Pennsylvanian subsurface stratigraphy of the Black Mesa Basin and Four Corners area in northeastern Arizona

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Authors Ijirigho, Bruce Tajinere

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Link to Item http://hdl.handle.net/10150/566529 PENNSYLVANIAN SUBSURFACE STRATIGRAPHY OF THE

BLACK MESA BASIN AND FOUR CORNERS AREA

IN NORTHEASTERN ARIZONA

by

Bruce Tajinere Ijirigho

A Thesis Submitted to the Faculty of the

DEPARTMENT OF GEOSCIENCES

In Partial Fulfillment of the Requirements For the Degree of

MASTER OF SCIENCE

In the Graduate College

THE UNIVERSITY OF ARIZONA

1 9 7 7 STATEMENT BY AUTHOR

This thesis has been submitted in partial fulfillment of re­ quirements for an advanced degree at The University of Arizona and is deposited in the University Library to be made available to borrowers under rules of the Library.

Brief quotations from this thesis are allowable without special permission, provided that accurate acknowledgment of source is made. Requests for permission for extended quotation from or reproduction of this manuscript in whole or in part may be granted by the head of the major department or the Dean of the Graduate College when in his judg­ ment the proposed use of the material is in the interests of scholar­ ship. In all other instances, however, permission must be obtained from the author.

APPROVAL BY THESIS DIRECTOR

This thesis has been approved on the date shown below:

Date ACKNOWLEDGMENTS

The investigation covered in this report was originally sug­ gested by Dr. Richard F. Wilson and developed under his direction.

Well logs and.sample descriptions were supplied by Dr. Richard F.

Wilson, Dr. Wesley Pierce of the Arizona Bureau of Geology and Mineral

Technology, and Mr. Jack Conely of the Arizona Oil and Gas Conserva­

tion Commission. The writer is especially indebted to Dr. Pierce who

gave very freely of his time to make suggestions, answer questions,

and provide both data and research material on the study area. His

advice and guidance greatly influenced the outcome of this research.

Dr. Richard F. Wilson, Dr. Joseph Schreiber, Jr., and Dr.

Dietmar Schumacher critically read this paper and made useful sugges­

tions. Their time, assistance, concern and friendship is gratefully

acknowledged as well as that of other faculty members and graduate

students who discussed and contributed to this effort.

The National Sports Commission of Nigeria, Union Oil Corpora­

tion of America, with the recommendation of Dr. Joseph Schreiber, Jr.,

and the Department of Geosciences, The University of Arizona, with the

recommendation of Dr. Richard F. Wilson, provided funds at one time or

another, without which it would have been impossible for the writer to

complete requirements culminating in the completion of this study.

To my family and friends, for their encouragement, patience and

assistance in the preparation of this manuscript, I am very deeply

grateful. TABLE OF CONTENTS

Page

LIST OF ILLUSTRATIONS ...... vi

ABSTRACT ...... vii

INTRODUCTION ...... 1

Purpose Area of Investigation Method of Investigation Previous Work ....

REGIONAL GEOLOGY ......

Tectonic Setting .... The Pedregosa Basin San Juan Basin . . . Paradox Basin . . .

Paleogeology ...... H ru oovn vn oo -F"Vi vo \o Units Underlying the Pennsylvanian ...... 11 Units Overlying the Pennsylvanian ...... 13

MOLAS FORMATION ...... 15

Previous W o r k ...... 15 Lower Boundary...... • • • 15 Upper Boundary ...... 15 Age of the Molas Formation...... 17 Lithologic Description ...... 18 Depositions! History and Environment...... 18 General Discussion ...... 20

HERMOSA F O R M A T I O N ...... 21

Previous W o r k ...... 21 Lower Boundary...... 23 Upper Bou n d a r y ...... 23 Age of the Hermosa Formation '...... 24 Lithologic Description ...... 25 Depositional History and Environment ...... 25 Discussion ...... 26

iv V

TABLE OF CONTENTS— Continued

Page

NACO FORMATION...... 29

Previous Work ...... 29 Lower Boundary...... 29 Upper Boundary...... 30 Lithologic Description...... 31 Age of the Naco F o r m a t i o n ...... 32 Depositional History and Environment ...... 32 General Discussion ...... 3^

REGIONAL TRENDS OF THE PENNSYLVANIAN ...... 36

General Discussion ...... 36

S U M M A R Y ...... * ...... 40

SUGGESTIONS FOR FURTHER STUDY ...... 4l

APPENDIX A: NAME AND LOCATION OF SUBSURFACE DRILL HOLES .... 42

APPENDIX B: NAME AND LOCATION OF SURFACE E X P O S U R E S ...... 4?

APPENDIX C: MAP CONSTRUCTION D A T A ...... 49

LIST OF REFERENCES...... 38 LIST OF ILLUSTRATIONS

Figure Page

1. Index map ...... in pocket

2. Pennsylvanian paleotectonic setting ...... 6

3. Pre- and post-Pennsylvanian paleogeology ...... 10

4. Pre-Pennsylvanian paleogeologic map ...... • in pocket

5» Summary of previous work on the Molas ...... 16

6. Isopach map of the Molas Formation . in pocket

7* Lithofacies map of the Molas Formation -» . .. . • . in pocket

8. Summary of previous work on the Hermosa Formation .... 22

9. Isopach map of the Hermosa and Naco Formations . . in pocket

10. Cross section A-A’ ...... in pocket

11. Cross section B-B* ...... in pocket

12. Cross section C-C* ...... in pocket

13* Fence diagram ...... in pocket

14. Lithofacies map of the Hermosa and Naco Formations in pocket

13. Paleoenvironmental map of halfway through the Hermosa and Naco Formations ...... in pocket

16. Isopach map of the entire Pennsylvanian system . • in pocket

17. Lithofacies map of the Pennsylvanian system .... in pocket

18. Paleotectonic map of the Pennsylvanian ...... in pocket

vi ABSTRACT

The Pennsylvanian system in northeast Arizona, correlated and analyzed from 59 subsurface well logs and eight surface exposures, is made up of the Molas and Hermosa Formations in the northeast and the

Naco Formation in east-central Arizona. The lower part of the Naco

Formation is a combination of terrestrial and fresh water deposits,

that is both lithologically and genetically similar to the Molas

Formation. The upper part of the Naco, a shallow marine deposit, is

lithologically, genetically, and time equivalent to the Hermosa

Formation. ,

Results of this investigation indicate that both the Hermosa

and the Naco Formations were deposited in response to the same tectonic

manifestations that caused the rapid subsidence of the Paradox Basin

in the north and the Pedregosa Basin in the south of the study area.

The striking lithologic similarity of the Pennsylvanian formations in

this area is the result of a shallow sea connection between the two

depositional basins.

The important tectonic elements that influenced deposition the

most are the Zunl-Deflance positive and the Uncompahgre uplift. The

Zuni-Deflance element defined in this study, extends from latitudes

34-36°N along the Arizona-New Mexico state line to as far west as

Range 26°E. Very drastic thinning over short distances, suggestive

of faulting were observed within the Naco and Hermosa Formations.

vii INTRODUCTION

The Pennsylvanian system in northeast Arizona is represented by the Hermosa and Molas Formations, in the north, and the Naco Forma­ tion in east-central Arizona and along the Mogollon Rim. The Naco and

Hermosa Formations are dominantly marine sequences of alternating lime­ stone and terrigeneous clastic units. The Kolas Formation, based upon studies by Wengerd and Strickland (1954, pp. 2166-68) consists of non­ marine claystone, siltstone, shale, and an upper marine red and green shale and sandstone.

Pennsylvanian rocks in most of the area studied overlie

Mississippian limestone and dolomite with a karst topography, charac­

terized by abundant sinkholes, caverns and well-developed collapse

features.

Purpose

Although numerous studies have been done on the Pennsylvanian

system of Arizona in the past (Wengerd and Strickland 1954; Wengerd and

Matheny 1958; Winters 1963; Brew 1965; McKee 1975; Ibirce 1976), no

attempt to carry out a detailed stratigraphic synthesis and correlation

of the system in the subsurface of northeastern Arizona has been pub­

lished.

The objective of this study was, therefore, to correlate in

detail the Hermosa and Molas Formations in the subsurface of the Black

1 2

Mesa basin and Four Corners area with the Naco Formation exposed and studied along the Mogollon Rim (Huddle and Dobrovolny 19^5? Winters

1963; Brew 1965) and present in the subsurface in east-central Arizona.

This new knowledge will help in determining the extent of the

Defiance and Zuni positive elements and also in defining the extent of the Pennsylvanian seas in the area of investigation. Havener and Pye

(1958), McKee (1975)1 and all previous workers are of the opinion that the Paradox Basin of the Four Corners area and northeast Arizona were at no time connected with the Pennsylvanian seas of east-central Ari­ zona. The new knowledge will also help in the refinement of the now generalized isopach, paleogeologic, paleotectonic and paleoenviron- mental interpretations of this area for the Pennsylvanian.

Area of Investigation

The area of investigation (Fig. 1 in pocket) is bounded by the

Arizona-New Mexico state line to the east, the Utah-Arizona state line to the north. Range 12E to the west and township 2N to the south. The area also encompasses the Fort Apache Indian Reservation exposures described by Winters (1951i 1963)1 the Mogollon Rim outcrops that ex­ tend into Coconino County that were previously studied by Jackson

(19511 1952), Huddle and Dobrovolny (1945), Brew (1965) and others.

The Black Mesa basin, an area of nearly circular downwarp some 90 miles in diameter extending from Coconino to Navajo and Apache counties, is also within the area of investigation. The Mogollon Rim is the southern extent of the Pennsylvanian strata studied. 3

An area along the New Mexico-Arizona state line, from township

4#N to 38N, and locally extending as far west as Range 26E is devoid of

Pennsylvanian rocks. The stratigraphic relations along this positive element is that of Permian elastics resting unconformably on Pre-

Cambrian quartzites and granites. This area is equivalent to the

DeChelly upwarp of Gregory (1917* pp. 111-112), which became referred to by later writers as the Defiance positive or uplift. Peirce, Keith and Wilt (1970) describe the Definace as a repeatedly active paleogeo- graphic feature that cannot be tied down with a rigid boundary. When a larger region is considered, it is common to link the Defiance with other influential paleogeographic features, such as the Zuni uplift to the southeast in New Mexico and the Kaibab positive in the Grand Canyon,

Flagstaff, and Jerome areas.

Method of Investigation

This study was conducted using drill hole logs and sample de­ scriptions from the American Stratigraphic Company furnished by the

Department of Geosciences at The University of Arizona, the Arizona

Oil and Gas Conservation Commission, and the Arizona Bureau of Geology and Mineral Technology. Well cuttings were examined where necessary to verify or properly establish the contacts between the Pennsylvanian and Mississippian Systems, the Hermosa and Molas Formations and the controversial Permian-Pennsylvanian boundary. These were then corre­ lated with the measured sections from Brew (1965) and Winters (1963), along the Mogollon Rim. Cross sections were constructed to correlate

the formations and illustrate facies changes within and across the 4 basins. Isopach maps were prepared to demonstrate the areal extent and thickness of each formation and for the total Pennsylvanian. These maps help in the restoration of the original depositional edge of the

formations and the entire Pennsylvanian. Lithofacies maps were pre­ pared for each formation and also the entire Pennsylvanian to and in

determining the environmental conditions that existed during the depo­

sition of the units. Paleogeologic, paleoenvironmental and paleotec-

tonic maps were constructed to help put into better perspective the

geologic history of this area during Pennsylvanian time.

Previous Work

The Pennsylvanian system in Arizona has been subjected to some

rigorous studies in the recent past by several workers (Huddle and

Dobrovolny 1945; Stoyonou 1936; Havener 1958; McKee 1975; Peirce 1976;

Brew 1965)• Prior to this, however, numerous studies by Ransome (1904,

Roth (1934) and others helped tremendously in defining the various

Pennsylvanian formations in the Colorado Plateau and adjacent regions.

Detailed review of previous work on each Pennsylvanian Formation will

be presented in a later section. REGIONAL GEOLOGY

Tectonic Setting

The late Mississippian and early Pennsylvanian in most of north-central and northeastern Arizona was a period of widespread emergence. Numerous positive areas (Fig. 2) were present in the area

for all or parts of the Pennsylvanian time. The extent of the Defiance-

Zuni, the most well-recorded positive area at this time, and its effect on sedimentation will be discussed in some detail in the next section.

The southern part of the study area lies within the Mogollon Rim — a

rugged mountainous area of Pre-Cambrian and Paleozoic rocks. The

Mogollon Rim region occupies the transition zone between the Colorado

Plateau and the basin and range Physiographic province.

The Kaibab-Zuni uplift as it is referred to by Fezner (i960)

is the least defined paleotectonic complex in this study area. Results

of previous investigations (Fezner i960) indicate that it extended from

west-central New Mexico across northeastern Arizona and into south­

western Utah.

The Uncompahgre uplift extended from east-central Utah south-

easternly across Colorado to north-central New Mexico. This tectonic

lineament then continued southwards as the San Luis uplift. These

tectonic elements were the main source of most of the clastic sediments

of the Colorado Plateau during the Pennsylvanian period.

5 6

L------

UTAH COLORADO

PARADOX BASIN

SAN JUAN BASIN

? ARIZONA NEW MEXICO I C

300 MILES

Figure 2. Pennsylvanian paleotectonic setting. — Modified from Fezner I960; Mallory 1976; and McKee 1976. 7

Another major positive area adjacent to the study area was the

Emery and Piute positive elements in south-central Utah. Herman and

Sharps (1956, p. ?8) first observed that Pennsylvanian sediments were

missing along the northwestern side of the Paradox Salt Basin; and

specifically noted two areas that were studied and verified by Fezner

(I960). Fezner suggested that DeHoines, Missouri, and Virgil sediments

were probably deposited over the uplift, but were removed by pre-

Wolfcampian erosion. He also added in his concluding remarks that the

Emery uplift became an effective clastic source in late Atokam-early

DesMoinesian time and acted as a low submerged arch throughout the rest

of the Pennsylvanian period.

The only other positive area in Arizona during the early

Paleozoic and most of the Pennsylvanian was the supposed Ensenada posi­

tive in the southwest part of the state. The evidence that a positive

area persisted in the southwest of Arizona is not as clear as that for

the Defiance positive area, because the record has been obscured by

intense post-Paleozoic metamorphism and erosion. Isopach data (McKee

1951) suggests, nevertheless, that a significant landmass existed in

the area. Work done by E. D. Wilson (1951) appears to support the

concept of a decrease in thickness of sediments westward in Arizona

during the Paleozoic. Measurements in southern California by Thompson

and Hazzard (1946), Hazzard (1933) also lend additional support to the

idea of a positive element in the southwest of Arizona.

During the Pennsylvanian, several elements were adjacent to

the area of study that had negative tendencies and greatly influenced 8 sedimentation patterns. Most notable of these were: (1) the Pedregosa

Basin in southeastern Arizona; (2) the San Juan Basin in northwestern

New Mexico, and perhaps the one that influenced the sedimentation pat­ terns the most in northeast Arizona; and is the Paradox Basin which extended southwards from Colorado and Utah. Because of the importance of these three negative elements in Arizona (during the Paleozoic), a brief description and general location of each of the basins will set the stage for later discussions in this study.

The Pedregosa Basin

This basin, south of the Kaibab-Zuni uplift in southeastern

Arizona, formed an extensive seaway during the Pennsylvanian. This

seaway was considered by Fezner (I960, p. 1390) as a northward exten­

sion of the Sonoran geosyncline. The Pedregosa Basin was the site of

deposition of at least 3,300 feet of Pennsylvanian and Permian car­

bonate and clastic marine sediments, based upon measurements in the

Chiricahua and Dos Cabezas mountains of southern Arizona by Sabins

(1957).

San Juan Basin

This basin lies in the southeastern part of the Colorado

Plateau in northwest New Mexico and comprises approximately the eastern

half of the Navajo physiographic section (Kelley 1957)• The basin is a

roughly circular depression located mostly in the northwestern corner

of New Mexico but extends slightly into southwestern Colorado. This

basin is largely defined by its rims and bordering tectonic elements

which includes the Zuni uplift, Defiance positive. Four Corners 9 platform, etc. Since it is outside the scope of this investigation to go into such detailed tectonics of surrounding areas of the basin, the reader is referred to an excellent paper by Kelley (1957).

The San Juan Basin had its tectonic evolution and form con­ trolled by late Paleozoic disturbances, but in spite of this, it is predominantly considered a laramide feature (Burton 1955t P* 88).

Paradox Basin

The Paradox Basin is asymmetric in outline and contains the

thickest Pennsylvanian Salt beds in the United States (Krumbein 1951, p. 69). It is an elongate northwest-trending basin of Pennsylvanian

and Permian age in southeastern Utah, southwestern Colorado, and ex­

tends into northern Arizona and New Mexico. The basin is approxi­

mately 200 miles long and 100 miles wide and is contiguous to and

parallel with the southwest edge of the uncompahgre uplift.

Paleogeology

Both the pre-Pennsylvanian and post-Pennsylvanian paleogeology

are summarized in Figure 4 (in pocket) and Figure 3. Rocks of the

Pennsylvanian in most parts of the study area rest unconformably upon

strata of Mississippian Age. The reader is referred to Figures 3 and

4 for the few notable exceptions.

Several workers (Armstrong 1962; McKee and Gutschick 1969; Brew

1965) have recognized through paleontologic investigations that a stra­

tigraphic break involving the uppermost Mississippian and lowermost

Pennsylvanian time exists over much of Arizona. The extent of this Units Directly Underlying the Pennsylvanian System LOCATIONS NORTHEAST EAST-CENTRAL DEFIANCE SYSTEM FORMATION ARIZONA ARIZONA BLACK MESA MOGOLLON RIM POSITIVE

Mississippian Redwall X X X X

Devonian Martin X

Pre-Cambrian Quartzites X X and Granites

Units Overlying the Pennsylvan ian System

Supai X X X X Permian Cutler X

Figure 3. Pre- and post-Pennsylvanian paleogeology 11 hiatus will be investigated further in discussing the lower boundary of the Pennsylvanian system.

Pre-Cambrian rocks underlying the Pennsylvanian on the flanks of the Defiance positive sure mostly quartzites and granites. The depo­ sitions! relationship between the Pennsylvanian rocks and the under­ lying formations and the causes of the stratigraphic variances in the

Defiance region has been a matter of speculation. A combination of facies change, erosion, and nondeposition are involved.

Units Underlying the Pennsylvanian

The pinchout of Lower Paleozoic rocks against the Defiance positive has been customarily ascribed to offlap, but subsurface pat­ terns are very suggestive of removal prior to deposition of Pennsyl­ vanian strata. The lateral change in paleogeology from Pre-Cambrian rocks in the east near the Defiance positive to Devonian rocks of the

Martin Formation and then finally to Mississippian limestones in the west of east-central Arizona (Fig. 4) has been regarded by some workers

(McKee 1951i p. 488) as the effect of Paleozoic seas shoaling and ending along the margins of the Defiance positive. However, my inter­ pretation from this study is that the Defiance was slightly submerged as a submarine arch during some of the Mississippian, which resulted in the deposition of a thin sediment cover over it. This arch was later uplifted during late Mississippian to early Pennsylvanian time

(Fezner I960; Brew 1965; Peirce et al. 1970) and exposed to extensive erosion. This resulted in the widespread unconformity recorded between 12

Mississippian* some Devonian, and Pre-Cambrian rocks on the one hand and the Pennsylvanian on the other.

The evidence from which I drew the above conclusions are as

follows:

1. As Peirce, Keith and Witt (1970, p. 4?) rightly stated, had the

Pre-Cambrian granitic rocks been in positive relationship to Missis-

sippian seas, one would expect that Mississippian strata should con­

tain more sand than they do.

2. Havener and Pye (1958) indicate that north-central Arizona

could have only been transitionally positive from Morrow through Virgil

time. This same view is held by Fezner (I960, p. 1401), who concluded

from the clastic ratio map of the Paradox Formation that the Defiance

uplift existed as a mildly positive submarine arch prior to regional

uplift during DesMoines time.

3» Conglomerates present above the Mississippian in most of east-

central Arizona that are disposed of simply as intraformational, have

been examined by Peirce (personal communication 1977) in Carrizo Creek

south to Amos Wash, who found them to contain first circle coarse

grained grits of quartz and feldspar believed to have been derived

from granitic rocks. The only granitic rocks present at the time these

conglomerates supposedly were eroded and deposited above the Missis­

sippian limestones, are the Pre-Cambrian granites that are exposed to­

day on the Defiance uplift. Peirce, Jones and Rogers (1977) explain

the presence of these conglomerates as the result of temporary marine

regressions that permitted mechanical transport along a stream system 13 with headwaters in the terrain of older Pre-Cambrian rocks to the east

and north of the sites of conglomerate deposition.

4. Logs examined for central points 4, 8, 24, and 51 of this study

reveal unconformities between the Devonian and overlying Pennsylvanian

with conglomerates of the type discussed above making up the lower part

of the Pennsylvanian strata. These conglomerates are not yet proven to

be the products of erosion of Pre-Cambrian granite as are those in

Carrizo Creek. To resolve this, therefore, more detailed petrographic

studies of these widespread conglomerates and a thorough examination

of all the evidence that may bear on their being derived from Pre-

Cambrian granite will be necessary.

In conclusion, I would like to add that the long period of

erosion referred to as the post-Redwall-pre-Naco hiatus by Brew (1965)

that spanned Morrowan and Atokam time in the Pennsylvanian and prob­

ably part or all of the Chesterian and possibly some Meramerican time

in the Mississippian could have stripped off all the thin cover of

Mississippiem strata deposited over the Defiance when it was still a

submarine arch.

Units Overlying the Pennsylvanian

The Pennsylvanian is everywhere overlain in the study area by

red beds of the lower member of the Permian Supai Formation. This

formation has been studied in detail in surface exposures (McKee 1945;

Huddle and Dobrovolny 1945; Jackson 1951; Winters 1963) and in the sub­

surface by Passmore (1969). 14

The entire formation is interpreted as being representative of

Deltaic plain,lagoonal and near shore sediments laid down in an overall

regressive phase of sedimentation (Van Houton 1961). MOLAS FORMATION

Previous Work

A summary of all previous work on the Molas Formation that is pertinent to this study is presented in Figure 5»

Paleontologic investigations to determine the age of the Molas were carried out by several workers (Thompson 1942; Bradish and Mills

1950; DiGiambattista 1952; Wengerd and Strickland 1954)• Merrill and

Winar (1958), from whose work the writer has drawn freely in this study, review some of the literature dealing with the Molas Formation and its equivalents in the Four Corners region, and discuss the dif­ ferences of opinion about its age and historical significance #

Lower Boundary

The Molas Formation at most places has a basal contact that is disconformable on Devonian and Mississippian limestones. This contact is everywhere defined as coincident with the boundary between the

Pennsylvanian system and the Devonian or the Mississippian systems.

Cross and Larson (1935)« in their interpretation of the Pennsylvanian-

Mississippian unconformity, believed the residuum that overlies the

Mississippian Leadville to be part of it, whereas the Molas included the red elastics above the 'residue.'

Upper Boundary

In the study area, the Molas Formation is overlain with a gra­

dational contact by the lower member of the Hermosa Formation. This

15 16

Reference Geographic Location Contribution

Cross, Howe and Molas Lake, south of Named the Molas Ransome (1904, Silverton, Colorado, p. 4) Needles Mountains Girty (1903, p. Needles Mountains Studied fauna indige­ 246) nous to the Formation, interpreted Molas to be early Pennsylvanian in age Cross et al. Tank Creek, Needles Reported "transition (1905) Mountains zone" between Molas and underlying formations Cross, Howe and Needles Mountains Measured a section in Irving (1907) which Molas rests with sharp contact on Lead- ville limestone. Huddle and Central Arizona Correlated basal part Dobrovolny (1945) of Naco Formation with the Molas in view of their lithologic and genetic similarity Wengerd and Needles Mountains Divided the Molas into Strickland (1954, three members: lower, pp. 2166-68) middle and upper, based on lithologic differ­ ences Merrill and Southwestern Colorado Recognized the three Winar (1958) members of the Molas, renamed the lower mem­ ber the Coalbank Hill; studied fauna and assigned the age of late Atoko-early Des Moines to the Molas Formation

Figure 5« Summary of previous work on the Molas 17 relationship also exists at the type locality, where the Molas is overlain by the Pinkerton Trail Formation. The contact is well ex­ posed at Molas Lake (Merrill and Winar 1958, p. 2125)t where red Molas- like shale occurs as thin partings along the bedding surfaces of the lower Pinkerton Trail limestones. Because of the gradational nature of the contact, the selection of the boundary at an outcrop is more or less arbitrary. Commonly chosen is the base of a blue-gray argil­ laceous limestone, lithologically characteristic of the Pinkerton

Trail Formation. However, where the Pinkerton Trail is absent, as at

Duray, the base of a coarse-grained, green sandstone is considered the base of the Hermosa (Cross, Howe and Irving 1907, p. 4*, Burbank 1930, p. 162).

Age of the Molas Formation

As much variation in the age assignments of the Molas Formation by different writers has been made as has been the placement of boun­

daries. M. L. Thompson (1942) identified fusulinids found in the upper

calcareous shales of the formation in northern New Mexico and stated

that they are Morrowan and early Atokan in age. Bradish and Mills

(1950, p. 60) believed the Molas to be Morrowan in age and the base of

the Hermosa to be Atokan. The dating of the Molas as Morrowan was on

the basis of stratigraphic position (Merrill and Winar 1958, p. 2111).

DiGiambattista (1952, p. 6) in his interpretation, stated that the

Molas deposition began in the Morrow and extended into DesMoines and

described the Molas as a formation that transgresses time lines.

Wengerd and Strickland (1954, pp. 2166-68) stated that the Molas 18

Formation contains important horizons between Morrow and Atoka, and

Atoka and DesMoines rocks in many areas of the Paradox Salt basin. In the absence of recent paleontological investigations, the writer con­ cludes that the Molas Formation ranges in age between Morrow and Des

Moines, depending on the locality.

Lithologic Description

V/engerd and Strickland (1954, p. 2168) divided the Molas into

three members, and described them as follows: "The lowest member is a section of varicolored claystone, predominantly red and containing many solution rounded limestone fragments of Mississippian age, which appears to be a limestone chert regolith cemented by calcareous silty

claystone. The middle member is highly variable siltstone and shale with some intrafornational conglomerate which was reworked by trans­

gressing seas of latest Atokan to earliest DesMoines age. The upper

section is a marine red and green shale-sandstone sequence, containing

abundant brachiopads, pelecypods, trilobites and fusulinids of Des

Moines age." This subdivision and lithologic description of the Molas

Formation was verified and adopted by later writers (Merrill and Winar

1958; Brew 1965). Even though it was difficult to recognize the sub­

divisions of Wengerd and Strickland (1954) from drill hole cuttings,

the lithologic description seems to be standard from one location to

another, except for minor details.

Depositional History and Environment

The depositional history and environment of the Molas Formation

is no different from that of the lower part of the Naco Formation, as 19 has been accurately observed by several previous writers (Huddle and

Dobrovolny 1945; Brew 19&5)* This stems from the lithologic and genetic similarity of both formations which caused some earlier writers to conclude that the Molas Formation of southern Colorado was the same as the lower part of the Naco Formation of central Arizona. Brew

(19651 p. 43) recognized that the general sequence observed for his alpha member was similar to that of the Molas and therefore adopted the three distinct environments recognized by Merrill and Winar in the

Molas Formation as probably represented in his alpha sequence.

To determine the environment of deposition of the Molas Forma­ tion of Colorado, Merrill and Winar (1958, pp. 2118-19) studied the clay minerals of the succession and found that kaolinite was dominant over illite in the undisturbed Coalbank Hill member and in the middle member. They therefore drew the boundary between the middle and the upper member, at the point where illite became dominant over kaolinite.

The following is the conclusion reached by Merrill and Winar about the environment of deposition of the Molas: (1) the Coalbank Hill member was the remains of an ancient soil formed contemporaneously with the karst features; (2) the middle member represented sediments deposited by streams in a terrestrial environment; and (3) the upper member comprises materials reworked and deposited by advancing marine waters.

The depositional history as interpreted by Cross et al. (1905» p. 5) and modified later by Cross said Larson (1935* P» 15) is that the

Mississippian-Pennsylvanian unconformity was the result of post-

Leadville uplift, followed by subareal erosion of the limestones with

reworking of the erosion product by the sea. 20

Later an influx of land-derived sediments occurred that mingled with the Leadville-derived boulders and cobbles, to produce the Molas

Formation. Cross and Larson (1935)i however, failed to add that the sea transgressed again due to submergence and resulted in the deposi­ tion of the fossiliferous upper member, above the predominantly land- derived sediments.

General Discussion

Isopach trends (Fig. 6, in pocket) for the Molas indicate a gradual thinning southwards from the Paradox Basin area. Noticeable thinning also occurs from east to west.

The pattern of isopachs suggest that the strata of the Molas are marginal to thicker deposits farther northeast in the Paradox

Basin. The Zuni-Kaibab lineament of Fezner (I960); (Fig. 2 of this study) seems to have been the positive element southwards against which the Molas Formation pinches out.

The lithofacies trends (Fig. 7, in pocket) of the Molas indi­ cates an area of predominantly shale deposition that coincides with

the deepest, thickest isopach trends (Fig. 6, in pocket). This trend changes into the Paradox Basin as more and more carbonates come into

the picture beyond the northern boundary of the state (McKee 1976);

surrounding this area of predominantly shale deposition are fine

elastics with varying proportions of limestone mixed in. The source

of elastics here (McKee 1976) is thought to be from the west and

northwest of the study area. HERMOSA FORMATION

Previous Work

A summary of all previous work on the Hermosa Formation, per­ tinent to this study, is presented in Figure 8.

This writer prefers to retain Hermosa Formation in place of

Honaker Trail despite the superiority of the terminology of Wengerd and Strickland (195*0, because their Honaker Trail Formation includes the early Permian Cutter carbonate facies that occur in the north­ western part of the Paradox Basin. Fezner (i960) also recognizes that the use of that terminology would be incorrect and misleading, espe­ cially if the investigation being conducted requires a Permo-

Pennsylvanian division in order to define the Pennsylvanian lithofacies.

Towards the margin and beyond the edge of the Paradox Basin, the con­

spicuous absence of the evaporitic Paradox Formation does not permit

the differentiation of the Pinkerton Trail or the Honaker Trail from

the restricted Hermosa Formation in the area of study.

Twenty-seven different sets of nomenclature used by companies

and other organizations in the oil industry were compiled and published

in i960 by the Nomenclature Committee of the Four Corners Geological

Society. With this flurry of nomenclature, it is left to the prac­

ticing stratigrapher to pick the one that best suits his purpose of

study.

21 22

Reference Geographic Location Contribution

Spencer(l900) Animas River, Durango First named the Hermosa quadrangle, Colorado Formation Cross and Animas River, Durango First used Hermosa as a Spencer (1900) quadrangle, Colorado mapping unit R. Roth (1934, Sec. 26 & 35, T.37N., Chose and first meas­ p. 945) R.9W, La Plata County, ured composite section Colorado at type locality Baker and •Gypsum Valley and Correlated black shale Reeside (1929) Paradox Valley, Colorado and anhydrite of Her­ mosa Formation with thick evaporite de­ posits of the Paradox Formation Bass (1944) Type locality of Roth Subdivided the Hermosa into three members; Upper Hermosa, Paradox member and the lower Hermosa Wengerd and Paradox Salt Basin, Elevated the Hermosa Strickland Four Corners area, to group rank, made up (1954) Colorado and Utah of Honaker Trail Forma­ tion, Paradox Formation and the Pinkerton Trail Formation Wengerd and Four Corners Region Sedimentational history Matheny (1958)

Figure 8. Summary* of previous work on the Hermosa Formation. 23

The nomenclature used for this study was adopted from the

American Stratigraphic Company which recognizes different zones (Ismay,

Desert Creek, Akah, and Baker Creek) within the Hermosa Formation, which is used synonymously with Hermosa Group in northeast Arizona. It is necessary to add here that the different zones recognized within the

Hermosa cannot be confidently projected southwards beyond a few wells in the extreme northeast corner of the State of Arizona.

Lower Boundary

Underlying the Hermosa Formation in northeastern Arizona is a sequence of red elastics, largely siltstone, shale and mudstone, but also containing minor amounts of sandstone, conglomerate and calcareous rocks called the Molas Formation. The contact between this sequence of rocks and the overlying Hermosa Formation is everywhere gradational.

Upper Boundary

The strata overlying the highest rocks of definite Pennsyl­ vanian age in northeastern Arizona are referred to the Cutler Forma­ tion, and in the subsurface near Four Corners they are represented mostly by Cutler evaporites believed to be of Wolfcamp age (McKee

1976).

The upper boundary currently recognized between Virgil and

Wolfcamp rocks is at the top of the marine limestone of the upper

Hermosa near the Paradox Basin, but lies within red beds of the Supai or Cutler Formations further south (J. A. Peterson 1969; McKee 1976).

Peirce (personal communication 1977) does not hold the view that the upper boundary of the Hermosa Formation is synonymous with 24 the PenneyIvamian-Permian boundary in northeast and north-central

Arizona as mentioned above. He is of the opinion that the conglomer­ ates that mark the boundary between the Esplanade sandstone of Wolfcamp- ian age and the Wescogame Formation of Virgilian age in Havasu Canyon of northwestern Arizona (McKee 1975) and that are also widespread in north-central and northeastern Arizona, could mark the Pennsylvanian-

Permian boundary. The Virgil-Wolfcamp boundary established for the

Havasu Canyon area has been projected (Museum of Northern Arizona 1976, map of the Grand Canyon National Park) into the rest of the Grand

Canyon area. These same extraformational conglomerates were also recog­ nized by Brew (1965) in a few of his sections of the Naco Formation.

Age of the Hermosa Formation

The inconsistent definitions of sections and their lithologic character, and a lack of good paleontological control has greatly con­ fused the dating of the Hermosa Formation, especially the upper bound­ ary. McKee (1976) considers the boundary between the Hermosa and Molas

Formations in the area of study to be of Atokan Age. The upper part of the Hermosa Formation in northeastern Arizona is certainly Virgilian in age (McKee 1976). Wengerd and Strickland (1954), based on fusulinid data, suggested that the Hermosa Group (which includes the Pinkerton

Trail Formation, Paradox Formation and the Honaker Trail Formation)

spans the entire period from Atokan to Wolfcampian time. This is,

however, erroneous because they regarded the lower part of the Rico

Formation as part of the upper Hermosa. This means that the Hermosa

Formation ranges in age from Atokan to Virgilian and probably includes 25 some parts of the Rico Member of the Cutler Formation which is pres­ ently regarded as Volfcampian in age.

Lithologic Description

A. C. Spencer (1900) was the first to name the Hermosa Forma­ tion and described.it as a heterogeneous series of rocks which is generally distributed in the San Juan region. In the area of study, the Hermosa Formation contains carbonate rocks and at the far north, anhydritic carbonate, interbedded with red and brown siltstone, shale, and some sandstone. The formation grades upward into maroon and brown sandstone, siltstone, and shale of the lacustrine and fluvial Cutler

Formation. The upper part of the Hermosa Formation grades downwards into a lower member that is characterized predominantly by fine to medium grained fossiliferous dolomite and limestone interbedded with dark gray silty shale. Locally, however, red siltstone and sandstone similar to the underlying Molas Formation are present within the lower part of the Hermosa.

Depositional History and Environment

The lower part of the Hermosa Formation (Pinkerton Trail For­ mation of Wengerd and Strickland 195*0 was deposited from late Atokan

to DesMoinesian time (McKee 1976). The lithologic association of car­

bonate, fine clastic, local traces of limestone conglomerate and a

variegated Molas-type clastic facies, suggests deposition in a rela­

tively stable neritic marine environment that probably existed over

the entire area of study. Because of the absence of the Paradox For­

mation in this area, a gradational relationship exists between the 26 upper and lower parts of the Hermosa Formation. As McKee (1976) rightly observes, depositions! environments that were established during the early Pennsylvanian time were maintained through Virgilian time. The upper part of the Hermosa consists almost entirely of stable to mildly unstable shelf-type limestone.

The entire Hermosa Formation, therefore, represents trans­ gressions and minor regressions of the sea that were mostly across low, flat land surfaces and adjacent shelves, marginal to the Cordilleran

Basin to the northwest and the Pedregosa Basin to the southwest, and under the direct influence of the Paradox Basin in the northeast.

Discussion

Isopach trends (Fig. 9$ in pocket) of the Hermosa Formation indicates a thinning from the north to south. The formation attains a thickness of more than 16$0 feet at the northeast end of the study area and thins to a minimum of 125 feet in less than 200 miles, and pinches out against the Defiance positive. This thinning is similar in style to that which takes place from east to west along the Mogollon Rim.

In spite of this thinning, the underlying Mississippian and Devonian strata tend to persist, suggesting that they were not exposed above base level for any significant length of time during the periodic

Pennsylvanian tectonic adjustment (Peirce 1976, p. 49).

The thinning of the Pennsylvanian section from the Paradox

Basin into the Black Mesa region in northeast Arizona is thought to have been caused by marine offlap (Fezner I960; Lessentine 1969, p.

105). 27

The drastic manner with which the Hermosa and the Naco Forma­ tions thin between certain drill holes (Figs. 10, 11 and 12, in pocket) represent one of the most interesting problems encountered in this study. Apparently this problem had been recognized by some workers

(Ross 1973; Peirce 1976). The thinning between well numbers 24 and

36 of this study (Fig. 10, in pocket) is not as drastic as those en­ countered within the Naco Formation, and is attributed to what Ross

(1973, p. 897) refers to as irregular deposition, suggestive of active structural adjustments during or shortly after the deposition of the formation. In the western portion of the study area, the Hermosa For­ mation thins to a little over 200 feet and remains that way into east- central Arizona, where Pennsylvanian strata of similar lithology and age are referred to as the Naco Formation (Fig. 13, in pocket).

Lithofacies trends for the Hermosa Formation (Fig. 14, in pocket) show a progression from predominantly carbonate rock in the extreme northern part of the study area to mudstone and calcareous mudstone to the south. The only notable exception to this is the ex­ tension of the predominantly carbonate area southward near the Arizona-

New Mexico state line and terminating against the Defiance positive.

Extending from the northeast, eastwards and terminating before reaching the Defiance positive is a tongue-like protrusion of predominantly sand-size clastic facies. Here, the percentage of sandstone to lime­ stone is between 50 and 80. This area is also reflected as being pre­ dominantly clastic by the paleoenvironmental map (Fig. 15, in pocket).

Rocks of the Hermosa adjacent to the Defiance positive are mostly fine clastic rocks and calcareous mudstone. 28

Limestones tend to dominate the northern part of the study area, because of its proximity to the Paradox Basin, which at this

time was the site of thick carbonate deposition. Heylmun (1958) recog­ nized a positive element that he called the Circle Cliffs uplift in

southern Utah, which Fezner (I960) tried to indicate as the source for

the Pennsylvanian clastic rocks of northern Arizona. McKee (1976) and

Mallory (1976) also point to a positive element in southwest Utah

called the Piute Positive as being the source of elastics for the north­

western part of the study area. The Piute and Emery uplifts are

doubtful as the sources of elastics for this part of Arizona as Missis-

sippian isopach trends for central and southern Utah indicate the pres­

ence of fairly thick deposits of limestone (Peirce, personal communi­

cation 1977). It is highly inconceivable that limestones would be the

source of coarse elastics. This writer is in support of a source to

the west and northwest of Arizona but the Paleozoic record in that

area has been so fragmented by latter tectonic activities, that being

more specific than this will be just a matter of speculation. More

detailed investigation, the nature of which is beyond the scope of

this study, is needed to adequately pinpoint a source for the wide­

spread Pennsylvanian elastics in Arizona. NACO FORMATION

Previous Work

Brew (1965) carried out a detailed study of the stratigraphy of the Naco Formation in central Arizona. Table 1 (pp. 12-20) of his excellent study is devoted to the nomenclatural history of Pennsyl­ vanian rocks, especially the Naco Formation in east-central Arizona.

Going into any such detail in this study will be merely repetitive.

The reader is therefore referred to Brew's work for an overview of all previous work done on the Naco Formation in this area of study.

Lower Boundary

In east-central Arizona, and within the area studied, the Naco

Formation is everywhere separated from the underlying Redwall lime­ stone by a distinct and easily recognizable disconformity that is approximately coincident with the boundary between the Pennsylvanian and Mississippian systems. This unconformity is recognizable in the subsurface and surface outcrops (Brew 1965) over a wide geographic area, including the Colorado Plateau and its margins. This boundary is, however, less distinct in southeastern Arizona where the systemic boundary is definable primarily on paleontological grounds. The top of the Redwall limestone in central Arizona is marked by karst top­ ography. Sinkholes, collapse features and residual knobs produce a local relief that is in the order of 10 to 20 feet but may be as much

as 40 feed and more in certain areas.

29 30

The contact between the Naco and the Redwall can be drawn above the last continuous ledge of gray or yellowish-gray limestone and be­ neath the overlying* dark* reddish-brown chert rubble and mudstone mix­ ture or undisturbed mudstone residuum.

Even though the change from bedded marine limestone to dis­ ordered chert rubble and mudstone is readily visible, in certain localities, the change appears gradational because of the broken dis­ articulated character of the upper Redwall which is infilled with the dark, reddish-brown mudstone and because of local blocks of Redwall within the residuum. In such localities, the formations^, boundary is placed at a point where limestone blocks are no longer dominant (Brew

1965).

Upper Boundary

The contact between the Naco and the overlying Supai Formation occurs in a gradational lithologic sequence throughout the area studied.

The lithologic similarity of the top of the Naco to the overlying Supai suecenion, makes recognition of the formational boundary difficult.

According to Brew (1965* p. 8l) "it is arbitrarily placed at the top of the uppermost grayish red and light gray mottled calcilutite over- lain by a thick, slope-forming, pale red siltstone and sandstone se­ quence. Elsewhere, in the field area, the boundary is placed at the top of the uppermost fossiliferous limestone of the trsmsitionsQ. beds."

Winters (1963, p. 8) places the transitional beds in the Naco Formation and Brew (1965, p. 8l) agrees with him for the following reasons: (l)

the alternating limestone and clastic beds of the gamma member of Brew 31 are more characteristic of the Naco than the Supai; and (2) the major part of the Supai is unfossiliferous whereas the transitional beds are

fossiliferous. This practice is in accord with the American Commission

on Stratigraphic Nomenclature (1961, p. 650). The Naco-Supai boundary

as defined here, is time-transgressive.

Lithologic Description

The Naco Formation displays great vertical and lateral varia­

tion in age and no single drill hole is representative. The lower part

of the formation, the alpha member of Brew (1965), is characterized by

angular to subangular chert fragments of various colors, but mostly

white, pink or light gray. This basal part of the Naco has most com­

monly been referred to as 1 chert rubble1 or 'breccia,1 1 residual soil,1

and 1 rubble breccia' by various authors (Anderson and Creasy 1958;

Huddle and Dobrovolny 1945, 1950; Merrill and Winer 1958). Overlying

this 'chert rubble' and still with the alpha member of Brew, is a well-

stratified reddish-brown, grayish-red, or grayish-purple mudstone, silt-

stone and very fine grained sandstone. The middle part of the forma­

tion, which corresponds with the beta member of Brew, consists of

alternations of resistant limestone, calcareous siltstone and sand­

stone, with thinner intervals of shaly mudstone and siltstone locally.

Brew (1965) reports the presence of chert nodules and conglomerates

within this interval. The interbedding of limestone and shale persists

into the upper part of the Naco where it grades into laminated, cross-

laminated, and thin bedded, pale red, grayish-red or reddish-brown

calcareous siltstone and very fine grained sandstone that weather to 32 form partially covered steep slopes (Brew 1965, p. 37). This member is locally fossiliferous, and is considered a transitional interval between the Naco and the Supai.

Age of the Naco Formation

In most of east-central Arizona, the basal part of the Naco

Formation is early DesMoines in age and is younger than the lowest

Pennsylvanian strata in both the southeastern and the Grand Canyon areas of Arizona (Brew 1965? McKee 1976). This means that the trans­ gression of the Pennsylvanian from southeastern to central Arizona took considerable time, during which a maximum amount of residuum developed in central Arizona. The top of the Naco Formation in central Arizona is certainly virgilian in age (Brew 1965; McKee 1976). However, Brew

(1965, p. 8l) claims to have found some unnamed species of Triticites in his gamma member at some localities, that appear transitional from

Virgilian forms to the lower Permian genera Pseudofusulina and Pseudo- schwagerina. These seem to represent younger evolutionary stages than those reached by the beta member Carrizo Faunas. Absence of diagnostic

Wolfcampian genera prevented him from assigning a Permian age to the sequences involved, so he considers them 'post-Virgilian1 in age but not Permian.

Depositional History and Environment

A striking similarity exists between the alpha member of the

Naco Formation, and the Molas Formation studied by Merrill and Winar

(1958). This similarity prompted Brew (1965, p. 43) to conclude that

the three distinct environments recognized in the Molas Formation are 33 probably represented in the alpha sequence. The basal residuum of the alpha member is undoubtedly terrestrial in origin. The overlying stratified sedimentary rocks may have been deposited in both fresh water and marine environments. The fossiliferous upper portions of the member are clearly marine (Brew 1965). The beta member is a pro­ duct of continuous deposition from the upper part of the alpha member.

Both paleontological and lithologic evidence points to a shallow epeiric sea that spread into this area from the southeast during

Pennsylvanian time. Northwest of the area where the Naco is encoun­ tered in this study, there is an abundance of fine elastics which represent the more shoreward facies of this formation. Towards the southeast the Naco thickens (Fig. 9, in pocket) and becomes progres­ sively carbonate-rich. This thinning of the fossiliferous unit in the beta member suggests that marine conditions persisted for only a short span of time as eventual outward growth of the Supai Delta, soon dis­ placed marine waters from this area (Brew 1965)• The upper part of

the Naco was deposited in a transitional environment and reflects the

change from dominantly marine conditions, into the non-marine condi­

tions of the lower beds of the Supai Formation. Brew (1965♦ p. 85)

attributes this periodic interfingering of marine limestone and mud­

stone with unfossiliferous redbeds of terrestrial or shallow marine

origin that are similar to those of the lower Supai Formation, to

oscillation of sea level and changing rates of sedimentation and sub­

sidence. Wedge-shaped clastic deposits representing channel fills,

and cross-laminated, ripple-marked beds, present in surface exposures 34 support Brew*s contention that these rocks were deposited on flood plains or as parts of small deltas.

General Discussion

Isopach trends (Fig. 9« in pocket) suggests several drastic thinning activities within the Naco Formation. The thinning from east to west along the Mogollon Rim was recognized by earlier workers and attributed (Brew 1965) to lateral gradation into terrestrial beds of the Supai Formation. The thinning towards the north represents a shoaling of the Pedregosa Basin in the southeast, which resulted in the eventual connection with the seas of the Paradox Basin. The thinning trend from west to east is indicative of an onlap relationship with the Defiance Positive. The same view is held by Peirce (1976), McKee

(1976), and several previous workers. The isopach trends also suggest a deep embayment around well numbers 9» 10, 11 and 59, that shallows to the south for a short distance before deepening again. The thickest isopach trends are towards the south and are manifestations of the

Pedregosa Basin.

The zero isopach line marks the actual extent of the Defiance uplift and represents the erosional or depositional edge in this area during the Pennsylvanian. The thinning between drill holes 6 and 57

(Figs. 10 and 13, in pocket) is so drastic that it cannot be ordinarily dismissed as a thinning abruptly against the Defiance Positive. This kind of thinning was also recognized by Peirce and Scurlock (1972) be­

tween two drill holes in southern Apache County where there is a loss

of 1200 feet of Pennsylvanian-Permian section. Between wells 6 and 57 35 of this study, there is a loss of 737 feet of section within 10.5 miles along the west edge of the Defiance uplift. Peirce (1976, p. 49) in explaining this kind of phenomenon writes, "the nature of this struc­

ture is not known, but it is probably late Mississippian-pre-Permian

in age and might represent north-south faulting of the then west mar­

gin of the Defiance positive." It is the opinion of both Peirce (per­

sonal communication 1977) and the writer that closer spaced studies of

these wells are required to reveal the actual nature of the faults.

It is possible for instance, that the 737 feet of thickness lost be­

tween wells 6 and 57 of this study were actually lost in much less

than 10.5 miles. Also Peirce (personal communication 1977) has sug­

gested that this south-north trending fault lineament could extend

northwards resulting in the thinning observed between wells 24 and 26

of this study (Fig. 10, in pocket).

Lithofacies trends (Fig. 14, in pocket) of the Naco Formation

are similar to those recognized by previous workers (McKee 1976; Peirce,

Jones and Rogers 1977)• The trends show a dominance of calcareous mud­

stone, siltstone and shale over east-central Arizona, with only two

exceptions. A small area adjoining the Defiance positive with shaly

limestone, and the south-central part of the study area where shales

and siltstones predominate over other lithologic types. The source

of these fine elastics was the mildly positive Defiance uplift. REGIONAL TRENDS OF THE PENNSYLVANIAN

General Discussion

Isopach trends of the Naco and Hermosa Formations (Fig. 9, in pocket) are very similar to the trends (Fig. 16, in pocket) of the entire Pennsylvanian system, because the Molas Formation is only present in part of the study area. A thinning of the Naco Formation

from south to north is indicated by the thickness trends. This thin­ ning northwards remains stable (Figs. 10, 11 and 13, in pocket) espe­ cially between drill hole number 51 and number 19 where the formation name changes to Hermosa.

Evidences from this study (contrary to the assumptions of

Havener and Pye 1958; McKee 1976; and various other workers) is sug­

gestive of a connection between the fast-sinking Paradox basin in the

north and the Pedregosa Basin in the southeast. This connection took

place after the reworking of the basal Naco and the Molas Formations.

These same marine processes continued and resulted in the deposition

of the Hermosa and the middle and upper members of the Naco Formation.

These two formations represent the periods of maximum transgression

during the Pennsylvanian time in both the northeast and north-central

Arizona. Figures 10, 11 and 13 (in pocket) indicate that a shallow

connection of between 200-250 feet existed through all of DesMoines

to Virgil times and seem to have occurred simultaneously with the

deepening of both the Paradox Basin in the northeast and the Pedregosa

Basin in the southeast.

36 37

The lithologic and genetic similarity of the Naco on the one hand and the Molas and Hermosa on the other, is more than just a co­

incidence, as has long been recognized by earlier writers. Huddle and

Dobrovolny (19^5), Wengerd and Matheny (1958, p. 2065), and Horvath

(I960, p. 20) correlated the basal residual material (alpha member of

Brew 1965) of the Naco with the Molas Formation of Colorado, before it

became evident through the paleontological investigations of Sabins

(1957)» Sabins and Ross (1965)1 Ross and Sabins (1965), and Brew (1965)

that they are not paleontologically correlative. However, Wengerd and

Matheny (1958, p. 2065), on the basis of both age and lithologic simi­

larity, correlated the Pinkerton Trail Formation of the Hermosa Group

with the middle member of the Naco in east-central Arizona. Wengerd

and Matheny (1958) also correlated the Paradox Formation of the Hermosa

Group with the upper member of the Naco and lower Supai Formations in

this part of the state. Paleontologic studies of the Naco (Brew 1965)

suggest that the middle and upper members of the formation span the

entire period from late DesMoines to Virgil. This age assignment of

Brew agrees with the DesMoines age assigned to the Pinkerton Trail and

the late DesMoines to early Virgil assigned to the Paradox Formation by

Wengerd and Matheny (1958). All interpretations so far indicate a

shallow marine environment of deposition for both the Naco and Hermosa

Formations. Fezner (i960, p. 1400), from his lithofacies and isopach

trends, recognized a band of low clastic and sand-shale ratio values

in the study area as one approaches the Defiance-Zuni positive areas.

He interpreted this as being the result of a marine accessway joining

the Paradox and Pedregosa seaways. Minor marine transgressions 38 occurred across this constricted area separating the two distinct land masses during Pennsylvanian high water levels.

These evidences add to the writers conviction that during most of the DesMoines and certainly early, but probably all of Virgil time, the seas of the Paradox and Pedregosa Basins had a shallow connection through the center of the study area. Thickness trends for the north­ ern portion of the study area are similar to those already described for the Hermosa Formation. There is a thickening tendency towards the

Paradox Basin in the north and Pedregosa in the south.

Lithofacies trends (Fig. 17, in pocket) of the entire Pennsyl­ vanian are also very similar to those for the Naco and Hermosa For­ mations, with only a little exception. The area northwest that showed a coarse clastic facies (between 50 to 80 percent sand, and 20 to 50 percent carbonate) for the Hermosa Formation, becomes influenced by

more fine elastics of the Molas Formation.

The paleoenvironmental map (Fig. 15, in pocket) accompanying

this study was derived by taking the lithology represented by the mid­

point through the total interval of the Hermosa and Naco Formations at

all control points. By so doing, the writer assumed that the rate of

subsidence during the deposition of these two formations proceeded

gradually and at a steady pace. Under normal practice, a well recog­

nized datum-plane is traced and either the lithology above or below

is consistently recorded at all the control points. The trends shown

by the paleoenvironmental map indicate an area of coarse elastics,

probably deltaic or shoreline marine deposits in the northwestern part

of the study area. This same trend was earlier observed from the 39 lithofacies of both the Hermosa and the entire Pennsylvanian system.

McKee (1976) supports a western source outside Arizona for the high percentage of sand that is typical of late Pennsylvanian and early

Permian sediments in Arizona. Figure 15 (in pocket) also shows a gradual facies change from sandstone to silt, to shale and limestone from west to east. This particular trend which also shows up in the lithofacies trends, indicates a deepening of the marine conditions suitable for the deposition of the fine elastics and limestones. There are fine elastics along the New Mexico-Arizona border in the north that the writer attributes to the Uncompahgre and probably the Zuni-Defiance uplifts. The limestones that indicate the periods of maximum trans­ gression seems to have extended north into the Paradox Basin and all the way down south into the Pedregosa Basin. The dominance of elastics towards the southwest of the study area suggests the presence of the more shoreward facies of the Naco. Adjacent to the Defiance positive area are limestones, and shales which further strengthens the theory that the Defiance was only mildly positive throughout the Pennsylvanian.

The paleotectonic map (Fig. 18, in pocket) indicates a deepening toward the Paradox and Pedregosa Basins and the main source of elastics as being from the northwest. SUMMARY

The Pennsylvanian system consists of the Hermosa and the Molas

Formations in northeastern Arizona and the Naco Formation in east- central Arizona. The basal part of the Naco is a terrestrial and fresh water deposit, similar to the Molas both lithologically and genetically.

The upper part of the Naco is lithologically, genetically, and time equivalent to the Hermosa Formation.

The Naco Formation spans the entire time period from early

Des Moines to Virgil, while the Hermosa Formation ranges in age from

Atoka to Virgil. The Molas ranges in age, depending upon locality

from Morrowan to DesMoinesian. Results of this investigation suggests a shallow marine connection between the Pedregosa Basin in southeastern

Arizona and the Paradox Basin in southern Colorado and Utah, during the period between the DesMoines and Virgil. This period of connection

also coincides with the period of maximum subsidence of both basins.

The Defiance-Zuni positive element was mildly positive during

most of the Pennsylvanian, and only contributed fine elastics. The

main source of elastics was northwest of the study area. The Defiance-

Zuni positive, defined from this study, extends from latitudes 3^0-*360N

along the New Mexico-Arizona state line and as far west as Range 26°E.

Very drastic thinning occurs within the sediments of the Her­

mosa and the Naco Formations over very short distances. This phenome­

non is attributed to irregular deposition, suggestive of active struc­

tural adjustments, during or shortly after deposition of the formations.

40 SUGGESTIONS FOR FURTHER STUDY

This thesis has revealed a few areas where further detailed

study is needed. The first has to do with a detailed paleontological

refinement of the Pennsylvanian-Permian boundary in the area of study.

The 'post-Virgil* of Brew (1965) could be either Virgil or Wolfcamp,

but this can only be established paleontologically. Also in estab­

lishing this controversial boundary it may be necessary to examine the

conglomerates found close to the Virgil-Wolfcarap boundary in a few

localities in the study area and which was the basis for the estab­

lishment of the Pennsylvanian-Permian boundary by McKee (1975) in the

Grand Canyon area.

Further studies also need to be done to determine the actual

extent of the Zuni-Defiance positive element in New Mexico (state) for

a complete tectonic picture of the entire area.

4l APPENDIX A

NAME AND LOCATION OF SUBSURFACE DRILL HOLES Elec. Cont. Subsurface Drill Holes Log # Pt. # Name Location Reference

D1934 1 Calif. Oil Co. #1 state 2519 C, NW, Sec. 12, T.14N., & #1-A state 2519 R. 18E AM. Strat./A.B.M. D2777 2 Tenneco Oil Co. #1-X Fort Apache NE, SB, Sec. 31, T.10N., R. 21E it II II Tract-56 II D2786 3 Tenneco Oil Co. #1 Federal-B SW, NE, Sec. 4, T.10N., R. 24E 11 II D1148 4 Pan Am. Petr. Corp. New Mexico- SW, NE. Sec. 25, T.12N., 11 II II Arizona Land Co. B-l R. 23E D1515 5 Union Oil of Calif-Cont. Oil #1 SW, SW, NE, Sec. 34, T.15N., 11 II It New Mexico-Arizona Land R. 19 E D1199 6 Pan Am. Petr. #1 New Mexico- C, SB, SB, T.13N, R. 25E it II If Arizona Land 'A* • 11 If II 03316 7 Lydia Johnson #1 Aztec SW, NE, NE, Sec. 33, T.14N., R. 20E D1168 8 Lion Oil (Monsanto) #1 Cabin SW, NE, Sec. 30, T.14N., R. l4E it II II Wash ii II II DII82 9 Pan Am. Petr. Co., Aztec Land C, SW, NE, Sec. 9, T.16N., R. & Cattle Co. #B-1 18E D1164 10 Pan Am. Petr. Co., #1 Aztec SB, NE, Sec. 5, T.16N., R.20E 11 It II Land & Cattle Co. 'A' it II II D3107 11 George B. Cree Jr. #1 Scorse- C, SW, SW, Sec. 33, T.lSN., Fee R.20E D3108 12 Crest Oil #1 Spurlock C, SW, NE, Sec. 3, T.17N., R.26E 11 II II 11 It II 96R 13 Gen. Petr. Corp. #14 Creager SW, SW, NW, Sec. 6, T.19N., State R.23B n II II D1163 14 Kerr-McGee Oil Indus. #1 C, NE, NW, Sec. 23, T.lSN., Hortenstein R.25E 11 II It D3388 15 Edward F. Doherty #1-15 Navajo SE, SB, Sec. 15, T.7N., R.7W II D1730 16 J.G. Brown & Assoc. #2 Chambers- SB, SW, NE, Sec. 27, T.21N., 11 II Sanders R. 28E 11 II II D2530 17 Texaco Inc. #2 Navajo Tribe-AG NW, NE, Sec. 21, T.41N., R.25B Elec. Cont. Subsurface 1Drill Holes Log # Pt. # Name Location Reference

D2543 18 Texaco #1 Navajo Ak NE, NE, Sec. 6, T.40N., R.25E AM. Strat./A.B.M. D2573 19 Texaco #1 Hopi Tribe-A NY/, NW, Sec. 15, T.26N., R.16E VI It II D2550 20 Atlantic Refining Co. #1 Hopi-9 C, SW, SB, Sec. 9» T.28N., R.15E II It II D3166 21 Pennzoil United #1-11 Hopi C, NW, NW, Sec. 11, T.29N., R.14E II II II D2592 22 Amerada Petr. #1 Hopi-5075 SB, NE, Sec. 8, T.29N., R.19E II II II D2597 23 Skelly Oil, Murphy Oil, Agui- SW, NE, Sec. 35» T.30N., R.17E It II II taine Oil #1 Hopi Tribe-A D3382 24 Gulf Oil Corp. #1 Navajo-CZ SB, NW, Sec. 21, T.29n., R.24E II II It II II II D2357 25 Tenneco Oil Co. #1 Navajo 8351 NW, SB, SW, Sec. 24, T.38N., R.19E II II II 299R 26 Amerada Petr. Corp. #1 Navajo SE, SW, NE, Sec. 3, T.31N., R.23E Black Mountain It II II 489R • 27 Sinclair Oil & Gas Co. #1 C, N)&, NE, Sec. 28, T.37N., R.14E Navajo Tribal 687R 28 The Texas Co.; Sinclair; Skelly C, S/2, NE, Sec. 34, T.42N., II II II #1 Navajo-A R.18E II II D2524 29 Texaco Inc. #1 Navajo-AM NE, NW, Sec. 36, T.39N., R.21E II D2382 30 Amerada Petr. Co. #1 Navajo SE, SE, Sec. 7, T.39N., R.24E It II II Tract-91 II II It D2975 31 American Mining Co. #1 Navajo C, SB, NY/, Sec. 28, T.38N., R.24E VI II II D3534 32 Cactus Drilling #1 Rock Point NW, SW, Sec. 1, T.39N., R.26E II II II D2123 33 Gulf Oil Corp. #1 Navajo-Garnet C, NE, NE, Sec. 16, T.41N., R.24E Ridge VI II II D3516 34 Consolidated Oil & Gas #1-1 NE, SW, SW, Sec. 1, T.41N., R.28E East Boundary Butte II II II D2576 35 Pure Oil #1 Pure-Sun-Tidewater- NE, SE, Sec. 32, T.38N . , R.30E Navajo Tract 103 II II II D3538 36 Odessa Natural Gas Co. #1 SE, SE, Sec. 33, T.37N., R.29E Aircodessa-Cove II II II D2773 37 Anadarko Production #1-135 NE, NW, NY/, Sec. 3, T.35N, R.30E Navajo Elec. Cont. Subsurface Drill Holes Log # Pt. # Name Location Reference

D3330 38 Union Oil Co. of Calif. #1 NE, NW, NW, Sec. 20, T.6N., R.6W AM. Strat./A.B.M. Navajo Tract 166 ti II II D3110 39 Curtis Je Little #1 Bear Springs SE, SE, Sec. 26, T.6N., R.oW II II D3379 40 Gulf Oil Co. #1 Navajo-Texaco C, SW, SW, Sec. 11, T.4N., R.7W 11 D3588 41 Union Texas Petr. #1-17 Navajo NW, SE, SE, Sec. 17, T.7N., R.10W 11 II II II II D3527 42 Curtis Little-Aircoil #1 West SE, NW, NW, Sec. 9, T.40N., R.22E 11 Dry Mesa 11 II II D3525 43 Cactus Drilling Co. #1 Navajo NW, NW, Sec. 14, T.36N., R.22E 85-15 D3528 44 Cactus Drilling Co. #1 Navajo SW, NE, Sec. 23, T.36N., R.24E 11 II II 88-18 11 II II DI787 45 Pan Am. Petr. Co. #1 Navajo NW, SW, Sec. 6, T.40N., R.28E Tribe-F 11 II II D3577 46 Buttes Gas & Oil #1-31 Navajo NE, NE, Sec. 31, T.35N., R.27E 11 II II D1356 47 British American #1 Navajo •C* NE, SW, SW, Sec. 5, T.40N., R.30E 11 II II D3331 48 Eastern Petr. Co. #1 Moqui Bardo NW, SW, Sec. 10, T.14N., R.11E 11 II II D2567 49 Vaughey, Vaughy & Blackburn SB, SB, Sec. 8, T.37N., R.27E #8-1 Navajo 11 II II D4341 50 Webb Resources Inc. #6-1 Webb NE, SE, Sec. 6, T.14N., R.22E Resources 11 II II D4342 51 Webb Resources Inc. #1-36 State NE, SE, Sec. 36, T.19N., R.17E 11 II II D4336 32 Webb Resources Inc. #30-1 Webb NW, SB, Sec. 30, .T.15N., R.25E Resources 11 II II D4337 53 Webb Resources Inc. #1-29 Rock­ SW, NW, SB, Sec. 29, T.14N., ing Chair Ranch R.20E F69 54 Argo Oil Corp. #1 State NE, NE. Sec. 22, T.15N., R.29E Geol. Sample Log Co. D1791 55 Roy Owen & Co. #12-1 Diablo NE, NE, NW, Sec. 12, T.20N., AM. Strat./A.B.M. Amarillo R.11E 1363 56 Eastern Petr. Co. State Coyote C, SW, SW, Sec. 27, T.10N., R.30E Schlumberger Microlog Canyon #1 Elec. Cent. ______Subsurface Drill Holes______Log # Pt. # Name Location Reference

None 57 Franco Arizona Oil Co. #1 SE, NE, Sec. 14, T.14N., R.26E Sample Log, Summary Government Description None 58 Hogback Oil Co. #1 NV, NW, Sec. 24, T.23N., R.30E ii it ii None 59 Great Basin Oil Co. Taylor- NW, NW, Sec. 21, T.17N., R.20E n ii ii Fuller #1 APPENDIX B

NAME AND LOCATION OF SURFACE EXPOSURES

4? No. Name Location Reference

1 Fossil Creek Canyon NE 1/9 Turret Peak Quadrangle Brew 19

2. East Verde River S 1/9 Pine Quadrangle 11 II

3. Tonto Creek NW 1/4, Sec. 16, T. 11 N., R. 12 E If II

4. Kohl Ranch Section Sec. 21, T. 11 N., R. 12 E It If

5. Big Springs Canyon W 1/9 Chediski Peak Quadrangle II II

6. Red Rock House C 1/9 Chediski Peak Quadrangle II II

II It 7. NE 1/4, NW 1/4, Sec. 7, T. 6 N., R. 20 E

8. Black River Sec. 1 and 12, T. 4 N., R. 20 E II II APPENDIX C

MAP CONSTRUCTION DATA

49 (Interval II) Molas Formation 0 O So t>0 •H •H 0« S3 @ (0 (0 p m P .5 ti m 10 to to 4 4aJ 0 # -p •P a m a p _ -p -p ti a ti ti H 5 rH ti © a 0 co S m s 0 S V 0 0 n O & $0) +> TJ 0 0 0 0 1 0 1 O •H 0 Am.Strat O «H to U • u ti -H g S-« O Qi Log # 'c ti a gC: • 0 jz 0 O i 0 m a a 3 d S3 S3 V) In to A tO Eh to P< % EH % p< hi % % D1934 1 D2777 2 D2786 3 Miss. 59 0 53 90 6 10 D D1148 4 D1515 5 D1199 6 D3516 7 D1168 8 D1182 9 D1164 10 D3107 11 D3108 12 96R 13 D1163 14 D3388 15 Miss. 34 0 0 22 65 12 35 L D1730 16 D2530 17 Miss. 80 0 0 39 49 41 51 M D2543 18 Miss. 82 0 0 72 89 10 11 D D2573 19 D2550 20 D3166 21 D2592 22 D2597 23 Miss. 71 0 0 71 100 0 0 D D3382 24 D2357 25 Miss. 75 0 0 65 87 10 13 D ' 299R 26 Miss. 73 10 14 23 32 40 54 M 489R 27 % (Interval II) Molas Formation 1

5 o 0,

H O percent percent Non-clastic Facies Sandstone s.s. Sh. Thickness Sh. Thickness Total percent Paleoenvir Non-clastic Map Data Underlying Unit Thickness Thickness h Map Data

28 Miss. 104 0 0 76 73 28 27 L 29 Miss. 68 0 0 46 68 22 32 L 30 Miss. 105 10 10 95 90 0 0 D 31 Nothing 25 0 0 25 100 0 0 D 32 Miss. 168 0 0 123 73 45 27 L 33 Miss. 160 0 0 130 81 30 19 D 34 Miss. 130 0 0 115 88 15 12 D 35 Miss. 98 23 23 60 6l 15 16 L 36 Miss. 83 25 30 58 70 0 0 K 37 Miss. 38 0 0 . 38 100 0 0 D 38 39 Miss. 19 0 0 19 100 0 0 D 40 Miss. 85 15 18 30 35 40 47 L 41 Miss. 75 25 33 50 67 0 0 K 42 Miss. 81 0 0 71 88 10 12 D 43 Miss. 76 0 0 64 84 12 16 D 44 Miss. 148 40 27 97 66 11 7 K 45 Miss. 93 10 11 83 89 0 0 D 46 Miss. 36 0 0 26 72 10 28 L 47 Miss. 123 0 0 85 6l 38 31 L 48 49 Miss.Miss 100 25 25 65 65 10 10 K 50 51 52 53 ti (Interval II) Molas Formation •H # O ho Pk (0 G) CO CO -p m -P 41 •S CO C (0 CO CO CO cd (d 0 0) 4-> cd 0 ed -P -p ■3 -p ti ti ti 1—1 P rH ti co cd O CO ^ 0J A: Q o 1 Am.Strat i* L 3 I T3 O • O 0 O 1 0 1 O •H m -H •H CO u • *rl • b ti -H e p O A Log # § o' 3 JC •

F69 54* D1791 55 96 5 6 " 1363 5 7 " 58s* 5 9 " 60

(Interval I) Hermosa and Naco Formations

D1934 1 550 20 3.6 475 86.4 55 10.0 D shale D2777 2 Miss. 1002 0 0 792 79.0 210 21 L shale D2786 3 Molas 804 0 0 520 64.7 284 35 L LS D1148 4 Dev. 999 5 0.5 589 59 405 40 L LS D1515 5 Dev. 980 7 0.7 633 65 270 34 L claystone D1199 6 P.Cam. 737 95 13 412 56 230 31 L shale D3316 7 Dev. 511 13 2.35 298 58.3 200 39 L shale D1168 8 Dev. 560 20 4 485 86.6 55 9.4 D silt D1182 9 Miss. 877 165 18.8 417 48 295 34 L silt D1164 10 Miss. 966 40 4 736 76 190 20 L silt D3107 11 Dev. 910 50 5.5 512 56 348 40 L sh. silt D3108 12 P.Cam. 350 15 4 150 43 185 53 M shale 96R 13 P.Cam. 434 13 3 4ll 95 10 2 D shale DH 63 14 P.Cam. 600 120 20 365 61 115 19 L LS D3388 15 Molas 515 40 8 311 60 164 32 L sh. silt D1730 16 Molas 135 0 0 91 67 44 33 L shale D2530 17 . Molas 1585 70 4 655 41 860 54 M shale (Interval I) Hermosa and Naco Formations

Am. Strat Thickness percent percent Sh. percent Non-clastic Paleoenvir. Map Data Sandstone Thickness s.s. Sh. Thickness Facies Map Data Unit Non-clastic

Log # Total Thickness Underlying ControlPoir No.

D2543 18 Molas 1400 24 2 691 49 685 49 MLS D2573 19 Miss. 264 14 5 175 66 75 28 L Dol D2550 20 Miss. 319 10 3 209 66 100 31 L Silt D3166 21 Miss. 350 40 11 235 67 75 19 L Silt D2592 22 Miss. 262 0 0 170 65 92 35 L Shale D2597 23 Molas 271 5 2 220 79 54 19 L Silt D3382 24 Dev. 128 25 20 86 67 17 13 L Silt D2357 25 Molas 875 275 31 385 44 215 25 M SS 299R 26 Molas 202 112 55 15 7 75 38 I SS 489R 27 Miss. 298 143 48 4o 13 115 39 I SS 687R 28 Molas 891 185 21 271 30 435 49 K SS D2524 29 Molas 898 74 8 312 35 512 57 M LS D2382 30 Molas 960 50 5 545 56 365 39 L Shale D2975 31 Molas 1071 10 1 537 50 494 57 L Shale 03534 32 Molas 858 10 1.1 412 49 436 50 M LS 02123 33 Molas 786 11 1.3 245 31 530 67 M Silt 03516 34 Molas 1680 0 0 714 42.5 966 58 M LS 02576 35 Molas 1025 0 0 460 45 565 55 M Shale 03538 36 Molas 639 54 8 211 33 374 59 M Dol 02773 37 Miss. 663 55 8 393 59 215 33 M Silt 03330 38 Molas 243 56 23 80 33 107 44 L Shale 03110 39 Molas 208 40 19 81 39 87 42 K LS 03379 40 Molas 369 0 0 180 49 189 51 M Dol 03588 41 Molas 593 145 24 310 52 138 24 K Silt 03527 42 Molas 1358 0 0 617 45 741 55 M LS 03525 43 Molas 650 4o 6 343 53 267 4l L Silt 43 (Interval I) Hermosa and Naco Formations

ti ------

n- o' 3 o' '} Control Poi No. Thickness percent Underlying Unit Total Sandstone S.S. Sh. percent Thickness percent Thickness Thickness Sh. Non-clastic Non-clastic Facies Map Data Paleoenvir. Map Data 03528 44 Molas 621 0 0 160 26 461 74 M LS DI787 45 Molas 1619 85 6 621 38 913 56 M Silt D3577 46 Molas 364 89 25 175 48 100 27 MLS D1356 47 Molas 1523 45 3 513 34 965 63 M LS D3331 48 Molas 438 10 3 345 77 83 20 L Silt D2567 49 Molas 1090 20 2 557 51 513 47 L Shale D4341 50 Dev. 415 0 0 330 80 85 20 D Silt D4342 51 Miss. 291 16 6 262 90 13 4 D Shale D4336 52 P.Cam. 468 35 8 328 70 105 22 L Shale 04337 53 Dev. 527 0 0 332 63 195 37 L Shale F69 54* 01791 55 Miss. 445 65 15 250 56 130 29 L LS 1363 56** None 5 7 " None 58** None 59 Dev. 1002 0 0 740 74 262 26 L Shale 60 Surface Exposures (Brew 1965) 1 Miss. 409 67 16 290 71 52 12 L Silt 2 423 28 7 322 76 74 17 L Silt 3 53 5 9 40 69 12 22 L Shale 4 223 0 0 191 85 33 15 D Shale 5 1075 68 6 752 70 255 24 L LS 6 846 47 5 641 76 158 19 L LS 7 761 2 0 525 69 235 31 L LS 82 706 11 2 360 51 336 47 LLS % Total Pennsylvanian System 1 1

d 1 o i

p cl- 4) E! Thickness percent Sandstone Sh. percent Non-clastic Thickness percent Sh. Non-clastic Facies MapData Total Thickness Thickness S.S. ControlPoinl No. Underlying Unit

D1934 1 550 20 4 475 86 55 10 D D2777 2 Mias. 1002 0 0 792 79 210 21 L D2786 3 Miss. 863 0 0 573 66 290 34 L D1148 4 Dev. 999 5 0.5 589 59 405 41 L D1515 5 Dev. 980 7 0.7 633 65 - 270 34 L D1199 6 P.Cam. 737 95 13 412 56 230 31 L 03316 7 Dev. 511 13 2 298 58 200 39 L D1168 8 Dev. 560 20 4 485 87 55 9 D DII82 9 Miss. 877 165 19 417 48 295 34 L D1164 10 Miss. 966 40 4 736 76 190 20 L D3107 11 Dev. 910 50 6 512 56 348 40 L D3108 12 P.Cam. 350 15 4 150 43 185 53 M 96R 13 P.Cam. 434 13 3 4ll 95 10 2 D DII63 14 P.Cam. 600 120 20 365 61 115 19 L D3388 15 Miss. 549 40 7 333 61 176 32 L D1730 16 Miss. 135 0 0 91 67 44 33 L D2530 17 Miss. 1665 70 4 694 42 901 54 M D2543 18 Miss. 1482 24 2 763 52 695 47 L D2573 19 Miss. 264 14 5 175 66 75 28 L D2550 20 Miss. 319 10 3 209 66 100 31 L D3166 21 Miss. 350 40 11 235 67 75 19 L D2592 22 Miss. 262 0 0 170 65 92 35 L D2597 23 Dev. 350 5 1 291 83 54 15 D D3382 24 Miss. 128 25 20 86 67 17 13 L D2357 25 Miss. 950 275 29 450 47 225 24 K 299R 26 Miss. 275 122 44 38 14 115 42 K Total Pennsylvanian System 3 o cu

Map Data percent Thickness Facies MapData Paleonvir Sh. percent Non-clastic Sh. Thickness Non-clastic percent Sandstone Thickness s.s. Thickness Total li Underlying Unit 27 Miss. 298 143 48 40 13 115 39 K 28 Miss. 995 185 19 347 35 463 47 M 29 Miss. 966 74 8 358 37 534 55 M 30 Miss. 1065 60 6 640 60 365 34 L 31 Miss. 1096 10 1 562 51 494 45 L 32 Miss. 1038 10 1 547 53 481 46 L 33 Miss. 946 11 1 375 40 560 59 M 34 Miss. 1810 0 0 829 46 981 54 M 35 Miss. 1123 23 2 520 46 580 52 M 36 Miss. 722 79 11 269 37 374 52 M 37 Miss. 701 55 8 431 61 215 31 L 38 Miss. 243 56 23 80 33 107 44 K 39 Miss. 227 4o 18 100 44 87 38 L 40 Miss. 454 15 3 210 46 229 51 M 41 Miss. 668 170 25 360 54 138 21 K 42 Miss. 1439 0 0 688 48 841 52 M 43 Miss. 726 40 6 407 56 279 38 L 44 Miss. 769 40 5 257 34 472 61 M 45 Miss. 1712 95 6 704 41 913 53 M 46 Miss. 400 89 22 201 50 n o 28 L 47 Miss. 1646 45 3 598 36 1003 61 M 48 Miss. 438 10 3 345 77 83 20 L 49 Miss. 1190 45 4 622 52 523 44 L 50 Dev. 415 0 0 330 80 85 20 D 51 Miss. 291 16 6 262 90 13 4 D 52 P.Cam. 468 35 8 328 70 105 22 L & $ (D § 1 4J E.

•H O PU

■5 Am.Strat -p e Log # o o percent MapData Sh. Sh. ® Sandstone percent ^ Sh. Sh. Thickness 5 § Non-clastic Thickness Non-clastic Facies Total Thickness Thickness S.S. & Map Data Paleonvir. Underlying Percent "g Unit

D4337 53 Dev. 527 0 0 332 63 195 37 L F69 54* D1791 55 Miss. 445 65 15 250 56 130 29 L 1363 56" Miss. None 57** Miss. None 58** Miss. None 59 Dev. 1002 0 0 740 74 262 26 L 60*** Surface Exposures (Brew 1965) 1 Miss. 409 67 16 290 71 52 12 L 2 Miss. 423 28 7 322 76 74 17 L 3 Miss. 53 5 9 40 69 12 22 L 4 Miss. 223 0 0 191 85 33 15 D 5 Miss. 1075 68 6 752 70 255 24 L 6 Miss. 846 47 5 641 76 158 19 L 7 Miss. 761 2 0 525 69 235 31 L 8# Miss. 706 11 2 360 51 336 47 L

•Supai overlying Pre-Cambrian quartzite. **Supai overlying Pre-Cambrian granite. ***Supai overlying Pre-Cambrian. #Brew's #10 LIST OF REFERENCES

American Commission on Stratigraphic Nomenclature. 1961. Code of Stratigraphic Nomenclature: American Assoc. Petrol. Geol. Inc., Tulsa.

Anderson, C. A. and S. C. Creasy. 1958. Geology and ore deposits of the Jerome area, Yavapai County, Arizona. U.S.G.S. prof, paper 308, 185 pp.

Armstrong, A. K. 1962. Stratigraphy and paleontology of the Mississip- pian System in southwestern New Mexico and adjacent southeastern Arizona. New Mexico Bur. of Mines and Mineral Res. Mem. 8, 99 pp.

Baker, A. A. and J. B. Reeside, Jr. 1929. Correlation of the Permian of southern Utah, northern Arizona, northwestern New Mexico and southwestern Colorado. Amer. Assoc. Petrol. Geol., Vol. 17, pp. 963-980.

Bass, N. W. 1944. Correlation of basal Permian and older rocks, southwest Colorado, northwest New Mexico, northeast Arizona and southeast Utah. U.S.G.S. Prelim. Chart 7, Oil and Gas Inv. Ser.

Bradish, B. B. and N. K. Mills. 1950. Pennsylvanian Rocks of the San Juan Basin. Guide Book of the San Juan Basin, New Mexico and Colorado, pp. 58-61.

Brew, D. C. 1963. Stratigraphy of the Naco Formation (Pennsylvanian) in central Arizona. Doctoral Dissertation, Cornell University. 201 pp.

Burbank, W. S. 1930. Revision of Geologic Structure and Stratigraphy in the Ouray District of Colorado. Proc. Colorado Sco. Soc. Vol. 12, pp. 151-232.

Burton, G. C . , Jr. 1955• Sedimentation and stratigraphy of the Dakota Formation in the San Juan Basin. In Geology of Parts of Paradox, Black Mesa and San Juan Basins: Four Corners Geol. Soc. Field Conference, pp. 78-88.

Cross, W. W . , E. Howe, W. H. Emmons and J. P. Iddings. 1905. Needle Mountains, Colorado. U.S.G.S. Geol. Atlas Folio 131. 138 pp.

58 59

Cross, C. W., E. Howe and J. D. Irving. 1907• Ouray, Colorado. U.S. G.S. Geol. Atlas Folio 153. 20 pp.

Cross, C. W . , E. Howe and F. L. Ransorae. 1904. Silverton, Colorado. U.S.G.S. Geol. Atlas Folio 120. j4 pp.

Cross, C. W. and E. S. Larsen. 1935• A brief review of the geology of the San Juan region of southwestern Colorado. U.S.G.S. Bull. 843. 138 pp.

Cross, C. W., and A. C. Spencer. 1900. Geology of Rico Mountains, Colorado. U.S.G.S. 21st Ann. Hep., Pt. 2, pp. 7-165•

DiGiambattista, C. D. 1952. Regional stratigraphy of the Four Corners area. Geological Symposium of the Four Corners Region. Four Corners Geol. Soc. pp. 5-9•

Fezner, R. W. i960. Pennsylvanian paleotectonics of the Colorado Plateau. Amer. Assoc. Petr. Geol. Vol. 44, pp. 1371-1413.

Girty, G. H. 1903. The carboniferous formations and fauna of Colorado. U.S.G.S. paper 16. 546 pp.

Gregory, H. E. 1917. Geology of the Navajo Country. U.S.G.S. paper 164, l6l pp.

Havener, K. C. 1958. Pennsylvanian framework of sedimentation in Arizona. Master's thesis, The University of Arizona, Tucson.

Havener, K. C. and W. D. Pye. 1958. Pennsylvanian paleogeography of Arizona. New Mexico Geol. Soc., 9th Field Conference Guide Book, pp. 78-81.

Hazzard, J. C. 1933• Notes on the Cambrian rocks of the eastern Mohave desert, California. Univ. of Calif, pub., Bull. Geol. Sci., Vol. 23, pp. 59-60, 67-70.

Herman, G. and S. L. Sharps. 1956. Pennsylvanian and Permian of the Paradox salt embayment. Intermountain Assoc. Petr. Geol. Guidebook, Seventh Field Conf. pp. 77-84.

Heylmun, E. G. 1958. Paleozoic stratigraphy and oil possibilities of Kaiparowits Region, Utah. Bull. Amer. Assoc. Geol., Vol. 42, No. 8, pp. 1781-1811.

Horvath, E. A. i960. Preliminary fusulinid zonation of the Naco Formation in east-central Arizona. Unpublished Master's thesis, University of Utah. 80 pp. 60

Huddle, J. W. and E. Dobrovolny. 19^5• Late Paleozoic stratigraphy and oil and gas possibilities of central and northeastern Arizona. U.S.G.S. Oil and Gas Inv. Prelim, Chart 10.

Huddle, J. W. and E. Dobrovolny. 1950. Devonian and Mississippian rocks of central Arizona. U.S.G.S. paper 233-D, pp. 67-112.

Jackson, R. L. 1951• The stratigraphy of the Supai Formation along the Mogollon Rim, central Arizona. Unpublished Master's thesis, The University of Arizona, Tucson. 82 pp.

Jackson, R. L. 1952. Pennsylvanian-Permian facies of the Supai Formation in central Arizona. Arizona Geol. Soc. Guide Book for Field Excursions in southern Arizona, pp. 143-146.

Kelley, V. C. 1957. Tectonics of the San Juan Basin and surrounding areas. Four Corners Geol. Soc. Guidebook, 2nd Field Conf. pp. 44-53.

Krumbein, W. C. 1951. Occurrence and lithologic association of evaporites in the United States. Jour, of Sed. Petrology, Vol. 21, pp. 63-81.

Lessentine, R. H. 1969. Kaiparowits and Black Mesa Basins; Strati­ graphic synthesis. In Four Corners Geol. Soc. Guidebook 5 — Geology and Natural History of the Grand Canyon Region, pp. 91-113.

Mallory, W. W. 1976. Middle and southern Rocky Mountains, Northern Colorado Plateau and Eastern Great Basin region. U.S.G.S. paper 853, pp. 265-299.

McKee, E. D. 1945. Oak Creek Canyon (Arizona). Plateau, Vol. 18, No. 2, pp. 25-32.

McKee, E. D. 1951. Sedimentary basins of Arizona and adjoining areas. Geol. Soc. Araer. Bull., Vol. 62, pp. 481-506.

McKee, E. D. 1975. The Supai Group — Subdivision and Nomenclature. U.S.G.S. Bull. 1395-J.

McKee, E. D. 1976. Introduction and regional analysis of the Pennsyl­ vanian System in Arizona. U.S.G.S. paper 853, pp. 295-310.

McKee, E. D. and R. C. Gutschick. 1969. History of the Redwall lime­ stone of northern Arizona. Geol. Soc. Am. Mem. 114. 726 pp.

Merrill, W. M. and R. M. Winar. 1958. Molas and associated forma­ tions in San Juan Basin-Needles Mountain area, southwestern Colorado. A.A.P.G. Bull., Vol. 42, No. 9, pp. 2107-2132. 61

Museum of Northern Arizona. 1976. Geologic Map of the Grand Canyon National Park, Arizona. Williams and Heintz Map Corp., Washington, D. C.

Passmore, V. L. 1969• Subsurface stratigraphy of the Supai Formation in east-central Arizona. Unpublished Master's thesis, The University of Arizona, Tucson. 48 pp.

Peirce, W. H. 1976. Elements of Paleozoic tectonics in Arizona. Arizona Geol. Soc. Digest, Vol. 10, pp. 37-56.

Peirce, W. H. 1977* Personal communication, The Arizona Bureau of Geology and Mineral Technology, Tucson.

Peirce, W. H., N. Jones and R. Rogers. 1977• A survey of uranium favorability of Paleozoic rocks in the Mogollon Rim and slope region — east-central Arizona. Arizona Bureau of Geol. and Min. Tech., Circular 19.

Peirce, W. H., S. B. Keith and J. C. Wilt. 1970. Coal, oil, natural gas, helium and uranium in Arizona. Arizona Bureau of Mines Bull. 182, University of Arizona, Tucson. 195 pp.

Peirce, W. H. and J. R. Scurlock. 1972. Arizona well information. Arizona Bureau of Mines Bull. 185, University of Arizona, Tucson. 195 PP*

Peterson, J. A. 1969. Petroleum Geology of the Four Corners area. World Petr. Congr., 5th New York Proc. Sec. 1, pp. 499-523.

Ransome, F. L. 1904. Geology and ore deposits of the Bisbee quad­ rangle , Arizona. U.S.G.S. paper 21, 168 pp.

Ross, C. A. 1975* Pennsylvanian and Early Permian depositional his­ tory. Southeastern Arizona, Amer. Assoc. Petr. Geol. Bull., Vol. 57, No. 5i pp. 887-912.

Ross, C. A. and F. F. Sabins, Jr. 1965. Early and Middle Pennsyl­ vanian fusulinids from southeast Arizona. Jour, of Paleon­ tology, Vol. 36, pp. 173-209.

Roth, R. I. 1934. Type section of the Hermosa Formation, Colorado. Bull. Amer. Assoc. Petr. Geol., Vol. 18, pp. 944-94?.

Sabins, F. F. 1957. Stratigraphic relations in Chiricahua and Dos Cabezos Mountains, Arizona. Amer. Assoc. Petr. Geol. Bull., Vol. 4l, pp. 466-510. 62

Sabins, F. F . , Jr. and C. A. Ross. 1963. Late Pennsylvanian and early Permian fusulinids from southeast Arizona. Jour, of Paleontology, Vol. 37, pp. 323-365.

Spencer, A. C. 1900. Naming of the Hermosa Formation. In Cross, C. W. and A. C. Spencer, Geology of Rico Mountains, Colorado. U.S.G.S. 21st Ann. Rep., Pt. 2, pp. 7-165*

Stoyonou, A. A. 1936. Correlation of Arizona Paleozoic Formations. Geol. Soc. Amer. Bull., Vol. 47, pp. 459-540.

Thompson, M. L. 1942. Pennsylvanian System in New Mexico. New Mexico Bur. of Mines and Min. Resources, Bull. 17. 92 pp.

Thompson, M. L. and J. C. Hazzard. 1946. Permian fusulinids of California. Geol. Soc. Amer. Bull., Vol. 17, pp. 38-40.

Van Houton, F. B. 1961. Climatic significance of red beds. In Nairn, A. E. M., ed., Descriptive paleo-climatology. Inter­ science Pub. Ltd., London, pp. 89-139*

Wengerd, S. A. and A. Matheny. 1958. Pennsylvanian system of the Four Corners area. Amer. Assoc, of Petr. Geol. Bull., Vol. 42, pp. 2048-2146.

Wengerd, S. A. and J. W. Strickland. 1954. Pennsylvanian stratigraphy of Paradox Salt Basin, Four Corners region, Colorado and Utah. Amer. Assoc. Petr. Geol. Bull., Vol. 38, No. 10, pp. 2157-2199*

Wilson, E. D. 1951* A resume of Arizona Geology. Arizona Bureau of Mines Bull. 171* l40 pp.

Winters, S. S. 1951* Permian stratigraphy in eastern Arizona. Plateau, Vol. 24, pp. 10-16.

Winters, S. S. 1963. Supai Formation (Permian) of eastern Arizona. Geol. Soc. Amer. Mem. 89. 99 PP* , LATE ATOKA - POST VIRGIL SERIES NORTHEAST 2 miles 62 "5 co J o 300 o d 200 0 - 400 0 -i 500 - 0 0 1 FEET 0 miles 107 13 i oiotl Scale Horizontal 26 i 39 i 52 i ILES M I - iue I Cos eto B- 1 -B B Section Cross II. Figure 65

HERMOSA 3 miles 73 NACO 4 miles 34 al dolomiticMarl al limy Marl Dolomite rz / T /T / // r / T | T 1T T _z / r 1| T | T 11 T 1 T r / J/ / i * i * 7 / / r r / T / . y / t 34 miles 34 J , (calcarenite -calcilutite) (calcarenite (argillaceous) RS ETO B-B - B SECTION CROSS Sandstone Limestone Limestone Mudstone Gypsum y / / / / / / / / / r / / / / / / / / / / — —Jj — — — — I I— — — I — II I — — - I I - — r i r i EXPLANATION

wt claeu nodules) calcareous (with 7 miles 37 Mudstone/siltstone ( solid = reddish brown) brown) = solid reddish ( aty covered Partly Limestone (calcirudite) Siltstone |cz> P A A A hr Chert/mudstone Chert p I p I A A A C I p 1 (silty/arenaceous) Limestone residuum siltstone Covered ----— -- Shale Shaly — — — r i M i \ ^ T 5 miles 55 AT CENTRAL EAST P tvl ? Geosciences Geosciences Bruce ijingho, 1977 Thesis

PENNSYLVANIAN SYSTEM FE MKE (1975) McKEE AFTER

LATE ATOKA - EARLY DES MOINES DES MOINES MISSOURI VIRGIL SERIES < CO 5 o _J s a: 5 6 o UJ o: 5 o (Z) < o LU $ cr lu < UJ u X o: o (/) cn LU h- 2 O) 5 5 Q LU UJ cr cr S u i 5 m £L UJ cr LU Z) CL UJ 0= cc s o o c < NORTHEAST A "o D C o> 200 o S 300 300 S 500 13 i oiotl Scale Horizontal 26 i 39 ! 52 i 9 miles 89 ILES M iue 0 Cos eto A- 1 -A A Cross Section 10.Figure 6 0 ie 5 6 1 ie 3 2 miles 52 3 miles 31 6 57 miles 70 16 al dolomiticMarl al limy Marl Dolomite l f f f r ~ r T T / r/t / T IT I T T / T / T/ I1 T T 1I T | T / / I ' I / / / / / / 10.5m. (calcarenite-calcilutite) SCIN A-A' SECTION S S O R C (argillaceous) Limestone Sandstone Limestone Mudstone Gypsum */7///////i / / / / / / / / / / — 1— — 1 — 1— — 1 — 1 1— — I 1 1— — 1 T 1 l 1 EXPLANATION

wt claeu nodules) calcareous (with Mudstone/siltstone (solid = reddish brown) brown) = (solid reddish aty coveredPartly Limestone (colcirudite) Siltstone — ^ — — I Io o c hr Chert/mudstone Chert I<-> T Q I Q I lQ I<= (silty/arenaceous) Limestone residuum siltstone Covered Shale Shaly r i r i AT CENTRAL EAST -z-Syi : T eC ^ o t ~T~.T.\r. toy* L<-> ira-ri k-- L I S L-_r*. riTir £->>Z t 7 A T-"- r» — A' l Ijingho, Bruce Bruce Ijingho, Thesis Geosciences 1977 FE BE D . (1965) C. D BREW AFTER UJ o a i u cr 2 2 o < h- < UJ < GO 2 < o o u_

DES MOINES MISSOURI VIRGIL POST VIRGIL SERIES EXPLANATION OF MAP SYMBOLS

• Subsurface well data O Surface exposure X . Contour of known thickness (Contour interval = 2 0 feet)

MILES

Figure 6. Isopach Map of the Molas Formation

9 6 0 *

2 9 8 •

2 0 8 .

* 128

• 2 6 4

• 4 3 4

4 6 8 .

0 8 4 6 EXPLANATION OF MAP SYMBOLS EXPLANATION OF MAP SYMBOLS • Subsurface well data • Subsurface well data O Surface exposure O Surface exposure X x Contour of known thickness Contour of known thickness X Contour of inferred thickness x \ Contour of inferred thickness (Contour interval = 2 0 0 feet) (Contour interval = 200 feet)

MILES Ijingho, Bruce Thesis

Geosciences

1977 Figure 9. Isopach Map of the Hermosa and Naco Formations Figure 16. Isopach Map of the Entire Pennsylvanian System Note: Figures 6,9,16. m i VD/ Lithofocies Symbols Chemical components predominant (ER 1/4) (ER I) (ER 4) _|s=J_ _UL = _1. 0 I r 100 O-i u V W X

80(CRl)-

Q R S T w C s$>*h s$ *h ss> sh *#>#h c (SSR I)■ 0) c o I o. E E o M N 0 P 8 o o u sh>ss sh >ss #h»s# $h>$# E 50(CR I) -5 0 - O) <5 u "O 1 J K L Q> & o 0 ls>0 l$»0 ls>0 ls>o c (E R I) 0) O)c w 0) OL 1 E F G H

0>ls 0>IS 0 >ls 0 >ls l20 (CR4)-

EXPLANATION OF MAP SYMBOLS A B C D

100' Subsurface well data ll-.l sh I sh I sh 4 Surface exposure Detrital components predominant Lithofocies boundaries a Anhydrite and gypsum sh Mudstone,claystone, siltstone. is Limestone and dolomite ss Sandstone.

Lithofocies Legend for Figures 7, 14, and 17

MILES

Figure 7 Lithofocies Map of the Molas Formation

UTAH COLORADO

NEW MEXICO

EXPLANATION OF MAP SYMBOLS

Subsurface well data Surface exposure Lithofocies boundaries

Ijingho, Bruce

MILES Thesis Geosciences

1977

Note Figures 7, 14,17 Figure 14. Lithofocies Map of the Hermosa and Naco Formations Figure 17 Lithofocies Map of the Pennsylvanian System £ ° t ^ (

m ?

4 O h POSITIVE

e x p l a n ^ I I ^ . subsurtoce well data

° B o s m o xi;> subsidence Sources of sediments Subsurfoce * * " da'°

° —

^e-oe"— eW,,P”"S D normol circulotion sil1- Marine, near shore, paleotectonic « o< « . 0 normal circulation Figure 18 Shale - M °rine' normal circulation _ shallow marine. Um„..«-SMl,0em".... Th,o«h to He"r,0M e ^ n q / A H 7 COLORADO

NEW MEXICO

Phoenix

Tucson

Douglas

LEGEND FEET

HERMOSA FORMATION

< 5 0 0

NACO FORMATION

MILES MOLAS FORMATION 6.5 13 MAP SCALE

Figure 13. Fence Diagram Ijirigho, Bruce Thesis

Geosciences 1977 & ' 7 9 /

{ ‘* 7 1

{ / D c f UTAH COLORADO

NEW MEXICO

Flagstaff a

Holbrook)/

Phoenix

APACHE

Tucson I_____

Douglas

COCONINO NAVAJO

Winslow A

OGOLLON RIM

EXPLANATION OF MAP SYMBOLS

Subsurface well data Surface exposure Contour of known thickness, line of cross section Contour of inferred thickness, county boundary line

MILES yj---- Ijirigho, Bruce Thesis

Geosciences Figure I. Index Map 1977 m i PENNSYLVANIAN SYSTEM "5 CO JD o 0 - - 300 o 0 - 00 4 -| 0 0 5 200 - 0 0 1 0 - FEET FEET 13 i oiotl Scale Horizontal 6 9 52 39 26 i r i i MISS. 25 miles 32.5 MIES S ILE M I - 65 i* l-l - [ MISS. a | 0|al 6 miles 76 iue 2 CosScin C1 -C C CrossSection 12. Figure ////////// MISS. 3 ie 59 miles 23 MISS. al dolomiticMarl 6 miles 36 al limy Marl Dolomite / r / / T i 7^“ r T i t / J / / / J T / T / T 1 1 1 T 1 T 7~ / / 1 t / / : T T / / T / / t , / 1 / t t T t t )

(calcarenite-calcilutite) ETO C-C' SECTION S S O R C (argillaceous) Limestone Sandstone Limestone Mudstone Gypsum i / / / / / / / / / r / / / / / / / / / / 1—- 1 —- I TI — — 1 I I— — T I r I 1 r i EXPLANATION

wt claeu nodules) calcareous (with 57 miles 57 Mudstone/siltstone (solid= reddish brown) brown) reddish (solid= aty coveredPartly Limestone (calcirudite) Siltstone CD I CD CD A ▲ ▲ hr Chert/mudstone Chert I CD A ▲ A CD CD | O CD CD I C (silty/arenaceous) Limestone residuum siltstone Covered m — Shale Shaly T _ T r i i i 9mls 58 miles 29 Ijingho, Bruce Bruce Ijingho, Geosciences Geosciences 1977 Thesis Thesis B q n c'/ / 9 7 7 W 7