Lithology and Subdivisions of 

the , . „ - nj, Jurassic ~ - -' - - - - Stump - - - - JL": •- Formation - - - - -

in Southeastern Idaho and 

dning

iGEOLOGlCAL SURVEY PROFESSIONAL PAPER 1035-C

Lithology and Subdivisions of 

the Jurassic Stump Formation 

in Southeastern Idaho and 

Adjoining Areas

By GEORGE N. PIPIRINGOS and RALPH W. IMLAY

UNCONFORMITIES, CORRELATION, AND NOMENCLATURE OF SOME 

TRIASSIC AND JURASSIC ROCKS, WESTERN INTERIOR UNITED STATES

GEOLOGICAL SURVEY PROFESSIONAL PAPER 1035-C

Marked rapid lateral changes in lithology, 

fossil content, and thickness of the Stump Formation 

are due principally to erosion associated with the 

Cretaceous (K) and Jurassic (]-4) unconformities

UNITED STATES GOVERNMENT PRINTING OFFICE, WASHINGTON 1979
UNITED STATES DEPARTMENT OF THE INTERIOR 

CECIL D. ANDRUS, Secretary

GEOLOGICAL SURVEY 

H. William Menard, Director

Library of Congress Cataloging in Publication Data

Pipiringos, George Nicholas, 1918-

Lithology and subdivisions of the Jurassic stump formation in southeastern Idaho and adjoining areas.

(Unconformities, correlation, and nomenclature of some Triassic and Jurassic rocks, western interior

United States) (Geological Survey Professional Paper 1035-C) 

Bibliography: p. 25

1. Geology, Stratigraphic Jurassic. 2. Geology Idaho. 3. Geology The West. 4. Petrology Idaho. 

5. Petrology-The West. I. Imlay, Ralph Willard, 1908-joint author. II. Title. HI. Series. IV. Series:

United States Geological Survey Professional Paper 1035-C. 

QE681.P49 551.7'6 78-1687

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

Washington, D.C. 20402 

Stock Number 024-001-03150-7
CONTENTS

Page

Abstract .................................................................................................................................................... Cl

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

Stump Formation ..................................................................................................................................... 1

Curtis Member .................................................................................................................................. 3

Redwater Member ............................................................................................................................. 9

Unconformities ......................................................................................................................................... 13

Stratigraphic sections ..................................................................................................•••••••••••••••••••••••••••••• '5

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

ILLUSTRATIONS

Page

FIGURE 1. Index map of the Western United States, showing distribution of Stump Formation ....................................................... C2

2. Index map of southeastern Idaho, western Wyoming, and northern Utah, showing location of measured sections of the

Stump Formation ....................................................................................................................................................... 4

3. Index map of southeastern Idaho and adjoining areas showing approximate margin of the Redwater Member of the Stump

Formation ................................................................................................................................................................... 6

4. Columnar sections of the Stump Formation from Wolverine Canyon, Idaho to Watton Canyon, Utah .......................... 7

5. Columnar sections of the Stump Formation from Blacktail Creek, Idaho to Telephone Creek. Wyoming ....................... 8

6. Columnar sections of the Stump Formation from Sheep Creek. Wyoming to Peoa, Utah ............................................... 9

7-16. Photographs showing:

7. Contact of the Stump Formation with the Preuss Sandstone at Indian Camp Hollow (loc. 3, fig. 5) .................. 11

8. Stump Formation at McCoy Creek (loc. 4, fig. 5) ...........................................................................•••••••••••••••••••••• 12

9. Sandstone unit of the Curtis Member at the start of Corral Creek trail (loc. 5, fig. 5) ......................................... 13

10. Type area of the Stump Formation .................................................................................•.......••.••••••••••••••••••••••••••• 14

11. Contact of the Stump Formation with the Preuss Sandstone at Stump Creek (loc. 8, fig. 4) ............................... 15

12. Ephraim Conglomerate, Stump Formation and Preuss Sandstone at Telephone Creek section (loc. 9, fig. 5) ..... 16

13. Ephraim Conglomerate, Stump Formation. Preuss Sandstone, and Twin Creek Limestone near junction of Sheep

Creek with Greys River (loc. 10, fig. 6) ......................................................................................... — ..-•. — ••••••• 17

14. Bedding features typical of the Curtis Member, sandstone unit of the Stump Formation ..................................... 18

15. Stump Formation on old U.S. Highway 30 near Evanston, Wyoming (loc. 17, fig. 6) .......................................... 20

16. Near view of contacts shown in figure \5B ...................................................................—•......—-•—•••••••••••••••••••••• 22

TABLE

——————————— Page

T\BLE 1. Thicknesses of the Stump Formation and its subdivisions

UNCONFORMITIES, CORRELATION, AND NOMENCLATURE OF SOME TRIASSIC 

AND JURASSIC ROCKS, WESTERN INTERIOR UNITED STATES

LITHOLOGY AND SUBDIVISIONS OF THE JURASSIC 

STUMP FORMATION IN SOUTHEASTERN IDAHO 

AND ADJOINING AREAS

By GEORGE N. PIPIRINGOS and RALPH W. IMLAY

ABSTRACT

The Stump Formation (called Stump Sandstone in previous reports) 

comprises the latest marine Jurassic beds near the Idaho-Wyoming border 

and adjoining parts of Utah, and it is divisible into two members. The lowest 

member is nearly identical with the Curtis Formation of Utah, and the 

upper member closely resembles and contains the same fossils as the sandy 

facies of the Redwater Shale Member of the Sundance Formation of 

Wyoming. The Stump Formation is herein divided from about the Salt 

Lake City area north through the Wyoming-Idaho thrust belt and east in the 

Uinta Mountains as far as northwest Colorado into the Middle Jurassic 

Curtis Member, which is reduced in stratigraphic rank in these areas from 

formation, and the Upper Jurassic Redwater Member, which is newly 

assigned to the Stump in these areas. The stratigraphic and geographic 

relations of the two members show that they were deposited in different seas 

that covered different areas, that erosion occurred before and after 

Redwater deposition, and that variations in the thicknesses of the members 

are in part depositional but are due principally to truncation of stratigraphic 

units directly under the Cretaceous (K.) and Jurassic (J-4) unconformities.

INTRODUCTION

This report discusses the lithologic characteristics, subdivisions, areal distribution, ages, and correlations of the 

latest marine Jurassic beds, called the Stump Formation, as 

exposed along the Wyoming-Idaho border and nearby in 

northern Utah. One principal and two supplementary 

reference sections are herewith established, and 18 

stratigraphic sections are described, based on field studies by 

the writers in 1975 and 1976. The regional distribution of the 

Middle and Upper Jurassic Stump Formation in the 

Western United States, shown in figure 1, is nearly the same 

as that of the Middle Jurassic Twin Creek Limestone as 

shown by Imlay (1967, p. 54). Locations of measured 

stratigraphic sections as well as localities mentioned in the

text are shown in figures 1, 2, and 3. Stratigraphic sections 

described at the end of the report are shown graphically in 

figures 4, 5, and 6. Localities in figure 4 lie west and localities 

in figures 5 and 6 lie east of the line representing the 

approximate western margin of the Redwater Member of 

the Stump Formation shown in figure 3.

Figures 7 through 16 are representative of the lithologic 

features and general appearance of the Stump Formation 

throughout the study area.

Thickness of the Stump Formation and its various 

subdivisions are summarized in table 1 from measured 

sections described in the section entitled "Stratigraphic 

sections."

STUMP FORMATION

The term Stump Formation includes the latest Jurassic 

marine sandstone, limestone, sandy shale, siltstone, and 

claystone overlying the red Middle Jurassic Preuss 

Sandstone in westernmost Wyoming, southeastern Idaho, 

and adjoining parts of northern Utah. Stump Formation is 

used in place of Stump Sandstone because sandstone is not 

the predominant rock type in all sections and because several 

other kinds of sedimentary rocks are present in most 

sections. The formation occurs in an area extending from the 

Blackfoot Mountains southeast of Idaho Falls eastward to 

the Hoback Range and Wyoming Range in western Wyoming and extending from the Snake River Range southward at 

least as far as Woodruff and Peoa in north-central Utah (fig. 

2). Its distribution coincides mainly with a belt of 

overthrusting that extends along the Wyoming-Idaho 

border southward into north-central Utah, but it occurs also 

in the Uinta Mountains in northeastern Utah east of the

Cl
C2

48'

46'

44'

42'

40'

38°

36

34'

32'

30'

128 C

TRIASSIC AND JURASSIC ROCKS, WESTERN INTERIOR UNITED STATES 

124° 120° 116° 112° 108° 104° 100' 96'

/

--CANADA

MONTANA

— — -—_ __ j Redwater Shale Member 

'N/Sundance Formation

SOUTH DAKOTA

T

NORTH DAKOTA

I——————————————————-4-

/ Type section '

I--——, _ r

NEBRASKA '

i i

L___.__ I

KANSAS

I OKLAHOMA

TEXAS

500 1000 KILOMETERS

i i i __i

FIGURE 1.— Distribution of Stump Formation (patterned) and location of type area, locality, and section, respectively, of Stump Formation, 

Curtis Formation, and Redwater Shale Member of Sundance Formation, Western United States.

overthrust belt. The formation ranges in thickness from 28 m 

to at least 120 m and thins from Idaho irregularly eastward 

and northward (table 1). Lithologically, the Stump Formation consists of a variety of marine sedimentary rocks that 

apparently change markedly within relatively short distances, as described by Mansfield and Roundy (1916, p. 76, 

81); Mansfield (1927, p. 99-101; 1952, p. 38); Gardner (1944); 

Thomas and Krueger (1946, p. 1269, 1276, 1278, 1285);

Rubey (1958, 1973); Oriel (1963); Cressman (1964, p. 52,53); 

Staatz and Albee (1963, 1966); Pampeyan and others (1967), 

Albee (1968); Schroeder (1969); and Rubey, Oriel, and 

Tracey(1975, p. 5).

These irregular lateral variations in facies and thickness in 

the Stump Formation have hitherto been perplexing. In 

places the Stump resembles only the Curtis Formation of the 

San Rafael Swell in east-central Utah; in other places the
UNCONFORMITIES, CORRELATION, AND NOMENCLATURE C3

Stump mainly resembles the Redwater Member of the 

Sundance Formation of Wyoming. Elsewhere, as in the 

western part of the Uinta Mountains, the Stump Formation, 

as used by Thomas and Krueger(l 946, stratigraphic sections 

1, 2, 3, p. 1276-1285), resembles both the typical Curtis 

Formation and the Redwater Member. It is now recognized 

(1) that the lower part of the Stump Formation throughout 

the Uinta Mountains is identical with the Curtis Formation 

of the San Rafael Swell and (2) that the upper part of the 

Stump is closely similar to the Redwater Member of the 

Sundance Formation farther to the north and to the east in 

Wyoming and northern Colorado (fig. 1). Furthermore, in 

the eastern part of the Uinta Mountains, the Curtis 

Formation, as used by Thomas and Krueger (1946, 

stratigraphic sections 4, 5, 6, p. 1276, 1287-1290), is identical 

with the Stump of the western Uintas, and likewise includes 

two members of which only the lower is equivalent to the 

type Curtis Formation. It seems best, therefore, to extend 

the name Stump Formation to all of the Uinta Mountains.

Similarly, the Stump Formation along the IdahoWyoming border includes beds in its lower part that are 

nearly identical with the Curtis Formation, and it includes 

beds in its upper part that closely resemble the silty to sandy 

facies of the Redwater Member of the Sundance Formation. 

As these lithologic subdivisions are not very thick, the 

Stump is at present the practical unit for mapping purposes, 

and accordingly it is herein retained as a formation that is 

divided into the Curtis Member below and the Redwater 

Member above.

At most places, the Stump Formation rests with apparent 

conformity on reddish beds of the Preuss Sandstone. 

Locally, however, that contact is very sharp, as at Blacktail 

Canyon, Indian Camp Hollow (fig. 7), McCoy Creek (fig. 8), 

Shale Creek, and on old U.S. Highway 30 (abandoned) east 

of Evanston, Wyo. The contact is gradational within several 

centimeters at Telephone Hollow and La Barge Creek and is 

gradational within about a meter at Sheep Creek near Greys 

River. In some places, the contact is marked only by an 

upward color change from red to gray and may even show 

intertonguing as at Corral Creek (fig. 9) and Fish Creek. In 

other places, as at Indian Camp Hollow, McCoy Creek, and 

Shale Creek, the contact is marked also by a slightly 

irregular surface and by an abrupt upward change from 

fine-grained red sandstone to hard, thin- to medium-bedded 

gray sandstone. The regional characteristics of the Preuss 

Sandstone have been discussed by Mansfield (1927, p. 98, 

99) and Imlay (1952, p. 1735, 1739).

The Stump Formation within the area of extensive thrust 

faulting in western Wyoming is overlain sharply and 

unconformably by continental beds of Early Cretaceous or 

locally younger ages (Mansfield, 1927, p. 101). In the Uinta 

Mountains the Stump is overlain by Upper Jurassic beds 

that have been assigned to the continental Morrison 

Formation and by unnamed Lower Cretaceous beds 

(Stokes, 1944, p. 969; 1955, p. 84; Hansen, 1965, p. 85, 86).

CURTIS MEMBER

The Curtis Member of the Stump Formation attains 

thicknesses of 76-113 m in the area between Stump Peak and 

Fish Creek but thins irregularly northward toward the 

Snake River, and it thins considerably eastward in western 

Wyoming to as little as 9 m in the Wyoming Range (table 1). 

Its lithologic and stratigraphic resemblance to the Curtis 

Formation of the San Rafael Swell shows that its equivalents 

extend considerably farther south in Utah than does the 

overlying Redwater Member whose southernmost exposures are in the Uinta Mountains.

The Curtis Member consists of two lithologic units, the 

lower dominantly sandstone and the upper chiefly clay shale. 

(See figs. 4 and 5.) The lower or sandstone unit is generally 

ledgy or cliff forming (figs. 7, 8, 9), ranges in thickness from 

6-77 m, thins northward and eastward, and is characterized 

by glauconitic, thin- to thick-bedded sandstone interbedded 

with some sandy siltstone and silty shale. Most of the 

sandstone beds are fine to very fine grained, but some are 

medium grained and many are silty. Ripple marks are 

common and some low-angle crossbedding is present. 

Predominant colors are greenish gray to brownish gray, but 

locally some beds are red and resemble sandstone in the 

Preuss Sandstone (loc. 12, fig. 4; loc. 5, figs. 6, 9). Many 

bedding interfaces are characterized by tracks and furrowed 

trails, by round to flat shale pebble impressions, by a few 

cubical salt casts as large as 6 mm, and locally by marine 

bivalves such Meleagrinella, Ostrea, and Camptonectes. At 

Watton Canyon (loc. 16, fig. 2) chert and shale pebbles and 

fragments of Pentacrinus are common. This also is true of 

conglomeratic beds near the base of the Curtis in the San 

Rafael Swell and in the Uinta Mountains.

The upper or shale unit of the Curtis Member varies 

considerably and irregularly in thickness from 35 m at Fish 

Creek (loc. 12, fig. 4) and possibly 73 m east of Evanston (loc. 

17, fig. 6) to a feather edge from these places both eastward 

and southward (figs. 4, 5, 6). The unit thins northward 

slightly and eastward considerably from exposures on 

Stump Creek and Fish Creek. The unit forms the top part of 

the Stump Formation at Wolverine Canyon (section 1), 

Stump Peak (section 7), and Fish Creek (section 12), but is 

absent at places where the Redwater Member is thickest in 

the Wyoming Range, as at Telephone Creek section (section 

9), Shale Creek (section 11), and La Barge Creek (section 

14). It has an apparent thickness of 73 m east of Evanston 

(section 17), but in that section the beds are vertical, rest 

sharply on the red Preuss Sandstone instead of on the lower 

sandstone unit of the Curtis, and consist mostly of soft 

claystone that could easily be duplicated in part by folding or 

faulting. The lower llm, containing some sandy beds at 

bottom and top, could conceivably be equivalent to the 

lower sandstone unit. Against such a possibility is the fact 

that a ledgy to cliff-forming sandstone is present at the base 

of the Stump Formation in every section along or near the 

Idaho-Wyoming border.
Indian Camp Hollow 3

Blacktail Canyon^T * 2

NAMES OF S

1. Wolverine C

2. Blacktail Cr

3. Indian Cam

4. McCoy Cre

5. Corral Cree

6. Tincup Cree

7. Stump Pea

8. Stump Cree

9. Telephone 

10. Sheep Cree

11. Shale Cree

12. Fish Creek

13. Salt Canyo

14. La Barge Cr

15. Fort Hill

16. Watton Ca

17. Evanston

18. Peoa
112°

FIGURE 2.-Location of measured sections of the Stump Formation in southeastern Idaho, western Wyoming, and

northern Ut
C6

44°,

113°

TRIASSIC AND JURASSIC ROCKS, WESTERN INTERIOR UNITED STATES

112" 111° 110°

42°

40°

109°

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(Type Curtis)

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100 KLOMETERS

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FIGURE 3.—Approximate margin of the Redwater Member of the Stump Formation (long-dashed line), southeastern Idaho and 

adjoining areas, based on lithology, unconformities, and occurrences of belemnites and ammonites. X, localities representing both 

Redwater and Curtis Members: +, localities representing only the Curtis Member.
UNCONFORMITIES, CORRELATION, AND NOMENCLATURE 

About 240 kilometers

C7

© ©

SALT Wasatch Fm 

CANYON (Eocenek

Ephraim \WOLVERINE 

CongCateXCANYON

Preuss 

Sandstone

(Middle 

Jurassic)

EXPLANATION

Sandy clay shale 

Silty clay shale 

Limy clay shale

P ° 01 

\°°<\

Conglomerate

Shaly sandstone 

Limy sandstone

OOolitic

X=Glauconitic

C=Crinoid

E=Echinoid

P=Pelecypod

R=Ripple marks

T=Trails

Sandy limestone 

Clay shale or Shaly limestone

claystone

© 

Limestone concretion Covered interval

<Z2> 

Chert nodule Gypsum nodule 50 KILOMETERS

FIGURE 4.—Columnar sections of the Stump Formation from Wolverine Canyon, Idaho, to Watton Canyon, Utah. Unconformities are 

represented by solid lines and presumably conformable contacts by dashed lines. *, fault contact. (See description of bed 6 in Wolverine 

Canyon section.)

The shale unit of the Curtis Member consists mostly of 

limy, greenish-gray to olive-green, soft, flaky to fissile 

claystone that contains some very thin platy sandstone beds, 

some fossiliferous, oolitic limestone slabs, and many large, 

flat, lenticular yellowish-gray limestone concretions that

weather nearly white. The limestone slabs contain oysters 

and crinoid stems, and the bedding surfaces of the thin 

sandstone beds bear tracks and trails. The base of the shale 

unit makes an abrupt but conformable contact with the 

underlying sandstone unit.
C8 TRIASSIC AND JURASSIC ROCKS, WESTERN INTERIOR UNITED STATES

About 100 kilometers

INDIAN CAMP 

Ephraim ConglomerateX HOLLOW

(Lower Cretaceous)

Preuss Sandstone 

(Middle Jurassic)

EXPLANATION 

Conglomerate Silty clay shale

O=Oolitic

X=Glauconitic

A= Ammonite

B=Belemnite

C=Crinoid

E=Echinoid

P=Pelecypod

R=Ripple marks

T=Trails

xl=Salt crystal casts

_:>IDAHO!B

o

PALE OR 

GRAYISH RED

Covered interval

^ 

Limestone concretion Chert pebble

50 KILOMETERS

FIGURE 5.—Columnar sections of the Stump Formation from Blacktail Canyon, Idaho, to Telephone Hollow, Wyo. Unconformities are 

represented by solid lines and presumably conformable contacts by dashed lines.

The shale unit is correlated with part of the Curtis 

Formation of Utah because (1) it is conformable with the 

underlying sandstone unit but unconformable with the 

overlying Redwater; (2) nearly identical greenish-gray shale

that contains light-gray limestone concretions occurs in the 

upper part of the Curtis Formation at Monks Hollow about 

30 km southeast of Provo, Utah (Baker, 1947); and (3) 

similar greenish-gray flaky shale occurs in both the upper
UNCONFORMITIES, CORRELATION, AND NOMENCLATURE C9

About 258 kilometers

// 1 Reported by Thomas and 

// Krueger (1946, p. 1282)

OOolitic 

X=Glauconitic 

A=Ammonite 

B=Betemnite 

P=Pelecypod 

R=Ripple marks 

W=Carbonized wood 

fragments

L-50

FIGURE 6.—Columnar sections of the Stump Formation from Sheep Creek, Wyo., to Peoa, Utah. Unconformities are represented by solid 

lines and presumably conformable contacts by dashed lines. Queried where correlation is in question.

and lower parts of the Curtis Formation at its type locality 

on the San Rafael Swell (Gilluly, 1929, p. 107, 108; Gilluly 

and Reeside, 1928, p. 79, 101).

The Curtis Member of the Stump Formation is assigned 

to the middle Callovian because (1) it unconformably 

underlies the Redwater Member of early to early middle 

Oxfordian age and (2) it overlies the Preuss Sandstone, 

which grades downward into beds of early Callovian age at 

the top of the Twin Creek Limestone.

REDWATER MEMBER

The Redwater Member of the Stump Formation is much 

less extensive than the Curtis Member. In southeastern 

Idaho the Redwater Member crops out north of the Snake 

River in the Snake River Range and in the southern part of

the Teton Range. South of the Snake River in Idaho it crops 

out in the Caribou Range in a belt from 19 to 24 km wide that 

extends from the Fall Creek area southeastward toward 

Thayne, Wyo. Its southernmost occurrence is in the Caribou 

Range. Belemnites have been reported from the top of the 

Stump Formation about 4 km southwest of Thayne on 

Smith Canyon and 2 km west of the forest boundary in the 

SE!/4 sec. 10, T. 6 S., R. 46 E., Idaho (U.S. Geological 

Survey Mesozoic loc. 12120). This occurrence needs confirmation because the Stump Formation is not shown at that 

location by Mansfield (1927, pi. 5). In western Wyoming the 

Redwater Member is present in the mountains bordering 

Greys River as well as farther east in the Wyoming and 

Hoback Ranges, but it has not been recorded from the west 

side of the Salt River Range.
CIO TR1ASSIC AND JURASSIC ROCKS, WESTERN INTERIOR UNITED STATES

TABLE \.-Thicknesses of the Stump Formation and its subdivisions 

[Thicknesses in meters, totals rounded; A, absent, queried where uncertain; C, covered; U, unknown]

Stump 

Redwater Member Curtis Member Formation

Numbered localities Sandstone Shale Total Shale Sandstone Total Total 

unit unit thickness unit unit thickness thickness

1. Wolverine Canyon ——— A A 

2. Blacktail Creek ———— 34 A 

3. Indian Camp Hollow — 18+ A

5. Corral Creek Trail — C C

7. Stump Peak ———————— A A

8. Stump Creek ——————— A A 

9. Telephone Creek ———— 54.5 A

11. Shale Creek ——————— 13.4 4

13. Salt Canyon ———————— A A

14. La Barge Creek ————— 11.3 5.6 

15. Fort Hill ————————— 23 3

17. Evanston —————————— 4.6 10.7

18. Peoa —————————————— 14.3 11.3

The Redwater Member ranges irregularly in thickness 

from about 15 to 55 m. At some places its uppermost beds 

are covered, and total thicknesses cannot be determined; for 

instance, at Blacktail Canyon, Indian Camp Hollow, Tincup 

Creek, and west of Fort Hill. Nonetheless, the available data 

suggest that the Redwater Member thins southward along 

the Wyoming Range in western Wyoming. 

Along the Idaho-Wyoming border and southward as far 

as Peoa, Utah, the Redwater Member consists of two 

lithologic units. The lower or shale unit is 2-1 1 m thick and 

consists of yellowish-gray to brown glauconitic chunky 

siltstone or claystone that is locally finely sandy and 

generally contains belemnites. Except for one occurrence at 

McCoy Creek (section 4) in Idaho, the lower shale unit has 

been definitely identified mainly on the flanks of the 

Wyoming Range in western Wyoming and in areas to the 

south near Evanston, Wyo., and Peoa, Utah. At Shale Creek 

(section 14) and La Barge Creek (section 15), the lower shale 

unit rests sharply on the sandstone unit of the Curtis 

Member and contains belemnites at its base, associated with 

many small, worn specimens of Gryphaea nebrascensis 

(Meek and Hayden). West of Fort Hill (section 16), the 

chunky lower shale unit of the Redwater Member contains 

belemnites but no gryphaeas and rests sharply on the flaky 

clay-shale unit of the Curtis Member. 

In addition to occurrences of Gryphaea at Shale Creek 

and La Barge Creek, small, worn specimens of Gryphaea 

nebrascensis occur together with belemnites in the Stump

0 19.8+ 44.2 64+ 64+ 

34 24.4 22.8 47 81 

18+ 21 24 45 63+ 

48 10.6 21.3 32 79 

U 7.3+ 55.4 63+ 63+ 

45 23.6 31.1 55 100

0 15.2 61 76 76 

0 30.5 69.2 100 100 

55 A 11.3 11 66 

34 2.7 6.1 9 43 

17 A 14.3 14 32 

0 35 77.7 113 113

0 A 41.1 41 41 

17 A 11.1 11 28 

26 1 10 11 37 

0 A 76 76 76 

15 73.1 A? 73 88 

25 29.3 12.5 42 67

Formation at the following U.S. Geological Survey 

Mesozoic localities:

16024. Basal part of Redwater Member on creek of 

Telephone Hollow 2 km above mouth of Deadman Creek, 

Afton quadrangle, Wyoming. 

16047. Unknown position in Redwater Member on White 

Creek 1 km upstream from bench mark 6758 and 91.4 m 

below waterfall SW. cor. NE!/4 sec. 30, T. 35 N., R. 117 

W., Bedford quadrangle, Wyoming. 

17897. Basal part of Redwater Member 1.2 km northwest of 

McCoy Creek, near center NW!4 sec. 6, T. 3 S., R. 46 E., 

Alpine quadrangle, Idaho. 

18183. From shale 9.1 m below top of Stump Formation 

near center of north line of NW!4 sec. 25, T. 3S., R. 45 E., 

Poker Peak quadrangle, Idaho. 

18185. From 36.6 to 61 m above base of Stump Formation, 

NW!4 sec. 1, T. 4 S., R. 45 E., Tincup Mountain 

quadrangle, Idaho. 

18187. From 61 to 71.6 m above base of Stump Formation, 

NE'/4 sec. 1, T. 4 S., R. 45 E., Irwin quadrangle, Idaho.

Fossils from Mesozoic fossil localities 16024 and 17897 

include the ammonite Cardioceras and are definitely from 

the basal part of the Redwater Member. Those from locality 

18185 are probably from the basal part of the Redwater 

Member if the members are similar in thickness to those at 

McCoy Creek about 9.6 km to the north. If so, the collection 

from locality 18187 was probably collected about 10.7 m
UNCONFORMITIES, CORRELATION, AND NOMENCLATURE Cll

FIGURE 7.—Contact of the Stump Formation with the Preuss Sandstone at Indian Camp Hollow (loc. 3, fig. 5). A, thin- and medium-bedded 

ledgy cliff-forming appearance typical of the sandstone unit of the Curtis Member. Contact dashed where inferred. Lower cliff is about 12 

m high. B, sharp, slightly channeling contact of the Stump with the Preuss. Hammer is about 28 centimeters long. In both views: 1, Curtis 

Member, sandstone unit; 2; Preuss Sandstone.

above the base of the Redwater Member. Apparently only 

the fossils from locality 18183 were collected high in the 

formation, but the reported occurrence in shale at that 

position seems peculiar and needs confirmation. In addition,

the fossils of Gryphaea nebrascensis in the Stump Formation of the Jackson quadrangle, Wyoming, as reported by 

Wanless, Belknap, and Foster (1955, p. 51,52), are probably 

also in the basal or lower part of the Redwater Member
C12 TRIASSIC AND JURASSIC ROCKS, WESTERN INTERIOR UNITED STATES

FIGURE 8.—Stump Formation at McCoy Creek (loc. 4, fig. 5). A, units: 1, Redwater Member, sandstone unit; 2, shale unit; 3, Curtis Member, 

shale unit; 4, sandstone unit; 5, Preuss Sandstone. Lower cliff is about 10 m high. /?, near view of contact between 4, Curtis Member, 

sandstone unit, and 5, Preuss Sandstone. The contact shows relief of about 3 cm. Hammer is about 28 cm long.
UNCONFORMITIES, CORRELATION, AND NOMENCLATURE C13

FIGURE 9.—Sandstone unit of the Curtis Member at the start of Corral Creek trail (loc. 5, fig. 5; vehicle parked on trail). Arrow points to 

Preuss-like red beds within the Curtis Member suggesting local intertonguing with the Preuss. (1) Preuss Sandstone; (2) Curtis Member, 

sandstone unit; (3) Curtis Member, basal part of shale unit. Redwater Member is present on ridge to the right but not visible in photograph.

because they occur in gray limestone that underlies massive 

ridge-forming, green, glauconitic sandstone and overlies 

softer, greenish sandy shale and sandstone.

The worn appearance of these gryphaeas, their preservation mostly as parts of the umbonal area, their occurrence 

mainly at or near the base of the Redwater Member, and 

their absence in the underlying Curtis Member indicate that 

they were derived from the Leeds Creek Member of the Twin 

Creek Limestone, which contains many well-preserved, 

unworn, and much larger specimens of Gryphaea 

nebrascensis. Evidently they were derived from that member 

during an interval of erosion after deposition of the Curtis 

Member.

The upper or sandstone unit of the Redwater Member 

consists mostly of ledgy to cliff-forming sandstone that is 

thin to thick bedded, crossbedded, highly glauconitic, 

calcareous, gray to greenish gray or locally nearly white. 

Most sequences contain interbeds of sandy siltstone or soft, 

clayey siltstone partings. Sandy oolitic limestone beds are 

present locally. Chert pebbles are present in some sections in 

various parts of the member. Belemnites and bivalves are 

fairly common, and ammonites occur locally.

This unit differs from the cliff-forming sandstone unit at 

the base of the Curtis Member in that it has more fossils, 

contains ammonites and belemnites, has claystone and 

siltstone beds that weather chunky instead of flaky or fissile, 

contains few trace fossils, has glauconite grains that commonly are larger than associated sand grains instead of the 

same general size, and lacks clay-pebble imprints or small 

cubical-shaped casts or imprints of salt crystals.

The upper sandstone unit of the Redwater Member rests 

conformably on the lower chunky shale unit of the Redwater 

Member where present, or sharply on the shale unit or the 

sandstone unit of the Curtis Member. A disconformable 

relationship with the Curtis Member is indicated by the 

sharpness of the contact, by a marked lithologic change, and

by the absence of the upper shale unit of the Curtis Member 

at some places (sections 12,14, and 15). The upper sandstone 

unit of the Redwater Member throughout most of the 

overthrust belt is overlain sharply and unconformably by red 

siltstone or conglomerates of the Lower Cretaceous 

Ephraim Conglomerate. In the Uinta Mountains it is 

overlain unconformably by the Upper Jurassic Morrison 

Formation.

The Redwater Member of the Stump Formation is 

correlated with the Redwater Shale Member of the Sundance Formation because it likewise contains belemnites in 

abundance from bottom to top, and it likewise contains 

Cardioceras. That genus occurs near the base of the member 

west of Fort Hill (section 16) and on the creek of Telephone 

Hollow (section 12), and in the lower part of the upper third 

of the member at McCoy Creek (section 4). The basal part of 

the Redwater Member on the creek of Telephone Hollow 

also contains Vaugonia quadrangularis(Hall and Whitfield) 

and Oxytoma wyomingensis (Stanton) along with 

Cardioceras and belemnites. In addition, the stratigraphically highest exposures of the member on McCoy Creek 

contain Oxytoma wyomingensis (Whitfield). The 

pelecypods occur in the Redwater Shale Member of the 

Sundance Formation as far east as the Black Hills and in the 

Middle and Upper Jurassic Swift Formation of Montana. 

The presence of Cardioceras shows that the Redwater 

Member of the Stump Formation is of early to early middle 

Oxfordian age.

UNCONFORMITIES

The lower contact of the Ephraim Conglomerate is an 

unconformity throughout the study area. The lower contact 

of the Redwater Member of the Stump is also an unconformity. The nature of the contact between the Curtis Member 

of the Stump and the Preuss Sandstone, however, is
C14 TRIASSIC AND JURASSIC ROCKS, WESTERN INTERIOR UNITED STATES

FIGURE 10.—Type area of the Stump Formation. A, southwestward view 01 an overturned but well-exposed section of the Stump Formation 

designated the principal reference section (loc. 7, fig. 4). A northwestward view of this locality was illustrated and described by Mansfield 

and Roundy (1916, p. 82, pi. 13a) as "a typical exposure of the Stump sandstone." 1, Curtis Member, sandstone unit; 2, Curtis Member, 

shale unit; 3, Ephraim Conglomerate. B, northeastward view of Stump Peak (arrow) on ridge held up by the sandstone unit of the Curtis 

Member. 1, Ephraim Conglomerate; 2, Curtis Member, sandstone unit; 3, Preuss Sandstone; 4, Twin Creek Limestone undivided, 

consisting principally of the Leeds Creek Member. North Fork of Stump Creek is in lower right of photograph. Contacts dashed where 

inferred.
UNCONFORMITIES, CORRELATION, AND NOMENCLATURE C15

FIGURE 11. Contact of the Stump Formation with the Preuss Sandstone at Stump Creek (loc. 8. fig. 4). 1, Stump Formation, sandstone

unit; 2, Preuss Sandstone.

uncertain. The contact is sharp and probably unconformable at localities 2, 3,4, 8, 11, 16, and 17; it is concealed at 

localities 1, 6, 7, and 18; it is conformable at localities 9, 13, 

14, and 15; and perhaps the Curtis Member and Preuss 

intertongue at localities 5, 10, and 12.

Marked differences in lithologic characteristics, fossils, 

and thicknesses occur within relatively short distances in the 

Stump Formation as now mapped. These differences are 

attributable primarily to truncation of units beneath the 

unconformities at the base of the Ephraim Conglomerate 

and at the base of the Redwater Member of the Stump 

Formation. (See figs. 4, 5, and 6.)

The unconformities at the base of the Ephraim, at the base 

of the Redwater, and at the base of the Curtis, where present, 

have been designated the K, J-4, and J-3 unconformities, 

respectively, by Pipiringos and O'Sullivan (1978).

The unconformity at the base of the Ephraim Conglomerate probably represents at least part of the late 

Tithonian; the one at the base of the Redwater Member 

represents most of the late Callovian; and the unconformity 

that is at least locally present at the base of the Curtis 

Member may represent a small part of the middle Callovian. 

The latest time represented by the unconformity at the base 

of the Redwater Member is dated accurately by the presence 

of ammonites of early Oxfordian age in the lower part of that 

member.

STRATIGRAPHIC SECTIONS

The Stump Formation was named after a sandstone 

sequence on Stump Peak in the Freedom quadrangle, Idaho, 

by Mansfield and Roundy (1916, p. 76, 81), who did not 

designate a type section. That sandstone forms a ridge that 

extends southeastward for 5 km through the peak. Near the 

northwest end of the ridge, an overturned sequence (loc. 7) is 

well exposed (fig. 10/4). Approximately 1.6 km to the 

southeast at Stump Peak (NE!4 NW'/4 sec. 16, T. 6 S., R. 45 

E.), the sequence of beds in the Stump Formation is the same 

and is in normal superposition, but it is less well exposed. 

About 2 km farther southeast, in the SE^NWVi sec. 22, 

outcrops are even poorer, and, in addition, much of the 

upper part of the Stump Formation is missing owing either 

to erosion or to faulting (fig. IQB). The sequence near the 

northwest end of the ridge (loc. 7) is the best exposed and the 

most accessible within the type area. Furthermore, locality 7 

was illustrated by Mansfield and Roundy (1916, pi. 13A), 

who stated that it shows a typical exposure of the Stump 

Formation. For these reasons, it is here selected as the 

principal reference section for the Stump Formation.

In addition, lithologically similar and better exposed 

reference sections also designated in this report that are 

readily accessible by car are to the southeast at Stump Creek 

(section 8), Crow Creek, and Fish Creek (section 12). The
TRIASS1C AND JURASSIC ROCKS, WESTERN INTERIOR UNITED STATES

FIGURE 12.—Ephraim Conglomerate, Stump Formation, and Preuss Sandstone at Telephone Creek section (loc. 9, fig. 5). 1, Ephraim 

Conglomerate; 2, Redwater Member, sandstone unit; 3, Curtis Member, sandstone unit; 4, Preuss Sandstone.

section on the north side of Crow Creek (SE'/^NW/^ sec. 17, 

T. 31 N., R. 119 W., Crow Creek quadrangle, Lincoln 

County, Wyo.) differs from that on Stump Creek by the 

presence of thin beds of oolitic limestone that contain 

crinoid columnals and the pelecypod Camptonectes. Such 

limestone beds occur within a claystone unit at the very top 

of the formation as well as 18.2-21.3 m lower.

All these sections from Stump Peak southward along the 

Idaho-Wyoming border, as well as at Watton Canyon, Utah, 

are represented only by lithologies closely similar to those in 

the Curtis Formation of northern Utah, and they do not 

contain any units that are lithologically or faunally comparable with the Redwater Member of the Sundance 

Formation.

Well-exposed and easily accessible sections for the 

Redwater Member of the Stump Formation are at McCoy 

Creek (section 4), Telephone Creek (section 9), Sheep Creek 

(section 10), Shale Creek (section 11), and La Barge Creek 

(section 14).

In the descriptions that follow, the crossbedding noted in 

the sandstone beds of the Redwater Member seems to be of 

the medium-angle, trough cross-stratified type, occurring in 

sets 0.5-2 m thick. The crossbedding in the sandstone beds of 

the Curtis Member is exclusively low angle, trough cross 

stratified in sets 3-10 cm thick. In general the Redwater 

Member was deposited by currents of lower velocities than 

the currents that deposited the Curtis Member.

Indications of the position of unconformities in the 

stratigraphic descriptions have been omitted in order to 

shorten the descriptions; for the most part insertion of the 

word unconformity is repetitive and unnecessary. In figures 

4, 5, and 6, the unconformities are shown by solid lines and 

conformable contacts by dashed lines.

For similar reasons the thicknesses of individual 

stratigraphic units are omitted in figures 4 and 6 but are 

summarized in table 1. Formation and member thicknesses 

in text and in table I, originally measured in feet, were 

converted to meters and rounded.
UNCONFORMITIES, CORRELATION, AND NOMENCLATURE C17

FIGURE 13.—Ephraim Conglomerate, Stump Formation, Preuss Sandstone, and Twin Creek Limestone near junction of Sheep Creek with 

Greys River (loc. 10, fig. 6). 1, Ephraim Conglomerate; 2, Red water Member, sandstone unit; 3, Curtis Member, shale and sandstone units 

undivided; 4, Preuss Sandstone; 5, Twin Creek Limestone undivided.

Section 1.— Wolverine Canyon 

[Stump Formation on north side of Wolverine Canyon in E'/iNE'/iNE'/S sec. 28, T. 1 S., R. 39 E.,

Ammon quadrangle. Bingham County. Idaho]

Thickness 

(meiers)

Ephraim Conglomerate (incomplete):

6. Mostly covered; base concealed; soil is grayish red; 

reported by Mansfield (1952, p. 63, pi. 1) to be in 

fault contact with underlying Stump Formation 3+ 

Stump Formation:

Curtis Member (incomplete): 

Shale unit (incomplete):

5. Clay shale, limy, gray; contains lenticular flattened

limestone concretions .......................................15.2+

4. Oolite slabs and thin limy siltstone and shale beds, 

sandy, gray, glauconitic; contains oysters, 

crinoid stems, echinoid spines, Camptonectes 

interbedded with some gray shale; unit makes 

slope ................................................................. 4.6

Sandstone unit:

3. Sandstone, very fine grained, flaggy, mostly gray, 

ripple-marked; bears many tracks and trails; 

contains many layers of olive-gray clay shale; 

basal meter contains slabs of oolite that bear 

crinoid columnals and oyster fragments .......... 21.3

2. Sandstone, ledgy to cliff-forming, thin- to 

medium-bedded, medium- to fine-grained, 

brownish-gray, glauconitic; some low-angle 

crossbedding, ripple-marked, some tracks and 

trails present; a thin oolite bed at top contains

Section 1.— Wolverine Canyon—Continued

Thickness 

(meters)

Stump Formation—Continued

Curtis Member (incomplete)—Continued 

Sandstone unit—Continued

crinoid columnals and oyster fragments, base of 

unit concealed................................................... 22.9

Partial thickness of Stump Formation ..... 64+

1. Covered interval, probably partly Preuss

Sandstone ........................................................ 4.6

Preuss Sandstone (Imlay, 1952, p. 1740) ........................................ 436

Section 2.—Blacktail Creek

[Stump Formation on west side of Fall Creek just south of Blacktail Canyon in NE'A sec. 34, T. 1 N. 

R. 42 E., Conant Valley and Commissary Ridge quadrangles, Bonneville County, Idaho]

Ephraim Conglomerate (incomplete):

5. Partly covered pale-red sandy siltstone with a bed 

of light-gray limestone at the base; basal contact 

concealed makes slope; limestone makes ledge 9+

Stump Formation:

Redwater Member: 

Sandstone unit:

4. Mostly covered. Some siltstone and silty sandstone,

ripple-marked, gray, base not exposed ............ 4.6

3. Sandstone, thin- to medium-bedded, crossbedded, 

glauconitic, ledgy at base, some shaly beds, some
CIS TRIASSIC AND JURASSIC ROCKS, WESTERN INTERIOR UNITED STATES

4QE

- *^,^ V%* -"•-ssfv'-'-'- ,w -«•, * ,i •" ""-

jV •>^,<, • _-.. - '

$Uflj> J^ .^ "^r- -

FIGURE 14.—Bedding features typical of the Curtis Member, sandstone unit of the Stump Formation. Exposure is on east side of U.S. 

Highway 89 about 400 m south of the Fish Creek stratigraphic section (loc. 12, fig. 4). Hammer is about 28 cm long.

Section 2.—Blacktail Creek—Continued

Thickness 

(meters)

Stump Formation—Continued 

Redwater Member—Continued 

Sandstone unit—Continued

oolitic beds, brownish-gray; contains belemnites, 

oysters, crinoid fragments, and some small chert 

pebbles ............................................................. 24.4

Thickness of Redwater Member ............... 34

Curtis Member: 

Shale unit:

2. Mostly covered clay shale, silty, medium-gray; 

contains thin oolitic limestone beds near base, 

just above a bed of olive-green clay shale about 1 

meter thick that rests sharply on underlying unit; 

uppermost meter may belong to Redwater 

Member ........................................................... 24.4

Sandstone unit:

1. Sandstone, thick- to thin-bedded, ledgy; some platy 

shale; glauconitic, ripple marked, slightly 

crossbedded; bears trails and some cubical salt

Section 2.—Blacktail Creek—Continued

Thickness 

(meters)

Stump Formation—Continued 

Curtis Member—Continued 

Sandstone unit—Continued

crystal casts. Rests fairly sharply on the underlying red siltstone ................................................ 22.8

Thickness of Curtis Member .................... 47

Thickness of Stump Formation .................. 81

Preuss Sandstone (Imlay, this report) ..............................................146

Section 3.—Indian Camp Hollow

[Stump Formation on ridge south of Indian Camp Hollow, about 1.6 km west of Fall Creek in SE'4 

sec. 13, T. 1 N., R. 42 E., Conant Valley quadrangle, Bonneville County, Idaho. See figure 7]

Ephraim Conglomerate (covered). 

Stump Formation (incomplete):

Redwater Member (incomplete): 

Sandstone unit (incomplete):

3. Sandstone and sandy limestone, medium- to 

thin-bedded, speckled, highly glauconitic,
UNCONFORMITIES, CORRELATION, AND NOMENCLATURE

Section 3.—Indian Camp Hollow—Continued Section 4.—McCoy Creek—Continued

Thickness 

(meters)

Stump Formation (incomplete)—Continued 

Redwater Member (incomplete)—Continued 

Sandstone unit (incomplete)—Continued

grayish-yellow, forms low ledge. Basal 4 m 

contains some chert pebbles, belemnites, Pinna, 

Gervillia, Camptonectes, and many oysters. Exact contact with underlying shale not observed. 

Estimated exposed thickness ............................ 18+

Curtis Member: 

Shale unit:

2. Clay shale, calcareous, soft, gray, flaky, contains 

some large, flat, yellowish-white limestone concretions ............................................................ 21

Sandstone unit:

1. Sandstone, cliff-forming, gray, mostly thick bedded 

to massive, some thin-bedded sandstone in middle fourth, upper 9 m is oolitic and contains many 

oysters and echinoid spines. Upper contact with 

clay shale is sharp and has a relief of about 7 cm. 

Lower contact with red shaly siltstone at top of 

Preuss Sandstone is very sharp ........................ 24

Thickness of Curtis Member .................... 45

Partial thickness of Stump Formation ..... 63+

Preuss Sandstone (Vine, 1959, p. 260) ............................................. 129

Section 4.—McCoy Creek

[Stump Formation on north side of McCoy Creek near center of E'/2 SW^ sec. 6, T. 3 S., R. 46 E. 

Alpine quadrangle, Bonneville County, Idaho. See figure 8]

Ephraim Conglomerate (incomplete):

8. Conglomerate, gray, clasts mostly black and white

chert ................................................................. 3+

Stump Formation:

Redwater Member: 

Sandstone unit:

7. Sandstone, gray, fine-grained, calcareous, oolitic, 

mostly thick bedded, ledgy; approximately the 

upper 5 is covered. Ammonites and belemnites 

found about 10 m below the highest exposure of 

the sandstone unit about 15m below the lowest 

exposure of the Ephraim Conglomerate .......... 45.7

Shale unit:

6. Siltstone, clayey, chunky, gray, glauconitic; upper 

1.2 m well exposed: contact with Curtis Member 

is covered ......................................................... 1.8

Thickness of Redwater Member ............... 48

Curtis Member: 

Shale unit:

5. Clay shale, calcareous, soft, flaky to fissile, containing large, flat, yellowish-white limestone 

concretions and some thin, platy sandstone beds; 

top 0.6 m covered ........................................... 10.6

Sandstone unit:

4. Sandstone, greenish-gray to brownish-gray, 

fine-grained, glauconitic, ripple-marked, thin- to 

medium-bedded; contains trails and salt-crystal 

casts; cliff forming ........................................... 6.0

3. Sandstone, shaly, glauconitic, forms recess in cliff 4.6

C19

Thickness

(meters)

Stump Formation—Continued 

Redwater Member—Continued 

Sandstone unit—Continued

2. Sandstone as at top of unit, basal contact very 

sharp, shows local relief of about 3 cm ........... 10.7

Thickness of Curtis Member .................... 32

Thickness of Stump Formation ................ 79

Preuss Sandstone (incomplete):

1. Sandstone, thin-bedded, very fine grained,

grayish-red and calcareous ............................... 30+

Section 5.— Corral Creek Trail

[Stump Formation at beginning of Corral Creek trail on north side oi Tincup Creek in SE corner sec. 

10, T. 5 S., R. 45 E., Freedom quadrangle. Caribou County, Idaho. See figure 9]

Ephraim Conglomerate (not examined). 

Stump Formation (incomplete):

Redwater Member (not exposed near road). 

Curtis Member (incomplete): 

Shale unit (incomplete):

9. Shale, fissile, soft, gray; contains a few thin beds of

sandstone ......................................................... 7.3+

Sandstone unit:

8. Sandstone, thick-bedded, gray ............................. 3.0

7. Siltstone and sandstone, reddish-brown .............. 4.6

6. Sandstone, thick- to medium-bedded, gray ......... 8.2

5. Sandstone, thin-bedded, gray .............................. 4.6

4. Sandstone, thick- to medium-bedded, gray ......... 13.7

3. Siltstone and sandstone, thin-bedded, dullbrownish-red .................................................... 3.0

2. Sandstone, thick- to medium-bedded, gray ......... 13.7

1. Covered ............................................................... 4.6

Partial thickness of Stump Formation ..63+ 

Preuss Sandstone (not examined).

Section 6.—Tincup Creek

[Stump Formation on Tincup Creek on south side of Idaho Highway 34, about 3.2 km northwest of 

Freedom in NE'/jSW'/i sec. 9, T. 5 S., R. 46 E., Freedom quadrangle, Cafibou County, Idaho 

(Mansfield. 1927, pi. 5)]

Ephraim Conglomerate (base concealed). 

Stump Formation:

Redwater Member: 

Sandstone unit:

7. Sandstone, thick- to thin-bedded, glauconitic, gray; 

some oolitic beds; contains some belemnites near 

middle; uppermost part is covered ................... 45.4

Curtis Member: 

Shale unit:

6. Shale, olive-green, flaky to fissile ........................ 1.2

5. Covered (probably underlain by soft shale) ......... 17.4

4. Shale, finely fissile to platy, olive-green; weathers 

yellowish; bears tracks and trails; contains 

medium-gray limestone concretions ................. 5

Sandstone unit:

3. Sandstone, medium- to thin-bedded, gray,

ripple-marked ................................................... 6.1

2. Siltstone and sandstone, red to gray, resembles

Preuss Sandstone ............................................. 2.1
C20 TR1ASS1C AND JURASSIC ROCKS, WESTERN INTERIOR UNITED STATES

FIGURE 15.—Stump Formation on old U.S. Highway 30 near Evanston, Wyo. (loc. 17, fig. 6). A, westward view of entire section. B,

1, Ephraim Conglomerate; 2. Redwater Member, sandstone unit; 3, shale unit;

Section 6. — Tincup Creek—Continued

Thickness 

(meters)

Stump Formation—Continued

Redwater Member—Continued 

Sandstone unit—Continued

Sandstone, thick- to medium-bedded, gray, 

ripple-marked; basal beds not exposed ............ 22.9

Thickness Curtis Member ......................... 55

Thickness of Stump Formation ................100

Preuss Sandstone (not examined).

Section 7.—Stump Peak 

[Principal reference section: Stump Formation on peak, about 1.6 km northwest of Stump Peak, near

center of NE14 sec. 7, T. 6 S.. R. 45 E., Freedom quadrangle. Caribou County, Idaho. Strata are

overturned, dip 25° W. See figure 10]

Ephraim Conglomerate (incomplete):

3. Siltstone, pale-red, sandy ..................................... 3+

Stump Formation: 

Curtis Member: 

Shale unit:

2. Claystone, limy, sandy near base, contains gray

limestone concretions, soft, gray, makes slope . 15.2

Section 7.—Stump Peak—Continued

Thickness 

(meters)

Stump Formation—Continued 

Curtis Member—Continued 

Sandstone unit:

1. Sandstone, thin- to medium-bedded, and sandy 

shale, gray, ripple-marked; bears tracks and 

trails; makes cliffs and ledges ........................... 61.0

Thickness of Stump Formation ................ 76

Preuss Sandstone eroded from top of peak.

Section 8.—Stump Creek

[Reference section: Stump Formation on north side of Stump Creek about 3.2 km west of Auburn, 

Wyo., in E'/2NW14 sec. 26, T. 7 S., R. 46 E., Freedom quadrangle. Caribou County, Idaho. See 

figure 11]

Ephraim Conglomerate (incomplete):

4. Siltstone, pale-red, sandy ..................................... 3+

Stump Formation: 

Curtis Member: 

Shale unit:

3. Claystone, soft, with thin interbeds of platy, 

ripple-marked sandstone that bear trails, and
UNCONFORMITIES, CORRELATION, AND NOMENCLATURE C21

B

. 1 * ._ -if _

northward view of upper part of the Red water Member in contact with conglomeratic beds in the lower part of the Ephraim Conglomerate. 

4, Curtis Member, shale unit; 5, Preuss Sandstone. Arrow points to hammer for scale.

Section 8.—Stump Creek—Continued

Thickness 

(meters)

Stump Formation—Continued 

Curtis Member—Continued 

Shale unit—Continued

shaly limestone; contains light-gray limestone 

concretions and some fossiliferous oolitic slabs 

found as float on claystone .............................. 30.5

Sandstone unit:

2. Sandstone, thick- to thin-bedded, cliff-forming at 

base; becomes shaly upward; contact with Preuss 

poorly exposed but appears to be moderately 

sharp ................................................................ 69.2

Thickness of Stump Formation ................100

Preuss Sandstone (incomplete):

1. Sandstone, thin-bedded, very fine grained, 

grayish-red, calcareous, locally contains gypsum 

and chert nodules, makes ledgy slope ...............

5+

Section 9.— Telephone Creek

[Reference section: Stump Formation on west side of creek of Telephone Hollow about 0.8 km north 

of Deadman Creek, near center of SE'/4 sec. 29, T. 25 N., R. 116 W., Afton quadrangle, Lincoln 

County, Wyo. See figure 12]

Thickness 

(meters)

Ephraim Conglomerate (incomplete):

6. Sandstone, gray to pinkish-gray

Stump Formation:

Redwater Member: 

Sandstone unit:

5. Covered ............................................................... 18.3

4. Sandstone, massive, cliff-forming, glauconitic, gray

.......................................................................... 11.3

3. Sandstone, silty, shaly to thin-bedded, gray ........ 9.1

2. Sandstone, medium- to thick-bedded, cliffforming, glauconitic, yellowish-gray, some 

crossbedding; contains belemnites, oysters, and 

Camptonectes; rests sharply on underlying unit 15.8 

Thickness of Redwater Member ............... 55
C22 TRIASSIC AND JURASSIC ROCKS, WESTERN INTERIOR UNITED STATES

y i

FIGURE 16.—Near view of contacts shown in figure 15 B. The hammer is on the lowest bed in the Ephraim Conglomerate. Note minor 

channeling at contact. The hammer is about 33 centimeters long. 1, Ephraim Conglomerate; 2, Redwater Member of Stump Formation, 

sandstone unit; 3, Redwater Member, shale unit.

Section 9.—Telephone Creek—Continued

Thickness 

(meters)

Stump Formation—Continued 

Curtis Member:

Sandstone unit:

1. Sandstone, silty sandstone, yellowish-gray, shaly to 

thin-bedded, ripple-marked; has irregular wavy 

bedding; grades downward into red Preuss 

Sandstone ........................................................ 11.3

Thickness of Stump Formation ................ 66

Preuss Sandstone (not examined).

Section 10.—Sheep Creek

[Stump Formation near intersection of Sheep Creek and Greys River in W'/£ sec. 4. T. 33 N.. R. 116 

W., Afton quadrangle, Lincoln County, Wyo. See figure 13]

Ephraim Conglomerate (incomplete):

8. Claystone, soft, red and green; contains nodules of

limestone; probably of Early Cretaceous age ... 3+

Stump Formation:

Redwater Member:

Section W.—Sheep Creek—Continued

Thickness 

(meters)

Stump Formation—Continued 

Redwater Member—Continued 

Sandstone unit:

7. Sandstone thin- to medium-bedded, very fine grained; greenish-gray; contains furrowed trails; 

grades into underlying beds; forms low cliffs ... 13.7 

6. Limestone, thick-bedded, oolitic, glauconitic, sandy, yellowish-gray; contains a few thin beds; 

belemnites and Camptonectes present .............. 9.8

5. Siltstone, sandy, massive, medium-gray, nonfissile;

makes slope ...................................................... 6.4

Shale unit (?):

4. Limestone, sandy, and limy sandstone, fine-grained, cliff-forming, medium- to dark-gray, 

glauconitic; some oolitic beds containing oysters 

in topmost 0.3 m; belemnites present at basal 

contact and higher; rests sharply on underlying 

unit .................................................................. 4.0

Thickness of Redwater Member ............... 34
UNCONFORMITIES, CORRELATION, AND NOMENCLATURE C23

Section 10.—Sheep Creek—Continued

Thickness

(meters)

Stump Formation—Continued 

Curtis Member: 

Shale unit:

3. Shale, fissile; weathers into pencil-like flakes; some 

very thin platy sandstone interbeds, 

medium-gray; rests conformably on thin beds of 

green tuff ......................................................... 2.7

Sandstone unit:

2. Sandstone and siltstone, red ................................ 2.4

1. Sandstone, silty, and sandy siltstone, gray .......... 3.7

Thickness of Curtis Member ................. 9

Thickness of Stump Formation ............ 43

Preuss Sandstone (not examined).

Section 11.—Shale Creek

[Stump Formation on ridge west of Shale Creek, and north of East Fork of Greys River about 0.4 

km east of its junction with the West Fork of Greys River, NEW sec. 20, T. 30 N., R. 116 W., Afton 

quadrangle, Lincoln County, Wyo.]

Ephraim Conglomerate (not examined). 

Stump Formation:

Redwater Member: 

Sandstone unit:

4. Sandstone, cliff-forming, medium- to thin-bedded, 

greenish-gray, glauconitic; contains one bed of 

bentonite about 4.9 m above base; Meleagrinella 

and Kallirhynchia common in lower part ........ 13.4

Shale unit:

3. Siltstone, soft, brown, clayey at base; contains 

many belemnites and small, worn specimens of 

Gryphaea nebrascensis (Meekand Hayden). One 

bentonite bed occurs 30 cm below top ............. 4.0

Thickness of Redwater Member ............... 17

Curtis Member:

Sandstone unit:

2. Sandstone, cliff-forming, medium- to thin-bedded, 

wavy-bedded, ripple-marked, yellowish-gray; 

rests sharply on underlying unit ....................... 14.3

Thickness of Stump Formation ................ 32

Preuss Sandstone (incomplete):

1. Sandstone, red, thin-bedded; makes steep ledgy

slope ................................................................. 3+

Section 12.—Fish Creek

[Stump Formation near Fish Creek along U.S. Highway 89 about 9.6 km south of Smoot in SE'/4 sec. 

32, T. 30 N., R. 118 W., and E'/4 sec. 5, T. 29 N., R. 118 W., Afton quadrangle, Lincoln County, 

Wyo. See figure 14]

Ephraim Conglomerate (incomplete):

8. Siltstone, pale-red, sandy, partly covered ............ 3+

Stump Formation: 

Curtis Member: 

Shale unit:

7. Clay shale, fissile, limy, gray; contains lenticular 

concretions ranging from several cm to more 

than a meter in length. At base is a gray oolitic 

bed, 5-13 cm thick, that contains crinoid stems 

and oysters ....................................................... 27.4

Clay shale, as above; contains limestone concretions as much as 20 cm in length. At base is a 

gray, slightly sandy, oolitic bed from 15 to 20 cm 

thick that contains oysters and crinoid fragments 7.6

6.

Section 12.—Fish Creek—Continued

Stump Formation—Continued 

Curtis Member - Continued 

Sandstone unit:

5. Sandstone, shaly to very thin bedded; some clay

shale and some silty clay shale, gray; bears ripple

marks and many tracks and trails .................... 13.7

4. Shale, sandy, gray, green, and red, ripple-marked;

bears tracks and trails ...................................... 15.2

3. Siltstone, red, about 3 m thick; becomes reddish

gray in top 1.6 m; barren of tracks and trails;

resembles the Preuss Sandstone ....................... 4.6

2. Shale, sandy, and shaly sandstone, gray to

greenish-gray, ripple-marked; contains a few

reddish zones ................................................... 24.4

I. Sandstone, medium- to thin-bedded to shaly, very

fine grained, gray, slightly glauconitic;

ripple-marked; forms low cliffs; lower 0.9-1.2 m

covered ............................................................. 19.8

Thickness of Stump Formation ................113

Preuss Sandstone (not examined).

Section 13.—Salt Canyon

[Stump Formation on west side of Salt Canyon south of Packstring Creek, SWViSEW sec. 27. T. 29 

N., R. 119 W., Salt Flat quadrangle, Lincoln County, Wyo.]

Ephraim Conglomerate (incomplete);

4. Siltstone, pale-red, sandy, clayey

Stump Formation: 

Curtis Member:

Sandstone unit: 

3. Sandstone,

3+

gray and greenish-gray, fine- to 

medium-grained, limy, thin-bedded, 

ripple-marked; bears many tracks and trails; 

contains many clayey siltstone partings; makes 

ledgy slope ....................................................... 10.6

Sandstone, gray and greenish-gray, very fine to 

fine-grained, medium-bedded, ripple-marked; 

makes ridge ...................................................... 30.5

Thickness of Stump Formation ................ 41

Preuss Sandstone (Mansfield, 1927, p. 99) ......................................396

Section 14.—La Barge Creek

[Stump Formation on ridge north of La Barge Creek in north-central part of sec. 17, T. 27 N., R. 15 

W., Coal Creek quadrangle, Sublette County, Wyo.]

Ephraim Conglomerate (incomplete):

5. Basal part consists of 1 m of sandy limestone 

underlain by 1.1 m of bright-green shaly 

sandstone that rests sharply on underlying unit 2+

Stump Formation:

Redwater Member: 

Sandstone unit:

4. Sandstone, calcareous, glauconitic, massive, 

cliff-forming, mostly light gray to brownish-gray; 

basal 1.8 m weathers white, fragments of carbonized wood common throughout ................. 11.3
C24 TRIASSIC AND JURASSIC ROCKS, WESTERN INTERIOR UNITED STATFS

Section 14.—La Barge Creek—Continued

Thick ness 

(meters)

Stump Formation—Continued

Redwater Member—Continued 

Shale unit:

3. Shale, silty to finely sandy, gray; bears two thin beds 

of bentonite; basal part contains belemnites and 

worn fragments of Gryphaeanehrascensis(Meek 

and Hayden) .................................................... 5.6

Thickness of Redwater Member ............... 17

Curtis Member:

Sandstone unit:

2. Sandstone, thin- to medium-bedded, light-gray;

forms top of low cliff ....................................... 1.8

1. Sandstone, shaly and sandy siltstone, light-gray; 

some beds as much as 2.5 cm thick; wavy bedding 

common; grades downward gradually into red 

sandstone at top of Preuss Sandstone ............. 9.3

Thickness of Curtis Member .................... 11

Thickness of Stump Formation ................ 28

Preuss Sandstone (Imlay, 1950, p. 41) .............................................152

Section 15.—Fort Hill

[Stump Formation on ridge west of Dutch George Creek and about 3.2 km west-northwest of Fort 

Hill in NW'/iNE'/jSE'/i sec. 3. T. 25 N.. R. 115 W., Fort Hill quadrangle. Lincoln County. Wyo.]

Ephraim Conglomerate (covered, soil is grayish red). 

Stump Formation:

Redwater Member: 

Sandstone unit:

5. Sandstone, medium- to thin-bedded, flaggy, white; 

some soft siltstone partings; upper contact 

covered ............................................................. 14

4. Sandstone and sandy coquinoid limestone, 

medium- to thin-bedded, greenish-gray, highly 

glauconitic; some partings of soft siltstone; some 

beds as much as 0.6 m thick; contains ammonites 

and belemnites in basal bed ............................. 9

Shale unit:

3. Claystone, chunky, limy, alternating with blocks of 

chunky limestone, yellowish-gray; contains 

belemnites in basal 15cm ................................ 3

Thickness of Redwater Member ............... 26

Curtis Member: 

Shale unit:

2. Clay shale, flaky, olive-green; contains limestone 

concretions. Upper contact with Redwater 

Member is marked by concretionary blocks that 

bear oysters ......................................................

Sandstone unit:

I. Sandstone, cliff-forming, yellowish-gray, thick- to 

thin-bedded, some shaly interbeds, medium- to 

fine-grained, ripple-marked; wavy bedding common; thicker beds contain much glauconite. 

Contact with red Preuss Sandstone as exposed 

on road 1.6 km north of measured section is 

marked by 15-30 cm of white bentonite ........... 10

Thickness of Curtis Member .................... 11

Thickness of Stump Formation ................ 37

Preuss Sandstone (not examined).

Section 16. — Wat ton Canyon

[Stump Formation on north side of Watton Canyon near center W 1/: sec. 26. 1.9 N.. R. 5 E.. 

Meachum Ridge quadrangle. Rich County. Utah]

Thickness 

(meters)

Wasatch Formation (incomplete):

2. Interbedded brownish-red sandy clay shale,

siltstone, and sandy claystone .......................... 3+

Stump Formation: 

Curtis Member:

Sandstone unit:

1. Sandstone, greenish-gray, coarse-grained to conglomeratic, thick- to medium-bedded, with thin 

sandy claystone partings. Pentacrinus columnals 

are common throughout; lower part makes ridge; 

basal contact poorly exposed ........................... 76

Total thickness of Stump Formation 76

Preuss Sandstone (not examined).

Section 17.—Evans ton

[Stump Formation on north side of old U.S. Highway 30 (abandoned) in NW'/iSW'/iSW'/i 

sec. 18. T. 15 N., R. 118 W.. about 17.6 km east of Evanston. Guild Hollow quadrangle, 

Umta County. Wyo. See figures 15 and 16]

Ephraim Conglomerate (incomplete):

11. Basal conglomerate stands vertically and forms a

high cliff 4.5-6

Stump Formation:

Redwater Member: 

Sandstone unit:

10. Sandstone, medium-bedded, medium-grained, 

cross bedded, highly glauconitic, grayish-yellow; 

contains some brown chert pebbles and the 

fossils Meleagrinella and Lopha. Contact with 

Ephraim Conglomerate is sharp and channeled 

9. Sandstone, fine-grained, silty, shaly, to very thin 

bedded, soft, grayish-yellow, glauconitic. A 

sandstone bed, about 0.3 m thick, is 1.5 m above 

base and contains carbonized wood fragments 

Shale unit:

8. Clay shale, chunky, dark-yellowish-gray, mostly 

covered; a belemnite found 2.4 m above probable 

base of Redwater Member ............................... 10.7

Thickness of Redwater Member ............... 15

0.6

4.0

Curtis Member: 

Shale unit:

7. Clay shale, flaky, greenish-gray, mostly covered . 15.3 

6. Clay shale, flaky, greenish-gray; some beds of platy,

fine-grained sandstone 12-25 mm thick ............ 45.7

5. Sandstone, limy, very thin bedded, wavy-bedded,

yellowish-gray, estimated thickness .................. 1.8

4. Clay shale, flaky, soft greenish-gray .................... 8.2

3. Limestone, sandy, thin- to medium-bedded, very

fine grained, mostly medium gray; some

greenish-gray partings ...................................... 0.9

2. Shale, flaky, rests sharply on underlying unit ...... 1.2

Thickness of Curtis Member ................. 73

Thickness of Stump Formation

Preuss Sandstone (incomplete):

1. Sandstone, pale-red, fine-grained, thin-bedded;

makes soft slope ............................................... 5+
UNCONFORMITIES, CORRELATION, AND NOMENCLATURE C25

Section 18.— Peoa

[Stump Formation northwest of Peoa in SE'/^SW 1^ sec. 11, T. 1 S., R. 5 E., Kamas quadrangle. 

Summit County, Utah]

Thickness 

(meters)

Ephraim Conglomerate (incomplete):

8. Interbedded red and green claystone and gray

limestone .......................................................... 3+

Stump Formation:

Redwater Member: 

Sandstone unit:

7. Sandstone, cliff-forming, medium-bedded, 

greenish-gray; upper 1.2 m consists of sandy 

limestone and bears fragments of oysters and 

other bivalves ................................................... 9.7

6. Siltstone, sandy, greenish-gray ............................. 4.6

Shale unit:

5. Clayey to finely sandy siltstone, greenish-gray; one

bentonite bed at top; base not exposed ........... 6.7

4. Covered (probably contains contact between

Redwater and Curtis Members) ....................... 4.6

Thickness of Redwater Member ........... 25

Curtis Member:

Shale unit (incomplete):

3. Clay shale, flaky; gray top not exposed ............... 29.3

Sandstone unit:

2. Sandstone, platy, thin- to medium-bedded, crossbedded, wavy-bedded, medium-grained, 

yellowish-gray; basal contact poorly exposed .. 12.5

Thickness of Curtis Member .................... 42

Thickness of Stump Formation ................ 67

Preuss Sandstone:

1. Sandstone and siltstone, grayish-red; makes slope

(Thomas and Krueger, 1946, p. 1282) ..............365

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Unconformities, Correlation, 

and Nomenclature of Some 

Triassic and Jurassic Rocks, 

Western Interior United States

GEOLOGICAL SURVEY PROFESSIONAL PAPER 1035

This volume was published 

as separate chapters A-C

CONTENTS

[Letters designate the separately published chapters]

(A) Principal unconformities in Triassic and Jurassic rocks, Western Interior United States — A preliminary survey, by George N. 

Pipiringos and Robert B. O'Sullivan.

(B) Stratigraphic relations of the Navajo Sandstone to Middle Jurassic formations, southern Utah and northern Arizona, by Fred Peterson 

and George N. Pipiringos.

(C) Lithology and subdivisions of the Jurassic Stump Formation in southeastern Idaho and adjoining areas, by George N. Pipiringos and 

Ralph W. Imlay.