Contributions to Late Cretaceous 

Stratigraphy and Paleontology, 

Western Montana 

U.S. GEOLOGICAL SURVEY BULLETIN 1962 
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Ave. 
Contributions to Late Cretaceous 

Stratigraphy and Paleontology, 

Western Montana 

A. Redefinition of Frontier FormationBeaverhead Group Contact, Lima Peaks Area, 

Southwestern Montana and Southeastern Idaho 

By T.S. DYMAN, J.C .. HALEY, and W.J. PERRY, JR. 

B. Biostratigraphic Correlation of Santonian and 

Campanian Formations in the Northwestern Part of 

Yellowstone National Park, and the Madison Range and 

Livingston Area of Southwestern Montana 

By R.G. TYSDAL and D.J. NICHOLS 

C. Occurrence and Significance of the Middle Turonian 

(Upper Cretaceous) Belemnite Actinocamax in 

Central Western Montana 

By WILLIAM A. COBBAN 

This volume is published as chapters A-C. 

These chapters are not available separately 

U.S. GEOLOGICAL SURVEY BULLETIN 1962 
U.S. DEPARTMENT OF THE INTERIOR 

MANUEL LUJAN, JR., Secretary 

U.S. GEOLOGICAL SURVEY 

Dallas L. Peck, Director 

Any use of trade, product, or firm names in this publication is for descriptive 

purposes only and does not imply endorsement by the U.S. Government. 

UNITED STATES GOVERNMENT PRINTING OFFICE: 1991 

For sale by the 

Books and Open-File Reports Section 

U.S. Geological Survey 

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Box 25425 

Denver, CO 80225 

Library of Congress Cataloging-in-Publication Data 

Contributions to Late Cretaceous stratigraphy and paleontology, western Montana. 

p. cm.-(U.S. Geological Survey bulletin; 1962) 

Includes bibliographical references. 

Supt. of Docs. no.: 119.3:1962 

Contents: Redefinition of Frontier Formation-Beaverhead Group Contact, 

Lima Peaks area, southwestern Montana and southeastern Idaho I by T.S. 

Dyman, J.C. Haley, and W.J. Perry, jr.-Biostratigraphic correlation of 

Santonian and Campanian Formations in the northwestern part of Yellowstone 

National Park, and the Madison Range and Livingston area of southwestern 

Montana I by R.G. Tysdal and D.J. Nichols-Occurrence and significance of 

the Middle Turonian (Upper Cretaceous) Belemnite Actinocamax in central 

western Montana I by William A. Cobban. 

1. Geology, StratigraphiC-Cretaceous. 2. Paleontology-Cretaceous. 

3. Geology-Montana. 4. Geology-Idaho. 5. Paleontology-Montana. 

I. Series. 

QE75.B9 no. 1962 

[QE688] 

557.3 S-dc20 

[551 '.7'5'09786] 90-25352 

CIP 
CONTENTS 

[Letters designate chapters] 

(A) Redefinition of Frontier Formation-Beaverhead Group contact, Lima Peaks area, 

southwestern Montana and southeastern Idaho, by T.S. Dyman, J.C. Haley, and 

W.J. Perry, Jr. V 

(B) Biostratigraphic correlation of Santonian and Campanian formations in the 

northwestern part of Yellowstone National Park, and the Madison Range and 

Livingston area of southwestern Montana, by R.G. Tysdal and D.J. 

Nichols 9 

(C) Occurrence and significance of the middle Turonian (Upper Cretaceous) 

belemnite Actinocamax in central western Montana, by William A. Cobban 21 

Volume Contents Ill 

Chapter A 

Redefinition of Frontier FormationBeaverhead Group Contact, Lima Peaks Area, 

Southwestern Montana and Southeastern Idaho 

By T.S. DYMAN, J.C. HALEY, and W.J. PERRY, JR. 

U.S. GEOLOGICAL SURVEY BULLETIN 1962 

CONTRIBUTIONS TO LATE CRETACEOUS STRATIGRAPHY 

AND PALEONTOLOGY, WESTERN MONTANA 
CONTENTS 

Abstract 1 

Introduction 1 

Stratigraphic nomenclature and contact relationships 2 

Lithologic relationships 4 

Distinctive upper Frontier lithologic units 5 

Discussion 5 

References cited 7 

Appendix 8 

FIGURES 

1. Stratigraphic chart of Lower and Upper Cretaceous (Albian to Campanian) rocks 

showing formal and informal geologic names used in this report 2 

2. Index map of the study area in Montana and Idaho showing geographic and 

geologic features and Frontier Formation-Beaverhead Group contact 3 

3. Generalized lithologic chart of upper part of Frontier Formation and lower part of 

Beaverhead Group showing major rock units exposed at three localities in the 

study area 6 

CONVERSION FACTORS 

Inch-pound units of measurement in this report may be converted to International System (SI) of metric units 

usng the following conversion factors: 

Multiply inch-pound unit By To obtain SI unit 

foot (ft) 0.3048 meter(m) 

mile (mi) 1.609 kilometer(km) 

inch (in.) 2.54 centimeter( em) 

VI Contents 
Redefinition of Frontier FormationBeaverhead Group Contact, Lima Peaks Area, 

Southwestern Montana and Southeastern Idaho 

By T.S. Dyman, J.C. Haley, and W.J. Perry, Jr. 

Abstract 

The Upper Cretaceous Frontier Formation and the 

overlying Upper Cretaceous lower part of the Beaverhead 

Group form a thick sequence of nonmarine, predominantly 

clastic sedimentary rocks south of Lima and Monida, Montana, 

north of the Continental Divide. The upper Frontier and lower 

Beaverhead have lithologies that are unique as well as 

common to both units, but the rocks are difficult to study 

because exposures are poor. Quartzite-clast conglomerates, 

lithic-rich sandstones with abundant limestone fragments, and 

limestone-pebble conglomeratic zones in the upper part of the 

Frontier Formation resemble those in the lower part of the 

Beaverhead Group. In the western part of the area, near Knob 

Mountain, an angular unconformity separates the two units 

and distinguishing them is easy. In the eastern part of the study 

area, near Humphrey, Idaho, the two units are conformable, 

and a mappable contact is difficult to identify. 

Two distinct lithologies are present in the uppermost 

Frontier Formation but are absent in the overlying Beaverhead 

beds: (1) conglomerates and conglomeratic sandstones derived 

from Cretaceous and Jurassic formations, and (2) green to 

olive-green porcellanites and tuffaceous and porcellanitic 

sandstones. Upper Frontier limestone conglomerates containing clasts derived from Jurassic and Cretaceous formations 

occur below the sub-Beaverhead unconformity and are interbedded with typical upper Frontier mudstones and sandstones. 

Clasts contain gastropod fragments and oolites derived from 

the Middle Jurassic Rierdon Formation and the Lower 

Cretaceous Kootenai Formation. Green porcellanitic beds are 

interbedded with and are stratigraphically above conglomerates with Mesozoic-derived limestone clasts. These porcellanites form distinct and laterally continuous beds throughout 

the area. 

Based on these new data, the Frontier-Beaverhead contact should be placed at the angular unconformity where it can 

be recognized. The contact separates two distinct lithologic 

Manuscript approved for publication, November 20, 1990. 

associations interpreted as depositional cycles. Where the 

unconformity is absent, the contact should be placed at the top 

of the uppermost green porcellanitic unit of the upper Frontier 

Formation. The porcellanitic unit (1) is exposed everywhere in 

the Lima Peaks region where the upper Frontier occurs, (2) 

represents an excellent time marker, and (3) is near the top of 

the Frontier depositional cycle above several thousand feet of 

monotonous Frontier rocks that cannot be easily subdivided 

Intervening conglomerates with Mesozoic-derived limestone 

clasts and conglomeratic sandstones aid in identifying the 

approximate stratigraphic position of the porcellanite beds. 

INTRODUCTION 

Contact relationships between the Upper Cretaceous 

lower part of the Beaverhead Group and the underlying 

Upper Cretaceous Frontier Formation and older rocks in the 

Lima region of southwestern Montana and adjacent 

northeastern Idaho (fig. 1) have not been fully established. 

Difficulties in establishing the nature of the contact can be 

attributed to the following reasons: (1) the Frontier Formation is poorly exposed because its abundant mudstones 

and shales commonly form debris flow slopes; (2) both the 

Frontier Formation and lower part of the Beaverhead Group 

are characterized by profound facies changes across a 

distance of 15 miles (25.3 km) paralleling the Continental 

Divide between Red Conglomerate Peaks and Little Beaver 

Creek (fig. 2); and (3) the region was thrusted and folded 

during emplacement of the Idaho-Montana thrust belt. 

Frontier strata may be locally repeated by thrusting, and 

cross faults cut the Frontier-Beaverhead contact. 

Facies relationships within the Beaverhead and 

Frontier, the nature of the Frontier-Beaverhead contact (is 

the contact conformable or unconformable?), and resultant 

implications for the tectonic history of this part of the 

Cordillera are the subjects of our ongoing research. Preliminary results suggest that the character of the subBeaverhead unconformity changes laterally from the back 

Frontier Formation-Beaverhead Group Contact, Lima Peaks Area, Montana and Idaho 
AGE WILSON (1970) 

Campanian 

Santonian 

Coniacian 

Turonian 

Cenomanian 

Albian 

RYDER AND 

SCHOLTEN (1973) 

Beaverhead 

Formation 

(lithic units, 

undivided) 

(part) 

NICHOLS AND 

OTHERS (1985) 

PERRY AND 

OTHERS (1989) 

Frontier 

Formation 

DYMAN AND 

OTHERS (1989) AND 

PRESENT REPORT 

limestone and 

quartzite conglomerate and 

quartzarenite, 

undivided4 

Blackleaf 

FormationS 

1 Sawmill Creek beds of Ryder and Scholten (1973) with interbedded quarzite-clast conglomerates and lithologies typical ofthe Aspen Formation. 

2 Clover Creek sandstone unit of Perry and others (1989) is correlative with Monida sandstone unit of Ryder and Scholten (1973) and lower part of 

Monida Formation of Wilson (1970) and Monida Sandstone of Perry and others (1989). 

3 Perry and others (1989) did not address these beds in their report. 

4 Formal and informal Beaverhead units are not addressed in this report. 

5 The Frontier Formation and Beaverhead Group are disconformable over part of their outcrop areas south of Lima and Monida, Montana, but age 

relationships have not been fully established. The upper part of the Frontier Formation may be Cenomanian or Turonian in age. The 

sub-Beaverhead unconformity cuts out beds as old as early Mesozoic and late Paleozoic. 

6 Cobban and Kennedy (1989) indicated that the Mowry Shale (and equivalent beds including the upper part of the Blackleaf Formation) are all or part 

Cenomanian in age. 

Figure 1. Stratigraphic chart of Lower and Upper Cretaceous (Albian to Campanian) rocks showing formal and informal geologic 

names used in this report. 

of the Tendoy thrust sheet near Red Conglomerate Peaks 

eastward to south of Monida, Montana, where the contact is 

conformable or disconformable (fig. 2). If confirmed, such 

a relationship would suggest the presence of a "progressive 

syntectonic unconformity" (Riba, 1976) within the Upper 

Cretaceous sequence. 

The purpose of this paper, therefore, is to briefly 

describe lateral and vertical facies variations within the 

uppermost Frontier and lowermost Beaverhead and to 

define a new Frontier-Beaverhead contact based on these 

new data. With recognition of the criteria defining the 

contact, the two formations can be more accurately mapped 

and dated, and facies will be better understood. Interpretation of the sedimentary-tectonic regime will be facilitated, which will aid understanding interrelationships of the 

thrust-belt and the Late Cretaceous foreland basin. 

STRATIGRAPHIC NOMENCLATURE 

AND CONTACT RELATIONSHIPS 

We experienced difficulties in understanding stratigraphic relationships regarding the Frontier-Beaverhead 

contact based on earlier published work, in part because of 

different nomenclature and in part because of the significant 

differences in where the contact was placed stratigraphically. Dillon (1947) was the first to discuss the contact 

relationships of Cretaceous rocks near the Continental 

Divide south of Lima. He described an angular unconformity between his Cenozoic rocks (rocks now assigned to 

the Beaverhead Group) and his underlying Mesaverde 

Formation (which contains rocks that are in part equivalent 

to the Frontier Formation). 

In the Lima area, Lowell and Klepper (1953, p. 241) 

identified an unconformable contact between the Beaverhead and underlying strata; underlying strata were described 

as being as old as the Mississippian Madison Limestone and 

as young as strata equivalent to rocks of the Late Cretaceous 

Montana Group. This stratigraphic relationship of their 

Beaverhead Formation and Montana Group equivalents was 

identified in the western part of the area of this study (sec. 

33, T. 15 S., R. 8 W., about 0.5 mi (0.8 km) north of Knob 

Mountain; fig. 2). 

Scholten and others (1955) defined all post-Kootenai 

and pre-Beaverhead Cretaceous rocks in the Lima region as 

Aspen Formation, but stated that rocks of the Upper 

Cretaceous Mesaverde Formation could be exposed south of 

Lima and to the northeast in the Ruby River valley about 25 

mi (40.2 km) northeast of Lima (see appendix for further 

details of use of the name Aspen Formation). A large part of 

their Aspen Formation is equivalent to rocks that we refer to 

as Frontier Formation. They stated that their Aspen 

Formation is overlain with profound angular unconformity 

by the Beaverhead Formation in the Lima region (Scholten 

and others, 1955, p. 368). 

Ryder and Scholten (1973) discussed the basal Beaverhead contact in detail, but their basal Beaverhead is 

equivalent in part to rocks that we consider to be either 

2 Contributions to late Cretaceous Stratigraphy and Paleontology, Western Montana 
/--'<AXIS OF BLACKTAIL-

/ SNOWCREST UPLIFT 

/ 

5 MILES 

MONTANA 

5 KILOMETERS 

Figure 2. Index map of the study area in Montana and Idaho showing mountain ranges, streams, sample localities 1-7 (solid 

triangles with numbers), and Frontier Formation (Kff)-Beaverhead Group (TKb) contact. Contact dashed where covered or poorly 

exposed and queried where unknown. Arrow on anticline indicates direction of plunge. 

Frontier Formation or the underlying Blackleaf Formation 

(fig. 1 ). They identified a profound angular unconformity 

between the Beaverhead and underlying rocks in the Red 

Conglomerate Peaks area and recognized that the unconformity diminished eastward through our study area. They 

suggested that the sequence may actually become conformable, and as evidence cited the following: (1) interbedding of Aspen Formation lithologic units (yellow shales 

and chert-bearing sandstones) with quartzite conglomerates 

along Sawmill Creek; and (2) the similarity in dips of the 

strata above and below their Aspen-Beaverhead contact 

along the Continental Divide south of Lima and Monida, 

Montana. On the west slope of Shine Hill (fig. 2), Ryder and 

Scholten (1973) designated conglomerate beds that are 

conformable with underlying and overlying strata as basal 

Beaverhead (see appendix for additional comments regarding the Shine Hill beds). Where no unconformity was 

observed, they placed the Aspen-Beaverhead contact at the 

"first appearance of conglomerates with Middle Proterozoic 

Belt Series (now Supergroup) quartzite clasts." Recent work 

has shown that Belt quartzite clasts also occur in conglomerates in the Blackleaf (Dyman and Nichols, 1988) and 

Frontier Formations (Dyman and others, 1989). Ryder and 

Scholten (1973) identified a minor(?) disconformity 

between their Aspen and Beaverhead Formations near 

Monida, where the Beaverhead lacks quartzite clast conglomerates. Ryder and Scholten's (1973) observations on 

changes in the sub-Beaverhead contact laid the groundwork 

for future studies. Wilson ( 1970) considered some of the 

conglomerates of Ryder and Scholten's (1973) Beaverhead 

Formation as part of his Aspen Formation, but his correlation chart (Wilson, 1970, p. 1850) clearly showed an 

unconformable relationship between the Aspen Formation 

(or unnamed conglomerate of Shine Hill) and the Beaverhead Formation. It should be noted, however, that Wilson 

worked primarily in an outcrop belt immediately north of 

our study area north of Interstate Highway 15 between Lima 

and Monida, Montana (fig. 1 ). The Beaverhead conglomerates in our study area are primarily limestone 

conglomerates of the Lima Conglomerate and equivalent 

distal sandstones. 

Skipp and others (1976) mapped post-Kootenai-preBeaverhead strata as their Lower Cretaceous sandstone and 

claystone unit, which they considered equivalent to the 

Frontier Formation-Beaverhead Group Contact, Lima Peaks Area, Montana and Idaho 3 
Aspen Formation. They identified a thrust contact placing 

Beaverhead over Aspen in the northern Edie Ranch 15-

minute topographic quadrangle (area near Red Conglomerate Peaks along the Continental Divide, fig. 2). Haley 

( 1986) believed that evidence supporting such an interpretation did not exist and considered the AspenBeaverhead contact (Aspen as used here is equal to our 

Frontier Formation) to be an angular unconformity as 

interpreted by earlier workers. 

Perry and others ( I983) discussed the Beaverhead and 

unnamed Upper Cretaceous rocks in their discussion of the 

petroleum potential of the region; they did not discuss 

contacts between the Beaverhead and underlying strata, 

which they grouped into one unit. Nichols and others (1985) 

and Dyman and Nichols (1988) stated that the "Shine Hill 

conglomerate beds," the basal Beaverhead of Ryder and 

Scholten (1973) are equivalent to the Frontier Formation 

and are in part Cenomanian in age based on a reinterpretation of Ryder and Scholten (1973) palynomorph 

assemblages. Perry and others (1989) also used the Frontier 

name for the youngest pre-Beaverhead sequence and 

recognized an angular unconformity separating the Frontier 

and Beaverhead rocks. 

Dyman and others (1989) presented detailed lithologic and petrologic data for the Frontier and subdivided the 

formation into three lithologic units, from base to top: lower 

volcaniclastic, middle mudstone-shale, and upper clastic 

(fig. 1). They recognized the angular unconformity between 

the Frontier and the overlying Beaverhead between Shine 

Hill and the Continental Divide (localities I and 2, fig. 2) 

and suggested that the Frontier-Beaverhead contact should 

be placed at the unconformity where it could be easily 

identified. As a result of detailed mapping, they recognized 

that limestone conglomerates in the basal Beaverhead 

contained much larger clasts (clasts greater than 6 in. 

(15.3 em) in diameter) than similar conglomerates in the 

uppermost Frontier (clasts less than 2 in. (2.4 em) in 

diameter). They also recognized that interbedded sandstones in both units were somewhat different. Basal Beaverhead sandstones are quartz-rich (quartzarenites), 

whereas upper Frontier sandstones are chert-rich (saltand-pepper sandstones). When an angular unconformity 

was not evident, the first appearance of either clastsupported limestone conglomerates or quartzarenites was 

established as the basal units of the Beaverhead. Our recent 

field investigations, however, indicate that upper Frontier 

limestone conglomerates are also clast-supported. 

LITHOLOGIC RELATIONSHIPS 

Facies of the uppermost Frontier and lowermost 

Beaverhead interval vary from one locality to another 

within the study area. These facies are discussed in the 

following paragraphs in order to better understand the 

criteria for redefining the formational contact. 

The sub-Beaverhead unconformity is well pronounced about 4 mi (6.4 km) west of Knob Mountain near 

Little Sheep Creek (locality I, fig. 2; N1

/z sees. 27 and 28, 

T. I5 S., R. 8 W., Gallagher Gulch 7.5-minute topographic 

quadrangle) where the Beaverhead Group rests unconformably on beds as old as the Triassic Thaynes Formation and 

as young as the Lower Cretaceous lower part of the 

Blackleaf Formation. To the northwest in the Tendoy 

Mountains, about 10 mi ( 16.1 km) northwest of Lima, the 

Beaverhead rests unconformably on older Mesozoic or 

Paleozoic strata. 

Near Knob Mountain, lithologic units in the basal 

Beaverhead are dominated by limestone conglomerates, and 

an angular unconformity occurs between the Frontier and 

the Beaverhead. The Frontier-Beaverhead contact near 

Knob Mountain is best exposed at the north end of a 

north-trending ridge (locality 2, figs. 2, 3; NW1

/4, sec. 30, 

T. 15 S., R. 8 W., Lima Peaks 7.5-minute topographic 

quadrangle). At this locality about 200 ft (60.9 m) of 

interbedded olive-green mudstone and siltstone, salt-andpepper sandstone, and quartzite conglomerate are exposed 

in a gully at the base of the ridge west of Little Beaver 

Creek. Limestone conglomerate of the basal Beaverhead 

Group is exposed at the top of the gully in angular 

discordance with the upper Frontier strata. Limestone 

conglomerates are overlain by, and interbedded with, 

quartzite-clast conglomerates and quartzarenites. No 

evidence of faulting could be recognized at the contact at 

this locality. 

About 6 mi (9.6 km) east of Knob Mountain, near 

Shineberger Creek (locality 3, fig. 2; NE1

/4 sec. 29, T. 15 S., 

R. 7 W., Snowline 7.5-minute topographic quadrangle), the 

angular unconformity is still present and the base of the 

Beaverhead is marked by limestone conglomerates grading 

upward into interbedded limestone conglomerates and 

quartzarenites. About 0.5 mi (0.8 km) to the southwest of 

locality 3 (fig. 2; S1/z sec. 29, T. 15 S., R. 7 W., Paul 

Reservoir I5-minute topographic quadrangle) quartziteclast conglomerates occur above the contact in the lower 

Beaverhead, but they are interbedded with limestone 

conglomerates and quartzarenites. The quartzite-clast 

conglomerates contain about 70 percent white, red, and gray 

quartzite, 15 percent dark-gray chert, I5 percent green to 

gray silicic volcanic clasts, and rare conglomerate and 

bedded chert clasts. 

About 12 mi (19.3 km) northeast of Knob Mountain, 

at Monida, Montana, along the northeast flank of the Lima 

anticline (fig. 2), the Frontier-Beaverhead contact may be a 

thrust fault. At Monida, salt-and-pepper plagioclase- and 

chert-bearing sandstones, olive-green to brown mudstones, 

and shales are abundant in the Frontier. Our recent mapping 

indicates that these beds are in angular discordance with tan, 

quartz-rich sandstones of the Monida sandstone unit of the 

4 Contributions to late Cretaceous Stratigraphy and Paleontology, Western Montana 
basal Beaverhead Group, from which they are separated by 

a covered interval more than 200ft (60.9 m) wide (locality 

7, fig. 2). Conglomerates at Monida occur only as discontinuous pebble lenses. 

At the eastern end of the study area, along Idaho 

Creek near Humphrey, Idaho, (locality 6, figs. 2, 3; WV2, 

sec. 6, T. 13 N., R. 36 E., Paul Reservoir 15-minute 

topographic quadrangle) lithologic relationships differ from 

those to the west. Salt-and-pepper sandstones, mudstones, 

and shales of the Frontier are overlain conformably by 

quartzite- and limestone-clast conglomerates. Ryder and 

Scholten (1973) recognized quartzite-clast conglomerates 

here and placed them in their "Divide quartzite conglomerate unit." Quartzite-clast conglomerates are abundant 

in both the upper Frontier and lower Beaverhead, and 

individual beds at locality 6 are thicker than those at 

localities 2 and 3. At localities 4 and 5 (fig. 2), along the 

west and east forks of Big Beaver Creek, typical Frontier 

rocks are overlain with apparent conformity by a mixed 

suite of quartzite-clast conglomerates and quartzarenites. 

The angular unconformity seems to disappear between 

localities 3 and 4. 

Quartzite-clast conglomerates in the upper part of the 

Frontier Formation resemble those in the lower part of the 

Beaverhead Group at localities 1-7. Lithic sandstones with 

abundant chert and limestone fragments and pebbleconglomeratic zones with abundant rounded to subangular 

limestone pebbles are present in both units. Near locality 2 

(fig. 2), in the upper Frontier Formation, sandstones with 

interbedded conglomeratic zones contain limestone clasts as 

much as 3 in. (7.6 em) in diameter. Our ongoing field 

studies suggest that these limestone clasts were derived 

from Jurassic and Cretaceous formations and are unlike 

clasts in the Beaverhead limestone conglomerates. Limestone conglomerates in the lower Beaverhead contain much 

larger limestone clasts (greater than 15 in. (38.1 em) in 

diameter) than the upper Frontier (as much as 2 in. (5.1 

em)), and conglomerates in the Beaverhead are clastsupported. Near locality 2, where strata are well exposed, 

distinguishing the Frontier and Beaverhead is best 

accomplished by identifying the angular unconformity 

separating the two units. 

DISTINCTIVE UPPER FRONTIER 

LITHOLOGIC UNITS 

Field mapping of Frontier and Beaverhead strata and 

recognizing a Frontier-Beaverhead contact in the area of 

this study are difficult tasks at localities 4 through 6 because 

the Frontier and Beaverhead are conformable. Quartzarenites are not always present in the Beaverhead, and the upper 

Frontier is typically poorly exposed. Two distinct lithologic 

units occur in the uppermost Frontier Formation at each of 

the localities studied but are absent from overlying Beaverhead beds: (1) conglomerates and conglomeratic sandstones 

derived from Cretaceous and Jurassic formations, and 

(2) bright green to olive-green porcellanites and tuffaceous 

and porcellanitic sandstones. At localities I through 6, a 

distinctive limestone conglomerate and interbedded conglomeratic sandstone occurs in the uppermost Frontier 

Formation (figs. 1 and 3). The conglomerate is rich in 

limestone clasts derived from the Kootenai gastropod 

limestone (uppermost Kootenai Formation) and Jurassic 

Rierdon Formation. Clasts include bioclastic limestones 

rich in high- and low-spired gastropods typical of the 

uppermost Kootenai, micritic limestone clasts typical of the 

lower Kootenai, and oolitic limestone clasts typical of the 

Rierdon Formation. Paleozoic limestone clasts are rare or 

absent (Dyman and others, 1989). The conglomerate and 

conglomeratic zones vary from a few feet to more than 

10ft thick (a meter to more than 3m) and may include one 

or more distinct beds. However, the unit is not present 

everywhere in the study area and laterally grades into 

olive-green to brown mudstone and siltstone beds most 

typical of the Frontier. 

Dark-green to olive-green and gray porcellanite, porcellanitic mudstone, and green tuffaceous and porcellanitic 

sandstone beds form the second distinct lithologic unit in 

the upper Frontier. The interval consists of one or more 

porcellanitic beds generally less than, but as much as 10 ft 

(3.1 m) thick interbedded with tuffaceous sandstone or 

porcellanitic sandstone beds. Porcellanite is hard and dense, 

may have small (less than 0.3 in. (0.6 em) in diameter) 

lithophysae, and is finely laminated. Some laminations 

show distinct color variations. Tuffaceous sandstone may be 

crossbedded and ripple-laminated, and is fine to coarse 

grained. Sandstone contains abundant volcanic rock 

fragments, chlorite, and biotite. Distinct porcellanite zones 

are thin to medium bedded and appear to thin and thicken 

laterally. Many of the tuffaceous beds appear to have been 

reworked in an aqueous environment. This porcellanitic 

zone is overlain, underlain, and interbedded with the distinct 

limestone conglomerate derived from Kootenai and Rierdon 

sources. The porcellanitic interval lies stratigraphically 

below the uppermost Frontier exposed at localities 2 and 3 

and lies immediately below the thick quartzite-clast 

conglomerate zones at localities 4 through 6. Two distinct 

porcellanite beds are present at locality 6 (fig. 3). 

DISCUSSION 

Criteria used by Dyman and others (1989) to establish 

the Frontier-Beaverhead contact are inadequate at localities 

4 through 6 (fig. 2). First, an angular unconformity cannot 

be identified at these localities. Second, limestone conglomerates are rare or absent in the basal Beaverhead. 

Upper Frontier limestone conglomerates with Jurassic and 

Cretaceous clasts lie below the unconformity at localities 2 

and 3 and are only locally present because of their fluvial 

Frontier Formation-Beaverhead Group Contact, Lima Peaks Area, Montana and Idaho 5 
WEST 

LITTLE BEAVER 

CREEK 

Locality 2 

200 FEET 

Quartzite clasts as much 

as 6 inches in diameter 

Limestone conglomerate of 

Knob Mountain 

Angular unconformity 

Typical lithologies of 

Frontier Formation 

Conglomeratic sandstone; 

conglomeratic clasts are 

Mesozoic clasts, especially 

Kootenai Formation 

Green porcellanite 

50 METERS 

SHINEBERGER 

CREEK 

Locality 3 

.· ············· .. ·.·.·.·.·.·.·.·.·.·.·. 

Quartzite clasts as much as 

6 inches in diameter 

Quartz-rich sandstone 

Angular unconformity 

At least five distinct beds of 

conglomeratic sandstone; 

conglomerate clasts are 

Mesozoic limestone 

Green porcellanite and 

tuffaceous sandstone 

Typical lithologies of 

Frontier Formation 

EXPLANATION 

Quartzite-clast conglomerate 

25 ~ ~ Limestone-clast conglomerate 

and conglomeratic sandstone 

100 

50 

0-0 ll.l>).)j)j)j.JI Sandstone, may be chert- or quartz-rich 

EAST 

IDAHO 

CREEK 

Locality 6 

············· 

·:::::::::::::::::::::::::: 

Quartz-rich sandstone 

Quartzite clasts as much 

as 7 inches in diameter 

Green porcellanite and 

tuffaceous sandstone 

Chert-rich and 

quartz-rich sandstone 

Green porcellanite and 

tuffaceous sandstone 

Conglomerate and conglomeratic 

sandstone; limestone clasts are 

Jurassic Rierdon Formation and 

Cretaceous Kootenai Formation 

Typical lithologies of 

Frontier Formation 

lmJ Siltstone, mudstone, or shale 

b. b. b. 

b.b.b. Porcellanite, porcellanitic or b. b. b. tuffaceous sandstone 

~ Covered interval 

Figure 3. Generalized lithologic chart of upper part of Frontier Formation and lower part of Beaverhead Group showing major 

lithologic units exposed at or near the Frontier-Beaverhead contact at localities 2, 3, and 6 (fig. 2). 

character. These beds are different from the basal Beaverhead limestone conglomerates at localities 2 and 3. Quartzite clast conglomerates with large clasts (greater than 6 in. 

(15.3 em) in diameter) occur throughout the Frontier and 

Beaverhead. The informal lithologic units established by 

Dyman and others (1989) are large-scale units and can be 

generally recognized, but they are inadequate map units. 

The green porcellanitic unit, however, is present at 

localities 1 through 6 (the stratigraphic position of Frontier 

beds at locality 7 cannot be adequately determined because 

of poor exposures) and is the best criteria for separating the 

Frontier and Beaverhead where no angular unconformity 

exists. The Frontier is absent at locality 1 and the angular 

unconformity is well exposed. The angular unconformity is 

well exposed at locality 2, and underlying and overlying 

rocks are typical for the two units. The green porcellanite 

zone, although poorly exposed, lies about 350 feet (1 06.7 

m) below the unconformity at this locality, within typical 

upper Frontier beds. At locality 3, the angular unconformity 

is poorly exposed, but the green porcellanite zone lies about 

6 Contributions to late Cretaceous Stratigraphy and Paleontology, Western Montana 
150 ft ( 45.7 m) below it and is well exposed. At localities 4 

through 6, where an angular unclJ-.lformity cannot be 

recognized, the green porcellanitic zone is still well exposed 

and can be easily mapped (fig. 3). 

Based on these new data, we recommend that the 

Frontier-Beaverhead contact be placed at the angular 

unconformity where it can be recognized. The contact 

separates two distinct lithologic associations interpreted as 

depositional cycles, in which each cycle contains several 

unique lithologic units and several lithologic units common 

to the other adjacent depositional cycle. Where the unconformity is absent, the contact should be placed at the top of 

the uppermost green porcellanitic unit of the upper Frontier 

Formation. The porcellanitic unit ( 1) is exposed everywhere 

in the Lima Peaks region where the upper Frontier occurs, 

(2) represents an excellent time marker, and (3) is near the 

top of the Frontier depositional cycle above several 

thousand feet of monotonous Frontier rocks that cannot be 

easily subdivided. 

REFERENCES CITED 

Cobban, W.A., and Kennedy, W.J., 1989, The ammonite Metengonoceras Hyatt, 1903, from the Mowry Shale (Cretaceous) 

of Montana and Wyoming: U. S. Geological Survey 

Bulletin 1787-L, 11 p. 

Dillon, E.L., 1947, Stratigraphy of an area near Lima, Beaverhead 

County, Montana: Urbana, Ill., University of Illinois, 

unpublished M.S. thesis, 103 p. 

Dyman, T.S., 1985, Stratigraphic and petrologic analysis of the 

Lower Cretaceous Blackleaf Formation and the Upper 

Cretaceous Frontier Formation (lower part), Beaverhead 

and Madison Counties, Montana: Pullman, Wash., Washington State University, unpublished Ph.D. dissertation, 

230 p. 

Dyman, T.S., and Nichols, D.J., 1988, Stratigraphy of the midCretaceous Blackleaf and lower part of the Frontier 

Formations in parts of Madison and Beaverhead Counties, 

Montana: U.S. Geological Survey Bulletin 1773, 31 p. 

Dyman, T.S., Perry, W.J.,Jr., Nichols, D.J., Davis, L.E., and Haley, 

J .C., 1989, Stratigraphy, petrology, and provenance of the 

Cenomanian to Turonian Frontier Formation near Lima, 

southwestern Montana, in French, D.E., and Grabb, R.F., 

eds., Geologic resources of Montana: Montana Geological 

Society 1989 Field Conference Guidebook, p. 103-114. 

Haley, J.C., 1986, Upper Cretaceous (Beaverhead) synorogenic 

sediments of the Montana-Idaho thrust belt and adjacent 

foreland-Relationships between sedimentation and tectonism: Baltimore, Md., The John Hopkins University, 

unpublished Ph.D. dissertation, 542 p. 

Lowell, W.R., and Klepper, M.R., 1953, Beaverhead Formation; a 

Laramide deposit in Beaverhead County, Montana: 

Geological Society of America Bulletin, v. 64, p. 235-244. 

Nichols, D.J., Perry, W.J., Jr., and Haley, J.C., 1985, Reinterpretation of the palynology and age of Laramide syntectonic 

deposits, southwestern Montana and revision of the Beaverhead Group: Geology, v. 13, no. 2, p. 149-153. 

Perry, W.J., Jr., Haley, J.C., Nichols, D.J., Hammons, P.M., and 

Ponton, J.D., 1989, Interactions of Rocky Mountain foreland and Cordilleran thrust belt in Lima region, southwest 

Montana, in Schmidt, C.J., and Perry, W.J., Jr., eds., 

Interaction of the Rocky Mountain foreland and the 

Cordilleran thrust belt: Geological Society of America 

Memoir 171, p. 267-290. 

Perry, W.J., Jr., Wardlaw, B.R., Bostick, N.H., and Maughan, 

E.K., 1983, Structure, burial history, and petroleum 

potential of frontal thrust belt and adjacent foreland, 

southwest Montana: American Association of Petroleum 

Geologists Bulletin, v. 67, p. 725-743. 

Ryder, R.T., and Ames, H.T., 1970, Palynology and age of 

Beaverhead Formation and their paleotectonic implications 

in Lima region, Montana-Idaho: American Association of 

Petroleum Geologists Bulletin, v. 54, no. 7, p. 1155-1171. 

Ryder, R.T., and Scholten, Robert, 1973, Syntectonic conglomerates in southwestern Montana; their nature, origin, 

and tectonic significance: Geological Society of America 

Bulletin, v. 84, p. 773-796. 

Scholten, Robert, Keenmon, K.A., and Kupsch, W.O., 1955, 

Geology of the Lima region, southwestern Montana and 

adjacent Idaho: Geological Society of America Bulletin, 

v. 66, p. 345-404. 

Skipp, Betty, and Hait, M.H., Jr., 1977, Allochthons along the 

northeast margin of the Snake River plain, Idaho: Wyoming 

Geological Association 29th Annual Field Conference 

Guidebook, p. 499-516. 

Skipp, Betty, Prostka, H.J., and Schleicher, D.L., 1976, 

Preliminary geologic map of the Edie Ranch quadrangle, 

Clark County, Idaho and Beaverhead County, Montana: 

U.S. Geological Survey Open-File Report 79-845, scale 

1:62,500. 

Tysdal, R.G., Dyman, T.S., and Nichols, D.J., 1989, Correlation 

chart of Lower Cretaceous rocks, Madison Range to Lima 

Peaks area, southwestern Montana: U.S. Geological Survey 

Miscellaneous Field Studies Map MF-2067, 16 p. 

Wilson, M.D., 1970, Upper Cretaceous-Paleocene synorogenic 

conglomerates of southwestern Montana: American 

Association of Petroleum Geologists Bulletin, v. 54, no. 10, 

p. 1843-1867. 

Frontier Formation-Beaverhead Group Contact, Lima Peaks Area, Montana and Idaho 7 
APPENDIX 

Aspen Formation: 

The use of the term Aspen for mid-Cretaceous rocks 

near Lima, Montana persisted through the early 1980's 

although Skipp and Hait (1977) questioned use of the term. 

They based their concerns on the identification of the 

Vaughn Member of the Blackleaf Formation in two drill 

holes in the footwall of the Tendoy thrust. Perry and others 

(1983) similarly identified the Blackleaf at the same 

stratigraphic level in two wells flanking the Centennial 

Valley east of our study area. The Blackleaf Formation is 

Albian and Cenomanian in age and is, therefore, in part 

equivalent to the Aspen Formation. The thick sequence of 

post-Blackleaf pre-Beaverhead strata is younger in age and 

was identified as probably being a Frontier equivalent by 

Perry and others (1983). A later detailed study of the 

Blackleaf Formation by Dyman (1985) and stratigraphic 

studies by Dyman and Nichols (1988) and Tysdal and others 

( 1989) clarified the Blackleaf-Frontier relationship and 

established the Frontier terminology. 

Shine Hill Beds: 

A significant source of confusion regarding the 

Frontier-Beaverhead contact deals with the outcrop belt of 

interbedded salt-and-pepper sandstones, mudstones and siltstones, quartzite-clast conglomerates, and porcellanites on 

the south flank of Shine Hill (SW1

/4NE1/4, sec. 17, T. 15 S., 

R. 7 W., Snowline 7.5-minute topographic quadrangle; fig. 

2). Scholten and others (1955), Ryder and Ames (1970), and 

Ryder and Scholten (1973) considered these beds to be 

basal Beaverhead outcropping beneath the Tendoy thrust. 

Ryder and Ames (1970) dated this sequence as Albian to 

Cenomanian based on palynomorph assemblages. This area 

was close to the Sawmill Creek locality of Ryder and 

Scholten (1973); they used the sequences of strata at this 

locality to support conformity between their Aspen and 

Beaverhead Formations. Wilson (1970) concluded that the 

quartzite-clast conglomerates were part of his Aspen rather 

than his Beaverhead Formation. Nichols and others (1985) 

also favored a pre-Beaverhead assignment for these strata 

but preferred to use the name Frontier Formation for them. 

Dyman and others (1989) illustrated that these rocks are 

probably part of the lower Frontier Formation. 

8 Contributions to Late Cretaceous Stratigraphy and Paleontology, Western Montana 
Chapter B 

Biostratigraphic Correlation of Santonian and 

Campanian Formations in the Northwestern 

Part of Yellowstone National Park, and the 

Madison Range and Livingston Area of 

Southwestern Montana 

By R.G. TYSDAL and D.J. NICHOLS 

U.S. GEOLOGICAL SURVEY BULLETIN 1962 

CONTRIBUTIONS TO LATE CRETACEOUS STRATIGRAPHY 

AND PALEONTOLOGY, WESTERN MONTANA 
CONTENTS 

Abstract 11 

Introduction 11 

Everts Formation 12 

Age 12 

Landslide Creek Formation 15 

Age 15 

Livingston Group and Livingston Formation 15 

Livingston Formation 16 

Age 16 

Cokedale Formation of Livingston Group 16 

Age 16 

Age relations near the Cokedale-Miner Creek contact 17 

Regional correlation 18 

Conclusions 18 

References cited 18 

FIGURES 

1. Index map of part of southwestern Montana showing mountain ranges, towns, and 

localities referenced in text 12 

2. Correlation chart of Santonian and Campanian formations (and bounding units) in 

the Madison Range, the Livingston, Mont., area, and the northwestern part of 

Yellowstone National Park 13 

3. Photomicrographs of stratigraphically significant pollen and spores from the Everts 

and Landslide Creek Formations, Yellowstone National Park 14 

CONVERSION FACTORS 

Inch-pound units of measurement in this report may be converted to International System (SI) of metric units 

using the following conversion factors: 

Multiply inch-pound unit By To obtain SI unit 

foot (ft) 0.3048 meter (m) 

mile (mi) 1.609 kilometer (km) 

inch (in.) 2.54 centimeter (em) 

10 Contents 
Biostratigraphic Correlation of Santonian and 

Campanian Formations in the Northwestern Part of 

Yellowstone National Park, and the Madison Range and 

Livingston Area of Southwestern Montana 

By R.G. Tysdal and D.j. Nichols 

Abstract 

Biostratigraphic correlation of Santonian and Campanian 

formations in the Madison Range and the Livingston area of 

southwestern Montana and the northwestern part of Yellowstone National Park was accomplished largely with palynomorphs. Palynomorph-bearing sedimentary rocks from upper 

strata of the Everts Formation in the Madison Range were 

deposited during the latest Santonian to earliest Campanian. 

Palynological samples from several horizons within upper 

strata of the Everts Formation in Yellowstone National Park 

yielded assemblages that range from Coniacian through Santonian in age. Molluscan megafossils from strata beneath the 

Everts Formation in the Madison Range and from just north of 

the park indicate that the Everts in both areas probably is no 

older than middle Santonian. Palynomorphs from lower strata 

of the Landslide Creek Formation, which overlies the Everts in 

the park, are earliest Campanian in age. 

In the vicinity of Livingston, Montana, palynomorphs 

from the lower part of the Cokedale Formation are of species 

that range from Coniacian through Santonian in age, but 

molluscan megafossils from beneath the Cokedale show that 

basal Cokedale strata are no older than middle Santonian. The 

middle part of the Cokedale yielded palynomorphs of middle 

to late Campanian age. Palynomorphs from the lower part of 

the Miner Creek Formation, which overlies the Cokedale, are 

of early Maastrichtian age and place an upper age limit on the 

Cokedale. 

These biostratigraphic data indicate that the Cokedale 

Formation in the vicinity of Livingston, Montana, was 

deposited during the same general time span as the Livingston 

Formation in the Madison Range. The lower part of the 

Landslide Creek Formation in Yellowstone National Park is 

nearly the same age as basal strata of the Livingston Formation 

in the Madison Range and Cokedale strata near the town of 

Livingston; strata of the Landslide Creek must be timeequivalent to at least parts of these two formations. 

INTRODUCTION 

In the course of conducting geologic studies in the 

Madison Range of southwestern Montana in the early 

1980's, the thick Upper Cretaceous sequence in the range 

was subdivided into formations by Tysdal and Simons 

(1985). The subdivision was accomplished through lithoand biostratigraphic correlation with formations present 

eastward in the vicinity of Livingston, Mont., and the 

northwestern part of Yellowstone National Park (fig. 1). As 

part of the biostratigraphic studies, new collections of plant 

microfossils (palynomorphs) were obtained from rocks in 

the park and are reported here for the first time. No new 

collections were obtained in the Livingston area, but we 

reevaluated collections of palynomorphs identified by E.B. 

Leopold and R.H. Tschudy in the 1960's. The fossils in 

these collections were reported in Roberts ( 1972) and were 

assigned provisional names at that time. We place our 

emphasis on updating identifications listed therein, in 

accordance with more current taxonomy and nomenclature, 

and on the biostratigraphic implications of certain species 

previously reported. 

In this paper we establish the ages of the Everts 

Formation and the lower part of the Landslide Creek 

Formation in Yellowstone National Park, and we show their 

biostratigraphic correlation with formations in the Madison 

Range and in the vicinity of Livingston, Mont. (fig. 1 ). Age 

relationships of the various formations are shown in the 

correlation chart of figure 2. In the following sections, a 

general description is provided for each formation of 

concern and is followed by a review of the age assignment 

and refinement thereof. 

Biostratigraphic Correlation of Santonian and Campanian Formations, NW Yellowstone National Park and SW Montana 11 
Tobacco 

Root 

Mts 

0 10 20MILES 

Bozeman 0 

0 Lennep 

a Wilsall 

Bridger 

Range 

Beartooth 

Mountains 

p_~CM• Gardiner 

I I I I I I I I 

0 10 20 30KILOMETERS g, 

<' Sl 

Figure 1. Index map of part of southwestern Montana 

showing mountain ranges, towns, and localities referenced in 

text. CM, Cinnabar Mountain; ME, Mount Everts. 

Everts Formation 

The Everts Formation was named by Fraser and 

others (1969) for rocks exposed on Mount Everts in the 

northwestern part of Yellowstone National Park. They 

described the formation as being about 1,250 ft (380 m) 

thick and consisting of interbedded light-colored lenticular 

sandstone and medium- to light-gray mudstone that is 

locally green, yellow, or brown, especially near the top. The 

formation contains altered volcanic ash. No type section 

was designated due to poor exposures and extreme local 

variability of the rocks of the formation. 

In the Madison Range, the Everts Formation is about 

1,400 ft ( 430 m) thick. It consists mainly of quartzose 

sandstone and interbedded siltstone, but the lower 200-300 

ft (60-90 m) is thin-bedded mudstone, siltstone, shale, and 

minor sandstone and coal (Tysdal and Simons, 1985). 

Age 

The Everts Formation was considered to be mainly of 

Campanian age by Fraser and others (1969) on the basis of 

lithologic correlation with the Cokedale Formation near 

Livingston, Mont. These authors stated that the lowermost 

part could be late Santonian in age, however. The Everts is 

gradational with the underlying Eagle Sandstone and 

contains mollusks that are generically similar to those 

present in the Eagle, but the mollusks of the Everts 

Formation are not age-diagnostic. Fraser and others (1969) 

reported the following mollusks from near the base of the 

formation: 

Ostrea sp. 

Cymbophora sp., cf. C. utahensis Meek 

Figure 2 (facing page). Correlation chart of Santonian and 

Campanian formations (and bounding units) in the Madison 

Range (col. 1 ), the Livingston, Mont., area (col. 2), and the 

northwestern part of Yellowstone National Park (col. 3). 

Boundaries of the Upper Cretaceous stages and Western 

Interior zone fossils are modified from Obradovich and Cobban (1975). There is no international agreement as to 

placement of the Campanian-Maastrichtian boundary; Obradovich and Cobban (1975) placed this boundary between the 

Baculites cuneatus and B. reesidei zone fossils. The ConiacianSantonian boundary has been adjusted to include the 5caphites depress us faunal zone in uppermost part of the Coniacian, 

reflecting current usage (W.A. Cobban, written commun., 

1989). Ages in K-Ar (potassium-argon) column are from Obradovich (1988), except that the 88.7 Ma of the 5. ventricosus 

zone is from Obradovich and Cobban (1975), after recalculation for new 40Ar decay constants (Steiger and Jager, 1977). 

Ages in the K-Ar column correspond to specific, indicated 

zone fossils in the column headed "Western Interior Zone 

Fossils." Fossils within braces in the latter column are not tied 

to specific ages, and no age (or age range) is implied other than 

biostratigraphic position within the sequence and the age 

constraint afforded by zone fossils that have been dated. 

Individual zone fossils, or sequences of zone fossils, within 

braces could be slightly younger or older than indicated by 

position in the figure. 

Column 1 is modified from Tysdal and others (1987). 

Column 2 is modified from Roberts (1972). Column 3 is from 

the present study. In column 1 (Madison Range), the two 

numbers are K-Ar ages on volcanic rocks. Clioscaphites saxitoniatus and 5caphites depressus occur together in both the 

Virgelle Sandstone and the Cody Shale of the Madison Range; 

hence, the two faunal zones overlap, and the two range zones 

are indicated by a single vertical bar. This overlap differs from 

findings in north-central Montana where C. saxitoniatus is 

wholly younger than 5. depressus (W.A. Cobban, oral commun., 1984, in Tysdal and others, 1987). Solid circle, microfossil collection and locality number referenced in text; *, 

megafossil collection, with locality number shown only if 

locality referenced in text. 

12 Contributions to Late Cretaceous Stratigraphy and Paleontology, Western Montana 
.!!2 (f) 'Cii 

>:- 0::: (/) 3 

E <( .2 GARDINER WESTERN INTERIOR w WQ.l 

ZONE FOSSILS NONMARINE w >-""":' (.9C 1 2 AREA > 

(No specific K-Ar age has been PALYNOMORPH ZONES <.9 z· ~2 MADISON LIVINGSTON (Yellowstone 

determined for fossils in braces) <( o.S (J)C RANGE AREA National 

~ :::::i 0 Park) ....J "0 

~ ~ Q.l 

(/) 

ctl 

..0 

Wodehouseia spinata f- c 

~~ ~::~~~: I' >:< :: <~~~· .... > 

Assemblage Zone (part) co 'Billman 

I ·.;:::; 

..c~ 

ut Creek 

Baculites grandis f- 70.1 70 'E ~ Sphinx Formation CJl~ Conglomerate Baculites baculus co 

co Miner Creek 

Baculites eliasi ~ r---?- Formation 

Baculites jenseni - - • 01612 

Baculites reesidei 

Baculites cuneatus 

-72 

::~~~ ~~~ ~~:-

Baculites compressus f-73.2 fDidymoceras chevennense } Aquilapollenites quadrilobus Exiteloceras jennevi -73.7 

Didymoceras stevensoni }I Interval Zone f-74.0 f-74 

Didymoceras nebrascence 

fBaculites scotti 1- 75.5 c t <<:~~>-<<~>~~::: .. 0 co 

-76 ·.;:::; .3- Baculites gregorvensis co :~:::; >~><~ :::~ E c. 

Baculites perplexus (late form) 0 :::l • 04120 II 0 

Baculites gilberti u.... l5 • 01815-1 c 76.8 c 

Baculites perplexus (early form) - ~ B c c CJ) 0 

Baculites sp. (smooth) co O'l t) c. c O'l 

Baculites asperiformis E ·:; c 

Baculites maclearni 

1-78 co ::J ·:; u ::J 

fBaculites obtusus Aquilapollenites senonicus 

f-79.2 

79.3 *B. obtusus 

Interval Zone 

Baculites sp. (weak flank ribs) f-80.1 c-80 79.8 Coked ale 

Formation Landslide 

Creek 

- Formation 

eo6368 

Baculites sp. (smooth) 

} 

f-82 

Scaphites hippocrepis Ill Pseudoplicapollis newmanii 

Scaphites hippocrepis II Interval Zone 

Scaphites hippocrepis I 

fe 06800 F-H 

1-84 1---- eo6285 :· .... ,.'-.'·-.'".'··'·, ..... ~ .... ~ .... 

e01611 • 06800 A-E 

Desmoscaphites bassleri f-84.4 Everts • 01610 Formation Eagle Everts 

f- c Sandstone Formation co • 04121 ·c: 

B Telegraph Creek 

Desmoscaphites erdmannii 

1 

Proteacidites retusus -86 c 

co -?-- Formation Eagle 

Clioscaphites choteauensis Interval Zone (/) 

Virgelle *23026 Sandstone 

Clioscaphites vermiformis Sandstone Telegraph Creek 

Clioscaphites saxitonianus 1- T Formation 1 Telegraph * 

ScapMes dep<essus j Creek Fm Cody 

c --r Shale 

Scaphites ventricosus, Inoceramus 1-88 co Cody * * 011919 

involutus '(3 

* Shale 

Scaphites preventicosus, Inoceramus Nvssapollenites .~ Cody c 

!::;:~~:~ ~~::~:: ~:~:~ * Shale 

deform is Interval Zone (part) f-88.7 0 

u 

Biostratigraphic Correlation of Santonian and Campanian Formations, NW Yellowstone National Park and SW Montana 13 
We collected plant microfossils (palynomorphs) from 

several horizons in the upper 400 ft (120 m) of the Everts 

Formation in Yellowstone National Park, from the Mount 

Everts measured section 1 of Fraser and others (1969, 

p. 99-1 00). The collection (USGS paleobotany localities 

D6800-A, B, C, D, E) yielded the following fossils, some of 

which are shown in figure 3: 

A 

E 

I 

Araucariacites sp. 

Cicatricosisporites sp. 

Corollina sp. 

Cupuliferoidaepollenites minutus (Brenner) Singh 

Cyathidites minor Couper 

F oraminisporis wonthaggiensis (Cookson and Dettmann) Dettmann 

Gleicheniidites senonicus Ross 

Hazaria sp. cf. H. canadiana Srivastava 

8 

F 

J 

Figure 3. Stratigraphically significant pollen and spores 

from the Everts and Landslide Creek Formations in Yellowstone National Park. A, Laevigatosporites sp.; 8, Cyathidites 

minor Couper; C, Stereisporites sp. 1; 0, Stereisporites sp. 2; 

E, Foraminisporites wonthaggiensis (Cookson and Dettmann) Dettman; F, Cicatricosisporites sp.; C, Corollina sp.; 

Laevigatosporites sp. 

Monocolpopollenites sp. 

Pityosporites sp. 

Proteacidites retusus Anderson 

Quadripollis krempii Drugg 

Taxodiaceaepollenites hiatus (Potonie) Kremp 

Vitreisporites pallidus (Reissinger) Nilsson 

The assemblage represents the Proteacidites retusus 

Interval Zone, which ranges from Coniacian through Santonian in age (fig. 2). 

We obtained no fossils from basal strata of the Everts 

Formation in Yellowstone National Park and none have 

been reported in the literature. The age of the basal strata of 

the Everts can be no older than the late Coniacian marine 

mollusk Inoceramus involutus (Sowerby) collected from the 

lower part of the Cody Shale, which lies stratigraphically 

c 

G H 

H, Vitreisporites pallidus (Reissinger) Nilsson; /, Monocolpopollenites sp.; }, Proteacidites retusus Anderson; K, Proteacidites sp.; L, Pseudoplicapollis newmanii Nichols and 

Jacobson. Specimens A, 8, E, F, C, H, I, and J are from the 

Everts Formation; C, 0, K, and L are from the Landslide Creek 

Formation. All specimens enlarged x1000. 

14 Contributions to late Cretaceous Stratigraphy and Paleontology, Western Montana 
below the Everts (fig. 2). The mollusk was collected about 

12 mi (20 km) northwest of Mount Everts, near Cinnabar 

Mountain (CM, fig. 1; USGS Mesozoic locality D11919, 

fig. 2). We have placed the basal contact of the Everts in 

Yellowstone National Park in the middle Santonian. This 

placement allows time for deposition of the middle and 

upper parts of the Cody Shale, the Telegraph Creek 

Formation, and the Eagle Sandstone, which, according to 

Fraser and others (1969), total about 2,000 ft (600 m) thick. 

In the Madison Range, a palynomorph assemblage 

from about 300 ft (90 m) below the top of the 1 ,400-ft-

( 425-m-) thick Everts yielded key forms of both the 

Proteacidites retusus and Pseudoplicapollis nevvmanii 

Interval Zones (USGS paleobotany collection D6285). The 

co-occurrence of these forms suggests that the upper strata 

of the Everts in the Madison Range were deposited during 

the latest Santonian to earliest Campanian (Tysdal and 

others, 1987). 

Basal strata of the Everts Formation in the Madison 

Range have not been dated. They are no older than early 

Santonian, however, because the marine mollusk Clioscaphites saxitonianus (McLearn) of that age was collected 

from basal strata of the Virgelle Sandstone (Tysdal and 

others, 1987), which lies directly beneath the Everts. In 

figure 2, the base of the Everts is shown as middle 

Santonian, which allows a short amount of time for 

deposition of Virgelle rocks above its fossil-bearing basal 

strata. 

Landslide Creek Formation 

The Landslide Creek Formation was named by Fraser 

and others (1969) for outcrops along Landslide Creek in the 

northwestern part of Yellowstone National Park, 2 mi 

(3 km) west of Gardiner, Mont. (fig. 1). It unconformably 

overlies the Everts Formation and is unconformably 

overlain by Tertiary volcanic rocks. The Landslide Creek is 

a nonmarine unit that consists of interbedded dark-colored 

sandstone, local conglomerate, and varicolored mudstone 

and claystone. Volcanic debris, including bentonite, occurs 

throughout the formation. Fraser and others (1969) found 

the formation to be poorly exposed and subject to extensive 

landsliding. They measured several partial sections to determine the lithologic composition of the formation and its 

thickness, which they gave as between 1,300 and 2,300 ft 

(400-700 m); but they could not determine the thickness 

more accurately due to poor exposures. No type section was 

designated. 

Age 

The Landslide Creek Formation was assigned a Late 

Cretaceous age on the basis of scattered fragments of 

dinosaur bones and a palynomorph assemblage collected by 

J.D. Love (J.D. Love, written commun., 1961, in Fraser and 

others, 1969, p. 36). No fossil report is known to exist for 

the dinosaur bones, but we reexamined the original fossil 

report concerning the palynomorph assemblage (USGS 

unpub. laboratory report F-58-32D, sample No. L58-33-

A). E.B. Leopold, who examined the collection and wrote 

the report, stated that the pollen and spores were rather 

undiagnostic and were of late Mesozoic age although 

probably not as young as Late Cretaceous. 

Palynomorphs were collected by us from the lower 

150ft (45 m) of the Landslide Creek Formation in Yellowstone National Park, from the Mount Everts measured 

section 1 of Fraser and others (1969, p. 97-99). The 

collection (USGS paleobotany localities D6800-F, G, H) 

yielded the following fossils, some of which are shown in 

figure 3: 

Camarozonosporites insignis Norris 

Cicatricosisporites sp. 

Cupuliferoidaepollenites minutus (Brenner) Singh 

Cyathidites minor Couper 

Foraminisporis wonthaggiensis (Cookson and Dettmann) Dettmann 

Gleicheniidites senonicus Ross 

Hazaria sp. cf. H. canadiana Srivastava 

Laevigatosporites sp. 

Proteacidites retusus Anderson 

Pseudoplicapollis newmanii Nichols and Jacobson 

Stereisporites sp. 

tricolpate pollen, undifferentiated 

trilete spores, undifferentiated 

The assemblage represents the Pseudoplicapollis 

newmanii Interval Zone, which is indicative of the earliest 

Campanian (fig. 2). 

Livingston Group and Livingston Formation 

The name Livingston Formation was applied by 

Weed (1893) to a thick sequence of volcaniclastic strata in 

the vicinity of Livingston, Mont. (fig. 1) and was extended 

to the Madison Range by Peale (1896). Roberts (1963, 

1972) redefined strata assigned to the Livingston near the 

town of Livingston, raised the unit to group status, and 

defined four new formations within the group. Formations 

of the Livingston Group, in ascending order, are as follows: 

Cokedale Formation, Miner Creek Formation, Billman 

Creek Formation, and Hoppers Formation. The Livingston 

has not been subdivided into formations in the Madison 

Range, however, and the name Livingston Formation is still 

used there. In this paper, we discuss the Livingston 

Formation in the Madison Range and the Cokedale 

Formation of the Livingston Group in the vicinity of the 

town of Livingston. A palynological assemblage from the 

basal part of the Miner Creek Formation also is discussed 

because it defines the upper age limit of the Cokedale 

Formation. 

Biostratigraphic Correlation of Santonian and Campanian Formations, NW Yellowstone National Park and SW Montana 15 
Livingston Formation 

The Livingston Formation in the Madison Range is 

preserved in a 30-square-mile (78-square-kilometer) area 

about 10 mi (16 km) southwest of the town of Big Sky, 

Mont. (fig. 1 ). The formation comprises a sequence of 

volcanic and volcaniclastic rocks that ranges from about 

1,800 to 2,800 ft (550-850 m) thick. It has been subdivided 

into three informal members (Beck, 1960; Hadley, 1980; 

Tysdal and others, 1987). The lower member is a composite 

unit of mudstone, siltstone, sandstone and conglomeratic 

sandstone, and minor tuff, basalt, and volcanic conglomerate; the middle member is composed of volcanic flows 

and flow breccia; and the upper member is composed of 

volcaniclastic sandstone and conglomeratic volcaniclastic 

sandstone (Tysdal and others, 1987). The formation is 

conformable with the underlying Everts Formation and, at 

least in some areas, with the overlying Sphinx Conglomerate (fig. 2). 

Age 

The lower member of the Livingston Formation in the 

Madison Range yielded palynomorphs of the earliest 

Campanian Pseudoplicapollis newmanii Interval Zone 

(USGS paleobotany collection D6368). Flows stratigraphically higher in the lower member yielded radiometric dates 

of 79.8±2.9 Ma and 76.8±2.5 Ma (shown in fig. 2, col. 1), 

which are early to middle Campanian and middle Campanian in age, respectively (Tysdal and others, 1987). 

Cokedale Formation of Livingston Group 

The Cokedale Formation is 1,550 ft (472 m) thick in 

the area of Livingston, Mont. (fig. 1), and consists of 

siltstone, sandstone, mudstone, water-laid tuff, bentonite, 

carbonaceous claystone, and, locally, coal. Roberts (1972) 

reported that the sedimentary strata were derived mainly 

from volcanic rocks of andesitic composition. The Cokedale 

is conformable with the underlying Eagle Sandstone and 

with the overlying Miner Creek Formation. 

Age 

The Cokedale Formation was assigned a Campanian 

age by Roberts (1972), who reported that it contains fossils 

of the Baculites obtusus faunal zone in its lower part. 

Roberts (1972, table 4) also published an extensive list of 

palynomorphs recovered from the lower and middle parts of 

the type section of the formation (USGS paleobotany 

localities D1610 and D1611 (lower part); D1815-1 and 

D4120 (middle part)). 

Mollusks of the Baculites obtusus faunal zone were 

reported in a lower tuffaceous zone of the Livingston Group 

near Livingston (Roberts, 1972, p. C39). Several tuffaceous 

zones are present within the lower strata of the type section 

of the Cokedale Formation (of the Livingston Group), 

which is 1,550 ft (472 m) thick (measured section 16 of 

Roberts, 1972, p. C77-C84). We are uncertain which 

tuffaceous zone within the type section of the Cokedale is 

the lower tuffaceous zone of the Livingston, because 

Roberts (1972) did not identify it in his Cokedale measured 

section. Nevertheless, table 4 of Roberts (1972) showed that 

palynomorph collections D 1851-1 and D4120 are from the 

middle part of the section (about 657 ft (200m) and 670 ft 

(204 m), respectively, above the base of the section). 

Therefore, megafauna of the B. obtusus faunal zone must 

have been obtained from stratigraphically lower than these 

palynomorph collections. 

Microfossils in the palynological collections just 

mentioned were identified by E.B. Leopold and R.H. 

Tschudy in the 1960's and were assigned provisional names 

(Roberts, 1972). We reevaluated palynomorph occurrence 

data of these collections. Emphasis was placed on updating 

identifications listed by Roberts (1972) in accordance with 

more current taxonomy and nomenclature, and on the 

biostratigraphic implications of certain species previously 

reported. The objective was to refine age determinations of 

the Cokedale Formation on the basis of palynology. Our 

results are summarized in the following paragraphs. Age 

determinations presented here are based on palynomorph 

biozones described by Nichols and others (1982). 

Palynomorph assemblages identified by E.B. Leopold 

and R.H. Tschudy from localities Dl610 and D1611 in the 

lower part of the Cokedale Formation include 20 species of 

spores and pollen. Among these, three species of the 

angiosperm pollen genus Proteacidites are biostratigraphically important. They indicate an age of Coniacian or 

Santonian (Proteacidites retusus Interval Zone, fig. 2). The 

genus Proteacidites also ranges throughout the Campanian 

and Maastrichtian, but the assemblages reported from the 

lower part of the Cokedale lack species that would indicate 

a post-Santonian age. 

A maximum age for the Cokedale was determined 

from fossils in strata beneath the formation. The Eagle 

Sandstone lies directly beneath the Cokedale and yielded a 

palynological collection (USGS paleobotany locality 

D4121) from its middle strata (Roberts, 1972). The fossils, 

which were originally identified by R.H. Tschudy and 

which we reexamined for our study, are indicative of the 

Proteacidites retusus Interval Zone. This collection, as that 

from the basal part of the Cokedale, could be as old as 

Coniacian. The maximum age of the microfossils is determined by megafossils from downsection. About 120 ft 

(37 m) below the top of the upper member of the Cody 

Shale, the marine mollusk Clioscaphites choteauensis was 

reported (Richards, 1957; Roberts, 1972; USGS Mesozoic 

locality 23026), which is middle Santonian in age. Basal 

strata of the Cokedale, therefore, can be no older than 

middle Santonian. 

16 Contributions to late Cretaceous Stratigraphy and Paleontology, Western Montana 
We know of no published references to agediagnostic microfossils or megafossils from between the 

base of the Cokedale and the upper member of the Cody (in 

the vicinity of Livingston) that would further restrict the 

lower age limit of the basal Cokedale. However, between 

the levels of the basal Cokedale plant microfossil collections and that of the megafossil from the upper member of 

the Cody lie about 1,000 ft (305 m) of strata (uppermost part 

of the Cody Shale, and all of the Telegraph Creek Formation 

and Eagle Sandstone). If these strata represent about the 

same amount of time as strata of the same formations in the 

Madison Range (fig. 2), then the basal strata of the 

Cokedale could be middle to late Santonian in age. 

The middle part of the Cokedale Formation yielded 

41 palynomorph species from localities D 1815-1 and 

D4120 (Roberts, 1972). Among these species, only two are 

in common with the assemblages from the lower part of the 

formation, suggesting that the lower and middle parts of the 

Cokedale are of significantly different ages. The biostratigraphically significant species from the middle part are as 

follows: Proteacidites (four species differing from those in 

the lower assemblage); the angiosperm pollen species Aquilapollenites trialatus (= Aquila 4 var. of Roberts, 1972, 

table 4 ), Fibulapollis scabratus ( = Aquila 29 of Roberts, 

1972, table 4), and Cranwellia sp. (=Aquila 9 of Roberts, 

1972, table 4 ); and the fern spore species Balmeisporites 

kondinskayae (= Charon-1 of Roberts, 1972, table 4) and 

Kuylisporites scutatus (= Hemi-4 of Roberts, 1972, table 4). 

This assemblage indicates a middle to late Campanian age 

(lower part of the Aquilapollenites quadrilobus Interval 

Zone). 

The upper age limit of the Cokedale Formation was 

determined from fossils in the lower part of the Miner Creek 

Formation, which overlies the Cokedale. The palynomorph 

assemblage from locality D 1612 (Roberts, 1972) in the 

lower part of the Miner Creek includes 46 species, of which 

only 7 are in common with those of the Cokedale 

Formation. Biostratigraphically important taxa from the 

Miner Creek are the angiosperm pollen species Aquilapollenites delicatus (=Aquila 6 of Roberts, 1972, table 4), A. 

quadrilobus (= Aquila 17 of Roberts, 1972, table 4), A. 

turbidus (=Aquila 2A of Roberts, 1972, table 4), Manicorpus calvus ( = Aquila 5 of Roberts, 1972, table 4 ), Kurtzipites circularis (= C3-sm22 of Roberts, 1972, table 4), and 

Proteacidites sp. This assemblage suggests that the lower 

part of the Miner Creek Formation could be as young as 

early Maastrichtian (upper part of the Aquilapollenites 

quadrilobus Interval Zone). Uppermost strata of the 

Cokedale Formation, therefore, are considered to be of 

earliest Maastrichtian age, based on this palynomorph 

assemblage and on molluscan megafossils from the Miner 

Creek Formation that also place an upper age limit on the 

Cokedale, as discussed in the following paragraphs. 

Age Relations Near the Cokedale-Miner 

Creek Contact 

The Campanian-Maastrichtian boundary, as selected 

by Obradovich and Cobban (1975), is at the top of the B. 

cuneatus faunal zone and base of the B. reesidei faunal zone 

of the Cretaceous Western Interior zone fossils (fig 2). 

Roberts (1972, p. C39) stated that "an upper tuffaceous zone 

[of the Livingston] in the lower part of the Miner Creek 

Formation represents the B. compressus and B. cuneatus 

faunal zones ... " Roberts (1972, p. C48) also wrote that a 

megafauna of these zones, collected near Wilsall, Mont. 

(fig. 1), about 25 mi (40 km) north of the type section of the 

Miner Creek, is from marine sandstone that correlates with 

the Lennep Sandstone near Lennep, Mont. (fig. 1). In the 

type section of the Miner Creek, the lithic correlative of 

these marine sandstones is the nonmarine Sulphur Flats 

Sandstone Member, which constitutes the lower 323 ft (98 

m) of the Miner Creek (Roberts, 1972). This lithic 

correlation suggests that the B. compressus and B. cuneatus 

megafauna! collection lies stratigraphically below the 

microfossils from USGS paleobotany locality D 1612, 

which was obtained from 421 ft (128m) above the base of 

the 1,350-ft- (411-m-) thick section, and is consistent with 

our conclusion that the palynomorph assemblage of 

collection Dl612 is of early Maastrictian age. 

On the basis of mapping in the area of Maudlow, 

Mont. (fig. 1), Skipp and McGrew (1977) reinterpreted 

Robert's (1972) correlation of the Sulphur Flats Sandstone 

Member of the Miner Creek Formation with the B. 

compressus- and B. cuneatus-bearing sandstone near 

Wilsall and the Lennep Sandstone near Lennep. Skipp and 

McGrew placed the Sulphur Flats Sandstone Member at 

about the level of the faunal zones of Baculites sp. (smooth) 

and B. perplexus (late form) (fig. 2). The entire Miner Creek 

Formation was considered to be Campanian, with the 

uppermost part time-equivalent to the Lennep Sandstone. 

We disagree with this reinterpretation and consider Robert's 

(1972) correlation of the Sulphur Flats Sandstone Member 

with the Lennep Sandstone to be more nearly correct, based 

on the following reasoning. 

Tschudy (in Roberts, 1972, p. C48) originally interpreted the palynomorphs from USGS paleobotany locality 

Dl612 (and a stratigraphically higher collection from 

locality D1613) in the Miner Creek Formation as containing 

species indicative of the upper one-fourth of the Campanian 

and the Maastrichtian. As described earlier, our reinterpretation of the palynomorphs assemblage in collection Dl612 

indicates an early Maastrichtian age, and the assemblage 

definitely is younger than the B. compressus and B. cuneatus faunal zones. The Campanian-Maastrichtian boundary is 

at the top of the B. cuneatus faunal zone and base of the B. 

reesidei faunal zone. The microfossil collections from 

paleobotany localities D1815-1 and D4120, near the middle 

of the Cokedale Formation, are middle to late Campanian in 

age. These data indicate (1) that at least the upper two-thirds 

Biostratigraphic Correlation of Santonian and Campanian Formations, NW Yellowstone National Park and SW Montana 17 
of the Miner Creek Formation is early Maastrichtian or 

younger, and (2) that the age of the Sulphur Flats Sandstone 

Member is late Campanian to early Maastrichtian in age. 

The age of the Sulphur Flats Sandstone Member is considerably younger than that assigned by Skipp and McGrew 

(1977) on the basis of mapping, and is in agreement with the 

age assignment and lithostratigraphic correlation of Roberts 

(1972). 

REGIONAL CORRELATION 

The newly reported and reevaluated biostratigraphic 

data reported on here, and existing data from the Madison 

Range, indicate that the Livingston Formation in the 

Madison Range and the Cokedale Formation in the vicinity 

of Livingston, Mont., were deposited during the same 

general time span. The lower part of the Landslide Creek 

Formation, in the northwestern part of Yellowstone 

National Park, is nearly the same age as the basal parts of 

the Livingston and Cokedale Formations, and overlying 

strata of the Landslide Creek must be time-equivalent of at 

least part of these two formations. 

The Livingston and Landslide Creek Formations are 

nonmarine and the Cokedale is largely nonmarine. All three 

formations contain abundant volcanic debris and fall within 

the span of time generally associated with deposition of the 

Elkhorn Mountains Volcanics (south of Helena, fig. 1) 

(Robinson and others, 1968; Tilling, 1974). This was a time 

of widespread volcanism in southwestern Montana, and the 

volcanic and volcaniclastic rocks had several local sources 

(Roberts, 1972). A local source may have existed for flows 

in the Livingston Formation in the Madison Range (Tysdal 

and others, 1987). Localized sources of volcanic rocks 

existed for time-equivalent rocks of the Cokedale in the 

Maudlow area (fig. 1) (Skipp and McGrew, 1977). Along 

the northeast flank of the Beartooth Mountains, volcanic 

rocks intertongue with the Eagle Sandstone (Rouse and 

others, 1937). The main phase of a stock that intruded these 

volcanics yielded rubidium-strontium dates of about 84 Ma 

(Meen and Eggler, 1987), which is about the SantonianCampanian boundary and time-equivalent with some of the 

strata of the formations discussed in the present report. 

CONCLUSIONS 

1. The Everts Formation is middle to late Santonian 

in age, and may be as young as early Campanian in the 

Madison Range. 

2. The lower part of the Landslide Creek Formation 

is early Campanian. The upper part of the formation has not 

been dated. 

3. The Cokedale Formation in the Livingston area 

ranges from middle or late Santonian to late Campanian in 

age. 

REFERENCES CITED 

Beck, F.M., 1960, Geology of the Sphinx Mountain area, Madison 

and Gallatin Counties, Montana, in Campau, D.E., and 

Anisgard, H.W., eds., West Yellowstone-Earthquake area: 

Montana Geological Society 11th Annual Field Conference 

Guidebook, p. 129-134. 

Fraser, G.D., Waldrop, H.A., and Hyden, H.J., 1969, Geology of 

the Gardiner area, Park County, Montana: U.S. Geological 

Survey Bulletin 1277, 118 p. 

Hadley, J.B., 1980, Geology of the Varney and Cameron 

quadrangles, Madison County, Montana: U.S. Geological 

Survey Bulletin 1459, 108 p. 

Meen, J.K., and Eggler, D.H., 1987, Petrology and geochemistry 

of the Cretaceous Independence volcanic suite, Absaroka 

Mountains, Montana; clues to the composition of the 

Archean sub-Montanan mantle: Geological Society of 

America Bulletin, v. 98, p. 238-247. 

Nichols, D.J., Jacobson, S.R., and Tschudy, R.H., 1982 (1983), 

Cretaceous palynomorph biozones for the central and 

northern Rocky Mountain region of the United States, in 

Powers, R.B., ed., Geologic studies of the Cordilleran thrust 

belt: Denver, Colorado, Rocky Mountain Association of 

Geologists, v. 2, p. 721-733. 

Obradovich, J.D., 1988, A different perspective on glauconite as a 

chronometer for geologic time scale studies: Paleoceanography, v. 3, p. 757-770. 

Obradovich, J.D., and Cobban, W.A., 1975, A time-scale for the 

Late Cretaceous of the Western Interior of North America: 

Geological Association of Canada Special Paper no. 13, 

p. 31-54. 

Peale, A. C., 1896, Description of the Three Forks sheet (Montana): 

U.S. Geological Survey Atlas, Folio 24, 10 p. 

Richards, P.W., 1957, Geology of the area east and southeast of 

Livingston, Park County, Montana: U.S. Geological Survey 

Bulletin 1021-L, p. 385-438. 

Roberts, A.E., 1963, The Livingston Group of south-central 

Montana: U.S. Geological Survey Professional Paper 

475-B, p. B8-B92. 

___ 1972, Cretaceous and early Tertiary depositional and 

tectonic history of the Livingston area, southwestern 

Montana: U.S. Geological Survey Professional Paper 

526-C, 126 p. 

Robinson, G.D., Klepper, M.R., and Obradovich, J.D., 1968, 

Overlapping plutonism, volcanism, and tectonism in the 

Boulder batholith region, Montana, in Coats, R.R., Hay, 

R.L., and Anderson, C.A., eds., Studies in volcanology: 

Geological Society of America Memoir 116, p. 557-576. 

Rouse, J.T., Hess, H.H., Foote, F., Vhay, J.S., and Wilson, K.P., 

1937, Petrology, structure, and relation to tectonics of 

porphyry inclusions in the Beartooth Mountains, Montana: 

Journal of Geology, v. 45, p. 717-740. 

Skipp, Betty, and McGrew, L.W., 1977, The Maudlow and Sedan 

Formations of the Upper Cretaceous Livingston Group on 

the west edge of the Crazy Mountains basin, Montana: U.S. 

Geolcgical Survey Bulletin 1422-B, 68 p. 

Steiger, R.H., and Jager, E., 1977, Subcommission on geochronology-Convention on the use of decay constants in geoand cosmochronology: Earth and Planetary Science Letters, 

v. 36, p. 359-362. 

18 Contributions to Late Cretaceous Stratigraphy and Paleontology, Western Montana 
Tilling, R.I., 1974, Composition and time relations of plutonic and 

associated volcanic rocks, Boulder batholith region, 

Montana: Geological Society of America Bulletin, v. 85, 

p. 1925-1930. 

Tysdal, R.G., Nichols, D.J., and Winkler, G.R., 1987, The Livingston Formation in the Madison Range of southwestern 

Montana: U.S. Geological Survey Bulletin 1665, 15 p. 

Tysdal, R.G., and Simons, F.S., 1985, Geologic map of the 

Madison Roadless Area, Gallatin and Madison Counties, 

Montana: U.S. Geological Survey Miscellaneous Field 

Studies Map MF-1605-B, with text, scale 1:96,000. 

Weed, W.H., 1893, The Laramie and the overlying Livingston 

formation of Montana: U.S. Geological Survey Bulletin 

105, p. 10-14. 

Biostratigraphic Correlation of Santonian and Campanian Formations, NW Yellowstone National Park and SW Montana 19 

Chapter C 

Occurrence and Significance of the 

Middle Turonian (Upper Cretaceous) 

Belemnite Actinocamax in 

Central Western Montana 

By WILLIAM A. COBBAN 

U.S. GEOLOGICAL SURVEY BULLETIN 1962 

CONTRIBUTIONS TO LATE CRETACEOUS STRATIGRAPHY 

AND PALEONTOLOGY, WESTERN MONTANA 
CONTENTS 

Abstract 23 

Introduction 23 

Locality of Actinocamax 23 

Coberly Formation 24 

Fossils of the Coberly Formation 25 

Actinocamax cf. A. manitobensis (Whiteaves) 25 

Distribution of middle Turonian Actinocamax and Rhynchostreon 25 

References cited 26 

FIGURES 

1. Map showing localities of Actinocamax and Rhynchostreon 24 

2. Photograph showing specimen of Actinocamax sp. 25 

CONVERSION FACTORS 

Inch-pound units of measurement in this report may be converted to International System (SI) of metric units 

using the following conversion factors: 

Multiply inch-pound unit By To obtain SI unit 

foot (ft) 0.3048 meter (m) 

mile (mi) 1.609 kilometers (km) 

inch (in.) 2.54 centimeter (em) 

22 Contents 
Occurrence and Significance of the Middle Turonian 

(Upper Cretaceous) Belemnite Actinocamax in 

Central Western Montana 

By William A. Cobban 

Abstract 

Two specimens of Actinocamax were recently found in 

the upper part of the Coberly Formation in Powell County, 

southeast of Drummond, Montana. Although badly weathered, 

the specimens are probably A. manitobensis (Whiteaves), a 

species known only from the ammonite zone of Collignoniceras woollgari of early middle Turonian age. The specimens 

were associated with Rhynchostreon suborbiculatum (Lamarck), an exogyrine bivalve known in the Western Interior only 

from rocks of middle Turonian age. The discovery of Actinocamax in the dominantly nonmarine Upper Cretaceous rocks of 

central western Montana is significant in precisely dating a 

marine transgression into this area. 

INTRODUCTION 

Age-diagnostic marine molluscan fossils were 

recently discovered in the Coberly Formation in central 

western Montana. According to Gwinn (1961 ), the Coberly 

consists of 570-650 ft (feet) (174-198 m (meter)) of 

"fossiliferous grey limestones and tan salt-and-pepper 

sandstones of early Late Cretaceous age lying between the 

Dunkleberg member of the Blackleaf formation below and 

the Jens formation above ... High-spired snail shells and 

oyster fragments are found throughout the member." 

While examining upper Coberly outcrops in 1987 in 

the Hoover Creek drainage 7.5 mi (mile) (12 km (kilometer)) southeast of Drummond (fig. 1), near the PowellGranite County line, an exogyrine bivalve, Rhynchostreon 

suborbiculatum (Lamarck), was found by C.A. Wallace, 

R.G. Tysdal, T.S. Dyman, and the author (all U.S. 

Geological Survey), and S.M. Vuke-Foster and E.T. Ruppel 

(both Montana Bureau of Mines and Geology). This find is 

significant in that in the Western Interior of the United 

Manuscript approved for publication, November 20, 1990. 

States R. suborbiculatum has been found only in marine 

rocks of middle Turonian age. Several specimens of this 

important guide fossil from the Carlile Shale of southcentral Colorado were illustrated by Stanton (1893, pl. 5, 

fig. 6, pl. 6, figs. 1, 2, pl. 8, fig. 1 ). The middle Turonian of 

the Western Interior has the following ammonite zonation, 

from oldest to youngest; Collignoniceras woollgari, Prionocyclus percarinatus, and P. hyatti. Rhynchostreon suborbiculatum has been found in the zones of C. woollgari and 

P. hyatti, which gives the bivalve a range entirely through 

the middle Turonian. 

In hopes of more closely dating the marine transgression represented by strata in the upper part of the 

Coberly Formation, the author, assisted by his son Robert, 

visited the Hoover Creek locality in 1989 in an attempt to 

find ammonites. We failed at this, but Robert discovered 

two badly weathered specimens of the belemnite Actinocamax associated with Rhynchostreon suborbiculatum. This is 

an important find inasmuch as Actinocamax is known in the 

middle Turonian of the Western Interior only from the zone 

of Collignoniceras woollgari (Cobban, 1983, p. 20), which 

suggests that the upper part of the Coberly is early middle 

Turonian. 

LOCALITY OF ACTINOCAMAX 

The two weathered specimens of Actinocamax (fig. 2) 

were found in brown-weathered, olive-gray, very fine 

grained, concretionary sandstone at USGS Mesozoic 

locality 012820 in the Hoover Creek valley about 71

/2 mi 

( 12 km) southeast of Drummond near the center of the NE1

/4 

sec. 17, T. 10 N., R. 11 W., Powell County. The specimens 

are from near the top of the Coberly Formation according to 

Middle Turonian Belemnite Actinocamax in Central Western Montana 23 
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•• I • COLORADO • ~Colorado Springs : 0 Montrose • 

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Figure 1. Map showing localities of middle Turonian Actinocamax (x) and Rhynchostreon suborbiculatum (solid circles) in Utah, 

Colorado, Kansas, Wyoming, South Dakota, Montana, and southern Manitoba. Dashed line is approximate position of western 

shoreline of the Western Interior seaway during early middle Turonian time (modified from Cobban and Hook, 1979, fig. 2). Not 

a palinspastic map. 

Gwinn's 1961 map. Masses of Rhynchostreon suborbiculatum occur in places in the concretionary parts of the 

sandstone. This member of the oyster family was also found 

by S.M. Vuke-Foster in the upper sandstone part of the 

Coberly at USGS Mesozoic locality D 12819 3.9 mi 

(6.3 km) farther southwest in the SW1

/4SW1/4 sec. 31, 

T. 10 N., R. 11 W., Powell County. 

COBERLY FORMA liON 

Gwinn (1961) named and briefly described the 

Coberly Formation on a map of the geology of the Drummond area. In that report Gwinn divided the Colorado 

Group into four formations, from oldest to youngest: 

Blackleaf Formation, Coberly Formation (new name), Jens 

24 Contributions to late Cretaceous Stratigraphy and Paleontology, Western Montana 
. 'S.1 

~ >.; ·7!J 

\¥ 

8 

Figure 2. Actinocamax sp., from the 

upper part of the Coberly Formation at 

USGS Mesozoic locality 012820 in the 

NE1/4sec. 17, T. 10 N., R. 11 W., Powell 

County, Montana. A, USNM 44211 0; 

8, USNM 442111. Natural size. 

Formation (new name), and Carter Creek Formation (new 

name). Wallace and others (1986) pointed out that the 

Carter Creek was misnamed for Carten Creek, and that the 

unit should be the Carten Creek Formation. 

In a later report, Gwinn (1965, p. 45--47) gave more 

details of the Coberly Formation and noted that it consisted 

of a "Basal gray mudstone-siltstone-olive sandstone facies," 

a "Medial limestone-oyster reef-associated tenigenous 

facies," and an upper "Sandstone facies." The dominantly 

calcareous middle unit with its brackish-water fossils is 

probably a bay or lagoon equivalent of the marine, 

calcareous Cone Member of the Marias River Shale farther 

northeast in the Wolf Creek area (Schmidt, 1978, p. 21, 22), 

which equates to the Bridge Creek Member of the 

Greenhorn Limestone of the Great Plains. A conspicuous 

unnamed white bentonitic bed observed by the present 

author in the calcareous middle part of the Coberly in the 

Hoover Creek area may be a westward equivalent of the 

1-m-thick bed of bentonite recorded in northwestern and 

east-central Montana (Cobban, 1951, p. 2185, 2186; Cobban, 1956, p. 1 002), and now known to cover much of the 

Western Interior (Elder, 1988, marker bed B). The bed 

probably persists northward into the Rocky Mountain 

Foothills of Alberta, where Stott (1963, p. 40) noted a 

widespread bed of bentonite near the base of the calcareous 

Vimy Member of the Blackstone Formation. 

FOSSILS OF THE COBERLY FORMATION 

Gwinn (1965, p. 45) observed only invertebrate 

bunows in the basal sandy unit of the Coberly Formation. 

The middle calcareous unit, however, contains abundant 

brackish-water fossils. Gwinn (1965, p. 45) described the 

unit a few miles southeast of Drummond as "mainly dark 

siltstone, mudstone and shale and beds of fetid black 

biomicritic limestone with thin-shelled gastropods and 

solitary pelecypods; in the dark mudstone-shale sequences 

are one- to four-feet thick oyster reefs (Ostrea soleniscus), 

from which radiate beds of coarse Ostrea debris and 

associated thick-shelled tunitellid-like gastropods." The 

tunitellid-like gastropods are Gymnentome coalvillensis 

(Meek), a species originally described from the Cretaceous 

rocks at Coalville, Utah (Meek, 1873, p. 502), and now 

known from localities as far south as Trans-Pecos Texas. 

The oysters are now assigned to Crassostrea soleniscus 

(Meek). Among other molluscan fossils from this part of the 

Coberly are the bivalve Cyrena securis Meek and the 

gastropod Admetopsis subfusiformis Meek, both of which 

were described from specimens from Coalville, Utah. 

Gwinn (1965, p. 47) observed that the upper 

sandstone unit of the Coberly contained "external molds of 

large pelecypods at the type section." These molds are 

probably Rhynchostreon suborbiculatum, which occurs 

abundantly in the upper sandstone at the locality where 

Actinocamax was found about one-half mile north of the 

type section. The bivalve Pleuriocardia sp. was also found 

with Actinocamax, and Crassostrea soleniscus, Cyrena 

securis, and Corbula sp. were found several feet below. 

ACTINOCAMAX CF. A. MANITOBENSJS 

(WHITEA VES) 

The two weathered specimens represent parts of small 

and large individuals that are probably Actinocamax manitobensis (Whiteaves, 1889, p. 189, pl. 26, figs. 3, 3a, 3b). 

Both specimens are conoded down to their centers, as if 

they were split longitudinally (fig. 2A, B). The smaller 

guard, 34 mm (millimeter) in length with a diameter of 6.8 

mm, is the alveolar end of a small, slender individual that 

closely resembles in size and shape the alveolar part of a 

small specimen of A. manitobensis illustrated by Jeletzky 

(1950, pl. 1, figs. la-c) from the Favel Formation near 

Treherne in southwestern Manitoba (fig. 1). The larger 

specimen is the apical part of a guard 40 mm in length with 

a diameter of 11.7 mm that closely resembles in size and 

shape the apical part of a large guard illustrated by Jeletzky 

(1950, pl. 1, figs. 4a-c). The two specimens from the 

Coberly Formation are kept at the National Museum of 

Natural History in Washington, D.C., where they have the 

catalogue numbers USNM 442110 and 442111. 

DISTRIBUTION OF MIDDLE TURONIAN 

ACTINOCAMAX AND RHYNCHOSTREON 

Actinocamax of middle Turonian age has been found 

in the zone of Collignoniceras woollgari in the Fairport 

Chalk Member of the Carlile Shale of central Kansas 

(Jeletzky, 1961, p. 507-515, pl. 72, figs. lA-E, 2A-C, text 

Middle Turonian Belemnite Actinocamax in Central Western Montana 25 
figs. 1 a, b, 2; Hattin, 1962, p. 54, 55, pl. 15, fig. C). Farther 

north, in western South Dakota, Actinocamax manitobensis 

was collected from the lower pa11 of the Pool Creek 

Member of the Carlile Shale in association with C. woollgari near Rapid City at USGS Mesozoic locality 23067 in 

sec. 16, T. 1 S., R. 8 E., Pennington County (fig. 1). 

Fragments of Actinocamax have also been found with C. 

woollgari in northeastern South Dakota in Cretaceous 

limestone that rests directly on Precambrian granite (Cobban, 1983, p. 20, pl. 7, figs. 6, 7), and occasional specimens 

have been found in glacial drift farther southeast in 

northeastern Iowa and western Illinois (Cobban, 1983, 

p. 20, text fig. 5). A few specimens of A. manitobensis, 

associated with C. woollgari, are present in collections of 

the U.S. Geological Survey from the basal pa11 of the Carlile 

Shale in east-central Montana (fig. 1). Jeletzky (1950, 1961) 

mentioned the occurrence of Turonian Actinocamax in 

Manitoba, Saskatchewan, Alberta, and British Columbia, 

and as far north as the lower Mackenzie Valley in the 

District of Mackenzie. Actinocamax is rare in Wyoming, 

where it is represented in the U.S. Geological Survey 

collections by one specimen from the Frontier Formation in 

the Jackson area and one specimen from the Frontier 

Formation near Casper (fig. 1 ). Both were found with C. 

woollgari. 

Rhynchostreon suborbiculatum has a greater stratigraphic range, and a more limited geographic range, than 

the middle Turonian Actinocamax. Many localities of Rhynchostreon are along a sandy belt that parallels the western 

shoreline of the Western Interior Cretaceous seaway (fig. 1 ), 

but in Utah and Colorado, a belt oflocalities trends eastward 

to the Pueblo-Colorado Springs-Walsenburg area. The 

bivalve has been found with Actinocamax at only one 

locality in western Montana and at one locality in western 

Wyoming (fig. 1). 

REFERENCES CITED 

Cobban, W.A., 1951, Colorado shale of central and northwestem 

Montana and equivalent rocks of Black Hills: American 

Association of Petroleum Geologists Bulletin, v. 35, no. 10, 

p. 2170-2198. 

___ 1956, Cretaceous rocks along part of southeast boundary 

of Glacier National Park, Montana: American Association 

of Petroleum Geologists Bulletin, v. 40, no. 5, p. 1001-

1104. 

___ 1983, Molluscan fossil record from the northeastem part 

of the Upper Cretaceous seaway, Westem Interior in 

Cobban, W.A., and Merewether, E.A., Stratigraphy and 

paleontology of mid-Cretaceous rocks in Minnesota and 

contiguous areas: U.S. Geological Survey Professional 

Paper 1253-A, p. 1-23, pis. 1-15. 

Cobban, W.A., and Hook, S.C., 1979, Collignoniceras woollgari 

woollgari (Mantell) ammonite fauna from Upper Cretaceous of Western Interior: New Mexico Bureau of Mines 

and Mineral Resources Memoir 37, 51 p., I2 pis. 

Elder, W. P., 1988, Geometry of Upper Cretaceous bentonite beds; 

implications about volcanic source areas and paleowind 

pattems, western interior, United States: Geology, v. I 6, 

p. 835-838. 

Gwinn, V.E., 1961, Geology of the Drummond area, centralwestern Montana: Montana Bureau of Mines and Geology 

Special Publication 21 (Geological Map 4), scale I inch to 

1 mile, with text. 

Gwinn, V .E., 1965, Cretaceous rocks of the Clark Fork Valley, 

central western Montana, in Geology of the Flint Creek 

Range, Montana: Billings Geological Society 16th Annual 

Field Conference Guidebook, p. 34-57. 

Hattin, D.E., 1962, Stratigraphy of the Carlile Shale (Upper 

Cretaceous) in Kansas: Kansas Geological Survey Bulletin 

156, 155 p., 27 pis. 

Jeletzky, J.A., I950, Actinocamax from the Upper Cretaceous 

of Manitoba: Geological Survey of Canada Bulletin 15, 

p. 1-27, pis. 1-3. 

___ 1961, Actinocamax from the Upper Cretaceous Benton 

and Niobrara Formations of Kansas: Journal of 

Paleontology, v. 35, no. 3, p. 505-531, pl. 72. 

Meek, F.B., 1873, Preliminary paleontological report, consisting 

of lists and descriptions of fossils, with remarks on the ages 

of the rocks in which they were found, etc.: U.S. Geological 

Survey of the Territories (Hayden), Sixth Annual Report, 

p. 429-518. 

Schmidt, R.G., 1978, Rocks and mineral resources of the Wolf 

Creek area, Lewis and Clark and Cascade Counties, 

Montana: U.S. Geological Survey Bulletin 1441, 91 p. 

Stott, D.F., 1963, The Cretaceous Alberta Group and equivalent 

rocks, Rocky Mountain Foothills, Alberta: Canada Geological Survey Memoir 317, 306 p. 

Stanton, T.W., 1893, [I894], The Colorado formation and its 

invertebrate fauna: U.S. Geological Survey Bulletin 106, 

288 p., 45 pis. 

Wallace, C.A., Schmidt, R.G., Lidke, D.J., and others, 1986, 

Preliminary geologic map of the Butte 1 °X2° quadrangle, 

western Montana: U.S. Geological Survey Open-File 

Report OF-86-292. 

Whiteaves, J.F., 1889, On some Cretaceous fossils from British 

Columbia, the Northwest Territory, and Manitoba: 

Geological Survey of Canada, Contributions to Canadian 

Palaeontology, v. I, p. 15I-196, pis. 20-26. 

26 Contributions to late Cretaceous Stratigraphy and Paleontology, Western Montana 

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