Correlations of the El Paso formation in western Texas, southwestern New Mexico, and southeastern Arizona based on insoluble residues
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Authors Dickinson, R. G. (Robert G.), 1930-
Publisher The University of Arizona.
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Link to Item http://hdl.handle.net/10150/551478 CORRELATIONS OF THE EL PASO FORMATION IN
WESTERN TEXAS, SOUTHWESTERN NEW
MEXICO, AND SOUTHEASTERN
ARIZONA BASED ON
INSOLUBLE
RESIDUES
by
Robert G. Dickinson
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
1960 STATEMENT BY AUTHOR
This thesis has been submitted in partial fulfillment of require ments for an advanced degree at the University of Arizona and is de posited in the University Library to be made available to borrowers under rules of the Library.
Brief quotations from this thesis are allowable without special permission, provided that accurate acknowledgment of source is made. Requests for permission for extended quotation from or reproduction of this manuscript in whole or in part may be granted by the head of the major department or the Dean of the Graduate College when in their judgment the proposed use of the material is in the interests of scholar ship. In all other instances, however, permission must be obtained from the author.
SIGNED:
APPROVAL BY THESIS DIRECTOR
This thesis has been approved on the date shown below: CORRELATIONS OF THE EL PASO FORMATION IN WESTERN TEXAS, SOUTHWESTERN NEW MEXICO, AND SOUTHEASTERN ARIZONA BASED ON INSOLUBLE RESIDUES
by
Robert G. Dickinson
ABSTRACT
Insoluble residues have been used as a basis for subdividing the El Paso formation into seven zones. Published paleontological data were used, where available, to support the delimitation of the zones. Residues from lower Canadian rocks contain a white to gray smooth chert, whereas overlying Canadian rocks have a chert that is olive brown to black in color.
The sandy dolostone beds at the base of the El Paso formation in the Franklin Mountains, Texas, have tentatively been considered to be of Upper Cambrian age. This is based on the Upper Cambrian age
of the basal El Paso formation dolostones in the Dos Cabezas Mountains
of Arizona, and the lithologic and residue similarities between the two
sections. Lower Canadian sediments thin to the east, north, and west
ii from the area of the Big Hatchet Mountains of New Mexico, suggesting that in the area a basin of deposition existed which had a structurally stable periphery that received little or no sedimentation.
iii TABLE OF CONTENTS
Page
INTRODUCTION ...... 1
Purpose of S tu d y ...... 1 Previous W o rk ...... 2 Localities and Sampling ...... 3 Acknowledgments...... 4
STRATIGRAPHY ...... 6
Resume of Early Paleozoic Geology ...... 6 Bolsa Quartzite ...... 8 Abrigo Limestone ...... 9 B liss Sandstone ...... 10 El Paso Formation ...... 11
INSOLUBLE RESIDUE ZONES OF THE EL PASO FORMATION . 19
Method of Study ...... 19
Sampling and Treatment of Samples ...... 19 Sample C lassificatio n ...... 20 Evaluation of Residues...... 25
Correlation Technique ...... 27 Residue Zones...... 28
Zone 1 ...... 28 Zone 2 ...... 29 Zone 3 ...... 29 Zone 4 ...... 30 Zone 5 . 31 Zone 6 ...... 31 Zone 7...... 32
Residues From Overlying Form ations ...... 32 Relative Value of the R e s id u e s ...... 33
iv Page
SUGGESTED CORRELATIONS...... 35
REFERENCES C IT E D ...... 38
LIST OF ILLUSTRATIONS
Plate Page
I. Correlations of the El Paso formation In western Texas, southwestern New Mexico, and southeastern Arizona Back based on insoluble residues ...... of rep o rt
II. Ordovician rocks in the Franklin Mountains...... 12
m . Photomicro-stereograph—El Paso formation insoluble residues ...... 21
IV. Photomicro-stereograph—sponge spicules and druse .... 22
V. Photomicro-stereograph— Big Hatchet Mountains in soluble residues ...... 23
Table - „ Page
1. Comparison of Canadian zones of the El Paso formation ...... 13
v INTRODUCTION
Purpose of Study
In southwestern New Mexico and western Texas Lower
Ordovician argillaceous limestones and dolostones are called the El
Paso formation or group. Beds of similar age in southeastern Arizona, near Morenci, are termed the Longfellow limestone, whereas strata to the south in the area of the Chiricahua Mountains are called El Paso formation. Sabins (1957) proposed the name El Paso formation for the
strata in the Chiricahua and Dos Cabezas Mountains, even though the lower part of the formation was Upper Cambrian. Epis and Gilbert
(1957) extended the name El Paso formation to Lower Ordovician strata in the Swisshelm and Pedregosa Mountains southwest of the Chiricahuas
and recognized that the lower part of the formation there was also Upper
Cambrian.
Kelley and Silver (1952, p. 55) proposed that the Middle and
Upper Cambrian Abrigo formation in southeastern Arizona was a
homotaxial equivalent of the Lower Ordovician El Paso formation in
southeastern New Mexico. This hypothesis was supported by Sabins
(1957) and Gillerman (1958). Subsequent to Sabins* report Epis and
Gilbert (1957) reported Lower Ordovician strata overlying the Abrigo 2 formation in the Swisshelm Mountains. This discovery seemed to nullify the previous hypothesis that the Abrigo transgressed the Cambrian and
Ordovician time boundary to become the El Paso formation in New
Mexico.
Work by Vanderpool (1950) indicated that the type section of the
El Paso formation in the Franklin Mountains, Texas, could be correlated with sections as much as 230 miles east of the Franklin Mountains on the basis of insoluble residues.
The writer made an insoluble residue study of the more prom inent exposures of the El Paso formation in southwestern New Mexico and southeastern Arizona in order to supplement the stratigraphic data currently known about the El Paso formation. The purpose of the study was (1) to determine what relationships existed between the insoluble residues present in the type section and the Lower Ordovician strata of southeastern Arizona, and (2) to determine if these relationships could be used as a basis for correlation.
Previous Work
Ordovician rocks were recognized by several early workers in West Texas and New Mexico (Jenny, 1874, p. 26; Richardson, 1904, p. 29; Gordon and Graton, 1906, p. 390-395; and Barton, 1917, p. 31).
The age, paleontology, and regional correlations have been discussed by Kirk (1934), Cloud mid Barnes (1946), Kottloski, et al. (1956), and 3
Flower (1958).
Gilbert (1875, p. 511-513) was the first to report rocks of
Ordovician age in Arizona. Lindgren (1905) recognized Ordovician
strata near Morenci and noted similarities between those beds and
certain parts of the Abrigo formation of southeastern Arizona and the
El Paso formation of southwestern New Mexico. These similarities
were also noted by Richardson (1909, p. 4), Ransome (1916, p. 49),
and Barton (1925, p. 50-54). The name El Paso formation was ex
tended to Arizona exposures by Sabins (1957). He supported Kelley
and Silver’s (1952) proposed transgressive relationship between the
Lower Ordovician New Mexico beds and the Cambrian Abrigo formation
in Arizona. The validity of this hypothesis was questioned by Epis and
Gilbert (1957) based on their discovery of El Paso formation equivalents
that overlay the Cambrian Abrigo formation in the Swisshelm and
Pedregosa Mountains.
Vanderpool (1950) correlated the El Paso formation with other
West Texas sections on the basis of insoluble residues.
Localities and Sampling
In order to evaluate the insoluble residue method of correla
tion sections of the El Paso formation were chosen that are well exposed,
easily accessible, and that have known paleontological subdivisions. A
section at each of the following localities (PI. I) was sampled through 4
10-foot Intervals: Franklin Mountains, Peloncillo Mountains, Blue
Mountain, and the Dos Cabezas Mountains.
The type section in the Franklin Mountains has been measured and described in detail by Cloud and Barnes (1946). Flower (1955) fur ther refined the paleontological subdivisions proposed by Cloud and
Barnes.
Gillerman (1958) measured and described the Peloncillo Moun tains section. The Blue Mountain section has been measured and de scribed by Sabins (1957) and the Dos Cabezas section by Jones and
Bachellor (1953).
To supplement the sections sampled by the writer E. H.
Vanderpool of the Midland Residue Research Laboratory, Midland,
Texas, generously loaned prepared residues from sections in the
Florida and Big Hatchet Mountains in New Mexico, and from a section near Portal, Arizona (PI. I).
Acknowledgments
The author wishes to acknowledge the following individuals who have aided in the thesis. Mr. E. H. Vanderpool of the Midland Residue
Research Laboratory, Midland, Texas, generously loaned prepared in soluble residues from three localities. He and his assistant, Mr.
Maylon Baker, further contributed through their discussions with the author of the many facets of the problem. 5
The study arose from discussions with Professor W. D. Pye
of the University of Arizona. Professors J. F. Schreiber, Jr., J. F.
Lance, and H. W. Miller, Jr., read the thesis and offered many help ful suggestions. The ideas expressed, however, are mine and I accept full responsibility for the interpretations of the material presented.
Martin L. Dickinson and J. T. Me Cleary assisted with some
of the field work. STRATIGRAPHY
Resume of Early Paleozoic Geology
Marine waters entered the southwestern New Mexico-south eastern Arizona area during the Middle Cambrian from the unstable shelf region of western Sonora. The sedimentary record indicates seas encroached on a stable shelf area and the shoreline extended through central and southeastern Arizona. By Dresbachian time the shoreline was in the area of the Arizona-New Mexico border and shal low-water limestones were being deposited to the west in the vicinity of
Bisbee, Arizona. In the northern half of the United States a negative movement at the beginning of the Dresbachian stage caused the seas to spread eastward from the unstable shelf across the stable shelf areas, whereas to the south the coastline retreated only a short distance east ward into New Mexico (Lochman-Balk, 1956, p. 552). Negative move ment during the early half of the Franconian permitted the sea to cover most of Arizona and southwestern New Mexico, extending as far east as the Rio Grande Valley.
The area lay at or near the profile of equilibrium during the
Trempealeaun stage with the only known record of sedimentation during the time being a thin sandstone in the vicinity of Silver City, New Mexico 6 7
(Flower, 1958, p. 66).
During the Gasconade stage of the Canadian epoch the sedi mentary record indicates shoreline conditions in the vicinity of the Rio
Grande Valley. A basin of deposition is indicated in the area of the
Big Hatchet Mountains by a considerable thickness of limestones. By middle Canadian time the region was completely inundated and shallow- water marine deposition was widespread. The western extent of the seas is unknown because Ordovician deposits have not been found west of the Sulfur Springs Valley area in Arizona. Deposits in that area do not indicate proximity to a shoreline and it may be reasonable to assume that the sea covered much of southern Arizona.
The onset of a positive movement extending north from the
Organ Mountains during upper Canadian time has been suggested by
Kelley and Silver (1952, p. 52). This may have also affected the area to the west, as sediments of this age are generally lacking there. A profile of equilibrium was again attained at the close of the Canadian and marine deposition was not resumed again until Upper Ordovician.
The extent of the Middle Ordovician uplift is unknown, but a karst topography developed in the vicinity of the Cab alios Mountains. The lack of Upper
Canadian sediments along the Arizona-New Mexico boundary indicates that the area was either a positive element during that time or the sedi ments deposited during the period were removed during the Middle
Ordovician hiatus. 8
The resumption of marine deposition throughout the area in the
Upper Ordovician is indicated by the presence of dolostones lying with little unconformity on the Canadian limestones. In parts of southeastern
Arizona Devonian strata conformably overlie the Canadian indicating a hiatus of considerable magnitude in that area.
Bolsa Quartzite
The base of the Paleozoic section in southeastern Arizona is a transgressive marine sandstone named the Bolsa quartzite by Ransome
(1904, p. 28). He assigned a Middle Cambrian age based on overlying fossiliferous limestones and shales. At the type locality of Escabrosa
Ridge in the Bisbee District, the basal conglomerate of the formation rests on a nearly smooth surface of Precambrian schist, granites, and
associated intrusives. The overlying clean, crossbedded quartzite be
comes thinner bedded and finer grained near the top.
In southern Arizona the Bolsa quartzite grades upward into the
shales and limestones of the Abrigo formation. Along the New Mexico-
Arizona border the overlying beds are dolostones, containing Upper
Cambrian Billingselia sp. (Sabins, 1957). The contact with the dolo-
stone is variable, being sharp at Blue Mountain, and gradational in the
Dos Cabezas Mountains.
Sabins (1957, p. 471) reported a Dytremacephalus from the
Upper Cambrian Aphelaspis zone from the top of the Bolsa quartzite in 9 the Dos Cabezas Mountains. This would indicate that the Bolsa quartzite rises in section to the east, inasmuch as the quartzite is overlain by
Middle Cambrian rocks at Bisbee. To the east, in New Mexico, the basal sand is called the Bliss sandstone. The age of the Bliss varies from place to place, being both Upper Cambrian and Lower Ordovician
(Flower, 1953). Sabins (1957) and Epis and Gilbert (1957) have recently indicated that the Bolsa quartzite and Bliss sandstone were at least in part lithogenetic equivalents.
Abrigo Limestone
The Abrigo limestone (Ransome, 1904, p. 30) of Middle and
Upper Cambrian age overlies the Bolsa quartzite in southeastern Arizona.
In the Bisbee area where the Abrigo formation was originally defined the
Bolsa quartzite grades upward through thin, sandy, micaceous shale layers to a limestone with conspicuous edgewise conglomerate. This limestone becomes increasingly sandy upward so that the upper part of most sections consists of sandstone or quartzite.
In the Bisbee area the Abrigo formation is overlain by the
Devonian Martin limestone. To the northwest in the Swisshelm Moun tains Epis and Gilbert (1957, p. 2239) have assigned the sandy dolostone between the Abrigo limestone and overlying El Paso formation to the El
Paso formation. This dolostone contains the Upper Cambrian brachiopod
Billings ell a sp. A similar dolostone is present at Blue Mountain and in 10 the Black Gap area near Bisbee. At Blue Mountain the dolostone is overlain by the El Paso formation and is included with it, whereas at
Bisbee the dolostone is included with the Abrigo limestone.
According to present usage, then, the Abrigo formation is re stricted to beds of Cambrian age. A sandy dolostone containing
Billingsella sp. is included with the Abrigo if the overlying beds are
Devonian and with the El Paso formation if they are Ordovician.
Bliss Sandstone
The Bliss sandstone (Richardson, 1904, p. 27) of Upper
Cambrian and Lower Ordovician age overlies the Precambrian in south western New Mexico and western Texas. At the type locality in the
Franklin Mountains the Bliss sandstone is a fine-grained quartzite with glauconitic beds in the upper part, Christina Lochman-Balk (1956, p„
544) considers the basal Bliss sandstone to be transgressive, and the overlying beds to represent "the slow and long continued fluctuations across the area of a sub-littoral environment produced by slight down warping or submarine current scour and a near-littoral environment developing as the local profile of equilibrium is restored."
The Bliss sandstone was originally assigned to the Cambrian on the basis of the brachiopod Lingulepis (Richardson, 1909, p. 3).
After considering a large Gasconade fauna in the Bliss sandstone near
Van Horn, Texas, Cloud and Barnes (1946, p. 69) regarded the formation 11 to be of Gasconade age. Their correlation was based on stratigraphic position, paleogeography, and the occurrence of Lingulepis. They rec ognized, however, that Lingulepis was not diagnostic and that in the
Franklin Mountains the first strati graphically significant fossils occur
150 to 165 feet above the top of the B liss sandstone in dolostone of middle Canadian age. Flower, in Kottloski, etaU (1956, p. 14), would assign the Bliss sandstone to the Canadian because of an absence of a definite lithologic break and absence of a Cambrian fauna in the lower beds.
Flower also recognizes two discrete faunal zones in the Bliss sandstone of New Mexico. They consist of a lower zone containing
Cambrian fossils of late Franconian age and an upper zone containing fossils of Early Ordovician age. Distinct lithologies are recognized for both zones.
The Bliss sandstone is everywhere overlain by the Lower
Ordovician El Paso formation. The contact is usually gradational, though a break in deposition may be present.
El Paso Formation
Richardson (1904, p. 29) originally named all of the Ordovician rocks in the Franklin Mountains (PI. H) the El Paso limestone. Later
Richardson (1909, p. 3-4) subdivided the Ordovician and retained the name El Paso limestone for the ’’lower formation which contains Lower PLATE H
ORDOVICIAN ROCKS IN THE FRANKLIN MOUNTAINS
A
The contact of the Montoya group (M) and the El Paso formation (E) in the Franklin Mountains, Texas.
B
The contact of the El Paso formation (E) and the Bliss sandstone (B) in the Franklin Mountains, Texas.
\ X \\ 12
ammmmmm
/ 13
Ordovician fossils." He suggested that the unfossiliferous interval at the base of the formation was Cambrian and Ordovician.
Cloud and Barnes (1946) subdivided the type section into three units and two subunits, based on faunal and lithologic evidence. In the
Cab alio Mountains Kelley and Silver (1952, p. 42) raised the formation to group status, naming the lower Canadian unit the Sierrete limestone, and the overlying middle Canadian unit the Bat Cave formation. Table
1 shows these relationships along with the faunal subdivisions recognized by Flower (1955, p. 67-68). In mapping, Kottloski, etaL (1956, p. 17) and Gillerman (1958, p. 21) have treated the El Paso formation as a single unit.
The thickness of the El Paso formation has been variously re ported to be 1,000 feet (Richardson, 1909, p. 3), 1,590 feet (Cloud and
Barnes, 1946, p. 368), and 1,355 feet (Kottloski, etaJU, 1956, p. 21).
The 1,480 feet of section measured during this study compares most favorably with the thickness reported by Cloud and Barnes.
The El Paso formation consists of inter bedded limestones and dolostones, with varying amounts of sand. In the Franklin Mountains a basal unfossiliferous sandy dolostone approximately 150 feet thick over- lies the Bliss sandstone. The contact appears gradational, though Cloud and Barnes (1946, p. 368) report that a disconformity is indicated "by pebbles of a foreign derivation. ” This basal unit was tentatively correlated with Gorman (middle Canadian) equivalents of the El Paso 14
TABLE 1
COMPARISON OF CANADIAN ZONES OF THE EL PASO FORMATION
Thickness Thick- (feet) Zones ness C&B* C&B* C&B* Kottioski, etal., 1956, p. 21 (feet) Units Zones Zones
Uppermost Fauna 335 1-7 C, B2b 253 ate Upper Canadian Third Piloceroid 90 8-10 B2b 280
Middle Upper Canadian 250 11-14 B2a 245
Second Piloceroid 190 14-15 B l, B2a 350
Upper Canadian Thin-bedded barren 40 16 Ri 50
McQueenoceras 70 17 Bl 70 Oolite 60 18-19 A _ 70 B arren 45 20 A QR
First Piloceroid 105 21-22 A 140
B arren 25 22-23 A 35 Middle Canadian First Endoceroid 85 23-24 A 100 Gasconade 80 25-27 A 135
Lower Ordovician Bliss 240 250 Canadian
♦Cloud and Barnes, 1946, p« 361-369. Adapted from Kottioski, et a l., 1956, p. 21. ~~ 15 formation at Beach Mountain near Van Horn, Texas. An alternative correlation of this zone with Tanyard (lower Canadian) equivalents was also suggested. Flower (1955, p. 67) and Kottloski, et al. (1956, p. 21) consider the dolostone to be lower Canadian on the basis of overlying middle Canadian strata.
In the Caballos Mountains a similar zone was assigned to the
Gasconade (lower Canadian) by Kelley and Silver (1952, p. 42) and named the Sierrete limestone. In the Florida Mountains the zone is anomalously thin (Flower, 1958, p. 69). The Gasconade beds in the
Big Hatchet Mountains form an unusually thick sequence of shales, dolostones, and cherty limestones.
A basal sandy dolostone, similar in appearance and thickness to that in the Franklin Mountains, is present below middle Canadian beds in the Chiricahua and Dos Cabezas Mountains. The only known fossil from this zone is a Billingsella sp. reported by Sabins (1957, p. 474) at Blue Mountain, indicating an Upper Cambrian age for these beds.
In the Franklin Mountains the first stratigraphically useful fossils occur approximately 150 to 165 feet above the Bliss sandstone
(Cloud and Barnes, 1946, p. 367). This occurrence marks the base of the middle Canadian and FlowerFs (1955, p. 67) first endoceroid zone. The zone is 100 feet thick and grades from arenaceous to silty dolostone, with minor chert. It can be recognized throughout south western New Mexico and in the Dos Cabezas Mountains (Flower, 1958). 16
Overlying the first endoceroid zone is 200 to 300 feet of lime stones and dolostones forming the first piloceroid and oolith zones
(Flower, 1955, p. 67). In the Franklin Mountains dolomitic limestone grades upward to silty dolostone with some glauconite near the top of the interval. Equivalents of these beds are recognized in southwestern
New Mexico, with part of the first piloceroid zone being present in the
Dos Cabezas Mountains (Flower, 1958, p. 69).
In the Franklin Mountains a 60-foot zone of arenaceous dolo stone marks the base of the upper Canadian (unit 17 of Cloud and Barnes,
1946, p. 366). This zone is not present in sections to the west. Inter- bedded cherty limestones and dolomitic limestones with some shaly mem bers in the upper part overlie the sandy zone. These beds represent
Subunits B1 and B2a of Cloud and Barnes (1946, p. 365) and the second piloceroid zone of Flower (1955, p. 67). Their equivalents are generally recognized in southern New Mexico sections as far west as the Big
Hatchet Mountains but are absent in Arizona (Kottloski, et al., 1956, p.
18). A second zone of arenaceous dolostone occurs between 280 and 360 feet below the top of the El Paso formation in the Franklin Mountains.
The zone marks the base of Subunit B2b of Cloud and Barnes (1946, p.
364) and forms Flower's third piloceroid zone. Cherty limestones with occasional interbeds of dolostone overlie the arenaceous zone which is present only as far west as the Florida Mountains.
In the Franklin Mountains the top of the El Paso formation is 17 marked by 40 feet of interbedded shales and limestones forming Cloud and Barnes Unit C. This unit is disconformably overlain by the Upper
Ordovician Montoya group.
The Montoya group overlies the El Paso formation in southern
New Mexico. In Arizona Montoya beds have been reported at Morenci
(Hill, 1959, p. 2) but are as yet unreported to the south where Devonian strata overlie the El Paso and Abrigo formations.
To the north and west of the Franklin Mountains the El Paso section becomes thinner. Kelley and Silver (1952, p. 54) report a karst topography in the upper part of the Bat Cave formation in the Caballos
Mountains and note a marked thickening of the El Paso formation south ward in the vicinity of the Organ Mountains. In accounting for this they state ’’bending or monoclinal up warping, trending westwardly, occurred between the Franklin and Organ Mountains in the late Canadian or
Champlain!an tim e."
Similar thinning is present in southwestern New Mexico and southeastern Arizona, but development of a karst topography at the top of the El Paso formation is unreported. Approximately 900 feet of El
Paso formation is present in the Florida Mountains. In the Big Hatchet
Mountains the Montoya group overlies middle and upper Canadian lime stones. Beneath these beds an unusually thick sequence of dolomitic
Gasconade beds rest on variable thicknesses of Bliss sandstone (Flower,
1958, p. 69). 18
In the Peloncillo Mountains the Montoya group overlies 150 to
300 feet of El Paso formation, with no upper Canadian sediments re ported (Gillerman, 1958). In the Dos Cabezas Mountains approximately
100 feet of middle Canadian limestones is conformably overlain by
Devonian shales.
The thinning of the El Paso formation in southeastern New
Mexico can be interpreted as depositional or erosional, or both. In
Arizona Gilluly (1956, p. 25) and Epis and Gilbert (1957, p. 224) con tend that uplift and erosion was insignificant. This is based on the fact that Devonian strata rest on a rather uniform blanket of Cambrian beds in southern Arizona instead of variable thicknesses as might be expected if erosion took place. Until more positive proof is found the erosional interpretation of Kelley and Silver would seem to be as valid as the one of non-deposition.
Correlations of the El Paso formation with equivalent forma tions in adjacent areas have been suggested by Cloud and Barnes (1946) and Kottloski, et aL (1956). The El Paso formation is considered to be equivalent to the Garden City formation of Utah, the Manitou dolomite of
Colorado, and the EUenburger and Marathon limestones of Texas. Kirk
(1934, p. 443-463) discussed the correlations of the formation in its broader aspects. INSOLUBLE RESIDUE ZONES OF THE EL PASO FORMATION
Method of Study
Sampling and treatment of samples. —The sections of the El
Paso formation that were sampled by the author were measured with a Brunton compass and tape or with a Jacob*s staff. Intervals of 10 feet were chip-sampled so that the chips were taken from as short vertical intervals as exposures would allow. The chips from one in terval were combined to form a single sample. Each sample was passed through a jaw crusher and rolls to reduce the particle size to approxi mately that of drill cuttings. A uniform portion of crushed sample, measured in a container 5.5 cubic centimeters in volume, was treated with 10 percent hydrochloric acid. After digestion of the soluble rock was complete the loose particles of clay size were removed by washing and decanting. The remaining residue was allowed to dry by evapora tion.
The residue from each sample was measured volumetrically to give the percent of the original sample. The residue was examined under a binocular microscope and classified qualitatively. A visual estimation of the quantity of materials was also made and the data plotted on log strips. 19 20
Sample classification. —The residues of the El Paso formation were classified according to a detailed system in current use by E. H.
Vanderpool of the Midland Residue Research Laboratory. Mr. Vender- poops classification is basically similar to the chart published with the paper on standardized terminology of insoluble residues (Ireland, et al.,
1947).
Examination of detailed logs of the El Paso formation indicate the following residue materials to be most significant: Smooth chert, granular chert, chalky chert, druse or quartz, sand-size or silt-size material (mostly quartz), argillaceous material, and glauconite. Sponge spicules, clay pellets, fossil imprints, and color of the smooth chert were also deemed to have some correlative value. These features are shown in log form by a system of black and white symbols (PI. I).
Systematic discussions of insoluble residues have been given by Ireland (1950, p. 140) and Hendricks (1952, p. 18). As recognized in this study smooth chert has a conchoidal to flat fracture surface de void of roughness (PI. HI). The color varies from white to gray or black and from olive brown to black. The chert is mostly opaque but some shows a slight translucency. A mottled or flocculated appearance may be present and spicular inclusions are not uncommon.
The granular chert varies in grain size from extremely fine grained to easily distinguishable grains that have a saccharoidal ap pearance. The color is usually white to gray but is sometimes darker. PLATE H
PHOTOMICRO-STEREOGRAPH—EL PASO FORMATION INSOLUBLE RESIDUES
A
Typical El Paso formation insoluble residues showing smooth chert (S), chalky chert (C), and argillaceous m aterial (A). The residues are from rocks 910 to 920 feet below the top of the El Paso formation in the Franklin Mountains (X5).
B
Chalky chert with some argillaceous material showing fossil molds, pellets, and a crinoid stem. Residues from rocks 115 to 120 feet below the top of the El Paso formation in the Florida Mountains (X5). 21 22
The chalky chert, named because of its textural resemblance to chalk, is mostly white or gray and varies from soft to hard. It grades from granular chert to argillaceous material and was distinguished primarily on its ability to abrade a metal probe. The chalky residue may repre sent compact microgranular chert, leached chert, or a silicified clay product.
Residue that is soft and argillaceous in appearance is included in a class termed clay and shale. Included here are flakes of shale and spongy masses of porous material.
Quartz includes clear to cloudy grains that vary in shape from euhedral to anhedral. Small quartz crystals and druse are included in this classification even though the crystals may represent secondary growth on silt grains (PL IV).
The quartz sand grains are variable in size, shape, and round ness; they are commonly frosted (PI. V). Occasional chert and feldspar grains can be noted. Silt consists of siliceous material that appears to be clastic in origin. It is difficult at times to distinguish between loose, fine-grained saccharoidal chert grains and silt. The sand and silt is found loose or embedded in any of the other types of residue. Glauconite is sparingly present in the residues as grains or as interstitial matrix.
Imprints of fossils are common in the residues of the El Paso formation. Casts and molds of brachiopods, conodonts, trilobites, gastropods, crinoid stems, and some indistinguishable forms are PLATE IV
PHOTOMICRO-STEREOGRAPH—SPONGE SPICULES AND DRUSE
A
Druse, consisting primarily of small euhedral quartz crystals. Some argillaceous material is present. The residues are from rocks 1,060 to 1, 070 feet below the top of the El Paso formation in the Big Hatchet Moun tains (X8).
B
Spicular residue from rocks 285 to 290 feet below the top of the El Paso formation in the Portal, Arizona section. Dolomoldic argillaceous material, sand, and sponge spicules are present (X8). 23 PLATE V
PHOTOMICRO-STEREOGRAPH—BIG HATCHET MOUNTAINS INSOLUBLE RESIDUES
A
Clean, well-rounded and frosted sand from the base of the Montoya group, 20 to 30 feet above the top of the El Paso formation (X8).
B
Chalky chert with frosted sand grains 840 to 850 feet below the top of the El Paso formation (X8). 24 25 present. Numerous small spherical, ellipsoidal or irregular masses of clay-like material are frequently present (PI. m). These grains have an oolitic appearance, but do not have the diagnostic characteristics of
oolites. A pelletoid origin is suggested for these objects. Cloud and
Barnes (1946, p. 99) have noted the pelleted condition of the Ellenburger
limestone and have suggested that the pellets were the result of mud
ingesting organisms.
Siliceous sponge spicules are common in the El Paso forma
tion residues (PL IV). They are usually loose but may be imbedded in
chert. Triaxon spicules seem to be restricted to residues from
Cambrian rocks whereas monaxons are more common in residues from
Ordovician rocks.
Evaluation of residues. —A genetic classification of insoluble
residues has been devised by Ireland (1936, p. 1090) and Hendricks
(1952, p. 10). They recognize two classes of residues: allogenic and
authigenic. The allogenic constituents are derived from earlier sedi
ments and include silt, sand, shale, and mineral fragments. The
authigenic constituents are formed at the same time or subsequent to
the deposition of the sediments. They are subdivided into syngenetic
and epigenetic components. The syngenetic residues are formed con
temporaneously with the sediments and consist of segregated chert,
shale partings, clay masses, pyrite, glauconite, and fossil fragments. 26
Epigenetic cherts, which include interstitial chert, quartz, siliceous oolite, anhydrite, and replaced fossils, are formed subsequent to dep osition of the sedim ents.
The smooth chert and some of the granular chert form the syngenetic residues most diagnostic in the El Paso formation. Differ ences in color and texture aid in differentiating the residue zones. The syngenetic argillaceous material is a characteristic residue in the El
Paso formation but cannot readily be used to subdivide the formation.
Glauconite is sparingly present in the El Paso formation.
Ireland (1952, p. 47) indicates that few Lower Ordovician beds have glauconite and notes that glauconite generally marks the top of the
Cambrian. Cloud and Barnes (1956, p. 97) conclude that the glauconite present in the Ellenburger group is not authigenic. This is probably true also for the El Paso formation. The presence of glauconite in the middle Canadian beds in the Franklin Mountain section indicates that glauconite is not a marker of the Cambrian there. Cloud and Barnes
(1946, p. 69) note that the glauconite in the Bliss sandstone in the
Franklin Mountains may reflect the character of adjacent source rock and that it has Little significance as a Cambrian marker.
Fossil fragments and pelletal remains are common in the El
Paso formation. Their relative abundance in certain zones of the for mation seem to aid in zone identification by supplementing the gross character of the zone, 27 The epigenetic residues are of diagnostic value but to a lesser degree than the syngenetic residues. Cloud and Barnes (1946, p. 95) conclude that dolomoldic cherts result from the leaching of dolostones that contain quantities of interstitial chert. A complex origin is in dicated. They also note that some dust and silt-size particles in lime stones become crystalline quartz particles in dolostones equivalent to the limestones.
The allogenetic mechanically deposited materials occur in zones that are only of local distribution. This is indicated by the sandy zones present in the Franklin Mountain section residues.
Correlation Technique
The gross character of the El Paso formation as indicated by the residues is that of an argillaceous carbonate sediment with varying amounts of chert and quartz sand or silt. The residues directly reflect sea-bottom environment and clastic conditions that existed at the time of deposition. Changes in sedimentation are also reflected in the residues.
Identification of the zones present within the formation was based on such factors as percentage of residue, association of types of residue, and position within the section. Paleontological correlations were used where the information was available.
The top of the El Paso formation is easily distinguished from 28 overlying formations by differences in residue type. At the type section sandy zones within the formation mark changes in sedimentation that correlate well with faunal breaks. These sandy zones are not present to the west and the subdivisions of the formation there are more arbi trary. The detailed residue characteristics vary in the western sec tions but retain their gross El Paso formation appearance. One notable difference in the residue of the type section and the sections near the
Arizona-New Mexico boundary is in the smooth chert, In the western
sections the smooth chert in the lower residues is white to gray, whereas the chert in the upper residues is olive brown to black. The lighter colored cherts are not present in the type El Paso section and may represent beds that are not present in the Franklin Mountains.
Residue Zones
Zone 1.—The basal sandy portion of the El Paso formation
forms Zone 1 in this study (PI. I). The arenaceous material ranges in
size from coarse sand to silt and is usually poorly rounded. Frosting,
much of which is probably a secondary growth, is commonly present.
Most of the sand is cemented with silica, but some argillaceous cement
or matrix is present within the zone in the Portal and Blue Mountain
sections. Glauconite is sparingly present in all of the sections except
the Blue Mountain and Portal sections. Abundant triaxon siliceous
sponge spicules occur in the middle and upper parts of the zone in the 29
Arizona sections. The middle part of the zone is characterized by only
5 to 10 percent residue which is mostly argillaceous, whereas the aver age for the zone is closer to 50 percent residue. In this study the zone is considered to be of Upper Cambrian age.
Zone 2 .—Zone 2 as recognized in this study is considered to be of lower Canadian age. The zone is about 400 feet thick in the Big
Hatchet Mountains but is not as distinct to the east and west where it is represented by 200 feet or less of section. No residues of this zone are recognized in the Franklin or Dos Cabezas Mountains sections.
The most prominent residue of the zone is a white to gray smooth chert. Druse varying from encrustations to small euhedral crystals makes up as much as 10 percent of some samples. Sand, silt, chalky and granular chert are present in varying quantities along with traces of monaxon siliceous sponge spicules and clay pellets. The per cent of residue varies from 1 to 50 percent and averages about 15 per cent.
Zone 3.—Zone 3 includes beds of middle Canadian age. In the
Franklin Mountains the zone is marked by abundant silt and some glauconite in the upper part of the zone. About 50 feet of the central part of the zone contains no silt, some granular chert, and an abundance of argillaceous material. Fossil molds are common and the residue av erages about 40 percent of the sample as compared to about 20 percent 30 for the rest of the zone. Minor amounts of olive-brown smooth chert are present,
To the west of the Franklin Mountains the zone is thinner, less distinct, and correlation with residues in the Florida Mountains and Big
Hatchet Mountains sections is not conclusive. In the Florida Mountains the zone is tentatively correlated with residues of dolomoldic granular chert averaging about 15 percent residue. In the Big Hatchet Mountains the residue consists of argillaceous material that is variable and not particularly characteristic. Residues from the upper part of the
Peloncillo and Dos Cabezas Mountains sections are very similar to those in the F ranklin Mountains. Only a trace of silt is present in the
Dos Cabezas Mountains, but the soft argillaceous material along with the cherts are unmistakably El Paso formation in character.
Zone 4 .—Zone 4 is equivalent to Cloud and BarnesT Subunit B1
(Table 1). In the Franklin Mountains the lower 60 feet of the zone con tains a sandy residue which is not found in sections to the west. Above the sand the residues are about half argillaceous material and half chert.
Roughly equal amounts of smooth,. chalky and granular chert are pres ent. The smooth chert is somewhat granular in appearance and olive brown in color. Spicules, fossil molds and pellets are present in the zone. The residues average about 20 percent.
In the Florida Mountains smooth chert is noticeably absent 31 from the residues. Zone 4 of the F r anklin Mountains is tentatively cor related with a zone consisting of chalky dolomoldic chert, along with some granular chert, argillaceous material, and minor amounts of sand. The residues of this zone in the Franklin Mountains correlate better with a zone of smooth and chalky chert in the Big Hatchet Moun tains. Here the residue only averages about 10 percent, but the olive chert is present, along with sponge spicules. Equivalents of the zone are not recognizable in sections west of the Big Hatchet Mountains.
Zone 5.—Zone 5, which is equivalent to Cloud and Barnes*
Subunit B2a (Table 1), is characterized by the predominance of dolomoldic argillaceous material. In the F ranklin Mountains some granular chert is present along with sponge spicules and clay pellets.
The residue averages between 15 and 20 percent.
In the Florida Mountains the residue is mostly argillaceous material in the lower half of the zone. The upper half contains about equal amounts of chalky chert and argillaceous material along with an abundance of fossil molds, sponge spicules and pellets in the upper half.
Residues from the upper part of the Big Hatchet Mountains section are mostly argillaceous material with a few fossil molds and are included here in Zone 5.
Zone 6.—Zone 6 is equivalent to Cloud and Barnes* Subunit
B2b (Table 1). In the Franklin Mountains 90 feet of sandy residue marks 32 the base of the unit. Above this the residue is mostly a grayish-orange argillaceous material. Some spicular brown to black smooth chert is present along with minor amounts of chalky chert, The top of the zone is marked by an increase from 15 percent to about 40 percent residue.
Abundant clay pellets are present In the Florida Mountains residues from the uppermost beds are included in this zone. These residues are unusual in that the smooth chert is white to blue gray, whereas in the Franklin Mountains the smooth chert is brown to black.
Zone 7. — Zone 7, at the top of the Franklin Mountains section, is 40 feet thick and is equivalent to Cloud and Barnes* Unit C. It is recognized only in this section and the residue consists of grayish-orange argillaceous material and greenish shale with some fossil molds.
Residues From Overlying Formations
In the Franklin, Florida, and Big Hatchet Mountains a thin sandy zone marks the base of the Montoya group. In the Peloncillo
Mountains the upper 185 feet (Unit 9) of the El Paso formation as mapped by Gillerman (1958, p. 108) is poorly exposed and was not sampled. In the Portal section the El Paso formation residues terminate with a res idue that is granitoid in appearance. The upper part of the El Paso for mation at Blue Mountain is poorly exposed. Samples were taken where outcrops permitted, but the residues were too incomplete to be of use. 33
Devonian shale overlies the El Paso formation. At the Dos Cabezas
Mountain section the El Paso formation terminates at the contact with the overlying Devonian shale.
Relative Value of the Residues
This study has demonstrated that the insoluble residues pres ent in the rocks of the El Paso formation can be used to help identify and correlate sections of the formation. The top of the El Paso forma tion can readily be identified. The contact at the base with the Bliss sandstone or Bolsa quartzite is usually sharp, but a gradational zone may be present that exhibits an increase in carbonate content upward.
The residues of the formation are not characteristic enough, however, to permit the delimitation of thin zones that can be correlated over long distances. Residues containing smooth chert that is white to gray are apparently diagnostic of lower Canadian rocks near the New
Mexico-Arizona border. Younger beds are characterized by a granular appearing smooth chert that is olive brown to black. The other promi nent residues in the formation—granular chert, chalky chert, and argillaceous material—are common throughout the formation and only serve to help identify the El Paso formation itself.
The individual zones established in this study may be more subjective than real. The residues in the Florida Mountains section are El Paso-like but do not show the apparent breaks present in the 34 type section. Some of the residues near the top of the section are sug gestive of residues from the overlying Montoya group. This may be a reflection of the faulted condition of the section. The upper residues in the Big Hatchet Mountains section are quite similar to equivalent residues at the type section, but it would be difficult or impossible to locate the exact position of any small group of samples within the for mation as a whole. When entire sections are considered, however, correlative and interpretational relationships are suggested.
In the Blue Mountain and Portal sections a thin zone of resi due contains an abundance of triaxon sponge spicules (PI. IV). These spicules are not diagnostic themselves, but when considered with the other residues the occurrence would seem to indicate a restricted zonule characteristic of that area. It is thus evident that in restricted areas' the study of insoluble residues should be greatly beneficial in correlating disconnected but similar sections. SUGGESTED CORRELATIONS
Current correlations of the El Paso formation (Kottloski, et aL ,
1956, and Flower, 1955, 1958) do not necessarily agree with the evi dence indicated by the insoluble residues in this study. The sandy dolo- stone forming the base of the El Paso formation in the Franklin Moun tains (Zone 1) is considered by Flower to be of lower Canadian age.
This relationship is based on similarities in lithology with nearby New
Mexico sections and the section at Beach Mountain near Van Horn,
Texas. Also the overlying beds are fossiliferous arid are of middle
Canadian age.
In this study it has been noted that the section in the Dos Cabezas
Mountains is remarkably similar to the lower part of the El Paso forma tion in the Franklin Mountains. Both sections have a basal sandy dolo- stone of similar thickness. Overlying the basal beds are typical El Paso formation limestones that are middle Canadian in age and that contain residues that are almost identical. A break in sedimentation between the two units in the Franklin Mountains is suggested by the presence of granules of an aphanitic rock (Cloud and Barnes, 1946, p. 368). Physical evidence of a similar br eak in the Dos Cabezas Mountains section was not noted; however, one is suggested by the marked change in lithology and the difference in age of the two units. 35 36
The basal dolostone in the Dos Cabezas Mountains has been correlated with similar beds at Blue Mountain (Flower, 1958, p. 66; and Sabins, 1957, p. 474) where Sabins found Billingsella sp. near the contact between the El Paso formation and the Bolsa quartzite. This occurrence established an Upper Cambrian age for these beds in the
Chiricahua-Dos Cabezas Mountains.
On the basis of the above relationships-—the Cambrian age of the basal El Paso dolostones in the Dos Cabezas Mountains and the lithologic and residue similarities between the basal dolostones in the
Dos Cabezas and Franklin Mountains—the dolostone beds at the base of the El Paso formation in the Franklin Mountains have been tentatively considered to be of Cambrian age in this study. It is fully realized that until such time as fossil material is identified from the dolostones at the base of the El Paso formation in the Franklin Mountains any cor relation or age assignment will be open to question.
Lower Canadian beds, which have a considerable thickness in the Big Hatchet Mountains, are not known in the Dos Cabezas Mountains
(Flower, 1958, p. 66) and in this study are not considered to be present in the Franklin Mountains. In the Swisshelm and Pedregosa Mountains a similar relationship also exists between Cambrian and Ordovician rocks (Epis and-Gilbert, 1957, p. 2231). Middle Canadian limestones overlie Upper Cambrian sandy dolostones, but beds of lower Canadian age are unreported. 37
This evidence indicates that a basin of deposition was present in the area of the Big Hatchet Mountains. The center of the basin re ceived several hundred feet of sediments and the beds become thinner both to the east and west. A northward thinning is also suggested.
Lower Canadian rocks are not known to be present in the Morenci area, and Kottloski, et aL (1956, p. 20) have noted that they thin northward from the Franklin Mountains. An area of structural stability that re ceived little or no sedimentation is thus indicated around the eastern, northern, and western periphery of the basin. Since information con cerning lower Canadian beds to the south of the Big Hatchet Mountains is not known to the writer no attempt has been made to suggest their ex tent or thicknesses.
The above relationships are further supported by the insoluble residues. The residues of Zone 3 show remarkable similarities in the
Dos Cabezas and Franklin Mountains but are variable and dissimilar in the intervening sections. This would seem to indicate an environment of deposition that was variable in areal extent and may reflect a con tinued instability during later Canadian times in the area of the Big
Hatchet Mountains. The relative thinness of upper Canadian beds in the Big Hatchet Mountains can be readily explained by erosional thinning of the formation during the Middle Ordovician hiatus. REFERENCES CITED
Cloud, P. E., Jr. 9 and Barnes, V. E., 1946, The Ellenburger group of central Texas: Texas Univ., Bur. Econ. Geol. Pub. 4621, 473 p.
Barton, N. H., 1917, A comparison of Paleozoic sections in southern New Mexico: U. S. Geol. Survey Prof. Paper 108-C, p. 31- 55.
______1925, A resume of Arizona geology: Univ. Arizona Bull. lid, Geol. ser., n. 3, 298 p.
Epis, R. C., and Gilbert, C. M. , 1957, Early Paleozoic strata in southeastern Arizona: Bull. Axner. Assoc. Petrol. Geol., v. 41, n. 10, p. 2223-2242.
Flower, R. H., 1953, Age of the Bliss sandstone. New Mexico: Bull. Amer. Assoc. Petrol. Geol., v. 32, p. 82-108.
______1955, Pre-Pennsylvanian stratigraphy of southern New Mexico: New Mexico Geol. Soc., 6th Field Conference, Guidebook of South-Central New Mexico, p. 65-70.
______: 1958, Cambrian-Mississippian beds of southern New Mexico: Roswell Geol. Soc., 11th Field Conference, Guide- . book of the Hatchet Mountains and the Cooks Range-Florida Mountain Areas, p. 61-78.
Gilbert, G. K., 1875, Report on the geology of portions of New Mexico and Arizona: U. S. Geog. and Geol. Surveys W. 100th Mer. (Wheeler), v. 3, p. 503-507.
Gillerman, E., 1958, Geology of the central Peloncillo Mountains, Hidalgo County, New Mexico and Cochise County, Arizona: New Mexico Bur. Mines Bull. 57, 152 p.
Gilluly, J ., 1956, General geology of central Cochise County, Arizona: U. S. Geol. Survey Prof. Paper, 281 p.
38 39
Gordon, C. H., and Graton, L. C., 1906, Lower Paleozoic formations in New Mexico: Science, new ser., v. 21, p. 390-395.
Heindricks, L-, 1952, Correlation between surface and subsurface sec tions of the Ellenburger group of Texas: Texas Univ., Bur. Econ. Geol. Kept, of Inv. n. 11, 44 p.
Hill, D ., 1959, Some Ordovician corals from New Mexico, Arizona, and Texas: New Mexico Bur. Mines Bull. 64, 24 p.
Ireland, H. A., 1936, Use of insoluble residues for correlation in Oklahoma: Bull. Amer. Assoc, of Petrol. Geol., v. 20, n. 8, p. 1086-1121.
Ireland, H. A., and others, 1947, Terminology for insoluble residues: Bull. Amer. Assoc. Petrol. Geol., v. 31, n. 8, p. 1479-1490.
Jenney, W. P ., 1874, Notes on the geology of western Texas near the thirty-second parallel: Am. Jour. Sci., 3rd ser., v. 7, p. 25-28.
Jones, S. M., and Bacheller, W. D., 1953, Measured sections near Bos Cabezas, Arizona: New Mexico Geol. Soc. Guidebook, 4th Ann. Field Conf., p. 149.
Kelley, V. C., and Silver, C., 1952, Geology of the Caballo Mountains: N. Mex. Univ. Pub. Geol. ser., n. 4* 286 p.
Kirk, Edwin, 1934, The Lower Ordovician El Paso limestone of Texas . and its correlatives: Am. Jour. Sci., 5th ser., v. 28, p. 443- 463.
Kottloski, F. E., Flower, R. H., Thompson, M. L., and Foster, R. W., 1956, Stratigraphic studies of the San Andres Mountains: New Mex. Bur. Mines and Min. Res. Mem. 1, 132 p.
Lindgren, W., 1905, The copper deposits of the Clifton-Morenci Bistrict, Arizona: U. S. Geol. Survey Prof. Paper 43, 375 p.
Lochman-Balk, Cristina, 1956, The Cambrian of the Rocky Mountains and southwest deserts of the United States and adjoining Sonora Province, Mexico: El Sistema Cambrico, su Paleogeografia y el Problema de su Base, Symposium, Part n , XX Congreso Geologico International, XX Session, Mexico, p. 529-662. 40
Ransome, F. L., 1904, The geology and ore deposits of the Bisbee quadrangle, Arizona: U. S. Geol. Survey Prof. Paper 21.
______1916, Some Paleozoic sections in Arizona and their cor relation: U. S. Geol. Survey Prof. Paper 98, p. 133-166.
Richardson, G. B., 1904, Report on a reconnaissance in Trans-Pecos Texas, north of the Texas and Pacific Railway: Univ. Texas Min. Survey Bull. 9, 119 p.
______1909, Description of the El Paso district: U. S. Geol. Survey Geol. Atlas, El Paso Folio, Texas, n. 116, lip .
Sabins, F. F., 1957, Stratigraphic relations in Chiricahua and Dos Cabezas Mountains, Arizona: Bull. Amer. Assoc. Petrol. Geol., v. 41, n. 3, p. 466-510.
Vanderpool, E. W., 1950, Correlation of the El Paso formation: West Texas Geol. Soc. Guidebook, 1950 Field Trip, p. 61-63. PLATE I
/ ' x < CORRELATIONS OF THE EL PASO FORMATION 1A \ / !— il X WESTERN TEXAS, SOUTHWESTERN NEW MEXICO, AND SOUTHEASTERN ARIZONA ------S5A1i!L_>____1 BASED ON INSOLUBLE RESIDUES
X.4Xf"S’"..••
w < MEXICO
SOUTHWESTERN NEW MEXICO - SOUTHEASTERN ARIZONA EL PASO FORMATION
LEGEND
SMOOTH CHERT SHALE OR CLAY 0 CLAY PELLETS
■ GRANULAR CHERT • GLAUCONITE
CHALKY CHERT m SAND * TRIAXON SPONGE SPICULES
DRUSE OR QUARTZ I I NO SAMPLES S MONAXON SPONGE SPICULES