U.S. Department of the Interior 

U.S. Geological Survey

Geology of Paleozoic Rocks in the 

Upper Colorado River Basin in Arizona, 

Colorado, New Mexico, Utah, and Wyoming^ 

Excluding the San Juan Basin

Regional Aquifer-System Analysis

Professional Paper 1411-A ^M

UTAH

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Geology of Paleozoic Rocks in the 

Upper Colorado River Basin in Arizona, 

Colorado, New Mexico, Utah, and Wyoming, 

Excluding the San Juan Basin

By ARTHUR L. GELDON

REGIONAL AQUIFER-SYSTEM ANALYSISUPPER COLORADO RIVER BASIN, EXCLUDING SAN JUAN BASIN

U.S. GEOLOGICAL SURVEY PROFESSIONAL PAPER 1411-A

2003
U.S. DEPARTMENT OF THE INTERIOR 

GALE A. NORTON, Secretary

U.S. GEOLOGICAL SURVEY 

Charles G. Groat, 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

Version 1.0 2003

Library of Congress Cataloging-in-Publication Data

Geldon, Arthur L.

Geology of Paleozoic Rocks in the Upper Colorado River Basin in Arizona, Colorado, New Mexico, Utah, and Wyoming, Excluding 

the San Juan Basin / by Arthur L.Geldon.

p. cm. (Regional aquifer-system analysis Upper Colorado River Basin, Excluding the San Juan Basin) 

(U.S. Geological Survey professional paper ; 1411-A) 

Includes bibliographical references. 

Supt.ofDocs.no. : I 19.16 : 1407-A

1. Aquifers Upper Colorado River Basin. 2. Groundwater flow Upper Colorado River Basin. 3. Water Chemistry. 

I. Title. II. Series. III. Series : U.S. Geological Survey professional paper ; 1411-A. 

GB1199.3.S686W55 1997

551.49'0978 dc20 96-26992

CIP

For sale by U.S. Geological Survey, Information Services

Box 25286, Federal Center

Denver, CO 80225

ISBN = 0-607-88574-2
FOREWORD

THE REGIONAL AQUIFER-SYSTEM ANALYSIS PROGRAM

The Regional Aquifer-System Analysis (RASA) program represents a systematic effort to 

study a number of the Nation's most important aquifer systems which, in aggregate, underlie much 

of the country and which represent important components of the Nation's total water supply. In 

general, the boundaries of these studies are identified by the hydrologic extent of each system, and 

accordingly transcend the political subdivisions to which investigations have often arbitrarily been 

limited in the past. The broad objective for each study is to assemble geologic, hydrologic, and 

geochemical information, to analyze and develop an understanding of the system, and to develop 

predictive capabilities that will contribute to the effective management of the system. The use of 

computer simulation is an important element of the RASA studies to develop an understanding of 

the natural, undisturbed hydrologic system and the changes brought about by human activities, and 

to provide a means of predicting the regional effects of future pumping or other stresses.

The final interpretive results of the RASA program are presented in a series of U.S. 

Geological Survey Professional Papers that describe the geology, hydrology, and geochemistry of 

each regional aquifer system. Each study within the RASA program is assigned a single 

Professional Paper number beginning with Professional Paper 1400.

Charles G. Groat 

Director
CONTENTS

	Page

Foreword.......................................................................................................................................................... iv

Abstract............................................................................................................................................................ Al

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

Location of study.................................................................................................................................... 2

Previous investigations........................................................................................................................... 2

System of numbering wells and springs................................................................................................. 4

Acknowledgments.................................................................................................................................. 4

Geologic setting................................................................................................................................................ 4

Stratigraphic and hydrogeologic nomenclature...................................................................................... 4

Precambrian rocks.................................................................................................................................. 5

General Paleozoic stratigraphy............................................................................................................... 7

Mesozoic rocks....................................................................................................................................... 9

Structure................................................................................................................................................. 10

Stratigraphy of Paleozoic hydrogeologic units and related rocks.................................................................... 12

Flathead aquifer...................................................................................................................................... 13

Component geologic units............................................................................................................ 13

Contacts........................................................................................................................................ 16

Gros Ventre confining unit..................................................................................................................... 17

Component geologic units............................................................................................................ 19

Upper contacts.............................................................................................................................. 20

Bighorn aquifer....................................................................................................................................... 20

Component geologic units of Cambrian age................................................................................ 21

Component geologic units of Ordovician age.............................................................................. 22

Contacts........................................................................................................................................ 24

Elbert-Parting confining unit.................................................................................................................. 24

Component geologic units............................................................................................................ 24

Contacts........................................................................................................................................ 26

Madison aquifer...................................................................................................................................... 26

Redwall-Leadville zone................................................................................................................ 26

Component geologic units.................................................................................................. 28

Contacts.............................................................................................................................. 31

Darwin-Humbug zone.................................................................................................................. 32

Component geologic units.................................................................................................. 33

Contacts.............................................................................................................................. 34

Four Corners confining unit................................................................................................................... 34

Belden-Molas subunit................................................................................................................... 35

Component geologic units.................................................................................................. 36

Contacts.............................................................................................................................. 39

Paradox-Eagle Valley subunit..................................................................................................... 39

Component geologic units.................................................................................................. 42

Upper contacts.................................................................................................................... 44

Paleozoic rocks of the Strawberry Valley area ...................................................................................... 47

Canyonlands aquifer............................................................................................................................... 48

Cutler-Maroon zone..................................................................................................................... 50

Component geologic units.................................................................................................. 51

Contacts.............................................................................................................................. 60

Weber-De Chelly zone ................................................................................................................ 61

Component geologic units.................................................................................................. 62

Upper contacts.................................................................................................................... 66

Park City-State Bridge zone ........................................................................................................ 66
VI CONTENTS

Component geologic units ...................................................................................................... 67

Upper contacts......................................................................................................................... 73

Summary and conclusions ................................................................................................................................ 73

Selected references............................................................................................................................................ 76

PLATES

[Plates are in pocket]

PLATE 1. Geographic and structural features of the Upper Colorado River Basin and vicinity in Arizona, Colorado, New Mexico, Utah, and Wyoming.

2. Generalized geology of the Upper Colorado River Basin and vicinity in Arizona, Colorado, New Mexico, Utah, and Wyoming.

3. Thickness and depth to the top of the Paleozoic rocks that comprise hydrogeologic units in the Upper Colorado River Basin and vicinity 

in Arizona, Colorado, New Mexico, Utah, and Wyoming.

4. Precambrian and Mesozoic rocks in contact with Paleozoic rocks of the Upper Colorado River Basin in Arizona, Colorado, New Mexico, 

Utah, and Wyoming, excluding parts of the San Juan Basin.

5. Changes in stratigraphic nomenclature and lithology within the Paleozoic rocks of the Upper Colorado River Basin in Arizona, 

Colorado, New Mexico, Utah, and Wyoming, excluding parts of the San Juan Basin.

6. Stratigraphic nomenclature, thickness, and lithology of the Flathead aquifer in the Upper Colorado River Basin and vicinity in 

Arizona, Colorado, New Mexico, Utah, and Wyoming.

7. Depths to the top of the Flathead and Madison aquifers in the Upper Colorado River Basin and vicinity in Arizona, Colorado, 

New Mexico, Utah, and Wyoming.

8. Stratigraphic nomenclature, thickness, and lithology of the Gros Ventre confining unit in the Upper Colorado River Basin and vicinity 

in Arizona, Colorado, New Mexico, Utah, and Wyoming.

9. Stratigraphic nomenclature, thickness, and lithology of the Bighorn aquifer in the Upper Colorado River Basin and vicinity in Arizona, 

Colorado, New Mexico, Utah, and Wyoming.

10. Stratigraphic nomenclature, thickness, and lithology of the Elbert-Parting confining unit in the Upper Colorado River Basin and vicinity 

in Arizona, Colorado, New Mexico, Utah, and Wyoming.

11. Stratigraphic nomenclature, thickness, and lithology of the Redwall-Leadville zone of the Madison aquifer in the Upper Colorado 

River Basin and vicinity in Arizona, Colorado, New Mexico, Utah, and Wyoming.

12. Stratigraphic nomenclature, thickness, and lithology of the Darwin-Humbug zone of the Madison aquifer in the Upper Colorado River 

Basin and vicinity in Arizona, Colorado, New Mexico, Utah, and Wyoming.

13. Stratigraphic nomenclature, thickness, and lithology of the Belden-Molas subunit of the Four Corners confining unit in the Upper Colorado 

River Basin and vicinity in Arizona, Colorado, New Mexico, Utah, and Wyoming.

14. Stratigraphic nomenclature, thickness, and lithology of the Paradox-Eagle Valley subunit of the Four Comers confining unit in the 

Upper Colorado River Basin and vicinity in Arizona, Colorado, New Mexico, Utah, and Wyoming.

15. Stratigraphic nomenclature, thickness, and lithology of the Cutler-Maroon zone of the Canyonlands aquifer in the Upper Colorado River 

Basin and vicinity in Arizona, Colorado, New Mexico, Utah, and Wyoming.

16. Stratigraphic nomenclature, thickness, and lithology of the Weber-De Chelly zone of the Canyonlands aquifer in the Upper Colorado River 

Basin and vicinity in Arizona, Colorado, New Mexico, Utah, and Wyoming.

17. Stratigraphic nomenclature, thickness, and lithology of the Park City-State Bridge zone of the Canyonlands aquifer in the Upper Colorado 

River Basin and vicinity in Arizona, Colorado, New Mexico, Utah, and Wyoming.
CONTENTS VII

ILLUSTRATIONS

FIGURE 1. Map showing areas covered by representative geologic reports in the Upper Colorado River Basin and vicinity............................................. A3

2. Photograph showing rocks ranging in age from Proterozoic to Permian exposed along the Colorado River in the

Grand Canyon, Ariz.........................................................................................................................................»^ 7

3. Photograph showing near-vertical beds of quartzite in the Early and Middle Proterozoic Uncompahgre Formation overlain by

subhorizontal dolomite, shale, and sandstone of the Devonian Elbert Formation at Box Canyon Falls, Ouray, Colo....................................... 8

4. Photograph showing rocks ranging in age from Proterozoic to Pennsylvania exposed along the Green River at the eastern

end of the Uinta Mountains in Dinosaur National Monument, Colo.................................................................................................................... 8

5. Geologic section showing deformational styles in the Paradox Basin, Colo........................................................................................................ 11

6. Geologic section showing deformational styles in the Uinta Mountains in northwestern Colorado ................................................................... 12

7. Schematic section showing time transgression and intertonguing of facies in the Cambrian sedimentary rocks of Wyoming,

Utah, and Colorado................................................................................................................................................................................................. 13

8-11. Photographs showing:

8. Cambrian Flathead Sandstone at Rawlins, Wyo.............................................................................................................................................. 14

9. Cambrian Tintic Quartzite at the base of a cliff on the west side of the Duchesne River, western Uinta Mountains, Utah........................ 15

10. Cambrian Sawatch Quartzite in Glenwood Canyon, Colo.............................................................................................................................. 15

11. Cambrian Ignacio Quartzite at Coalbank Pass in the San Juan Mountains, Colo.......................................................................................... 16

12. Stratigraphic section showing relations among lower and middle Paleozoic rocks, Wind River Mountains to Sierra Madre, Wyo.................. 17

13. Stratigraphic section showing relations among Cambrian formations in southwestern Colorado and southeastern Utah................................... 18

14-18. Photographs showing:

14. Cambrian Gros Ventre Formation in the channel of Clear Creek, a tributary of the Green River near the northwestern end

of the Wind River Mountains, Wyo................................................................................................................................................................. 19

15. Cambrian Dotsero Formation overlain by Ordovician Manitou Dolomite in Glenwood Canyon, Colo....................................................... 21

16. Ordovician Bighorn Dolomite (cliff-forming unit) in the Salt River Range of the Overthrust Belt in Wyoming........................................ 23

17. Devonian and Mississippian Darby Formation and Mississippian Lodgepole Limestone on the upthrown side of the Hoback Fault,

at the juncture of the Gros Ventre and Hoback Ranges in Hoback Canyon, Wyo........................................................................................ 25

18. Devonian Parting Formation in fault contact with Ordovician Manitou Dolomite in Glenwood Canyon at

Glenwood Springs, Colo.................................................................................................................................................................................. 26

19. Map showing extent of lithologic subdivisions of the Elbert Formation in the Upper Colorado River Basin..................................................... 27

20. Diagram showing depositional model for Mississippian carbonate formations in Wyoming.............................................................................. 29

21. Photograph showing cavernous Mississippian Leadville Limestone in Glenwood Canyon at Glenwood Springs, Colo.................................... 30

22. Map showing pre-Mississippian geology in Wyoming ........................................................................................................................................ 32

23. Schematic section showing Stratigraphic relations in the Darwin-Humbug zone of the Madison aquifer........................................................... 34

24. Stratigraphic section showing relations among Pennsylvanian and Permian formations in northwestern Colorado........................................... 37

25. Photograph showing Pennsylvanian Molas Formation at its type locality, Molas Lake in the San Juan Mountains, Colo................................ 38

26. Photograph showing Pennsylvanian Belden Formation at Ruedi Reservoir on the Fryingpan River southeast of

Glenwood Springs, Colo......................................................................................................................................................................................... 38

27. Photograph showing lower member of the Pennsylvanian Hermosa Formation north of Durango, Colo........................................................... 39

28. Stratigraphic section showing relations among Pennsylvanian and Permian formations in southeastern Utah................................................... 40

29. Photograph showing bedded gypsum and gypsiferous mudstone overlain by sandstone in the Pennsylvanian

Eagle Valley Evaporite near Eagle, Colo............................................................................................................................................................... 42

30. Map and schematic section showing distribution of depositional facies in the Eagle Valley Evaporite and contemporaneous

Pennsylvanian formations, northwestern Colorado................................................................................................................................................ 44

31. Photograph showing Pennsylvanian Hermosa Formation exposed in the Goosenecks of the San Juan River west of

Mexican Hat, Utah.................................................................................................................................................................................................. 45

32. Geologic section showing stratigraphy and structure in Strawberry Valley area, Utah....................................................................................... 48

33. Photograph showing interbedded sandstone, shale, and dolomite in the Pennsylvanian Minturn Formation at Vail, Colo................................ 52

34. Stratigraphic section showing relations among Pennsylvanian and Permian clastic geologic units in west-central Colorado ........................... 53

35. Photograph showing interbedded sandstone and conglomerate in the Pennsylvanian Gothic Formation (of Langenheim, 1952)

on the Crystal River south of Carbondale, Colo. .................................................................................................................................................. 54

36. Photograph showing Pennsylvanian, Permian, and Triassic formations in the Eagle River valley near Eagle, Colo......................................... 55

37. Fence diagram showing relations among Permian formations in southwestern Colorado and southeastern Utah.............................................. 56
VIH CONTENTS

38-43. Photographs showing:

38. Arkosic conglomerate, sandstone, and sandy siltstone hi the Permian Cutler Formation along the Uncompahgre River

in the San Juan Mountains, north of Ouray, Colo. ....................................................................................................................................... 57

39. Permian Cedar Mesa Sandstone and Organ Rock Shale (of Baars, 1962) at Natural Bridges National Monument, Utah ......................... 58

40. Permian Organ Rock Shale (of Baars, 1962) and De Chelly Sandstone in Monument Valley, Utah........................................................... 59

41. Normal fault in the upper plate of the Darby Thrust Fault exposed by the Snake River as it cuts through the Salt River Range

at Astoria Hot Springs, southwest of Jackson, Wyo. ..................................................................................................................................... 62

42. Pennsylvanian Tensleep Sandstone overlain by interbedded carbonate rocks and sandstone of the Permian Park City Formation,

east flank of Wind River Mountains, northwest of Dubois, Wyo. ................................................................................................................. 62

43. Northeast-dipping beds of Pennsylvanian and Permian Weber Sandstone hi Irish Canyon, Colo., at the eastern end

of the Uinta Mountains.................................................................................................................................................................................... 63

44. Stratigraphic section showing facies changes within the Weber Sandstone and Maroon Formation in Utah and Colorado .............................. 64

45. Stratigraphic section showing relations among Permian formations in southeastern Utah .................................................................................. 65

46. Photograph showing Pennsylvanian Tensleep Sandstone and Permian to Triassic Goose Egg Formation dipping

northeasterly in the upper plate of the Bell Springs Thrust Fault, north of Rollins, Wyo.................................................................................... 67

47. Stratigraphic section showing relations among Permian formations hi southwestern Wyoming......................................................................... 68

48. Photograph showing Permian lower part of the State Bridge Formation underlain by Permian Schoolhouse Member of the

Maroon Formation and overlain by Mesozoic rocks on South Canyon Creek west of Glenwood Springs, Colo. ............................................. 69

49. Stratigraphic section showing relations among Permian and Triassic formations in the Uinta Mountains and Wasatch Range, Utah.............. 70

50. Stratigraphic section showing relations among Permian formations in the western part of the Upper Colorado River Basin,

Arizona, Utah, and Wyoming................................................................................................................................................................................. 71

51. Photograph showing Permian Kaibab Formation in Marble Canyon, Ariz........................................................................................................... 72

TABLES

TABLE 1. Generalized Stratigraphic and hydrogeologic nomenclature of Precambrian, Paleozoic, and lower Mesozoic rocks in the

Upper Colorado River Basin .................................................................................................................................................................... [in pocket]

2. Stratigraphic nomenclature for the Pennsylvanian System in the Paradox Basin................................................................................................. 46
CONTENTS IX

METRIC CONVERSION FACTORS

Multiply By To obtain

acre

acre-foot (acre-ft)

acre-foot per year (acre-ft/yr)

cubic foot per second per mile ((ft3s)/mi)

foot (ft)

foot per day (ft/d)

foot per year (ft/yr)

foot squared per day (ft2/d)

gallon per minute (gal/min)

inch (in.)

inch squared (in.2 )

mile (mi)

square foot (ft2 )

square mile (mi2 )

0.4047

0.001233

1,233.0

0.001233

0.04557

0.3048

30.48

0.3048

0.3048

0.09290

0.06309

2.540

25.40

6.452

1.609

0.0929

2.590

hectare (h)

cubic hectometer (hm3 )

cubic meter (m3 )

cubic hectometer per year (hm3/yr)

cubic meter per second per kilometer

((m3/s)/km)

meter (m)

centimeter (cm)

meter per day

meter per year (m/yr)

meter squared per day (m2/d)

liter per second (L/s)

centimeter (cm)

millimeter (mm)

centimeter squared (cm2 )

kilometer (km)

square meter (m2 )

square kilometer (km2 )

A millidarcy is 0.987 x 10" 11 centimeter squared. Temperature in degrees Fahrenheit (°F) can be converted to temperature in degrees Celsius (°C) by using the following equation:

°C = 5/9 (°F-32)

ALTITUDE DATUM

Altitudes in this report are referenced to the National Geodetic Vertical Datum of 1929 (NGVD of 1929) a geodetic 

datum derived from a general adjustment of the first-order level nets of the United States and Canada, formerly called Sea Level 

Datum of 1929, or mean sea level.
REGIONAL AQUIFER-SYSTEM ANALYSIS UPPER COLORADO RIVER BASIN IN ARIZONA, COLORADO, NEW 

MEXICO, UTAH, AND WYOMING, EXCLUDING THE SAN JUAN BASIN

GEOLOGY OF PALEOZOIC ROCKS IN THE

UPPER COLORADO RIVER BASIN IN ARIZONA,

COLORADO, NEW MEXICO, UTAH, AND WYOMING,

EXCLUDING THE SAN JUAN BASIN

By Arthur L. Geldon

ABSTRACT

The geology of the Paleozoic rocks in the Upper Colorado River Basin in 

Arizona, Colorado, New Mexico, Utah, and Wyoming, was studied as part of 

the U.S. Geological Survey's Regional Aquifer-System Analysis Program to 

provide support for hydrogeological interpretations. The study area is segmented by numerous uplifts and basins caused by folding and faulting that 

have recurred repeatedly from Precambrian to Cenozoic tune.

Paleozoic rocks in the study area are 0-18,000 feet thick. They are underlain by Precambrian igneous, metamorphic, and sedimentary rocks and are 

overlain in most of the area by Triassic formations composed mostly of shale. 

The overlying Mesozoic and Tertiary rocks are 0-27,000 feet thick.

All Paleozoic systems except the Silurian are represented in the region. 

The Paleozoic rocks are divisible into 11 hydrogeologic units.

The basal hydrogeologic unit consisting of Paleozoic rocks, the Flathead 

aquifer, predominantly is composed of Lower to Upper Cambrian sandstone 

and quartzite. The aquifer is 0-800 feet thick and is overlain gradationally to 

unconformably by formations of Cambrian to Mississippian age.

The Gros Ventre confining unit consists of Middle to Upper Cambrian 

shale with subordinate carbonate rocks and sandstone. The confining unit is 

0-1,100 feet thick and is overlain gradationally to unconformably by formations of Cambrian to Mississippian age.

The Bighorn aquifer consists of Middle Cambrian to Upper Ordovician 

limestone and dolomite with subordinate shale and sandstone. The aquifer is 

0-3,000 feet thick and is overlain unconformably by Devonian and Mississippian rocks.

The Elbert-Parting confining unit consists of Lower Devonian to Lower 

Mississippian limestone, dolomite, sandstone, quartzite, shale, and anhydrite. 

It is 0-700 feet thick and is overlain conformably to unconformably by Upper 

Devonian and Mississippian rocks.

The Madison aquifer consists of two zones of distinctly different lithology. 

The lower (Redwall-Leadville) zone is 0-2,500 feet thick and is composed 

almost entirely of Upper Devonian to Upper Mississippian limestone, dolomite, and chert. The overlying (Darwin-Humbug) zone is 0-800 feet thick 

and consists of Upper Mississippian limestone, dolomite, sandstone, shale, 

gypsum, and solution breccia. The Madison aquifer is overlain conformably 

by Upper Mississippian and Pennsylvanian rocks.

The Madison aquifer in most areas is overlain by Upper Mississippian to 

Middle Pennsylvanian rocks of the Four Corners confining unit. The lower

part of this confining unit, the Belden-Molas subunit, consists of as much as 

4,300 feet of shale with subordinate carbonate rocks, sandstone, and minor 

gypsum. The upper part of the confining unit, the Paradox-Eagle Valley 

subunit, in most places consists of as much as 9,700 feet of interbedded 

limestone, dolomite, shale, sandstone, gypsum, anhydrite, and halite. Locally, 

the evaporitic rocks are deformed into diapirs as much as 15,000 feet thick. 

The Four Corners confining unit is overlain gradationally to disconformably 

by Pennsylvanian rocks.

The uppermost Paleozoic rocks comprise the Canyonlands aquifer, which 

is composed of three zones with distinctly different lithologies. The basal 

(Cutler-Maroon) zone consists of as much as 16,500 feet of Lower Pennsylvanian to Lower Permian sandstone, conglomerate, shale, limestone, dolomite, 

and gypsum. The middle (Weber-De Chelly) zone consists of as much as 

4,000 feet of Middle Pennsylvanian to Lower Permian quartz sandstone with 

minor carbonate rocks and shale. The upper (Park City-State Bridge) zone 

consists of as much as 800 feet of Lower to Upper Permian limestone, dolomite, shale, sandstone, phosphorite, chert, and gypsum. The Canyonlands 

aquifer is overlain disconformably to unconformably by formations of Triassic 

and Jurassic age.

INTRODUCTION

In anticipation of increased water use for the development of 

local coal and oil resources and to meet the water needs of an 

expanding population, the U.S. Geological Survey from 1981 to 

1990 systematically appraised the ground-water resources of 

the Upper Colorado River Basin (UCRB). According to Taylor 

and others (1983, 1986), specific objectives of this study 

(henceforth referred to as the UCRB-RASA) included:

1. Identification of aquifers and confining units among consolidated sedimentary rocks of Cambrian to Tertiary age;

2. Determination of the extent, thickness, and hydrologic 

characteristics of aquifers and confining units;

3. Determination of the availability of water from the 

aquifers;

Ai
A2 REGIONAL AQUIFER SYSTEM ANALYSIS UPPER COLORADO RIVER BASIN

4. Determination of the geochemical characteristics of the 

ground water;

5. Analysis of the regional flow system under steady-state 

conditions; and

6. Analysis of the flow-system responses to hypothetical 

ground-water withdrawal or injection.

The regional analysis of the Upper Colorado River Basin is 

described in the several chapters of USGS Professional Paper 

1411. The UCRB-RASA is one of several U.S. Geological 

Survey RASA studies nationwide, as discussed in the foreword 

to this report.

Because the occurrence, movement, and chemical quality of 

water in the region are in large part controlled by the structure 

and stratigraphy of the host rocks, a lengthy analysis was made 

of the stratigraphy of the Paleozoic rocks in the UCRJB. This 

analysis attempted to (1) correlate stratigraphic units from area 

to area; (2) clarify problems of ill-defined geologic unit boundaries in areas where differing schemes of stratigraphic nomenclature come together; and (3) provide a lithological basis for 

grouping a large number of geologic units into a relatively 

small number of hydrogeologic units (aquifers and confining 

units). This report describes the extent, thickness, lithology, 

and contact relations of the Paleozoic rocks in the UCRJB, as related to their occurrence in hydrogeologic units listed in plate 

1. This report also describes the Precambrian and Triassic 

rocks in contact with the Paleozoic rocks. Sources for the 

stratigraphic material used for interpretation include unpublished logs of petroleum industry boreholes prepared by the 

American Stratigraphic Company, lithologic logs of damsite 

exploration holes provided by the U.S. Bureau of Reclamation 

(written commun., 1983-85), and measured sections and other 

information from numerous geologic reports cited in the text 

and listed in the "Selected References" section.

LOCATION OF STUDY

The UCRJB, as defined by the Colorado River Compact of 

1922, encompasses the drainages of the Green and Colorado 

Rivers above the mouth of the Paria River at Lees Ferry, Ariz., 

and the internally drained Great Divide Basin of Wyoming. 

The UCRJB includes about 113,500 mi2 of land in western Colorado, eastern Utah, southwestern Wyoming, northeastern Arizona, and northwestern New Mexico. Because most of the San 

Juan Basin, an area of about 14,600 mi2, was excluded for separate investigation, this report does not cover most of the land 

in New Mexico and some of the land in southwestern Colorado 

and northeastern Arizona that are in the San Juan Basin region 

of the UCRB. However, the RASA study area includes some 

land peripheral to the UCRJB from which geologic and hydrologic information was obtained to support interpretations. The 

area of the UCRB-RASA is about 100,000 mi2 .

The UCRJB, including the San Juan Basin, extends from latitude 35°46' N. to latitude 43°27' N. and from longitude

105°38' W. to longitude 112° 19' W. Maximum dimensions of 

this area are about 560 mi from north to south and about 320 mi 

from east to west. Principal towns in the UCRB include Grand 

Junction, Montrose, Delta, Paonia, Glenwood Springs, Aspen, 

Craig, Steamboat Springs, Meeker, Gunnison, Cortez, and Durango, Colo.; Price, Vernal, Manila, Moab, Monticello, and 

Blanding, Utah; Rock Springs, Green River, Pinedale, and 

Kemmerer, Wyo.; Page and Kayenta, Ariz.; and Shiprock and 

Farmington, N. Mex.

PREVIOUS INVESTIGATIONS

Since the pioneering geologic work of the Powell, Hayden, 

Wheeler, and King surveys of the 1860's and 1870's, numerous 

geologic studies have been made in parts of the UCRJB, particularly in the Colorado Plateaus province and in the Uinta 

Mountains. Areas described in some of the more important literature are shown in figure 1.

Particularly useful in this investigation were reports that contained regional, subregional, or statewide syntheses of geologic 

information. Notable among these efforts is the Geologic Adas 

of the Rocky Mountain Region, published in 1972 by the Rocky 

Mountain Association of Geologists. Organized by stratigraphic system, papers in this atlas by Lochman-Balk (Cambrian), 

Foster (Ordovician), Baars (Devonian), Craig (Mississippian), 

Mallory (Pennsylvanian), and Rascoe and Baars (Permian) 

contain extensive discussions of stratigraphic relations between, and the depositional history of, Paleozoic stratigraphic 

units. Updates of this information for the State of Colorado 

were provided in papers by Ross and Tweto, De Voto, and 

Maughan compiled in the book "Colorado Geology," published 

in 1980 by the Rocky Mountain Association of Geologists. The 

stratigraphy of Utah is discussed in some detail by Hintze 

(1973); the stratigraphy of Arizona is discussed cursorily by 

Wilson (1962). A book entitled "Rocky Mountain Sedimentary 

Basins," published in 1965 by the American Association of 

Petroleum Geologists, is a compilation of papers on the depositional and tectonic history of areas within and peripheral to 

the UCRB, including the Overthrust Belt (Armstrong and Oriel, 

1965), Kaiparowits and Black Mesa Basins (Lessintine, 1965), 

Paradox Basin (Ohlen and Mclntyre, 1965), Uinta Basin (Osmond, 1965), San Juan Basin (Peterson and others, 1965), 

Piceance and Eagle Basins (Quigley, 1965), and Oquirrh Basin 

(Roberts and others, 1965). For the Colorado Plateaus province 

alone, a 1983 book by Baars entitled, "The Colorado Plateau 

a geologic history," contains the most comprehensive regional 

synthesis of previously published discussions of Paleozoic 

stratigraphy and geologic history.

Many subregional syntheses of information on the Paleozoic 

rocks were reviewed during the UCRB-RASA. Representative 

of these reports are studies by Baars (1958), Cooper (1960), 

Parker and Roberts (1963), Benson (1966), Campbell (1972), 

Gerhard (1972), Middleton and others (1980), and Ross (1986)
GEOLOGY OF PALEOZOIC ROCKS, UPPER COLORADO RIVER BASIN A3

108°

107°

SOU^DAiW OF

UFPSH COLORADO''

RIVER BASN

Richmond 

(1945)

Branson

and Branson

(1941)

Armstrong 

43° Oriel

Rubey 

and others

Anderman 956'WYOMING

r^-iif Hansen1, v Levering

and 

ioddard 

(1950)

3weto and 

-jLovering \105 

1)977)

Singewald 

(1951)

othersM Hunt\Witkind V41933)

Gregory 

ahd Moore

,Lipman >-=-- Luedke and Lewis 

and.

\ Campbtel 

IT1965K

.

fothers (19641 0 Sulliv

Witkihd and 

Thaden (1963)

Baker and 

Crittenden (1961); 

Baker (1964, 1972, 40'

1973,1976)

Doelling 

(1975) x

Gregory'- 

(1951)

Wanek' 

t and Stephens 

"Vr. (1953)

Ekten ) [7][ 7^ A

and Houser fW,,,.;,-^--' > ' J 

..^..,^-:<1.965i__Jj'±''Jl':lk»;S. '' 

<S,pShtrocJ; / j^' x

'jregor^i ^^ ""^ - 

(1938)] | MEXICO

(1956)

ARIZONA K.,s

'^JI i 

Cooley and others (1969); 

Irwin and others (1971)

Peterson \ 

and others 

r (1965)

25 50 75

I

100 MILES

I"' 11 I T

0 25 50 75 100 KILOMETERS

FIGURE 1. Areas covered by representative geologic reports in the Upper Colorado River Basin and vicinity (areas of overlap not

shown).
A4 REGIONAL AQUIFER SYSTEM ANALYSIS UPPER COLORADO RIVER BASIN

on the Cambrian to Mississippian rocks; reports by Conley 

(1972), Nadeau (1972), Rose (1977), Mallory (1979), McKee 

(1979), Roberts (1979), and Sando (1979) on the Mississippian 

rocks; and reports by Langenheim (1952, 1954), Wengerd and 

Strickland (1954), Wengerd (1957, 1958), Kunkel (1958, 

1960), McKelvey and others (1959), Merrill and Winar (1961), 

Read and Wanek (1961), Baars (1962, 1979), Kirkland (1963), 

Boggs (1966), Hallgarth (1967), Mallory (1967, 1971, 1975), 

Maughan (1967, 1979), McKee (1967, 1975, 1982), Sheldon 

and others (1967), Freeman (1971), Bartleson (1972), De Voto 

(1972), Hite and Cater (1972), Sando and others (1975), 

Freeman and Bryant (1977), Irtem (1977), Welsh and others, 

(1979), Steele-Mallory (1982), De Voto and others (1986), 

Dodge and Bartleson (1986), Johnson (1987, 1989), and 

Johnson and others (1990) on the Pennsylvanian and Permian 

rocks.

SYSTEM OF NUMBERING WELLS AND SPRINGS

Wells and springs are numbered in this report according to 

the U.S. Bureau of Land Management system. The first one or 

two letters in the site-identification number represent the principal survey meridian. The UCRB is referenced to seven principal survey meridians; symbols adopted for these meridians in 

this report are

G - Gila and Salt River

N - Navajo 

NM - New Mexico 

S - Sixth

SL - Salt Lake

U - Uintah 

UT-Ute

Letters and numbers following the symbol for the principal 

survey meridian in the site identification number refer, in order, 

to quadrant, township, range, section, quarter section, quarterquarter section, quarter-quarter-quarter section, and number of 

well or spring within the smallest physical boundary (multiple 

ground-water sites within the smallest physical boundary are 

numbered consecutively). Quadrants and divisions of sections 

are labeled from A to D in a counter-clockwise direction starting with the northeast quadrant or section division. Quadrant 

designations usually are upper case; section division designations usually are lower case. Zeros or dashes are used to separate quadrant, township, range, and section designations. As an 

example, a well numbered SC06-89-09bda! is the first well in 

the northeast quarter of the southeast quarter of the northwest 

quarter of Section 9, Township 6 South, Range 89 West, in the 

southwest quadrant of the Sixth principal survey meridian.

ACKNOWLEDGMENTS

The author is indebted to Charles (Chuck) Spencer, U.S. 

Geological Survey, who helped gain access to the unpublished

petroleum-industry logs used in this report, and to the U.S. 

Bureau of Reclamation (Denver, Grand Junction, and Salt Lake 

City offices) for providing unpublished exploration-hole logs.

GEOLOGIC SETTING

Exposed rocks in the Upper Colorado River Basin range in 

age from Precambrian to Tertiary (pi. 2). Precambrian sedimentary, metamorphic, and igneous rocks crop out in the center 

of uplifted areas. Paleozoic rocks also crop out in uplifted 

areas. Mesozoic rocks have widespread surface exposure, 

particularly in the southern part of the area. Tertiary sedimentary rocks crop out extensively in structural basins north of the 

Uncompahgre Plateau. Tertiary intrusive and extrusive rocks 

are widespread in the Colorado Plateaus and Southern Rocky 

Mountains.

STRATIGRAPHIC AND HYDROGEOLOGIC 

NOMENCLATURE

The extent, thickness, and lithology of Paleozoic rocks described in this report (table 1, oversize) were determined from 

examination of more than 700 lithologic logs of oil and gas 

wells and exploratory boreholes (American Stratigraphic Co., 

unpublished), lithologic logs of damsite boreholes (U.S. 

Bureau of Reclamation, unpublished), and more than 200 published surface Stratigraphic sections. Data sites generally were 

selected at intervals of 10 to 20 mi for compiling Stratigraphic 

information on maps and correlation diagrams. More widely 

spaced intervals were used in areas of sparse data, particularly 

in the deep structural basins of Wyoming and Utah. In thrustfaulted areas, such as the Overthrust Belt (pi. 1), part or all of a 

geologic formation can be repeated two or more times 

vertically. In these areas, fault-repeated beds were not included 

in calculating thicknesses of Paleozoic strata and depths to the 

top of the Paleozoic rocks.

Formation tops and bottoms were picked by tracing 

lithologic intervals between boreholes and measured sections 

plotted at vertical scales ranging from 1:1,200 to 1:4,800 

(depending on total plotted thickness). The Paleozoic column 

was divided into three vertical intervals for correlation. These 

intervals (see table 1) were (1) the top of the Weber-De Chelly 

zone of the Canyonlands aquifer to the top of the Paleozoic 

rocks; (2) the top of the Redwall-Leadville zone of the Madison 

aquifer to the bottom of the Weber-DeChelly zone; and (3) the 

top of the Precambrian rocks to the bottom of the RedwallLeadville zone. In many instances, formation tops and bottoms 

identified on geologic logs were reinterpreted.

The areal extent of individual formations, as mapped in 

this study, may differ from interpretations shown in other 

reports for some areas. Existing Stratigraphic nomenclature 

in the UCRB is the result of over 100 years of geological
GEOLOGY OF PALEOZOIC ROCKS, UPPER COLORADO RIVER BASIN A5

investigation. One unfortunate result of numerous individual 

geologic efforts in isolated parts of the UCRB over this long 

period of time has been a system of nomenclature that varies 

from geographic area to geographic area without any consistent basis for recognized name changes within correlative 

stratigraphic sequences. Many name changes are based on 

facies changes of local extent; some merely reflect the limits 

of geographically preferred terms within a homogeneous 

stratigraphic sequence. Some name changes are based on inferred depositional history; others are based on relatively 

small variations in the age of a homogeneous stratigraphic 

sequence.

Formations cited in this report are lithostratigraphic units, as 

defined by the North American Stratigraphic Code (North 

American Commission on Stratigraphic Nomenclature, 1983, 

p. 855-856). According to this code, lithostratigraphic units 

are recognizable only on the basis of observable rock characteristics; they cannot be based on inferred geologic history, depositional environment, or biological sequence. Nor do " * * * 

inferred time-spans, however measured, play [any] part in differentiating or determining the boundaries of any lithostratigraphic unit * * *. The body [of the unit] in some places may 

be entirely younger than hi other places," provided it does not 

contain identifiable regional unconformities. Many of the previously established criteria for delimiting Paleozoic formations 

in the study area do not conform to this code.

An attempt was made in compiling stratigraphic information 

during this study to preserve as many of the long-established 

geologic names as possible but in such a manner that name 

changes within correlative stratigraphic sequences had a consistent basis. Accordingly, formation boundaries within correlative sequences were demarcated in this report on the basis of 

(1) an identifiable lithologic variation, or (2) an identifiable 

boundary between depositional centers. The term "equivalent" 

was used where geologic formations were correlated on the 

bases of borehole lithologic logs, but where paleontological 

and other information necessary for unequivocal stratigraphic 

designation was lacking. For example, in southwestern Colorado, rocks similar to the Bright Angel Shale and Muav Limestone, respectively, are designated "Bright Angel equivalent" 

and "Muav equivalent." Some of the geologic names used in 

this report are not used by the U.S. Geological Survey (USGS) 

but are used widely by academic and industry geologists in 

parts of the UCRB. These names were felt to be more useful 

for regional correlation and discussion than names accepted by 

the USGS. Sources for names not accepted by the USGS are 

cited where these names appear throughout the report.

Two types of correlative sequences were recognized: (1) 

Sequences of essentially homogeneous lithology that are 

slightly time-transgressive; and (2) sequences of diverse 

lithology that represent a depositional trend within an 

essentially integral time horizon. Examples of the first type of 

lithologic sequence include the basal Cambrian IgnacioTapeats - Tintic - Lodore - Sawatch - Flathead sandstone and

quartzite sequence; the Mississippian Leadville-RedwallMadison-Lodgepole-Mission Canyon limestone and dolomite 

sequence; and the Pennsylvanian and Permian De ChellyCoconino-White Rim - Weber - Wells - Tensleep sandstone 

sequence (table 1). Examples of the second type of sequence 

include the mostly Devonian Elbert-Parting-Darby carbonateclastic sequence; the Mississippian and Pennsylvanian 

Paradox-Manakacha-Round Valley-Eagle Valley-Moffat Trail 

carbonate-evaporite-clastic sequence; and the Permian KaibabToroweap-Park City-Phosphoria-lower State Bridge-lower 

Goose Egg carbonate-clastic sequence (table 1).

Because the information in this report was compiled for an 

analysis of ground-water flow systems, stratigraphic sequences 

are grouped into hydrogeologic units for mapping and discussion. A hydrogeologic unit in this report is defined as a group 

of geologic formations or members of formations that are related stratigraphically and share hydrologic properties that are 

similar or vary systematically as a result of changing depositional environments. Hydrogeologic units listed in table 1 include aquifers, confining units, and their subdivisions (zones 

and subunits). They consist of either a single correlative sequence, such as those described in the previous paragraph, or 

several correlative sequences. The second type of hydrogeologic unit is represented by the Cutler-Maroon zone of the Canyonlands aquifer, which consists of a sequence of interbedded 

carbonate and clastic rocks (the upper member of the Hermosa 

Formation and equivalents) overlain by a sequence of red beds 

(the Cutler Group, Maroon Formation, and equivalents).

Hydrogeologic unit information was compiled initially on 

1:1,000,000-and 1:2,000,000-scale maps. A 10 mix 10 mi grid 

was placed over each l:2,000,000-scale map of the individual 

hydrogeologic units, and the grid-center thicknesses were added 

to determine the total thickness of Paleozoic rocks at each grid 

center. Grid-center total thicknesses were contoured to determine the regional distribution of the Paleozoic rocks. A similar 

method combining data for Mesozoic and Tertiary rocks was 

used to determine depths to the top of the Paleozoic rocks, the 

top of the Madison aquifer, and the top of the Flathead aquifer 

throughout the region. Variations in the thickness of the Paleozoic rocks and depths to the top of these rocks in the UCRB 

and vicinity are shown on plate 3.

PRECAMBRIAN ROCKS

The Precambrian rocks in the UCRB consist mostly of unnamed metamorphic and plutonic rocks of Archean and Proterozoic age (pi. 4). Proterozoic sedimentary rocks are 

preserved in a few areas (table 1).

The Archean rocks are part of the Wyoming cratonic 

province (Karlstrom and others, 1987, fig. 1), that extends from 

the Yellowstone region and Beartooth Mountains on the 

Montana-Wyoming border south to the northern Sierra Madre 

and the north flank of the Uinta Mountains (Hedge and others,
A6 REGIONAL AQUIFER SYSTEM ANALYSIS UPPER COLORADO RIVER BASIN

1986. fig. 1). The southern boundary of this province, the 

Cheyenne Belt (pi. 1), is an arcuate band of thrust faulting, 

recumbent folding, and mylonitization, which Duebendorfer 

and Houston (1987, p. 566) interpreted as a zone of crustal 

accretion along a passive continental margin. North of the 

Cheyenne Belt in Wyoming, the Archean rocks consist of a 

granite-gneiss complex overlain by a supracrustal sequence of 

quartzite, metagraywacke, metaconglomerate, slate, phyllite, 

schist, iron-formation, serpentinite, greenstone, and amphibolite. These metamorphic rocks are intruded by granite, granodiorite, quartz diorite, diorite, and gabbro plutons (Love and 

Christiansen, 1985; Hedge and others, 1986, Duebendorfer and 

Houston, 1987). On the north flank of the Uinta Mountains, the 

Red Creek Quartzite consists of intensely fractured quartzite, 

subordinate quartz-mica schist and amphibolite, and minor 

calc-silicate rock, marble, metagraywacke, and pegmatite 

(Hansen, 1965b, p. 22-32). The Red Creek Quartzite is approximately 2.5 billion years old and more than 20,000 ft thick 

(Hedge and others, 1986;Tweto, 1987). In Wyoming, Archean 

metamorphic rocks are 2.6 to 3.0 billion years old, whereas the 

plutonic rocks are 2.6 to 2.7 billion years old (Love and 

Christiansen, 1985; Hedge and others, 1986, pi. 1).

A second period of Proterozoic tectonic activity accompanied by igneous intrusion is indicated by 1.6- to 1.8-billionyear-old metamorphic and plutonic rocks that extend from the 

southern Sierra Madre in Wyoming south through Utah and 

Colorado into northeastern Arizona (Karlstrom and others,

1987. fig. 1). These rocks constitute an accretionary terrane 

that Reed and others (1987) called the Colorado province. The 

metamorphic rocks of the Colorado province in the Sierra Madre and Colorado are derived from sedimentary and volcanic 

rocks. The metasedimentary rocks include biotite gneiss, 

schist, and migmatite, with subordinate hornblende gneiss, 

calc-silicate rock, marble, metagraywacke, and quartzite; the 

metavolcanic rocks include quartz-feldspar gneiss (metatuff), 

greenstone, and amphibolite (Tweto, 1980a; Reed and others, 

1987). In Utah, 1.7-billion-year-old metamorphic rocks exposed in canyons of the Colorado and Dolores Rivers northeast 

of Moab include biotite gneiss and schist, hornblende schist, 

and migmatite (Dane, 1935, p. 22-23; Hintze, 1973, p. 157- 

158). In the Grand Canyon of northeastern Arizona, metamorphic rocks of Colorado province age (1.65 billion years) are 

assigned to the Vishnu Schist (fig. 2). As described by Billingsley and others (1987, p. 20), the Vishnu Schist consists of 

amphibolite, hornblende schist, anthophyllite-cordierite schist, 

sillimanite-bearing quartz-feldspar schist, and migmatite 

gneiss.

In the Colorado province of Colorado and Wyoming, the 

metamorphic rocks are invaded by calc-alkaline plutons that 

collectively constitute nearly half of the Early Proterozoic terrane (Reed and others, 1987, p. 861). Plutons of variably 

foliated monzonitic granite, granodiorite, and tonalite are the 

most widespread, but small plutons, dikes, and sills of gabbro, 

diabase, quartz diorite, and trondhjemite occur (Reed and

others, 1987, p. 861). According to Hedge and others (1986, pi. 

1), the Early Proterozoic plutonic rocks of Colorado and 

Wyoming were emplaced 1.6 to 1.7 billion years ago. In the 

Grand Canyon, the Vishnu Schist is intruded by the Zoroaster 

Plutonic Complex of foliated and nonfoliated granitic plutons, 

some of which postdate the metamorphism (Billingsley and 

others, 1987, p. 22).

Considerably less metamorphosed than the Early Proterozoic rocks, sedimentary rocks of the Uncompahgre Formation in 

and near the San Juan Mountains of southwestern Colorado and 

unnamed slightly metamorphosed, sedimentary and volcanic 

rocks exposed in the Defiance Plateau of Arizona apparently 

were deposited in a marine setting after the tectonic events that 

deformed and metamorphosed the Early Proterozoic rocks. 

The Uncompahgre Formation is an 8,000-ft-thick sequence of 

crossbedded quartzite (fig. 3), conglomerate, slate, and phyllite 

(Hedge and others, 1986, p. 10). The Defiance Plateau sequence consists of quartzite, phyllite, schist, silicified limestone, and greenstone (Cooley and others, 1969, p. 10-11). 

The age of the Uncompahgre Formation is constrained by dated 

rocks beneath it and by the cross-cutting Eolus Granite as between 1.6 and 1.45 billion years (Hedge and others, 1986, p. 

10). Thus, the Uncompahgre Formation is considered Early 

and Middle Proterozoic.

Middle Proterozoic history apparently was dominated by the 

emplacement of granitic and monzonitic plutons throughout 

the UCRB. These plutons, which range from 1.48 to 1.35 billion years old, include the Sherman Granite in the Sierra Madre, the Silver Plume Granite in the Front Range, the St. Kevin 

Granite in the Sawatch Range, the Eolus Granite in the San 

Juan Mountains, quartz monzonite intrusives in the Uncompahgre Plateau and Paradox Basin, and nonfoliated granitic plutons 

in the Zoroaster Plutonic Complex of the Grand Canyon 

(Hintze, 1973, p. 157-158; Hedge and others, 1986, pi. 1; Billingsley and others, 1987, p. 22).

The Precambrian culminated with mild tectonic and igneous 

activity, accompanied by the deposition of sedimentary rocks 

between about 1.2 billion and 800 million years ago. These 

sedimentary rocks have not been metamorphosed. Igneous 

rocks include the 1-billion-year-old Pikes Peak Granite in the 

Front Range of Colorado (Hedge and others, 1986, pi. 1) and 

the 1.1-billion-year-old Cardenas Lavas (the top of the Unkar 

Group) in the Grand Canyon (Beus and Lucchita, 1987, p. 13). 

The latest sedimentary deposits of Proterozoic age include the 

Uinta Mountain Group in the Uinta Mountains and vicinity and 

the Grand Canyon Supergroup in the Grand Canyon area.

Sedimentary rocks of the Uinta Mountain Group (Wallace 

and Crittenden, 1969) unconformably overlie the Archean Red 

Creek Quartzite in the Uinta Mountains and are encountered in 

boreholes in the Uinta, Piceance, and Sand Wash Basins (pi. 4). 

The majority of this unit consists of red, gray, pink, and white 

quartzite and arkosic sandstone with lenses and interbeds of red 

and olive-green argillite and fissile shale (fig. 4). In the western 

Uinta Mountains and Uinta Basin, the quartzite and sandstone
GEOLOGY OF PALEOZOIC ROCKS, UPPER COLORADO RIVER BASIN A7

FIGURE 2. Rocks ranging in age from Proterozoic to Permian exposed along the 

Colorado River in the Grand Canyon, 

Ariz. Bv, Proterozoic Vishnu Schist; 

 Ct, Cambrian Tapeats Sandstone; Cb, 

Cambrian Bright Angel Shale; -em, 

Cambrian Muav Limestone; Mr, Mississippian Redwall Limestone; PPs, 

Pennsylvanian and Permian Supai 

Group; Ph, Permian Hermit Shale; PC, 

Permian Coconino Sandstone; Ptk, Permian Toroweap Formation and Kaibab 

Formation.

are overlain by as much as 5,000 ft of olive-green and black 

siltstone and claystone with quartzite and arkosic sandstone interbeds, that constitute the Red Pine Shale. The Uinta Mountain Group is as much as 24,000 ft thick in the Uinta Mountains 

(Hansen, 1965b, p. 32 38). As indicated by intrusive rocks and 

the age of the Red Pine Shale, the Uinta Mountain Group probably was deposited between 1,440 and 950 billion years ago 

(Hedge and others, 1986, p. 10).

The 13,000-ft-thick Grand Canyon Supergroup consists of 

the Unkar Group, Nankoweap Formation, and Chuar Group 

(Beus and Lucchita, 1987, p. 10). The Unkar Group, which 

was deposited between 1.25 and 1.1 billion years ago (Donald 

Elston, U.S. Geological Survey, oral commun., 1987), includes 

the Bass Limestone, Hakatai Shale, Shinumo Quartzite, interbedded sandstone, siltstone, and mudstone of the Dox Formation, and the Cardenas Lavas. The Nankoweap Formation 

consists mostly of sandstone and conglomerate. The Chuar 

Group, which was deposited between 1,070 and 820 million 

years ago (Beus and Lucchita, 1987, p. 12), is composed of 

shale and interbedded limestone of the Galeros and Kwagunt 

Formations overlain by interbedded sandstone, conglomerate, 

and breccia of the Sixty Mile Formation. The Grand Canyon 

Supergroup apparently was removed by erosion north and east 

of the Paria River (pi. 4), and its exact thickness between the 

Grand Canyon and Paria River is unknown.

GENERAL PALEOZOIC STRATIGRAPHY

Formations representing all Paleozoic systems, except the 

Silurian, are present in the study area (table 1). As evidenced

by limestone inclusions of Silurian age in khnberlite diatremes 

along the Colorado-Wyoming border (Ross and Tweto, 1980, 

p. 52-53), Silurian marine deposits probably were present at 

one time but have since been removed by erosion. Paleozoic 

rocks of the UCRB were deposited during five major marine 

incursions.

Formations of Cambrian to Mississippian age (pi. 5) predominantly consist of marine carbonate rocks and are relatively 

thin when compared to overlying formations of mostly Pennsylvanian and Permian age (some of these formations are partly 

Mississippian or partly Triassic). Formations of Cambrian age 

comprise a transgressive marine sequence of sandstone, shale, 

and carbonate rocks. (In this report, the term "shale" includes 

claystone, mudstone, siltstone, sandy shale, carbonaceous 

shale, marl, and argillite.) Formations of Ordovician age consist mostly of limestone and dolomite, with a thin intervening 

sandstone unit present locally. The Ordovician rocks formerly 

covered a much larger area, but, because of erosion, are now restricted to northwestern Colorado and the northwestern Green 

River Basin and adjacent areas in Wyoming. Formations of 

Devonian age consist of a lower mixed carbonate-shale-sandstone sequence and an upper limestone-dolomite sequence. 

Formations of Mississippian age consist mostly of a thick carbonate sequence that locally is capped by a thin sequence of 

variable carbonate, shale, and sandstone lithology. Formations 

of Cambrian to Mississippian age generally are less than 4,500 

ft thick, but they are as much as 5,500 ft thick in the High Plateaus region of Utah and 6,500 ft thick in the Overthrust Belt of 

Wyoming.

Formations of mostly Pennsylvanian and Permian age predominantly consist of terrigenous or marine sandstone and
A8 REGIONAL AQUIFER SYSTEM ANALYSIS UPPER COLORADO RIVER BASIN

FIGURE 3. Near-vertical beds of quartzite in the Early and Middle Proterozoic 

Uncompahgre Formation overlain by subhorizontal dolomite, shale, and 

sandstone of the Devonian Elbert Formation at Box Canyon Falls, Ouray, 

Colo.

shale. The basal sequence in this interval, of Mississippian and 

Pennsylvanian age, consists of partly marine and partly 

terrigenous shale with subordinate interbeds of limestone and 

dolomite. Formations of Pennsylvanian age predominantly 

consist of interbedded carbonate rocks, sandstone, and shale of 

marine origin. However, thick sequences of marine evaporites 

are present in the Paradox and Eagle Basins, and thick terrigenous deposits of sandstone, shale, and conglomerate are present 

in northwestern Colorado. Formations of Pennsylvanian and 

Permian age predominantly consist of partly marine and partly 

eolian sandstone and terrigenous red beds of variable shale, 

sandstone, and conglomerate. Formations of Permian age 

predominantly consist of interbedded carbonate rocks, sandstone, and shale of marine origin and locally contain interbedded anhydrite. Formations of Permian and Triassic age consist 

of terrigenous red beds with minor to subordinate carbonate 

rocks and gypsum-anhydrite.

Formations of mostly Pennsylvanian and Permian age are 

characterized by abrupt changes in facies. Nomenclatural

FIGURE 4. Rocks ranging in age from Proterozoic to Pennsylvanian exposed 

along the Green River at the eastern end of the Uinta Mountains in 

Dinosaur National Monument, Colo. Units shown are Bu, Proterozoic 

Uinta Mountain Group; CI, Cambrian Lodore Formation; Mm, Mississippian Madison Limestone; Mh, Mississippian Humbug Formation; Md, 

Mississippian Doughnut Shale; Pr, Pennsylvanian Round Valley Limestone; and Pm, Pennsylvanian Morgan Formation. The shaly upper part 

of the Lodore Formation is equivalent to the Gros Ventre Formation of 

Wyoming and the Ophir Shale of the western Uinta Mountains and 

southeastern Utah.

variation from area to area is based on arbitrary groupings of 

stratigraphic sequences. The total thickness of these rocks 

generally is less than 2,000 ft in Wyoming and less than 4,000 

ft elsewhere. However, these rocks are as much as 10,500 ft 

thick in the Paradox basin and 17,500 ft thick in the Elk 

Mountains.

The total thickness of the Paleozoic rocks ranges from 0 to 

about 18,000 ft (pi. 3). The Paleozoic rocks are missing in the 

center of the Uinta Mountains, Uncompahgre Plateau, Sawatch 

Range, Park Range, Gore Range, and Front Range (see pi. 1 for 

locations of geographic areas discussed in this paragraph) 

because of erosion or nondeposition. Thicknesses increase 

generally westward, reflecting repeated marine incursions from 

the west throughout the Paleozoic. However, depositional
GEOLOGY OF PALEOZOIC ROCKS, UPPER COLORADO RIVER BASIN A9

centers on the eastern side of the area occur. Thicknesses of 

8,000-16,000 ft in the Paradox Basin and 8,000-18,000 ft in 

the Eagle Basin-Elk Mountains area are the combined result of 

evaporite flowage and the deposition of large volumes of terrigenous material derived from the ancestral Rocky Mountains 

(of Pennsylvanian and Permian age). On the western side of 

the UCRB, maximum thicknesses generally range from 7,000 

to 8,000 ft. Thicknesses in the Overthrust Belt of Wyoming are 

allochthonous; Paleozoic rocks present in the area were deposited in foreland basins of the Cordilleran miogeosyncline 50- 

60 miles to the west (Royse and others, 1975; Peterson, 1977). 

Paleozoic rocks are more than 25,000 ft deep in several 

structural basins but less than 2,500 ft deep in and near uplifted 

areas (pi. 3). Abrupt changes in the thickness of the overlying 

Mesozoic and Tertiary rocks occur on the western edge of the 

Wind River Mountains, on the eastern edge of the Overthrust 

Belt, and on the northern and southern edges of the Uinta 

Mountains because of thrust faults. Paleozoic rocks are 

26,000-27,000 ft deep in parts of the Green River, Great Divide, Washakie, and Uinta Basins; 15,000-22,000 ft deep in 

parts of the Sand Wash and Piceance Basins, and the High Plateaus region; 5,000-10,000 ft deep in parts of the Henry Mountains, Kaiparowits, and Kaibito Basins, the Douglas Creek 

Arch, and the Rock Springs Uplift; and generally less than 

5,000 ft deep elsewhere. The Paleozoic rocks are less than 

2,500 ft deep in large parts of the area south of the Uncompahgre Plateau and east of the Colorado and Green Rivers. They 

also generally are less than 2,500 ft deep in the White River 

Plateau, Elk Mountains, and Eagle Basin, where they form 

most of the land surface.

MESOZOIC ROCKS

Paleozoic rocks in the study area are overlain nearly everywhere by rocks of Triassic age (pi. 4). Lower Triassic rocks 

comprise the base of the Triassic System in most areas. However, these rocks were either eroded or never deposited east of 

the Monument Up warp and northwestern Paradox Basin and 

south of the southern Piceance Basin and Elk Mountains. In 

most of this area, Upper Triassic rocks form the base of the 

Triassic System. The Upper Triassic rocks are missing in an 

area encompassing the southeastern corner of the Piceance 

Basin, eastern West Elk Mountains, and western Elk Mountains and in a small part of the southern Gore Range. In these 

areas, largely eolian rocks of Jurassic age, either the Wingate 

Sandstone or Entrada Sandstone (see Peterson, 1988, for 

detailed stratigraphic discussion of Jurassic rocks in the southern Rocky Mountain region) overlie the Paleozoic rocks. 

Triassic rocks also are missing in some areas of the Wyoming 

Overthrust Belt where the Wasatch Formation, a unit of 

Tertiary age mostly consisting of shale and fine-grained sandstone (see Oriel, 1969, for detailed description of the Wasatch 

Formation at the eastern edge of the Overthrust Belt), caps the 

Paleozoic rocks.

Lower Triassic rocks in contact with Paleozoic rocks in the 

study area include the Moenkopi Formation, Woodside Shale, 

upper part of the State Bridge Formation, upper part of the 

Goose Egg Formation, and Dinwoody Formation (see Hansen, 

1965b, and Stewart and others, 1972a, for detailed descriptions). Upper Triassic rocks in contact with Paleozoic rocks in 

the study area include the Chinle and Dolores Formations (see 

Stewart and others, 1972b, for detailed descriptions).

The Moenkopi Formation is divided into numerous members 

on the basis of lithologic variations that do not persist throughout the region. Although shale is the predominant lithology, 

sandstone, conglomerate, and carbonate rocks also are present 

in the formation.

In northeastern Arizona and southeastern Utah west of the 

Monument Upwarp and south of the Capitol Reef Fold and 

Fault Belt (pi. 1), members of the Moenkopi Formation in contact with Paleozoic rocks are lithologically diverse. The 

Timpoweap Member consists of a laterally variable sequence 

of gray and yellow limestone, siltstone, sandstone, and chertpebble conglomerate. The Sinbad Limestone Member consists 

of yellowish-gray, olive-gray, and yellowish-orange limestone 

and dolomite with siltstone interbeds. The lower red member 

consists mostly of grayish-red and light-brown, micaceous 

siltstone. The ledge-forming member consists of grayish-red, 

reddish-brown, orange, and gray siltstone, sandy siltstone, and 

very fine grained sandstone.

In the Defiance Plateau, Monument Upwarp, and northwestern Paradox Basin, the Moenkopi Formation, in contact with 

Paleozoic rocks, mostly consists of siltstone, sandstone, and 

conglomerate. The lower massive sandstone member consists 

of grayish-yellow, very fine grained sandstone. The Hoskinnini Member consists of reddish-brown sandy siltstone and silty, 

very fine grained sandstone. The Tenderfoot Member consists 

of reddish-brown siltstone and conglomerate with interbedded 

gypsum near the bottom of the unit.

In most of southeastern Utah where the Moenkopi Formation 

is the basal Triassic unit, the lower slope-forming member 

overlies the Paleozoic rocks. The lower slope-forming member 

consists of grayish-red, yellowish-gray, and light-greenishgray siltstone and sandy siltstone. The equivalent of this unit 

in northwestern Colorado, the eastern Uinta Mountains, and the 

southeastern Washakie Basin is the undivided Moenkopi Formation. The undivided Moenkopi Formation consists of red, 

brown, orange, yellow, and gray siltstone with minor amounts 

of mudstone, very fine grained sandstone, and gypsum.

Stratigraphic equivalents of the Moenkopi Formation are 

composed mostly of shale. The Woodside Shale, in the Uinta 

Basin and western Uinta Mountains, consists of red siltstone 

and claystone with some interbeds of very fine grained sandstone. The upper part of the State Bridge Formation from the 

Piceance Basin and White River Plateau to the Park Range 

consists of red siltstone with subordinate claystone and sandstone layers. The upper part of the Goose Egg Formation in the 

eastern Sand Wash, Washakie, and Great Divide Basins
A10 REGIONAL AQUIFER SYSTEM ANALYSIS UPPER COLORADO RIVER BASIN

consists of red anhydritic and dolomitic shale (the Freezeout 

Shale Member) capped by a thin limestone bed (the Little Medicine Member). The Dinwoody Formation consists of lightgray and greenish-gray limy siltstone and claystone with interbedded friable, fine-grained sandstone, crystalline limestone 

and dolomite, and minor gypsum.

In many areas, Upper Triassic rocks in contact with 

Paleozoic rocks predominantly consist of sandstone and 

conglomerate. The Shinarump Member of the Chinle Formation, which overlies the Paleozoic rocks in the Defiance Plateau 

area, consists of yellowish-gray and yellow-orange, friable, 

fine- to coarse-grained sandstone and chert-pebble conglomerate. The Moss Back Member of the Chinle Formation and the 

lower member of the Dolores Formation, which form the basal 

Triassic sequence in the Paradox Basin and San Juan Mountains, are very similar to the Shinarump Member. The Gartra 

Member of the Chinle Formation, which caps the Paleozoic 

rocks in a small area southwest of Glenwood Springs, Colo., 

also is composed of sandstone and conglomerate.

Shale members of the Chinle Formation overlie Paleozoic 

rocks in three areas. On the north flank of the Uncompahgre 

Plateau, the Paleozoic rocks are overlain by the Church Rock 

Member and red siltstone member of the Chinle Formation. 

The Church Rock Member is composed of reddish-brown, 

reddish-orange, and light-brown siltstone with lenses and 

persistent beds of pink and light-greenish-gray fine-grained 

sandstone and sandy siltstone. The red siltstone member in this 

area consists of reddish-brown and grayish-red siltstone with 

lenses of limestone-pebble conglomerate. South of the 

Uncompahgre Plateau, near Placerville, Colo., the red siltstone 

member again overlies Paleozoic rocks. In this area, however, 

the unit contains a large proportion of red, fine-grained sandstone interbedded with the siltstone. In the Four Corners area, 

Paleozoic rocks are overlain by the Petrified Forest Member of 

the Chinle Formation. The Petrified Forest Member consists of 

red, greenish-gray, purple, yellow, and blue claystone, clayey 

siltstone, and clayey sandstone with lenses of coarse-grained 

sandstone and conglomerate.

STRUCTURE

The UCRB is situated in an unstable foreland region between the stable North American Craton to the east (Great 

Plains physiographic province) and the block-faulted Cordilleran Geosyncline to the west and south (Basin and Range physiographic province). Tectonic activity in the UCRB began in 

the Precambrian, continued repeatedly throughout the Paleozoic, and culminated on a regional scale in the Tertiary (Grose, 

1972; Kent, 1972; Hintze, 1973; Peterson, 1977; Stone, 1977, 

1986; Tweto, 1980c; De Voto and others, 1986; Hansen, 

1986a).

The Paleozoic rocks in the UCRB have been deformed into 

numerous synclines and anticlines (pi. 1). Many mountain

ranges, including the Wind River Mountains, Gros Ventre 

Range, Uinta Mountains, San Juan Mountains, Front Range, 

and Sawatch Range, essentially are large anticlinoriums with 

Precambrian cores and limbs composed of folded and faulted 

Paleozoic, Mesozoic, and Tertiary sedimentary rocks (see sections B-B', D-D', and G-G', pi. 2). Many of the basins and uplifts, particularly in the Colorado Plateaus province, are 

distinctly asymmetrical. Such folds, including those forming 

the White River Plateau, Piceance Basin, Uinta Basin, San 

Rafael Swell, Circle Cliffs Uplift, Henry Mountains Basin, 

Monument Upwarp, and Kaibab Plateau, are steep to overturned on one limb and gently homoclinal on the opposite limb 

(see sections B-B', D-D', E-E', and H-H', pi. 2). Some folds, 

such as those forming the Rock Springs Uplift, Rawlins Uplift, 

Douglas Creek Arch, and Defiance Plateau, are nearly symmetrical (see sections D-D' and /-/', pi. 2).

Most major fold axes trend northwesterly or north-northeasterly. The Uinta Mountains, however, consist of two domes 

with the longer axes aligned approximately east-west (pi. 1). 

The two domes formed by the intersection of an east-westoriented anticline with the axes of the previously uplifted Moxa 

Arch on the west and the Rock Springs Uplift-Douglas Creek 

Arch structural trend on the east (Ritzma, 1969; Hansen, 

1986a). According to Hansen (1986b, p. 40), uplift began during latest Cretaceous time, reached its peak from Paleocene to 

Oligocene time, and continued into the Quaternary with largescale tilting of the eastern Uinta Mountains and both normal 

and reverse movement along new and preexisting faults.

Domes of small areal extent that resulted from the intrusion 

of Tertiary igneous rocks occur in the southern part of the Colorado Plateaus province (see pis. 1 and 2). These domes form 

the San Juan Mountains (including the outlying San Miguel, 

Rico, and La Plata Mountains), the Abajo Mountains, the Henry Mountains, Navajo Mountain, Sleeping Ute Mountain, the 

Carrizo Mountains, and La Sal Mountains.

Faults are associated with most uplifts (pi. 1). The most 

prevalent faults are high-angle, reverse, or normal faults 

(Grose, 1972, p. 36). High-angle normal faults transect most 

ranges in the Southern and Middle Rocky Mountains provinces 

and are the dominant type of fault in the Colorado Plateaus 

province. High-angle normal faults, arranged en echelon, border the Gore Range, Sawatch Range, Uncompahgre Plateau, 

Gunnison Plateau, and the High Plateaus of Utah (see sections 

D-D', E-E', F-F', and H-H', pi. 2). The Uncompahgre Plateau 

essentially is a horst over which Mesozoic rocks are drapefolded (Stone, 1977; Heyman and others, 1986). A prominent 

zone of faulting known as the Colorado Lineament (Warner, 

1980) extends northeastward from northern Arizona to the 

Southern Rocky Mountains and includes the Needles Fault 

Zone of the Canyonlands region and the Homestake Shear 

Zone of the Sawatch Range (pi. 1).

One of the most complex structural features in the UCRB is 

the Paradox Basin (fig. 5), an area characterized by northwesttrending anticlines, synclines, and high-angle faults. The
GEOLOGY OF PALEOZOIC ROCKS, UPPER COLORADO RIVER BASIN All

FEET 

10,000 1

5,000 

N6VD 

OF 1929"

-5,000 

-10,000 

-14,600 

Lisbon

PARADOX BASIN 

Paradox

UNCOMPAHGRE 

PLATEAU

VERTICAL EXAGGERATION x 5

20 MILES

10 15 20 KILOMETERS 

EXPLANATION

Cretaceous undifferentiated

Jurassic undifferentiated

Triassic undifferentiated

Permian Cutler and Rico Formations

Pennsylvanian upper member of 

Hermosa Formation

Pennsylvanian Paradox Member of 

Hermosa Formation

Pennsylvanian lower member of 

Hermosa Formation

Mississippian Leadville Limestone and 

Devonian Ouray Limestone

Devonian Elbert Formation

Cambrian Muav Limestone and 

Bright Angel Shale

Cambrian Ignacio Quartzite

Precambrian granitic and 

metamorphic rocks

Fault Barbs indicate relative directions 

of movement

FIGURE 5. Geologic section showing deformational styles in the Paradox Basin, Colo. Modified from Baars (1983, p. 73); location of

section shown on plate 2.

anticlines were formed by the mobilization and intrusion of salt 

in the Hermosa Formation as thousands of feet of Cutler Formation sediments were being eroded from the rising Uncompahgre Plateau (Baars, 1983, p. 59-78). Consequently, 

deformation decreases in intensity away from the Uncompahgre Plateau as the thickness of the Cutler Formation decreases 

(Kelley, 1958, p. 31). The salt-cored anticlines are arranged en 

echelon into five systems (pi. 1). At the crests of the anticlines 

are grabens that formed by the collapse of the salt cores and 

overlying sediments in response to salt solution (Shoemaker 

and others, 1958). The collapse breccia, known locally as cap 

rock, floors prominent flat-bottomed valleys sparsely covered 

with Quaternary alluvium.

Thrust faults border the west and south sides of most uplifted areas in the Southern and Middle Rocky Mountains

and Wyoming Basin provinces. Thrust faults bordering the 

Wind River, Gros Ventre, Uinta, and Elk Mountains, the 

Front and Park Ranges, the Sierra Madre, the White River 

Plateau, and the Rock Springs and Rawlins Uplifts can have 

as much as 40,000 ft of stratigraphic displacement (see sections A-A', B-Bf, and C-C", pi. 2). Paleozoic and Mesozoic 

rocks in the lower plate of the Wind River Fault (section AA', pi. 2) may extend to the crest of the Wind River Mountains beneath outcropping Precambrian rocks. Similarly, 

Paleozoic rocks in the lower plate of the Uinta-Sparks Fault 

(pi. 1) extend beneath the Precambrian (Proterozoic) Uinta 

Mountain Group on the north flank of the eastern Uinta 

Mountains (fig. 6).

In contrast to these "thick-skinned" thrusts, thrust faults in 

the Overthrust Belt typically do not extend into the
A12 REGIONAL AQUIFER SYSTEM ANALYSIS UPPER COLORADO RIVER BASIN

DOUGLAS CREEK 

ARCH

Willow Blue 

Creek Mountain FEET

10.000 -, Rangely c .. 

Km* Kmv^ Fault

YAMPA PLATEAU

Yam pa 

Fault

UINTA MOUNTAINS

Douglas 

Mountain Browns 

Park

Owiyukuts Uinta 

Plateau

-=. -Km- =- =-

 I't 7TTTT7 n i i 11 

-10.000

VERTICAL EXAGGERATION x 2

10 15 MILES

J

Tertiary rocks, undifferentiated 

Cretaceous Mesa Verde Group

5 10 15 KILOMETERS 

EXPLANATION

n 

Mz

Cretaceous Mancos Shale

Mesozoic rocks, undifferentiated 

Paleozoic rocks, undifferentiated 

Proterozoic Uinta Mountain Group

Fault Barbs indicate relative directions 

of movement

FIGURE 6. Geologic section showing deformational styles in the Uinta Mountains in northwestern Colorado. Modified from Hansen (1986a, fig. 3);

location of section shown on plate 2.

Precambrian basement (see section A-A', pi. 2). Detachment 

typically occurs within Cambrian shale and carbonate layers 

but also occurs within Triassic, Jurassic, and Cretaceous shale 

layers (Royse and others, 1975, p. 44). Stratigraphic throw on 

each of the major thrust faults is about 20,000 ft (Armstrong 

and Oriel, 1965, p. 1857), but numerous imbricate thrust 

faults with smaller throw are present in the hanging walls of 

the major thrusts (see, for example, Royse and others, 1975, 

pis. 1 and 2). From west to east, the major thrust faults in 

Wyoming are the Tunp, Absaroka, Darby-Hogsback, and 

Jackson-Prospect; in Utah, the leading edge of the Overthrust 

Belt is marked by the Charleston Thrust Fault (pi. 1). Asymmetric folds and Basin and Range-style, high-angle, normal 

faults occur in the hanging walls of the major thrusts (Blackstone, 1977, p. 374-375). Typical of these younger faults is 

the Hoback Fault bordering the west side of the Hoback 

Range (pi. 1).

Large parts of the UCRB contain no visible faults of appreciable length. Small outcrops of lower and middle Paleozoic rocks in the Green River Basin northwest of Pinedale, 

Wyo. (pi. 2), may be the remnants of a gravity-slide block 

from the Wind River Mountains to the east. Other than this 

structure and small faults concentrated around the crests of 

intervening arches, few large faults are known in the Green 

River, Great Divide, Washakie, Sand Wash, Piceance, and 

Uinta Basins. Similarly, much of the area between the San 

Rafael Swell and Circle Cliffs Uplift on the west and the 

Paradox Basin on the east virtually is free of faults.

Notable exceptions are the Needles Fault Zone (which controls the course of the Colorado River through the area), 

grabens bordering the Abajo Mountains Dome, and a zone 

of north-trending faults between the Colorado and San Juan 

Rivers in the southwestern part of the Monument Upwarp.

STRATIGRAPHY OF PALEOZOIC

HYDROGEOLOGIC UNITS AND

RELATED ROCKS

Eleven hydrogeologic units consisting of Paleozoic rocks 

have been designated in the study area. Jji this section of 

the report, lateral variations in Stratigraphic nomenclature, 

thickness, and lithology within each hydrogeologic unit are 

discussed in detail. Contacts between geologic units at the 

tops and bottoms of the hydrogeologic units also are discussed, in order to show how the hydrogeologic units relate to each other. Paleontologic discussion is minimized in 

keeping with the hydrogeologic emphasis of the UCRBRASA; for more thorough discussions of the paleontology, 

numerous references are given throughout the remainder of 

the report. Hydrogeologic units from the Flathead aquifer 

to the Madison aquifer (table 1) are considered to transmit 

ground water as a composite aquifer system, the Four Corners aquifer system. Substantial discussion of this aquifer 

system is contained in Professional Paper 1411-B (Geldon, 

in press).
GEOLOGY OF PALEOZOIC ROCKS, UPPER COLORADO RIVER BASIN A13

FLATHEAD AQUIFER

The Rathead aquifer (pi. 6) is composed of beach and littoral 

sediments deposited during the initial advance of the Paleozoic 

seas across the region (Kent, 1972; Lochman-Balk, 1972). 

Component geologic units include the Rathead Sandstone, 

lower part of the Lodore Formation, Sawatch Quartzite, Ignacio Quartzite, Tapeats Sandstone, Tintic Quartzite, and unnamed equivalents (table 1 and pi. 5). These formations 

become progressively younger from west to east across the region in the direction of marine advance (fig. 7). On the western 

side of the region, the component formations are Lower to Middle Cambrian (Noble, 1922, p. 38-39; Foster, 1947, p. 1548; 

Anderman, 1956, p. 50; Baker, 1976); on the eastern side, component formations are Middle to Upper Cambrian (Thomas, 

1951, p. 32-33; Baars, 1958, p. 95-97; Keefer and Van Lieu, 

1966, p. 14-15; Tweto and Levering, 1977, p. 15).

The Rathead aquifer thickens toward depositional centers in 

the Uinta Basin, Overthrust Belt, southwestern Colorado, and 

northeastern Arizona (pi. 6). Its maximum thickness within the 

UCRB currently is estimated from borehole data to be about 

800 ft. However, measured sections in the Wasatch Range, 

18-27 mi west of the UCRB (Baker and Crittenden, 1961; Baker, 1973) indicate that the Rathead aquifer may be as much as 

1,200 1,300 ft thick in Wyoming. Thinned by erosion or nondeposition, the aquifer is missing in the center and on the north

flank of the Uinta Mountains, east of the Sand Wash and Eagle 

Basins, in the Uncompahgre Plateau and southern Piceance 

Basin, and in much of the Defiance Plateau and Four Corners 

area. The aquifer is at or near the surface of the flanks of 

uplifted areas, but it typically is 7,000 34,000 ft deep in structural basins (pi. 7).

COMPONENT GEOLOGIC UNITS

The Rathead aquifer in southwestern Wyoming consists of 

the Rathead Sandstone. In the Gros Ventre Range, the Rathead Sandstone is composed of white, gray, tan, and maroon, 

fine- to medium-grained, crossbedded sandstone and quartzite 

with a basal interval of quartz-pebble conglomerate and partings of green, micaceous shale in upper layers (Foster, 1947, 

p. 1544; Simons and others, 1988, p. 8). Similarly, the Rathead Sandstone in the Wind River Mountains consists of pink, 

reddish-brown, tan, and gray laminated, fine- to coarsegrained sandstone overlying an arkosic-pebble conglomerate. Most of the sandstone layers in the Wind River Mountains are quartzitic, some are glauconitic or hematitic, and 

upper layers contain partings of green and grayish-green, micaceous shale (Keefer and Van Lieu, 1966, p. 14-15). In the 

Rawlins area, the Rathead Sandstone (fig. 8) consists of a 

basal interval of arkosic conglomerate, a middle interval of 

light-gray and pink quartzitic sandstone, and an upper interval

WEST

Wasatch Range, 

Utah

Wind River Mountains, 

___Wyoming___

Eastern Uinta Mountains, 

Colorado

EAST 

Colorado

ORDOVICIAN

 ~=^^^~=- Formation ~^:

Not to scale

EXPLANATION 

Carbonate rocks 

Shale 

Sandstone and quartzite

Index map showing 

general trend of section

FIGURE 7. Schematic section showing time transgression and intertonguing of facies in the Cambrian sedimentary rocks of Wyoming, Utah, and Colorado. 

Baars (1983, p. 54) showed similar stratigraphic relations and time transgression in the Cambrian rocks between the Grand Canyon area of Arizona and 

the San Juan Mountains of southwestern Colorado.
A14 REGIONAL AQUIFER SYSTEM ANALYSIS UPPER COLORADO RIVER BASIN

FIGURE 8. Cambrian Flathead Sandstone at 

Rawlins, Wyo.

of red and purplish-gray, friable to quartzitic, medium-grained 

sandstone (Berry, 1960, p. 70-71).

Similar to the Flathead Sandstone, the Lodore Formation at 

Cross Mountain consists of white, orange, and yellow quartzite, quartzitic sandstone, and glauconitic sandstone with shale 

partings near the top (Wilson, 1957). To the west, in Dinosaur 

National Monument, this sandstone interval grades into gray, 

pale-green, and pink, medium- to coarse-grained, pebbly sandstone overlain by an interval predominantly consisting of shale 

(Hansen and others, 1983). Both the sandstone and shale intervals are included in the Lodore Formation, despite their contrasting lithologies (Untermann and Untermann, 1954). 

Because the upper (shaly) interval contains an Upper Cambrian 

fauna, the entire Lodore Formation traditionally has been considered Upper Cambrian. However, the lower and thicker 

(sandy) part of the formation is unfossiliferous, and its age realistically cannot be established unequivocally. In this report, 

the upper (shaly) part of the Lodore Formation is considered to 

be equivalent to the Gros Ventre Formation, on the basis of 

both lithology and fossils, and is included with the Gros Ventre 

Formation in the Gros Ventre confining unit. The lower 

(sandy) part of the Lodore Formation, on the basis of lithology 

and stratigraphic position, is inferred to be correlative with the 

Middle Cambrian Flathead Sandstone to the north and the Upper Cambrian Sawatch Quartzite to the south and is believed to 

be intermediate in age between these two formations. On the 

basis of this interpretation, the lower part of the Lodore Formation is included with the Flathead Sandstone and Sawatch 

Quartzite in the Flathead aquifer.

From the western Uinta Mountains south to the vicinity of 

Lake Powell, beds equivalent to the Flathead Sandstone are

assigned to the Tintic Quartzite. In the Duchesne River and 

Lake Fork drainages of the western Uinta Mountains, the Tintic 

Quartzite (referred to as the Pine Valley Quartzite by Huddle 

and McCann, 1947b, and Huddle and others, 1951) consists of 

light-yellowish-brown conglomeratic sandstone overlain by 

massively bedded, greenish-gray sandstone (fig. 9). The sandstone layers can be calcareous, quartzitic, or arkosic, and thin 

to thick intervals of shale are present. In the Wasatch Range 

and northwestern Uinta Basin, the Tintic Quartzite consists of 

white, tan, and pink, fine- to medium-grained quartzite with 

pebbly to conglomeratic layers near the base and interbedded 

green shale near the top (Baker and Crittenden, 1961; Baker, 

1973). Similarly, the Tintic Quartzite penetrated by boreholes 

in southeastern Utah consists of massively bedded, white, 

green, pink, and maroon, fine- to medium-grained, locally 

glauconitic sandstone with feldspathic, coarse-grained sandstone and conglomerate in the lower 50-70 ft and interbeds of 

green and red, micaceous shale in the upper part of the formation (Cooper, 1960, p. 69).

In the Piceance Basin, White River Plateau, and mountainous areas of northwestern Colorado, the equivalent of the Flathead Sandstone and Tintic Quartzite is called the Sawatch 

Quartzite. The Sawatch Quartzite in the southern White River 

Plateau (Hallgarth, 1959; Bass and Northrop, 1963) consists of 

light-gray, brown, and locally lavender dolomitic quartzite, 

quartzitic sandstone, and sandstone in beds 2-5 ft thick, with 

scattered layers of brown and gray dolomite and sandy dolomite and partings of light-greenish-gray shale (fig. 10). At the 

base is a 1- to 2-ft-thick layer of conglomeratic quartzite. A 75- 

ft-thick layer of dark-brown, thin-bedded glauconitic and sandy 

dolomite occurs 65-100 ft below the top of the formation. This
GEOLOGY OF PALEOZOIC ROCKS, UPPER COLORADO RIVER BASIN A15

FIGURE 9. Cambrian Tintic Quartzite at 

the base of a cliff on the west side of 

the Duchesne River, western Uinta 

Mountains, Utah.

FIGURE 10. Cambrian Sawatch Quartzite 

in Glenwood Canyon, Colo.

dolomitic zone persists into the northern Sawatch Range, 

where it is manifested as interlayered brown dolomitic sandstone and sandy dolomite (Tweto and Levering, 1977, p. 15- 

19). Above and below the dolomitic zone in the northern Sawatch Range, the Sawatch Quartzite consists mostly of white, 

vitreous quartzite (Bryant, 1979, p. 14). In the Crested Butte 

area of the Elk Mountains, the Sawatch Quartzite consists of 

white and brown, medium- to coarse-grained sandstone; pink, 

red, and green, glauconitic sandstone; and white quartzite, with

a thin basal conglomerate (Mallory, 1957). In the McCoy area, 

at the southern end of the Park Range, the Sawatch Quartzite 

consists of light-gray and white, quartz-pebble conglomerate 

and friable sandstone, with thin layers of micaceous shale near 

the top of the formation (Dormer, 1949, p. 1218-1221).

In most of southwestern Colorado, the lateral equivalent of 

the Sawatch Quartzite is the Ignacio Quartzite. In the San Juan 

Mountains, the Ignacio Quartzite consists of massively bedded, 

pink and reddish quartzite overlain by white, friable to
A16 REGIONAL AQUIFER SYSTEM ANALYSIS UPPER COLORADO RIVER BASIN

quartzitic sandstone and quartzite with shale partings (fig. 11). 

A basal conglomerate or conglomeratic sandstone is present 

locally (Baars and .Knight, 1957, p. 114; Baars and others, 

1987, p. 345).

In the southeastern corner of Utah and in northeastern Arizona, the Ignacio Quartzite grades into beds equivalent to the 

Tapeats Sandstone of the Grand Canyon area. As described by 

Noble (1922, p. 37-39), the Tapeats Sandstone in the Grand 

Canyon predominantly consists of chocolate-brown, mediumto coarse-grained sandstone (fig. 2), but the top of the formation is a thin interval of white crossbedded sandstone with 

green shale layers. Thin shale layers also occur from the 

middle to the top of the brown sandstone sequence, and lenses 

of quartz-pebble conglomerate occur throughout the formation. 

At the base of the formation is an arkosic conglomerate 

containing quartz pebbles and fragments of Precambrian rocks. 

Throughout the Grand Canyon area, the Tapeats Sandstone 

varies irregularly from friable to quartzitic.

CONTACTS

Formations comprising the Flathead aquifer overlie Precambrian igneous, metamorphic, and sedimentary rocks unconformably throughout the study area. This unconformity is 

revealed in the Uinta Mountains only by the eastward truncation of the Red Pine Shale (Kinney, 1955, p. 23-24). In most 

areas, however, the Precambrian rocks are truncated noticeably 

by the erosional surface on which the Paleozoic rocks were 

deposited (Baars, 1958, p. 93; Keefer and Van Lieu, 1966, p. 

14-15; Irwin and others, 1971, p. 5-6; Tweto and Levering,

1977, p. 15; Hansen, 1986a, fig. 11). In southwestern 

Colorado, angular discordance between Precambrian and Paleozoic sedimentary rocks reaches extreme development and is 

as much as 70°-90° (Baars, 1958, p. 93). Relief on the erosional surface is barely detectable in most areas, but in the Wind 

River Mountains and Sawatch Range, 25-60 ft of irregularity 

has been observed (Richmond, 1945; Tweto, 1949, p. 160- 

161). In the Grand Canyon, the Precambrian terrain has a relief 

of as much as 900 ft, and the Tapeats Sandstone was not deposited where fault-block hills of Precambrian rocks stood as islands in the Cambrian sea (McKee, 1969, p. 42).

In contrast to the base of the Flathead aquifer, upper surfaces 

of component formations generally are conformable with or 

gradational into overlying Paleozoic formations, although 

unconformities are present locally. For example, the Flathead 

Sandstone is conformably overlain by the Gros Ventre Formation at the northwestern end of the Wind River Mountains and 

grades into the Gros Ventre Formation and Gallatin Limestone 

at the southeastern end of this range, but the Flathead Sandstone has been truncated by pre-Mississippian erosion southeast of the Rawlins Uplift (fig. 12). Similarly, the upper part of 

the Lodore Formation in the Uinta Mountains grades northward 

into rocks equivalent to the Gros Ventre Formation and westward into the Ophir Shale. However, the Lodore Formation is 

overlain unconformably by Mississippian rocks at the southeastern end of the Uinta Mountains (Kinney, 1955, p. 23-24) 

and has been eroded completely from the north flank of this 

range and from small areas on the south flank of the range 

(Huddle and others, 1951; Hansen, 1965b, p. 38). At the 

northeastern end of the Sawatch Range, the contact between the 

Sawatch Quartzite and Peerless Formation generally is

FIGURE 11. Cambrian Ignacio Quartzite 

at Coalbank Pass in the San Juan 

Mountains, Colo.
GEOLOGY OF PALEOZOIC ROCKS, UPPER COLORADO RIVER BASIN A17

WIND RIVER MOUNTAINS

Sinks Sweetwater 

Canyon Canyon

 28 miles X 50 miles

GREAT DIVIDE 

BASIN

Lost Soldier 

Oil Field

RAWLINS 

UPLIFT

Rawlins 

Hills

WASHAKIE 

BASIN

Sage 

Basin

V

SIERRA 

MADRE

Haggarty 

Creek

 26 miles- -34 miles- -26milesEXPLANATION

Datum is top of Precatnbrian

Limestone and dolomite

Limestone

Dolomite

Shale and sandstone

Sandstone

Conglomerate

Igneous and metamorphic rocks

FEET 

300-

200- 

100-

0

0

I 1 

20 30 MILES

FIGURE 12. Stratigraphic section showing relations among lower and middle Paleozoic rocks, Wind River Mountains to Sierra Madre, Wyo. Compiled 

from Barlow (1951), Ritzma (1951), Berry (1960), and Keefer and Van Lieu (1966); location of section shown on plate 6.

gradational, but in the Gore Range, both units have been truncated by pre-Pennsylvanian erosion (Donner, 1949, p. 1221; 

Singewald, 1951, p. 11). The Sawatch Quartzite is overlain unconformably by the Manitou Dolomite in the southern Sawatch 

Range (Dings and Robinson, 1957, p. 11). The Ignacio Quartzite grades westward into the Bright Angel Shale (fig. 13), but 

locally it has been truncated or removed by pre-Devonian erosion (Loleit, 1963, p. 27-29: Baars and others, 1987, p. 345). 

Contacts between the Tapeats Sandstone and equivalent strata 

and the Bright Angel Shale and equivalent strata from the

Grand Canyon to the San Juan River are transitional (Irwin and 

others, 1971, p. 5-6). The Tintic Quartzite conformably is 

overlain by the Ophir Shale (Cooper, 1960, p. 69).

GROS VENTRE CONFINING UNIT

Shaly sediments deposited seaward of Cambrian shorelines 

and on top of beach and littoral sands as the sea transgressed 

make up the Gros Ventre confining unit (pi. 8). Component 

geologic units include the Gros Ventre Formation, the upper
M

HIGH

PLATEAUS 

REGION

Phillips 1-US-E

CASTLE

VALLEY

SAG

Tiger 41-15 JackCurtis

UTAH I COLORADO

I

SAN RAFAEL 

SWELL

Austral

1-27 Humble 

Federal 1-Woodside

Phillips 

2-Onion Creek

PARADOX BASIN

Mobil 

1-Moon Mesa

Penrose and Tat

5-Scott

Igneous and 

metamorphic rocks

77

Limestone Dolomite

Sandstone and quartzlte 

Siltstone and claystone

EXPLANATION

FEET 

500-

400- 

300- 

200- 

100-

0-

Datum is top of Cambrian

^ 

FIGURE 13. Stratigraphic section showing relations among Cambrian formations in southwestern Colorado and southeastern Utah. Compiled from Baars and Knight (1957

pared by American Stratigraphic Co. Thickness of basal sandstone unit extrapolated from plate 6 where wells do not fully penetrate the formations; location of sec
GEOLOGY OF PALEOZOIC ROCKS, UPPER COLORADO RIVER BASIN A19

(predominantly shaly) part of the Lodore Formation, the Bright 

Angel Shale, the Ophir Shale (Formation), and unnamed equivalents (table 1 and pi. 5). These geologic units decrease in age 

from Early and Middle Cambrian on the western side of the 

area to Late Cambrian on the eastern side (Huddle and others, 

1951; Untermann and Untermann, 1954, p. 25; Baker and Crittenden, 1961; Middleton and others, 1980; Baars, 1983, p. 51; 

Love and others, 1993).

Becoming thicker toward depositional centers in the greater 

Green River, Paradox, and Kaiparowits Basins in the UCRB 

and the Wasatch Range west of the UCRB, the Gros Ventre 

confining unit reaches a maximum thickness of about 1,100 ft 

in the UCRB (pi. 8). Because of erosion or nondeposition, the 

confining unit is not present in the central third of the study 

area.

COMPONENT GEOLOGIC UNITS

In Wyoming, the Gros Ventre confining unit consists of 

the Gros Ventre Formation (fig. 14). In the northwestern corner of the study area, the Gros Ventre Formation is separable 

into three members, which in ascending order are the Wolsey 

Shale, Death Canyon Limestone, and Park Shale Members 

(Middleton and others, 1980). The Wolsey Shale Member in 

the Snake River Range of the Overthrust Belt consists of interbedded olive-gray to light-gray, fissile, micaceous shale 

and flat-pebble-limestone conglomerate (Wanless and others, 

1955, p. 12). Eastward, the Wolsey Shale Member contains 

less limestone and more sandstone, and in the Gros Ventre 

Range and northwestern Wind River Mountains, it consists of 

interbedded greenish-gray, tan, and pink micaceous, sandy 

shale and glauconitic, hematitic, and quartzitic sandstone 

(Foster, 1947, p. 1540-1548; Keefer and Van Lieu, 1966, p.

15-16). The Death Canyon Limestone Member in the Overthrust Belt and Gros Ventre Range consists of thinly to 

massively bedded, gray to bluish-gray, tan, and brown, crystalline limestone and dolomitic limestone with interbeds of 

oolitic limestone, limestone breccia and conglomerate, and 

green shale (Wanless and others, 1955, p. 13; Oriel, 1969, p. 

6; Simons and others, 1988, p. 8). Eastward, in the northwestern Wind River Mountains, the Death Canyon Limestone 

Member consists of thinly bedded, gray, crystalline limestone 

underlain by limestone and shale (Keefer and Van Lieu, 

1966, p. 16). The Park Shale Member in the Overthrust Belt, 

Gros Ventre Range, and northwestern Wind River Mountains 

consists of fissile, grayish-green, micaceous, glauconitic 

shale with scattered interbeds of shaly sandstone, platy limestone, and flat-pebble-limestone conglomerate (Wanless and 

others, 1955, p. 13; Keefer and Van Lieu, 1966, p. 16; Oriel, 

1969, p. 6).

As the Gros Ventre Formation grades laterally into the Flathead Sandstone, Sawatch Quartzite, and Lodore Formation 

eastward and southward from the Wind River Mountains, the 

number of sandstone layers increases, the number of carbonate and shale layers decreases, and the Gros Ventre Formation 

loses its tripartite identity. At the southeastern end of the 

Wind River Mountains, the Gros Ventre Formation consists 

of interbedded shale and sandstone with numerous thin layers 

of limestone and flat-pebble-limestone conglomerate in the 

upper half of the formation (Keefer and Van Lieu, 1966, p. 

17). In the Rawlins area, the Gros Ventre Formation (locally 

called the Buck Springs Formation) consists of interbedded 

red and grayish-green sandy shale, siltstone, and glauconitic, 

micaceous sandstone (uppermost Cambrian rocks described 

by Berry, 1960, p. 70-71).

FIGURE 14. Cambrian Gros Ventre 

Formation in the channel of Clear 

Creek, a tributary of the Green River 

near the northwestern end of the Wind 

River Mountains, Wyo.
A20 REGIONAL AQUIFER SYSTEM ANALYSIS UPPER COLORADO RIVER BASIN

In the southeastern Uinta Mountains, the upper (shaly) part 

of the Lodore Formation is very similar in lithology to the Gros 

Venire Formation of the Rawlins area. In Dinosaur National 

Monument, the upper part of the Lodore Formation (fig. 4) 

consists of pink, tan, and greenish-gray, glauconitic shale that 

is interbedded with tan to pale-green glauconitic sandstone and 

overlain by ledge-forming, light-brown to greenish-gray 

sandstone (Hansen and others, 1983).

The equivalent of the Gros Ventre Formation from the southwestern Uinta Mountains to the vicinity of Lake Powell in 

southeastern Utah is the Ophir Shale. Outcrops are rare in the 

Uinta Mountains because of pre-Mississippian erosion, but a 

110-ft-thick sequence of interbedded shale and glauconitic 

sandstone described by Huddle and others (1951) in the Moon 

Lake area between rocks that they called Pine Valley Quartzite 

and Upper Cambrian(?) limestone (interpreted in this report to 

be the Tintic Quartzite and Maxfield Limestone), probably is 

the Ophir Shale. In the Wasatch Range west of the Uinta Basin 

(14 26 mi west of the divide separating streams draining into 

the UCRB from those draining into the Basin and Range 

province), outcrops of the Ophir Shale (locally called Ophir 

Formation) consist of olive-green, micaceous shale overlain, in 

turn, by gray limestone and dolomite, and olive-green to brown 

sandstone and shale (Baker and Crittenden, 1961; Baker, 

1964). Consistent with outcrops in the Wasatch Range, the 

Ophir Shale in boreholes within the UCRB consists of grayishgreen and red shale and sandy shale with numerous interbeds 

of beige and red, commonly glauconitic limestone and sandstone (Cooper, 1960, p. 69-73).

Considering lateral facies variations, there is no lithological 

basis for distinguishing the Bright Angel Shale from the Ophir 

Shale, and the names are applied loosely among geologists 

working in southeastern Utah and southwestern Colorado 

(Baars, 1958, p. 97). The distinction between the Bright Angel 

Shale and unnamed equivalent strata in southeastern Utah and 

southwestern Colorado and the Ophir Shale in this report arbitrarily is made along an axis of thinning that extends in a curve 

from the Uncompahgre Plateau of southwestern Colorado to 

the Fish Lake Plateau of southeastern Utah. Where the Bright 

Angel Shale crops out in the Grand Canyon (fig. 2), the formation consists of thinly bedded, green and tan, micaceous shale 

and sandstone with scattered layers of brown limestone and 

dolomite and green and reddish-purple crossbedded, glauconitic sandstone (Noble, 1922, p. 39^2).

UPPER CONTACTS

Contacts between formations comprising the Gros Ventre 

confining unit and overlying Cambrian and Mississippian formations vary from gradational to unconformable. From the 

Overthrust Belt to the eastern Wind River Mountains, the Gros 

Ventre Formation is overlain unconformably by the Gallatin 

Limestone of Cambrian age (Foster, 1947, p. 1547; Keefer and

Van Lieu, 1966, p. 18). At the eastern end of the Wind River 

Mountains, however, the Gros Ventre Formation grades into 

the Gallatin Limestone (fig. 12). East and south of the Wind 

River Mountains, the Gros Ventre Formation has been truncated by pre-Mississippian erosion and is overlain unconformably 

by the Madison Limestone of Mississippian age. This unconformity at the southeastern end of the Uinta Mountains is indicated only by a westward thinning of the Lodore Formation 

(Kinney, 1955, p. 22-23). The contact between the Ophir 

Shale (Formation) and Maxfield Limestone is gradational 

where it can be observed in the Wasatch Range (Baker and 

Crittenden, 1961; Baker, 1964). Locally, in the Wasatch Range 

and Uinta Mountains, the Maxfield Limestone has been 

removed by erosion, and the Ophir Shale is overlain unconformably by Mississippian rocks. In the subsurface of southeastern Utah, the Ophir Shale is overlain conformably by the 

Maxfield Limestone (Cooper, 1960). In the Grand Canyon and 

areas to east, the Bright Angel Shale and equivalent strata grade 

upward and laterally into the Muav Limestone and equivalent 

strata (fig. 13).

BIGHORN AQUIFER

The Bighorn aquifer (pi. 9) consists of carbonate rocks deposited at the peak of the first Paleozoic marine transgression 

and the erosional remnants of a second Paleozoic marine incursion (Foster, 1972; Kent, 1972; Lochman-Balk, 1972). Component geologic units deposited during the initial transgression 

include the Gallatin Limestone, Dotsero Formation, Peerless 

Formation, Muav Limestone and equivalents, Maxfield Limestone, Lynch Dolomite, and Manitou Dolomite (table 1 and pi. 

5). On the basis of faunal evidence, these formations are considered to be mostly Middle to Upper Cambrian (Bass and 

Northrop, 1963, p. 10; Baker, 1972; Middleton and others, 

1980; Baars, 1983, p. 51), but the Lynch Dolomite could be Upper Cambrian and Lower Ordovician (Clark, 1963, p. 62-63), 

and the Manitou Dolomite is Lower Ordovician (Bass and 

Northrop, 1963, p. 16-17). The spatial distribution of these formations indicates either progressive onlap or pre-Mississippian 

erosion from west to east across the area.

Component geologic units deposited during the second 

marine incursion include the Harding Sandstone, Fremont 

Limestone, and Bighorn Dolomite (table 1). The Harding 

Sandstone and the Lander Sandstone Member of the Bighorn 

Dolomite, which represent the beach and littoral deposits of the 

second marine advance, are preserved in isolated areas at the 

southeastern end of the Wind River Mountains in Wyoming 

and in the Sawatch Range and Elk Mountains in Colorado 

(Foster, 1972, p. 85; Ross and Tweto, 1980). The Fremont 

Limestone is preserved only at the southern end of the Sawatch 

Range and in the Elk Mountains (Ross and Tweto, 1980). The 

main body of the Bighorn Dolomite is preserved north and 

west of the Rock Springs Uplift in Wyoming (Foster, 1972). 

On the basis of faunal evidence, the erosional remnants of the
GEOLOGY OF PALEOZOIC ROCKS, UPPER COLORADO RIVER BASIN A21

second marine advance generally are considered to be Middle 

and Upper Ordovician (Dings and Robinson, 1957, p. 13; 

Keefer and Van Lieu, 1966, p. 23-25). However, the existence 

of Silurian carbonate xenoliths in diatremes on the ColoradoWyoming border (Ross and Tweto, 1980, p. 52-53) and the 

prevailing carbonate lithology of Silurian deposits near the 

study area (Kent, 1972, p. 57) indicate that the second marine 

advance persisted until the Silurian in the area of the UCRB. 

The uppermost part of the Bighorn Dolomite, the Leigh 

Dolomite Member contains a fauna that could be interpreted as 

Early Silurian (Wanless and others, 1955, p. 15-16).

The Bighorn aquifer generally thickens from east to west 

across the study area, but a slight reversal of this trend occurs 

in the Sawatch Range and vicinity because of the presence of 

remnant Ordovician rocks. Thicknesses on the western side of 

the area range from 1,200 to 3,000 ft; the maximum thickness 

on the eastern side is about 400 ft. Whether thinned by erosion 

or nondeposition, the geologic units that comprise the Bighorn 

aquifer are missing in the central part of the UCRB and along 

most of its eastern edge. The aquifer is at or near land surface 

on the flanks of uplifted areas, but it typically is 5,000-34,000 

ft deep in structural basins. The top of the Bighorn aquifer is 

less than 1,500 ft above the Flathead aquifer in most areas (see 

pi. 7 for depths to the top of the Flathead aquifer). However, 

the Bighorn aquifer is as much as 2,500 ft above the Flathead 

aquifer in the Green River Basin and in the Overthrust Belt of 

southwestern Wyoming and is as much as 4,000 ft above the 

lower aquifer in the Henry Mountains Basin and High Plateaus 

region of southeastern Utah.

COMPONENT GEOLOGIC UNITS OF CAMBRIAN AGE

Cambrian rocks included in the Bighorn aquifer in southwestern Wyoming are assigned to the Gallatin Limestone, 

which also is known as the Boysen Formation (Foster, 1947). 

In the Gros Ventre Range and Overthrust Belt, the Gallatin 

Limestone consists of thin- to medium-bedded, gray, bluishgray, and brown-mottled, finely to coarsely crystalline limestone and dolomitic limestone with interbeds of sandy, oolitic, 

and bioclastic limestone, limestone conglomerate, and green 

shale (Foster, 1947, p. 1540-1548; Wanless and others, 1955, 

p. 14; Oriel, 1969, p. 7; Rubey and others, 1975, p. 3). At the 

northwestern end of the Wind River Mountains, the Gallatin 

Limestone is divisible into three members (Middleton and others, 1980), which in ascending order include the Du Noir Limestone Member, Dry Creek Shale Member (of Shaw, 1957), and 

Open Door Limestone Member. The Du Noir Limestone 

Member consists of thinly bedded, gray, very glauconitic and 

oolitic limestone with some layers of flat-pebble conglomerate. 

The Dry Creek Shale Member consists of greenish-gray shale 

with minor interbeds of gray limestone. The Open Door 

Limestone Member, which comprises most of the formation, 

consists of thinly to massively bedded, gray limestone with a 

few layers of flat-pebble conglomerate and irregular patches of

granular limestone. Southeast of the Wind River Mountains, at 

Crooks Gap, the Gallatin Limestone has been reduced by preMississippian erosion to a thin interval of purple, sandy limestone (Thomas, 1951, p. 32). Nineteen miles southeast of this 

outcrop, in the Lost Soldier oil field, the Gallatin Limestone is 

missing (Barlow, 1951).

Equivalents of the Gallatin Limestone in northwestern Colorado include the laterally gradational Dotsero Formation 

(fig. 15) and Peerless Formation. Both of these formations 

are characterized by major changes in lithology within short 

distances. At the southern end of the Axial Basin Arch, for 

example, the Dotsero Formation varies from predominantly 

pink and brown glauconitic dolomite to varicolored glauconitic and quartzitic sandstone, shale, and oolitic dolomite 

within a horizontal distance of about 18 mi (American Stratigraphic Co., unpublished drilling logs). At the southeastern 

end of the White River Plateau, the Dotsero Formation 

consists of thinly bedded, tan and gray, glauconitic dolomite 

and flat-pebble-limestone conglomerate with interbeds of 

greenish-gray shale and a capping layer of algal limestone

FIGURE 15. Cambrian Dotsero Formation overlain by Ordovician Manitou 

Dolomite in Glenwood Canyon, Colo.
A22 REGIONAL AQUIFER SYSTEM ANALYSIS UPPER COLORADO RIVER BASIN

(Bass and Northrop, 1963, p. 10). Toward the Sawatch 

Range, the algal limestone bed pinches out, and the Dotsero 

Formation grades into the Peerless Formation (Gerhard, 

1972, p. 6). On the west side of the Sawatch Range, the 

Peerless Formation consists of grayish-orange dolomitic 

sandstone and sandy dolomite and red, ochre, and gray shale, 

with a few beds of flat-pebble conglomerate (Bryant, 1979, p. 

14-15). On the east side of the Sawatch Range, the Peerless 

Formation can be nearly all sandstone, shale, or dolomite but 

commonly consists of tan, maroon, and green sandy dolomite, flat-pebble conglomerate, dolomitic sandstone, and 

shale (Tweto, 1949, p. 161-165; Tweto and Levering, 1977, 

p. 19). On the east side of the Gore Range, the Peerless Formation in ascending order consists of thinly to massively 

bedded, purple and black pebbly quartzite; brown-weathering 

dolomite; thinly bedded, green shale with interbedded dolomite; and thinly bedded, olive-green and brown dolomite 

with interbedded green shale (Singewald, 1951, p. 9).

Outcrops in the Wasatch Range described by Baker and Crittenden (1961) and Baker (1972,1973) indicate that the Gallatin 

Limestone extends continuously into southeastern Utah west of 

an area of pre-Mississippian erosion. In the Wasatch Range, 

however, strata equivalent to the Gallatin Limestone are assigned to the Maxfield Limestone. The thickness of the 

Maxfield Limestone varies substantially within short distances 

because of the pre-Mississippian erosion, and locally the formation has been removed entirely. Fairly complete sections 

consist of thinly to massively bedded, gray, yellow, and brown, 

mottled limestone with oolitic or pisolitic beds near the base 

overlain by massively bedded, medium-gray to nearly white 

dolomite. On the southwestern side of the Uinta Mountains, 

light-gray and brown limestone mapped by Huddle and others 

(1951) as Upper Cambrian(?) limestone is interpreted in this report to be an erosional remnant of the Maxfield Limestone. In 

southeastern Utah, northwest of an axis of thinning that extends 

from the vicinity of Lake Powell to the Uncompahgre Plateau, 

the Maxfield Limestone (locally called Bowman-Hartman 

Limestone) in boreholes consists of massively bedded, gray 

and tan, commonly glauconitic, fine-grained, sucrose, oolitic or 

stromatolitic limestone with thin to thick intervals of white, tan, 

and brown dolomite and thin interbeds of green, gray, and 

black shale (Cooper, 1960, p. 73).

Overlying the Maxfield Limestone in boreholes in southeastern Utah, predominantly dolomitic strata, probably equivalent 

to the upper dolomite interval of the Maxfield Limestone in the 

Wasatch Range, generally have been assigned to the Lynch Dolomite (Hintze, 1973). The Lynch Dolomite in southeastern 

Utah (Cooper, 1960, p. 73) predominantly consists of massively bedded, gray, brown, and beige, fine-grained, crystalline, 

sucrose, oolitic, stromatolitic, and cherty dolomite with 

intervals of grayish-green, micaceous shale, sandstone, and 

limestone. The nondolomitic beds are most abundant toward 

the base and eastern margin, where the Lynch Dolomite grades 

into the Maxfield Limestone and Ophir Shale.

South and east of the limits of Maxfield-Lynch terminology, 

equivalent strata are assigned to the Muav Limestone or are 

unnamed. The Muav Limestone crops out in canyons of the 

Colorado and Little Colorado Rivers south of Lees Ferry, Ariz. 

McKee and Resser (1945) divided the Muav Limestone in the 

Grand Canyon (fig. 2) into seven members overlain by dolomite. The five lowest members pinch out eastward and become 

carbonate tongues in the Bright Angel Shale. Noble (1922) 

considered the Muav Limestone in the Grand Canyon to be divisible into four informal stratigraphic units, which in ascending order consist of (1) thinly bedded, gray and buff, mottled, 

oolitic limestone interlayered with intraformational conglomerate; (2) thinly bedded, mottled limestone, intraformational 

conglomerate, micaceous to calcareous sandstone, and shale; 

(3) crystalline limestone and dolomite with intraformational 

conglomerate; and (4) massively bedded, vuggy dolomite. 

Eastward, in Arizona, Utah, and Colorado, unnamed beds 

equivalent to the Muav Limestone become increasingly shaly, 

as they grade into beds equivalent to the Bright Angel Shale 

(fig. 13).

As designated in this report, the Lynch Dolomite and beds 

equivalent to the Muav Limestone incorporate most of the 

rocks assigned to the Aneth Formation by Knight and Cooper 

(1955) in the Four Corners area. The Aneth Formation consists 

of brown, gray, and green, shaly, glauconitic, and oolitic dolomite with black shale interbeds that are particularly abundant in 

the upper part of the formation. On the basis of fish plates 

found in the Shell 1-Bluff well (SLD 39-23-32abb), Knight and 

Cooper (1955) assigned the Aneth Formation to the Devonian 

System. However, Clark (1963, p. 62-63) indicated that the 

Aneth Formation in other wells also contains Cambrian and Ordovician trilobite, brachiopod, and conodont fossils. The age 

of the Aneth Formation, therefore, is questionable. For the 

Aneth Formation to exist as a separate, lithologically and 

paleontologically distinct formation requires an abrupt scouring of lithologically similar Cambrian carbonate rocks. (See, 

for example, Parker and Roberts, 1963, p. 42.) Such profound 

erosion is unlikely to have occurred in the relatively stable 

tectonic setting of the Four Corners area. More likely, as 

suggested by Clark (1963, p. 64), most of the so-called Aneth 

Formation is a lateral facies equivalent of the Lynch Dolomite 

and Muav Limestone. Assuming that the fish plates in the Shell 

1-Bluff well were identified correctly, some or all of the beds 

designated as Aneth Formation in this .well probably represent 

a basal facies of the Devonian Elbert Formation that may not 

extend far beyond the vicinity of the well.

COMPONENT GEOLOGIC UNITS OF ORDOVICIAN AGE

In southwestern Wyoming, the entire Ordovician sequence 

is assigned to the Bighorn Dolomite (fig. 16). In this area, the 

Bighorn Dolomite is divisible into three members: the Lander 

Sandstone Member, the unnamed middle member (most of the 

formation), and the Leigh Dolomite Member. The Lander
GEOLOGY OF PALEOZOIC ROCKS, UPPER COLORADO RIVER BASIN A23

FIGURE 16. Ordovician Bighorn Dolomite 

(cliff-forming unit) in the Salt River 

Range of the Overthrust Belt in 

Wyoming. The thickness, here, has 

been doubled by imbricate thrust 

faults.

Sandstone Member occurs in lenticular bodies less than 5 ft 

thick at the southeastern end of the Wind River Mountains 

(Keefer and Van Lieu, 1966, p. 22). It is a tan and gray, fineto coarse-grained sandstone that contains fragments of 

Cambrian carbonate rocks. The unnamed middle member of 

the Bighorn Dolomite, as described by Foster (1947, p. 1548- 

1549) in the Gros Ventre Range, by Oriel (1969, p. 7) in the 

Overthrust Belt, and by Keefer and Van Lieu (1966, p. 22) in 

the Wind River Mountains, is a massively bedded, beige and 

light-gray mottled, granular dolomite that is about 300-1,000 

ft thick. The Leigh Dolomite Member, varying from 0 to 85 ft 

thick, consists of very thin bedded (flaggy), white, light-gray, 

and pink, fine-grained dolomite (Foster, 1947, p. 1549; Keefer 

and Van Lieu, 1966, p. 22).

In northwestern Colorado, the Ordovician sequence in 

ascending order consists of the Manitou Dolomite, the Harding 

Sandstone, and the Fremont Limestone. The Harding Sandstone is the lateral equivalent of the Lander Sandstone Member 

of the Bighorn Dolomite; the Fremont Limestone is the lateral 

equivalent of the unnamed middle member of the Bighorn 

Dolomite. The Manitou Dolomite generally is the only 

Ordovician formation present. However, erosional remnants 

of the Harding Sandstone and Fremont Limestone occur in the 

southern Elk Mountains, and the Harding Sandstone 

constitutes the entire Ordovician sequence between the 

Sawatch and Gore Ranges.

The Manitou Dolomite predominantly consists of dolomite but varies in texture and bedding characteristics from 

area to area. In Glenwood Canyon on the southeastern side 

of the White River Plateau, the formation (fig. 15) is divisible 

into a lower member consisting of gray, thin-bedded,

limestone-pebble conglomerate, brown limestone and dolomite, and greenish-gray, limy shale, and an upper member 

consisting of brown, thin-bedded, siliceous dolomite (Bass 

and Northrop, 1963, p. 14). In the southern Sawatch Range 

and Elk Mountains, the Manitou Dolomite consists of predominantly gray, thin- to medium-bedded, fine-grained to 

crystalline dolomite with stringers and nodules of chert and 

interbeds of pink shale (Dings and Robinson, 1957, p. 11; 

Mallory, 1957; Gerhard, 1972, p. 8; Bryant, 1979, p. 15). In 

the Gore Range, the Manitou Dolomite consists of white and 

bluish-gray crystalline dolomite with siliceous layers (Singewald, 1951, p. 9).

The Harding Sandstone is less than 10 ft thick in most places where it is present. Variations in texture are best observed 

in two places where the Harding Sandstone is about 40 feet 

thick. In the Minturn area, at the northeastern end of the Sawatch Range, the Harding Sandstone consists of lenticular 

masses of white quartzite overlain by thin-bedded green and 

maroon sandstone, quartzite, and conglomerate with shale interbeds (Tweto and Levering, 1977, p. 21-22). In the 

Garfield area, at the southern end of the Sawatch Range, the 

Harding Sandstone characteristically consists of white, bluishgray, and black quartzite (Dings and Robinson, 1957, p. 12).

The Fremont Limestone is present only in the southern Elk 

Mountains and Sawatch Range. In the Crested Butte area, at 

the southern end of the Elk Mountains, the Fremont Limestone consists of massively bedded, gray and brown, finegrained dolomite (Mallory, 1957). In the Garfield area, at the 

southern end of the Sawatch Range, the Fremont Limestone 

consists of massively bedded, bluish-gray crystalline dolomite 

(Dings and Robinson, 1957, p. 13).
A24 REGIONAL AQUIFER SYSTEM ANALYSIS UPPER COLORADO RIVER BASIN

CONTACTS

Contacts between Cambrian and Ordovician formations, 

between Ordovician formations, and between Ordovician and 

younger formations generally are unconformable. In southwestern Wyoming, for example, the Bighorn Dolomite unconformably overlies the Gallatin Limestone and underlies the 

Devonian Darby Formation from the Snake River Range to the 

southern Wind River Mountains. The pre-Ordovician erosional surface has relief ranging from 100 ft in the northwestern 

Wind River Mountains to 3 ft in the southeastern part of this 

range (Keefer and Van Lieu, 1966, p. 20), and, locally, the 

Lander Sandstone Member of the Bighorn Dolomite fills channels cut into this surface. The pre-Devonian erosional surface 

has a relief of as much as 20 ft; breccia and sandstone deposits 

at the base of the Devonian Darby Formation fill channels cut 

into this surface (Keefer and Van Lieu, 1966, p. 23-28). From 

the southern end of the Wind River Mountains to the area west 

of Rawlins, pre-Mississippian erosion has removed rocks from 

Devonian to Cambrian age; in this area, the Mississippian 

Madison Limestone from west to east successively truncates 

the Darby Formation, Bighorn Dolomite, and Gallatin Limestone (fig. 12).

In northwestern Colorado, contacts between the Dotsero 

and Peerless Formations of Cambrian age and the Manitou 

Dolomite of Ordovician age generally are gradational (Gerhard, 1972, p. 10-11). However, because the Ordovician formations are erosional remnants, the Manitou Dolomite does 

not overlie the Dotsero and Peerless Formations wherever 

they occur. Where the Manitou Dolomite is missing, the Ordovician Harding Sandstone, Devonian Parting Formation, or 

Devonian to Mississippian(?) Dyer Dolomite may overlie the 

Dotsero and Peerless Formations. The Ordovician Manitou 

Dolomite, Harding Sandstone, and Fremont Limestone are 

separated from each other and from Devonian rocks by regional unconformities (Tweto and Levering, 1977, p. 21-22).

In southwestern Colorado, southeastern Utah, and northeastern Arizona, major erosional unconformities separate 

Cambrian carbonate formations from Devonian and Mississippian rocks. Throughout most of its areal extent, the 

Maxfield Limestone-Lynch Dolomite sequence is overlain 

unconformably by the Elbert Formation (Cooper, 1960, p. 

73). However, in the Wasatch Range and Uinta Mountains 

bordering the western Uinta Basin, the Lynch Dolomite and 

Maxfield Limestone successively have been truncated by preMississippian erosion and are overlain unconformably by 

Mississippian formations (Huddle and others, 1951; Baker 

and Crittenden, 1961; Baker, 1973). The Muav Limestone 

and unnamed equivalent strata to the east are overlain unconformably by the Devonian Temple Butte and Elbert Formations, although where observed in the Grand Canyon, the 

unconformity generally parallels bedding (Irwin and others, 

1971, p. 7).

ELBERT-PARTING CONFINING UNIT

The Elbert-Parting confining unit (pi. 10) is composed of the 

lithologically diverse initial deposits of a third Paleozoic 

marine transgression (Baars, 1972; Kent, 1972). Component 

geologic units include the Darby, Parting, and Elbert Formations and the Cottonwood Canyon Member of the Madison and 

Lodgepole Limestones (table 1 and pi. 5). The Temple Butte 

Formation of the Grand Canyon area grades into the Elbert 

Formation along an indefinite boundary at or near the southwestern edge of the UCRB. Paleontological data indicate that 

most of the component formations are Upper Devonian (Bass 

and Northrop, 1963, p. 20-21; Benson, 1966; Keefer and Van 

Lieu, 1966, p. 27; Baars and others, 1987, p. 346). However, 

channel deposits at the base of the Darby Formation in the 

Wind River Mountains contain Early Devonian fish remains, 

and the upper part of the Cottonwood Canyon Member 

contains Early Mississippian conodonts (Sando, 1979, p. 5).

Formations comprising the Elbert-Parting confining unit 

apparently were deposited in three basins, which are separated 

by areas where the formations are thin to absent (pi. 10). In 

Wyoming, the Darby Formation and Cottonwood Canyon 

Member thicken westward from zero on the Rock Springs 

Uplift to about 1,100 ft in the Overthrust Belt. The thickness 

of the Parting Formation in northwestern Colorado and the 

Uinta Basin increases from zero to more than 150 ft toward the 

center of its depositional basin. The thickness of the Elbert and 

Temple Butte Formations in southwestern Colorado, southeastern Utah, and northeastern Arizona increases from zero at the 

edges of the Uncompahgre Plateau, San Juan Mountains, San 

Juan Basin, and Grand Canyon area to more than 300 ft in the 

High Plateaus region and more than 400 ft in the Black Mesa 

Basin. The Elbert-Parting confining unit is missing in 

Wyoming east of the Rock Springs Uplift; in the Uinta Mountains and most of the Uinta Basin; in northwestern Colorado 

north of the Yampa River, south of the Piceance Basin and Elk 

Mountains, and east of the Sawatch and Gore Ranges; in the 

Uncompahgre and Gunnison Plateaus; and in parts of the San 

Juan Mountains and Four Comers Platform. Thickness and 

lithofacies patterns indicate that geologic units that comprise 

the Elbert-Parting confining unit were eroded from the centers 

of the White River Plateau and Sawatch Range but did not 

extend much beyond present limits in other areas.

COMPONENT GEOLOGIC UNITS

Rocks comprising the Elbert-Parting confining unit in 

Wyoming are assigned mostly to the Darby Formation, which 

has extremely variable lithology. However, despite the lateral 

discontinuity of individual layers, the formation as a whole 

becomes increasingly more clastic eastward across its area of 

extent.

In the Overthrust Belt and Gros Venire Range, the Darby 

Formation (fig. 17) is divisible into three units, which Benson
GEOLOGY OF PALEOZOIC ROCKS, UPPER COLORADO RIVER BASIN A25

FIGURE 17. Devonian and Mississippian Darby Formation and Mississippian 

Lodgepole Limestone on the upthrown side of the Hoback Fault, at the 

juncture of the Gros Ventre and Hoback Ranges in Hoback Canyon, Wyo.

(1966) considered equivalent to the lower member and Birdbear Member of the Jefferson Formation and the Three Forks 

Formation. The lowest unit consists of dark-brownish-gray, 

fine- to medium-crystalline and sucrose, petroliferous dolomite 

and limestone with interbedded light-gray to white sandstone 

and siltstone, green and red claystone and mudstone, and, 

locally, minor solution breccia or anhydrite. The middle unit 

consists of massively bedded, brownish-gray, finely crystalline 

dolomite. The upper unit consists of thinly bedded, green, 

gray, brown, and red, dolomitic shale, shaly dolomite, solution 

breccia, and anhydrite overlain by gray, shaly to silty, finegrained dolomite.

To the east, at the northwestern end of the Wind River 

Mountains, the Darby Formation chiefly consists of 

varicolored dolomite and limestone overlain by gray and tan 

cherty dolomite and grayish-green shale (Richmond, 1945). 

Sandstone layers progressively increase in abundance southward in the Wind River Mountains (Keefer and Van Lieu,

1966, pi. 2) and predominate on the western flank of the Rock 

Springs Uplift.

Overlying the Darby Formation west of the Rock Springs 

Uplift is a thin (0-80 ft thick) unit, which is assigned to the 

Cottonwood Canyon Member of the Lodgepole Limestone in 

the Overthrust Belt and western Gros Ventre Range and to the 

Cottonwood Canyon Member of the Madison Limestone elsewhere (Sando, 1979). According to Benson (1966, p. 2599), 

this unit consists of dark-gray, carbonaceous shale, yellowbrown, silty, crinoidal dolomite and, locally, a basal layer of 

pebbly sandstone or siltstone.

In northwestern Colorado and the Uinta Basin of Utah, the 

Parting Formation makes up the Elbert-Parting confining unit. 

The Parting Formation, like the Darby Formation, exhibits 

major changes in lithology over short distances (Campbell, 

1972, p. 56). In the southern Sawatch Range, for example, the 

Parting Formation consists mostly of gray dolomite with sandstone and sandy limestone interbeds overlying varicolored 

shale and limestone (Dings and Robinson, 1957, p. 14). On the 

northwest side of the Sawatch Range, the Parting Formation 

consists of tan and white, poorly sorted quartzite with greenishgray sandstone and shale interbeds and a thin basal layer of 

green clay-shale (Tweto and Levering, 1977, p. 24-26). In 

Glenwood Canyon west of the Sawatch Range, the Parting 

Formation (fig. 18) consists of interbedded light-green, micaceous shale and sandstone, black shale and dolomite, and tan 

quartzite (Bass and Northrop, 1963, p. 19-20). In the Wilson 

Creek oil field, on the Axial Basin Arch, the Parting Formation 

consists of dolomite with interbeds of red and green shale 

(Ross, 1986, p. 99). Extreme lithologic variability from outcrop to outcrop is characteristic of the Parting Formation, but 

regionally, clastic layers decrease and carbonate layers increase 

from the edges to the center of the depositional basin.

In southwestern Colorado, southeastern Utah, and northeastern Arizona, the Elbert Formation comprises the Elbert-Parting 

confining unit. The Elbert Formation, like other components of 

this hydrogeologic unit, is lithologically diverse. On the flanks 

of the San Juan Mountains, the Elbert Formation (fig. 3) predominantly consists of green, red, and purple shale with interbedded limestone, dolomite, and quartzite (Baars and Knight, 

1957, p. 118; Baars and others, 1987, p. 346). At the southwestern edge of the study area, the Elbert Formation consists 

almost entirely of dolomite and limestone. Throughout most of 

the region, though, the Elbert Formation contains a basal sandstone interval, a middle carbonate interval, and an upper shale 

interval.

The basal sandstone interval extends discontinuously from 

the Defiance Plateau to the Uncompahgre Plateau and from the 

San Juan Mountains to the area west of the Colorado and Green 

Rivers (fig. 19). It ranges from less than 5 to about 125 ft thick 

and consists predominantly of white, light-gray, and red, poorly sorted, commonly glauconitic sandstone and quartzite with 

minor interbeds of shale, limestone, and dolomite. This interval commonly is called the McCracken Sandstone Member of
A26 REGIONAL AQUIFER SYSTEM ANALYSIS UPPER COLORADO RIVER BASIN

FIGURE 18. Devonian Parting Formation in fault contact with Ordovician Manitou Dolomite in Glenwood Canyon at Glenwood Springs, Colo.

the Elbert Formation (Knight and Cooper, 1955). However, 

this name often has been applied inappropriately to the first 

thick sequence of sandstone or quartzite penetrated by drilling 

and can include considerable thicknesses of underlying carbonate rocks and shale (see, for example, Parker and Roberts, 

1963, p. 40).

The middle carbonate interval comprises most of the Elbert 

Formation. As described by Cooper (1960, p. 76), this interval 

consists of thin-bedded, very fine grained to sucrose, locally 

anhydritic dolomite with thin interbeds of grayish-green, waxy 

shale, red, clayey shale, and sandstone. The sandstone beds 

increase in abundance downward in the interval.

From the San Juan Mountains to nearly the western edge of 

the UCRB, the Elbert Formation is capped by a shale interval 

(fig. 19) that ranges from less than 5 to 30 ft thick. The shale 

most typically is waxy green. However, the green layers 

locally are interbedded with purple or red layers. The shale 

locally contains discontinuous interbeds of dolomite. Where 

the shale interval is absent, the contact between the Elbert 

Formation and the overlying Ouray Limestone is difficult to 

distinguish.

CONTACTS

A major regional unconformity separates formations in the 

Elbert-Parting confining unit from underlying formations. The 

Darby, Parting, Elbert, and Temple Butte Formations rest on 

formations ranging in age from Precambrian to Ordovician.

Geologic units comprising the Elbert-Parting confining unit 

are overlain conformably in most areas by Devonian and 

Mississippian rocks. In northwestern Colorado, the Parting 

Formation is overlain conformably to transitionally by the 

Upper Devonian to Mississippian(?) Dyer Dolomite (Tweto 

and Levering, 1977, p. 27). Similarly, the Elbert Formation in 

southwestern Colorado, southeastern Utah, and northeastern 

Arizona is overlain conformably to gradationally by the Upper 

Devonian Ouray Limestone (Baars and others, 1987, p. 346). 

However, the Temple Butte Limestone in the Grand Canyon is 

overlain unconformably by the Mississippian Redwall

Limestone (Beus and Lucchita, 1987, p. 7), and the Darby 

Formation and Cottonwood Canyon Member of the Madison 

and Lodgepole Limestones in Wyoming are overlain unconformably by other members of the Madison and Lodgepole 

Limestones (Wanless and others, 1955, p. 19; Keefer and Van 

Lieu, 1966, pi. 2).

MADISON AQUIFER

The Madison aquifer of the Northern Great Plains (Downey, 

1984) extends into the UCRB, where it is divisible vertically 

into two zones with different lithologic and hydrologic 

properties. The lower zone, which consists almost entirely of 

limestone and dolomite, is named the Redwall-Leadville zone 

in this report, after the principal component geologic units in 

Arizona, Colorado, and Utah. The upper zone, which consists 

of interbedded carbonate rocks, sandstone, shale, solution 

breccia, and gypsum, is named the Darwin-Humbug zone in 

this report, after the two geologic units that comprise most of 

the interval. As shown on plate 7, the Madison aquifer is at or 

near land surface on the flanks of uplifted areas, but it typically 

is 5,000 to 32,000 ft deep in structural basins.

REDWALL-LEADVILLE ZONE

The Redwall-Leadville zone of the Madison aquifer (pi. 11) 

consists almost entirely of limestone and dolomite deposited 

during the maximum extent of the third Paleozoic marine transgression (Craig, 1972; Kent, 1972). Component geologic units 

include the Dyer Dolomite, Ouray Limestone, Oilman Sandstone, Leadville Limestone, and Redwall Limestone; the Mission Canyon Limestone below the lowest evaporite zone of 

Sando (1977); and the main bodies of the Lodgepole and Madison Limestones (table 1 and pi. 5). All the carbonate formations are so similar in lithology that they probably represent a 

single depositional history. In an attempt to establish limits for 

these geologic units on the basis of criteria other than stateline 

preference, some geologic units were delineated on the basis of
GEOLOGY OF PALEOZOIC ROCKS, UPPER COLORADO RIVER BASIN A27

112° 111° 110° 109° 108°

39°

38°

37'

36°

COLORADO 

NEW MEXICO

Boundary of 

study area

EXPLANATION 

Basal sandstone interval

25 50

I

0 25 50

r

75

75

I

100 MILES

100 KILOMETERS

FIGURE 19. Extent of lithologic subdivisions of the Elbert Formation in the Upper Colorado River Basin. The middle 

carbonate interval extends to the boundaries of the Elbert Formation. The basal sandstone and upper shale intervals 

do not extend throughout the area where the Elbert Formation is present; boundaries of these intervals are as shown.

lithologic changes. For example, the boundary between the 

Leadville and Redwall Limestones along the Colorado-Utah 

border was established at the change from randomly cherty 

limestone and dolomite on the east to a four-fold sequence of 

cherty, oolitic, or anhydritic limestone and dolomite alternating 

with generally nondescript limestone and dolomite on the west. 

The eastern facies was assigned to the Leadville Limestone; the 

western facies to the Redwall Limestone. The boundary 

between the two formations undulates about the State line, 

broaching areas previously assigned exclusively to one 

formation or the other. All other Mississippian geologic units 

were delimited along axes of thickening or thinning, presumably coincident with changes in the depositional setting. 

Devonian formations were delimited on the basis of overlying 

Mississippian formations.

Some established geologic names were not used in this 

report because no consistent lithological, paleontological, or 

inferred paleodepositional criteria could be identified for 

delineating these geologic units. For example, the Madison 

and Brazer Limestones in the Gros Venire Range and 

Wyoming part of the Overthrust Belt, as used by Wanless and 

others (1955), are not distinguished readily by lithology (Wanless and others, 1955, p. 22). However, in the same area, the 

names "Lodgepole Limestone" and "Mission Canyon Limestone," as used by Sando (1967, 1977, 1979) are applied consistently. Consequently, the latter names are used in this report.

The Lodgepole and Mission Canyon Limestones also are 

recognizable in the Utah part of the Overthrust Belt adjacent to 

the UCRB (in the Wasatch Range) and in the western Uinta 

Mountains. However, in the Utah part of the Overthrust Belt,
A28 REGIONAL AQUIFER SYSTEM ANALYSIS UPPER COLORADO RIVER BASIN

the names "Fitchville Formation," "Gardison Limestone," and 

"Deseret Limestone" are applied in ascending order to strata 

equivalent to the Lodgepole and Mission Canyon Limestones 

(see, for example, Baker, 1973). The Lodgepole and Mission 

Canyon equivalents in the western Uinta Mountains, respectively, have been called either "Madison Limestone" (Huddle 

and others, 1951) or "Gardison Limestone" (Hintze, 1973) and 

"Deseret Limestone" (Huddle and others, 1951; Hintze, 1973). 

Within the Utah Salient of the Overthrust Belt in the UCRB and 

adjacent areas of the Uinta Basin, either the Wyoming or Utah 

nomenclature could be applied. In this report, the FitchvilleGardison-Deseret terminology is not used because it generally 

has been applied outside the UCRB, and if used in the UCRB, 

would only pertain to a relatively small area. Exclusive of the 

Uinta Mountains, the rocks in question simply are called 

"Lodgepole and Mission Canyon equivalents."

In the Uinta Mountains, the nomenclature of the Mississippian rocks is complicated further because the names "Madison 

Limestone" and "Deseret Limestone" have been extended 

throughout the range, even though rocks equivalent to the 

Mission Canyon Limestone are not present in the eastern part 

of the range (Hansen, 1965a, p. 39). As a result, different lithologic criteria have been used to distinguish the Madison and 

Deseret Limestones in different parts of the Uinta Mountains 

(Huddle and McCann, 1947b; Untermann and Untermann, 

1954). To simplify discussion, all Mississippian carbonates 

below the Humbug Formation in the Uinta Mountains herein 

are called "Madison Limestone," even though it is recognized 

that either the Lodgepole-Mission Canyon or FitchvilleGardison-Deseret terminology could be extended justifiably 

into the western Uinta Mountains.

Ages of the geologic formations included in the RedwallLeadville zone are well established by abundant fossil 

evidence. The Dyer Dolomite and Ouray Limestone are mostly 

Upper Devonian, but upper layers contain Early Mississippian 

(Kinderhookian) brachiopods, corals, and foraminifera (Baars 

and Knight, 1957, p. 121; Bass and Northrop, 1963, p. 22-23; 

Nadeau, 1972, p. 97-98; Tweto and Levering, 1977, p. 28; 

Baars and others, 1987, p. 346). On the basis of stratigraphic 

position and brachiopods found in equivalent strata in the 

Wasatch Range, Ferris Mountains, and Washakie Basin 

(Thomas, 1951; Baker, 1973), the Oilman Sandstone and sandstone at the base of the Madison Limestone probably are Lower 

Mississippian (Kinderhookian). The Leadville Limestone 

(Armstrong and Mamet, 1976, p. 20), the main bodies of the 

Madison and Lodgepole Limestones (Kinney, 1955, p. 30-31; 

Sando, 1967, 1977, 1979), Lodgepole equivalents in the 

Wasatch Range and western Uinta Basin (Baker, 1973), and the 

Whitmore Wash and Thunder Springs Members of the Redwall 

Limestone (McKee, 1979, p. 200-204) contain abundant 

brachiopods, corals, and foraminifera, indicating that these 

geologic units all are Lower Mississippian (Kinderhookian to 

Osagean). Fossil evidence indicates that the part of the Mission 

Canyon Limestone included in this hydrogeologic unit in the

Overthrust Belt (Sando, 1979), the Mission Canyon equivalent 

in the Wasatch Range and Uinta Basin (Baker, 1973), the upper 

part of the Madison Limestone in the Uinta Mountains (Schell, 

1969), and the Mooney Falls and Horseshoe Mesa Members of 

the Redwall Limestone (McKee, 1979) are Lower to Upper 

Mississippian (Osagean to Meramecian).

As a consequence of repeated marine incursions from the 

west, an eastward-rising sea floor during deposition, and uplift 

and erosion on the east as the Mississippian sea withdrew, the 

Redwall-Leadville zone generally becomes thinner eastward. 

The Redwall-Leadville zone decreases in thickness from a 

range of 1,300 to 2,500 ft on the west side of the area to less 

than 200 ft on the east side (pi. 11). Counter to this trend, however, the unit thins over the San Rafael Swell and Yampa Plateau, possibly as a result of syndepositional uplift, and thickens 

abruptly in a narrow belt extending northward from the Eagle 

Basin of Colorado to the Great Divide Basin of Wyoming. This 

thickening may be the result of either an anomalously high rate 

of sediment accumulation in a tectonically subsiding trough or 

the apparent result of post-depositional folding or faulting. 

Geologic units that comprise the Redwall-Leadville zone have 

been eroded from the central Uinta Mountains, White River 

Plateau, S a watch Range, and San Juan Mountains and either 

were eroded from or never deposited in the Uncompahgre, 

Gunnison, and Defiance Plateaus, the Sneffels Horst, and the 

area east of the Park and Gore Ranges.

COMPONENT GEOLOGIC UNITS

In the Overthrust Belt of Wyoming and western Gros Ventre 

Range, the Redwall-Leadville zone of the Madison aquifer 

consists of the Paine and Woodhurst Members of the Lodgepole Limestone (fig. 17) and the overlying Mission Canyon 

Limestone below the lowermost evaporite zone identified by 

Sando (1977) within the Mission Canyon Limestone. The 

Lodgepole Limestone and the part of the Mission Canyon 

Limestone that lies below the evaporite zones are about equally 

thick. The Paine Member of the Lodgepole Limestone consists 

of dark-gray, thinly bedded, silty and shaly, mostly fine 

grained, locally cherty limestone. The overlying Woodhurst 

Member consists of thinly bedded, dark-gray, alternately silty 

and fine-grained or oolitic and crinoidal, fossiliferous limestone (Sando, 1979, p. 5; Sando andDutro, 1981). The Mission 

Canyon Limestone below the evaporite zones consists of thickly bedded, light-gray to bluish-gray, oolitic, crinoidal, crystalline limestone and thinly bedded, cherty, fine-grained dolomite 

and dolomitic limestone (Sando, 1977, p. 176; 1979, p. 8-10; 

Sando and Dutro, 1981).

According to Sando (1967, p. 532-533), changes in 

mineralogical composition, texture, bedding character, and 

marker beds prevent extending the stratigraphic nomenclature 

of the Overthrust Belt beyond its eastern margin. Thus, 

Mississippian carbonate rocks in Wyoming from the eastern
GEOLOGY OF PALEOZOIC ROCKS, UPPER COLORADO RIVER BASIN A29

Upper part of 

Mission Canyon Limestone

Lower part of Mission Canyon Limestone \

FIGURE 20. Depositional model for Mississippian carbonate formations in Wyoming. Modified from Rose (1977, fig. 5); arrows indicate dkection in which 

depositional environment of geologic unit progressed. The Darwin Sandstone is a member of the Amsden Formation.

Gros Ventre Range to the Rawlins Uplift and Sierra Madre are 

assigned to the Madison Limestone. As interpreted by Rose 

(1977), the Madison Limestone is a shallow-marine shelf deposit, and the Lodgepole Limestone is a shelf-margin deposit 

(fig. 20). The Mission Canyon Limestone was deposited over 

the former shelf margin as the sea withdrew at the end of 

Osagean time.

In the eastern Gros Ventre Range and Wind River Mountains, the Madison Limestone is divisible into six members 

(Sando, 1977, 1979, 1982). The lowest member, the Devonian and Lower Mississippian Cottonwood Canyon Member, 

is similar in lithology to the Darby Formation and is included 

with it in the Elbert-Parting confining unit. The uppermost 

member, the Bull Ridge Member, is similar in lithology to 

the Mission Canyon Limestone above the base of the evaporite zones and is included with this interval in the DarwinHumbug zone of the Madison aquifer. The remaining members of the Madison Limestone are the Little Bighorn and 

Woodhurst Members (which are equivalent to the Lodgepole 

Limestone), the Big Goose Member, and the Little Tongue 

Member.

The Madison Limestone becomes increasingly more dolomitic from northwest to southeast along the Wind River 

Mountains as lower members pinch out and upper members 

thin because of erosion (Sando, 1967, p. 533). The stratigraphically lowest member in the Redwall-Leadville zone, 

the Little Bighorn Member is 49-102 ft thick and consists 

mostly of thickly bedded, crinoidal dolomite and dolomitic 

limestone. The overlying Woodhurst Member, 195-335 ft 

thick, consists mostly of thinly bedded, fine-grained to 

crystalline, pelletal and oolitic limestone and dolomitic limestone interbedded with dolomitic mudstone. Next in succession, the Big Goose Member is 210-328 ft thick and consists 

mostly of thickly bedded, cherry, fine- to coarse-grained,

fossiliferous dolomite, dolomitic limestone, and subordinate 

limestone; beds commonly are shattered and brecciated. The 

uppermost member in the Redwall-Leadville zone, the Little 

Tongue Member, is 119-239 ft thick; it consists mostly of 

medium- to thick-bedded, cherry, fine- to coarse-grained, fossiliferous limestone and dolomite. An interval of solution 

breccia overlain by shattered and brecciated beds generally is 

present at the base of the Little Tongue Member but has been 

removed by erosion in the southeastern Wind River Mountains. Beds of red siltstone and sandstone are present in solution cavities throughout the Little Tongue Member.

From the southeastern Wind River Mountains east to the 

Rawlins Uplift and Sierra Madre, the Woodhurst, Big Goose, 

and Little Tongue Members make up most of the Madison 

Limestone (see Sando, 1967, fig. 3; 1979, fig. 5, section AA'}. In this area, the basal 5-35 feet of the Madison Limestone consists of sandstone, siltstone, and conglomerate (Thomas, 1951, p. 34; Keefer and Van Lieu, 1966, p. 33; Sando, 

1967, p. 557; 1979, p. 12), that on the basis of sparse brachiopods may be equivalent to the Gilman Sandstone of Colorado, 

a deposit of probable Early Mississippian age. Similar deposits of sandstone and conglomerate between rocks of definite 

Cambrian and Madison lithologies in die western Uinta 

Mountains (Huddle and McCann, 1947b; Huddle and others, 

1951) also may be a Gilman Sandstone equivalent.

In the Wasatch Range and western Uinta Basin, the Lodgepole equivalent consists in ascending order of (1) few inches to 

20 ft of gray to brown, pebbly sandstone and sandy dolomite; 

(2) 100-260 ft of thinly to massively bedded, light- to darkgray, vuggy dolomite; and (3) 500-900 ft of thinly to massively bedded, medium- to dark-gray, cherty limestone and dolomite that become more dolomitic toward the north, west, and 

south (Baker and Crittenden, 1961; Baker, 1964, 1972, 1973). 

The Mission Canyon equivalent consists of 375-585 ft of
A30 REGIONAL AQUIFER SYSTEM ANALYSIS UPPER COLORADO RIVER BASIN

thickly to massively bedded, light- and dark-gray-banded, 

fine- to coarse-grained, cherty limestone and dolomite (Baker 

and Crittenden, 1961; Baker, 1964, 1972, 1973).

In general, the Madison Limestone of the Uinta Mountains 

is very similar in lithology to Mississippian deposits in the 

Overthrust Belt, Gros Ventre Range, and Wind River Mountains. As shown by Rose (1977, fig. 8), equivalents of the 

Lodgepole and Mission Canyon Limestones in the western 

Uinta Mountains grade eastward into a sequence of typical marine-shelf lithology. In the western Uinta Mountains, the 

Lodgepole equivalent ("the Madison or Gardison Limestone") 

consists predominantly of thinly bedded, dark-gray, finegrained to crystalline, cherty limestone and dolomitic limestone with shale partings (Huddle and McCann, 1947b). The 

lower Mission Canyon equivalent ("the Deseret Limestone") 

consists of thickly bedded, light- to dark-gray and brown, finegrained to crystalline, cherty limestone and dolomitic limestone (Huddle and McCann, 1947b; Huddle and others, 1951). 

In the eastern Uinta Mountains, the Madison Limestone (fig. 

4) consists mostly of thickly to massively bedded, light- to 

dark-gray and tan, fine- to medium-grained, sparsely fossiliferous, locally dolomitic, and commonly cherty limestone (Kinney, 1955, p. 26; Ritzma, 1959, p. 22; Hansen and others, 

1983). Shaly carbonate beds near the base can be traced into 

Colorado, where they are assigned to the Upper Devonian and 

Lower Mississippian(?) Dyer Dolomite (Hallgarth, 1959).

In northwestern Colorado, the Dyer Dolomite, Oilman 

Sandstone, and Leadville Limestone comprise the RedwallLeadville zone. In the White River Plateau and southeastern 

Sawatch Range, the Dyer Dolomite consists mostly of gray, 

fossiliferous limestone overlain by gray, fine-grained to finely 

crystalline limestone and dolomite with shale interbeds and

sparse chert (Dings and Robinson, 1957, p. 14; Bass and 

Northrop, 1963, p. 21-22). To the east and north, limestone 

layers become less numerous, and on the northeastern side of 

the Sawatch Range, the Dyer Dolomite consists almost entirely 

of dolomite (Campbell, 1972, p. 60; Tweto and Levering, 

1977, p. 27-28). Overlying the Dyer Dolomite in areas that 

probably were above the sea intermittently or adjacent to land 

masses at the time of deposition is the Oilman Sandstone (De 

Voto, 1980a, p. 58). In the Sawatch Range, the Oilman Sandstone consists of yellow and light-gray, fine- to mediumgrained sandstone, sandy dolomite, and limestone-chert-sandstone breccia that, together, commonly are less than 25 ft thick 

(Nadeau, 1972, p. 86; Tweto and Levering, 1977, p. 29-30; 

Bryant, 1979, p. 21). According to Bass and Northrop (1963, 

p. 26-27) and Conley (1972, p. 107-108), a 15- to 30-ft-thick 

interval at the base of the Leadville Limestone in the White 

River Plateau that consists of sandy dolomite with local interbeds of dolomitic sandstone and chert breccia probably is 

equivalent to the Oilman Sandstone. The Leadville Limestone 

in northwestern Colorado (fig. 21) typically consists of thinly 

bedded, medium- to dark-gray, fine- to medium-grained, locally cherty limestone and dolomite overlain by thickly to massively bedded, light-gray and bluish-gray, finely to coarsely 

crystalline, oolitic limestone (Dings and Robinson, 1957; Bass 

and Northrop, 1963; Conley, 1972; Nadeau, 1972; Bryant, 

1979; De Voto, 1980a). The upper facies forms about one-half 

to two-thirds of the formation. At the northeastern end of the 

Sawatch Range, the upper facies has been altered hydrothermally into vuggy, dark-gray and white banded or pearly-white 

dolomite (Tweto and Levering, 1977, p. 30-32).

In southwestern Colorado, southeastern Utah, and northeastern Arizona, the equivalent of the Dyer Dolomite is the Ouray

FIGURE 21. Cavernous Mississippian 

Leadville Limestone in Glenwood 

Canyon at Glenwood Springs, Colo. 

Large thermal springs discharge from 

the formation in this area.
GEOLOGY OF PALEOZOIC ROCKS, UPPER COLORADO RIVER BASIN A31

Limestone. This formation typically consists of gray, tan, or 

beige, shaly or sandy limestone and dolomite with interbeds of 

green and gray, waxy shale (Baars and Knight, 1957, p. 121; 

Cooper, 1960, p. 76; Baars and others, 1987, p. 346). In most 

areas, an interval of green or gray waxy shale as much as 15 ft 

thick separates the Ouray Limestone from overlying Mississippian rocks (Parker and Roberts, 1963, p. 41).

The Ouray Limestone is overlain in southwestern Colorado 

by the Leadville Limestone and to the west, in Arizona and 

Utah, by the Redwall Limestone. Consistent with its lithology 

farther north, the Leadville Limestone, where it crops out in the 

San Juan Mountains, consists of a thin interval of limestone and 

dolomite overlain by massively bedded, oolitic, bioclastic, 

crystalline limestone (Baars and Knight, 1957, p. 121; De Voto, 1980a, p. 59-63; Baars and others, 1987, p. 346). In the subsurface of the Paradox Basin and Four Corners area, however, 

the Leadville Limestone becomes increasingly more dolomitic 

and cherty westward and grades into the Redwall Limestone.

In northeastern Arizona and southeastern Utah, the Redwall 

Limestone (fig. 2) consists of four alternately transgressive and 

regressive sequences, which McKee (1963, 1979) designated 

the Whitmore Wash, Thunder Springs, Mooney Falls, and 

Horseshoe Mesa Members. The Whitmore Wash Member consists of thinly bedded, fine-grained dolomite and thickly bedded, bioclastic, and oolitic limestone and dolomite. The 

Thunder Springs Member consists of thin-bedded, fine-grained 

dolomite, bioclastic and pelletal limestone, and bedded chert, 

which locally is replaced by anhydrite. From south to north, 

dolomite layers in the Thunder Springs Member increase in 

abundance and gradually become the only carbonate rock type 

present. The Mooney Falls Member, the thickest part of the 

Redwall Limestone, consists of thickly to massively bedded, 

locally cherty, limestone and dolomite layers that alternately 

are fossiliferous, stromatolitic, oolitic, or fine grained. The uppermost member, the Horseshoe Mesa Member, grades northwestward from thinly bedded, commonly stromatolitic or 

oolitic, fine-grained limestone to cherty dolomite.

CONTACTS

The Redwall-Leadville zone of the Madison aquifer overlies 

rocks-of Precambrian to Late Devonian age (Mallory, 1979, p. 

209). In southwestern Wyoming, Mississippian carbonate 

rocks progressively overlie Devonian, Ordovician, Cambrian, 

and Precambrian rocks from west to east (fig. 22). From the 

Wasatch Range to the Duchesne River area of the western Uinta Mountains, the Mississippian rocks cut progressively deeper 

into the Cambrian depositional sequence (Huddle and McCann, 

1947b; Baker, 1964, 1973). South and east of the Uinta Basin, 

predominantly Upper Devonian carbonate rocks generally rest 

on older Devonian carbonate and clastic rocks (Mallory, 1979, 

pi. 2), indicating only a slight hiatus prior to deposition of rocks 

that comprise the Redwall-Leadville zone.

The predominantly Upper Devonian carbonate rocks are 

overlain either by the Oilman Sandstone and basal sandstone 

layers in the Madison Limestone or by Mississippian carbonate 

rocks. The Oilman Sandstone unconformably overlies the 

Dyer Dolomite in the vicinity of the Sawatch Range but disconformably overlies it to the west (Bass and Northrop, 1963, p. 

26; Tweto and Lovering, 1977, p. 28; De Voto, 1980a, p. 61). 

Where a basal sandstone is present in the Madison Limestone, 

it generally rests unconformably on Cambrian rocks (Huddle 

and others, 1951; Ritzma, 1951, p. 66). Where the Oilman 

Sandstone has been removed by erosion, as in the southern Sawatch Range, the contact between the Dyer Dolomite and 

Leadville Limestone is an unconformity with as much as 30 ft 

of relief (Dings and Robinson, 1957, p. 15; Nadeau, 1972, p. 

81). The Leadville Limestone unconformably overlies the 

Ouray Limestone in the San Juan Mountains but grades into it 

in the Paradox Basin to the west (De Voto, 1980a, p. 59-60). 

The Redwall Limestone unconformably overlies the Ouray 

Limestone in southeastern Utah (Cooper, 1960, p. 76) and the 

Temple Butte Formation in the Grand Canyon area of northeastern Arizona (McKee, 1969, p. 44).

Within the Mississippian sequence, contacts between formations or members of formations generally are conformable or 

disconformable (see, for example, McKee, 1979, p. 203). 

However, the contact between the Oilman Sandstone and Leadville Limestone is an unconformity (Tweto and Lovering, 

1977, p. 28; De Voto, 1980a, p. 61).

The upper surface of the Redwall-Leadville zone is an unconformity that progressively truncates older rocks from west 

to east across the region. North of the Uinta Mountains, from 

the Overthrust Belt to the Rock Springs Uplift, the Upper Mississippian Darwin Sandstone Member of the Amsden Formation unconformably overlies a progressively thinner interval of 

Upper Mississippian rocks at the top of the Mission Canyon 

and the Madison Limestones; east of the Rock Springs Uplift, 

the Darwin Sandstone Member rests on Lower Mississippian 

layers in the Madison Limestone (Sando, 1967, fig. 3; 1979, 

fig. 5). Similarly, from the Wasatch Range east to the eastern 

Uinta Mountains, the Upper Mississippian Humbug Formation 

rests on strata in the Deseret and Madison Limestones that progressively increase in age from Late to Early Mississippian. 

South and east of the Uinta Mountains, an erosional surface 

overlain by the Lower Pennsylvania Molas Formation cuts 

progressively deeper into the Redwall and Leadville Limestones from west to east. The uppermost layers of the Redwall 

Limestone, on the west, are Upper Mississippian, whereas the 

uppermost layers of the Leadville Limestone, on the east, are 

Lower Mississippian. In the eastern Gore Range and western 

San Juan Mountains, the Molas Formation rests on Upper Devonian rocks. Thus, from west to east, formations forming the 

top of the Redwall-Leadville zone increase in age from Late 

Mississippian to Late Devonian. Coincident with deepening of 

the erosional surface, relief on the surface increases from a few 

feet in the western part of the region to more than 100 ft in the
A32

111

REGIONAL AQUIFER SYSTEM ANALYSIS UPPER COLORADO RIVER BASIN

110° 109° 108°

75 100 KILOMETERS 

EXPLANATION 

Devonian

Ordovician

Cambrian

Precambrian

GROS VENTRE 

FORMATION

FIGURE 22. Pre-Mississippian geology in Wyoming. Geologic units in contact with overlying Mississippian rocks are shown.

eastern part (Keefer and Van Lieu, 1966, p. 33; McKee, 1969, 

p. 46; De Veto, 1980a, p. 68-69). Where the Mississippian 

rocks have been deeply eroded, a rubble of carbonate blocks, 

sand, and red clay and silt fills caverns and solution-widened 

fractures as much as 100 ft below the erosional surface.

DARWIN-HUMBUG ZONE

The Darwin-Humbug zone of the Madison aquifer (pi. 12) 

consists of carbonate and clastic rocks that accumulated at the 

close of the Mississippian during the transition from a regressing to a transgressing sea (Craig, 1972; Kent, 1972). Component geologic units are characteristic of a fluctuating but 

generally shallow marine environment (fig. 20). Component 

geologic units include the Humbug Formation, the Bull Ridge 

Member of the Madison Limestone, the Mission Canyon Limestone above the base of the lowest evaporite zone (referred to

as the upper part of the Mission Canyon Limestone in this 

report), and the Darwin Sandstone Member of the Amsden 

Formation (table 1 and pi. 5). Paleontological data (Sando, 

1979, p. 9-12) indicate that the upper part of the Mission Canyon Limestone and the Bull Ridge Member of the Madison 

Limestone are Lower to Upper Mississippian (upper Osagean 

to Meramecian). The Darwin Sandstone Member is unfossiliferous (Sando and others, 1975, p. 20), and the Humbug Formation contains poorly preserved, nondiagnostic fossils (Huddle 

and McCann, 1947b; Kinney, 1955, p. 31; Schell, 1969, p. 

145). Nevertheless, both the Darwin Sandstone Member and 

the Humbug Formation are believed to be Upper Mississippian 

(Meramecian to Chesterian) on the basis of their stratigraphic 

position between datable formations (Sando and others, 1975, 

p. 21; Mallory, 1979, p. 214-216).

The Darwin-Humbug zone is thin and has the most restricted 

occurrence of the hydrogeologic units composed of Paleozoic
GEOLOGY OF PALEOZOIC ROCKS, UPPER COLORADO RIVER BASIN A33

rocks in the UCRB. The Darwin-Humbug zone occurs only in 

and near the Great Divide Basin, the north flank of the Wind 

River Mountains, the Gros Ventre Range, the Overthrust Belt, 

the Uinta Mountains, and the Uinta Basin. The Darwin-Humbug zone is less than 200 ft thick in the Wind River Mountains 

and Great Divide Basin, but it is 500 to more than 700 ft thick 

in depositional centers within the Gros Ventre Range and Overthrust Belt and nearly 800 ft thick in the western Uinta Mountains and northwestern Uinta Basin. Lateral and vertical 

gradation into the Madison Limestone and the lower part of the 

Mission Canyon Limestone and erosion during Cretaceous and 

Tertiary uplift of the Uinta Mountains limit the areal extent of 

the Darwin-Humbug zone.

COMPONENT GEOLOGIC UNITS

In the Uinta Mountains and Uinta Basin, which take in most 

of the extent of the Darwin-Humbug zone, rocks comprising 

the hydrogeologic unit are assigned to the Humbug Formation. 

The Humbug Formation in the eastern Uinta Mountains (fig. 4) 

typically consists of interbedded limestone and sandstone with 

some shale layers (see Untermann and Untermann, 1954, p. 

30-31; Kinney, 1955, p. 28; Hansen, 1965b, p. 40; Hansen and 

others, 1983). Sandstone layers characteristically are reddish 

brown, tan, yellow, white, and gray, fine grained to medium 

grained, and cemented by silica, calcite, or hematite. Limestone layers are gray to bluish gray, fine grained, and commonly brecciated; locally they contain nodules and lenses of chert. 

Shale layers are gray, red, and black; locally they are limy. In 

the western Uinta Mountains, the Humbug Formation consists 

of brecciated sandstone and limestone, with sandstone breccias 

grading laterally into limestone breccias (Huddle and McCann, 

1947b; Huddle and others, 1951). The sandstone breccias are 

white and gray, fine grained, and cemented by calcite; limestone breccias are light gray and brown, fine grained, and 

sparsely cherty. In the Wasatch Range above and below the 

Charleston Thrust Fault (the leading edge of the Overthrust 

Belt) and, presumably, in the western Uinta Basin, the Humbug 

Formation consists of light- to dark-gray, cherty limestone with 

dolomitic layers interbedded with buff to gray, fine- to medium-grained, limy to quartzitic sandstone (Baker and Crittenden, 1961; Baker, 1964). In the southwestern Uinta Basin, 

the Humbug Formation in boreholes consists of light-gray, tan, 

and beige sandstone and limestone with some intervals of dolomite, dark-gray, green, tan, and red siltstone and sandstone, 

and, locally, anhydrite. Anhydrite layers can comprise as much 

as 11 percent of the formation. Throughout its area of occurrence, the Humbug Formation characteristically is thinly to 

thickly bedded.

In southwestern Wyoming, the lower part of the Humbug 

Formation grades laterally into either the upper part of the 

Mission Canyon Limestone or the Bull Ridge Member of the 

Madison Limestone (as used by Sando, 1977, 1979). Prior to 

establishment of the Bull Ridge Member, strata included in this

interval were variously assigned to the upper part of the Brazer 

Limestone and lower part of the Amsden Formation (Foster, 

1947), Sacajawea Formation (Branson and Branson, 1941), 

Sacajawea Member of the Madison Limestone (Sando, 1967), 

or upper member of the Madison Limestone (Keefer and Van 

Lieu, 1966). The upper part of the Humbug Formation grades 

laterally into the Darwin Sandstone Member of the Amsden 

Formation (fig. 23).

The upper part of the Mission Canyon Limestone in the Salt 

River Range, Wyoming Range, and western Gros Ventre 

Range consists of limestone, dolomite, and solution breccia, 

with interbeds of red shale in the upper part of the interval (Foster, 1947, p. 1556-1557; Wanless and others, 1955, p. 22-31; 

Sando, 1977, p. 176). The limestone and dolomite generally 

are gray and pink, fine grained to finely crystalline, and cherty. 

The solution breccias are concentrated at the bottom and top of 

the stratigraphic interval (Sando, 1977, pi. 1); they consist of 

blocks and fragments of limestone and dolomite in a matrix of 

sandstone and siltstone (see Sando and Dutro, 1981, Haystack 

Peak section). The breccias apparently resulted from collapse 

following dissolution of gypsum interbeds, which are preserved in Hoback Canyon at the northern end of the Hoback 

Range. In the Hoback Canyon area, the upper part of the Mission Canyon Limestone contains a third solution breccia interval and, atypically, numerous interbeds of red and green 

gypsiferous shale (Wanless and others, 1955, p. 27-29; Sando, 

1977, pi. 1).

East of the Overthrust Belt and western Gros Ventre Range, 

the upper part of the Mission Canyon Limestone grades into 

the Little Tongue and Bull Ridge Members of the Madison 

Limestone (Sando, 1977, pi. 1). The contact between these 

two members of the Madison Limestone was placed by Sando 

(1977) at the base of the upper of two solution breccia intervals, the lateral equivalent of the middle solution breccia interval in the Mission Canyon Limestone. The Little Tongue 

Member, a component geologic unit of the Redwall-Leadville 

zone, was described previously. The Bull Ridge Member 

consists of a basal solution breccia interval, a medial limestone collapse breccia interval, and an upper interval of undisturbed limestone, dolomite, and siltstone (Sando, 1967, p. 

539). The lower solution breccia interval consists of chaotically bedded, red and yellow mudstone, siltstone, and sandstone with angular fragments of limestone, dolomite, and 

chert, that become progressively larger upward in the interval 

(Sando, 1967, p. 538). In the collapse breccia interval, blocks 

of fine-grained, bioclastic limestone tens of feet in diameter 

and rotated only slightly out of original bedding attitude lie in 

a matrix of Darwin-like sandstone (Sando, 1967, p. 539). 

Above the collapse breccia interval, the carbonate rocks consist of gray and tan, thin- to medium-bedded, fine-grained to 

pelletal, locally stromatolitic or cherty limestone and dolomite 

(Keefer and Van Lieu, 1966, p. 30; Sando, 1967, p. 539; 

1979, p. 12). Throughout the Bull Ridge Member, sinkholes 

and solution cavities filled with quartz sandstone and shale
A34 REGIONAL AQUIFER SYSTEM ANALYSIS UPPER COLORADO RIVER BASIN

SOUTHWEST

UINTA 

MOUNTAINS

WIND RIVER 

MOUNTAINS

NORTHEAST

RAWLINS 

UPLIFT

IZr-I:r: Doughnut Shale ~

_= Horseshoe Shale

^-^of Amsden Formation-^~^^~^

znHumbugn 

Formation

Darwin Sandstone! 

Member of . : . . ' '.: 

Amsden Formation

Bull Ridge . .

: Member of V '...; ' '.: 

Madison Limestone

Darwin Sandstone

.. Member of ..

Amsden Formation

/ . I / , I ./ ..,/ Madison Limestone.

/ I / T/ / i / I /

/.I

/ I /

\ /I T T I./.I

7 T

Not to scale EXPLANATION 

Sandstone

Sandstone and shale 

Shale

Limestone and dolomite 

Limestone breccia

FIGURE 23. Schematic section showing stratigraphic relations in the Darwin-Humbug zone of the Madison aquifer. Horizontal distance is about

200 miles.

related to deposition of the overlying Amsden Formation 

occur (Sando, 1967, p. 539).

The Darwin Sandstone Member of the Amsden Formation, 

in general, consists of thinly to massively bedded, gray, white, 

beige, and red, fine- to medium-grained, quartz sandstone that 

commonly is crossbedded (Sando and others, 1975, p. 20; 

Maughan, 1979, p. 27). The rock is weakly to moderately well 

cemented by calcite in most areas; locally, as in the Overthrust 

Belt, it is quartzitic (Wanless and others, 1955, p. 32). Thin 

interbeds of shale and carbonate rocks are present locally. 

Angular blocks and fragments of limestone occur in the sandstone above the contact with the Madison and Mission Canyon 

Limestones in most places (Maughan, 1979, p. 27). Because 

the Darwin Sandstone Member was deposited on a hummocky 

karst surface, abrupt changes in thickness occur from place to 

place (Mallory, 1967, p. 6). In some areas, the Darwin Sandstone Member is present only in caverns and sinkholes 

(Mallory, 1967); in other areas, it is more than 300 ft thick.

CONTACTS

Geologic units that comprise the Darwin-Humbug zone of 

the Madison aquifer grade down into the parts of the Madison 

and Mission Canyon Limestones that are in the RedwallLeadville zone of the Madison aquifer. Geologic units in the

Darwin-Humbug zone are overlain conformably by the Doughnut Shale and the Horseshoe Shale Member of the Amsden 

Formation of Mississippian and Pennsylvanian age (Huddle 

and others, 1951; Baker and Crittenden, 1961; Keefer and Van 

Lieu, 1966, pi. 2; Sando and others, 1975, p. 21). Internally, an 

unconformity separates the Darwin Sandstone Member of the 

Amsden Formation from the underlying Mission Canyon 

Limestone (Wanless and others, 1955, p. 12) and Bull Ridge 

Member of the Madison Limestone (Sando, 1967, fig. 3; Sando 

and others, 1975, pi. 4). In the area of the Rawlins Uplift, between the southeastern end of the Wind River Mountains and 

the northwestern end of the Sierra Madre, the Bull Ridge 

Member has been removed entirely by erosion, and the Darwin 

Sandstone Member of the Amsden Formation unconformably 

overlies the Little Tongue Member of the Madison Limestone. 

A disconformity near the top of the Humbug Formation noted 

by Ritzma (1959, p. 23) may be the lateral continuation of the 

pre-Darwin unconformity.

FOUR CORNERS CONFINING UNIT

A widespread confining unit in the UCRB separates the 

Madison and underlying aquifers from Pennsylvanian and 

Permian rocks that comprise the Canyonlands aquifer. This 

confining unit is named the Four Corners confining unit in this
GEOLOGY OF PALEOZOIC ROCKS, UPPER COLORADO RIVER BASIN A35

report, as a symbol of its hydrologic importance in the four 

States joined at the Four Corners Arizona, Colorado, New 

Mexico, and Utah. The Four Corners confining unit is divisible 

vertically into two subunits with different lithologic and hydrologic properties. The lower subunit, which consists of shale 

with subordinate carbonate rocks and relatively minor sandstone and gypsum, is called the Belden-Molas subunit, after the 

two formations that comprise the zone in northwestern 

Colorado and typify the range in lithology within. The upper 

subunit, which is characterized by thick deposits of gypsum, 

anhydrite, and halite, is called the Paradox-Eagle Valley 

subunit, after the two geologic units that contain most of the 

evaporite deposits within the interval.

BELDEN-MOLAS SUBUNIT

The Belden-Molas subunit of the Four Comers confining 

unit (pi. 13) consists of formations and members of formations 

predominantly composed of black and red shale that were deposited on eroded Mississippian carbonate and clastic rocks, at 

first subaerially and later subaqueously, as a fourth Paleozoic 

sea advanced across the area (Kent, 1972; Mallory, 1972). 

Component geologic units include the Horseshoe Shale 

Member of the Amsden Formation, Doughnut Shale (Formation), Molas Formation, Belden Formation, lower member of 

the Hermosa Formation (Pinkerton Trail Formation of 

Wengerd and Strickland, 1954), Surprise Canyon Formation 

(of Billingsley and Beus, 1985), and Watahomigi Formation 

(table 1 and pi. 5). Because of lithologic similarity, component 

geologic units are delimited primarily along axes of thinning 

between depositional centers.

Although the name "Manning Canyon Shale" has been applied to rocks equivalent to the Doughnut Shale in the central 

and western Uinta Mountains (Ritzma, 1959; Schell, 1969, p. 

146), mapping in the Wasatch Range (Baker and Crittenden, 

1961; Baker, 1964, 1972, 1973) indicates that the Manning 

Canyon Shale is restricted to the upper plate of the Charleston 

Thrust Fault, where it occurs between the Upper Mississippian 

Great Blue Limestone and the Pennsylvanian and Permian 

Oquirrh Formation. Recent drilling in the Wasatch Range just 

west of the UCRB, at SLD 05-05-1 Ibb, indicates that the Great 

Blue Limestone and Manning Canyon Shale do not extend into 

the UCRB (Bruce Bryant, U.S. Geological Survey, oral commun., 1990). However, strata, equivalent in lithology and age 

to the upper part of the Great Blue Limestone and the lower part 

of the Manning Canyon Shale, extend beneath the thrust plate 

from the Wasatch Range to the UCRB. In the Wasatch Range 

the autochthonous rocks are called the "Doughnut Formation." 

Hence, the name "Doughnut Shale" is extended from the eastern Uinta Mountains, where Hansen and others (1983) used the 

name unequivocally, into the remainder of the Uinta Mountains 

and the Uinta Basin, and the name "Manning Canyon Shale" is 

not used in the UCRB in this report.

Abundant paleontological evidence (mainly brachiopods, 

pelecypods, gastropods, corals, bryozoans, and foraminifera) 

indicates that component formations become younger from 

west to east across the area. Fossils collected in the Wasatch 

Range and Uinta Mountains indicate that the lower part of the 

Doughnut Shale is Upper Mississippian (Chesterian); the unfossiliferous upper part of this formation may be Lower Pennsylvanian (Huddle and others, 1951; Kinney, 1955, p. 35-36; 

Ritzma, 1959, p. 23-25; Baker, 1964). The Horseshoe Shale 

Member of the Amsden Formation decreases in age from Late 

Mississippian to Early Pennsylvanian (Morrowan) eastward 

across Wyoming (Sando and others, 1975, p. 24-25). In Colorado, the Molas Formation is Upper Mississippian and Lower 

Pennsylvanian (Chesterian to Morrowan) in the western part of 

its depositional area and Lower to Middle Pennsylvanian (Morrowan to Desmoinesian) in the eastern part (Wengerd, 1957, p. 

135; Merrill and Winar, 1961, p. 87; Bass and Northrop, 1963, 

p. 30; Tweto and Lovering, 1977, p. 33-35). Overlying the 

Molas Formation, the Belden Formation in northwestern Colorado is Lower Pennsylvanian (Morrowan) on the west and Middle Pennsylvanian (Atokan) on the east (Dings and Robinson, 

1957, p. 17-18; Bass and Northrop, 1963, p. 40-41; Tweto and 

Lovering, 1977, p. 35-38); the lower member of the Hermosa 

Formation is Middle Pennsylvanian (Atokan and Desmoinesian) in southwestern Colorado (Wengerd, 1958, p. 118). The 

Surprise Canyon and Watahomigi Formations in northeastern 

Arizona comprise an Upper Mississippian to Middle Pennsylvanian (Chesterian to Atokan) sequence (McKee, 1982, p. 37; 

Billingsley and Beus, 1985, p. 31). The spatial distribution of 

the formations that comprise the Belden-Molas subunit indicates that the fourth Paleozoic sea encroached from the west in 

Late Mississippian time and spread eastward during Early and 

Middle Pennsylvanian time.

The Belden-Molas subunit thickens and thins erratically (pi. 

13) as a result of irregularities in the depositional surface, lateral gradation into other Mississippian and Pennsylvanian geological units, and, to some degree, erosion associated with 

Pennsylvanian-Permian and Laramide uplifts. The Horseshoe 

Shale Member of the Amsden Formation in Wyoming and the 

Surprise Canyon and Watahomigi Formations in Arizona and 

southeastern Utah generally are less than 200 ft thick. The 

Doughnut Shale, although thinned locally by uplift of the Uinta Mountains, Axial Basin Arch, and Rock Springs Uplift, generally thickens toward depositional centers in the Washakie 

Basin and the Utah salient of the Overthrust Belt. The Doughnut Shale is more than 400 ft thick in its eastern depositional 

center and 1,200-1,300 ft thick at the western edge of the 

UCRB. In the southern UCRB, the Molas Formation and lower member of the Hermosa Formation thicken toward a trough 

that meanders around the western edges of the Uncompahgre 

Plateau and Paradox Basin. Maximum thicknesses in the center of this trough generally are between 800 and 900 ft. However, the Belden Formation, where it crops out in northwestern 

Colorado, can be as much as 1,000 ft thick (Bass and Northrop,
A36 REGIONAL AQUIFER SYSTEM ANALYSIS UPPER COLORADO RIVER BASIN

1963, p. 31-34); in the subsurface, this formation is 1,000- 

4,300 ft thick (the maximum known thickness occurs in the 

American Quasar 1-9 Benton well, SC02-85-0966). The 

Belden-Molas subunit is absent throughout most of Wyoming, 

the central UCRB, and the eastern and western margins of the 

UCRB.

COMPONENT GEOLOGIC UNITS

North of the Rock Springs Uplift in Wyoming, from the 

Overthrust Belt to the Rawlins Uplift, rocks comprising the 

Horseshoe Shale Member of the Amsden Formation are assigned to the Belden-Molas subunit. As described by Sando 

and others (1975, p. 23-24), the Horseshoe Shale Member generally consists of fissile, red, gray, and purple sandy siltstone 

and mudstone with thin beds of fine-grained calcareous sandstone and silty, sandy, or shaly limestone and dolomite. The 

carbonate and sandstone layers locally exceed the shale layers 

in abundance. According to Mallory (1967, p. 12-13), beds of 

pisolitic hematite or hematitic bauxite as much as 3 ft thick 

commonly occur in the lower part of the member.

From the vicinity of the Rawlins Uplift south to the Uinta 

Basin, strata equivalent to the Horseshoe Shale Member are assigned to the Doughnut Shale (fig. 4). In general, the Doughnut 

Shale of the eastern and central Uinta Mountains consists of red 

shale and sandstone overlain by black to dark-gray carbonaceous shale containing interbeds of greenish sandstone, green 

and tan sandy limestone, black shaly limestone, and bituminous 

coal (Untermann and Untermann, 1954; Kinney, 1955; Hansen, 

1965b; Hansen and others, 1983). Similarly, in the western 

Uinta Mountains, the Doughnut Shale in ascending order consists of (1) red, purple, and maroon shale with some interbedded limestone and quartzitic to pebbly sandstone; (2) fissile, 

dark-gray to black shale with some interbedded limestone; and 

(3) interbedded gray shale and Limestone with minor sandstone 

(Huddle and McCann, 1947a). Limestone layers increase westward; the Doughnut Shale in the Wasatch Range and western 

Uinta Basin consists of dark-gray to black shale with thin interbeds of rusty-weathering, gray, fine-grained, quartzitic sandstone and quaitzite overlain by thinly bedded, black limestone 

with shale interbeds (Baker and Crittenden, 1961; Baker, 

1964). At the southwestern edge of the Uinta Basin, the 

Doughnut Shale in ascending order generally consists of (1) 

red, purple, and maroon mudstone and siltstone with limestone 

interbeds; (2) dark-gray, black, and brown shale with interbedded limestone and gray, brown, and white sandstone; and (3) 

interbedded greenish-gray, gray, and black shale and limestone 

with minor sandstone and coal.

At the southern edge of the Sand Wash Basin and the southern and eastern edges of the Uinta Basin, the Doughnut Shale 

grades into the Molas and Belden Formations (fig. 24). The 

Molas Formation in northwestern Colorado typically is a discontinuous deposit of poorly stratified purplish-red and ochrecolored claystone and siltstone containing nodules and boulders of limestone and chert; thicknesses range from inches to 

130 ft (Bass and Northrop, 1963, p. 30; De Voto and others,

1986, p. 39). On the northeast flank of the Sawatch Range, 

however, the Molas Formation has been altered to gray 

carbonaceous shale and white conglomeratic sandstone (Tweto 

and Levering, 1977, p. 33). Similarly, the Molas Formation in 

the Rico Mountains of southwestern Colorado (see pi. 1 for location) is a pebbly quartzite, locally called the Larsen Quartzite 

(McKnight, 1974, p. 13-16). Elsewhere in southwestern Colorado, the Molas Formation (fig. 25) consists of unstratified 

fragments of limestone and chert in a matrix of red silt and clay 

overlain by poorly to well-stratified red to varicolored shale 

and limy shale with lenses and interbeds of sandstone and limestone; the total thickness ranges from 0 to about 150 ft (Wengerd, 1957, p. 118; Merrill and Winar, 1961, p. 83-88; Baars and 

others, 1987, p. 347). This characteristic lithology continues 

throughout southeastern Utah and northeastern Arizona wherever the Molas Formation is identifiable (see, for example, 

Heylmun, 1958, p. 1789; Irwin and others, 1971, p. 20-21).

Overlying the Molas Formation in northwestern Colorado is 

the Belden Formation. The Belden Formation (fig. 26), typically consists of fissile, black to dark-gray, micaceous mudstone and siltstone with interbedded limestone and dolomite 

(Brill, 1944, p. 624-627; Bass and Northrop, 1963, p. 31-41; 

Tweto and Lovering, 1977, p. 34-38). Carbonate layers exceed 

shale layers toward the center of the Belden Formation's depositional area (pi. 13). Gypsum and anhydrite generally are not 

present, but they comprise 1-6 percent of the rocks in a northwest-trending belt north of the White River Plateau and in the 

vicinity of Ruedi Dam. Beds of gray, black, brown, and green, 

micaceous sandstone and orange, arkosic conglomerate are 

present, particularly around the margins of the depositional 

area, where they comprise 10-30 percent of the formation. 

Thickening of the Belden Formation in a belt trending northwest from the vicinity of Eagle, Colo., to the Danforth Hills in 

part is related to thick intervals of arkosic sandstone concentrated in the lower part of the formation. Characteristically, the 

shale within this belt is maroon, red, and purple, as well as 

black and gray. The sandstone and reddish shale are interpreted to be pulses of terrigenous sediment eroded from the ancestral Front Range Uplift, to the north and east. The Molas and 

Belden Formations in the vicinity of the Colorado-Utah State 

line atypically consist entirely of red, maroon, and purple shale 

with sandstone and carbonate interbeds that are interpreted to 

be of mostly terrigenous or tidal-flat origin.

The Molas Formation in southwestern Colorado, southeastern Utah, and northeastern Arizona, from the Uinta Basin to 

the Kaibab Plateau, is overlain by the lower member of the 

Hermosa Formation. The lower member of the Hermosa Formation generally consists of gray, crystalline to sandy, fossiliferous limestone interbedded with and underlain by 

greenish-gray, dark-gray, and black shale (fig. 27); locally, 

the unit contains interbeds of red shale, sandstone, or limestone conglomerate (Wengerd, 1958, p. 115; Baars and 

others, 1987, p. 347). Stratigraphic relations among Pennsylvanian and Permian formations in southeastern Utah are 

shown in figure 28.
o-2

Cu

00
A38 REGIONAL AQUIFER SYSTEM ANALYSIS UPPER COLORADO RIVER BASIN

FIGURE 25. Pennsylvania!! Molas Formation at its type locality, Molas Lake, in 

the San Juan Mountains, Colo.

FIGURE 26. Pennsylvania!! Belden Formation at Ruedi Reservoir on the Fryingpan River southeast of Glenwood 

Springs, Colo. The formation here 

consists of shale with thin limestone 

interbeds.

In the vicinity of the Marble Platform and Kaibab Plateau, 

the Molas Formation and lower member of the Hermosa 

Formation grade into the Surprise Canyon Formation and the 

Watahomigi Formation of the Supai Group (fig. 2). The 

Surprise Canyon Formation, which occurs as channel fillings 

in the Redwall Limestone, consists of red-brown, brown, and 

gray, medium- to coarse-grained sandstone, limestone-chert 

conglomerate, coarse-grained limestone, and siltstone. The

thickness of these rocks ranges from 0 to 80 ft in the eastern 

Grand Canyon and Marble Canyon. The Watahomigi 

Formation in Marble Canyon consists of red and reddishbrown mudstone and siltstone with interbedded gray and red, 

fine-grained, jasper-bearing limestone and dolomite and a 

basal conglomerate interval. The basal conglomerate consists 

of chert pebbles in a matrix of reddish-orange, very fine 

grained sandstone or siltstone. The Watahomigi Formation is
GEOLOGY OF PALEOZOIC ROCKS, UPPER COLORADO RIVER BASIN A39

FIGURE 27. Lower member of the Pennsylvania:] Hermosa Formation north of 

Durango, Colo. The lower member 

here consists of massively bedded limestone with thin shale interbeds. Dark 

streaks on the cliff face are seeps of 

water emanating from the shale 

intervals.

92-206 ft thick in the eastern Grand Canyon and Marble 

Canyon (McKee, 1982, p. 41).

CONTACTS

Although the base of the Belden-Molas subunit is a 

pronounced unconformity over most of the region, contacts 

between geologic units within the Belden-Molas subunit and 

contacts with formations in overlying hydrogeologic units 

generally are conformable. For example, the Horseshoe Shale 

Member of the Amsden Formation grades laterally into the 

Moffat Trail Limestone Member or is overlain conformably by 

the Ranchester Limestone Member of the Amsden Formation 

(Sando and others, 1975, p. 24). Contacts between the Doughnut Shale and the Pennsylvanian Round Valley Limestone are 

poorly exposed; where visible, they are conformable (Huddle 

and others, 1951; Kinney, 1955, p. 37; Baker and Crittenden, 

1961; Hansen, 1965b, p. 43). The Molas Formation is overlain 

unconformably by the Belden Formation (De Voto, 1980b, p. 

77) but grades into the lower member of the Hermosa Formation (Merrill and Winar, 1961, p. 86). The Belden Formation 

grades into the Gothic Formation (of Langenheim, 1952), 

Minturn Formation, and Eagle Valley Evaporite of Pennsylvanian age (see Tweto and Lovering, 1977, p. 35; Bryant, 1979, 

p. 25). The lower member of the Hermosa Formation is overlain conformably or gradationally by the Paradox and upper 

members of the Hermosa Formation; locally, this contact is a 

disconformity beneath channel sandstone, carbonaceous shale, 

and coal (Wengerd, 1958, p. 118). The Surprise Canyon 

Formation is overlain unconformably by the Watahomigi Formation (Billingsley and Beus, 1985, p. 27). The Watahomigi

Formation contains a depositional hiatus between Morrowan 

and Atokan intervals but is overlain conformably by the Pennsylvanian Manakacha Formation of the Supai Group (McKee, 

1982, p. 158).

PARADOX-EAGLE VALLEY SUBUNIT

The Paradox-Eagle Valley subunit of the Four Corners 

confining unit (pi. 14) consists of sediments that accumulated 

during the maximum stage of the fourth Paleozoic marine 

advance (Kent, 1972; Mallory, 1972). Associated with carbonate rocks laid down on shallow marine shelves are bedded 

evaporites deposited in marginal basins restricted by shoals and 

the clastic debris shed from rising land masses onto coastal 

plains and intertidal areas. Component geologic units include 

the Moffat Trail Limestone Member of the Amsden Formation, 

the Round Valley Limestone, the Eagle Valley Evaporite, the 

Paradox Member of the Hermosa Formation, and the 

Manakacha Formation of the Supai Group (table 1 and pi. 5). 

On the basis of abundant paleontological evidence (mainly 

brachiopods, corals, and foraminifera), the sedimentary rocks 

comprising the Paradox-Eagle Valley subunit apparently 

increase in age from Late Mississippian (Chesterian) to Middle 

Pennsylvanian (Desmoinesian) in a south-southeasterly direction (age information from Kinney, 1955, p. 42-43; Wengerd, 

1958, p. 115; Bass and Northrop, 1963, p. 43-46; Baker, 1964; 

Hansen, 1965b, p. 43-44; Mallory, 1971, p. 18-20; Sando and 

others, 1975, p. 31; McKee, 1982, p. 107; Blakey and Baars, 

1987). The sea, therefore, appears to have advanced from the 

north and west toward the south and east at the time of 

deposition.
o s
>18-11-27ac SLD 16-10-28cd SLD 15-09-27cd

-8 miles >K

SLD16-11-11cb SLD 16-12-27ab

8 milesO1 SLD 15-12-07CC

0 

D

ROCK TYPE 

Sandstone

Sandstone and shale Red, purple, or orange shale 

Gray or black shale Limestone or dolomite and shale 

Limestone or dolomite and sandstone

EXPLANATION

Limestone or dolomiteCherry limestone or dolomite

Limestone or dolomite and anhydriteAnhydrite

HaliteNo sample

LINE SYMBOLS

Contact between geolo

jagged where grada

Contact between lithol

jagged where grada

SlD15-12-07cc

J_

Borehole with designat

by geographic loca

FIGURE 28. Stratigraphic section showing relations among Pennsylvanian and Permian formations in southeastern Utah.
A42 REGIONAL AQUIFER SYSTEM ANALYSIS UPPER COLORADO RIVER BASIN

The thickness of the Paradox-Eagle Valley subunit increases 

irregularly toward the centers of the depositional basins of the 

component geologic units (pi. 14). Maximum thicknesses are 

between 300 and 400 ft in depositional basins of the Moffat 

Trail Limestone Member and Manakacha Formation and about 

500 ft in the depositional basin of the Round Valley Limestone. 

Thicknesses penetrated by drilling exceed 4,000 ft in the Eagle 

Valley Evaporite depositional basin and 9,000 ft in the Paradox 

Member depositional basin, but thicknesses in these two basins 

are distorted by diapiric intrusion of halite and anhydrite (Kite 

and Lohman, 1973, p. 28; this report, fig. 5). Because of lateral 

and vertical gradation into other formations, nondeposition 

over ancestral uplifts, and erosion, the Paradox-Eagle Valley 

subunit is thin or absent in four areas: (1) A northwesterly 

trending belt extending from the Front Range of Colorado to 

the Green River Basin of Wyoming; (2) the Uinta Mountains 

and Axial Basin Arch; (3) a northwesterly trending belt extending from the Sawatch Range and southern Elk Mountains in 

Colorado to the Uncompahgre Plateau and southwestern Uinta 

Basin in Utah; and (4) a northerly trending belt extending from 

the Kaibito and Kaiparowits Basins in the vicinity of the UtahArizona State line to the San Rafael Swell and Wasatch Plateau 

in southeastern Utah.

COMPONENT GEOLOGIC UNITS

The Moffat Trail Limestone Member of the Amsden 

Formation comprises the Paradox-Eagle Valley subunit in the 

Wind River Mountains, Gros Ventre Range, and Overthrust 

Belt of Wyoming. As described by Sando and others (1975, p. 

30), the Moffat Trail Limestone Member primarily consists of

thinly to thickly bedded, light-gray, medium- to coarsegrained, fossiliferous limestone with chert nodules and lenses. 

Locally, the Moffat Trail Limestone Member contains interbeds of yellowish-brown and beige dolomite or dolomitic limestone, fine-grained sandstone, or dark-gray fissile shale.

The Round Valley Limestone comprises the Paradox-Eagle 

Valley subunit in the greater Green River Basin, Uinta, Sand 

Wash, and Piceance Basins and adjacent uplifted areas (the 

Uinta Mountains and Wasatch Range). In the eastern Uinta 

Mountains, the Round Valley Limestone (fig. 4) consists of 

thinly to massively bedded, light-gray, fine- to coarse-grained, 

cherty limestone (Kinney, 1955, p. 40-41; Hansen, 1965b, p. 

43). In the Duchesne River area of the western Uinta Mountains, the Round Valley Limestone consists of gray, white, and 

brown, cherty, fine-grained, oolitic, shaly and sandy limestone 

with interbedded limy sandstone (Huddle and McCann, 

1947a). Similarly, in the Wasatch Range and western Uinta 

Basin, the Round Valley Limestone consists of light- to 

medium-gray, moderately to coarsely crystalline, cherty limestone with some thin beds of buff and gray sandstone (Baker, 

1964). In the southeastern Uinta Basin, the Round Valley 

Limestone in boreholes consists of buff, gray, and brown 

cherty limestone with oolitic and sandy layers and some interbeds of white, gray, and buff sandstone and greenish-gray, 

light-gray, black, and red shale.

The Round Valley Limestone grades into the Eagle Valley 

Evaporite in northwestern Colorado east of the Douglas Creek 

Arch and south of the Sand Wash Basin (fig. 24). The Eagle 

Valley Evaporite (fig. 29) consists of evaporites, carbonate 

rocks, and clastic rocks that can be grouped into at least 10 

depositional cycles exhibiting lateral facies changes from 

hypersaline to penesaline to marine-shelf Ethologies (De Voto

FIGURE 29. Bedded gypsum and gypsiferous mudstone overlain by sandstone 

in the Pennsylvania!! Eagle Valley 

Evaporite near Eagle, Colo.
GEOLOGY OF PALEOZOIC ROCKS, UPPER COLORADO RIVER BASIN A43

and others, 1986, p. 42-43; Dodge and Bartleson, 1986, p. 114- 

118). The hypersaline facies, consisting of massively bedded 

halite with thin interbeds of black shale, anhydrite, and 

carbonate rocks, was deposited in five areas that were actively 

subsiding grabens at the time of deposition (fig. 30). Peripheral 

to these areas, the penesaline facies was deposited in shallow 

seas, as evidenced by stromatolites, mud cracks, and raindrop 

imprints (Dodge and Bartleson, 1986, p. 118). The penesaline 

facies consists of black, gray, white, and tan siltstone, mudstone, and anhydrite (or gypsum) with minor interbeds of limestone, dolomite, sandstone, and conglomerate (see description 

at Dotsero, Colo., by Bass and Northrop, 1963, p. 42-43). Near 

the eastern and western depositional limits of the Eagle Valley 

Evaporite, where the formation grades into the Minturn and 

Gothic Formations, the penesaline and hypersaline facies contain numerous interbeds of red, maroon, tan, and gray arkosic 

conglomerate, grit, sandstone, siltstone, mudstone, limestone, 

and dolomite (Mallory, 1971, pi. 2). At its northern depositional limits, where the Eagle Valley Evaporite grades into the 

Round Valley Limestone, the marine shelf facies of the Eagle 

Valley Evaporite consists of thickly bedded limestone and 

thinly bedded black shale, with some conglomeratic sandstone 

and minor anhydrite (less than 5 percent of the formation). 

Mounds of algal limestone, dolomitized toward depositional 

centers, are present in both the marine shelf and penesaline 

facies.

Analogous to the Eagle Valley Evaporite and Round Valley 

Limestone south of the Uinta Basin and Uncompahgre Plateau, 

the Paradox Member of the Hermosa Formation also consists of 

a hypersaline facies grading outward to penesaline and marine 

shelf facies. However, the Paradox Member contains fewer 

sandstone intervals and thicker, more laterally extensive deposits of halite (see Dodge and Bartleson, 1986, p. 116, for a comparison of lithofacies distributions in the two geologic units). 

Like the Eagle Valley Evaporite and its equivalents, thickness 

and depositional limits of the Paradox Member cannot be established precisely because of vertical and lateral gradation into 

other geologic units. (Several, but not all, classification 

schemes commonly used for rocks in the Paradox Member are 

listed in table 2.) For this report, the top of the Paradox Member 

(fig. 31) generally was placed at the top of a thick interval of 

cherty limestone and dolomite underlain by interbedded anhydrite, dark-gray to black mudstone, tan, gray-brown, and gray 

siltstone, and limestone or dolomite and overlain by interbedded sandstone, shale, and carbonate rocks typical of the upper 

member of the Hermosa Formation (fig. 28). In some areas, 

particularly in the eastern Paradox Basin or adjacent to the Uncompahgre Uplift, where the capping layer of cherty limestone 

and dolomite is not present, the top of the Paradox Member was 

placed at the top of the distinctive rocks that normally underlie 

the carbonate interval. The bottom of the Paradox Member 

generally was placed at the base of the lowest anhydrite interval, although toward the margins of deposition, the base of the 

Paradox Member was interpreted in some boreholes to be either

a thick interval of cherty or anhydritic dolomite, dark-gray and 

black anhydritic mudstone, tan siltstone, or light-colored, locally cherty or anhydritic sandstone.

The Paradox Member of the Hermosa Formation consists of 

chemical, biogenic, and clastic sediments that accumulated 

during 29 cycles of sea level fluctuation in a barred trough adjacent to the ancestral Uncompahgre Uplift (Hite and Cater, 

1972; Hite and Lohman, 1973). In the largest part of this 

trough, an area of more than 11,000 mi2 south of the presentday Uncompahgre Plateau, the Paradox Member consists of an 

evaporite facies, predominantly composed of halite. A typical 

evaporite cycle of rising and falling salinity in ascending order 

consists of (1) black, calcareous, silty, carbonaceous shale, (2) 

black and gray silty dolomite, (3) gray and white nodular and 

laminated anhydrite, (4) gray, red, and tan halite with potash 

salts (mainly sylvite and carnallite) and anhydrite laminae, (5) 

anhydrite, (6) silty dolomite, and (7) black shale. The top of the 

halite interval is a disconformity produced by removal of 5-10 

ft of salt between regressive and transgressive phases. Typically, the black shale layers are repeated at intervals of 100-300 ft 

(Hite and Lohman, 1973, figs. 6 and 7; Baars, 1983, p. 70).

In the deep northeastern part of the Paradox Basin, an area 

of about 3,000 mi2, the salt has been squeezed into five systems of northwest-trending diapiric anticlines (Cater, 1970); 

bedding in the cores of these structures is disrupted severely. 

In the center of these anticlines, salt comprises 70-80 percent 

of the Paradox Member, which is interpreted to be 2,500- 

15,000 ft thick (see, for example, fig. 5). At the crest of the 

anticlines is an interval of brecciated caprock that formed by 

dissolution of salt layers in the Paradox Member and collapse 

of overlying sedimentary rocks. In Salt Valley, Utah, the 

caprock is 500-1,000 ft thick and consists of gypsum, siltstone, claystone, and subordinate black shale, dolomite, limestone, and sandstone (Wollitz and others, 1982). In Moab 

Valley, Utah, jumbled masses of gypsum, black shale, and 

dolomite, 800 ft thick, form the caprock (Baars and Doelling, 

1987, p. 276). Migration of salt into the anticlines thinned or 

removed salt from adjacent synclines. For example, salt flowage into the Paradox Valley and Gypsum Valley Anticlines 

completely removed salt from the intervening Dry Creek 

Syncline. Salt thicknesses can vary from 0 to more than 

10,000 ft within a horizontal distance of less than 3 mi (Hite 

and Lohman, 1973, p. 15) because of salt fiowage.

On the southwestern edge of the Paradox Basin, carbonate 

sediments accumulated under relatively shallow marine conditions. Evaporite cycles are traceable into the carbonate 

sequence (Hite and Cater, 1972, p. 136). A typical carbonate 

cycle, in an order parallel to the evaporite cycle, consists of 

(1) black calcareous shale, (2) silty dolomite and limestone, 

(3) algal limestone, (4) pelletal and foraminiferal limestone, 

(5) siltstone, sandstone, or very silty dolomite, and (6) black 

shale. The disconformity corresponding to the top of the 

halite in the evaporite cycle occurs at the top of the pelletal 

and foraminiferal limestone.
A44 REGIONAL AQUIFER SYSTEM ANALYSIS UPPER COLORADO RIVER BASIN

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FIGURE 30 (above and facing page). Map and schematic section showing distribution of depositional facies in the Eagle Valley Evaporite and contemporaneous Pennsy Ivanian formations, northwestern Colorado. A, Map showing depositional facies in the Eagle Valley Evaporite, laterally equivalent geologic formations, and syndepositional uplifts. Modified from Dodge and Bartleson (1986, fig. 6). B, Schematic section showing relation of depositional 

facies in the Eagle Valley Evaporite and equivalents to tectonic setting. Based on De Voto and others (1986, fig. 3); Dodge and Bartleson (1986, fig. 7).

On the northeastern edge of the Paradox Basin, where the 

Paradox Member grades into the upper and lower members of 

the Hermosa Formation, clastic sedimentary rocks derived 

from erosion of the ancestral Uncompahgre Uplift interfinger 

with evaporite facies sediments. In this area, the Paradox 

Member consists of greenish-gray, micaceous to arkosic sandstone and conglomerate; green, gray, and brownish-red sandy 

shale; dark-gray to black carbonaceous and micaceous fossiliferous limestone and dolomite with thin beds of gypsum; and, 

locally, thin coal seams near the base (Eckel and others, 1949, 

p. 8-12; Larsen and Cross, 1956, p. 46; Wengerd, 1957,p. 133- 

135; McKnight, 1974, p. 19-20,23-26).

In the vicinity of the Kaibab Plateau and Marble Platform, 

the Paradox Member grades into the Manakacha Formation of 

the Supai Group (fig. 2). The Manakacha Formation consists

of a lower cliff-forming unit and an upper slope-forming unit. 

The lower unit consists of orange-pink, reddish-brown, and 

red, very fine grained to medium-grained sandstone and siltstone and gray, red, and orange limestone with thin layers of 

jasper. The upper unit consists of reddish-brown, orange, and 

red siltstone, mudstone, and very fine grained sandstone with 

nodules and sparse interbeds of fine-grained limestone 

(McKee, 1982, p. 40, 391-399).

UPPER CONTACTS

Contacts between formations comprising the Paradox-Eagle 

Valley subunit and overlying formations are disconformable to 

gradational. The Moffat Trail Limestone Member of the Amsden Formation is overlain conformably by the Ranchester
GEOLOGY OF PALEOZOIC ROCKS, UPPER COLORADO RIVER BASIN A45

UNCOMPAHGRE 

UPLIFT BURNS BASIN

FRONT RANGE 

UPLIFT

Meeker 

halite basin

Eagle 

halite basin

B EXPLANATION

Not to scale

Clastic facies 

Marine shelf facies 

Penesaline facies

Hypersaline facies

Area where Eagle Valley Evaporite 

and equivalents are missing because 

of erosion or nondeposition

Fault Barbs indicate relative directions 

of movement

FIGURE 31. Pennsylvanian Hermosa 

Formation exposed in the Goosenecks 

of the San Juan River west of Mexican 

Hat, Utah. The band delineated in the 

center of the picture is cherty 

limestone of the Ismay cycle, which 

generally is considered to be the top of 

the Paradox Member.
Molas 

Formation

Molas 

Formation

Molas 

Formation

Molas 

Formation .

Molas 

Formation

Molas 

Formation

Red shalewith 

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GENERAL LITHOLOGY

NlSVa H3AIH OOV^OIOD HHddH SISATVNV WH1SAS OV TVNOIOH^ 9PV
GEOLOGY OF PALEOZOIC ROCKS, UPPER COLORADO RIVER BASIN A47

Limestone Member of the Amsden Formation (Sando and others, 1975, p. 30). The Round Valley Limestone in the Wasatch 

Range and western Uinta Basin appears to be overlain 

conformably by the Weber Sandstone of Pennsylvanian age 

(Baker, 1964), but in the Uinta Mountains, the Round Valley 

Limestone is overlain disconformably to gradationally by the 

Morgan Formation of Pennsylvanian age (Huddle and 

McCann, 1947b; Kinney, 1955, p. 44; Ritzma, 1959, p. 26). 

The Eagle Valley Evaporite grades laterally into the Minturn 

and Gothic Formations and the lower part of the Morgan Formation and is overlain conformably by the upper part of the 

Morgan Formation and the Maroon Formation (Mallory, 1971, 

p. 14-18 and pi. 2); all formations in contact with the Eagle 

Valley Evaporite are Pennsylvanian in age. The Paradox 

Member of the Hermosa Formation is overlain gradationally by 

the upper member of the Hermosa Formation (Baars, 1983, p. 

69). The Manakacha Formation is separated from the overlying Wescogame Formation of Pennsylvanian age by a widespread erosional surface characterized by many small to 

moderately deep channels (McKee, 1982, p. 40).

PALEOZOIC ROCKS OF THE STRAWBERRY 

VALLEY AREA

Some Paleozoic rocks that crop out in the Strawberry Valley 

area of the UCRB occur nowhere else in the UCRB. They are 

present in the Strawberry Valley area only because cumulative 

movement on the Charleston Thrust Fault and other thrust 

faults have displaced rocks normally found many miles to the 

west in the Basin and Range physiographic province (Roberts 

and others, 1965). As shown in figure 32, the typical 

Mississippian to Permian sequence present east of the 

Strawberry Valley area in the Uinta Basin and Uinta Mountains 

underlies the Mississippian to Permian rocks above the 

Charleston Thrust Fault and presumably transmits water into 

the UCRB from areas north of the fault where the 

autochthonous rocks crop out (Baker, 1964). Consequently, 

the allochthonous rocks are not included in any of the UCRB 

hydrogeologic units. However, because of their geologic 

importance, the allochthonous rocks are described briefly in 

this section.

The oldest Paleozoic geologic unit found above the Charleston Thrust Fault but not below it is the Great Blue Limestone 

of Late Mississippian age. According to Baker (1972), the 

Great Blue Limestone characteristically consists of 2,800 ft of 

very thinly bedded, dark-gray to black, cherty limestone with 

intervals of black shale as much as 50 ft thick and, near the bottom, thin interbeds of olive-brown-weathering quartzite. Conformably overlying the Great Blue Limestone is the Manning 

Canyon Shale of Late Mississippian and Early Pennsylvanian 

age. The Manning Canyon Shale consists of 1,650-1,800 ft of 

brown to black shale with numerous thin interbeds of brown to 

reddish-brown-weathering quartzite and pebbly sandstone and 

thinly to thickly bedded, gray to black, cherty limestone

(Baker, 1972). The Oquirrh Formation conformably overlies 

the Manning Canyon Shale.

The Oquirrh Formation consists of five members and is 

about 25,000 ft thick in the Charleston thrust sheet (Baker, 

1976). The lowermost member, the Bridal Veil Limestone 

Member, is Lower to Middle Pennsylvanian and approximately 

equivalent to the Round Valley Limestone (Baker, 1964). It 

consists of 1,250 ft of thinly to thickly bedded, medium- to 

dark-gray limestone with some interbedded dark-gray to black 

shale. The overlying Bear Canyon Member, of Middle Pennsylvanian age, consists of 4,000-8,350 ft of gray to tan, limy to 

quartzitic sandstone with numerous thin to thick beds of gray to 

black, sandy and cherty limestone. Next in succession, the 

Middle Pennsylvanian Shingle Mill Limestone Member consists of 250-500 ft of thinly bedded, dark-gray, cherty limestone. Above the limestone, the Upper Pennsylvanian 

Wallsburg Ridge Member consists of about 7,900 ft of lightgray to red, fine- to medium-grained quartzite with some interbedded platy, light-gray, limy sandstone and gray to blue-gray, 

cherty limestone. The uppermost member of the Oquirrh 

Formation, the Lower Permian Granger Mountain Member, 

consists of 5,000-7,300 ft of gray to tan, limy, silty sandstone 

with some interbedded gray, red, and buff quartzite, light-gray 

sandstone, and thin to thick beds of gray limestone.

The uppermost Paleozoic geologic units present above, but 

not below, the Charleston Thrust Fault are the Kirkman 

Limestone and Diamond Creek Sandstone, both of which are 

Lower Permian (Baker, 1976). The Kirkman Limestone, 

which unconformably overlies the Oquirrh Formation, consists 

of 0-1,600 ft of gray and black laminated, locally phosphatic 

limestone and sandy limestone with some interbedded gray, 

buff, and red, medium-grained sandstone and a basal boulderconglomerate. The overlying Diamond Creek Sandstone consists of 165-1,000 ft of thinly to massively bedded, white, 

light-gray, buff, and red, medium- to coarse-grained, limy to 

quartzitic sandstone with a few thin beds of silty sandstone, red 

to gray, sandy limestone, and gray and black laminated limestone.

The Park City Formation, which in this area, consists of the 

Grandeur Member, Meade Peak Phosphatic Shale Tongue of 

the Phosphoria Formation, and Franson Member (Baker, 

1976), is present above and below the Charleston Thrust Fault. 

However, the fault has brought a greatly thickened sequence of 

these rocks into the UCRB (Bissel, 1952; Baker, 1964, 

unpublished AMSTRAT drilling logs). Thicknesses of the 

Park City Formation in measured sections and a borehole 

above the fault (at SLD 03-05-16dcb) range from about 1,430 

to 1,900 ft. In contrast, the Park City Formation in an outcrop 

north of the fault and in a borehole through the fault (at SLD 

05-05-1 Ibb) ranges from 624 to 870 ft thick (Baker, 1964; 

Bruce Bryant, U.S. Geological Survey, oral commun., 1990).

Only the uppermost strata of the allochthonous sequence 

extend into the Strawberry Valley area. Bissell (1952) mapped 

about 11,100 ft of the Oquirrh Formation on the west side of 

Strawberry Valley. From the ages given by Bissell (1952),
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Berryport 

Canyon

Rattlesnake 

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Brumley 

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Strawberry 

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CHARLESTON THRUST FAULT

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J_____I

2 KILOMETERS

FIGURE 32 (above and facing page). Geologic section showing stratigraphy and structure in Strawberry Valley area, Utah. Modified from se

information from Bissell (1952) and unpublished data from borehole SLD 05-05-1 Ibb provided by Bruce Bryant (U.S. Geological Surve

should be considered generalized because of sparse subsurface information and problems in reconciling geologic maps by Baker (1976) a

CO

o -
GEOLOGY OF PALEOZOIC ROCKS, UPPER COLORADO RIVER BASIN A49

Qa Alluvium

TKp Price River Formation

Kmv Mesaverde Formation

Km Mancos Shale and Mowry Formation

Kd Dakota Sandstone

Jm Morrison Formation

Jc Curtis Formation

Je Entrada Sandstone

Jt Twin Creek Limestone

Jn Nugget Sandstone

la Ankareh Formation

It Thaynes Formation

lw Woodside Shale

Pp

Pd

Pk

Pog

Pow

EXPLANATION

Pennsylvanian and Permian rocks above thrust fault 

Park City Formation 

Diamond Creek Sandstone 

Kirkman Limestone

Oquirrh Formation, Granger Mountain Member 

Oquirrh Formation, Wallsburg Ridge Member

Pennsylvanian and Permian rocks below thrust fault

Park City Formation

Weber Sandstone

Round Valley Limestone 

Doughnut Shale 

Humbug Formation 

Madison Limestone and equivalents

Pp

Pw

Pr

Md

Mh

Mm

Cmo

 t

p u

Maxfield Limestone and Ophir Shale 

Tintic Quartzite 

Precambrian rocks

Fault Barbs indicate relative movement 

11 TOO1

'' K Mountain 

Hobble-. - s I 

Creek_ '- $

42°00

10 KILOMETERS
A50 REGIONAL AQUIFER SYSTEM ANALYSIS UPPER COLORADO RIVER BASIN

C multiple-aquifer extends from the upper part of the Supai 

Group to the Kaibab Limestone and, thus, includes all Paleozoic rocks above the Four Corners confining unit. To be consistent with current practice of the U.S. Geological Survey for 

naming hydrogeologic units (Laney and Davidson, 1986), the 

C multiple-aquifer herein is named the Canyonlands aquifer 

because of its importance as a source of water in the Canyonlands region of Utah, as well as in other deeply dissected areas 

oftheUCRB.

The Canyonlands aquifer vertically is divisible into three 

zones with different lithologic and hydrologic properties. The 

lowermost zone, the Cutler-Maroon zone, consists mostly of 

interbedded clastic and carbonate rocks and is named after the 

two geologic units within the zone most characteristic of its 

lithology and most often used as sources of water. The middle zone, the Weber-De Chelly zone, consists almost entirely 

of quartz sandstone and is named for the two most prominent 

water-bearing formations within this zone. The uppermost 

zone, the Park City-State Bridge zone, consists alternately of 

carbonate rocks, carbonate and clastic rocks, or shale, and is 

named for the two geologic units most representative of the 

extensive regional variations in lithology within the uppermost zone.

Depths to the top of the Canyonlands aquifer generally coincide with depths to the top of the Paleozoic rocks shown on 

plate 3. The aquifer is at or near land surface on the flanks of 

the White River, Uncompahgre, Defiance, and Kaibab Plateaus, the Sawatch and Gore Ranges, and the Uinta, Elk, and 

San Juan Mountains and has considerable exposure in the San 

Rafael Swell, Waterpocket Fold (Capitol Reef-Circle Cliffs 

area), Monument Upwarp, Overthrust Belt, Eagle Basin, and 

Paradox Basin. The aquifer is less than 5,000 ft deep in most 

areas south of the Uncompahgre Plateau, although it is more 

than 10,000 ft deep in the High Plateaus region. Widespread 

areas exist north of the Uncompahgre Plateau the Uinta, 

Piceance, Sand Wash, and greater Green River Basins where 

the aquifer is 15,000 to more than 25,000 ft deep.

CUTLER-MAROON ZONE

The Cutler-Maroon zone of the Canyonlands aquifer (pi. 

15) consists of clastic, carbonate, and evaporite sediments 

that accumulated during the fourth Paleozoic depositional cycle at a time of intense tectonic activity (Kent, 1972; Mallory, 

1972; Rascoe and Baars, 1972). In response to this activity, 

land masses on the east and south rose to mountainous 

heights, and the sea ebbed and flowed but eventually withdrew to the north and west. Arkosic sandstone and shale 

eroded from the rising mountains were deposited between the 

mountain fronts and coastal areas. Quartz sandstone accumulated in coastal dune fields and shoreline areas. Evaporites 

precipitated in restricted marine basins, and carbonate rocks 

accumulated in shallow seas. In general, the depositional pattern is characterized by abrupt facies changes. Consequently,

stratigraphic nomenclature is extremely variable across the region. Component geologic units include the Ranchester 

Limestone Member of the Amsden Formation, upper member 

of the Hermosa Formation (Honaker Trail Formation of 

Wengerd, 1958), Rico Formation, Gothic Formation (of Langenheim, 1952), Minturn Formation, Morgan Formation, 

main body of the Maroon Formation, Cutler Formation, Halgaito Shale (of Baars, 1962), Elephant Canyon Formation (of 

Baars, 1962), Cedar Mesa Sandstone (of Baars, 1962), Organ 

Rock Shale (of Baars, 1962) Supai Formation, Wescogame 

Formation, Esplanade Sandstone, and Hermit Shale (table 1 

and pi. 5).

On the basis of sparse to locally abundant vertebrate, invertebrate, and plant remains, component geologic units are considered to be Lower Pennsylvanian (Morrowan) to Lower 

Permian (Leonardian). The Ranchester Limestone Member in 

the Gros Ventre Range, Wind River Mountains, and Rawlins 

area contains an Early to Middle Pennsylvanian (Morrowan to 

Atokan) fauna (Sando and others, 1975, p. 34). The Morgan 

Formation in the eastern Uinta Mountains contains a Middle 

Pennsylvanian (Desmoinesian) fauna (Kinney, 1955, p. 42-44; 

Hansen, 1965b, p. 46-50). According to Bartleson (1972), the 

Minturn and Gothic Formations in northwestern Colorado, on 

the basis of paleontological evidence, are Middle Pennsylvanian (Atokan to Desmoinesian), and the main body of the Maroon Formation, on the basis of its stratigraphic position above 

the Minturn and Gothic Formations and below the Permian and 

Triassic State Bridge Formation, is considered to be Middle 

Pennsylvanian to Lower Permian (Desmoinesian to Wolfcampian). Similar to the Gothic-Maroon sequence to the north, the 

upper member of the Hermosa Formation, Rico Formation, and 

component geologic units in the Cutler Formation or Cutler 

Group (of Baars, 1962) in southwestern Colorado and southeastern Utah are Middle Pennsylvanian (Desmoinesian) to 

Lower Permian (Leonardian), according to Rascoe and Baars 

(1972) and Blakey and Baars (1987). Component geologic 

units in the Supai Formation or Group and Hermit Shale in 

northeastern Arizona comprise an Upper Pennsylvanian to 

Lower Permian (Virgilian to Leonardian) sequence (Rascoe 

and Baars, 1972; McKee, 1982). Together, geologic units 

within the Cutler-Maroon zone indicate a regional south-southwesterly decrease in age accompanying the progression of 

depositional environments.

The Cutler-Maroon zone thickens and thins erratically (pi. 

15), reflecting the distribution of syndepositional basins and 

uplifts, lateral gradation of component geologic units into formations that comprise other hydrogeologic units, and erosional 

thinning. The Ranchester Limestone Member of the Amsden 

Formation is relatively thin throughout its depositional area but 

thickens to more than 300 ft in the Overthrust Belt and to about 

400 ft east of the Rawlins Uplift (toward the Hanna Basin). The 

Morgan Formation thickens toward two depositional centers, 

one in the Uinta and Green River Basins and the other in the 

Piceance Basin. In both depositional centers, maximum
GEOLOGY OF PALEOZOIC ROCKS, UPPER COLORADO RIVER BASIN A51

thicknesses are between 1,000 and 1,500 ft. The Minturn Formation or Gothic Formation and the overlying main body of the 

Maroon Formation form a clastic wedge extending from the 

ancestral Front Range and Uncompahgre Uplifts to the Piceance and Uinta Basins. This clastic wedge generally exceeds 

10,000 ft thick around the northern end of the Sawatch Range 

and in the Hoosier Pass area of the Gore Range and is 3,000- 

7,000 ft thick in most of the Elk Mountains and White River 

Plateau, but because of gradation into the Eagle Valley Evaporite, it abruptly thins to less than 2,000 ft in the central Eagle Basin. The upper member of the Hermosa Formation, the Rico 

Formation, and the Cutler Group (Formation) generally thicken 

from less than 1,500 ft to more than 10,000 ft toward the northern edge of the Paradox Basin, although some thinning occurs 

over the Monument Upwarp. The Supai Group (Formation) 

and Hermit Shale generally thicken northwesterly, increasing 

from less than 600 ft thick in the Defiance Plateau and eastern 

Grand Canyon to more than 1,500 ft thick in the Lees Ferry area 

and Kaiparowits Basin.

Geologic units that comprise the Cutler-Maroon zone are 

missing because of erosion in the center of the White River 

Plateau, Sawatch Range, Park Range, Gore Range, San Juan 

Mountains, and Uinta Mountains and probably were never 

deposited in a large area extending northwestward from the 

Front Range to the southern Wind River Mountains and northern Green River Basin, on and adjacent to the Uncompahgre 

Plateau, and in small areas in the Wyoming part of the Overthrust Belt, the northwestern corner of the Uinta Basin, and the 

High Plateaus region (pi. 15).

COMPONENT GEOLOGIC UNITS

The Ranchester Limestone Member of the Amsden Formation comprises the Cutler-Maroon zone in the Wyoming part of 

the Overthrust Belt, the Gros Ventre Range, the Wind River 

Mountains, the Great Divide Basin, and the Rawlins Uplift. 

The Ranchester Limestone Member consists of carbonate rocks 

with subordinate clastic rocks and, locally, interbeds of gypsum 

and anhydrite (Mallory, 1967, p. 14; Sando and others, 1975, p. 

32-33). The carbonate rocks include thinly to thickly bedded, 

yellowish-gray, light-gray, and purple, fine-grained to coarsely 

crystalline dolomite and dolomitic limestone and fine- to 

medium-grained limestone. Chert lenses and nodules are 

abundant, particularly in the dolomite layers. Thinly bedded, 

red and green shale and thin intervals of white and pink, fineto medium-grained quartz sandstone occur throughout the 

member; sandstone beds are abundant in the upper half and 

predominate between the Wind River Mountains and Gros 

Ventre Range, in parts of the Wyoming Overthrust Belt, on the 

northern edge of the Great Divide Basin, and in an area on and 

near the Rock Springs Uplift (Mallory, 1967, pis. 2,3, and 15). 

Gypsum and anhydrite interbeds occur at the northern end of 

the Wind River Mountains (Sando and others, 1975, p. 33) and 

at the northern end of the Hoback Range (Wanless and others, 

1955, p. 34).

In the southern Green River Basin, strata equivalent to the 

Ranchester Limestone Member are assigned to the Morgan 

Formation despite virtually no change in lithology from areas 

to the north and west (Mallory, 1967, fig. 4; Sando and others, 

1975, pi. 7). As described by Hansen and others (1983), the 

Morgan Formation in the southeastern Uinta Mountains (fig. 4) 

is divisible into two members. The lower member consists of 

variegated shale and cherty, fossiliferous limestone with thin 

layers of sandstone. The upper member, which comprises 

about two-thirds of the formation, consists of thinly bedded to 

massively bedded, red, tan, and gray quartz sandstone with 

layers of red shale in the lower part and thin interbeds of gray 

and pink cherty limestone throughout. The two-fold division of 

the Morgan Formation is traceable into the northeastern Uinta 

Mountains, but in this area, Hansen (1965b) chose to include 

beds equivalent to the upper member of the Morgan Formation 

in the lower part of the Weber Sandstone. In this report the 

beds assigned by Hansen to the lower part of the Weber Sandstone are retained in the Morgan Formation to preserve stratigraphic continuity and avoid introducing substantial lithologic 

heterogeneity into the Weber Sandstone. The Weber Sandstone of this report, therefore, is a nearly homogeneous formation composed of light-colored, quartz sandstone.

Between the eastern and western Uinta Mountains, considerable changes occur in the Morgan Formation. On the basis of 

descriptions of the formation by Huddle and McCann (1947b), 

Huddle and others (1951), and Kinney (1955, p. 40-42), the 

lower and upper members apparently merge west of Dinosaur 

National Monument. Limestone beds in the formation pinch 

out westward and do not extend beyond the Lake Fork of the 

Duchesne River. West of the Whiterocks River, in the central 

Uinta Mountains, sandstone layers in the upper part of the formation become light colored and grade into the Weber Sandstone. The remaining Morgan Formation becomes 

predominantly reddish brown in color. In the Duchesne River 

area of the western Uinta Mountains, the Morgan Formation is 

near its depositional edge and consists almost entirely of interbedded sandstone, siltstone, and mudstone.

In the southwestern Uinta Basin, interbedded cherty 

limestone and dolomite, light-colored, orange, and red sandstone, and gray, tan, red, and varicolored shale occur between 

beds of typical Weber Sandstone and Round Valley Limestone 

lithologies (fig. 28). Superficially, these beds resemble the 

lower part of the Weber Formation at its type locality along the 

Weber River in the Uinta Mountains west of the UCRB and 

could be assigned to the Weber Sandstone (Samuel Johnson, 

U.S. Geological Survey, oral commun., 1990). However, in 

this report, distinction between the Weber Sandstone where it 

contains carbonate interbeds in the western UCRB and the underlying Morgan and Elephant Canyon Formations consistently was made based on the relative thickness and abundance of 

carbonate intervals. Tops of the Morgan and Elephant Canyon 

Formations were placed where carbonate intervals became 

more than several tens of feet thick and began to equal or
A52 REGIONAL AQUIFER SYSTEM ANALYSIS UPPER COLORADO RIVER BASIN

FIGURE 33. Interbedded sandstone, shale, 

and dolomite in the Pennsylvanian 

Minturn Formation at Vail, Colo.

exceed sandstone intervals in abundance. On the basis of these 

criteria and their lithology, the beds in question in the southwestern Uinta Basin were assigned to the Morgan Formation. 

In the eastern Eagle Basin, the lower part of the Morgan Formation and the Eagle Valley Evaporite grade into the Minturn 

Formation (figs. 24 and 30). The Minturn Formation (fig. 33) 

consists of interbedded sandstone, pebbly sandstone (grit), conglomerate, and shale with irregularly spaced intervals of limestone and dolomite and minor evaporite beds (Chronic, 1957; 

Boggs, 1966; Tweto and Levering, 1977, p. 40-48). The 

sandstone, grit, and conglomerate commonly are arkosic, but 

feldspathic, graywacke, and quartz sandstone layers also are 

present. The arkosic rocks typically are micaceous and poorly 

sorted. The sandstone layers, in general, become coarser 

grained, thicker, and more numerous eastward as shale and 

evaporite layers become less abundant. Shale intervals in the 

Minturn Formation are gray to black; most commonly, they 

consist of micaceous sandy shale and siltstone, but claystone 

layers are present. Limestone layers in the formation are bluish 

gray to brownish gray and very fine grained to sandy. 

Dolomite layers in the formation generally are gray to black 

and either finely crystalline, bioclastic, or cherty. Some of the 

dolomite was formed by hydrothermal replacement of limestone and is gray and tan, vuggy, and coarsely crystalline. 

Many of the carbonate layers pinch out westward or grade 

laterally into clastic layers; in transition zones, mixed carbonate-clastic rocks, such as conglomerate consisting of quartz and 

pegmatite pebbles in a matrix of dolomite or sandy dolomite, 

may occur. Although most of the Minturn Formation is grayish 

green, tan, yellow, and pink, upper layers grade to predominantly red (see Tweto and Levering, 1977, fig. 13). The top of 

the Minturn Formation is the Jacque Mountain Limestone

Member (fig. 34), an interval of gray and pink limestone, about 

20-25 ft thick, that in alternate layers is oolitic, sandy, 

bioclastic, or stromatolitic (Boggs, 1966, fig. 6).

Lithologic criteria used to distinguish the Minturn Formation from the overlying Maroon Formation in the eastern Eagle Basin and Gore Range become unusable about 7 mi west 

of Avon, Colo. (Boggs, 1966, p. 1403 and fig. 2). In this area, 

the Jacque Mountain Limestone Member becomes covered 

and intercalated with evaporite deposits. Although the Jacque 

Mountain Limestone Member may be present west of the axis 

of the Eagle Basin, in the White River Plateau and Elk Mountains, this particular limestone interval cannot be identified reliably among numerous other limestone intervals in the area. 

As an example, Langenheim (1954, p. 1768) noted that limestone intervals identified as the Jacque Mountain Limestone 

Member in measured sections near Glenwood Springs and 

Dotsero, Colo., within 20 mi of each other, were in reality 

separated by 1,500 feet of intervening strata. Similarly, the 

Jacque Mountain Limestone Member loses its identity a short 

distance to the south of its type locality at Minturn, Colo. De 

Voto (1972, p. 161) indicated that limestone beds in the 

Minturn-Maroon section at Hoosier Pass, 20 mi south of Minturn, cannot be correlated with confidence with limestone 

beds at Minturn. Because of these correlation problems, Langenheim (1952, 1954) felt that the Jacque Mountain Limestone Member was not a useful stratigraphic marker in the Elk 

Mountains and White River Plateau and, in these areas, rejected the Minturn Formation as a mappable unit. Instead, Langenheim established the Gothic Formation and defined its top 

as the change from predominantly tan, green, and gray clastic 

rocks to predominantly red clastic rocks. The predominantly 

red rocks were assigned to the Maroon Formation. Bartleson
Q

ELK 

MOUNTAINS

Crested Butte 

area

South Canyon Creek

Dolomite Member of

State Bridge Formation

WHITE RIVER 

PLATEAU

Glenwood Springs 

area

Chinle Formation

Q'

PARK 

RANGE

McCoy 

area

JURASSIC

PENNSYLVANIAN

Entrada Sandstone

Upper member of State Bridge F

Lower member of State Bridge F

.Schoolhouse Member of Maroon 

Maroon Formation

-'Jacque Mountain 

Limestone Member

Minturn Formation

Datum is the base of the Entrada SandstoneLimestone beds in the Gothic and Maroon Forma

^

EXPLANATION

Quartz sandstone

ShaleSiltstone

ConglomerateLimestone and dolomite

Gray, tan, green, pink, and black sandstone, 

conglomerate and shale

Predominantly red sandstone, 

conglomerate, and shale

Conformable contact Gradatlonal contact 

Unconformable contact

Approximate position of PennsylvanlanPermian transition within Maroon Formation

FEET 

1,000-,

500-

\ 

15

I 

30 MILES

FIGURE 34. Stratigraphic section showing relations among Pennsylvanian and Permian clastic geologic units in west-central Colorado. Compiled from reports by Brill 

Chronic (1957); location of section shown on plate 15.
A54 REGIONAL AQUIFER SYSTEM ANALYSIS UPPER COLORADO RIVER BASIN

FIGURE 35. Interbedded sandstone and 

conglomerate in the Pennsylvanian 

Gothic Formation (of Langenheim, 

1952) on the Crystal River south of 

Carbondale, Colo.

(1972) and Bryant (1979) accepted Langenheim's terminology in subsequent reports on the Elk Mountains and Sawatch 

Range.

The Gothic Formation, as defined by Langenheim (1952, 

1954) consists of all the predominantly light colored clastic 

and carbonaceous rocks between the Belden and Maroon 

Formations. The Gothic Formation is characterized by extreme lenticularity, with individual layers traceable for no 

more than 2 mi within an outcrop area and untraceable between outcrop areas. The base of the formation in the Elk 

Mountains and White River Plateau is the lowest prominent 

sandstone above shale and limestone typical of the Belden 

Formation. In the Sawatch Range, according to Bryant (1979, 

p. 25-27), the base of the Gothic Formation is gradational into 

the Belden Formation and consists of green, gray, and red 

limy shale, shaly limestone, and sandy limestone interbedded 

with dark-gray to black carbonaceous shale; the contact with 

the Belden Formation is drawn where the rocks become predominantly light colored. The upper contact of the Gothic 

Formation is an abrupt to gradational color change from gray, 

green, and tan clastic rocks to predominantly red clastic rocks. 

In the Elk Mountains and White River Plateau, the Gothic 

Formation (fig. 35) predominantly consists of siltstone with 

lesser amounts of sandstone and conglomerate and irregularly 

spaced limestone beds. The clastic rocks typically are feldspathic and locally micaceous; calcite cement may be present. 

The limestone layers typically are either massively bedded 

and sandy (grading into sandstone) or thinly bedded, organic, 

and shaly (with shale interbeds), but massive reef deposits 

also occur. In the Sawatch Range and vicinity, the Gothic 

Formation consists of limy sandstone and siltstone and silty to 

sandy limestone with interbeds of pebbly, arkosic sandstone, 

conglomerate, breccia, gypsum, and anhydrite (Bryant, 1979,

p. 27). In general, the Gothic Formation becomes finer 

grained from south to north, containing more siltstone and 

less conglomerate and progressively finer grained sandstone 

layers in that direction (Langenheim, 1954, p. 1769).

Deposits that could be classified as either Gothic Formation 

or Mintum Formation are encountered in drill holes between 

the Belden Formation or Eagle Valley Evaporite and the 

Maroon Formation in the Piceance Basin. These deposits 

consist of sandstone, siltstone, and mudstone with interbeds of 

limestone, dolomite, and, locally, anhydrite. The top of the 

sequence generally is characterized by a limestone interval, 5 

20 ft thick, and a color change upward from predominantly 

gray, white, tan, orange, grayish green, and black to predominantly red, reddish orange, reddish brown, purple, and maroon. 

Where a thick layer of limestone marks the top of the sequence, 

the color change may occur well below the limestone layer. Alternately, a thick sequence of light-colored rocks may intervene 

between predominantly red rocks of typical Maroon Formation 

lithology and the first thick limestone layer below the typical 

Maroon Formation beds. If the first thick limestone layer is 

equivalent to the Jacque Mountain Limestone Member of the 

Minturn Formation and rocks below it are assigned to the 

Minturn Formation, then the Maroon Formation uncharacteristically would include a color change in some areas of the 

Piceance Basin. On the other hand, if the color change is used 

to distinguish the Maroon Formation from the Gothic Formation, then the Maroon Formation uncharacteristically would include thick limestone intervals in some parts of the Piceance 

Basin. As neither system of nomenclature is satisfactory in the 

Piceance Basin, beds between intervals of typical Belden Formation or Eagle Valley Evaporite and Maroon Formation 

lithologies in this report are designated as undifferentiated 

Minturn-Gothic Formation.
GEOLOGY OF PALEOZOIC ROCKS, UPPER COLORADO RIVER BASIN A55

FIGURE 36. Pennsylvanian, Permian, and 

Triassic formations in the Eagle River 

valley near Eagle, Colo. E, Eagle 

Valley Evaporite; M, main body of 

Maroon Formation; S, Schoolhouse 

Member of Maroon Formation; SB, 

State Bridge Formation. The main 

body of the Maroon Formation here 

consists of fluvial and eolian sandstone 

interbedded with shale.

Throughout northwestern Colorado, the Morgan Formation, 

Eagle Valley Evaporite, Minturn Formation, and Gothic 

Formation are overlain gradationally by the Maroon Formation 

(figs. 24 and 34). The main body of the Maroon Formation (fig. 

36) consists of conglomerate, sandstone, siltstone, and 

mudstone, with thin intervals of limestone, and, locally, 

gypsum (Langenheim, 1954; Bass and Northrop, 1963, p. 46- 

54; Bryant, 1979, p. 29-40; Johnson, 1987). The clastic rocks 

predominantly are red, reddish brown, reddish orange, maroon, 

and purple. However, intervals of gray limestone and shale (interpreted as tongues of the Minturn and Gothic Formations) occur in the lower part of the main body of the Maroon 

Formation, and intervals of tan and light-gray quartz sandstone 

(interpreted either as tongues of the Schoolhouse Member or as 

diagenetically altered horizons) occur near the top of the main 

body of the Maroon Formation. Clastic layers typically are arkosic, micaceous, calcareous, and hematitic. Sandstone layers 

are well sorted to poorly sorted, very fine to coarse grained, and 

grade into conglomerate layers. Conglomerate layers contain 

clasts ranging from gravel to cobble size. Limestone layers, 

which usually are less than 3 ft thick, are most abundant in the 

lower part of the main body of the Maroon Formation. Typically, these carbonate rocks are fine grained and silty to muddy 

and grade into siltstone over distances of a few hundred feet. 

The main body of the Maroon Formation, in general, is characterized by extreme lenticularity, with individual beds no more 

than about 30 ft thick and traceable for no more than a mile.

South of the crest of the Uncompahgre Plateau and west of 

the crest of the San Juan Mountains, strata equivalent to the 

Mintum (or Gothic) and Maroon Formations grade into the upper member of the Hermosa Formation, Rico Formation, and 

Cutler Formation. From the Monument Upwarp west to the

San Rafael Swell and High Plateaus, tongues of quartz sandstone alternate with red beds within the Cutler. The U.S. Geological Survey considers the quartz sandstone and red-bed 

sequences to be members of the Cutler Formation, whereas 

Baars (1962) assigned these sequences formation status and elevated the Cutler in the area to group rank. In ascending order, 

the formations comprising the Cutler Group in the southern 

two-thirds of the Monument Upwarp and vicinity are the Halgaito Shale, Cedar Mesa Sandstone, Organ Rock Shale, and 

White Rim Sandstone. As shown on plate 15, the Halgaito 

Shale in the northern Monument Upwarp and in areas to the 

west grades into the Elephant Canyon Formation. The Rico 

Formation north and west of the Monument Upwarp also 

grades into the Elephant Canyon Formation, but it becomes indistinguishable in the southeastern Henry Mountains Basin and 

eastern Kaiparowits Basin. The Organ Rock Shale pinches out 

in the vicinity of the San Rafael Swell, causing the Cedar Mesa 

and White Rim Sandstones to merge into a single body of sandstone (fig. 37), which in earlier reports was called either Coconino Sandstone (see, for example, Hunt and others, 1953) or 

Cedar Mesa Sandstone (see, for example, Baars, 1983), but is 

now referred to as White Rim Sandstone (the preferred usage 

in this report) or Toroweap Formation (George Billingsley, 

U.S. Geological Survey, written commun., 1988). The White 

Rim and Coconino Sandstones are included in the Weber-De 

Chelly zone and are described later in this report. The Cedar 

Mesa Sandstone is similar in lithology to the White Rim and 

Coconino Sandstones but is included in the Cutler-Maroon 

zone, because the Organ Rock Shale inhibits ground-water 

flow between the Weber-De Chelly and Cutler-Maroon zones. 

The upper member of the Hermosa Formation consists of 

limestone, shale, sandstone, and conglomerate interbedded in
R

KAIPAROWITS 

BASIN

HENRY MOUNTAINS 

BASIN

Kaibab Limestone 

Toroweap Formation

Elephant Canyon 

Formation

FOUR 

CORNERS 

PLATFORM

FEET 

2,000 - 1,500-

1,000-

500-

0

0 10 20 30 MILES

EXPLAN

Quartz sandstone 

Redbeds Sandstone 

Limestone and dolo

Sandstone, shale, an

Arkosic sandstone, 

Igneous and metamoFault Barbs indicate 

FIGURE 37. Fence diagram showing relations among Permian formations in southwestern Colorado and southeastern Utah. Modified from Kunkel (1958, p. 165); loca
GEOLOGY OF PALEOZOIC ROCKS, UPPER COLORADO RIVER BASIN A57

FIGURE 38. Arkosic conglomerate, sandstone, and sandy siltstone in the 

Permian Cutler Formation along the 

Uncompahgre River in the San Juan 

Mountains, north of Ouray, Colo.

intervals a few feet to more than 50 ft thick. Nearly everywhere, the bottom of the member is characterized by an interval 

of sandstone with interbedded shale. Sandstone and conglomerate layers are thickest and most abundant in the vicinity of the 

San Juan Mountains and Uncompahgre Plateau. Carbonate 

layers increase in thickness and number westward and predominate in the southern Monument Upwarp. In the San Juan 

Mountains, the upper member of the Hermosa Formation consists of greenish-gray, brown, and maroon, micaceous sandstone; arkosic sandstone and conglomerate; and brownish-red, 

black, and green shale; with a few thin beds of gray limestone 

(Eckel and others, 1949, p. 10-12; Wengerd, 1957, p. 133; 

McKnight, 1974, p. 26-27; Baars and others, 1987, p. 347). 

Farther west, at the confluence of the Green and Colorado Rivers in the northern Monument Upwarp, the upper member of 

the Hermosa Formation consists of blue, greenish-gray, and 

gray limestone with chert concretions; gray, green, red, and 

purple mudstone, siltstone, and limy shale; and white, gray, 

greenish-gray, red, and purple limy, arkosic, and shaly sandstone (McKnight, 1940, p. 22-23). In the southern Monument 

Upwarp along the San Juan River, the upper member of the 

Hermosa Formation (fig. 31) predominantly consists of gray, 

finely crystalline, cherty limestone and red, purple, gray, and 

tan limy, sandy siltstone with a few thin layers of gray and 

brown, fine-grained, limy sandstone (Gregory, 1938, p. 64-65; 

Wengerd, 1963; O'Sullivan, 1965, p. 10-20).

The Rico Formation is transitional in lithology between the 

upper member of the Hermosa Formation and the Cutler Formation. Its top and bottom are distinguished by lithologic criteria that are not persistent throughout the area. In the San Juan 

Mountains, the Rico Formation consists of predominantly reddish brown, maroon, pink and gray, micaceous, and arkosic 

sandstone, pebbly sandstone, sandy shale and conglomerate,

with thin intervals (less than 10 ft thick) of maroon, red, and 

gray, sandy and shaly limestone and black limy shale (Eckel 

and others, 1949, p. 13-15; Larsen and Cross, 1956, p. 46-47). 

In the northern Monument Upwarp, the Rico Formation similarly is composed of brownish-red, purple, maroon, brown, and 

gray sandstone, arkosic sandstone, sandy shale, and limy shale, 

with eight thin intervals of bluish-gray to greenish-gray nodular 

limestone (McKnight, 1940, p. 26-28). In the southern Monument Upwarp, the Rico Formation consists of reddish-brown, 

red, purple, and gray siltstone, with eight to nine intervals of 

fossiliferous, gray and white limestone and quartz sandstone. 

These eight to nine marker beds are 0-36 ft thick individually; 

intervening siltstone intervals are 16-136 ft thick (O'Sullivan, 

1965, p. 23-31).

The Cutler Formation is 8,000 to more than 9,000 ft thick on 

the southwestern side of the Uncompahgre Plateau, but it 

pinches out abruptly to the north and east against faults bordering the plateau (fig. 37). The Cutler Formation consists of a 

coarse-grained arkosic facies from the Uncompahgre Plateau 

and San Juan Mountains to the northeastern Paradox Basin and 

a finer grained red-bed facies from the southwestern Paradox 

Basin to the Monument Upwarp and northeastern Arizona 

(Kunkel, 1960, p. 91-93). The coarse-grained facies (fig. 38) 

consists of massively bedded sandstone, grit, and conglomerate 

with interbeds of claystone, siltstone, and sandy shale and scattered interbeds of earthy, nodular limestone; the rocks are dominantly purplish red and reddish brown, but red, brown, orange, 

pink, and gray intervals, also, are present (Dane, 1935, p. 39- 

40; Eckel and others, 1949, p. 16-17; Bush and others, 1959, p. 

309-312; Luedke and Burbank, 1962; McKnight, 1974, p. 30- 

31). The various rock types grade into each other and interfinger laterally over distances of a few thousand feet. The sandstone, grit, and conglomerate typically are arkosic and
A58 REGIONAL AQUIFER SYSTEM ANALYSIS UPPER COLORADO RIVER BASIN

micaceous and commonly contain some calcite cement. Conglomerate layers, which are concentrated in the upper half of 

the formation, are composed of gravel- to boulder-sized clasts 

of igneous and metamorphic rocks in a matrix of coarsegrained, angular sandstone; the average size of the clasts and 

the number of conglomerate layers increase in a northeasterly 

direction toward the Uncompahgre Plateau. The finer grained 

facies consists of red, reddish-brown, brown, and purple, medium- to coarse-grained, arkosic sandstone, siltstone, and mudstone with some interbedded quartz sandstone, cherty 

limestone, and gypsum or anhydrite (Baker, 1933, p. 29 30; 

McKnight, 1940, p. 37-47; Shawe and others, 1968, p. 24-25). 

Quartz sandstone layers are most abundant near the base and 

top of the formation, where the Cutler Formation grades into 

the Cedar Mesa and De Chelly Sandstones.

The Halgaito Shale, which is about 750 ft thick (Baars, 1983, 

p. 83), consists of reddish-brown (mottled gray and green), 

fine-grained silty sandstone and siltstone with thin lenticular 

beds of gray limestone and, locally, interbeds of silt-pebble 

conglomerate, limestone conglomerate, gypsiferous sandstone, 

and gypsum (Gregory, 1938, p. 42; Kirkland, 1963, p. 84; Irwin 

and others, 1971, p. 23; Blakey, 1979, p. 119-120; Blakey and 

Baars, 1987, p. 362). The sandstone and siltstone are cemented 

with calcite. The formation characteristically is thinly bedded, 

with sandstone and shale beds commonly less than 1 ft thick 

and limestone and gypsum beds commonly less than 2 ft thick 

(Witkind and Thaden, 1963, p. 8; O'Sullivan, 1965, p. 34).

The Elephant Canyon Formation, which is as much as 

1,500 ft thick, consists of tan and light-grayish-brown, crystalline to sucrose, cherty limestone; tan and beige, finely crystalline to chalky, cherty dolomite; and white, gray, and tan,

fine-grained, quartz sandstone with red, purple, and green siltstone and mudstone, arkosic sandstone, and anhydrite 

(Kunkel, 1958, p. 163-164; Baars, 1979, p. 3). In the San 

Rafael Swell, limestone and sandstone in beds 3-50 ft thick 

underlie the White Rim Sandstone. Because of their stratigraphic position, these beds are interpreted in this report to be 

the top of the Elephant Canyon Formation, although Baker 

(1946), who first described them, interpreted the beds to be in 

the Hermosa Formation.

The Cedar Mesa Sandstone, for the most part, consists of 

light-gray, white, tan, beige, and grayish-orange, fine-grained 

quartz sandstone weakly to firmly cemented with calcite (Gregory, 1938, p. 43^5; Hunt and others, 1953, p. 41-42; Kunkel, 

1958, p. 164-166; Thaden and others, 1964, p. 14-19; O'Sullivan, 1965, p. 36-46; Irwin and others, 1971, p. 24; Baars, 1979, 

p. 3; Blakey and Baars, 1987, p. 362). The sandstone typically 

occurs in layers 5-40 ft thick that display large-scale crossbedding (fig. 39). Reddish-brown, red, and greenish-gray siltstone 

and mudstone beds, 1-13 ft thick, are interbedded with the 

sandstone; many of these beds contain limestone nodules. Thin 

beds of bluish-gray limestone occurring in the formation are 

most numerous near the base and northwestern edge where the 

Cedar Mesa Sandstone grades into the Elephant Canyon Formation. Along its eastern edge, where it grades into the Cutler 

Formation, the Cedar Mesa Sandstone consists of red and purple gypsiferous shale, brownish-red and gray, friable, gypsiferous sandstone, gray and purple cherty limestone and 

conglomeratic limestone, and pink and white gypsum and anhydrite. The change from the quartz sandstone to the gypsiferous facies of the Cedar Mesa Sandstone is abrupt, occurring in 

a northeast-trending zone about 1 mi wide (Sears, 1956, p.

FIGURE 39. Permian Cedar Mesa Sandstone and Organ Rock Shale (of 

Baars, 1962) at Natural Bridges National Monument, Utah.
GEOLOGY OF PALEOZOIC ROCKS, UPPER COLORADO RIVER BASIN A59

FIGURE 40. Permian Organ Rock Shale 

(of Baars, 1962) and De Chelly Sandstone in Monument Valley, Utah.

184-187). The Cedar Mesa Sandstone is about 1,400 ft thick 

in the center of its depositional area (Baars, 1983, p. 85).

The Organ Rock Shale (fig. 40) consists of reddish-brown 

and orange-red (mottled gray and green) limy mudstone, siltstone, and very fine grained silty sandstone with beds of limestone-pellet conglomerate (Gregory, 1938, p. 46; Hunt and 

others, 1953, p. 42; Kunkel, 1958, p. 166; Mullens, 1960, p. 

272-274; Witkind and Thaden, 1963, p. 10-12; Thaden and 

others, 1964, p. 19-29; Lewis and Campbell, 1965, p. 11-13; 

O'Sullivan, 1965, p. 46-49; Blakey, 1979, p. 121-122; Baars, 

1987, p. 282; Blakey and Baars, 1987, p. 363). In Monument 

Valley, the formation contains thin beds of grayish-pink limestone. Along its northeastern edge where it grades into the 

Cutler Formation, the Organ Rock Shale contains layers of 

purple and red, coarse-grained, arkosic sandstone. Near the 

base and top of the formation where it grades into the Cedar 

Mesa and De Chelly Sandstones, the Organ Rock Shale contains layers of light-gray, white and pink, fine- to mediumgrained quartz sandstone. These sandstone layers are crossbedded and as much as 40 ft thick. In general, bedding intervals vary from inches to more than 10 ft, but in many places, 

bedding is obscure. The Organ Rock Shale is more than 900 

ft thick in the center of its depositional area (Baars, 1983, p. 

88-89).

In the Defiance Plateau, the upper member of the Hermosa 

Formation pinches out, and the Rico Formation and Cutler 

Group grade into the Supai Formation. The Supai Formation 

consists of reddish-brown and reddish-orange, fine-grained 

sandstone, silty sandstone, and siltstone with beds of gypsiferous sandstone, siliceous limestone, and mudstone-pellet conglomerate (Read and Wanek, 1961; Irwin and others, 1971, p.

17-18). Some of the sandstone is crossbedded. A basal conglomerate consisting of gravel- to boulder-sized clasts of 

quartzite, granite, volcanic rocks, and limestone in a matrix of 

fine-grained sandstone is present in many places. This conglomerate layer is 2-5 ft thick. In general, the formation is 

thinly to thickly bedded.

In the Black Mesa, Kaibito, and Kaiparowits Basins, the 

upper member of the Hermosa Formation grades into the 

Wescogame Formation; the Halgaito Shale grades into the 

basal slope unit of the Esplanade Sandstone; the Cedar Mesa 

Sandstone grades into the main cliff and upper cliff-slope units 

of the Esplanade Sandstone; and the Organ Rock Shale grades 

into the Hermit Shale. The Wescogame Formation and 

Esplanade Sandstone are included in the Supai Group (fig. 2) 

as defined by McKee (1982).

The Wescogame Formation, which is 98-240 ft thick in the 

eastern Grand Canyon and Marble Canyon (McKee, 1982, p. 

41), consists of reddish-brown, reddish-orange, pink, and red, 

fine-grained sandstone and siltstone with interbedded 

mudstone and limestone. Sandstone is the dominant constituent, but proportions of all rock types are extremely variable 

(McKee, 1982, p. 49).

The Esplanade Sandstone, which is 262-444 ft thick in the 

eastern Grand Canyon and Marble Canyon (McKee, 1982, p. 

41), predominantly consists of very fine grained sandstone 

(McKee, 1982, p. 48). The basal slope unit is composed of reddish-brown, reddish-orange, red, and gray, very fine grained 

sandstone, siltstone, and mudstone, with a basal conglomerate 

layer 3-5 ft thick. The main cliff unit consists of grayish-white, 

gray, pale-orange, reddish-orange, reddish-brown, and pink, 

fine-grained, limy, crossbedded sandstone with interbeds of
A60 REGIONAL AQUIFER SYSTEM ANALYSIS UPPER COLORADO RIVER BASIN

reddish-brown to red siltstone and mudstone and very sparse 

interbeds of limestone. The upper cliff-slope unit consists of 

interbedded sandstone, siltstone, and mudstone similar to rocks 

present in the other two units but eroded into a characteristic 

ledge and slope topography. According to Phoenix (1963, p. 

10), sandstone beds in the upper unit typically are 2-10 ft thick. 

The Hermit Shale (fig. 2) consists of thinly bedded, reddishbrown and reddish-orange mudstone, siltstone, and very fine 

grained sandstone with lenses of light-colored, fine-grained 

sandstone (Noble, 1922, p. 64-65; Phoenix, 1963, p. 10-11; 

McKee, 1982, p. 391-398). In the eastern Grand Canyon and 

Marble Canyon, the Hermit Shale is 76-710 ft thick (McKee, 

1982, p. 36).

CONTACTS

Contacts between geologic units that comprise the CutlerMaroon zone of the Canyonlands aquifer and component geologic units of the underlying Four Corners confining unit generally are gradational. However, the Wescogame Formation 

rests on the eroded surface of the Manakacha Formation, which 

contains conglomerate-filled channels as much as 80 ft deep 

(McKee, 1982, p. 161). Where the Four Corners confining unit 

is missing because of erosion or nondeposition, particularly on 

the eastern and western fringes of the study area, component 

geologic units in the Cutler-Maroon zone unconformably overlie older geologic units. On the eastern side of the UCRB, the 

Maroon, Cutler, and Supai Formations overlie Precambrian 

igneous and metamorphic rocks in areas that were highlands 

intermittently before and during deposition. Such areas include 

the Gore Range, Uncompahgre Plateau, and Defiance Plateau. 

The relief on the basal unconformity in the Defiance Plateau 

ranges from 15 to 75 ft (Irwin and others, 1971, p. 18). Westward from the Monument Upwarp to the San Rafael Swell and 

Kaiparowits Basin, the Cutler Group progressively truncates 

older rocks, resting on Pennsylvanian rocks in the east and 

Mississippian rocks in the west (Kunkel, 1958, p. 164).

Contacts among geologic units comprising the CutlerMaroon zone generally are conformable to gradational. The 

Minturn Formation is overlain conformably by the Maroon 

Formation (Tweto and Levering, 1977, p. 55). The Gothic 

Formation is gradational into the Maroon Formation everywhere (Langenheim, 1952, p. 561; Bryant, 1979, p. 25). The 

upper member of the Hermosa Formation is overlain conformably by the Rico Formation, and a transition zone as 

much as 25 ft thick is present in most areas (Baker, 1933, p. 

25; 1936, p. 21; Dane, 1935, p. 34; O'Sullivan, 1965, p. 23). 

The Rico Formation, in turn, grades laterally and vertically 

into the Cutler Group or Formation (Baker, 1933, p. 29; 1936, 

p. 29; 1946, p. 39; Dane, 1935, p. 41; McKnight, 1940, p. 49- 

50; 1974, p. 31; O'Sullivan, 1965, p. 35). Vertical shifts in 

the Rico-Cutler contact occur because fossiliferous limestone 

layers that define the top of the Rico Formation are discontinuous. As one of these limestone layers pinches out, the

contact shifts vertically to the next fossiliferous limestone layer (Baker, 1946, p. 35-36).

The Cutler Formation grades into the Halgaito Shale, Cedar 

Mesa Sandstone, and Organ Rock Shale and becomes the Cutler Group. Within the Cutler Group, contacts between included formations generally are gradational vertically and laterally 

(fig. 37). The Halgaito Shale grades into the Elephant Canyon Formation. The Elephant Canyon Formation and Halgaito Shale grade into the Cedar Mesa Sandstone. The Cedar 

Mesa Sandstone generally grades into the Organ Rock Shale; 

in the southern Monument Upwarp, this transition zone is 60- 

100 ft thick (Mullens, 1960, p. 270). In the northern Monument Upwarp, however, the Cedar Mesa Sandstone-Organ 

Rock Shale contact is an irregular surface with as much as 40 

ft of relief. Baker (1946, p. 39) interpreted this surface to be 

erosional, but Thaden and others (1964, p. 19) interpreted it 

as depositional.

Within the Supai Group and Hermit Shale, contacts between formations generally are unconformable. The Esplanade Sandstone overlies the Wescogame Formation 

unconformably. The contact surface contains conglomeratefilled channels as much as 50 ft deep (McKee, 1982, p. 161). 

The Esplanade Sandstone, in turn, is overlain unconformably 

by the Hermit Shale (Noble, 1922, p. 64). This unconformity 

is a very irregular surface with channels as much as 55 ft deep 

and hills as much as 114 ft high (Phoenix, 1963, p. 11; 

McKee, 1982, p. 161).

Contacts between geologic units in the Cutler-Maroon zone 

and geologic units in overlying zones of the Canyonlands 

aquifer north of the Uncompahgre Plateau generally are conformable to gradational, although local unconformities exist. 

The Ranchester Limestone Member of the Amsden Formation 

is overlain conformably to transitionally by the Tensleep 

Sandstone of Pennsylvanian and Permian age (Sando and others, 1975, p. 33). The Morgan Formation intertongues with 

and grades into the Weber Sandstone of Pennsylvanian and 

Permian age (Thomas and others, 1945; Untermann and Untermann, 1954, p. 33; Kinney, 1955, p. 44; Hallgarth, 1959; 

Bass and Northrop, 1963, p. 47-48; Hansen, 1965b, p. 50). 

Where the Schoolhouse Member of the Maroon Formation 

pinches out east of the White River Plateau, the main body of 

the Maroon Formation is overlain conformably to unconformably by the Permian and Triassic State Bridge Formation 

(Freeman, 1971, p. 4; Freeman and Bryant, 1977, p. 185). 

Atypically, the State Bridge, Maroon, and Gothic Formations 

are truncated from north to south in the Elk Mountains by an 

erosional surface on which the Jurassic Entrada Sandstone 

was deposited (Brill, 1944, p. 638; Langenheim, 1952, p. 563; 

1954, p. 1755). This erosional surface also appears to truncate the Maroon Formation on the east side of the Gore Range 

(Lovering and Goddard, 1950, p. 36; Singewald, 1951, p. 10- 

13).

South of the Uncompahgre Plateau, the upper surface of 

the Cutler-Maroon zone is an unconformity in most areas
GEOLOGY OF PALEOZOIC ROCKS, UPPER COLORADO RIVER BASIN A61

where the undivided Cutler Formation or the Organ Rock 

Shale is at the top of the Paleozoic rocks. In the Uncompahgre Plateau, San Juan Mountains, and northern Paradox Basin, the Cutler Formation generally is overlain with angular 

discordance by the Dolores Formation of Triassic age; 

locally, in and near the San Juan Mountains, however, this 

contact is gradational (Eckel and others, 1949, p. 16; Bush 

and others, 1959, p. 308; Luedke and Burbank, 1962). In the 

central Monument Upwarp, the Organ Rock Shale is overlain 

disconformably by the Hoskinnini Member of the Triassic 

Moenkopi Formation (Read and Wanek, 1961, pi. 2; Thaden 

and others, 1964, p. 28-29).

Where the White Rim or De Chelly Sandstone is present, the 

contact with the underlying Cutler Formation or Organ Rock 

Shale generally is gradational. From the east side of the Monument Upwarp to the vicinity of the Colorado-Utah State line, 

the undivided Cutler Formation or Organ Rock Shale grades 

into the De Chelly Sandstone. According to Witkind and 

Thaden (1963, p. 12) and O'Sullivan (1965, p. 47), the Organ 

Rock-De Chelly transition occurs over a vertical distance of 

25-65 ft. On the west side of the Monument Upwarp and in the 

eastern Henry Mountains Basin, contacts between the Organ 

Rock Shale and White Rim Sandstone are conformable to gradational (McKnight, 1940, p. 51; Hunt and others, 1953, p. 45; 

Steele-Mallory, 1982, p. 9).

The Supai Formation and Hermit Shale, also, are overlain 

conformably by Permian sandstones. In the Defiance Plateau 

area of northeastern Arizona, red beds of the Supai Formation 

are overlain transitionally by the De Chelly Sandstone (Read 

and Wanek, 1961, pi. 2; Irwin and others, 1971, p. 18). To the 

west, in the Lees Ferry area and in the Grand Canyon, the 

Hermit Shale conformably is overlain by the Coconino 

Sandstone of Permian age (Noble, 1922, p. 64; Phoenix, 1963, 

p. IDWEBER-DE CHELLY ZONE

The Weber-De Chelly zone of the Canyonlands aquifer (pi. 

16) consists almost entirely of quartz sandstone deposited in 

coastal dune fields, estuaries, and shoreline areas as the sea receded and then readvanced near the end of the Paleozoic Era 

(Kent, 1972; Mallory, 1972; Rascoe and Baars, 1972; Blakey, 

1979; Fryberger and Koelmel, 1986). Component geologic 

units include the Wells Formation, Tensleep Sandstone, Weber 

Sandstone, Schoolhouse Member of the Maroon Formation 

(Johnson and others, 1990); Fryingpan Member of the Maroon 

Formation (Johnson, 1989); White Rim Sandstone (of Baars, 

1962); De Chelly Sandstone, and Coconino Sandstone (table 1 

and pi. 5).

Component geologic units in the Weber-De Chelly zone are 

sparsely fossiliferous. Nevertheless, their ages can be established fairly reliably on the basis of contained fossils (mainly 

fusulinids) and the ages of geological formations underlying, 

overlying, or intertonguing with the component geologic units.

The existing evidence indicates that the Tensleep Sandstone 

and Wells Formation are mostly Middle and Upper Pennsylvanian (Desmoinesian to Virgilian); the Weber Sandstone is Middle Pennsylvanian to Lower Permian (Desmoinesian to 

Leonardian); and the Coconino, White Rim, and De Chelly 

Sandstones and the Schoolhouse and Fryingpan Members of 

the Maroon Formation are Lower Permian (Keefer and Van 

Lieu, 1966; Mallory, 1967; Irwin and others, 1971; Baars, 

1979; Fryberger and Koelmel, 1986; Johnson, 1989; Johnson 

and others, 1990; Love and others, 1993.) Together, the variously named sandstone formations comprise a single, timetransgressive sequence that becomes progressively younger 

from north to south.

Component geologic units in the Weber-De Chelly zone 

thicken and thin more or less independently (pi. 16). The Tensleep Sandstone thickens from less than 200 ft to more than 700 

ft concentrically toward the vicinity of Rock Springs, Wyo. 

The Wells Formation is about 300 ft thick at the eastern edge 

of the Overthrust Belt in Wyoming. On the basis of interpolation between data from boreholes in the UCRB and the type 

section of the Weber Sandstone in the Wasatch Range northwest of Salt Lake City, Utah, the Wells Formation appears to 

thicken westward to about 1,000 ft at the surface-water divide 

between the UCRB and the Basin and Range province. The 

Schoolhouse and Fryingpan Members of the Maroon Formation, together with the Weber Sandstone, comprise a depositional sequence that thickens westward from 0 ft in the Eagle 

Basin and Glenwood Springs areas of Colorado to about 1,600 

ft in the western Uinta Mountains. Interpolation between outcrops in the western Uinta Mountains (Huddle and McCann, 

1947b; Huddle and others, 1951) and an outcrop north of the 

Charleston Thrust Fault (Baker, 1964) indicates that the Weber 

Sandstone may be as much as 4,000 ft thick at the UCRBBasin and Range divide west of Strawberry Valley. The White 

Rim Sandstone increases in thickness westward from 0 ft on the 

west side of the Monument Upwarp to more than 1,000 ft in the 

Capitol Reef-San Rafael Swell area. The De Chelly Sandstone 

is less than 200 ft thick in the Kaibito, Blanding, Paradox, and 

San Juan Basins, but thickens concentrically toward the Black 

Mesa Basin, where it is more than 1,000 ft thick. The Coconino 

Sandstone thins northward from about 600 ft in the eastern 

Grand Canyon to less than 100 ft in the Lees Ferry area of 

Arizona and probably pinches out in the southern Kaiparowits 

Basin (Hunt and others, 1953, p. 46).

Rocks comprising the Weber-De Chelly zone are missing in 

much of the study area south of the White River, east of the 

Green and Colorado Rivers, and north of the San Juan River. 

Geographic areas where the hydrogeologic unit is thin to absent 

include the Park Range, Gore Range, Front Range, White River 

Plateau, Elk Mountains, southern Piceance Basin, Uncompahgre Plateau, San Juan Mountains, northern and eastern Paradox 

Basin, and Monument Upwarp.
A62 REGIONAL AQUIFER SYSTEM ANALYSIS UPPER COLORADO RIVER BASIN

FIGURE 41. Normal fault in the upper 

plate of the Darby Thrust Fault 

exposed by the Snake River as it cuts 

through the Salt River Range at 

Astoria Hot Springs, southwest of 

Jackson, Wyo. The Pennsylvanian 

and Permian Wells Formation on the 

right has been uplifted against the 

Permian Phosphoria Formation and 

Triassic Dinwoody Formation on the 

left (downstream) side of the fault. 

This interpretation is based in part on 

written communication from James A. 

Peterson of the University of Montana 

(1988).

FIGURE 42. Pennsylvanian Tensleep 

Sandstone overlain by interbedded 

carbonate rocks and sandstone of the 

Permian Park City Formation, east 

flank of Wind River Mountains, northwest of Dubois, Wyo.

COMPONENT GEOLOGIC UNITS

In the Overthrust Belt and western Green River Basin of 

Wyoming, rocks comprising the Weber-De Chelly zone are assigned to the Wells Formation. The Wells Formation (fig. 41) 

consists of massively bedded, light-gray, tan, and pink, quartzitic, fine-grained, quartz sandstone with thin interbeds of finegrained dolomite and limestone and dark-gray mudstone 

(Wanless and others, 1955, p. 34-35; Oriel, 1969, p. 8; Rubey 

and others, 1975, p. 3). Generally less than 20 ft thick, the

carbonate intervals thicken and become more numerous westward, and comprise as much as 30 percent of the formation at 

the UCRB-Basin and Range divide.

The Wells Formation grades into the Tensleep Sandstone 

along an axis of thinning that extends longitudinally through 

the western Green River Basin. The Tensleep Sandstone (fig. 

42) consists of crossbedded, light-gray, tan, and white, finegrained, friable to quartzitic or calcareous, quartz sandstone 

with thin interbeds of chert and fine-grained dolomite and limestone (Foster, 1947, p. 1558; Gudim, 1956, p. 70; Berry, 1960,
GEOLOGY OF PALEOZOIC ROCKS, UPPER COLORADO RIVER BASIN A63

FIGURE 43. Northeast-dipping beds of 

Pennsylvania!! and Permian Weber 

Sandstone in Irish Canyon, Colo., at 

the eastern end of the Uinta Mountains. The full thickness of the formation is exposed. (In the left foreground 

is an outcrop of cherty limestone and 

sandstone of the Pennsylvanian 

Morgan Formation.)

p. 15; Keefer and Van Lieu, 1966, p. 40; Mallory, 1967, p. 21). 

The carbonate layers, which comprise as much as 20 percent of 

the formation, are concentrated in the lower part; they generally 

are less than 10 ft thick and either pinch out laterally or grade 

into sandstone.

South of the Green River and Washakie Basins, the Tensleep 

Sandstone and Wells Formation thin and grade into the Weber 

Sandstone (fig. 43). In the western Uinta Mountains and Uinta 

Basin, the Weber Sandstone is a marine deposit consisting of 

light-gray and white, fine-grained, friable to quartzitic or calcareous, quartz sandstone with thin interbeds of fine-grained, 

finely crystalline, and sandy limestone and dolomite, and maroon, brown, and gray siltstone and mudstone (Huddle and 

McCann, 1947b; Fryberger and Koelmel, 1986). Generally 

less than 30 ft thick, the carbonate intervals thicken and become more numerous southward, and comprise as much as 30 

percent of the formation in the western Uinta Basin and Wasatch Plateau. In the vicinity of the Whiterocks River, marine 

beds interfinger with and grade into an eolian facies of the Weber Sandstone (fig. 44), which consists of massively crossbedded, light-gray, tan, and white, fine- to medium-grained, friable 

to quartzitic or calcareous, quartz sandstone (Untermann and 

Untermann, 1954, p. 36; Kinney, 1955, p. 46; Ritzma, 1959, p. 

26; Hansen, 1965b, p. 49).

North and west of the White River Plateau, the Weber Sandstone either terminates abruptly against the Maroon Formation 

(Johnson and others, 1990) or, as depicted in figure 44, thins 

and grades into eolian and fluvial beds that intertongue with the 

Maroon Formation and gradually lose their identity in the eastern Eagle Basin (Fryberger and Koelmel, 1986). The uppermost tongue of this eolian/fluvial sequence traditionally has

been called the Schoolhouse Tongue of the Weber Sandstone 

(Maughan, 1980), based on the interpretation that it represents 

a natural transition from the dune fields farther west to the alluvial fan deposits of the Maroon Formation. The natural transition is caused by increasing proximity to the source of the 

sediment, the ancestral Rocky Mountains. The Schoolhouse 

Tongue, which has a maximum thickness of about 220 ft, consists of planar to crossbedded, yellowish-gray, gray, and white, 

fine- to coarse-grained, calcite- or quartz-cemented, commonly 

petroliferous, subarkosic to arkosic sandstone with micaceous 

intervals and interbeds of greenish-gray and red shale (Brill, 

1944; Hallgarth, 1959; Bass and Northrop, 1963; Fryberger and 

Koelmel, 1986). On the basis of extensive field work and petrological examination, Johnson and others (1990) concluded 

that the Schoolhouse Tongue differed from red eolian deposits 

near the top of the Maroon Formation only in color. According 

to Johnson and others (1990), the Schoolhouse Tongue and other tongues of light-colored sandstone near the top of the Maroon Formation were originally red but were bleached by 

hydrocarbons migrating from the Belden Formation up a fault 

in the East Rifle Creek area and then laterally through the Maroon Formation. Consequently, the Schoolhouse Tongue was 

not to be considered an extension of the Weber dune field but 

diagenetically altered Maroon Formation, and Johnson and others (1990) renamed the Schoolhouse Tongue, the Schoolhouse 

Member of the Maroon Formation. At the time of this writing 

(1990), a consensus of opinion regarding the origin and naming 

of the Schoolhouse rocks has not been reached.

In the Elk Mountains and southeastern White River Plateau, 

a layer of crossbedded, light-brown and reddish-orange, very 

fine grained to medium-grained quartz sandstone occurs
A64 REGIONAL AQUIFER SYSTEM ANALYSIS UPPER COLORADO RIVER BASIN

UINTA MOUNTAINS

PICEANCE 

BASIN

WHITE RIVER 

PLATEAU

S1

EAGLE 

BASIN

UTAH COLORADO

EXPLANATION

Undifferentiated Mesozoic rocks

State Bridge Formation (Triassic and Permian)

 Mostly reddish brown siltstone and claystone

Park City Formation (Permian) Marine limestone, 

sandstone, and shale with phosphatic beds

Weber Sandstone (Permian and Pennsylvanian), 

marine facies Carbonate or quartz-cemented 

quartz sandstone with limestone interbeds

Weber Sandstone, eolian facies Light-colored 

quartz sandstone with large-scale crossbedding

FEET 

1.000-1

500-

0

Permian light-colored, subarkosic to arkosic sandstone Lower intervals 

assigned to Maroon Formation. Uppermost interval called Schoolhouse 

Member of Maroon Formation by Johnson and others (1990) or 

Schoolhouse Tongue of Weber Sandstone by previous workers 

(for example, Fryberger and Koelmel, 1986). Interpreted either as 

Maroon sand sheets and fluvial interbeds bleached by hydrocarbons 

(Johnson and others, 1990) or as the depositional edge of the 

Weber dunefield (for example, Fryberger and Koelmel, 1986)

Main body of Maroon Formation (Permian and Pennsylvanian)

 Reddish-brown and reddish-orange sandstone, conglomerate, 

and shale of eolian and fluvial origin

0

I 

25

I 

50

\ 

75 100 MILES

FIGURE 44. Stratigraphic section showing facies changes within the Weber Sandstone and Maroon Formation in Utah and Colorado. Modified from

Fryberger and Koelmel (1986); location of section shown on plate 16.

between the Maroon Formation and typical reddish-brown siltstone beds of the State Bridge Formation. This sandstone, 

which Freeman (1971) called the sandstone of the Fryingpan 

River and included in the State Bridge Formation, has a maximum thickness of 400 ft. Johnson (1989) recognized that the 

sandstone of the Fryingpan River is related more to eolian deposits near the top of the Maroon Formation, such as the 

Schoolhouse Member, than to the coastal plain deposits that 

typify the State Bridge Formation (Bryant and Martin, 1988) 

and renamed the sandstone the Fryingpan Member of the Maroon Formation. According to Johnson (1989), the Fryingpan 

Member is the remnant of a dune field that accumulated against

an ancestral Sawatch Range. This dune field may have been as 

much as 80 mi2 in area, but its eastern half has been removed 

by erosion. The current northern, western, and southern limits 

of the Fryingpan Member are depositional pinchouts.

The Weber Sandstone grades into the White Rim Sandstone 

along an axis of thinning extending from the southern end of 

the Uinta Basin southwesterly to the Wasatch Plateau. In the 

San Rafael Swell, Capitol Reef Fold and Fault Belt, and Circle 

Cliffs Uplift, the White Rim Sandstone (called Coconino 

Sandstone in some older U.S. Geological Survey reports) consists of gray, tan, and white, massively crossbedded, friable to 

carbonate-cemented, very fine grained to fine-grained quartz
GEOLOGY OF PALEOZOIC ROCKS, UPPER COLORADO RIVER BASIN A65

KAIPAROWITS 

BASIN

Byrd 5-Govt

CIRCLE CLIFFS 

UPLIFT

Shell 1-Soda

HENRY MOUNTAINS 

BASIN MONUMENT UPWARP

Kissinger 1- 

Rincon Dome

Skelly 1-A 

Nokai Dome

Copper 

Canyon

Kaibab Formation J

Toroweap 

Formation

19miles-

: . : White Rim Sandstone. 

.'..... (of Baars, 1962). .:

-13 milesMoenkopi

DeChelly Sandstone 

. (of Baars, 1962) :.,

-14 milesFormation

Organ Rock Shale 

(of Baars, 1962)

Carbonate beds in Toroweap Formation not to scale 

Datum is base of Moenkopi Formation

EXPLANATION 

Limestone and dolomite 

White, gray, and tan quartz sandstone

Orange and orange-pink quartz sandstone and minor siltstone 

Red and reddish-brown shale

FEFJ 

200-i

100-

10 MILES

FIGURE 45. Stratigraphic section showing relations among Permian formations in southeastern Utah. Location of section shown on plate 16.

sandstone (Gilluly, 1929; Gregory and Moore, 1931; Baker, 

1946; Hunt and others, 1953; Smith and others, 1963; Davidson, 1967). To the east, in the Monument Upwarp, the White 

Rim Sandstone generally is a white, pale-yellow, and lightgray, crossbedded, fine-grained, friable to carbonate-cemented, 

petroliferous, quartz sandstone (McKnight, 1940; Baker, 1946; 

Hunt and others, 1953; Baars and Seager, 1970; Steele-Mallory, 1982; Baars, 1987). At its depositional edge in the White 

Canyon area of the Monument Upwarp, the White Rim Sandstone consists of pale-orange, silty sandstone and sandy siltstone (Thaden and others, 1964, p. 29).

South and west of the Circle Cliffs Uplift, the White Rim 

Sandstone grades into interbedded carbonate rocks, sandstone, 

shale, and anhydrite of the Permian Toroweap Formation and 

ceases to be an identifiable unit (fig. 45). However, as the White 

Rim Sandstone loses its identity, another sandstone body, the 

Coconino Sandstone, appears beneath the Toroweap Formation 

and thickens southward toward the Grand Canyon. A third 

sandstone body in the area, the De Chelly Sandstone, underlies 

and interfingers with the Coconino Sandstone and equivalent 

strata from the Defiance Plateau to central Arizona. According 

to Blakey (1979), the main body of the De Chelly Sandstone and

its equivalent in central Arizona, the Schnebly Hill Formation, 

were deposited in a small basin centered about Holbrook, Ariz. 

(location shown on pi. 1). With increasing aridity, progradation 

of inland dunes across coastal beach areas and mud flats resulted 

in accumulation of the Coconino Sandstone on top of the 

Schnebly Hill Formation on the west side of the Holbrook Basin 

and the Black Creek Member of the De Chelly Sandstone on the 

east side of the Holbrook Basin (Blakey, 1979; Blakey and Middleton, 1987). The Schnebly Hill Formation and the Black 

Creek Member of the De Chelly Sandstone do not extend into 

the study area and are not discussed further.

The Coconino Sandstone, where it crops out in Marble 

Canyon, the canyon of the Little Colorado River, and the Grand 

Canyon (fig. 2) is a massively crossbedded, light-tan to yellowish-gray, silica-cemented, fine- to medium-grained, quartz 

sandstone (Noble, 1922, p. 66-67; Phoenix, 1963, p. 11). The 

De Chelly Sandstone in the UCRB is distinguished from the 

Coconino Sandstone mainly by a change to a predominantly 

pale orange color. In Monument Valley and along Comb 

Ridge, the De Chelly Sandstone (fig. 40) consists of crossbedded, reddish-orange, pale-orange, tan, and gray, fine- to 

medium-grained, friable to quartzitic or calcareous, quartz
A66 REGIONAL AQUIFER SYSTEM ANALYSIS UPPER COLORADO RIVER BASIN

sandstone with red shale layers near the base that are transitional into the Organ Rock Shale (Baker, 1936; Gregory, 1938; 

Mullens, 1960; Read and Wanek, 1961; Witkind and Thaden, 

1963; O'Sullivan, 1965; Irwin and others, 1971; Blakey and 

Baars, 1987). South of Canyon de Chelly in the Defiance Plateau, the De Chelly Sandstone is split by an interval of red and 

brownish-orange, calcareous siltstone and silty sandstone that 

thickens southward and merges with the Supai Formation 

(Read and Wanek, 1961, p. 4-6). Pierce (1964) termed this 

interval the Oak Springs Member and the underlying and overlying sandstone intervals the Hunters Point and White House 

Members. The Hunters Point Member consists of reddishorange, evenly bedded, silty quartz sandstone, whereas the 

White House Member is slightly feldspathic but otherwise 

identical to the De Chelly Sandstone of the Monument Upwarp 

(Blakey, 1979, p. 123-124).

UPPER CONTACTS

Contacts between geologic units comprising the Weber-De 

Chelly zone and overlying Permian and Triassic formations 

generally are conformable but vary with the tectonic setting. 

The Wells Formation grades laterally into the Grandeur Member of the Phosphoria Formation (Peterson, 1984, p. 46). However, the Tensleep Sandstone generally is overlain 

disconformably by the Permian Phosphoria and Park City Formations and the Permian and Triassic Goose Egg Formation 

(Keefer and Van Lieu, 1966, p. 41; Mallory, 1967, p. 25). In 

the Uinta Mountains, the Weber Sandstone is overlain gradationally to disconformably by the Park City Formation 

(Thomas and others, 1945; Huddle and McCann, 1947b; 

Hansen, 1965b, p. 58). However, equivalents of the Weber 

Sandstone in northwest Colorado, the Schoolhouse and Fryingpan Members of the Maroon Formation, are overlain unconformably by the Permian and Triassic State Bridge Formation 

(Johnson, 1989; Johnson and others, 1990). On the west side 

of its depositional area, the White Rim Sandstone generally is 

overlain conformably to gradationally by either the Toroweap 

or Kaibab Formation of Permian age (Gregory and Moore, 

1931; Baker, 1946; Hunt and others, 1953; Smith and others, 

1963; Davidson, 1967). In the San Rafael Swell, however, the 

White Rim Sandstone is overlain unconformably by either the 

Kaibab Formation (Welsh and others, 1979, p. 143) or, where 

erosion has removed the Kaibab Formation, the Triassic Moenkopi Formation (Gilluly, 1929, p. 81; Hawley and others, 1965, 

p. 17). East of where the Kaibab Formation terminates, the 

White Rim Sandstone generally is overlain unconformably by 

the Moenkopi Formation (Hunt and others, 1953, p. 45; Baars 

and Seager, 1970, p. 714), but in the vicinity of the confluence 

of the Green and Colorado Rivers, the White Rim Sandstone is 

overlain conformably by red beds that have been interpreted as 

either Cutler Formation or Moenkopi Formation (Steele, 1987, 

p. 5). On the Monument Upwarp and Defiance Plateau, the De 

Chelly Sandstone is overlain disconformably but with

increasing hiatus southward by either the Hoskinnini Member 

of the Moenkopi Formation or the Shinarump Member of the 

Upper Triassic Chinle Formation (Mullens, 1960, p. 274-275; 

Read and Wanek, 1961, pi. 2). High-angle crossbeds of the 

Coconino Sandstone in the Lees Ferry area are truncated by 

flat-lying beds of the Toroweap Formation (Phoenix, 1963, p. 

12), but the contact between the two formations in Marble Canyon and the Grand Canyon generally is interpreted to be conformable (Beus and Lucchita, 1987, p. 7).

PARK CITY-STATE BRIDGE ZONE

The Park City-State Bridge zone of the Canyonlands aquifer (pi. 17) consists of carbonate, clastic, and evaporite sediments deposited in a shallow sea, marginal restricted basins, 

and coastal lowlands during a fifth and final Paleozoic marine 

advance (Kent, 1972; Rascoe and Baars, 1972; Peterson, 

1984). Component geologic units include the Kaibab, Toroweap, Park City, and Phosphoria Formations; and Permian 

parts of the Permian and Triassic Goose Egg and State Bridge 

Formations (table 1 and pi. 5). Following McKelvey and others (1959), the Park City, Phosphoria, and Goose Egg Formations in this report are named according to the prevailing rock 

types that, in varying proportions, are common to all three 

formations. Subdivisions of the Park City and Phosphoria 

Formations are called "members." Where members of either 

formation extend into the other formation, they are called 

"tongues."

Permian and Triassic parts of the Goose Egg and State 

Bridge Formations are distinguished by limestone intervals 

that pinch out eastward. In the Goose Egg Formation, the uppermost Permian horizon is the Ervay Limestone Member 

(Maughan, 1980, p. 106; Peterson, 1984, p. 28). Where the 

Ervay Limestone Member pinches out, it is impossible to 

distinguish the Permian-Triassic boundary. Similarly, the top 

of the Permian cannot be identified reliably in the State 

Bridge Formation in the absence of the South Canyon Creek 

Dolomite Member. In the absence of paleontological information, the top of the Park City-State Bridge zone where either the Goose Egg or State Bridge Formation comprises the 

zone generally was chosen in this report as the stratigraphically highest carbonate interval present in measured surface sections and borehole logs. If no carbonate beds were present, 

the entire Goose Egg or State Bridge Formation was assigned 

to the Chinle-Moenkopi confining unit (of Freethey and 

Cordy, 1991, table 1). Parts of the Goose Egg and State 

Bridge Formations included in the Park City-State Bridge 

zone, respectively, are called the lower part of the Goose Egg 

Formation and lower part of the State Bridge Formation in 

this report.

Abundant paleontological evidence (mainly brachiopods, 

pelecypods, gastropods, cephalopods, scaphopods, fusulinids, 

conularids, and conodonts) indicates that component geologic
GEOLOGY OF PALEOZOIC ROCKS, UPPER COLORADO RIVER BASIN A67

units in the Park City State Bridge zone are entirely Permian 

in age. The Park City and Phosphoria Formations are Lower 

to Upper Permian (Leonardian to Guadalupian) according to 

McKelvey and others (1959, p. 36-40) and Peterson (1984, p. 

28). Similarly, the lower parts of the Goose Egg and State 

Bridge Formations are Lower to Upper Permian (Bass and 

Northrop, 1963, p. 47-49; Maughan, 1980, p. 106-109; 

Peterson, 1984, p. 25). The Toroweap Formation is a Lower 

Permian deposit, and the overlying Kaibab Formation is a 

Lower to Upper Permian deposit (Hallgarth, 1967; Rascoe 

and Baars, 1972). The Kaibab Formation becomes younger 

from southwest to northeast, either as a result of northwesterly 

onlap (Heylmun, 1958, p. 1800; Smith and others, 1963, p. 

10) or southwesterly erosion (Baker, 1946, p. 52-53).

The Park City-State Bridge zone is restricted, because of 

erosion or nondeposition, to the northern and western parts of 

the UCRB (pi. 17). North of the Uinta Mountains, the Park 

City and Phosphoria Formations thicken from less than 300 ft 

on the Rock Springs Uplift to more than 500 ft in the Washakie 

Basin and more than 600 ft in the Overthrust Belt. In the southern Uinta Mountains and Uinta Basin, the Park City Formation 

thickens westward from less than 100 ft on the Yampa Plateau 

to about 550 ft at the UCRB-Basin and Range divide (below 

the Charleston Thrust Fault). The Park City Formation also 

thickens eastward from the Yampa Plateau and is more than 

500 ft thick where it grades into the lower part of the State 

Bridge Formation in the northwestern corner of the White River Plateau. The lower part of the State Bridge Formation is 

more than 400 ft thick in the northern White River Plateau but 

becomes thinner in all directions away from this area. The 

eastern equivalent of the Park City and Phosphoria Formations 

in Wyoming, the lower part of the Goose Egg Formation, 

generally is less than 300 ft thick. Equivalents of the Park City

Formation, south of the San Rafael Swell, the Toroweap and 

Kaibab Formations, thicken westward from 0 ft near the 

Colorado and Green Rivers to about 800 ft in the High Plateaus 

region.

COMPONENT GEOLOGIC UNITS

The lower part of the Goose Egg Formation comprises the 

Park City-State Bridge zone from the vicinity of Steamboat 

Springs, Colo., to north of the Rawlins Uplift in Wyoming, 

along the northeastern edge of the study area. The lower part 

of the Goose Egg Formation (fig. 46) consists of the Opeche 

Shale, Minnekahta Limestone, Glendo Shale, Forelle Limestone, Difficulty Shale, and Ervay Limestone Members (fig. 

47). The carbonate members, which generally are interpreted 

as tongues of the Park City Formation (Maughan, 1980; Peterson, 1984), typically are 6-22 ft thick; intervening shale 

members typically range in thickness from 40 to 100 ft (Keefer 

and Van Lieu, 1966, p. 49). Carbonate members in the Rawlins 

Uplift typically consist of gray to purplish-gray, very fine 

grained to crystalline limestone and shaly limestone (Berry, 

1960, p. 67-68). Carbonate members in the northern Great 

Divide Basin range from limestone to dolomite in composition 

(Thomas, 1951, p. 35-36). Shale members in the Goose Egg 

Formation typically consist of red and reddish-brown siltstone 

and mudstone with thin layers of fine- to medium-grained 

sandstone, gypsum, anhydrite, and carbonate rocks (Thomas, 

1951, p. 35-36; Gudim, 1956, p. 70-71). In the Rawlins Uplift 

and other areas at the western limits of the Goose Egg Formation, many of the shale layers are green or greenish gray (Berry, 

1960, p. 16). Accompanying this color change, carbonate and 

chert interbeds thicken and become more numerous. At Green

FIGURE 46. Pennsylvanian Tensleep Sandstone and Permian to Triassic Goose Egg Formation dipping northeasterly in the upper plate of the Bell Springs

Thrust Fault, north of Rawlins, Wyo.
A68 REGIONAL AQUIFER SYSTEM ANALYSIS UPPER COLORADO RIVER BASIN

U

GROS GREEN

OVERTHRUST VENTRE RIVER

BELT RANGE BASIN

Snake

River Flat Sheep 

Canyon Creek Mountain

«21 miles* < 35 miles

WIND RIVER MOUNTAINS

Bull SweetLake Squaw water 

Canyon Creek Creek

47 miles 5H<-29 miles-> <35 miles>

GREAT DIVIDE RAWLINS 

BASIN UPLIFT

Raw I ins 

Hills

WIND 

RIVER 

BASIN

Rattlesnake 

Hills

Datum is top of Permian

EXPLANATION

TC

RE

FR

MP

LC

GR

Limestone and dolomite with chert and shale

Chert

Sandstone and conglomerate

Green and gray shale

Red shale with sandstone

Dark-gray to black shale with phosphorite, 

chert, and carbonate rocks

PARK CITY AND PHOSPHORIA FORMATIONS 

Ervay Limestone Member 

Tosi Chert Member or Tongue 

Retort Phosphatic Shale Member or Tongue 

Franson Member or Tongue 

Rex Chert Member

Meade Peak Phosphatic Shale Member or Tongue 

Lower chert member or tongue 

Grandeur Member or Tongue

FEET 

200-1

100-

I 

25 50 MILES

FZ

DF

FO

GL

MN

OP

GOOSE EGG FORMATION 

Freezeout Shale Member 

Ervay Limestone Member 

Difficulty Shale Member 

Forelle Limestone Member 

Glendo Shale Member 

Minnekahta Limestone Member 

Opeche Shale Member

FIGURE 47. Stratigraphic section showing relations among Permian formations in southwestern Wyoming. Modified from McKelvey and others (1959) 

based on reports by Richmond (1945), Foster (1947), Wanless and others (1955), Berry (1960), Keefer and Van Lieu (1966), and Peterson (1984); 

location of section shown on plate 17.
GEOLOGY OF PALEOZOIC ROCKS, UPPER COLORADO RIVER BASIN A69

FIGURE 48. Permian lower part of the 

State Bridge Formation underlain by 

Permian Schoolhouse Member of the 

Maroon Formation and overlain by 

Mesozoic rocks on South Canyon 

Creek west of Glenwood Springs, 

Colo. S, Schoolhouse Member of 

Maroon Formation; L, lower shale 

member of State Bridge Formation; 

SC, South Canyon Creek Dolomite 

Member of State Bridge Formation. 

U, upper shale member of State 

Bridge Formation and Chinle Formation (Triassic); E, Entrada Sandstone 

(Jurassic).

Mountain on the Sweetwater Arch, for example, carbonate and 

chert layers comprise the upper fourth of the Goose Egg 

Formation (Thomas, 1951, p. 36).

From the southern Sand Wash Basin to the Elk Mountains, 

strata equivalent to the lower part of the Goose Egg Formation arbitrarily are assigned to the lower part of the State 

Bridge Formation. The lower part of the State Bridge Formation (fig. 48) includes the lower shale member and the South 

Canyon Creek Dolomite Member. The lower shale member, 

which makes up most of the lower part of the State Bridge 

Formation, consists of thinly bedded, micaceous, limy siltstone and claystone with interbeds of fine- to medium-grained 

sandstone that become coarser and more numerous southward 

(Brill, 1944, p. 635; Donner, 1949, p. 1228-1229; Bass and 

Northrop, 1963, p. 48^9; Freeman, 1971; Freeman and Bryant, 1977; Maughan, 1980, p. 109). The lower shale member 

typically is reddish brown, brownish red, and red but contains 

yellow and greenish-gray intervals along its western margin, 

from the vicinity of State Bridge, Colo., to the southwestern 

White River Plateau. The South Canyon Creek Dolomite 

Member, which is equivalent to the Franson Member of the 

Park City Formation and the Forelle Limestone Member of 

the Goose Egg Formation (Maughan, 1980), is 1-10 ft thick 

in measured sections (Stewart and others, 1972b, p. 46-47). 

The South Canyon Creek Dolomite Member consists of gray 

and white, sandy and shaly, algal limestone and dolomite 

(Brill, 1944, p. 635; Donner, 1949, p. 1228-1229; Bass and 

Northrop, 1963, p. 48 49); where the member pinches out 

east of Eagle, Colo., and south of the Fryingpan River 

(Freeman and Bryant, 1977, p. 186), the lower and upper 

shale members of the State Bridge Formation become 

indistinguishable.

The Goose Egg and State Bridge Formations grade laterally 

into the greenish-gray shale facies of the Park City Formation 

(fig. 49). hi drill holes and in surface sections described by 

Brill (1944, p. 640-642), this facies predominantly consists of 

dark-gray, greenish-gray, and olive-green gypsiferous siltstone 

and mudstone with intervals of fine-grained sandstone, limestone, and dolomite. Intervals of red and yellow shale and 

sandstone persist from the Goose Egg and State Bridge Formations. This facies, on the basis of limited subsurface data, 

appears to comprise most of the Park City Formation in the 

Sand Wash, Washakie, and Great Divide Basins. On the southeastern flank of the Uinta Mountains, the facies comprises the 

upper half of the formation (Untermann and Untennann, 1954, 

p. 38; Schell and Yochelson, 1966; Hansen and others, 1983). 

West of Dinosaur National Monument, the greenish-gray shale 

facies becomes a tongue in the Franson Member of the Park 

City Formation (fig. 49) and changes back into a predominantly 

red siltstone and sandstone interval. This red-bed interval is 

called the Mackentire Tongue of the Woodside Shale (Huddle 

and others, 1951; Kinney, 1955, p. 49-51; McKelvey and 

others, 1959, p. 34-35).

Over most of its extent, from the Uinta Mountains to the Uinta Basin, the Park City Formation consists of three stratigraphic 

intervals: the Grandeur Member, the Meade Peak Phosphatic 

Shale Tongue of the Phosphoria Formation, and the Franson 

Member (figs. 47, 49, 50). The Grandeur Member and Meade 

Peak Phosphatic Shale Tongue successively pinch out eastward 

from a line extending through the east-central Uinta Mountains 

to the Rock Springs Uplift (Peterson, 1984, fig. 12). In the 

Wind River Mountains and on the northern edge of the Green 

River Basin, the Franson Member is overlain by the Tosi Chert 

and Retort Phosphatic Shale Tongues of the Phosphoria
A70 REGIONAL AQUIFER SYSTEM ANALYSIS UPPER COLORADO RIVER BASIN

V

WASATCH RANGE UINTA MOUNTAINS

Mill Creek Franson 

Canyon Canyon

-26 miles

Lake 

Fork

Whiterocks 

River

Brush 

Creek

V

Split 

Mountain

Woodsjde Shale '

/ _-Mackentire TongueWoodside Shale,

Franson 

Member

Meade Peak

Phosphatic

Shale Tongue

of Phosphoria

Formation

Grandeur 

Member

Datum is the base of the Triassic

EXPLANATION 

Red beds

Limestone, dolomite, and chert with minor sandstone and shale 

Quartz sandstone, locally cherty or calcareous

Gray to black shale containing chert, phosphate, and interbeds 

of phosphorite and limestone

FEET

200-,

100-

0 25 50 MILES

FIGURE 49. Stratigraphic section showing relations among Pennian and Triassic formations in the Uinta Mountains and Wasatch Range, Utah. 

Modified from McKelvey and others (1959, p. 14), based on reports by Huddle and others (1951), Cheney and others (1953), Untermann and 

Untermann (1954), and Kinney (1955); location of section shown on plate 17.

Formation and the Ervay Limestone Member. According to 

Peterson (1984), the Ervay Limestone Member also overlies 

the Franson Member on the Rock Springs Uplift.

Except for tongues of the Phosphoria Formation and 

Woodside Shale and the greenish-gray shale facies, the Park 

City Formation predominantly consists of carbonate rocks and 

subordinate sandstone layers (fig. 42). The Grandeur Member 

consists of interbedded limestone, dolomite, and sandstone in 

thin to massive beds (McKelvey and others, 1959, p. 12-15). 

The limestone and dolomite layers are yellow, brown, black, 

and gray, slightly phosphatic, commonly cherty, and 

fossiliferous. The carbonate beds typically are sandy and grade 

into sandstone (Huddle and McCann, 1947b; Hansen, 1965b, p. 

52; McKelvey and others, 1959, p. 12). Sandstone layers typically are gray, brown, and light yellow, calcareous, cherty, fine

to coarse grained, and friable. The basal 5-15 feet of the Grandeur Member in the Wind River Mountains is a conglomerate 

composed of siltstone, sandstone, quartzite, and chert clasts in 

a matrix of limestone or sandstone (Keefer and Van Lieu, 1966, 

p. 44). Carbonate and sandstone layers in the western Uinta 

Mountains commonly are cavernous and brecciated (Huddle 

and McCann, 1947b; Huddle and others, 1951).

The Franson Member consists of white, gray, brownishgray, and yellow limestone, dolomite, and subordinate sandstone in thin to massive beds (McKelvey and others, 1959, p. 

15-19). The limestone and dolomite are vuggy, sandy to silty, 

fine grained to crystalline, and fossiliferous; they commonly 

contain chert nodules and are locally shaly. Sandstone layers 

are fine to coarse grained, cherty, and calcareous. Interbeds of 

dolomitic mudstone are present in some areas.
w

CIRCLE

KAIBAB KAIPAROWITS CLIFFS 

PLATEAU BASIN UPLIFT

SAN

RAFAEL HIGH 

SWELL PLATEAUS

Union 1-

Bass Judd Byrd 1- Circle Pleasant Boulder Black ARC01- 

Trail Hollow Govt Cliffs Creek Canyon Box Hiawatha

UINTA 

MOUNTAINS

H Ellis

Quintana 3-1 

Duchesne 20-1 Bridger 

River Burt Station

OVERTHRUST

BELT

UnionCarter 

1-Govt 

Heath

Shell 1- 

Smith 

Fork

< 53miles-> 27 miles 35 miles 31 miles I 36 miles Similes 34 miles 131 miles |< 56 miles ><-50 mil

Moenkopi Formation Woodside Shale

LATE PERMIAM '""LATE

Kaibab 

Formation

osphona 

Formation Franson Member

Meade Peak 

Phosphatic Shale Tongue 

of Phosphoria Formation

Park City Formation

Toroweap 

Formation

Grandeur 

Member

G

Datum is base of Triassic

EXPLANATION

Limestone, dolomite and minor chert

£" Chert

Dark-gray and black phosphatic shale and

phosphorite with chert and minor carbonate rocks

Sandstone

FEET 

300-1200-

100-

0

0

I 

50 100 MILES

FIGURE 50. Stratigraphic section showing relations among Permian formations in the western part of the Upper Colorado River Basin, Arizona, Utah, and Wyoming. 

(1922), Gilluly (1929), Huddle and McCann (1947a), Hunt and others (1953), Wanless and others (1955), and Davidson (1967), and from unpublished logs preparelocation of section shown on plate 17.
A72 REGIONAL AQUIFER SYSTEM ANALYSIS UPPER COLORADO RIVER BASIN

The Ervay Limestone Member is mostly limestone in the 

western part of the area and dolomite in the eastern part 

(McKelvey and others, 1959, p. 19-20). It grades southward 

into interbedded chert, shale, sandstone, and carbonate rocks of 

the Tosi Chert Tongue of the Phosphoria Formation. It grades 

westward into sandstone and chert of the Shedhorn Sandstone 

(a facies equivalent to the Park City, Phosphoria, and Goose 

Egg Formations that terminates in the northern Gros Ventre 

Range, north of the UCRB).

The Park City Formation grades into the Phosphoria Formation in the western and northern Green River Basin, as shale 

and chert intervals progressively predominate over carbonate 

and sandstone intervals (fig. 50). The Phosphoria Formation in 

the study area (fig. 41) consists of the Grandeur Tongue of the 

Park City Formation, lower chert member, Meade Peak Phosphatic Shale Member, Franson Tongue of the Park City Formation, Rex Chert Member, Retort Phosphatic Shale Member, and 

Tosi Chert Member (McKelvey and others, 1959, p. 20-31). 

The Grandeur and Franson Tongues are thinner than but otherwise similar to the Grandeur and Franson Members of the Park 

City Formation. The lower chert member typically consists of 

chert with subordinate amounts of carbonate rocks and mudstone. The Meade Peak Phosphatic Shale Member typically is 

composed of fissile, dark-gray, black, and brown phosphatic to 

limy mudstone with brown and gray, pelletal, oolitic, and nodular phosphorite, chert, and dark-gray and black, cherty and 

phosphatic carbonate rocks. South and east of the Overthrust 

Belt in Wyoming, the Meade Peak Phosphatic Shale Member 

gains carbonate and chert layers as it grades into the Grandeur 

and Franson Tongues of the Park City Formation. The Rex 

Chert Member, which extends no farther east than the western 

part of the Overthrust Belt, consists of black, gray, and white

chert, carbonate rocks, and mudstone. At its eastern limit, the 

Rex Chert Member grades laterally into the Franson Tongue 

and Retort Phosphatic Shale Member. The Retort Phosphatic 

Shale Member is similar to the Meade Peak Shale Member but 

contains a greater proportion of shale to dolomite and phosphorite (McKelvey and others, 1959, p. 30). The Tosi Chert Member predominantly consists of columnar chert, but interbeds of 

dark-gray mudstone, sandstone, carbonate rocks, and phosphorite transitional into the Retort Phosphatic Shale Member and 

Shedhorn Sandstone also are present.

At the southern end of the Uinta Basin, the Meade Peak 

Phosphatic Shale Tongue of the Phosphoria Formation pinches 

out, making distinction impossible between the Grandeur and 

Franson Members of the Park City Formation (fig. 50). The undifferentiated Park City Formation consists of cherty dolomite 

and limestone with a few shale interbeds. In the San Rafael 

Swell, equivalent strata are assigned to the Kaibab Formation.

From the San Rafael Swell south to the Kaiparowits Basin, a 

sequence of interbedded light-yellow, white, gray, and tan 

sandstone, sandy limestone and dolomite, shale, anhydrite, and 

gypsum occurs between rocks typical of the White Rim Sandstone and Kaibab Formation. Geologists working in the area, 

including Gilluly (1929), Gregory and Moore (1931), Baker 

(1946), Hunt and others (1953), Smith and others (1963), and 

Davidson (1967), alternately have assigned these rocks to either the Coconino (White Rim) Sandstone or the Kaibab Limestone (Formation). In the Kaibab Plateau, rocks of similar 

mixed carbonate-clastic lithology occupying the same stratigraphic position are assigned to the Toroweap Formation 

(McKee, 1969, p. 39). In the northern Kaibab Plateau and Lees 

Ferry area, for example, the Toroweap Formation consists of 

laterally discontinuous layers of red, reddish-brown, tan, white,

FIGURE 51. Permian Kaibab Formation in 

Marble Canyon, Ariz., a regional 

discharge area for aquifers in the 

Paleozoic rocks of the Upper Colorado 

River Basin.
GEOLOGY OF PALEOZOIC ROCKS, UPPER COLORADO RIVER BASIN A73

and light-yellow, fine- to medium-grained, friable to limy sandstone, cherty limestone, and silty mudstone (Gregory and 

Moore, 1931, p. 39; Phoenix, 1963, p. 12). Following Heylmun (1958), the rocks of disputed nomenclature in this report 

are assigned to the Toroweap Formation.

The Kaibab Formation (fig. 51) ranges from mostly limestone and dolomite in uplifted areas to mostly dolomite in 

structural basins. In the San Rafael Swell, the formation consists of limestone with sandy layers that grade laterally into 

limy sandstone (Gilluly, 1929, p. 82; Baker, 1946, p. 50-51; 

Hunt and others, 1953, p. 46-47; Welsh and others, 1979, p. 

145). In the Capitol Reef Fold and Fault Belt and Circle Cliffs 

Uplift, carbonate layers similarly grade laterally into sandstone 

layers. However, many of the limestone beds have been dolomitized, retaining a relict oolitic texture (Gregory and Moore, 

1931, p. 42; Smith and others, 1963, p. 9; Davidson, 1967, p. 

13-14). Lenses of gray shale occur in the Capitol Reef Fold 

and Fault Belt, and partings of green, glauconitic sandstone occur in the Circle Cliffs Uplift. From the northern Kaibab Plateau to the Lees Ferry area, the formation changes westward 

from a sandy dolomitic limestone with thin shale interbeds in 

the upper part to a crystalline limestone with sandstone and 

shale layers near the base and top (Gregory and Moore, 1931, 

p. 39; Phoenix, 1963, p. 13). Inmost uplifted areas, the Kaibab 

Formation is characterized by asphalt-filled vugs. East of the 

San Rafael Swell, Capitol Reef Fold and Fault Belt, Circle 

Cliffs Uplift, and Kaibab Plateau in the Henry Mountains and 

Kaiparowits Basins the formation mostly consists of dolomite (Heylmun, 1958, p. 1800; Welsh and others, 1979, p. 

146). Throughout its extent, the Kaibab Formation is characterized by bedding ranging from inches to 10 ft in thickness, a 

vuggy appearance, colors of gray, beige, tan, light yellow, and 

white, and inclusions of chert (with calcite and quartz in some 

areas) as layers, fragments, nodules, and geodes.

UPPER CONTACTS

Component geologic units in the Park City-State Bridge 

zone are overlain conformably to unconformably by Triassic 

formations composed mostly of shale. The contact between the 

Phosphoria and Dinwoody Formations in the Overthrust Belt is 

an unconformity (Wanless and others, 1955, p. 39). The Park 

City Formation is overlain unconformably by the Dinwoody 

Formation on the north slope of the Uinta Mountains (Hansen, 

1965b, p, 64) but conformably in the Wind River Mountains 

(Keefer and Van Lieu, 1966, p. 47). On the south slope of the 

Uinta Mountains, the Woodside Shale and Moenkopi Formation conformably overlie and intertongue with the Park City 

Formation (McKelvey and others, 1959, p. 19; Schell and 

Yochelson, 1966, p. 67). Permian and Triassic members of the 

State Bridge Formation were deposited without an intervening 

erosional hiatus and, thus, are conformable (Freeman, 1971, p. 

7). Permian and Triassic members of the Goose Egg

Formation, however, are separated by an erosional hiatus 

(Peterson, 1984, p. 28). The Kaibab Formation throughout its 

depositional area is overlain unconformably by the Moenkopi 

Formation. Except for channels as much as 25 ft deep in the 

Lees Ferry area, this unconformity is barely discernible in the 

Kaibab Plateau-Marble Platform region (Gregory and Moore, 

1931, p. 45; Phoenix, 1963, p. 13; McKee, 1969, p. 47). From 

the Circle Cliffs Uplift to the San Rafael Swell, however, the 

erosional surface on top of the Kaibab Formation is hummocky, contains channels as much as 100 ft deep and, in places, 

completely cuts out the underlying unit (Gilluly, 1929, p. 82; 

Baker, 1946, p. 51; Davidson, 1967, p. 13-15).

SUMMARY AND CONCLUSIONS

The Upper Colorado River Basin (UCRB) is situated in parts 

of four physiographic provinces the Middle Rocky Mountains, Wyoming Basin, Southern Rocky Mountains, and Colorado Plateaus. Within each physiographic province, numerous 

uplifts and basins occur. Thrust faults and high-angle normal 

and reverse faults are associated with many of the uplifts. Tectonic activity has occurred repeatedly since the Precambrian.

Formations comprising all Paleozoic systems except the 

Silurian are present in the UCRB. The Paleozoic rocks were 

deposited during five major marine incursions. Thicknesses 

range from 0 in the interiors of most uplifts to about 18,000 ft 

in the Elk Mountains of Colorado. The Paleozoic rocks are at 

or near land surface on the flanks of uplifts but are 2,500- 

27,000 ft deep in structural basins.

The Paleozoic rocks are underlain by Precambrian igneous, 

metamorphic, and sedimentary rocks. Cambrian to Mississippian formations consist of limestone and dolomite with subordinate sandstone, quartzite, and shale. Pennsylvanian and 

Permian formations consist of sandstone, conglomerate, and 

shale with subordinate carbonate rocks and locally thick intervals of bedded evaporites. The Paleozoic rocks are overlain in 

most areas by Triassic formations predominantly composed of 

shale. In a few small areas, Jurassic sandstone or Tertiary 

sandstone and shale overlie the Paleozoic rocks.

The Paleozoic rocks are divisible on the basis of lithologic 

and hydrologic properties into 11 hydrogeologic units. The 

basal unit, the Flathead aquifer, includes the Flathead Sandstone, lower part of the Lodore Formation, Sawatch Quartzite, 

Ignacio Quartzite, Tapeats Sandstone, Tintic Quartzite, and 

unnamed equivalents. Component geologic units decrease in 

age from Early and Middle Cambrian on the west to Middle and 

Late Cambrian on the east. The thickness of the Flathead 

aquifer ranges from 0 to 800 ft. Regionally, almost the entire 

thickness of the aquifer consists of quartzite and friable to 

quartzitic sandstone. A basal conglomerate interval, a few feet 

to more than 50 ft thick, is present throughout most of the area, 

and the sandstone locally is conglomeratic. Carbonate rocks
A74 REGIONAL AQUIFER SYSTEM ANALYSIS UPPER COLORADO RIVER BASIN

comprise 5-20 percent of the unit toward depositional centers, 

particularly in northwestern Colorado, where the sandstone and 

quartzite commonly are dolomitic. Shale layers occur with 

increasing frequency toward the upper part of the unit and can 

be nearly as abundant as sandstone and quartzite layers on the 

southern and eastern edges of the region, where Cambrian 

sandstone and shale formations are gradational. Formations in 

the Rathead aquifer are underlain with slight to substantial 

unconformity by Precambrian rocks and are overlain in most 

areas conformably to gradationally by other Cambrian 

formations. In some areas, such as the eastern Great Divide 

Basin, the eastern Uinta Mountains, and the Sawatch Range, 

component geologic units are overlain unconformably by 

formations of Cambrian to Mississippian age.

Overlying the Rathead aquifer in most areas is the Gros 

Ventre confining unit. The Gros Ventre confining unit includes 

the Gros Ventre Formation, upper part of the Lodore Formation, Bright Angel Shale, Ophir Shale, and unnamed equivalents. Component geologic units decrease in age eastward from 

Early and Middle Cambrian to Late Cambrian. The thickness 

of the Gros Ventre confining unit ranges from 0 to 1,100 ft. 

Regionally, the Gros Ventre confining unit is composed of 

claystone, siltstone, and sandy shale with subordinate interbeds 

of sandstone, limestone, and dolomite. The sandstone 

commonly is micaceous and glauconitic, but quartzitic layers 

are present, particularly near the base and margins where 

Cambrian shale formations grade into sandstone formations of 

the underlying Flathead aquifer. At the margins of depositional 

centers, the sandstone and shale tend to be present in subequal 

amounts. Carbonate rocks progressively increase in abundance 

toward depositional centers, where they can be nearly as 

abundant as shale layers. In the northern UCRB, the Gros 

Ventre confining unit is overlain unconformably in most areas 

by formations of Cambrian to Mississippian age, but at the 

eastern end of the Wind River Mountains, the Gros Ventre 

Formation grades into the Cambrian Gallatin Limestone. In the 

western Uinta Mountains and areas to the south and east in 

Utah, Colorado, and Arizona, component geologic units 

generally are overlain conformably to gradationally by other 

Cambrian formations.

The third hydrogeologic unit in the Paleozoic sequence, the 

Bighorn aquifer, includes the Gallatin Limestone, Dotsero 

Formation, Peerless Formation, Muav Limestone, Maxfield 

Limestone, Lynch Dolomite, Manitou Dolomite, Harding 

Sandstone, Fremont Limestone, Bighorn Dolomite, and 

unnamed equivalents. Component geologic units generally are 

considered to be Middle Cambrian to Late Ordovician in age. 

The thickness of the Bighorn aquifer ranges from 0 to 3,000 ft. 

Regionally, the aquifer consists of limestone and dolomite with 

subordinate shale layers and generally less than 5 percent sandstone layers. Cambrian carbonate rocks within the Bighorn 

aquifer typically are glauconitic and oolitic and contain flatpebble or edgewise conglomerate layers; in the Four Corners 

area, the Cambrian rocks are shaly. Ordovician carbonate

rocks within the Bighorn aquifer can be granular, crystalline, or 

fine grained, and the Manitou Dolomite tends to be siliceous. 

Shale and sandstone layers comprise less than 20 percent of the 

Bighorn aquifer and are most abundant toward the bottom and 

margins of the unit, where component geologic units grade into 

other Cambrian formations. In all areas, the upper surface of 

geologic units comprising the Bighorn aquifer is an unconformity upon which Devonian and Mississippian rocks were 

deposited.

The next hydrogeologic unit in the Paleozoic sequence, the 

Elbert-Parting confining unit, includes the Darby, Parting, 

Elbert, and Temple Butte Formations, and the Cottonwood 

Canyon Member of the Lodgepole and Madison Limestones. 

Component geologic units are Early Devonian to Early 

Mississippian in Wyoming and Late Devonian in age 

elsewhere. The thickness of the Elbert-Parting confining unit 

ranges from 0 to 700 ft. Regionally, the Elbert-Parting 

confining unit is characterized by highly variable proportions 

of limestone, dolomite, sandstone, quartzite, shale, and 

anhydrite. Generally, the Darby, Elbert, and Temple Butte Formations contain increasing thicknesses of carbonate rocks and 

decreasing thicknesses of clastic rocks westward across the 

UCRB, and the Parting Formation becomes more carbonaceous 

toward the center of its depositional basin. In most areas, carbonate rocks comprise at least 50 percent of the confining unit. 

Shale layers generally comprise at least one-third of the confining unit and locally exceed carbonate layers in abundance. 

Sandstone and quartzite layers rarely comprise more than onethird of the confining unit, but they predominate on the southeastern edge of the Darby-Cottonwood Canyon depositional 

basin, on the northeastern edge of the Parting depositional 

basin, and at the base of the Elbert Formation. Anhydrite layers 

comprise as much as 10 percent of the Elbert-Parting confining 

unit in the Overthrust Belt west of Kemmerer, Wyo. Component geologic units in Wyoming and the Grand Canyon area are 

overlain unconformably by Mississippian carbonates, whereas 

the Elbert and Parting Formations generally are overlain conformably by formations of Devonian and Mississippian age.

Above the Elbert-Parting confining unit is the Madison 

aquifer, which is divisible into two lithologically distinct zones, 

the Redwall-Leadville zone and the Darwin-Humbug zone. 

The Madison aquifer of the UCRB is an extension of the 

Madison aquifer of the Northern Great Plains.

The Redwall-Leadville zone includes the Dyer Dolomite, 

Ouray Limestone, Gilman Sandstone, Leadville Limestone, 

and Redwall Limestone; the lower part of the Mission Canyon 

Limestone; and the main bodies of the Lodgepole and Madison 

Limestones. Component geologic units mostly are Late 

Devonian to Late Mississippian in age. The thickness of the 

Redwall-Leadville zone ranges from 0 to 2,500 ft. Limestone, 

dolomite, and bedded and nodular chert comprise more than 95 

percent of the Redwall-Leadville zone, with the proportion of 

limestone to dolomite decreasing away from uplifted areas. 

Regional tracing of stratigraphic markers between outcrops and
GEOLOGY OF PALEOZOIC ROCKS, UPPER COLORADO RIVER BASIN A75

boreholes indicates that limestone beds grade laterally into 

dolomite beds, such that neither the proportions nor sequence 

of limestone and dolomite can be used to establish contacts 

between Devonian and Mississippian formations. Sandstone 

and shale, concentrated in the interval between Devonian and 

Mississippian carbonate deposits and at the top of the 

Mississippian sequence, comprise 5-10 percent of the 

Redwall-Leadville zone in areas interpreted to have been sites 

of shallow marine or intermittently subaerial deposition. The 

upper surface of the Redwall-Leadville zone is an 

unconformity that progressively truncates older rocks from 

west to east across the region.

Overlying the Redwall-Leadville zone in and near the Great 

Divide Basin, the north flank of the Wind River Mountains, the 

Gros Ventre Range, the Overthrust Belt, the Uinta Mountains, 

and the Uinta Basin is the Darwin-Humbug zone. The DarwinHumbug zone includes the Humbug Formation, the Bull Ridge 

Member of the Madison Limestone, the upper (evaporitic) part 

of the Mission Canyon Limestone, and the Darwin Sandstone 

Member of the Amsden Formation. Component geologic units 

are Early and Late Mississippian in age. The thickness of the 

Darwin-Humbug zone ranges from 0 to 800 ft. Characteristically, the hydrogeologic unit consists of variable proportions of 

carbonate rocks, sandstone, shale, gypsum, and solution 

breccia. Carbonate rocks comprise more than 75 percent of the 

 Darwin-Humbug zone in the centers of depositional areas. 

Sandstone layers increase in abundance away from depositional 

centers as carbonate layers decrease. Carbonate layers typically 

are brecciated, and sandstone layers are brecciated in the western part of the area. Gypsum layers are abundant at the northern 

end of the Hoback Range in Wyoming. Contacts with Mississippian and Pennsylvanian formations that comprise the overlying Four Corners confining unit generally are conformable.

The Four Corners confining unit is divisible upward into the 

Belden-Molas and Paradox-Eagle Valley subunits. The 

Belden-Molas subunit includes the Horseshoe Shale Member 

of the Amsden Formation, the Doughnut Shale, the Molas, 

Belden, Watahomigi, and Surprise Canyon Formations, and the 

lower member of the Hermosa Formation. Component 

geologic units are Late Mississippian to Middle Pennsylvanian 

and become younger from west to east across the area. The 

Belden-Molas subunit consists of as much as 4,300 ft of darkgray, black, and red shale with subordinate limestone, 

dolomite, sandstone, and minor evaporite layers. In most areas, 

shale comprises 50 to more than 75 percent of the BeldenMolas subunit. However, in the Washakie Basin and depositional centers south of the Uinta Mountains and Axial Basin 

Arch, limestone and dolomite layers can equal or exceed shale 

layers in abundance and locally comprise more than 75 percent 

of the subunit. Sandstone layers comprise about one-third of 

the Belden-Molas subunit where it thins on the flanks of 

uplifted areas. Contacts with overlying geologic units of Late 

Mississippian to Pennsylvanian age generally are conformable 

to gradational.

In most areas, the Belden-Molas subunit is overlain by the 

Paradox-Eagle Valley subunit, which includes the Moffat Trail 

Limestone Member of the Amsden Formation, the Round 

Valley Limestone, the Eagle Valley Evaporite, the Paradox 

Member of the Hermosa Formation, and the Manakacha 

Formation. Component geologic units are Late Mississippian 

to Middle Pennsylvanian in age and become younger in a 

south-southeasterly direction. The thickness of the ParadoxEagle Valley subunit ranges from 0 to more than 9,000 ft, 

except in small areas of the Paradox Basin where salt diapirs as 

much as 15,000 ft thick are present. Regionally, the ParadoxEagle Valley subunit consists of varying proportions of 

limestone, dolomite, shale, sandstone, anhydrite (or gypsum), 

and halite. Anhydrite, halite, shale, and minor carbonate rocks 

are the dominant lithologies in and near the Paradox and Eagle 

Basins. This hypersaline facies grades outward into a 

penesaline facies composed of limestone, dolomite, shale, 

anhydrite, and sandstone, which, in turn, grades into a marineshelf facies composed of limestone and dolomite with subordinate shale and minor sandstone. The marine-shelf facies 

predominates from the Uinta and Sand Wash Basins to the 

northern edge of the study area. On the southern edge of the 

study area a facies consisting of red shale and sandstone, 

subordinate carbonate rocks, and minor anhydrite predominates. Contacts between component geologic units and formations in the overlying Canyonlands aquifer generally are 

gradational to disconformable.

The Canyonlands aquifer, in ascending order, consists of the 

Cutler-Maroon, Weber-De Chelly, and Park City-State Bridge 

zones. Each of these zones has distinct lithologic and hydrologic properties.

The Cutler-Maroon zone of the Canyonlands aquifer 

includes the Ranchester Limestone Member of the Amsden 

Formation, upper member of the Hermosa Formation, Rico 

Formation, Gothic Formation, Mintum Formation, Morgan 

Formation, the main body of the Maroon Formation, Cutler 

Formation, Halgaito Shale, Elephant Canyon Formation, Cedar Mesa Sandstone, Organ Rock Shale, Supai Formation, 

Wescogame Formation, Esplanade Sandstone, and Hermit 

Shale. Component geologic units are Early Pennsylvanian to 

Late Permian and become younger in a south-southwesterly 

direction. Regionally, the Cutler-Maroon zone consists of as 

much as 16,500 ft of sandstone, conglomerate, shale, limestone, dolomite, and gypsum-anhydrite. Sandstone and 

conglomerate generally make up 50 to more than 75 percent 

of the Cutler-Maroon zone within and adjacent to uplifted areas on the east, south, and west. The sandstone in these areas 

predominantly is red, arkosic, micaceous, coarse grained, and 

friable; most of the interbeds are siltstone or mudstone; carbonate intervals are thin and sparsely distributed. Away from 

these uplifts, the rocks become predominantly gray, green, 

tan, and pink; arkosic sandstone layers become finer grained, 

more indurated, and less numerous; quartz sandstone intervals 

thicken and predominate over arkosic intervals; siltstone and
A76 REGIONAL AQUIFER SYSTEM ANALYSIS UPPER COLORADO RIVER BASIN

mudstone intervals thicken and equal or exceed sandstone in 

abundance; limestone and dolomite intervals thicken and 

comprise as much as 45 percent of the rock material; thin 

gypsum or anyhdrite beds occur locally. In northern and 

central parts of the study area, the Cutler-Maroon zone 

consists of limestone and dolomite with subordinate shale 

interbeds, generally less than 25 percent sandstone interbeds, 

and, locally, minor interbeds of gypsum or anhydrite. Contacts between component geologic units and overlying Pennsylvanian and Permian rocks generally are conformable to 

gradational, but local unconformities exist. In southeastern 

Utah east of the Monument Upwarp and in western Colorado 

south of the Piceance Basin, component geologic units of the 

Cutler-Maroon zone generally are the youngest Paleozoic 

rocks and are overlain conformably to unconformably by 

Mesozoic rocks.

The middle division of the Canyonlands aquifer, the WeberDe Chelly zone, includes the Wells Formation, Tensleep Sandstone, Weber Sandstone, White Rim Sandstone, Coconino 

Sandstone, De Chelly Sandstone, and the Schoolhouse and 

Fryingpan Members of the Maroon Formation. Component 

geologic units decrease in age southward from Middle and Late 

Pennsylvanian to Late Permian. Over most of the study area, 

the Weber-De Chelly zone consists of as much as 4,000 ft of 

light-colored, quartz sandstone with generally thin interbeds of 

siltstone, mudstone, limestone, dolomite, and anhydrite that 

comprise no more than 10 percent of the thickness of the zone. 

However, carbonate rocks constitute 10-30 percent of the 

Weber-De Chelly zone on the western edge of the UCRB, from 

the Wasatch Plateau north to the Overthrust Belt, and in parts 

of the Green River and Great Divide Basins. Shale layers 

constitute as much as 30 percent of the Weber-De Chelly zone 

near its eastern and western depositional edges in Colorado, 

Utah, and New Mexico. Contacts between component 

geologic units and overlying formations of Permian and 

Triassic age are gradational to unconformable.

The uppermost zone within the Canyonlands aquifer, the 

Park City-State Bridge zone, is present only in the northern and 

western parts of the UCRB. It includes the Kaibab, Toroweap, 

Park City, and Phosphoria Formations and the lower (Permian) 

parts of the Goose Egg and State Bridge Formations. Component geologic units decrease in age from Early to Late Permian 

southward. The thickness of the Park City-State Bridge zone 

ranges from 0 to 800 ft. In Wyoming and northwestern Colorado, a facies consisting of red shale with subordinate sandstone, gypsum-anhydrite, limestone, and dolomite grades 

westward into a depositional sequence consisting of varying 

proportions of limestone, dolomite, greenish-gray to black 

shale, phosphatic shale, phosphorite, chert, and sandstone. To 

the south, in Utah and Arizona, the shale and phosphatic intervals pinch out, and gypsum-anhydrite layers locally comprise 

5-30 percent of the Park City-State Bridge zone. Component 

geologic units in the Park City-State Bridge zone are overlain 

conformably to unconformably by Triassic formations.

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74 p.

Smith, J.F., Jr., Huff, C.H., Hinrichs, E.N., and Luedke, R.G., 1963, Geology of the Capitol Reef area, Wayne and Garfield Counties, Utah: 

U.S. Geological Survey Professional Paper 363, 102 p.

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 1980b, Geologic map of the northernmost Park Range and southernmost Sierra Madre, Jackson and Routt Counties, Colorado: U.S. Geological Survey Miscellaneous Investigations Map 1-1113, scale 

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1:48,000.

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764, scale 1:250,000.

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 1972b, Stratigraphy and origin of the Triassic Moenkopi Formation 

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A84 REGIONAL AQUIFER SYSTEM ANALYSIS UPPER COLORADO RIVER BASIN

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19-28.

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Map MF-761, scale 1:250,000.

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Investigations Map OM-145, scale 1:150,000, 2 sheets.

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137.

 1958, Pennsylvanian stratigraphy, southwest shelf, Paradox Basin, in 

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Mountain Association of Geologists, p. 75 85.
GEOLOGY OF PALEOZOIC ROCKS, UPPER COLORADO RIVER BASIN A85

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Geologists Sixteenth Annual Field Conference Guidebook, p. 153 168.

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Arizona Bureau of Mines Bulletin 171, 140 p.

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measured sections A symposium: Denver, Colo., Rocky Mountain 

Association of Geologists, p. 54 58.

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Utah: U.S. Geological Survey Professional Paper 453, 110 p.

Witkind, I.J., and Thaden, R.E., 1963, Geology and uranium-vanadium 

deposits of the Monument Valley area, Apache and Navajo Counties, 

Arizona: U.S. Geological Survey Bulletin 1103, 171 p.

Wollitz, L.E., Thordarson, William, Whitfield, M.S., Jr., and Weir, J.E., Jr., 

1982, Results of hydraulic tests in U.S. Department of Energy's wells 

DOE-4, 5, 6, 7, 8, and 9, Salt Valley, Grand County, Utah: U.S. 

Geological Survey Open-File Report 82-346, 71 p.

Zapp, A.D., 1949, Geology and coal resources of the Durango area, La 

Plata and Montezuma Counties, Colorado: U.S. Geological Survey 

Oil and Gas Investigations Map OM-109, scale 1:31,680.
U.S. DEPARTMENT OF THE INTERIOR 

science lor a changing world U.S. GEOLOGICAL SURVEY

PROFESSIONAL PAPER 1411-A

Geographic and structural features PLATE 1

Geldon, A.L., 2002. Geology of Paleozoic rocks in the Upper Colorado River Basin in 

Arizona, Colorado, New Mexico, Utah, and Wyoming, excluding the San Juan Basin

CROOKS 

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GEOGRAPHIC FEATURES

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ARIZONA

BASIN AND|RANGE

___L

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112°

110° 

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INDEX MAP SHOWING LOCATION OF UPPER COLORADO RIVER BASIN 

WITH RESPECT TO PHYSIOGRAPHIC PROVINCES

EXPLANATION

4-

Anticline 

Syncline

-t > Plunging anticline

f- Dome or doubly plunging 

anticline

Fault, generally high angle

Fault zone

Graben

Horst

Thrust fault, teeth on upper 

plate

Boundary of structural feature, shown only where boundary 

does not coincide with a fault

Structural basin 

Uplift

Map of structural features modified from maps by Grose (1972), Baars (1983), and 

Taylor and others (1983), based mainly on Williams (1964), Roberts and others (1965), 

Ritzma (1969), Williams and Hackman (1971), Haynes and others (1972), Cashion 

(1973), Hackman and Wyant (1973), Tweto (1976), Tweto and others (1976, 1978), 

Snyder (1980a, 1980b, 1980c), Hansen (1986a), Stone (1986), Blackstone and 

DeBruin (1987), and Lageson (1987) and on isopach and lithofacies maps prepared 

for this report.

Map of physiographic provinces modified from Howard and others (1972).

Base from U.S. Geological Survey 

U.S. base map, 1:2,500,000 GEOGRAPHIC AND STRUCTURAL FEATURES OF THE UPPER COLORADO RIVER BASIN AND VICINITY IN ARIZONA, COLORADO, NEW MEXICO, UTAH, AND WYOMING

By

Arthur L. Geldon 

2002
U.S. DEPARTMENT OF THE INTERIOR

science for a changing world U.S. GEOLOGICAL SURVEY

PROFESSIONAL PAPER 1411-A

Geology and geologic cross sections PLATE 2

Geldon, A.L, 2002, Geology of Paleozoic rocks in the Upper Colorado River Basin in 

Arizona, Colorado, New Mexico, Utah, and Wyoming, excluding the San Juan Basin

SALT RIVER 

RANGE

WYOMING 

RANGE

GREEN RIVER 

BASIN

WIND RIVER MTS

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5,000-

NGVDof 1929- 

-5,000

SAN RAFAEL SWELL UINTA BASIN UINTA MOUNTAINS

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UPPER COLORADO

RIVER BASIN

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36'

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-5,000 -

-10,000-

-15,000-

-20,000

D

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FEET I

DOUGLAS CREEK 

ARCH

PICEANCE BASIN WHITE RIVER PLATEAU EAGLE BASIN GORE

= RANGE

 5

FRONT 

» RANGE

15,000-1

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KAIPAROWITS 

BASIN

CIRCLE 

CLIFFS

UPLIFT

PARADOX BASIN

FEET

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5,000

NGVD of 1929 

-5,000

MONUMENT UPWARP UNCOMPAHGRE 

PLATEAU :

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Valley

PARADOX 

BASIN

UNCOMPAHGRE 

PLATEAU

SAN JUAN 

MOUNTAINS

FEET 

15,000-i

10,000-

5,000 - 

NGVD of 1929 -

-5,000

-10,000-

-15,000

G

FOUR CORNERS PLATFORM

FEET

15,000-i

10,000-

5,000

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-5,000-

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-15,000

La Plata 

Mountains

SAN JUAN MOUNTAINS

| Needle | 

.5 Mountains jj 

^M | M«

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-5,000

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BASIN

TYENDE 

SADDLE

MONUMENT 

UPWARP

FEET 

10,000

5,000-| K 

NGVDof 1929 

-5,000

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VERTICAL EXAGGERATION X 2

GEOLOGIC CROSS SECTIONS

EXPLANATION 

Geologic Map Units Quaternary alluvium and colluvium not shown

Tertiary sedimentary rocks 

Tertiary igneous rocks 

Mesozoic sedimentary rocks

Permian formations composed of shale, sandstone, chert, carbonate rocks, 

evaporites, and phosphorite. Not shown generally in Overthrust Belt 

because of scale

Permian and Pennsylvanian quartz sandstone. Includes minor interbedded 

carbonate rocks and shale. Not shown in White River Plateau, Elk 

Mountains, Monument Upwarp, and Grand Canyon area because of 

scale

Permian and Pennsylvanian formations composed of sandstone, shale, 

and interbedded carbonate rocks. Not shown in Wyoming, except in 

Rawlins Uplift, because of scale

Eagle Valley Evaporite and Paradox Member of Hermosa Formation

Bedded evaporites of Pennsylvanian age. Shown only where prominent 

outcrops are present

Belden and Molas Formations Black shale with interbedded carbonate rocks 

and minor gypsum overlying a thin red shale regolith. Formations are mostly 

Pennsylvanian in age. Shown only where Eagle Valley Evaporite crops out 

in northwestern Colorado

Mississippian, Devonian, Ordovician, and Cambrian formations Composed 

of limestone and dolomite with interbedded quartzite, sandstone, and 

shale

Precambrian sedimentary rocks and slightly metamorphosed sedimentary 

rocks

Precambrian igneous and metamorphic rocks

Geologic Cross Section Units 

Sedimentary rocks Igneous rocks

T Tertiary sedimentary 

rocks

Mesozoic

sedimentary

rocks

Permian and 

Pennsylvanian 

sedimentary 

rocks

Cretaceous sedimentary 

rocks

Jurassic and Triassic 

sedimentary rocks

Pennsylvanian

Paradox Member

of Hermosa Formation

Mississippian, Devonian, 

Ordovician, and 

Cambrian sedimentary 

rocks

Precambrian 

sedimentary rocks

Tertiary volcanic 

rocks

Tertiary intrusive 

rocks

Cambrian intrusive 

rocks

Precambrian granitic 

rocks

Precambrian 

metamorphic rocks

Precambrian 

igneous and 

metamorphic rocks

Line Symbols

Fault Barbs (in figures 5 and 6) indicate relative directions of movement 

Geologic contact Dashed where approximately located

 A' Location of geologic cross section shown on plate 2 and figures 5 and 6

The geologic map was compiled from 1:500,000-scale State geologic maps prepared 

by Dane and Bachman (1965), Wilson and others (1969), Tweto (1979), Hintze (1980), 

and Love and Christiansen (1985). Geologic cross section A-A' was prepared from 

reports by Richmond (1945), Rubey (1973), and Royse and others (1975), and unpublished borehole logs; sections B-B' through H-H' were modified from Hintze (1980) and 

Tweto (1980b); section /-/' was prepared mainly from Harshbarger and Repenning 

(1954), O'Sullivan and Beikman (1963), Haynes and others (1972), and unpublished 

borehole logs. The intersection points of cross sections are not shown here and elsewhere in this report. The sections are taken from the work of other authors and thus 

represent different interpretations and generalizations. Showing the intersection points 

could give the misleading impression that errors were made in drawing one or both of 

the intersecting sections.

Base from U.S. Geological Survey 

U.S. base map, 1:2,500,000 GENERALIZED GEOLOGY OF THE UPPER COLORADO RIVER BASIN AND VICINITY IN ARIZONA, COLORADO, NEW MEXICO, UTAH, AND WYOMING

By

Arthur L. Geldon 

2002
__ U.S. DEPARTMENT OF THE INTERIOR 

science 1ma changing world U.S. GEOLOGICAL SURVEY

PROFESSIONAL PAPER 1411-A

Thickness of and depth to top of Paleozoic rocks PLATE 3

Geldon, A.L., 2002 Geology of Paleozoic rocks in the Upper Colorado River Basin jn 

Arizona, Colorado, New Mexico, Utah, and Wyoming, excluding the San Juan Basin

110° 110°

42

Strawberry

Valley area\.,Os^

/ 'raining Gorge

AREA EXCLUDED FROM STUDY

43

42

BOUNDARY OF

UPPER COLORADO

RIVER BASIN

112

"N/

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RIVER BASIN

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THICKNESS OF PALEOZOIC ROCKS DEPTH TO TOP OF PALEOZOIC ROCKS

EXPLANATION

Area where the Paleozoic rocks crop out (generalized). Blue 

indicates Canyonlands aquifer, purple indicates geologic 

units below Canyonlands aquifer

Area where the Paleozoic rocks are missing because of 

erosion or nondeposition or are thrust beneath Precambrian 

rocks

Area where the top of the Paleozoic rocks is below the 

Canyonlands aquifer (see table 1 for component 

geologic units)

Thickness of Paleozoic rocks

-1,000 Line of equal thickness of Paleozoic rocks, excluding 

Paleozoic rocks above Charleston Thrust Fault in 

Strawberry Valley area, Utah Interval generally 

is 1,000 feet; 2,000 feet in northwestern Colorado 

near Sawatch Range because of abrupt thickness changes

Depth to top of Paleozoic rocks

-5,000 Line of equal depth to top of Paleozoic rocks Interval 

north of Uncompahgre Plateau is 5,000 feet; interval to 

south is 2,500 feet

Sources of information used to complete 

depth to top of Paleozoic rocks map

Except where noted, map prepared from 

maps showing (1) depth to top of 

Glen Canyon Group and equivalents, (2) 

thickness of Glen Canyon Group and 

equivalents (both from Geoffrey Frcethey 

and Gail Cordy, U.S. Geological Survey, 

written commun., 1984-85); and (3) 

thickness of Chinle and Moenkopi 

Formations and equivalents, either from 

Freethey and Cordy (written commun., 

1984-85) in shaded area or Stewart and 

others (1972a, 1972b) in unshaded area

Sources for area

A: Richmond (1945); Wanless and others (1955)

B: Hansen (1965b); Schell (1969)

C: Huddle and McCann (1947b); Huddle and others

(1951); Bissell (1952); Baker (1976);

Bruce Bryant (U.S. Geological Survey,

oral commun., 1990)

D: Donner (1949); Bass and others (1955); 

Severy (1955); Sharps (1955); Bass and 

Northrop (1963); Segerstrom and Young (1972); 

Stewart and others (1972a, 1972b); Snyder 

(1980a, 1980b); and American Stratigraphic Company 

(unpublished drilling logs)

E: Hubert (1954); Stewart and others (1972a); 

Bryant and Martin (1988)

F: Welder (1954); Freeman (1971, 1972); 

Stewart and others (1972a)

G: Thomas and others (1945); Mull (I960); 

Bass and Northrop (1963); Lohman (1965); 

Gaskill and Godwin (1966a, 1966b); Gaskill 

and others (1967); Godwin (1968); Stewart 

and others (1972a, 1972b); Collins (1977); 

and Maclachlan (1987)

H: Eckel and others (1949); Cater (1955a, 1955b); 

Cater and others (1955); Bush and others (1959, 

I960); Donnell (1960); Luedke and Burbank (1962); 

Stewart and others (1972a); and American 

Stratigraphic Company (unpublished drilling logs)

I: Zapp(1949)

J: Harshbarger and Repenning (1954); Strobell (1956); 

Cooley and others (1964); Stewart and others (1972a); 

and Hackman and Olson (1977)

K: Gregory and Moore (1931); Phoenix (1963); 

Witkind and Thaden (1963); Cooley and others 

(1964); Stewart and others (1972a, 1972b); 

and American Stratigraphic Company (unpublished 

drilling logs)

Base from U.S. Geological Survey 

U.S. base map, 1:2,500,000 THICKNESS AND DEPTH TO THE TOP OF THE PALEOZOIC ROCKS THAT COMPRISE HYDROGEOLOGIC UNITS IN THE UPPER COLORADO RIVER BASIN AND VICINITY

IN ARIZONA, COLORADO, NEW MEXICO, UTAH, AND WYOMING

By

Arthur L. Geldon 

2002
^USGS U.S. DEPARTMENT OF THE INTERIOR

science for a changing world U.S. GEOLOGICAL SURVEY

PROFESSIONAL PAPER 1411-A

Precambrian and Mesozoic rocks PLATE 4

Geldon, A.L, 2002. Geology of Paleozoic rocks in the Upper Colorado Fiver Basin in 

Arizona, Colorado, New Mexico, Utah, and Wyoming, excluding the San Juan Basin

110°

43°

42

XxV-^ / " '/ -'- / ;

^\^.MfO - x i X^T*

^( r*f'~f~^, ^ y v

^^f^SSrK; y'

^k -x | x- -\ - j, ^ -* | xi > - ^ _. -«. i * -i - ^ »

^^ v.x :^^^v;:'^ r-w;:\ 38»rrv- - , , '^x' x--'. :, -:,'/^'- 3

^JJ' ///,/_-!' -xV,/J>i 'r-V.^ \x-V''x--\^ v -'' \- - \ x ^' :Lf~Jj-

^^>^kc^^'^:

- .enyi- , , _ x/ ( 7-\-, 'f'V;\ V i -'A-J^'

AREA EXCLUDED FROM STUDY

BOUNDARY OF

UPPER COLORADO

RIVER BASIN

112

1:2,000,000

Information used to compile this map 

was obtained from geologic maps by 

Wilson and others (1969), Tweto (1979; 

1980a, p. 38-39), Hintze (1980), and Love 

and Christiansen (1985); Stratigraphic 

columns in Hintze (1973); measured 

surface Stratigraphic sections from reports 

cited in the Selected References section, 

and unpublished borehole logs prepared 

by the American Stratigraphic Company

0

r

0

25

I

50 

I

75

n i i i

25 50 75 100 KILOMETERS

PRECAMBRIAN ROCKS

100 MILES 

I

43'

42

DINWOOD^FORMATION

JOLORA

LOWER 

OPE-FORMING 

WOODSIDE £>MJEMB"ETTfclF MOENKO

40° v SHALE

X1 V vvy/ . v vv /' ^

\::\ ^; i^ - N ::: ^):^/

x^/v=| MOSSBACK XvV^;:,^

MEMBER OF

40 »)l FORMATIDN 

2^ 3/1 MonticeUo

S

INBAD AND TIMPOWEAP 

MEMBERS OF

a

LORADO 

LOWER RED MEMBER NEW ME?

NKOPI 

la

RI7ON

Kaycn

o

SANDSTONE I \" SfMlNARUMP 

MEMBER dF I \= MEMBER OF C HINLE 

S" FORMATIC N 

O

AREA EXCLUDED FROM STUDY

BOUNDARY OF

UPPER COLORADO

RIVER BASIN

Map based mainly on reports 

by Stewart and others (1972a, 

1972b) and Love and others 

(1993) and on unpublished 

borehole logs prepared by the 

American Stratigraphic Company

25

I

1:2,000,000

50 75

I

100 MILES

^ I I I 

25 50 75 100 KILOMETERS

MESOZOIC ROCKS

EXPLANATION

Precambrian rocks

Sedimentary rocks and low-grade metamorphic rocks Includes the Uinta 

Mountain, Unkar, and Chuar Groups, Uncompahgre Formation, and unnamed 

rocks in the Defiance Plateau-Four Corners area

Granitic rocks and related intrusives

Metamorphosed sedimentary rocks Includes gneiss, schist, quartzite, and 

marble

Metamorphosed volcanic rocks Includes greenstone, amphibolite, and 

meta-tuff

Borehole with lithologic log used to prepare map 

Measured surface Stratigraphic section used to prepare map

Mesozoic and Paleozoic rocks

Jurassic

Entrada and Wingate Sandstones 

Tan, white, gray, pink, and red, 

locally conglomeratic sandstone

Triassic

Lower Member of Dolores

Formation; Gartra, Mossback, 

and Shinarump Members of 

Chinle Formation Yellow, tan, 

gray, and orange sandstone and 

conglomerate with siltstone

Hoskinnini and Tenderfoot 

Members of Moenkopi 

Formation Red and brown 

sandstone, conglomerate, and 

siltstone

Church Rock, red siltstone, and 

Petrified Forest Members of 

Chinle Formation; lower slopeforming and lower red members 

of Moenkopi Formation; and 

Woodside Shale Generally red, 

locally gray, green, or variegated 

claystone and siltstone, with thin 

sandstone layers

Ledge-forming member of 

Moenkopi Formation Red, 

brown, and gray fine-grained 

sandstone and siltstone

Sinbad and Timpoweap 

Members of Moenkopi 

Formation Gray, yellow, 

orange, and green limestone, 

dolomite, siltstone, and 

sandstone

Dinwoody Formation Green 

and gray shale and limestone 

with anhydrite

Goose Egg and State Bridge 

Formations (upper part) 

Mostly red and brown, 

locally green siltstone and 

claystone with thin sandstone, 

anhydrite, and carbonate 

layers

Mesozoic rocks eroded or not 

deposited Paleozoic rocks 

overlain by Tertiary Wasatch 

Formation

Mesozoic and Paleozoic rocks 

thrust beneath Precambrian 

rocks or area in which 

Mesozoic and Paleozoic rocks 

are missing because of erosion 

or nondeposition

Area where Paleozoic rocks 

crop out

Base from U.S. Geological Survey 

U.S. base map, 1:2,500,000 PRECAMBRIAN AND MESOZOIC ROCKS IN CONTACT WITH PALEOZOIC ROCKS OF THE UPPER COLORADO RIVER BASIN IN ARIZONA, COLORADO, NEW MEXICO, UTAH, AND WYOMING,

EXCLUDING PARTS OF THE SAN JUAN BASIN

By

Arthur L. Geldon 

2002
^USGS

science for a changing world

U.S. DEPARTMENT OF THE INTERIOR 

U.S. GEOLOGICAL SURVEY

PROFESSIONAL PAPER 1411-A

Stratigraphic nomenclature and lithology PLATE 5

Geldon, A.L., 2002. Geology of Paleozoic rocks in the Upper Colorado River Basin in 

Arizona, Colorado, New Mexico, Utah, and Wyoming, excluding the San Juan Basin

32

14

FEET 

1,000-1

500-

1,500 - 

1,000 -

\

25

I

50

HORIZONTAL

75

\

100 MILES

1 1 1 1

25 50 

HORIZONTAL

75 100 MILES

CAMBRIAN TO MISSISSIPPIAN ROCKS MISSISSIPPIAN TO PERMIAN ROCKS

1

2

3

4

5

6

7

8

9

10

11

12

13

14

15

16

17

18

19

20

21

22

23

24

25

26

27

28

29

30

31

32

33

34

35

36

37

38

39

40

41

42

43

44

45

46

47

48

49

50

EXPLANATION

Localities

Snake River Canyon (Wanless and others, 1959)

Granite Creek (Foster, 1947; Wanless and others, 1959)

Boulder area (Love, 1950)

Beaver Creek (Keefer and Van Lieu, 1966)

Rawlins area (Berry, 1960)

Amerada 1-Fossil (American Stratigraphic Co., unpublished)

Champlin 1-Brady 12-11 (American Stratigraphic Co., unpublished)

Gulf 1-Slater Creek (American Stratigraphic Co., unpublished)

Lake Fork (Huddle and others, 1951)

Whiterocks River (Kinney, 1955)

Diamond Mountain (Ritzma, 1959)

Johnson Draw (Untermann and Untermann, 1954)

Cross Mountain (Wilson, 1957)

Juniper Mountain (Abrassart and Clough, 1955)

Tenneco 1-Antimony Canyon (American Stratigraphic Co., unpublished)

American Metals Climax 1-Red Hills (American Stratigraphic Co., unpublished)

General Petroleum 1-Schutte (American Stratigraphic Co., unpublished)

Northwestern White River Plateau (Hallgarth, 1959)

Southeastern White River Plateau (Bass and Northrop, 1963)

Minturn area (Tweto and Lovering, 1977)

Hoosier Pass area (Singewald, 1951)

Cement Creek (Mallory, 1957)

Midwest Exploration 1-Elk Ridge (American Stratigraphic Co., unpublished)

Bass Trail (Noble, 1922)

Sinclair 1-Navajo (American Stratigraphic Co., unpublished)

Shell 1-Bluff (American Stratigraphic Co., unpublished)

Gulf 1-Fulks (American Stratigraphic Co., unpublished)

Stag Mesa (Baars and Knight, 1957)

Cactus Drilling 1-Navajo 85-15 (American Stratigraphic Co., unpublished)

Union 1-Navajo 166 (American Stratigraphic Co., unpublished)

Sheep Mountain (Richmond, 1945)

Squaw Creek (Keefer and Van Lieu, 1966)

California 3-Green Mountain (American Stratigraphic Co., unpublished)

Exxon 1-Bullpen Creek (American Stratigraphic Co., unpublished)

Mountain Fuel Supply 1-Broff (American Stratigraphic Co., unpublished)

Rock Creek (Huddle and others, 1951)

Hells Canyon (Thomas and others, 1945)

Black Box, composite (Gilluly, 1929; American Stratigraphic Co., unpublished)

Main Elk Creek (Thomas and others, 1945; Bass and Northrop, 1963)

Elk Mountains, composite (Mallory, 1957; Bryant, 1979)

Pando area (Tweto, 1949)

Pan American 1-Charles (American Stratigraphic Co., unpublished)

Animas River (Larsen and Cross, 1956; Wengerd, 1957)

Tenneco 1-Johns Valley (American Stratigraphic Co., unpublished)

Superior 14-2 (American Stratigraphic Co., unpublished)

Comb Wash, composite (Gregory, 1938; American Stratigraphic Co., unpublished)

Underwood 1-32 Jacob Lake (American Stratigraphic Co., unpublished)

Lees Ferry area, composite (Phoenix, 1963; McKee, 1982)

Sinclair 1-Navajo (American Stratigraphic Co., unpublished)

Tenneco 1-Navajo 8939 (American Stratigraphic Co., unpublished)

Bonito Canyon (Read and Wanek, 1961)

Rock Types

Quartz sandstone and quartzite

Arkosic and graywacke 

sandstone

Red shale and fine-grained 

sandstone

Glauconitic and micaceous shale 

and fine-grained sandstone

Gray shale, limestone, and 

dolomite

Limestone and dolomite

Limestone, dolomite, sandstone, 

and shale

Anhydrite and halite with shale 

and carbonate interbeds

BOUNDARY OF

UPPER COLORADO

RIVER BASIN

14

EXPLANATION

Stratigraphic fence diagram 

showing Cambrian to 

Mississippian rocks

Stratigraphic fence diagram 

showing Mississippian to 

Permian rocks

0 25 50 75 100 MILES

|.l..'.' I 

I I I I I

0 25 50 75 100 KILOMETERS

INDEX MAP TO FENCE DIAGRAMS

Line Symbols

 Contact between geologic formations or groups

 - Contact between different lithologies within a geologic formation or group

Base of Paleozoic rocks uncertain because of incomplete penetration by 

boreholes or measurement of surface Stratigraphic sections in vicinity

Borehole or measured surface Stratigraphic section. Boreholes are indicated 

by reference to American Statigraphic Company

Symbols Used for Geologic Units 

Permian

PC Cutler Formation

Pcm Cedar Mesa Sandstone of Baars (1962)

Pco Coconino Sandstone

Pd De Chelly Sandstone

Pe Elephant Canyon Formation of Baars 

(1962)

Pg Goose Egg Formation, lower part

Ph Hermit Shale

Pha Halgaito Shale of Baars (1962)

Permian and Pennsylvanian

PPm Maroon Formation

PPs Supai Formation or Group

Pennsylvanian

Pb Belden Formation

Pev Eagle Valley Evaporite

Pg Gothic Formation of Langenheim (1952)

Ph Hermosa Formation

Pennsylvanian and Mississippian

PMa Amsden Formation

PMbm Belden and Molas Formations

PMd Doughnut Shale

Mississippian

Mh Humbug Formation 

Ml Leadville Limestone

Devonian

Dd Darby Formation

Ddy Dyer Dolomite

De Elbert Formation

Ordovician

Ob Bighorn Dolomite

Cambrian

Cb Bright Angel Shale and equivalents

Cd Dotsero Formation

Cf Flathead Sandstone

Cg Gallatin Limestone

Cgv Gros Ventre Formation

Ci Ignacio Quartzite

 1 Lodore Formation

Pk Kaibab Formation

Po Organ Rock Shale of Baars (1962)

Pp Park City Formation of McKelvey 

and others (1959)

Pph Phosphoria Formation of McKelvey 

and others (1959)

Psc Schoolhouse Member of Maroon 

Formation

Ps State Bridge Formation, lower part

Pt Toroweap Formation

Pw White Rim Sandstone of Baars (1962)

PPw Weber Sandstone 

PPwe Wells Formation

Pm Minturn Formation

Pmo Morgan Formation

Pr Rico Formation

Prv Round Valley Limestone

Pt Tensleep Sandstone

PMhm Hermosa and Molas Formations

PMm Molas Formation

PMmc Manning Canyon Shale

Mm Madison Limestone

Mml Mission Canyon and Lodgepole 

Limestones

Mr Redwall Limestone

Do Ouray Limestone

Dp Parting Formation

Dt Temple Butte Formation

Om Manitou Dolomite

Cly Lynch Dolomite

Cm Muav Limestone and equivalents

Cma Maxfield Limestone

Co Ophir Shale

Cp Peerless Formation

Cs Sawatch Quartzite

Ct Tintic Quartzite

Ctp Tapeats Sandstone and equivalents

CHANGES IN STRATIGRAPHIC NOMENCLATURE AND LITHOLOGY WITHIN THE PALEOZOIC ROCKS OF THE UPPER COLORADO RIVER BASIN IN ARIZONA, COLORADO, NEW MEXICO, UTAH, AND WYOMING,

EXCLUDING PARTS OF THE SAN JUAN BASIN

By

Arthur L. Geldon 

2002
U.S. DEPARTMENT OF THE INTERIOR 

science fora changing world U.S. GEOLOGICAL SURVEY

PROFESSIONAL PAPER 1411-A

Thickness and llthology of the Flathead aquifer PLATE 6

Geldon, A.L., 2002. Geology of Paleozoic rocks in the Upper Colorado River Basin jn 

Arizona, Colorado, New Mexico, Utah, and Wyoming, excluding the San Juan Basin

43

;xc".' x *'~* I -er>3i / x/ V-XL "Nil .\v ' ',- X - ^NS. / s ,

rxfe

, AND EQUIVALENTS i' Rook (Si ^"a^*^ \

i^.'.f./,'.-,^--.f.'.^.r.Tr^r-,-. >>« -..; ^-,'.^,\'.\ i-vvX/r^^/v^v\^-1^£;v.f\-v-T^---w

0 TINTIC 

QUARTZITE

? UTAH

AREA EXCLUDED FROM STUDY

43

BOUNDARY OF

UPPER COLORADO

RIVER BASIN

AREA EXCLUDED FROM STUDY

39

BOUNDARY OF

UPPER COLORADO

RIVER BASIN

107°

25

I

1:2,000,000

50 

I_____

75

I

100 MILES

I

i i i r

25 50 75 100 KILOMETERS

STRATIGRAPHIC NOMENCLATURE AND THICKNESS

25

I

1:2,000,000

50 75 

I

100 MILES

25 50 75 100 KILOMETERS

LITHOLOGY

EXPLANATION

Area where Flathead aquifer is missing because of erosion or nondeposition 

or thrust under Precambrian rocks

 Borehole with lithologic log used to prepare map

+ Measured surface stratigraphic section used to prepare map

Stratigraphic Nomenclature and Thickness

Area where Flathead aquifer crops out (generalized)

 700 Line of equal thickness Approximately located in southwestern Wyoming and 

northeastern Utah because of sparse control. Interval is 100 feet

Approximate boundary between component geologic units

L' Location of stratigraphic cross section shown in figures 12 and 13

Lithology

-60-

Quartzitic, dolomitic, and glauconitic sandstone and quartzite with 

conglomerate and shale interbeds

Quartzitic, dolomitic, and glauconitic sandstone and quartzite with 

conglomerate and shale interbeds and 5 to 20 percent interbedded 

limestone and dolomite

Line of equal percent sandstone, quartzite, and conglomerate Location 

is approximate because of generally sparse control. Interval is 20 percent

Approximate boundary between lithofacies

Base from U.S. Geological Survey 

U.S. base map, 1:2,500,000 STRATIGRAPHIC NOMENCLATURE, THICKNESS, AND LITHOLOGY OF THE FLATHEAD AQUIFER IN THE UPPER COLORADO RIVER BASIN AND VICINITY

IN ARIZONA, COLORADO, NEW MEXICO, UTAH, AND WYOMING

By

Arthur L. Geldon 

2002
USGS U.S. DEPARTMENT OF THE INTERIOR

science for a changing world U.S. GEOLOGICAL SURVEY

PROFESSIONAL PAPER 1411-A

Depths to top of Flathead and Madison aquifers PLATE 7

Geldon, A.L., 2002. Geology of Paleozoic rocks in the Upper Colorado River Basin in 

Arizona, Colorado, New Mexico, Utah, and Wyoming, excluding the San Juan Basin

110°

43

AREA EXCLUDED FROM STUDY

43

42°'

x-Yr^'''M 40°

BOUNDARY OF

UPPER COLORADO

RIVER BASIN

107°

m

-^j^l^l^r^ "^Y-^"^^' 1 '

" 1^^VS 

'~^>^' '\ '~ /" v'' 'A? ;V

<.(^ ^--- ' / v ^ - - > i J^N

i^ate:^^!

p^rr"

^-^-V^^ l 37

*Iauajo j

Reservoir ^S

AREA EXCLUDED FROM STUDY

; :;

X/7:'^:/-^-

 5,000 

EXPLANATION

Area where aquifer to which depth is shown crops out (generalized)

Area where aquifer to which depth is shown is missing because 

of erosion or nondeposition or is thrust under Precambrian rocks

Line of equal depth of top of aquifer Interval is 5,000 feet, except 

south and west of Uncompahgre Plateau, where interval is 

2,500 feet

BOUNDARY OF

UPPER COLORADO

RIVER BASIN

25

I

1:2,000,000

50

I_____

75

I

108°

100 MILES 25

I

1:2,000,000

50

I_____

75 

I

108°

100 MILES

1 I I I 

25 50 75 100 KILOMETERS

DEPTH TO TOP OF FLATHEAD AQUIFER

1 1 I I 

25 50 75 100 KILOMETERS

DEPTH TO TOP OF MADISON AQUIFER

Base from U.S. Geological Survey 

U.S. base map, 1:2,500,000 DEPTHS TO THE TOP OF THE FLATHEAD AND MADISON AQUIFERS IN THE UPPER COLORADO RIVER BASIN AND VICINITY IN ARIZONA, COLORADO, NEW MEXICO, UTAH, AND WYOMING

By

Arthur L. Geldon 

2002
USGS U.S. DEPARTMENT OF THE INTERIOR 

science tor a changing world U.S. GEOLOGICAL SURVEY

PROFESSIONAL PAPER 1411-A

Thickness and lithology of the Gros Ventre confining unit PLATE 8

Geldon, A.L., 2002. Geology of Paleozoic rocks in the Upper Colorado River Basin in 

Arizona, Colorado, New Mexico, Utah, and Wyoming, excluding the San Juan Basin

110

43

AREA EXCLUDED FROM STUDY

BOUNDARY OF

UPPER COLORADO

RIVER BASIN

107°

36

25

I

1:2,000,000

50 75

I

100 MILES

\ I I I 

25 50 75 100 KILOMETERS

STRATIGRAPHIC NOMENCLATURE AND THICKNESS

110°

43

- - ', p\'- x q

t-^A

V X s ~» - ' ^ - Kx^;\x «,

'^*-* "// ^x< ' s v * ^~,- - ^r " ' N X. f > ~~*T /Jt^ > - vi'ihigd'i-fi.^/L v s >v>_J

""T^r/^i ^ s \ : x ' ^^,^7] },- -' ~, irs?~~r>tss.

6^^#^^^

^^^^7v 

^w^^:- 

';^^^i^^L/^ 

^^^¥^^^^^ 

^^iii^^1^^^^ 

T^^CH\ 

^T^%^v^'V^i%^ _^v ^Q>V' .^ v4/ ^^vW' .-"i ^^xV \:^Vp _\r v>. ^^^ J^%~x '-N: - : " x :VN ' v: ^ ^/^^^^<^ *:^-*:^ ^r^s. \v>-- v :V x

<r yy/ 4 \\ x r/\- . v A. x ri oj v \ '/L^~ /^-T-T- > \ ' r/ - v \ 'Wv \ V \ " r, - .> *

AREA EXCLUDED FROM STUDY

BOUNDARY OF 

UPPER COLORADO 

BASIN

36

25

1:2,000,000

50

I____

75 100 MILES 

_J

25

I 

50 75 100 KILOMETERS

LITHOLOGY

EXPLANATION

Area where Gros Ventre confining unit is missing because of erosion or 

nondeposition or thrust under Precambrian rocks

Borehole with lithologic log used to prepare map 

Measured surface stratigraphic section used to prepare map

Stratigraphic Nomenclature and Thickness

-200

Area where Gros Ventre confining unit crops out (generalized)

Line of equal thickness Interval is 100 feet, except in northeastern corner 

of Arizona, where interval is 50 feet

Approximate boundary between component geologic units

Lithology

-20-

Siltstone and claystone, with less than 10 percent, each, sandstone and 

carbonate rocks

Siltstone and claystone, with 10-70 percent sandstone and less than 10 

percent carbonate rocks

Siltstone and claystone, with 10-50 percent carbonate rocks and less 

than 10 percent sandstone

Siltstone and claystone, with sandstone and carbonate rocks each greater 

than 10 percent and together generally no more than 50 percent of 

the unit

Line of equal percent sandstone Location is approximate because of sparse 

control. Interval is 20 percent

Approximate boundary between lithofacies

Base from U.S. Geological Survey 

U.S. base map, 1:2,500,000 STRATIGRAPHIC NOMENCLATURE, THICKNESS, AND LITHOLOGY OF THE GROS VENTRE CONFINING UNIT IN THE UPPER COLORADO RIVER BASIN AND VICINITY

IN ARIZONA, COLORADO, NEW MEXICO, UTAH, AND WYOMING

By

Arthur L. Geldon 

2002
U.S. DEPARTMENT OF THE INTERIOR 

science for a changing world U.S. GEOLOGICAL SURVEY

PROFESSIONAL PAPER 1411-A

Thickness and lithology of the Bighorn aquifer PLATE 9

Geldon, A.L., 2002. Geology of Paleozoic rocks in the Upper Colorado Fiver Basin in 

Arizona, Colorado, New Mexico, Utah, and Wyoming, excluding the San Juan Basin

110 110

43

42

GALLATIN 

LIMESTONE

BIGHORN 

DOLOMITE

FIELD 

LIMESTON 

AND 

LYNCH 

LOMITE

- '»'."; ,~\i fj 

MUAV LIMESTONE 

AND EQUIVALENTS

AREA EXCLUDED FROM STUDY

43

PEERLESS FORMATION, 

MANITOU DOLOMITE, 

HARDING SANDSTONE, 

39° AND FREMONT LIMESTONE

112

BOUNDARY OF

UPPER COLORADO

RIVER BASIN

36

112

108°

rvoir /^

AREA EXCLUDED FROM STUDY

112

38° -

BOUNDARY OF

UPPER COLORADO

RIVER BASIN

36

25

1:2,000,000

50 75 

I

100 MILES

I I I I 

25 50 75 100 KILOMETERS

STRATIGRAPHIC NOMENCLATURE AND THICKNESS

25

I

1:2,000,000

50 75

I

100 MILES

25 50 75 100 KILOMETERS

LITHOLOGY

EXPLANATION

Area where Bighorn aquifer is missing because of erosion or nondeposition 

or thrust under Precambrian rocks

 Borehole with lithologic log used to prepare map

4- Measured surface stratigraphic section used to prepare map

Stratigraphic Nomenclature and Thickness

-400-

Area where Bighorn aquifer crops out (generalized)

Line of equal thickness Inten/al is 200 feet. In the southwestern corner

of the area, the 1,100-foot contour is shown to aid interpretation. In Wyoming, 

the 1,900-foot contour is shown

Approximate boundary between component geologic units

Lithology

-60-

Limestone and dolomite with shale interbeds and generally less than 5 

percent sandstone interbeds

Limestone and dolomite with shale and sandstone interbeds that locally 

exceed the carbonate rocks in abundance

Line of equal percent carbonate rocks Location generally is approximate. 

Interval is 20 percent

Approximate boundary between lithofacies

Base from U.S. Geological Survey 

U.S. base map, 1:2,500,000 STRATIGRAPHIC NOMENCLATURE, THICKNESS, AND LITHOLOGY OF THE BIGHORN AQUIFER IN THE UPPER COLORADO RIVER BASIN AND VICINITY

IN ARIZONA, COLORADO, NEW MEXICO, UTAH, AND WYOMING

By

Arthur L. Geldon 

2002
^USGS U.S. DEPARTMENT OF THE INTERIOR 

science for a changing world U.S. GEOLOGICAL SURVEY

PROFESSIONAL PAPER 1411-A

Thickness and lithology of the Elbert-Parting confining unit PLATE 10

Geldon, A.L., 2002. Geology of Paleozoic rocks in the Upper Colorado River Basin in 

Arizona, Colorado, New Mexico, Utah, and Wyoming, excluding the San Juan Basin

43

42

r-^.-W*--'

'/-,r\;*,^r

u.:rA'',\ v:-, ,V.«Q

K' 'C '» ' i iv'' /

200

TEMPLE BUTTE 

FORMATION 

100

AREA EXCLUDED FROM STUDY

110

 - 40°

39° -

112

BOUNDARY OF

UPPER COLORADO

RIVER BASIN

36

AREA EXCLUDED FROM STUDY

39

112

BOUNDARY OF

UPPER COLORADO

RIVER BASIN

36

25

I

1:2,000,000

50

I____

75

I

100 MILES 

I

25

I

1:2,000,000

50

I_____

75 100 MILES

~ 

25

I 

50

I 

75 100 KILOMETERS

STRATIGRAPHIC NOMENCLATURE AND THICKNESS

1 I I I 

25 50 75 100 KILOMETERS

LITHOLOGY

EXPLANATION

Area where Elbert-Parting confining unit is missing because of erosion 

or nondeposition or thrust under Precambrian rocks

 Borehole with lithologic log used to prepare map

-f Measured surface stratigraphic section used to prepare map

Stratigraphic Nomenclature and Thickness

-100-

Area where Elbert-Parting confining unit crops out (generalized)

Line of equal thickness Interval is 100 feet, except in Parting Formation 

depositional area, where interval is 50 feet

Approximate boundary between component geologic units

Lithology

-25-

Dolomite, limestone, and shale, with less than 20 percent sandstone 

and quartzite interbeds

Dolomite, limestone, and shale, with 5-10 percent anhydrite and less 

than 25 percent sandstone and quartzite interbeds

Dolomite, limestone, sandstone, quartzite, and shale

Sandstone, quartzite, and shale, with less than 25 percent limestone and 

dolomite interbeds

Line of equal percent carbonate rocks Location generally is approximate 

because of sparse control. Interval is 25 percent

Approximate boundary between lithofacies

Base from U.S. Geological Survey 

U.S. base map, 1:2,500,000 STRATIGRAPHIC NOMENCLATURE, THICKNESS, AND LITHOLOGY OF THE ELBERT-PARTING CONFINING UNIT IN THE UPPER COLORADO RIVER BASIN AND VICINITY

IN ARIZONA, COLORADO, NEW MEXICO, UTAH, AND WYOMING

By

Arthur L. Geldon 

2002
U.S. DEPARTMENT OF THE INTERIOR 

science for a changing world U.S. GEOLOGICAL SURVEY

PROFESSIONAL PAPER 1411-A

Thickness and lithology of the Redwall-Leadville zone PLATE 11

Geldon, A.L., 2002. Geology of Paleozoic rocks ir the Upper Colorado River Basin jn 

Arizona, Colorado, New Mexico, Utah, and Wyoming, excluding the San Juan Basin

110°

43° ,43°

V N i v

\~JTi N 108°

42°

LODGEPOLE \c. 

LIMESTONE (EXCEPT *

COTTONWOOD 

CANYON MEMBER) 

AND LOWER PART

OF MISSION

CANYON LIMESTONE

AND EQUIVALENTS41 C

KemnriJrer

O

MADISON 

LIMESTONE

(EXCEPT 

COTTONWOOD

Rock {SrvV'SS-^C^YON AND 

BULL RIDGE 

MEMBEBS)

.WYOMING)

)LORAD

Vv>\ K*>t>er\

40° \-*o >c,

»X

//r"V-l ^>i|%-\ « < , Veu.fMvJ ' sV 106°.-} V

'-: I '^fe 'Vj> v r-T^t \

>^^'^;-^;v,-~l;;-

' v ~x - _' X V ' s ~x - 'CV X

/^tot'i^hbtst1 .^ i>K^ v 1 

\',> ' '^^O^r^ '» ;" /I

i-700-

 i/'V-'.-'-v" 400

' \ -' V - ' i i vK^ "V s ' ~ - J

f^AV':^/

\\

s i

.300

39

DOLOMITE, 

Gil

SANDSTONE, 

AND LEADVIL 

StQNE^

Gfenwood S;'

200-

106°

N ' J «\ S " S ' - i\K ^V " ' ^>>>^ I" ^ -^^v.v^^Jbw^-^v^-

^ i \ F>-, ^'.^SS^/A -^T*

:.39°

I 0«

112°

38°

 L^-^HvT '' > 'T-°

., r ;,^yr^;,^^^^^^^^>>^^ ^ :v4kr ^ -; &%-;. -* -;4; a;^ ^si1 ' V- -r v '''''"'->'-7

rXnticello 107°

OURAY AND

REDWALL 

LIMESTONES

,700-

,600-

Cortex

L0/ce 

Potue//

Wy/Pagosa 

I Springs,

BOUNDARY OF

. UPPER COLORADO

RIVER BASIN

37' ^

.Lee. 

Ferrv

I

NQWT/O 

, Reseruoir

.- ^---^ 37°

rarminqlpn£

AREA EXCLUDED FROM STUDY

"400.

-300-

36°

112° J

- 36°

110C

flQo 09

25

I

1:2,000,000

50

I____

75

I

100 MILES

25 50 75 100 KILOMETERS

STRATIGRAPHIC NOMENCLATURE AND THICKNESS

110°

sTv_-//^40°

l/-l.\-.

V^^-d 38

t^"T*r^< » ' x 'J?

' - i N \ x:.' T-r~

AREA EXCLUDED FROM STUDY

\ /: .V'.'^Z'i 

\ h'{--'^-^'^

BOUNDARY OF

UPPER COLORADO

RIVER BASIN

36

25

I

1:2,000,000

50

I______

75

I

100 MILES 

_I

25

I 

50 75 100 KILOMETERS

LITHOLOGY

EXPLANATION

Area where Redwall-Leadville zone is missing because of erosion 

or nondeposition or thrust under Precambrian rocks

Borehole with lithologic log used to prepare map 

Measured surface stratigraphic section used to prepare map

Stratigraphic Nomenclature and Thickness

-300-

Area where Redwall-Leadville zone crops out (generalized)

Line of equal thickness Interval is 100 feet, except in the Overthrust Belt 

area of Wyoming, where interval is 500 feet

Approximate boundary between component geologic units

Lithology

-25-

Limestone and dolomite, locally brecciated or marbleized, with less than 

5 percent sandstone and shale interbeds

Limestone and dolomite, locally brecciated or marbleized, with 5-10 

percent sandstone and shale interbeds

Line of equal percent dolomite Interval is 25 percent 

Approximate boundary between lithofacies

Base from U.S. Geological Survey 

U.S. base map, 1:2,500,000 STRATIGRAPHIC NOMENCLATURE, THICKNESS, AND LITHOLOGY OF THE REDWALL-LEADVILLE ZONE OF THE MADISON AQUIFER IN THE UPPER COLORADO RIVER BASIN AND VICINITY

IN ARIZONA, COLORADO, NEW MEXICO, UTAH, AND WYOMING

By

Arthur L. Geldon 

2002
U.S. DEPARTMENT OF THE INTERIOR 

science for a changing world U.S. GEOLOGICAL SURVEY

PROFESSIONAL PAPER 1411-A

Thickness and llthology of the Darwin-Humbug zone PLATE 12

Geldon, A.L, 2002. Geology of Paleozoic rocks in the Upper Colorado River Basin in 

Arizona, Colorado, New Mexico, Utah, and Wyoming, excluding the San Juan Basin

43

UPPER PART 

OF MISSION 

CANYON LIMESTONE 

AND DARWIN 

SANDSTONE 

MEMBER OF

AMSDEN 

FORMATION

42° BULL RIDGE MEMBER 

OF MADISON LIMESTONE 

AND DARWIN SANDSTONE

MEMBER OF AMSDEN 

k107° FORMATION

'-' 40°

' ' I / I ' X \ ' ' X '., / 1 / ' ' ' ' V ' il / I / ' ' / ' x t | XT-*!/

 *' - ' x , - f-l^-trr.*

/ ~ ' I , ' /x'

AREA EXCLUDED FROM STUDY

112

BOUNDARY OF

UPPER COLORADO

RIVER BASIN

107°

36

108°

25 

I

1:2,000,000

50 

I____

75

I

100 MILES

\ 

25 50 75 100 KILOMETERS

STRATIGRAPHIC NOMENCLATURE AND THICKNESS

110°

009°

43° .43°

' -r-

. 7* '

108°

i ^ -^' -^ s ^. ' ^

42°

'/:

\

"r \ i

:-».-Ate

'42°

i107°

I X N ' X I../ X ' X

fc fx^'WK*.'

i / t ' \ ' I / t ' X P / \\/ X ' /

'^y»J

I X V ' X

' X - , X^ .

I / I / X ' / 1 / x

-50-

V/tH

o RtV 'I

Duchesne

40°

-25-

-50-

-75-

v\X|X

' / 'x.

I / I / X

' I

'x 'i / I / x ' 

' X ' X , ^ I

' \

*- - v

X X ' X

39C

~A i / x ' x

^ - < 

' \

kAtv''. A''X-V^/ 'V;'^', A'\§J^', >

^xJ^l^x/^^^/^X/,^^

x v

x _x, I / X x

A/ ' x ,Sx - .' x ' x , x,: -*X ' vr«x , x - . \ ' V?x i \ a . ' x ' x , x - ' x ' ^<?^..=^-^< - x , x ~ .' \ ' , xf, x - 'U ' x , \ -\ ' v ' x

ii2^:'-Ax>rxi^>:-^:''-x' -'-X.v-/-;- -'-'i.-j,'-\< ~'-"^-,'-), x/'/v-.'-s- -'-''--.'-..y-1 '^-.'- J -'-"--.i:. ^y<- 

A y V' &f// ^ Tz'f.-y ^'' -^?';/'^ '' -J"xCTv^ -^ -v XVxf V -\y^x>Q -N V,V'' 4 ''' - v/'f -^ -~^y f

* T7 ^;: i:^^V-*V '' XS I'"F' :*^^^ N' Xx"f'"V x' ^K'''xQx^T^V x' ; ^1$^ : \:^ ,^V p - 

38°--i;'r'x/rx '-^/V/,x '; 'i.^/V'^r* :" W'''-"^ C'/V' 1 ''^ c1^'^'Xi: X x/'>'''^>:.cr/«V^Vl ' : f./-'''/^^

AREA EXCLUDED FROM STUDY

BOUNDARY OF

UPPER COLORADO

R'VER BASIN

107°

36

25

I

1:2,000,000

50 75

I

100 MILES

I I I I 

25 50 75 100 KILOMETERS

LITHOLOGY

EXPLANATION

Area where Darwin-Humbug zone is missing because of erosion 

or nondeposition or thrust under Precambrian rocks

 Borehole with lithologic log used to prepare map

+ Measured surface stratigraphic section used to prepare map

Stratigraphic Nomenclature and Thickness

Area where Darwin-Humbug zone crops out (generalized)

-200 Line of equal thickness Interval is 100 feet

 Approximate boundary between component geologic units

Lithology

-25-

Sandstone and shale with less than 25 percent limestone and dolomite 

interbeds

Sandstone, shale, limestone, and dolomite; carbonate rocks commonly 

are brecciated. Anhydrite or gypsum present locally

Line of equal percent sandstone Location generally is approximate because 

of sparse control. Interval is 25 percent

Approximate boundary between lithofacies

Base from U.S. Geological Survey 

U.S. base map, 1:2,500,000 STRATIGRAPHIC NOMENCLATURE, THICKNESS, AND LITHOLOGY OF THE DARWIN-HUMBUG ZONE OF THE MADISON AQUIFER IN THE UPPER COLORADO RIVER BASIN AND VICINITY

IN ARIZONA, COLORADO, NEW MEXICO, UTAH, AND WYOMING

By

Arthur L. Geldon 

2002
USGS U.S. DEPARTMENT OF THE INTERIOR

science for a changing world U.S. GEOLOGICAL SURVEY

PROFESSIONAL PAPER 1411-A

Thickness and Hthology of the Belden-Molas subunit PLATE 13

Geldon. A.L., 2002. Geology of Paleozoic rocks in the Upper Colorado River Basin in 

Arizona, Colorado, New Mexico, Utah, and Wyoming, excluding the San Juan Basin

HORSESHOE

SHALE MEMBER

OFAMSDEN

FORMATION

HORSESHOE SHALE 

MEMBER OF AMSDEN 

FORMATION

'^ v^'V-x' ' -'-40 ^^-;--ry^ ^?8te3>

AND LOWER MEMBER OF j ARIZ 

FORMATI

SURPRISE 

NYON AND 

ATAHOMIGI 

FORMATION

AREA EXCLUDED FROM STUDY

BOUNDARY OF

UPPER COLORADO

RIVER BASIN

25

I

1:2,000,000 

50 75

I

100 MILES

_J

25 50 75 100 KILOMETERS

STRATIGRAPHIC NOMENCLATURE AND THICKNESS

43

^V;:-; > f-;<.{: :-$. \ ->.Y^^r^iX^-^ :'^2^ 

i'fe?/^^ l^l\7,';;;>^:^

'fc:L'£/<'-'<^

} AREA EXCLUDED FROM STUDY

BOUNDARY OF

UPPER COLORADO

RIVER BASIN

107°

36

25

I

1:2,000,000

50

I____

75

I

100 MILES

I I I I 

25 50 75 100 KILOMETERS

LITHOLOGY

EXPLANATION

Area where Belden-Molas subunit is missing because of erosion or 

nondeposition or thrust under Precambrian rocks

Borehole with lithologic log used to prepare map 

Measured surface stratigraphic section used to prepare map

Stratigraphic Nomenclature and Thickness

Area where Belden-Molas subunit crops out (generalized)

 wo Line of equal thickness Interval, in feet, is variable

- Approximate boundary between component geologic units

JV- N' Location of stratigraphic cross section shown in figure 24

Lithology

Shale, limestone, and dolomite with less than 10 percent sandstone 

interbeds

Shale, limestone, dolomite, and sandstone

-so Line of equal percent limestone and dolomite Interval is 25 percent

 Approximate boundary between lithofacies

Base from U.S. Geological Survey 

U.S. base map, 1:2,500,000 STRATIGRAPHIC NOMENCLATURE, THICKNESS, AND LITHOLOGY OF THE BELDEN-MOLAS SUBUNIT OF THE FOUR CORNERS CONFINING UNIT

IN THE UPPER COLORADO RIVER BASIN AND VICINITY IN ARIZONA, COLORADO, NEW MEXICO, UTAH, AND WYOMING

By

Arthur L. Geldon 

2002
^USGS U.S. DEPARTMENT OF THE INTERIOR

science for a changing world U.S. GEOLOGICAL SURVEY

PROFESSIONAL PAPER 1411-A

Thickness and lithology of the Paradox-Eagle Valley subunit PLATE 14

Geldon, A.L., 2002 Geology of Paleozoic rocks in the Upper Colorado River Basin jn 

Arizona, Colorado, New Mexico, Utah, and Wyoming, excluding the San Juan Basin

MOFFAT TRAIL 11 n 

LIMESTONE MEMBER OF 

AMSDEN FORMATION

43

42

V-r-HM:

oosevelt

D VAL£EY

/ x ; ,'-"^yr»"'»',- ;,,

EAGLE VALLEY 

EVAPORITE

 y s. "^ V N "~f I ^ff"

f^JW<! -'-^C

 NEW MEXICO

AREA EXCLUDED FROM STUDY

39

BOUNDARY OF

UPPER COLORADO

RIVER BASIN

36

112

25

I

1:2,000,000

50

I_____

75 100 MILES

\ 

25 50 75 100 KILOMETERS

STRATIGRAPHIC NOMENCLATURE AND THICKNESS

110

43'

106°;'tA

^xV\ 

' Ifr '"'

' ' JJ - .

\ AREA EXCLUDED FROM STUDY

BOUNDARY OF

UPPER COLORADO

RIVER BASIN

36

112

25

I

1:2,000,000

50

I_______

75 100 MILES

25 50 75 100 KILOMETERS

LITHOLOGY

EXPLANATION

Area where Paradox-Eagle Valley subunit is missing because of erosion 

or nondeposition

Borehole with lithologic log used to prepare map 

Measured surface stratigraphic section used to prepare map

Stratigraphic Nomenclature and Thickness

 woArea where Paradox-Eagle Valley subunit crops out (generalized)

Line of equal thickness Interval is 100 feet, except in centers of depositional 

areas of Eagle Valley Evaporite and Paradox Member of Hermosa Formation, 

where interval is 1,000 feet. Interval is variable south of Craig, Colorado. Small 

salt diapirs in the Paradox basin, where thicknesses reach 15,000 feet, are not 

shown because of scale

Approximate boundary between component geologic units

Lithology

-25-

Limestone, dolomite, and shale, with less than 10 percent sandstone and less 

than 5 percent anhydrite interbeds

Limestone, dolomite, sandstone, and shale, with less than 5 percent anhydrite 

interbeds

Limestone, dolomite, sandstone, shale, and anhydrite

Limestone, dolomite, shale, and anhydrite, with less than 10 percent sandstone 

interbeds

Anhydrite, gypsum, halite, and shale, with less than 25 percent sandstone, 

limestone, and dolomite interbeds

Line of equal percent limestone and dolomite Interval is 25 percent 

Approximate boundary between lithofacies

Base from U.S. Geological Survey 

U.S. base map, 1:2,500,000 STRATIGRAPHIC NOMENCLATURE, THICKNESS, AND LITHOLOGY OF THE PARADOX-EAGLE VALLEY SUBUNIT OF THE FOUR CORNERS CONFINING UNIT

IN THE UPPER COLORADO RIVER BASIN AND VICINITY IN ARIZONA, COLORADO, NEW MEXICO, UTAH, AND WYOMING

By

Arthur L. Geldon 

2002
U.S. DEPARTMENT OF THE INTERIOR 

science for a changing world U.S. GEOLOGICAL SURVEY

PROFESSIONAL PAPER 1411-A

Thickness and lithology of the Cutler-Maroon zone PLATE 15

Geldon, A.L., 2002 Geology of Paleozoic rocks in the Upper Colorado River Basin in 

Arizona, Colorado, New Mexico, Utah, and Wyoming, excluding the San Juan Basin

RANCHESTER

LIMESTONE MEMBER OF ' 1 ° 

AMSDEN FORMATION

41

UPPER MEMBER OF 

HERMOSA FORMATION

AND ELEPHANT 

CANYON FORMATION

UPPER MEMBER OF

HERMOSA FORMATION,

ELEPHANT CANYON

FORMATION, CEDAR

MESA SANDSTONE,

AND ORGAN ROCK SHALE

/ > - , ^N. ' 1^ t x ^ - ' ^i - i. x - ^

:f/,* /A-' CM > /- r vixJ ,//> r ' c

M All ON A 

O CUTLER FC RMAA-flON^lfcd FORMATION, /! ^min9t°HALGArrO SHALE/teEDAR MESA

IfWD CUT/ER FpRJVIATION

0

3

SANDSTONE, AN 

ROCK SHA

AREA EXCLUDED FROM STUDY

WESCOGAME FORMATION,

ESPLANADE SANDSTONE,

AND HERMIT SHALE

50 75 100 KILOMETERS

UPPER

MEMBER OF

HERMOSA

FORMATION,

HALGAITO SHALE,1

CEDAR MESA

SANDSTONE,

AND ORGAN

ROCK SHALE

38

BOUNDARY OF 

UPPER COLORADO RIVERBASIN

37

25

STRATIGRAPHIC NOMENCLATURE AND THICKNESS

110°

43

41

AREA EXCLUDED FROM STUDY

BOUNDARY OF

UPPER COLORADO

RIVER BASIN

36

25

I

1:2,000,000

50

I____

75

I

100 MILES

I I \ \ 

25 50 75 100 KILOMETERS

LITHOLOGY

EXPLANATION

Area where Cutler-Maroon zone is missing because of erosion or nondeposition or is thrust under Precambrian rocks

Borehole with lithologic log used to prepare map 

Measured surface stratigraphic section used to prepare map

Stratigraphic Nomenclature and Thickness

Area where Cutler-Maroon zone crops out (generalized)

 100 Line of equal thickness Interval, in feet, is variable

 Approximate boundary between component geologic units 

R - R' Location of stratigraphic cross section shown in figures 34 and 37

Lithology

-25-

Sandstone and conglomerate with subordinate shale and less than 10 

percent limestone and dolomite layers

Shale with subordinate sandstone and less than 20 percent limestone and 

dolomite layers; may contain 1-16 percent gypsum and anhydrite

Shale with less than 10 percent, each, sandstone and carbonate layers

Shale with subordinate carbonate layers and less than 10 percent 

sandstone layers

Limestone and dolomite with subordinate shale and less than 20 percent 

sandstone layers

Limestone and dolomite with subordinate shale, less than 20 percent 

sandstone, and 5-20 percent anhydrite/gypsum layers

Limestone, dolomite, sandstone, and shale

Line of equal percent sandstone and conglomerate In some areas, 

location is approximate because of sparse control. Interval is 25 percent

Approximate boundary between lithofacies

Base from U.S. Geological Survey 

U.S. base map, 1:2,500,000 STRATIGRAPHIC NOMENCLATURE, THICKNESS, AND LITHOLOGY OF THE CUTLER-MAROON ZONE OF THE CANYONLANDS AQUIFER IN THE UPPER COLORADO RIVER BASIN AND VICINITY

IN ARIZONA, COLORADO, NEW MEXICO, UTAH, AND WYOMING

By

Arthur L. Geldon 

2002
musts U.S. DEPARTMENT OF THE INTERIOR 

science fora changing world U.S. GEOLOGICAL SURVEY

PROFESSIONAL PAPER 1411-A

Thickness and lithology of the Weber-De Chelly zone PLATE 16

Geldon, A.L., 2002. Geology of Paleozoic rocks in the Upper Colorado River Basin in 

Arizona, Colorado, Mew Mexico, Utah, and Wyoming, excluding the San Juan Basin

110°

41

SCHOOLHOUSE 

MEMBER OF

MAROON 

FORMATION

JA 9. x;

S \ »' Vfc, ^^. \ S '

- ' x«-^>V^~, J

»DE CHELLY 9 

SANDSTONE

AREA EXCLUDED FROM STUDY

FRYINGPAN 

MEMBER OF

MAROON 

FORMATION

38

BOUNDARY OF

UPPER COLORADO

RIVER BASIN

37

3& 112'

25

I

1:2,000,000

50

I_____

75 

I

100 MILES 

_I

25 50 75 100 KILOMETERS

STRATIGRAPHIC NOMENCLATURE AND THICKNESS

110°

43°

' x " V x~ l _ ^\ .

 .pr^,- ^X^,..

AREA EXCLUDED FROM STUDY

112'

38

BOUNDARY OF

UPPER COLORADO

RlVE R BASIN

37° -4

107°

36'

25

I

1:2,000,000

50

I______

75 100 MILES

25

\ 

50 75 100 KILOMETERS

LITHOLOGY

EXPLANATION

Area where Weber-De Chelly zone is missing because of erosion or nondeposition or thrust under Precambrian rocks

Borehole with lithologic log used to prepare map 

Measured surface stratigraphic section used to prepare map

Stratigraphic Nomenclature and Thickness

Area where Weber-De Chelly zone crops out (generalized)

200 Line of equal thickness Location is approximate in central Wyoming because 

of sparse control. Interval is 200 feet, except near Bluff, Utah, and in 

Wyoming, where interval is 100 feet, and in the Strawberry Valley area of Utah, 

where interval is 2,000 feet

Approximate boundary between component geologic units

T' Location of stratigraphic cross section shown in figures 44 and 45

Lithology

Predominantly white, light-gray, tan, and orange quartz sandstone, with 

conglomerate layers and less than 10 percent shale, limestone, and 

dolomite

Predominantly white, light-gray, tan, and orange quartz sandstone, with 

10-30 percent shale interbeds

Predominantly white, light-gray, tan, and orange quartz sandstone, with 

10-30 percent limestone and dolomite interbeds

Approximate boundary between lithofacies

Base from U.S. Geological Survey 

U.S. base map, 1:2,500,000 STRATIGRAPHIC NOMENCLATURE, THICKNESS, AND LITHOLOGY OF THE WEBER-DE CHELLY ZONE OF THE CANYONLANDS AQUIFER IN THE UPPER COLORADO RIVER BASIN AND VICINITY

IN ARIZONA, COLORADO, NEW MEXICO, UTAH, AND WYOMING

By

Arthur L. Geldon 

2002
U.S. DEPARTMENT OF THE INTERIOR

science for a changing world U.S. GEOLOGICAL SURVEY

PROFESSIONAL PAPER 1411-A

Thickness and lithology of the Park City-State Bridge zone PLATE 17

Geldon, A.L, 2002. Geology of Paleozoic rocks in the Upper Colorado River Basin in 

Arizona, Colorado, New Mexico, Utah, and Wyoming, excluding the San Juan Basin

PHOSPHORIA 11 ( 

FORMATION

U'

LOWER 

PART OF 

GOOSE

EGG 

FORMATION

V

*w:$^pm MMi^m&m x ^ " * > x -^ n N \J Jx x ** x ~ ., x vW ^v

Rr : I - -H4- :&- ' \ x * b\ < - '%N

fl>' ^0' ' X 'J7 V ' ' ' 4 7^ V' ' ' ' ^S :lv^^A^-;:>'^

PHOSPHORIA 

FORMATION

-\A \ :^<~; :^'K^^(-k^'^^%^f^^\^-? i\ rj \ V''^'!^ ',' "A'' '» ;'"'T' '* > ^rrH- '' ^t^V'K ;^sL''^/ 'T^''\' /t'

^\^&^;>:V'/^>^V'^^-^^^^^ ^fO X It- \» S K^' I N-3, - ' ;^-^' ' ' J- - \ -- , - ' :""Ai ' ' \-) - 

frfe-v- yL - '/' ^'-*->- \2s~f-L^'\- -fe^^'^^%-v^ ^-\ ,V ' ' ' x-T \ , - ' ' ^,x-Xs\y X 

/^*& \S / * /( - - ^ " ' ?~' - - N " / >5VAx Jtincik)r>-x^ J x - V "~x -' -' ~* ~ '}+,-.'* ~fertirr^ LOW

^V^Ac«:|^-,:i: v,\x>- >Jfc, T^>£W1 i : :'> v,'^v- -^>v:5rT OF^

KAIBAB

AND 

ORO 

RMATIO

fei^S^'

AREA EXCLUDED FROM STUDY

U *-.;*-*::: ^1/109

38

BOUNDARY OF

UPPER COLORADO

RIVER BASIN

37

36'

108°

25

I

1:2,000,000 

50 75

I

100 MILES

\

25 50

I I 

75 100 KILOMETERS

STRATIGRAPHIC NOMENCLATURE AND THICKNESS

110°

43°

y/'; ',-/,r-x''

108°

42°

funtenelle 

f Resnnnii-

-25-

\

o

42°

v-i

1107°

^filing Gorge f 

Reservoir]

/WYOMING 

:OLORAD( v»

x_

\ ^\

40°

<V-3Q 

\S i 'x- ' x x^. "_ 'x - rVr^1 Vjf'\^:l' x-i^«/l'\ 

^>.', '"V^A!- '"^

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1:2,000,000 

50 75

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100 MILES

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25 50 75 100 KILOMETERS

LITHOLOGY

EXPLANATION

Area where Park City-State Bridge zone is missing because of erosion 

or nondeposition or is thrust under Precambrian rocks

Borehole with lithologic log used to prepare map 

Measured surface stratigraphic section used to prepare map

Stratigraphic Nomenclature and Thickness

Area where Park City-State Bridge zone crops out (generalized)

200 Line of equal thickness Interval is 100 feet

 ^ Approximate boundary between component geologic units

 V Location of stratigraphic cross section shown in figures 47, 49, and 50

Lithology

-50-

Predominantly limestone and dolomite, with interbeds of chert,

phosphorite, and shale and less than 10 percent, each, sandstone and 

anhydrite layers

Limestone, dolomite, and sandstone with chert, phosphorite, and shale 

interbeds

Limestone, dolomite, sandstone, and anhydrite (5-30 percent of unit), 

with typically less than 5 percent shale layers

Dark-gray, green, and red shale, with subordinate limestone and dolomite 

layers and less than 10 percent, each, sandstone and anhydrite layers

Sandstone and shale, with less than 10 percent limestone and dolomite

Predominantly red shale with 5-20 percent anhydrite layers and less 

than 30 percent dolomite layers

Line of equal percent limestone, dolomite, chert, and phosphorite 

Interval is 25 percent

Approximate boundary between lithofacies

Base from U.S. Geological Survey 

U.S. base map, 1:2,500,000 STRATIGRAPHIC NOMENCLATURE, THICKNESS, AND LITHOLOGY OF THE PARK CITY-STATE BRIDGE ZONE OF THE CANYONLANDS AQUIFER IN THE UPPER COLORADO RIVER BASIN AND VICINITY

IN ARIZONA, COLORADO, NEW MEXICO, UTAH, AND WYOMING

By

Arthur L. Geldon 

2002
^USGS

science lor a changing world

U.S. DEPARTMENT OF THE INTERIOR 

U.S. GEOLOGICAL SURVEY

PROFESSIONAL PAPER 1411-A

Stratigraphic and hydrogeologic nomenclature TABLE 1

Geldon, A.L., 2002 Geology of Paleozoic rocks in the Upper Colorado River Basin in 

Arizona, Colorado, New Mexico, Utah, and Wyoming, excluding the San Juan Basin

Table 1. Generalized stratigraphic and hydrogeologic nomenclature of Precambrian, Paleozoic, and Mesozoic rocks in the Upper Colorado River Basin [only Mesozoic formations immediately overlying the Paleozoic rocks are listed. Abbreviations used in this 

table include: Fm = Formation; Mbr = Member; Ss = Sandstone; Ls = Limestone; Dol = Dolomite; Sh = Shale. Colors relate component geologic units to hydrogeologic units and are symbolic of the predominant lithology in the hydrogeologic unit: 

yellow and brown indicate sandstone and quartzite; shades of green indicate mostly shale; shades of blue indicate mostly carbonate rocks; other colors indicate mixed lithology. Contacts within series are generalized]

SOUTHWESTERN WYOMING NORTHWESTERN COLORADO NORTHEASTERN UTAH SOUTHEASTERN UTAH NORTHEASTERN ARIZONA SOUTHWESTERN COLORADO

MAXIMUM

THICKNESS,

IN FEET

PERIOD OR 

SYSTEM

ERA OR 

ERATHEM

HYDROGEOLOGIC 

UNIT

EPOCH OR SERIES Northern

Monument

Upwarp

Overthrust 

Belt

Rawlins 

Uplift

Eastern 

Eagle Basin

Southeastern 

Uinta Mountains

San Rafael 

Swell

Wind River 

Mountains

White River 

Plateau

Elk 

Mountains

Southwestern 

Uinta Basin

Henry 

Mountains Basin

Marble 

Platform

Defiance 

Plateau

Four Corners 

Platform

San Juan 

Mountains

Late or 

Upper

JURASSIC

Not discussed

in this report.

(See Freethey

andCordy, 1991)

Early or 

Lower Wingate Sandstone

Not discussed

in this report.

(See Freethey

andCordy, 1991)

Late or 

Upper

Chinle Formation

Chinle Formation Dolores Formation

Petrified Forest Mbr

TRIASSIC Shinarump Member Shinarump Member

Early or 

Lower

Chinle-Moenkopi 

confining unit

Little Medicine Moenkopi Formation Moenkopi Formation Moenkopi Formation Moenkopi Formation

Mbr 

Freezeout Sh Mbr

Moenkppi 

Formation Dinwoody 

Formation

Dinwoody 

Formation Woodside Shale Hoskinnini Member Lower Red Member

upper shale 

member

upper shale 

Ervay Limestone member

_ ember 2 TostCh 

Mbr

Late or 

Upper

Guadalupian Phosphatic 

Shale Mbr b

S Canyon Cr Dol Mbr S. Canyon Cr Dol Mbr State

Bridge

Formation

Glendo Shale Mbr

Mackentire Tongue Park City-State Bridge zone

1 MeadePeak of Woodside Shale

Phosohatic

lower shale Kaibab Formation

member

lower shale 

member

Kaibab Formation Opeche Shale Member

 Meade Peak Kaibab Formation

Phosphatic Shale 

Member h

Phosphatic Park City Formation

Shale Member D

Toroweap Formation

Shale Member b White Rim 

Leonardian Sandstone Coconino Sandstone White House Mbr De Chelly Sandstone Weber-De Chelly zone Oak Springs Mbr

Grandeur 

Member

Organ Rock 

Shale

Organ Rock 

Early or Shale

Lower

1 Grandeur Member 3 Hunters Point Mbr White Rim 

Sandstone

Cedar Mesa 

Sandstone

Cedar Mesa 

Sandstone

Cutler Formation

Weber 

Cutler Formation Wolfcampian Sandstone Esplanade 

Sandstone

Supai Formation

Fryingpan Member of* 

Maroon Formation

Schoolhouse Member 

of Maroon Formation

Weber Sandstone

Elephant

Canyon

Formation

Elephant

Canyon

Formation Weber Sandstone Cutler-Maroon zone

Morgan Formation 

and equivalents 9

i/Vescogame Formation Late or 

Upper

Maroon Formation

Wells 

Formation

Maroon Formation Maroon Formation Missounan Tensleep 

Sandstone Tensleep 

Sandstone

I jacque MI LS MDr Desmoinesian PENNSYLVANIAN Minturn Formation Paradox Member Paradox Member Paradox Member Paradox Member Paradox Member Paradox Member Paradox-Eagle Valley subunit Morgan Formation Manakacha Formation Ranchester

Limestone

Member Ranchester Belden Formation Belden Formation Belden Formation

Limestone

Member

Ranchester

Limestone

Member

Early or 

Lower

Round Valley Limestone

Round Valley Molas Formation Molas Formation Molas Formation Watanomigi Formation Molas Formation Molas Formation Limestone

Horseshoe Sh Mbr Molas Formation Molas Formation Molas Formation

Belden-Molas subunit Moffat Trail Ls Mbr Doughnut Shale Doughnut Formation Surprise Canyon 

Formation Late or 

Upper

Chesterian Horseshoe Sh Mbr Horseshoe Sh Mbr

Meramecian Humbug Formation Humbug Formation Darwin-Humbug zone

Mission Canyon 

Limestone

Little Tongue Mbr Little Tongue Mbr

MISSISSIPPIAN Mooney Falls Mbr Mooney Falls Mbr Mooney Falls Mbr

Woodhurst 

Member

Woodhurst 

Member

Woodhurst 

Member Early or Leadville Limestone Leadville Limestone Leadville Limestone

Lower

Thunder Springs 

Member

Thunder Springs 

Member

Thunder Springs 

Member

Redwall Limestone Redwall Limestone Madison Limestone

Redwall Limestone

Kinderhookian Whitmore Wash Leadville Limestone Leadville Limestone Redwall-Leadville zone

basal sandstone mbr Gilman Sandstone Member

x_^--x_^~s-^ S*.

Dyer Dolomite

Gilman equivalent 

Dyer Dolomite

Canyon Member

Ouray Limestone Ouray Limestone Ouray Limestone Ouray Limestone Ouray Limestone Ouray Limestone Ouray Limestone

Late or 

Upper

Temple Butte 

Formation Darby 

Formation

Darby 

Formation Parting Formation Parting Formation Parting Formation Elbert Formation Elbert Formation Elbert Formation Elbert Formation Elbert Formation Elbert Formation Elbert-Partmg confining unit DEVONIAN

Early or 

Lower

Leigh Dolomite Member Leigh Dolomite Member Late or 

Upper Bighorn Dolomite Bighorn Dolomite Fremont Limestone

 N . . . *^~^^^s

Harding Sandstone

Bighorn aquifer I Lander Ss Mbr ORDOVICIAN Harding Sandstone

Early or 

Lower W//////'////////,

en 

Limestone Member Dotsero Lynch Dolomite Lynch Dolomite Formation Lynch Dolomite Gallatin Peerless Formation

Limestone Dry Creek Shale Peerless Formation

Late or Member 2

Upper

Muav 

Muav 12 equivalent Gros Ventre confining unit

equivalent Du Noir Limestone 

mber Sawatch Quartzite Maxfield Limestone Maxfield Limestone Muav 

Limestone

Bright Angel 

equivalent Sawatch Quartzite Maxfield Limestone Gros Ventre 

Formation

Sawatch Quartzite

Park Shale 

Member

Ignacio Quartzite

Gros Ventre 

Formation

Bright Angel 

CAMBRIAN Death Canyon equivalent

Limestone

Member

Flathead 

Sandstone Lodore Formation 8 Ignacio Quartzite

Flathead aquifer

Wolsey Shale 

Member

Flathead 

Sandstone

Tapeats 

equivalent Tintic Quartzite

Flathead 

Sandstone

Tapeats 

Sandstone

Tintic Quartzite Tintic Quartzite

Early or 

Lower

Not discussed

in this report.

(See Hedge and

others, 1986)

Basal confining 

unit

Red Pine Shale

Nankoweap Fm

Uinta Mountain 

Group Uinta Mountain 

Group

St. Kevin Granite

Slightly metamorphosed

sedimentary and

volcanic rocks

Uncompahgre 

Formation

Granitic and

metamorphic

rocks

Zoroaster 

Complex

Granitic and

metamorphic

rocks (?)

Granitic and

metamorphic

rocks

Granitic and

metamorphic

rocks

Granitic rocks Granitic rocks Granitic and

metamorphic

rocks

Granitic and

metamorphic

rocks

Granitic and

metamorphic

rocks

Metamorphic rocks

Granitic and 

metamorphic 

rocks (?) 14

Granitic and

metamorphic

rocks (?)

Granitic and

metamorphic

rocks (?)

Red Creek 

Quartzite

FOOTNOTES

1. As suggested by McKelvey and others (1959), designation of the rocks of Park City/Phosphoria 

age as either "Park City Formation" or "Phosphoria Formation" is based on the predominant rock 

types, and each formation can include tongues of the other. Members of the Park City 

Formation are denoted by the letter a; members of the Phosphoria Formation are denoted by 

the letter b.

2. Of Shaw (1957); included in Open Door Limestone in some reports (for example, Keefer 

and Van Lieu, 1966).

3. Of Maughan (1980); also called South Canyon Creek Member (by Freeman, 1971, for example).

4. Of Johnson (1989); formerly considered a member of the State Bridge Formation (Freeman, 1971).

5. Of Langenheim (1952); also called "Minturn Formation."

6. The name "Mackentire Tongue of Woodside Shale," as used by McKelvey and others (1959), is applied 

to a sequence of red shale within the Park City Formation in the Uinta Mountains, even though the 

Woodside Shale generally is considered to be Triassic. Therefore, either the Mackentire Tongue is 

not a tongue of the Woodside Shale, or the Woodside Shale is partly Permian.

7. As indicated by Hallgarth (1959) and correlations made during this study, the lowermost beds of the 

Madison Limestone in the southeastern Uinta Mountains correlate with the uppermost beds of the 

Dyer Dolomite of northwestern Colorado. Therefore, either the uppermost Dyer Dolomite is Mississippian, 

as shown here, or the lowermost Madison Limestone in the southeastern Uinta Mountains is Late Devonian.

8. According to Untermann and Untermann (1954), fossils from the upper (shaly) part of the Lodore 

Formation where it crops out in the southeastern Uinta Mountains date the upper part of the Lodore 

Formation (an equivalent of the Gros Ventre Formation) as Late Cambrian. However, the lower part of the 

Lodore Formation (an equivalent of the Flathead Sandstone, Sawatch Quartzite, and Tintic Quartzite) is 

unfossiliferous. The age of the lower part of the Lodore Formation here is inferred to be Middle and 

Late Cambrian from its geographic position relative to equivalent quartzite/sandstone units. These 

formations range from Middle Cambrian on the north and west to Late Cambrian on the east.

9. Even though the Morgan Formation is considered to be Middle Pennsylvanian where it crops out in 

the Uinta Mountains (for example, Hansen and others, 1983), it can be traced southward in the 

subsurface into beds of the Elephant Canyon Formation of Baars (1962). Because the Elephant Canyon 

Formation is Early Permian where it crops out in the Monument Upwarp, both the Morgan and Elephant 

Canyon Formations must be Pennsylvanian and Permian in age where they merge (north of the San 

Rafael Swell).

10. The Round Valley Limestone correlates in the subsurface with the Eagle Valley Evaporite and the 

Paradox Member of the Hermosa Formation, both of which are Middle Pennsylvanian in age. Because 

the Round Valley Limestone where it crops out in the Uinta Mountains is Early Pennsylvanian, it is 

inferred to be time-transgressive in the subsurface. Hence, in the southwestern Uinta basin, where it 

merges with the Paradox Member, the Round Valley Limestone is interpreted to be Early and Middle 

Pennsylvanian. Similarly, the Doughnut Shale (Formation) is interpreted to be time-transgressive and 

is considered Late Mississippian and Early Pennsylvanian in the southwestern Uinta basin.

11. The Cutler Formation in southeastern Utah becomes divisible into several distinct units, to which 

the U.S. Geological Survey assigns member rank. Baars (1962), however, assigned these units 

formation rank and the Cutler, group rank, in southeastern Utah. A sequence of carbonate and clastic 

rocks that grades into the lowermost shaly beds of the Cutler was designated by Baars (1962) as the 

Elephant Canyon Formation. The nomenclature of Baars (1962) regarding the Cutler rocks is used 

in this report.

12. Cambrian units cropping out in the Grand Canyon, the Tapeats Sandstone, Bright Angel Shale, 

and Muav Limestone, were traced during this study into northeastern Arizona and southwestern 

Colorado by means of borehole lithologic logs. Because no names for the shale and carbonate 

units currently are recognized by the U.S. Geological Survey in Colorado, the names "Bright 

Angel equivalent" and "Muav equivalent" were used beyond the Grand Canyon area where 

rocks characteristic of the Bright Angel Shale and Muav Limestone, respectively, were identified. 

An equivalent of the Tapeats Sandstone crops out in the San Juan Mountains of Colorado, where 

it is called the Ignacio Quartzite. In this report, an axis of thinning in southwestern Colorado was 

considered the boundary between the extension of the Tapeats Sandstone beyond the Grand 

Canyon area, the "Tapeats equivalent," and the Ignacio Quartzite. As shown by Baars (1983, p. 54), 

the Cambrian geologic units become progressively younger from the Grand Canyon to the San Juan 

Mountains. Hence, in the Defiance Plateau and Four Corners platform columns, the ages of the Tapeats 

equivalent, Ignacio Quartzite, Bright Angel equivalent, and Muav equivalent are depicted as intermediate 

between ages in outcrop areas to the west and east.

13. Excluding salt diapirs of small areal extent that can be as much as 15,000 feet thick.

14. Although Precambrian rocks do not crop out and have not been penetrated by boreholes in the 

Overthrust Belt within the Upper Colorado River Basin, Archean granitic and metamorphic rocks 

are exposed in the Farmington complex, about 30 miles west of the Utah-Wyoming State line 

(Bryant, 1988).