Foraminifera from the Arctic Slope of Alaska

189 Pages·2010·13.06 MB·English

Foraminifera from the
Arctic Slope of Alaska
GEOLOGICAL SURVEY PROFESSIONAL PAPER 236-C
Prepared in cooperation 'with the U.S.
Department of the Navy^ Office of Naval
Petroleum and Oil Shale Reserves
Foraminifera from the
Arctic Slope of Alaska
By HELEN TAPPAN
Part 3, Cretaceous Foraminifera
GEOLOGICAL SURVEY PROFESSIONAL PAPER 236-C
Description and illustrations of Cretaceous Foram
inifera, ranging from Valanginian to Senonian
in age, and the evidence they supply for correlation
and interpretation of paleoecology and geologic
history. Prepared in cooperation with the U.S.
Department of the Navy, Office of Naval Petroleum
and Oil Shale Reserves
UNITED STATES GOVERNMENT PRINTING OFFICE, WASHINGTON : 1962
UNITED STATES DEPARTMENT OF THE INTERIOR
STEWART L. UDALL, Secretary
GEOLOGICAL SURVEY
Thomas B. Nolan, Director
For sale by the Superintendent of Documents, U.S. Government Printing Office
Washington 25, D.C.
OUTLINE OF THE REPORT
General Introduction
Part 1. Triassic Foraminifera
2. Jurassic Foraminifera
3. Cretaceous Foraminifera
4. Pleistocene Foraminifera

CONTENTS
Page (cid:9)Page
Abstract-__________________________________________ 91 Foraminiferal studies in northern Alaska—Continued
Introduction-____-__--__---_____-_-________________ 91 Source of material—Continued
Stratigraphy of the Cretaceous of northern Alaska._____ 92 Subsurface material_________________________ 107
Early Lower Cretaceous formations _______________ 93 Test wells and core tests__-__-_-_-----__- 107
Okpikruak formation.--__--_-._______-___-_-_ 93 Arcon Point Barrow core test l_---__- 108
Fortress Mountain formation.___-_-___-_-____ 93 Avak test well !_.__.________----- 108
Torok formation..-_________________________ 93 East Topagoruk test well !______ — -- 108
Topagoruk formation--..-_____--__-____-___- 93 Fish Creek test well 1__-_______ 108
Nanushuk group______________________________ 94 Gubik test well 1_____________- 109
Tuktu formation__________________________ 94 Gubik test well 2_____________-_____ 109
Chandler formation.________________________ 95 Oumalik core test 2_________________ 109
Grandstand formation_______________________ 95 Oumalik core test ll_-______-_---_-~ 109
Ninuluk formation._________________________ 95 Oumalik test well l_________-_--__-_ 109
Kukpowruk formation.._____________________ 95 Sentinel Hill core test l_____-_--_--_ 109
Corwin formation.-__________________________ 96 Simpson core hole 3--_-_--__-_------ 109
Colville group-_________________________________ 96 Simpson core hole 8-__-_-------_---_ 109
Seabee formation.__________________________ 96 Simpson core hole 10________________ 109
Schrader Bluff formation.___________________ 97 Simpson core hole ll____-___-_----_- 109
Prince Creek formation..____________________ 97 Simpson core test 13_ ____-_--------- 109
Ignek formation._______--________-_-__-___--__- 97 Simpson core test 25________-__----_ 109
Foraminiferal studies in northern Alaska.______________ 98 Simpson core test 30_ ____-__-_----__ 109
Source of material- _____________________________ 98 Simpson test well !_________________ 109
Areas of outcrop, and locality register.________ 98 Skull Cliff core test 1_____________ 109
1945 field season__-_-_-__-___-_-__-_____ 99 South Barrow test well l_-___-____-_ 109
Chandler River area._______________ 99 South Barrow test well 2._-_-_---__- 109
Colville River area__________________ 99 South Barrow test well 3_-__-_------ 109
1946 field season_-________-_--_--__-__-_ 99 South Barrow test well 4____________ 110
Umiat area_-_-___-_--_--____-_____ 99 Square Lake test well l._____ —______ 110
Maybe Creek-Wolf Creek area.______ 99 Titaluk test well 1__________________ 110
Kurupa-Oolamnagavik Rivers area___ 99 Topagoruk test well !__________.____ 110
Sagavanirktok River area____________ 99 Umiat test well 1___-_----_--------_ 110
1947 field season_-__-_-_________________ 99 Umiat test well 2------------------- 110
Colville River area__________________ 99 Umiat test well 3------------------- 110
Ipnavik, Etivluk and Kurupa Rivers Umiat test well 8------------------- 110
area___________________________ 100 Umiat test well 9------------------- 110
Kigalik and Awuna Rivers area______ 101 Umiat test well ll_______-__-------- 110
Utukok Rivers and Corwin-Cape Beau Seismograph shot hole samples ___________ 110
fort area_ ____-__-__-__„__________ 103 1946 shot holes—-._____-._ — ———— HO
Upper Ikpikpuk River area__________ 104 1948 shot holes-__-_---------- — --- 111
Colville River area, between Ninuluk 1949 shot holes--_-___----- —— __- 111
and Prince Creeks-_______________ 104 1953 shot holes--.-------.---------- 111
Nanushuk and Anaktuvuk Rivers area_ 105 Foraminiferal evidence for correlation of the Cretace
1948 field season____---_-_-_--__________ 105 ous of Alaska_______---_----_---------------- HI
Chandler River area._______________ 105 Microfaunal zones-------------------------- HI
Upper Colville River area__________ 106 Correlation with Canada-—__________-__---- 113
1949 field season________________________ 106 Lower Cretaceous___-------------------- 113
Carbon Creek and Titaluk anticlines__ 106 Upper Cretaceous----------------------- 113
Kokolik and Kukpowruk Rivers area__ 106 Correlation with conterminous United States.._ 115
Colville River area__________________ 106 Lower Cretaceous----------------------- 115
Kiruktagiak and Okokmilaga Rivers Upper Cretaceous_______________---__- 116
area___________________________ 106 Correlation with Europe-____________________ 116
1950 field season________________________ 107 Lower Cretaceous_________-__-_-----_- 116
Siksikpuk and Nanushuk Rivers area_ _ 107 Upper Cretaceous_____------------------ 117
Driftwood anticline—Utukok River re Problems in taxonomy and the species concept-____ 118
gion_ ___________________________ 107 Genetic and physiological criteria-____________ 118
1951-52 field season___________________ 107 Morphological criteria.____________--------_- 118
Chandler River area_ _______________ 107 Ecological criteria_____-----__--_------------ 120
Awuna River area__ ________________ 107 Evolutionary criteria.._-________-___-_---_-- 121
VI CONTENTS
Foraminiferal studies in northern Alaska—Continued Page Foraminiferal studies in northern Alaska—Continued Page
Biostratigraphical relations of the Cretaceous Fora- Systematic descriptions of Foraminifera—Continued
minifera of Alaska_-____-_--_--______-________ 122 Lituolidae_______-___-_-_____-____-.____-__ 133
Limiting environmental factors.______________ 122 Textulariidae______-___________-_--_____ 139
Depth_ ______________________________ 122 Verneuilinidae. _____________________________ 142
Salinity_____________________________ 123 Valvulinidae_ ______________________________ 151
Substratum- ___________________________ 123 Trochamminidae. _ _ _______________________ 152
Food Supply_-_-_-_-_-_-_--_-___-__ 123 Miliolida e. _ ______________________________ 157
Temperature. _-__-_-_---_____-_________ 123 Rzehakinidae___ _ _____-_____-_^-__-_______ 157
Turbulence and currents.________________ 123 Nodosariidae_ ______________________________ 161
Turbidity______________________!_____ 124 Glandulinidae______________________________ 182
Biofacies in the Cretaceous of Alaska__________ 124 Polymorphinidae_ __________________________ 182
Inland facies—Fluviatile environment_____ 126 Turrilinidae __ ____________________________ 184
Coastal facies—Supralittoral and littoral Caucasinidae__ _ ____________________________ 188
(intertidal) environment_______________ 126 Chilostomellidae_ ___________________________ 189
Offshore facies—Inner sublittoral environ Nonionidae-_______________________________ 190
ment ________________________________ 127 Alabaminidae_ _____________________________ 190
Offshore facies—Outer sublittoral environ Eponididae_ ______-_-_-___-______--___.____ 191
Conorboididae_ _ __________________________ 191
ment-. ______________________________ 127
Valvulineriidae_ ____________________________ 194
Offshore facies—Open-sea environment- _ _ _ 127
Asterigerinidae. ____________________________ 195
Systematic descriptions of Foraminifera___________ 128
Heterohelicidae_ ____________________________ 196
Rhizamminidae_ _ _ ________________________ 128
Rotaliporidae____ _ __________________________ 196
Saccamminidae_ ____________________________ 129
Gavelinellidae_ _ ____________________________ 197
Hyperamminidae_ ___-----_____-____________ 129 Anomalinidae_ _-__-__--____-___-__-________ 199
Ammodiscidae__ __________________________ 130 References-______-_-__-____--__-_______---___--____ 200
Reophacidae_ ______________________________ 132 Index. ______________________________________ 205
ILLUSTRATIONS
[Plates 29-58 follow index]
PLATE 29. Bathysiphon, Saccammina, Hyperamminoides, Glo- PLATE 51. Eponides
mospira, Glomospirella 52. Conorboides
30. Ammodiscus, Reophax, Haplophragmoides 53. Conorbina, Eurycheilostoma
31. Haplophragmoides 54. Valvulineria, Eoeponidella
32. Ammobactdites, Vemeuilinoides 55. Heterohelix, Hedbergella, Globorotalites
33. Spiroplectammina, Textularia, Flabellammina, Uvi- 56. Gavelinella
gerinammina 57. Gavelinella
34. Vemeuilinoides, Siphotextularia, Gaudryina 58. Gavelinella, Anomalinoides Page
35. Gaudryina, Gaudryinella FIGURE 10. Cretaceous strata of northern Alaska_______ 94
36. Gaudryina, Arenobulimina, Pseudoclavulina, Mili- 11. Index map of outcrop and seismic shothole
ammina samples, Colville River region.-_________ 100
37. Miliammina, Quinqueloculina, Psamminopelta 12. Index map of outcrop and seismic shothole
38. Trochammina samples, between Canning and Colville
39. Trochammina Rivers____________________________ 101
40. Lenticulina 13. Index map of outcrop samples, between Cape
41. Lenticulina, Saracenaria Lisburne and Carbon Creek _____________ 103
42. Saracenaria, Marginulinopsis 14. Location of wells and core tests in Naval
43. Marginulinopsis, Marginulina Petroleum Reserve 4--_--_----------___ 108
44. Marginulinopsis, Marginulina, Rectoglandulina, 15. Correlation of Alaskan and Canadian Cre
Lingulina taceous strata______-_____--_--_-__--_- 114
45. Nodosaria, Dentalina
16. Correlation of Cretaceous strata of Alaska
46. Vaginulina, Astacolus, Vaginulinopsis
with western interior and Gulf Coast of the
47. Vaginulinopsis, Citharina, Citharinetta, Frondicu-
United States.---.__-.___-__-_____ 115
laria, Oolinet, Paleopolymorphina, Pyrulinoides,
17. Lithologic and faunal facies of the Nanushuk
Globulina
48. Neobulimina, Praebulimina and Colville groups.______-__-__-__-__- 125
49. Praebulimina, Caucasina, Lacosteina 18. Depositional environments in northern Alas
50. Pallaimorphina, Noniondla ka during the Cretaceous-____-----_---- 126
FORAMIN-IFERA FROM THE ARCTIC SLOPE OF ALASKA
By HELEIT TAPPAN i
PART 3. CRETACEOUS FORAMINIFERA
ABSTRACT and different assemblages occur in contemporaneous beds of
distinct facies. Even the generically similar faunal facies of
A fauna of 155 species of Foraminifera was obtained from
the different formations are characterized by distinct species,
Cretaceous strata of northern Alaska, ranging in age from
however, and useful faunal zones can be recognized. Some of
Early Cretaceous (Valanginian) to Late Cretaceous (Senon-
the more tolerant species also have sufficiently wide geographic
ian). Material was obtained both from surface samples col
range to be useful in interregional correlation, such as with
lected over a period of about seven years, and from cores and
Canada, and the Western Interior and Gulf Coast of the
cuttings from the 76 wells and core tests drilled in Naval
United States.
Petroleum Reserve No. 4, in the Arctic Coastal Plain province
INTRODUCTION
of northern Alaska.
Fifty-eight genera are represented, belonging to 28 families, This report is the third of a series describing the
and the majority are long ranging and environmentally tol
Foraminifera of northern Alaska. The material de
erant genera. Although only 58 of the species are agglutinated
scribed was obtained during the field exploration and
forms, representing a little over one-third of the number of
species, they dominate the assemblages in numbers of speci drilling program conducted by the U.S. Navy in Na
mens. The Lituolidae, Verneuilinidae, and Textulariidae char val Petroleum Reserve No. 4, and adjacent areas of
acterize these assemblages. Another one-third of the species the Arctic Slope of Alaska. The U.S. Geological
belong to the Nodosariidae, the remaining one-third of the
Survey cooperated with the U.S. Navy in -the geologi
species belong to the Turrilinidae Caucasinidae, and various
cal aspects of this program. A general discussion of
rotaliform families and include the stratigraphically impor
tant forms. The Seabee formation, of Turonian age, contains these investigations, with an outline map showing the
the only planktonic Foraminifera found in the northern Alaska location of the Reserve, may be found in the first of
Cretaceous, a single species each of Heterotielix and Hedfoer- this series (Tappan, 1951 c), which described the Tri-
gella.
assic fauna. The second part (Tappan, 1955) de
The impoverished faunal assemblages are the result of an
scribed the Jurassic Foraminifera, and the present sec
adverse depositional environment, and not due to subsequent
destruction, such as by secondary weathering. The inter- tion covers the foraminiferal fauna of the Cretaceous.
tonguing marine and nearshore and nonmarine Cretaceous The Cretaceous sediments are near-shore sands and
strata are each characterized by distinct microfaunal facies. clays, commonly with intertonguing marine and non-
The nonmarine formations contain charophyte oogonia, but
marine strata and those of the Lower Cretaceous are
no Foraminifera; brackish-water and intertidal deposits con
typically graywackes. This shallow, muddy-water
tain a few species of arenaceous Foraminifera, commonly rep
resented by stunted specimens. The near-shore marine deposits depositional environment was an inhibiting factor in
consist largely of a turbidity facies throughout much of the the faunal development, hence the faunal aspect is
northern Alaska Cretaceous, and the high turbidity and turbu quite unlike that of equivalent strata of the Gulf Coast
lence and resultant rapid deposition are the dominant con
of the United States. In the latter area, a single sam
trolling factors of the marine sedimentary environment. The
ple may contain from 100 to 300 species of Foramini
species of agglutinated Foraminifera occur in the turbidity
facies as large robust specimens, whereas some of these species fera, whereas in Alaska about one-third of the samples
were represented only by stunted specimens in the brackish were barren, the remainder containing from two to ten
environment. The agglutinated forms are commonly crushed species or rarely as many as 20 species. Thus, the total
and variously distorted in preservation. The rarer calcareous
fauna of 155 species represents a composite fauna of
species and the extremely rare Radiolaria are represented in
almost the entire Cretaceous section, from beds of Val
this facies by pyritic casts, an indication of their rapid burial.
More offshore facies contain the calcareous and agglutinated anginian, Albian, Cenomanian, Turonian, and Seno-
species in approximately equal numbers, and in these sedi niaii age, and many of these species, particularly of the
ments both the calcareous Foraminifera and the siliceous Nodosariidae, are represented only by a few specimens
Radiolaria may occur as original shells, rather than as pyritic
in a single sample. Arenaceous species dominate the
casts.
Lower Cretaceous faunas, but a few calcareous species
Both the faunal and lithologic facies cross time lines, so that
similar assemblages appear in the same facies of different ages, become locally abundant in the cleaner Upper Creta
ceous sediments. Planktonic assemblages are non-ex
istent, except for a single Turonian zone, which con-
1 Mrs. Alfred R. Loebllch, Jr.
91
92
FORAMINIFERA FROM THE ARCTIC SLOPE OF ALASKA
tains two primitive species, both occurring only rarely. Patton, Jr., Richard G. Ray, Hillard N. Reiser, Ed
Considerably more than 2000 Cretaceous outcrop sam ward G. Sable, Karl Stefansson, Irvin L. Tailleur,
ples, and cuttings and cores from about 170,000 feet of Raymond M. Thompson, Robert F. Thurrell, Jr., Max
well sections, and hundreds of samples from seismo L. Troyer, Edward J. Webber, Charles L. Whitting-
graph shot holes were examined over the past decade, ton, and James H. Zumberge.
in order to accumulate even these impoverished Creta Samples were also made available from seismograph
ceous faunas. The poorly diversified character of the shot holes taken by crews of the United Geophysical
faunas combined with a considerable amount of distor Company. These samples supplied additional strati-
tion in preservation resulted in an extremely difficult graphic information in some areas where outcrops were
problem of identification. In the early part of these poor, particularly in the Coastal plain region.
studies, it was thought that a far greater number of In the early stages of this study, microfossil samples
species was represented, and only after considerable were examined and picked by the writer and Alfred
study was their total reduced to the present number. R. Loeblich, Jr. in Washington. Later all samples
Many of the species, as illustrated on the accompany were prepared and picked in the Fairbanks laboratory
ing plates, will seem at first glance to be too inclusive, and only the mounted slides supplied for study. These
but all gradations have been observed between the ex were prepared in Fairbanks by Tatiana Aschurkoff,
tremes, and no taxonomic or stratigraphic advantage Clyde Foster, William N, Lockwood, Octavia T. Pratt,
could be seen to result from any further subdivision Dorothy J. West, and Lucy Wiancko, under the direc
of the species. In spite of the specialized local en tion of William N. Lockwood, Robert M. Chapman,
vironment, relative scarcity of specimens, and predomi Thomas G. Roberts, Arthur L. Bowsher, and Harlan
nance of long-ranging arenaceous genera, the Fora- Bergquist.
minifera do show relationships to other faunas and the Acknowledgment is also made of the continued as
species can be used for both local correlations within sistance of Alfred R, Loeblich, Jr., formerly with the
the Reserve and long-range correlation with other areas U.S. National Museum, now with California Research
of the world. Corp., La Habra, California, in early washing and
This study was made possible only by the full co picking of samples, in discussions of various taxonomic
operation of the geologists of the U.S. Geological Sur problems, in preparation of the illustrations and for
vey engaged in studies of Naval Petroleum Reserve helpful criticism throughout the study.
No. 4 during the past decade. Aid was given in ob Illustrations of the fauna are shaded camera lucida
taining material and information by Ralph L. Miller, drawings prepared by the writer and by Patricia
George Gates, and George Gryc. Harlan R. Bergquist Isham, scientific illustrator, Smithsonian Institution.
has cooperated in all phases of the micropaleontologic Cretaceous material from Canada, for comparative
study, and I am indebted to him for many helpful dis use, was supplied by R. T. D. Wickenden, of the Geo
cussions and suggestions on both stratigraphic and tax logical Survey of Canada, and Canadian foraminiferal
onomic problems. Thomas G. Payne also was of in types were loaned by C. R. Stelck, University of Al
estimable aid in the determination and understanding berta, Canada, and J. H. Wall, Research Council of
of the many facies changes in the sediments, and the Alberta. Type specimens of Canadian species de
resultant problems of correlation. scribed by A. Nauss were loaned by Stanford Univer
Lithologic studies of the well samples were made by sity, California.
Florence Rucker Collins, A. Samuel Keller, T. G. Rob
erts, and Florence Robinson, and in many instances STRATIGRAPHY OF THE CRETACEOUS OF NORTHERN
ALASKA
subsurface formational contacts were based on these
lithologic studies, where they did not coincide with the Early work in the Cretaceous of northern Alaska
faunal or time boundaries. was of reconnaissance nature as the relative inaccessi
Cretaceous outcrop material and stratigraphic infor bility of the area made field work difficult and hazard
mation lias been supplied by many of the Survey geolo ous. Early publications include those of Schrader
gists during the period 1945 to 1952, during the course (1902,1904), Leffingwell (1919), and Smith and Mertie
of the geologic mapping program in northern Alaska. (1930). In 1945 the U.S. Geological Survey in coop
I am indebted for these samples to William L. Barks- eration with the U.S. Navy began geologic field studies
dale, Robert S. Bickel, William P. Brosge, Robert M. of the Naval Petroleum Reserve and adjacent areas
Chapman, Robert L. Detterman, William A. Fischer, north of the Brooks Range. With the aid of bush
George Gryc, A. Samuel Keller, Charles A. Kirschner, planes, helicopter, weasels, radio, etc., much more
Ernest H. Lathram, Marvin L. Mangus, William W. lengthy and detailed geologic work could be done. Use
93
CRETACEOUS FORAMINIFERA
of aerial photographs aided in the mapping, and labo spira^ Haplophragmoides, a few Nodosariidae, and sim
ratory study of rock samples, micropaleontologic, and ple Discorbidea and Chilostomellidae. A few species
macropaleontologic studies aided in the understanding limited to the Fortress Mountain formation and the
of the stratigraphic problems. equivalent Torok formation, include Gaudryina tail-
The near-shore, rapidly changing facies of the Cre leuri (Tappan), Trochammina, eilete Tappan, Vaginu-
taceous sediments made correlation difficult between Unopsis pachynota ten Dam, Marginulina sulcifera
the discontinuous outcrops; this was further compli (Reuss), and Conorbina sp. The first two of these are
cated by the great amount of lithologic change from described from these strata and the V'aginulinopsis
the more consolidated sediments near the Brooks from the Hauterivian (Neocomian) of the Nether
Range to the loose sands and clays of the coastal plain. lands ; the Marginulina ranges from Neocomian to Al-
Macrofossils were sparse in part of the section, and bian strata in Europe, and the Conorbina occurs in the
truly diagnostic forms were only rarely obtained. The Clearwater formation in Canada, which is equivalent
dominance of long-ranging arenaceous genera of Fora- in age to the Fortress Mountain.
minifera prevented the full use of micropaleoiitology
TOROK FORMATION
for correlation until after a considerable period of
study. The Torok formation was described by Gryc, Pat-
New stratigraphic names were finally proposed after ton, and Payne (1951, p. 160), with the type locality
the facies and correlations had been largely worked on the Chandler River and its tributary, Torok Creek.
out (Gryc, Patton and Payne, 1951; Gryc and others, Originally the formation was more inclusive, but it
1956; Sable, 1956), and the present stratigraphic usage was restricted and redefined by Patton in 1956 (p. 222)
is shown in figure 10. As a basis for a biostratigraphic when the equivalent conglomerates and sandstones of
discussion, a brief summary of the Cretaceous forma the southern part of the region were separated as the
tions follows, in ascending order. Megafossils listed Fortress Mountain formation. The more northerly ex
were identified by R. W. Imlay and reported in the posures of the redefined Torok formation are predomi
above-mentioned formational descriptions. nately shales, and exposures consist of small cutbanks
along the creeks. The Torok formation is approxi
EARLY LOWER CRETACEOUS FORMATIONS mately 6,000 feet in thickness, and locally is much
crumpled and faulted. The macrofossils in the Torok
OKPIKRUAK FORMATION
formation, like those of the equivalent Fortress Moun
Typically exposed along the Okpikruak River, this
tain formation, indicate a late Early Cretaceous age.
formation was named by Gryc, Patton and Payne
In the type area the Torok formation has relatively
(1951, p. 159). It is about 2,400 feet thick at the type
few microfossils and these are predominantly aggluti
locality, and is a fine-grained graywacke-type sand
nated species. Farther west the Torok formation ap
stone, dark clay and silt shale. The early Lower Cre
parently is transgressive and includes younger beds,
taceous (Valanginian) pelecypod Bucliia crassicollis
equivalent in age to the Topagoruk formation of the
(Keyserliiig) occurs throughout most of the formation,
coastal plain, with the fauna characteristic of those
but the microfauiia is extremely scarce, including only
deposits. The Torok formation in the subsurface of
long-ranging species of such genera as TrocJiammina
the coastal plain is of more off-shore character and has
and Haplophragmoides.
a well defined and diversified microfauna including
FORTRESS MOUNTAIN FORMATION numerous Nodosariidae, Polymorphinidae and Discor
bidea in addition to the agglutinated species of Lituo-
In the southern half of the Arctic Foothills province
lidae, Textulariidae, Verneuilinidae, and Trochammi-
this formation unconformably overlies the Okpikruak
nidae.
formation, the type section being along the Kirukta-
giak River and on Castle Mountain, the name being TOPAGORUK FORMATION
from the nearby Fortress Mountain. Defined by Pat- 111 the subsurface section, a silty shale unit overlies
ton (1956, p. 219), it consists of graywacke-type con the Torok formation, and is laterally equivalent to the
glomerates and sandstones intercalated with dark-gray upper part of the outcropping Torok formation, the
clays and silts, and is approximately 10,000 feet in Tuktu formation, and part of Grandstand formation.
thickness in the type section. The rare macrofossils Described as the Topagoruk member of the Umiat for
include Aucellina dowlingi McLearn, Beudanticeras mation in 1951 (Gryc, Patton and Payne, p. 162) it
sp., Lemuroceras sp. and Inoceramus sp., which indi was then regarded as including all marine Nanushuk
cate a late Early Cretaceous age. Foraminifera in beds above the Tuktu member. The Topagoruk was
clude long-ranging species of Bathysiphon, G-lomo- raised to formational rank by Robinson, Rucker, and