Porvenir Formation 

(New Name) and Other 

Revisions of Nomenclature of 

Mississippian, Pennsylvania!^ and 

Lower Permian Rocks, 

Southeastern Sangre de Cristo 

Mountains, New Mexico

GEOLOGICAL SURVEY BULLETIN 1537-8

Porvenir Formation 

(New Name) and Other 

Revisions of Nomenclature of 

Mississippian, Pennsylvanian, and 

Lower Permian Rocks, 

Southeastern Sangre de Cristo 

Mountains, New Mexico

By ELMER H. BALTZ and DONALD A. MYERS

CONTRIBUTIONS TO STRATIGRAPHY 

GEOLOGICAL SURVEY BULLETIN 1537-B

Results of new biostratigraphic studies and mapping 

are discussed to provide a basis for revisions of 

nomenclature of some of the Paleozoic rocks

UNITED STATES GOVERNMENT PRINTING OFFICE, WASHINGTON : 1984
UNITED STATES DEPARTMENT OF THE INTERIOR 

WILLIAM P. CLARK, Secretary

GEOLOGICAL SURVEY 

Dallas L. Peck, Director

Library of Congress Cataloging in Publication Data

Baltz, Elmer Harold, 1927

Porvenir formation (new name) and other revisions of nomendature of Mississippian, Pennsylvanian, and lower Permian rocks, southeastern Sangre de Cristo Mountains, New Mexico. 

(Contributions to stratigraphy)(Geological Survey bulletin 1537-B) 

Bibliography: 39 p. 

1. Geology, Stratigraphic Paleozoic. 2. Geology, Stratigraphic Nomenclature Sangre de

Cristo Mountains (Colo. and N. Mex.) 

I. Myers, Donald A., 1921- II. Title. III. Series IV. Series: Geological Survey Bulletin 1537-

B. 

QE654.B27 551.7'5'097895 82-600110

For sale by the Branch of Distribution

U.S. Geological Survey

604 South Pickett Street

Alexandria, VA 22304
CONTENTS

Page

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

Introduction .................................... 2

Late Paleozoic regional setting ....................... 3

History of nomenclature ............................. 6

Pre-Pennsylvanian sedimentary rocks .................... 6

Pennsylvanian and Lower Permian rocks ................. 9

Nomenclature of southeastern Sangre de Cristo Mountains .......... 11

General discussion .............................. 11

Pre-Pennsylvanian sedimentary rocks ................. 13

Magdalena Group ............................ 13

Sandia Formation ............................ 14

Madera Group .............................. 19

Porvenir Formation .............................. 20

Type locality and type section ..................... 20

Contacts with adjacent rocks ...................... 26

Facies ................................... 26

Principal reference locality ....................... 27

Age .................................... 32

Alamitos Formation .............................. 32

Lithologic description .......................... 33

Thickness ................................. 35

Contacts with adjacent rocks ...................... 35

Age .................................... 36

References cited .................................. 36

ILLUSTRATIONS

FIGURE 1. Map of New Mexico showing location of Sangre de Cristo Mountains B3

2. Map showing uplifts and sedimentary basins of Pennsylvanian and

Early Permian time in part of northern New Mexico. ... 5

3. Correlation chart showing historical summary of age assignments 

and nomenclature of Mississippian, Pennsylvanian, and Lower 

Permian rocks, central New Mexico and southern Sangre de 

Cristo Mountains ......................... 8

4. Age assignments, nomenclature, and correlation of mapped rockstratigraphic units of southeastern Sangre de Cristo Mountains 12

5. Index map of part of southeastern Sangre de Cristo Mountains, 

showing localities of type and principal reference localities of 

Porvenir Formation and areas of the three fades ...... 16

6. Geologic map of type locality of Porvenir Formation and locality

of section of Alamitos Formation ............... 20

7. Stratigraphic sections of Porvenir Formation .......... 22

8. Explanation of symbols used in figures 7 and 10 ....... 24

9. Geologic map of principal reference locality of Porvenir Formation 30

10. Composite stratigraphic section of Alamitos Formation .... 34

ill

CONTRIBUTIONS TO STRATIGRAPHY

PORVENIR FORMATION (NEW NAME) 

AND OTHER REVISIONS OF 

NOMENCLATURE OF MISSISSIPPIAN,

PENNSYLVANIAN, AND LOWER

PERMIAN ROCKS, SOUTHEASTERN

SANGRE DE CRISTO MOUNTAINS,

NEW MEXICO

By ELMER H. BALTZ and DONALD A. MYERS

ABSTRACT

In the Sangre de Cristo Mountains in New Mexico, Precambrian rocks are overlain 

at most places by thin sandstone and carbonate rocks of Mississippian age that were 

deposited in shallow seas on a widespread erosional surface of low relief.

The Pennsylvanian and Lower Permian rocks of this region are syntectonic deposits 

of the structurally deep Paleozoic Rowe-Mora basin which is now mainly the site of 

the Sangre de Cristo Mountains; the eastern part of the basin is in the subsurface 

of the Cenozoic Las Vegas basin. The mainly marine rocks of the Rowe-Mora basin 

thicken northward from about 2,200 ft (670 m) near Pecos to more than 6,730 ft (2,050 

m) near Mora. Nonmarine arkoses and red beds of Late Pennsylvanian and Early Permian ages are locally only 300 ft (90 m) thick, but are as much as 3,000 ft (915 m) 

thick in the deep parts of the Rowe-Mora basin. In the southern part of the present 

mountains, unconformities within the section indicate that intrabasinal uplifts were recurrently active in Pennsylvanian and Early Permian time; locally, Lower Permian 

nonmarine rocks truncate all older sedimentary rocks and lie on the Precambrian basement.

A varied stratigraphic nomenclature has arisen for the mainly marine rocks, which 

were originally assigned to the Magdalena Group and were considered to be entirely 

Pennsylvanian. Recently completed detailed mapping and biostratigraphic studies in 

the Las Vegas-Mora area of the southeastern Sangre de Cristo Mountains provide 

a basis for recommending some adjustments and revisions of the nomenclature of the 

southeastern part of the mountains. This revised nomenclature retains, where possible 

and useful, the previous terminology, and also reflects regional classifications based 

on both lithologic and biostratigraphic data acquired in the last 25 years.

Pre-Pennsylvanian rocks are referred to the Espiritu Santo Formation and the overlying Tererro Formation that, together, constitute the Arroyo Penasco Group. This group 

is tentatively assigned entirely to the Mississippian.

Bl
B2 CONTRIBUTIONS TO STRATIGRAPHY

The use of the term Magdalena Group is discontinued in the southeastern part of 

the mountains. To the north, where mainly marine rocks of Pennsylvanian age have 

not been subdivided, the Magdalena Group is still in use.

The name Sandia Formation is retained for Lower and Middle Pennsylvanian rocks 

that consist of marine and nonmarine shale, conglomeratic sandstone, sandstone, carbonaceous to coaly shale, and thin beds of limestone. The thickness of the Sandia ranges 

from about 10 ft (3 m) at the south to more than 5,000 ft (1,525 m) at the north. 

Brachiopods from the lower part of the formation are Morrowan age; fusulinids from 

near the top are late Atokan age.

The Madera Limestone, or Formation, of earlier reports on this area is raised to 

group status. The Madera Group includes the Porvenir Formation (named here) and 

the overlying Alamitos Formation (name here adopted). The Porvenir Formation is 

the lower, gray limestone member, and the Alamitos is the upper, arkosic limestone 

member of the Madera Formation of former usage. The Porvenir Formation lies conformably on the Sandia Formation and is overlain disconformably, and, locally, unconformably by the Alamitos Formation.

The Porvenir Formation is mainly marine and consists of three laterally intergrading 

fades. At the type locality, and generally south of Sapello River, the Porvenir is mostly 

limestone with interbedded thin to thick gray shale and minor amounts of sandstone. 

North and northwest of the type section, the Porvenir is mostly gray shale that contains 

thick units of limestone and some thin sandstones. Northeast of the type section, near 

the eastern front of the mountains, the Porvenir consists of shale, limestones, sandy 

and oolitic limestones, and thin to thick arkosic sandstones. At the type section, the 

Porvenir is 1,065 ft (325 m) thick; north of the type section, the formation is about 

1,615 ft (491 m) thick east of Rociada, about 1,170 ft (357 m) thick at the principal 

reference section northwest of Manuelitas, and about 700 ft (213 m) thick at Mora 

River. Fusulinids from the Porvenir are of early to late Des Moinesian age.

The Alamitos Formation is gray to greenish-gray and red-weathering silty to marly 

shale interbedded with arkose, conglomerate, nodular limestone, and sandy and arkosic 

limestone. Most of the limestone and shale and some of the sandstone is marine; some 

sandstones, however, probably are nonmarine fluviatile deposits. The basal part of 

the Alamitos is arkose and conglomerate or arkosic limestone that grades laterally 

into sandstone. At most places, the basal arkoses contain interbedded maroon-weathering shale. The top of the formation is mapped as the top of the highest marine beds. 

Thickness ranges from a feather edge at the south to more than 1,285 ft (390 m) 

at the north. The formation contains fusulinids of late Des Moinesian, Missourian, Virgilian, and, locally, early Wolfcampian ages.

The Alamitos is overlain with local angular unconformity by nonmarine rocks of the 

Sangre de Cristo Formation. The Sangre de Cristo Formation is mainly Early Permian 

age at the south, but, at Mora River, it also may contain beds of Late Pennsylvanian 

(Virgilian?) age.

INTRODUCTION

In the Sangre de Cristo Mountains of north-central New Mexico 

(fig. 1) rocks of Mississippian, Pennsylvanian, and Early Permian ages 

are exposed widely. The lithologies, ages, thickness variations, and 

facies of these rocks in the southern part of the mountains have been 

known generally since U.S. Geological Survey studies by Read and 

others (1944), Northrop and others (1946), and Read and Wood (1947). 

However, the details of stratigraphy still are not known well because
PORVENIR FORMATION, SANGRE DE CRISTO MOUNTAINS, N. MEX. B3

103°

50 100 MILES

FIGURE 1. Map of New Mexico showing location of 

Sangre de Cristo Mountains (stippled).

of the stratigraphic and structural complexity of the rocks and the 

rugged terrain that is poorly accessible.

A varied stratigraphic nomenclature has evolved, partly for the 

reasons just cited, and partly because of differences of approach of 

different investigators. Therefore, the purposes of this report are to 

review the history of nomenclature and to specify some adjustments 

and revisions of stratigraphic terminology that are consistent with 

recent regional geologic and paleontologic findings as well as with 

older work. The revised terminology of the Paleozoic rocks will be 

applicable to recently completed mapping by the U.S. Geological Survey in the southeastern part of the mountains.

LATE PALEOZOIC REGIONAL SETTING

Precambrian metamorphic and igneous rocks of the Sangre de Cristo 

Mountains are overlain at most places by generally less than 150 ft 

(46 m) of sandstone and carbonate rocks that are thought to be entirely
B4 CONTRIBUTIONS TO STRATIGRAPHY

of Mississippian age. These rocks were deposited in shallow seas upon 

a widespread erosion surface of low relief (Baltz and Read, 1960; 

Armstrong and Mamet, 1974).

In Early Pennsylvanian (Morrowan) time, tectonic events began to 

produce the basins and uplifts of the so-called Ancestral Rocky Mountains. The Pennsylvanian and Early Permian marine and nonmarine 

rocks of north-central New Mexico were deposited syntectonically in 

one of these deep structural basins the Rowe-Mora basin (Read and 

Wood 1947; Brill, 1952; Baltz, 1965, 1978; Bachman, 1975; Armstrong 

and others, 1979). Paleozoic intrabasinal anticlinal uplifts occurred in 

the southern part of the Rowe-Mora basin and the adjacent Pecos 

shelf (Northrop and others, 1946; Read and Wood, 1947). Later, most 

of the Rowe-Mora basin (fig. 2) was uplifted to form the Cenozoic 

Sangre de Cristo Mountains; however, the eastern part of the basin 

is now in the subsurface of the Cenozoic Las Vegas basin east of 

the mountains.

The Rowe-Mora basin was bounded by major Paleozoic positive elements. At the west was an uplift, or series of uplifts, that may have 

been parts of the ancient Uncompahgre uplift (fig. 2). The Canoncito 

uplift, which may have been part of the Uncompahgre uplift, is exposed east of Santa Fe where it has been modified by Cenozoic uplift, 

faulting, and erosion and incorporated with the Sangre de Cristo 

Mountains. At the east, in the subsurface of the Great Plains, is the 

ancestral Sierra Grande uplift or arch (Foster and others, 1972, p. 

14-15), a major Paleozoic tectonic feature whose configurations and 

history are poorly understood because of the sparsity of deep drill 

holes in northeastern New Mexico.

The mainly marine Pennsylvanian rocks of the Rowe-Mora basin 

generally thicken northward. At the south, near Pecos, rocks of Morrowan through Virgilian age are about 2,200 ft (670 m) thick (Read 

and Wood, 1947, fig. 7). Southeast of Mora, rocks of Morrowan 

through Missourian age are more than 6,730 ft (2,050 m) thick (Baltz 

and O'Neill, 1980a). Isopachs of theoretically restored Pennsylvanian 

rocks indicate that the rocks might have been as much as 8,500 ft 

(2,590 m) thick originally in the axial part of the basin southeast of 

Taos prior to Cenozoic uplift and erosion of the upper part of the 

section (Baltz, 1965, fig. 5). This inferred thickness is consistent with 

known directions of thickening of various units (Baltz and Read, 1956, 

p. 50-S1; Sutherland, 1963, fig. 10).

Pronounced east-west variations in thickness of Pennsylvanian rocks 

occur across the southern part of the Rowe-Mora basin and the Paleozoic Pecos shelf. Southeast of Santa Fe, Pennsylvanian rocks are locally about 300 ft (135 m) thick (Booth, 1976, 1977) on the southern 

part of the Paleozoic Canoncito uplift. In the Rowe-Mora basin near
PORVENIR FORMATION, SANGRE DE CRISTO MOUNTAINS, N. MEX. B5

COLORADO 104°

35° 

100 KILOMETERS

50 MILES

EXPLANATION

Major uplift Pennsylvanian-Early Permian 

anticlines and minor uplifts

Present Sangre de 

Cristo Mountains

FIGURE 2. Uplifts and sedimentary basins of Pennsylvanian and Early Permian time in 

part of northern New Mexico.

Pecos, the Pennsylvanian rocks are about 2,200 ft (670 m) thick, 

whereas on the Paleozoic Bernal uplift these rocks are locally only 

about 675 ft (205 m) thick. On the Paleozoic Tecolote uplift southwest 

of Las Vegas, the thickness ranges from locally absent at the south 

(Northrop and others, 1946), to about 1,000 ft (305 m) south of Montezuma. The variations in thickness and the lithologies of the Pennsylvanian rocks clearly represent recurrent episodes of Paleozoic tectonic 

activity in the region.
B6 CONTRIBUTIONS TO STRATIGRAPHY

Read and others (1944) and Read and Wood (1947, p. 225) recognized that facies changes accompanied the general northward thickening of the Pennsylvanian rocks of the Sangre de Cristo Mountains. 

At the south, the deposits are mainly limestones, but also some shale 

and sandstone, that characterized the slowly subsiding, tectonically 

unstable Pecos shelf. To the north, in what was the deeper part of 

the Rowe-Mora basin, shaly rocks predominate, coarse sandstone and 

arkose are common, and limestone is subordinate.

Lower Permian terrestrial red beds and arkoses of the Sangre de 

Cristo Formation are preserved in a broad belt around the southern 

part of the mountains and in hogbacks along the eastern front. The 

Sangre de Cristo Formation generally is conformable with the underlying Pennsylvanian rocks in the central part of the Rowe-Mora basin 

southwest of Pecos, but locally is unconformable with the Pennsylvanian on the Canoncito uplift, on the Bernal and Tecolote uplifts, and 

on the north flank of the subsurface Sierra Grande uplift. In the latter 

two areas, the Sangre de Cristo bevels Pennsylvanian rocks to rest 

on the Precambrian (Northrop and others, 1946; Read and Wood, 1947; 

Baltz, 1965; Foster and others, 1972). The Sangre de Cristo Formation 

is locally about 300 ft (90 m) thick on the southern part of the Canoncito uplift; a short distance east, near the trough of the Rowe-Mora 

Basin, these rocks are more than 3,000 ft (915 m) thick (Booth, 1976, 

p. 37). The Sangre de Cristo Formation thins irregularly eastward 

across the Pecos shelf and is locally only 300-500 ft (90-150 m) thick 

on the Bernal and Tecolote uplifts. The formation thickens northward 

along the eastern front of the Sangre de Cristo Mountains and is 

as much as 2,700 ft (830 m) thick east of Mora. In the Mora River 

area, the lower part of the Sangre de Cristo contains nonmarine rocks 

of probable Late Pennsylvanian age, although most of the formation 

is Early Permian.

HISTORY OF NOMENCLATURE 

PRE-PENNSYLVANIAN SEDIMENTARY ROCKS

Pre-Pennsylvanian sandstone, dolomitic limestone, limestone breccia 

and conglomerate, crystalline limestone, and sandy limestone lie on 

Precambrian basement rocks at most places in the Sangre de Cristo 

Mountains and at places in all the other ranges of north-central New 

Mexico. The pre-Pennsylvanian age of these rocks originally was not 

known and they were included in the basal part of the Magdalena 

Group of Pennsylvanian age by early investigators (Barton, 1922, 

1928a) of the Sangre de Cristo Mountains. Thompson (1942, p. 19) 

first suggested that a thin limestone beneath Pennsylvanian rocks at
PORVENIR FORMATION, SANGRE DE CRISTO MOUNTAINS, N. MEX. B7

Gallinas Canyon in the eastern part of the mountains may be of middle 

or early Paleozoic age.

Later, these rocks continued to be classified in the Magdalena Group 

(fig. 3) in reports of the U.S. Geological Survey, as the lower limestone member of the Pennsylvanian Sandia Formation. Read and 

Wood (1947) and Northrop and others (1946) recognized that part or 

all of this member might be Mississippian or older, and Henbest (1946) 

reported the Mississippian foraminifer Endothyra baileyi in the lower 

limestone member of the Sandia at unspecified localities in the southern Sangre de Cristo Mountains.

Armstrong (1955) and Fitzsimmons, Armstrong, and Gordon (1956) 

described the pre-Pennsylvanian rocks in the Nacimento Mountains 

of northwestern New Mexico and named them the Arroyo Penasco 

Formation. The upper part of the Arroyo Penasco contains megafossils 

of probable Late Mississippian (Meramecian) age; identifiable megafossils were not found in the lower part (Fitzsimmons, and others, 1956, 

p. 1941). Armstrong (1955) extended the name Arroyo Penasco Formation to rocks in similar stratigraphic position in the Sangre de 

Cristo Mountains and concluded that they were Late Mississippian, 

based on studies of microfossils.

Baltz and Read (1960) determined that the pre-Pennsylvanian sedimentary rocks in the Sangre de Cristo Mountains contain two distinctive lithologic units separated by an unconformity. The lower unit, 

consisting of a basal sandstone and overlying sandy limestone, dolomitic limestone, and chert-bearing limestone was named the Espiritu 

Santo Formation. The upper unit, consisting of limestone breccia, 

limestone conglomerate, crystalline limestone, and sandy clastic limestones was named the Tererro Formation and was subdivided into 

three members. No identifiable fossils were found in the Espiritu 

Santo Formation; it was classified as Upper Devonian(?) because of 

its stratigraphic position and lithologic similarity to Upper Devonian 

rocks of southern Colorado. The Tererro Formation was classified as 

Lower and Upper Mississippian mainly on the basis of a scanty 

brachiopod fauna.

Sutherland (1963) recognized the Espiritu Santo and Tererro Formations in the south-central part of the Sangre de Cristos, and also 

noted the unconformable relation of the two formations. He separated 

the basal sandstone from the Espiritu Santo and named it the Del 

Padre Sandstone. Sutherland noted that no identifiable fossils had 

been discovered in the Del Padre or in the overlying carbonate rocks 

of the Espiritu Santo, and he concluded (1963, p. 25-26) that the age 

of the Del Padre and Espiritu Santo is unknown, but presumably 

Paleozoic. He classified the Tererro as Late Mississippian, probably 

Meramecian, because of its microfossils.
Read and others (1944) and Read and 

Wood (1947 fig. 1 and p. 234-235)

Sandia, Manzanita, 

Manzano, Los Pinos Mts. Sangre de Cristo Mountains

Armstrong 

(1955)

Baltz and Read 

(1960)

Sutherland 

(1963, fig. 6)

Armstrong and Mamet 

(1974, figs. 1 and 2)

Abo 

Formation

South North

Bursum 

Formation

Arkosic 

limestone 

member

Sangre de Cristo 

Formation

g^. \ -

on ^> Major *<g E s interval of

< E F S arkose and ^~

= <irkosic limestone

Gray

limestone 

member

Upper

clastic

member

Lower 

limestone 

member (present

locally)

c ^ ( Major interval 

2 §^ > pf dark shale, 

cj a) £ X limestone,and

,EE/ sandstone ^^ >

^ y <D V4______________g.*=-° /Major interval 

« > of sandstone, E S shale =513

Tentatively classified 

as lower limestone 

member of Sandia 

Formation. May be

Mississippian or older

(Armstrong, 

1967, reclassified the

Arroyo Penasco

Formation as

Late and EarlyMississippian)

Arroyo

Penasco

Formation

South North

Del Padre Sandstone

La Pasada

and 

Flechado Formations

8d Hh-^

o

Del Padre

Sandstone

Member

Precambrian rocks

FIGURE 3. Historical summary of age assignments and nomenclature of Mississippian, Pennsylvanian, and Lower Permian rocks 

of central New Mexico (left-hand column) and southern Sangre de Cristo Mountains, New Mexico (remainder of diagram).
PORVENIR FORMATION, SANGRE DE CRISTO MOUNTAINS, N. MEX. B9

Armstrong (1967) continued to include all the pre-Pennsylvanian 

sedimentary rocks in the Arroyo Penasco Formation, but he reported 

Early Mississippian microfossils in the lower part of the formation 

in the Sangre de Cristo Mountains and classified the entire sequence 

as Mississippian. Later, Armstrong and Mamet (1974) accepted the 

Tererro and Espiritu Santo Formations and extended these terms 

through a wide region in northern New Mexico. They reclassified 

Sutherland's Del Padre Sandstone as the basal member of the Espiritu 

Santo Formation, and, on the basis of microfossils, classified the Espiritu Santo as Early Mississippian (Osagean) and the Tererro as Late 

Mississippian (Meramecian and Chesterian). They raised the term Arroyo Penasco to group status to include both the Espiritu Santo and 

Tererro Formations.

PENNSYLVANIAN AND LOWER PERMIAN ROCKS

The first geologic map of the Sangre de Cristo Mountains in Colorado and New Mexico was published by Stevenson (1881) to accompany his classic summary report on the geology of this region. He 

summarized the previous scanty observations of the Pennsylvanian 

rocks, published a composite stratigraphic section of these rocks in 

the Mora-Sapello area of New Mexico, and gave lists of Pennsylvanian 

fossils. He referred to the rocks only as "the Carboniferous rocks."

The term "Sangre de Cristo conglomerate" was the first name applied to the Carboniferous rocks of the Sangre de Cristo Mountains 

west of Trinidad, Colo. by Hills (1899). Later, Melton (1925, p. 811- 

812) subdivided these rocks into the "Upper Sangre de Cristo conglomerate" and the "Lower Sangre de Cristo conglomerate,"specifying that 

these rocks are Permian and Pennsylvanian. Melton named the marine 

part of the lower unit the "Veta Pass limestone member." Melton 

(1925, fig. 1) correlated his "Lower Sangre de Cristo conglomerate" 

with the mainly marine Pennsylvanian rocks in the southern part of 

the Sangre de Cristo Mountains in New Mexico that had been referred 

to the Magdalena Group by Lee (1909, p. 33-38) and Darton (1922, 

p. 201). Melton (1925, fig. 1) correlated his "Upper Sangre de Cristo 

conglomerate" with the nonmarine arkoses and red beds above the 

Magdalena in New Mexico that had been assigned to the Abo Sandstone of Permian age by Lee (1909) and Darton (1922). Darton (1928a, 

p. 255-274; 1928b) continued to classify the mainly marine rocks as 

the Pennsylvanian Magdalena Group and the overlying nonmarine 

rocks as the Permian Abo Sandstone.

Read and others (1944) were the first to subdivide and to map various lithologic units of Mississippian, Pennsylvanian, and Early Permian ages in the southern part of the Sangre de Cristo Mountains. They
B10 CONTRIBUTIONS TO STRATIGRAPHY

applied parts of the then-existing terminology (fig. 3, left-hand columns) of central New Mexico in the Sangre de Cristos. Marine and 

mixed marine-nonmarine rocks of Pennsylvanian age, and the rocks 

now known to be Mississippian, were included in the Magdalena 

Group. Nonmarine arkoses and red beds above the Magdalena were 

classified as the Sangre de Cristo Formation of Pennsylvanian and 

Permian(?) age.

Read and others (1944) subdivided the Magdalena Group into the 

Sandia Formation and the overlying Madera Limestone, formation 

names that were derived from the Sandia and Manzanita Mountains 

east of Albuquerque (Read and Wood, 1947). The Sandia Formation, 

a mainly clastic unit of Early and Middle Pennsylvanian age, was 

subdivided into a lower limestone member and an upper clastic member. Later, Read and Wood (1947, fig. 1) excluded the (Mississippian) 

lower limestone member from the Sandia, and, thereby, from the Magdalena Group.

Read and others (1944) subdivided the Madera Limestone into a 

lower gray limestone member and an upper arkosic limestone member 

in the southern part of the Sangre de Cristo Mountains. Read and 

Wood (1947) indicated that, from south to north, the upper part of 

the arkosic limestone member of the Madera grades laterally into nonmarine beds of the overlying Sangre de Cristo Formation, so that, 

in their view, the lower part of the Sangre de Cristo Formation becomes progressively older to the north. They wrote (1947, p. 225): 

"Farther north, in the Sangre de Cristo Mountains, equivalents of 

the Sandia and Madera formations show major changes in lithology 

and marked thickening. Since this area is now being mapped, it is 

not advisable to recommend a final nomenclature."

The general rock-stratigraphic terminology of Read and Wood (1947) 

for Pennsylvanian and Lower Permian rocks the Sandia Formation, 

the Madera Limestone and its two members, and the Sangre de Cristo 

Formation have continued to be used in U.S. Geological Survey reports on the southern Sangre de Cristo Mountains, although the Madera is called the Madera Formation, and its two members are called, 

simply, the upper and lower members (for example, Baltz, 1972; 

Johnson, 1973).

Brill (1952), by a series of stratigraphic sections and paleontologic 

analyses, extended the terminology of the Sandia Formation and the 

Madera Limestone and its two members northward from the southern 

Sangre de Cristo Mountains into Colorado.

Sutherland (1963) and Sutherland and Harlow (1973) reported the 

results of extensive paleontologic and stratigraphic investigations of 

the south-central and southwestern parts of the Sangre de Cristo 

Mountains. Sutherland (1963, p. 30) reviewed the previous stratig-
PORVENIR FORMATION, SANGRE DE CRISTO MOUNTAINS, N. MEX. Bll

raphic nomenclature and proposed changes. He did not use the term 

Magdalena Group for this region because he considered it to be nearly 

synonymous with Pennsylvania!!. He reported (1963, p. 30) that there 

were no consistent criteria for delineating the Sandia Formation in 

this region and did not use the terms Sandia and Madera because 

he believed that the stratigraphic relations of the Pennsylvanian rocks 

to the Madera Limestone of the Sandia Mountains were unknown. 

The name Sangre de Cristo Formation was retained by Sutherland 

(1963, p. 38-39) for the arkoses and red beds above the mainly marine 

Pennsylvanian rocks.

Sutherland (1963) proposed new names for Pennsylvanian rocks of 

the south-central and southwestern parts of the mountains. Rocks previously assigned to the Sandia Formation and to the lower gray limestone member of the Madera were combined in stratigraphic sections 

and were named the La Pasada Formation (Sutherland, 1963, p. 30) 

for exposures near Dalton Picnic area along the Pecos River. Rocks 

above the La Pasada, that previously were assigned to the arkosic 

limestone member of the Madera, were named the Alamitos Formation (Sutherland, 1963, p. 36) for exposures north and southwest of 

Pecos.

Northward from the Pecos area, the mainly carbonate upper part 

of the La Pasada becomes more shaly, the lower part becomes more 

conglomeratic, and the entire unit thickens greatly. On Rio Pueblo 

southwest of Taos, rocks approximately equivalent to the La Pasada 

are mostly shale and sandstone with subordinate limestone. The rocks 

of this northern facies were named the Flechado Formation by Sutherland (1963, p. 33). In the Rio Pueblo area, the Flechado is overlain 

by rocks assigned to the Alamitos Formation by Sutherland. He (1963, 

p. 30, pi. 1) did not delineate any of these formations on the geologic 

map because of extensive covered areas in the high, heavily timbered 

country.

NOMENCLATURE OF SOUTHEASTERN 

SANGRE DE CRISTO MOUNTAINS

GENERAL DISCUSSION

Northrop and others (1946) published the first detailed geologic map 

of the southeastern foothills of the Sangre de Cristo Mountains. They 

established Paleozoic rock-stratigraphic units suitable for depicting 

complex stratigraphic relations along the then-unnamed Paleozoic 

Tecolote uplift (fig. 2) which is near the eastern structural front of 

the present mountains. The stratigraphy of the Pennnsylvanian and 

Permian rocks was illustrated by detailed stratigraphic sections. They 

used the stratigraphic nomenclature for Mississippian, Pennsylvanian,
B12 CONTRIBUTIONS TO STRATIGRAPHY

and Permian rocks that Read and others (1944) had used farther west 

(% 4).

Baltz (1972) remapped part of the foothills belt and also the Gallinas 

Creek area (fig. 5), recognizing and extending the Paleozoic rockstratigraphic units of Northrop and others (1946). Recent mapping 

(Baltz and O'Neill, 1980a,b) determined that these units could be 

traced northward past Mora through part of the area of facies change 

and thickening of various units that was described briefly by Read 

and Wood (1947).

The present writers have continued biostratigraphic studies of the 

southeastern part of the mountains and have additional new fusuh'nid

SOUTH NORTH

Northrop and others (1946) 

Southeastern foothills

Baltz (1972) 

Gallinas Creek area

This report

Baltz and O'Neill (1980 a,b) 

Sapello and Mora River areas

Sangre de Cristo

Formation

(at the south, locally 

ies on Precambrian rocks)

Sangre de Cristo 

Formation

West East

Precambrian metamorphic and igneous rocks

Sangre de Cristo 

Formation

(Local angular 

unconformity)

FIGURE 4. Age assignments, nomenclature, and correlation of mapped rock-stratigraphic units of the southeastern Sangre de Cristo Mountains, N. Mex.
PORVENIR FORMATION, SANGRE DE CRISTO MOUNTAINS, N. MEX. B13

and megafossil data that provide corroborative evidence for extending 

the Pennsylvanian and Lower Permian rock-stratigraphic units and 

for correlating between areas where Cenozoic faults and erosion have 

removed parts of the section. The paleontologic data also provide a 

good basis for regional correlations and, therefore, for recommending 

some revisions of the stratigraphic terminology of the southeastern 

part of the mountains. In recommending these revisions, we believe 

it is desirable to retain, where possible and useful, the terminology 

of previous published literature that reflects the regional unity of extensive mapped bodies of rocks of generally similar lithology and age. 

Our revised nomenclature for the southeastern Sangre de Cristo 

Mountains is summarized in the right-hand column of figure 4.

PRE-PENNSYLVANIAN SEDIMENTARY ROCKS

The pre-Pennsylvanian sedimentary rocks of the southeastern 

Sangre de Cristo Mountains are included by the present writers in 

the Espiritu Santo and Tererro Formations of Baltz and Read (1960), 

and constitute the Arroyo Penasco Group of Armstrong and Mamet 

(1974). A locally thin sandstone at the base of the section is considered 

to be the Del Padre Sandstone Member (as assigned by Armstrong 

and Mamet, 1974) of the Espiritu Santo Formation. The overlying 

carbonate part of the Espiritu Santo remains unnamed, as do the 

informal carbonate units within this part of the Espiritu Santo that 

were described by Baltz and Read (1960).

We tentatively accept the assignment of the Arroyo Penasco Group 

entirely to the Mississippian by Armstrong and Mamet (1974). However, we continue to note the abundant evidence of unconformity between the Espiritu Santo and the Tererro in the Sangre de Cristo 

Mountains, as reported by Baltz and Read (1960), Sutherland (1963), 

and Clark and Read (1972). Identifiable megafossils still have not been 

reported in the Espiritu Santo, and its Mississippian age in the Sangre 

de Cristo Mountains is established by a meagre microfauna.

MAGDALENA GROUP

We recommend that the term Magdalena Group no longer be used 

in the southern part of the Sangre de Cristo Mountains. As described 

by Lee (1909) and Darton (1922, 1928a), the Magdalena Group of this 

region originally included the entire undivided section of mainly 

marine limestone, shale, and sandstone between the underlying Precambrian basement and the overlying arkoses and red beds that they 

assigned to the Abo Sandstone. The Magdalena was thought then to 

be entirely Pennsylvanian, and the Abo was thought to be entirely 

Permian. As is now known, the Magdalena of this region included
B14 CONTRIBUTIONS TO STRATIGRAPHY

rock units of considerable lithologic diversity and stratigraphic complexity that range in age from Mississippian through Early Permian, 

and the overlying arkoses and red beds (Sangre de Cristo Formation) 

are locally partly of Late Pennsylvanian as well as Permian age. Furthermore, the continued use of the term Magdalena Group in this 

region inhibits additional formal classification of its included units.

Rather than restrict the Magdalena Group locally, or raise its status 

to supergroup, the most reasonable procedure seems to be to discontinue its use in the southern part of the Sangre de Cristo Mountains, 

as was proposed by Sutherland (1963, p. 30). The usage of Magdalena 

Group already has been discontinued by the U.S. Geological Survey 

for the Manzano and Manzanita Mountains of central New Mexico 

(Myers, 1973). However, farther north in the Sangre de Cristo Mountains, where marine and mixed marine-nonmarine rocks of Pennsylvanian age have not been subdivided, the term "Magdalena Group" is 

still in use in a restricted sense for rocks between the Arroyo Penasco 

Group and the Sangre de Cristo Formation (Bachman, 1953; Clark 

and Read, 1972, p. 31).

SANDIA FORMATION

Throughout most of the Sangre de Cristo Mountains in New Mexico, 

the Arroyo Penasco Group or, locally, Precambrian rocks are overlain 

by a complex sequence of Pennsylvanian shale, sandstone, conglomeratic sandstone, and subordinate amounts of thin limestone. The shales 

commonly are carbonaceous, and thin units of highly carbonaceous 

shale and coal are present at many places. In the southeastern part 

of the mountains these mixed marine-nonmarine rocks have been mapped as the Sandia Formation.

In the area of the Paleozoic Tecolote uplift (fig. 2), the thickness 

of the Sandia Formation ranges from about 10 ft (3 m) at the south 

(Northrop and others, 1946) to locally only 90 ft (27 m) near Montezuma (fig. 5). At the west, the Sandia is about 500 ft (152 m) thick 

at locality 1 (fig. 6). To the north, a little south of Rito Cebolla and 

about 1 mi (1.6 km) west of the structural front of the mountains, 

the Sandia is about 1,000 ft (305 m) thick. Farther north, 1 mi north 

of Mora River, the Sandia is at least 5,080 ft (1,548 m) thick, with 

an unknown but probably small (400-600 ft; 120-180 m) amount cut 

out by Cenozoic faults near the base (Baltz and O'Neill, 1980a). 

Throughout this region, despite the changes in thickness, the overall 

lithologies remain about the same as just described, with two notable 

exceptions: from Sapello River north, a major part of the formation 

is shale; and from Rito Cebolla north, the upper third contains several 

thick units of coarse to conglomeratic, highly arkosic sandstone. 

Feldspathic sandstones are present at the south, but there the feld-
PORVENIR FORMATION, SANGRE DE CRISTO MOUNTAINS, N. MEX. B15

spar grains tend to be small, highly weathered, and generally inconspicuous.

Our paleontologic data for the Sandia Formation in the southeastern 

part of the Sangre de Cristo Mountains are meagre but are definitive 

of its age. Brachiopods from the lower part of the formation in the 

western part of the Gallinas Creek area (loc. 1, fig. 6) are of Early 

Pennsylvanian (Morrowan) age (J. T. Dutro, Jr., written commun., 

1979) and are similar to Morrowan brachiopod faunas reported from 

the lower part of the La Pasada Formation by Sutherland and Harlow 

(1973). Brachiopods from the lower part of the Sandia about 1 mi 

north of Mora River also are Morrowan (J. T. Dutro Jr., written 

commun., 1978). Fusulinids are rare in the Sandia. However, 

Fusulinella aff. F. juncea Thompson found near the top of the Sandia 

east of Gallinas and near the top of the Sandia just north of Rito 

Cebolla indicate late Atokan age. Fusulinella cf. F. devexa Thompson, 

found in the upper part of the Sandia at the north side of Sanguijuela 

Arroyo, also suggests late Atokan age. Abundant fusulinids at many 

places in the basal part of the overlying Madera Group are early Des 

Moinesian age.

Sutherland (1963, p. 29-30) reported that his studies in the western 

part of the Sangre de Cristo Mountains yielded no criteria for consistently delineating the Sandia Formation (of various authors) from the 

overlying Madera Limestone. Therefore, he did not use the terms 

Sandia and Madera Formations and he combined rocks equivalent to 

the Sandia and lower part of the Madera in his La Pasada and 

Flechado Formations. He reviewed the problems, as then reported 

in the literature, of lithologic and paleontologic regional correlations 

of Pennsylvanian rocks among various mountain ranges in New 

Mexico, and he concluded that the stratigraphic relations of the Pennsylvanian formations of the Sangre de Cristos to the Madera of the 

Sandia Mountains were unknown.

In the southeastern part of the Sangre de Cristo Mountains, 

lithologic and paleontologic bases exist for separating the Sandia Formation from the Madera. Generally south of Sapello River, the upper 

part of the Sandia consists of dark-gray shale that contains interbeds 

of thin to thick sandstone, sandy limestone, and thin micritic limestone. Nearly everywhere south of Sapello, the basal part of the overlying Madera is thick, ledge-forming, light-gray limestone. Northward 

from Sapello River past Mora River, the upper part of the Sandia 

is also mainly dark-gray shale that contains varied proportions of interbedded thin to thick sandstones and thin, micritic limestones. Here, 

the lower part of the Madera Group contains a heterogeneous assemblage of carbonate and clastic rocks that are lithologically distinct 

from the Sandia, as will be discussed. Although the lithology of the
B16 CONTRIBUTIONS TO STRATIGRAPHY

36°00

105C 3CT 105"15'

35°45'
PORVENIR FORMATION, SANGRE DE CRISTO MOUNTAINS, N. MEX. BIT

EXPLANATION

Fades of Porvenir Formation 

Carbonate

Preserved parts of shale-carbonate 

Preserved parts of sandstone-shale-carbonate

 Eastern front of mountains

3a,D,C Locality of composite section

y4 Locality of section

0 5 10 KILOMETERS

0 5 MILES

FIGURE 5. Index map of part of southeastern Sangre de Cristo Mountains, N. Mex., 

showing localities of type section (loc. 1), principal reference section (Iocs. 3a-3c), 

Mora River section (loc. 4) of the Porvenir Formation of the Madera Group, and 

stratigraphic section (loc. 2) of the Alamitos Formation. Contacts of facies of the 

Porvenir are generalized because facies merge into each other through several miles. 

Unpatterned areas west of the front of the mountains indicate areas where Porvenir 

has been removed by Cenozoic erosion.

basal Madera varies laterally, a contact can be mapped by physical 

tracing. Inasmuch as the contact is mainly conformable and is locally 

transitional through a few feet, there is surely some minor local variation of its mapped stratigraphic position. Additionally, the potential 

exists for minor miscorrelations across covered areas and areas of 

Cenozoic faults. Nevertheless, our fusulinid data indicate that the contact is near the Atokan-Des Moinesian boundary throughout this region.

Since the time of Sutherland's (1963) report, a large amount of new 

data on the mountain ranges of central New Mexico has been published. These new data bear on the regional-correlation problems that 

he discussed. The Sandia Formation and the Madera Formation of 

the Sandia Mountains have been mapped, and their stratigraphy and 

paleontology discussed by Kelley and Northrop (1975). They (p. 31) 

described a transitional contact between the Sandia and Madera, and 

they indicated that its stratigraphic position varies somewhat from 

place to place. Kelley and Northrop (1975, p. 49) did not express 

a firm opinion on the age of the Sandia, but they reported megafossil 

evidence from localities scattered throughout the Sandia Mountains
B18 CONTRIBUTIONS TO STRATIGRAPHY

that suggests a possible age span of Morrowan through early Des 

Moinesian.

At good exposures in the northern part of the Sandia Mountains, 

the Sandia Formation lies on the Mississippian Arroyo Penasco Group 

and is overlain by ledge-forming limestones of the Madera Formation 

of Read and others (1944) and Kelley and Northrop (1975, fig. 20). 

In this area, at the ridge called "Crest of Montezuma" about 1 1A mi 

(1.7 km) east of Placitas, the Sandia is composed of conglomerate, 

sandstone, gray shale, and a little thin, sandy limestone, all about 

110 ft (33.5 m) thick where we have measured it. In this vicinity, 

the thickness ranges from locally absent to about 150 ft (45 m). We 

found Beedeina arizonensis and Wedekindellina sp. of early Des 

Moinesian age in the interval 56-117 ft (17-52 m) above the base of 

the ledge-forming limestones of the Madera at the Crest of Montezuma. These data indicate that the underlying upper part of the 

Sandia is no younger than earliest Des Moinesian, which is consistent 

with the data presented by Kelley and Northrop (1975).

The type locality of the Sandia Formation (Herrick, 1900) is near 

the northern end of the Manzanita Mountains, which are contiguous 

with and south of the Sandia Mountains. The Manzanita Mountains 

were mapped by Myers and McKay (1976), and the Manzano Mountains to the south also have been mapped. A summary of the stratigraphy and the fusulinid data of post-Atokan Pennsylvanian and Lower 

Permian rocks of these ranges was presented by Myers (1973). In 

the Manzanita and Manzano Mountains, the Sandia in most places 

rests on Precambrian rocks, but locally on Mississippian rocks referred 

to the Arroyo Penasco Group; has heterogeneous clastic and carbonate 

lithology similar to that in the Sandia Mountains; and ranges in thickness from about 60 ft (18 m) (Myers, 1969), to a little more than 

300 ft (90 m), depending on local relief on the top of the Precambrian. 

In this region, fusulinids indicate late Atokan age for the upper part 

of the Sandia and early Des Moinesian age for the overlying limestones 

of the Madera. Whether Morrowan- age rocks are present locally in 

the Sandia is not known.

In summary, the general lithologies, stratigraphic relations to 

bounding rocks, thickness variations, and (at least the minimum) age 

of the Sandia in its typical areas of central New Mexico are similar 

to those features of the Sandia Formation in the southeastern part 

of the Sangre de Cristo Mountains. The only striking difference between the two regions is the great northward thickening of the Sandia 

Formation north of the Paleozoic Pecos shelf in the Sangre de Cristo 

Mountains. Therefore, we retain the name Sandia Formation for these 

Lower and Middle Pennsylvanian rocks in the southeastern Sangre 

de Cristo Mountains.
PORVENIR FORMATION, SANGRE DE CRISTO MOUNTAINS, N. MEX. B19

Baltz and O'Neill (1980a) subdivided the Sandia Formation into five 

informal lithologic units north of Mora River where it is more than 

5,000 ft (1,525 m) thick to determine and portray the Cenozoic structure and to determine places suitable for measuring the thickness of 

the formation. No attempt was made to extend the correlation of these 

informal units or to determine their stratigraphic usefulness outside 

the area where they were mapped. Nevertheless, with additional 

study, the Sandia probably could be subdivided in many places to 

understand its complex internal stratigraphy in the parts of the 

Sangre de Cristo Mountains where it is extremely thick.

MADERA GROUP

In the southeastern part of the Sangre de Cristo Mountains, the 

Sandia Formation is overlain by limestone, shale, and sandstone mapped by Northrop and others (1946) and Baltz (1972) as the Madera 

Formation. These rocks are lithologically generally similar to, and 

their overall age span is the same as, the Madera Formation in its 

typical region of the Sandia Mountains, and the Madera Group (Myers, 

1973) in the Manzanita and Manzano Mountains. Therefore, the term 

Madera is retained and is hereby raised to group status for the southeastern Sangre de Cristo Mountains (fig. 4).

The lower part of the Madera Group in the southeastern Sangre 

de Cristo Mountains is here named the Porvenir Formation. The Porvenir Formation is mainly marine and consists of three laterally intergrading facies. (See fig. 5 for facies distribution.) At the south, the 

Porvenir consists of thin to massive limestones and interbedded gray 

shales and minor amounts of sandstone. At the north, near the eastern 

front of the mountains, the Porvenir consists of limestone, sandy and 

oolitic limestone, gray shale, and thin to thick quartzose and arkosic 

sandstones. Also at the north, but in the western interior part of 

the mountains, the Porvenir consists of gray shale, subordinate 

amounts of thin to thick limestone, and minor amounts of sandstone. 

Fusulinids indicate that the Porvenir is of early to late Des Moinesian 

age; it is the lower member of the Madera of Northrop and others 

(1946) and Baltz (1972), and it is the informally designated "formation 

of El Porvenir" of Baltz and O'Neill (1980a,b).

The name Alamitos Formation (of Sutherland, 1963) is hereby 

adopted for the unit of limestone, sandy limestone, nodular limestone, 

gray> greenish-gray, and red shales, and conglomeratic arkoses that 

rests on the Porvenir Formation and that forms the upper part of 

the Madera Group in the southeastern part of the mountains. The 

Alamitos in this area is mainly marine, but also contains probable 

nonmarine rocks. It contains rocks of late Des Moinesian, Missourian, 

and Virgilian ages, and, locally, of Early Permian (early Wolfcampian)
B20 CONTRIBUTIONS TO STRATIGRAPHY

105°25'

'/2 MILE

FIGURE 6. Geologic map of type locality of Porvenir Formation (loc. 1) and locality 

of stratigraphic section of Alamitos Formation (loc. 2). For regional location 

see figure 5. Geology from Baltz (1972).

age. The Alamitos is the upper member of the Madera of Northrop 

and others (1946) and Baltz (1972), and the Alamitos Formation of 

Baltz and O'Neill (1980a,b).

The Alamitos is overlain by the nonmarine rocks of the Sangre de 

Cristo Formation which is mainly Early Permian in the southeastern 

part of the mountains, although, at the north near Mora River, the 

Sangre de Cristo includes at the base some nonmarine rocks of probable Late Pennsylvanian age.

N

PORVENIR FORMATION 

TYPE LOCALITY AND TYPE SECTION

The type locality of the Porvenir Formation is along the U.S. Forest 

Service Johnson Mesa road on the ridge south of Canovas Canyon 

which is a south tributary of Gallinas Creek about 12.5 mi (20 km) 

northwest of Las Vegas. (See fig. 5.) This locality is in the Santa
PORVENIR FORMATION, SANGRE DE CRISTO MOUNTAINS, N. MEX. B21

EXPLANATION

Quaternary alluvium

Quaternary landslide deposits

Permian Sangre de Cristo Formation

Permian and Pennsylvanian Alamitos Formation '

Pennsylvanian Porvenir Formation

Pennsylvanian Sandia Formation

Mississippian Arroyo Pefiasco Group

Precambrian metamorphic and igneous rocks

CONTACT Dashed where approximately located

SYNCLINE

HIGH-ANGLE FAULT H, upthrown side; arrows indicate relative horizontal movement 

Dashed where approximately located; dotted where concealed

REVERSE FAULT R, upthrown side. Dashed where approximately located; queried 

where probable

THRUST FAULT SHOWING DIP T, upthrown side.

LINE OF STRATIGRAPHIC SECTION

STRIKE AND DIP OF BEDS 

Inclined

Overturned

FUSULINID COLLECTION FROM UPPER PART OF ALAMITOS FORMATION Dot on 

leader shows locality. Stratigraphic position, as traced to section (loc. 2), is shown 

on fig. 10

FIGURE 6. Continued.

15

Fe National Forest, near the center of sec. 23, T. 17 N., R. 14 E. 

A geologic map of the area is shown on figure 6, a graphic type section 

of the Porvenir at this locality is shown on figure 7, and an explanation 

of lithologic and other symbols for the section is shown on figure 8. 

In this area, and farther north and south, the steeply east-dipping 

rocks of the Porvenir Formation crop out in a series of topographically 

high hogback ridges.

The name of the formation is derived from exposures in the hogbacks near El Porvenir Campground (fig. 5). However, the type locality was chosen farther south because almost the entire formation is 

preserved and is well exposed in cuts on the Johnson Mesa road, 

as are the underlying Sandia Formation and parts of the overlying 

Alamitos Formation. The thickness of the Porvenir Formation is about 

1,065 ft (325 m) at the type section. An unknown amount of the upper 

part of the formation may be missing because of a concealed strike-slip
B22 CONTRIBUTIONS TO STRATIGRAPHY

I II 3=P R sp. Millerella sp.

III ' '. ' B. aff. apachensis

Sandia Formation

FIGURE 7. Stratigraphic sections of the Porvenir Formation at the type locality (loc.
PORVENIR FORMATION, SANGRE DE CRISTO MOUNTAINS, N. MEX. B23

B. aff. rockymontana

B. aff. joyitaensis

f- B. aff. socorroens

B. aff. novamexicana 

B. ct. rockymontana 

W. cf. coloradoensis

- B. aff. arizonensis 

~W. cf. excentrica 

F. aff. dosensis

ABBREVIATIONS OF 

FUSULINID GENERA

B. Beedeina

W. Wedekindellina

F. Fusulinella

Sandia

. aff. oakensis

Formation

1), principal reference locality (Iocs. 3a,b,c), and Mora River locality (loc. 4). Horizontal distances not to scale. See figure 5 for regional location of sections. Symbols 

used are explained in figure 8.
B24

r. w . .o.'-.oV?.

CONTRIBUTIONS TO STRATIGRAPHY

Sandstone

Conglomeratic

Fine to coarse-grained

Shaly

Highly cross-bedded

Arkosic

Thick- to thin-bedded

Sandy

Nodules

Arkosic

Calcarenite, bioclastic with quartz sand 

Poorly exposed 

Concealed

B. sulphurensis Fusulinids. Leader shows bed from which collection was made

-*-B. aff. oakensis Fusulinids collected near locality of section. Arrow indicates stratigraphic

position as traced to section 

Weathering-color symbols for some shale beds (shale beds not marked

by symbols are predominately gray) 

Reddish to maroon

Greenish-gray to olive-green 

Purple

FIGURE 8. Explanation of symbols used in stratigraphic sections (figs. 7 and 10).

fault (fig. 6) within the formation; however, based on observations 

of this part of the section elsewhere in the vicinity, the amount is 

believed to be small.
PORVENIR FORMATION, SANGRE DE CRISTO MOUNTAINS, N. MEX. B25

At the type section, the lower 580 ft (177 m) of the Porvenir consists 

mainly of ridge-forming, highly fossiliferous limestones with intervening nonresistant units of calcareous shale, siltstone, and a few thin 

beds of fine- to coarse-grained quartz sandstone that locally contains 

traces of weathered yellowish-pink potash feldspar. Several <l-in.- 

to 3-ft-thick beds of highly carbonaceous to coaly shale are present 

locally. Bedding of the limestones ranges from almost shaly to massive. Several thick limestone units are dense and nearly structureless 

internally, and, as shown by lateral tracing away from the roadcuts, 

thicken and thin, suggesting that they are bioherms or biostromal 

banks. Similar biohermal or biostromal-bank limestones are present 

in the lower part of the Porvenir at many places in the Gallinas Creek 

area, the foothills area, and also southward from the type locality 

to the southernmost exposures of the Porvenir near Bernal that were 

mapped as the gray limestone member of the Madera by Read and 

others (1944).

At the type section, the ridge-forming lower part of the Porvenir 

is overlain by gray shale, sandy and silty shale that contains finegrained to silty sandstone, and a few beds of shaly limestone. This 

unit, including a concealed upper part, is about 310 ft (94 m) thick. 

It can be recognized north and south of the type locality, although, 

to the south it becomes more calcareous, and to the north more sandy. 

This unit and overlying beds generally are absent in the eastern foothills south of Sapello River because of unconformity with the Alamitos 

Formation on the Paleozoic Tecolote uplift. In the eastern foothills, 

the Porvenir is no more than 600 ft (180 m) thick.

The stratigraphically highest part of the Porvenir at the type section 

is a unit, about 175 ft (53 m) thick, of fossiliferous limestone, shaly 

limestone, calcareous shale, siltstone and thin beds of sandstone, and 

a thin bed of limestone-pebble conglomerate. These rocks form minor 

ridges. The rocks are predominantly gray, but contain two thin beds 

of greenish-gray shale that weather purple locally. Notably, not far 

above the base of this unit are several beds of cross-laminated to 

cross-bedded, bioclastic calcarenite that contains much silt, sand, and 

granules of angular quartz. We informally designate these beds as 

a "marker zone" in the upper part of the Porvenir. As determined 

elsewhere, the stratigraphically lowest occurrence of the fusulinid 

Beedeina sulphurensis at places is within the marker zone. Although 

the marker zone has not been mapped, it appears to be widespread 

in the southeastern Sangre de Cristos. Similar sandy, bioclastic rocks 

have been observed in similar stratigraphic position from north of 

the San Miguel-Mora County line (fig. 5) to at least as far south as 

east of San Geronimo southwest of Las Vegas. Locally, however, the 

zone is absent by nondeposition. On the Paleozoic Tecolote uplift, this
B26 CONTRIBUTIONS TO STRATIGRAPHY

part of the section probably is absent because of the unconformity 

between the Porvenir and the overlying Alamitos Formation.

CONTACTS WITH ADJACENT ROCKS

At the type section, the Porvenir Formation lies on shale containing 

interbedded thin micritic limestones assigned to the Sandia Formation. 

The basal contact of the Porvenir, previously chosen (Baltz, 1972) 

because of its mappability, is at the base of ridge-forming thick limestones and marks a relatively abrupt vertical transition from the predominantly shaly upper part of the Sandia that occurs throughout 

the region south of Sapello River (fig. 5). North of Sapello River, 

the contact is at the base of biohermal and stromatolitic-mound limestones, and a complexly varied zone of interbedded limestone, sandy 

limestone, sandy oolite, and conglomeratic sandstone, as will be discussed. Regionally, the contact is mainly conformable.

At the type section, the Porvenir Formation is overlain by a locally 

thin, arkosic sandstone that contains subangular to angular clasts of 

fine to coarse, reddish-pink, little-weathered potash feldspar. This 

sandstone, assigned to the Alamitos Formation, is overlain by a sequence of red-weathering silty, shaly sandstone, thin limestones, arkosic limestone, and arkosic conglomerate, all of which are fairly well 

exposed in the roadcuts and are assigned also to the Alamitos. The 

contact is disconformable locally because of slight channeling at the 

base of the Alamitos but is unconformable in much of the eastern 

part of the mountains where the upper part of the Porvenir is missing.

FACIES

Three facies of the Porvenir have been recognized (fig. 5): a southern, predominantly carbonate facies; a shale-carbonate facies; and a 

northern, sandstone-shale-carbonate facies. All the facies are laterally 

intergradational through several miles, and each facies locally contains 

lithologic units that are characteristic of the other facies. Because 

of the gradual lateral transitions of the facies, no contacts can be 

mapped between them and they are considered as regional lithologic 

variations within the Porvenir.

The Porvenir at the type locality is characteristic of the southern, 

predominantly carbonate facies that was deposited in shallow seas on 

the technically slightly unstable Pecos shelf in the southern part of 

the Rowe-Mora basin.

The Porvenir thickens northward from the type locality and the 

proportion of gray shale throughout the formation increases northward. This shale-carbonate facies is well exposed in the interior hogback belt at Sapello River north of Hermit Peak, and at Manuelitas 

Creek east of Rociada where the formation is 1,615 ft (491 m) thick.
PORVENIR FORMATION, SANGRE DE CRISTO MOUNTAINS, N. MEX. B27

Relatively thick units of limestone are interbedded in the shales, but 

the limestones are, generally, thin even-bedded rocks; biohermal and 

biostromal limestones are not common. Thick to thin sandstones are 

present, but they constitute a minor part of the formation. Only the 

lower 1,000 ft (300 m) of the shale-carbonate facies of the Porvenir 

is preserved from Cenozoic erosion in synclines in the topographically 

and structurally higher part of the mountains northwest of Hermit 

Peak and Rociada. These rocks are similar to the lower part of the 

Porvenir at Manuelitas Creek. They consist of units of even-bedded 

limestone and intervening thick units of calcareous shale containing 

a few beds of sandstone and thin beds of limestone. The sediments 

of the shale-carbonate facies were deposited on the eastern margin 

of the central deep part of the Rowe-Mora basin, as that configuration 

of the basin existed in Des Moinesian time.

Northeastward in the interior hogback belt east and northeast of 

Rociada (Baltz and O'Neill 1980b), the shale-carbonate facies of the 

Porvenir thins, and contains increasingly greater amounts of 

feldspathic to arkosic sandstone, until, near the San Miguel-Mora 

County line, it becomes indistinguishable from the sandstone-shalecarbonate facies described next.

Generally near and a little south of Sapello River, in the eastern 

part of the mountains, the lower part of the carbonate facies grades 

northward into a facies that contains thick, arkosic sandstones, gray 

shale, sandy shale, and sandy limestones. The basal part of this sandstone-shale-carbonate facies sporadically contains biohermal and 

stromatolitic limestones and interbedded lenticular conglomeratic 

sandstone as far north as Rito Cebolla. This facies of the Porvenir 

has been mapped to several miles north of Mora River (Baltz and 

O'Neill 1980a) and has been recognized by the authors north of the 

area of figure 5. The thickness of the sandstone-shale-carbonate facies 

of the Porvenir is about 1,170 ft (357 m) at localities 3a,b, and c 

(fig. 5) northwest of Manuelitas, about 1,140 ft (347 m) at the northwest margin of Fragoso Ridge, and about 700 ft (213 m) at Mora 

River (loc. 4, fig. 7). This northern facies appears to have occupied 

a north-trending area of Paleozoic intrabasinal uplift (or slow subsidence), that was structurally slightly lower than the Tecolote uplift 

south of Sapello (fig. 2), but that was structurally slightly higher than 

the part of the Rowe-Mora basin to the west in which the shale-carbonate facies was deposited.

PRINCIPAL REFERENCE LOCALITY

Because the Porvenir changes considerably northeastward from the 

carbonate facies at the type locality to the sandstone-shale-carbonate 

facies north of Sapello, a principal reference locality is specified for
B28 CONTRIBUTIONS TO STRATIGRAPHY

the northern facies (fig. 5). Parts of the northern facies are well exposed at many places along New Mexico Highway 94 from about 1.5 

to about 4.8 mi (2.4-7.7 km) northwest of Manuelitas. However, the 

rocks mainly dip gently west and it is difficult to find a single locality 

where they can be measured conveniently and continuously. Therefore, a composite stratigraphic section (Iocs. 3a-3c, fig. 7) that was 

measured westward from near San Isidro Cemetery and church, across the lower valley of Canon del Horno, and west along the ridge 

south of that canyon is designated as the principal reference locality. 

A geologic map of the principal reference locality is shown on figure 

9.

The basal part of the Porvenir and the upper part of the Sandia 

Formation are fairly well exposed along the north edge of the valley 

north of the Bahai school (loc. 3a, fig. 9). Part of the Porvenir above 

the basal limestones is concealed here, but good exposures of this 

part of the section exist northeast of San Isidro Cemetery and along 

New Mexico Highway 94. A distinctive limestone exposed in the roadcuts near the middle of locality 3a was traced south and was correlated 

west across the valley of Canon del Horno to a similar limestone in 

the valley at locality 3b. Beds near the top of section 3b were traced 

west across an anticline to locality 3c near the crest of the ridge south 

of Canon del Horno. The total thickness of the northern facies at 

this reference locality is about 1,170 ft (357 m).

The basal part of the Porvenir at the principal reference locality 

is a persistent zone of thin limestones that characteristically contain 

small to large biohermal mounds. Isolated, small outcrops of the Porvenir southeast of San Isidro Cemetery (fig. 9) are circular biohermallimestone mounds as much as 60 ft (18 m) in diameter; one of these 

was illustrated by Baltz and Read (1956, p. 70). Small biohermal 

mounds are well exposed near the mouth of Canada del Rocio southwest of Bahai school. Similar small bioherms and small stromatolitic 

mounds are present in the lower part of the Porvenir about 3 mi 

(4.8 km) north of Sapello near the eastern edge of the mountains. 

The basal limestone zone has been mapped south continuously from 

the reference section to the Sapello River (Baltz and O'Neill, 1980b) 

where it merges into thick limestones characteristic of the basal part 

of the carbonate facies of the Porvenir.

Northeast of the reference section, the basal limestone zone contains 

thin, lenticular beds of arkosic sandstone that locally contains limestone pebbles. In places, as about 1.2 mi (2 km) north of Manuelitas, 

these sandstones thicken locally to form a massive ledge and they 

cut out underlying limestone, to rest disconformably on the Sandia 

Formation. Farther northeast, the sandstones become thin again and 

are underlain by limestone. The basal part of the Porvenir cannot
PORVENIR FORMATION, SANGRE DE CRISTO MOUNTAINS, N. MEX. B29

be traced entirely between Rito Cebolla and Mora River because it 

is cut out locally by Cenozoic reverse faults. However, the upper part 

of the formation can be traced, and the basal limestone zone of the 

reference section appears to be equivalent to the complex zone of 

lenticular sandy oolite, sandy limestone, limestone, and conglomeratic 

sandstone mapped as the base of the Porvenir (Baltz and O'Neill, 

1980a) from La Canada del Guajalote northward past Mora River. 

The correlation of the basal zone is confirmed by the presence of abundant early Des Moinesian fusulinids near locality 4 (figs. 5, 7). 

Fusulinids are particularly abundant in the lenses of sandy oolite that 

occur at and just above the base of the Porvenir about 1,500 ft (455 

m) north of Mora River and about 500 ft (150 m) south of the river.

Above the basal limestones at the reference section (loc. 3a), is 

a 150-ft- (45-m-) thick unit of gray shale and calcareous shale containing several parallel-bedded limestones. To the south, this unit grades 

into the lower part of the carbonate facies south of Sapello River. 

To the north, the unit persists north of Rito Cebolla. The unit is 

thin or is not present at locality 4 at Mora River where intraformational unconformities have caused stratigraphically higher arkosic 

sandstones to rest on the lower part of the Porvenir.

Above the shale and limestone unit, at roadcuts at locality 3a (fig. 

7), is a sequence, almost 100 ft (30 m) thick, of coarse-grained to 

conglomeratic arkosic sandstones, some of which are almost a "grass" 

of detritus derived from a granitic terrane. The sandstones exhibit 

large-scale trough crossbedding. Above these rocks are poorly exposed 

sandstone, shale, and limestone. All these rocks are informally designated as the sandstones of Fragoso Ridge (fig. 7). North of the reference section, the entire stratigraphic interval designated as the sandstones of Fragoso Ridge becomes a massive sequence of fine-grained 

to conglomeratic sandstones with only minor intervals of shale. At 

the northwest end of Fragoso Ridge (fig. 5) south of Rito Cebolla, 

the sandstone sequence is about 200 ft (60 m) thick and forms massive 

ridges above the poorly exposed shales and thin limestones of the 

lower part of the Porvenir. North of Rito Cebolla past Mora River, 

the sandstones of Fragoso Ridge persist and form hogbacks in the 

eastern part of the mountains where they are represented by arkosic 

conglomerates and sandstones with interbedded shale and thin limestone that form the lower half of the Porvenir. From La Canada del 

Guajalote north to locality 4, reddish-weathering shales are present 

locally in this interval.

Southwest of locality 3a of the reference section, the sandstones 

of Fragoso Ridge thin and become interbedded with shale and limestone. Some of the lower sandstones persist southwestward into the 

carbonate facies a little past the upper part of Canon Bonito (fig. 

5). The sandstones of Fragoso Ridge mainly die out to the west but
B30 CONTRIBUTIONS TO STRATIGRAPHY
EXPLANATION

Quaternary alluviumQuaternary alluvium on low-pediment remnantsQuaternary gravel on low-terrace remnantsQuaternary gravel on intermediate pediment

Quaternary or Tertiary gravel on high pediment

Pennsylvanian Alamitos FormationPennsylvanian Porvenir FormationPennsylvanian Sandia FormationCONTACT Dashed where approximately located

ANTICLINE Dotted where concealed

SYNCLINE Dotted where concealedNORMAL FAULT D, downthrown; U, upthrown side. Dotted where concealed.

LINE OF STRATIGRAPHIC SECTION 

«*x*» .«»« CORRELATIVE BEDS TRACED BETWEEN STRATIGRAPHIC SECTIONS 

_£u_ STRIKE AND DIP OF BEDS

«"'B FUSULINID COLLECTION FROM LOWER PART OF PORVENIR FORMATION Dot on leader shows locality. Stratigraphic position as traced to 

locality 3a, is shown on right side of section (fig. 7)

FIGURE 9. Geologic map of principal reference locality of Porvenir Formation. Composite Stratigraphic section 

(Iocs. 3a,b,c) is the principal reference section for the sandstone-shale-carbonate facies. For regional location see figure 5. Geology from Baltz and O'Neill (1980b).

s

H

o »

M

O M 

O

2 

O

GO 

Zg M 

X

w

CO
B32 CONTRIBUTIONS TO STRATIGRAPHY

are represented by several thin, slightly arkosic sandstones in the 

lower part of the shale-carbonate facies east and west of Rociada.

Above the interval of the sandstones of Fragoso Ridge at locality 

3c of the reference section, the Porvenir is mainly silty to sandy gray 

shale that contains thin to thick beds of arkosic sandstone, limestone, 

and sandy limestone. The "marker zone" of sandy, bioclastic calcarenite, that is found in the upper part of the Porvenir at the type locality, forms a well-defined ledge at locality 3c. A thin limestone above 

the marker zone contains the fusulinid Beedeina sulphurensis. The 

marker zone was traced northward almost to the San Miguel-Mora 

County line in the interior hogback zone east of Rociada but was 

not recognized farther north.

At locality 4 at Mora River, the uppermost part of the Porvenir 

contains the fusulinid Beedeina aff. B. rockymontana (Roth and Skinner) that is found stratigraphically below the "marker zone" farther 

south. Therefore, the Porvenir at Mora River does not contain rocks 

as young as in the areas farther south, probably because of unconformity with the overlying Alamitos Formation.

AGE

The Porvenir Formation is within the fusulinid faunal zone of 

Beedeina (formerly, the genus Fusulina), and is entirely of Des 

Moinesian age. The basal beds of the formation contain Beedeina aff 

B. arizonensis (Ross and Sabins) associated with biologically advanced 

forms of Fusulinella that are similar to F. famula Thompson. The 

association of these forms indicates that the rocks are of early Des 

Moinesian age. The lower, but not basal, beds also contain Wedekindellina, which genus has been found throughout the lower two-thirds 

of the Porvenir Formation. Plectofusulina spp. also is found throughout the formation, but is more common in the upper part where it 

is associated with Beedeina sulphurensis (Ross and Sabins). B. sulphurensis is the youngest fusulinid that has been found by the writers 

in the formation and it indicates late Des Moinesian age.

ALAMITOS FORMATION

The Alamitos Formation in the southeastern Sangre de Cristo 

Mountains is generally similar to the formation at its type section 

near Pecos, about 25 miles west of Las Vegas, that was described 

by Sutherland (1963, p. 36-38), although there are variations in 

lithologic details and thickness between the two regions. At its type 

section northwest of Pecos, the Alamitos consists of arkosic sandstone 

and conglomerate; olive-gray, gray, and red shale; and nodular limestone, sandy limestone, and gray to olive-gray, thin- to thick-bedded 

limestone. All these rocks are complexly interbedded and are marine
PORVENIR FORMATION, SANGRE DE CRISTO MOUNTAINS, N. MEX. B33

and nonmarine. In the type section the Alamitos is about 1,275 ft 

(390 m) thick. Its age in that area is late Des Moinesian, Missourian, 

and Virgilian. According to Sutherland (1963), the Alamitos Formation 

is approximately equivalent to the arkosic limestone member of the 

Madera Formation as assigned by Brill (1952) in the Pecos area.

LITHOLOGIC DESCRIPTION

A composite stratigraphic section of the Alamitos (fig. 10) at the 

type locality of the Porvenir Formation (fig. 6) is shown to illustrate 

the general lithology of the Alamitos in the southeastern part of the 

Sangre de Cristo Mountains. In the southeastern part of the mountains, the Alamitos consists of a heterogeneous assemblage of gray 

to greenish-gray silty shale and interbedded arkosic sandstones and 

conglomerates, nodular gray limestones, sandy and arkosic limestones, 

and some thick-bedded gray limestone. Nearly all the limestones and 

shales, and some sandstones, contain marine fossils; however, some 

of the sandstones have bedding characteristics that indicate they are 

probably nonmarine, fluviatile deposits. Characteristically, many of 

the shales are marly and commonly contain limestone nodules and 

interbedded nodular limestones. Many shales weather to a distinctive 

olive green; other shales weather distinctive maroon to purplish red.

Throughout most of the southeastern part of the mountains, the 

lowest beds of the Alamitos are arkosic, crossbedded sandstones and 

conglomerates that contain granule- to small-pebble-size angular to 

subangular clasts of little-weathered reddish-pink potash feldspar. At 

some places, the basal beds are arkosic limestones that grade laterally 

into arkosic sandstone. Locally, thin distinctively green arkosic sandstone is at or near the base.

At most places, red- to maroon-weathering shale is interbedded with 

the basal arkoses of the Alamitos or is not far above them and provides 

an excellent criterion for distinguishing the Alamitos from the Porvenir, especially at the north where parts of the Porvenir also contain 

arkose. At some outcrops of the basal arkoses of the Alamitos, red 

shale is not present, but lateral tracing for short distances usually 

discloses red-shale interbeds. At places, a few shale beds in the upper 

part of the Porvenir weather locally to a purplish hue, as at the type 

locality (loc. 1) and in roadcuts at Mora River (loc. 4). However, the 

purplish hue is distinctive and almost always is of limited (a few 

meters) extent.

Although arkosic sandstones and conglomerates are present 

throughout the Alamitos, the thickest arkoses generally are in the 

upper half or third of the formation. These rocks commonly contain 

irregularly shaped pebbles of quartzite, other metamorphic rocks, and 

granite. At many places in the upper part of the Alamitos, fluviatile
B34

LOG. 2

CONTRIBUTIONS TO STRATIGRAPHY 

.1 Sangre de Cristo Formation

J^^-SH*-7"- aff- creekensis

ui:4 L.\J R,G ABBREVIATIONS OF

FUSULINID GENERA

T. Triticites

B. Beedeina

FEET METERS 

200 

g. aff. sulphurensis

B. sp. 

Millerella sp.

FIGURE 10. Composite stratigraphic section of the Alamitos Formation 

along U.S. Forest Service road (loc. 2) and at the type locality of 

Porvenir Formation (loc. 1). Localities shown on figures 5 and 6. Symbols used are explained in figure 8. Base of section at locality 2 is 

about 3,000 ft (915 m) northwest of top of section at locality 1.

arkosic conglomerates form massive units that commonly are interbedded with unfossiliferous red shales. These rocks are similar to some 

parts of the overlying Sangre de Cristo Formation and locally cause 

confusion in determining the contact with that formation. However, 

the uppermost part of the Alamitos contains fossiliferous marine limestone, sandy limestone, and commonly olive-green shale. The top of 

the Alamitos (the equivalent upper member of the Madera of past
PORVENIR FORMATION, SANGRE DE CRISTO MOUNTAINS, N. MEX. B35

usage) is mapped at the top of the highest marine beds by Northrop 

and others (1946), Baltz (1972), and Baltz and O'Neill (1980a,b).

THICKNESS

Near the eastern front of the mountains south of Montezuma, the 

Alamitos is absent locally, and it is only about 180 ft (55 m) thick 

about 1 mi (1.6 km) southwest of Montezuma. Farther west, the 

Alamitos is about 715 ft (218 m) thick at locality 2 (figs. 6 and 10) 

south of Gallinas Creek. The formation thickens northward and is at 

least 1,285 ft (390 m) thick about 1.5 mi (2.4 km) northwest of Sapello 

where part is cut out by a Cenozoic fault in the upper part of the 

formation. Between Rito Cebolla and Mora River, the formation is 

locally only about 100 ft (30 m) thick. At Mora River (east of loc. 

4) the Alamitos is about 1,050 ft (320 m) thick.

CONTACTS WITH ADJACENT ROCKS

On the Paleozoic Tecolote uplift from Montezuma south, the 

Alamitos lies unconformably on the Porvenir Formation and locally 

overlaps it to the south. The Alamitos is overlain unconformably by 

the Sangre de Cristo Formation that laps southward onto Precambrian 

rocks (Northrop and others, 1946).

At the west, from the vicinity of locality 2 northward past Sapello 

River, the contact of the Alamitos and Porvenir is locally disconformable but the hiatus may be small, inasmuch as Beedeina sulphurensis 

is present in both formations. Not far east of locality 2, the Alamitos 

is folded sharply along the Canon del Medio anticline and thins because 

of local angular unconformity with the overlying Sangre de Cristo 

Formation. (See Baltz, 1972, sheet 2, section F-F'.)

In the eastern part of the mountains between Rito Cebolla and 

Mora River, the contact of the Alamitos and Porvenir is locally unconformable. In this area, where the Alamitos is thin (100-250 ft; 30-75 

m), the contact with the Sangre de Cristo Formation apparently is 

a local angular unconformity.

At Mora River (loc. 4) and farther north, the contact of the Alamitos 

and Porvenir is unconformable, as is shown by thinning of the Porvenir and because the fusulinid-bearing youngest rocks of the Porvenir, just below the contact, are older than the marker zone of the 

Porvenir farther south. The contact of the Alamitos and the Sangre 

de Cristo here seems to be transitional, and the oldest part of the 

Sangre de Cristo here could be Late Pennsylvanian (Virgilian?), although our paleontologic data from these rocks currently are too 

sketchy to be certain.
B36 CONTRIBUTIONS TO STRATIGRAPHY

AGE

Fusulinids occur at many places in the lower part of the Alamitos. 

The stratigraphically lowest fusulinids are Beedeina sulphurenesis of 

late Des Moinesian age. Near locality 2 of this report (figs. 5, 6, and 

10), Triticites aff. T. creekensis Thompson was found in nodular limestones about 40 ft (12 m) stratigraphically below the top of the 

Alamitos at locality A (fig. 6) along an abandoned road. This form 

indicates an Early Permian (early Wolfcampian) age.

North of New Mexico Highway 65, a few hundred yards northeast 

of Western Life Camp (fig. 6), a limestone near the middle of the 

Alamitos contains Triticites nebrascensis of early Missourian age. 

West of Tecolote Creek about 1.3 mi (2 km) southeast of Blue Haven 

Camp (fig. 5), fusulinids belonging to the group of Triticites secalicus 

were found in limestone about 150 ft (45 m) below the top of the 

Alamitos. These triticites suggest a mid-Virgilian age. Therefore, in 

the western part of the Gallinas Creek area, the Alamitos contains 

marine rocks representing Middle and all the Upper Pennsylvanian 

Series, as well as part of the Lower Permian.

We did not find fusulinids in the upper part of the Alamitos farther 

north. Most of the brachiopods, pelecypods, and gastropods we collected from the upper part from Sapello River northward are definitive only of Late Pennsylvanian age (J. T. Dutro, Jr., written commun., 1980). However, shale just below the top of the Alamitos in 

roadcuts a little less than 1 mi (1.6 km) west of Sapello contains Isogramma cf. 1. renfrarum Cooper, Stegocoelia (Taosid) cf. S. (T.) percostata (Girty), and Orthomyalina sp. which are suggestive of Virgilian age (J. T. Dutro, Jr. and E. L. Yochelson, written commun., 

1980). Therefore, rocks of probable Virgilian age are present in the 

Alamitos at least as far north as Sapello.

North of Rito Cebolla, where the Alamitos is locally thin, only the 

Des Moinesian part containing Beedeina sulphurensis is present. At 

Mora River (east of loc. 4) the Alamitos has thickened considerably. 

The lower-middle part contains Beedeina sulphurensis. Brachiopods 

and pelecypods from near the top of the Alamitos indicate a Late 

Pennsylvanian, probably Missourian age, according to J. T. Dutro, 

Jr.

REFERENCES CITED

Armstrong, A. K., 1955, Preliminary observations on the Mississippian System of northern New Mexico: New Mexico Bureau of Mines and Mineral Resources Circular 

39, 42 p.

 1967, Biostratigraphy and carbonate facies of the Mississippian Arroyo Penasco 

Formation, north-central New Mexico: New Mexico Bureau of Mines and Mineral 

Resources Memoir 20, 80 p.
PORVENIR FORMATION, SANGRE DE CRISTO MOUNTAINS, N. MEX. B37

Armstrong, A. K., Kottlowski, F. E., Stewart, W. J., Mamet, B. L., Baltz, E. H., 

Siemers, W. T., and Thompson, Sam III, 1979, The Mississippian and Pennsylvanian (Carboniferous) Systems in the United States New Mexico: U.S. Geological 

Survey Professional Paper 1110-W, p. W1-W27.

Armstrong, A. K., and Mamet, B. L., 1974, Biostratigraphy of the Arroyo Penasco 

Group, Lower Carboniferous (Mississippian), north-central New Mexico, in New 

Mexico Geological Society Guidebook, 25th Field Conference, Ghost Ranch, 1974: 

p. 145-158.

Bachman, G. O., 1953, Geology of a part of northwestern Mora County, New Mexico: 

U.S. Geological Survey Oil and Gas Investigations Map OM-137.

 1975, New Mexico, in Paleotectonic investigations of the Pennsylvanian System 

in the United States, Part 1; Introduction and regional analyses of the Pennsylvanian System: U.S. Geological Survey Professional Paper 853-L, p. 233-243.

Baltz, E. H., 1965, Stratigraphy and history of Raton Basin and notes on San Luis 

Basin, Colorado-New Mexico: American Association of Petroleum Geologists Bulletin, v. 49, p. 2041-2075.

 1972, Geologic map and cross sections of the Gallinas Creek area, Sangre de 

Cristo Mountains, San Miguel County, New Mexico: U.S. Geological Survey Miscellaneous Geologic Investigations Map 1-673, 2 sheets. 

-1978, Resume of Rio Grande depression in north-central New Mexico, in Invited

papers, Guidebook to Rio Grande rift in New Mexico and Colorado: New Mexico 

Bureau of Mines and Mineral Resources Circular 163, p. 210-228.

Baltz, E. H., and O'Neill, J. M., 1980a, Preliminary geologic map of the Mora River 

area, Sangre de Cristo Mountains, Mora County, New Mexico: U.S. Geological 

Survey Open-file Report 80-374.

 1980b, Preliminary geologic map of the Sapello River area, Sangre de Cristo 

Mountains, Mora and San Miguel Counties, New Mexico: U.S. Geological Survey 

Open-file Report 80-398.

Baltz, E. H., and Read, C. B., 1956, Second day, Kearny's Gap and Montezuma via 

Mineral Hill and Gallinas Canyon, Las Vegas to Mora to Taos, in New Mexico 

Geological Society 7th Field Conference, 1956, Guidebook of southeastern Sangre 

de Cristo Mountains, New Mexico: p. 49-81.

 1960, Rocks of Mississippian and probable Devonian age in Sangre de Cristo

Mountains, New Mexico: American Association of Petroleum Geologists Bulletin,

v. 44, p. 1749-1774. 

Booth, F. 0., 1976, Geology of the Galisteo Creek area, Lamy to Canoncito, Santa

Fe County, New Mexico: Golden, Colo., Colorado School of Mines, M. S. thesis,

122 p.

 1977, Geologic map of the Galisteo Creek area, Lamy to Canoncito, Santa Fe

County, New Mexico: U.S. Geological Survey Miscellaneous Field Studies Map

MF-823. 

Brill, K. G., Jr., 1952, Stratigraphy in the Permo-Pennsylvanian zeugogeosyncline of

Colorado and northern New Mexico: Geological Society of America Bulletin, v.

63, p. 809-880. 

Clark, K. F., and Read, C. B., 1972, Geology and ore deposits of Eagle Nest area,

New Mexico: New Mexico Bureau of Mines and Mineral Resources Bulletin 94,

152 p. 

Darton, N. H., 1922, Geologic structure of parts of New Mexico, in Contributions

to economic geology, 1921; Part 2 Mineral fuels: U.S. Geological Survey Bulletin

726, p. 173-275.

 1928a, "Red beds" and associated formations in New Mexico, with an outline 

of the geology of the state: U.S. Geological Survey Bulletin 794, 356 p.

 1928b, Geologic map of New Mexico: U.S. Geological Survey.
B38 CONTRIBUTIONS TO STRATIGRAPHY

Fitzsimmons, J. P., Armstrong, A. K., and Gordon, MacKenzie, Jr., 1956, Arroyo 

Penasco Formation, Mississippian, north-central New Mexico: American Association of Petroleum Geologists Bulletin, v. 40, no. 8, p. 1935-1944.

Foster, R. W., Frentress, R. M., and Riese, W. C., 1972, Subsurface geology of eastcentral New Mexico: New Mexico Geological Society Special Publication 4, 22 p.

Henbest, L. G., 1946, Stratigraphy of the Pennsylvanian in the west half of Colorado 

and in adjacent parts of New Mexico and Utah [abs.]: American Association of 

Petroleum Geologists Bulletin, v. 30. D. 750-751.

Herrick, C. L., 1900, The geology of the White Sands of New Mexico: Journal of 

Geology, v. 8, p. 112-126.

Hills, R. C., 1899, Description of the El Moro quadrangle [Colorado]: U.S. Geological 

Survey Atlas, Folio 58.

Johnson, R. B., 1973, Geologic map of the Pecos quadrangle, San Miguel and Santa 

Fe Counties, New Mexico: U.S. Geological Survey Geologic Quadrangle Map GQ1110.

Kelley, V. C., and Northrop, S. A., 1975, Geology of Sandia Mountains and vicinity, 

New Mexico: New Mexico Bureau of Mines and Mineral Resources Memoir 29, 

135 p.

Lee, W. T., 1909, Stratigraphy of the Manzano Group, in Lee, W. T., and Girty, 

G. H., 1909, The Manzano Group of the Rio Grande Valley, New Mexico: U.S. 

Geological Survey Bulletin 389, 141 p.

Melton, F. A., 1925, Correlation of Permo-Carboniferous redbeds in southeastern Colorado and northern New Mexico: Journal of Geology, v. 33, p. 807-814.

Myers, D. A., 1969, Geologic map of the Escabosa quadrangle, Bernalillo County, New 

Mexico: U.S. Geological Survey Geologic Quadrangle Map GQ-795.

 1973, The Upper Paleozoic Madera Group in the Manzano Mountains, New 

Mexico: U.S. Geological Survey Bulletin 1372-F, p. F1-F13.

Myers, D. A., and McKay, E. J., 1976, Geologic map of the north end of the Manzano 

Mountains, Tijeras and Sedillo quadrangles, Bernalillo County, New Mexico: U.S. 

Geological Survey Miscellaneous Investigations Map 1-968.

Northrop, S. A., Sullwold, H. H., Jr., MacAlpin, A. J., and Rogers, C. P., Jr., 1946, 

Geologic map of a part of the Las Vegas basin and of the foothills of the Sangre 

de Cristo Mountains, San Miguel and Mora Counties, New Mexico: U.S. Geological 

Survey Oil and Gas Investigations Preliminary Map 54.

Read, C. B., Wilpolt, R. H., Andrews, D. A., Summerson, C. H., and Wood, G. 

H., Jr., 1944, Geologic map and stratigraphic sections of Permian and Pennsylvanian rocks of parts of San Miguel, Santa Fe, Sandoval, Bernalillo, Torrance, and 

Valencia Counties, north-central New Mexico: U.S. Geological Survey Oil and Gas 

Investigations Preliminary Map 21.

Read, C. B., and Wood, G. H., Jr., 1947, Distribution and correlation of Pennsylvanian 

rocks in late Paleozoic sedimentary basins of northern New Mexico: Journal of 

Geology, v. 55, p. 220-236.

Stevenson, J. J., 1881, Report upon geological examinations in southern Colorado and 

northern New Mexico during the years 1878 and 1879, with an appendix upon 

the Carboniferous invertebrate fossils of New Mexico, by C. A. White: U. S. Geographical Surveys West of the One-hundredth Meridian [Wheeler Survey], v. Ill, 

Supplement, Geology, 420 p., and 38 p. appendix.

Sutherland, P. K., 1963, Paleozoic rocks, in Miller, J. P., Montgomery, Arthur, and 

Sutherland, P. K., 1963, Geology of part of the southern Sangre de Cristo Mountains, New Mexico: New Mexico Bureau of Mines and Mineral Resources Memoir 

11, p. 22-46.
PORVENIR FORMATION, SANGRE DE CRISTO MOUNTAINS, N. MEX. B39

Sutherland, P. K., and Harlow, F. H., 1973, Pennsylvanian brachiopods and biostratigraphy in southern Sangre de Cristo Mountains, New Mexico: New Mexico Bureau 

of Mines and Mineral Resources Memoir 27, 173 p.

Thompson, M. L., 1942, Pennsylvanian System in New Mexico: New Mexico Bureau 

of Mines and Mineral Resources Bulletin 17, 92 p.

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