U.S. GEOLOGICAL SURVEY BULLETIN 1733-C

Chapter C

Mineral Resources of the Rio Chama

Wilderness Study Area,

Rio Arriba County, New Mexico

By JENNIE L RIDGLEY and CARL L LONG 

U.S. Geological Survey

RUSSELL A. SCHREINER 

U.S. Bureau of Mines

U.S. GEOLOGICAL SURVEY BULLETIN 1733

MINERAL RESOURCES OF WILDERNESS STUDY AREASNORTHERN NEW MEXICO
DEPARTMENT OF THE INTERIOR 

DONALD PAUL MODEL, Secretary

U. S. GEOLOGICAL SURVEY 

Dallas L Peck, Director

UNITED STATES GOVERNMENT PRINTING OFFICE: 1988

For sale by the

Books and Open-File Reports Section

U.S. Geological Survey

Federal Center

Box 25425

Denver, CO 80225

Library of Congress Cataloging-in-Publication Data

Ridgley, Jennie L.

Mineral resources of the Rio Chama Wilderness Study Area, Rio Arriba 

County, New Mexico.

(Mineral resources of wilderness study areas northern New Mexico ; ch. C) 

(U.S. Geological Survey bulletin ; 1733-C)

Bibliography: p.

Supt. of Docs, no.: I 19.3:1733-C

1. Mines and mineral resources New Mexico Rio Chama 

Wilderness. 2. Rio Chama Wilderness (N.M.) I. Long, Carl L II. Schreiner, 

Russell A. III. Title. IV. Series. V. Series: U.S. Geological Survey bulletin ; 

1733-C.

QE75.B9 no. 1733-C 553'.09789'52 88-600021 

[TN24.N6]
STUDIES RELATED TO WILDERNESS

Bureau of Land Management Wilderness Study Areas

The Federal Land Policy and Management Act (Public Law 94-579, October 21, 

1976) requires the U.S. Geological Survey and the U.S. Bureau of Mines to conduct mineral 

surveys on certain areas to determine the mineral values, if any, that may be present. Results 

must be made available to the public and be submitted to the President and the Congress. 

This report presents the results of a mineral survey of a part of the Rio Chama Wilderness 

Study Area (NM-01Q-059), Rio Arriba County, New Mexico.

CONTENTS

Abstract Cl 

Summary Cl 

Introduction C2

Investigations by the U.S. Bureau of Mines C2 

Investigations by the U.S. Geological Survey C4 

Appraisal of identified resources C4 

Mining history C4 

Mineral appraisal C4

Assessment of potential for undiscovered resources C4 

Geology C4

Geologic setting C4 

Description of rock units C5 

Geochemistry C7 

Geophysics C7

Aeroradiometric study C7 

Aeromagnetic and gravity study C7 

Aeromagnetic data C8 

Gravity data C8 

Mineral and energy resources C8 

Oil and gas C8 

Industrial minerals C8 

Clinoptilolite C8 

Gypsum C9 

Limestone CIO 

Metals CIO 

Uranium CIO 

Geothermal energy CIO 

Recommendations for future work Cll 

References cited Cll 

Appendix C13

FIGURES

1. Summary map showing location of wilderness study areas along the Rio

Chama, northern New Mexico; mineral resource potential; and principal mines 

and prospects in the Rio Chama Wilderness Study Area and vicinity C3

2. Geologic map of the Rio Chama Wilderness Study Area C6

3. Map showing lines of magnetic intensity in the Rio Chama Wilderness Study 

Area C9

4. Map showing Bouguer gravity of the Rio Chama Wilderness Study 

Area CIO

Contents

MINERAL RESOURCES OF WILDERNESS STUDY AREASNORTHERN NEW MEXICO

Mineral Resources of the

Rio Chama Wilderness Study Area,

Rio Arriba County, New Mexico

By Jennie L Ridgley and Carl L Long 

U.S. Geological Survey

Russell A. Schreiner 

U.S. Bureau of Mines

ABSTRACT

The Rio Chama Wilderness Study Area (NM-010-059), 

Rio Arriba County, N. Mex., has inferred subeconomic sand 

and gravel, limestone, and sandstone resources. The study 

area has moderate mineral resource potential for 

undiscovered limestone and gypsum resources in the 

subsurface; low mineral resource potential for undiscovered 

oil and gas, for undiscovered silver, manganese, tin, 

vanadium, zinc, uranium, and all other metals, and for 

clinoptilolite; and low resource potential for undiscovered 

geothermal energy.

SUMMARY

The Rio Chama Wilderness Study Area, Rio Arriba 

County, N. Mex., is in the western part of the Chama Basin 

(fig. 1) approximately 3.5 mi (miles) south of El Vado and El 

Vado Reservoir. The Jicarilla Apache Indian Reservation is 

just west of the northern part of the study area, and the Santa 

Fe National Forest is adjacent to the study area on the west 

and south. The Chama River Canyon Wilderness, managed 

by the U.S. Forest Service, is contiguous to the southern 

boundary of the study area. The Rio Chama cuts through the 

study area and forms part of its western boundary. Access to 

the study area is by an unmarked dirt road that joins New 

Mexico Highway 112 south of El Vado and by unmarked 

roads that intersect U.S. Highway 84 at Cebolla and New 

Mexico Highway 112 east of El Vado. In this area the Rio 

Chama cuts a steep canyon through the mesas, the relief 

being as much as 900 ft (feet). The river is accessible in only 

a few places.

The Rio Chama Wilderness Study Area is in the 

southeastern part of the Colorado Plateaus physiographic 

province. Sedimentary rocks in the study area are folded and 

faulted and are part of a complex fold belt that separates the 

Chama Basin from the San Juan Basin to the west. The 

structural features formed primarily during the Late 

Cretaceous and early Tertiary (see geologic time chart in 

appendix) (Landisand Dane, 1967). However, movement on 

some structures near the study area occurred earlier than 

that (Ridgley, 1987a). Faulting in the study area is generally 

limited to displacements of less than 200 ft along high-angle, 

normal faults.

Rocks exposed in the study area range in age from 

Jurassic to Quaternary. No Tertiary rocks are present. In the 

subsurface, rocks of Pennsylvanian age unconformably 

overlie Precambrian rocks and are in turn overlain by rocks of 

Permian and Triassic age. Jurassic rocks exposed in the 

study area are the Entrada Sandstone, Wanakah Formation, 

and Morrison Formation. Cretaceous rocks are represented 

by the Burro Canyon(?) Formation, Dakota Sandstone, and 

Mancos Shale.

About one-half of the study area is under lease for oil 

and gas, but no test holes have been drilled. In 1981 most of 

the study area was covered with mining claims; however, 

these have been abandoned. The wilderness study area has 

been prospected for uranium. Two uranium prospects are 

located near the wilderness boundary (fig. 1); neither has 

produced any uranium. The only identified resources in the 

study area are sand and gravel, limestone, and sandstone.

The Rio Chama Wilderness Study Area has moderate 

potential for limestone and gypsum in the subsurface (fig. 1). 

This assessment applies to the entire study area because 

any resources present would be in the subsurface. Extension

Rio Chama Wilderness Study Area C1
of the geology from the nearby Gallina Mountain area 

indicates that Pennsylvanian limestone, which is quarried for 

road metal in the southern part of the Chama Basin, underlies 

the study area. On the basis of known relationships of the 

facies distribution of the gypsum and limestone in the Wanakah Formation, gypsum can be expected to have an irregular 

distribution in the subsurface in the study area.

The Rio Chama Wilderness Study Area has low mineral 

resource potential for undiscovered oil and gas resources, for 

undiscovered resources of silver, manganese, tin, vanadium, 

zinc, uranium, and all other metals, and for clinoptilolite; and 

low resource potential for undiscovered geothermal energy 

(fig. 1). Favorable oil and gas host and source rocks and 

structural and stratigraphic traps may exist in the 

Pennsylvanian rocks that underlie the study area. However, 

extensive faulting of the rocks and close proximity to a deep 

dissected canyon and basin margin could permit flushing of 

hydrocarbons. Clinoptilolite is found approximately 5 mi 

south of the study area. However, rocks containing this 

zeolite do not extend into the study area. No uranium 

deposits are known to be present in the study area. Geochemical and aeroradiometric surveys did not detect any 

anomalies that would indicate the presence of buried 

deposits of these commodities. Extensive faulting and 

proximity of the study area to a steep, dissected canyon 

could permit migration of ground water, which might oxidize 

and remove uranium or metal concentrations.

There are no known geothermal energy sources in the 

form of buried intrusions or warm springs in the study area. 

However, two warm springs are within 0.25 mi to the north of 

the study area (fig. 2). The springs emanate from a fault that 

cuts the west limb of the Rio Chama anticline. Warm water 

circulating through the fault discharges at the springs; the 

source of heat that warms the water is not known. There is 

low potential for geothermal resources throughout the study 

area.

INTRODUCTION

The U.S. Geological Survey and the U.S. Bureau of 

Mines studied 5,232 acres of the Rio Chama Wilderness 

Study Area (NM-010-059). The study of this acreage 

was requested by the U.S. Bureau of Land Management. 

In this report the studied area is called the "wilderness 

study area" or simply the "study area."

This report presents an evaluation of the mineral 

endowment (identified resources and mineral resource 

potential) of the study area and is the product of several 

separate studies by the U.S. Bureau of Mines (USBM) 

and the U.S. Geological Survey (USGS). Identified 

resources are classified according to the system of the 

USBM and USGS (1980), which is shown in the appendix 

of this report. Identified resources are studied by the 

USBM. Mineral resource potential is the likelihood of 

occurrence of undiscovered metals and nonmetals, 

industrial rocks and minerals, and energy sources (coal, 

oil, gas, oil shale, and geothermal sources). It is classified

EXPLANATION

M/C Geologic terrane having moderate resource potential for 

gypsum and limestone in the subsurface, with a certainty level of C Applies to entire study area

L/B Geologic terrane having low resource potential for oil, gas, 

silver, manganese, tin, vanadium, zinc, uranium, and 

all other metals, and for geothermal energy, with a certainty level of B Applies to entire study area

L/C Geologic terrane having low resource potential for clinoptilolite, with a certainty level of C Applies to entire 

study area

 < Adit 

X Prospect

Levels of certainty

B Data indicate geologic environment and suggest level of 

resource potential

C Data indicate geologic environment and resource potential, but do not establish activity of resource-forming 

processes

according to the system of Goudarzi (1984), which is also 

shown in the appendix. Potential for undiscovered 

resources is studied by the USGS.

The Rio Chama Wilderness Study Area, Rio 

Arriba County, N. Mex., is along the northern part of the 

Rio Chama in the western part of the Chama Basin (fig. 

1). The study area is bounded on the northwest by the 

Jicarilla Apache Indian Reservation and on the south and 

west by the Santa Fe National Forest. The Chama River 

Canyon Wilderness, managed by the U.S. Forest Service, 

is contiguous to the southern study area boundary. The 

study area is approximately 3.5 mi south of El Vado and 

El Vado Reservoir and may be reached by an unmarked 

dirt road that joins New Mexico Highway 112 south of El 

Vado and by unmarked roads that intersect U.S. 

Highway 84 at Cebolla and New Mexico Highway 112 

east of El Vado. Access is by public and private roads 

that are passable only in dry weather. The study area is 

characterized by steep canyons and mesas and has as 

much as 900 ft relief. Canyon walls are rugged, and the 

river is accessible in only a few places. Elevation of the 

mesa tops is consistently about 7,500 ft. The Rio Chama 

flows through the study area and forms part of its western 

boundary.

Investigations by the 

U.S. Bureau of Mines

The Rio Chama Wilderness Study Area was 

examined by the U.S. Bureau of Mines personnel in 

1985. Prior to field investigations, published and 

unpublished literature relating to the study area was 

reviewed for information concerning mineral deposits, 

occurrences, mineralized areas, and mining activity. 

Land status plats were acquired from the U.S. Bureau of 

Land Management State Office, Sante Fe, N. Mex. Six 

employee-days were spent in the field.

C2 Mineral Resources of Wilderness Study Areas Northern New Mexico
106°45' 106°30'

T29N

T28N

T27N

36°30' 

T26N

T25N

T24N

El Vado 

Reservoir

APPROXIMATE BOUNDARY OF THE

RIO CHAMA WILDERNESS STUDY

AREA (NM-010-059)

APPROXIMATE BOUNDARY OF

THE CHAMA RIVER CANYON

WILDERNESS AREA

Rl E R2E R3E R4E

5 MILES 

J

Figure 1. Summary map showing location of wilderness study areas along the Rio Chama, northern New 

Mexico; mineral resource potential; and principal mines and prospects in the Rio Chama Wilderness Study Area 

and vicinity, Rio Arriba County, N. Mex.

Rio Chama Wilderness Study Area C3
Field investigations by U.S. Bureau of Mines 

personnel included examination of mines and prospects 

within 1 mi of the study area and the collection of seven 

panned-concentrate samples along the Rio Chama in and 

near the study area. All samples were analyzed for gold 

and silver by fire assay, inductively coupled plasma, and 

atomic-emission spectroscopy, and for 50 elements by 

semiquantitative optical-emission spectroscopy by the 

USBM, Reno Research Center, Reno, Nev. All analytical 

data are in Schreiner (1986, table 1 and appendix A).

Investigations by the 

U.S. Geological Survey

An assessment of the mineral resource potential of 

the Rio Chama Wilderness Study Area was conducted 

during the summers of 1985 and 1986. As part of this 

assessment, a geologic map was prepared at a scale of 

1:24,000 (Ridgley, in press); about 65 percent of this map 

includes new geologic mapping for this area of the 

Chama Basin, and the rest represents modification of 

existing geologic mapping (Landis and Dane, 

1967; Ridgley, 1983). No new geochemical data were 

gathered for this study, but data from a report prepared 

for the U.S. Forest Service on the Chama River Canyon 

Wilderness and contiguous roadless areas (Ridgley, 

1986) were used. Geophysical studies included an 

evaluation of existing aeroradiometric data by J.S. Duval 

and an evaluation of existing aeromagnetic and gravity 

data by C.L. Long.

Acknowledgments. The USGS thanks the several 

ranchers in the area for providing location information 

and access to the study area.

APPRAISAL OF IDENTIFIED RESOURCES

By Russell A. Schreiner 

U.S. Bureau of Mines

Mining History

Uranium occurrences were discovered during the 

late 1950's in the southern Chama Basin. The basin was 

prospected during the uranium boom starting in the late 

1960's. Uranium exploration in and near the study area 

concentrated on the Cretaceous Burro Canyon 

Formation; several small roll-front deposits were 

discovered approximately 8-16 mi east of the study area 

(Saucier, 1974). In 1981 most of the study area was 

covered with mining claims (Light, 1982), which have 

since been abandoned.

Mineral Appraisal

The only mineral resources identified in the study 

area were common industrial materials. The following 

inferred subeconomic resources are present: sand and 

gravel along the river bed of the Rio Chama, limestone in 

the Jurassic-age Todilto Limestone exposed in a small 

area at the base of the canyon of the Rio Chama, and 

sandstone in the Jurassic- and Cretaceous-age 

formations exposed in the walls of the canyon of the Rio 

Chama. Because of the abundance of these materials in 

the region, the distance from markets and their lack of 

unique properties, it is unlikely they would be developed 

in the near future.

Seven panned-concentrate samples were taken 

along the Rio Chama in and near the study area. One 

sample contained silver, determined by fire assay 

(Schreiner, 1986, table 1). Semiquantitative 

optical-emission spectroscopic analysis of the other 

samples showed no element concentrations that could be 

considered anomalous for a panned-concentrate sample. 

No known mineral occurrences containing elements in 

the concentrates are present in the area. Detailed 

sampling would be required to determine the significance 

of the analytical value.

Two uranium prospects, Cebolla 2 and Heart 3, are 

within 1 mi of the southern boundary of the study area 

(fig. 2). Uranium occurs in small, local concentrations in 

amounts as much as 0.37 percent equivalent uranium 

(determined by radiometric assay), associated with fossil 

bone fragments in the Morrison Formation at the 

Cebolla 2 prospect and in limonite-stained limestone 

fragments along the contact between the Todilto and 

upper member of the Wanakah at the Heart 3 prospect 

(Hilpert, 1969; Light, 1982). A stream-sediment sample 

taken just outside the southeastern boundary of the study 

area at the mouth of Berry Canyon contained a minor 

concentration of uranium (5 ppm) (Ridgley and Light, 

1983).

ASSESSMENT OF POTENTIAL FOR 

UNDISCOVERED RESOURCES

By Jennie L. Ridgley and Carl L. Long 

U.S. Geological Survey

Geology

Geologic Setting

The Rio Chama Wilderness Study Area is along 

the western margin of the Chama Basin in the 

southeastern part of the Colorado Plateaus physiograC4 Mineral Resources of Wilderness Study Areas Northern New Mexico
phic province. Rocks in the study area are folded and 

faulted and form part of the Archuleta anticlinorium, a 

complex series of folded and faulted anticlines, synclines, 

and domes that separate the Chama Basin from the San 

Juan Basin to the west. The structural features formed 

mainly during the Laramide orogeny, of Late Cretaceous 

and early Tertiary age. However, movement occurred on 

some structures near the study area earlier than that; 

these movements influenced distribution and thickness of 

the sediments being deposited in the study area (Landis 

and Dane, 1967; Ridgley, 1987a, 1987b). Results of 

drilling in areas to the north, west, and south and 

examination of exposures of older rocks to the south and 

east indicate a complex structural history for the study 

area. Rocks of several ages are beveled or absent over 

some of the structural features; Laramide or later 

structures may not accurately reflect older structural 

features, which could contain large fault displacements 

or amplitudes of folds (Landis and Dane, 1967) that 

could affect the location of structural or stratigraphic 

traps for hydrocarbon accumulation.

Faulting in the study area is generally limited to 

displacements of less than 200 ft, although faults having 

displacements in excess of 200 ft are present. Traces of 

the faults commonly are short; however, a few can be 

mapped for several miles. Most of the faults are highangle, normal faults. In the northern part of the study 

area, faults are so closely spaced that it is difficult to show 

all the faults on the map; thus, only the major faults are 

shown.

Rocks exposed in the study area range in age from 

Jurassic to Quaternary. No Tertiary rocks are present. In 

the subsurface, rocks of Pennsylvanian age unconformably overlie Precambrian rocks and are overlain by rocks 

of Permian and Triassic age.

Description of Rock Units

Individual rock units mapped in the study area are 

grouped into several map units in this report (fig. 2). A 

detailed geologic map may be found in Ridgley (in press).

Middle Jurassic Entrada Sandstone and Wanakah 

Formation and Upper Jurassic Morrison Formation, 

undivided (unit Ju^. The Entrada Sandstone is 

composed of orange, tan, or white, medium-grained 

sandstone that crops out in only a few places in the 

southern part of the study area as a result of a structure 

that brings older units to the surface. The Entrada is not 

completely exposed; a partial thickness of 140 ft is 

present.

In the study area the Wanakah Formation consists 

of the basal Todilto Limestone Member and an overlying 

unnamed upper member. The Todilto consists ©f 

limestone and, locally, gypsum that overlies the limestone 

in discontinuous lenses. The distribution of limestone

and limestone-gypsum facies reflects changes in 

precipitation from calcium carbonate to calcium sulfate 

(Ridgley, 1984) at the time the Todilto was being 

deposited. Interbedded sandstone and mudstone and 

minor diamictite and limestone characterize the upper 

member. Sandstone is dominant in the lower two-thirds 

of the upper member and mudstone in the upper third. 

Limestone is locally present near the top of the upper 

member. The diamictite, which is present at the base of 

the upper member, represents debris flows originating 

from uplifted areas along the Archuleta anticlinorium 

just to the west of the study area (Ridgley, 1987a). 

Exposures of the Wanakah are poor. The estimated 

thickness is about 100 ft.

The Morrison Formation is composed of two 

members. The lower member consists of interbedded 

light-reddish-brown fluvial sandstone and reddish-brown 

mudstone. Sandstone, which is locally characterized by 

multiple stacking of channels, is dominant. This member 

crops out only in the southern part of the study area. The 

overlying Brushy Basin Member is composed of green, 

tan, and maroon mudstone and some buff-colored 

sandstone. The upper sandstone units are commonly 

conglomeratic. The total Morrison Formation is about 

575 ft thick.

Lower Cretaceous Burro Canyon (?) Formation and 

Upper Cretaceous Dakota Sandstone, undivided (unit 

Kdb/ Sandstone and conglomeratic sandstone are 

characteristic of the Burro Canyon(?) Formation. A 

mudstone interval separates two thick sandstone 

sequences at a few localities; elsewhere the Burro 

Canyon(?) is composed only of sandstone. The Burro 

Canyon name is queried because detailed stratigraphic 

studies that would tie these sandstone sequences to those 

of the Burro Canyon at its type locality in western 

Colorado have not been completed. The Burro 

Canyon(?) Formation is as much as 140 ft thick.

Rocks of the Dakota Sandstone are sandstone, 

shale, and locally conglomeratic sandstone. The 

sandstone and shale are commonly carbonaceous. The 

Dakota Sandstone forms the cap rock of the mesas and 

steep canyon walls over most of the study area. The 

upper part of the Dakota is absent over parts of the study 

area. Total thickness is as much as 200 ft in the study 

area.

Upper Cretaceous Mancos Shale (unit Kmu^. The 

Mancos Shale consists of five units in the study area; the 

entire Mancos is not present. The Hartland Shale Beds, 

at the base, consist of gray, fossiliferous shale, bentonite 

beds, and minor amounts of sandstone. The fossils are 

equivalent in age to the Hartland Shale Member of the 

Greenhorn Limestone of eastern Colorado and Kansas 

(Sageman, 1985). Overlying the Hartland Shale Beds are 

the Bridge Creek Limestone Beds, which are composed 

primarily of limestone at the base and interbedded

Rio Chama Wilderness Study Area C5
106°45' 106°37'30"

3B°30'

2 MILES

Figure 2. Geologic map of the Rio Chama Wilderness Study Area, Rio Arriba County, N. Mex. Geology mapped 1985-86 by 

J.L. Ridgley; prospect and adit from Schreiner (1986). Base from U.S. Geological Survey 1:24,000, Navajo Peak, 1953; El Vado, 

1983.

limestone and shale in the upper part. These beds are Juana Lopez Member and middle shale member. Both

commonly used as a regional datum for correlation. The members are composed primarily of shale. The Mancos

lower shale member overlies the Bridge Creek is about 625 ft thick in the study area.

Limestone Beds and is composed mainly of shale and Quaternary surficial deposits (units Qal, Qg, and

siltstone. Overlying the lower shale member are the Qt^. Quaternary deposits include unconsolidated 

C6 Mineral Resources of Wilderness Study Areas Northern New Mexico
Qal Qg Qt

CORRELATION OF MAP UNITS

^ 

Holocene

Pleistocene(?)

QUATERNARY

Unconformity

Upper Cretaceous 

Lower Cretaceous

Upper and Middle 

Jurassic

CRETACEOUS

JURASSIC

Qal 

Qg 

Qt 

Kmu 

Kdb

Ju

LIST OF MAP UNITS 

Alluvium (Holocene)

Gravels (Holocene and Pleistocene?) 

Talus (Holocene or Pleistocene?) 

Mancos Shale (Upper Cretaceous)

Dakota Sandstone (Upper Cretaceous) and Burro Canyon(?) 

Formation (Lower Cretaceous), undivided

Morrison Formation (Upper Jurassic), Wanakah Formation 

and Entrada Sandstone (Middle Jurassic), undivided

Contact Dashed where approximately located

Fault Dashed where approximately located, dotted where 

concealed; bar and ball on downthrown side

Uranium adit 

Uranium prospect 

Warm spring

Anticline Showing trace of axial plane and plunge; approximately located

Syncline Showing trace of axial plane and plunge; approximately located

alluvium of streams that are of Holocene age, gravels of 

Holocene and Pleistocene(?) age, and talus of Holocene 

or Pleistocene(?) age.

Geochemistry

The U.S. Geological Survey did not conduct a 

geochemical survey of the study area; some samples were 

taken within the study area during geochemical sampling 

in 1980-1981 of the adjacent Chama River Canyon 

Wilderness and Roadless Areas. As part of this earlier 

survey, stream-sediment and panned-concentrate 

samples were collected from two first-order drainages 

inside the Rio Chama Wilderness Study Area. Sample 

sites were in the drainage adjacent to the east side of 

Navajo Peak and the drainage from Lobo Canyon 

(Ridgley, 1986, samples 221 and 223). Samples were also 

collected from drainages just to the south of the study

area and within the Chama River Canyon Wilderness. 

First-order drainages just to the west of the Rio Chama 

Wilderness Study Area and within a proposed U.S. 

Forest Service roadless area were also sampled (Ridgley, 

1986, samples 215-217,220). All samples were collected 

upstream from the stream mouth to avoid contamination 

during flood stage of the Rio Cebolla and the Rio 

Chama. In addition to the stream-sediment samples, 

three rock samples were collected from the Morrison and 

Burro Canyon(?) Formations near Aragon Spring, just 

west of the northern part of the study area (Ridgley, 

1986, samples 128-130).

The rock, stream-sediment, and pannedconcentrate samples were analyzed by U.S. Geological 

Survey laboratories by the six-step semiquantitative spectrographic analysis technique (Matooka and Grimes, 

1976). Additional details on analytical methods and the 

chemical analyses are found in Ridgley (1986). The 

panned-concentrate sample from Lobo Canyon (sample 

223), within the study area, contained anomalous 

concentrations of copper (70 ppm); the drainage next to 

Navajo Peak yielded no anomalous values. In the 

drainages adjacent to the study area, anomalous 

concentrations of beryllium (5 ppm), manganese (1,500 

ppm), and cobalt (200 ppm) were detected in streamsediments from Long Canyon; a weakly anomalous 

concentration of uranium (5 ppm) was detected in 

stream sediments from Berry Canyon; and an anomalous 

concentration of manganese (1,000 ppm) was detected in 

a sandstone sample from the upper part of the Morrison 

Formation near Aragon Spring. None of the anomalies 

that were detected is considered to be indicative of 

mineral resources.

Geophysics

Aeroradiometric Study

Aerial gamma-ray spectroscopy is a technique that 

provides estimates of the near-surface (0-20 in. depth) 

concentrations of percent potassium (K), parts per 

million equivalent uranium (eU), and parts per million 

equivalent thorium (eTh). Aerial gamma-ray spectroscopic data for New Mexico have been compiled and 

processed to produce a series of 1:1,000,000 maps 

(Duval, 1983). The Rio Chama Wilderness Study Area 

has overall low radioactivity, the concentrations of 

radioactive elements being 0.9-1.1 percent K, 1.7-2.6 

ppm eU, and 6.5-8 ppm eTh. No anomalies were 

detected within or near the study area (J.S. Duval, 

written commun., 1986).

Aeromagnetic and Gravity Study

Gravity and aeromagnetic data were obtained from 

existing files as part of the mineral resource evaluation of 

the Rio Chama Wilderness Study Area. These data

Rio Chama Wilderness Study Area C7
provide information on general surface and subsurface 

distribution of rock masses and structural features.

Aeromagnetic Data

The aeromagnetic data are from a compilation of 

magnetic data for the state of New Mexico by Cordell 

(1984) and are shown in figure 3. The magnetic survey of 

the Rio Chama area was flown at 1,000 ft above ground 

level, and the flight lines were oriented north-south at a 

spacing of approximately 1 mi apart. Magnetic values 

vary from an average of about -70 nT (nanoteslas) over 

the study area to 60 nT just northeast of the area. The 

only notable anomaly in the area is the symmetrical 

magnetic high northeast of the study area. This anomaly 

probably indicates a structural high in the basement rock 

or an intrabasement susceptibility contrast between the 

nonmagnetic, flat-lying Cretaceous, Jurassic, and older 

Mesozoic and Paleozoic sedimentary rocks and the more 

magnetic crystalline basement rocks.

Gravity Data

Gravity data were obtained from a file collected by 

the U.S. Department of Defense (National Oceanic and 

Atmospheric Administration National Geophysical Data 

Center). The 1967 gravity formula (International 

Association of Geodesy, 1967) and a reduction density of 

2.67 g/cm3 (grams per cubic centimeter) were used to 

compute the Bouguer gravity anomaly values. Using the 

method of Plouff (1977), we corrected for terrain by 

computer for a distance of 100 mi from each station. The 

results are shown in figure 4. Although the study area 

includes only one gravity station, there were enough 

stations in the surrounding area to get a general regional 

signature of the gravity. The Bouguer values decrease to 

the northwest from -252 mGal (milligals) at the 

southeast corner of the study area to -260 mGal at the 

northwest corner, indicating a thickening of the 

sedimentary section toward the San Juan Basin.

Mineral and Energy Resources

Oil and Gas

The Dakota Sandstone and Burro Canyon(?) 

Formation, which yield oil in the eastern part of the San 

Juan Basin, are at the surface over most of the study area 

and thus would not contain oil or gas resources. 

Pennsylvanian strata, which have yielded oil and gas in 

the western part of the San Juan Basin, have not been 

sufficiently drilled to determine the potential for the 

existence of favorable facies and structural and stratigraphic traps at depth. Several structural traps (parts of

anticlines) occur in the study area (Ridgley, in press); 

however, these structural features are cut by numerous 

faults that could serve as conduits for migration of oil and 

fresh water.

Fitter (1958) reported that at the Skelly Oil 

Company No. 1 Crittenden drill hole, spudded in 1948, 

shows of oil were found in the Pennsylvanian rocks at two 

horizons. The well was drilled 14 mi south of the study 

area in sec. 36, T. 24 N., R. 1 E. Lithologic data from the 

drill hole indicated that the Pennsylvanian strata 

consisted of gray, fine- to medium-grained crystalline 

limestone, gray and maroon shale, and arkosic sandstone 

(Fitter, 1958).

Lookingbill (1955) reported a thick sequence 

(1,864 ft) of limestone and black shale of possible 

Pennsylvanian age in a dry oil-test well, Hall No. 1 Silver, 

which was drilled 3 mi west of the study area, on Gallina 

Mountain. At this locality the presence of fresh water at 

three horizons suggested that if hydrocarbons had been 

present they would have been flushed away. This thick 

sequence of Pennsylvanian rocks does not appear to be 

present at South El Vado dome, about 4 mi north of the 

study area (Foster and Stipp, 1961), where the Precambrian was encountered at 1,815 ft in the Helmerich and 

Payne No. 1 El Vado. This oil-test hole was spudded in 

the Dakota Sandstone. The limestone and black shale of 

the Pennsylvanian rocks are possible reservoirs or source 

rocks. The thickness of the Pennsylvanian rocks in the 

study area is not known.

According to Ryder (1983), in an analysis of oil and 

gas potential of some wilderness lands in northern New 

Mexico, Pennsylvanian reservoir rocks in the Chama 

Basin are very susceptible to flushing by fresh water. This 

is likely due to the deep dissection of the region, exposing 

potential reservoirs at the surface, and the proximity of 

the strata to uplifted margins of the basin. For these 

reasons he assigned a low potential for hydrocarbon 

resources in the area he evaluated. The Rio Chama 

Wilderness Study Area is north of the area Ryder 

evaluated. Although favorable structural traps occur in 

the study area (Landis and Dane, 1967; Ridgley, 1983), 

the lack of any oil or gas production and dry holes drilled 

on structural features directly to the north, where greater 

overburden exists, support the premise that there may 

have been flushing of the rocks. For these reasons, the 

resource potential for oil and gas is rated as low, with a 

certainty level of B (fig. 1), throughout the study area.

Industrial Minerals

Clinoptilolite

The zeolite mineral clinoptilolite has been found as 

aggregates visible to the unaided eye in mudstone and as 

solid beds of altered tuff in approximately 20-30 percent

C8 Mineral Resources of Wilderness Study Areas Northern New Mexico
106°37'30"

APPROXIMATE BOUNDARY OF THE

RIO CHAMA WILDERNESS STUDY AREA

(NM-010-059)

Figure 3. Map showing lines of magnetic intensity in the Rio Chama Wilderness Study Area, Rio Arriba County, N. Mex. 

Contour interval 20 nanoteslas.

of the Brushy Basin Member of the Morrison Formation 

in the Chama River Canyon Wilderness, south of the 

study area (Christine Turner-Peterson, oral commun., 

1985). The clinoptilolite-bearing fades of the Brushy 

Basin, which is characterized by distinctive orange 

outcrops, is not present in the study area. The 

clinoptilolite-bearing facies changes laterally into the 

analcime-bearing facies of the Brushy Basin Member 

approximately 5 mi south of the study area. Thus, the 

resource potential for clinoptilolite is low, with a 

certainty level of C (fig. 1), throughout the study area.

Gypsum

Gypsum, as much as 105 ft thick (Ridgley, 1983), 

occurs in the upper part of the Todilto Limestone 

Member of the Wanakah Formation in the Chama River

Canyon Wilderness south of the study area. Although the 

Todilto occurs in the study area, no gypsum is exposed. 

Gypsum does crop out adjacent to the southern 

boundary of the study area. Results of detailed surface 

and subsurface reconnaissance of the Todilto by Ridgley 

(unpub. data, 1984) show that the gypsum has an 

irregular distribution in the Chama Basin and eastern 

part of the San Juan Basin and in the study area. The 

distribution of the gypsum facies is controlled by 

underlying topographic relief on the top of the Entrada 

sand dunes, which exerted control on lateral and vertical 

salinity gradients in the marine waters from which the 

Todilto was precipitated (Ridgley, 1984). The lower half 

of the gypsum facies is commonly interbedded with 

limestone; the upper half of the gypsum facies is nearly 

pure gypsum in most places.

Rio Chama Wilderness Study Area C9
106°45' 

36° 

32' 

30"

106°42'30" 106°40'

,6P

APPROXIMATE BOUNDARY OF THE

RIO CHAMA WILDERNESS STUDY AREA

(NM-010-059)

1 MILE

Figure 4. Map showing Bouguer gravity of the Rio Chama 

Wilderness Study Area , Rio Arriba County, N. Mex. Contour 

interval 2 milligals; dot, gravity station.

The gypsum in the Todilto Limestone Member has 

been mined for years at White Mesa, San Ysidro, 

N. Mex., and has been extracted locally at Cerro Blanco, 

near Gallina. Both areas are more than 10 mi south of 

the study area. The potential for gypsum resources in the 

subsurface of the study area is moderate, with a certainty 

level of C (fig. 1).

Limestone

Pennsylvanian limestone is projected to be present 

only in the subsurface. The nearest Pennsylvanian 

outcrops are along the southern margin of the Chama 

Basin. In this area the limestone is hard and dense and 

can be broken into fragments suitable for road metal. 

The U.S. Forest Service has several quarries from which 

they mine the limestone for road metal used on National 

Forest roads. Drilling at Gallina Mountain, 

approximately 3 mi to the west of the study area, 

indicated an 1,815-ft Pennsylvanian section of limestone 

and shale. Thus, Pennsylvanian limestone underlies the 

study area; and the mineral resource potential for 

undiscovered limestone resources in the subsurface is 

moderate, with a certainty level of C (fig. 1), throughout 

the study area.

Metals

The limited geochemical sampling by the USGS in 

1980-81 dfd not indicate the presence of any metallic

resources in the study area. One of the pannedconcentrate samples collected by the USBM had 

anomalous amounts of silver; the rest of the samples had 

only slightly elevated values of manganese, tin, vanadium, 

and zinc (Schreiner, 1986). The samples were not 

collected from first-order drainages, but were taken from 

gravel bars along the Rio Chama, which is greater than a 

first- or second-order stream; thus, the material could 

have come from anywhere upstream. None of these 

elements was detected in anomalous concentrations in 

samples collected by the USGS in 1980-81 from firstorder drainages in the same area. The mineral resource 

potential for silver, manganese, tin, vanadium, zinc, and 

all other metals is considered to be low, with a certainty 

level of B (fig. 1).

Uranium

There are small uranium prospects near the study 

area boundary (figs. 1, 2; Schreiner, 1986; Light, 1982). 

At these prospects the uranium is locally confined to 

sandstone and (or) bone fragments. Throughout the 

Colorado Plateaus all members of the Morrison 

Formation, the Todilto Limestone Member of the Wanakah Formation, the Burro Canyon(?) Formation, and the 

Dakota Sandstone may host uranium occurrences or 

deposits. No radioactivity was detected through the aeroradiometric survey, nor were any prospects found in the 

study area. During the 1940's and early 1950's the 

Colorado Plateaus were extensively prospected for 

uranium under a program supported by the U.S. Atomic 

Energy Commission, and no uranium occurrences were 

noted in the study area. The Anaconda Company also 

extensively explored and drilled for uranium in the 1970's 

in the areas to the north, east, and south of the study 

area. The only uranium-mineralized rock encountered 

was in Martinez Canyon near Ghost Ranch, about 10 mi 

southeast of the study area (Saucier, 1974).

Although no uranium anomalies were detected in 

the study area, the Morrison, Wanakah, and Burro 

Canyon(?) Formations and the Dakota Sandstone 

contain sandstone or limestone of a composition similar 

to that which is associated with favorable uranium host 

rocks in these formations elsewhere on the Colorado 

Plateaus. The mineral resource potential for uranium is 

considered to be low, with a certainty level of B (fig. 1), 

on the basis of the lack of anomalies in the study area and 

the proximity of the study area to a deep, dissected 

canyon that could permit the migration of oxidizing 

ground water that could remove any concentration of 

uranium from the rocks.

Geothermal Energy

No warm springs or evidence for buried intrusions 

was found in the study area. However, two warm springs 

were recently identified by personnel from the U.S.

C10 Mineral Resources of Wilderness Study Areas Northern New Mexico
Forest Service and the BLM (Bruce Sims, oral commun., 

1987; Tom Mottl, oral commun., 1987) about 0.25 mi 

north of the study area at Ward ranch (fig. 2). One 

spring, shown on the El Vado 7 ^-minute quadrangle, is 

on the west side of the river; the other spring is on the 

east side of the river. Both springs are associated with a 

fault near the crest of the Rio Chama anticline that cuts 

the west limb. Warm water, about 90-100 °F, emanates 

from the springs; no chemical analyses are available. The 

source of the heated water is not known. The mineral 

resource potential for geothermal energy is low, with a 

certainty level of B based on the lack of evidence for 

geothermal activity in the study area and the presence of 

warm springs near the study area.

Recommendations for Future Work

The resource potential for oil and gas in the vicinity 

of the study area could be assessed more accurately if 

more detail were known about the underlying 

Pennsylvanian rock units.

Detailed sampling and appropriate chemical 

analysis of individual tuff beds in the Brushy Basin 

Member of the Morrison Formation would be necessary 

to see if rock units contain anomalous amounts of 

elements of potential economic interest.

Drilling would help delineate the thickness, purity, 

and extent of the gypsum resources.

Analysis of the regional gravity and magnetic data 

did not reveal reasons to suggest that mineral resources 

occur in the study area. However, detailed geophysical 

surveys might provide information on subsurface stratigraphy that would aid in the definition of structural traps 

or offer prospective exploration targets.

REFERENCES CITED

Cordell, Lindrith, 1984, Composite residual total intensity 

aeromagnetic map of New Mexico: National Oceanic and 

Atmospheric Administration Geothermal Resources of 

New Mexico, Scientific Map Series, scale 1:500,000.

Duval, J.S., 1983, Composite color images of aerial gamma-ray 

spectrometric data: Geophysics, v. 48, p. 722-735.

Fitter, F. L., 1958, Stratigraphy and structure of the French 

Mesa area, Rio Arriba County, New Mexico; 

Albuquerque, University of New Mexico, M.S. thesis, 

71 p.

Foster, R.W., and Stipp, T.F., 1961, Preliminary geologic and 

relief map of the Precambrian rocks of New Mexico: New 

Mexico Bureau of Mines and Mineral Resources Circular 

57, 37 p.

Goudarzi, G.H., compiler, 1984, Guide to preparation of 

mineral survey reports on public lands: U.S. Geological 

Survey Open-File Report 84-787, 42 p.

Hilpert, L.S., 1969, Uranium resources of northwestern New 

Mexico: U.S. Geological Survey Professional Paper 603, 

166 p.

International Association of Geodesy, 1967, Geodetic 

reference System, 1967: International Association of 

Geodesy Special Publication No. 3, 116 p.

Landis, E.R., and Dane, C.H., 1967, Geologic map of the Tierra 

Amarilla quadrangle, Rio Arriba County, New Mexico: 

New Mexico Bureau of Mines and Mineral Resources, 

New Mexico Institute of Mining and Technology, 

Geologic Map 19, scale 1:62,500; pamphlet, 16 p.

Light, T.D., 1982, Mineral resources investigation of the 

Chama River Wilderness and contiguous RARE II 

further planning area, Rio Arriba County, New Mexico: 

U.S. Bureau of Mines Open File Report MLA 108-82, 

13 p.

Lookingbill, J.L., 1955, Geology of the Gallina uplift, Rio 

Arriba County, New Mexico: Compass, v. 33, no. 1, 

p. 40-54.

Matooka, J.M., and Grimes, D.J., 1976, Analytical precision of 

one-sixth order semi-quantitative spectrographic 

analyses: U.S. Geological Survey Circular 738, 25 p.

Plouff, Donald, 1977, Preliminary documentation for a 

FORTRAN program to compute gravity terrain 

corrections based on topography digitized on a 

geographic grid: U.S. Geological Survey Open-File 

Report 77-535.

Ridgley, J.L., 1983, Geologic map of the Chama River Canyon 

Wilderness and contiguous roadless area, Rio Arriba 

County, New Mexico: U.S. Geological Survey 

Miscellaneous Field Studies Map MF-1523-C, scale 

1:48,000.

____ 1984, Paleogeography and facies distribution of the 

Todilto Limestone and Pony Express Limestone member 

of the Wanakah Formation, Colorado and New Mexico: 

Geological Society of America Abstracts with Programs, 

v. 16, no. 4, p. 252.

____ 1986, Geochemical map of the Chama River Canyon 

Wilderness and contiguous roadless area, Rio Arriba 

County, New Mexico: U.S. Geological Survey 

Miscellaneous Field Studies Map MF-1523-D.

____ 1987a, Mid-Jurassic tectonic control on deposition and 

isolation of upper clastic member of the Wanakah 

Formation, Chama Basin, New Mexico: Geological 

Society of America Abstracts with Programs, v. 19, no. 5, 

p. 329.

____ 1987b, Surface to subsurface cross-sections showing 

correlation of the Dakota Sandstone, Burro Canyon(?) 

Formation, and upper part of the Morrison Formation in 

the Chama El Vado area, Chama Basin, Rio Arriba 

County, New Mexico: U.S. Geological Survey 

Miscellaneous Field Studies Map MF-1496-D. 

. in press, Geologic map of the Rio Chama Wilderness

Study Area, Rio Arriba County, New Mexico: U.S. 

Geological Survey Miscellaneous Field Studies Map 

MF-2046, scale 1:24,000.

Ridgley, J.L., and Light, T.D., 1983, Mineral resource potential 

map of the Chama River Canyon Wilderness and 

contiguous roadless area, Rio Arriba County, New

Rio Chama Wilderness Study Area C11
Mexico: U.S. Geological Survey Miscellaneous Field 

Studies Map MF-1523-B, scale 1:48,000, includes 

pamphlet, 8 p.

Ryder, R.T., 1983, Petroleum potential of wilderness lands in 

New Mexico: U.S. Geological Survey Circular 902-1, 29

PSageman, B.B., 1985, High-resolution stratigraphy and paleobiology of the Hartland Shale Member Analysis of an 

oxygen-deficient epicontinental sea, in Pratt, L.M., 

Kauffman, E.G., and Zelt, F.B., eds., Fine-grained 

deposits and biofacies of the Cretaceous western interior 

seaway Evidence of cyclic sedimentary processes: 

Society of Economic Paleontologists and Mineralogists,

Field Trip Guidebook No. 4, Midyear Meeting, August 

1985, Golden, Colo., p. 110-121.

Saucier, A.E., 1974, Stratigraphy and uranium potential of the 

Burro Canyon Formation in the southern Chama Basin, 

New Mexico: New Mexico Geological Society, 25th Field 

Conference, 1974, Guidebook, p. 211-217.

Schreiner, R.A., 1986, Mineral investigation of a part of the Rio 

Chama Wilderness Study Area, Rio Arriba County, New 

Mexico: U.S. Bureau of Mines Open File Report MLA 

38-86, 10 p.

U.S. Bureau of Mines and U.S. Geological Survey, 1980, 

Principles of a resource/reserve classification for 

minerals: U.S. Geological Survey Circular 831, 5 p.

C12 Mineral Resources of Wilderness Study Areas Northern New Mexico
APPENDIX
DEFINITION OF LEVELS OF MINERAL RESOURCE POTENTIAL 

AND CERTAINTY OF ASSESSMENT

Definitions of Mineral Resource Potential

LOW mineral resource potential is assigned to areas where geologic, geochemical, and geophysical characteristics define a geologic environment in which the existence of resources is unlikely. This broad 

category embraces areas with dispersed but insignificantly mineralized rock as well as areas with few 

or no indications of having been mineralized.

MODERATE mineral resource potential is assigned to areas where geologic, geochemical, and geophysical 

characteristics indicate a geologic environment favorable for resource occurrence, where interpretations 

of data indicate a reasonable likelihood of resource accumulation, and (or) where an application of 

mineral-deposit models indicates favorable ground for the specified type(s) of deposits.

HIGH mineral resource potential is assigned to areas where geologic, geochemical, and geophysical characteristics indicate a geologic environment favorable for resource occurrence, where interpretations of 

data indicate a high degree of likelihood for resource accumulation, where data support mineral-deposit 

models indicating presence of resources, and where evidence indicates that mineral concentration has 

taken place. Assignment of high resource potential to an area requires some positive knowledge that 

mineral-forming processes have been active in at least part of the area.

UNKNOWN mineral resource potential is assigned to areas where information is inadequate to assign low, 

moderate, or high levels of resource potential.

NO mineral resource potential is a category reserved for a specific type of resource in a well-defined 

area.

Levels of Certainty

U/A

UNKNOWN

POTENTIAL

H/B

HIGH POTENTIAL

M/B 

MODERATE POTENTIAL

L/B

LOW

POTENTIAL

H/C

HIGH POTENTIAL

M/C 

MODERATE POTENTIAL

L/C

LOW

POTENTIAL

H/D

HIGH POTENTIAL

M/D 

MODERATE POTENTIAL

L/D

LOW POTENTIAL

N/D

NO POTENTIAL

u 

cc

o

LU 

LU

B C 

LEVEL OF CERTAINTY

A. Available information is not adequate for determination of the level of mineral resource potential.

B. Available information suggests the level of mineral resource potential.

C. Available information gives a good indication of the level of mineral resource potential.

D. Available information clearly defines the level of mineral resource potential.

Abstracted with minor modifications from:

Taylor, R. B., and Steven, T. A., 1983, Definition of mineral resource potential: Economic Geology,

v. 78, no. 6, p. 1268-1270. 

Taylor, R. B., Stoneman, R. J., and Marsh, S. P., 1984, An assessment of the mineral resource potential

of the San Isabel National Forest, south-central Colorado: U.S. Geological Survey Bulletin 1638, p.

Goudarzi, G. H., compiler, 1984, Guide to preparation of mineral survey reports on public lands: U.S. 

Geological Survey Open-File Report 84-0787, p. 7, 8.
RESOURCE/RESERVE CLASSIFICATION

IDENTIFIED RESOURCES

Demonstrated

Measured Indicated

Inferred

UNDISCOVERED RESOURCES

Probability Range

 (or) 

Hypothetical i Speculative

ECONOMIC

MARGINALLY 

ECONOMIC

SUBECONOMIC

Reserves Inferred Reserves

Marginal Reserves

Demonstrated 

Subeconomic Resources

Inferred 

Marginal Reserves

Inferred

Subeconomic

Resources

+

Major elements of mineral resource classification, excluding reserve base and inferred reserve base. Modified from 

U. S. Bureau of Mines and U. S. Geological Survey, 1980, Principles of a resource/reserve classification for 

minerals: U. S. Geological Survey Circular 831, p. 5.
GEOLOGIC TIME CHART 

Terms and boundary ages used in this report

EON

Phanerozoic

Proterozoic

Archean 

pre-Arc

ERA

Cenozoic

Mesozoic

Paleozoic

Late Proterozoic

Middle Proterozoic

Early Proterozoic

Late Archean

Middle Archean

Early Archean 

hean 1

PERIOD

Quaternary

Neogene 

Subperiod

Tertiary 

Paleogene 

Subperiod

Cretaceous

Jurassic

Triassic

Permian

Pennsylvanian 

Carboniferous

Periods 

Mississippian

Devonian

Silurian

Ordovician

Cambrian

__ 3SOO ?_ -

EPOCH

Holocene

Pleistocene

Pliocene

Miocene

Oligocene

Eocene

Paleocene

Late 

Early

Late 

Middle 

Early

Late 

Middle 

Early

Late

Early

Late 

Middle 

Early

Late 

Early

Late 

Middle 

Early

Late 

Middle 

Early

Late 

Middle 

Early

Late

Middle 

Early

 -

BOUNDARY AGE 

IN 

MILLION YEARS

-0.010

- 1.7 

- 5

- 24

ID

- 55

- 66

- 96

1 Oo

-*> 240

- 290 

A . oin

_ "Jen

- 410

- 500 

- *v 570 1

- 900 

- 1600

- 2500

-3000 

- 3400

1 Rocks older than 570 m.y. also called Precambrian, a time term without specific rank.

2 Informal time term without specific rank.

U.S. GOVERNMENT PRINTING OFFICE:1988-573-047/66043