Uppermost Cretaceous and 

Tertiary Stratigraphy of 

Fossil Basin, Southwestern 

Wyoming 

By STEVEN S. ORIEL and JOSHUA I. TRACEY, JR. 

GEOLOGICAL SURVEY PROFESSIONAL PAPER 635 

New subdivisions of the J,ooo-Joot-thick 

continental Evanston, Wasatch, Green River, 

and Fowkes Formations facilitate understanding 

of sediment genesis and Jl7yoming thrust-belt 

tectonic events 

UNITED STATES GOVERNMENT PRINTING OFFICE, WASHINGTON 1970 
UNITED STATES DEPARTMENT OF THE INTERIOR 

WALTER J. HICKEL, Secretary 

GEOLOGICAL SURVEY 

William T. Pecora, Director 

Library of Congress catalog-card No. 70-604646 

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

Washington, D.C. 20402 - Price 65 cents (paper cover) 
Abstract __________________________________________ _ 

Introduction ______________________________________ _ 

Purpose ______________________________________ _ 

Earlier work_ .. __ - __ - ___________________ - _-- _- __ 

Acknowledgments __ . ___________________________ _ 

General relations ___ -- _________________________ _ 

Evanston Formation _______________________________ _ 

N arne and usage _______________________________ _ 

Lower member _____ - ___________________ - ______ _ 

Hams Fork Conglomerate Member ______________ _ 

~ain bodY-------------------------------------

Lower con tact_ ________________________________ _ 

Fossils and age_--_--_-- __________ - _____ - ______ _ 

Lower member_. __________________________ _ 

Hams Fork Conglomerate ~ember __________ _ Main body _______________________________ _ 

Origin ________________________________________ _ 

Tectonic implications ________________________ ..: __ 

Wasatch Formation ________________________________ _ 

N arne and usage _______________________________ _ 

Definition _________________________________ _ 

Veatch's subdivisions _______________________ _ 

Subdivisions used here ______________________ _ 

Basal conglomerate member _____________________ _ 

Lower member ________________________________ _ 

~ain body ____________________________________ _ 

Sandstone tongue ______________________________ _ 

~udstone tongue ______________________________ _ 

Bullpen Member---- ___________________________ _ 

Tunp ~ember---- _____________________________ _ 

Fossils and age ________________________________ _ 

Basal conglomerate member _________________ _ 

Lower member ____________________________ _ 

~ain body ________________________________ _ 

Sandstone and mudstone tongues ____________ _ 

Bullpen Member ___________________________ _ 

CONTENTS 

Page Wasatch Formation-Continued 

1 

2 

2 

2 

2 

5 

5 

5 

6 

6 

9 

10 

11 

11 

12 

12 

13 

14 

14 

14 

14 

16 

16 

17 

17 

18 

20 

20 

21 

22 

27 

27 

27 

27 

28 

28 

Fossils and age-Continued· Page 

Tunp Member______________________________ 28 

Origin--------~-------------------------------- 28 

Tectonic implications ____________ -_-------------- 29 

Green River Formation ___ .. _______ ------------------ 30 

Name and usage __________________ -------------- 30 

Definition __________________ -_-------------- 30 

Lithologic heterogeneity. ______ --_----------- 30 

Subdivisions used here_______________________ 30 

Fossil Butte Member ____________ -_-------------- 30 

Angelo ~ember_ .. ________________ -------------- 31 

Fossils and age ___________________ --_----------- 32 

Origin_________________________________________ 32 

Tectonic implications ______________ -------------- 33 

Fowkes Formation _____________________ -_--------,.-- 33 

Name and usage________________________________ 33 

Definition _____________________ - _____ -_-_--- 33 

Subsequent usage _____________ ------------.,.- 33 

Suggested usage____________________________ 33 

Subdivisions used here ________ --_----------- 34 

Sillem ~ember ___________________ -------------- 34 

Bulldog Hollow Member_________________________ 35 

Gooseberry Member ______________ --------------- 35 

Fossils and age _________________ -_-------------- 36 

Origin_________________________________________ 37 

Tectonic implications____________________________ 37 

Some regional relations _____ ------------------------- 38 

Lower strata of the Wasatch_____________________ 39 

Relations of Iower.units------------------------- 39 

Relations of tongues of the Wasatch and Green 

River Formations_____________________________ 39 

Fowkes-N orwood-Bridger relations ___________ -_--- 41 

Type sections for members defined in this report_ __ -_--_ 41 

References cited ____________________________ -_------ 4 7 

IndeX--------------------------------------------- 51 

ILLUSTRATIONS 

FRONTISPIECE. Photograph of Fossil Butte, type locality for a new member of the Green River Formation, showing slumping 

near the contact with underlying varicol~red mudstones in the Wasatch Formation. 

FIGURE 1. Map showing the location of the Fossil basin in southwestern Wyoming and nearby geographic features ___ _ 

2. Topographic map of the northern part of the Fossil basin showing location of geographic features ________ -_ 

3-7. Photographs of the Evanston Formation: 

3. Lower units, west side of Commissary Ridge _____________________________________ --_-------------

4. Ridges and flatirons formed by boulder beds in the Hams Fork Conglomerate Member __ -------------

5. Type section of the Hams Fork Conglomerate Member _____ , _____________________ -·---------------

v 

Page 

3 

4 

7 

8 

9 
VI CONTENTS 

FIGURE 3-7. Photographs of the Evanston Formation-Continued 

TABLE 

6. Quartzite pebbles and cobbles in the Hams Fork Conglomerate Member, south end of Commissary 

Ridge-------------------------------------------------------------------------~---------

7. Main bodY----------------------------------------------------------------------------------

8. Geologic map of part of the Kemmerer quadrangle showing the divergence of boulder conglomerate beds 

from the basal contact of the Evanston Formation __ · ____________________________________________ _ 

9-15. Photographs of the Wasatch Formation: 

9. Lower member, north side of Morgan Canyon ______________________________________________ _ 

10. Color-banded mudstone and siltstone in the main body, southwest side of Fossil Butte ___________ _ 

11. Lenses of moderately well sorted brown conglomerate in mudstones of the main body ____________ _ 

12. "Algal log" in the mudstone tongue _______________________________________________________ _ 

13. Diamictite in the Tunp Member __________________________________________________________ _ 

14. Block of Ephraim Conglomerate in diamictite of the Tunp Member ___________________________ _ 

15. Geometric relations of the Tunp Member __________________________________________________ _ 

16. Map showing locations of the Eocene lakes in which the Green River Formation was deposited ___________ _ 

TABLES 

1. Nomenclature of uppermost Cretaceous and Tertiary stratigraphic units in the Fossil basin ______________ _ 

2. Fossils from the lower member of the Wasatch Formation in the Sage quadrangle, Lincoln County, Wyo __ _ 

3. Dominant rock types and sequences of Upper Cretaceous and Tertiary stratigraphic units in the Fossil 

basin and adjoining areas ____________________________________________________________________ _ 

4. Approximate ages of the stratigraphic units in the Fossil basin and adjoining areas ______________________ _ 

Page 

10 

11 

15 

18 

18 

19 

21 

23 

24 

25 

33 

Page 

5 

26 

38 

40 

.. 
UPPERl\:fOST CRETACEOUS AND TERTIARY STRATIGRAPHY 

OF FOSSIL BASIN, SOUTHWESTERN WYOMING 

BY STEVEN S. ·.ORIEL and JosHuA I. TRACEY, Jn. 

ABSTRACT 

More than 7,000 feet of uppermost Cretaceous and Tertiary 

continental strata in the northern Fossil basin, along the 

southern part of the western Wyoming thrust belt, is here subdivided into newly defined formal and informal rock-stratigraphic units. Recognition of these units makes possible the 

dating of some thrust-fault movement, of the development of 

the Fossil structural basin, and of some later block faulting, as 

well as reinterpretations of the origins of the strata. 

The Evanston Formation, which is more than 2,000 feet thick 

and more extensive in the Fossil basin than formerly recognized, 

consists of an unnamed lower member, the Hams Fork Conglomerate MemiJer, and the main body. The lower member consists of as much as 500 feet of gray to dark-gray mudstone, 

siltstone, claystone, and carbonaceous fine-grained, but partly 

gritty and conglomeratic, sandstone a11d is of latest Cretaceous, 

probably Lance, age. The Hams Fork Conglomerate Member, 

previously mapped erroneously as the Almy Formation along 

the east side of the l!"'ossil basin, consists mainly of 450-1,000 

feet of latest Cretaceous (Lance) boulder conglomerate and 

interstratitied partly conglomeratic brown and gray sandstone 

and gray partly carbonaceous mudstone; sources of the wellrounded boulders and pebbles were the nearby upper Paleozoic 

and Mesozoic formations and lower Paleozoic units of the Paris 

thrust sheet in Idaho. The main body of the Evanston, 400 to 

more than 1,400 feet thick, consists mainly of Paleocene but 

also latest Cretaceous light to dark-gray carbonaceous sandy 

to clayey partly quartzitic siltstone, gray, tan, yellow, and 

brown sandstone and . conglomerate, carbonaceous to lignitic 

claystont', ironstone, lignite, and, locally, thin beds of coaL 

The 'Vasatch Formation is subdivided into seven mapped 

units: 

1. The basal conglomerate member, from a few feet to several 

hundred feet thick, consists mainly of buff sandstone pebbles and cobbles in a matrix of sand, all derived principally 

from the Nugget Sandstone but including a few clasts from 

other units. 

2. The lower unnamed member, as much as 300 feet thick, consists of interbedded light- to darl.:-gray, brown, pink, and red 

·sandy mudstone, black carbonaceous silty claystone, gray, 

vnrtly gritty and conglomeratic sandstone, and brown to 

light-gray finely c-rystalline and pisolitic limestone. 

3. The main body, directly beneath the Green River Formation, 

ranges in thickness from 1,500 to 2,000 feet, where fully 

represented, and consists of banded variegated-mainly red, 

purple, yellow, 'and gray-mudstone with interbedded claystone, siltstone, sandstone, and marlstone and lenses of 

well-rounded and well-sorted conglomerate. Mudstone is 

dominant near the center of the basin and grades laterally 

into more abundant sandstone and conglomerate toward the 

basin margins. 

4. The sandstone tongue is 40-50 feet thick in the southern part 

of the mapped area, where it divides the lower member of 

the Green River Formation into two units, and it pinches 

out northward. It consists of well-sorted medium- to coarsegrained brown crossbedded sandstone and green and gray 

mudstone. 

5. The mudstone tongue, as much as 50 feet thick, lies between 

the two members of the Green River Formation and consists 

of dark- to brick-red mudstone which grade~ basinward into 

pink and gray-green claystone. 

6. The Bullpen Member, which overlies the Green River Fonilation and is 400 feet thick, consists of red, salmol}, green, 

and gray mudstone, fine- to coarse-grained partly conglomeratic sandstone, and thin but extensive beds of brown 

to white limestone similar to that in the Green River 

Formation. 

7. The Tunp Member is a 200- to 500-thick peripheral diamictite 

facies of the Wasatch Formation. It consists of dark-red 

conglomeratic mudstone and rtlbble breccia with a great 

rauge in grain size; blocks from older nearby formations 

commonly as large as 20 feet -in diameter lie in a matrix of 

V€'ry poorly sorted red mudstone. 

Although the basal and upper parts of the formation are 

undated, most of the Wasatch in the Fossil basin is of early 

Eocene age. Unit 1 (previous list) is unfossiliferous but is tentatively assigned to the lower Eocene. Fossils from unit 2 indicate an early Eocene, probably Gray Bull (of Granger, 1914), 

age. Unit 3 contains abundant fossils of both early and middle 

early Eocene (Gray Bull and Lysite) ages. Units 4 and 5 are 

probably of early Eocene age. Unit 6, the Bullpen Member, may 

be late early (Lost Cabin) or middle (Bridger) Eocene age. 

Unit 7, the Tunp Member, intertongues with units 2 through 6, 

as well as with members of the Green River Formation. 

In the Fossil bas~n, the Green River Form~tion is divided 

into the Fossil Butte Member and the overlying Angelo l\iemIJer. Near the center of the basin, the Fossil Butte Member (200-

270 feet thick) is dominantly laminated organic-rich buff to 

brown marlstone, limestone, siltstone, and mudstone and indudes oil shale and volcanic ash; the prolific fossil fish beds at 

Fossil Butte are in this member. The Angelo Member, as much 

ns 200 feet thick, is mainly white- to blue-white-weatherh1g 

limestone, madstone, and mudstone and includes siliceous 

limestone, chert, sandstone, volcanic ash, and low-grade oil 

shale. It contains less organic matter than the lower member. 

The laminated strata of both members grade laterally (shoreward) through ostracodal and -gastropodal to algal limestone. 

Although the formation is commonly assigned a late early 

1 
2 UPPERMOST CRETACEOUS AND TERTIARY STRATIGRAPHY OF FOSSIL BASIN, WYOMING 

Eocene (Lost Cabin) age in the Fossil basin, the topmost strata 

may be younger or older. 

The Fowkes Formation, though previously assigned erroneously to the Wasatch Group, overlies both the 'Vasatch and 

the Green River Formations. The formation is divided into 

three new members: the Sillem, the Bulldog Hollow, and the 

Gooseberry. The Sillem Member, from 100 to 400 feet thick, consists of a basal conglomerate unit with pebbles of dark-gray 

chert and quartzite and interbedded sandstone and mudstone 

and an upper unit of mainly pale-Ilink, gray, and green-gray 

partly tuffaceous mudstone, siltstone, and claystone. The Bulldog 

Hollow Member, from 200 to 2,000 feet thick, consist.<; of pale- to 

dark-green, blue-green, and white tuffaceous and ashy mudstone 

and green to buff and brown Yery tuffaceous sandstone with 

abundant biotite and magneti1te. The Gooseberry Member, more 

than 200 feet thick though incompletely represented, consists of 

puddingstone, poorly packed rounded pebbles and cobbles of 

Paleozoic limestone, chert, and quartzite and sparse basalt, 

rhyolite, and andesite in a matrix of calcareous rhyolitic ash 

and ash-bearing very fine grained to subaphanitic limestone. 

The Fowkes Formation is middle to late Eocene in age, although 

the Gooseberry Member, assigned to the Fowkes provisionally, 

may be as young as Pliocene. 

Both stratigraphic and geometric relations establish that the 

~"ossil basin region had moderate relief during deposition of the 

described strata; many modern topographic features are exhumed from an Eocene landscape. Compositioos of some conglomera:tes, however, record reversals of relative elevations of 

some features. Major movements along the thrust faults from 

the Absaroka fault westward had ended by latest Cretaceous 

time. Sinking of the Fossil basin, begun in latest Cretaceous time, 

continued well illlto the Eocene. 

INTRODUCTION 

PURPOSE 

This report presents new data on the stratigraphy of 

the more than 7,000 feet of uppermost Cretaceous and 

lower Tertiary rocks in the northern part of Fossil basin 

in southwestern Wyoming. The data affect earlier interpretations of both stratigraphic sequence and geologic 

history. The repor.t revises rock nomenclature for the 

region and discusses briefly the bearing of the new data 

on such general questions as origin and tectonic 

implications. 

The rock sequence in the Fossil basin in some respects 

is similar to, but in other respects differs from, that 

along the western margin of the Green River Basin. An 

important objective is to determine precise relations between these sequences. 

Information presented here was gathered during five 

summers since 1955 in the course of mapping Tertiary 

rocks of the Sage and J(emmerer 15-minute quadrangles 

(Rubey, Tracey, and Oriel, 1968; Rubey, Oriel, and 

Tracey, 1968) and part of the Cokeville 30-minute quadrangle, in cooperation with William W. Rubey, who 

studied the older rocks. These quadrangles lie in southwestern Wyoming (fig. 1) and include the south end of 

the thrust belt and the northern part of the Fossil 

structural basin. 

EARLIER WORK 

Publications on the geology of westernmost Wyoming are based largely on the surface mapping of 

Veatch (1907') and Schultz (1914). In one field season, 

during the summer of 1905, Veatch and his associates, 

including Schultz, prepared both topographic and geologic maps for some 1,800 square miles, including Kemmerer, Sage, Evanston, and a strip south of Evanston. 

In the course of this work, Veatch reoognized and defined virtually all the stratigraphic units now in use 

from the Nugget Sandstone up to and including subdivisions of the Wasatch. He also recognized and delineated, with remarkable accuracy, the major structural 

elements of ·this complexly faulted region. 

During the following field season, in 1906, Schultz 

and his associates continued this work, mapping a strip 

northward along the eastern edge of the thrust belt from 

Kemmerer to the southern flank of the Gros Ventre 

Range. Some 2,200 square miles was mapped topographically and geologically in an area that includes complex 

structural and facies relations. 

The general stratigraphic relations of the Green 

River and Wasatch Formations were studied extensively by Sears and Bradley ( 1924), and detailed 

studies of the Green River Formation were published 

by Bradley (1926, 1929 a, b, 1930, 1931, 1948, 1959, 1963, 

1964, 1966). 

Recently published descriptions of lower Tertiary 

rock relations in the Green River Basin that have an 

important bearing on this work are those by Bradley 

(1964), Oriel (1962), and Lawrence (1963). · 

Data on subsurface rocks and structures and their 

relation to surface features have appeared in the 1950, 

1955, and 1960 field conference guidebooks of the 

Wyoming Geological Association and in the 1959 guidebook of the Intermountain Association of Petroleum 

Geologists. 

The general relations of the western Wyoming thrust 

belt were summarized by Rubey and Hubbert (1959) 

and Armstrong and Oriel ( 1965). 

ACKNOWLEDGMENTS 

Investigation of uppermost Cretaceous and Tertiary 

strata was undertaken at the suggestion of W. W. Rubey 

as a probable means of dating tectonic events in the 

Idaho-Wyoming thrust belt. The mapping on which 

this study was based, especially in areas where geometric relations are critical, was done with him. Important 

pieces of new information and several critical fossil 

localities were found by him, and many new working 
111.30' 

43° 

oo· 

<;:A R I B ·O U · 

42° 

00' 

R I C H 

111·oo· 

INTRODUCTION 

30' 11o·oo· 

Big Piney0 

0 

3 

30' 

EXPLANATION 

1o9·oo· 

D 

Cenozoic rocks 

D 

Cretaceous and older rocks 

~---------~ 

WYOMING 

10 20 30 MILES 

SWEETWAT 

0 Fort Bridger 

UINTA 

WYOMING -------------uTAH---

\..)\ t'i' ,_ .,,_j"' ----

/'·-'""D""u C H E N S E 

z 

w 

w 

a: 

CJ 

FIGURE I.-Location of the Fossil basin in southwestern Wyaming and nearby geographic features. Geologic maps recently 

completed include the (1) Sage, (2) Kemmerer, and (3) Fort Hill15-minute quadrangles and the {4) Cokeville 30-minute 

quadrangle. Area of figure 2 shown 'by hachured outlline. 

36~690-7~2 
4 UPPERMOST CRETACEOUS AND TERTIARY STRATIGRAPHY OF FOSSIL BASIN, WYOMING 

0 5 

FIGURE 2.-Topographic map of the northern part of the Fossil 

basin showing the location of topographic and geographic 

features. Area of figure 8 shown by hachurecl outline. Dry 

holes drilled for oil and gas in the area include the following, 

mentioned in the text: (1) National Cooperative Refinery 

Association 1 Arthur H. Linden, (2) National Cooperative 

CO NTOUR INTERVAL 200 FEET 

10 MILES DATU M IS MEAN SEA LEVEL 

Refinery Association 1 Government-Lansen, (3) Amerada 

Petroleum Co. 1 Chicken Creek unit, (4) Hoxsey Oil Co. 1 

Government, and (5) Roy Steele 1 Government. (From parts 

of the Preston and Ogden 1: 250,000 topographic maps of the 

U.S. Geological Survey.) 
EVANSTON FORMATION 5 

ideas emerged frmn discussions with him. The success 

of the investigation, therefore, is in large measure 

attributable to Rubey. 

Fossils collected by us were identified by C. L. Gazin 

and D. H. Dunkle of the U.S. National Museum and 

by Roland W. Brown, William A. Cobban, Estella B. 

Leopold, G. Edward Lewis, Raymond Peck, John B. 

Reeside, I. Gregory Sohn, Dwight W. Taylor, and Jack 

A. Wolfe of the U.S. Geological Survey. The manuscript has benefited from the constructive criticism and 

suggestions of M. R. Mudge and W. C. Culbertson. 

GENERAL RELATIONS 

The Fossil basin, as used in this report, is a small 

structural basin (called the "Fossil syncline" by Veatch, 

1907, and by Bradley, 1959) in the southern part of the 

Wyoming over~thrust belt. It extends from near the 

head of Hams Fork (T. 27 N., R. 117 W.) southward 

past Evanston to the north flank of the Uinta Mountains (fig. 1) . The western margin of the basin is 

bounded on the north by the Tunp Range and on the 

south by unnamed en echelon ridges east of the Crawford Mountains. The eastern margin of the basin is 

bounded by a belt of Mesozoic rocks that underlies the 

prominent north-trending Oyster Ridge (fig. 2). These 

rocks formed a topographic barrier between the Fossil 

basin and Green River Basin during deposition of 

many of the Tertiary units. The barrier is informally 

referred to as the Oyster Ridge barrier in this report. 

The rock units within the Fossil basin and their relations are shown in table 1. 

Uppermost Cretaceous and lower Tertiary rocks of 

the Fossil basin were deposited while the structural 

basin was forming. The sediments consisted of muds and · 

clays, sand, nnd gravel of normal fluviatile transport 

and of mixed and very heterogeneous material from clay 

size to coarse angular debris-including boulders and 

huge blocks-probably transported by gravitational 

processes. In early Eocene time, the coarse and fine material that settled around the margin of the basin formed 

a peripheral facies, the "Wasatch facies" of Spieker 

(1946, p. 138), that was predominaU:tly fluviatile. Sediments deposited in the central part of the basin formed 

a lacustrine facies at the same time. The two facies con,-

stitute a genetic set or assemblage that is mapped as the 

Wasatch Formation and the Green River Formation. 

At times, the fluviatile sediments encroached upon the 

margilis of the lakes, or conglomeratic and rubbly'mud-. 

flows thickened parts of the peripheral deposits. At other 

times, the lake spread over lowlands that had formerly 

received fluviatile and other peripheral deposits. 

TABLE 1.-N omenclature of uppermost Cretaceous and Tert-iary 

stratigraphic units in the Fossil basin 

Veatch (1907) 

Bridger(?) Formation 

Green River Formation 

-5 c. Knight Formation 

~ e Fowkes Formation 

~ <.!l Almy Formation 

Evanston Formation 

Adaville Formation 

Q) 

.c 

E 

Q) 

::!: 

g-

::1 

1-

This report 

Fowkes Formation 

Gooseberry Member 

Bulldog Hollow Member 

Sillem Member 

c: 

0 

:;:; 

E "'

~ ..r::. 

~ 

~ 

Upper mudstone unit 

Lower conglomerate unit 

Lower member 

Basal conglomerate member 

Eyanston. Formation 

Main body 

Hams Fork Conglomerate Member 

Lower member 

Adaville Formation 

EVANSTON FORMATION 

NAME AND USAGE 

Coal-bearing strata exposed north of the town of 

Evanston, in the vicinity of Almy (fig. 1), were first 

formally defined as the Evanston Formation by Veatch 

(1907, p. 76), though he mentioned them in an earlier 

report (1906, p. 332). The Evanston was described by 

him· (1907, p. 77) as . 

* * * consisting of yellow, gray, and black carbonaceous shales 

and irregular brown and yellow sandstone beds, but differs 

from the Adaville [Formation, Upper Cretaceous] in containing pronounced conglomerate beds below the upper coals * * *. 

The c{>als are much dirtier:· and less persistent * * * . The 

upper limit o"f the Evanston is fixed by the pronounced sandstones and conglomerates which marl{ the base of the Almy 

* * *. The Evanston is characterized by coal and by dark-colored 

clays and by a relatively small propol'ltion of sandy and conglomeratic material, while . the Almy is more predominantly 

arenaceous and conglomeratic, and in places shows. a reddish 

tinge not seen in the Evanston. 

The distribution of the formation, as ma;pped by Veatch. 

(1907, pl. 3, p. 77), was limited to three small areas 

near Evanston. 

The name Evanston was appli~d by Schultz (1914, 

pl. 1, p. 68-69) much farther north in westeJ;n Wyoming to strata that were subsequently assigned to the 

Hoback Formation (Eardley and others, 1944; Dorr, 
6 UPPERMOST CRETACEOUS AND TERTIARY STRATIGRAPHY OF FOSSIL BASIN, WYOMING 

1952). The na.me Evanston has been little used by 

geologists in western Wyoming and adjoining areas. 

Gazin (1956, p. 707) described a Paleocene mammalian fauna in the Fossil basin, from gray beds (fig. 

7) 3 miles east of Fossil (fig. 2), and tentatively referred the beds to the Evanston Formation. Our studies 

confirm this assignment and show that the Evanston 

Formation is widely distributed in the basin and includes many of the rocks mapped as Almy Formation 

by Veatch. Not only is the formation far more extensive 

than hitherto realized, but recognition of the unit is 

critical to tectonic interpretations of the region and to 

the precise dating of some significant events. 

The Evanston Formation may be distinguished from 

the overlying Wasatch Formation principally by its lack 

of color in contrast to the characteristic reds, oranges, 

and purples of the Wasatch and by the pebble composition of the conglomerate beds. Evanston conglomerates are well sorted whereas many conglomerates of 

the Wasatch Formation are poorly sorted, have a muddy 

matrix, and locally include large angular boulders composed of rock from Paleozoic and Mesozoic formations 

now exposed nearby as well as reworked pebbles from 

the Evanston Formation. Fine-grained detrital rocks 

of the main body of the Evanston are paJer than the 

somewhat darker grays in comparable strata in the lower 

sandstone and mudstone member of the Wasatch. 

The Evanston differs from the underlying Adaville 

Formation principally in the presence of conglomerates 

that contain clasts as large as boulders and in its heterogeneity. The Evanston includes thick apparently lenticular units of sandstone and conglomerate that alternate ·with thick poorly exposed units which consist 

dominantly of mudstone. The Adaville, however, is 

more uniform in its alternation of widespread thin 

beds of sandstone, mudstone, coal, and ironstone and 

seems to be the product of cyclic deposition, although 

it too includes numerous lenses. 

The Evanston Formation is exposed in an extensive 

belt along the eastern periphery of the Fossil basin, 

in large bands associated with liries of disturbance along 

the southern and southwestern parts of the basin, and in 

scattered small areas within the basin, most of which 

are also associated with disturbed zones. 

Rocks in the eastern peripheral belt have been traced 

southward for more than 30 miles from Commissary 

Ridge, where they are possibly 2,000 feet thick. Excellent exposures (fig. 5) near the middle of the ~uth 

boundary of the Kemmerer quadrangle (north western 

part of sec. 31, T. 21 N., R. 116 W., and sec. 36, T. 21 N., 

R. 117 W.) are more than 1,200 feet thick. 

Veatch (1907, p. 80) reported a maximum thickness 

of 1,600 feet east of the SE cor. sec. 13, T. 16 N., R. 120 

W., but thicknesses probably exceed 2,000 feet in the 

Evanston area. Many beds that Veatch assigned to the 

Almy Formation are boulder conglomerates belonging to the Hams Fork Conglomerate Member of the 

Evanston Formation. Reconnaissance examination of 

rocks 6 miles northeast of Almy in Whitney Canyon and 

to the north indicates that at least part of the rocks 

assigned by Veatch ( 1907, pl. 3) to the Almy Formation east of the Medicine Butte fault belongs to the 

Evanston Formation. 

In this report the Evanston Formation is divided 

into three units: ( 1) a lower dominantly mudstone 

member of Late Cretaceous age and ( 2) the Hams Fork 

Conglomerate Member (new name), which is chiefly 

of latest Cretaceous age and which grades upward and 

tongues laterally into (3) the dominantly silty main 

body of the Evanston Formation, chiefly of Paleocene 

age. 

LOWER MEMBER 

The lowest unit recognized in the Evanston Formation is exposed beneath the Hams Fork Conglomerate 

Member (fig. 3) in the northernmost part of the Kemmerer quadrangle on the west side of Commissary 

Ridge, 21h miles east of Hams Fork. This unit, mapped 

as the unnamed lower member, consists mainly of gray 

to very dark gray mudstone, 1 siltstone, claystone, and 

gray carbonaceous sandstone. The sandstone is fine 

grained to gritty. 2 Conglomerate is present at the base 

of the member along Corral Creek and its .tributaries, in 

the southern part of the Cokeville quadrangle, and includes both granules and pebbles that are composed 

mainly of quartzite and chert. Thin lignite and coal 

beds within the member have been prospected, particularly on the north side of Corral Creek. 

The lower member is as much as 500 feet thick and 

apparently pinches out southward. 

HAMS FORK CONGLOMERATE MEMBER 

NAME AND .TYPE 

Extensive exposures of the Evanston Formation 

along the east side of the Fossil basin are characterized 

by a thick sequence of conglomeratic beds in the lower 

t The term "mudstone" is· used in this report for indurated finegrained detrital rocks consisting of indefinite mixtures of clay and silt 

particles and some sand grains. It is distinguished from siltstone, which 

is composed predominantly of silt particles, and from claystone, which 

is composed predominantly of indurated clays. The term "shale" is 

restricted to fine-grained fissile detrital rocks. 

2 "Grit" and "gritty" are used here for detrital rocks that include 

angular quartz and chert grains of very coarse sand and granule size. 
EVANSTON FORMATION 7 

FIGURE 3.-Lower units of the Evanston Formation on the west 

side of Commissary Ridge. The lower member of the Evanston 

(Kel) unconformably overlies the Jurassic Twin Creek Limestone (Jt) and successively higher units (Jp, Preuss Redbeds, and 

Js, Stum11 Sandstone) to the north and conformably underlies 

the Hams Fork Conglomerate Member of the Evanston (Keh). 

part of the formation. These beds, here named the 

Hams Fork Conglomerate Member of the Evanston 

Formation, dip rather uniformly from 20° to 35° \iV. 

in this part of the area and form the striking hogback 

ridges (fig. 4) north :md south of Moyer, from 

Hams bench mark (hill 7923) 2 miles north of Hams 

Fork on . Commissary Ridge southward to a point 2 . 

miles north-northwest of Elkol. This belt of exposures 

is designated the type area. The section that was 

measured 1-1% miles west of the strip mine north of 

Elkol, near the middle of the eastern part of sec. 36, 

T . 21 N., R. 117 \iV., is designated the type section 

(p. 40-42, fig. 5) . Another representative section is well 

exposed at Morely bench mark (hill 7759), 2% miles 

south of Hams Fork. 

ROCK'S INCLUDED 

The Hams Fork Conglomerate Member consists of 

as many as nine beds of boulder conglomerate (fig. 3) 

interstratified with thick beds of coarse partly conglomeratic brown sandstone and gray mudstone; the 

unit forms the lowest several hundred to 1,000 feet of 

the Evanston Formation at most places along the east 

Westward dips of resisoont Hams Fork beds decrease upward 

in the section until they nearly parallel those in the unconformably overlying reel \Vasatch Formation (Tw). View is north-

\YUrd toward Corra l and Spring Creeks from a point on the 

Dempsey trail in the NE1,4•SE1,4 sec. 32, T. 24 N., R. 116 W. 

side of Fossil basin. Ridgelines of conglomerate consist of long trains of loosely packed cobbles and boulders that form a resistant lag concentrate (fig. 4A) . In 

some places, a series of trains can be recognized as the 

outcropping of a sequence of dipping beds (fig. 4B); 

in others, the boulders spew downslope, covering the 

hillside and making it diffi.culJt to distinguish dipping 

beds. In a few places, the conglomeratic sandstone is 

indurated and the unit is well exposed. Individual 

boulder beds are exposed here and there in borrow pits 

or test pits, where they are thin-mainly less than 5 

feet thick. In many places, the greater apparent thickness of the boulder trains probably results from concentration of the resistant boulders and winnowing of the 

finer grained material in a sequence of thin gravel beds. 

Pebbles, cobbles, and boulders from individual beds 

are sparse at some places and closely packed in others. 

The matrix of the conglomerate ranges from coarse 

crossbedded sand or granule gravel to clayey fine sand 

or silt. The pebbles and boulders are heterogeneous in 

composition, size, and rounding. They generally range 

in diameter from 1 inch to 1 foot, although a few are as 
8 UPPERMOST CRETACEOUS AND TERTIARY STRATIGRAPHY OF FOSSIL BASIN, WYOMING 

FIGURE 4.-Ridges and flatirons formed by boulder beds in the 

Hams Fork Conglomerate Member of the E'vanston Formation. 

A, View northward across Twin Creek from the SE1,4SW1,4 

sec. 19, T. 21 N., R. 116 W. The Hams Fork Conglomerate 

Member (Keh) dips about 25° W., overlying the Adaville FOTA 

B 

mation (Kav) nearly conformably. They are overlapped on the 

west by the more gently dipping Wasatch (Tw) and Green 

River (Tgr) Formations. B , View southeastward from the 

NE. cor. sec. 30, T. 22 N., R. 116 W., of the flatirons formed 

by west-dipping (25°) conglomerate beds. 
EVANSTON FORMATION 9 

FIGURE 5.-Type section of the Hams Fork Conglomerate Member of the Evanston Formation (Keh) viewed northward from 

the SE14 SW14 sec. 19, T. 21 N., R. 116 W. Boulder conglomerate beds are here almost conformable with the underlying 

Cretaceous Adaville Formation (Kav). The red main body of 

much as 2 feet; in most places they are dominantly very 

well rounded and subspherical (fig. 6). 

Light- to dark-gray quartzite, gray and brown quartzitic sandstone, and pink to red conglomeratic quartzite 

are the most common lithologies among the pebbles (fig. 

6). Gray, brown, and black cherts are common. Gray, 

blue, or black limestone, although absent from some 

beds, is sparse in some and is a major component in 

others. 

Much of the quartzite and limestone is derived from 

Mesozoic and upper Paleozoic formations that are exposed not far a way (less than 1 mile to the east), but 

the degree of rounding and sphericity suggest greater 

transport (fig. 6) ; some is derived from formations 

that are now exposed at a considerable distance ( 40 

miles) to the west. The red and pink conglomeratic 

quartzite, for example, resembles most closely the Cambrian and Precambrian Brigham Quartzite, and the 

gray quartzitic arkose resembles the Worm Creek 

Quartzite Member of the Cambrian St. Charles Limestone, now exposed no closer than the Bear River Range 

in southeastern Idaho. Some of the chert and limestone 

probably was derived from lower and middle Paleozoic 

formations exposed in the Bear River Range above the 

Paris thrust fault (Oriel •and Armstrong, 1966, p. 2618) . 

the Wasatch Formation (Tw) overlaps gray and yellow beds 

in both the main body (TKe) and the Hams Fork Gonglomerate Member of the Evanston; all three units are overlapped 

by the white-weathering Fossil Butte Member of the Green 

River Formation (Tgf) . 

DISTRIBUTION AND THICKNESS 

The Hams Fork Conglomerate Member has been 

recognized throughout the belt mapped as Almy by 

Veatch (1907, pl. 3) along the east side of the Fossil 

basin. The belt extends northward into the Cokeville 

quadrangle where it is overlapped by the Wasatch Formation. Another exposed belt of the member mapped 

as Almy by Veatch (1907, pl. 3) extends southwestward 

from Evanston. 

The member is 455 feet thick where measured in the 

NEJ.4 sec. 36, T . 21 N., R.l17 W. (fig. 5) . The National 

Cooperative Refinery Association 1 Arthur H . Linden 

oil test in sec. 19, T. 24 N., R. 117 W., is reported to 

have penetrated 1,382 feet of Evanston conglomerates, 

probably of the Hams Fork Member, and its 1 Government-Larsen oil test in sec. 33, T. 24 N., R. 117 W ., is 

reported to have drilled through 1,310 feet of the unit. 

The thicknesses of the member in these boreholes, however, may be somewhat less because the attitude of bedding may be steeper than assumed. The member is about 

1,000 feet thick where examined at other localities. 

MAIN BODY 

The main body of the Evanston Formation in the 

Fossil basin consists·of light- to dark-gray carbonaceous 
10 UPPERMOST CRETACEOUS AND TERTIARY STRATIGRAPHY OF FOSSIL BASIN, WYOMING 

FIGURE 6.-Well-rounded and subspherical mainly quartzite 

pebbles and cobbles in the Hams Fork Conglomerate Member 

of the Evanston Formation on the south end of Commissary 

Ridge in the NE1,4NW1,4 sec. 5, T. 22 N., R. 116 W. The larger 

clasts close to and above the pick are of purple conglomeratic quartzite derived from the Cambrian and Precambrian 

Brigham Quartzite. 

sandy to clayey siltstone (fig. 7) interbedded with gray, 

tan, yellow, and brown sandstone and conglomerate 

and carbonaceous to lignitic claystone. Ironstone and 

lignite beds are common and coal beds are sparse except 

locally. 

Many beds of light-gray siltstone containing scattered sand grains are cemented by calcite; some are 

cemented by silica to form a quartzitic siltstone that 

spalls on weathering and forms angular chips. The 

quartzitic siltstone is restricted to this formation in the 

Fossil basin and has been recognized at many localities, 

including the type section. 

Conglomerate beds within the main body of the 

Evanston are generally low in the section and in places 

can be traced laterally into the Hams Fork Conglomeratic Member. Light-gray beds dominate the upper part 

of the main body of the formation, and thin discontinuous brownish-red to brick-red layers are found locally 

near the top. Siltstone, sandstone, and claystone in the 

main body are somewhat paler than the darker grays 

and grayish browns of the Hams Fork Conglomerate 

Member. 

The main body is more than 250 feet thick where 

measured beneath an angular unconformity at the base 

of the Wasatch Formation in the small badland buttes 

south of U.S. Highway 30N in the NE% sec. 15 and the 

NW% sec.14, T. 21 N.,R.117W. (fig. 7). 

In the Hoxsey Oil Co. 1 Government test in sec. 14, 

T. 21 N., R. 117 W., spudded about 100 feet below the 

contact of the Evanston Formation with the overlying 

Wasatch, about 1,355 feet of the main body of the formation was penetrated before older rock was entered; 

the Hams Fork Conglomerate Member is absent. 

Small and comparatively thin exposures of the main 

body of the Evanston Formation are on and around 

the south end of the Tunp Range, for example in sees. 

3 and 4, T. 21 N., R. 118 W., along Collett Creek in the 

southeastern part of T. 21 N., R. 119 W., and west of 

Elk Mountain in the east hal:f ofT. 20 N., R. 120 W., 

where the rocks were assigned by Veatch (1907) to the 

Knight Formation. 

The Evanston Formation does not underlie the 

Wasatch Formation everywhere that the Wasatch 

occurs in the Fossil basin, for the overlapping Wasatch 

rests directly on Paleozoic and Mesozoic rocks in many 

places. The Evanston is known from drill-hole information in parts of the basin, however, and thicknesses 

apparently are similar to those in surface exposures. 

LOWER CONTACT 

The Evanston Formation rests with marked angular 

unconformity on virtually all older formations now exposed in the Fossil basin. 

Along the eastern margin of the basin, strata of the 

Hams Fork Conglomerate Member of the Evanston Formation now dip westward and strike roughly parallel 

to the Oyster Ridge barrier. From Hams Fork southward almost to Little Muddy Creek, the formation seems 

to rest conformably on the Adaville Formation (fig. 5). 

Locally, however, it truncates individual beds of the 

Adaville. North of Hams Fork, the Evanston rests directly first on older Cretaceous formations, the Hilliard 

and the Frontier, and then on formations in the thrust 

sheet above the Absaroka fault, from the Pennsylvanian 

and Permian Wells up to the Jurassic Twin Creek 

Limestone (fig. 3) ; in the Cokeville quadrangle, the 
EVANSTON FORMATION 11 

FIGURE 7.-Main body af the Evanston Formation. The badlands exposed in the NE14 sec. 15, T. 21 N., R. 117 W., co·nsist 

dominantly of light- to medium-gray and partly y-ellowish siltstone and claystone. Vertebrate remains of Tiffany age (Wood 

and others, 1941) have been found in these exposUI."eS near the base of the distant badlands left of center in the photograph. 

Fossil Butte forms the skY'line an the right. 

Evanston Formation rests on beds as high, stratigraphically, as the Lower Cretaceous Gannett Group. 

Boreholes drilled through the Evanston Formation 

along the eastern side of the basin have entered diverse 

units below. In the N ationa1 Cooperative Refinery Association 1 Arthur H. Linden oil test, the Evanston is 

tmderlain by the Twin Creek Limestone; in the same 

company's 1 Government-Larsen oil test, it is underlain 

by the Phosphoria Formation; in the Hoxsey Oil Co. 1 

Government oil test, it is underlain by the Wells Formation. 

Farther west, in the Sage quadrangle, the formation 

rests on rocks of Triassic and Jurassic age. 

FOSSILS AND AGE 

The Evanston Formation is Late Cretaceous and 

Paleocene in age, as previously reported (Rubey and 

3~6-469 0---70-·3 

others, 1961). Additional fossil data are presented 

below. 

LOWER MEMBER 

The lower member has yielded well-preserved Late 

Cretaceous leaves, pollen, and spores at several places. 

One collection of leaves from about 50 feet above the 

base of the member in the NE1,4SE~SE~ sec. 29, T. 24 

N., R. 116 W ., was identified (J. A. Wolfe, written 

commun., Dec. 22, 1959) as the dicotyledons Dryophyllum subfalcatum Lesquereux, OinnarJWmum linijoli1tm 

Knowlton, and Dombeyopsis obtusa Lesquereux; these 

forms are of probable Lance or latest Cretaceous age. 

Samples from the same horizon and locality (USGS 

Paleobot. loc. D1493) contain the following pollen and 

spores: 

Araucariacites attskalis Cookson 

Proteacid.ites retttsus Anderson 

P. callosus Cookson 
12 UPPERMOST CRETACEOUS AND TERTIARY STRATIGRAPHY OF FOSSIL BASIN, WYOMING 

Smilaaipit~s sp. 

Pinttspollenites labdacus ( Potonie) Raatz 

Cicatricosisporitcs cf. C. dorogensis Patonie and Gellenticb 

Monoletes major Cookson 

Tr·iplanosporites sinuosus Pflug 

Pollenites ( Tricolporopollenites) cognittts Potonie 

Tricolporopollenites kruschii ( Potonh~) Pflug 

Tamodiaepbllenites 'hiattts ( Potonie) Thiergart 

Sphagnumsporites setcreoidcs Potonie and Venitz 

M o.nosulaites minimus Cookson 

A biCS[JOllenites 

Although the collection is surely of Late Cretaceous age, 

it does not contain species peculiar to Lance pollen floras 

and may be older than Lance (E. B. Leopold, written 

commun., 1960). 

Two 9ther collections from the lower member in the 

NE~SE~ sec. 29, T. 24 N., R. 116 W., at the head of 

CorraJ Creek (north of Trail Creek in fig. 2), contain 

Sequoia reichenbachi ( Geinitz) · Heer, Dryophyllwm 

sub falcatwm Lesquereux, and Ficus sp., all of Late Cretaceous age (R. W. Brown, written commun., 1954). A 

collection from Camp Creek,· in the NW~NEl4 sec. 17, 

T. 24~ :N.; R .. 116 W., includes Protophyllocladus subintegrijoliiis (Lesquereux) Berry, Ficus· planicostata Lesquer€mx, and ·Oinnamonu1n affine Lesquereux. (R. W. 

Brown, \V,ritten comm un., 1.~58). Two other collections 

from the north side of Spring Creek, in south-central 

sec. s,·T. 24 N., R.116'W., includeDryophyllum subfalcatwm Lesquereux, FiCus' sp., Myrica torreyi Lesquereux, anq. a poorly preserved calyx resembling the calyx 

of Paleoaster inquirenda Knowlton, all of Late Cretaceous age (R. W .. B:vown, written commun., 1954) .. 

HAMS FORK CONGLOMERATE MEMBER 

The Hams Fork Conglomerate Member includes 

several forms of Late Cretaceous age. The Lance Triceratops jaw reported. previously (Rubey and others, 

1961) was found 218 feet above the base of the member 

400 feet south-southeast of tl1.~ NW. cor. sec. 31, T. 21 

N., R. 116 W. Leaves from about 75 feet and 325 feet 

above the base of. the member in the NE~ s~c. 36, T. 21. 

N., R. 117 W., were identified (R. W.· Brown, written 

commun., s.ept~ ~9, 1954) . as the Late Cretac~us Protophyllocladus subintegrifolius (Lesquereux) Berry and 

Ficus sp. Gastropods from the upper part of the member, in the NW%SW% sec. 19, T. 21 N., R. 116 W. 

(Meso~oic loc. 27590), include Cleopatra? 2 ·spp., cf. 

Amerianna, Physa sp.; the •collection is more likely 

Cretaceous than Tertiary (D. W. Taylor, written 

commun., May 10, 1960). · 

Pollen and spores were identified in samples collected 

from the Hams Fork Member. Samples from 105 feet 

(USGS Paleobot. loc. D1391A) and 145 feet (D1391B) 

above the base of the member and from 94 feet below 

the top of the member (D1392A) in a section measured 

from the SE%NE% to the SE:%NW% sec. 36, T. 21 N., 

R.117 W., include the following: 

Alsophilidites 

Deltoidospora 4 spp. 

Guthorlisporites Bharwaj 

0 smundacidites 

Cyathidites 

N eoraistrickia Potonie 

Ephedra 

Schizaeoisporites psettdodorogensis PotonU\ 

Pityosporites cf. labdacus Potonie 

Pityosporites 3 spp. 

Tamodi.aepollenites hiattts ( Potonie) Thiergart 

· AI f!noletes undet. 

Alnus 

Qttercoipollenites henrici Potonie 

Proteacidites retttstts Anderson 

Tricolpopollenites kruschi subsp. contorttts (Pflug and 

Thomson) 

Tricolporopollenites kruschi subsp. pseudolaesus Potonie 

JJf ultiporopollenites 

Dinoflagellata 

Erdtmanipollis 

Triletes undet. 

Dicots undet. 

Selaginellites cf. ariadnae Miner 

· -Gicatricosisporites 

Triv_estibulopollcnites betuloides Thomson and Pflug 

·:AlL 'three collections represented a . single assemblage 

·~hat lo.~es types upward in the section; the assemblage 

resembles that of the Lewis and Lance Formations on 

the southern flank of the Green River Basin and is 

latest Cr~t~ceou.s in age (E. B. Leopold, written 

commun., Mar. 23, 1959). 

Three other samples (USGS Paleobot. loc. D1679, 

samples .1, 2, m~d 3) from the lower p.art of the Hams 

Fork Conglomerate Member in the NW%~E% seq. 7; 

T. 21 ~~' R. 116 W., are also of ;Late Cretaceous age and 

· in~lude the f~llowfng (:E. B. Leopold, written commun.,, 

Mar. 19, 1965) : . . . 

· .Aqttilapf?llCrl,itCS 

Cicatricosisporit~s 

Appendicisporites . 

· ClassopOlli~ cla~soides Pflug 

Proteacidites · · 

Sterioisporites ·· 

Hymenozonotriletes reticulatus Bolchovitina 

Sporopollis? 

Podocarpidites bifo~mis Zaklinskaya 

Eucommiidites 

M.t\1~ BODY 

The main body of the Evanston Formation is mo.stly 

of Paleocene age; but because the basal part of it inter- , ... '' . . . . 
EVANSTON FORMATION 13 

tongues with the Hams Fork Conglomerate Member, 

some strata of latest Cretaceous age are present. 

The Paleocene age is well documented in the l{emmerer quadrangle by a variecl vertebrate fauna found 

between 250 and 300 feet below the top of the formation; 

the fauna is of early late Paleocene (Tiffany) age 

( Gazin, 1956, p. 708). 

The gray mudstone and siltstone hills (fig. 7) in 

which the vertebrate remains were found, in the NEJ4 

sec. 15, T. 21 N., R. 117 \V., were also sampled for pollen 

(USGS Paleobot. loc. D1680-2). The sample includes 

the following forms: 

]jf orni·1Jites temtipoltts Anderson 

Pachysandra (large form) 

Nyssoipollenites 

A.lntts, six-pored 

Pice a 

Cary a 

The pollen confiem a middle or late Paleocene age (E. 

B. Leopold, written commun., l\iar. 19, 1965). Another 

sample (USGS Paleobot. loc. D1680-1), some 30 feet 

lower stratigraphically and the l~.w~st horizon exposed 

in a gully at the base of the hills, however, includes the 

following forms of L'tite .. Cretaceou·s age: 

G-icatricosi8porites. · 

Gleicheniidites senonicus Ross . 

Pimtspollenites 

A. raucariacidites 

P1·oteacidites 

A.ppendicisporites 

Leaves from th~ lower part qf the main body, in the 

SE1,4NW1,4 sec. 36, T. 2i N., . R. 117 · W., include 

~Liboced1'Us sp., .~Quercus greeruandica· Heer, and 

~Platanus ra:ynoldsi Ne,vberry and.·are assign~d a probable Paleocene age (R. W. Br0Wn, written· commum, 

Sept. 23, 1958) .. Samples c·ollecte~ for i?ollen at the same 

locality 1 fo9t (D1392-B) and ~bout 2oo· feet. (D1392-

C) above the Hams Fork Conglomerate Member include 

the :following : 

1Jfontipites tenuipqltts Apderson. (abundant) 

Tri1Joropollenites robttsttts Potonie 

Pm·iporopollenites 

TricolzJopollenites rnicrohenrici Potonie 

Pityosporites 

,Tricolporopollenites cf, kruschi Potonie 

Tricolpopollenites rnic1·o·retioit.laturn' Pfh:ig ~nd . Th01;nson 

A.lmts · . · . ·. ' 

The pollen collections are regarded {E. B. Leopold, 

\Vt;itten · coh:1n1ltn.; ·Mar.· 23, 1959) ·as middle· 'and late 

Paleocene in age. · . · · · · ... · . . .· 

Another sample collected along Collett Creek, about 

100 yards N. 45° \V. from B~1 (bench :mark) 6783, in 

N\V1,4NE·1,4 sec. 26, T. 21 N., R. 119 W. (USGS Paleobot. loc. D 1681-A) , includes the following pollen : 

Gm·ya (dominant) 

Nyssoipollenites 

]jf ornipites 

Kurtzipites 

Ulmipollenites 1tndulosus Wolff 

M onocolpopollenites 

cf. Engelhardtia 

Salicoidites 

Alnus, six-pored 

A late Paleocene, possibly Tiffany~ age is inferred· (E. B. 

Leopold, written commun., 1965). Leaves from the same 

locality, however, include Protophyllocladus subin{egrifoliu8 (Lesquereux) Berry, v,rhich is assigned a Late 

Cretaceous age (R. W. Brown, written commun., 1958). 

Possibly strata of both ages arc present. 

Two other leaf collections .fron1 the main body are of 

Paleocene ·age. One collection from about 1 mile northnortheast of Nugget, in the S'\V%.SE1,4 sec. 33, T. 22 N., 

R. 118 vV., includes Ll/ etasequoia occidentalis (Newberry) Chaney, Betula stevensoni Lesquereux, and 

Platanus raynoldsi Newberry (R~ W. Brown, written 

commun., 1958). The other, from the center of the NW~ 

sec. 23, T. 21 N., R. 117 W., about 1 mile south of the 

vertebrate locality and about 100 feet below the top· of 

the Evanston Formation, includes Fagus or Zelkova 

sp., Oarya antiquora :Ne,vberry, Rhamnus or Ficus sp., 

Laurophyllunt sp., and Oarpites sp. (R. W. Brown, 

written commun., 1955). 

Tl~e Cretaceous and Paleocene ·ages of the Ev:anston 

Formation in the.: northern part of the , Fossil basin, 

therefore, are well supported by paleontologic data.and 

agree with the age assignment in the type locality to 

the· south (Rubey and· others, 1961). A~though ·the 

Evanston bridges both the. C,retaceous and Paleocene, 

it is curious that no fossils of early and 1 early middle 

Paleocene ag~. h.ave been 'found .. The absen~e of .. ~uch 

fossils may reflect (a) incomplete sampling, (b) a possi., 

ble hiatus within the Evanston ~ormation that-we have 

been unable to recognize, or (c) possibly inadequate current standards . for · dating this part of the . geologic 

sequence·;. that is, early Paleocene index fossil$ may .be 

indicative of facies rather. than age, and. conditions in 

the Fossil basin may h~ve been uns~l.itabl~ for them. Our 

evidence. is insufficient to choose between th~ three 

alternatives. ; . 

ORIGIN 

I ~, J I 

· The Evanston .Formation ·probably is the- tesult o£ 

both syntectonic and posttectonic nonmarine deposition. 

·Prevalence of drab-colgred· mudstone, presence· ·of 

lignitic beds and coal, lenticularity of individual ·beds; 
14 UPPERMOST CRETACEOUS AND TERTIARY STRATIGRAPHY OF FOSSIL BASIN, WYOMING 

and irregular distribution of terrigenous lithologies indicate that the environments of deposition of the 

Evanston Formation included streams, marshes, and 

probably ponds. Rock colors as well as moderate abundance of ferrous carbonate and oxides indicate a chemically reducing condition, in contrast to an oxidizing 

condition prevalent during deposition of the overlying 

Wasatch Formation. Both the strata and the enclosed 

organic remains indicate a very humid warm-temperate 

climate, as suggested by Brown .( 1962, p. 96). 

Excellent rounding and well-developed sphericity of 

pebbles and boulders in the Hams Fork Conglomerate 

Member suggest moderate transport in a large drainage 

system. This inference is supported by the presence of 

clasts that were derived from formations now exposed 

no closer than 60 miles to the west. 

The divergence of boulder conglomerate beds from the 

basal contact of the formation (fig. 8) and the diversity 

in age of the stratigraphic units underlying the Evanston Formation are· evidence that there was moderate 

topographic relief both within and, along the edges of 

the basin during deposition. The persistence of relief 

within the area is evident at numerous localities where 

theW asatch and, in places, the Green River Formations 

overlap the Evanston Formation. 

TECTONIC IMPLICATIONS 

The Hams Fork Conglomerate Member of the Evanston Formation rests unconformably on rocks both below 

and above the Absaroka thrust fault in T. 23 N., R. 116 

W. Movement along the Absaroka thrust fault resulted 

in drag folding of Upper Cretaceous and older rocks 

beneath the fault and formed the Lazeart syncline (fig. 

8). The west limb of the syncline north of Hams Fork 

is truncated by the Evanston Formation. Therefore, 

major movement along the fault at this place preceded 

deposition of the Evanston Formation, if the syncline 

did indeed form at the time of thrusting (Oriel and 

Armstrong, 1966, p. 2616-2617). 

In at least one locality (sec. 29, T. 23 N., R. 116 W.), 

some beds of the Hams Fork Conglomerate Member lie 

beneath the fault and are deformed (fig. 8). Moreover, 

south of Hams Fork, basal beds of the Evanston Formation are folded and lie along the axis of the Lazeart 

syncline (fig. 8). These observations indicate that 

although major movement on the Absaroka fault preceded deposition of the Hams Fork Conglomerate Member, a minor pulse occurred after deposition of the basal 

Evanston strata. 

Several miles south of Hams Fork, fossils from the 

uppermost part of the Adaville Formation and from the 

Hams. Fork Conglomeratic Member of the Evanston 

Formation are assigned a Late Cretaceous (late l\{onta.na 

and Lance) age (J. A. Wolfe and E. B. Leopold, written 

commun., 1959, 1965; Dorf, 1955). Thus, all these data 

are evidence that major movement along the Absaroka 

thrust fault in the vicinity of Hams Fork took place in 

Cretaceous (probably early Lance) time and that deposition of the Evanston started during the deformation and 

ended considerably later, in late Paleocene time. 

The abundance of rounded coarse detritus from formations now exposed in thrust sheets in southeastern 

Idaho suggests elevated source areas resulting from 

earlier deformation there and possibly recurrent movement along the Paris thrust fault (Oriel and Armstrong, 

1966). 

Basal beds of the Evanston Formation along the east 

side of the Fossil basin dip about 20°-40°W. Successively younger beds decrease in dip gradually upward 

(fig. 3) until the uppermost beds of the formation are 

almost horizontal and subparallel to beds of the overlying Wasatch Formation. These data indicate that the 

Fossil basin began taking shape in latest Cretaceous 

time and continued forming in Paleocene time. 

WASATCH FORMATION 

NAME AND USAGE 

DEFINITION 

The name Wasatch lva:s first used by Hayden in 

1869-considerably before currently •accepted rules for 

definition of a new unit were formulated. Hayden's 

complete description of the unit (p. 91) is as follows: 

~Immediately west of Fort Bridger commences one of :the most 

remarkable and extensive groups of tertiary beds seen in the 

West. They are wonderfully variegated, some ·shade of red 

predominating. This group, to which I have given the name 

of Wasatch group, is composed of variegated sands and clays. 

Very little calcareous matter is found in these beds. 

In Echo and Weber [

3

] Canons are wonderful displays of 

conglomerates, fi·fteen hundred to two thousand feet in thickness. Although this group occupies a vast area, and attains a 

thickness of three to five thousand feet, yet I have never known 

any remains of animals to be found in it. I regard it, however, 

as of middle tertiary age. 

In a subsequent publication Hayden ( 1870, p. 113-

114) stated of the Wasatch: 

I have included in this group all the variegated beds which 

we have observed west of Carter's Station, and we have noticed 

especially that some shade of red bas prevailed in the clays and 

sands, as well as in the conglomerates of this group. Some of 

the sandstones in the upper portion of Echo Canon are noticea'ble for their deep yellow hue. 

a The sharp northwesterly bend in the railroad in fig. 1 is at the 

mouth of Echo Canyon where Echo Canyon Creek flows into the northwesterly flowing Weber River. 
0 

WASATCH FORMATION 

CONTOUR INTERVAL 40 FEET 

DATUM IS MEAN SEA LEVEL 

2 MILES 

EXPLANATION 

G 

Quaternar y sediments Alluvium and colluvium 

Eocene strata T g f, Fossil Butte Member of Green River Formation Twt, Tunp Member of Wasatl'h For- mation 

Tw, main body of Wasatch Fonnation 

Paleocene and 

~ Upper Cretaceous 

Evanston Formation 

T Ke, main body Keh , Han1,s Fork Conglome1·ate Mem- ber b, mapped l1·ace of boulde·r conglom- erate bed 

~:\~~)( .. ... 

;::::~. 

·/jty)) 

:~:.'k!i;i<( 

;((f<:i'!//: 

Cret aceous strata 

Kav, Adaville Forma.tion Kh . Hillia1·d Shale Kh s, sandstone unit of Hilliard Shale Kfu , Kf m, Kfl , upper, middle, an<l lower me mbe1·s of Frontier For- mation 

Jurassic Twin Creek Limestone 

Triassic Thaynes Limestone 

Permian Phosphoria Formation. 

Per mian and Pennsylvanian 

Wells Forma tion 

Line symbols Dashed where appro.rima tely {orated; 

dotted where t01U'ealed 

Contact 

>-- u ---""Fa ult0 ···-· 

U , ~~pt rOll ll t1ide; D . downthrown Hide: T. upper plote of lhr?.tst .fault 

--t--- --t--

Anticline Syncline 

----.2!! -t- ~ Inclined Vertical Overturned 

Strike and dip of beds 

~ 

Mine or prospect pi t 

FIGURE 8.-Geologic map of part of the Kemmerer quadrangle, Lincoln Cow1ty, Wyo. (from Rubey, Oriel, and 

Tracey, 1968) , showing the divergence of boulder conglomerate beds (b) from the basal contact of the 

Evanston Formation, 

15 
16 UPPERMOST CRETACEOUS AND TERTIARY STRATIGRAPHY OF FOSSIL BASIN, WYOMING 

Another statement in the same report ( 1870, p. 106) is 

somewhat more descriptive: 

* * "' ·near Quaking Asp Summit [we] enter upon the borders 

of the great valley of Salt Lake * * * [in which] we have the 

curiously variegated beds of the 'V•asatch group, which present 

almost every variety of shade of color from white and yellow to 

a deep brick-red, the red and purple tints so predominating that 

they give a singularly curious aspect to the scenery. 

Hayden's "type section" of ·his "'\Vasa.tch Group consists of exposures along the tracks of the Union Pacific 

Railroad from the uppermost variegated beds in contact with overlying Bridger Formation near Carter, 

westward to the lowest conglomerates in Echo Canyon-a distance of nearly 70 miles. He named the group 

for Wasatch at the head of Echo Canyon, east of which 

are the variegated beds and west of which are the 

massive conglomerates. 

VEATCH'S SUBDIVISIONS 

Veatch (1907, p. 88) tried to subdivide the group 

within the Fossil basin into more homogeneous units 

as follows: 

In the Wasatch group as thus defined by Hayden the field 

work of the season of 1905 showed three divisions: (1) A ba.sal 

member composed of reddish-yellow sandy clays, in many places 

containing pronounced conglomerate 'beds, which has been named 

the Almy formation; (2) a great thickness o.f light-colored 

rhyoiitic ash beds containing intercalated lenses of white limestones with fresh-water shells and leaves-the Fowkes formation; and (3) a group of reddish-yellow sandy clays with irregular sandstone beds [the Knight for:mation] closely resembling 

(1) lithologically and ·separated from (1) ·and (2) by a pronounced period of folding and erosion. 

T·he Fowkes Formation, one of several criteria used 

for separation of the Knight and Almy Formations, actually overlies both the Knight and the Almy, as well as 

the Green River Formation (Tracey and Orie.I, 1959, 

p. 129, 130; Eardley, 1959, p, 167). It was erroneously 

placed by Veatch between the Knight and Almy Formations because near the Almy settlement it adjoins 

older rocks, although it is separated from them by normal faults that parallel the strike of the beds. 

West o£ Almy in the bluffs on the west side of the 

Bear River are exposures of white to light-gray strata 

overlain by red beds, which Veatch (1907, p. 90) interpreted as evidence that the Fowkes is overlain by the 

Knight Formation. However, the white strata here, unlike the rhyolitic tuff and ash of other Fowkes exposures, consist of fresh-water limestone. Both the 

composition and the included gastropods and leaves 

(Veatch, 1907, p. 92) clearly indicate that the white beds 

on the west side of the Bear River are tongues of Green 

River limestone in the Wasatch Formation and not the 

younger Fowkes Formation. 

Other criteria used by Veatch for distinguishing between similar lithologies of the Almy and I\:night Formations were the steeper dips of the Almy strata, which 

he stated were overlain with pronounced angular unconformity by the I\:night Formation, and the presence 

of conspicuous conglomerate beds in the Almy. Veatch 

(1907, p. 89) stated that the Almy was commonly exposed in the type region only along lines of structural 

disturbance and noted the presence in the Abny of 

crushed and cemented qua.rtzite pebbles, a product of 

the great force involved in the disturbance of the 

strata. 

Applying these concepts, Veatch and Schultz mapped 

extensive belts of the Almy Formation. Most of their 

outcrops of Almy along lines of structural distur•bance, 

however, are the Hams Fork Conglomerate Mem:ber of 

the Evanston Formation. The poorly sorted calcareous 

conglomerate northeast of Sage mapped a.s Almy by 

Veatch belongs in the Fowkes Formation. 

Many conglomerate beds within the "Vasatch Formation are in a peripheral facies which can be traced 

laterally into basinal facies represented by the variegated dominantly mudstone beds of Veatch's I\:night 

Formation. Where the conglomerate beds cannot be 

traced, as in the Almy type area, they are found to be 

sep~rated from the l{night by normal faults rather 

than by an angular unconformity. Accordingly, there 

is no basis for separating the Almy and I\:night Formations except if they are considered peripheral and 

basinal facies of the vVasatch Formation, and we recommend that the names not be used with any implication 

that one underlies or is older than the other (Oriel, 

Gazin, and Tracey, 1962). 

SUBDIVISIONS USED HERE 

The name Wasatch is used here in much the same 

manner as defined by Hayden ( 1869), as mapped by 

Peale ( 1879, p. 636; 1883), a.nd as understood by Veatch, 

although our subdivisions of the formation are considerably different. Our usage is similar to that of others who 

have mapped moderate areas of the Green River and 

nearby basins, especially Bradley (1964, p. A20), 

Pipiringos (1961), Masursky (1962), Oriel (1961), and 

Culbertson (1965), who assigned mainly variegated red 

strata (fig. 10) to the Wasatch but who also included 

some nonred-green and gray-beds in the unit. 

TheW asatch Formation is here subdivided into seven 

units on the basis of mappable lithologic facies and 

their stratigraphic relations to the Green River Formation. The units, from bottom to top of the formation, 

are: a local unnamed basal pebble-to-boulder conglomerate member, in places fractured and recemented ; a 

.... 
·., 

.... 

WASATCH ·FORMATION 17 

local unnamed lower member in places unconformable 

with the overlying main body of the Wasatch; the unnamed main body of the Wasatch Formation; a sandstone tongue; a mudstone tongue; an upper memberthe Bullpen Member; and a peripheral member-the 

Tunp Member, which is laterally equivalent to parts of 

the other units (tables 1, 3, 4). 

BASAL CONGLOMERATE MEMBER 

Lenticular conglomerate locally forms the basal member of the 'Vasatch Formation and is oomposed chiefly of 

pebbles and cobbles of tan to buff sandstone and quartzitic sandstone derived from the Triassic ( ~) and 

Jurassic ( ~) Nugget Sandstone. Pebbles of gray quartzite, probably from the Pennsylvanian and Permian 

'V ells Formation, and of tan to bluish-gray limestone, 

from the Triassic Thaynes Formation and the Jurassic 

Twin Creek Limestone, a.re common in places. Large 

cobbles of gray porous conglomeratic sandstone, though 

sparse, are diagnostic of the unit because they are the 

most widespread pebbles found other than those of the 

Nugget Sandstone. Their source is not known, although 

they resemble the Triassic Higham Grit (W. ,V. Rubey, 

oral commun., 19·58). 

The conglomerate is exposed locaily in channels and 

hollows in folded Mesozoic rocks at the south end of 

Tunp Range, northeast of Nugget, and on the extensive 

exposures of Nugget Sandstone south and southwest of 

Nugget. It ranges in thickness from a few feet, in areas 

where it is spread thinly over the older rocks, to several 

hundred feet, where it fills deep channels. 

In a few places where the conglomerate is thick, it 

contains packed subrounded to angular blocks of quartzitic sandstone as much as several feet across. In other 

places, pebbles and cobbles are scattered in a fairly 

homogeneous quartz sand matrix that also was probably 

derived from the Nugget Sandstone. Beds of conglomerate with abundant limonite a.re common. Fractured 

recemented quartzite pebbles similar to the "Almy 

pebbles" shown by Veatch (1907, p. 16) are characteristic of the unit. 

LOWER MEMBER 

An irregular sequence of beds of drab-colored mudstone, sandstone, conglomerate, and limestone locally 

underlies typical red beds of the main body of the 

Wasatch along the southern part of the Tunp Range, 

conformably in most places and with apparent angular 

unconformity in others. The sequence is here assigned 

to the Wasatch Formation because it includes · variegated beds typical of other parts of the form~ion, but ' 

it is not formally named pending clarification of its 

relation to subdivisions of the Wasatch in the southern 

part of the Fossil basin. 

ROCKS INCLUDED 

Fine-grained detrital rocks of the lower member 

include light- to dark-gray, brown, pink, and red sandy 

mudstone and black carbonaceous silty claystone, in 

beds generally 5-10 feet thick. These are interbedded 

with beds commonly 1-5 feet thick of yellow- to brownweathering gray sandstone, flaggy irregularly crossbedded coarse-grained sandstone, mid grit and pebble 

conglomerate that contain abundant grains, granules, 

and pebbles of black chert. The flaggy beds weather to 

loose contorted slabs. Brown sandstone conglomerate 

or grit that contains small gray clay balls and angula.r 

fragments a quarter to a half inch in diameter is 

common . 

Thin lenses of limestone are found locally. The most 

common kind of limestone is muddy brown, fissile, and 

carbonaceous. One variety is extremely hard, dark 

brown, and finely crystalline, and occurs in beds 1 inch 

to several inches thick that weather grayish brown or 

orange brown. Slabs of this rock ring when struck by a 

hammer. 

In a few places, light-gray to light-brown algal limestone and pisolitic limestone form beds 5-20 feet thick 

that are interbedded with red to gray mudstone and red 

diamictite. Near Morgan Canyon in the NWli.J,NEli.J, 

sec. 16, T. 22 N., R. 118 W., three beds of pisolitic limestone 5-10 feet thick (fig. 9A.) a.re formed of algal 

pisolites (fig. 9B), which are mostly 1-5 inches in diameter. These beds are overlain by brown shaly limestone, 

gray carbonaceous mudstones, and yellow- to brownweathering sandstone and grit that are faulted against, 

and apparently unconformrubly overlain by, red variegated mudstone of the main body of the Wasatch 

Formation. 

The lower member grades into the main body in the 

small basin of North Bridger Creek, west of Elk Mountain in the northwestern part of T. 20 N., R. 119 W. 

Light-gray silty mudstone of the Evanston Formation 

is overlain with slight unconformity by a thin bed of 

the basal conglomerate member of the Wasatch. This 

conglomerate, containing rounded pebbles derived from 

the Nugget Sandstone, is overlain by pebble grit, con-

. taining abundant black chert pebbles, by thin beds of 

brown hard, ringing limestone, and by gray, red, and 

maroon mudstone, black carbonaceous clay, and yellow 

sandstone that in several hundred feet grade into 

variegated beds of the main body. 

The unit is intermediate not only in position but, except for local concentrations of algal and pisolitic lime-
18 UPPERMOST CRETACEOUS AND TERTIARY STRATIGRAPHY OF FOSSIL BASIN, WYOMING 

B 

FIGURE 9.-Lower member of the Wasatch Formation. A, Three 

beds of west-dipping algal and pisolitic limestone (Twl) in the 

lower member of the Wasatch Formation on the north side of 

Morgan Canyon in the NW1,4NE14 sec. 16, T. 22 N., R. 118 W. 

The limestone overlies red mudstone (Twr), which rests unconformably on Permian strata (Pp). B, Closeup of limestone bed 

in A, showing pisolites as much as 3 inches in diameter. 

stone, in composition between the upper part of the 

Evanston Formation and higher more typical parts of 

the Wasatch Formation. However, diagnostic features 

of the Wasatch, to which it is here assigned, prevail. 

DISTRIBUTION AND THICKNESS 

The lower member of the ·wasatch is present on the 

south end of the Tunp Range in the Sage quadrangle. 

The strata are nearly continuously eA'})OSed along the 

east side of the range for 3 miles north of U.S. Highway 

30N, and patches cover parts of the exposed surface and 

sides of the large domelike exposure of Nugget Sandstone south of the highway. The lower member overlies 

gray mudstone of the Evanston Formation along Collett 

Creek and in the basin of North Bridger Creek. P robably not more than 300 feet of beds are present at any 

locality. The unit varies greatly in thickness from place 

to place because it was deposited on an irregular topographic surface of moderate relief, because it has been 

variously compacted, and because it has been folded and 

faulted against older rocks at the edge of the basin. The 

lower member has not been recognized either ·on the east 

side of the Fossil basin or in drill holes. 

MAIN BODY 

ROCKS INCLUDE D 

The main body of theW asatch Formation within the 

Fossil basin consists predominantly of banded, variegated mudstone (fig. 10) interbedded with claystone, 

siltstone, sandstone, conglomerate, and light-gray marlstone. Thin lentils of brown to dark-gray limestone are 

present in a few places directly below or near the margins of beds of the Green River Formation. 

Colors range from deep red and maroon through 

various hues of red to purple, brown, yellow, tan, and 

light to dark gray. Horizontal color bands on weathered 

slopes (fig. 10) range in thickness from 1 to 10 feet and 

are mostly 2-5 feet thick, whereas virtually all fresh 

mudstone is mottled. The bands are brightest, in red, 

maroon, and purple hues, in rthe upper predominantly 

mudstone part of the unit not far beneath beds of the 

Green River Formation; in the lower sandy part of the 

unit, they are mostly drab shades of red, pink, tan, and 

gray. Colors arc related to lithology in that sandy or 

conglomeratic strata are less intensely colored than silty 

or muddy strata. Nevertheless, a sequence of clearly defined bright bands is evident even in fresh exposures of 

virtually homogeneous mudstone. At a distance, they apFIGURE 10.-Color-banded mudstone and siltstone in the main 

body of the Wasatch Formation. The exposure is on the southwest side of Fossil Butte in the NW1

4 sec. 6, T. 21 N., R. 117 W. 
> 

WASATCH F ORMATION 19 

pear to be sharply defined, but on close examination the 

color bands are exceedingly diffuse. 

The upper mudstone part of the unit consists largely 

of bedded silt and fine sand with much clay binder. More 

pure claystone beds generally contain abundant disseminated grains of angular quartz sand. The clay 

sloughs and spalls on exposure and probably is montmorilloilitic. Prominent siltstone, sandstone, and conglomerate beds are indurated with calcium carbonate. 

Moderately well sorted well-rounded pebble conglomerate is confined to deposits that fill channels cut into the 

variegated mudstone beds (fig. 11), whereas beds of 

gritty poorly sotted gravel conglomerate that contain 

abundant chips and angular fragments of black chert 

are laterally extensive and are not confined to chatmels. 

Conglomerate and crossbedded sandstone are more ' tc71'"'--:-;-:--:JS~~~~~;:&!~~I!:J~~ 

abundant in the lower part of the section, particularly 

in peripheral areas of the basin. The type exposures of 

Veatch's Almy are not notably conglomeratic and are 

only moderately representative of the peripheral conglomerate facies of the main body of the Wasatch 

Formation. More representative conglomeratic facies 

can be seen west of liVasatch on U.S. H ighway 30S, 9 

miles west of Evanston, where the east-west gradation 

from basinal to peripheral facies is well exposed. 

Detailed mapping may delineate the basinal muddy 

and peripheral conglomeratic facies of the Wasatch, at 

least in the south half of the Fossil basin, and demonstrate the possible validity of the Almy as a peripheral 

member and the Knight as a basinal member of the 

main body of the ·wasatch Formation. Until they are 

mapped, however, the names Almy and Knight should 

not be used. 

The peri phera 1 sandy to conglomeratic facies of the 

liVasatch discussed here is not the same as the conglomeratic mudstone or diamictite facies of the northern part 

of the Fossil basin, which was mapped separately as the 

Tunp Member of the Wasatch, atld is discussed below. In 

many places, however, it lies between Tunp diamictite 

and the basinal facies. 

DI STRIBUTION AND THICKNESS 

The main body of the Wasatch Formation is exposed 

in much of the Fossil basin. It includes most of the areas 

mapped as Knight Formation by Veatch (1907, pl. 3) in 

the northern and eastern parts of the basin. Near 

Evanston, on the east side of the Bear River, it includes 

beds mapped as both Almy and Knight Formations by 

Veatch. 

About 1,000 feet of beds is exposed along U.S. Highway 30N from the east side of the Tunp Range to the 

base of the Green River Formation at Fossil Butte. 

About 1,100 feet of Tertiary rocks was penetrated several miles to the north, in the Amerada Petroleum Co. 

36.6-469 0-70- 4 

FIGURE 11.-Lenses of moderately well sorted brown conglomerate in mudstones of the main body of the iVasatch Formation. Uppe1·, Conglomerate fills channels cut into reel mudstone 

in the NE1,4 sec. 12, T. 21 N., R. 117 W., near the periphery of 

the Fossil basin: scale is indicated by the pipe-tobacco can. 

Lowe1·, Conglomerate fills channels cut into banded and variegated mudstone farther southwest nearer the center of the 

basin. 

1 Chicken Creek unit well (sec. 30, T. 22 N., R.117 W.), 

in a hole that statted 400 feet below the base of the Green 

River Formation. The National Cooperative Refinery 

Association 1 Government-Larsen test well (sec. 33, 

T. 24 N., R. 117 W.) penetrated a comparable thickness. It began about 400 feet below the base of the Green 

River Formation and is reporiecl to have penetrated 

1,030 feet of the Wasatch Formation. The main body of 

the Wasatch is 1,512 feet thick in the Roy Steele 1 Government borehole, in the NEJ4NE:!4 sec. 29, T . 20 N., 

R. 118 W., 2% miles southeast of Elk Mountain near the 

center of the Fossil basin. 

The thickness of the Wasatch Formation near the 

south end of the basin may be as much as the 2,000 feet 

reported by Veatch (1907, p. 89) for his Almy Formation in the type area. 
20 UPPERMOST CRETACEOUS AND TERTIARY STRATIGRAPHY OF FOSSIL BASIN, WYOMING 

Toward the edges of the basin, the main body of the 

Wasatch generally thins. In a few places it is overlapped by beds of the Green River Fonnation (fig. 5) 

that rest directly on formations of Paleozoic and Mesozoic age. In some places, however, the "T asatch Formation may be very thick near an edge of the basin, because 

of high-angle faulting that dropped the basin while 

theW asatch Formation was being deposited. 

LOWER CONTACT 

The surface upon which the Wasatch Formation was 

deposited had in many places considerable topographic 

relief. Along the margins of the basin, rocks here assigned to the main body of the Wasatch Formation rest 

unconformably on all older fonnations exposed nearby, 

from the upper part of the Evanston Fonnation down 

to and including the Wells Formation. In a few places, 

beds of the Wasatch Formation rest on older Paleozoic rock, such as the Bighorn Dolomite of Ordovician 

age, as in the SW% sec. 25, T. 21 N., R. 119 W. The 

considerable relief that existed during deposition of the 

main body is well demonstrated near the basin's margins 

where lower beds of the Wasatch butt against steep 

topographic highs of Mesozoic rocks and where both 

are overlapped by higher beds of the Wasatch. 

The main body conformably overlies the. lower unnamed member of the Wasatch Formation in relatively 

few parts 9f the Fossil basin; at these places the contact is transitional. Where uppermost beds of the Evanston directly underlie the main body of the Wasatch 

Fonnation, the contact is apparently conformable. Indeed, in a few localities, including the type sections of 

the Evanston and Almy Fonnations, the dominantly 

light gray mudstone beds below contain a few thin red 

and yellow mudstone beds, and the varicolored mudstone beds above contain several gray mudstone bands; 

the rocks at these localities seem to be gradational. In 

some of these places, however, beds within the Evanston 

are folded into both small and broad open folds, whereas 

basal strata of the Wasatch Fonnation dip gently and 

more uniformly. 

SANDSTONE TONGUE 

A comparatively thin tongue of sandstone with some 

green mudstone divides the Fossil Butte Member of the 

Green River Formation into two units in the southeastern part of the Sage and southwestern part of the 

l{emmerer quadrangles. It has been traced only a few 

miles south of the quadrangle boundary, as far as the 

north side of Elk Mountain where it is 40-50 feet thick. 

The tongue is well exposed within bluffs of the Green 

River Fonnation along Clear Creek and close to the 

Angelo Ranch, south and southeast of Fossil, but it 

thins and disappears to the north. 

Most of the unit consists of well-bedded cross-laminated medium- to coarse-grained bro·wn sandstone composed mostly of quartz but containing abundant black 

chert grains. Southeast of the southeast corner of the 

Sage quadrangle, the unit consists of several extensive 

sandstone beds, sandstone lentils, and interbedded green 

and gray mudstone. We regard this unit as a tongue of 

the Wasatch Formation because its dominantly detrital 

components are traceable into the thick sequence of 

sandstone, claystone, red mudstone, and conglomerate 

of Elk Mountain which we assign to the Wasatch Form.ation, although it is interbedded with thin laminated 

limestone beds of the Green Rive.r Formation. 

The sandstone tongue of the 'iVasatch Formation 

probably was derived from the south and spread northward onto the laminated mudstone, siltstone, and limestone of the lower part of the Fossil Butte Member of 

the Green River Formation. The source of the detritus 

may have been the Uinta Mountains, which were shedding detritus into the Green River Basin at about the 

same time (Lawrence, 1963). The unit represents -an encroaching dominantly sand tongue from a single source 

and may have formed a.s a delta which spread into the 

lake of Green River age rather than as alluvium along 

the southern margin of a receding lake. Despite uncertainties regarding genesis, it is assigned to the 'Vasatch 

Formation on the basis of lithology. ~ether the unit 

is of more than local significance is not known. 

MUDSTONE TONGUE 

A thin but ext~nsive tongue of the Wasatch Formation separates the Angelo Member from the Fossil 

Butte Member of the Green River Formation over a 

large part of their area of outcrop. The unit consists 

of dark-red to brick-red mudstone along the northwest 

side of the Hams Fork Plateau. Basinward the Fossil 

Butte and the Angelo Members of the Green River 

Formation thicken, and the mudstone tongue of the 

'Vasatch thins from a maximum of about 50 feet and 

changes to light-red or pink and light-grayish-green to 

light-greenish-gray claystone. The clay is "soft" in a 

fresh exposure and may be montmorillonitic in that it 

slakes and cracks. Toward Tunp Range, the unit 

thickens and in places becomes conglomeratic, merging 

with the peripheral Tunp Member of the Wasatch 

Formation. 

Over a large central part of the basin, where thick 

sections of the Green River Formation are exposed, 

beds equivalent to the mudstone tongue of the "' ... asatch 

Formation are represented by a few feet of light-gray 

to greenish-gray thin-bedded shale or claystone at the 

base of the Angelo Member of the Green River Formation. The equivalent of the tongue in the southern or 

western part of the basin is not known. · 
WASATCH FORMATION 21 

FIGURE 12.-Algal log in the mudstone tongue of the Wasatch 

Formation. The cylinder of limestone was probably deposited 

by algae as an encrustation on a fragment of a tree branch. 

The mudstone tongue of the \Vasatch represents 

muds, silts, and clays that were carried into the Green 

River lake chiefly from the north and west. This tongue 

ma.y be related to mudflows and slides of weathered 

material coimected with · the formation of the Tunp 

Member of the \V asatch or possibly with an increasing 

amount of volcanic material over the region. 

The mudstone tongue is characterized by "algal 

logs"-cylindrical forms that appear to be the encrustations of sticks, twigs, and logs by accretionary growth 

of brown laminar limestone, probably deposited by 

calcareous algae (fig. 12). The interior surface seems 

to be the mold of sticks or logs, in places preserving a 

grainlike or barklike surface. Small forms are one-half 

inch thick, several inches \Yide, and 4-6 inches long; 

the longest one is millstone shaped, 6-8 inches thick, 

and 18 · inches in diameter and has a. central openmg 

6 inches in diameter. The "front" and "back" surfaces 

are almost plane fractures. 

The algal logs are locally common, are widely distributed over the northern part of the area, and in 

places can be used as horizon markers. They are 

abundant in the mudstone tongue wherever their 

stratigraphic positions can be accurately determined, 

and for this reason they have been used as indicators 

of the former presence of the tongue where they are 

abundant on a weathered surface. 

BULLPEN MEMBER 

NAME AND TYPE 

A moderate to thick sequence of red, pink-salmon, 

green, and gray mudstone, eA'tensive but thin beds of 

limestone, fine- to coarse-grained sandstone, and conglomerate is exposed in the central and south-central 

parts of Fossil basin. It is here named the Bullpen 

Member of the \Vasatch Formation for exposures that 

cap bluffs of the Green River Formation south of Bullpen Creek, in the southeastern part of the Sage and the 

southwestern part of the Kemmerer quadrangles. 

A sequence measured in the N\V1,4 sec. 1, T. 20 N., 

R. 118 W. (p. 42), is here designruted the type section. 

Although the section is incomplete, it is moderately 

>vell exposed and contains more common lithologies 

than the complete sections measured to the northwest 

and southwest where conglomerate and diamictite along 

the periphery of the Fossil basin are more abundant. 

Veatch recognized these rocks on Hams Fork Plateau and suggested (1907, p. 99) "* * * that they 

represent outlying Bridger areas. These outcrops have 

a reddish cast, not like typical Bridger, and the suggested correlation is based more on their position above 

the typical Green River than on their lithologic 

resemblance rto the Bridger of the type locality." We 

assign these rocks to the Wasatch Formation because 

they resemble \Vasatch strata elsewhere and do not 

resemble the Bridger Formation lithologically and because these strata above the Green River Formation 

grade laterally into the indivisible peripheral units also 

assigned to the Wasatch Formation. 

ROCKS INCLUDED 

The Bullpen Member of the ·wasatch Formation 

contains layered sequences of red to pink, green, and 

li ght-gray claystone and muustone in the central part 

of the Fossil basin, especially northeast and southeast 

of E lk Mountain. The pastel hues of the banded claystone and mudstone gi,·e a "peppermint candy" aspect 

to ridgetops over a \Yide area. The claystone is in many 

')laces soft sloughing bentonitic clay apparently identical to thinner and less widely distributed beds of the 
22 UPPERMOST CRETACEOUS AND TERTIARY STRATIGRAPHY OF FOSSIL BASIN, WYOMING 

mudstone tongue of the vVasatch Formation on Hams 

Fork Plateau. The mudstone is both silty and sandy 

claystone. Siltstone beds are mainly light gray and 

yellow. 

Cross-laminated fine- to coarse-grained sandstone 

and gritty granule conglomerate are abundant northeast of Elk ~fountain in beds 5-40 feet thick. The beds 

seem to be identical in composition and texture with 

those of the sandstone tongue of the "'V asatch Formation and are found over much the same area. 

Salmon-colored to red mudstone, brown and gray 

sandstone beds, and pebbly conglomeratic sandstone 

are especially characteristic of the upper half of the 

member. They are dominant especially from Elk Mountain to Sillem Ridge. Toward the west edge of the 

basin-both northeast and southeast of Sage-sandstone and conglomerate are more abundant, coarser, 

and more poorly sorted, approaching the diamictite 

facies of the Tunp Member of the Wasatch Formation. 

Pebbles and boulders are well rounded to angular and 

apparently were derived from ~fesozoic rocks exposed 

in nearby ridges and from Paleozoic rocks exposed west 

of the Crawford fault (Rubey, Tracey, and Oriel, 

1968). The member may also coarsen southward toward 

the center of the Fossil basin, but this observation is 

based on reconnaissance. 

The limestone is mainly slabby and thin bedded. 

Some beds are dark brown and petroliferous to almost 

black on fresh surfaces and nearly white, light tan, or 

brown on weathered surfaces; other beds are white to 

light gray and partly argillaceous to marly. Some beds 

are subaphanitic laminated limestone very similar to 

the limestone of underlying members of the Green River 

Formation. 

Many of the limestone beds are resistant and form 

extensive butte and mesa caps, as well as ledges, beneath 

which less resistant beds of mudstone and claystone are 

preserved. In the Sage and ICemmerer quadrangles 

prominent beds of limestone and laminated siltstone, 

though thin, have been mapped in the Bullpen and the 

Tunp Members of the Wasatch Formation (Rubey, 

Tracey, and Oriel, 1968; Rubey, Oriel, and Tracey, 

1968). 

DISTRIBUTION AND. THICKNESS 

The Bullpen is considered a member of the Wasatch 

Formation on the basis of its dominant lithologies and 

because it. grades laterally southward into the sandy 

and conglomeratic sequence at Elk ]\fountain that 

resembles parts of the peripheral conglomeratic facies 

of the Wasatch. Southeast of Bullpen Creek this member grades into claystone and mudstone, which are 

interbedded with increasing amounts of limestone south 

of the ICemmerer quadrangle, where it would be feasible 

to map the limestone beds as an upper member of the 

Green River Formation. North of U.S. Highway 30N, 

near the Tunp Range, the Bullpen :Member merges 

laterally with rubbly mudstone .of the Tunp ~fember of 

the "'Vasatch Formation. North and south of Sage, along 

Boulder Ridge, the Bullpen ~fember grades westward 

into blocky breccia in a matrix of salmon -colored sandstone and mudstone of the Tunp Member. 

A complete section, 400 feet thick, was measured on 

the south side of Elk Mountain where the Bullpen 

Member is overlain by about 60 feet of gray tuffaceous 

mudstone and conglomerate of the Sill em Member. of 

the Fowkes Formation. 

Another section of the Bullpen Member, about 300 

feet thick, was measured on the northeast end of Sillem 

Ridge, in the Elh sec. 21, T. 21 N., R. 119 W. This and 

other sections nearby are cut by normal faults, and the 

measurements required care. Eroded remnants of the 

unit, not overlain by younger rocks, are found north 

and east of Sillem Ridge at numerous localities. In the 

southern parts of sees. 25 and 26, T. 21 N., R. 118 W., 

for example, the lmver 250 feet of the unit is preserved. 

North of U.S. Highway 30N, along the Hams Fork 

Plateau, a few small isolated mounds rest on the Green 

River Formation. The mounds range in thickness from 

a few· feet to slightly more than 100' feet. Greater thicknesses probably are preserved to the south. 

LOWER CONTACT 

The contact between the Bullpen ~fember of the 

"'iV asatch Formation and underlying beds of the Green 

' River Formation is, in most places, both conformable 

and gradational. Limestones below grade upward to 

gray madstone and green mudstone, which are overlain 

by either sandstone or reel mudstone. The base of the 

lowest continuous resistant sandstone or red mudstone 

is easily traceable in the field. In some places an uppermost white limestone of the Green R.iver Formation is 

sharply and directly overlain by clark-red mudstone. 

Regionally, the contact is gradational and crosses 

isochronous surfaces, because at least parts of the lower 

beds of the unit are laterally equivalent to some of the 

upper beds of the Green River Formation. 

TUNP MEMBER 

NAME AND TYPE 

A peripheral lithologic unit of the "'Vasatch Formation in the Fossil basin ranges fron1 conglomeratic 

mudstone to a rubbly breccia. It is here named the Tunp 

Member, for excellent exposures in the Tunp Range. 

No type section is given because of the rubbly and 

poorly stratified nature of the unit and because of 

extreme variability in thickness and composition; but 
WASATCH FORMATION 23 

characteristic exposures are found along Dempsey 

Ridge of the Tunp Range in Tps. 23, 24, and 25 N., R. 

118 W., here designated the type area. 

R OCKS INCLUDED 

The Tunp Member is best described as diamictite 

(Flint and others, 1960; Tracey and others, 1961). It 

consists chiefly of dark-red to medium-red conglomeratic mudstone and blocky breccia in a mudstone matrix 

(figs. 13, 14). Fresh .exposures show an extremely unsorted aggregate of small to large angular fragments, 

poorly romi.ded fragments, 'Yell-rounded pebbles to 

boulders, and blocks of heterogeneous lithology in an 

unsorted red sandy mudstone matrix. In some places, 

the mudstone fills spaces between packed fragments 

and blocks and forms only half the bulk of the material; 

in others, scattered pebbles, boulders, or blocks are dispersed in mudstone. 

The fragments and boulders are locally derived from 

formations that are now exposed short distances a way 

(fig. 13). For this reason, composition varies from outcrop to outcrop; it also varies in a vertical section indicating changes in source of the fragments during the 

co.urse of deposition. In one exposure along Dempsey 

Ridge, NvV1,4SW1,4 sec. 10, T . 24 N., R. 118 W., fragments and blocks were identified as gray quartzitic 

sandstone and sandy limestone of the Wells Formation, 

tan sandy Thaynes Limestone, tan quartzitic Nugget 

Sandstone, Twin Creek Limestone, and Preuss Redbeds. A hundred feet higher in the same section, large 

angular blocks of Ephraim Conglomerate are the chief 

constituent of the unit (fig. 14) . In at least one locality, 

blocks of Ephraim Conglomerate have a maximum 

diameter of 20 feet. 

East of Hams Fork and west of Commissary Ridge, 

i~ a part of the basin _bounded by the Adaville, Frontier, and other formatiOns of Late Cretaceous age, the 

member contains blocks of sandstone derived from these 

formations. Along Boulder Ridge north and south of 

Sage it contains abundant angular fragments and blocks 

chiefly of limestones from upper and lower Paleozoic 

formations now exposed in the Crawford Mountains a 

few miles to the southwest. In plaoes the blocks are very 

large and may be slump or slide blocks of the older 

limestones. One extremely large block of Bighorn DoloFIGURE 13.-Diamictite in the Tunp Member of the Wasatch Formation. Poorly sorted pebbles and blocks of upper Paleozoic 

and Mesozoic rocks in a matrix of maToon to brownish-red mudstone along the ridge east of Pole Creek in sec. 8, T. 26 N .. R~W . 
24 UPPERMOST CRETACEOUS AND TERTIARY STRATIGRAPHY OF FOSSIL BASIN, WYOMING 

FIGURE 14.-Block of Ephraim Conglomerate in diamictite of 

the Tunp Member of the Wasatch Formation in the NE14 

NWJ4 sec. 3, T. 21 N., R. 119 W. 

mite, more than 600 feet long, lies on the ridge in the 

NE% sec. 6, T. 21 N., R. 119 vV., and is surrounded 

by fragments and blocks of other lithology in a conglomeratic matrix containing salmon-colored sandstone 

and mudstone resembling and grading eastward into 

the mudstone of the Bullpen Member. Another much 

larger mass of lower Paleozoic limestone forms Eli Hill 

in the SW. cor. sec. 25, T. 21 N., R. 120 \¥". It is surrounded by Tertiary rocks and can be interpreted as a 

mass of bedrock that slumped onto Tertiary muds at 

the edge of the Fossil basin during deposition of the 

Wasatch Formation. It is therefore possible to interpret 

this hill of Paleozoic rock as a "boulder" within the 

Tunp Member of the \¥" asatch Formation, although on 

the geologic map Rubey, Tracey, and Oriel (1968) have 

accepted the alternate explanation that it is a klippe of 

the Crawford thrust fault, the buried trace of which 

lies in Bear River valley (fig. 2). 

Large boulders scattered in mudstone are present in 

the main body of the \¥"asatch Formation, in the mudEXPLANATION OF FIGURE 15 

A. 'l'unp diamictite (Twt) fills channels cut into Mesozoic rocks 

(Jp, Preuss Redbeds; Jt, Twin Creek Limestone; J"'R n, Nugget 

Sandstone; "'R a, Ankareh Formation; lit, Thaynes Limestone) on Rock Creek Ridge in western part of T. 23 N. , 

R. 118 W . Holocene r ockslides ( Qrs) are associated with the 

fault (hachured line) on the east side of Rock Creek a nd 

dam the ponds along the stream. The Permian Phosphoria 

Formation (Pp) is exposed east of the fault. Stereopair of 

Yertical air photographs (scale about 1: 62,500) is from 

U.S. Army Map Service high-altitude photography AT~121, 

roll 3, negatives 401 and 402. The channels of diamictite 

drained eastward in Eocene time and emptied into Fossil 

Lake along a large apronlike delta that now forms the 

8,468-foot Rock Creek bench-mark point (Sage quadstone tongue of the vVasatch, and in the Bullpen Member not far from the boundary of the Tunp Member. 

The gradation from the Tunp Member into more typical Wasatch lithology takes place in a lateral distance 

of several hundred feet, although in a few places the 

boulders are found half a mile or more basinward and 

in other places the gradation takes place in less than a 

hundred feet. 

DISTRIBUTION AND THICKNESS 

The Tunp Member is exposed in a narrow belt arotmd 

the periphery of the Fossil basin and in channels about 

normal to the belt. 

The Tunp extends along the northwest, north, and 

northeast sides of the Fossil basin as far north as Big 

Park, in theSE% sec. 7, T. 27 N., R. 117 W. The member is especially ''ell exposed along the crest of Dempsey 

Ridge in the Tunp Range overlooking Dempsey Basin 

and in the Cokeville quadrangle on the northeast side 

of Fossil basin, west of Commissary Ridge, between 

Lake Creek and Pole Creek, for example, in the SW% 

sec. 8, T. 25 N., R. 117 \¥". Exposures on both sides of 

the basin are similar in the poor degree of sorting and 

in matrix composition but differ in the composition of 

coarse clasts, which reflects differences in the older rock 

formations exposed nearby. The member is 100-200 feet 

thick in most places, 'but exceeds 500 feet locally. The 

exposed width of the member ranges from a few hundred feet to several miles; in general the Tunp extends 

from the contact with old rocks basin ward to a short 

distance beyond the edges of Green River limestone 

tongues. 

Channels of this member are especially well displayed 

along Rock Creek Ridge. The channels along 'Yhich the 

diamictite was transported are cut into steeply dipping 

mainly Jurassic strata on R;Qck Creek Ridge (fig. 15A) 

in the northern part of the Sage quadrangle and in the 

southern part of the Cokeville quadrangle. Two deltalike deposits of Tunp diamictite extended into the lake 

rangle), in the E"¥2 sec. 21, sees. 22 and 27, T. 23 ., R. 118 

W., on Dempsey Ridge. The fault along Rock Creek 

dt·opped the channel deposits on Rock Creek Ridge at least 

800 feet with r espect to the delta deposits on Dempsey 

Ridge. 

B. Intertonguing of Tunp diamictite (Twt) with limestone bells 

of the Green River Formation on Dempsey Ridge in view 

northward from about the center of sec. 3, T. 2.3 N., R. 116 

W. The limestones include a lower bed (Tgf) that can be 

traced eastward into the Fossil Butte l\lember of the 

Green River, a middle unit (Tga) that is a tongue of the 

Angelo Member, and an upper bed (Is) that lies within the 

Bullpen l\lember of the Wasatch Formation. The Tunp 

grades eastward (out of the photograph) into the main 

body of the Wasatch (Tw), the mudstone tongue (Twm), and 

the Bullpen ~!ember ( Twb). 
WASATCH FORMATION 25 

A 

B 

FIGUJ!E 15.- Geometric relations of Tunp 1\Iember of Wasatch Formation. 
26 UPPERMOST CRETACEOUS AND TERTIARY STRATIGRAPHY OF FOSSIL BASIN, WYOMING 

TABLE 2.-Fossils from the lower member of the Wasatch Formation in the Sage quadrangle, Lincoln County, Wyo. 

T .. 22 N., R. 118 W. T. 21 N., R. 118 W. Location __________________ _ 

Sec. 4 Sec. 9 Sec. 16 Sec. 34 Sec. 3 Sec. 10 Sec. 16 Sec. 18 

Sample ______ --.-- __________ _ 3 4 6 8 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 

T.20N., 

R. 119 W. 

Sec.2 

28 

---------1--------------------------------------------------------------

:b J; ...... C'l 

<0 0 

~ 

I I t- OQ ...... 00 ~ t- ~ 0> .., ~ 

~ ~ C'l 12 0 

1B <0 t- ~ i8 i8 00 .., OQ 

Paleontologic locality ~ 0 <0 C'l ~ 

~ C'l 0 ~ .., ~ 0> ~ <0 M C'l 0 i5 i5 <0 <0 0 <0 i5 0 <0 i5 ~ 0 0> i5 i5 i5 i5 0 <0 numbers _____________ -- ___ C'l C'l C'l ~ C'l C'l ~ ~ C'l C'l ~ 0 ,~ C'l C'l C'l C'l C'l C'l C'l C'l C'l C'l N C'l C'l C'l 

CHAROPHYTAI 

Maedlerlella n. sp ___________________________ --~- ---- ---- ---- ---- ---- ---- ---- ---- ---- ---- X -------- ---- ---- ---- ---- ---- ---- -------- ---- ---- X X 

Harrisichara sp _________________________________ ---- ---- ---- ---- ---- ---- ---- ---- ---- ---- ---- -------- X ---- ---- X ---- ---- -------- ---- ---- ---- ----------

POLLEN AND SPORES 2 

Anemia _____________________ ________ X ____________ ---- ---- ---- ---- ---- ---- ---- ---- ---- ---- -------- ---- ---- ---- ---- ---- ---- -------- ____________ ----------

Alnus, pores 6 ______________________________________________ ---- ---- ---- ---- ---- ---- ---- ---- -------- ---- ---- X X X ____________ ----------

Alnus, pores 4-5 ________________________________________ ---- ---- X ---- ---- ---- ---- ---- ---- -------- ---- ---- X ---- X X X ____________ ----------

• Araucariacidites australis Cookson ______________________________________________ ---- ---- ---- ---- ---- ---- ____ ---- ---- -------- ---- ---- ---- ---- X ____ -------- ____________ ----------

Carya _______________________ --"- ____ X ________ ---- ____ ---- ---- X ---- ---~ X ---- ---- ---- -------- ---- ---- X ---- X X X ---- ________ ----------

Cedrella type _______________________________ -~-- ____________ -------------------- ________ -------------------- X ____ ---- X -------- ____________ ----------

Eucommia __________________ ____________________________________ ---- ____ ---- ---- ____________ -------- ________ ---- ____ X ____ -------- ____________ ----------

Fremontia type _____________________________________________ ---- ---- ---- ---- ---- ________ ---- -------- ________ ---- ____ X ____ -------- ____________ ----------

• Gleicheniidites senonicus Ross ______________________________________________________ ---- ---- ---- ---- ---- ____________ -------- ________ ---- ____ ---- ____ X ____________ ----------

Juglans _____________________ ____________________________________ ---- ________ ---- ____________ -------- ________ X ____________ -------- ____________ ----------

*Erdtmanipollis _____________ ____________________________________ ---- ________________________ -------- ____ ____ ____ ____ ____ ____ X ____________ ----------

Platycarya __________________________ X X ____________________ X ________ X ____________ -------- ____ ____ ____ ____ 1 1 ____________ ----------

Pistillipollenites _____________ ________ X ________________________ X ________________________ -------- ________________________ -------- ____________ ----------

Pterocarya __________________ ____________________________________ ---- ________________________ -------- ________________ X X -------- ____________ ----------

Sporites arcifer Thiergart_ ___________________________________ ---- ·---- ____ ---- ---- ____________ -------- ________ ---- ____ X ____ -------- ____________ ----------

Retitricolpites cf. R. 

tYtilgai'is Pierce ____________________________________________________________________________ -------- ____________________ X X ____________ ----------

raxodiurr. type _________________________________________________ ---- ____ ---- X ---- ---- ---- -------- ____ ---- ________ ---- ____ -------- ____________ ----------

TJlmaceae cf. Parasporia ____ ____________ X ____________________ X ________ X ____________ -------- ________ X X X X ____________ ----------

TJlmaceae Ulmus or Zelkova _ ________________________________________ ---~ ____ X ____________ -------- ________ X ____ X X -------- ____________ ----------

OSTRACODES 3 

"Pseudocypris" pagei (Swain) ________________________________________________________________________________ ' __ -------- ________________________ -------- ________ X ----------

Pseudocypris? sp ________________________________________________________________________ X -------- X ________________________________________ ----------

GASTROPODS 4 

Land snails 

Grangerella _________________ ____________________ X ________________________________________ -------- ________________________ -------- ____________ ----------

Discus ______________________________ -~-- ____________________________________ X ____________________________________________ -------- ____________ ----------

Oreoconus n. sp. b __________ X? ____________ X ____ X ____________ ---~ X? ________________________________________________ -------- ____________ ----------

Glypterpes veternus __________ X? ____________________________________ ---~ ____________________ -------- ---- ________ ---- ---- ---- -------- ---- ---- ---- ----------

Fresh-water snails 

Elimia noduli/era (Meek) _______ X? ________________ X X X ____________________________ -------- ________________________ -------- ____________ ----------

Biomphalaria pseudo- . 

ammonius (Schlotheim) __________ ---.- -.--- ____ X? ____ ____ ____ ____ ____ ____ ____ X ________ ----,--- ·---- ________ "--- ________ -------- X X X? ----------

Omalodiscus________________ ____ ____ ____ ____ ____ ____ ____ ____ ____ ____ ____ ____ ____ ____ ____ ____ X· ________________________ -------- ____________ ----------

Physa cf. P. bridgerensis _____ ________________________________________ X? ____ ____ ____ ____ ____ . X? X? X? ________________ -------- X? ________ ----------

P. pleromatis White ________________________________________________________________________ -------- ____________________________________ X X?----------

VERTEBRATES5 

Meniscotherium cf. priscum I 

L~~:~~:~;~~~~~~~~~~~~~~~~~ ~~~~ ~~~~ ~~~~,~~~~ ~~~~ ~~~~ ~~~~ ~~~~ ~~~~ ~~~~ ~~~~ :~~~ ~~:~ :~:~ -~- :~~~ ~~~~~~~~ -X- ~:~~ ~~~~ ~~~: :::: ~:~: ::::~::: ::~: :::~ ~::~ ~~::~::~~: 

t R. A. Peck, 6-12-61, 1-5-62. 2 E. B. Leopold and H. M. Pakiser, 8-25-61, 8-20-62, 8-21-62. 3 R. A. Peck, 1-5-62; Sohn, 4-15-59, 11-3-59, 2-12-64. 

4 D. W. Taylor, 1Q-5-59, 4-11-60, 4-2o-60, 11-6-61. 5 C. L. Gazin, 11-7-61; D. H. Dunkle, Io-8-58. 
WASATCH FORMATION 27 

in which the Green Ri~er Formation was deposited and 

now form several large rounded peaks along the crests 

of Rock Creek and Dempsey Ridges. 

FOSSILS AND AGE 

Although the basal and upper parts of the :formation 

are undated, the early Eocene age of most of the 

Wasatch in the Fossil basin is well established. 

BASAL CONGLOMERATE MEMBER 

Only an indeterminant planorbid fresh-water snail 

(USGS Cenozoic loc. 22035) has been found in the basal 

conglomerate member of the Wasatch Formation. The 

unit is tentatively assigned to the early Eocene, although 

it may be older. 

LOWER MEMBER 

Numerous fossils have been collected from the lower 

member, as shown in table 2; they indicate an early 

Eocene age. Attempts to refine the age assignment 

further, however, have not been entirely successful. 

An earliest Eocene or Gray Bull (Granger, 1914) age 

is suggested by a tooth of M eni:wotherium, although the 

genus has been found in uppermost Paleocene or Clark 

Fork Beds (C. L. Gazin, written commun., Nov. 7, 

1961). The presence of the ostracode "Pseudooypris" 

pagei suggests either a latest Paleocene or earliest 

1. USGS Cenozoic loc. 21995, Lincoln County, Wyo., Sage quadrangle. 

NEJANEJA sec. 4, T. 22 N., R. 118 W., 1,200 ft west, 700ft south 

of NE cor., elevation 7,900 ft. Shells from higher of two lim&-

stones. D. W. Taylor, 1956. 

2. USG'S Cenozoic loc. 22001 (field loc. 315b), a little below 1. 

NEJANE~ sec. 4, T. 22 N., R. 118 W., 1,100 ft west, 900 ft south 

of NE cor., elevation 7,840 ft. 

3. USGS Paleobot. loc. D1685-1 (field loc. 710b), SW~NE~ sec. 4, 

T. 22 N., R. 118 W., 1,400 ft west, 2,100 ft south of NE cor., 

elevation 7,560 ft. Sample is gray clay, faulted against red clay 

of Wasatch Formation (main body). 

4. USGS Paleobot. loc. D1685-2 (field loc. 710c) ; 30 ft north of 3. 

Sample is gray clay faulted against red clay. 

5. USGS Cenozoic Joe. 22627 (field Joe. 712). SE%SE~ sec. 4, T. 22 N., 

R. 118 W., 200 ft west, 500 ft north of SE cor., on top of knob, 

elevation 7,480 ft. 

6. USG'S Cenozoic Joe. 22628 (field loc. 712-B), about 30ft lower than 

sample 5, south side of knoll. 

7. USGS Cenozoic loc. 22049 and 22623 (field loc. 3il3a). SW~SE~ 

sec. 9, T. 22 N., R. 118 W. Top of peak, elevation 7,761 ft. 

Uppermost of three pisolitic limestone beds. 

8. USGS Cenozoic "loc. 22623; same location as sample 7. 

9. USGS Cenozoic Joe. 22624 (field loc. 313dl). 500 ft SE of localities 

22049 and 22623 and 150 ft lower. Middle pisolitic limestone bed. 

10. USGS Paleobot. loc. D1686 (field loc. 340a-61) 'SWJASEJA sec. 9, 

T. 22 N., R. 118 W., 2,750 ft west and 1,000 ft north of SE cor. 

Gray clay from badger hole at top. of saddle, 900 ft north and 

150 ft higher than 11. 

11. USGS Cenozoic loc. 22004 (field loc. 340). Center of north line of 

sec. 16, T. 22 N., R. 118 w., elevation 7,400 ft. Limestone apparently overlying pisolitic beds of samples 9 and 10. 

12. USGS Cenozoic loc. 22632 (field loc. 718). 2,700 ft west and 140 ft 

south of NE cor. sec. 16, T. 22 N., R. 118 W. ; about 300 ft SW 

and 80 ft lowet· than sample 10. 

13. USGS Cenozoic loc. Z2629, USGS Paleobot. loc. D1700 (field loc. 

715). Center NE% sec. 16, T. 22 N., R. 118 W., elevation 7,380 ft. 

·Pisolitic limestone overlying gray clay and gray slabby limestone. 

Eocene age, whereas the charophyte M aedleriella indicates an Eocene age ( R. E. Peck, written commun., 

Jan. 5, 1962). The gastropods, on the other hand, are 

surely of Eocene age; the absence of latest Paleocene 

and earliest Eocene forms similar to those found in the 

Green River Basin suggests thrut the snails may be of 

post-Gray Bull age (D. W. Taylor, written commun., 

Nov. 6, 1961). All rthe pollen samples, except D1687, 

indicate an Eocene age, and four samples (D1685-1, 

D1685-2, D1686, and D1700) are of early Eocene age. 

Sample D1687 could be either Eocene or Paleocene, although a few Cretaceous forms are also present that 

may have been reworked from the nearby Evanston 

Formation exposures (E. B. Leopold, written commun., 

Oct. 20 and 21, 1962). 

MAIN BODY 

The main body of the Wasatch is of early Eocene 

(Gray Bull and Lysite) age in th~ Fossil basin-a determination based on numerous vertebrate collections from 

strata formerly assigned mainly to the !{night Formation by Veatch (Gazin, 1952, p. 9-10; 1959, p. 132-133; 

1962). 

Lowest beds of the main body, just above gray Evanston mudstone in the center of the basin west of Elk 

Mountain, are of earliest Eocene or Gray Bull age, as 

1 indicated by the condylarth H aplomylus speirianus 

14. USGS Cenozoic loc. 22630 (field loc. 716). 100 ft east and 100 ft 

south of center sec. 16, T. 22. N., R. 118 W., elevation 7,550 ft. 

Gray limestone. 

15. USGS Cenozoic loc. 22631 (field loc. 717). NW~NE% sec. 16, 

T. 22 N., R. 118 W., 2,100 ft west and 1,040 ft south of NE cor. 

Coarse-grained salt-and-pepper sandstone. 

16. Field loc. 621, 300 ft north of 14. Slabby gray limestone in red 

clay. 

17. USGS Cenozoic loc. 21996 (field loc. 12h). SW%SE% sec. 34, 

T. 22 N., R. 118 W., ·about 500 ft NE of quarter cor. between 

sec. 34 and sec. 3. 

18. USGS Cenozoic loc. 22047 (field loc. 12). NW%NW%NW% sec. 3, 

T. 21 N., R. 118 W., about 100 ft south of quarter cor. between 

sec. 34 and sec. 3. 

19. USGS Cenozoic loc. 20915 (field loc. 12), same as sample 18. 

20. USGS Paleobot. loc. D1684 (field loc. 704). SW:I4SE% sec. 3, T. 21 

N., R. 118 W., 2,000 .ft west, 400 ft north of SE t:or. sec. 3. Gray 

carbonaceous clay interbedded with coarse-grained brown 

sandstone. 

21. Field loc. 701, SE%SW% sec. 10, T. 21 N., R. 118 W., 3,500 ft 

west, 2,100 ft south of NE cor. Slabby limestone. 

22. USGS Paleobot. loc. D1683-1 (field loc. 701a) 250ft north of 701; 

gray clay in gully. 

23. USGS Paleobot. loc. D1683-2 (field loc. 701a), same as sample 22. 

Lignite interbedded with gray clay. 

24. USGS Paleobot. loc. D1687 (field loc. 703a). SE~SE% sec. 16, 

T. 21 N., R. 118 W. 500 ft west, 1,900 ft north of SE cor. Gray 

silty clay and lignite. 

25. USGS Cenozoic loc. 22033 (field loc. 401). NW%NE% sec. 18, 

T. 21 N., R. 118 W. About 900 ft SE of quarter cor. between 

sec. 7 and sec. 18. 

26. USGS Cenozoic loc. 22625 (field loc. 401d), same as sample 25. 

27. USGS Cenozoic loc. 22626 (field loc. 401e), 100 yd west of sample 

26. Gray limestone. 

28. Field loc. 402, NWJANE% sec. 2, T. 20 N., R. 119 W., 2,150 ft 

west, 500 ft south of NE cor. (south of Sage Quadrangle). 

Brown limestone. 
28 UPPERMOST CRETACEOUS AND TERTIARY STRATIGRAPHY OF FOSSIL BASIN, WYOMING 

(Cope) and associated early Eocene genera ( Gazin, 

1962, p. 13) .. Although these strata are assigned to the 

main body, they probably correlate with beds in the 

unnamed lower member. 

Numerous collections from Fossil Butte (frontispiece), 40-100 feet below the lowest Green River beds, 

and from Knight establish the middle· early Eocene 

(Lysite) age of these strata ( Gazin, 1952, p. 9-10; 1962, 

p. 13-15). Additional collections of Hyracotherium 

vasacciense (Cope) have been made by us from the 

SE~ sec. 5, T. 20 N., R.117 W. (112ft stratigraphically 

above the Evanston Formation), and from the NEl4 

NEl4 sec. 1, T. 20 N., R.118 W. Ooryphodon fragments 

were found at both localities as well as in the following 

other localities: SE14.NE14 sec. 1, T. 22 N., R. 118 W.; 

SE%,NW14 ooc. 22, T. 21 N., R. 118 W.; NE1JJ,NW1t4 

sec. 21, T. 24 N., R.117 W.;·NW~{t,SElA, sec. 3, T. 21 N., 

R. 118 W.; NEl4SEl4 sec. 1, T. 21 N:, R. 118 W.; and 

the center of NW1t4 sec. 32, T. 21 N., R. 117 W. 

SANDSTONE AND MUDSTONE TONGUES 

Only gastropods have been collected from the sandstone tongue of the Wasatch. One collection (USGS 

Cenozoic loc. 21999) from 2 miles south of the Kemmerer quadrangle on a butte east of South Fork of Twin 

Creek consists of the land snail Oreoconus n. sp. b1 

(D. W. Taylor, written commun., Apr. 11, 1960), a 

species found in both lower and higher units of the 

Wasatch. The same form was found in another collection 

(22048) from the SW%,SW% sec. 18, T. 20 N., R. 117 

W. (D. W. Taylor, written commun., Oct. 5, 1959). 

No fossils were found in the mudstone tongue. 

The sandstone and the mudstone tongues are probably 

of early Eocene age; available evidence is inadequate for 

a more precise age assignment. 

BULLPEN MEMBER 

Several collections of mollusks from the Bullpen 

Member include the following forms (D. W. Taylor, 

written commun., Apr. 15 and 20, 1960): 

Locality USGS 

Cenozoic Sec- Town- Ranye Mollusk 

colin. Location in section tion ship (W. (N.) 

22024 NWUNWUSWU------ 22 21 119 Oreoconus n. sp. b?. 

22025 NWUNWUSWU------ 22 21 119 Planorbidae indet. 

22030 SEUSWUSWU------- 21 21 119 Valvata?, Elimia 

nodulijera (Meek)?. 

20913 NWUNEUSEU------ 32 .21 117 Biomphalaria 

pseudoammonius 

(Schlotheim), 

Drepanotrema?, 

Physa. 

21992 NWU------~---------- 13 20 119 Elimia nodulifera 

(Meek) 

The species . are characteristic of those in lower and 

middle Eocene strata in Wyoming and Utah. The member, therefore, may be latest early or middle Eocene in 

age. 

The limestone beds within the Bullpen Member also 

contain bones and scales identified (D. H. Dunkle, written commun., May 8, 1956) as Asineops sp. and Lepisosteus sp., both of which are abundant in Green River 

strata in western Wyoming. 

TUNP ME·MBER 

Correlation of parts of the Tunp Member with lower 

or upper units of the Wasatch Formation is demonstrated in numerous places along Dempsey Ridge and 

especially well in the 81;2 sec. 3 and sec. 10, T. 23 N., R. 

118 W., where three thin tongues of limestone wedge out 

into the Tunp Member (fig. 15B). The two lower limestone tongues are traceable eastward into the Fossil 

Butte and the Angelo Members of the Green River Formation, and the upper limeston~ bed is traceable into 

limestone beds in the Bullpen Member of the W as.:<ttch 

Formation. Thus, the Tunp Member is equivalent in age 

to the whole Wasatch Formation in Fossil basin and is 

likely of early Eocene age, although parts may be slightly younger (table 4). No fossils have been found in the 

Tunp Member. 

ORIGIN 

The complex heterogeneity in composition of rocks assigned to the Wasatch Formation suggests a marked 

range in continental depositional environments. Most 

of the formation is of alluvial origin. At least some of 

the detritus, however, has barely been transported, if at 

all, and seems to be the product of residual weathering. 

Large volumes of detritus moved as mudflows and rockslides rather· than as saltating or suspended particles 

in a stream. Still other detritus may have been transported by streams and deposited within the lake in 

which the Green River Formation was deposited. 

The alluvial origin of much of the Wasatch is shown 

by many exposures of the main body. Extensive bright:ly 

colored bands of mudstone, which were deposited on 

flood plains, are cut by lens-shaped channels now filled 

by well-sorted conglomerate. deposited as well-rounded 

and fairly clean gravel. Exposures are too discontinuous 

in the northern Fossil basin· to permit mapping of these 

ancient stream courses. 

The basal conglomerate member illustrates deposits 

that formed after little or no transport. The rocks consist almost entirely of Nugget detritus now resting on 

the Nugget Sandstone. The conglomerate matrix consists of disaggregated Nugget sand grains. Coarser 

clasts are rounded, but this rounding may reflect spher-
, 

WASATCH FORMATION 29 

oidal weathering in a more humid climate than at present rather than abrasion during transport. 

Around the periphery of the basin, other parts of the 

Wasatch also grade outward from the basin from wellsorted detrital beds through conglomerate to poorly 

sorted sedimentary breccia. At several places, this sedimentary breccia resembles a talus slope formed on an old 

surface of Mesozoic rocks; in a sense the talus represents 

a glimpse of an exhumed Eocene landscape. Interstices 

between the talus blocks are filled with red mud or pink 

sand like that elsewhere in the Wasatch Formation· in ' a few places the ta.lus blocks are cemented by Green 

River limestone, thus preserving an old shoreline of the 

Eocene ] ake. . 

. Gravitational sliding and solifluction were probably 

the chief agents of transport for the Tunp Member 

(Tracey and others, 1961). The lack of sorting and 

rounding, the presence of large blocks scattered in sandy 

mudstone, the absence of bedding, and the steep topographic slopes along which the deposits accumulated 

suggest that gravity predominated over running water. 

The deposits appear to have formed from mudflows and 

slides of both weathered material and fresh blocks of 

older rocks on steep slopes bounding the basin. The intertonguing relation between the Wasatch-Tunp diamictit.e and Green River limestones suggests that at least 

some of the mudflows may have swept into the Eocene 

lake as large deltas. Abundant water acting as a lubricant is likely, and inferred periods of heavy rainfall are 

consistent with the savanna climate commonly interpreted for the region. 

At least some of the strata assigned to the sandstone 

and mudstone tongues of the Wasatch may also have 

been deposited within the lake, possibly as deltas, offshore bars, and blanket bottom deposits but an alluvial . . ' or1g1n can also be inferred from the available data. 

Numerous green mudstone beds suggest possible local 

reducing environments. 

Thin and extensive limestone beds in the Bullpen 

~{ember indicate that the flood plains on which 1nost 

of these strata were deposited were, during brief intervals, flooded by the Eocene lake. Whether these intervals of lake expansion reflect periods of especially 

heavy rainfall or abrupt sinking of the Fossil basin is 

not known. 

The evidence from rock composition and fossils supp~rts a very wet warm temperate to semitropical 

ch~ate (Van Houten, 1961, p. 122) for the region 

dunng Wasatch deposition. Red upland soils formed 

in moderately wooded areas giving way downslope to 

savanna environments (VanHouten, 1964, p. 33) with 

abundant streams and ponds. The paucity of coal indicates that the area was moderately well drained. 

TECTONIC IMPr..ICATIONS 

The presence of considerable relief around the 

periphery of the Fossil basin is amply documented .by 

the great ranges in sorting and O'rain size of Wasatch 

detritus, by the overlap of higher strata over lower 

strata onto older rock formations, and by channeling, 

as well as by observed local facies of Wasatch strata. 

Movement on all the thrust faults exposed north and 

west of the Fossil basin had ceased before Wasatch 

deposition, for the formation unconformably o,verlies 

traces of t~e faults; gross elements of present topography, reflecting structure of the western Wyoming thrust 

belt, had already formed by earliest Eocene time. 

Many of the present topographic features are 

exhumed elements of an early Eocene landscape. Some, 

however, are not. The Tunp Member on Boulder Ridge, 

north and south of Sage, for example, records an apparent reversal of relief. Boulder Ridge is bounded on the 

west now by the wide valley of the Bear River. Yet 

the Tun p Member on the ridge contains enormous 

blocks, as much as 600 feet in maximum diameter of 

Paleozoic carbonate rocks and fragments of Cretac:ous 

rocks. The source of these clasts must have been a 

moderately high and steep ·mountain to the west, which 

was capped by the upper plate of the Crawford thrust 

fault. Post-Wasatch normal faulting likely downdropped this mountain after Tunp deposition; erosion 

alone could not account for the present topography because of the greater resistance of formations above the 

Crawford fault than below it. Data are inadequate to 

date the normal faulting. 

Other localities at which Wasatch detritus now 

stands considerably higher than the source formations 

incl':de Rock Creek Ridge, where blocks of conglomerate 1n the ~unp Member lie on the crest of the ridge, 

1,500 feet higher than present exposures several miles 

to the west of the. Ephraim Conglomerate from which 

t~1ey were derived. The large exposures of Tunp diamictite that form rounded prominences on Dempsey Ridge 

are 800 feet or more h1gher than those on Rock Creek 

Ridge. 

Def~rmation during the Eocene, presumably associated w1th block faulting, is recorded along the east side 

of the Tun p Range where the main body overlies the 

lower unnamed member of the Wasatch with angular 

unconformity. Some block faults of Eocene age have 

also been recognized farther east in the Fort Hill 

quadrangle (Oriel, 1969). The mudflows and ~ockslides 

believed to have formed the diamictite facies may have 

been triggered by earthquakes as well as by heavy 

rainstorms. 

Broad open and gentle folds have been recognized 1 locally in Wasatch strata. Regionally the structure of 
30 UPPERMOST CRETACEOUS AND TERTIARY STRATIGRAPHY OF FOSSIL BASIN, WYOMING 

Wasatch and Green River strata in the Fossil basin is 

a synclinorium to which the name Fossil syncline was 

applied by Veatch (1907, p. 110, pl. 4). Mapping and 

drilling in the Sage, Kemmerer, and adjoining quad-· 

rangles indicate that structures in Tertiary strata do 

not reflect deeper and tighter structures in older rocks; 

rather, they reflect differential compaction and draping 

over buried topography and, in places, primary sedimentary dips. 

GREEN RIVER FORMATION 

NAME AND USAGE 

DEFINITION 

The Green River Formation was named by Hayden 

(1869, p. 90-91) for the sequence 

* • * composed of thinly laminated chalky shales * • *, best 

displayed along Green River. They are evidently of purely freshwater origin, and of middle tertiary age. The layers are nearly 

horizontal, and, as shown in the valley of Green River, present 

a peculiarly banded appearance * * •. One of the marked features of this group is the great amount of combustible or 

petroleum shales * * *. 

Despite widespread usage, the name is still used 

mainly in the original sense for. the light-colored 

laminated calcareous beds between the red-hued beds 

of the underlying Wasatch Formation and the greenhued beds of the overlying Bridger Formation. 

LITHOLOGIC HETEROGENEITY 

The Green River Formation in the Fossil basin is a 

heterogeneous sequence whose unity is principally in 

primary structure and somewhat in color. Its heterogeneity is best expressed by an inventory of rock compositions including: white, buff, and brown aphanitic 

relatively pure to clayey limest.one; white indurated 

ostracode and gastropod coquina; algal limestone; marlstone; light- to dark-gray, green, and brown mudstone 

and claystone; light- to medium-gray and tan siltstone; 

white- and brown-weathering gray sandstone, which 

has claystone and chert fragments in places; oil shale 

and petroliferous madstone and mudstone; silicified 

limestone and chert; volcanic ash and tuff. 

Nevertheless, the sequence constitutes a ma:ppahle 

formation. The light shades of tan, yel1ow, white, green, 

and brow:n contrast markedly, even from a distance, 

with the more vivid shades of reds predominating in 

both 'the underlying and overlying units. Closer examination shows the overwhelming dominance throughout the unit of the thinly laminated structure and 

argillaceous strata mentioned by Hayden in his first 

published description (1869). 

SUBDIVISIONS USED HERE 

The Green River Formation of the Fossil basin is 

here divided into two units: a lower or Fossil Butte 

Member, characterized by tan to buff ledge-forming 

limestone, madstone, and brown oil shale in which are 

the principal fish-bearing beds; and an upper or Angelo 

Member, characterized by white-weathering limestone 

that contains much nodular and slabby chert and by 

grayish -green cia ystone. 

FOSSIL BUTTE MEMBER 

NAME AND TYPE 

The Fossil Butte Member of the Green River Formation is here named for the excellent exposures on the 

south side of Fossil Butte (frontispiece) and along .the 

north and east sides of Fossil Ridge, 10 miles west of 

J{emmerer, where the most extensive fossil fish quarries 

have been worked. The beds near the southeast end of 

the butte, in the SW14NW14 sec. 5, T. 21 N., R. 117 W., 

have been selected as the type section of the member 

(seep. 43-44) .. ROCKS INCLUDED 

The Fossil Butte Member at the type section consists 

of four units, each characterized by several dominant 

rock ty.pes. A basal mudstone unit rubout 45 feet thick 

consists of beds of light-gray fine-grained to very fine 

grained calcareous sandstone, mudstone, and siltstone. 

Above .this unit is a tannish-gray limestone unit about 

75 feet thick, containing light-gray to tan limestone, 

shaly limestone, siltstone, and chocolate-colored paper 

shale capped by. a 6-foot bed of dark-yellowish-brown 

mudstone. This is overlain by a buff shale unit 45 feet 

thick consisting of predominantly buff-weathering laminated limy shale beds, organic paper shale, and thinly 

laminated oil shale, alternating with beds of white to 

buff madstone. Thin ash beds 14 to 2 inches thick are 

scattered throughout. The main bed quarried for fossil 

fish is 10 feet below the top of this unit. The uppermost 

unit, 40 feet thick, is marked by the presence of several 

bands made up of thin beds of rich oil shale that weather 

a cha-racteristic light-grayish white that seems bright 

blue in sm1light. This unit is capped by a ledge-forming 

limestone that weathers orange yellow, speckled by 

rusty spots. Several of the oil shale beds contain scattered to packed small crystals of calcite pseudomorphous after evaporite minerals, and these give the beds 

a coarse sugary texture. 

Ash beds 1-5 mm thick are common, and beds as much 

as 20 mm thick are present in the upper half of the 

member. Some of these beds, near the fish beds, are characteristic enough to be traced over a fairly large part of 

the Fossil basin, but as yet we have not been able to 
GREEN RIVER FORMATION 31 

correlate sequences of ash falls with those in the Fort 

Hill quadrangle in the Green River Basin. 

A tongue of crossbedded sandstone which we assign 

to the Wasatch Formation separates the lower mudstone section of the member from the upper part in 

the south end of the Kemmerer and Sage quadrangles. 

The tongue reaches a maximum thickness of about 50 

feet, and it pinches out to the north and east within 

Fossil Ridge. North and east of the limits of the sandstone tongue, the lower mudstone unit of the Fossil 

Butte Member contains only minor amounts of organic 

shales or laminated limestone beds. In the headwaters 

of Clear Creek, however, in sec. 33, T. 21 N., R. 118 W., 

about 40 feet of laminated carbonaceous shale, including oil shale, and huff laminated limestone with fishbearing beds similar to those in the upper part of the 

Fossil Butte Me;mber lie beneath a 40-foot ledge of the 

sandstone tongue. In the Roy Steele 1 Government well 

! miles to the south-southwest, in the NE·lJ!NE'lJ.iNElJ.t 

sec. 29, T. 20 N., R. 118 W., 323 feet of the Green River 

type of shale was reported in the interval 560-883 feet, 

above mudstone of the Wasatch Formation and below a 

65-foot bed of sandstone that we interpret as the sandstone tongue of the Wasatch. Apparently the lower 

part of the Fossil Butte Member thickens to the south, 

along the trend of the Fossil synclinal axis of Veatch 

(1907), although very little of the lower part of the 

member is exposed south of the l{emmerer and Sage 

quadrangles. · 

Facies changes within the Fossil Butte Member are 

similar to those described for the Green River Formation in other basins. Organic-rich limestones and shales 

near the central, deeper parts of the Fossil basin grade 

laterally through ostracoda] and gastropodal limestones to algal limestones, marking the near-shore 

shallow-water lacustrine deposits of the Green River 

Formation (Bradley, 1926, p. 125-126). 

DISTRIBUTION AND THICKNESS 

The Fossil Butte Member is the most extensive part 

of the Green River Formation in the Fossil basin. This 

member extends farther toward peripheries of the basin 

than other parts of the formation. Thin limestone units 

observed in the southern part of the basin probably 

represent tongues of the Fossil Butte Member that 

extend into detrital rocks shed by the ancient Uinta 

Mountains (Anderman, 1955 ; Lawrence, 1963). 

The Fossil Butte Member is 267 feet thick in the 

valley of the South Fork of Twin Creek 3 miles south 

of the l{emmerer quadrangle. It is 208 feet thick on 

Fossil Butte (frontispiece) near the center of the Fossil 

basin. 

Buff-weathering laminated limestone ledges extend 

northward and northwestward from the center of the 

basin and remain fairly uniform. Interbedded tan, 

brown, and gray claystone and mudstone, however, 

grade through shades of green into red mudstone and 

coarser detrital rocks of the Wasatch Formation. On 

Tunp Range, WW3t of Dempsey Basin and several miles 

north of the Kemmerer and Sage quadrangles, the limestone ledges thin from 50 feet to an edge in red clay of 

the Tunp Memjber of the Wasatch; the horizon of the 

limestone is recognizable even beyond its edge for it is 

marked in the Wasatch Formation by a surface of 

abundant algal logs (fig. 12) , as on the north side. of 

Pink Butte in sec. 28, T. 24 N., R. 117 W., and east of 

Hams Fork along the northern part of the Kemmerer 

quadrangle. 

LOWER CONTACT 

The contact of the Green River Formation and the 

main body of the Wasatch Formation is apparently 

sharp and conformable in most places. Commonly, it is 

marked by a bench or by numerous slump blocks heading at the contact (frontispiece): The slumps result 

from water seeping down through the more permea;ble 

siltstone and sandstone beds of the Green River and 

through block fractures of the jointed shale and limestone of the Green River into the less permeable mudstone of theW asatch. 

In a few places, the contact at the base of the Green 

River is also gradational vertically. Within a :few feet 

red mudstone below the Green River grades upward to 

very calcareous green mudstone, gray madstone, and 

limestone. 

The regional relation between the two units, however, 

is far more complex. Because the two :formations are 

known to grade into one another in part laterally, the 

lower contact of the Green River Formation is not 

isochronous. Moreover, individual limestone beds of the 

Green River Formation overlap the lower unit of the 

Wasatch Formation, and in places, rest directly on 

l\{esozoic and Paleozoic rocks with angular unconformity. The irregularity of this unconformable surface 

indicates a moderate amount of topographic relief 

around the edges of the Fossil basin even during deposition of the Green River Formation. 

ANGELO MEMBER 

NAME AND TY:PE 

Between the mudstone tongue and the Bullpen Member of the Wasatch Formation is a sequence of strata 

here named the Angelo Member of the Green River 

Formation for the excellent exposures high on the 

buttes overlooking the Angelo Ranch along the South 

Fork of Twin Creek, a;bout 2.7 miles south of the Kemmerer quadrangle. Exposures in the type area are on 

these buttes and on spurs of Fossil Ridge, in the south-
32 UPPERMOST CRETACEOUS AND TERTIARY STRATIGRAPHY OF FOSSIL BASIN, WYOMING 

east corner of the Sage quadrangle. A section measured 

in the NW1;4 sec. 1, T. 20 N., R. 118 W., is here designated the type section (see p. 44-45). 

ROCKS INCLUDED 

The Angelo Member consists mainly of white- to 

blue-white-weathering limestone, madstone, and mudstone, but includes siliceous limestone, chert, lightto medium-gray marly mudstone and claystone, and 

some sandstone beds and lenses. In general, very light 

tan to buff limestone is dominant in the northern parts 

of the Sage and Kem.merer quadrangles, whereas the 

member is whiter and more siliceous southward. A few 

thin to moderately thick units of low-grade oil shale 

that weather to brown papery shale are in the central 

part of the Fossil basin. The moderately organic shales 

and limestones and the subaphanitic marly limestones 

within the basin grade laterally through ostracoda! and 

gastropodal limestone to algal limestone near the periphery of the basin, as in the Fossil Butte Mmrrber. 

DISTRIBUTION AND THICKNESS 

The Angelo Member is well represented in the buttes 

and mesas of the Hams Fork Plateau in the central part 

of the Fossil basin, from about the north edges of the 

Sage and Kemmerer quadrangles southward. The southern limits of the member have not been determined. 

Reconnaissance traverses suggest that the member intertongues with conglomerates shed by the Uinta Mountain uplift in the south-central part of the Fossil basin 

as observed by Veatch ( 1907, p. 97) . 

The Angelo Member is about 200 feet thick in the central part of the basin but thins markedly and pinches 

out near the edges of the basin. 

FOSSILS AND AGE 

The Fossil Butte Member contains one of the best 

preserved and most extensive fossil assemblages known 

in North America. Fish,'insects, and leaves abound, and 

even rays, bats, and birds are represented. Yet the precise age of the unit is not known. This reflects partly 

the absence of comparable forms in the standard and 

reference sections used to subdivide the North American continental Tertiary and partly the neglect, until 

very recently, of modern studies of the faunas and 

floras. 

Fossils previously reported from strata here assigned 

to the Fossil Butte Member include several forms of 

fish (Cope, 1877,1878, 1884; Leidy, 1873; Thorpe, 1938; 

Hesse, 1939), a sting ray (Schaeffer and Mangus, 1965), 

bats (Jepsen, 1966), snakes (Schaeffer and Mangus, 

1965), birds (Wetmore, 1933), insects (Scudder, 1890; 

Cockerell, 1920), and plants (Lesquereux, 1883; 

Brown, 1929, 1934), as well as abundant fresh-water 

mollusks, ostracodes, and algal deposits. 

Fragments of similar fossils (fish, birds, insects, 

plants, mollusks, and ostracodes) have been found by 

us in the overlying Angelo Member, but these are far 

less abundant and more poorly preserved than in the 

Fossil Butte Member. 

Mollusks found by us in both members at numerous 

localities include Physa plermnatis White, Elinda? 

nodulifera (Meek), Bellamya paludinaeformis (Hall), 

Oreoconus n. sp. b, and Plesielliptio? (D. W. Taylor, 

written commun., Apr. 11 and 20, 1960). In addition, the 

fresh-water snail Biomphalaria pseudoammornius 

( Schlotheim) was found in several exposures of the Angelo Member. 

Ostracodes found in both members at several localities 

have been identified (I. G. Sohn, written commun., 

Apr. 15, 1959, Feb. 12, 1964) as "Hemicyprinotus" 

watsoensis Swain, ProcypTois TavenTidgensis Swain, 

and Pseudocypris sp. undescribed. 

Despite the abundance of well-preserved fossils, age 

assignments of the Green River Formation have been 

based on mammalian faunas from Wasatch strata that 

intertongue with the formation ( Gazin, 1959, p. 135). 

The absence of diagnostic fossils from the overlying 

Bullpen Member of the Wasatch Formation precludes 

a precise age assignment for the Green River Formation 

in the Fossil basin. Although it commonly has been assigned a late early Eocene age ( Gazin, 1959; McGrew 

and Roehler, 1960; Schaeffer and Mangus, 1965), the 

topmost strata may be younger or older than Lost 

Cabin. 

ORIGIN 

The lacustrine origin of the Green River Formation, 

recognized by Hayden (1869), has been amply demonstrated by the studies of Bradley (1926, 1929a, 1929b, 

1930, 1931, 1948, 1959, 1963, 1964, 1966) in his notable 

contributions to paleolimnology. 

The abundance of varves, organic matter, and oil 

shale and the excellent preservation of abundant fish in 

exposures near the central part of the Fossil basin indicate that the lake in which the strata accumulated, 

named Fossil lake by .Jepsen (1966, p. '1338), was thermally stratified and po~ibly deeper than 100 feet (Bradley, 1930, p. 101-10~; 1963, p. 636). The abundance of 

algal, gastropodal, and ostracoda! limestones, indices 

to shallow-water shore. phases of the lake (Bradley, 

1926), indicates that the shores of Fossil lake were along 

the present margins of the Fossil basin, although the 

lake mav have been connected briefly with the Eocene 

Gosiute lake in the Green River Basin (fig. 16). Eocene 

talus deposits of older rocks cemented by Green River 

limestone preserve· the ancient lake shore at several lo-
FOWKES FORMATION 33 

SALT LAKE o 

CITY 

0 100 

eeker 

N 

1 

200MILES 

FIGURE 16.-Locations of the Eocene lakes (showing maximum 

extent of each) in which the Green River ]!,ormation was deposited. (Modified from Schaeffer and Mangus, 1965.) 

calities. Fluctuations in the lake size are recorded in 

intertongues of Green River beds with Wasatch strata 

around the margin of the basin. The w.asatch tongues 

indicate (a) drops in lake level, (b) mudflows and rockslides into the lake, and (c) several "floods". of detritus 

that may have heen deposited within the lake as deltas 

and bottom sediments. 

Although Green River strata are now more than 1 

mile above sea level, they were likely deposited at elevations of 1,000 feet or less (Bradley, 1930, p. 93-95·; 

1963, p. 633). The climate was humid subtropical to 

tropical (Bradley, 1966) and had a mean annual temperature of about 65°F and a rainfall of about 40 

inches (Bradley, 1930, p. 93-95; 1963, p. 633). The 

paucity of evaporites (Fahey, 1962) indicates that Fossil lake did not undergo as great a saline cycle as did 

nearby lakes Uinta and Gosiute; whether this reflects 

continuous replenishment of the smaller lake by abundant streamflow or the ending of lacustrine deposition 

in the Fossil basin before the onset of a so mew hat drier 

climate is not known. 

TECTONIC IMPLICATIONS 

along the flanks of the basin do not necessarily indicate 

postdepositional compressional deformation. Observed 

structures probably reflect, as in the Wasatch, differential compaction, draping over buried topography and, 

in places, primary dips. The overlap of underlying 

strata by Green River beds, which in places rest directly 

on older rocks, as well as other observed relations along 

the periphery of the basin, indicates that the area 

continued to be one of moderate relief. 

FOWKES FORMATION 

NAME AND USAGE · 

DEFINITION 

The Fowkes Formation was named and defined by 

Veatch (1907, p. 90) as 

a thick series of light-colored beds composed largely of rhyolitic 

ash and containing thin layers of white limestDne. These beds 

are well exposed [2 miles east of Almy] in the valley east of the 

Almy Hills and thence northward to the Narrows [of the Bear 

River]. This formation is named for the Fowkes ranch, about 9 

miles [north] from Evanston, around which these beds are 

well e~posed. 

Veatch (1907, p. 88) defined the Fowkes Formation 

as the middle formation of the Wasatch Group. He 

believed it was underlain by the dominantly reddish 

yellow beds of the Almy Formation and overlain by 

the dominantly reddish yellow ·beds of the Knight 

Formation, all of the Wasatch Group. 

SUBSEQUENT USAGE 

Since Veatch's definition of the Fowkes, the unit has 

been a source of perplexity, if not confusion, to geologists working ·in the region. Almost nowhere has such 

a unit been found to subdivide the Wasatch Formation 

(or Group). For this reason and possibly because of the 

limited areal extent of the unit, the name has not been 

use.d except in brief reviews of Veatch's report. An 

exception was the erroneous use of the name for another 

unit in the northern Wasatch Range (Eardley, 1944). 

SUGGESTED USAGE 

Because of the structural complexity of the Almy area 

along the east side of the Bear River, Veatch failed, in 

his reconnaissance study, to recognize all the faults in 

the vicinity of his type locality. He therefore emerged 

with an erroneous interpretation of the stratigraphic 

The moderate depths at which the varied organic- sequence. 

rich fish-bearing strata near the middle of the Fossil Detailed study of Fowkes exposures farther north and 

basin must have been deposited indicate a continued reconnaissance studies in the type locality have estabdownwarp of this part of the earth's crust. Fossil basin, lished beyond question that rocks assigned by Veatch 

formed by latest Cretaceous time, continued to sink to the Fowkes Formation overlie, and are therefore 

through the middle and late early Eocene.. I younger than, rocks assigned by him to both the Almy 

·Gentle folds and moderately steeply dipping strata and the !{night, as well as to the Green River. The 
34 UPPERMOST CRETACEOUS AND TERTIARY STRATIGRAPHY OF FOSSIL BASIN, WYOMING 

Fowkes Formation is, in fact, the youngest formation 

of unquestioned Tertiary age (Tracey and Oriel, 1959, 

p.130) mapped by usin the region. 

The name Fowkes is retained, despite Veatch's erroneous interpretation of the po~ition of the formation 

in the section, because th·~ rocks assigned to the formation constitute a rock-stratigraphic unit easily distinguished from others on the basis of lithologic 

characteristics. 

SUBDIVISIONS USED HERE 

The Fowkes Formation is here divided into three 

new members : the Sillem Member at the base, consisting 

of pale-gray and pinkish-gray mudstone and gray 

conglomerate; the Bulldog Hollow Member in the middie, consisting of green tuffaceous mudstone and sandstone; and the Gooseberry Member at the top, consisting 

of light-gray to white calcareous and tuffaceous 

puddingstone. 

SILLEM MEMBER 

NAME AND TYPE 

Directly above the Bullpen Member of the Wasatch 

Formation is a distinctive rock unit that was not 

mapped consistently by Veatch (1907, pl. 3) in the few 

places in which it is exposed. Some exposures were 

assigned to the Fowkes Forp1ation, others to the Almy, 

and still others to Quaternary units: The composition 

of the rocks differs from that of the typical Fowkes. 

However, because we have studied the unit only locally, 

because the upper part of the unit grades upward into 

typical Fowkes strata, and because Veatch included 

the unit, in at least a few places, in his Fowkes Formation (as in the NE14, sec. 8, T. 17 N., R. 120 W.), it is 

assigned here to the Fowkes Formation. 

The unit is here named the Sillem Member of the 

Fowkes for the best exposures seen on Sillem Ridge 

and in the badlands 1-2 miles north -northeast of Sage, 

here designated the type area. The type section was 

measured north of Sage, from about the center of sec. 5, 

T. 21 N., R. 119 W., to about the center of sec. 33, T. 22 

N., R. 119 W. (seep. 46). 

ROCKS INCLUDED 

The Sillem Member consists of a basal conglomeratic 

unit and an upper pale mudstone uriit. The conglomerate 

is absent from some sections examined by us, and in a 

few others its lithologic distinctiveness is equivocal. 

The most extensive, though rather poor, exposures of 

the unit are along butte and ridge tops, as on the crest 

of Sillem Ridge, where the concentration of pebbles 

probably is exaggerated by the ablation of finer 

particles. 

The basal conglomeratic unit includes conglomerate, 

sandstone, mudstone, and claystone. The conglomerate 

consists dominantly of very well rounded pebbles and 

boulders, some of which exceed 1 foot in diameter 

although most are less than 8 inches. The composition 

of the pebbles is distinctive and differs from that of 

the conglomerates in underlying and overlying formations. In the Sillem, they are largely medium- to darkgray, in part black-flecked conglomeratic quartzite, 

dark-colored chert, and dark-colored Paleozoic limestone, at least some of which was derived from the 

Madison Limestone. The source of the conglomeratic 

quartzite may be the Brigham Quartzite in southeastern 

Idaho. Sandstone in the unit ranges from crossbedded 

coarse- to medium-grained very calcareous light-gray 

"salt-and-pepper" (dark-gray and black chert is the 

"pepper") beds to very poorly indurated muddy paletan, pink, and light-gray beds that may contain some 

volcanic ash. The mudstone and claystone is also pale 

pink, tan, and gray. 

The upper unit of the Sillem Member consists dominantly of mudstone and claystone that grade from very 

pale pink, yellow, and gray in the lower part through 

predominantly pale gray in the middle to pale green 

and gray in the· upper part. Green and purple mottling 

and thin bands are common, as are reworked chips of 

volcanic ash. The upper part of the unit includes some 

coarser volcanic debris comparable to that in the overlying unit, such as scattered biotite flakes, magnetite, 

amphibole laths, glass, and secondary silica in the form 

of opal. Interbedded with the mudstone and claystone 

are thin beds of madstone, ostracoda! and algal limestone, and pale-gray to greenish-gray and brown sandstone, containing lentils of chert conglomerate locally. 

Beds of poorly indurated pale-pinkish-tan sandstone 

with angular pebbles and chips of white to very light 

gray ash are abundant. The lower part of the middle 

unit also includes scattered lentils, at different stratigraphic horizons, of conglomerate comparable in pebble 

composition to the basal conglomeratic unit. 

DISTRIBUTION AND THICKNESS 

The Sillem Member is 100-400 feet thick in the Sage 

quadrangle. Remnants of the member have been observed, but not measured, at many other localities. The 

unit is exposed along the east side of Boulder Ridge in 

a south-southeastward-trending belt and on Sillem 

Ridge. The member is also present west of the Bear 

River, along the east side of the Bear Lake Plateau, 

and it has been recognized near the mouth of Acock 

Canyon, about 14 miles north of Evanston. The exposure 

at Acock Canyon is only a few hundred feet thick. 
FOWKES FORMATION 35 

LOWER CONTACT 

The basal contact of the Fowkes Formation is not 

well exposed in most of the formation's area of distribution. It is moderately well exposed at four localities 

where the position of the Fowkes Formation on beds 

within the Bullpen Member of the Wasatch Formation 

can be dmnonstrated. These localities include the northeastern part of sec. 5, T. 21 N., R. 119 W.; the central 

part of sec. 22, T. 21 N., R. 119 W.; sec. 19, T. 21 N., 

R. 119 W.; and the northeastern part of sec. 8, T. 17 N., 

R.120W. 

At all these -localities, the basal beds of the Fowkes 

Formation seem to rest conformably on Bullpen strata. 

The contact, however, may be a disconformity and the 

stratigraphic range of beds directly beneath the contact 

may be considerable for the region. 

The co11tact between the Fowkes and Almy Formations as mapped by Veatch ( 1907, pl. 3) was examined 

by us in several reconnaissance traverses along the belt 

on the east side of the type Almy exposures. Because 

Veatch's implied conformable stratigraphic contact 

truncates individual beds on both sides of it, we tentatively interpret the contact as a fault. 

BULLDOG HOL·LOW MEMBER 

NAME AND TYPE 

The middle part of the Fowkes Formation, here 

named the Bulldog Hollow Member for extensive exposures along Bulldog Hollow, includes most of the 

rocks assigned to the Fowkes hy-Veatch (1907, pl. 3) 

and most exposures in the formation's type locality. It 

is the most extensively exposed and probably thickest 

part of the formation. 

The section here designated (with some misgivings) 

as the type section for the Bulldog Hollow Member is 

that measured in the western part of sec. 33, T. 22 N ., 

R. 119 W. (see p. 46). The member is thinner and more 

poorly formed and exposed in this section than at many 

other localities ·along Bulldog Hollow, south of Sage, 

and along the east side of the Crawford Mountains; 

however, the member has both a base and a top in the 

selected unfaulted section, whereas structural relations 

have not been determined farther south. 

ROCKS INCLUDED 

The membel." is dominantly pale- to dark-green, bluegreen, and white tuffaceous and ashy mudstone and 

green to buff and :brown tuffaceous calcareous sandstone. These rocks contain amphibole laths, biotite plates 

with well-preserved crystal faces, minute feldspar 

crystals, quartz, and glass. Both tuff and ash are of 

rhyolitic composition. Disaggregation of the poorly to 

1noderately indurated sandstone facilitates the testing 

of the grains with a magnet. All samples examined in 

this unit contain at least some magnetite; a few contain 

5, possibly as much as 10, percent, in sharp contrast to 

all underlying formations which contain virtually no 

magnetite. In addition, the matrix of some sandstone 

beds weathers to a distinctive blue efHorescence; the 

composition of the matrix was not determined. In a few 

places, tuffaceous sandstone contains an opaline cement. 

The Bulldog Hollow Member -also contains some lenses 

of light-gray calcareous conglomerate similar to that 

in the overlying Gooseberry Member. 

DISTRIBUTION AND THICKNESS 

The Bulldog Hollow Member is more extensively 

exposed than the other two members of the Fowkes 

Formation. It has been mapped in a south-southwestward -trending belt from the west-central part of the 

Sage quadrangle to its southern edge. It has also been 

recognized in discontinuous belts along the east side 

of the Bear River almost as far south as Evanston. Almost all the exposures mapped as Fowkes by Veatch 

(1907, pl. 3) are assigned to the Bulldog Hollow Member; the exposures on the west side of the Bear River, 

west of the old Almy settlement, however, are here assigned to the Green River Formation. 

The member is only 200 feet thick north of Sage but 

thickens greatly southward. It may be as much as several thousand feet thick (Veatch, 1907, table opposite 

}J. 50) south of the Sage quadrangle. 

LOWER CONTACT 

The base of the Bulldog Hollow Member is apparently gradational downward into the underlying Sillem 

1\iember. The proportions of volcanic tuff and ash in 

sandstone and mudstone decrease downward, and the 

greens and whites of the Bulldog Hollow Member grade 

to pale gray and very pale greenish gray. The base of 

the Bulldog Hollow Member is placed at the base of the 

lowest moderately tuffaceous sandstone that contains 

observable biotite, amphibole, and magnetite grains. 

GOOSEBERRY MEMBER 

NAME AND TYPE 

The uppermost part of strata provisionally included 

in the Fowkes Formation is a puddingstone 4 here 

named the Gooseberry Member for exposures near 

Gooseberry Springs in the west-central part of the Sage 

'The term "puddingstone" is used here for conglomerate that differs 

from all others in the Fossil basin sequence. The rock consists of 

very well rt;mnded and spherical pebbles and cobbles so sparsely packed 

in a matrix of white ashy marl that very few are in contact with one 

another. Pebbles and cobbles in all the other conglomerates, in contrast, are tightly packed and have numerous points of contact. 

Diamictite differs from· puddingstone in the extreme angularity and 

lack Qf size sorting of coarse clasts. 
36 HPPERMOST CRETACEOUS AND TERTIARY STRATIGRAPHY OF FOSSIL BASIN, WYOMING 

quadrangle. The unit is tentatively retained in the 

Fowkes Formation because the underlying Bulldog 

Hollow Member contains lenses of somewhat similar 

conglomerate. However, it is possible that the Gooseberry puddingstone is an easternmost remnant of the 

Salt Lake Formation. 

The type aren, of the Gooseberry is the conglomerrute 

ledge exposures rubout 2 miles northeast of Sage. The 

section here designated the type section is that measured 

in the Nlh sec. 33, T. 22 N., R. 119 W. (seep. 45), although the section is incomplete. 

ROCKS INCLUDED 

The Gooseberry Member consists of light-gray to 

white puddingstone, calcareous rhyolitic ash, and tuff 

and ash bearing very finely crystalline to subaphanitic 

limestone. 

The puddingstone consists of sparsely to moderately 

tightly packed cobbles and pebbles in a matrix of white 

to pale-buff silty and tuffaceous highly calcareous sandstone, madstone, and sandy limestone. Most clasts are 6 

inches or less in diameter, but a few are as much as 1 

foot. Packing of the well-rmmded to subangular coarse 

clasts in most beds.is so poor that few cobbles are in contact with others; most beds, therefore, are puddingstone. The cobbles and pebbles are mainly of quartzite, 

chert, and limestone from Paleozoic formations hut are 

also volcanic rocks of unknown derivation that range in 

composition from rhyolite to vesicular basalt. The presence of volcanic pebbles, the poor packing, and the 

white to light-buff calcareous matrix distinguish this 

conglomerate from those in all other stratigraphic units. 

DISTRIBUTION AND THICKNESS 

The extent of the Gooseberry Member as mapped by 

Rubey, Tracey, and Oriel (1968) is confined to the 

area northeast of Sage that was mapped as the Almy 

Formation by Veatch (1907, pl. 3). Rocks of similar 

composition, however, have been observed at m-any localities to the west on ;the Bear Lake Plateau. (fig. 1). 

Somewhat similar rocks have been noted southward at 

some localities mapped as Fowkes by Veatch (1907, 

pl. 3), but whether they are exposures of the Gooseberry 

or simply conglomerate lenses in the Bulldog Hollo~ 

Member has not been ascertained. 

·The member, though incompletely represented (it 

has no stratigraphic top), is about 200 feet thick in the 

Sage quadrangle. 

LOWER CONTACT 

The nature of the base of the Gooseberry Member has 

not been ascertained. Where examined looally, the upper 

part of the underlying Bulldog Hollow Member apparently grades into the Gooseberry. Moreover, the presence in the Bulldog Hollow Member of Gooseberry-like 

conglom.erate lentils also suggests ·a gradational contact. 

However, a moderwtely great range in thicknesses of 

the Bulldog I-Iollow Member suggests that the base of 

the Gooseberry may be an angular unconformity. Regional dips of the members of the Fowkes Formation 

(the Bulldog I-Iollow Member south of Sa.ge, dips 

m~ainly south, whereas the Gooseberry exposures north 

of Sage dip gently northward) also make an angular 

unconformity likely. 

FOSSILS AND AGE 

The Fowkes Formation in the Fossil basin is of Eocene and possible early Oligocene age. The uppermost 

part, however,may be as young as Pliocene. 

Only ostracodes and gastropods have been found in 

the Sillem Member. Ostracodes were collected in the 

NE*NW*NE* sec. 5, T. 21 N., R. 119 W. (Tertiary 

loc. 21741), and in the NW* sec. 4, T. 21 N., R. 119 W. 

(Tertiary loc. 21704), and were identified as "Hemicyprinotus" watsoensis Swain, Procyprois ravenridgensi:r 

Swain, and Pseudocypris~ sp. undescribed (I. G. Sohn, 

written commun., Apr. 15, 1959, Feb. 12, 1964) ; these 

fossils indicate only an Eocene age. The gastropods, 

though too poorly preserved to be useful for age deter·· 

minations, included three forms of fresh-water snail~; 

and were collected from USGS Cenozoic localities 22621 

and 22622 in sec. 12, T. 24 N., R. 120 W.; the first is 650 

feet west and 550 feet south of the northeast corner 

of the seotion, and the second is 2,000 feet west and 1,000 

feet south of the northeast corner. 

On the basis of fossils and stratigraphic position, 

the age of the Sillem Mem,ber is more probably middle 

than late Eocene. 

Both gastropods ·and leaves have been collected from 

the Bulldog HoUow Member. The gastropods have been 

identified as Biomrphalaria pseudoammonius ( Schlotheim) and Oreoconus planispira Taylor (McKenna) 

and have been assigned ·a late middle to late Eocene age 

(D. W. Taylor, written commun., May 29, 1957; McKenna and others, 1962) . The collections were made at the 

following localities : 

USGS Cenozoic loc. 20082, 300 ft E., 1,900-2,400 ft N. of 

SW cor. sec. 20, T. 21 N., R. 119 

w. 

20083, 250 ft W., 600 ft N. of SE 

cor. sec. 19, T. 21 N., R. 119 W. 

20084, NWX sec. 16, T. 20 N., R. 119 

w. 

20146, north side, Fowkes Canyon, 

sec. 33, T. 17 N., R. 120 W. 

22198, NE}~NE%NEX sec. 29, T. 16 

N., R. 120 W. 

The leaves were collected near the top of the Bulldog 

Hollow Member in sec. 4, T. 21 N., R.. 119 W., and were 
FOWKES FORMATION 37 

identified as E quisetwm sp. 31nd Lygodiwm k(JIUlfussi 

Heer, to which an Eocene age is assigned (R. W. Brown, 

wri,tten commun., Sept. 23, 1958). The age of the member, therefore, is middle or late Eocene. 

The radiogenic age of the hornblende in a sample of 

the Bulldog Hollow Member has been determined, by 

means of the potassium-argon method, by Richard Lee 

Armstrong (written commun., Mar. 5, 1967) of the 

!{line Geology Laboratory at Yale University. The sample was collected in the SE%NE1)J,SE% sec.19, T. 21 N., 

R. 119 W. The following data were furnished by 

Armstrong : 

Percent 

K: 0.72, 0.72 

Ar: 1.39X IQ-6 cc radiogenic Ar•o 

70 percent air Ar in analyzed sample 

Constants used: KXtJ=4.72X IQ-toyr-t 

KXe=0.584X IQ-toyr 

K40/K=0.0119 atm (atmosphere) percent 

Date: 47.7 m.y. (million years) ±1.5 m.y., or middle Eocene 

(Evernden and others, 1964, p.165, 189) 

The result probably should be considered a maximum possible 

age because of possible contramination ·by older material, although such contamination seems unlikely in this sample. 

Although the Bulldog Hollow Member may be as 

young as late Eocene, it probably i~ of middle Eocene 

age. 

Fossils have not been found in the Gooseberry Member within the Sage quadrangle. Reconnaissance west 

of the quadrangle in the Bear Lake Plateau, however, 

resulted in a collection of some fossil bones west of Pegram Creek in the NE%NE'% sec. 29, T. 15 S., R. 45 E., 

in Idaho, from puddingstone similar to that in the 

Gooseberry, despite the previous assignment of these 

rocks to theW asatch Formation (Mansfield, 1927, pl. 9). 

The bone fragments included Leporidae teeth identified 

(Mary Dawson, written commun., Mar. 31, 1967) as 

probable llypolagus of possibly late Miocene or early 

Pliocene age. This fossil from strata that can be assigned only with uncertainty to the Gooseberry and the 

inferred angular unconformity at the base of the member in the Sage quadrangle suggest that the Gooseberry 

may be considerably younger than the Sillem and Bulldog Hollow Members of the Fowkes Formation. Perhaps Gooseberry strata should be assigned to the Salt 

Lake rather than to the Fowkes Formation or established as ·a new formation. Tentative assignment here 

of the Gooseberry Member to the Fowkes Formation is 

based on the close association areally of the Gooseberry 

with other members of the Fowkes and on the similarities in composition of the conglomerates in both the 

Bulldog Hollow and the Gooseberry Members. 

The apparent disparity in ages for members of the 

Fowkes, suggested by the tenuous available data, closely parallels that determined for the Salt Lake Formation in its type locality in northern Utah. A lower tuff 

unit there, which closely resembles the Bulldog Hollow 

Member in composition (Eardley, 1959, p. 167), is also 

considera:bly older than other Salt Lake strata. This tuff 

unit, named the Norwood Tuff and assigned an early 

Oligocene age by Eardley (1944), contains vertebrates 

which, when reexamined, were assigned (C. L. Gazin, 

written commun., Nov. 9, 1959) a late Eocene ·age. The 

overlying Salt Lake strata, in contrast, are assigned 

a Pliocene and possibly a late Miocene 'age. Geologists 

working in the region have found the contact between 

the two formations extremely difficult to map because of 

similarity in composition. 

ORIGIN 

The Fowkes Formation probably was deposited mainly as alluvium but also in small lakes and ponds during a time of increasing volcanic activity in the region. 

Heterogeneity of detrital fragments, moderately good 

size sorting and rounding of coarse clasts, and sedimentary structural features suggest that the bulk of the 

material was deposited in fresh water. The poorly sorted 

puddingstone in the Gooseberry Member may have been 

deposited as a mudflow. Some interbedded ash layers in 

the formation may have been deposited subaerially. The 

source and direction of transport of the great volume of 

volcanic debris are not known. 

TECTONIC IMPLICATIONS 

The Fowkes Formation is limited in distribution to 

a belt along the western part of the Fossil basin 

(Veatch, 1907, pl. 3). Although deposition of the unit 

may possibly have been confined to a downwarp or 

trough formed within the Fossil basin in middle or late 

Eocene time, the evidence suggests otherwise. Faults 

that cut underlying Tertiary strata also ·cut the Fowkes 

Formation, and gentle folds of both are concordant. 

The present distribution, therefore, seems to reflect postdepositional normal faulting that dropped Fowkes 

strata, thereby preserving them. Strata that formerly 

were more extensive and that remained elevated were 

no doubt removed by erosion. This erosion probably 

also accounts for extensive lag concentrates of pebbles 

and cobbles that were assigned a . Quaternary age by 

Veatch (1907, pl. 3), both north and south of Sage. 

The relations of the units assigned here to the Fowkes 

to those rna pped farther west, such as Norwood Tuff 'and 
38 UPPERMOST CRETACEOUS AND TERTIARY STRATIGRAPHY OF FOSSIL BASIN, WYOMING 

Salt Lake Formation, are too imperfectly known to 

permit detailed tectonic reconstructions. In general, 

however, deposition o£ these units seems to have reflected 

basin-and-range :faulting, particularly farther west, and 

extensive volcanism. 

The composition of the Sillem Member in exposures 

both west and east of Boulder Ridge suggests that the 

mountain of Paleozoic and Cretaceous formations (p. 

28) that supplied detritus for the Tunp Member of the 

Wasatch was downfaulted by middle to late Eocene 

time. 

SOME REGIONAL RELATiONS 

The precise relations of the Fossil basin rock units 

to comparable units in adjoining areas remain somewhat enigmatic. Most of the units cannot be traced 

continuously from this basin to others. Although almost 

all the units seem to have lithologic counterparts in 

the stratigraphic sequences of nearby areas (table 3) , 

current age assignments deny or make questionable precise temporal equivalence. The age assignme}\ts, however, are not unequivocal, for they are based il1 large 

part on different fossil forms in the different areas. 

TABLE 3.-Dominant rock types and sequences of Upper Cretaceous and Tertiary stratigraphic units in the Fossil basin and adjoining areas 

[Most of the units are not temporal equivalents] 

Dominant rock types Northeastern Utah, Echo Canyon area Fossil basin, northern part Green River Basin, Fort Hill area 

Light-gray and bufi tufiaceous conglomerate. Salt Lake Formation. Gooseberry Member of Fowkes Formation. 

White to green tufiaceous and ashy sandstone, Norwood Tuff of Eardley (1944). Bulldog Hollow and Sillem Members Bridger Formation. 

mudstone. of Fowkes Formation. 

Unconformity 

Red and salmon mudstone and gray and brown Bullpen Member of Wasatch Formasandstone, thin bufi limestone. tion. 

Laminated marlstone and limestone, algal lime- Angelo Member of Green River For- Upper tongue of Green River Formastone. mation. tion. 

Gray-green and pink mudstone. Mudstone tongue of Wasatch Forma- Upper tongue of Wasatch Formation. 

tion. 

Laminated organic marlstone, limestone, oil shale, Fossil Butte Member of Green River Middle tongue of Green River Formaash. Formation (upper part). tion. 

Brown sandstone and green mudstone. Sandstone tongue of Wasatch Forma- New Fork Tongue of Wasatch Formation. tion. 

Light-gray and buff laminated limestone and Fossil Butte Member of Green River Fontanelle Tongue of Green River Formarlstone. Formation (lower part). mation. 

Red, purple, a11d tan, banded and variegated Wasatch Formation. Main body of Wasatch Formation. La Barge Member of Wasatch Formamudstone. tion. 

Angular unconformity 

Boulder conglomerate and gray sandstone and Evanston(?) Formation. Evanston Formation. Chappo Hoback(?) 

mudstone. Member of Wasatch Formation. 

Formation. 

Red conglomerate and sandstone. Echo Canyon Conglomerate of Basal part, Chappo Member of Wasatch 

Williams and Madsen (1959). Formation. 

Angular unconformity 

Tan sandstone, gray mudstone, some coal. I Wanship Formation of Eardley (1952) ·I Adaville Formation. Adaville(?) Formation. 

Dark-gray marine mudstone. Hilliard Shale. Hilliard Shale. 

Gray sandstone and mudstone and coal. Frontier Formation. Frontier Formation. Frontier Formation. 
SOME REGIONAL RELATIONS 39 

In general, the Fossil basin units seem to be intermediate in age between somewhat older comparable 

units to the southwest, in northeastern Utah, and younger units to the mist, in the western Green River Basin 

(table 4). There being a progressively younger age, 

from west to east, for analogous rock units in the region 

both is predicted by and supports the conclusion that 

orogeny and thrust faulting in the cordilleran region 

progressed from west to east (Oriel and Armstrong, 

1966, p. 2619). The generalization, however, is by no 

means true for all the units. 

LOWER STRATA OF THE WASATCH 

Progressively younger ages from west to east are 

perhaps best illustrated by strata that have been assigned to the Wasatch Formation beneath the Green 

River Formation. 

The main body of the Wasatch Formation is well 

dated in the Fossil basin. The base of the main body is 

no older .than earliest Eocene (Gray Bull) and the top 

no younger than middle early Eocene (Lysite). Comparable rocks in the Green River Basin, where they are 

assigned to the La Barge Member of the Wasatch 

(Oriel, 1962, p. 2168-2170), are younger. Although 

most of the La Barge Member is late early Eocene 

(Lost Cabin age), the basal part may be as old as 

middle early Eocene (Lysite). 

West of the Fossil basin, strata formerly assigned 

to the Wasatch Formation in part of its extended type 

locality at Echo Canyon, Utah (Hayden, 1869, p. 9'1), 

are now subdivided into several units in northeastern 

Utah (Mullens and Laraway, 1964; Williams and Madsen, 1959). A basal unit of red conglomerate, sandstone, 

and shaly sandstone underlies with angular unconformity other strat•a previously assigned to the Wasatch. 

The red strata beneath the unconformity are now 

assigned to the Echo Canyon Conglomerate; they contain Cretaceous fossils of late ( ~) Niobrara age near the 

base (Williams and Madsen, 1959, p. 123). The Echo 

Canyon Conglomerate is overlain by brown conglomeratic sandstone and gray sandy siltstone assigned to the 

Evanston( n Formation (Mullens and Laraway, 1964). 

These beds are overlain by other mainly brownish red 

beds still assigned to the Wasatch Formation and to 

the Eocene. Thus, the deposition of the Wasatch-like 

strata began earlier (in the Late Cretaceous) in the 

Echo Canyon area than it did in the Fossil basin a-1~ea 

and seems to have continued until well into the Eocene. 

RELATIONS OF LOWER UNITS 

The Evanston Formation, too, has lithologic counterparts both to the east and to the west. Evanston strata 

in the Fossil basin are of latest Cretaceous to l·ate, but 

not latest, Paleocene (Tiffany) age. Similar strata 

assigned to the Evanston ( ~) Formation in the Echo 

Canyon area in Utah (Mullens and La-raway, 1964) 

are probably also of very late Cretaceous age, according to pollen identified by E. B. Leopold (written 

commun. toT. E. Mullens, Mar. 27, 1963). 

Drab-colored, mainly gray to pale-green-gray, 

stra:ta are also extensive to the east, in the ·Green River 

Basin. Extensive exposures in the Hdback area were 

initially assigned to the Evanston Formation (Schultz, 

1914, p. 69, pl. 1) hut are now included in the Hoback 

Formation (Eardley and others, 1944; Dorr, 1952, p. 

64--71). Simila.r strata have been drilled farther south, 

in the La Barge area and southward, where they are 

assigned to the Hoback ( ? ) and are believed to intertongue with the Chappo Member of the Wasatch Formation, which underlies the La Barge l\{ernber with 

angul·ar unconformity (Oriel, 1969). The drab-colored 

Hoback strata in the Green River Basin are, in general, 

somewhat younger than the Evanston in the Fossil 

basin. The Hoback is assigned a middle to late Paleocene and very ~arly Eocene age (Dorr, 1952, p. 68; 1958, 

p. 1229-1232). The Chappo Member of the Wasatch, 

with which the Hoback intertongues, is assigned a latest 

Paleocene (Clarkforkian) 5 and earliest Eocene (Gray 

Bull) •age (Oriel, 1962, p. 2168) . 

RELATIONS OF TONGUES OF THE WASATCH 

AND GREEN RIVER FORMATIONS 

Subdivision of the Green River Formation by two 

Wasatch tongues in the Fossil basin, as in the western 

·part of the Green River Basin, raises the question of 

possible contemporaneity: Although the tongues resemble each other in stratigr31phic position and lithology, availruble fossil evidence indicates that the Fossil 

basin tongues probably are older. 

The sandstone tongue of the Wasatch in the Fossil 

basin is similar in both composition and apparent stratigraphic position to the New Fork Tongue of the 

W rusatch in the Green 'River Basin ( ta:ble 3; Oriel, 

1961). Moreover, the Wasatch mudstone tongue in the 

Fossil basin somewhat resembles the upper tongue in 

the Green River ~asin. The analogous Green River 

Formation units, therefore, are the lower and upper 

parts of the Fossil Butte Member and the Angelo Member in the Fossil basin and the Fontenelle, middle, and 

upper tongues, respectively, in the Green River Basin 

(table 3). 

5 Although the validity of the Clarkforklan as the latest Paleocene 

provincial age has· been questioned (Wood, 1967; D. W. Taylor, written 

commun., 1967), a generally accepted revision of the classlficatlon of 

the North American continental Tertiary is not available. Even If rocks 

previously dated as Clarkforkian prove to be of Gray Bull age, the 

fact that the Chappo and parts of the Hoback are younger than the 

upper part of the Evanston is not invalidated. 
40 

0 

0 

a:: 

L.IJ 

a.. 

>-

0: 

<( 

1-

0: 

UJ 

1-

CJ) 

::J 

0 

UJ 

u 

<( 

1-

UJ 

0: 

u 

:I: 

u 

0 

a.. 

LIJ 

<l> 

c: 

<l> 

(.) 

0 

-~ 

0 

J. 

<l> 

c: 

<l> 

(.) 

0 

LIJ 

<l> 

c: 

<l> 

(.) 

~ c;; 

a.. 

"' ::::0 

0 

i 

u 

~ 

Note: T., Tongue 

UPPERMOST CRETACEOUS AND TERTIARY STRATIGRAPHY OF FOSSIL BASIN, WYOMING 

TABLE 4.-Approa:imate ages of the stratigraphic units in the Fossil basin and adjoining areas 

TERTIARY PROVINCIAL 

AGES (Wood and 

others, 1941); 

CRETACEOUS REFERENCE SEQUENCE 

Chadron ian 

Duchesnean 

Uintan 

Bridgerian 

Lost Cabin 

age 

c: 

"' 

~ Lysite 

~ age 

Gray Bull 

age 

Ch~rkforkian 

Tiffanian· · 

Torrejonian 

Dragon ian 

f'uercan 

Hell 

·Lance Creek 

Formation Formation 

Ma,ntana 

· Group 

Colorado 

Group 

* 

Paleontologic dates are indicated by:l-.:..··, vertebrates;(:, mollusks; 

_,leaves; O, pollen; ,,, , other forms 

NORTHEASTERN 

UTAH 

Echo Canyon area 

Salt Lake Formation 

Wanship Formation of 

Eardley (1952) 

Frontier Formation · · 

·c:so 

* 

* * 

*· 

NORTHERN 

FOSSIL BASIN 

Gooseberry Member of 

Fowkes Formation 

Evanston Formation 

Adaville Formation 

Hilliard Shale 

Frontier Formation 

WESTERN GREEN RIVER BASIN 

Fort Hill area 

Adaville(?) Formation. 

Hilliard Shale 

Frontier Formation 
TYPE SECTIONS FOR MEMBERS DEFINED IN TIDS REPORT 41 

The Fossil basin atid Green River Basin are separated 

by the moderately continuous Oyster Ridge barrier. At 

one locality, however, in the west-central part ofT. 15 

N., R. 118 W., Wasatch strata can apparently he traced 

from one of the basins into the other (Veatch, 1907, pl. 

3). We have noticed a few thin Green River limestones 

in this area. It seems likely that detailed mapping of 

these limestones northward along both sides of the 

Oyster Ridge barrier will determine their positions 

within the estrublished stratigraphic sequences· in the two 

basins. · 

In the Green River ·Basin, the various tongues are 

moderately well daJted. The Fontenelle Tongue is of 

latest early Eocene age, for the underlying La Barge 

Member and overlying New Fork Tongue of the 

Wasatch both contain mammals of Lost Cabin age 

( Gazin, 1952, 1962). Upper strata of the Green River 

intertongue with the Bridger Formation of middle 

Eocene age (Brrudley, 1964). 

In the Fossil basin, the tongues are not •as well dated. 

The presence of Lysite age m•ammals in Wasatch strata 

just a few feet below ·Green River strata suggests that 

the basal part of the Fossil Butte Member may he of 

Lysite or middle early Eocene age. ·Although available 

fossil control does not require it, the topmost Green 

River strata have been regarded as probably older 

tfuan middle Eocene ( Gazin, 1959, fig. 1; Schaeffer and 

Mangus, 1965, p. 12-13). This interpretation is supported by the presence of Wasatch strata above the 

highest Green River beds, although .these Wasatch 

beds are not dated more precisely than as latest early 

or middle Eocene. 

Current interpretations, therefore, though better 

supported by the dating of units below tthe Green River 

than by the dating of those above, suggest that the 

Green River ·tongues in the Fossil basin oa.re somewhat 

older than those in the Green Riv~r Basin. 

FOWKES-NORWOOD-BRIDGER RELATIONS 

The abundance of tuff and ash in strata above the 

Wasatch and Green River Formations in northeastern 

Utah and in the Fossil basin and Green River Basin 

suggests that the tuff and the ash reflect the same period 

of volcanic' aCtivity, in the region. Yet the available 

bases for dating tlu~ several units are both intriguing 

and perplexing. Although the Fowkes Formation, the 

Norwood Tuff, and the Bridger ·Formation may prove 

to be of the same age, the ·likelihood now is that they ·are 

not. The relations of these units are among the least 

understood. 

The Bulldog Hollow Member and underlying Sillem 

Mmnber of the Fowkes in the Fossil basin resemble 

strata assigned to the Norwood Tuff in Utah. Mollusks 

from the Bulldog Hollow Member indicate a middle or 

late Eocene age; leaves, an Eocene age; hornblende, an 

age of 47.7+1.5 m.y. (middle Eocene), from a potassium-argon determination. 

The similar Norwood Tuff contains vertebrates of 

late Eocene age ( Gazin, 1959, p. 137), gastropods of late 

early to middle Eocene age (D. vV. Taylor, written 

commun., toT. E. Mullens, Jan. 16, 1963), biotite of 37.5 

m.y. at the type locality (Evernden and others, 1964, p. 

161, 183), and biotite of 68+8 m.y. and 74+8 m.y. at the 

south end of Cache Valley (Williams, 1964, p. 271; 

Heylmun, 1965, p. 13). · 

The Bridger Formation in the Green River Basin 

differs in appearance and composition from the dominantly rhyolitic Bulldog Hollow Member of the Fowkes. 

It is considerably darker in color, ranging from neutralgray to dark-green and chocolate-brown tuffaceous mudstone and gray to brownish-gray tuffaceous mudstone. 

Moreover, it consists dominantly of andesite tuff, although it also includes rhyolite (Bradley, 1964, p. A49). 

Abundant fossil mammals establish the age of most of 

Bridger· as middle Eocene, although the upper part may 

be younger (Bradley, 1964, p. A48). Biotites have not 

been dated from the Bridger Formation, but some from 

approximately correlative beds elsewhere in Wyoming 

are 45.4-49.0 m.y. old (Evernden and others, 1964, p. 

165). 

Thus, our earlier belief that the Bu1ldog Hollow 

Member of the Fowkes is equivalent to the Norwood 

Tuff and is younger than the Bridger Formation is not 

well supported. Conflicts among the data remain to be 

resolved. 

The probably younger age of tne ·Gooseberry Member 

ofthe Fowkes Formation and the possible equivalence . 

of the Gooseberry to many strata assigned to the Salt 

Lake Formation are discussed on a previous page. The 

range in ages of strata that have been assigned to the 

Salt Lake Formation and other .stratigraphic problems 

are discussed by Heylmun ( 1965). 

TYPE SECTIONS . FOR MEMBERS DEFINED IN THIS 

REPORT 

Evanston Formation at type section for Hams Fork Conglomerate 

Member 

( 

Measured near middle of eastern part of sec. 36, T. 21 N., R. 117 W., 17'2 miles 

northwest of Elkol 

Wasatch Formation (partial) : 

Main body: Ft in 

Mudstone, sandy and silty; mottled red, green, 

light gray, and yellow; partly covered at top 

of hill by blocks of Green River limestone 

float__________________________________ 62 

Sandstone, medium-grained, light-gray; calcareous with salt-and-pepper texture; forms 

dark-brown cross bedded ledge __________ -- 14 
42 UPPERMOST CRETACEOUS AND TERTIARY STRATIGRAPHY OF FOSSIL BASIN, WYOMING 

Evanston Formation at type section for Hams Fork Conglomerate 

Member-Continued 

Wasatch Formation (partial)-Continued 

Main body-Continued 

Sandstone, medium- to fine-grained, clayey, Ft in 

yellow; forms yellow slope_______________ 16 

Angular unconformity. 

Partial thickness, Wasatch Formation___ 92 

Evanston Formation: 

Main body: 

Claystone, slightly to moderately silty, 

light-gray to pale-pinkish-gray; yellow 

stains along fractures____________________ 15 

Sandstone, fine- to medium-grained, very calcareous, dark-brown to very dark gray; 

forms ledge----------------------:------ 1 6 

Claystone, light-gray ____________________ ·__ 9 

Claystone, slightly silty, dark-gray__________ 5 

Claystone, silty, light-gray_________________ 3 

Siltstone, light-pinkish-gray________________ 20 

Sandy siltstone and silty very fine grained to 

fine-grained sandstone; light gray with 

random yellow streaks___________________ 3 

Sandstone, clayey, fine-grained to very fine 

grained, yellow; interbedded with mottled 

light-gray, pinkish-gray, and yellow siltstone__________________________________ 6 

Claystone, medium- to dark-gray and partly 

silty; grading downward to light-gray 

siltstone_______________________________ 10 

Sandstone, fine- to medium-grained, lightgray salt-and-pepper; very thinly cross 

laminated · with abundant carbonaceous 

streaks in some cross laminae_____________ 3 6 

Siltstone, light-gray to pinkish-gray; yellow 

to orange mottling and bright-orange 

laminae of clayey siltstone_______________ 15 

Claystone and silty and clayey siltstone, lightgraY---------------------------------- 10 

Sandstone, mainly fine to very fine grained; 

contains some medium sand grains and 

silt; noncalcareous, carbonaceous; fossil 

leaves, limonite concretions, and yellow staining_ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ 2 6 

Claystone, medium-gray; grades downward 

to light-gray siltstone___________________ 18 

Sandstone, fine-grained, silty, noncalcareous, 

light-gray; weathers to light gray and 

yellow with dark-red-brown ferruginous 

layers; contains some limonite nodules____ 3 

Claystone, slightly silty in part, medium- to 

light-gray______________________________ 13 

Siltstone, somewhat clayey, light-gray; yellow 

splotches______________________________ 10 

Mudstone, light-gray; yellow and yellowbrown mottling ________ -----------______ 8 

Evanston Formation at type section for Hams Fork Conglomerate 

Member-Continued 

Evanston Formation-Continued 

Main body-Continued 

Sandstone, fine-grained, very calcareous, salt- Ft in 

and-pepper; light gray but weathers to 

mottled brown, yellow, dark gray and 

purplish gray___________________________ 1 

Siltstone and slightly to very silty claystone, 

light- to medium-gray; yellow and yellowbrown mottling; forms small badland______ 40 

Siltstone to very fine grained sandstone with 

scattered medium sand grains, noncalcareous, salt-and-pepper, light-gray; some yellow along bedding and joints_____________ 5 

Siltstone, poorly indurated, pinkish-gray; 

yellow and yellow-brown splotches; grades 

downward to slightly silty light- to mediumgray claystone____ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ 8 

Lignite, very thinly laminated to papery_____ 2 

Conglomerate, containing well-rounded clasts 

as much as 8 in. in diameter; mainly lightgray quartzite; some black to gray chert 

and pink conp;lomeratic quartzite_________ 5 

Siltstone, quartzitic, light-gray; contains scattered 

dark-gray chert grains _____________ _:_________ 4 

Interbedded yellow-brown siltstone and light-gray 

mudstone; yellow and brown mottling _________ 14 

Interbedded light- to medium-gray, yellow-weathering claystone and pinkish-gray clayey siltstone; laminae of red-mottled dark-gray and 

dark-brown silty claystone___________________ 8 

Claystone, black, very slightly to moderately silty; 

weathers light to medium gray_______________ U5 

Thickness, main body of Evanston __________ 257 

Hams Fork Conglomerate Member: 

Sandstone, poorly sorted, medium-grained to 

very fine grained; thin layers of coarsegrained to conglomeratic sandstone; very 

light gray; weathers to yellow orange; forms 

prominent ledge________________________ 13 

Sandstone, fine- to medium-grained; some 

gritty beds and highly carbonaceous to lignitic laminae near middle; poorly indurated; 

greenish gray___________________________ 15 

Claystone, medium-gray; tan-weathering 

streaks and layers of light-gray siltstone___ 15 

Claystone, slightly silty, black ______________ 8 

Interbedded light-gray mudstone, tan siltstone, and light-gray to brown fine-grained 

to very fine grained sandstone, partly covered ________________________________ 26 

Ironstone, dark-chocolate to reddish-brown; 

weathers to purple ________________ --_--_ 

Claystone, medium- to dark-gray___________ 1 

6 

6 
TYPE SECTIONS FOR MEMBERS DEFINED IN TIDS REPORT 43 

Evanston Formation at type section for Hams Fork Conglomerate 

Member-Continued 

Evanston Formation-Continued 

Hams Fork Conglomerate Member-Continued 

Sandstone, very fine grained, buff to gray; Ft in 

weathers yellow to tan; very calcareous and 

thinly cross bedded______________________ 4 

Interbedded v0ry dark gray claystone, brown 

slightly silty claystone, and tan to gray siltstone__________________________________ 40 

Covered, probably claystone and siltstone as above_________________________________ 85 

Sandstone, fine- to medium-grained; crossbedded with abundant conglomeratic cross 

laminae; most well-rounded clasts are less 

than 1 in. in diameter but a few are larger_ 30 

Interbedded fine-grained sandstone and 

conglomerate with well-rounded quartzite 

and chert pebbles as much as 3 in. in diameter in matrix of medium- to coarse-grained 

sandstone______________________________ 5 

Sandstone, medium- to fine-grained, light-gray 

salt-and-pepper; lenses of coarse-grained to 

gritty sandstone; thinly laminated and cross 

laminated______________________________ 35 

Covered, probably fine-grained to very fine 

grained sandstone_______________________ 4 

Sandstone, poorly sorted, coarse- to finegrained, crossbedded; weathers olive light 

brown with abundant irregularly shaped 

calcareous nodular light-gray sandstone___ 6 

Covered_________________________________ 6 

Sandstone, moderately well sorted, mediumgrained, salt-and-pepper, crossbedded, yellow to yellow-brown_____________________ 5 

Covered, probably tan to light-brown finegrained sandstone_____ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ 5 

Sandstone, very well laminated, tan; weathers 

to light brownish gray; forms ledge________ 1 

Covered, probably sandstone_______________ 14 

Sandstone, fine-grained, salt-and-pepper, very 

light gray; abundant scattered medium and 

coarse grains; moderately well laminated 

with 2-inch layers of cross laminae________ 7 6 

Covered, probably sandstone_______________ 13 

Sandstone, medium- to coarse-grained, partly 

gritty, cross bedded______________________ 3 

Covered, probably sandstone and conglomerate with pebbles and cobbles of well-rounded 

quartzite______________________________ 70 

Sandstone, medium-grained, and boulder conglomerate with quartzite clasts, crossbedded; weathers yellow, olive, and brown~ 10 

Boulder conglomerate; consists mainly of 

light-gray quartzite but includes boulders 

of medium- to dark-gray quartzite, pink 

conglomeratic quartzite, black chert, and 

dark-gray limestone_____________________ 18 

Evanston Formation at type section for Hams Fork Conglomerate 

Member-Continued 

Evanston Formation-Continued 

Hams Fork Conglomerate Member-Centinued 

Boulder conglomerate as above; matrix of Ft in 

medium- to coarse-grained sandstone; weathers light olive drab______________________ 15 

Total thickness, Hams Fork Conglomerate ~ember _______________________________ 455 

Total thickness, Evanston Formation _______ 712 6 

Adaville Formation (partial): 

Covered, probably interbedded yellow to 

greenish-yellow sandstone and medium- to 

dark-gray mudstone_____________________ 43 

~udstone, medium-gray; abundant chips of 

ironstone______________________________ 10 

Covered, light-gray- to yellow-gray-weathering slope, probably sandstone and siltstone_ 10 

Interbedded gray mudstone, yellow siltstone, 

and very fine grained light-gray, brownweathering salt-and-pepper sandstone_____ 25 

Coal____________________________________ 1 

Covered_________________________________ 44 

~udstone, medium-gray; capped by ironstained yellow-brown sandstone___________ 5 

Interbedded dark-gray mudstone, dark-brownstained sandstone with leached calcareous 

nodules, and light-yellow to tan sandstone; 

thin interbeds of reddish-brown ironstone__ 40 

Total measured thickness, Adaville Formation____________________________ 178-

Base of measured section. 

Wasatch Formation (partial) at the type section for Bullpen Member 

[Measured in the NW~ sec. 1, T. 20 N., R. 118 W.) 

Wasatch Formation: 

Bullpen Membe~: 

Top of butte. 

Limestone, finely crystalline, buff; weathers 

to yellow, tan, and brown chips and slabs Ft in 

on tan silty slope at top of butte_________ 10 

Limestone, finely crystalline to sublithographic, tan; contains sparse ostracodes; 

forms ledge ___________________________ - 1 

Claystone, green, partly marly; some interbeds of mudstone; green with tan and 

brown mottling ________________________ 13 

~udstone and claystone, mottled brownish 

red, brown, green, and tan______________ 14 

Claystone, green; contains thin layers of 

green mudstone and very calcareous claystone and light- to medium-gray marlstone 

and calcareous claystone________________ 11 
44 UPPERMOST CRETACEOUS AND TERTIARY STRATIGRAPHY OF FOSSIL BASIN, WYOMING 

Wasatch Formation (partial) at the type section tor Bullpen 

Member-Continued 

Wasatch Formation-Continued 

Bullpen Member-Continued 

Siltstone, brown; grades downward to tan Ft in 

and brown limestone and upward to brown 

mudstone______________________________ 6 

Limestone, chalky, white to pale-yellow; thinly 

laminated to 3-inch-thick beds; forms ledge_ 1 

Mudstone and claystone, green_____________ 4 

Mudstone and claystone, red and brown; thin 

layers of green and gray_________________ 9 

Mudstone and claystone, mainly green but 

partly yellow and brown mottled_________ 9 

Limestone, buff, tan, and brown; weathers 

to small chips in brown silty soiL_______ 4 

Limestone, grading downward from tan, 

well indurated, very finely crystalline, 

and partly algal to white and chalky______ 4 6 

Mudstone, green; contains green and tan 

slightly silty claystone and tan marly 

mudstone______________________________ 9 

Mudstone, maroon; a little green and purple 

mottling_____________ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ 4 

Mudstone, brown; some layers of brownand green-mottled claystone and very thin 

layers of tan limestone__________________ 25 

Sandstone, fine-grained to very fine grained, 

very calcareous, light-gray; form;; tan 

spheroidally weathering ledge_ .. _ _ _ _ _ _ _ _ _ _ 1 

Limestone, mainly very finely crystalline; 

some ostracoda! coquinas in tan, brown, and 

buff laminae; forms brown silty slope with 

abundant limestone chips________________ 10 

Limestone, recrystallized ostracoda! coquina, 

tan; forms ledge________________________ 1 

Mudstone and siltstone, brown_____________ 6 

Sandstone, ranging from brown, very fine 

grained, and very calcareous to medium 

gray, slightly calcareous, fine grained, and 

poorly indurated_______________________ 7 

Sandstone, brown, medium-grained, moderately well sorted; contains scattered 

dark chert; moderately well and evenly 

laminated and cross laminated; forms 

ledge-----~---------------------------- 6 

Sandstone, brown, fine-grained and muddy; 

poorly exposed_________________________ 8 

Claystone, partly silty, shaly, mainly dark 

brown; some yellow with thin seams of 

purple_________________________________ 14 

Incomplete thickness, Bullpen Member__ 177 6 

Green River Formation: 

Angelo Member (partial): 

Thinly interlaminated claystone and marlstone, tan, yellow, and pink, and limestone, 

finely crystalline, well-indurated, light-gray and buff ______________________________ _ 5 

Wasatch Formation ( part·ial) at the type section tor Bullpen 

M embe1·-Continued 

GI'een River Formation-Continued 

Angelo Member (partial) -Continued 

Limestone; forms brown, orange, and yellow Ft in 

chips in brown silty soiL________________ 4 

Limestone, very finely crystalline and thinly 

laminated, medium-brown; fossil fish 

fragments______________________________ 6 

Limestone, very finely crystalline, tan to 

purplish-tan; abundant flat gastropods_____ 7 

Oil shale, low-grade_______________________ 6 

Partial thickness, Angelo Member (185 ft 

thick at this locality) ·of Green River 

Formation_________________________ 17 

Green River Formation at the type section of the Fossil Butte 

Mf.mber 

[Measured at the east end of the south-facing scarp of Fossil Butte, SW.)4NW.)4 sec. 5, T. 21 N., R. 117 W.] 

Green River Formation: 

Angelo Member (partial) : 

Top of butte. Ft in 

Limestone, marly, light-gray to white, thinbedded; contains chert nodules; thin as bed 

2 feet above base of unit_________________ 7 

Shale, limy, grayish-tan, laminated; contains 

some oily beds__________________________ 9 

Limestone, marly, light-gray, thin-bedded____ 1 

Shale, silty, greenish-gray and rust-colored; 

contains plant fragments_________________ 1 

Limestone, marly, and calcareous shale, 

light-gray to white; contains chert nodules 

and evaporite crystal cavities____________ 10 

Oil shale, laminated_______________________ 8 

Limestone, shaly, light-gray________________ 2 

Shale, greenish-gray, crumbly______________ 3 6 

Limestone, shaly, light-gray, massive to laminated; ash beds near top_________________ 3 

Shale, green- and olive-gray, mottled__ _ _ _ _ _ _ 1 6 

Partial thickness (rounded), Angelo 

Member___________________________ 39 

Fossil Butte Member: 

Limestone, chalky to white, pale-orange-yellow; 

laminated in top foot; marly; weathers to 

yellow below, grayish tan on fresh fracture; contains small ironstone blebs that 

----

weather to rusty spots ______ .____________ 6 6 

Shale, marly, grayish-tan, laminated________ 5 6 

Oil shale, brown; weathers bluish gray at 

top and light tan below; contains evaporite crystal pseudomorphs of calcite_______ 4 6 

Chalk, white, soft_________________________ 6 

Shale, marly, and siltstone, tan to light-gray__ 4 6 

-,. 
TYPE SECTIONS FOR MEMBERS DEFINED IN THIS REPORT 45 

G1·een R·ive1· Fm·mation at the type section ot the Fossil B1ttte 

III ember-Continued 

Green River Formation-Continued 

Fossil Butte Member-Continued 

Oil shale, brown, soft to limy and hard; con- Ft in 

tains beds with abundant evaporite pseudomorphs______________________________ 5 

Shale, limy, pink to tan ________________ ~-- 2 

Limestone, porous; contains ash bed_ _ _ _ _ _ _ _ 1 6 

Shale, light-tan, varved____________________ 1 6 

Oil shale; weathers light bluish gray; fissile___ 1 

Marlstone, light-grayish-tan, soft_ _________ - 1 

Shale, light-tan to buff, papery; and blueweathering oil shale; thin ash beds ___ ----- 7 6 

Oil shale, low-grade; weathers light gray_--_- 1 6 

Shale, laminated, buff-weathering ______ -_-_- 1 6 

Ash, calcareous, pink______________________ 6 

Shale, laminated, buff-weathering __________ - 4 

Ash, calcareous, pink-weathering; bright yellow on fracture ________________________ -

Shale, laminated; contains fossil fish ____ - ___ -

Limestone, chalky, pinkish-tan ____________ _ 

Shale, laminated, calcareous, buff; thin ash beds _________________________________ _ 

Limestone, chalky, light-buff; rust-colored 

ash zone at base; unit is very irregular ____ _ 

Shale, limy, laminated, carbonaceous; in beds 

1-3 ft thick alternating with 6-in. beds of 

carbonaceous siltstone __________________ _ 

Shale, light-tan, papery; contains thin beds of 

dark-brown oil shale ___________________ _ 

Shale, light-tan to light-gray, laminated·- ___ _ 

Limestone, chalky, white ___ - __ - ___ --_- ___ -

Shale, laminated; limy at top ______________ -

Limestone, buff, chalky, massive, irregular; 

fish fragments ___________ - __ - ___ --_-----

Mudstone, calcareous, dark-yellowish-brown 

to gray; thin gypsum veins ______________ -

Shale, papery; chocolate colored on fresh surface 

Limefttone, chalky, yellow-weathering ______ _ 

Shale and shaly limestone, rusty-tan to gray, laminated _____________________________ _ 

Limestone, light-gray, bluish-gray-weathering, massive, fossiliferous _______________ _ 

Limestone, light-gray to buff, chalky to 

blocky, brecciated _________________ ---_-

Limestone, shaly, light-gray to buff ________ _ 

Limestone, shaly, rusty-tan, brecciated _____ _ 

Limestone, light-tan, hard, silty, mediumbedded _______________________________ _ 

Siltstone, shaly, light-bluish-gray; purplish 

gray at top ___________________________ _ 

Limestone, silty, pale-buff, brecciated ______ _ 

Siltstone, shaly, buff to gray, yellow-weathering, oolitic ______________________ ----_--

Limestone, light-tan to buff, chalky, sandy __ _ 

Siltstone, light-bluish-gray to greenish-gray, 

oolitic; gypsum veins ___________________ _ 

Sandstone, light-gray to tan, fine-grained ___ _ 

2 

2 

5 

2 

10 

7 

7 

2 

2 

6 

9 

2 

5 

3 

21 

3 

4 

5 

4 

3 

1 

6 

6 

4 

8 

6 

6 

6 

6 

6 

6 

6 

6 

6 

6 

Green River Formation at the type section ot the Fossil Butte 

Member-Continued 

Green River Formation-Continued 

Fossil Butte Member-Continued 

Siltstone, limy, light-gray, ledge-forming, Ft in 

massive to brecciated; veined with gypsum_ 1 

Siltstone, medium- to light-bluish-gray______ 4 

Mudstone, sandy, light-gray; rusty colored 

near base; calcareous____________________ 5 6 

Sandstone, light-gray, fine-grained to very 

fine grained, calcareous__________________ 1 

Siltstone and claystone, gray to pale-olivegray; muddy partings___________________ 5 

Covered zone above terrace (assumed top of 

Wasatch Formation) _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ 17 

Total thickness (rounded), Fossil Butte 

Member of Green River Formation___ 208 

Green River Formation at the type section of the Angelo Member 

[Measured on bluff overlooking the Angelo ~anch, west of South Fork Twin Creek, 

in the NW~ sec. 1, T. 20 N., R. 118 W.] 

Wasatch Formation: 

Bullpen Member (partial): 

Covered at top of butte; tan slope of weathered 

marlstone and thin-bedded yeilow, brown, 

and tan limestone _____________________ _ 

Limestone, brown, blocky _________________ _ 

Interbedded chalky-white marlstone and 

greenish-gray claystone _________________ _ 

Claystone, green, soft ____________________ _ 

Claystone, mottled · brownish red, brown, 

green, and tan; forms reddish band ___ _ 

Claystone, greenish-gray __________________ _ 

Claystone, silty, brown to red _____________ _ 

Marlstone, tan; and greenish-gray claystone_ 

Limestone, tan, flaggy, thinly laminated; 

forms 1-ft ledge above chalky-white marlstone _________________________________ _ 

Claystone, green _________________________ _ 

Claystone, mottled red, brown, and green; 

forms pink band _____________________ _ 

Mudstone, buff-weathering ___________ ~ ____ _ 

Limestone, tan, aphanitic, hard; 6-in ledge 

at top of white marlstone _______________ _ 

Claystone, greenish-gray, soft _____________ _ 

Claystone, maroon; green and purple mottling_ 

Covered; brown soft slope; variegated purple, 

brown, and green claystone ____________ -_ 

Sandstone, quartz, calcareous, thin-bedded __ _ 

Covered; mudstone ______________________ _ 

Limestone, sandy, thin-bedded; ostracode 

coquina grading down to brown sandy mudstone _____________________________ _ 

Covered; brown mudstone and fine-grained 

poorly indurated sandstone _____________ _ 

Sandstone, brown, laminated ______________ _ 

Ft in 

10 

1 

9 

4 

14 

8 

5 

4 

3 

4 

13 

4 6 

3 6 

12 

4 

25 

1 

7 

3 

9 

1 
46 UPPERMOST CRETACEOUS AND TERTIARY STRATIGRAPHY OF FOSSIL BASIN, WYOMING 

Green R·iver Formation at the type section of the Angelo J Green River Formation at the type section ot the Angelo 

Member-Continued JJf ember-Continued 

Wasatch Fonnation-Continued 

Bullpen Member (partial)__:_Continued 

Sandstone, brown, coarse-grained; cross bedded Ft in 

inplaces _______________________________ 15 

Partial thickness, Bullpen Member of 

Wasatch Formation _________________ 160 

Green River Formation: 

Angelo Member: 

Oil shale, low-grade, brown, papery; and 

brown claystone __ ---------------------- 10 

Limestone, yellow- to buff-weathering, thinly 

lamina ted ___________________________ - - - 6 

Covered; brown soil; yE.Ilow, brown, orange 

limestone chips on surface _____________ -- 4 

Limestone, brown, petroliferous, thinly lam- · 

inated; fish fragments___________________ 6 

Covered; purplish-tan limestone fragments; 

flat gastropods_________________________ 6 6 

Oil shale, low-grade, brown________________ 6 

Claystone, brown ______________________ --- 2 6 

Claystone, greenish-gray _________________ - 2 

Limestone, shaly, soft_____________________ 6 

Claystone, greenish-gray; thinly bedded lime-

. stone that weathers to orange, brown, and 

dark-brownish-gray chips________________ 9 6 

Limestone, tan, buff-weathering, ledge-forming___________________________________ 1 

Covered; tan and greenish-gray banded slope; 

alternating green claystone and tan calcareous shale with thin beds of sandy limestone_________________________________ 23 

Covered; white slope containing chips and 

slabs of tan limestone___________________ 14 

Marlstone, hard, dark-brown, ledge-forming; 

weathers orange; banded_______________ 1 

Covered; white to light-tan slope with abundant limestone chips; mostly fissile greenish-gray calcareous shale__________ _ _ _ _ _ _ 23 

Limestone, light-brown, hard, crystalline; 

weathers tan__________________________ 2 

Claystone, olive-brown, hackly, hard__ _ _ _ _ _ 1 7 

Sandstone, gray, fine-grained, poorly sorted; 

grains of angular chert and clay_______ _ _ _ _ 1 

Covered; tan slope; fissile Hmy grayish-white 

shale with thin beds of brown hard limestone__________________________________ 30 

Limestone, algal· or concretionary, slab by to 

thin-bedded, white-weathering; hard, ledge 

forming to soft, covered_________________ 10 

Oil shale, papery, brown___________________ 1 

Green River Formation-Continued 

Angelo Member-Continued 

Shale, calcareous, white-weathering; contains Ft in 

chalky limestone and chert_______________ 4 

Limestone, tan to brown; weathers white____ 1 

Mudstone, gray, calcareous________________ 4 

Limestone, tan, thin-bedded________________ 5 

Mudstone, bluish-green; and claystone; gray 

to white limEstone chips_________________ 15 

Total thickness, Angelo Member of Green 

River Formation ___________________ 194 

Fossil Butte Member (top only): 

Shale, calcareous, buff- to white-weathering__ 10 

Oil shale, dark-brown; weathers blue; 3-cm 

beds of "sugar oil shale," filled with 1-mm 

calcite pseudomorphs after evaporite 

crystals________________________________ 1 

Fowkes Formation at type sections for its members 

[Measured from theSE~ sec. 5, T. 21 N., R. 119 W., to the NE~ sec. 33, T. 22 N., 

R.ll9 W.] 

Fowkes Formation: 

Gooseberry Member (incomplete) : 

Covered interval at top of hill; loose gravel Ft in 

float; possibly puddingstone conglomerate__ 60 

Covered interval on hillslope; limy sandstone 

and silt in float_________________________ 60 

Puddingstone; pebbles as much as 4 in.; lightgray chert dominant, set in white sandy 

limestone matrix; flat pebbles parallel bedding. 1-ft lenticular calcareous sandstone 

bed___________________________________ 8 

Limestone, light-gray to white, very sandy to 

calcareous sandstone; biotite and dark mineral grains abundant. Forms rounded 

weathered surface. Contains five lentils of 

"puddingstone" about 2 in. thick, 1 ft to 

several feet in length; lentils grade laterally and vertically into limestone ________ _ 

Puddingstone; conglomerate in sandy limestone matrix __________________________ _ 

Limestone, white; contains thin layers of 

sparse granule-and-pebble conglomerate 1-3 

in. thick near base. Upper 3 ft is white. 

Massive limestone with beds as much as 

1 ft thick of laminated pinkish-tan limestone. Cross laminated and contorted in 

places; separated in others to form calcitefilled vugs as much as 1 in. high and 1 ft 

6 

1 

long. Resembles travertine_______________ 5 

6 
REFERENCES CITED 47 

Fowkes Formation at type sections for its members-Continued , Fowkes For1nation at type 8ections tor its members-Continued 

Fowkes Formation-Continued 

Gooseberry Member (incomplete) -Continued 

Puddingstone, coarse-grained; light-gray at a Ft in 

distance; white limestone matrix. Contains 

crude beds 2-6 in. thick of finer and coarser 

pebbles floating in a limestone matrix. 

Pebbles well rounded and cobbles to as 

much as 4 in. of white, gray, black, and tan 

quartzite; brown, black, and gray chert and 

pinkish-white porcellenite(?); sparse volcanic pebbles; flat to well-rounded pebbles of 

dark-gray limestone_____________________ 9 

Approx. thickness (incomplete; rounded), 

Gooseberry Member of Fowkes Formation ____________________________ 150 

Bulldog Hollow Member: 

Sandstone, light-green to olive-brown, mediu in- to fine-grained; clayey matrix; 

abundant biotite, magnetite, dark chert 

grains; interbedded very fine grained sandstone, mudstone, and coarse-grained sandstone. Topmost beds crossbedded, dipping 

20° E; 3-ft pebble conglomerate 20 ft below 

top; white tuffaceous claystone bed 50 ft 

above base _____________________________ 131 

Sandstone, medium-green to dark-green, very 

fine grained to medium-grained; dark-green 

clay rna trix; very abundant magnetite_____ 5 

Sandstone, light-green to olive-brown, medium- to coarse-grained; biotite and magnetite_________________________________ 48 

Sandstone, light-grayish-green, mediumgrained________________________________ 5 

Covered interval; unit consists chiefly of soft 

dark-green sand that contains magnetite grains _________________________________ 40 

Gravel, black, tan; and gray chert and quartzite pebbles to as much as 6 in. in diameter; 

broken limestone-indurated puddingstone 

with pebbles floating in sandy limestone rna trix _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ 2 

Sandstone, greenish-tan, very fine grained to 

medium-grained; magnetite, chert grains 

and black mineral grains_________________ 3 

Gravel, as above__________________________ 5 

Total thickness, Bulldog Hollow Member of Fowkes Formation____________ 239 

Sillem Member: 

Mudstone, clayey, pale-tan to greenish-gray; 

pink mottling; thin beds of white tuffaceous 

claystone______________________________ 15 

Claystone, calcareous silty, light-gray; brown 

calcareous concretions___________________ 1 

Sandstone, pale-gray to pale-tan, fine·grained, 

poorly sorted, clayey; moderately abundant 

dark grains and mica; angular fragments of 

claystone______________________________ 5 

Fowkes Ji"'ormation-Continued 

Sillem Member-Continued 

Claystone, pale-green to pale-tan, silt.y; Ft in 

biotite flakes___________________________ 9 

Mudstone, pale-tan to light-greenish-gray; 

weathers to gray and pink bands; silty and 

sandy; micaceous 10ft above base________ 14 

Mudstone; pale-greenish-gray siltstone and 

fine-grained muddy sandstone; weathers to 

gray with pink mottling_________________ 15 

Sandstone, muddy, very fine grained, palegreenish-gray; contains brown and tan 

beds. V cry silty and muddy at top of unit. 

Slope weathers to an encrusted mud sur- face___________________________________ 20 

Mudstone, shaly; and siltstone, pale-greenishgray__________________________________ 1 

Sandstone, light-greenish-gray; fine grained 

grading down to coarse grained___________ 2 

Mudstone, silty, shaly; mottled pink, tan, 

and brown------------~---------------- 6 

Sandstone, olive-drab, green to light-green, 

coarse-grained; clayey matri~; grains dominantly quartz and black chert___________ 4 6 

Sandstone, coarse-grained, crossbedded, lightgray "salt and pepper"; about 10 percent 

dark grains, black chert, minor magnetite, 

and interbedded thin mudstone and conglomerate beds; lenticular conglomerate as 

much as 2ft thick; granules and pebbles of 

chert and quartz; some clay balls as much 

as 6 in. in diameter_____________________ 21 

Covered below. 

Total thickness, exposed Sillem Member 

of Fowkes Formation ________________ 108 

Total thickness (rounded), exposed 

Fowkes Formation __________________ 497 

REFERENCES CITED 

Anderman, G. G., 1955, Tertiary deformational history of •a 

portion of the north flank of the Uinta Mountains in the 

vicinity of Manila, Utah, in Wyoming Geol. Assoc. Guidebook lOth Ann. Field Conf., Green River Basin, 1955 : p. 

130-134. 

Armstrong, F. C., and Oriel, S. S., 1965, Tectonic development 

of Idaho-Wyoming thrust belt: Am. Assoc. Petroleum 

Geologists Bull., v. 49, no. 11, p. 1847-1866. 

Bradley, W. H., 1926, Shore phases of the Green River formation in northern Sweetwater County, Wyoming: U.S. Geol. 

Survey Prof. Paper 140-D, p. 121-131. 

---1929a, Algae reefs and oolites of the Green River Formation: U.S . .Oeol. Survey Prof. Paper 154-G, p. 203-223, pls. 

28-48. [ 1930] . 

---1929b, The occurrence and origin of analcite and 

meerschaum beds in the Green River formation of Utah, 

Colorado, and 'Vyoming: U.S. Geol. Survey Prof. Paper 

15~A, p. 1-7, pls. 1-3. 
48 UPPERMOST CRETACEOUS AND TERTIARY STRATIGRAPHY OF FOSSIL BASIN, WYOMING 

---1930, The varves and climate of the Green River epoch: 

U.S. Geol. Survey Prof. Paper 158-E, p. 87-110, pls. 11-14. 

---1931, Origin and microfossils of the oil shale of the 

Green River formation of Colorado and Utah: U.S. Geol. 

Survey Prof. Paper 168, 58 p., 28 pls. 

---1948, Limnology and the Eocene lakes of the Rocky 

Mountain region: Geol. Soc. America Bull., v. 59, no. 7, p. 

635-648. 

---1959, Revision of stratigraphic nomenclature of Green 

River formation of Wyoming: Am. Assoc. Petroleum 

Geologists Bull., v. 43, no. 5, p. 1072-1075. 

---1963, Paleolimnology, Chapter 23 of Frey,· D. G., ed., 

Limnology in North America: Wisconsin Univ. Press, p. 

621-652. 

---1964, Geology of Green River 'Formation ,and associated 

Eocene rocks in southwestern Wyoming and adjacent parts 

of Colorado and Utah: U.S. Geol. Survey Prof: Paper 496-

A, 86 p. [11965]. 

---1966, Tropical lakes, copropel, and oil shale : Geol. Soc. 

America Bull., v. 77, no. 12, p. 1333-1338. 

Brown, R. ,V., 1929, Additions to the flora of the Green River 

formation: U.S. Geol. Survey Prof. Paper 154-J, p. 279-292 

[1930]. 

---1934, The recoguiz,able species of the Green River flora: 

U.S. Geol. Survey Prof. Paper 185-C, p. 45-77 [1935]. 

---1962, Paleocene flora of the Rocky Mountains and Great 

Plains: U.S. Geol. Survey Prof. Paper 375, 119 p. 

Cockerell, T. D. A., 1920, Eocene insects from the Rocky Mountains: U.S. Natl. Mus. Proc., v. 57, p. 233-260. 

Co,pe, E. D., 1877, A contribution to the knowledge of the 

ichthyological fauna of the Green River shales, in Hayden, 

F. V., Bulletin of the United States Geological and Geographical Survey of the Territories: v. 3, no. 4, p. 807-819. 

---1878, Descriptions of fishes . from the Cretaceous and 

Tertiary deposits west of the Mississippi River, in Hayden, 

F. V., Bulletin of the United States Geological and Geographical·Survey of the Territories: v. 4, p. 67-77. 

--- 1884, The Vertebrata of the Tertiary formations of the 

West: u.s: Geol. Survey Terr. (Hayden), Rept. 3, 1009 p. 

Culbertson, W. C., 1965, Tongues of the Green River and Wasatch 

Formations in the southeastern part of the Green River 

Basin, Wyoming, in Geological Survey research 100.1): U.S. 

Geol. Survey Prof. Paper 525-D, p. D139-D143. 

Dorf, Erling, 1955, Paleobotanical correlations of Late Cretaceous deposits in southwestern 'Vyoming, in Wyoming Geol. 

Assoc. Guidebook, .. lOth Ann. Field Conf., Green River Basin, 

1955 : p. 96-99. 

Dorr, J. A., Jr., 1952, Early Cenozoic stratigraphy and vertebrate 

paleontology of the Hoback Basin, Wyoming : Geol. Soc. 

America Bull., v. 63, no. 1, p. 59-93. 

---1958, Early Cenozoic vertebrate paleontology, sedimentation, and orogeny in central western Wyoming : Geol. Soc. 

America Bull., v. 69, no.10, p.1217-1243. · 

Eardley, A. J., 1944, Geology of the north-central WasatcbMountains, Utah: Geol. Soc. America Bull., v. 55, no·. 7, p. 819-894. 

---1952, Wasatch hinterland, in Geology of the central 

Wasatch Mountains, Utah: Utah Geol. Soc. Guidebook to the 

Geology of Utah, no. 8, p. 52-60. 

--- 1959, Review of geology of northeastern Utah and southwestern Wyoming, in Illltermountain As,soc. Petroleum Geologists Guidebook lOth Ann. Field Conf., Wasatch and Uinta 

Mountains transition area, 1959: p. 166-171. 

Eardley, A. J., Horberg, Leland, Nelson, V. E., and Church, 

Victor, 1944, Hoback-Gros Ventre-Teton [Wyo.] field conference: Michigan Univ., Rocky Mtn. Field Sta., 2 map 

sheets. 

Evernden, J. F., Savage, D. E., Curtis, G. H., and James, G. T., 

1964, Potassium-argon dates and the Cenozoic mammalian 

chronology of North America: Am. Jour. Sci., v. 262, no. 2, 

p. 145-198. 

Fahey, J. J., 1962, Saline minerals of the Green River formation, 

with a section on X-ray powder data for saline minerals of 

the Green River formation, by M. E. Mrose: U.S. Geol. 

Survey Prof. Paper 405, 50 p. 

Flint, R. F., Sanders, J. E., and Rodgers, John, 1960, Symmictite--A name for nonsorted terrigenous sedimentary rocks 

that contain a wide range of particle sizes: Geol. Soc. America Bull., v. 71, no. 4, p. 507-509; a'ddendum-Diamictite, a 

substitute term for symmictite, v. 71, no. 12, pt. 1, p. 1809 .. 

Gazin, C. L., 1952, The lower Eocene Knight formation of western 

'Vyoming and its mammalian faunas: Smithsonian Misc. 

Colln., v. 117, no. 18, 82 p. 

--- 1956, The occurrence of Paleocene mammalian remains in 

the Fossil Basin of southwestern Wyoming : Jour. Paleontology, v. 30, no. 3, p. 707-711. 

--- 1959, Paleontological exploration and dating of the early 

Tertiary deposits in basins adjacent to the Uinta Mountains 

[Utah-'\Vyo.-Colo.], in Intermountain Assoc. Petroleum 

Geologists Guidebook, lOth Ann. Field Conf., Wasatch and 

Uinta Mountains transition area, 1959: p. 131-138. 

--- 1962, A further study of the lower Eocene mammalian 

faunas of southwestern 'Vyoming: Smithsonian Misc. Colin., 

v. 144, no. 1 (Smithsonian lust. Pub. 4474), 98 p. 

Granger, Walter, 1914, On the names of the lower Eocene faunal 

horizons of Wyoming and Mexico: Am. Mus. Nat. History 

Bull. 33, 'P· 201-207. 

Hayden, F. V., 1869, Preliminary field report [third annual] ot 

the United States Geological Survey of Golorado and New 

Mexico : 155 p. 

--- 1870, Sun pictures of Rocky Mountain scenery, with a 

description of the geographical and geological features and ' 

some account of the resources of the Great 'Vest: New York, 

Julius Bien, 150 p. 

Hesse, C. J., 1939, Fossil fish localities in the Green River Eocene 

of Wyoming: Sci. Monthly, v. 48, no. 2, p. 147-151. 

Heylmun, E. B., 1965, Reconnaissance of the Tertiary sedi.mentary rocks in western Utah : Utah Geol. and Mineralog. 

Survey Bull. 75, 38 p. 

.Jepsen, G. L., 1966, Early Eocene bat from Wyoming: Science, 

v. 154,no.3754,cover,p. 1333-1339. 

Lawrence, J. C., 1963, Origin of the Wasatch Formation, Cumberland Gap area, Wyoming: Wyoming Univ. Contr. Geology, 

v. 2, no. 2, p.151-158. 

Leidy, Joseph, 1873, Contributions to the extinct vertebrate 

fauna of the Western Territories, in Hayden, F. V., U.S. 

Geol. and Geog. Survey of the Terr., Ann. Rept. 1, 1867: 

358 p. 

Lesquereux, Leo, 1883, Contributions of the fossH flora of the 

Western Territorieg..:.-Part 3, The Cretaceous and Tertiary 

floras in Hayden, F. V., U.S. Geol. and Geog. Survey of the 

Terr., Ann. Rept. 8, 187 4 : 283 p. 

McGrew, P. 0., and Roehler, H. ,V., 1960, Correlation of Tertiary 

units in southwestern Wyoming, in 'Vyoming Geol. Assoc. 

Guidebook, 15th Ann. Wield Conf., Overthrust belt of southwestern Wyoming and adjacent areas, 1960: p. 156-158. 

McKenna, M. C., Robinson, Peter, and Taylor, D. W., 1962, Notes 

on Eocene Mammalia and Mollusca from Tabernacle Butte, 

Wyoming: Am. Mus. Novitates, no. 2102, 33 p. 

\. 
.r 

REFERENCES CITED 49 

Mansfield, G. R., 1927, Geography, geology and mineral resources 

of part of southeastern Idaho, with llescriptions of Carboniferous and Triassic fossils, by G. H. Girty: U.S. Geol. 

Survey Prof. Paper 152, 453 p. 

Masursky, Harold, 1962, Uranium-bearing coal in the eastern 

part of the Red Desert area: U.S. Geol. Survey Bull. 1099-B, 

152 p. 

Mullens, T. E., and Laraway, \V. H., 1964, Geology of the Devils 

Slide quadrangle, Morgan and Summit Counties, Utah: U.S. 

Geol. Survey Mineral Inv. Field Studies Map MF-290. 

Oriel, S. S., 1961, Tongues of the Wasatch and Green River formations, Fort Hill area, Wyoming, in Short papers in the 

geologic and hydrologic sciences: U.S. Geol. Survey Prof. 

Paper 424-B, p. B151-B152. 

---1962, Main body of Wasatch Formation near La Barge, 

Wyoming: Am. Assoc. Petroleum Geologists Bull., v. 46, 

no. 12, p. 2161-2173. 

---1969, Geology of the Fort Hill quadrangle, Lincoln 

County, 'Vyoming: U.S. Geol. Survey Prof. Paper 594-M, 

·10 p. 

Oriel, S. S., and Armstrong, 1!,. C., 1966, Times of thrusting in 

Idaho-"ryoming thrust belt-Reply: Am. Assoc. Petroleum 

Geologists Bull., v. 50, no. 12, p. 2614-2621. 

Oriel, S. S., Gazin, C. L., and Tracey, J. I., Jr., 1962, E:ocene age 

of Almy Formation, ·wyoming, in its type area: Am. Assoc. 

Petroleum Geologists Bull., v. 46, no. 10, p. 1936-1937. 

Peale, A. C., 1879, Report on the geology of the Green River 

district [Wyoming], in Hayden, F. V., U.S. Geol. and Geog. 

Survey of the Terr., Ann. Rept. 11, 1877: p. 509-646. 

---1883, [Geologic map of] parts of western Wyoming, 

southeastern Idaho, and northeastern Utah, in Hayden, 

F. V., U.S. Geol. and Geog. Survey of the Terr., Ann. Rept. 

12, 1878. 

Pipiringos, G. N., 1962, Uranium-bearing coal in the central part 

of the Great Divide Basin: U.S. Geol. Survey Bull. 1099-A, 

104 p. [1962]. 

Ruhey, W. W., and Hubbert, M. K., 1959, Overthrust belt in 

geosynclinal area of western Wyoming in light of fluidpressure hypothesis, part 2 of Role of fluid pressure in 

mechanics of overthrust faulting: Geol. Soc. America Bull., 

v. 70,no.2,p.167-205. 

Rubey, W. W., Oriel, S. S., and Tracey, .J. I., Jr., 1961, Age of 

the Evanston formation, western Wyoming, in Short papers 

in the geologic and hydrologic sciences: U.S. Geol. Survey 

Prof. Paper. 424-B, p. B153-B154. 

--1968, Preliminary geologic map of the Kemmerer quadrangle, Lincoln County, Wyoming: U.S. Geol. Survey openfile map. 

Ru!Jey, "r· ·w., Tracey, J. I., Jr., and Oriel, S. S., 1968, Preliminary geologic map of Sage quadrangle, Lincoln County, 

Wyoming: U.S. Geol. Survey open-file map. 

Schaeffer, Bobb, and Mangus, Marlyn, 1965, Fossil lakes from 

the Eocene: Nat. History, v. 74, no. 10, p. 10-21. 

Schultz, A. R., 1914, Geology and geography of a portion of 

Lincoln County, Wyoming: U.S. Geol. Survey Bull. 543, 

141 p. 

Scll:dder, S. H., 1890, The Tertiary insects of North America, in 

Hayden, F. V., U.S. Geol. Survey of the Terr. Rept. 13, 

734 p. 

Sears, J. D., and Bradley, ,V. H., 1924, Relations of the Wasatch and Green River formations in northwestern Colorado and southern 'Vyoming with notes on oil shale in the 

Green River formation: U.S. Geol. Survey Prof. Paper 

132-F, p. 93-107. 

Spieker, E. M., 1946, Late Mesozoic and early Cenozoic history 

of central Utah: U.S. Geol. Survey Prof. Paper 205-D, p. 

117-161. 

Thorpe, M. R., 1938, Wyoming Eocene fishes in the Marsh Collection: Am. Jour. Sci., ser. 5, v. 36, no. 214, p. 279-295. 

Tracey, J. I., Jr., and Oriel, S. S., 1959, Uppermost Cretaceous 

and lower Tertiary rocks of the Fossil Basin [Wyoming], in 

Intermountain Assoc. Petroleum Geologists Guidebook, 10th 

Ann. Field Conf., Wasatch and Uinta Mountains transition 

area, 1959: p. 126-130. 

Tracey, J. I., Jr., Oriel, S. S., and Rubey, W. W., 1961, Diamictite facies of the 'Vasatch formation in the Fossil basin, 

southwestern 'Vyoming, in Short papers in the geologic 

and hydrologic sciences: U.S. Geol. Survey Prof. Paper 

424-B, p. B149-B150. 

Van Houten, F. B., 1961, Climatic significance of red beds, 

Chapter 5 of Nairn, A. E. M., ed., Descriptive palaeoclimatology: New York, Interscience Publishers, Inc., p. 89-139. 

---1964, Tertiary geology of the Beaver Rim area, Fremont 

and Natrona Counties, \Vyoming: U.S. Geol. Survey Bull. 

1164, 99 p. [1965]. 

Veatch, A. C., 1906, Coal and oil in southern Uinta County, 

Wyoming: U.S. Geol. Survey Bull. 285-F, p. 331-353. 

---1907, Geography and geology of a portion of southwestern 

Wyoming, with special reference to coal and oil: U.S. 

Geol. Survey Prof. Paper 56, 178 p. 

'Vetmore, Alexander, 1933, Fossil bird remains from the Eocene 

of Wyoming-Condor: v. 35, no. 3, p. 115-118. 

Williams, J. S., 1964, The age of the Salt Lake Group in Cache 

Valley, Utah-Idaho: Utah Acad. Sci., Arts, and Letters 

Proc., v. 41, no. 2, pt. 2, p. 269-277. 

Williams, N. C., and Madsen, J. H., Jr., 1959, Late Cretaceous 

stratigraphy of the Coalville area, Utah, in Intermountain 

Assoc. Petroleum Geologists Guidebook, 10th Ann. Field 

Conf., Geology of the Wasatch and Uinta Mountain transition area, 1959: p. 122-125. 

Wood, H. E., 2d, chm., and others, 1941, Nomenclature and 

correlation of the North American continental Tertiary: 

Geol. Soc. America Bull., v. 52, no. 1, p. 1-48. 

Wood, R. C., 1967, A review of the Clark Fork vertebrate fauna: 

Breviora, no. 257, p. 1-30. 

A Page 

Absaroka fault. _______________________________ 10,14 

Acknowledgments .•. __ -------- __________ ----- S 

Acock Canyon_______________________________ 34 

Adaville Formation _____________________ 6, 10, 14,23 

Algallogs ________________ .. __ .. -------- ___ -- _- 21 

Algal pisolites. _. _____ . ______ ---------- ____ --- 17 

Alroy ________________________ .---- ________ --_ 5, 16 

Alroy Formation ___________________ 6, 9, 16, 17, 19,33 

Amerada Petroleum Co. 1 Chicken Creek unit 

welL.---------------------------- 19 

Angelo Member, Green River Formation.---- 20, 

28, 30,81, 39 

Angelo Ranch •. ------------------------------ 20,31 

Armstrong, R. L., written communication---- 37 

B Badland buttes ______________ ---- __________ -_. 10 

Basal conglomerate member, Wasatch Formation. __ . _______ . _______ ---- ____ -_- 17,27 

Bear Lake Plateau. __ . ______ ---- __ --- .... __ - __ 34,37 

Bear River ___________________________________ 16,19 

Bear River Range____________________________ 9 

Bear River valley---------------------------- 24 

Big Park.------------------------------------ 24 

Bighorn Dolomite---------------------------- 20,23 

Boulder conglomerates. _______ ----_. ______ -_. 6 

Boulder Ridge _________________________ 22, 29, 34,38 

Bridger Formation ________________________ 16, 30,41 

Brigham Quartzite. __ -------- ___ ------_______ 9, 34 

Brown, R. W., written communication _______ 13,37 

Bulldog Hollow __ ---------------------------. 35 

Bulldog Hollow Member, Fowkes Formation •. ---------------------. 34, 35, 36,41 

Bullpen Creek _______________ ------------._--- 21,22 

Bullpen Member, Wasatch Formation________ 17, 

B1, BB, 29, 31, 32 

c 

Cache Valley __ --------------------------_____ 41 

Camp Creek. _______ ------------------------_ 12 

Carter _____________________ ------------------- 16 

Chappo Member, Wasatch Formation._______ 39 

Clear Creek. ______ - ___________ ._ .• _______ .• __ 20,31 

CoaL ________________________ --------------. 6, 10,29 

Cokeville quadrangle.------------------ 2, 6, 9,10,24 

Collett Creek. _____ .------ ________________ 10, 13,18 

Color, Evanston Formation __________________ 5, 6, 9 

Green River Formation •• ---------------- 30 

Wasatch Formation, basal conglomerate 

member__________________________ 17 

Bullpen Member______________________ 21 

lower member ••. --------------------.- 17 

main bodY---------------------------- 18 

mudstone tongue_____________________ 20 

Commissarv Ridge _______________________ 6, 7,23,24 

Corral Creek. ___ ----------------------------- 6, 12 

Crawford fault._. ___ -------------________ 22, 24,29 

Crawford Mountains ________________________ 5,23,35 

D 

Dawson, Mary, written communication....... 37 

Dempsey Basin.----------------------------- 24,31 

Dempsey Ridge ....• __ •• __ ._._. ________ 23, 24, 28, 29 

Diamictite •••.•• ------------------------------ 29 

Dip, Evanston Formation, Hams Fork 

Conglomerate Member___________ 6 

INDEX 

[Italic page numbers indicate major references] 

Distribution and thickness, Evanston Formation, Hams Fork Conglomerate 

Page 

Member_. ____ •. _. _____ ------_.--. 7, 9 

Fowkes Formation, Bulldog Hollow 

Member .• ------------------------ 35 

Gooseberry Member__________________ 36 

Sillem Member.---------------------- 34 

Green River Formation, Angelo member-- 32 

Fossil Butte Member_________________ 31 

Wasatch Formation, Bullpen Member ___ - 22 

lower member------------------------ 18 

Tunp Member________________________ 24 

Dunkle, D. H., written communication_______ 28 

E 

Earthquakes. ___________ -----------~ __ -- ____ - 29 

Echo Canyon, Utah __________________________ 16,39 

Echo Canyon Conglomerate__________________ 39 

Eli Hill .• _-------------------- __ ------------- 24 

Elk Mountain ____________________ 10, 17, 19, 20,21, 27 

ElkoL .. _____ ---------------------------- __ --- 7 Ephraim Conglomerate ______________________ 23,29 

Evanston •.•. ------------------------------ 2, 5, 9,19 

Evanston Formation ______________ 6, 17, 18, 20,26,35 

age.-------------------------------------- 6 

color _______ -- __ --------------------------_ 5, 6 

exposures •.. -_. ___ ----_._-- __ -----.---____ 6 

Hams Fork Conglomerate Member ____ -__ 6, 1E! 

dip___________________________________ 6 

distribution and thickness._. __ ._._.__ 7, 9 

fossils and age.----------------------- 1! 

lithology ___ ------- __ ----------------- 9 

origin __________ ----------------------_ 9 

lower contact_____________________________ 10 

lower member---------------------------- 6 

fossils and age._--- __ ----------------- 11 

main body __ ----------------------------_ 6, 9 

color _______ --------.. ----------------- 9 

exposures ___ • __ -- .. --.- ___ --.. --_----_ 10 

fossils and age.----------------------- 1B 

lithology _______ ---- __ -_._------. ___ -__ 9 

thickness ________________ ---- __ --_____ 10 

name and usage__________________________ 6 

origin _________ .. _____ . _________ ------_____ 18 

sorting. __ ._. ___ . __ ---- __ -- ____ ------_____ 6 

tectonic implications_____________________ 14 

thickness ______________ -------- ______ ----- 6 

Exposures, Evanston Formation _____________ 6,10 

Green River Formation, Angelo Member__ 31 

Fossil Butte Member_________________ 30 

F 

Faulting _________________________ 6, 9, 10, 14, 22, 24,29 

Fontenelle Tongue .•• ------------------------ 41 

Fort Hill quadrangle.------- __ ------ __ ---- ___ 29,31 

Fossil •••. --------------------- ____ ----------- 6, 20 

Fossil basin _______ --------------------------- 5 

Fossil Butte.--------------------------- 19,28, 30,31 

Fossil Butte Member, Green River Formation ____________ ------- _____ 20, 28,80; 39 

Fossil Ridge _______________ . ______ . ___________ 30, 31 

Fossil syncline •••• _-----------------_________ 5 

Fossils: 

Abiespollenites. ______ • _ __ __ __ __ __ __ __ __ _ _ _ 12 

Alnus--------------------------------- 12, 13,26 

Fossils-Continued Page 

Alsophilidites __ __ . _ ----- _ __ __ __ ______ __ __ _ 12 

Amerianna. _____ -------- ________________ • 12 

Anemia .•. -------------------------------- 26 Appendicisporites. ___ . ___________________ . 12 

AquilapoUenites ... _ -------- __ ____ ____ _ ___ _ 12 

Araucariacidites __________ ---- __ ____ ____ __ _ 13 

Araucariacites australis •• ____________ .____ 11, 26 

Asineops_. ___ ----------- ____________ ---- _ 28 

bats _______ ---------- ________ ------_______ 32 

Bellamy a paludinae{ormis ____________ . _ _ _ _ 32 

Betula stevensonL _____ --..• _________ -__ .. 13 

Biompha Zaria pseudoammonius ___ . _ _ 26, 28, 32, 36 

birds. ________ • ________ -___ .- ________ --___ 32 

bones and scales-------------------------- 28 

Carpites. _. ____________ -- __ .• ________ -_. _. 13 

Carya •••• ----------- __ ------ __ ---- __ ----- 13,26 antiquora. _________ . ____ • _______ .- ___ . 13 

CedreUa ____ _ ------ ____ ------------------ _ 26 

charophytes ••... ______ ------ __ ---- ______ . 26,27 

Cicatricosisporites. _______ -------------- __ . 12 

dorogensiB ... --- __ -_ --.--.. -.. -_.-.-.. - 12 

Cinnamomum affine---------------------- 12 

linifolium ... -- ___ . _ .. _ -- _______ -------- __ 11 

ClassopoUis classoides ••• _ ---- __ ---- __ ----. 12 

Cleopatra._ .. --._. _________ . ______ • __ -_-_. 12 

condylarth. _______ ---------------------- _ 27 

Coryphodon ..• _________ • _- _ -- __ -- __ --- _- _- 28 

Cyathidites •. ___ • ___________ -- ________ -. _ _ _ 12 

DeUoidospora. _. _______ -___ -- ________ --. _. 12 

dicots. ____________ . _________ . _______ • _ __ _ 12 

Dinoflagellata ___________ -------- __ ____ __ _ 12 

dinosaurs ___ --------------------- __ ------- 12 

Discus •• _________ --_ .. -.--------- ___ ------ 26 

Dombeyopsis obtusa ___ -------------------- 11 

Drepanotrema ____ ------------------------- 28 

DryophyUum subfalcatum. _. _.--------.. -- 11, 12 

Elimia noduli/era .••. ------------------ 26, 28,32 

Engelhardtia.- ___ .- _------- ------ ___ ---.-- 13 

Ephedra •• _------------------------------- 12 

Equisetum.-------- __ --------------------- 37 

ErdtmanipoUis ___ -- ____ ---------- __ ------- 12,26 

Eucommia .. -----. _ ------------.---.------ 26 

Eucommiidites. __________ -. -- __ -- ______ --- 12 

Fagus _____ . _____ -- ________ . ____ • ___ -____ - 13 

Ficus .. __ ---------- ____ ------ ________ .. ___ 12,13 

planicostata •. ______ ------ ______ ------- 12 

fish ___ ------------------------------------ 30,32 

Fremontia •. ___ ------ _ ------- ___ ---------- 26 

gastropods ______ ----------- 12, 16,26,27,28,36,41 

Gleichenitdites senonicus ____ • ___________ -_- 13, 26 

Glypterpes veternus __________ -------- ____ _ 26 

GrangereUa. _. _______ • _____ • ____ . _______ . _ 26 

GuthOrliBporites ____ • _______ • _ _ _ _ _ __ _ _ __ _ _ _ 12 

Haplomylus speirianus .• ------------------ 28 

Harrisichara _. ________ . ____________ .• ____ • 26 

Hemicyprinotus watsoensfs _ • _____________ • 32, 36 

Hymenozonotriletes reticulatus. ______ • ____ • 12 

Hypolagus ••. ___ . _______ . ________________ • 37 

Hyracotherium vasacciense. __________ .-.--- 28 

insects. __ • __ •. _____________________ • ___ -. 32 

Juglans ••••• _ •• ___________ •• _____________ • 26 

Kurtzfpites. ______________________ . _. ____ • 13 

~:L~~~~~~~~~~~~~~~:~~~~~~~~~~~~-ii:i6. 32, !! 

Lepisosteus. _______________ •• ____ • ________ 26, 28 

51 
52 

Fossils-Continued Page 

Leporidae .. ----------------· .... ··------_ 37 

Ly:Jodium kaulfussL._____________________ 37 

Maedleriella ... -_ ...... __________ . ____ . ___ . 26,27 

mammals _____ . ___ ... ______ . ___ ..... ______ 6, 41 

1\ifeniscotherium. __ • _ .. ______ . ___________ .. 27 

priscum _____ -----·-·--· ------------. __ 26 

Metasequoia occidentalis_____________________ 13 

mollusks •.•• ------------- _____________ 28, 32,41 

Momipites________________________________ 13 

tenuipolus. __ .• _____________ . ________ . 13 

1\ifonocolpopollenites. _ ..• _ .. ___ . ____ .. __ __ _ 13 

Monoletes .. -_.- --- _____ • ___ .•. ___ . _ __ _ _ __ _ 12 

major. __ . _________ . ___ ..•. __ .. ______ ._ 12 

Monosulcites minimus _____ ---··-·- __ _____ 12 

Multiporopollenites. __ .... _ _ _ _ _ _ _ __ __ ____ _ 12 

Myrica torreyL .. ________ ... _________ . __ __ _ 12 

Neoraistrickia .•...• __ •. ____________ . _ __ __ _ 12 

Nyssoipollenites ___ _______________________ . 13 

Omalodiscus __ • ___ • _________ . ___ .• _____ . _ _ 26 

Oreoconus. _. _______________ . _. __ • _____ 26, 28,32 

planispira ___ __ • ____ . ____ . _. _ __ _ _ __ __ _ 36 

Osmundacidites. _______ .__________________ 12 

ostracodes .. _-.-- ... _____________ .. _ 26, 27, 32,36 

Pachysandra ___ -- .•.. ____________ .________ 13 

Paleoaster inquirenda. _____ . _. ___________ . 12 

Parasporia ____ . ---- .. -~ ____ . _____________ . 26 

Periporopollenites __ •. __ • ___ .. _ .. _. ____ . _ _ _ 13 

Phvsa ____ --------- __ .• ___ .. ______________ 12,28 

bridgerensis. ___ •.•. ____ _ ___ _ _ __ __ _____ 26 

pleromatis •. ___________ .. _ --. __ ----..• 26,32 

Picea. __ • _____ . _ •. _ ••• __ • ____ . ___ . ___ •. _ _ _ 13 

Pinuspollenites ••. ·-------- --------------- 13 labdacus ____________ • __ . __ . ___ . ___ • _ _ _ 12 

Pistillipollenites .•.•. _ .. _ .•.. ______________ 26 

Pityosporites ___ .... ____ .• __ . ____________ . _ 12, 13 

labdacus. __________ .... __ •. ________ .. _ 12 

Planor bidae •• _. _ . __ . __ .. ____ . _ .. _______ . . 28 

Platanus raynoldsi.. _ • __ • ____ • ____ . _ _ _ _ _ _ _ 13 

Platycarya_. ____ ._. _______ .. _. __ ... ___ .___ 26 

Plesielliptio ....•.. _____ •. ____ • ___ -~- _ __ __ _ 32 

Podocarpidites biformis____________________ 12 

pollen._. __ ---.. __ . _________ .. _________ 11, 26,27 

Pollenites (Tricolporopollenites) cognitus.. 12 

Procyprois ravenridgensis .. __ .• ____ • _______ · 32, 36 

Proteacidites. __ •. ---- __ __ __ __ ____ __ _ _ __ _ _ _ 12 

callosus ___ _ .. ________________ .• _ _ __ __ _ 11 

retusus ________________________________ 11,12 

Protophyllocladus subintegrifolius_ •. ___ . __ • 12, 13 

Pseudocypris _____ ___ .. __________ .... __ . 26, 32,36 

pagei. .•. ----.. ______ . --- ___ -~- _______ 26,27 

Pterocarya. ----•. ----.. ------ ____________ • · 26 

Quercoipollenites henrici _________ . ___ . __ • _ _ 12 

rays_--------- __ -- ____________ -----_______ 32 

Retitricolpites ______ .• __ __ __ __ __ _____ ___ __ _ 26 

vulgaris •... __ ---. __________________ ••. 26 

Rhamnus._------ __ ------•. ______ ------•. _ 13 

Salicoidites ____ _______ -------------- _ _____ _ 13 

Schizaeoispnrites pseu,dadorogensis__________ 12 

Selaginellites ariadnae_____________________ 12 

Sequoia reichenbachL. -------------------- 12 · Smilacipites ____ ______________________ •. _ _ _ 12 

snakes •.... ---- __ ---- ____ .. _______________ 32 

Sphagnumsporites setereoides __ • _ ~ __ . ____ ~ _ 12 

spores •• ---.. _. __ . _________ ------ _________ 11,26 

Sporites arcifer __ _ .. __ __ __ __ __ __ __ __ __ ___ _ _ 26 

Sporopollis ______ ___ -~ ____ __ __ __ ____ __ _ ____ 12 

Sterioisporites •. ____ •. ______ ...• ____ __ _ __ _ _ 12 

Taxodiaepollenites hiatus ___________ ••• ____ 12 

Taxodium •. _. _ .• ______________ .. ____ __ ___ 26 

teeth. _________ .. __ .. _________ -------_____ 27 

Triceratops _____ ._._ .. ____ ._ .. _--._. __ .. --

Tricolpopollenites kruschi contortus ••• ___ .. microhenricL. _. ________ . __ . ___ • ___ • _. 

microreticulatum. __________ . _ ..•.. __ • _ 

Tricolporopollenites kruschL .• _. ___ • _ •• _ •. 

kruschi 'J)Beudolaesus •• _____ ---- __ ..... Triletes. _______ • _____ • ___ • __ . _______ • _ ••• _ 

Triplanosporites sinuosus __ • _. _. _. ______ •• 

Triporopollenites robustus ___ . __ ... _ .• ____ _ 

12 

12 

13 

13 

13 

12 

12 

12 

13 

INDEX 

Page 

Fossils-Continued 

Trivestibulopollenites betuloides ____ . ____ . _. 12 

Ulmaceae .. -------------------- __ --------- 26 

Ulmipollenites undulosus ____ _ . ___ .. __ __ __ _ 13 

Ulmus ___________ .. _____ • __ ---- ______ .. ___ 26 

Valvata ____ ... _ -- ______ ... _____ .. __ -- ____ _ 28 

vertebrates •..... _____ . __ ---- __ . ___ . 12, 26, 37,41 

Zelkova. ___ .. __ -------- __ ---- _______ . _____ 13,26 

Fowkes Formation _____ -------------- _____ 16, SS, 41 

Bulldog Hollow Member ______________ 34,36,41 

distribution and thickness____________ 35 

lower contact .. ______ .. _____ ..... _____ 35 

rocks included _______ . _____ ._ .. ____ .. _ 35 

type section. _________________ ._______ 35 

fossils and age____________________________ 86 

Gooseberry Member ___________________ 34,85, 41 

distribution and thickness____________ 36 

rocks Included________________________ 36 

type section. _____________ ._._._______ 36 

name and usage .... ---------~-:__________ SS 

origin ______ . ______________________ ._______ 87 

Sillem Member.-------------------- 22,84,37,41 

distribution and thickness____________ 34 

rocks Included _________ ------_________ 34 

type section. _______ .-- ____ .. _. ____ .. _ 34 

subdivisions used here .• ------------------ 84 

tectonic implications______________________ 87 

Frontier Formation ___________________________ 10,23 

G 

Gannett Group _______________________ -----.-_ 11 

Gazin, C. L., written communication _________ 27,37 

Gooseberry Member, Fowkes Formation. __ 34, 85,41 

Gooseberry Springs ____ -------------------___ 35 

Green River Basin ________ ... 2, 5, 12, 26, 31, 32, 39,41 

Green River Formation______________________ 2, 

5, 14, 16, 18, 19, 20, 27, 28, 35 

Angelo Member _________________ 20, 28, 30,81, 39 

distribution and thickness. ____ ._. __ ._ 32 

type exposure __________ .. _____________ 31 

Fossil Butte Member.-------------- 20, 28,90, 39 color _____ .... _______________ . ______ .__ 30 

distribution and thickness____________ 31 

lower contact ______ ------------------_ 31 

rocks included _______________ ..•.... _. 30 

type section and exposures. ____ ... _.- 30 

fossils and age____________________________ S! 

lithologic heterogeneity_ .. _. ___ . ___ ... ____ SO 

name and usage__________________________ SO 

origin ________________ .. _____ . __ .__________ S! 

subdivisions used here____________________ SO 

tectonic implications_____________________ 98 

Gros Ventre Range___________________________ 2 

H 

Hams bench mark .•. ------------------------- Hams Fork _______________________ 5, 6, 7, 10, 14, 23,31 

Hams Fork Conglomerate Member, Evanston 

Formation _____________________ 6, 12,16 

Hams Fork Plateau .• --------------------- 20,22,32 

Hayden, F. V., quoted .• ------------------ 14, 16,30 

Higham GriL.-----------------------------~ 17 Hilliard Formation _________________ ·__________ 10 

Hoback. ___ .----... _ ............ __ ---,-----.. - 39 

Hoback Formation .. ------------------------- 5,39 Hogback ridges _________ . ___ . ____ .. __ . ____ ---- 7 

Hoxsey Oil Co. 1 Government test_ __________ 10,11 

Idaho-Wyoming thrust belL_________________ 2 

Introduction. _______ . ____ --- _______ ---.• ----- ! 

K 

Kemmerer __ ••• ------------------------------ 2, 30 

Kemmerer quadrangle ... 2, 6, 13, 20, 22, 28, 30, 

31, 32 

Knight. ____ . ____________ .. _.----. _____ .•.. --. 28 

Knight Formation ______________ 10, 16, 19, 26, 33 

L 

La Barge Member, Wasatch Formation ...... . 

Lake Creek. __ • __ ------- ___ .---_----------.-- Lance Formation .... __ . _____ . ______ . ___ ._. __ _ 

Page 

39 

24 

12 

Lazeart syncline _______ ._ ... ___ .. ________ .____ 14 

Lens-shaped channels. ___ .. ___ . ___ .. ______ .__ 28 

Lenses _____ . ___ . ___ .. --- ___ .. ---- ____ .. __ ._ .. _ 6 

Leopold, E. B. written 

communication __________ 12, 14, 26, 39 

Lewis Formation ... -------------------------- 12 

Lignite. ___ .-.-.--------.------------------·-- Lithology, Evanston Formation, Hams Fork 

Conglomerate Member ____ .. ____ _ 

main body_. __ • ___ ._ ... ___ .---.. _____ 9 

Green River Formation__________________ SO 

Wasatch Formation, basal conglomerate 

member.------------------------- 17 

Bullpen Member_____________________ 21 

lower member_. __________ . ____ . ___ .__ 17 

main body_. __ • ____ . _____ .. ____ ._____ 18 

mudstone tongue------------------___ 20 

sandstone tongue--------------------- 20 

Tunp Member________________________ 23 

Little Muddy Creek·------------------------- 10 

Lower contact, Evanston Formation. __ ._____ 10 

Green River Formation, Fossil Butte 

Member.......................... 31 

Wasatch Formation, Bullpen Member.. 22 

main bodY---------------------------- 20 

Lower member, Evanston Formation ________ 6,11 

Wasatch Formation _______________________ 17,!7 

M 

Madison Limestone___________________________ 34 

Magnetite. _____ -----··--·-··-···------······· 35 

Main body, Evanston Formation ____________ 6,9, 12 

Wasatch Formation ____________________ 17, 1B,e7 

Medicine Butte fault. .. ______________________ 6 

Morely bench mark ______ . _____________ .. ___ .. 7 

Morgan Canyon. ____ .. _______ . _____________ .. 17 

Moyer .• ___ . _____ . ____________ . ________ ... __ ._ 7 

Mudflows __________ ..... ____ ... _____________ ._ 29 

Mudstone tongue, Wasatch Formation._. __ 17, 20, SB 

N 

National Cooperative Refinery Association, 

1 Arthur H. Linden oil test_______ 9,11 

1 Government-Larsen oil test. __________ 9, 11,18 

New Fork Tongue, Wasatch Formation._. ___ 39,41 

North Bridger Creek _________________________ 17,18 

Norwood Tuff ________________________________ 37,41 

Nugget.. ____________________ .. ______________ . 13;17 

Nugget Sandstone ____________________ 2, 17, 18, 23,28 

0 

Origin, Evanston Formation_________________ 18 

·Hams Fork Conglomerate Member... 9 

Fowkes Formation_______________________ 87 

Green River Formation__________________ SS 

Wasatch Formation ______ ..... __ ----..... !8 

sandstone tongue ... --.... -......... -- 20 

Oyster Ridge .•.. --.---.-------.-------------- Oyster Ridge barrier ___________ · _____ · _______ 5,10,41 

p 

Paris thrust fault.-------·--------------------- 9,14 

Peck, R. E., written communication_________ · 27 

Phosphoria Formation .•.•. ------------------- 11 

Pink Butte •. -------------------------~------- 31 

Pole Creek ••• -------------------------------- 24 

Preuss Redbeds •• ___ ------.. ----------------- 23 

Purpose ofreport.---------------------------- S 
R 

Relations, generaL---------------------------

regionaL .••. ------------------------------ Evanston, Hoback, and Wasatch 

Formations ______ --------- __ -_-- __ 

Fowkes Formation, Norwood Tuff, 

Bridger Formation. _______ -- __ --_ 

lower strata of the Wasatch._-- __ -_---

tongues of tho Wasatch and Green 

Page 

5 

S8 

S9 

41 

S9 

River Formations________________ 89 

Rock Creek Ridge ____ -------------------- 24, 27,29 

Roy Steele 1 Government well -------------- 19,31 

Rubey, W. W., oral communication___________ 17 

s 

Sage _______________________________ 2, 16, 22, 29, 35,36 

Sage quadrangle. ______ 2, 11, 18, 20, 22, 30, 31, 32, 35, 37 

Salt Lake Formation _________________________ 37,41 

typo locality _______ -- __ ------------------- 37 

Sandstone tongue, Wasatch Formation. ___ 17, 20,28 

S!llem Member, Fowkes Formation _____ 22, 84, 37,41 

S!llem Ridge. _____ -_-_- __ -------_------------ 22 

Sohn, I. G., written communication .• -------- 32,36 

Sorting, Evanston Formation _____ ----------- 6 

Wasatch Formation, basal conglomerate 

member _________ ----------------- 17 

Tunp Member________________________ 23 

South Fork, Twin Creek _____________________ 28,31 

Spring Creek.------- __ -- ______ -- ______ -----_- 12 

St. Charles Limestone, Worm Creek Quartzite 

Member__________________________ 9 

T 

Taylor, D. W., written communication________ 12, 

26, 32, 36, 41 

Tectonic implications, Evanston Formation.. 14 

Fowkes Formation.- __ --_----_---_------- 87 

Green River Formation__________________ 88 

Wasatch Formation_______________________ 29 

Thaynes Formation__________________________ 17 

Thaynes Limestone __________________ --------- 23 

Thickness, Evanston Formation______________ 6 

Evanston Formation, main bodY--------- 10 

Wasatch Formation.--------------------- 19 

basal conglomerate member___________ 17 

sandstone tongue_____________________ 20 

Trail Creek ______ -----_--- ______________ ---___ 12 

INDEX 

Page 

Tunp Member, Wasatch Formation___________ 17, 

19, 20, 22, 28,29, 38 

Tunp Range _________ ------------- 5, 10, 19, 20, 22,31 

Twin Creek, South Fork _____________________ 28,31 

Twin Creek Limestone ____________________ 10, 17,23 

Type area, Wasatch Formation, Tunp Member.------------------------------ 23 

Type exposure, Green River Formation, 

Angelo Member___________________ 31 

Type locality, Salt Lake Formation ______ ~___ 37 

Type sections ____ ---------------------------- 41 

Evanston Formation, Hams Fork Conglomerate Member _______________ _ 

Fowkes Formation, Bulldog Hollow Member_- __ -- ________ -________ -_______ 35 

Gooseberry Member__________________ 36 

Sillem Member_______________________ 34 

Green River Formation, Fossil Butte 

Member _________ -----____________ 30 

Wasatch Formation, Bullpen Member____ 21 

u 

Uinta Mountains ______ --------------------- 5, 20,31 

uplift ______________ ----------------------- 32 

Unconformity, Evanston Formation_________ 10 

. Wasatch Formation, lower member_______ 17 

v Varves. ____ --- __ ~-___________________________ 32 

Veatch, A. C., quoted ___________________ 5, 16,21,33 

w 

Wasatch. ______ ---- ______ -____________________ 19 

Wasatch facies of Spieker ____ ------------ ____ _ 

Wasatch Formation ________________ 2, 5, 6, 9, 14, 31,37 

basal conglomerate member______________ 17 

color__________________________________ 17 

fossils and age ________________ ----_--_ 27 

lithology_____________________________ 17 

sorting_______________________________ 17 

thickness ____ -- __ ---- ________ ------___ 17 

Bullpen Member _____________ 17,21,28,29,31,32 

bedding _________ -- _______ --- ______ --_ 22 

color _________ ---------------- __ ---____ 21 

distribution and thickness .• __________ 22 

faulting ____________________________ --- 22 

fossils and age _____________________ --- 28 

lithology __________________ ------_____ 21 

Wasatch Formation-C.ontinuod 

Bullpen Member-Continued 

53 

Page 

lower contact __________ ------------___ 22 

type section__________________________ 21 

Chappo Member. ________________________ . 39 

La Barge Member________________________ 39 

lower member____________________________ 17 

color ____________ --- __ ---______________ 17 

distribution and thickness .. -----.----- 18 

fossils and age________________________ 27 lithology ________ --___________________ 17 

unconformity __________ -------------__ 17 

main body ___________ ---------------- _____ 17,18 

color ___________ --- __ ---_--- ________ --_ 18 

distribution and thickness____________ 19 

fossils and age ___ --------------------_ 27 lithology_____________________________ 18 

lower contact ________ ----------------- 20 

mudstone tongue. ________________________ 17, tO 

color__________________________________ 20 

fossils and age_~ ___ ~-_________________ 28 

lithology_._____________________________ 20 

name and usage__________________________ 14 

New Fork Tongue ________________________ 39,41 

origin_____________________________________ 28 

sandstone tongue _________________________ 17,20 

fossils and age________________________ 28 

lithology_____________________________ 20 

origin_________________________________ 20 

thickness_____________________________ 20 

subdivisions used here____________________ 16 

tectonic implications_____________________ 29 

thickness_________________________________ 19 

Tunp Member ___________ 17, 19, 20, 22, 29, 38 

channels ____ --- ______ ---- ______ ----___ 24 

distribution and thickness____________ 24 

fossils and age._______________________ 28 

lithology_____________________________ 23 

sorting ______ -- ______ --- ___________ -__ 23 

type area_____________________________ 23 

Veatch's subdivisions_____________________ 16 

Wells Formation _____________________ 11, 17. 20, 23 

Whitney Canyon----------------------------- 6 

Wolfe, J. A., written communication _________ 11, 14 

Worm Creek Quartzite Member, St. Charles 

Limestone________________________ 9