Stratigraphic Nomenclature of 

Cambrian and Lower Ordovician Rocks 

of Easternmost Southern Arizona and 

Adjacent Westernmost New Mexico

GEOLOGICAL SURVEY BULLETIN 1 * 7 2-B
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Stratigraphic Nomenclature of 

Cambrian and Lower Ordovician Rocks 

of Easternmost Southern Arizona and 

Adjacent Westernmost New Mexico

By PHILIP T. HAYES

CONTRIBUTIONS TO STRATIGRAPHY

GEOLOGICAL SURVEY BULLETIN 1372-B

The areal extent is expanded for four 

Stratigraphic units and restricted for 

one unit, and one term is abandoned

UNITED STATES GOVERNMENT PRINTING OFFICE, WASHINGTON : 1972
UNITED STATES DEPARTMENT OF THE INTERIOR 

ROGERS C. B. MORTON, Secretary

GEOLOGICAL SURVEY 

V. E. McKelvey, Director

Library of Congress catalog-card No. 72-600143

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

Washington, D.G. 20402 - Price 25 cents

Stock Number 2401-2183
CONTENTS

Page

Abstract.... . .. ................................................................................................... Bl

Introduction............................................................................................................ 1

Stratigraphy........................................................................................................... 5

Bolsa Quartzite and Abrigo Formation in all but

easternmost southern Arizona-.-.....-. ......................................... 5

Bolsa Quartzite...................................................................................... 5

Abrigo Formation ....... ................................................................. 5

Lower member............................................................................... 7

Middle member.............................................................................. 7

Sandy member............................................................................... 8

Copper Queen Member................................................................ 8

Bliss Sandstone and El Paso Limestone east of

long 108°45' W.................................................................................. 9

Bliss Sandstone..................................................................................... 9

El Paso Limestone............................................................................... 10

Cambrian and Ordovician rocks of Arizona-New Mexico

border area........................... .............................. .......... . H

Swisshelm and Pedregosa Mountains--...-.----...... .. .. . 11

Morenci area.......................................................................................... 12

Dos Cabezas Mountains...............................------..-.---....-.---.--..--.--..--..-. 14

Chiricahua Mountains--.-------..---.....-----.----...----------..--------.....-------. 15

Peloncillo Mountains...... ...................................................... .... .. 16

Aravaipa area................................................................ . . 17

Summary of proposed nomenclatural changes.--...------...-------..---.....---- 17

Arizona west of problem area................................................................... 17

New Mexico east of long 108°45' W.................................... .. . 18

The problem area........................................................ ... .. ....... 18

Swisshelm and Pedregosa Mountains......--.-.---...-.-.--....---..----.......-- 18

Morenci area..................................... ........ ..... ..... ... ... .- 18

Peloncillo, Chiricahua, and Dos Cabezas Mountains..................... 19

Aravaipa area............ . ........ ........... . ...... .. . . - -- 19

References cited..-----.-.......... ............................... . .. . ... 20

ILLUSTRATIONS

Page

FIGURE 1. Map of southeastern Arizona, southwestern

New Mexico, and extreme western Texas......................... . B2

2. Diagrammatic stratigraphic cross section................................. 6

in

CONTRIBUTIONS TO STRATIGRAPHY

STRATIGRAPHIC NOMENCLATURE 

OF CAMBRIAN AND LOWER ORDOVICIAN

ROCKS OF EASTERNMOST SOUTHERN

ARIZONA AND ADJACENT WESTERNMOST

NEW MEXICO

By PHILIP T. HAYES

ABSTRACT

The Bolsa Quartzite and overlying Abrigo Formation, both of Cambrian 

age, have become firmly established in all but easternmost southern Arizona 

as the basic stratigraphic units of the oldest depositional sequence of the 

Paleozoic. The Bliss Sandstone of Cambrian and Ordovician age and the 

overlying El Paso Limestone of Early Ordovician age have become similarly 

firmly established in southern New Mexico east of long 108°45' W. as the 

basic units of the oldest depositional sequence of the Paleozoic there. 

Terminology in the intervening area, where the Arizona and New Mexico 

sequences merge, has not been uniform.

In the southwestern part of this intervening area, where Cambrian rocks 

typical of the Bolsa Quartzite and the Abrigo Formation are overlain by 

Ordovician rocks typical of the El Paso Limestone, all these terms are 

usable. Farther to the north and east the Bolsa has largely lapped out, 

and all of the Abrigo except the uppermost part has merged into a sandstone sequence. I recommend that the sandstone sequence be referred to the 

Coronado Sandstone, that the overlying carbonate sequence, here of uppermost 

Cambrian and Early Ordovician age, be referred to the El Paso Limestone, 

and that the term Longfellow Limestone be abandoned. I also recommend 

that the dolomitized equivalents of the top member of the type Abrigo, the 

Copper Queen Limestone Member, be referred to the Copper Queen Member 

of the Abrigo wherever preserved.

INTRODUCTION

In 1904, Ransome named the basal two formations of the Paleozoic sequence in the Mule Mountains of southeastern Arizona (loc. 

65, fig. 1) the Bolsa Quartzite and the overlying Abrigo Limestone, 

both of Cambrian age. In the same year, Richardson (1904) 

named the basal two formations of the Paleozoic sequence in the 

Franklin Mountains of extreme western Texas (loc. 45, fig. 1)

Bl
B2 CONTRIBUTIONS TO STRATIGRAPHY

110° 109°

33" 

110° 109°

FIGURE 1. Map of southeastern Arizona, southwestern New Mexico, 

and extreme western Texas, showing Cambrian and Lower Ordovician localities examined (X) or reported in literature ( ) and 

approximate positions of some facies boundaries (solid lines). 

Large capital letters refer to areas discussed in text. Numbers 

refer to localities mentioned in text; see list on facing page.

the Bliss Sandstone and the overlying El Paso Limestone, which 

were respectively assigned Cambrian and Ordovician ages. A 

year later, Lindgren (1905) named the basal two formations of 

the Paleozoic in the Morenci area, near the east edge of Arizona 

(loc. 84, fig. 1), the Coronado Quartzite and the Longfellow Lime-
CAMBRIAN-ORDOVICIAN ROCKS, ARIZONA AND NEW MEXICO B3

108° 107"

Truth or Consequences

Silver City X

.o

E

UNITED STATES

MEXICO

0 10 20 30 40 50 MILES

0 10 20 30 40 50 KILOMETERS

El Paso

33 s

32°

108°

23. Peloncillo Mountains

24. Big Hatchet Mountains

45. Franklin Mountains

57, 58, 59. Chiricahua Mountains

60. Dos Cabezas Mountains

61. 62. Pedregosa Mountains 

63, 64. Swisshelm Mountains

65. Mule Mountains

76. Aravaipa area

77. Santa Catalina Mountains

78. Galiuro Mountains

84. Morenci area

102. Galiuro Mountains

150. Nantac Rim

stone, which also were respectively assigned Cambrian and Ordovician ages. The names Bolsa and Abrigo have since been applied 

to Cambrian rocks in numerous isolated areas of southern Arizona 

and with expectable minor revisions in boundaries, refinements
B4 CONTRIBUTIONS TO STRATIGRAPHY

of age assignments, and subdivisions into local formally and informally named members have become firmly established and 

almost universally accepted as the basic unit names for Cambrian 

rocks in all but easternmost southern Arizona. Similarly, the 

names Bliss and El Paso have been applied to Upper Cambrian 

and Lower Ordovician rocks in numerous isolated areas in southern New Mexico and far-western Texas and with similar revising, refining, and subdividing have become firmly established 

and almost universally accepted as the basic unit names for outcropping Upper Cambrian and Lower Ordovician rocks east of 

about long 108°45' W. in southern New Mexico and far-western 

Texas.1 There has been no such uniformity of nomenclature for 

the Cambrian and Ordovician rocks that crop out at various 

localities in the intervening area. In this intervening area the 

terms Coronado Quartzite and Longfellow Limestone have been 

applied only in their immediate type area in the Morenci vicinity. 

In the Dos Cabezas'Mountains (loc. 60, fig. 1), Jones and Bacheller (1953) used the names Bolsa and Abrigo even though the 

Abrigo was recognized as being partly of Ordovician age. In the 

Chiricahua (Iocs. 57-59, fig. 1) and Peloncillo Mountains (loc. 

23, fig. 1), Sabins (1957a, b) and Gillerman (1958), respectively, 

used the names Bolsa and El Paso even though the El Paso rocks 

were recognized as being partly of Cambrian age. In the Swisshelm and Pedregosa Mountains (Iocs. 61-64, fig. 1), Epis and 

Gilbert (1957) and Epis (1958) divided the sequence, in ascending 

order, into the Bolsa, the Abrigo, and two unnamed units of 

Cambrian age and the El Paso Limestone of Ordovician age. 

Although Epis and Gilbert contributed greatly to an understanding 

of stratigraphic relations across the region, the nomenclature 

problem has remained unresolved.

The purpose of this paper is to propose a standard nomenclature 

for the problem area (areas A', B, and B' in fig. 1) of southeasternmost Arizona and southwesternmost New Mexico. The 

rocks and some of their lateral facies changes in the areas to the 

east and west are described first; then the lithologic and stratigraphic relations of the rocks of the problem area are briefly 

reviewed; and, finally, the probable relations of the rocks of the 

problem area to the rocks to the east and west are discussed. I 

draw heavily on the large body of data that has previously been 

published on the region, as well as on the data I accumulated in

*As originally defined by Richardson (1904), the El Paso included all Ordovician rocks at 

the type locality. Later he revised the El Paso to include only the Lower Ordovician rocks 

and included all later Ordovician rocks in his Montoya Limestone (Richardson, 1908). It 

is in its revised sense that the El Paso has been used so extensively.
CAMBRIAN-ORDOVICIAN ROCKS, ARIZONA AND NEW MEXICO B5

having examined these rocks at nearly 50 localities in the region, 

including 13 localities in the problem area. A diagrammatic 

section (fig. 2) shows the interpreted stratigraphic relations and 

recommended nomenclature in the parts of Arizona and New 

Mexico under discussion.

STRATIGRAPHY

BOLSA QUARTZITE AND ABRIGO FORMATION IN ALL BUT EASTERNMOST

SOUTHERN ARIZONA

The lithology, age, subdivisions, and correlations of the Bolsa 

Quartzite and Abrigo Formation in much of southeastern Arizona 

have been recently reviewed by Krieger (1968c) and briefly 

summarized by Lochman-Balk (1971), and the following descriptions are adapted in part from their excellent papers.

BOLSA QUARTZITE

The Bolsa Quartzite, 344 feet thick at its type section (Hayes 

and Landis, 1965) in the Mule Mountains (loc. 65, fig. 1), ranges 

in thickness from a little more than 30 m (100 ft) to about 150 

m (500 ft) in areas A and A' shown in figure 1. Though the thickness varies locally owing to some relief on the underlying Precambrian surface, regionally it tends to be greater in the southern 

part of the region. In the southern part of the region the Bolsa 

lies on older Precambrian schists and granitic rocks; in the 

northern part of the region it lies on younger Precambrian sedimentary rocks, some of which formerly were occasionally confused with the Bolsa (Krieger, 1961). The Bolsa consists almost 

entirely of quartzitic siliceous sandstone. From base to top the 

sandstone decreases in grain size and feldspar content from commonly conglomeratic and somewhat feldspathic in the lower part 

to fine grained and very sparsely feldspathic in the upper part; 

commonly a few thin interbeds of siltstone and mudstone occur 

near the top. The Bolsa grades, generally rather abruptly, upward into the Abrigo Formation. It contains virtually no diagnostic fossils, but its age is considered to be Middle Cambrian 

by virtue of its transitional relations with the overlying Abrigo 

whose basal part is known to be Middle Cambrian. Regional 

correlations suggest that the age of the top of the Bolsa may 

decrease slightly from west to east across areas A and A' shown 

in figure 1. (See also fig. 2.)

ABRIGO FORMATION

The Abrigo Limestone at its type locality,2 as described by 

Hayes and Landis (1965), comprises four members: in ascending

balled Abrigo Formation except near its type locality.
B6 CONTRIBUTIONS TO STRATIGRAPHY
CAMBRIAN-ORDOVICIAN ROCKS, ARIZONA AND NEW MEXICO B7

order, the shaly member, the ribbed limestone member, the sandy 

member, and the Copper Queen Limestone Member. Each member 

can be widely correlated in southeastern Arizona, but because most 

members change lithologically across the region, Krieger (1968c) 

used the terms lower and middle members for the shaly and ribbed 

limestone members and combined the sandy and Copper Queen 

Limestone members into a single upper member, which she 

recognized is at least locally divisible into lower and upper parts. 

I agree that the terms lower and middle are more appropriate for 

regional use and are accordingly used here. Because I believe that 

her upper member is everywhere divisible into two parts where 

the upper part has not been removed by erosion and because I 

further believe that the upper part is of special stratigraphic 

significance, I will here continue to use the term sandy member 

for the lower part of Krieger's upper member and propose that 

the name Copper Queen Member be applied to the upper part on 

a regional basis. The lower, middle, sandy, and Copper Queen 

are described individually in the following paragraphs.

LOWER MEMBER

Within the region designated by A and A! in figure 1, the 

lower member of the Abrigo generally ranges in thickness from 

75 to 135 m (250-450 ft), the thickest sections being toward the 

west. The member is characterized by predominant relatively 

fine grained clastic rocks, such as siltstone and mudstone or 

shale; but thin beds of sandstone are not uncommon, especially 

near the base; and thin beds of dolomite or limestone are generally common, especially in the upper part. Northward and eastward 

the amount and coarseness of sandstone seem to increase. The 

upper contact is fairly abrupt at most localities, but it appears 

to be conformable at all localities. Various parts of the member 

have yielded fossils, chiefly trilobites, at several localities, and all 

these fossils indicate a Middle Cambrian age. On the basis of 

regional correlations I believe that the top of the member is 

very nearly the same age throughout the region under discussion.

MIDDLE MEMBER

The middle member of the Abrigo, within the region designated 

by A and A' in figure 1, generally ranges in thickness from about 

45 to 90 m (150-300 ft). In the southern part of the region the 

member is made up almost entirely of very thin-bedded carbonate, 

usually limestone, that is marked by abundant silty bands that 

characteristically stand out in relief on the outcrop. Farther north 

the lower part of the member contains one or more beds of resistant sandstone at the base, and in the Santa Catalina Mountains
B8 CONTRIBUTIONS TO STRATIGRAPHY

(loc. 77, fig. 1) the sandstone at the base of the member is 

particularly conspicuous and has been separately designated as 

the Southern Belle Member (Creasey, 1967) .a Still farther northward, such as in the northern Galiuro Mountains (loc. 102, fig. 1), 

the middle member is made up almost entirely of sandstone but 

can be recognized by its stratigraphic position between the more 

regionally uniform lower and sandy members. Fossils, chiefly 

trilobites, from the carbonate facies of the member indicate that 

it is almost entirely of early Late Cambrian (Dresbach) age; 

only the basal beds may, at least locally, be of Middle Cambrian age.

SANDY MEMBER

Where completely preserved within the region designated by 

A and A' in figure 1, the sandy member ranges in thickness from 

131/2 to 54 m (45-180 ft). At several localities in the western part 

of the region its top and the overlying Copper Queen Member 

were presumably removed by pre-Upper Devonian erosion, and 

in some of these localities only a few meters of the sandy member 

remains. The member is everywhere characterized by interbedded 

brown-weathering glauconitic crossbedded sandy dolomite and 

dolomitic sandstone that at many localities display remarkable 

chip conglomerate beds. Eastward the member seems to become 

more sandy and less dolomitic. Fossils in the member indicate 

an early Late Cambrian (Dresbach) age.

COPPER QUEEN MEMBER

In area A (fig. 1) the Copper Queen Member of the Abrigo is 

missing, probably owing to pre-Devonian erosion, in most western 

sections and is less than 30 m (100 ft) thick elsewhere; in area 

Af (fig. 1), however, it is completely preserved and apparently 

ranges in thickness from 36 to 54 m (120-180 ft). At the type 

section of the Abrigo, in the Mule Mountains (loc. 65, fig. 1), 

the only mountain range in which the Copper Queen has heretofore been recognized, the Copper Queen consists mostly of thinbedded limestone interbedded with a few thin layers of sandy 

or argillaceous limestone. In most other mountain ranges in areas 

A and A' the member consists dominantly of thin-bedded dolomite 

interbedded with minor sandy layers. Fossils that have been 

found in the member indicate a late Late Cambrian (Franconia) 

age, but to my knowledge fossils have not been found in the 

upper part of the member, at localities where it seems to be most 

completely preserved. The upper part, thus, could be of latest

3Named the Southern Belle Quartzite and recognized as a distinct formation by Stoyanow 

(1936).
CAMBRIAN-ORDOVICIAN ROCKS, ARIZONA AND NEW MEXICO B9

Late Cambrian (Trempealeau) age. In area A (fig. 1) the Copper 

Queen is disconformably overlain by Upper Devonian rocks. In 

area A', discussed in more detail under "Cambrian and Ordovician 

Rocks of Arizona-New Mexico Border Area," it is conformably 

overlain by Ordovician strata.

BLISS SANDSTONE AND EL PASO SANDSTONE EAST OF LONG 108° 45' W.

The regional stratigraphy of the Bliss Sandstone and El Paso 

Limestone in southwestern New Mexico has been described most 

recently by Kottlowski (1963), who concentrated mostly on lithologic characteristics, and by Flower (1969), who added considerably to knowledge of the regional distribution of faunal zones 

and of the lithologic character of subdivisions based on these 

zones. Flower (1959, 1969) suggested that because the age of 

the Bliss in its type section is uncertain and because the Bliss 

contains beds of both Cambrian and Ordovician ages in some areas, 

a "readjustment of formational names may be required when 

the age of the Bliss is definitely established." Certainly a much 

better knowledge of the age of various parts of the Bliss in various 

areas would be highly desirable; and if and when that knowledge 

becomes available, the formation should, if possible, be divided 

into lithologic members of distinct ages. For decades, however, 

the name Bliss has been usefully applied to the dominantly sandstone sequence that underlies the El Paso Limestone, regardless 

of age, and that usefulness will remain. Flower (1964) has also 

proposed elevation of the El Paso to group status and has proposed many formational divisions. These divisions are useful 

faunal zones, and some are lithologically distinctive; but herein 

the El Paso is more conveniently described as a single formational 

unit.

BLISS SANDSTONE

In the southern part of the region that comprises areas C, D, 

E, and F (fig. 1), the Bliss Sandstone ranges in thickness from 

about 30 to 90 m (100-300 ft) in most sections, and in the northern part of that region it ranges in thickness from a few meters 

to about 45 m (150 ft). Variations in thickness are due partly 

to irregularities on the underlying Precambrian surface and partly to a general northward thinning and eventual pinchout not far 

north of the area shown. In areas E and F the Bliss consists 

predominantly of sandstone; but toward the north, oolitic hematite is fairly common, and thin carbonate units are present. The 

sandstones of the Bliss are commonly glauconitic and hematitic 

and generally are less thoroughly cemented than those of the Bolsa 

Quartzite. In area D the upper part of the Bliss contains considerable thin-bedded, usually silty, carbonate that is very similar

471-714 O - 72 - 2
BIO CONTRIBUTIONS TO STRATIGRAPHY

to carbonate in the basal part of the overlying El Paso Limestone. 

In that area, the Bliss-El Paso contact is arbitrary but has 

generally been placed at the top of the highest conspicuous noncalcareous or nondolomitic sandstone (fig. 2). In area C the 

lower part of the Bliss contains much dolomite, and the upper 

part, as used by Zeller (1965) in the Big Hatchet Mountains (loc. 

24, fig. 1), contains no nondolomitic sandstone. If Zeller had 

followed the practice generally employed to the east, he probably 

would have included the upper part of his Bliss in the basal El 

Paso. As noted by Flower (1969), details of the age of the Bliss 

at many localities are uncertain owing to the general sparsity of 

diagnostic fossils. However, the available faunal evidence and the 

lithologic correlations clearly indicate, despite the presence of 

depositional breaks within the formation at various localities 

(Flower, 1969; Lochman-Balk, 1971), that in general both the 

base and the top of the Bliss are progressively older from east 

to west. Throughout most, or all, of the areas D and E the lower 

part of the Bliss is of late Late Cambrian age and the upper part is 

of earliest Early Ordovician age. In area F the entire Bliss may be 

of Ordovician age. Conversely, in area C, rocks of Bliss lithology 

may be entirely of Cambrian age, although unfossiliferous sandy 

dolomites and dolomitic sandstones included in the upper part of 

the Bliss by Zeller (1965) are likely Ordovician.

EL PASO LIMESTONE

The El Paso Limestone, nearly 500 m (1,600 ft) thick at its 

type locality in the Franklin Mountains (loc. 45, fig. 1), thins 

both northward and westward, primarily owing to Middle Ordovician erosion on top. Although the El Paso is made up largely 

of limestone, all sections contain some dolomite, and some sections are almost completely dolomitized. The basal beds of the 

formation, which are of variable thickness, are sandy and (or) 

silty, and they grade upward into beds which almost everywhere 

consist of nearly pure carbonate but which in some places contain 

chert. In the thicker sections toward the south there are higher 

sandy horizons and many variations in the texture and bedding 

of the carbonates, but these higher sandy horizons are not of 

importance to the present discussion. Throughout areas C, D, E, 

and F (fig. 1) the El Paso is of Early Ordovician (Canadian) 

age, and in area C its base may very nearly coincide with the base 

of the Ordovician. Wherever exposed in areas C, D, E, and F, the 

El Paso is disconformably overlain by the Montoya Group of 

Middle and Late Ordovician age.
CAMBRIAN-ORDOVICIAN ROCKS, ARIZONA AND NEW MEXICO Bll

CAMBRIAN AND ORDOVICIAN ROCKS OF ARIZONA-NEW MEXICO

BORDER AREA

SWISSHELM AND PEDREGOSA MOUNTAINS

Epis and Gilbert (1957) and Epis (1958) described the Cambrian and Ordovician rocks at several localities in the structurally 

complex Pedregosa and Swisshelm Mountains, which are in area 

A' (fig. 1), and they correlated their sections with sections in 

areas A and B' (fig. 1). I have examined all their localities, and 

although most localities are difficult to study because of structural 

complications, steep dip slopes, or poor exposures, I believe that 

these investigators correctly interpreted the sequence and described it well. A section in the northern Swisshelm Mountains 

(loc. 64, fig. 1) is best exposed and least disturbed and therefore 

is most reliably measured and described. This section as largely 

remeasured by me is briefly described in the following paragraphs.

At the base of the Paleozoic in the northern Swisshelm Mountains is about 90 m (300 ft) of quartzite that Epis and Gilbert 

(1957) assigned to the Bolsa Quartzite and correlated with the 

Bolsa of the Mule Mountains (loc. 65, fig. 1). I fully concur 

with them.

Above the Bolsa is 132 m (434 ft) (390 ft as measured by 

Epis and Gilbert, 1957) of rock that Epis and Gilbert (1957) 

assigned to the Abrigo Formation. Rock in the lower 90 m (295 

ft) of this sequence is dominantly siltstone and mudstone interbedded with minor sandstone and carbonate, and it unquestionably 

is assignable to the lower member of the Abrigo as it is known 

to the west. The upper 42 m (139 ft) of rock assigned to the 

Abrigo by Epis and Gilbert (1957) is thin-bedded limestone which 

yields fossils of Dresbach age and which is undoubtedly assignable to the middle member of the Abrigo as it is used to the west.

Next above is 54.5 m (180 ft) (measured as 195 ft by Epis and 

Gilbert, 1957) of brown-weather ing dolomitic sandstone which in 

the upper part is interbedded with much sandy dolomite. This 

unit was informally referred to as "Upper Cambrian sandstone" 

by Epis and Gilbert (1957), who compared it to the Bliss Sandstone and correlated it with the sandstone high in the Abrigo of 

the Mule Mountains (loc. 65, fig. 1). Krieger (1968c) referred the 

unit to the lower part of her upper member of the Abrigo. These 

correlations are undoubtedly correct, and the Upper Cambrian 

sandstone unit of Epis and Gilbert (1957) unquestionably represents the sandy member of the Abrigo as used in areas to the west.

Above the sandy member in the northern Swisshelm Mountains 

is 68 m (223 ft) (measured as 235 ft by Epis and Gilbert, 1957)
B12 CONTRIBUTIONS TO STRATIGRAPHY

of thin- to thick-bedded dolomite containing sandy layers in the 

basal 45 m (148 ft) and containing lenses of white chert in the 

upper part of an upper, 23-m-thick (75-ft) nonsandy unit. Beds 

near the base of the lower, 45-m-thick interval yielded species 

of Billingsella of late Late Cambrian (Franconia) age. The upper, 

23-m-thick nonsandy unit is apparently barren of fossils. The entire 68-m-thick interval was left unnamed by Epis and Gilbert 

(1957) but was assigned to the Cambrian by them. Both the 

lithology of the rock and the presence of Billingsella clearly 

indicate that at least the lower 45 m of the interval represents 

the Copper Queen Member of the Abrigo in areas to the west and 

can properly be given that designation here. The barren 23-mthick chert-bearing dolomite at the top is conformably overlain 

by limestones that have yielded Ordovician fossils, and I tentatively conclude that this 23-m-thick interval, though dolomitized, is 

more similar to the overlying Ordovician beds than to the underlying Cambrian beds.

Epis and Gilbert (1957) measured 225 feet of limestone that 

contains Ordovician gastropods and cephalopods, and they reasonably assigned the beds to the El Paso Limestone. If the underlying 

23-m-thick (75-ft) unit of barren dolomite is also assigned to 

the El Paso as I think proper then the El Paso at this 

locality is about 90 m (300 ft) thick. The El Paso is disconformably overlain by Upper Devonian beds.

MORENCI AREA

The Cambrian and Ordovician strata of the Morenci area (loc. 

84, fig. 1) were divided by Lindgren (1905) into the Coronado 

Quartzite of Cambrian age and the Longfellow Limestone of assigned Ordovician age. With the permission of the Phelps Dodge 

Co., I examined the Coronado Quartzite in the Morenci pit area 

and, with the assistance of George C. Cone, remeasured the Longfellow Limestone 6 km (3% miles) east of Morenci along the 

San Francisco River.

The Coronado, 74 m (243 ft) thick as measured by Lindgren 

(1905) where we viewed it southwest of Morenci, is made up 

dominantly of rather resistant siliceous sandstone. Some conglomerate is interbedded near its unconformable basal contact with 

Precambrian diorite, and some shale is interbedded in the upper 

part. To my knowledge, no closely diagnostic fossils have yet 

been found in the Coronado, though it has yielded linguloid 

brachiopods.

The Longfellow Limestone as measured by us consists from 

base to top of:
CAMBRIAN-ORDOVICIAN ROCKS, ARIZONA AND NEW MEXICO B13

(1) 12.8 m (42 ft) of sandy grayish-red dolomite;

(2) 9.1m (30ft) of fine-grained brownish-gray dolomite;

(3) 4.2 m (14 ft) of interbedded sandy and nonsandy dolomite;

(4) 8.2 m (27 ft) of cliff-forming dolomitic quartz sandstone ;

(5) 36.5 m (120 ft) of laminated to cross-laminated dolomite 

which has minor slightly sandy layers and which has 

yielded Early Ordovician fossils from its upper half;

(6) 24.7 m (81 ft) of relatively thick bedded dolomite;

(7) 18 m (59 ft) of indistinctly bedded saccharoidal dolomite; and

(8) 4.5 m (15 ft) of medium-dark-gray dolomitic crinoidal 

limestone that appears to be disconformable at the 

base and top.

On the basis of the lithologic correlations with distant sections to 

the southeast and south and a fossil-bearing section I recently 

measured about 40 km (25 miles) to the northwest (loc. 150, 

fig. 1), the lower four units, or 34.3 m (113 ft), of the Longfellow 

here that is, to the top of the resistant sandstone ledge 

are probably of Cambrian age. The remaining part except unit 

8, or the top 4.5 m (15 ft), is probably of Early Ordovician age. 

The top 4.5 m is undoubtedly the unit from which Hill (1959) 

identified corals of approximate Trenton age, and it almost 

certainly represents the basal beds of the Second Value Dolomite 

of the Montoya Group as it is known in southwestern New 

Mexico.

For the following reasons, I propose that the term Longfellow 

Limestone be abandoned: The term has never been used outside 

the Morenci vicinity; the formation as originally defined includes 

beds of Trenton age at the top that almost certainly are separated 

by a major disconformity from the beds below; and the lower 

113.5 m (373 ft) of beds are similar in age and lithology to the 

lower 100 m or so of the El Paso Limestone as it is used in the 

nearest sections to the south and southeast. The medium-darkgray limestone at the top should be referred to the Second Value 

Dolomite, and the remainder of the formation, to the El Paso 

Limestone. The lower four units, or 34.3 m (113 ft), of rocks of 

probable Cambrian age could properly be distinguished as a 

separate member. Although the term Coronado Quartzite has not 

previously been used outside the Morenci area, its original definition still appears to be valid. The term can usefully be applied 

to similar rocks to the south and west that lie between Precambrian rocks and the El Paso Limestone. Such rocks apparently
B14 CONTRIBUTIONS TO STRATIGRAPHY

are a sandstone facies of the Abrigo Formation. Because in most 

areas the rocks included in the Coronado are dominantly sandstone rather than true quartzite, the formation is here designated 

the Coronado Sandstone.

DOS CABEZAS MOUNTAINS

A section of Cambrian and Ordovician strata about 3 miles 

west of Dos Cabezas, Ariz., was discussed by Darton (1925) and 

Stoyanow (1936), measured by Jones and Bacheller (1953), and 

further discussed by Sabins (1957b) and Epis and Gilbert (1957) ; 

more recently the rocks there and in the nearby Chiricahua 

Mountains were discussed by Krieger (1968c). With the assistance of George C. Cone, I remeasured the section near Dos Cabezas, and I generally concur with the correlations by Epis and 

Gilbert (1957) and Krieger (1968c).

As described by Jones and Bacheller (1953) and Sabins 

(1957b), the Cambrian and Ordovician rocks near Dos Cabezas 

(loc. 60, fig. 1) are divisible into two principal conformable lithologic units of approximately the same thickness: a lower, sandstone unit of Cambrian age and an upper, carbonate unit of 

Cambrian and Ordovician age. Regardless of how various parts 

of these units may correlate with rocks of other areas, the two 

units as recognized by those workers are obvious ones that any 

field geologist would normally select for mapping.

The lower unit, which unconformably overlies Precambrian 

schist, was called the Bolsa Quartzite both by Jones and Bacheller 

(1953) and by Sabins (1957b) ; and the upper unit, which is disconformably overlain by Upper Devonian shale, was called the 

Abrigo Limestone by Jones and Bacheller and the El Paso Limestone by Sabins.

The upper, carbonate unit as remeasured by us is 89.9 m 

(295 ft) thick and consists from base to top of:

(1) 24.4 m (80 ft) of cross-laminated sandy dolomite and 

dolomitic sandstone;

(2) 13.7 m (45 ft) of medium-gray dolomite with scattered 

sandy stringers;

(3) 6.4 m (21 ft) of very sandy dolomite and dolomitic sandstone like that at the base;

(4) 26.8 m (88 ft) of medium-gray dolomite that contains 

scattered sandy layers and silt-filled burrows; and

(5) 18.6 m (61 ft) of medium-gray dolomite which contains 

chert stringers and lenses and which has yielded fossils of Early Ordovician age from the upper part. 

On the basis of the fossils found in this section and lithologic 

correlation with sections in other areas, the top two units, or
CAMBRIAN-ORDOVICIAN ROCKS, ARIZONA AND NEW MEXICO B15

45.4 m (149 ft), of the carbonate unit are at least partly, and 

probably entirely, of Ordovician age and are correlative with the 

El Paso Limestone; the lower three units, or 44.5 m (146 ft), of 

the carbonate unit are almost certainly correlative with the Copper Queen Member of the Abrigo Formation.

The lower, sandstone unit near Dos Cabezas as remeasured by 

us is 97.5 m (320 ft) thick and consists from base to top of:

(1) 1.8 m (6 ft) of arkosic conglomerate;

(2) 5.2 m (17 ft) of resistant siliceous feldspathic sandstone ;

(3) 51 m (168 ft) of partially poorly exposed sandstone thatis dolomitic in part, glauconitic in part, and siliceous in 

part; and

(4) 39.5 m (129 ft) of somewhat dolomitic largely crosslaminated sandstone.

The upper 39.5 m of rock is lithologically similar to the sandy 

member of the Abrigo Formation and, although much sandier and 

less dolomitic than is typical of the sandy member, is probably 

equivalent to it. It is also lithologically similar to and probably 

coeval with the Cambrian part of the Bliss Sandstone as the 

Bliss occurs in western New Mexico. The lower 58 m of the 

sandstone unit is probably equivalent to the middle member of 

the Abrigo and possibly in part to the lower member of the 

Abrigo, although it is much sandier than typical Abrigo of areas 

to the west. Only a few beds in the unit bear much lithologic 

resemblance to the Bolsa Quartzite of areas to the west, and 

probably no part of the unit is so old as the Bolsa as it is used 

to the west.

For these reasons, I believe that the 97.5-m-thick sandstone unit 

here is most properly assignable to the Coronado Sandstone and 

that the 89.9-m-thick carbonate unit can properly be assigned 

to the El Paso Limestone. The 44.5 m (146 ft) of partly sandy 

dolomite at the base of the carbonate unit could be recognized as 

a distinct member of the El Paso, equivalent to the Copper Queen 

Member of the Abrigo.

CHIRICAHUA MOUNTAINS

The Cambrian and Ordovician sequence in the northern Chiricahua Mountains (Iocs. 57-59, fig. 1) is similar to that of Dos 

Cabezas. A basal sandstone unit, mapped by Sabins (1957a) as 

the Bolsa Quartzite, is similar to the sandstone near Dos Cabezas 

that I assign to the Coronado Sandstone, but the basal sandstone 

of the Chiricahua Mountains is even more difficult to relate to 

the Abrigo lithologically than is the Coronado Sandstone near 

Dos Cabezas. The sandstone of the Chiricahua Mountains con-
B16 CONTRIBUTIONS TO STRATIGRAPHY

tains glauconitic beds and, in the eastern part of the mountains, 

hematitic units. The glauconitic and hematitic beds give the unit 

a Bliss-like aspect. An upper carbonate unit in the Chiricahua 

Mountains, mapped by Sabins (1957a) as the El Paso Limestone, 

is generally thicker than the El Paso Limestone near Dos Cabezas, but is otherwise similar. The carbonate unit includes a 

basal sandy dolomite which has yielded Billingsella from one 

locality; this occurrence strengthens the correlation of this part 

of the carbonate unit with the Copper Queen Member of the 

Abrigo Formation.

As with the Dos Cabezas section, I believe that the basal sandstone unit should be referred to the Coronado Sandstone rather 

than to the Bolsa Quartzite and that the upper carbonate was 

properly assigned to the El Paso Limestone. Also, as near Dos 

Cabezas, the sandy dolomite beds of Cambrian age at the base of 

the El Paso could be distinguished as a member of the El Paso 

equivalent to the Copper Queen Member of the Abrigo.

PELONCILLO MOUNTAINS

In the central Peloncillo Mountains (loc. 23, fig. 1), Gillerman 

(1958) mapped and described the Cambrian and Ordovician sequence, and with the assistance of George C. Cone, I remeasured 

it. A 120-m-thick (396 ft) basal unit of partly glauconitic and 

partly hematitic sandstone that rests unconformably on Precambrian granite was assigned to the Bolsa Quartzite by Gillerman (1958). Conformably overlying that is a 168-m-thick (553 

ft) carbonate unit which he referred to the El Paso Limestone 

and which he assigned a Cambrian and Ordovician age. Cherty 

limestone near the middle of the unit yielded Early Ordovician 

cephalopods to Gillerman (1958). Rocks in the basal 26 m (86 

ft) of the carbonate formation are sandy, especially toward the 

top, and as noted by Gillerman (1958), they strongly resemble 

beds at the base of the El Paso in the Chiricahua Mountains 

which have yielded Billingsella of Late Cambrian age. Gillerman 

(1958, p. 24) noted about 30 m (100 ft) of very cherty dolomite at 

the top of the Ordovician sequence at one locality which he "referred doubtfully to the Montoya" Limestone of Middle and Late 

Ordovician age. I have examined this locality and am confident 

that it is a local cherty part of the El Paso and that the El Paso 

is overlain directly by Devonian shale in the central Peloncillo 

Mountains.

I believe that Gillerman (1958) correctly correlated the lower 

part of his El Paso of the Peloncillo Mountains with Cambrian 

beds at the base of the El Paso in the Chiricahua Mountains, and 

also that he properly assigned the entire carbonate unit to the
CAMBRIAN-ORDOVICIAN ROCKS, ARIZONA AND NEW MEXICO BIT

El Paso Limestone. As in the Chiricahua and Dos Cabezas area, 

the partly sandy dolomite beds of the basal 26 m (86 ft) could 

properly be distinguished as a distinctive member of the El Paso 

equivalent to the Copper Queen Member of the Abrigo Formation. 

On the other hand, I do not believe that the Cambrian sandstone 

unit at the base of the sequence in the Peloncillo Mountains should 

be referred to the Bolsa Quartzite. Rather, it should be assigned 

either to the Bliss Sandstone or to the Coronado Sandstone because (1) it is lithologically more like the Bliss or Coronado than 

the Bolsa and (2), less significantly, the sandstone unit of the 

Peloncillo Mountains is at least largely an age equivalent of the 

Coronado or the lower part of the Bliss of areas to the east, 

whereas it is probably entirely younger than any of the Bolsa 

in most of southern Arizona. Because the Cambrian and Ordovician sequence of the Peloncillo Mountains is closer spatially 

and lithologically to Arizona surface sections of equivalent rocks 

than to other New Mexico sections, the term Coronado seems 

preferable to Bliss.

ARAVAIPA AREA

Several small outcrop areas of sandstone and quartzite that 

occur near Aravaipa (loc. 76, fig. 1) were described by Simons 

(1964) and included in the Bolsa Quartzite. Simons noted that 

the Bolsa as he used it there might include beds of Precambrian 

age (assignable to the Troy Quartzite). That seems to be true 

of the section I examined at Imperial Mountain (loc. 76). Above 

the probable Precambrian at Imperial Mountain, George C. Cone 

and I measured 59 m (194 ft) of sandstone and quartzite that 

is of probable Cambrian age. From lithologic comparisons with 

the Bolsa Quartzite and Abrigo Formation in the northern Galiuro 

Mountains (loc. 102, fig. 1), I believe that the Cambrian sandstone and quartzite of Imperial Mountain probably includes 

equivalents of both the Bolsa and the lower member of the 

Abrigo. This correlation, along with the impracticability of trying 

to separate the two units on Imperial Mountain, leads me to conclude that the Cambrian sandstones and quartzites of the Aravaipa 

area (and in other localities in area B in fig. 1) preferably should 

be assigned to the Coronado Sandstone (whose type locality is 

about 90 km (55 miles) distant) rather than to the Bolsa Quartzite (whose type locality is about 170 km (105 miles) distant).

SUMMARY OF PROPOSED NOMENCLATURAL CHANGES 

ARIZONA WEST OF PROBLEM AREA

The only nomenclatural proposal for the Cambrian and Lower 

Ordovician rocks in Arizona in area A (fig. 1) is the extension
B18 CONTRIBUTIONS TO STRATIGRAPHY

of the term Copper Queen Member of the Abrigo Formation to 

all places where the member is still preserved above the sandy 

member (fig. 2). The Copper Queen Member is absent in most 

western sections, but in several eastern sections, equivalent rocks 

of the requisite lithology have been recognized by Krieger (1968c) 

as the upper unit of her upper member of the Abrigo. Besides 

separating lithologically distinct units, the contact between the 

Copper Queen and underlying rocks has regional stratigraphic 

significance in that it very nearly coincides with the boundary 

between the Dresbachian and Franconian Stages of Bell, Berg, 

and Nelson (1956) of the Upper Cambrian. Wherever the Copper 

Queen Member occurs in area A, it is disconformably overlain 

by Devonian strata.

NEW MEXICO EAST OF LONG 108°45' W.

No nomenclatural changes are recommended for the Cambrian 

and Ordovician rocks in New Mexico east of long 108°45' W., but 

I do urge a consistent definition of the Bliss-El Paso contact in 

western New Mexico. There, fairly thick carbonate units occur 

beneath fairly thick sandstone units. Choosing as the top of the 

Bliss the top of the highest conspicuous nearly carbonate-free 

sandstone as most geologists have done seems reasonable 

and is preferable to choosing the top of a very dolomitic sandstone or a sandy dolomite, as has been done in certain areas.

THE PROBLEM AREA

SWISSHELM AND PEDREGOSA MOUNTAINS

Krieger (1968c) has correlated units informally designated by 

Epis and Gilbert (1957) and Epis (1958) as "Upper Cambrian 

sandstone" and "dolomite" with the lower and upper units, 

respectively, of her upper member of the Abrigo and has referred 

all the strata between the Bolsa Quartzite and the El Paso Limestone to the Abrigo Formation. I basically concur with her but 

suggest that most of the dolomite, or upper unit, can properly 

be referred to the Copper Queen Member of the Abrigo and 

that the uppermost part is assignable to the El Paso Limestone.

MORENCI AREA

The term Coronado Quartzite should be changed to Coronado 

Sandstone.

The term Longfellow Limestone should be abandoned. The 

distinctive beds of approximate Trenton age at the top of the 

Longfellow as originally defined by Lindgren (1905) should be 

assigned to the Second Value Dolomite; the remainder of the 

original Longfellow should now be recognized as El Paso Lime-
CAMBRIAN-ORDOVICIAN ROCKS, ARIZONA AND NEW MEXICO B19

stone; and the sandy beds of probable Cambrian age at the base 

may be separated as a member equivalent in age to the Copper 

Queen Member of the Abrigo Formation.

PELONCILLO, CHIRICAHUA, AND DOS CABEZAS MOUNTAINS

In the Peloncillo, Chiricahua, and Dos Cabezas Mountains (Iocs. 

23 and 57-60, fig. 1), I suggest that rocks of Cambrian age 

formerly assigned by Gillerman (1958) and Sabins (1957a, b) to 

the Bolsa Quartzite be referred instead to the Coronado Sandstone. Krieger (1968c) has suggested that in the Chiricahua 

Mountains, and presumably in the Dos Cabezas, these rocks be 

called the Abrigo Formation. Admittedly, much of the rock in 

the unit is a facies equivalent of much of the Abrigo, and in the 

Dos Cabezas Mountains at least, equivalents of specific parts of 

the Abrigo can be tentatively identified. Nevertheless, the rocks 

in this unit are so different from the Abrigo as it is generally 

known and so similar to the Coronado that the term Coronado 

seems more reasonable. The rocks near Dos Cabezas are not much 

sandier than the very sandy facies of the Abrigo as used by 

Krieger (1968a, b) in the northern Galiuro Mountains at localities 78 and 102 (fig. 1) ; but the latter locality is not far from 

other, less sandy sections of the Abrigo, and in the Galiuro 

Mountains, distinguishing the several members is reasonably 

easy. The rocks in the Dos Cabezas and Chiricahua Mountains, 

on the other hand, are more conveniently related to the Coronado 

or to the Bliss sections of New Mexico. In figure 2, the section of 

the Galiuro Mountains may roughly be pictured as occurring 

near the east edge of area A', and the section at Dos Cabezas may 

be roughly pictured as occurring near the west edge of area B'.

I propose no change in the use of the term El Paso Limestone in 

the Peloncillo, Chiricahua, and Dos Cabezas Mountains as used 

by Sabins (1957a, b) and Gillerman (1958), but I do suggest 

that the lower, partly sandy dolomites of Cambrian age in the 

lower part of the formation could be recognized as a distinctive 

member of the El Paso which is equivalent to the Copper Queen 

Member of the Abrigo Formation.

ARAVAIPA AREA

Rocks assigned by Simons (1964) to the Bolsa Quartzite 

probably include equivalents of the Troy Quartzite of Precambrian 

age as well as equivalents of the Bolsa Quartzite and the lower 

member of the Abrigo Formation. I believe that the Cambrian 

rocks there preferably should be referred to the Coronado Sandstone.
B20 CONTRIBUTIONS TO STRATIGRAPHY

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