\ \

Cretaceous Paleogeography 

of Southeastern Arizona 

and Adjacent Areas

GEOLOGICAL SURVEY PROFESSIONAL PAPER 658-B
Cretaceous Paleogeography 

of Southeastern Arizona 

and Adjacent Areas

By PHILIP T. HAYES

MESOZOIC STRATIGRAPHY IN SOUTHEASTERN ARIZONA

GEOLOGICAL SURVEY PROFESSIONAL PAPER 658-B

Brief descriptions of local Cretaceous 

sequences their correlation, interpretation^ 

and economic potential

UNITED STATES GOVERNMENT PRINTING OFFICE, WASHINGTON : 1970
UNITED STATES DEPARTMENT OF THE INTERIOR 

WALTER J. HICKEL, Secretary

GEOLOGICAL SURVEY 

William T. Pecora, Director

Library of Congress catalog-card No. 74-607329

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

Washington, D.C. 20402 - Price 50 cents (paper cover)
CONTENTS

Abstract_______________________________

Introduction. ________________________________

Paleogeography______________________________

Pre-Cretaceous surface._________________________

Early Cretaceous paleogeography_______________

Early Late Cretaceous disturbance______________

Late Late Cretaceous paleogeography.__________

Latest Cretaceous-earliest Tertiary orogeny________

Regional stratigraphy.______________________________

Geologic setting-_____________________________

Lower Cretaceous volcanics-__-------_-----__-___

Bisbee Group and correlatives __________________

Pinkard Formation and correlatives_______ ________

Fort Crittenden Formation and correlatives________

Salero Formation and correlatives____________

Descriptions of local sequences_______________________

Principal study area________________________

Mule Mountains, Ariz., to Cabullona Basin, 

Sonora___ ______________ ______

Huachuca Mountains and Canelo Hills. _______

Patagonia Mountains._____________________

Whetstone and Empire Mountains______ _ 

Santa Rita Mountains________________

Sierrita Mountains____________________

Areas to west_____________________ ________

Tucson Mountains___-___-_---_-_______-____

Roskruge Mountains__________________

Silver Bell Mountams____---_---__-----____-

Page

Bl

1

3

3

4

5

5

7

8

8

9

9

15

16

17

17

17

17

19

21

21

23

24

26

26

26

26

Page

Descriptions of local sequences Continued 

Areas to west Continued

Vekol Mountains..._______________ B27

Other areas-___________________________ 27

Areas to east____________ _ ______ _ 27

Dragoon Mountains and Tombstone area. __ 27 

Dos Cabezas and northern Chiricahua Mountains ______________ _ ____________________ 28

Pedregosa and central and southern Chiricahua

Mountains-. ___________ _____ ________ 28

Peloncillo Mountains, N. Mex. and Ariz_______ 29

Big Hatchet and Animas Mountains, N. Mex__ 30

Little Hatchet Mountains, N. Mex __ 30

Other areas----- ________ ________ 32

Areas to north________________ __________ 32

Winchester and Little Dragoon Mountains___ 32

Northern Santa Catalina Mountains area_-____ 32

Morenci to Christmas area________ ______ 33

Silver City-Santa Rita area, New Mexico _ 33

Outlying regions_______________ __________ 34

Sonora, Mexico________----_--------- ___ 34

Southwestern Arizona______________-_____-__ 35

Northern Arizona and New Mexico.______-__- 35

Western Texas and ad joining areas ________ 36

Economic geology of Cretaceous strata___ _________ 36

References cited__________-__-_----_--_------------- 37

Index.__________________________________________ 41

ILLUSTRATIONS

FIGURE 1. Map of southeastern Arizona and adjacent areas, showing areas for which large-scale geologic maps have been 

published. _____________________________________________________________________.

2. Paleogeology and topography of southeastern Arizona and adjacent areas at end of Jurassic and beginning of 

Cretaceous time____________________________________________________________

3. Paleogeographic maps of southeastern Arizona and adjacent areas during the Cretaceous____ 

4. Map of southeastern Arizona and adjacent areas, showing location of geographic features mentioned in text. _

5. Correlation chart of Cretaceous formations in southeastern Arizona and southwestern New Mexico.------------

6. Line of columnar sections, showing inferred correlations of rocks of Bisbee age______________________ _

Page 

B2

3

6

8

10

12

in
MESOZOIC STRATIGRAPHY IN SOUTHEASTERN ARIZONA

CRETACEOUS PALEOGEOGRAPHY OF SOUTHEASTERN 

ARIZONA AND ADJACENT AREAS

By PHILIP T. HATES

ABSTRACT

The surface geology and topography of the report region at 

the beginning of Cretaceous time were diverse. During early 

Early Cretaceous time, the region was shedding sediments southeastward toward a sea in Mexico, and some volcanic activity 

occurred in a part of southeastern Arizona. By early Aptian 

time, the sea had advanced northwestward nearly to Arizona, and the region became the locus of coastal-plain sedimentation. By Albian time, the sea had advanced into Arizona 

and may have made connection with Pacific waters across 

northern Sonora. Later in Albian time, this connection may have 

been broken, and prograding deltaic sedimentation pushed the 

sea southeastward out of Arizona. Near the end of Early Cretaceous time, general tilting of the region caused the seas to 

retreat from areas south of Arizona and to advance northward 

across much of New Mexico and westward into Arizona north 

of lat 32°30' N. Compressional tectonism is late Turonian 

time made southeastern Arizona a mountainous source area 

for sediments transported northwestward to the sea. By early 

Campanian time, broad valleys in this mountainous area were 

receiving largely fluvial sediments from the surrounding 

mountains. The region was the scene of widespread volcanism 

in late Campanian and probably Maestrichtian time. This was 

followed by plutonism and tectonism of the Laramide orogeny 

at the end of the Cretaceous and beginning of the Tertiary.

This sequence of events is interpreted from the Cretaceous 

strata preserved in southeastern Arizona and adjacent areas 

and from the probable relations of these strata to Cretaceous 

strata of surrounding regions. The oldest Cretaceous rocks in 

southeastern Arizona are volcanics and associated sedimentary 

rocks assigned an early Early Cretaceous age. These are 

succeeded mostly south of lat 32° N. by the Bisbee Group and 

correlatives of late Early Cretaceous age a thick sequence of 

rocks that is largely of marine origin toward the east and of 

continental origin toward the west. Strata of early Late Cretaceous age in Arizona are found only in areas north of about 

lat 32°30' N. and are represented by the Pinkard Formation 

and correlatives of near-shore continental and marine origin. 

Upper Upper Cretaceous sedimentary rocks dominantly of 

fluvial origin, represented by the Fort Crittenden Formation 

and correlatives, are only locally present and are in unconfonnable relation with earlier Cretaceous strata. Conformably 

overlying these strata are the Salero Formation and correlatives made up dominantly of andesitic and rhyolitic volcanics.

Most Cretaceous strata in southeastern Arizona are only of

modest economic value or potential, but the youngest are 

commonly altered and locally contain disseminated copper 

deposits. Limestones of the Bisbee Group are locally quarried, 

and some of them offer possibilities as reservoir rocks for oil 

and gas.

INTRODUCTION

Much new information on Cretaceous rocks and 

their relations to other rocks has been gathered in the 

past several years as a result of geologic mapping by 

the U.S. Geological Survey in twelve 15-minute quadrangles in the area south and southeast of Tucson, 

Ariz. This principal study area, which includes the 

Sierrita, Santa Kita, Empire, Whetstone, Patagonia, 

Huachuca, and Mule Mountains, was mapped by J. K. 

Cooper, S. C. Creasey, Harald Drewes, T. L. Finnell, 

E. K. Landis, K. B. Kaup, F. S. Simons, and me (fig. 

1). This work, supplemented by data from the literature and my observations on Cretaceous localities in 

nearby areas in Arizona, New Mexico, Sonora, and 

Chihuahua makes it possible for the first time to present a coherent, though very imperfect, history of 

Cretaceous events in southeastern Arizona and adjacent 

areas. The imperfection of the story is due to several 

factors: (1) although Cretaceous rocks crop out in most 

ranges in the region, these exposures are separated by 

much more extensive areas where Cretaceous rocks 

either have been removed by post-Cretaceous erosion or 

have been buried by younger deposits that, to date, have 

been virtually unpenetrated by drill holes; (2) Cretaceous rocks in many areas outside our area of mapping 

have been only superficially examined; (3) in many 

areas throughout the region, Cretaceous rocks have 

been faulted, folded, and, in places, altered to such an 

extent that they are particularly subject to misinterpretation ; and (4) great thicknesses of the Cretaceous 

sequence in the region, particularly toward the west, 

are devoid of fossils that are useful for precise stratigraphic zonation. Some of these factors offer nearly inBl
B2

112'

MESOZOIC STRATIGRAPHY IN SOUTHEASTERN ARIZONA

111° 110° 109° 108'

33

32'

31-'

/"~T T~ II_ _ 

i i

\ ARIZONA | NEW MEXICO

\TEXAS

cnwnuA CHIHUA-\ SONORA S HUA \

'-^

 %/3So

^^»

i i it

50

I

100 MILES

75

... i

150 KILOMETERS

_I

1. Kansome (1904)

2. Eansome (1923)

3. Wfflden (1964)

4. Krieger (1968d)

5. Krieger (1968a)

6. Krieger (1968c)

7. Krieger (1968b)

8. Simons (1964)

9. Creasey (1967a)

10. Lindgren (1905)

11. Morrison (1965)

12. Grfegs and Wagner (1966)

13. Elston (1957)

14. Jicha (1954)

15. Jones, Hernon, and Moore (1967)

16. Pratt (1967)

17. Cooper (1960)

18. Brown (1939)

19. Cooper and Silver (1964)

20. Sabins (1957a)

21. GiUerman (1958)

22. Flege (1959)

23. Drewes (1970b)

24. Creasey (1967b)

25. Gilluly (1956)

26. Drewes (1970a)

27. Hayes and Kaup (1968)

28. Hayes and Landis (1964)

29. Zeller (1958b)

30. Wrucke and Brotnfield (1961)

31. Zeller (1962)

32. Zeller and Alper (1965)

33. Zeller (1958a)

34. Bromfield and Wrucke (1961)

35. Lasky (1947)

FIOUEE 1. Southeastern Arizona and adjacent areas, showing areas for which large-scale (1:62,500 or larger) geologic maps 

have been published. Shading indicates relatively recent detailed mapping; stippling indicates reconnaissance, preliminary, 

or relatively old mapping.
CRETACEOUS PALEOGEOGRAPHY B3

surmountable difficulties, but others will be overcome 

as new areas are studied in detail, as existing and newly 

developed methods of sedimentary analysis and correlation are applied to the rocks, and as drill holes penetrate Cretaceous rocks in areas where they are now 

covered by younger deposits.

In this report, my interpretations of the Cretaceous 

history of the region, illustrated by a series of paleogeographic maps, are presented first. The paleogeographic maps are drawn without regard to variously 

postulated large thrust or strike-slip displacements in 

the region in the belief that even if post-Cretaceous 

displacements measurable in tens of miles did occur, 

such displacements would only change the configuration of some features and would not invalidate the 

overall patterns presented. The paleogeographic interpretations are followed by a description of the 

regional stratigraphic framework that has evolved and 

upon which the paleogeographic interpretations are 

largely based. Following this are summary descriptions of Cretaceous rocks at many localities throughout the region that form the basis for the stratigraphic 

framework. In these descriptions are found most of 

the references to the numerous papers and unpublished

data from which I have so freely drawn. At the end 

of the report are comments on the economic geology 

of Cretaceous strata in the region.

PALEOGEOGRAPHY 

PRE-CRETACEOUS SURFACE

The surface geologic and topographic features of 

southeastern Arizona and adjacent areas at the end of 

the Jurassic Period and beginning of the Cretaceous 

Period were diverse (fig. 2). They resulted from Triassic and Jurassic faulting, plutonism, volcanism, and 

erosion in different parts of the region. Southeastern 

Arizona, in general, was positive late in Jurassic time 

and was a source area for sediments now represented by 

the Morrison Formation of northern Arizona (Harshbarger and others, 1957, p. 51-57). Southeastern Arizona probably also contributed sediments eastward to 

Chihuahua and western Texas to a seaway whose sediments are now preserved as the Malone Formation 

(Albritton and Smith, 1965, p. 37-38). Sediments from 

the region may also have been shed southwestward to 

western Sonora, where Upper Jurassic sedimentary 

rocks may still be preserved in the vicinity of El 

Antimonio (fig. 4). The topography in the southeastern

112° 108°

 ' ' -Triassic red beds! 

' (Relatively Jow)',- C- ' ' '.-". - : 

.Diverse. are& covered Jtrjpstly^isy 

Paleozoic strata jaut-with/fiij^ 

areas ,of PrecalfnbHan anil «! 

Jurassic plutonic rocks:ari4J 8 

>1pw areasspf Triassic and I 

Jurassic Atolcanic and epiclas- -" * 

tic rocks;tCclrisidefabJe;local>e)jef)

/l'X'"M'osWy Triassic' sedimentary '. '.'. " '. X'X"X'."-~'Xf

Mostly Permian strata 

(Near sea level but with 

i scattered hills)

Jurassic marine rocks 

(Near sea level)

-' X'-rocks toward the south

 . .' " and west and Permian 

".-" ". . sedimentary rocks toward. 1

\

CHIlJNjJAHUA

FIGURE 2. Paleogeology and topography of southeastern Arizona and adjacent areas at end of Jurassic and beginning of Cretaceous

time.
B4 MESOZOIC STRATIGRAPHY IN SOUTHEASTERN ARIZONA

Arizona positive region was irregular, particularly 

toward the west. Local relief there, which was measurable in many hundreds or even thousands of feet, was 

controlled largely by the character and structure of 

the underlying rocks.

The rocks exposed at the beginning of Cretaceous 

time were greatly diverse in age and character (fig. 2). 

Over a large part of the region, gently tilted and littlefaulted dominantly carbonate rocks of Permian age, 

which had been eroded into a gently rolling topography, were at the surface. In southernmost Arizona, 

however, there were many topographically low areas 

underlain by volcanic or epiclastic rocks of Triassic 

and Jurassic age and topographically high areas held 

up by plutonic rocks of the same ages or by uplifted 

blocks of older Paleozoic or Precambrian rocks. In 

western New Mexico between lat 32° and 33° N. there 

was a broad west-northwesterly trending upwarped 

area largely underlain by Precambrian granitic rocks. 

A similar high area can be postulated to the west in 

Arizona, but evidence for it is less compelling.

EARLY CRETACEOUS PALEOGEOGRAPHY

The positive area that existed in southeastern Arizona at the outset of the Cretaceous Period probably 

remained virtually unchanged through about the first 

half of Early Cretaceous time and continued to shed 

sediments southeastward to a seaway in Mexico. This 

seaway may have advanced from the Gulf of Mexico 

to northern Chihuahua by late Neocomian time (fig. 

2>A ). At about this time in southeastern Arizona, there 

was local volcanic activity in the vicinity of the present 

Sierrita, Santa Rita, and Huachuca Mountains (fig. 4), 

as indicated by the presence of volcanics in the quartzite of Whitcomb Hill in the Sierrita Mountains area, in 

the Temporal and Bathtub Formations in the Santa 

Rita Mountains, and in the Glance Conglomerate in 

the Huachuca Mountains (fig. 5). Low areas in these 

ranges and probably elsewhere were the sites of fanglomerate deposition during the same general time 

interval.

By early Aptian time, the sea had advanced to a 

position closer to Arizona, and coastal-plain sediments 

were deposited in extreme southwestern New Mexico 

and extreme southeastern Arizona (fig. SB). These 

sediments are preserved in the Hell-to-Finish Formation of Zeller (1965) in the Big Hatchet Mountains 

of New Mexico, in the basal part of the Howells Eidge 

Formation in the Little Hatchet Mountains of New 

Mexico, and in beds low in the Bisbee Formation or 

Group in several places in extreme southeastern 

Arizona (fig. 5). Farther west in southeastern Arizona,

fanglomerate deposition, now represented in several 

ranges by the Glance Conglomerate, continued in 

valleys in foothill areas adjacent to the old mountainous area farther west. The Etholen Conglomerate and 

generally equivalent Torcer Formation of the Sierra 

Blanca area in western Texas (fig. 4) are interpreted 

by Albritton and Smith (1965, p. 45) to have been 

deposited near a shoreline and may have been deposited at about this same time of seaway expansion 

in early Aptian time.

Westward and to a lesser extent northward and 

probably eastward, general but irregular seaway expansion continued through Aptian time; and by the beginning of Albian time, the seaway may have made 

connection with Pacific waters across northern Sonora 

(fig. 3C). The general but irregular westward advance 

of the sea from southwestern New Mexico into southeastern Arizona is interpreted from correlations of 

rocks of the Bisbee Group and equivalents discussed 

on pages B9-B15 Marine limestones are much thicker in 

southwestern New Mexico than in southeastern Arizona and apparently occur at a stratigraphically lower 

position. That the sea may have made connection with 

Pacific waters, at least in late Aptian time, is indicated 

by the presence of fossils of Pacific affinities noted by 

Stoyanow (1949, p. 50-58) in rocks of Aptian age in 

the Mule Mountains area, and by the presence of 

Bisbee-like rocks of Aptian and Albian age as far west 

as the Santa Ana-Altar area (fig. 4) in Sonora (Popenoe and others, 1960, p. 1517-1518).

The maximum advance of the sea into southwestern 

Arizona occurred in early Albian time (fig. 2>C). Marine waters then advanced as far west as the position of 

the present Patagonia Mountains and as far north as 

the northern part of the present Chiricahua Mountains (fig. 4). Flood-plain sediments probably of the 

same age were deposited as far northwest as the present Boskruge Mountains, but areas as far west as the 

present Vekol Mountains apparently remained slightly 

positive throughout Early Cretaceous time. Brackishwater sediments were deposited on the flood plain in 

areas as far northwest as the present Tucson Mountains. 

This is indicated by limestones that contain brackishwater fossils in the Amole Arkose of Brown (1939). 

(See fig. 5.) Even as late as early Albian time, mendip 

hills of older bedrock projected through the coastalplain sediments in the vicinity of the present Whetstone and Empire Mountains. At this time of maximum 

advance, rudistid reefs and biostromes flourished in 

shallow off-shore waters in the vicinity of the present 

Mule Mountains and in areas to the east that extend 

into New Mexico. Fossil rudistid banks of the same
CRETACEOUS PALEOGEOGRAPHY B5

age are preserved in the Campagrande Formation of 

the Sierra Blanca area of western Texas (Albritton and 

Smith, 1965, p. 62). Conglomerate and interbedded 

limestone mapped beneath the Cox Sandstone by King, 

King, and Knight (1945) in the Hueco Mountains 

northwest of the Sierra Blanca area may have been 

deposited near the shoreline of the early Albian sea.

By middle Albian time (as represented by rocks 

equivalent to the Fredericksburg Group of Texas), the 

sea had apparently retreated from southeastern Arizona 

and probably from western Sonora as well, but it seems 

to have remained briefly in southwestern New Mexico 

(fig. 3Z>), as indicated by marine fossils of probable 

Fredericksburg age near the top of the U-Bar Formation of Zeller (1965) (fig. 5). The Cintura Formation 

and equivalents in southeastern Arizona of this general 

age are interpreted to have been deposited on the subaerial part of a prograding delta. Later in middle 

Albian time, continental deltaic sedimentation extended 

across the New Mexico Pandhandle and is now represented by the lower parts of the Corbett Sandstone and 

the Mojado Formation of Zeller (1965). The regression 

of the sea from Arizona may have been due more to a 

slight northeastward tilting of the region than to a 

eustatic lowering sea of level. This is indicated by the 

fact that marine sediments of Fredericksburg age spread 

northward and eastward over areas in western Texas 

not covered by older Cretaceous marine sediments 

(Albritton and Smith, 1965).

General northeastward regional tilting continued 

into late Albian and early Cenomanian time (as represented by rocks equivalent to the Washita Group of 

Texas). By this time, sedimentation had apparently 

ceased altogether in southernmost Arizona and Sonora, 

and the seas spread over much of New Mexico and into 

eastern Arizona north of lat 32°30' N. (fig. 3#). This 

latter transgression is represented by the Beartooth 

Quartzite and Colorado Formation and equivalents of 

New Mexico and by part of the Pinkard Formation of 

Arizona (fig. 5). Marine sedimentation resumed briefly 

during part of this time in southeastern New Mexico, 

as indicated by the presence of marine fossils of 

Washita age in the upper part of the Mojado Formation of Zeller (1965) in the Big Hatchet Mountains 

area.

During most of Turonian time (as represented by 

rocks equivalent to the Eagle Ford Shale of Texas), 

conditions presumably remained much as they were 

during late Albian and Cenomanian time, when seas 

covered much of New Mexico and northeastern Arizona 

while southeastern Arizona and Sonora remained 

emergent.

EARLY LATE CRETACEOUS DISTURBANCE

The first pulses of the Piman phase (Drewes, 1968) 

of the Laramide orogeny in southeastern Arizona took 

place sometime before mid-Late Cretaceous time. This 

disturbance consisted of compressional tectonism that, 

in the position of the present Huachuca Mountains 

(fig. 4), thrust faulted rocks of the Bisbee Group and, 

in the position of the present Empire Mountains and 

elsewhere, isoclinally folded those rocks into northwesttrending structures before the onset of deposition of 

the Fort Crittenden Formation and younger units.

The disturbance cannot be precisely dated. Although 

it could have taken place steadily or intermittently 

throughout Turonian, Coniacian, and Santonian time, 

I think it is more probable, on the basis of broad 

regional evidence, that the tectonism occurred largely 

or entirely in late Turonian time (fig. 3F). Mountains 

uplifted during the disturbance may thus have been 

the source for the detrital sediments of the Gallup 

Sandstone of late Turonian age, the basal formation of 

the Mesaverde Group, which spread far northeastward 

in northwestern New Mexico over lower Turonian 

marine shales. An unconformity described by Dane 

(1960, p. 53-55) at the base of beds of Niobrara age in 

northwestern New Mexico and southwestern Colorado 

indicated submarine erosion in that area in late Turonian time that may have been roughly coincident with 

tectonism in southeastern Arizona. Similarly, at many 

localities in western Texas, the top of the Eagle Ford 

Shale of Turonian age has been interpreted as a surface 

of subaerial erosion or marine planation (West Texas 

Geol. Soc. 1959, p. 37). Such a hiatus is also apparent 

in southern California where Turonian or younger 

rocks rest locally on rocks of Albian age but more 

commonly on rocks of Neocomian or older age 

(Popenoe, 1954).

LATE LATE CRETACEOUS PALEOGEOGRAPHY

After the tectonism of postulated late Turonian age, 

southeastern Arizona was an eroding mountainous 

area, and, probably through Coniacian, Santonian, and 

into Campanian time it was a prime source area for 

the continental sediments of the Mesaverde Group of 

New Mexico and northeastern Arizona (fig. 36r). Sediments probably also were shed east-southeastward during this time across a low plain toward western Texas 

and Chihuahua.

Early in late Campanian time, the seas made a last 

major advance toward southeastern Arizona owing 

either to a general subsidence of much of the Western 

United States and Mexico or to a eustatic change in sea 

level (fig. 3ZT). This advance is recorded in northwest381-840 70-
B6 MESOZOIC STRATIGRAPHY IN SOUTHEASTERN ARIZONA

As

MOUNTAINS

 ^COASTAL 

LOWLAND

t==5 prr~ -

PLAIN x -SEAA. LATE NEOCOMIAN(?) B. EARLY APTIAN

D. MIDDLE ALBIAN -. LATE ALBIAN TO EARLY CENOMANIAN

G. SANTONIAN

\OLD MOUNTAINS""""""//,

PIEDMONT' 

PLAIN

H. EARLY LATE CAMPANIAN

FIGURE 3. Paleogeographic maps of southeastern Arizona and adjacent areas during the Cretaceous.
CRETACEOUS PALEOGEOGRAPHY B7

C. EARLY ALBIAN

5C*'"" 

A ACTIVELY RISING i

MOUNTAINS

fl LATE TURONIAN

X

x

X

"""

X

X

X X X^s.

X X X X

XXX

VOLCANIC

X x FIELD x

XXX

*V-^^ xxx

XXX

V s

^y^

X ;

X 

t

X S U/J

X X X X. X | '

\ \

X X X X \ 1

XXX X X j (

s

LOW PLAIN

1

^

___ c~

svv

_^_

 FLOOD

 -PLAIN

/. LATEST CAM PAN I AN

ern New Mexico by the Lewis Shale. A northwestward 

advance of the sea may have extended to the vicinity of 

the present Cabullona Basin in Sonora (fig. 4), where 

the Cabullona Group of Taliaferro (1933) (fig. 5) was 

deposited. This thick group of rocks, though largely 

of fluvial origin, contains fossils of brackish-water 

invertebrates that may have thrived in an estuarine 

environment. Broad but deep intennontane valleys

in southeastern Arizona and southwesternmost New 

Mexico, tributary to the estuary, locally received great 

thicknesses of dominantly fluvial sediments ranging 

in composition from clays to conglomerates; intermittently, fanglomerates derived from bordering 

mountains were deposited in the valley areas. These 

valley sediments in Arizona and southwestern New 

Mexico are now represented by the Fort Crittenden 

Formation and its equivalents. Between the valley 

areas were low mountains that supplied sediment to 

the valleys and to the seas beyond.

Near the end of Campanian time, the seas once again 

receded far to the east; and southern Arizona, southwestern New Mexico, and much of Sonora became the 

scene of widespread volcanic activity (fig. 37) which 

initiated the later stages of the Piman phase of the 

Laramide orogeny.

LATEST CRETACEOUS-EARLIEST TERTIARY OROGENY

The later stages of the Piman phase of the Laramide 

orogeny in southeastern Arizona and adjacent areas in 

late Campanian time were heralded by the extrusion of 

vast quantities of andesitic volcanics over a wide area 

(fig. 37). This volcanism is recorded by the lower part 

of the Salero Formation and its many correlatives (fig. 

5). Seismic activity accompanying the volcanism must 

have caused great slope instability in the remaining 

mountainous areas. This is indicated by megabreccias 

in several areas, as epitomized by the Tucson Mountain 

Chaos of Kinnison (1959) in the present Tucson Mountains (fig. 4). The volume of andesitic lavas extruded 

was so great that they may have once covered most 

areas of older bedrock. The extrusion of andesitic volcanics was followed, at least in areas west of long 110° 

W. by the explosive extrusion of great volumes of rhyolitic tuffs, as recorded by the upper part of the Salero 

Formation and its correlatives. In some areas, there 

was crustal deformation between the extrusion of the 

andesitic and rhyolitic volcanics. During this period of 

volcanism, southern Arizona and surrounding country 

was a source of the continental sediments preserved in 

the Fruitland and Kirtland Formations of northwestern New Mexico and in the upper part of the locally 

preserved Aguja Formation of western Texas and 

equivalents in Chihuahua.

During Maestrichtian time, mainly between 65 and 

69 million years ago, the crustal rocks of southeastern 

Arizona and surrounding areas were intruded by 

numerous plutonic bodies, chiefly of diorite, granodiorite, and quartz monzonite. During this time, too, the 

area was a source for continental sediments deposited in 

areas far to the northeast and east. The end of Cretaceous time in southeastern Arizona was a time of
B8 MESOZOIC STRATIGRAPHY IN SOUTHEASTERN ARIZONA

112° 111' 110" 109 a 108 C

33'

Kingston 0

32'

31'

o Santa Rita 

Silver City

COOKS 

RANGE

TUCSONNpTucson

MTS :

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MTS

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MTS

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Tombstone

V

LITTLE

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MTS

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SIERRA 

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A:

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V

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50 100 MILES

75 150 KILOMETERS

FIGURE 4. Map of southeastern Arizona and adjacent areas, showing location of geographic features mentioned in text. Letters 

on inset map refer to localities in outlying regions: M, McCoy Mountains, Calif.; N, New Water Mountains, Ariz.; C, Castle 

Dome Mountains, Ariz.; V, Vekol Mountains, Ariz.; A, El Antimonio, Sonora; SA, Santa Ana-Altar area, Sonora; T, ElTigre, 

Sonora; SB, Sierra Blanca area, Texas; LC, Lower Rio Conchos area, Chihuahua; BB, Big Bend area, Texas.

relative quiescence in which there was local volcanic 

activity and sedimentary deposition in low areas prior 

to the onset of the Helvetian stage of the Laramide 

orogeny in early Tertiary time (Drewes, 1968).

REGIONAL STRATIGRAPHY 

GEOLOGIC SETTING

Southeastern Arizona is a part of the Basin and 

Range physiographic province and as such is characterized by numerous elongate mountain ranges of 

widely variable structure and rock constituents separated by larger areas of intermontane valleys and 

basins. Exposures of rocks older than late Tertiary are 

mostly in the ranges, whereas late Tertiary and younger 

rocks are largely in intermontane basins.

The oldest rocks in the region are widely distributed 

metamorphic rocks of early Precambrian age generally 

assigned to the Final Schist; in many areas these were

intruded by plutonic rocks, dominantly granite to 

quartz diorite, which are also early Precambrian. These 

crystalline rocks are locally overlain in the northern 

part of the region (but not in the southern part) by 

dominantly clastic sedimentary rocks assigned to the 

Apache Group and Troy Quartzite and by diabase all 

of late Precambrian age.

Paleozoic rocks in the region, more than 1 mile 

(1,600 m) thick in some ranges, are nearly all sedimentary strata of marine-shelf origin. Cambrian, Devonian, Mississippian, Pennsylvanian, and Permian strata 

are present in ranges throughout the region; Ordovician strata are present only near the east edge of the 

region; and Silurian strata are not present anywhere 

in southeastern Arizona.

Pre-Cretaceous Mesozoic rocks of the region include 

volcanic, sedimentary, and plutonic rocks. Volcanic and 

associated sedimentary rocks, assigned to a number of 

local formations, occur only in the western part of the
CRETACEOUS PALEOGEOGRAPHY

region, where they are locally distributed but are thousands of feet thick in places. Plutonic rocks ranging 

from granite to diorite are present in several ranges 

in the central and western parts of the region but are 

not known in the easternmost ranges.

Kocks younger than Cretaceous layered rocks include 

plutonic rocks of latest Cretaceous and early Cenozoic 

age, hypabyssal rocks of early and middle Cenozoic age, 

volcanics of early, middle, and late Cenozoic age, and 

continental sedimentary rocks of middle and late Cenozoic age.

Structural features of the region are of many ages 

and are diverse in character, but only those of Mesozoic 

and Cenozoic age that had an effect on the original 

distribution and character of Cretaceous rocks or that 

have since affected their distribution are of concern 

here.

The principal Triassic and Jurassic structural features are normal faults, some with displacements of 

thousands of feet. The largest of these has a westnorthwest trend, but faults with other trends are 

known.

Structures of Late Cretaceous and early Cenozoic age 

are largely of compressional origin and include thrust 

and reverse faults, tear faults, and sharp folds. Trends 

are variable, but a majority of folds have northwesttrending axes.

The major middle and late Cenozoic structural features in the region are the large, generally northerly 

trending, range-front faults (now largely buried by 

later basin-fill deposits) that border the present ranges.

LOWER CRETACEOUS VOLCANICS

Volcanic rocks assigned an Early Cretaceous age are 

known in the area covered by this report (fig. 4) in 

and near three ranges the Huachuca, Santa Eita, and 

Sierrita Mountains of southeastern Arizona. Unnamed 

volcanics that were tentatively assigned to the Lower 

Cretaceous by Gilluly (1956, p. 68-69) in the Dragoon 

Mountains of Arizona are here (p. B28) thought more 

likely to be of Triassic or Jurassic age, and a volcanic 

unit in the Little Hatchet Mountains of New Mexico 

that was assigned in Early Cretaceous age by Lasky 

(1947) is here (p. B31) considered to be of Late Cretaceous age. Lower Cretaceous volcanics may be present 

in the Baboquivari Mountains and elsewhere but have 

not yet been identified as such.

The volcanics of the region that are assigned an 

Early Cretaceous age are included in the Glance Conglomerate of the Bisbee Group in the Huachuca Mountains, in the Temporal and Bathtub Formations in the 

Santa Eita Mountains, and in the quartzite of Whitcomb Hill in the Sierrita Mountains area (fig. 5). None 

of the formations have been dated on the basis of 

radiometric or fossil evidence but have been assigned 

to the Lower Cretaceous on the basis of their relations' 

to rocks of known age. Conglomerate beneath volcanics 

in both the Glance of the Huachucas and the Temporal 

of the Santa Eitas rests on surfaces of profound relief 

carved on granitic rocks as young as Jurassic, as determined on the basis of radiometric dating, and the 

quartzite of Whitcomb Hill rests with apparent disconf ormity on rocks assigned to the Triassic. The upper 

contact of the Glance volcanics of the Huachucas is 

parallel but may be disconformable. The overlying 

conglomerate grades upward into rocks known to be 

of late Early Cretaceous age. The Bathtub Formation, 

which overlies the Temporal Formation in the Santa 

Eita Mountains, is overlain with slight unconformity 

by the upper Lower Cretaceous Bisbee Group. The 

quartzite of Whitcomb Hill in the Sierrita Mountains 

area has a locally disconformable and locally gradational contact with the arkose of Angelica Wash which 

is assigned a late Early Cretaceous age. These relations 

all suggest a closer relation of these volcanic-bearing 

units to upper Lower Cretaceous rocks than to any of 

the Triassic or Jurassic rocks beneath them.

Although these volcanics of Early Cretaceous age all 

occur in a rather restricted part of southeastern Arizona and although it seems reasonable to assume that 

all were formed during the same general period of 

volcanism, the rocks are quite different in three ranges, 

and no specific correlations are implied. The volcanics 

in the Glance Conglomerate in the Huachucas are 

rhyodacitic lavas and flow breccias interbedded with 

conglomerates; the volcanics of the Temporal and 

Bathtub Formations include tuffs and lavas and range 

in composition from andesite to rhyolite; and the volcanics of the Whitcomb Hill unit are rhyolitic tuff 

lenses in predominant quartzite.

BISBEE GROUP AND CORRELATIVES

Eocks of late Early Cretaceous age that are referred 

to as the Bisbee Group (or Bisbee Formation where it 

has not been formally divided into units of formation 

rank) are present in southeastern Arizona, southwestern New Mexico, and northern Mexico between longs 

108° and 111° W. and between lats 31° 10' and 32°30' 

N. Eocks that are considered general time-stratigraphic 

correlatives of the Bisbee are not known to the north of 

the above-defined area but are present as much as 36 

miles (58 km) to the west and much greater distances 

to the southwest, south, and east.
BIO MESOZOIC STRATIGRAPHY IN SOUTHEASTERN ARIZONA

1

Upper Cretaceous

Lower Cretaceo

European stages

e 

.2

1

3

Campanian

Santonian 

and Coniacian

t: 

o

Cenomanfan

e 

to

c

13.

Neocomian

Areas to west

1

Veko 

Mountains

-^-

F

 ^*

:hi 

Ihy 

-7

Ve 

orm

ipuk 

olite

kol 

ation

2

S Iver Bell 

Mountains 

(Richard and 

Courtr ght, 1960)

Rhyolite

Silver Bell 

Formation

-v.

m

^ 

i

sec

x 

Cla 

nc

 ^

x 

\rk 

im 

roc

**.

flin

KF 

x^t

 7^

3SK

ent 

ks

m.

^-*

~^, 

ary

^-« 

"^s_

3

Roskfuge 

Mountains

^m

.x-

 "».

i

1! 

F

^v

C 

F

- 

.* *.

OS

Rhy

oa 

ornr X-N

 *,

)CO

irm

 v_

.x- 

<ru 

olit

Jsi( 

ati

,x~ 

,7-

raq

ati

7-j

*^~ 

e

ie

on

«x>

 ^*.

U6

in

-'

**^ 

--^

4

Tucson 

Mountains 

(Brown, 1939; 

K nn son, 1959)

-^*

>*» 

XCa

ji ^

 xMountain 

Rhyolite

Tu 

flou 

Cn

 V. 

^^^

An 

Ar

 

:so 

nt 

ao

_*--

no

(OS

, *

n 

n 

s

***r

_*-

e 

e

-^_

%_

Principal study area

5

Sierrita Mounta ns 

(Thorns, 1967 

J. R.Cooper, 1970)

VI

-V.

Red Boy 

Rhyolite *%M i- i^i~i»,ii-«ii^i'- 

Demetrie 

Formation

.X"

Qu

hi ^~

^*

l\rl( 

Ang 

W

artz

cor v_-

ise

el 

ash

ite 

nb

-v.

x^

of

ca

_/-* 

of

HI -x-

 - 

^

6

Santa Rita 

Mountains

( 1 ^jBisbee Group £ a 

Sa

Forrr

Fc

Jritte 

"orm

 ^

 **.

ero 

at

rt 

nd

ati

 ^

 *. 

/

-^ 

on

tn 

n

^^

^ 

n

Apache 

Canyon 

Fm.

Willow 

Canyon 

Fm.

Gla *^x 

atht

 *^^

mpo

 *-* 

ice 

-~s

b

 ^

al

^^

 ^_ 

Fm 

-^*- 

Fm

~NgL

- ^ 

**-

1

Empire and 

Whetstone 

Mountains

-*~ " 

F

1 Bisbee Group u

**. 

Sal 

orm

BtO

tion

Turney 

Ranch Fm.

( 2 )

Apache 

Canyon 

Fm.

Willow 

Canyon 

Fm.

Glance Cgl.

8

Patagonia 

Mountains

Volcanics

 ^^ 

-^.

**^

F

_^-

-^ * 

Bisb

orrna

^-^ - 

*s~^ 

it

:ion

9

Huachuca 

Mountains 

and Canelo 

Hills

 x. - 

J

j ) \Group Risbee

ROC

ones 

in

Fo

Srtte

Form

 ^ ^*.

r* ^^ 

Cin

S C

M 

aarl

rt

nd

ati

x^

-*«. 

tur

^* 

f

S3

t

an

on

_xa F

 V*

X*

m.

Mural 

L mestone

Morita 

Formation

G

^^x

lan 

Cg

-^.

ce

. 

x^«

10

Mule Mounta ns 

and 

Cabullona 

Basin

 >_ -

) \Bisbee Grouo 

^ * * 

Cabu 

Grol 

Talia 

(19

.f

Cint

110 

PC 

fer 

33)

^~ 

ura

-^. ^

a 

f

0

Fm

Mura 

Limestone

Morta 

Formation

Gla nee

FIGUEE 5. Correlation chart of Cretaceous formations in southeastern Arizona and southwestern New Mexico, showing their 

inferred time relations with the European stages and with Cretaceous strata of the gulf coast region. Footnotes: f1) Turney
CRETACEOUS PALEOGEOGRAPHY Bll

Areas to east

11

Dragoon 

Mounta ns 

and 

Tombstone area

V

F

 *.

Brc 

olc

** f

Bi< 

orn

s-<

nc 

an

^

^ 

be 

lat

 *^

3

CS

 v

^-^

e 

on

^*r

^

 ~*

12

Dos Cabezas 

and Northern 

Chiricahua 

Mounta ns 

(Sabins, 1957a>

 s. 

^S

~+,

^^

N

 x_

^v

«* 

PfX

^

^\ 

Bs 

Gr

'^ 

r F 

> 

be<

HIP

*^.

m.

 *

^^.

13

Pe'dregosa 

and Southern 

Chiricahua 

Mounta ns

-V

 ^

*rA

C

Sec

<"^

s~*.

tide

las 

im

_^-

Bis 

Gr

-** 

sit

tic 

enl 

ks

****

*Sb«

Mip

S

ary

-*v.

^^

 >-

.X^1

^»

1.4

Central Pe oncillo 

Mountains 

(G Herman, 1958)

*~* 

 >

* »

CD

1a

 ^

1

^ 

-s>

"' 

Job 

3ul

«-x

l>*

^ 

nn)

S<

 ^

( 3

( 4 

( 5

 N*,

 ^^

 *> 

15

Little Hatchet 

Mounta ns

-x. K-S,

V

R

lid 

olc

ing 

Sh

Sk 

Ra

C

^

^

ilg 

mi

bo 

a,e

jnk 

ich 

gl.

**~s

1 

s

ie

"«-.

Cor ben 

Sandstone

 s

^

* 

o

5

Playas Peak Fm. ills Ridge Fm.

|

16

Big Hatchet 

and An mas 

Mountains, 

(Zeller, 1965; 

Zeller and 

Alper, 1965)

_^-

*~\ 

f

~~

:o«

Spr

rm

^

** 

Moi 

arm

'- 

bo

ing

at

?-,

ack

atir

)n

^^

-N

3-

on

^*

U-Bar 

Formation

Hdl-toFinish Fm.

Areas to north

17

W nchester 

and 

Little Dragoon 

Mountains

^^ s

S

-^. *

Group/- Bisbee 

-*-*- 

Voc 

roc 

over 

cla 

ed m 

roc ~Y'

»-^

Cn 

Mo

Gla * ^

ani 

ks 

yir 

stic 

jnt

is

^

tur 

ta

ce

 ^^ 

c

g

 v.

-V 

a a 

Frt

C

s~*

nd

s.

i.

18

Northern 

Santa Catalina 

Mounta ns area

_*"

C 

F

A 

F

OU(

orrr

Fi 

)rm

 , 

bu

ati

-

ca 

ag

ati 

?_

^-> 

rst 

on

n 

in

19

Morenci to 

Christmas 

aree

V

F(

 

olc

^-> 

Pin 

Km

ini

_^- 

tar 

atk

x

**** 

t 

m

20

Silver City 

and Santa 

Rita area

Andesites

^> ^-« 

C 

F

B

Q

olo 

orn

ear

ua

^^

rad 

lati

?

too

tzi 'v.

-^. 

o 

on

th

e 

^^

Gulf 

coast

region

Navarro

Group

Taylor 

Group

Austin 

Chalk

Eagle 

Ford 

Shale

1 Woodbine 

Formation

Washita 

Group

 Fredericksburg 

Group

TrinityGroup

Nuevo 

Leon Group 

of Mexico

Durango 

Group 

of Mexico

.» 

in

Cretaceous Upper 

Lower Cretaceous

Ranch Formation, (2) Shellenberger Canyon Formation, (3) Still Ridge Formation, (*) Carbonate Hill Limestone, and (8) McGhee Peak Formation.
B12 MESOZOIC STRATIGRAPHY IN SOUTHEASTERN ARIZONA

EMPIRE 

MOUNTAINS

(FIN NELL, 197O) 2

WHETSTONE: 

MOUNTAINS

(TYRRELL, 1957)

Turney

Ranch

Formation

_ -

Shellenberger

Canyon

Formation

Apache

Canyon

Formation

wv

HUACHUCA 

MOUNTAINS 

(HA YES, 1970)

Cintura 

Formation

E3E~Upper membeT 

Lower member

4

MULE: 

MOUNTAINS

(HA YES, 197O)

SOUTHERN 

CHIRICAHUA 

MOUNTAINS

(EPIS, 1956)

-1000 

METERS 0--0 FEET Interbedded sandstone, 

siltstone, and mudstone

Limestone

Interbedded limestone 

and clastic rocks

Volcanics

FIGTJRE 6. Line of columnar sections, showing inferred correlations of rocks of Bisbee Age from the Empire Mountains, Ariz., to

the Big Hatchet Mountains, N. Mex.

The thickness of the Bisbee is extremely variable 

both regionally and locally owing to the great local 

relief of the underlying surface and to the variable 

amounts of early Late Cretaceous erosion (fig. 6). It 

has a maximum known thickness of about 15,000 feet 

(4,500 m) in the Empire Mountains area and in the 

Dragoon Mountains (fig. 4), but it rarely exceeds 

10,000 feet (3,000 m) in thickness in other areas.

The Bisbee changes markedly in facies from east to 

west and from south to north. In its southeasternmost 

outcrops, most of the lower half of the Bisbee is made 

up of relatively thick bedded and relatively pure limestones of marine origin, and much of the remainder of 

the Bisbee is made up of quartzose or slightly feldspathic sandstone interbedded with shales. But the 

proportion of limestone decreases westward, and the 

carbonates present in the northwesternmost sections are 

relatively thin bedded or platy and are generally silty

or argillaceous. Sandstones in the group are increasingly feldspathic or arkosic westward.

Eange-to-range correlation of lithologic divisions 

within the Bisbee can generally be no better than tentative. Better correlation is precluded partly by the virtual absence of diagnostic fossil species in western 

sections and the sparsity or absence of such fossils in 

thick parts of eastern sections, partly by regional facies 

changes and intertonguing, and partly by structural 

complexities that cause uncertainties in establishing 

the proper sequence in some areas. As a result of these 

difficulties, only one formational division name has 

been used in more than three ranges; many names have 

been used in a single range. Most of the correlations 

presented here must be considered tentative. They are 

based on the scant fossil data available, on lithology, and 

on known and interpreted trends in facies and thickness.

Conglomerate is present at the base of the Bisbee 

in nearly all areas. It is called the Glance Conglomer-
CRETACEOUS PALEOGEOGRAPHY B13

8

LITTLE

HATCHET

MOUNTAINS

(MODIFIED FROM

LASKY, 1947)

6

NORTHERN

CHIRICAHUA

MOUNTAINS

(SA BINS, 1957B)

7

CENTRAL

PELONCILLO

MOUNTAINS

(GILLERMAN, 1958)

9

BIG

HATCHET

MOUNTAINS

(ZELLER, 1965)

Q.

m o

Still ^i__ 

Ridge ^^

Formation,__ ~~^~

"""Carbonate Hill Limestone

JTucson

50 MILES I

50 KILOMETERS

MEXICO

ate in most areas in Arizona where the Bisbee is of 

group rank (fig. 5). The thickness, age, and lithologic 

makeup of the conglomerate at the base of the Bisbee 

vary both locally and regionally (fig. 5). Local variations are due to the very irregular nature of the underlying surface, particularly in western areas. In some of 

these areas, the Glance Conglomerate may range in 

thickness from zero (over old topographic highs) to 

many hundreds or even thousands of feet within a few 

miles. Obviously the age of the conglomerate on or 

near the tops of high areas is somewhat younger than 

that deposited in intervening low areas. The thickness 

of conglomerate at the base of the Bisbee in eastern 

areas is rarely more than tens of feet.

Fortunately, one sequence of distinctive beds a few 

hundred feet thick in the middle part of the Bisbee of 

most areas appears to be widely correlative and forms 

at least a tentative basis for correlating beds above and 

below. The critical sequence is the upper member of 

the Mural Limestone in the Mule Mountains. This 

member consists dominantly of relatively thick bedded 

and relatively pure limestone which at several horizons

381-840 ^TO 3

is replete with species of the foraminifer Orbitolma\ 

rudistid-rich bioherxns and biostromes also are characteristic. Fossil evidence indicates that the member is 

correlative with the upper part of the Trinity Group 

and possibly with the lowest part of the Fredericksburg Group of Texas.

The Mural Limestone in the Mule Mountains is correlated with the Orbitolina-b&axmg Mural Limestone 

in the Huachuca Mountains to the west (fig. 6). 

Although of the same age there, the Mural in the 

Huachucas is somewhat thinner bedded, and the entire 

formation thins northward within the range.

Correlation of the upper member of the Mural 

Limestone in the Mule Mountains with rocks in the 

Pedregosa-southern Chiricahua Mountains area to the 

east (fig. 4) is less certain because in the latter area 

limestone units occur through several thousand feet of 

the Bisbee. However, only the highest few hundred 

feet of limestone in. that area is relatively pure and 

thick bedded, is known to bear Orbitolina^ and contains 

rudistid bioherms. On the basis of these facts, the 

highest few hundred feet of limestone in the Bisbee in
B14 MESOZOIC STRATIGRAPHY IN SOUTHEASTERN ARIZONA

the Pedregosa-southern Chiricahua area is correlated 

with the upper member of the Mural Limestone in the 

Mule Mountains. Lower limestones in the Pedregosa 

area are presumed to pinch out westward and to be 

time equivalents of nonmarine clastic beds in the 

Morita Formation in the Mule Mountains (fig. 6).

Farther eastward and northward in the northern 

Chiricahua Mountains and in the central Peloncillo 

Mountains are units made up of relatively impure and 

relatively thin bedded limestone. These units are only 

a few hundred feet above the base of the Bisbee and 

have not yielded Orbitolina. The limestone unit in the 

Peloncillos the Carbonate Hill Limestone of Gillerman (1958) has yielded a fauna of probable Aptian 

age and is thus apparently older than the upper member of the Mural Limestone. Both limestone units are 

probably correlative with limestone units low in the 

sequence in the southern Chiricahua Mountains area 

(fig. 6, cols. 5, 6, 7). Possibly sediments equivalent to 

the Mural Limestone were never deposited in the 

Peloncillo Mountains or northern Chiricahua Mountains areas, but it is equally possible that they were 

removed by erosion in early Late Cretaceous time.

Farther east, in the Little Hatchet and the Big 

Hatchet Mountains of New Mexico, limestone is the 

dominant lithology through several thousand feet of 

stratigraphic section. In the Big Hatchet Mountains, 

this thick limestone section makes up the TJ-Bar Formation of Zeller (1965). Beds in the upper several 

hundred feet of the TJ-Bar most closely resemble the 

upper member of the Mural Limestone in both age and 

lithology. The beds are thick to massive, contain rudistid bioherms, are Orbitolina bearing, and were considered by Zeller (1965, p. 66) to be of late Trinity 

and Fredericksburg(?) age. On the assumption that 

the upper few hundred feet of the TJ-Bar Formation 

of Zeller (1965) is approximately equivalent to the 

upper member of the Mural Limestone, the lower 

several thousand feet of the TJ-Bar, which is largely of 

Aptian age (Zeller, 1965, p. 66), would then be equivalent to most of the Morita Formation and the lower 

member of the Mural Limestone of the Mule Mountains (fig. 6). As explained in detail in a later section 

of this report (p. B31), the Howells Kidge Formation, 

Playas Peak Formation, and Broken Jug Limestone in 

the Little Hatchet Mountains probably are faulted 

repetitions of the same unit. These formations, like 

the U-Bar Formation of Zeller (1965), are very thick 

dominantly limestone units whose upper few hundred 

feet is characterized by thick-bedded to massive 

rudistid-bearing bioherms and OrbitoHna-bQ&Tmg 

beds. Because of their fossil content and lithology,

these upper parts are correlated with the upper member of the Mural Limestone (fig. 6).

Correlation of the Mural Limestone northwestward 

with rocks of the Bisbee Group in the Whetstone, 

Empire, and Santa Rita Mountains is not certain. It is 

here considered likely that the Apache Canyon Formation in and near those ranges is correlative with the 

Mural Limestone (fig. 6). Limestone units in the 

Apache Canyon, in general, are much different from 

those in the Mural in that the Apache Canyon limestones are thin bedded to platy and argillaceous and 

have yielded brackish-water fossils. However, in its 

southernmost exposures in the Whetstone Mountains 

the exposures closest to the Huachuca Mountains 

limestone units in the Apache Canyon are relatively 

thick bedded. The northernmost exposures of Mural 

Limestone in the Huachuca Mountains contain thinner 

bedded limestone than is typical in exposures farther 

south. If this correlation is correct, the Morita Formation in the Mule and Huachuca Mountains must be a 

general correlative of the lithologically similar Willow 

Canyon Formation in the Whetstone, Empire, and 

Santa Rita Mountains (fig. 6).

The Mural Limestone apparently pinches out northward from the Mule Mountains. Thin beds of limestone 

having little resemblance to the Mural are present in 

the very thick Bisbee Formation in the Dragoon Mountains and in the undivided Morita and Cintura Formations in the Little Dragoon Mountains. These beds must 

be thin northwestward extensions of some of the many 

limestone beds present in the lower half of the Bisbee 

Formation in the Pedregosa-southern Chiricahua 

Mountains area, but no specific correlations are possible 

now.

Farther west, thin beds of fresh- or brackish-water 

limestone are present in the arkose of Angelica Wash 

in the Sierrita Mountains vicinity and in the Amole 

Arkose of Brown (1939) in the Tucson Mountains. 

The parts of those units in which limestone beds occur 

may be generally equivalent to the Apache Canyon 

Formation. The Cocoraque Formation in the Roskruge 

Mountains area, still farther west, is considered to be 

a general equivalent of the Amole Arkose but contains 

no limestone.

The Cintura Formation, which gradationally overlies the Mural Limestone in the Mule and Huachuca 

Mountains, is considered on the basis of stratigraphic 

position to correlate with the formations that gradationally overlie the units here correlated with the 

Mural Limestone. The Cintura is thus considered 

roughly correlative with the Moj ado Formation of 

Zeller (1965) in the Big Hatchet Mountains area; 

with the Corbett Sandstone in the Little Hatchet
CRETACEOUS PALEOGEOGRAPHY B15

Mountains; with the Shellenberger Canyon Formation and possibly in part with the overlying Turney 

Kanch Formation in or near the Whetstone, Empire 

(see p. B22), and Santa Rita Mountains; and with the 

upper parts of the arkose of Angelica Wash in the 

Sierrita Mountains vicinity and the Amole Arkose 

of Brown (1939) in the Tucson Mountains (fig. 5).

All these units that are considered correlative with 

the Cintura Formation consist mostly of interbedded 

sandstone, siltstone, and shale or mudstone; most contain thin impure limestone beds in their lower parts. 

The sandstone units are typically in channel relation 

with underlying siltstone or mudstone; most of them 

are cross-laminated and grade upward into finer beds. 

The sequence is interpreted to represent dominantly 

fluviatile deposits of the subaerial portion of a delta 

that prograded eastward over the Mural Limestone and 

its correlatives. Beds of marine origin near the top of 

the Moj ado Formation of Zeller (1965) in the Big 

Hatchet Mountains may represent a minor westward 

transgression of the seas that did not extend far west 

of the area in the present Big Hatchet Mountains. 

Rocks in western Texas of Fredericksburg and early 

Washita age that are general equivalents of the Cintura Formation are of marine origin.

The clastic sediments preserved in the Bisbee probably were derived primarily from western source 

areas and secondarily from northern and local source 

areas. This concept follows naturally from the conclusion that the seas represented by marine limestones of 

the Bisbee transgressed from the southeast, and it is 

supported by the westward change in composition of 

sandstones in the group. Little petrographic work has 

been done on sandstones of the Bisbee in New Mexico, 

but sandstone beds of the Mo j ado Formation in the 

Big Hatchet Mountains area are dominantly quartzose, 

and a few are slightly feldspathic (Zeller, 1965, p. 68). 

Sandstones of the Corbett Sandstone of the Little 

Hatchet Mountains are similar. To the west in the 

Mule and Huachuca Mountains, the average feldspar 

content of 42 samples examined in thin section exceeds 

11 percent; most samples are f eldspathic sandstone or 

subarkose according to the classification of Pettijohn 

(1957, p. 291). The average feldspar content of 

eight samples from the Bisbee in the Santa Rita 

Mountains exceeds 23 percent, and the average of nine 

samples from the arkose of Angelica Wash in the 

Sierrita Mountains vicinity, farther west, is about 27 

percent. Most samples from the Angelica Wash strata 

are classifiable as true arkoses. The percentage of 

rock fragments and fine detrital matrix in the Bisbee 

sandstones also tends to increase westward.

The total age range of the rocks of the Bisbee Group 

is uncertain because the lowest and highest parts of 

the sequence are barren of closely datable fossils. 

However, on the basis of fairly reliable age assignments for the middle part of the group and lithologic 

correlations with the more completely dated Cretaceous 

rocks of the Big Hatchet Mountains, an approximation can be made for the total age range of the Bisbee 

in most areas. In the type area of the Bisbee Group in 

the Mule Mountains, fossil evidence indicates that 

rocks in the Morita Formation about 600 feet (180 m) 

below the Mural Limestone are equivalent to strata in 

the lower part of the Trinity Group of Texas, that the 

Aptian-Albian boundary is in the lower part of the 

lower member of the Mural Limestone, and that the 

uppermost part of the Mural Limestone is of late 

Trinity age or may be as young as the Fredericksburg 

Group of Texas (p. B18). The Carbonate Hill Limestone of Gillerman (1958) in the central part of the 

Peloncillo Mountains, which is here correlated approximately with strata in the lower part of the 

Morita Formation, has yielded a fauna of Aptian age 

(p. B29). Fossils from the U-Bar Formation of Zeller 

(1965) in the Big Hatchet Mountains area indicate 

that strata within 1,200 feet (360 m) of the base of the 

formation are of Trinity age, that the Aptian-Albian 

boundary is roughly 1,000 feet (300 m) below the top 

of the formation, and that the uppermost part of the 

U-Bar may be as young as the Fredericksburg Group 

of Texas (Zeller, 1965, p. 64-66). Fossils from the 

upper 1,086 feet (332 m) of the Mo j ado Formation of 

Zeller (1965) in the Big Hatchet Mountains area indicate a middle or late Washita (of Texas) age. From 

these faunal data and the regional lithologic correlations made in this report, it seems probable that the 

Bisbee Group represents most of Aptian and Albian 

time. It is possible, of course, that rocks high in the 

Bisbee Group in western areas, such as the Turney 

Ranch Formation in or near the Whetstone, Empire, 

and Santa Rita Mountains, are as young as early Late 

Cretaceous and that lowest rocks of the Bisbee in 

some areas may be as old as the Neocomian.

PINKARD FORMATION AND CORRELATIVES

Strata of early Late Cretaceous age, generally referred to the Pinkard Formation, unconformably overlie Paleozoic rocks in areas north of lat 32°55' N. in 

southeastern Arizona. Strata of similar age and lithology in southwestern New Mexico north of lat 32°20' N. 

are referred to the Colorado Formation. The Colorado 

Formation overlies the Beartooth Quartzite (or probable equivalents of earliest Late Cretaceous age or
B16 MESOZOIC STRATIGRAPHY IN SOUTHEASTERN ARIZONA

possibly of latest Early Cretaceous age) with apparent conformity, and it overlies Paleozoic or Precainbrian rocks unconformably.

The Pinkard and Colorado Formations are distinctly different in lithology from any Cretaceous 

strata farther south in southeastern Arizona and 

probably have no age equivalents there (fig. 5). They 

are made up chiefly of sandstones and shales of 

shallow-water marine origin but include some continental coastal-plain and lagoonal sediments. Fossils 

from these formations indicate that they are age 

equivalents of the Graneros Shale and Greenhorn 

Limestone in southeastern Colorado and thus are 

roughly equivalent to the lower part of the Mancos 

Shale in northwestern New Mexico and northeastern 

Arizona (Cobban and Reeside, 1952). The Pinkard 

and Colorado Formations apparently represent rocks 

near the southwestern wedge edge of the thick Upper 

Cretaceous sequence of the western interior of North 

America and have little relation to Cretaceous rocks 

farther south.

FORT CRITTENDEN FORMATION AND CORRELATIVES

The Fort Crittenden Formation, of late Late Cretaceous age, occurs only in the Santa Rita MountainsCanelo Hills-Huachuca Mountains (fig. 4) area. It is 

as much as thousands of feet thick and consists dominantly of conglomerate, sandstone, and shale of continental origin but includes thin tuff beds in its upper 

part. The formation unconformably overlies folded 

and faulted strata of the Bisbee Group and is overlain with apparent conformity by the dominantly volcanic Salero Formation. On the basis of vertebrate 

and nonmarine invertebrate fossils and apparently 

conformable relations with the overlying radiometrically dated volcanics of the Salero Formation, the 

Fort Crittenden Formation is presumed to be of early 

Campanian age. Rocks of the Fort Crittenden appear 

to be dominantly of fluvial origin but may include 

some beds deposited in lakes and marshes.

The Fort Crittenden probably is equivalent to part 

or all of the Cabullona Group of Taliaferro (1933) 

in the Cabullona Basin area of Sonora, Mexico. Rocks 

of this group, which have yielded dinosaur bones of 

Late Cretaceous age, are similar in general to rocks 

of the Fort Crittenden, but rocks of the Cabullona 

Group contain proportionately much less conglomerate 

and more sandstone and shale (p. B18). My interpretation is that the Fort Crittenden Formation and 

the Cabullona Group of Taliaferro (1933) were once 

coextensive and that the Cabullona Group was deposited farther from the source area.

Rocks lithologically similar to parts of the Fort Crittenden Formation occur with apparently conformable 

relations beneath probable Upper Cretaceous volcanics 

in several other areas in southeastern Arizona and 

southwestern New Mexico. These include the Claflin 

Ranch Formation of Richard and Courtright (1960) 

in the Silver Bell Mountains area, the American Flag 

Formation in the northern part of the Santa Catalina 

Mountains, the Ringbone Shale in the Little Hatchet 

Mountains area, and unnamed units in the southern 

part of the Winchester Mountains and in the 

Pedregosa-southern Chiricahua Mountains area. All 

these units are considered to be roughly correlative with 

the Fort Crittenden.

Two additional rock units that have been included as 

upper formations of the Bisbee Group, but which are 

here considered as likely general equivalents of the Fort 

Crittenden Formation, are the Johnny Bull Sandstone 

of Gillerman (1958) in the central Peloncillo Mountains and Skunk Ranch Conglomerate in the Little 

Hatchet Mountains area. Neither formation is overlain 

by Upper Cretaceous volcanics, but both seem to be 

lithologically more similar to the Fort Crittenden Formation than to underlying parts of the Bisbee Group. 

The Skunk Ranch Conglomerate has a disconf ormable 

basal contact, but the basal contact of the Johnny Bull 

Sandstone appears to be conformable.

The Cowboy Spring Formation of Zeller and Alper 

(1965) in the Animas Mountains may also be partly 

equivalent to the Fort Crittenden (p. B30).

In many other areas in the region, the Fort Crittenden Formation or correlative rocks are absent and 

Upper Cretaceous volcanics disconf ormably or unconformably overlie older rocks. Some of these areas, such 

as the Empire Mountains and Tombstone vicinity, lie 

directly between areas where the Fort Crittenden or 

similar rocks are present. I believe that rocks correlative with the Fort Crittenden are absent in these areas 

due to nondeposition and that the Fort Crittenden 

Formation and correlatives were deposited in broad 

valleys between mountainous highlands.

Even though there are many differences between the 

rocks of the Fort Crittenden Formation and correlatives and rocks of the Bisbee Group, it is difficult to 

distinguish between the two in places. Both units contain clastic rocks of fluvial origin which locally contain 

an abundance of fossil wood and which may contain 

fresh-water mollusks, but in the region discussed here, 

only the Bisbee contains limestone and other rocks of 

marine origin along with marine and brackish-water 

fossils. This does not preclude the possibility of freshwater limestone in the Fort Crittenden or its correlatives, but none has been recognized to date. Relatively
CRETACEOUS PALEOGEOGRAPHY B17

well sorted conglomerates which contain rounded 

stream-worn clasts and poorly sorted fanglomeratetype conglomerates which contain more angular locally 

derived clasts can be found in both units; but the 

poorly sorted conglomerates are much more common in 

the Bisbee, and the well-sorted conglomerates are 

greatly dominant in the Fort Crittenden and correlatives. Sandstones are also helpful in distinguishing the 

two. Average sandstone in the Bisbee ranges from 

slightly feldspathic in the east to arkose in the west, 

although occasional beds of graywacke are present; 

most sandstone samples from the Fort Crittenden and 

correlatives are lithic or feldspathic graywacke or subgray wacke, although some arkose is present. (See Pettijohn, 1957, p. 291.) Eock colors, particularly of shales, 

may also be helpful in distinguishing the two units. 

Although both units contain rocks of red and green 

hues, red-hued rocks are more characteristic of the Bisbee whereas green- to olive-hued rocks are more common in the Fort Crittenden. There are other subtle 

differences in lithologic characteristics in the two units, 

but the ones enumerated above are most obvious and 

therefore most useful.

SALERO FORMATION AND CORRELATIVES

The Salero Formation in the Santa Rita and Empire 

Mountains is as much as 5,000 feet (1,500 m) thick and 

is composed of andesitic to dacitic rocks overlain by 

rhyolitic welded tuff which in turn is overlain by a 

dominantly clastic sedimentary member. The andesitic 

to dacitic rocks in the lower part of the formation 

locally have layers containing exotic blocks of older 

rock. The Salero overlies the Fort Crittenden Formation with apparent conformity where that formation is 

present, or unconformably overlies the Bisbee Group 

where the Fort Crittenden is absent. On the basis of a 

radiometric age determination of the rhyolitic tuff and 

the formation's apparently conformable relations with 

the Fort Crittenden Formation, the Salero is probably 

late Campanian and possibly earliest Maestrichtian in 

age (p. B24). The Salero has been intruded by rocks 

radiometrically dated as very late Cretaceous and is 

overlain by a variety of rocks assigned to the Tertiary 

or Quaternary.

Andesitic rocks very similar in lithology to those of 

the lower part of the Salero and in similar relations to 

older Cretaceous rocks are widely distributed in southeastern Arizona and southwestern New Mexico. At 

many localities west of long 110° W., these are overlain by rhyolitic tuffs, some of which have been radiometrically dated as late Campanian or Maestrichtian. 

Andesitic rocks in the region that are considered as at

least approximate correlatives of the lower part of the 

Salero Formation include the Silver Bell Formation of 

Richard and Courtright (1960) in the Silver Bell 

Mountains area, the Demetrie Formation of Thorns 

(1967) in the Sierrita Mountains vicinity, most of the 

Tucson Mountain Chaos of Kinnison (1959) in the 

Tucson Mountains, the Roadside Formation in the 

Roskruge Mountains area, the Vekol Formation in the 

Vekol Mountains, the Cloudburst Formation in the 

Santa Catalina Mountains area, the lower part of the 

Bronco Volcanics in the Tombstone area, the Nipper 

Formation of Sabins (1957a) in the Chiricahua Mountains, the Hidalgo Volcanics in the Little Hatchet 

Mountains, and unnamed rocks in many other areas 

(%. 5).

Rhyolitic tuffs in the region that are considered correlatives of the rhyolitic tuffs of the Salero Formation 

include the Cat Mountain Rhyolite of Brown (1939) 

in the Tucson Mountains, the Red Boy Rhyolite of 

Thorns (1967) in the Sierrita Mountains, the Roskruge 

Rhyolite in the Roskruge Mountains, the upper part of 

the Bronco Volcanics in the Tombstone area, possibly 

part or all of the Sugarloaf Quartz Latite in the 

Dragoon Mountains area, unnamed rocks at the top of 

the Cabullona Group of Taliaferro (1933) in the 

Cabullona Basin area in Sonora, and an unnamed rhyolite in the Silver Bell Mountains.

Units comparable to the upper part of the Salero 

Formation in the Santa Rita Mountains have not been 

identified elsewhere in the region.

DESCRIPTIONS OF LOCAL SEQUENCES

PRINCIPAL STUDY AREA

MULE MOUNTAINS, ARIZ., TO CABULLONA 

BASIN, SONORA

(Fig. 5, col. 10)

Many thousands of feet of strata of Cretaceous age 

are exposed in continuous outcrops that extend about 

40 miles (65 km) south-southeastward from the north 

end of the Mule Mountains, Ariz., to the south edge of 

the Cabullona Basin, Sonora (fig. 4). Rocks in all but 

the south end of this large outcrop area are of Early 

Cretaceous age and are assigned to the Bisbee Group. 

At the south end, separated from the Bisbee Group by 

a major west-northwest-trending fault, is the Upper

Cretaceous Cabullona Group of Taliaferro [1933).

The Bisbee Group, named for the city of Bisbee in 

the Mule Mountains, is divided, in ascending order,

into the Glance Conglomerate, the Morita Formation,

the Mural Limestone, and the Cintura Formation, all 

of which have principal reference sections in the Mule
B18 MESOZOIC STRATIGRAPHY IN SOUTHEASTERN ARIZONA

Mountains. The following descriptions of the formations of the Bisbee Group, except as otherwise noted, 

are taken from Hayes (1970).

The Glance Conglomerate is a poorly sorted angular 

boulder to granule conglomerate whose thickness and 

lithologic detail are strongly controlled by the relief 

and lithology of the underlying surface. The Glance 

rests unconformably on a surface of high relief carved 

on Precambrian metamorphic rocks, Paleozoic sedimentary rocks, and Jurassic granite. In the Mule Mountains, it ranges in thickness from wedge-edges over 

buried high areas to many hundreds of feet; and according to Taliaferro (1933), it is as much as 2,500 

feet (750 m) thick in Sonora just north of the Cabullona Basin. Conglomerate near the base of the formation is made up of clasts derived from the immediately 

underlying rocks, whatever they may be, whereas 

higher in the formation the clasts are of more diverse 

origin but are all of rock types now exposed at the 

surface somewhere in the Mule Mountains. The 

Glance, which is increasingly fine grained toward the 

top, grades upward into the Morita Formation.

The Morita Formation, 2,600-3,000 feet (800-900 m) 

thick in the Mule Mountains and, according to Taliaferro (1933), as much as 5,000 feet (1,500 m) thick just 

north of the Cabullona Basin, is made up mostly of 

repeated sequences of pinkish-gray feldspathic sandstone that grades upward into grayish-red siltstone and 

mudstone. Siltstone and mudstone are dominant in 

most of the formation, but sandstone is dominant in 

the upper part. The formation, which grades upward 

into the Mural Limestone, contains a few thin units of 

impure fossiliferous limestone in the upper part.

The Mural Limestone, 500-700 feet (150-215 m) 

thick, is divided into lower and upper members. The 

lower member consists of interbedded calcareous mudstone, impure fossiliferous limestone, and friable calcareous siltstone and sandstone, whereas the upper 

member is made up dominantly of relatively thick 

bedded limestone. High in the upper member, which 

grades upward into the Cintura Formation, are interbeds of pinkish-gray feldspathic sandstone.

The Cintura Formation, as much as 1,830 feet (570 

m) thick, is lithologically similar to the Morita Formation. It contains a few thin beds of fossiliferous 

limestone in the lower part.

Stratigraphically useful fossils from the Bisbee 

Group in the area have been collected only from horizons in the upper part of the Morita Formation and 

from the Mural Limestone. On the basis of these, about 

the upper 600 feet (180 m) of the Morita Formation 

and about the lower one-fourth of the lower member of

the Mural Limestone may be correlated with the lower 

part of the Trinity Group of Texas; most of the remainder of the Mural Limestone is correlated with the 

upper part of the Trinity Group; and the uppermost 

part may be of late Trinity age or may be as young as 

the Fredericksburg Group of Texas. Probably the 

Glance Conglomerate and lower part of the Morita 

Formation are older than the Trinity, but they are 

probably not pre-Aptian. The Cintura Formation may 

correlate largely with the Fredericksburg Group and 

may, in part, be as young as the Washita Group of 

Texas.

The Cabullona Group of Taliaferro (1933) was divided by him into five conformable formations which, 

in ascending order, are the Snake Kidge Formation, 

the Camas Sandstone, the Packard Shales, a unit informally called the upper red beds, and an unnamed 

rhyolite tuff. The following descriptions are based on 

the work of Taliaferro (1933) and a visit I made in 

1967 with Harald Drewes and Amador Osoria, then a 

geologist with the Mexican government.

The Snake Kidge Formation, more than 3,000 feet 

(600 m) thick, consists of polymictic conglomerate, 

pale-yellowish-brown to light-gray locally pebbly sandstone, and pale-yellow, pink, and gray shale. Petrified 

wood and fresh-water mollusks are abundant in some 

beds, and dinosaur bones were found in the upper part 

of the formation.

The Camas Sandstone, 1,220 feet (370 m) thick, consists of crossbedded largely tuffaceous sandstone with 

minor interbedded pale-red and pale-green shale.

The Packard Shales, 1,800-2,500 feet (550-750 m) 

thick, is made up dominantly of greenish-gray shale 

with minor interbedded standstone and bentonite. The 

formation contains carbonized plant fragments and 

fresh-water mollusks.

The upper red beds, more than 2,000 feet (600 m) 

thick, is made up mostly of pale-red shale and pale-red 

to light-gray sandstone but contains very minor siliceous tuff in thin beds.

The rhyolite tuff, as much as 800 feet (250 m) thick, 

is made up of white to gray siliceous tuff.

The Late Cretaceous age assignment of the Cabullona 

Group of Taliaferro (1933) is based on identification of 

dinosaur bones from high in the Snake Kidge Formation and on lithologic resemblances of all but the rhyolite tuff unit to rocks of the Upper Cretaceous Fort 

Crittenden Formation in the Santa Rita and Huachuca 

Mountains in Arizona. The plant remains and freshwater mollusks in the group are not useful for close 

dating, and none of the tuff of the group has been dated 

by radiometric methods. According to Taliaferro (1933,
CRETACEOUS PALEOGEOGRAPHY B19

p. 28), "The evidence afforded by the dinosaur remains, 

although perhaps not conclusive, indicates that the beds 

belong to the upper part of the Upper Cretaceous and 

are probably Senonian." This tentative age assignment 

allows a correlation with the Fort Crittenden Formation and suggests that the Cabullona Group is younger 

than the Pinkard Formation in the Morenci area or 

the Colorado Formation in the Silver City area, New 

Mexico (fig. 5). The rhyolite tuff unit at the top of the 

Cabullona Group may be equivalent to rhyodacitic tuff 

in the upper part of the Salero Formation in the Santa 

Rita Mountains and correlatives. If this is the case, it 

is notable that there are no andesitic rocks conformably 

beneath the rhyolitic tuffs in the Cabullona Basin as 

are found in most parts of the region.

HUAGHUGA MOUNTAINS AND GANELO HILLS 

(Fig. 5, col. 9)

Cretaceous strata, totaling many thousands of feet 

in thickness, are exposed in discontinuous outcrops 

throughout the length of the northwest-trending 

Huachuca Mountains and are also extensively exposed 

in the similarly trending Canelo Hills to the west and 

northwest (fig. 4). Lower Cretaceous rocks, all assigned to the Bisbee Group, are prevalent in the 

Huachucas, whereas Upper Cretaceous rocks assigned 

to the Fort Crittenden Formation and unnamed units 

are prevalent in the southern Canelo Hills. The following brief description of the Cretaceous in the 

Huachucas is taken from Hayes (1970), and the description of the Cretaceous in the Canelo Hills is 

derived from unpublished data of my own and of 

Robert B. Raup and Frank S. Simons.

The Bisbee Group in the Huachuca Mountains, as 

in the Mule Mountains, is divided in ascending order 

into the Glance Conglomerate, the Morita Formation, 

the Mural Limestone, and the Cintura Formation; 

only the Cintura is represented in the Canelo Hills 

area. The Morita and Cintura Formations in the 

Huachucas are basically similar to those formations 

in the Mules; but the Glance Conglomerate in most 

areas in the Huachucas contains a volcanic member 

not present in the Mules, and the Mural Limestone in 

the Huachucas is somewhat different from that in 

the Mules.

The Glance Conglomerate in the Huachuca Mountains is divided into lower and upper conglomerate 

units and a middle volcanic unit. In the northern part 

of the range, the volcanic unit is locally absent, and 

the two conglomerate units are indistinguishable. In 

the southern part, the upper conglomerate unit is 

locally absent. The lower conglomerate unit, like the

Glance Conglomerate in the Mule Mountains, is a 

poorly sorted angular boulder to granule conglomerate 

whose thickness and lithologic detail are strongly 

controlled by the relief and lithology of the underlying surface. It rests uncomformably on a surface of 

high relief carved on Paleozoic sedimentary rocks, 

Triassic and Jurassic volcanic rocks, and Jurassic 

quartz monzonite. The lower conglomerate, where distinguishable from the upper conglomerate, ranges in 

thickness from about 300 feet (90 m) to nearly 2,000 

feet (600 m). The volcanic unit is made up of very 

dusky red to grayish-purple generally porphyritic 

rhyodacitic lava and flow breccias that locally contain exotic blocks as much as several hundred feet 

long of limestone locally derived from Paleozoic 

formations. The unit ranges in thickness from 0 to 

nearly 1,500 feet (460 m). The upper conglomerate is 

similar to the lower but contains debris derived from 

the volcanic member. The base of the upper unit is 

interpreted to be a minor intraformational unconformity. The thickness of the upper conglomerate 

ranges from 0 to at least 750 feet (230 m). The total 

thickness of the Glance Conglomerate in the Huachuca 

Mountains ranges from about 300 feet (90 m) near the 

north end of the range to about 3,600 feet (1,100 m) 

in the central part of the range.

The Morita Formation in the Huachuca Mountains 

is very similar to that in the Mule Mountains but contains a somewhat lower proportion of sandstone in the 

Huachucas. Its thickness in the Huachuca Mountains 

ranges from about 3,000 feet (900 m) in the northern 

part to about 4,200 feet (1,280 m) in the central part.

The Mural Limestone in the Huachuca Mountains, 

as in the Mule Mountains, can be divided into lower 

and upper members. The lower member in the Huachucas is basically similar to that in the Mules but 

contains a somewhat higher proportion of mudstone 

and a lower proportion of sandstone. The upper member in the Huachuca Mountains is made up of thinner 

bedded limestone than the upper member in the Mule 

Mountains and is interbedded with calcareous shale 

and siltstone and argillaceous limestone which together make up about one-third of the member. Thickness 

of the Mural in the Huachuca Mountains ranges from 

about 300 feet (90 m) near the north end of the mountains to about 800 feet (250 m) in the central part.

The Cintura Formation in the Huachuca Mountains 

and Canelo Hills area is basically similar to that in 

the Mule Mountains. Thickness of the formation in 

the Huachuca Mountains, zero to apparently more 

than 2,000 feet (600 m), is highly variable due to the 

effects of faulting and erosion that transpired after
B20 MESOZOIC STRATIGRAPHY IN SOUTHEASTERN ARIZONA

deposition of the Cintura and before deposition of the 

overlying Fort Crittenden Formation of Late Cretaceous age. Thickness of the formation in the Canelo 

Hills is unknown inasmuch as the base is not exposed 

there.

Fossil collections of stratigraphic value from the 

Bisbee Group in the Huachuca Mountains have all 

come from the Mural Limestone. Considered together 

these indicate a late Trinity to Fredericksburg age 

for the formation there, and they fairly well substantiate the lithologic correlation of the Mural in the 

Huachuca Mountains with that in the Mule Mountains. Presumably, the generally thicker sequence of 

rocks beneath the Mural in the Huachuca Mountains 

indicates that the Glance there, especially the volcanic 

unit and lower conglomerate, is probably older than 

the Glance in the Mule Mountains and that it might 

well be of early Early Cretaceous age.

A sequence of conglomerate, sandstone, and shale 

referred to the Fort Crittenden Formation unconformably overlies the Bisbee Group on a surface of 

low local relief in a series of interrupted exposures on 

the southwest side of the Huachuca Mountains and 

on the northeast side of the Canelo Hills. The formation, as it occurs here, can be divided into three informal members that grade into one another vertically 

and probably laterally. At the base is a conglomeratic 

member, next above it is a shale member, and above 

that is the upper conglomeratic member.

The basal conglomeratic member of the Fort 

Crittenden, which ranges in thickness from tens of 

feet to as much as 600 feet (180 m), is made up of 

conglomerate, conglomeratic graywacke, siltstone, and 

mudstone. The conglomerate, set in graywacke matrix, 

is mostly made up of well-rounded pebbles and cobbles 

of resistant sandstones and volcanic rocks. Shale and 

siltstone are like those in the shale member.

The shale member is made up largely of pale-olive 

to yellowish-brown or pale-red fissile shale and massive claystone but contains many beds of dusky-yellow 

locally pebbly graywacke. Fresh-water mollusks are 

locally common near the base of the member. The top 

of the member is not exposed on the southwest side of 

the Huachuca Mountains, but the unit is at least 650 

feet (200 m) thick there and according to E. B. Eaup 

(oral conunun., 1969) is about 1,200 feet (365 m) 

thick locally on the northeast side of the Canelo Hills.

The upper conglomeratic member is present only on 

the northeast side of the Canelo Hills. It is generally 

similar in lithology to the lower conglomerate member 

except that its pebbles and cobbles are not as well 

rounded and its bedding locally is more conspicuous.

At least 2,700 feet (825 m) of the member, whose top 

is nowhere preserved at the surface, is present in the 

area (E. B. Eaup, oral commun., 1969).

Cretaceous rocks younger than the Fort Crittenden 

Formation are not in contact with that formation on 

the northeast side of the Canelo Hills; but on the 

west side are strata, informally referred to as 

"volcanic and sedimentary rocks of Jones Mesa" by 

Hayes and Eaup (1968), that probably include correlatives of the upper part of the Fort Crittenden 

Formation and the lower part of the Salero Formation as well as sedimentary rocks and interbedded tuffs 

of Jurassic age. The lowest exposed part of this 

sequence of strata, whose base is missing along a fault, 

consists of at least several hundred feet of pale-pink 

to yellowish-brown feldspathic sandstone, minor similarly colored siltstone and shale, and a 20- to 50-footthick bed of light-gray biotite-rich tuff. These lower 

beds were once considered as possible equivalents of 

the upper part of the Fort Crittenden Formation 

(Hayes and Drewes, 1968, p. 56); but on the basis of 

a potassium-argon age determination of 165 ± 6 m.y. 

(million years) for biotite from welded tuff in the 

beds (from SW^NW^, sec. 25, T. 23 S., E. 18 E.) 

made by E. F. Marvin, H. H. Mehnert, and Violet 

Merritt of the U.S. Geological Survey (written 

commun., Sept. 23, 1969), the beds are now believed 

to be of Jurassic age. These Jurassic beds are overlain 

by a conglomeratic unit whose thickness is unknown 

because of internal faulting but which is probably at 

least 1,000 feet (300 m). This conglomeratic unit is 

dominantly siliceous material in a tuffaceous or feldspathic sandstone matrix in the lower part and is dominantly andesitic material in a graywacke matrix in 

the upper part; interbedded with the conglomerate is 

poorly exposed drab shale, olive graywacke, and at 

least one 30-foot-thick (9 m) bed of light-gray tuff. 

The conglomeratic unit apparently grades upward 

into a unit, probably at least 2,000 feet (600 m) thick, 

of dominantly gray crystal-lithic welded and nonwelded tuff and tuffaceous sandstone. High in this 

unit are interbeds of grayish-green to olive andesitic 

mulflow, lava, agglomerate, and conglomerate.

Biotite separated from a welded tuff in the upper 

unit of the Jones Mesa rocks yielded a potassiumargon age of 72 m.y. (S. C. Creasey, written commun., 

1964). This unit is similar in age and general lithology 

to the Salero Formation in the Santa Eita Mountains 

and is considered correlative. The underlying conglomerate unit probably represents the Fort Crittenden Formation which there lies uncomformably on 

Jurassic beds with the Bisbee Group missing.
CRETACEOUS PALEOGEOGRAPHY B21

PATAGONIA MOUNTAINS 

(Fig. 5, col. 8)

Sedimentary rocks of Early Cretaceous age are preserved in a triangular outcrop area of about 3 square 

miles on the east slope of the Patagonia Mountains, 

and volcanic rocks of probable Late Cretaceous age 

are preserved in a separate outcrop area at the north 

end of the range. The Lower Cretaceous rocks are 

considered correlative with the Bisbee Group but are 

not formally divided and therefore are referred to as 

the Bisbee Formation. These rocks were formerly 

assigned by Stoyanow (1949) to the Molly Gibson 

Formation. The Upper Cretaceous volcanics are probably equivalent to much of the Salero Formation. The 

brief descriptions that follow are summarized from 

preliminary data obtained from work in progress by 

F. S. Simons.

The Bisbee Formation in the Patagonia Mountains 

is at least 2,200 feet (670 m) thick and rests disconformably on a unit of dominant silicic volcanics of 

probable Triassic age. Above a basal conglomerate 

made up of detritus from the underlying volcanics is 

roughly 900 feet (275 m) of very fine grained clastic 

rocks that have been thoroughly altered to hornfels 

near a large intrusive body. Above that is a sequence 

nearly 1,400 feet (425 m) thick, of dominant siltstone 

and mudstone and subordinate sandstone and limestone. The siltstone and mudstone range from variably 

hued gray to pale purple and are commonly calcareous. Sandstone, relatively more abundant in the lower 

part of the 1,400-foot-thick sequence, is varicolored 

and generally feldspathic or arkosic. Limestone, relatively more abundant in the middle part of the 

sequence, occurs mostly in units less than 5 feet thick, 

is generally silty or sandy, and is rich in molluscan 

debris. Some tuffaceous material occurs in the upper 

part. The top of the Bisbee is cut out by faults in 

the area.

Fossils from the Bisbee Formation in the Patagonia 

Mountains are considered by E. W. Imlay of the U.S. 

Geological Survey (written commun., 1967) to indicate a correlation of their containing rocks with the 

Trinity Group of Texas. This supports the correlation with the type Bisbee Group in the Mule 

Mountains.

Rocks, of unknown thickness, that are lithologically 

similar to and probably correlative with the lower 

part of the Salero Formation in the Santa Rita Mountains are present around the north end of the Patagonia Mountains. Because of their proximity to the 

Salero in the Santa Ritas, the rocks are not described 

here. Rocks analogous to the Fort Crittenden Formation are not known in the Patagonia Mountains.

WHETSTONE AND EMPIRE MOUNTAINS 

(Fig. 5, col. 7)

Lower Cretaceous rocks are extensively exposed in 

and near the Whetstone and nearby Empire Mountains (fig. 4), and rocks of Late Cretaceous age occur 

in the Empires. The Lower Cretaceous Bisbee Group 

in the Whetstone Mountains was divided into several 

new formations by Tyrrell (1957). Creasey (1967b), 

who mapped the Whetstone Mountains, did not use 

Tyrrell's formations but included all the Lower Cretaceous strata in the Bisbee(?) Formation. Finnell 

(1970) has adopted Tyrrell's formations, with some 

modifications for use in the Empire Mountains area. 

Finnell's usage is followed here, but the following 

brief descriptions of the Bisbee Group in the Whetstone and Empire Mountains are taken from all three 

workers. Descriptions of the Upper Cretaceous rocks 

in the Empires are taken from unpublished data of 

T. L. Finnell.

The Bisbee Group is divided, in ascending order, 

into the Glance Conglomerate and the Willow Canyon, 

Apache Canyon, Shellenberger Canyon, and Turney 

Ranch Formations. The group rests on a surface of 

widely variable relief carved on Permian rocks in the 

Whetstone Mountains and on rocks ranging in age 

from Precambrian to Triassic in the Empire Mountains area. As a result of the great local relief of the 

underlying surface, the thickness of the Glance is 

extremely variable. Locally, near the north end of the 

Empire Mountains, the Willow Canyon, Apache Canyon, and basal one-third of the Shellenberger Canyon 

Formations grade laterally into a thick conglomeratic 

sequence assigned to the Glance that was deposited 

around the margins of a very high area underlain by 

Precambrian crystalline rocks. There, the upper twothirds of the Shellenberger Canyon Formation rests 

on the Glance Conglomerate.

The thickness and lithology of the Glance Conglomerate in these ranges, as in the Mule and Huachuca 

Mountains, is strongly controlled by the topography 

and lithology of the underlying surface. In the 

Whetstone Mountains and the southern part of the 

Empire Mountains, its clasts are largely derived from 

the Paleozoic formations which underlie it, and its 

thickness ranges from less than a foot to 400 feet 

(120 m). In the area around the north end of the 

Empire Mountains, in the vicinity of the abovementioned high area made up of Precambrian crystalline rocks, the Glance is as much as 5,600 feet 

(1,700 m) thick, and its clasts are largely derived 

from the Precambrian. The Glance is overlain by the 

Willow Canyon Formation with gradational contact.
B22 MESOZOIC STRATIGRAPHY IN SOUTHEASTERN ARIZONA

The Willow Canyon Formation consists predominantly of alternating units of sandstone and siltstone, 

but in the upper 300 feet (90 m) it includes subordinate thin beds of silty limestone and calcareous 

sandstone. Sandstone in the formation is light yellowish gray, light pinkish gray, and light yellowish 

brown, arkosic, crossbedded, and locally conglomeratic. The siltstone is commonly dark reddish brown in 

the lower two-thirds of the formation and commonly 

olive gray to greenish gray in the upper one-third. 

The Willow Canyon ranges in thickness from 0 to 570 

feet (175 m) in the Whetstone Mountains and from 

0 to at least 3,000 feet (900 m) in the Empire Mountains. The Willow Canyon is overlain by the Apache 

Canyon Formation with gradational contact.

The Apache Canyon Formation in the Empire 

Mountains and in the northern part of its main outcrop belt in the Whetstone Mountains consists of 

interbedded thinly laminated dark-gray silty limestone, dark-gray fissile shale, calcareous siltstone, and 

arkosic sandstones; one thin gypsum bed can commonly be found in the lower part. In the southern part 

of the Whetstones, limestone makes up a larger percentage of the formation, and most of it is lighter 

gray, thicker bedded, and not thinly laminated as it 

is to the north. In the Whetstone Mountains, the 

Apache Canyon is 550-740 feet (167-225 m) thick. 

In the Empire Mountains the formation is locally at 

least 1,600 feet (490 m) thick, and laterally it grades 

completely into the Glance Conglomerate near the 

north end of the range.

The Shellenberger Canyon Formation consists of 

interbedded shale, siltstone, sandstone, and some limestone. The shale and siltstone are commonly shades of 

olive brown, olive gray, greenish gray, and reddish 

brown. The sandstone is olive brown, olive green, olive 

gray, and pinkish gray, fine to very coarse grained, 

arkosic, massive to crossbedded, and lenticular. Some 

sandstone beds are conglomeratic at the base. Limestone, mainly restricted to the lower 1,300 feet 

(395 m) of the formation, is mostly thinly laminated 

and dark gray, but two beds about 1,000 and 1,300 

feet (300 and 395 m) above the base are distinctive 

brown-weathering sandy limestone rich in molluscan 

debris. The formation generally ranges in thickness 

from 3,950 to 4,330 feet (1,200 to 1,320 m), except near 

the north end of the Empire Mountains where the 

basal 1,000 feet (300 m) grades laterally into the 

Glance Conglomerate over a Precambrian high. The 

Shellenberger Canyon Formation is comformably 

overlain by the Turney Ranch Formation.

The Turney Ranch Formation, at least 3,200 feet 

(975 m) thick, consists of pale-red siltstone and

shale alternating with light-pinkish-gray to paleorange medium- to coarse-grained arkosic crossbedded 

sandstone.

The fossils closely diagnostic of age that have been 

found in the Bisbee Group in these ranges are dinosaur bones from between 1,000 and 1,300 feet (300 and 

395 m) above the base of the Shellenberger Canyon 

in the Empire Mountains and the clam Trigonia n.sp. 

from about 800 feet (240 m) above the base of the 

Shellenberger Canyon in the Whetstone Mountains. 

The dinosaur bones are considered by Miller (1964, 

p. 378) to be Early Cretaceous, and the Trigonia, considered with accompanying invertebrates, indicates, 

according to Tyrrell (1957, p. Ill), a late Early Cretaceous age (late Trinity or early Fredericksburg). 

Although a general correlation of the Bisbee Group in 

these ranges with that in the Huachuca and Mule 

Mountains seems certain, correlation of individual 

formations is more tenuous. On the basis of lithologies 

and known facies trends in the various ranges, the 

Apache Canyon Formation is tentatively considered 

to approximately correlate with the Mural Limestone 

(fig. 6). The Willow Canyon Formation, then, is considered a rough correlative of the Morita Formation, 

and the Shellenberger Canyon Formation is believed 

to be roughly equivalent to the Cintura Formation. 

The Turney Ranch Formation may be younger than 

any part of the Bisbee Group in the Mule or Huachuca Mountains, but on the basis of its lithology it is 

believed to properly belong to that group rather than 

being correlative with any of the known Upper Cretaceous formations of the region. Although the above 

correlations are favored here, a case could be made 

for correlating the Turney Ranch with the Cintura, 

which it resembles; for correlating at least the basal 

part of the Shellenberger Canyon with the Mural; 

and for correlating both the Apache Canyon and 

Willow Canyon Formations with the Morita.

Rocks that are correlated with the Upper Cretaceous Fort Crittenden Formation are locally exposed 

west of the north end of the Empire Mountains, and 

probable correlatives of the younger Upper Cretaceous 

Salero Formation are more widely exposed in the 

Empires; no Upper Cretaceous strata have been recognized in the Whetstone Mountains. The rocks correlated with the Fort Crittenden Formation include 

conglomerate, conglomeratic graywacke, and olive 

mudstone. These overlie isoclinally folded beds of the 

Turney Ranch and Shellenberger Canyon Formations 

with sharp angular unconformity. Elsewhere in the 

range, the Bisbee Group is overlain by a thick series 

of conglomerate, andesitic breccia, and rhyolitic tuff 

that is very similar to the Salero Formation in the
CRETACEOUS PALEOGEOGRAPHY B23

Santa Eita Mountains. As in the Santa Eita Mountains, the Salero in the Empire Mountains locally 

contains large exotic blocks of older formations.

SANTA RITA MOUNTAINS 

(Fig. 5, col. 6)

Formations assigned to the Cretaceous System in 

the Santa Eita Mountains (fig. 4) include the local 

Temporal and Bathtub Formations, which are dominantly volcanic units of early Early Cretaceous age; 

the Bisbee Group of late Early Cretaceous age, which 

is divided into the same formations as in the Empire 

and Whetstone Mountains; and the Fort Crittenden 

and Salero Formations of late Late Cretaceous age. 

The older two formations are exposed only in the 

southern part of the mountains. The Bisbee Group 

occurs in many outcrop areas but is most extensively 

exposed in the northern part of the range. The Fort 

Crittenden occurs in several places, but its most informative exposures are in the southeastern part of 

the range. The Salero Formation also occurs in several 

areas but is most completely exposed to the southwest. 

The following descriptions of Cretaceous strata in the 

Santa Eita Mountains are abstracted from Drewes 

(1970c).

The Temporal Formation, 1,000-2,000 feet (300- 

600 m) thick, is divided into three members. The lower 

member is rhyolitic to andesitic tuff, welded tuff, lava 

flows, and poorly sorted conglomerate. The middle 

member is conglomerate, rhyolitic tuff, and porphyritic latite flows. The upper member is boulder and 

cobble conglomerate, rhyodacite breccia, and lenses of 

other volcanic rock. Locally, the lower two members 

grade laterally into a thick unit of andesitic flows and 

volcanic breccia. The Temporal Formation rests on a 

surface of considerable relief carved in granite dated 

by two radiometric methods as Jurassic. The Temporal is overlain by the Bathtub Formation with a general disconformity but locally with slight angular 

unconformity.

The Bathtub Formation also consists of volcanic 

and sedimentary rocks divided into three members 

and is 1,500-2,300 feet (460-700 m) thick. The lower 

member is poorly sorted boulder conglomerate and 

volcanic sandstone. The middle member is rhyolitic 

tuff breccia and andesitic lava. The upper member is 

largely dacite volcanic breccia but contains some rhyolitic tuff and lava. The Bathtub Formation is overlain 

with slight unconformity by the Glance Conglomerate 

of the Bisbee Group.

The Glance Conglomerate in the Santa Eita Mountains, as the basal conglomeratic unit of the Bisbee

Group, is basically similar to the Glance in the ranges 

to the east and southeast. In most areas in the Santa 

Eita Mountains, the formation is only a few tens to a 

few hundred feet thick, but locally it is as much as 

1,500 feet (450 m) thick. Clasts in the conglomerate 

range from pebbles to boulders and are derived in large 

part from the nearest underlying formation, whatever 

it may be. The Glance rests on rocks as old as Precambrian granodiorite and as young as the Bathtub 

Formation of an assigned Early Cretaceous age; it 

locally rests on one of several Paleozoic formations. 

The Glance grades upward into the Willow Canyon Formation and locally intertongues with that 

formation.

The Willow Canyon Formation in the Santa Eita 

Mountains, about 2,200 feet (670 m) thick, is similar 

to the same formation in the Empire Mountains. It 

consists dominantly of interbedded arkosic sandstone 

and siltstone and contains scattered thin conglomeratic 

units in the lower part and thin impure limestone beds 

in the upper part. The formation contains a higher 

proportion of coarser clastic rock toward the west 

than toward the east. It is overlain by the Apache 

Canyon Formation with an arbitrary gradational 

contact.

The Apache Canyon Formation in the Santa Eita 

Mountains, 1,500-2,000 feet (450-600 m) thick, is 

made up largely of siltstone and mudstone with interbeds of fine-grained arkosic sandstone and arkose; an 

important subordinate lithology which allows correlation with the Apache Canyon in the Empire Mountains area, is limestone. Limestone in the formation is 

either thinly platy laminated rock or blocky fracturing calcarenite. Pebble conglomerate occurs sparingly 

in the Apache Canyon. The formation is gradationally 

overlain by the Shellenberger Canyon Formation.

Less than 1,000 feet (300 m) of the basal part of the 

Shellenberger Canyon Formation is represented in the 

Santa Eita Mountains. Here, as in the Empire Mountains, the formation is made up of dark-colored siltstone and shale with intercalated beds of olive-brown 

sandstone and minor limestone. The upper part of the 

Shellenberger Canyon and its contact with the presumably overlying Turney Eanch Formation are not 

exposed in the Santa Eitas.

A maximum of about 1,500 feet (450 m) of beds 

assigned to the Turney Eanch Formation is exposed 

in the Santa Eita Mountains. These beds consist dominantly of grayish-red siltstone interbedded with 

subordinate but conspicuous lenses of generally resistant feldspathic sandstone. The base of the Turney
B24 MESOZOIC STRATIGRAPHY IN SOUTHEASTERN ARIZONA

Ranch is not exposed in the Santa Ritas. The formation is overlain with slight angular unconformity by 

the Fort Crittenden Formation.

Fossils found to date in the Bisbee Group in the 

Santa Rita Mountains are dominantly of brackishwater origin and are only sufficient to indicate a 

Cretaceous age. The formations of the group are 

assigned to the Lower Cretaceous on the basis of 

regional lithologic correlations.

The oldest Upper Cretaceous strata in the Santa 

Rita Mountains are assigned to the Fort Crittenden 

Formation, whose reference section is in the southeastern part of the range. There, the Fort Crittenden rests 

with slight angularity on the Turney Ranch Formation. The Fort Crittenden, which is as much as 5,500 

feet (1,670 m) thick, is divided into five informal 

members in its reference section. The members, in 

ascending order, are: (1) A shale member, a few feet 

to 550 feet (170 m) thick, which consists dominantly 

of olive-gray shale but contains a thin lenticular basal 

conglomerate and a medial pelecypod-bearing siltstone 

unit; (2) a red conglomeratic member, as much as 

1,000 feet (300 m) thick, made up of about 35 percent 

pebble and cobble conglomerate derived from the 

Bisbee Group and older rock, 50 percent sandstone 

(subarkose to subgraywacke), and 15 percent siltstone 

and mudstone; (3) a brown-weathering conglomerate 

member, 2,030 feet (620 m) thick where measured, 

made up of 10-40 percent pebble and cobble conglomerate derived largely from granitic rocks, 20-50 percent arkosic sandstone, and 20-30 percent siltstone and 

mudstone; (4) another red conglomerate member, at 

least 1,400 feet (425 m) thick, that is similar to the 

lower one except that it contains considerable sedimentary breccia derived largely from the Bisbee 

Group; and (5) rhyolitic tuff, about 65 feet (20 m) 

thick, that is intercalated within the upper red conglomerate. Rocks on the west side of the Santa Rita 

Mountains that are assigned with little doubt to the 

Fort Crittenden Formation are conformably overlain 

by the Salero Formation.

Fossil fresh-water invertebrates, vertebrates including dinosaurian remains, and wood from the 

shale member of the Fort Crittenden Formation 

collectively indicate a late Late Cretaceous (Santonian 

to Maestrichtian) age and perhaps more likely late 

than early in this interval. The following evidence for 

a late Campanian age for the upper part of the 

apparently conformably overlying Salero Formation 

suggests that the type Fort Crittenden may, then, be 

of early Campanian age.

The Salero Formation conformably overlies the 

Fort Crittenden Formation only locally on the west 

side of the Santa Rita Mountains. Elsewhere in the 

range, it unconformably overlies a surface of some 

relief carved on a Jurassic granite. The Salero, with 

a composite maximum thickness of about 5,000 feet 

(1,500 m), is divided into four vertically sequential 

members and a fifth member that is a lateral facies, 

largely of one of the sequential members. The sequential members include a lower member of dacitic flows 

and tuff breccia, 400 feet (120 m) thick; an exoticblock-bearing member with a dacitic volcanic matrix, 

1,000 feet (300 m) thick; a rhyodacite welded tuff 

member at least 1,200 feet (360 m) thick; and an 

upper member, estimated to be 2,000-2,500 feet (600- 

750 m) thick, containing conglomerate, agglomerate, 

tuff, quartzite, and red beds. The fifth member is an 

arkosic fanglomerate that is largely a lateral facies 

of the welded tuff member and partly of the upper 

member. The Salero Formation has been intruded by 

plutonic rocks radiometrically dated as latest Cretaceous and Paleocene and is unconformably overlain by 

Cenozoic deposits.

A biotite separate from the welded tuff member 

yielded a potassium-argon age of 72 ±2 m.y,, which, 

according to Gill and Cobban (1966, p. A35), indicates a late Campanian age for the member. This age 

assignment is supported by a potassium-argon date of 

67 m.y. for biotite from a diorite that has intruded the 

Salero Formation. These data and the apparently 

conformable position of the Salero above the Fort 

Crittenden Formation indicate that the Salero is 

probably late Campanian and possibly earliest 

Maestrichtian in age.

SIERRITA MOUNTAINS

(Fig. 5, col. 5)

Rocks that are tentatively assigned to the base of 

the Cretaceous System in the Sierrita Mountains 

vicinity are included in the quartzite of Whitcomb 

Hill (Cooper, 1970). This unit, which ranges in thickness from about 300 feet (90 m) to nearly 600 feet 

(180 m), is made up of very light gray well-sorted 

orthoquartzite that contains lenses of medium-lightgray flinty rhyolitic tuff in the upper part. The unit 

rests with apparent disconformity on the formation of 

Rodolfo Wash of Triassic age and is overlain with a 

locally disconformable and locally gradational contact by the arkose of Angelica Wash of Early Cretaceous age. The locally gradational contact with the 

Angelica Wash rocks suggests an approximate corre-
CRETACEOUS PALE0GEOGRAPHY B25

lation of the quartzite of Whitcomb Hill with one of 

the volcanic units assigned to the base of the 

Cretaceous in the Santa Eita Mountains (the Bathtub 

or Temporal Formation) and with volcanic rocks in 

the Glance Conglomerate in the Huachuca Mountains. 

Assignment of an Early Cretaceous age to the quartzite of Whitcomb Hill remains tentative, however, 

because of the strong lithologic resemblance of the 

unit to the Stevens Mountain Bhyolite of Thorns 

(1967) in the west side of the Sierrita Mountains, a 

unit which, with good reason, is assigned a Triassic 

or Jurassic age.

Cretaceous strata are present in disconnected outcrops in various parts of the Sierrita Mountains. The 

following brief descriptions of these rocks are summarized from Cooper (1970) and Thorns (1966, 1967).

Above the quartzite of Whitcomb Hill in the Sierrita Mountains vicinity is the arkose of Angelica 

Wash. At one locality, ill-sorted metamorphosed conglomerate, which probably represents the basal part 

of the Angelica Wash strata, rests on the Whitcomb 

Hill strata with a gradational contact. At other 

localities, where the conglomerate is absent, the 

Angelica Wash strata rest on the Whitcomb Hill 

strata with a disconfonnable contact.

The arkose of Angelica Wash is lithologically different in its two principal outcrop areas, and the 

rocks exposed in the two areas may represent different 

facies of equivalent strata or different parts of the 

formation. The latter interpretation is favored by 

Cooper (1970). As interpreted by him, the lower 2,000 

feet (600 m) of Angelica Wash strata consists 

dominantly of thin- to medium-bedded arkose with 

subordinate interbedded siltstone that, where not significantly altered, is generally grayish red and slightly 

calcareous. Above the arkose and siltstone is 1,600 feet 

(485 m) of feldspathic grit and pebble conglomerate. 

The grit and conglomerate unit thickens to the northeast at the expense of the underlying arkose and 

siltstone. The upper several thousand feet of the 

Angelica Wash strata contains feldspathic sandstone 

and grit, pebble conglomerate, orthoquartzite, argillite, and limestone. The limestone beds are lenticular 

and contain pelecypods, gastropods, algal (?) heads, 

and fresh-water ostracodes that are of little use in 

dating.

Cooper (1970) has noted the great similarity in lithology of the arkose of Angelica Wash to the Amole 

Arkose of Brown (1939) in the Tucson Mountains and 

the similarity of both of these units to parts of the 

Bisbee Group in the Santa Rita Mountains. Possibly

the upper part of the Angelica Wash strata, whose 

pebble conglomerates have a graywacke matrix and 

whose limestones are apparently of fresh-water origin, 

is equivalent to the Upper Cretaceous Fort Crittenden 

Formation in the Santa Ritas, but correlation with the 

Lower Cretaceous Bisbee Group is favored here. Most 

of the sandstones of the arkose of Angelica Wash are 

intermediate in composition between the typical graywackes of the Fort Crittenden Formation and the feldspathic sandstones of the Bisbee Group in areas to the 

east. Regional facies changes within the Bisbee indicate a marked thinning of marine elements westward, 

and the absence of true marine limestones in the Sierrita Mountains equivalents is to be expected as is the 

transition into more feldspathic or arkosic sandstone. 

The arkose of Angelica Wash is overlain by the Demetrie Formation of Thorns (1967) with angular unconformity. This fact, incidentally, indirectly strengthens 

the correlation of the arkose of Angelica Wash with 

the Bisbee Group rather than with the Fort Crittenden 

Formation in that the Demetrie is correlated with little 

hesitation with the lower part of the Salero Formation, 

a unit which conformably overlies the Fort Crittenden 

in the Santa Rita Mountains and which unconf ormably 

overlies the Bisbee Group in the Empire Mountains.

The Demetrie Formation of Thorns (1967), the next 

formation younger than the arkose of Angelica Wash 

in the Sierrita Mountains, is a several-thousand-footthick sequence of andesitic to dacitic breccias and flows 

locally containing conglomerate and rhyolite tuff. 

Richard and Courtright (1960) and later workers correlated rocks included in the Demetrie with their Silver 

Bell Formation in the Silver Bell Mountains area, and 

that correlation is accepted here.

The youngest layered rock assigned a Cretaceous age 

in the Sierrita Mountains is the Red Boy Rhyolite of 

Thorns (1967). The Red Boy, whose maximum thickness is probably less than 1,000 feet (300 m), is made 

up dominantly of massive rhyolite tuff and tuff breccia. 

The formation overlies the Demetrie Formation of 

Thorns (1967) with apparent angular unconformity, 

is overlain with angular unconformity by gravel and 

basaltic andesite lava of middle or late Tertiary age, 

and has been intruded by andesite dikes and plugs that 

are petrographically like known lower Tertiary andesite dikes and plugs of the range. These geologic relations and compositional similarities, as previously 

suggested by Richard and Courtright (1960), clearly 

indicate correlation of the Red Boy Rhyolite with the 

Cat Mountain Rhyolite of Brown (1939) in the Tucson 

Mountains and, thus, with the upper part of the Salero 

Formation in the Santa Rita Mountains.
B26 MESOZOIC STRATIGRAPHY IN SOUTHEASTERN ARIZONA

AREAS TO WEST

TUGSON MOUNTAINS 

(Fig. 5, col. 4)

In the central and northern Tucson Mountains (fig. 

4), the Cretaceous sequence as described by Brown 

(1939) consists of a lower volcanic member, the Recreation Redbeds, and the Amole Arkose; the Amole 

Arkose is 2,275 feet (695 m) thick in one measured 

section. On the basis of a potassium-argon age determination for andesite prophyry intruding the Recreation Redbeds (Damon and others 1 ) and regional 

correlations (Hayes and Drewes, 1968), the Recreation 

Redbeds and underlying volcanics are now considered 

to be of Triassic age. The Amole Arkose yielded a 

sparse fauna considered by A. A. Stoyanow (Brown, 

1939, p. 719) to be of Late Cretaceous age but which, 

on the basis of further collections, was considered by 

J. B. Reeside, Jr. (McKee, 1951), to be probably Early 

Cretaceous. The Amole Arkose as seen in its type area 

is very similar in many lithologic details to rocks of 

the Bisbee Group of known Early Cretaceous age in 

the Empire and northern Santa Rita Mountains and is 

here believed to be an approximate correlative.

In the southern Tucson Mountains, Kinnison (1958) 

studied the Amole Arkose of Brown (1939) and reported ostracodes from the lower part of the sequence 

that are no younger than Early Cretaceous, but he 

found pollen no older than Late Cretaceous in the 

upper part. Possibly these pollen-bearing Upper Cretaceous beds in the southern part of the mountains are 

unconformable on underlying parts of the Amole and 

are younger than any Amole in the type area. They 

may be more closely allied to Upper Cretaceous sedimentary rocks known elsewhere in the region.

In the central and northern Tucson Mountains, the 

Tucson Mountain Chaos of Kinnison (1959), 330 feet 

(100 m) thick in one section, rests with angular unconformity on the Amole Arkose of Brown (1939) of 

probable Early Cretaceous age and is overlain with 

apparent conformity by the Cat Mountain Rhyolite of 

Brown (1939). Except for a local basal conglomerate 

member, the Tucson Mountain Chaos consists of a 

chaotic jumble of exotic blocks of dominant Cretaceous 

and Paleozoic rocks set in an andesitic matrix, and it is 

very similar to the exotic-block-bearing member of the 

Salero Formation in the Santa Rita Mountains. The 

Cat Mountain Ehyolite is a welded tuff unit, at least 

800 feet (240 m) thick, which has been dated by the 

potassium-argon method as 65.6 and 70.3 m.y. (Biker1 Damon, P. E., and others, 196T, Annual Progress report COO-689-T6 

to Research Division, United States Atomic Energy Commission; Correlation and chronology of ore deposits and volcanic rocks: Tucson, 

Arizona Univ., Geochem. Section, Geochronology Labs., unpub. rept.

man and Damon, 1966, p. 1232) dates comparable to 

that obtained for biotite from a sample of the lithologically similar welded tuff member of the Salero Formation (p. B24). There is little doubt that the Tucson 

Mountain Chaos and the Cat Mountain Rhyolite are 

comparable in age to the Salero.

ROSKRUGE MOUNTAINS 

(Fig. 5, col. 3)

On the east side of the Roskruge Mountains (fig. 4), 

about 10 miles (16 km) west of the Tucson Mountains, 

is a sequence of gray-green arkose and graywacke, gray 

quartzite, red and gray mottled mudstone, and pebble 

conglomerate, estimated to be about 2,000 feet (600 m) 

thick, which was named the Cocoraque Formation by 

Heindl (1965a). He noted the lithologic similarity of 

the formation to the Amole Arkose of Brown (1939) 

in the Tucson Mountains. In view of regional relations, 

a correlation of the two units seems reasonable. The 

base of the Cocoraque is not exposed. The formation is 

unconformably overlain by the Roadside Formation.

The several-thousand-foot-thick Roadside Formation, consisting of andesitic and dacitic breccias and 

flows and beds of pebbly mudstone to boulder conglomerate and breccia, was stated by Heindl (1965a, p. Hll) 

to be equivalent to the Claflin Ranch and Silver Bell 

Formations of Richard and Courtright (1960) in the 

Silver Bell Mountains area. The overlying Roskruge 

Rhyolite, possibly as much as 4,000 feet (1,200 m) 

thick, yielded radiometric dates of about 70 to 72 m.y. 

(Bikerman, 1967) and was tentatively correlated by 

Heindl (1965a, p. H14) with the Cat Mountain Rhyolite of Brown (1939) in the Tucson Mountains. The 

Roadside Formation and the Roskruge Rhyolite together are probably equivalent to the Salero Formation in the Santa Rita Mountains.

SILVER BELL MOUNTAINS

(Fig. 5, col. 2)

A sequence of arkosic sedimentary rocks of unknown 

thickness comprises the oldest known Cretaceous unit 

in the Silver Bell Mountains area (fig. 4). These rocks 

have not been described in detail or have I seen them, 

but presumably they are equivalent to the Cocoraque 

Formation in the Roskruge Mountains area and, hence, 

are probably of Early Cretaceous age. Relations with 

younger Cretaceous rocks in the area are uncertain.

The Claflin Ranch Formation of Richard and Courtright (1960) in the Silver Bell Mountains area, when 

named, was described as resembling the Tucson Mountain Chaos of Kinnison (1959) in the Tucson Mountains "except for the absence of large limestone blocks," 

and the two units were correlated with one another.
CRETACEOUS PALEOGEOGRAPHY B27

The Silver Bell Formation of Richard and Courtright 

(1960), dominantly andesitic breccias, overlies their 

Claflin Ranch Formation and is overlain by "pyroclastics and ignimbrites" that were correlated with the Cat 

Mountain Rhyolite of Brown (1939) in the Tucson 

Mountains. All these units are probably generally correlative with the Salero Formation in the Santa Rita 

Mountains.

VEKOL MOUNTAINS

(Fig. 5, col. 1)

The Mesozoic rocks in the Vekol Mountains area 

(fig. 4) were described by Heindl (1965b). He suggested no definite correlation of units there with Lower 

Cretaceous formations to the east, but he did note the 

general similarity of the Phonodoree Formation in the 

Vekol Mountains area to the much thicker Recreation 

Redbeds of Brown (1939) in the Tucson Mountains. 

If the two formations are indeed correlative and the 

Recreation Redbeds are Triassic in age, as is now 

believed likely (p. B26), then there may be no Lower 

Cretaceous in the Vekol Mountains, because the Vekol 

Formation, which overlies the Phonodoree, is most 

probably correlative with Upper Cretaceous volcanics 

in areas to the east. Very possibly, Lower Cretaceous 

rocks related genetically to the Bisbee Group were 

never deposited as far west in Arizona as the Vekol 

Mountains.

The Vekol Formation, 2,000-3,000 feet (600-900 m) 

thick, includes lenses of conglomerate, gray-green pebbly arkose and graywacke, green and maroon mudstone, and beds of quartzite, arkosic quartzite, aphanitic 

claystone, and minor interlayered andesite. Heindl 

(1965b) compared gray-green and purplish-gray volcanic conglomerate beds in the Vekol Formation with 

those in the Claflin Ranch and Silver Bell Formations 

of Richard and Courtright (1960), although he implied 

no correlations. The Vekol Formation is overlain by 

the Chiapuk Rhyolite which Heindl (1965b) considered 

to be contemporaneous with the Cat Mountain Rhyolite of Brown (1939) in the Tucson Mountains. It 

is here considered possible, if not probable, that both 

the Vekol Formation and the Chiapuk Rhyolite are 

general equivalents to the Salero Formation in the 

Santa Rita Mountains (fig. 5).

OTHER AREAS

Strata of definite or probable Cretaceous age occur 

in several other ranges within 60 miles (100 km) west 

of the Santa Cruz River but have not yet been studied 

in any detail. In the several small ranges south of the 

Sierrita Mountains, extensive areas have been mapped 

in reconnaissance (Wilson and others, 1969) as being

underlain by Cretaceous sedimentary and volcanic 

rocks, and Harald Drewes and I have briefly examined 

several of these areas. We believe that rocks mapped 

as Cretaceous sedimentary rocks a few miles southeast 

of Arivaca (fig. 4), near Oro Blanco, represent correlatives of the Lower Cretaceous Bisbee Group, that 

rocks mapped as Cretaceous sedimentary rocks south 

and west of Arivaca more likely belong to the Triassic 

System, and that rocks mapped as Cretaceous andesite 

north of Arivaca represent correlatives of the Upper 

Cretaceous Salero Formation.

In the Baboquivari Mountains, Heindl and Fair 

(1965) described strata of probable Mesozoic age, but 

they did not suggest any definite correlations with 

Cretaceous or other Mesozoic rocks to the east. Accompanied by Harald Drewes, I have walked over the 

sequence in the Baboquivaris and, on the basis of that 

brief visit, am unable to make definite correlations, but 

the following possibilities are presented. The Ali 

Molina Metamorphic Complex probably contains the 

oldest of the Mesozoic (?) strata in the range, and 

these may be equivalent to Triassic volcanics known in 

the Sierrita and Santa Rita Mountains (Hayes and 

Drewes, 1968). The Pitoikam Formation, about 9,200 

feet (2,800 m) thick, was suggested by Heindl and 

Fair (1965, p. 16) to be partly equivalent to the Ali 

Molina, and I believe that all or most of the Pitoikam 

could certainly be of Triassic and (or) Jurassic age. 

The Chiltepines Member at the top of the Pitoikam, 

however, bears some resemblance to the Bisbee Group 

in areas to the east, and it may be a sourceward equivalent of the Bisbee. The overlying Mulberry Wash Volcanic Formation, 3,000 feet (900 m) thick, is largely 

volcanic and could be either Triassic and (or) Jurassic 

or Upper Cretaceous. The Chiuli Shaik Formation, 

about 2,000 feet (600 m) thick, has lithologies in common with the Salero Formation and seems to be a likely 

correlative. In conclusion, it seems that in the Baboquivari Mountains, correlatives of the Bisbee Group, if 

present, belong to a more landward and sourceward 

facies than the Bisbee in areas to the east and that 

equivalents of the Fort Crittenden Formation, if 

present, are of a more volcanic facies than the Fort 

Crittenden in areas to the east.

AREAS TO EAST

DRAGOON MOUNTAINS AND TOMBSTONE

AREA 

(Fig. 5, col. 11)

In the Dragoon Mountains (fig. 4) and a few miles 

to the west in the Tombstone area is a thick sequence 

of rocks similar in lithology to the combined Glance 

Conglomerate, Morita Formation, and Cintura Forma-
B28 MESOZOIC STRATIGRAPHY IN SOUTHEASTERN ARIZONA

tion in the Mule Mountains that was described in detail 

by Gilluly (1956, p. 76-82) and called the Bisbee 

Formation. Although a few impure fossiliferous limestone beds are present in the sequence, no lithologic 

equivalent of the Mural Limestone is present. However, 

there is little doubt that the Bisbee Formation in the 

Dragoon Mountains vicinity is a general landward 

equivalent of the Bisbee Group in the Mule Mountains. 

Gilluly (1956, p. 78) estimated that the formation is 

about 15,000 feet (4,500 m) thick in the east-central 

part of the range.

Beneath the Bisbee Formation in the South Pass 

area in the Dragoon Mountains is an unnamed sequence 

of exotic-block-bearing volcanic rocks. Gilluly (1956, p. 

68) described these rocks as "chiefly andesite and rhyolitic pyroclastic rocks but with some interbedded flow 

breccias" and, with some evidence, tentatively regarded 

them as Cretaceous; he suggested, however, that they 

could be Triassic or Jurassic. The rocks resemble volcanics here regarded as Lower Cretaceous in the Glance 

Conglomerate in the Huachuca Mountains, but they 

also resemble the Walnut Gap Volcanics in the Little 

Dragoon Mountains area which Cooper and Silver 

(1964, p. 72-73) regarded as Triassic or Jurassic and 

which Hayes and Drewes (1968) regarded as Late 

Triassic. Inasmuch as volcanics of Triassic and Jurassic 

age seem to have a wider distribution in southeastern 

Arizona than volcanics of Early Cretaceous age, the 

volcanics in the South Pass area are here tentatively 

considered to be Triassic or Jurassic. If they are Cretaceous, they are the northernmost known occurrence 

of Lower Cretaceous volcanics in southeastern Arizona.

In the Tombstone area, the Bronco Volcanics, estimated to be 5,000-6,000 feet (1,500-1,800 m) thick 

(Gilluly, 1956, p. 88), unconformably overlies deformed strata of the Bisbee Formation. The Bronco is 

made up of andesitic breccia in the lower part and 

dominant quartz latite and quartz latite tuffs above. 

The formation has been intruded by the Schieffelin 

Granodiorite whose age, according to the potassiumargon method of dating, is 72 m.y. (Creasey and Kistler, 1962). The Bronco, formerly assigned a Cretaceous 

or Tertiary age, is very likely equivalent to the Upper 

Cretaceous Salero Formation in areas to the west.

The Sugarloaf Quartz Latite in and near the southeast side of the Dragoon Mountains, as described by 

Gilluly (1956, p. 90-93), is comparable in lithology to 

the upper part of the Bronco Volcanics. The Sugarloaf 

was assigned the same general age as the Bronco by 

Gilluly, and it seems probable that much, if not all, of 

the Sugarloaf is equivalent to at least the upper rhyodacitic part of the Salero Formation. This correlation 

is bolstered by a potassium-argon age determination

(K. F. Marvin, H. H. Mehnert, and Violet Merritt, 

written commun., 1969), of 72.8 ±2.5 m.y. for biotite 

separated from welded tuff which was collected by 

Harald Drewes from the type locality of the Sugarloaf.

DOS CABEZAS AND NORTHERN CHIRICAHUA 

MOUNTAINS 

(Fig. 5, col. 12)

The Bisbee Group in the Dos Cabezas and northern 

Chiricahua Mountains (fig. 4) was described by Sabins 

(1957b), who recognized the Glance Conglomerate at 

the base and an undivided upper part. The Glance, 

which unconformably overlies Permian strata, ranges 

in thickness from 20 to perhaps 1,000 feet (6 to perhaps 

300 m), and the clasts that comprise it vary considerably in composition. Above the Glance, Sabins measured 700 feet (212 m) of siltstone and associated 

coarser elastics, 220 feet (67 m) of interbedded limestone, siltstone, and shale that pinch out northwestward in the Dos Cabezas, and 1,650 feet (500 m) of 

sandstone and siltstone. The top of the Bisbee is missing due to erosion throughout the area. I suspect that 

all the exposed strata above the Glance Conglomerate 

are general equivalents to the Morita Formation in the 

Mule Mountains (fig. 6). The limestone member may 

be approximately equivalent to impure limestones far 

beneath the probable equivalent of the upper member 

of the Mural in the Pedregosa Mountains (p. B29).

North of the Dos Cabezas Mountains, strata equivalent to the Bisbee Group are apparently absent, probably due to nondeposition.

The Nipper Formation of Sabins (1957a) along the 

east side of the Chiricahua Mountains consists of 

andesitic flows, volcanic conglomerates, and associated 

sediments and is a probable equivalent of the lower part 

of the Salero Formation and correlatives. The Nipper 

Formation lies with angularity on Lower Cretaceous 

and Paleozoic rocks and is overlain by the Faraway 

Ranch Formation of Enlows (1951), which was tentatively assigned a mid-Tertiary age by Fernandez and 

Enlows (1966, p. 1028).

PEDREGOSA AND CENTRAL AND SOUTHERN 

CHIRICAHUA MOUNTAINS

(Fig. 5, col. 13)

The Bisbee Group as it occurs in the Pedregosa 

Mountains (fig. 4) and adjoining parts of the southern 

Chiricahua Mountains has been described by Epis 

(1956). There the Glance Conglomerate is 30-150 feet 

(9-45m) thick. It is overlain by 1,350 feet (950 m) of 

beds assigned to the Morita Formation. Above that are 

3,120 feet (950 m) of interbedded marine and nonmarine strata that at various horizons have similarities 

to both the Morita Formation and the lower member
CRETACEOUS PALEOGEOGBAPHY B29

of the Mural Limestone in the Mule Mountains. Calcareous algae from limestones in the lower part of this 

sequence are believed by Konishi and Epis (1962) to 

indicate a tropical marine environment within the 

lower littoral and upper infralittoral zones. Above 

those beds is 200 feet (60 m) of OrbitoUna-be&ring 

marine limestone that is here correlated with the upper 

member of the Mural Limestone in the Mule Mountains (fig. 6). This limestone is overlain by 3,200 feet 

(970 m) of beds assigned by Epis (1956) to the Cintura Formation. For reasons discussed in the second 

following paragraph, I believe that the highest 500 feet 

(150 m) of these strata assigned to the Cintura is probably of late Late Cretaceous age and approximately 

correlative with the Fort Critteiiden Formation in the 

Huachuca and Santa Eita Mountains.

A previously undescribed sequence of strata correlative with the Bisbee Group was examined in reconnaissance during the present study along the Snowshed 

Trail on the east side of the central Chiricahua 

Mountains. There, above a thin basal conglomerate 

resting unconformably on Permian strata, is an estimated 4,500 feet (1,350 m) of strata somewhat similar 

to the basal 4,500 feet of beds described by Epis (1956) 

in the Pedregosa Mountains, except that the strata 

contain abundant interbedded dark-gray shale and less 

limestone. Above these strata are some thick-bedded 

marine limestone beds, one of which yielded a fossil 

identified by W. A. Cobban (written commun., 1960) 

as Trigonia cf. T. stolleyi Hill. Trigonia stolleyi is a 

Trinity form that was identified by Stoyanow (1949) 

from beds in the Mule Mountains area that are here 

considered to be a part of the lower member of the 

Mural Limestone.

Epis (1956) described a largely conglomerate sequence that is as much as 4,000 feet (1,200 m) thick and 

lies between the Bisbee Group and overlying propylitized andesites in the Pedregosa Mountains area. The 

conglomerates are made up of generally well rounded 

pebbles, cobbles, and occasional boulders derived from 

the Bisbee Group and various Paleozoic formations. 

Epis (1956) reasonably considered these conglomerates as approximate correlatives of the Cabullona 

Group of Taliaferro (1933) in Sonora and of the 

Skunk Ranch Conglomerate in the Little Hatchet 

Mountains in New Mexico. Possibly, the top 500 feet 

(180 m) of the poorly exposed underlying strata assigned by Epis (1956) to the Cintura Formation of 

the Bisbee Group is also of Late Cretaceous age. These 

uppermost strata assigned to the Cintura by Epis 

resemble much of the sandstone and shale of the Cabullona Group of Taliaferro and some beds in the Fort 

Crittenden Formation. They include at several horizons, thin conglomeratic sandstone beds that contain 

debris apparently derived from the Bisbee Group and 

include at least one bed of volcanic conglomerate. As 

stated by Epis (1956), the contact between the Bisbee 

Group and Upper Cretaceous strata must be "an unconformity of considerable significance, although * * * 

strata above and below it generally have the same 

strike and dip."

An estimated 2,500 feet (750 m) of andesitic flows, 

agglomerates, breccias, and tuff breccias in the Pedregosa Mountains, described by Epis (1956), gradationally overlies the thick sequence of sedimentary 

rocks of probable Late Cretaceous age. These volcanics 

are similar in lithology and stratigraphic relations to 

the Salero Formation in the Santa Rita Mountains and 

are undoubtedly approximately correlative. Epis (1956, 

p. 180) tentatively correlated these andesites in the 

Pedregosa Mountains with similar andesites in the 

Christmas (fig. 4) and nearby Stanley districts that 

Richard and Courtright (1960) have since correlated 

with their Silver Bell Formation in the Silver Bell 

Mountains area.

PELONCILLO MOUNTAINS, N. MEX. AND ARIZ. 

(Fig. 5, col. 14)

Gillerman (1958) described the Bisbee Group in the 

central Peloncillo Mountains in New Mexico (fig. 4), a 

few miles east of the New Mexico-Arizona State line. 

At the base, resting on an erosion surface of considerable relief carved on Paleozoic rocks, is the McGhee 

Peak Formation of Gillerman (1958), 370 to about 

600 feet (110 to about 180 m) thick, which includes 

some conglomerate at the base but is generally comparable to the 700 feet (210 m) of strata above the 

Glance Conglomerate in the Dos Cabezas and northern 

Chiricahua Mountains. Above the McGhee Peak is the 

Carbonate Hill Limestone of Gillerman (1958), which 

is probably about 225 feet (68 m) thick. It has yielded 

a fauna of Aptian age and was correlated by Gillerman (1958) with the Quajote Member of the Lowell 

Formation of Stoyanow (1949) part of the lower 

member of the Mural Limestone of this report. It is 

here correlated on the basis of lithology with the 

limestone unit in the Bisbee Group in the Dos Cabezas 

and northern Chiricahua Mountains (fig. 6). Above 

the Carbonate Hill Limestone is the Still Ridge Formation of Gillerman (1958), which is 685 feet (208 m) 

thick in one section. This unit, which includes some 

limestone, may also be somewhat older than the upper member of the Mural Limestone in the Mule 

Mountains (fig. 6). The Still Ridge Formation is overlain by the Johnny Bull Sandstone of Gillerman 

(1958), which is more than 1,000 feet (300 m) thick.
B30 MESOZOIC STRATIGRAPHY IN SOUTHEASTERN ARIZONA

This unit was conjecturally assigned to the Lower 

Cretaceous by Gillerman but is here believed to be 

of possible late Late Cretaceous age and, hence, not 

properly a part of the Bisbee Group. The formation 

contains a siliceous pebble conglomerate bed near the 

apparently conformable base and includes much darkcolored subgraywacke interbedded with lighter colored 

sandstones and brown shales. Although the formation has yielded no fossils, the nature of the thin 

conglomerate units and the subgraywacke suggests a 

possible correlation with the Fort Crittenden Formation and equivalents rather than with the Bisbee 

Group.

On and near the west side of the southern Peloncillo 

Mountains in Arizona, just north of the United 

States-Mexico border, rocks mapped as the Bisbee 

Formation by Cooper (1959) have not been studied in 

detail but have some features that are worthy of note. 

The base of the formation, poorly exposed in very 

limited outcrops, consists of a few feet of limestone 

cobble and pebble conglomerate resting unconformably on Permian strata. Not far above the base is an 

unusual massive graywacke that contains pebbles and 

cobbles of volcanic rock, the easternmost known occurrence of volcanic cobbles in the lower part of the 

Bisbee. Above this, the Bisbee in the southern Peloncillo Mountains area seems to be similar to that in 

the Pedregosa Mountains in that marine limestone 

beds interbedded with sandstones and mudstones of 

probable fluviatile origin occur within a few hundred 

feet of the base and are found through perhaps 

several thousand feet of section. Some limestone beds 

high in the sequence are thick and massive and appear 

to be biohermal; these may be equivalent to the upper 

part of the type Mural Limestone in the Mule 

Mountains.

BIG HATCHET AND ANIMAS MOUNTAINS, N. MEX. 

(Fig. 5, col. 16)

A thick sequence of Lower Cretaceous rocks in the 

Big Hatchet Mountains area of southwestern New 

Mexico (fig. 4) was described in detail by Zeller 

(1965). The lowest stratigraphic unit, 1,274 feet (388 

m) thick, is the Hell-to-Finish Formation of Zeller 

(1965), consisting dominantly of mudstone and siltstone with subordinate arkose and limestone; there 

is conglomerate at the base. Above the Hell-to-Finish 

is the dominantly limestone U-Bar Formation of 

Zeller (1965), which is about 3,500 feet (1,060 m) 

thick. The formation has yielded a rather rich fauna 

of mollusks and Orbitolina and is considered to be of 

Aptian and Albian age. As suggested by Zeller (1965), 

a general correlation of the upper part of the formation with the Mural Limestone in the Mule Mountains 

is reasonable (fig. 6). Overlying the U-Bar is the 

Moj ado Formation of Zeller (1965). The lower 4,109 

feet (1,253 m) of the formation consists chiefly of 

unfossiliferous sandstone and shale and may be approximately equivalent to the Cintura Formation in 

the Mule Mountains. The upper 1,086 feet (331 m) of 

the Mo j ado consists of sandstone and shale and calcareous beds which yield marine fossils that are considered to be of middle to late Washita age and thus 

may be younger than any Lower Cretaceous strata 

assigned to the Bisbee Group elsewhere in this report. 

They may be closely related to strata of very early 

Late Cretaceous age known farther north in the Silver 

City-Santa Rita area of New Mexico.

In the Animas Mountains, west of the Big Hatchet 

Mountains, Zeller and Alper (1965) recognized the 

Hell-to-Finish, the U-Bar, and the Mo j ado Formations; these are overlain by a conglomeratic unit, the 

Cowboy Spring Formation of Zeller and Alper (1965). 

In the Animas Mountains, the Hell-to-Finish Formation is extremely variable in thickness owing to relief 

on the underlying surface carved in Permian rocks. 

The U-Bar Formation is only about one-half as thick 

as it is in the Big Hatchet Mountains area as a result, 

according to Zeller and Alper (1965), of its deposition 

over an actively rising anticline. The Cowboy Spring 

Formation was described as conformably overlying the 

Mo j ado Formation and was assigned a late Early 

Cretaceous or early Late Cretaceous age. Zeller and 

Alper (1965) also noted that some observers have suggested that the formation may be correlative with the 

lithologically similar Skunk Ranch Conglomerate in 

the Little Hatchet Mountains. This correlation was not 

accepted by Zeller and Alper (1965) because of the 

presumed Trinity age of the Skunk Ranch and the 

apparently conformable relations of their Cowboy 

Spring Formation on the post-Trinity Mojado Formation. Inasmuch as I believe that the Skunk Ranch Conglomerate is of late Late Cretaceous age (see p. B31) 

and inasmuch as rocks of this age in many places in 

the region overlie Lower Cretaceous rocks with parallel 

but disconformable contact, it is here suggested that 

the Cowboy Spring Formation may indeed be equivalent to the Skunk Ranch and may be of late Late 

Cretaceous age.

LITTLE HATCHET MOUNTAINS, N. MEX. 

(Fig. 5, col. 15)

All the Cretaceous strata of the structurally complex 

Little Hatchet Mountains in New Mexico (fig. 4) were 

considered to be of Early Cretaceous age and were
CRETACEOUS PALEOGEOGRAPHY B31

included in the Bisbee Group by Lasky (1947, p. 

16-26). The sequence there, as described by him in 

ascending order, includes (1) the Broken Jug Limestone, as much as 5,000 feet (1,500 m) thick but whose 

base is not exposed; (2) the PAysa-bearing Ringbone 

Shale, as much as 650 feet (200 m) thick, which in 

most places rests on the Broken Jug with an erosional 

unconformity with possible relief of more than 2,000 

feet (600 m); (3) the Hidalgo Volcanics, with a maximum thickness that may exceed 5,000 feet (1,500 m) 

and which overlies the Ringbone with a disconf ormable 

but nearly parallel contact; (4) the Howells Ridge 

Formation, about 5,000 feet (1,500 m) thick, which is 

lithologically very similar to the Broken Jug Limestone and is described as overlying the Hidalgo Volcanics with a disconformable contact having a relief 

of at least 1,200 feet (350 m); (5) the conformably 

overlying Corbett Sandstone, about 4,000 feet (1,200 

m) thick; (6) the Play as Peak Formation, more than 

3,000 feet (900 m) thick, which is similar in lithology 

to the Broken Jug Limestone and Howells Ridge 

Formation and which overlies the Corbett with a contact described as disconformable; and (7) the Skunk 

Ranch Conglomerate, which contains boulders derived 

from both Cretaceous and Paleozoic formations and 

which overlies the Playas Peak with a disconformable 

contact. The total composite thickness of the Bisbee 

Group as described by Lasky is about 26,000 feet 

(8,000 m).

Although the general high quality of Lasky's (1947) 

work in the Little Hatchets is not questioned, I consider it very likely that at least two of the disconformities described by Lasky (1947) in the sequence are 

strike faults and that the section has been repeated. 

Zeller (1965, p. 73-75) expressed serious suspicions 

about the validity of the sequence as described but 

offered no suggestions as to what he believed were the 

actual relations. I have visited the Little Hatchet 

Mountains briefly three times and, although I did not 

walk out the possible fault contacts, I crossed them at 

several points. On the basis of those visits to the area 

and of lithology, fauna, and regional stratigraphic 

relations, a reconstruction of the sequence in the Little 

Hatchet Mountains is tentatively offered here. Even 

though my interpretation of the sequence in the range 

is used in making my regional paleogeographic interpretations, it is not now proposed that formal changes 

should be made in the stratigraphic terminology of 

the area until someone has completed a detailed restudy 

of the area. However, the term Bisbee Group is not 

used in the Little Hatchet Mountains in this paper.

If the "disconformable contacts" at the base of the 

Howells Ridge and Playas Peak Formations are indeed

faults, as I believe they are, then the Broken Jug Limestone, Howells Ridge Formation, and Playas Peak 

Formation probably are actually the same formation. 

All are similar in lithology and contain very similar 

<9rfoY0Zm#-bearing faunas of Trinity age. All can then 

be correlated with the lithologically and faunally 

similar U-Bar Formation of Zeller (1965) in the nearby Big Hatchet Mountains area (fig. 5). The Corbett 

Sandstone, which conformably overlies the Howells 

Ridge, can then be correlated with the lithologically 

nearly identical lower 4,000 feet (1,200 m) or so of the 

Moj ado Formation of Zeller (1965).

The Ringbone Shale, which overlies the Broken Jug 

Limestone in the northern part of the range with 

erosional unconformity, I believe is approximately correlative with the Fort Crittenden Formation in southeastern Arizona and should not be considered as a 

Bisbee Group equivalent. At the base of the Ringbone 

is a conglomerate containing debris derived from 

Lower Cretaceous rocks. In the shales are fossil remains 

of the gastropod Physa which are also locally abundant 

in the Fort Crittenden Formation. The shales in the 

Ringbone are much more similar to those in known 

Upper Cretaceous rocks in southeastern Arizona and 

Sonora than to Lower Cretaceous shales in the region. 

Richard and Courtright (1960) previously postulated 

a post-Bisbee age for the Ringbone Shale.

The Skunk Ranch Conglomerate, which overlies the 

Playas Peak Formation in the southern part of the 

Little Hatchet Mountains with erosional unconformity, 

contains debris derived from Lower Cretaceous and 

Paleozoic rocks. The Skunk Ranch may be a thick 

equivalent of conglomerates at the base of the Ringbone. Very reasonably, Epis (1956) considered the 

Skunk Ranch to be a general correlative of the Upper 

Cretaceous Cabullona Group of Taliaferro (1933).

The Hidalgo Volcanics which disconf ormably overlie 

the Ringbone Shale are here considered approximately 

equivalent to the lower part of the Salero Formation 

in. southeastern Arizona. On the basis of lithologic 

similarity and an interpretation of the geologic relations similar to that made here, Richard and Courtright (1960) tentatively correlated the Hidalgo 

Volcanics with their Silver Bell Formation in the 

Silver Bell Mountains area, a formation that is here 

correlated with the lower part of the Salero Formation.

In summary, if the section in the Little Hatchet 

Mountains is reconstructed as proposed here, there is 

a sequence of Lower Cretaceous rocks, about 9,000 feet 

(2,750 m) thick (with the base not exposed), that is 

closely comparable to the sequence in the Big Hatchet 

Mountains and that can be reasonably correlated with 

sections to the west in southeastern Arizona. Above the
B32 MESOZOIC STRATIGRAPHY IN SOUTHEASTERN ARIZONA

Lower Cretaceous rocks are formations that appear to 

be similar to and correlative with Upper Cretaceous 

formations in southeastern Arizona.

OTHER AREAS

Cretaceous rocks crop out in several other areas in 

southwestern New Mexico. In. some of these areas, the 

rocks are so similar to those in nearby areas already 

described that no further description is useful here, 

and in some areas the rock exposures are so limited 

that they are of little value in regional interpretations. 

The Cretaceous rocks along the west side of the Tres 

Hermanas Mountains, however, are worthy of brief 

mention.

In the Tres Hermanas Mountains, both the upper 

and lower contacts of the Cretaceous rocks are fault 

zones, and therefore the total thickness is unknown; 

but Kottlowski and Foster (1962, p. 2097) measured 

1,530 feet (486 m) of exposed beds between the faults 

which, in ascending order, they described as follows: 

374 feet (114 m) of chert conglomerate, arkosic to 

quartzose sandstone, pale-red siltstone, and gray silty 

limestone; 395 feet (120 m) of gray coarsely crystalline massive limestone with scattered lenses of 

limestone-pebble conglomerate near the top; about 35 

feet (11 m) of sandstone; 318 feet (97 m) of limestonepebble to boulder conglomerate; 70 feet (21 m) of 

sandstone and chert conglomerate; and 338 feet (103 

m) of sparsely fossiliferous gray limestone. Poorly 

preserved pelecypods from the limestone indicate an 

Early Cretaceous age, and the rocks were compared 

by Kottlowski and Foster (1962, p. 2096) to the Lower 

Cretaceous limestones in the Big Hatchet and the Little 

Hatchet Mountains. No doubt they are generally correlative and are of Aptian and (or) early Albian age.

This incomplete sequence in the Tres Hermanas 

Mountains is significant because of the presence of so 

much conglomerate in the limestone interval. It suggests that the Tres Hermanas area was very near a 

relatively high and rugged coastline in Aptian and 

early Albian time.

AREAS TO NORTH

WINCHESTER AND LITTLE DRAGOON MOUNTAINS

(Fig. 5, col. 17)

Rocks assigned to the Bisbee Group and mapped as 

two units the Glance Conglomerate and the undivided 

Morita and Cintura Formations are present in the 

southern part of the Little Dragoon Mountains (fig. 

4) and in the nearby Gunnison and Steele Hills 

(Cooper and Silver, 1964:, p. 73-76). There is some 

suggestion that the Glance Conglomerate, which locally

may exceed 1,000 (300 m) feet in thickness, interfingers 

southward with finer clastic sediments. The combined 

Morita and Cintura Formations are at least 2,500 feet 

(760 m) thick in the area and may be much thicker. 

The rocks in the Little Dragoon area locally appear to 

be similar to the Bisbee Formation in the Dragoon 

Mountains but elsewhere may more closely resemble 

the Bisbee in the Whetstone and Empire Mountains 

area.

Rocks assignable to the Bisbee have not been recognized north of the Steele Hills and are presumably 

absent due to nondeposition.

Cooper and Silver (1964, p. 76-78) described a 

sequence, estimated to be 4,000 feet (1,200 m) thick, 

of feldspathic sandstone, siltstone, conglomerate, and 

a few small lenses of rhyolitic tuff and flow breccia 

that crop out in several places along the base of the 

Winchester Mountains. The well-rounded conglomerates in the lower sequence contain fragments of diverse 

rocks including limestone conglomerate believed to 

represent the Glance Conglomerate. Probably, the 

sequence of sedimentary rocks is of Late Cretaceous 

age and is a general equivalent of the Fort Crittenden 

Formation. It is overlain by about 950 feet (290 m) of 

dominantly andesitic rocks. The andesitic rocks are 

probably approximately equivalent to the lower part 

of the Salero Formation. Cooper and Silver (1964, 

p. 78) assigned a Cretaceous (?) age to all these 

unnamed rocks.

NORTHERN SANTA CATALINA MOUNTAINS AREA

(Fig. 5, col. 18)

The American Flag Formation, named and described 

by Creasey (1967a, p. 41-44) for exposures on the 

northeast slopes of the Santa Catalina Mountains (fig. 

4), is a sequence more than 2,000 feet (600 m) thick 

of graywacke, olive-hued siltstones, and conglomerates 

with well-rounded pebbles to boulders probably derived 

from Paleozoic and Precambrian rocks. The formation 

has yielded the fresh-water mollusks Unio and Viviparus. Where I viewed the formation, it has many 

lithologic characteristics that are similar to those of 

the Fort Crittenden Formation, and it is therefore 

considered to be a probable general equivalent. It was 

assigned a Cretaceous (?) age by Creasey (1967a, p. 

42). The formation rests unconformably on Mississippian strata; no older Cretaceous rocks are known in 

the area.

A few miles north of the Santa Catalina Mountains, near Mammoth, the Cloudburst Formation, as 

described by Heindl (1963, p. E5-E13) and Creasey 

(1967a, p. 49-55), is a possible general equivalent of at 

least the lower part of the Salero Formation. Assigned
CRETACEOUS PALEOGEOGRAPHY B33

a Late( ?) Cretaceous or early Tertiary age by Creasey 

(1967a), it consists of conglomerates and andesitic to 

latitic flows. The formation was correlated by Creasey 

(1967a, p. 10) with similar rocks in the Christmas area 

which overlie lower Upper Cretaceous sedimentary 

rocks and which were correlated by Richard and Courtright (1960) with their Silver Bell Formation in the 

Silver Bell Mountains area.

MORENCI TO CHRISTMAS AREA 

(Pig. 5, col. 19)

Cretaceous rocks that are very different in character 

from those in areas to the south are present at several 

localities between Morenci and Christmas north of lat 

32°55' N. in Arizona (fig. 4).

The Cretaceous strata at Morenci were first described 

by Lindgren (1905, p. 73-74), who named them the 

Pinkard Formation; they have not been studied in 

detail since. At Morenci, the Pinkard Formation rests 

with erosional unconformity on Mississippian limestone and is unconformably overlain by Tertiary rocks. 

About 200 feet (60 m) of strata at the base of the 

formation is preserved there. It consists of dark fissile 

shale and some sandstone and has yielded marine 

fossils that indicate a Colorado or early Late Cretaceous age.

In the Deer Creek area a few miles east of Christmas, Cretaceous strata containing coaly beds were 

examined first by Walcott (1885) and have since been 

described to some extent by Campbell (1904), Ross 

(1925), and Willden (1964) but have never been 

formally named. Willden (1964) divided these rocks 

into two unnamed units, a lower sedimentary unit and 

an upper volcanic and sedimentary unit, which are 

separated by a "widespread erosional unconformity 

with a small angular discordance at some places." The 

lower sedimentary unit of the Christmas area, as much 

as 500 feet (150 m) thick, is similar to the Pinkard 

Formation in the Morenci area, but it contains some 

thin coaly beds in the lower part and some higher 

conglomerate beds that were derived mostly from lower 

Paleozoic and upper Precambrian rocks. Marine invertebrate fossils and plant fossils from the unit indicate 

an early Late Cretaceous age, the same as that of the 

Pinkard Formation. The unit rests unconformably on 

Pennsylvanian rocks.

The unnamed volcanic and sedimentary unit is 

apparently at least 3,000 feet (900 m) thick locally. It 

was subdivided by Willden (1964, p. E27) into (1) a 

basal unit several hundred feet thick of andesitic 

agglomerate, mudflows, and flow breccias; (2) a unit 

as much as 300 feet (90 m) thick of conglomerate, 

sandstone, mudstone, and tuff; (3) a unit at least

1,000 feet (300 m) thick of andesitic agglomerate, mudflows, tuff, and flow breccias; and (4) an upper unit at 

least 1,000 feet (300 m) thick of andesitic flow breccias, 

agglomerate, and mudflows. According to Creasey 

(1967a, p. 55) these rocks "were intruded by a quartz 

diorite porphyry whose isotopic age by the K/Ar 

method using biotite is 63 million years." This volcanic 

and sedimentary unit was correlated by Richard and 

Courtright (1960) with their Silver Bell Formation in 

the Silver Bell Mountains and by Creasey (1967a, p. 

55) with the Cloudburst Formation in the northern 

Santa Catalina Mountains area. Both correlations seem 

reasonable.

Cretaceous strata in the Aravaipa area (fig. 4) were 

most recently described by Simons (1964). Rocks 

referred by him to the Pinkard Formation are as much 

as 1,000 feet (300 m) thick and are intermediate in 

lithologic character between the Pinkard Formation in 

the Morenci area and the lower sedimentary unit in 

the Christmas area; they apparently contain no coaly 

beds and much less conglomerate than sandstone, siltstone, and shale. Unconformably overlying the Pinkard 

Formation are the Williamson Canyon Volcanics 

andesitic and dacitic rocks probably at least 2,500 feet 

(750 m) thick that undoubtedly represent the unnamed 

volcanic and sedimentary unit in the Christmas area. 

Simons (1964, p. 47) noted the close similarity of rocks 

in the Williamson Canyon Volcanics to rocks in the 

lower part of the Bronco Volcanics in the Tombstone 

area but made no definite correlation. On the basis of 

accumulated regional evidence, such a correlation certainly seems reasonable. Krieger (1968b) assigned a 

Late Cretaceous and (or) Tertiary age to the Williamson Canyon Volcanics.

SILVER CITY-SANTA RITA AREA, NEW MEXICO 

(Pig. 5, col. 20)

Two sedimentary formations of Cretaceous age are 

recognized in the Silver City-Santa Rita area: the 

Beartooth Quartzite at the base and the overlying 

Colorado Formation. These units were first defined by 

Paige (1916) and have since been mapped by various 

workers in surrounding areas, most recently by Jones, 

Hernon, and Moore (1967). The following brief 

descriptions of these formations and of the overlying 

andesitic volcanics of probable Cretaceous age are 

taken largely from these two sources and partly from 

a general summary paper by Kottlowski (1963).

The Beartooth Quartzite rests unconformably on 

rocks ranging in age from Precambrian to Permian 

and is overlain with apparent conformity by the 

Colorado Formation. It is 50-140 feet (15-48 m) thick 

and consists largely of fine to very fine grained thin-
B34 MESOZOIC STRATIGRAPHY IN SOUTHEASTERN ARIZONA

bedded to massive locally crossbedded sandstone.

The Colorado Formation, possibly as much as 2,000 

feet (600 m) thick locally, comprises a lower shale 

member about 200 feet (60 m) thick and an upper, 

sandstone member. The shale member consists of darkgray generally fissile partly sandy shale that contains 

a few beds of fine-grained sandstone. The sandstone 

member consists of an alternating series of shale, sandstone, and mudstone beds. The top of the Colorado 

Formation in the area is an erosional unconformity.

Marine invertebrate fossils from the middle of the 

shale member support a correlation with the Graneros 

Shale of northeastern New Mexico and Colorado and 

thus suggest a late Cenomanian age (Cobban and 

Eeeside, 1952). Fossils from the lower part of the sandstone member indicate a correlation with the Greenhorn 

Limestone in northeastern New Mexico and Colorado.

Fossils useful for dating have not been found in the 

Beartooth Quartzite or in the upper part of the sandstone member of the Colorado Formation. Darton 

(1928, p. 38), however, correlated the Beartooth on the 

basis of lithology and stratigraphic position with the 

Sarten Sandstone in the Cooks Range, about 30 miles 

(50 km) east-southeast of Santa Rita, which has 

yielded a fauna considered to be correlative with the 

Washita or Fredericksburg Groups of Texas. Because 

of their apparent conformity with the overlying Colorado Formation, the Beartooth Quartzite and the 

Sarten Sandstone are most likely of late Washita 

(early Cenomanian) age. Thus, they both may be 

equivalent to the upper part of the Moj ado Formation 

of Zeller (1965) in the Big Hatchet Mountains (fig. 

5). The upper part of the sandstone member of the 

Colorado Formation must be younger than the Greenhorn and may represent much of Turonian time.

The oldest rocks unconformably overlying the Colorado Formation are unnamed andesitic breccias, lavas, 

and agglomerates of probable Late Cretaceous age. 

These rocks are similar in lithology and general stratigraphic position to the Salero Formation in southeastern Arizona and are probably approximately 

equivalent. According to Callaghan (1953), they may 

also be equivalent to altered and mineralized andesitic 

and latitic breccias in the Kingston area, New Mexico, 

25 miles (40 km) farther east.

OUTLYING REGIONS

SONORA, MEXICO

In Sonora, Mexico, Cretaceous sedimentary and volcanic rocks, few of which have been studied in detail, 

are present at many localities. Lower Cretaceous rocks 

similar in general to the Bisbee Group in southeastern

Arizona occur in several areas in northern Sonora within 75 miles (110 km) of the United States-Mexico 

border. Rocks of similar age, but which contain interbedded volcanics in increasing amounts westward, are 

present at several localities in east-central Sonora 

between 110 and 185 miles (180 and 300 km) south of 

the border. Other than the rocks of the Cabullona 

Group of Taliaferro (1933) already described (p. B18), 

Upper Cretaceous sedimentary rocks are not known in 

Sonora. Uppermost Cretaceous volcanics may be widely 

distributed but, if so, have not generally been distinguished from Cenozoic volcanics.

In the Sierra de los Ajos (fig. 4), both the Glance 

Conglomerate and the Morita Formation of the Bisbee 

Group are present according to Imlay (1939, p. 1736- 

1737). The Glance there is at least 5,000 feet (1,500 m) 

thick, and the Morita, though not measured, is at least 

several thousand feet thick. The Morita is similar to 

the Morita of the Mule Mountains in Arizona, except 

for the presence of a coal bed several thousand feet 

above the base.

Imlay (1939, p. 1733-1735) also described Lower 

Cretaceous rocks in the El Tigre area, about 50 miles 

(80 km) south of the United States-Mexico border 

near long 109° 10' W. He measured 2,850 feet (870 m) 

of Cretaceous strata there between an unconformable 

contact with upper Paleozoic limestone at the base and 

an unconformable contact with Tertiary conglomerates 

at the top. The Cretaceous sequence which consists of 

interbedded sandstone, shale, and limestone bearing 

marine invertebrate fossils of Aptian age seems to 

be similar, in general, to the basal several thousand feet 

of the Bisbee Group in the Pedregosa Mountains and 

in the southern part of the Peloncillo Mountains in 

Arizona.

In the Santa Ana-Altar area in northwestern Sonora, mollusks that Popenoe, Imlay, and Murphy (1960, 

p. 1517-1518) considered as most likely of Albian age 

have been collected by various workers from several 

localities. At one of these localities, 8 miles (13 km) 

west of Santa Ana, I examined the rocks and found 

that they resemble rocks of the Bisbee Group in southeastern Arizona. Tentatively, these rocks are considered 

as western equivalents of at least the Albian part of 

the Bisbee Group.

Rocks of Cretaceous age at several localities in eastcentral Sonora, between 110 and 185 miles (180 and 

300 km) south of the United States-Mexico border, 

were described by King (1939). In that region, the 

Cretaceous strata overlie sedimentary rocks of Triassic 

and Jurassic age and are overlain by volcanics of CP %/

probable Tertiary age. Toward the east (near long 

109° W.), the Cretaceous is represented by many
CRETACEOUS PALEOGEOGRAPHY B35

thousands of feet of fossiliferous marine strata of 

Albian age, the upper half of which contains some 

interbedded andesite and agglomerate. Toward the 

west, according to King (1939, p. 1659), "the limestones thin out, the clastic sedimentary rocks thicken 

and contain great quantities of volcanic detritus, and 

there are thick lava flows."

SOUTHWESTERN ARIZONA

Sedimentary sequences of unequivocal Cretaceous 

age have not been identified in southwestern Arizona 

although they probably exist. The westward thinning 

of Cretaceous sedimentary sequences in the ranges west 

of the Santa Cruz River and the apparent absence of 

Cretaceous sedimentary strata in the Vekol Mountains (p. B27), however, suggest that any Cretaceous 

sedimentary sequences that may be present in southwestern Arizona probably have no direct relation to 

those in the southeastern part of the State.

Wilson (1933, p. 79-80) briefly described a sequence, 

estimated to be more than 1,000 feet (300 m) thick, 

that consists dominantly of greenish-gray shale and 

apparently unfossiliferous limestone and subordinately 

of sandstone and conglomerate to which he assigned 

a Cretaceous (?) age in the Castle Dome Mountains 

(fig. 4). He stated that the rocks were practically 

identical with those in a sequence about 25 miles (40 

km) to the north in the New Water Mountains. I 

have seen some of these rocks in the New Water 

Mountains and similar strata in other nearby ranges 

and believe they may be approximately equivalent 

to a thick series of moderately metamorphosed strata 

in the McCoy Mountains, about 50 miles (80 km) 

west of the New Waters in California, from which 

E. C. Beaumont (oral commun., 1968) collected 

fragments of dichotoledenous plant fossils that C. 

B. Read stated (oral commun., 1969) can be no older 

than Albian.

Volcanic rocks, largely andesitic, that have been 

assigned a Cretaceous age occur in many places in 

southwestern Arizona (Wilson and others, 1969). 

Many of these may be general equivalents of the 

Upper Cretaceous Salero Formation in southeastern 

Arizona.

NORTHERN ARIZONA AND NEW MEXICO

Cretaceous strata in northern Arizona and New 

Mexico differ greatly from those in southeastern Arizona. However, certain major events that took place 

in Cretaceous time affected the regimens of sedimentation and erosion in both regions, so the Cretaceous

rocks in the northern region merit a brief summary 

description here.

The oldest Cretaceous rocks in this northern region 

are represented by the Burro Canyon Formation, 

which occurs only in northeasternmost Arizona and 

northwesternmost New Mexico (Craig and others, 

1955, p. 160). The Burro Canyon gradationally overlies the Morrison Formation of Late Jurassic age and 

has yielded nonmarine fossil vertebrates, invertebrates, 

and plant remains of Aptian or Trinity aspect from its 

upper part (Simmons, 1957, p. 2526). The formation 

is truncated southward by a post-Burro Canyon and 

pre-Late Cretaceous erosion surface (Craig and others, 

1955, p. 161). The Burro Canyon may well be an age 

equivalent of at least a part of the Bisbee Group in 

southeastern Arizona; however, I believe that the two 

units were never physically connected across the intervening region but that this intervening region was an 

upland source area that may have contributed sediments to both units.

Unconformably overlying the Burro Canyon Formation, where it remains, and Jurassic or older strata 

elsewhere throughout northern Arizona and New 

Mexico, is a thick sequence of both marine and nonmarine formations that represents, with only a few 

minor breaks, all of Cretaceous time from late Albian 

or early Cenomanian through the Maestrichtian. 

Numerous papers of both local and regional scope have 

been written about the lithologies, ages, correlations, 

environments of deposition, and intertonguing relations of the many stratigraphic units involved. Although outdated in part, the regional correlation 

paper of Cobban and Reeside (1952) probably remains 

the best general reference for the region as a whole.

The lowest formations in this nearly complete 

sequence of Upper Cretaceous and uppermost Lower 

Cretaceous strata contain rocks of marine origin 

deposited in late Albian, Cenomanian, and early Turonian time in or near the margins of a shallow sea 

that advanced from the east and northeast. Rocks deposited during the early phases of this initial advance 

are roughly correlative with the uppermost part of the 

Moj ado Formation in the Big Hatchet Mountains 

area of southwestern New Mexico, with the Beartooth 

Quartzite and Colorado Formation in the Santa RitaSilver City area of New Mexico, and with the Pinkard 

Formation in the Morenci-Christmas area in Arizona.

From late Turonian until early Campanian time, 

there was a general eastward and northeastward regression of the seas (interrupted by minor transgressions) 

from northern Arizona and northwestern New Mexico 

which resulted in deposition of the largely continental rocks of the Mesaverde Group in those areas while
B36 MESOZOIC STRATIGRAPHY IN SOUTHEASTERN ARIZONA

marine shales were being deposited in northeastern 

New Mexico. There are no known time equivalents 

of these rocks in southernmost southeastern Arizona. 

This area probably was an eroding upland from which 

was derived some of the detrital sediment preserved in 

the Mesaverde Group.

Another major transgression of the sea into northwestern New Mexico took place in Campanian time 

and resulted in deposition of the Lewis Shale. The 

Lewis may be an approximate correlative of the Fort 

Crittenden Formation in southeastern Arizona and of 

the Cabullona Group of Taliaferro (1933) in Sonora.

The final eastward and northeastward regression of 

the Cretaceous sea from northern Arizona and New 

Mexico began in late Campanian time and resulted in 

the deposition of regressive sandstone deposits and 

overlying continental sediments. The regressive sandstones are the Pictured Cliffs Sandstone in northwestern New Mexico and the somewhat younger 

Trinidad Sandstone in northeastern New Mexico; the 

overlying continental sediments are preserved in the 

Fruitland and Kirtland Formations and younger 

rocks in northwestern New Mexico and in the Vermejo 

Formation in northeastern New Mexico. The lower of 

these rocks, at least, are probably approximate timeequivalents of the Salero Formation and correlatives 

in southeastern Arizona.

WESTERN TEXAS AND ADJOINING AREAS

Cretaceous rocks are widely distributed in western 

Texas and in adjacent parts of Mexico and central 

Texas. These rocks are too far removed from southeastern Arizona to require detailed description in 

this report, but a brief summary of their ages and 

lithologies is pertinent.

Eocks of Neocomian age are not known to be 

definitely present in western Texas but apparently 

are present in the lower Kio Conchos area and elsewhere in northern Chihuahua (fig. 4). The rocks of 

presumed Neocomian age in Chihuahua, the Las Vigas 

Formation of Scott (1940), are dominantly red and 

gray shales interbedded with sandstone and thin 

layers of limestone (King and Adkins, 1946, p. 284).

The oldest Cretaceous strata in western Texas are 

in the Etholen Conglomerate and Torcer Formation, 

both largely of marine origin, which Albritton and 

Smith (1965) believed might be equivalent to one 

another, at least in part. These formations have not 

yielded fossils that allow an unequivocal age assignment. The Torcer Formation overlies the Malone 

Formation of Late Jurassic age with apparent conformity and underlies the Yucca Formation with apparent conformity; the Yucca Formation, in turn, 

conformably underlies rocks of definite early Albian 

age (Albritton and Smith, 1965, p. 38, 50, 52). Because 

marine rocks of Neocomian age are not present in 

any direction, except possibly to the south, the Etholen 

Conglomerate and Torcer Formation are here tentatively considered to be of early Aptian age and the 

Yucca Formation of late Aptian age although a 

Neocomian age for the lower of these is possible.

Bocks of marine origin that are equivalent to the 

Trinity, Fredericksburg, and Washita Groups in central Texas and are assigned to various formations are 

widely distributed in western Texas and have been 

most recently described in detail by Albritton and 

Smith (1965), King (1965), and Maxwell, Lonsdale, 

Hazzard, and Wilson (1967); and their occurrence in 

northern Chihuahua has been summarized by Cordoba 

(1969). These formations were deposited in seas that 

transgressed from the south, and only the younger 

formations are present in northern parts of western 

Texas.

Cretaceous strata younger than those correlative 

with the Washita Group are very sparsely preserved 

in westernmost Texas, but in the Big Bend area, nearly all the Upper Cretaceous is represented (Maxwell 

and others, 1967). There, all Upper Cretaceous strata 

older than late Campanian are of marine origin, 

whereas rocks of late Campanian and Maestrichtian 

asre are continental sandstones and shales that contain o

some coal beds. The lower of these rocks of continental origin, represented in the upper part of the Aguja 

Formation, are here considered to be roughly equivalent to the Salero Formation in southeastern Arizona.

ECONOMIC GEOLOGY OF CRETACEOUS STRATA

The layered Cretaceous rocks are only of limited 

direct economic importance at present and seem to 

offer only a modest potential for future importance.

Although in many mineralized areas in the region 

the plutonic bodies responsible for introducing mineralizing solutions are younger than most of the Cretaceous layered rocks, strata older than the Salero 

Formation and equivalents seem to have been very 

poor host rocks for base-metal mineralization. The 

andesites of the Salero and equivalents, on the other 

hand, have been altered at many localities, and some 

contain disseminated copper deposits of value. The 

chief value in understanding the stratigraphy of the 

older Cretaceous rocks in these areas is in the interpretation of the local structure and geologic history. 

In areas such as Bisbee in the Mule Mountains, the 

principal base-metal mineralization is of pre-Bisbee
CRETACEOUS PALEOGEOGRAPHY B37

age (Bryant and Metz, 1966, p. 202-203), and sandstones in the Bisbee Group contain trace amounts of 

base-metal ore minerals but not to the degree that they 

have importance as fossil placers.

Limestone from the Mural Limestone is presently 

quarried, for use in copper smelters, from a locality 

just east of the Mule Mountains in Arizona and from 

another locality just south of the Mule Mountains in 

Sonora. In several areas east of the Mule Mountains, 

the Mural Limestone might be a good source of cement rock if economic factors should warrant its 

exploitation.

The fossil reef-mounds or bioherms present in the 

Mural Limestone and correlatives in southeasternmost 

Arizona and to the east in New Mexico might, under 

proper structural conditions, serve as reservoir rocks 

for oil or gas in some of the intermontane basins. 

Other rocks in the Cretaceous sequence appear to be 

far too impermeable to be good potential reservoir 

rocks for hydrocarbons or to serve as good aquifers 

for ground water.

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INDEX

AgujaFormation.-.----.. ..... B7.36

Ali Molina Metamorphic Complex.. _. _ _ 27 

American Flag Formation___.-.-____ 16,82 

AmoleArkose_......______.___. 4,14,86

Angelica Wash, arkose.-.-_.________ 14,35 

Animas Mountains - __. _ _.. _. _.. SO 

Apache Canyon Formation, Santa Eita

Mountains.______..__ 23

Santa Rita Mountains, correlatives.. .. 14

Whetstone and Empire Mountains.___. 22

correlatives__________.__ 14

Apache Gronp.-___.____________ 8

Aravaipaarea_._...____________ 33

B

Baboquivari Mountains.___________ 27

Bathtub Formation. -_...__._____ 4,33

volcanics.__..____...-__. 9

BeartoothQuartzite________..__... 5,15,33

Bibliography. .- _. _ _. 37

Big Hatchet Mountains......__..___ SO

Bisbee Formation, Dragoon Mountains___ 28

D ragoon Mountains, correlatives__.. _ 14

Patagonia Mountains..__.___ ... 21

Peloncillo Mountains__.___....__ 30

Bisbee Group.age___________.__ 15

conditions of deposition....-...-_---.. 4

correlatives.____...._...___.._ 9

Dos Cabezas and northern Chiricahua

Mountains......_______... 28

economic geology....-----....._ _... 37

fossils._. ..... .. ......... .. 12

Glance Conglomerate...____...__ 12

Huachuca Mountains._.. __ ... 19

Little Dragoon Mountains. ___. __ _ 32

Mule Mountains_________._-.-.. 17

Mural Limestone..----.-._-___.-... 13

Pedregosa and central and southern Chiricahua Mountains...______ 28 

Peloncillo Mountains___ _-..-___. 29 

Santa Rita Mountains.____ _. __. 23 

similarity to Fort Crittenden Formation. 16 

Whetstoneand Empire Mountains___.- 21 

Broken Jug Limestone----------_---------- 14, SI

Bronco Volcanics___ -...-....--..--...--..- 28

Burro Canyon Formation..._--.--.-._... 35

Cabullona Group....-.........-..-...-,... 7,16,18

Camas Sandstone.._.. .-._.... 18 

Campagrande Formation____............. 5

CaneloHills .....-.. 19

Carbonate Hill Limestone_---------_..... 14,39

Castle Dome Mountains.____-----____ 35

Cat Mountain Rhyolite_ _------------_ 17,36

Chiapuk Rhyolite.-... .....- ..... .. 27

Chiltepines Member, Pitoikam Formation_ 27 

Chiricahua Mountains.._________.... 38

ChiuliShaik Formation.----.---------.-.---- 27

Christmas area.. _...----.--- _. _ ------- SS

Cintura Formation, Canelo Hills.. ----------- 19

conditions of deposition__._..-..... 5

[Italic page numbers indicate major references]

Page

Cintura Formation, Canelo Hills Continued

Huachuca Mountains.____.. __. B19

correlatives_______._____. 14

Mule Mountains__._...___-___ 18

correlatives ......_. 14

Cintura Formation and Morita Formation 

undivided, Little Dragoon Mountains..__....-.----...-------.- 32

Claflin Ranch Formation_____.____ 16,36 

Cloudburst Formation.-------------____ 17,83

Cocoraque Formation._____._-.-___ 14,86

Colorado Formation______.____ 5,15,54

CorbettSandstone...__________ 5, U,S1

Cowboy Spring Formation____-...__- 16,80

Cox Sandstone..-___.__.______. 5

Cretaceous rocks, difficulties of studying._. - 1

economic geology.- ____..-.---.-_. 36

mapping.._____._.___-.---_-_.. 1

D

Deer Creek area__.____._._._... 33 

Demetrie Formation--...---___-....---. 17,3£ 

Dos Cabezas Mountains______-.._..- 38 

Dragoon Mountains....--_.-----.-.-.----.- 37

E

Eagle Ford Shale ..._....-...-. -- . 5

Early Cretaceous paleogeography...... -... 4

Early Late Cretaceous disturbance....-_... 5

Economic geology, Cretaceous strata.--...-.. 86

EITlgrearea. - - 34

Empire Mountains.--.-------..-. --------- HI

EtholenConglomerate._.--._-... ...-- 4,36

F

Faraway Ranch Formation.... - 28

Fort Crittenden Formation, conditions of

deposition-_---._------------- 7

correlatives..--..__...--.__..---..---- 16

Huachuca Mountains and Canelo Hills... 20

Santa Rita Mountains_____... -_- 24

Fossils, Bisbee Group__ ._-_--------- 12

Early Cretaceous.._-------------------- 4

Fredericksburg Group, Texas.. _ --------- 5,13

Fruitland Formation..--.,------.------.--_.- 7,36

G

Gallup Sandstone ___-.-___- ------._ ---- 5

Geologic setting--------. ..-.- ..-.. 8

Glance Conglomerate, Bisbee Group--------- 12

conditions of deposition.__...------.... 4

Dos Cabezas and northern Chiricahua

Mountains__......----.-----...- 28

Huachuca Mountains_.-..---.----.-..-. 19

volcanics.---------------------------- 4,9

Little Dragoon Mountains._-.----. .--- 32

Mule Mountains...-....--.----.------.--- 18

Pedregosa and central and southern Chiricahua Mountains.------------- 28

Santa Rita Mountains..------.---.------- 23

Sierra delos Ajos..._.- ------------- 34

Whetstone and Empire Mountains. ------- 21

Graneros Shale___-_._ ----------- . 16

Greenhorn Limestone--...-__.---...--------. 16

H Page

Hell-to-Finish Formation....__ ... .. B4,30 

Hidalgo Volcanics_.__................... 17, SI

Howells Ridge Formation..... __._.__. 4, U,S1

Huachuca Mountains.._____.__.__ 19

Johnny Bull Sandstone_.___----------- 16,29

Jones Mesa rocks.._----------__......... 20

Kirtland Formation__....._. ..-..-.__ 7,36

Laramideorogeny..-------.--.--.-..--------- 5,7

Las Vigas Formation__________------- 36

Late Late Cretaceous paleogeography....--.. 5

Latest Cretaceous-earliest Tertiary orogeny. _ 7

Lewis Shale,.--.----.-----..---------.-..---. 7,36

Little Dragoon Mountains-_--. -- 32

Little Hatchet Mountains.. _ --------------- SO

reconstructed section._...._... ..-.. 31

Lowell Formation, Quajote Member.. -------- 29

M 

McCoy Mountains._. ..... -. ..-.... 35

McGheePeak Formation...--_--------.---..- 29

MaloneFormation___--------_._... 3,36

Mancos Shale... .. -------------- ... 16

Mesaverde Group....- ..... ....... .- 5,35

Mojado Formation_.-___ ._...... 5,14,80

Molly Gibson Formation..._-------_-_. 21

Morenciarea___ .-_ ..----.----. 88

Morita Formation, Huachuca Mountains..... 19

Huachuca Mountains, correlatives. ------- 14

Mule Mountains.-------_-. -._----- 18

correlatives.-. 14 

Pedregosa and central and southern Chiricahua Mountains.--- ------- 28

Sierra delos Ajos.------------------------ 34

Morita Formation and Cintura Formation undivided, Little Dragoon Mountains.. - - 32 

Morrison Formation-. -.. - --.-- S 

Mulberry Wash Volcanic Formation._-._- - 27 

Mule Mountains____________.. 17 

Mural Limestone, Bisbee Group.-. --------- 13

economic geology____----__-__.------ 37

Huachuca Mountains__------_....__ 19 ,

correlatives_____--------------- 13

Mule Mountains..------------------_... 18

correlatives__..__-..----_---_----- 13

N 

New Water Mountains_-___-___ .. 35

Nipper Formation..,___________ .. 17,38

Packard Shales_________--_.__.

Paleogeography, Early Cretaceous.._. 

early Late Cretaceous.------------

latest Cretaceous-earliest Tertiarylate Late Cretaceous..-.. .. 

pre-Cretaceous..--- .__-------

Patagonia Mountains.--..__.. ...

Pedregosa Mountains_.......___.

B41
B42 INDEX

Page

Phonodoree Formation. ___________ B27 

Pictured Cliffs Sandstone.__________ 36 

Final Schist. .... .....__..._.__._._ 8

Pinkard Formation.._____________ 5,33 

correlatives.________________ 15 

Pitoikam Formation, Chiltepines Member... 27 

Playas Peak Formation.._________... 14.3J 

Pre-Cretaceous surface.____________ 3

Q, R

Quajote Member, Lowell Formation____. 29

Recreation Redbeds_____________. 26 

Red Boy Rhyolite.. 17,25

Ringbone Shale._______________ 16,3i 

Roadside Formation.____...__....... 17,26

Roskruge Mountains_____________. $6 

Roskruge Rhyolite- _..... _.... . 17,26

S

Salero Formation, conditions of deposition__ 7

correlatives________________ 17

economic geology__________.. 36

Empire Mountains._.________ 22

Santa Rita Mountains.__________ 24

Santa Ana-Altar area.________ ___. 34

Santa Catalina Mountains area. __ _____ 52

Santa Rita Mountains___________... %S

Sarten Sandstone_______________ 34

Schieffelin Granodiorite........._.__.--- 28

Page

Shellenberger Canyon Formation, Santa Rita

Mountains..._.. B15.S3

Whetstone and Empire Mountains ... 15,22

Sierra de los Ajos_______ 34

Sierrita Mountains..._______ 24

Silver Bell Formation....._. . 17,27

Silver City-Santa Rita area... 33 

Skunk Ranch Conglomerate___ 16,3f 

Snake Ridge Formation_____ .. 18 

Sonora, Mexico..___...___ 84 

Stevens Mountain Rhyolite___ 25 

Still Ridge Formation................ 29

Study area, boundaries_____ 1 

geologic setting_....__ 8

local sequences. _ 17 

Sugarloaf Quartz Latite-__.. . - 17,25

Temporal Formation________ .. 23 

volcanics_____.___ 4,9 

Tombstone area___._____ 27 

Toreer Formation.__ __ -- 4,36 

Tres Hermanas Mountains...__.. .. 32 

Trinidad Sandstone.-----__... -- - 36 

Trinity Group, Texas_______...-. ... 13 

Troy Quartzite_ - - 8 

Tucson Mountain Chaos..__.. .- 7,17,26 

Tucson Mountains___._____ . 26 

Turney Ranch Formation Santa Rita

Mountains_____________ 15,23 

Whetstone and Empire Mountains .. 15,22

U,V Page

U-Bar Formation._____.. ___ B5,14,30>

Vekol Formation....___ .__ .. 17,27

Vekol Mountains________.._____ ST

Vermejo Formation_____ __ 36

Volcanics, Bathtub Formation._______ 9

Bronco Volcanics___ ...... 28

Glance Conglomerate__...____ 4,9>

Hidalgo Volcanics-.... ... 17,31

Lower Cretaceous__ 9>

Mulberry Wash Volcanic Fonnation__. 27

Temporal Formation.__.. ___ 4,9-

Walnut Gap Volcanics. . __ 28

Whitcomb HiU quartzite.... . ........ 4,9-

Williamson Canyon Volcanics._____ 3&

W

Walnut Gap Volcanics___________ 28

Washita Group, Texas______-___ 5- 

Whetstone Mountains_____________ SI 

Whitcomb HiU quartzite___.--___ 24 

volcanics___________________ 4,9- 

Williamson Canyon Volcanics. ________ 33- 

Willow Canyon Formation, Santa Rita Mountains............................. 23.

Santa Rita Mountains, correlatives _ 14

Whetstone and Empire Mountains____ 22

correlatives_______._____. 14

Winchester Mountains____..-..____ S£

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