Origin and stratigraphic relations of cambrian quartzites in southeast Arizona

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Authors Bryant, Jeffrey Wayne, 1949-

Publisher The University of Arizona.

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Link to Item http://hdl.handle.net/10150/555103 ORIGIN AND STRATIGRAPHIC

RELATIONS OF CAMBRIAN QUARTZITES

IN SOUTHEAST ARIZONA

by

Jeffrey Wayne Bryant

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 8 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.

SIGNED: UJ

APPROVAL BY THESIS DIRECTOR

This thesis has been approved on the date shown below:

( 9 r f " Date ACKNOWLEDGMENTS

I would like to thank my major advisor. Dr. Joseph F. Schreiber,

Jr., for his assistance in this study and his willingness to accompany me into the field on many occasions. Dr. Schreiber not only gave freely of his time to discuss aspects of this study, but also took some of the photographs for this thesis.

I would like to thank the other members of my committee, Drs.

Karl W. Flessa and Richard F. Wilson, who critically reviewed this the­ sis and provided assistance during this study. Thanks are due also to

Dr. Dietmar Schumacher, former Assistant Professor of Geosciences, for his help during the initial stages of this study.

I would like to acknowledge the Phelps Dodge Corporation and the numerous ranchers of Cochise County who freely allowed access to their land.

I am very grateful to the Union Oil Company of California Founda­ tion, which provided scholarship support for the academic year 1977-78.

Finally, very special thanks are due to my wife, Mary Ann, for her patience, encouragement, and support throughout the course of this study.

iii TABLE OF CONTENTS

Page

LIST OF ILLUSTRATIONS...... vi

LIST OF T A B L E S ...... viii

A B S T R A C T ...... ix

INTRODUCTION ...... 1

Statement of the Problem Area of Study ...... Methods of Study . . .

Previous Work ...... H MhJ 4>

BOLSA QUARTZITE...... 9

Name and Type L o c a l i t y ...... 9 General Description ...... 9 Distribution and Stratigraphic Limits ...... 10 Petrology...... 10 Sedimentary Structures ...... 14 Thickness ...... 17 Paleontology and A g e ...... 17 C o n t a c t s ...... 20

BOLSA QUARTZITE IN COCHISE COUNTY ...... 22

Mule Mountains ...... 22 Whetstone Mountains...... 23 Dragoon Mountains ...... 25 Little Dragoon Mountains ...... 27 Swisshelm and PedregosaMountains...... 29 Dos Cabezas Mountains...... 31

CORONADO QUARTZITE ...... 43

Name and Type L o c a l i t y ...... 43 General Description ...... 43 Distribution and Stratigraphic Limits ...... 44 Petrology...... 46 Sedimentary S t r u c t u r e s ...... "...... 50 Thickness...... 56 Paleontology and A g e ...... 56 C o n t a c t s ...... 58

iv V

TABLE OF CONTENTS— Continued

Page

CONDITIONS OF DEPOSITION ...... 59

Introduction ...... 59 Dos Cabezas and Chiricahua M o u n t a i n s ...... 59 Swisshelm Mountains...... 63 Morenci A r e a ...... 64 Regional Relations of the Cambrian Strata in Southeast A r i z o n a ...... 66

SUGGESTIONS FOR FUTURE STUDY ...... 68

APPENDIX A: CAMBRIAN QUARTZITE LOCALITIES EXAMINED ...... 69

APPENDIX B: MEASURED STRATIGRAPHIC SECTIONS ...... 71

Dos Cabezas Mountains...... 71 Phelps Dodge Lime Quarry, Clifton ...... ;... 76

REFERENCES CITED ...... 81 LIST OF ILLUSTRATIONS

Figure Page

1. Location M a p ...... 3

2. Cambrian Correlation Chart ...... 7

3. Basal Conglomerate, Bolsa Quartzite in the Whetstone M o u n t a i n s ...... 12

4. Interbedded Shale and Sandstone, Bolsa Quartzite in the Barren Hills a Few Kilometers Northwest of the Swisshelm M o u n t a i n s ...... 13

5. Wedge-planar Cross-stratification, Bolsa Quartzite in the Dos Cabezas Mountains...... 15

6. Tabular-planar Cross-stratification, Bolsa Quartzite in the Swisshelm Mountains...... 16

7. Scolithus Tubes (Vertical Burrows), Bolsa Quartzite in the Whetstone Mountains...... 18

8. Horizontal Burrows on Bedding Plane, Bolsa Quartzite in the Little Dragoon M o u n t a i n s ...... 19

9. Contact between Bolsa Quartzite and Rattlesnake Point Granite in the Dos Cabezas Mountains...... 34

10. Quartzite Pebble-cobble-boulder Conglomerate, Bolsa Quartzite in the Dos Cabezas Mountains...... 35

11. Cumulative Weight Percent Curve for Unit 3, Bolsa Quartzite in the Dos Cabezas Mountains...... 39

12. Homfels Unit, Lower Member of the Abrigo Formation in the Dos Cabezas Mountains...... 40

13. Typical Abrigo-type Weathering, Abrigo Formation in the Dragoon Mountains ...... 41

14. Contact between Bliss Sandstone Equivalent and Metcalf Granite near Morenci ...... 48

15. Glauconite Surrounding Quartz Grains;1 from Unit 10, Bliss Sandstone Equivalent near Morenci ...... 51

vi vii

LIST OF ILLUSTRATIONS— Continued

Figure Page

16. Zoned Dolomite Replacing Quartz Grains; from Unit 14, Bliss Sandstone Equivalent near Morenci ...... 52

17. Top Sandstone Unit of Bliss Sandstone Equivalent near Morenci ...... 53

18. Contact between Dolomite Intraclast and Sandstone; from Unit 17, Bliss Sandstone Equivalent near M o r e n c i ...... 54

19. Quartz Grain Showing Quartz Overgrowths Typical of Quartzarenites in Southeast Arizona ...... 55

20. Fucoidal Markings on Bedding Plane, Bliss Sandstone Equivalent near M o r e n c i ...... 57

21. Bowie Mountain, between the Dos Cabezas and Chiricahua M o u n t a i n s ...... 60

22. Contact between the Pinal Schist and BoIsa Quartzite in the Northern Chiricahua Mountains ...... 62

23. Inferred Stratigraphic Relations of Cambrian Forma­ tions in Southeast Arizona ...... 67

24. The Dos Cabezas S e c t i o n ...... 72

25. Lime Quarry Section near M o r e n c i ...... 77 LIST OF TABLES

Table Page

I. Described Localities of the Bolsa Quartzite in Southeast Arizona ...... 5

II. Petrographic Data, Dos Cabezas Section ...... 36

III. Petrographic Data, Lime Quarry Section ...... 47

viii ABSTRACT

An investigation of the Cambrian Bolsa and Coronado Quartzites was made to describe regional stratigraphic relationships and conditions of deposition in southeast Arizona. The Bolsa Quartzite consists mainly of siliceous quartzarenite which changes from coarser grained and feld- spathic near the base to finer grained and quartzose near the top. A basal conglomerate is common and varies in thickness and composition according to the geographic location of the outcrop and the lithology of the underlying Precambrian rock units. The Bolsa ranges between 100 and 150 meters in thickness.

The Coronado Quartzite is composed of more lithologies than the

Bolsa Quartzite, consisting of shale, siltstone, sandstone, dolomite, and glauconitic and hematitic sandstone. The Coronado and the lower part of the Longfellow Limestone are correlated to the Bliss Sandstone of New Mexico. These units were deposited in an offshore area receiving terrigenous and carbonate sedimentation.

The Bolsa Quartzite was laid down during a major transgression from the west over the Precambrian basement. During a minor regression the Sandy Member of the Abrigo Formation was deposited; then the major transgression continued, laying down the Coronado Quartzite and the

Bliss Sandstone. All the Cambrian units in southeast Arizona are time- transgressive from west to east.

ix INTRODUCTION

A regional investigation of the basal Cambrian formations in southeastern Arizona was made to determine stratigraphic variations and relations. Of particular interest was the origin of the Cambrian strata west of the Sulphur Spring Valley in Cochise County, and in the Clifton-

Morenci area in Greenlee County.

Statement of the Problem

The purpose of this study was to examine the lesser known Cam­ brian strata west of the Sulphur Spring Valley and compare it to the . well-studied Bolsa Quartzite east of the Sulphur Spring Valley.

Because the study area is located in the Basin and Range physio­ graphic province, outcrops of rock generally cannot be traced from area to area, and great care must be taken in making correlations, especially with the non-fossiliferous Cambrian quartzites. A number of workers in the past have made correlations without paying attention to facies changes or the lateral thickening or thinning of units. This has led to a number of different interpretations of Cambrian geology in southeast

Arizona. In the Dos Cabezas Mountains, this is borne out by the fact that virtually every worker in the area has presented a different inter­ pretation of the Cambrian section.

The sedimentary strata of the Clifton-Morenci area illustrate another problem. The lower Paleozoic sedimentary rocks in this area are geographically isolated from other outcrops of similar rocks and

1 2 have been assigned different formation names than those used throughout the adjacent regions. These formation names, with one exception, have never been extended beyond the type area, nor should they be. In this study, an attempt has been made to place the Cambrian strata in this area into a more regional picture.

Area of Study

The general area of study is shown on Figure 1. The area stud­ ied in detail is in Cochise and Greenlee Counties. Cambrian outcrops were studied in the Mule Mountains, Dragoon Mountains, Little Dragoon

Mountains and adjacent Johnny Lyon Hills, Whetstone Mountains, Dos

Cabezas Mountains, northern Chiricahua Mountains, Swisshelm Mountains and adjacent Barren Hills, the area east and northeast of Morenci, and

Silver City, New Mexico (Appendix A). All areas are fairly easily ac­

cessible, usually by gravel and dirt roads that can be negotiated with

a pick-up truck or carryall, and in some cases a sedan.

Methods of Study

Two sections were measured and sampled, one near Morenci,

Greenlee County, and the other near the town of Dos Cabezas, Cochise

County. These sections were measured using a Brunton compass, tape,

and a Jacob staff as described by Compton (1962). Samples were col­

lected from each separate lithologic unit.

Lithologic descriptions were made in the field and supplemented

by examination of thin sections. Rock colors were assigned using the

Rock-Color Chart (Goddard and others, 1948); stratification terminology LQ - L ime Qua r ry Globe Phoenix Section

DC - Dos C a b eza s (GREENLEE Section I « * L 0 \ °Morenci BH - Bar r e n Hills g r a \h a m PINAL JLH-Johnny Lyon Hills

TH- Tombstone Hills

0 ip 20 3,0 4 0 50 M l

0 10 20 30 40 50 60 70 80

PIMA fo'iCOCHISE 3 \ \ Benson 114® 112° 110®

f SANTA CRUZ i \% .

ME X I CO

Figure 1. Location Map. 4 is after that of McKee and Weir (1953); and grain roundness is from the

Powers (1953) roundness scale.

Laboratory studies consisted of petrographic analyses of all the sampled units. Thin sections representative of the various lithologies were point counted using the line method (Galehouse, 1969, p. 814).

Thin section data were converted to sieve size data (Friedman, 1958), from which graphic mean, inclusive graphic standard deviation, and in­ clusive graphic skewness were calculated using the methods of Folk and

Ward (1957).

Photomicrographs of thin sections were taken using a Leitz petrographic microscope, Leica MD camera, and Kodacolor 400 film.

Previous Work

Although rocks of Cambrian age have been known to occur in

southeast Arizona since the time of the early reconnaissance surveys

(Parry, 1857; Gilbert, 1875), they were not described in any detail un­

til the early years of the twentieth century.

The name Bolsa Quartzite was proposed by Ransome (1904, p. 28)

for exposures of the basal Cambrian quartzites in Bolsa Canyon on the

southeast side of Escabrosa Ridge in the Mule Mountains near Bisbee,

Cochise County, Arizona. The name was later extended by him to the

basal Cambrian quartzites of the southern Dragoon Mountains (Ransome,

1913, p. 126) and the Tombstone Hills (Ransome, 1916, p. 148).

Table I lists the workers who have described the Bolsa Quartzite

at various localities in southeast Arizona, and Figure 2 shows the evo­

lution of Cambrian terminology in the study area. 5

Table I. Described Localities of the BoIsa Quartzite in Southeast Arizona

LOCALITY INVESTIGATORS Mule Mountains Ransome (1904) Hayes and Landis (1964, 1965)

Tombstone Hills Ransome (1916) Darton (1925) Gilluly (1956)

Dragoon Mountains Ransome (1913) Darton (1925) Cedarstrom (1946) Gilluly (1956)

Little Dragoon Mountains Darton (1925) Heineman (1927) Stoyanow (1936) Cook (1938) Enlows (1939) Gilluly (1956) Cooper and Silver (1964)

Whetstone Mountains Darton (1925) Stoyanow (1936) Gilluly (1956) Burnette (1957) Tyrrell (1957) Creasey (1967a)

Huachuca Mountains Alexis (1949) Weber (1950) Hayes and Raup (1968) Hayes and Cone (1975)

Swisshelm Mountains Loring (1947) Gilluly (1956) Epis and Gilbert (1957)

Pedregosa Mountains Epis (1956, 1958)

Peloncillo Mountains Quaide (1953) Gillerman (1958)

Chiricahua Mountains Raydon (1953) Brittain (1954) Sabins (1955, 1957a, 1957b) Chakarun (1973) 6

Table I, Continued.

LOCALITY INVESTIGATORS Dos Cabezas Mountains Barton (1925) Jones and Bacheller (1953) Sabins (1957a, 1957b)

Galiuro Mountains Krieger (1961, 1968a, 1968b, 1968c, 1968d) Hayes and Cone (1975)

Arivaipa area Simons (1964) Hayes (1975)

Rincon Mountains Acker (1958)

Santa Catalina Mountains Barton (1925) Bruhn (1927) Stoyanow (1936) McKenna (1965) Creasey (1967b) Shride (1967)

Tucson Mountains Barton (1925) Brown (1939) Bryant (1952)

Waterman Mountains McClymonds (1957, 1959a) Heindl and McClymonds (1964)

Slate Mountains McClymonds (1959b) Heindl and McClymonds (1964) Hayes (1975)

Vekol Mountains McClymonds (1959b) Heindl and McClymonds (1964) Chaffee (1974) 7

Southeast Sou thwest Mule Mountains Arizona Swisshelm Mountains Dos C a b e z a s M o u ntains Mo re nci Area New APPROXIMAT E West of the Sulphur Hayes and Epis and Jones and Mexico Ransome Stoyanow Spring Gilluly Hayes Da r ton Sa bins Krieger Hayes This Lindgren Hayes This AGE Landis Vo Hey Gilbert Bacheller (19041 119361 (1965) (19721 Hayes (1972) 119561 (1957) 119721 (19251 (1953) (1957a) [1968el 119721 Thesis j (19051 Thesis E I Pa s o Early El Paso El Paso El Pa s o Paso EI Paso Li mestone Ordovician r i g o El Paso El Paso Longfellow El PasoAb l imestone LimestoneDescribed L imestone Li mestone Limestone Trempea leaua n Ab rigo Copper Copper i Copper ! Copper ! Copper Limestone Formation L i mestone Limestone Franconian Queen Queen Lst. ' Queen Do I om i te Queen Queen Limestone Unit L imestone Member Member Member Mem b e r Bliss Upper i Sandy ! Sandy Sandy L i mestone Lower Sandy Cambrian Bliss Abrigo Ab r igo Member Member Sandstone Member d Unit Member Coronado Coronado o CL Abrigo Sandstone Dresbachian R ibbeo Sandstone u. Mid die Middle u. M id d le ll M idd I e Quartzi te Sandstone Limestone ' Formation Abrigo Bolsa Bolsa Coronado Limest. o' Equivalent o L imestone Bolsa oMember .^Member w Member 01 Me mber Member

Coc h iseS h a I y Lowe r L imestone Lowe r Quartzite Quartz ite Lower Sandstone Lower

Middle Member Member Member Forma t ion Sandstone Member Member

Bolsa Bolsa Bolsa Bolsa Bolsa BolsaBolsa Bolsa Bolsa Cambrian

Qua rtzite Quartzite Qua rtzite Quart zi te Quartzite Quartz i te Quartzite Quar t zite Quartzite

Krieger divides the Abrigo Formation in the Swisshelm and Mule Mountains the same way as in the Dos Ca bezas Mountains.

Figure 2. Cambrian Correlation Chart. 8

The Coronado Quartzite was named by Lindgren (1905, p. 59) for exposures of the basal Cambrian quartzite resting unconformably on Pre- cambrian granite near Morenci, Greenlee County, Arizona. Lindgren

(1905, p. 62) tentatively correlated the Coronado with the Bolsa Quartz­ ite, as did Darton (1925, p. 45), Stoyanow (1936, p. 478), and Wilson

(1962, p. 26). Hayes (1972, p. 18) renamed the formation the Coronado

Sandstone and extended the name to a number of areas that had previous­ ly been mapped as containing Bolsa Quartzite. His reasons for extend­ ing the Coronado were 1) he believed the Cambrian strata in the Arizona

Arizona-New Mexico border area were younger than the Cambrian strata to the west, and 2) he saw a lithologic similarity between the Coronado

Sandstone in the Morenci area and the strata in the areas he renamed.

This will be discussed later on in this thesis. BOLSA QUARTZITE

Name and Type Locality

The BoIsa Quartzite was named by Ransome (1904, p. 28) as de­ scribed in the Introduction. The type section, on the north slope of

Mount Martin, was remeasured by Hayes and Landis (1965).

General Description

The Bolsa Quartzite consists of yellowish- to pinkish-gray to pale- and grayish-red, brown-weathering orthoquartzite or firmly cement­ ed siliceous sandstone made up of rounded to subrounded grains. The tabular beds, separated by shaly or silty partings, range in thickness from a few centimeters to about 3 meters with the average being 0.5 to

1.5 meters. The thickest beds are generally in the lower part of the formation and the thinnest are in the upper part. The texture and com­ position of the Bolsa change rather systematically from coarse-grained and feldspathic near the base to fine-grained and quartzose near the top.

The Bolsa Quartzite is one of the more erosion-resistant rock units of southern Arizona, and is much more resistant than the underly­ ing Precambrian rocks or the overlying Abrigo Formation. Because of this, the Bolsa crops out as a cliff above a slope of its own rubble or forms rugged blocky hills and ridges.

9 10

Distribution and Stratigraphic Limits

The Bolsa Quartzite is found in a large area of southeast

Arizona, generally bounded by the New Mexico border on the east, the

Mexico border on the south, the Vekol Mountains on the west (Chaffee,

1974), and the Pinal Mountains on the north (Krieger, 1968e). Bolsa

Quartzite has been reported from the Plomosa Mountains near Quartzite in western Arizona by Miller (1970), but little is known about the Bolsa in that part of the state.

The Bolsa Quartzite unconformably overlies Precambrian igneous, metamorphic, or sedimentary rocks throughout its area of occurrence, and is conformably overlain by the Abrigo Formation, except in the area around Globe, where the Bolsa is unconformably overlain by the Devonian

Martin Formation (Krieger, 1968e).

Petrology

The Bolsa Quartzite is made up of about 85 percent orthoquartz­ ite or siliceous sandstone, with the remainder consisting of conglomer­

ate, generally at or near the base, and interbeds of siltstone and

shale, generally in the upper part of the formation.

The basal part of the Bolsa is commonly made up of a conglomer­

ate ranging from 0 to 20 meters in thickness that grades upward into a

gritty quartzite. The composition and texture of the conglomerate

varies according to the geographic location of the outcrop and the li­

thology of the underlying Precambrian rock units. West of the Sulphur

Spring Valley and south of the Little Dragoon Mountains, the basal 11 conglomerate generally consists of subrounded to subangular quartz and quartzite pebbles in beds less than a meter in thickness. Figure 3 shows a conglomerate typical of this area. In other localities the basal conglomerates have features unique to each particular location, and these are discussed in the appropriate sections of this thesis.

The lower third of the BoIsa Quartzite is usually medium- to coarse-grained with thin layers and lenses of granule conglomerate and is commonly feldspathic. Feldspar content is controlled to an extent by the composition of the underlying PreCambrian rock units. At places where the Bolsa Quartzite overlies granitic rocks, the average feldspar content is between 10 and 20 percent. Where it overlies Pinal Schist, feldspar content is between 5 and 15 percent; Hayes and Landis (1965, p. 8), however, have suggested that the higher values may be derived from nearby granitic rocks. Where the Bolsa overlies Precambrian sedi­ mentary rocks, the feldspar content is usually less than 5 percent. In most areas, the feldspar is altering to sericite and clay minerals, but in some localities, such as the Barren Hills, the feldspar appears to be fresh with a pinkish color and a euhedral shape.

The middle third of the Bolsa Quartzite is mostly medium- to fine-grained quartzose. sandstone with less than 5 percent feldspar.

Fining upward, the middle third grades into the upper third, which is made up of fine- to very fine-grained sandstone with less than 2 per­ cent feldspar. The upper part of the Bolsa contains thin interbeds of shaly siltstone, silty shale, and shale (Figure 4). 12

Figure 3. Basal Conglomerate, Bolsa Quartzite in the Whetstone Mountains.

This is typical of the subrounded to subangular quartz and quartzite pebble conglomerates found in the Bolsa west of the Sulphur Spring Valley. 13

Figure 4. Interbedded Shale and Sandstone, Bolsa Quartzite in the Barren Hills a Few Kilometers Northwest of the Swisshelm Mountains. 14

North and northwest of the Dragoon Mountains the entire BoIsa

Quartzite takes on the aspect of the upper part as it appears in the south. This is because of the abundance of fine-grained, silty sand­ stone and red siltstone in the formation. Krieger (1968e, p. 27) states that the reason for the abundance of the siltstone is because of the presence of regolithic material derived from a Precambrian diabase.

Another reason for the finer grained and more mature appearance of the

Bolsa is the fact that in many areas in the north it rests on sediments of the Precambrian Apache Group, so that the formation could have been derived from reworked sediments rather than primary rocks as it is in the south.

Glauconite is rare in the Bolsa Quartzite and is only found in a few localities, generally near the top of the formation. Hematite is commonly found as a stain in the cement or as a coating on quartz grains. Hematite locally occurs as discrete grains, as does magnetite.

Hematite also occurs as a cement, generally in a few thin beds in the upper part of the formation. Carbonates are not present in the Bolsa, except as a very minor part of the cement in a few areas.

Sedimentary Structures

Small- and medium-scale, wedge-planar, and tabular-planar cross­ stratifications (Figures 5 and 6) are present throughout the Bolsa

Quartzite, but the majority occur in the lower two-thirds of the forma­ tion. The upper third commonly displays parallel lamination, but beds with parallel lamination are found throughout the formation. Most Figure 5 Wedge-planar Cross-stratification, Bolsa Quartzite in the Dos Cabezas Mountains. I

Figure 6. Tabular-planar Cross-stratification, Bolsa Quartzite in the Swisshelm Mountains. 17 cross-strata dip in a westerly direction, but in some localities a wide variety of orientations is evident.

Thickness

The thickness of the Bolsa Quartzite varies greatly throughout southeast Arizona. The thickness is greatest and least variable south of the Little Dragoon Mountains, ranging from 100 to 150 meters. North of the Dragoon Mountains, the thickness of the Bolsa is locally much more variable. The thickest sections in the north are generally much thinner than those in the south. This is probably due to the greater relief on the underlying surface in the north (Shride, 1967, p. 71).

Thickness of the Bolsa Quartzite will be further discussed under each locality heading in this thesis.

Paleontology and Age

No age diagnostic fossils have been found in the Bolsa Quartzite.

However, fucoidal tracks and trails on bedding surfaces and Scolithus tubes in beds locally are abundant, generally in the upper part of the formation. Scolithus tubes (Figure 7) are only found in sandstone beds, and are typically about 1 centimeter in diameter and 10 to 15 centimeters in length. Tracks and trails (Figure 8) are found on both sandstone beds and shale interbeds.

Ransome (1904, p. 30) assigned a Middle Cambrian age to the

Bolsa Quartzite based upon its conformable relation with the overlying

Abrigo Limestone, the lower part of which is known from fossil evidence to be of late Middle Cambrian age. This age assignment has been 18

Figure 7. Scolithus Tubes (Vertical Burrows), Bolsa Quartzite in the Whetstone Mountains.

End view. Figure 8. Horizontal Burrows on Bedding Plane, Bolsa Quartzite in the Little Dragoon Mountains. 20 generally accepted by all subsequent workers for the BoIsa Quartzite.

However, the base of the Paleozoic is known to be younger eastward and northward from the study area, and the basal Cambrian rocks to the south in Sonora and to the west in California are known to be of Early Cam­ brian age (Cooper and Arellano, 1956; Stewart, 1970); This means that the Bolsa Quartzite to the west in the Slate and Vekol Mountains, and the Bolsa mapped by Miller (1970) in western Arizona may be of Early

Cambrian age.

Contacts

The basal contact of the Bolsa Quartzite with the underlying

Precambrian rocks is unconformable. Generally, the contact is sharp, but where the Bolsa is underlain by the Troy Quartzite the contact is obscure. The actual relations between the Bolsa and the Troy were not understood for many years, until Krieger (1961, 1968e) and Shride (1967) resolved the problem of where to place the contact.

The Bolsa is everywhere overlain conformably by the Abrigo For­ mation . The term Abrigo Limestone is restricted to the type area on

Mount Martin. Although the contact is gradational, it can usually be placed where the quartzites of the Bolsa give way to the shales or silt- stones of the Abrigo. Locally, the placement of the contact is more arbitrary, as quartzite and shale may be present through a stratigraphic

interval of as much as 50 meters. Gilluly (1956, p. 15) suggests place­ ment of the contact at the highest quartzite bed below the lowest lime­

stone bed. Fossil evidence in the Abrigo Formation suggests that the 21 top of the BoIsa may be younger in the east than in the west (Hayes and

Cone, 1975, p. 13-14).

i BOLSA QUARTZITE IN COCHISE COUNTY

Mule Mountains

The basal Cambrian quartzite in the Mule Mountains was first described by Bumble (1901), who correlated it to his Dragoon Quartzite.

He failed, however, to describe satisfactorily the stratigraphic posi­ tion of this unit, and obscured the correlation by referring to rock units between it and the underlying schist. Ransome (1904, p. 28) at first intended to use the term Dragoon Quartzite, but reluctantly aban­ doned it in favor of a new term, Bolsa Quartzite, so he could complete­ ly redefine the unit.

The Bolsa Quartzite in the Mule Mountains rests unconformably on eroded Precambrian Pinal Schist. The base of the Bolsa is marked by a basal conglomerate, ranging in thickness from 15 to 20 centimeters, composed of subrounded to subangular pebbles of quartz and quartzite with some small rounded cobbles of quartz as much as 10 centimeters in diameter. Ransome (1904, p. 30), Gilluly (1956, p. 15), and Hayes and

Landis (1965, p. 8) have suggested that some of these pebbles may have been derived from quartz veins in the underlying Pinal Schist. When the author examined the Pinal Schist on the north slope of Mount Martin, some outcrops of resistant metaquartzite were found that are weathering

out as quartz pebbles. These pebbles probably were an important source

of the basal conglomerate, as many of the conglomerate pebbles examined were composed of quartzite rather than of quartz.

22 23

The basal conglomerate grades up into a coarse-grained to granu­ lar siliceous sandstone containing about 10 percent feldspar grains.

The texture and composition of the Bolsa Quartzite in the Mule Mountains changes systematically from coarse-grained and feldspathic near the base to finer grained and more quartzose near the top. Limonite and hematite stain the cement throughout the formation and form a coating on the quartz grains.

The Bolsa Quartzite is laminated throughout, with tabular-planar and wedge-planar cross-laminations in the lower half. Beds are thin- to

thick-bedded, averaging about 60 centimeters in thickness, and separated by distinct parting planes.

No fossils diagnostic of age have been found in the Bolsa Quartz­

ite in the Mule Mountains. Even trace fossils are relatively scarce,

but tracks, trails, and Scolithus tubes do occur in the upper part of

the formation.

The Bolsa Quartzite is 105 meters thick at its type section on

Mount Martin (Hayes and Landis, 1965, p. 7) and ranges in thickness

from 90 to about 140 meters (Hayes and Landis, 1964) throughout the

Mule Mountains. The formation is overlain conformably by the Abrigo

Limestone, and the contact is placed where the.silicified sandstone and

siltstone of the Bolsa give way to claystone and thinly interbedded ar­

gillaceous limestone of the Abrigo.

Whetstone Mountains

Bumble (1901) reported Cambrian quartzite from the Whetstone

Mountains. He correlated these quartzites to his Dragoon Quartzite. 24

The name Dragoon Quartzite has fallen into disuse as described in the previous section. Darton (1925, p. 297) correlated the basal Cambrian quartzite in the Whetstone Mountains with the BoIsa Quartzite and re­ corded 48 meters of thickness. Stoyanow (1936, p. 480) reported 122 meters of thickness, and all Workers in the area since then have report­ ed about the same thickness. Darton may have looked at the Bolsa in an area where it is cut by Laramide dikes and only measured a partial section.

The Bolsa Quartzite in the Whetstone Mountains rests unconfora- ably on eroded Precambrian Whetstone Granite and Pinal Schist. The base of the formation is marked by a basal conglomerate ranging in thickness from 30 centimeters to 5 meters. Actually, the thickness of 5 meters

reported by Burnette (1957, p. 7-8) includes a considerable amount of

coarse-grained siliceous sandstone, and the actual thickness of the

basal conglomerate is probably nowhere greater than 1 meter. The basal

conglomerate consists of subrounded to subangular pebbles of quartzite,

jasper, and quartz, much of it rose quartz. The conglomerate is gener­

ally thicker where it overlies the Pinal Schist.

The lower part of the Bolsa Quartzite in the Whetstone Mountains

is arkosic, with feldspar making up about 20 percent of the rock. This

is probably due to the close proximity of the Whetstone Granite. Other

than the high percentage of feldspar, the Bolsa here is very similar to

the Bolsa Quartzite in the Mule Mountains, grading upward from coarser

grained and feldspathic to finer grained and quartzose. The top part

of the formation is shaly with thin interbeds of quartzite. Thin shale 25 beds are found throughout the formation. The Bolsa Quartzite is lami­ nated throughout, with the middle part being distinctly cross-laminated with tabular-planar and wedge-planar cross-laminations.

Although no diagnostic fossils have been reported from the Bolsa

Quartzite in the Whetstone Mountains, trace fossils are very abundant, especially in the upper part. Numerous bedding planes covered with tracks, trails, horizontal burrows, and Scolithus tubes were found in the northern Whetstones; Hayes and Cone (1975, p. 11) report the same from the western Whetstones.

The Bolsa Quartzite ranges in thickness between 100 and 150 meters in the Whetstone Mountains (Burnette, 1957; Creasey, 1967b).

The formation is overlain conformably by the Abrigo Formation, but the

contact is sometimes obscure as there is a zone with 30 meters of thin

quartzite and shale layers between the massive quartzites of the Bolsa

and the limestones of the Abrigo. Gilluly (1956, p. 15) suggests plac­

ing the contact at the top of the last thick quartzite bed in the Bolsa.

Dragoon Mountains

Durable (1901) gave the name Dragoon Quartzite to sane pre-

Devonian quartzite beds about 120 meters thick in the Dragoon Mountains.

As related previously, the name Dragoon Quartzite has fallen into dis­

use. Ransome (1913, p. 126) extended his Bolsa Quartzite into the south­

ern Dragoon Mountains to include rocks that he correlated with his

section in the Mule Mountains.

The Bolsa Quartzite in the Dragoon Mountains rests unconfora-

ably on eroded Precambrian Pinal Schist and gneissic granite. The base 26 of the Bolsa is marked by a conglomerate ranging in thickness from 0 to

1.3 meters, consisting of subrounded pebbles of quartz and quartzite, with few pebbles exceeding 3 centimeters in diameter. The basal con­ glomerate grades up into a coarse-grained arkosic quartzite with some quartz pebbles as large as 1 centimeter in diameter. The remainder of the formation greatly resembles the Bolsa Quartzite in the Whetstone and Mule Mountains. It is a coarse- to medium-grained quartzite that grades upward into a finer grained quartzite and interbeds of siltstone and shale. The formation is generally cross-laminated throughout with tabular-planar and wedge-planar cross-laminations.

No diagnostic fossils have been found in the Bolsa Quartzite in

the Dragoon Mountains, but tracks and trails on bedding planes and

Scolithus tubes in the beds are common, especially in the upper part.

Gilluly (1956, p. 15) reported a thickness of 92 meters, but

indicated that the section may have been faulted and could have been as

thick as the section in the Mule Mountains to the south. Because of the

severe faulting and metamorphism by dikes cutting through the formation,

no section was measured for this thesis in the Dragoon Mountains.

The Bolsa Quartzite in the Dragoon Mountains is conformably

overlain by the Abrigo Formation. A 15 meter zone of thin-bedded quartz­

ite and shale lies between the massive quartzite of the Bolsa and the

thin-bedded limestone of the Abrigo. The contact generally is placed

at the last thick quartzite bed of the Bolsa. 27

Little Dragoon Mountains

Kellogg (1906) reported quartzites in the Little Dragoon Moun­

tains and compared these quartzites to the Bolsa Quartzite in the Mule

Mountains to the south. Cooper and Silver (1964, p . 45), in their de­

tailed report on the Little Dragoon Mountains and the adjacent Johnny

Lyon Hills, divided the Bolsa Quartzite into four transitional units:

1) a basal conglomerate that ranges in thickness and character accord­

ing to the underlying Precambrian geology and topography as described

below, 2) a lower quartzite bed containing granule conglomerate and

some pebble conglomerate beds, 3) a higher quartzite unit characterized

by fine- to medium-grained vitreous quartzites, and 4) an upper unit of

quartzite or sandstone and interbedded shale that grades into the over-

lying Abrigo Formation.

The Bolsa Quartzite in the Little Dragoon Mountains and the ad­

jacent Johnny Lyon Hills rests unconformably on a higher relief Precam­

brian surface composed of sedimentary rocks of the Apache Group of

Ransome (1903, p. 28), diabase sills, and Pinal Schist. The basal con­

glomerate of the Bolsa here differs markedly from those to the south

and east. At places where the Bolsa rests on the Dripping Spring Quartz­

ite of the Apache Group or on the Pinal Schist, the basal conglomerate

generally consists of reworked pebbles, cobbles, and boulders of quartz,

schist, and quartzite. The conglomerate is up to 12 meters in thickness.

Cooper and Silver (1964, p . 43-44) have shown that the thicker sections

of conglomerate represent valley filling facies, with the basal conglom­

erate consisting of rounded boulders of quartz, quartzite, schist, and 28 sandstone as much as 1 meter in diameter. The thinner sections of con­ glomerate represent areas where the Bolsa Quartzite lapped up against

Precambrian hills, the basal conglomerate consisting of angular to rounded cobbles and boulders in a very coarse-grained matrix. General­ ly, the thinner conglomerates are associated with the thinner sections of Bolsa, while the thicker conglomerates are associated with the thick­ er sections of Bolsa.

Where the Bolsa Quartzite overlies Pinal Schist, diabase sills, or the Pioneer Shale of the Apache Group the basal conglomerate gener­ ally resembles that to the south, consisting of well-rounded to subround­ ed pebbles of quartz and quartzite. Cooper and Silver (1964, p. 45) suggest that the well-rounded pebbles are reworked pebbles from the

Barnes Conglomerate of the Apache Group.

The basal conglomerate grades up into a coarse- to medium­

grained quartzite with very little feldspar, generally less than 5 per­

cent. The Bolsa Quartzite in the Little Dragoon Mountains is very

similar to the sections in the south, grading upward into fine- to medium-grained quartzites, and interbedded with shale and siltstone near

the top. The major sedimentary structure is parallel lamination; some

tabular-planar and wedge-planar cross-strata are locally abundant in

the lower part.

No age diagnostic fossils have been found in the Bolsa Quartzite

in the Little Dragoon Mountains or the adjacent Johnny Lyon Hills, but

tracks and trails on bedding planes and Scolithus tubes in beds are

abundant in the upper part of the formation. 29

The thickness of the Bolsa Quartzite in the Little Dragoon Moun­ tains ranges from 102 meters to as little as 4 meters where it laps out against inferred Precambrian hills (Cooper and Silver, 1964, p. 46). In the Johnny Lyon Hills, the Bolsa ranges in thickness from 119 to 146 meters (Cooper and Silver, 1964, p. 46). The thinning of the formation in the Little Dragoon Mountains appears to be due to onlap of a pre-

Bolsa surface of considerable relief.

The Bolsa Quartzite in this area is overlain conformably by the

Abrigo Formation. Cooper and Silver (1964, p. 45) place the contact at the highest quartzite bed 30 centimeters or more in thickness.

Swisshelm and Pedregosa Mountains

Loring (1947) was the first to describe Bolsa Quartzite from the Swisshelm Mountains. Gilluly (1956) examined the Cambrian strata in the northern Swisshelm Mountains and measured a partial section.

Epis and Gilbert (1957) made a detailed study of the early Paleozoic rocks in the Swisshelm Mountains. They measured approximately 100 me­ ters of Bolsa Quartzite, followed by a sequence of Abrigo Formation,

Upper Cambrian Sandstone, Dolomite, and the El Paso Limestone. Epis and Gilbert (1957, p. 2236) compared the Upper Cambrian Sandstone to the Bliss Sandstone of New Mexico, but it has since been shown that the

Upper Cambrian Sandstone and the overlying dolomite unit are correlative

to the Sandy and Copper Queen Members of the Abrigo Formation, respec­

tively (Krieger, 1968e; Hayes, 1972, p. 11-12).

Epis (1958) reported essentially the same section from the Ped­

regosa Mountains and noted that the Upper Cambrian Sandstone is 30. noticeably thicker. He stated that this unit may continue northward and eastward from the Sulphur Spring Valley to form most of the upper part of the Bliss Sandstone (Epis, 1958, p. 2755). This hypothesis will be examined further under the section on conditions of deposition.

The Bolsa Quartzite in the Swisshelm Mountains rests on an eroded surface of Precambrian granite. The lower part of the Bolsa is coarse-grained and feldspathic; many of the feldspars are angular and pink with a fresh appearance. No basal conglomerate was found by the author either in the Swisshelm Mountains or the barren Hills to the northwest. Epis and Gilbert (1957, p. 2235) reported, however, that the base of the Bolsa Quartzite was pebbly. The texture of the Bolsa does not change much throughout the formation, generally remaining

coarse-grained and slightly feldspathic. The lower part of the forma­

tion is strongly cross-stratified with tabular-planar and wedge-planar

cross-laminations in many orientations with dips varying from steep to

shallow. There are concentrations of heavy minerals along the planes

of the cross-laminations in the lower 10 meters of the formation that

abruptly disappear higher in the section.

Toward the middle of the section, clay drapes become apparent

on undulating bedding surfaces; many beds thicken and thin laterally

and in some cases wedge out. Near the top of the formation, the Bolsa

consists of interbedded quartzites and shales. Shale pebbles are found

in the bottom part of some of the quartzite beds.

Diagnostic fossils have not been found in the Bolsa Quartzite

in this area, but tracks and trails on bedding planes and Scolithus

tubes in the beds are locally abundant, especially in the Barren Hills. 31

The Bolsa Quartzite in the Swisshelm and Pedregosa Mountains ranges in thickness from 100 to 160 meters (Epis and Gilbert, 1957, p.

2235; Epis, 1958, p. 2752), but thickness is generally difficult to de­ termine because of numerous faults in the area. The Bolsa is conform­ ably overlain by the Abrigo. Formation. The contact is easily found at the point where the last thick bed of quartzite is overlain by the siltstones of the Abrigo.

Dos Cabezas Mountains

The lower Paleozoic rocks near the town of Dos Cabezas in the

Dos Cabezas Mountains were first described by Gilbert (1875), who col­ lected some Ordovician fossils from the limestone beds above the basal quartzites. Darton (1925, p. 296) divided the section into formations.

He correlated the basal 46 meters of quartzite and the overlying 61 meters of slabby sandstone and limestone with the Bolsa Quartzite, al­ though he called the unit the Bolsa Sandstone and correlated the over- lying limestones and dolomites with the Abrigo Limestone. Darton (1925, p. 296), noting the presence of Ordovician fossils near the top of this

section and comparing the Abrigo Limestone in the Dos Cabezas Mountains with the Ordovician El Paso Limestone of New Mexico and the Longfellow

Limestone near Morenci, suggested that these units may be interrelated.

Jones and Bacheller (1953) essentially divided the section the same way,

but preferred the term Bolsa Quartzite to Bolsa Sandstone.

In redefining the whole section, Sabins (1957a) correlated the

strata between the Precambrian granite and the sandy dolomites with the

Bolsa Quartzite; the overlying beds were assigned to the El Paso 32

Formation, which is what he called the El Paso Limestone. His reason for these correlations was that he believed the El Paso Limestone and the Abrigo Formation to be laterally contiguous; that is, both being part of the same time-transgressive rock unit (Sabins, 1957a, p. 475).

Sabins’ (1957a) interpretation differs from that of Epis and Gilbert

(1957), that the El Paso Limestone overlies the Abrigo Formation with a sandstone unit, the Upper Cambrian Sandstone, between the two units.

This problem will be discussed further in the section of this thesis on

conditions of deposition.

Krieger (1968e) reinterpreted Sabins’ section, dividing his

Bolsa Quartzite into two formations. The lower quartzite unit was re­

tained in the Bolsa Quartzite, but the middle and upper parts were

placed in the Abrigo Formation. The sandy dolomite beds below the lime­

stones of the El Paso Limestone were also placed in the Abrigo. The

author believes that Krieger has best interpreted the section in the

Dos Cabezas Mountains, and her units, with some modifications, were used

in describing the measured section in Appendix B (see also Figure 2).

Hayes (1972, p. 15) correlated Sabins' (1957a) Bolsa Quartzite

with the Coronado Quartzite near Morenci and called it the Coronado

Sandstone. His reasons for doing so are not clear, as he was aware of

the similarities of the section in the Dos Cabezas Mountains to the

Bolsa Quartzite and Abrigo Formation to the south and west (Hayes, 1972,

p. 15). To the south in the Swisshelm Mountains, essentially the same

section crops out, but Hayes (1972, p. 11) did not rename this section. 33

In this thesis Hayes terminology for the strata in the Dos Cabezas

Mountains has not been used; the much more common terminology from south­ east Arizona has been used instead.

The Bolsa Quartzite in the Dos Cabezas Mountains rests uncon-

formably on the Precambrian Rattlesnake Point Granite (Figure 9) and

consists of siliceous feldspathic sandstone and a thick basal

conglomerate.

The basal part of the Bolsa Quartzite consists of a quartzite

pebble-cobble-boulder conglomerate (Figure 10) that is 5.2 meters thick

(Appendix B ) . The basal conglomerate consists of well-rounded to

rounded pebbles * cobbles, and boulders of metaquartzite as large as 1

meter in diameter, although most clasts are smaller. Above the basal

conglomerate the Bolsa consists of a fining upward sequence of sili­

ceous feldspathic sandstones with thin lenses and beds of quartzite peb­

ble conglomerate. A representative sample of this lithology was

examined petrologically, and results are shown in Table II.

Thin section A in Table II is representative of the Bolsa Quartz­

ite in the Dos Cabezas Mountains. Although rocks stratigraphically

lower may be slightly coarser grained and more feldspathic, and rocks

stratigraphically higher may be finer grained and slightly less feld­

spathic, they are all subarkoses as described by Pettijohn (1954).

Composition is as shown in Table II. The feldspars are chiefly

orthoclase, although there are noticeable quantities of plagioclase.

All the feldspars are altered; sericite is the principal alteration

product. Figure 9. Contact between Bolsa Quartzite and Rattlesnake Point Granite in the Dos Cabezas Mountains.

Head of hammer rests on granite and handle rests on basal conglomerate. Arrow points to contact. Figure 10. Quartzite Pebble-cobble-boulder Conglomerate, Bolsa Quartzite in the Dos Cabezas Mountains. H § B 8 & 2 & B U is unimodal grain distribution. grain unimodal is U U-f is unimodal grain distribution with a secondary fine mode. fine secondary a with distribution 5.grain Unit of unimodal is U-f quartzite the with interbedded quartzarenite friable a is D

o\ JJI JJ» W N> of positions for B Appendix See — Section. Cabezas Dos Data, Petrographic II. Table A is A C is a quartzite from Unit 5 of the Abrigo Formation. theAbrigo of 5 Unit from quartzite isa C B is a dolomite from Unit 3 of the Abrigo Formation. theAbrigo 3of Unit from dolomite isa B 0 - 70 - 96 3 - 73 %

•H I 4J 4J

PRET (PERCENT) (PERCENT) YE ROUNDNESS TYPES r-4 u o d cd 5 4J cn o o *3 i§ cn 4J o a d

g g g , a l 4J o bo id

s I a to a g5 .9 .57 1.49 03 U M M M .3 .55 2.13 id id 8 .2 2 U-f - U .28 .92 :85

s STATISTICAL PARAMETERS

*US fl s 2 > 2 CL cd O g bO m > 1 U-f .17 0 U .07

37

As a part of this study, the quartz grain extinction types in the quartzarenites were observed and compared to those reported by

Blatt and Christie (1963) for typical orthoquartzites and arkoses. The percentages reported by Blatt and Christie (1963, p. 577) for quartz grain extinction types are, for a typical arkose: 23.6 percent non- unduiatory, 73.8 percent undulatory, and 2.6 percent polycrystalline.

For an orthoquartzite the percentages are: 43.1 percent non-undulatory,

55.1 percent undulatory, and 1.8 percent polycrystalline.

The quartz grain extinction types in the BoIsa Quartzite differ from those of a "typical" rock in that both the non-undulatory and poly­ crystalline percentages are higher than they "should" be. Blatt and

Christie (1963, p. 574) account for a high percentage of non-undulatory quartz in a rock by preferential destruction of the relatively unstable undulatory and polycrystalline quartz through several sedimentary cycles, and account for a high percentage of polycrystalline quartz with a source area of primary crystalline rocks. Thus, it appears that the

Bolsa Quartzite in the Dos Cabezas Mountains may have had at least two source areas. This is quite possible, as a few miles to the east there are outcrops of Precambrian Pinal Schist that contain a number of quartz­ ite beds. These beds could have been the source for some of the sand in the Bolsa. The Rattlesnake Point Granite was probably the source for some of the sediment, and almost certainly was the source for the

feldspars.

Statistical analysis of the grain sizes from the thin sections was based on the method of Friedman (1958). The statistical parameters 38 were calculated using the methods of Folk and Ward (1957), and inter­ preted according to Folk (1974, p. 45-47). The graphic mean shows the

Bolsa Quartzite, less the basal conglomerate, to have a composition of coarse sand; the inclusive graphic standard deviation shows the sediment is moderately sorted, and the inclusive graphic skewness shows the sedi­ ment to be fine-skewed.

The cumulative weight percent (Figure 11) curve shows a major concave up-slope break at about +2.0 phi. This probably reflects the transition from transport by traction to transport by intermittent sus­ pension, as this roughly corresponds to the midpoint of the transition between Rubey's Impact Law and Stokes* Law of particle settling (Visher,

1969, p. 1080). A second slope break at +3.0 phi represents the sepa­ ration of transportation by intermittent suspension from that of true suspension, as this is the lower limit of the transition between Rubey's

Impact Law and Stokes' Law (James and Oaks, 1977, p. 1504).

The Bolsa Quartzite in the Dos Cabezas Mountains shows tabular- planar and wedge-planar cross-stratification in places, but generally has few sedimentary structures, appearing massive in outcrop.

Immediately overlying the Bolsa Quartzite is a brownish homfels unit about 15 meters thick that greatly resembles the lower part of the

Abrigo Formation to the south and west (Figures 12 and 13). Above this unit are almost 30 meters of siltstone with a single dolomite bed in the middle. These units surely represent the Lower and Middle Members of

the Abrigo Formation, although they are thinner than those found to the

south and west. Overlying these units are about 100 meters of Figure 11. Cumulative Weight Percent Curve for Unit 3, Bolsa Quartzite Bolsa 3, forUnit Curve Percent Weight Cumulative 11. Figure

CUMULATIVE PERCENT in the Dos Cabezas Mountains. Cabezas the Dos in RI SZ I PHI IN SIZE GRAIN eod lp break slope second is soe break slope first 39

40

Figure 12. Hornfels Unit, Lower Member of the Abrigo Formation in the Dos Cabezas Mountains.

This unit greatly resembles the Abrigo Formation to the west. Compare with Figure 13. 41

>

Figure 13. Typical Abrigo-type Weathering, Abrigo Formation in the Dragoon Mountains. 42 interbedded quartzite and friable sandstone which represent a thick section of the Sandy Member of the Abrigo Formation. The petrography of some of these units is given in Table II. CORONADO QUARTZITE

Name and Type Locality

The Coronado Quartzite was named by Lindgren (1905, p. 59) for exposures in the Horenci area of Greenlee County, Arizona. Hayes (1972, p. 13-14) changed the name to Coronado Sandstone when he extended the name to the south and west.

General Description

The Coronado Quartzite consists chiefly of yellowish- to pink pinkish-white and maroon brown-weathering orthoquartzites and firmly cemented sandstones made up of subrounded to rounded grains of moder­ ately sorted coarse sand. Grain size generally decreases upward in the section. The Coronado is much more varied lithologically than the Bolsa

Quartzite, containing beds of shale, siltstone, dolomite, and hematitic and glauconitic sandstone. In many parts of the formation, the cement­ ing material is dolomite or calcite rather than silica as in the Bolsa.

The Coronado Quartzite commonly is more resistant than the un­ derlying Precambrian rocks but not much more resistant than the overly­

ing Longfellow Limestone, so it usually crops out as a cliff. Many of

the cliffs are also capped by the lower part of the Longfellow. Else­ where, the Coronado forms caps on some mountains and ridges in the area.

43 44

Distribution and Stratigraphic Limits

The Coronado Quartzite is found only in the area from which it was originally described. The name was never used beyond the type area until Hayes (1972) extended the name Coronado Sandstone to the south and west to include strata heretofore mapped as BoIsa Quartzite. In the previous section on the BoIsa Quartzite in the Dos Cabezas Mountains, it can be seen that Hayes' extension of the Coronado into that area was invalid.

Not only is Hayes' (1972) extension of the Coronado invalid, but the term Coronado Quartzite itself no longer serves a useful purpose in southeast Arizona stratigraphy. Hayes (1972, p. 13) proposed that the term Longfellow Limestone be abandoned in favor of the more widely recognized El Paso Limestone. If Hayes had done the same for the Coro­ nado Quartzite and replaced it with a more widely used stratigraphic unit, southeast Arizona stratigraphy could have been made simpler rather than more complex.

During field work in the Morenci area, the author was struck by the similarity of the Coronado Quartzite and the lower Longfellow

Limestone to descriptions of the Bliss Sandstone from western New Mexico.

The Bliss in the Silver City, New Mexico area was examined to confirm these descriptions.

Lochman-Balk (1956, p. 544) describes the Bliss Sandstone as follows: "The basal few feet consist of clean, fine grained, white to yellow sandstone with a sporadic thin conglomerate. The succeeding beds are siltstones, shales, thin- to medium-bedded glauconitic and 45 hematitic sandstones, oolitic hematites, arenaceous limestones and silty dolomites which alternate both vertically and laterally."

Lewis (1962, p. 7-8) divided the Bliss Sandstone near Silver

City, New Mexico, only 100 kilometers distant from Morenci, into six members and suggested the name Bliss Formation rather than Bliss Sand­ stone. 'The members described by Lewis are: 1) a lower quartzite that is slightly calcareous, 2) a lower hematitic sandstone, 3) a thin- bedded glauconitic sandstone, 4) a middle quartzite with minor calcare­ ous cement and some glauconite and hematite, 5) a middle calcareous sandstone which is hematitic and cross-laminated, and 6) an upper glauconitic sandstone with less glauconite than member three, which is very dolomitic.

Flower (1969, p. 44) indicated that the Bliss Sandstone shows wide variation, consisting of shaly layers, dolomitic sands, thin layers of pure limestone and, toward the west, a considerable interval of mod­ erately sandy dolomite. Flower (1953) has stated that the Bliss ranges in age from Middle Franconian to Early Ordovician in the eastern part of its range, but that in the western part (Flower, 1965, p. 115) the Bliss may be as old as Dresbachian (early Late Cambrian).

The Coronado Quartzite and lower Longfellow Limestone measured

section (Appendix B) appears to fit these descriptions of the Bliss

Sandstone very well, allowing for some regional variations, and greatly

resembles the Bliss outcrops near Silver City, New Mexico, 100 kilomet­

ers to the east. Because Hayes (1972, p. 13) has already reassigned

the Longfellow Limestone to the El Paso Limestone, a unit which 46 conformably overlies the Bliss Sandstone throughout most of its range, there is no problem in correlating the Coronado Quartzite and the lower

Longfellow Limestone to the Bliss. Henceforth in this thesis, these rocks will be referred to as the Bliss Sandstone equivalent.

Petrology

The Bliss Sandstone equivalent in the Morenci area is made up of many different lithologies. Table III shows the petrographic analysis of typical lithologies collected in the Morenci area from the section described in Appendix B.

The Bliss Sandstone equivalent rests unconformably on the Pre—

Cambrian Morenci Granodiorite and Metcalf Granite (Figure 14). The basal part of the formation is a quartz and quartzite pebble conglomer­

ate that ranges in thickness from 0 to 15 meters and consists of sub­

rounded to subangular pebbles of quartzite and quartz in a matrix of

coarse sand. The basal conglomerate (unit 1) grades up into a dolomit-

ic sandstone (unit 2), the petrology of which is shown by thin section

A in Table III. The quartz grain extinction types differ greatly from

those reported for the rest of the formation in that an overwhelming

amount of non-undulatory quartz is present. This seems to indicate a

source area of reworked sediments. The fact that there is no feldspar

in the rock would tend to support this concept. Although no outcrops

of Precambrian sedimentary rocks are present in the area, the Pinal

Schist does crop out a few kilometers to the north, and quartzite mem­

bers of that unit could have provided the sediment. The methods used

in determining statistical parameters have been touched on previously Table III. Petrographic Data, Lime Quarry Section. QUARTZ-GRAIN GRAIN STATISTICAL TYPES ROUNDNESS PARAMETERS COMPOSITION (PERCENT) (PERCENT) (PERCENT) 3 tf o N s S I a 2 rtJ 01 fc. ”3 g 01 0# 01 u A o 8 u ii ji 1 3 § N I 2. 01 a i <0 B I'S 18 ? s I •3 HK 8| •di | I O ■§•8 E I s I i I 1 N Q 1 I 1 Ft, tn m ll If 5 8 II Al 81 - - 1 1 - — — 17 — 91 4 5 56 44 .48 .87 .16 U-f7

B2 55 - 11 14 12 7 — 1 — — 70 26 4 40 60 3.18 .69 -.10 U-c8 1 b C3 93 - 1 4 2 - — — — — 66 25 3 51 49 .89 .82 w a

D4 64 — - 2 19 15 — - — — 72 25 9 53 47 1.27 .64 .10 U

E5 17 - 2 - 4

F6 86 - 1 -- - — — 13 — 76 23 1 53 47 1.41 .52 -.03 U ^A is a quartzarenite from Unit 2 of the Bliss Sandstone equivalent, is a siltstone from Unit 4. is a quartzite from Unit 9. is a quartzarenite from Unit 11. ■?E is a dolomite from Unit 14. is a quartzarenite from Unit 17. MJ-f is unimodal grain distribution with a secondary fine mode. qU-c is unimodal grain distribution with a secondary coarse mode. 9U is unimodal grain distribution. 48

Figure 14. Contact between Bliss Sandstone Equivalent and Metcalf Granite near Morenci.

Boot is resting on granite; arrow points to contact. Photo by Dr. Joseph F. Schreiber, Jr. 49 in this thesis, so only results will be reported in this section. This unit is a moderately sorted coarse sand with a secondary mode in the

fine sand.

Next in the section is a sequence of shale, siltstone, and dolo- mitic sandstone (units 5-8). The latter rock type is about the same

as that described above. The shale is generally dark green and poorly

exposed. The siltstone, shown petrologically by thin section B in

Table III, has a high percentage of glauconite and hematite. Feldspar

and clay content are also high. The siltstone is a moderately sorted

coarse silt with a secondary mode in the very fine sand.

Quartz grain extinction types for all rock units in the Bliss

Sandstone equivalent stratigraphically above the first dolomitic sand­

stone are remarkably similar (Table III). All show a non-undulatory

content close to 70 percent, an undulatory content close to 25 percent,

and a polycrystalline content close to 5 percent. These figures, plus

the observation that feldspar is present in most of the rock units in

question, lead me to conclude that, although the major source of sedi­

ment was a reworked deposit, another source of sediment could have been

primary crystalline rocks in the area, possibly Precambrian topographic

highs on the crystalline basement.

Immediately above the shale, siltstone, and dolomitic sandstone,

there is a thick quartzarenite unit (unit 9), shown petrologically by

thin section C in Table III. This unit is a moderately sorted coarse

sand with a near symmetrical size distribution curve. Above this unit

are some glauconitic and hematitic sandstone beds (units 10-11), shown 50 petrologically by thin section D in Table III. The most unusual feature of these beds is the large amount of glauconite and hematite surrounding the quartz grains (Figure 15). The physical limits of glauconite forma­ tion will be discussed in the section of this thesis on conditions of deposition, and related to the deposition of the Bliss Sandstone equiva­ lent. These units are composed of moderately well sorted medium sand and have a near symmetrical size distribution curve with a hint of fine skewness.

Overlying these beds is a thick sequence of sandy dolomite and dolomitic sandstone (units 10-17), shown petrologically by thin sec­ tions E and F, respectively, in Table III. The dolomitization is secon­ dary, as shown by quartz grains replaced by dolomite in Figure 16.

Dolomitization has obscured any recognizable fossils and may have re­ placed glauconite in parts of the formation. The upper sandstone units contain intraclasts of dolomite that weather out leaving tabular holes in the rock (Figure 17). Figure 18 shows the contact between the sand­ stone and an included intraclast. Figure 19 shows a typical quartz grain from the top unit in the Bliss Sandstone equivalent cemented by quartz overgrowths in optical continuity with the grain. This figure

is also typical of quartzarenites from southeast Arizona.

Sedimentary Structures

Small- and medium-scale wedge-planar and tabular-planar cross­

stratifications are present throughout the Bliss Sandstone equivalent

in the Morenci area. In the upper sandstone units, these 51

Figure 15. Glauconite Surrounding Quartz Grains; from Unit 10, Bliss Sandstone Equivalent near Morenci.

Crossed nicols, magnification X 50. 52

Figure 16. Zoned Dolomite Replacing Quartz Grains; from Unit 14, Bliss Sandstone Equivalent near Morenci.

Crossed nicols, magnification X 400. 53

Figure 17. Top Sandstone Unit of Bliss Sandstone Equivalent near Morenci.

Weathering pattern is caused by less resistant dolomite in­ traclasts weathering out, leaving behind the hard sandstone. Photo by Dr. Joseph F . Schreiber, Jr. 54

Figure 18. Contact between Dolomite Intraclast and Sandstone; from Unit 17, Bliss Sandstone Equivalent near Morenci.

Crossed nicols, magnification X 50. 55

Figure 19. Quartz Grain Showing Quartz Overgrowths Typical of Quartz- arenites in Southeast Arizona.

This grain is from Unit 17, Bliss Sandstone equivalent near Morenci. Crossed nicols, magnification X 150. 56 cross-laminations are very conspicuous, as the upper surfaces of the

laminations are lined with dolomite, which weathers out leaving the

sandstone standing in bold relief. At places where the formation is not cross-laminated, parallel laminations generally are displayed.

Thickness

The Bliss Sandstone equivalent is 90 meters thick in the Lime

quarry section (Appendix B). The formation thickens and thins in the

Morenci area, mainly at the expense of the lower beds. This probably

reflects a Precambrian basement of varied relief.

Paleontology and Age

Fucoidal markings on bedding planes (Figure 20) and Scolithus

tubes in beds locally are abundant in the Bliss Sandstone equivalent in

the Morenci area.

Fossils have been found in beds that were formerly in the

Longfellow Limestone, but which I have placed in the Bliss Sandstone

equivalent. Lingullela lineolta (Walcott) was found by Lindgren

(Walcott, 1912) in beds 5 meters above the top of his Coronado Quartz­

ite. The presence of this brachiopod may suggest a Middle to Late Cam­

brian age, but this is not definitive, as the only other known locality

is in northern Arizona, in the Middle Cambrian Tonto Group (Stoyanow,

1936, p. 478).

Because the Bliss Sandstone in New Mexico is conformably over-

lain by the El Paso Limestone, known to be of Early Ordovician age 57

Figure 20. Fucoidal Markings on Bedding Plane, Bliss Sandstone Equiva­ lent near Morenci.

Photo by Dr. Joseph F. Schreiber, Jr. 58

(Hayes and Cone, 1975, p. 50), it is probable that the Bliss Sandstone equivalent in the M o r e n d area is of Late Cambrian age.

Contacts

The basal contact of the Bliss Sandstone equivalent with the underlying Precambrian rocks is unconfonaable and sharp. The Precam- brian rocks generally are very weathered, and one must go 10 or more meters down-section to find any fresh looking rocks. The formation is conformably overlain by the El Paso Limestone, although in some areas the El Paso has been eroded away. The contact can be placed where the sandy dolomite and dolomitic sandstone of the Bliss Sandstone equiva­ lent give way to the relatively pure dolomite and limestone of the El

Paso. CONDITIONS OF DEPOSITION

Introduction

McKee (1951) has shown on his isopach map of the Cambrian that southeast Arizona was part of a slowly sinking shelf covered by water which connected the Cordilleran and Sonoran geosynclines. Eardley

(1949, pi. 3) termed this shelf the "Arizona Sag". This shelf was bor­

dered on the north by the Defiance Positive area and on the south by the

Ensenada Positive area.

The Bolsa Quartzite is generally believed to represent shallow

water nearshore deposition in a sea transgressing from the southwest

over a peneplain carved on Precambrian rocks (Lochman-Balk, 1971). The

upward decrease in grain size, feldspar content, and cross-stratification

all indicate an increasing depth of water and a greater distance from

the source area as deposition progressed (Hayes and Landis, 1965, p.

7). Although the above paragraphs describe the general depositional

setting for the Bolsa Quartzite, a number of localities must be elabo­

rated on further.

Dos Cabezas and Chiricahua Mountains

Bowie Mountain (Figure 21), located between the Dos Cabezas and

Chiricahua Mountains and held up by a thick resistant quartzite member

of the Pinal Schist, has been interpreted by Sabins (1957a, p. 470) as

a Precambrian monadnock. To the. west of Bowie Mountain, in the Dos

Cabezas Mountains, the Bolsa Quartzite contains a thick basal

59 Figure 21. Bowie Mountain, between the Dos Cabezas and Chiricahua Mountains.

Bowie Mountain is composed of a very resistant quartzite member of the Pinal Schist, and is the probable source of the basal conglomerate of the Bolsa Quartzite in the Dos Cabezas Mountains. 61

conglomerate composed of well-rounded quartzite pebbles, cobbles, and

boulders. Lenses and beds of well-rounded quartzite pebble conglomer-

, ate also occur throughout the lower part of the formation. Sabins

(1957a, p. 471) states that the monadnock that makes up Bowie Mountain

was the source of this conglomerate. I would tend to agree, as the

Bolsa Quartzite in the Dos Cabezas Mountains rests on a quartz monzonite

and does not have a local source for the quartzite pebbles, cobbles, and

boulders of the conglomerate. There is additional evidence, however.

The basal part of the Bolsa Quartzite in the Dos Cabezas Mountains has

a fluvial aspect to it; the basal conglomerate thickens and thins abrupt­

ly, suggesting channels, and the lenses and beds of pebble conglomerate

in the overlying beds are also suggestive of channels. A striking fea­

ture has to be the roundness of the components of the conglomerate com­

pared to the subrounded to subangular pebbles normally found in the

Bolsa. This is suggestive of some kind of transport, probably fluvial,

for the rocks to have been deposited in such a condition. Fluvial de­

posits would have to come from the east, the Bowie Mountain area, as

the sea was transgressing from a westerly direction.

East of Bowie Mountain, in the northern Chiricahua Mountains

where the Bolsa Quartzite rests unconformably on the Pinal Schist, no

basal conglomerate is evident (Figure 22). Apparently, after the sea

had advanced over and/or around Bowie Mountain, there was no longer a

source for the basal conglomerate. 62

Figure 22. Contact between the Pinal Schist and Bolsa Quartzite in the Northern Chiricahua Mountains.

Point of hammerhead is at point of contact. Note the ab­ sence of a basal conglomerate. 63

Swisshelm Mountains

In the northern Swisshelm Mountains and in the Barren Hills a few kilometers to the northwest of the Swisshelms, a sedimentary se­ quence occurs in the Bolsa Quartzite which is quite unlike those found elsewhere and which apparently has never been described. The author believes this section, which shows up especially well in the Barren

Hills, to be a clastic tidal flat deposit.

The Bolsa Quartzite in this area consists of a coarse-grained sandstone to granule conglomerate with variable sorting, characterized by small-scale wedge-planar and trough cross-stratification. The beds are separated by numerous thin lenticular shaly partings, and range in thickness from 25 centimeters to 1 meter. Fragments of shale are typi­ cally included near the base of the sandstone beds, but may be found in any part. Thin lenses of granule conglomerate underlie many of these sandstone beds and probably represent scours. The upper surfaces of the sandstone beds are undulating and covered by a thin veneer of clay, possibly representing clay drapes. Many of the sandstone beds are bur­ rowed, and Scolithus tubes locally are abundant. Bedding is generally lenticular because the wedge-planar cross-stratification fills wide planar erosional scours. Cross-stratification typically dips in many directions.

Hereford (1977) found essentially the same stratigraphic se­ quence in his Facies D and Facies E of the Tapeats Sandstone in central

Arizona. He interpreted both facies as tidal flat environments.

Hereford (1977, p. 205) further suggests that the coarse detrital 64 fragments and granules may have been lag conglomerates. The thin inter­ beds of siltstone and shale suggest that deposition may have been fre­ quently interrupted, and the beds of coarse-grained shale fragments may have been deposited from suspension. The detrital shale fragments in the sandstone were probably derived by undercutting and erosion of the

fine-grained sediments. Seeland (1969) has suggested that many of the sedimentary structures associated with transgressive sandstones may have been extensively, but not entirely, reworked by the advancing sea. This may account for the lack of many of the sedimentary structures normally associated with clastic tidal flat deposits, which were summarized by

McClure (1977). Immediately above the Bolsa Quartzite is the typical

tidal flat facies of the Abrigo Formation, resembling those described by McClure (1977) from areas to the west.

Morenci Area

One of the more striking features of the Bliss Sandstone equiva­

lent in the Morenci area is the abundance of glauconite. Glauconite is

rarely encountered in the Bolsa Quartzite, although is is quite common

in the overlying Abrigo Formation. Cloud (1955) gives an excellent sum­

mary of the physical limits of glauconite formation with the following

conclusions. Glauconite is known to originate only in water of normal

salinity. Glauconite formation requires slightly reducing conditions

and is facilitated by the presence of decaying organic matter. Depth

of formation is normally moderate to shallow, and a moderate temperature

is required. Sedimentary influx is slight, probably just enough to

provide needed elements, micaceous minerals, or bottom muds of high iron 65 content. Glauconite is found mainly in calcareous detrital sediments and is commonly associated with remains and fecal pellets of sediment- ingesting organisms.

The Bliss Sandstone equivalent was probably deposited in a ma­ rine environment much as the Bolsa Quartzite was. The exact relation of the Bliss Sandstone equivalent to the Bolsa Quartzite is unclear.

Stoyanow (1942, p. 1265) believed that the deposition of the Coronado

Quartzite did not correspond to the deposition of the Bolsa Quartzite or to the sandy facies of the Abrigo Formation, but that it marked the initial stage of a Late Cambrian-Early Ordovician transgression that culminated in the deposition of the Longfellow Limestone.

Sedimentation probably took place in shallow water relatively far from shore where sandstones and carbonates accumulated. Water depth was less than 50 meters, and the sediments formed a soft sea floor.

Moderate currents can be inferred from the presence of intraclasts; ir­ regularly laminated, cross-laminated, and poorly bedded sediments; and abundant quartz grains of varying size. These currents would tend to cause the bottom to be agitated, so the glauconite probably formed in the bottom muds. Some was transported into the area, as shown by the rounding of some grains. The compacted and squeezed look of some of the glauconite suggests incorporation of the glauconite into the sediments before the glauconite had hardened. Glauconite in the Bliss Sandstone equivalent has been replaced in many instances by hematite or limonite, and possibly by carbonate minerals. 66

Regional Relations of the Cambrian Strata in Southeast Arizona

Kelley and Silver (1952) and Sabins (1957a, p. 471) believed that the Bolsa Quartzite was a time-transgressive unit laterally con­ tiguous with the Bliss Sandstone, and that the Abrigo Formation was laterally contiguous with the El Paso Limestone. Epis and Gilbert

(1957) and Epis (1958) have shown that the El Paso Limestone overlies the Abrigo Formation in the Swisshelm and Pedregosa Mountains, and the

Abrigo has a clastic facies near its top that they correlated with the

Bliss Sandstone. Gilluly (1956, p. 24-26) has stated that the sandstone / beds found in the upper Abrigo represent a regressive sandstone that remained at sea level till the advent of the Devonian sea, and that Or­ dovician rocks were not deposited west of the Sulphur Spring Valley, as there is no evidence that any rocks were eroded away from the top of the

Abrigo. Where the Abrigo Formation is overlain by Devonian rocks, the contact is generally a paraconformity with no scours or channels.

Figure 23, adapted from Epis (1958, p. 2755), shows the inferred stratigraphic relations of Cambrian strata in southeast Arizona. Figure 23. Inferred Stratigraphic Relations of Cambrian Formations in Southeast Arizona. SUGGESTIONS FOR FUTURE STUDY

Two problems for future study were recognized during the course of this study. The relationship of the Coronado Quartzite and Long­ fellow Limestone to the Bliss Sandstone should be studied in detail.

Although it has been established that there is a strong lithologic si­ milarity between the two units, a detailed petrologic and paleontologic study needs to be made so that the Bliss Sandstone can be formally ex­ tended into Arizona and the Coronado Quartzite retired, as the Long­ fellow Limestone has been.

In this thesis it can be seen that a facies change exists in the Bolsa Quartzite between the east and west sides of the Sulphur Spring

Valley and between the Dragoon and Little Dragoon Mountains. A further investigation into whether the facies are tectonically or depositionally controlled should be made. McClure (1977, p. 29) conjectured a relation­ ship between rapid facies changes in the Abrigo Formation and the later­ al displacement in the Paleozoic and Mesozoic as discussed by Purves

(1976) and Titley (1976), respectively. Perhaps additional study could throw some light on this problem.

\

68 APPENDIX A

CAMBRIAN QUARTZITE LOCALITIES EXAMINED

1. Mule Mountains: N*$ SWk Sec. 7, T. 23 S., R. 24 E., Bisbee Quadran­ gle, Cochise County, Arizona. Examined Hayes and Landis' (1965) measured section of Bolsa Quartzite and Abrigo Limestone.

2. Whetstone Mountains: NWk SE^ Sec. 36, T. 17 S., R. 18 E., Benson Quadrangle, Cochise and Pima Counties, Arizona. Examined section of Bolsa Quartzite and McClure's (1977) measured section of Abrigo Formation.

3. Dragoon Mountains: NEk Sec. 24, T. 17 S., R. 23 E. and S0g NW*% Sec. 19, T. 17 S., R. 24 E., Pearce Quadrangle, Cochise County, Arizona. Examined section of Bolsa Quartzite and Abrigo Formation.

4. Little Dragoon Mountains: SE^s Nt% Sec. 16, T. 15 S., R. 22 E., Dragoon Quadrangle, Cochise County, Arizona. Examined Gilluly's (1956) measured section of Bolsa Quartzite and Abrigo Formation near Seven Dash Ranch.

5. Johnny Lyon Hills: NW% SE^s Sec. 21, T. 14 S., R. 21 E., Dragoon Quadrangle, Cochise County, Arizona. Examined section of Bolsa Quartzite and Abrigo Formation.

6. Swisshelm Mountains: NWk NW$i Sec. 2, T. 20 S., R. 27 E., Swisshelm Mountain Quadrangle, Cochise County, Arizona. Examined Epis and Gilbert's (1957) measured section of Bolsa Quartzite, Abrigo Forma­ tion, Upper Cambrian Sandstone, Dolomite, and El Paso Limestone.

7. Barren Hills: SWk Sec. 6, T. 19 S., R. 27 E., Squaretop Hills Quadrangle, Cochise County, Arizona. Examined section of Bolsa Quartzite and Abrigo Formation.

8. Dos Cabezas Mountains: W% NW*s Sec. 4, T. 15 S., R. 27 E., Dos Ca- bezas Quadrangle, Cochise|County, Arizona. Measured section of Bolsa Quartzite and Abrigo Formation (Appendix B).

9. Northern Chiricahua Mountains:

a. SEJj NW% Sec. 20, T. 26 S., R. 31 E., Vanar Quadrangle, Cochise County, Arizona. Examined Sabins' (1957a) measured section of Bolsa Quartzite and El Paso Limestone at Blue Mountain.

69 70

b. NW*c NW*£ Sec. 1, T. 15 S., R. 28 E., Cochise Head Quadrangle, Cochise County, Arizona. Examined Sabins' (1957a) measured section of Bolsa Quartzite and El Paso Limestone at Apache Pass.

10. Phelps Dodge Lime Quarry near Horenci: S% St% Sec. 8, T. 4 S., R. 30 E., Clifton Quadrangle, Greenlee County, Arizona. Measured sec­ tion of Coronado Quartzite and lower Longfellow Limestone (Appendix B).

11. Silver City, New Mexico: SW% NWk Sec. 9, T. 18 S., R. 14 W . , Silver City Quadrangle, Grant County, New Mexico. Examined section of Bliss Sandstone and El Paso Limestone. APPENDIX B

MEASURED STRATIGRAPHIC SECTIONS

Dos Cabezas Mountains

NW% Sec. 4, T. 15 S., R. 27 E., Dos Cabezas Quadrangle, Cochise County, Arizona. Section measured in a south-southeasterly direction on the dipslope of the ridge to the south of Arizona state highway 186. Section can be reached by taking the dirt road to the south about one mile east of the town of Dos Cabezas. Follow road about .7 mile to the Chiricahua Ranches office, located at the gap in the ridge. Section is on ridge to the east of the office. See Figure 24.

Cambrian:

Abrigo Formation (incomplete):

Unit Unit Thickness No. Description Feet . Meters

Copper Queen Member

7 Dolomite, very sandy; light brownish gray (SYR 6/1), weathers same; fine- to medium-crystalline; thinly laminated; thin interbeds of dolomitic sandstone ...... Unmeasured

Sandy Member

6 Quartzarenite; medium gray (N5), weathers very light gray (N7); fine to medium sand, angular to subangular, moderately sorted; minor amounts of hematite, micas, and feldspar altering to seri- cite; silica cement with some clay; thick-bedded with wedge-planar and tabular-planar cross­ stratification; well exposed, forms resistant ledge on dipslope...... 22.0 6.7

5 Quartzarenite; very light gray (N7), weathers moderate reddish-brown (10R 4/6); coarse to me­ dium sand, subrounded to subangular, moderately sorted; slightly feldspathic; silica cement;

71 Figure 24. The Dos Cabezas Section.

Section measured from base of prominent rock unit on left, across saddle and down dipslope on right. Chiricahua Moun­ tains in background. 73

Unit Unit Thickness No. Description Feet Meters

very resistant; interbedded with a much less resistant friable quartzarenite; very pale orange (10YR 8/2), weathers moderate reddish brown (10R 4/6); coarse to medium sand, subround­ ed to subangular, moderately sorted; slightly feldspathic, abundant tremolite; thin- to thick- bedded with tabular-planar cross-stratification; well exposed, forms dipslope, with resistant beds forming ledges; Scolithus tubes abundant in friable beds, rare in resistant beds ...... 292.0 89.0

Thickness of Sandy Member ...... 314.0 95.7

Middle Member

4 Siltstone, shaly; moderate brown (SYR 3/4), weath­ ers dark reddish-brown (10R 3/4); silt to very fine sand, subrounded to subangular, very poorly sorted; clayey matrix; some hematite staining; very thin to shaly bedding; poor exposure, forms saddle ...... 43.0 13.1

3 Dolomite, sandy; medium dark-gray (N4), weathers dark yellowish-brown (SYR 3/4); medium- to fine- crystalline; very clayey; sand grains are fine to medium sand, subangular to subrounded; some hema­ tite grains; thick single bed; gnarly weathering; good exposure, forms resistant bed in middle of saddle ...... 1.0 0.3

2 Siltstone, shaly; same as unit 4 ...... 43.0 13.1

Thickness of Middle Member ...... 87.0 26.5

Basic igneous dike ...... 17.0 5.2

Lower Member

1 Homfels; brownish black (SYR 2/1) and dark yellowish- brown (10YR 4/2), weathers moderate brown (SYR 4/4); aphanitic, with lenses of unaltered pyrite, limonite pseudomorphs after pyrite, and laminae of quartz grains altering to sericite; very dense; thin-bedded, with the finer material forming re­ sistant laminae 5 to 10 mm thick; apparent original composition was limy siltstone with finer grained 74

Unit Unit Thickness No. Description Feet Meters

claystone interbeds; well to poorly exposed, forms gentle dipslope...... 49.0 14.9

Thickness of Lower M e m b e r ...... 49.0 14.9

Total thickness of incomplete Abrigo Formation 450.0 137.1

Bolsa Quartzite:

5 Homfels; light gray (N7), weathers moderate yellowish-brown (10YR 5/4); apanitic; microcrys­ talline quartz, quartzite clasts, feldspars and micas, all altering to sericite; siliceous; thin- to thick-bedded; original composition could have been a clean siltstone with some coarser grained areas; good exposure, forms resistant ledge on d i p s l o p e ...... 16.0 4.9

4 Subarkose, siliceous; pale red (5R 6/2), weathers dusky red (5R 3/4); medium to coarse sand, sub-' rounded, poorly sorted; lenses of medium pebble conglomerate; some hematite staining; feldspars mostly orthoclase, some plagioclase, all altering to sericite, make up 10 percent of rock; silica cement with some clay; thin-bedded; good expo­ sure, forms gentle dipslope ...... 62.0 18.9

3 Subarkose, siliceous; moderate yellowish-brown (10YR 5/4), weathers pale red (10R 6/2); coarse to very coarse sand, subrounded, poorly sorted; some hematite staining; feldspars mostly ortho­ clase, but more plagioclase than in unit 4, al­ tering to sericite, make up 15 percent of rock; clayey matrix; thin- to thick-bedded; good expo­ sure, forms back side of ridge ...... 89.0 27.1

2 Subarkose, siliceous; medium light-gray (N6), weathers moderate brown (SYR 3/4); coarse to very coarse sand, granules, fine pebbles, sub- angular to subrounded, very poorly sorted, lenses and beds of well-rounded medium pebble conglomer­ ate; hematite staining; feldspars mostly ortho­ clase, some plagioclase, all altering to sericite make up 20 percent of rock; clayey matrix; bedding obscure with tabular-planar cross-lamination; good exposure, forms prominent ridge ...... 48.0 14.6 75

Unit Unit Thickness No. Description Feet Meters

1 Quartzite pebble-cobble-bounder conglomerate; pale yellowish-brown (10YR 6/2), weathers same; boulders are as large as 1 meter, generally much smaller, average about 20 centimeters; well-rounded, very poorly sorted; matrix is clayey, coarse-grained, subangular to subround­ ed, moderately sorted orthoclase altering to sericite, make up about 5 percent of matrix; massive; good exposure, forms lower part of prominent ridge; unconformity at base ...... 17.0 5.2

Total thickness of Bolsa Quartzite ...... 232.0 70.7

Unconformity

Precambrian:

Rattlesnake Point Granite:

1 Quartz monzonite, greenish gray (5GY 6/1), weathers light brown (SYR 5/6); coarse-grained with granit­ ic porphyritic texture, abundant large light col­ ored euhedral feldspar phenocrysts, milky quartz, and dark greenish-gray ferromagnesian grains; well to poorly exposed, forms slope at base of ridge . Unmeasured 76

Phelps Dodge Lime Quarry, Clifton

S*5 S\h Sec. 8, T. 4 S., R. 30 E . , Clifton Quadrangle, Greenlee County, Arizona. Section measured in a westerly direction from floor of ravine across from quarry. Section can be reached by taking the road that turns off to the east from U. S. Highway 666 at the old Clifton rail­ road station. Follow the road up the west side of the San Francisco River about .7 mile to the bridge. Cross the bridge and follow the road up the east side of the river about 2.5 miles to the access road to the Phelps Dodge Lime Quarry (look for the aerial tramway). Follow access road up the hill to the top, then along the top to where the road makes a broad U to go into the quarry. The section is in the ravine inside the U. See Figure 25.

Ordovician:

El Paso Limestone (unmeasured):

Unit Unit Thickness No. Description Feet Meters

1 Dolomite; grayish red (5R 4/2) weathers yellow­ ish gray (5Y 8/1); fine- to medium-crystalline; irregularly laminated, thinly bedded; good ex­ posure, caps hill; contains Ordovician fossils Unmeasured

Bliss Sandstone equivalent, consisting of the lower member of the Long­ fellow Limestone and the Coronado Quartzite:

17 Quartzarenite; very pale orange (10YR 8/2), weathers moderate yellowish-brown (10YR 5/4); coarse to medium sand, subrounded to subangular, moderately sorted; abundant intraclasts of me­ dium to fine crystalline sandy dolomite; silica cement in part, becoming more dolomitic near the intraclasts; thick-bedded with tabular- planar cross-stratification; weathers differ­ entially, with intraclasts much less resistant than the surrounding rock weathering out leaving tabular shaped holes; well exposed, forms cliff near top of h i l l ...... 16.0 4.9

16 Dolomite, sandy; pale brown (SYR 5/4), weathers moderate yellowish-brown (10YR 5/4); medium- to coarse-crystalline; abundant hematite between rhombs; small amounts of fine to coarse sand, subangular to angular, poorly sorted; slightly 77

I I

Figure 25. Lime Quarry Section near Morenci.

Section measured from bottom of ravine to top of hill. Pic- ture taken from Phelps Dodge lime quarry. 78

Unit Unit Thickness No. Description Feet Meters

conglomeratic at base with quartzite pebbles as large as 25 mm; thick-bedded to massive; well ex­ posed, forms steep h i l l s l o p e ...... 61.0 18.6

15 Quartzarenite; yellowish gray (5Y 7/2), weath­ ers grayish orange (10YR 7/4); medium sand, sub­ rounded, moderately sorted; contains intraclasts of very silty fine-crystalline dolomite, but not as numerous as in unit 17; silica cement in part, becoming more dolomitic near intraclasts; hematite grains and staining; thick-bedded; weathers dif­ ferentially, with the intraclasts less resistant than the surrounding rock, but generally more re­ sistant than those in unit 17; well exposed, forms cliff on h i l l s l o p e ...... 14.0 4.3

14 Dolomite, sandy; pale red (5R 6/2), weathers pale brown (5YR 5/2); fine- to medium-crystalline; hematite grains and staining, glauconite moder­ ately abundant; moderate amount of fine to medium sand, subrounded, moderately sorted; possible fos­ sils but dolomitization has obscured any recog­ nizable structures; thick-bedded; well exposed; forms base of c l i f f ...... 5.5 1.7

13 Dolomite, sandy; pale brown (SYR 5/4), weathers moderate yellowish-brown (10YR 5/4); medium crys­ talline; hematite grains and staining; moderate amounts of medium to coarse sand with granules near base; unit becomes sandier toward top; subangular, moderately sorted; pisolitic structures are faintly apparent in the lower part of the unit, but details have been obscured by dolomitization; Scolithus tubes present throughout unit; thick- bedded; well exposed, forms steep hillslope with some minor c l i f f s ...... 86.0 26.2

12 Quartzarenite, dolomitic; pale brown (SYR 5/2), weathers moderate brown (SYR 4/4); fine sand to granules, subangular, poorly sorted; hematite staining; thick-bedded to massive; weathers dif­ ferentially with granules more resistant; well exposed, forms prominent r i d g e ...... 37.0 11.3

11 Quartzarenite, glauconitic and hematitic; dusky red (5R 3/4), weathers same; coarse sand, sub­ rounded, well sorted; glauconite and hematite in 79

Unit Unit Thickness No. Description Feet Meters

patches between quartz grains, hematite stain­ ing; thin-bedded; well exposed, forms slope be­ neath ridge ...... 15.5 4.7

10 Quartzarenite, glauconitic, dusky yellowish- green (10GY 3/2) weathers dusky yellow-green (5GY 5/2); medium to coarse sand, subrounded, moderately sorted; glauconite in patches between quartz grains; hematite grains and staining; thin-bedded; well exposed, forms slope ...... 10.0 3.0

9 Quartzarenite; light gray (N7), weathers grayish orange-pink (SYR 7/2); mostly medium sand with patches of fine sand and coarse sand, subrounded, moderately sorted; silica cement; hematite grains and staining; thick-bedded, well exposed, forms c l i f f ...... 26.0 7.9

8 Quartzarenite, dolomitic; dusky yellow-green (5GY 5/2), weathers grayish red (5R 4/2); very fine sand with granules interspersed throughout, subrounded, moderately sorted; dolomitic cement; glauconite and hematite in patches between quartz grains; fucoidal markings present; thin- bedded, laminated; well exposed, forms slope at base of cliff ...... 0.5 0.2

7 Shale; dark greenish-gray (5G 6/1), weathers same; very thin to shaly bedding; poor exposure, forms slope covered by debris from unit 9 . . . . 4.0 1.2

6 Quartzarenite, dolomitic; grayish brown (SYR 3/2), weathers dark reddish-brown (10R 3/4); fine sand, subangular, well sorted; dolomitic cement; hematite and glauconite grains, hema­ tite staining; thin-bedded; well exposed, forms thin resistant ledge between shale units .... 1.5 0.5

5 Shale, same as unit 7 ...... 3.5 1.1

4 Siltstone, sandy; greenish gray (5G 6/1), weathers moderate olive brown (5Y 4/4); coarse silt, fine to coarse sand, subrounded, very poorly sorted; ■ clayey matrix; hematite grains and staining; thin- bedded; fair exposure, forms slight ledge between shale u n i t s ...... 2.0 0.6 80

Unit Unit Thickness No. Description Feet ' Meters

3 Shale, same as unit 7 ...... 3.0 0.9

2 Quartzarenite, dolomitic; grayish orange (10YR 7/4), weathers moderate yellowish-brown (10YR 5/4); fine to coarse sand, subrounded, poorly sorted; dolomitic cement; hematite staining, some micas; thick-bedded; good exposure, forms l e d g e ...... 6.0 1.8

1 Quartz-quartzite pebble conglomerate; moderate yellowish-orange (10R 6/6), weathers light olive gray (5Y 6/1); pebbles fractured, subrounded; matrix is clayey, coarse to very coarse sand, subrounded, moderately sorted; hematite stain­ ing; thin-bedded; good exposure, forms base of ledge; unconformity at b a s e ...... 0.5 0.2

Total thickness of Bliss Sandstone equivalent 292.0 89.1

Unconformity

Precambrian:

Metcalf Granite:

Granite; weathers dark reddish-brown (10R 3/4), unweathered color cannot be determined from out­ crop due to the deep weathering of the granite; coarse-grained; light gray quartz, feldspar mostly orthoclase, some perthite, very little plagioclase; biotite, hornblende, magnetite or ^ ilmenite; poorly exposed, forms slope covered by debris from overlying quartzarenites ...... Unmeasured REFERENCES CITED

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