), 

a borehole penetrated 141 m (463 ft) of "Kalahari 

deposits" (A. W. Rogers, 1934, p. 10).

Dune crests reportedly are bare except for grasses 

(Stipagrostis and Eragrostis sp.). Dune slopes sup-
358 A STUDY OF GLOBAL SAND SEAS

20°

-20C

• >\-3 .-: '••ate-- "^.• x^-$£*:*££-tf

"Wipli

sag ^sk^is

EXPLANATION 

LINEAR DUNES

Simple, short

Mostly simple, some compound 

SIMPLE PARABOLIC DUNES 

SIMPLE SHEETS AND STREAKS

\ Rietfonieinl •^;-V;-: :';-;•".•:••'.•'.•-" 

JA ' V' .•-•-'-"-•v"'Ku

'••<Jr : ^:^:^ 

><P ^'/fev-:^x:V:

ABIEKWASPUTS S:;^:;^S •

ROCK OR GRAVEL DESERT PLAIN WITH NO LARGE SAND DUNES

29° VEGETATED PLAINS

BEDROCK OUTCROPS OR BARRIERS

—— ISOHYET—Average annual rainfall, in millimetres

—— BOUNDARY OF SAND SEA

22 23°

2^c

100 150 KILOMETRES MAP LOCATION 

I

25 50 75 MILES

DISTRIBUTION AND MORPHOLOGY OF EOLIAN SAND in the western Kalahari Desert, southern Africa. Map based on Landsat 

imagery. Isohyets from Grove (1969). (Fig. 233.)

port shrubs and trees as much as 3 m (10 ft) tall, and and Acacia haematoxylon) that grow to heights of 

interdune areas have trees (mainly Acacia giraf/ae 5 m (16 ft) (Grove, 1969, p. 199).
REGIONAL STUDIES OF SAND SEAS, USING LANDSAT (ERTS) IMAGERY 359

Dunes in the lower Molopo River area above 

Abiekwasputs (fig. 233) are described (Wellington, 

1955, pi. 8A) as longitudinal ridges with 

Y-junctions opening to the northwest (upwind); 

they are 10 to 25 m (33 to 82 ft) high and are 

spaced about 300 m (1,000 ft) apart (Goudie, 1969, 

p. 404). The distribution of these dunes was 

measured on aerial photographs by Goudie (1969), 

who found that their branching is random except 

where breaks of underlying slope and other 

topographic influences occur.

Interpretation of Landsat Imagery

Dunes in the southwest Kalahari Desert are 

mainly of linear (longitudinal) types; barchans and 

other varieties described by some workers (Lewis, 

1936, p. 30; Grove, 1969, p. 199) are mostly too small 

to be discerned on Landsat imagery and on Skylab 

photographs . An exception (fig. 233) is a field of 

parabolic dunes between Reitfontein and the Auob 

River, which is evident on Landsat transparencies.

Most of the Kalahari sand sea consists of 

southeast-trending linear dunes of apparently simple form which cover about 100,000 km2 (62,100 

mi2 ). Width, length, and wavelength (distance from 

crest to crest) of these dunes were measured on 

Landsat transparencies of six 2,500-km2 (1,550-mi2 ) 

sample areas in and around the regions shown in 

chapter J, figure 169A. Results are discussed in 

chapter J. Simple linear dunes of the Kalahari observed on space imagery average 0.3 km (0.2 mi) in 

width and 26.0 km (16 mi) in length and have an 

average wavelength of 0.7 km (0.4 mi). Their aspect 

on imagery made during the rainy season implies 

that flanks of the dunes are stabilized by vegetation.

Very large, irregularly distributed linear sand 

features, described previously as "stringer dunes" 

(McKee and Breed, 1976, fig. 59), cover 15,000 km2 

(9,300 mi2) and trend eastward from the Blydeverwachterplato to the Molopo River valley. There, 

they merge with the sand sea of simple linear dunes 

just described, and the alinement both of dunes and 

of other sand features swings southward (fig. 234). 

The extent of vegetative cover on the large sand 

features is not known. They are shown as areas of 

"Kalahari sand" on some earlier maps (Mabbutt, 

1955, pi. IV).

20°30' 

\

•2.

o

Kurumanriuier

<*"X. V 

Hakskeenpan Q^

Pans

Pans*

"Abiekwasputs Pan

40 KM 

I

20 Ml

u

ABANDONED DRAINAGES of the lower Molopo River, Nossob 

River, and Kurumanrivier (white), playas or pans, (blue and 

white), and dunes and invasive sand sheets (yellow). Landsat 

false-color imagery E1198-08000. Elongate sand bodies (sheets 

or very large linear dunes) extend undeflected across badlands 

(bluish-green in false-color) in the southwest corner and merge 

with linear dunes that continue south from the area shown in 

chapter J, figure 169A (Fig. 234.)
360 A STUDY OF GLOBAL SAND SEAS

These large east-trending sand features are observed on Landsat imagery (fig. 234) to cross hilly 

country and abandoned river channels without 

change of course or of shape, which is a common 

characteristic of linear dunes. Measurements of 

these large sand features on Landsat imagery 

(McKee and Breed, 1976, fig. 59) show that they 

range in length from 50 to more than 100 km (31 to 

63 mi) and have an average width of 2.3 km (1.4 

mi). If they are linear dunes ridges, they are among 

the longest and widest dunes of linear type seen on 

imagery of sand seas (chapter J, table 36).

Climatic Regimes

The Kalahari Desert is dominated by high atmospheric pressure in the winter and low pressure 

in the summer (fig. 226). During the winter, surface

wind flow follows a counterclockwise trend, from 

east-northeast winds at Ghanzi to northerly winds 

at Upington (Royal Navy and South African Air 

Force, 1944, fig. 2). During the summer, anticyclonic circulation is weak, and winds are variable. Development of a thermal low over the 

Kalahari Desert during this season promotes wind 

flow from the southwest in the region of the desert 

near Upington and Keetmanshoop (Schulze, 1965, 

p. 235-238). (See also the annual sand roses for 

Keetmanshoop and Upington, fig. 233, which 

reflect this southwest component.)

Annual rainfall in the Kalahari Desert ranges 

from 144 mm (5.5 in.) at Keetmanshoop and 204 

mm (8 in.) at Upington in the west to more than 400 

mm (16 in.) at Ghanzi in the northeast. Isohyets are 

roughly parallel from northwest to southeast, with

SAND ROSES FOR 12 MONTHS FOR GHANZI, Botswana, in the northeastern part of the Kalahari Desert. Although monthly wind 

distributions tend to be complex, resultant drift directions from month to month are toward the southwest. (Fig. 235.)
80

60

- 40

z 

o

I£L 

O

20

I I I

REGIONAL STUDIES OF SAND SEAS, USING LANDSAT (ERTS) IMAGERY

i80 80

361

60

40

20

J FMAMJ JASON D 

MONTHS OF THE YEAR

AVERAGE MONTHLY RAINFALL versus average monthly drift 

potential of Upington, South-West Africa. Season of highest 

drift potential (June-October) corresponds to season of least 

rainfall, which increases the probability of sand movement during this period. (Fig. 236.)

rainfall increasing toward the northeast (fig. 233). 

The driest season in this region is winter, and the 

wettest season is summer. Summer rainfall occurs 

mostly in the form of thunderstorms. These begin 

earliest in the northeastern part of the region (near 

Ghanzi) and during the summer extend westward 

across the desert (Schulze, 1972, p. 515, fig. 3).

Direction and Amount of Sand Drift

Evidence of vegetation on Landsat imagery, and 

data from published sources (Grove, 1969; Flint and 

Bond, 1968) confirm that most of the Kalahari 

Desert east of the 200-mm (8-in.) isohyet is a 

relatively inactive sand sea. However, most of the 

present-day resultant drift directions are parallel or 

subparallel to trends of all linear dunes and (or) 

sand streaks visible on Landsat imagery. Dune 

alinements seem continuous throughout the 

southern Kalahari Desert, from the less vegetated 

southwestern part to the heavily vegetated regions 

of presumably less active dunes in the northwest 

and east. Distinct stages of dune development in

20

MarientaK./ s

JFMAMJJASOND 

MONTHS OF THE YEAR

VARIATION IN DRIFT POTENTIAL during the year at four stations in the Kalahari Desert: Ghanzi and Tsane, Botswana 

(northeast and southeast desert, respectively); and Mariental 

and Gobabis, South-West Africa (northwest desert). Sand 

movement at stations with high drift potentials (Ghanzi, 

Upington) usually occurs during well-defined seasons of high 

drift potential, with periods of much lower drift potentials the 

remainder of the year. (Fig. 237.)

this region, thus, cannot be deduced on the basis of 

morphology alone, as can be done in the Sahel 

(described earlier in this chapter), where crossed 

dune trends clearly indicate two periods of dune 

growth.

Most present-day wind regimes in the Kalahari 

Desert are complex (fig. 233), although resultant 

drift directions at the various stations are relatively 

steady during the year (fig. 235). The region of less 

vegetated, presumably active sand in the south-
362 A STUDY OF GLOBAL SAND SEAS

western part of the desert is characterized by obtuse bimodal winds, as shown by the annual sand 

rose for Upington (fig. 233). The weaker southwest 

mode occurs principally during the summer. Additionally, the effective wind regime at Upington (fig. 

189) is similar on the basis of energy and directional 

characteristics (chapter F, fig. 105) to present-day 

effective winds associated with linear dunes in 

other regions. This relationship indicates that linear 

dunes visible on Landsat imagery of the Upington 

region may have developed in response to winds 

similar to those occuring in the region today.

The average drift potential of nine stations in the 

Kalahari Desert is 191 VU, indicating that the desert 

as a whole has relatively little energy available for 

sand movement (chapter F, table 16). However, 

drift potentials within the desert range widely from 

36 VUat Gobabis to 520 VUat Upington. Most stations have low drift potentials, which, combined 

with the effects of vegetation in weakening effective winds, may mean that these areas have negligible amounts of sand drift under present-day conditions. The important exception to this pattern is at 

Upington, where the season of minimum rains 

coincides with the season of highest drift potential 

(fig. 236), as in India-Pakistan. The time of highest 

drift potential at a station depends upon its position 

in the Kalahari Desert. At Upington (southwest 

desert), the highest drift potential is in August (fig.

236); at Gobabis and Mariental (west and northwest 

desert), it is in September (fig. 237); and at Tsane 

and Ghanzi (eastern desert), it is in September and 

October. The greatest range of drift potential during 

the year is observed at the sites with the highest annual drift potentials (Upington, Ghanzi, figs. 236,

237).

Arabian Sand Seas of Saudi

Arabia, Oman, Yemen, and

Adjacent States

Summary of Conclusions

Large compound and complex linear, crescentic, 

star, and dome-shaped dunes are observed on Landsat imagery of Arabian sand seas. Dunes of the Rub' 

al Khali, in the southern part of the Arabian Peninsula, are distributed according to type into three 

regions — crescentic dunes in the northeast, star 

dunes along the eastern and southern margins, and 

linear dunes throughout the western half.

The compound crescentic dunes in Al 'Uruq al 

Mu'taridah (northeastern Rub' al Khali) are 

unusually large, with a mean width (horn to horn) 

of 2.8 km (1.7 mi) and a mean length of 2.1 km (1.3 

mi). Presence of a field of smaller south-facing 

crescentic ridges at the north edge of Al 'Uruq al 

Mu'taridah might be interpreted as evidence of at 

least two major episodes of dune building.

Compound linear dunes at the western (downwind) margin of the Rub' al Khali are the largest 

observed in this study, averaging 1.5 km (1 mi) 

wide. Compound linear dunes in the southwestern 

Rub' al Khali have mean widths of 0.7 km (0.4 mi) 

and lengths of commonly more than 100 km (60 

mi). Their southwest trend is parallel to the annual 

resultant drift direction computed for Al 'Ubaylah. 

Large compound linear dunes, similar in width and 

length to linear dunes of the Namib Desert, SouthWest Africa, occur in the Wahiba Sands, Oman.

Sheets of sand associated with linear, crescentic, 

and star dunes occur in the Ad Dahna' and the sand 

seas in the northern part of the Arabian Peninsula. 

Giant dome-shaped dunes with a mean diameter of 

1.2 km (0.8 mi) fill the Nafud ath Thuwayrat, Nafud 

as Sirr, and Nafud Shuqayyiqah.

Average annual precipitation is less than 100 mm 

per year (0.39 in./yr) throughout most of the sandy 

regions of the Arabian Peninsula. Surface wind circulation over the Arabian Peninsula is controlled in 

the winter by the Sahara High of the African continent and in the summer by a large low-pressure cell 

over the Indian subcontinent. The northern deserts 

of Arabia experience high wind energies. The most 

northerly regions, near Badanah, have highest drift 

potentials in the spring (April); farther southeast, 

near Dhahran, maximum drift potentials occur during June. Low to intermediate annual drift potentials may occur in the Rub' al Khali.

Annual resultant drift directions in An Nafud 

and Ad Dahna' trend in a broad arc from east 

through south, exactly paralleling the trend of the 

sand seas. Annual resultant drift directions in the 

Rub' al Khali are toward the east near Ash Shariqah, toward the north along the eastern margin, and 

toward the southwest in the western part of the 

desert.

Unimodal, bimodal, and complex wind distributions in An Nafud and Ad Dahna' are roughly compatible with the variety of dune types in the region. 

Wind data for the Rub' al Khali are incomplete, but 

the unimodal effective wind distribution at Al
REGIONAL STUDIES OF SAND SEAS, USING LANDSAT (ERTS) IMAGERY 363

'Ubaylah is compatible with the crescentic dunes 

observed near the station.

Introduction

Sand seas with very large dunes extend over 

795,000 km2 (477,000 mi2) of the Arabian Peninsula 

(I. G. Wilson, 1973, table 1). Main sand seas are the 

Rub' al Khali and Wahiba Sands in the south and 

the An Nafud, Ad Dahna', and numerous smaller 

sand seas in the north. Landsat imagery has been 

used to map the distribution and morphology of 

eolian sand in the southern part of the Arabian 

Peninsula (fig. 238) and to illustrate the varieties of 

dunes and their distribution in the northern sand 

seas. Climatic data are shown by precipitation 

isohyets (fig. 238) and sand roses (figs. 238, 243).

Geologic quadrangle maps of the U.S. Geological 

Survey published between 1956 and 1963 

(Bramkamp and others, 1956; Bramkamp and 

Ramirez, 1958, 1959a, b, 1960, 1963; Bramkamp, 

Gierhart, and others, 1963; Bramkamp, Ramirez, 

and others, 1963; Ramirez and others, 1963a, b; and 

Brown and others, 1963) show the general distribution and morphology of the sand. Names used 

herein conform in spelling to usage on the U.S. 

Geological Survey map of the Arabian Peninsula 

(U.S. Geological Survey, 1963). Two index maps 

show distribution of dune areas (Holm, 1960, fig. 1; 

1968, fig. 3), and three maps show eolian landforms 

in the eastern part of the Rub' al Khali (Glennie, 

1970, enclosures 1-3). Other useful maps are the 

U.S. Department of Commerce, U.S. Air Force 

Operational Navigation Charts J-6, J—7, H-5. 

and H-6, at a scale of 1:1,000,000.

The Rub' al Khali

Review of Previous Work

Much of southern Arabia is a structural basin 

with its axis plunging gently northeastward into the 

Persian Gulf (Powers and others, 1966, p. D106). 

The Rub' al Khali sand sea (fig. 238) covers about 

560,000 km2 (216,000 mi2) of the region (I. G. 

Wilson, 1973, p. 86). It extends from the United 

Arab Emirates westward almost 1,500 km (930 mi) 

to the foothills of the Yemen Mountains. Sources of 

eolian sand in the Rub' al Khali are unknown, 

although some authors believe that the sand has 

been transported by wind from alluvial (wadi) sediments that were eroded from Paleozoic and 

Mesozoic sandstones (Holm, 1960, p. 1370; Brown,

1960, p. 157). The growth of dunes to as much as 

300 m (1,000 ft) high in the Arabian sand seas, such 

as those described by Brown, Layne, Goudarzi, and 

MacLean (1963), may require thousands of years (I. 

G. Wilson, 1971a, p. 183). A Pleistocene age for the 

large dunes of the Al 'Uruq al Mu'taridah, in the 

eastern Rub' al Khali, is suggested by Glennie 

(1970, p. 96).

Two forms of crescentic dunes were recognized 

in the eastern Rub' al Khali (fig. 238) and described 

by Glennie (1970, p. 88-89) as "predominantly 

barchan dunes, both simple and complex," and as 

"giant sand massifs in various forms, often of complex barchanlike structure with their axes transverse to the dominant winds." The latter dunes are 

termed "giant crescentic massifs" by Holm (1960, p. 

1372, fig. 5) and are herein referred to as "compound crescentic dunes," using the classification 

described in chapter J. (See also chapter J, table 27.)

Compound linear dunes of a "hooked" variety 

are recognized in the north-central Rub' al Khali 

(Holm, 1960, p. 1371-1372; 1968, fig. 3). Linear 

dunes 100 m (330 ft) high, 20-200 km (12-125 mi) 

long, and 1-2 km (0.6-1.2 mi) wide, separated by 

flat interdune corridors, are described in the 

Qa'amiyat region of the southwestern Rub' al Khali 

by Bunker (1953, p. 428-429) and by Holm (1960, p. 

1373). These dunes, which have subsidiary linear 

ridges oblique and parallel to the main ridge (Holm, 

1960, fig. 7), are classified as compound linear 

dunes (chapter }, tables 25, 26, 36).

Star dunes are recognized in the Ramlat as 

Sahama at the southeastern margin of the Rub' al 

Khali by Thesiger (in Bagnold, 1951, fig. 4), Beydoun (1966, p. H5), and Glennie (1970, p. 87, figs. 

70-71). "Pyramidal" (star) dunes in the Rub' al 

Khali and in the northern sand seas are described 

by Holm (1960, p. 1371, 1373). Star dunes on the 

edge of the 'Irq as Subay' east of Zalim (about lat 

22°30' N., long 43° E.) were sectioned and sampled 

by McKee (1966).

Interpretation of Landsat Imagery

Landsat imagery and Skylab photographs show 

that dunes in the Rub' al Khali are distributed by 

type into three principal areas: (1) the northeast, Al 

'Uruq al Mu'taridah area, characterized by crescentic dunes, (2) the eastern and southern margins of 

the sand sea, characterized by star dunes, and (3) 

the western half of the sand sea, consisting mainly 

of linear dunes. The great extent of linear dunes
364 A STUDY OF GLOBAL SAND SEAS

- - •—— - - ——- - _ -' _-_;' SAUDI ARABIA_______

77°

25 50 75 MILES

DISTRIBUTION AND MORPHOLOGY OF EOLIAN SAND m Saudi Arabia, Oman, Yemen, and adjacent States of the southern Arahigher in elevated

westward — from about long 50° E., to the Jabal are some of the largest crescentic dunes observed in

Tuwayq-Al 'Arid escarpment at about long 45°7' this study (chapter J, tables 38, 39). These crescenE., is apparent in the regional oblique view on a tic dunes are composed of curved segments with

Skylab photograph (fig. 239). shpfaces that have a mean width (horn to horn) of

The northeastern Rub' al Khali includes the Al 2.8 km (1.7 mi) (fig. 240). The dunes have a mean

'Uruq al Mu'taridah sand sea (fig. 238), in which length of 2.1 km (1.3 mi) and are spaced an average
REGIONAL STUDIES OF SAND SEAS, USING LANDSAT (ERTS) IMAGERY

52°

PERSIAN GULF Ash Sha

SAUDI ARABIA / 

OMAN

365

EXPLANATION

LINEAR DUNES 

Simple, short

Mostly simple, some compound 

Compound feathered

Complex 

With star dunes

Feathered, with star dunes 

superimposed

With crescentic dunes

superimposed 

CRESCENTIC DUNES 

Simple barchanoid ridges 

Compound 

Barchanoid and short ridges

Barchanoid ridges

Complex crescentic ridges

with star dunes superimposed 

STAR DUNES 

Simple and some compound

Complex stars with dome-shaped 

dunes overlapping

UNDIFFERENTIATED COMPLEX

DUNES 

SHEETS AND STREAKS

BEDROCK OUTCROP OR BARRIER

ROCK OR GRAVEL PLAIN WITH

NO LARGE SAND DUNES 

PLAYA

700—— ISOHYET—Average annual rainfall,

in millimetres 

———— BOUNDARY OF SAND SEA

- INTERMITTENT DRAINAGE—Showing 

direction of flow

bian Peninsula. Map based on Landsat imagery. Isohyets estimated from vegetation signature and station records. Precipitation is 

areas. (Fig. 238.)

of 2.6 km (1.6 mi) from crest to crest. Their gentler 

(stoss) slopes are covered by smaller crescentic 

dunes, as shown in chapter J, fig. 174B. Thus, they 

are compound barchanoid or crescentic forms similar in size and pattern to dunes in the Peoples 

Republic of China, the western Sahara, and

elsewhere (chapter J, fig. 175 and tables 38, 39). 

Toward the east and south, in Al 'Uruq al 

Mu'taridah^ these compound crescentic dune ridges 

grade into tomplex ridges with star dunes on their 

crests (McKee and Breed, 1976, fig. 56; chapter J, fig. 

174).
RED SEA

YEMEN

, Najran

Al 'Aritf

RED LINEAR DUNES EXTENDING 600 km (360 mi) across the western Rub' al Khali to the foothills of Yemen. Skylab oblique 

photograph SL4-143-4643. Dunes in theQa'amiyat region have an average crest-to-crest distance of 2.1 km (1.3 mi) and are commonly more than 100 km (60 mi) long. (Fig. 239.)

Dunes at the southeastern margin of the Rub' al 

Khali, along the border of Saudi Arabia with Oman 

(fig. 238) are mainly star dunes and isolated crescentic dunes (very wide barchans or very short 

"transverse" ridges). The isolated crescentic dunes 

in Oman at about lat 20° N., long 55° E.. have slipfaces that face north, opposite those of the southward-facing crescentic slipface segments of barchanoid ridge dunes in Al 'Uruq al Mu'taridah. The 

southern barchanoid ridge dunes are white on 

false-color imagery in contrast with the yellow of 

the dunes farther north. Their different size, orientation, and color suggest that these dunes in the 

southeastern part of the Rub' al Khali may be ac-
REGIONAL STUDIES OF SAND SEAS, USING LANDSAT (ERTS) IMAGERY 367

NORTHEASTERN RUB' AL KHALI, Al Jiwa- Al BatTn area. Landsat imagery E1130- 06251. Groups of small crescentic dune 

ridges, in the area marked by smoke plumes from oil flares, seem 

to be migrating southward and overriding much larger compound crescentic dunes of the northern Al 'Uruq al Mu'taridah. 

(Fig. 240.) '

tively migrating northward under the influence of 

strong southwest monsoon winds (fig. 238).

Star dunes along the eastern and southern 

margins of the Rub' al Khali, mostly in Oman and 

Yemen, are large isolated compound forms, shown 

in detail on an aerial photograph (chapter J, fig. 

179). The star dunes seem to "fan out" from the 

mouths of intermittent streams which flow northward from the southern highlands into the Rub* al 

Khali. Star dunes are larger and redder in a northward direction, where they merge with barchanoid 

dune ridges, forming complex dunes that have 

southeast-facing slipfaces (McKee and Breed, 1976, 

fig. 56). This relationship suggests that some sand 

in the star dunes along the southern margin of the 

Rub' al Khali may be derived from the wadi 

alluvium with which they seem, on the imagery, to 

be associated.

West of Al 'Uruq al Mu'taridah region of mainly 

crescentic dunes is a sand sea of dominantly linear 

dunes. At the boundary between the two major 

dune types (lat 20° N., long 53° E.) is a region of 

complex dunes that have both linear and crescentic 

elements (fig. 241). These include the "hooked" 

dunes described by Holm (1960, p. 1371 -1372; 1968, 

fig. 3). Very large compound linear dunes extend 

west of the region of complex dunes for hundreds 

of kilometres, through the Qa'amiyat region to 

foothills in Yemen (fig. 239). At the downwind end

NORTH-CENTRAL PART OF THE RUB' AL KHALI, west of Al 'Uruq al Mu'taridah. Landsat imagery E1166- 06254. Dune patterns 

change from large crescentic dunes in the east to linear (seif) dunes in the west. In the zone west of the compound crescentic dunes 

are smaller crescentic ridges. Complex combinations of linear and crescentic dunes ("hooked dunes") occur in the center of the 

area. (Fig. 241.)
368 A STUDY OF GLOBAL SAND SEAS

of this sand sea, at the Jabal Tuwayq are the largest 

linear dunes seen on Landsat imagery during the 

present study (fig. 239; chapter J, fig. 169F and 

tables 36, 37). They average 1.5 km (0.9 mi) in 

width and are spaced an average of 3.2 km (2 mi) 

apart.

Measurements in the sand sea of linear dunes 

were made on eight 2.500-km2 (1,500-mi2) sample 

areas of images. At the upwind end of the field, 

there were 25 ridges per 50-km (30-mi) distance. 

The widths of the dunes and interdunes corridors 

are nearly equal, averaging 2 and 2.1 km (1.3 mi), 

respectively. At the downwind end of the field, 

dunes are fewer (18 per 50-km (30-mi) distance) 

and narrower (0.7 km (0.4 mi)), as opposed to wider 

interdune areas (2.8 km (1.8 mi)). Although the upwind and downwind distributions of dunes thus 

differ, a plot of the measurements of all the samples 

against their distance downwind (expressed as a 

percentage of the total length of the field) shows no 

consistent trend.

The Wahiba Sands

Review of Previous Work

The Wahiba Sands is a sand sea of approximately 

16,000 km2 (10,000 mi2 ), east of the Rub' al Khali, in 

Oman (I. G. Wilson, 1973, table 1). The large linear 

dunes of the Wahiba Sands are Pleistocene features 

and do not reflect the trends of present-day winds, 

according to Glennie (1970, p. 90-95). The largest 

dune ridges are joined by numerous subsidary 

ridges oblique or parallel to the main trend, as 

shown on aerial photographs (Glennie, 1970, fig. 

74). Thus, the ridges are compound linear dunes 

(chapter J, table 25).

Interpretation of Landsat Imagery

Compound linear dunes in the Wahiba Sands 

(fig. 242) have a mean width of 1.1 km (0.7 mi) and 

are spaced an average of 1.6 km (1 mi) apart. Individual ridges are as much as 100 km (60 mi) long 

and have an average length of 31.3 km (20 mi). As 

in the Namib sand sea (fig. 223), crescentic dunes 

occur along the coast, and linear dunes are farther 

inland. At the north end of both the Namib sand sea 

and the Wahiba Sands, linear dunes are truncated 

along an intermittent stream (Glennie, 1970, fig. 

74). Linear dunes in the Wahiba Sands may be 

alined subparallel to the resultant direction of

59°00'

Sam pie area

si .8-3

I

SOUTHERN PART OF THE WAHIBA SANDS, Oman. Landsat 

imagery E1126- 06024. Outlined area is a sample of compound 

linear dunes on which measurements were made. (Fig. 242.)

effective winds, as suggested by the Al Masirah 

sand rose (fig. 238). A good correspondence of 

dimensionless ratios (Strahler, 1958, p. 292-293) of 

measured mean widths and mean lengths occurs in 

the Wahiba Sands and the Namib Desert. Mean 

wavelengths (spacing) of linear dunes in both 

deserts is dissimilar (table 44). Spacing is much 

greater between the linear dunes of the Namib than 

between the linear dunes of the Wahiba Sands (table 44).

Northern Sand Seas 

Review of Previous Work

Sand seas in the northern part of the Arabian 

desert include An Nafud, Ad Dahna', Nafud ath
REGIONAL STUDIES OF SAND SEAS, USING LANDSAT (ERTS) IMAGERY 369

TABLE 44 — Planimetric similarity of linear dunes of the Wahiba Sands, Oman, and linear dunes of the Namib 

Desert, South-West Africa, shown by comparison of scale ratios derived from their measurements

[Subscript to sand sea indicates first or second of pair. Subscript to L, W, and X indicates first or second of sand sea pair]

Sand sea

Mean _ _ Mean Mean _ _ _ _ _ _ _ Degree of

dune L /L_ dune Wn /W_ dune X n /X_ £,/W, L n /W_ L n /L L..A_ W, /A W_/X_ correspon-

'/34-v* 12 12 11 22 11 22 11 22 j

length 

L

width 

W

wavelength 

A

dence l

Wahiba sands— 31.25

1.16

1.06

.88

1.20

1.62

2.20

0.74 29.5 30.7 19.3 12.27 0.65 0.40 Good

1 Degree of correspondence is based on the maximum difference in scale ratios. 0.01-0.20 = Excellent; 0.21-0.39 = Very Good; 

0.40-0.59 = Good; 0.60-0.79 = Fair; 0.80-0.99 = Poor.

Thuwayrat, Nafud as Sirr, and others southwest of 

Ad Dahna' (fig. 243). The largest and least studied 

is An Nafud, which covers about 72,000 km2 

(45,000 mi2) (I. G. Wilson, 1973, table 1: this 

chapter, fig. 243). Dunes of this region reportedly 

reach heights of 100 m (330 ft) (Holm, 1960, p.

1373). An Nafud may furnish some of the sand of 

Ad Dahna' and the other northern sand seas (Holm, 

1960, p. 1370).

Ad Dahna' is an arc-shaped sand sea that extends 

1,200 km (750 km) southeastward from An Nafud 

to the northern Rub' al Khali (Holm, 1960, p. 1370,

36° 38° 40° 42° 44° 46° 48° 50° 52°

30°

0 50 100 150 200 250 KILOMETRES

I II II I

0 50 100 MILES

OUTLINE MAP OF NORTHERN ARABIAN PENINSULA Resultant drift directions are parallel to elongation of An Nafud, Ad Dahna', 

and other northern sand seas, shown by stippled area (sand sea patterns modified from Holm, 1960, fig. 1). Arrows on sand roses 

indicate resultant drift directions; numbers near sand roses are drift potential, DP (on bottom), resultant drift potential, RDP (on top), 

and RDP/DPin parentheses (computation of sand roses is described and terms defined in chapter F and in fig. 189). Sand rose for 

Ha'il is based on computations by Bagnold (1953) and is not to scale (DP and RDP are not available for Ha'il). (Fig. 243.)
370 A STUDY OF GLOBAL SAND SEAS

45°00

'.Sand 

streaksLinear dunes

Dome dunes

40 KM

20 Ml

\

PART OF AD DAHNA'OF SAUDI ARABIA. Landsat false-color imagery E1209-07041. Complex dunes composed of linear ridges 

and giant dome-shaped dunes fill the valleys, illustrating topographic control of sand sea boundaries. Dune sand appears yellow in 

false-color imagery. Blue-green areas are mostly sandstone and limestone bedrock, with a thin sand cover (yellow). Red areas along 

stream valleys are vegetated. (Fig. 244.)

fig. 1). Star dunes in Ad Dahna' are reported to be 

150-170 m (500-560 ft) high (Holm, I960, p. 1370). 

Southwest of Ad Dahna' are numerous elongate 

arcs of eolian sand. Unlike Ad Dahna', sands of the 

inner arcs do not extend to the Rub' al Khali. The 

northern sand seas are dominated by giant domeshaped dunes (chapter J. fig. 184), each separated 

from the next by deflation hollows that are commonly vegetated and crossed by low sand ridges 

(Holm, 1953, p. 108-110).

Dome-shaped dunes in the Nafud ath Thuwayrat 

(fig. 243) are commonly 1-1.5 km (0.5-1 mi) in 

diameter and 100-150 m (330-500 ft) high; compound varieties are as much as 5 km (3 mi) long 

(Holm, 1953, p. 108-109). The upper surfaces of 

some dome-shaped dunes have crescentic dune
REGIONAL STUDIES OF SAND SEAS, USING LANDSAT (ERTS) IMAGERY 371

ridges, so they are here classed as complex dunes 

(chapter }, fig. 184).

Interpretation of Landsat Imagery

Dunes in the northern and southern parts of An 

Nafud are complex types, formed of linear ridges, 

some with star dunes. Compound crescentic dune 

ridges occur along the west (upwind) margin and in 

the center of the sand sea. These ridges are spaced 

so closely that they obscure the interdune areas. 

The crescentic-shaped hollows observed in An 

Nafud by Bagnold (1951, p. 85) and by Holm (1960, 

p. 1370, fig. 3) may be the slipfaces of these nearly 

overlapping dunes.

Broad sheets of sand and linear dunes are characteristic of Ad Dahna' and the northern sand seas, 

north of the valleys of WadI Rima' and Wadi al 

Batin (fig. 244). At the junction of the sand-filled 

valleys of these intermittent streams, linear dunes 

grade into dome-shaped dunes of the Nafud ath 

Thuwayrat, Nafud as Sirr, Nafud Shuqayyiqah, and 

the southern part of Ad Dahna'. Dome-shaped 

dunes in the Nafud ath Thuwayrat, measured on 

sample areas of Landsat imagery have a mean 

diameter of 1.2 km (0.8 mi). They are the largest 

dunes of this type observed during the study 

(chapter }, table 42). The sand seas in which they 

occur fill valleys that are bounded on both east and 

west by sedimentary rock. Dome-shaped dunes in 

these sand seas increase in size from west to east in 

a downwind direction across each valley.

Surface Wind Flow and Precipitation

Surface wind circulation on the Arabian Peninsula is mainly controlled during winter by the 

Sahara High of the African continent, and during 

summer by a large low-pressure cell on the Indian 

subcontinent. In winter, clockwise flow of air from 

the Sahara High and its extension over Arabia produces westward surface wind flow in northern 

Arabia and south-southwestward flow in the Rub' 

al Khali (fig. 245A). During the spring and summer, 

the center of high pressure over eastern North 

Africa shifts northwestward to approximately lat 

35° N., long 15° E. (over the Mediterranean Sea; fig. 

245B). Also during this time, low pressure deepens 

over Asia and, by summer, extends as a trough over

the Arabian Peninsula. This situation results in 

northwesterly ("shamal") winds over much of the 

peninsula. On the southeast coast, surface wind 

flow into the same region of low pressure results in 

southwesterly winds. From August through 

November the thermal low over Asia weakens, and 

the center of high pressure near the eastern part of 

northern Africa shifts from the Mediterranean Sea 

southeastward into Libya. This is a season of weak, 

directionally variable winds over much of the Arabian Peninsula.

Average annual rainfall is less than 100 mm (3.9 

in.) at most stations near the An Nafud, Ad Dahna', 

and the Rub' al Khali (figs. 238, 243). Only Ha'il 

(102 mm or 4 in.) and Salalah (106 mm, or 4.1 in.) 

within the regions shown in figures 238 and 243 

have recorded more than 100 mm (3.9 in.) average 

annual rainfall, based on available data. Vegetation 

(red on Landsat false-color imagery) is visible only 

in the sand regions near oases. From north to south 

across the peninsula, average annual rainfall is 41 

mm (1.6 in.) at Badanah, 35 mm (1.3 in.) at Rafha', 

98 mm (3.8 in.) at Dhahran, 84 mm (3.3 in.) at Ar 

Riyan, and 58 mm (2.3 in.) at Al Masirah (U.S. 

Naval Weather Service, 1974b).

Direction of Sand Drift

Annual resultant drift directions in the An Nafud 

and Ad Dahna' are toward the east near Turayf and 

Badanah and toward the south-southeast near 

Dhahran and Ar Riyan (fig. 243). The curvature of 

annual resultant drift direction in the northern 

regions closely parallels trends of the An Nafud, Ad 

Dahna', and other sand seas. The curvature resembles in scale and orientation the clockwise trend of 

annual resultant drift directions in Algeria (fig. 

206).

Monthly resultant drift directions in the An 

Nafud are usually eastward during the winter 

months but shift toward the south in the summer. 

For example, monthly resultant drift directions at 

Badanah (fig. 246) are toward the east from December through April but are toward the southeast 

from June through October. At Dhahran, on the 

Persian Gulf, the resultant drift direction is toward 

the southeast most of the year but shifts to the 

south during March-May (fig. 247).
372

40° 50°

A STUDY OF GLOBAL SAND SEAS

60° 60° 50° 40°

80°

40°

10°

SEA-LEVEL MEAN-PRESSURE CONTOURS (in millibars) on the Arabian Peninsula and adjacent 

regions for (A) January and (B) June. Average trends in surface wind flow indicated by arrows. L, area 

of low air pressure; H, area of high pressure. Trough of low pressure over Arabian Peninsula in June 

indicated by dashed line. Modified from Crutcher and Meserve (1970). (Fig. 245.).
REGIONAL STUDIES OF SAND SEAS, USING LANDSAT (ERTS) IMAGERY 373

DP=28 

FEB.

DP=53 

MAY

DP=22 

DEC.

SAND ROSES FOR 6 MONTHS FOR BADANAH, Saudi Arabia. 

Resultant drift direction (arrow) is generally toward the east 

from December through April, and toward the southeast from 

June through October. Drift potential, in vector units, is given 

for each month. (Fig. 246.)

Wind distribution in the An Nafud -northern Ad 

Dahna' region (fig. 243) range from unimodal 

(Dhahran) to bimodal (Badanah) to complex 

(Rafha'). This range of wind regimes accounts for 

the wide variety of dune forms in the region (fig. 

244).

Annual resultant drift directions in the Rub' al 

Khali (fig. 238) are toward the south-southwest 

near Al 'Ubaylah and toward the east along the 

coast of the Trucial States near Ash Shariqah. 

Along the southeastern part of this coast, the resultant drift direction seems to be generally toward the 

north, based on data from the island station of Al 

Masirah.

At Ash Shariqah, on the coast of the Trucial 

States in the northermost Rub' al Khali, resultant 

drift directions are toward the east or southeast 

most of the year (fig. 248). Greatest directional 

variability of effective winds occurs during the late 

summer through early fall (August and September, 

fig. 248) at Ash Shariqah. Resultant drift directions

DP=21 

SEPT.

DP=19 

DEC.

SAND ROSES FOR 12 MONTHS FOR DHAHRAN, Saudi Arabia. 

Compare with sand roses for Badanah (fig. 246). The wind 

regime at Dhahran is more directionally steady from month to 

month than at Badanah; wind distribution is usually unimodal 

at Dhahran but may be bimodal or complex at Badanah. Resultant drift directions (arrows) are more toward the south at 

Dhahran than at Badanah. Drift potential, in vector units, is 

given for each month. (Fig. 247.)

vary little from month to month at Al 'Ubaylah, in 

the northern Rub' al Khali (fig. 249). This suggests 

that effective winds farther downwind from Al 

'Ubaylah in the western Rub' al Khali, in the region 

of linear dunes, may also be relatively steady in 

direction. The eastern and central parts of the Rub' 

al Khali are characterized by crescentic and linear 

dunes (fig. 240), which are often associated with 

narrow wind distributions (chapter F, fig. 105). Star 

dunes occur along the southern margin of the Rub' 

al Khali, a region which may be subject to wind 

flow from the southwest during the summer.
374 A STUDY OF GLOBAL SAND SEAS

OP=53 

MAR.

DP=33 

MAY

DP=32 

APR.

DP=20 

MAY

DP=30 

JUNE

DP=17 

DEC.

SAND ROSES FOR 6 MONTHS FOR ASH SHARIQAH, Arabia. 

Resultant drift direction (arrow) is generally toward the east 

from December through May; toward the southeast from 

August through September. Late summer through early fall is the 

season of greatest directional variability of effective winds 

(August sand rose) and is also the season of lowest drift potentials. Drift potential, in vector units, is given for each month. 

(Fig. 248.)

Amount of Sand Drift

The average drift potential of the northern sand 

seas (wind stations shown in figure 243) is 489 VU, a 

high value compared to that of most other desert 

regions around the world (chapter F, table 16). 

Highest drift potentials at stations in An Nafud, Ad 

Dahna', and the Rub' al Khali may occur in the 

spring or early summer, depending upon location. 

At many stations along the Persian Gulf, the season 

of high drift potentials is associated with strong 

north or northwesterly winds that are locally 

known as the shamal winds. During that season the 

wind may blow for 2 or 3 days at 22-26 knots 

(41-48 km/hr), then diminish to 13-17 knots 

(24-31 km/hr) for several more days under cloudDP=7

NOV.

DP=7 

DEC.

SAND ROSES FOR 9 MONTHS FOR AL 'UBAYLAH, Arabia, in 

the Rub' al Khali sand sea. Sand roses are not available for July, 

August, and September. Monthly resultant drift directions (arrows) are relatively steady toward the south or southeast for 

most of the year. Resultant drift directions at Al 'Ubaylah continue the trend of a broad tradewind arc suggested by data from 

stations in the An Nafud farther north (fig. 243). Surface wind 

data for sand roses published by permission of the Arabian 

American Oil Co. Drift potential, in vector units, is given for 

each month. (Fig. 249.)

less skies (ARAMCO Survey, 1974, p. 2). In the 

northern sand seas (including the An Nafud), highest drift potentials occur in April at Badanah, in 

May at Al Qaysumah to the southeast, and in June 

at Dhahran still farther to the southeast (fig. 250). 

Much of the potential sand movement in the northern sand seas occurs during sharply defined 

seasons, rather than distributed evenly throughout
REGIONAL STUDIES OF SAND SEAS, USING LANDSAT (ERTS) IMAGERY 375

the year. In the Rub' al Khali, highest drift potentials at Ash Shariqah and Al 'Ubaylah occur in 

March (fig. 251). At Al Masirah, the highest drift 

potentials occur in July (299 VL/) at the peak of the 

southwest monsoon winds. The drift potential at Al 

'Ubaylah, approximately 200 VU, suggests that the 

Rub' al Khali may not be as windy as An Nafud.

The Thar Desert of India and 

Pakistan

Summary of Conclusions

Vegetated compound parabolic dunes of a distinctive rakelike shape are the most widespread

100

M A M J J A S 

MONTHS OF THE YEAR

DRIFT POTENTIAL DURING THE YEAR at Badanah, Al 

Qaysumah, and Dhahran, Arabia. Location of stations shown in 

figure 243. Season of highest drift potentials occurs early in the 

year in the northwestern An Nafud (Badanah) but later at 

locatities closer to the Persian Gulf (Dhahran). (Fig. 250.)

type of eolian landform in the Thar Desert. Clusters 

of these dunes average 2.6 km (1.6 mi) long and 2.4 

km (1.5 mi) wide. Parabolic dunes extend from the 

Rann of Kutch northward and eastward to Bikaner 

and Jodhpur and occupy an area of at least 100,000 

km2 (60,000 mi2). Smaller, apparently simple crescentic dunes and short linear dunes occur in small 

fields surrounded by the parabolic dunes.

Compound crescentic dunes with an average 

wavelength of 1.3 km (0.8 mi) occur in a broad band 

along the northwest margin of the Thar Desert, 

from approximately lat 26°40' N., to lat 29°40' N. 

Eroded, heavily vegetated crescentic dunes occur 

east of Jodhpur and on the Gujarat Plain in fields 

oriented parallel to the eastern shore of the Rann of 

Kutch. Linear dunes, some of which may be compound forms, are oriented northeast-southwest 

along both the east and the west margins of the 

desert. Sand streaks and sheets, similar in appearance to those observed on Landsat imagery of 

other deserts, are oriented approximately northeast-southwest along the east margin of the sand 

sea near Jodhpur and Banner.

Average annual rainfall in the Thar Desert 

ranges from less than 100 mm (3.9 in.) along the

M A M J j A s

MONTHS OF THE YEAR

DRIFT POTENTIAL DURING THE YEAR at Ash Shariqah and Al 

'Ubaylah, Arabia. Location of stations shown in figure 238. Both 

stations probably experience highest drift potentials in March. 

Monthly drift potentials are not available for Al 'Ubaylah for July 

through September. Data for Al 'Ubaylah published by permission of the Arabian American Oil Co. (Fig. 251.)
376 A STUDY OF GLOBAL SAND SEAS

northwest margin of the desert to more than 400 

mm (15.8 in.) along the southeast margin. Presentday effective winds in the Thar Desert are mainly 

from the west-southwest or southwest (southwest 

monsoon). These winds result from air flow into a 

thermal low-pressure cell that develops over the Indian subcontinent during the summer. Average annual drift potentials are highest in the south and 

decrease northward; however, relatively little wind 

energy occurs at present in the Thar Desert compared to other desert regions. Highest drift potentials at most stations in the Thar Desert occur in 

June, usually preceding the time of maximum rainfall by 1 or 2 months.

Present-day low-energy unimodal wind regimes 

are roughly compatible with the parabolic, crescentic, and linear dune morphologies in the Thar 

Desert. Parabolic dunes and sand streaks aline with 

resultant drift directions of the present-day winds. 

The compound parabolic dunes, which are the most 

widespread and distinctive feature of the sand sea, 

may have formed several thousand years ago and 

not in the relatively low-energy wind regime of today. The parabolic dunes occur in a region of approximately 200 mm (7.9 in.) average annual rainfall and are mostly vegetated. Ground studies by 

other workers suggest that surfaces of these dunes 

are weakly cemented. However, less vegetated 

crescentic dunes in numerous places within the 

sand sea, surrounded by vegetated linear and 

parabolic dunes, may be active in the present wind 

regime.

Introduction

The Thar Desert extends westward in northwestern India from the Aravalli Range to the vegetated flood plain of the Indus River and from the 

Rann of Kutch northeastward into the State of Punjab, India (fig. 252). The southern and western parts 

of the desert lie mostly in Pakistan. Physiographically, the region consists of low hills and 

sand dunes lying on sandy alluvium that is underlain by caliche-cemented concretionary beds. Few 

topographic barriers interrupt the sea of sand, except for scattered outcrops of limestone and 

sandstone of Jurassic age near Jaisalmer (fig. 252).

Early work in the Thar Desert was by British 

geographers (Frere, 1870; Blanford, 1877). The 

geology of India is described by Wadia (1939), 

Auden (1950), and Krishnan (1960). Indian and

Pakistani studies, mainly for agricultural and sandcontrol purposes, are numerous. Recent geological 

fieldwork by Western scientists has been limited to 

the east margin of the desert, along the Aravalli 

Range (Goudie and others, 1973), and in the Rann 

of Kutch (Glennie and Evans, 1976), and to the 

Porali Plain west of the main dune areas, near 

Karachi (Verstappen, 1966,1968a; Snead and Frishman, 1968). Modern geomorphological studies of 

the main dune area (Verstappen, 1968a, 1970) are 

based mostly on interpretations of aerial photographs. Useful maps are the U.S. Department of 

Commerce, U.S. Air Force Operational Navigation 

Charts H-8 and J-8; and U.S. Army Map Service, 

Series 1301, Sheets NF 42, NG 42, NH 43, NG 43, 

and NH 42; all maps are at a scale of 1:1,000,000.

Landsat imagery has been used to map regional 

distribution and morphology of eolian sand in the 

Thar Desert. The map (fig. 252) shows eolian sand 

in relation to precipitation isohyets (in millimetres 

per year) and potentially effective sand-moving 

winds.

Review of Previous Work

Thirty-four samples of sand from fixed and active dunes in the eastern part of Rajasthan were 

collected and analyzed by Goudie, Allchin, and 

Hedge (1973, p. 247-248). The samples had an 

average median grain size of 0.148 mm, compared 

with the median diameters of 0.1 -0.15 mm for sand 

in the central Gujarat Plain, 0.125 mm in Punjab, 

and approximately 0.15 mm for sand in western Rajasthan. A mean diameter of 0.14-0.15 mm was 

determined for sand from the Porali Plain in 

southern Pakistan (Goudie and others, 1973, p. 248). 

The sand in general is well rounded (Wadia, 1939, 

p. 291).

Sand of the Thar Desert is composed mostly of 

quartz, with some hornblende and feldspar. It includes calcareous grains, mainly foraminifer tests 

(Wadia, 1939, p. 291), and salt particles (Qadri, 

1957, p. 169). Sand of the Porali Plain (Verstappen, 

1968a, p. 208) also is mainly quartz but has a high 

CaCO3 content, due in part to the presence of 

foraminifer and ostracode remains. Fixed dunes of 

the region are said to commonly have a caliche 

crust.

The sands are derived from numerous sources including deflating flood plain deposits, especially 

along the Indus River Valley, weathered materials
REGIONAL STUDIES OF SAND SEAS, USING LANDSAT (ERTS) IMAGERY 377

from the Aravalli Range, and sand of former 

shorelines (Seth, 1963, p. 449). Depth of sand in the 

Thar Desert is several metres (Krishnan, 1960, p. 

514). Horizontally bedded fine-grained slightly indurated sandstone which "exactly resembles the 

windblown sand of the dunes" is reported to occur 

at depths greater than 100 m (330 ft) in wells along 

a road connecting Karachi, Hyderabad, Banner, and 

Jodhpur (Seth, 1963, p. 449).

Old, dissected dunes of the Gujarat Plain, in the 

southeastern part of the desert, are dark brownish 

red (7.5YR 5/8) (Goddard and others, 1948) and 

they protrude through white, fixed dunes (Goudie 

and others, 1973, p. 247-248). Sands in all types of 

dunes on the Porali Plain in Pakistan are light 

yellowish brown (10 YR 6/4) (Goddard and others, 

1948; Verstappen, 1968a, p. 204). Old fixed dunes in 

the Thar Desert are vegetated with perennial and 

annual grasses, shrubs, mainly Calligonum 

polygonoides and HaloxyJon salicornicum, and low 

scattered trees, especially Acacia sp. and Prosopis 

sp. (Roy, 1969, p. 16-17).

Scientists at the Central Arid Zone Research Institute (CAZRI) at Jodhpur, India have established 

three categories of eolian sand bodies in the Thar 

Desert, based on field determinations of relative age 

and stabilization. These categories are (1) old dissected dunes of indeterminate type and sand 

"shields," (2) stabilized parabolic, longitudinal, and 

transverse dunes, and (3) active small-scale 

barchan, shrub-coppice, and low-longitudinal ridge 

dunes (Singh and others, 1972).

Old well-vegetated dissected dunes and sand 

shields (sheets?) of the first category occur in the 

eastern part of the Thar Desert in the Jodhpur area, 

along the western slopes of the Aravalli Range, and 

on the Gujarat Plain of India (Singh and others, 

1972, p. 51-52). Middle Stone Age artifacts are 

associated with these dunes which are thought to 

have formed under conditions of aridity more extensive than those of the present (Goudie and 

others, 1973, p. 243, 249, 252-255).

Fixed parabolic dunes of the second category 

northwest of Mandar, India, at about lat 25° N. (fig. 

252), are characteristically 35-70 m (115-230 ft) 

high but may be as much as 150 m ( 490 ft) high. 

They average 2.5 km (1.5 mi) long, are variably 

spaced about 250 m (820 ft) apart, and are oriented 

N. 50°-55° E. (Verstappen, 1968a, p.210). Farther 

inland near Jodhpur, Bikaner, and Jaisalmer, groups

of 15-20 parabolic dunes that range in length from 

1 to 3 km (0.6-1.9 mi) and attain heights of 30-70 

m (100-230 ft) have been described by Singh, 

Ghose, and Vats (1972, p. 52). These parabolic 

dunes extend for great distances (as much as 6 km 

or 4 mi). Their arms are nearly parallel and more 

uniformly spaced than in those dunes to the south. 

At about lat 26° N., remnants of parabolic dunes are 

only faintly recognizable on aerial photographs, 

and fixed longitudinal dunes predominate 

(Verstappen, 1968a, p. 210-211).

The fixed longitudinal dunes of the second 

CAZRI category in the Thar Desert were observed 

by Verstappen (1968a, p. 202-203) to have the same 

N. 55° E. orientation as dunes of similar type north 

of the Miani Hor Lagoon on the Porali Plain (fig. 

206), which are 20-50 m (65-165 ft) high, 90-350 

m (300-1,150 ft) wide, and as much as 5 km (3 mi) 

long. The fixed longitudinal dunes of the Thar, like 

those of the Porali Plain, are believed by Verstappen (1968a, p. 210, 218), to have been derived by 

blowing out of the noses of parabolic dunes. Both 

parabolic and longitudinal dunes of the Porali Plain 

(and by analogy, dunes of the second CAZRI 

category in the Thar) are tentatively assigned by 

Verstappen (1966, p. 7; 1968a, p. 203-204) to the 

Atlanticum Period, circa 5,000 years before the 

present.

Areas of active eolian deposition of the third 

CAZRI category include the desert between 

Phalodi and Jodhpur, between Banner and 

Jaisalmer, between Loharu and Bhiwani, and along 

the courses of the Sutlej and old Ghaggar Rivers 

(Seth, 1963, p. 449-450). The present northeastward movement of sand and the concurrent 

development of active small-scale barchans, low 

longitudinal ridge dunes, and shrub-coppice dunes 

are attributed by most workers to the erosion of 

sand from fixed dunes which have been overgrazed 

or subjected to farming (Khalil, 1957, p. 241; Roy, 

1969, p. 16-17; Chaudri, 1957, p. 144; Christian, 

1959, p. 7-8). On the Porali Plain, and in the Thar 

Desert, the only dunes presently forming, by reactivation of the parabolic dunes, are barchans 

(Verstappen, 1966, p. 7; 1968a, p. 203, 210-211).

Interpretation of Landsat Imagery

Some of the dunes referred to in the literature 

have been observed on Landsat imagery of the Thar 

Desert (fig. 252). Eroded and heavily vegetated
378 A STUDY OF GLOBAL SAND SEAS

70'

25 MAP LOCATION

DISTRIBUTION AND MORPHOLOGY OF EOLIAN SAND in the Thar Desert of India and Pakistan (above and facing page). Map 

based on Landsat (ERTS) imagery. Isohyets are modified from Rao (1958) and from Pramanik (1952). (Fig. 252.)

crescentic dunes visible on images of the Gujarat 

Plain may be some of the old, dissected dunes of the 

first CAZRI category (also described by Goudie and 

others, 1973). They are in a region that now 

receives 400-500 mm (16-20 in.) rainfall annually. 

The old dunes are partly covered by vegetated sand 

streaks. Clusters of compound parabolic dunes 

described by Singh, Ghose, and Vats (1972), and by

Verstappen (1968a) are clearly visible in figure 253. 

Dunes on the Porali Plain in Pakistan, however, are 

not visible on Landsat imagery.

Compound parabolic dunes with many arms in 

rake-shaped clusters have been observed during 

this study only in the Thar Desert. Parabolic dunes 

observed in the other sand seas studied are 

U-shaped, with long trailing arms (chapter J, fig.
REGIONAL STUDIES OF SAND SEAS, USING LANDSAT (ERTS) IMAGERY 379

EXPLANATION

LINEAR DUNES 

Simple, short

Mostly simple, some compound

CRESCENTIC DUNES 

Barchanoid ridges

Compound barchanoid ridges 

COMPOUND PARABOLIC DUNES

SHEETS AND STREAKS 

Simple

Compound, with linear elements 

BEDROCK OUTCROP OR BARRIER 

DESERT PLAIN WITH NO LARGE DUNES 

PLAYA 

VEGETATED PLAIN

WIND ROSE—Length of arm is proportional to 

percentage of wind observations from a given 

direction. Percentage of observations given where 

too long for graphic portrayal

— 'iOO—— ISOHYET—Average annual rainfall, 

in millimetres

69°30'

—————— BOUNDARY OF SAND SEA

—— INTERMITTENT DRAINAGE—Showing direction 

of flow

(Fig. 252. —Continued.)

183). The parabolic dunes can be discerned on imagery from the north edge of the Rann of Kutch as 

far north as Bikaner (fig. 252) and are the dominant 

dune type of the Thar Desert. In the southernmost 

Thar, along the Rann of Kutch, dune clusters are 

massed (fig. 253), but farther inland, the clusters 

are an average of 2.6 km (1.6 mi) long and 2.4 km 

(1.5 mi) wide, have an average of seven arms, and, 

although variably spaced, are an average of 2.3 km 

(1.4 mi) apart. The rakelike arrangement of the 

crests of parabolic dune arms is apparent in a 

sketch by A. S. Goudie (written commun. to 

McKee, 1974) (fig. 254).

Comparison of imagery made during the dry 

season with that made after the onset of the monsoon rains confirms that the linear dunes, and the 

parabolic dunes with which they are associated15 , 

are seasonally covered by vegetation. However,

15 NOTE. —The problem of distinguishing linear dunes from detached arms of 

parabolic dunes on the basis of morphology alone is great. Parabolic arms have 

linear form and develop as parallel sand ridges but are structurally very different 

from linear dunes (Chapter A. table 1; chapter E, table 9). Subsequent correct 

genetic interpretation of the dune field depends on type of dune identified.

E. D. McKee, editor.

Compound 

parabolic dunes

Rann of Kutch

PARABOLIC DUNE CLUSTERS along the southern margin of the 

Thar Desert. Landsat imagery E1137-05214. (Fig. 253.)

fields of crescentic dunes surrounded by the linear 

and parabolic dunes (fig. 255) showed no evidence 

of vegetation. The zone of crescentic dunes shown 

in figure 255 includes an area sketched from aerial 

photographs by Verstappen (1968a, fig. 3, right) and 

described by as him containing active barchans. It 

probably represents a major area of modern eolian 

activity. The crescentic dunes, whose curved segments are too small to measure on the imagery, 

have wavelengths of as much as 0.5 km (0.3 mi).

The vegetated linear dunes shown in figure 255 

may be some of the "stabilized longitudinal dunes" 

of the second CAZRI category, believed by Verstappen (1968a, fig. 3, right) to have formed from 

associated parabolic dunes.
380 A STUDY OF GLOBAL SAND SEAS

RAKELIKE ARRANGEMENT OF CRESTS of parabolic dune arms 

comprising compound forms near Jodhpur, India (lat 26°30' N., 

long 72°5' E.). Sketch traced from a survey map of India based 

on aerial photography (from A. S. Goudie, written commun. to 

McKee, 1974). (Fig. 254.)

In the western part of the Thar Desert adjacent to 

the Indus River flood plain, in a region that 

generally receives less than 100 mm (3.9 in.) annual 

rainfall, are fields of large dunes here interpreted as 

linear and crescentic types (figs. 252, 256). The latter resemble the compound crescentic ridges common to many other sand seas described in this 

chapter and compared in chapter J (tables 38, 39). 

Parabolic dunes grade westward into these large 

dunes, but generally dunes of the parabolic type are 

not observed on imagery of the more arid, western 

part of the desert (fig. 252). Segments of compound 

crescentic dunes, measured on imagery (fig. 256), 

average 1.5 km (1 mi) from horn to horn, have an 

average wavelength of 1.3 km (0.8 mi), and their 

avalanche slopes, which face N. 5°-10° W., have a 

more westerly trend than do the northeast-facing 

active crescentic dunes on imagery of the desert 

near Umarkot (fig. 255). The large linear dunes on 

the west margin of the sand sea average 2 km (1.2 

mi) wide and are commonly 20 km (12.5 mi) long; 

they are interpreted here to be compound linear 

dunes (fig. 256).

VEGETATED PARABOLIC AND LINEAR DUNES surrounding 

fields of barren crescentic dunes in the southwestern part of the 

Thar Desert. Landsat imagery E1137-05212. (Fig. 255.)

In the eastern part of the desert near Jodhpur and 

Banner are sheets and streaks of sand which appear 

as yellow and brown on false-color imagery indicating that the sand is actually red and partly 

vegetated.

Surface Wind Flow and Precipitation

Surface wind flow in the Thar Desert is from the 

southwest during the summer and from the northeast during the winter. The summer southwesterly 

flow occurs when a thermal low-pressure cell 

develops over the Indian subcontinent due to solar 

heating (fig. 245B). The winter northeasterly flow 

is a result of subsidence from a high-pressure cell 

which develops over central Asia during this 

season (fig. 245A).
REGIONAL STUDIES OF SAND SEAS, USING LANDSAT (ERTS) IMAGERY 381

Most of the desert receives more than 100 mm (4 

in.) of rain per year. (See isohyets, fig. 252.) This 

rainfall occurs mainly during the summer southwest monsoon season, figure 257.

Annual resultant drift directions are toward the 

northeast at most stations in the region, as shown 

on figure 252. Resultant drift directions trend more 

northward from Bhuj (N. 73° E.) to Ganganagar (N. 

31° E.). Resultant drift directions at all stations 

aline within 10° with the trends of large parabolic 

dunes visible on Landsat imagery, except near 

Jodhpur.

Monthly resultant drift directions show a southward shift at most stations during the winter ( fig. 

258).

Maximum drift potentials at all Indian stations 

studied occur during June. Hyderabad and 

Jacobabad, in Pakistan, however, record maximums 

in July and May, respectively. The summer maximum of drift potential in the Thar Desert is illustrated in figure 259. Drift potentials are greater during all 12 months at southern stations and are 

progressively less toward the north (figs. 252, 258).

Takla Makan and Ala Shan

Deserts of the Peoples

Republic of China

Summary of Conclusions

Major sand seas in northwestern China are in a 

structural and topographic basin (Tarim Basin) in 

the Takla Makan Desert and in low areas on stony 

plains in the Ala Shan Desert farther east. The 

Takla Makan sand sea, west of the playa Lop Nor, 

may be divided into four regions characterized by 

distinctive dune assemblages. Large compound 

crescentic ridge dunes in the Cherchen Desert, 

south and west of the Tarim River, grade southward and westward into crossing sets of crescentic 

dune ridges with distinctive chevron patterns. 

Dome-shaped and linear dunes occur in the northcentral part of the sand sea, and complex dunes occupy the south-central part of the sand sea. Dunes 

that seem to be simple barchanoid, dome-shaped, 

and linear characterize the western Takla Makan 

Desert, west of the Ho-t'ien Ho.

Compound crescentic dunes are the main dune 

type in approximately 33,000 km2 (20,500 mi2) of 

the Pa-tan-chi-lin Sha-mo of the Ala Shan Desert.

These dunes grade into probable reversing dunes 

and star dunes near mountain ranges along the 

eastern and southern margins of the sand sea. To 

the south and east, in the Ya-pu-lai Sha-mo, 

Yamalik Dunes, and Wu-lan-pu-ho Sha-mo, domeshaped dunes and star dunes are in elongate fields 

that parallel the trends of bounding valley sides. 

Unusually broad crescentic ridges, not seen 

elsewhere during this study, occur in the T'eng-koli Sha-mo at the southeastern margin of the Ala 

Shan Desert.

Average annual rainfall in the Takla Makan 

Desert commonly is less than 100 mm (4 in.). 

Average annual rainfall in the Ala Shan Desert increases from less than 100 mm (4 in.) in the northwest to more than 200 mm (8 in.) in the southeast. 

Effective winds in the Takla Makan Desert are 

mainly from the north and northeast in the eastern 

part of the Tarim Basin, and from the west and 

northwest in the western part. Winds in each area 

tend to be directionally steady throughout the year.

Crescentic and linear dunes, or combinations of 

these types, commonly occur in areas of the Takla 

Makan Desert that have both unimodal and bimodal present-day wind regimes. Star dunes and 

reversing dunes, common in many parts of the Ala 

Shan Desert, may be attributable to the great directional variability of effective winds there. Little 

wind energy is available for sand movement in 

either the Takla Makan or Ala Shan Deserts as 

compared with other desert regions. Wind energy 

in both deserts is greatest in the spring.

Introduction

Landsat imagery has been used to map and 

describe the distribution and morphology of eolian 

sand in the Taklan Makan and Ala Shan Deserts of 

the Peoples Republic of China. Sand seas in both 

deserts are centered at about lat 40° N. and are the 

highest latitude sand seas included in this study. 

Meteorological data covering surface winds and 

precipitation at climatic stations in northern China 

were obtained mainly from the National Climatic 

Center, Asheville, North Carolina. Additional data 

were obtained from reports by U.S. Army Air 

Forces Weather Division (1945), Dalrymple, 

Everett, and Wollaston (1970), and others. The 

sand-moving potential of surface winds is represented by sand roses, and average annual rainfall is 

shown by precipitation isohyets on the maps (fig. 

260, 263).
382 A STUDY OF GLOBAL SAND SEAS

40 KM

•^-t>

71°OQ' 

\

Ml-

"? ^

*: ^ 

tf/*^>

n^9 <^

*QrJ&° X

iSt*

r>^ w&:**f

;^;>- w r.»^^ •w

^

WESTERN THAR DESERT. Landsat imagery E1101 - 05201; 

E1120-05263. A, Compound linear dunes south of the junction of the Indus and Sutlej Rivers. Vegetation and salt flats occur in interdune areas subject to periodic flooding. B, Compound crescentic dunes south of Sukkur, Pakistan. The extreme 

aridity of the western part of the desert is shown by the sharp 

demarcation of irrigated, vegetated flood plain from the dune 

country. (Fig. 256.)

Sand seas of the Takla Makan Desert in the 

Tarim Basin of northwestern China (fig. 260) were 

first described by 19th century Russian and 

Swedish explorers (Bohdanowicz, 1892; Pvetsov 

(1895), in Hedin, 1905a; Obrutschev, 1895; and 

Hedin, 1905a, b). Regional geology of the Tarim 

Basin has been described by Norin (1941). Recent 

Soviet and Chinese investigations include sampling 

of eolian sand around the periphery of the Tarim 

Basin but do not include studies of the main sand 

seas in the interior of the desert. Useful maps of the 

Takla Makan and Ala Shan Deserts are the U.S. 

Army Map Service 1301 Series, sheets NJ 43, NJ 44, 

NJ 46, NK 46, NK 47, NK 48, NI 49; and the U.S. 

Department of Commerce, U.S. Air Force Opera-
REGIONAL STUDIES OF SAND SEAS, USING LANDSAT (ERTS) IMAGERY 383

140

70° 72° 74°

J FMAMJ JASOND 

MONTHS OF THE YEAR

RELATION OF RAINFALL PATTERNS to effective winds at 

Jaisalmer and at Barmer, Thar Desert. Maximum rainfall precedes 

time of maximum winds by about 1 month at each station. 

Modified from McKee, Breed, and others (1974, fig. 27). (Fig. 

257.)

tional Navigation Charts F-6, F-7, F-8, F-9, G-7, 

G-8, and G-9.

Recent publications about the Takla Makan 

Desert are mostly in Russian or Chinese (listed in 

Murzayev, 1967, p. 580-615), but some have been 

translated into French (Petrov, 1962) and English 

(Petrov, 1966,1967; Murzayev, 1967). A glossary of 

geographic names used in central Asia is included 

by Murzayev in his publication (1967, p. 533-579). 

A book on the physical geography of China 

(Zaychikov and others, 1965, p. 533-579) includes 

information about the Takla Makan sand sea 

gathered by the Sinkiang Multi-Field Expedition of 

1957-59.

Early work in the Ala Shan Desert was by Scandinavian geologists (Hbrner, 1936; Norin, 1941). In 

1957, Chinese and Soviet members of the Central 

Huang Ho Complex Expedition studied eolian processes in the Ala Shan and O-erh-to-ssu sand seas, 

followed in 1958 by the Tsinghai-Hansui Expedition of the Chinese Academy of Sciences, which 

explored the eastern and southern parts of the Ala 

Shan, including the T'eng-ko-li Sha-mo. In 1959,17

30°

28°

26°

24C

Ganganagar/—

NJi

2 T/1

^Jacobabad

±] 

5 'li/ THAR Bikaner^ —

3_ \ ,0_\ 

6 \0l

DESERT

JodhpurX

I?/ IJL 

27 \ 3

OUTLINE MAP OF THE THAR DESERT, India and Pakistan, with 

resultant drift directions for June (solid arrows) and January 

(dashed arrows). Also shown, drift potential (lower number) 

and resultant drift potential (upper number) for June and January. January values are in parentheses. (Fig. 258.)

M A M J J A S 

MONTHS OF THE YEAR

GRAPH OF DRIFT POTENTIAL at two representative stations in 

the Thar Desert. Both Bhuj and Barmer have highest drift potentials in June Lower drift potentials at Barmer illustrate northward decrease of drift potential within the desert. (Fig. 259.)
384 A STUDY OF GLOBAL SAND SEAS

41

_____1_______LJ

DISTRIBUTION AND MORPHOLOGY OF EOLIAN SAND in the Takla Makan Desert, Peoples Republic of China. Map based on

Landsat imagery. Isohyets are not recorded (Fig. 260.)

field teams of Chinese and Soviet investigators P'en-ti, southern Dzungaria, and the Takla Makan

began a 3-year Complex Sand Expedition into the Desert. Field stations were established for studies

Ala Shan and O-erh-to-ssu Deserts, the Ch'ai-ta-mu of sand stabilization and reforestation, vegetation
REGIONAL STUDIES OF SAND SEAS, USING LANDSAT (ERTS) IMAGERY 385

150 KILOMETRES

50 75 MILES

(Fig. 260. —Continued)

EXPLANATION

LINEAR DUNES 

Simple, short

Compound, two sets superimposed 

Complex, with scattered crescentic ridges

CRESCENTIC DUNES 

Simple barchanoid ridges

Compound 

Barchanoid ridges

Discontinuous barchanoid ridges

Barchanoid ridges with long straight segments

Complex crescentic ridges 

With linear elements superimposed

Ridges chevron-shaped with linear and

crescentic elements superimposed 

With undiscernable patterns

SIMPLE, AND SOME COMPOUND, STAR DUNES

DOME DUNES 

Simple and compound

Compound 

In linear chains

Elongated

SAND SHEETS AND STREAKS 

Compound with linear elements

BEDROCK OUTCROP OR BARRIER 

ROCK AND GRAVEL PLAIN WITH 

NO LARGE DUNES

PLAYA 

VEGETATED PLAIN

BOUNDARY OF SAND SEA

INTERMITTENT DRAINAGE—Showing direction 

of flow

was surveyed, and about 300 eolian sand samples 

were collected. Results of those surveys were 

reported by Petrov (1961,1966, 1967), but locations 

of dune areas described in the Soviet literature are 

difficult to relate to dunes of the Ala Shan Desert as 

observed on Landsat imagery.

The Takla Makan Desert 

Review of Previous Work

Sand seas of the Takla Makan Desert (fig. 260) 

occupy about 261,000 km2 (162,000 mi2) in the

center of the Tarim Basin (I. G. Wilson, 1973, table 

1), which is one of the largest basins with no exterior drainage (530,000 km2 , or 330,000 mi2) on 

Earth (Norm, 1941, p. 1). This basin is of late Tertiary tectonic origin and is nearly ringed by high 

glaciated mountains composed of Paleozoic, 

Mesozoic, and Tertiary strata (Norin, 1941, p. 4; 

Suslov, 1961, p. 533-534). The surface of the Tarim 

Basin slopes gently eastward, from an elevation of 

1,400 m (4,600 ft) at So-ch'e to 780 m (2,560 ft) at 

Lop Nor, a 2,000 km2 (1,240 mi2) play a into which 

all drainage of the basin seeps (fig. 260). The
386 A STUDY OF GLOBAL SAND SEAS

Yarkand-Tarim-Ho'tien Ho drainage system carries 

water across the desert to Lop Nor during flood 

periods in July and August, when snow melts in the 

surrounding Tien Shan and Kunlun Mountains. 

Other streams, such as the Ni-ya Ho and K'o-li-ya 

Ho, flow only a short distance across the piedmont 

and into the sands.

The sand sea in the middle of the basin is ringed 

by a border of alluvial fans, braided river channels, 

and swampy salt marshes (fig. 260). In historic 

time, cultivated areas on the periphery of the sand 

sea have been inundated by eolian sands, as the 

flow of the Ni-ya Ho and other rivers fed by 

glaciers in the Kunlun Mountains have diminished 

(Norin, 1941, p. 30).

Lowered water tables around the margins of the 

sand sea have contributed to the restriction of poplar forests which were extensive until about 1,500 

years ago (V. M. Sinitsyn, in Zaychikov and others, 

1965, p. 588; Suslov, 1961, p. 557). Poplars, tamarisk, 

Russian thistle, dogbane, and reeds are now 

restricted to old stream valleys and interdune 

marshes. Except for thin covers of grass (Aristida 

pinnata, AgriophyJIum arenarium, Corispermum 

sp. (Petrov, 1962, p. 147-150) and uncommon 

saltbushes (Haioxylon sp.), the sand seas are 

"almost completely devoid of vegetation" (Petrov, 

1962, p. 147, 150; 1967, p. 306-328; Suslov, 1961, p. 

558).

The Soviet-Chinese Complex Sand Expedition 

samples sands from peripheral areas of the Takla 

Makan Desert, including the K'a-t'e Sha-mo and 

dune fields near Guma (Hotien) and A-k'o-su (fig. 

260). All the sands were from relatively small dune 

fields, many of which formed during histroic time 

and are of "insignificant thickness" (Petrov, 1967, 

p. 278-283, 295, 300-301, 308-335, table 33). 

Peripheral eolian sands of the Tarim Basin are 

generally fine and include large amounts of silt. 

They are typically grayish yellow and are believed 

to have formed in place from the winnowing of 

nearby alluvial sands (Petrov, 1967, p. 283, 301, 307, 

331, table 33).

The Soviet and Chinese scientists recorded no 

sand samples from the large dunes in the main sand 

seas of the Takla Makan Desert, but Petrov (1967, p. 

327) stated that the sands there are similar to the 

muddy-yellow peripheral sands in texture and 

composition. Dunes in the main sand sea may have 

formed by processes described by Hedin (1905a, p.

458-459), in which detrital material eroded from 

mountains around the Tarim Basin is transported 

by streams eastward toward the playa, Lop Nor, 

and then the sand and silt are transported by winds 

westward into the sand sea.

Large dunes in the Cherchen Desert in the 

eastern Takla Makan region (fig. 260) are described 

(Hedin, 1905a, p. 270) as "regularly formed and 

linked together, crescentic in shape, with a steep 

leeward flank on the west and a long gentle slope 

on the east." Rows of subsidiary crescentic ridges 

are on the long slopes of these crescentic ridges, as 

shown on Hedin's profile sketches (1905a, figs. 

238-257, p. 271-275). Hedin apparently was the 

first student of desert dunes to describe the form 

classified in chapter J as compound crescentic. 

These dunes were called "complex barkhan ridges" 

by Petrov (1967, p. 295-298), who recognized that 

they were of the same form as dunes in the Peski 

Karakumy, U.S.S.R. The dunes were described by 

Hedin (1905b, p. 400) as "remarkably uniform" in 

height, ranging only within 10-15 m ( 33-49 ft) of 

a measured 89.5 m (293.6 ft) and reaching a maximum of 100 m (330 ft).

Between the dunes of the Cherchen Desert are 

flat-floored interdune basins (the bahirs of Hedin, 

1905a, p. 234-243, 269-276, 311-328, 360-369; 

1905b, p. 408-409). Interdune areas in the interior 

of the Cherchen Desert are commonly covered to a 

depth of 1 -2 m (3 -7 ft) by silt or horizontal layers 

of extremely fine yellow clay that is eroded into 

yardangs (Hedin, 1905a, p. 317-318, 321-324).

Interpretation of Landsat Imagery

Takla Makan sand seas west of Lop Nor can be 

divided, on the basis of dune types observed on 

Landsat imagery, into four sections (fig. 260): (1) 

the Cherchen Desert in the eastern part of the Takla 

Makan Desert, (2) the north-central part of the 

Takla Makan south of Kucha, (3) the south-central 

part of the Takla Makan, near K'o-li-ya Ho and Niya Ho, and (4) western sand seas between the Hot'ien Ho and the Yarkand River.

The main part of the eastern Takla Makan 

Desert, west of Lop Nor, is known as the Cherchen 

Desert. Very large compound crescentic dune 

ridges in the northern part of the Cherchen Desert 

are separated by interdune basins commonly 1.7 km 

(1 mi) long and 1.2 km (0.8 mi) wide. Interdune 

areas near the Tarim River are subjected to periodic
REGIONAL STUDIES OF SAND SEAS, USING LANDSAT (ERTS) IMAGERY 387

•mCOMPOUND CRESCENTIC DUNES and closed elongate interdune areas in the Cherchen Desert, northern Takla Makan 

Desert south of the Tarim River, Peoples Republic of China. 

Landsat imagery E1128-04253. Dunes and interdune basins 

were measured in the outlined sample area. At the east (upwind) edge of the sand sea (adjacent to the sample area) a 700-

flooding. Several that are adjacent to the river 

valley contain lakes, whereas others contain salt 

flats (fig. 261). Interdune areas observed on Landsat 

imagery of the Cherchen Desert closely resemble 

interdune areas in other sand seas, where they are 

classed by Glennie (1970, p. 60-61, 98) as "interdune inland sabkhas."

Measurements of the large barchanoid dunes in 

the Cherchen Desert (fig. 261) show that the ridges 

are composed of crescentic segments with a mean 

horn-to-horn width of 3.2 km (2 mi) and a mean 

length of 2.2 km (1.4 mi) and are spaced an average 

of 3 km (1.9 mi) apart. They are the largest dunes of 

compound crescentic form to be noted on Landsat 

imagery (chapter J, table 38). The large dunes are 

overridden south of T'ieh-kan-li-k'o by a field of 

much smaller barchanoid dune ridges (fig. 261)

km2 (453-mi2 ) field of smaller crescentic (barchanoid) dune 

ridges encroaches westward over the larger compound 

barchanoid ridges. Patterns of both sets of dunes are enhanced 

by snow. To the south, the pattern is a complex chevronlike 

combination of linear and crescentic elements. (Fig. 261.)

composed of segments with a mean width of 0.9 km 

(0.6 mi) and a mean length of 0.8 km (0.5 mi) and 

spaced an average of 0.9 km (0.6 mi) apart. The 

smaller ridges are oriented toward the southwest, 

as are the big dunes, in agreement with the resultant drift direction of present-day winds (fig. 260). 

Difference in size of the two sets of dunes might be 

interpreted as evidence of two different episodes of 

dune-building. A similar development of two sets 

of crescentic dunes is described earlier in the section on the eastern Rub' al Khali, Saudi Arabia (fig. 

240).

The compound crescentic dune ridges in the 

Cherchen Desert grade westward through a zone of 

complex ridges into dome-shaped and linear dunes 

directly south of the Tarim River. Measurement of 

the dome-shaped dunes in this area shows that they
388 A STUDY OF GLOBAL SAND SEAS

81°00' 1

i V*

f I 

1

ESCARPMf/vr

20 Ml

PROBABLE TOPOGRAPHIC CONTROL oi position and height 

of dunes by an escarpment along the Ho-t'ien Ho, an intermittent stream that crosses the western Takla Makan Desert. Landsat imagery E1078-04481. (Fig. 262.)

have a mean diameter of 1.1 km (0.7 mi). A sample 

of these dunes is compared with dome-shaped 

dunes in other deserts (chapter J, tables 42, 43). 

Some of the dome-shaped dunes in the Cherchen 

Desert have linear "tails" that extend downwind 

(southward), subparallel to the resultant drift direction at Kucha (fig. 260). The dome-shaped dunes 

grade southward and westward into fields of short 

linear dunes which occupy the central portion of 

the Takla Makan sand sea northeast of Ho-t'ien Ho 

(fig. 260).

Dunes in the south-central Takla Makan Desert 

between Cherchen and Nochiang are mainly complex ridges in which two trends (south and west), 

can be observed on Landsat imagery (figs. 260, 261). 

Linear elements predominate in some areas, and 

crescentic elements predominate in others in the 

southern part of the desert. The two trends result in 

a chevronlike dune pattern first described by Hedin 

(1905a, p. 364). The linear elements may represent 

full development of the dunes that were called 

"thresholds" by Hedin, for they connect and lead 

up to adjacent crescentic dune ridges in at least one 

of the regions he investigated during four crossings 

of the desert (Hedin, 1905a, p. 315-327, 360-362, 

figs. 263-264; 1905b, p. 409).

Sand seas west of the Ho-t'ien Ho are called the 

Bel'kum and Tagkum Sands, divided at lat 38°30' N. 

by a large escarpment (Norin, 1941, p. 3). The 

escarpment is the only major rock outcrop visible 

on imagery of the interior of the main Takla Makan 

sand sea and is composed of folded Tertiary strata 

(Norin, 1941. p. 3). It seems to be an important 

topographic barrier to sand movement. Compound 

crescentic dune ridges are piled up along the north 

(upwind) side, but such massed features are absent 

on the south side, where only scattered linear 

ridges, dome-shaped dunes, and simple barchanoid 

ridges occur (fig. 262). N. A. Belyayevskiy (in 

Murzayev, 1967, p. 56) reported that dunes near the 

escarpment rise to 300 m (1,000 ft) above the surrounding plain. The general size of dunes in the 

western part of the Takla Makan Desert is given as 

60 m (200 ft) (Norin, 1941, p. 3). The western boundary of the Takla Makan sand seas is at the 

Yarkand River.

The Ala Shan Desert 

Review of Previous Work

The Ala Shan Desert is a hilly plain about 700 km 

(435 mi) east of the Takla Makan Desert, at the east 

end of the Ho-hsi-tsou-lang (fig. 263). Sand seas occupy about 65 percent of the Ala Shan Desert, between the intermittent Jo Shui on the west, and the 

perennial Huang Ho (Yellow River) on the east. To 

the south, eolian sands are bounded by foothills of 

the Nan Shan Range, and to the east, by the Ho-lanshan Range and the valley of the Huang Ho. To the 

north, scattered dune fields occur in numerous 

depressions on the stony plains of northern China
REGIONAL STUDIES OF SAND SEAS, USING LANDSAT (ERTS) IMAGERY 389

and Mongolia. Main sand seas in the Ala Shan 

Desert are known as the Pa-tan-chi-lin Sha-mo, 

Yamalik Dunes, Ya-pu-lai Sha-mo, T'eng-ko-li Shamo, and Wu-lan-pu-ho Sha-mo (fig. 263).

The Pa-tan-chi-lm Sha-mo supports shrubs 

(Hedysarum mongolicum, Calligonum sp., Haloxylon sp., Cargana microphylla), sages (Artemisia 

sphaerocephala), gramen (Psammochlea villosa), 

annual grasses (Agriophyllum gobicum and 

Pugionium cornutum), and clumps of Ephedra sp. 

In some interdune areas and especially around interdune lakes are reeds (Phragmites communis), 

dogbane (Apocynum hendersonii), and tamarisk 

(Tamarix ramosissima) (Zaychikov and others, 

1965, p. 345, 547; Petrov, 1966, p. 252-253; 1967, p. 

26). Vegetation is reported to be sparse in the 

Yamalik Dunes and is generally restricted to interdune areas in the T'eng-ko-li Sha-mo. In the Ya-pulai Sha-mo, vegetation is mostly the shrub 

(Hedysarum scoparium), sagebrush (Artemisia 

sphaerocephala), and grass (Agriophyllum 

arenarium). In the Wu-lan-pu-ho Sha-mo, adjacent 

to the Huang Ho (fig. 260), Ordos sage (Artemisia 

ordosica), gramen, and Hedysarum scoparium 

grow on the dunes, and Nitraria schoberi and even 

reeds (Phragmites communis) grow in interdune 

areas (Petrov, 1966, p. 252).

The Pa-tan-chi-lin Sha-mo in the central part of 

the Ala Shan Desert (fig. 263) are fine grained and 

red, (Petrov, 1966, p. 243). Sand of the T'eng-ko-li 

Sha-mo, in the southern part of the desert, is "muddy yellow, fine grained, and well winnowed"; very 

fine grains (0.25-0.1 mm) account for 98.3 percent 

of the sand in some areas, whereas lag gravel and 

coarse sand occur in the interdune areas (Petrov, 

1966, p. 247). The Yamalik Dunes, in the northeastern part of the desert, are composed of red sand 

deflated from the stony plains and gray sand winnowed from alluvium (Petrov, 1966, p. 251). The 

Ya-pu-lai Sha-mo, in the south-central part of the 

Ala Shan Desert, is made up of fine sand (Petrov, 

1966, p. 253). The Wu-lan-pu-ho Sha-mo, at the east 

margin of the desert, is made up of fine sand with 

some silt, according to Petrov, who stated that it is 

derived partly from local alluvium but also comes 

from the interior of the Ala Shan Desert. Sand and 

silt of the Wu-lan-pu-ho Sha-mo commonly migrate 

into the Huang Ho (Petrov, 1966, p. 252).

Suggested sources of sand in the Ala Shan Desert 

are outcrops of Cretaceous sandstone (Petrov, 1966,

p. 243) and extensive Quaternary and modern 

alluvial-lacustrine sediments of the Jo Shui 

drainage system (Norin, 1941). The sand-carrying 

capacity of the Jo Shui is not known, but the 

amount of mud carried in suspension at normal 

high water was measured at Hei-ch'eng (Horner, 

1936, p. 729-730, fig. 7) at more than 40,000 tons per 

day, and most of the sediment is deposited 

upstream (south) from the Ka-shun-no-erh and Sokuo-no-erh. Dominant west and northwest winds 

are reported to carry, in single day, several tons of 

sand eastward from the lower Jo Shui across the 

gravel plains toward the sand seas of the Ala Shan 

Desert (Horner, 1936, p. 735).

Thickest sand deposits in the Ala Shan Desert occur in its western, driest part (Petrov, 1962, p. 141). 

Sand in the Pa-tan-chi-lin Sha-mo, in the center of 

the Ala Shan Desert, fills depressions and covers 

rock outcrops to an estimated depth of 150 m (490 

ft) or more (Petrov, 1966, p. 243). Main sand ridges 

in the Pa-tan-chi-lin Sha-mo move very slowly 

southeastward under the influence of dominant 

northwest winds (D. Fedorovich, 1961, in 

Zaychikov and others, 1965, p. 53), but small 

barchans and barchanoid ridges in the interdune 

areas move northeastward as much as 14 m (46 ft) 

per year because orientation of the main dune 

ridges affects wind directions in the interdune 

areas (Petrov, 1966, p. 244).

Height of dunes in the Ala Shan Desert are 

reported (Petrov, 1962, p. 141; 1966, p. 243-244, 

252), as follows: Large crescentic dunes in the main 

body of the Pa-tan-chi-lin Sha-mo average 300 m 

(990 ft), with a maximum height of about 400 m 

(1,310 ft); isolated star and reversing dunes in the 

northern part of the field are as much as 90 m (295 

ft) high. The Yamalik Dunes are as much as 20-25 

m (65-80 ft) high, and dunes in the Wu-lan-pu-ho 

Sha-mo are as much as 25-30 m (80-100 ft) high 

(Petrov, 1966, p. 251, 252).

Interpretation of Landsat Imagery

Dunes of the Pa-tan-chi-lin Sha-mo cover about 

33,000 km2 (20,500 mi2) in the center of the Ala 

Shan Desert (fig. 264). Northwest (upwind) gentle 

slopes of large crescentic dune ridges are covered 

with subsidiary crescentic dunes (fig. 264), so the 

dunes are compound crescentic (large barchanoid) 

ridges in the classification system used for Landsat 

imagery. They are the "complex barchan hill-
390 A STUDY OF GLOBAL SAND SEAS

Ka-shun-no-erh 

100° I 10^

104' 105°

MONGOLIA

_ f PEC

So-Kuo-no-erh / /}

He'i-ch'engo / A ^wT\ L—— ( -^^

^ ^ ^O

MAP LOCATION 25 75 MILES

DISTRIBUTION AND MORPHOLOGY OF EOLIAN SAND in the Ala Shan Desert, Peoples Republic of China (above and facing 

page). Map based on Landsat imagery. Isohyets from Petrov (1967) and World Meteorological Organization station data. (Fig. 263.)

shaped ridges" of Petrov (1966, p. 243). Measurements of the crescentic segments on Landsat imagery (fig. 264) show that they have a mean width 

(horn to horn) of 2.9 km (1.8 mi) and a mean length 

of 2.2 km (1.3 mi). The ridges are spaced an average 

of 2.9 km (1.8 mi) apart. Numerous lakes occur in 

interdune areas. The crescentic dunes of the Patan-chi-lin Sha-mo differ in pattern from those in 

the Cherchen Desert described earlier (fig. 261) but 

are closely similar to those of the Ak-bel Kum on 

the south and east shores of Po-ssu-t'eng Hu in the

Tarim Basin (fig. 260). Differences in dune patterns 

(as opposed to differences in dune types) in the Patan-chi-lin Sha-mo and Cherchen Desert seem to be 

due mainly to differences in relative size and spacing of the dune and interdune elements (chapter ]). 

Compound crescentic dune ridges of the Pa-tanchi-lin Sha-mo are compared in chapter ] (tables 38, 

39) with similar dunes in other deserts.

Toward the southeast margin of the Pa-tan-chilin Sha-mo (fig. 264B) dune ridges are shorter, distinctly S-shaped, and sharp crested. They are in-
REGIONAL STUDIES OF SAND SEAS, USING LANDSAT (ERTS) IMAGERY 391

EXPLANATION

MOSTLY SIMPLE, SOME COMPOUND, LINEAR DUNES

CRESCENTIC DUNES 

Simple barchanoid ridges

Compound barchanoid ridges

Complex with 

Bulbous ridges

Feathered ridges

Feathered ridges with linear elements

Reversing ridges

Ridges with linear elements superimposed 

SIMPLE, AND SOME COMPOUND, STAR DUNES 

SIMPLE AND COMPOUND DOME-SHAPED DUNES 

SHEETS AND STREAKS

Compound, with linear elements 

BEDROCK OUTCROP OR BARRIER 

ROCK OR GRAVEL PLAIN WITH NO LARGE DUNES 

PLAYA OR SALT MARSH 

VEGETATED PLAIN OR MARSH

—200—— ISOHYET—Average annual rainfall, in millimetres

—————— BOUNDARY OF SAND SEA

— • • — - INTERMITTENT DRAINAGE—Showing direction of flow 

(Fig. 263. —Continued.)

terpreted here as reversing dunes. Isolated dunes at 

the extreme eastern and southern margins of this 

sand sea are interpreted here as star dunes.

Small crescentic dune ridges, dome-shaped 

dunes, and small star dunes of the Ya-pu-lai Shamo, Yamalik Dunes, and Wa-lan-pu-ho Sha-mo fill 

abandoned stream valleys and other low areas on 

the stony plains of the eastern Ala Shan Desert. 

Dome-shaped dunes and star dunes in the Yamalik 

Dunes tend to be in linear patterns that parallel the 

trends of bounding valley sides (fig. 265A).

Dunes in the T'eng-ko-li Sha-mo at the downwind (southeastern) margin of the Ala Shan Desert 

are broad ridges of a complex variety not seen 

elsewhere. The broad crescentic ridges seem to lack 

main slipfaces, but the tops of the ridges have 

clusters of star dunes at irregular intervals (fig. 

265B). Southwest of the dunes are elongate salt flats 

here interpreted as deflation hollows. Dunes in the 

T'eng-ko-li Sha-mo are reported (Petrov, 1966, p. 

247) to be more than 100 m (328 ft) high.

Surface Wind Flow and Precipitation

Surface wind circulation over the Takla Makan 

and Ala Shan Deserts is controlled principally by

the central Asiatic high-pressure cell and a thermal 

low-pressure cell which develops over the Indian 

subcontinent in the summer. During the winter, 

subsidence from the central Asiatic high tends to 

produce northerly to northeasterly winds across the 

Takla Makan and Ala Shan Deserts (fig. 266A). 

During the spring the central Asiatic high weakens, 

its center shifts 10° westward, and a thermal low 

begins to develop over the Indian subcontinent (fig. 

266B). At this time, both the Takla Makan and Ala 

Shan Deserts lie in a zone between the high- and 

low-pressure cells, and also during this time the 

highest drift potentials occur, as discussed later. By 

summer time (fig. 266 C) low pressure dominates 

much of Asia, especially India, and wind regimes in 

the deserts are weaker and more directionally 

unstable than at other times of the year.

Mountains that ring the Takla Makan Desert and 

those in and around the Ala Shan Desert may 

deflect wind flow, resulting in variations from the 

trends of wind direction and strength as just discussed and as shown in figure 266. In addition, cold 

frontal passages, associated with midlatitude 

cyclones, may produce the westerly winds observed at some stations (figs. 267, 268), particularly 

during the spring.

The Takla Makan Desert receives less than 100 

mm (4 in.) precipitation per year (fig. 260). Average 

annual precipitation is only 30 mm (1.2 in.) at 

Charkhlik and Cherchen, and in the interior of the 

Tarim Basin is commonly zero (Zaychikov and 

others, 1965, p. 532, 555). In the Lop Nor area, 

average annual precipitation is about 10 mm/yr (0.4 

in./yr) (Petrov, 1967, p. 306).

The climate of the Ala Shan Desert is transitional 

from the desert climate of the Tarim Basin to the 

steppe climate of Inner Mongolia (Petrov, 1967, p. 

22). Average annual rainfall increases from northwest to southeast in the Ala Shan Desert (fig. 263). 

The southern and eastern margins of the desert 

may receive approximately 200 mm (8 in.) of rainfall per year (fig. 263).

Direction of Sand Drift

Annual resultant drift directions differ widely 

from place to place within the Takla Makan Desert, 

but resultant drift directions at each station are 

mostly steady throughout the year (fig. 260). At 

Kucha, in the northern part of the Tarim Basin, annual resultant drift directions are south or
392 A STUDY OF GLOBAL SAND SEAS

103°00'

101°00'

PA-TAN-CHI-LIN SHA-MO, Ala Shan Desert, Peoples Republic 

of China. Landsat imagery E1424- 03262; E1117- 03222. A, The 

main mass of sands, showing compound crescentic dune 

ridges, many with interdune lakes. To the northwest are playas

southeastward (fig. 269), subparallel to the trend of 

the dome-shaped and linear dunes of the northern 

and central parts of the sand sea. In the western 

Tarim Basin —including the Bel'kum and Tagkum 

Sands —resultant drift directions may be toward 

the southwest as at Pa-ch'u or toward the southeast 

as at So-ch'e or east as at Khotan (fig. 260). Resultant drift directions in the Cherchen Desert near 

T'ieh-kan-li-k'o show that the large transverse 

(crescentic) dunes normally are associated with 

unimodal or acute bimodal wind distributions, such 

as that at T'ieh-kan-li-k'o. Dunes in the southern 

part of the Cherchen Desert near Nochiang, 

however, are complex combinations of linear and 

crescentic ridges in a chevronlike pattern (figs. 260, 

261). This complexity may be a result of intersectof the Jo Shui intermittent drainage system. 8, East edge of the 

sands, where they are bounded by the Ya-pu-lai Shan; sharply 

recurved S-shaped dunes are interpreted as reversing 

barchanoid ridges. Star dunes are also evident. (Fig. 264.)

ing wind patterns as suggested by Hedin (1905a, p. 

152, 360-362); however, available wind data for 

Nochiang, about 60 km (37 mi) from these dunes 

(fig. 260 and chapter F) do not confirm Hedin's interpretation.

Annual resultant drift directions in the Ala Shan 

Desert (fig. 263) are toward the southeast except at 

Shan-tan, which is in an intermontane valley (fig. 

263). Resultant drift directions are relatively steady 

throughout the year, but some wind regimes are 

complex from month to month. For example, 

monthly wind regimes tend to be complex at Chilan-t'ai (fig. 268). The average RDP/DP (fig. 189) is 

0.40 for stations in the Ala Shan Desert versus an 

average RDP/DP of 0.60 for stations near the Takla 

Makan Desert. This difference reflects the greater
REGIONAL STUDIES OF SAND SEAS, USING LANDSAT (ERTS) IMAGERY 393

directional variability of wind regimes in the Ala 

Shan Desert and may account for the common occurrence there of reversing dunes and star dunes 

(fig. 264). Star dunes are associated with complex 

annual wind distributions.

Amount of Sand Drift

The average drift potential of stations in the Ala 

Shan Desert (129 VU) is slightly greater than the 

average drift potential of stations in the Takla 

Makan Desert (82 VU), but both deserts have low 

drift potentials compared with other deserts around 

the world (chapter F, table 16). These low values 

may occur because the deserts are positioned 

relatively near the center of the central Asiatic

high-pressure cell, where winds tend to be weak, 

and because they are to some degree sheltered by 

mountains.

Drift potentials in the Takla Makan Desert are 

highest in the northeast, near Charkhlik, and west 

at Ai-ssu-la-k'o-chan, off the map at lat 39°47' N., 

long 75°47' E. Minimum values occur at stations 

along the southern desert margin (fig. 260). 

Springtime is the season of highest drift potentials 

in both the Takla Makan and Ala Shan Deserts 

(figs. 270, 271), because they are in the zone between the high-pressure cell in China and the lowpressure cell in India (fig. 266B). Some stations also 

have a winter season of relatively high drift potentials (fig. 270B).
394 A STUDY OF GLOBAL SAND SEAS

104°30

T'emg4to41 Sha-mo

DUNE FIELDS IN THE EASTERN ALA SHAN DESERT (above and 

facing page). Landsat imagery E1224-03165; E1133-03112. A, 

Yamalik Dunes fill valleys on the stony plains. B, Complex dune 

ridges in the T'eng-ko-li Sha-mo, continuous to the southeast 

with the area shown in A. To the east is the partly snow-covered 

Ho-lan-shan Range. East of Ho-lan-shan is part of the Huang Ho 

valley. (Fig. 265.)
REGIONAL STUDIES OF SAND SEAS, USING LANDSAT (ERTS) IMAGERY 395

(Fig. 265. —Continued.)

B C

MEAN SEA-LEVEL PRESSURE (in millibars of mercury) distribution over the Takla Makan and Ala Shan Deserts of China for 3 months 

of the year. H, high-pressure cell; L, low-pressure cell. Trends of surface wind flow are shown by solid arrows; dashed arrows indicate winds which may result from frontal passages or cyclones, or from deflection of prevailing winds by mountains. A, January; B, 

April; C, June. (Fig. 266.)
396 A STUDY OF GLOBAL SAND SEAS

DP=~\ 

FEB.

DP=7 

APR.

DP=7 

JUNE

r

DP=4 

FEB. APR.

£tf>=18 

JUNE

DP=3 

AUG.

DP=1 

OCT.

DP=-\ 

DEC.

SAND ROSES FOR 6 MONTHS FOR KHOTAN, Peoples 

Republic of China, illustrating the eastward resultant drift direction along the southwestern margin of the Takla Makan Desert, 

west of the region of complex dunes (fig. 260). As at So-ch'e 

(fig. 260) effective winds are directionally steady throughout the 

year. Drift potential, in vector units, is given for each month. 

(Fig. 267.)

£tf>=9 

AUG.

FEB.

DP=A 

OCT.

SAND ROSES FOR 6 MONTHS FOR KUCHA, Peoples Republic 

of China, illustrating southward resultant drift directions in the 

north-central Tarim Basin. Monthly resultant drift directions 

vary little because of directional steadiness of effective winds. 

This station also exhibits low drift potentials characteristic of 

stations near the Takla Makan sand seas. Drift potential, in vector units, is given for each month. (Fig. 269.)

DP=29 

JUNE

DP=-\2 

AUG.

DP=10 

OCT.

SAND ROSES FOR 6 MONTHS FOR CHI-LAN-T'AI, Peoples 

Republic of China, illustrating the complex wind regimes which 

may occur from month to month in the mountainous, eastern 

Ala Shan Desert. Resultant drift directions are relatively steady 

(southeasterly, with the exception of August) during the year. 

Drift potential, in vector units, is given for each month. (Fig. 

268.)
REGIONAL STUDIES OF SAND SEAS, USING LANDSAT (ERTS) IMAGERY

60r

397

i i i i i i i i i i

FMAMJJASONO

J F 

B

M A M J J A S 

MONTHS OF THE YEAR

VARIATION IN DRIFT POTENTIAL during the year at representative stations within the Takla Makan Desert. A, Charkhlik, 

Cherchen, and Keriya. B, Kucha, A-k'o-su. Most stations have 

highest drift potentials in the spring (A). Northern stations also 

have relatively high drift potentials in the summer. Part 8 also illustrates the decrease in average drift potential from the east end 

of the Takla Makan Desert along the south edge toward Keriya. 

(Fig. 270.)

MONTHS OF THE YEAR

VARIATION IN DRIFT POTENTIAL during the year at Chi-lant'ai and Mao-mu on the east and west margins of the Ala Shan 

Desert, Peoples Republic of China. These stations have higher 

average monthly and annual drift potentials than most stations 

in the Takla Makan Desert but, in common with them, experience highest drift potentials in the spring. (Fig. 271.)

A STUDY OF GLOBAL SAND SEAS

GLOSSARY

Prepared by MARGUERITE GLENN

HIS GLOSSARY defines many of the terms 

used in this Professional Paper; it is for the 

convenience of the reader who may not be a 

specialist on deserts or eolian deposits. Many of the 

common physiographic, geologic, meteorological, 

and mathematical terms used are not defined here 

because their meanings are well established.

Entries and their synonyms are printed in 

boldface. The most commonly used term for any 

one meaning is the one that is defined, and the synonymous entries are referred to it. When more than 

one definition is accepted for an entry, the definitions will be numbered to show the currently more 

common or preferred usage. Geographic areas of 

usage are shown in parentheses following some 

terms.

Many sources were used in preparation of this 

glossary. Especially helpful were "A Desert Glossary," by R. O. Stone (1967), and "Glossary of 

Geology," published by American Geological Institute (1972).

Some entries are terms used for the first time in 

this paper, and they are so identified; for example: 

(McKee, this paper).

Acute Bimodal wind distribution. Wind distribution with two 

modes whose peak directions itnersect at an angle of 90° 

or less (Fryberger, this paper).

Adhesion ripple or Antiripplet. Irregular sand ridge 

transverse to wind direction, formed when dry sand is 

blown across a smooth moist surface. It may be 30 -40 

cm (12 -16 in.) long and a few centimetres (about 1 in.)

high. The crest is asymmetrical and migrates upwind. 

The stoss side is steeper than the lee side.

Adhesion wart. A small irregular wartlike sand accumulation 

made by wind that changes direction rapidly while 

blowing on a moist sand surface.

Akle (North Africa). See Fishscale dune pattern. 

Anchored dune. See Fixed dune.

Angle of repose. Maximum angle at which loose detritus is 

stable (commonly 32° —34° for dry dune sand).

Antiripplet. See Adhesion ripple.

Arm (of dune). The trailing outer extension of a parabolic or 

star dune.

Arroyo (Southwestern United States), Dry wash, or Wadi 

(North Africa). Channel of an ephemeral or intermittent 

stream. It commonly has vertical walls of unconsolidated detritus 60 cm (2 ft) or more high.

Avalanche bedding. Steeply inclined bedding in dunes produced by avalanche of sand down the slipface of the 

dune.

Avalanche slope. See Slipface.

Backshore. The part of a beach that is landward of a berm or 

beach crest. In opposition to foreshore.

Bahr (Lake Chad). Seasonally flooded interdune area.

Bajada (Southwestern United States). A broad alluvial slope at 

the base of a mountain range. Fan forms may or may not 

be present.

Bajir (China). See Interdune corridor.

Barchan, Barcan, Barchane, Barkan, or Barkhan. Crescentshaped sand dune. Windward slope is gentle and lee 

slope or slipface is at the angle of repose of dry sand. 

Horns of the crescent extend downwind.
400 A STUDY OF GLOBAL SAND SEAS

Barchanoid dune. Any dune of the barchan or barchanoidridgetype,

Barchanoid ridge. Asymmetrical wavy dune ridge, oriented 

transverse to wind direction with gently dipping windward slopes and steeply dipping (32°-34°) lee slopes, 

commonly separated from downwind wavy dune ridges 

by open interdune corridors. It consists of coalesced 

barchans in rows.

Basin. A depressed area without a surface outlet, into which 

runoff from the surrounding terrain drains.

Basketweave dune pattern. Type of parallel wavy dune complex in which the dune ridges are offset, forming a 

chevron or herringbone pattern of ridges and interdune 

hollows.

Berg wind (Namib Desert, South-West Africa). A local name 

for an east wind.

Blowout or Reactivated dune. Saucer-, cup-, or trough-shaped 

hollow formed by wind erosion on a preexisting sand 

deposit. The adjoining accumulation of sand derived 

from the depression, where readily recognizable, is 

commonly considered part of the blowout.

Brink. The top of the slipface of a dune. It may correspond to 

the crest.

Caliche. An essentially calcium-carbonate deposit remaining 

in or on soil following loss of water through evaporation 

or other processes.

Calcrete. Hard, dense layer of caliche in soil.

Captation. The trapping of irregular eolian sand masses 

against cliffs or mountains, thus forming climbing or 

hanging dunes.

Chevron dune. A V-shaped variety of a parabolic dune.

Clay dune. Eolian accumulation of sand-sized clay aggregates.

Claypan. Playa or dry lake formed in a shallow, undrained 

depression that has a hard, sunbaked surface of clay.

Climbing dune. Sand deposited by wind against a cliff or 

mountain slope.

Coastal dune. Sand dunes on low-lying land abandoned or 

built up by the sea.

Cold desert. Arid region in which the mean annual temperature is less than 18°C (64.4°F), such as the Gobi 

Desert or some Arctic and Antarctic regions, where 

plant and animal life is restricted by low temperature.

Colluvium. The sediment on a slope or at the base of a slope 

formed by mass-wasting or unconcentrated sheet 

runoff.

Complex dune. A combination of two or more different dune 

types in a single dune, in contrast to compound dune, 

which is a combination of two or more dunes of the 

same type.

Complex wind distribution. Wind distribution with more 

than two modes or with poorly defined modes (Fryberger, this paper).

Compound linear dune. A major longitudinal dune ridge with 

small linear ridges formed on it. The minor ridges may 

be parallel to the main ridge or diverge from it, as in 

feathered seif dunes.

Contorted bedding. All disturbed strata, regardless of cause, 

where deformation occurred after deposition but before 

lithification. Structures are restricted mostly to simple 

sets of strata or cross-strata with unaffected sets of 

strata above and below.

Couloir (North Africa). Open interdune corridor.

Crescentic dune. (1) See Barchan; (2) in chapters J and K used 

in classification of Landsat (ERTS) imagery patterns for 

all barchans, barchanoid ridge, and transverse type 

dunes.

Crescentic dune ridge. (1) See Barchanoid ridge; (2) used in 

chapters J and K as a sand ridge or elongate dune with 

arclike or barchanoid segments.

Crescent ripple. A small ripple in the shape of a moon in its 

first or last quarter. The horns or arms of the ripple extend downcurrent.

Crest. A dune summit. It is the highest natural projection of a 

dune.

Cumulative frequency distribution curve or Cumulative 

curve. A curve drawn to represent the percentage of occurrences of a number of observations of a variable less 

than or greater than any given value for an entire sample.

Deflation. Removal or "blowing out" of fine-grained sediment 

by the wind.

Deflation basin. Hollow surface formed by removal of sand 

and dust by eolian action. It commonly has a rim of 

resistant material surrounding the depression.

Deflation ripple. See Granule ripple.

Desert. An arid or semiarid region characterized by an excess 

of evaporation over precipitation.

Desert pavement. A sheetlike residual concentration of windpolished closely packed gravels, or rock fragments, 

mantling a desert surface where wind has removed fine 

material. Gravels or fragments commonly are cemented 

by mineralized solutions (AGI).

Desert polish. Smooth and polished surfaces on rocks caused 

by the action of windblown sand and dust.

Desert varnish, Desert lacquer, or Desert patina. Surface 

stain or crust of manganese or iron oxide which characterizes many exposed rock surfaces in deserts. It coats 

outcropping rocks, boulders, and pebbles, imparting a 

brown or black color and a bright luster to their surfaces.

Desiccation crack, Mud crack, Shrinkage crack, or Sun 

crack. Small fissure or crack formed by shrinkage of 

clay or clayey beds in drying by the sun.

Dikaka. Accumulation of dune sand covered by scrub or grass 

vegetation; extended to include plant-root cavities in 

dune sediments (calcified root tubules).
GLOSSARY 401

Discriminant analysis. A statistical procedure for classifying 

subsequent samples into categories previously defined 

and differentiated on the basis of samples from known 

populations.

Dissipation structure. Wavy, irregular layers in sediments, 

resulting from the modification of original stratification 

by the concentration of colloidal materials (clay 

minerals, hydrous iron oxides, and humic compounds) 

(J. J. Bigarella, written commun., 1975).

Dome dune. Low circular or oval mound formed where dune 

height is inhibited by unobstructed strong winds. It 

generally lacks a slipface.

Draa (North Africa). Large-scale accumulation of eolian sand. 

Used by I. G. Wilson (1973).

Drift potential (DP). A measure, in vector units, of the sandmoving power of the wind. It is derived from reduction 

of surface wind data through a weighting equation and 

usually represents 1 year (Fryberger, this paper).

Dund (India). Interdune area filled by a lake.

Dune. Accumulation into a mound or ridge of windblown sediment, commonly having a gentle upwind slope and one 

or more steep lee slopes (slipfaces).

Dune-extradune depositional system. A system containing 

all the sediments of a dune field and marginal area. It includes dune and interdune sediments and associated extradune sediments, such as alluvial-fan, wadi, serir, 

stream, sabkha, playa, lake, beach, and tidal-flat 

deposits (Lupe and Ahlbrandt, this paper).

Dune-interdune depositional system. A system containing 

only dune and interdune sediments (Lupe and 

Ahlbrandt, this paper).

Dune massif. A compound star dune.

Dune spacing index. A measure of the average number of 

dune ridges crossing a 50-km-long (31.1-mi-long) line 

normal to the trend of dune ridges in a given area.

Dune valley. See Interdune.

Elb (Algeria). A transverse dune (Capot-Rey, 1945, p. 392).

Elephant-head dune (Colorado Desert, Calif., U.S.A.). Small 

sand shadow whose windward face is covered with 

vegetation and with a long tapering snout of sand extending to the lee.

Elongate blowout dune. Wind-excavated basin with a crescent-shaped rim of sand about the lee side. It differs 

from blowout dune in that it has an elongate form, and 

there is slight migration of the basin and rim in the 

direction of the prevailing wind.

Eolianite. All consolidated sedimentary rock formed from 

wind-deposited sand, commonly having large-scale 

eolian-type cross-strata.

Eolian sand. Windblown sand.

Eolian sandstone. Sedimentary rock formed of consolidated 

windblown sand. See Eolianite.

Erg (North Africa). See Sand sea. 

Established dune. See Fixed dune. 

Extra dune. See Satellite dune.

Extradune. Area marginal to dune field which contains sediments of the same age and source as the dunes (Lupe 

and Ahlbrandt, this paper).

Falling dune. Sand accumulation (sloping at the angle of 

repose for dry sand) to the lee of a cliff or mountain side 

as sand is blown off the top.

Fan (alluvial). A sedimentary deposit having a distinctive convex upward surface that radiates downslope from a 

point where a stream emerges from a canyon floor onto 

a plain with more gentle gradient.

Fanglomerate. Indurated alluvial-fan gravel.

Feathered dune. A variety of compound linear dune in which 

subsidiary ridges diverge from a main ridge.

Festoon structure or Festoon-type cross bedding. A crosslamination pattern resulting from repetition of a twostep process: (1) Erosion of plunging troughs and (2) filling of the troughs by thin concave upward layers 

generally conforming to the shape of the trough floors 

(fig. 157). Festoon pattern is most conspicuous on vertical faces cut at right angles to longitudinal axes in a 

series of superimposed troughs plunging in the same 

direction (Knight, 1929, p. 58). The troughs may be filled 

symmetrically or asymmetrically.

Fishhook dune. See Hooked dune.

Fishscale dune pattern, Akle, or Peak and Fulji topography.

Type of parallel wavy dune pattern in which the interdune areas are enclosed by crescentic elements of the 

dune ridges.

Fixed dune. Nonmigratory dune fixed by vegetation or by cementation.

Fluid threshold shear velocity. That shear velocity at which 

sand movement starts as a result of the shearing stresses 

imparted to the sand by the wind. (See Bagnold, 1941, 

p. 88.)

Frosted sand grains. Typical sand grain of eolian desert sediments, whose etched and pitted surface is created by impact with other wind-transported grains and causes a 

scattering of light. It is the opposite of a glassy or 

polished sand grain.

Fulji or Fulje. (1) A depression (interdune) between barchans 

or barchanoid ridges, especially where dunes are pressing closely on one another (Arabia); (2) blowout or 

small parabolic dune (Australia).

Giant crescent dune pattern. Type of parallel wavy dune pattern in which ridges are composed of coalesced 

megabarchans and are separated by open or closed interdune hollows.

Gibber (Australia). Gravel plain.

Grain flowage. A type of sand avalanching in which individual grains move independently of each other, in
402 A STUDY OF GLOBAL SAND SEAS

opposition to avalanching by mass movement of slumping.

Granule ripple. Unusually large wind ripples composed in part 

of detritus approaching or attaining granule size, 2—4 

mm (0.08 -0.16 in.). They are commonly associated with 

local concentrations of lag material.

Granulometric control. The ability of various grain sizes to 

control the shape or dimension of eolian bedforms, such 

as ripples or dunes (I. G. Wilson, 1973).

Graphical measures. Graphical method of obtaining statistical 

values of grain size in which selected values from points 

along a cumulative frequency curve are used in formulas to calculate the desired statistical data.

Guern. See Khurd.

Hairpin dune. A greatly elongated parabolic dune that has 

migrated downwind, its horns drawn out parallel to 

each other, formed where wind is in conflict with 

vegetation and where winds are strong and of constant 

directions.

Hammada or Hamada. A bare rock surface in a desert. 

Hanging dune. See Falling dune.

Hardpan. Cemented or indurated layer of soil usually composed of calcium carbonate, silica, iron oxide, or clay, at 

or some distance beneath the ground surface.

High-energy wind environments. A wind environment with 

an annual drift potential of 400 vector units or more.

Histogram. Multiple-bar diagram showing relative abundances of specimens, materials, or other quantitative 

determinations divided into a number of regularly arranged classes.

Hooked dune or Fishhook dune. Dune consisting of a long 

sinuous ridge forming the shaft and a well-defined crescent forming the hook.

Horns or Arms. The pointed ends of a dune, especially the forward extensions of a barchan dune.

Hot desert. Arid region in which the mean annual temperature 

is greater than 18°C (64.6°F) (Stone, 1967, p. 230).

Impact threshold shear velocity. The minimum shear 

velocity required to maintain sand in saltation. (See 

Bagnold, 1941, p. 88.)

Impact threshold wind velocity. The minimum wind velocity 

required to maintain sand in saltation. (See Bagnold, 

1941, p. 32.)

Inselberg. Prominent residual steep-sided rocky hills rising 

abruptly from a plain or desert.

Interdune. Relatively flat area between dunes.

Interdune corridor, Interdune hollow, or Interdune area.

Continuous flat or gently sloping surface between dune 

ridges or rows of dunes.

Interior drainage, Centripetal drainage, or Internal drainage.

Drainage toward the lowermost part of an enclosed 

basin.

Intermediate-energy wind environments. Wind environments with an annual drift potential of 200 -399 vector 

units.

Irq. (1) (Arabia) Elongate dune or belt of elongate dunes 

(Stone, 1967, p. 255); (2) (North Africa) narrow 

longitudinal dune or a seif (Stone, 1967, p. 263).

Isohyet. Line on a map connecting points which receive equal 

amounts of average rainfall.

Khurd (Algeria), Guern. A high (80-100 m (262-328 ft)) 

pyramid-shaped sand dune with curved slopes, formed 

by the intersection of seifs (Capot-Rey, 1945, p. 393).

Kurtosis. The quality, state, or condition of peakedness or flatness of the graphic representation of a statistical distribution.

Lag gravel. Residual accumulation of coarse detrital particles 

(larger than sand size) from which the fine material has 

been deflated.

Laguna (Southwestern United States). Shallow ephemeral lake 

in the lower part of a bolson, fed by intermittent 

streams. See also Play a.

Lee dune. Dune formed to the lee of an obstruction.

Lee slope, lee side, leeward side. The downwind side of a 

dune or other protuberance in the path of a wind.

Leptokurtic (1) A frequency distribution that has a concentration of values about its mean, greater than for the corresponding normal distribution; (2) a narrow frequencydistribution curve that is more peaked than the corresponding normal distribution curve.

Lettau equation for rate of sand drift. The equation suggested 

by Heintz Lettau (University of Wisconsin, Madison, 

written commun., 1975) for the rate of sand drift. This 

rate is a function of grain size and drag velocity (shear 

velocity) of the wind. See chapter F, fig. 92.

Linear dune, Longitudinal dune, or Seif. Parallel, straight 

dune with slipfaces on both sides and with its length 

many times greater than its width.

Loess. Soft, porous, yellow- or buff-colored accumulation of 

wind-laid particles that are of silt size or smaller.

Longitudinal dune. See Linear dune.

Low-energy wind environment. A wind environment with an 

annual drift potential of less than 200 vector units.

Low latitude desert. Hot and dry desert located between lats 

15° and 35° N. or lats 15° and 35° S. in the region of 

subtropical high-pressure air masses and the trade 

winds.

Mean grain size. The diameter equivalent of the arithmetic 

mean or average grain size.

Medano. Sand dune (Spanish term).

Megabarchan. Giant barchan, 100 m (328 ft) or more in height. 

These dunes commonly coalesced into ridges to form 

parallel wavy dune patterns. Each crescent in the ridge 

normally has one major slipface.
GLOSSARY 403

Mesokurtic. Closely resembling a normal frequency distribution — A distribution curve that is neither leptokurtic 

(very peaked) nor platykurtic (flat across the top).

Middle latitude desert. An arid region between lats 35° and 50° 

N. or lats 35° and 50° S. that owes its existence either to 

its location in the deep interior of a continent or to high 

mountains across the path of the moisture-bearing prevailing wind.

Migration (dune). Movement of a dune due to transfer of sand 

from windward to the leeward side.

Miniature terrace-and-cliff structure. A succession of abrupt 

rises or steps of about 2.54 mm (0.1 in.), each ascending 

an inclined bedding plane.

Moderate-energy wind environment. A wind environment 

with an annual drift potential of 200 —399 vector units.

Modified lee slope or surface. A dune slipface or slipfaces 

altered by slumping, grain flowage, or deposition of suspended load.

Moment measures. The expected values of each of the powers 

of a random variable that has a given distribution; a 

weighted measure of central tendency; in sedimentology they are related to the center of gravity of the particle-size-distribution curve and are defined about the 

mean value of the variable.

Monsoon. Type of wind system in which there is a complete or 

almost complete reversal of prevailing direction from 

season to season. It is especially prominent within tropics on eastern sides of great landmasses.

Morphology. The shape or physiography of land-surface 

features.

Mud polygon, Desiccation polygon, or Mud crack polygon.

Block of fine-grained sediment, bounded by mud cracks 

or shrinkage cracks, that commonly has three to five 

sides, although in some examples it may have as many 

as eight sides.

Narrow unimodal wind distribution. A wind regime that produces a distribution of drift potential on a sand rose in 

which 90 percent or more of the drift potential lies within a 45° arc of the compass.

Nefud. A high sand dune. See also Sand sea.

Observer bias. Tendency for observers to record wind directions from prime directions instead of from intermediate 

directions of the compass.

Obtuse bimodal wind distribution. A wind regime that produces a distribution of drift potential on a sand rose that 

has two modes whose peaks intersect at an angle greater 

than 90°.

Oghurd (North Africa). A massive summit above the general 

sand dune level, or a massive mountainous dune resting 

on an underlying rocky topographic feature (Stone, 

1967, p. 263).

Omiribi (Kalahari Desert, Africa). See Arroyo.

Onshore wind. Winds that blow from the sea onto a land surface.

Orographic desert. See Rain shadow desert.

Oscillation ripples. Symmetrical ripple marks consisting of 

sharp, narrow, relatively straight crests between broadly 

rounded troughs.

Oued. See Arroyo.

Packing. The manner of arrangement or spacing of the solid 

particles in a sediment or sedimentary rock.

Pan. (1) Natural basin or depression that intermittently contains water that may leave a saline deposit; (2) a dry 

lake or playa.

Parallel ripples. Ripple marks with relatively straight crests, 

oriented transverse to wave or current direction and 

having a symmetrical or asymmetrical profile.

Parabolic dune. A U-shaped or V-shaped dune representing a 

type of blowout in which the middle part has moved forward with respect to the sides or arms. Open end of U or 

V faces upwind and the arms commonly are anchored 

by vegetation. One to three slipfaces occur on the convex outer part of the nose and arms of the dune.

Parallel sinuous ripples. Ripple marks in which the horizontal 

distance, normal to flow, is many times the wavelength, 

and the crests swing from side to side as viewed in plan.

Parallel straight dune, Seif, or Longitudinal dune. A linear 

ridge of windblown sand whose length is much greater 

than its width, and which commonly has slipfaces along 

both sides. It moves in a direction parallel to its length.

Parallel wavy dune complex. A group of crescentic dune segments that have coalesced into wavy ridges. Each crescentic segment of the ridge commonly is as wide as it is 

long, and the segments are asymmetrical. All segments 

of a ridge have their major slipfaces oriented normal to 

wind directions.

Patina. A thin film of Desert varnish.

Peak and Fulji topography. See Fishscale dune pattern.

Pediment. A broad surface or plain formed in a desert terrain 

by erosion at a mountain base. It may be bare bedrock or 

veneered by a thin layer of alluvium.

Piedmont. A surface lying or formed at the base of a mountain. 

In desert regions it is a plain or slope and may include a 

pediment, bajada, or both.

Platykurtic. (1) A frequency distribution that has a concentration of values about its mean less than for the corresponding normal distribution; (2) a broad, flat-topped 

frequency distribution curve that is less peaked than the 

corresponding normal distribution curve.

Playa (Southwestern United States), Clay pan, Dry lake, Salt 

flat, or Salt pan. An extremely flat vegetation-free area 

of clay, silt, and (or) evaporite minerals in the lowermost part of a basin having interior drainage in an arid 

or semiarid region. It is formed by a temporary lake 

which has evaporated, leaving behind fine sediment.
404 A STUDY OF GLOBAL SAND SEAS

The term is also applied to the temporary lake. (Spanish 

term meaning beach, shore, or strand.)

Playa lake. Temporary or ephemeral lake in the desert.

Plinth. Lower and outer parts of seif, beyond the slipface boundaries. This part of the dune has never been subjected to 

sand avalanches (Bagnold, 1941, p. 229).

Polypyramid. A star dune.

Precipitation ridge (Cooper, 1958, p. 55). See Retention ridge.

Prevailing or predominant wind. A wind that blows most of 

the time from one particular direction.

Procedure bias. Error introduced into a wind summary when 

observations originally recorded from 36 points of the 

compass are summarized into 16 directions. It results in 

disproportionate representation of observations from 

the prime directions of the compass at the expense of 

the intermediate directions.

Produne. The part of the dune lying beyond the dune front and 

gently sloping down to the desert floor across which the 

dune is advancing.

Pyramidal dune or Polypyramid. See Star dune.

Raindrop sand crater. A thin detached layer or shell of sand, 

roughly circular with thin margin, formed by raindrops 

striking dry sand. Center of the shell is depressed and 

margin is raised slightly above the general sand level. 

After drying, the shell remains firm and retains the 

same shape; on a tilted sand surface it has a raised lower 

rim.

Rain shadow desert or Orographic desert. Arid land on the 

lee side of a mountain or a mountain range which intercepts moisture-laden air.

Recurved dune. A dune in which a forward extension is 

curved back toward main part of dune as by deflection 

of wind or by opposing action of two or more wind 

durections. See also Reversing dune and Sigmoidal 

dune.

Reg (Algeria). A large gravel deposit on a desert surface. It 

differs from serir in that most of the fine detritus has not 

been removed (Gautier, 1935, p. 62).

Resultant drift direction (ROD). The direction of the resultant drift potential.

Resultant drift potential (RDP). A measure in vector units, of 

the net sand-moving power of the wind at a station. 

Vector unit totals from various directions on a sand rose 

are treated as vector quantities and resolved trigonometrically to a resultant, the magnitude of which is 

the resultant drift potential, RDP, the direction of which 

is the resultant drift direction, RDD.

Resultant drift potential/drift potential (RDP/DP). A dimensionless parameter which is a measure of the variability 

of a wind regime without regard to specific directional 

components or total energy of environment.

Retention ridge or Precipitation ridge. A ridge formed 

parallel to shore by deposition of sand on the landward 

margin of the backshore. It accumulates against a 

vegetation barrier and is a nearly stabilized dune.

Reversing dune. A dune that tends to grow upwards but migrates only a limited distance because seasonal shifts in 

direction of dominant wind cause it to move alternately 

in nearly opposite directions.

Rhourd. A pyramid-shaped sand dune, formed by the intersection of other dunes (Aufrere, 1934, p. 139). See also 

Khurd

Ripple. Any topographic deviation on the bedding surface of a 

sedimentary deposit that resembles a ripple of water.

Ripple height. The difference in elevation between the lowest 

point of a trough and the highest point of an adjoining 

crest in a rippled sand surface.

Ripple index. Wavelength of a ripple divided by height of a 

ripple (or ratio of wavelength to height).

Ripple symmetry index. The length of the horizontal projection of the stoss side divided by length of the horizontal 

projection of the lee side of a ripple (or ratio of stoss side 

to the lee side of a ripple).

Ripple wavelength. The horizontal distance between the 

deepest points of two troughs or the horizontal distance 

between two crests in a rippled sand surface.

Rising dune. See Climbing dune.

Roughness factor during sand driving (K'). The focus during 

sand driving, or that height, above the surface, at which 

lines depicting logarithmic height versus wind velocity 

for several wind velocities converge. See also Bagnold, 

1941, p. 59.

Sabkha. See Sebkha.

Salina. A place where crystalline salt deposits are formed, 

such as a salt flat, a salt pan, a salada, especially a saltincrusted playa or a wet playa.

Saltation. Bounding movement of rock particles, usually sand 

size, when carried by wind.

Sand avalanche. Movement of large masses of sand down a 

dune face when the angle of repose is exceeded, or 

when the dune is disturbed. It may consist of mass 

movement (slumping) or grain flowage or both.

Sand sea, Erg (North Africa). Vast region covered with sand 

and occupied by dunes.

Sand drift. (1) A deposit of eolian sand formed as the result of 

a decrease in wind velocity. It is commonly developed 

on the leeward side of windbreaks, such as vegetation, 

boulders, rock outcrops, or other irregular surface relief. 

(2) Used in chapter F (this paper) as a general term for 

movement of sand by wind occurring in a desert or 

along the shore.

Sand dune. Ridge or pile of windblown sand. See Dune.
GLOSSARY 405

Sand fall. Sand swept over a cliff or escarpment. See also Falling dune.

Sand glacier. Sand accumulation shaped as a broad fanlike 

plain that develops where sand is blown up the sides of 

a mountain, through passes and saddles, to spread out 

on the opposite side.

Sand levee. See Whaleback.

Sand ridge. (1) A parallel straight or linear dune; (2) a 

relatively coarse-grained high-crested widely spaced 

ripple of sand.

Sand ripple. A ripple mark formed by wind in dry sand; the 

wavelength depends on wind strength and remains constant with time. See Ripple.

Sand rose. A circular histogram depicting the amount of sand 

potentially moved by winds from various compass 

directions at a given geographic locality.

Sand shadow. (1) Small mound or dune that forms around 

clumps of vegetation, behind rocks, or around other 

obstructions; (2) eolian deposit formed in the lee of a 

fixed obstruction. See also Sand drift.

Sand sheet. Accumulation of sand in essentially flat laminae 

forming a sheetlike or blanketlike deposit. It has no slipfaces, but has distinct geographic boundaries.

Sand streaks. See Stringers.

Sand strip. Long, narrow strip of sand that extends for a considerable distance downwind from each horn of a dune.

Satellite dune or Extra dune. Auxiliary or smaller dune 

associated with main dune.

Sebkha, Sabkha, Sebkra, and many others (especially North 

Africa and Arabia). A flat area of clay, silt, or sand commonly with saline incrustations; a surface of deflation 

in which dry, loose particles are removed down to the 

level of the groundwater or to the zone of capillary concentration (Friedman and Sanders, 1978); includes: (1) 

Coastal sebkha — Coastal flat that occurs just above 

level of normal high tide in hot, arid, desert climate. (2) 

Inland sebkha — Flat inland areas of clay, silt, or sand, 

often with saline incrustations. See also Playa, Clay 

pan. (3) Interdune sebkha.

Seif, Sif, Sief, Er (North Africa and Arabia), Linear dune, or 

Longitudinal dune. Linear dune which, in groups, comr 

monly makes a parallel straight pattern oriented in the 

direction of prevailing wind or winds. It characteristically has two slipfaces.

Semiarid. Partially arid. It refers to region in which the mean 

annual rainfall is 30^40 cm (12—16 in.) according to 

some geographers, or between 25 -50 cm (10 and 20 in.) 

according to others.

Serir (Egypt and Libya). A rough desert surface of fairly large 

rounded pebbles with no fine material remaining between pebbles (Gautier, 1935, p. 62).

Shear sorting. Sorting of sediments, as in a sand dune, 

whereby smaller grains tend to move toward the zone of 

greatest shear strain, the shear plane, and the larger 

grains toward the zone of least shear. In some dunes it is 

characterized by a lamination of fine-grained minerals 

and occurs in a zone between moving and residual sand 

(Stone, 1967, p. 246).

Shrinkage crack. See Desiccation crack.

Shrub-coppice dune. Small streamlined dune that forms to the 

lee of vegetation on a smooth very shallow sand surface.

Sigmoidal dune. S-shaped steep-sided sharp-crested dune 

formed under the influence of alternating and opposing 

winds of roughly equal velocities (Holm, 1957). See also 

Reversing dune and Recurved dune.

Silcrete. A secondary deposit of siliceous material in soils of 

hot, arid, and semiarid regions.

Silk (North Africa). See Seif.

Singing sand, or Acoustical, Barking, Booming, Musical, 

Roaring, Sonorous, Sounding, Whispering, or Whistling sand. Terms used for sand that, when sliding 

down a slipface, emits a musical tone or a humming or 

booming sound.

Skewness. The state of a frequency distribution which 

bunches on one side of the average and tails out on the 

other side. Skewness results from lack of coincidence of 

the mode, median, and arithmetic mean of the distribution. It is measured by the quotient of the difference between the arithmetic mean and mode divided by the 

standard deviation.

Slipface. Steep face on the lee side of a dune, usually at the 

angle of repose of dry sand (commonly 30° -34°).

Slumping. A mass movement in which grains normally remain 

relatively cohesive within sand sheets, even though individual groups of laminae may be warped, stretched, or 

otherwise contorted. This movement is in contrast to 

sand-flow avalanching during which laminae are being 

progressively destroyed by the separation and dispersion of the component grains.

Slump mark. A surface marking formed on a foreset deposit by 

slumping or mass avalanching. It may consist of a crack 

or step fault resulting from tensional stresses near the 

avalanche summit or of wrinkles and other compressional structures in the zone of compression below. 

Dendritic and other varieties of slump marks also may 

form.

Southeast trades. Winds persistently from the southeast in the 

Southern Hemisphere, caused by counterclockwise circulation about permanent oceanic high-pressure cells, 

centered about lat 20° S.

Stabilized dune. See Fixed dune.

Stabilized free dune or active form. A dune stabilized by 

vegetation but still retaining its initial form.
406 A STUDY OF GLOBAL SAND SEAS

Star dune. A pyramidal dune, roughly star-shaped or resembling a pinwheel, with three or more radial buttresses or 

arms extending in various directions from a high central 

cone. Slipfaces dip in at least three directions.

Stellate rose. A star dune.

Stoss side. Side of dune facing dominant wind direction and 

direction from which dune has migrated. It is opposite 

the lee side.

Straat (South Africa). See Interdune corridor. 

Street. See Interdune corridor.

Stringers. Elongate sand bodies that have no slipfaces. They 

are varieties of sand sheets that have stringlike shape 

and that commonly, though not exclusively, develop 

along the margins or at the downwind extremity of a 

sheet. The term "streak" is used instead of "stringer" in 

chapters J and K, which are based on observations of 

Landsat images.

Surface creep. The slow movement of large detrital grains as a 

result of being pushed by the impact of smaller saltating 

grains.

Surface wind. Wind near ground-surface level. It is usually 

measured at a height of 10 m (32.8 ft) or less.

Suspended load. The part of the total wind load that is carried 

for a considerable period of time in suspension, free 

from contact with the desert floor. It consists mainly of 

silt and finer detritus.

Suspension. A mode of sediment transport in which the upward currents in eddies of turbulent flow are capable of 

supporting weight of particles and keeping them indefinitely held in the air.

Swash zone. Area of a beach where water rushes up onto it 

following the breaking of a wave.

Tabular-planar cross-strata. Set of cross-strata bounded by 

planar, essentially parallel surfaces.

Thematic map. Interpretive drawing, based on ERTS-1 color 

mosaic, which expresses with patterns the relationships 

of features observed on the imagery.

Thermal low. An area of low atmospheric pressure, caused by 

heating of the land surface by solar radiation, resulting 

in expansion of adjacent air.

Traction. A mode of sediment transport in which particles are 

swept along, or are immediately above and parallel to, 

the ground surface. Movement may be by rolling, sliding, dragging, pushing, or saltation.

Trade wind desert. See Low latitude desert.

Transverse dune. Asymmetric sand ridge (leeward slope, 

steep; windward, gentle) in which long dimension is 

normal to dominant wind direction. It has one slipface. 

It shows largely horizontal strata (apparent dip) in cross 

sections parallel to crest, in contrast to curving strata of 

barchanoid ridges viewed in similar sections.

Tropical desert. See Low Latitude desert.

Trough cross strata. Set of cross-strata whose lower bounding 

surface is curved surface of erosion. It results from 

channeling and subsequent deposition. Overlapping sets 

may show festoon pattern.

Two-storied barchan. A compound barchan.

Umbracer dune. Type of longitudinal dune that tapers to a 

point downwind, formed under constant wind direction 

in the lee of an obstacle. It may form behind prominent 

bedrock obstacles, or more commonly behind clumps of 

bushes (Shrub-coppice dune).

Unidirectional dune field. Dune field in which dunes migrate 

in only one principal direction.

Upsiloidal dune. See Parabolic dune.

Uruq. (1) (Arabia) Elongate or seif dune (Stone, 1967, p. 256); 

(2) (North Africa) chain of elongate dunes (Stone, 1967, 

p. 264).

U-shaped dune. See Parabolic dune.

Vector unit (VU). Number arbitrarily used in computation and 

derived from application of a weighting equation for 

sand movement by wind to surface wind data. The 

meaning of a vector unit in terms of sand transport 

kg/m2/yr (Ib/ft2/yr) will differ as different weighting 

equations or other variables are used, but its value is 

directly proportional to the effective wind energy of the 

environment.

Ventifact. Wind-polished or abraded pebble.

Wadi. See Arroyo.

Wash. (1) See Arroyo; (2) alluvium, especially coarse 

alluvium.

Wedge-planar cross-strata. Set of cross-strata bounded by 

oblique erosion surfaces that separate it from other sets 

of cross-strata.

Weighting equation. A function (used in this report) to weight 

surface winds of different velocities according to their 

relative ability to move sand. See chapter F.

Weighting factor for surface winds. A numerical expression 

of the rate at which wind of a certain velocity moves 

sand compared to winds of other velocities.

Whaleback or Sand levee. Coarse residue or platform built up 

and left behind by the passage of a long continued succession of seif dunes along the same path (Bagnold, 

1941, p. 242).

Wide unimodal wind distribution. A wind regime that produces a distribution of drift potential on a sand rose that 

has a single peak or mode on the compass and an arc of 

more than 45°.

Winddrift dune or Windrift dune. Linear dune deposited on 

the lee slide of blowout areas.

Wind regime. The pattern of winds characteristic of a particular region.
GLOSSARY 407

Wind rose. A circular histogram depicting the percentage occurrence of wind speed groups from a given set of compass directions, at a certain geographic locality. It has 

arms proportional in length to the number (or percentage) of observations of wind from a given direction.

Wind shadow. The area adjacent to a slope, cliff, or escarpment which is protected from the direct action of the 

wind blowing over it.

Wind shadow dune. See Umbracer dune and Shrub-coppice 

dune.

Wind sweep. Windward slope of an advancing dune, or that 

portion of the windward slope of a dune up which the 

main wind currents pass.

Windward slope. The upwind side of a dune. 

Xerophyte. Plant adapted to an arid environment.

Yardang or Yarding. (1) Sharp salient ridge of incompetent 

sedimentary material oriented parallel to the direction 

of the prevailing effective wind and presumably produced by the abrasion of wind-driven sand; (2) irregular 

ridge bounded by rounded troughs formed by eolian erosion; (3) landscape form produced in limestone or 

sandstone regions by infrequent rains combined with 

wind action resulting in a surface covered with a fine 

and compact lace work of sharp ridges pitted by corrosion.

409

A STUDY OF GLOBAL SAND SEAS

SELECTED REFERENCES

Ahlbrandt, T. S., 1973, Sand dunes, geomorphology and 

geology, Killpecker Creek area, northern Sweetwa;er 

County, Wyoming: Wyoming Univ. Ph. D. thesis, 174 p.; 

available from Xerox University Microfilms, Ann Arbor, 

Mich. [U.S.A.], no. 73-25,539, 212 p.

____1974a, Dune stratigraphy, archaeology, and the 

chronology of the Killpecker dune field, in Michael 

Wilson, ed., Applied geology and archaeology — The 

Holocene history of Wyoming: Wyoming Geol. Survey 

Kept. Inv. 10, p. 51 -60.

____ 1974b, The source of sand for the Killpecker sand-dune 

field, southwestern Wyoming: Sed. Geology, v. 11, no. 1, p. 

39 -57.

_____ 1975, Comparison of textures and structures to distinguish eolian environments, Killpecker dune field, 

Wyoming: Mtn. Geologist, v. 12, no. 2, p. 61 -63.

Airy, G. B., 1845, Tides and waves: [London] Encyclopedia 

Metropolitans, v. 5, p. 241 -396.

Alimen, Henriette, 1965, The Quaternary era in the northwest 

Sahara, in H. E. Wright, Jr., and D. G. Frey, eds., International studies on the Quaternary: Geol. Soc. America Spec. 

Paper 84, p. 273-291.

Alimen, Marie-Henriette, Doudoux-Fenet, Daniele, Ferrere, 

Jacqueline, and Palau-Caddoux, Marguerite, 1957, Sables 

quaternaires du Sahara nord-occidental (Saoura-Ougarta): 

Algeria Service de la Carte Geologique Bull. 15, 207 p. 

[1958].

Alien, J. E., and Balk, Robert, 1954, Mineral resources of Fort 

Defiance and Tohatchi quadrangles, Arizona and New 

Mexico: New Mexico Bur. Mines and Mineral Resources 

Bull. 36, 192 p.

Alien, J. R. L., 1968, Current ripples — Their relations to patterns of water and sediment motion: Amsterdam, Netherlands, North-Holland Publishing Co., 433 p.

Almeida, F. F. M. de, 1953, Botucatu, a Triassic desert of South 

America: Internet. Geol. Cong., 19th, Algiers 1952, 

Comptes Rendus, sec. 7, pt. 7, p. 9 - 24.

_____1954, Botucatu, a Traissic desert of South America: 

[Brazil] Div. Geologia e Mineralogia Notas Prelim, e 

Estudos 86, 21 p.

Almeida, F. F. N. de, and Barbosa, Octavio, 1953, Geologia das 

quadrfculas de Piracicaba e Rio Claro estado de Sab Paulo 

[Geology of the Piracicaba and Rio Claro quadrangles, SSb 

Paulo]: [Brazil] Div. Geologia e mineralogia Boletim 

143, 96 p.

American Geological Institute, (Margaret Gary, Robert 

McAfee, Jr., and C. L. Wolf, eds.), 1972, Glossary of 

geology, with a foreword by lan Campbell: Washington, 

857 p.

ARAMCO Survey, Projects Construction Services (Shaik 

Mahboob, compiler), 1974, AER-716, Southern area climate, estimated climatic information for Shaybah EPI 

151-192 and EPI 169-29: Arabian American Oil Co., 

Dhahran, Saudi Arabia, 35 p. and appendix [34] p.

Auden, J. B., 1950, Introductory report on the ground-water

resources of western Rajasthan: New Delhi, India Geol.

Survey Bull., ser. B, no. 1, 59 p. 

Aufrere, L6on, 1928, L'orientation des dunes et la direction des

vents: [Paris] Acad. Sci. Comptes Rendus, v. 187, p.

833-835. 

____1930, L'orientation des dunes continentales: Internet.

Geog. Cong., 12th, Cambridge, England, 1928, Proc., p.

220-231. 

____1932, Morphologic dunaire et meteorologie saharienne:

Assoc. Geographes Frangais Bull. 56, p. 34—47. 

____ 1934, Les dunes du Sahara algerien: Assoc.

Geographes Franqais Bull. 83, p. 130-142.

Averitt, Paul, Detterman, J. S., Harshbarger, J. W., Repenning, 

C. A., and Wilson, R. F., 1955, Revisions in correlation 

and nomenclature of Triassic and Jurassic formations in 

southwestern Utah and northern Arizona: Am. Assoc. 

Petroleum Geologists Bull., v. 39, no. 12, p. 2515-2524.

Baars, D. L., 1961, Permian blanket sandstones of the Colorado 

Plateau, in J. A. Peterson and J. C. Osmond, eds., Geometry of sandstone bodies — A symposium, 45th Ann, Mtg., 

Atlantic City, N.J., 1960: Tulsa, Okla., Am. Assoc. 

Petroleum Geologists, p. 179-207.

____1962, Permian System of Colorado Plateau: Am. Assoc. 

Petroleum Geologists Bull. v. 46, no. 2, p. 149-218.

____1972, Southwestern area, in Permian System, in

Geologic Atlas of the Rocky Mountain region, United 

States of America: Rocky Mtn. Assoc. Geologists, p. 

148-165.

Bagnold, R. A., 1933, A further journey through the Libyan 

desert: Geog. Jour., v. 82, p. 103-129.

____1935, The movement of desert sand: Geog. Jour., v. 85, 

p. 342 -369.

_____ 1937, The transport of sand by wind: Geog. Jour., v. 89, 

p. 409 -438.

____1941. The physics of blown sand and desert dunes: London, Methuen & Co., Ltd., 265 p.

____ 1951, Sand formations in southern Arabia: Geog. Jour., 

v. 117, pt. 1, p. 78-86.

____ 1953, The surface movement of blown sand in relation 

to meterology, in Desert Research — Internal. Symposium, Jerusalem, 1952, Proc.: Israel Research Council 

Spec. Pub. 2, p. 89-96.
410 A STUDY OF GLOBAL SAND SEAS

Baker, A. A., 1936, Geology of the Monument Valley —Navajo 

Mountain region, San Juan County, Utah: U.S. Geol. 

Survey Bull. 865, 106 p.

Baker, A. A., Dane, C. H., and Reeside, J. B., 1936, Correlation 

of the Jurassic formations of parts of Utah, Arizona, New 

Mexico, and Colorado: U.S. Geol. Survey Prof. Paper 183, 

66 p.

Barnard, W. S., 1973, Duinformasies in die Sentrale Namib: 

Tegnikon [South Africa, Stallenbosch Univ.], December, 

p. 2 -13.

Bartenstein, Helmut, 1968, Present status of the Paleozoic 

paleogeography of northern Germany and adjacent parts 

of northwest Europe, in D. T. Donovan, ed., Geology of 

shelf seas — Inter-Univ. Geol. Gong., 14th, Proc.: Edinburgh, London, Oliver and Boyd, p. 31 —54.

Beard, D. C., and Weyl, P. K., 1973, Influence of texture on 

porosity and permeability of unconsolidated sand: Am. 

Assoc. Petroleum Geologists Bull., v. 57, no. 2, p. 349 -369.

Beheiry, S. A., 1967, Sand forms in the Coachella Valley, 

southern California: Assoc. Am. Geographers Annals, v. 

57, no. 1, p. 25^8.

Belly, Pierre-Yves, 1964, Sand movement by wind, with Addendum 2, by Abdel-Latif Kadib: U.S. Army Corps of 

Engineers, Coastal Eng. Research Center Tech. Memo. 1, 

[85 p].

Berner, R. A., 1969, Goethite stability and the origin of red 

beds: Geochim. et Cosmochim. Acta, v. 33, no. 2, p. 

267 -273.

Besler, Helga, 1972, Geomorphologie der Dunen: Namib und 

Meer, [South-West Africa, Swakopmund], v. 3, p. 25-35.

Bettenay, Eric, 1962, The salt lake systems and their associated 

aeolian features in the semi-arid regions of Western 

Australia: Jour. Soil Sci., v. 13, p. 10-17.

Beukes, N. J., 1970, Stratigraphy and sedimentology of the Cave 

Sandstone Stage, Karroo System, in Internet. Union Geol. 

Sci. Symposium, 2d, South Africa, 1970, Proc. and 

Papers — Gondwana stratigraphy and paleontology: 

Marshalltown, Transvaal, South Africa, Geol. Soc. South 

Africa, p. 321 -341.

Beydoun, Z. R., 1966, Geology of the Arabian Peninsula — 

Eastern Aden Protectorate and part of Dhufar: U.S. Geol. 

Survey Prof. Paper 560-H, 49 p.

Bigarella, J. J., 1965, Sand-ridge structures from Parana coastal 

plain [Brazil]: Marine Geology, v. 3, p. 269-278.

____1972, Eolian environments — their characteristics, 

recognition, and importance, in J. K. Rigby and W. K. 

Hamblin, eds., Recognition of ancient sedimentary environments: Soc. Econ. Paleontologists and Mineralogists 

Spec. Pub. 16, p. 12-62.

____1973a, Paleocurrents and the problem of continental 

drift: Geol. Rundschau, v. 62, no. 2, p. 447-477.

____ 1973b, Textural characteristics of the Botucatu 

Sandstone: Boletim Paranaense Geoci^ncias, no. 31, p. 

85 -94.

____ 1975a, Structures developed by dissipation of dune and 

beach ridge deposits: Catena, v. 2, no. 1-2, p. 107-152.

____ 1975b, Lagoa dune field, State of Santa Catarina, 

Brazil — A model of eolian and pluvial activity, in International symposium on the Quaternary, southern Brazil,

July 15—31,1975: Boletim Paranaense Geociencias, no. 33, 

p. 133 -167.

Bigarella, J. J., Alessi, A. H., Becker, R. D., and Duarte, G. M., 

1969, Textural characteristics of the coastal dune, sand 

ridge, and beach sediments: Boletfm Paranaense Geociencias, no. 27, p. 15-80.

Bigarella, J. J., Becker, R. D., and Duarte, G. M., 1969, Coastal 

dune structures from Parana [Brazil]: Marine Geology, v. 

7, p. 5 -55.

Bigarella, J. J., and Oliveira, M. A. M., 1966, Preliminary note 

about the directions of sand grain transportation at Furnos 

and Botucatu in the seventieth part of Parana Basin 

[Brazil]: Boletfm Paranaense Geografia, nos. 18-20, p. 

247 -256. [In Portuguese.]

Bigarella, J. J., and Popp, J. H., 1966, Contributions to the study 

of recent shoreline sediments; IV — Shore and dunes of 

Barra do Sul (SC) [Santa Catarina, Brazil]: Boletim Paranaense Geografia, nos. 18 -20, p. 133 -149. [In Portuguese; 

English abs.]

Bigarella, J. J., and Salamuni, Riad, 1961, Early Mesozoic wind 

patterns as suggested by dune bedding in the Botucatu 

sandstone of Brazil and Uruguay: Geol. Soc. America Bull., 

v. 72, no. 7, p. 1089-1106.

___1967, Some paleogeographic and paleotectonic features 

of the Parana Basin, in J. J. Bigarella, R. D. Becker, and I. D. 

Pinto, eds., Problems in Brazilian Gondwana geology: Internat. Symposium on the Gondwana Stratigraphy and 

Paleontology, 1st, Mar del Plata, 1967, p. 235-301.

Blanford, W. T., 1877, Geological notes on the Great Indian 

Desert between Sind and Rajputana: India Geol. Survey 

Records, v. 10, p. 10-21.

Bohdanowicz, Karol, 1892, Geologicheskiia izsliedovaniia v 

Vostochnam Turkestanie—Geograficheskoe obshchestvo 

SSSR Tibetskaia ekspeditsii 1889-1890, Trudy no. 2 

[Geological research in eastern Turkestan — Works of 

1889-1890 Tibet expedition]: St. Peterburg, Tipografiia M. 

M. Stasiulevicha, 167 p. [In Russian.]

Boocock, C., and van Straaten, O. J., 1962, Notes on the geology 

and hydrogeology of the central Kalahari region, 

Bechuanaland Protectorate: Geol. Soc. South Africa 

Trans., v. 65, pt. 1, p. 125-176.

Boulet, R., Guichard, E., and Vieillefon, J., 1971, Observations 

pedologiques et leurs relations avec les faits geomorphologiques dans le delta su Senegal — Comparison avec les 

observations effectuees au Niger {Pedology and its relation to geomorphology in the Senegal delta — Comparison 

with observations made on the Niger]: Assoc. Senegal. 

Etude Quaternaire Quest African, Bull. 29, p. 103-114.

Brady, L. F., 1935, Preliminary note on the occurrence of a 

primitive theropod in the Navajo: Am. Jour. Sci., ser. 5, v. 

30, no. 177, p. 210-215.

____1939, Tracks in the Coconino sandstone compared with 

those of small living arthropods: Plateau, v. 12, no. 2, p. 

32-34.

Bramkamp, R. A., Gierhart, R. D., Brown, G. F., and Jackson, 

R. O., 1956, Geology of the southern Tuwayq quadrangle, 

Kingdom of Saudi Arabia: U.S. Geol. Survey Misc. Geol. 

Inv. Map I-212A, scale 1:500,000.
SELECTED REFERENCES 411

Bramkamp, R. A., Gierhart, R. D., Owens, L. D., and Ramirez, 

L. F., 1963, Geologic map of the western Rub' al Khali 

quadrangle, Kingdom of Saudi Arabia: U.S. Geol. Survey 

Misc. Geol. Inv. Map I-218A, scale 1:500,000.

Bramkamp, R. A., and Ramirez, L. F., 1958, Geology of the 

northern Tuwayq quadrangle, Kingdom of Saudi Arabia: 

U.S. Geol. Survey Misc. Geol. Inv. Map I-207A, scale, 

1:500,000.

___1959a, Geology of the northwestern Rub' al Khali quadrangle, Kingdom of Saudi Arabia: U.S. Geol. Survey Misc. 

Geol. Inv. Map I-213A, scale 1:500,000.

____1959b, Geology of the Wadi al Batin quadrangle, 

Kingdom of Saudi Arabia: U.S. Geol. Survey Misc. Geol. 

Inv. Map I-203A, scale 1:500,000 [I960].

___1960, Geographic map of the Jawf-Sakakah quadrangle, 

Kingdom of Saudi Arabia: U.S. Geol. Survey Misc. Geol. 

Inv. Map I-201B, scale 1:500,000. [1961]. 

.1963, Geologic map of the Darb Zubaydah quadrangle,

Kingdom of Saudi Arabia: U.S. Geol. Survey Misc. Geol. 

Inv. Map I-202A, scale 1:500,000.

Bramkamp, R. A., Ramirez, L. F., Brown, G. F., and Pocock, 

A. E., 1963, Geologic map of the Wadi ar Rimah quadrangle, Kingdom of Saudi Arabia: U.S. Geol. Survey Misc. 

Geol. Inv. Map I-206A, scale 1:500,000.

Breed, C. S., and McKee, E. D., 1973, Sand dunes in desert 

areas: Tucson, Ariz., Remote sensing in arid lands, 4th 

Ann. Conf., Arizona Univ., Proc., p. 160-171.

Broin, T. L., 1957, Stratigraphy of the Lykins Formation of 

eastern Colorado: Colorado Univ. Ph. D. thesis, 256 p.; 

available through Univ. Microfilms, Ann Arbor, Mich.

Brookfield, Muriel, 1970, Dune trends and wind regime in 

central Australia, in Piedmont plains and sand formations 

in arid and humid tropic and subtropic regions: Zeitschr. 

Geomorphologie, Supp. 10, p. 121 -153.

Brown, G. F., 1960, Geomorphology of western and central 

Saudi Arabia: Internal. Geol. Cong., 21st, Copenhagen, 

Rept. 21, pt. 21, p. 150-159.

Brown, G. F., Layne, Newton, Goudarzi, G. H., and MacLean, 

W. H., 1963, Geologic map of the northeastern Hijaz quadrangle, Kingdom of Saudi Arabia: U.S. Geol. Survey Misc. 

Geol. Inv. Map I-205A, scale 1:500,000.

Bryson, R. A., 1974, A perspective on climatic change: Science, 

v. 184, no. 4138, p. 753-760.

Bucher, W. H., 1919a, On ripples and related sedimentary surface forms and their paleogeographic interpretation: Am. 

Jour. Sci., 4th ser., v. 47, no. 279, p. 149-210.

____1919b, Fossil ripples and their paleogeographic interpretation, pt. 2 o/ On ripples and related sedimentary 

surface forms and their paleogeographic interpretation: 

Am. Jour. Sci., 4th ser., v. 47, no. 280, p. 241 -269.

Bunker, D. G., 1953, The south-west borderlands of the Rub' al 

Khali: Geog. Jour., v. 119, pt. 4, p. 420^30.

Camp, C. L., 1936, A new type of small bipedal dinosaur from 

the Navajo sandstone of Arizona: California Univ. Pubs. 

Geol. Sci. Bull., v. 24, no. 2, p. 39-55.

Campbell, C. V., 1971, Depositional model — Upper Cretaceous Gallup beach shoreline, Ship Rock area, northwestern New Mexico: Jour. Sed. Petrology, v. 41, no. 2, p. 

395 -409.

Campbell, R. L., Jr., 1968, Stratigraphic applications of dipmeter data in mid-continent: Am. Assoc. Petroleum 

Geologists Bull., v. 52, no. 9, p. 1700-1719.

Campos, L. F. Gonzaga de, 1889, Secgao geologica: [Brazil] Sao 

Paulo Commissao Geog. Geol. da Provincia Relatorio, 

1889, Annexe, p. 21 -34.

Capot-Rey, Robert, 1943, La morphologic de L'Erg Occidental: 

Algiers Univ. Inst. Recherches Sahariennes Travaux, v. 2, 

p. 69 -103.

____1945, Dry and humid morphology in the western Erg: 

Geog. Rev., v. 35, no. 3, p. 391 -407.

____ 1947a, L'Edeyen de Mourzouk: Algiers Univ. Inst. 

Recherches Sahariennes Travaux, v. 4, p. 67 -109.

____ 1947b, Chronique — Exploration de L'Erg Oriental: 

Algiers Univ. Inst. Recherches Sahariennes Travaux, v. 4, 

p. 181 -187.

____ 1953, Le Sahara franqais: Paris [France] Presses Univ.,

564 p.

Capot-Rey, Robert, and Capot-Rey, Francoise, 1948, le deplacement des sables eoliens et la formation des dunes desertiques, d'apre"s R. A. Bagnold: Algiers Univ. Inst. Recherches Sahariennes Travaux, v. 5, p. 47 -80.

Carroll, Dorothy, 1958, Role of clay minerals in the transportation of iron: Geochim. et Cosmochim. Acta, v. 14, nos. 

1 -2, p. 1 -27.

Chaudhri, I. I., 1957, Succession of vegetation in the arid 

regions of West Pakistan Plains, in Food and Agricultural 

Council of Pakistan and UNESCO, Symposium on soil erosion and its control in the arid and semiarid zones, 

Karachi, Nov. 1957: p. 141 -156.

Chavaillon, Jean, 1964, Etude stratigraphique des formations 

Quaternaires du Sahara nord-occidental (Colomb-Bechar a 

Reggane): [France] Centre Recherches sur les Zones 

Arides, Serie Geologic no. 5, 393 p.

Chepil, W. S., 1945, The transport capacity of the wind, Pt. 3 of 

Dynamics of wind erosion: Soil Sci., v. 60, no. 6, p. 

475 -480.

Chepil, W. S., and Woodruff, N. P., 1963, The physics of wind 

erosion and its control, in A. G. Norman, ed., Advances in 

agronomy, v. 15: New York, London, Academic Press, p. 

211-302.

Christian, C. S., 1959, An arid zone research institute for India: 

Arid Zone [UNESCO Newsletter], no. 5, p. 6-9.

Chu, Chen-jen, Lieu, Hua-hsun, Ch'en, En-chiu, Wu, Kungch'eng, Mi, Kuo-yuan, Hsiao, Yu-ch'uan, Meng, Te-cheng, 

and Hsu, Chen-fu, 1962, The natural characteristics and 

the melioration of the southwestern section of the 

Taklamakan Desert of Sinkiang, in Academia Sinica Sand 

Control Group, eds., Research on sand control: U.S. Joint 

Publications Research Service JPRS 19993, Tech. Trans. 

63 -31183, p. 1 -46. [Figs, omitted.]

Conant, L. C., and Goudarzi, G. H., compilers, 1964, Geologic 

map of the Kingdom of Libya: U.S. Geol. Survey Misc. 

Geol. Inv. Map I-350A, scale 1:2,000,000.

_____1967, Stratigraphic and tectonic framework of Libya: 

Am. Assoc. Petroleum Geologists Bull., v. 51, no. 5, p. 

719-730.

Cooke, R. U., and Warren, Andrew, 1973, Geomorphology in 

deserts: Los Angeles, California Univ. Press, 374 p.
412 A STUDY OF GLOBAL SAND SEAS

Cooper, W. S., 1958, Coastal sand dunes of Oregon and 

Washington: Geol. Soc. America Mem. 72, 169 p.

____1967, Coastal dunes of California: Geol. Soc. America 

Mem. 104, 131 p.

Cordani, U. G., and Vandoros, Paul, 1967, Basaltic rocks of the 

Parand Basin, in J. J. Bigarella, R. D. Becker, and I. D. Pinto, 

eds., Problems in Brazilian Gondwana geology: Internet. 

Symposium on the Gondwana Stratigraphy and Paleontology, 1st, Mar del Plata, 1967, p. 207-231.

Cornish, Vaughan, 1897, On the formation of sand dunes: 

Geog. Jour., v. 9, p. 278-309.

Cressey, G. B., 1928, The Indiana sand dunes and shore lines of 

the Lake Michigan Basin: Geog. Soc. Chicago, Bull. 8 

[Chicago Univ. Press], 80 p.

Crone, A. J., 1974, Experimental studies of mechanically infiltrated clay matrix in sand: Geol. Soc. America Abs. with 

Programs, v. 6, no. 7, p. 701.

____1975, Laboratory and field studies of mechanically infiltrated matrix clay in arid fluvial sediments: Boulder, 

Colo., Colorado Univ. Ph. D. thesis, 162 p.: available from 

Xerox Univ. Microfilms, Ann Arbor, Mich., no. 76-3897, 

174 p.

Crutcher, H. L., 1957, On the standard vector deviation wind 

rose: Jour. Meteorology, v. 14, p. 28 -33.

____1966, Components of 1,000-mb winds (or surface 

winds) of Northern Hemisphere: Washington, U.S. Govt. 

Printing Office, [NAVAIR 50 -1C -51], 74 p.

Crutcher, H. L., and Baer, Ledolph, 1962, Computations from 

elliptical wind distribution statistics: Jour. Applied 

Meteorology, v. 1, p. 522-530.

Crutcher, H. L., and Meserve, J. M., 1970, Selected level 

heights, temperatures and dew points for Northern Hemisphere: Washington, U.S. Govt. Printing Office, [NAVAIR 

50-1C-52, Sept. 1966], 410 p.

Cuvillier, J., 1930, Revision du nummulitique 6gyptien: Institut 

d'Egypte Mem., v. 16, 371 p. [In French.]

Dake, C. L., 1921, The problem of St. Peter sandstone: Missouri 

Univ. School Mines and Metallurgy Bull., Tech. Ser., v. 6, 

no. 1, 225 p.

Dalrymple, P. C., Everett, K. R., and Wollaston, Sarah, 1970, 

Environments of Central Asian Highlands: U.S. Army 

Natick Labs. Tech. Rept. 71-19-ES, Earth Sci. Lab. Ser. 

ES -62, 58 p.

Daveau, Suzanne, 1965, Dunes ravinees et depots du Quaternaire Recent dans le Sahel Mauritanien: Rev. Ge"og. Afrique Occidentale, v. 1, no. 2, p. 7-47.

Denny, C. S., Warren, C. R., Dow, D. H., and Dale, W. J., 1968, A 

descriptive catalog of selected aerial photographs of 

geologic features in the United States: U.S. Geol. Survey 

Prof. Paper 590, 79 p.

Dingier, J. R., 1975, Wave-formed ripples in nearshore sands: 

San Diego, Calif., California Univ. Ph. D. thesis, 136 p.; 

available from Xerox Univ. Microfilms, Ann Arbor, Mich., 

no. 75-11,227, 152 p.

Dresch, Jean, and Rougerie, G., 1960, Observations morphologiques dans le Sahel du Niger: Rev. Geomorphologie Dynamique, v. 11, no. 4-6, p. 49-58. [In French; English abs.]

Dubief, Jean, 1952, Le vent et le deplacement du sable au 

Sahara: Algiers Univ. Inst. Recherches Sahariennes Travaux, v. 8, p. 123 -164.

Eckel, E. B., 1959, Geology and mineral resources of 

Paraguay — A reconnaissance, with sections on Igneous 

and metamorphic rocks, by Charles Milton and E. B. Eckel, 

and Soils, by P. T. Sulsona: U.S. Geol. Survey Prof. Paper 

327, 110 p.

Emmett, W. R., Beaver, K. W., and McCaleb, J. A., 1972, Pennsylvanian Tensleep reservoir, Little Buffalo Basin oil field, 

Big Horn Basin, Wyoming: Mtn. Geologist, v. 9, no. 1, p. 

21-31.

Engel, C. G., and Sharp, R. P., 1958, Chemical data on desert 

varnish: Geol. Soc. America Bull., v. 69, no. 5, p. 487-518.

Falke, Horst, ed., 1972, Rotliegend — Essays on European

Lower Permian: Leiden, Netherlands, E. J. Brill & Co., Internat. Sed. Petrographical Ser., v. 15, 299 p. 

Finkel, H. J., 1959, The barchans of southern Peru: Jour.

Geology, v. 67, no. 6, p. 614-647. 

____1961, The movement of barchan dunes measured by

aerial photogrammetry: Photogrammetric Eng., v. 27, no.

3, p. 439-444. 

Fisher, R. A., 1936, The use of multiple measurements in taxonomic problems: Annals of Eugenics, v. 7, p. 179—188. 

Flint, R. F., and Bond, Geoffrey, 1968, Pleistocene sand ridges

and pans in western Rhodesia: Geol. Soc. America Bull., v.

79, no. 3, p. 299-314. 

Folk, R. L., 1962, Of skewnesses and sands: Jour. Sed.

Petrology, v. 32, no. 1, p. 145-146.

____ 1968a, Bimodal supermature sandstones — Product of 

the desert floor: Internet. Geol. Cong., 23d, Prague, 1968, 

Proc., Genesis and classification of sedimentary rocks, sec. 

8, p. 9-32.

____ 1968b, Petrology of sedimentary rocks: Austin, Tex., 

Hemphill, 170 p.

___ .1969, Grain shape and diagenesis in the Simpson Desert, 

Northern Territory, Australia: Geol. Soc. America Abs. 

with Programs for 1969, pt. 7, p. 68 -69.

____1971a, Longitudinal dunes of the northwestern edge of 

the Simpson Desert, Northern Territory, Australia, [pt.] 1, 

Geomorphology and grain size relationships: Sedimentology, v. 16, p. 5 —54.

____1971b, Genesis of longitudinal and oghurd dunes elucidated by rolling upon grease: Geol. Soc. America Bull., v. 

82, no. 12, p. 3461 -3468.

____ 1976, Reddening of desert sands, Simpson Desert,

Northern Territory, Australia: Jour. Sed. Petrology, v. 46, 

no. 3, p. 604-615.

Folk, R. L., and Ward, W. C., 1957, Brazos River bar — A study

in the significance of grain-size parameters: Jour. Sed.

Petrology, v. 27, no. 1, p. 3-27. 

Fourtau, R., 1902, Sur le gres nubien: [Paris] Acad. Sci. Comptes

Rendus, v. 135, p. 803 -804. 

Frazier, D. E., and Osanik, A., 1961, Point-bar deposits, Old

River Locksite, Louisiana: Gulf Coast Assoc. Geol. Socs.

Trans., v. 11, p. 121 -137. 

Frere, H. B. E., 1870, Notes on the Runn [Rann] of Cutch and

neighboring region: Royal Geog. Soc. [London] Jour., v. 40,

p. 181 -207. 

Friedman, G. M., 1961, Distinction between dune, beach, and

river sands from their textural characteristics: Jour. Sed.

Petrology, v. 31, no. 4, p. 514-529.
SELECTED REFERENCES 413

__ 1967, Dynamic processes and statistical parameters 

compared for size frequency distribution of beach and 

river sands: Jour. Sed. Petrology, v. 37, no. 2, p. 327 -354.

__1966, Textural parameters of beach and dune sands, in 

Abstracts for 1965: Geol. Soc. America Spec. Papers 87, 

p. 60.

__ 1973, Textural parameters of sands — Useful or use-

_ 1970, Notes on some major dune types in southern 

Africa: South African Geog. Jour., v. 52, p. 93-101. 

.1972, Climate, weathering, crust formation, dunes and

less?: Geol. Soc. America Abs. with Programs, v. 5, no. 7,

p. 626-627. 

Friedman, G. M., and Sanders, J. E., 1978, Principles of sedimentology: New York, John Wiley & Sons. 

Fiirst, Manfred, 1970, Beobachtungen an quartaren Buntsedimenten der zentralen Sahara [Observations on variegated

sediments in the central Sahara]: Abhandlungen des

Heissischen Landesamtes fur Bodenforschung, no. 56, p.

129-150. 

Garlick, W. G., 1969, Special features and sedimentary facies of

stratiform sulphide deposits in arenites [with discussion],

in C. H. James, ed., Sedimentary ores, ancient and modern

[revised]: Inter-Univ. Geol. Cong., 15th, Univ. Leicester

[England], Dec. 1967, Proc., Leicester Univ. Dept. Geology

Spec. Pub. 1, p. 107-169. 

Garrels, R. M., and Christ, C. L., 1965, Solutions, minerals, and

equilibria: New York, Harper and Row, 450 p. 

Gautier, E. F., 1935, Sahara —The Great Desert: New York,

Columbia Univ. Press, 280 p. [A translation by D. F.

Mayhew.] 

Gees, R. A., 1965, Moment measures in relation to the depositional environments of sands: Eclogae Geol. Helvetiae, v.

58, no. 1, p. 209-213. 

Gevers, L. W., 1936, The morphology of western Damaraland

and the adjoining Namib Desert of South-West Africa:

South African Geog. Jour., v. 19, p. 61 -79. 

Gill, W. D., 1967, The North Sea basin: World Petroleum Cong.,

7th, Mexico, 1967, Proc., Origin of oil, geology, and

geophysics, v. 2, p. 211 -219. 

Gilmore, C. W., 1926, Fossil footprints from the Grand Canyon:

Smithsonian Misc. Colln., v. 77, no. 9, 41 p. 

____1927, Fossil footprints from the Grand Canyon; second

contribution: Smithsonian Misc. Colln., v. 80, no. 3, 78 p. 

1928, Fossil footprints from the Grand Canyon; third

contribution: Smithsonian Misc. Colln., v. 80, no. 8, 16 p.

Gilreath, J. A., and Maricelli, J. J., 1964, Detailed stratigraphic 

control through dip computations: Am. Assoc. Petroleum 

Geologists Bull., v. 48, no. 12, p. 1902 -1910.

Glennie, K. W., 1970, Desert sedimentary environments, in 

Developments in sedimentology [v.] 14: Amsterdam, London, New York, Elsevier Publishing Co., 222 p.

____ 1972, Permian Rotliegendes of northwest Europe interpreted in light of modern desert sedimentation studies: 

Am. Assoc. Petroleum Geologists Bull., v. 56, no. 6, p. 

1048-1071.

Glennie, K. W., and Evans, G., 1976, A reconnaissance of the 

recent sediments of the Ranns of Kutch, India: Sedimentology, v. 23, p. 625 -647.

Goddard, E. N., Chm., and others, 1948, Rock-color chart: Natl. 

Research Council (reprinted by Geol. Soc. America, 1951, 

1970), 6 p.

Goudie, A. S., 1969, Statistical laws and dune ridges in 

southern Africa: Geog. Jour., v. 135, pt. 3, p. 404^406.

fluvial features of the Central Namib Desert, near 

Gobabeb, South-West Africa: Madoqua, Series II, v. 1, no. 

54-64, p. 15-31.

Goudie, A. S., Allchin, Bridget, and Hedge, K. T. M., 1973, The 

former extensions of the Great India Sand Desert: Geog. 

Jour., v. 139, pt. 2, p. 243-257.

Gradzinski, Ryszard, and Jerzykiewicz, Tomasz, 1972, Additional geographical and geological data from the PolishMongolian palaeontological expeditions, in Results of the 

Polish-Mongolian palaeontological expeditions, Pt. 4: 

Palaeontologia Polonica, no. 27, p. 17 -30.

____ 1974a, Dinosaur- and mammal-bearing aeolian and 

associated deposits of the upper Cretaceous in the Gobi 

Desert (Mongolia): Sed. Geology, v. 12, p. 249-278.

_____I974b, Sedimentation of the Barun Goyot Formation, in

Results of the Polish-Mongolian palaeontological expeditions, Pt. 5: Palaeontologia Polonica, no. 30, p. Ill -146.

Greeley, Ronald, Iversen, J. D., Pollack, J. B., Udovich, Nancy, 

and White, Bruce, 1974, Wind tunnel simulations of light 

and dark streaks on Mars: Science, v. 183, no. 4127, p. 

847 -849.

Greenwood, Brian, 1969, Sediment parameters and environment discrimination — An application of multivariate 

statistics: Canadian Jour. Earth Sci., v. 6, p. 1347-1358.

Gregory, H. E., 1917, Geology of the Navajo country — A 

reconnaissance of parts of Arizona, New Mexico, and 

Utah: U.S. Geol. Survey Prof. Paper 93, 161 p.

Griffiths, J. C., 1967, Scientific method in analysis of sediments: New York, McGraw-Hill Book Co., 508 p.

Griffiths, J. F., and Soliman, K. H., 1972, The northern desert 

(Sahara), Chap. 3, in H. E. Lansberg, ed., World survey of 

climatology, climates of Africa, v. 10: Amsterdam, New 

York, London, Elsevier Publishing Co., p. 75-132.

Grove, A. T., 1958, The ancient erg of Hausaland, and similar 

formations on the south side of the Sahara: Geog. Jour., v. 

124, pt. 4, p. 526-533.

____ 1960a, Geomorphology of the Tibesti region, with 

special reference to western Tibesti: Geog. Jour., v. 126, pt. 

1, p. 18-31.

____ 1960b, [A note] in J. R. V. Prescott and H. P. White, 

Sand formations in the Niger Valley between Niamey and 

Bourem: Geog. Jour., v. 126, pt. 2, p. 202 -203.

____ 1969, Landforms and climatic change in the Kalahari

and Ngamiland: Geog. Jour., v. 135, pt. 2, p. 191-212. 

Grove, A. T., and Warren, Andrew, 1968, Quaternary landforms and climate on the south side of the Sahara: Geog. 

Jour., v. 134, pt. 2, p. 194-208.

Hack, J. T., 1941, Dunes of the western Navajo country: Geog. 

Rev., v. 31, no. 2, p. 240-263.

Hamblin, W. K., 1961, Micro-cross-Lamination in upper

Keweenawan sediments of northern Michigan: Jour. Sed.

Petrology, v. 31, no. 3, p. 390 -401. 

Hand, B. M., 1967, Differentiation of beach and dune sand,

using settling velocities of light and heavy minerals: Jour.

Sed. Petrology, v. 37, no. 2, p. 514-520.
414 A STUDY OF GLOBAL SAND SEAS

Hanley, J. H., and Steidtmann, J. R., 1973, Petrology of 

limestone lenses in the Casper Formation, southernmost 

Laramie Basin, Wyoming and Colorado: Jour. Sed. 

Petrology, v. 43, no. 2, p. 428-434.

Hanley, J. H., Steidtmann, J. R., and Toots, Heinrich, 1971, 

Trace fossils from the Casper Sandstone (Permian), 

southern Laramie Basin, Wyoming and Colorado: Jour. 

Sed. Petrology, v. 41, no. 4, p. 1065-1068.

Harms, J. C., and Fahnestock, R. K., 1965, Stratification, bed 

forms, and flow phenomena (with an example from the 

Rio Grande), in Primary sedimentary stmctures and their

hydrodynamic interpretation — A symp

Geologists and Mineralogists Spec. Pub.

Harms, J. C., MacKenzie, D. B., and McCu

Stratification in modern sands of the Red River, Louisiana: 

Jour. Geology, v. 71, no. 5, p. 566-580.

Harshbarger, J. W., Repenning, C. A., and 

Stratigraphy of the uppermost Triassic 

rocks of the Navajo country [Colorado P

rwin, J. H., 1957, 

and the Jurassic 

ateau]:U.S. Geol.

Survey Prof. Paper 291, 74 p.

Hatchell, W. O., 1967, A stratigraphic study of the Navajo 

Sandstone, (Upper Triassic (?) -Jurassic , Navajo Mountain, Utah and Arizona: Albuquerque, N. Mex., New Mexico Univ., unpub. M.S. thesis, 121 p.

Haughton, S. H., 1969, Geological history of southern Africa: 

Cape Town, Geol. Soc. South Africa, 535 p.

Haun, J. D., and Kent, H. C., 1965, Geologic history of Rocky 

Mountain region: Am. Assoc. Petroleum Geologists Bull., 

v. 49, no. 11, p. 1781 -1800.

Hedin, Sven, 1896, A journey through the TaMa-Makan Desert, 

Chinese Turkistan: Geog. Jour., v. 8, July to December, p. 

264-278.

____ 1899, Through Asia: New York, London, Harper & 

Bros., v. 1, p. 1 -649; v. 2, p. 653-1255.

____1905a, The Tarim River, in Scientific results of a 

journey in central Asia, 1889-1902, v. 1: Stockholm, 

Swedish Army Lithographic Institute, 52 3 p.

1905b, The central Asian deserts,

sands, Pt. 2, in Scientific results of a jcurney in central

Asia, 1899-1902, v. 2: Stockholm,

Lithographic Institute, p. 379 -718. 

Henderson, Junius, 1924, Footprints in Pennsylvanian sandstones of Colorado: Jour. Geology, v. 32,

Hesselberg, T., and Bjorkdal, E., 1929, Uber

gesetz der Windunruhe: Beitraege zur Ph

mosphare, v. 15, p. 121 -133. [In German

Hills, E. S., ed., 1966, Arid Lands — A geogr

London, Methuen & Co., Ltd., and Paris

Hogue, Mominul, 1975, An analysis of cros

Gargaresh calcarenite (Tripoli, Libya)

Paleowinds: Geol. Mag., v. 112, no. 4, p.

)sium: Soc. Econ. 

12, p. 84-115. 

bin, D. G., 1963,

sand-dunes, and

Swedish Army

10. 3, p. 226 -229.

das Verteilungsrsik der Frein At-

•]

phical appraisal:

UNESCO, 461 p.

-stratification of 

and Pleistocene 

393^01.

Holm, D. A., 1953, Dome-shaped dunes of the central Nejd, 

Sauda Arabia: Internal. Geol. Cong., 19th, Algiers, 1952, 

Comptes Rendus, sec. 7, pt. 7, p. 107-112.

____ 1957, Sigmoidal dunes — A transitional form [abs]: 

Geol. Soc. America Bull., v. 68, no. 12, pt. 2, p. 1746.

____1960, Desert geomorphology in the Arabian Peninsula: 

Science, v. 132, no. 3437, p. 1369-1379.

____ 1968, Sand dunes, in R. W. Fairbridge, ed., The encyclopedia of geomorphology: New York, Reinhold Book 

Corp., p. 973-979.

Hbrner, N. G., 1936, Geomorphic processes in continental 

basins of central Asia: Internal. Geol. Cong., 16th, 

Washington, D.C., 1933, Rept., v. 2, p. 721-735.

Hubert, J. F., 1960, Petrology of the Fountain and Lyons Formations, Front Range, Colorado: Colorado School Mines 

Quart., v. 55, no. 1, p. 1 -242.

Huntington, Ellsworth, 1907, Some characteristics of the 

glacial period in nonglaciated regions: Geol. Soc. America 

Bull., v. 18, p. 351-388.

Jones, J. R., 1971, Ground-water provinces of Libyan Arab 

Republic, in G. Carlyle, ed., Symposium on the geology of 

Libya, Tripoli, 1969: Univ. Libya Fac. Sci. Press, p. 

449 -457.

Jordan, G. F., 1962, Large submarine sand waves: Science, v. 

136, no. 3519, p. 839-848.

Kadar, Lazl6, 1966, Az eolikus felszmi formak termeszetes 

rendszere [Natural systems of eolian landforms]: Foldrajzi 

Ertesfto, v. 15, no. 4, p. 413 -448.

Kawamura, R., 1951, Study on sand movement by wind: Tokyo 

Univ. Inst. Sci. and Technology Rept., v. 5, no. 314.

Kent, P. E., and Walmsley, P. J., 1970, North Sea progress: Am. 

Assoc. Petroleum Geologists Bull., v. 54, no. 1, p. 168-181.

Khalil, M. S., 1957, The role of vegetation in checking erosion 

in arid and semiarid tracts, in Food and Agricultural 

Council of Pakistan and UNESCO, Symposium on soil erosion and its control in the arid and semiarid zones, 

Karachi, Nov. 1957: p. 237 -260.

Kiersch, G. A., 1950, Small-scale structures and other features 

of Navajo sandstone, northern part of San Rafael Swell, 

Utah: Am. Assoc. Petroleum Geologists Bull., v. 34, no. 5, 

p. 923-942.

King, D., 1960, The sand ridge deserts of South Australia and 

related aeolian landforms of Quaternary arid cycles: Royal 

Soc. South Australia Trans., v. 83, p- 99-108.

Knight, S. H., 1929, The Fountain and Casper formations of the 

Laramie Basin — A study on genesis of sediments: Wyoming Univ. Sci. Pub., Geology, v. 1, no. 1, p. 1-82.

Koch, G. S., Jr., and Link, R. F., 1970, Statistical analysis of 

geological data: New York, John Wiley & Sons, 375 p.

Krishnan, M. S., 1960, Geology of India and Burma [4th ed.]: 

Madras, India, Higginbothams, Ltd., 604 p.

Krumbein, W. C., and Graybill, F. A., 1965, An introduction to 

statistical models in geology: New York, McGraw-Hill 

Book Co., 475 p.

Kuenen, P. H., 1960, Experimental abrasion; [pt.] 4, Eolian action: Jour. Geology, v. 68, no. 4, p. 427 -449.

Kuenen, P. H., and Perdok, W. G., 1962, Experimental abrasion; 

[pt.] 5, Frosting and defrosting of quartz grains: Jour. 

Geology, v. 70, no. 6, p. 648 -658.

Kukal, Zdenek, 1971, Geology of recent sediments: London, 

New York, Academic Press, 490 p.

Laming, D. J. C., 1966, Imbrication, paleocurrents, and other 

sedimentary features in the lower New Red Sandstone, 

Devonshire, England: Jour. Sed. Petrology, v. 36, no. 4, p. 

940 -959.

Langmuir, Donald, 1971, Particle-size effect on the reaction 

goethite = hematite + water: Am. Jour. Sci., v. 271, no. 2, 

p. 147 -156.

Le Ribault, Loi'c, 1974, L'eroscopie, m^thode de determination 

de 1'histoire ge"ologique des quartz d§tritiques [Exoscopy, 

method to determine the geologic history of detrital
SELECTED REFERENCES 415

quartz]: Rev. Geographic Phys. et GSologie Dynam., v. 16, 

no. 1, p. 119-130. [In French.]

Lewis, A. D., 1936, Sand dunes of the Kalahari within the borders of the Union: South African Geog. Jour., v. 19, p. 

22-32.

Leprun, J. C., 1971, Nouvelles observations sur les formations 

dunaires sableuses fixees du Ferlo nord occidental 

(Senegal): Assoc. Senegal. Etude Quarternaire Quest Africain, Bull. 31 -32, p. 69 -78.

Lindsay, J. F., 1973, Reversing barchan dunes in Lower Victoria 

Valley, Antarctica: Geol. Soc. America Bull., v. 84, no. 5, p. 

1799-1806.

Logan, R. F., 1960, The central Namib Desert, South-West 

Africa: Natl. Acad. Sci. -Natl. Research Council Pub. 758, 

162 p.

Maack, Reinhard, 1941, Algumas observacoes a1 respeito da exist£ncia e da extensab do arenito superior Sao Bento ou 

Caiua no estado do Parana [Some observations regarding 

the existence and enlargement of the Superior Sab Bento 

or Caiu6 Desert, Parana^: Curitiba, Parana, Brazil Mus. Arquivos Paranaense, v. 1, p. 107-129.

Mabbutt, J. A., 1955, Erosion surfaces in Namaqualand and the 

ages of surface deposits in the south-western Kalahari: 

Geol. Soc. South Africa Trans. and Proc., v. 58, p. 13-30.

____ 1967, Denudation chronology in central Australia; 

structure, climate, and landform inheritance in the Alice 

Springs area, in J. N. Jennings and J. A. Mabbutt, eds., 

Landform studies from Australia and New Guinea, with a 

foreword by Prof. E. S. Hills: Canberra, Australian Natl. 

Univ. Press, p. 144-181.

____ 1968, Aeolian landforms in central Australia: Australian Geog. Studies, v. 6, no. 2, p. 139-150.

Mabesoone, J. M., 1963, Coastal sediments and coastal development near Cadiz (Spain): Geologic en Mijnbouw, no. 2, p. 

29^3.

McConnell, R. B., 1959, Notes on the geology and geomorphology of the Bechuanaland protectorate: Internet. 

Geol. Cong., 20th, Mexico, 1956, Assoc. de Servicios 

Geologicos Africanos, Actas y Trabajos de las reuniones 

celebradas en Mexico en 1956, p. 175 -186.

MacGregor, P. A., 1955, Development of the theories of the circulation of the atmosphere over South Africa: South 

African Geog. Jour., v. 49, p. 41 —52.

McKee, E. D., I934a, An investigation of the light-colored 

cross-bedded sandstones of Canyon de Chelly, Arizona: 

Am. Jour. Sci., 5th ser., v. 28, no. 165, p. 219-233.

____ I934b, The Coconino sandstone — Its history and 

origin: Carnegie Inst. Washington Pub. 440, p. 77—115.

____ 1938, Structures in modern sediments aid in interpreting ancient rocks: Carnegie Inst. Washington Pub. 501, p. 

683-694.

____ 1940, Three types of cross-lamination in Paleozoic 

rocks of northern Arizona: Am. Jour. Sci., v. 238, no. 11, p. 

811 -824.

____ 1944, Tracks that go uphill [in Coconino sandstone, 

Grand Canyon, Arizona]: Plateau, v. 16, no. 4, p. 61-72.

____1945, Small-scale structures in Coconino sandstone of 

northern Arizona: Jour. Geology, v. 53, no. 5, p. 313 -325.

_____1947, Experiments on the development of tracks in fine 

cross-bedded sand: Jour. Sed. Petrology, v. 17, no. 1, p. 

23 -28.

_ 1952, Uppermost Paleozoic strata of northwestern 

Arizona and southwestern Utah, in Utah Geol. Soc. 

Guidebook to Geology of Utah: no. 7, p. 52-55.

__1954, Stratigraphy and history of the Moenkopi Formation of Triassic age: Geol. Soc. America Mem. 61, 133 p.

__ 1957, Primary structures in some Recent sediments: 

Am. Assoc. Petroleum Geologists Bull., v. 41, no. 8, p. 

1704-1747.

__ 1966, Structures of dunes at White Sands National

Monument, New Mexico (and a comparison with structures of dunes from other selected areas): Sedimentology, 

v. 7, no. 1, Spec. Issue, p. 3-69.

McKee, E. D., and Bigarella, J. J., 1972, Deformational structures in Brazilian coastal dunes: Jour. Sed. Petrology, v. 42, 

no. 3, p. 670-681.

McKee, E. D., and Breed, C. S., I974a, An investigation of major 

sand seas in desert areas throughout the world, in Third 

Earth Resources Technology Satellite-1 Symposium, 

Washington, D. C., Dec. 10-14, 1973: Natl. Aeronautics 

and Space Admin. Spec. Pub. NASA SP-351, p. 665-679.

____ I974b, Preliminary report on dunes, in Skylab 4 visual 

observations project report, JSC -09053, June 1974, NASA 

TM X-58142, p. 9-1 to 9-9.

______ 1976, Sand seas of the world, in R. S. Williams, Jr., and

W. D. Carter, eds., ERTS —1, A new window on our planet: 

U.S. Geol. Survey Prof. Paper 929, p. 81 -88.

______1977, Desert sand seas, chap. 2, in G. P. Carr and others,

eds., Skylab explores the Earth: Natl. Aeronautics and 

Space Admin. Spec. Paper 380. [NASA SP - 380], p. 5 - 48.

McKee, E. D., Breed, C. S., Fryberger, S. G., Gebel, Dana, and 

McCauley, C. K., 1974, A synthesis of sand seas 

throughout the world — Type III, Final Report for 1 July 

1972-31 March 1974: NASA Earth Resources Survey 

Program, NASA -CR -139266, 95 p. [Goddard Space Flight 

Center, Greenbelt, Md.]

McKee, E. D., and Douglass, J. R., 1971, Growth and movement 

of dunes at White Sands National Monument, New Mexico, in Geological Survey research 1971: U.S. Geol. Survey 

Prof. Paper 750-D, p. D108-D114.

McKee, E. D., Douglass, J. R., and Rittenhouse, Suzanne, 1971, 

Deformation of lee-side laminae in eolian dunes: Geol. 

Soc. America Bull., v. 82, no. 2, p. 359-378.

McKee, E. D., and Moiola, R. J., 1975, Geometry and growth of 

the White Sands dune field, New Mexico: U.S. Geol. 

Survey Jour. Research, v. 3, no. 1, p. 59-66.

McKee, E. D., Oriel, S. S., Berryhill, H. L., Jr., Cheney, T. M., 

Cressman, E. R., Crosby, E. J., Dixon, G. H., Fix, C. E., 

Hallgarth, W. E., Ketner, K. B., MacLachlan, M. E., 

Maughan, E. K., McKelvey, V. E., Mudge, M. R., Myers, D. 

A., and Sheldon, R. P., 1967, Paleotectonic maps of the 

Permian System: U.S. Geol. Survey Misc. Geol. Inv. Map 

1^50, 164 p.

McKee, E. D., Oriel, S. S., Swanson, V. E., MacLachlan, M. E., 

MacLachlan, J. C., Ketner, K. B., Goldsmith, J. W., Bell, R. 

Y., and Jameson, D. J., 1956, Paleotectonic maps of the 

Jurassic system, with a separate section on paleogeography, by R. W. Imlay: U.S. Geol. Survey Misc. Geol. Inv. 

Map I-175.

McKee, E. D., Reynolds, M. A., and Baker, C. H., Jr., 1962a, 

Laboratory studies on deformation in unconsolidated sediment, in Short papers in geology, hydrology, and topogra-
416 A STUDY OF GLOBAL SAND SEAS

phy: U.S. Geol. Survey Prof. Paper 450 - D, p. D151 - D155. 

_ 1962b, Experiments on intraformational recumbent

folds in crossbedded sand, in Short papers in geology, hydrology, and topography: U.S. Geol. Survey Prof. Paper 

450-D, p. D155-D160.

McKee, E. D., and Tibbitts, G. C., Jr., 1964, Primary structures 

of a seif dune and associated deposits in Libya: Jour. Sed. 

Petrology, v. 34, no. 1, p. 5 -17.

Madigan, C. T., 1936, The Australian sand-ridge deserts: Geog. 

Rev., v. 26, no. 2, p. 205 -227.

___ 1938, The Simpson Desert and its borders: Royal Soc. 

New South Wales Jour, and Proc. , v. 71, pt. 2, p. 503 -535. 

.1946, The Simpson Desert Expedition, 1939, Scientific

reports; No. 6, Geology — The sand formations: Royal Soc. 

South Australia Trans., v. 70, p. 45-63, 205-227.

Maher, J. C., 1954, Lithofacies and suggested depositional environment of Lyons sandstone and Lykins formation in 

southeastern Colorado: Am. Assoc. Petroleum Geologists 

Bull., v. 38, no. 10, p. 2233-2239.

Manton, W. I., 1968, The origin of associated basic and acid 

rocks in the Lebombo-Nuanetsi igneous province, 

Southern Africa, as implied by strontium isotopes: Jour. 

Petrology, v. 9, pt. 1, p. 23 -39.

Margolis, S. V., and Krinsley, D. H., 1971, Submicroscopic 

frosting on eolian and subaqueous quartz sand grains: 

Geol. Soc. America Bull., v. 82, no. 12, p. 3395 -3406.

Martins, L. R., 1967, Aspectos texturais e deposicionais dos 

sedimentos praiais e eolicas da planicie costeira do Rio 

Grande do Sul [Brazil]: Escola de Geologia, Rio Grande do 

Sul. Fed. Univ., Spec. Pub. 13,102 p.

Marzolf, J. E., 1969, Regional stratigraphic variations in primary features of the Navajo Sandstone, Utah: Geol. Soc. 

America Abs. with Programs for 1969, pt. 5, p. 50-51.

Mason, G. C., and Folk, R. L., 1958, Differentation of beach, 

dune, and aeolian flat environments by size analysis, 

Mustang Island, Texas: Jour. Sed. Petrology, v. 28, no. 2, p. 

211-226.

Maughan, E. K., and Wilson, R. F., 1960, Pennsylvanian and 

Permian strata in southern Wyoming and northern Colorado, in Guide to the geology of Colorado: Geol. Soc. 

America, Rocky Mtn. Assoc. Geologists, and Colorado Sci. 

Soc., p. 34^2.

Meigs, Peveril, 1953, World distribution of arid and semi-arid 

homoclimates, in Reviews of research on arid zone hydrology: Paris, Arid Zone Programme-1, UNESCO, p. 

203 -209.

Meinster, B., and Tickell, S. J., 1976, Precambrian aeolian 

deposits in the Waterberg Supergroup: South Africa Geol. 

Soc. Trans., p. 191 -199.

Melton, F. A., 1940, A tentative classification of sand dunes — 

Its application to dune history in the southern High 

Plains: Jour. Geology, v. 48, no. 2, p. 113 -174.

Merk, G. P., 1960, Great sand dunes of Colorado, in Guide to 

the geology of Colorado: Geol. Soc. America, Rocky Mtn. 

Assoc. Geologists, and Colorado Sci. Soc., p. 127-129.

Merriam, Richard, 1969, Source of sand dunes of southeastern 

California and northwestern Sonora, Mexico: Geol. Soc. 

America Bull., v. 80, no. 3, p. 531 -533.

Miller, A. K., and Thomas, H. D., 1936, The Casper Formation

(Pennsylvanian) of Wyoming and its cephalopod fauna: 

Jour. Paleontology, v. 10, no. 8, p. 715 -738.

Miller, R. L., and Kahn, J. S., 1962, Statistical analysis in the 

geological sciences: New York, John Wiley & Sons, 483 p.

Moiola, R. J., Spencer, A. B., and McKee, E. D., 1973, Linear discriminant analysis — A technique for analyzing sand 

bodies: Geol. Soc. America Abs. with Programs, 1973 Ann. 

Mtgs., v. 5, no. 7, p. 741 -742.

Moiola, R. J., Spencer, A. B., and Weiser, Daniel, 1974, 

Differentiation of modem sand bodies by linear discriminant analysis: Gulf Coast Assoc. Geol. Socs. Trans., v. 24, 

p. 321 -326.

Moiola, R. J., and Weiser, Daniel, 1968, Textural parameters — 

An evaluation: Jour. Sed. Petrology, v. 38, no. 1, p. 45-53.

Monod, Theodore, 1958, Majdbat al-Koubra"; Contribution a" 

1'etude de l'"empty quarter" ouest-saharien: Frangais 

d'Afrique Noire Inst. Mem. 52, 406 p.

____ 1961, Majabat al-Koubra4 (supplement): Fran§ais 

d'Afrique Noire Inst. Bull. 23, no. 3, p. 591 -637.

Munsell Color Co., 1954, Munsell soil color charts: Baltimore, 

Md.

Murzayev, E. M., 1967, Nature of Sinkiang and formation of the 

deserts of central Asia: U.S. Joint Publications Research 

Service JPRS 40,229, TT 67-30944, 617 p. [Technical 

translation from Russian — Priroda sin'tszyana I formirovaniye pustyn' tsentral'nay Azii: Akad. Nauk SSSR 

Inst. Geograffi, 1966.]

Nairn, A. E. M., ed., 1961, Descriptive palaeoclimatology: New 

York, Interscience Publishers, 380 p.

____ 1964, Problems in palaeoclimatology, in NATO 

palaeoclimates conf., Univ. Newcastle-upon-Tyne and 

Durham, England, 1963, Proc.: New York, Interscience 

Publishers, 705 p.

Newell, N. D., and Rigby, J. K., 1957, Geological studies on the 

Great Bahama Bank, in Regional aspects of carbonate 

deposition: Soc. Econ. Paleontologists and Mineralogists 

Spec. Pub. 5, p. 15 -72.

Newell, N. D., Rigby, J. K., Whiteman, A. J., and Bradley, J. S., 

1951, Shoal-water geology and environments, Eastern 

Andros Island, Bahamas: Am. Mus. Nat. History Bull., v. 

97, art. 1, p. 1 -29.

Norm, Eric, 1941, The Tarim Basin and its border regions: 

Leipzig Akad. Verlagsgesellschaft, Regionale Geologic der 

Erde, v. 2, pt. 4b, 40 p.

Norris, R. M., 1966, Barchan dunes of Imperial Valley, California: Jour. Geology, v. 74, no. 3, p. 292 -306.

___1969, Dune reddening and time: Jour. Sed. Petrology, v. 

39, no. 1, p. 7-11.

Norris, R. M., and Norris, K. S., 1961, Algodones dunes of 

southeastern California: Geol. Soc. America Bull., v. 72, 

no. 4, p. 605 -620.

Obrutschev, V. A., 1895, [Uber] Ueber die verwitterungs und 

deflationsprocesse in Central-Asien: St. Petersburg, 

Russisch-Kaiserlich Mineralogische Gesell. Verb., ser. 2, 

no. 33, p. 229-272.

Opdyke, N. D., 1961, The palaeoclimatological significance of 

desert sandstone, chap. 3, in A. E. M. Nairn, ed., Descriptive Palaeoclimatology: New York, Interscience Publishers, p. 45 -60.
SELECTED REFERENCES 417

Opdyke, N. D., and Runcorn, S. K., 1960, Wind direction in the 

Western United States in the Late Paleozoic: Geol. Soc. 

America Bull., v. 71, no. 7, p. 959-971.

Pacheco, J. A. do Amaral, 1913, Notas sobre a geologia do valle 

do Rio Grande a partir da f6z do Rio Pardo ate a sua confluencia com o Rio Paranahyba; exploragab do Rio Grande 

e de seus affluentes: [Brazil] S3b Paulo Commissab Geog. 

e Geol., p. 33-38.

Page, W. D., 1972, The geological setting of the archaeological 

site at Oued el Akarit and the paleoclimatic significance of 

gypsum soils, southern Tunisia: Boulder, Colo., Colorado 

Univ. unpub. Ph. D. thesis, 111 p.; available from Xerox 

Univ. Microfilms, Ann Arbor, Midi., no. 73 -1812, 121 p.

Peabody, F. E., 1940, Trackways of Pliocene and Recent salamandroids of the Pacific Coast of North America: 

Berkeley, Calif., California Univ., unpub. M.A. thesis.

Pederson, S. L., 1953, The stratigraphy of the (Pennsylvanian 

and Permian) Casper and Fountain formations of 

southeastern Wyoming and north-central Colorado: 

Laramie, Wyo., Wyoming Univ., unpub. M.A. thesis, 87 p.

Peirce, H. W., 1963, Stratigraphy of the De Chelly Sandstone of 

Arizona and Utah: Tucson, Ariz., Arizona Univ., Ph. D. 

thesis, 206 p.; available from Univ. Microfilms, Ann Arbor, Midi., no. 63 -3650, 291 p.

Pesce, Angelo, 1968, Gemini space photographs of Libya and 

Tibesti — A geological and geographical analysis: Tripoli, 

Petroleum Exploration Soc. Libya, 81 p.

Peterson, J. A., 1972, Jurassic System, in Geologic atlas of the 

Rocky Mountain region, United States of America: Rocky 

Mtn. Assoc. Geologists, p. 177-189.

Peterson, J. A., and Osmund, J. C., eds., 1961, Geometry of 

sandstone bodies — A symposium, 45th Ann. Mtg., Atlantic City, N. J., 1960: Tulsa, Okla., Am. Assoc. Petroleum 

Geologists, 240 p.

Petrov, M. P., 1961, Geographic explorations in the deserts of 

Central Asia: U.S. Joint Publications Research Service 

JPRS 9221, 31 p. [Technical translation from Russian.]

___1962, Types de deserts de 1'Asie centrale: Annales de 

Geographic, no. 384, v. 71, p. 131 -155.

___ 1966, The Ordos, Alashan and Peishan, v. 1 of The 

deserts of Central Asia: U.S. Joint Publications Research 

Service JPRS 39,145, p. 241 -260. [Translated from Russian.]

____1967, The Hoshi Corridor, Tsaidam and Tarim Basin, v.

2 of The deserts of Central Asia: U.S. Joint Publications

Research Service JPRS 42,772, 335 p. [Translated from

Russian.] 

Pettijohn, F. J., Potter, P. E., and Siever, Raymond, 1972, Sand

and sandstone: Berlin, New York, Springer-Verlag, 618 p. 

Poldervaart, Arie, 1955, Kalahari sands: Pan-African Cong. on

Prehistory, 3rd, Livingstone, Northern Rhodesia, 1955, p.

106 -114. 

Poole, F. G., 1962, Wind directions in late Paleozoic to middle

Mesozoic time on the Colorado Plateau, in Short papers in

geology, hydrology, and topography: U.S. Geol. Survey

Prof. Paper 450-D, p. D147-D151. 

___ 1964, Palaeowinds in the Western United States, in A.

E. M. Nairn, ed., Problems in palaeoclimatology: NATO

Palaeoclimates Conf., Univ. Newcastle-upon-Tyne and

Durham, England, 1963, Proc.; New York, Interscience

Publishers, p. 394-405 [1965]. 

Powers, R. W., Ramirez, L. F., Redmond, C. D., and Elberg, E.

L., Jr., 1966, Geology of the Arabian Peninsula — Sedimentary geology of Saudi Arabia: U.S. Geol. Survey Prof.

Paper 560-D, 147 p. 

Pramanik, S. K., 1952, Hydrology of the Rajasthan Desert —

Rainfall, humidity, and evaporation, in Symposium on

the Rajputana Desert, India, 1952, Proc.: India Natl. Inst.

Sci. Bull. 1, pt. 4, Meteorology and Hydrology, p. 183-197. 

Prescott, J. R. V., and White, H. P., 1960, Sand formations in the

Niger Valley between Niamey and Bourem: Geog. Jour., v.

126, pt. 2, p. 200-203. 

Price, W. A., 1950, Saharan sand dunes and the origin of the

longitudinal dunes — A review: Geog. Rev., v. 40, no. 3, p.

462 -465. 

Pryor, W. A., 1971a, Petrology of the Permian Yellow Sands of

northeastern England and their North Sea basin

equivalents: Sed. Geology, v. 6, p. 221 -254. 

___ 1971b, Petrology of the Weissliegendes sandstones in

the Harz and Werra-Fulda areas, Germany: Geol.

Rundschau, v. 60, no. 2, p. 524-551. 

___ 1973, Permeability-porosity patterns and variations in

some Holocene sand bodies: Am. Assoc. Petroleum 

Geologists Bull., v. 57, no. 1, p. 162-189.

Qadri, S. M. A., 1957, Wind erosion and its control in Thar, in 

Food and Agricultural Council of Pakistan and UNESCO, 

Symposium on soil erosion and its control in the arid and 

semiarid zones, Karachi, Nov. 1957: p. 169 -184.

Raisz, Erwin, 1952, Landform map of North Africa: Boston 

[Mass.], 02114, 130 Charles St., scale 1:3,801,600.

Ramirez, L. F., Elberg, E. L., Jr., and Helley, H. H., 1963a, 

Geologic map of the south central Rub' al Khali quadrangle, Kingdom of Saudi Arabia: U.S. Geol. Survey Misc. 

Geol. Inv. Map I-219A, scale 1:500,000.

___1963b, Geologic map of the southeastern Rub' al Khali 

quadrangle, Kingdom of Saudi Arabia: U.S. Geol. Survey 

Misc. Geol. Inv. Map I-220A, scale 1:500,000.

Range, Paul, 1927, Geologie der Kiistenwuste Sudwestafrikas 

zwichen dem Kuiseb und der Luderitzbucht — Eisenbahn: 

Internet. Geol. Cong., 14th, Madrid, 1926, Comptes Rendus, v. 3, p. 901 -905.

Ratner, Benjamin, 1950, A method for eliminating directional 

bias in wind roses: Monthly Weather Review, v. 78, no. 10, 

p. 185 -188.

Rao, K. N., 1958, Some studies on rainfall of Rajasthan with 

particular reference to trends: Indian Jour. Meteorology 

and Geophysics, v. 9, no. 2, p. 97 -116.

Rawson, R. R., and Turner, C. E., 1974, The Toroweap Formation — A new look, in T. N. V. Karlstrom, G. A. Swann, 

and R. L. Eastwood, eds., Geology of northern Arizona, 

with notes on archaeology and paleoclimate, pt. 1 of 

Regional studies: Geol. Soc. America Rocky Mtn. Sec. 

[Guidebook 27, pt. 1], p. 155-190.

Read, C. B., 1951, Stratigraphy of the outcropping Permian 

rocks around the San Juan Basin, in New Mexico Geol. 

Soc. Guidebook 2d Field Conf., The south and west sides 

of the San Juan Basin, New Mexico and Arizona, 1951: p. 

80-84.
418 A STUDY OF GLOBAL SAND SEAS

Read, C. B., and Wanek, A. A., 1961, Stratigraphy of outcropping Permian rocks in parts of northeastern Arizona and 

adjacent areas: U.S. Geol. Survey Prof. Paper 374-H, 10 p.

Reiche, Parry, 1938, An analysis of cross-lamination — The 

Coconino sandstone: Jour. Geology, v. 46, no. 7, p. 

905 -932.

Reineck, H. E., and Singh, I. B., 1973, Depositional sedimentary 

environments with reference to terrigenous elastics: New 

York, Heidelberg, Berlin, Springer-Verlag, 439 p.

Reynolds, M. W., Ahlbrandt, T. S., Fox, J. E., and Lambert, P. 

W., 1975, Description of selected drill cores from Paleozoic 

rocks, Lost Soldier oil field, south-central Wyoming; pt. I, 

Wells 114A; tract 13, C-128; tract 4, C-14; tract 10, T-l; 

tract 10, C-2: U.S. Geol. Survey Open-File Rept. 75-662, 

73 p.

___1976, Description of selected drill cores from Paleozoic 

rocks, Wertz oil field, south-central Wyoming; pt. I, Wells 

27 ABC; 46 ABC&E; 42 B; West Wertz 2: U.S. Geol. Survey 

Open-File Rept. 76-377, 56 p.

1977, Preliminary description of cores from selected

wells, Wertz oil field, south-central Wyoming; pt. 2: U.S. 

Geol. Survey Open-File Rept.

Reynolds, M. W., and Fox, J. E., 1973, Description of selected 

drill cores from Paleozoic and Precambrian rocks, Lost 

Soldier oil field, south-central Wyoming; pt. II, wells tract 

11, T-l; 109A; tract 13, C-115; 103; tract 13, C-127; tract 

14, T -11; tract 9, M-l; U.S. Geol. Survey Open-File Rept. 

76 -64, 50 p.

Rice, C. M., 1951, Dictionary of geological terms (exclusive of 

stratigraphic formations and paleontologic genera and 

species): Ann Arbor, Mich., Edwards Bros., 465 p.

Ries, Heinrich, and Conant, G. D., 1931, The character of sand 

grains: Am. Foundrymen's Assoc. Trans., v. 2, no. 10, p. 

353-392.

Rigby, J. K. and Hamblin, W. K., eds., 1972, Recognition of ancient sedimentary environments: Soc. Econ. Paleontologists and Mineralogists Spec. Pub. 16, 340 p.

Rittenhouse, Gordon, 1971, Pore-space reduction by solution 

and cementation: Am. Assoc. Petroleum Geologists Bull., 

v. 55, no. 1, p. 80-91.

Rogers, A. W., 1934, The build of the Kalahari: South African 

Geog. Jour., v. 17, p. 3-12.

____1936, The surface geology of the Kalahari: Royal Soc. 

South Africa Trans., v. 24, p. 57-80.

Rogers, John, and Tankard, A. J., 1974, Surface textures of some 

quartz grains from the west coast of southern Africa: 

Southern Africa Electron Microscopy Soc. Proc., v. 4, p. 

55 -56.

Roy, B. B., 1969, Technical report — Progress of research, in 

Central Arid Zone Research Inst., Jodhpur, Ann. Rept.: p. 

12 -20.

Royal Navy and South African Air Force, 1944, Introduction; 

The west coast of Africa from River Congo to Olifants 

River, with an appendix on the climates of St. Helena and 

Tristan da Cunha, pt. 1, in Weather on the coasts of 

southern Africa, v. 2: p. iii-viii; pt. 1, p. 1-61.

Rumney, G. R., 1968, Climatology and the world's climates: 

New York, Macmillan Co., 656 p.

Sagan, C., Veverka, J., Fox, P., and others, 1973, Variable

features on Mars, 2, Mariner 9 global results: Jour. Geophys. Research, v. 78, no. 20, p. 4163-4196.

Sahu, B. K., 1964, Depositional mechanisms from the size 

analysis of clastic sediments: Jour. Sed. Petrology, v. 34, 

no. 1, p. 73-83.

Salamuni, Riad, and Bigarella, J. J., 1967, The Botucatu Formation, in J. J. Bigarella, R. D., Becker, and I. D., Pinto, eds., 

Problems in Brazilian Gondwana geology: Internal. Symposium on the Gondwana Stratigraphy and Paleontology, 

1st, Mar del Plata, 1967, p. 197-206.

Schiffers, Heinrich, 1971, Die Sahara und ihre Randgebiete; 

Darstellung eines Naturgrossraumes Gesamtbearbeitung, 

Bd. 1, Physiogeographie: Munich, Weltforum Verlag, 

674 p.

Schlee, John, Uchupi, Elazar, and Trumbull, J. V. A., 1964, 

Statistical parameters of Cape Code beach and eolian 

sands, in Geological Survey research 1964: U.S. Geol. 

Survey Prof. Paper 501 -D, p. D118-D122.

Schuchert, Charles, 1918, On the Carboniferous of the Grand 

Canyon of Arizona: Am. Jour. Sci., 4th ser., v. 45, p. 

347-361.

Schulze, R. R., 1965, General Survey, pt. 8 o/ Climate of South 

Africa: South Africa Weather Bur. Pub. WB 28, 322 p.

____ 1972, South Africa, chap. 15, in H. E. Lansburg, ed., 

World survey of climatology, climates of Africa, v. 10: 

Amsterdam, New York, London, Elsevier Publishing Co., 

p. 501 -586.

Seely, M. K., and Sandelowsky, B. H., 1974, Dating the regression of a river's end point: South Africa Archeological Soc. 

Bull., Goodwin Series no. 2, p. 61 -64.

Selley, R. C., 1968, A classification of paleocurrent models: 

Jour. Geology, v. 76, no. 1, p. 99-110.

____ 1970, Ancient sedimentary environments — A brief 

survey: Ithaca, N.Y., Cornell Univ. Press, 237 p.

Seth, S. K., 1963, A review of evidence concerning changes of 

climate in India during the protohistorical and historical 

periods, in Changes of climate: UNESCO and World 

Meteorol. Organization Symposium, Rome, 1961, Proc., 

Arid Zone Research [v.] 20, p. 443^454.

Sevon, W. D., 1966, Distinctions of New Zealand beach, dune, 

and river sands by their grain-size distribution characteristics: New Zealand Jour. Geology and Geophysics, v. 9, 

p. 212-223.

Sharp, R. P., 1963, Wind ripples: Jour. Geology, v. 71, no. 5, p. 

617-636.

____ 1966, Kelso dunes, Mohave Desert, California: Geol. 

Soc. America Bull., v. 77, no. 10, p. 1045-1073.

Shea, J. H., 1974, Deficiencies of clastic particles of certain 

sizes: Jour. Sed. Petrology, v. 44, no. 4, p. 985 —1003.

Shepard, F. P., and Young, Ruth, 1961, Distinguishing between 

beach and dune sands: Jour. Sed. Petrology, v. 31, no. 2, p. 

196-214.

Shergold, J. H., Druce, E. C., Radke, B. M., and Draper, J. J., 

1976, Cambrian and Ordovician stratigraphy of the eastern 

portion of the Georgina Basin, Queensland and eastern 

Northern Territory: Internat. Geol. Gong., 25th, Australia, 

1976, Field Excursion 4C Guidebook, 54 p.

Sherzer, W. H., and Grabau, A. W., 1909, The Sylvania 

Sandstone; its distribution, nature and origin, chap. Ill, in
SELECTED REFERENCES 419

A. W. Grabau and W. H. Sherzer, The Monroe formation 

of southern Michigan and adjoining regions: Michigan 

Geol. and Biol. Survey Pub. 2, p. 61-86.

Shotton, F. W., 1937, The Lower Hunter sandstones of north 

Worcestershire and east Shropshire [England]: Geol. Mag. 

no. 882, v. 74, no. 12, p. 534-553.

____ 1956, Some aspects of the New Red desert in Britain: 

Liverpool and Manchester Geol. Jour., v. 1, pt. 5, p. 

450^65.

Simons, F. S., 1956, A note on Pur-Pur dune, Viru Valley, Peru: 

Jour. Geology, v. 64, no. 5, p. 517-521.

Singh, S., Ghose, B., and Vats, P. C., 1972, Genesis, orientation, 

and distribution of sand dunes in arid and semi-arid 

regions of India: Central Arid Zone Research Inst, 

Jodhpur, Ann. Rept., p. 50-53.

Sinitsyn, V. M., 1959, Tsentralnaya Aziya: Moscow, Gosudar. 

Izd. Geog. Lit., 456 p.

Smith, D. B., 1972, The Lower Permian in the British Isles, in 

Horst Falke, ed., Rotliegend — Essays on European Lower 

Permian: Leiden, Netherlands, E. J. Brill & Co., p. 1 -33.

Smith, D. B., and Francis, E. A., 1967, Geology of the country 

between Durham and West Hartlepool [England]: Great 

Britain Geol. Survey Mem., 354 p.

Smith, H. T. U., [1943], Aerial photographs and their applications: New York, D. Appleton-Century Co., 372 p.

____1946, Sand dunes: New York Acad. Sci. Trans., ser. 2, v. 

8, no. 6, p. 197-199.

____1953, Classification of sand dunes [abs.], in Deserts actuels et anciens: Internat. Geol. Gong., 19th, Algiers, 1952, 

Comptes Rendus, sec. 7, p. 105. [In English.]

____ 1956, Giant composite barchans of the northern Peruvian deserts [abs.]: Geol. Soc. America Bull., v. 67, no. 12, 

pt. 2, p. 1735.

____ 1963, Eolian geomorphology, wind direction, and 

climatic change in North Africa — final report: U.S. Air 

Force Cambridge Research Lab., Geophysics Research 

Directorate [Contract AF 19(628)-298], AFCRL-63^43, 

49 p.

____1965, Dune morphology and chronology in central and 

western Nebraska: Jour. Geology, v. 73, no. 4, p. 557-578.

____ 1968, Nebraska dunes compared with those of North 

Africa and other regions, in C. B. Schultz and J. C. Frye, 

eds., Loess and related eolian deposits of the world: Internat. Assoc. Quaternary Resarch Gong., 7th, Colorado, 

U.S.A., 1965, Proc., v. 12, p. 29 -47.

____ 1969, Photo-interpretation studies of desert basins in

northern Africa — Final report (pt. 1), March 1963-July 

1968: U.S. Air Force Cambridge Research Lab., 

AFCRL-68-0590, 60 p.

Snead, R. E., and Frishman, S. A., 1968, Origin of sands on the 

east side of the Las Bela valley, West Pakistan: Geol. Soc. 

America Bull., v. 79, no. 11, p. 1671 -1676.

South African Weather Bureau, 1960, Climate of South Africa; 

pt. 6, Surface winds: Pretoria, 202 p.

Stanley, K. O., Jordan, W. M., and Dott, R. H., Jr., 1971, New hypothesis of Early Jurassic paleogeography and sediment 

dispersal for Western United States: Am. Assoc. 

Petroleum Geologists Bull., v. 55, no. 1, p. 10-19.

Steidtmann, J. R., 1974, Evidence for eolian origin of crossstratification in sandstone of the Casper Formation, 

southernmost Laramie Basin, Wyoming: Geol. Soc. 

America Bull., v. 85, no. 12, p. 1835-1842.

Stokes, W. L., 1961, Fluvial and eolian sandstone bodies in Colorado Plateau, in J. A. Peterson and J. C. Osmond, eds., 

Geometry of sandstone bodies — A symposium, 45th Ann. 

Mtg., Atlantic City, N.J., April 25-28, 1960: Tulsa, Okla., 

Am. Assoc. Petroleum Geologists, p. 151 —178.

Stone, R. O., 1967, A desert glossary: Earth-Sci. Rev., v. 3, no. 4, 

p. 211 -268.

Strahler, A. N., 1958, Dimensional analysis applied to fluvially 

eroded landfonns: Geol. Soc. America Bull., v. 69, no. 3, p. 

279 -299.

Stride, A. H., 1963, Current-swept sea floors near the southern 

half of Great Britain: Geol. Soc. London Quart. Jour., v. 

119, pt. 2, no. 474, p. 175-199.

Suslov, S. P., 1961, Physical geography of Asiatic Russia 

[English translation by N. D. Gershevsky]: San Francisco, 

London, W. H. Freeman & Co., 594 p. [First published in 

Russian in Leningrad and Moscow, 1947.]

Tanner, W. F., 1964, Eolian ripple marks in sandstone: Jour. 

Sed. Petrology, v. 34, no. 2, p. 432^433.

____ 1965, Upper Jurassic paleogeography of the Four Corners region: Jout. Sed. Petrology, v. 35, no. 3, p. 564-574.

____1966, Numerous eolian ripple marks from Entrada Formation: Mtn. Geologist, v. 3, no. 3, p. 133 -134.

____ 1967, Ripple mark indicies and their uses: Sedimentology, v. 9, no. 2, p. 89-104. 

Terwindt, J. H. J., 1971, Sand waves in the southern bight of the

North Sea: Marine Geology, v. 10, no. 1, p. 51 -67. 

Thesiger, W., 1949, A further journey across the Empty

Quarter: Geog. Jour., v. 113, p. 21 -46. 

Thompson, D. B., 1969, Dome-shaped aeolian dunes in the

Frodsham Member of the so-called "Keuper" Sandstone

Formation (Scythian-?Anisian; Triassic) at Frodsham,

Cheshire (England): Sed. Geology, v. 3, no. 4, p. 263-289. 

____ I970a, Sedimentation of the Triassic (Scythian) red

pebbly sandstones in the Cheshire Basin and its margins:

Geol. Jour., v. 7, pt. 1, p. 183-261. 

____ 1970b, The stratigraphy of the so-called "Keuper"

Sandstone Formation (Scythian-?Anisian) in the PermoTriassic Cheshire Basin: Geol. Soc. London Quart. Jour., v. 

126, p. 151-181.

Thompson, M. L., and Thomas, H. D., 1953, Systematic paleontology of fusulinids from the Casper Formation: Wyoming 

Geol. Survey Bull. 46, pt. 2, p. 15 -56.

Thompson, W. O., 1949, Lyons sandstone of Colorado Front 

Range: Am. Assoc. Petroleum Geologists Bull., v. 33, no. 1, 

p. 52-72.

____1954, Lyons sandstone in Denver basin [Colo.] [abs.]: 

Am. Assoc. Petroleum Geologists Bull., v. 38, no. 6, p. 

1311.

Tieje, A. J., 1923, The redbeds of the Front Range in Colorado— A study in sedimentation: Jour. Geology, v. 31, 

no. 3, p. 192-207.

Tillman, R. W., 1971, Multiple group discriminant analysis of 

grain size data as an aid in recognizing environments of 

deposition: Internat. Sedimentological Gong., 8th, 

Heidelberg, Program with Abs., p. 102.
420 A STUDY OF GLOBAL SAND SEAS

Trask, P. D., 1931, Compaction of sediments: Am. Assoc. 

Petroleum Geologists Bull., v. 15, no. 3, p. 271 -276.

Tricart, Jean, 1959, Geomorphologie dynamique de la moyenne 

vallee du Niger (Soudan): Annales Geographic, no. 368, p. 

333 -343.

____ 1965, Rapport de la mission de reconnaissance 

geomorphologique de la vallee moyenne du Niger: Institut 

Francois d'Afrique Noire M6m. 72, 196 p.

Tricart, Jean, and Brochu, Michel, 1955, Le grand erg ancien du 

Trarza et du Cayor (Sud-Ouest de la Mauritanie et Nord 

du Senegal): Rev. Geomorphologie Dynam., v. 4, p. 

145 -176.

Twenhofel, W. H., 1926, Treatise on sedimentation: Baltimore, 

Md., The Williams & Wilkins Co., 661 p.

____1945, The rounding of sand grains: Jour. Sed. Petrology, 

v. 15, no. 2, p. 59-71.

Twidale, C. R., 1972, Evolution of sand dunes in the Simpson 

Desert, central Australia: Inst. British Geographers Pub. 

56, [reprinted from Trans., July 1972], p. 77—169.

Udden, J. A., 1898, The mechanical compositions of wind 

deposits: Augustana Library Pub., no. 1, 69 p.

____ 1914, Mechanical composition of clastic ^sediments: 

Geol. Soc. America Bull., v. 25, p. 655-744.

U.S. Air Force [MATS], 1956, Aeronautical chart 541, Sebha 

Oasis, Algeria-Libya.

U.S. Army Air Forces Weather Division, 1945, Weather and climate of China, Pts. A and B: Rept. 890; U.S. Air Weather 

Service Tech. Rept. 105-34.

U.S. Geological Survey, 1963, Map of the Arabian Peninsula: 

U.S. Geol. Survey Misc. Geol. Inv Map 1-270 B-2, scale 

1:200,000.

U.S. Naval Weather Service, 1967, World-wide airfield summaries — Middle East: Asheville, N.C., U.S. Natl. Weather 

Records Center, v. 2, pt. 1, p. 1 -334; v. 2, pt. 2, p. 335 -698.

_____1968, World-wide airfield summaries — Africa (northern half): Asheville, N.C., U.S. Natl. Weather Records 

Center, v. 9, pt. 1, 559 p.

______I974a, World-wide airfield summaries — China, North

Korea, Mongolia: Asheville, N.C., U.S. Natl. Weather 

Records Center, v. 12, pt. 1, 371 p.; v. 12, pt. 2, 322 p.

____ I974b, World-wide airfield summaries — Middle East:

Asheville, N.C., U.S. Natl. Weather Records Center, v. 2, 

pt. 2, 338 p.

U.S. Weather Bureau and U.S. Army Air Forces, 1944, Northern Africa: U.S. Weather Bureau Prelim. Rept. 41, p. 1 —23.

Urvoy, Y., 1935, Terasses et changements de climat quaternaires a Test du Niger: Annales de Geographic, v. 44, no. 

249, p. 254-263.

____1942, Les bassins du Niger; etude de geographic physique et de pa!6ogeographie: Institute Francais de L'Afrique 

Noire, Mem. no. 4, 141 p.

Vail, C. E., 1917, Lithologic evidence of climatic pulsations: 

Science, New Ser., v. 46, p. 90-93.

Van de Kamp, P. C., 1973, Holocene continental sedimentation 

in the Salton basin, California — A reconnaissance: Geol. 

Soc. America Bull., v. 84, no. 3, 827-848.

Verstappen, H. T., 1966, Landforms, water, and land use west 

of the Indus Plain: Nature and Resources, v. 2, no. 3, p. 

6-8.

__1968a, On the origin of longitudinal (seif) dunes: 

Zeitschr. Geomorphologie, v. 12, no. 2, p. 200-220.

__ 1968b, Geomorphology at the Central Arid Zone 

Research Institute, India: Nature and Resources, v. 4, no. 3, 

p. 6-9.

. 1970, Aeolian geomorphology of the Thar Desert and

paleo-climates, in Piedmont plains and sand-formations in 

arid and humid tropic and subtropic regions: Zeitschrift 

fur Geomorphologie, supp. v. 10, p. 104 —120.

Verstappen, H. T., and van Zuidam, R. A., 1970, Orbital 

photography and the geosciences — A geomorphological 

example from the Central Sahara: Geoforum, v. 2, p. 

33^7.

Visher, G. S., 1971, Depositional processes and the Navajo 

Sandstone: Geol. Soc. America Bull., v. 82, no. 5, p. 

1421 -1423.

Wadia, D. N., 1939, Geology of India: London, Macmillan and 

Co., 460 p.

____1953, Geology of India [3d ed.]: London, Macmillan and 

Co., 531 p.

Walker, T. R., 1967, Formation of red beds in modern and ancient deserts: Geol. Soc. America Bull., v. 78, no. 3, p. 

353-368.

____1976, Diagenetic origin of continental red beds, in Horst 

Falke, ed., The continental Permian in west, central and 

south Europe: NATO Advanced Study Inst., Mainz, Germany, 1975, Proc., p. 240-282.

Walker, T. R., and Crone, A. J., 1974, Mechanically-infiltrated 

clay matrix in desert alluvium: Geol. Soc. America Abs. 

with Programs, v. 6, no. 7, p. 998.

Walker, T. R., and Harms, J. C., 1972, Eolian origin of flagstone 

beds, Lyons Sandstone (Permian), type area, Boulder 

County, Colorado, in Environments of sandstone, carbonate, and evaporite deposition: Mtn. Geologist, v. 9, no. 2 -3, 

p. 279-288.

Walker, T. R., and Honea, R. M., 1969, Iron content of modern 

deposits in the Sonoran desert — A contribution to the 

origin of red beds: Geol. Soc. America Bull., v. 80, no. 3, p. 

535 -543.

Wellington, C. E., 1968, A method of reducing observing and 

procedure bias in wind-direction frequencies: Meteorological Mag., v. 97, no. 1155, p. 293 -302.

Walther, Johannes, 1888, [Uber] Ueber Ergebnisse einer 

Forschungsreise auf der Sinaihalbinsel und in der 

Arabischen Wiiste: Berlin Gesellschaft fur Erdkunde 

Verh., 15, p. 244-255.

Warren, Andrew, 1969, A bibliography of desert dunes and 

associated phenomena, in W. G. McGinnies and B. J. Goldman, eds., Arid lands in perspective: Am. Assoc. Adv. Sci. 

and Arizona Univ. Press, p. 75 -99.

____1970, Dune trends and their implications in the central 

Sudan, in Piedmont plains and sand-formations in arid 

and humid and subtropic regions: Zeitschrift fiir Geomorphologie, supp. v. 10, p. 154—180.

____1972, Observations on dunes and bi-modal sands in the

Tenere Desert: Sedimentology, v. 19, no. 1-2, p. 37-44. 

Washburne, C. W., 1930, Petroleum geology of the State of Sao 

Paulo, [Brazil]: Sao Paulo Commisab Geog. e Geol. 

Boletfm 22, 272 p.
SELECTED REFERENCES 421

Weimer, R. J., and Land, C. B., Jr., 1972, Lyons Formation (Permian), Jefferson County, Colorado — A fluvial deposit, in 

Environments of sandstone, carbonate, and evaporite 

deposition: Mtn. Geologist, v. 9, no. 2-3, p. 289-297.

Wellington, J. H., 1955, Southern Africa — A geographical 

study: v. 1, Physical geography: London, Cambridge Univ. 

Press, 528 p.

Wentworth, C. K., 1932, The mechanical composition of sediments in graphic form: Iowa Univ. Studies in Natural 

History, v. 14, no. 3, 127 p.

White, L, P., 1971, The ancient erg of Hausaland in southwestern Niger: Geog. Jour., v. 137, pt. 1, p. 69-73.

Wilks, S. S., 1962, Mathematical statistics: New York, John 

Wiley & Sons, 644 p.

Williams, G. E., 1968, Formation of large-scale trough crossstratification in a fluvial environment: Jour. Sed. 

Petrology, v. 38, p. 136-140.

Wills, L. J., 1948, The paleogeography of the Midlands: London, 

Hodder and Stoughton, Ltd., 144 p.

____ 1956, Concealed coalfields — A paleogeographical 

study of the stratigraphy and tectonics of mid-England in 

relation to coal reserves: London, Glasgow, Blackie and 

Son,208 p.

Wilson, I. G., I971a, Desert sandflow basins and a model for the 

development of ergs: Geog. Jour., v. 137, pt. 2, p. 180—199.

____ 197lb, Journey across the Grand Erg Oriental: Geog. 

Mag., v. 43, p. 264-270.

____ 1972, Aeolian bedforms — Their development and

.1973, Ergs: Sed. Geology, v. 10, no. 2, p. 77-106.

origins: Sedimentology, v. 19, no. 3-4, p. 173-210.

Wilson, R. F., 1958, The stratigraphy and sedimentology of the 

(Jurassic) Kayenla and (?Triassic) Moenave formations, 

Vermilion Cliffs region, Utah and Arizona: Stanford Univ. 

unpub. Ph. D. thesis, 167 p.

Wopfner, H., and Twidale, C. R., 1967, Geomorphological 

history of the Lake Eyre basin, in J. N. Jennings and J. A. 

Mabbutt, eds., Landform studies from Australia and New 

Guinea: Cambridge [England] Univ. Press, p. 119-143.

Yaalon, D. H., and Ganor, E., 1973, The influence of dust on 

soils during the Quaternary: Soil Sci., v. 116, p. 146-155.

Yakubov, T. F., and Bespalova, R. Y., 1961, Soil-formation 

processes during the invasion of sands by plants in the 

northern deserts of the Caspian region: Soviet Soil Sci., no. 

6, p. 651 -658.

Yu, Shou-chung, Li, Po, Ts'ai, Wei-ch'i and T'an, Chien-an, 

1962, A survey o\' the Gobi of western Inner Mongolia and 

Pa Tan Chi Lin desert, in Academia Sinica Sand Control 

Group, eds., Resetarch on sand control: U.S. Joint Publications Research Service JPRS 19993, Tech. Trans. 

63-31183, p. 244-276.

Zaychikov, V. T., [ed.], and others, 1965, The physical geography of China: U.S. Joint Publications Research Service 

JPRS 32,119, TT 65-32612, 634 p. [Technical translation 

from Russian.]

Zingg, A. W., 1953, \Vind tunnel studies of the movement of 

sedimentary material, in J. S. McNown and M. C. Boyer, 

eds., Hydraulics Conf., 5th, Iowa [U.S.A.], 1952, Proc.: 

Iowa Univ., p. 111 -135.

A STUDY OF GLOBAL SAND SEAS

INDEX

[Italic page numbers indicate major references]

Abiekwasputs, Africa ...............

Acacia sp. ..........................

Ad Dahna'..........................

Africa. See Abiekwasputs, Cave Sandstone, Dwyka Group, Kalahari Desert, Karroo System, Mariental, Nambi 

Desert, Pelican Point, Upington. 

See also individual countries.

AgriophyUum sp. ....................

Akjoujt, Mauritania, linear dune in....

Al Haruj al Asway, Libya ............

Al Uruq al MuHaridah, crescentic dune

Page

355

358

362, 368

386, 389

261

79

362

68

381

152, 155

267

275

Al Uwaynat, Libya...............

Ala Shan Desert, China ..........

barchanoid dune in..........

crescentic dune in ..........

star dune in ................

Algeria. See Beni Abbes; Bordj Omar 

Driss; Erg Irarrarene; 

Grand Erg Occidental; 

Grand Erg Oriental; 

Hassi Messaoud; Sahara, 

northern. 

Algodones Dunes, California ......... 267

Alluvial fans ................. 27, 122, 221, 386

sand ........................... 27

sediments, unconsolidated ....... 29

Alluvium ........................... 376

modern ........................ 72

Alteration, mineral, as cause of red pigment .................. 65

postdepositional chemical ....... 191

Aluminum silicates .................. 69

An Nafud, Saudi Arabia ............. 363, 368

crescentic dune in .............. 275

Analysis, discriminant............... 31, 55

energy-dispersive X-ray ......... 68

linear .......................... 57

linear regression................ 143

regression...................... 262

of ripple marks, in Coconino Sandstone .................. 200

scanning electron microscope .... 68

whole phi ...................... 56

X-ray diffraction................ 68

Anhydrite .......................... 196, 225

Antarctica. See Victoria Valley. 

Aoukar dunes, Sahara desert, transverse dune in........... 271

Aoukar sand seas, crescentic dune in

................... 310, 313, 317

Apocynum hendersonii..........

Aprons ........................

Arabian sand seas ............

barchan dune in ..........

crescentic dune in ........

dome dune in ..............

hooked dune in............

linear dune in.............

star dune in ..............

Arenites, feldspathic, of Zambia

Page

389

104

362

363 

362 

362 

367 

362 

362 

190 

Aristida sp. ..................... 336, 340, 386

Arkose, in Casper Formation ......... 221

in Lyons Sandstone .............. 217

Arroyos ............................ 196

Artemisia sp. ....................... 389

Atar, Mauritania, linear dune in...... 261

Atlanticum Period ................... 377

Augite ............................. 65, 69, 79

Australia. See Giles, Great Sandy Desert, Great Victoria Desert, Oodnadatta, Simpson Desert. 

Australian dunes, clay coatings on sand

of ..................... 72

Avalanches, wet .................... 133

Avalanching ............... 103, 122, 133, 192,

200, 218, 232, 258

Aztec Sandstone, Nevada and California .................... 190, 209

B

Bahama Islands, carbonate sands in .. 24

Bairdestheria barbosai .............. 235

Bajirs .............................. 282

Barra do Sul, Brazil, dome dune in .... 99

Barun Goyot Formation, Mongolia .... 190, 230

contorted bedding in ............ 231

feldspar in ..................... 231

interdune deposit in ............. 230, 232

quartz in ....................... 231

stratification in ................. 231

transverse ridge dune in ......... 223

Basin, interior desert................ 215

sinking ......................... 191, 196

Beach sands ........................ 55

Bedding, contorted .................. 112, 189

in Barun Goyot Formation........ 231

in Casper Formation............. 223

in Coconino Sandstone ........... 201

in Navajo Sandstone ............ 213

penecontemporaneous contorted,

in Navajo Sandstone .... 216

Bedforms, categorized ............... 173

Bedrock, in Libya .................... 65,72

Beni Abbes, Algeria, star dune in .....

Berg Winds .........................

Bilma, Niger, linear dune in ..........

Blowout. See Dune, blowout.

Bonito Canyon ......................

Bordj Omar Driss, Algeria, star dune

Botucatu Sandstone, Brazil....... 190,

stratification in .................

Brady field .........................

Brazil, coastal dune in................

interdune structure in ...........

studies in.......................

See also Cabo Frio, Florinopolis, 

Guairamar, Jardim Sao 

Pedro, Joaquina Beach, 

Joaquina Hill, Lagoa dune 

field, Parana Basin, Porto 

Novo, Praia do Leste, 

Sambaiba Sandstone, 

Santa Caterina. 

Break-aparts .......................

Breccias ...........................

Buckhorn Wash, Utah ...............

Bushveld Sandstone, Transvaal. See 

Cave Sandstone.

Cabo Frio, Brazil, parabolic dune in... 

Caiua Sandstone ....................

Calcite .............................

Caliche .............................

carbonate ......................

gypsum ........................

zones ..........................

CaUigonum sp. ......................

Candonopsis pyrrformis candona......

Canyon De Chelly ...................

Carbonate ..........................

caliche .........................

clast ...........................

sands, in Bahama Islands ........

Cargana microphylia ................

Carmel Sea .........................

Casper Formation, Wyoming...... 190,

contorted bedding in ............

feldspar in .....................

festoon structures in ............

interdune deposits in ............

limestone in ....................

orthoquartzite in ................

quartz in .......................

ripple marks in .................

stratification in .................

Page

142, 167

352

164

206

169

197, 233

235

243

6, 24, 30

109

89

112

112,121

212

95

234

191, 211

376

67

67

66

340, 389

235

205

78

67

67

24

389

215

195,221

223

221

221, 222

224

221

221

221

223

222

423
424 INDEX

Casper Formation, Wyoming—Continued

trace fossils in .................. 224

Cave Sandstone, Africa .......... 190, 197, 236

barchan dune in ................ 237

feldspar in ..................... 237

parabolic dune in ............... 237

quartz in ....................... 237

ripple marks in ................. 238

stratification in ................. 237

tracks of vertebrate animals in... 237 

transverse dune in .............. 237

Cenozoic ........................... 190

"Chain of stars" .................... 13

Chalcedony ......................... 212

Chemical alteration, postdepositional. 191 

Cherchen Desert, China, barchanoid

dune in ................ 154

crescentic dunes in.............. 381

Chert .............................. 191

Cheshire Basin, England ............. 197

Chevron ............................ 24, 381

China. See Ala Shan Desert, Cherchen 

Desert, Mao-Mu, Pa-tanchi-lin Sha-mo, Takla 

Makan Desert. 

Classification, dune ................... 4, 8, 89

Clast, carbonate .................... 67

Clastic material..................... 23

sands .......................... 24, 72

Clay ..................... 23, 67, 123, 196, 226

authigenic...................... 225

coatings, on sand................ 69, 78

of Australian dunes ......... 72

Climate, of Arabian Sand Seas ........ 371

effect on dune color ............. 64, 67

effect on dune formation.. 78,106,122,169 

of Kalahari Desert .............. 360

of Namib Desert ................ 352

of northern Sahara .............. 327, 341

of Sahel........................ 322

of southern Sahara .............. 322

of Takla Makan Desert.......... 391

of Thar Desert.................. 381

of western Sahara .............. 314

Coconino County, Arizona, barchan

dune in ................ 90

Coconino Sandstone, Arizona ....... 3, 190, 197

contorted bedding in ............ 201

rain pits in ..................... 200

ripple marks in ................. 199

slump marks in ................. 200

stratification in ................. 199

trails of invertebrate animals .... 202

Colloidal material ................... 127

Colluvium .......................... 123

Colorado Plateau .................... 190, 243

Colorado River delta, fluvial sand in... 30 

Conchostraca assemblage, of Santana

facies, Botucatu ........ 235

Corispermum sp. .................... 386

Cornulaca sp........................ 340

Couloirs ............................ 282

Cow Springs Sandstone .............. 190

Cretaceous .................. 65, 233, 338, 389

Early .......................... 225

Late ........................... 190, 231

sedimentary rocks .............. 65

Upper.......................... 230

Cross-strata ............... 5, 87, 189, 199, 206,

212,218,226,227,229 

lenticular ...................... 192

Page

Cross-strata—Continued

trough ......................... 192, 221

tubular-planar .................. 97, 99

Cyperaceae......................... 122

D

Data, quarter phi grain-size .......... 24, 55

surface wind ................... 141

whole phi ...................... 56

De Chelly Sandstone ................. 190, 204

feldspar in ..................... 205

interdune deposit in ............. 197, 206

orthoquartzite in................ 205

ripple marks in ................. 207

stratification in ................. 206

trails of invertebrate animals in .. 207 

transverse dune in .............. 197

Defiance uplift...................... 208

Deposits, accretion .................. 103

alluvial ........................ 228

fan ........................ 196

avalanche ...................... 112

carbonate ...................... 66

See also Caliche, 

flood plain...................... 196

fluvial ......................... 23

fluviatile .................... 27, 191, 196

glacial ......................... 236

glaciofluviatile ................. 27

impermeable ................... 23

inland dune..................... 55

interdune................. 23, 87,107, 191

in Barun Goyot Formation ... 230, 232 

in Casper Formation ........ 224

in De Chelly Sandstone ...... 197, 206

in Fezzan .................. 55, 109

in Lyons Sandstone ......... 218

in Navajo Sandstone .... 209, 212, 214

in Rotliegendes ............. 225

in White Sands National Monument ................. 109, 206

See also Interdune area, 

lacustrine ...................... 191, 196

lag ........... 191, 194, 218, 221, 225, 389

marine ..................... 191, 196, 209

permeable...................... 23

river channel................... 196

sedimentary .................... 219

serir ........................... 24, 216

stream ......................... 209, 219

subaqueous ................... 3, 233, 243

Detritus ........................ 109, 193, 196

arkosic......................... 219

Dinosaur remains ....... 193, 209, 214, 230, 232

Dolomite ........................... 225

Dome-shaped dunes. See Dunes, dome.

Doney Crater, Arizona ............... 201

Drift potential.......... 146, 150, 316, 325, 345,

353,362,374,376,391 

associated with barchanoid dunes 152 

associated with linear dunes ..... 155

associated with star dunes ....... 165

Dune ................................. 4, 8, 89

barchan ..... 9, 24, 28, 88, 89, 141,151, 258

in Arabian sea sands ........ 363

in Cave Sandstone .......... 237

in Coconino County, Arizona . 90 

in Libyan Desert............ 269

in Namib Desert............ 153

inRub'alKhali.............. 269

Dune—Continued

barchan—Continued

in Sahara Desert......

in Sahara of Mali 

in Vallee de L'Azaouk . 

barchanoid ...............

269 

269 

317 

151 

in Ala Shan Desert.......... 152, 155

in Cherchen Desert ......... 154

in Namib Desert............ 153

in Navajo Sandstone ........ 215

in Takla Makan Desert.. 142,152, 381,

387, 389

in Thar Desert.............. 154

in Wahiba Sands. ........... 154

wind environments of....... 152

See also Dune, transverse.

barchanoid ridge, in Killpecker

dune field.............. 91

in Mao-Mu (Ting-hsin)....... 155

in White Sands National Monument ................ 90, 97, 152

blowout.................. 90, 94, 118, 192

defined .................... 11

in Lagoa dune field.......... 114

captation....................... 127

in Lagoa dune field.......... 127

climbing ....................... 24

coastal............ 24, 30, 36, 72, 194, 220

in Brazil.................... 6, 24, 30

in Lyons Sandstone ......... 220

color ........................... 7, 63

as result of airborne dust.... 63

as result of climate.......... 64, 67

as result of grain size........ 80

as result of mineral alteration 65 

as result of moisture ........ 65, 79

explanation of.............. 63

complex.........'............... 13

defined .................... 6, 260

in Namib Desert............ 346, 349

in Takla Makan Desert...... 381, 387

compound ...................... 13, 107

defined .................... 8, 260

crescentic .._............ 142, 151, 260, 265

insAl Uruq al Mu^taridah..... 362

in Ala Shan Desert. ......... 267

in An Nafud, Saudi Arabia... 275 

inAoukar sand seas ..... 310, 313, 317

in Arabian sea sands ........ 362

in Cherchen Desert, China ... 381 

defined .................... 258, 309

in Gran Desierto, Mexico .... 269

in Great Sand Dunes National

Monument ............. 269

in Nebraska Sand Hills ...... 267

in Namib Desert........ 269, 346, 349

in northern Sahara ......... 326

in Pa-tan-chi-lin Sha-mo...... 381

in Persia Gulf Coast......... 269

in Peski Karakumy. ......... 267

in Rubsal Kahali............ 362

in Sahara Desert............ 310

in southern Sahara ......... 317

in Takla Makan Desert...... 387, 389

in Thar Desert.............. 271, 375

in Vallee de L'Azaouk ....... 321

in western Sahara .......... 310, 313

See also Dune, star.

development of ................. 87

dissipation of, in Lagoa dune field 124

dome .......... 24, 28, 88, 98, 141, 260, 279
Page 

Dune—Continued

produne—Continued

in Arabian sea sands ........ 362

in Barra do Sul............. 99

in Frodsham Member ....... 197, 228

in Grand Erg Occidental..... 280

in Killpecker dune field ...... 98, 280

in Nafud as Sirr ............ 362

in Nafud ath Thuwayrat..... 362

in Nafud Shuqayyiqah ....... 362

in Parana .................. 99

in Praia do Leste ............ 99

in Santa Caterina ........... 99

in Takla Makan Desert.. 280, 381, 391 

in White Sands National Monument .............. 98, 152, 279

double barchan ................. 5

forms .......................... 260

hanging ........................ 24, 127

in Lagoa dune field,......... 127

hooked, in Arabian sea sands .... 367

immobile, in western Sahara ..... 312

inland.......................... 27, 44

linear .............. 102, 107, 109, 141, 155,

193,260,261,313,317 

in Arabian sea sands........ 362

in Akjoujt .................. 261

inAtar..................... 261

in Bilma.................... 164

defined .................... 11, 258

in Erg Bilma Region ......... 164

in Erg Hammami Region ..... 164

in Erg Makteir. ............. 142

in Fort Gouraud, ............ 156, 164

in Giles, Australia .......... 163

interdune surfaces in ....... 109

in Jabal Tuwayq ............ 368

junctures in ................ 156

in Kalahari Desert .......... 360

in Mariental................ 163

in Namib Desert ............ 346, 349

in Navajo Indian Reservation 261 

in Peski Karakumy .......... 141, 161

in Qu'amiyat ............... 367

in Rotliengendes ............ 226

inRub^al Khali.............. 260, 362

in Sabha ................... 156, 161

in Sahara Desert............ 261, 310

in Simpson Desert........... 141, 157

in southern Sahara ......... 317

in Takla Makan Desert...... 381

in Upington................. 156

in western Sahara .......... 310, 313

longitudinal, in Namib Desert.... 349

See also Dune, linear; Ridge,

linear.

massifs. See Dune, star, 

migration .............. 108, 227, 233, 367

oghurd. See Dune, star.

parabolic .............. 24, 28, 88, 94, 114,

122, 193,220,261,277 

in Cabo Frio ................ 95

in Cave Sandstone .......... 237

defined .................... 11, 259

in Indiana dunes ............ 95

in Lagoa dune field ....... 96, 114, 122

in Lyons Sandstone ......... 220

in Thar Desert........... 95, 277, 375

in White Sands National Monument .............. 95, 152, 277

produne........................ 24

INDEX

Page 

Dune—Continued

dome—Continued

pyramidal. See Dune, star.

reversing ........ 29, 88, 103, 114, 123, 195

defined .................... 12

in Great Sand Dunes National

Monument ............. 104, 195

in Kelso dune field, Mojave

Desert ................. 105

in Lagoa dune field .......... 105, 123

in Namib Desert ............ 346, 349

in Takla Makan Desert...... 389

in Victoria Valley ........... 104

in White Sands National Monument ................. 106

seif ............................ 24

in Sabha ................... 103

See aJso Dune, linear; Ridge, 

linear.

simple, defined ................. 260

linear, in Great Sandy

Desert ............. 141, 157, 163

linear, in Great Victoria

Desert ............. 141, 157, 163

linear, in Kalahari

Desert ............. 141, 156, 163

star ...... 24, 29, 88, 106, 141, 165, 261, 275

in Ala Shan Desert.......... 275

in Arabian sea sands ........ 362

in Beni Abbes .............. 142, 167

in Bordj Dinar Driss ......... 169

defined .................... 9, 259

in Erg Irarrarene ........... 169

in Ghudamis ................ 142, 165

in Gran Desierto ............ 107, 275

in Grand Erg Occidental..... 165, 326

in Grand Erg Oriental........ 107,142,

165,275,326 

in Hassi Messaoud .......... 167

in high-energy wind regime .. 142 

interdune deposits .......... Ill

in Irq as Subay ............. 277

in low-energy wind regime ... 142 

in Namib Desert........ 275, 346, 349

in northern Sahara ...... 326, 338, 341

in Ramlat as Sahama ........ 363

in Rub al Khali !* ........ 107, 275, 362

in Sierra del Rosario ........ 275

in Takla Makan Desert...... 389

in Zalim, Saudi Arabia ...... 106

stringer, in Kalahari Desert...... 359

transverse 24, 28, 88, 93, 141, 151, 191, 258 

in Aoukar dunes ............ 271

in Cave Sandstone .......... 237

in De Chelly Sandstone ...... 197

defined .................... 9

in Frodsham Member ....... 229

in Killpecker dune field ...... 94

in Namib Desert ............ 349

in Navajo Sandstone ........ 215

in Rotliegendes ............. 226

in Takla Makan Desert...... 392

in White Sands National

Monument............ 93, 97, 193

transverse ridge, in Barun Goyot

Formation ............. 233

in Namib Desert............ 153

varieties ....................... 260

Dust, airborne ...................... 73

as cause of dune color ........... 63

Dwyka Group, Africa ................ 236

425

Page

Earth Resources Technology Satellite. 

See Images, ERTS-1; Landsat-1.

Egypt. See Great Western Desert.

England. See Cheshire Basin, Frodsham 

Member of so-called Keuper Sandstone Formation, 

Keuper Sandstone, Lower 

Mottled Sandstone, 

Yellow Sands of Durham.

Entrada Sandstone ..................

Environments, depositional...........

Eolianites...........................

Ephedra sp. .........................

Epidote ....................... 65, 69,

Eragrostis sp. .......................

Erg Bilma Region, Niger, linear dune

Erg Chech, Algeria ............... 326

Erg er Raoui ........................

Erg Hammami Region, Mauritania, linear dune in ............

Erg-Iguidi...........................

Erg Irarrarene, Algeria, star dune in .. 

Erg Makteir, Mauritania, linear dune in 

Ergs................................

ERTS-1. See Images, ERTS-1; Landsat-1. 

Estheriella sp. .......................

Etjo Sandstone, South-West Africa.

See Cave Sandstone. 

Euestheria mendesi..................

Evaporites ..........................

Experiments, wave-tank .............

Extradune, defined ..................

Fans, alluvial................ 27, 122

Faults ..............................

Fauna. See Vegetation.

Feidjs ..............................

Feldspar ...........................

authigenic ......................

in Barun Goyot Formation ........

in Casper Formation.............

in Cave Sandstone ..............

in De Chelly Sandstone ..........

in Frodsham Member............

in Kalahari Desert ..............

in Lower Mottled Sandstone ......

in Lyons Sandstone..............

in Navajo Sandstone ............

in Thar Desert..................

Feldspathic sand ....................

Killpecker dune field ............

Lyons Sandstone ................

Ferric hydrate......................

See also Limonite. 

Ferromagnesian silicate minerals.....

alteration of ....................

See also Augite, Epidote, Hornblende. 

Festoon cross-lamination.............

Festoon structures, Casper Formation. 

Fezzan, Libya, inland dune deposit in ..

interdune deposit in.............

Floods, flash, effect on dunes .........

Florinopolis, Brazil ..................

Fluvial sand ........................

in Colorado River delta ..........

Fluviatile deposits ...................

190

27

24

389

231,357

357

164

329,335

326, 335

164

326, 335

169

142

310

235

235

217

177

243

, 221,386

112, 121

282

124, 191

228

231

221

237

205

228

356

227

218

211

376

24

29

220

63,68,78

65

63

221

221, 222

55

55, 109

124, 130

196

30

30

27, 228
426 INDEX

Folding, penecontemporaneous .......

Folds.................. 112, 121,213,

gentle ..........................

stairstep .......................

Footprints. See Tracks, of vertebrate

animals. 

Foresets ............ 89, 105, 121, 192,

Forest Sandstone, Rhodesia. See Cave

Sandstone. 

Fort Flatters, Algeria. See Bordj Omar

Driss, Algeria.

Fort-Gouraud, Mauritania, linear dune 

in .....................

Fossils, marine ......................

Fossils. See Dinosaur remains, Trace

fossils. 

Fountain Formation .................

Four Corners area...................

Frodsham Member of so-called Keuper 

Sandstone Formation, 

England ...............

dome dune in ...................

feldspar in .....................

illite in.........................

quartz in .......................

transverse dune in ..............

Front Range highlands, of Lyons Sandstone ..................

Frosting ........................ 189,

process ........................

Fuljes ..............................

Ganado.............................

Garnet .............................

Ghudamis, Libya, sand rose for .......

star dune in ....................

Giles, Australia, linear dune in .......

Glaciofluviatile deposits .............

Gobi Desert, Mongolia ...............

Goethite ............................

Gondwana beds, Africa ..............

Grain, frosted.......................

size, effect on pigment...........

Gromineae .........................

Gran Desierto, Mexico, crescentic dune 

in .....................

star dune in ....................

Grand Canyon ......................

Grand Erg Occidental, Algeria ........

dome dune in ...................

quartz in .......................

star dune in ....................

Grand Erg Oriental, Algeria and Tunisia ....................

star dune in........ 107, 142, 165,

See also Ghudamis, Libya. 

Granite, at Lagoa dune field ..........

Great Dune at Kerzaz ................

Great Escarpment...................

Great Sand Dunes National Monument, 

Colorado ..............

crescentic dune in ..............

reversing dune in ...............

Great Sandy Desert, Australia, simple 

linear dune in ...... 141,

Great Victoria Desert, Australia, simple linear dune in... 141, 

Great Western Desert, Egypt.........

Green River Desert..................

5

223, 230

112

105

216,218

156, 164

224

221

205

228

197, 228

228

228

228

229

218

191,211

24

282

206

356

165

142, 165

163

27

230

78

236

31

80

122

269

107, 275

3, 197

329

280

334

165, 326

335

275, 326

114, 124

335

346, 349

29, 89

269

104, 195

157, 163

157,163

329

212

Page 

Guairamar, Parana, Brazil, retention

ridge in................ 97

Gujarat Plain, India ................. 375

Gulf of Sidra ........................ 67

Gypsum ......................... 78, 191, 196

caliche......................... 67

sand, in White Sands National

Monument ............. 24, 28

H

Halite .............................. 226

Haloxylon sp. ....................... 386, 389

Hassi Messaoud, Algeria, star dune in. 167 

Hedysarum sp....................... 389

Hematite, in Libya .................. 63, 69, 78

in Rotliegendes ................. 225

Hermit Shale ....................... 197

Holocene ........................... 67

Hornblende .................... 65, 69, 79, 376

Humic compounds ................... 122, 127

I

Illite, in Frodsham Member........... 228

in Libya ........................ 69, 73

Illite-montmorillonite, in Libya ........ 69, 73

Ilmenite ............................ 69, 356

Images, ERTS-1 ........... 6, 95, 102, 141, 150,

169, 173,257, 309

India. See Gujarat Plain, Thar Desert. 

Indiana dunes, Lake Michigan shore,

parabolic dune in....... 95

Indurated rocks ..................... 24

Interdune area . 107, 122, 189, 220, 282, 336, 389 

in Lagoa dune field, ............. 122, 130

in Rub al Khali.................. 282

in Sahara Desert................ 282

in White Sands National Monument .................. 282

Interdune deposits. See Deposits, interdune. 

Interdune sabkhas .................. 193

Iron, source of ...................... 69

Iron-bearing minerals ............... 63, 69, 79

Iron oxide ...... 7,63,69,78, 191, 211,227,338

Irq as Subay, Saudi Arabia, star dune

in ..................... 277

I

Jabal as Sawda' Libya ...............

Jabal Tuwayq, linear dunes in ........

Jardim Sao Pedro, Parana, Brazil, retention ridge in.........

Joaquina Beach, Brazil...............

Joaquina Hill, Brazil.................

Junctures, of linear dunes ............

79

368

97 

114 

127 

156 

Jurassic ............... 189, 190, 209, 233, 376

Jurassic, Late ....................... 235

Jurassic, Lower ..................... 209

Kalahari Desert, Africa 

feldspar in ........

linear dune in.....

quartz in ..........

........ 355

........ 356

........ 360

........ 356

simple linear dune in........ 141, 156, 163

stringer dune in ................. 359

Kanab area ......................... 212

Kaolin..............................

Kaolinite ...........................

in Libya ........................

Karroo System, Africa ...............

Kayenta Formation..................

Kelso dune field, Mojave Desert, California, elongate ridge in.

reversing dune in ...............

Keuper Sandstone, England....... 190,

Killpecker dune field, Wyoming.......

barchanoid ridge dune in ........

dome dune in...................

feldspathic sand ................

interdune structure in...........

quartzose sand .................

transverse dune in ..............

Kinlichee ...........................

Kyanite, detrital ....................

205

228

69, 73

236

211

105

105

197, 228

6, 89

91

98, 280

29

109

29

94

207

357

Lacustrine deposits ................ 27, 29, 228

Lagoa dune field, Brazil.............. 114

blowout dune in................. 114

captation dune in ............... 127

dissipation of dune in............ 124

granite in ...................... 114, 124

hanging dunes in ................ 127

interdune areas in .............. 122, 130

parabolic dune in............. 96,114, 122

ponds in........................ 130

reversing dune in ............... 105, 123

soil horizons in.................. 130

stringers in..................... 127

Lake, desert ........................ 225

Lamb Point Tongue .................. 211, 214

Laminae, fadeout.................... 112

Landsat-1 .......................... 6

See oJso Images, ERTS-1. 

Landsat imagery. See Images,

ERTS-1. 

Laramie Basin, Wyoming ............ 221

Lateritic soils ....................... 63

Lava ............................... 236

Lettau equation for sand drift........ 141, 145

Leupp, Arizona ..................... 5

Lias. See Jurassic, Lower.

Libya, bedrock in.................... 216

hematite in..................... 63, 69, 78

illite in ......................... 69, 73

illite-montmorillonite in .......... 69, 73

kaolinite in ..................... 69, 73

studies in....................... 89

western, eolian deposits ......... 63

See also Al Haruj al Asway; Fezzan; 

Ghudamis; Jabal as Sawda; Ramlat Zallaf; Ramli 

al Kabir; Sabha; Sahara, 

northern; Sahra 1 Awbari; 

Saljra' Marzuq; Sa^ra' 

Rabyanah. 

Libyan Desert, barchan dune in....... 269

Limestone .......................... 376

in Casper Formation............. 221

lenticular ...................... 225

marine ......................... 65

aphanitic .................. 221

in Navajo Sandstone ............ 211

Limonite ............................ 63, 68

Linear discriminant analysis ......... 57

Linear regression analysis ........... 143
INDEX 427

Littoral sand........................

Lost Soldier Field, Wyoming ..........

Lower Hunter Sandstone. See Lower

Mottled Sandstone. 

Lower Mottled Sandstone, England 190,

feldspar in .....................

quartz in .......................

stratification in .................

Lyons Sandstone, Colorado ....... 190,

arkose in .......................

coastal dunes in.................

feldspar in .....................

Front Range highlands...........

interdune deposits in............

parabolic dunes in ..............

quartz in .......................

quartzose sand in ...............

rain pits in .....................

ripple marks in .................

slump marks in .................

stratification in .................

trails of invertebrate animals in ..

M

27, 30

243

197,227

227

227

227

197,217

217

220

218

218

218

220

218

220

218

218

218

218

219

Magnetite .......................... 69

Makgabeng Formation, Transvaal.... 191

Mali. See Sahara, southern; Sahara,

western. 

Mantle, granitic..................... 127

Mao-Mu (Ting-hsin), China, barchanoid

ridge dune in ........... 155

Maps, thematic ..................... 6

Marble Canyon ..................... 197

Mariental, South-West Africa, linear

dunes in ............... 163

sand rose for ................... 163

Marine aphanitic limestone .......... 221

Marl ............................... 109

Material, detrital.................... 127

Mauritania. See Akjoujt; Atar; Erg 

Hammami Region; Erg 

Makteir; Fort-Gourard; 

Sahara, southern; Sahara, western. 

Measurement, systems of ............ 17

Mesozoic ..... 15, 65, 81, 190, 197, 243, 363, 385

Mexico. See Gran Desierto.

Mica ........................... 205, 228, 231

Minerals, ferromagnesian silicate, alteration of................ 63

Miocene............................ 347

sandstones ..................... 334

Misiones Formation, Paraguay ....... 235

Model, dune-extradune .............. 243

Moenkopi Formation, Arizona ........ 190

Mogollon Rim, Grand Canyon......... 197

Moisture, effect on dune color ........ 65, 79

effect on dune formation ........ 78, 94, 97,

113,194 

role in structure type ............ 112

Mongolia. See Gobi Desert.

Monument Valley ................... 206

"Morphology, Provenance, and Movement of Desert Sea Sands, 

The" .................. 6

Morphometry, of crescentic dunes 265, 269, 297 

of dome dunes .................. 281, 302

of linear dunes .................. 261, 296

of parabolic dunes .............. 277

of star dunes ................... 275, 299

Page 

Mosaics, ERTS ...................... 6

Mudstone .......................... 229, 237

N

N summaries........................

Nafud as Sirr .......................

dome dunes in ..................

Nafud ath Thuwayrat................

dome dune in ...................

Nafud Shuqayyiqah, dome dune in ....

Namib Desert, South-West Africa .....

barchan dune in ................

barchanoid dune in..............

complex dune in ................

crescentic dune in........... 269,

linear dune in...................

longitudinal dune in.............

quartz in .......................

reversing dune in ...............

star dune in................. 275,

transverse ridge dune in .........

Navajo Indian Reservation, Arizona, 

linear dune in..........

sand streaks in .................

Navajo Sandstone ............... 189,

barchanoid dune in..............

contorted bedding in ............

feldspar in .....................

interdune deposit in......... 209,

limestone in ....................

orthoquartzite in................

penecontemporaneous contorted 

bedding in .............

quartz in .......................

ripple marks in .................

stratification in .................

transverse dune in ..............

Nazlini Canyon......................

Nebraska Sand Hills, crescentic dune

143

369

362

368

362

362

346

153

153

346, 349

346, 349

346, 349

349

349

346, 349

346, 349

153, 349

261

281

190, 209

215

213

211

212,214

211

211

216

211

212

212

215

207

267

230

389

349

338,341

368

190, 209

Negegt Basin, Mongolia ..............

Niger. See Bilma; Erg Bilma Region;

Sahara, southern. 

Nitraria schoberi....................

Northern Sahara, crescentic dune in..

star dune in................. 326,

Northern Sand Seas .................

Nugget Sandstone ...................

Nyamandlovu Sandstone, Rhodesia.

See Cave Sandstone.

O

Oliveni, Hawaii ..................... 24

Oodnadatta, Australia, wind regine at. 157 

Orthoquartzite ................... 65,191, 205

in Casper Formation............. 221

in De Chelly Sandstone .......... 205

in Navajo Sandstone ............ 211

Oved Saoura........................ 334

Overthrusts ........................ 112

Pachecoia acuminata ................ 235

Pachecoia rodriguesi ................ 235

Pakistan. See Porali Plain, Thar Desert. 

Polaeolimnadia petrii ................ 235

Paleosol (A horizon] ................. 124

Paleozoic ... 15, 65, 190, 197, 217, 339, 363, 385

Page 

Paleozoic, Upper .................... 243

Palygorskite ........................ 67, 73, 78

Paraguay. See Misiones Formation.

Parana Basin ....................... 233

Parana, Brazil, dome dune in ......... 99

Parnaiba Basin ..................... 233

Pa-tan-chi-lin Sha-mo, China, crescentic

dune in ................ 381

Peel, colloidal....................... 127

Pelican Point, South-West Africa ..... 153

Pennsylvanian sandstone.......... 35,190, 221

Permeability ........................ 33

Permian Rotliegendes. See Rotliegendes. 

Permian sandstone ........... 35,190,197, 204,

217,221,225,227 

Permian Satanka Formation. See Satunka Formation.

Persian Gulf Coast, crescentic dune in. 269 

Peru. See Pur-pur dune. 

Peski Karakumy, U.S.S.R., crescentic

dune in ................ 267

simple linear dune in ............ 141, 161

Petroleum .......................... 190, 243

Phi grade scale...................... 23

Photography, aerial.............. 173, 257, 309

Skylab ......................... 257, 309

still, in laboratory ............... 173

Phragmites communis................ 389

Physics, sand ....................... 4

Piramboia Facies.................... 235

Pitting.............................. 189

Plateau du Mangueni................ 340

Playa deposits..................... 27, 29, 232

Pleistocene ..................... 357, 363, 368

early...........................

late ............................

sandstones .....................

Pond, desert ........................

ephemeral......................

interdunal......................

in Lagoa dune field, Brazil.......

Porali Plain, Pakistan................

Porto Novo, Brazil, retention ridge in ., 

Praia do Leste, Brazil, dome dune in... 

Precambrian.......................

Preservation, of markings............

Psammochlea vilJosa................

Pugionium cornutum................

Pur-pur dune, Peru ..................

Qa'amiyat, compound linear dune in .. 

Quartz ....................... 24, 65,

in Barun Goyot Formation........

in Casper Formation.............

in Cave Sandstone ..............

in Frodsham Member............

in Grand Erg Occidental.........

in Kalahari Desert..............

in Lower Mottled Sandstone ......

in Lyons Sandstone..............

in Namib Desert ................

in Navajo Sandstone ............

in Rotliegendes .................

In Sahra'Marzuq ...............

sanastone ......................

in Thar Desert..................

See also Chevron. 

Quartzite, feldspathic ...............

67

349

334

196

214

109

130

376

97

99

190

5

389

389

267

367

124, 191

231

221

237

228

334

356

227

218

349

211

225

339

197, 205

376

217
428 INDEX

Quartzite—Continued 

lenticular dolomitic .,

Quartzose sand ..........

Killpecker dune field 

in Lyons Sandstone ...

Page

...... 217

...... 24

...... 29

...... 220

Quaternary alluvium ............. 72, 334, 389

Quaternary dune sand ............... 72

R

Rain pits ........................... 5, 87, 191

in Coconino Sandstone........... 200

in Lyons Sandstone .............. 218

Ramlat as Sahama, star dune in ....... 363

Ramlat Zallat, Libya ................. 327, 338

Ramli al Kabir, Libya ................ 329

"Red Desert Soils" .................. 66

Regression analysis ................. 262

Remote sensing. See Images, ERTS-1.

Reptile remains, in Cave Sandstone ... 237

Rhodesia. See Cave Sandstone.

Ridge .............................. 24

beach dune ..................... 97

defined ........................ 11

elongate in Kelso dune field ...... 105

linear .......................... 88

precipitation, United States west

coast .................. 96

retention ....................... 96

in Guairamer............... 97

in Jardim Sao Pedro, Brazil.. 97 

in Porto Novo, Brazil........ 97

sand. See Dune, linear. 

Ripple index (RI)............ 174, 192, 200, 224

Ripple marks ................... 5, 87,189,191

in Casper Formation............. 223

in Cave Sandstone .............. 238

in Coconino Sandstone ........... 199

in De Chelly Sandstone .......... 207

in Lyons Sandstone .............. 218

in Navajo Sandstone ............ 212

Ripple symmetry index (RSI).......... 174

Ripples ............................. 24, 173

adhesion ................... 192, 196, 226

River sands ......................... 55

Rocky Mountains, Colorado and Wyoming .................. 243

Rotliegendes, northwestern Europe ... 190, 225 

hematite in ..................... 225

interdune deposits in ............ 225

linear dune in................... 226

quartz in ....................... 225

stratification in ................. 229

transverse dunes in ............. 226

Rub'al Khali, Saudi Arabia ........... 363

barchan dune in ................ 269

crescentic dune in .............. 362

interdune areas in .............. 282

linear dune in ................... 260, 362

star dune in ................. 107, 275, 362

Sabha, Libya ........................ 6, 68

linear dune in................... 156, 161

sand rose for ................... 165

seif dune in ..................... 103

Sahara Desert ...................... 64

barchan dune in ................ 269

crescentic dune in .............. 310

interdune area in ............... 262

Sahara Desert—Cotinued

linear dune in..............

of Mali, barchan dune in.........

of Mauritania, sand streaks in....

northern, of Algeria .............

of Libya....................

of Tunisia ..................

southern, of Mali................

of Mauritania ..............

of Niger....................

western, of Mali ................

of Mauritania ..............

of Senegal..................

Sahel ..............................

Sahra AwbarT, Libya ....... 63, 68, 79,

SahriTMarzuq, Libya ....... 63, 68, 79,

quartz in .......................

f

ahra*Rabyanah, Libya .............. 

alt ................................

Sambaiba Sandstone, Brazil..........

Sampling ...........................

San Rafael Swell....................

Sand, alluvial.......................

drift. See Sand migration, 

feldspathic, in Killpecker dune 

field ...................

littoral .........................

migration ......................

quartzose, in Killpecker dune field, 

Wyoming ..............

ridges. See Dune, linear, 

rose............... 141, 147, 163,

serir ...........................

sheets .. 11, 87, 156, 167, 261, 281, 

in Upington.................

in Vallee de L' Azaouk.......

See also Stringers, 

shields .........................

streaks..................... 261,

in Navajo Indian Reservation 

in Sahara of Mauritania .....

See also Stringers. 

Sandstones, ancient .................

origin ..........................

Santa Caterina, Brazil, dome dune in .. 

Santana facies ......................

Sarir Kalanskiyu ....................

Sarir Tibasti........................

Satanka Formation ..................

Satellite sensing. See Images, ERTS-1. 

Saudi Arabia, studies in..............

See also An Nafud, Irq as Subay, 

Rub 'al Khali, Wahiba 

Sands, Zalim.

Scanning electron microscope analysis 

Sebkha, interdune ...................

inland..........................

Sediment arkosic ....................

Sedimentary rocks, Cretaceous.......

Tertiary........................

Sedimentary structures, of dunes .....

minor ..........................

primary ........................

Sediments, alluvial, unconsolidated ... 

fluvial .........................

Seifs. See Dune, linear. 

Senegal. See Sahara, western. 

Sensing, remote. See Images, ERTS-1. 

Serra Geral basaltic lava flows .......

Settling, mineral ....................

Shale ............................ 65

261, 310

269

281

326

326

326

317

317

317

310

310

310

317

326, 338

326, 339

339

79, 329

196

190,233

23

211

23

29

23

141

29

165, 310

23

313,375

156

320

377

281, 375

281

281

15, 189

189

99

235

329

79

217

89

68

225

196

224

65

65

89

5

5

29

347

234

24

,217,237

Shamal winds .......................

Shatt al Jarid .......................

Shurtz Sandstone ...................

Sidra, Gulf of.......................

Sierra del Rosario, star dune in .......

Silica ........................ 69, 73,

Silicate, aluminum ..................

ferromagnesian .................

Silt content .........................

Siltstone........................ 211,

calcareous .....................

micaceous......................

Simpson Desert, Australia ...........

simple linear dune in ............

Size, grain ..........................

Skeleton, vertebrate .................

Skylab 4 ............................

Slipfaces, study of...................

Slump marks ................... 5, 87,

in Coconino Sandstone...........

in Lyons Sandstone..............

Slumping ................... 104,113,

Soil horizons ........................

in Lagoa dune field..............

Sonoran Desert .....................

Sossus Vlei .........................

Southern Sahara, crescentic dunes in .

linear dune in...................

Spanish Sahara .....................

Staurolite ..........................

Stereonets ..........................

Stipagrostis sp.......................

Straate .............................

Strata, brecciated...................

marine .........................

Stratification, of Barun Goyot Formation .................

of Butucatu Sandstone...........

of Casper Formation.............

of Cave Sandstone ..............

of Coconino Sandstone...........

of De Chelly Sandstone ..........

of Frodsham Member............

of Lower Mottled Sandstone .....

of Lyons Sandstone..............

of Navajo Sandstone ............

of Rotliegendes .................

Streak, defined......................

Stringers .................... 87, 127,

defined ........................

in Lagoa dune field, Brazil.......

Structures, deformational............

dissipation .....................

interdune ......................

in Brazil ...................

in Killpecker dune field......

penecontemporaneous.. Ill,121,

rotated.........................

Studies, sand-texture ................

statistical ......................

textural ........................

See also Texture. 

Subarkose beds .....................

calcareous .....................

371,374

336

211

67

275

191, 211

69

79

23

217,229

214

208, 217

63, 78

141, 157

23

231,232

6

87, 200

189, 191

200

218

121,231

130

130

30

352

317

317

310

357

97, 194

349, 357

282

112

190

231

235

222

237

199

206

229

227

218

212

226

11

261,281

11

127

111, 121

127

107

109

109

229,231

112

4

5

24

205

221

Tacuarembo Sandstone, Uruguay ..... 235

Takla Makan Desert, China .......... 381, 385

barchanoid dune in . 142,152, 381, 367, 389 

complex dune in ................ 381, 387
INDEX 429

Page 

Takla Makan Desert, China—Continued

crescentic dune in .............. 387, 389

dome dune in................ 280, 381, 391

linear dune in................... 381

reversing dune in ............... 389

star dune in .................... 389

transverse dune in .............. 392

Tojnarix rojnosissima ................ 389

Tarim Basin ........................ 381, 385

Tensleep Sandstones, Wyoming.... 35, 221, 237

Terminology, dune .................. 284

Tertiary ......................... 65, 347, 357

late ............................ 385

sedimentary rocks .............. 65

volcanic rocks .................. 65

Textural parameters ................ 24, 55

Texture, of Barun Goyot Formation ... 231 

of Botucatu Sandstone ........... 235

of Casper Formation............. 221

of Cave Sandstone .............. 237

of Coconino Sandstone ........... 199

of De Chelly Sandstone .......... 205

of Frodsham Member............ 228

of Lower Mottled Sandstone ..... 227

of Lyons Sandstone .............. 217

of Namib Desert ................ 349

of Navajo Sandstone ............ 210

of Rotliegendes ................. 225

Thar Desert, India and Pakistan ...... 375

barchanoid dune in.............. 154

crescentic dune in .............. 271, 375

feldspar in ..................... 376

parabolic dune in ............ 95, 277, 375

quartz in ....................... 376

Thrusts, stairstep ................... 105

Toroweap Formation, Grand Canyon .. 197 

Tourmaline ......................... 334, 356

Trace fossils, in Casper Formation .... 224

Traces, faunal ...................... 190, 202

Tracings, laboratory................. 173

Tracks, of vertebrate animals .... 189, 193,197

in Cave Sandstone .............. 237

Trails, of invertebrate animals, in Coconino Sandstone......... 202

in De Chelly Sandstone .......... 207

Page 

Trails of invertebrate animals—Continued

in Lyons Sandstone .............. 219

Transport distance, effect on pigment. 80 

Transvaal. See Cave Sandstone, 

Makgabeng Formation, 

Waterberg Supergroup 

Trenching .......................... 5, 89

Triassic ....... 189, 190, 197, 209, 228, 236, 357

Tunisia, gypsum caliches in .......... 67

See oJso Grand Erg Oriental; Sahara, northern.

U,V

U.S.S.R. See Peski Karakumy. 

Upington, South Africa, linear dune in. 156 

sand sheets in .................. 156

Upper Nemegt Beds. See Barun Goyot

Formation. 

Uruguay. See Tacuarembo.

Vallee de L'Azaouk, barchan dune in .. 317 

crescentic dune in .............. 321

sand sheets in .................. 320

Vegetation.... 122, 235, 340, 349, 357, 386, 389

effect on dune formation ....... 94, 97, 235,

336,358 

Victoria Valley, Antarctica, reversing

dune in ................ 104

Volcanic rocks, Tertiary ............. 65

W

Waddan, Libya...................... 68

Wadis .............................. 196, 225

Wahiba Sands, Arabia ............... 363, 368

barchanoid dune in.............. 154

Warps. See Folds, gentle.

Waterberg Supergroup, Transvaal.... 191

Weber Sandstones ................ 35,190, 243

Wentworth grade scale .............. 23

Wertz field, Wyoming ............... 243

Western Sahara, crescentic dune in... 310, 313 

immobile dune in ................ 312

linear dune in................... 310, 313

Page

White Rim Sandstone ................ 190

White Sands National Monument...... 6, 33,89

barchanoid ridge dune in....... 90, 97,152

dome dune in ................ 98, 152, 279

gypsum sand in ................. 24, 28

interdune area in ............... 282

interdune deposit in ............. 109, 206

parabolic dune in ............ 95, 152, 277

reversing dune in ............... 106

transverse dune in............. 93, 97, 193

planar cross-stratification ....... 206

Wind, effect on dune formation ...... 73, 94, 99,

102,107, 152,227,243,373 

effective ............... 141, 155, 262, 280,

282,317,343,376 

See also Wind, sand-moving, 

energy ......................... 141, 150

regime .............. 8, 141, 157, 327, 336,

341,354,361,373 

associated with barchanoid

dunes ................. 152

associated with linear dunes. 155, 262 

associated with star dunes... 165 

classification of ............ 141, 148

sand-moving ................. 87, 103, 141

Wingate Sandstone.................. 190

Wu-lan-pu-ho Sha-mo ................ 381

Wyoming, western, parabolic dune in . 96

X,Y,Z

X-ray analysis, energy-dispersive ..... 

X-ray diffraction analysis ............

68

68

Yamalik Dunes ...................... 381, 389

Ya-pu-lai Sha-mo .................... 381

Yardangs........................... 386

Yellow Sands of Durham, England .... 190, 226

Zalim, Saudi Arabia, star dune in ..... 106

Zambia, feldspathic arenites in....... 190

Zion Canyon, Utah ................... 212, 214

Zircon ............................. 334, 356