Stratigraphy and Depositional Environment 

of the Dutch Hairbor M^niber 

of the Unalaska Formation, 

Unalaska Island, Alaska

G E O L O G I C A L S U k V E Y B tj L L E T I N 1 4 5 7-B

Stratigraphy and Depositional Environment 

of the Dutch Harbor Member 

of the Unalaska Formation, 

Unalaska Island, Alaska

By STEPHEN M. LANKFORD and JAMES M. HILL 

CONTRIBUTIONS TO STRATIGRAPHY

GEOLOGICAL SURVEY BULLETIN 145 7-B

Sedimentological characteristics and regional 

significance of a Miocene coarse clastic 

turbidite on the Aleutian ridge

UNITED STATES GOVERNMENT PRINTING OFFICE, WASHINGTON: 1979
UNITED STATES DEPARTMENT OF THE INTERIOR 

CECIL D. ANDRUS, Secretary

GEOLOGICAL SURVEY 

H. William Menard, Director

Library of Congress Cataloging in Publication Data

Lankford, Stephen M.

Stratigraphy and depositional environment of the Dutch Harbor Member of the 

Unalaska Formation, Unalaska Island, Alaska.

(Contributions to stratigraphy) (Geological Survey Bulletin 1457-B)

Bibliography: p. B14.

1. Geology, Stratigraphic-Miocene. 2. Turbidities-Alaska-Unalaska Island.

3. Geology-Alaska-Unalaska Island. I. Hill, James M., joint author. II. Title. 

III. Series. IV. Series: United States. Geological Survey. Bulletin 1457-B 

QE75.B9no. 1457-B [QE694] 557.3'08s [551.7'8] 78-606176

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

Washington, D. C. 20402

Stock Number 024-001-03141-8
CONTENTS

	Page

Abstract __________________________________________ Bl

Introduction ______________________________________ 1

Unalaska Formation _________________________________ 3

Dutch Harbor Member __________________________________ 4

Exposure and areal extent ___________________________ 4

Lithology ______________________________________ 4

Alteration ______________________________________ 8

Sedimentary structures _____________________________ 10

Age _________ ____________ __ ____ 11

Depositional environment _______________________ ____ 12

Speculations on the regional significance of the Unalaska Formation ______ 13

References cited ___________________________________ 14

ILLUSTRATIONS

Page

FIGURE 1. Index map showing location of Unalaska Island __________ g2

2. Generalized geologic map of Unalaska Island ______ __ 2

3. Aerial photograph showing location and partial extent of the Unalaska Formation and the Dutch Harbor Member _______ 3

4. Type section of the Dutch Harbor Member _____________ g 

5-9. Photographs showing:

5. Lenticular channel deposit _____________________ 8

6. Clasts in sandstone matrix exhibiting diamictite texture _____ 9

7. Typical conglomerate with graded bedding ____________ 10

8. Tabular planar cross-stratification in very fine grained sandstone

near top of the Dutch Harbor Member ________ ____ 11

9. Possible convolute bedding in sandstone ________ ______ 12 

10. Schematic Miocene cross section across Aleutian arc showing possible site of deposition and stratigraphic extent of the Unalaska 

Formation _______________________________ 13

III

CONTRIBUTIONS TO STRATIGRAPHY

STRATIGRAPHY AND DEPOSITIONAL

ENVIRONMENT OF THE DUTCH HARBOR

MEMBER OF THE UNALASKA FORMATION,

UNALASKA ISLAND, ALASKA

By STEPHEN M. LANKFORD and JAMES M. HILL

ABSTRACT

A part of the Unalaska Formation of Drewes, Fraser, Snyder, and Barnett was reexamined in 1976 and a new suite of fossils collected. This Tertiary formation is exposed 

over about 70 percent of Unalaska Island and is 900-16,700 meters thick. It consists 

mainly of volcanic breccia, flows, tuff, and intercalated sedimentary rocks 1 cm to 

more than 100 m thick. A 126-m-thick sequence of early Miocene(?) sandstone and 

conglomerate, all thermally altered, was measured and examined in detail. This sequence, herein designated the Dutch Harbor Member, shows evidence of deposition by 

turbidity currents and debris flows.

,The stratigraphic position of the Dutch Harbor Member within the Unalaska Formation is not well known, but it may be near the top of the formation. Fossils collected within the member include the bivalves Chlamys and Pododesmus of Miocene 

age.

INTRODUCTION

Unalaska Island, near the east end of the insular Aleutian arc, is 

perched atop the mostly submerged Aleutian ridge. This ridge separates the abyssal northern Pacific Ocean from the Bering Sea (fig. 1). 

About 70 percent of the island is covered by Tertiary volcanic and 

sedimentary rocks named the Unalaska Formation (Drewes and 

others, 1961). The thickness of the Unalaska Formation has not 

been determined, but on the basis of topographic data it is at least 

900 m thick. From calculations on the regional dip, Drewes, Fraser, 

Snyder, and Barnett (1961) figure that it could be as thick as 16,000 

m; they suspect that the actual thickness is of the order of 5,000- 

10,000 m.

During August 1976, we examined the Unalaska Formation and 

collected a new suite of fossils in the vicinity of the original collection site reported by Drewes, Fraser, Snyder, and Barnett (1961). 

The study area extends about 1-4 km southeast of the village of

Bi
B2 CONTRIBUTIONS TO STRATIGRAPHY

180° 150°

-SIBERIA

BERING SEA

Kodiak -

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0 200 400 KILOMETERS

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APPROXIMATE SCALE 

AT LATITUDE 52° N

50°

FIGURE 1. Location of Unalaska Island near east end of Aleutian arc.

Unalaska on Unalaska Island (fig. 2), where a sequence of sedimentary rocks 126 m thick occurs. This distinctive sequence of sedimentary rock is here named the Dutch Harbor Member. A measured

Area of figure 3

EXPLANATION

53° 15'

50 KILOMETERS

167°30' 167°00'

FIGURE 2. Generalized geologic map of Unalaska Island. Modified from Drewes, 

Fraser, Snyder, and Barnett (1961).
DEPOSITIONAL ENVIRONMENT, UNALASKA FORMATION B3

FIGURE 3. Aerial photograph showing location and partial extent of the Unalaska 

Formation and the Dutch Harbor Member, U.S. Navy photograph KAD-2 No. 13, 

June 20, 1951.

section (fig. 3) is herein designated the type section of the Dutch 

Harbor Member of the Unalaska Formation. The sequence is 

bounded by volcanic rocks that were not studied in detail.

The Dutch Harbor Member rests conformably upon, and is overlain by, undifferentiated aquagene volcanic rocks of the Unalaska 

Formation (fig. 3). Typically it strikes about N. 30° W. and dips 

15°-25° NE. The member consists predominantly of sandstone interbedded with pebble and cobble conglomerate and scattered stringers 

of siltstone and shale as much as several centimeters thick. The section is discontinuously exposed along road cuts and small slides.

UNALASKA FORMATION

Drewes, Fraser, Snyder, and Barnett (1961, p. 590) described the 

Unalaska Formation as "a thick sequence of coarse and fine
B4 CONTRIBUTIONS TO STRATIGRAPHY

sedimentary and pyroclastic rocks intercalated with dacitic, andesitic, and basaltic flows and sills ***". They further state that 

greenish-gray argillite beds that are found predominantly along the 

south coast of the island are interrupted by abundant albitized 

andesite and basalt sills, domical masses, igneous pods, and pillow 

lava. Coarse sedimentary rocks in the Unalaska Formation include 

abundant graywacke, mudstone, and tuffaceous sandstone. Conglomerate beds that are found mainly on the northern part of the 

island occur in association with agglomerate and coarse volcanic 

breccia. The conglomerates are poorly bedded and are composed 

mostly of andesite and basalt clasts.

In the study area, the Unalaska Formation has been divided into 

a lower volcanic sequence, the Dutch Harbor Member, and an upper 

volcanic sequence. The volcanic sequences are here used as informal 

units.

DUTCH HARBOR MEMBER

EXPOSURE AND AREAL EXTENT

The Dutch Harbor Member is discontinuously exposed in a band 

about half a kilometer wide and 3l/2 km long. The easternmost part 

of the member is truncated by the Captains pluton, but it may be 

exposed on the other side of the pluton. To the northwest, the Dutch 

Harbor Member is concealed by the glacial alluvium that underlies 

the village of Unalaska and by Dutch Harbor. The member is probably present on Amaknak Island and possibly on the Makushin 

Peninsula, but logistical and time constraints precluded investigation of these areas.

Most of the Dutch Harbor Member is covered by low but dense 

vegetation and by a thick soil horizon, but enough rock is exposed to 

show that individual beds are lenticular and cannot be traced far 

laterally. No marker beds were found, and correlation with the sequence in other areas will be difficult. Where exposed, the member 

is characterized by typical well-indurated, light- to mediumgreenish-gray, very fine or fine-grained sandstone.

LITHOLOGY

The volcanic rocks immediately below and above the Dutch Harbor Member consist predominantly of andesitic flows, tuff, and breccia; some basalt and dacite are present (Drewes and others, 1961). 

The volcanic beds in the area are typically only a few meters thick. 

The breccia contains angular to rounded andesite clasts that are 

poorly bedded or scattered in the matrix. At one locality, just above 

the top of the Dutch Harbor Member, graded bedding occurs within 

an exposed volcanic breccia. The volcanic rocks also contain thin,
DEPOSITIONAL ENVIRONMENT, UNALASKA FORMATION B5

highly lenticular stringers of shale less than 1 cm thick and less 

than 2 m long.

Examination by microscope reveals that the dominant primary 

minerals in the andesite units are plagioclase and clinopyroxene occurring as microphenocrysts and in the groundmass. Plagioclase occurs in equant to elongate laths that are commonly pilotaxitic. The 

groundmass is slightly intersertal to holocrystalline; glass is rarely 

dominant (Drewes and others, 1961).

At the type section, the Dutch Harbor Member is 126 m thick. It is 

composed predominantly of light- to medium-greenish-gray, very 

hard, indurated sandstone (fig. 4). The sandstone is mostly very fine 

to fine grained and moderately to well sorted; individual grains, 

which are mostly subrounded, range from subangular to rounded. 

Bedding in the sandstone is commonly obscure. The beds are slightly 

wavy and average 10-30 cm thick but are as much as 1-2 m thick. 

Petrographic analysis of sandstone in units 2, 5, 7, 8, 10, 13 and 18 

(fig. 4) indicates that grain-to-grain contacts are common; there is 

little matrix, and the sandstone is compacted. About 50 percent of 

the sandstone is andesite fragments that contain abundant pilotaxitic plagioclase laths. Individual laths of plagioclase, which commonly are compositionally zoned and display albite twinning, make 

up approximately 25 percent of the rock. Quartz is about 1-3 percent of the rock; other minor components are magnetite, pyrite, and 

pyroxene. Spherulites of chlorite and epidote as much as several millimeters in diameter are common. Chlorite and epidote are common 

interstitial minerals.

Rhythmically bedded sandstone and conglomerate, which are 

common in the Dutch Harbor Member, are most common in beds 

7-11 and 17-19 (fig. 4). The lenticular conglomerate beds, generally 

0.3-1 m thick and about 1-3 m apart, persist laterally for about 40 

m or less (fig. 5). The conglomerate clasts are supported by a matrix 

composed of very fine to fine-grained sandstone. In some beds (beds 

12, 15, 19, fig. 4) pebbles and cobbles occur as isolated clasts within 

the matrix (fig. 6A). Bed 19 contains a large angular clast 20 cm 

wide in a sandstone matrix (fig. 6B) along with scattered small 

well-rounded to angular pebbles. Texturally these deposits are diamictites. Clasts are generally subrounded, but they range from well 

rounded to angular and average about 2 cm in diameter. Clasts are 

composed of microporphyritic andesite; this andesite is very similar 

in composition to rocks in volcanic sequences that bound the Dutch 

Harbor Member.

Beds 2 and 18 (fig. 4) contain scattered siltstone and shale stringers that are medium gray, slightly sandy, and less than 4 cm thick. 

These stringers extend laterally for only a few meters.
B6 CONTRIBUTIONS TO STRATIGRAPHY

Thickness, 

in meters

1 oo

125 

100 

75 

Fossils

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(

1

Lithology

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Descripiton

Base of upper volcanic sequence

19 Sandstone, light-gray, conglomeratic, very 

fine to medium-grained: angular to subangular volcanic clasts to 10 cm. Forms 

beds that grade from cobble to sand size; 

isolated pebbles suspended in matrix

'8 Conglomerate, light-green, s Ity, sandy. 

Conglomerate clasts grade from several 

centimeters to fine sand size; poorly 

sorted; beds as much as 0.3 m thick

M Sandstone, light-green; mostly concealed

EXPLANATION

3-zT ^

Shale or Covered interval vcneu'a 

clay stone

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Siltstone Poorly exposed 

interval

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Conglomerate

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16

1 5 Sandstone, light-green, very fine to finegrained; moderately sorted; scattered clasts 

to 3cm

14 Sandstone, light-green,fine-to medium- grained where exposed; 

contains beds that grade from medium to fine grained in a few 

centimeters; mostly covered

FIGURE 4. Type section of the Dutch Harbor Member.
DEPOSITIONAL ENVIRONMENT, UNALASKA FORMATION B7

50 

25 

0 

Thickness, 

in meters

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Fossils

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Lithology

13 Sandstone, light-greenish-gray, fine grained, 

moderately sorted; partly concealed

12 Sandstone, medium-greenish-gray, very fine 

to fine - grained, moderately sorted; subangular 

grains; scattered cobbles suspended in sandstone matrix; includes conglomerate beds 

0.5 to 1 m thick; well-rounded clasts to 15 

cm; graded bedding

1 1 Conglomerate, light-green, matrix-supported: clasts to 5 cm

10 Sandstone, medium-green, very fine to finegrained, moderately sorted; subangular 

grains; contains pebble conglomerate lenses 

to 0.3 m thick; well-rounded clasts to 1 cm; 

graded bedding; some convoluted bedding 

9 Sandstone, dark-green, fine-grained, moderately sorted; interbeds of 

conglomerate to 10 cm thick, clasts to 5 cm; load clasts

-8 Conglomerate, medium-greenish-gray, sandy; clasts to 15 cm across, 

subrounded to well- rounded; poorly sorted; matrix-supported 

with graded bedding; flame structures and load clasts

7 Sandstone, light-green, very fine grained, 

moderately sorted; angular to subangular 

grains; suspended clasts to 2 cm; conglomerate beds 0.3 to 1 m thick

6 Sandstone, light-green, very fine grained.

ding somewhat obscure; partly concealed

5 Sandstone, light-gray, very fine grained, 

moderately sorted; subangular grains; scattered well -rounded clasts to 2 cm suspended 

in matrix 

4

3 Sandstone, medium-gray, fine-grained, 

moderately sorted; partly concealed

2 Sandstone, medium-gray, moderately sorted; 

shale stringers to 0.5 m long, 4 cm thick; 

includes some graded bedding

1 

Base of Dutch Harbor Member

Lower volcanic sequence

Description

FIGURE 4. Type section continued.
B8 CONTRIBUTIONS TO STRATIGRAPHY

FIGURE 5. Lenticular channel deposit that pinches out locally within about 40 m,

Dutch Harbor Member.

Though beds 10 and 13 are poorly exposed, small outcrops suggest 

that these beds are lithologically more homogeneous than other 

parts. The exposures that are present are composed of light-green 

sandstone similar to that exposed in most of the section. The only 

observed sedimentary structure was exposed in bed 13, and it consists of sand grains that grade from coarse to fine within about 2 cm. 

There is in this part of the section a notable lack of siltstone and 

sandstone interbeds.

ALTERATION

All of the Dutch Harbor Member has been thermally altered. The 

member and its bounding volcanic rocks contain abundant (to 25 

percent) authigenic, metamorphic, and secondary minerals. Euhedral pyrite cubes are sparse to abundant in the section. Chlorite and 

epidote occur both as spherules and as interstitial material that 

appear to be derived from an altered volcanic matrix. Plagioclase 

has been partially albitized. The mineral assemblage suggests 

greenschist-facies metamorphism (Williams and others, 1954). 

Drewes, Fraser, Snyder, and Barnett (1961) believe that the 

metamorphism of these rocks was caused by the intrusion of three 

plutons into the Unalaska Formation. One intrusive body, the Captains pluton (fig. 2), crops out near the type locality of the Dutch 

Harbor Member. Numerous dikes, some as much as several meters 

thick, intrude both the Dutch Harbor Member and the surrounding
DEPOSITIONAL ENVIRONMENT, UNALASKA FORMATION B9

A, Isolated cobble clasts.

B, Angular 20-cm wide clast in pebbly sandstone.

FIGURE 6. Clasts in sandstone matrix exhibiting diamictite texture.
BIO CONTRIBUTIONS TO STRATIGRAPHY

FIGURE 7. Typical conglomerate that grades upward, Dutch Harbor Member. Horizontal scale approximately 16 cm.

volcanic rock and appear to radiate from the Captains pluton. The 

Dutch Harbor Member strikes into the Captains pluton, but poor 

exposures preclude exact determination of the contact. The Captains 

pluton is probably middle Miocene (13 m.y.) in age as determined by 

potassium-argon age dating (D. W. Scholl, oral commun., 1976). A 

potassium-argon date from the Shaler pluton, which also intrudes 

the Unalaska Formation, yielded an age of 11±3 m.y. (Marlow and 

others, 1973).

SEDIMENTARY STRUCTURES

The most common sedimentary structure in the Dutch Harbor 

Member is graded bedding. Subtle grading occurs within sandstone 

beds (beds 2, 8, 10, 12 and 13, fig. 4). Prominent grading is characteristic of beds forming lensoidal channel deposits (fig. 7); these deposits grade upward from cobble or pebble conglomerate to fine or 

very fine grained sandstone over an interval of 5-50 m (beds 7-11,
DEPOSITIONAL ENVIRONMENT, UNALASKA FORMATION Bll

FIGURE 8. Tabular planar cross-stratification in very fine grained sandstone near top 

of the Dutch Harbor Member. Horizontal scale approximately 0.5 m.

17-19). Cross-stratification, though rare (fig. 8), was found at one 

place in an outcrop near the top of the member just east of the type 

section. The tabular planar crossbedding has foreset beds about 15 

cm long that dip N. 70° E. at 26°.

Conglomerate clasts on the bottom of the channel beds deform the 

underlying finer grained sediment to form load structures (fig. 7) 

and convolute bedding (fig. 9). The absence of lamination within 

many sandstone beds may be the result of bioturbation. Bed 9, for 

example, contains what appear to be worm tubes; the tubes are 

roughly circular in cross section and about half a centimeter in 

diameter. Beds 7, 9, 12, and 15 contain bivalve burrows fairly commonly; the burrows are as close as 5 cm apart, 15-20 cm long, and 

oriented perpendicular to bedding planes.

AGE

Fossils collected from the Dutch Harbor Member include bivalves, 

barnacle plates, burrow fillings, and a vertebra (W. O. Addicott, 

written commun., 1976). The bivalves, collected from beds 7 and 10 

(fig. 4), are of the genera Chlamys and Pododesmus and are probably 

of Miocene age (W. O. Addicott, written commun., 1976). Earlier fossil collections from the lower part of the Dutch Harbor Member include bones and teeth of a marine mammal resembling a sea cow, 

probably of the genus Cornwallius; this genus generally indicates an
B12 CONTRIBUTIONS TO STRATIGRAPHY

FIGURE 9. Possible convolute bedding in sandstone, Dutch Harbor Member. Scale is

15 cm long.

early Miocene age (Drewes and others, 1961). W. O. Addicott (written commun., 1976) stated that the fossil evidence "seems to indicate 

an early or possibly middle Miocene age ***".

Most of the fossils have been transported and fragmented such 

that much of the original shell material is missing. Because they 

were transported rapidly by turbidity currents, however, the ages of 

the fossils and deposition of the Dutch Harbor Member are probably 

not significantly different. Therefore, on the basis of fossil evidence, 

we assign the Dutch Harbor Member a Miocene (probably early 

Miocene) age.

DEPOSITIONAL ENVIRONMENT

The presence of channel deposits, graded bedding, load structures, 

and cross-stratification all suggest proximal turbidite deposition of 

the Dutch Harbor Member. The diamictite texture of beds within 

the member and the occurrence of large angular clasts as much as 

20 cm in diameter (bed 19) are perhaps more characteristic of debris 

flows. These structures indicate that the Dutch Harbor Member was 

laid down rapidly as deposits transitional between proximal turbidite flows and debris flows. Although the dominant mode of deposition was rapid, the preservation of bivalve burrows and the occurrence of lenticular silt and shale stringers suggest alternate periods 

of slow deposition. The textures and structures present in the volcanic rocks that bound the member suggest that the volcanic rocks
DEPOSITIONAL ENVIRONMENT, UNALASKA FORMATION B13 

SOUTH PACIFIC OCEAN ALEUTIAN RIDGE BERING SEA NQRTH

Km SEA LEVEL Km

. , , Pelagic deposits

t, v / 

A A

Deformed older volcanic 

and sedimentary rocks

FIGURE 10. Miocene cross section across Aleutian arc showing possible site of deposition and stratigraphic extent of the Unalaska Formation.

were deposited partly as submarine ash flows. Turbidite and debris 

flow deposition occurred on a slope, probably along the edge of a 

rapidly filling submarine basin (Crowell, 1957; Stanley, 1969).

SPECULATIONS ON THE REGIONAL SIGNIFICANCE 

OF THE UNALASKA FORMATION

Drewes, Fraser, Snyder, and Barnett (1961, p. 591) roughly divided the Unalaska Formation into three main parts that are 

lithologically distinct: "argillite south of Beaver Bay, graywacke and 

conglomerate in the northern bulge area and south of Makushin 

Bay, and coarse pyroclastic deposits in northeastern Unalaska Island, separated by wide transition zones." Interbedded coarse clastic 

rocks occur within the argillite zone, and fine-grained material occurs within the northern zone of sandstone and conglomerate beds. 

The regional dip suggests that the argillite is stratigraphically 

below the coarse-grained rock (Drewes and others, 1961). We speculate that the older part of the Unalaska Formation was deposited in 

relatively deep water. The complete absence of fossils in the argillite 

may be additional evidence of rapid and deep deposition (Drewes 

and others, 1961). The Dutch Harbor Member and other young parts 

of the Unalaska Formation contain fossils that are restricted to shallow water. These rocks and fossils suggest that the Unalaska Formation represents deposits in a rapidly filling basin that contained 

fine-grained distal turbidites near the bottom of the basin. As the 

basin filled, deposition became increasingly proximal. The Unalaska 

Formation may have been deposited in a summit or interarc basin 

(fig. 10) similar to present-day graben-controlled basins formed by 

rifting of the Aleutian ridge, (Scholl and others, 1975, fig. 2).

The basal argillaceous part of the Unalaska Formation contains 

most of the pillow structures on the island as well as numerous 

dikes and sills that appear to have been intruded into unconsolidated sediment (Drewes and others, 1961). Though the stratigraphically higher coarse sediments contain abundant volcanic flows and
B14 CONTRIBUTIONS TO STRATIGRAPHY

breccia, the dikes and sills seem to have been intruded later. This 

relation can possibly be accounted for by a rapidly changing vertical 

level of the volcanic source. Deep submarine fissures and vents may 

have supplied the volcanic material found in the argillaceous rocks. 

If the volcanic source was then building up faster than the basin was 

being filled, a steepening slope would provide a site of deposition for 

coarse-grained proximal turbidites and debris flows overlying older 

argillaceous deposits.

The Unalaska Formation appears to have been deposited in a 

basin adjacent to the submarine flanks of a middle Tertiary volcanic 

arc south of the study area. The proximal turbidite units and debris 

flows that make up the Dutch Harbor Member and other parts of the 

Unalaska Formation were probably deposited in an interarc basin 

perched on the summit of the Aleutian ridge.

REFERENCES CITED

Crowell, J. C., 1957, Origin of pebbly mudstones: Geol. Soc. America Bull., v. 68, p. 

993-1010.

Drewes, Harald, Fraser, G. D., Snyder, G. L., and Barnett, H. F., 1961, Geology of 

Unalaska Island and adjacent insular shelf, Aleutian Islands, Alaska: U. S. Geol. 

Survey Bull. 1028-S, p. S583-S676.

Marlow, M. S., Scholl, D. W., Buffington, E. C., and Alpha, Tau Rho, 1973, Tectonic 

history of the central Aleutian arc; Geol. Soc. America Bull., v. 84, p. 1555.

Scholl, D. W., Marlow, M. S., and Buffington, E. C., 1975, Summit basins of Aleutian 

ridge, North Pacific: Am. Assoc. Petroleum Geologists Bull., v. 59, p. 799-816.

Stanley, D. J., 1969, Sedimentation in slope and base-of-slope environments in Stanley, D. J., ed., The new concept of continental margin sedimentation: Washington 

Am. Geophys. Inst, p. DJ 5-8 1-25.

Williams, Howell, Turner, F. V., and Gilbert, C. M., 1954, Petrography: San Francisco, W. H. Freeman and Co, 406 p.