Age and Correlation of 

Cretaceous Rocks Previously 

Assigned to the Morrison (?) 

Formation, Sanpete-Sevier 

Valley Area, Central Utah 

By IRVING j. WITKIND, LARRY A. STANDLEE, 

and KEVIN F. MALEY 

In central Utah, rocks previously assigned to 

the qualified Morrison (?) Formation of Late 

Jurrassic age are now believed to be part to 

the Cedar Mountain Formation of Early Cretaceous age 

U.S. GEOLOGICAL SURVEY BULLETIN 1584 
DEPARTMENT OF THE INTERIOR 

DONAlD PAUl HODEl, Secretary 

U.S. GEOLOGICAL SURVEY 

Dallas l. Peck, Director 

UNITED STATES GOVERNMENT PRINTING OFFICE, WASHINGTON: 1986 

For sale by the Branch of Distribution 

Books and Open-File Reports Section 

U.S. Geological Survey 

Federal Center 

Box 25425 

Denver, CO 80225 

Library of Congress Cataloging in Publication Data 

Witkind, Irving jerome, 1917-

Age and correlation of Cretaceous rocks previously assigned to the 

Morrison(?) Formation, Sanpete-Sevier Valley area, central Utah. 

(U.S. Geological Survey bulletin ; 1584) 

Bibliography: p. 

Supt. of Docs. No.: I 19.3:1584 

1. Geology, Stratigraphic-Cretaceous. 2. Geology-Utah-Sanpete 

Valley Region. 

I. Standlee, Larry A. II. Maley, Kevin F. Ill. Title. IV. Series. 

QE75.89 no. 1584 557.3 s 8~317 

[QE686] [551.7'7] 
CONTENTS 

Abstract 1 

Introduction 1 

Acknowledgments 1 

Previous work 1 

Stratigraphic relations 3 

Lithology 3 

Lower unit 4 

Upper unit 5 

Other exposures 5 

Thickness 6 

Contact relations 6 

Current studies 6 

Paleontologic data 6 

Conclusions 7 

References cited 8 

Appendix A 9 

FIGURES 

1. Index map of central Utah 2 

2. Exposures in the Red Rocks area near Sterling, Utah 4 

TABLES 

1. History-of-usage chart 3 

2. Fossil content of samples collected from lower unit 7 

3. Fossil content of samples collected from upper unit 8 

Contents Ill 

Age and Correlation of Cretaceous Rocks 

Previously Assigned to the Morrison(?) Formation, 

Sanpete-Sevier Valley Area, Central Utah 

By Irving j. Witkind,1 Larry A. Standlee/ and Kevin F. Malef 

Abstract 

Beds of conglomerate, sandstone, mudstone, and freshwater limestone exposed in the Sanpete-Sevier Valley area of 

central Utah have been assigned, in the past, to the qualified 

Morrison(?) Formation, of Late Jurassic age. In our view these 

beds are neither part of the Morrison Formation nor of Jurassic 

age. We divide these beds into an upper unit that consists 

primarily of beds of reddish-brown coarse conglomerate, and 

a lower unit that consists of variegated mudstone containing 

interleaved thin beds of limestone, sandstone, and conglomerate. The two units intertongue. Diagnostic plant microfossils 

of Early Cretaceous age have been recovered from our upper 

unit, and bivalves, also of Early Cretaceous age, have been 

found in our lower unit. In addition, well-rounded, polished 

stones, considered by some geologists to be gastroliths, 

indicative of the Lower Cretaceous Cedar Mountain Formation, 

are plentiful in the lower unit. Our lower unit is lithologically 

much like the upper member of the Cedar Mountain Formation as exposed in the San Rafael Swell to the east. We believe 

that our upper and lower units are Early Cretaceous in age. 

We are uncertain about the correlation of the conglomerate 

beds that form our upper unit; they may be a newly recognized 

lithofacies at the top of the Cedar Mountain Formation, a 

conglomeratic facies of the undivided Indianola Group, or in 

part Cedar Mountain and in part Indianola Group. We do not 

assign a formal name to this upper unit. We believe that our 

lower unit is correlative with the upper member of the Cedar 

Mountain Formation, exposed elsewhere on the Colorado 

Plateaus. Consequently, we propose that in the Sanpete-Sevier 

Valley area, the strata composing our lower unit henceforth 

be assigned to the Lower Cretaceous Cedar Mountain 

Formation. 

INTRODUCTION 

Two of the more troublesome stratigraphic problems in the Sanpete-Sevier Valley area of central Utah 

(fig. 1) are the age and correlation of a series of sedimentary beds that have been assigned, in the past, to the 

Jurassic Morrison(?) Formation. Despite the fact that 

each of us interprets the structural history of this sector 

of central Utah in different ways, we are in firm agreement that the beds in question are neither Jurassic in age 

nor part of the Morrison Formation. On the basis of 

evidence presented in this paper we believe the beds are 

1

U.S. Geological Survey, Federal Center, Denver, Colorado 80225 2

Conoco Exploration Research, P.O. Box 1267, Ponca City, Oklahoma, 74603 3 1360 Kensington Avenue, Salt Lake City, Utah, 84105 

of Early Cretaceous age and that some of them are correlative with the upper member of the Cedar Mountain 

Formation of the San Rafael Swell, Utah. 

ACKNOWLEDGMENTS 

Co-authors Standlee and Maley acknowledge with 

sincere thanks the financial support and technical 

assistance given them by Chevron, U.S.A., Denver, Colorado, and Placid Oil Company, Salt Lake City, Utah, 

respectively. 

PREVIOUS WORK 

E. M. Spieker, originally with the U.S. Geological 

Survey and later a member of the faculty at Ohio State 

University, was among the early workers in central Utah. 

During his early studies in and near the Wasatch Plateau 

(Spieker and Reeside, 1926; Spieker, 1931), Spieker identified a series of ''variegated shales, sandstones, and conglomerates" as being "possibly Morrison" (1946, p. 125). 

Subsequently, as a result of additional field work, Spieker 

decided that these beds were indeed Morrison. He was 

influenced by the fact that these strata were lithologically 

much like the Morrison strata exposed to the east in the 

San Rafael Swell and, moreover, were in the stratigraphic 

position commonly occupied by the Morrison Formation. 

As his field mapping progressed and his work extended 

westward into the Sanpete-Sevier Valley sector of central Utah, he became less certain about his identification. 

Two factors disturbed him: First, some units in these 

Morrison strata are lithologically like units in the overlying undivided Indianola Group of earliest Late 

Cretaceous age. And second, he became concerned about 

the gradational relations between the Morrison and the 

Indianola strata; the units apparently intertongue. Seemingly the entire Early Cretaceous sequence was missing. 

Despite a diligent search, Spieker and his colleagues failed 

to find an unconformity at the top of the presumed Morrison Formation. He was also unable to find any fossils 

that might help resolve the dilemma. Thus, in spite of 

some cogent reasons for retaining the unqualified Morrison assignment, Spieker (1946, p. 126) decided: 

Review of the evidence leads to no satisfactory conclusion, 

* * * it seems best to designate the beds by the qualified 

term Morrison(?). 

Previous Work 1 
112° 00' 

40° 

00' 

45' 

30' 

15' 

T 

18 

s 

1 

zn 

s 

39° 

00' 

45' 

45' 30' 15' 

Scofield 

10 20 

() 

'

. rYFish Lake 

10 

111° 00' 45' 30' 

J:q~ ~pu 

)'&' A 

~)"~ ~u 

<9a 

0-tc~~. ~~ iS 

~ 

~~ ~ 8 Cedar 

Mountain 

110° 15' 

380 (/1 30' L_ __ R_1_W __ ~ __ R1_EL__R_2_E ____ R_3_E_L __________ _L ___________ _L ______ ~ __ _L __ _L __________________ ~ 

Figure 1. Map of central Utah showing geographic features mentioned in text, sample localities (X), and location of 

measured section. 

Stokes (1944, p. 965-966) was the first to recognize 

that the beds originally grouped as Morrison Formation 

on the San Rafael Swell included units of both Late 

Jurassic and Early Cretaceous age (table 1). He assigned 

the Upper Jurassic beds to the Morrison Formation, and 

divided the Lower Cretaceous beds into an upper ''Cedar 

Mountain shale'' and a lower ''Buckhorn conglomerate.'' 

Subsequently both units were combined to form the 

Cedar Mountain Formation (Hale and Van De Graff, 

1964). Stokes (1972, p. 26) inferred that the Morrison 

Formation of the San Rafael Swell pinched out to the 

west beneath the Wasatch Plateau, and that the Lower 

Cretaceous upper "shale" member of the Cedar Mountain Formation persisted westward beyond the Wasatch 

Plateau into the Sanpete-Sevier Valley area. 

In the intervening years subsequent workers, also 

unable to establish firmly the age and correlation of the 

qualified Morrison(?) beds in the Sanpete-Sevier Valley 

2 Age and Correlation of Cretaceous Rocks Previously Assigned to the Morrison(?) Formation, Utah 
Table 1. History-of-usage chart; correlation not implied. Stokes (1944) was the first to recognize that Spieker's qualified Morrison(?) Formation (1931, 1946) contained units of both jurassic and Cretaceous age. The Buckhorn Conglomerate Member is 

confined essentially to the San Rafael Swell. We believe that the Morrison Formation pinches out west of the San Rafael Swell, 

and that the upper unit of this paper pinches out east of the Sanpete-Sevier Valley area. Both pinchouts are concealed beneath 

the Wasatch Plateau. We are uncertain about the age of the Twist Gulch Formation. In central Utah, the Twist Gulch appears 

to grade into the overlying Cedar Mountain Formation of Early Cretaceous age. We infer, thus, that the Twist Gulch, although 

dated as Middle jurassic, may extend into the Late jurassic. We know of no fossil evidence, however, to support this younger 

age, and so show a hiatus between the Twist Gulch and Cedar Mountain Formations 

Witkind and Maley Standlee 

interpretation interpretation 

(This paper) (This paper) 

Central Utah Central Utah 

Upper Indianola Indianola 

Cretaceous Group, Group 

undivided undivided 

(Includes upper 

unit of this 

paper) Upperuni\ 

of this 

paper 

en 

:::> c: 0 0 

w ·;; 

u IU 

E ~ 0 w u.. a: Lower c: u Cedar '.§ Cretaceous Mountain Lower c: Formation unit :I 

0 

(Consists of of this ~ 

lower unit of ... paper IU 

this paper) "C 

Q) 

u 

Upper 

Jurassic 

u 

U5 ? ? en 

< a: 

:::> 

.., Twist Twist Middle Gulch Gulch Jurassic Formation Formation 

area, have continued to refer to them as "Morrison(?)," 

and to assign them either to the Late Jurassic (Witkind, 

1983, p. 47) or Early Cretaceous (Stuecheli and Collinson, 1984). We suspect that this hesitancy in accepting 

Stokes' views reflects the fact that Stokes, although he 

found a few dinosaur bones, was unable to find agespecific index fossils within Cedar Mountain strata (1944, 

p. 967). 

Hale and 

Van De Graff 

(1964) 

Stokes (1944) Spieker ( 1 946) 

San Rafael Swell San Rafael Swell San Rafael Swell 

and central Utah 

Tununk Shale Mancos Shale Mancos Shale (Mancos Shale) 

Dakota Sandstone Dakota Sandstone Dakota Sandstone 

c: 

0 

·;; 

IU 

E 

0 Cedar u.. Mountain c: Shale '.§ 

c: 

:I 

0 

~ 

... Morrison (?) IU 

"C 

Q) Formation u 

Buckhor~ ;:conglomerate Member 

Vc onglomerate Buckhorn t~ 

I Morrison Morrison 

Formation Formation 

Summerville Formation 

Curtis Formation 

Entrada Formation 

STRATIGRAPHIC RELATIONS 

Lithology 

Spieker (1949, p. 18) recognized four distinct 

lithologies in the units he assigned to the Morrison(?) Formation: conglomerate, sandstone, shale (we believe these 

"shale" beds are best described as variegated calcareous 

Stratigraphic Relations 3 
mudstone), and freshwater limestone. Only rarely are all 

these lithologies represented in any one exposure. In 

places, as along the west flank of the San Pitch 

Mountains-known to geologists as the Gunnison Plateau 

(fig. 1)-the Morrison(?) strata consist chiefly of coarse 

conglomerates (Spieker, 1946, p. 18), but also include, 

according to Standlee (1982, p. 367), "thin-grey-green 

shale beds interbedded with red shales, [and] sandstones 

* * * . '' Elsewhere, as in the Red Rocks area (near Sterling, at the southeast corner of the Gunnison Plateau, 

fig. 1), where the Morrison(?) is perhaps best exposed, 

the beds consist of variegated calcareous mudstone rich 

in light-gray limestone nodules (commonly about 5-8 em 

(2-3 in) in diameter), with interleaved thin beds of freshwater light-gray limestone, light-brown sandstone, and 

reddish-brown conglomerate. The variegated mudstone 

beds are conformably overlain by, and interfinger with, 

a thick sequence of coarsely conglomeratic reddish-brown 

beds. 

Spieker (1949, p. 18) tentatively assigned all these 

units to the Morrison(?) Formation. He noted: 

Elsewhere [the Morrison(?) Formation] seems to be thinner, 

excepting possibly the southeastern part of the Gunnison 

Plateau [the Red Rocks area], where a problematic section 

WEST 

of red conglomerates and variegated beds about 1 ,800 feet thick 

is tentatively assigned to the formation. 

To facilitate our discussion we divide the above 

sequence of beds into two informal units-a lower unit 

composed of the variegated mudstone with intercalated 

thin beds of freshwater limestone, sandstone, and conglomerate, and an upper unit composed primarily of the 

coarse conglomerate beds. Figure 2 shows the general 

appearance of the units. Appendix A gives a measured 

section of strata of the lower and upper units, formerly 

called Morrison(?), that are exposed in the Red Rocks 

area. 

Lower unit 

Where exposed in the Sanpete-Sevier Valley area 

the lower unit consists of variegated calcareous mudstone 

beds that contain variable amounts of conglomerate, 

sandstone, and limestone nodules. The limestone nodules 

appear to be characteristic; in places where Morrison(?) 

strata are concealed beneath detritus, the strata are identified on the basis of a profusion of these nodules in the 

float. In the Red Rocks area a thin bed of aphanic lightgray limestone is interlayered in the mudstone sequence. 

EAST 

----- Upper unit -------+4------------- Lower unit --------------

(Chiefly reddish-brown 

conglomerate beds) 

(Variegated mudstone beds with intercalated beds of light-gray limestone, tan to 

reddish-brown sandstone and conglomerate. Contains abundant limestone 

nodules and sparse rounded and polished gastroliths). 

Light-gray to tan conglomeratic sandstone 

Figure 2. View northward of lower and upper units (formerly called Morrison(?) Formation) as exposed in the Red Rocks 

area, southeast flank of the Gunnison Plateau, near Sterling, Utah. Strata range in attitude from vertical to overturned to the west. 

4 Age and Correlation of Cretaceous Rocks Previously Assigned to the Morrison(?) Formation, Utah 
Upper unit 

Our upper unit is indistinguishable lithologically 

from conglomerate beds that belong to the Indianola 

Group (Spieker, 1946, p. 125). We suspect that our upper 

unit, on the basis of its lithology and stratigraphic position, is either part of the Indianola Group, part of the 

Cedar Mountain Formation, or part of both. Although 

we are uncertain about its correlation, we are certain that 

it is not part of the Upper Jurassic Morrison Formation 

of the Colorado Plateaus. 

In the Red Rocks area, the conglomerate beds that 

form our upper unit locally have been folded into a tight 

isoclinal syncline. These conglomerate beds are conformably overlain, in the axial part of the syncline, by a thin 

light-brown sandstone bed. Two factors favor assigning 

these conglomerate beds to the Lower Cretaceous Cedar 

Mountain Formation (Spieker's qualified Morrison(?) 

Formation): They contain fossils of Early Cretaceous age 

(page 6 and table 2), and the thin, light-brown sandstone 

bed that rests on them is lithologically much like beds 

of the Sanpete Formation, the basal unit of the overlying Indianola Group (where the group can be differentiated farther to the east near the mouth of Sixmile 

Canyon, fig. 1). In this interpretation, then, the conglomerate beds could be considered as a newly recognized 

lithology of the Cedar Mountain Formation. Craig (1981) 

has shown that the Cedar Mountain Formation thickens 

to the northwest across the San Rafael Swell, and that 

sediment transport was generally from the west. This suggests that in Early Cretaceous time our study area was 

near the Sevier orogenic highlands in west-central Utah; 

thus, the coarse conglomerate beds of our upper unit may 

be contemporaneous in part with the upper shale member 

of the Cedar Mountain Formation to the east. Co-author 

Standlee favors this interpretation. 

Another interpretation, favored by co-authors 

Witkind and Maley, suggests that the conglomerate beds, 

rather than being restricted to the Cedar Mountain Formation, are part of the overlying undivided Indianola 

Group. Several factors favor this interpretation: the conglomerates are lithologically similar to conglomerates in 

the overlying Indianola Group; and some of the shales 

within the conglomerate beds of our upper unit (table 2) 

contain fossils that range up into the Late Cretaceous. 

Late Cretaceous is the accepted age of the Indianola 

Group. Moreover, the conglomerate beds clearly represent a drastic change in stream regimen, and thus are best 

viewed as synorogenic deposits derived from newly 

formed mountains to the west-the generally accepted 

origin of the Indianola Group (Spieker, 1946; Harris, 

1959; Armstrong, 1968; Lawton, 1982). 

The fluvial deposits that compose the Cedar Mountain Formation seemingly were derived from source 

areas not far west of the Sanpete-Sevier Valley area. 

Stokes (oral commun., 1984) interprets the Buckhorn 

Conglomerate Member of the Cedar Mountain Formation, as exposed in the San Rafael Swell, to be local flashflood deposits that were spread eastward across terrain 

of low relief. After deposition of the Buckhorn Conglomerate Member, eastward-flowing streams, heading 

in the newly formed uplands west of the Sanpete-Sevier 

Valley area, deposited the mudstone beds that now form 

the upper member of the Cedar Mountain Formation. 

Rejuvenation of those streams, presumably as a result of 

the growth of thrust-related mountains, resulted in 

deposition of the eastward-pointing wedge of conglomerate that forms our upper unit. 

Unable to determine whether these conglomerate 

beds of our upper unit are Cedar Mountain or part of 

the undivided Indianola, we have agreed to disagree pending further work. Co-author Standlee, influenced by the 

Early Cretaceous age assigned to the taxa contained 

within the conglomerate beds, proposes that these beds 

be considered a new-and the uppermost-lithologic unit 

of the Cedar Mountain Formation. Co-authors Witkind 

and Maley propose that our upper unit be provisionally 

assigned to the undivided Indianola Group. They are 

strongly influenced by the fact that the change from 

mudstone to conglomerate is distinct and easily 

recognized and thus forms an excellent contact for mapping purposes. Inherent in this interpretation is a change 

of age for the Indianola Group from "Late Cretaceous" 

to "Early and Late Cretaceous" in the Sanpete-Sevier 

Valley area. 

Other Exposures 

In Lake Fork, near Thistle, Spieker's Morrison(?) 

strata appear as thick beds of light-gray and reddishbrown mudstone that contain limestone nodules and thin 

beds of sandstone and conglomerate. These beds, possibly 

correlative with our lower unit, are overlain by reddishbrown, fine- to medium-grained beds of quartzose sandstone that intertongue with the light-gray sandstone beds 

of the Sanpete Formation of the Indianola Group. These 

reddish-brown sandstone beds may be correlative with 

our upper unit. 

In the Cedar Hills, co-author Witkind, unable to 

distinguish Morrison(?) conglomerate beds from other 

similar conglomerate beds assigned to the Indianola, 

grouped all conglomerate beds as part of the undivided 

Indianola Group. He included in the Morrison(?) 

Formation only the pink and variegated calcareous 

mudstone beds that contain abundant light-gray limestone 

nodules. 

In the northern part of the Gunnison Plateau, early 

workers, such as Hunt (1950), seemingly included the 

mudstone beds (our lower unit) with the Middle Jurassic 

Twist Gulch Formation, and the overlying conglomerate 

beds (our upper unit) with the Upper Cretaceous Indianola Group. 

Stratigraphic Relations 5 
Thickness 

Spieker (1949, p. 18) indicated that the Morrison(?) 

is about 550 m (1,800 ft) thick east of Thistle (in Lake 

Fork), of equal thickness in the southeastern part of the 

Gunnison Plateau, and about 400 m (1,300 ft) thick in 

Salina Creek Canyon (east of Salina). Co-author Witkind 

believes that the Morrison(?) Formation is about 245 m 

(800 ft) thick along the Middle Fork of Pole Creek (in 

the Cedar Hills). Co-author Maley has measured a 

thickness of 368 m (1,206 ft) of Spieker's Morrison(?) 

strata in the Red Rocks area (appendix A). Although our 

thicknesses differ from Spieker's, these differences may 

reflect our differing interpretations of which units should 

be included in the Morrison(?) Formation. 

Contact relations 

Throughout the Sanpete-Sevier Valley area all units 

grade into one another or intertongue. In the Red Rocks 

area the variegated mudstone beds of our lower unit intertongue with the overlying conglomerate beds of our upper 

unit. In the Gunnison Plateau the conglomerate beds of 

our upper unit are lithologically like and to us indistinguishable from the conglomerate beds of the overlying 

Indianola Group. Thus, we concur with Spieker (1949, p. 

19) that these Morrison(?) strata grade into and apparently 

intertongue with both the overlying beds of the Indianola 

Group and the underlying beds of the ''Arapien shale". 

(Spieker originally divided the Arapien Shale into two 

members, a Twist Gulch Member at the top and a Twelvemile Canyon Member at the base. Since Spieker's work, the 

Twist Gulch has been raised to formational rank and the 

term Twelvemile Canyon Member abandoned and replaced 

by the term Arapien Shale (Witkind and Hardy, 1983). The 

lower intertonguing referred to by Spieker, therefore, involves our lower unit and the Twist Gulch Formation). 

CURRENT STUDIES 

In 1980, W. L. Stokes visited the Red Rocks area 

and examined the sequence of Morrison(?) beds that 

makes up our lower unit. He reiterated his views that these 

specific beds were most likely correlative with the upper 

"shale" member of the Lower Cretaceous Cedar Mountain Formation. His identification was based on: (1) gross 

lithologic similarities with units in the upper member of 

the Cedar Mountain Formation exposed to the east in the 

San Rafael Swell, (2) the abundant limestone nodules, and 

(3) most significantly, the presence in these beds of distinctive well-rounded and polished stones which are probably 

gastroliths. Stokes (oral commun., 1980) suggested that 

these distinctive stones could serve as "index fossils" for 

Cedar Mountain strata. 

Paleontologic data 

Although Stokes was firm in his identification of 

the beds, we, along with others, have hesitated to accept 

his views pending supporting paleontologic evidence. We 

believe that we now have some evidence to support Stokes' 

identification of our lower unit as part of the Cedar 

Mountain Formation. 

Co-author Maley extensively sampled both our 

lower and upper units in the Red Rocks area for 

microfossils (fig. 1). Palynologist Gerald Waanders of 

Waanders Palynology Consulting, Inc., San Marcos, 

California identified and assigned ages to the forms listed 

in tables 2 and 3. Palynologist R. H. Tschudy of the U.S. 

Geological Survey reviewed the fossil lists. 

Most of the plant microfossils found in both units 

(tables 2 and 3) are long ranging; their assigned ages range 

from Jurassic to Cretaceous. Tschudy, who has just completed a comprehensive study of the Cedar Mountain 

and Burro Canyon Formations, reports (oral commun., 

1984) that of the palynomorphs that came from our lower 

unit (table 2), none are diagnostic of an Early Cretaceous age. On the other hand, Tschudy notes (oral commun., 1984) that three of the plant microfossils found 

in mudstone and black shale lenses interleaved in the 

coarse conglomerate beds that make up our upper unit 

(table 3) are indeed indicative of an Early Cretaceous age. 

Two forms, attributed by Waanders to Concavissimisporites punctatus and Pilosisporites trichopapillosus, 

range from Barremian to Aptian-Albian. In addition, 

Tschudy suggests that the microfossil identified by 

Waanders as Costatoperforosporites foveolatus is also 

diagnostic of the Early Cretaceous, and assigns this form 

an Aptian-Albian Age. 

Co-author Standlee sampled mudstone lenses intercalated in conglomerate beds exposed along the northwest 

flank of the Gunnison Plateau (fig. 1); they contained 

non-marine palynomorphs of late Albian age (Standlee, 

1982, p. 367). We believe that these conglomerate beds 

are correlative, in part, with the coarse conglomerate beds 

that make up our upper unit. 

Thus, our samples reveal that our upper unit contains plant microfossils unquestionably of Early 

Cretaceous age; diagnostic microfossils have not been 

found, as yet, in our lower unit. 

Although we have been unable to use plant microfossils to demonstrate an unequivocal Early Cretaceous 

age for our lower unit, some macrofossils found in Morrison(?) strata in the Red Rocks area do indicate that these 

strata are of that age. Bivalves, collected by P. J. 

Stuecheli, a graduate student at Ohio State University, 

were identified and dated by J. H. Hanley of the U.S. 

Geological Survey. Stuecheli (1984, p. 71) reports that: 

Bivalve specimens* * *collected * * *about 10m below the 

lowest of the major coarse conglomerate beds * * * have been 

identified as belonging to the freshwater Genus 

6 Age and Correlation of Cretaceous Rocks Previously Assigned to the Morrison(?) Formation, Utah 
PROTELL/PT/0, a form which ranges from the Barremian (Early 

Cretaceous) to the early Cenomanian (earliest Late 

Cretaceous)." 

The implication is strong, thus, that our lower unit is no 

older than Early Cretaceous. 

Consequently, we consider that both our units are 

Early Cretaceous in age. This coincides with the views 

of Stuecheli and Collinson (1984) who also believe that 

all Morrison(?) strata (that is, both our lower and upper 

units) are Early Cretaceous in age. Stuecheli and Collinson, however, retain the qualified term, "Morrison(?)," 

for these units, while recognizing that the Lower Cretaceous "Morrison(?) Formation" of central Utah is probably unrelated to the Upper Jurassic Morrison Formation of the Colorado Plateaus. 

Figure 1 shows our sample localities; tables 2 and 

3 contain our paleontologic data. As the site where coauthor Maley collected the microfossils is structurally 

complex and about 200 meters (600ft) from his measured 

section (Appendix A), we are unable to designate, on the 

measured section, beds that are correlative with those that 

contained the microfossils. In general, however, the fossiliferous units were in the lower part of our upper unit. 

CONCLUSIONS 

We cite below the factors that strongly influence us 

in our belief that our lower unit (of Spieker's Morrison(?) 

Formation) is correlative with the upper member of the 

Cedar Mountain Formation of Early Cretaceous age. 

The strata that compose our lower unit: 

1. Are strikingly similar, lithologically, to units 

that form the upper member of the Cedar 

Mountain Formation, as exposed in the San 

Rafael Swell, 

2. Contain distinctive, well-rounded and 

polished stones, possibly gastrolithsStokes' "index fossils" of the Cedar Mountain Formation, and 

3. Contain macrofossils that range from Barremian to Cenomanian (Steucheli, 1984, 

p. 71), implying that our lower unit is of 

Early Cretaceous age. 

If the variegated mudstone beds and intercalated 

units that make up our lower unit are indeed of Early 

Cretaceous age, many of the stratigraphic problems that 

so puzzled Spieker (1946, p. 125-126; 1949, p. 18-20) are 

resolved. Moreover, assigning these beds to the Cedar 

Mountain Formation rather than the Morrison Formation suggests that Morrison strata pinch out east, rather 

than west, of the Sanpete-Sevier Valley area, presumably 

somewhere beneath the Wasatch Plateau, as inferred by 

Stokes (1972, p. 26) and Standlee (1982, p. 367). 

Although we are uncertain about the correlation of 

the beds of coarse conglomerate that make up our upper 

unit, we believe, as do Stuecheli and Collinson (1984), that 

these conglomerate beds are not correlative with the Upper 

Jurassic Morrison Formation as exposed on the San 

Rafael Swell to the east. We believe that these conglomerate beds are of Early Cretaceous age, and either 

are a newly recognized lithologic unit at the top of the 

Table 2. Fossil content of samples collected from lower unit (variegated mudstones), Red 

Rocks area, southwest of Sterling, Utah 

[Samples collected by K. F. Maley. Paleontologic determinations by G. Waanders, Waanders Palynology 

Consulting, Inc., San Marcos, Calif., 92069] 

Sample 

No. 

2 

3 

Fossils identified 

Inferred 

Abundance age of 

sample 

Environment 

of 

deposition 

Classopollis classoides...... Rare..... Jurassic Nonmarine. 

to Early 

Cretaceous. 

?Eucommiidites minor......... • •• do.... • ••• do..... Do. 

Exesipollenites~lus...... • •• do.... • ••• do..... Do. 

Classopollis classoides...... Rare..... Jurassic 

to Early 

Cretaceous. 

Undifferentiated bisaccates.. Rare..... Indeterminate. 

Nonmarine. 

Indeterminate. 

4 Sample not collected ••••••••• 

5 Classopollis classoides...... Rare..... Jurassic 

to Early 

Cretaceous. 

Nonmarine. 

6 Classopollis classoides...... Rare..... Jurassic Nonmarine. 

to Early 

Cretaceous. 

Conclusions 7 
Table 3. Fossil content of samples collected from upper unit (conglomerate beds), Red Rocks 

area, southwest of Sterling, Utah 

[Samples collected by K. F. Maley. Paleontologic determinations by G. Waanders, Waanders Palynology 

Consulting, Inc., San Marcos, Calif., 92069] 

Inferred Environment 

Sample Fossils identified Abundance age of of 

No. sample deposition 

2c Apicula tisporis ~· Rare •••• Aptian to Nonmarine. 

Appendicisporites ~·············· ••• do ••• 

Araucariacites australis •••••••••••••• do ••• 

early Albian. 

•••••• do...... Do. 

• ••••• do...... Do. 

Cicatricosisporites australiensis ••••• do ••••••••• do...... Do. 

Cicatricos is porites hal lei......... • •• do... o ••••• do...... Do. 

Concavissimisporites punctatus •••••••• do ••••••••• do...... Do. 

Deltoidospora spp ••••••• o.......... . .. do •• o ...... do...... Do. 

Gleicheni idi tessenonicus.......... • •• do... • ••••• do...... Do. 

Lycopodiumsporites~·............ • •• do... • ••••• do...... Do. 

Osmundacidites ~·................ • •• do... • ••••• do...... Do. 

Pilosisporites trichopapillosus.... • •• do... • ••••• do...... Do. 

Undulatisporites ~·............... • •• do... • ••••• do...... Do. 

3c Araucariacites australis Rare •••• Probable Nonmarine. 

Aptian to 

?early Albian. 

Cos tatoperfor os porites foveola tus.. • •• do... • • o ••• do...... Do. 

4 Cicatricosisporites venustus ••••••• Rare •••• Early to Late Nonmarine. 

Cretaceous. 

Deltoidos para ~·................. • •• do... • ••••• do...... Do. 

Perotrilites sp ••••••••••••••••••••••• do ••••••••• do...... Do. 

?Sphagnum spp...................... • •• do... • ••••• do...... Do. 

Triporolites sp ••••••••••••••••••••••• do ••••••••• do...... Do. 

4a Deltoidospora ~·····••••••••••••• Rare •••• Indeterminate Nonmarine. 

?Schizos paris reticulata........... • •• do... • ••••• do...... Do. 

?Sphagnum spp...................... • •• do... • ••••• do...... Do. 

7 Deltoidospora ~· •• o.............. Rare.... Cretaceous ?Marginal 

marine. 

Spiniferites ramosus.(Microplankton) ••• do ••••••••• do...... Do. 

7a Chomotriletes fragilis ••••••••••••• Rare •••• Indeterminate IndeterCedar Mountain Formation, a conglomeratic facies of 

the undivided Indianola Group, or in part Cedar Mountain Formation and in part Indianola Group. 

The fossils collected from our lower unit indicate 

that it is no older than Early Cretaceous. Furthermore, 

all data suggest strongly that our lower unit is correlative 

with the upper part of the Cedar Mountain Formation. 

Consequently, we recommend that the strata that form 

our lower unit, previously assigned to the Upper Jurassic 

Morrison(?) Formation, henceforth be assigned to the 

Lower Cretaceous Cedar Mountain Formation. 

REFERENCES CITED 

Armstrong, R. L., 1968, Sevier orogenic belt in Nevada and 

Utah: Geological Society of America Bulletin, v. 79, 

p. 429-458. 

Craig, L. C., 1981, Lower Cretaceous rocks, southwestern 

Colorado and southeastern Utah, in Wiegand, D. L., ed., 

minate. 

Geology of the Paradox Basin: Guidebook, Rocky Mountain Association of Geologists, p. 195-200. 

Hale, L. A., and Van De Graff, F. R., 1964, Cretaceous 

stratigraphy and facies patterns-northeastern Utah and 

adjacent areas, in Sabatka, E. F., ed., Geology and mineral 

resources of the Uinta Basin: Guidebook, Intermountain 

Association of Petroleum Geologists, Thirteenth Annual 

Field Conference, p. 115-138. 

Harris, H. D., 1959, Late Mesozoic positive area in western 

Utah: American Association of Petroleum Geologists 

Bulletin, v. 43, p. 2636-2652. 

Hunt, R. E., 1950, Geology of the northern part of the Gunnison Plateau, Utah: Columbus, Ohio, Ohio State University, Ph. D. thesis, 267 p. 

Lawton, T. F., 1982, Lithofacies correlations within the Upper 

Cretaceous Indianola Group, central Utah, in Nielsen, D. 

L., ed., Overthrust belt of Utah: Utah Geological Association Publication 10, p. 199-213. 

Spieker, E. M., 1931, The Wasatch Plateau coal field, Utah: 

U.S. Geological Survey Bulletin 819, 210 p. 

8 Age and Correlation of Cretaceous Rocks Previously Assigned to the Morrison(?) Formation, Utah 
___ 1946, Late Mesozoic and early Cenozoic history of central 

Utah: U.S. Geological Survey Professional Paper 205-D, 

p. 117-161. 

___ 1949, The transition between the Colorado Plateaus and 

the Great Basin in central Utah: Utah Geological Society, 

Guidebook to the Geology of Utah, no. 4, 106 p. 

Spieker, E. M., and Reeside, J. B., Jr., 1926, The Upper Cretaceous shore line in Utah: Geological Society of America 

Bulletin, v. 37, p. 429-438. 

Standlee, L. A., 1982, Structure and stratigraphy of Jurassic 

rocks in central Utah: their influence on tectonic development of the Cordilleran foreland thrust belt, in Powers, R. 

B., ed., Geologic studies of the Cordilleran thrust belt: 

Guidebook, Rocky Mountain Association of Geologists, vol. 

1, p. 357-382. 

Stokes, W. L., 1944, Morrison Formation and related deposits 

in and adjacent to the Colorado Plateau: Geological Society 

of America Bulletin, v. 55, p. 951-992. 

Appendix A 

Section of Morrison(?) Formation in the Red Rocks area near 

Sterling, Utah (fig. 1) 

[Section extends northwestward from the NW 1/4, sec. 18, T. 19 S., R. 

2 E. into theSE 114, sec. 12, T. 19 S., R. 1 E. Measured by K. F. Maley] 

Sanpete(?) Formation, Indianola Group 

Sandstone, tan to yellowish-tan, thin-bedded, 

fine-grained, quartzose; grains chiefly subangular. Well sorted. Cemented by calcite; 

friable. Few well-rounded quartzite and 

Thickness 

Meters Feet 

limestone cobbles and boulders in basal part 23 75 

Morrison(?) Formation 

(Upper unit) 

Conglomerate and conglomeratic sandstone, 

reddish-brown. Composed chiefly of wellrounded cobbles and boulders of light-tan 

quartzite, reddish-purple quartzite, and 

dark-blue limestone. Matrix is reddishbrown, fine- to coarse-grained sandstone 

and mudstone. Few interleaved thin sandstone lenses. Cemented by limonite and 

calcite. Forms moderate to steep slopes, 

thinly veneered with loose well-rounded cobbles and boulders . . . . . . . . . . . . . . . . . . . . 236 775 

Total thickness of upper unit . . . . . . . . 236 775 

*U.S. GOVERNMENT PRINTING OFFICE: 1986-676-047:46004 

___ 1972, Stratigraphic problems of the Triassic and Jurassic 

sedimentary rocks of central Utah, in Plateau-Basin and 

Range Transition Zone, central Utah: Utah Geological Association Publication 2, p. 21-27. 

Stuecheli, P. J., 1984, The sedimentology, age, and depositional 

setting of the Morrison(?) Formation in central Utah: 

Columbus, Ohio, Ohio State University, M.S. thesis, 

101 p. 

Stuecheli, P. J., and Collinson, J. W., 1984, Sedimentology 

of synorogenic conglomerates of the Lower Cretaceous 

Morrison(?) Formation, central Utah: Geological Society of America Abstracts with Programs, v. 16, no. 3, 

p. 200. 

Witkind, I. J., 1983, Overthrusts and salt diapirs, central Utah: 

Geological Society of America Memoir 157, p. 45-59. 

Witkind, I. J., and Hardy, C. T., 1983, The Arapien Shale of 

central Utah-A dilemma in stratigraphic nomenclature: 

U.S. Geological Survey Bulletin 1537-A, p. A5-A20. 

Morrison(?) Formation-Continued 

(Lower unit) 

Mudstone, light-reddish-brown to reddishbrown, forms smooth rounded slopes . . . 14 45 

Conglomerate, reddish-brown. Interbedded 

thin lens of light reddish-brown shale . . . 2 5 

Mudstone, reddish-brown and variegated . . 9 30 

Conglomerate, reddish-brown . . . . . . . . . . . . 2 5 

Mudstone, light-reddish-brown to reddishbrown . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9 30 

Sandstone, light-reddish-brown, thin-bedded, 

quartzose, fine- to medium-grained . . . . . 3 10 

Mudstone, light-reddish-brown and variegated. 

Contains small, round, light-gray limestone 

nodules that also mantle surface . . . . . . . . . 12 40 

Shale, sandy, dark-gray to black . . . . . . . . . . . 2 7 

Mudstone, light-reddish-brown and variegated. 

Forms rounded slope partly covered by scree 53 174 

Limestone, light-gray to white, massive, aphanic 20 65 

Sandstone, light-tan to white, fine- to very fine 

grained; well sorted. Cemented by calcite. 

Cross-bedded. Few thin conglomerate lenses at 

base . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6 20 

(Base of section covered by unconsolidated 

deposits of sand and gravel.) 

Total thickness of lower unit . . . . . . . . 132 431 

Total thickness of exposed Morrison(?) 

Formation . . . . . . . . . . . . . . . . . . . . . . . 368 1,206 

Appendix A 9 




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