Post-Carboniferous Stratigraphy, 

Northeastern Alaska 

By R. L. DETTERMAN, H. N. REISER, W. P. BROSGE,and]. T. DUTRO,JR. 

GEOLOGICAL SURVEY PROFESSIONAL PAPER 886 

Sedirnentary rocks of Permian to 

Quaternary age are named, 

described, and correlated with 

standard stratigraphic sequences 

UNITED STATES GOVERNMENT PRINTING OFFICE, WASHINGTON 1975 
UNITED STATES DEPARTMENT OF THE INTERIOR 

ROGERS C. B. MORTON, Secretary 

GEOLOGICAL SURVEY 

V. E. McKelvey, Director 

Library of Congress Cataloging in Publication Data 

Detterman, Robert L. 

Post-Carboniferous stratigraphy, northeastern Alaska. 

(Geological Survey Professional Paper 886) 

Bibliography: p. 45-46. 

Supt. of Docs. No.: I 19.16:886 

1. Geology-Alaska. I. Detterman, Robert L. II. Series: United States. Geological Survey. Professional Paper 886. 

QE84.N74P67 551.7'6'09798 74-28084 

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

Washington, D.C. 20402 

Stock Number 024-001-02687-2 
CONTENTS 

Page 

Abstract _ _ _ _ _ _ __ _ _ _ _ _ _ _ _ _ _ _ _ _ _ __ _ _ _ _ _ _ _ _ __ _ _ _ _ __ __ _ _ _ _ _ _ __ 1 

Introduction __________ ---------- ____ ---------------- ____ __ 1 

Purpose and scope ----------------------~------------- 1 

Geographic setting ------------------------------------ 1 

Previous work and acknowledgments ------------------ 1 

Geologic setting -------------------------------------- 2 

Stratigraphy _______________________ ----------------- ______ 5 

Sadlerochit Group ------------------------------------ 5 

Echooka Formation________________________________ 8 

Joe Creek Member ---------------------------- 8 

lkiakpaurak Member-------------------------- 10 

Ivishak Formation -------------------------------- 11 

Kavik Member-------------------------------- 11 

Ledge Sandstone Member---------------------- 12 

Fire Creek Siltstone Member ------------------ 13 

Shublik Formation ------------------------------------ 14 

Karen Creek Sandstone________________________________ 16 

Page 

Stratigraphy__:_Continued 

Kingak Shale ---------------------------------------- 18 

Ignek Formation (abandoned) -------------------------- 20 

Okpikruak Formation (geographically restricted) ________ 21 

Kongakut Formation ---------------------------------- 21 

Bathtub Graywacke _ _ _ _ _ _ __ _ ___ _ ___ __ __ __ __ _____ _ _ ___ 25 

Nanushuk Group-------------------------------------- 28 

Tuktu Formation---------------------------------- 29 

Chandler Formation ------------------------------ Colville Group _______________________________________ _ 

Seabee Formation --------------------------------

Prince Creek Formation -------------------------- Schrader Bluff Formation _________________________ _ 

Sagavanirktok Formation _____________________________ _ 

Gubik Formation---------- ___________________________ _ 

31 

32 

32 

34 

35 

37 

39 

List of fossil collections ------------------------------------ 41 

References cited ------------------------------------------ 45 

ILLUSTRATIONS 

FIGURE Page 

1. Index map of Alaska showing location of report area ---------------------------------------------------------------- 2 

2. Map of northeastern Alaska showing location of type sections and reference sections of formations described in this 

report-------------------------------------------------------------------------------------------------------- 3 

3. Generalized geologic map of northeastern Alaska-------------------------------------------------------------------- 4 

4. Correlation diagram showing post-Carboniferous stratigraphic sequence in northeastern Alaska ------------------------ 6 

5-14. Stratigraphic columns: 

5. Type sections, Echooka and Ivishak Formations -------------------------------------------------------------------- 9 

6. Reference section, Shublik Formation; type section, Karen Creek Sandstone ------------------------------------------ 15 

7. Reference sections, Kingak Shale ---------------------------------------------------------------------------------- 18 

8. Type and reference sections, Kongakut Formation ----------------------------------.,..------------------------------- 24 

9. Type and reference sections, Bathtub Graywacke-------------------------------------------------------------------- 28 

10. Reference sections, Tuktu and Chandler Formations ---------------------------------------------------------------- 30 

11.· Measured sections, Seabee and Prince Creek Formations ------------------------------------------------------------ 33 

12. Generalized sections, Schrader Bluff Formation ____________________________________________________ ------------------ 36 

13. Type sections, members of Sagavanirktok Formation ---------------------------------------------------------------- 38 

14. Measured section, Gubik Formation -------------------------------------------------------------------------------- 41 

TABLES 

Page 

TABLE 1. Foraminifera distribution chart for the reference section of the Kingak Shale, Ignek Valley _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ 22 

2. Foraminifera distribution chart for Kongakut Formation------------------------------------------------------------ 26 

3. Foraminifera distribution chart for the Nuwok Member of the Sagavanirktok Formation------------------------------ 40 

III 
POST -CARBONIFEROUS STRATIGRAPHY, 

NORTHEASTERN ALASKA 

By R. L. DETTERMAN, H. N. REISER, W. P. BROSGE, and J. T. DuTRO, JR. 

ABSTRACT 

Post-Carboniferous sedimentary rocks exposed in northeastern 

Alaska constitute an almost continuous sequence representing all 

systems from Permian to Quaternary. Because the rocks are well 

exposed, only slightly deformed, and very fossiliferous, they comprise 

an important biostratigraphic reference section. Regional and local 

unconformities are present, and minor hiatuses can be identified in 

the stratigraphic record. The rocks are divided into 3 groups, 14 

formations, and 16 members; some are newly named, others revised. 

The Ignek Formation is abandoned, and the Okpikruak Formation is 

excluded from the stratigraphic sequence in northeastern Alaska. 

The Sadlerochit Formation is raised to group rank and divided into 

the Echooka (Permian) and Ivishak (Lower Triassic) Formations. The 

Echooka includes the Joe Creek and Ikiakpaurak Members (both 

new), and the Ivishak is divided into the Kavik, Ledge Sandstone, and 

Fire Creek Siltstone Members (all new). The Shublik Formation 

(Middle and Upper Triassic) is informally divided into siltstone, 

limestone and dolomite, and clay shale members; it is separated from 

the Kingak Shale (Jurrassic) by the (Upper Triassic) Karen Creek 

Sandstone (new). Lower Cretaceous (Neocomian) rocks are mapped as 

the Kongakut Formation (new). The Kongakut includes the clay 

shale, Kemik Sandstone, pebble shale, and siltstone members. The 

Bathtub Graywacke (new) may be in part equivalent to the Fortress 

Mountain Formation. The Nanushuk and Colville Groups are extended into northeastern Alaska to replace the Ignek Formation. The 

Nanushuk includes the Tuktu and Chandler Formations, and the 

Colville is subdivided into its subordinate Seabee, Prince Creek, and 

Schrader Bluff Formations. All Tertiary rocks are included in the 

redefined Sagavanirktok Formation, which is divided into the Sagwon, Franklin Bluffs, and Nuwok Members (new). The Gubik Formation (Pleistocene) is extended into northeastern Alaska. 

Post-Carboniferous rocks are mainly sandstone, siltstone, shale, 

and conglomerate, and include both marine and terrestrial deposits 

with a cumulative thickness of about 8,500 m (28,000 ft). Marine 

transgressions and regressions are identified in the stratigraphic 

sequence, and a major shift from a northern source area for the older 

rocks to a southern source for the younger rocks is demonstrated. This 

change took place during the Early Cretaceous, and the Bathtub 

Graywacke is the first unit to clearly reflect a southerly source area. 

Post-Carboniferous orogeny in northeastern Alaska started during 

the Aptian Stage of the Lower Cretaceous. Pre-Aptian sandstones are 

mature, clean, quartz arenites, whereas most post-Aptian sandstones 

are lithic arenites or graywackes. 

INTRODUCTION 

PURPOSE AND SCOPE 

This summary of post-Carboniferous stratigraphy in 

northeastern Alaska specifically encompasses all or part 

of five 1:250,000-scale quadrangles: Mount Michelson, 

Demarcation Point, Barter Island, the north edge of the 

Table Mountain, and part of the Sagavanirktok (fig. 1). 

The objective of the geologic mapping and detailed 

stratigraphic and paleontologic studies during 1969-72 

was to investigate surface outcrops of rocks that were 

penetrated in drilling the discovery well in the Prudhoe 

Bay oil field in 1968. The fieldwork was supported by 

helicopter from a base camp at the G. William Holmes 

Research Station on Lake Peters (fig. 2). 

GEOGRAPHIC SETTING 

The post-Carboniferous rocks are exposed along the 

north flank of the Brooks Range and along the flanks of 

the Third Range, the Shublik Mountains, and the Sadlerochit Mountains (Reiser and others, 1971). Permian 

and lower Mesozoic strata are present in several infolds 

within the Brooks Range, mainly near the upper 

Echooka, Canning, Aichilik, and Kongakut Rivers. Upper Mesozoic rocks underlie the foothills north of the 

Brooks Range, and the Tertiary sequence is best exposed along streams on the Arctic Coastal Plain (fig. 3). 

Bedrock exposures are generally good in mountainous areas and almost uniformly poor in the foothills and 

the coastal plain, except where actively eroded by 

streams. The area is tundra covered, with few trees or 

brush to obscure bedrock. The highest peaks in the 

Brooks Range are within the report area, and the topography there has been strongly modified by glaciation. 

Many small valley glaciers and perennial snow fields 

occur within the range, and all the major rivers flow in 

glacially carved, broad, steep-walled valleys. Deposits 

of former glacial advances obscure bedrock in many 

places in the foothills and on the coastal plains. 

PREVIOUS WORK AND ACKNOWLEDGMENTS 

Post-Carboniferous rocks have been known in northeastern Alaska since the pioneer work of Leffingwell 

(1919, p. 113-130). Maddren (1912) briefly examined 

some of the rocks along the Canada-Alaska boundary 

about the same time as Leffingwell but did little detailed mapping of post-Carboniferous strata. During 

194 7-53 and in 1968 the U.S. Geological Survey conducted reconnaissance geologic surveys of small parts of 

the area. Reports by Gryc and Mangus (194 7), Whittington and Sable (1948), Morris (1953), Keller, Morris, 

1 
2 POST-CARBONIFEROUS STRATIGRAPHY, NORTHEASTERN ALASKA 

EXPLANATION 

1. Barter Island quadrangle 

2. Sagavanirktok quadrangle 

3. Mount Michelson quadrangle 

4. Demarcation Point quadrangle 

5. Table Mountain quadrangle 

0 100 200 300 MILES I I I I 11 I 

0 100 200 300 KILOMETRES 

FIGURE 1.-Index map of Alaska showing location of report area. 

and Detterman (1961), Brosge, Dutra, Mangus, and 

Reiser (1962), and Reiser and Tailleur (1969) summarize the results of these investigations. Small areas 

were mapped in detail by Sable (1965) and Reed (1968) 

for doctoral theses. 

The discovery of oil at Prudhoe Bay in 1968 precipitated the recent detailed geologic mapping and stratigraphic studies by the Geological Survey and many 

private companies. Some preliminary results have been 

published by Brosge and Tailleur (1969, 1970), Detterman (1970a, b, 1971, 1973), Reiser (1970), Reiser, Dutro, Brosge, Armstrong, and Detterman (1970), Reiser, 

Brosge, Dutro, and Detterman (1971), and Tourtelot 

and Tailleur (1971). The present report, however, is the 

first to make major changes and additions to the stratigraphic nomenclature of the post-Carboniferous rocks of 

northeastern Alaska. This is due largely to the use of 

the helicopter, which has facilitated access to all parts of 

the area, making it possible to designate new and better 

reference sections as well as to locate new stratigraphic 

units. 

Grateful acknowledgment is made to the many 

geologists in private industry who were working in the 

area at the time of this investigation. They are too 

numerous to list here, but several must be acknowledged; these include M.D. Mangus of Calderwood and 

Mangus, C. G. Mull of Humble Oil and Refining 

Company, and S. L. Blanton, Jr., of Sun Oil Company. 

Also, we gratefully acknowledge the work of R. W. 

Imlay, D. L. Jones, N.J. Silberling, W. 0. Addicott, and 

H. R. Bergquist of the U.S. Geological Survey, who 

identified many collections of fossils obtained during 

the geologic mapping. The project was also greatly 

facilitated by logistic support given by the .Arctic 

Research Laboratory, Point Barrow, Alaska. 

GEOLOGIC SETTING 

Northeastern Alaska contains diverse sedimentary, 

metamorphic, and igneous rocks that range in age from 

Precambrian to Quaternary. All systems of the 

Paleozoic and Mesozoic as well as most of the Tertiary 
149° 147° 144° ,.---

ARCTIC 

oce~N 

70° 

69° 

0 20 40 60 MILES 

0 20 40 60 80 KILOMETRES 

FIGURE 2.-Map of northeastern Alaska showing location of type and reference sections. Numerals refer to stratigraphic columns on figures 4-13. 

141° 

0' 

~ 

"\:-JI 

'"'"' .J.I :\ z, 

=n(j 

rn\> 0 z

~~ >I> 

j 

5 I 

~I 

- ' I 

I 

1 

z 

1-3 

=::o 

0 

t::l 

c 

() 

1-3 

0 

z 

Clj 
149° ,.-- 147° 144° 

ARcr,c 

oce-4N 

0 20 40 60 MILES 

~ 

~ 

Upper Cretaceous to 

Quaternary rocks 

0 20 40 60 80 KILOMETRES 

EXPLANATION 

[2] 

Jurassic and 

Lower Cretaceous rocks 

~ Permian and 

Triassic rocks 

FIGURE 3.-Generalized geologic map of northeastern Alaska. 

.D 

Carboniferous 

and older rocks 

141° .p... 

~ r:n 

~ C1 

~ t:C 

0 

z 

~ ::a 

0 

c:: 

r:n 

~ ~ 

~ ~ ~to<: 

z 

0 

~ :X:: 

tr:l 

> 

~ ::a 

z 

> 

~ r:n 

~ 

> 
STRATIGRAPHY 5 

are represented. Carboniferous and older rocks underlie 

all the mountain ranges; the post-Carboniferous rocks 

flank the mountains and underlie the foothills and coastal plain. Many tectonic episodes are represented by 

unconformities between rock units, and the provenance 

of the sediments has changed several times. 

The post-Carboniferous sequence (fig. 4) is mainly 

composed of marine clastic rocks that unconformably 

overlie the older strata. Nonmarine clastic rocks of Late 

Cretaceous and early Tertiary age are present locally in 

the coastal plain, where they overlie the marine strata. 

Unconsolidated Quaternary surficial deposits mantle 

all of the units, generally with strong angularity. The 

post-Carboniferous rocks at the surface are moderately 

to strongly warped into northeast-trending folds that 

generally parallel the front of the Brooks Range. The 

intensity of folding decreases slightly toward the north, 

but orogenic activity has continued along the Arctic 

Coast, where Quaternary deposits have been uplifted 

and slightly folded. Faults cut all the rocks in many 

places. 

STRATIGRAPHY 

Post-Carboniferous rocks form a complex stratigraphic sequence that is widely distributed throughout 

the Mt. Michelson and Demarcation Point quadrangles 

(figs. 3 and 4). Most of the names given to rock units by 

Leffingwell (1919) are retained, but many are modified 

' or revised, and one,· lgnek Formation, is abandoned. 

Some new formations are recognized, mainly in areas 

that Leffingwell was unable to reach when he did his 

geologic mapping between 1906 and 1914. 

The Sadlerochit Formation is here raised to group 

status, and the former Echooka and Ivishak Members 

become formations; both are in turn divided into new 

members. The Echooka Formation is divided into the 

Joe Creek and lkiakpaurak Members; the Kavik, Ledge 

Sandstone, and Fire Creek Siltstone Members are the 

new units of the Ivishak Formation. The Shublik Formation and Kingak Shale are retained much as Leffingwell defined them (1919, p. 115-120), but new and 

better reference sections are provided and a new 

stratigraphic unit, the Karen Creek Sandstone, is established to include strata between the two formations. 

Leffingwell established the lgnek Formation (1919, p. 

120-125) for a sequence of rocks exposed in lgnek Valley 

and along the lower part of Ignek Creek. He considered 

these rocks to be of Jurassic(?) age. Subsequent investigations (Gryc and Mangus, 194 7) revealed that Early 

Cretaceous fossils occur in part of these beds and, later 

still (Keller and others, 1961), that part of the sequence 

was of Late Cretaceous age. Present usage is to place 

strata above the Kingak Shale and below Tertiary beds 

in the lgnek Formation. As this is obviously impractical 

and has led to numerous discrepancies, we recommend 

that the term lgnek Formation be abandoned. Most of 

the rocks included in the lgnek are lithologic and age 

equivalents of formations and members of parts of the 

Nanushuk and Colville Groups, names that are widely 

used in northern Alaska. We propose to extend this 

usage into northeastern Alaska. Additionally, there are 

Early Cretaceous rocks exposed in the Mt. Michelson 

and Demarcation Point quadrangles that do not 

lithologically fit any present nomenclature. For these 

rocks we here establish the Kongakut Formation and 

Bathtub Graywacke. The Kongakut Formation is divided into clay shale, Kemik Sandstone, pebble shale, 

and siltstone members. 

All Tertiary strata in northern Alaska are currently 

placed in the Sagavanirktok Formation (Gryc and 

others, 1951, p. 167). The type section at Franklin 

Bluffs, described originally in only general terms, is 

here described in considerable detail as the Franklin 

Bluffs Member of the Sagavanirktok .. Leffingwell(l919, 

p. 129-130) described poorly consolidated late Tertiary 

beds from Carter Creek near the Arctic coast. He did not 

name this unit, but the term N uwok has been used 

informally for many years. We formalize this name as 

the Nuwok Member of the Sagavanirktok Formation 

and describe the type section. The lowest part of the 

Sagavanirktok is named and described as the Sagwon 

Member. The youngest bedded rocks exposed in northeastern Alaska are part of the Gubik Formation of 

Pleistocene age. 

SADLEROCHIT GROUP 

The Sadlerochit Formation was named by Leffingwell 

(1919, p. 113), who used both terms ((formation" and 

((sandstone" to designate this unit. He considered these 

strata to be Pennsylvanian in age. Smith (1939, p. 32) 

reported, however, that by the late 1930's G. H. Girty 

had become convinced that the fauna of the Sadlerochit 

should be regarded as Permian in age. Subsequent work 

by the U.S. Geological Survey (Keller and others, 1961) 

divided this formation into two lithologic units, the. 

Echooka and Ivishak Members, which were, respectively, of Late Permian and Early Triassic age. Additional 

detailed investigations of the Sadlerochit by the U.S. 

Geological Survey between 1969 and 1971 indicated 

that further subdivision of the unit was needed. As the 

name Sadlerochit is well established for this sequence of 

beds, we raise it here to group status, and raise the 

Echooka and Ivishak Members to formational status. 

This change in rank is essential to permit additional 

subdivision into members that will facilitate description and correlation between different localities, and 

between surface and subsurface sections. 

The Sadlerochit Group is a heterogeneous assemblage of rocks that includes orthoquartzite, chert, 
E 

Q) 

~ (/) 

Series 

and 

Stage 

Central area 

Gryc and others (1956) . . 

Dett~rman, Sicked, and Gryc (1963) Leff1ngwell (1919) Keller, Morns, 

Patton and Tailleur (1964) and Detterman 

Imlay and Detterman (1973) (1961) 

Northeastern area 

This report 

Characteristic 

megafossils in 

northeastern Alaska 

> r-S-url-i-ci-al_d_e-~--im~----------~S-urt~ic-i-al_d_e-po-s-im-.-u-p-la_n_d_g-ra_v_e-1 --------~ 

~ Pediment gravel Gubik Formation (Pleistocene) ~ ~-r------------------tT-r-r.-,-.-~r-rlll-.-.-r-r-r.-,-o-.-r-r-rr------------,_ ____________ +----.------------------~------~----------~.A~rc=t~ic~a~c~a~rt~e~ri~an~a~--------4 

~ Pliocene Chlamya nuwokensis :§ Nuwok Member 

0 

> 

~ i= 

a: 

w 

1-

Miocene 

Oligocene 

Sandstone 

Eocene 

Paleocene 

Sagavanirktok 

Formation 

..>.<: ? ?·-----l .Sc: 

~~ 

*§ 

~u. 1------? ?'-------1 

Franklin Bluffs Member 

Sagwon Member 

1---+-----1 Maestncht1an . . II I I I I I I I I I I I I I I I I I I I I I Ill I I I ?DJI]? 

? ? 

Campanian Bluff 

Metasequoia occidentalis 

Trapa microphylla 

(/) 

::::1 

0 

w 

(.) 

;:: 

w 

a: 

(.) 

0 

Schrader 

~a. Formation Santonian lgnek Formation, ~ e 

& upper part 8 (.!) a. 

::::> Coniacian 

Turonian ? ° [OJ ?·~~~-..-,-,,-rTirTIIT~Il-r~fll 

Cenomanian ? ° ?llj_~_L~_L~~_L~_L~LL~~~~ o 

Albian 

Tuktu Formation 

Torok Formation 

·~~~~~ro-r-ro-11? 

... L~-------A-p-t-ia_n ______ -t,-rnrr I I I I I I? I I I I I I 

~. 1 1 1 I I I .... · o _3 I 

c: 

as 

Barremian 

Hauterivian 

·e L.._ ____________ -1 Okpikruak Formation 

lgnek Formation, 

lower part 

·?I I I I '?· 

..>.<: 

::I .ca. 

U):::l 

2e as(!) 

z 

Chandler Formation 

Tuktu Formation 

~---L----------------------------------~ 

Bathtub Graywacke 

11-ullll [rill ITII 1111-1111 

-c: 

::I 0 ..::.:::-=::; 

as as cne 

Siltstone member 

Pebble shale member 

Paragastroplites spiekeri 

Aucellina (?) sp. 

j I Valanginian ~ ~ Kemik Sandstone Member Simbirsk!tes spo . Formation Astarta tgnekensts 

c: ... o, 

:li::L 

Kemik Buchia sublaevis Berriasian Sandstone Clay shale member Buchia okensis 

L___..I __ .L....-L---------------'---------(---------------------? 1 1 1 1 ? 1 1 1 1 ? 1 Membe? Buchia subokensis 

en 

'"0 

0 

UJ 

<-3 

0 

> :::0 

to 

0 

z 

:;j 

t%j 

:::0 

0 

e 

UJ 

UJ 

<-3 

=:o 

~ 

~ '"0 

:I: 

~>-< 

z 

0 

~ :I: 

t%j 

> UJ 

<-3 

t%j 

=:o 

z 

> t"" 

> UJ 

~ 

> 

8 POST-CA~BONIFEROUS STRATIGRAPHY, NORTHEASTERN ALASKA 

limestone, sandstone, siltstone, and shale. The nomenclature established by Keller and others (1961, p. 178) 

was an attempt to provide greater continuity for the 

formation. A detailed study of many more sections of the 

Sadlerochit in recent years permits further revision 

that will show even greater lithologic continuity. We 

here propose two new units within the Echooka Formation; they are in ascending stratigraphic order the Joe 

Creek Member and the Ikiakpaurak Member. The 

Ivishak Formation is also divided into the Kavik, Ledge 

Sandstone, and Fire Creek Siltstone Members. The new 

members are described individually and type sections 

are established. 

When Leffingwell named the Sadlerochit Formation 

(1919, p. 113), he indicated it was typically exposed 

along the south flank of the Sadlerochit Mountains. The 

mountains are 64 km ( 40 mi) long, and there are some 

changes in lithology and thickness over that distance. 

We selected a type locality, here designated as the south 

slope of the Sadlerochit Mountains at a point immediately north of the mesa near the east end of Ignek 

Valley. At that locality the Sadlerochit Group is about 

200m (650ft) thick. 

ECHOOKA FORMATION 

The Echooka was designated the lower member of the 

Sadlerochit Formation by Keller and others (1961, p. 

178) and the type section was designated on Kemik 

Creek between latitudes 69°22' N., and 69°23' N. The 

beds exposed there contain elements of both the Joe 

Creek and Ikiakpaurak Members; consequently, this 

remains the type section for the entire formation, but 

new and more completely exposed type sections are established for each new member. The lower 43 m (140ft) 

of the Kemik Creek section is equivalent to the Joe 

Creek Member, and the remainder is now correlated 

with the Ikiakpaurak Member. 

JOE CREEK MEMBER 

Name and distribution. -A sequence of calcareous 

siltstone, chert, and limestone is here named the Joe 

Creek Member for exposures near Joe Creek, a tributary of the Firth River in the northern part of the Table 

Mountain quadrangle. The type section, exposed along 

the south slope of the mountains north of the creek, 18.5 

km (11.5 mi) N. 68° W. from the point where Joe Creek 

crosses the Canada-United States boundary, lat 

68°59'30" N., long 141 °26' W. (fig. 2, loc. 5). The 

member is also well exposed in the mountains along the 

southern edge of the Demarcation Point quadrangle. 

Reconnaissance mapping south of the type area indicates that the member is present in the headwaters of 

the Coleen River, where a thick and well-exposed section was briefly investigated. The member is probably 

exposed also throughout the northern and eastern parts 

of the Table Mountain quadrangle, and thin interbeds of 

the member are present in many sections of the formation along the north front of the Brooks Range. 

Thickness and stratigraphic relation.-The type 

section of the Joe Creek Member is 113m (372ft) thick 

(fig. 5). A slightly thicker but less well-exposed section 

is present on the upper Kongakut River 64 km (40 mi) to 

the west, and the section is probably somewhat thicker 

to the south. The section thins rapidly toward the 

northwest, where it is interbedded with the lkiakpaurak Member, and is missing in most of the northeastern exposures of the Echooka Formation. 

The type section of the Joe Creek member has three 

parts. The bottom unit is poorly exposed, predominantly 

dusky-yellow limy mudstone and calcareous siltstone, 

about 60 m (200 ft) thick. Overlying this is about 27 m 

(90 ft) of chert and siliceous siltstone. The remainder of 

the section is calcarenite and bioclastic limestone. 

The fine-grained rocks in the lower part of the 

member are transgressive onto the underlying Wahoo 

Limestone of the Lisburne Group. The actual contact is 

not exposed in any of the sections investigated, but beds 

within a few feet of the contact indicate no angular 

discordance, and the contact is considered to be a disconformity. The Ikiakpaurak Member overlies all sections 

of the Joe Creek Member in the area investigated. At 

the type section these overlying beds are about 27m (90 

ft) thick. The contact is considered gradational and 

conformable. 

Lithology.-The lower part of the Joe Creek 

Member is primarily a thin-bedded calcareous siltstone 

and limy mudstone that is 15 to 30 percent detrital 

quartz. Rounded detrital calcite grains are present in 

about the same quantity. Euhedral dolomite is a minor 

but distinctive part of the rock that suggests partial 

dolomitization after burial. The matrix, mainly clay, 

forms 20 to 30 percent of the rock. Grain size ranges 

from 0.02 to 0.05 mm. 

The siltstone and limy mudstone in the lower part of 

the member are poorly indurated and do not form good 

exposures, but their dusky-yellow to moderate-yellowbrown color makes than a readily mappable unit. Calcarenites interbedded with the siltstone and limy 

mudstone are tan. The entire lower unit is formed of 

thin beds, generally about 1 em (% in. or less) thick. 

The medium to massively bedded cherts of the middle 

unit of the member are probably all of secondary origin. 

They are subvitreous, gray to bluish gray to greenish 

gray and are composed of both microgranular and 

spherulitic chalcedonic quartz. The spherulitic quartz is 

formed mainly in sponge spicules and radiolarian tests. 

··-·The limestones in the upper part of the member are 

clastic rocks. Most are probably quartz calcarenites, 
STRATIGRAPHY 9 

.:.! § 1 

:5 ~ Fire Creek 

2 

Tributary of 

March Creek 

3 

Kavik River 

4 

Tributary of 

lkiakpaurak 

Creek 

5 

Tributary of 

Joe Creek .Ee 

(/)~ 

LITHOLOGIC SYMBOLS 

Sandstone and 

conglomeratic 

sandstone 

Siltstone 

Claystone 

Shale 

Quartzite and 

quartzitic 

siltstone 

Limy mudstone 

Limestone 

concretions 

Pebble shale 

Lower Cretaceous 

*I 

*2 

c 

0 

~ 

Conglomerate 

Clay ironstone 

nodules METRES FEET 

90 300 *3 

E 

0 

LL. 

co 

.:.! 

Pebble shale 

Limestone and 

sandy limestone 

Bedded ~ chert 

Siliceous 

cement 

Phosphate 

nodules 

Covered 

interval 

*I Fossil collection 

See sectwn entitled, "List of Fossil 

Collections" for description 

\ 

\ 

\ 

\ 

\ 

\ 

0 

0 

.r:. 

u 

w 

*4 

*5 

FIGURE 5.-Type sections for members of the Echooka and Ivishak Formation, Sadlerochit Group. 

with 10 to 30 percent detrital quartz. The quartz grains 

are well rounded and generally less than 1 mm in 

diameter. A few of the beds are bioclastic limestone or 

microcoquinite, almost entirely formed of rounded 

fragments of brachiopods, bryozoans, corals, gastropods, and Foraminifera. Some of the limestone has 

been partly dolomitized, but the euhedral dolomite generally forms no more than 5 to 10 percent of the rock. 

Glauconite is a common constituent of the calcarenites. 

Several thin sections of these limestones contain an 

opaque material believed to be a petroleum residue 

within visible pore space in the rock. Bedding within the 

upper part of the member is mainly thin to medium 

and irregular. 

Age.-The limestone and calcarenite in the upper 

part of the member are abundantly fossiliferous; some 

beds are a brachiopod coquinite. The lower part contains 

scattered fossils, and the chert beds contain little but 

sponge spicules and radiolarian tests. The brachiopods 

were identified by Dutro, who considers the fauna to be 
10 POST-CARBONIFEROUS STRATIGRAPHY, NORTHEASTERN ALASKA 

correlative with faunal zones Ea to G of Bamber and 

Waterhouse (1971) in the adjoining Yukon Territory. 

The age of these zones range from Wolfcampian (early 

Sakmarian) to Guadalupian (early Kazanian). The Joe 

Creek Member contains the oldest fossils yet discovered 

in the Echooka Formation of northeastern Alaska. 

The Early Permian (Wolfcamp) age is based on collections from the upper Kongakut River and one from 

Flood Creek, all within the lower part, that are correlated with faunal zone Ea. The main elements of this 

collection are Attenuatella sp. and Chonetes sp. Four 

collections, including three from the type section, are 

correlated with faunal zone F of Bamber and 

Waterhouse (1971, p. 164-182) and thus are correlated 

with parts of the Leonardian and early Guadalupian 

(Artinskian and Ufimian) Stages of the late Early Permian and early Late Permian. The collections from the 

type section (fig. 5) are all from the limestone and calcarenite overlying the chert beds. Diagnostic 

brachiopods include Anidanthus sp., Waagenoconcha 

sp., Septospirifer sp., Derbyia sp., Yakovlevia sp., Horridonia sp., Spiriferella sp., and Kochiproductus sp. 

Faunal zone G is represented by one collection from 

near the top of the member on the upper Kongakut 

River, but is commonly found at the base of the member 

along the north flank of the Brooks Range. Most of the 

zone G collections from the north side of the range are 

from the basal part of the overlying Ikiakpaurak 

Member, but some probably represent thin interbeds of 

the Joe Creek Member. The main elements of this 

Guadalupian (Kazanian) fauna 'include Arctitreta sp., 

Kuvelousia sp., Horridonia sp:, Punctospirifer sp., and 

N eospirifer sp. 

In addition to the brachiopod fauna the Joe Creek 

Member also contains abundant bryozoans and corals, 

and, less commonly, trilobites and pelecypods. The trace 

fossil Zoophycos is found throughout the Echooka Formation. Zoophycos is long ranging but in northern 

Alaska is known only from the Echooka Formation, and 

is considered a diagnostic fossil for that stratigraphic 

unit. Microfossils have not been identified in the Joe 

Creek Member. 

IKIAKPAURAK MEMBER 

Name and distribution.-The name Ikiakpaurak 

Member is here applied to the orthoquartzite, quartzitic 

sandstone, and siltstone that form the main part of the 

Echooka Formation along the north side of the eastern 

Brooks Range. 

The member is well exposed at many localities in the 

eastern Brooks Range. The type locality is on a tributary of Cache Creek, 8.5 km (5.25 mi) N. 45° E. of the 

junction of Cache Creek and the Canning River (fig. 2, 

loc. 4), lat 69°27' 45" N., long 145°53'30" W., in Ikiakpaurak Valley on the south flank of the Shublik Mountains. Here the member is 88 m (290ft) thick, but this 

includes two thin interbeds of the Joe Creek Member 

(fig. 5). The member is exposed at numerous localities 

within the range and also overlies the Joe Creek 

Member at Joe Creek. 

Thickness and stratigraphic relations.-The Ikiakpaurak Member is 85 m (280ft) thick at the type locality, excluding the two thiri interbeds of the Joe Creek. 

Most measured sections of the member range from 6l to 

107 m (200 to 350ft). The unit thins persistently and 

rapidly to the north. About 30 to 40 m (100 to 130ft) is 

exposed on the south side of the Sadlerochit Mountains; 

only about 11 m (35 ft) is present on the north side, and 

the member is missing in parts of the subsurface along 

the north coast. The apparent northward thinning of the 

member probably is due primarily to nondeposition before the time when the northward-transgressing sea 

.covered the northern part of the area. The contact between the Ikiakpaurak Member and the overlying Kavik 

Member of the Ivishak Formation is conformable to 

disconformable in most exposures but is locally a disconformity, particularly north of the type locality. The contact of the type Ikiakpaurak with the underlying Joe 

Creek Member is conformable to gradational, with local 

intertonguing of the two members. North of the type 

locality, the Ikiakpaurak lies disconformably on the 

Lisburne Group. 

Lithology.-The Ikiakpaurak Member consists 

mainly of dark highly quartzose sandstone and siltstone 

with minor interbeds of silty shale. Locally, in the Sadlerochit and Shublik Mountains, well-defined basal 

channel conglomerates are present. The pebble- to 

cobble-sized clasts in the channel conglomerate are all 

well rounded, about 95 percent black chert derived from 

the underlying cherty limestone of the Lisburne Group. 

The sandstones are mainly fine to very fine grained 

mature quartz arenites. The subround to subangular 

grains are commonly cemented by silica that has formed 

overgrowths on the original grains so that they are 

tightly interlocking. Thus, the rock could be termed an 

orthoquartzite. Calcite is less commonly the cementing 

material. Generally the rocks with calcite cement also 

contain about 10 percent of detrital glauconite and 

other impurities and should be termed glauconitic 

quartz wacke (Williams and others, 1958). The 

glauconitic beds are most abundant in the basal part of 

the member. Chert grains in some of the basal 

sandstones probably were derived from the basal chert 

channel conglomerate. 

The siltstone and silty shale are essentially finegrained versions of the quartz arenites· in a siliceous 

clay matrix. Silica is commonly the cementing material, 

although authigenic calcite is present in a few beds. 

Age.-Two well-defined faunal zones are found in 
STRATIGRAPHY 11 

the lkiakpaurak Member; both are early Late Permian 

in age and are equated with the late Guadalupian 

(Kazanian) Stage. The lower fauna is mainly from the 

basal21 m (70ft) of the member and is correlative with 

the uppermost zone of the Joe Creek Member. A few of 

the main elements of the brachiopod fauna include 

Kuuelousia sp., Yakouleuia sp., Waagenoconcha sp., 

Spiriferella sp., and Neospirifer sp. The upper zone is 

much less prolific than the lower and contains mainly 

Martinia sp., Paraconularia sp., Kochiproductus sp., 

and Permophricadothyris sp. 

The lower zone of the lkiakpaurak Member and the 

upper zone of the Joe Creek Member are approximately 

equivalent parts of an arctic Permian fauna that can be 

correlated with similar assemblages from arctic Canada, Greenland, Spitzbergen, and Novaya Zemlya. The 

lkiakpaurak contains no fossils older than early Late 

Permian, and :as the member rests directly on the Lisburne Group in many places, this indicates that the 

Permian rocks were deposited by progressive onlap of a 

northward-transgressive sea. 

A few microfossils were obtained from samples 46 to 

53 m (150 to 175ft) above the base of the type locality. 

These fossils, identified by H. R. Bergquist, include 

Spiroplectamina aff. S. clauata Cushman and Waters, 

Frandicularia woodwardi Howchin, Ammodiscus 

bradynus Spandel, and A. nitidus Parr. According to 

Bergquist (written commun., 1972), these fossils indicate a Permian age, but a precise zonation within the 

Permian cannot be made. 

IVISHAK FORMATION 

The Ivishak was designated the upper member of the 

Sadlerochit Formation by Keller and others (1961, p. 

178), and the type locality was established along the 

east side of Flood Creek between lat 69°02'40" N. and 

69°03' 20" N. The beds exposed on Floor Creek are not 

entirely characteristic of the formation as exposed over 

most of northeastern Alaska, but parts of the recessive 

Kavik, Ledge Sandstone, and Fire Creek Siltstone 

Members are present there, and Flood Creek is retained 

as the type locality for the formation. New type sections 

are established for each of the new members. 

KAVIK MEMBER 

Name and distribution.-The name Kavik Member 

is here applied to a recessive-weathering unit of silty 

shale and siltstone overlying the resistant quartzose 

lkiakpaurak Member of the Echooka Formation and 

underlying the massive Ledge Sandstone Member of the 

Ivishak Formation. The Kavik Member is a persistent 

saddle-forming unit in nearly all exposures of the Sadlerochit Group in northeastern Alaska. Good exposures 

of the member are rare and generally can be found only 

where the beds are cut by small actively eroding 

streams. One such locality along the Kavik River is here 

designated the type locality; the member is exposed on 

both flanks of a small anticline between lat 69°17' N. 

and 69°18' N., long 146°52' W. (fig. 2, loc. 3). 

Thickness and stratigraphic relations.-The Kavik 

Member is 85 m (278ft) thick at the type locality. This is 

one of the thinner sections of the member; it ranges from 

about 37 m (120 ft) on the Clarence River (eastern Demarcation Point quadrangle) to 213m (700ft) on Eagle 

Creek (central Mt. Michelson quadrangle). The change 

in thickness is rapid and nondirectional. A section on 

Pogopuk Creek, 8 km (5 mi) west of the type locality, is 

nearly twice as thick as at the type locality. These rapid 

changes are apparently related to the amount and type 

of sediments supplied and the depositional environment 

that existed when these beds were laid down. 

The contact with the underlying lkiakpaurak 

Member of the Echooka Formation is generally not well 

exposed owing to the incompetent nature of the basal 

beds of the Kavik Member. Strata exposed within a few 

feet of the contact indicate no apparent angular discordance, and the contact is believed to be generally disconformable. However, at a few localities, notably between 

the J ago River and Lake Schrader, there is a suggestion 

of a slight angular unconformity. The unconformity is 

present, also, in the Sadlerochit Mountains and at 

Prudhoe Bay, where the member lies directly on the 

Lisburne Group (Fackler and others, 1971). 

Lithology.-The Kavik Member consists of thinbedded, laminated, silty shale and siltstone. A few thin, 

very fine grained, argillaceous sandstone beds occur 

locally within the member. The laminae are best developed and more distinctive in the southern part of the 

outcrop area. They are seen in thin section as bands of 

fairly clean detrital quartz grains alternating with 

darker bands with a high content of sericitic clay. Organic material is commonly concentrated in the clayrich bands, adding to the overall dark color. Quartz 

forms about 30 to 40 percent of the rock, generally in 

well-rounded grains about 0.02 to 0.03 mm in diameter. 

A few grains of garnet and zircon are present, but the 

main constituent is sericitic clay. The clay locally contains some fairly large grains of secondary authigenic 

calcite. Pyrite cubes, some of which are altered to limonite, are common in these rocks. 

The few interbedded sandstones are mainly very fine 

grained quartz arenites with a clay-rich matrix. Most 

are thin bedded and grade into siltstone. 

Age.-The Kavik Member contains an ammonite 

and pelecypod fauna of Early Triassic age identified by 

N.J. Silber ling of Stanford University; this is the suite 

of rocks labeled nammonite zone" by Keller and others 

(1961, p. 179). According to Silberling, the two diagnostic fossils from the Kavik are Ophiceras commune Spath 

and Claraia stachei Bittner. These indicate a late Gries-
12 POST-CARBONIFEROUS STRATIGRAPHY, NORTHEASTERN ALASKA 

bachian age for at least part of the Kavik Member. Both 

have been found about 15m (50ft) above the base at the 

type locality. Otoceras boreale Spath from slightly older 

Griesbachian beds was reported by Keller, Morris, and 

Detterman (1961, p. 187) from a faulted section on 

Kashivi Creek. 

The presence of these fossils indicates that the base of 

the Triassic System in northeastern Alaska probably 

corresponds to the base of the Kavik Member. Uppermost Permian fossils found in the under lying beds are 

late Guadalupian (Kazanian); this, as well as the 

change in lithology, suggests a short hiatus between the 

Ivishak and Echooka Formations. 

Only a few microfossils have been obtained from beds 

of the Kavik Member, and all, according to Bergquist, 

indicate an age older than that suggested by ammonites 

and pelecypods. The data cannot be exactly equated, 

however, as the microfossils and megafossils did not 

come from the same section. They did come from nearly 

identical lithology and position above the base of the 

member but are from sections about 50 km (30 mi) 

apart. The fossils include Ammodiscus bradynus Spandel and A. nitidus Parr of Permian age, and a few specimens of Textularia fuscalignensis Cushman and Waters 

of Pennsylvanian age. 

The age discrepancy cannot be resolved at present. 

Three possibilities exist: the fossils were reworked, they 

extend higher in the section than previously recorded, 

or there was no break in deposition. 

LEDGE SANDSTONE MEMBER 

Name and distribution.-The new name Ledge 

Sandstone Member is here applied to the resistant massive sandstone that forms prominent hogback ridges 

and cuestas along the north flank of the Brooks Range 

and along the flanks of the Sadlerochit and Shublik 

Mountains. Outcrops of this light-colored iron-stained 

quartzitic sandstone along the south side of the Sadlerochit Mountains are referred to by Leffingwell (1919, 

p. 113) in his original definition of the Sadlerochit Formation. Keller, Morris, and Detterman (1961, p. 179) 

informally named this sandstone the cuesta-forming 

unit. We here name this unit the Ledge Sandstone 

Member after exposures on Ledge Creek, a tributary of 

the Sadlerochit River. The massive resistant sandstone 

forms numerous ledges in this stream near the east end 

of the Sadlerochit Mountains. 

The type section for the Ledge Sandstone Member is 

here designated as the section exposed along a small 

eastern tributary of Marsh Creek on the north side of 

the Sadlerochit Mountains, lat 69°41' N., long 

144°50'30" W. (fig. 2, loc. 2). 

The member is present in all outcrops of the Sadlerochit Group in northeastern Alaska but is thickest 

and best developed along the north side of the Brooks 

Range and in the Sadlerochit and Shublik Mountains, 

where it forms the flanking beds for the older rock units. 

Within the Brooks Range massive sandstone beds are 

absent, and the member becomes much thinner and 

finer grained southward. Thin sandstone units have 

been mapped along the north edge of the Table Mountain quadrangle, but the southern limit of these beds is 

not known. The Ledge Sandstone is present in the subsurface at Prudhoe Bay, where it is the main producing 

unit in the field. 

Thickness and stratigraphic relations.-The Ledge 

Sandstone Member is 58 m (189 ft) thick at its type 

locality, where it is overlain unconformably by Cretaceous rocks. It ranges from about 12m (40ft) thick south of 

Wahoo Lake to at least 120 m (390 ft) in an incomplete 

section near Monument No. 5 on the Canada-Alaska 

boundary. It is 141m (463ft) thick in the subsurface at 

Prudhoe Bay (Fackler and others, 1971) and about 15m 

(50 ft) thick on Joe Creek (Reiser and others, 1974; 

Mountjoy, 1967). 

The contact with the underlying Kavik Member is 

generally not well exposed except in stream cuts; where 

seen it is apparently conformable. The contact with the 

overlying Fire Creek Siltstone Member is also conformable. In two areas the upper contact of the Ledge 

Sandstone Member is known to be an unconformity: 

along the north flank of the Sadlerochit Mountains, 

including the type section, and in the Bathtub Ridge 

syncline along the upper Kongakut River. In both areas 

Lower Cretaceous and Jurassic shale rests directly on 

the sandstone with slight angularity. 

Lithology.-The Ledge Sandstone Member is 

primarily a clean, massive, quartz arenite. Beds range 

from about 0.6 to 3m (2 to 10ft) thick, and most are a 

medium light gray to dark reddish brown on weathered 

surfaces and light gray on fresh surfaces. In thin sections these rocks are seen to be 50 to 60 percent quartz, 

generally in subround to well-rounded grains 0.05 to 0.1 

mm in diameter. Chert clasts form 30 to 40 percent of 

the rock. Some of the chert is highly weathered and 

tripolitic; these grains are white and earthy. Minor accessory minerals include a few grains of highly weathered plagioclase feldspar, zircon, tourmaline, and pyrite. The pyrite is locally abundant and often altered to 

limonite, giving the sandstone a blotchy appearance 

and a characteristic reddish-brown weathered surface. 

These rocks are cemented by silica, but only rarely does 

it form overgrowths on the detrital grains. Crossbedding, ripple marks, ball-and-pillow structures, and flute 

casts are common features of the member in all but the 

northernmost exposures. 

Locally the sandstone is conglomeratic, generally in 

thin well-defined zones in the upper part of the member. 
STRATIGRAPHY 13 

The constituents are subangular to well-rounded 

granules to small pebbles of quartz and chert, part of 

which is tripolitic. The conglomerate beds are more 

numerous and contain coarser clasts, up to 2.5 em (1 in.) 

in diameter, in the northernmost exposures. The conglomerate disappears rapidly to the south and is generally missing in outcrops south of the mountain front. 

A few thin siltstone and silty shale beds are intercalated with the sandstone. Two of these units are present 

in the type section. The silty zones generally become 

thicker in a southerly direction and locally divide the 

sandstone into well-defined lower and upper units. The 

siltstones are fine-grained versions of the sandstone, 

with a sericitic clay matrix. 

Age.-The Ledge Sandstone Member has only 

sparse fossils. The massive sandstone beds in the northern part of the area contain the brachiopod.Lingula sp. 

Although of little value for age determination, Lingula 

is an indicator of the depositional environment. It is 

found primarily in shallow nearshore environments, 

and modern forms can live in brackish water. 

Ammonites are found at a few localities where the 

upper sandstone beds become thinner and finer grained 

than at the type area. Most are fragments and scraps 

that cannot be identified, but a few complete specimens. 

were identified by N.J. Silberling as Euflemingites cf. 

E. romunderi Tozer. According to Silverling (written 

commun., 1971), these are diagnostic of the Romunderi 

Zone of middle Early Triassic (Smithian) age. Since 

these fossils are from the upper part of the Ledge 

Sandstone Member, and the underlying Kavik Member 

contains fossils oflate Griesbachian age, deposition was 

probably continuous throughout this part of the Early 

Triassic. The Dienerian Stage is not represented by 

fossils, but there are ample unfossiliferous beds 

between the two zones to account for this stage. 

FIRE CREEK SILTSTONE MEMBER 

Name and distribution.-The Fire Creek Siltstone 

Member is here named for the siltstone and silty shale 

sequence that overlies the Ledge Sandstone Member 

and underlies the Shublik Formation. These rocks are 

present along the north flank of the Brooks Range and 

along the Shublik and Sadlerochit Mountains, but good 

exposures are restricted to stream cuts. The member is 

named after Fire Creek, where the type section is completely exposed along the west side of the canyon (fig. 2, 

loc. 1, and fig. 5) at lat 69°31'45" N., long 145°13'30" W. 

Good exposures are present at a few localities within the 

Brooks Range, mainly near the Marsh Fork of the Canning River, the upper Kongakut River, and along the 

west fork of the Aichilik River (Reiser and others, 

1971, 1974). 

Pre-Cretaceous erosion stripped the member from 

some of the area now forming the north flank of the 

Sadlerochit Mountains where the Early Cretaceous 

Kongakut Formation lies on the Ledge Sandstone 

Member, and also in part of the Bathtub Ridge syncline 

on the upper Kongakut River. The member is absent 

from much of the area between the Aichilik River and 

the Canadian boundary, probably because of Quaternary erosion. It is known to be present in the subsurface 

along the north coast (Fackler and others, 1971) and 

probably is present as far south as Porcupine Lake 

(Brosge and others, 1962). 

Thickness and stratigraphic relations.-The type 

section on Fire Creek is 33m (110ft) thick; and thickness of the member ranges from 0 to 135 m (0 to 440 ft) 

elsewhere. Local variations in thickness are common, 

and due in part to pre-Shublik erosion, but most result 

from unequal distribution of sediments during deposition. In general the member becomes thicker south and 

west ~f the type section and changes from siltstone to 

shale, reflecting increased distance from the source area 

(Detterman, 1970a). 

The contact between the Fire Creek Siltstone 

Member and the underlying Ledge Sandstone is conformable and gradational, reflecting only a change in 

grain size of detrital sediments. The contact with the 

overlying Shublik Formation is probably a disconformity in some areas. Minor pre-Shublik erosion has removed strata in the northern part of the study area, but 

beds on opposite sides of the contact are concordant. The 

contact between the two units is probably conformable 

in the southernmost exposures in the study area. 

Lithology.-The Fire Creek Siltstone Member consists primarily of thin-bedded to massive siliceous 

siltstone that is commonly laminated. Minor silty shale 

and argillaceous sandstone are present locally. The rock 

is medium dark gray to black on fresh surfaces and 

weathers to lighter shades of gray. The light and dark 

laminated beds characteristic of some of the outcrops 

are made up of clay-rich dark layers alternating with 

quartz-rich light layers. Most of the rocks are cemented 

by silica, and secondary authigenic calcite has replaced 

the silica locally. Silica content increases to the south. 

Mud lumps, worm trails, and clay ironstone concretions 

are common features of the beds; flute and load casts and 

drag marks are less common. 

Thin sections show that these rocks are 40 to 80 percent distinct mineral grains in a siliceous sericitic clay 

matrix. The individual grains are all well rounded and 

mainly 0.01 to 0.025 mm in diameter. Quartz forms 40 

to 60 percent of the rock. Chert locally is as much as 20 

percent of the coarse-grained siltstone, and secondary 

calcite locally amounts to 10 to 15percent. Where present, the calcite forms aggregates that are much larger 

than any of the detrital grains; some are 0.5 to 1 mm in 
14 POST-CARBONIFEROUS STRATIGRAPHY, NORTHEASTERN ALASKA 

diameter. Accessory minerals usually make up only a 

few percent of the rock. Pyrite altered to limonite is the 

most common accessory, but a few grains of zircon and 

garnet are present. Organic material is present in some 

of the laminated beds, generally concentrated in the 

clay-rich laminae. 

Age.- Fossils in the Fire Creek are sparse, 

and most are fragments that cannot be identified. A few 

good specimens of the ammonite Euflemingites cf. E. 

romunderi Tozer and the brachiopod Lingula sp. have 

been found. These are the same fossils that were found 

in the upper part of the underlying Ledge Sandstone 

Member. The fossils were identified by N.J. Silberling, 

who states (written commun., 1971) that the ammonite 

is the index fossil of the Romunderi Zone of middle Early 

Triassic (lower Smithian) age. 

Elsewhere in northern Alaska, beds mapped by Patton and Tailleur (1964, p. 431-438) as the lower shale 

member of the Shublik Formation in the Killik-Itkillik 

Rivers region may be in part equivalent to the Fire 

Creek. They report a paleoniscoid fishBoreosomus identified from a few bone fragments; this fish is known only 

from the Early Triassic. The invertebrate molluscan 

fauna from correlative beds in the Killik-Itkillik region 

contains only Middle and Late Triassic forms. How~ver, 

Euflemingites romunderi Tozer, Posidonia mimer 

Oeberg, and Pseudomonotis boreas Oeberg were found 

in the shale member near Galbraith Lake (83 km (52 

mi) S 45° W. of Flood Creek) (Silberling and Patton, 

1964) and may indicate a correlation with the Fire 

Creek Siltstone Member. 

The Ivishak Formation contains nearly all of the positively identified Early Triassic invertebrate fossils in 

Alaska. This identification is based on both ammonites 

and pelecypods from 25 recent collections. Not all stages 

of the Lower Triassic are represented by fossils, but 

unfossiliferous beds lying between good faunal horizons 

seemingly indicate that deposition was continuous and 

that a nearly complete Lower Triassic section is present. 

SHUBLIK FORMATION 

Name and distribution.-Leffingwell (1919, p. 115) 

named and described the Shublik Formation for a sequence of dark limestone and shale exposed at Shublik 

Island, in the Canning River, near the mouth of Cache 

Creek. He recognized the many structural complications of the Shublik Island section (p. 116) and obtained 

the stratigraphic details from a section on Camp 263 

Creek, near the southeastern end of the Sadlerochit 

Mountains. During the recent helicopter-supported 

geologic investigations a more complete exposed section, including both upper and lower contacts, was discovered on Fire Creek, a western tributary of the Sadlerochit River (Detterman, 1970a; Tourtelot and Tailleur, 1971). This locality (fig. 2, loc. 6) is here designated 

the reference section for the Shublik Formation; it is 

located 13.4 km (6.3 mi) N. 84° W. of the confluence of 

Fire Creek with the Sadlerochit River, lat. 69°31'45" N., 

long. 145°12' W. 

The distinctive lithology and abundant fossils make 

the Shublik Formation a readily recognized stratigraphic unit in northern Alaska. As a result, the formation is mapped across the entire width of the State. This 

widespread correlation is undoubtedly due in large part 

to the included abundant faunal remains, as the 

lithologic character of the strata changes considerably 

across the State and the rocks probably should be divided into more than one formation. However, present 

usage is well established and probably will be continued. 

Within the area of this report (fig. 3), the main exposures of the Shublik Formation are in a narrow belt 

along the north flank of the Brooks Range and along the 

Sadlerochit and Shublik Mountains (Reiser and others, 

1971). As this is a structurally complex area, the beds 

are missing locally, for example east of the Egaksrak 

River and along the northwest flank of the Sadlerochit 

Mountains.Elsewhere the beds are locally duplicated. 

Structural lows account for the presence of the formation within the Brooks Range near Porcupine and 

Wahoo Lakes, along the West Fork Aichilik River, and 

along Joe Creek. The formation is generally the same as 

at the type locality; however,, at Porcupine Lake the 

Shublik also-includes a thick sequence of cherty rocks 

not found at the type locality. The typical formation is 

recessive-weathering and does not form good exposures 

except in stream gorges, but the distinctive coloration 

and abundant fossils make these rocks readily mappable nonetheless; in. addition,!they are the,only dominantly calcareous Mesozoic rocks in northern Alaska. 

Thickness and stratigraphic relations.-The Shublik Formation represents a condensed sequence of rock 

of remarkably uniform thickness; most sections are 91 

to 137m (300 to 450ft) thick. The reference section is 

140m (458ft) thick and probably represents about the 

maximum thickness for the formation north of Porcupine Lake (fig. 6). The upper clay-shale member of the 

Shublik Formation is similar in many respects to the 

overlying Kingak Shale of Jurassic age, and in sections 

where the intervening Karen Creek Sandstone is missing the shale probably has been mapped as part of the 

Kingak; this may account for the somewhat thinner 

sections reported by Keller, Morris, and Detterman 

(1961). Likewise, in sections more than 150 m (500 ft) 

thick, structural duplication ofbeds may have occurred. 

Such duplication may account for part of the apparent 

thickness of about 550 m (1,800 ft) at Porcupine Lake, 

where about 150 m (500 ft) of rocks similar to the type 
STRATIGRAPHY 15 

c: 

0 

:= 

cu 

E 

t£ 

~ 

:0 

::l 

.r:. 

(/J 

Q; 

.tl 

E 

Q) 

E 

Q) 

·n; 

.r:. 

1/) 

~ 

u 

Q; 

.tl 

E 

Q) 

E 

Q) 

~ 

E 

0 

0 

'0 

'0 

lij 

Q) 

c: 

.9 

1/) 

Q) 

E 

:.:J 

Q)'-

c: Q) 

o.tl 

t;;E 

~e 

6 

Fire Creek 

*4 

*5 

*6 

7 

Karen Creek 

LITHOLOGIC SYMBOLS 

Limestone 

~ 

~ 

Siltstone and calcareous siltstone 

Sandstone and calcareous sandstone 

Siliceous cement 

Dolomite 

Shale 

~ 

~ 

Phosphate nodules 

and limestone 

concretions 

Covered interval 

*2 Fossil collection 

See section entitled, "List of Fossil 

Collections" for description 

METRES FEET 

45 150 

FIGURE G.-Reference section for the Shublik Formation and type 

section for the Karen Creek Sandstone. 

Shublik are overlain by an estimated 400 m (1,300 ft) of 

Triassic cherty rocks not reported elsewhere in northeastern Alaska. 

The contacts of the Shublik Formation are generally 

not well exposed; the reference section on Fire Creek is 

one of the few localities in which both upper and lower 

contacts are visible. At Fire Creek the beds appear to be 

conformable with the underlying Fire Creek Siltstone 

Member and overlying Karen Creek Sandstone. The 

Karen Creek Sandstone is locally missing in northeastern Alaska and the Kingak Shale rests directly on the 

Shublik, so the upper contact of the formation is probably a disconformity there. At Porcupine Lake the location of the upper contact is uncertain. The fossiliferous 

cherty beds in the upper part of the Shublik are overlain 

with apparent conformity by about 30 m (100 ft) of 

unnamed unfossiliferous black chert and shale· and 

green argillite, which is succeeded by about 100 m or 

dark-gray sandstone of uncertain age. 

In most of northeastern Alaska the Shublik Formation is divided informally into three members: in ascending order, siltstone, limestone and dolomite, and 

clay shale (fig. 6). Patton and Tailleur (1964, p. 431) also 

used a threefold division for the Shublik in the KillikItkillik area, but a comparison with their sections indicates a considerable change in lithology; a chert 

member occupies the place of the limestone and dolomite member, and a limestone member is in the place of 

the clay shale member. Another threefold division is 

recognized at Porcupine Lake, where the apparent 

stratigraphic succession is, in ascending order, a shale 

and limestone member composed of the same rock types 

found in the reference section, but with less abundant 

carbonate rocks; a unit of shale, chert, and limestone; 

and a unit of chert and shale. The lower contacts of the 

two cherty units may be faulted, and these units may be 

parts of a single member . 

Lithology.-All the Shublik Formation north of 

Porcupine Lake is dark gray to sooty black on fresh 

surfaces, and the limestone and dolomite, particularly 

the thin-bedded units, weather light gray to yellowish 

gray. Phosphate nodules and concretions are abundant, 

and most of the pelecypods are phosphatized. The 

nodules and concretions are mainly 0.6 to 1.3 em(~ to% 

in.) in diameter and round to irregularly shaped. They 

consist primarily of isotropic carbonate fluorapatite, although in some the mineral is collophane. Some nodules 

are ooliths showing concentric banding around quartzgrain nuclei. Nodules are scattered throughout the formation but are most abundant in the siltstone and 

limestone members, where nodules form beds 2.5 to 15 

em (1 to 6 in.) thick (Detterman, 1970a, b). The phosphate from ·these nodules gives the rock a characteristic 

bluish color. 

The siltstone member at the base of the Shublik is 

primarily composed of angular to subangular quartz 

grains, 0.02 to 0.05 mm in maximum dimension. Many 

of the grains are elongate, two to three times longer 

than they are wide, oriented parallel to bedding. Calcite, mostly of secondary origin, is the cementing material, constituting 20 to 40 percent of the siltstone. Phosphate grains with quartz nuclei are fairly common in 

some beds, and minor amounts of plagioclase and sericite are also present. The dark coloration is due to the 

high organic content, but the exact nature of the organic 

material was not determined. 

The limestone and dolomite member of the Shublik 
16 POST-CARBONIFEROUS STRATIGRAPHY, NORTHEASTERN ALASKA 

contains many coquinite layers, most of which are 

somewhat phosphatized. In thin section these limestones are seen to be primarily composed of tightly compressed flat pelecypod fragments. The several rocks 

studied in thin section are 40 to 90 percent calcite and 10 

to 20 percent secondary dolomite. Chemical analyses of 

the rocks (Detterman, 1970b), however, indicate that 

dolomitization is essentially complete in some beds. 

Subround quartz grains amount to as much as 20 percent of some of the beds; most grains are silt size. These 

beds probably should be termed silty arenaceous 

limestone. The limestone is thin bedded to massive, and 

shale is interbedded with the thin-bedded units. 

The clay shale at the top of the formation is a very soft, 

incompetent rock that does not form good exposures. A 

few silty, very fine grained calcareous sandstone beds 

are present near the top, and limestone concretions are 

fairly common there. Phosphate nodules are a minor 

part of the section. 

The limestone in the unit of shale, chert, and 

limestone at Porcupine Lake is part black and sooty and 

part gray, hard, and very fine grained. The chert and 

silty shale in this unit are dominantly gray to black and 

weather black, brown, and orange. The overlying chert 

and shale unit contains conspicuous light-grayweathering olive-green chert and silicified siltstone, in 

addition to black chert and shale, and small amounts of 

brown chert and limestone. 

Age.-The Shublik Formation is the most richly 

fossiliferous stratigraphic unit in northeastern Alaska. 

Ubiquitous flat pelecypods of the monotid and halobiid 

genera are found in great numbers; many coquinite 

beds occur throughout the section. These pelecypods 

have a restricted stratigraphic range and occur 

worldwide; thus they make excellent horizon markers 

within the formation. Ammonites are sporadically 

abundant, as in Ignek Valley and near Wahoo Lake, and 

provide more refined age assignments for the beds in 

which they occur. 

The lowest beds in the Shublik contain far fewer fossils than the middle and upper parts of the section. The 

ammonite Leiophyllites(?) sp. was found about 8 m (27 

ft) above the base of the siltstone member at the reference locality; this genus is considered to represent the· 

lower part of the Anisian Stage of the Middle Triassic. It 

overlies by approximately 15 m (50 ft) a specimen of 

Euflemingites romunderi Tozer in the Fire Creek 

Siltstone Member of the Ivishak Formation of middle 

Early Triassic (lower Smithian) age according toN. J. 

Silberling (written commun., 1971). Fossils characteristic of the Spathian Stage have not been found but 

are probably represented by the 15 m (50 ft) interval 

between the two ammonite collections. Deposition across the formation boundary at the reference section is 

considered to be essentially continuous and conformable. Daonella {rami Kittl of early Ladinian age has been 

found at the top of the siltstone and the base of the 

limestone members. 

The limestone member, except for the basal beds, is of 

early Late Triassic (Karnian) age. Many fossils are 

found including Halobia cf. H. zitteli, Halobia ornatissima, Lima sp., Gryphaea sp., Camptonectes sp., Leptochondria nationalis, and the ammonites Tropites sp., 

Holotropites sp., Sirentites sp., Arctosirentites cf. A. 

canadensis Tozer, Juuauites sp., and Arcestes(?) sp. 

Rhynchonellid brachiopods and gastropods are also 

common throughout these beds. These fossils indicate 

that the entire Karnian State is present. 

Numerous vertebrate fragments were found in the 

limestone member on the north side of lgnek Valley 

near the west end of the Sadlerochit Mountains. According to C. A. Repenning of the U.S. Geological Survey, 

these bones represent the ichthyosaur family Shastosauridae (written commun., 1972). Unidentifiable 

· bone fragments are present in other collections from the 

member. 

Fossils in the clay shale member are primarily 

confined to the limestone concretions and limy 

sandstone beds in the upper part and include the 

pelecypods M onotis cf. M. obtusicostata Westermann, 

Monotis cf. M. scutiformis pinensis Westermann, 

Halobia cf. H. fallax Mojsisovics, and Halobia cf. H. 

lineata Mojsisovics. These beds are correlated with the 

middle Norian Stage of the Late Triassic. Fossils of the 

late Norian Stage are found at the base of the overlying 

Karen Creek Sandstone. The completeness of the fossil 

record suggests that deposition was continuous 

throughout the entire Triassic. 

The shale and limestone member at Porcupine Lake 

contains Halobia cf. H. zitteli and tropitid ammonites, 

indicating a Karnian age. The unit of shale, chert, and 

limestone contains Monotis sp. and Halobia sp., probably of middle Norian age. The overlying unit of chert 

and shale contains M onotis sp. of middle or late Norian 

age and Monotis sp. similar toM. subcircularis or M. 

ochotica, which are of late Norian age. The sequence of 

fossils indicates that the Shublik at Porcupine Lake 

may be equivalent in age to the limestone and dolomite 

and clay shale members and to part of the Karen Creek 

Sandstone of the type area and that the cherty units 

are younger than the chert member of the Killik-

! tkillik area. 

KAREN CREEK SANDSTONE 

Name and distribution.-The Karen Creek 

Sandstone is here named for a thin sequence of dark, 

resistant, quartzitic sandstone that lies between the 

recessive-weathering Shublik Formation and the overlying Kingak Shale. The type section is the west bank of 
STRATIGRAPHY 17 

the upper part of Karen Creek (fig. 2, loc. 7), 5.1 km (3.2 

mi) S. 48° E. of the outlet of Lake Schrader, lat 69°22' N., 

long 144°49' W. These beds were referred to the base of 

the Kingak Shale by Reed (1968, p. 56). 

The Karen Creek Sandstone has a restricted distribution. It is best exposed along the north front of the 

Brooks Range between the Kavik and Aichilik Rivers, 

where it forms distinctive hogback ridges that are readily mappable. Fairly good exposures of the sandstone 

are present at a number oflocalities in Ignek Valley and 

along the north side of Kikiktat Mountain. It also underlies small areas between Lake Schrader and the Sadlerochit Mountains but has not been found within the 

Brooks Range. 

Beds that are probably lithologically equivalent to 

the Karen Creek Sandstone are penetrated in drilling 

along the Arctic Coast. In the subsurface similarlooking sandstones were named the Sag River 

Sandstone (Rickwood, 1970; Fackler and others, 1971). 

This unit occupies the same stratigraphic position and 

is lithologically very similar to the Karen Creek 

Sandstone, but a correlation between the two has not 

yet been established. 

Thickness and stratigraphic relations.-Measured 

sections of the Karen Creek Sandstone range in thickness between 3m (10ft) on the Kavik River to 38m (125 

ft) near the J ago River. rhe type section is 21 m (70ft) 

thick (fig. 6). These sections indicate there is a persistent but nonuniform thinning from east to west along 

the Brooks Range. A similar decrease in section is 

apparent northward from the Brooks Range; 6 m (19ft) 

is present along Fire Creek arid slightly more in Ignek 

Valley, whereas 32 m (105 ft) is exposed to the south 

near the upper Sadlerochit River. Sections of Sag River 

Sandstone encountered in drilling along the north coast 

exhibit a pattern of thinning in an easterly and southerly direction, the reverse of that seen in outcrop (Fackler and others, 1971). 

The provenance of the Karen Creek Sandstone cannot 

be precisely determined from present data. Strictly on 

the basis of outcrop information, the apparent source 

w·ould be to the southeast; however, petrographic 

examination of thin sections strongly suggests that the 

provenance for the sediments was the same as for the 

underlying Shublik Formation and Sadlerochit Group, 

that is, from the north. Also, the presence of chert and 

shale at Porcupine Lake suggests that deeper water lay 

to the south. 

The contact between the Karen Creek Sandstone and 

the underlying Shublik Formation is considered to be 

conformable. The bottom side of the lowest sandstone 

bed is undulatory in some exposures but is always resting on the clay shale at the top of the Shublik. Fossils in 

the lower part of the sandstone and in the upper part of 

the shale indicate, also, that no significant break in 

deposition occurred between the two stratigraphic 

units. The upper contact with the Kingak Shale is 

structurally conformable, but the lithology and faunal 

content of the immediate overlying rocks change 

considerably and possibly indicate a disconformity. 

Lithology.-The Karen Creek Sandstone is primarily a very fine grained, massively bedded, dark, siliceous 

quartz arenite. There is little or no lateral change in 

composition of the rock in exposures immediately adjacent to the north front of the Brooks Range. Thin sections show that these rocks are 45 to 75 percent quartz 

in subround to well-rounded grains 0.07 to 0.15 mm in 

diameter. Chert grains form another 10 to 20 percent. 

Secondary calcite is as much as 10 percent of some beds, 

and siderite replaces the calcite in a few. All the thin 

sections examined showed a dark organic stain 

throughout that may be responsible in part for the overall dark color. Accessory minerals account for less than 

5 percent of the rock and generally include collophane, 

glauconite, sericite, zircon, plagioclase, pyrite, limonite, and locally ilmenite and leucoxene. 

Large irregular to colloform phosphate nodules are 

common throughout the Karen Creek Sandstone. Many 

of the nodules are as much as 7.6 em (3 in.) in diameter, 

considerably larger than any noted in the underlying 

Shublik Formation. Some nodules are ooliths showing a 

distinct accretionary banding around quartz-grain 

nuclei but with no orientation of the ooliths. Reed (1968, 

p. 58) presents good evidence that the nodules in the 

Karen Creek were formed penecontemporaneously 

with the deposition of the sandstone and suggests that 

they were not derived from the underlying Shublik 

Formation. 

The northward thinning of the Karen Creek 

Sandstone away from the mountain front is accompanied by a considerable change in its lithologic character. Much of the silica is replaced by calcite, and some of 

the rocks are arenaceous limestones. In some beds the 

calcite has been altered to dolomite and siderite. The 

upper 0.6 m (2 .ft) of the Fire Creek section is nearly pure 

dolomite and siderite. This northerly change to dominantly calcareous rocks apparently reflects a depositional peculiarity of the area, as the presumably equivalent Sag River Sandstone present in the subsurface 

along the north coast is similar to the Karen Creek 

Sandstone exposed along the mountain front. 

Age.-The Karen Creek Sandstone must be considered the uppermost stratigraphic unit of the Triassic on 

the basis of the pelecypods Monotis ochotica ochotica 

(Keyserling) and Gryphaea keilhaui Boehm, which are 

found in considerable numbers in the lowermost beds in 

the northernmost exposures. According toN. J. Silberling (written commun., 1969), these fossils are charac-
18 POST-CARBONIFEROUS STRATIGRAPHY, NORTHEASTERN ALASKA 

teristic of the upper Norian Stage of Late Triassic age. 

Fossils have not been found in any of the exposures 

immediately adjacent to the north front of the Brooks . 

Range. The presence of phosphate nodules in these beds 

also suggest a correlation with the highly phosphatic 

rocks ofthe Shublik Formation. The overall lithology of 

the Karen Creek Sandstone, on the other hand, is 

different enough from the Shublik to suggest a change 

in depositional environment, and logically the Karen 

Creek should be considered the beginning of the 

Jurassic. These beds may actually cross the TriassicJurassic boundary, but until definite evidence is found, 

they will be considered uppermost Triassic. 

KINGAK SHALE 

Name and distribution.-The Kingak Shale was 

named and described by Leffingwell (1919, p. 119) for 

exposures of dark shale at Kingak Cliff, near Camp 263 

Creek, and at the southeast end of the Sadlerochit . 

Mountains. The shale is exposed along both sides of the 

Sadlerochit River at this locality but, owing to structural complications, good sections are hard to find. The 

Kingak is a soft shale unit that forms poor exposures; it 

is responsive to even the mildest tectonic activity. Two 

reference sections (fig. 2, locs. 8 and 9, and fig. 7) are 

designated to supply stratigraphic details that are not 

completely exposed in Leffingwell's type locality. The 

section from lgnek Valley (fig. 2, loc. 8) is exposed beneath the sandstone capping the mesa near the east end 

of the valley, lat 69°33'30" to 69°34' N., long 145°20' to 

145°20'30" W. This section is about 19.3 km (12 mi) west 

ofLeffingwell's type locality and contains only Middle 

and Upper Jurassic rocks; it rests disconformably on the 

Shublik Formation. The other reference section is exposed along the west bank of the Aichilik River, lat 

69°31'15" to 69°32' N., long 143°03' to 143°05' W. (fig. 2, 

loc. 9); it contains a complete Jurassic section, but parts 

are duplicated by folding and faulting. 

The Kingak Shale underlies the lowlands north of the 

mountain front, where it forms a belt of subd~d topography 1.6 to 10 km (1 to 6 mi) wide parallel to the 

mountains. Exposures are confined to stream cutbanks, 

with rubble and float covering the hills between 

streams. Recent mud slides on hill slopes are commonly 

a clue to the presence of the underlying shale. The series 

of discontinuous cutbanks about 10 km (6 mi) long on 

the west side of the Canning River, along with Black 

Island in the Canning River, is perhaps the best known 

occurrence of the Kingak. Another extensive outcrop is 

present along the west bank of the Aichilik River, and is 

here designated a reference locality (fig. 7) along with 

the one exposed under the mesa at the east end oflgnek 

Valley. 

Exposures of the Kingak Shale are rare within the 

Q) 

(ij 

.r:. 

en 

~ 

as 

8 

Mesa section 

lgnek Valley 

N 

... 

c: 

:::> 

(") 

... 

·c: 

:::> 

""" ... 

c: 

:::> 

Cl METRES FEET c: 

120 400 :i: 

60 

30 

Ln 

... 

c: 

:::> 

200 U) 

... 

c: 

:::> 100 

~.g 

.g~ii3 

~ E 

LITHOLOGIC SYMBOLS 

Clay shale 

Silty shale 

Claystone 

~ 

~ 

~ 

~ 

Siltstone 

Sandstone and 

conglomerate 

Clay ironstone beds 

and concretions 

Claystone nodules Siliceous cement 

Covered interval 

*2 Fossil collection 

See section entitled, "List 

of Fossil Collections" for 

description 

9 

Aichilik River 

(composite) 

·~ 

Q) Q) 

Q) c: ... 0 U(ij 

c:'O 

Q) c: ... as ~en 

FIGURE 7.-Reference sections for the Kingak Shale. 

Brooks Range. One of the few localities is along Joe 

Creek, in the southeastern part of the map area, where a 

fairly thick sequence of beds is exposed along the south 

bank of the creek (Reiser and others, 1974). Other small 

patches of Kingak are present between the upper 
STRATIGRAPHY 19 

Echooka and Kavik Rivers (Reiser and others, 1971). 

Thickness and stratigraphic relations.-Stratigraphic measurements of the Kingak Shale are impaired by folding and faulting and by the lack of continuously exposed sections. Leffingwell (1919, p. 119) 

estimated a thickness of about 1,200 m (4,000 ft) for his 

type locality near Camp 263 Creek. This may be somewhat excessive, but a similar thickness is apparently 

present along the Canning River, and 915 m (3,000 ft) is 

reported from Kemik Creek (Keller and others, 1961, p. 

192). The thickness of the Kingak changes rapidly 

within short distances. Exposures in Ignek Valley 

range between 46 and 366m (150 and 1,200 ft) and lie 

between 1,200 m (4,000 ft) sections on the Canning 

River and at Camp 263 Creek. 

There are few good horizon markers in the Kingak 

Shale that can be followed with confidence while correlating detailed sections. Fortunately, there are fairly 

abundant ammonites and pelecypods with restricted 

stratigraphic range that can be used as indicators of 

duplication or omission of strata. Numerous diastems 

can be demonstrated within the Kingak by using a 

combination of these faunas and their associated 

lithologies. These same criteria are used to show the 

disconformable nature of both the upper and lower 

contacts. 

Lithology.-The Kingak Shale consists primarily of 

shale. However, siltstone, claystone, and clay ironstone 

are important subordinate elements of the stratigraphic 

sequence. The shales are uniformly dark gray to dark 

olive gray and black, but some have distinctive features 

that make assignment to a specific part of the section 

possible. 

The lowest part of the Kingak is an extremely fissile 

black paper shale as much as 180m (600ft) thick. The 

shale fractures and weathers into thumbnail-sized silvery fragments. Large cannonball concretions occur 

through an interval of about 45 m (150 ft) in the middle 

of the fissile shale unit. Overlying the fissile shale beds 

are 100 m (300 ft) to 300 m (1,000 ft) of soft dark-gray 

clay shale and locally claystone. The upper part of this 

sequence contains a few beds and nodules of clay ironstone that characteristically weather a bright brick red. 

Thin-bedded siltstone and silty shale overlying the 

clay shale constitute the most resistant part of the Kingak Shale. Thin sections show that the siltstone is 

about 75 to 80 percent rounded quartz grains generally 

less than 0.05 mm in diameter. Siderite makes up 5 to 10 

percent of the siltstone, and there are minor amounts of 

plagioclase, zircon, and pyrite and a few grains of phosphate and glauconite. The matrix is a siliceous clay. The 

siltstone mineralogy is strikingly similar to that of the 

Karen Creek Sandstone. This siltstone and silty shale 

sequence contains the most prolific ammonite and 

pelecypod fauna of the Jurassic in northeastern Alaska. 

Black clay shale with siltstone interbeds and irregularly shaped, gray, clay-ironstone nodules overlies the 

siltstone unit and forms the upper part of the Kingak 

Shale north of the Brooks Range. 

The rocks exposed on Joe Creek are mainly a darkgreenish-gray siltstone with interbeds of shale and clay 

ironstone. These beds are slightly younger than most of 

the strata exposed on the north side of the range and 

probably represent a sequence that was almost entirely 

removed there. 

Age.-The Kingak Shale was considered to be 

Early Jurassic by Leffingwell (1919, p. 119). Subsequent investigations have shown that probably all 

parts of the Jurassic are included in the beds now 

mapped as Kingak. The stages are not all represented 

by fauna, but there are sufficient unfossiliferous beds to 

represent intervals not accounted for by fossils. Owing 

to the many diastems characteristic of the Kingak 

deposition, no single exposure contains all the presently 

known stages. 

The Early Jurassic, with sparse fossils in northeastern Alaska, is represented by Amaltheus cf . . A. stokesi 

(Sowerby) and the pelecypod Otapiria tailleuri Imlay. 

The pelecypod indicates a probable Sinemurian age, 

and the ammonite is Pliensbachian (Imlay and Detterman, 1973). These fossils are from the fissile clay shale 

and claystone in the lower part of the sequence. 

Leffingwell (1919, p. 119) based his age assignment 

for the Kingak Shale in part on the presence of the 

crinoid Pentacrinus subangularis var. alaska Springer. 

He collected many beautiful specimens on Black Island 

in the Canning River. We collected this crinoid at a 

number of additional localities, it may be basal Middle 

Jurassic rather than Early Jurassic, as dwarf forms of 

Pentacrinus we:r:e associated with the basal Bajocian 

ammonite Pseudolioceras. However, there may be two 

species of Pentacrinus in northern Alaska, one a dwarf 

and the other a robust form similar to that from Black 

Island. The two are never found together, and the large 

form has never been located with other fossils but does 

underlie Amaltheus on the Aichilik River. 

The siltstone and shale sequence of the Kingak carries a prolific ammonite and pelecypod fauna of Middle 

Jurassic age. Beds at the base contain abundant 

Pseudolioceras maclintocki (Haughton), P. whiteavesi 

(White), and Canavarella cf. C. belophora Buckman, all 

of basal Bajocian age. The next higher beds contain the 

middle Bajocian ammonite Arkelloceras sp., which in 

.turn is overlain by abundant Arctioceras kochi Spath, 

A. kochi var.pseudolamberti Spath, andChoffatia cf. C. 

subbakeriae (d'Orbigny), oflate Bathonian age. Much of 

the Callovian Stage is apparently missing in northern 

Alaska, but Cadoceras sp., Pseudocadoceras grewingki 
20 POST-CARBONIFEROUS STRATIGRAPHY, NORTHEASTERN ALASKA 

(Pompeckj), and Reineckia cf. R. stuebeli Steinmann 

were collected. The pelecypod Inoceramus cf. I. lucifer 

Eichwald is fairly abundant in parts of the Bajocian and 

Batho.nian. 

Beds of Late Jurassic age contain a sparse ammonite 

fauna in their lower part, includingCardioceras sp. and 

Cardioceras (Scarburgiceras) sp. of early Oxfordian, 

and Amoeboceras (Prianodoceras) cf. A. (P.) transitorium Spath oflate Oxfordian age. The overlying beds 

contain only the pelecypod Buchia, but the various 

species occupy a restr~cted stratigraphic range and 

permit fairly precise zonation.Buchia mosquensis (Von 

Buch) and B. rugosa (Fischer), characteristic of the 

Kimmeridgian and early Tithonian Stages, are found in 

the highest beds north of the Brooks Range. Strata of 

latest Tithonian age are found along Joe Creek where 

they contain Buchia fischeriana (d'Orbigny) and B. unschensis. These beds disconformably overlie the Shublik 

Formation and indicate a Late Jurassic marine 

incursion. 

We collected many microfossil samples from measured sections of the Kingak Shale. Most are closely tied 

to ammonites and pelecypods, and in general the age as 

determined from the microfauna correlates fairly well 

with that obtained from the megafauna. 

All 43 samples collected from the dark fissile clay 

shale, dated as Early Jurassic from a sparse megafauna, 

are barren. In general this is in keeping with the scarcity of megafauna! remains in these same bed~. Apparently the Early Jurassic seas in northeastern Alaska 

were not ecologically suited to a large biomass. 

A rapid expansion of both micro- and megafauna occurred at the beginning of the Bajocian Stage (Middle · 

Jurassic), and continued throughout the remainder of 

Jurassic time. A total of 95 samples were collected, 

about 80 percent of which contained microfossils. The 

microfossils obtained from the reference section in Ignek Valley are listed in table 1. 

The reference section of Kingak Shale in Ignek Valley 

is one of the few exposed sections of Jurassic rocks in 

northeastern Alaska that contains both a mega- and 

microfauna that is well developed and diversified. The 

megafauna consists of ammonites and pelecypods that 

are known to have restricted stratigraphic range and 

worldwide distribution in the boreal region.' Presumably the microfauna also should show these properties, 

but it does not. Bergquist states (written commun., 

1972): 

***Despite the large assemblage, however, the foraminifera in 

general are not particularly useful in delimiting stages of the Jurassic 

because many are long ranging or they appear in beds that are older or 

younger than those from which they were described. Most of the 

arenaceous forms range throughout the entire section although some 

were originally described from the Lower Jurassic (ToarcianPliensbachian) beds of northern Alaska and had been considered 

indicative of rocks ofEarly Jurassic age, and some species which were 

described from beds of Late Jurassic age occur only in older beds in · 

this section. The range or occurrence of some of the calcareous forms 

also seems erratic and many species occur in beds younger than those 

from which they were described. This apparent age discrepancy may 

be due to the fact that previously we have not had completely sampled 

sections of Middle and Upper Jurassic rocks which provided diagnostic megafossils and foraminifera with which to compare the known 

Jurassic faunas. 

There is no ready explanation for the apparently unrestricted range of many of the Foraminifera in the 

Ignek Valley section, other than the fact that they occur 

through a longer interval than originally suspected. If it 

were only a matter of older forms occurring in younger 

beds, it could be explained by cannibalization and reworking of older beds into younger deposits, but the 

presence of presumed Late Jurassic forms in Middle 

Jurassic beds cannot be explained as easily. Apparently 

a reevaluation of the published age assignment of the 

Foraminifera for the Jurassic of northern Alaska is in 

order. 

One possible correlation can be made in the 

Foraminifera from the Ignek Valley reference section. 

Rectoglandulina quinquecostata Bornemann from the 

base of unit 5 and top of unit 6 is known to occur, in 

northern Alaska and Germany, only in the Toarcian 

Stage. In Ignek Valley it underlies Inoceramus lucifer 

ofBajocian age and may indicate that the dark clay 

shale at the base of that section is Early Jurassic. 

IGNEK FORMATION (ABANDONED) 

Leffingwell (1919, p. 120) applied the name Ignek 

Formation to a series of dark shales with coal of ttred 

beds" and subordinate sandstones. He considered these 

rocks, which overlie the Kingak Shale, to be Jurassic(?), 

a·nd the youngest Mesozoic unit in northeastern Alaska. 

The type locality is on the south side of Red Hill in Ignek 

Valley, at the west end of the Sadlerochit Mountains, 

where about 800 m (2,600. ft) of beds are exposed along 

the north bank of Ignek Creek. Subsequent investigations be Gryc and Mangus (1947) and Keller, Morris and 

Detterman (1961) determined that the formation included both Lower and Upper Cretaceous beds. Keller, 

Morris, and Detterman redefined the Ignek (p. 203) to 

include only those rocks that were the lithologic equivalent of the Nanushuk and Colville Groups, and placed 

the lowest Cretaceous beds in the Okpikruak Formation, which included the basal Kemik Sandstone 

Member. The sandstone along the west side of Canning 

River, near Shublik Springs, was considered by them to 

be the lower part of the Ignek Formation. We consider 

these beds to be the Kemik Sandstone Member. The 

upper part of the type section of the Ignek Formation is 

now considered the Seabee Formation, and the lower 

part the Kongekut Formation. 

During the recent investigations we studied many 

more sections of Cretaceous rocks in northeastern Alas-
STRATIGRAPHY 25 

about 30 m (100 ft) above the base of the clay shale 

member contain only one species, Buchia sublaevis 

Keyser ling of early Valanginian age (Imlay, 1959). The 

Berriasian Stage is not represented by megafossils at 

the type locality, but the diagnostic Buchia okensis 

Pavlow and B. subokensis Pavlow are present on Kemik 

Cree~. 

The upper part of the Kemik Sandstone Member at 

Bathtub Ridge has a sparse megafauna consisting of 

ammonites, pelecypods, and belemnites. The Hauterivian ammonite Simbirskites sp., in its first reported 

occurrence in northern Alaska, places a lower age limit 

on the overlying pebble shale member. North of the 

Brooks Range the Kemik contains a facies-controlled 

pelecypod fauna slightly different from that found at the 

section on the upper Kongakut. This fauna is characterized by Astarte ignekensis Imlay, originally believed 

to be of middle Albian age (Imlay, 1961, pl. 24), but the 

presence ofSimbirskites sp. in the sandstone at Bathtub 

Ridge indicates the fauna also extends down into the 

Neocomian beds. 

The pebble shale member has only a few poorly preserved pelecypods that are provisionally identified as 

Aucellina(?) sp. This identification, if correct, would indicate a possible Aptian to Albian age for these beds, 

which are a widespread horizon marker in both surface 

and subsurface. Primarily on the basis' of lith<;>logy, 

. these beds are more likely to be N eocomian than 

Aptian. However, a persistent and widespread Lower 

Cretaceous unconformity is present in many parts of 

northern Alaska at the base of this pebble shale. The 

overlying siltstone member and Bathtub Graywacke 

have produced no datable fossils. A minimum age for 

the pebble shale is delimited, however, by the presence 

of Paragastroplites spiekeri (McLearn) of middle Albian 

age in <;>ver-lying strata on Arctic Creek. 

Many of the microfossil samples from the Kongakut 

Formation are barren. The upper 152 m (500 ft) of the 

siltstone member has produced no microfossils, but a 

sparse fauna from the underlying beds helps determine 

their age. The fossiliferous samples are listed in table 2. 

Sample 70ADt-209, unit 1, number 25 is of considerable 

interest; it contains a diversified fauna including 

Glomospirella arctica Chamney, Bathysiphon scintillata Chamney, Ammodiscus mackenziensis Chamney, 

Haplaphragmoides goodenoughensis Chamney, and 

Ammobaculites reophacoides Chamney. According to 

Bergquist (written commun., 1972) these fossils are 

characteristic of the Barremian rocks ofthe Richardson 

Mountains in the adjoining Yukon Territory, Canada. A 

few specimens of Gaudryina richteri Grabert were also 

found in this sample; this is an upper Hauterivian fossil 

according to Bergquist. This microfauna supports the 

age as determined from the megafauna and permits a 

more precise assignment for the pebble shale member. 

A feature of some importance in interpreting the 

microfauna is the presence of a Jurassic-to-Cretaceous 

transition or mixed phase at the base of many sections. 

The characteristic Late Jurassic fauna includes Ammobaculites coprolithiformis, H aplophragmoides canui, 

Gaudryina milleri, and Reophax metensis. Associated 

with these Foraminifera are the typical Early Cretaceous Haplaphragmoides topagorukensis, Gaudryina 

tailleuri, Bathysiphon brosgei, and B. vitta. 

The existence of a transition or mixed zone at the base 

of the Kongakut Formation may help to solve some 

problems of correlation in northern Alaska resulting 

from age interpretations based on microfauna as opposed to megafauna. Bergquist (1966, p. 100) alluded ~o 

the problem of a Late Jurassic microfauna associated 

with Early Cretaceous Buchias at Kemik Creek; this 

condition is now known to occur at numerous localities. 

The key to the solution is the combination of the two 

microfaunas. The reason the faunas are mixed is not 

entirely clear. An obvious reason is that Jurassic rocks 

were reworked in the Cretaceous, and this probably is a 

prime factor. However, another possible cause is that 

certain Foraminifers were designated Jurassic or Cretaceous, when in reality they occurred in beds with poor 

stratigraphic control. Finally, the Jurassic forms may 

actually have a longer range than originally thought . 

BATHTUB GRAYWACKE 

Name and distribution.-The name Bathtub 

Graywacke is here applied to a thick sequence of 

graywacke and conglomerate with siltstone and shale 

interbeds that is exposed along Bathtub Ridge in the 

upper Kongakut River area (fig. 2, loc. 12). The type 

section is about 0.8 km (1/2 mi) west of the type section for 

the Kongakut Formation, on the north flank of Bathtub 

Ridge, lat 69°05'30" to 69°06'15" N., long 142°18' W. (fig. 

2, loc. 12). The Kongakut is commonly exposed with the 

Bathtub Graywacke at many localities. Bathtub Ridge 

is approximately 30 km (20 mi) long, and the upper 

resistant part of the ridge is entirely formed of this 

graywacke and conglomerate. 

North of the Brooks Range the graywacke is exposed 

in a broad belt of discontinuous outcrops between the 

Okpilak and Okerokovik Rivers. A series of outcrops 

along Sabbath Creek, an eastern tributary of the J ago 

River, lat 69°37' to 69°41' N., long 143°30' to 143°33' W., 

exposes a thick sequence of graywacke, conglomerate, 

siltstone, and shale; t~is is considered a reference section of the Bathtub Graywacke (fig. 2, loc. 13, and fig. 9). 

Thickness and stratigraphic relations.-The best 

exposed sections of the formation are in the type area 

along the north flank of Bathtub Ridge, where up to 750 

m (2,460 ft) is exposed. The section there is incomplete, 
26 POST-CARBONIFEROUS STRATIGRAPHY, NORTHEASTERN ALASKA 

however, so the actual thickness may be closer to the Formation of the Nanushuk Group along Sabbath 

1,300 m (4,250 ft) present along Sabbath Creek, north of Creek and at several other localities east of the Okpilak 

the Brooks Range. River. The act.ual contact was covered, but the beds 

The lower contact with the Kongakut Formation ap- above and below appear structurally conformable. 

pears to be conformable; it is placed at the base of the However, the Tuktu Formation overlies the pebble 

lowest massive graywacke. A few thin graywacke beds shale member of the Kongakut Formation west of the 

are present in the underlying siltstone member of the Hulahula Riber, so the upper contact is at least locally 

Kongakut, so the contact is probably gradational. unconformable. 

The Bathtub Graywacke is overlain by the Tuktu Lithology.-The Bathtub Graywacke consists 

TABLE 2.--Foraminifera distribution 

(R = rare {1-10); C = common (11-25); A = 

Transition fauna 

a 

s:l. a s:l. s:l. OS s:l. 

E-< OS 

-c E-< 

a c:: c:: a -c 

s:l. OS OS c:: a ~ OS s:l. s:l. s:l. s:l. s:l. ~ a OS s:l. a s:l. OS Q) E-< OS :0 OS E-< gj s:l. E-< z s:l. E-< s:l. j -c ,Q s:l. -~ ... Q) OS a -~ OS ~ a j 8 ~ ~ ~ E-< s:l. E-< :::1 > Q) 

~ OS s:l. a ~ a -~ ~ -~ .lid .g .Be:: .g ::l ~ OS :::1 ... as.9 ~ E' ] ...c: E-< s:l. 

~ s:l. .E ~ :a ~ 

~~ Q) c:s ~ § -~ s:l. s:l. ~ ~ j _g 

i E-< ~ OS OS "i5. ae >. ..( ~ E-< _g E-< ~ ~ Q) s:l. a Q) c:: ·;; c:: ~ ::l c:: -~ s:l. ~ § ·;; .lid 

~ OS -~ -a. ~ j ~ ~cS 01 

~ t 8 'ti ~ OS s:l. c:: 8 ~ ~ c:: -~ ..... 0 s:l. 1ll c ~ s:l. s:l. ~ ~ a 01 

~0 ~ s:l. 01 -~ !1;j g. .~ ~ s:l. 01 ...c: s:l. :.;; c:s 01 ::l c ...c: "' 01 E-< a 0 gj ~ g s:l. E-< C) _g E: 01 §- f} ~ 01 ~ ~ :::1 E-< •t ] C) ~ E-< -~ g ;~ z :! :; ... l ~ .E .5 .g -~ -~ -e ~ -~ ... :::1 j .E ll! -~ .S, c:s 

~ .8 ~ ~ e- .t:! ·;; E: ~ :; :; 

i? :::: -g ~ ..s ~ ~ "f. '".:! ~ .5 ~ E: c:s "' :; g. g. ~ g. E: ·.g ~ ]' a g. ,g 1il g. "@> c:s -~ .g .2 -o E: "1::1 

:::1 E: g. ~ ~ ~ i:! ~ E: E: c:s ~ c:s 

Sample number ft m CQ ~ ~ C!l C!l :X:: E... ~ ~ en ~ ~ 

69ADt-143, unit 1 0--70 0--21.3 R R R c R R R c c R unit 3 100--220 30.5-67.0 c c c R 69ADt-52A 300--400 91.4-121.9 R R R R 53 A Base Base R R R R 53B 0--75 0--22.9 R R R R c R R 60A 0--50 0--15.2 R R R R R R R c R R 60B 50--150 15.2-45.7 R R R R c R c 70ARr-426A 0--200 0--61.0 v R v A R R R 426B 200--400 61.0--121.9 R R R R R c c R 

4260 600--800 182.9--243.8 c R R R 430 0--25 0--7.6 R c R R R 

25-50 7.6--15.2 R A v R c 40 12.2 R R R R 53 16.2 R R c R c 60--65 18.3-19.8 R A R R R c 80--85 24.4-25.9 R R A c R 

95-105 28.9--32.0 120--130 36.6--39.6 R 

130--145 39.6--44.2 R R 

145-155 44.2-47.2 155-170 47.2-51.2 R 

175-180 53.3-54.9 R 184-190 56.0--57.9 R R R 

70ADt-240, unit 4 0--50 0--15.2 A R R 

50--100 15.2-30.5 c R 

100--150 30.5-45.7 R R c R 

200--250 61.0--76.2 R R R 

250--280 76.2-85.3 R 

69ADt-143, unit 4 210--310 64.0--94.5 R R c 

70AJ)t-213A 0--50 0--15.2 R R 

239 200 61.0 c R 

70ARr-426E 800--1,000 243.8-304.8 R R c R 

426EE 1,000--1,200 304.8-365.8 R c R 

71ADt-288, unit 4 0--200 0--61.0 A R R R 

Type section 

70ADt-209, unit 1, #18 1,400--1,450 426.7-428.3 R R R R #22 1,150--1,200 350.5-365.8 R R #21 1,200--1,350 365.8-411.5 R R R R #23 1,100--1,150 335.3-350.5 R #24 1,050--1,100 320.0--335.3 R R #25 900--1,050 274.3-320.0 R R c R 

70ADt-211 75-100 22.9--30.5 R R 70ADt-213, #2 1,000--1,050 304.8-320.0 R R R R #4 900--950 274.3-289.6 R R 

#8 700--750 213.4-228.6 c #9 650--700 198.1-213.4 R 

#10 600--650 182.9--198.1 c R 

#11 550--600 167.6--182.9 R R 

214, #1 400--450 121.9--137.2 R R 

#3 350--400 106.7-121.9 R #4 300--350 91.4-106.7 R R R #6 100 30.5 
STRATIGRAPHY 27 

mainly of subfeldspathic lithic graywacke (Williams 

and others, 1958, p. 302) with interbeds of siltstone, 

shale, and conglomerate. The conglomerate primarily 

black chert, is a major constituent only at the reference 

locality, although similar conglomerate and pebbly 

sandstone beds are present in the type area. 

The graywacke is a dark-grayish to green rock, fine to 

coarse grained, and thin to massively bedded. Small 

angular lithic fragments are a common feature of many 

chart for Kongakut Formation 

abundant (26-50); V = very abundant (>50)] 

Transition fauna 

R == == -- --

R 

R 

R" R R 

ii R 

R == ii -- -- ii -- -- ii --

~ R == ~ R R R 

R --

c -- --

R 

R -- A 

beds. Some of the units are cross bedded and others are 

graded. Flute and load casts are common on the thinbedded fine-grained graywacke. The overall depositional pattern of the Bathtub Graywacke is cyclic, 

with units of siltstone and shale following each major 

unit of graywacke or ·conglomerate. The duration of 

each cycle became shorter as time progressed, probably in response to increased orogenic activity in the 

source area. 

R -- --

R -- R 

R 

R 

R R 

R -- -- -- -- R 

R -- -- -- --

-- -- -- -- c == R R --

c -- -- -- -- c -- R R R -- -- R R R 

R 

c --

R 

ii == ii 

R 

R 

R ~ -- -- .-- -- R 

-- c 

c -- -- R R R -- -- R --

R 

R == 

-- R R R 

-- R 

R 

v 

R R --

R 

R R -- R ~ 

R 

R R -- -- -- -- R C 

c ~ ~ -- -- -- -- c ~ ~ R R __ __ __ __ R 

R 

R -- -- -- -- A -- C 

R 

c :: __ __ __ v -- ii c 

Type section 

R 

R -- R R -- -- R --

__ C == ~ R -- R 

R R R __ R R R -- R --

R ii -- == -- -- --

R R 

R 

R R 

R R 

~ ii 

-- -- -- -- R 

-- -- -- -- R 

R 

R 

R 

R R R R R 

R 

R R 
28 POST-CARBONIFEROUS STRATIGRAPHY, NORTHEASTERN ALASKA 

Thin sections show that lithic clasts, consisting of 

chert, quartzite, phyllite, slate, shale, and siltstone, 

form 40 to 70 percent of the rock. Most are subround to 

round with little size sorting. Subangular quartz is the 

only primary mineral grain of major importance. The 

feldspar content is generally no more than 5 to 10 percent of the total rock; this probably reflects a source area 

in the Brooks Range, an area of relatively few igneous 

rocks. The matrix is mainly sericitic clay and chlorite. A 

few beds contain minor amounts of secondary calcite, 

but calcareous cement is rather uncommon for these 

rocks. Isotropic, well-rounded grains of phosphate are 

present in most thin sections, which suggests that beds 

at least as young as the Shublik Formation were being 

eroded and reworked. Plant debris is common, particu12 

Type section, 

Bathtub Ridge 

13 

Reference section, 

Sabbath Creek 

METRES FEET 

180 600 

120 400 

60 200 

LITHOLOGIC 

SYMBOLS 

r-::::::::1 

t:::=.:::l 

Conglomerate 

Conglomeratic 

~ 

~ 

sandstone 

Sandstone 

Graywacke 

~ 

~ 

Siltstone 

Shale 

Clay ironstone 

nodules 

Calcareous 

cement 

Covered interval 

larly at the reference locality, where many stems and 

twigs are present. Carbonaceous material occurs in all 

thin sections. 

The provenance of sediments for the Bathtub 

Graywacke was clearly south in the ancestral Brooks 

Range; this is based on directional sedimentary features 

and greater thicknesses of sandstone (graywacke) in the 

southern exposures. The character of these beds is entirely different from any of the older Mesozoic 

sandstones. The older sandy beds are quartz arenites, 

whereas the Bathtub is primarily graywacke. Lithic 

clasts in the graywacke and conglomerate suggest that 

some of the older Mesozoic rocks were being eroded and 

included in the Bathtub sediments. The source of some 

older Cretaceous rocks may have been to the south, also, 

but the Bathtub Graywacke is the first unit that we can 

definitely prove to have had a southern source area. 

Age.-The age of the Bathtub Graywacke is not 

known directly from fossils. Invertebrate remains have 

not been located in these beds, and plant fossils collected 

for paleobotanical identification gave disappointing results. According to J. A. Wolfe (written commun., 1971), 

the only identifiable material was Equisetum, which is 

long ranging and of little use for age determinations. 

The pollen and spore samples produced similar results. 

They were examined by R. A. Scott, who states (written 

commun., 1972) that a few fragments of the marine alga 

Tytthodiscus were found. This is common in Upper 

Jurassic and Lower Cretaceous rocks of northern Alaska. In addition a few reworked spores of Devonian age 

were identified. All samples collected for Foraminifera 

were barren. 

The age of these beds can be determined fairly accurately, however, from faunal remains in the underlying 

and overlying beds. The underlying Kongakut Formation is at least as young as Hauterivian, on the basis of 

ammonites, and may be as young as Barremian, as 

suggested by Foraminifera. One poor collection of 

pelecypods from the Kongakut pebble shale was identified by D. L. Jones (written commun., 1972) asAucellina? sp. This would suggest that beds underlying the 

Bathtub were as young as Aptian. Although the Aptian 

Stage has never been positively identified in northern 

Alaska, it is present a short distance to the east, in 

northern Canada (Norris, 1972). The overlying Tuktu 

Formation contains ammonites of middle Albian age, so 

the Bathtub Graywacke probably represents an early 

Albian deposit that is at least in part equivalent to the 

Fortress Mountain Formation of Central Alaska. 

NANUSHUK GROUP 

o o The Nanushuk Group was defined by Gryc, Patton, 

FIGURE 9.-Type and reference sections for the Bathtub Graywacke. and Payne (1951) as a sequence of rocks typically ex-
STRATIGRAPHY 29 

posed in the central part of the northern foothills about 

240 km (150 mi) west of this report area. These rocks 

have been subdivided and redefined several times since 

then (Gryc and others, 1956; Detterman and others, 

1963). The group contains both marine and nonmarine 

formations that are mapped along the Sagavanirktok 

and Ivishak Rivers (Keller and others, 1961). Recent 

investigations in northeastern Alaska have shown that 

rocks included in the lower part of the Ignek Formation 

in the western Sadlerochit Mountains are better considered part of the Nanushuk Group, and the term is here 

extended into that area. 

A few small rubble exposures west of the Kavik River 

are mapped as (!Nanushuk Group undivided" (Reiser 

and others, 1971). A fairly thick sequence of the 

Nanushuk Group is exposed south and east of the Sadlerochit Mountains. These rocks can be identified as 

part of the Tuktu and Chandler Formations. The 

Nanushuk Group is missing north and northwest of 

the Sadlerochit Mountains. This area was a structural 

high during Triassic to Neocomian time, and the Nanushuk may never have been deposited there. If deposited, 

it was eroded away before the Colville Group was 

deposited. TUKTU FORMATION 

Name and distribution.-The Tuktu Formation 

was originally defined as a member of the Umiat Formation by Gryc, Patton, and Payne (1951) and later 

raised to a formation within the Nanushuk Group by 

Detterman (1956a). Its type locality was established at 

Tuktu Bluffs on the Chandler River. Rocks that are 

considered correlative with this formation are best exposed in the ar.ea between the east end of the Sadlerochit· 

Mountains and the Okerokovik River. One reference 

section (fig. 2, loc. 14) is well exposed along Arctic 

Creek, lat 69°27'30" to 69°30' N., long 144°30' to 144°34' 

W. Another reference section was measured along Sabbath Creek (fig. 2, loc. 15). Good exposures are present, 

also, along· the Kekiktuk and Hulahula Rivers, and 

small ridgetop rubble traces occur between the Okpilak 

and Jago Rivers (Reiser and others, 1974). 

Thickness and stratigraphic relations.-The reference section for the Tuktu Formation along Arctic 

Creek is 215m (700ft) thick (fig.'10). At this locality the 

Tuktu unconformably over lies the pebble shale member 

of the Kongakut Formation; this is not a complete section as the overlying rocks have been removed by erosion. A more complete section of the formation is present, however, at the reference section on Sabbath 

Creek, where about 520 m (1,700 ft) was measured (Fig. 

10). A 65-m (220 ft) covered interval separates the 

Tuktu Formation from the underlying Bathtub 

Graywacke; this covered interval is here included with 

the Tuktu for convenience in mapping, thus making the 

Sabbath Creek section comparable to the thick sections 

exposed in the Killik-Etivluk region about 450 km (280 

mi) to the west. 

The lower contact with the Bathtub Graywacke, 

while not actually exposed, probably should be considered as a disconformity inasmuch as the Tuktu Formation is known to be unconformable on the Kongakut 

Formation at Arctic Creek. The Tuktu Sea must therefore have been transgressive across the area. The upper 

contact with the Chandler Formation is conformable. 

Lithology.-The Tuktu Formation is mainly an interbedded sequence of thin-bedded fine-grained 

greenish-yellow calcareous sandstone, dark siltstone, 

and shale. Several massive yellowish-brown sandstone 

units occur at intervals throughout the section. Many of 

the sandstones on Arctic Creek contain abundant 

prisms of broken Inoceramus shells; some are almost 

Inoceramus-prism calcarenite. Sole markings are a 

diagnostic feature of most of the Tuktu sandstones and 

siltstones. These are mainly in the form of flute and load 

casts, although skip and drag marks and flame structures are also present, suggestive of deepwater turbidite 

deposition. However, the Inoceramus-prism beds would 

indicate a shallow-water depositional site, and the Sabbath Creek section is extensively crossbedded. In addition, many of the crossbedded sandstones contain lenses 

and stringers of pebble conglomerate suggestive of 

shallow-water deposition. These pebbly and conglomeratic beds are very similar to the Tuktu as exposed in the K urupa and Oolamnagavik Rivers area 386 

km (240 mi) to the west (Chapman and others, 1964). 

· Several thick beds of shale occur throughout the section on Arctic Creek. Clay ironstone nodules and small 

limestone concretions are fairly abundant throughout 

the shale, and mud lumps are common. Carbonaceous 

material and plant scraps are common at Sabbath 

Creek. In general the Tuktu Formation in northeastern 

Alaska is very similar to that in the more northerly and 

westerly exposures in its type area in the Chandler and 

Colville Rivers region. 

Age.-The Tuktu Formation contains a sparse molluscan fauna, primarily in the sandstones on Arctic 

Creek. The diagnostic element of this fauna is the ammonite Paragastroplites spiekeri (McLearn), which according to Imlay (1961) is indicative of the middle Albian Stage of the Early Cretaceous. These same beds 

contain the Inoceramus prisms, and although no complete specimens were found, Inoceramus is fairly common in the Albian beds of the type Tuktu Formation. A 

few unidentifiable pelecypods and the chaetopod worm 

Ditrupa cornu Imlay are found in the lower sandstones. 

Ditrupa is common in the middle and late Albian beds 
30 

c: 

0 

~ 

E 

6 

u. 

~ :I 

..... 

14 

Arctic Creek 

.~ 

POST-CARBONIFEROUS STRATIGRAPHY, NORTHEASTERN ALASKA 

15 

Sabbath Creek 

···-···-·-

:::..;...·_f=R·::-:-: 

···=··· 

-----a> 

:':::·~-:-_:_.:: ~~ 

X 

~~~~o;p~;;,~o 

~-~ --=;.~{:_ 

:-:-:-:-.-:·:·.-·_.·_.·_ :_'\ ··-·· ······· 

16 

Sabbath Creek 

X 

-----

~-~-d.~~~Ob~ 

:::::-=:::: 

-=-~-=-==-~ o,oo.o .,D~C:.-0 

c.- cac.Cio-et -oc:::. 

x·~·· 

~:~-~~ .. -f'g~::J 

X 

'?~o 0 O~.O~oO.) 

.. _:_[ oa.oc.. o 

X 

.:.;_ -__:_:-=.:·:=( - • 0 •. -

.=-:..:..:.::::~=c oo ~ -

Oo-O--o-~- 0•00·00-0 

~-~--=-""':"7" 

a· oo · o - a 

E>~=~ 

--~ 

---:z 

---&3 

- -::-~ 

~a~~ct;o~;;-~( 

---:=\.. 

'g~O: :oc:-~o"o o 

~~~ =-:. == .. ::.;_-_;_;-

:.:_ -,;e_·_ 

I 

FIGURE 10.-Reference sections for the Tuktu and Chandler Formations. 

LITHOLOGIC 

SYMBOLS 

Sandstone 

F3 

~ 

Graywacke 

~ 

~ 

Conglomeratic 

sandstone 

Conglomerate 

Siltstone 

~ 

~ 

Silty shale 

Clay shale 

Calcareous 

cement 

Limestone 

concretions 

Clay ironstone 

nodules 

Covered interval 

METRES FEET 

180 600 
STRATIGRAPHY 31 

farther west, but is· also found _in Neocomian beds on 

Arctic Creek. 

A few Foraminifera were found in shale samples collected for microfossils along the Sadlerochit River. Two 

are considered diagnostic of the middle and late Albian 

Stage: Verneuilinoides borealis Tappan and Trochammina ribstonensis Wickenden subspecies rutherfordi 

Stelck and Wall. In addition, specimens of Bathysiphon 

brosgfd Tappan, Glomospirella gaultina (Berthelin), 

Ammodiscus rotalarius Loeblich and Tappan, and 

Gaudryina were found. These microfossils are all 

characteristic of the Tuktu Formation in its type area. 

CHANDLER FORMATION 

Name and distribution.-The Chandler Formation 

was first described by Gryc, Patton, and Payne (1951, p. 

164) as the nonmarine formation of the Nanushuk 

Group. It was subsequently divided into the Killik and 

Niakogon Tongues (Detterman, 1956a) which, in the 

type area, grade northward into the marine equivalent 

of the Chandler. 

In northeastern Alaska, the Chandler Formation is 

confined to a small area between the lower Okpilak 

River and the Okerokovik River. A good section exposed 

along Sabbath Creek (fig. 2, loc. 16) is considered a 

reference section for northeastern Alaska, and was the 

only section investigated. in detail. The rocks are mapped as Chandler Formation, undivided. Both tongues of 

the formation may be present, but bentoninte characteristic of the Niakogon Tongue was not seen along 

Sabbath Creek, and the rocks are more typical of the 

Killik Tongue. 

Thickness and stratigraphic relations.-The Chandler is 1,456 m ( 4, 775ft) thick at the reference section on 

Sabbath Creek (fig. 10). This is somewhat thicker than 

at the type area but not unusually so. Northeastern 

Alaska represents a basin of deposition that probably 

was separated from the area to the west, so the general 

character and thickness could be expected to be somewhat different. In general, however, there is good correlation between the two areas. 

The Chandler Formation conformably overlies the 

Tuktu Formation at the reference section. The contact is 

placed at the base of a massive pebble-cobble conglomerate with fairly abundant white quartz. Sandstones 

above the conglomerate are primarily medium- to 

coarse-grained salt-and-pepper type, in contrast to the 

fine-grained greenish calcareous rock below the contact. 

The presence of white quartz clasts in the conglomerate 

and the salt-and-pepper sandstone are prime characteristics of the Chandler formation in the type area. 

The upper contact is not exposed in northeastern 

Alaska. The Colville Group is present about 16 km (10 

mi) to the north and in all probability unconformably 

overlies the Chandler Formation. 

Lithology.-The Chandler Formation is entirely 

nonmarine in northeastern Alaska. The Grandstand 

and Ninuluk Formations, the marine equivalents of the 

Chandler, have not been identified but presumably may 

be present in the subsurface near the north coast. 

Cyclic deposition of polymictic conglomerate, saltand-pepper sandstone, siltstone, and shale is characteristic of the formation. The rocks contain abundant 

features indicating fluvial deposition including cutand-fill channels and point-bar-type crossbedding in the 

sandstones and conglomerates. The coarse clastic rocks 

are overlain by dark siltstones and silty shale units 

containing abundant plant debris; these are interpreted 

as being overbank fluvial deposits. 

The polymictic conglomerate consists mainly of varicolored chert, black and gray being the most common 

colors, white quartz, gray quartzite from the Echooka 

Formation, limestone derived from both the Lisburne 

Group and Shublik Formation, and minor amounts of 

other rock types. Most clasts are well rounded and 1.3 to 

5 em (¥2 to 2 in.) in diameter, although the size varies 

from fine granules to 15-cm (6 in.) cobbles. Many of the 

conglomerate beds are lenticular, and cut-and-fill structures are common. Most beds are poorly consolidated, 

having a matrix of clay and sand, and many show 

graded bedding. 

Sandstone associated with the conglomerate is 

primarily of the salt-and-pepper type, medium to coarse 

grained, and massive; it is 40-70 percent dark lithic 

fragments, 10-15 percent quartz, 5-10 percent feldspar, 

and minor accessory minerals in a clay matrix. 

Sandstone interbedded with siltstone between conglomerate bed~ is generally thin bedded, fine grained, 

gray, and slightly calcareous. Mud lumps and ironstone 

concretions are common in· the thin bedded sandstone. 

Much of the siltstone and shale is micaceous and 

carbonaceous and dark-gray to black. Plant debris is 

abundant in all of these fine clastic rocks, but no coal 

beds were seen. Coal is a common feature of the Chandler Formation in the type area, but the deposits in 

northeastern Alaska apparently represent a river flood 

plain rather than the deltaic coal swamps of the type 

area. 

Age.-No identifiable fossil material was obtained 

from the Chandler Formation in the area of this report, 

so the age of the beds cannot be determined directly. The 

formation is, however, considered to be of middle and 

late Albian age, because it overlies the early middle 

Albian Paragastroplites beds of the Tuktu Formation, 

and because it contains no bentonite or tuff. All Cretaceous strata in northern Alaska of Cenomanian or 

younger age contain abundant bentonite or tuff as beds 
32 POST-CARBONIFEROUS STRATIGRAPHY, NORTHEASTERN ALASKA 

and lithic fragments; this is also true of the Tertiary 

strata. Consequently, the Chandler Formation in 

northeastern Alaska cannot be younger than late Albian.· 

COL VILLE GROUP 

The Colville Group was originally defined as a (!series" by Schrader·(1902) for a sequence of rocks exposed 

along the lower Colville River, about 160 km (100 mi) 

west of the report area. These beds were later redefined 

as the Colville Group by Gryc, Patton, and Payne (1951) 

and Gryc and others (1956). The group includes the 

Seabee, Prince Creek, and Schrader Bluff Formations, 

which were further divided into marine members and 

nonmarine tongues. The group was mapped only in the 

central and western parts of northern Alaska. Beds 

farther east, believed to be in part equivalent, were 

mapped as the upper part of the Ignek Formation by 

Keller, Morris, and Detterman (1961). During therecent investigations we have studied many more sections 

of these rocks, and here extend the term Colville Group 

into northeastern Alaska. The Ignek Formation is 

abandoned. The stratigraphic units of the Colville 

Group can be easily recognized and mapped in the 

northeast, so the extension of the term into this area 

is justified, particularly because the Ignek Formation 

included a heterogeneous assemblage of rocks of 

several ages. SEABEE FORMATION 

Name and distribution.-The Seabee Formation 

was originally defined as a member of the Schrader 

Bluff Formation by Gryc, Patton, and Payne (1951, p. 

166). The member was redefined as a formation by 

Whittington (1956, p. 246) and further divided into the 

Shale Wall Member (Detterman and others, 1963, p. 

269) and Ayiyak Member (Detterman, 1956b, p. 253). 

The formation was defined to include all marine strata 

in the Col ville Group below the nonmarine Prince 

Creek Formation. These rocks include a lower bentonitic clay shale; in part a fissile organic shale (Shale Wall 

Member), and an upper sandstone and siltstone unit 

(Ayiyak Member). 

The best exposures of the Seabee Formation in northeastern Alaska are in Ignek Valley (fig. 2, loc. 17) and 

along the north side of the Sadlerochit Mountains. In 

these areas the formation contains the distinctiye ((red 

beds" after which Ignek Valley is named. These highly 

colored ((red beds" are very prominent and can be seen 

for many miles, particularly the ones near Red Hill. 

Leffingwell (1919, p. 121) considered the beds to be 

burnt coal. It is now believed that these beds were 

formed by the oxidation or possibly burning of the 

highly organic paper shale at the base of the Seabee 

Formation. This shale, when heated, turns red. The actual source of the heat is not known; it could have been 

produced by a chemical reaction or by burning of the 

shale. Similar beds in the Smoking Hills, east of the 

Alaska-Yukon boundary, in northern Canada give off 

great clouds of smoke, although no fire is visible. 

Other outcrops of the Seabee Formation are found as 

discontinuous cutbanks along many of the streams in 

the foothills and in the coastal plains (Reiser and others, 

1971 and 1974). Geologic structures on the coastal 

plains are mainly flanked by low-dipping beds; consequently, the area of outcrop is generally broad. Beds of 

the Shale Wall Member are poorly consolidated and do 

not form good exposures except where capped by the 

overlying sandstone of the Ayiyak Member. 

Thickness and stratigraphic relations.-Most exposures of the formation are incomplete and generally 

covered by rubble and mudflows formed of the weakly 

consolidated rocks. Consequently, many of the stratigraphic details, as well as possible changes in facies and 

thickness, are not well understood. One fairly good section of both members was obtained from the south side 

of Ignek Valley, along Ignek Creek (figs. 2 and 11), 

where approximately 260 m (850 ft) of beds are preserved (lat 69°33'30" N., long 145°50' W. At this locality 

the Shale Wall Member is 120 m (400ft) thick and is: 

separated by a fault from the overlying Ayiyak 

Member. Displacement along the fault is minor. No 

other sections of the formation were measured in northeastern Alaska, so direct comparisons with other areas 

cannot be made. However, on the basis of the general 

stratigraphic details of other outcrop sections and the 

interval penetrated by drilling along the north coast 

(Fackler and others, 1971), this 260m (850ft) is probably a minimum thickness for the formation in northeastern Alaska. 

The contact between the members of the Seabee Formation is a sharp sandstone-on-slale break. The contact 

with the underlying beds is a major Cretaceous unconformity throughout northern Alaska. In the area of this 

report the Seabee rests on beds ranging in age from 

Early Cretaceous to Middle Jurassic. At many localities 

on the Arctic Coastal Plain the formation is unconformably overlain by stratified to unsorted surficial deposits. 

Elsewhere, the sandstone of the Ayiyak Member grades 

into sandstone of the overlying Prince Creek and 

Schrader Bluff Formations. 

Lithology.-The Shale Wall Member of the Seabee 

is mainly a dark, poorly consolidated, thinly bedded, 

bentonitic clay shale. The bentonite occurs primarily as 

beds 1.3 to 5 em (% to 2 in.) thick every metre or so. 

About 57 m (175ft) ofthe upper part ofthe Ignek Creek 

section is composed of the fissile, organic paper shale. In 

this shale the bentonite beds are no more than 0.6 em (14 
c 

0 

~ 

E 

~ 

Q) 

Q) 

~ Q) 

(/) 

Q; 

.0 

E 

Q) 

~ 

~ Q) 

iij 

.r::. 

(/) 

17 

South side of 

lgnek Valley 

c .... oa> 

~.0 ClE tUCD 

(/)~ 

STRATIGRAPHY 

18 

Ridge southwest 

of Kavik airstrip 

19. 

Sag won 

LITHOLOGIC SYMBOLS 

Sandstone 

Graywacke 

Conglomeratic 

sandstone 

Siltstone 

Silty shale 

Clay shale 

Coal 

G 

Tuff 

Carbonaceous 

shale 

Bentonite 

Pebble shale 

Limestone 

concretions 

Clay ironstone 

nodules 

Manganese 

nodules 

Covered 

interval 

FIGURE 11.-Measured sections of the Seabee and Prince Creek Formations. 

METRES 

120 

90 

60 

30 

33 

FEET 

400 

300 

200 

100 
34 POST-CARBONIFEROUS STRATIGRAPHY, NORTHEASTERN ALASKA 

in.) thick and occur every 5 to 10 em. Large limestone 

concretions are present throughout much of the section, 

but somewhat more abundant in the lower part. 

The upper part of the Shale Wall Member is a bedded 

tuff that weathers various shades of gray, green, and 

pink. This rock, as seen in thin section, is a devitrified 

welded tuff composed of 90 percent glass shards. The 

shards show good parallel orientation, with a few sharp 

crescentic spears that are parts of broken bubbles. Devitrification has produced mainly cristobalite and 

feldspar. In some rocks the process is nearly complete; 

and in others it has barely started. Crystals of 

plagioclase, orthoclase, and quartz are present in a few 

of the tuffs but are nowhere more than a few percent of 

the total rock; opaque crystallites are more common and 

may constitute 10 percent of some specimens. 

The Ayiyak Member is an interbedded sequence of 

sandstone, siltstone, and shale. The repetition of the 

various lithologic types is somewhat cyclic (fig. 11). The 

sandstone beds are 6 to 12 m (20 to 40 ft) thick and 

separated by 30 to 45 m (100 to 150ft) of siltstone and 

shale with minor tuff beds in the upper part. The 

sandstone is thin to medium bedded, fine grained, argillaceous, and micaceous. These rocks weather grayish 

orange to dark yellowish orange. Some of the sandstone 

appears to have a tuffaceous matrix, but the rock was 

not examined in thin section. 

Age.-No diagnostic megafossils were collected 

from the Seabee Formation in northeastern Alaska, so a 

precise correlation with beds in the type locality near 

Umiat is impossible at this time. Large limestone concretions are common to both areas, and they contain a 

diagnostic ammonite and pelecypod fauna in the region 

west of this report area. This fauna includes the 

ammonites Scaphites sp., Borissjakoceras sp., and 

Watinoceras sp., and the pelecypods Inoceramus 

labiatus (Schlotheim) and Inoceramus aff. I. cuvierii 

Sowerby (Jones and Gryc, 1960). According to Jones 

these fossils indicate a middle to late Turonian age for 

these beds. 

A few radiolarian microfossils were found in samples 

from the reference section of the Shale Wall Member 

along Ignek Creek. These include Cenodiscus sp., 

Cenosphaera sp., Spongurus sp., and Theorcorys sp. According to Bergquist (written commun., 1971) these 

radiolarians are found in Turonian to Santonian rocks 

and indicate a possible correlation with the beds in the 

type area where the same radiolarians are found 

(Bergquist, 1966). Two samples obtained from the Seabee Formation contained the Turonian Foraminifera 

H aplophragmoides spiritense Stelck and Wall, V erneuilinoides cf. V. fischeri Tappan, Bathysiphon vitta 

Nauss, Ammodiscus cretaceous (Reuss), and Saccommina sp. According to Bergquist (written commun., 

1972) these are similar to species found in the Turonian 

Kaskapaw Formation of Alberta. 

A positive correlation based on fossils cannot be made 

between northeastern Alaska and the type locality, but 

a distinctive lithology is present in both areas and there 

can be little question that the beds in northeastern 

Alaska should be included in the Seabee Formation. 

PRINCE CREEK FORMATION 

Name and distribution.-The Prince Creek Formation was named by Gryc, Patton, and Payne (1951, p. 

166), who further divided it into a lower Tuluvak 

Tongue and an upper Kogosukruk Tongue. The type 

locality is along Prince Creek, a tributary of the lower 

Colville River about 160 km (100 mi) west of this report 

area. As defined, the formation includes all Late 

Cretaceous nonmarine beds above the Seabee Formation. The Prince Creek intertongues with its marine 

· equivalent, the Schrader Bluff Formation. 

In the area of this report the Prince Creek and 

Schrader Bluff Formations are not mapped separately 

(Reiser and others, 1971 and 1974), primarily because of 

the isolated, discontinuous cutbank exposures of these 

rocks. Some of these strata were originally included as 

the upper member of the Ignek Formation by Keller, 

Morris, and Detterman (1961), but as previously 

explained (p. 32) the units of the Colville Group can be 

easily recognized and mapped in northeastern Alaska. 

The Prince Creek Formation underlies the northernmost hills at the south edge of the Arctic Coastal 

Plain. They form a northeast-trending belt 8 to 24 km (5 

to 15 mi) wide between the Sagavanirktok and Aichilik 

Rivers; this belt also contains the Schrader Bluff Formation. The hills are mainly rubble covered, and the 

two formations are not always distinguishable. However, stream cutbank exposures are generally preserved 

well enough that not only the formation but the subunits can be determined. 

Thickness and stratigraphic relations.-A complete 

section of the Prince Creek Formation has not yet been 

located in northeastern Alaska, so the aggregate thickness is unknown. The two partial sections obtained (fig. 

11, locs. 18 and 19) indicate that the Tuluvak Tongue is 

at least 270m (800ft) thick and the Kogosukruk 70 m 

(230ft) thick. The Tuluvak west of the Kavik River, lat 

69°37' N., long 146°54' W., compares favorably with 

that reported in the type area (Brosge and Whittington, 

1966, pl. 54), but the Kogosukruk is considerably thinner than it is to the west. Only the upper part of the 

Kogosukruk, including the contact with the overlying 

Tertiary beds, is exposed in the bluff opposite Sagwon 

(fig. 2, loc. 19), lat 69°23'15" N., long 146°14' to 146°17' 

W., so the actual thickness may correspond to the 350m 

(1,150 ft) present in the type area. 
STRATIGRAPHY 35 

The stratigraphic relations between the tongues of either the Late Cretaceous or early Tertiary, but strathe Prince Creek and the members of Schrader Bluff tigraphic evidence suggests that it is between the two. 

Formation are almost impossible to determine in north- Siltstone and shale are a major part of both tongues of 

eastern Alaska, as the discontinuous outcrops rarely the Prince Creek Formation. Most of these are dark and 

contain a contact between any of the subunits. The contain considerable plant debris. The plant material is 

contacts are assumed to be gradational as they are in concentrated in some beds forming carbonaceous shale 

the type area. The Kogosukruk is overlain conformably and coal units as much as 1.2 m (4ft) thick in parts of the 

by early Tertiary beds near Sagwon, and the Tuluvak is Kogosukruk. Coal was not found in the Tuluvak Tongue 

in apparent conformity with the Seabee Formation in northeastern Alaska, although it is present in the 

along Juniper Creek. Throughout most of northeastern type area. The Tuluvak does, however, contain considAlaska the Prince Creek Formation is unconformably erable carbonaceous material in the form of plant stems, 

overlain by stratified to unsorted surficial deposits. twigs, and leaves. 

Lithology.-As defined, the Prince Creek contains Age.-The nonmarine Prince Creek Formation has 

all of the Late Cretaceous nonmarine strata above the yielded no identifiable fossils in northeastern Alaska. 

Seabee Formation (Gryc and others, 1951, p. 166). These Plant fragments are common, but most are nondescript 

are mainly sandstone, conglomerate, siltstone, shale, stems of little value. The age of these rocks is based 

coal, and carbonaceous shale. The rocks are in general entirely on analogy with similar beds in the type area 

poorly consolidated and do not form good exposures; this where they intertongue with fossil-bearing marine 

is particularly true of the Kogosukruk Tongue. The strata of the Schrader Bluff Formation. These fossils are 

Kogosukruk Tongue is finer grained and darker than considered to represent the Santonian and lower Camthe Tuluvak Tongue, and it contains most of the thick panian Stages of the Late Cretaceous (Jones and Gryc, 

coal beds. 1960, p. 153). In the type area for these formations the 

The sandstone is primarily a subfeldspathic lithic lowest part of the Tuluvak underlies and the Kogosukarenite, 30 to 60 percent clasts of chert, quartzite, shale, ruk overlies all parts of the Schrader Bluff Formation. 

and phyllite. Quartz makes up another 30 to 40 percent, Thus, the Prince Creek probably represents a greater 

feldspar about 5 to 8 percent, and sericitic clay matrix 5 part of the Late Cretaceous than does the marine sequto 8 percent. Some of the sandstone contains a tuffaceous ence. An earlier age limit is placed on these strata by the 

or bentonitic matrix, and tuff is also present as fact that they overlie the late Turonian beds of the 

clasts in some of the conglomeratic beds. Units of clean, Seabee Formation. The Kogosukruk may be in part of 

porous sandstone 3 to 15m (10 to 50ft) thick are fairly Maestrichtian age but can be no younger than Cretacecommon in the Tuluvak Tongue, but sandstone of the ous, as the overlying basal Sagavanirktok Formation 

Kogosukruk is mainly thin bedded and dirty. Mostof contains a Paleocene flora. 

the Tuluvak sandstones contain a few pebbles 0.6 to 5 

em(~ to 2 in.) in diameter, of the same composition as 

the lithic fragments in the sandstone. 

The sandstone at the top of the Kogosukruk section at 

Sagwon (fig. 11, loc. 19) is of special interest. This rock is 

highly saturated by petroleum and gives off a strong 

odor of crude oil when fractured. The rock is stained a 

dark brown, and the odor is very strong even at a distance of 9 to 12 m (30 to 40 ft). This same bed has been 

traced in numerous outcrops from Sagwon to the Arctic 

Coast near the mouth of the Aichilik River, a distance of 

260 km (160 mi). This bed locally contains lenses of 

conglomerate, and pebbles of tasmanite are included 

with the other lithic clasts. The tasmanite was probably 

derived by the erosion of a Jurassic source bed to the 

south of this area (Boneham and Tailleur, 1972). 

The oil-saturated sandstone is considered the uppermost unit of the Upper Cretaceous, primarily because it 

is more indurated and darker than the overlying rocks. 

In addition, in sections east of Sagwon the overlying 

rocks are not the same, indicating a disconformable 

relationship. This hiatus could, admittedly, be within 

SCHRADER BLUFF FORMATION 

Name and distribution-The Schrader Bluff Formation was defined by Gryc, Patton, and Payne (1951, p. 

165) as the uppermost marine unit of the Cretaceous in 

central Alaska, and the type locality was designated on 

the lower Anaktuvuk River at Schrader Bluff, after 

which it was named. They further divided the formation 

into three members: in ascending order, the Seabee, 

Tuluga, and Sentinel Hill. Whittington (1956, p. 249--

252) redefined the Schrader Bluff. He raised the Seabee 

to formation status, abandoned the Tuluga Member, 

and established two new members, Rogers Creek and 

Barrow Trail. The Sentinel Hill Member remained unchanged (fig. 4). 

In northeastern Alaska the formation is present in 

discontinuous cutbanks along some of the major 

streams on the Arctic Coastal Plain. It is currently 

mapped as undivided from the Prince Creek Formation 

(Reiser and others, 1971 and 1974). The members, as 

well as the formation, can be separated in individual 

outcrops but are combined for mapping convenience. 
36 POST-CARBONIFEROUS STRATIGRAPHY, NORTHEASTERN ALASKA 

The most complete section is along the Canning River, 

starting opposite the west end of the Sadlerochit Mountains and continuing north for about 13 km (8 mi). Most 

ofthe outcrops are between the Sagavanirktok andJago 

Rivers. 

Thickness and stratigraphic relations.-Partial 

sections of the three members of the Schrader Bluff 

Formation investigated along the lower Canning River, 

lat 69°36' to 69°42' N., long 146°14' to 146°17' W. (fig. 2, 

loc. 20, and fig. 12), indicate that the formation is at 

least 330 m (1,100 ft) thick. These sections were not 

investigated in detail, so the thickness there may be 

considerably greater-more like that at the type locality at Schrader Bluff (Detterman and others, 1963). 

Stratigraphic relations between the Schrader Bluff 

LITHOLOGIC 

SYMBOLS 

Sandstone 

F3 

~ 

Conglomeratic 

~ 

~ 

sandstone 

Siltstone 

Silty shale 

Clay shale 

Bentonite 

Tuff 

Limestone 

concretions 

20 

Lower Canning River 

£ 

~ 1---v-- --\ 

co 

METRES FEET 

120 400 

·FIGURE 12.-Generalized sections for the Schrader Bluff Formation. 

and Prince Creek Formations are uncertain in northeastern Alaska. They probably can be determined with 

additional work but, at present, the contacts are considered as gradational between the intertonguing marine 

and nonmarine units, as in the type area. 

Lithology.-The Rogers Creek Member, the lowest 

stratigraphic unit of the formation, consists primarily of 

rusty-weathering bentonitic clay shale with thin interbeds of very fine grained sandstone and siltstone. Load 

and flute casts, suggesting turbidity current deposition, 

are fairly abundant on the base of most sandstone beds. 

The siltstone is micaceous and tuffaceous. 

The Barrow Trail Member is mainly sandstone of the 

feldspathic wacke type, thin to massively bedded, fine to 

coarse grained, and commonly tuffaceous. A few beds 

contain small pebbles of chert and quartz. Interbeds of 

siltstone and shale are common but not as abundant as 

in the underlying Rogers Creek Member. Tuff and bentonite are also common, both as interbeds and as the 

matrix of some sandstone and siltstone units. The tuff 

gives these rocks an overall light-gray color. One tuff 

examined in thin section was seen to be welded, with 

good parallel orientation of the shards. A few unburst 

bubbles were still visible, and the shards were only 

slightly devitrified. In general, however, the tuff content of the rocks in northeastern Alaska is considerably 

less than in the type area near Umiat. 

The Sentinel Hill Member is mainly thin-bedded, 

light-gray to tan, tuffaceous siltstone and silty shale. 

Locally the siltstone contains a few small chert granules 

and large laminated limy concretions. A few dark finegrained calcareous sandstone interbeds occur near the 

base of the section. The sandstone contains abundant 

carbonaceous material and a few chert pebbles and 

mud lumps. 

Age.-Few megafossils have been found in the 

Schrader Bluff Formation in northeastern Alaska. The 

recent investigations obtained only numerous small 

fish fragments in a tuffaceous siltstone bed along the 

west side of the Jago River; these have not been identified. Keller, Morris, and Detterman (1961, p. 206) reported finding the pen of a large squid, Teusoteuthis 

longus Logan, in correlative beds along Juniper Creek. 

This squid is common in the Niobrara Formation of 

Kansas, which is from the Coniacian and Santonian 

Stages of the Late Cretaceous. This age is in keeping 

with that obtained from pelecypods in the Schrader 

Bluff type area, where fossiliferous beds have produced 

Inoceramus steenstrupi de Loriol and I. patootensis de 

Loriol characteristic of the Santonian and Campanian 

Stages (Jones and Gryc, 1960, p. 153). 

Most of the shale samples collected for microfossils 

from the Schrader Bluff Formation were barren. One 

sample obtained from the Sentinel Hill Member along 
STRATIGRAPHY 37 

the east side of the Canning River contained a few 

specimens of the arenaceous foraminifer H aplophragmoides rota Nauss. According to Bergquist (written 

commun., 1972), this species is common in the Schrader 

Bluff Formation and also in the Grizzly Bear Shale of 

the Belly River Group (Campanian Stage) of Alberta, 

Canada. 

SAGAVANIRKTOK FORMATION 

Name and distribution.-The Sagavanirktok Formation was named by Gryc, Patton, and Payne (1951, p. 

167) for a sequence of poorly consolidated siltstone, 

sandstone, conglomerate, and lignite exposed in 

Franklin Bluffs along the lower Sagavanirktok River. 

These rocks are considered to be Paleocene and Eocene 

on the basis of fossil flora reportedly collected from them 

(MacNeil and others, 1961, p. 1807; Keller and others, 

1961, p. 208). Another sequence of the Sagavanirktok 

Formation consisting of poorly consolidated sandstone 

and siltstone along Carter Creek was briefly investigated by Morris (1953). The Carter Creek section contains fossils oflate Miocene to Pliocene age, according to 

MacNeil (1957), who considered these beds to be the 

same age as the Nuwok Formation of Dall (1920). 

The discovery of oil at Prudhoe Bay and the subsequent increased geologic investigation of the Arctic 

Coastal Plain by geologists of many petroleum companies and the U.S. Geological Survey resulted in an 

accumulation of data which in turn provoked considerable confusion as to what strata should be included in 

the Sagavanirktok Formation. Many of the wells drilled 

near Prudhoe Bay penetrated thick coal beds that are 

believed to be Tertiary, but the type locality at Franklin 

Bluffs contains no coal and there is only a minor amount 

at Carter Creek. In addition, the fossil flora which indicated a Paleocene and Eocene age for the type locality 

was in fact collected near Sagwon and not at Franklin 

Bluffs; the beds at Franklin Bluffs are younger than 

Eocene. 

The recent geologic investigations of northeastern 

Alaska covered many of the exposures of poorly consolidated rock on the Arctic Coastal Plain. In an attempt to 

dispel the confusion surrounding the stratigraphic 

limits of the formation, we here include all the beds 

above the top of the Upper Cretaceous Prince Creek 

Formation and below the Quaternary (Gubik Formation) surficial deposits in the Sagavanirktok Formation. 

The Sagavanirktok is further divided into three newly 

named members: in ascending order, the Sagwon, 

Franklin Bluffs, and Nuwok Members. Type sections 

are designated for each member, as no single outcrop 

contains a complete sequence. 

The Sagwon Member is best exposed in bluffs along 

the west side of the Sagavanirktok River about 3 km (2 

mi) northwest ofSagwon (fig. 2, loc. 23). The type section 

starts at V ABM Gard and continues south for about 1.6 

km ( 1 mi) along the river bluff, lat 69°23'30" to 69°24'30" 

N., long 148°39'30" to 148°41' W. Other sections of the 

member are present in discontinuous outcrop along the 

streams on the coastal plain as far east as the Canning 

River. The Sagwon has not been identified east of the 

Canning River, but may be present under the surficial 

deposits. The westernmost occurrence of these rocks is 

in the White Hills, about 32 km (20 mi) northwest of 

Sagwon. Fairly good exposures are present along Fin 

Creek near its junction with Juniper Creek. 

The Franklin Bluffs Member is well exposed in a 

number of small stream gullies that cut the west side of 

Franklin Bluffs, a prominent landmark on the Arctic 

Coastal Plain about 48 km (30 mi) from the coast (fig. 2, 

loc. 22). The type section is designated as along the 

stream 1.8 km (1.1 mi) S. 10° W. of V ABM Greta, lat 

69°49' N., long 148°39' to 148°41' W. The member is 

partly exposed along most of the streams on the coastal 

plains between the White Hills and the Niguanak 

River; it is more widely distributed than any other part 

of the Sagavanirktok Formation, and generally forms 

the northernmost low hills on the Arctic Coastal Plain. 

The name N uwok Member is here proposed for the 

sequence of rocks well exposed in a series of low bluffs 

along the east side of Carter Creek about 2.4 km (1 V2 mi) 

south of Camden Bay (fig. 2, loc. 21). These strata were 

originally named the Nuwok Formation by Dall (1919). 

Although the name was used later by Dall (1920), Leffingwell (1919), and MacNeil (1957), it has never been 

formally accepted by the U.S. Geological Survey. The 

relationship of the beds on Carter Creek to the 

Sagavanirktok, Formation was unknown when MacNeil 

(1957, p. 120) named a pelecypod after the Nuwok, 

Chlamys nuwokensis, and since the Carter Creek beds 

were apparently much younger than the Franklin 

Bluffs section, MacNeil assumed that the rocks belonged to different formations. Additional work has 

shown that the fossiliferous beds on Carter Creek directly overlie strata equivalent to the Franklin Bluffs 

Member and that all are part of one nearly continuous 

Tertiary sequence. We therefore assign the N uwok 

Member to the Sagavanirktok Formation and restrict it 

to the upper 80 m (266ft) of strata exposed in the bluffs 

at the type section, lat 69°57' N., long 144°39'30" W. 

This locality is the only known occurrence of the 

member. Beds of the Gubik Formation (Pleistocene) 

overlie the Nuwok Member at Carter Creek. 

Thickness and stratigraphic relations. -Although a 

complete section of the Sagavanirktok Formation has 

not been found at any one locality, a sequence representative of the formation can be compiled (fig. 13). By 

correlating partly exposed sections, a minimum thickness of about 1,152 km (3,780 ft) is indicated, but there 
38 POST-CARBONIFEROUS STRATIGRAPHY, NORTHEASTERN ALASKA 

c: 

~g 

.em 

:::~E (!) .... 

0 

LL. 

l» 

..0 

E 

Q) 

~ 

21 

Carter Creek 

LITHOLOGIC SYMBOLS 

Sandstone 

D 

Silty 

~ shale 

§ 

Conglomerate Clay shale 

Gravel Limestone 

~ 

EiJ . § 

Pebbly Coal 

sandstone 

~ § 

Bentonite 

Siltstone 

~ . Clay 

~ ironstone 

Mudstone nodules 

~ Pebbly 

. 

Covered 

~ 

mudstone interval 

*1 Fossil collection 

See section entitled, "List of Fossil 

Collections" for description 

METRES FEET 

90 300 

23 

Sag won 

Kogosukruk Tongue of 

Prince Creek Formation 

FIGURE 13.' -Type sections for members of the Sagavanirktok 

Formation. 

may be as much as 1,500 or 1,800 m (5,000 or 6,000 ft). 

Wells drilled along the north coast penetrate between 

600 and 1,500 m (2,000 and 5,000 ft) of Sagavanirktok 

rocks. 

The Sagwon Member is 143 m (470ft) thick at the 

type section, where it is unconformably overlain by terrace gravel, and a similar section is present in the White 

Hills. A somewhat thicker section may be present near 

the junction of Fin and Juniper Creeks, where Keller, 

Morris, and Detterman (1961) reported 625 m (2.045 ft) 

of Sagavanirktok rocks. The lower 365 m (1,200 ft) of 

that section is probably equivalent to the Sagwon, although some of the basal beds may be Upper Cretaceous. The contact between the Sagwon and the underlying Kogosukruk Tongue is conformable and apparently 

gradational; it can be identified with confidence only 

where exposures are good, as both stratigraphic units 

contain coal and poorly consolidated rock. The 

sandstone of the Kogosukruk is somewhat more indurated and darker than the Sagwon, and the coal is 

slightly higher grade. 

The Franklin Bluffs Member is at least 900 m (3,000 

ft) thick and may be as much as 1,500 m (5,000 ft) thick. 

Only about 105 m (350 ft) is actually exposed beneath 

the high-level terrace gravel at the type section. Consequently, the partly exposed section along Carter 

Creek is listed as a reference locality (fig. 13, column 

21). The contact with the underlying Sagwon Member is 

probably conformable, although not visible in these 

poorly exposed sections. The upper contact is, at least in 

part, an unconformity where the number is overlain by 

unconsolidated terrace gravel. Elsewhere, as on Carter 

Creek, these rocks appear to be conformable and gradational into the overlying Nuwok Member. 

The Nuwok Member is the youngest Tertiary unit 

exposed in northeastern Alaska. The type section is 

about 80 m (270 ft) thick and is the only known occurrence of these rocks. The lower contact is placed at the 

base of a poorly consolidated sandstone and is conformable and gradational. 

Lithology.-The Sagwon Member is the coalbearing sequence of the Tertiary in northeastern Alaska. The coaly beds are mainly lignite and carbonaceous 

shale, and individual beds are as much as 6 m (20 ft) 

thick with abundant shale partings. The coal is interbedded with dark-gray to brown fissile clay shale and 

siltstone that are slightly bentonitic and contain a few 

clay ironstone nodules. Massive units of poorly consolidated sandstone and conglomerate form the upper part 

of the Sag-Won section. The sandstone is a lithic arenite 

composed of 60 to 70 percent clasts of chert and 

quartzite, which are also the main constituents of the 

conglomerate. Quartz, minor feldspar, and carbonaceous material make up most of the remainder. All thin 
STRATIGRAPHY 39 

sections of sandstone contain not more than 5 percent 

matrix, usually sericitic clay or montmorillonite. 

Crossbedding of the shallow-water to deltaic type is 

common in both sandstone and copglomerate, and indicated a source to the southwest. 

The Franklin Bluffs Member is a cyclic-bedded subaerial deposit. The cycle of deposition is repeated four or 

five times in northeastern Alaska, but only one cycle is 

exposed at Franklin Bluffs. At that locality (fig. 13) the 

cycle starts with a thick unit of thinly laminated gray to 

brown clay and silt beds suggestive of a playa lake 

deposit. These beds commonly contain randomly distributed small chert pebbles and mud lumps along the 

bedding planes. Most pebbles are on the upper surface of 

the clay units and are of a size and shape that could be 

moved by wind. Desiccation cracks are preserved in a 

few beds at the south end of the bluff section. Thin 

sections of these rocks show them to be about 75 percent 

clay with well-developed platy arrangement of the mica. The silt laminae are composed mainly of quartz and 

feldspar grains. Organic material is commonly present 

along bedding planes, and there is considerable limonite staining. Overlying the laminated silt and clay are 

massive units of pink, tan, orange, and yellow unconsolidated sand and gravel. Limonitic zones several inches thick locally cement the sand and gravel into wellindurated rock. Large-scale irregular crossbedding, 

probably of eolian origin, is common in some sand units. 

Beds of volcanic ash are inter layered with the sand and 

gravel. 

The depositional environment of the Franklin Bluffs 

Member is imperfectly known largely owing to poor 

exposures. The combination of lithologic types is 

suggestive, however, of semiarid conditions in which 

varved silt and clay beds were deposited in large shallow lakes. The varved sediments were then overlain by 

red-bed-type sands and gravel deposited by water and 

wind. The organic content of the sediments is markedly 

less than that of the underlying Sagwon Member; this 

might further confirm a semiarid environment. 

TheN uwok Member represents a return to nearshore 

marine deposition. The section on Carter Creek is 

within 2.4 km (1.5 mi) of the present coast and at 46 m 

(150ft) altitude, so marine deposition is not surprising 

considering the young age of these beds. The sequence 

starts with a crossbedded sand unit capped by a pebble 

conglomerate. The sand contains a few thin-shelled 

pelecypods and probably represents a beach deposit. 

The conglomerate is overlain by pebbly mudstone and 

siltstone with a few thin silty limestone interbeds that 

are interpreted as lagoonal deposits. The section is 

capped by about 15m (50ft) of unconsolidated sand with 

a few chert and quartz pebbles. This unit is cross bedded 

and locally cemented by limonite; it probably was 

deposited as a barrier beach deposit similar to those 

formed along the Arctic Coast today. 

Age.-The Sagavanirktok Formation contains fossil flora and fauna that indicate a Tertiary age. The flora 

was collected from the coal-bearing Sagwon Member 

and includes such early Tertiary forms as Metasequoia 

occidentalis (Newberry) Chaney, Trapa microphylla 

Lesquereux, Cinnamonum ficoides Hollick, and Pterospermites conjunctious Hollick. These are correlated 

with Paleocene and Eocene beds elsewhere in Alaska 

(MacNeil and others, 1961; Keller and others, 1961). 

The Franklin Bluffs Member has produced no fossils, 

and probably will not produce many if the paleogeography has been correctly interpreted. Stratigraphic 

breaks cannot be picked within the surface exposures, 

largely because outcrops are poor, but deposition is assumed to have been nearly continuous. Since the 

member represents most of the exposed Tertiary beds, 

we suggest that the Franklin Bluffs Member represents 

at least the Oligocene(?) and Miocene(?) strata, and may 

possibly include more of the Tertiary sequence. 

The Nuwok Member contains a molluscan fauna that 

has been known for many years (Dall, 1919, 1920; Lef. 

fingwell, 1919; Morris, 1953; MacNeil, 1957). The main 

elements of this fauna are Arctica carteriana MacNeil 

and C hlamys nuwokensis MacNeil. These fossils are 

considered by MacNeil to be late Miocene or early 

Pliocene (1957, p. 101), although they bear little resemblance to Miocene and Pliocene faunas in southern 

Alaska. TheN uwok contains a very prolific microfauna 

including foraminifers and ostracodes that were assigned a similar age by Todd (1957). Recent collections 

of microfossils were studied by Bergquist, who considers 

the fauna to be more closely related to latest Pliocene or 

early Pleistocene forms (written commun., 1972). The 

age as determined by Bergquist seems to be more in 

keeping with the stratigraphic assignment of these beds 

which is late Miocene(?) and Pliocene. Microfossils from 

the type section are listed in table 3. Bergquist considers 

the following species to be endemic to the Nuwok 

Member: Elphidie.lla(?) brunescens Todd, Elphidium 

discoidale (d'Orbigny), Trifarina fluens (Todd), Nonion 

cf. N. labridoricum (Dawson), Melon is erucopsis (Todd), 

Globulina auriculata subsp. arctica Hoglund, and 

Cibicides perlucidus Nuttall. 

The uppermost beds of the Carter Creek section may 

be of Pleistocene age as suggested by the microfauna, 

since the late Tertiary megafauna was not found in the 

upper 15m (50ft). A stratigraphic break is not evident 

within or below these unconsolidated sands; consequently, they are included as part of the Carter Creek 

section. 

GUBIK FORMATION 

Name and distribution.-The Gubik Formation 
40 POST -CARBONIFEROUS STRATIGRAPHY, NORTHEASTERN ALASKA 

was originally termed the Goobic Sands by Schrader 

(1902, p. 249-250) and Gubik Sand by Schrader (1904, p. 

93). He applied the name to Pleistocene unconsolidated 

deposits along the Colville River on the Arctic Coastal 

Plain in central Alaska. This stratigraphic unit was 

later redefined by Gryc, Patton, and Payne (1951, p. 

167) as the Gubik Formation. The formation was 

studied in considerable detail in northwestern Alaska 

by Black (1964), who divided it into three units: in 

ascending order, the Skull Cliff, Meade River, and Barrow. We recognize the Gubik Formation in northeastern 

Alaska. 

The recent geologic investigations were primarily 

concerned with the indurated bedrock and secondarily 

with the unconsolidated surficial materials on the Arctic Coastal Plain. A few sections of the Gubik were 

investigated along the Niguanak River and in the area 

between Carter and Marsh Creeks. In addition, the formation was noted at a number of other localities. Although its exact area is unknown, it is probably present 

on the coastal plain throughout northeastern Alaska. 

The section on the Niguanak River (fig. 2, loc. 24) is 

about 120 m ( 400 ft) above sea level and 32 km (20 mi) 

from the coast. This is probably about the southernmost 

occurrence of the formation, but the Gubik can be expected to underlie most areas to the north. 

Thickness and stratigraphic relations.-The Gubik 

Formation is at least 10 m (35 ft) thick along the 

Niguanak River, lat 69°49'30" N., long 143°05'30" W., 

where an incomplete section was measured (fig. 14). The 

base of the sequence is not exposed, so the actual thickness is unknown, but it probably is less than the 60+ m 

(200+ ft) exposed near Point Barrow (Black, 1964). 

The deposit is unconformably overlain by poorly 

stratified sand and gravel interpreted as glacial outwash. The lower contact, also an unconformity, is not 

TABLE 3.-Foraminifera distribution chart for the Nuwok Member of the Sagavanirktok Formation 

[R = rare (1-10); C = common (11-25); A = abundant (>25)) 

Sample number 69ADt-150 69ADt-150 70ADt-150 70ADt-150 70ADt-150 70ADt-150 70ADt-150 No.1 No.2 

Position below metres 44.2-Base 13.1-44.2 67.0--79.2 59.4-67.0 44.2-59.4 21.3-44.2 1.2-21.3 

top of member feet 145-Base 44-145 220--260 195-220 145-195 70--145 4-70 

Elphidiella? brunescens Todd ---------------- R A A A A A A 

Elphidium discoidale? (d'Orbigny) ------------ c R R A R 

cf. E. hughesi Cushman and Grant ________ R 

ustruletum Todd ------------------------ R 

sp. -------------------------------------- R R R Anomalina? sp. ______________________________ A R R R 

Cassidulina cf. C. subglobosa Brady ---------- R Cassidella sp. ________________________________ R R c 

Cibicides aff. C. gramus Todd ---------------- R R R R c 

aff. C. perlucidus Nuttall ---------------- R R R R R 

lobatulatus (Walker and Jacob) ---------- R 

sp. ----------.. --------------------------- R R A R 

Cornuspira sp. ------------------------------ R R R 

Bulimina sp. -------------------------------- c A A A A A 

Dentalina sp. -------------------------------- R R R R 

Fissurina semimarginata (Reuss) ______________ R R 

globulosa Bornemann -------------------- R 

sp. -------------------------------------- R R 

Falsocibicides sp. ---------------------------- R 

Glandulina laevigata d'Orbigny -------------- R R R 

Globulina inaequalis Reuss ------------------ R R R 

sp. -------------------------------------- c R c 

Globobulimina auriculata sub sp. arctica Hoglund c c R c R c Gyroidina sp. ________________________________ R R R 

Lagena cf. L. striata (Montagu)_ _______________ R R 

sp. -------------------------------------- R R 

Fissurina marginata (Montagu) -------------- R 

Melonis crucopis (Todd) ---------------------- R c c c R A 

Nonion cf. N. labriodoricum (Dawson) --------- c R R c c 

sp. -------------------------------------- R R 

Quinqueloculina sp. __________________________ R R 

Scutuloris? sp. _____________________ -- ___ - __ - R R R R R 

Hahlo{i..hragmoides sp. ________________________ R 

Mi io inella circularis? (Bornemann) ---------- R R R 

Robertinoides? charlottensis (Cushman)-------- R 

Polymorphina sp. ---------------------------- R R R 

Pullenia salisbury R. E. and K. C. Stewart R 

Oolina laevigata d'Orbigny _______________ -- __ - R 

squamosa (Montagu) -------------------- R R R 

Trifarina fluens (Todd) ---------------------- R A A R 
LIST OF FOSSIL COLLECTIONS 41 

24 

Niguanak River 

:··.· .... · .. : .. -... ~ ... · ... ·.~. · .. : ~ 

.·.· ... ·.·. : .. · 

~ 

Base of 

exposure 

METRES FEET 

12 40 

0 0 

LITHOLOGIC 

SYMBOLS 

~ . 

. 

Gravel 

D . 

. 

Sand 

[23 . 

. 

Pebbly sand 

Clay 

EJ 

Wood 

*I Fossil collection 

See section entitled, "List 

qf' Fossil Collections" for 

description 

FIGURE 14.-Measured section of the Gubik Formation. 

exposed where the section was measured but is exposed 

16 km (10 mi) further north along the Niguanak, where 

the Gubik overlies shale of Late Cretaceous age. The 

formation also overlies late Tertiary beds between Carter and Marsh Creeks. 

Lithology.-The Gubik Formation exposed along 

the Niguanak River is primarily clean crossbedded 

sand, with a few small pebbles of black chert in the 

upper part (fig. 14). The sand units are 1.5 to 3m (5 to 10 

ft) thick and are separated by thin beds of dark-bluishgray laminated silt and clay. The deposit is considered 

to be marine, although fossils have not been found at 

this locality. 

Coarse gravel is the main constituent of the Gubik 

Formation exposed between the Canning and Kavik 

Rivers (Reiser and others, 1971 ). The clasts are primarily roller shaped, 8 to 13 em (3 to 5 in.) long, composed of 

gray quartzite, tuff, gray chert, and minor limestone 

that is highly weather. The gravel contains a considerable amount of sand and silt and has a characteristic 

rusty-orange color caused by limonite staining. 

Remnants of a high-level gravel terrace cap many of 

the hills along the south edge of the Arctic Coastal 

Plain, and also at many places on the coastal plain. This 

is a clean gravel primarily of cobble-sized clasts composed of light-colored quartz, gray and green tuff, gray 

to black chert, and minor amounts of limestone. The 

abundance of light-colored constituents gives these 

gravels a characteristic white weathered surface considerably different from the rusty-orange-weathering 

gravel of the Gubik Formation. The gravel in the Gubik 

generally contains much sand and silt, which is absent 

f:r:om the white gravel. The relationship between these 

two deposits is not entirely known, although they are 

commonly closely associated throughout the coastal 

plan. The Gubik gravels are believed to be formed in 

part from a reworking of the white gravel. 

The Gubik Formation exposed in northeastern 

Alaska is probably equivalent to the Barrow unit of the· 

formation, as described by Black (1964, p. 77-88). 

Age.-The Gubik Formation is of Pleistocene age, 

but the exact position within the Pleistocene i$ not 

known. Black (1964, p. 89) equated the Skull Cliff unit 

with the Illinoian Glaciation, the Meade River unit with 

the Sangamon Interglaciation, and the Barrow unit 

with the Wisconsin Glaciation. A carbon-14 age of over 

34,000 years was obtained from wood collected from the 

unconformity between the Gubik and the overlying 

outwash gravel at the locality on the Niguanak River. 

Porter (1966, p. 98) obtained a carbon-14 age of13,270± 

160 yea:r:s for a sample from the lower part of the Itkillik 

Glaciation, which he equates with the Wisconsin Glaciation. If the Gubik, as exposed in northeastern Alaska, 

is equivalent to the Barrow unit, as suggested, then all 

parts of the formation are older than the Wisconsin 

Glaciation. The outwash gravel overlying the Gubik on 

the Niguanak is considered to be derived from the Itkillik Glaciation. 

The lower limit of the Gubik, also, cannot be placed 

precisely. In the area between Carter and Marsh Creeks 

the formation unconformably overlies fossiliferous late 

Pliocene beds, so the Gubik is probably entirely 

Quaternary. A few microfossils were obtained from a 

shale sample in this area. They include Glomospira sp., 

Eggerella sp., Valvulinera sp., Biloculinella sp., and 

Cribroelphidium sp., which have been found previously 

in the Gubik Formation, as well as Holocene deposits of 

the Arctic Ocean (Bergquist, written commun., 1972), 

but these are of little value for precise age determinations. 

LIST OF FOSSIL COLLECTIONS 

This is a partial listing of major megafossil collections 

obtained in northeastern Alaska between 1969 and 

1972, giving location and content for each sample. Collections are listed by stratigraphic unit, and those with 

numeral prefixes are keyed to sections shown in figures 

5 to 14. Some of the geographic features listed here are 

not shown in figure 2 but can be found on the appropriate 1:250,000 quadrangle map. 
42 POST-CARBONIFEROUS STRATIGRAPHY, NORTHEASTERN ALASKA 

SADLEROCHIT GROUP 

ECHOOKA FORMATION 

JOE CREEK MEMBER (LOWER AND UPPER 

PERMIAN) 

1. 23464-PC (U.S. Geological Survey, Permian. 

and Carboniferous locality number); Table 

Mountain quadrangle; type section, mountain 

north of Joe Creek; lat 68°59'30" N., long 

141°26' W.; 7.7 km (4.8 mi) west of VABM 

Raeburn: Kochiproductus sp. (Guadalupian). 

2. 2346:>--PC; same locality: Derbyia sp., Yakoulevia sp., Horridonia sp., Spiriferella sp., 

Kochiproductus sp., and stenoporoid bryozoans 

(Leonardian to Guadalupian). 

3. 23462-PC; same locality: Waagenoconcha sp., 

Rhynchopora sp., Cleiothyridina sp., and Tomiopsis(?) sp. (Leonardian to Guadalupian). 

4. 23461-PC; same locality: Septospirifer sp. 

5. 23460-PC; same locality: Martinia sp. 

23459-PC; Demarcation Point quadrangle; 

mountain northeast of Bathtub Ridge; lat 

69°06'20" N, long 142°08' W.; 11.6 km (7.2 mi) 

N. 5° E. of point where Kongakut River enters 

Table Mountain quadrangle; 100 m (350 ft) 

above base: Septospirifer(?) sp., and straparollid snails. 

23458-PC; same locality; 80.7 m (265 ft) above 

base: Anidanthus(?) sp., Waagenoconcha sp., 

Spiriferella sp., and Septospirifer sp. (Leonardian to Guadalupian). 

23457-PC; same locality; 19.8 m (65 ft) above 

base: Chonetes sp. and Attenuatella sp. 

(Wolfcampian). 

72ADt-388, unit 1; Sagavanirktok quadrangle; 

east bank of Flood Creek; lat 69°00' N., long 

147°55' W.; 6.4 km (4 mi) south of junction with 

Ivishak River; 27.4 m (90 ft) above base: 

Anidanthus sp., Attenuatella sp., Martinia sp., 

Cancrinella(?) sp., Tomiopsis(?) sp., Straparollus sp., and horn corals (Wolfcampian). 

72ADt-388, unit 2; same locality; 128 to 158.5 m 

(420 to 520 ft) above base: Martiniopsis sp., 

Cancrinella(?) sp., and Attenuatella sp., 

(Wolfcampian to Leonardian). 

57 AMg3; north side of Joe Creek; 16.1 km (10 mi) 

west of Alaska-Canada boundary; lat 68°58' 

N., long 141°24' W.; lower part below chert 

beds: Chonetinella sp., Martina(?) sp., Attenuatella sp., and Spiriferella sp., (Wolfcampian). 

IKIAKPAURAK MEMBER (UPPER PERMIAN) 

1. 24378-PC; Mt. Michelson quadrangle; type 

section, Ikiakpaurak Valley; lat 69°27'45" N., 

long 145°53'30" W.; 11.6 km (7.2 mi) N. 49° E. of 

Shublik Island: Stenoscisma(?) sp. 

2. 24377-PC; same locality: Attenuatella sp., 

and Chonetes cf. C. superba (Gobbett) (Guadalupian). 

3. 24376--PC; same locality: Arctitreta cf. A. 

kempei (Wiman), Megousia sp., Spiriferella 

keilhauii (Von Buch), Dielasma sp., Pterospirifer(?) alatus (Schlotheim), and Pseudogastrioceras(?) sp. 

24381; Mt. Michelson quadrangle; ridge east of 

Pogopuk Creek; lat 69°18'30" N., long 

146°34'30" W.; 9.1 to 10.7 m (30 to 35ft) above 

base: Neophricodothyris asiatica (Chao), 

Stenoscisma(?) sp., Liosotella(?) pseudohorrida 

(Wiman), stenoporid and fenestrate bryozoans, 

and echinoderm debris (Guadalupian). 

24382; same locality: 28.9 to 30.8 m (95 to 101 ft) 

above base: Chonetes cf. C. superba (Gobbett), 

Attenuatella sp., Spiriferella saranae (de Verneuil),Rhynchopora sp., and pelecypod prisms. 

24383; same locality; 41.5 to 45.4 m (136 to 149ft) 

above base: Megousia sp., Stenoscisma cf. S. 

kochi (Dunbar), Pterospirifer alatus 

(Schlotheim), Rhynchopora sp., stenoporid 

bryozoans, and horn corals (Guadalupian). 

24384; same locality; 51.2 to 54.3 m (168 to 178ft) 

above base: N eophricodothyris sp., N eospirifer 

sp., and gastropods (Guadalupian). 

24396; Mt. Michelson quadrangle; north side of 

Kikiktat Mountain; lat 69°26' N., long 144°36' 

W.; 0 to 1.5 m (0 to 5 ft) above base: Megousia 

weyprechti (Toula) and Spiriferella saranae (de 

Verneuil) (Guadalupian). 

24397; same locality; 1.8 to 12.5 m (6 to 41 ft) 

above base: Derbyia(?) sp., Megousia sp., 

Stenoscisma sp., and Spiriferella sp. (Guadalupian). 

24398; same locality; 18.6 to 24.7 m (61 to 81 ft) 

above base: Waagenoconcha irginae (Stuckenberg), Megousia(?) sp., Pterospirifer alatus 

(Schlotheim), Spiriferella sp., and gastropods 

(Guadalupian). 

IVISHAK FORMATION (LOWER TRIASSIC) 

KA VIK MEMBER 

1. M6060 (U.S. Geological Survey Menlo Park 

Mesozoic locality); Mt. Michelson quadrangle; 

stream cut, right bank, Kavik River; lat 

69°17'45" N., long 146°22' W.: Ophiceras commune Spath (Griesbachian). 

Collections from this locality made prior to 1969 
LIST OF FOSSIL·COLLECTIONS 43 

(Keller and others, 1961) contained Ophiceras 

commune Spath, Ophiceras cf. 0. greenlandicum, Proptychites cf. P. rosenkrantzei, Claraia 

stachei Bittner, and Otoceras boreale Spath 

(Griesbachian). 

LEDGE SANDSTONE MEMBER 

70ADt-270, unit 9; Mt. Michelson quadrangle; 

north side ofKikiktat Mountain; lat 69°26'30" 

N., long 144°36'30" W.; 85.3 m (280 ft) above 

base ofmember:Euflemingites cf.E. romunderi 

Tozer (Smithian). 

FIRE CREEK SILTSTONE MEMBER 

1. M6050; Mt. Michelson quadrangle; ridge west 

of Fire Creek; lat 69°31'30" N., long 145°17'30" 

W.: Euflemingites romunderi Tozer (Smithian). 

M6061; Mt. Michelson quadrangle; mountain 

south of Wahoo Lake; lat 69°01'50" N.; long 

146°54'50" W.; 70.1~76.2 m (230-250 ft) above 

base of member: Euflemingites cf. E. romunderi 

·Tozer (Smithian). 

SHUBLIK FORMATION (UPPER TRIASSIC) 

1. M6067; Mt. Michelson quadrangle; Fire Creek; 

lat 69°31'45" N., long 145°12'20" W.: Monotis cf. 

M. obtusicostata Westermann, H alobia cf. H. fallax Mojsisovics, H. cf. H. lineata Mojsisovics, and 

Gryphaea sp. (Norian). 

2. M6059; same locality: Monotis scutiformis 

pinensis Westermann, and Halobia cf. H. fallax 

Mojsisovics (Norian). 

3. M6058; same locality: Monotis cf. M. scutiformis 

Westermann, H alobia cf. H. fallax Mojsisovics, 

Gryphaea sp., and rhynchonellid brachiopods 

(Norian). 

4. M6057; same locality: Halobia cf. H. zitteli 

Lindstrom, H. ornatissima, and Sirenites sp. 

(Karnian). 

5. M6056; same locality: Halobia cf. H. zitteli 

Lindstrom, Leptochondria nationalis Smith, 

Gryphaea sp., Lima sp., arcestid ammonites, 

rhynchonellid brachiopods, and gastropods· 

(Karnian). 

6. M6055; same locality: unidentified pectenacids. 

7. M6054; same locality: Daonella {rami Kittl 

(Ladinian). 

8. M6053; same locality: Daonella {rami Kittl, 

Lima sp., Camptonectes sp., and spiriferid 

brachiopods (Ladinian). 

9. M6052; same locality: Daonella {rami Kittl, and 

Leiophyllites sp. (Anisian to Ladinian). 

M6070; Mt. Michelson quadrangle; east bank, 

Echooka River; 3.2 km (2 mi) N. 25° E. of Wahoo 

Lake; lat 69°07'20" N., long 146°53' W.; 28.3 m 

(93 ft) above base: Daonella {rami Kittl (Ladinian). 

M6071; same locality; 37.5 m (123 ft) above base: 

H alobia cf. H. ornatissima (Karnian). 

M6072; same locality; 46.6 to 48.7 m (153 to 160ft) 

above base: Arctosirenites cf. A. canadensis Tozer, Juuauites sp., Arcestes sp., and Hatobia cf. H. 

ornatissima (Karnian). 

M6073; same locality; 57.6 to 57.9 m (189 to 190ft) 

above base: H alobia zitteli, H. ornatissima, and 

Psioidea sp. (Karnian). 

M6074; same locality; 57.9 to 68.6 m (190 to 225ft) 

above base: Halobia sp., Psioidea(?) sp., and ammonites. 

M6075; same locality; 109.8 m (360ft) above base: 

Monotis subcircularis and M. ochotica densistriata (Norian). 

72ABe312B; Arctic quadrangle; near top of southwest side of Mount Annette; lat 68°45' N., long 

146°29' W.; in chert and shale unit: Monotis sp. 

indet. (middle or upper Norian). 

72ABe284C; Arctic quadrangle; hill about 14.5 km 

(9 mi) east of Mount Annette; lat 68°47' N., long 

146°12' W.; in chert and shale unit: Monotis sp. 

indet. but similar to M. subcircularis or M. 

ochotica of late Norian age. 

· 72ABe314; Arctic quadrangle; hill 1.6 km (1 mi) 

south-southwest of Mount Annette; lat 68°44'30" 

N.,.long 146°29' W.; in unit of shale, chert, and 

limestone: Monotis sp. indet., and Halobia sp. 

indet. but probably of Norian type (probably 

middle Norian). 

72ABe316A; Arctic quadrangle; hill 4.8 km (3 mi) 

northeast of Mount Annette; lat 68°46'30" N., 

long 146°23' W.; in (lower? part of) shale and 

limestone member: H alobia cf. H. zitteli group 

(Karnian or lower Norian). 

68ATo12 (M6065); Arctic quadrangle; south bank 

of Porcupine Lake; lat 68°47'5" N., long 146°28' 

W.; in shale and limestone member: H alobia cf. 

H. zitteli-ornatissima group, and tropitid ammonites (upper Karnian). 

68ATo11; Arctic quadrangle; creek about 2.4 km 

(1 Y2 mi) northwest of Porcupine Lake; lat 68°48' 

N., long 146°31' W.; in shale and limestone 

member: H alobia cf. H. zitteli-ornatissima group 

(Karnian). 

KAREN CREEK SANDSTONE (UPPER TRIASSIC) 

69ADt-106; Mt. Michelson quadrangle; Fire 

Creek; lat 69°32'10" N., long 145°11'25" W.; 

base of formation: M onotis ochotica ochotica 

(Keyserling), and Gryphaea keilhaui Boehm 

(la.te Norian). 
44 POST-CARBONIFEROUS STRATIGRAPHY, NORTHEASTERN ALASKA 

KINGAK SHALE (JURASSIC) 

1. 29856 mes. loc. (U.S. Geological Survey 

Mesozoic locality); Mt. Michelson quadrangle; 

east end oflgnek Valley; 10.9 km (6.8 mi) S. 75° 

E. of Katakturuk Canyon; lat 69°33 130" N., 

long 145°20 1 W.: Cardioceras (Scarburgiceras) 

sp. and Inoceramus sp. (Oxfordian). 

2. 29877 mes. loc.; same locality: Arcticoceras cf. 

A. kochi Spath (Bathonian). 

3. 29855 mes. loc.; same locality: Cranocephalites ignekensis Imlay (Bathonian). 

4. 29875 mes. loc.; same locality: Cranocephalites sp. Inoceramus sp., and Grammatodon(?) 

sp. (Bathonian). 

5. 70ADt-215, unit 5 1; same locality: Inoceramus sp. 

6. 29854 mes. loc.; same locality: Inoceramus cf. 

I. ambiguus and belemnites (Bajocian). 

7. 29876 mes. loc.; same locality: Inoceramus 

lucifer Eichwald, Oxytoma sp., Meleagrinella 

sp., and ammonite fragments (Bajocian). 

8. 30075 mes. loc.; Demarcation Point quadrangle; west bank Aichilik River; 4 km (2.5 mi) N. 

30° E. of VABM Atte; lat 69°33 1 N., long 

143°05 1 W.: Arctioceras kochi Spath, A. kochi 

var. pseudolamberti Spath, and C hoffatia cf. C. 

subbakeriae (d'Orbigny) (Bathonian). 

9. 30074 mes. loc.; same locality: Amaltheus cf. 

A. stokesi (Sowerby) and Ostrea sp. (Pliensbachian). 

10. 30073 mes. loc.; same locality: Pentacrinus 

sp. and pelecypod fragments (Early Jurassic). 

29883 mes. loc.; Mt. Michelson quadrangle; west 

bank, Kavik River; lat 69°16 120" N., long 

146°22 1 W.; lower 45.7 m (150ft): Otapiria tailleuri Imlay (Sinemurian to early Bajocian). 

30135 mes. loc.; Demarcation Point quadrangle; 

ridge west of Okerokovik River; 12.2 km (7.6 

mi) S. 80° W. ofV ABM Matte; lat 69°28 1 45" N., 

long 143°25 150" W.; position unknown: 

Pseudolioceras maclintocki (Haughton) (basal 

Bajocian). 

29885 mes.loc.; Mt. Michelson quadrangle; ridge 

west of Kaviak Creek; lat 69°27 130" N., long 

145°04 130" W.; position unknown: Pentacrinus 

subangularis var. alaska Springer and Inoceramus cf. I. lucifer Eichwald (Bajocian). 

29884 mes. loc.; same locality; about 15.2 m (50 

ft) lower than 29885: Canavarella cf. C. 

belophora Buckman, Pseudolioceras cf. P. 

maclintocki (Haughton), and Inoceramus cf. I. 

lucifer Eichwald (basal Bajocian). 

30267, 30268, 30269, 30270 mes. loc.; Mt. 

Michelson quadrangle; lgnek ·valley; 0.8 km 

(0.5 mi) south of entrance to Katakturuk 

Canyon; lat 69°351 N., long.145°36130" W.; 33.5 

to 97.5 m (110 to 320 ft) above base:, 

Canavarella sp., Pseudolioceras maclintocki 

(Haughton), and Erycitoides sp. (basal Bajocian). 

30266 mes. loc.; Mt. Michelson quadrangle, west 

bank of Canning River opposite Shublik Island; lat 69°241 N., long 146°101 W.; upper part 

of section, exact position unknown: Arkelloceras cf. A. mclearni Frebold sp. and Inoceramus sp. (early middle Bajocian). 

30136 mes. loc.; Demarcation Point quadrangle; 

west bank of Aichilik River; lat 69°33 1 N., long 

143°05 1 W.; about 426 m (1.400 ft) above base of 

Kingak Shale: Cadoceras sp. (Callovian). 

30076 mes. loc.; Table Mountain quadrangle; 

south bank of Joe Creek; lat 68°57 120" N., long 

141°23 130" W.; 18.5 _km (11.5 mi) west of 

Alaska-Canada boundary: B uchia rugosa 

(Fischer) (Kimmeridgian to Tithonian). 

Black Island in the Canning River has been known for 

many years as a locality for well-preserved Pentacrinus 

subangularis var. alaska Springer. Many specimens of 

this fossil have been collected for museums. During the 

present investigation a numb_er of new localities were 

found that contain equally well preserved material. 

Localities in the Mt. Michelson quadrangle, in addition 

to Black Island, include Fire Creek, lat 69°32 110" N., 

long 145°11 125" W.; at the junction of Gravel Creek with 

the Sadlerochit River, lat 69°29130" N., long 145°05130" 

W.; on the ridge west ofKaviak Creek, lat 69°27 130" N., 

long 145°04 130" W.; and on the mountain 1.6 km (1 mi) 

west of the upper Sadlerochit River, lat 69°19 140" N., 

long 145°23 1 W. Localities in the Demarcation Point 

quadrangle include the west bank of the Aichilik River, 

lat 69°33 1 N., long 143°051 W.; and on a ridge west of the 

Okerokovik River, lat 69°28 1 45" N., long 143°25 1 50" W. 

KONGAKUT FORMATION (LOWER CRETACEOUS) 

1. M5815 (U.S. Geological Survey, Menlo Park, 

Mesozoic locality number); Demarcation Point 

quadrangle; north flank of Bathtub Ridge; lat 

69°06110" N., long 142°171 W.: Aucellina(?) E?P· 

(Aptian?). 

2. M5817; same locality: Simbirskites sp., 

Lytoceras sp., belemnites, and brachiopods 

(Hauterivian). 

3. M5818; same locality: Buchia sublaevis (Imlay) 

(Valanginian). 

70ADt-214; Demarcation Point quadrangle; north 

side of Bathtub Ridge; lat 69°07 1 45" N., long 

142°37' W.; 30.5 m (100 ft) above base: Buchia 

sublaevis (Imlay) (Valanginian). 
REFERENCES CITED 45 

M5581; Sagavanirktok quadrangle; east side of 

Kemik Creek; lat 69°21'41"' N., long 14 7°21'43" 

W.; position unknown: Buchia keyserlingi(?) 

(Berriasian). 

M5584; Mt. Michelson quadrangle; divide between 

Kavik River and Juniper Creek; lat 69°28'30" N., 

long 146°38'20" W.; Buchia keyserlingi(?) (Berriasian). · 

KEMIK SANDSTONE MEMBER (LOWER 

CRETACEOUS) 

1. 69ADt-29; Mt. Michelson quadrangle; Ignek 

Valley; lat 69°34'58" N., long 145°42'50" W.: 

Astarte ignekensis Imlay, Ditrupa cornu Imlay, 

Panope sp., and Pleuromya sp. (Valanginian to 

Albian). 

70ABe-262; Mt. Michelson quadrangle; north 

side of Sadlerochit Mountains; lat 69°38' N., 

long 145°25' W.; position unknown: Astarte ignekensis Imlay and Ditrupa sp. (Valanginian 

to Albian). 

69ADt-51; Mt. Michelson quadrangle; Ignek 

Valley; lat 69°33'20" N., long 145°27'45" W.; 

upper part of sandstone: Astarte ignekensis Imlay andPleuromya sp. (Valanginian to Albian). 

NANUSHUK GROUP 

TUKTU FORMATION (LOWER CRETACEOUS) 

1. 70ABe-134A; Mt. Michelson quadrangle; ridge 

east of Arctic Creek; lat 69°29'30" N., long 

144°32'30" W.: Paragastroplites spiekeri 

(McLearn) (Albian). 

2. 70ABe-135; same locality: Inoceramus sp. 

prisms. 

3. 70ABe-135B; same locality; lat 69°30' N., long 

144°31' W.: Paragastroplites spiekeri (McLearn) 

(Albian). 

SEABEE FORMATION (UPPER CRETACEOUS) 

SHALE WALL MEMBER 

71ADt-353; Demarcation Point quadrangle; 

west bank of Jago River; lat 69°54'30" N., 

long 143°24'30" W.: abundant fossil fish, not 

identified. 

SAGAVANIRKTOK FORMATION (TERTIARY) 

NUWOK MEMBER (LATE MIOCENE? AND PLIOCENE) 

1. M4148, 4427 (U.S. Geological Survey, Menlo 

Park, Cenozoic locality); Mt. Michelson quadrangle; bluff on east side of Carter Creek; 3.2 

km (2 mi) south of Arctic Ocean; lat 69°56' 45" 

N., long 144°39'50" W.: Chlamys cf. C. 

nuwokensis MacNeil, Thyasira alaskana 

Kauffman, Astarte sp., Terebratula aff. T. 

grandis Davidson, Buccinum sp., and Polinices(?) sp. (late Miocene or Pliocene). 

2. M414 7; same locality: Cyclocardia cf. C. 

nuwokensis (Dall), Cyrtodaria sp., Astarte sp., 

and Terebratula sp. (late Miocene or Pliocene). 

GUBIK FORMATION (PLEISTOCENE) 

1. 70ADt-275; Demarcation Point quadrangle; 

tributary of Niguanak River; lat 69°49'30" N., 

long 143°05'10" W.: Populus (Salicaceae) sp.; this 

wood dated by C-14 method at >34,000 years b.p. 

REFERENCES CITED 

Bamber, E. W., and Waterhouse, J. B., 1971, Carboniferous and 

Permian stratigraphy and paleontology, northern Yukon Territory, Canada: Alberta Soc. Petroleum Geologists Bull., v. 19, no. 

1, p. 29-250. 

Basye, Dale, 1969, Secrecy shroud lifts on giant Prudhoe Bay Field: 

Oil and Gas Jour., v. 67, no. 47, p. 49-54. 

Bergquist, H. R., 1966, Micropaleontology of the Mesozoic rocks of 

northern Alaska: U.S. Geol. Survey Prof. Paper 302-D, p. 93-227. 

Black, R. F., 1964, Gubik Formation of Quaternary age in northern 

Alaska: U.S. Geol. Survey Prof. Paper 302-C, p. 59-91. 

Boneham, R. F., and Tailleur, I. L., 1972, Leiospheridia (Acritarcha) 

in the Mesozoic oil shales of northern Alaska, in Geological 

Survey research 1972: U.S. Geol. Survey Prof. Paper 800-B, 

p. B17-B19. 

Brosge, W. P., Dutro, J. T., Jr., Mangus, M.D., and Reiser, H. N., 1962, 

Paleozoic sequence in eastern Brooks Range, Alaska: Am. Assoc. 

Petroleum Geologists Bull., v. 46, p. 2174-2198. 

Brosge, W. P., and Tailleur, I. L., 1969, Isopach maps of upper 

Paleozoic and Mesozoic rocks, northern Alaska: U.S. Geol. Survey 

open-file report, 10 p. 

--1970, Depositional history of northern Alaska, in Adkison, 

W. L., and Brosge, M. M., eds., Proceedings of the geologic 

seminar on the North Slope of Alaska: Los Angeles, Pacific Sec. 

Am. Assoc. Petroleum Geologists, p. D1-D18. 

Brosge, W. P., and Whittington, C. L., 1966, Geology of the 

Umiat-Maybe Creek region, Alaska: U.S. Geol. Survey Prof. 

Paper 303-H, p. 501-638. 

Chapman, R. M., Detterman, R. L., Mangus, M.D., 1964, Geology of 

the Killik-Etiuluk Rivers region, Alaska: U.S. Geol. Survey Prof. 

Paper 303-F, p. 325--407. 

Dall, W. H., 1919, Mollusks, Recent and Pleistocene: Report of the 

Canadian Arctic Expedition 1913-18, v. 8, pt. A. Ottawa. 

--1920, Pliocene and Pleistocene fossils from the Arctic coast of 

Alaska and the auriferous beaches of Nome, Norton Sound, 

Alaska: U.S. Geol. Survey Prof. Paper 125--C, p. 23-37. 

Detterman, R. L., 1956a, New and redefined nomenclature of the 

Nanushuk Group, in Gryc, George, and others, Mesozoic sequence 

in Colville River region, northern Alaska: Am. Assoc. Petroleum 

Geologists Bull., v. 40, no. 2, p. 233-244. 

--1956b, A new member of the Seabee Formation, Colville Group, 

in Gryc, George, and others, The Mesozoic sequence in Colville 

River region, northern Alaska: Am. Assoc. Petroleum Geologists 

Bull., v. 40, p. 253-254. 

--1970a, Sedimentary history of Sadlerochit and Shublik 

Formations in northeastern Alaska, in Adkison, W. L., and 

Brosge, M. M., eds., Proceedings of the geologic seminar on the 
46 POST-CARBONIFEROUS STRATIGRAPHY, NORTHEASTERN ALASKA 

North Slope of Alaska: Los Angeles, Pacific Sec. Am. Assoc. 

Petroleum Geologists, p. 1-13. 

--1970b, Analysis of Shublik Formation rocks from Mt. Michelson quadrangle, Alaska: U.S. Geol. Survey open-file report, 

1 p., 3 charts. 

---1971, Arctic Mesozoic correlation chart: U.S. Geol. Survey 

open-file report, 1 sheet. 

---1973, Mesozoic sequence in Arctic Alaska, in Proceedings 6f2d 

International Arctic Symposium: Am. Assoc. Petroleum 

Geologists Mem., p. 37~387. 

Detterman, R. L., Bickel, R. S., and Gryc, George, 1963, Geology of the 

Chandler River region, Alaska: U.S. Geol. Survey Prof. Paper 

303-E, p. 223-324. 

Fackler, W. C. (chm., North Slope Stratigraphic Committee), 1971, 

West to east stratigraphic correlation section Pt. Barrow to Ignek 

Valley, Arctic North Slope, Alaska: Alaska Geol. Soc., Anchorage, Alaska. 

Gryc, George, and Mangus, M.D., 1947, Preliminary report on the 

stratigraphy and structure of the area of the Shaviovik and 

Canning Rivers, Alaska: U.S. Geol. Survey open-file report, 7 p. 

Gryc, George, Patton, W. W., Jr., and Payne, T. G., 1951, Present 

Cretaceous stratigraphic nomenclature of. northern Alaska: 

Washington Acad. Sci. Jour., v. 41, no. 5, p. 159-167. 

Gryc, George, and others, 1956, Mesozoic sequence in Colville River 

region, northern Alaska: Am. Assoc. Petroleum Geologists Bull., 

v. 40, no. 2,p. 209-254. 

Imlay, R. W., 1959, Succession and speciation of the pelecypod 

Aucella: U.S. Geol. Survey Prof. Paper 314-G, p. 155-169. 

---1961, Characteristic lower Cretaceous megafossils from northern Alaska: U.S. Geol. Survey Prof. Paper 335, p. 74. 

Imlay, R. W., and Detterman, R. L., 1973, Jurassic paleobiogeography 

of Alaska: U.S. Geol. Survey Prof. Paper 801, 34 p. 

Jones, D. L., and Gryc, George, 1960, Upper Cretaceous pelecypods of 

the Genus Inoceramus from northern Alaska: U.S. Geol. Survey 

Prof. Paper 334-E, p. 149-165. 

Keller, A. S., Morris, R. H., and Detterman, R. L., 1961, Geology ofthe 

Shaviovik and Sagavanirktok Rivers region, Alaska: U.S. Geol. 

Survey Prof. Paper 303-D, p. 169-222. 

Leffingwell, E. de K., 1919, The Canning River region, northern 

Alaska: U.S. Geol. Survey Prof. Paper 109, 251 p. 

MacNeil, F. S., 1957, Cenozoic megafossils of northern Alaska: U.S. 

Geol. Survey Prof. Paper 294-C, p. 99-126. 

MacNeil, F. S., Wolfe, J. A., Miller, D. J., and Hopkins, D. M., 1961, 

Correlation of Tertiary formations of Alaska: Am. Assoc. 

Petroleum Geologists Bull., v. 45, no. 11, p. 1801-1809. 

Maddren, A. G., 1912, Geologic investigations along the CanadaAlaska boundary: U.S. Geol. Survey Bull. 520,_ p. 297-314. 

Mangus, M.D., and Pessel, G. H. (chm., North Slope Stratigraphic 

Committee), 1972, Northwest to southeast stratigraphic correlation section Prudhoe Bay to lgnek Valley, Arctic North Slope, 

Alaska: Alaska Geol. Soc., Anchorage, Alaska, 1 sheet. 

Morris, R. H., 1953, Reconnaissance study of the Marsh anticline, 

northern Alaska: U.S. Geol. Survey open-file report, 6 p. 

Mountjoy, E. W., 1967, Triassic stratigraphy of northern Yukon 

Territory: Geol. Survey Canada Paper 6~19, p. 28-31. 

Norris, D. K., 1972, Structural and stratigraphic studies in the 

tectonic complex area of northern Yukon Territory, north of 

Porcupine River: Canada Geol. Survey, Report of activities, Paper 

72-1, Part B, p. 91-99. 

Patton, W. W., Jr., and Tailleur, I. L., 1964, Geology of the 

Killik-Itkillik region, Alaska: U.S. Geol. Survey Prof. Paper 

303-G, p. 409-500. 

Porter, S. C., 1966, Pleistocene geology of Anaktuvuk Pass, central 

Brooks Range, Alaska: Arctic lnst. North America, Tech. Paper 

18, 100 p. 

Potter, P. E., and PettUohn, F. J., 1963, Paleocurrents and basin 

analysis: Berlin, Springer-Verlag, 291 p. 

Reed, B. L., 1968, Geology of the Lake Peters area, northeastern 

Brooks Range: U.S. Geol. Survey Bull. 1236, 132 p. 

Reiser, H. N., 1970, Northeastern Brooks Range-a surface expression of the Prudhoe Bay section, in Adkison, W. L., and Brosge, M. 

M., eds., Proceedings of the geological seminar on the North Slope 

of Alaska: Los Angeles, Pacific Sec. Am. Assoc. Petroleum 

Geologists, p. K1-K13. 

Reiser, H. N., Brosge, W. P., Dutro, J. T., Jr., and Detterman, R. L., 

1971, Preliminary geologic map, Mt. Michelson quadrangle, 

Alaska: U.S. Geol. Survey open-file report, 2 sheets. 

---1974, Preliminary geologic map of the Demarcation Point 

quadrangle, Alaska: U.S. Geological Survey open-file map, 

1 sheet. 

Reiser, H. N., Dutro, J. T., Jr., Brosge, W. P., Armstrong, A. K., and 

Detterman, R. L., 1970, Progress map, geology of the Sadlerochit 

and Shublik Mountains, Mt. Michelson C-1, C-2, C-3, and C-4 

quadrangles, Alaska: U.S. Geol. Survey open-file report, 4 sheets. · 

Reiser, H. N., and Tailleur, I. L., 1969, Preliminary geologic map of 

Mt. Michelson quadrangle, Alaska: U.S. Geol. Survey open-file 

report, 1 sheet. 

Rickwood, F. K., 1970, The Prudhoe Bay field, in Adkison, W. L., and 

Brosge, M. M., eds., Proceedings of the geological seminar on the 

North Slope of Alaska: Los Angeles, Pacific Sec. Am. Assoc. 

Petroleum Geologists, p. L1-L11. 

Rucklin, H., 1938, Stromungsmarken im unteren Muschelkalk des 

Saarlandes: Senckenbergiana 20, p. 94-114. 

Sable, E. G., 1965, Geology of the Romanzof Mountains, Brooks 

Range, northeastern Alaska: U.S. Geol. Survey open-file report, 

218 p. 

Schrader, F. C., 1902, Geological section of the Rocky Mountains in 

northern Alaska: Geol. Soc. America Bull. 13, p. 233-252. 

---1904, A reconnaissance in northern Alaska: U.S. Geol. Survey 

Prof. Paper 20, 139 p. 

Silberling, N.J., and Patton, W. W. Jr., 1964, Triassic rocks ofBrooks 

Range, in Geological Survey research 1964: U.S. Geol. Survey 

Prof. Paper 501-A, p. A116. 

Smith, P. S., 1939, Areal geology of Alaska: U.S. Geol. Survey Prof. 

Paper 192, 100 p. 

Todd, Ruth, 1957, Foraminifera from Carter Creek, northeastern 

Alaska: U.S. Geol. Survey Prof. Paper 294-F, p. 223-235. 

Tourtelot, H. A., and Tailleur, I. L., 1971, The Shublik Formation and 

adjacent strata in northeastern Alaska: U.S. Geol. Survey 

open-file report, 62 p. 

Whittington, C. L., 1956, Revised stratigraphic nomenclature of 

Colville Group, in Gryc, George, and others, Mesozoic sequence in 

Colville River region, northern Alaska: Am. Assoc. Petroleum 

Geologists Bull., v. 40, p. 244-253. 

Whittington, C. L., and Sable, E. G., 1948, Preliminary geologic report 

of the Sadlerochit River area: U.S. Geol. Survey open-file 

report, 18 p. 

Williams, Rowel, Turner, F. J., and Gilbert, C. M., 1958, 

Petrography-an introduction to the study of rocks in thin 

sections: San Francisco, W. H. Freeman Co., 406 p. 

U.S. GOVERNMENT PRINTING OFFICE: 1975-0-689-910/79