Six New Paleozoic and 

Mesozoic Formations in 

East-Central Alaska

By EARL E. BRABB

CONTRIBUTIONS TO STRATIGRAPHY

GEOLOGICAL SURVEY BULLETIN 1274-1

Definition and description of some 

sedimentary rocks in the Kandik basin

UNITED STATES GOVERNMENT PRINTING OFFICE, WASHINGTON : 1969
UNITED STATES DEPARTMENT OF THE INTERIOR 

WALTER J. HICKEL, Secretary

GEOLOGICAL SURVEY 

William T. Pecora, Director

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

Washington, D.C. 20402 - Price 25 cents (paper cover)
CONTENTS

Page

Abstract................................................................................................................... II

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

Acknowledgments.......................................................................................... 1

Upper Devonion to Upper Mississippian rocks............................................... 2

Ford Lake Shale........................................................................................... 2

Permian rocks........................................................................................................ 7

Step Conglomerate....................................................................................... 7

Middle Triassic to Lower Cretaceous rocks..................................................... 9

Glenn Shale.................................................................................................... 9

Lower Cretaceous rocks....................................................................................... 13

Kandik Group................................................................................................ 13

Keenan Quartzite.................................................................................. 14

Biederrnan Argillite.............................................................................. 16

Kathul Graywacke................................................................................ 21

References cited.................................................................................................... 25

ILLUSTRATIONS

Page 

FIGURE 1. Index map showing locations of stratigraphic sections............... 13

2. Photograph of contact between the Ford Lake Shale and the

Calico Bluff Formation .............................................................. 4

3. Stratigraphic column showing relations of the new formations

named and described in this report........................................... 5

4-10. Photographs of:

4. A part of the type section of the Ford Lake Shale.. 6

5. Limestone in the Glenn Shale............................!........... 11

6. A typical exposure of the Keenan Quartzite............... 15

7. The type section of the Biederrnan Argillite............... 17

8. Rhythmic interbeds of argillite, siltstone, and sandstone of the Biederrnan Argillite ............................ 18

9. The type section of the Kathul Graywacke.............. 22

10. Faulted beds of the Kathul Graywacke along the

Kandik River .............................................................. 23

TABLES

Page

TABLE 1. Fossils from the Step Conglomerate.............................................. 19

2. Triassic faunal sequence near Nation........................................... 12

CONTRIBUTIONS TO STRATIGRAPHY

SIX NEW PALEOZOIC AND MESOZOIC FORMATIONS 

IN EAST-CENTRAL ALASKA

By EARL E. BRABB

ABSTRACT

Six of 25 new map units established by regional geologic mapping in the 

Charley River and Eagle quadrangles are formally defined and named as follows: Ford Lake Shale (Upper Devonian to Upper Mississippian), Step Conglomerate (Permian), Glenn Shale (Middle Triassic to Lower Cretaceous), 

and the Keenan Quartzite, Biederman Argillite, and Kathul Graywacke 

three formations within the Lower Cretaceous Kandik Group.

INTRODUCTION

Regional geologic mapping by the author from 1960 to 1963 and 

by Michael Churkin, Jr., from 1962 to 1963 in the Charley River 

(1:250,000) and Eagle D-l (1:63,360) quadrangles has established 

approximately 25 new rock-stratigraphic units of Precambrian, Paleozoic, and Mesozoic age. Most of these units are shown on preliminary 

geologic maps of these quadrangles by Brabb and Churkin (1964, 

1965) released in open files of the U.S. Geological Survey. Five of the 

units have already been named, and a sixth has been identified with 

a unit in the Yukon Territory for which a name has already been 

published (Churkin and Brabb, 1965; Brabb, 1967). The purpose of 

this report is to define six additional names for formations that have 

extensive geographic distribution, so that the formations can be 

readily identified on published versions of the geologic maps and in 

subsequent geologic reports. Additional mapping in greater detail is 

desirable before formal names can be proposed for the remaining 

dozen or more units. The six new formations are described from oldest to youngest.

ACKNOWLEDGMENTS

In addition to mapping part of the regional geology, Michael Churkin, Jr., assisted by Arne Aadland, worked out the sequence of forII
12 CONTRIBUTIONS TO STRATIGRAPHY

mations in the Step Mountains that led to the naming of the Step 

Conglomerate in this report. Michael Churkin and N. J. Silberling, 

U.S. Geological Survey and Stanford University, measured one of the 

Triassic sequences that formed part of the data for Silberling's summary in table 2. R. N. Passero and H. L. Roepke, in 1960, J. C. 

Melik and R. L. Taylor, in 1961, Arne Aadland, in 1962, and D. 

L. Giles and R. H. Rohrbacher, in 1963, assisted in the regional 

geologic mapping. D. L. Jones identified the mollusks of Cretaceous 

age, and R. E. Grant identified the fossils given in table 1. R. W. 

Imlay identified one fauna of probable Jurassic age. R. A. Scott identified spores and pollen of late Mesozoic and Cenozoic age. J. A. 

Wolfe identified plants of Cretaceous age, and S. H. Mamay identified plants of Paleozoic age. Geologists of British Petroleum Co., Ltd. 

and Mobile Oil Co. kindly contributed several fossil collections and 

other material that helped date some of the formations discussed in 

this report.

UPPER DEVONIAN TO UPPER MISSISSIPPIAN ROCKS

FORD LAKE SHALE

The Ford Lake Shale is here named for exposures in the type section the east and west banks of the Yukon River (fig. 1) from about 

2 miles east of Ford Lake to about 2 miles northeast of Ford Lake, 

Eagle D-l quadrangle (1:63,360). The basal part of the formation in 

the type section and the top of the underlying Nation River Formation of Late Devonian age are concealed beneath alluvium at the 

mouth of Shade Creek. The top of the Ford Lake Shale is exposed at 

Calico Bluff (fig. 2), where it grades vertically upward into limestone 

of the overlying Calico Bluff Formation of Late Mississippian age. In 

the Step Mountains, the Ford Lake Shale is overlain unconformably 

by the Step Conglomerate of Permian age. The stratigraphic relationships of these formations are shown in figure 3.

The Ford Lake Shale consists predominantly of grayish-black 

siliceous shale and laminated grayish-black chert that splits with a 

slabby parting (fig. 4). Yellow sulfate minerals are common along 

weathered surfaces and give many outcrops of the shale and chert a 

distinctive bronze tinge. Brownish-black phosphate concretions, some 

as large as 4 inches in maximum dimension, and very pale orange 

carbonate concretions a few feet in length are common. Several limestone and dolomite beds and lenses occur in the upper part of the 

formation.

A section of the Ford Lake Shale about 1,000 feet thick is exposed 

on the west bank of the Yukon River near Calico Bluff, and several
EAST-CENTRAL ALASKA 13

Base by U.S. Geological Survey. 1956

1. Type section for the Ford 

Lake Shale.

2. Type section for the Step 

Conglomerate.

3. Type section for the Glenn 

Shale.

4. Type section for the Keenan 

Quartzite.

5. Reference section for the 

Keenan Quartzite.

7. Reference section for the 

Biederman Argillite.

8. Type section for the Kathul 

JraSrwacke.

6. Type section for the Bieder- 9. Type locality for the KandLk

man Argillite. Group.

FIGURE 1. Locations of sections discussed in text.

hundred feet of an additional (?) section are exposed on the east bank 

from ^ to \l/z miles downstream from the mouth of Shade Creek. 

The presence of several folds and the difficulty of correlating across 

the Yukon River make it impossible to determine the exact thickness 

of the formation in its type section. In the vicinity of Adams Peak, 

however, about 4 miles north of Ford Lake, the attitudes and the 

outcrop width of a homoclinal but more poorly exposed sequence indicate that the Ford Lake Shale is about 2,000 feet thick.

Few fossils have been found in the lower part of the Ford Lake 

Shale, and fossils from the upper part of the formation have not yet
14 CONTRIBUTIONS TO STRATIGRAPHY
EAST-CENTRAL ALASKA 15

SYSTEM

TERTIARY

CRETACEOUS

JURASSIC

PERMIAN

MISSISSIPPIAN

DEVONIAN

SERIES

Upper

- *~^-*-~s 

Lower

 p

_

Upper

Middle

Upper

Lower

Upper

ROCK UNIT

Unnamed nonmarine sandstone, mudstone and conglomerate 3000±ft

 ^-^-? ~^T*t-^~^ 

Unnamed

nonmarine

rocks near

Seventymile

River

 ^^^~ -

Kandik

Group

Missing

f~ ^-UNCONFORMI TY-^~~-^~~

' Kathul

Graywacke

1500 + ft

*~^~ LOCAL UNCONFORMITY ~ 

Biederman

Argillite

5000 + ft

Keenan Quartzite 

1000 ft max

Glenn Shale

5000 ± ft

Step

Conglomerate

2000 ± ft

Tahkandit

Limestone

350ft

Calico Bluff Formation 

1500± ft

Ford Lake Shale

2000+ ft

Nation River Formation

4000 ± ft

FIGURE 3. Stratigraphic relations of the new formations named and described

in this report.

been examined. Brachiopods and wood of Late Devonian or Early 

Mississippian age from the lower part of the formation in its type 

section were reported by Brabb and Churkin (1967, p. D9) from locality 60ABa 322. Plants from the Ford Lake Shale near the Tatonduk River (fig. 1) were discussed at length by David White (see 

Mertie, 1933, p. 419), who considered them to be of Devonian or, 

at latest, Early Mississippian age.
16 CONTRIBUTIONS TO STRATIGRAPHY

FIGURE 4. Part of the type section of the Ford Lake Shale along the west bank 

of the Yukon River about 2 miles northeast of Ford Lake. The shale and 

chert beds at this locality are laminated, but they split with a slabby parting. 

The cliff is about 100 feet in height and is capped with river-terrace deposits.

Plant collections from the Ford Lake Shale in the Step Mountains 

(fig. 1) were made by Michael Churkin, Jr., and Arne Aadland in 

1962 from shale in the Charley River B-2 quadrangle (Field No. 

62ACn 1114, lat 65°28.6' N., long 141°32.8' W.) and from siltstone 

in the Charley River B-2 quadrangle (Field No. 62ACn 1116, lat 

65°27.9' N., long 141°33.6' W.). The following statements were made 

by Sergius H. Mamay (written commun., 1962), who examined the 

plants:

Collection 1114 contains a very poorly preserved small plant axis with coarse 

longitudinal striations and the basal part of a lateral appendage. The striations 

suggest sphenopsid affinity but no nodal structure is present. Generic identification is impossible.
EAST-CENTRAL ALASKA 17

Collection 1116 contains (1) Several surface impressions of a fairly large 

stem with broad longitudinal ribs. This is obviously of calamarian origin but 

the nodal organization is not shown in this fragment, so that a generic identification cannot be made. (2) Several nondescript stem compressions. (3) A few 

specimens of dichotomizing axes, one of which has several lateral appendages 

attached. These are probably the bases of pinnule stalks, but are not diagnostic 

without foliar laminae.

The few fossils found in the lower part of the Ford Lake Shale and 

the gradational relations of the Ford Lake to its underlying and 

overlying units indicate that the Ford Lake is Late Devonian to Late 

Mississippian in age.

PERMIAN ROCKS

STEP CONGLOMERATE

TYPE SECTION AND AREAL DISTRIBUTION

The Step Conglomerate is here named after the Step Mountains 

(fig. 1), which lie between the Kandik and Nation Rivers at about 

lat 65°30' N., Charley River C-l, C-2, B-l, and B-2 quadrangles 

(1:63,360). The formation forms part of the flanks of a doubly plunging anticline and consists mainly of chert-pebble conglomerate and 

sandstone and a few thin interbeds of bioclastic limestone. A section 

examined about 2^4 miles northeast of bench mark 3977 (Nat) in 

the B-2 quadrangle extends from the NEy4 sec. 20, T. 8 N., R. 31 E., 

in the C-l quadrangle, where the contact with the uppermost shale 

and limestone beds of the underlying Ford Lake Shale is exposed, to 

the SE^4 sec. 28 in the B-l quadrangle, where the contact with an 

overlying grayish-black argillite, tentatively mapped as the Biederman Argillite, crops out. This section seems to have the best exposures of the Step Conglomerate and is designated the type section. 

The outcrop width and the attitudes indicate that the formation 

there is approximately 2,000 feet thick.

The Step Conglomerate is exposed over a wide area between the 

Yukon, Black, and Little Black Rivers (fig. 1). It has not as yet been 

recognized south of lat 65°25' N.; in this area rocks of the same age 

are mainly limestone.

LITHOLOGY AND DISTINGUISHING FEATURES

Most of the clasts in the Step Conglomerate are rounded chert 

pebbles 4-20 millimeters in maximum dimension. A few pebble-size 

clasts of sandstone were also observed in polished sections of the conglomerate. Most of the chert pebbles are various shades of gray, 

ranging from white to black; a few are green or red. Most of the pebbles are in a matrix of sand-size chert and quartz grains, and a few
18 CONTRIBUTIONS TO STRATIGRAPHY

are in a matrix of light-gray chert or calcite. The chert-pebble conglomerate grades upward into a very light gray sandstone and quartzite composed of chert and quartz grains. This quartzite is difficult to 

distinguish from the younger Keenan Quartzite of Early Cretaceous 

age without fossils or stratigraphic control.

There are at least two limestones in the lower part of the Step 

Conglomerate. One limestone is about 30 feet thick; it is light gray, 

thinly bedded, bioclastic, and resembles the Tahkandit Limestone of 

Permian age. The other limestone is about 20 feet thick; it is light 

brown and has many sand- and pebble-size rounded clasts of chert.

, AGE AND STRATIGRAPHIC RELATIONS

Brachiopods are abundant in the limestone, less common in the 

quartzite, and rare in the conglomerate. Fossils from the Step Conglomerate, identified by Richard E. Grant (written commun., 1965), 

are given in table 1. Grant believed that the fossils are of Permian 

age and are quite similar to faunas from the type Tahkandit Limestone of Permian age. Collections 22352-PC, 22359-PC, and 22360- 

PC are significant in dating large areas of rocks exposed in the headwaters of the Little Black River, 40-60 miles west and 10 miles east 

of the Step Mountains; the rocks in that area are now mapped as 

Step Conglomerate.

The occurrence of limestone in the Step Conglomerate similar to 

the Tahkandit Limestone, the occurrence of a 75-foot-thick chertpebble conglomerate at the base of the Tahkandit Limestone (Brabb 

and Churkin, 1967, p. D12), and the similarity of the faunas in the 

two formations indicate that the Step Conglomerate and Tahkandit 

Limestone are lateral facies. Extension of the name Tahkandit to the 

Step Mountains area and designation of the Step Conglomerate as 

a member of the Tahkandit were considered but rejected inasmuch 

as the Step is a distinctive mappable conglomerate unit about six 

times as thick as the Tahkandit. Moreover, the conglomerate at the 

base of the Tahkandit has not been observed outside the type section, 

so the name Tahkandit is most closely associated with a limestone 

formation.

The absence of the Mississippian Calico Bluff Formation and of 

Pennsylvanian rocks beneath the Step Conglomerate indicates that 

the Step Conglomerate rests unconformably on the Ford Lake Shale. 

A similar major unconformity at the base of the Tahkandit has only 

recently been recognized (Brabb and Churkin, 1967, p. D12-D14). 

The Step Conglomerate in the headwaters of the Little Black River 

area seems to rest unconformably on unnamed sedimentary and volcanic rocks of Paleozoic and probable Precambrian age. The rocks
EAST-CENTRAL ALASKA 19

TABLE 1. Fossils from the Step Conglomerate 

[Identified by R. E. Grant]

Fossils

Kochiproductus

Liosotella pseudohorrida 

(Wiman) ............

Meeousia................

USGS locality1

21790-PC sA1(N

21792-PC

9

*

X

21789-PC

v

22333-PC

7

22352-PC

'

X

22359-PC

'

22360-PC

?

X

7

Fossils

Muirwoodia sp....... 

NeophricadoStreptorhynchus

Waagenoconcha

cnnoid columnals 

pelecypod.. ..............

USGS locality1

| 21790-PC

X 

X 

X

$

r-l

R

rH 

N

X

21792-PC

X

v

21789-PC | 22333-PC

X 

X

22352-PC

v

22359-PC

?

X 

X

22360-PC

X 

X

See following table for collection localities.

USGS No. 

21789-PC

Field No. 

63ACn 1563

21790-PC 63ACn 1641

21701-PC 

21792-PC

22333-PC 

22352-PC

22359-PC

22360-PC

63ABa 4087 

63ABa 4083

62ACn 1113 

63ABa 4121

63ABa 4042 

63ABa 4112

Locality 

From sandy limestone in lower part of Step Conglomerate; Charley

River B-l quadrangle, lat 65°28.4' N., long 141°28.6' W. Collector,

Michael Churkin, Jr., 1963. 

From sandstone in the lower part of the Step Conglomerate; Charley

River B-l quadrangle, lat 65°29.5' N., long 141°24.8' W. Collector,

Michael Churkin, Jr., 1963. 

From quartzite in the Step Conglomerate; Charley River B-2 quadrangle,

lat 65°28.9' N., long 141°33.5' W. Collector, Earl E. Brabb, 1963. 

From quartzite in lower part of Step Conglomerate; Charley River C-l

quadrangle, lat 65°31.2' N., long 14P26.9' W. Collector, Earl E.

Brabb, 1963. 

From bioclastic limestone in lower part of Step Conglomerate; Charley

River B-2 quadrangle, lat 65°28.7' N., long 141°33.0/ W. Collector,

Michael Churkin, Jr., 1962. 

From quartzite within the Step Conglomerate; about 3 miles east of Takoma Bluff and 60 miles west of the Step Mountains, Charley River

B-6 quadrangle, lat 65°29.4' N., long 143°34.3' W. Collector Earl E.

Brabb, 1963. 

From Step Conglomerate; about 12 miles east of the Step Mountains.

Charley River C-l quadrangle, lat 65°3l.ff N., long 141°00.4' W. Collector, Earl E. Brabb, 1963. 

From crinoidal limestone float presumably within Step Conglomerate;

about 3 miles east of Takoma Bluff and 60 miles west of Step Mountains, Charley River C-6 quadrangle, lat 65°30.2' N., long 143°34.6'

W. Collector, Earl E. Brabb, 1963.

overlying the Step Conglomerate are the Glenn Shale of Middle 

Triassic to Early Cretaceous age and in some places the Biederman 

Argillite of Early Cretaceous age. These relations suggest that the 

top of the formation is also bounded by an unconformity.

MIDDLE TRIASSIC TO LOWER CRETACEOUS ROCKS

GLENN SHALE

TYPE SECTION AND AREAL DISTRIBUTION

Shale exposed along the banks and in the bed of Washington 

Creek (fig. 1) from 2 to 4 miles northwest of bench mark 2452
110 CONTRIBUTIONS TO STRATIGRAPHY

(Glenn) in the Charley River A-3 quadrangle (1:63,360) is here 

named the Glenn Shale. The type section extends from a fault in the 

NW% sec. 24, T. 5 N., R. 26 E., where the lower part of the formation is in contact with volcanic rocks of presumed Precambrian age, 

to the Keenan Quartzite of Early Cretaceous age in the NW^4 sec. 

12, T. 5 N., R. 26 E., in the Charley River B-3 quadrangle (1: 

63,360).

The Glenn Shale has been recognized over an area of more than 

2,000 square miles from Glenn Creek (fig. 1), for which it is named, 

to the headwaters of the Black River near the Alaska-Yukon Territory boundary, and westward as far as Eureka Creek. Phyllite and 

quartz-chlorite semischist overlying the Step Conglomerate in the 

vicinity of Indian Grave Mountain are thought to be a local metamorphic facies and are tentatively included in the Glenn Shale.

LITHOLOGY

The Glenn Shale in its type section along Washington Creek consists predominantly of grayish-black fissile carbonaceous shale, which 

grades upward into grayish-black massive argillite and siltstone containing carbonate "cannonball" concretions a few inches in diameter. 

There is a 50-foot-thick dark-gray fossiliferous limestone at the base 

of the formation along Washington Creek; at other localities, such as 

along Trout Creek, this limestone is several hundred feet thick and 

is a conspicuous part of the formation. Unusually fossiliferous limestone beds in the lower part of the Glenn Shale, about half a mile 

northeast of the mouth of the Nation River, are shown in figure 5. 

Well-known but relatively thin oil shales (see Mertie, 1930, p. 131- 

132) occur within this limestone and a few tens of feet above it 

about half a mile southwest of the mouth of the Nation River and 

along Trout Creek.

THICKNESS

The type section has not been accurately measured, but judging 

from attitudes and outcrop width, the formation seems about 5,000 

feet thick. Repetition of fossil-bearing strata and steep attitudes, 

however, indicate that the Glenn Shale is tightly folded in some 

areas, so the thickness of the formation in its type section could be 

less. In the Step Mountains, the Glenn Shale is only a few hundred 

feet thick.

AGE AND STRATIGRAPHIC RELATIONS

Shale and limestone in the lower part of the Glenn Shale near the 

mouth of the Nation River (fig. 1) contain abundant pelecypods, 

many ammonites, and a few brachiopods; these fossils have long been
EAST-CENTRAL ALASKA

FIGURE 5. Limestone in the Glenn Shale, consisting largely of cephalopods. 

Locality is about half a mile northeast of the mouth of Nation River.

correlated with the Karnian and Norian Stages of the Upper Triassic 

(see Martin, 1916, 1926; Smith, 1927; Mertie, 1930). Unfortunately, 

the diagnostic faunas are from different localities or from extensively 

folded and faulted sections, so the faunal sequence is in doubt. A 

schematic summary of the inferred faunal sequence pieced together 

from isolated localities by N. J. Silberling is given in table 2. The 

principal difference in this scheme from those previously published is 

Silberling's recognition of faunas of Middle Triassic (Ladinian) age. 

This age is based on the discovery of Daonella cf. D. degeeri at the following locality:

USGS M2138 (Field No. 63ACn 1776), Charley River A-1 quadrangle, lat 65° 

14.4' N., long 141°23.9' W., from calcareous shale on the west bank of Hard 

Luck Creek. Collected by Michael Churkin, Jr., 1963.

The following fossils were collected from the stratigraphically lowest exposures of the Glenn Shale in its type section, about 100 feet 

stratigraphically above the highest exposures of volcanic rocks of the 

Tinder Group of Precambrian age:

USGS M2155 (Field No. 63 ABa 4061), Charley River A-3 quadrangle, lat 65° 

14.9' N., long 142° 18.3' W. 

Monotis cf. M. subcircularis 

Heterastridiuml sp. 

Age: late Norian (according to Silberling).
112 CONTRIBUTIONS TO STRATIGRAPHY

TABLE 2. Schematic summary of the Triassic faunal sequence in the vicinity

of Nation

[The sequence is inferred, in part, from faunas collected at separate localities. Prepared 

by N. J. Silberling]

Stratigraphic

Substage 

9

Diagnostic fossils

Upper Norian..................Monotis subcircularis Gabb;

Heterastridium sp.

thicknesses 

9

Middle Norian................Monotis scutiformis pinensis

Westermann; Halobia cf. H. fallax 

Mojsisovics; Himavatites? sp.

Few tens of feet.

Upper Karnian to 

middle Norian.

Upper Karnian to 

middle Norian.

Uppermost Ladinian 

or lower Karnian.

Halobia spp....................... .....................Few hundreds of

feet at most.

Halobia cordillerana Smith; 

Monotis scutiformis typica 

Kiparisova.

Nathorstites aff. N. gibbosus Stolley; 

"Cladiscites" martini Smith; 

Discophyllites sp; 

Proclydonautilus sp; 

Germanonautilus brooksi Smith; 

all of the pelecypods and brachiopods described by Smith (1927) 

from the upper Yukon except 

Halobia cordillerana.

Few feet.

20 to 30 feet. 

About 10 feet.

Lower Ladinian..............Daonella cf. D. degeeri Bohm................Several feet.

? ? Few tens of feet. 

(Tahkandit Limestone of Permian age)

These fossils and the sequence worked out by Silberling (table 2) 

suggest that a few hundred feet of section ranging in age from Ladinian to early Norian have been faulted out along Washington Creek.

The prolific pelecypod and ammonite faunas of Triassic age in the 

Glenn Shale have been found only in the area south of lat 65°25/ N., 

from the Alaska-Yukon boundary to the Coal Creek area (fig. 1).

Otapiria sp. and Pentacrinus subangularis var. alaska of probable 

Jurassic age were reported by Imlay (1967, p. B7-B8) from an unknown stratigraphic position within the Glenn Shale about 3 miles 

southwest of the mouth of the Nation River (fig. 1). No fossils of
EAST-CENTRAL ALASKA ,113

certain Jurassic age have as yet been found within the area shown in 

figure 1.

Buchia okensis of Early Cretaceous (Berriasian) age has been identified by D. L. Jones from argillite in the middle part of the Glenn 

Shale along Washington Creek. This fossil was originally identified 

as Aucella crassicollis by T. W. Stanton (see Mertie, 1930, p. 139, 

USGS collection 2674).

No fossils were found in the upper part of the Glenn Shale in its 

type section, but the following fossils, identified by D. L. Jones, were 

collected from argillite and shale in the upper part of the formation on 

the west bank of the Nation River (fig. 1) near the mouth of Tindir 

Creek:

M1026 (Field No. 60 ABa 552), Charley River B-l quadrangle, lat 65°25' N., 

long 141°23.7' W. Collected by Earl E. Babb, 1960. 

Polyptychites sp. 

Buchia cf. B. crassicollis 

Age: Early Cretaceous (probably Valanginian).

M1027 (Field No. 60 ABa 553), Charley River B-l quadrangle, lat 65°24.9' N., 

long 141° 24.2' W. Collected by Earl E. Babb, 1960. 

Buchia cf. B. crassicollis 

Age: Early Cretaceous (probably Valanginian).

In summary, fossils indicate that the Glenn Shale ranges in age 

from Middle Triassic (Ladinian) to Early Cretaceous (probably 

Valanginian). All of the diagnostic fossils have been found south of 

lat 65°25' N.

The Glenn Shale rests on the Tahkandit Limestone or the Step 

Conglomerate, but the contact is not exposed. Presumably, beds of 

Early Triassic age are missing, and thus the contact between the 

Glenn Shale and the Tahkandit Limestone or the Step Conglomerate 

is considered to be an unconformity. The Glenn Shale is overlain, 

apparently conformably, by the Keenan Quartzite of Early Cretaceous (Valanginian) age and locally, unconformably, by unnamed 

nonmarine sedimentary rocks of Late Cretaceous and Tertiary age.

LOWER CRETACEOUS ROCKS

KANDIK GROUP

The name Kandik Formation was formally proposed by Mertie 

(1930) for several thousand feet of predominantly shale and sandstone exposed in the valleys of the Kandik and Yukon Rivers (fig. 

1). The Kandik Formation, of Early Cretaceous age, is herein raised 

to group status and is subdivided into three newly named formations in ascending order, the Keenan Quartzite, the Biederman Ar-
114 CONTRIBUTIONS TO STRATIGRAPHY

gillite, and the Kathul Graywacke. The type locality for the Kandik 

Group is in the vicinity of the Kandik River and is herein considered 

to be along the valley of the Yukon River from the vicinity of the 

mouth of Glenn Creek to the top of Biederman Bluff.

KEENAN QUARTZITE 

TYPE SECTION AND AREAL DISTRIBUTION

The Keenan Quartzite is best exposed along the west bank of the 

Yukon River half a mile downstream from the mouth of Glenn Creek 

(fig. 1), Charley River B-3 quadrangle (1:63,360). Keenan Creek, 

for which the formation is named, is a small tributary of Glenn Creek. 

The formation at the Yukon River locality, which is the type section, 

consists of about 150 feet of light- to dark-gray fine-grained massive 

quartzite which is overlain, apparently conformably, by tightly folded 

siltstone and argillite of the lower part of the Biederman Argillite. It 

is underlain, apparently conformably, by siltstone beds of the upper 

part of the Glenn Shale. When the Yukon River is at low stage, the 

Keenan Quartzite is also exposed on the east bank of the Yukon River 

about half a mile northeast of the mouth of Glenn Creek. From there 

northeastward it forms resistant ridges between the Kandik and Nation Rivers.

A supplementary reference section is well exposed along an unnamed tributary of the Kandik River (fig. 1) in the E^ sec. 23, T. 

7 N., R. 29 E., in the Charley River B-2 quadrangle. Here the Keenan 

Quartzite is several hundred feet thick and has interbeds of black 

shale and argillite. The formation is thickest (approx. 1,000 feet) in 

the areas about 5 miles east and 15 miles southwest of the mouth of 

Van Hatten Creek in the Charley River D-2 and C-3 quadrangles. 

Figure 6 shows a typical exposure of the formation east of Van Hatten Creek. The Keenan Quartzite is also exposed at many other localities in a 2,000-square-mile area extending from the AlaskaYukon boundary to tributaries of the Yukon River near the abandoned settlements of Woodchopper and Coal Creek.

LITHOLOGY AND DISTINGUISHING FEATURES

At most localities, the Keenan Quartzite is light gray on fresh surfaces and white or very pale orange on weathered surfaces. With 

increasing iron oxide content, it takes on shades of red and brown, and 

with increasing carbon content, it takes on darker shades of gray 

and black. In thin section, the rock consists of rounded and wellsorted fine or very fine quartz grains with secondary overgrowths of 

quartz filling the interstices between the grains. Many of the quartz 

grains are rimmed by chlorite. At a few localities the cement is cal-
EAST-CENTRAL ALASKA 115

FIGURE 6. Blocky rubble characteristic of the Keenan Quartzite along ridges a 

few miles east of the mouth of Van Hatten Creek (see fig. 1). Partings in the 

quartzite are probably along joints inasmuch as there are no other indications of bedding.

cite or iron oxide. Rounded sand-size chert grains are a minor constituent; some samples contain microcline, muscovite, hornblende, 

and epidote. That no chert-pebble conglomerate has as yet been found 

in the Keenan Quartzite is useful in distinguishing it from the quartzite beds in the Step Conglomerate. Glauconite occurs in the lower part 

of the Keenan Quartzite about 5 miles south of the Step Mountains.

AGE AND STRATIGRAPHIC RELATIONS

The pelecypod Buchia "sublaevis" of Early Cretaceous (Valanginian) age, according to D. L. Jones (written communs., 1960, 

1963), has been found in the Keenan Quartzite at the following localities:

USGS M2057 (Field No. 63ABa 3882), Charley River C-3 quadrangle, lat 65°

38.7' N., long 142°23.1' W. Collected by Earl E. Brabb, 1963. 

USGS M2059, Charley River B-2 quadrangle, lat 65°29.7' N., long 141°34' W.

Collected by geologists of Mobil Oil Co., 1962. 

USGS M2060 (Field No. 63ACn 2505), Charley River C-4 quadrangle, lat 65°

34' N., long 142°44.8' W. Collected by Michael Churkin, Jr., 1963. 

USGS M2061 (Field No. 63ACn 2541), Charley River C-4 quadrangle, lat 65°

33.8' N., long 142°47.9' W. Collected by Michael Churkin, Jr., 1963.
116 CONTRIBUTIONS TO STRATIGRAPHY

USGS M2062 (Field No. 63ACn 2623), Charley River C-4 quadrangle, lat 65°

33.3' N., long 142°37.3' W. Collected by Michael Churkin, Jr., 1963. 

USGS M2063 (Field No. 63ACn 2822), Charley River B-3 quadrangle, lat 65°

18.3' N., long 142°03.6' W. Collected by Michael Churkin, Jr., 1963. 

USGS M1764 (Field No. 62ABa 2601), Charley River D-1 quadrangle, lat 65°

46.6' N., long 141 °00' W. Collected by Earl E. Brabb, 1962. 

USGS M1765 (Field No. 62ABa 2632), Charley River D-3 quadrangle, lat 65°

46.9' N., long 142°07.1' W. Collected by Earl E. Brabb, 1962. 

USGS M1766 (Field No. 62ABa 2646), Charley River C-4 quadrangle, lat 65°

34' N., long 142°44.8' W. Collected by Earl E. Brabb, 1962.

In addition, D. L. Jones identified a belemnite at M2059 and 

Buchia cf. B. crassicollis of Valanginian age at the following locality:

M1022 (Field No. ABa 797), Charley River D-1 quadrangle, lat 65°45.2' N., 

141° 15.3' W. Collected by Earl E. Brabb, 1960.

Collection M9389 (Field No. 1509A) contains an Inoceramus? sp. 

(see Mertie, 1930, p. 139) collected by Eliot Blackwelder in 1915 

from the middle part of the Keenan Quartzite in its type section.

In summary, fossils indicate that the Keenan Quartzite is of Early 

Cretaceous (Valanginian) age.

The Keenan Quartzite apparently represents an interruption in the 

deposition of the argillaceous sediments that constitute the underlying Glenn Shale and the overlying Biederman Argillite. Though it 

seems conformable with these formations at most localities, the occurrence of glauconite in the lower part of the Keenan Quartzite near 

the Step Mountains and the thinness of the Glenn Shale in that area 

could be interpreted as indicating an unconformity. The thinness of 

the Glenn Shale could be due to faulting, however. Additional 

geologic mapping in greater detail in the Step Mountains is needed 

before the problem can be solved.

In the headwaters of the Black River near the Alaska-Yukon Territory boundary, the Keenan Quartzite seems to be overlain unconformably by the Kathul Graywacke of Early Cretaceous (Albian) 

age; here the intervening Biederman Argillite is missing.

BIEDERMAN ARGILLITE

TYPE SECTION AND AREAL DISTRIBUTION

The Biederman Argillite is here named for the excellent exposures 

in its type section along Biederman Bluff (fig. 7), a newly named 

geographic feature on the west side of the Yukon River about 4 miles 

northwest of the mouth of the Kandik River (fig. 1) in the Charley 

River B-4 quadrangle. The type section extends from the banks of 

the Yukon River to the top of the bluff in the NW% sec. 32, T. 7 

N., R. 25 E. Additional exposures are present along the Yukon River 

both upstream and downstream from the type section, but folds,
EAST-CENTRAL ALASKA 117

FIGURE 7. Type section of the Biederman Argillite at Biederman Bluff. The 

peak at the top of the photograph is about 1,000 feet above the level of the 

Yukon River (at the bottom of the picture). The dark band in the center of 

the photograph is massive argillite; the other rocks are argillite with many 

interbeds of siltstone and sandstone.
118 CONTRIBUTIONS TO STRATIGRAPHY

faults, landslides, covered areas, and the scarcity of fossils for stratigraphic control make it difficult to establish the sequence of rocks 

beyond the type section. Inasmuch as neither the top nor the base 

of the formation are exposed in the type section, a supplementary 

reference section is herein established. It extends from the top of the 

Keenan Quartzite in its type section on the Yukon River half a mile 

downstream from the mouth of Glenn Creek to the base of the Kathul 

Graywacke in its type section about 1 mile southeast of bench mark 

3122 (Nat) on Kathul Mountain. This reference section is 12-18 

miles southeast of Biederman Bluff (fig. 1).

The Biederman Argillite underlies an area of more than 2,000 

square miles from Coal Creek (fig. 1) to the Alaska-Yukon Territory 

boundary. 

LITHOLOGY AND DISTINGUISHING FEATURES

In its type section and at most other localities, the Biederman 

Argillite is mainly dark-gray or grayish-black argillite in beds a few 

inches to a few feet thick. The argillite has many thin interbeds of 

fairly well sorted medium-gray siltstone and light-gray fine-grained 

sandstone and quartzite, which give outcrops of the formation a 

rhythmically bedded appearance (fig. 8). The siltstone and sandstone 

beds characteristically have small-scale cross-laminations, graded 

beds, convolute bedding, and other sedimentary structures that sugFlGURE 8. Rhythmic interbedding of argillite, siltstone, and sandstone a 

characteristic of the Biederman Argillite at Biederman Bluff.
EAST-CENTRAL ALASKA 119

gest current action and instability of the basin floor during deposition 

of the sediment.

At many localities the siltstone and sandstone are sparse and the 

Biederman Argillite has a massive appearance. The argillite commonly weathers to needlelike forms a few inches long. Many of the 

samples will "ring" when struck with a hammer. Axial-plane cleavage 

is well developed at many localities; the formation as a whole is extensively folded and faulted.

Greenish-gray chert, siliceous shale, grayish-black argillite, and 

chert-limestone breccia exposed along the lower reaches of the Kandik River and its tributaries about 5 miles north of Kathul Mountain have been included in the Biederman Argillite, but they could be 

upfolded rocks of Paleozoic age. A few thin beds of chert-pebble conglomerate definitely occur in the Biederman Argillite on the southwest bank of the Yukon River about 4 miles downstream from the 

mouth of the Charley River; however, unlike the Step Conglomerate, 

this conglomerate in the Biederman Argillite has a matrix of grayishblack argillite.

THICKNESS

The type section was not measured in detail, but it is estimated 

to be approximately 1,000 feet thick. The entire formation is at least 

5,000 feet thick, but probably does not exceed 10,000 feet.

AGE AND STRATIGRAPHIC RELATIONS

Fossils are scarce in the Biederman Argillite. No fossils have been 

found in the type section, and only the following fossils, identified 

by D. L. Jones, were found in the reference section:

USGS M3783 (Field No. lot 18) from lower part of Biederman Argillite, within 

a few hundred feet stratigraphically above the Keenan Quartzite, Charley 

River B-3 quadrangle, lat 65° 18.4' N., long 142°05.V W. Collected by E. M. 

Kindle, 1906. 

Inoceramus sp. 

Pinna sp. 

Polyptychites sp.

Age: Early Cretaceous (Valanginian).

USGS M13428 (Field No. 25AMt 207) probably very close to, or at, M3783. 

Collected by J. B. Mertie, Jr., 1925.

Inoceramus sp. fragments and a belemnite.

USGS M2064 (Field No. 63ACn 2825) probably very close to, or at, M3783. 

Collected by Michael Churkin, Jr., 1963.

Inoceramus sp.

USGS M3785 (Field No. lot 19) from float near the top of the Biederman Argillite, on the north bank of the Yukon River near Kathul Mountain, Charley 

River B-3 quadrangle, approximate lat 65°20' N., long 142° 16' W. Collected 

by E. M. Kindle, 1906.

Buchia "sublaevis" of Valanginian age.
120 CONTRIBUTIONS TO STRATIGRAPHY

Unfortunately, collection M3785 may well have been from rocks 

washed a few miles downstream from the richly fossiliferous localities 

near the mouth of Glenn Creek; it is here discounted in determining 

the age of the upper part of the Biederman Argillite.

E. M. Kindle, in 1906, collected Inoceramus sp. and Buchia sp. 

(formerly Aucella) from an unknown stratigraphic position within 

the Biederman Argillite on the south bank of the Yukon River about 

4 miles downstream from the mouth of the Charley River (see Mertie, 

1930, p. 139, collection M3784), and Eliot Blackwelder found a plant 

identified by F. H. Knowlton as Chondrites heeri Eichwald, from an 

unknown position with the Biederman Argillite on the south bank of 

the Yukon River about 1 ^ miles upstream from the mouth of the 

Kandik River (see Mertie, 1930, p. 140). The following collections 

identified by D. L. Jones are from rocks questionably assigned to the 

Biederman Argillite in an area of extensively folded and faulted 

rocks along Woodchopper and Coal Creeks (fig. 1), about 20 miles 

west of Biederman Bluff:

USGS M1763 (Field No. 62ABa 2353) from carbonaceous shale along an old 

meander of Coal Creek, Charley River B-5 quadrangle, lat 65°20.4' N., long 

143°06.2' W. Collected by Earl E. Brabb, 1962.

Buchia sp., possibly B. "sublaevis."

USGS M13429 (Field No. 25AMt 227) from argillite on the east bank of Woodchopper Creek, Charley River B-5 quadrangle, lat 65°20.2' N., long 143° l& 

W. Collected by J. B. Mertie, Jr., 1925; re-collected by Earl E. Brabb, 1960 

(USGS M1023, Field No. 60ABa 1206).

Buchia "sublaevis" of Valanginian age.

USGS M1025 (Field No. 60ABa 1203), from limestone talus at the base of a 

massive limestone exposed on the west valley slope of Woodchopper Creek, 

Charley River B-5 quadrangle, lat 65° 19.5' N., long 143°20.2' W. Collected 

by R. N. Passero and Earl E. Brabb, 1960. 

Inoceramus sp. of Jurassic or Cretaceous age.

An extensive pelecypod and brachiopod fauna of Jurassic or Cretaceous age from this limestone at locality Ml025 was reported by 

Mertie (1938, p. 220). The stratigraphic positon of this limestone 

within the Mesozoic sequence could not be determined, but the limestone is most closely associated geographically with the Biederman 

Argillite.

The Biederman Argillite has been examined at more than 100 

localities over a 2,000-square-mile area, but no additional fossils have 

been found. Ten samples of the argillite and siltstone at widely separated localities were processed by Richard A. Scott for spores or 

pollen, but all samples were barren.

In conclusion, fossils and stratigraphic relations indicate that the 

lower part of the Biederman Argillite is Early Cretaceous (Valangin-
EAST-CENTRAL ALASKA 121

ian). The type section and most of the formation are in general undated; however, the few fossils that have been found are consistent 

with an Early Cretaceous age. The great thickness of the formation, 

in contrast to thinner formations in the area that include several 

series or even two systems, suggests that additional stages of the 

Cretaceous may be represented in the Biederman Argillite. Pending 

paleontologic documentation, however, the formation is considered 

to be Early Cretaceous (Valanginian).

At most localities the Biederman Argillite rests conformably on 

the Keenan Quartzite and is overlain unconformably by the Kathul 

Graywacke. On the northeastern flank of the large anticline in the 

Step Mountains, however, the Biederman Argillite seems to rest 

directly on the Step Conglomerate. Although an unconformable relationship is possible, it should be noted that exposures are poor in 

the area between the Step Mountains and the Nation River; thus the 

Keenan Quartzite may have been overlooked, and the argillite above 

the Step Conglomerate may be the Glenn Shale rather than the 

Biederman.

KATHUL GRAYWACKE

TYPE SECTION AND AREAL DISTRIBUTION

Conglomerate and sandstone of graywacke type exposed on Kathul 

Mountain (fig. 1) is here named the Kathul Graywacke. The type 

section extends from grassy slopes (fig. 9) about a mile southeast of 

bench mark 3122 (Kat) in the Charley River B-3 quadrangle (1: 

63,360), where medium- to coarse-grained graywacke of the Kathul 

Graywacke in contact with shale of the underlying Biederman 

Argillite is exposed, to the upper slopes of Kathul Mountain about 

half a mile southeast of bench mark 3122, where the youngest beds 

of the Kathul Graywacke crop out along the trough of a northeasttrending syncline.

The Kathul Graywacke extends continuously from Kathul Mountain to the middle and upper reaches of the Kandik River and the 

Alaska-Yukon border, underlying an area of about 275 square miles. 

The formation underlies an additional 40 square miles in an area 

adjoining the border between the Kandik River and tributaries of the 

Black River, at about lat 65° 50' N. The formation is fairly well exposed along most of the Kandik River and its tributaries; its conglomerate boulders are one of the principal hazards in traveling 

along the Kandik River by boat.

LITHOLOGY AND DISTINGUISHING FEATURES

In the type section, the Kathul Graywacke consists of beds of 

pebble-conglomerate and sandstone a few inches to as much as 50
122 CONTRIBUTIONS TO STRATIGRAPHY

FIGURE 9. Type section of the Kathul Graywacke on Kathul Mountain. The 

blocky outcrops between the grassy slopes and the crest of the mountain are 

chiefly conglomerate and sandstone of graywacke type. The Biederman Argillite underlies the grassy slopes in the middle foreground.

feet thick that grade upward to thin beds of siltstone and argillite. 

The conglomerate and sandstone is greenish gray on fresh surfaces 

and light olive gray on weathered surfaces. The argillite is dark gray 

or grayish black. Grayish-green, gray, and black rounded chert 

pebbles and grains are conspicuous but not the major constituents of 

the conglomerate and coarse-grained sandstone. The clasts are mainly 

a poorly sorted mixture of reworked sandstone, argillite, and limestone; quartz, plagioclase, and potash feldspar grains; volcanic, granitic(?), and metamorphic rocks; and detrital chlorite, epidote, hornblende, muscovite, and biotite. The clasts and grains are in a matrix 

of more than 10 percent by volume of argillaceous material, most of 

which has been altered to chlorite and (or) epidote. The surface of 

many quartz grains and extensive parts of chert and feldspar grains 

seem in thin section also to have been replaced by chlorite. The green 

color of the volcanic and some metamorphic clasts and the green 

detrital and secondary epidote and chlorite, in combination with poor 

sorting and an abundant matrix, serve to distinguish these graywackes from all other sedimentary formations in the region.

The graded sets of conglomerate, sandstone, and argillite are common throughout the formation, but outside the type section which
EAST-CENTRAL ALASKA 123

FIGURE 10. Faulted beds of the Kathul Graywacke along the Kandik River 

near the mouth of Big Sitdown Creek (fig. 1). These beds are similar in 

appearance to those in the Biederman Argillite, but the occurrence of poorly 

sorted greenish graywacke beds near these rocks led us to map them as 

Kathul Graywacke.

probably has less than 10 percent argillite massive argillite and 

rhymically bedded argillite, siltstone, and sandstone (fig. 10) similar 

in appearance to the Biederman Argillite make up a substantial and 

possibly even a major part of the Kathul Graywacke. The poorly 

sorted greenish graywacke beds in or near these rhythmically bedded 

rocks were used to distinguish them from the Biederman Argillite. 

The widespread occurrence of potash feldspar on stained slabs of the 

Kathul Graywacke was a useful laboratory technique for confirming 

the field identifications.

Pebble- and boulder-size clasts of argillite are common in sandstones of the Kathul Graywacke exposed along the Kandik River. 

These clasts appear to have been eroded from nearly contemporaneous argillaceous beds. Convolute structures also suggest instability 

of the basin floor during deposition of the sediment. Small-scale crosslaminations are common, and measurements at four localities along 

the upper part of the Kandik River suggest that the basin currents 

flowed from east to west. An eastern source for the sediments is not 

in accord with the composition of the clasts, however. The only reasonable source for the volcanic, metamorphic, and granitic(?) clasts,
124 CONTRIBUTIONS TO STRATIGRAPHY

and the chlorite and epidote, is in the terrain south and west of 

Kathul Mountain, not in Canada.

THICKNESS

The Kathul Graywacke is about 1,500 feet thick in its type section 

on Kathul Mountain, and it seems to be several thousand feet thick 

in the middle and upper reaches of the Kandik River in Alaska.

AGE AND STRATIGRAPHIC RELATIONS

Nondiagnostic plant fragments are fairly common in the Kathul 

Graywacke, but six samples of argillaceous rocks from the formation 

examined by Richard A. Scott for spores or pollen were all barren. 

Invertebrate fossils are exceedingly rare. The following collections 

were identified by David L. Jones:

M1021 (Field No. GOABa 791) from sandstone (graywacke) in lower part of

Kathul Graywacke, on west bank of Kandik River, Charley River D-l quadrangle, lat 65°48.8' N., long 141°07.3' W. Collected by Earl E. Brabb, 1960.

Poorly preserved pelecypods and gastropods. No age determination. 

M2058 (Field No. 63ABa 3933) from sandstone (graywacke) in lower part of 

Kathul Graywacke, Charley River D-l quadrangle, lat 65°55.4' N., long 141° 

00.1' W. Collected by Earl E. Brabb, 1963.

Pholadomya sp. No age significance.

Field No. KPO 2043, from olive-green siltstone near the crest of Kathul Mountain, Charley River B-3 quadrangle, lat 65°21.4' N., long 142°16.2' W. Collected by geologists of British Petroleum Co., 1962.

Poorly preserved pelecypods. No age determination.

Stratigraphic relations of the Kathul Graywacke are somewhat uncertain because of the scarcity of fossils for stratigraphic control, poor 

exposures, structural complications, and difficulties in distinguishing 

the formation from the Biederman Argillite. The Kathul Graywacke 

rests conformably on the Biederman Argillite in the vicinity of 

Kathul Mountain (fig. 1), but in the Step Mountains and in the 

headwaters of the Black River the formation apparently rests unconformably on the Biederman Argillite, Keenan Quartzite, or Step 

Conglomerate. The Kathul Graywacke is overlain unconformably by 

unnamed and poorly consolidated conglomerate, sandstone, mudstone, and thin coal seams near the Alaska-Yukon Territory boundary at lat 65°45'. Pollen from the shale is late Tertiary, according 

to R. A. Scott (written commun., 1962). At other localities, Scott 

has found pollen ranging in age from Late Cretaceous to late Tertiary 

in this unnamed formation (see fig. 3).

Fossils indicate that the Kathul Graywacke is marine, and Mesozoic or younger. Stratigraphic relations indicate that the formation 

is (1) Early Cretaceous (Valanginian) or younger, (2) older than
EAST-CENTRAL ALASKA 125

late Tertiary, and (3) probably older than Late Cretaceous. The 

Kathul Graywacke is here provisionally considered to be of Early 

Cretaceous (Albian) age on the basis of the following evidence. The 

formation is most similar, lithologically, to unnamed nonmarine conglomerate, sandstone, and mudstone exposed along the Yukon River 

in the vicinity of the mouth of the Seventymile River (figs. 1,3). Like 

Kathul Graywacke, this unnamed formation has clasts of chert, 

quartz, volcanic rock, plagioclase and potash feldspar, chlorite, and 

biotite. Like the Kathul Graywacke, this unnamed formation marks 

an abrupt change in the regimen a change from terrains contributing mainly chert, quartz, and argillaceous material to terrains contributing these materials plus metamorphic, granitic(?), and volcanic 

rocks and their mineral constituents, such as chlorite, plagioclase, and 

potash feldspar. Both the Kathul Graywacke and the unnamed formation seem to rest unconformably on older units, possibly reflecting 

the Aptian orogeny which affected many areas in Alaska (Gates and 

Gryc, 1963). The unnamed formation contains plants of probable 

Early Cretaceous (Albian) age, according to J. A. Wolfe (written 

commun., 1963), and thus, if the two formations are correlative, the 

Kathul Graywacke may also be Albian.

REFERENCES CITED

Brabb, E. E., 1967, Stratigraphy of the Cambrian and Ordovician rocks of eastcentral Alaska: U.S. Geol. Survey Prof. Paper 559-A, 30 p.

Brabb, E. E., and Churkin, Michael, Jr., 1964, Preliminary geologic map of the 

Charley River quadrangle, east-central Alaska: U.S. Geol. Survey openfile map, Aug. 17, 1964, scale 1:250,000.

 1965, Preliminary geologic map of the Eagle D-l quadrangle, eastcentral Alaska: U.S. Geol. Survey open-file map, Feb. 3, 1965, scale, 1: 

63,360.

 1967, Stratigraphic evidence for the Late Devonian age of the Nation 

River Formation, east-central Alaska, in Geological Survey research 1967: 

U.S. Geol. Survey Prof. Paper 575-D, p. D4-D15.

Churkin, Michael, Jr., and Brabb, E. E., 1965, Ordovician, Silurian, and Devonian biostratigraphy of east-central Alaska: Am. Assoc. Petroleum Geologists Bull., v. 49, no. 2, p. 172-185.

Gates, G. O., and Gryc, George, 1963, Structure and tectonic history of Alaska, 

in Childs, O. E., and Beebe, B. W., Backbone of the Americas tectonic 

history from pole to pole; a symposium: Am. Assoc. Petroleum Geologists 

Mem. 2, p. 264-277.

Imlay, R. W., 1967, The Mesozoic pelecypods Otapiria Marwick and Lupherella 

Imlay, new genus in the United States: U. S. Geol. Survey Prof. Paper 

573-B, 11 p.

Martin, G. C., 1916, Triassic rocks of Alaska: Geol. Soc. America Bull., v. 27, 

p. 685-718.

 1926, The Mesozoic stratigraphy of Alaska: U.S. Geol. Survey Bull. 

776, 493 p.
126 .CONTRIBUTIONS TO STRATIGRAPHY

Mertie, J. B., Jr., 1930, Geology of the Eagle-Circle district, Alaska: U.S. Geol.

Survey Bull. 816, 168 p. 

 1933, The Tatonduk-Nation district, Alaska: U.S. Geol. Survey Bull.

836, p. 347-443.

1938, Tertiary deposits of the Eagle-Circle district, Alaska: U.S. Geol.

Survey Bull. 917-D, p. 213-264. 

Smith, J. P., 1927, Upper Triassic marine invertebrate faunas of North America: 

U.S. Geol. Survey Prof. Paper 141, 262 p.