By Stoyanow (1936) at the Excellent Exposure of the Beds on Mount Martin in the Male Mountains

The Devonian stratigraphy of Cochise, Pima, Santa Cruz Counties, Arizona and Hidalgo County, New Mexico

Item Type text; Thesis-Reproduction (electronic)

Authors LeMone, David V., 1932-

Publisher The University of Arizona.

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Link to Item http://hdl.handle.net/10150/553919 THE DEVONIAN STRATIGRAPHY CF COCHISE, PIMA, SANTA CRUZ COUNTIES, ARIZONA AND HIDALGO COUNTY, NEW MEXICO

by David V* I# Mona

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A Thesis Submitted to the Faculty of the DEPARTMENT OF GEOLOGY In Partial Fulfillment of the Requirements For the Degree of

MASTER OF SCIENCE In the Graduate College

UNIVERSITY OF ARIZONA

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STATEMENT BY AUTHOR

This thesis has been submitted in partial fu lfill­ ment of requirements for an advanced degree at the University of Arizona and is deposited in the University Library to be made available to borrowers under the rules of the library• Brief quotations from this thesis are allowable with­ out special permission, provided that accurate acknowledgement of source is made. Requests for permission for extended quo­ tation 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 their Judgment the proposed use of the material is in the interests of scholarship# In all other instances, however, permission must be obtained from the author.

SIGNED: %/Kg -

APPROVAL BY THESIS DIRECTOR This thesis has been approved on the date shown below:

2- ^ Date ofessor of Geology TAB IE OF CONTENTS

INTRODUCTION Purpose and Scope of Investigation .... Nature and Extent of the Devonian Rocks Acknowledgements...... PRB-DEVONIAN ROCKS ...... Cochise, Pima, Santa Cruz Counties, Arizona and Hidalgo County, New Mexico ...... Ahrigo Formation ...... Rincon Limestone ...... Peppersauoe Canyon Sandstone El Paso Formation ...... Southwestern New Mexico ...... Southern Arizona and Northern Sonora, Mexico ... Central Arizona ...... Northern Arizona ...... Four Corners Area and Southwestern Colorado •••• DEVONIAN ROCKS ...... Cochise, Pima, Santa Cruz Counties, Arizona and Hidalgo County, New M exico...... Southwestern New Mexico ...... Southern Arizona and Northern Sonora, Mexico ... Central Arizona ...... Northern Arizona ...... Four Corners Area and Southwestern Colorado •••• PAIEONTOLOGY ...... MSTAMGRPHISM ...... STRUCTURE ...... DEPOSITI0NAL ENVIRONMENT ...... POST-DEVONIAN ROCKS ...... Cochise, Pima, Santa Cruz Counties, Arizona and Hidalgo County, New Mexico PAIEOGBOGRAPHT, ...... Page APESNDIX----DESCRIPTIONS OF MEASURED SECTIONS .... 63 REFERENCES CITED ...... 105

LIST OF ILLUSTRATIONS P late 1. Correlation of Upper Devonian Rocks ...... in pocket Figure 1* Location of Thesis Area ...... in pocket 2 . Generalised Devonian Lithofacies Map ...... in pocket 3. Pre-Devonian Paleogeographie Map ...... in pocket *+• Distribution of Devonian Rocks in pocket 5. Basal Post-Devonian Paleoge©graphic Map ..... in pocket

, ill ABSTRACT

The Devonian rocks of the southwest consist of essen­ tially five basic facies and formations• They are: the euxinio black shale Fereha formation, the marginal geosynclinal facies of the Cerros de Murcielagos sequence and the Muddy Peak lime* sto n e, the coarse c la s tic Swisshelm form ation, the embayment or near shore Northeastern Arizona and Southwestern Colorado se­ quence, and the stable shelf Martin formation* Numerous other formations have been described in the literature, but represent only minor lithologic variations and paleontological subdivisions* late Devonian seas advanced across Arizona from the south­ west in the Caborea region of Northern Sonora, Mexico and from the northwest from the area of the Cordllleran Geosyncline* A positive area existed in East Central and Northern and Central Western New Mexico* Evidence of arching with closure towards the southwest along the trend of "Mazatzal land" is shown in the post- Devonian Mississippian erosion surface. The existence of positive movements in th is arch is not e stab lish ed fo r Devonian sediments* Mazatzal land existed probably only as a few offshore islands in Devonian time in Central Arizona* INTRCDUCTICE

Pnrtiose and Scone of laygtlgatlop

The purpose of this paper is to present results of a study of Devonian roeks in southeastern Arizona and adja­ cent lev Mexico* A series of sections measured hy the writer are given in the appendix# These show stratigraphic vari­ ation in the Devonian within the area studied, and have been used in interpreting the sedimentary history# Available data from the literature have been compiled for the thesis area and bordering areas in an attempt to establish a concept of the regional framework of Devonian sedimentation, distribu­ tion of facies, and valid usage of formations! names. Problems of regional and local correlation of Devonian rooks are discussed. Regional correlations are shown to depend on the concept of the sedimentary framework accepted, but local correlations can be more securely based on details of lithol­ ogy. (fete result of the study has been the delineation of areas that would probably be most advantageous for further research on the Devonian of the region#

Nature and Extent of the Devonian Rocks

Within the thesis area, Southeastern Arizona and South­ western New Mexico, the Devonian rocks consist largely of carbonate 2 formations, predominantly dolomite, in the western part, and clastic rocks, predominantly shales, in the eastern part. Devonian stratigraphy and lithology Is regionally com­ plex (Plate 1), bat the rocks consist for the most part of fine elastics and dolomites with local variations. The thickness of the Devonian sequence ranges from over 1300 feet in the ex* trams northwestern corner of Arizona to a feather edge in the southern extension of the transcontinental arch, (Bardley, 1951), in northeastern Arizona, southwestern Colorado and Northwestern Hew Mexico. The exposures of the Devonian rocks are discontinuous . in the southwestern half of Arizona, southwestern Hew Mexico, Mexico, Nevada and p o rtio n s of southw estern Colorado. The rocks are exposed commonly in belts along the fronts of the ranges• Correlation within a belt is excellent, but regional correlation is questionable. The distance between outcrop belts ranges from several miles to hundreds of miles. The Colorado River drainage system, and the western edge of the Colorado Plateau have continuous outcrops. In other areas the Devonian rocks are known from subsurface information. The nomenclature of the Devonian is complex and not clearly understood, not only in the thesis area, but region­ ally. A number of formations described in the literature are based largely on faunal variation or peculiar facies. The lower contact of the Devonian is locally difficult to determine despite the fact that a time gap of two periods 3 exists between the Devonian and the underlying formations* Certain non*fossiliferous sandstone w its in Central and Northwestern Arizona, now considered to be Cambrian, nay aetually belong to the Devonian sequanta* The upper eon* taet is also difficult to determine precisely*

Initial guidance on the thesis was given by Mr* R* M* Byington of the Pan American Petroleum Corporation* The writer wishes to acknowledge the stimulating discussions and helpful suggestions concerning the many aspects of the Devonian he has enjoyed with his fellow graduate students and others* Dr. John lance, Dr. Donald Bryant, Dr* E* B. Mayo, Dr* W illard Pye and D r. Halsey M ille r, as w ell as other members of the faculty of the University of Arizona are gratefully acknowledged for their assistance in the prep* aration of this thesis* FRS ^DEVONIAN ROCKS

Cochisef Pima, Santa Cruz Countiesf Arizona and Hidalgo County, New Mexico

The relative ineessabillty of stratlgraphle sections, the pattern of economic development of mineral resources in Arizona and southern New Mexico, and the use of paleontolog­ ical evidence to indicate formation boundaries, have led to the present confusion that exists in the stratigraphic ter-- mlnology of the lower Paleozoic. The Devonian rocks of the thesis area are underlain by e ith e r the tipper Cambrian and Lower' Ordovician B1 Paso fo r­ mation, which occurs east of the Sulfur Springs valley in cen­ tra l Cochise County, or the Middle and Upper Cambrian Abrigo formation, vhleh occurs west of the Sulfur Springs Valley* Some discussion of the stratigraphic relationships' between these two formations and of the history of their nomenclature is necessary for a complete understanding of the Devonian stratigraphy* Abrigo Formation

The Abrigo formation within the thesis area is con** fined to central and western Cochise, Pima, and Santa Cruz Counties, Arizona (figure 3 ). O rdovician, S ilu ria n , Lower Devonian, and probably

■ " ' " ^ . 5 Middle Devonian rocks are absent in the dlseonforBlty with the overlying Martin formation* The eontaot of the Upper Cambrian with the Devonian is difficult to determine in many eases and the reeks are everywhere in apparent conformity* The Upper Cambrian beds are relatively flat-lying as may be exemplified in the Whetstone Mountains, where in the Cambrian rooks below the contact no more than 40 feet of stratigraphic difference was noted in over two miles laterally (Tyrrell, 1957)* The post-Upper Cambrian, pre-Devonian uplift was epelrogenlc throughout the thesis area* There is no evidence of channel­ ing in the Upper Cambrian* The Abrlgo formation shows no ob­ servable phenomena of s tru c tu ra l deform ation th a t is in terru p ted by the dlsconformlty* The Abrlgo formation becomes progressively younger in age to the east (McKee, 19&+7» Sabins, 1957)» thereby indicating a west to east transgression* , The Abrlgo form ation was named by Ransoms (190&+) fo r exposures in the Mule Mountains. Ransome described the forma­ tion as being predominantly thin bedded and conspicuously lam* inated due to alternation of thin irregular sheets of chert and gray limestoz» 4 The limestone layers are generally 2 to 3 inches thick and the chert beds are thinner» T ito uppermost rocks of the Abrlgo form ation of Ransoms have been separated into three cliff*forming formations in southeastern Arizona, each having separate regional areas of occurrence (Stoyanow, 1936)* The formations are the Copper 6 Queen limestone, the Rincon limestone, and the Feppersauce Canyon quartzite« The contact between the Upper Cambrian and the De­ vonian sequences is not always easily distinguishible, nor is the Devmiian everywhere in contact with one of the lithol­ ogic u n its described by Stoyanow as form ations. In a number of instances, typical of which is the Waterman Mountains sc* quence (MeGlymonds, 1957) f the contact is observable with no recognizable cliff-forming member below and with no known pa­ leontological evidence. The Copper Queen limestone was named by Stoyanow (1936) at the excellent exposure of the beds on Mount Martin in the Male Mountains. The unit forms a distinctive minor gray cliff below the slope-forming Martin formation. The thickness of the Copper Queen limestone at the type locality is 8l fe e t* The limestone is gradational into the underlying Abrigo for* nation. Individual beds are known to be gradational laterally. At the top of the unit, in contact with the Martin formation, an eight foot quartzite member, locally known as the “Parting quartzite*, grades laterally into a sandstone. The trilobite fauna of the Copper Queen limestone is younger than that of the Rincon limestone and the Feppersauce Canyon sandstone (Stoyanow, 1949). The area of distribution of the limestone is south-central Cochise County, Arizona.

Rincon limestone The Rincon limestone, named by Stoyanow (1936) from an exposure In the Whetstone Mountains, represents the upper­ most part of the Abrigo formation as limited by Bans one 190*t« It is typically a pink coarsely crystalline cliff-forming lime* stone in contact with the Devonian Martin formation. The Rin­ con limestone is 42 feet thick at the type locality; however, in the Whetstone Mountains it is variable from 15 to 90 feet (Tyrrell, 1957)• The limestone is gradational into the under­ lying Abrigo formation. Individual units are known to be gra­ dational laterally. The trilobite fauna of the Rincon limestone is younger than the Feppersauee Canyon sandstone and older than the Copper Queen limestone (Stoyanow, 1949)* The lithologic and cliff-forming character of the Rincon limestone and the • ■ . . . . . - ■ - , . ■ ■ Copper Queen limestone Indicates that they are probably facies equivalents• The area of distribution of the Rincon limestone is north central and western Cochise County, Santa Cruz County, and northw estern Pima County. .

Feppersauee Canyon Sandstone The Feppersauee Canyon sandstone was named by Stoyanow for exposures in Feppersauee Canyon in the northern Santa Cats- lina Mountains• The Feppersauee Canyon sandstone is a thin bedded alternating sequence of siliceous brown sandstone and pink quartzite which is apparently gradational into the under­ lying Abrigo formation* There is a possibility that the Fep­ persauee Canyon sandstone may be related to the “Parting quart­ zite” of the Copper Queen limestone type section. The trilobite 8 fauna of the Peppersauce Canyon sandstone is older than that of the Copper Queen limestone and the Rincon limestone (Stoya- now, 19^ 9)o The distribution of the sandstone is limited to the type area (figure 3 )» El Paso Formation The El Paso limestone was named by Richardson in 19CN- for 1200 feet of Ordovician rocks in the Franklin Mountains near El Paso, Texas. Richardson later (1908) restricted the El Paso limestone to the lower 1000 feet of Canadian rocks» Sabins (1955) extended the unit to the Chlrleahua Mountains and used the term formation rather than limestone as the El Paso beds in that area are predominantly dolomitic rather than calcareous• At the type locality the sequence is typl«- cally a gray fossiliferous dolomitic limestone which is massive to thin bedded, contains thin bedded chert similar to that of the Abrlgo formation, and weathers typically brownish in color. The El Paso formation occurs in eastern Cochise County, Arizona and Hidalgo County, Hew Mexico within the thesis area (figure 3 ). The El Paso formation is lithologically similar to the Abrlgo formation. There is an apparent lithologic change in the Sulfur Springs valley, a north-south valley in eastern Cochise County, from a typically more dolomitic sequence of El Paso formation to a typically more calcareous sequence of the Abrlgo formation. The El Paso formation is overlain by the Swisshelra formation and the Fereha formation within the thesis 9 a re a . Sabins (1957) proposed that the Abrigo and El Paso formations are equivalent and that they transgressed time lines by becoming progressively younger to the east* The El Paso formation as restricted by Richardson (1908) is later than the Abrigo form ation as described by Ransome (190*0 • Should symomoay be followed the earlier name Abrigo forma* tion should be extended into southern New Mexico and west Texas* However, for convenience, at present the practice is to consider that the occurrence of any Ordovician fossils indicates that the total formation is equivalent to the El Paso formation* An analogous situation exists between the basal Upper Cambrian and lower Ordovician Bliss sandstone (Richardson, 190*0 and the Bolsa quartzite (Ransome, 190*0, although in this ease the New Mexico-Arizona border has been serving as the boundary between the two formations* The west* ernmost occurrence of the Lower Ordovician fossils, and hence of the El Paso formation, is east of the Sulfur Springs valley in the Chiricahua Mountains. The Lower OrdovleianrDevonian contact is difficult to establish because of apparent conformity. There is ho recog* nizable cliff-forming unit or peculiar lithology to guide the stratigrapher, as is the case with the Abrigo formation* The dlfferentatlon is made, however, on the basis of color, type of carbonate, and the character of rocks above and below the 10 diseenforalty* The basal Dercmian Is eonmonly a dark gray to black, calcareous shale (within the thesis area), and a smooth slope-forming unit* The basal Devonian Swisshelm formation, a peculiar Devonian faeies apparently restricted to a local area in southeastern Arizona, is characteristically a reddish brown sandy dolomite (Bpls, et ale, 1957)* The uppermost El Paso formation, within the thesis area, is typically a slope and step-forming unit, of dolomite and shale * It weathers commonly to a buff or brown color*

Southwestern Haw Mexico

The pale ©geolog ie surface on which the Devonian was de­ posited in southwestern Sew Mexico is more complex than in the thesis area (figure 3). The stratigraphic section underlying the Devonian rocks becomes progressively younger to the east. The formations are, in order of their occurrence from west to east, the Upper Cambrian and lever Ordovician El Paso formation, the Middle and Upper Ordovician Montoya group, and the Silurian Fusselman dolomite. The El Paso formation (Sabins, 1955) or group (Kelly and Silver, 1952), previously discussed in some detail for the thesis area, thickens gradually to the east into west Texas, partially, at least, at the expense of the underlying Bliss sandstone. The formation becomes progressively younger in age to the east. It is possible that the overlying Montoya group, separated from the original El Paso formation by Rich­ ardson (1908) to include rocks of Champlainlan and Cincinnatian 11 age may arcs* time lines and grade Into the El Paso formation and not be recognized in Hidalgo County and eastern Coehlse Countyo The El Paso formation or group forms a feather edge against a positive area to the north in eentral and portions of northwestern Hew Msxieo as do a ll other pre-rBennsylvanlan sedim ents. The Montoya lim estone was named by Rlehardson (1908) to include the 250 feet of Champlainlan and Clnelxmatlan rocks of the E l Paso form ation as o rig in a lly d escrib ed . The Montoya is difficult to distinguish from the El Paso formation as the formations are apprently conformable. The accepted boundary at the type locality occurs at a non^eberty limestone contain* ing characteristic galena fossils. The Montoya group is over- la in disconformably by the Pusselman lim estone. The Montoya has been elevated to group rank by Kelly and Silver (1952) who define four formations, In ascending order, the Cable Canyon sandstone, the Upham dolomite, the Aleman formation, and the Cutter formation. The Cutter formation was originally the lower member of the overlying Silurian Fusselman dolomite as described by Barton (1916). The Montoya group is e ith e r truncated by erosion and forms an angular unconformity with the overlying Devonian or is an unrecognized facies of the more western El Paso formation. The truncation or facies change occurs at or near the Luna County w estern h erd er. The Montoya group Is in contact w ith Devonian reeks at the feathering out edge of the positive area 12 to the north (figure 3 ), The Fuss©loan limestone was originally described by Richardson (1908) from exposures in the Franklin and Hueeo Mountains, Texas• Dunham (1935) designated it as a dolomite because of its lithologic character• The formation includes rocks of Hiagaran and Alexandrian age (Flower, 1955)* The lower member of the formation as described by Darton* (1916) , is now included in the Montoya group• The Fusselman thins to the north in both the Sierra Cuehlllo and Caballe Mountains# The Fusselman is not present west of eastern lama County or Sierra County# ,

Southern Arizona, and Northern Sonora. Mexico In southern Arizona formations underlying the surface upon which Devonian sedimentation occurred include the Abrigo formation, the El Faso formation, and the longfellow limestone# The Abrigo formation and the El Paso formation relationships are discussed in detail in the section on the thesis area. The northern lim it of the Abrlgo-Devonian contact is approximately 30 miles north of the Pima County northern boundary at Winkle- man. At Clifton-Morenci in Greenlee County, the formation underlying the Devonian is known as the Longfellow limestone (lln d g ren , 1905). The Upper Cambrian and Lower Ordovician Longfellow limestone is 400 feet thick# It is similar lithol­ ogically to both the Middle andl Upper Cambrian Abrigo formation 13 and the Upper Cambrian and Lower Ordovician B1 Paso formation. Barton noted as early as 1925 the striking sim ilarity, MI ex­ amined these rocks in 1919 and was deeply impressed with the strong resemblance of the Longfellow and the El Paso lime­ stones •li An analogous situation exists with the underlying Coronado quartzite • The Upper Cambrian and possibly Middle Cambrian Coronado quartzite is related to the Middle Cambrian Bolsa quartzite and the Upper Cambrian and Lower Ordovician Bliss sandstone. West of the thesis area, little is known of Devonian and earlier stratigraphy* Cambrian and Devonian rocks in the Slate and Vekel mountains show much the same relationships that they do in the thesis area* Eldred Wilson (personal communi­ cation) reports that the only known recognizable Paleozoic for# mations in southwestern Arizona are in the Growler Pass area southwest of Ajo* No details of the Devonian stratigraphy and relationships are available there* In northern Sonora, the Esperanza limestone (Malchay and Velasco, 195*+), which is probably equivalent to the Abrlgo formation, underlies the Devonian at Cananea* The Capote quartz* ite underlying the Esperanza limestone is probably equivalent to the Bolsa quartzite* Near Caborea the Middle Cambrian Arrojos formation is the youngest definitely known preDevonian forma* tion* Ordovician and/or Silurian rocks may be present as a dolomltle sequence; however, the age of this sequence has not been established (Cooper and Arellano, 19*+6)» lb

Future work may establish the desirability of extending the Abrigo formation to include those rocks now referred to as Bsperanza limestone and Longfellow limestone» It is also prob-? able that the name Bolsa should be extended to Include the rocks now referred to as Capote quartzite and Coronado quartzite* C entral Arizona

The surface formed by the pre-Devonian rocks in Central Arizona may be subdivided into two provinces, a southern one with a Cambrian Troy quartzite and Younger Freeambrlan complex, and a northern one with a Tapeats sandstone and Older Precam* brlan complex (figure 3)* The dividing line between the two previnces is generally accepted as being in the Christopher Mountain area near Payson. In the southern Cambrian Troy quartzite and Younger PreCambrian complex in central Arizona, the contact of the pre- Devonian and Devonian sediments is a regional angular unconfor­ mity with respect to the Younger Precamhrlan Apache group (Ban- some, 1916)i In most areas the break appears to be a disconformity. The formation known to be in contact with the Devonian in most places is the Dripping Spring quartzite of the Apache group. The relationships would appear to he relatively simple and a problem only of distribution of formations; however, the quartzite and sandstone relationships of the area are one of the major problems. A basal Devonian (?) sand is developed at a number of localities within this area, eommonly occurring as a channel sand. The basic problem confronting the geologist working 15 In this area Is one of distinguishing between the Individual sandstones and quartzites whleh are easily confused. These units Include the Dripping Spring quartzite, the Troy quartz­ ite, and the Devonian basal sandstone. Moreover, it is possible that the formation called the Troy quartzite, considered to be Precambrlan by Ransoms (1915) and to be Cambrian by Darton (1932), may actually represent two different units of different ages# If so, the Cambrian "Troy quartzite", which contains fossils, might really be the Bolsa quartzite. The lithologic similarity is probably a result of the fact that the formations represent different generations of the same source sands# A careful ex­ amination, however, of the underlying formations and contacts, and the type of sedimentation, cementation, and color of the different formations will usually identify the units (A# Schrlde, personal communication)# The northern Tapeats sandstone and the Older Precambrlan complex is less difficult to work with# The Devonian rocks rest

x . on Precambrlan granite, the Older Precambrlan sequence, and the Tapeats sandstone# The Devonian beds would seem to represent either a complete or partial reworking of the Tapeats sandstone by advancing Devonian seas# Only partial reworking seems more probable# The lower and Middle Cambrian Tapeats sandstone and the Middle and Upper (?) Cambrian Troy quartzite would appear to have formed in two basins of deposition, as they are distinct lithologically# Typically the Cambrian Troy quartzite is a 16 medium to eearse grained sandstone, frequently a quartzite, that always occurs with the Younger Preeamhrian Apache group to whieh it is genetically related. The Tapeats sandstone is a coarse, poorly sorted eonglomeratle sandstone* The writer is of the opinion that the basil sandstones and quartzites represent the littoral facies of an advancing Cambrian sea* The Bliss sandstone, the Bolsa quartzite, the Cambrian Troy quartzite, the Tapeats sandstone and the Capote quartzite are all considered to be an equivalent littoral facies of an advancing Cambrian sea spreading from the Cordilleran Geo­ syncline* The formations referred to differ in lithology and age correlation* This may be simply explained as being the re­ sultant of differing rates of advancement of the shore lines and differing types of source rocks*

: ’ ‘ " " ; : 4 Horthern Ari gion*

The pre-Devonian rocks of northern Arizona form a dis- conformable contact with the Devonian rocks* The area discussed includes all of Arizona north of the central area and a section in the Harquahala Mountains in north central Yuma County (fig­ ure 3) ♦ The pre-Devonian rocks of the area in contact with the Devonian are the Tonto Group which includes, in ascending order, the Tapeats sandstone, the Bright Angel shale, and the Muav lime­ stone (Noble, 191*0* Between Beach Springs and Jerome, Arizona and surrounding the positive area in east Central Arizona, New Mexico, and Colorado, 17 the Bright Angel shale and the Muar line stone prohahly form a regional angular unconformity with the Devonian sequence* Ho sections are available to positively prove this* The strum* turally complex section in the Harquahala Mountains indicates a thin, but nearly normal Tapeats sandstone section (250 feet minimum) overlain by fossiliferous Cambrian shales (20 fe e t minimum) that may be correlated with the Bright Angel shale (Bldred Wilson, personal communication)* The diseonformity between the Devonian and pre-Devon* lan rocks in the northern area is always with the Muav lime* stone and never with the Bright Angel shale* The Grand Canyon area is the only region where the diseonf ormity is well marked; the underlying Muqv limestone is out by a number of erosion channels filled with calearenltes of Devonian age* In north­ western Arizona at the unconformity there is a sequence of non* fossiliferous beds that may be either post-Muav or Devonian in age* These beds are referred to as the Supra-Muav (Wood, 1955)* The beds may either be a regressive post-Muav facies or a trans­ gressive Devonian facies* The writer regards the Supra-Muav as a transgressive facies partially on the basis of the lack of fos- sils, which would be expected if the sparsely fossiliferous Muav were reworked and partially on the fact that the Tapeats sand­ stone of the Central Arizona area is reworked* Wood (1957) re*

• - ...... gards the Supra-Muav as a regressive facies* It is probable that the Bright Angel shale arid the Muav limestone, together, are facies equivalents to the A^rojos for­ mation, the Abrigo formation, the Esperanza line stone, the 18 Xongfellow limestone and the El Paso formation.

Four Corners Area and Southwestern Colorado

The Devonian rocks of the four corners area and south* western Colorado lie on the Cambrian Ignacio quartzite (Cross and Spencer, I 899) with probable local areas in which the De­ vonian is in contact with the pre-Cambrian# The Ignacio quartz­ ite presents a similar problem to that of the Tapeats sandstone in central Arizona# The Ignacio quartzite is in part of Devon* ian age (Barnes, 195*0 • The upper portion of the formation represents a reworked sand facies of an advancing Devonian sea while the lower part of the section consists of unreworked Cambrian rocks. The lithologic break between formationsr there­ fore , appears to be gradational# The actual formatlonal break is lower in the section and consists of san dlseonformably resting on sand; consequently, it is nearly impossible to lo* cate it precisely. The Ignacio quartzite may be correlated with the Tapeats sandstone and all other equivalent transgressive litto ral Cam­ brian and Ordovician basal sands as far south as the Capote quartzite and as far east as the Bliss sandstone. DEVONIAN ROCKS

Cochise| Pima, Santa Cruz CountiesT Arizona and Hidalgo CountyT New Mexico The Devonian rocks of the thesis area may be separated into two major divisions, which border each other at the Sul­ fur Springs v a lley in eastern central Cochise County (figure 3)« These are the western carbonate division, including the PAcacho de Calera formation (Stoyanow, 1936), the lower Ouray formation (Stoyanow, 1936), and the Martin formation (Ransome, 190*0, and the eastern elastic division, including the Percha Shale (Gordon, 1907) and the Swisshelm formation (Spls, et a l., 1957)♦ Martin Formation

The Martin limestone was named by Ransome (1904) for the exposures at Mount Martin near Blsbec* The unit has since been extended northward into central Arizona and because of lithologic variation designated the Martin formation (Huddle and Dobrovolny, 1952)* The Martin formation has been corre­ lated as far north as the Grand Canyon (McNair, 1951)• The Martin formation contains Upper and possibly some Middle De­ vonian rocks in western Cochise County, Santa Cruz County, and Pima County, Arizona (figure 4)» The belts of Martin formation are discontinuously

19 20 scattered throughout the thesis area west of the Sulfur Springs Valley# West of Tucson in Pima County only the Waterman Moun*? tains southeast of Sllverbell and the Growler Pass area souths west of Ajo contain sections of the Martin formation. The Martin formation throughout the thesis area is un* derlain by the Middle and Upper Cambrian Abrigo formation and o v erlain by the M lsslsslpplan Bscabrosa lim estone. Ransoms describes the Martin as rarely being topographieally eonspis* uous. The Martin beds average about four feet in thickness at the type locality. The most common beds are hard, dark gray compact limestones which alternate with beds of lighter hue and with calcareous shales of a decidedly pinkish tin t. The lower half of the formation has more shale than the upper half. The upper contact of the Devonian and the Mlsslsslpplan is dlffl* cult to determine. The lower contact in the type area is gene erally accepted as being at the "Parting quartzite" of the Copper Queen limestone member (Donald 1. Bryant, personal com? munlcatlon). The thickness of the formation at the type locality as measured by Ransom is 3*+0 f e e t. A thin section taken from an undisclosed horizon in the .. . . V C. . • * • - t i. .* -C - Martin formation by Titcoab (1932) indicates that it is an even, fine grained dark limestone with small veins of hematite-colored chert with included crystals of calelte. Two chemical analyses of the Martin formation show the following compositions: 21 Ransome (1904) Bonillas et al, (1916) Representative Sample Composite sample S i02 8*52 sio2 10*3 2 .0 A12°3» Fe2°3» A1203

FeO, T102) P20^ o*64 MgO 14*2 MgO 0.55 CaO 28.5 CaO 50.0? S o.2

An Insoluble residue examination by Titeomp (1932) of i 'f a representative sample from near the type locality showed a few small apatite crystals, chert, llmonlte, siliceous frag» ments of fossils, and a very few miscellaneous heavy minerals. The total Insoluble residue was 10.6# of the sample* The Martin formation at the type locality is largely comprised of calcareous beds, although an examination of the composite chemical analysis of Bonillas Indicates that some dolomite is present. The Martin formation is characteristically dolomitlc In its lithology. The Martin sequence at the type locality is typical either because of dedolomitisation (Cooper, 1957) or of the nature of environment of deposition of the car­ bonate. The Martin formation typically consists of 20 to 30 u n its of variously hued yellow, red, brown, and gray beds, in order of their importance, of dolomite, limestone, shale, sandstone, and chert. The basal one quarter to one third of the formation is 22 largely elastic within the thesis area# The Martin formation becomes more c la s tic northward Into c e n tra l Arizona (Stoyanow, 1936)# Carbonate rocks of the Martin have a very high slit content and are usually fine or medium grained# Chert is an excellent local correlation feature* Local correlation, that is, within a belt of outcrops of a mountain range itself, is excellent; conversely, regional correlation of the Martin is difficult, in that local facies are not continuous regionally# The Martin formation was subdivided by Stoyanow (1936) into a lower Picacho de Calera formation, the restricted Martin, and an upper Lower Ouray formation, largely on faunal evidence# The Picacho de Calera and Lower Ouray formations do not meet the definition of a formation as they are not continuous mapable u n its • Picacho de Calera Formation

The Picacho de Calera formation was named for the ex­ posures in the Picacho de Calera Hills in Pima County near R llllto, 25 miles northwest of Tucson, at the R iillto Cement Company^ quarry® The formation was named for a distinctive fauna in the basal 73 feet of the Martin formation# The fcre­ mation is not a continuous lithologic mapable unit regionally, despite the fact that it may be considered a faunal zone® It is proposed in this paper that the Picacho de Calera formation either be completely abandoned to avoid nomenclature! confusion or be retained as a faunal zone of the Martin formation® 23 lower Ouray Formation The type locality of the lower Ouray formation is in Peppersauce Canyon in the northern Santa Catalina Mountains approximately 25 miles north of Tucson* The lithologic basis for the separation of the lower Ouray from the upper part of the Martin formation is questionable* The formation was named by Stoyanow (1936) because of the occurrence of a distinctive braehiopod index species which occurs in the lower part of the Ouray formation* The formation is not a mapable lithologic unit regionally despite the fact that it may be considered a faunal sons* The thickness.of the unit at the type locality is 150 feet* It is proposed that the lower Ouray formation be completely abandoned to avoid nomenclature! confusion*

Swisshelm Formation The Swisshelm formation was named by Bpls, Gilbert) and lagenhelm (1957) for the undescribed rocks of the Swiss* helm and Pedrogosa Mountains in southeastern Cochise County* Loring (19*»5), in the northern Swisshelm Mountains, however, noted that the Devonian section there is similar in many as­ pects to the Martin formation and correlated the Swisshelm section with it# The Swisshelm formation occurs between the eastern fine elastic and carbonate sequence of the Pareha formation, and the western sandy and silty calcareous and dolomltlc se* quence of the Martin formation,and probably grades laterally into both* The formation consists largely of sandstone, which 21+ is dominantly calcarenite, and silts tone with lesser amounts of impure carbonate and shale* The coarser elastics are very characteristic of the lower portion of the formation* The thickness of the formation at the type locality is 615 fe et* Theareal distribution of the formation is not established (Sabins, e t a l . , 1957). ' The Svisshelm formation represents a high energy en# vlronment of sedimentation, at least in the lower parts, bounded by what is generally considered to be two low energy environments of sedimentation. The source area for the sed~ iments may have been a nearby positive area or possibly a nearby reef or bank contributing ealcarenites* The formation in the upper portion seems to be gradational into Martin type lithology* Bereha Formation

The Fereha formation (Gordon, 1907) was named for the sequence at fercha Creek in Sierra County, New Mexiee* The Fereha formation and the Portal facies of the Percha formation occur in the areas east of the outcrops of the Swisshe1m fore raatipn and the Martin formation in the Chirieahua, Dos Cabezas, Feloneillo, and Big Hatchet Mountains* ; Satisfactory sections of the Percha are limited because of the slope-forming characteristics of the formation* The Percha formation is typically a dark gray to black calcareous to non-calcareous shale which alternates with limestone lenses 25 that become more prominent toward the top of the formation* The limestone lenses appear to be gradational into the Missiselppian* Portal Formation

The Devonian Portal formation type section is at Portal, Arizona in eastern Coehise County, (Sabins, 1957)* The thick* ness of the formation is 3*f2 feet at the type locality 2 m iles northwest of the town of Portal♦ The Portal formation was sep# arated as a stratigraphic unit largely on a faunal basis* The lithologic difference between the Pereha formation and the Per* tal formation is minor when the distance between outcrops is taken into consideration* It is proposed in this paper that the Portal formation be considered a facies of the Pereha for* mation* Southwestern Hew Mexico The Devonian of southwestern Mew Mexico consists of shale with minor siltstones, limestones, and calcar#nites, and is locally very fos si lifer ous * The sequence was originally referred to as the Pereha shale (Gordon, 1907)# The Pereha shale was divided into four separate formations by Stevenson (19^2 , 19^ 5) which are, in order from oldest to youngest, the Onate formation, the Sly Gap formation, the Contradero forma­ tion, and the Pereha shale* The term Canutillo was used by Stevenson in 1942, but he later restricted it to Texas (Steven­ son, 1945) and proposed the new name Onate* The HThree Forks" beds of the San Andres Mountains (Kottlowski, et al*, 1956) is 26 used as a faunal seme designation, not a formation* The terms Chloride formation (Keyes, 190*+), Ferchian series (Keyes, 1922), and Bella shale (Keyes, 1908) are no longer aceepted* The Sil~ urian-Devonlan and the Deronian-Mississippiah eontaets are reeog^ nizable* In Hidalgo County, however, where the Devonian is under lain by the Upper Cambrianelower Ordovician B1 Fas© formatinn, the contact may be difficult to determine* Formations formerly included in the Pereha shale of Gordon (1907) w ill be discussed separately to avoid confusion* - Pereha formation

Gordon (1907) named the Pereha shale for a sequence of shales carrying a Devonian fauna in an undesignated type local# ity in Sierra County* The formation is 200 feet thick in Sierra County and 500 feet thick in Grant County* The Pereha shale, as originally described by Gordon, is underlain by the Mimbres limestone (equivalent to the present El Paso formation, Montoya Group, and Fusselman dolomite), and overlain by the lake Valley limestone (equivalent to the Caballero formation and the Lake Valley formation)* The Pereha shale as defined by Gordon (1997) is equivalent to the entire Devonian sequence of southwestern Hew Mexico* Stevenson (19^2) divided the Devonian into three sepa# rate formations, based on sedimentary and faunal breaks which are, in ascending order, the Cariutlllo formation, the Sly Gap formation, and the Pereha shale* The Pereha shale (Stevenson, 27 19^5) was further subdivided Into an upper Box member, consis­ ting of a fosslllferous limestone and shale sequence, and a lower Ready Pay member, consisting of black, fissile, carbon* aceous non-fosslllferous shales, Stevenson (19^5) established a type section at Pereha Greek In Sierra County# A cyclemenold ammonold was found In the Pereha In the Lake Valley quadrangle and Identified by Miller and Collins ©a (1951)# Cyclemenold ammonolds are use^jas the b asis of a fau n al break between the Upper Devonian and Mtssisslppian at the alter* nate world type section In the Sehlefergeblrge in Germany, as they do not occur In the Mlssisslppian rocks# StaInbrook (194-7) considered the Pereha shale to be of Mlssisslppian age on the basis of several fossils with no known Devonian equivalents# There are, however, no apparent Mlssisslppian equivalents either, thereby Invalidating the basis of his suggested age determin­ ation. The Ready Pay member of the Pereha shale has been cor­ related by B ills on (1950) with the Upper Devonian (?) and Klnderhooklan Woodford shale and the Chattanooga shale of Kin* derhook age# The term Pereha formation is used by Kelly and Silver (1952) in their report on the Caballo Mountains to in* elude the lithologic variations within the unit#

Canutillo formation

The Canutillo formation of Middle Devonian age was named by Helson (1940) for the 175 feet of exposures opposite Vinto, Texas in the Franklin Mountains. The formation at the type lo* eality consists largely of light brown eherty limestone overlying 2 8 the Fusselman formation* The upper kO feet of the seetion In the type locality is black, fissile shale which Stevenson (19^5) has tenatively correlated to the Ready Pay member of the Fereha formation* In order to avoid confusion in the nomenclature in New Mexico he proposed that the Middle Devonian rocks of Hew Mexico be named the Onate formation and the Cazratlllo formation be restricted to Texas*

Onate Formation

The Onate formation was named by Stevenson (19^5) for the 86 feet of seetion exposed on Onate Mountain in the San Andres Mountains* The formation is a grayish brown to buff, variable and intergradational series that is known to be gra­ dational laterally* The formation averages 35 feet in thick­ ness in the San Andres Mountains* The overlying Sly Gap for* mation is distinctly light yellow at the contact, while the Onate is grayish brown* The underlying Silurian Fusselman dolomite forms a recognizable contact with the Onate. The Onate formation has been tentatively correlated with the Mid­ dle Devonian Canutlllo formation in Texas; however, the pale­ ontological evidence is questionable (Kottlowskl, et al», 1956)*

Sly Gap Formation

The S ly Gap form ation was named by Stevenson (19*+2) for a formation consisting of thin alternating layers of fos- siliferous shale and siltstone with a few beds of limestone* The formation varies in thicjkness from 0 to 135 fe e t in the San Andres Mountains and rests on the Canutlllo formation or 29 Fusselman dolemlte* Stevenson (19^5) established a type sec­ tion at Sheep Mountain in Sly Gap in the San Andres Mountains• The formation was divided into a number of faunal zones. Fau­ nal zones K and L are called the "Three Forks" beds because of the similarity of the fauna to that of the Three Forks limestone in Montana (Kottlovskl, et a l., 1956)* The age es­ tablished for the "Three Forks” beds is Middle Gassadogam or Middle Upper Devonian.

Contradero Formation - - ' The name Contradero formation was applied by Stevenson (1945) to a series of carbonaceous shales and limestones above '1 . ' the Sly Gap formation and underlying the Caballero formation of Mississippian age. The type locality of the formation is in Rhodes Pass in the San Andres Mountains. It is a local feature ranging from 0 to 70 feet and Is found only in the San Andres Mountains. The formation was further restricted (Kottlowski, et al., 1956) by assigning approximately the up­ per 20 feet to the Pereha formation. It is tentatively proposed in this paper that the Onate formation, the Sly Gap formation and the Contradero formation be eonsidred, as the Ready Pay and Box, members of the Pereha form ation. * Southern Arizona and Northern Sonora, Mexico

Four formations form five major subdivisions of lithol­ ogic types in southern Arizona and northern Sonora* Mexico; they x 30 a r e : an tin-named form ation a t the Cerros M urcielagos; the Mar­ tin formation, which may he subdivided into a calcareous and dolomitic facies; the Swlsshela formation; and the Fereha for­ mation* (figure U-)* The Cerros Mureielagos section in Northern Sonora (Cooper and Arellano, 19^6) has not been formally named, but would appear to represent a distinct formation* The Martin formation (Ransoms, 190*0» is recognized over a large area in southern Arizona and northern Sonora, Mexico, tentatively dii- vlded into a limestone facies and a dolomite facies* The Swisshelm formation, apparently limited in lateral extent, is restricted to a small area in southeastern Arizona* The Fereha formation includes rocks that have been referred to the Portal formation and the Morenel shale in southeastern Arizona* The formations will be discussed separately.

Cerros Mureielagos Devonian Sequence

Cooper and A rellano (19^6) describe a lower Upper De­ vonian sequence of limestone and dolomite 16 miles westvnorthwest of Gaborca 280 meters (915 feet) thick* The sequence occurs on three isolated hills and has no apparent upper or lower contact* The age (Frasnian) was based on the occurrence of a character-, istic fauna of stromatoporods, braehiopods, gastropods, and corals, probably equivalent to the Haekberry shale, Independence shale and Onate formation faunas* The fauna was collected from a restricted zone; consequently, the unit might include consid­ erably older and younger Devonian rocks* The Cerros Mureielagos beds probably represent a formation 31 distinct from the Ifartln, In view of the considerable thickness. It appears to be a southwestern geosynclinal phase of the De? vonian, In part equivalent to the Martin, which consists of shelf deposits.

Martin formation

The Martin formation occurs between two distinctive formations. The lower contact of the Martin formation is dis- conformable and locally conglomeratic. The upper contact is gradational. Individual beds, groups of beds, and faunal zones are excellent local, and less reliable regional, key horizons of the Martin formation. The Martin formation is tentatively divided into a dolomltle faeies and a calcareous facies in this paper. The calcareous faeies has been extended from the type section near Bisbee to include the Lower C ry stallin e lim estone a t Cananea, The dolomltle faeies of the Martin formation in­ cludes, in this paper, the shelf carbonates in southern Ari­ zona north of the limestone facies of the formation (figure W. The limestone faeies of the Martin formation at Cananea, the Lower Crystalline limestone of Mulebay and Velasco (19$^), is 200 to 250 feet thick. The lower contact is dlseonformable and the upper contact gradational. The limestone has been re­ ported to contain individual beds with up to 12# MgO, indi­ cating a dolomltle character'in part. The thickness of the beds in the formation is variable from a few inches to three feet* Poorly preserved small splrlfers and erlnolds are re­ ported k s being Devonian forms» The typical limestone faeles of the Martin formation Is exposed In the Mole Mountains (Ransoms, 1904)• It Includes dark gray to pinkish limestone and pink to gray shale* The sequence Is predominantly shale In the lower portion of the section and limestone In the upper* The fossils of the Martin formation, both In the cal­ careous and dolomltlc faeles, are very well preserved and com­ monly s 111cIfled. The fossils commonly occur as blostromes which locally may be used as key horizons * The age of the fauna at Blsbee as established by H. S* Williams (Ransoms, 1904) was equivalent to the High Point zone of the Naples formation and of the Ithaea formation In New York* Williams also correlated the Martin at Blsbee with the Middle Devonian of Russia* The c o rre la tio n was in v alid ated In 1922 by Obrut- schew* The circum stances leading to the c o rre la tio n and I ts subsequent Invalidation are discussed at length by Stoyanew (1936)* The Martin formation fauna throughout its area of occurrence closely resembles that of the Haekberry shale fauna of Iowa* Stoyanow (1948) also mentions aspects of the Independence shale fauna, Cedar Valley limestone fauna, and the lower Ouray formation fauna within the Martin forma- tion throughout its area of occurrence* Fenton indicates that the Haekberry shale fauna is more closely related to the Asiatic forms (Grabau, 1924) than to the eastern United States and European forms* No clymenoid ammonoids, which are 33 restricted to the Upper Devonian, have been recovered from the Martin formation. Titcomb (1932) was able to correlate the Devonian fauna of the Martin formation at Bisbee (Frasnian) on a world-wide basis. The dolomitic facies of the Martin formation from the Dragoon Mountains in central Cochise County is tentatively correlated to the limestone facies of the Martin formation in the Mule Mountains in Southern Cochise County. The area of transition is in the vicinity of the Tombstone Hills• The dolomite facies of the Martin formation, like the limestone facies, is a complex of 20 to 30 successive lithol­ ogic types. The outstanding feature of the facies is the predominance of an Impure silty and clayey dolomitic char­ acter. The characteristically dolomitic sequence also in­ cludes minor limestones. The carbonates of the Martin forma­ tion are only rarely coarsely crystalline. Shales predominate locally in portions of the section. Sandstones occur as cal-* carenites and as minor siliceous sandstone lenses, especially in the lower part of the formation. Calcarenltes have been reported from only a few localities; however, as they are very difficult to observe on the outcrop, they may be very widely spread throughout the sequence both laterally and ver­ tically. Well rounded and frosted quartz grains occur as sand stringers and as minor constituent in the carbonates. Vari­ ations in thickness of the Devonian are apparently the result of deposition on an eroded surface of low relief. 3^ The Martin formaticMi is reported from southwestern Arl* zona at Growler Pass and from the Harquahala Mountains near Salome, where more than 180 feet of section has been measured (Bldred Wilson, personal communication). These sections in­ dicate that the Devonian carbonates were deposited in south­ western Arizona but no detailed information is available. The Martin formation as interpreted from the faunal studies mentioned above, is Upper Devonian in age. Stoyanow considered the fauna of the lower Picacho de Calera formation to be equivalent to the Cedar Valley limestone fauna, and that of the Lower Ouray formation to the presently defined Ouray limestone fauna (Burbank, 19*K))« The Martin formation, or rather the faunal zone remaining, contains typically the Hackberry shale fauna with possibly some aspects of the old­ er Independence shale fauna. The units named by Stoyanow are better considered as faunal zones than as formations. In this paper it Is proposed that the name Martin for­ mation be extended to include the sequence of rocks at Cananea re fe rre d to as the Lower C ry sta llin e lim estone.

Swisshelm Formation

The Swisshelm formation (Bpls, et,al*,. 1957),is reported only from the Swisshelm andPedrogosa Mountains in southeastern Cochise County, Arizona. The sequence, where well exposed, forms a brown and yellow slope in contrast to the overlying gray cliffs of the Mississippian and underlying gray step-slope topography of the Upper Cambrian-Lower Ordovician El Pase 35 formation# The Swisshelm formation is a separate sandy facies between an eastern fine elastic Pereha formation sequence and a western carbonate Martin formation sequence# The formation may be roughly divided into two units# The upper portion of the sequence consists of predominantly impure carbonates that may grade laterally into the Martin formation, both units ap­ pear to have similar lithologic and paleontolegle aspects# The lower half of the sequence, chiefly slltstone and sand­ stone , is not related to the Martin or Pereha formations lith­ ologically# The age of the Swisshelm formation is Upper Devonian Seneean or Prasnlan# Correlation of biostratigraphic zones indicate that the characteristic elements are similar in as­ pect to those reported from the Martin formation, the Sly Gap formation and the Contradero formation* The lower portion of the section has aspects suggestive of the Independence shale fauna (Stainbrook, 1948)* The lower half also con­ tains a fauna similar in aspect to those of both the Sly Gap and Onate formations* The upper half of the formation has a characteristic Haekberry shale fauna (Bpis et al., 1957)•

Pereha Formation

Two formations have been recognized in southern Ari* zona that are lithologically similar to the Pereha formation* v - These formations, the Portal formation and the Morenei shale, are both apparently Seneean (Prasnlan) in age* 36 Sabins (1957) named the Portal formation. Lower Upper Devonian in age, because he was not certain of the correlation with the Pereha formation of Upper Upper Devonian age. The Portal formation in the Chiricahua Mountains consists of cal­ careous and siliceous, gray to black shales alternating with argillaceous, nodular limestones which are sparsely fossil- iferous. Sabins (1957) divides the Portal formation into h members. Member 1 , which rests disconformably on the El Paso formation, consists of very thin bedded limestone and calcareous sh a le ; member 2 consists of black siliceous shales; member 3 forms a gradational contact with member 2 and is similar lith­ o lo g ically to membeifL; member h- is sim ila r to members 1 and 3 * except the units of limestone and shale are much thicker« The age of the Portal formation is Senecan (Prasnian)• Ostracods from members 1 and 3 were examined by S» A. Levinson of the Humble Oil Company Research Laboratories and determined to he of Middle or Upper Devonian age. S. P. Ellison of the University of Texas has indicated that the conodont fauna is equivalent to that of the Rhinestreet shale of the Naples group which is Fingerlakesian in age. The braehiopod fauna was ex­ amined by G. A. Coe$er in 1955 who indicated that the fauna was P ere h a-lik e, but high Chemung, th a t i s , high P rasn ian . Rosseau Flower identified a clymenoid ammonite from the for­ mation. The Portal formation is tentatively correlated with the Morenci shale by Sabins (1957). The Morenci shale was described by Lindgren (1905) for 37 the 150 feet of Upper Devonian rocks exposed at Clifton-Morenci in Greenlee County, Arizona* The fauna of the Morenci shale has been correlated with that of the Martin formation (Stoya* now, 1936)* In this paper It is tentatively proposed to extend the name Pereha formation into southeastern Arizona to include the areas where the names Portal formation and Morenci shale are in use. The Morenci shale, or the Morenci formation, to con­ sider lithologic variations, should, perhaps, properly be used as the regional name because it has priority. However, the name Percha is well established by usage over a wide area and, conversely, the name Morenci has been used only locally. To avoid fu rth e r confusion, synomony is not proposed a t th is tim e. The name Santa Rita limestone was proposed for a sec­ tion thought to be Middle Devonian in age by Stauffer in 1928 in the Santa Rita Mountains, in Pima County, later work by Reid (1928) indicated that the abnormally thick section in** eluded thrust remnants. The name is now abandoned.

SaaSDil Arizona.

The Devonian rocks that w ill be discussed in this por­ tion of the report include those exposed in southern Navajo County, Gila County, northern Pinal County and western Yavapai County, Arizona. The exposures in this region are considered by the writer to be entirely of the doloaltlc facies of the Devonian Martin formation. The area of Martin formation ex­ posures is confined to the southwestern rim of the Colorado 38 Plateau with the exeeption of a number of smattered areas east and northeast of Maricopa County. The northern faeies relationship between the Percha and Martin formations is unknown; however, resent work on the San Carlos Indian reservation by the U. S. Geological , Survey indicates that a number of critical sections are avail­ able in this area. Several form ation names have been proposed and applied in Central Arizona. They are: the Crook formation, (Short, e t a l . , 1943), the lower Ouray formation (Stoyanew, 1936), the Island Mesa beds (Stoyanow, 1936), and the Jerome forma­ tion (Stoyanow, 1930). The Crook formation (Short et a l., 1943) was divided from the Martin formation at Superior. The unit, which is the basal 77 feet of the Martin, was based on the occurrence of a fauna, described by Harshman as equivalent to that of the Cedar Valley limestone. The name was never adopted for regional use and is now abandoned. The lower Ouray formation (Stoyanow, 1936) has been discussed in detail earlier in the thesis. It is considered to be only a faunal zone in the Martin formation. The Island Mesa beds (Stoyanow, 1936) are exposed ap*? proximately 12 miles northeast of Jerome in western Yavapai County.The Island Mesa beds consist of 122 feet of distinctly arenaceous beds containing a fauna younger than the Jerome formation fauna. The arenaceous character of the formation may be ascribed to the presence of calcarenites. The fauna 39 of the Island Mesa beds has Wen deseribed by Stoyanow (1946), and Is apparently non-diagonostic. The Jerome formation was named by Stoyanow (1930) for exposures on Mount Mingus near Jerome In western Yavapai County# The name was proposed to Indicate a formation equivalent to the Martin formation, but supposedly deposited in a separate basin north of Mazatzal land, a barrier trending roughly north­ east-southwest across the center of the state which effectively divided the Devonian seas Into 2 separate basins. The Jerome formation fauna is grossly equivalent to that of the Martin formation (Stoyanow, 1936). The Martin formation may be broadly separated Into 3 regional members similar to those deseribed by Huddle and Dob- rovolny (1950)• The 3 members are tentatively correlated a- cross central Arizona into northern Arizona. Distances between known outcrops are great; consequently, facies variation makes regional correlation somewhat nebulous. The Martin formation in central Arizona may be considered to be a shelf (?) impure dolomltlc carbonate sequence with local arenaceous units, which may be either siliceous or calcareous. Shales and minor chert are present. Three major problems present themselves concern? ing the lithology of the Martin formation; they are:. the lower contact, the correlation problem with reference to the infer­ ences of Mazatzal land, and the upper contact. The lower contact of the Martin formation with older rocks south of Christopher Mountain near Payson is locally difficult to determine• However, the Martin formation lies in most places on the Troy quartzite. The Troy quartzite is generally fine grained, non-calcareous, and cross bedded; con­ versely, the Martin formation is basally a calcarenite and flat bedded. Similar distinctions may be made north of Chris­ topher Mountain near Payson in the areas of outcrop of the Tapeats sandstone. Precambrian rooks north of Christopher Mountain form lower contacts with the Martin formation,in some places. Locally, however, the Tapeats sandstone is be­ low the contact and may be shown to be reworked and grada­ tional. This indicates that at least the upper portion of the underlying section may be in part Devonian in age. Chan* nels are known to occur at the lower contact. Sections taken in the channels are atypical, with a thick lower sandstone unit. The channels may be observed at Roosevelt Dam, the south rim of Salt River Canyon on U. S. highway 60, and a number of other localities. The precise nature of the lith­ ology and age of the channels is unknown. Conversely, a number of isolated hills are reported. The hills may selec­ tively cut out part or all of the Devonian section. These minor variations of channels and especially isolated hills are believed by the writer to be extremely limited in lateral extent and to have been greatly overemphasized by some workers The earlier workers took scattered sections in the area, and unfortunately, in thajarea of greatest accessability. Because of this a lap out by non-deposition on a regional basis seemed apparent# This lap out was interpreted as taking place onto a positive area referred to as Mazatsal land# Stoy- anow (1936^.1940) conceived the idea of a great southwest-north­ east positive area through central Arizona, that would effectively split the state in half and divide Devonian deposition into 2 basins. Huddle and Dobrovolny (1950), as more sections became available, began to shrink Mazatsal land. Unfortunately, they overemphasized its importance also# This writer tentatively still further restricts Mazatzal land# Examination of sections in the surrounding area suggests that a number of resistant older Precambrian hills of a very limited aerial extent oc­ cupied the position of Mazatzal land. The Devonian laps out on these islands• The Martin formation is eorrelatable across the area. The suggested relations are shown in,figure 4. The upper contact of the Martin has been referred to as being sharply disconf©ratable, with a regolith locally de­ veloped. The writer believes that the upper contact is more gradational in nature and may represent continuous sedimen­ tation. The term, regolith, which has been used locally, is unfortunate as it implies subaerial erosion# Subaqueous e* rosion may be a better possibility. The upper part of the Martin formation in central Arizona is considered by Huddle and Dobrovolny (1950) to be probably equivalent to the Haekberry shale# The Devils Gate formation of Nevada has been tentatively correlated with the lower portion of the section# Fossil plants from the Martin in the Salt River area have been identified as possibly of middle Devonian age (Curt Teichert, personal communication)« It is proposed that the name Jerome formation he aban­ doned and replaced by the name Martin formation. It is simi­ larly proposed that the names Island Mesa beds, Crook formation and Lower Ouray formation be either abandoned or used only as faunal zones.

Northern Arizona

The Devonian rocks in northern Arizona may be divided laterally into 3 facies; they are: the northwest geosynclinal facies; the Martin (?) shelf facies; and the Four Corners em- bayment facies. The northwestern geosynclinal facies includes Upper Devonian and possibly Middle and Lcwer Devonian rocks which are referred to the Muddy Peak limestone (McNair, 1951)• The Martin formation Includes the shelf facies in northern Ari­ zona. The Four Corners embayment is described in a later sec­ tion of this paper. The northwestern Arizona geosynclinal facies, confined primarily to northern Mohave County (McKee, 1951> McNair, 1951), is correlated with the Upper Devonian Muddy Peak limestone, named for outcrops on Muddy Peak in the Muddy Mountains, Clark County, southern Nevada. The sequence may also include Middle and Lower Devonian rocks. The Muddy Peak limestone thickens rapidly toward the Cordilleran geosyncline and probably rep­ re se n ts an embayment of th a t fe a tu re . The sequence in n o rth ­ western Arizona is underlain by a thick section of undated rocks >3 the youngest of which has been tentatively assigned to the Or* dovician Pogonip formation by McNair (1951)* However, he has no faunal basis and only uncertain lithologic evidence for this correlation. The non-fossillferous doloaitic pre-Devonian (?) sequence is referred to regionally as the Supra-Muav (Wood, 1955, 1956)* The Supra-Muav represents either a regressive Upper Cambrian-Ordovician (?) facies (McKee, 19^5, McNair, 1951, Wood, 1956) or a transgressive Devonian (?) facies. The possibility should be considered that the Supra-Muav is related to the post-Cambrian pre-Upper Devonian uplift and represents the accumulation of material redeposited from the Upper portion of the Cambrian sequence. The Supra-Muav is thickest in the area of geosynclinal (?) accumulation and wedges out toward the Martin shelf (?) facies where it is only locally present (Wood, 1955, 1956). The Martin formation shelf (?) facies is tentatively considered to include the Devonian rocks at Mount Elden, near F la g s ta ff, the Temple B utte lim estone of the Grand Canyon, the Devonian sequence of the Xampai cliffs (Wood, 1955)9 and a ll other Devonian rocks known from outcrops or subsurface information in northern Arizona except those in the extreme northwestern and northeastern corners of the state. The re­ lationship between the Martin formation and the Ouray-Elbert* Aneth sequence of the Four Corners area is unknown. Well information w ill be required to establish these critical relationships. 44 The upper contest of the Martin formation in northern Arizona is gradational and locally conglomeratic and breccia- like, A surface having 3 to 4 feet of relief is reported by W, and F, Peirce (unpublished manuscript, 1955) as being der veloped on the Devonian a t Peach S prings, The Temple Butte limestone contains a zone of rounded dolomitle pebbles con­ sidered to be at the upper contact. Lithologically the Devonian is , as in central Arizona, a complex dolomitle carbonate sequence with a variety of al­ ternating rock types throughout the Martin formation area* Stoyanow (1936) indicates a correlation between the Devonian sequence at Jerome, Peach Springs, Mt, Blden, and the Grand Canyon, The lower contact of the Martin formation is grada­ tional into the upper reworked surface of the Tapeats sand­ stone in southern portion of northern Arizona, The lower contact in the rest of northern Arizona, exclusive of the Four Corners area, is related to either the Muav or Supra- Muav, Ho area has been observed in which the Devonian rests on B right Angel sh a le . In the Grand Canyon the Temple Butte limestone is locally absent by non-rde posit ion (Walcott, 18833* Channels containing a fresh water Devonian fish fauna are,ob­ served below the Temple Butte limestone. No evidence exists to correlate these channels with the pre-Martin channels ob­ served in Central Arizona* The age of the Temple Butte limestone is considered by Stoyanow (1936) to be equivalent to that of the Jerome for­ mation*

Four Corners Area and Southwestern Colorado

Three formations are observed in the Four Corners area and southwestern Colorado; in ascending order, they are: the Aneth formation (Knight and Cooper, 1955), known only from subsurface data; the Elbert formation (Cross, 19040, which has been divided into an Upper Elbert formation and a lower McCracken sandstone member; and the Ouray lim estone as r e s t r ic ­ ted by Burbank (1931)*

Aneth Formation

The Aneth formation (Knight and Cooper, 1955) is typi­ cally a dark dolomite with alternating gray, brown, and black shales, gray siltstones and lighter dolomites* The Aneth for­ mation underlies the McCracken member of the Elbert formation and overlies Tonto group or Four Corners equivalents* The for­ mation extends over an elipsoidal area of 2600 square miles in the Four Corners area* The formation ranges in thickness from 0 to 170 feet* The type section occurs at Shell Oil Company’s Bluff Unit* No* 1, T39S, R23E* See. 32, near Blanding San Juan County, Utah. The formation is known only from subsurface data*

Elbert Formation

The Elbert formation (Cross, 1904-) was named for expos­ ures on Elbert Creek, a western tributory of the Animas River entering it just above Roekwood* The formation consists of multicolored shales and thin buff or gray limestone. The most persistant feature of the formation is a crumbling shale member that contains casts of salt crystals. The El­ bert formation is exposed in southwestern Colorado and known from subsurface data in the Four Corners Area. The thick­ ness of the Elbert formation at the type locality is feet* The formation increases in dense earthy limestone toward the upper contact. The Elbert formation has Wen divided into 2 members, the Upper Elbert formation and the McCracken sand* stone member based on subsurface data (Knight and Cooper, 1955). The type locality for the subdivision is at Shell Oil Bluff Unit Ho. 1, T39S, R23E, See. 32 mar Blending San Juan County, Utah. The contact of the McCracken sandstone member and the Upper Elbert formation is transitional. The McCracken sandstone consists of predominately white, light gray to red, fine to medium grained, poorly sorted, glau­ conitic sandstorm ranging in thickness from 0 to 580 f e e t. The thickness of the sandstone member at the type locality is 112 f e e t. The McCraeken sandstone is believed to be equivalent to the Ignacio quartzite (Cooper, 1955) at least in part, at Baker’s Bridge, Colorado, which was assigned a Devonian age by Barnes (19$h-). The writer suspects that the McCracken sandstone represents a regressive facies of par­ tially reworked Cambrian Ignacio quartzite. The Upper Elbert formation ranges from 0 to 307 feet and consIts of thin ^7 bedded, sugary, dense dolomite, locally anhydritic, commonly with frosted quartz grains. The dolomite alternates with thin gray to green, waxy and red clayey shales, generally sandy* The McCracken sandstone and Upper Elbert are believed to interfinger laterally with undifferentiated Elbert forma? tio n .

Ouray Limestone

The Upper Devonian Ouray limestone is known from ex­ posures in southwestern Colorado and the subsurface of the Four Corners area. Spencer (1900) proposed the name for the only pre-Carboniferous rock section in the San Juan region of southwestern Colorado. The sequence was named for the excellent exposures at the junction of Canon Creek and the Uncompahgre River near Ouray, Colorado* The form ation con­ sists of 100 to 300 feet of massive limestone. W* Cross (19040 indicated that the Ouray limestone was a lithologic unit that contained both Mississipplan and Devonian facies, overlying the Devonian Elbert formation. Cross et al. (1905) said that the Ouray formation could not be divided at the time boundary because it is a continuous lithologic unit* W. S. Burbank (1930) indicated that the major portion of the Ouray formation as defined by Cross (1905) is Mississip­ plan in age. Burbank tentatively divided the Ouray formation into Mississipplan and Devonian rocks on a lithologic basis in the Ouray district. Burbank in 1931 restricted the Ouray limestone to the pre-Carboniferous sequence in southwestern Colorado. The Mississippian portion of the section was named the Leadville limestone. J. C. Cooper (1955) established the thickness of the Ouray limestone as from 0 to 238 feet in the Four Corners area, gradually thickening to the northwest* It is described as being overlain uneonformably by the Mississip­ pian Madison formation and underlain by the Upper Devonian Elbert formation* PADS ONTOLOGY

The paleontology of the Devonian rocks of the area Is relatively little known. This paper w ill not be concerned with comment on faunal correlation beyond that mentioned In the dis* cussIons of the formations# The macrofauna of the Devonian of the regional area Is prolific and only locally well described; however, addi­ tional work and compilation of available Information Is nec­ essary In order to evaluate the fauna. The most important macrofaunas are the brachiopods, corals and crlnoids* The braehlopod fauna Is variable and widespread. Corals are var­ iable and locally prolific; at one locality in central Arizona 19 species were recovered (Curt Teichert, personal communi­ cation). The crlnoids are small and commonly only the stem is preserved. Crlnoids are restricted to the upper portion of the section. Differentiation between species may be pos­ sible on the basis of configuration of the axial canal and arrangement of the crenella. The critical examination of the erinoid fauna might possibly lead to establishing a wide­ spread paleontological division between the Devonian and Mis- sissippian rooks. The macrofauna occurs as either bioherms or biostromes. Preservation of specimens by replacement by silica is common in the Devonian rocks; internal structures of brachiopods are preserved as siliceous fossils.

49 50 The microfauna of the Devonian rocks has been preli­ minarily examined only in the Pareha formation. The Fereha formation is known to contain a prolific conodont fauna which has been very useful in precise dating in the Devonian. The ostracod fauna is widespread but virtually unknown* The paleobotany of the Devonian rocks is unknown* Several localities have been reported in central and northern Arizona as containing plant remains. The preservation of specimens at these localities has been described as being excellent. Algae have been observed in a number of local­ ities ; however, satisfactory description of size and form is not available* Spores have been recovered from a test specimen sub* mitted to the University geochronology laboratories on Tumamoc Hill* Tito specimen examined was collected from the lower per* tion of the Devonian at the Pieaeho de Calera Hills* METAMORPHISM

The metamorphlc equivalents of the Devonian roeks have not been examined in detail; however, the examination of these rock types may indicate correlation possibilities and key mapping horizons of use in structural interpretation in areas of static metamorphism. Several papers are avails able to aid the geologist in determining possible meta-equi­ valents of Devonian rocks. In the Feloneillo Mountains, Hidalgo County, New Mexico,the metamorphlc sequence has been discussed (Gillerman, 1957). In the Chirieahua Mountains, Eastern Cochise County, Arizona, two papers are available. Sabins (1955) describes the section in the northern portion of the mountains. Brittian (19^9), near Hillsboro, describes the metamorphlc sequence of the Devonian rocks. The Fereha formation sequence typically is converted to hornfels and minor marble * Gilluly (1956), in central Cochise county, indicates that the Martin dolomitic, sandy, and shaly strata are very favorable for metamorphism. In areas of contact metamor­ phism, the Martin formation is more widely altered than the underlying Abrlgo formation and the overlying Eseabrosa lime­ stone. Fred Peirce (manuscript in preparation) has investi­ gated the Devonian metaequivalents in the northern Santa Catalina Mountains, Northern Pima County, Arizona. The

51 52 dynamic met amorphic equivalents of the Devonian rocks have not been examined or recognized in the thesis area* Dedolomitization in Cochise County has been discussed by Cooper (1957)* The writer is of the opinion that the pro­ cess of dedolomitization is relatively restricted rather than regional in extent. The dolomltlsatlon of the Devonian rooks is probably diagenetic or possibly primary in origin. The rocks above and below the Devonian are not dolomltlzed. The process of dolomltization is spontaneous under the proper conditions of current velocity, current direction, current stability, depth of water, oxidation-reduction potential, acidity- alkalinity, salinity, and temperature (PettiJohn, 1957)* The writer is not prepared to comment on the complex dolo­ mite problem; however, he feels, on the basis of lithologic relations, that the conditions necessary for dolomltization existed in the Devonian seas* STRUCTURE

The southwestern half of Arizona and portions of Southwestern New Mexico are structurally complex with re­ gional block faulting, thrust faulting, metamorphism, and igneous activity* The Devonian rocks are particularly sus­ ceptible to structural movements, commonly forming the sole of thrusts and typically being thinned or thickened by bed­ ding plane faulting. The field geologist is cautioned to exercise care in studying the relationships of the Devonian rocks in structurally complex areas.

53 DBPCSITIONAL ENVIRONMENTS

The Devonian rocks discussed In the regional area rep­ resent a complex sequence of rock types Including dolomites, limestones, ealcarenltes, shales, slltstones, argillites, and chert. Systematic laboratory analyses of the Devonian rocks will be necessary In order to evaluate the critical rates of deposition, the marine paleoeeology, and the establishment of environments of deposition. Five basic environments of deposition exist. They are: stable shelf, geosynclinal border, embayment, coarse clastic, and euxinlc black shale. The stable shelf environment is reflected by the oc­ currence of the Martin formation In Arizona. In general, the Martin formation is thin, but vertical variations are pro­ nounced. The formation consists of multiple lithologic units and is abundantly fosslllferous. Impure carbonates are dom­ inant; shale is a subordinate component. Mottled, laminated, sacharoldal dolomite, as well as cross-bedded ealcarenltes are common. Sandstones, both calcareous and quartzitle, re­ flect maturity. Apparent marginal geosynclinal accumulation of sedi­ ments is recorded at Cerros Murcielagos in Sonora, Mexico and in the Muddy Peak limestone in extreme northwestern Arizona. 55 The sequence is thicker than the stable shelf Martin sequence, The sequence is typified by a greater percentage of carbonates, elastics are observed but are minor in extent® The embayment environm ent, observed in southw estern Colorado and the Four Corners area, develops unusual rock types. The environment reflects more clearly than the stable shelf transgressions and regressions. A greater percentage of elas­ tics are common. Carbonates are poorly developed and impure, The area of occurrence of an individual facies or formation is difficult to determine, local basins and highs are common® A coarse elastic environment may Indicate several pos­ sibilities. The rocks exemplifing this environment are devel­ oped in the Swlsshelm formation. The area of occurrence of the Swisshelm formation may have been positive or nearly positive throughout the Devonian. The formation reflects a high energy environment. The formation may have extended considerably farther northward and southward. The euxlnic black shale environment is typified by the Percha formation. The formation was probably not depos- ited in a deep water basin because scour channels (Kottlowski, et al., 1956) exist within the black shale sequence. The Swisshelm formation possibly formed a restrictive barrier in part, thereby restricting the circulation of the sea water in the late Devonian seas. The resultant conditions may, therefore, have developed stagnation and the formation of a reducing environment of deposition. POST-DEV ON IAN ROCKS

Cochisef Pima, Santa Cruz CountiesT Arizona and Hidalgo Countv, New Mexico

The basal post-Devonian rocks both within the thesis area and regionally are problematical because of the normally gradational and poorly exposed character of the contact* The nomenclature of the Mississippian is relatively stable and well-defined. The problems of Mississippian correlation, facies, and nomenclature are only cursorily examined as a regional survey of the Mississippian rocks is now in prepa­ ration (George Thomas, personal communication)• The Devonian rocks within the thesis area are in con­ tact with the Mississippian Escabrosa limestone (Ransoms, 190*0, or the Mississippian lake Valley formation (Cope, 1882). Both formations are considered to be basal KLnderhookian in age within the thesis area. The Escabrosa (Spanish for cliffy) limestone was named for exposures on Escabrosa Ridge Southeast of the town of Bisbee, in the Mule Mountains, Cochise County, Arizona (Ransome, 190*0. The basal portion of the Mississippian is massive and regionally forms prominent ridges and outcrops. The Misslssippian-Devonian contact is seldom well exposed be­ cause of the accumulation of talus on the underlying slope formed by the Devonian Martin formation.

56 57 The Bseahrosa limestone is typically a white to light gray, coarse, granular, crinoidal limestone (Ransome, 190^)» The beds of the formation are ccamonly massive but may be thin bedded in the lower part. The Rseabrosa limestone is not known to contain shales or siliceous sandstones. Chert is common in the middle and upper portions of the limestone formation, lo­ cally forming beds up to 5 feet in thickness (Tyrrell, 1957)o Dolomite is locally common within the lower portion of the Es- cabrosa limestone. The Lake V alley form ation (Cope, 1882) is applied w ithin New Mexico and is tentatively correlated with the Bscabrosa lim estone. The Mississippian-Devonian contact within the area is Interpreted as being gradational. No direct structural, paleon­ tological, or stratigraphic evidence is available to indicate that a disconformity exists between the Devonian and Mississip- plan within the area. A general set of criteria has been de­ veloped within the thesis area to indicate the position of the contact; they are: Basal Mississippian characteristics - 1. Coarsely crystalline. 2. Light gray to white in color. 3 . Abundant large crinoid columnslias. 4. Vertical cliff former. 5* Limestone. 58

Uppermost Devonian characteristics 1. Fine to medium crystalline. 2. Dark gray to buff in color. 3. Crinoid oolunmellas commonly absent or, if present, small* Slope former. ■5» Dolomite to silty dolomite* The criteria are of necessity flexible and only uncom­ monly is the complete set of characteristics developed clearly. PA IE OROGRAPHY

The history of the earlier Paleozoic rocks of the thesis area and the regional area discussed is complex. Many reasonable hypotheses may be advanced concerning this sequence at the present stage of development of knowledge of strati­ graphy and sedimentation. The writer presents what h# con­ siders to be a plausible development of the Upper Devonian sequence. The disconformable surface on which the Devonian rocks are deposited consists of a complex of Older and Younger Pre- cambrian, Cambrian, Ordovician, and Silurian rocks (Figure 3)* The Ordovician and Silurian rocks are virtually confined to southwestern New Mexico. In general, with the exception of those areas where PreCambrian rocks are in contact with the Upper Devonian, the pre-Devonian sequence becomes younger to the e a s t. The uplift that occurred between the Cambrian and Upper Devonian was probably epeirogenic as evidenced by the lack of erosional features and the apparently structureless contact. The upper and lower boundaries of the Upper Devonian have not been rigorously defined; consequently, isopach maps are, because of this inherent error and the thinness of the formation, at best, of questionable value.

59 60 The deposition of the Upper Devonian sequence indicates the presence of 5 basic sedlmentational environments and, at least, 4- major regional tectonic features. The sedlmentational environments have been discussed already. The regional tec­ tonic features include the complex system of positive areas in southwestern Colorado, northwestern New Mexico, and north­ eastern Arizona; the inferred positive area south of Cananea (see measured Section-Mulchay and Velasco, 1954-); the area of Ensenada land in southwestern Arizona; the Cordilleran geo­ syncline; and the geosyncline present south of the Caborca region in Sonora (Figure 4-)» In Upper Devonian time the sea encroached from the south and the west across a surface of low relief in Arizona, The advance of the seas across the area is reflected in the ages of the sediments from west to east. The western Martin formation is older than the eastern Percha formation and the Lower Ouray-Elbert sequence. The Muddy Peak limestone in northern Mohave County and the sequence at Cerros Murcielagos in northern Sonora are typical, thick, marginal geosynclinal sediments and in­ dicate the areas from which the seas advanced in the Upper Devonian. The greatest part of Arizona is covered by the Martin formation which reflects a typical stable shelf en­ vironment, in the multiple lithologic variations within the formation and the abundance of fossils. The basal portion of the Martin reflects locally^those rocks over which the seas have advanced. This problem exists in both southern Coco­ nino County, Arizona and in the Four Corners area. W ithin the Four Corners area the embayment environment is typified by the development of unusual rock types which re­ flect stable shelf transgressions and regressions. local basins and highs are common0 In southern Arizona as the Devonian seas advanced a bar­ rier was reached in Central Cochise County which was reflected in the coarse clastic sequence of the Swisshelm formation. The Swisshelm formation may either represent a biohermal develop­ ment or a structurally positive area. The high energy environ­ ment is also locally observed in the Martin formation in Central Arizona. This region of coarse elastic environment in Central Arizona has been referred to as Mazatzal Land} however, it probably represents only a few islands in the Devonian sea lying off the west coast of the positive of major proportions in the general Four Corners region. ' !- ' The coarse clastic area in southeastern Arizona is ap­ parently genetically related to the Fercha euxinic black shale environment to the east. This region (Swisshelm formation) probably restricted the circulation of the sea waters with the resultant formation of conditions of stagnation and reducing conditions. The Fercha formation was probably not deposited in a deep water basin because scour channels exist within the black shale sequence* The transition into the overlying Mlssissippian rocks 62 is everywhere observable. A disconformity does not appear to exist between Devonian and Mississippian, but rather, contin­ uous sedimentation seems to have occurred (Figure 5)» APPENDIX DESCRIPTIONS CF MEASURED SECTIONS

Rincon Mountains. Colossal Cave. East Section. Pima County. Sec 9 T16S, RITE Arizona Mississippian: Escabrosa Limestone Limestone: creamy gray weathered; homogeneous gray fresh surface; products rubble; forms vertical cliff; exposure good; base covered. Eleven feet from base apparent thrust fault in Mississippian. Devonian: Martin Limestone Unit Thickness No. in F eet 1 Covered. 24- 2 Dolomite: weathers light red; fresh sur­ face mottled and banded alternating light • and dark reds; forms irregular cliff; ex­ posure good: base covered; laminated in part; contains lenticular white chert * 10 3 Covered. 4-0 4- Dolomite: weathers gray; fresh surface hom­ ogeneous olive gray; forms irregular slope; exposure poor; products rubble; gradational base; phaneric; solution channels develop on su rfa c e • 10 5 Calcareous dolomite: weathers gray: fresh surface gray; homogeneous to banded color distribution; slope former; exposure fair; base gradational; aphanitic; solution chan­ n els developed on su rfa c e • 10 6 Dolomite: weathers gray; fresh surface orange (mottled); forms irregular slope; poor to covered exposure; products rub­ ble; massive; rough surface (solution channels). 10 7 Covered. 27 63 6N- Unit Thickness No. in F eet 8 Silty limestone: weathers reddish gray? fresh surface homogeneous to handed lam* inated reds; forms irregular cliff; ex­ posure good and covered; products rubble; thin bedded (6 inches); base covered; wea­ thers in thin slabs. 6 9 Dolomite: weathers creamy gray; fresh sur­ face homogeneous to banded reddish gray; forms irregular cliff; exposure fair to Covered; products rubble: base covered; laminated in part; aphanitie. 10 10 Dolomite: weathers cream; fresh surface gray (homogeneous); forms regular slope; exposure fair to covered; products rub­ ble: base covered; thin to medium bedded (6 inches to 2 feet); aphanitie; solution channels. 10 11 Covered. **7 12 Dolomite: weathers cream; fresh surface homogeneous gray; Irregular slope former; exposure poor to covered; products rub­ ble; aphanitie. 5 13 Sandy dolomite: weathers gray; fresh sur­ face reddish gray; banded and mottled: forms irregular slope; exposure poor to covered ^ products rubble ; base gradational and covered; massive; medium bedded; sur­ face rough; solution channels. 10 l b Dolonltlc limestone: weathers dark erean- ish gray; fresh surface banded and mottled reddish gray: forms irregular slope; ex­ posure fair to covered; products rubble; base gradational; phaneric: rough outcrop surface replete with solution channels. 10 15 Calcareous dolomite: ereamish gray; fresh surface banded to mottled; forms ir re gus­ lar slope; exposure poor; products rubble; base covered; aphanitie: nodular pink chert; concretions of silica; surface rough and cut with solution channels, 10 16 Covered. 21 65 Unit Thickness Ho. in F eet 17 Sandy, doloadtio conglomerate (grades into a cream colored aphanitic dolomite at top of section); weathers gray; fresh surface gray; forms irregular cliff; ex­ posure poor; products rubble; base cov­ ered; massive; surface has solution channels. 10 18 Covered. 19 19 Dolomltle limestone: weathers dark gray# ish brown; fresh surface gradational, mottled gray; fores irregular slope; ex­ posure poor and covered; products rubble; surface texture rough phanerle; in deter­ minate fossils. 10 20 Dolomltle limestone 1 weathers brownish gray; fresh surface banded to mottled brownish gray; forms a rolling slope; exposure very poor and covered; products rubble; base covered. 10 21 Covered. 5 22 Dolomltle limestone 1 weathers grayish brown; fresh surf aw banded to mottled gray; forms rolling slope; poor to cove ered exposure* products rubble and soil; crystalloblastlc. 2 23 Covered. 12

330 Cambrian Rincon Limestone Limestone: weathers dark brownish red; fresh surface homo­ geneous, gradational* banded, reddish brown: forms irregular cliff: exposure good, products rubble; jointing poor; base gradational; granular, aphanitic and phanerle locally.

Mlsslssippian: Sseabrosa Limestone 66 Limestone: weathers dark gray, fresh surface homogeneously black; forms vertical cliff; exposure good; products rubble and soil; excellent jointing developed; base covered; abundant calcareous crinoid columellas in good condition. Devonian: Martin Limestone Unit Thickness No. in Feet 1 Covered. 43 2 Shaly dolomltlc limestone: weathers light gray: fre sh surface gray; homogeneous co l­ or distribution; forms irregular slope; ex­ posure fair to good; excellent jointing; base gradational: aphanitic; concretions of calcite and silica* 8 3 Dolomltlc limestone t light gray weathering; fresh surface homogeneous gray; exposures fair to poor; products rubble; jointing well developed; aphanitic; concretions of calcite and silica. 10 b Dolomite: weathers gray; fresh surface horn*- ogeneous grayish red; forms an irregular cliff: exposure excellent: products rubble; jointing fairly well developed; base grada­ tional; bed thicknesses 1/2 to 2 fe e t (med­ ium). 10 5 Dolomite: weathers brown; fresh surface hom*r ogeneous red; forms regular slope: products rubble; fair jointing; base gradational and covered; medium bedded (1 f o o t) ; a p h a n itic . 5 6 Limestone: weathers pinkish gray; fresh sur­ face homogeneous reddish gray; forms irregular slope; exposure fair: products rubble; joint­ ing poor; gradational; covered base; aphanit­ ic; rare; poorly preserved brachiopods. 10 7 Covered. 4-5 8 Dolomite: weathers brown; fresh surface gra­ dational; homogeneous grayish black to black: forms a regular slope; exposure fair; products rubble; base irregular and gradational; apha*? nitic; contains nodular white chert and concre­ tions of calcite and silica; abundant, excel­ lently preserved brachiopods. 10 Onit Thickness Mo, 1* Feet 9 Selenitic liases tone: weathers gray; fre sh surface homogeneous gray; forms regular elope; exposure fair to poor; products, rubblet gradational; thin bedded (6 inches); aphanltie to phaa- eric; contains white nodular chert and concretions of ealeite, silica and iron; abundant brachiopod fauna, well pre­ served, 10 Calcareous dolnite t weathers brownish gray; fresh surface homogeneous to mottled gray; forms irregular cliff; exposure fair: products rubble; joint­ ing poor to absent; medium bedded (l£ feet); concretions of ealeite; excel­ lently preserved, abundant, calcareous crinoids and braohiopods, 10 11 Covered* 18 12 Very fine sandy dolomltic limestone: weathers wddlsh brown; fresh surface banded reddish gray; forms a rolling slope; poor exposure; products rubble; jointing excellent; medium bedded (1 foot); fine sand, matrix aphanltie: ; excellent preservation of differentially weathering crinoids cblumnellas* " 13 Limestone: weathers brownish gray; fresh surface banded reddish gray; forms reg­ ular slope; exposures poor and covered; products rubble and soil: jointing poor to absent; thin bedded (o inches);; apha- n ltic; poorlyipreserved orInbid column- e lie 's , 9 14 Covered, 10 15 Sandy limestone: weathers brown: fresh surface mottled reddish brown; forms Ir­ regular slope* exposure poor land covered; base sharp and covered; medium;grained, dull to rough, poorly sorted, subangular to subrounded quarts sand matrix;-apha- n l t i c . 8 68 Unit Thickness No. in Feet 16 Limestone (calcareous shale interbeds): weathers dark gray; fre sh surface homogen­ eous to mottled dark gray; poor exposure; products rubble and soil: poor jointing; base covered; medium bedded (1 foot);aph* anitic; concretions of calcite, iron, and silica; possibly partially mineralized. 8 17 Covered (probably incompetent alternating limestone and calcareous shales). 17 18 Silty limestone: weathers gray to olive gray; fresh surface dark gray; homogeneous color distribution; fair exposure; products rub­ ble; poor to absent jointing; medium bedded (1-2 feet); aphanitie; weathered surface has peculiar mottled ellve gray and dark gray appearance. 7 19 Limestone, (graded to silty limestone with some Interbedded incompetent calcareous shales and limestones): weathers gray to grayish olive brown; fre sh surface homogen­ eous gray; forms rounded to vertical cliff; exposure fair: products rubble and soil; tabular thin to medium bedded (2 inches to 2 feet); aphanitie; poorly preserved brach- iopods and calcareous stromatoporoids. 10 20 Covered (gray limestone rubble). 4- 21 Dolomite: weathers brownish buff to cream; fre sh surface gray: homogeneous color d is ­ tribution; forms step: exposure good; pro­ ducts rubble; fair jointing; tabular thin bedded (6 inches); aphanitie; smooth sur­ faced outcrop. 1 22 Covered (gray limestone rubble and calca­ reous soil). 26 290 Cambrian: Rincon Limestone Sandy limestone: weathers brownish red, fresh surface mottled reddish dark brown; massive; poorly sorted sand; smooth to pol­ ished subangular to subrounaed feldspar and quartz; crystallo* b la s t1c calcite matrix; very poorly preserved trilobite tails; very rough sandy surface texture to outcrop. 69 P eloR cillo Mountains (G ranite Gap) Hidalgo Co* Now Mexico T27S, R21W Misslssippian: lake Valley lisastone (Bscabrosa licestone) limestone: white, weathers gray-white; forms rounded c liff 5 forms rubble$ massive; very coarse-grained; abundant well preserved crlnoid columellas. Devonian: Pereha shale Unit Thickness No* in F eet 1 Covered with rubble from the overlying Misslssippian formation* 2 Limestonet similar to underlying rooks, except less clear-exposed and fine grained; shale as below forms a very light colored soil: greater than $0$ limestone* Similar sequence of limestone and shale; limestone pink on fresh surface. 10 ■ b Similar sequence of limestone and shale* 10 5 Similar sequence of limestone and shale; first appearance of pink limestone* 10 6 Similar sequence of limestone and shale; limestones thinner bedded. 10 7 Similar sequence of limestone and shale; shales predominate over limestone* 10 8 Beginning of the gradational change to unit of alternating limestone* and shales; shaly limestone; red; weathers brownish; homogeneous in color; forms an irregular cliff; exposure good to covered; base gra­ dational and.Indistinct; bed thickness of limestone;about 2 feet; surface texture: dull and rough: medium to coarse grained; contains.erlnoids and possibly fragments Of other fossils* Limestone: light gray in color; weathers gray and brown; homogeneous color d lstrl* , button; forms rounded cliff; gradational and covered bate; medium^grained; fairly preserved crinoids, possibly other fossil fragm ents. 10 Feloncillos-Granite Gap Section Unit Thickness No. in Feet 10 Similar to underlying unit; top not exposed• 8 11 Similar to underlying unit, except more mas­ siv e , 10 12 Shaly limestonet black in color, weathers brown gray; homogeneous and g rad atio n al color distribution; forms rounded cliff; exposure good to covered; forms rubble; base gradational; beds are nodular and lenticular; small fairly preserved cri- noids; aphanitie; poorly jointed. 10 13 Similar to the underlying unit, except for the appearance of small erinoids; probably somewhat more s i l t y . 10 l*t Limestones black, weathers a greenish gray; color distribution homogeneous; forms irreg­ ular slope; exposure fair; forms rubble; fair jointing; nodular in part; base gradational; ap h a n itie; lo c a lly lim o n itic stain in g prom­ in e n t. 10 15 Shaly limestone: black; weathers tan and black; color distribution homogeneous; forms irregular cliffs exposure good; products rubble; fair jointing; base gradational; laminated to thin bedded; crystalline tex­ ture; aphanitie: except for shaly character of bedding could be called a limestone. 10 16 Similar shaly limestone to that above; ex­ cept being more finely bedded, less calca­ reous, probably becoming more silty . 10 17 Shaly limestone* black; weathers brownish gray: homogeneous in color distribution; set in a brown groundmass are a series of lenticular black nodules of limestone; no apparent difference in composition of the two; it is suggested that the brown ground- mass has a slightly higher silt content; bed thickness is variable from-J- inch to if feet thick; bed is laminated locally; the surface is dull and smooth; aphanitie crystalline texture; poor jointing. 10 71 Unit Thickness Ho* in F eet 18 Shaly limestone $ black; weathers brown­ ish gray; hoeogeneous color distribution; forms Irregular slope; exposures fair to coveredI productsare rubble; poor joint­ ing ; bedding $-»2 inches in thickness; nodular in part; aphanitie* 10 letite porphyry dike* (30 feet above dike cor* e re d ). 30 19 Free another area about *K)-N-5 feet of black, fissile shale was observed which was apparently underlain by what was as* sunted to be El Paso formation* However, as was pointed out by Gillerman in a personal communication, there really is no positive proof against the existence of the Silurian in the series* ^ 5 lower most Ordovleian-CaabrianC?): El Paso formation Sffarft *rtww Mississippian* Bseabrosa limestone Devonian; Martin limestone Unit Thickness Ho. in Feet 1 Dolomite * light gray to light medium gray; weathers pale yellow brown to pale red; forms slope; exposures M r; bods vary and.commonly

Unit Thickness No* in Feet lb- Covered. 5

15 Limestone like Unit 13; no crystalline nodules; hryasoa-like fossils conmcm. 3 16 Covered. 4 17 Limestone; similar to Unit 13 except stromatoporoids; nodular masses coamon. li 18 Covered. 3 19 Sandstone (quartz 50)6, ealcite 50)6); pale red to medium gray; weathers gray­ ish orange pink; forms step; vertically jointed; medium bedded: fine-medium sand size grains; weathers Slack; in places f r ia b le . 2 20 Limestone similar to Unit 13 except no brycsoa like fossils; medium to thickly bedded; has grains of frosted quartz which weather out; fosslllfcrous; diffi­ cult to extract. 5 21 Dolomite like Unit 2 ; forms step; sili­ ceous brachiopods. Si- 22 Limestone * dolomitie; medium dark gray; weathers pale yellow brown; forms step; medium bedded; compact; fine to medium crystalline; weathered surface pitted and granular; forms blocky rather than rounded beds; quarts sand lenses locally. 4 23 Sandstone (lines with quartz $ 20)6) * med­ ium lig h t gray; forms depression under u n it 22; th in .to medium bedded; . medium to coarse grain size (sand); locally fri­ able; weathers very granular. 2 24 Limestone $ dolomitie: medium light gray; weathers.light gray to pale red; forms slopei no visible bedding; very thickly bedded; fine to medium crystalline; wea­ thered surface, rounded and fairly smooth; few lenses of quarts sand; weathers by exfoliation,commonly; white ealcite blebs and s trin g e rs common. 19 Unit Thickness No. in Feet 25 Sandstone (ealeite 80^ quartz 20^ ); very light gray to white; weathers tan; forms step; bedding indistinct; quartz grains rounded and frosted; medium to coarse sand; in places fri- a b le . 3 26 Covered. 4 27 Limestonet light gray; weathers tan; forms step; thickly bedded; weathers to granular pitted surface; quarts grains scattered throughout. 4 28 Sandstone (70# ealeite, 30# quartz); grayish pink: weathers white making distinct bed; similar otherwise to Unit 24. 4 29 Limestone, similar to Unit 27 except thin bedded. 2 30 Dolomite (limy): pale red; forms step; thickly bedded; finely crystalline; smooth silty weathering surface: cal­ otte blebs in dolomite; weathering forms p i t s • 5 31 Covered. 13 32 Sandstone: pale purple to pinkish gray; mottled;.w ithers pale red; forms steps; thickly bedded; coarsely crystalline; wea­ thers to granular surface; the scattered frosted quartz grains standing out in re­ l i e f . 7 33 Covered. 20 34 Limestone: grayish purple to light red pur­ ple; weathers pale red purple; has bluish gray spots locally; forms step; thickly bedded5 medium-crystalline; weathered sur­ face granular and pitted; at base small red chert fragments common. 10 75 Unit Thlakntss No® in Feet 35 Limestone (upper 1/3 dolomite); dark reddish brown to grayish red; weathers pale'red to grayish red; forms steps; medium bedded; medium and coarsely crys­ talline ; siltstone parting planes common; grades upward into dolomite* 17 36 Limestone: alternating with short covered intervals; light gray to brownish gray; forms steps between covered intervals; thickly bedded; medium crystalline; aph- anitic locally; base disconformable * 8

269

Cambrian* Rincon limestone

Northeast Whetstone Mountains^ Cochise Countyt Arizona SWAeSee°3V f l 8S® R ig T * ** Mississippian* Escabrosa limestone Devonian: Martin limestone Unit Thickness No* in Feet 1 Dolomite: limy; medium gray; weathers light medium gray; forms slope below Escabrosa Is.; medium to thickly tedded; finely crystalline; becomes more limy toward top. 15 2 Dolomite * limy; pinkish gray; weathers light yellow brown; forms step; thickly bedded; aphanitic tb finely crystalline; beds weather rounded; quartz nodules com­ mon. / 10 3 Covered. 5 4 Dolomite: limy; pinkish gray; weathers very light gray (almost white) to light tan; forms cliff; tedding indistinct; very thickly tedded; medium crystalline; quartz sand common, locally making up 2uf of rock. 12 76 Unit Thickness Hoe in Feet 5 Dolomite ! like Unit 1, exeept more dolo- mitio and fresh surface is dark gray. 10 6 Covered. 3* 7 Dolomite like Unit 1: has quarts nodules; forms step ; more do lo m itie. 2 i 8 Covered• 3 9 Dolomite like W it 4: thickly to very thickly bedded; forms prominent cliff below the Bseabrosa; no fossils visible• 4-0 - V • • * . 10 Dolomites limy; dark grays weathers light olive gray; forms slope; ®®dium bedded; fine crystalline; smooth wea­ thering surface; silicifled fossils! corals, crinoid stems. 6 11 Limestone s dolomite and silty; medium gray; weathers yellow gray to ©live gray; forms c liff; beds not well developed; medium to thick bedded; fine to medium crystalline; sand lenses locally; quarts nodules and gray chert: silicifled brach- ionods; gradational into Unit 12# 15 12 Dolomite t limy, medium gray; weathers light gray;>lope forming; thinly bedded; finely crystalline. 9 13 Lim stone like Unit 11: 2 feet from base is a 5” layer of chert, - 4- IV Covered. 8 15 Limestonei locally dblomitlci red gray; weathers yellow brown (silty); forms prom­ inent cliff; thinly to thickly'bedded; medium crystalline; very fossiliferous; silielfled brachlopods$ Atrypa commonly in lenses; basal foot is cwrSely crystal­ line gray Is., with many crinoid stems* 20 16 Covered. 4- 77

Unit Thickness No. in Feet 17 limestone: black; weathers black; forms step; reedina bedded; medita crystalline; cherty; 2 inch black chert layer at top; small silicified crinoid stems* 3 18 Limestone: impure; medium gray; wea­ thers gray tan (silty); forms slope; beds nodular; thin bedded; medium crystalline * 7 19 Sandstones calcareous with some quarts grains; red-brown; weather yellow brown; medium to coarsely crystalline; quarts grains coarse sand size; weathers to a granular surface• 1 20 Dolomite, (Is. locally)s otherwise sim­ ilar to Unit 18. 7 21 Limestone: dolonitic in upper half; med­ ium grayt weathers yello brown; forms prominent cliff; medium bedded; finely crystalline; sandy and silty locally; bedding planes commonly covered with ;;»: bryasoan like fossils. 18 22 Sandstone: limestone cement; quarts grains light gray with green tint; forms step; weathers brownish; friable on weathered surface. 2 23 Covered, 4-

24" Sandstone like Unit 22. 2 25 Calcareous sandstone similar to Unit 22 but b lack . 3 26 Limestone: dolomitic; light gray; wea­ thers yellowish brown; forms slope; medium bedded; finely crystalline; weathers to a smooth silty surface. 5i" 27 Dolomite: limy, dark gray; weathers light gray; forms step; bedding indis­ tinct; thickly bedded; finely crystal­ line; weathers to a smooth surface. 5& 78 Unit Thickness Ho. In F eet 28 Xlaestone: blacks weathers dark gray; forms step; thinly bedded; aphanltte. 2 29 Covered. 3 30 Limestone with sands light to medium gray; weathers medium gray; forms steps; bedding indistinct; finely crystalline; upper 1 foot contains thin slitstone layers; weathers orange where silty . 9 2$0 Horthwest Whetstone Mountains. Cochise Coimtvr Arizona Devonian* Martin Limestone Unit Thickness Ho. in F eet Limestone * dolomltio; moderage orange pink; weathers light pinkish gray; forms base Bseabrosa c liff; very thickly bed­ ded; medium crystalline; upper contact slightly undulating surface with typical Bseabrosa. Limestonet pale red; weathers pink; forms step; no visible beading; fine crystalline; this unit extremely vuggy indicating solu­ tion (not indicated In other sections in Whetstones)• Sandstone (lime sandstone)* pale red; wea­ thers light gray; forms step; very thickly bedded; fine sand size grains• 8 k C o w e d . k 5 Sandstone * like Unit 3. except more: dolo- mitle and weathers; light yellowish; brown. 7 6 Covered. 5 7 Sandstone (chiefly lime sandstone, but some quarts)* light gray; weathers light yellow brown; forms step; medium bedded; very fine sand size grains; weathers to a silty surface and into rounded nodules. 79

Unit Ihiekness Ho. In Feet 8 Limestonet dolonitic (probably a lime slltstone); light gray; weathers light yellow brown; forms prominent cliffs very thickly bedded; fucoida1 markings on bedding planes. 20 9 Limestone s doloaitie as Unit 8, except commonly very thin; thin-medium bedded. 20 10 Sandstone (dolonitie sandstone); light gray with brown in places (mottled im­ pure and pure limestone); weathers light yellow brown; thickly bedded: fine sand size grains; medium crystalline on fresh break. 2 11 Mostly covered, few outcrops of limestone; light gray to light yellow brown; thin bedded; nodular; impure. 2*f 12 Dolomite (silty)s light medium gray; wea­ thers light yellow brown; forms cliff; thickly bedded: ealcite nodules common; weathers to silty; some fine sand; very fossiliferous locally; sllicifled brach- iopods mostly. 13 Sandstone (lime sandstone): dark gray; weathers black; forms step; medium bea­ ded; medium crystalline; small irregular chert nodules. 1 l1* Limestonex yellow brown; forms slope; thin bedded. 4 15 Sandstone, like Unit 13• 2 16 Sandstone (lime and quarts)* medium olive gray; weathers light yellow brown; medium bedded. 3 17 Covered. 10 18 Limestone: light medium gray: weathers same; forms step; thin bedded with well developed tabular beds; aphanitic to finely crystalline; weathered surface pitted and rough. 9 Unit Thickness No. in Feet 19 Limestone, sandstone (some fine quartz grains): medium olive gray brown; forms slope; thinly bedded; fine"sand size grains; commonly friable; portions corn­ e re d . . 5 20 Dolomite (limy, very fine doloaitie sand­ stone): light medium gray to pale red; wea­ thers light yellow brown and silty; forms step: thickly bedded; fine to medium crys­ talline; ealcite nodules common; no fossils observed. 7 21 Limestone: light medium to medium gray; wea­ thers same; forms step; medium to thickly bedded; bedding not well developed every­ where; aphanitlc to finely crystalline; lower 5’"nodular; upper part bedding more Stromatonorold zone and gastropods in upper part (M- feet); other fossils, chiefly bry- ozoans on bedding planes. 19 22 Sandstone, like Unit If. 9 23 Sandstones chiefly quartz sand with lime cement; pale pink to cream; weathers yel­ low brown; forms prominent step; thickly bedded. 2 2l+ Limestone, (in part conglomeratic): medium gray; weathers light medium gray; forms step; bedding irregular and thickly bedded; generally unit is nodular with quartz sand filling Interstices"which weather brown; limestone nodules aphanitlc. 7 25 Sandstone (lime sandstone): light gray; wea­ thers light tan to white; forms step; medium crystalline; cross bedded; quartz sand common and weathers out in relief; lower contact is slightly cross-cutting: lowermost beds con­ tain chips of purple Rincon as a thin 1 inch to b inches conglomerate at the base. 5 25? Cambrian: Rincon Limestone Typically coarsely crystalline, clastic, purple. 81 aec^zz^Ti^ ^R2lBgSnak9 Tankf Cochisg Gountyt Arizona

Mis sis sIpplan: Bscabrosa limestone limestonet weathers grays fresh surface gray, homogeneous color distribution; forms rounded cliff; fair to poor exposure; pro­ ducts, rubble; poor jointing; tabular bed, possibly wedging out on Devonian eroslbnal surface; fine to medium crystalline; concretions of caleite and silica• Devonianr Martin limestone Unit Thickness No* in Feet 1 Covered* 5 2 Doloraltic limestone: weathers brownish gray; fresh surface medium gray; homo­ geneous color distribution; regular to irregular slope; exposure fair; products, rubble and soil; base covered: crystal­ line texture; aphanitic; smooth surface te x tu re • 2 3 Covered. Ik Dolomltle limestones weathers gray: fresh surface reddish gray: banded to mottled color distribution; forms regular slope; poor to covered exposure; forms rubble and soil; poor jointing; gradational base; massive; aphanitic texture; concretions of iron; solution channels present; rough su rfa ce. 5 5 Dolomltle limestone: weathers gray; fresh surface reddish gray; banded and mottled color distribution; forms regular slopes poor to covered exposure: products rubble and soils jointing poor to absent; base sharp and irregular; m&ssive; concretions of iron; solution channels develop rough su rfa ce. > 6 Covered. 7 Dolomite: weathers brown; fresh surface dark brown; mottled color distribution; forms regular slope; exposure poor to covered; products, rubble; jointing ab­ sent to poor; concretions of iron. 3 82 Unit Thickness Ho# in F eet 8 Dolomitet weathers gray brown: fresh surface grayish red brown; color dis­ tribution mottled; forms regular slope: poor exposure; products rubble and soil; fair jointing; massive; similar to unit below except gradational changes color and some indications of shale intervals; solution channels formed on surface; rough texture* ID 9 Calcareous dolomite $ weathers gray; fresh surface gray; homogeneous color d istri­ bution; forms irregular slope; fair ex­ posure % products rubble and soil; base gradational; massive; very rough elephant hide texture to surface of outcrops; lime­ stone increases in part; some indications of shale interbeds, crystalline texture; a p h a n itic • 10 10 Dolomitet weathers tanniah gray; fresh surface gray; gradational, homogeneous and mottled color distribution; forms rounded c liff; exposure good to poor; products rubble; base g rad atio n al; mas­ sive; weathered surface extremely rough. 10 11 Dolomite: weathers gray; fresh surface gray; mottled color distribution; forms irregular cliff; fair exposure; products rubble and s o il; base g rad atio n al; mas­ sive; fossils not observed* 10 12 Dolomite: weathers gray; fresh surface gray; homogeneous color distribution; similar to bed below except many minor recemented fractures; fossils absent; slope forms in part; surface very rough because of differential weathering be­ tween recemented fractures and the dolomite* 10 Dolomite: solution channels make very rough surface; fractures apparently recemented essentially with calcite. 10 Ik Dolomite: wecthers gray;]fresh surface gray; homogeneous color distribution; individual dolomite crystals observed; surface very rough. 10 83 Unit Thickness Ho* in F eet 15 Dolomite % weathers brownish gray; fresh Surface dark gray; mottled color distribution; forms rounded cliff; exposure good; products rub­ ble and soil; fair jointing; base gradational; beds 2 feet thick to massive; crystalline texture; aph- anitic; concretions of dolomite; abundant, well preserved crinoid columnslias, dolomite preservation. 10 16 Dolomitet weathers grays fresh sur­ face dark gray; color distribution homogeneous; forms rounded cliff; exposure good; products rubble; jointing fair; base gradational; beds ^*2 feet; similar to unit below* 10 17 Dolomites weathers gray; fresh sur­ face dark gray; color distribution homogeneous; forms rounded cliff; exposure good; products rubble; fair jointing; base covered; mas­ sive aphamltle to crystalloblastic; silt may be present; recrystallized dolomite evident• 10 18 Dolomltie sandstonei weathers brown; fresh surface brown; homogeneous col­ or distribution; forms irregular cliff; exposure good; products rubble; poor jointing; variable beds thickness; medium grained sand; subangular; dull to rough grains; aphanitic dolomite matrix; calcite concretions; solution channels• 5 19 Covered (probably reddish, silty dolo- mitic shales)* 57 20 Sandy dolomite t weathers dark gray; fresh surface black; homogeneous col­ or distribution; forms irregular cliff; fair to poor exposure; products are rub­ ble and soil; base gradational; fine sand; aphanitic* 5 8N- U nit Thickness No. in F eet 21 Dolomite and dolomltlc sandstone (grades from a sandy fades at base to a dolomite at top)t veatbars cream; fresh surface reddish gray; mottled Color distribution; fair exposure; products, rubble; medium suoangular to subrounded sand, aphanitle matrix and dolomite• 10 22 Dolomltlc sandstonet weathers brown; fresh surface reddish brown; homogen­ eous color distribution; forms irreg­ ular c liff; fair exposure; productsf soil; base covered; bed thickness in­ determinate ; fine, subrounded, polished dolomltlc sandstone; matrix dolomltlc; rough surface cut by solution channels. 10

2?9 Cambriant Rincon limestone limestone t weathers red, fresh surface homogeneous to mottled red; forms irregular cliff; exposure fair; products, rubble; rough surface: contains lenticular, white chert and concretions of calcite and silica*

Misslssipplan: Escabrosa Limestone Limestone* weathers light; fresh surface homogeneous light gray: forms vertical cliff; exposure good; products rubble; fair joint­ ing; base sharp, irregular (?); medium crystalline; massive; well preserved crinoid columnslias. Devonian* Martin Limestone Unit Thickness No. in Feet 1 Dolomltlc limestonet weathers brown; fresh surface homogeneous and grada­ tional brown; forms rounded cliff; ex­ posure fair; products rubble; jointing poor; base sharp and covered; medium bedded (1 foot); rough outcrop; apha- nltic to phaneric crystalline texture; fairly well preserved brachlopods. 13 85 Unit Thickness Ho. in Feet 2 Shale: weathers brownish red; fresh sur­ face tan to brownish red (homogeneous); forms regular slope; exposure largely cov­ ered; products, soil; base covered; dolo- raitic and calcareous in part. 36 3 Dolomite: weathers gray; fresh surface gray; color distribution gradational; homogeneous, banded and mottled; forms vertical to irregular cliff: exposure fair; products rubble; Jointing varies from excellent to fair; medium to thick bedded (1 foot to 3 feet); granular, aph- anitic and phanerio crystalline texture; contains rare layered chert intervals; concretions of calelte and iron; impres­ sions of brachiopods, and some very poorly preserved crinoids and corals. 82 4 Sandy calcareous dolomite: weathers gray, fresh surface homogeneous and gradational from black to red; forms irregular slope; exposure poor to covered; products rubble; very poorly sorted, angular, dull feldspar grains: matrix aphanitic; poorly preserved crinoia columellas. 10 5 Quartzites weathers brown; fresh surface banded brownish red; forms vertical cliff; exposure good; products rubble; excellent jointing; base sharp; thin bedded (3 inches to 6 inches): composed of rounded to sub­ rounded quartz grains with a silicious dol- oraitic matrix. 7 6 Covered (reddish calcareous shale probably) 11 7 Dolomite: weathers red; fresh surface, hom­ ogeneous red; forms step; exposure good: products rubble; base sharp; medium bedded; granular to aphanitic. 2 8 Calcareous sandy shale: weathers red: fresh surface reddish pink (homogeneous); forms regular slope; exposure poor and covered; products soil; calcareous cement; quartz and calcite grains scattered locally. 44 86 Unit Thickness Ho. in F eet 9 Dolomite s weathers dark gray; fresh surface homogeneous black; products rubble: gradational; thin bedded (6 inches): pabanltlc to pbameflc; con­ tains white nodular chert and concre­ tions of calotte; silica and Iron; abundant brachiopod fauna, well pre­ served. 10 10 Calcareous dolomites weathers brownish gray; fresh surface homogeneous to mot­ tled gray; forms irregular cliff; ex­ posure fair; products rubble; jointing peer to absent; medium bandea (1* feet); concretions of calotte excellently pre­ served; abundant, calcareous crinolds and brachiopods. 10 11 Covered. 18 12 Very fine sandy iolomitie limestone: weathers reddish brown; fresh surface banded reddish gray; forms a rolling slope; poor exposure; products rubble; jointing excellent; medium bedded (1 foot); fine sand; matrix aphanitie; excellent preservation of differen­ tially weathering orinoid columnellas. 1 13 limestone: weathers brownish gray; fresh surface banded reddish gray; forms regular slops; exposure poor to abundant; thin bedded (6 Inches); aph- anltic; poorly preserved crlnoid col­ umellas. ’ ' 9 l b Covered. 10 15 Sandy limestone % weathers brown: fresh surface mottled reddish brown; forms' irregular slope; exposure poor and cov­ ered; base sharp and covered; medium grained, dun to rough, poorly sorted, subangular to subrounded quarts sand; matrix aphanitie. 8 8? Unit Thickness No. In Feet 16 limestone (calcareous shale interbeds): weathers dark gray; fresh surface homo­ geneous to mottled dark gray; poor ex­ posure; products rubble and soil; poor jointing; base covered; medium bedded (1 foot); aphanitic; concretions of ca1- eite, iron and silica; possibly partially mineralized. 8 1? Covered (probably incompetent alternating limestone and calcareous shales). 17 13 Silty limestone: weathers gray to olive gray; fresh surface dark gray; homogen­ eous color distribution; fair exposure; products rubble; poor to absent jointing; medium bedded (1-2 fe e t); aphanitic; wea­ thered surface peculiar mottled olive gray and dark gray. 7 19 limestone % (graded to silty limestone with some interbedded incompetent calcareous shales and limestone); weathers gray to grayish olive brown; fresh surface homogen­ eous gray; forms rounded to v e r tic a l c l i f f ; exposure fair: products rubble and soil; tabular thin to medium bedded (2 inches to 2 feet); aphanitic; poorly preserved brach- iopods and calcareous stromatoporoids. 10 20 Covered (gray limestone rubble). 4 21 Dolomite : weathers brownish buff to cream; fresh surface gray, homogeneous color dis­ tribution: forms step: exposure good; pro­ ducts rubble; fair jointing; tabular thin bedded (6 inches); aphanitic; smooth sur­ faced outcrop. 1 22 Covered (gray limestone rubble and calca­ reous soil). 26 35% Cambrian: Rincon Limestone Sandy limestone: weathers brownish red; fresh surface mottled red­ dish dark brown; massive; poorly sorted sand; smooth to polished, subangular to subrounded, feldspar and quartz: crystalloblastic calcite matrix: very poorly preserved trilobite tails; very rough sandy surface texture to outcrop. 88

C0WltT> ArttQ M Mississippian: Bseabresa Linastone Limestone: gray; weathers light gray; color distribution homo­ geneous; forms rounded cliff; exposure fair; products rubble; Jointing fair; base gradational; massive; fine to medium and coarse grained; large erlaoid columnsHas* Devonian: Martin Limestone Unit No. Thickness in Feet 1, Slightly silty dolomite: dark gray; weathers bufft color distribution homogeneous; forms rolling slope; exposure poor and covered: products rubble; jointing excellent; base cov­ ered; surface smooth; fine grained; iron stained calcareous fissures, 26 2 Covered with limestone soil* 29 3 Similar to Unit 6; grayish black to red; weathers brown: (crossed possi­ ble zone of movement). *K) h Similar to Unit 6. N- 5 Similar to Unit 6; partially covered; gray to red in color. 10 6 Silty dolomite: weathers buff: dark reddish"gray; color distribution homo­ geneous; forms irregular slope; exposure fair; products rubble; jointing excel­ lent: base gradational: fine grained; caleite fissures; poorly preserved brach- iopods• 10 7 Shale: gray; weathers buff to red; color distribution gradational; forms rolling slope; exposure poor and covered$ products soil; jointing poor; base covered: calca­ reous fissures; also minor silty dolomite u n its . 14- 8 Covered with brown rubble and soil. IN- 89 Unit Thickness No. In Feet 9 Slightly silty dolomite* gray* weathers buff to gray; color distribution homo* geneous; forms irregular cliff; exposure good; products rubble; jointing excel­ lent; base covered; surface texture rough; fine grained. 22 10 Similar to 11; medium to coarse grained at top; badly fractured lower part. 13 11 Dolomite* gray; weathers light gray; col­ or distribution homogeneous; fine grained; ' forms irregular slope; exposure fair; pro­ ducts rubble; jointing excellent; base cov­ ered; surface rough; concretions of calclte; stringers of calclte* 10

12 Covered with rubble. 15 13 Dolomite* gray; weathers gray; color dis­ tribution homogeneous; forms rolling slope; exposure poor and covered; products rubble; jointing fair; base covered; surface smooth; aphanltlc to fine grained; concretions and stringers of calclte. 1 lU- Covered with rubble and soil. 13

250 Upper Cambrian* Rincon limestone Slightly calcareous dolomitle sandstone; light brown; weathers brown; color distribution mottled; forms irregular slope; ex­ posure poor and covered; products m il; jointing poor; base gra dational; fine to coarse grained.

Deepwell Canyon. Cochise Countv. Arizona W A Sec 11T15S, R21E Mississippian* Bscabrosa Limestone Limestone* dark gray; weathers gray; color distribution homo­ geneous and gradational* medium to coarse grained; abundant erinold columnslias well preserved, calcareous; forms rounded cliff; exposure good; products rubble; base sharp and covered; concretions of calclte...... w . • - z Devonian* Martin Formation 90 Unit Thickness No. in Feet 1 Covered. 2 Similar to Unit 3. 10 3 Dolomite $ grayish red; weathers brown; col** or d istrib u tion homogeneous; forms irregular cliff; exposure fair to poor; products rub­ ble; jointing fair; base sharp; beds 1/2 to 2 fe e t thick; surface texture smooths fine grained at base; black fragments in the dol­ omite as stringers; chert, locally iron stained. 10 k Shalei buff; weathers buffs color distri­ bution gradational and mottled; forms ir ­ regular slope; exposure poor and covered; products soil; jointing poor; surface tex­ ture smooth. 8 5 Covered with rubble• 20 6 Dolomitet olive gray; weathers dark brown­ ish gray; color distribution mottled; forms irregular slope; exposure fair and covered; products rubble; jointing fair; bas# sharp; medium crystalline; concretions of silica. 12 7 Badly fractured dolomite: possibly some faulting; much caleite in the section. 6 8 Similar to Unit 9; medium to coarse grained; concretions of caleite. 10 9 Dolomite: dark gray; weathers gray; color d istrib u tion homogeneous; forms v e r tic a l cliff; exposure good; products rubble; joint­ ing poor to fair; base gradational; surface texture very rough, like elephant hide; iron stained calcareous blebs and concretions• 10 10 Similar to Unit 11, partially covered. 30 11 Dolomite: dark gray; weathers gray; color d istrib u tion homogeneous; forms irregular, cliff; exposure good to fair; products rub­ ble: jointing fair and excellent; base gra­ dational; surface texture smooth; aphanitic to finely crystalline; concretions of cal­ eite; brachiopods. 10 91 Unit No* Thickness in F eet 12 Covered with rubble» 4- 13 Fine dolomitic sandstone alternating with dolomitic layers: brown and gray; weathers to dark gray: color distri­ bution banded; forms irregular cliff; exposure covered; products rubble; jointing fair: base covered: beds ap­ proximately six inches thiex; fine sand; subrounded; surface texture smooth to rough; sand composed of q u arts in p a r t; crystalline texture; aphanitic: cement dolomitic; concretions of calcite; cal* cite also occurs as fissure fillings; well preserved brachiopods* 10 14- Covered with rubble* 7 15 Quartzite: reddish brown; weathering reddish brown; color distribution homo­ geneous and mottled; forms irregular cliffs exposure fair; products rubble; jointing excellent; base covered; fine quartz sand cemented with calcite. 5 16 Covered with rubble* 14 17 Slightly sandy siltstone: reddish brown; weathers reddish brown; color distribu­ tion homogeneous; forms irregular cliff; exposure fair; products soil; jointing fair; base gradational; minor calcite fissures* 6 18 Covered with white marly material and rubble from above* 8 19 Dolomitic siltstones red; weathers red; color distribution homogeneous; slope regular; exposure fair; products rubble; jointing poor to fair; Vase gradational; surface smooth; fissures contain calcite* 10 20 S im ilar to Unit 21* 3 21 Shale: buff to red at top; weathers buff to red: color distribution gradational and mottled: forms irregular slope; exposure poor and covered; jointing poor; base cov­ ered; smooth.surface texture* 10 92

Unit Thickness Mo. in Feet

22 Covered with rubble • 15 23 Dolonitic sandy siltstone: olive brown; weathers olive; color distribution gra­ dational and mottled; forms regular slope; exposure poor and covered; products soil; jointing poor; base covered; bed thickness one fo o t; forms silic e o u s co n cretio n s. 1 24 Covered with limestone soil and rubble. 17 25 Dolomltie sandstonet ealeite in fissures; dark grayish brown to brownish gray; wea­ thers dark brown to dark reddish brown; color distribution gradational, banded and mottled; forms irregular slope; ex­ posure fair; products rubble $ at the very top thin lens of well rounded pebbles; jointing fair to excellent; base grada­ tional; ranges from fine sand to pebbles; sorting fair: composed of quartz, mica, limestone and dolomite; dolomltie aphani- tie cement* 10 26 Very slightly silty dolomite: color dis­ tribution homogeneous; slightly sandy at top; gray: weathers’ light gray; forms ir­ regular cliff; exposure:fair; products rubble; jointing excellent; base grada­ tional and covered; bed thickness 3*6 inches| iron stained calcareous concre­ tions; aphanitic. 7 2? Slightly silty dolomite % grayish brown; weathers gray buff; color distribution homogeneous; forms irregular slope: ex­ posure fair; products rubble: jointing excellent: base sharp; aphanitic; becomes more thinly bedded at the base and is par­ tially covered at the top* 9 28 limestone breccia conglomerate: gray; wea­ thers gray: color distribution homogeneous: forms regular slope: exposure fair: products rubble; jointing fair; lenticular in extent; base sharp; composed of limestone; calca­ reous cement* 2 27& 93 Upper Cambrians Rincon Formation (?) Sandstone and quartsite % brownish red; weathers reds color distribution mottled and banded; forms irregular cliff; ex­ posure fair to covered; products rubble: jointing fair; base gradational; bed 1*2 feet thick; concretions of calcite and iron# Qgclaise co%nt%, Ariima

Mississippiant Bseabrosa Limestone limestone s white t weathers light gray; color distribution hom­ ogeneous; forms irregular c liff: exposure good; products rubble: abundant excellent large crinoid columellas; very coarse grained base gradational but recognisable# Devonians Martin Formation Unit Thickness Ho# in Feet 1 Covered with very light brown soil# 18 2 Limestone: light gray: weathers dark gray; color distribution homogeneous; forms regular slope: exposure poor; products rubble; jointing poor; base gradational: surface texture rough; small crinoid columnslias; medium grained# 10 3 Covered with rubble# 6 4 Silty limestones reddish brown; weathers to buff-red; color distribution homo­ geneous and gradational; forms regular slope; exposure poor to covered; poor jointing with come calcite: base cov­ ered; surface texture smooth; aphanltlc; brachlopods and crinolds observed# 5 5 Covered with brown soil and rubble # 12 6 Calcareous dolomites pink: weathers pinkish red; color distribution homo­ geneous: forms regular slope; exposure poor and covered; products soil and rub­ ble; jointing poor; base gradational and covered; very badly preserved brachlopods; surface rough; aphanltlc# \ Covered with light hrown rubble• Similar to Unit 11$ very badly covered• Similar to Unit 11$ small erinoid colum- aellas; more henatitle* S im ilar to Unit 11$ reddish ch e rt lik e concretions• liimestonet dark reddish gray: weathers buff to yellow brown; color distribution homogeneous; forms regular slope; expos­ ure poor: products soil; jointing poor; tabular in form; base covered; surface smooth;s silty; aphanltle. Covered; forms slightly lighter brown soil than normal. Limestone: gray; weathers gray; color dis­ tribution homogeneous; forms regular slope; exposure poor and covered; products soil; jointing poor: base sharp; massive; medium to coarse grained; surface rough; fairly well preserved braehiopods and corals. Forms a very fine dark brown soil covered largely with rubble • Limestone: reddish brown; weathers reddish brown: color distribution homogeneous and banded; forms irregular slope; exposure fair: calcite fills fractures; aphanltle to fine grained; laminated in part* Limestone: reddish gray to gray; lamin­ ated; weathers gray to red gray; color distribution gradational and banded; forms irregular slope; exposure poor to covered; products rubble; jointing poor; laminae thickness 1/16 inch: gradational; surface smooth; layered, nodusdr and len­ ticular chert, red in color; poorly pre­ served braehiopods, corals and gastropods. 95 Unit Thickness No. in Feet 17 Limestone: reddish gray to black; weathers gray to reddish gray; color distribution gradational and banded; forms irregular slope; exposure poor and covered; products rubble; jointing poor; nodular and irreg­ ular blebs of chert; red in color; calca­ reous concretions medium to fine grained; fractures filled with calcite. 10 18 Limestone: red to grayish red; weathers red to grayish red; color distribution gradational; forms irregular slope; ex­ posure fair and covered; products rubble and soil; jointing poor; base gradational; surface rough; red layered and nodular chert; chert weathers out; fine grained to aphanitic. 10 19 Covered. 15 20 Limestone: light to dark reddish gray; wea­ thers to grayish red; color distribution gradational, banded and mottled; forms ro ll­ ing slope; exposure poor and covered; pro­ ducts rubble; jointing poor; gradational; medium grained to finely crystalline; lam­ inated in parts, minor chert. 8 21 Limestone: gray to reddish dark gray; wea­ thers gray; color distribution homogeneous; exposure fair and covered; products rubble; jointing poor to fair; base gradational; lenticular red chert; some very minor sands developed. 10 22 Limestone: grayish white; weathers white; color distribution homogeneous; forms irreg­ ular slope; exposure fair to covered; pro­ ducts rubble; jointing poor; massive; sur­ face rough; some well rounded sandstone. 10 23 Covered with rubble; forms brown soil. 8 24 Limestone: red; weathers red; color distri­ bution mottled; forms irregular slope; ex­ posure fair to covered; products rubble; jointing poor; lenticular and irregular in form: base irregular; aphanitic; laterally lenticular; siliceous concretions. 3 266 96 Upper Cambrian* Abrigo Formation Alternating shales and thin bedded limestones with dark gray to black cherte ifalse County. Arizona Mississippian: Eseabrosa Limestone Limestone: w hite: weather# lig h t gray* homogeneous and grada­ tional color distribution| forms rounded cliff: exposure good to fa ir| products, rubble; surface rough; abundant well pre* served crinoids; very coarse grained. Devonian: Fercha shale Unit Thickness Ho. in Feet 1 Slightly calcareous dolomite: dark gray; weathers light brown; color distribution, homogeneous; forms rounded cliff: expos­ ure fair to poor; probably contains a high silt content; base gradational; beds heter­ ogeneously laminated. 10 2 Silty dolomite: dark gray: weathers dark brown; almost similar to the Abrigo forma* tlon: color distribution homogeneous; forms rounded cliff: exposurev fair; products, rubble; jointing poor; base gradational; surface texture smooth; aphanitie. 10 3 Limestone: black; weathers buff; color dis­ tribution , homogeneous; exposure, good; products, rubble; jointing fair; forms rounded e llff; base gradatlnmal; hetero­ geneous laminae; surface texture smooth; calcite fills fractures. 10 4 Similar to Unit 5 except for decreasing amount of shale. 10 5 Limestone (similar to Unit 6): interbedded with shales; green; weathers green: forms an irregular slope: base of shale irregular and gradational with the limestone; shale contains calcareous concretions• 10 6 Similar to Unit 7» not laminated, partial­ ly covered« 10 9 7

Unit T h ic k n e s s No. i n F e e t 7 Limestone: black; weathers tan and black; color distribution, homogeneous and gra­ dational; forms irregular cliff; exposure fair to coveredt aphanitic; contains cal­ careous concretions; not laminated; slightly silty layers separate. 10 8 Covered. 16 9 Limestone: more lenticular and laminated than Unit 10. 6 10 Limestone and laminated limestone: black; weathers brown and black; color d is trib u ­ tion, homogeneous; forms irregular cliff; exposure good; products rubble; poor joint­ ing; gradational base; heterogeneously lam­ inated; surface texture smooth; aphanitic; iron and calcareous concretions. 10 11 Limestone, similar to Unit 11: more lenti­ cular; locally hemetitle: sometimes lamin­ ated; less pronounced silt layers. 10 12 Limestone and shale: black; weathers black; color distribution homogeneous and grada­ tional; forms Irregular cliff; exposure good; products rubble; jointing poor; tab­ ular; base sharp; bed thickness about 2 inches; bed structure laminated and heter­ ogeneous; aphanitic; limestone nodules with calcite fillings. 10 13 Shale: black; weathers black; color distri­ bution homogeneous; forms irregular cliff; exposure good to fair; jointing excellent; base gradational; heterogeneous laminated structure; calcareous in some shale partings. 11

lb Shale: black; weathers black; color distri­ bution homogeneous; forms irregular slope; exposure good: products soil; jointing poor; limonitic staining. 10

1 5 Very slightly calcareous shale: black; wea­ thers black; color distribution homogeneous; forms irregular and regular slope; exposure fair; products soil; jointing excellent; base sharp; minor laminitic staining. 10 9 8

Unit T h ic k n e s s H0e i n F e e t 16 Marly shale: brownish green: weathers brownish green; color distribution horn* ogeneousj forms regular slope; exposure fair; products soil; base sharp# 1 17 Similar to Unit 18. 3 18 Similar sequence of limestone shale: frac­ turing replaced with calcite; iron stain­ ing, some minor silt and very fine sand­ stone # 10 19 Limestone: dark gray: weathers brownish gray; color distribution homogeneous; forms irregular cliff; exposure fair to covered: products rubble; jointing poor; partially laminated; very poorly preserved braohlopods partially replaced by iron. 7 20 Covered with talus• 6 21 Laminated limestone: black: weathers buff and dark gray; color distribution homogen­ eous; forms irregular cliff; exposure good; products rubble and soil; jointing excellent; laminae homogeneous; base gradational; sur­ face texture smooth; aphanitic# 8 22 Dark gray bedded limestone and laminated shale break: color distribution homogeneous and slightly banded; forms irregular cliff; exposure good; products rubble; slabby in parts at the top} bed thickness 1*2 inches in the limestone: laminated heterogeneously; aphanitic; hematltlc concretions in bedding. 10 23 Limestone: nodular: black: weathers buff to dark gray; color distribution homogeneous; . forms irregular cliff; exposure good; joint­ ing fair; laminated; surface texture smooth. 10 2h Limestone alternating with shale: dark gray limestone, thin and nodular; shale black and weathers brownish gray; color distribution homogeneous; forms irregular cliff; exposure good: base sharp and even; laminated homogen­ eously; surface texture smooth; aphanitic limestone; possibly some local structure in the section. 10 99 Unit Thickness Wo* in Feet 25 Similar to Unit 26• 8 26 Shaly limestone t black; weathers brownish black; color distribution homogeneous; forms irregular cliff; exposure good to fair; products soil; jointing excellent; fractures filled with recrystallized cal­ otte; base gradational; homogeneously lam­ inated; aphanitie; concretions of ealeite* 10 27 Shaly limestone * black$ weathers brownish black; color distribution homogeneous; forms irregular cliff; exposure fair to poor; pro­ ducts rubble; jointing excellent; laminated gradationally and homogeneously; aphanitie; llmonlte crystallized in fractures * 10 28 Calcareous shale, (whole section slightly metamorphosed); black; weathers black; col­ or distribution homogeneous; forms irregular cliff; exposure fair; products soil; joint­ ing excellent; base sharp and irregular; •§• to inch bedding; surface texture smooth* 10 255 I«ower Ordovician: El Paso Formation limestone: grayish white; weathers brown; color distribution hom­ ogeneous: forms irregular cliff; exposure fair to covered; products soil; jointing poor to fair; base gradational; surface texture dull; silty with very fine sandstone in part*

ma County T Arizona

Mississippian: Escabrosa Limestone Limestone: light gray, weathers light gray; color distribution homogeneous; forms vertical c liff; exposure good: products rubble; jointing poor: base gradational; massive; coarsely crystalline; , well preserved large erinoids• Devonian: Martin Formation U n it Thickness No* in Feet 1 Dolomite: reddish gray; weathers brown

Univ. of Arizona Library 100 Unit Ho. Thickness ■ ~ ...... - 4 • • • • - * ...... color distribution homogeneous; forms irregular cliff; exposure fair; products rubble; jointing fair; base gradatlcmai; bed thick* ness approximately 2 feet; concre- tions or caleite; fine to medium grained. 6 2 Similar to Units 1 and 3, grada* tional into each. 10 3 Similar to Unit 4 only darker gray. 10 4 Dolomites reddish grays weathers brown; color distribution homogem* ecus and gradational; forms vertical cliff; exposure good; products rub* ble; jointing excellent; base sharp; beds 2 feet to massive in thickness; surface texture smooth; aphanitie to fine grained. 10 5 Similar to Unit 6. 4 6 Dolomitic limestones reddish gray, wea­ thers to buff; color distribution mottled; forms irregular cliffs exposure fair and covered; products rubble; jointing excel­ lent; base covered; surface texture smooth; concretions of caleite; coarse grained; grades in bed size from 3 inches at the bottom to 2 feet at the top. * 10 7 Covered with rubble. 9 8 Dolomites gray; weathers buff; color dis­ tribution homogeneous; forms vertical cIlff: exposure good; products rubble; jointing excellent; base covered; bed thickness 2 feet; surface texture smooth; aphanitie; abundant well preserved brach- lopods. 10 9 Covered with white soil. 36 10 Non-fosslliferous unit similar to 12. 10 11 Similar to Unit 12 except jointing less well developed and more caleite concre­ tio n s . 2.0 101 Unit Thickness Hp# in Feet 12 Dolomitic limestonet gray $ weathers brown; color distribution homogen­ eous! forms rounded to vertical c liff; exposure fair; jointing fair; surface smooth; abundant brachiopods; massive; finely crystalline. 10 13 Covered with very light soil probably derived from shaly unit. 31 14- Slightly silty dolomite: gray to red­ dish gray; weathers brown; color dis­ tribution gradational; exposure fair and covered; products rubble; base sharp; grades into fine grained dolo­ mitic sandstone at top; beds in sand­ stone i-l inch thick. 5 15 Quarts* horizon probably associated with nearby ore deposition (Indiana m ine), 4 16 Similar to Unit 17; develops unusual sandy weathering very pronouncedly. 3 1? Calcareous dolomite* gray; weathers light reddish brown; color distribu­ tion gradational; surface texture rough; forms irregular cliff; expos­ ure fair: products rubble; jointing excellent; medium to coarse grained; concretions of calcite; corals. 10 18 Similar to Unit 19; jointing better* fossils completely replaced by calcite; brachiopods and gastropods; fresh col­ or gradational into light gray. 10 19 Slightly silty dolomite* black; wea­ thers brownish to light brown; color distribution homogeneous; forms irreg­ ular cliff; exposure fair and covered; products rubble; jointing fair to ex­ cellent; base sharp; fine grained* con­ cretions of oalacite; iron stained cal­ cite fracture filling. 10 20 Similar to Unit 21. h 102 Unit Thickness Ho. in Feet 21 Slightly silty dolomiter black, dark gray brown to grayish blacks color distribution banded j forms irregular cliff $ exposure fairs products rub­ ble; jointing fair; base gradational; $ foot to massive bedding; medium crystalline; iron stained jointing. 10 22 Silty dolomite s gray; weathers brown; color distribution homogeneous; forms vertical cliff; exposure goods products rubble; jointing poor; base sharp; poor­ ly preserved molds of gastropods and braehiopods; surface texture smooth. 2 23 Calearenite t gray; weathers grayish brown; color distribution mottledt forms rounded cliff; exposure good; products rubble and soil; massive hematitle concretions; nodular and lenticular chert; subrounded to roun^ ded well sorted caleite grains. 8 2b limestones red and whites weathers red and white; color distribution mottled; forms vertical cliff; ex­ posure good; products rubble; join­ ting poor; base gradational; concre­ tions of caleite; medium to coarsely crystalline• 8 25 Dolomite % black; weathers black and browns color d is trib u tio n homogeneous, banded and mottled; forms rolling slope; exposure fairs products rubble; base gradational; bed thickness approximately one fo o t; a p h a n itie ; dolom itie iron stained concretions• 11 26 Calcareous dolomites pink; weather* buff; color distribution mottled; forms Irregular cliff; exposure fair; products rubble; jointing poor; base covered; aphanitie to medium crystal­ lin e ; bed thickness approxim ately one foot; calcareous concretions. 2 103 Unit Thickness Ho. in Feet 27 Dolomite: dark gray to fclaek: wea­ thers gray to black; color distri­ bution gradational and mottled; forms irregular cliff; exposure good and covered; products rubble; jointing excellent; base sharp; aphanitic to medium crystalline; badly recrystal- lized corals and bryozoans; iron con­ c re tio n s . 7 28 Silty dolomite: black; weathers gray; color distribution homogeneous; forms irregular cliff; exposure fair to cov­ ered; products, rubble; jointing excel­ lent; base gradational; bed thickness variable from 2-13 inches; some very badly recrystallised corals andbryo- soans: aphanitic to finely crystalline; hematitic and calcareous concretions. 12 29 Dolomitei black; weathers blackish gray and brown; color distribution mottled; forms irregular c liff; exposure good; products rubble; jointing poor; base sharp; bed thickness variable from •£- 2 feet; gradationally laminated; aphan­ itic; surface texture rough; badly re- crystallized blabs indicate fossils, not recognisable; hematitic concretions; hematitic fracture fillings in the upper part of the section. 25 30 Dolomitet dark pinkish gray; weathers buff to dark gray; color distribution banded on the weathered surface, homo­ geneous on the fresh surface; forms vertical cliff; exposure good; products rubble; jointing fair; base sharp; lam­ inated; surface texture rough; very minor hematitic concretions. 5 31 Calcareous mudstonet green and red; wea­ thers green and red; color distribution banded; forms rolling slope; exposure poor and covered; products sell; jointing poor; base covered; forms very calcareous s o i l . 6 Unit Thickness Ho. in Feet 32 Covered. 10 33 Slightly silty dolomite % grays weathers tan to brown; color distribution homo­ geneous; forms irregular c liff; exposure good; products rubble; jointing fair; base gradational; beds variable from to i-;ii- feet in thickness; surface texture smooth; hematite filling fractures; aph- a n itie . 9 3*+ Slightly silty dolomite: blacks weathers grayish'brown; color distribution homo­ geneous; forms irregular cliff; exposure good; products rubble; base sharp; apha- nltie; small blebs of hematite; concre­ tions of ealcite; rough surface texture; middle four feet covered. 11 35 Dolomitic sandstone: dark gray; weathers brown; color d is trib u tio n homogeneous on fresh surface, mottled on weathered sur­ face; forms vertical cliff; exposure good; products rubble: jointing poor: base sharp; line sand to medium sand, rounded, well sorted; sand is mostly quartz; high degree of dolomitic cementation; aphanltlc matrix; hematitic concretions• 1 36 Shales and marls: greenish brown; weathers brown; color distribution homogeneous; forms rolling slope; exposure poor; pro­ ducts soil; base covered. 5 37 Sandy silty dolomite: blaek; weathers brown; distribution homogeneous; forms irregular cliff; exposure fair; products rubble: jointing excellent; base covered; bed thickness 1-6 inches; laminated; very sandy; chert; dolomite aphanltlc; calclte recrystallised in fractures. -9 ...... 3%% Upper Cambrian: Abrigo formation Red shales and marls: (marls in contact); light green; weathers brown; color distribution homogeneous; forms regular slope; bed thickness averages & inch; atari averages between 50 and 12 feet in the Waterman Mountains* REFERENCES CITED

Barnes, H.. 1954. Age and stratigraphic relations of Ignacio Quartzite in Southwestern Coloradoi Amer« Assoc. Pet­ rol. Qeole Bull., vol# 38, p« 1780-1791. B rittain, Richard l., MS 1954, Geology and ore deposits of the western portion of the Hilltop Mine Area, Cochise County, Arizonat 97 pages, University of Arizona. Burbank. W. S., 1930, Revision of geologic structure and stratigraphy in the Oroy D istrict of Colorado, and its bearing on ore depositions Colo. Sci. Soc. Pro­ ceedings, vol. 12, no. 6, p. 151-232. Cooper, G. A. and Arellano, A. R. V., 1946, Strata near Ca- borca, Northwest Sonora, Mexico* Amer. Assoc. P e tro l. Geol. Bull., vol. 30, p. 606*612. Cope, B. D., 1882, Geological age of lake valley mines of New Mexico* Eng. and Min. J o u r., v o l. 34, p . 2 l4 . Cross, W. 1904, A new Devonian Formation in Colorado* Amer. Jour. Sci., 4th., vol. 18, p. 245-252. Cross, W. and Howe, B ., 1905. Red beds of Southwestern Colo­ rado and their correlations* Geol. Soc. Amer. B ull., vol. 16, p. 447-496. Cross. V. and Spencer, A. C., 1899, La Plata Folio No. 60, U. S. G. S ., p . 8 . ’ D arton, N. H ., 1916, Geology and underground w ater of Luna County, New Mexico* U. S. G, S . B u ll. 618, 188 pp. ______‘ 1925, Resume Arizcma Geology* Arizona Bureau of Mines Bulletin 119. Dunham, K. C ., 1935, The geology of the Organ Mountains: New Mexico Bureau of Mines and Min. Res. Bull# 11, p. 12- 261* New Mexico School of Mines Bull. #11, 1935. Epis, R. C. and Gilbert, C. M., 1956, Sandy facies of tapper Devonian Strata in Southeastern Arizona, (Abst.): Geol. Soc. America Program of Reno, Nevada, Meeting, March 29 - 31, p. 15.

105 106 Flower, R., 1953» Paleozoic sedimentary rooks of Southwestern Hew Mexico: N. Hex* Geol. Soc* Guidebooks, 4th» Field Conference, p, 106#112* Flower, R., 1955) New Max. Geol. Soc. Guidebook, 6th. Field Conference. Gordon, C. H., 1907) Mississippian (Lower Carboniferous) for­ mations in the Rio Grande Valley, Hew Mexico: Am. Jour. Sci., 4th, toI. 24, p. 58-64. Gilluly. James, 1956. General Geology of Central Cochise County Arizona: u. S. Geol. Survey Prof. Paper 28l, p. 25-29* Huddle. J.W. and Debrcvolny, Ernest, 1950, Devonian and Mis- sissippian rocks of Central Arizona: u. S. Geol. Survey Prof. Paper 233-D. Kelley, Vincent C. and Silver, Coswell, 1952, Geology of the Caballo Mountains: Dhiv. of New Mexico Pubs, in Geology, no. 4 . Keyes, C. R., 1904, Unconformity of the cretaceous on older rocks in Central Hew Mexico: Aaer. Jour. Set., 4th, v* 18, p . 360—362* Keyes, C. R.. 1908. Genesis of the lake Valley, Hew Mexico, silver deposits: Am. Inst. Min. Eng. Bl-mon. Bull* 19, p . 7- 21. Knight, R. H. and Cooper, J. C., 1955, Four Corners Geol. Soc. Guidebook. K ottslow ski, Frank B ., Flower, R*, Thomson, M. L ., F o ste r, R. V., 1956, Stratigraphic studies of the San Andres Mountains, Hew Mexico: New Mex. Bur. Mines Memoir 1. Lindgren, Waldemar, 1905, The copper deposits of the Cllfton- Morenci, Arizona: U. S. Geol. Survey Prof. Paper 43. McClymonds, Heal E ., MS 1957, S tratig rap h y and stru c tu re of the southern po rtio n of the Waterman Mountains, Pima County, A rizona, 157 pp* McKee, B. D., 1945, Cambrian history of the Grand Canyon Re­ gion: Carnegie Inst. Wash. Pub. 563, 168 pp. McKee. B. D., 1947, Paleozoic seaways In Western Arizona: Amer. Assoc. Petrol. Geol. Bull*, vol. 31, no. 2, p. 282-92. McKee, E.D.. 1951. Sedimentary basin of Arizona and adjoining areas: Geol. Soc. America Bull., vol. 62, p. 481-505. 107 McNair, A. EL. 1951* Paleozoic stratigraphy of part of Northern Arizona $ Amer. Assoc. Petrol. Qeol., vol. 35, no. 3, P* 532. M iller, A. K. and Collinson, C., 1951, A clyraenoid: Amer. Jour. Set., vol. 2^9, p. 600-603. t Mulchay, Roland B. and Velasco, Ruben, 195^, Sedimentary rocks at Cananea, Sonora Mexico and tentative correlations with the sections at Bisbee and the Swisshelta Mtns., Arizona: Trans. A. I • M. B*, p. 628*632. Nelson, 1. A ., 1950, Franklin Mountains? W. Texas Qeol. Society Guidebook, Sierra Blanca, Franklin Mtns., Texas, 37-40. Pettijohn, F. J., 1949, Sedimentary rocks: Harper Geoscience Series, Harper & Bros., New York, New York. Fettijohn, F. J . , 1957, Sedimentary rocks: Harper Geoscience Series, Harper & Bros., New York, N. Y. Ransoms, F. I., 1904, Geology and ore deposits of the Bisbee Quadrangb,-•* * . Arizona* - U. S. - ' Geol. ». * * ■ Survey • • P ro f. Paper 21* Ransoms, F. L., 1915, The Paleozoic section of the Ray Quad­ rangle, Arizona: Wash. Acad. Scl. Jour., vol. 5, p. 380- 388. Richardson, C. B., 1904, Report of a reconnaissance in Trans- Pecos Texas: univ. Texas Min. Surv. Bull* 9, p. 11-113• Richardson, C.B., 1908, Paleozoic Formations in the Trans- Pecos Texas: Amer. Journ. S c l., 4 th , v o l. 25, p . 474-484. Ruff, Arthur W., MS 1952, The geology and ore deposits of the Indiana Mine Area, Pima County, Arizona: Univ. A rlz., 64 : pae^r . . i ::' Sabins, F. F ., 1955, Geology of the Cochise Head and Western Part of Vanar Quadrangle, Arizona * unpublished Ph. D. Dis­ sert ion, Yale University, 151pp. _ 1957, Stratigraphic relations in Chirieahua and Dos Cabezos Mountains, Arizona: Bull^ Amer. Assoc. Petrol. Geol., vol. 4l, no. 3 , p. 466*510. Shorty M. N. e t a le , 1^-3, QeolOgy and ere d ep o sits of th e / Superior Mining Area, Arizona: Univ. Arlz. , Ariz. Bureau Mines BhU . 151* Cross, W. and Spencer, A. C., 1900, Geology of the Rico Moun­ tains, Colorado* u. S. G. S. 2lst. Ann. Rept., Pt. 2, p. 37-78. ' 108 StaInbrook, Me A,, 19^7, Brachlopoda of the Percha Shale of New Mexico and Arizona$ Jour, of Paleontology, vole 21, p. 297-328* Stevenson, F. V., 194-2* N. Mex. Bur. Mines and Mineral re­ sources, Bull* 18, p , 23-24-e Stevenson, Fi V,, 194-5• Devonian of New Mexicoi Jour. Qeol*, ▼ole..53, P* 217-245. S toy anew, A. A.. 1930, Certain aspects of the Devonlc In Ari* zonat Pan-An. Geol*, vol. 53, p* 316-17• _ ■ " " ....t 194-2, Paleozoic paleogeography of Arizona: Geol. Soc. America Bull., vol. 53, p. 1255-1282. Stoyanow. A. Ae, 194-9* Sequence of Cambrian Tlloblte fauna in Southeastern Arizona (Abstract): Geol. Soc* Aster. Bull., vol. 60, p. 1922. Titcomb, Jane, 1932, The Devonian Section of Bisbee, Arizonat M.A. thesis, Uhlv. of Minn. Tyrrell, Jr., W illis, Ph. 1956, The Cambrian and Devonian Car* bonate rocks at Yampai C liffs, Mohave County, Arizona: Univ. of Arlz. Thesis, 228 pages*

CURRENT TERMINOLOGY PROPOSED TERMINOLOGY THIS PAPER

Greenlee Co., Four Corners Northwestern North - Central Central Southwestern South-Central Southeastern Arizona Greenlee Co. Southwestern Sonora, Mexico Swisshelm Mountains Europe Series Stage Four Corners Area Northwestern Arizona Southwestern New Mexico, Caborca Area Area Arizona Arizona Arizona Arizona Arizona Chirichua Mountains Swisshelm Mountains Arizona New Mexico Caborca Area Cananea Area Chiricohuo Mountains and adjacent areas

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CORRELATION OF UPPER DEVONIAN ROCKS PLATE I nv o rzn Libra Arizona of Univ.

RRENT TERMINOLOGY PROPOSED TERMINOLOGY THIS PAPER

western South-Central Southeastern Arizona Greenlee Co. Southwestern Sonora, Mexico Greenlee Co., Swisshelm Mountains Four Corners Area Northwestern Arizona Southwestern New Mexico, Caborca Area All other areas izona Arizona Chirichua Mountains Swisshelm Mountains Arizona New Mexico Caborca Area Cananea Area Chiricahua Mountains and adjacent areas

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