XRIGIN AND CHARACTER OF 

OESSLIKE SILT IN UNGLACIATED

IBERIA, U.S.S.R.

GEOLOGICAL SURVEY PROFESSIONAL PAPER 1262
Origin and Character of 

Loesslike Silt in Unglaciated 

South-Central Yakutia, Siberia, U.S.S.R.

By TROY L. PEWE and ANDRE JOURNAUX

GEOLOGICAL SURVEY PROFESSIONAL PAPER 1262

UNITED STATES GOVERNMENT PRINTING OFFICE, WASHINGTON: 1983
UNITED STATES DEPARTMENT OF THE INTERIOR 

JAMES G. WATT, Secretary

GEOLOGICAL SURVEY

Dallas L. Peck, Director

Library of Congress Cataloging in Publication Data 

Pewe, Troy Lewis, 1918-

Origin and character of loesslike silt in unglaciated 

south-central Yakutia, Siberia, U.S.S.R.

(Geological Survey Professional Paper; 1262) 

Bibliography: p. 43-46. ^\ *^

1. Loess Russian S.F.S.R. lAkutskaia A.S.S.R. 

I. Journaux, Andre. II. Title. III. Series. 

QE579.P48 1983________552' .5________82-21022

For sale by the Distribution Branch, U.S. Geological Survey, 

604 South Pickett Street, Alexandria, VA 22304
CONTENTS

Page

Abstract ________________________________ i

Introduction _____________________________ 1

Acknowledgments __________________________ 3

Physical setting ___________________________ 3

Physiography and general geology ______________ 3

Climate ___________________________ 6

Permafrost __________________________ 7

Geomorphology ________________________ H

Distribution and thickness of upland silt _____________ 17

Color and texture _______________________ 20

Mineral and chemical composition _______________ 29

Field relations _________________________ 31

Fossils 

Origin

Page

_ 33 

_ 34

Marine and estuarine hypotheses _________ ___ 34

Weathering hypothesis ______________ ___ 34

Lacustrine and fluviatile hypotheses ___________ 35

Eolian hypothesis _______________________ 37

Field relations ________________________ 38

Mechanical composition ________________ 39

Petrographic character _______________ 39

Age and correlation _____________________ 40

Summary ______________________________ 43

References cited ________________________ 43

ILLUSTRATIONS

Page

FIGURE 1. Index map of Yakutia, U.S.S.R __________________________________________________ 2

2. Map of central Yakutian lowland ______________________________________________ 3

3. Physiographic diagram of the region of the Lena, lower Aldan, and lower Amga Rivers, central Yakutia ___ __ 4

4. Map showing generalized extent of glaciers in Yakutia during middle Pleistocene time ___________ _ __ _ _ 7

5. Graphs showing climatic data for Yakutsk, Yakutia ______________________________________ 10

6-10. Photographs showing:

6. Ice wedge in silt of Tyungyulyu Terrace at Syrdakh Lake ______________________-___ __ 12

7. Satellite images of the Lena-Amga area, south-central Yakutia ____________________ 13

8. Alas of Tyungyulyu in loess on Tyungyulyu Terrace ____________________________ 14

9. Eastern half of Olong-Erien alas with large closed-system pingo in loess, 75 km east of Yakutsk on Abalakh

Terrace ____________________________________________________ 15

10. Baydjarakhs, pyramid-shaped forms remaining after thawing of ice wedges, left bank Aldan River _ 16

11. Diagrammatic section of loess-capped sand terraces near Mamontova Gora along the Aldan River, Yakutia __ 17

12. Photograph showing Lena River valley from atop "Pillars of Lena," 255 km upstream from Yakutsk ____ __ 18

13. Sketch of loess-covered terrace of Ilanskjo Village on Cambrian dolomitic limestone, 70 km upstream from Pokrovsk 19

14. Diagrammatic sketch of upland silt mantling terraces west of Pokrovsk showing location of silt samples 20 

15-21. Graphs showing cumulative-frequency grain-size curves for:

15. Loess from edge of alases on Tyungyulyu Terrace, 40 km west of Yakutsk 22

16. Twenty-seven samples of upland silt on high terraces in central Yakutia _______________ 23

17. Loess blanketing terraces along the lower Aldan River, Yakutia _______ 24

18. Loess mantling Tyungyulyu Terrace west of Lena River, central Yakutia __ _ 25

19. Upland loess near sandy terraces and sandy flood plains along Lena River, central Yakutia _____ ___ 26

20. Reworked upland loess and B soil horizon, illustrating relatively high clay content _____________ 27

21. Retransported upland loess at various depths in section, illustrating vertical uniformity of texture _ 28

22. Sketch showing location of sample of upland silt mantling dolomitic limestone on right limit of Lena River, 12 km

upstream from Pokrovsk ________________________________________________ 29

23. Cumulative-frequency grain-size curves for upland loess at various distances from Lena River _________ 30

24. Sketch map showing location of loess samples along Lena River and lower Aldan River analyzed for heavy-mineral

content ________________________________________________ 32

25. Photograph of late Quaternary silt containing ice wedges, Mamontova Gora, left limit of Aldan River ___ 36 

26-29. Graphs showing cumulative-frequency grain-size curves for:

26. Sand from Lena-Aldan Rivers area ______________________________________ 37

27. Silt from Yakutia ______________________________________________________ 39

28. Upland silt from near Yakutsk, volcanic ash from Fairbanks, Alaska, and modern wind-deposited dust from

Germany, Kansas, and Tempe, Ariz _______________________________ ___ 40

29. Upland silt from central Yakutia and loess from Czechoslovakia, Alaska, Illinois, China, New Zealand, France,

and Uzbekistan _____________________________________________ 41

30. Diagrammatic stratigraphic section of perennially frozen late Quaternary silt in the exposure of the 50-m-high terrace at

Mamontova Gora _____________________________________________________ 42

in
IV CONTENTS

TABLES

Page

TABLE 1. Data on Quaternary sediment samples collected in central Yakutia, Siberia, U.S.S.R ________________ 8

2. Thickness of silt in central Yakutia, Siberia, U.S.S.R ______________________________________ 19

3. Mechanical properties of sand and loesslike silt from central Yakutia and loess and ash from other parts of the world 21

4. Percentage distribution of heavy minerals in sediments from central Yakutia, Siberia, U.S.S.R ___ __________ 30

5. Average grain-size values of samples of upland silt along the Lena and Aldan Rivers in south-central Yakutia, U.S.S.R.,

analyzed for heavy-mineral content ____________________________________ 32

6. Chemical analysis of Quaternary loess from central Yakutia, Siberia, U.S.S.R _______________________ 33

7. CaCO3 in Quaternary sediments from central Yakutia, Siberia, U.S.S.R __________________________ 33
ORIGIN AND CHARACTER OF LOESSLIKE SILT IN UNGLACIATED 

SOUTH-CENTRAL YAKUTIA, SIBERIA, U.S.S.R.

By TROY L. PEWE and ANDRE JouRNAux1

ABSTRACT

Loesslike silt mantles upland terraces and low plateaus throughout unglaciated south-central Yakutia but is thickest along the south 

side of the lower Aldan River valley and the east side of the Lena River 

valley. The silt is probably loess deposited during glacial advances by 

winds blowing southward from the Verkhoyansk Range and eastward 

across the broad vegetation-free flood plain of the braided Lena River.

The well-sorted uniform tan silt is well displayed along the Aldan 

and Lena Rivers; the thickest exposure measured, more than 60 m, is 

on the Tyungyulyu Terrace on the east side of the Lena River. On the 

west side of the valley, it is 10-25 m thick but thins rapidly to a 

featheredge west of Yakutsk. Almost all scarps along the south side of 

the Aldan River are capped by 10-35 m of silt.

The texture and mineral composition of the loesslike silt are uniform throughout south-central Yakutia, whether it overlies limestone, poorly consolidated sandstone, alluvium, and glacial outwash. 

All silt samples examined contained a high percentage of quartz and 

feldspar. The silt stands in sheer cliffs and is massive, with little or no 

stratification.

The origin of the loesslike silt has been ascribed to disintegration in 

place of country rock by a marine, estuarine, lacustrine, fluvial, residual, or eolian source, or to a combination of these processes. The 

marine and estuarine hypotheses have never had strong support, but 

the lacustrine, fluvial, and residual hypotheses have been advanced 

by many Soviet workers.

The most widely accepted explanation of the origin of the upland silt 

is that it is a combination of lacustrine and alluvial deposits formed on 

great flood plains and marshy plains. This origin is unlikely, however, 

because there are no shorelines, wave-cut beaches, deltas, mudcracks, 

or ripple marks. Neither distinct stratification nor an appreciable 

amount of clay exists in the silt. Moreover, there is no definite upper 

boundary to the deposits, as would be expected of lacustrine deposits.

The loesslike silt has also been described as a residual deposit 

formed by the breakdown, by freezing and thawing, of the underlying 

rocks. The silt bears no chemical, mineralogic, or textural relation to 

the underlying strata, however, and it is too thick to represent only 

breakdown of rocks in place.

The widespread mantle of uniform loesslike silt is here considered 

to be windblown, derived from glacial outwash in braided streams and 

on broad plains, because: (1) it occurs as a surficial mantle; (2) it is 

lithologically independent of the underlying material; (3) it is 

stratified indistinctly or not at all, except in retransported material; 

(4) it is associated with sand dunes; (5) it contains fossils of land 

animals; (6) its sorting and texture are similar to that of loess and 

windblown dust from many places elsewhere in the world; (7) its 

grains are angular and relatively unweathered.

'Centre de Geomophologie du Centre National de le Recherche Scientific, Caen, France.

INTRODUCTION

A well-sorted uniform tan loesslike silt mantles the 

river terraces and low rolling uplands of much of the 

unglaciated part of Siberia, especially in south-central 

Yakutia (fig. 1), where it forms a blanket a few centimeters to many meters thick. The silt of central Yakutia, 

referred to in the Russian literature as clay loam, 

loesslike loam, dusty loam, glacial loam and, rarely, as 

loess, has been mentioned since before the turn of the 

century. During the past 75 years, workers in Yakutia 

have been concerned with its origin. It has been 

classified as a fluviatile, marine, estuarine, lacustrine, 

residual, and eolian deposit, and a combination of these.

Throughout this report, we shall refer to the upland 

sediments of central Yakutia as "loess-like silt," or 

"upland silt," and sometimes for brevity, as "silt."

We believe that the widespread silt on the terraces 

and uplands is loess and was mostly deposited during 

periods of glacial advance by winds blowing across outwash plains and valley trains in broad valleys. The tan 

silt on the ridges and hill slopes interfingers with layers 

of gray-to-black perennially frozen silt in drainageways 

and small valley bottoms. This black, frozen silt has 

been retransported from the hill slopes by rill wash, 

creep, solifluction, incorporating much organic debris, 

including many vertebrate remains. In a few places, two 

or more stratigraphic units can be recognized in the silt, 

but as we saw relatively few good stratigraphic exposures, it has not been possible to subdivide the silt 

stratigraphically; consequently the silt is treated as a 

single unit in this discussion.

This report is in part the result of a cooperative project 

proposed by Pewe to the Academy of Sciences of the 

U.S.S.R. and the National Academy of Sciences of the 

U.S.A. Pewe and Journaux visited the Lena-Aldan area 

in 1969 while participating in the excursion of the 

Periglacial Commission of the International Geographical Union. Because of the striking similarity of the 

distribution, character, and stratigraphy of the 

loesslike silt exposed in central Yakutia to the perennially frozen Quaternary silt exposed in unglaciated cen-
ORIGIN AND CHARACTER OF LOESSLIKE SILT, YAKUTIA, SIBERIA

500 KILOMETERS

FIGURE 1. Index map of Yakutia, U.S.S.R. Area of field research near Yakutsk (shaded area) represented in physographic diagram

of figure 3.
PHYSICAL SETTING

tral Alaska (Pewe 1955, 1975a,b), Pewe returned in 

1973 to make further observations and to collect silt, 

paleontological, and radiocarbon samples. The 1973 

visit was in part made in connection with the Second 

International Conference on Permafrost (Pewe, 

1973a,b,c). In order to understand more fully the origin, 

distribution, and characteristics of the silt, the exposures examined by Pewe and Journaux in 1969 were 

revisited and more samples collected. In addition, observations were made and samples collected west of 

Yakutsk and as far as 100 km east and northeast of 

Yakutsk. Field work was conducted along the Lena 

River upstream from Yakutsk for a distance of 250 km. 

For comparison with the Yakutian silt, loess deposits 

were examined in western and southwestern U.S.S.R., 

central Europe, New Zealand, and North America.

ACKNOWLEDGMENTS

The authors deeply appreciated the cooperation and 

aid of the many persons in various countries who made 

this study possible. P. I. Melnikov, corresponding 

member of the Academy of Sciences, U.S.S.R., arranged 

the cooperation of the Academy and offered the use of 

the facilities of the Permafrost Institute of the Siberian 

Division of the Academy in Yakutsk, of which he is 

Director. Felix Are and E. M. Katasonov, of the Permafrost Institute, graciously aided in many of the logistics 

problems in the field and vigorously discussed the origin 

hypotheses both in the field and in the office. Robert M. 

Dillon, formerly of the Building and Research Advisory 

Board of United States National Academy of Sciences, 

aided in preliminary arrangements. Pewe's visit in 

1973 was in part funded by the U.S. National Academy 

of Sciences as chief United States delegate to the Second 

International Conference on Permafrost. Part of his 

participation in the study was funded by a grant (No. 

GA38598) from the National Science Foundation of the 

United States. Katasonov collected silt samples U and V 

from Churapacha. Duwayne Anderson, formerly of the 

U.S. National Science Foundation, kindly provided 

satellite imagery for the region, and the late R. J. E. 

Brown of the National Research Council in Canada 

provided some Soviet literature and translations. 

George Soleimani, U.S. Geological Survey, helped 

translate the Russian literature. Jaromir Demek, 

former Director of the Institute of Geography of the 

Czechoslovakian Academy of Sciences (C.S.S.R.), 

kindly had the Pleistocene mollusks identified. J. Pellerin, Deputy Director of the Centre de Geomorphologie 

(C.N.R.S.), Caen, France, guided the mechanical, 

mineralogical, and chemical analyses of the silt samples, made at the Centre de Geomorphologie under the 

direction of Andre Journaux. Radiocarbon analyses of

samples collected by Pewe were made at the Smithsonian Institution Radiation Biology Laboratory under 

the direction of Robert Stuckenrath. James T. Bales, 

under the direction of Roger Slatt, formerly Professor of 

Geology at Arizona State University, calculated the 

statistical parameters of the sediment samples.

Finally, the authors appreciate the helpful suggestions of D. M. Hopkins, U.S. Geological Survey, and 

A. L. Washburn, former Director, Quaternary Research 

Center, University of Washington, Seattle, Wash., 

U.S.A., both of whom visited central Yakutia in 1969; 

Oscar J. Ferrians Jr., U.S. Geological Survey, who 

visited central Yakutia in 1973,1975, and 1976; and the 

late Roger J. E. Brown, of the National Research Council, Ottawa, Canada, who visited central Yakutia in 

1966 and 1973.

PHYSICAL SETTING 

PHYSIOGRAPHY AND GENERAL GEOLOGY

Unglaciated south-central Yakutia lies almost 200 

km south of the Arctic Circle in the largest Siberian 

republic and, with an area of 3,077,900 km2, is the 

second republic in the entire U.S.S.R. The area under 

consideration lies in the central Yakutian lowland, at 

an elevation of 50-400 m (fig. 2); it is drained by the 

Vilyuy, Lena, Amga, and Aldan Rivers. To the south, 

the lowland grades into the Prelensko Plateau; to the 

north, it is bounded by the towering Verkhoyansk 

Range. The mountains, sculptured by past glaciers, 

reach 2,295 m above sea level; small glaciers still exist 

in the east end. Crescentic terminal moraines lie on the 

sloping outwash plain that extends from the mountains 

southward to the Aldan River (fig. 3).

0 100 200 KILOMETERS

i____i____I

FIGURE 2. Central Yakutian lowland (shaded area), a region 

of well-developed alases, thaw depressions that form in areas 

of thick ice-rich silt deposits. From Solov'ev (1959, fig. 1).
ORIGIN AND CHARACTER OF LOESSLIKE SILT, YAKUTIA, SIBERIA 

129° 130° 131° 132°

64

FIGURE 3. Physiographic diagram of the region of the Lena, lower Aldan, and lower Amga Rivers, central 

T., Tyungyulyu; A, Abalakh; M, Magan. Lettered triangles mark sediment sample locations (see table 1). 

table 2). Basic physiographic data south of Aldan River are from Solov'ev (1959, fig. 9); north of river from
133° 134° 135°

PHYSICAL SETTING 

136°

100 KILOMETERS

64°

63°

62°

Yakutia. Fine-dotted area, major flood plain and low flood-plain terraces. Major high terraces: B, Bestayakh; 

First number (1-35) indicates site of thickness measurement, second number, thickness of silt in meters (see 

satellite photography. Drawn by Susan M. Selkirk.
ORIGIN AND CHARACTER OF LOESSLIKE SILT, YAKUTIA, SIBERIA

The study area is bounded by the Lena, Aldan, and 

Amga Rivers (fig. 3). The greatest part of the area consists of four silt-covered terraces 50-300 m above the 

major rivers: the Bestyakh, Tyungyulyu, Abalakh, and 

Magan Terraces, from lowest to highest. The Emilsk 

Terrace, separately mapped in other reports, is here 

combined with the Magan Terrace, The type localities of 

all four terraces lie within 50 km of Yakutsk and are 

described in detail by Solov'ev (1959). They are underlain by Cenozoic rocks to the north, Mesozoic rocks in 

the south-central part of the study area, and by 

Paleozoic rocks at the southernmost edge. Besides these 

high-level terraces, four low flood-plain terraces bound 

the Lena and Aldan Rivers.

The Bestyakh Terrace, the lowest of the upper terraces, is the most restricted in area and extent. In the 

study area, it occurs on the east side (right limit) of the 

Lena River extending northward from the vicinity of 

Pokrovsk to the mouth of the Aldan River (fig. 3). It is 

1-10 km wide and 55-75 m above the river and has a 

maximum relief of 30 m. The terrace is underlain by 

60-115 m of cross-bedded homogeneous clean well-sorted sand (table 1, sample P). The surface exhibits 

windblown ridges 2-10 m high and small merged 

parabolic sand dunes. The silt cover, widespread on the 

higher terraces (fig. 3), is not present on this terrace nor 

on the modern flood-plain terraces. The scarp is cut by 

precipitous active gullies 20-30 m deep, some eroded by 

spring sapping.

The Tyungyulyu Terrace is widespread in the area 

but occurs mainly adjacent to the Bestyakh Terrace east 

of the Lena River. It is as much as 40 km wide and 

65-100 m above the river; it has a maximum relief of 70 

m. It is blanketed by a well-sorted silt as much as 60 m 

thick, and characterized by a vast complex of ice wedges 

and well-developed thermokarst topography This topography is characterized by a multitude of alases and 

steep-walled valleys. Lowering of as much as 30-50 

percent of the terrace surface by melting of the groundice leaves interalas areas as ridges and connected 

smooth areas 5-10 m high.

The Abalakh Terrace occupies a large area in the 

central Yakutia lowland and is 115-135 m above river 

level. It is blanketed with a thick silt layer, in places 65 

m thick. The thermokarst relief is the same as on the 

Tyungyulyu Terrace, but it is more dissected and has a 

higher density of alases.

The Magan Terrace, a gently undulating plain, covers 

many hundreds of square kilometers, but in some areas 

consists of relatively narrow remnants between 

drainageways (fig. 3). The terrace is 155-175 m above 

major rivers. Valleys 80-100 m deep penetrate the 

Magan Terrace. In some valleys cut into the Magan 

Terrace there have been formed small strips of Tyungyulyu and Abalakh Terraces with alas relief. The silt 

cover on the Magan Terrace is 6 15 m thick, and alas 

development is very poor.

The study area is underlain by the lower Aldan depression (Alekseev, 1961), an asymmetrical basin trending 

east with its axis along the lower Aldan River. The 

south flank dips gently northward, and the north flank, 

which crops out in the Verkhoyansk Range, is near 

vertical (Solov'ev, 1959; Alekseev, 1961, fig. 20; 

Katasonov and Solov'ev, 1969). Dolomitized Cambrian 

limestone crops out along the Lena River in the southern part of the area (fig. 3), where it is overlain by sandy 

shale and conglomerate of Late Jurassic age; and the 

limestone in turn is overlain by sandstones and shales of 

Early Cretaceous age. The axis of the downwarp contains Oligocene, Miocene, and Pliocene deposits, and 

early Pleistocene fossiliferous sediments (Vangengeim, 

1961) exposed under the silt-covered terrace surfaces 

along the rivers. The stratigraphy is particularly well 

exposed at Mamontova Gora (Vangengeim, 1961; 

Giterman, 1963; Boyarskaya and Malayeva, 1967; 

Rosanov, 1968; Sudakova, 1969; Markov, 1973; 

Baranova and others, 1975; Pewe and others, 1977) on 

the Aldan River, 310 km upstream from its junction 

with the Lena River (fig. 3).

Much of central Yakutia has not been glaciated (fig. 4) 

(Giterman, 1963; Baranova, and others, 1968; Kind, 

1972,1975) but it was almost entirely rimmed by glacial 

ice in middle Pleistocene time. Glacier-clad mountains 

stood to the north, east, and south, and the front of the 

continental ice sheet was in northwest Yakutia. 

Glaciers probably approached to within 140 km of 

Yakutsk. During glacial advances, all the major rivers 

drained glaciated terrain and were heavily laden with 

sediment, filling the wide valleys with glacial outwash. 

Except in the Verkhoyansk Range, the extent of glaciation in Yakutia is highly controversial. Figure 4 shows 

one of the larger estimates of the extent of middle Pleistocene glaciation. Late Pleistocene glaciation was much 

less extensive, but its extent is also controversial.

CLIMATE

The central Yakutia area has an extreme continental 

climate characterized by a great range between summer 

and winter temperatures (fig. 5). The absolute minimum temperature recorded at Yakutsk is -60°C, the 

absolute maximum is 38°C. Oymyakon, on the northeast edge of the area, is noted as, with the exception of 

Antarctica, the coldest spot on Earth; -67.7°C was reliably recorded there in February 1933 (Filippovich, 

1974). The mean annual number of days of freezing 

temperatures at Yakutsk is 205, and freezing temperatures have been reported for every month of the year 

(Gavrilova, 1973).
PHYSICAL SETTING

The mean annual precipitation is 246 mm (fig. 5). 

Thunderstorms occur during the summer, but most precipitation falls in light showers. Sixty-five percent of the 

annual precipitation falls between May and September.

Wind patterns in central Yakutia include a long, relatively calm winter period from September to May and a 

short, slightly windy summer period from June to 

August. A 75-year record at Yakutsk (Gavrilova, 1973) 

indicates that the average wind velocity in winter is 

about 2.2 m/s and in summer about 3.0 m/s. The mean 

annual wind velocity at Yakutsk is 2.4 m/s. High winds 

are uncommon. During the winter 49 percent of all days 

are calm, and during the summer, 16 percent. Cyclones

move across Yakutia from west to east, and are the most 

common circulation process except in winter when the 

Siberian anticyclone spreads in a northeastern direction. Little is known about the general wind pattern 

between the Aldan River and the Verkhoyansk Range, 

but local winds may spread south from the mountains.

PERMAFROST

Central Yakutia lies in an area of widespread permafrost. Permafrost, or perennially frozen ground, is 

naturally occurring material that has been at a temperature of 0°C or colder continuously for 2 or more years. 

Permafrost is defined on the basis of temperature alone

700°

200 400 600 KILOMETERS

FIGURE 4. Generalized extent of glaciers in Yakutia during middle Pleistocene time (Samarov Glaciation). Boundary of Yakutia indicated 

by dotted pattern. Extent of mountain glaciers from Baranova and others (1968, fig. 24); extent of continental ice sheet from Soviet 

Ministrov SSSR (1969, p. 72).
TABLE 1. Data on Quaternary sediment samples collected in central Yakutia, Siberia, U.S.S.R.

I All samples collected by Troy L. Pewe, except where indicated]

Sediment Thickness 

sample site no. Lab 

(fig.3) (fig.3) No.

A _ .

B ______

C ____.

D ______

E ______

F ____.

jj

I _____

J

K _____

L _____

N ___..

P ____.

Q ..__.

R __._.

S ____.

_ _ ___2 1315-2

. ___ _3 1315-3

. __ 31 841-1

. __ _8 1315-8

. __ _7 1315-7

._ _ 32 841-2

. _ __4 1315-4

. _ _ _5 1315-5

.__ _ _6 1315-6

. __ 12 1316-2

_ ___ 11 1316-1

_ __ 10 1315-10

. ___ 9 1315-9

......29 1317-9

_ ___ 1 1315-1

.____. 34 841-4

. ___ 13 1316-3

. ___ 33 841-3

._ _ 14 1316-4

Date 

Material collected

Sandy 

loess

Loess

. __ 7/21/73

__ 7/21/73 

. __ 7/22/69

_ 7/23/73

Sandy-silty 

river alluvium ____7/23/73

Loess 7/23/69

Clayey 

loess

Sand

Sandy 

loess 

Eolian 

sand

Sandy 

loess

Loess 

Loess .

.____7/22/73

. -7/22/73

.____7/22/73

. __ 7/25/73

.____7/25/73

___ -7/25/73 

._ 7/25/73

_ _ -8/3/73

- 7/19/73 

______ 8/3/69

___ _ 7/27/73 

_ ___ 8/3/69

.__ 7/27/73

Location

Right limit of 

Aldan River, 30 

km upstream 

from mouth of 

Tumara River. 

Right limit of 

Aldan River, 30 

km upstream 

from mouth of 

Tumara River. 

Left limit, 244 km 

from mouth of 

Aldan River. 

Left limit, 244 km 

from mouth of 

Aldan River. 

Ust'Tatta Village

Left limit of Aldan 

River 284 km 

from mouth. 

Mamontova Gora 

Mamontova Gora 

Mamontova Gora

East side of Lake 

Syr dak.

10 km south of 

Syrdak Village.

10 km north of 

Matte Village 

Edge of Tyungyulyu alas at 

Tyungyulyu 

Village. 

53 km west of 

Yakutsk

3 km west of 

Yakutsk 

2 km east of Bestayakh Village.

9 km east of Bestayakh Village.

0.6 km south of 

Maiya Village. 

1 km west of Abalakh Lake

Stratigraphy

1 m from top of 

cliff, Tyungyulyu Terrace.

2 m from top of 

cliff, Tyungyulyu Terrace.

Silt cliff of 

Abalakh 

Terrace. 

Silt cliff of 

Abalakh 

Terrace. 

Flood plain alluvium 3 m 

above river 

level. 

Silt cliff of 

Abalakh Terrace. 

1 m from top of cliff 

7 m from top of cliff 

23 m from top of 

cliff 

1 m below surface 

of Tyungyulyu 

Terrace. 

Edge of alas cliff, 

Tyungyulyu 

Terrace. 

25 cm below surface in roadcut. 

1 m below surface 

in thermokarst 

pit.

Top of Magan Terrace, sand under 

turf. 

3 km from bluff of 

Magan Terrace. 

Low sand dune 

on Bestayakh 

Terrace. 

Edge of alas on 

edge of Tyungyulyu Terrace. 

Edge of alas

Abalakh Terrace, 

16 cm from surface.

GranuloAge metric

Late 

Quaternary.

Holocene

Late 

Quaternary.

Holocene 

Wisconsinan. 

pre-Wisconsinan

Tertiary 

Holocene(?)

Late 

Quaternary.

X 

X

X 

X 

X

X

X 

X 

X

X 

X

X 

X

X

X 

X

X

X 

X

Analysis performed

Heavy 

mineral Chemical CaC

XXX 

__ __ X 

X 

X X

X _ __ X 

X ____ __

X X X 

X X X 

X X X 

X X X 

__ _ X 

__ _ _ X

X X 

X ____ X

X X X 

X _ _

X ____ 

X X X 
T ____

U ____

V ____. w

X __ _

Y __-_

Z _.__

AA __.

DD __.

FF ____

GG __

______ 15 1316-5

_ _ T2-1 1399-4

_ _ T2-3 1399-5

_ ___ 16 1316-6

. ___ 17 1316-7

_ __ 18 1316-8

_ __ 19 1316-9

._ __20 1316-10

. _ _22 1317-2

. ___ 23 1317-3

. ___ 27 1317-7

__ _ 24 1317-4

___ 26 1317-6

___ 25 1317-5

T ,HPQQ

Alluvial

sand _

loess _ 

Loess

sand _

Silt from

limestone

_ 7/27/73

. __ 19731

. __ 19731

___7/29/73

__ 7/30/73

 7/30/73

___7/30/73

(2)

_ 7/30/73

_ 7/31/73 

_ 7/31/73

__ 8/2/73

_ 7/31/73

_ _ 8/1/73

Edge of Abalakh

Lake, Tyungyulyu Terrace. 

Churapacha

Pokrovsk, 70 km

up Lena from 

Yakutsk. 

Pokrovsk, 70 km

up Lena from 

Yakutsk.

Pokrovsk, 70 km

up Lena from 

Yakutsk

Pokrovsk, 70 km

up Lena from 

Yakutsk. 

7 km west of Pokrovsk.

River 12 km 

upstream from 

Pokrovsk . 

Left limit of Lena

River 12 km 

upstream from 

Pokrovsk . 

Left limit of Lena

River 12 km

upstream from 

Pokrovsk.

River 40 km 

upstream from 

Pokrovsk. 

Ilanskjo Village,

70 km upstream 

from Pokrovsk.

limit of Lena 

River south of 

Yakutsk.

1-m depth from

west side of lake.

10 m above Lena

River at river 

bank. 

1 km west of river,

45 cm deep, 

Tyungyulyu 

Terrace. 

5 km west of river,

30 cm deep, 

Tyungyulyu 

Terrace.

30 cm deep, 6 km 

west of river. 

1.5-m depth, lens

of sand.

tured limestone 

at base of loess 

section 3. 

1 m above BB

1.7 m below surface at contact

with underlying 

limestone. 

Top of cliff-head

dune derived 

from Bestyakh 

Terrace. 

5 m below top of Late

cliff in tributary. Quaternary 

147 m above river

on limestone 

cliff.

XXXXXXXXXXXXXX

XXXXXXXXXXXX

__ X 

____ X 

X X

____ X 

__ X 

____ X

XX

XX

XX

____ X

XX

XX

Collected by E. M. Katasonov.
10 ORIGIN AND CHARACTER OF LOESSLIKE SILT, YAKUTIA, SIBERIA

Jan Feb Mar Apr May June July Aug bept uct rwov uec j

0° Centigrade (freezing point)

-10.3°Centigrade annual mean temperatur

-50 -

MEAN TEMPERATURES

50.0

40.0

30.0

20.0

10.0

0.0

24.7 centimeters mean annual precipitation

Record: 75 years

MEAN PRECIPITATION

20 co

10

0 a.

- G °

Q LU 4

UJ C/>

S CC 3

">£ 2

0 c/3 i

z oc f

i£ Q

-

^^ ^^ ^~- -^.

I ___ ^^^2.4 meters per second mean monthly wind velocity">%--^^___^^ 

> i i i i i i i i i i

MCAM MnWTWI V \A/IMH \/FI nTITY

100

Jan Feb Mar Apr May June July Aug Sept Qct Nov Dec Jan

MEAN PERCENT OF CLEAR, PARTLY CLOUDY, AND CLOUDY DAYS

99 mean annual clear days; 46 mean annual partly

cloudy days; 220 mean annual cloudy days

FIGURE 5. Climatic data for Yakutsk, Yakutia, From Gavrilova (1973).
PHYSICAL SETTING 11

notwithstanding the type of sediment, rock, or the ice 

content. Most permafrost is consolidated by ice. Permafrost occurs in about 50 percent of the U.S.S.R. and is 

reported to be 1,600 m thick in northern Siberia. The 

frozen ground thins progressively to the south and can 

be differentiated into two broad zones: the continuous 

and the discontinuous. In the continuous zone permafrost is present almost everywhere except under lakes 

and rivers that do not freeze to the bottom. The discontinous zone includes permafrost-free areas that increase 

progressively in size and number from the north to the 

south.

The temperature of permafrost is measured at the 

level of zero annual amplitude, that is, at a depth of 

about 10 or 15 m, where the seasonal temperature 

change in the ground is hardly detectable. The temperature of permafrost at the depth of minimum annual 

seasonal change varies from about 0°C at the south limit 

of permafrost to 10°C in northern Alaska and -13°C 

in northeastern Siberia. Its thickness also increases 

northward.

Melnikov (1966) has shown that the thickness of permafrost in Yakutia ranges from near 100 m in the 

southern part to more than 900 m in the north. The 

temperature of the frozen ground at the depth of zero 

annual temperature change ranges from about 1°C in 

the south to 12°C in the north. The general thickness 

of permafrost in central Yakutia is about 300-350 m.

The ice content is probably the most important feature of permafrost affecting human activity in the 

north. Almost as important is the evidence it provides 

concerning past climates. Ice content ranges from ice in 

the pores between the grains to small ice segregations to 

large massive bodies. Various classifications have been 

proposed to describe the different sizes, shapes, and 

distributions of ground ice (Shumskii and others, 1955; 

Pewe, 1966; Mackay, 1972).

The most conspicuous and controversial type of ice in 

the permafrost is the large ice wedge or mass, characterized by parallel or subparallel foliated structures. 

Most foliated ice masses occur as wedge-shaped vertical, 

or inclined sheets or dikes 1-cm to 3-m wide and 1- to 

10-m high when seen in transverse cross sections (fig. 6). 

Some masses seen on the face of frozen cliffs may appear 

as horizontal bodies in a few centimeters to 3-m thick 

and 0.5-15 m long. Their true shape can be seen only in 

three dimensions. Ice wedges are part of a polygonal 

network of ice enclosing polygons or cells of frozen 

ground 3-30 m or more in diameter. They grow in almost any kind of frozen sediment, including fractured 

bedrock, but seem to grow to their largest size, both 

vertically and horizontally, and most commonly in 

areas of widespread thick loess deposits.

They are common in the ice-rich silt, referred to as 

"Edoma" by Tomirdiaro (1975), that covers much of the

Arctic, from northeast Siberia to central Alaska and the 

Yukon. They are abundant and well developed in central Yakutia; gigantic wedges are exposed along the 

Aldan, Lena, and Yana Rivers (Toll, 1895; Popov, 1955, 

1969; Rusanov, 1968; Washburn, 1973,1980; Pewe and 

others, 1977).

GEOMORPHOLOGY

Although the silt-covered terraces are generally flat 

or gently rolling, the permafrost and the nature of the 

silt result in a number of distinctive surface features.

Wherever large ground-ice masses are present in 

permafrost, thawing caused by a disturbance of insulating vegetation, for example, or by general climatic 

change, can produce thermokarst topography. Thermokarst is an uneven topography of mounds, sink holes, 

tunnels, caverns, and short ravines. A thermokarst feature that is especially typical of central Yakutia is the 

alas (spelling after Fyodorov, 1974) (Solov'ev, 1959, 

1973; Czudek and Demek, 1970; Katasonov, 1963, 

1979). Alases are broad, steep-sided depressions that 

form as small depressions coalesce and sediment is 

washed into the bottom. The depression thus has fairly 

steep walls and a grass-covered flat bottom. They are 

3-40 m deep and as much as 0.1-15 km in diameter. 

They tend to be round or oval and many contain small 

lakes (figs. 7, 8). These areas, where ground ice has 

almost completely disappeared, are important to the 

agriculture of the area (Solev'ev, 1959, 1973; Shilo, 

1978). Where the thawed sediments refreeze, closedsystem pingos are common; conical ice-cored hills as 

high as 30 m formed by the pressure of freezing water 

(fig. 9). On the Tyungyulyu and Abalakh Terraces, as 

much as 50 percent of the Pleistocene surface has been 

modified by alases, many of which formed during the 

past 7,000 years, some as a result of human activity 

(Are, 1973).

Many spectacular steep-walled gullies cut the lip of 

silt terraces on the left limit of the lower Aldan River. 

Here the abundant water created by the melting of ice 

wedges cuts the easily erodable silt into gullies, leaving 

interfluve areas as pyramid-shaped remnants. Such 

remnants, where mainly the result of the thawing of ice 

wedges, are called baydjarakhs (fig. 10). The competency that allows such features to stand also permits the 

silt to form steep cliffs and gullies elsewhere where 

eroded by water. Gullies form where runoff is concentrated, as below culverts, in ditches, or where vegetation has been disturbed, for example, as by cultivation 

on a slope. The steep walls of many alases are gullied, 

and many of the gullies on the left limit of the Aldan 

River are spectacular. Like the cliffs in loess in China, 

the Mississippi valley, central Alaska, France, and 

elsewhere, the silt cliffs in central Yakutia apparently
12 ORIGIN AND CHARACTER OF LOESSLIKE SILT, YAKUTIA, SIBERIA

FIGURE 6. Ice wedge in silt of Tyungyulyu Terrace at Syrdakh Lake, 70 km northeast of Yakutsk. Photograph 3452 by T. L.

Pewe, July 25, 1973.
PHYSICAL SETTING 13

FIGURE 7. Adjacent satellite images of the Lena-Amga area, south-central Yakutia. See figure 3. Courtesy D. M. Anderson and Lawrence 

Gato, U.S. Army, Cold Regions Research Engineering Laboratory. Prepared from ERTS-1 imagery, courtesy NASA.
14 ORIGIN AND CHARACTER OF LOESSLIKE SILT, YAKUTIA, SIBERIA

J
PHYSICAL SETTING 15

feb

S

O

I

cd

~n QJ

w

E

Sto 

W

I 

oi
oS3 

O

oi

W

FIGURE 10. Baydjarakhs, pyramid-shaped remnants resulting from thawing of ice wedges, left bank Aldan River, 224 km above junction with Lena River. From Washburn (1973,

fig. 10.2, p. 234.
DISTRIBUTION AND THICKNESS OF UPLAND SILT 17

stand for many years. Along the lower Aldan River the 

cliffs are as much as 25 m high. The stability of these 

cliffs may be due to the angularity of the grains and the 

strengthening effects of concretionary rods and tubes.

DISTRIBUTION AND THICKNESS 

OF UPLAND SILT

The silt is thickest near the major rivers draining 

glaciated areas, but absent on the flood plains and low 

flood plain terraces. It is especially thick along the south 

side of the Aldan River where it blankets all the high 

terraces and the tops of ridges and hills. The blanketing 

distribution is also recorded in the central and eastern 

part of the Vilyuy River basin (Alekseev, 1970) (fig. 2). 

Rusanov (1968, fig. 5) and Sudakova (1969, fig. 11) describe the thick cap of silt on the terraces on the left 

limit of the lower Aldan (fig. 11). Along the Lena River, 

silt is 10-25 m thick on the edge of the west side of the 

valley but thins rapidly to a featheredge west of 

Yakutsk (fig. 3). On the Tyungyulyu Terrace it reaches 

a maximum thickness of 60 m near Syrdakh in the 

general region between the junction of the Aldan and 

Lena Rivers (table 2). On the edge of the Tyungyulyu 

Terrace adjacent to the the Bestyakh Terrace the silt is 

very thin, but it rapidly thickens eastward (Solov'ev, 

1973, p. 34) and northward toward Syrdakh (Are, 1973). 

All thicknesses of loess reported from the river bluffs 

and inland toward Tyungyulyu and Maiya are at elevations no higher than 200 m above the level of the rivers. 

The silt is thin and locally absent on the Magan Terrace.

The silt is only a few meters thick on glacial and 

glaciofluvial deposits (fig. 3) on the north (right) side of 

the Aldan River (Vangengeim, 1961; Katasonov and 

Solov'ev, 1969). Just southwest of the study area (fig. 3), 

on the steep limestone cliffs of the "Pillars of the Lena" 

(fig. 12), the loess is thin to absent 200 m or more above 

the Lena River, but on the north side (left limit) of the 

river it is 7-25 m thick on the terraces (fig. 13), which 

are only 30-40 m above the river. In general, silt is

80-meterhigh terrace

50-meter-high terrace

thickest in the bottoms of small valleys and on lower 

slopes and thinner on the highlands, especially on the 

Magan Terrace. Are (1973, p. 16-20) describes 60 m of 

silt at Syrdakh (fig. 3), but he does not state if this 

thickness is in a small valley or on the general terrace 

level.

Hilltops, where the original silt thickness has not 

been supplemented by slopewash, are probably the only 

place where total original thickness can be approximated, modified only by the amount removed by erosion. Some scarps of the terraces along the Lena River 

and almost all scarps along the south side of the Aldan 

River are capped with 10-35 m of silt. This does not 

represent the original thickness of the silt as the upper 

part has been washed away (Sudakova, 1969).

In general, it appears from exposures west of Pokrovsk (figs. 3,14) that the silt is thicker on the Abalakh 

Terrace than on the Tyungyulyu Terrace. Solov'ev 

(1959, p. 43) states that the Abalakh Terrace is covered 

with "limnitic-alluvial clay," 60 m thick, the top part 

pierced with ice veins. Alases, which form best in thick 

silt, are well developed on both the Tyungyulyu and 

Abalakh Terraces.

Detailed measurements of loess thickness over a 

large area, similar to those made in Illinois by Smith 

(1942), in Iowa by Davidson and Handy (1952) and Ruhe 

(1969), and in parts of Alaska by Pewe (1955; Pewe and 

Holmes, 1964) have not yet been made in central 

Yakutia. As seen from the air, however, the loess forms 

a widespread cover, evident in the well-developed dendritic drainage patterns on the terraces (fig. 7).

The thickness reported here (table 2) include measurements from exposures and bore holes. Although silt 

has plainly washed into depressions in some localities 

measured, no coarse sediment was observed, so the 

measurements may give a reliable estimate of the total 

amount present.

The thick deposits on the south side (left limit) of the 

Aldan River face the enormous apron of glaciofluvial

30-meter-high terrace

ZZZ^Xl5-meter-high terrace Low flood-

....... .vxv . terrace

EXPLANATION

Sand and gravel Gray loess Brown loess Sandy-clayey sediment

FIGURE 11. Loess-capped sand terraces near Mamontova Gora along the Aldan River, Yakutia. Slightly modified from Rusanov (1968, fig. 5).
18 ORIGIN AND CHARACTER OF LOESSLIKE SILT, YAKUTIA, SIBERIA

rV i^* : -^fir ,

:i:;. «r v. ?! 

13 

C

a

T3

2

I

<

Jf **

I -i ~

be

> 

ca

J3 

I

CN
DISTRIBUTION AND THICKNESS OF UPLAND SILT 

TABLE 2. Thickness of silt in central Yakutia, Siberia, U.S.S.R.

19

Thickness 

site no. 

(fig. 3)

1 __

2 _.

3 __

4 __

5 __

6 __

7 __

8 __

9 __

10 __

11 __

12 __

13 __

14 _.

15 _.

16 __

17 __

18 -

19 __

20 -

21 __

Thickness 

(m) Location

30-35 Chuysakaya Mountain, right limit of the Aldan

River, 30 km upstream From mouth of Tumara

River.

25-32 Tettigi, left limit of the Aldan River, 130 km from

mouth.

25-30 Rossypnoy Perekat, left limit of the Aldan River, 244

40-65 km from mouth.

5-8 285 km from the mouth on the right limit of the Aldan

River, overlies glaciofluvial material.

25 310 km from the mouth on the left limit of the Aldan

River at Mamontova Gora.

7- 8. 5 Krest Khal'dzhay, right limit of the Aldan River, 360

km from mouth.

60 Syrdakh.

50 Tyungyulyu.

.0 53 km west of Yakutsk.

2+ Bluff west of Yakutsk, 0.5 km from the edge.

5-101 Tabaga Cape, left limit of Lena River, 30 km south of

Yakutsk.

.0 On Bestyakh terrace 2 km south of N. Bestyakh

Village.

8+ At alas, Bestyakh-Maiya Road, edge of Tyungyulu

Terrace.

.0 On Bestyakh Terrace 25 km south of N. Bestyakh

Village.

10+ 7 km southeast of Maiya Village.

31 Abalakh Terrace near Abalakh.

20 Churapacha.

25 On the Abalakh Terrace, 6 km west of Pokrovsk

Village.

7 12 km upstream from Pokrovsk on the left limit of the

Lena River.

10-15 On the Tyungyulyu Terrace, 1-5 km west of

Pokrovsk.

7 Ilankjo Village, left limit of the Lena River, 70 km

upstream from Pokrovsk.

Source

Katsanov and Solov'ev (1969, p. 21) Katasonov and

Ivanov (1973, p. 18).

Katasonov and Solov'ev (1969, p. 22).

Katasonov and Solov'ev (1969, p. 22) Katasonov and

Ivanov (1973, p. 24).

Katasonov and Solov'ev (1969, p. 23).

Pewe and others (1977).

Katasonov and Solov'ev (1969, p. 27) Vangengiem

(1961, fig. 20).

Are (1973, p. 16, 20).

Are (1973, p. 12).

Pewe, 1973 field data.

Pewe, 1973 field data.

Katasonov and Solov'ev (1969, p. 12).

Pewe, 1969 field data.

Pewe, 1973 field data.

Pewe, 1969 field data.

Katasonov and Solov'ev (1969, p. 41).

Katasonov and Solov'ev (1969, p. 43).

Solov'ev (1973, p. 30).

E. M. Katasonov (oral commun, 1973).

Pewe, 1973 field data.

E. M. Katasonov (oral commun, 1973).

Pewe, 1973 field data.

Sediment 

sample 

(flg.3)

A,B

C

G,H,I

J

M

N

0

P

D

Z

BB, CC

X, Y

FF

FIGURE 13. Loess-covered terrace of Ilanskjo Village on Cambrian dolomitic limestone, 70 km upstream from Pokrovsk on left limit of Lena

River. See figure 3. Loess is 7 m thick at gulley.
20 ORIGIN AND CHARACTER OF LOESSLIKE SILT, YAKUTIA, SIBERIA

terrain and glacial moraines emanating from the Verkhoyansk Range to the north (fig. 3). Such a distribution 

is very similar to distribution in central Alaska where 

thin loess is present on the apron of glaciofluvial debris 

emanating from the towering Alaskan Range and terminating at the Yukon-Tanana Upland to the north 

mantled by loess of great thickness (Pewe, 1955,1968). 

Although loess thicknesses of 10-35 m are reported 

from northern Yakutia (Tomirdiaro and others, 1974), 

the thickest deposits in the Republic appear to be along 

the Lena and Aldan Rivers in central Yakutia. This 

relation, too, is similar to the distribution of loess in 

central Alaska where loess as much as 60-100 m thick 

occurs on the north side of the Tanana River near Fairbanks (Pewe, 1955, 1968; 1982), the thickest known 

loess deposits in the State.

COLOR AND TEXTURE

The unfrozen upland silt is commonly tan, although 

grayish-tan silt is not rare; when wet or frozen, it is 

brown to black. In many localities, the frozen silt is gray 

to black and has thin dark carbonaceous layers and 

iron-stained bands and mottling.

As an aid to understanding the mechanical composition of the upland silt, analyses were completed on 27 

samples; analyses were also done on several samples of 

river silt and eolian and fluvial sand (table 1). The 

mechanical analyses (granulometric analyses) were 

made at the Centre de Geomorphologie in Caen, France, 

by sedimentation in water. Grains smaller than 20 yam 

were separated by sieving. For comparison, silt samples 

from other countries were analyzed in the same laboratory by the same method: windblown dust from Tempe, 

Arizona, and loess collected by Pewe from Alaska, New 

Zealand, and Czechoslovakia, and from China (near 

Peking) collected by R. J. E. Brown (table 3).

The silt examined is well sorted, especially on highlands away from river flood plains and sand terraces and 

from low areas where silt has been retransported short 

distances. On the high edges of major alases, as, for 

example, near Maiya or Syrdakh (fig. 3) (samples R, J 

and K; table 1), mechanical analyses (fig. 15) reveal that 

the sediments are 70-80 percent silt, 1-15 percent sand, 

and about 15 percent clay2. Because the clay content is 

low, the material has little plasticity.

In general, the mechanical analyses of upland silt 

throughout the area show that the mechanical composition and texture of the tan silt is remarkably uniform 

(figs. 16,17,18) (table 3). The range of texture of the 27 

samples is shown by the shaded envelope in figure 16, 

the average texture is sand 17 percent, silt 70 percent, 

and clay 13 percent. Solov'ev (1959) states that on the 

Abalakh Terrace near Churapacha, the upper clayey 

loam is 70-90 percent silt and is unbedded. Tomirdiaro 

(1975b) states that this uniform texture exists from the 

Aldan River to the north coast and even to the 

Novosibirsk Archipelago. Some samples near the sandy 

Magan or Bestyakh Terraces may be as much as 40 

percent very fine sand (fig. 19, samples Q and O) and 

some of the silt adjacent to the Aldan and Lena River 

flood plains may be 20-25 percent fine sand (fig. 19, BB,

2 In this report the U.S. Department of Agriculture classification is used: very fine sand, 

0.10-0.05 mm; silt, 0.05-0.005 mm; clay, 0.005-0.002 mm.

w

Magan Terrace

Quaternary . sand . and gravel

Thin-bedded Cambrian limestone ,

 I I I _l I I

FIGURE 14. Upland silt mantling terraces west of Pokrovsk, showing location of silt samples. Vertical exaggeration 150 x. Stratigraphic relations

and silt thicknesses from E. M. Katasonov (oral commun., July 30, 1973).
COLOR AND TEXTURE 21

TABLE 3. Mechanical properties of sand and loesslike silt from central Yakutia and loess and ash from other parts of the world

[Sedimentological terms from Folk (1974). Compiled by J. Bales. See Table 1 and cumulative-frequency curves (figs. 15-21, 23, 26-29)]

Sediment 

sample

(fig. 3) Material

Graphic mean Median 

(Md)4>

Inclusive graphic

standard deviation

(sorting) (o/) <#>

Inclusive graphic

skewness

(SKI)

Graphic 

kurtosis

A_______Loess _______ 6.20

B_______Sandy loess. ___ 4.78

C_______Loess _______ 6.58

D_______Loess _______ 6.14 

E__- -----Sand-silty river

alluvium ______ 4.39

F_______Loess __________ 6.71

G_______Loess _______ 7.47

H __________Loess _______ 7.43

I _______Loess _______ 7.14

J _______Loess _______ 5.80

K ______Loess _______ 5.58

L_______Clayey loess ___ 6.90

M ______Loess _______ 6.27

N ___Sand ________ 1.93

O____ _ _Sandy loess ____ 4.94

P_______Eolian sand ___ 2.98

Q_______Sandy loess ___ 5.03

R_______Loess _______ 6.27

S_______Loess _______ 6.90

T________Loess ________ 6.64

U ___Loess _______ 7.53

V_______Loess _______ 7.33

W _____Loess _______ 6.27

X_______Loess _______ 7.21

Y_______Loess _______ 7.05

Z_______Loess _______ 7.19

AA ______Alluvial sand ___ 2.16

BB ______Sandy loess ___ 7.59

CC ________Loess ________ 8.43

DD ______Sandy loess ___ 5.94

EE ______Eolian sand ___ .83

FF _______Loess ________ 7.41

GG_______Siltfrom

limestone ___ 5.63

Tomi _____Loess _______ 5.45

Dust, German ___________ 5.42

Volcanic Ash, Fairbanks _ ____ 6.24

Dust, Kansas ___________ 6.84

Dust, Arizona ____________ 7.80

Loess, New Zealand _ __ ____ 8.10

Loess, Czechoslovakia. _______ 7.37

Loess, Alaska ____________ 5.84

Loess, China ___________ 7.94

Loess, Illinois ____________ 6.07

5.44

4.57

5.57

5.89

3.78

5.80

6.70

6.75

6.88

5.27

5.27

5.80

5.72

1.84

4.64

2.84

4.18

5.11

5.80

5.72

6.27

6.38

5.44

5.64

5.8

6.06

2.15

5.51

6.27

5.01

.71

5.89

5.21

5.44

5.50

6.15

5.90

6.65

7.80

5.95

5.50

7.65

5.95

2.33

1.60

2.58

1.97

1.75

2.44

2.67

2.77

2.14

2.15

1.87

3.02

2.54

.69

3.24

.55

2.99

2.45

2.97

2.47

3.20

2.74

2.69

3.28

2.99

6.33

.59

4.68

4.25

3.10

.57

3.36

1.40

1.70

.95

1.28

2.41

2.87

2.83

2.96

1.36

2.84

1.23

0.58 

.50 

.65 

.36

.48 

.61 

.42 

.39 

.27 

.49 

.43 

.53 

.40 

.29 

.23 

.43 

.51 

.84 

.48 

.58 

.59 

.52 

.52 

.70 

.54 

.63

-.11 

.58 

.63 

.43 

.36 

.64

.45

.23

.17

.026

.44

.46

.10

.56

.26

-.10 

.075

1.43

2.49

1.42

1.47

1.05

1.12

1.08

1.07

1.06

1.41

1.86

.97

1.19

1.05

1.02

.89

1.90

1.96

1.05

1.15

1.08

1.01

1.44

1.11

.93

3.24

1.51

1.15

.84

1.34

1.17

1.01

1.33

3.83

1.02

1.23

1.26

1.47

.92

.98

1.12

.83

1.64

CC, and DD) similar to the sandy loess adjacent to 

braided glacial streams in Alaska (Pewe and Holmes, 

1964; Trainer, 1961).

The clay content is 10-20 percent where the silt is 

little transported. Where the silt is reworked, as in 

valley bottoms, alases, or thermokarst lakes, it contains \ 

more clay (20-40 percent) and minute organic fragments (figs. 20, 21, samples G, H, FF). Samples taken 

close to the surface (probably from the B soil horizons) 

are also slightly higher in clay (fig. 20, samples L, 25 cm 

below surface and S, 16 cm below the surface). Detailed 

sampling of silt for clay content in relation to soil age 

and depth, location, and rate of silt accumulation (see 

Ruhe, 1969; Smith, 1942) remains to be done on these 

deposits.

Samples taken at various depths from several sections (for locations see fig. 3) demonstrate the vertical

uniformity of the silt. Three samples (G, H, and I, taken 

at depths of 1, 7, and 23 m, respectively) from a 25-mhigh cliff at Mamontova Gora (Pewe and others, 1977), 

two samples (U and V, from 2 and 3 m deep, respectively) from Churapacha, and two samples (BB and 

CC, from the bedrock surface and 1 m above, respectively; fig 22) from the silt overlying dolomitic limestone at a quarry 12 km south of Pokrovsk (fig. 3) and 

very similar in texture (table 3 and figs. 19 and 21) and 

other sedimentologic parameters (table 3). Similar vertical uniformity is apparent in a 29.5-m-thick section of 

loess on the north coast of Yakutia (Tomirdiaro and 

others, 1974, table 1). The samples from the limestone 

quarry emphasize the independence of the silt from the 

underlying bedrock.

In an attempt to gage lateral uniformity, samples (W, 

X, Y, Z) of silt were taken at various distances (fig. 14)
22 ORIGIN AND CHARACTER OF LOESSLIKE SILT, YAKUTIA, SIBERIA

100

90

80

o 70 

oc

ID 

Q.

- 60

o

z

ID§ 50

ID 

OC

> 40

EXPLANATION

Samples

./

 **'

30

20 7

f 

0.1 0.05 0.01 0.005 

DIAMETER, IN MILLIMETERS

0.001 0.0005 0.0001

FIGURE 15. Cumulative-frequency grain-size curves for loess from edge of alases on Tyungyulyu Terrace, 40 km west of Yakutsk. See figure 3

for locations.
COLOR AND TEXTURE 23

100

90

80

70

£ 60

50

I I I I I I I l

EXPLANATION

- Average of 27 upland 

silt samples

> 40

30

20

10

1.0 0.5 0.1 0.05 0.01 0.005 

DIAMETER, IN MILLIMETERS

0.001 0.0005 0.0001

FIGURE 16. Average cumulative-frequency grain-size curve for 27 samples of upland silt on high terraces in central Yakutia. Range of

texture of samples shown by cross-hatched area.
24 ORIGIN AND CHARACTER OF LOESSLIKE SILT, YAKUTIA, SIBERIA

100

90

80

70

I I I I f

EXPLANATION

Samples

 A

 . B

 C

 .- D

______ C

50

40

20

10

0. 5 0.1 0.05 0.01 0.005 

DIAMETER, IN MILLIMETERS

0.001 0.0005 0.0001

FIGURE 17. Cumulative-frequency grain-size curves for loess blanketing terraces along lower Aldan River. Distance of sample locations 

up Aldan River from mouth: A and B, 30 km; C and D, 244 km; F, 284 km. See figure 3 for locations.
COLOR AND TEXTURE 25

57U

ou

h5 70

O

<r

LU 

Q_

Z en

O

Z

LU

0 50

LU

(E

LU

> 40

^

0

§ 30

o 

20

10

0 

EXPLANATION

Samples

 M

- T

1

f' 

*

<s s

<

S

\

/

'

/ 

f

ft

/I

I

1

'

/

r

f

/

r

^

/,'

s

^ 

/

^

* '

^,-A

^*

^

^^ 

^-*

j*

-*

...

.-* 

-«-

--- "*

1.0 0.5 0.1 0.05 0.01 0.005 0.001 0.0005 O.OOC

DIAMETER, IN MILLIMETERS 

FIGURE 18. Cumulative-frequency grain-size curves for loess mantling Tyungyulyu Terrace west of Lena River. See figure 3 for locations.
26 ORIGIN AND CHARACTER OF LOESSLIKE SILT, YAKUTIA, SIBERIA

100

10

0.01 0.005 

DIAMETER, IN MILLIMETERS

0.001 0.0005 0.0001

FIGURE 19. Cumulative-frequency grain-size curves for upland loess near sandy terraces (Q and O) and near sandy flood plains (BB, CC, 

and DD) along Lena River. Samples BB and CC are in same section, respectively 1 cm and 70 cm above bedrock. See figures 3 and 22.
COLOR AND TEXTURE 27

100

p\

0.05 0.01 0.005 

DIAMETER, IN MILLIMETERS

0.001 0.0005 0.0001

FIGURE 20. Cumulative-frequency grain-size curves for reworked upland loess and B soil horizon illustrating relatively high clay content.

See figures 3, 12.
28 ORIGIN AND CHARACTER OF LOESSLIKE SILT, YAKUTIA, SIBERIA

100

0.01 0.005 

DIAMETER, IN MILLIMETERS

0.001 0.0005 0.0001

FIGURE 21. Cumulative-frequency grain-size curves for retransported upland loess at various depths in section, illustrating vertical 

uniformity of texture. Samples G, H, I, Mamontova Gora; U, V, Churapacha. See figures 3, 30, and table 1.
MINERAL AND CHEMICAL COMPOSITION 29

away from the Lena River in the Pokvorsk area to determine whether the percentages of sand, silt, and clay 

changed (see Ruhe, 1969, p. 71). Within distance covered, only 6 km, no significant changes were seen in the 

the size distribution (fig. 23).

MINERAL AND CHEMICAL COMPOSITION

A number of chemical and mineral analyses of representative samples were made at the Centre de Geomorphologie, Caen, France. Heavy mineral analyses were 

made of 27 samples of the upland silt and of 3 samples of 

local fluviatile and eolian sand for comparison. The 

minerals were separated by bromoform (2.87 sp gr) after 

washing with HC1 (20 percent) and sieving in three 

granulometric fractions. Fourteen samples were 

analyzed for 11 oxides. Thirty samples were analyzed 

for calcium carbonate content alone, and 16 by X-ray 

for types of clay minerals present. Petrographic examination reveals that the silt grains, although slightly 

iron-stained, are angular and fresh.

The mineralogy of the loesslike silt is nearly uniform 

(table 4); typical samples contain abundant quartz, 

mica, and feldspar, with a lesser amount of heavy minerals. These include 30 to more than 70 percent 

hornblende; 12-30 percent epidote, and lesser amounts 

of hypersthene and garnet, and very small amounts of 

zircon, anatase, tourmaline, rutile, disthene, monazite,

METERS

0-

5- 

10- 

15-

20-

Excavation ,

face ->/ Massive

r ~n silt i / i

Massive 

silt

/ Excavated

// / 

^20 centimetersLoess sample 

rtft CC

Sandy loess 

sample BB

Frost-rived 

fragments of 

limestone 

bedrock

FIGURE 22. Location of samples of upland silt mantling dolomitic 

limestone on right limit of Lena River, 12 km upstream from 

Pokrovsk.

and other heavy minerals. The analyses show that, in 

addition to mineral uniformity in the loesslike silt geographically, there is vertical uniformity. Samples from 

various levels in the cliff at Mamontova Gora (table 1, 

samples G, H, I) and two samples (BB-CC) from a section over limestone 12 km upstream from Potrovsk (fig. 

22) are practically the same mineralogically and chemically with respect to each other.

The absence of heavy minerals in the limestone that 

underlies the silt upstream from Yakutsk along the 

Lena River (sample GG, table 4) confirms the independence of the silt and bedrock.

On a local scale, the mineralogy of floodplain sandysilty alluvium from near the mouth of the Tatta River 

(sample E) is very similar to nearby upland silt (sample 

S, table 4). Sands of the Magan and Bestyakh terraces 

(samples N and P, table 4) are also similar to adjacent 

silts.

On a larger scale, differences in heavy-mineral content between samples from the Lena River and the 

lower Aldan River may indicate general regional differences despite the small number of samples. In both, 

hornblende, epidote, hypersthene, and garnet constitute 80-90 percent of the heavy minerals present. The 

samples from the Lena River area, however, are considerably higher in hornblende and epidote and lower 

in hypersthene and garnet than those from the lower 

Aldan River. Percentages are: hornblende, 61.0 for the 

Lena River samples, 46.8 for the Aldan River samples; 

epidote, 24.1 and 20.0; hypersthene, 1.4 and 8.5; garnet, 5.6 and 12.7. A "mineralogy index" defined as

,, M (epidote + hornblende) , ,, = - - hypersthene gives

garnet

M = 14.9 for the Lena area and M = 4.6 for the Aldan 

(fig. 24).

To determine the statistical confidence level for the 

mineralogical differences described here (fig. 24), we 

calculated a probability value (P), using the "t" test. 

This value was less than 0.005 and indicates a high 

degree of confidence. Further, to determine whether the 

mineralogic differences merely reflected differences in 

grain-size distribution, we compared textural parameters (defined by Folk, 1974) for the samples from the two 

areas. Despite the mineralogic differences, the average 

values of these parameters are essentially the same for 

the two groups (table 5). Thus, the mineralogic differences seem to reflect a real division between the upland 

silt of the Lena River area and that of the lower Aldan 

River.

Chemical analyses (table 6) shows that the upland silt 

is nearly constant in chemical composition over large 

areas. The chemical analyses of the upland silt on the
30 ORIGIN AND CHARACTER OF LOESSLIKE SILT, YAKUTIA, SIBERIA

TABLE 4. Percentage distribution of heavy minerals in sediments from Yakutia, Siberia, U.S.S.R.

[Sample No. 30, loess from Peking, China, collected by R. J. E. Brown, National Research Council of Canada, Ottawa, 1973. Analyses made at Centre de Geomorphologie, Caen, France]

Sediment 

sample A 

(fig. 3)

Mineral Loess

Hornblen 

Epidote 

Hypersth 

Garnet

Sphene 

Zircon

Staurolit( 

Pyroxene 

(monoclir 

Anatase 

Tourmali 

Rutile

Disthene 

Sillimani 

Andalusi 

Chloritou 

Topaz

Monazite

de

ene

* 

s 

ii(:)

ne

61.6 

20.2 

5.8 

8.2 

.7 

.7 

.3

te

te 

I

.3 

.3 

.7 

.3

.3

Total __ ___ ____ 99.7

100 

90 

80

H

JZi 70 

o 

cc

LLJ 

0.

z 

CUMULATIVE FREQUENCY, to w.> 01a -» 

co _»o 

EXPLANATION

0

Sam 

 - - W

 X

 Y

 -- - z

as 

0

fcfc

5

Dies

^.^

C D E F G H I J

AlluLoess Loess vium Loess Loess Loess Loess Loess

42.4 

28.0 

1.7 

5.9 

.8 

.8 

5.9

.8 

1.7

.8 

8.4

56.5 

15.6 

14.4 

10.6

.7 

.3

.5 

.5

-

-

.3

.2 

.3

44.7 

17.4 

16.3 

13.9

1.4

4.1 

1.1 

.3 

.5

.3

31.4 

17.2 

11.2 

19.4 

1.5 

8.9 

6.7

3.7

58.8 

19.8 

7.7 

11.4 

.4 

.4

1.1 

.4

 

45.4 

12.1 

12.1 

16.8 

1.5 

1.1

5.5 

.7 

.4 

1.1 

.4

.7

46.3 

27.1 

3.9 

11.9 

.6 

5.6

.6 

.6 

1.1 

.6 

.6

.6 

.6

63.0 

27.3 

.6 

3.6

1.8

.6

.6

1.8

.6

97.2 99.9 100.0 100.0 100.0 97.8 100.1 99.9

1 ..-^" 1

^

^

Y

-

*

^'

/

i

/

1

f

in

/,

$?'/ f

/ 

/

f

'/

*

It

S

s1 

^

"

{P

ff ^

f'

^

-^'

.-"' 1

"^

B^-

^*

i*-" 

.^

w> ^

-4-

*

*£

-Z4-

;£*

_ +

 £^-

 m""

0.1 0.05 0.01 0.005 0.001 0.0005 0.0001

DIAMETER, IN MILLIMETERS

FIGURE 23. Cumulative-frequency grain-size curves for upland loess. Distances from Lena River: W, 10 m; X, 1 km; Y, 5 km; Z, 6 km.

See figures 3, 13.
FIELD RELATIONS 

TABLE 4. Percentage distribution of heavy minerals in sediments from Yakutia, Siberia, U.S.S.R.-Continued

31

Sediment 

sample 

(fig. 3)

W

Mineral Loess Sand Loess Sand Loess Loess Loess Loess Loess

Hornblende ______ 68.6 55.1 51.7 60.8 54.5 69.9 63.1

Epidote ____________ 25.5 33.9 29.7 19.3 13.0 21.3 25.4

Hypersthene ______ .7 .5 1.7 .3

Garnet____________ 2.6 5.1 9.9 4.1 7.1 3.9 3.1

Sphene ____________ 1.8 1.9 3.3 2.3 1.7 .9 3.5

Zircon __________ .4 3.5 1.6 9.3 15.3 1.4 1.7

Staurolite _______ __ __ __ .6 5.6 __ __

Pyroxenes _______ ____ ____ __ ____ __ ____ ____

(monoclinic) ________ ____ ____ 1.0 _-__ _-_- -___ 1.0

Anatase ______ ___ .4 __ .7 __ __ 1.9 .3

Tourmaline -_______ ____ ____ .3 __ __-_ -___ .3

Rutile __________ __ .5 1.0 __ __ __ 

Disthene__________ __._ __ ____ 1.2 .5 ____ .7

Sillimanite________ __ ____ .2 ____ ____ -___ __

Andalusite_______ __ __ __ .6 1.1 .5 .3

Chloritoid ________ ____ ____ __ __ ____ ____ __

Topaz ___________ ____ ____ __ __ __ ____ __

Monazite________ _______ ____ ___ __ _____________

Total _____ _ ____ 100.0 100.0_____99.9_____99.9_____98.8_____99.8_____99.3

Sediment

sample Y Z AA BB CC DD EE FF 

(fig. 3)

	Sandy 

Minerals Loess Loess Sand loess Loess Loess Sand Loess

Hornblende ________ 67.8 61.8 37.3 60.6 58.8 43.7 46.5 56.4

Epidote __________ 22.3 24.1 45.6 24.1 23.6 30.9 30.0 28.7

Hypersthene __________ .9 1.2 1.1 2.9 2.9

Garnet__________ 4.3 7.3 10.4 5.6 8.4 9.1 10.3 4.9

Sphene _________ .9 2.1 4.4 2.4 4.6 4.1 3.4

Zircon __________ .9 2.1 4.1 2.8 2.4 5.8 2.5 1.5

Staurolite _______ __ __ .5 __ __ .1 .8 __

Pyroxenes ________ __ __ __ __ __ __ __ __

(monoclinic) _______ .9 ___ __ __ ___ .6 __ -___

Anatase ________ .9 .5 1.0 1.6 1.4 .8 .5

Tourmaline ________ ____ ____ __ ____ __ __ __ -___

Rutile ______________ ____ .5 .5 .4 .8 .8 1.6 ____

Disthene_________ .5 1.0 __ .4 .4 .3 __ .5

Sillimanite__ ________ ____ ____ __ ____ ____ .1 __ ____

Andalusite __________ ____ ____ __ __ ____ .1 __ .9

Chloritoid ____________ ____ ____ __ ____ ____ ____ __

Topaz ____________ ____ ____ ____ ____ __ ____ __ .5

Monazite_________ .5______.5______.5_____1.6______A_______LI______A_________

Total __________ 99.9 99.9 99.9 99.9 100.0 99.7 99.9 100.2

60.3

26.2

.4

4.4

1.9

2.4

1.2

1.6

100.0

73.6

19.9

2.1 

1.1 

1.6

.5

99.8

GG

Silt

from

limestone Loess

57.8

34.5

.2

3.6

2.2

.2

99.9

50-m terrace along the Aldan River presented by 

Rusanov (1968, table 8) are almost the same as those 

listed for the same area in this paper. The chemical 

analyses are also similar to those analyses of loess along 

the Main River in northeast Siberia (Tomirdiaro, 1972, 

table 2). No chemical or mineralogical analyses are 

readily available for the bedrock in the Verkhoyansk 

Range or upstream on the Aldan or Lena Rivers. The 

calcium carbonate composition of the silt ranges from

less than 2 percent to about 7 percent and is fairly 

consistent over the area under consideration (table 7). 

All loesslike silt samples analyzed by X-ray contain 

montmorillonite, chlorite, and illite, and most samples 

contain kaolinite.

FIELD RELATIONS

The massive silt overlies various substrates with a 

sharp contact: limestone along the Lena River, alluvial
32 ORIGIN AND CHARACTER OF LOESSLIKE SILT, YAKUTIA, SIBERIA

TABLE 5. Average grain-size values of samples of upland silt along the 

Lena and Aldan Rivers in south-central Yakutia, U.S.S.R., analyzed 

for heavy-mineral content 

[Parameters and word descriptions from Folk, 1974, and Folk and Ward, 1957. See figs. 2,24]

Mechanical 

property

Aldan River

Group 

(6 samples) Remarks

Lena River

Group 

(15 samples) Remarks

Graphic mean 

Mz __________

Median Md ___

Inclusive graphic standard 

deviation 

(sorting), al<j)

Inclusive graphic skewness, 

Sk, _______

Graphic kurtosis, KG ___

6.91

6.27

Very poorly 

2.43 sorted

.44 Strongly

coarse-skewed

1.20 Leptokurtic

6.60

5.33

Very poorly 

3.26 sorted

Strongly 

.66 coarse-skewed

1.35 Leptokurtic

sand on the left limit of the Aldan River, and glaciofluvial deposits at places on the right limit of the Aldan 

River.

The upland silt is massive, showing little or no 

stratification or jointing except in the retransported 

fades; however, near valley bottoms where some silt 

has been retransported, crude stratification is apparent. 

The faint stratification consists of iron oxide-stained 

horizons, organic films, vague colored bandings of short 

lateral extent and thin seams of ice, "Taber ice," which 

have grown parallel to the very indistinct bedding of the 

retransported silt. Differences of moisture content at 

certain horizons outline faint stratification. In no instance does the faintly developed stratification resemble fluvial or lacustrine bedding. It is only in the frozen

Hornblende 

Epidote 

Hypersthene 

Garnet

Number of 

samples

M

Percent 

61.0 

24.1 

1.4 

5.6

15

14.9

Hornblende 

Epidote 

Hypersthene 

Garnet

Number of 

samples

M

20.0

8.5

12.7

6 

4.6

FIGURE 24. Location of loess samples along Lena River and lower Aldan River analyzed for heavy-mineral content. Heavy lines 

encircle two different mineral suites based on average percentage of composition and differences of "mineralogy index," M. 

See text for explanation of equation. Only 10 samples of Lena River silt analyzed for hypersthene.
FOSSILS 

TABLE 6. Chemical analysis of Quaternary loess from central Yakutia, Siberia, U.S.S.R.

[All calculations in weight percent. Analyses made at Centre de Geomorphologie, Caen, France. Samples collected by Troy L. Pewe]

33

Sediment 

sample 

(fig.3) Sediment SiO2 A12O., Fe2O3 TiO2 MaO

A ______Loess ______ 59.01 11.84 4.60 0.715 0.163

G ___ _ Loess ______ 59.94 12.32 5.36 .724 .145

H _ _ Loess _ ____ 58.49 1.10 5.21 .736 .152

I- ___ Loess ______ 59.12 12.81 6.70 .715 .217

J __ .Loess - __ 64.31 11.92 4.42 .669 .149

O ___ Loess ___ 69.19 11.29 2.92 .72 .151

S ___ _ Loess ______ 61.77 12.32 4.76 .723 .173

X _ ___ Loess ______ 61.20 11.29 3.48 .622 .146

BB __ __Sandy loess 64.91 12.38 3.97 .725 .173

CC__ ___Loess _ ___ 63.04 12.66 3.98 .786 .138

DD__ __ Loess ______ 65.37 10.79 3.60 .628 .174

FF___ Loess ___ 57.91 11.40 4.59 .715 .165

GG- __ Silt from

limestone 2.49 .76 .86 .07 .142

TABLE 7. CaCO3 in Quaternary sediments from central Yakutia, 

Siberia, U.S.S.R.

[Analyses made at Centre de Geomorphologie, Caen, France. Samples collected by Troy L. 

Pewe]

Sediment Weight 

sample percent 

(fig. 3) Sediment CaCO3

A Loess 6.8

B Loess =2

E Alluvium <2

I T iflf^QQ A. ^\

J Loess <2

K Loess <2

M Loess =3

N _____________ ___ ____Sand ___________________ _ <2

O Loess <2

Q Loess <2

X ___ __ __ Loess _ _ _ __ _ 7.6

Y Loess 4.7

AA Sand <2

BB ___ _ _ _ Sandy loess. ______ <2

CC __ _ __ _ _ Loess __ _ _____ __ <2

DD Loess <2

EE ____________________Sand __ ___ ____________ <2

FF ____________________Loess______ __ ____________ 7.6

301 ____________________Loess__________-___-_____-_ 6.3

'Collected in China by R.J.E. Brown, 1973.

or freshly thawed sediments that the bedding can be 

seen; after the silt has been thawed for years, it is tan 

instead of gray to black, and most of the indistinct bedding can no longer be seen. This retransported silt has 

the same texture and composition as the tan loesslike 

silt away from the depressions (figs. 15, 20, and 21; 

tables 3, 4, and 6) but is distinguished by a higher ice 

content and a fetid odor, as well as by faint stratification. 

Because of the uniform texture, composition, and 

color of the silt, structural disturbance is rarely evident.

Loss on 

CaO MgO K2O Na2O P2O5 H2O ignition

7.19 1.43 2.56 2.18 0.81 2.25 7.79

4.83 .974 2.82 2.04 .53 3.14 7.15

4.82 .958 2.74 2.08 .497 3.01 8.48

4.21 .855 2.73 1.73 .55 3.60 6.59

4.91 1.055 3.12 2.61 .421 1.32 4.26

4.48 .826 3.14 2.58 .370 1.45 3.87

5.09 1.01 2.89 2.20 .629 3.05 5.42

7.25 1.02 2.90 2.50 .331 2.51 6.24

3.82 .813 2.91 2.27 .551 3.26 3.97

4.02 .820 2.89 2.22 .510 3.82 4.81

4.73 .975 2.97 2.45 .435 1.62 4.84

7.04 1.16 2.71 2.26 .566 1.00 8.88

32.44 17.05 .32 0 .350 .25 45.39

Where stratification is visible, however, minor folds and 

faults are common and, near the boundaries of ice 

wedges, the strata are commonly bent upward.

FOSSILS

The upland silt represents the greatest repository of

late Quaternary flora and fauna in central Yakutia.

Fossils in glacial and flood-plain deposits of equivalent

Q n*f> OT*O 1 CkCC O V\l lYl/^QYl'f" QYl/i loCC TXrol 1 Tyi*O COY*\7£ifi £kGT\£k 

cially the Pleistocene mammal fossils. Fossil remains

are uncommon in the silt on ridges or low hills but

common in lowlands and slight depressions where re-

^"VQT"l OT\f"l'W*^"O/^ CSll'f' Vl O G Q/^/^ll TV! Ill O*t~O/l

This report does not consider in detail the flora and

TQimci CIT 4~r\& cil'f' dlT*fiQ/i\7 T*OT\OT*^" o/H r\\7 A IOKGOO^T" ( 1 Qfi 1 1

Vangengeim (1961), Rusanov (1969), Motuzko and

others (1969), Markov (1973), Pewe and others (1977),

and other investigators. In summary, the silt deposits

Q Y*O (* r\ OT*O/^"^O>*1 rjdn V\\7 Till YY"I O>*f"ll 1 C >*OTY"I Q 1 Yl C f\T nA flYYI m lltr! 7 / O

primigenius of a late type, Equus caballus, subsp. B

(small form), Bison prisons aff. derninutus W. Grom,

muskox, moose, caribou, and other large mammals and

rodents such as Lemmas and Dicrostonyx. These fossils

are especially common on the terraces of the Aldan

River valley. Some, such as the large horse and the

long-horn bison, are older fossils. These older remains 

may be from the lower levels of the silt or reworked from 

the underlying sand terraces (Vangengeim, 1961, p. 34). 

Although a considerable number of specimens in central Yakutia have been identified, it remains to relate 

individual fossils to specific stratigraphic units within 

the silt as suggested by Pewe and others (1977). 

It is not uncommon for many of the skeletons to be 

found with several of the bones joined together, and 

Vangengeim (1961, p. 38-39) reports recovery of an 

entire skeleton. Some of the widely reported carcasses, 

or partial carcasses, of ice-age mammals, including the 

Berezovka mammoth, have come from this silt (Shilo,
34 ORIGIN AND CHARACTER OF LOESSLIKE SILT, YAKUTIA, SIBERIA

1978). Partial carcasses of Pleistocene mammals have 

also been recovered from the perennially frozen retransported silt in Alaska (Pewe, 1975a).

Aquatic fossils in the silt include two mollusk species 

collected by Pewe on the south side of the Aldan Valley: 

Valvata piscinalis Mull, and Valvata cristata (O. F. 

Muller) (identified by J. Vasatko, Czechoslovakia 

Academy of Science, Brno, CSSR, written commun., 

1974). Solov'ev (1959) reports aquatic mollusks at various depths in the upper of two major clayey loam layers 

near Churapacha.

The retransported frozen silt contains a varied 

megaflora in the form of peat, sticks, twigs, pods of plant 

remains, and isolated tree limbs and stumps. Study of 

such specimens and pollen analysis indicate the predominance of herbaceous tundra and forest-tundra vegetation at the time of silt accumulation (Vangengeim, 

1961; Giterman and Golubeva, 1967).

ORIGIN

Although the origin of loess has been a controversial 

subject worldwide for about 100 years, most of the discussions have centered on the loess in China, central 

United States, and later, Alaska. Less is known about 

the probable origin of the widespread loesslike silt in 

the lowlands of unglaciated eastern Siberia. Marine, 

estuarine, lacustrine, fluvial, weathering, and eolian 

processes have been invoked to explain the loesslike 

silt. The marine and estuarine hypotheses have had 

little support; but the lacustrine, fluvial, and residual 

hypotheses, either separately or in combination, have 

had widespread support and are currently strongly held 

by Soviet workers, especially by researchers working 

with frozen ground. In recent years, however, the eolian 

hypothesis has been advocated by some workers (Tomirdiaro and others, 1974; Tomirdiaro, 1975b; Pewe 

and others, 1977).

MARINE AND ESTUARINE HYPOTHESES

Many of the river valleys in central Yakutia, especially in the north, are less than 100 m above sea level. It 

has been suggested that much of the loesslike silt could 

result from inundation by an advancing sea (Wright, 

1902). To deposit such uniform silt at both high and low 

elevations, however, flooding the valleys many hundreds of meters deep would have been required (fig. 2).

Moreover, deltas, shorelines, and beaches would be 

present if the water level had been constant for a long 

period of time. The silt would stratify and would contain 

large amounts of clay, mud cracks or ripple marks, and 

marine fossils, but none of these features are present.

WEATHERING HYPOTHESIS

Berg (1960) proposed that loess forms in place as the 

underlying rock breaks down. His hypothesis exerted a

profound influence over many Soviet scientists, but now 

it seems to have little support in the western part of the 

Soviet Union. In Yakutia, however, many workers have 

argued more recently that the loesslike silt there is a 

product of breakdown by seasonal freezing and thawing 

(Sudokova, 1959; Popov, 1965, 1967, 1972, 1976; Agadzhanyan and others, 1973; Danilova, 1973), a combination of frost action and chemical weathering (Chigir, 

1972; Konishchev, 1972; Konishchev and Rogov, 1972), 

or chemical weathering alone, a "loessification" process 

in place (Morozova, 1971). According to this theory, the 

upland silt of central Yakutia is in the initial stages of 

loess formation and not yet as well formed as the loess of 

the Russian plains.

If the upland silts were formed in place by disintegration of local country rock, the following features would 

be expected:

1. The mineralogy of the silt and the underlying 

rock would be similar, allowing for differential resistance to weathering. In central 

Yakutia, the silt overlies many substrates, including dolomitic limestone, alluvium, poorly 

consolidated sands, glacial outwash, and till of 

diverse provenance. In all areas, the mineralogy and chemistry of the silt is similar despite the great diversity of underlying material.

In the southern part of the area, the upland 

silt lies directly on dolomitic limestone, but 

samples (W, X, Y, Z, BB, CC, DD, and FF; 

fig. 3) overlie the limestone and could not 

have been derived from the weathering, 

either chemical or mechanical, of the underlying rock. These samples contain a suite of 

heavy minerals similar to other samples, minerals not present in the underlying bedrock 

(tables 1, 2, and 4). The percentage of calcium 

carbonate in these samples is actually about 

the same as in the rest of the mapped area, 

or slightly less; yet, one would expect a tremendously high concentration of calcium carbonate in loess if it had originated from the 

underlying limestone. On top of dolomitic 

limestone cliffs 147 m above the Lena River 

at the Pillars of the Lena, a sample (tables 1 

and 4) of weathered limestone was taken from 

a crevice deep in the rock in a dry environment. Although the sample is a well-sorted 

silt, it contains no heavy minerals and is pure 

calcium carbonate (fig. 27). The silt occurs 

high on the bluffs and could not have originated from some other local bedrock at higher 

altitudes and been transported to the area 

(figs. 13, 14, and 22). It is evident, therefore, 

that the silt in these localities did not come 

from the underlying or nearby bedrock.
ORIGIN 35

Sediments produced by rock disintegration 

would undoubtedly contain some large particles, especially of the more resistant minerals, but such resistant particles are scarce, At 

some localities, angular pieces of resistant 

limestone as much as 5 cm in diameter occur 

at the base of the loesslike silt, probably broken from the underlying limestone by frost 

action. The massive loesslike silt overlies 

these frost derived fragments on a sharp contact that marks (fig. 22) a great change in 

textural, chemical, and mineralogical composition.

If silt accumulated on top of a hill or a flat-lying 

area through the disintegration of underlying 

bedrock, the material should be finer and 

more weathered at the surface than that 

closer to bedrock. The vertical uniformity of 

size distribution evidenced at Mamontova 

Gora (fig. 21), at consecutive depths of 2 m (U) 

and 3 m (V) (fig. 3) at Churapacha on the 

Abalakh Terrace, and by samples BB and CC 

in loesslike silt overlying dolomitic limestone 

(figs. 19 and 22) contradicts this expectation.

Mechanical disintegration, probably the dominant process of bedrock weathering in subarctic climates, depends largely on the action of 

alternate freezing and thawing (cryolithic 

processes). Where a thick layer of breakdown 

residuum develops, it might be expected to 

shield the underlying rock from further disintegration. On hillsides, the silt might be removed as fast as it forms, but it would accumulate on flat hilltops and ridges. The 

depth of seasonal freeze and thaw of the 

ground in central Yakutia ranges from 1 to 3 

m with deepest penetration in gravel and 

least penetration in silt. Under present 

climatic conditions seasonal freeze and thaw 

of bedrock probably does not occur under a 

protective mantle of silt thicker than 1-2 m. 

In past colder periods, seasonal penetration of 

frost may have been slightly deeper in the 

nonperennially frozen ground. It is true that, 

in the past, well-drained silt may have been 

perennially frozen, but if no frequent alternation of freeze and thaw occurred, little disintegration would take place. Because much 

more than 3-4 m of upland silt is present on 

the relatively flat terraces and uplands, including the highest terrace, it is clear that the 

material could not have originated in place 

from seasonal frost action.

Residual silt on hilltops, ridges, plateaus, or terraces would contain no carbonaceous layers 

or soil horizons if the material were formed by

a progressive downward disintegration of the 

underlying bedrock. Sections of the silt do, 

however, reveal carbonaceous layers and soil 

horizons.

In summary, a number of characteristics that would 

be expected in the loesslike silt if it were formed by 

disintegration in place are not observed. Together the 

lack of these characteristics argue convincingly against 

the disintegration hypothesis.

LACUSTRINE AND FLUVIATILE HYPOTHESES

The most popular explanation of the origin of the 

upland silt in central Yakutia is that the loesslike silt is 

a combination of lacustrine and alluvial deposits formed 

on great flood plains and marshy plains (Popov, 1953; 

Solov'ev, 1959; Boyarskaya and Malayeva, 1967; 

Katasonov and Solov'ev, 1969; Motuzko and others, 

1969; Agadzhanyan and others, 1973; Ivanov and 

Katasonov, 1973; Katasonov and Ivanov, 1973; 

Konishchev, 1973; Popov, 1973). Periglacial researchers concerned with various forms of ground ice favor this 

hypothesis because of the faint stratification where the 

silt has flowed into shallow depressions when large 

amounts of segregated ice melts. The quantity of ground 

ice present indicated, they thought, that the silt had 

been deposited on vast partly flooded plains.

It has long been known (Bunge, 1884; Toll, 1895) that 

ground ice of various types and quantity (fig. 6) is widespread in the loesslike silt cover of the high and low 

terraces of central Yakutia, as well as on the coastal 

plain of the north. The lacustrine-alluvial hypothesis 

evolved over the years in an attempt to explain the 

different types and distribution of ground ice. According 

to Tomirdiaro and others (1974), until the early 1950's 

of the 20th century, it was believed that most of the ice 

in the ground was remnant ice and snow from Pleistocene glaciers buried by clayey alluvium; this idea is 

the so-called glacial firn theory. It is now known that the 

glaciers were not that extensive (fig. 4) and that the 

foliated ground-ice wedges (figs. 6, 25) formed in thermal contraction cracks in the perennially frozen 

ground. Many scientists thought that the ice wedges 

must have grown syngenetically in the saturated sediments of a gigantic flood plain and invoked great floods 

and colossal lacustrine-alluvial plains to account for the 

great vertical extent of the ice, from modern flood plains 

to high terraces (Popov, 1953, 1965).

A number of factors combine to make the fluvial and 

lacustrine hypotheses unlikely. Fluviatile silt is well 

stratified and crossbedded, individual beds are lens 

shaped, and, though individual beds are fairly well 

sorted, samples collected over a broad area or from a 

thick section are poorly sorted. The upland silt, however, is unstratified and uniform in texture. Moreover, 

though fluviatile silt is abundant on the flood plains of 

the Lena and Aldan Rivers, it is typically of larger grain
36 ORIGIN AND CHARACTER OF LOESSLIKE SILT, YAKUTIA, SIBERIA

size than the upland silt (fig. 26 and table 3, sample E). 

It is also difficult to explain, in the context of the fluvial 

hypothesis, the presence of as much as 25 m of silt on 

bedrock bluffs as much as 50-100 m above the river 

level and the character of the silt as a nearly continuous 

blanket over a surface with 100-200 m of relief.

The lacustrine hypothesis is also improbable for several reasons:

1. No known barriers capable of damming water 

200 m deep, 150 km up the Lena River from 

Yakutsk and 300 km up the Aldan River from 

its mouth existed in the area where the silt 

was deposited.

2. No features such as preserved shorelines, 

wave-cut benches, and deltas, which would be 

expected to form in a lacustrine environment, 

are evident in the silt.

3. Lacustrine deposits have a limited vertical extent, but the loesslike silt occurs at various 

elevations and even on the moraines at the 

foot of the Verkhoyansk Range, hundreds of 

meters above the Aldan River.

4. Lacustrine silt would be stratified and might 

even contain varves. The only stratification in 

the upland silt is produced by isolated carbonaceous layers and iron-stained horizons, 

and, in most places, stratification is absent. 

Crude stratification is outlined by concentrations of ground ice and by slight differences

in grain size. In the retransported materials 

that were carried by slopewash to shallow depressions, however, this crude stratification 

disappears upon thawing and complete drying 

of the silt in cliffs.

An appreciable amount of clay could be expected 

in the deposits of any large lake. The average 

cumulative-frequency curve of 27 samples 

from the upland silt has a very low content of 

clay, only about 5-15 percent.

As would be expected of lacustrine deposits, the 

upland silt bears little lithologic relation to 

the underlying rock. This characteristic, however, is typical of any transported sediment.

Some forms of life would have existed in these 

lakes. So far as we are aware, no lacustrine 

fossils have been found in the high upland silt, 

although gastropods and pelecypods have 

been found in the reworked material of the 

valley bottoms. The fossils in the valley bottoms probably were derived from thermokarst 

lakes (alases) that existed at the time of silt 

accumulation.

Land fossils would be absent or scarce in lacustrine deposits, as they are in the nonretransported upland silt. But land fossils are preserved in the upland silt although they are 

fragmentary and show evidence of transport. 

These features, however, are to be expected in

FIGURE 25. Panorama of late Quaternary silt containing ice wedges exposed at Mamontova Gora, left limit of Aldan River, 310 km upstream 

from junction with Lena River. View downstream. Photographs 3427, 3428, 3429, and 3430 by T. L. Pewe, July 22, 1974. (Reproduced by 

the courtesy of Quaternary Research.)
ORIGIN 37

transported sediments regardless of the 

transport mechanism.

9. Mud cracks and ripple marks would be expected 

in lacustrine silt, but none have been observed.

All but two of these features of lacustrine deposits are 

contrary to the observed nature of the upland silt. The 

two features that are consistent are typical of deposits 

transported by any mechanism. The observed characteristics of the silt in central Yakutia cannot be explained by the lacustrine and fluviatile hypotheses 

alone. Moreover, radiometric and paleontologic dating 

show that the silt accumulated in middle and late Pleistocene glacial times (Vangengeim, 1961; Sher, 1971; 

Pewe and others, 1977), not during a warm period when 

melting would inundate the region. The remains of

100

90 

steppe animals such as Siaga (Sher, 1967, 1969, 1971) 

and steppe tundra (Yurtsev, 1972; Hopkins, 1976; 

Mathews, 1976) confirm the general dryness of the climate.

EOLIAN HYPOTHESIS

Although the idea that the silt in central Yakutia is 

eolian in origin is not new, it has not been described and 

evaluated in detail. Obruchev (1945), a longtime Soviet 

leader in loess studies, mentioned that loess existed in 

central Yakutia. Volkov and others (1969) have demonstrated that the widespread silt in southwest Siberia is 

eolian in origin. Recently, Tomirdiaro (1972) and Tomirdiaro and others (1974) recognized that the silt in 

northern Yakutia is loess. Vangengeim (1961, p. 37) 

referred to the silt as dusty loam, "the formation of

0.1 0.05 0.01

DIAMETER. IN MILLIMETERS

FIGURE 26. Cumulative-frequency grain-size curves for sand from Lena-Aldan Rivers area. E, flood-plain alluvium, Ust'Tatta 

Village; N, sand, top of Magan Terrace, 53 km west of Yakutsk; P, sand dune on Bestyakh Terrace; AA, alluvial sand, 7 km 

west of Pokrovsk; EE, eolian sand from cliff-head dune, 40 km upstream from Pokrovsk on Lena River. See table 1, figure 3.
38 ORIGIN AND CHARACTER OF LOESSLIKE SILT, YAKUTIA, SIBERIA

which the majority of geologists have correlated with 

unusual physical-geographical conditions in glaciated 

regions." Rusanov (1968) mapped all the silt on the high 

terraces of the lower Aldan River valley as loess. Giterman and Golubeva (1967) referred to the sediments on 

the high terraces as loess but did not provide supporting 

data. Fedorovich (1972) recently mentioned that the 

study of the silt in Yakutia should be undertaken to 

provide new contributions to loess science. Our studies 

of the silt in southcentral Yakutia, and comparisons 

with similar deposits in other parts of the world, support 

the identification of the deposits as loess.

Features and characteristics of eolian-deposited silt 

fall into three groups: field relations, mechanical composition, and petrographic character (Smith and Frazer, 

1935).

FIELD RELATIONS

Topographic distribution. Loess characteristically 

mantles preexisting topography, "filling up the gulleys, 

covering minor depressions, lying deepest in the depressions and thinning-out up the flanking slopes of the 

higher ridges" (Barbour, 1930, p. 468). The silt in central Yakutia conforms closely to this pattern.

It is draped over river terraces of varous levels and 

thinly over the glacial outwash and moraines emanating from the Verkhoyansk Range. It is absent on the 

flood plain, low floodplain terraces, and the sandy Bestyakh Terrace. It is not known why the silt is absent 

from the Bestyakh Terrace, possibly because the terrace 

surface, part of a late Pleistocene sandy flood plain of the 

Lena River, was a source of windblown silt, not an area 

of accumulation. In general, the high Magan Terrace 

has little or no loess because: (1) the terrace, in most 

areas, is distant from the major rivers (fig. 3); (2) the 

Lena River is narrow and has a small flood plain where 

it is near this terrace and; (3) the terrace was upwind 

from a major glacial flood plain, the source of silt.

Independent lithologic character of the deposits. 

Wind-deposited material may differ mineralogically 

and texturally from the underlying material. In southcentral Yakutia, uniform silt covers glacial till, dolomitic limestone, poorly consolidated sandstone, and alluvium. At these several localities, the fine texture of 

the silt contrasts strongly with the texture of the underlying material, but is very similar to that of the typical 

tan upland silt in south-central Yakutia (fig. 4) and 

northern Yakutia (fig. 27).

Decrease in thickness away from source of supply. 

The greatest thickness of the silt blanket is near its 

source, the flood plains and low terraces of the Lena and 

Aldan Rivers. The silt is 2-5 m thick on the bluff of the 

Magan Terrace west of Yakutsk and thins westward to a 

featheredge within a few kilometers (fig. 3). Such

marked thinning is consistent with present-day westerly prevailing winds and may indicate similar wind patterns during the Pleistocene from the west.

Absence of distinct stratification. Absence of distinct 

stratification, a characteristic of loess, is a conspicuous 

feature of the upland untransported silt. The only suggestion of stratification is imparted by thin carbonaceous horizons and iron-stained horizons.

Color and texture. Wind-deposited silt, like that described here, is generally light colored except where 

stained by solutions or carbonaceous inclusions; the texture is generally uniform and the clay component 

makes up no more than 10-15 percent of the sediment.

Association with other evidences of wind action. 

Smith and Fraser (1935, p. 19) state that sand dunes and 

ventifacts may be expected near the source of material. 

Well-developed, vegetated sand dunes cover the entire 

narrow Bestyakh Terrace adjacent to the wide Lena 

River from Pokrovsk to the mouth of the Aldan River 

(fig. 3). The eolian forms exist as ridges 2-10 m high and 

as small merged parabolic dunes. An active cliff-head 

dune 20 m high occupies the edge of the Bestyakh Terrace on the right limit of the Lena River about 40 km 

upstream from Pokrovsk. This dune and other dunes are 

evidence of eolian action still going on where sediment 

source areas are nearby. Small dust clouds raised today 

from the almost completely vegetated braided-stream 

deposits of the major rivers in central Yakutia suggest 

that enormous clouds of dust may have come from the 

unvegetated braided streams present during the Pleistocene. It has been demonstrated by many workers that 

no more wind is necessary to blow this dust than is 

present today, as winds up to 20 m/s are more than 

strong enough to bear quantities of dust in both periglacial areas and hot desert areas (Bryan, 1927, p. 39-40; 

Pewe, 1951; Warn, 1953, p. 70-71; Pewe and others, 

1976; Pewe and others, 1981). Chigir (1972), however, 

believes that much higher wind velocities are necessary 

and that such winds were produced by the nearness of 

glaciers. Instead, only larger source areas than now 

available are necessary, in our opinion, and they were 

provided by the wide unvegetated, braided Lena and 

Aldan Rivers in Pleistocene time.

Fossils of air-breathing animals. Fossils of airbreathing animals should logically be expected to be 

present in the silt if the material is eolian. Middle and 

late Pleistocene vertebrate fossils are distributed 

widely in the silt blanketing the terraces on the Lena, 

Aldan, and Vilyuy Rivers (for example, Alekseev, 1961; 

Vangengeim, 1961; Rusanov, 1968; and others). Fossils 

present include remains of mammoth, horse, bison, and 

other mammals. The preservation of many of the 

specimens shows evidence of very little transportation.

No land gastropods have been reported in the upland
ORIGIN 39

silt in Yakutia. Russell (1944, p. 34) regarded land gastropods as being characteristically present in loess. 

Some other loess deposits, however, in the upper 

Mississippi Valley and most of the loess in Alaska, do 

not contain land gastropods (Pewe, 1955, p. 720-721). 

Also, Dr. T. C. Yen (oral commun., June 27, 1950), 

former paleontologist at the United States National 

Museum, Washington, B.C., reported that much of the 

loess of China and the Rhine Valley contained no terrestrial gastropods so this evidence is not conclusive.

MECHANICAL COMPOSITION

If the upland silt is loess, the grain size and degree of 

sorting would be similar to that of windblown dust or 

volcanic ash that has been transported a considerable 

distance (Udden, 1898, p. 31-60; Swineford and Frye, 

1945, p. 252; Warn and Cox, 1951, p. 559; Pewe, 1955, 

fig. 11; and Pewe and others, 1976), or similar to silt 

known to be loess. Cumulative-frequency curves of mechanical analyses of windblown dust from Kansas 

(Swineford and Frye, 1945, p. 252) and Germany 

(Zeuner, 1949, p. 27) and Arizona (Pewe and others, 

1981) are similar to the average cumulative-frequency

curve of the upland silt from central Yakutia (fig. 28). 

It was thought that a great similarity of grain size and 

degree of sorting between the upland silt of Yakutia and 

deposits of silt of known eolian origin elsewhere in the 

world, would constitute a strong argument for the eolian hypothesis. For comparison, samples of silt long 

known to be loess were collected from Czechoslovakia, 

Alaska, Illinois, China, New Zealand, France, and Uzbekistan. All but one of the samples were analyzed by 

the same method in the same laboratory as the Yakutian samples. The cumulative-frequency curve of a typical sample from Yakutia is strikingly similar to curves 

of loess from other parts of the world (fig. 29).

PETROGRAPHIC CHARACTER

Angular grains have long been considered typical of 

loess (Twenhofel, 1932; Charlesworth, 1957), and 

scanning-electron-microscope analysis supports that 

assumption (Cegla and others, 1971). The silt grains 

from Yakutia are clearly angular, especially the light 

minerals such as quartz. It has been suggested that 

loess grains should also be largely unweathered and 

clay minerals almost absent (Smith and Fraser, 1935;

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FIGURE 27. Cumulative-frequency grain-size curves of silt from Yakutia. Sample GG is silt from weathered dolomitic limestone in 

crevice 147 m above Lena River, 250 km south of Yakutsk. Sample Tomi is loess from northern Yakutia (Tomirdiaro and others, 

1974, table 2).
40 ORIGIN AND CHARACTER OF LOESSLIKE SILT, YAKUTIA, SIBERIA

Charlesworth, 1957), though the degree of weathering 

would depend on the age and rate of deposition of the 

deposit and the effects of diagenetic processes. The silt 

from Yakutia, like middle and late Pleistocene loess 

from other parts of the world, is relatively fresh but 

shows some weathering under the scanning electron 

microscope.

The heavy-mineral content of the silt in the Lena and 

Aldan Rivers area (table 4) confirms the independence 

of the silt from the underlying deposits, in contrast to 

Sudakova's (1969, p. 55) claim that the microscopic 

component is inherited from the underlying rocks. It 

also indicates the general uniformity of the silt, though 

it can be used to distinguish the Lena River and Aldan 

River flood plains (fig. 24). Heavy-mineral content in 

loess has been used to distinguish source areas in many 

parts of the world (Kay and Graham, 1943; Pewe, 1955; 

Frye and others, 1962; Goldthwait, 1968; Journaux and 

others, 1969; Codarcea and others, 1972).

Summary. Many points of similarity between the 

characteristics of loess and the loesslike silt in central

Yakutia support the eolian hypothesis. In light of this 

evidence we conclude that the silt on the terraces and 

plateaus of the major river valleys such as the Lena, 

Aldan, and Vilyuy Rivers in south-central Yakutia is 

loess.

AGE AND CORRELATION

Glaciers pushed southward and westward from the 

Verkhoyansk Range in pre-Wisconsinan and Wisconsinan time, advancing almost as far as the Aldan River 

(fig. 4). During advances of glaciers from this range and 

ranges farther southeast and of continental glaciers to 

the west (fig. 4), braided silt-laden melt-water streams 

such as the Lena, Aldan, and Vilyuy Rivers flowed over 

wide vegetation-free flood plains and spread glacial 

flour over the outwash plains. Winds picked up some of 

the silt on the flood plains and outwash plains and 

redeposited it as loess on the lowlands, mainly the high 

terraces and low plateaus.

At least two major periods of loess deposition are 

recorded in the upland silt in central Yakutia, according

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FIGURE 28. Cumulative-frequency grain-size curves for upland silt (sample K) from near Yakutsk, volcanic ash from Fairbanks, Alaska, 

and modern wind-deposited dust from Germany (Zeuner, 1949, p. 27), Kansas (Swineford and Frye, 1945, p. 252), and Tempe, Ariz. 

Samples from Alaska, Arizona, and Siberia collected by T. L. Pewe. Siberian and Arizona samples analyzed at Centre de Geomorphologie du Centre National de la Recherche Scientifique, Caen, France; Alaskan sample analyzed by U.S. Army Corps of Engineers, 

Rock Island, 111.
AGE AND CORRELATION 41

to Pewe and others (1977). On the basis of biostratigraphic studies and radiometric dating, we believe that 

the loess here is middle and late Pleistocene in age, 

correlative to Maximum Glaciation and later glaciations equivalent to pre-Wisconsinan and Wisconsinan 

glaciations in North America.

On the basis of biostratigraphic studies, Vangengeim 

(1961) believes that the loess first began to accumulate 

during the time of the Maximum Glaciation (Samarov) 

in the Verkhoyansk Range. Further, the silt deposits on 

the terraces, at least the upper part, are characterized 

by a late Pleistocene fauna consisting largely of numerous remains of Mammuthus primigenius of late type, 

Equus caballus, subsp. B. (small form), Bison prisons 

aff. deminutus W. Grom, and other species. The fossils 

are found not only at Mamontova Gora, but also 

elsewhere on the terraces of the Aldan River valley 

(Vangengeim, 1961, p. 38-39). This fauna has been 

described at Mamontova Gora by Motuzko and others 

(1969, p. 63). Giterman and Golubeva (1967, p. 237) 

believe that the loess on the high terraces is correlative 

with the Samarov (Maximum) and Zyryan Glaciations.

Much of the stratigraphic information is from the 

well-known section at Mamontova Gora, where perennially frozen ice-rich silt and associated flora and vertebrate fauna of late Quaternary age are well exposed. 

It is true that on some of the higher terraces along the 

Aldan, mammalian remains of older types are also present, as reported by Motuzko and others (1969) and Vangengeim (1961). This is to be expected, because the older 

silt could be present on the older, higher terraces. In 

fact, Motuzko and others (1969, p. 65) report remains of 

a long-horned bison and large horse in the lower silt of 

the 50-m-high terrace. At Mamontova Gora, Vangengeim (1961, p. 33) reports remains of an early-type 

mammoth and large horses in an exposure in the northern part of the area but late-type mammoths and small 

horses elsewhere in the area. She (1961, p. 34) believes 

that the older fauna was derived from the base of the silt 

section or from the top of the underlying sand.

Alekseev (1961, table 3) reports some early radiocarbon dates of wood from central Yakutia and one from an 

exposure of "clay loam/sandy loam" at a depth of 17 m 

on the right bank of the Aldan River, 50 km from its

100

90

80

70

- 60

50

EXPLANATION

 New Zealand

 Czechoslovakia

 Alaska

 Sample K, Siberia

 China

 Illinois

 Uzbekistan

 France

> 40

30

20

0.5 0.1 0.05 0.01 0.005 

DIAMETER, IN MILLIMETERS

0.001 0.0005 0.0001

FIGURE 29. Cumulative-frequency grain-size curves for upland silt from central Yakutia (sample K) and loess from Czechoslovakia, 

Alaska, Illinois, China, New Zealand, France, and Uzbekistan. Samples from all areas except Illinois analyzed at Centre de 

Geomorphologie du Centre National de la Recherche Scientifique, Caen, France; Illinois sample analyzed by U.S. Army Corps of 

Engineers, Rock Island, 111. All samples except those from France collected by T. L. Pewe; sample from France collected by Andre 

Journaux.
42 ORIGIN AND CHARACTER OF LOESSLIKE SILT, YAKUTIA, SIBERIA

mouth. The wood fragment was dated by the solid carbon method as being more than 20,000 years old.

Radiocarbon dates for what appears to be the upper 

loess unit where exposed in the 50-m-high terrace at 

Mamontova Gora have been presented in Markov (1973, 

p. 4 5, 163). These dates are on samples from depths of 

1-8 m but not from one continuous section or from one 

locality; therefore, the depth below the surface does not 

define stratigraphy. The dates and sample depth reported are: 26,800±600 years B.P., 5.5 m; 40,600±500 

years, 3 m; and 44,000± 1,900 years, 8 m. We believe 

that the nature of erosion and deposition of these sediments is such that at a depth of 3 m in one area, the 

sediments may be 20,000 years old, whereas at this 

depth at another locality, the age may be 40,000 years. 

At Mamontova Gora, truncation of the top of the upper 

loess unit is indicated by an unconformity.

In an attempt to better understand the stratigraphy 

of the loesslike silt, Pewe in 1973 collected carefully 

located organic specimens in a vertical section at 

Mamontova Gora (Pewe and others, 1977). This section 

comprises two thick silt units and an overlying thin (1-2 

m thick) silt layer of loess and retransported loess of 

Holocene age (fig. 30). The radiocarbon dates on the 

1973 samples ranged from about 42,000 to 46,000 years 

B.P. for the thick upper loess and greater than 46,000 

years B.P. for the thick lower loess. Samples collected by 

M. S. Ivanov and V. V. Kastukevich in 1974 indicate a 

range from about 34,000 to greater than 56,000 years 

B.P. for the upper loess and greater than 56,000 years 

B.P. for the lower loess (fig. 30). Location and dates of 

the radiocarbon samples, dating organizations, and location of silt samples for mineralogical and chemical 

examinations area shown in figure 30.

On the basis of the biostratigraphy, radiocarbon 

dates, and relation to the glacial record of nearby areas, 

we believe that the age of the upper thick loess in 

south-central Yakutia and the middle silt unit of 

Mamontova Gora, dated at 26,000 to greater than 

56,000 years B.P., is Wisconsinan. This age correlates to 

the Sartan and Zyryan Glaciations and included interstadials and interglaciations of Siberia. Although the 

youngest date now available from the upper loess on the 

50-m-high terrace at Mamontova Gora (26,000 years) 

does not provide evidence that the age of the loess corresponds to the time of the Sartan Glaciation, supposed 

to have begun about 25,000 years ago (Kind, 1972, p. 

56-7; 1975, fig. 1), the unconformity at the top of this 

unit indicates truncation of the section. Kind (1972, p. 

57) cites a date of 20,900±300 years B.P. from loesslike 

material on a terrace on the Yenisei River. Until 

younger dates are determined from the upper part of the 

upper thick loess and dates are obtained from the lower 

part of the Holocene silt, the relation of the upper loess

415±40 years B.P.d) 

Permafrost table (2) 

=^ (3)

Unconformity

- 34,020i1,500 years B.P. (4) 

42,150*3,700 years B.P. (5) 

Ice wedge

46,700*1,500 years B.P. (7) 

>56,000 years B.P. (4) 

>56,000 years B.P. (4)

Unconformity (?) 

56,000 years B.P. (4)

46,000 years B.P. 18)

56,000 years B.P. (4)

>43.500 years (9) 

(10!

56,000 years (4) 

Unconformity

(11)

FIGURE 30. Diagrammatic stratigraphic section of perennially frozen late Quaternary silt in the exposure of the 50-m-high 

(Abalakh) terrace at Mamontova Gora, left limit of the Aldan 

River 310 km from its mouth, central Yakutia. Radiocarbon material dated in U. S. and loesslike silt samples collected by T. 

L. Pewe, 1973. Radiocarbon material dated in U.S.S.R. collected by M. S. Ivanov and V. V. Kastukevick, 1974 (P. I.Melnikov, written commun., June 6, 1975). From Pewe and others, 

1977 (fig. 3). (Reproduced by the courtesy of Qitatemary Research.) (1) Radiocarbon date on a root 1 m below the surface, 

SI 1968 (SI numbers indicate laboratory number of Smithsonian 

Institution, United States). (2) Depth to permafrost is about 1-2 

m under the forest. Flat-topped ice wedges indicate a lower permafrost table with thawing down to the top of ice wedges sometime in the past. (3) Loess sample G. See figure 21 for mechanical analyses; tables 3, 4, and 6 for chemical and mineralogical 

analyses of samples G-I. (4) Radiocarbon date from Permafrost 

Institute, Yakutsk. (5) Radiocarbon date on tree fragments, SI 

1965. (6) Loess sample H. (7) Radiocarbon date from two small 

fragments of unidentified late Quaternary mammal ribs, SI 

1972. (8) Radiocarbon date on wood fragments, SI 1967. (9) 

Radiocarbon date on wood fragments, SI 1966. (10) Loess sample I. (11) Crossbedded brown sand of early and middle Pleistocene age.
SUMMARY 43

to the Sartan Glaciation is speculative. The base of the 

upper loess is more than 56,000 years old, and possibly 

as old as 100,000 years. The top may be as young as 

10,000 years. No definitive dates are yet available to 

mark the boundaries, but we believe the boundaries will 

prove to be of the order of those ages.

The lower loess is definitely beyond the range of conventional radiocarbon dating. It may be Wisconsinan in 

age, but a Samarov age is a strong possibility, correlative with the Maximum Glaciation of Siberia and older 

than the last interglacial period. Mammalian remains 

support the hypothesis that the loess first began to accumulate in Maximum time (Vangengein, 1961; Giterman and Golubeva, 1967); if it did, interglacial beds 

may be found separating it from the Wisconsinan beds.

Alekseev (1970) believes that the silt beds along the 

lower Vilyuy River with large ice wedges and mammalian remains were deposited in the second half of the 

Pleistocene. He suggests that they represent a large 

interval of time, from the Riss Glaciation to the end of 

the Wurm Glaciation.

It is hoped that additional dating of loess samples 

from the units exposed on the high terraces along the 

Aldan River and elsewhere will soon be undertaken.

SUMMARY

Loesslike silt mantles the upland terraces and low 

plateaus throughout south-central Yakutia, reaching 

maximum thickness along the south side of the Aldan 

River valley and the east side of the Lena River valley. 

It is well exposed in the river cuts in these areas, the 

greatest thickness recorded being more than 60 m on 

the Tyungyulyu Terrace. The texture and mineral composition are uniform throughout central Yakutia, 

whether the silt overlies limestone, poorly consolidated 

sandstone, alluvium, or glacial outwash. All loesslike 

silt samples examined contain a high percentage of 

quartz and feldspar and lesser amounts of hornblende, 

epidote, hypersthene, and garnet. Most samples contain 

a small amount of sphene, zircon, and rutile.

The loesslike silt is massive except where retransported and has developed crude stratification. Vertebrate fossils, not common in the untransported silt, 

are very common in the retransported silt in shallow 

depressions. No land snails, typical in loess deposits in 

some areas, have been found in these deposits.

Hypotheses advanced to explain the origin of the 

upland silt proposes marine, estuarine, lacustrine, fluvial, residual, or eolian sources, or a combination of 

these. A marine or estuarine source is unlikely because 

of the absence of evidence of deltas, shorelines, beaches, 

clay, mud cracks, ripple marks, and marine or 

brackish-water fossils. Moreover, such an origin would 

require a rise of sea level or a subsidence of the land of

many meters in late Pleistocene time, an inundation not 

borne out by geologic evidence.

The upland silt is not of fluviatile origin because (1) it 

is unstratified and contains no individual beds or lenses 

of other sediments, (2) it occurs as a nearly continuous 

blanket over a surface of irregular topography with 

relief of 200 or 300 m and is more than 200 m above the 

major rivers; and (3) no fresh-water fossils are present.

The lacustrine hypothesis is strongly supported by 

workers studying the ice wedges in the perennially frozen ground. They believe that the loesslike silt is a 

combination of lacustrine and alluvial deposits formed 

on great flood plains and marshy plains. But there are 

several reasons for believing this origin unlikely. No 

evidence of shorelines, wave-cut beaches, or deltas are 

present; nor are mud cracks, ripple marks, or freshwater fossils found. Neither stratification nor an appreciable amount of clay exists in the silt. No definite upper 

limit, to be expected under a lacustrine hypothesis, is 

present.

The hypothesis that loesslike silt is a product of the 

breakdown in place of the underlying rocks, mainly by 

frost action, has also received strong support from many 

workers. Evidence against this hypothesis includes: (1) 

the minerals in the silt are not everywhere similar to 

the underlying bedrock, (2) no large particles of more 

resistant minerals are present, (3) the silt does not become progressively coarser toward bedrock, (4) mechanical disintegration by alternate freezing and thawing 

could not produce untransported silt 60 m thick on flat 

terraces, and (5) the silt contains undisturbed carbonaceous layers.

Evidence for the eolian origin of the upland silt is 

abundant: (1) the silt mantles older topography, (2) it is 

lithologically independent of the underlying material, 

(3) stratification is indistinct or absent, (4) it is associated with sand dunes, (5) it contains fossils of airbreathing land animals, (6) its sorting and texture are 

similar to those of loess and windblown dust from many 

places elsewhere in the world, and (7) the grains are 

angular and relatively fresh.

Central Yakutia has not been glaciated. However, 

glaciers from the Verkhoyansk Range on the north and 

west as well as glaciers in the ranges south and east and 

the continental glacier on the west almost surrounded 

the interior of Yakutia during times of glacial maxima 

(fig. 4). We believe the upland silt to be loess deposited 

mainly during periods of glacial expansion by winds 

blowing across the unvegetated outwash plains and 

flood plains of glacial streams.

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NOTE: Translations by CRREL (Cold Regions Research and Engineering Laboratories) available from Federal Scientific and Technical 

Information, Springfield, Va. 22151.