; Geology of the Area East 

and Southeast of 

. Livingston, Park County 

* Montana

K

*

GEOLOGICAL SURVEY BULLETIN 1021-L

' Prepared as part of a program of

the Department of the Interior for 

. development of the Missouri

River basin

A CONTRIBUTION TO GENERAL GEOLOGY

GEOLOGY OF THE AREA EAST AND SOUTHEAST OF 

LIVINGSTON, PARK COUNTY, MONTANA

By PAUL W. RICHARDS

ABSTRACT

The area lies generally east and southeast of Livingston, Park County, Mont.

^ It is bordered on the east by the 110° 15' meridian of longitude, on the west by 

the Yellowstone River and the 110° 30' meridian, and on the north and south by 

the 45° 45' and 45° 30' parallels of latitude. The area lies across the boundary

». of the Great Plains and Rocky Mountains physiographic provinces where the 

Crazy Mountains syncline adjoins the Beartooth Mountains and the Absaroka 

 >. Range southeast of Livingston. Altitudes range from 4,200 feet to about 10,000 

feet. The Yellowstone River drains the area, and the smaller Shields River, which 

drains the land north of the mapped area, joins it near Livingston. The average 

annual rainfall of the area is about 15 inches. Livingston, which had a population

'* of 7,683 in 1950, is the only town within the area.

Pre-Cambrian metamorphic and igneous rocks, which include a part of the 

Stillwater complex, are exposed in the Beartooth Mountains. The sedimentary

^ rocks range in age from Middle Cambrian to Upper Cretaceous and possibly 

Tertiary. They are at least 15,000 feet thick and crop out along the mountain

v flanks and in the plains.

The Paleozoic strata consist mainly of Cambrian shale and limestone, dolomite

» of Ordovician age, Devonian and Mississippian limestone and shale, and quartzite 

of Pennsylvanian age. The Silurian, Permian, and Triassic systems are not represented. Mesozoic strata include Jurassic shale and sandstone and a thick section 

of Cretaceous shale and sandstone. A thick sequence of tuffaceous beds, the 

Livingston formation, forms the upper part of the Upper Cretaceous series.

, With the possible exception of the uppermost part of the Livingston formation, 

there are no Tertiary deposits within the mapped area. Quaternary deposits 

include small moraines and terrace and pediment gravels, as well as a few land-

* slides and alluvial fans.

The rocks are complexly folded and faulted in much of the area. Southeast of 

Livingston the west and north flanks of the Beartooth Mountains are bordered

** by high-angle faults. A near-vertical fault that has as much as 1,800 feet displacement within the mapped area marks the west edge of the Beartooth Moun-

*** tains. High-angle reverse faults that dip northeastward along the north side 

of the mountains have displacements of as much as 3,000 feet.

* The area north of the Beartooth Mountains is the southwest edge of the Crazy 

Mountains syncline, which is a 100-mile-long structural downwarp that is nearly

385
386 CONTRIBUTIONS TO GENERAL GEOLOGY

alined with the Bighorn Basin of Wyoming and Montana to the southeast. 

With the exception of the Mission Creek and Livingston anticlines, which are 

close to the mountain front, folds and faults within the Crazy Mountains syncline 

trend at right angles to the mountain front. Some of these folds are nearly 

isoclinal; all are faulted along one flank, and all but Hunters anticline plunge 

moderately to steeply away from the mountains.

During the early part of this century coal was mined and coked along Coke 

Creek west of Livingston, but coal has not been mined for other tK<in domestic 

use within the mapped area. Thin coal beds that occur in the Cretaceous strata 

above the Virgelle sandstone west of Mission Creek are in about the same stratigraphic position as those mined along Coke Creek.

Neither oil nor gas has been produced, and only four exploratory wells have 

been drilled deeper than 1,500 feet. Only one of these, the Richfield 1 Weiss, 

was located on a structure with possible surface closure. It is on the axis of 

Mission Creek anticline west of a fault that crosses the axis. The test was abandoned in Jurassic strata without known shows of oil or gas. The only other 

anticline with mapped surface closure is Hunters anticline.

The exposed bentonite beds are thin and lie beneath thick overburden. Limestone had been quarried and kilned in the Yellowstone River canyon south of 

Livingston in the first decade of the century, but has not been utilized since. 

Calcite occurs in veins in much of the area of outcrop of the Livingston formation; 

during World War II it was mined in adjacent areas, reportedly for its optical 

properties.

Metallic mineral deposits have not been discovered. The Stillwater complex 

contains chromite near Boulder River a few miles southeast of Mount Rae, but 

no chromite has been discovered in the Stillwater complex within the mapped area.

INTRODUCTION 

LOCATION AND EXTENT OF THE AREA

This report and the accompanying maps describe the geology of 

about 250 square miles in Park County, Mont. The area lies south 

and east of the Yellowstone River and includes the Mount Rae, 

Elton, Mission, and Livingston Peak 7K-minute quadrangles and 

the area east of the Yellowstone River in the Brisbin and Livingston 

7K-minute quadrangles. The area is thus bounded on the east by the 

110° 15' meridian of longitude, on the west by the Yellowstone 

River and the 110° 30' meridian, and on the north and south by the 

45° 45' and 45° 30' parallels of latitude as shown in figure 58.

PURPOSE OF REPORT

This report was prepared as part of the Interior Department 

program for the development of the Missouri River basin. Sedimentary rocks and their structures were studied to evaluate the oil 

and gas possibilities of the area, and the surficial deposits were examined to indicate their value as aggregate.

FIELD WORK AND ACKNOWLEDGMENTS

The area was mapped during the summers of 1949 and 1950; the 

writer was assisted by G. E. Prichard in 1949 and by A. A. Meyerhoff
t "--*- 

V v i v 

 ; : -: !|YEtLOWSTpNE 

?' '-.' ' ': ^Scife-V: NATIONAL':'

FIGURE 58. Index sketch map showing relation of mapped area to Crazy Mountains syncline, Bighorn Basin, 

ern Wyoming.
388 CONTRIBUTIONS TO GENERAL GEOLOGY!

in 1950. All geologic data were drawn on aerial photos of 1:24,000 * 

scale and later transferred to topographic base maps. Altitudes for 

the control of structure contours were taken from points of intersection of formation contacts and topographic contours (pi. 34). *

PREVIOUS WORK AND PUBLICATIONS

The geology of the area was discussed briefly by Hayden (1872, « 

1873) in the 5th and 6th Annual Reports of the U. S. Geological 

Survey of the Territories. A geologic map of the Livingston one- h 

degree quadrangle appeared in Folio 1 of the U. S. Geological Survey 4 * 

geologic atlas series (Iddings and Weed, 1894). Parts of the area 

covered by this report were mapped by Weed (1893), Stone and 

Calvert (1910), and Lammers (1937). Geomorphic problems have * 

been discussed by Alden (1932) and Horberg (1940).

A report by the writer on the geology of this area was placed on * 

open file in Geological Survey offices on July 9,1952. 1 ^

GEOGRAPHY

SURFACE FEATURES AND RELIEF *.

The area covered by this report includes the northwest corner of 

the Beartooth Mountains and adjacent parts of the Yellowstone *' 

River valley. The Beartooth Mountains are part of the Middle 

Rocky Mountains physiographic province, and most of the mountainous part of the area lies within the Gallatin National Forest. -t; 

The Yellowstone River flows northward from Yellowstone National 

Park between the Beartooth Mountains and the Gallatin Range to 

Livingston where it turns eastward and crosses the south edge of the 

Crazy Mountains syncline. The Crazy Mountains syncline, named ,f

from the mountains located about in the center of the 100-mile-long

synclinal area, is part of the Great Plains. *

Altitudes within the area range from 4,200 feet on the Yellowstone 

River to more than 10,000 feet in the mountains in the southern 

part of the area. A large part of the valley is below an altitude of *' 

5,000 feet, whereas, many of the ridges and peaks of the mountains x 

are 8,000 feet or more in altitude.

CLIMATE AND WATER SUPPLY

The average annual rainfall at Livingston is about 15 inches. 

Other climatic data are summarized in the table below. The Yellow- > 

stone River is the main stream of the area; it is joined from the north 

by the Shields River which drains much of the area west of the Crazy 

Mountains and east of the Bridger Range. Several perennial streams «

i Richards, P. W., 1952, Structural geology of the Crazy Mountains synclinc-Beartooth Mountains 

border east of Livingston, Mont.: U. S. Qeol. Survey open-file report.
Climalological Data for Livingston, Park Cou

[Average date through 1930 of last killing frost in spring, May 16; first killing frost in autumn, September 20; le

summaries of the United States, U. S. Weather B

Temperature, 'in degrees Fahrenheit:

Length 

of 

record, 

in years

39

28 

28 

28 

28

28

Through 19

Jan.

0.63

25.4 

34.6 

16.2 

60 

-39

Feb.

0.58

28.3 

38.1 

18.5 

64 

-34

Mar.

0.88

34.6 

45.4 

23.9 

75 

-26

Apr.

1.39

44.0 

56.3 

31.6 

89 

2

May

3.08

52.1 

65.4 

38.8 

92 

10

June

1.98

60.4 

74.7 

46.1 

99 

29

July

1.47

68.2 

84.0 

52.4 

106 

35

A

1
390 CONTRIBUTIONS TO GENERAL GEOLOGY *

that rise in the Beartooth Mountains enter the Yellowstone River 

within the area. The discharge of the Yellowstone River near 

Livings ton was an average of about 3,600 second-feet for 23 years <?~ 

during times that records were kept between 1897 and 1949. During 

the same period the maximum discharge of the Yellowstone River * 

was 30,600 second-feet on June 20, 1943, and the minimum daily 

discharge was 590 cfs on January 22, 1940. The average discharge of 1 

the Shields River a few miles above its mouth for the 18 years during 

which records were kept between 1921 and 1949 was 146 cfs. ^

SETTLEMENT AND POPULATION «J

Livingston, the county seat of Park County, is the only town 

within the area. It had a population of 7,683 in 1950. The main line <(. 

of the Northern Pacific Railway goes through Livingston; a branch 

extends southward from Livingston to Gardiner, Mont., at the north < 

entrance to Yellowstone National Park, and a branch runs northward 

from Livingston into the Shields River valley. Highways U. S. 10 

and U. S. 89 pass through Livingston.

MET AM ORPHIC AND IGNEOUS ROCKS * 

METAMOBPHIC BOCKS <

The metamorphic rocks are a series of interbedded steeply dipping 

gneiss, schist, quartzite, and some marble. They are of pre-Cambrian 

age and are older than the unmetamorphosed Belt series, which is 

not found within the area.

STILLWATEB COMPLEX *

The Stillwater complex occurs only in the southeast corner of the * 

Mount Rae quadrangle. It is an ultrabasic intrusive mass which, ^ 

because of its chromite content, has been studied carefully at the 

type locality near Stillwater River canyon about 25 miles to the 

southeast of Mount Rae. In the Stillwater area the complex is divided < 

into four zones: (1) the basal zone which is comprised of norite; (2) 

an ultramafic zone, consisting of bronzitite, harzburgite, which is " 

associated with chromite near the middle of the zone, and dunite; 

(3) the banded zone, which is made up of norite, gabbro, and anorthosite; and (4) the upper zone, composed of anorthosite, norite, and 

gabbro (Peoples and Howland, 1940, p. 378). i

The westernmost exposure of the Stillwater complex is in the 

Mount Rae quadrangle and it includes norite and anorthosite, which 

are probably part of the banded and upper zones (Howland and 

others, 1949, pi. 34). It is separated from the gneiss to the south 

and from Paleozoic strata on the west by faults. Shale of Cambrian
GEOLOGY, AREA EAST AND SOUTHEAST OF LIVINGSTON, MONT. 391

,» age overlies the Stillwater complex along the north side of the 

outcrop. The Stillwater complex is younger than the metamorphic

* rocks but older than the granite in the Beartooth Mountains (Peoples

s and Howland, 1940, p. 376, 382). No deposits of chromite have been

reported in the mapped area. Considerable prospecting for chromite

has been carried on in the area east of West Boulder River a few

%. miles southeast of the Mount Rae quadrangle (Howland and others,

1949).

* GRANITE

(-V Pink coarse-grained granite of pre-Cambrian age occurs in a small 

area south of the west end of the Stillwater complex. It is in fault 

contact with the Stillwater complex and possibly in fault contact

* with older metamorphic rocks to the east and west. The contact of 

the granite and the gneiss is concealed by talus and morainal debris. 

Granite is not distinguished from the metamorphic rocks on the

f. geologic map.

DIABASE AND GABBRO

Diabase dikes were mapped along the north fork of Deep Creek

and near Blacktail Lake. In the latter area a dike that strikes easty ward through Blacktail Lake is nearly vertical and ranges from 20

to 40 feet in width. It extends a distance of at least 1 mile west of the

lake and a few hundred feet east of the lake to a moraine. A similar 

, dike, perhaps the same one but offset by a fault and concealed by

the moraine, starts 1,200 feet to the south and continues eastward

for a distance of at least 2,000 feet. 

A An irregular mass of gabbro is associated with the diabase in the

north fork of Deep Creek. The rocks were determined by A. H.

Makela of the Geological Survey. No dikes were observed in Paleozoic

* or younger rocks within the mapped area. Thick dikes and sills do 

occur, however, in the valleys of the Yellowstone River and Shields 

River north of the area. 

v

SEDIMENTARY ROCKS 

»

The sedimentary rocks, ranging in age from Middle Cambrian

* into Late Cretaceous and perhaps Tertiary, are about 15,000 feet 

thick. These strata, which are described briefly in plates 35 and 36, 

are seemingly concordant although the Silurian, Permian, and Triassic 

.j systems are missing. Paleozoic formations dip steeply northward 

"^ along the Beartooth Mountains' front and are exposed in southwardfacing cliffs. The overlying Jurassic strata likewise dip steeply and

* crop out in a narrow belt close to the base of the mountains, and the 

Cretaceous rocks dip northward from the edge of the mountains 

into the Crazy Mountains syncline.
392 CONTRIBUTIONS TO GENERAL GEOLOGY

Paleozoic formations (fig. 59) are mostly marine; the Jurassic 

system is continental and marine; and the lower one-third of the 

Cretaceous strata is mostly marine, while the upper two-thirds is 

continental. Two unconformities within the sequence represent at 

least one geologic period each. These occur between the Upper 

Ordovician Bighorn dolomite and the Devonian Jefferson limestone, 

and between the Pennsylvanian Quadrant quartzite and the Middle 

Jurassic Piper formation. In addition, an unconformity below the 

Bighorn dolomite represents Early and Middle Ordovician, and an 

erosional unconformity below the Amsden formation represents part 

of the Mississippian and perhaps part of the Pennsylvanian periods. 

Little is known of the unconformities that are within formations and 

represent considerably less than a period.

CAMBRIAN SYSTEM

The Cambrian system, which is about 1,000 feet thick near Shell 

Mountain, consists of a conformable sequence of shale and limestone

FIGURE 59. Paleozoic strata along north Hank of the Beartooth Mountains. View southeastward to 

Rough Draw. In descending order: Mm, Madison limestone; Dtj, Three Forks shale and Jefferson 

limestone; Ob, Bighorn dolomite; "Cgs, Grove Creek and Snowy Range formations; "Cp, Pilgrim limestone; m. Middle Cambrian Park shale, Meagher limestone, Wolsey shale, and Flathead quartzite; 

p g, pre-Cambrian gneiss.
GEOLOGY, AREA EAST AND SOUTHEAST OF LIVINGSTON, MONT. 393

above a lenticular basal sandstone. No Lower Cambrian rocks are 

known to occur in the area. Middle Cambrian strata are mostly 

shale, whereas Upper Cambrian strata are largely limestone. These 

strata have been divided into 4 Middle Cambrian and 3 Upper 

Cambrian formations. Narrow outcrops of the formations, caused 

by the very steep slopes on which the rocks are exposed, led the 

author to combine the 7 formations into 3 cartographic units. The 

4 Middle Cambrian formations were mapped together, and the 3 

Upper Cambrian formations were mapped as 2 units. The system 

lies upon upturned pro-Cambrian rocks that include granite, the 

ultrabasic Stillwater complex, and metamorphosed sedimentary rocks.

MIDDLE CAMBRIAN SERIES

The Middle Cambrian series is 625 feet thick and includes the basal 

Flathead quartzite, Wolsey shale, Meagher limestone, and Park shale 

which were accorded formational rank by Weed (1900) and redescribed 

by Deiss (1936). These formations are well exposed in saddles at 

the heads of East Baldy Basin and Rough Draw. The following 

stratigraphic section was measured at the head of Rough Draw, and 

the photograph (fig. 60) was taken at the head of East Baldy Basin.

FIGURE 00.---Cambrian strata north of Livingston Peak. View nortmvara across sadau- at neau 01 KasL 

Baldy Basin showing Upper Cambrian Pilgrim limestone ( p) in cliff and Middle Cambrian formations (-Cps, Park shale; -Cm, Meagher limestone; -Cw, Wolsey shale; -Cf, Flathead quartzite).
394 CONTRIBUTIONS TO GENERAL GEOLOGY "'

Section of Middle Cambrian strata between head of Rough Draw and crest of Shell 

Mountain, all in or near SW}i sec. 21, T. 3 S., R. 11 E. (unsurveyed) , Park

County, Mont. ^»

Pilgrim limestone: Basal part is a gray dense to finely crystalline limestone, much of which occurs as edgewise conglomerate; unit weathers 4D 

to light blue or light green but is exposed only in a few places.

Park shale: peet ^ 

Shale and limestone; gray mostly finely crystalline glauconitic lime- ^\ 

stone and greenish-gray shale. Limestone in beds as much as 3 feet 

thick; the thicker beds are crystalline, probably fragmental; many <,. 

limestones are ripple marked and many occur as flat-pebble conglomerate. _________________________________________________ 92 *

Shale, greenish-gray; mostly concealed_________________________ 119

Shale and limestone; interbedded greenish-gray shale and gray micaceous, probably silty, limestones, many marked by raindrop ., 

impressions__________________________________________________ 19

Shale, brownish-gray, weathers somewhat greenish-gray, notably

fissile; may include thin beds of limestone.-___________________ 56

Shale and limestone; greenish-gray shale and gray crystalline (frag- .^- 

mental?) platy limestone; some limestone beds have abundant 

"bottom markings" on bedding planes, other limestones occur as 

flat-pebble conglomerate___________________________________ 94

Total Park shale____________________________ 380

Meagher limestone: <'j 

Limestone and shale; 1-inch beds of light-gray dense limestone in 

soft green shale. Unit weathers light yellowish gray and is conspicuous largely because of its color; it forms small ledges locally. 

Upper and, particularly, lower contacts gradational________________65 <'

Total Meagher limestone_________________________________65

Wolsey shale: ^ 

Shale, greenish-gray, flaky, and few thin beds of gray silty brownweathering limestone_______________________________________ 29

Limestone, dense and finely crystalline, brown-weathering; some 

occurs as flat-pebble conglomerate. A little shale interbedded with ^ 

limestone___________________________________________________ 11

Shale, greenish- and reddish- to brownish-gray; some of color probably 

result of weathering. Includes few thin beds of crystalline, in part, 

glauconitic limestone. Contact with Flathead quartzite concealed.. ___65 '*'

Total Wolsey shale_.____________________________ 105

Flathead quartzite:

Quartzite and sandstone; gray to reddish-gray thick-bedded to mas- . ,4? 

sive sandstone that is mostly quartzite in upper 50 feet. Lower 

25 feet contains hematite nodules. Layers of quartz granules, up 

to a few millimeters in diameter, occur in basal few feet. Lower .^ 

part of formation in part crossbedded__----------------------- 75 { ,

Total Flathead quartzite_______.___-___-_--_________--_--__75 « 

Total Middle Cambrian series_____________________________ 625

Pre-Cambrian metamorphic rocks. *
GEOLOGY, AREA EAST AND SOUTHEAST OF LIVINGSTON, MONT. 395 

FIATHEAD QUARTZITE

The Flathead quartzite is gray to reddish-gray sandstone and 

quartzite. Gray quartz granules a few millimeters in diameter are 

common in the basal few inches. The topmost few feet of the Flathead 

in the outcrop at the head of Rough Draw is quartzite, whereas the 

underlying rock is interbedded sandstone and quartzite. Limonite 

and hematite nodules are common in the lower 25 feet.

The Flathead is not more than 75 feet thick in most outcrops, and 

it is absent in a number of localities, notably above the Stillwater 

complex and along much of the ridge north of the north fork of Deep 

Creek. Its absence is seemingly due to nondeposition over low hills 

of pre-Cambrian rock that remained above the sea bottom during 

transgression of Middle Cambrian seas.

WOLSEY SHAIE

The Wolsey shale is about 100 feet thick and consists mostly of 

grayish-purple, brownish-gray, and greenish-gray shale. Limestone 

occurs in thin layers in most localities. Wherever the Flathead is 

missing "the Wolsey lies upon the pre-Cambrian rocks. The basal 

part of the Wolsey shale is commonly covered. Although the formation 

was not measured in more than one locality, it is not noticeably 

thinner where it lies directly on the pre-Cambrian than where it is 

underlain by the Flathead quartzite.

MEAGHER LIMESTONE

The Meagher limestone consists of 65 feet of thin-bedded gray 

limestone and greenish-gray shale. The unit is distinct in appearance 

from the overlying and underlying beds (fig. 60) because the limestone makes small ledges and the weathered limestone and shale are 

light yellowish-gray. The Meagher is exposed in only a few places 

in the mapped area and is but a thin representative of the formation 

in adjacent areas to the north and west. According to Deiss (1936, 

p. 1331), the Meagher ranges more in thickness than any other 

Cambrian formation and is more than 400 feet thick along Beaver 

Creek in the Big Belt Mountains.

PARK SHAIE

The Park shale is 380 feet thick and consists of interbedded greenishgray and brownish-gray shale and gray crystalline glauconiticlimestone. 

Much of the limestone occurs as flat-pebble conglomerate. The lower 

300 feet is shale, but limestone becomes abundant and is dominant in 

the upper 80 feet. As the upper part is commonly concealed by 

talus from the overlying Pilgrim limestone, the top of the Park shale 

is difficult to determine. Hanson (1952, p. 15) notes that the contact 

is a "gradual passage" from shale to limestone in the Cooke City area,
396 CONTRIBUTIONS TO GENERAL GEOLOGY)

which is in the Beartooth Mountains about 50 miles southeast of 4- 

Livings ton.

Although the Park shale is the uppermost Middle Cambrian forma- «- 

tion in south-central Montana, the contact between the Park shale 

and Pilgrim limestone does not everywhere coincide with the contact 

of Middle and Upper Cambrian strata. Denson noted that a Middle 

Cambrian fauna occurs in the basal part of the Pilgrim limestone at ^ 

Nixon Gulch in the Three Forks quadrangle west of Livingston 

(Lochman and Duncan, 1944, p. 5). <

The Upper Cambrian series is 400 feet thick, which is in agreement 

with the reported average thickness for the series in the Livingston 

one-degree quadrangle (Iddings and Weed, 1894). Terminology of the 

Upper Cambrian formations is more complex, than that of the Middle 

Cambrian formations, and detailed reviews of the nomenclature have 

been discussed by Deiss (1936), Sloss and Laird (1947), Lochman 

(1950), and Hanson (1952).

Peale (1893) divided the Upper Cambrian strata in the area of 

Three Forks, Mont, into the Mottled limestone, Dry Creek shale, " 

and Pebbly limestone beds. These and the underlying Obolella shale 

(Park shale) were, according to Peale, the members of the Gallatin 

formation. Iddings and Weed (1894) referred to all of the Upper 

Cambrian strata in the Livingston quadrangle as the Gallatin limestone.

Weed (1900) established in central Montana, a standard section 

for Cambrian strata and described type localities in the Little Belt 

Mountains. His Upper Cambrian series consisted of the Pilgrim 

limestone, Dry Creek shale, and Yogo limestone. Dorf and Lochman 

(1940) proposed for the Upper Cambrain of south-central Montana 

the Maurice, Snowy Range, and Grove Creek formations. These 

would apply to the Upper Cambrian starta of the Beartooth 

Mountains.

There is apparent agreement by those who have written on Upper 

Cambrian stratigraphy of Montana that Weed must have considered 

the Dry Creek shale and Yogo limestone in the Little Belt Mountains 

to be stratigraphic equivalents of the Dry Creek shale and Pebbly 

limestone described by Peale in the Three Forks area. Deiss (1936, 

p. 1337), Sloss and Laird (1947, p. 1413-1415), and Lochman (1950, 

p. 2205-2206) have shown the fallacy of this interpretation and the 

limestone beds that Weed called Yogo limestone are probably of 

Devonian age.

The work of Sloss and Laird (1947, p. 1407-1409) and Lochman 

(1950) has indicated that Weed's type Dry Creek shale occurs, at
GEOLOGY, AREA EAST AND SOUTHEAST OF LIVING STON, MONT. 397

t least in part, above a pre-Devonian unconformity and that it is therefore partly, and perhaps wholly Devonian age. Lochman (I960, fig. 2)

* called these beds the Maywood formation, a term introduced by

, Emmons and Calkins (1913, p. 64-65) for strata in the Phillipsburg

area in western Montana. In the general area of Three Forks, beds

that Lochman considered to be the stratigraphic correlatives of Weed's

\ Dry Creek (the Maywood formation) overlie either Peale's Dry Creek

shale or Pebbly limestone. Lochman suggested that the unit first

** called Dry Creek shale by Peale be considered a member of Dorf and 

_< Lochman's (1940) Snowy Range formation and that Peale's Pebbly 

limestone beds become the Sage pebble-conglomerate member of their 

Snowy Range formation.

», The formation names used in this report are the Pilgrim limestone, 

Snowy Range formation, and Grove Creek formation. The reasons

* for their selection are discussed under the formation descriptions that 

follow.

Section of Upper Cambrian and Upper Ordovician series between head of Rough 

Draw and crest of Shell Mountain, all in or near SE}i sec. 21, T. 3 S., R. HE. 

(unsurveyed) , Park County, Mont.

Bighorn dolomite: Light-gray massive dolomite.

Grove Creek formation:

Limestone and shale; gray dense and crystalline limestone interbedded with green shale; stringers of sandstone and siltstone in 

unit. Limestone occurs as flat-pebble conglomerate and in rounded 

pebbles; weathers brownish gray in upper few feet. Unit is about Feet 

half limestone. _ ____-__________-___-__-__---_--__-__________- 50

Total Grove Creek formation_-._____-_---___-___.__.___.___ 50

Snowy Range formation:

Shale and limestone; shale largely concealed; exposed shale is greenish 

gray. Limestone in ledges is crystalline (fragmental ?) glauconitic 

limestone.- _ ____________--___--_--_--__---_---__-__-_______.. 100

Limestone, light-gray; weathers gray to bluish gray; all but lower few 

, feet is in form of columns. Lower 8 feet is thin-bedded flat-pebble 

conglomerate. _ _-__-___-___-__----_-_--_---__-__-______-_-___ 33

Shale, greenish-gray; few thin beds of flat-pebble limestone at base.. 36

Total Snowy Range formation______________________________ 175

Pilgrim limestone:

Limestone, mottled light-yellowish- and brownish-gray, finely crystalline, thin- to thick-bedded, cliff-forming. Much is oolitic. 

Thin stringers of sandstone and siltstone common _______________ 105

Limestone, gray, finely crystalline; contains sandy streaks. Basal 8 

feet is brown. Thickness probably ranges considerably from locality 

of measured section._________________________________________ 24
398

Section of Upper Cambrian and Upper Ordovician series between head of Rough 

Draw and crest of Shell Mountain, all in or near SE}i sec. 21, T. 3 S., R. 11 E. 

(unsurveyed), Park County, Mont. Continued

Pilgrim limestone Continued

Limestone, gray, dense and finely crystalline; much occurs as breccia 

or edgewise congolmerate. Unit weathers light blue or green and 

makes basal part of Pilgrim cliff in part of area, but unit is concealed Feet 

in most places_____________________________________________ 46

Total Pilgrim limestone______________-_____-_________._____ 175

Total Upper Cambrian series_______^_______________.______ 400

Park shale: Gray glauconitic limestone and greenish-gray shale.

PILGRIM LIMESTONE

The Pilgrim limestone is 175 feet thick and crops out as the first 

cliff-forming unit above the pre-Cambrian rocks. The lower member 

is 70 feet thick and is commonly concealed by talus from the cliffforming upper part. The basal 46 feet is a flat-pebble and edgewise 

conglomerate composed of gray dense and finely crystalline limestone. 

The limestone strata have been so broken that much of the edgewise 

conglomerate is best described as a breccia. This unit weathers 

light blue or green and is a lighter shade than the overlying limestone. 

(See figure 61.) This basal unit is seen only in few places.

The upper part of the basal member of the Pilgrim consists of gray 

finely crystalline limestone that includes many thin sandy streaks 

and an 8-foot unit of brown limestone at the base. This limestone, 

like the underlying unit, is not well exposed.

The upper member of the Pilgrim is 105 feet thick near Shell 

Mountain and consists mostly of light-yellowish-gray partly oolitic 

limestone that contains many irregularly shaped masses of brown 

oolitic limestone which are about 1 inch long. Because of the irregular pattern of the light and dark limestones, Walcott (1891) called 

the unit the "Mottled limestone."

As pointed out in the discussion of the Park shale, the contact 

between the Park and the Pilgrim limestone is gradational. Dorf 

and Lochman (1940, p. 550) stated that the limestones in the top 

of the Park shale contain rounded limestone pebbbles whereas the 

basal limestones of the Pilgrim contain flat-pebble and edgewise 

conglomerate. This criteria, if it holds true in the area near Livingston, could not be applied by the writer, partly because the upper 

part of the Park shale is poorly exposed.

In 1940 Dorf and Lochman proposed that the term Pilgrim limestone be replaced in south-central Montana by the Maurice formation. Their justification for the introduction of new names lies in their 

statement that lithologic changes of Upper Cambrian strata between
GEOLOGY, AREA EAST AND SOUTHEAST OF LIVINGSTON, MONT. 399

FIGUHE 61. Pilgrim limestone. View eastward along anticline south of Suce Creek.

central and south-central Montana warrant the recognition of these 

different units (Dorf and Lochman, 1940, p. 542). The Pilgrim in the 

Beartooth Mountains is mainly mottled oolitic limestone overlying 

edgewise conglomerate or brecciated limestone. The Pilgrim consists 

of limestone and shale in the Little Belt Mountains, where the formation was named by Weed (1899 a, b, and 1900). The limestone occurs 

in massive beds and in beds of flat pebbles. Hanson (1952, p. 16), 

however, reported the occurrence of beds of oolitic limestone in the 

Pilgrim in the Little Belt Mountains, and the Pilgrim contains both 

oolitic and pebbly limestones and shale in the area of Three Forks. 

In outcrops between these three areas, the Pilgrim contains mottled 

and flat-pebble limestones. Lochman and Duncan (1944, p. 12) 

pointed out that the south-central and central Montana sites of 

deposition were "open" and "contiguous" during Late Cambrian. 

The writer concurs with Hanson (1952, p. 16) that 

It seems best, in the interests of simplified nomenclature, to extend the term 

Pilgrim to include differing facies so long as these facies have enough in common 

to distinguish the stratigraphic unit of which they are a part, from subjacent 

and superjacent units.

It seems to the writer that the "Maurice formation" might be suitably 

applied to rocks in one or two mountainous uplifts. However, the 

difficulties of separating the "Maurice" from the Pilgrim limestone 

where the two interfinger in basins between the outcrops where the 

formations are named detract so much from the value of a new formational name as to invalidate the use of "Maurice."
400 CONTRIBUTIONS TO GENERAL GEOLOGY 

SNOWY RANGE AND GROVE CREEK FORMATIONS

The Snowy Range and Grove Creek formations were named by 

Dorf and Lochman (1940) for strata above the Pilgrim limestone 

(Maurice formation of Dorf and Lochman) in south-central Montana. 

The type locality of the Snowy Range formation is about 25 miles 

south of Livingston near the Snowy Range Ranch on the east fork 

of Mill Creek, Park County, Mont. The type locality of the Grove 

Creek formation is along Grove Creek, a tributary to the Clarks 

Fork of the Yellowstone River along the Beartooth Mountains front 

5 miles southeast of Red Lodge, Carbon County, Mont.

Dorf and Lochman reported that the formations are remarkably 

uniform in thickness and lithology along the Beartooth Mountains, 

and the sections (p. 397) measured near Shell Mountain support their 

statement. The two formations were mapped together because their 

outcrops are so narrow.

The Snowy Range formation is 175 feet thick near Shell Mountain 

and consists of a lower 36 feet of greenish-gray shale, a middle 33 

feet of flat-pebble limestone conglomerate overlain by "columnar" 

limestone (fig. 62) and an upper 106 feet of inter-bedded poorly 

exposed greenish-gray shale and light-gray dense and crystalline 

glauconitic limestone. Of these beds, the lower 34 feet are seemingly 

the stratigraphic equivalents of Peale's Dry Creek shales (see Lochman, 1950, fig. 1); and the remainder of the formation is in part 

correlative with and in part younger than Peale's Pebbly limestones 

(Lochman, 1950, figs. 1 and 2).

The Grove Creek formation is 50 feet thick. It consists predominantly of conglomeratic limestone and shale, but stringers of sandstone and siltstone are common. Many of the greenish-gray limestone 

pebbles are rounded. These are particularly noticeable among the 

flat-pebble conglomerates.

At the south base of Elephant Head Mountain 22 feet of Grove 

Creek strata are well exposed directly beneath the Bighorn dolomite. 

Of these 22 feet the upper one-half consists of thin platy limestones 

and a little fissile greenish-gray shale. The limestones weather yellowish gray to brownish gray and most occur as flat-pebble conglomerates. 

Many thin purple layers in the upper half are highly argillaceous. 

The uppermost 2 or 3 feet is alternate thin beds of shale and gray 

dense limestone. Rounded limestone pebbles are not common in the 

upper half but are abundant in the lower half which is mainly greenishgray shale and greenish-gray dense flat-pebble limestone conglomerate.

The Snowy Range formation is used herein because of the inconsistencies in the use of Dry Creek shale that have been pointed out \>y 

Devonian and Cambrian stratigraphers. The formation in this area 

apparently includes beds in the stratigraphic position of Peales' Dry
-v :_ ;."- ' Tr, i~¥?'~'*-&Z'<- ?'«-;r,iv_>^!*^I»wq£»r;it' 

GEOLOGY, AREA EAST AND SOUTHEAST OF LIVINGSTON, MONT. 401

FIGUUE 02. Columnar limestone in Snowy Range formation. Algal (?) limestone in lower part of Snowy 

Range formation has columnar structure locally.

Creek shales and Pebbly limestones and still younger beds. The 

work of Dorf and Lochman (1940) and Lochman (1950) indicates 

that the Grove Creek formation, which is a distinct lithologic unit 

throughout the Beartooth Mountains uplift, is younger than any 

Cambrian strata described by Peale or Weed in the Three Forks area 

and Little Belt Mountains. Its distinctness in both lithology and 

age merit formational rank for the unit. Both formations are mappable as lithologic units, and their boundaries on the accompanying
402 CONTRIBUTIONS TO GENERAL GEOLOGYi

geologic map represent lithologic changes but not necessarily faunal 

or age changes.

OBDOVICIAN SYSTEM 

BIGHORN DOLOMITE

The Bighorn dolomite near Shell Mountain is 200 feet thick and 

consists of 155 feet of massive yellowish-gray dolomite at the base, 

25 feet of light-gray thin-bedded blocky-weathering dolomite, and, 

at the top, 20 feet of interbedded dolomite and dolomitic limestone. 

The massive basal member is readily distinguished in outcrops from 

the underlying Pilgrim limestone because of the latter's thin bedding 

(fig. 63), high CaCO2 content, and pronounced mottling of weathered

FIGURE 63. Bighorn dolomite and Pilgrim limcsinm. Vim -upward from soutluu^i <lope of Shell 

Mountain toward West Boulder Eiver beyond dark ridge. The lower member (155 feet thick) of the 

Bighorn dolomite (Ob-1) and the Pilgrim limestone (Cp) make the upper and lower ledges respectively. 

The Cambrian Grove Creek ( g) and Snowy Range (6s) formations between the ledges and the Cambrian Park shale (Cps) beneath the Pilgrim limestone are largely covered by talus.

surfaces. A change in lithology from beds that are predominantly 

dolomite to beds of dark-brown and gray sandy and argillaceous 

limestone marks the contact as herein described of the Bighorn dolomite and the overlying Jefferson limestone. The basal member of the 

Bighorn is thinner and much less conspicuous in the canyon of the 

Yellows tone River south of Livingston than it is near Shell Mountain. 

Ordovician strata have not been described in the area west of Canyon 

Mountain west of the Yellowstone River.

A section of Bighorn dolomite measured by the writer north of 

Livingston Peak 4 miles northwest of Shell Mountain is 380 feet thick.
GEOLOGY, AREA EAST AND SOUTHEAST OF LIVINGSTON, MONT. 403

This is nearly twice the thickness of the Bighorn near Shell Mountain 

but less than the 438 feet of Ordovician strata measured nearby by 

Tomlinson (1917, fig. 2). The Livingston Peak 7K-minute topographic sheet calls the 9,314-foot peak of pre-Cambrian gneiss Livingston Peak, whereas this peak was referred to by Tomlinson (1917, 

p. 117), and also is referred to locally as "Old Baldy." The Livingston Peak of Tomlinson's report is the 8,631-foot limestone prominence 1 mile northeast of the gneiss peak. The 380-foot unit (fig. 64)

FIGURE 64.- Middle part of Jli^huru dolomite near Livin^ston Peak. View eastward from south slope of 

peak north of Livingston Peak showing rcdbed unit of Bighorn dolomite (Ob-ms) between upper (Ob-u) 

and lower (Ob-1) massive dolomite members.

is divisible into (1) a massive basal member, 120 feet thick (159 feet 

where measured by Tomlinson), (2) interbedded red, yellow, and 

gray silty and dolomitic shale, greenish-gray siltstone, and thin 

beds of limestone and dolomite that total 60 feet, (3) brecciated 

dark-gray limestones, about 30 feet thick, (4) massive slightly petroliferous dolomite, 140 feet thick, that is slightly darker than the basal 

member, and (5) light-gray dolomite, about 25 feet thick. No 

section of similar lithology or thickness was seen elsewhere in the 

area. Of these five units only the basal dolomite was recognized 

at Shell Mountain, and the upper four units presumably pinch out 

along the outcrop eastward and westward from Livingston Peak.

The upper massive member,*as well as the basal member are 

Ordovician; Edwin Kirk (personaljcommunication, November 17,1950) 

identified Receptaculites, a typical Bighorn fossil collected by the 

writer from near the middle of the upper massive member. Judging
404 CONTRIBUTIONS TO GENERAL GEOLOGY!

from the difference in thickness of the basal member and overlying 

variegated beds in sections measured by Tomlinsori (1917, fig. 2) and 

the writer, it seems that the variegated shales and siltstones may lie 

in one or more channels that were cut into the basal member of the 

Bighorn. However, inasmuch as the Devonian strata described by 

Tomlinson (1917, fig. 3) are similar in lithology and thickness to units 

at Shell Mountain, the extra thickness of Bighorn strata measured by 

Tomlinson and the writer near Livingston Peak may be partly 

Devonian strata and partly Bighorn strata repeated by faulting. 

Thus the topmost 25 feet of light-gray blocky-weathering dolomite 

and the 140 feet of massive dolomite beneath it may overlie a northward dipping reverse fault and be a repetition of the Bighorn dolomite that lies beneath the varicolored beds. The dark-gray limestone 

beneath the upper massive dolomite unit closely resembles and may 

very well be Jefferson limestone, and the underlying varicolored siltstone, shale, and dolomite would then be basal Devonian. The writer 

believes that the exceptional thickness of the Bighorn in this locality 

is explained more readily by fault repetition than by sedimentation 

processes.

The massive member of the Bighorn dolomite in the Bighorn 

Mountains is generally considered to be Upper Ordovician. The 

Lander sandstone member (Miller, 1930) in the Wind River Mountains, Wyoming, and the Middle Ordovician Harding sandstone 

equivalent (Kirk, 1930) in the Bighorn Mountains, both of which 

underlie the massive dolomite member, have not been found in the 

area near Livingston. Here the massive dolomite overlies the Upper 

Cambrian (Trempeleau) Grove Creek formation; therefore, all Lower 

and Middle Ordovician strata are represented by a hiatus within 

the mapped area.

DEVONIAN SYSTEM 

JEFFERSON LIMESTONE AND THREE FORKS SHALE

The Jefferson limestone is 390 feet thick at Shell Mountain, and 

Tomlinson (1917, fig. 3) showed 434 feet at the 8,631-foot limestone 

peak, 1 mile northeast of the point shown as Livingston Peak on the 

topographic map. Dark-brown argillaceous limestone, in part brecciated and dolomitic, containing thin sandy streaks, make up the 

lower 230 feet. This is overlain by nearly 90 feet of lighter gray 

limestone, and it is followed by 70 feet of intensely brecciated limestone, the upper 40 feet of which makes dark ledges.

An 80-foot zone of argillaceous beds above the Jefferson was called 

the Three Forks formation by Tomlinson (1917, fig. 3). A unit of 

like thickness at Shell Mountain is mostly concealed but contains 

shale and argillaceous limestone and dolomite which weather yellowish 

brown. The unit is herein called the Three Forks shale but was
GEOLOGY, AREA EAST AND SOUTHEAST OF LIVINGSTON, MONT. 405

mapped with the Jefferson limestone. Both formations are shown 

in figure 65. The effects of weathering upon the Three Forks shale 

is shown in figure 66.

Section of Jefferson limestone and Three Forks shale between head of Rough Draw 

and crest of Shell Mountain, all in or near SW/* 1 sec. 21, T. 3 S., R. 11 E. (unsurveyed), Park County, Mont.

Madison limestone: Basal part is cliff-forming interbedded limestone and

chert. 

Three Forks shale:

Shale and limestone, largely concealed; thin beds of brown and orangebrown dolomite in upper few feet; basal 10 feet is dolomitic yellowish-gray shale with small ironstone nodules; middle is concealed, feet 

weathers to yellowish-brown soil.____-_____-___----_---_.--___- 80

Total Three Forks shale.. _______ _______ i _. ___-___-._--.__-- 80

Jefferson limestone: 

>, Limestone breccia; rock breaks into small fragments but is resistant

to erosion and is nearly as prominent in ledges as basal unit of

Madison limestone; light to medium gray and dense to finely

crystalline. . ________________________________________________ 42

Limestone, gray, brecciated, and yellowish- to greenish-gray argillaceous limestone; forms slopes and saddles___-_______---_--------__ 30

Limestone, medium-gray, sugary texture, thin-bedded, and platy... 36 

Limestone; interbedded light-olive-gray dense limestone and yellow

and green silty limestone; beds 10 feet below top contain Atrypa 

^ cf. A. devoniana Webster... - ___________________-_______--__._ 52

Limestone, brownish-gray; tnin yellow silty dolomite bed near base.. 45 

Limestone, brownish-gray, thin- and thick-bedded; thin zone of yellow

calcareous shale near base; upper beds contain Atrypa and Coenites. 28 

Limestone, brownish-gray, dense, mostly thick-bedded _.._______.__ 35

Limestone, gray, dolomitic; interbedded darker gray limestone. _..-. 30 

Limestone, brownish-gray, thin-bedded; weathers to dark surface.... 22

Limestone, brownish-gray, brecciated -_--_________--__-_______-__ 35

Limestone, brownish-gray, thin- to thick-bedded; weathers very dark

gray and forms ledges. _______________________________________ 35

Total Jefferson limestone____________________________________ 390

Bighorn dolomite: Dolomitic limestone and dolomite.

Both the Jefferson limestone and Three Forks shale were called 

Upper Devonian by Sloss and Laird (1947, p. 1426). Two small 

collections of fossils taken from about 175 and 250 feet above the 

base of the Jefferson limestone were identified by Edwin Kirk (personal communication, February 3, 1950) who stated that the fossils 

are Middle or Upper Devonian; a more precise determination of age 

was not possible from the collections.
406 CONTRIBUTIONS TO GENERAL GEOLOGY!

O -3
GEOLOGY, AREA EAST AND SOUTHEAST OF LIVINGSTON, MONT. 407

FIGURE 66. Cave in Three Forks shale along axis of Lion Mountain anticline. View westward from 

West Boulder Meadows showing cave weathered from the softer shales and siltstones at top of Devonian 

strata. Cave is about 50 feet high at entrance. Roof of cave is cherty bed of Madison limestone. Most 

of Madison limestone is exposed to right of cave.

CARBONIFEROUS SYSTEMS 

MISSISSIPPIAN SYSTEM

MADISON IIMESTONE

The Madison limestone is 860 feet or more thick at Shell Mountain. 

Its contact with the overlying Amsden formation lies along the northward-facing slope of Shell Mountain; therefore, a few feet at the top 

of the formation may not have been included in the measured section. Although the Madison is more than 860 feet thick, this thickness 

does not approach the 1,500 feet assigned by Iddings and Weed (1894) 

in the Livingston (1-degree) quadrangle or the 1,800 feet ascribed to 

the Madison near Livingston by Lammers (1937, p. 270).

The following section was measured on the southwest slopes of 

Shell Mountain. Fossils listed in the section were collected by the 

author and were described by Geological Survey paleontologists, the 

corals by Helen Duncan and the brachiopods by J. S. Williams and 

Edwin Kirk.
408 CONTRIBUTIONS TO GENERAL GEOLOGY

Section of Madison limestone between head of Rough Draw and crest of Shell Mountain, all in or near SW% sec. 21, T. 3 S., R. 11 E. (unsurveyed), Park County, 

Mont.

Madison limestone: (The contact with the Amsden formation is on the 

dip slope on the north side of Shell Mountain. A few feet of the topmost beds of the Madison limestone that crop out only on the dip slope are 

not described below.)

Limestone, light- to medium-gray, finely crystalline and sugary;

contains chert lenses; unit somewhat brecciated, forms ledge and Feet 

dip slope on top of Madison limestone__---__-__-_-_..----_______ 62

Limestone breccia, mostly concealed; limestone mostly light to 

medium gray, finely crystalline; contains a little red silty material 

which weathers orange_______________________________________ 49

Limestone and chert; light-gray finely crystalline limestone and 

lenses of gray chert; unit weathers gray and forms cliffs locally; some 

beds in upper part are dark-gray limestone____________________ 81

Limestone; upper half massive light-brown sugary limestone, cherty, 

weathers light gray; lower half mostly concealed. Limestone in 

upper part gives strong petroleum odor when broken by hammer. _ 95 

Unit is highest topographic point on Shell Mountain.

Limestone; yellowish-gray, dolomitic; lower 6 feet slabby dolomitic 

limestone and upper part somewhat siliceous; chert occurs in nodules 

and lenses._________________________________________________ 55

Limestone, light-gray, crystalline, massive; weathers bluish gray and

forms cliff; stylolitic; some beds full of crinoid columnal plates____ 48

Limestone, light-gray, finely crystalline, thin-bedded; thin red 

argillaceous zones throughout unit; many fragments of crinoid stems 

in upper 7 feet.___________-_-___-__.._----______-_-_---__---_ 25

Limestone, light-gray; in part finely crystalline, massive and thin 

bedded; forms small ledges; contains Homalophyliitesl, Caninoid? 

corals, Clisiophyllid? coral, Lithostrotion sp____-______--__--__-_ 38

Limestone, light- to medium-gray, finely crystalline; contains a few 

flat limestone pebbles in base, a few thin stringers of red to purple 

silty material, and several beds of crinoid fragments.___________ 43

Limestone, gray; in part sandy, contains many crinoid columnal

fragments and a few thin purple silty or argillaceous stringers.___ 24

Limestone, medium-gray, dense, silty, shaly, and sandy (very fine 

sand grains); saddle west of highest point of Shell Mountain on 

this unit; beds in saddle weather yellow and are probably argillaceous. This zone is marked both here and in surrounding area 

by small, 4 to 6 feet high, algal (?) mounds. Bedding of limestone 

about reefs is broken_________________________________________ 50

Limestone, dense and finely crystalline, and in alternate bands of 

medium and dark gray; many of lighter gray layers are sandy (very 

fine grains); thin layers of argillaceous and silty limestone in unit 

weather gray and yellow; many layers of crinoid stem fragments in 

unit; topmost 2 feet is composed of limestone and shell fragments 

that are partly rounded; beds 15 feet below top contain Schuchertellal 

sp. indet., Choneles cf. C. loganensis Girty, productid of dictyoclostidtype, Spirifer centronatus Winchell, Punclospirifer cf. P. transversus

--_-.___.-----^------------------------------ 108
GEOLOGY, AREA EAST AND SOUTHEAST OF LIVINGSTON, MONT. 409

Section of Madison limestone between head of Rough Draw and crest of Shell Mountain, all in or near SW% sec. 21, T. 3 S., R. 11 E. (unsurveyed), Park County, 

Mont. Continued

Madison limestone Continued

Limestone, gray; mostly crystalline, ^crinoidal, weathers gray, mostly ?eet 

massive and cliff forming.____________________________________ 51

Limestone, medium- to dark-gray, dense, thin-bedded; weathers to 

medium gray; lowermost few feet contain yellow-weathering silty 

or argillaceous layers; beds 8 feet below top contain Camarotoechia 

cf. C. herrickiana Girty; beds near middle contain Leptaenat sp. 

indet., Schuchertella? sp. indet., fragmentary mold, Spirifer cf. S. 

centronatus Winchell, large var., Punctospiriferl, sp. indet., Composita? sp. indet., Dielasma? sp. indet.; and beds just above lowest 

yellow-weathering beds contain Leptaena cf. L. analoga (Phillips), 

dictyoclbstid? fragment, Camarotoechia sp, indet., Rhynchotretaf 

cf. R. elongatum Weller, Spirifer centronatus Winchell, var. indet., 

Composita sp. indet_.___________________________.____________ 75

Limestone and chert; gray dense limestone and interbedded gray 

chert in 2-inch-thick lenses that are as much as 4 feet long. Chert 

is as much as 40 percent of unit, and the unit is widespread and a 

very prominent marking horizon____-__________________________ 56

Total measured Madison limestone-_-___-___-_-___---___---_- 860 

Three Forks shale: Shale and limestone, largely concealed; weathers to 

yellowish-brown soil.

The base of the Madison limestone is well marked by 50 feet of 

cherty thin-bedded limestone beds that weather to a very rough, 

sharp surface. These basal beds stand in ledges above the easily 

eroded Three Forks shale. The limestone beds in the Madison are 

characterized by their light-gray color. Many beds contain abundant 

crinoid columnals. Several silty layers, notably in the upper part, 

weather red or purple.

Argillaceous and sandy limestones about 325 feet above the base 

contain 4- to 6-foot high bioherm like structures of presumed algal 

origin. The bedding of the enclosing limestone is broken. This unit 

is well exposed on the south slope of Shell Mountain and below the 

top of the 8,631-foot limestone peak 1 mile northeast of the gneiss 

peak shown as Livingston Peak on the topographic map of the Livingston Peak 7K-minute quadrangle.

Extensive erosion dissected the top of the Madison limestone prior 

to Amsden deposition. Sloss and Hamblin (1942, p. 318) have described red sandstone of Amsden age in solution channels 200 feet 

below the top of the Madison in the canyon of the Yellowstone River 

south of Livingston. The contact of the two formations is exposed 

in very few other places, and little is known regarding the effect of 

the pre-Amsden erosion upon the Madison.

394095 57 4
410 CONTRIBUTIONS TO GENERAL GEOLOGY

MI8SISSIPPIAN AND PENNSYLVANIAN SYSTEMS

AMSDEN FORMATION

The Amsden formation, which is the lower part of the Quadrant 

formation mapped by Iddings and Weed (1894), is poorly exposed 

along the northern front of the Beartooth Mountains. .It ranges 

in thickness, from 111 feet at the Yellowstone River canyon south of 

Livingston (Gardner and others, 1946, p. 72) to 300 feet in the 

northeast corner of sec. 25, T. 2 S., R. 10 E. In the SE# sec. 35, 

T. 2 S., R. 10 E. along the north side of Dry Creek the Amsden is 140 

feet thick.

Locally, as along Dry Creek, the Amsden is divisible into a lower 

unit of siltstone, shale, and limestone, a middle unit of thin limestone 

beds, and an upper unit composed largely of siltstone beds that are 

at least partly red. In some places the Amsden is difficult to recognize 

as a separate unit. For example, the limestone in the southeastern 

part of sec. 36, T. 2 S., R. 9 E. looks like Madison limestone but 

seems to lie, presumably unfaulted, above the basal strata of the 

Amsden that can be traced westward to the Yellowstone River. 

The contact between the Amsden formation and the Madison limestone is evidently very irregular, owing to the erosion of the Madison 

limestone prior to or accompanying deposition of the Amsden formation.

The Amsden formation in the Pryor Mountains and the Bighorn 

Mountains near the Montana-Wyoming border is in large part Pennsylvanian in age. Fusulinids collected from near the middle of the 

Amsden in those areas were identified by L. G. Henbest of the 

Geological Survey (personal communication, 1953) as being of probable Atoka (early middle Pennsylvanian) age. The precise age of 

the Amsden formation of the Livingston area is unknown, but it is 

probably close to that of the Amsden in the Pryor Mountains.

PENNSYLVANIAN SYSTEM 

QUADRANT QUARTZITE

The Quadrant quartzite as herein described (also by Gardner and 

others, 1946, p. 72) is the upper massive quartzite member of the 

Quadrant quartzite mapped by Iddings and Weed (1894) in the 

Livingston quadrangle. The Quadrant is 100 feet thick and forms a 

persistent sequence of quartzite and sandstone lying conformably 

upon the Amsden formation. It is a correlative of the Tensleep 

sandstone in the Bighorn Basin, Wyoming, and is of Pennsylvanian 

age.

JURASSIC SYSTEM

The Jurassic system in the mapped area includes marine and 

continental Middle and Upper Jurassic rocks. It is represented by
GEOLOGY, AREA EAST AND SOUTHEAST OF LIVINGSTON, MONT. 411

the marine Ellis group and the continental Morrison formation, each 

of which is about 400 feet thick. Three formations, the Piper, Kierdon, and Swift, make up the Ellis group. The Piper is Middle 

Jurassic, and the Kierdon and Swift formations arid the overlying 

Morrison formation are Late Jurassic. The following description of 

the group was made from the outcrops along Dry Creek ridge southeast of Livings ton.

Section of Ellis group on south slope of Dry Creek ridge near the southeast corner of 

sec. 26, T. 2 S., R. 10 E., Park County, Mont.

Morrison formation: Red soil. 

Ellis group:

Swift formation:

Sandstone, light-gray, mostly medium-grained, calcareous, glauconitic, crossbedded, brown-weathering; forms ledges; many Feet 

Gryphaea shells in several beds.___________________________ 80

Total Swift formation--____-________-______-______^____ 80

Rierdon formation: 

Concealed; olive-gray shale and a little siltstone found by digging. 87 

Limestone, gray, oolitic; weathers light gray, forms ledges, somewhat crossbedded______________________________________ 8

Total Rierdon formation._______________________________ 95

Piper formation:

Concealed; soil is red__.__-_---------_--_-_-__---__-_--___-_ 98

Limestone and shale; gray dense partly fossiliferbus limestone

and brownish- and yellowish-gray shale.____________________ 26

Limestone; mostly gray platy dense limestone; fossiliferous zone 

10 feet below top; unit not well exposed, may include some 

shale and siltstone._______________________________________ 37

Concealed; digging reveals calcareous greenish-gray shale and 

thin dense gray limestone beds in lower part and reddish- and 

greenish-gray calcareous shale in upper part; part of shale in 

upper one-half may be silty__-__-_____-________^___-_____- 73

Conglomerate; angular chert pebbles as much as 1 inch in diameter in calcareous sandstone like underlying unit.____________ 1

Sandstone, yellowish-gray; probably reworked Quadrant quartzite- ___--______-_____--_---_-----__-_---_--____________ 5

Total Piper formation____-_-__----_-_--_--___________ 240

Total Ellis group.____.__________________________ 415

Quadrant quartzite: Yellowish-gray quartzite.
412 CONTRIBUTIONS TO GENERAL GEOLOGY!

MIDDLE JURASSIC SERIES

PIPER FORMATION

The Piper formation, which is 240 feet thick on Dry Creek ridge 

and 297 feet thick (Imlay and others, 1948) at the mouth of the lower 

canyon of the Yellowstone River south of Livingston, lies unconformably upon the Quadrant quartzite of Pennsylvanian age. At Dry 

Creek ridge the Piper consists of a basal sandstone and conglomerate 

6 feet thick, shale and probably some siltstone 73 feet thick, fossiliferous limestone and shale 63 feet thick, and an upper unit that is 

nearly 100 feet thick and seems to be largely red and green calcareous 

shale, though it is largely concealed. There seems to be no gypsum, 

which is typical of the Piper formation farther east, and if there are 

thin beds within the formation the gypsum has been leached from the 

outcrops.

An erosional, but nearly parallel, unconformity separates the Piper 

from the underlying Quadrant quartzite. The basal 5 feet of sandstone in the Piper at Dry Creek ridge is presumably reworked sandstone of the Quadrant quartzite. Although the unconformity truncates progressively older rocks from south to north, it does so at such 

a low angle that no angular discordance is observable. Forty miles 

south of Livingston near Gardiner, Mont., the Piper overlies the 

Triassic Chugwater formation. None of the 137 feet of Chugwater 

and 167 feet of the underlying Permian Phosphoria formations near 

Gardiner (Wilson, 1934, p. 652) is found near Livingston. In the 

Sweetgrass arch about 250 miles north of Livingston the Sawtooth 

formation (Piper equivalent) lies upon limestone of Mississippian 

age (Imlay and others, 1948).

Although the Piper formation appears to consist predominantly 

of marine shale and limestone beds at Dry Creek ridge, it contains 

considerable amounts of red siltstone at the mouth of the canyon of 

the Yellowstone River south of Livingston. The formation in the 

longitude of Livingston includes normal marine strata of the Sawtooth 

formation of western Montana and redbeds of the eastern Montana 

Piper formation (Imlay and others, 1948), and, for convenience, 

the rocks in the mapped area are called Piper.

UPPER JURASSIC SERIES

RIERDON FORMATION

The marine Rierdon formation is 95 feet thick and consists of a 

basal gray oolitic limestone, 8 feet thick, and calcareous gray to olivegray shale. Most of the shale is concealed between the ledges of the 

oolitic limestone and sandstone ledges of the overlying Swift formation. 

Imlay (Imlay and others, 1948) describes a gradational contact 

between the Piper and Rierdon formations.
GEOLOGY, AREA EAST AND SOUTHEAST OF LIVINGSTON, MONT. 413

SWIFT FORMATION

The Swift formation, which is about 80 feet thick, is a ledge-forming 

calcareous sandstone that crops out in ledges or ridges along most of 

the mountain front. The sandstone is mostly medium grained with 

many dark mineral grains that give a "salt-and-pepper" appearance 

to the rock. Most beds are crossbedded, very calcareous, fossilferous, 

and glauconitic.

Although the Swift seems to be conformable with the Rierdon 

formation, a pronounced unconformity separates the Swift from 

underlying formations in central Montana (Imlay and others, 1948). 

The shale above the basal oolitic limestone is completely cut out by 

the unconformity in the area between Livingston and the outcrops 

along the northern edge of the Three Forks quadrangle north of 

Manhattan, Mont., about 50 miles northwest of Livingston, for in the 

latter area the Swift formation rests upon the basal oolitic limestone 

of the Rierdon. Southward from Livingston, however, the Rierdon 

changes little in thickness, being 81 feet thick near Gardiner (Imlay 

and others, 1948).

MORRISON FORMATION

The continental mudstones and sandstones of the Morrison formation, which is about 400 feet thick, lie upon the sandstone of the 

Swift with apparent conformity. Most of the Morrison is covered 

by soil and talus. The soil above the lower part is red, and in most 

localities three or four lenses of yellowish-gray sandstone stand in 

low ledges.

CRETACEOUS SYSTEM 

LOWER CRETACEOUS SERIES

KOOTENAI FORMATION

The Kootenai formation, which is more than 300 feet thick throughout the area, consists of a basal chert-pebble conglomerate overlain 

by continental reddish- to yellowish-gray mudstones and sandstones. 

The conglomerate forms ridges along the mountain front whereas 

the overlying beds are poorly exposed. The basal conglomerate 

ranges considerably in thickness. It is at least 8 feet thick along the 

south slope of Dry Creek ridge, 25 feet thick near the southwest 

corner of sec. 23, T, 3 S., R. 11 E., and 25 feet near the mouth of the 

canyon of the Yellows tone River south of Livingston. Most of the 

pebbles in the conglomerate are gray chert and are as much as 1% 

inches long. The base of the conglomerate is assumed to represent 

the base of the Cretaceous deposits.

394095 57-
414 CONTRIBUTIONS TO GENERAL GEOLOGY

LOWER AND UPPER CRETACEOUS SERIES

COLORADO SHALE

The name Colorado shale has been used in parts of Montana for 

the thick predominantly shale sequence that lies above the Kootenai 

formation and, in most places, below the Virgelle sandstone or Eagle 

sandstone. Where the Telegraph Creek formation is identified beneath 

the Virgelle or Eagle sandstones, the Colorado shale underlies the 

Telegraph Creek (Cobban and Reeside, 1952a, chart lOb). The 

Colorado shale, which includes sandstone, particularly in westcentral Montana, contains both Lower and Upper Cretaceous strata; 

its vertical range therefore does not coincide with the Upper Cretaceous Colorado group.

Cobban (1951) compared the Colorado shale of central Montana 

with equivalent rocks in the Black Hills area. From his study it is 

evident that some formational names of the Black Hills can be used 

as members of the Colorado shale in central Montana. Some formation names in use in the Bighorn Basin, Wyoming, are not common 

to the Black Hills and central Montana areas but have been used 

around the Pryor Mountains and the Bighorn Mountains in southcentral Montana. Throughout the following discussion units of the 

Colorado shale are compared, where possible, with named units in 

central Montana or the Bighorn Basin. The Colorado shale was 

measured in part along West Boulder River and in part along Boulder 

River a short distance east of the Mount Rae quadrangle. These 

locations are further described in the stratigraphic column (pi. 36).

The Colorado shale along Boulder and West Boulder Rivers is 

3,100 feet thick and consists of gray shale and sandstone. Although 

more sandstone than shale crops out, most of the formation is probably 

shale. The formation is, however, much more sandy than the equivalent formations farther east (see Richards and Rogers, 1951). Reeside 

(1944) has indicated that Livingston is less than 200 miles east of 

the west edge of the Rocky Mountains-Great Plains Cretaceous 

deposits.

For convenience of discussion, the Colorado shale is divided into 

10 units, and these are compared, where possible, with the Black Hills 

and central Montana or Bighorn Basin formations.

(1) The basal 30 feet is gray marine shale that overlies the sandstone and mudstone of the Kootenai formation. Although the shale 

was seen only near the West Boulder River it may occur elsewhere 

but is concealed beneath soil and grass cover.

(2) Thin-bedded flaggy sandstone about 30 feet thick makes low 

ridges along the mountain flank. The sandstone beds are very fine 

grained and variably silty and shaly. Bedding planes have abundant 

trails and other "bottom markings." The unit is similar to the "First
GEOLOGY, AREA EAST AND SOUTHEAST OF LIVINGSTON, MONT. 415

Cat Creek sand" in central Montana and the Fall River sandstone 

of the Black Hills (Cobban, 1951, p. 2173-2175). It may be essentially 

equivalent to the Greybull sandstone member of the Cloverly formation in the Bighorn Basin.

(3) The 285 feet of beds above the flaggy sandstone is presumably 

mostly shale, although the lower 100 feet is well covered by talus 

and soil. A thin ledge-forming sandstone about 40 feet below the top 

contains Lingula. Other exposed strata are gray shale. This unit is 

at least in part correlative with the Skull Creek shale of the Black 

Hills (Cobban, 1951, p. 2175-2176).

(4) A light-gray to white sandstone 20 feet thick makes a conspicuous white ledge in the few places that it is exposed. Most of the sandstone is medium to fine grained and friable. The sandstone is in 

about the stratigraphic position of the Muddy sandstone member 

of the Thermopolis shale in the Bighorn Basin and the Newcastle 

sandstone of the Black Hills area.

(5) The light-gray sandstone is overlain by 330 feet of gray shale. 

The shale includes several bentonite beds, most of which are only a 

few inches thick. It is slightly sandy in the lower part, and sand is 

abundant in thin layers and stringers in the upper 160 feet. The unit 

is well exposed west of West Boulder River but not elsewhere. These 

bentonitic and sandy shale beds are largely equivalent to the upper 

part of the Thermopolis shale in the Bighorn Basin.

(6) The overlying shale, which is 115 feet thick, is a little more 

sandy. The middle one-third is perhaps more than half fine-grained 

sandstone. Several thin beds of siliceous sandstone or siltstone 

resemble the Mowry shale. Siliceous concretions in these beds 

contain ammonites that were collected and tentatively identified by 

Cobban and Reeside (personal communication) as Neogastroplites, 

which is characteristic of the Mowry shale (Cobban and Reeside, 

1951, p. 1892-1893; Cobban, 1951, fig. 2).

(7) The above-described 755 feet of shale and sandy shale in the 

third through sixth units that overlies the flaggy sandstones near the 

base of the Colorado shale have little resistance to erosion and, for 

the most part, are well concealed. A thick-bedded or massive 

sandstone above these shale layers is resistant and forms cliffs and 

ridges. It is 100 feet or less thick and its base serves as the contour 

horizon for the structure contour map. Owing to its prominence 

and usefulness as a marker bed the sandstone is herein named the 

Boulder River sandstone member of the Colorado shale.

The Boulder River sandstone member is 100 feet thick in the SE% 

sec. 11, T. 3 S., R. 12 E. in the McLeod Basin quadrangle along the 

west side of the Boulder River valley. The member forms an almost 

continuous ridge from Boulder River westward to the Yellowstone
416 CONTRIBUTIONS TO GENERAL GEOLOGY

River south of Livingston. It very likely constitutes one of the 

sandstone ridges along the north flank of the Gallatin Range south 

of Coke Creek west of Livingston.

The member crops out on the south slope of a hill west of West 

Boulder River in the NEK (unsurveyed) sec. 26, T. 3 S., R. 11 E., 

Park County, Mont. The hill is marked on the Mount Rae quadrangle map by an altitude of 6,763 feet. Here the member is about 

65 feet thick and consists of gray to yellowish-brown mostly finegrained sandstone. Above it, and below the crest of the hill, are 145 

feet of thin-bedded, in part shaly, sandstone.

The presence of ammonites of Mowry age in siliceous beds below 

the Boulder River sandstone member and the siliceous beds above 

suggest that the member may be of Mowry (Albian) age and older 

than the Frontier formation in and near the Bighorn Basin in 

Wyoming. See, for example, the discussion of Cobban and Reeside 

(1952b, p. 1961) on the Big Elk sandstone member of the Colorado 

shale near Harlowton in central Montana. The Big Elk sandstone 

member, like the Boulder River sandstone member, lies above siliceous 

beds that contain characteristic ammonites of Mowry age and below 

siliceous beds of undetermined age.

(8) Overlying the Boulder River sandstone member is nearly 290 

feet of thin-bedded sandstone that contains many layers of chert 

pebbles. These beds are well exposed in the Boulder River valley in 

sec. 11, T. 3 S., R. 11 E. but are only partially exposed elsewhere. 

A chert-pebble conglomerate of this unit that is exposed east of the 

Yellowstone River near the mouth of the canyon of the Yellowstone 

River appears to be much like the basal conglomerate of the Kootenai 

formation.

Several beds of siliceous shale and sandstone in the unit weather 

bluish gray, similar to siliceous beds of the Mowry shale in the Bighorn 

Basin. Other shale is black, very hard, and probably highly siliceous, 

too. This unit, therefore, possesses physical characteristics of both 

the Frontier formation and the Mowry shale. Chert pebbles are 

typical of the Frontier formation, where as siliceous beds are characteristic of the Mowry shale (Rubey, 1929).

(9) The 255 feet of sandstone and shale overlying units 7 and 8 

were measured in the Boulder River valley in the same locality that 

the Boulder River sandstone member was measured. These beds are 

concealed in the West Boulder River section. The lower 100 feet of 

this unit is predominantly shale with thin-bedded calcareous sandstone. A friable sandstone near the base contains chert pebbles that 

are as much as 1 inch in diameter. Chert pebbles also occur in soil 

near the top of this 100-foot unit. The upper 155 feet includes thin-
GEOLOGY, AREA EAST AND SOUTHEAST OF LIVINGSTON, MONT. 417

bedded to massive gray to brown sandstone that is ledge forming 

locally.

(10) The upper part of the Colorado shale was measured along 

West Boulder River. Most of the section is grass covered, and only 

ledges of sandstone and a little shale are exposed. The unit is at 

least 1,500 feet but probably not more than 1,650 feet thick. Cobban 

and Reeside collected Scaphites ventricosus, an ammonite of middle 

Niobrara age, from shale nearly 800 feet above the top of the Boulder 

River member, or about 250 feet above the base of this unit. This 

shale of Niobrara age is exposed on the north side of a gully near 

the west edge and about 900 feet south of the north border of sec. 25, 

T. 3 S., R. 11 E. The fossils were collected from near the top of the 

slope.

Near Livingston, on the east bank of the Yellowstone River the 

upper part of the Colorado shale is very sandy. Thin-bedded sandstone and dark-gray shale underlie the Virgelle sandstone, which 

crops out between the airfield and the Yellowstone River bridge 

east of Livingston. These sandy shale beds are at least 450 feet 

thick, and perhaps considerably more. Cobban collected an ammonite of upper Niobrara age Clioscaphites choteauensis from this unit 425 

feet below the Virgelle sandstone. Lithologically similar beds that 

lie between the shale of Niobrara age and the Virgelle sandstone 

or Eagle sandstone in central and south-central Montana are called 

the Telegraph Creek formation (Cobban, 1951, p. 2195, Richards 

and Rogers, 1951). The Telegraph Creek formation, however, contains higher faunal zones in these more easterly areas than that of 

which Clioscaphites choteauensis is indicative (Cobban and Reeside, 

1952a, chart lOb). Although the equivalent lithologic unit of the 

Telegraph Creek formation is recognized within the mapped area, 

the beds are so poorly exposed that their base could not be followed, 

and the unit has been mapped with the Colorado shale.

The shale of Niobrara age, thickens westward from 200 feet north 

of the Bighorn Mountains to 635 feet on the Kevin-Sunburst dome 

in northwestern Montana and has been described by Cobban (1951, 

p. 2192-2193). The rocks of Niobrara age which are more than 1,000 

feet between the beds containing Scaphites ventricosus and Clioscaphites choteauensis in the Livingston area thus appear to be exceptionally thick.

UPPER CRETACEOUS SERIES

VIRQEUE SANDSTONE AND UNDIVIDED YOUNGER STRATA

The Eagle sandstone in central Montana overlies the Colorado 

shale, or where recognized, the Telegraph Creek formation. In outcrops along the Yellowstone River near Billings, Mont., and along the
418 CONTRIBUTIONS TO GENERAL GEOLOGY

Missouri River south of the Bearpaw Mountains the Eagle consists of 

three units: a basal sandstone member (the Virgelle member) a 

middle carbonaceous unit that locally contains coal, and an upper 

sandstone unit. The Virgelle sandstone is distinguished in northwestern and north-central Montana as a formation that lies above 

the Colorado shale, or Telegraph Creek formation, and below continental strata called the Two Medicine formation (Stebinger, 1914, 

p. 62-63).

The threefold nature of the Eagle sandstone is not readily recognizable throughout the Livingston area. The Virgelle sandstone is 

traceable along the northern front of the Beartooth Mountains. 

At the old town of Cokedale, about 7 miles west of Livingston, beds 

above the Virgelle contain coking coal, which was mined during the 

first of the century, and interbedded gray sandstone and tuffaceous 

sandstone occur above the coal zones. Other coal beds have been 

prospected or mined in Coal Mine Mountain south of McLeod in the 

McLeod Basin quadrangle just east of the mapped area. A little 

coal was mined from beds that may be at about the same stratigraphic 

level but which are included with the Livingston formation on the 

geologic map in the NW# sec. 19, T. 2 S., R. 11 E. near Mission 

Creek.

Above the coal-bearing strata is a sequence of gray sandstone and 

dark-gray shale that grades upwards into the Livingston formation. 

The unit is about 1,300 feet thick along the West Boulder River in 

sec. 24, T. 3 S., R. 11 E. and less than 100 feet along the Yellowstone 

River just east of Livingston. The thick sequence in sec. 24 is well 

covered except for the gray sandstone, and the concealed beds are 

thought, judging from spotty outcrops, to be mostly gray shale. 

The thinner section of gray marine shale and associated sandstone 

between the Virgelle sandstone and the Livingston formation near 

Livingston seems most likely to be due to the deposition of tuffaceous 

beds of the Livingston formation a little earlier there than at the 

West Boulder River locality.

The above described strata are presumably correlative with the 

Eagle sandstone and Claggett shale, but those formation units cannot 

be differentiated here. The map of Parsons (1942, fig. 2) indicates 

the presence of the Eagle sandstone and Claggett shale beneath the 

"Livingston igneous series" north of McLeod in the northeastern part 

of T. 2 S., R. 13 E. Those beds, however, are part of the tuffaceous 

strata in the lower part of the Livingston formation as mapped by 

Weed (1893, pi. 1) and by the writer. Although the beds may be of 

the same age as the Eagle sandstone and Claggett shale farther east 

the lithology is largely that of the Livingston formation.
GEOLOGY, AREA EAST AND SOUTHEAST OF LIVINGSTON, MONT. 419

The Virgelle sandstone is partially covered near West Boulder 

River but is about 100 feet thick. It crops out in a conspicuous 

ledge between the Yellowstone River and the airfield east of Livingston. Between these two localities the Virgelle ranges considerably 

in thickness and is not different in appearance from other gray sandstone in the Colorado shale, except that on the east side of Mission 

Creek it weathers to a very light gray which is characteristic of the 

Virgelle sandstone in many localities in west-central Montana.

UPPER CRETACEOUS SERIES AND TERTIARY SYSTEM

IIVINQSTON FORMATION

Weed (1893) applied the name Livingston formation to the thick 

sequence of tuffaceous strata exposed near the town of Livingston. 

Hayden had observed these beds as early as 1871 (Hayden, 1872) 

and Lindgren (1886) mentioned them in 1886, but Weed was the 

first to describe the formation in considerable detail. Stone and 

Calvert (1910) had worked out the general stratigraphic relationship 

of the formation in the Crazy Mountains syncline.

The Livingston formation was divided into three members by 

Weed (1893, p. 21-31): (1) the lower "leaf beds" consisting of sandstone, conglomerate, and shale composed "largely of angular or but 

slightly water-worn debris of volcanic eruptions and ash showers," 

(2) a middle unit of "volcanic agglomerate," described as consolidated 

volcanic ejectamenta that rests upon the lower beds of the Livingston 

formation and thins westward from the area drained by the Boulder 

River, and (3) the "Livingston conglomerate," the shale and sandstone that contain nonvolcanic pebbles in conglomerate layers.

Weed thought that the upper beds, which were described as gray 

crossbedded sandstone, gray shale, and lenses of limestone, were 

probably the Fort Union formation. A younger age for the fossils in 

the upper beds was also noted by Weed (1893, p. 35). The rocks of 

Paleocene age (Fort Union) were included with the Livingston formation by Iddings and Weed (1894); however, the Livingston formation 

is considered by the Geological Survey to be both Cretaceous and 

Tertiary in age (Wilmarth, 1938, p. 1201). Brown (1949) mapped 

the contact between Cretaceous and Paleocene rocks (Fort Union) in 

the Crazy Mountains syncline, and he referred to the /Paleocene rocks 

as "part of the Livingston formation." The rocks of Paleocene age 

as mapped by Brown are north of the area mapped for this report. '^|

Folding and faulting within the area make accurate measurements 

of the Livingston formation difficult. Based upon measurements in 

three localities shown in the stratigraphic column, the Livingston 

exposed within the mapped area is estimated to be about 7,000^666
420 CONTRIBUTIONS TO GENERAL GEOLOGY

thick. This includes the lower part of Weed's Livingston conglomerates. The uppermost zone of the formation in the Livingston Peak 

quadrangle was traced on aerial photos westward into a uniformly 

striking, northward-dipping sequence north of Cokedale which is 

about 7 miles west of Livingston. The part of the Livingston formation between this horizon and the base near Cokedale is 8,000 feet 

thick. The combined thickness of the Livingston and the underlying 

strata to the base of the Virgelle sandstone is about 9,000 feet north 

of Cokedale and between 8,500 feet and 9,000 feet east of Livingston. 

As the beds above the Virgelle sandstone and beneath the Livingston 

formation thin from about 1,330 feet from West Boulder River to 

about 100 feet east of Livingston, the overall thickness of the strata 

from the base of the Virgelle sandstone to the uppermost mapped 

zone of the Livingston formation within the area seems to be nearty 

uniform between Cokedale and the West Boulder River. Because of 

difficulties in measuring the strata, the figures given for thicknesses 

may be in error by 10 percent or possibly more.

This range in thickness of the beds above the Virgelle sandstone 

represents the interfingering of tuffaceous and nontuffaceous beds. 

The base of the Livingston formation is difficult to delineate; the 

lower contact represents, as could best be determined, the change 

from predominantly nonvolcanic debris to predominantly volcanic 

debris in the Livingston formation.

The Livingston formation within this area may be divided into 

five units, but there are no sharp contacts between them. The lower 

900 feet along the east side of the Livingston Peak quadrangle is 

made up mostly of brown and green, with some blue tuffs. They 

are fine to coarse grained, and some layers contain abundant leaf 

impressions. The lower part of this unit is very well exposed in 

Mission Creek syncline, and the basal part makes a blue escarpment 

in the syncline on the west side of West Boulder River. Two 50-foot 

beds of yellowish-gray tuffs containing large dark-brown round 

concretions occur at the top of this unit. The two beds with these 

"cannon ball" concretions occur above a zone of dark-brown tuff 

and are separated by a few feet of nonconcretionary tuff. The concretions are particularly well exposed north and south of the Yellowstone River less than 1 mile east of the Elton 7% minute quadrangle.

The concretions crop out on the southwest flank of Hunters anticline in sec. 35, T. 1 S., R. HE. and south of the Yellowstone River 

along the fault in the NE% sec. 2, T. 2. S., R. 11 E. Similar concretions occur locally, but sparsely, in other beds of tuff, and the identity 

of the two concretion beds as a marker horizon disappears west of 

Mission Creek. Carbonaceous shale occurs locally beneath the concretion beds around Hunters anticline. A line has been drawn on the
GEOLOGY, AREA EAST AND SOUTHEAST OF LIVINGSTON, MONT. 421

map showing the base of the concretion zone east of the longitude 

of Mission Creek.

A wedge of coarse volcanic conglomerate and breccia (Weed's 

agglomerate member) overlies the concretions south of Springdale, 

which is a small settlement in the Yellowstone River valley 1 mile 

east of the area. This unit thickens southeastward from Springdale 

and is offset westward just north of the Yellowstone River by the 

Greeley fault. Parsons and Stow (1942) have described the source 

of the material as vents along the front of the Bear tooth Mountains 

southeast of Springdale. Although no thick section of the volcanic 

conglomerate and breccia appears north of the Yellowstone River in 

outcrop, thin beds of breccia, or conglomerate, of volcanic rocks 

occur above the concretion zone around Hunters anticline. These 

thin beds undoubtedly represent the more northwesterly deposits 

of the so-called Livingston agglomerate or igneous member.

About 1,000 feet of greenish- and yellowish-gray tuff overlies the 

breccia. These beds are much like the tuff in the lowest unit of the 

Livingston, and the two units cannot be separated in areas where the 

breccia zone is absent. Above the tuff beds are about 2,000 feet of 

gray to yellowish-gray tuff and tuffaceous sandstone and interbedded 

gray to reddish-gray shale. The shale is conspicuous along U. S. 

Highway 10 west of Livingston, south of U. S. Highway 10 west of 

Mission station of the Northern Pacific Railway opposite the mouth 

of the Shields River, and along the county road west of Hunters 

anticline north of the Yellowstone River. Part, and perhaps all, of 

the red color of the shale comes from oxidization during weathering.

The uppermost 3,000 feet of the formation within the area is exposed 

in the northern part of the Mission and Elton quadrangles. This is 

a series of gray tuff, tuffaceous sandstone, shale some of which weather 

reddish gray and a few thin beds of conglomerate that contain 

pebbles of chert, limestone, quartzite, and volcanic rock. Chert is 

the most abundant constituent of the conglomerate. Most of the 

limestone and chert were derived from Paleozoic formations. The 

conglomerate is coarser and thicker along the east flank of the BridgetRange (Weed, 1893, pi. 4) than in the mapped area; hence, the 

source of the conglomerate must have been largely or wholly from the 

Bridger Range or even farther west.

The volcanic origin of much of the material in the rocks of the 

Livingston formation has been discussed by Weed (1893) and Stone 

and Calvert (1910). A few samples collected by the writer in 1949 

were examined by Robert L. Smith of the Geological Survey. The 

majority of the samples described in the literature, as well as those 

examined by Smith, are andesitic crystal tuff and sedimentary tuff. 

Smith noted a strong alteration of the mineral grains and abundant
422 CONTRIBUTIONS TO GENERAL GEOLOGY

 v

zeolitic material cementing the grains. Most of the samples that have j 

been examined microscopically and described in the literature very ] 

likely had been selected to illustrate the pyroclastic origin of the 

material in the beds, but detrital quartz and fragments of metamorphic rocks are common to abundant in many of the tuffs. 

Subaerial and subaqueous deposits are interbedded in the Livingston, the latter type seemingly predominant. Fresh-water and brack- r 

ish-water mollusks (Weed, 1893, p. 33), good leaf impressions, and < 

one known collection of marine invertebrates (Stone and Calvert, 

1910, p. 665) give proof that some of the formation was deposited in 

water. A bed of massive tuff west of the trail in the central part of / 

sec. 23, T. 1 S., R. 11 E. encloses a vertical tree stump. A sample of 

the tuff was identified by Smith as an andesitic crystal tuff; detrital 

quartz that is found in many beds of water-deposited tuff was missing. 

Both the thin section and field examination indicate the bed to be a 

subaerial accumulation of volcanic ash. No volcanic flows were 

seen within the quadrangle.

Tuffaceous sandstone and shale, which were described by Wentworth J | 

and Williams (1932, p. 41) as rocks containing less than 50 percent 

volcanic ejectamenta, are difficult to distinguish from the tuff in the j 

field. Many quartz grains that appear rounded when viewed with a 

hand lens appear under the binocular microscope to be rounded on i 

one side but angular on other sides. The roundness may thus be a 

feature of the rock's pyroclastic origin rather than being the result of 

stream abrasion. No bentonite was seen in the Livingston formation, ' 

but the reddish-gray shales in the upper part may be bentonitic.

Little has been said of the age of the Livingston formation since 

the work of Stone and Calvert (1910) other than Brown's map (1949) 

showing the Upper Cretaceous-Paleocene boundary. McMannis 

(1955, p. 1408) recently has stated that the red (or purple) shale and 

associated beds are of Lance (Hell Creek) age. The determination 

was largely based upon study of vertebrate remains found in and near w 

Bozeman Pass, which is about 12 miles west of Livingston.

QUATERNARY SYSTEM

Except for possibly the upper part of the Livingston formation the 

only Cenozoic deposits in the mapped area are unconsolidated stream 

and glacial material and landslide masses, and these are probably ^ 

Pleistocene and Recent. Alden (1932, pi. 1) shows no surficial ^ 

deposits older than Pleistocene.

STREAM TERRACES AND VALLEY ALLUVIUM

The valleys of the Yellows tone River and Shields River have broad 

alluvial floors that include a narrow flood plain and low terraces that 

rise to nearly 60 feet above river level. These low terraces are, for ^
GEOLOGY, AREA EAST AND SOUTHEAST OF LIVINGSTON, MONT. 423

the most part, so discontinuous that they have been mapped with 

the alluvium.

Remnants of formerly extensive higher terraces occur along the 

Shields River and the Yellowstone River; these are the number two 

and three levels of Alden (1932). Most of the terraces are at one of 

three general levels 200, 300, and 400 feet above the river. Two 

small terrace remnants 500 feet above the Yellowstone River on each 

side of Mission Creek about 2 miles south of U. S. Highway 10 were 

evidently cut by Mission Creek.

Gravels in the flood plain of the Shields River 2 miles north of 

the mouth of the river are made up of about 75 percent volcanic rock; 

the remainder is limestone and sandstone. Most of the gravel is less 

than 6 inches in diameter, although some boulders are as much as 16 

inches across. The Shields River drainage basin includes no metamorphic rocks or granite; the streams traverse Paleozoic to Cretaceous 

sedimentary rocks. The large volume of igneous rocks in the floodplain gravel presumably comes mostly from dikes and sills in the 

Crazy Mountains area.

The lithology of the pebbles in the Yellowstone River terraces 

differs from place to place, reflecting the composition of rocks exposed along the tributary streams. The gravel deposits range from 

less than 5 feet to more than 30 feet thick. Gravel in a low terrace 

along U. S. Highway 10 just east of Mission Creek includes the 

following rock types: (1) Gneiss, about 50 percent of all material 

between 3 inches and 12 inches in diameter, (2) granite, almost all 

the few boulders more than 12 inches in diameter, (3) limestone, 25 

percent of rock 3 inches to 12 inches in diameter, and (4) sandstone, 

quartzite, and volcanic rock, 25 percent of rock 3 inches to 12 inches 

in diameter. A terrace at about the same level along the highway in 

sec. 28. T, 1 S., R. 12 E. has material similar in lithology to the above 

described deposit, but volcanic rock makes up about 25 percent of 

the aggregate most of which occurs in the place of limestone. Hence, 

it appears that the greater abundance of limestone in the terrace 

near the mouth of Mission Creek resulted from the transportation of 

limestone gravel from its source in the mountains only a few miles to 

the south.

Gravel in the road cut between the Yellowstone River and the 

Park County airport east of Livingston is of two ages. The lower 

layer, which is about 20 feet thick, consists mostly of gneiss and volcanic rocks that are so deeply weathered that they can be disintegrated by two or three hammer blows. No similar deposit was seen 

elsewhere. The younger gravel overlying this weathered deposit 

consists mostly of volcanic rocks.
424 CONTRIBUTIONS TO GENERAL GEOLOGY

The two small high terraces along Mission Creek in sec. 7, T. 2 S., 

R. 11 E. contain boulders as much as 5 feet in diameter, 90 percent 

of which are gneiss. Material below 12 inches in diameter is about 60 

percent gneiss and 40 percent limestone, quartzite, and sandstone. 

Very few volcanic rocks are present. Both size and lithology of the 

gravel suggest that the gravel was part of the Mission Creek flood 

plain at a higher level.

MORAINES

Small glaciers existed in most of the canyons in the Beartooth 

Mountains during the Pleistocene, but only the larger glaceirs pushed 

beyond the mouths of then1 canyons. Lateral moraines extend for 

a mile down Mission Creek from the mouth of the canyon in sec. 5, 

T. 3 S., R. 11 E. Most of the valley floor of West Boulder River 

within the quadrangle is a ground moraine with abundant boulders 

and depressions. Lateral moraines are as high as 800 feet above the 

river level on the west side of West Boulder River, where they lie on 

top of the upland slopes in front of the mountains.

Westward-flowing streams, such as Pine Creek, that enter the 

Yellowstone River south of Livingston have moraines at their canyon 

mouths. These have been described by Horberg (1940, p. 298).

ALLUVIAL FANS

Alluvial fans extend as pedimentlike deposits from Dry Creek 

ridge westward and northward to the Yellowstone River and cover 

the rear edges of several terraces. The material consists mostly of 

angular fragments of limestone, which range in size from silt particles 

to boulders as large as 6 feet; however, most of the material is only 

a few inches in diameter. Pits have been opened in the fans and the 

material crushed and used for road metal.

LANDSLIDES

Landslides along Mission Creek and along the north flank of Mission Creek anticline have sandstone and shale of the Virgelle sandstone and Colorado shale. Small slides have taken place along the 

sides of West Boulder River valley where the slopes were steepened 

during glaciation.

Movement continues slowly in the small slides along Mission 

Creek in sec. 28, T. 2 S., R. 11 E. The largest mass, which seems to 

have been part of one slide, covers all of sec. 22, T. 2 S., R. 11 E. and 

much of the adjacent sections. The mass movement of the Virgelle 

sandstone and the overlying sandstones and shale seems to be in 

part caused by high topographic relief and in part by a northwarddipping section of interbedded shale and sandstone along the north 

flank of Mission Creek anticline, both of which facilitate gravitative 

slipping.
GEOLOGY, AREA EAST AND SOUTHEAST OF LIVINGSTON, MONT. 425

STRUCTURAL GEOLOGY

GENERAL FEATURES

The area covered by this report includes the northwest corner of 

the Beartooth Mountains and a sector of the southwest edge of the 

Crazy Mountains syncline. Sedimentary rocks within much of the 

mapped area are greatly distorted; many faults and folds in the 

Crazy Mountains syncline even strike perpendicularly to the mountain front.

The Crazy Mountains syncline is a large northwestward-trending 

downwarped structural area that lies to the northwest of the better 

known Bighorn Basin of Wyoming and Montana. The syncline is 

about 100 miles long and not more than 50 miles wide and is bordered 

by mountains most of the way from its northwest end around its 

west side to its southeast end, as illustrated by figure 58. The east 

side of the syncline is difficult to define, because the syncline merges 

into the plains area of central Montana. A line of anticlines and 

domes that extend southeastward from the Little Belt Mountains to 

to the Pryor Mountains marks, rather arbitrarily, the syncline's 

east edge.

The boundary between the Crazy Mountains syncline and the 

Bighorn Basin is also difficult to define. Alpha and Fanshawe (1954, 

p. 77) stated that the Nye-Bowler lineament is the northern structural boundary of the Bighorn Basin. This lineament, which is 

essentially a long complexly faulted anticline, was shown by Wilson 

(1936) to trend generally northwestward 56 miles from the abandoned 

postoffice of Bowler just west of the Pryor Mountains to the Beartooth Mountains front near Nye, which is near the Stillwater River. 

Alpha and Fanshawe (1954, p. 77) would extend the lineament 

60 miles farther northwestward along the mountain front to Livingston, but their report indicates that the Bighorn Basin as a structural unit pinches out where the lineament converges with the mountain front near Nye. Further discussion of, as well as a definition of, 

the south edge of the Crazy Mountains syncline is beyond the r wpe 

of this report.

Figure 58 shows the relation of the Nye-Bowler lineament defined 

by Wilson to the Crazy Mountains syncline and the northern part 

of the Bighorn Basin. The axis of the Crazy Mountains syncline has 

not been closely determined but seems to lie about as shown in the 

illustration. The axis of the Bighorn Basin in Wyoming has been 

shown by Pierce and others (1947), and the northward continuation 

of the axis into Montana, where it is covered in part by pre-Cambrian 

and Paleozoic rocks of the Beartooth Mountains overthrusts, has 

been shown by Fanshawe and Alpha (1954).
426 CONTRIBUTIONS TO GENERAL GEOLOGY

Both the Crazy and Castle Mountains in the northwestern part 

of the Crazy Mountains syncline are composed mainly of Tertiary 

intrusive igneous rocks, which are complex both structurally and 

petrographically. Had these igneous bodies never formed and if 

mountains had formed along the east edge of the syncline, the Crazy 

Mountains syncline would appear to be similar, superficially at 

least, to the Bighorn Basin.

The Beartooth Mountains have been discussed by many writers, 

among them Bevan (1923), Bucher, Thorn, and Chamberlin (1934), 

Wilson (1934), Lammers (1937), and Chamberlin (1945). The mountains trend northwestward from Wyoming into Montana, as a broad, 

faulted anticlinal structure about 80 miles long and 40 miles wide. 

They are bordered on the south by the volcanic rocks of the Yellowstone plateau and the Absaroka Range, on the east and north by the 

Bighorn Basin and the Crazy Mountains syncline, and on the west by 

the Yellowstone River valley. Most of the central part of the mountains is igneous and pre-Cambrian metamorphic rock. Volcanic rocks 

of the Yellowstone plateau and the Absaroka Range areas extend 

northward in irregular outline onto the south edge of the Beartooth 

Mountains. A patch of the volcanic rocks and some Paleozoic sedimentary rocks occur within the west-central part of the mountains 

in the Mill Creek drainage basin 25 miles south of Livingston.

East of Stillwater River canyon, the mouth of which is about the 

midpoint of the north flank of the Beartooth Mountains (see fig. 58), 

pre-Cambrian and Paleozoic rocks have been thrust eastward and 

northeastward upon Mesozoic and Tertiary rocks in the Bighorn 

Basin and the Crazy Mountains syncline. West of Stillwater River 

canyon, however, the faults along the north edge of the mountains 

dip steeply northward. Chamberlin (1945) has shown northeastwardtrending zones of thrusts and overturned folds crossing the Bighorn 

Mountains and the Beartooth Mountains. The direction of asymmetry alternates from southwestward to northeastward from one 

zone to the adjacent zone (Chamberlin, 1945, fig. 1). The Beartooth 

Mountains west of Stillwater River canyon are in one of these zones 

in which the folds along the mountain flank have the steeper dip on 

their southwest side, and faults along the mountain edge dip steeply 

northeastward.

The Beartooth Mountains were described by Horberg and others 

(1949) as being part of the depositional platform area east of the 

main Rocky Mountain geosyncline. Deformation of this foreland, 

or platform, area is characterized by asymmetrical anticlines that 

have been broken by high-angle reverse faults and by thrust faults 

that were formed during a later stage of deformation than the highangle reverse faults.
GEOLOGY, AREA EAST AND SOUTHEAST OF LIVINGSTON, MONT. 427

The west end of the Beartooth Mountains is outlined by steep 

northward-dipping faults on the north, a nearly vertical fault on the 

west, and a northward-dipping thrust (Wilson, 1934) on the south. 

An eastward-striking fault along Elbow Creek about 25 miles south 

of Livingston and a second fault along Mill Creek just south of Elbow 

Creek, divide the mountains into north and south blocks.

The displacement along the Elbow and Mill Creeks fault zone is 

indicated by the map of Iddings and Weed (1894) to be at least 5,000 

feet, the north side having moved upward relative to the south block. 

Although Iddings and Weed indicated that the Elbow Creek fault, 

which is the main one of the two faults, dies out west of the headwaters of Boulder River, the Tectonic map of the United States 

(King, P. B., and others, 1944) shows it to continue eastward to the 

general longitude of the Still water River canyon.

Within the area covered by this report the mountain flank structures are characterized by high-angle normal and reverse faults, 

strike-slip faults, possibly one low-angle thrust fault, and several 

faulted anticlines. Similar structures prevail in the plains north of 

the Beartooth Mountains but the trend of structures in the latter area 

is nearly perpendicular to the main trend of the mountain folds and 

faults. In the discussion of these individual structures the names 

given by Lammers (1937) are used, except that the Dry Creek ridge 

anticline is herein called the Livingston anticline and other names are 

somewhat modified for simplicity.

The high-angle, nearly vertical, Deep Creek normal fault (Lammers, 

1937; Horberg, 1940; Pardee, 1950) marks the west edge of the north 

block of the Beartooth Mountains. Its continuation north of the 

Suce Creek fault is probably the Stumbo Mountain fault, although 

Lammers (1937, p. 278) considered the fold in the limestone of Paleozoic age north of Suce Creek and east of the Yellowstone River canyon 

to be the north end of the Deep Creek fault. The trace of the fault has 

not been shown south of Deep Creek on the accompanying geologic 

map, but it presumably is covered by surficial material along the edge 

of the Yellowstone River valley. A second, nearly vertical fault of 

major displacement, the Lost Creek fault, extends eastward from 

Davis Creek almost to the Boulder River south of Mount Rae.

The Suce Creek fault is a high-angle reverse fault that extends from 

Suce Creek southeastward to Davis Creek. Although it may be a 

low-angle thrust fault along the lower part of Suce Creek, the fault 

dips as much as 80° northward in the canyons southeast of Livingston 

Peak. This fault, which has more than 1 mile stratigraphic throw 

south of Livingston Peak, moved pre-Cambrian gneiss upward into 

contact with Paleozic strata as high stratigraphically as the Madison 

limestone. A somewhat similar reverse fault along Dry Creek has
428 CONTRIBUTIONS TO GENERAL GEOLOGY

brought the Madison limestone in the Livingston anticline opposite 

Jurassic rocks. These reverse faults trend parallel to the mountain 

front, or about northwest. Smaller reverse faults and other faults 

which seem to be tear faults trend at right angles to the reverse faults.

Between Davis Creek and West Boulder River are the Mount Lion 

syncline and anticline, which are tightly folded against the Lost 

Creek fault. The Livingston anticline was "thrust" southward along 

the Dry Creek fault indicating a close relationship of folding to the 

mountain flank faulting. Limestone of Paleozoic age east of the 

Yellowstone River south of Livingston have been folded into a large 

overturned anticline that overlies the Suce Creek fault. The fold 

appears as a monocline in the walls of the Yellowstone River canyon, 

but the fold is overturned southward in sec. 16, T. 3 S., R. 10 E., as 

can be seen in the cross-sectional view afforded along Suce Creek.

North of and parallel to the mountain front are the long Mission 

Creek syncline and anticline. These trend northwestward from near 

Boulder River and die out west of Mission Creek. This same trend 

is followed by the previously mentioned Livingston anticline, which 

strikes northwestward through the town of Livingston. Both of 

these anticlines have a continuous northwesterly plunge.

The Cretaceous strata that dip away from the mountain flank 

into the Crazy Mountains syncline have been folded and faulted 

rather severely in the area east of Mission Creek. The trend of the 

folds and the faults is almost perpendicular to the trend of the mountain-flank structures. The same Cretaceous strata west of Mission 

Creek trend around the plunging Livingston anticline but are otherwise 

little affected by folding and faulting.

The faults east of Mission Creek are presumably high angle, 

although only the Greeley fault is seen in cross-sectional view. Its 

plane is visible along the north side of the Yellowstone River on the 

south slope of Buffalo Hump.

Anticlines and synclines north of the mountain flank and east of 

the longitude of Mission Creek strike about parallel with the associated faults. The folding south of the Yellowstone River is locally 

very tight and is isoclinal in part of the northeastward-plunging Elton 

and Greeley anticlines. Hunters anticline north of the Yellowstone 

River has a faulted east flank, and beds west of the fault are overturned locally. Although the dip of the fault along the east side of 

the anticline cannot be seen, it probably dips northwestward and 

passes beneath the anticline. This anticline is the only one within 

the area with surface structural closure, with the exception of closure 

against a fault near the northwestern end of the Mission Creek anticline and a probable fault closure on the Livingston anticline.
GEOLOGY, AREA EAST AND SOUTHEAST OF LIVINGSTON, MONT. 429 

AGE OF DEFORMATION

The folding of the pre-Cambrian strata was the first period of 

intense deformation decipherable in the rocks of the mapped area; 

in places the gneiss and schist were nearly vertical when Middle 

Cambrian seas covered them. From Cambrian time until late in the 

Cretaceous or early in the Tertiary the area was alternately subjected 

to periods of erosion and deposition. During this time the movements were seemingly largely vertical, with little or no horizontal 

movement that would fold the rocks. The unconformities in the 

sedimentary section separate strata that are essentially parallel.

During the deposition of the continental Judith River strata 

throughout central Montana in Late Cretaceous time the north edge 

of the present Beartooth Mountains was probably land. Deposition 

of Weed's agglomerate member (the igneous member of Parsons and 

Stow) in the Livingston formation is considered by Parsons and Stow 

(1942, p. 345) to have started during Judith River time and to have 

originated from volcanic centers near the north edge of the present 

Beartooth Mountains.

Limestone cobbles in younger beds of the Livingston formation 

are evidence that the area occupied by the present Bridger Range 

was undergoing erosion by latest Cretaceous or early Tertiary time 

(Weed, 1893, p. 30-31). Thus a long period of uplift of mountain 

areas located on about the west and south edges of the Crazy Mountains syncline is indicated.

The youngest strata within the area are latest Cretaceous or early 

Tertiary in age, and these were seemingly folded along with the 

older Cretaceous rocks. There is no evidence to indicate that extensive folding took place prior to the orogeny that deformed the Livingston formation. It seems probable, however, that more than one 

period of folding affected the area, even after deposition of the 

Livingston formation and the Pal eocene (?) strata in the present 

CT&Z.J Mountains area. The almost perpendicular relationship of 

the trends of the faults and folds of the mountain flanks to the folds 

in the nearby syncline suggests two distinct intervals of folding.

The writer considers the following sequence of deformation probable, though not necessarily the only possible one.

(1) Early mountain uplift, Judith River time plus or minus, 

depending upon the age of the breccia (igneous or agglomerate) 

member of the Livingston formation, when the north flank of the 

Beartooth Mountains was the site of small volcanoes.

(2) Initiation of zones of weakness along the mountain edge and in 

the syncline, with perhaps attendant faulting and some folding, from 

Judith River(?) time on.
430 CONTRIBUTIONS TO GENERAL GEOLOGY

(3) Outlining of the north block of the Beartooth Mountains by 

the Deep Creek fault along the west and the Elbow Creek and Mill 

Creek faults to the south. The north edge was marked by a northward-steepening of beds and by the high-angle Lost Creek fault. 

Although these three steps are listed separately, they may have been 

closely related and may have been essentially contemporaneous.

(4) Compressive forces acting presumably southwestward caused 

folding and reverse faulting along the north flank of the mountains; preexisting structures were modified. This stage was later 

than the faulting that outlined the west flank of the mountains, because the Deep Creek fault along the west edge of the Beartooth 

Mountains was cut by the Suce Creek fault that originated during 

this period of deformation.

(5) Compression, possibly from the northwest, led to the formation 

of such structures as Hunters anticline and fault. A force couple, 

with eastward directed forces north of the area and westward directed 

forces south of the area, may have given the same results a series of 

parallel anticlines such as Hunters, Elton, and Greeley.

The time of folding and faulting plays an as yet unknown part in 

the accumulation of oil and gas. Although no commercial quantities 

of oil or gas have been recovered within the Crazy Mountains syncline, 

such factors as the extensive igneous intrusions of Tertiary age, complexity of structures, and inadequate testing by drilling may be 

responsible for the lack of discoveries to date. The calcite veins 

(described on p. 432) almost certainly are fillings of tensional fractures 

that may have formed during the compression of stage 5 (described 

above). Whether they originated then or later is unknown, however 

the fractures might have been an avenue of escape for any trapped 

hydrocarbons. If the source of the calcite was the limestone bed of

Paleozoic age, the tensional fractures were deep. Their crosscutting 

trends and the current hot spring activity at Hunters Hot Springs 

just northeast of the Elton quadrangle indicate a relatively late age 

for their formation.

ECONOMIC GEOLOGY

OIL AND GAS

Oil and gas have not been recovered in commercial quantities from 

the Crazy Mountains syncline west of the Dry Creek field (Tps. 6 and 

7 S., R. 21 E.). Exploratory wells that were drilled deeper than 1,500 

feet within the mapped area are described below and are shown on 

the structure contour map. The relationship of the time of origin of 

the geologic structures to the accumulation of oil and gas was discussed 

briefly above.
GEOLOGY, AREA EAST AND SOUTHEAST OF LIVINGSTON, MONT. 431

Operator and lessee

Richfield 1 Weiss.. .......

Mid-American Oil Co. 

1 Burgess-Preston.

Co. 1 Burgess. 

R. O. Tarrant 1 Petcrson.

Location

SWKSEJiSWM sec. 20,

T. 2S., R. HE. 

NE^NE^SWM sec. 28, 

T. 2S., R. HE. 

SE^SW^NWM sec. 28,

T. 2S., R. HE. 

NJ^SWMNWJi sec. 5, T. 

2S., R. 12 E.

Lowest formation 

reached

Morrison(?).____

Colorado shale.. 

.....do...........

Kootenai (?).....

Total 

depth

4,117

1,680 

2,900

3,180

Remarks

Abandoned.

Drilling suspended.

Abandoned, heavy 

flow of water.

Possibilities of finding oil and gas within the area depend in large 

part upon suitable structures and reservoir rocks. The mapped area 

is not so favorable in either respect as the Bighorn Basin. Most 

anticlines along the edge of the Crazy Mountains syncline are tightly 

folded and complicated by faults. The fault along the east flank of 

Hunters anticline may considerably influence the structural closure 

of that anticline at depth. On the other hand, the only structural 

closure on Mission Creek anticline was probably caused by faulting. 

A fault that crosses this anticline west of Mission Creek seems to have 

caused less than 500 feet of closure in the northwestward-plunging 

Mission Creek anticline west of the fault. Such anticlines as El ton 

and Greeley plunge so steeply that there is little likelihood of closure 

in the structure.

The Permian Phosphoria formation and the Pennsylvanian Tensleep 

sandstone, which are good reservoir rocks in the Bighorn Basin, may 

not yield oil within this area. The Permian rocks are absent in all 

outcrops, and the Quadrant quartzite, which is the stratigraphic 

equivalent of the Tensleep sandstone, has been largely cemented with 

quartz. Sandstones of Cretaceous age similar to producing sands in 

the Bighorn Basin have been tested by several wells, but shows of oil 

or gas have not been reported. Limestones of Devonian and Mississippian age may be suitable reservoirs in the area, but no well has 

reached them.

Igneous intrusions of Tertiary age in the Crazy Mountains syncline 

had an as yet unknown effect upon oil and gas accumulation in the 

area. Although the search for oil and gas in this area and other parts 

of the Crazy Mountains syncline has so far been unsuccessful, a 

sufficient number of wells have not been drilled to adequately test the 

region. Nevertheless, the area is less promising than other basins in 

eastern Montana and Wyoming.
432 CONTRIBUTIONS TO GENERAL GEOLOGY

COAL

Considerable coking coal was mined prior to 1908 near Cokedale, 

7 miles west of Livingston, but the total tonnage produced was apparently unrecorded (Calvert, 1912, p. 37-38). The coal occurred in 

northward-dipping beds not many feet above the Virgelle sandstone. 

A thin bed of coal in what is considered to be about the same stratigraphic horizon in the W% sec. 20, T. 2 S., R. 11 E. on the Joe Weiss 

ranch was mined for household use, but the small workings have 

caved in and no coal is visible in the outcrop.

CALCITE

Many veins of calcite, most of which are shown on the geologic 

map, occur within the Livingston formation. These veins strike 

northwest and are nearly vertical. Most range from 2 or 3 inches to 

6 or 8 inches in thickness. The veins were mined east of the Elton 

quadrangle, the calcite reportedly used for its optical properties.

LIMESTONE AND DOLOMITE

In the formations of Cambrian age the Pilgrim limestone is the 

only one that is exposed in an accessible locality. The upper unit of 

the Pilgrim crops out in the canyon of the Yellowstone River 3 miles 

south of Livingston. It is readily identified in hand specimen by its 

oolitic structure. The weathered surface of the limestone in many 

localities is mottled, but the mottling is not notable in the Yellowstone 

River canyon. Hanson (1952) has described this and other limestone 

formations of Cambrian age. Near Shell Mountain where it was 

measured it is 175 feet thick; the upper 100 feet is massive ledgeforming largely oolitic limestone, and the lower 75 feet is mostly 

limestone breccia.

The Bighorn dolomite of Ordovician age consists of a basal massive 

member made up of light-gray and light-yellowish-gray dolomite 

that is 150 feet thick near Shell Mountain and an upper member 

consisting of about 50 feet of thin-bedded dolomite. The massive 

member crops out at the south end of the Yellowstone River canyon 

south of Livingston, but it is not readily distinguished by its topographic form.

Most beds in the Jefferson limestone of Devonian age are very 

argillaceous or silty. Limestone in the Madison limestone of Mississippian age is less argillaceous than the Devonian strata, and many 

beds are dolomitic. The basal 40 feet of cherty limestone in the 

Madison is very resistant to weathering and is a good marker zone 

in most localities. Part of the Madison is nearly pure calcium carbonate. Limestone from the upper part of the Madison was quarried
GEOLOGY, AREA EAST AND SOUTHEAST OF LIVINGSTON, MONT. 433

and reduced in stone kilns in the canyon south of Livingston. Some 

of the kilns are still standing, even though they operated between 

1900 and 1915 (Perry, 1949, p. 42). The average analyses of two 

samples from the quarried limestone is 97 percent calcium carbonate 

and 2.5 percent silica and alumina (Perry, 1949, p. 42). The Devonian 

and Mississippian strata dip steeply northward where they crop out 

in canyons along the edge of the mountains.

The Amsden formation of Mississippian and Pennsylvanian age 

contains some beds of limestone, but the limestone ranges considerably 

in thickness and lithology from one locality to another. Thin-bedded 

argillaceous limestones crop out along the southward-facing slopes 

near the top of Dry Creek ridge in sees. 26 and 35, T. 2 S., R. 10 E.

SHALE

Shale and claystone make up much of the Piper, Rierdon, and 

Morrison formations; shale in the Rierdon is calcareous. Dark-gray 

shale is interbedded with gray sandstones in the Colorado shale, and 

reddish-gray shale, which is possibly bentonitic, is abundant in the 

upper part of the Livingston formation. Most of the shale in the 

area is covered by soil; roadcuts and landslides along streams provide 

the best exposures.

QYPSUM

No gypsum was observed within the area. Thin beds may occur in 

the Piper formation, but there is little likelihood of finding gypsum 

in other formations. The redbecls in the Permian and Triassic rocks, 

which contain much gypsum in Wyoming, were removed by preJurassic erosion and are absent north of Cinnabar Mountain 40 miles 

south of Livingston.

BENTONITE

No thick beds of bentonite, such as those that characterize the 

Upper Cretaceous strata farther east in Montana and Wyoming, 

were seen within the area. Thin beds are common in the lower part 

of the Colorado shale (see plate 36), but these are concealed by soil 

throughout most of their outcrop area. Thicker beds of bentonite 

may occur stratigraphically higher, but there is no evidence that 

they are present.

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5th Ann. Field Conf.: Billings, Mont., p. 72-79. 

Bevan, Arthur, 1923, Summary of the geology of the Beartooth Mountains.

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434 CONTRIBUTIONS TO GENERAL GEOLOGY

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GEOLOGY, AREA EAST AND SOUTHEAST OF LIVINGSTON, MONT. 435

Lammers, E. C. H., 1937, The structural geology of the Livingston Peak area,

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Lindgren, Waldemar, 1886, Eruptive rocks of Montana: U. S. Bur. Census,

10th Census, p. 719-737. 

Lochman, Christina, 1950, Status of Dry Creek shale of central Montana: Am.

Assoc. Petroleum Geologists Bull., v. 34, p. 2200-2222. 

Lochman, Christina, and Duncan, D. C., 1944, Early Upper Cambrian faunas of

central Montana: Geol. Soc. America Special Paper 54. 

McManis, W. J., 1955, Geology of the Bridger Range, Montana: Geol. Soc.

America Bull., v. 66, p. 1385-1430.

Miller, A. K., 1930, The age and correlation of the Bighorn formation of northwestern United States: Am. Jour. Sci., 5th ser., v. 20, p. 195-213. 

Pardee, J. T., 1950, Late Cenozoic block faulting in western Montana: Geol.

Soc. America Bull., v. 61, p. 359-406. 

Parsons, W. H., 1942, Origin and structure of the Livingston igneous rocks,

Montana: Geol. Soc. America Bull., v. 53, p. 1175-1185. 

Parsons, W. H., and Stow, M. H., 1942, Origin and structural relationships of the

igneous member of the Livingston formation, Montana: Am. Geophys.

Union Trans. 23d Ann. Mtg., pt. 2, p. 344-345. 

Peale, A. C., 1893, The Paleozoic section in the vicinity of Three Forks, Mont.:

U. S. Geol. Survey Bull. 110. 

Peoples, J. W., and Howland A. L., 1940, Chromite deposits of the eastern part

of the Stillwater complex, Stillwater County, Mont.: U. S. Geol. Survey

Bull. 922-N. 

Perry, E. S., 1949, Gypsum, lime, and limestone in Montana: Mont. Bur. Mines

and Geology Mem. 29. 

Pierce, W. G., Andrews, D. A., and Keroher, J. K., 1947, Structure contour map

of the Bighorn Basin, Wyoming and Montana: U. S. Geol. Survey Oil and

Gas Inv. Prelim. Map 74. 

Reeside, J. B., Jr., 1944, Thickness and general character of the Cretaceous

deposits in the western interior of the United States: U. S. Geol. Survey

Oil and Gas Inv. Prelim. Map 10. 

Richards, P. W., and Rogers, C. P., Jr., 1951, Geology of the Hardin area, Big

Horn and Yellowstone Counties, Mont.: U. S. Geol. Survey Oil and Gas

Inv. Map OM 111. 

Rubey, W. W., 192.9, Origin of the siliceous Mowry shale of the Black Hills

region: U. S. Geol. Survey Prof. Paper 154-D. 

Sloss, L. L., and Hamblin, R. H., 1942, Stratigraphy and insoluble residues of

Madison group (Mississippian) of Montana: Am. Assoc. Petroleum Geologists Bull., v. 26, p. 305-335.

Sloss, L. L., and Laird, W. M., 1947, Devonian system in central and northwestern Montana: Am. Assoc. Petroleum Geologists Bull., v. 31, p. 1404-1430. 

Stebinger, Eugene, 1914, The Montana group of northwestern Montana: U. S.

Geol. Survey Prof. Paper 90-G. 

Stone, R. W., and Calvert, W. R., 1910, Stratigraphic relations of the Livingston

formation of Montana: Econ. Geology, v. 5, p. 551-557, 652-669, 741-764. 

Tomlinson, C. W., 1917, The middle Paleozoic stratigraphy of the central Rocky

Mountain region: Jour. Geology, v. 25, p. 112-134, 244-257, 373-394. 

Walcott, C. D., 1891, Correlation papers; Cambrian: U. S. Geol. Survey Bull. 81. 

Weed, W. H., 1893, The Laramie and the overlying Livingston formation in

Montana: U. S. Geol. Survey Bull. 105. 

 1899a, Description of the Fort Benton quadrangle, Mont.: U. S. Geol

Survey Geol. Atlas, folio 55.
436 CONTRIBUTIONS TO GENERAL GEOLOGY1

Weed, W. H., 1899b, Description of the Little Belt Mountains quadrangle, Mont.: 

U. S. Geol. Survey Geol. Atlas, folio 56.

 1900, Geology of the Little Belt Mountains, Mont.: U. S. Geol. Survey

20th Ann. Rept., pt. 3, p. 257-461. 

Wentworth, C. K., and Williams, Howel, 1932, The classification and terminology

of the pyroclastic rocks: Nat. Research Council Bull. 89, p. 19-53. 

Wilmarth, M. G., 1938, Lexicon of geologic names of the United States: U. S.

Geol. Survey Bull. 896. 

Wilson, C. W., Jr., 1934, Geology of the thrust fault near Gardiner, Mont.:

Jour. Geology, v. 42, p. 649-663.

 1936, Geology of Nye-Bowler lineament, Stillwater and Carbon Counties, 

Mont.: Am. Assoc. Petroleum Geologists Bull., v. 20, p. 1161-1188.
INDEX

Page 

A 

Acknowledgments.......................... 380,388

Age of deformation of the area.... ......... 429-430

Alluvial fans-_ ............................. 424

Alluvium................................... 422^23

Amsden formation, lithology............... 410,433

Atrypa....................................... 405

devoniana................ ................ 405

B

Bcartooth Mountains, structure............ 426-427

Belt series...--...-...-......------------....- 390

Bentonite............ ..................... 433

Bibliography............................... 433-436

Big Elk sandstone member of the Colorado

shale.-.....-.--...--............. 416

Bighorn dolomite, lithology............ 402-404,432

Blacktail Lake, occurrence of diabase dike.... 391

Boulder River sandstone member of the

Colorado shale.............. 415-416,417

Bridget- Range.........................__ 421,429

Buffalo Hump................................. 428

Calcitc, in Livingston formation.............. 432

Camarolechla................................. 409

herrickiana. ............................... 409

sp.---------........-.-...-.-.....-.....-. 409

Choneles...................................... 408

loganensis.................._............ 408

Claggett shale.....--.---.---...-.---......... 418

Claystone.--..-.....-...........------.---..- 433

Climate...-...-.---.--...-..-...-..--...-. 388-389 

Clioscaphites choteauensis...................... 417

Coal, coking................................ 418,432

Coal Mine Mountain.__.__................... 418

Coenites............................. ........ 405

Cokedale...--..-...--..-------.--.--..- 418,420,432

Colorado shale, landslides.............--.-..-. 424

Hthology-.....--..--.--...--...-..-.... 414-417

Composita sp................................. 409

Crazy Mountains syncline, boundaries.---.-. 425

D 

Deep Creek fault........................... 427,430

Diabase dikes, occurrence.......-...-.-.-.... 391

Dielasma sp---------------------------------- 409

Dolomite................................... 432-433

Dry Creek ridge, alluvial funs....-.........'.. 424

Dry Creek shale of Peale................... 396,400

Dry Creek shale of Weed..................... 396

E

Eagle sandstone, lithology.................. 417-418

Economic geology...--..--.---..-...-.-...- 430-433

Page 

Elbow Creek fault.......................... 427,430

Ellis group, stratigraphic section............ 411

Elephant Head Mountain, Grove Creek formation. ..--.--....-..--.._---..-...-..-.. 400

Elton anticline.....---..-..------..--..--.- 428,430

Extent of the area.-...--.--.......-...-.-.-.. 380

Fall River sandstone------..---.---.. ....... 415

Faults............ ...... ... . . 427,428

Field work................................. 380,388

First Cat Creek sand......-...-.....-..--.. 414-415

Flathead quartzite, lithology................. 395

stratigraphic section.....-..--...-..-_.___. 394

Fort Union formation........................ 419

Frontier formation......--..-..--......--.... 416

O 

Oabbro, occurrence_.-.---.----.-.-.--...--. 391

Oallatin limestone of Iddings and Weed...... 396

Gas possibilities....._............... .__. 430-431

Geography................................. 388-390

Granite, occurrence_.....-..-.-..-....-.... 391

Greeley anticline...-....................... 428,430

Greeley fault-..-.-.---..--..-...-...,...--. 421,428 

Greybull sandstone........................... 415

Grove Creek, type locality of Grove Creek 

formation......-.....-..--...--..-...-...-.. 400

Grove Creek formation of Dorf and Loch man. 396 

Grove Creek formation, lithology........... 400-401

stratigraphic section...................... 397

Oryphaea..................................... 411

Gypsum..---..--.---.--...-..--..---.--..--. 433

H

Hanson, A. M., quoted........................ 399

Homalophyllites............................... 408

Hunters anticline ................ 420,421,428,430

Hunters fault_.---.--.--..--.---.---..--..- 430

Hunters Hot Springs...--..-.-.-..-...-...... 430

Jefferson limestone, lithology........... 404-40P, 432

stratigraphic section...................... 405

Kevin-Sunburst dome.----.--. ....-..-...-.. 417 

Kootenai formation, lithology................ 413

Landslides._..-...--..-.--......-...-...-.. 424

Leptaena..................................... 409

analoga................................... 409

sp.....--..--..--...-.--.---..--...-..--.. 409

Limestone---..-..--..--..-..--..---.---.-- 432-433 

Lingula...................................... 415

437
438 INDEX

Page 

Lithostrotionsp............................... 408

Livlngston, settlement-..__ .. ___.. 390

Livingston formation, lithology..______ 419-422 

Weed's divisions..-..-_........__... 419

Livingston igneous series... -.. .___ 418 

Livingston Peak.........-....--....-....--. 402,403

Livingston Peak of Tomlinson__......-.--- 403

Location of the area.._____.__....._ 386

Lost Creek fault........................ 427,428,430

M

Madison limestone, lithology..__ 407,409,432-433

stratigraphicsection__..._______ 408-409

Maurice formation of Dorf and Lochman..... 396,

398,399, 400 

Maywood formation of Lochman............. 397

Meagher limestone, lithology..... __.-..-.-- 395

stratigraphic section......-.......-...-.-- 394

Metamorphic rocks...___....-.--.-.-....-. 390

Mill Creek fault -- --------.------.- 427

Mission Creek, landslides..............._-. 424

lateral moraines--...__..........._.. 424

terraces..._____..-....-.__...._ 423,424

Mission Creek anticline.--..--------___ 428

Mission Creek syncline_-... --.. ........ 428

Moraines, lateral..._..__---------------- 424

Morrison formation, lithology................ 413

Mottled limestone of Peale.___ ..___ 396 

Mottled limestone of Walcott -..... ....... 398

Mount Lion anticline..-- --------- ------- 428

Mount Lion syncline_..-.--.---.------..-.-- 428

Mowry shale___..-... .-.. --.-__.. 415,416 

Muddy sandstone..__-.. ------..---.. 415

N 

Neogastroplites................................ 415

Nye-Bowler lineament, boundary of the Bighorn Basin.____________ 425

Oboktta shale (Park shale) of Peale..----- 396

Oil possibilities.-----.----....--.------- 430-431

Old Baldy of Tomlinson. . _. _ 403

Park shale, lithology .-....... ... 395-396

stratigraphic section.___.....____.. 394 

Pebbly limestone of Peale. ___. __ 396,400-401 

Pilgrim limestone, lithology--..---- 398-399,432

stratigraphic section__......_.__ 397-398

Pilgrim limestone of Weed............._..-. 396

Pine Creek, moraines_._ .--.- ..-- 424 

Piper formation, lithology_......__.__ 412

stratigraphic section... .___.__..... 411 

Punctospirifer--....--........................ 408

transversus.......-....---...-............. 408

sp_.___.....-....-- . ......-...-. 409

Purpose of report_. -.--.-.. ... _ 386

Quadrant formation of Iddings and Weed. 410 

Quadrant quartzite..._.._ .. 410

R Page 

Receptaculites................................. 403

Rhynchotreta....1............................. 409

elongatum................................ 409

Rierdon formation, lithology-..-._..._... 412

stratigraphic section____________ 411

Rough Draw, stratigraphic section at_ __ 394,

397-398.405,408-409

S

Sage pebble-conglomerate member of Lochman._______________ 397 

Scaphites ventricosus. . ____________1. 417 

Schuchertella sp________________ 408,409 

Shale.--...-__-._....__--.-..-.-.-..... 433

Shell Mountain, stratigraphic section at.__ 394, 

397-398,405,408-409

Shields River, flood plain..__._______ 423 

Skull Creek shale ------------------------ 415

Snowy Range formation, lithology-..__.. 400-401

stratigraphic section____________ 397 

Snowy Range formation of Dorf and Lockman._________________ 396 

Snowy Range Ranch, type locality of Snowy

Range formation..._____... 400 

Spirifer..................................... 408, 409

centronatus............................. 408,409

Springdale..._________.__.____ 421 

Stillwater complex, lithology________ 390-391 

Stream terraces..-.___.......___-..-. 422-424

Structural geology, age of deformation__.. 429-430

general features..-_......._. ___. 425-428

Stumbo Mountain fault._._________ 427 

Suce Creek fault............................ 427,430

Surface features._ . . -- ..- 388 

Swift formation, h'thology...._...---. 413

stratigraphic section, . __.. __. __. 411

Telegraph Creek formation...........___ 414,417

Thermopolis shale.._...__.-.-.--.__ 415

Three Forks shale, lithology- _._...___ 404

stratigraphic section...................... 405

Two Medicine formation....__________ 418

U

U. S. Highway 10, exposures of Livingston formation__.__ . - - 421 

terrace remnants.____......___._ 423

Virgelle sandstone, landslides..-.-..--.-.----- 424 

lithology-----.... _ .. -. .- 418

W 

Water supply..........._............... . 388,390

West Boulder River, landslides..._____. 424

lateral moraines.....___..--..---.----.- 424 

Wolsey shale, lithology--______..___ 395

stratigraphic section.._...._.......... 394

Yellowstone River, alluvial fans__....._. 424

terraces.-...-__.-.._..--.-..--.----.. 423

Yogo limestone of Weed.._.____._._ 396

o
PLATES 37-43
PLATE 37

[Figures natural size unless otherwise Indicated]

FIGURES 1,2. Streptelasma trilobatum Whitesves (p. 474).

1. Calyx; 2, left alar side, USNM 124800. Upper Ordovlclan, red shaly beds In uppermost 

part of Bighorn dolomite, loc. Dl (CO), South Fork of Rock Creek, Johnson County, 

Wyo. 

3, 5-7. "Holophragma" sp. (p. 474).

3. View of the cardinal side, X2; 7, calyx, X2, USNM 124801.

5. Alar side; 6, same view, X2, USNM 124801. From Upper Ordovician, red shaly beds 

In uppermost part of Bighorn dolomite, loc. Dl (CO), South Fork of Rock Creek, 

Johnson County, Wyo. 

4, 8. Streptelasma cf. S. latusculum (Billings) (p. 474).

4. View of counter side; 8, calyx, USNM 124803. Upper Ordovician, red shaly beds in 

uppermost part of Bighorn dolomite, loc. Dl (CO), South Fork of Rock Creek, Johnson 

County, Wyo. 

9. Favosites (Paleofavosiles) cf. F.prolificus (Billings)'(p. 474).

Fragment of corallum, USNM 124804. Upper Ordovician, red shaly beds in uppermost 

part of Bighorn dolomite, loc. Dl (CO), South Fork of Rock Creek, Johnson County, 

Wyo. 

10,11. Sceptropora cf. S.facula Ulrich (p. 474).

10,11. Oblique and lateral views of one of the articulating segments, X20, USNM 124805. 

Upper Ordovician, red shaly beds In uppermost part of Bighorn dolomite, loc. Dl (CO), 

South Fork of Rock Creek, Johnson County, Wyo. 

12-15. HesperortMs cf. H. laurentina (Billings) (p. 475).

12,13. Dorsal valve, external and internal views, X3, USNM 124806. (Right side of valve 

broken after photographing interior.)

14. Interior of ventral valve, X4, USNM 124807.

15. Interior of dorsal valve, showing bladclike braohlophore, X3. All from Upper Ordovlcian, Red River formation, loc. r>9id (CO), shell oil Co., Pine unit No. i well, 

9,103-9,116 ft. 

16,19,20, 23. DinOTthit (Plaesiomys (?)) cf. D. (P.) occidental Ladd (p. 475).

16. Lateral view; 19, posterior view; 20, 23, dorsal and ventral YlOW3, USNM 124808. 

Upper Ordovician, red shaly beds in uppermost part of Bighorn dolomite, loc. Dl (CO), 

South Fork of Rock Creek, Johnson County, Wyo. 

17,18,21,22. Dinorthis (Pionorlhis (?)) cf. D. (P.) occidentalis Okulitch (p. 475).

17. 18. Lateral and posterior views; 21, 22, dorsal and ventral views, USNM 124809. 

Upper Ordovician, red shaly beds in uppermost part of Bighorn dolomite, loc. Dl 

(CO), South Fork of Rock Creek, Johnson County, Wyo.
GEOLOGICAL SURVEY BULLETIN 1021 PLATE 37

CORALS, BRYOZOAN, AND BRACHIOPODS (ORTHACEA), BIGHORN AND 

RED RTVER FORMATIONS
GEOLOGICAL SURVEY BULLETIN 1021 PLATE 38

BRACHIOPODS (ORTHACEA AND RHYNCHONELLACEA), BIGHORN

FORMATION
PLATE 38

[Figures natural size unless otherwise Indicated]

FIGURES 1, 2, 5, 6. Dinorthis (Pi<mortftis(?)) n. sp. (p. 475).

1, 2. Ventral and dorsal views; 5,6, lateral and posterior views, USNM 124810. Upper 

Ordovician, red shaly beds in uppermost part of Bighorn dolomite, loc. Dl (CO), 

South Fork of Rock Creek, Johnson County, Wyo. 

3, 4, 7, 8,11. Dinorthis(1) sp. (p. 475).

8, 7,11. Lateral, posterior, and anterior views; 4, 8, Dorsal and ventral views, USNM

124811. Upper Ordovician, rod shaly beds in uppermost part of Bighorn dolomite,

loc. Dl (CO), South Fork of Rock Creek, Johnson County, Wyo. (The ventral

valve of Okulitch's two cotypes for Pionorthis occidental^ may belong to this species.)

9,10,12-14. Rhynchotrema lowense Wang (p. 476).

9,13. Dorsal and ventral views, X 2; 10,12,14, Anterior, posterior, and lateral yiews, 

X 2. USNM 124813. Upper Ordovician, red shaly beds in uppermost part of 

Bighorn dolomite, loc. Dl (CO), South Fork of Rock Creek, Johnson County, 

Wyo. 

15,17-19. Dinorthisd) (Pionorthis(?)) n. sp. (p. 475).

15,19. Dorsal and ventral views; 17, 18, posterior and lateral views, USNM 124812. 

Upper Ordovician, red shaly beds in the uppermost part of Bighorn dolomite, loc. 

Dl (CO), South Fork of Rock Creek, Johnson County, Wyo. 

16, 20-25. Lepidocyclus gigas Wang (p. 477).

16, 20, 23, Lateral, anterior, and posterior views; 21, 24, dorsal and ventral views 

(specimen slightly distorted), USNM 124814. 22, 25, dorsal and ventral views of 

undistorted specimen, USNM 124815, All from Upper Ordovician, red shaly beds 

in uppermost part of Bighorn dolomite, loc. Dl (CO), South Fork of Rock Creek, 

Johnson County, Wyo.
PLATE 39

FIGURES 1-5. Lepidocyclus perlamellosa (Whitfleld) (p. 477).

1, 2. Dorsal and ventral views, X 1; 3, 4, 5, posterior, lateral, and anterior views, X 1, 

USNM 124816. Upper Ordovician, red shaly beds of uppermost part of Bighorn dolomite, loc. Dl (CO), South Fork of Rock Creek, Johnson County, Wyo. 

6-8,12,13. Hypsiptycha cf. H. anticostiensis (Billings) (p. 478).

6, 7, 12. Posterior, anterior, and lateral views, X 2; 8, 13, ventral and dorsal views, X 2, 

USNM 124817. Upper Ordovician, red shaly beds in uppermost part of Bighorn dolomite, loc. Dl (CO), South Fork of Rock Creek, Johnson County, Wyo. 

9-11,14,15. Hypsiptycha cf. H. hybrida Wang (p. 478).

9,14. Dorsal and ventral views, X 2; 10,11,15, posterior, lateral, and anterior views, X 2, 

USNM 124818. Upper Ordovician, lower shale member, Stony Mountain formation, 

loc. D91f (CO), Shell Oil Co., Pine Unit No. 1 well, 8,986-9,010 ft. 

16,17. Isotelust sp.

16. Cranidium, damaged, X 2, USNM 124821.

17. Pygidium X 2, USNM 124822. Upper Ordovician, lower shale member, Stony Mountain formation loc. D91f (CO), Shell Oil Co., Pine Unit No. 1 well, 8,986-9,010 ft. 

18-20,22,23. Hypsiptycha cf. H. hybrida Wang (p. 478).

18. 22, 23. Posterior, anterior, and lateral views, X 2; 19, 20, ventral and dorsal views, X 2, 

USNM 124819. Upper Ordovician, red shaly beds in uppermost part of Bighorn dolomite, 

loc. Dl (CO), South Fork of Rock Creek, Johnson County, Wyo. 

21,24,25-27. Lepidocyclus capax (Conrad) (p. 477).

21, 24, 27. Lateral, posterior, and anterior views, X 1; 25, 26, dorsal and ventral views, X 1, 

XJSNM 124820. Upper Ordovician, red shaly beds fa uppermost part of Bighorn dolomite, loc. Dl (CO), south Fork of Rock Creek, Johnson County, Wyo.
GEOLOGICAL SURVEY BULLETIN 1021 PLATE 39

BRACHIOPODS (RHYNCHONELLACEA) AND TRILOBITE, BIGHORN 

AND STONY MOUNTAIN FORMATIONS
GEOLOGICAL SURVEY BULLETIN 1021 PLATE 40

BRACHIOPODS (SPIRIFERACEA AND STROPHOMENACEA), STONY 

MOUNTAIN, RED RIVER, AND BIGHORN FORMATIONS
PLATE 40

[Figures natural size unless otherwise indicated]

1-3. Catazyga sp. (p. 479).

1, 2, 3. Dorsal, ventral and lateral views of a fragmentary silicifled specimen, X 3, USNM 

124823. Upper Ordovician, Red River formation, loc. D91d (CO), Shell Oil Co., Pine 

Unit No. 1 well, 9,103-9,116 ft.

4. Strophomena cf. S. vetusta James (p. 482).

Interior of dorsal valvo, cut by coring bit, USNM 124824. Upper Ordovician, lower shale 

member, Stony Mountain formation, loc. D91f (CO), Shell Oil Co., Pine Unit No. 1 

well, 8,986-9,010 ft.

5. 7ygospira cf. Z. resupinata Wang (p. 479).

Ventral view of ventral valve, X 3, USNM 124825. Upper Ordovician, Red River formation, loc. D91e (CO), Shell Oil Co., Pine Unit No. 1 well, 9,023-9,043 ft. 

6-9,12. Zygospira cf. Z. aequualvis Twenhofel (p. 479).

6. 8. Ventral and dorsal views, X 3.

7. 9, 12. Anterior, lateral, and posterior views, X 3, USNM 124826. Upper Ordovician, 

Red River formation, loc. D91c (CO), Shell Oil Co., Pine Unit No. 1 well, 9,122-9,128 ft. 

JO, 11,13,16. Strophomena hecuba Billings (p. 432).

10,11,13. Dorsal valve, dorsal, lateral, and posterior views, USNM 124827. Upper Ordovician, upper dolomitic member, Stony Mountain formation, loc. D90e (CO), Empire 

State Oil Co., Hathaway No. 1 well, 8,556-8,664 ft.

16. Dorsal view of a less nasute specimen, USNM 124828. Upper Ordovician, redshalybeds in uppermost part of Bighorn dolomite, loc. Dl (CO), South Fork of Rock Creek, 

Johnson County, Wyo. 

14. Strophomena cf. S. rugulifera Wang (p. 483).

Ventral view, USNM 124829. Upper Ordovician, Red River formation, loc. D91e (CO),

Shell Oil Co., Pine Unit No. 1 well, 9,023-9,043 ft. 

.45,17,19-21. Megamyonia cf. M. ceres (Billings) (p. 484).

15. Interior of a ventral valve, USNM 124830. 

19. Interior of a dorsal valve, USNM 124831.

17, 20, 21. Lateral, ventral, and posterior views of a ventral valve, USNM 124832. All 

from Upper Ordovician, lower shale member, Stony Mountain formation, loc. D91f 

(CO), Shell Oil Co., Pine Unit No. 1 well, 8,986-9,010 ft. 

18. Megamyonia sp. (cf. M. sp., Wang, 1949, p. 34, pi. 9C) (p. 485).

Ventral view of ventral valve, USNM 124833. Upper Ordovician, lower shale member, 

Stony Mountain formation, loc. D91f (CO), Shell Oil Co., Pine Unit No. 1 well, 8,986- 

9,010 ft. 

22. T/ioerodcmta sp. (p. 480).

Dorsal view, X 2, USNM 124834. Upper Ordovician, red shaly beds of the uppermost part 

of Bighorn dolomite, loc. Dl (CO), South Fork of Rock Creek, Johnson County, Wyo. 

23-25. Megamyonia cf. M. unicostata (Meek and Worthen). (p. 483).

23. Ventral view of ventral valve, Immature, tentatively referred this species, X 2, USNM 

124835.

24. Interior of ventral valve, a rubber mold made from cast, USNM 124836. Upper Ordovician, Red River formation, loc. D92b (CO), Shell Oil Co., Little Beaver No. 1 well, 

8,531-8,540 ft.

25. Ventral view of ventral valve, associated with Diceromyonia sp. USNM 124837. Upper 

Ordovician, lower shale member, Stony Mountain formation, loc. D91f (CO), Shell Oil 

Co., Pine Unit No. 1 welf,"8,986-9,010 ft. 

.26-28. Thaerodonta cf. T. recedens (Sardeson) (p. 481).

26. Internal cast of ventral valve, associated with Megamyonia cf. M. unicostata, USNM 

124838.

27. Interior of dorsal valve, a rubber mold, X 5, USNM 124839.

28. Interior of ventral valve, a rubber mold of cast shown in fig. 26, slightly distorted to 

show delthyrial cavities, X 2, USNM 124838. All from Upper Ordovician, Red River 

formation, loc. D92b (CO), Shell Oil Co., Little Beaver No. 1 well, 8,531-8,540 ft.
PLATE 41

(Figures natural size unless otherwise indicated]

FIGURES 1, 2. Qpikinal afl. <5. limbrata Wang (p. 485).

1. Interior of large dorsal valve, USNM 124840.

2. Interior of small dorsal valve, USNM 124841.

Upper Ordovician, lower shale member, Stony Mountain formation, loc. D91f (CO),

Shell Oil Co., Pine Unit No. 1 well, 8,986-9,010 ft. 

3, 4, 7. Megamyonia aff. N. nitens (Billings) (p. 484).

Posterior, ventral, and lateral views, USNM 124842. Equals in part "Leptaena nitens" 

Billings as described by Twenhofel, 1928. Upper Ordovician, red shaly beds in uppermost part of Bighorn dolomite, loc. Dl (CO), South Fork of Eock Creek, Johnson 

County, Wyo.

6, 6, 9,12,16. Diceromyonia storeya Okulitch. (p. 487). 

5,12. Dorsal and ventral views, X 2;

6, 9,16. Anterior, posterior, and lateral views, X 2, USNM 124843. Upper Ordovician, red 

shaly beds in uppermost part of Bighorn dolomite, loc. Dl (CO), South Fork of Rock 

Creek, Johnson County, Wyo. 

8,10,11. Holtedahlina cf. H. moniquensis Foerste (p. 486).

8. Exterior of a dorsal valve, X 2, USNM 124844.

10. Interior of dorsal valve, X 2, USNM 124845.

11. Interior of dorsal valve, X 2, USNM 124846. 

All specimens poorly silicifled and fragmentary. All from Upper Ordovician, Red River

formation, loc. D91d (CO), Shell Oil Co., Pine Unit No. 1 well, 9,103-9,116 ft. 

13-15,17-21. DiceroMyonia cf. D. ignota (Sardeson) (p. 487).

13. Interior of ventral valve, X 2, USNM 124847.

14,15, 21. Anterior, posterior, and lateral views, X 2.

18, 20. Ventral and dorsal views, X 2, USNM 124848. Upper Ordovician, red shaly beds 

in uppermost part of Bighorn dolomite, loc. Dl (CO), South Fork of Rock .Creek, Johnson County, Wyo.

17. Interior of ventral valve showing narrow ridge between diductor scars, USNM 124849.

19. Interior of dorsal valve, X 2, USNM 124850. Upper Ordovician, lower shale member, 

Stony Mountain formation, loc. D91f (CO), Shell Oil Co., Pine Unit No. 1 well, 8,986- 

0,010 ft. 

22-26. Diceromyonia n. sp. (aff. D. tersa) (p. 487).

22, 24, 25. Posterior, lateral, and anterior views, X 2.

23,26. Ventral and dorsal views, X 2, USNM 124851. Upper Ordovician, red shaly beds 

In uppermost part of Bighorn dolomite, loc. Dl (CO), South Fork of Kock Creek, Johnson County, Wyo.
(iEOI.CHiU'AI. SURVEY BULLETIN 1021 PLATE 41

BRACHIOPODS (STROPHOMENACEA AND PUNCTATE FORMS), STONY 

MOUNTAIN, RED RIVER, AND BIGHORN FORMATIONS
GEOLOGICAL SURVEY BULLETIN 1021 PLATE 42

TKILOBITES, GRAPTOLITi,, AMJ FJS11, W1NMPEG AND DEADWOOD

FORMATIONS
PLATE 42

FIOURES 1-4. Fragmentary fish plates.

1, 2, 4. Eriptychius americanus Walcott, X 3, X 3, X 4, USNM 20868, 208C9, 20870.

3. Astraspis desiderata Walcott, X 3, USNM 20871. Winnipeg formation, loc. D69 (00),

Shell Oil Co., Pine Unit No. 1 well, 9,525-9,531 ft. 

5,6,8-12. Kirkella afl. K. fillmoTensis Hintze (p. 493).

5. Pygldlum, X 2, USNM 124852.

6. Ventral view of fragmentary posterior portion of free chock and dorsal view of Immature 

cranldlum, X 3, USNM 124853.

8. Immature pygidlum, X 3, USNM 124854.

9. Left free cheek, Immature, X 2, USNM 124855.

10. Hypostomo, broken, but showing characteristic "wings," X 2, USNM 124857.

11. Oranldlum, Immature, damaged, X 3, USNM 124856.

12. Oranidlum, damaged, rubber cast of original, X 2, USNM 124858. All from Lower 

Ordovician, Deadwood formation, loc. D66e (CO), Shell Oil Co., Plno Unit No. 1 well, 

9,660-9,666 ft. 

7. Ogyginuat sp. (p. 494).

Pygldium, X 1, USNM 124859. Lower Ordovician, Doadwood formation, loc, D66o (CO), 

Shell Oil Co., Pine Unit No. 1 well, 9,660-9,666 ft.

13. Apatokephalus cf. A. canadensis Kobayashi (p. 499).

Oranldium, X 4, USNM 124860. Lower Ordovician, Deadwood formation, loc. D66o 

(CO), Shell Oil Co., Pine Unit No. 1 well, 9,660-9,666 ft.

14. Hormotomal sp.

Two small specimens, X 1, USNM 124861. Lower Ordovician, Doadwood formation,

loo. D66e (CO), Shell Oil Co., Pine Unit No. 1 well, 9,660-9,666 ft. 

15,16,19,20. Megalaspidella cf. M. orthometopa Harrlngton (p. 492).

15. Cranidium, lacking palpebral lobes, X 2, USNM 124862.

16. 20. Pygldium, dorsal and posterior views, X 3, USNM 124863. 

19. Fragmentary hypostome, rubber cast, X 4, USNM 124864. Lower Ordovician, Deadwood formation, loc. D66d-e (CO), Shell Oil Co., Pine Unit No. 1 well, 9,660-9,690 ft.

17. Kirkellat sp. (p. 492).

Pygidlum, X 2, USNM 124865. Probably same as those figured above. Lower Ordovician, Deadwood formation, loc .D66d (CO), Shell Oil Co., Pine Unit No. 1 well, 9,672- 

9,678 ft.

18. Protopliomerops cf. P. superciliosa Eoss (p. 503).

Cranidium, X 3, USNM 124866. Lower Ordovician, Deadwood formation, loc. D66d

(00), Shell Oil Co., Pine Unit No. 1 well, 9,672-9,678 ft. 

21,22. Ataphettust sp. (p. 494).

21. Cranidium and ventral surface of pygidtum, X 2, USNM 124868.

22. Pygidium, X 2, USNM 124867. Lower Ordovician, Deadwood formation, loc. D66b 

(CO), Shell Oil Co., Pine Unit No. 1 well, 9,698 ft.

23. Unidentified pygidium (p. 503).

X 3, USNM 124869. This should be compared with Hintze, 1952, pi. IX, fig. 19. Lower 

Ordovician, Doadwood formation, loc. D66d (CO), Shell Oil Co., Pine Unit No. 1 well, 

9,678-9,684 ft.

24. Dictyonema sp.

X 1, USNM 124870. Lower Ordovician, Deadwood formation, loc. D70 (00), Shell Oil 

Co., Rich; y area, Northern Pacific K. E. No. 1 well, 10,484 ft.
PLATE 43

FIGURES 1-4,6,7. Kayseraspis afl. K. asaphelloides Harrlngton (p. 497).

1. Fragmentary cranldlum and immature pygidium with terminal spine, X 2, 

TTSNM 124871.

2. Oranidium lacking palpebral lobes, USNM 124872.

3. Pygidium immature but with mature proportions, X 2, USNM 124873.

4. Mature pygidium cut by coring bit; terminal spine incomplete, X 2, USNM 124874. 

6, 7. Immature pygidia, showing slight change In shape and in definition of segmentation, X 4, USNM 124875,124876. All from Lower Ordovician, Deadwood formation, 

loc. D66b (CO), Shell Oil Co., Pine Unit No. 1 well, 9,701-9,708 ft. 

5,12,13. Megalaspis planilimbata var. eydopyge Harrington (p. 490). 

5. Pygidium X 2, USNM 124877.

12. Cranidium with pathologic(?) development of one muscle scar and obverse of 

pygidium shown in flg. 13, X 2, USNM 124878.

13. Small pygidium, X 2, USNM 124879, Lower Ordovician, Deadwood formation,

loc. D66b (00), Shell Oil Co., Pine Unit No. 1 well, 9,701-9,705 ft. 

8. NanortMsl sp.

X 2, USNM 124880. Dorsal valve, dorsal view. Lower Ordovician, Deadwood formation, loc. D66b (CO), Shell Oil Co., Pine Unit No. 1 well, 9,703-9,710 ft. 

9,10. Unidentified hypostomes (p. 490,494,497).

9. Associated with Asaphellust sp. and Megalaspis planilimbata var. cydopyge X 2, 

USNM 124881.

10. Associated with Kayseraspis afF. K. asaphelloides, X 2, USNM 124882. Lower 

Ordovician, Deadwood formation, loc. D66b (CO), Shell Oil Co., Pine Unit No. 1 

well, 9,701-9,709 ft. 

11,17. Lloydia cf. L. saffordi (Billings) (p. 489).

11. Small pygidium, X 2, USNM 124883.

17. Pygidium, X 2, USNM 124884. Lower Ordovician, Deadwood formation, loc. 

D66b (CO), Shell Oil Co., Pine Unit No. 1 well, 9,709 ft. (Species also present, 

D66c (CO), 9,690-9,696 ft.)

14. Syntrophild brachiopod, not identified generically.

Dorsal valve, X 2, USNM 124885. Lower Ordovician, Deadwood formation, loc. 

D66a (CO), Shell Oil Co., Pine Unit No. 1 well, 9,711 ft.

15. Unidentified pygidium (p. 503). 

X 2, USNM 124886. Compare with Boss, 1951, pi. 19, figs. 30,31. Lower Ordovician. 

Deadwood formation, loc. D66a (CO), Shell Oil Co., Pine Unit No. 1 well, 9,715 ft.

16. DidymogTaplusflsp. or Tetragr-aptiLst sp.

Immature, X 4, USNM 124887. Lower Ordovician, Deadwood formation (associated 

with Bryograptustsp.'), loc. D66a (CO), Shell Oil Co., Pine Unit No. 1 well, 9,715 ft. 

18-20. Leiostegium manitouensis Walcott (p. 489).

18. Cranidium, decorticated, X 2, USNM 124888.

19. Hypostome, X 4, USNM 124889.

20. Cranidium, X 2, USNM 124890. All from Lower Ordovician, Deadwood formation, loc. D70a (CO), Shell Oil Co., Richey area, Northern Pacific R. R. No. 1 well, 

10,500-10,509 ft. 

21, 22, 25, 26. Hystricurus sp. (p. 488).

Four cranidia, X 4, USNM 124891, 124892, 124893, 124894, showing change in median 

preglabellar furrow with growth. 25,26, may belong to separate species (cf. H. robustus

Ross). All from Lower Ordovician, Deadwood formation, loc. D70a (00), Shell

Oil Co., Eichey area, Northern Pacific E. E. No. I well, 10,500-10,509 ft.

23, 24, 27-30. Halru-lla sp. (p. 600).

23. Front of glabella, preglabellar field, and rim, X 3, USNM 124895.

24. Cranidium immature, X 4, USNM 124896.

27. Oraniaium, tocfciug preglabollar a«Ja, « 3, VSNM i24st>7.

28. Free cheek, showing granulose ornamentation of ocular platform, X 3, USNM 124898.

29. Obverse of pygidium shown in flg. 30, fragmentary, X 2, USNM 124899.

30. Pygidium, lacking rear of axis, X 2, USNM 124900. All from Lower OrdoTiclan, 

Deadwood formation, loc. D70a (C), Shell Oil Co., Bichey area, Northern Pacific 

R. R. No. 1 well, 10,600-10,609 ft.
GEOLOGICAL SURVEY BULLETIN 1021 PLATE 43

BRACHIOPODS, TRILOBITES, AND GRAPTOLITE, DEADWOOD

FORMATION