Revision of the Lower Part 

of the Tertiary System in the

Central and \Vestern Uinta Basin, 

Utah_____ __________

GEOLOGICAL SURVEY BULLETIN 1405G

Revision of the Lower Part 

of the Tertiary System in the

Central and \Vfestern Uinta Basin, 

Utah

By THOMAS D. FOUCH

CONTRIBUTIONS TO STRATIGRAPHY

GEOLOGICAL SURVEY BULLETIN 1405-C

Correlation of lower Tertiary 

stratigraphic units recently penetrated 

in northeastern Utah

UNITED STATES GOVERNMENT PRINTING OFFICE, WASHINGTON : 1976
UNITED STATES DEPARTMENT OF THE INTERIOR 

THOMAS S. KLEPPE, Secretary

GEOLOGICAL SURVEY 

V. E. McKelvey, Director

Library of Congress Cataloging in Publication Data

Fouch, Thomas D.

Revision of the lower part of the Tertiary system in the central and western Uinta Basin,

Utah.

(Contributions to stratigraphy) (Geological Survey Bulletin 1405-C) 

Bibliography: p.

Supt. of Docs, no.: I 19.3:1405-C 

1. Geology, Stratigraphic Tertiary. 2. Geology, Stratigraphic Nomenclature Utah Uinta

Basin.

I. Title. II. Series. III. Series: United States Geological Survey Bulletin 1405-C. 

QE75.B9 No. 1405-C [QE691] 557.3'08s [ 551.7'8'0979221] 75-619374

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

Washington, D. C. 20402 

Stock Number 024-001-02770-4
CONTENTS

Page

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

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

North Horn Formation .............................................................................................. 2

Flagstaff Member of the Green River Formation...................................................... 4

Colton Formation....................................................................................................... 5

Wasatch Formation..................................................................................................... 6

References cited........................................................................................................... 6

ILLUSTRATIONS

Page 

FIGURE 1. Index map of northeastern Utah............................................................. C2

2. Generalized section showing nomenclature of the lower part of the

Tertiary System, central Uinta Basin .................................................. 3

CONTRIBUTIONS TO STRATIGRAPHY

REVISION OF THE LOWER PART OF THE

TERTIARY SYSTEM IN THE CENTRAL AND

WESTERN UINTA BASIN, UTAH

By THOMAS D. FOUCH

ABSTRACT

Much of the lower part of the Tertiary System in the central and western Uinta Basin of 

northeastern Utah has been shown by recent drilling to consist of a thick section of lacustrine 

rocks. This lacustrine sequence is continuous with the overlying Eocene Green River 

Formation and is equivalent to surface exposures of the Flagstaff Limestone and the Colton 

Formations. In the central and western Uinta Basin, the lower boundary of the Green River 

Formation is moved downward to the base of the sequence of carbonate, mudstone, and 

sandstone beds, which is the base of the Flagstaff. Thus, the Green River is partly Paleocene 

in age. The Flagstaff is reduced in stratigraphic rank to a member of the Green River 

Formation. The Flagstaff consists of gray and brown carbonate and sandstone and gray to 

green mudstone units. The Flagstaff in much of the basin separates variegated red, gray, and 

green mudstone and sandstone units of the Paleocene and Eocene Colton Formation from 

the Paleocene and Upper Cretaceous North Horn Formation. The section of predominantly 

red beds on the north side of the basin, beneath the main body and above the Flagstaff 

Member of the Green River Formation, is assigned to the Colton Formation. The Wasatch 

Formation includes a sequence of red, gray, and green variegated sandstone, mudstone, and 

minor carbonate units which extends continuously downward from the base of the Eocene 

Uinta Formation to the top of the Upper Cretaceous Price River Formation, equivalent, or 

older units.

INTRODUCTION

Recent regional and detailed examinations of the stratigraphy of the 

lower part of the Tertiary System in northeastern Utah have demonstrated the need for several changes in nomenclature and extension of 

existing terminology to new areas to accommodate the results of both 

surface and subsurface studies and to clarify the stratigraphic meaning of 

terms used. Several changes in stratigraphic terminology are set forth in 

this paper which are to be applied in the central and western Uinta Basin 

only, an area bounded on the east by the general position of the Green 

River (fig. 1).

Some of the Upper Cretaceous and lower Tertiary rocks of the Wasatch 

Plateau were subdivided by Spieker and Reeside (1925) into the Price

River Formation and the lower member, Flagstaff Limestone Member

ci
C2

112°

CONTRIBUTIONS TO STRATIGRAPHY

111° 110° 109° 108°

40° -

39° -

25 50 75

I

50

T 

100 KILOMETRES

100 MILES

_I

FIGURE 1. Index map of northeastern Utah showing area of the report, Tertiary sedimentary rocks (patterned), and line of section A-A' (fig. 2).

(named for exposures on Flagstaff Peak, T. 20 S., R. 5 E., Salt Lake 

meridian), and the upper member of the Wasatch Formation. At that 

time, the Wasatch was considered to be early Eocene in age. Spieker 

recognized the problem of assigning the name Wasatch Formation to a 

rock sequence that contained units representing a longer time period than 

believed to be present at the type locality of the Wasatch Formation, and 

later he (Spieker, 1946) designated formational status to former members 

of the Wasatch Formation in central Utah. In doing so, he restricted the 

use of the term Wasatch Formation from central Utah. Though he did not 

resolve the uncertainty associated with the term Wasatch, Spieker felt that 

in view of the widespread usage of the name Wasatch by geologists, it 

might still serve to designate variegated sediments of the age indicated by 

the vertebrate fossils of the type locality. As described by Hayden (1869) 

the Wasatch includes strata exposed along the Union Pacific Railroad 

between Echo Canyon, Utah, and Carter Station, Wyo. (T. 17 N., R. 115 

W., north of the map boundary).

NORTH HORN FORMATION

Spieker (1946) renamed the lower member of the Wasatch Formation as 

the North Horn Formation and designated the exposures at North Horn
REVISION, TERTIARY SYSTEM, UTAH C3

Mountain in Tps. 18 and 19 S., R. 6 E., Salt Lake meridian, as its type 

locality. He characterized the variegated shale, sandstone, conglomerate, 

limestone, and other beds as representing typical flood-plain, channel, 

and scattered lacustrine deposits.

The North Horn Formation is considered to be of latest Cretaceous and 

Paleocene age on the basis of vertebrate remains (Gilmore, 1946; Gazin, 

1938, 1939, 1941) and palynomorph, ostracode, and charophyte assemblages (Griesbach and MacAlpine, 1973; Newman, 1974).

Uppermost Cretaceous and Paleocene deposits have been identified 

(Ryder and others, 1976) on outcrop exposures on the southwest flank of 

the basin and in drill holes in the central and western Uinta Basin (Fouch, 

1975). The term North Horn Formation is here extended from the southwest flank of the basin to the northern, central, and western Uinta Basin to 

include the variegated mudstone, sandstone, conglomerate, and local 

deposits of carbonate which underlie the Flagstaff Member of the Green 

River Formation (as reassigned in this paper; fig. 2). The North Horn 

Formation is interpreted to contain rocks of alluvial, paludal, and local 

lacustrine origin.

 Member boundary 

Formation boundary

FIGURE 2. Generalized section from outcrops near Willow Creek-Indian Canyon to the 

north-central Uinta Basin showing nomenclature of the lower part of the Tertiary 

System. Uinta Formation includes saline facies and equivalent lacustrine rocks assigned to the Uinta by Dane (1954). Line of section shown in figure 1.
C4 CONTRIBUTIONS TO STRATIGRAPHY

FLAGSTAFF MEMBER OF THE GREEN RIVER FORMATION

The Flagstaff Limestone Member of the Wasatch Formation (Spieker 

and Reeside, 1925) was elevated to formational status and termed the Flagstaff Limestone (Spieker, 1946). The Flagstaff was described as consisting 

of freshwater limestone interbedded with gray shale, sandstone, gypsum, 

oil shale, and volcanic ash with local accumulations of coal. Spieker 

considered the Flagstaff to have the form of a tongue of the Green River 

strata between flood-plain deposits, and he believed the Flagstaff to 

represent the beginning of widespread lacustrine conditions which 

continued uninterrupted through the deposition of the Green River 

Formation (1946, p. 136). However, Spieker chose not to designate the 

Flagstaff Limestone a tongue of the Green River Formation because of its 

extent and possible Paleocene age, though he considered the unit to represent an extension in area as well as in time of the Eocene Uinta Lake of 

Bradley (1930).

The Flagstaff Limestone was considered by Spieker to be of uncertain 

age, but on the basis of the presence of freshwater mollusk species he 

believed it to be more likely of late Paleocene than of Eocene age. La 

Rocque (1951, 1960) described the molluscan fauna of the Flagstaff in 

detail and subdivided the formation into three gross units (1960, p. 73-75). 

He considered the lowest unit to be of Paleocene age, the middle unit to be 

of Paleocene or Eocene age, and the upper unit to be of Eocene age. La 

Rocque attributed the termination of the Flagstaff Lake to encroachment 

of alluvial sediments (upper member of the Wasatch Formation, Spieker 

and Reeside, 1925; Colton Formation of Spieker, 1946) and to merger with 

Lake Uinta which spread into its area from the north.

Newman (1974), on the basis of palyomorph assemblage, assigns the 

main body of the Flagstaff Limestone at Soldier Summit in the southwestern part of the Uinta Basin to the Paleocene but considers the uppermost part of the unit to be of Eocene age. S. R. MacAlpine and F. R. 

Griesbach (oral commun., 1970-74) believe the main body of the Flagstaff on the south-central flank of the Uinta Basin to be of Paleocene age 

on the basis of ostracode, charaphyte, and palynomorph assemblages; 

however, they recognize that some rocks assigned to the Flagstaff along 

the Wasatch Plateau are of Eocene age.

A continuous section of organic-rich rocks of lacustrine origin in the 

center of the Uinta Basin has been penetrated by oil and gas tests drilled 

since 1969 (fig. 2). The section is in part equivalent to the Colton Formation and the Flagstaff Limestone. The lower part of this sequence of carbonate, muds tone, and sandstone beds can be traced from outcrop 

exposures of the Flagstaff on the south flank of the basin to the subsurface of the central and western Uinta Basin where it is continuous with 

carbonate, mudstone, and sandstone beds of the Green River Formation 

(Ryder and others, 1976; Fouch, 1975). The Flagstaff exposed along the
REVISION, TERTIARY SYSTEM, UTAH C5

southwest side of the Uinta Basin is underlain by the North Horn Formation and is overlain by the Col ton Formation; however, in the central part 

of the basin, the variegated rocks of the Col ton have graded laterally into 

lacustrine rocks of the Green River Formadon. This central core of carbonate, sandstone, and mudstone of interpreted lacustrine origin is not 

entirely accommodated by the existing outcrop-derived nomenclature, 

and it is reasonable to view the lacustrine sequence and associated tongues 

as part of the Green River Formation. S. R. MacAlpine (oral commun., 

1974) recognizes no microfossil evidence from the subsurface to indicate 

unconformities within this Paleocene and lower Eocene sequence. Ryder, 

Fouch, and Elison (1976) cite microfossil information which places the 

Paleocene-Eocene boundary near the top of the Flagstaff on the northcentral flank of the basin.

The term Flagstaff Member of the Green River Formation is applied 

here to dominantly medium- to dark-gray carbonate, light-gray sandstone, and light-gray to gray-green claystone beds, which are between the 

variegated mudstone and sandstone beds of the Col ton and North Horn 

Formations or underlie the predominantly gray-brown carbonate and 

claystone of the main body of the Green River. Though the Flagstaff 

contains much limestone, many other rock types are present in abundance 

and so the word "limestone" is not included in the name of the member.

The inclusion of the Flagstaff with the Green River Formation is 

consistent with Spieker's observation that the Flagstaff on the Wasatch 

Plateau had the form of a tongue of the Green River Formation. Within 

the subsurface of the western and central Uinta Basin, the unit is demonstrated to be a part of the Green River Formation. This usage of the Green 

River Formation extends its age in northeastern Utah into the Paleocene.

COLTON FORMATION

Strata.formerly designated the upper member of the Wasatch Formation were named the Colton Formation by Spieker (1946, p. 139) for 

exposures near Colton, Utah, T. 11 S., Rs. 8 and 9 E., Salt Lake meridian, 

the type locality. He interpreted the irregular and discontinuous red beds 

of the Colton to be of flood-plain and channel origin and enclosed in and 

gradational with lacustrine rocks of the underlying Flagstaff Limestone 

and the overlying Green River Formation.

The section of red beds on the north side of the basin beneath the main 

body of the Green River Formation and overlying the Flagstaff Member of 

the Green River Formation is here assigned to the Colton Formadon 

because of its condnuity in the subsurface of the east-central part of the 

basin with the Colton Formation of the southwest flank of the basin 

(Ryder and others, 1976; Fouch, 1975, fig. 5).

Although Spieker found no definidve paleontologic evidence in the 

Colton Formation, he considered the unit to be of early Eocene age.
C6 CONTRIBUTIONS TO STRATIGRAPHY

Newman (1974) assigned an early Eocene age to the Colton Formation in 

the southwest part of the basin, but Eocene palynomorphs were recovered 

from only the upper half of the unit. S. R. MacAlpine and F. R. Griesbach 

(oral commun., 1972-74), on the basis of palynomorph, ostracode, and 

charophyte assemblages, placed the Paleocene-Eocene boundary on the 

south-central flank of the basin within the upper third of the formation 

and on the north flank of the basin near the top of the underlying Flagstaff 

Member of the Green River Formation. This evidence, then, indicates a 

late Paleocene and early Eocene age for the Colton Formation in the 

western and central Uinta Basin.

WASATCH FORMATION

In 1946 Spieker elevated the members (lower, Flagstaff Limestone, 

upper) of the Wasatch to formation status and abandoned the term 

Wasatch Formation for strata contained in the former members. 

However, in view of the widespread usage of Wasatch to designate a 

variety of rocks of differing physical description, age, and origin (Fisher 

and others, 1960; Abbott, 1957), it is recommended that the name Wasatch 

Formation be retained in the central and western Uinta Basin. Where the 

Flagstaff Member of the Green River Formation is not present to separate 

the variegated sandstone, mudstone, and minor carbonate units of the 

Colton and North Horn Formations (as used in this paper) and to verify 

stratigraphic position, the designation as Wasatch Formation is 

preferable to assignment of undifferentiated variegated rocks to the 

Colton or North Horn Formation. The Wasatch Formation in the area of 

this report includes the predominantly red, gray, and green variegated 

sequence of sandstone, conglomerate, mudstone, and minor and discontinuous carbonate beds which, in the subsurface of the northern Uinta 

Basin, extend continuously from the base of the Eocene Uinta Formation 

to the Upper Cretaceous Price River Formation.

REFERENCES CITED

Abbott, W. O., 1957, Tertiary of the Uinta Basin (Utah): in Intermountain Assoc. Petroleum Geologists 8th Ann. Field Conf. Guidebook, p. 102-109.

Bradley, W. H., 1930, The varves and climate of the Green River epoch: U.S. Geol. Survey 

Prof. Paper 158-E, p. 87-110.

Dane, C. H., 1954, Stratigraphy and facies relationships of upper part of Green River Formation and lower part of Uinta Formation in Duchesne, Uintah, and Wasatch 

Counties, Utah: Am. Assoc. Petroleum Geologists Bull., v. 38, p. 405-425.

Fisher, D. J., Erdmann, C. E., and Reeside, J. B., Jr., 1960, Cretaceous and Tertiary formations of the Book Cliffs, Carbon, Emery, and Grand Counties, Utah, and Garfield 

and Mesa Counties, Colorado: U.S. Geol. Survey Prof. Paper 332, 80 p.

Fouch, T. D., 1975, Lithofacies and related hydrocarbon accumulations in Tertiary strata 

of the western and central Uinta Basin, Utah, in Bolyard, D. W., ed., Symposium on 

deep drilling frontiers of the central Rocky Mountains: Rocky Mtn. Assoc. Geologists, p. 163-173.
REVISION, TERTIARY SYSTEM, UTAH C7

Gazin, C. L., 1938, A Paleocene mammal fauna from central Utah: Washington Acad. Sci. 

Jour., v. 28, p. 271-277.

____1939, A further contribution to the Dragon Paleocene fauna of central Utah: Washington Acad. Sci. Jour., v. 29, p. 273-286.

____1941, The mammalian fauna of the Paleocene of central Utah, with notes on the

geology: U.S. Natl. Mus. Proc., v. 91, no. 3121, 53 p. 

Gilmore, C. W., 1946, Reptilian fauna of the North Horn formation of central Utah: U.S.

Geol. Survey Prof. Paper 210-C, p. 29-53. [1947].

Griesbach, F. R., and MacAlpine, S. R., 1973, Reconnaissance palynology and micropaleontology of the Late Cretaceous-Early Tertiary North Horn Formation, central

Utah (abs.): Geol. Soc. America Abs. with Programs, v. 5, no. 6, p. 483. 

Hayden, F. C., 1869, Review of leading groups, in U.S. Geol. Survey Terr. 3d Ann. Rept.,

p. 189-192. 

La Rocque, A., 1951, Molluscan fauna of the Flagstaff formation, central Utah (abs.):

Geol. Soc. America Bull., v. 62, p. 1457. 

_____1960, Molluscan faunas of the Flagstaff formation of central Utah: Geol. Soc.

America Mem. 78, 100 p. 

Newman, K. R., 1974, Palynomorph zones in early Tertiary formations of the Piceance

Creek and Uinta Basins, Colorado and Utah, in Rocky Mtn. Assoc. Geologists, 25th

Field Conf. Guidebook, p. 47-55. 

Ryder, R. T., Fouch, T. D., and Elison, J. H., 1976, Early Tertiary sedimentation in the

western Uinta Basin, Utah: Geol. Soc. America Bull, (in press). 

Spieker, E. M., 1946, Late Mesozoic and early Cenozoic history of central Utah: U.S. Geol.

Survey Prof. Paper 205-D, p. 117-161. 

Spieker, E. M., and Reeside, J. B., Jr., 1925, Cretaceous and Tertiary formations of the

Wasatch Plateau, Utah: Geol. Soc. America Bull., v. 36, no. 3, p. 435-454.

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