UNITED STATES

DEPAR'MENT OF INTERIOR

GEOLOGICAL SURVEY

Geology Report for Proposed Norton Sound

OCS Sand and Gravel Lease Sale

Gordon R . Hess and C. Hans Nelson

Ope n-Fi l e Report

82-997

This report is preliminary and has not been reviewed for conformity w i t h U . S . G e o l o g i c a l Survey editorial standards and stratigraphic nomenclature.

Any use of trade names i s for descriptive purposes only and does not imply endorsement by the USGS.

TABLE OF CONTENTS

Page

......................................................... Introduction 1

Methods and Data Base ........................................... 2

Geophysical Records ............................................ 2

................................................. Bottom sampling 3

............................................... photographic data 3

.................................................. Geologic Background 4

...................................... Surfieial Sediment ~istribution 7

.......................................................... is cuss ion 8

................................ unconsolidated surface sediments 8

...................................... Lag gravel over bedrock 8

............................. Lag gravel over glacial deposits 9

............................. Basal transgressive medium sands 10

Inner shelf sand sheets ...................................... 11

~istribution of sand and gravel bodies .......................... 13

Data Limitations ..................................................... 17

Summary .............................................................. 18

........................................................... References 20

Figure Captions ...................................................... 24

In t roduc t ion

The nor thern Bering Sea i s a broad, shal low e p i c o n t i n e n t a l s h e l f r eg ion

covering approximately 200,000 ]on2 of s u b a r c t i c sea f l o o r between nor thern

Alaska and t h e U. S.S.R. (Fig. 1). The s h e l f can b e d iv ided i n t o f o u r gene ra l

morphologic a r eas : (1) t h e western pa*, a n a r e a of undulat ing, hummocky

r e l i e f formed by g l a c i a l g rave l and t r a n s g r e s s i v e - marine sand s u b s t r a t e

(Nelson and Hopkins, 1972); (2) t h e sou theas t e rn p a r t , a r e l a t i v e l y f l a t

f e a t u r e l e s s p l a i n with f ine-grained t r a n s g r e s s i v e - marine sand s u b s t r a t e

(McManus, e t a l , 1977); ( 3 ) t h e no r theas t e rn p a r t , a complex system of sand

r i d g e s and shoa l s with f i ne - t o medium- gra ined t r a n s g r e s s i v e sand s u b s t r a t e

(Nelson e t a l , 1978); and ( 4 ) t h e e a s t e r n p a r t , a broad f l a t marine r e e n t r a n t

(Norton Sound) covered by Holocene s i l t and very f i n e sand (Nelson and

Creager , 197 7 . The nor thern Bering Sea i s a f f e c t e d by a numbex of dynamic f a c t o r s :

winter s e a ice , sea l e v e l s e tup , s torm waves and s t r o n g c u r r e n t s (geostxophic,

t i d a l , and s torm). The s e a i s covered by pack ice f o r about h a l f t h e year ,

from November to May. A narrow zone of s h o r e f a s t ice develops around t h e

margin of t h e s e a during winter months. During t h e open water season, t h e sea

is subject t o occas iona l s t r o n g no r the r ly winds, i n t h e f a l l , s t r o n g

southwester ly winds cause high waves and storm su rges a long t h e e n t i r e west

Alaskan coast . Throughout t h e year , t h e r e is a con t inua l northward f low of

water with c u r r e n t s i n t e n s i f y i n g on t h e e a s t s i d e of s t r a i t a r e a s (Coachman a t

al., 1975). Although d i u r n a l t i d a l ranges a r e s m a l l , s t ong t i d a l c u r r e n t s a r e

found i n s h o r e l i n e a r e a s and wi th in c e n t r a l Norton Sound (Fleming & Haggarty,

1966; Cacehione e t al., 1982).

Thi s r e p o r t reviews t h e methodology employed and t h e d a t a c o l l e c t e d over

a pe r iod of near ly 20 yea r s i n t h e nor thern Bering Sea. A b r i e f geologic

h i s t o r y and background a r e presented followed by a d i scuss ion of d i s t r i b u t i o n

of sediment t ypes and d i s t r i b u t i o n of s p e c i f i c sand and g rave l bodies . The

Limi ta t ions o f t h e d a t a base and needs f o r f u r t h e r s tudy are expla ined and a

b r i e f summary of resource p o t e n t i a l and environmental cons ide ra t ions is given.

Methods and Data Base

The majo r i ty of d a t a app l i cab le t o t he eva lua t ion of sand and g rave l

resources and environmental hazards of t h e i r e x p l o i t a t i o n , were c o l l e c t e d o n

s e v e r a l U. S.G. S. c r u i s e s aimed a t assessment of p o t e n t i a l environmental

hazards t o exp lo ra t ion and product ion 05 o i l and gas resources. Much of t h e

d a t a c o l l e c t e d and ana lyses completed cannot be appl ied , however some s t u d i e s

of s u r f i c i a l sediment d i s t r i b u t i o n , s p e c i f i c sediment bodies , and dynamics of

sediment t r a n s p o r t provide t h e d a t a base f o r t h i s repor t .

Geophysical Records

High-resolut ion se i smic - r e f l ec t ion p r o f i l i n g d a t a provide ba thymetr ic

in format ion as w e l l a s subbottom informat ion on sediment t h i ckness and

morphology. A q u a l i t a t i v e assessment of the nature of t h e sediment can be

made on t h e b a s i s of a c o u s t i c cha rac t e r . Side-scan sonar imagery y i e l d s

informat ion on bottom morphology and l a t e r a l e x t e n t of d i s c r e t e sediment

bodies a s wll a s another q u a l i t a t i v e assessment of sediment nature. The

t r a c k l i n e coverage of geophysical d a t a used i n t h i s r e p o r t is shown i n F igures

2A & 2B.

Bottom sampling

An extens ive a r r a y of bottom samples were analyzed t o provide t h e

sediment da ta used i n t h i s repor t . Figure 3 shows t h e loca t ion of a l l sample

s t a t i o n s . The samples include simple grab samples of t h e s u r f i c i a l sediment,

box cores pene t ra t ing up t o severa l 10 ' s of centimeters i n subs t ra t e , and Kie l

and Alpine vibracores pene t ra t ing up t o 7 m i n t o t h e seafloor. I n addi t ion , a

s e r i e s of deepex holes, up t o 75 m i n depth, were d r i l l e d within 3 m i l e s of

t h e coas t o f f Nome, as p a r t of a precious metal resource evaluat ion i n t h e

l a t e 1960's.

Photographic da ta

TV and Black and White s t i l l photography were co l l ec ted at numerous

s t a t ions . T h i s type of da ta provide q u a l i t a t i v e information on sea f l o o r

morphology, a c t i v e processes, and t h e nature of s u r f i c i a l sediment.

U.S.G.S. operated c r u i s e s were conducted with ttm broad emphases, The

f i r s t being a regional , reconnaissance, survey t o ca tegor ize and c l a s s i f y

a reas a s t o sediment type, sediment dynamics, a c t i v e t ec ton ics , and o the r

regional c h a r a c t e r i s t i c s . Secondly, c r u i s e s o r por t ions of c ru i ses , were

devoted t o d i s c r e t e survey a reas o r ob jec t ives t o de l inea te s p e c i f i c f e a t u r e s

a nd/o r p he nome na . I n add i t ion t o information from U.S. Geological Survey c r u i s e s , numerous

data from Universi ty of Washington c r u i s e s a r e included i n t h e da ta set.

Similar ly , da ta c o l l e c t e d during opera t ions by NOAA sh ips , U.S. Coast Guard

ships , and research vesse l s of Scripps I n s t i t u t i o n were a l s o incorporated i n t o

t h e data se t .

Geologic Background

The nor thern Bering Sea i s bounded by t h e Seward Peninsula on t h e north,

Yukon-Koyukuk geologic province on t h e east, t h e Yukon d e l t a and St . Lawrence

I s l a n d on t h e south , and t h e Chukotsk Peninsula of S i b e r i a on t h e west (Fig.

1). The United S t a t e s - Russia Convention Line of 1867 marks t h e western end

of t h e a r e a t h a t i s l i k e l y t o b e inc luded i n any sand and g rave l resource

l e a s e sa l e .

Three subbasins u n d e r l i e t h e nor thern Bering Sea. The northwest Bering

Sea is unde r l a in by sha l low basement, mainly Precambrian through lower

Mesozoic rocks. Geophysical d a t a show t h a t t h e basement i s o v e r l a i n by an

average of 1 lan of rocks of la te Neogene and Quaternary age ( F i s h e r e t a l ,

1982). The second and t h i r d subbasins a r e s epa ra t ed by a s t r u c t u r e , t h e Yukon

Horst (See Fishe r e t a l . , 1982, Fig. l o ) , which s t r i k e s northwest from near

t h e mouth of the Yukon River. Rocks i n t h e St . Lawrence subbasin, west of t h e

h o r s t , a r e l o c a l l y a s t h i c k as 5 km. The subbas in east of t h e h o r s t con ta ins

f i l l as t h i c k as 6.5 km.

1 n t e r n of p o t e n t i a l sand and g rave l resources , t h e l a t e P le i s tocene

(>10,000 yea r s B.P.) and Holocene ( ~ 1 0 , 0 0 0 y e a r s B.P.) sedimentat ion is t h e

f a c e t of geologic h i s t o r y of t h e g r e a t e s t impact and i n t e r e s t . The

d i s t r i b u t i o n of l a te P le i s tocene and Holocene su r f ace sediment on t h e no r the rn

Bering Sea f l o o r i s patchy and dependent upon l o c a t i o n s of s e a f l o o r bedrock,

p re - l a t e P l e i s tocene g l a c i a l deb r i s , la te Holocene r i v e r borne sediment

i n f l u x , modern bottom c u r r e n t s , and p a s t e u s t a t i c sea- leve l changes.

To a s s e s s t h e e f f e c t of t h e s e f a c t o r s t h e nor thern Bering Sea c a n b e

d iv ided i n t o t w provinces, Chir ikov Basin on t h e west, and t h e shal lower

(General ly (20 m deep) Norton Basin i n the c e n t r a l and e a s t . The l a s t late-

Ple i s tocene and Holocene t r a n s g r e s s i o n began about 12,000 t o 13,000 y e a r s

ago. A narrow seaway developed from Anadyr S t r a i t (between S t . Lawrence

I s l a n d and S i b e r i a ) t o Bering S t r a i t (Hopkins, 19791, and t h e n from Shpanberg

Strait (between St. Lawrence Island and Yukon Del ta ) t o Bering Strait (Nelson

and Creager, 1977). The narrow seaways expanded t o f i l l t h e deeper western

area of Chirikov Basin u n t i l about 10,000 yea r s ago.

The l a t e P l e i s tocene t o Holocene s h o r e l i n e t r a n s g r e s s i o n depos i ted a t h i n

sequence of t r a n s g r e s s i v e d e p o s i t s on t h e margins of Chirikov Basin. On some

margins, only a t h i n g rave l l a g is found over bedrock outcrops or g l a c i a l

depos i t s . These Lags developed as t h e t r a n s g r e s s i v e s h o r e l i n e remrked

bedrock or g l a c i a l depos i t s , removed f i n e r gra ined sediment, and l e f t a g rave l

l a g (Nelson and Hopkins, 1972).

I n o t h e r a r e a s of Chir ikov Basin, t h e t y p i c a l sequence is la te

P le i s tocene f reshwater pea ty s i l t o v e r l a i n by t r a n s g r e s s i v e sand. The t und ra

and f reshwater si l t developed where topographic e l e v a t i o n s of bedrock o r

g l a c i a l moraines *re not present . A s t h e s h o r e l i n e t r ansg res sed over t h e

emergent f reshwater pea ty mud, a b a s a l coarse- t o medium-grained sand was

deposited. A f ine-grained i n n e r s h e l f sand was depos i ted immediately o f f t h e

s h o r e l i n e as it t r ansg res sed ; t h i s genera l ly o v e r l i e s the b a s a l coa r se r sand

and forms a b l anke t depos i t now covering most of t h e c e n t r a l and southern

Chir ikov basin.

The e n t i r e Norton Sound r e g i o n remained emergent u n t i l about 10,000 yea r s

ago. Radiocarbon d a t e s i n Norton Sound show t h a t from 10,000 t o 9,500 yea r s

B.P., t h e s h o r e l i n e r ap id ly t r ansg res sed eastward over Norton Sound and b u r i e d

tundra p e a t depos i t s . Marine sandy s i l t interbedded with very f i n e sand

Layers o v e r l i e t h e f reshwater peaty muds. Above t h i s sequence i n c e n t r a l

Norton Sound is b io tu rba t ed , sandy s i l t der ived from t h e Yukon River (McManus

e t a l . , 1977; Howard and Nelson, 1982). The s u r f i c i a l Holocene d e p o s i t s i n

Norton Sound vary from f ine-gra ined sand surrounding t h e d e l t a and i n a t rough

a long nor thern Norton Sound t o very f i n e sand and coa r se s i l t i n c e n t r a l and

e a s t e r n Norton Sound.

The t h i c k b l anke t of Holocene s i l t and interbedded sand l a y e r s i n Norton

Sound d i f f e r s from t o t h e t h i n t r a n s g r e s s i v e sequence of sand depos i ted i n

Chir ikov Basin. Thick s e c t i o n s of Holocene sediment have been depos i ted i n

southern Norton Sound because of prograda t ion of t h e Yukon Delta. Only 2 m o r

l e s s of b i o t u r b a t e d mud has been depos i ted i n t h e more d i s t a l a r e a s of

nor thern and e a s t e r n Norton Sound (Nelson and Creager, 1977).

Numerous subsurf ace a l l u v i a l channels , covered by t h e t r a n s g r e s s i v e

depos i t s , have been mapped i n t h e Norton Sound r eg ion (Fig. 4 ) . I n Chir ikov

bas in , t h e l i m i t e d g r i d of se i smic d a t a does not permit d e t a i l e d mapping of

t h e subsurface channels , b u t major channels a r e known extending west of P o r t

Clarence, i n t h e s e a v a l l e y extending south from King I s l a n d (Hopkins et dl.,

19761, and i n t h e c e n t r a l p a r t of Chirikov Basin. These channel depos i t s have

not been i d e n t i f i e d i n cores .

Ear ly and middle P l e i s tocene c o n t i n e n t a l g l a c i a t i o n extending off S i b e r i a

t o t h e c e n t r a l Chirikov Basin, and l o c a l v a l l e y g l a c i a t i o n extending o f f s h o r e

from Seward Peninsula have been mapped by se ismic r e f l e c t i o n p r o f i l i n g and by

sediment sampling ( G r i m and Mmanus, 1970; Nelson and Hopkins, 1972; Tagg and

Greene, 1973; Hopkins, 1975, 1979). The g l a c i a l moraines a r e p r e s e n t i n t h e

subsurface of c e n t r a l Chir ikov Basin (Fig. 5) and emerge toward l and as grave l

r idges . Sequences of moraines and outwash were documented i n the nearshore

a r e a s of f Nome and from d r i l l h o l e s (Nelson and Hopkins, 1972).

The o t h e r major geologic event t h a t s i g n i f i c a n t l y inf luenced t h e

d i s t r i b u t i o n of l a te P le i s tocene and Holocene depos i t s is t h e change i n

p o s i t i o n of t h e a c t i v e Yukon D e l t a l obe on t h e Bering Shelf . About 16,000

y e a r s ago, t h e Yukon River apparent ly c rossed t h e p re sen t Bering s h e l f i n t h e

v i c i n i t y of Cape Romanzof, 100 km south of t h e p re sen t Yukon d e l t a , and

depos i ted a d e l t a i c sequence south of St. Lawrence I s l and (Knebel and Creager,

1973). A8 sea level rose , va r ious a c t i v e lobes developed f a r south of Norton

Sound (Nelson and Creager, 1977). The p re sen t a c t i v e d e l t a lobe f i r s t

developed i n southern Norton Sound after 2,500 years B.P. (Dupre, 1978).

Since t h e n t h e Yukon River has prograded s i g n i f i c a n t l y i n t o Norton Sound.

Surf i c i a l Sedimerrt D i s t r i b u t i o n

Analyses of s u r f i c i a l sediment samples from over 467 s t a t i o n s were

compiled and computer-contoured maps of sediment d i s t r i b u t i o n were prepared.

The r e s u l t i n g maps a r e meant t o be a n ex tens ion and refinement of maps

generated by McrJlanus and o t h e r s at t h e Unfversi ty of Washington (McManus e t

a l . , 1970, 1977).

Caut ion should b e used i n i n t e r p r e t i n g contoured data. Contours imply a

g rada t ion i n va lue from one a r e a t o another t h a t may not e x i s t . I n genera l ,

areas of r e l a t i v e l y closely-spaced contours a r e suspec t and may r ep resen t a

sha rp boundary between widely d i f f e r e n t sediment types.

The sand con ten t maps (Fig. 6A and 6B) show sandy a r e a s o r s h o a l s i n

c e n t r a l and -stern Shpanberg S t r a i t , e a s t e r n Bering Strai t , nor th-cent ra l and

no r theas t Norton Sound, south of S t . Lawrence I s land , i n shoa l s west of t h e

mouth of t h e Yukon River , and over rrmch of the c e n t r a l Chirikov basin.

Figures 7 A and 7B show a g rave l d i s t r i b u t i o n c o n t r o l l e d by t h e presence o f

g l a c i a l moraines and outwash, bedrock, a l l u v i a l depos i t s , and ad jacen t

t e r r e s t r i a l sources. The g rave l concen t r a t e s a r e products of t h e winnowing of

f i n e m a t e r i a l by s t r o n g c u r r e n t s through t h e straits and a long t h e Seward

Peninsula. Axeas of gxavel abundance a r e r e f l e c t e d by areas of low sand

content .

'She mean sediment g r a i n s i z e (Fig. 8 A and 8B) d i s t r i b u t i o n map was

prepared by c a l c u l a t i n g t h e f i r s t moment parameters f o r each sediment

sample. This map is a composite of t h e a r e a s of maximum content of each

sediment s i z e c l a s s , i .e . , g r ave l , sand, s i l t , and clay. Again, cau t ion must

b e used i n i n t e r p r e t a t i o n . Apparent t r a n s i t i o n o r grad ing from one average

g ra in - s i ze t o another may not be r e a l . The map of modal sediment s i z e (Fig.

9A and 9B) i s very s imi la r t o t h e mean gra in-s ize map b u t i n gene ra l shows

va lues 1/2 fl c o a r s e r t h a n t h e va lues of t h e mean gra in-s ize map. To s imp l i fy

i n t e r p r e t a t i o n and summarize t he d i s t r i b u t i o n of sediment o n t h e nor thern

Bering Seaf loor , g rave l , sand, and mud ( s i l t and c l a y ) abundances a r e

po r t r ayed on Figures 8 B and 98. F igure 8B i s based on mean gra in-s ize and

f i g u r e 9B is based on modal ana lys i s . Sand-size m a t e r i a l c h a r a c t e r i z e s t h e

ma jo r i t y of bo th s u r f i e i a l sediment maps with a plume of muddy sediment

extending northwest from t h e Yukon d e l t a , mud-rich sediment i n e a s t e r n Norton

Sound, and g rave l r i c h sediment off t h e Seward Peninsula and i n the s t r a i t s .

Discussion

Unconsolidated Surface Sediments

Lag grave l over bedrock

Very t h i n s u r f i c i a l covers of g rave l ove r o l d e r Precambrian t o Cretaceous

bedrock outcrops (Fig. 1 0 ) occur i n t h e a r e a west of Nome near Sledge I s l and ,

northward toward P o r t Clarence, and i n a l a r g e a r e a from P o r t Clarence a long

t h e York c o a s t l i n e t o Cape Pr ince of Wales (Nelson and Hopkins, 1972; Nelson,

1982) . Sampling i n t h e s e a r e a s r e v e a l s only s c a t t e r e d occurrences of grave l

sugges t ing t h a t on ly small , t h i n (few c m t h i c k ) pockets of g rave l a r e present:

over t h e s e bedrock l o c a t i o n s and t h a t d i s t r i b u t i o n of t h e g rave l s i s q u i t e

patchy. The sporadic , t h i n pockets of g rave l over bedrock w u l d not be a

renewable resource because t h e s e r e l i c t g rave l s = r e produced by s h o r e l i n e

sedimentat ion during pe r iods of lower s e a l e v e l and a r e not be ing replenished.

Environmental change from mining, however, m u l d leave a s u b s t r a t e of

s c a t t e r e d pebbles over bedrock and muld a l t e r t h e a l r eady high concen t r a t ion

of suspended sediment. Also high va lues of suspended sediment a l ready occur

s p o r a d i c a l l y i n t h e Alaskan c o a s t a l water of t h i s reg ion because of large

q u a n t i t i e s of suspended sediment c r e a t e d by storm even t s (Nelson, 1971; Nelson

and Creager, 1977; Cacchione and Drake, 1982).

Lag g rave l over g l a c i a l d e p o s i t s

Gravels were depos i ted by t h e Holocene s h o r e l i n e t r a n s g r e s s i o n a s it

r e m r k e d g l a c i a l till. A s u b s t a n t i a l s u r f a c e a r e a of t h i s grave l t ype occurs

o u t to t h e t h r e e mile l i m i t off N o m e , in a large area southwest of Cape P r ince

of wales, and nor th and northwest of St. Lawrence Island (Fig. 10 1. The

l o c a t i o n of t h e s e g rave l s c o r r e l a t e s with subsurface occurrence o f g l a c i a l

till. Where t h e g rave l has been pene t r a t ed it is t h i n , l e s s t h a n 30 c m t h i c k ,

and without a mat r ix of silt o r mud. Beneath t h e t h i n veneer of r e l i c t l a g

g rave l over glacial depos i t s , t h e till is composed of pebbly sandy silts.

The complete lack of any shal low c o r i n g i n t h e s e reg ions , p revents

d e t a i l e d knowledge of t h e th i ckness of t h e gravel lags and t h e resource

p o t e n t i a l cannot be estimated. The techniques f o r mining w u l d b e d i f f i c u l t

t o a s c e r t a i n because of unknown th i cknesses and v a r i a b i l i t y of g rave l type.

Addi t iona l complications e x i s t i n t h e Nome nearshore reg ion because t h e r e l i c t

g rave l s a r e r i c h i n gold i n c e r t a i n l oca t ions . The gold resource should b e

considered a long with the sand and g rave l resource. A s s e s s i n g t h e gold

resource is complex because of t h e he te rogenei ty of depos i t s near Nome,

e s p e c i a l l y where s u r f a c e and subsurface a l l u v i a l channels have been i n - f i l l e d

by f i n e r sands (Nelson and Hopkins, 1972).

The mining o r skimming o f f of t h i s c l e a n r e l i c t l a g g rave l would change

t h e s u b s t r a t e of t h e mined region. The new s u b s t r a t e w u l d be one of muddy

g rave l t h a t m u l d not provide t h e same bouldery, c l e a n g rave l s u b s t r a t e as a t

present . The mining of such g rave l s and t h e genera t ion of large sediment

plumes by mining t o some e x t e n t emulates t h e Seward Peninsula coas t where

c o a s t a l water f r equen t ly con ta ins e l eva t ed l e v e l s of suspended sediment caused

by storm surge ebb flow (Nelson, 1971; Nelson and Creager, 1977; Cacchione and

Drake, 1982).

Basal t r a n s g r e s s i v e medium sands

Coarse- t o medium-grained sand covers reg ions p a r a l l e l i n g t h e g rave l s ;

p a r t i c u l a r l y a long t h e w s t e r n edge of Seward Peninsula from Sledge I s l and t o

Cape P r ince of Wales and perhaps i n bands through Bering S t r a i t and Anadyr

Strait (Fig, t o ) . They are poor ly assessed i n t e r m s o f th ickness ; where they

have been pene t r a t ed they t e n d t o b e only a few cent imeters (Fig. 11) . The

only except ion t o t h i s is northwest of P o r t Clarence where large, l i n e a r

r i d g e s of t h i s sand have been r e m r k e d by s t r o n g c u r r e n t s i n t o sand wave

f i e l d s ( F i e l d e t al . , 1981).

The resource p o t e n t i a l of t r ansgxess ive sands in most reg ions w i l l b e

inf luenced by t h e i r t h i n n e s s and in te rbedding with over ly ing f iner -gra ined

sands and underlying P le i s tocene muds. I n terms of environmental

cons ide ra t ions t h i s sand produces a d i s t i n c t s u b s t r a t e f o r c e r t a i n s e t s of

fauna such a s sand d o l l a r s (Nelson e t a l . , 1981). I f t h e mil-sorted sands

a r e mined o u t t h i s s u b s t r a t e w u l d no longer e x i s t . A t t h i s p o i n t t h e

r e l a t i o n s h i p s of t h e s e coarse- and medium-grained sands t o b i o l o g i c a l food

cha ins and mammals a r e not w e l l assessed. Determination of long term e f f e c t s

of mining this s u b s t r a t e cannot be made with t h e p re sen t data base.

Inner s h e l f sand s h e e t s

Throughout most of c e n t r a l Chir ikov Basin and extending toward Norton

Sound and i ts western edge is a s h e e t of f ine-grained sand of about 125

microns mean g r a i n s i z e diameter and c o n s i s t i n g of about 8 0 % sand and 20%

coa r se to medium s i l t (Fig. 10). This sand s h e e t c o n s i s t s of sands layed down

by t h e shore l i n e t r a n s g r e s s i o n throughout t h e Holocene and i s a t h i n shee t

ove r ly ing a very widespread a r e a of Northern Bering Sea. Its th i ckness is not

wel l assessed , s i n c e only a few v ib raco res have pene t r a t ed i t s e n t i r e

t h i ckness (Fig. 11, co re s i n Chir ikov b a s i n ) ; i n d i c a t i o n s a r e t h a t it rarely

exceeds more t h a n L meter, except where it may f i l l i n subsur face and su r f ace

channels (Fig. 4 ) .

Thi s widespread sand s h e e t i s a p o t e n t i a l resource i f t h i s very f i n e sand

is of t h e proper grade for development purposes. It can be skimmed o f f over

wide regions and i s a very cons i s t en t ma te r i a l throughout t h e e n t i r e Chirikov

Basin region. This uniformity means t h a t l i t t l e processing o r s i z i n g of t h e

ma te r i a l might b e required t o provide f i n e sand sources.

I£ t h i s s u b s t r a t e i s s t r ipped off t o t h e coarser sands below or more

l i k e l y t o t h e underlying Ple is tocene peaty mud, t h e su r face s u b s t r a t e i n such

regions would be changed. Environmental e f f e c t s of t h i s a r e p red ic tab le

because t h i s f i n e sand sheet i s a h a b i t a t f o r Ampilicid amphipods. The

Ampilicid amphipods are a food source f o r whales, p a r t i c u l a r l y t h e Grey whale

species. I f wide regions of t h i s sand are used as a resource and it is

s t r ipped o f f completely t h e d i s t r i b u t i o n of a major food source f o r t h e grey

whales tmuld be changed. I n addi t ion , mining operat ions causing l a r g e

sediment plumes could a l t e r t h e normal environment of t h i s region which is not

prone to high q u a n t i t i e s of suspended sediment i n t h e water column (Drake e t

a l . , 1979).

Holocene sediment covers t h e region of Norton Sound (Fig. 1 0 ) . This

deposi t v a r i e s from 14 meters th ickness , close t o t h e Yukon Delta, to a t h i n

( 1-2 meter) , very f i n e sand sheet over northern Norton Sound and may be absent

i n t h e north c e n t r a l region. Again t h i s widespread sheet of very f i n e sand-

coarse s i l t is a minable resource i f such sands a r e required f o r any

development purposes.

Like t h e inner shel f sands, i f s u r f i e i a l Holocene deposi t s of Norton

Sound a r e s t r ipped o f f , t h e underlying Pleistocene peaty mud w i l l form t h e new

subst ra te . The food source and ecologica l r e l a t ionsh ips of t h i s change i n

s u b s t r a t e are not -11 known and relationshLp t o higher mammal food chains a r e

not w e l l es tabl ished.

D i s t r i b u t i o n of sand and g rave l bod ie s

A number of sand and g rave l bod ie s have been def ined i n the Norton Basin

a r e a on t h e b a s i s of topography and su r f ace g r a i n size. The th i ckness of

t h e s e bod ie s and consequent ly t o t a l volumes cannot be es t imated because t h e r e

a r e only very shal low vibracoxes, genera l ly l e s s than 2 meters i n ' pene t r a t ion ,

a v a i l a b l e over t h e s e regions. Their geometry can only be determined from

s u r f a c e r e l i e f and e s t ima te s of t h e i r genera l th ickness . This a l s o holds t r u e

f o r t h e genera l grade of material s i n c e t h e r e a r e no sha l low s t r a t i g r a p h i c

c o r e s through t h e s e sand and g rave l bodies . The homogeneity of t h e m a t e r i a l

is unknown and t h e only d a t a a v a i l a b l e i s i n t h e upper 2 meters o r from t h e

s u r f a c e samples c o l l e c t e d over them. Table I summarizes t h e c h a r a c t e r i s t i c s

of t h e s e s h e l f sand bodies .

Two g rave l bodies are known i n t h e Northern Bering Sea a rea . The first

Lies west of St. Lawrence I s l a n d and appears t o b e a l a r g e o l d beach r i d g e

formed by a Holocene s t i l l - s t a n d of t h e sea level. a t approximately minus 30

meters of water depth (Fig. 12) . The r idge c o n s i s t s of f i n e g rave l and

extends approximately 30 km t o t h e no r theas t from t h e northwest Cape of St .

Lawrence Island and has a n undefined th i ckness because t h e r e are no sha l low

c o r e s wi th in t h i s g rave l body.

The second known g rave l depos i t occurs e a s t of N o m e off t h e Nome River

a r e a wi th in 3 mi l e s of shore. It is a n outwash f a n c r e a t e d dur ing P le i s tocene

t imes of lower s ea l e v e l (Nelson and Hopkins, 1972). This grave l body is -11

shown i n t h e topography and se ismic p r o f i l e s of t h e region ( ib id ; Tagg and

Green, 1973) and has been pene t r a t ed by d r i l l ho l e s provid ing co re c u t t i n g s

b u t no d e t a i l e d s t r a t i g r a p h i c sec t ions . It appears t o b e a t l e a s t s e v e r a l

meters t h i c k . However, t h e r e i s not s u f f i c i e n t d e t a i l i n t h e se i smic

p r o f i l i n g d a t a nor i n t h e d r i l l i n g t o assess t h e s p e c i f i c known volumes o r

size d i s t r i b u t i o n of t h i s outwash f a n depos i t .

The s e r i e s of t h i n , re l ic t , l a g g rave l s over g l a c i a l till has been

descr ibed i n t h e previous s e c t i o n of t h i s repor t . A s ha s been noted, t h e s e

cover wide a r e a l reg ions over t h e nor thern Bering Sea b u t where t h e y have been

pene t r a t ed by v ib raco res or box co res t hey a r e q u i t e t h i n , genera l ly lass t h a n

.5 m i n th ickness . They do not r ep re sen t thick grave l depos i t s b u t do

r ep re sen t wide r eg ions of a g rave l occurrence. Outwash channels and a l l u v i a l

channels i n t h e s e re l ic t g l a c i a l d e p o s i t s have t h e g r e a t e s t p o t e n t i a l as

grave l resources. I n add i t i on , t h e subsurface s t r u c t u r e i s poor ly known

because of t h e d i f f i c u l t y of ob ta in ing good p r o f i l e d a t a i n coarse-grained

s u r f i c i a l depos i t s . The only good way t o a s s e s s such a l l u v i a l channels is t o

have a shallow-core d r i l l i n g program and such work has not y e t been undertaken

i n t h e nor thern Bering Sea.

Large, deep, outwash and/or f l u v i a l channels a r e observed on se i smic

r e f l e c t i o n p r o f i l e s c o l l e c t e d over c e n t r a l Chirikov bas in . These deep,

f i l l e d , channels t y p i c a l l y a r e i n c i s e d 60 t o 80 meters i n t o t h e sea f l o o r and

occas iona l ly over 100 meters. Assessment of t h e t r u e width is somewhat

d i f f i c u l t as t h e c r o s s i n g ang le is not known. Oblique c ros s ings produce

expansive c ross -sec t ions whereas more or thogonal c ros s ings y i e l d a narrow,

s teeper -s ided record of the channel (Fig. 13 A & B).

Txackline d e n s i t y is not g r e a t enough t o r e l i a b l y connect t h e s e d i s c r e t e

c ros s ings i n t o a coherent drainage system. The channels a r e completely f i l l e d

and show no s u r f a c e expression, s o s idescan records a r e of no a i d i n

determining t r e n d o r c o n t i n u i t y of channels. Thei r occurrence i n Chir ikov

Basin sugges ts t h e upper p a r t o f the f i l l has been revmrked dur ing

t r a n s g r e s s i o n and a thin veneer of coarse- t o medium-grained sand deposited.

A complete lack of deep c o r e informat ion from wi th in t h e channels l eaves t h e

na tu re of t h e f i l l i n g m a t e r i a l unknown. The d e t a i l of i n t e r n a l s t r u c t u r e s een

wi th in t h e channel f i l l sugges ts it is not coarse-grained b u t r a t h e r con ta ins

numerous s i l t and mud horizons. Good subsur face p e n e t r a t i o n i n hi.gh-

r e s o l u t i o n se i smic p r o f i l e s i n r a r e l y observed i n coarse-grained depos i t s .

Coarse-grained m a t e r i a l m u l d l i k e l y b e p re sen t i n t h e channel f i l l as

channel-lag d e p o s i t s and i n point-bar p o r t i o n s of t h e f i l l . Exp lo i t a t i on of

disseminated pockets of sand and g rave l m u l d r e q u i r e removal of f ine-grained

depos i t s t o ga in access t o t h e t a r g e t g rave l lenses . Del inea t ion of p o t e n t i a l

g r a v e l zones w u l d r e q u i r e d e t a i l e d se i smic surveys t h a t a t p r e s e n t do not

e x i s t . Working and removal of s i g n i f i c a n t volumes of f i n e r gra ined d e p o s i t s

would genera te a n ex tens ive sediment plume i n a n a r e a of t y p i c a l l y low

suspended sediment concent ra t ions (Drake e t al . , 1979).

A series of l a r g e , l i n e a r , medium- t o f ine-grained sand s h o a l s are

p re sen t sou theas t of Bering S t r a i t s near P o r t Clarence (F ig . 14A). These sand

shoa l s a r e m l l mapped i n t h e s u r f i c i a l bathymetry and a number of shal low

v ib raco res p e n e t r a t i n g up t o 6 m i n t o t h e s h o a l s have been taken. Soma

d e f i n i t i o n of t h e s e sand bodies i s p o s s i b l e from s u r f i c i a l r e l i e f (Fig. 14B)

and subsurface c o r i n g informat ion (Fig. 14C) (Nelson e t al . , 1982).

These anc i en t s h o r e l i n e shoa l s a r e 15-30 km i n length , 3-7 km i n width,

and 10-15 m i n r e l i e f with a known minimum th i ckness of 6 m of c l ean , very

wel l s o r t e d medium-to-fine-sand with a very low mat r ix content . They comprise

a p o s s i b l e clean-sand source but it is a non-renewable source because t h e s e

s h o a l s were depos i ted as anc ien t s h o r e l i n e sediments during a series of s t i l l-

s t ands in t h e l a te Pleistocene-Holocene rise of sea l e v e l i n t h e p a s t 18,000

bod ie s a r e by-in-large r e l i c t o r pal impsest d e p o s i t s and a s such r ep resen t a

non-renewable resource. Once mined, t h e s u b s t r a t e w u l d be changed.

The na ture of t h e d a t a base makes assessment of environmental impacts

specu la t ive and i n f e r e n t i a l . I n a r e a s where t h e under ly ing m a t e r i a l d i f f e r s

from t h e sand and grave l , a change i n s u b s t r a t e i s one of t h e l i k e l y products

of mining or s t r i p p i n g . Such a change a f f e c t s bottom dwell ing organisms t h a t

depend o n a c e r t a i n bottom c h a r a c t e r f o r t h e i r h a b i t a t . Dis rupt ion of t h i s

lower p o r t i o n of t h e food c h a i n could have a n e f f e c t o n t h e b i o l o g i c community

of a g iven area.

The genera t ion of a suspended sediment plume will change t h e background

suspended sediment l eve l s . High l e v e l s of suspended sediment a r e not unusual

i n much of t h e nor thern Bering Sea, however, t h e r e are d i s t i n c t areas of low

suspended sediment va lues , and i n t r o d u c t i o n of sediment laden water could

i n c r e a s e suspended sediment concent ra t ions .

Addit ional data aimed s p e c i f i c a l l y a t sand and g rave l assessment i s

needed i n much of t h e area. Once t a r g e t e d a s a p o t e n t i a l resource a rea ,

d e t a i l e d s t u d i e s w u l d be necessary t o accu ra t e ly de f ine t h e resource and any

p o t e n t i a l environmental hazards a s s o c i a t e d with i ts exp lo i t a t i on .

R e f e r e nces - Cacchione, D. A., Drake, DO E., and Wiberg, P., 1982, Veloc i ty and bottom-

s t r e s s measurements i n t h e bottom boundary l aye r , o u t e r Norton Sound,

Alaska, Geoloqie e n Mijnbouw, v. 61, p. 71-78.

Cl ine , J. D, and Holmes, M. L., 1977, Submarine seepage of n a t u r a l gas i n

Norton Sound, Alaska, Science, 198, p. 1149-1153.

Coachman, L. K., Aagaard, K., and Tripp, R. B., 1975, Bering S t r a i t : The

r e g i o n a l phys i ca l oceanography, Univ. of Washington Press, S e a t t l e ,

Washington.

Drake, D. E. , Totman, C. E., and Wiberg, P. L., 1979, Sediment t r a n s p o r t

dur ing t h e winter on t h e Yukon p r o d e l t a Norton Sound, Alaska, Your. Sed.

Pe t ro l . , v. 49, p. 1171-1180.

Dupre, W. R. , 1978, Yukon d e l t a c o a s t a l p rocess s tudy , In: Annual Report of

P r i n c i p a l I n v e s t i g a t o r s f o r Year Ending March, 1978, NOAA/OCSEAP, p. 384-

446.

Dupre, W. R., 1980, Seasonal v a r i a t i o n s i n d e l t a i c sedimentat ion on a high-

l a t i t u d e ep icon t inen ta l s h e l f , In: Nio, S. C., Schattenhelm, R. T., and

Van Weering, T. C. E., eds., I A S Spec. Pub., Blackwell Sci . Pub., London,

i n press.

F i e l d , M. E., Nelson, C . H e , Cacchione, D. A., and Drake, D. E., 1981,

Migra t ion of sand waves o n t h e Bering Sea ep ieon t inen ta l shelf, In:

N i t t roue r , C. A., ed., Sedimentary Dynamics of Cont inenta l Shelves,

E l sev ie r , Amsterdam, i n press.

Fi she r , M . A., Pat ton , W. W. Jr., and Holmes, M. L., 1982, Geology of Norton

Basin and c o n t i n e n t a l s h e l f beneath northwestern Bering Sea, Alaska, Am.

Assoc. Petrol. Geol. Bull . , v. 66, p. 225-285.

Flaming, R. Ha and Heggarty, DO, 1966, Oceanography of t h e sou theas t e rn

Chukchi Sea, In: Wilimovsky, N. J., and Wolf , J. M. , eds., Environment of

Cape Thompson, Alaska, U . S . Atomic Energy Coxrunission, pr 679-694.

G r i m , M. S. and MManus, D. A * , 1970, A sha l low se ismic-prof i l ing survey of

t h e nor thern Bering Sea, Marine Geology, v. 8, p. 293-320. .

Holmes, M. L. and Thor, D. R., 1982, D i s t r i b u t i o n of gas-charged sediment i n

Norton Basin, nor thern B r i n g Sea, Geologie e n M i jnbouw, v. 61, p. 79-90.

Hopkins, D. Me, 1975, Time s t r a t i g r a p h i c nomenclature f o r t h e Holocene epoch,

Geology, v. 3, p. 10.

Hopkinst D. M e I 1979, Landscape and c l ima te of Beringia dur ing l a t e

P l e i s tocene and Holocene t i m e , In: Laughlin, W. S. and Harper, A. B. ,

eds., The F i r s t Americans: Or ig ins , a f f i n i t i e s and adap ta t ions , Gustav

F isher , New York, p. 15-41.

Hopkins, D. M., Nelson, C . H., Per ry , R. B., and ~ l p h a , Tau Rho, 1976,

Physiographic subdiv is ions of the Chirikov Basin, nor thern Bering Sea,

USGS Prof. Paper 759-B.

Howard, J. D. and Nelson, C . H. , 1982, Sedimentary s t r u c t u r e s o n a delta-

in f luenced sha l low s h e l f , Norton Sound, Alaska, Geologie en M i j nbouw, v.

Knebel, H. J. and Creager, J. S., 1973, Yukon River: evidence f o r ex t ens ive

migra t ion dur ing t h e Holocene t r ansg res s ion , Science, v. 179, p. 1230-

1232.

Maanus, Do A., Venkatarathnam, K. , Echols, R. J., and Holmes, M. L., 1970,

Bottom samples and se ismic p r o f i l e s of t h e nor thern Bering Sea, and

a s s o c i a t e d s t u d i e s , U. S. Geol. Survey, Office of Marine Geology F i n a l

Report, Contract No. 14-08-0001-11995, 115 p.

MManu8, D. A * , Ventkatarathnam, K., Hopkins, D. M . , and Nelson, C. H., 1977,

D i s t r i b u t i o n of bottom sediments on t h e c o n t i n e n t a l s h e l f , Northern Bering

Sea, U.S. Geol. Survey P ro fes s iona l Paper 759-C, 31 p.

Nelson, C. H., 1971, Northern Bering Sea, a model f o r depos i t i ona l history of

A r c t i c s h e l f p l ace r s : e c o l o g i c a l impact of p l a c e r development, Proc. F i r s t

In t e rna t . C o d . on Por t and Ocean Eng. Under Arctic Conditions, v. 1, p.

246-2540

Nelson, C. H., 1982, La te Pleistocene-Holocene t r a n s g r e s s i o n i n d e l t a i c and

non-deltaic areas of t he Bering e p i c o n t i n e n t a l s h e l f , In: Nelson, C. H.

and Nio, S. C., eds., The Northeas te rn Bering Shelf : New Pe r spec t ives of

Epicont inenta l Shelf Processes and Deposi t ional Products , Geologie e n

Mijnbouw, v. 61, p. 5-18.

Nelson, C. H., Cacchione, D. A., Drake, D. E., and F ie ld , M . E., 1978, Areas

of a c t i v e l a rge - sca l e sand wave and r i p p l e f i e l d s with scour p o t e n t i a l o n

t h e Norton Basin sea f loo r , In: Environmental Assessment of t h e Alaskan

Cont inenta l She l f , Annual Reports of t h e P r i n c i p a l Inves t iga to r s , U.S.

Dept. o f Commerce, NOAA, OCSEAP, Boulder, CO, 12: 29 1-307.

Nelson, C. H. and Creager, J. S O , 1977, Displacement of Yukon-derived sediment

from Bering Sea t o Chukchi Sea dur ing Holocene t i m e , Geology, v. 5, p.

141-146.

Nelson, C. H., Dupre, W. R., Field, M. E., and Howard, J. D., 1982, V a r i a t i o n

i n sand body types on t h e Eas te rn Bering Sea e p i c o n t i n e n t a l s h e l f ,

Geologie e n M i jnbouw, v. 61, p. 37-48.

Nelson, C. H. and Hopkins, D. M., 1972, Sedimentary processes and d i s t r i b u t i o n

o f gold i n t h e nor thern Bering Sea, USGS prof . paper 689, 27 p.

Nelson, C. H., Rowland, R. W . , Stoker, S O , and Larsen, B. R., 1981, Interplay

of physical and b i o l o g i c a l sedimentary structures of the Bering

epicontinental s h e l f , In: Hood, DO W . and Calder, J. A., eds., The Eastern

Bering Sea Shelf: I t s Oceanography and Resources, v. 2, NOAA-OCSEAP

Juneau Regional Of f i ce , Univ. o f Wash. Press , Sea t t l e , Wash., p. 1265-

1296.

Tagg, A. R. and Greene, H. G., 1973, High-resolution se i smic survey of a

nearshore area, Nome, Alaska, USGS prof. paper 795-A, p. A1-A23.

Figure 1.

Figure 2A.

Figure 2B.

Figure 3.

Figure 4.

F igure 5.

Figure 6 A .

Figure 6B.

Figure 7A.

Figure 713.

Figure 8A.

Figure 8B.

F igure 9A.

Figure 9B.

Figure 10.

F igure Captions

Locat ion map and gene ra l i zed bathymetry of nor thern Bering Sea.

Contour i n t e r v a l i s 10 m.

Trackl ines and d a t a t y p e c o l l e c t e d p r i o r t o 1980. Inc ludes USGS,

NOAA, and Univers i ty of Washington.

Survey lines and sample s t a t i o n s of 1980 USGS c ru i se .

S t a t i o n l o c a t i o n map. Locat ions of p r o f i l e s of f i g u r e 11 shown

by s o l i d l i n e s A-A' and B-8'.

Locat ion of f i l l e d and b u r i e d channels.

Elements of p re - t r ansg res s ive geologic history i n no r theas t e rn

Bering Sea showing l o c a t i o n s of s e a f l o o r and near-surface bedrock

outcrops , g l a c i a l moraines, and a l l u v i a l channels. (For complete

coverage of a l l u v i a l channel d i s t r i b u t i o n s e e figure 4) .

Percent sand i n surface sediment. Contour i n t e r v a l 5%.

Simpl i f ied map of sand-size m a t e r i a l content of s u r f i c i a l

sediment.

Percent g rave l i n s u r f a c e sediment. Contour i n t e r v a l 5%.

Simpl i f ied map of g rave l size m a t e r i a l i n s u r f i c i a l sediment.

Mean g r a i n s i z e for s u r f a c e sediment. Contour i n t e r v a l 0.5 g.

Gravel, sand, and mud con ten t of s u r f i c i a l sediment based on mean

g r a i n size.

Modal g r a i n s i z e f o r s u r f a c e sediment. Contour i n t e r v a l 0.5 g.

Gravel, sand, and mud con ten t of s u r f i c i a l sediment baaed on

modal ana lys i s .

Map of no r theas t e rn Bering s h e l f s u r f i c i a l geology.

Figure I I. Near-surface l a t e P l e i s tocene and Holocene s t r a t i g r a p h y i n Norton

Sound (A-A' ) and Chirikov Basin (B-B'). (See f i g u r e 3 f o r

l o c a t i o n s ) . In p r o f i l e A-A' the d a t e of 1500 yea r s BP i n c o r e C

d a t e s i n f l u x of f reshwater and Yukon River Delta lobe. Xn

p r o f i l e B-B', t h e r eg ion of sand r i d g e s i n northeast ' Chir ikov

Basin extends from King I s l a n d shoa l t o P o r t Clarence.

F igure 12. Locat ion of sand bod ie s on t h e e a s t e r n Bering epiccrntinerrtal

s h e l f .

F igure 13. High-resolution se i smic r e f l e c t i o n p r o f i l e s over f i l l e d a l l u v i a l

channels , c e n t r a l Chirikov Basin.

F igu re 14A. Locat ion map of a c t i v e l a r g e sandwaves o f f P o r t Clarence.

Bathymetric p r o f i l e s of f i g u r e 14B shown by s o l i d l i n e s .

F igure 14B. Bathymetxic p r o f i l e s a c r o s s a r e a of l a r g e sandwaves.

Figure 14C. Mean g r a i n s i z e of s u r f a c e sediment i n a r e a of l a r g e sandwaves.

Tah le 1. o l a r a c t e r i s t i c s of Ilcrinq SllelF Sand Dndit?a

Linea r t i d a l Macrot ida l f unne l- sand r l d q e s s h a p d bay and

e s tua ry .

Shore -pa ra l l ek Outer edge of sub- s h o ~ l s t i d a l f l a t a In i+ b a r r i e r r c s o t i d a 1 r eq ions. i a l m d s l

D a l t a f r o n t Of Zmhore ex t ena iona ( sub - i ce ) of major c h u r n e l s d i n t r l b u t a r lea.

5-35 1-3 4-32 Fine sand

5-10 0.5-1 15 do.

20-30 2-4 5-15 Ftru? t o v e r y f l ne sand In t h a l v c q , g raded sand beds i n overbank mud

Lees ide s h o a l s Lee of i s l a n d s or 25-100 5-25 10-20 Very f i n e s and peninsulas i n t e r - r u p t ing s t r o n g g e o s t r o p h l c hot tam c u r r e n t s .

P a r a l l e l l amina t ion , s u r f a c e r i p p l e f i e l d s , sand waves obse rved

Sam? a s & w e

Trough c rosebedd tnq graded sand beds wi th f l a t l m i n a - t i o n , c r o s s lamina- t i o n l n v e r t i c a l sequence

Enclosed by t i d a l f l a t and s h e l f mud, shore- pe rpend icu la r , v a t y lng Ln s i z e and shape--stmetimes s t a o i d a l .

Enclosed by t i d a l f l a t and a h e l C mad, s h o r e p a r a l l e l , c o n s t s t e n t l l l i t e d size and shape.

Enclosed by g raded avcrbank sand beds i n mud, ahore p e r p e n d i c u l a r , Large-scale t r o u q h c r o s a b e d s i n t h a l r a q sand beds.

Rhythlc f l a t 1-t- Enc lowd b y a h e l f nand and n a t l o n a a l t e r n a t i n g aud, o r i e n t a t i o n p a r a l l e l to w i t h occas t o n a l she 1 f c u r r e n t s no t mhorel l n e , t h i n r i p p l e l a a i n a - widely va ry lnq m h a p and mi=, t t o n n ve ry Cine sand slza w i t h r y t h i c

f l a t l a a l n a t l o n i n t e r r u p t e d by r i p p l e s .

Ancient shore- S h o r e l t n e d e p o s i t s 15-30 3-7 10-15 Pine t o n e d i m s a n d i n t e r - i l t e r n a t i n g r l p p l e E n c l o a e d b y s h e l f n a n d a n d m u d , ltn s h o a l s fo-d d u r i n q st l l l - i n t e r r u p t e d nea r s u r f a c e and t r o u g h c r o e r p r a l l e l t o a n c i e n t s t r m d l i n a a ,

s t and6 of ma l eve l . b y p b b l e l a y s and mud i m l n a t t o n v t t h h lqh ang le f o r e a t s i n t e r r u p t e d t l r a p l s h iqh-anqla f o r e s e t by r i p p l e u rd t r o u g h c r o s a l r i -

beds , b ~ o t u r h a t i o n n a t m n , a t o m pebble and a h e l l COnmOn l a g s , b i o t u r b a t i m Ln l o u r and

off ahore sequences .

Morainal G l a c i a l deposition 5-75 5-25 10-15 Mediurrcoarse sand and Rare. t r ough c r o s s - Encloaed by s h e l f s and and md, f e a t u r e s during l w s t a n t i s of q r ave 1 l a m i n a t t o n anel aCze and u h a p v a r i a b l e , not

s e a l e v e l . shell l a m i n a t i o n s s h o r e p a r a l l e l or p a r p e d i c u l u , c o a r s e and v a r i a b l e g r a i n size.

- 150 j Sparker (USGS/UW, 1967,1969) 450 j Sparker 1 km grid (USGS, 1967) 40 cu. in. Air gun (USGS/NOAA, 1969)

- - - - -. -. - -

60 kj Areer, Uniboom, and 3.5 kHz -..-..-. . . . . . . . . . . . . . . . . . Uniboorn and 3.5 kHz

- 20 0 20 40 60 80

_,_._.-- - - - -.- -

Vlbracore station r

Fig: 6

(Yukon) modern river sandy silt inter- bedded with thin sand layers Holocene

(Chirikov) transgressive inner shelf fine sand

trons-

,S

Pleistocene

Pre - Cambr ian- Cenozoic

Fig. 10

0 S O 0 ' 1000 1500 V,E. 2 1 x 1 1

M e t e r s

BATHY METRIC PROFILES

VERTICAL SCALE Datum is sea level

HORlf ONTAL SCALE

0 5 10 15 20 - (Kilometers) (Meters)

Fig. 1 4 8