I 

Coalfields of New Mexico: 

Geology and Resources 

U.S. GEOLOGICAL SURVEY BULLETIN 1972 

Prepared in cooperation with the New Mexico 

Bureau of Mines and Mineral Resources 
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Ave. 
Coalfields of New Mexico: 

Geology and Resources 

Edited by CAROL L. MOLNIA, DANIEL A. JOBIN, 

and JOSEPH T. O'CONNOR 

U.S. Geological Survey, and 

FRANK E. KOTTLOWSKI 

New Mexico Bureau of Mines and Mineral Resources 

Prepared in cooperation with the New Mexico 

Bureau of Mines and Mineral Resources 

Thickness and distribution of coal beds, 

estimates of the resources, and descriptions 

of methods used for calculating resources 

U.S. GEOLOGICAL SURVEY BULLETIN 1972 
U.S. DEPARTMENT OF THE INTERIOR 

MANUEL LUJAN, JR., Secretary 

U.S. GEOLOGICAL SURVEY 

Dallas L. Peck, Director 

Any use of trade, product, or firm names in this publication is for descriptive 

purposes only and does not imply endorsement by the U.S. Government. 

UNITED STATES GOVERNMENT PRINTING OFFICE: 1991 

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 

Coalfields of New Mexico: geology and resources I edited by Carol L. Molnia ... 

[et al.]. 

p. em. - (U.S. Geological Survey bulletin ; 1972) 

"Prepared in cooperation with the New Mexico Bureau of Mines and Mineral 

Resources." 

Includes bibliographical references. 

Supt. of Docs. no.: I 19.3:1972 

1. Coal-New Mexico. 2. Coal-Geology-New Mexico. I. Molnia, Carol 

L. II. New Mexico. Bureau of Mines and Mineral Resources. Ill. Series. 

QE75.B9 no. 1972 

[TN805.N6] 

557.3 s-dc20 91-11586 

[553.2'4'09789] CIP 
PREFACE 

Calculation of the coal resources of New Mexico is an important part of the 

evaluation of State, Federal, and privately owned energy potential. As such, it bears 

directly on the economic growth and development potential of many areas within the 

State. To be of most use, coal resource data must accurately reflect the quantity of coal 

present and its accessibility to development. In this report, the State Geologist of New 

Mexico and the U.S. Geological Survey describe the primary geologic factors that 

influence the quantity and accessibility of the coal resources of New Mexico. The report 

gives greatest emphasis to the San Juan basin, an area that has provided much of the 

publicly available data and that retains a large portion of present coal development 

interest. 

The chapters that follow include brief geological descriptions of New Mexico's 

coalfields, current estimates of the amount of coal resources present in each of them, 

analyses of the probable accuracy of such estimates, determinations of thickness of known 

and projected coal beds or coal zones, and discussions of the geologic factors that affect 

the coal resources. 

The authors have assessed the current state of knowledge of the coal resources of 

New Mexico, pointing out inadequacies in the data base and understanding of the 

resources. Though our primary data source has been the National Coal Resources Data 

System of the U.S. Geological Survey, we have also used data from other sources to make 

this report as complete as possible. 

This report is a product of many people's efforts. Besides the authors and editors, 

other major contributors from the U.S. Geological Survey include Dorsey Blake, for 

guidance in computer operations; Courteney Williamson, for data entry, validation, and 

graphics generation; Noreen H. Rega, for data base development, validation, and resource 

calculation; Mary E. Lemaster and Patricia T. Kerr, for resource calculation and data 

validation; and Andre D. Bush and Paula M. Washington, for digitizing and boundary data 

processing. Margaret F. Johnson and Brian R. Schachte helped with new record 

processing and provided graphics display support; Frank E. Andreani helped with data 

formatting, processing, and updating. 

Assistance was also given by Laura N.R. Roberts, in computer software use; Jean 

K. Dillinger, Annabel B. Olson, and James E. Fassett, in San Juan basin geology; and 

Margaret S. Ellis, in data validation. Many of the personnel above helped with drafting, 

as did Arthur C. Clark. J. Daniel Cathcart photographed the illustrations. The assistance 

of the secretarial staff in the preparation of the text is also appreciated. 

The authors of chapter E were aided by contributions from other members of the 

New Mexico Bureau of Mines and Mineral Resources, particularly the drafting of Michael 

Wooldridge and the useful suggestions of Orin J. Anderson and JoAnn C. Osburn. 

CONTENTS 

[Letters designate the chapters] 

(A) Geologic framework and major coal-bearing formations of the San Juan basin, by 

Morris W. Green, James W. Mytton, Dorothy T. Sandberg, and 

Nancy K. Gardner 1 

(B) Coal resources of the San Juan basin, by Laura R.H. Biewick, 

Antoinette L. Medlin, Judy F. Hunter, and Kathleen K. Krohn 15 

(C) Coal resource estimation in the San Juan basin using geostatistical methods, by 

Lewis W. Boger, Jr., and Antoinette L. Medlin 35 

(D) Geology and coal resources of the Raton coalfield, by Charles L. Pillmore 45 

(E) Geology and coal resources of New Mexico's small coalfields, by 

Frank W. Campbell, Gretchen K. Hoffman, Frank E. Kottlowski, and 

Brian W. Arkell 69 

Contents V 
METRIC CONVERSION FACTORS 

Data in this volume are reported in customary inch-pound units because the metric system is not currently in use 

by the coal industry of the United States. Readers wishing to convert measurements to the International System 

of units (SI) may use the following factors: 

VI Contents 

U.S. customary unit 

Acre 

Acre-foot 

British thermal unit (Btu) 

Btu/lb 

Foot (ft) 

Inch (in.) 

Mile (mi) 

Pound (lb) 

Short ton (ton) 

Square miles (mi2

) 

Ton/acre-foot 

Sl conversion 

=4,046.87 square meters 

= 1,233.49 cubic meters 

=1,055.056 joules 

=2,326 joules per kilogram 

=0.3048 meters 

=0.0254 meters 

=1.609 kilometers 

=0.4536 kilograms 

=0.9072 metric tons 

=2.59 square kilometers 

=0. 7355 kilograms per cubic meter 
Chapter A 

Geologic Framework and Major 

Coal-Bearing Formations of the 

San Juan Basin 

By MORRIS W. GREEN, JAMES W. MYTTON, 

DOROTHY T. SANDBERG, and NANCY K. GARDNER 

Upper Cretaceous strata preserved in a 

Laramide-age structural basin host 

New Mexico's largest coal deposits 

U.S. GEOLOGICAL SURVEY BULLETIN 1972 

COALFIELDS OF NEW MEXICO: GEOLOGY AND RESOURCES 
CONTENTS 

Abstract 3 

Introduction 3 

Location and geography 3 

Geologic setting 4 

Tertiary tectonic history and structure 4 

Paleozoic and Mesozoic tectonics and sedimentology 4 

Coal geology 8 

References cited 11 

FIGURES 

Al. Generalized geologic map of the San Juan basin and adjacent region S 

A2. Stratigraphic correlation chart of the San Juan basin 6 

A3. Diagrammatic cross section of the San Juan basin 7 

A4. Structure contour perspective on the base of the Dakota Sandstone, San Juan 

basin 8 

A5. Time-stratigraphic geologic section of Cretaceous rocks, San Juan basin 9 

A6. Fence diagrams showing stratigraphic rise of the Pictured Cliffs Sandstone across 

the San Juan basin 10 

A 7. Correlation of well logs showing lenticular nature of coal within the Fruitland 

Formation 12 

AS. Map of Upper Cretaceous formations, fields, areas, and mines containing 

strippable low-sulfur coal in the San Juan basin 13 

2 Contents 
Geologic Framework and Major Coal-Bearing 

Formations of the San Juan Basin 

By Morris W. Green, James W. Mytton, Dorothy T. Sandberg, and Nancy K. Gardner 

Abstract 

The San Juan basin, New Mexico's leading coal 

producing area, is a structural basin formed during the Laramide orogeny (80 to 40 million years ago). The basin lies 

primarily in northwest New Mexico but extends into southwest 

Colorado and northeast Arizona and covers an area of about 

26,000 square miles on the southeast margin of the Colorado 

Plateau physiographic province. Approximately 12,000 feet of 

Paleozoic and Mesozoic rocks are preserved in the basin. 

Cretaceous rocks, covered by Tertiary rocks in the central part 

of the basin, account for approximately one-half of the total 

thickness. The sedimentary interval in the basin locally hosts 

some of the Nation's most important deposits of coal, uranium, 

oil, and gas. Coal deposits occur in deltaic and coastal plain 

lithofacies throughout the Upper Cretaceous interval over 

relatively wide areas of the basin. The geographic location and 

stratigraphic position of coal beds of Cretaceous age in the San 

Juan basin were determined by the location of ancient 

shorelines along the western border of an epicontinental sea 

during Late Cretaceous time. Coal deposits originated from 

thick accumulations of organic matter (peat) in paludal 

environments on deltaic and lower coastal plains landward of 

shorelines. These environments formed as a result of periodic 

transgression and regression of the sea. The coal beds tend 

generally to be elongate to the northwest, parallel to the 

shoreline of the sea, which retreated progressively farther 

northeast with each successive major transgressive-regressive 

cycle of Late Cretaceous time. By the end of the Cretaceous 

Period, the sea had withdrawn from the region completely. 

The major Cretaceous coal-bearing units, in ascending 

order, are the Crevasse Canyon and Menefee Formations of the 

Mesaverde Group and the Fruitland Formation, which 

contains by far the largest coal resources in the San Juan basin. 

The thickness and distribution of coal in the Fruitland are 

inversely related to increase in thickness and stratigraphic rise 

of the underlying Pictured Cliffs Sandstone, especially where 

Manuscript approved for publication January 10, 1991. 

the Fruitland Formation intertongues with the upper part of the 

Pictured Cliffs. Typically, the coal beds are highly lenticular 

and difficult to correlate between drill holes; they can be 

correlated with certainty only where the holes are closely 

spaced. For these reasons, coal resource calculations can only 

be made for coal zones, rather than individual beds. Fields or 

areas in the San Juan basin where the Fruitland Formation is 

the current or potential coal producer are the Navajo field and 

Bisti and Star Lake areas. The remaining fields and areas are 

current or potential producers of coal from the Mesaverde 

Group and its equivalents, the most notable being the Gallup 

field. 

INTRODUCTION 

The San Juan basin of northwest New Mexico is the 

State's leading producer of coal. The basin's coal and its 

other energy mineral deposits--uranium, oil, and gasmake it one of the Nation's most important energy-rich 

sedimentary basins. The coal deposits, restricted in 

occurrence to the upper part of the basin sedimentary 

sequence in formations of Cretaceous age, supply fuel for 

the electric power industry throughout the southwestern 

United States. 

This report contributes to the joint effort by the U.S. 

Geological Survey and the New Mexico Bureau of Mines 

and Mineral Resources to provide a current overview of the 

geology and coal resources for the State of New Mexico. 

LOCATION AND GEOGRAPHY 

The San Juan basin is located primarily in northwest 

New Mexico. The northern and western areas of the basin 

extend, respectively, into neighboring southwest Colorado 

and northeast Arizona. The basin has dimensions of 

approximately 200 miles north to south and 130 miles east 

to west. The basin is irregularly circular and covers an area 

Framework and Major Coal-Bearing Formations of the San Juan Basin 3 
of about 26,000 square miles on the southeast margin of the 

Colorado Plateau physiographic province. 

The basin is bounded on all sides by mountain ranges: 

the Zuni Mountains on the south, the Nacimiento Mountains 

on the east, the La Plata and San Juan Mountains on the 

north in Colorado, and the Defiance uplift and the Chuska 

and Carizzo Mountains on the west near the Arizona-New 

Mexico border. The boundary of the basin is generally 

placed where the contact between Cretaceous rocks and 

underlying older rocks crops out near the flanks of the 

surrounding mountain ranges (fig. A 1 ). 

GEOLOGIC SETTING 

The San Juan basin, like other major present-day 

sedimentary basins in the Western Interior of the U.S., 

formed during the Laramide orogeny, which spanned the 

time interval between the Late Cretaceous and the middle 

Tertiary (80 to 40 million years ago). Approximately 12,000 

feet of rocks ranging in age from Cambrian to Cretaceous 

are preserved in the basin (fig. A2). Only Ordovician and 

Silurian age rocks are absent in the sequence. Cretaceous 

rocks, covered by Tertiary rocks in the central part of the 

basin, account for approximately one-half of the total 

thickness of the Paleozoic and Mesozoic sequence. 

The sedimentary interval in the basin locally hosts 

some of the Nation's most important deposits of coal, 

uranium, oil, and gas. Large uranium deposits occur in 

fluviolacustrine sandstone lithofacies of the Upper Jurassic 

Morrison Formation in the southern part of the basin. Oil, 

gas, and coal deposits occur in marine and coastal plain 

lithofacies throughout the Upper Cretaceous interval over 

much of the basin. 

TERTIARY TECTONIC HISTORY AND 

STRUCTURE 

The San Juan basin is a structural basin bounded by 

uplifts which formed as a result of Laramide crustal 

movements. The basin is asymmetrical north to south, 

having its deeper axial part in the north-northeastern portion 

(fig. A3). Because the basal Upper Cretaceous Dakota 

Sandstone is uniformly distributed and widespread in the 

basin, it is frequently used in depicting Laramide 

deformation (fig. A4). 

The San Juan basin apparently formed on an 

internally stable, subs.iding crustal block surrounded by 

crustal blocks which were uplifted to form the cores of 

adjacent mountain ranges. Differential subsidence and uplift 

of crustal blocks in the San Juan basin (as well as elsewhere 

in the Western Interior) apparently resulted from regional 

tectonic compression (crustal shortening) attendant to active 

4 Coalfields of New Mexico: Geology and Resources 

western plate margin tectonism associated with westward 

motion of the North American plate during the time of the 

Laramide orogeny. 

Locally, pre-Tertiary sedimentary rocks are sharply 

upturned against the flanks of surrounding uplifts. 

Structurally deformed sedimentary units strike parallel to 

the flanks of marginal uplifts and dip steeply basinwardlocally exceeding 80°-across the hinge lines separating 

the uplifted blocks and the subsided block. Basinward, the 

dip angle of the units abruptly decreases to 3°-5°. Local 

structural features, generally confined to the hinge areas of 

the basin, include normal faults and fault zones, small 

anticlines and synclines, structural platforms, and monoclines. With the exception of faults and fault zones, which 

trend normal to the flanks of uplifts, local structural features 

trend parallel to the basin margin. Relative to basin margin 

areas, the basin interior is essentially structureless, 

indicating relative stability of the crustal block flooring the 

basin. 

PALEOZOIC AND MESOZOIC 

TECTONICS AND SEDIMENTOLOGY 

Paleozoic and Mesozoic rocks are exposed in laterally 

continuous belts of outcrop around the margin of the San 

Juan basin. Underlying metasedimentary and plutonic rocks 

of the Precambrian basement are exposed in the cores of 

adjacent uplifts just outside the basin. The Paleozoic and 

Mesozoic formations in the basin were depositionally 

continuous with rocks of equivalent age contained in other 

Laramide basins of the Colorado Plateau and the Western 

Interior. These formations are products of sedimentary 

depositional systems that covered much larger areas than 

the Tertiary San Juan basin. 

The Paleozoic rocks in the basin were deposited on a 

relatively stable, tectonically inactive continental platform 

which constituted the western margin of the continent 

throughout the era. Westward, across the Paleozoic 

continental margin, terrestrial red beds of conglomerate, 

sandstone, and shale intertongue with marginal marine and 

marine limestone, siltstone, claystone, and evaporite 

deposits of the Paleozoic continental slope. Sediment source 

areas, including the ancestral Rocky Mountains, lay within 

the area of the present Western Interior of the continent. 

Mesozoic sediments of the Western Interior 

apparently were deposited differentially and sporadically 

through time from the Middle Triassic to the Late 

Cretaceous in a north-south elongate geosynclinal trough 

which spanned the entire Western Interior of the continent. 

Maximum development of the trough occurred during the 

Cretaceous. Sediment source areas lay west of the trough in 

the Cordilleran orogenic belt, which formed along the 

tectonically active western edge of the North American 

plate. Epeirogenic subsidence of the Western Interior 
Carrizo 

Mtns 

COLORADO 

NEW MEXICO 

·: T 

San Juan 

basin 

T 

EXPlANATION 

Quaternary basalt 

. T Tertiary sedimentary rocks ..................... ...,., ................. ...~ 

===-=-=-== ==~ISk_ :== Kirtland and Fruitland Formations =- Kkf =- -_-- -_-_ (Upper Cretaceous) -Shown as Kkf 

-=-=-=-=-= =-= Kf -=- where undifferentiated 

10 20 40 MILES 

• Albuquerque 

... ·. K~f ·: Menefee Formation (Upper Cretaceous) 

Kmfc Cleary Coal Member 

I-- K - Cretaceous rocks ~ undifferentiated 

\ pK - Pre-Cretaceous rocks 

' 

Geology not shown 

Figure A 1. Generalized geologic map of the San Juan basin and adjacent region showing distribution of Cretaceous and younger 

rocks. (Modified from Beaumont, 1982.) 

Framework and Major Coal-Bearing Formations of the San Juan Basin 5 
SOUTH 

Ma ZUNI UPLIFT OUTCROPS 

t-= EOCENE cr: 

~ PALEOCENE 

66 f-----1-------...j 

144 

208 

245 

286 

320 

360 

408 

438 

505 

570 

U) 

::::> 

0 

LU 

u 

~ UPPER w 

cr: 

u 

u 

U5 

<( 

cr: 

cr: 

::::> 

"""') 

u 

U5 

U) 

<( 

a: 

1-

z 

<( 

~ cr: 

LU 

ll... 

z 

z 

LU 

ll... 

u:i 

U) 

~ 

z 

<( 

z 

0 

> 

LU 

0 

z 

<( 

a: 

al 

::; 

<( 

u 

LOWER 

UPPER 

MIDDLE 

UPPER 

MIDDLE 

LOWER 

ATOKAN 

CHESTERIAN 

MERAMECIAN 

OSAGEAN 

UPPER 

MIDDLE 

LOWER 

SILURIAN 

ORDOVICIAN 

UPPER 

MIDDLE 

LOWER 

PRECAMBRIAN 

CREVASSE 

CANYON 

F1 

MADERA FM (SW) 

SAN JUAN BASIN SUBSURFACE 

NORTH 

SW COLORADO OUTCROPS 

SAN JOSE FM 760 m 

MENEFEE FM 0-670 m 

POINT LOOKOUT SS 0-90 m 

EL VADO SS MBR (NE\ 

TOCITO SS LENTIL .f , 

MANCOSSH 

240-700 m 

? 

Figure A2. Stratigraphic correlation chart of the San juan basin. (Modified from Molenaar, 1977; absolute time scale from 

Geological Society of America.) 

6 Coalfields of New Mexico: Geology and Resources 
., 

iil 

3 

~ 0 

... 

~ 

~ Q. 

~ 

.!!. 

0 

... 

~ 

= t!) 

~ 

... 

:r 

OQ 

., 

0 

3 

~ cs· 

:s 

Ill 

a 

:r 

t!) 

tl) 

~ 

= 

c 

~ 

= 8l 

:r 

....... 

~ z 

sw 

10,000 -

6000 -

4000 -

2000 -

-- SEA 

6 LEVEL 

~ 

~ -2000 

-4000 -

~000 J ~ ~~== -8000 -1 I I~ 

-10,000- sw 

c:: 

0 

> c::C:: 

coO 

u·.;:; 

a> co cnE 

C/)'-

coo >U. 

Q) 

u 

Albuquerque0 

\ 

\ 

\ 

\ 

\ 

\ 

\ 

\ 

\ 

..... 

~ 

ii: 

-...... \ '.... COLORADO 

-...... \ 

C/) 

~Q) 

:.=c:: 

u.8 

'Ocn 

a>-c '-c:: 

::leo ti(J) 

a: 

Precambrian 

basement 

Paleozoic rocks, undivided 

10 20 30 40 

I I I --~--1 

10 20 30 40 50 KILOMETERS 

VERTICAL EXAGGERATION X 21 

Figure AJ. Diagrammatic cross section of the San juan basin. (Modified fro~ Stone and others, 1983, fig. 1 0.) 

NE 

50 MILES 
ELEVATION, 

IN FEET 

12,000 ~ 8,000 

4,000 

0 

Figure A4. Structure contour perspective on the base of the Dakota Sandstone, San Juan basin. (Modified from 

Thaden and Zech, 1984.) 

apparently resulted from tectonic compression of the crust 

between the Cordilleran region and the interior craton east 

of the trough as the western edge of the plate collided with 

the developing Cordilleran magmatic arc of the orogenic 

belt. 

Western Interior trough sediments of Triassic age 

derived from Cordilleran source areas consist dominantly of 

conglomerate, sand, silt, and clay deposited in fluvial, 

lacustrine, and eolian depositional environments. These 

sediments were deposited in a number of large subbasins, 

which formed in the Western Interior as a result of 

differential subsidence of individual crustal blocks within 

the geosynclinal trough. On the northern and southern ends 

of the trough near the continental margins, Triassic and 

Jurassic continental sediments locally intertongue with 

marine sequences deposited during periodic marine 

invasions into the trough. 

During the Cretaceous Period, maximum subsidence 

of the trough and high sea levels, resulting from an increase 

in the rate of sea-floor spreading east of the continent, 

caused marine waters to cyclically invade the entire 

Western Interior from its northern and southern ends to 

form the Rocky Mountain seaway. During this period the 

rate of sedimentary infill of the trough was at its maximum. 

Sediments consisting of cobbles, sand, carbonaceous silt, 

clay, and peat were deposited on deltas, coastal plains, and 

offshore areas along the western margin of the seaway. 

Generally, coarse-grained terrestrial lithofacies in the west 

change into or intertongue with fine-grained, timeequivalent, marine lithofacies to the east across the trough. 

During this cycle of sedimentation, the Cretaceous shoreline 

underwent at least five major transgressions and regressions 

(Molenaar, 1983). 

Climatic conditions during the period of Cretaceous 

deposition were conducive to the luxuriant growth of 

8 Coalfields of New Mexico: Geology and Resources 

vegetation along margins of the seaway, resulting in local 

thick accumulations of peat and organic debris. These 

organic accumulations later compacted and altered to form 

the coal deposits preserved today in the San Juan basin and 

other Laramide basins of the Western Interior. 

COAL GEOLOGY 

The geographic locations and stratigraphic positions 

of coal beds of Late Cretaceous age in the San Juan basin 

were determined by the changing location of the shoreline 

along the western border of an epicontinental sea of that 

time. The coal deposits originated from thick accumulations 

of detrital organic matter (peat) in paludal environments on 

deltas and lower coastal plains. These environments were 

present in the San Juan basin as a result of periodic 

transgression and regression of the Cretaceous sea. The coal 

beds tend generally to be elongate toward the northwest, 

parallel to the shoreline. 

With each successive major transgressive-regressive 

cycle, the northwest-trending shoreline retreated 

progressively farther northeast until, by the end of the 

Cretaceous Period, the sea had withdrawn from the region 

completely (fig. A5). At times the shoreline remained in one 

position long enough for thick coastal sandstone to be 

deposited and for adjacent swamps to maintain the delicate 

balance necessary for thick deposits of organic matter to 

accumulate and alter to coal. The sedimentary record of 

each major transgressive-regressive cycle includes at least 

one coal-bearing unit. Although nearly all Cretaceous rocks 

in the San Juan basin contain some coal, the major coalbearing units of Cretaceous age in the basin are, in 

ascending order, the Crevasse Canyon, Menefee, and Fruitland Formations. 
SSW ...,__ ______ _ _ _ _ _ 200 MILES (320 KILOMETERS) ------------- NNE 

ZUNI BASIN ZUNI UPLIFT SAN JUAN BASIN 

Ma 

.--------------------------------------------------------~~~~~~~~~~~~T-66 

. 

-

E) 

EXPLANATION 

Nonmarine rocks 

Marine and coastal sandstone 

Marine shale, siltstone, and minor 

amounts of sandstone and limestone 

Hiatus or section removed by erosion 

Kcht Sandstone exposed at Tsaya Canyon 

Kph 

Ked a 

Kcbp 

Kth 

Kthfr 

Kthc 

Ktha 

Ka 

1 Of Dakota 

20f Mancos. 

Hosta Tongue of Point Lookout Ss 

Dalton Ss Mbr of Crevasse Canyon Fm 

Borrego Pass Sandstone Lentil of 

Crevasse Canyon Formation 

Tres Hermanos Formation 

Fite Ranch Mbr of Tres Hermanos Fm 

Carthage Mbr of Tres Hermanos Fm 

Atarque Ss Mbr of Tres Hermanos Fm 

Atarque Sandstone 

z 

<( 

i= 

::r:: 

u 

a: 

tn 

<( 

<( 

~ 

Figure AS. Time-stratigraphic geologic section of Upper Cretaceous rocks, San Juan basin (Molenaar and Baird, 1991 ). 

Framework and Major Coal-Bearing Formations of the San Juan Basin 9 

70 

75 

80 

85 

90 

95 
A 

FEET 

2000 

1600 

1200 

800 

400 

20 MILES 

A' 

FEET 

2500 

2000 

1500 

1000 

500 

9 

2 3 4 

10 

A' 

5 6 7 8 9 

GRID UNITS 

EXPLANATION 

Upper shale member of 

the Kirtland Formation 

Lower member of 

the Kirtland Formation 

Fruitland Formation 

Pictured Cliffs Sandstone 

Lewis Shale 

10 

Huerfanito Bentonite Bed-Datum 

Figure A6. Cross sections A-A' through E-E', showing stratigraphic rise of the Pictured Cliffs Sandstone across the San Juan 

basin (from Fassett and Hinds, 1971, pl. 2); also shown are locations of section H-1-f and of drill holes H-1 through H-35, 

presented in figure A7. A, Index map showing lines of sections. Numbered points indicate locations of oil and gas wells; electric 

logs of these wells were used in constructing stratigraphic cross sections. B and C, Fence diagrams based on sections A-A' 

through E-E '. Vertical scales show feet above datum (the Huerfanito Bentonite Bed); horizontal scale shows grid unit across 

basin (approximately 10 mi each). 

1 0 Coalfields of New Mexico: Geology and Resources 
Coal beds in the Dileo and Gibson Coal Members of 

the Crevasse Canyon Formation (fig. AS) have long been 

mined in the southwest part of the San Juan basin. Where 

the Gibson Member of the Crevasse Canyon Formation and 

the Cleary Coal Member of the Menefee Formation merge, 

several coal beds are currently being strip-mined at the 

McKinley Mine (fig. A8, No. 6), northwest of Gallup 

(Wilson, 1977, p. 25S). 

The Menefee Formation, in general, contains coal 

beds at its base and its top but is essentially barren in the 

middle part. In the northwestern part of the basin, the 

coal-bearing units are called the lower and upper coalbearing members (Hayes and Zapp, 19SS). In the southern 

part of the basin, the Menefee is divided into two members, 

a lower coal-bearing member, called the Cleary Coal 

Member, and the overlying Allison Member, which 

generally includes some coal at the top. Miller (1984) has 

named the coal-bearing interval at the top of the formation 

the La Vida Beds of the Allison Member. The upper 

coal-bearing unit generally underlies, or intertongues with, 

the lower part of the overlying Cliff House Sandstone. 

Along the east side of the San Juan basin the lower coal 

member crops out and can be traced from the southeast 

northward, nearly to the State line. Along outcrops on the 

west side of the basin the Menefee Formation in most places 

includes only a few coal beds except locally where it 

intertongues with overlying or underlying sandstones 

(Beaumont, 1971, p. 23). North of the San Juan River the 

number and thickness of coal beds increase in both coalbearing members. 

A distinctive marker bed, called the Huerfanito Bentonite Bed (fig. AS) of the Lewis Shale, fell as volcanic ash 

into the Late Cretaceous marine seaway between the time of 

deposition of Cliff House transgressive sands and the final 

regression marked by the Pictured Cliffs sands. The Huerfanito Bentonite Bed is a time-stratigraphic marker named 

and traced in the subsurface throughout the San Juan basin 

by Fassett and Hinds (1971). They used this stratigraphic 

marker to demonstrate the stratigraphic rise of the Pictured 

Cliffs Sandstone as the sea retreated northeastward, and the 

influence of this rise on coal beds in the overlying Fruitland 

Formation. Figure A6 shows the lines of section constructed 

by Fassett and Hinds (1971, plate 2) using the Huerfanito 

Bentonite Bed as a datum to show the stratigraphic rise 

northeastward of the Pictured Cliffs and the change in 

thickness of the overlying Kirtland Shale. Figures A6B and 

C are computer-generated fence diagrams, based on cross 

sections A-A' through E-E', to illustrate the concept of the 

stratigraphic rise. Panel E-E' in figure A6B and A-C in 

figure A6C parallel the Cretaceous shoreline and suggest 

essentially no stratigraphic change. Figure A6B also shows 

the general changes in thickness of members of the Kirtland 

Shale. The Kirtland is thickest in the northern part of the 

basin. (See fig. A6B, line A-A'). The complicated changes 

in thickness of its members are discussed in detail by Fassett 

and Hinds ( 1971, p. 23-28). 

The Fruitland Formation, which overlies the Pictured 

Cliffs Sandstone, contains by far the largest coal resources 

in the San Juan basin. Most of the coal occurs in lenticular 

beds in the lower part of the formation. Coal has been 

surface mined from the Fruitland near the San Juan River in 

the western part of the basin for many years. The thickness 

and distribution of coal in the Fruitland is closely related to 

the increase in thickness and stratigraphic rise of the 

Pictured Cliffs Sandstone, especially where the lower part 

of the Fruitland Formation intertongues with the upper part 

of the Pictured Cliffs. Figure A 7 is a computer-generated 

plot of drill holes showing examples of Fruitland coal and 

the underlying Pictured Cliffs in a line extending northeastward across the basin for about 40 miles. In the plot, the 

datum is the base of the Pictured Cliffs Sandstone, and the 

data are interpreted from geophysical logs of oil- and 

gas-test holes. Typically, the coal beds are highly lenticular 

and difficult to correlate between drill holes. The thickest 

coal beds are generally near the base of the Fruitland, but 

they can be correlated with certainty only where drill holes 

are closely spaced. For these reasons, coal resource 

calculations can only be made for coal zones rather than for 

individual beds. The coal beds as shown in figure A 7 are, in 

places, at least 20 feet thick, and there is a suggestion of two 

coal zones between drill holes H-9 to H-3S. The thickest 

Fruitland coal in the basin is south of Durango, Colo., near 

Carbon Junction, where one bed consists of 80 feet of 

interbedded coal and partings (Zapp, 1949). 

The San Juan basin is subdivided into 21 individual 

coalfields or coal areas underlain by strippable low-sulfur 

coal (fig. A8). Those fields or areas in which the Fruitland 

Formation is the current producer are the Navajo field and 

the Fruitland, Bisti, and Star Lake areas. The remaining 

fields or areas have coal resources-either developed or 

undeveloped-in the Mesaverde Group and its equivalents, 

the most notable being the Gallup field. 

REFERENCES CITED 

Baars, D.L., 1962, Permian System of Colorado Plateau: American 

Association of Petroleum Geologists Bulletin, v. 46, p. 

149-218. 

Beaumont, E. C., 1971, Stratigraphic distribution of coal in the San 

Juan basin, in Shomaker, J.W., Beaumont, E.C., and Kottlowski, F.E., eds., Strippable low-sulfur coal resources of 

the San Juan basin in New Mexico and Colorado: New 

Mexico Bureau of Mines and Mineral Resources Memoir 

25, p. 15-30. 

Framework and Major Coal-Bearing Formations of the San Juan Basin 11 
... 

~ 

("') 

0 

I» 

5 

1'1) 

c:: 

Cll 

0 

..... 

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1'1) 

~ 

~ 1'1) 

)( 

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0 

0 

~ 

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= 0.. 

;:11:::1 

1'1) 

Cll 

0 

~ n 

1'1) 

Cll 

H VERTICAL SCALE H' 

H-5 

21 23N 8W 

~ 

METERS 0 I 0 FEET 

H-4 

21 23N 8W 

n 

H-6 

12 23N 8W 

H-1 

15 50 

n H-25 

11 25N 5W 

27 22N 9W 

H-35 

H-29 1 26N 4W 

44 185 

4 

2 

H-12 H-17 H-21 

2 

H-7 

18 24N 6W 3 24N 6W 20 25N 5W 

33 24N 7W 

29 26N 4W 

H-26 

216 n H-9 

~:5 ~51 

1 25N 5W n 

166 

25 24N 7W 

H-33 

ll 

10 

10 26N 4W 

78 I I 

9 

6 

I I- 57 

7 

8 

4 

~: ~ 149 

~:7 

f2 n~, ~ 149 

l133 

8 ~~5 

/1 ~ 136 

I I 

218 

9 

16 

2 

8 

I ~ 97 

f.- 200 I I I I I I- 64 I f- 69 

23 

3 

?2 

10 

2 

6 

174 

8 ~;3 9 

--8 

I 

8 

4 

4 3 

34 11 I I- 27 

11 

26 

7 8 

157 

3 

3 

16 11 ==~6 -132 I I 

104 I I I I 

37 

98 

11 

93 

118 4 

I I 

78 I r 86 

I I ~ 69 1183 I 180 

54 I I I I I t- 60 

Figure A7. Correlation of well logs along section H-1-f (fig A6A) showing lenticular nature of the coal beds (black) within the Fruitland Formation (no pattern). Stippled 

pattern represents Pictured Cliffs Sandstone; datum is the base of the Pictured Cliffs. Numbers next to columns give bed thicknesses in feet. 
109° 

37° ,-p1 oso COLORADO 107° 106° 

-~- -NEW MEXICO - - - - --Monero field - - - - -

\ 

Baker 

I Arroyo 

I area 

<!:: 18 Shiprock0 

~~B ( ~~~ 

c=,~ <l::l.l.l 

:") 

I Toadlena 

0 Farmington 

\'"' 

) 

Grants 0 

350 I 

°Chama 

Kmf \ 

lierraV\K ~~mf\ Amarilla 

field 

/ 

LApproximate base of 

Cubao \ Dakota Sandstone 

La Ventana 

field 

area 

0 Albuquerque 

--~---------------------------L------------------------~------------------------~ 

50 MILES 

I 

EXPlANATION 

Active Mines, Permitted Mines, and Mine Permits in Progress 

Fruitland Formation 1. Black Diamond 7. Mentmore 13. La Ventana 

2. San juan 8. Arroyo No. 1 14. Star Lake 

Menefee Formation 3. Navajo 9. La Plata 15. Gateway 

Crevasse Canyon Formation 4. Burnham 10. Gallo Wash 16. Bisti 

5. De-Na-Zin 11. South Hospah 17. Carbon No. 2 

6. McKinley 12. Lee Ranch 

Figure A8. Fields, areas, and mines containing strippable low-sulfur coal in Upper Cretaceous formations of 

the San Juan basin. (Modified from Kottlowski and others, 1983.) 

___ 1982, Geology of New Mexico coal deposits and geologic 

setting for field trip, in Coal-bearing sequences and modem 

concepts for exploration and development: American 

Association of Petroleum Geologists short course, March 

1982. 

Fassett, J.E., and Hinds, J.S., 1971, Geology and fuel resources of 

the Fruitland Formation and Kirtland Shale of the San Juan 

basin, New Mexico and Colorado: U.S. Geological Survey 

Professional Paper 676, 76 p. 

Finch, W.l., Huffman, A.C., Fassett, J.E., eds., 1989, Coal, 

uranium, and oil and gas in Mesozoic rocks of the San Juan 

basin-Anatomy of a giant energy-rich basin, in Coal and 

hydrocarbon resources of North America: International 

Geological Congress, 28th, Field Trip Guidebook T120, v. 

1, 99 p. 

Hayes, P.T., and Zapp, A.D., 1955, Geology and fuel resources of 

the Upper Cretaceous rocks of the Barker dome-Fruitland 

area, San Juan County, New Mexico: U.S. Geological 

Survey Oil and Gas Investigations Map OM-144, scale 

1:62,500. 

Kottlowski, F.E., Campbell, F.W., Roybal, G.H., and Hatton, K.S., 

1983, New Mexico, in 1983 Keystone coal industry manual: 

New York, McGraw-Hill, p. 577-586. 

Miller, R.L., 1984, Subdivisions of the Menefee Formation and 

Cliff House Sandstone (Upper Cretaceous) in southwest San 

Juan basin, New Mexico: U.S. Geological Survey Bulletin 

1537-A, A29-A53. 

Framework and Major Coal-Bearing Formations of the San Juan Basin 13 
Molenaar, C.M., 1977, San Juan basin time-stratigraphic 

nomenclature chart, in Fassett, J.E. and James, H.L., eds., 

Guidebook of San Juan basin III, northwestern New 

Mexico: New Mexico Geological Society, 28th Field 

Conference, 1977, p. xii. 

___ 1983, Major depositional cycles and regional correlations 

of Upper Cretaceous rocks, southern Colorado Plateau and 

adjacent areas, in Reynolds, M.W., and Dolly, E.D., eds., 

Mesozoic paleogeography of the west-central United States: 

Denver, Colo., Rocky Mountain Section, Society of 

Economic Paleontologists and Mineralogists, p. 201-224. 

Molenaar, C.M., and Baird, J.K., 1991, Stratigraphic cross 

sections of Upper Cretaceous rocks in the northern San Juan 

basin, Southern Ute Indian Reservation, chapter C of 

Geology and mineral resources of the Southern Ute Indian 

Reservation: U.S. Geological Survey Professional Paper 

1505-C, p. C1-C12. 

14 Coalfields of New Mexico: Geology and Resources 

Stone, W.J., Lyford, F.P., Frenzel, P.F., Mizell, N.H., and Padgett, 

E.T., 1983, Hydrogeology and water resources of the San 

Juan basin, New Mexico: New Mexico Bureau of Mines and 

Mineral Resources Hydrologic Report 6, 70 p. 

Thaden, R.E., and Zech, R.S., 1984, Preliminary structure contour 

map on the base of the Cretaceous Dakota Sandstone in the 

San Juan basin and vicinity, New Mexico, Arizona, 

Colorado, and Utah: U.S. Geological Survey Miscellaneous 

Field Studies Map MF-1673, scale 1:500,000. 

Wilson, J.C., 1977, The McKinley Mine, in Fassett, J.E., and 

James, H.L., eds., Guidebook of San Juan basin III, 

northwestern New Mexico: New Mexico Geological 

Society, 28th Field Conference, 1977, p. 253-255. 

Zapp, A.D., 1949, Geology and coal resources of the Durango 

area, La Plata and Montezuma Counties, Colorado: U.S. 

Geological Survey Oil and Gas Investigations Preliminary 

Map OM-109, scale 1:31,680. 
Chapter B 

Coal Resources of the 

San Juan Basin 

By LAURA R. H. Bl EWICK, ANTOl N ETTE L. MEDLIN, 

JUDY F. HUNTER, and KATHLEEN K. KROHN, 

A demonstration of the capabilities of the 

National Coal Resources Data System 

U.S. GEOLOGICAL SURVEY BULLETIN 1972 

COALFIELDS OF NEW MEXICO: GEOLOGY AND RESOURCES 
CONTENTS 

Abstract 17 

Introduction 17 

Procedures 17 

Data preparation 17 

Boundary definition 19 

Resource calculations 25 

Results 25 

Considerations and issues 27 

References cited 33 

FIGURES 

Bl-B8. Maps of the San Juan basin showing: 

B 1. Areas defined for estimates of coal resources in the Fruitland and 

Menefee Formations 18 

B2. Isopachs of total coal in the Fruitland Formation 19 

B3. Thickness of overburden on top of coal in the Fruitland 

Formation 20 

B4. Isopachs of total coal in the Menefee Formation 21 

B5. Thickness of overburden on top of coal in the Menefee 

Formation 22 

B6. Digitized boundaries showing generalized land categories in areas 

underlain by the Fruitland Formation 23 

B7. Digitized boundaries showing generalized land categories in areas 

underlain by the Menefee Formation 24 

B8. Number of coal horizons in the Fruitland Formation 27 

TABLES 

B 1. Estimates of Federally owned subbituminous coal resources in the Fruitland 

Formation, San Juan basin, New Mexico 28 

B2. Estimates of Federally owned subbituminous coal resources in the Menefee 

Formation, San Juan basin, New Mexico 32 

16 Contents 
Coal Resources of the San Juan Basin 

By Laura R.H. Biewick, Antoinette L. Medlin, Judy F. Hunter, and Kathleen K. Krohn 

Abstract 

A working data base of stratigraphic information for the 

Upper Cretaceous Menefee and Fruitland Formations, the two 

major coal-bearing units within the San Juan basin, was 

retrieved from the NCRDS (National Coal Resources Data 

System) master data base for New Mexico using the PACER 

data storage and retrieval system on a 32-bit minicomputer. 

These data were reviewed, and data from other sources were 

coded and added. Then subsets of data were retrieved, 

representing drill holes that had penetrated the entire thickness 

of either of the formations within the digitized boundary areas. 

The coal resources of both formations were calculated 

from this data set using GARNET, one of the graphic analysis 

and volume calculation programs of NCRDS. Because of the 

lenticular nature of the coal beds and the large area under 

study, the resource assessments were made for total coal 

within each of the formations, rather than for individual coal 

beds. 

The GARNET program uses a point location file, a grid 

file of coal thickness, and a boundary file to calculate coal 

volume; then it multiplies the volume by a density factor, 

which depends on the coal's rank, to produce a coal tonnage 

estimate. These estimates, for the New Mexico part of the San 

Juan basin, are 168 billion short tons of coal in the Fruitland 

Formation and 21 billion short tons of coal in the Menefee 

Formation. Each estimate is presented in three ways: (1) as a 

single resource tonnage; (2) as tonnages in the measured, 

indicated, inferred, and hypothetical categories; (3) as 

tonnages in various generalized land ownership categories; 

and (4) as tonnages in various overburden categories by 

township, range, and county. The GARNET program was also 

used to produce coal isopach, overburden, and generalized 

land ownership maps. 

INTRODUCTION 

The two predominant coal-bearing sequences in the 

San Juan basin, the Upper Cretaceous Menefee and Fruitland Formations (fig. B 1), have been studied using 

traditional and computerized methods. This study had four 

objectives: 

Manuscript approved for publication January 10, 1991. 

1. To estimate the total coal resources in the Menefee and Fruitland Formations in the San Juan 

basin, within the limitations of the available data. 

2. To estimate the approximate amounts of the total 

coal resources that occur in areas within various 

generalized categories of coal mineral rights 

ownership. 

3. To estimate the amounts of the total coal 

resources within various categories of overburden thickness. 

4. To demonstrate the capabilities of the U.S. 

Geological Survey's National Coal Resources 

Data System (NCRDS) for coal resource 

calculations. 

The coal resource estimates presented in this chapter 

were calculated using the data and programs of the NCRDS. 

PACER is the data base formatting, storage, and retrieval 

program and GARNET is the graphic analysis and volume 

calculation program of NCRDS. A 32-bit minicomputer 

was used for this study. All of the techniques and 

procedures illustrated here can be applied at various scales, 

to areas ranging from federal lease tracts to whole States or 

regions. Pertinent factors are the amount, reliability, and 

distribution of available data; the accuracy of boundary 

definitions; and the categories of resource calculations 

required. 

PROCEDURES 

Data Preparation 

A working file of stratigraphic information for the 

San Juan basin was retrieved from the NCRDS master data 

base for New Mexico (NMSTRAT) using PACER. These 

data had been compiled from well logs by geologists of the 

U.S. Geological Survey (USGS) and the New Mexico 

Bureau of Mines and Mineral Resources. Additional data 

from recent studies and other sources were coded and added 

to the working file by the USGS project geologists and 

NCRDS staff. The geologists checked the designations of 

stratigraphic units and, where necessary, corrected the 

working file using the PACER updating capability. Data 

from this working file were used to produce several 

products for the geologists' analyses and approval. 

Coal Resources of the San juan Basin 17 
36° 

McKINLEY 

Gallup 0 

'-------------., 

r--.1'-t_ 

Los Alamos0 I 

Los--L_ L/ 

ALAMOS L..,..., 1 

'( 

I 

I 

I 

I 

I 

I 

I 

-------~ 

BERNALILLO a Albuquerque 

50 MILES 

EXPLANATION 

V77J Area underlain by lLLLJ Fruitland Formation 

Area defined for estimates of 

resources in the Menefee Formation 

Figure 81. Location of areas defined for estimates of coal resources in the Fruitland and Menefee Formations in the San Juan 

basin, New Mexico. Area of the Fruitland is bounded by the formation's outcrop; area shown for the Menefee is bounded by a 

limit-of-estimates line based on available drill hole data. 

Because the Fruitland Formation is the only 

formation in the San Juan basin represented by sufficient 

NCRDS data to allow detailed analysis, it is discussed first 

in this report. In order to retrieve data representative of the 

coal in the complete Fruitland Formation, a single PACER 

request was made for all drill hole records having Fruitland 

Formation coal lithostratigraphic units; partial sections were 

excluded. The request yielded 2,513 records, which were 

processed using standard NCRDS software to sum the 

thicknesses of all coal horizons from the same drill hole. 

This procedure resulted in total Fruitland Formation coal 

values for 630 randomly spaced point locations. These point 

18 Coalfields of New Mexico: Geology and Resources 

locations and values were then used for input to the 

GARNET program for graphic display and calculation of 

coal tonnage estimates. 

The first GARNET operation was to use the randomly 

spaced data point locations to create an evenly spaced grid 

of estimated coal thickness values. These values were then 

displayed as contours or isolines at intervals designated by 

the data analyst. An optimal grid spacing of 3 miles was 

selected based on the spacing of random data points over the 

area. The GARNET software provides two gridding 

algorithm options for interpolation of randomly spaced data: 

the quadratic algorithm for dense, evenly spaced points and 
the planar algorithm for sparse, unevenly distributed points. 

Fruitland Formation coal thickness data were best 

represented by the planar gridding option because of the 

distribution of the data points. The planar algorithm 

averages the values over a larger area than the quadratic 

algorithm and produced a coal isopach map satisfactory to 

the geologists' interpretation of the data (fig. B2). 

A second PACER request to the working file 

retrieved values for the depth to the top (overburden) of the 

Fruitland Formation coal zone. These overburden values 

were then gridded using the GARNET program. Sufficient 

data points were not available to control the overburden 

contours at the outcrop line in three locations, so the 

GARNET point-editing capability was used to add control 

points at these three locations to generate the map shown in 

figure B3. This map was approved by the geologists 

Outcrop of Fruitland Formation 

10 20 30 MILES 

and compares generally to figure 27 in the Fassett and Hinds 

( 1971) study of this area. 

Similar procedures were used to generate maps of the 

Menefee Formation coal and overburden thicknesses (figs. 

B4 and BS). 

Boundary Definition 

NCRDS includes the capability to calculate coal 

resource tonnage estimates from isopach maps within a 

boundary defining an area of interest. Very generalized land 

ownership categories were defined in this study to show the 

concept of estimating coal resources by the following areas 

of interest: 

National parks and monuments 

National forest lands 

Figure 82. Isopach map of total coal in the Fruitland Formation. Dots represent data points. Contour interval 5 feet. See figure 

B1 for location of the area shown here. 

Coal Resources of the San Juan Basin 19 
Outcrop of Fruitland Formation 

10 20 30 MILES 

Figure 83. Thickness of overburden on top of coal in the Fruitland Formation. Dots represent data points. Contour interval 500 

feet. See figure 81 for location of the area shown here. (Note: configuration of the land surface is very generally represented by 

the available data.) 

Other federal surface and/or subsurface coal ownership 

Indian lands and reservations 

State and privately owned lands 

Counties 

Digital files were created to store the boundary data that 

define each of these areas. Township and range boundaries 

determined areas used to estimate coal resource tonnages 

for federal lands. In all areal categories, the data were used 

to generate tonnage estimates in the following overburden 

categories: 

0-500 feet 

500-1 ,000 feet 

1,000-2,000 feet 

2,000-3,000 feet 

More than 3,000 feet 

20 Coalfields of New Mexico: Geology and Resources 

The GARNET program can process data and 

calculate results within any digital boundary that can be 

defined by 20,000 points or less. The boundary categories 

defined above provide an evaluation of approximate coal 

resources in the basin to illustrate the capabilities and 

techniques of NCRDS on a regional scale. The accuracy of 

the GARNET software tonnage estimates depends on the 

available data, the selected map scale, the digital boundary 

accuracy, and the chosen grid interval. 

A 1:500,000 scale State of New Mexico Land Status 

Map (DOl, BLM edition of 1982) was used to digitize the 

boundaries of counties and townships and ranges, and the 

generalized boundaries of Indian reservations, national 

parks, national monuments, and national forests. Mineral 

ownership categories shown on figures B6 and B7 were also 
37',---------------------------10~8_0 

__________________________________________________ 1~07~------~ 

10 20 30 MILES 

Limit for estimates of 

resources in the 

Menefee Formation 

Figure 84. Isopach map of total coal in the Menefee Formation. Dots represent data points. Contour interval 5 feet. See figure 

B 1 for location of the area shown here. 

compiled from various Bureau of Land Management 

1:100,000-scale land status maps (1978-1983). These 

boundaries are highly generalized. 

Boundaries for each area of interest were digitized 

using equipment with an accuracy of 0.005 inch. Data from 

appropriate categories (political, township, range, county) 

Coal Resources of the San Juan Basin 21 
1oso 10r 37°.---------------------------~----------------------------------------------------~-------, 

10 20 30 MILES 

... 

. · 

Limit for estimates of 

resources in the 

Menefee Formation 

Figure 85. Thickness of overburden on top of coal in the Menefee Formation. Dots represent data points. Contour interval 500 

feet. See figure B1 for location of the area shown here. (Note: configuration of the land surface is very generally represented by 

the available data.) 

22 Coalfields of New Mexico: Geology and Resources 
were combined using the GARNET boundary command. 

The overburden category boundaries were retrieved directly 

by subtracting the gridded file of the elevations at the top of 

the coal beds from the gridded file of the surface elevations; 

then the overburden categories were combined with the 

political, land ownership, reliability, and coal thickness 

categories to define the final subareas for resource 

estimates. More than 300 subareas were defined with unique 

Outcrop of Fruitland Formation 

10 20 30 MILES 

boundaries for individual coal resource tonnage 

calculations. 

Localities of Menefee Formation coal data in 

NMSTRA T are densely distributed in the central and 

southeastern portions of the basin. In these two areas data 

are sufficient to allow estimates of coal resources using 

NCRDS. The Menefee boundary used for the isopach and 

overburden maps (figs. B4 and B5) represents an irregular 

National forests 

EXPlANATION n Other Federal ownership State ownership 

National parks, monuments, 

and recreation areas 

~ Indian ownership Private ownership 

Figure 86. Digitized boundaries of land categories in area underlain by the Fruitland Formation. Boundaries are highly 

generalized and are intended to represent only the general proportions of each category in a given area. Ownership status of 

specific parcels of land should not be inferred from this map. See figure 81 for location of area shown here. 

Coal Resources of the San Juan Basin 23 
37 o,_ ____________________________ 10~8_0 

______________________________________________________ 1

1

07_0 ______ -, 

10 20 30 MILES 

EXPLANATION 

National forests 

National parks and monuments 

Other Federal ownership 

Indian ownership 

State ownership 

Private ownership 

for estimates of 

resources in the 

Menefee Formation 

Figure 87. Digitized boundaries of land categories in areas underlain by the Menefee Formation. Boundaries are highly 

generalized and are intended to represent only the general proportions of each category in a given area; in certain cases, categories 

may be misapplied. Ownership status of specific parcels of land should not be inferred from this map. See figure 81 for location 

of area shown here. 

24 Coalfields of New Mexico: Geology and Resources 
limit-of-estimate line generated by the geologists. This 

artificial boundary is used instead of an outcrop boundary to 

enclose the area best represented by the available data. 

A small, isolated cluster of wells in the northeast 

portion of the basin also provided Menefee coal data. The 

coal in this small area is less than 5 feet in total thickness 

and is quite distant from the other Menefee coal to the south. 

No reliable resource calculation could be made for the small 

set of data from this isolated area. 

Resource Calculations 

The GARNET program uses a point location file, a 

gridded coal isopach file, and a boundary file ·to calculate 

the volume of coal, then the appropriate density factor for 

the rank of coal being considered is applied to produce a 

coal tonnage estimate. Coal resource volumes are calculated 

by determining the area (acreage) and average thickness for 

all of the grid cells of the coal isopach grid that fall within 

the area defined by the boundary file and a selected radius 

from the data point locations. The U.S. Geological Survey 

has designated specific radii from known coal data points as 

defining certain reliability classifications of coal resource 

tonnage estimates (Wood and others, 1983), but any radii 

can be selected and used in the GARNET program. These 

volumes are then multiplied by the density factor 

appropriate for the rank of the coal under consideration. For 

coal in the Menefee and Fruitland Formations, a density 

factor of 1, 770 tons per acre foot was selected. 1 

The data included in NMSTRAT for the coal-bearing 

rocks older than the Fruitland and Menefee Formations (in 

descending order: Crevasse Canyon Formation, Gallup 

Sandstone, Tres Hermanos Formation, and Dakota 

Sandstone) are from localities scattered sparsely across the 

San Juan basin. Coal data in NMSTRAT are insufficient to 

allow use of computer methods to generate coal tonnage 

estimates for these rock units. The latest estimates by the 

New Mexico Bureau of Mines and Mineral Resources for 

the Crevasse Canyon Formation coal resources, shown 

below, were derived from coal data for the southern portion 

of the San Juan basin using a planimeter. Resource 

calculations done by conventional methods, using measured 

and indicated resource categories based on radii from 

known data points (Woods and others, 1983, p. 11), yielded 

the following estimate of coal in the Crevasse Canyon 

Formation, in beds more than 1.2 feet thick under less than 

250 feet of overburden (Frank W. Campbell, New Mexico 

Bureau of Mines and Mineral Resources, oral commun., 

1985): 

1

Minimum thicknesses specified by Wood and others (1983, table 

3) were not used in classifying coal resources for these estimates. Coal 

quality data are insufficient to discriminate between bituminous and 

subbituminous coal. Resource estimates in this report represent total coal. 

CREVASSE CANYON FORMATION 

Resource 

classification 

Measured ..... . 

Indicated ..... . 

RESULTS 

Acres 

38,000 

151,000 

Average 

thickness 

(feet) 

3.5 

3.5 

Estimated 

tons 

(millions) 

325 

1,275 

The coal resources of the Fruitland and Menefee 

Formations were estimated by several different techniques 

for comparative purposes. The resource estimation 

techniques used were selected on the basis of data 

distribution, the accuracy and scale of boundary definitions, 

the size of area to be included, and research goals. All the 

estimated coal tonnages shown below are reported to the 

nearest million tons, which is deemed to be the maximum •-

appropriate level of precision for this study. 

Calculations using a single large radius from known 

data points, the Fruitland Formation outcrop, and the 

limit-of-estimate boundary of the Menefee Formation gave 

the following estimate of total coal resources: 

Average Estimated 

Formation Acres thickness tons 

(feet) (millions) 

Fruitland 3,720,299 25.4 167,501 

Menefee 1,216,901 9.8 21,099 

Calculations using the radii specified by Wood and 

others (1983, fig. 4), the Fruitland Formation outcrop, and 

the limit-of-estimate boundary of the Menefee Formation 

gave this estimate of coal resources in the four reliability 

categories used by the USGS: 

Formation Average Estimated 

and resource Acres thickness tons 

classification (feet) (millions) 

Fruitland: 

Measured .... 71,225 23.8 3,001 

Indicated ..... 400,686 23.7 16,774 

Inferred ....... 2,533,367 26.1 116,980 

Hypothetical 715,022 24.3 30,738 

Menefee: 

Measured ..... 17,152 9.6 290 

Indicated ..... 143,997 8.7 2,229 

Inferred ....... 835,090 9.8 14,438 

Hypothetical 220,661 10.6 4,140 

The use of boundaries for some of the very 

generalized land ownership categories and a single large 

radius produced the following approximate total coal 

resource estimates: 

Coal Resources of the San Juan Basin 25 
Ownership and 

overburden 

thickness (feet) 

National forests: 

0-500 

500-1,000 

1,000-2,000 

2,000-3,000 

>3,000 

Total 

National parks, 

monuments, and 

recreation areas: 

2,000-3,000 

>3,000 

Total 

Other federal 

ownership: 

0-500 

500-1,000 

1 ,000-2,000 

2,000-3,000 

>3,000 

Total 

Indian lands: 

0-500 

500-1,000 

1,000-2,000 

2,000-3,000 

>3,000 

Total 

State lands 

unclassified: 

National forests: 

0-500 

National parks, 

monuments and 

recreation areas: 

0-500 

Other federal 

ownership: 

0-500 

500-1,000 

1 ,000-2,000 

2,000-3,000 

>3,000 

Total 

Acres 

Average 

thickness 

(feet) 

Fruitland Fonnation 

11,894 

6,894 

19,068 

22,590 

197,232 

257,678 

38,360 

7,728 

46,088 

343,165 

227,083 

553,550 

601,801 

323,498 

2,049,097 

209,267 

139,483 

328,728 

245,185 

211,296 

1,133,959 

46,700 

Menefee Fonnation 

13,949 

19,673 

313,608 

76,565 

79,664 

36,452 

57,294 

563,583 

0.1 

0.9 

2.1 

10.4 

36.6 

46.7 

53.7 

14.0 

12.8 

14.5 

33.2 

47.4 

20.1 

18.0 

14.2 

16.4 

26.6 

37.9 

7.4 

11.2 

10.8 

12.7 

10.1 

7.3 

9.1 

Estimated 

tons 

(millions) 

1 

11 

72 

416 

12,778 

13,278 

3,170 

735 

3,905 

8,842 

5,284 

13,352 

36,480 

26,498 

90,456 

7,450 

4,435 

8,282 

7,115 

9,939 

37,221 

3,129 

182 

391 

6,308 

1,637 

1,552 

458 

869 

10,824 

26 Coalfields of New Mexico: Geology and Resources 

Ownership and 

overburden 

thickness (feet) 

Indian lands: 

0-500 

500-1,000 

1,000-2,000 

2,000-3,000 

>3,000 

Total 

State lands 

unclassified: 

Acres 

Average 

thickness 

(feet) 

Menefee Fonnation-Continued 

166,273 

8,745 

309 

49,952 

22,492 

247,771 

14,456 

11.4 

7.1 

9.2 

4.2 

7.6 

16.3 

Estimated 

tons 

(millions) 

3,345 

109 

5 

370 

303 

4,132 

416 

Detailed resource estimates for the "Other Federal 

ownership" category, classified by overburden, county, and 

township and range, are given in tables B 1 and B2 at the end 

of the chapter. 

A comparison of the total coal resources tonnage 

estimate calculated by the computer and the summation of 

resource numbers for the various multiple resource 

calculations shows some differences: 

Method of calculation 

Based on a single large radius .... 

Total of four reliability categories 

Estimated total coal resources 

(millions of tons) 

Fruitland 

Formation 

167,501 

Menefee 

Formation 

21,099 

of Wood and others (1983) . . . . . 167,493 21,097 

Total of estimates for various land 

ownership categories .......... . 147,989 15,944 

The significant "shortfall" in the estimates tallied 

from the land ownership categories results mainly from the 

exclusion of privately owned resources from these 

estimates. Other, smaller differences in the total resource 

estimates are mostly attributable to three factors: 

1. The size of the area being estimated (estimates 

for small areas have a greater margin of error 

than those for large areas). 

2. The grid cell interval. 

3. The GARNET resource calculation procedure 

that includes or excludes all of a particular grid 

cell depending on its intersection with a 

boundary. 
CONSIDERATIONS AND ISSUES 

The variability in number of coal beds across the 

basin (fig. B8) demonstrates the discontinuous nature of 

coal beds within the Fruitland Formation coal zone. A 

comparison of figure B8 with figure B2 will indicate the 

variability in the number of coal beds in which a given total 

coal thickness occurs. This information can be used, along 

with interburden data, to define areas most favorable for 

development. 

Several refinements would improve the utility of the 

results of these resource calculations. Some of these could 

be accomplished fairly soon: 

1. Improving acreage and tonnage estimates, 

especially with reference to federal ownership, 

by using digital boundary data recorded from 

1: 1 00,000-scale or larger scale maps. 

e10 •1o 

2. Calculating resources by thickness category of 

individual coal horizons; that is, summing coal 

horizons whose thicknesses fall within a given 

range, such as 10-20 feet or 20-30 feet. These 

resource numbers categorized according to overburden thickness would reflect information of 

value for potential development. 

Other, longer range improvements would require 

additional data gathering and study: 

1. Expansion and refinement of the stratigraphic 

data base; location and encoding of additional 

coal stratigraphic data. 

2. Further review and analyses of correlations 

within the data base. 

3. Gathering and encoding sufficient data on coal 

quality to allow resource estimates to be 

subdivided into coal quality categories. 

e7 •4 •s .3 .1 107° 

37° 

12. •g 6 .a •2 .4 .3 

/ .7 .14 .7 .4 

.6 .6 .10 .s 

.a .3 .s .4 

.7 

.a 

.7 .7 .4 

.2 

.4 .s .6.s .s .10 .s .6 .s .3 .4 .a .4 

.4 .3 .z e3 .7 .a 

.4 .12 .6 .7 .a .s .4 .4 .4 .2 .2 .4 .12 

e6 e11 

.3 .4 

.3 .2 .2 •• 3 .6 .4 .6 .6 .s .s .s .2 2 .6 .6 

.6 

.s .3 .1 .a 6 

.4 

.4 .3 .2 .s .4 .6 .s .6 .4. .s .s .a .3 .4 .7 .s e3 e7 .7 

.3 

.4 

.6 

.a 

.s .3 e2 .2 .2 .s .2 e3 .4 e3 .3 .4 .s .s .s .6 .6 

.1 .a 

.s e1 .4 .3 .6 .s 

.s .s .2 .3 .4 .a .6.7 .6 .a •1 .4 .4 .3 .2 .3 .3 .s .3 .3 .7 .s .3 .s .a .s .7 

.s .a 

.1 .3 .4 .2 .s .s •4 e6 .s 

.7 e7 .4 

.4 .6 

.s .3 .6 .4 .s 

e7 

.2 .3 

.2 

.4 .7 

e6 4 

.4 

• 

.2 .2 .1 

.2 

e3 .4 .1 

36° Outcrop of Fruitland Formation 

.4 

e1 

10 20 30 MILES 

Figure 88. Number of coal horizons in the Fruitland Formation at drill hole localities. See figure B1 for location of area shown here. 

Coal Resources of the San Juan Basin 27 
Table 81. Estimates of Federally owned subbituminous coal Table 81. Estimates of Federally owned subbituminous coal 

resources in the Fruitland Formation, San juan basin, New resources in the Fruitland Formation, San juan basin, New 

Mexico Mexico-Continued 

[Estimates may include some coal already mined but exclude resources in 

Average Millions of national parks, monuments, and national forests] Location and 

overburden total short tons 

Acres thickAverage Millions of thickness Each Location and (feet) ness Total 

overburden total short tons (feet) interval 

thickness Acres thick-

(feet) ness Each Total Rio Arriba County--Continued (feet) interval 

McKinley County 

T. 25 N., R. 1 E. 

500-1,000 1,604 1.8 5.06 

1,000-2,000 1,091 2.2 4.24 9.30 

T. 19 N., R. 5 W. 

0- 500 9,042 11.0 176.75 176.75 T. 25 N., R. 2 W. 

>3,000 23,975 16.7 708.20 708.20 

T. 20 N., R. 5 W. 

0- 500 14,419 7.3 186.87 T. 25 N., R. 3 W. 

500-1,000 8,248 6.8 99.00 285.87 >3,000 22,751 30.3 1,218.81 1,218.81 

T. 20 N., R. 6 W. T. 25 N., R. 6 W. 

0- 500 22,015 8.7 337.37 2,000-3,000 21,276 14.6 549.68 549.68 

500-1,000 567 12.4 12.43 349.80 

T. 25 N., R. 7 W. 

T. 20 N., R. 7 W. 1,000-2,000 571 12.6 12.73 

0- 500 14,287 8.6 216.87 216.87 2,000-3,000 18,085 16.6 529.85 542.58 

T. 20 N., R. 8 W. T. 26 N., R. 2 W. 

0- 500 1,712 26.4 79.86 79.86 >3,000 19,435 18.9 650.74 650.74 

Total for McKinley County --------------- 1,109.15 T. 26 N., R. 6 W. 

2,000-3,000 21,677 20.9 802.87 802.87 

Rio Arriba County T. 26 N., R. 7 W. 

T. 23 N., R. 1 W. 2,000-3,000 18,763 24.5 811.91 811.91 

0- 500 485 .3 .23 T. 27 N., R. 5 W. 500-1,000 1,163 2.6 5.39 

1,000-2,000 2,291 4.2 16.82 >3,000 22,629 47.2 1,892.03 1,892.03 

2,000-3,000 4,199 9.5 70.93 93.37 T. 27N., R. 6W. 

T. 23 N., R. 6 w. 2,000-3,000 9,229 40.2 656.10 

1,000-2,000 13,355 10.1 239.37 239.37 >3,000 10,985 50.7 986.45 1,642.55 

T.23N.,R. 7 W. T. 27 N., R. 7 w. 

1,000-2,000 9,807 9.2 159.62 2,000-3,000 18,811 40.6 1,351.17 1,351.17 

2,000-3,000 710 10.0 12.52 172.14 T. 28 N., R. 5 W. 

T. 24 N., R. 1 E. >3,000 17.337 59.6 1,827.52 1,827.52 

0- 500 2,797 . 5 2.69 T. 28 N., R. 6 W. 

500-1,000 195 .2 .07 2.76 2,000-3,000 1, 720 60.6 184.32 

T. 24 N., R. 1 W. >3,000 13,636 56.5 1,362.54 1,546.86 

1,000-2,000 5,348 10.9 103.35 T. 28 N., R. 7 W. 

2,000-3,000 13,762 17.2 418.02 2,000-3,000 17,106 54.8 1,657.97 1,657.97 

>3,000 1,535 36.7 99.77 621.14 

T. 29 N., R. 5 W. 

T. 24 N., R. 2 W. >3,000 8,016 63.6 902.29 902.29 

2,000-3,000 5,721 17.6 178.07 

>3,000 17,056 24.5 740.21 918.28 T. 29 N., R. 6 W. 

>3,000 10,450 60.2 1,113.41 1,113.41 

T. 24 N., R. 3 W. 

2,000-3,000 6,858 22.0 266.86 T. 29 N., R. 7 W. 

>3,000 13,977 25.8 637.02 903.88 2,000-3,000 3,288 77.3 449.53 

>3,000 17,607 75.3 2,348.00 2,797.53 

T. 24 N., R. 6 W. 

1,000-2,000 17,018 13.2 398.42 T. 30 N., R. 5 W. 

2,000-3,000 4,753 14.2 119.21 517.63 >3,000 13,518 48.6 1,163.93 1,163.93 

T. 24 N., R. 7 W. T. 30 N., R. 6 W. 

1,000-2,000 2,740 8.4 40.49 2,000-3,000 557 77.7 76.59 

2,000-3,000 16,300 13.0 374.45 414.94 >3,000 20,789 55.1 2,027.38 2,103.97 

28 Coalfields of New Mexico: Geology and Resources 
Table 81. Estimates of Federally owned subbituminous coal Table 81. Estimates of Federally owned subbituminous coal 

resources in the Fruitland Formation, San juan basin, New resources in the Fruitland Formation, San juan basin, New 

Mexico-Continued Mexico-Continued 

Location and Average Millions of Location and Average Millions of 

overburden total short tons overburden total short tons 

thickness Acres thick- thickness Acres thick-

(feet) ness Each Total (feet) ness Each Total (feet) interval (feet) interval 

Rio Arriba County--Continued San Juan County--Continued 

T. 30 N., R. 7 W. T. 23 N., R. 13 w. 

2,000-3,000 9,597 56.9 966.77 0- 500 9,633 21.1 358.95 358.95 

>3,000 5,397 59.5 568.14 1,534.91 T. 24 N., R. 8 w. 

T. 31 N., R. 5 W. 1,000-2,000 22,492 10.5 419.73 419.73 

>3,000 4,688 33.1 275.03 275.03 

T. 24 N., R. 9 W. 

T. 31 N. I R. 6 w. 1,000-2,000 21,648 13.2 506.25 506.25 

2,000-3,000 5,759 39.0 397.39 

>3,000 7,255 32.4 415.34 812.73 T. 24 N., R. 10 W. 

500-1,000 2,308 21.3 87.16 

T. 31 ~., R. 7 W. 1,000-2,000 18,269 19.7 635.40 722.56 

2,000-3,000 484 26.9 23.05 23.05 

T. 24 N., R. 11 W. 

T. 32 N., R. 5 W. 0- 500 2,285 22.2 89.79 

2,000-3,000 4,572 36.3 293.42 293.42 500-1,000 19,198 22.0 746.58 

T. 32 N., R. 6 W. 1,000-2,000 1,212 14.4 30.92 867.29 

>3,000 3,434 29.0 176.48 176.48 T. 24 N., R. 12 w. 

Total for Rio Arriba County ------------- 30,292.45 0- 500 4,249 33.3 250.20 

500-1,000 7,024 26.9 334.79 584.99 

San Juan County T. 24 N., R. 13 w. 

0- 500 838 33.2 49.27 49.27 T. 21 N., R. 8 W. 

0- 500 5,015 18.9 167.37 167.37 T. 25 N., R. 8 W. 

T. 22 N., R. 8 W. 1,000-2,000 16,435 11.3 327.30 

0- 500 11,686 18.0 373.04 2,000-3,000 7,146 12.4 156.35 483.65 

500-1,000 9,455 19.3 322.46 T. 25 N., R. 9 W. 1,000-2,000 1,663 17.3 50.97 746.47 1,000-2,000 19,291 12.1 412.48 412.48 

T. 22 N., R. 9 W. T. 25 N., R. 10 W. 

0- 500 21,013 18.5 686.93 1,000-2,000 20,530 15.2 551.86 551.86 

500-1,000 277 10.2 4.99 691.92 

T. 22 N., R. 10 W. T. 25 N., R. 11 W. 

500-1,000 2,330 21.5 88.83 0- 500 19,313 26.4 903.31 903.31 1,000-2,000 22,085 14.6 569.32 658.15 

T. 22 N., R. 11 W. 25 N., R. 12 W. 0- 500 7,154 28.0 354.85 354.85 T. 

500-1,000 5,521 24.4 238.29 

T. 23 N., R. 8 W. 1,000-2,000 16,192 17.3 494.82 733.11 

500-1,000 4,698 14.7 122.19 

1,000-2,000 18,898 10.2 340.39 462.58 T. 26 N., R. 8 W. 

1,000-2,000 2,761 13.3 65.09 

T. 23 N., R. 9 W. 2,000-3,000 21,262 18.8 708.43 773.52 

0- 500 378 21.1 14.11 

500-1,000 13.795 12.0 293.56 T. 26 N., R. 9 W. 

1,000-2,000 6,782 12.2 146.65 454.32 1,000-2,000 16,149 16.0 458.26 

2,000-3,000 2,565 23.9 108.46 566.72 

T. 23 N., R. 10 W. 

0- 500 7,608 25.8 347.17 T. 26 N., R. 10 W. 

500-1,000 14,440 20.2 516.39 1,000-2,000 20,393 15.2 546.72 

1,000-2,000 4,000 16.5 116.67 980.23 2,000-3,000 815 12.8 18.52 565.24 

T. 23 N., R. 11 W. T. 26 N., R. 11 W. 

0- 500 15,496 33.8 928.07 1,000-2,000 11,269 15.9 317.00 317.00 

500-1,000 3,761 31.2 207.99 1,136.06 

T. 23 N., R. 12 W. 

T. 27 N., R. 8 W. 

1,000-2,000 3,091 36.1 197.63 

0- 500 16,641 31.0 914.10 914.10 2,000-3,000 20,130 35.1 1,250.66 1,448.29 

Coal Resources of the San Juan Basin 29 
Table 81. Estimates of Federally owned subbituminous coal Table 81. Estimates of Federally owned subbituminous coal 

resources in the Fruitland Formation, San Juan basin, New resources in the Fruitland Formation, San Juan basin, New 

Mexico-Continued Mexico-Continued 

Location and Average Millions of Location and Average Millions of 

overburden total short tons overburden total short tons 

thickness Acres thick- thickness Acres thick-

(feet) ness Each Total (feet) ness Each Total (feet) interval (feet) interval 

San Juan County--Continued San Juan County--Continued 

T. 27N., R. 9W. T. 30 N., R. 12 W. 

1,000-2,000 1,686 41.5 123.75 1,000-2,000 3,747 20.6 136.76 

2,000-3,000 16,554 36.3 1,062.33 1,186.08 2,000-3,000 2,367 21.9 91.54 228.30 

T. 27 N., R. 10 W. T. 30 N., R. 13 W. 

1,000-2,000 15,983 29.0 820.87 500-1,000 291 13.8 7.13 

2,000-3,000 5,014 25.3 224.68 1,045.55 1,000-2,000 7,714 21.6 294.49 301.62 

T.27N.,R. 11 w. T. 30 N., R. 14 W. 

1,000-2,000 11,984 20.1 427.14 427.14 0- 500 401 16.2 11.48 

500-1,000 11,751 20.6 428.24 

T. 28 N., R. 8 W. 1,000-2,000 1,428 24.6 62.13 501.85 2,000-3,000 17,661 48.7 1,522.29 1,522.29 

28 N., R. 9 W. T. 30 N., R. 15 W. T. 0- 500 9,030 17.4 277.57 2,000-3,000 17,699 40.1 1,256.76 1,256.76 500-1,000 692 28.6 34.94 312.51 

T. 28 N., R. 10 W. T. 31N., R. 6W. 1,000-2,000 9,702 30.2 517.84 2,000-3,000 3,659 43.4 281.31 281.31 2,000-3,000 8,065 32.0 456.50 974.34 

T. 28 N. , R. 11 W. T. 31 N., R. 7 w. 

2,000-3,000 13,394 47.8 1,132.53 1,000-2,000 16,244 18.4 528.81 528.81 >3,000 1,641 43.9 127.64 1,260.17 

T.28N.,R. 12 W. 

31 N., R. 8 W. 1,000-2,000 3,580 17.5 111.16 111.16 T. 

2,000-3,000 2,273 71,0 285.57 

T. 28 N. , R. 13 W. >3,000 17,299 59.2 1,811. 78 2,097.35 

1,000-2,000 1,275 14.1 31.83 31.83 

T.31N.,R. 9 w. 

T. 29 N., R. 8 W. 2,000-3,000 17,512 49.3 1,527.82 

2,000-3,000 20,538 60.8 2,210.17 2,210.17 >3,000 526 61.8 57.58 1,585.40 

T.29N.,R. 9 w. T. 31 N., R. 10 W. 

2,000-3,000 20,436 41.4 1,498.00 1,498.00 2,000-3,000 20,306 39.3 1,413.61 1,413.61 

T. 29 N., R. 10 W. T. 31 N., R. 11 W. 

1,000-2,000 7,926 25.2 353.65 2,000-3,000 22,382 35.9 1,421.46 1,421.46 2,000-3,000 9,602 26.6 452.43 806.08 

T. 31 N., R. 12 W. 

T. 29 N., R. 11 W. 2,000-3,000 22,510 31.1 1,237.96 1,237.96 

1,000-2,000 17,664 15.3 477.78 477.78 

T. 31 N., R. 13 W. 

T. 29 N., R. 12 W. 500-1,000 2,293 16.5 66.87 

1,000-2,000 4,453 18.4 144.99 144.99 1,000-2,000 1,618 31.8 90.93 

T. 29 N., R. 13 W. 2,000-3,000 3,395 31.6 190.01 347.81 

1,000-2,000 2,849 16.7 84.15 84.15 T. 32 N., R. 6 W. 

T. 30 N., R. 8 W. 2,000-3,000 9,654 40.5 691.72 691.72 

2,000-3,000 15,717 57.9 1' 611.04 T. 32 N., R. 7 W. 

>3,000 765 61.9 83.78 1,694.82 2,000-3,000 204 45.0 16.27 16.27 

T. 30 N., R. 9 W. T. 32 N., R. 8 W. 

2,000-3,000 18,945 39.7 1,329.51 1,329.51 >3,000 15,045 58.8 1,565.95 1,565.95 

T. 30 N., R. 10 W. T. 32 N., R. 9 W. 

2,000-3,000 19,547 31.2 1,079.20 1,079.20 >3,000 13,297 54.9 1,292.39 1,292.39 

T. 30 N., R. 11 W. T. 32 N., R. 10 W. 

1,000-2,000 5,402 20.2 192.63 2,000-3,000 7,811 56.7 783.60 

2,000-3,000 12,024 30.7 653.99 846.62 >3,000 20,455 67.5 2,445.28 3,228.88 

30 Coalfields of New Mexico: Geology and Resources 
Table 81. Estimates of Federally owned subbituminous coal Table 81. Estimates of Federally owned subbituminous coal 

resources in the Fruitland Formation, San Juan basin, New resources in the Fruitland Formation, San Juan basin, New 

Mexico-Continued Mexico-Continued 

Location and Average Millions of Location and Average Millions of 

overburden total short tons overburden total short tons 

thickness Acres thick- thickness Acres thick-

(feet) ness Each Total (feet) ness Each Total (feet) interval (feet) interval 

San Juan County--Continued Sandoval County--Continued 

T. 32 N., R. 11 W. T. 21 N., R. 1 W. 

2,000-3,000 13,086 48.8 1,130.57 1,130.57 0- 500 4,751 1.0 8.67 

T. 32 N., R. 12 W. 500-1,000 6,917 1.6 19.24 

2,000-3,000 2,298 40.9 166.44 166.44 1,000-2,000 1,726 .6 1.84 29.75 

T. 32 N., R. 13 W. T. 21 N., R. 2 w. 

1,000-2,000 20,721 2.5 92.38 500-1,000 3,029 34.3 183.74 2,000-3,000 1, 777 5.0 15.69 108.07 1,000-2,000 2,197 42.3 163.96 347.70 

Total for San Juan County --------------- 53,514.82 T. 21 N., R. 3 w. 

1,000-2,000 15,955 6.2 176.27 

Sandoval County 2,000-3,000 6,885 12.4 150.80 327.07 

T. 17 N., R. 2 W. T. 21 N., R. 4 W. 

500-1,000 16,913 4. 7 140.72 0- 500 8,140 3.3 47.79 47.79 1,000-2,000 5,466 3.2 30.43 171.15 

T. 17 N., R. 3 W. T. 21 N., R. 5 W. 0- 500 21,631 7.6 291.22 291.22 500-1,000 9,860 8.1 141.88 

T. 17 N., R. 4 W. 1,000-2,000 12,904 6.9 157.33 299.21 

0- 500 21,389 9.6 363.78 363.78 T. 21 N., R. 6 W. 

T. 18 N., R. 1 W. 500-1,000 17,406 12.6 389.24 

0- 500 3,028 3.3 17.71 17.71 1,000-2,000 2,810 11.4 56.78 446.02 

T. 18 N., R. 2 W. T. 21 N., R. 7 W. 

0- 500 7,651 5.6 75.38 75.38 0- 500 7,224 12.6 160.80 

500-1,000 8,672 11.2 171.21 

T. 18 N., R. 3 w. 1,000-2,000 6,828 9.4 114.08 446.09 

0- 500 22,567 14.6 584.03 

500-1,000 125 4.2 .92 584.95 T. 22 N., R. 1 W. 

500-1,000 2,918 1.0 4.96 

T. 18 N., R. 4 W. 1,000-2,000 5,541 2.1 20.32 

500-1,000 1,898 8.5 28.46 28.46 2,000-3,000 1,582 1.3 3.68 28.96 

T. 19 N., R. 2 W. T. 22 N., R. 6 W. 

0- 500 4,271 1.4 10.44 10.44 1,000-2,000 22,888 7.2 292.82 292.82 

T. 19 N., R. 3 w. T. 22 N., R. 7 W. 

0- 500 7,498 4.1 54.57 54.57 500-1,000 8,589 11.9 181.40 

1,000-2,000 14,285 9.4 238.53 419.93 

T. 19 N., R. 4 W. 

0- 500 15,010 4.9 130.25 130.25 T. 23 N., R. 1 W. 

0- 500 359 .4 .22 

T. 20 N., R. 1 W. 500-1,000 1,337 2.1 4.95 

500-1,000 336 .7 .39 1,000-2,000 2,688 4.2 19.89 

1,000-2,000 764 2.9 3.96 4.35 2,000-3,000 1,351 2.1 4.98 30.04 

T. 20 N., R. 2 W. T. 23 N., R. 6 W. 

0- 500 4,405 1.3 10.24 1,000-2,000 12,103 6.9 147.89 147.89 

500-1,000 15,503 .7 19.30 

1,000-2,000 1,312 5.3 12.24 T. 23 N., R. 7 W. 

2,000-3,000 12,408 6.6 144.57 186.35 1,000-2,000 10,002 9.8 173.00 173.00 

T. 20 N., R. 3 W. Total for Sandoval County --------------- 5,539.58 

0- 500 8,150 10.3 148.40 

500-1,000 12,880 8.6 196.72 

1,000-2,000 6,724 7.5 89.15 434.27 

T. 20 N., R. 4 W. 

0- 500 11,594 10.3 211.56 

500-1,000 11,089 9.1 178.50 390.06 

Coal Resources of the San Juan Basin 31 
Table 82. Estimates of Federally owned subbituminous coal Table 82. Estimates of Federally owned subbituminous coal 

resources in the Menefee Formation, San Juan basin, New resources in the Menefee Formation, San Juan basin, New 

Mexico Mexico-Continued 

[Estimates may include some coal already mined but exclude resources in 

national parks, monuments, and national forests] Location and Average Millions of 

overburden total short tons 

Location and Average Millions of thickness Acres thickoverburden total short tons (feet) ness Each Total 

thickness Acres thick- (feet) interval 

(feet) ness Each Total (feet) interval San Juan County--Continued 

McKinley County T. 23 N., R. 8 TN. 

0- 500 20,667 9.4 342.70 342.70 

T. 15 N., R. 6 TN. 

0- 500 9,175 8.5 137.69 137.69 T. 23 N., R. 9 TN. 

0- 500 20,492 12.0 435.29 

T. 15 N., R. 7 TN. 500-1,000 775 17.8 24.35 459.64 

0- 500 15,445 6.7 184.21 184.21 

T. 23 N., R. 10 W. 

T. 15 N., R. 8 TN. 0- 500 2,706 11.0 52.60 

0- 500 3,770 5.6 37.01 37.01 500-1,000 8,293 14.6 214.15 

1,000-2,000 15,053 13.3 353.91 620.66 

T. 16 N., R. 5 TN. 

0- 500 14,820 7.2 189.39 189.39 T. 23 N., R. 11 TN. 

0- 500 5,339 24.8 234.12 

T. 19 N., R. 7 TN. 500-1,000 5,519 20.9 204.42 

500-1,000 607 7.9 8.47 8.47 1,000-2,000 7,797 17.9 247.53 686.07 

T. 19 N., R. 8 TN. T. 23 N., R. 12 TN. 

0- 500 3,115 5.8 31.91 0- 500 16,641 10.7 316.30 316.30 

500-1,000 3,794 7.8 52.12 84.03 

T. 23 N., R. 13 TN. 

T. 19 N., R. 9 TN. 0- 500 12,735 4.8 108.60 108.60 

0- 500 1,470 4.0 10.39 10.39 

T. 24 N., R. 8 TN. 

T. 20 N., R. 7 TN. 0- 500 737 9.9 12.84 12.84 

0- 500 9,963 16.0 281.41 

500-1,000 3,414 8.1 48.61 330.02 T. 24 N., R. 9 TN. 

0- 500 4,831 8.7 74.45 

T. 20 N., R. 8 TN. 500-1,000 4,842 6.0 50.99 

0- 500 4,895 10.3 89.03 1,000-2,000 3,240 2.2 12.72 138.16 

500-1,000 6,477 7.6 86.67 175.70 

T. 24 N., R. 10 TN. 

Total for McKinley County --------------- 1,156.91 0- 500 1,580 14.2 39.68 

500-1,000 1,544 22.3 60.94 

San Juan County 1,000-2,000 7,275 15.1 194.47 

2,000-3,000 9,894 6.6 115.13 410.22 

T. 21 N., R. 8 TN. 

0- 500 5,014 9.7 85.97 85.97 T. 24 N., R. 11 TN. 

0- 500 5,818 28.1 289.71 

T. 21 N., R. 13 TN. 500-1,000 7,256 23.4 300.96 

0- 500 3,074 2.4 13.25 13.25 1,000-2,000 2,119 5.4 20.19 610.86 

T. 22 N., R. 8 TN. T. 24 N., R. 12 TN. 

0- 500 22,943 15.3 620.63 620.63 0- 500 10,869 22.2 427.79 

500-1,000 404 13.9 9.92 437.71 

T. 22 N., R. 9 TN. 

0- 500 21,004 21.1 783.72 T. 24 N., R. 13 TN. 

500-1,000 326 21.5 12.42 796.14 0- 500 838 5.5 8.11 8.11 

T. 22 N., R. 10 TN. T. 25N., R.llTN. 

0- 500 2,905 17.9 91.93 1,000-2,000 6,053 11.8 126.59 

500-1,000 8, 778 13.9 215.63 2,000-3,000 7,744 11.5 157.24 283.83 

1,000-2,000 12,080 10.7 229.15 536.71 

T. 25 N., R. 12 TN. 

T. 22N., R.11TN. 0- 500 789 13.1 18.34 

500-1,000 3,525 10.6 66.32 500-1,000 1, 776 18.8 58.96 

1,000-2,000 1,849 10.2 33.28 99.60 1,.000-2 '000 2,450 17.8 76.98 154.28 

32 Coalfields of New Mexico: Geology and Resources 
Table 82. Estimates of Federally owned subbituminous coal 

resources in the Menefee Formation, San Juan basin, New 

Mexico-Continued · 

Location and Average Millions of 

overburden total short tons 

thickness Acres thick-

(feet) ness Each Total (feet) interval 

San Juan County--Continued 

T. 26 N., R. 11 W. 

2,000-3,000 1,417 

>3,000 7,731 

T. 27 N., R. 11 W. 

7.6 

4.2 

>3,000 9,380 12.0 

T. 28 N., R. 10 W. 

>3,000 331 23.1 

T. 28 N., R. 11 W. 

>3,000 15,333 11.6 

T. 28 N., R. 12 W. 

2,000-3,000 2,519 

>3,000 465 

T. 29N., R.llW. 

>3,000 2,040 

T. 30 N., R. 11 W. 

>3,000 2,659 

T. 31 N., R. 11 W. 

>3,000 15,976 

T. 32 N., R. 11 W. 

>3,000 3,379 

7.9 

3.0 

8.1 

6.0 

6.4 

7.1 

18.93 

57.96 

198.49 

13.54 

315.34 

35.06 

2.45 

29.11 

28.22 

181.27 

42.19 

Total for San Juan County ---------------

Sandoval County 

T. 16 N., R. 3 W. 

0- 500 4,735 

T. 16 N., R. 4 W. 

0- 500 16,870 

T. 19 N., R. 1 W. 

500-1,000 

1,000-2,000 

2,000-3,000 

T. 19N., R. 2W. 

0- 500 

500-1,000 

1,000-2,000 

T. 19N., R. 3W. 

0- 500 

500-1,000 

1,000-2,000 

T. 19 N., R. 4 W. 

500-1,000 

1,000-2,000 

2,000-3,000 

4,242 

440 

13,694 

2,925 

5,088 

3,091 

2,108 

7,212 

13,248 

2,693 

4,969 

1,184 

6.5 

5.3 

5.5 

6.5 

5.0 

6.5 

6.2 

7.0 

7.0 

6.5 

6.2 

8.7 

7.8 

5.3 

54.59 

159.22 

41.57 

5.02 

120.55 

33.67 

56.14 

38.36 

25.94 

83.37 

145.22 

41.21 

68.79 

11.09 

76.89 

198.49 

13.54 

315.34 

37.51 

29.11 

28.22 

181.27 

42.19 

7,664.84 

54.59 

159.22 

167.14 

128.17 

254.53 

121.09 

Table 82. Estimates of Federally owned subbituminous coal 

resources in the Menefee Formation, San Juan basin, New 

Mexico-Continued 

Location and 

overburden 

thickness 

(feet) 

Acres 

Average 

total 

thickness 

(feet) 

Millions of 

short tons 

Each 

interval Total 

Sandoval County--Continued 

T. 21 N. , R. 6 W. 

0- 500 5,433 17.7 169.79 169.79 

T.21N.,R.7W. 

0- 500 22,725 15.4 618.59 618.59 

T. 22 N., R. 6 W, 

0- 500 8,171 6.1 87.71 87.71 

T. 22 N. , R. 7 W. 

0- 500 22,844 5.3 213.36 213.36 

T. 23 N., R. 7 W. 

0- 500 6,162 2.6 27.77 27.77 

Total for Sandoval County 2 ,001. 96 

REFERENCES CITED 

Crowley, S.S., Medlin, A.L., and Smith, R.J., 1981, Guide for the 

calculation of coal resources using the computer program 

GARNET: U.S. Geological Survey Open-File Report 

81-563, 34 p. 

Fassett, J.E., and Hinds, J.S., 1971, Geology and fuel resources of 

the Fruitland Formation and Kirtland Shale of the San Juan 

basin, New Mexico and Colorado: U.S. Geological Survey 

Professional Paper 676, 76 p. 

Krohn, K.K., Carey, M.A., Carter, M.D., and Medlin, A.L., 1981, 

Guide to the use of PACER, the data retrieval and update 

system for the National Coal Resources Data System 

(NCRDS): U.S. Geological Survey Open-File Report 

82-291' 99 p. 

Wood, G.H., Kehn, T.M., Carter, M.D., and Culbertson, W.C., 

1983, Coal resource classification system of the U.S. 

Geological Survey: U.S. Geological Survey Circular 891, 

65 p. 

Coal Resources of the San Juan Basin 33 

Chapter C 

Coal Resource Estimation in 

the San Juan Basin Using 

Geostatistical Methods 

By LEWIS W. BOGER, jR., and ANTOINETTE L. MEDLIN 

Resources of the Fruitland coal zone 

estimated by the kriging technique 

U.S. GEOLOGICAL SURVEY BULLETIN 1972 

COALFIELDS OF NEW MEXICO: GEOLOGY AND RESOURCES 
CONTENTS 

Abstract 37 

Introduction 37 

Geostatistical methods 37 

Data preparation 37 

Model selection 38 

Results 39 

Conclusions 42 

References cited 43 

FIGURES 

Cl. Semi-variogram for coal thickness in the Fruitland Formation 38 

C2-C5. Maps of the area underlain by the Fruitland Formation in the San Juan basin 

showing: 

C2. Locations of data collection points and grid blocks used for 

kriging 39 

C3. Isopachs of kriged coal thickness values 40 

C4. Estimate of thickness variance of coal beds, based on original kriged 

data 42 

C5. Modified estimate of thickness variance of coal beds, generated by 

adding data for theoretical drill holes 43 

TABLES 

Cl. Kriged coal tonnages and kriging variance for lOxlO-km blocks in the area 

underlain by the Fruitland Formation, San Juan basin, New Mexico 41 

36 Contents 
Coal Resource Estimation in the San Juan Basin 

Using Geostatistical Methods 

By Lewis W. Boger, Jr., and Antoinette L. Medlin, 

Abstract 

This chapter describes the application of the geostatistical method known as kriging to estimate coal resources of the 

Fruitland coal zone in the San Juan basin. The study should be 

considered experimental because the method was used to 

estimate resources over a very large area (7,500 square miles), 

and the data were not homogeneous. 

A semi-variogram model for coal thickness was 

developed for the entire Fruitland Formation (Upper 

Cretaceous). It was used to estimate the coal resources in the 

deposit using large 1 Ox1 0-km (6.2x6.2-mi) panels. A brief test 

also shows how maps of kriging variance can be used to 

project how much the resource estimate could be improved by 

additional data-collection points in particular locations. In 

addition, we attempted to calculate semi-variograms for ash, 

sulfur, and Btu, but the data were insufficient to support this 

effort. 

Total in-place coal resources of the Fruitland Formation 

estimated by this technique were 159,984 million tons, which 

compares favorably with the GARNET isopach technique 

result of 167,501 million tons derived by Biewick and others 

(this volume, chap. B). However, since this study is 

experimental, further work is necessary before these results 

should be used for purposes other than observing trends, 

designing sampling programs, or gross estimates of in-place 

coal. 

INTRODUCTION 

The geostatistical method known as kriging is a 

useful technique for estimating coal tonnages at a point or 

over an area of ground. Kriging makes use of a semivariogram model to create weighting functions for values 

(in this case, coal thicknesses) at observed sample points. 

Manuscript approved for publication January 10, 1991. 

Estimated thickness may be calculated by summing the 

products of the sample values and their respective weights. 

Weighting functions are determined so that the estimate is 

unbiased and has minimum error variance. Variance is a 

measure of the difference between the value expected and 

the observed value. A good overview of the technique can 

be found in the first four chapters of Mousset-Jones (1980); 

for a detailed explanation see Journel and Huijbregts (1978). 

A geostatistical software system on the NCRDS 

Prime 9750 computer was used to create a semi-variogram 

model and perform kriging for coal thickness data, to 

attempt to define semi-variograms for ash, sulfur, and Btu, 

and to create kriging variance maps. The following sections 

present further details of data preparation, semi-variogram 

model selection, results, and conclusions. 

GEOSTATISTICAL METHODS 

Data Preparation 

A geostatistical analysis leading to the estimation of 

the quantity of a coal resource requires geologic analysis of 

the region and separation of the data into geologically 

homogeneous groups. When the data cannot be so grouped, 

the quality of the estimates will be lower. Standard 

statistical studies of the data are done to assure a reasonable 

degree of statistical homogeneity within subsets. 

The same PACER data set retrieved from NCRDS for 

the GARNET estimation (Biewick and others, this volume) 

was used in the geostatistical estimation. Only drill hole 

data representing the complete Fruitland coal zone were 

used. Outcrop data and measured sections were eliminated 

to improve the homogeneity in the data set. The data were 

converted from the PACER format to a format suitable for 

input to the geostatistical programs. In this conversion, 

latitudes and longitudes were converted to kilometers in the 

Universal Transverse Mercator Coordinate System. The 

Coal Resource Estimation in the San Juan Basin 37 
data set was then subjected to standard statistical tests 

mentioned above to ascertain the consistency of the data, 

and it was checked for any points with identical locations. 

Duplicate locations will cause the kriging program to fail. 

Coal thicknesses were summed for all samples with the 

same identifier (drill-hole name), yielding total Fruitland 

coal thicknesses identical to those that were used in the 

GARNET estimate. 

Model Selection 

Because an underlying premise of geostatistics is that 

the variable of interest has some degree of continuity within 

the area of study, a semi-variogram model must be selected 

which best depicts this continuity. The semi-variogram is a 

curve representing the degree of continuity of the variable: 

in this case, coal thickness (fig. Cl). For this application, 

gamma H, the value of the semi-variogram, is defined as 

one-half the mean squared difference in total coal thickness 

(in feet) between drill holes located a given distance apart. 

In general, the semi-variogram is an increasing function of 

distance because, usually, the farther samples are from one 

N 

1-

u. 

z 

:i 

<( 

~ 

~ 

200 

~ 100 

Nugget 

Sill -

5 10 15 

another, the greater the difference between the sample 

values. 

The semi-variogram of thickness shown in figure Cl 

was constructed from the Fruitland data set. In this case, at 

a distance of separation of 6.5 mi, determined by the 

flattening of this curve, the values become independent of 

one another. This plateau of constant variance is termed the 

"sill," and the horizontal distance at which the sill is reached 

is called the "range." The range defines the area of spatial 

influence within a given data set. They-intercept is termed 

the "nugget." The nugget is a component of uncertainty that 

is not statistically predictable from the available data. The 

nugget comprises variability on a scale smaller than can be 

quantified given the spacing of the data samples, errors in 

the interpretation of the geophysical logs, and other factors 

characterized as noise. 

The data available from the NCRDS detailed geochemical data base (USCHEM) for the Upper Cretaceous 

Fruitland Formation were not sufficient in number or 

distribution to develop any sort of statistical model for any 

of the basic coal quality parameters. Additional data were 

retrieved from a second coal quality data base (USAL YT), 

which contains only data from standard proximate and 

20 25 30 35 40 

SEPARATION OF DATA POINTS, IN MILES 

Figure Cl. Semi-variogram for coal thickness in the Fruitland Formation, San Juan basin, New Mexico. See text for explanation 

of "gamma H," "nugget," "range," and "sill." 

38 Coalfields of New Mexico: Geology and Resources 
ultimate coal analyses. This data set included data from 107 

Fruitland Formation coal samples, but they were all 

clustered in the vicinity of the Navajo mine in the northwest 

comer of the basin. Again the distribution was insufficient 

to support the kriging analysis for the Fruitland coal. 

Several models for the distribution of Btu, ash, and sulfur 

values were tested, but the "best" model had a range of less 

than 2 mi. This result indicates that the data are essentially 

only valid for the point locations they represent; no reliable 

basin models could be developed. 

~ I 

181 I 185 

180r~ r . 175 

. ·:::: . 

15~- . · .. ::1 

1~5 

lfsd 1~5 

171 12p 

. . .. .. '120 ··.~~i·~~ ·1.) 5 . 

.. 

. . . 9.1 9~ .. .. : 

~ ........... ; .. =.~~=: 85 

~ ....... ~~ :- ..... c__ ~ 

9 61 65 

h----rt 

~ . · ... 60 

~~ 

.. 

: 

f----- 31 35 ~ ~ 

30 25 

1 5 

I 

10 

10 20 

Results 

The kriging technique was developed for use in mine 

planning and development. It produces the most reliable 

estimates when applied to relatively small, geologically 

homogeneous areas where the distribution of data is fairly 

uniform. 

Using the kriging technique to determine the coal 

resources of a large area where the coal beds are thin and 

irregular is an experimental application of the method. 

'\ _\ I 

(__ 

1\ 190 195 

170 ·\ 166 

j~ 

~ 

160 

11 

165 

140 ~136 

130 1135 : 

1~ .. . . . 110 : 

. . : 100 . .. 1~5l .. .. ":7 I 

80 

v .. 70: 75 

.. 50' 

u 

46 

IJ 

40 45 -

( 

~ 20 v= 16 

th~ '--' 

~ ~ 

10 ~ ~ 15 

I 

20 30 MILES 

30 40 KILOMETERS 

Figure C2. Locations of data collection points and 1 Ox1 0-km (6.2x6.2-mi) blocks used for kriging to estimate coal resources 

in the Fruitland Formation, San Juan basin, New Mexico (table C1 ). See figure B1 of Biewick and others (this volume, chap. B) 

for location of area shown. 

Coal Resource Estimation in the San Juan Basin 39 
Outcrop of Fruitland Formation 

10 20 30 MILES 

10 20 30 40 KILOMETERS 

Figure CJ. lsopachs of kriged coal thickness values, in feet, for the Fruitland coal zone in the San Juan basin, New Mexico. See 

figure 81 of Biewick and others (this volume, chap. B) for location of area shown. 

Further work is necessary before the results should be used 

for purposes other than observing trends, designing 

sampling programs, or gross estimates of in-place coal. 

The range, sill, and nugget parameters obtained from 

the construction of the semi-variogram were used in the 

kriging to estimate coal thickness at the grid intersections of 

a regularly spaced grid (fig. C2). The coal isopach map 

derived from these points (fig. C3) is generally similar to the 

one generated by the GARNET program (Biewick and 

others, this volume, fig. B2); the differences are due to the 

different gridding algorithms and interpolations used in the 

two techniques. The kriging algorithm also produces 

variance estimates at the grid nodes, which were contoured 

to produce the variance map in figure C4. This map 

40 Coalfields of New Mexico: Geology and Resources 

represents the general reliability of the isopach map by 

indicating the potential variation of the estimated values. 

High variance values can be seen on the southern and 

western edges, in the northeast comer, and in the southcentral parts of the contoured area. This high variance 

probably reflects the lack of data in these areas. 

Because kriging variance is not a function of the 

values encountered at sample locations but a function of the 

number of sample points, their relative locations, and the 

spatial variability model, maps of the variance can be very 

useful in designing future data collection efforts. 

Hypothetical drill-hole locations can be inserted to assess 

their impact on the precision of the estimate. Eight such 

hypothetical drill-hole locations were added to the data set 
Table C1. Kriged coal tonnages and kriging variance for 1 Ox1 0-km (6.2x6.2-mi) blocks of the Fruitland Formation, San juan 

basin, New Mexico 

Block Kriged Coal Kriging Block Kriged Coal Kriging Block Kriged Coal Kriging 

No. thick- (millions vari- No. thick- (millions vari- No. thick- (millions vari-

(fig. ness 1 of short ance (fig. ness 1 of short ance (fig. ness 1 of short ance 

C2) (feet) tons) (ft 2 ) C2) (feet) tons) (ft2 ) C2) (feet) tons) (ft2 ) 

20 6.1 268.20 53 93 27.4 1,196.52 7 144 40.0 1, 751.51 24 

37 19.5 854.45 58 94 20.6 898.89 21 145 26.3 1,749.20 14 

38 21.9 957.02 21 95 16.0 699.58 19 146 18.0 786.00 13 

39 14.1 616.35 39 96 15.9 693.41 18 147 16.8 733.87 13 

40 12.3 538.28 41 97 17.8 776.47 16 148 15.0 655.93 15 

41 8.7 381.08 10 98 18.1 789.98 10 149 16.6 727.70 27 

42 6.2 269.99 58 99 15.1 658.34 10 150 18.4 805.56 50 

43 20.4 892.72 83 100 13.6 593.43 8 151 11.9 519.73 52 

47 8.5 373.34 32 101 22.1 966.38 4 152 19.9 868.32 24 

48 14.7 644.43 13 102 24.0 1,049.92 14 153 19.5 853.49 12 

49 6.6 289.02 15 103 30.1 1,314.83 14 154 21.2 928.94 20 

so 7.7 335.73 27 104 34.0 1,486.20 11 155 16.1 702.69 13 

51 8.6 374.92 19 105 18.6 811.77 19 156 21.8 952.25 21 

52 12.0 525.37 13 106 12.3 538.71 71 157 36.6 1,601.66 27 

53 22.0 964.32 10 107 24.3 1,062.51 33 158 59.5 2,600.19 24 

54 20.6 902.52 10 108 28.0 1,223.55 11 159 67.4 2,945.76 31 

55 28.2 1,232.48 31 109 33.2 1,452.61 6 160 67.1 2,934.17 28 

56 29.2 1,274.99 83 110 29.8 1,302.98 7 161 59.5 2,600.84 18 

62 11.7 510.11 120 111 14.6 638.35 8 162 42.7 1,866.01 26 

63 9.4 410.78 31 112 20.1 877.85 10 163 25.1 1,096.10 15 

64 21.5 939.65 19 113 17.0 744.15 11 164 20.6 902.56 44 

65 34.8 1, 521.62 18 114 12.7 556.12 10 167 11.3 493.40 68 

66 30.5 1,332.20 12 115 16.2 706.93 5 168 20.1 878.33 52 

67 15.8 689.26 17 116 14.0 612.19 16 169 30.5 1,335.61 22 

68 14.1 618.71 13 117 18.1 792.74 20 170 36.6 1,600.35 34 

69 9.2 402.69 36 118 15.5 677.19 14 171 47.5 2,078.53 19 

70 7.2 317.05 11 119 25.5 1,113.64 5 172 58.0 2,534.71 42 

71 12.2 533.33 9 120 32.7 1,428.33 15 173 58.6 2,561.00 31 

72 16.5 720.18 13 121 23.3 1,018.91 19 174 33.8 1,477.23 20 

73 18.6 814.48 5 122 19.7 861.85 27 175 31.7 1,387.44 12 

74 17.8 778.22 25 123 14.5 636.03 15 176 25.4 1,110.84 24 

75 11.8 515.75 83 124 15.6 680.60 20 177 22.8 997.43 19 

76 19.2 840.94 22 125 19.4 848.42 12 178 19.4 848.02 25 

77 20.7 907.33 11 126 24.0 1,051.71 12 179 19.6 858.08 4 

78 24.0 1,050.40 18 127 30.9 1, 351.92 10 180 13.6 595.00 48 

79 14.1 617.70 10 128 34.2 1,494.29 15 181 17.4 758.98 116 

80 13.8 602.40 12 129 34.2 1,496.34 10 182 13.9 608.65 69 

81 12.7 556.78 10 130 39.5 1,728.98 27 183 23.5 1,029.84 37 

82 11.9 521.61 5 131 44.0 1,923.44 10 184 30.8 1,345.54 57 

83 10.2 445.38 9 132 41.4 1 t 811.12 10 185 36.6 1 t 601.40 15 

84 12.2 532.85 52 133 36.9 1,612.86 16 186 35.5 1,550.53 22 

85 26.7 1,167.88 58 134 18.4 803.89 27 187 54.8 2,396.98 42 

86 29.3 1,282.64 23 137 16.8 732.08 45 188 66.1 2 '891. 83 25 

87 32.1 1,404.28 17 138 35.7 1,559.28 23 

88 24.4 1,065.71 7 139 51.9 2,270.45 17 189 50.2 2,196.19 48 

190 37.4 1,637.88 24 

89 26.8 1,170.63 12 140 60.2 2,632.16 10 191 33.1 1,449.15 12 

90 30.7 1,340.73 45 141 53.2 2,325.26 27 192 30.2 1,322.84 46 

91 25.2 1,104.02 6 142 52.8 2,308.94 24 

92 25.4 1,112.02 8 143 48.5 2,119.78 25 Total --- 159,983.71 

1Kriged thicknesses are rounded here, but were carried out to three decimal places for the 

calculation of coal tonnages. 

Coal Resource Estimation in the San Juan Basin 41 
10 20 30 40 KILOMETERS 

Figure C4. Estimate of thickness variance of coal beds in the Fruitland Formation, based on kriged original data. See figure B1 

of Biewick and others (this volume, chap. B) for location of area shown. 

in locations of high variance, and a second variance map 

was generated (fig. C5). A comparison of figures C4 and C5 

illustrates how much the estimate can be improved by a 

limited amount of selected drilling. (Note the southeastern, 

eastern, and northwest areas of the figures.) 

Average coal thicknesses were computed for each 

IOxiO-km (6.2x6.2-mi) grid block within the basin (fig. C2) 

using block kriging. Coal tonnages were derived from these 

thicknesses using a value of 43,737,400 tons per foot of 

thickness (rounded from 43,737,408 tons/ft, which equals 

1,770 tons/acre ft x 247.104 acres/km2xiOO km2 per grid 

block). Results are shown in table Cl. Blocks not listed 

there were not represented by enough data to allow kriging. 

Total in-place coal resources estimated by this method are 

42 Coalfields of New Mexico: Geology and Resources 

159,983 million tons; this compares favorably with the 

GARNET total coal estimate of 167,501 million tons-a 

difference of less than 5 percent. 

CONCLUSIONS 

As previously stated, the kriged results of this portion 

of the San Juan basin study should be considered with an 

understanding of their limitations: 

1. The area of study is much larger than the typical 

mine site application. 
10 20 30 40 KILOMETERS 

Figure CS. Modified estimate of thickness variance of coal beds in the Fruitland Formation, generated by adding data for eight 

theoretical drill holes to the original kriged data. Compare with figure C4. 

2. The data set was constructed of summed 

thickness values and cannot be considered to be 

homogeneous. 

3. The clustering of data in some areas and the 

scarcity of data in others bias the results. 

4. Determining a single semi-variogram model for 

the entire deposit, rather than determining a 

separate semi-variogram model for each lOxlOkm block, smooths possible localized variations 

within the area of this study. 

5. Variances that are high relative to low tonnages 

shown for some blocks in table C 1 are 

attributable to one or more of the above four 

items; they indicate unreliable estimates over 

some large areas of the basin. 

A further demonstration of the kriging method would 

be better carried out in an area of similar size where more 

data are available and closer control can be imposed on data 

quality. 

REFERENCES CITED 

Joumel, A.G., and Huijbregts, Ch.J., 1978, Mining geostatistics: 

New York, Academic Press, 600 p. 

Mousset-Jones, P.F., ed., 1980, Geostatistics: New York, 

McGraw-Hill, 168 p. 

Coal Resource Estimation in the San juan Basin 43 

Chapter D 

Geology and Coal Resources 

of the Raton Coalfield 

By CHARLES L. PI LLMORE 

Stratigraphic and environmental 

framework of an area of coal-bearing 

Late Cretaceous and Paleocene rocks 

U.S. GEOLOGICAL SURVEY BULLETIN 1972 

COALFIELDS OF NEW MEXICO: GEOLOGY AND RESOURCES 

CONTENTS 

Abstract 49 

Introduction 49 

Geologic setting 52 

Stratigraphy 53 

Pierre Shale and Trinidad Sandstone 53 

Vermejo Formation 54 

Raton Formation 55 

Poison Canyon Formation 55 

lgneousrocks 55 

Coal resources 56 

Coal deposits in the Vermejo Formation 58 

Castle Rock district 58 

Rosado district 59 

Brilliant district 60 

Dawson and Koehler districts 61 

Other areas 61 

Coal deposits in the Raton Formation 61 

York Canyon district 62 

Upper York (Left Fork) district 63 

Cottonwood Canyon district 63 

Ancho Canyon district 63 

Chimney Divide district 64 

Potato Canyon district 65 

Crow Canyon district 65 

Brilliant district 66 

Other coal beds in the Raton Formation 66 

Conclusions 67 

References cited 67 

FIGURES 

D 1. Location map of coal mines, abandoned coal mining towns and camps, and 

other geographic features in and near the Raton coalfield 50 

D2. Map showing locations of the Raton and San Juan basins 52 

D3. Stratigraphic chart of Upper Cretaceous and Paleocene rocks of the New 

Mexico portions of the Raton and San Juan basins 53 

D4. Map showing areal distribution of coal-bearing Upper Cretaceous and 

Paleocene rocks in the Raton basin 53 

D5. Generalized geologic map of the Raton coalfield 54 

D6. Diagrammatic geologic cross section and columnar sections across the 

northwestern part of the Raton coalfield 56 

D7. Map showing Western Interior seaway of Late Cretaceous time and locations of 

the Raton and San Juan basins 58 

D8. Map of the Raton coalfield showing districts that have demonstrated coal 

resources 62 

D9. Map of the Raton coalfield showing geographic subdivisions used to describe 

inferred coal resources 63 

D 10. Diagrammatic stratigraphic section showing relations of coal beds in the central 

and eastern parts of the Raton coalfield 65 

Contents 47 
TABLES 

D 1. General stratigraphic description of the Raton coalfield 59 

D2. Representative proximate analyses of selected coal beds in the Raton 

coalfield 60 

D3. Ranges of volatile matter and sulfur in 164 core samples of the major coal beds 

in the Raton coalfield 60 

D4. Demonstrated coal resources of commercial thickness within mining districts of 

the Raton coalfield 61 

D5. Estimated minimum inferred coal resources within subdivisions of the Raton 

coalfield 64 

48 Contents 
Geology and Coal Resources of the Raton Coalfield 

By Charles L. Pi II more 

Abstract 

The Raton basin is a broad, arcuate depositional trough 

of structural origin that extends about 85 miles from near 

Gardner, Colo., to Cimarron, N.Mex. It is the southernmost of 

the Laramide intracratonic folded basins at the eastern margin 

of the Rocky Mountains and is a sister basin to the San Juan 

basin, which lies to the west and contains older but related 

rocks. The Raton coalfield is the New Mexico portion of the 

area within the Raton basin that is underlain by coal-bearing 

rocks. The coalfield covers an area of about 900 square miles 

and contains large resources of high-quality coking coal in 

rocks of the Vermejo Formation of Late Cretaceous age and the 

Raton Formation of Late Cretaceous and Paleocene age. Coal 

has been mined along the eastern margin of the coalfield since 

about 1870, but only the York Canyon surface mine and the 

Cimarron underground operation, in the north-central part of 

the coalfield, are presently active (1991 ). Coal beds of the 

Vermejo Formation were deposited in contemporaneous fluviodeltaic plain and back-barrier coastal environments and are 

the thickest and most extensive coal beds in the Raton field. 

The coal beds of the Raton Formation accumulated in poorly 

drained backswamp environments on flood plains of 

meandering streams that drained a broad alluvial plain. These 

coal deposits are lenticular in shape and less extensive than 

those of the Vermejo Formation. 

Recent field and subsurface investigations within the 

coalfield permit delineation of 14 principal coal districts, 

based on the areal distribution of the thickest coal beds in both 

formations. Nearly 1.5 billion tons of demonstrated coal 

resources have been calculated for these districts. Castle Rock, 

the largest unmined district, is in the west-central part of the 

coalfield and contains about one-third of the demonstrated 

resources. The remainder of the resources are distributed 

among 13 smaller districts, located mostly in the northern part 

of the field. In addition to the demonstrated resources, about 8 

billion tons of inferred resources are estimated for the Raton 

field-more than twice earlier figures. The inferred resources, 

which are mainly in thinner beds, are distributed throughout 

the coalfield in 15 geographic subdivisions. 

Manuscript approved for publication January 10, 1991. 

INTRODUCTION 

The Raton coalfield occupies the New Mexico 

portion of the Raton Mesa coal region, the southernmost 

part of the Northern Great Plains coal province (Trumbull, 

1959). The coalfield covers an area of about 900-1,000 mi2 

in northeastern New Mexico and contains large resources of 

high-quality coking coal in rocks of the Vermejo (Upper 

Cretaceous) and Raton (Upper Cretaceous and Paleocene) 

Formations. An early estimate (Read and others, 1950) 

tabulated 4. 71 billion tons of coal in beds 14 in. thick or 

greater, beneath less than 3,000 ft of overburden. A more 

recent appraisal indicates identified coal resources of about 

9.5 billion tons, more than twice that earlier figure. 

Coal was discovered in the coalfield by the Long 

Expedition in about 1821 (Lee, 1917) and has been mined 

commercially since about 1870. Mining activity was 

concentrated along the eastern margins of the field until 

1966, when the York Canyon mine was opened in the 

west-central part of the coalfield, about 26 mi west of 

Raton. At present, the York Canyon surface mine and the 

Cimarron mine, about 6 mi to the northwest, are the only 

active mines. The locations of these mines and other 

geographic features are shown on figure D 1. 

The following brief discussion of the location and 

general geologic setting of the Raton coalfield is from 

various reports by Pillmore (1969a; 1969b; 1976), Pillmore 

and others (1984), Pillmore and Flores (1984; 1987), Wanek 

(1963), and Lee (1917). Resource estimates shown here 

have been augmented and changed from those calculated by 

Pillmore (1969b ), using data supplied by Kaiser Coal Corp., 

for the large part of the coalfield in the coal districts and 

subdivisions west of Raton, and by Santa Fe Mining Corp. 

for the Yankee subdivision, east of Raton. I am indebted to 

both of these corporations for allowing use of their 

proprietary subsurface data to improve these estimates. 

Pittsburg & Midway (P&M) Coal Mining Co. purchased 

Kaiser's mines and coal resources in 1989. Updates on the 

resources and expected production of the York Canyon and 

Cimarron mines and the approval to publish this report are 

much appreciated. 

Raton Coalfield 49 
~~ .1_5'------------~--------------------~----~1~05~0~0' ________________________________________ __ 

00' 

o··· 

~C./ n(:i. 

'-.t·· 

I 

) 

\ 

j 

i 

\ 

\. 

\ 

--··· "-.... 

~ 

'---.··.\_ l .. ··~ .. ~ 

\ 

· .. ~ 

~ 

\ 

\._ 

\ 

\~ 

\~ 

~ ... ·~ ~ · .. 

\ · .. \ 

\.} 

··. \ 

""··. :. ! .. 

\ \<; . '1.-, 

··\~ 

<; 

\ 

\ 

Figure Dl. Location of coal mines, abandoned coal mining towns and camps, and other geographic features in and near the 

50 Coalfields of New Mexico: Geology and Resources 
\ .. 

"--") --··. \.._ ... ,. (..,_ '100 •• ... \ <;oal c~~. ;:;-'""" r···~ .··~ .. · _,..-- : 

/ --··· -. 

0 Willow 

0 Van Houton 

~ 

~ Koehler 

Raton coalfield, New Mexico. 

Gardiner~ 

EXPLANATION 

~ Coal mines 

0 Abandoned mining 

towns and camps 

10 MILES 

Raton Coalfield 51 
GEOLOGIC SETTING 

The Raton coalfield lies within the southern half of 

the Raton basin, a large, arcuate, asymmetric structural 

basin. This basin is the southernmost of the Laramide 

intracratonic folded basins at the eastern margin of the 

Rocky Mountains (Baltz, 1965) and is a sister basin to the 

San Juan basin, which lies to the west (fig. D2) and contains 

older but related rocks (fig. D3). The Raton basin extends 

from near Gardner, Colo., on the north, to Cimarron, N. 

Mex., on the south-a distance of about 85 mi. The 

structural basin is approximately 70 mi wide at its widest 

point, along the boundary between Colorado and New 

Mexico, and narrows both to the north and south. The 

coalfield is about 50 mi wide at the State boundary. The 

basin is bounded on the east by the Sierra Grande arch in 

New Mexico and the Las Animas arch in Colorado. The 

northern limit is defined by the Apishapa arch (fig. D4). On 

the west side of the basin, sedimentary rocks of Permian to 

SAN MIGUEL 

Tertiary age are steeply tilted to overturned along the east 

flank of the Sangre de Cristo Mountains. The axis of the 

basin, which generally separates more steeply dipping strata 

from the gently dipping beds to the east, is somewhat 

sinuous and lies near the west side of the basin. 

'The Raton coalfield lies entirely in Colfax County, N. 

Mex. The State line separating the Raton coalfield from the 

Trinidad coalfield, to the north, nearly coincides with the 

drainage divide between the Purgatoire River in Colorado 

and the Canadian River in New Mexico. Coal-bearing rocks 

in the Raton field underlie a highly dissected plateau whose 

elevation rises gradually from about 7,000 ft in the eastern 

part to approximately 9,500 ft in the western part. The 

coalfield's eastern and southern boundaries, in most places, 

are marked by nearly horizontally bedded, sandstonecapped escarpments standing several hundred feet above the 

adjoining high plains. Its western margin is marked by more 

steeply dipping beds that form hogback ridges and parallel 

valleys along the eastern front of the Sangre de Cristo 

SAGUACHE 

_;_~-------

Newcomb 0 

McKINLEY 

! l 

SANDOVAL 

50 

CONEJOS 

Reservoir I 

) 

100 MILES 

Figure D2. Locations of the Raton and San Juan basins. Kpc, Pictured Cliffs Sandstone; Kvt, Vermejo Formation and Trinidad 

Sandstone, undivided; all of Late Cretaceous age. (From Fassett, 1976, fig. 1 ). 

52 Coalfields of New Mexico: Geology and Resources 
SAN JUAN RATON 

BASIN BASIN 

0 POISON 

CANYON 

FORMATION 

NACIMIENTO w FORMATION w z z w DE CRISTO w u MOUNTAINS u 0 0 w w ...J ...J <( <( 0.. 0.. 

OJO ALAMO 

SANDSTONE 

RATON 

FORMATION 

KIRTLAND VERMEJO CJ) 

:::> CJ) SHALE FORMATION 0 :::> AND w 0 u w FRUITLAND / / <( 

u / I-

~ FORMATION / / TRINIDAD w / a: w / / SANDSTONE u a: / / a: u / 

/ w a: / / / 0.. 

w / / 0.. 0.. / 

/ 

/ :::> 0.. / 

:::> PICTURED / / 

/ 

CLIFFS / / PIERRE / / SHALE SANDSTONE / 

/ 

LEWIS 

SHALE 

Figure 03. Stratigraphy of Upper Cretaceous and Paleocene 

rocks of the New Mexico portions of the Raton and San Juan 

basins. 

Mountains. Faults are rarely observed in outcrop, but coal 

offsets and faults with minor displacement are relatively 

common features in underground and surface mines in the 

coalfield. The Vermejo Park anticline, with about 2,500 ft of 

structural relief, is the only major structure in the coalfield. 

The position of Vermejo Park and the distribution of the 

coal-bearing rocks of the Vermejo and Raton Formations 

are illustrated on the geologic map in figure D5. The cross 

section in figure D6 shows the anticline, and the 

stratigraphic sections in the same figure show changes in the 

Vermejo Formation and some of the principal Raton 

Formation coal beds. 

STRATIGRAPHY 

The stratigraphy of the Upper Cretaceous and Paleocene rocks of the Raton coalfield is shown in table D 1, and 

their relationship with equivalent units in the San Juan basin 

is shown in figure D3. The offshore-marine Pierre Shale 

(Campanian to Maastrichtian) and the overlying marginalmarine Trinidad Sandstone (Maastrichtian) underlie the 

nonmarine Upper Cretaceous and Paleocene rocks in the 

basin. The position of the Raton basin with respect to the 

Late Cretaceous epeiric sea is shown in figure D7. Non38° 105° 

37° 

104° 

COLORADO 

- w MExicO?--

I 

20 40 MILES 

'I I 

20 40 KILOMETERS 

I 

/ 

~ 

L:J 

INDEX MAP 

Figure 04. Areal distribution of coal-bearing Upper 

Cretaceous and Paleocene rocks in the Raton basin. The Raton 

coalfield is the New Mexico portion of the stippled area. 

marine sedimentary rocks in the coalfield, from oldest to 

youngest, include the coal-bearing Vermejo Formation 

(Maastrichtian) and Raton Formation (Maastrichtian and 

Paleocene) and the non-coal-bearing Poison Canyon 

Formation (Maastrichtian and Paleocene), which overlies 

and intertongues with the Raton Formation. Much of the 

following discussion of the rocks and their depositional 

environments is from Pillmore and Flores (1987). 

Pierre Shale and Trinidad Sandstone 

The oldest map unit shown on figure D5 is the 

Trinidad Sandstone and older rocks unit of Late Cretaceous 

age. In most parts of the map area, this unit includes only 

the Trinidad Sandstone and the Pierre Shale. The Pierre 

formed in prodeltaic and offshore-marine environments and 

consists of 2,000-2,700 ft of dark, silty, noncalcareous 

shale. The Pierre Shale grades up into the cliff-forming 

Trinidad Sandstone, which was deposited in 

contemporaneous delta-front and interdeltaic barrier-bar 

environments (Pillmore and Flores, 1987). The Trinidad 

Sandstone underlies the coal-bearing formations of the 

Raton coalfield and consists of very fine grained to 

medium-grained, calcareous to slightly clayey sandstone 

that ranges in thickness from 0 to 130 ft. Zones of abundant 

Ophiomorpha trace-fossil bioturbation are characteristic of 

its upper part. 

Raton Coalfield 53 
10 

10 20 30 KILOMETERS 

EXPLANATION 

Basalt lava flows (Holocene to Miocene) 

Syenodlorite intrusive (Miocene) 

Poison Canyon Formation (Paleocene and 

Upper Cretaceous) 

Raton Formation (Paleocene and 

Upper Cretaceous) 

-

LJfuj 

Vermejo Formation (Upper Cretaceous) 

Trinidad Formation (Upper Cretaceous) and 

older rocks 

--+----.Iii' Anticline, showing plunge 

A ___ A' Location of cross section shown in figure D6 

Figure 05. Generalized geology of the Raton coalfield, New Mexico. 

Vermejo Formation 

The Vermejo Formation consists of interbedded 

sandstone, siltstone, shale, carbonaceous shale, and coal that 

together form steep, generally debris-covered slopes above 

the cliffs of the Trinidad Sandstone. The Vermejo 

Formation ranges in thickness from about 375ft at Vermejo 

Park and along the western border of the coalfield to 0 ft in 

the eastern part, east and south of Raton, N. Mex. Coal beds, 

as thick as 12 ft, occur near the top and bottom of the 

formation. The Vermejo Formation was deposited 

conformably on the Trinidad Sandstone in contemporaneous fluviodeltaic plain and back-barrier 

environments. The upper part of the Vermejo Formation in 

the west-central part of the coalfield was deposited in an 

alluviated upper delta plain (Flores and Tur, 1982). The 

54 Coalfields of New Mexico: Geology and Resources 

Vermejo Formation intertongues with the Trinidad 

Sandstone along the southern margin of the coalfield, from 

a point north of Cimarron northeastward about 11 mi to 

Dawson, N. Mex. (Wanek, 1963), but this relationship has 

not been seen in any other areas of the field. 

The organic material that ultimately formed the 

extensive coal beds in the lower part of the Vermejo 

Formation accumulated in poorly drained, brackish-water 

swamps or marshes behind barrier islands throughout most 

of the coalfield and also along the lower reaches of 

distributary channels of a prograding delta system in the 

northernmost part of the field. The thick back-barrier coal 

deposits are aligned subparallel to a north- to northeasttrending, eastward-prograding, Late Cretaceous shoreline, 

whereas the coal deposits related to the distributary 

channels are more randomly oriented. Coal beds that formed 
landward, in the upper part of the formation, accumulated in 

poorly drained backswamps on flood plains of meandering 

streams in the upper reaches of a fluviodeltaic plain (Pillmore and Flores, 1987). 

Raton Formation 

The Raton Formation consists of sandstone, siltstone, 

mudstone, coal, carbonaceous shale, and conglomerate. It 

ranges in thickness from more than 2,000 ft in the westcentral part of the coalfield to about 1, 100 ft in the eastern 

part. A basal conglomeratic sandstone bed marks the lower 

contact and forms a persistent cliff throughout much of the 

Raton coalfield. Lee (1917) originally divided the Raton 

Formation into a basal conglomerate, a lower coal zone, a 

cliff-forming or barren series, and an upper coal zone. 

However, because the basal conglomerate is absent in the 

northeastern part of the coalfield, near Raton, it is here 

included in the lower coal zone, as described fully in 

Fillmore and Flores (1987). As redefined, this zone contains 

all of the Cretaceous part of the Raton Formation. Thus only 

three zones, as modified from Lee (1917), are considered to 

be consistent and identifiable throughout the Raton basin: 

the lower coal zone, the barren series, and the upper coal 

zone. 

The lower coal zone, 100--300 feet thick, generally 

has a basal sequence of ledge-forming, conglomeratic 

channel sandstone 10--30 ft thick (locally absent), which 

grades up into slope-forming, overbank, flood-plain 

deposits. The flood-plain deposits consist of interbedded 

sequences of mudstones, siltstones, carbonaceous shales, 

and thin coal beds (mostly noncommercial) interbedded 

with lenticular channel and tabular crevasse-splay 

sandstones. The tabular crevasse-splay sandstones show 

rippled and small-scale cross lamination. The carbonaceous 

shale beds and thin coal beds were deposited in well-drained 

backswamps that formed repeatedly and expanded over the 

flood plain during nonflood conditions. However, in the 

eastern part of the coalfield, about 3 mi northeast of Raton, 

poorly drained swamp conditions existed over a large area 

(approximately 30 mi2

) for a prolonged time at the end of 

the Cretaceous. Peat deposits accumulated in this swamp, 

nearly uninterrupted by detrital deposits, to form a 6-ft-thick 

coal bed known as the Sugarite coal bed at the top of the 

lower coal zone of the Raton Formation. The palynological 

break that defines the Cretaceous-Tertiary (K-T) boundary 

occurs near the top of the coal bed in a kaolinitic, iridiumenriched claystone bed that apparently formed as a result of 

asteroid impact (Fillmore and Flores, 1987). This K-T 

boundary claystone bed has been found at several sites in 

the Raton coalfield and at other sites as far north as Alberta, 

Canada. It is useful as a chronostratigraphic marker. 

The barren series, 175-600 ft thick, is dominated by 

cliff-forming, multiple-stacked, en echelon channel 

sandstones that are mostly fine to medium grained. The 

channel sandstones are nested to form a series of ledges and 

cliffs, but they are locally interbedded with and laterally 

grade into minor flood-plain deposits of mudstone and 

siltstone. Associated backs.wamp carbonaceous shale and 

coal beds are mostly thin and limited in extent. 

The upper coal zone, 600--1,100 ft thick, consists of 

flood-plain deposits of sandstone, mudstone, siltstone, and 

carbonaceous shale interbedded with thick beds of coal, 

which represent occasional prolonged backswamp 

accumulations of peat. Coal beds in the upper coal zone are 

generally thicker and less restricted than those in the lower 

coal zone; however, most are lenticular and less than 3 ft 

thick. The upper zone includes several commercial beds, 

attaining thicknesses of 10 ft or more, and many are 

considered economically minable. The flood-plain and 

backswamp deposits of the upper coal zone are interbedded 

with crevasse-splay and channel sandstones. 

Poison Canyon Formation 

The Poison Canyon Formation overlies the Raton 

Formation over most of the eastern part of the basin but to 

the west and southwest it intertongues with all zones of the 

Raton and thickens at the expense of the Raton. In this area 

the Poison Canyon typically consists of thick to massive, 

lenticular, ledge-forming beds of coarse-grained to conglomeratic arkosic channel sandstone intercalated with beds 

of nonresistant, yellowish-gray- to grayish-orangeweathering, sandy, micaceous mudstone. These finegrained rock types represent overbank flood-plain deposits. 

They grade laterally into and are interbedded with the 

channel sandstones. The Poison Canyon Formation is 

barren of coal and is interpreted as deposits of braided 

streams in an upper alluvial plain. 

Igneous Rocks 

Igneous flows, dikes, and sills, although not shown in 

figure D5, crop out in many places in the Raton coalfield. 

Basalt flows 3.5-4.0 m.y. old (Scott and Fillmore, 1989; 

Scott and others, 1990) cap the mesas along the northeastern 

border of the field, and lamprophyric dikes of mafic to 

intermediate composition, mostly about 25 m.y. in age 

(Scott and Fillmore, 1989) are found in almost all parts of 

the field. The dikes generally caused little alteration of the 

intruded beds; in contrast, the sills commonly intruded and 

stoped along coal beds, especially in the Raton coal zone of 

the Vermejo Formation, and have assimilated, coked, 

altered, and destroyed much coal (Fillmore, 1976). It is not 

known if the coking character of the coal beds in the Raton 

coalfield can be attributed to heat from igneous activity at 

depth. 

Raton Coalfield 55 
A 

ELEVATION, 

IN FEET 

9000 

CASTLE ROCK 

DISTRICT 

8000 700~ :?:r'~~----· 6000 

5000 

3 MILES 

3 KILOMETERS 

VERTICAL EXAGGERATION X 2.5 

EXPLANATION 

Conglomeratic 

sandstone 

Siltstone 

Coal beds 

Sandstone 

Mudstone 

Altered coal 

beds 

VERMEJO 

VERMEJO PARK 

ANTICLINE 

FORMATION 

Chimney Divide 

I bed 

FEET 

METERiS 80 20 

10 40 

0 0 

TRINIDAD SANDSTONE 

COAL BEDS OF THE VERMEJO FORMATION 

Figure 06. Diagrammatic geologic cross section and columnar sections showing Vermejo Park anticline and lithologic 

shown on figure 05. The cross section is extended diagrammatically to the east to show the thinning of the Vermejo Formation. 

COAL RESOURCES 

The Raton basin contains modest coal resources 

compared to some coalfields now being prospected, 

developed, and mined elsewhere in the western United 

States; however, the coal from the Raton field has high 

heating values, is of high rank, yields a high-quality coke, 

and may be of greater economic importance than coal from 

other larger fields. The coal is all high-volatile A to B 

bituminous rank; some representative coal analyses are 

given in table D2, and additional data on volatile matter and 

sulfur are shown in table D3 (Fillmore, 1976). 

The Raton coalfield is unusual in western coal lands 

in that it consists almost entirely of fee land, where domestic 

energy companies have owned and developed the mineral 

rights over a long period. Under these circumstances, the 

buried coal resources of the field have not been thoroughly 

evaluated by either the State or the Federal Government. 

However, various field surveys and surface investigations 

have been carried out, beginning with the earliest territorial 

surveys and work by Orestes St. John in the late 1800's (St. 

56 Coalfields of New Mexico: Geology and Resources 

John, 1896), followed by W. T. Lee's investigations in the 

early 1900's (Lee, 1917). The U.S. Geological Survey 

(USGS) began investigations in the coalfield again in the 

mid-1900's (Wanek, 1963; Fillmore, 1969a and b, 1~76), 

and since that time the work has been sporadic. The 

underground resources of large parts of the field have been 

explored by drilling and evaluated by Kaiser Steel 

Corporation ( 1954-84 ), Kaiser ·Coal Corporation 

(1984-89), and, most recently, by F&M Coal Mining 

Company (1989-present). These companies have provided 

much useful information but have asked not to have specific 

drilling sites and depth and thickness data published. 

Coal resources for the various districts in the Raton 

coalfield are listed as demonstrated resources in table D4 

(Fillmore, 1976). The demonstrated category includes 

measured and indicated resources calculated by standard 

techniques from drill hole data and limited outcrop 

information. F&M Coal Company prefers not to release 

resource information in any more detailed resource categories. The company's tonnage calculations are based on 85 

lbs/ft3 or 1851 tons/acre ft for bituminous coal in place, as 
COTIONWOOD CANYON 

DISTRICT 

CROW CANYON DISTRICT 

VERMEJO FORMATION 

TRINIDAD SANDSTONE 

A' 

ELEVATION, 

IN FEET 

9000 

8000 

·--~~7000 

6000 

5000 

changes and coal beds in the Vermejo Formation across the northwestern part of the Raton coalfield. Trace of cross section 

compared to 1800 tons/acre ft, which is the figure 

commonly used by the U.S. Geological Survey (Wood and 

others, 1983) to calculate bituminous coal in place. 

Coal beds of potential commercial interest-here 

considered to be those beds at least 30 in. thick--occur 

throughout much of the area that is underlain by coalbearing rocks. However, many of the beds are of limited 

extent, and available data are too sparse to allow the beds to 

be considered separately in this report. The most extensive 

and valuable deposits are the R(l.ton and Vermejo coal beds, 

in the Vermejo Formation, and a group of coal beds that 

include the York Canyon and Upper Left Fork coal beds, 

presently being mined, in the upper coal zone of the 

overlying Raton Formation. The distribution of these 

formations is shown on the geologic map (fig. D5). The 

areas underlain by the beds of former, present, or future 

commercial importance are here informally called coal 

districts, and the most important of these districts are shown 

on figure D8. 

Both formations also contain beds less than 30 in. 

thick. Demonstrated resources have not been calculated for 

these beds and they are listed here as inferred resources. To 

show a rough distribution of these inferred resources, the 

coalfield has been arbitrarily divided into 15 geographic 

subdivisions (fig. D9), which overlap with but are distinct 

from the districts defined for the demonstrated resources 

(fig. D8). Minimum total coal thicknesses in both the 

Vermejo and Raton Formations have been estimated for 

each of the various subdivisions that make up the Raton 

coalfield. In each subdivision, drilling records, electric logs, 

and outcrop data were examined and interpreted, and a 

value representing the minimum total coal thickness of beds 

14 in. thick or greater was assigned for each formation 

(table D5). The numbers are based on geologic subsurface 

and surface data, but the values are subjective in that no 

statistical approach was used for their generation. The 

resources are listed as inferred rather than hypothetical 

because of the large amount of data available throughout 

much of the coalfield; however, estimates for the southern 

part of the coalfield (the Ponil and Lower Bremmer 

subdivisions) are less reliable than those for other parts 

because drill holes there are more widely spaced. When 

Raton Coalfield 57 
Figure D7. Western Interior seaway during Late Cretaceous 

time, showing the locations of the Raton and San Juan basins. 

(Modified from Gill and Cobban, 1966, fig. 15.) 

these inferred resources (table D5) are added to the 

demonstrated resources calculated for the districts (table 

D4), the total gives a rough indication of the potential coal 

resources of the entire coalfield. 

Coal Deposits in the Vermejo Formation 

As shown in figure D6, the principal economic coal 

beds of the Vermejo Formation are the Raton coal bed (not 

to be confused with the formation of the same name), which 

lies at the base, and the Vermejo coal bed, which is near the 

top in the west-central part of the coalfield and is shown in 

the sections at Castle Rock and Vermejo Park. Although 

other coal beds as thick as 3-4ft occur in the Vermejo, only 

these two are known to have sufficient extent and thickness 

to be considered potentially economic. The most 

economically important districts, defined by coal deposits in 

the Vermejo Formation that have not yet been mined, are 

Castle Rock and Rosado (fig. D8). · 

58 Coalfields of New Mexico: Geology and Resources 

The Raton coal bed underlies most of the Raton 

coalfield. However, subsurface investigations indicate large 

areas where much of the coal has been altered or destroyed 

by sills that have intruded the Raton coal bed. In some areas, 

the presence of sills is known only from isolated drill holes 

and the extent of intrusive activity is uncertain. Several 

large districts in the coalfield are defined by the presence of 

thick coal in the coal zone on or immediately above the 

Trinidad Sandstone. Most of these districts have been 

extensively mined and, because only sketchy records 

remain, the areal extents of these thick coal beds are 

uncertain. The mines that saw most of the early activity are 

those at or near the abandoned mining towns of Gardiner, 

Brilliant, Willow, VanHouten, Koehler, and Dawson, and 

they are essentially worked out. (The Brilliant district, as 

shown in fig. D8, is a north and northwest extension of the 

old Gardiner and Brilliant districts.) Coal deposits of these 

old districts are described by Lee (1917; 1924). 

Castle Rock District 

The Castle Rock district contains the largest known 

coal deposits in the coalfield. The Raton and Vermejo coal 

beds underlie about 25,000 acres, or nearly 40 mi2

, in the 

Castle Rock district (fig. D8). This large district extends 

from the western margin of the coalfield about 4 mi 

eastward, nearly to Vermejo Park, and has been traced in a 

north-south direction for about 9 mi. Along the western 

margin of the district the rocks dip eastward as steeply as 

25°-30°. In the areas considered minable, the stratigraphic 

distance from the Trinidad Sandstone to the Raton coal bed 

ranges from 5 to 35ft (mostly 10--15 ft or less); the Vermejo 

coal bed lies about 250 ft above the Raton coal bed. The 

coal beds range in thickness from 3 to 15 ft and constitute 

a demonstrated coal resource containing more than 500 

million tons (table D4). The overburden ranges from 0 along 

the outcrop to more than 3,000 ft below the high mesas in 

the southwestern part of the bed area. The Raton coal bed 

underlies fine-grained rock sequences consisting mostly of 

mudstone and shale. The V ermejo coal bed also mostly 

underlies fine-grained rocks, but locally the basal 

conglomerate of the Raton Formation rests directly on the 

coal bed. 

According to corporate mining experts, problems 

related to roof rock and depth of cover in the Castle Rock 

district can be solved by the use of yieldable arches and 

modem longwall mining methods; however, the economics 

of using these methods will be the chief factor controlling 

the development of this district. Mining problems would be 

more severe in the areas of steeply dipping coal seams, 

along the western margin of the coalfield, but the rocks dip 

more gently in most parts of the district, and mining is not 

expected to be too difficult. 
Table 01. General stratigraphic description of the Raton coalfield, New Mexico 

AGE 

w 

z 

w 

u 

0 

w 

....J 

~ 

(/) 

::> 

0 

w 

u 

~ w 

a: 

u 

a: 

w 

a.. 

a.. 

::> 

FORMATION NAME 

POISON CANYON 

FORMATION 

RATON FORMATION 

VERMEJO 

FORMATION 

GENERAL DESCRIPTION 

SANDSTONE-Coarse to conglomeratic; beds 15-50 ft 

thick; interbeds of yellow-weathering, clayey sandstone. 

Thickens to west at expense of underlying Raton 

Formation intertongues with Poison Canyon Formation to 

the west 

UPPER COAL ZONE-Very fine grained sandstone, siltstone, and mudstone with carbonaceous shale and thick 

coal beds 

BARREN SERIES-Mostly very fine to fine grained 

sandstone with minor mudstone, siltstone, carbonaceous 

shale, and thin coal beds 

LOWER COAL ZONE-Same as upper coal zone; coal 

beds mostly thin and discontinuous. Conglomeratic 

sandstone at base; locally absent 

SANDSTONE-Fine- to medium-grained; also mudstone, 

carbonaceous shale, and extensive thick coal beds. 

Local sills 

LITHOLOGY 

.- .:·.: .J 

:~~:-::;;:-::-~ 

:~·~">: ·= ·~~J 

APPROXIMATE 

THICKNESS 

IN FEET 

:2.::/:i: >500 

<:~-.·.•;:· -1 

-:::..·. :.:: .:.1 

Jf{!·.:~·:' .... ,. ... .... :·;;.:.-:, 

~~ 0?-2,100 

> ~- K·T BOUNDARY 

-< ; ,· .. . · ; · . . 

-~·:':~ ~( ~~ ·~ 

~.~ 0-380 

TRINIDAD SANDSTONE SANDSTONE-Fine- to medium-grained; contains cast of .·: .· .·. ·.. 0_130 

r----------------------+---O~p~h_io_m_o_r~p_ha ________________________________ ~·~~c~···~-?,.Ac\ ~------------~ 

PIERRE SHALE 

Coal bed 

Sill 

Sandstone 

SHALE-Silty in upper 300 ft. Grades up to fine-grained 

sandstone. Contains limestone concretions 

,......,....~ . . ,..,. .,..... . .,..... 

EXPlANATION 

Conglomeratic sandstone 

Shale 

Clayey sandstone 

w 2,000-2,700 

Mudstone 

Carbonaceous shale 

Siltstone 

Rosado District Entries developed in the Vermejo coal bed in the 

Rosado district, on the southeast flank of the Vermejo Park 

anticline, could provide access to the large underground 

resources of the Castle Rock district to the west of Vermejo 

Park. Exploitation of the Castle Rock district from the 

Rosado district might prove to be less disruptive 

environmentally than any other approach. 

South of Vermejo Park, in the Rosado district, the 

Raton and Vermejo coal beds underlie an area of about 

9,500 acres, mainly in Juan Baca Canyon. These beds 

constitute a demonstrated coal resource of about 127 million 

tons (table D4) and appear to form an eastward extension of 

the Castle Rock district, though the continuation of these 

· beds from one district to the other is uncertain. The Vermejo 

coal bed is present throughout most of the district and 

constitutes the greater part of the resource. Locally, the 

basal conglomerate of the Raton Formation rests directly ~n 

the coal, but in most parts of the district it lies 15-30 ft 

above the coal bed. The beds dip south about 10°-15° along 

the south rim of Vermejo Park, south of the Vermejo Park 

anticline, but dips flatten rapidly away from the structure. 

The Raton and Vermejo coal beds also crop out on the 

flanks of the Vermejo Park anticline and underlie the area 

north of Vermejo Park. These areas do not appear to contain 

resources sufficient to define a separate district. At the old 

Bartlett (Dead Easy) mine, at the north entrance to Vermejo 

Park, the Vermejo coal bed is about 6 ft thick, and coal was 

mined for several years for local ranch use. Both coal beds 

locally reach a thickness greater than 8 ft at outcrops around 

Raton Coalfield 59 
Table 02. Representative proximate analyses of selected coal beds in the Raton coalfield, New Mexico 

[Data in percent, except for Btu) 

Mine or location Coal bed Volatile Fixed Ash Sulfur Btu Source 

matter carbon of data 

Raton Formation 

York Canyon mine - York Canyon 35.7 54.9 8.8 0.6 14,340 1 

Chimney Divide --- Chimney Divide 38.4 47.6 13.4 .5 13,980 1 

Ancho Canyon ----- Ancho Canyon -- 36.3 54.0 8.6 .5 13,835 1 

Brilliant -------- Tin Pan ------- 37.0 46.5 16.5 .6 12,470 2 

Yankee ----------- Yankee -------- 38.7 48.7 12.6 . 6 12,700 2 

Vermejo Formation 

Vermejo Park ----- Vermejo ------- 28.2 53.7 18.0 0.5 10,030 3 

Raton --------- 25.4 60.5 14.1 .5 11,440 3 

Dawson (No. 3) --- do --------- 38.2 49.3 12.5 .8 13,230 2 

Koehler (No. 1) -- do --------- 37.5 50.0 12.5 .7 13,100 2 

Van Houten (No.4) do --------- 37.1 51.6 11.3 .9 13,220 2 

SOURCES OF DATA 

1. Bulk core sample data courtesy of Kaiser Steel Corporation. Btu results obtained 

from coal washed in heavy liquid (specific gravity 1.4). 

2. Mine analysis, moisture free, selected from Ellis (1936, p. 44-48). 

3. Weathered outcrop sample analysis courtesy of u.s. Bureau of Mines (generally higher 

ash and lower calorific values); low volatile content probably caused by intrusive 

rocks. 

Table D3. Ranges of volatile matter and sulfur in 164 core 

samples of the major coal beds in the Raton coalfield, New 

Mexico 

[Moisture- and ash-free basis. Data from whole-bed core samples washed 

in a heavy liquid (specific gravity about 1.5). Samples included partings 

and coal splits, so aggregate values represent the character of coal that 

would result from a beneficiation process. Data courtesy of Kaiser Steel 

Corporation, 1976] 

Sample locality 

and coal bed 

York Canyon mine area: 

York Canyon main bed 

Cimarron mine area: 

Upper Left Fork bed 

Lower Lef4 Fork bed 

Castle Rock area: 

Raton bed ---------- Vermejo bed -------- Central area: 

Ancho bed ---------- Green bed ---------- Brown bed ---------- Potato Canyon bed --

Number Volatile 

of matter 

samples (percent) 

8 39.1-41.4 

17 35.6-40.1 

10 37.4-41.0 

41 29.2-42.5 

34 32.4-41.9 

21 43.1-46.1 

18 40.6-45.4 

9 37.2-39.8 

6 39.6-44.0 

Sulfur 

(percent) 

0.40-0.59 

.44- .56 

.48- .57 

.60- .90 

.63- .93 

.50- .65 

.46- .69 

.45- .55 

.51- .74 

the perimeter of Vermejo Park, but the beds seem less 

extensive than in the Castle Rock district, and sills probably 

have intruded the coal locally. The extent of the coal beds 

north from Vermejo Park is unknown. 

60 Coalfields of New Mexico: Geology and Resources 

Brilliant District 

The Brilliant district is north and northwest of Raton 

(fig. D8). It consists of about 16,000 acres in the area 

drained by Dillon Canyon and its tributary, Coal Canyon, 

and in the part of the Railroad Canyon drainage west of 

Interstate Highway 25. Coal was mined extensively from 

the Raton coal bed in the old Blossburg mining district (not 

shown on fig. D8), which is south of the Brilliant district 

and includ~d the mines at Blossburg, Gardiner, and Brilliant 

in Dillon Canyon. Undisturbed coal resources in the Raton 

coal zone have been defined by subsurface investigations in 

the Brilliant district, mainly north and northwest of the old 

mines. Potentially economic coal beds extend also under the 

area east of Interstate 25, redefined as the Brilliant East 

subdistrict. Demonstrated coal resources in the Brilliant 

district total 79 million tons (table D4 in beds of the Raton 

coal zone. The Raton coal zone locally consists of two or 

three coal beds separated by partings as much as 10 ft thick; 

the coal beds in the zone range in thickness from 3 to 8 ft 

(Lee, 1924). The Brilliant district is potentially economic 

because of the high quality of its coal and its close 

proximity to Raton and to rail transportation in Railroad 

Canyon. 

Brilliant East subdistrict.-The Brilliant East subdistrict includes roughly 5,000 acres east of Interstate 25, as 

shown on figure D8. The eastward extent of the Raton coal 

zone beneath the basalt cap of Bartlett Mesa is uncertain 

(fig. D5); however, the Raton coal zone is known to be 
Table 04. Demonstrated coal resources of commercial 

thickness (>30 in.) within mining districts of Raton coalfield, 

New Mexico 

[Courtesy of Kaiser Coal Corporation] 

Average Approx- coal 

District imate Coal bed thick- area or zone 

(acres) ness 

(feet) 

Resources in the Vermejo Formation 

Castle Rock -- 25,600 Vermejo ------- 5.5 

Raton --------- 6.0 

Demonstrated 

res ources 

(106 

tons) 

250 

270 

tons (table D4). The Dawson district (fig. D8), owned by 

Phelps Dodge Corporation, produced 33 million tons of coal 

between 1899 and 1950 and surely has large reserves 

remaining. Some drilling ·has been done in the district in 

recent years, but the resulting data are not available. Wanek 

(1963) calculated demonstrated resources of 196 million 

tons of coal in beds of the Vermejo Formation in the 

Dawson district, mainly based on surface investigations. 

The district is of interest because of its relatively easy 

access to transportation (the Santa Fe Railway crosses the 

district in the Vermejo River canyon) and possible outcrop 

mine entries. 

Rosado .., ______ 9,500 Vermejo ------- 5.5 102 Other Areas 

Raton --------- 4.0 

Brilliant ---- 4,200 do --------- 5.0 

Brilliant East 3,200 do --------- 5.0 

Koehler 1 ----- 4,500 do --------- 5.0 

Dawson2 ------ ll, 200 do --------- 3.0 

Vermejo Formation total ------------------

Resources in the Raton Formation 

York Canyon 

Upper York 

Cottonwood 

5,500 York Canyon--- 5.0 

9,375 Upper Left Fork 6.0 

Lower Left Fork 4.0 

Canyon ------ 4,000 Cottonwood 5.5 

Ancho Canyon: 

Ancho ------- 2,200 Ancho zone 5.0 

GachupinBracket --- 1,600 Ancho, Bracket 4.0 

Chimney Divide: 

Caliente 

Canyon ---- 5,400 Chimney Divide- 3.0 

"L" Seam ------ 2.5 

Salyers Ridge 3,900 Chimney Divide 3.0 

Crow Canyon--- 7,040 Green--------- 6.5 

5,700 Brown--------- 5.0 

Brilliant ----- 4,200 --------------- 4.0 

Potato Canyon - 11,500 Potato Canyon - 4.0 

25 

79 

30 

19 

196 

971 

6 

94 

39 

40 

25 

ll 

23 

17 

21 

86 

55 

26 

70 

Raton Formation total ------------------- 513 

Total for both formations --------------- 1,484 

1 Partly mined out; remaining tonnage estimated. 2Modified from Wanek (1963). 

present, and 30 million tons of demonstrated resources were 

assigned to this subdistrict following preliminary subsurface 

evaluation. 

Dawson and Koehler Districts 

Coal was produced from the coal mines at Dawson 

from the late 1800's until 1950, and at Koehler from 1906 

until 1966, when production was started at York Canyon. 

The Koehler district (fig. D8) produced 14 million tons of 

coal and still contains demonstrated resources of 19 million 

The intrusion of sills appears to have destroyed much 

of the coal in the Vermejo Formation in areas east of 

Vermejo Park and along the Vermejo River south of the 

Ancho subdistrict (fig. D8). During the summer of 1989, a 

large area in Van Bremmer Canyon was the focu_s of heavy 

drilling activity in the search for coal-bed methane by 

Pennzoil Corporation. Preliminary evaluation of the data 

indicates the presence of significant coal beds in the 

Vermejo Formation and also suggests that the Castle Rock 

and Vermejo Park-Rosado thick coal trends possibly extend 

south into this area. 

In most districts of the coalfield, both the Vermejo 

and Raton Formations contain thin, local coal beds in 

addition to those thicker, more extensive beds that define 

the districts. Coal resources in the Vermejo Formation in 

beds 14 in. thick or greater are inferred to underlie the 

subdivisions of the coalfield shown on figure D9. The 

resources listed in table D4 are based on geologic inference 

and represent a minimum estimate of inferred coal resources 

contained in both the Vermejo and Raton Formations. The 

estimate for the Upper Bremmer-Gachupin and Lower 

Bremmer subdivisions are probably low, based on the new 

Pennzoil drilling data. 

Coal Deposits in the Raton Formation 

A large part of the coal resource of the Raton 

coalfield is in coal beds of the Raton Formation. As 

described above, these beds were formed in poorly drained 

swamps on flood plains developed along meandering 

streams of a broad, latest Cretaceous and early Paleocene 

alluvial plain. Because of their fluvial setting, these swamps 

were not as extensive as the back-barrier swamps that 

formed the Raton coal bed. The proximity of the Raton 

basin at this time to an actively uplifting source area, the 

San Luis Highland (Tweto, 1980), usually precluded the 

prolonged stable conditions that would have been needed to 

create widespread thick accumulations of peat and, hence, 

widespread thick coal. deposits. However, multiple beds 

Raton Coalfield 61 
37°00' ______ ____f_O_!.QRADO _____ _ 1 04°30' 

···\ '\ 

·-- ~ 

I 

· . .-;... 

GACHUPIN-BRACKET 

SUBDISTR ICT 

\s10 MILES 

Limit of Rato) 

Formation 

I 

I 

I 

Figure 08. Districts of the Raton coalfield, New Mexico, that have demonstrated coal resources, as outlined by subsurface 

exploration. 

ranging in thickness from 2 to 4 ft together with the thicker 

beds that define the districts constitute a viable resource in 

the coalfield. Many areas underlain by the upper coal zone 

of the Raton contain aggregate coal thicknesses in excess of 

15 ft, in beds 14 in. thick or greater, which constitutes a 

potential resource of several billion tons, in addition to the 

resources reported for the coal districts discussed below. 

Because the Raton Formation coarsens to the west 

and interfingers with beds of the overlying Poison Canyon 

Formation, commonly only thin coal streaks occur along the 

western margin of the coalfield, and thick coal deposits 

appear to be restricted to areas that lie east of a line that 

trends north to northwest about 2-3 mi west of Vermejo 

Park. The principal Raton Formation coal districts are 

defined by coal beds that lie east of Vermejo Park in the 

central part of the Raton coalfield. Some of these beds are 

shown on the Casa Grande 15' geologic quadrangle map 

(Pillmore, 1969a). Several other districts are to the east in 

the adjacent Brilliant 15' quadrangle, including the Brilliant 

district, which is partly in the Raton 15' quadrangle. 

York Canyon District 

The York Canyon district (fig. D8) constitutes an area 

of about 6,500 acres east of Vermejo Park, where presently 

62 Coalfields of New Mexico: Geology and Resources 

only surface mining is being carried out (the underground 

mine was closed in 1986). The York Canyon coal bed lies 

about 1 ,200--1 ,280 ft above the base of the Raton 

Formation, and it ranges in thickness from a few inches in 

the southeastern part of the outcrop to more than 12ft near 

the main entries of the underground mine. The coal bed is 

consistently at least 6 ft thick throughout the bed area 

northeast of the mine entry. Measured underground coal 

resources in 1969 totaled 30 million tons in beds 4 ft thick 

or greater (Pillmore, 1976), but the coal bed has been mined 

out underground where it was 5 ft thick or greater (1988), 

and remaining underground resources of coal less than 5 ft 

thick are uncertain. At West Ridge, on the west side of the 

district (fig. D8), the York Canyon coal bed and some 

thinner beds that overlie the York Canyon are being 

strip-mined. In the West Ridge deposit, remaining strippable coal reserves are estimated at about 2 million tons (Roy 

Pillmore, P&M Coal Co., oral commun., 1991), and the life 

of the strip mine is estimated at about 3 yr. Production to 

date ( 1991) from the York Canyon coal bed totals about 20 

million tons. Minable resources of strippable coal in the 

York Canyon district remaining after mining to date are 

about 2 million tons. 
COLORADO 

------- - NEW MEXICO 

1 04°30' ----\-

Stubblefield-Catskill --···"'\ . 

Tin Pan- · \ 

Brilliant · ~: 

Formation 

10 MILES 

36°30' L_ _______ __L __ __:::idr!@!l:Q!L _______________ _____j__ _________ _ 

Figure 09. Geographic subdivisions of the Raton coalfield, New Mexico, used to describe inferred coal resources. 

Upper York (Left Fork) District 

Coal beds of the Upper York district (fig. 08) 

underlie nearly 9,400 acres 4 mi north of the York Canyon 

mine. The Left Fork coal deposit consists of two beds that 

are about 300 ft beneath the York Canyon coal bed. They 

are about 50-60 ft apart stratigraphically and lie 900--950 ft 

above the base of the Raton Formation. These beds 

constitute the lowest commercial coal deposits in the Raton 

Formation in the central part of the coalfield. The beds 

range in thickness from about 3lf2 to 11 ft, based on 

extensive drilling data, and demonstrated resources exceed 

130 million tons (table 04). Areas where the Left Fork coal 

beds possibly could be strip-mined extend north to the State 

line and south toward the York Canyon strip mine, but they 

are considered nominally economic, and the district should 

be regarded as a deposit to be mined primarily by 

underground methods. An underground test mine was 

opened on the upper seam in 1969, and the coal was found 

to be of excellent quality. Entries for a new mine called the 

Cimarron mine were begun late in 1983, and coal is 

presently being produced by longwall mining methods. 

Minable reserves in the upper seam presently being mined 

total 16 million tons, and production from the Cimarron 

mine will be 1.8 million tons per year (Roy Pillmore, oral 

commun., 1991). 

Cottonwood Canyon District 

The Cottonwood Canyon district (fig. 08) is about 7 

mi east of York Canyon, a short distance south of the York 

Canyon mine road, New Mexico Highway 555. The 

Cottonwood Canyon coal zone is in the upper coal zone of 

the Raton Formation, about 1,100-1 ,200 ft above the base 

of the Raton Formation. It underlies about 4,000 acres and 

ranges in thickness from 3 to 8 ft. Demonstrated resources 

of this district are estimated at 40 miiiion tons (table 04), 10 

million of which are considered strippable, depending on 

market conditions and equipment used. The multiple thinseam occurrence of the coal and the dissected hili-andvalley terrain of the eastern part of the coalfield both make 

conventional strip-mining techniques impractical, and 

stripping ratios are difficult to assess. The resources 

considered strippable would change if demand and price of 

coal increased sufficiently. 

Ancho Canyon District 

The Ancho Canyon district (fig. 08) is considered 

here as two subdistricts: the Ancho, which lies north of the 

Vermejo River, and the Gachupin-Bracket, which lies to the 

south. 

Raton Coalfield 63 
Table 05. Estimated minimum inferred coal resources within subdivisions of the Raton coalfield, New Mexico 

Inferred coal resources 

Subdivision or area 

(see fig. 08) 

Area 

(acres) 

Raton Formation Vermejo Formation Total 

for both 

formations 

( 106 tons) 

Bartlett ------------- Yankee --------------- Tin Pan-Brilliant ---- stubblefield-Catskill 

Patten-Vasquez -------

Castle Rock extended - Upper Bremmer-Gachupin 

Salyers-Chimner Divide 

Crow-Deadhorse ------

York Canyon ----------

Vermejo Sills -------- Vermejo Sills South -- Dawson-Koehler2 ------

Ponil2 --------------- Lower Bremmer2 -------

14,950 

24,310 

41,350 

59,780 

22,820 

53,210 

52,410 

41,350 

77,820 

3,590 

10,560 

11,760 

29,890 

91,270 

46,230 

Total for all subdivisions 

Thickness1 

(feet) 

6 

3 

6 

6 

5 

0 

5 

6 

4 

4 

5 

4 

2 

3 

3 

Resources 

(106 tons) 

166 

134 

459 

1,106 

211 

0 

485 

459 

576 

26 

97 

87 

110 

502 

236 

4,654 

Thickness 1 

(feet) 

2 

0 

4 

10 

4 

3 

4 

4 

4 

3 

3 

3 

3 

2 

4 

Resources 

(10 6 tons) 

55 

0 

306 

553 

168 

295 

388 

306 

576 

20 

58 

65 

165 

303 

216 

3,474 

221 

134 

765 

1,659 

379 

295 

873 

765 

1,152 

46 

155 

152 

275 

805 

452 

8,128 

1

Estimated average total thickness of coal. 2

Modified from Wanek (1963). Does not include most demonstrated resources at Dawson 

and Koehler districts (table 02). 

Ancho subdistrict.-The Ancho Canyon coal zone 

lies roughly in the same stratigraphic position as the 

Cottonwood Canyon coal bed. It underlies about 2,200 acres 

north of the Vermejo River and contains about 25 million 

tons (table D4) of coal considered strippable. No 

underground mining is planned in this subdistrict. The coal 

bed lies mostly less than 100ft beneath the crests of ridges 

in this dissected portion of the coalfield. The coal occurs in 

a zone as much as 15 ft thick, which contains several shale 

partings. These partings are expected to cause problems 

during mining. The maximum discrete bed thickness is 

about 4ft. 

Gachupin-Bracket subdistrict.-The Ancho Canyon 

coal zone also underlies the Gachupin-Bracket subdistrict 

(fig. D8). The subdistrict consists of about 1,600 acres. The 

zone is as thick as 9 ft and contains coal beds as thick as 4 

ft, most of which include shale partings. Strippable 

demonstrated resources of the Ancho coal bed total about 9 

million tons. A second coal bed, called the Bracket, lies 

about 40-60 ft above the Ancho and contains estimated 

strippable demonstrated resources of about 2 million tons, 

giving a total of 11 million tons (table D4). The 

southwestern and western limits of the subdistrict have not 

been completely defined, and underground reserves may 

eventually be proven and outlined. No underground 

operations are planned at present. 

64 Coalfields of New Mexico: Geology and Resources 

Chimney Divide District 

The Chimney Divide coal bed and its equivalents 

underlie a large area that is usually divided into two 

subdistricts (fig. D8): 

1. The Salyers Ridge subdistrict, which includes 

Salyers Ridge (between Salyers and Road 

Canyons) and Chimney Divide (between the East 

Fork of Chimney Canyon and Salyers Canyon); 

and 

2. The Caliente Canyon subdistrict, which includes 

the areas that lie to the east of the East Fork of 

Chimney Canyon, and the Caliente Canyon area. 

Because of the similarities of the subdistricts, they are not 

discussed individually. 

The Chimney Divide coal bed and its equivalents 

crop out below the crests of the long fingerlike ridges and 

high drainage divides throughout an area of more than 50 

mi2 along the drainage divide between the Vermejo and 

Canadian Rivers. The coal bed commonly consists of two 

beds about 2 ft thick separated by a shale parting as thick as 

1 ft. The maximum thickness of coal in the zone is about 4.5 

ft. A coal bed termed the "L" bed locally lies 20-30 ft 

beneath the Chimney Divide coal bed and averages about 30 

in. thick. Total demonstrated coal resources for the district 

exceed 60 million tons (table D4). The coal is of good 
quality for power generation but not particularly suited for 

metallurgical purposes. These coal beds are the highest beds 

in the sequence and lie near the top of the upper coal zone 

of the Raton Formation, about 1,800 ft above the base. 

Lee ( 1924) discussed the coal beds in the Raton 

Formation in the Brilliant and Raton quadrangles and 

described the thickness, stratigraphic position, and mines of 

each bed. Several beds as much as 8 ft thick occur in the 

eastern part of the field and are of commercial value. 

However, most beds are less than 4 ft thick, are areally 

restricted, contain partings of shale or bone, and were 

considered by Lee to be less desirable for the manufacture 

of coke. Figure D 10 shows the general relations of some of 

the beds in the eastern part of the coalfield to those in the 

central part. 

Potato Canyon District 

The Potato Canyon coal zone underlies an area of 

about 6,500 acres, mainly on the ridge dividing Coal and 

Potato Canyons and along adjacent ridges and valleys, 

CENTRAL 

PART OF 

RATON 

COAL FIELD 

EASTERN PART OF 

RATON COAL FIELD 

POISON CANYON 

FORMATION 

YORK CANYON COAL BED 

(ANCHO CANYON AND 

COTTONWOOD CANYON 

COAL BEDS POSSIBLY 

EQUIVALENT) 

UPPER } LOWER LEFT FORK COAL BEDS 

RATON 

FORMATION 

VERMEJO 

FORMATION 

TRINIDAD SANDSTONE 

FEET METERS 

1000 300 

200 

500 

100 

POTATO 

CANYON 

COAL BED 

TIN PAN 

COAL BED 

GREEN COAL 

BED 

BROWN COAL 

BED 

Figure D10. Diagrammatic stratigraphic section showing 

relations of coal beds in the central and eastern parts of the 

Raton coalfield, New Mexico (from Pillmore, 1976). 

though it also extends south into the heads of Crow and 

Coal Canyons. The zone lies about 950-1 ,050 ft above the 

Trinidad Sandstone. In Potato Canyon the zone is as thick as 

8.4 ft and has a total coal thickness as great as 7.2 ft, but 

individual beds within the zone rarely reach 3 ft in thickness 

(Lee, 1924). The coal zone is characterized by several shale 

partings. It was excavated along the outcrop for several 

hundred yards on both sides of Potato Canyon and is also 

exposed in bulldozer cuts at the head of Coal Canyon. The 

coal zone is 6 ft thick near the mine in Potato Canyon and 

is 7.5 ft thick (including 6.3 ft of coal) 2.5 mi farther south, 

in the head of a tributary to the Canadian River called Coal 

Canyon. An experimental mine, opened in 1981, was driven 

2,000 ft into the south wall of Potato Canyon to test the 

continuity and quality of the coal. The test was completed in 

1982 and the mine was closed. Total demonstrated coal 

resources in the district are 70.4 million tons (table D4). 

Small parts of the district are underlain also by the Green 

coal bed on the south (fig. D8) and by the Tin Pan coal bed 

in the northeast; both lie stratigraphically beneath the Potato 

Canyon coal bed. 

Crow Canyon District 

The Crow Canyon district (fig. D8) is defined by two 

areally overlapping coal beds: the Green, which is the 

highest stratigraphically, and the Brown. These may 

correlate, respectively, with the upper and lower Left Fork 

coal beds in the Upper York district to the west, but this 

speculation is based solely on stratigraphic position. 

Green coal bed.-The Green coal bed crops out in the 

bottom of Crow Creek and has been traced in the subsurface 

throughout an area of several square miles. It overlies a 

large portion of the Brown coal bed area and extends to the 

south and east several miles (fig. D8). The bed occurs as a 

zone, as thick as 16 ft, composed of alternating thin coal 

layers and carbonaceous shale partings mostly less than 1 ft 

thick. It lies in the lower part of the upper coal zone of the 

Raton Formation, approximately 700-750 ft above the 

Trinidad Sandstone. The coal bed at location 386 of Lee 

(1924, p. 171) may be this bed; he described it as a zone 

12.9 ft thick containing 9.6 ft of coal. Lee reported a second 

zone 12.5 ft thick that lies 125ft stratigraphically above the 

Green coal bed, but it contains only 3.1 ft of coal and is not 

considered economic under present conditions. 

The Green coal bed underlies about the same size area 

as the Potato Canyon coal bed, but outcrops of the Green are 

sparse and thickness ranges are uncertain. The coal bed 

contains demonstrated coal resources of 86 million tons 

(table D4). 

Brown coal bed.-The Brown coal bed averages 5 ft 

in thickness and lies about 100 ft beneath the Green coal 

bed, near the base of the upper coal zone. It is one of the 

lowest beds in the eastern part of the coalfield. It may 

correlate with the Tin Pan bed, which lies in approximately 

Raton Coalfield 65 
the same stratigraphic position in the Brilliant district. In the 

vicinity of Crow, Coal, and Potato Canyons, the Brown coal 

bed underlies a poorly defined area of several square miles, 

presumed to be similar in size to the area underlain by the 

Green coal bed, and contains demonstrated resources of 55 

million tons (table D4). The Brown coal bed is about 

600-650 ft above the Trinidad Sandstone (Kaiser Coal 

Corporation, written commun., 1976). 

Brilliant District 

Several Raton Formation coal beds occur in the 

Brilliant district, including the Tin Pan, Rombo Canyon, 

and Savage Canyon beds. These and other beds underlie 

ridges in ·the Brilliant district and parts of the Tin PanBrilliant subdivision (fig. D9). For instance, a 6-ft coal zone 

that crops out in Jones Canyon, a tributary of the Canadian 

River, about 0. 7 mi west of Raton, may be equivalent to the 

Tin Pan coal bed or the Potato Canyon seam, but the 

correlation is indefinite and its lateral extent is not known. 

The coal resources that can be inferred to be present in these 

and all other coal beds in the Tin Pan-Brilliant subdivision 

total 459 million tons (table D5) of which 26 million tons 

(table D4) are the demonstrated resources in coal beds of the 

Raton Formation in the Brilliant district. 

The Tin Pan coal bed underlies an area of about 

25,000 acres, mostly north of the Canadian River, extending 

westward from a point about 4 mi northwest of Raton (Lee, 

1924 ). The coal bed lies 615-720 ft above the Trinidad 

Sandstone (Kaiser Coal Corporation, written commun., 

1976). Near Brilliant, the zone containing the Tin Pan bed is 

as much as 13.3 ft thick and has. a total coal thickness of9.4 

ft (Lee, 1924), but individual coal beds in the zone rarely 

reach thicknesses greater than 5 ft and the bed generally 

contains one or more shale partings. The coal bed crops out 

in canyons adjacent to and along Dillon Canyon and the 

Canadian River. Coal was produced from the Tin Pan coal 

bed for several years at Brilliant; but, according to Lee 

( 1924 ), the coal is softer than the older coal of the Raton 

coal bed and produces a weak and "in some ways inferior" 

coke. However, a satisfactory coking blend is obtained 

when this coal is mixed with coal from the Raton coal bed. 

Separate resource estimates for the Tin Pan coal bed were 

not calculated because the bed was largely mined out from 

mines in Dillon Canyon. The unmined portions of the bed 

are included in resource estimates for Tin Pan-Brilliant 

subdivision (fig. D9; table D5). 

The lowest coal bed of commercial thickness in the 

Raton Formation is in the Sugarite zone, which lies from 80 

to more than 100 ft above the base of the Raton Formation 

and extends throughout an area of about 64,000 acres in the 

eastern part of the coalfield (Lee, 1924). Recent subsurface 

investig~tions reveal that in the old Blossburg district of Lee 

(1924), west of Raton, a zone equivalent to the Sugarite is 

40-50 ft thick and lies 140-190 ft above the base of the 

66 Coalfields of New Mexico: Geology and Resources 

Raton Formation (Kaiser Coal Corporation, written commun., 1976). The coal bed is as thick as 5.5 ft in the mine 

at Sugarite and nearby localities; in other places, it is thinner 

and contains several shale partings. The Sugarite coal bed 

underlies an undetermined area beneath the basalt-capped 

Bartlett Mesa in the Bartlett subdivision (fig. D9), and it is 

also present in the northern part of the Yankee subdivision, 

where it underlies Barela Mesa and extends north into 

Colorado. Although the coal is noncoking in character, it 

has high heating value and was sought after as domestic fuel 

because its high resin content causes it to bum freely, 

without notable clinker (Lee, 1924). 

Other Coal Beds in the Raton Formation 

Parts of the Raton coalfield contain several coal beds 

in addition to those that define individual districts. Lee's 

reports ( 1917; 1924) and Fillmore's reports and maps 

(1969a, b; 1974; 1976) indicate that many parts of the field 

that have been investigated contain as much as 15 to 20ft of 

coal in beds 14 in. thick or greater. Table D5 shows 

minimum coal resource values based on minimum total coal 

thicknesses inferred in the subdivisions shown on figure D9. 

Geophysical and drilling records indicate the 

presence of other coal beds in various areas, and field 

investigations have discovered several more. For instance, 

southwest of Vermejo Park, beds as thick as 5 ft crop out at 

the heads of Pooler and Juan Baca Canyons, but these beds 

could not be traced along outcrop for any great distance, and 

subsurface data are not sufficient to define the limits of the 

beds. These coal beds lie at about the same stratigraphic 

position as those in the Upper York (Left Fork) district to 

the northeast. A higher coal zone, which is as thick as 9 ft, 

underlies about 600 acres at the head of Juan Baca Canyon, 

but it does not contain sufficient reserves to warrant 

development at this time. West of Vermejo Park, a coal bed 

as thick ·as 5 ft underlies ridges in the drainage area of 

Mestas Canyon. This coal bed may also be stratigraphically 

equivalent to one of the Left Fork beds. Again, the bed area 

appears to be too small to warrant development. However, 

a coal zone that may have commercial importance crops out 

north of Vermejo Park, in Spring Canyon; it includes about 

5-6 ft of coal, underlies an area of unknown extent, and 

warrants further investigation. The inclusion of these and 

other known coal beds in table D4 would significantly add 

to resource estimates, but detailed correlation studies would 

be needed to determine whether such inclusion is warranted. 

Subsurface investigations in the Yankee subdivision 

show inferred coal resources of about 134 million tons 

(table D5) contained in approximately 24,000 acres, most of 

which lie beneath the basalt caps of Barela, Horse, and 

Johnson Mesas, about 3-5 mi northeast of Raton. Drilling 

information provided by Santa Fe Mining Corporation 

shows that about 16,000 acres of the subdivision, lying 

mostly beneath Barela and Horse Mesas, contains 85 
million tons of coal that could be classed as demonstrated 

resources. The Yankee is the easternmost subdivision in the 

coalfield, and the coal is contained mostly in the Sugarite 

coal bed (lower coal zone), and the Kellog, Dirty, and 

Yankee coal beds (upper coal zone). The Raton Formation 

thins to the east across the coalfield, and the Yankee coal 

bed, which is near the base of the upper coal zone, is only 

300-400 ft above the top of the Trinidad Sandstone. The 

Yankee coal bed is possibly stratigraphically equivalent to 

the Tin Pan or one of the other lower beds in the upper coal 

zone described above, but outcrops are obscured by soil and 

vegetation cover, so tracing of the beds on the ground is 

nearly impossible. According to Lee (1924), the coal rarely 

occurred in beds thicker than 2.5-3 ft, and comparatively 

little coal has been mined from this bed. Thicker coal occurs 

in the Kellog and Dirty coal beds of the district, mainly in 

the northern part beneath Barela Mesa. Coal beds of the 

upper coal zone are absent in the eastern part of the Yankee 

subdivision beneath the basalt flows that cap the eastern part 

of Johnson Mesa; it is unlikely that the Sugarite coal bed is 

of minable extent and thickness beneath the mesa. 

Lee (1924) provides descriptions of many coal beds 

and zones in the eastern part of the coalfield that are not 

included or described here. Geophysical records of oil wells 

drilled in 1972, and more recent drilling by Pennzoil 

Corporation for coal-bed methane in 1989, suggest that coal 

deposits of potential commercial value underlie a large area 

around Van Bremmer and Cerrososo Canyons. The quality, 

thickness, and areal extent of any beds in this area have yet 

to be determined. Information from outcrops in the Cimarron area, at the southern limit of the coalfield, does not 

suggest the presence of thick coal beds in either the 

Vermejo or Raton Formation in that area. 

CONCLUSIONS 

The Vermejo and Raton Formations contain more 

than 9 billion tons of coal resources in the Raton coalfield. 

These resources are sufficient to sustain large-scale mining 

operations to meet nearly any predictable market need. 

However, even though the coal is of high quality and a 

sought-after product, difficult mining conditions and high 

production costs may preclude large-scale development in 

the face of competitively priced coal from large mines in the 

Powder River basin in Wyoming. 

REFERENCES CITED 

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. 

Ellis, R.W., 1936, Analyses of New Mexico coals: U.S. Bureau of 

Mines Technical Paper 569, 108 p. 

Fassett, J.E., 1976, What happened during Late Cretaceous time in 

the Raton and San Juan basins-with some thoughts about 

the area in between, in Ewing, R.C., and Kues, B.S., eds., 

Guidebook of Vermejo Park, northeastern New Mexico: 

New Mexico Geological Society, 27th Field Conference, 

1976, p. 185-190. 

Flores, R.M., and Tur, S.M., 1982, Characteristics of deltaic 

deposits in the Cretaceous Pierre Shale, Trinidad Sandstone, 

and Vermejo Formation, Raton basin, Colorado: The 

Mountain Geologist, v. 19, p. 25-40. 

Gill, J.R., and Cobban, W.A., 1966, The Red Bird section of the 

Upper Cretaceous Pierre Shale in Wyoming: U.S. 

Geological Survey Professional Paper 393-A, 73 p. 

Lee, W.T., 1917 [1918], Geology of the Raton Mesa and other 

regions in Colorado and New Mexico, in Lee, W.T., and 

Knowlton, F.H., Geology and paleontology of Raton Mesa 

and other regions in Colorado and New Mexico: U.S. 

Geological Survey Professional Paper 101, p. 9-221. 

__ 1924, Coal resources of the Raton coal field, Colfax 

County, New Mexico: U.S. Geological Survey Bulletin 752, 

254 p. . 

Pillmore, C.L., 1969a, Geologic map of the Casa Grande 

quadrangle, Colfax County, New Mexico, and Las Animas 

County, Colorado: U.S. Geological Survey Geologic 

Quadrangle Map GQ-823, scale 1:62,500. 

__ 1969b, Geology and coal deposits of the Raton coal field, 

Colfax County, New Mexico: Mountain Geologist, v. 6, 

p. 125-142. 

__ 1974, Geologic and structure contour maps of the Ute 

Creek 1° SE quadrangle, Colfax County, New Mexico: U.S. 

Geological Survey Open-File Report 74-1086, 2 sheets, 

scale 1 :24,000. 

__ 1976, Commercial coal beds of the Raton coal field, 

Colfax County, New Mexico, in Ewing, R.C., and Kues, 

B.S., eds., Guidebook of Vermejo Park, northeastern New 

Mexico: New Mexico Geological Society, 27th Field 

Conference, 1976, p. 227-247. 

Pillmore, C.L. and Flores, R.M., 1984, Field guide and discussions 

of coal deposits, depositional environments, and the 

Cretaceous-Tertiary boundary, southern Raton basin, New 

Mexico and Colorado, in Lintz, Joseph, Jr., ed., Western 

geological excursions, v. 3: Geological Society of America 

Guidebook, Annual Meeting, Reno, Nev., 1984; Reno, 

Nev., MacKay School of Mines, Department of Geology, 

p. 1-55. 

__ 1987, Stratigraphy and depositional environments of the 

Cretaceous-Tertiary boundary interval and associated rocks, 

Raton basin, New Mexico and Colorado, in Fassett, J.E., 

and Rigby, J.K., Jr., eds., The Cretaceous-Tertiary boundary 

in the San Juan and Raton basins, New Mexico and 

Colorado: Geological Society of America Special Paper 

209, p. 111-130. 

Pillmore, C.L., Tschudy, R.H., Orth, C.J., Gilmore, J.S., and 

Knight, J.D., 1984, Geologic framework of theIr anomaly 

at selected K{f boundary sites, Raton basin, New Mexico 

and Colorado: Science, v. 223, no. 4641, p. 1180-1182. 

Read, C.B., Duffner, R.T., Wood, G.H., Jr., and Zapp, A.D., 1950, 

Coal resources of New Mexico: U.S. Geological Survey 

Circular 89, 24 p. 

Raton Coalfield 67 
Scott, G.R., and Pillmore, C.L., 1989, Geologic and structure 

contour maps of the Raton 1h0 x1 o quadrangle, Colfax and 

Union Counties, New Mexico and Las Animas County, 

Colorado: U.S. Geological Survey Open File Report 

89-282, 2 sheets, scale 1: 100,000. 

Scott, G.R., Wilcox, R.E., and Mehnert, H.H., 1990, Geology of 

volcanic and subvolcanic rocks of the Raton-Springer area, 

Colfax county, New Mexico: U.S. Geological Survey 

Professional Paper 1507, 58 p. 

St. John, Orestes, 1896, Report on the Vermejo Northside coal area 

[letter to Maxwell Land Grant Company], reproduced in 

Pillmore, C.L., 1976, Third day road log * * *, in Ewing, 

68 Coalfields of New Mexico: Geology and Resources 

R.C., and Kues, B.S., eds., Guidebook of Vermejo Park, 

northeastern New Mexico: New Mexico Geological 

Society, 27th Field Conference, 1976, p. 66-68. 

Trumbull, J.y.A., 1959, Coal fields of the United States: U.S. 

Geological Survey Map, scale 1:5,000,000. 

Wanek, A.A., 1963, Geology and fuel resources of the 

southwestern part of the Raton coal field, Colfax County, 

New Mexico: U.S. Geological Survey Coal Investigations 

Map C-45, 2 sheets, scale 1 :48,000. 

Wood, G.H., Jr., Kehn, T.M., Carter, M.D., and Culbertson, W.C., 

1983, Coal resource classification system of the U.S. 

Geological Survey: U.S. Geological Survey Circular 891, 

65 p. 
Chapter E 

Geology and Coal Resources of 

New Mexico's Small Coalfields 

By FRANK W. CAMPBELL, GRETCHEN K. HOFFMAN, 

FRANK E. KOTTLOWSKI, and BRIAN W. ARKELL 

New Mexico Bureau of Mines and Mineral Resources 

Prepared in cooperation with the New Mexico 

Bureau of Mines and Mineral Resources 

Descriptions of 11 fields outside the 

San juan and Raton basins, which may 

hold more than 2 billion tons of coal 

U.S. GEOLOGICAL SURVEY BULLETIN 1972 

COALFIELDS OF NEW MEXICO: GEOLOGY AND RESOURCES 
CONTENTS 

Abstract 71 

Introduction 71 

Salt Lake field 71 

Datil Mountains field 73 

Sierra Blanca field 73 

Rio Puerco field 7 4 

Tierra Amarilla field 74 

Cerrillos field 7 5 

Carthage field 75 

Hagan field 7 5 

Tijeras field 76 

Jomada del Muerto field 76 

Engle field 76 

References cited 76 

FIGURE 

El. Map showing coalfields, rail lines, and pertinent localities in New Mexico 72 

70 Contents 
Geology and Coal Resources of 

New Mexico's Small Coalfields 

By Frank W. Campbell, Gretchen K. Hoffman, Frank E. Kottlowski, and 

Brian W. Arkell 

New Mexico Bureau of Mines and Mineral Resources 

Abstract 

The small coalfields of New Mexico, outside the San 

Juan basin and the Raton field, may contain resources of more 

than 2 billion tons of coal, which is mostly subbituminous but 

includes some anthracite and coking coals. Fields with 

reasonable economic reserves are the Salt Lake, Sierra Blanca, 

Datil Mountains, Cerrillos, and Carthage fields. The coal beds 

are in the lower part of the Upper Cretaceous Mesaverde 

Group or its equivalents, and the coals have medium ash 

content (1 0-20 percent) and low sulfur content (less than 1 

percent). 

INTRODUCTION 

Most of New Mexico's coal is in two major areas: the 

San Juan basin in the northwest in the Colorado Plateau 

physiographic province, and the Raton area in the northcentral part of the State in the Great Plains province. The 

other coalfields in the State are relatively small and are in 

the southeastern part of the Basin and Range province and 

the southeastern part of the Colorado Plateau province. 

Among these "small" coalfields (Tabet and Frost, 

1978), the ones that contain the largest amounts of resources 

are the Salt Lake field and the Datil Mountains field in 

west-central New Mexico and the Sierra Blanca field in 

south-central New Mexico (fig. El). The Cerrillos and 

Carthage fields have been mined extensively in the past and 

still contain usable resources. The Hagan, Tijeras, Jornada 

del Muerto, and Engle coalfields contain lesser amounts of 

coal resources. The Rio Puerco and Tierra Amarilla fields 

are outliers of the San Juan basin coal sequences. 

These small coalfields are of considerable historical 

interest. The Spanish used small amounts of coal from 

Manuscript approved for publication January 10, 1991. 

several of them as early as the 17th century. Anthracite was 

mined from the Cerrillos field as early as 1835. Mining 

began on a significant scale in 1861, when the U.S. Army 

troops at Fort Craig opened a mine in the Carthage field. 

Present economic interest in the small coalfields is largely 

confined to the Sierra Blanca field, because of its location 

on the Southern Pacific Railway, and the Salt Lake 

coalfield, which lies about 50 miles east of the power plants 

in east-central Arizona. 

SALT LAKE Fl ELD 

The Salt Lake coalfield (fig. El), in west-central New 

Mexico, covers about 750 mi2 straddling the Cibola-Catron 

County line in Tps. 1-8 N. and Rs. 15-21 W. This is a 

transitional area between the Zuni-Gallup basin to the north 

and the Datil-Mogollon volcanic field to the south. New 

Mexico Highway 32 provides access to U.S. Highway 60 to 

the south at Quemado and northward to Interstate 40 at 

Gallup. 

Structurally, the Salt Lake field is simple, with a few 

low-displacement normal faults, and some small-scale 

flexures. Dips are generally less than 5°. 

Upper Cretaceous coal-bearing units crop out in a 

westward-opening arcuate belt along Carrizo Creek. Most 

of the coal beds occur in the Moreno Hill Formation 

(McLellan and others, 1983a), which correlates northward 

and eastward with the Carthage and Fite Ranch Members of 

the Tres Hermanos Formation, the Pescado Tongue of the 

Mancos Shale, the Gallup Sandstone, and the lower part of 

the Crevasse Canyon Formation (Hook and others, 1983). 

Minable coals are in the lower member of the Moreno 

Hill Formation, which has a maximum thickness of 798 ft; 

individual beds reach a maximum thickness of 13.2 ft but 

average 4.1 ft. Some thin coals (1-3 ft) are found in the 

Upper Cretaceous Dakota Sandstone in the western part of 

New Mexico's Small Coalfields 71 
107 ° 106° 105° -----~-----

Fort Craigo 

.,..-Tierra Amarilla 

l.f' Field 

rillos Field 

Tijeras Field 

Albuquerque 

Jornada del 

• Muerto Field 

Carthage Field Carrizo 

Alamogordo 

,._._.__._ __ \ ______ _l_-----

3201 

I I r _ _l ______ J.._ __ 

100 MILES I I 50 

I I 

I 

_I 

\ 

Hobbs 

LL _____ J 

Figure E1. Coalfields, rail lines, and pertinent localities in New Mexico. Railroads identified here are the Atchison, Topeka, 

and Santa Fe (AT &SF) and the Southern Pacific (SP). 

72 Coalfields of New Mexico: Geology and Resources 
the field. Coals in the Salt Lake field are of a high-volatile 

C to B bituminous rank, as shown below: 

Proximate analyses 

(123 samples; data in 

percent, except Btu/lb) 

Moisture... . . . . 11.01±5.60 

Ash .. .. . . . .. . . 18.04±8.51 

Volatile matter . 31.65±5 .53 

Fixed carbon... 37.41±7.25 

Btu/lb: 

As received... 9,244±1,507 

Mineral matter 

free . . . .. .. .. 11 ,342±1 ,659 

Major oxides (36 samples; 

data in percent) 

Si02 ••••••••••• 

Al20 3 ......... 

Fe20 3 •.••••••• 

Ti02 ........ .. 

CaO .......... . 

MgO ......... . 

Na20 ......... . 

K20 .......... . 

54.28±7.91 

23.12±5.30 

3.84±2.23 

1.61±0.65 

5.01±3.51 

0.72±0.40 

0.33±0.29 

0.86±2.42 

Ultimate analyses 

(81 samples; 

data in percent) 

Carbon ........ 51.49±6.75 

Hydrogen. . . . . . 4.23±3.34 

Nitrogen . . . . . . . 0.98±0.12 

Oxygen........ 9.92±2.15 

Sulfur . . . . . . . . . 0.91±1.69 

Trace elements 

(3 samples; data in 

parts per million) 

As............ 1 

Cu............ 18 

Hg ............ 8 

Li............. 4 

Mn...... ... . . . 210 

Pb............. 6 

Sb............. 15 

Se............. 1 

Th .......... .. 10 

u ············· 5 

Zn ............ 70 

The Salt Lake coalfield is estimated to have coal 

resources of 480 million tons (coal beds with minimum 

thickness of 1.2 ft) and coal reserves of 240 million tons 

(minimum thickness of 2.5 ft), based on recent geologic 

mapping, drilling, and coal-resource evaluation of the field 

by the New Mexico Bureau of Mines and Mineral 

Resources and the U.S. Geological Survey (Anderson, 

1981, 1982; Campbell, 1981, 1984; McLellan, Haschke, 

and Robinson, 1982; McLellan, Robinson, and others, 1982; 

McLellan, Haschke, and others, 1983a, b; McLellan, Robinson, and Haschke, 1983; McLellan and others, 1984; 

Roybal, 1982; and Roybal and Campbell, 1981). Out of 

these total resources and reserves, 144 million tons has a 

stripping ratio of 20:1 or less (Campbell and Roybal, 1984 ). 

DATIL MOUNTAINS FIELD 

The Datil Mountains coalfield (fig. E1) lies at the 

junction of Socorro, Catron, and Cibola Counties, in the 

northern foothills of the Datil, Gallinas, and Bear 

Mountains, generally in the upper drainage basin of the Rio 

Salado between Riley and Hickman. The field covers about 

760 mi2

• Access to the rugged area is by ranch roads and 

New Mexico Highway 52 to Alamo. 

The geological structure of the field is complicated by 

broad-scale folding, igneous intrusions, and faulting, mostly 

of Laramide and Tertiary age. Southward the coal-bearing 

units are overlain by thick volcanic tuffs and flows. The coal 

beds are in the Tres Hermanos and Crevasse Canyon 

Formations. The Crevasse Canyon Formation coal beds are 

the time equivalent of the Dileo Coal Member of the 

Crevasse Canyon Formation in the San Juan and Acoma 

basins (Molenaar, 1974). Coals range from subbituminous 

A to high-volatile C bitumi~ous in rank, as shown below: 

Proximate analyses 

(26 samples; data in 

percent, except Btu/lb) 

Moisture....... 7.42±5.66 

Ash .. .. .. .. .. . 12.50±5.60 

Volatile matter. 36.20±4.00 

Fixed carbon... 43.77±4.63 

Btu/lb: 

As received ... 10,871±1 ,597 

Mineral matter 

free ......... 12,453±1,712 

Major oxides (7 samples; 

data in percent) 

Si02 ••••••••••• 

A1 20 3 ••••••••• 

Fe20 3 ••••••••• 

Ti02 ........ .. 

CaO .......... . 

MgO ......... . 

K20 .......... . 

Na20 ......... . 

58.42±8.22 

16.83±1.85 

4.64±0.72 

1.22±0.17 

4.59±0.86 

1.35±0.41 

0.81±0.19 

0.50±0.18 

Ultimate analyses 

(26 samples; 

data in percent) 

Carbon ........ 62.41±6.77 

Hydrogen . . . . . . 4.98±0.42 

Nitrogen....... 1.10±0.19 

Oxygen. . . . . . . . 0.46±8.37 

Sulfur .. .. .. .. . 0.57±0.12 

Trace elements 

(3 samples; data in 

parts per million) 

As ........... . 

Cu ........... . 

Hg ........... . 

Li ............ . 

Mn ........... . 

Ni ............ . 

Pb ............ . 

Sb ............ . 

Se ............ . 

Th ........... . 

u ............ . Zn ........... . 

8±9 

15±11 

0.35±0.31 

11±7 

151±330 

8±4 

8±4 

13±17 

3±2 

8±4 

3±1 

14±9 

Read and others (1950) estimated resources of the 

Datil Mountains area as more than a billion tons, but recent 

detailed mapping and drilling suggest this estimate is too 

high. For the eastern part of the field, Osburn (1982, 1983, 

1984) estimated measured and indicated resources as 85 

million tons in beds averaging 2. 7 ft in thickness and 

attaining a maximum of 4 ft. However, Winchester ( 1921) 

reported thicker coal beds in the northwest part of the 

coalfield. 

SIERRA BLANCA FIELD 

The Sierra Blanca field, also known as the Capitan 

field, is in south-central New Mexico, on the northeast 

margin of the Tularosa basin, in Lincoln and Otero 

Counties. Coal.:.bearing units crop out on the edges of the 

Sierra Blanca syncline and also flank the extrusive-intrusive 

complex of Sierra Blanca on its east, north, and west sides, 

covering about 435 mi2• Structurally, the field is a northplunging syncline, which has limbs dipping 15°-29°. The 

geology of the field is further complicated by many faults, 

dikes, and sills. 

U.S. Highway 54 and the Southern Pacific Railway 

cut across the west edge of the field, and U.S. Highway 380 

trends southeastward across the northern part. The coal 

seams have been mined near Capitan, White Oaks, Fort 

Stanton, and Carrizozo. 

New Mexico's Small Coalfields 73 
Minable coals appear to be southeastward equivalents 

of the Crevasse Canyon Formation (Arkell, 1983; Hook and 

others, 1983). Available analyses indicate that the coals are 

high-volatile C and B bituminous: 

Proximate analyses 

(14 samples; data in 

percent, except Btu/lb) 

Moisture ...... . 

Ash .......... . 

Volatile matter . 

Fixed carbon ... 

Btu/lb: 

5.53±4.51 

13.51±5.32 

31.46±7.91 

47.24±5.93 

As received ... 11,175±1,787 

Mineral matter 

free ......... 12,983±2,047 

Major oxides (4 samples; 

data in percent) 

Si02 ••••••••••• 

A1 20 3 ••••.•••• 

Fe20 3 ••••••••• 

Ti02 •••••••••• 

CaO .......... . 

MgO ......... . 

K20 .......... . 

Na20 ......... . 

60.19±6.42 

15.78±1.26 

2.60±0.29 

1.25±0.10 

4.41±0.48 

0.88±0.11 

0.32±0.03 

0.65±0.14 

Ultimate analyses 

(12 samples; 

data in percent) 

Carbon ........ 61.33±7.74 

Hydrogen. . . . . . 4.58±0.49 

Nitrogen . . . . . . . 1.17±0.16 

Oxygen ........ 13.37±5.78 

Sulfur......... 0.75±0.16 

Trace elements 

(4 samples; data in 

parts per million) 

As . .. .. .. .. .. . 8.13±0.25 

Cu .. .. .. .. .. .. 14.04±6.33 

Hg .. .. .. .. .. .. 0.1 0±0.05 

Li .. .. .. .. .. . .. 8.52±1.10 

Mn ............ 32.73±30.17 

Ni............. 4.38±2.13 

Pb. . . . . . . . . . . . . 7 .97±3.26 

Sb............. 1.60±0.77 

Se............. 2.81±0.78 

Th .. .. .. .. .. .. 5.10±2.21 

u .. .. .. .. .. . .. 2.85±0.96 

Zn .. . .. .. .. . .. 8.49±7.42 

Where they are near igneous intrusions, the coals are of 

coking quality. Read and others (1950) estimated original 

resources of about 1.6 billion tons. However, the steep dips 

of many of the coal beds and the numerous faults, dikes, and 

sills, make mining difficult. Coal beds north of Carrizozo 

may be favorable for strip mining, but reserve calculations 

for them are proprietary. Seam thickness, as determined 

from sparse data, average 2.3 ft, but several lenses near 

Capitan (Bodine, 1956) are as much as 7 ft. 

RIO PUERCO FIELD 

The Rio Puerco coalfield is a small outlier of the San 

Juan basin (fig. E1), lying about 15 miles southeast of the 

main basin. Interstate 40 crosses the southern tip of the 

field, along the lower part of Rio Puerco drainage. 

The coal-bearing units are within the Rio Puerco fault 

zone occur in narrow, steeply dipping fault blocks outlined 

by a north-northeast-trending swarm of high-angle faults on 

the border between the Rio Grande rift and the San Juan 

basin. 

Outcropping coal beds are in the Dileo and Gibson 

Coal Members of the Crevasse Canyon Formation. The 

Dileo coal beds are thin; those in the Gibson Member 

appear to average 2.5 ft in thickness, although seams as 

thick as 9.6 ft have been mined for local use in the northern 

part of the field (Shomaker and others, 1971 ). The coal beds 

7 4 Coalfields of New Mexico: Geology and Resources 

appear to range from subbituminous A to high-volatile C 

bituminous in rank, based on analyses of three as-received 

samples: 

Proximate analyses 

(3 samples; data in 

percent, except Btu/lb) 

Moisture. . . . . . . 16.27±5.84 

Ash .. .. .. .. . .. 8.60±1.64 

Volatile matter. 34.67±2.62 

Fixed Carbon . . 40.47±1.82 

Btu/lb: 

As received... 9,473±195 

Mineral matter 

free . . . . . . . . . 10,452±208 

Ultimate analyses 

(2 samples; 

data in percent) 

Carbon . . . . . . . . 55.05±0.85 

Hydrogen...... 6.15±0.35 

Nitrogen . . . . . . . 1.00±0.00 

Oxygen ........ 29.00±1.60 

Sulfur . . . . . . . . . 0.93±0.41 

All data on bed characteristics and coal quality for the Rio 

Puerco field are based on outcrop data, as no drilling data 

are available. The total reserves for the northern part of this 

field, within 250 ft of the surface, are estimated at 185 

million tons. Resources (0-250 ft) for the southern part of 

the Rio Puerco field are estimated at 175 million tons. 

Because of the paucity of data for these coal beds, the steep 

dip of the beds, and the abundance of high-angle faults 

within them, the coal resource potential in this field is 

considered to be low. Information that could be gained by 

drilling would help to clarify the true coal potential and the 

extent of the coal-bearing formation. 

TIERRA AMARILLA FIELD 

The Tierra Amarilla coalfieid in north-central New 

Mexico, in the southeast comer of the Tierra Amarilla Land 

Grant and in the eastern part of the Chama basin, is an 

outlier of the San Juan basin, about 12 miles east of the 

eastern margin. U.S. Highway 84 skirts the east edge of the 

field. 

The coal beds, in the Menefee Formation of the 

Mesaverde Group, are thin and lenticular; the maximum 

coal seam thickness is 4.1 ft. Two analyses indicate the 

coals are subbituminous A in rank and give these averages: 

Proximate analyses 

(2 samples; data in 

percent, except Btu/lb) 

Moisture ...... . 

Ash .......... . 

Volatile matter. 

Fixed Carbon .. 

Btu/lb: 

18.70±0.80 

8.50±0.80 

32.60±0.50 

40.20±1.10 

As received... 9,875±235 

Mineral matter 

free ......... 10,883±156 

Ultimate analyses 

(1 sample; 

data in percent) 

Carbon ........ 57.20±0.00 

Hydrogen . . . . . . 6.1 0±0.00 

Nitrogen . . . . . . . 1.30±0.00 

Oxygen. . . . . . . . 26. 70±0.00 

Sulfur . . . . . . . . . 1.05±0.05 
Landis and Dane (1969) estimated the total resources 

to be 4.5 million tons of inferred coal in the Tierra Amarilla 

field. 

CERRILLOS FIELD 

The Cerrillos field is in north-central New Mexico, in 

the broken foothill country north of the Ortiz Mountains and 

south of the broad valley of Rio Galisteo; it is traversed by 

the main line of the Atchison, Topeka, and Santa Fe 

Railway. New Mexico Highway 14 crosses the field from 

south to north and serves the main town, Madrid. 

The field is a complex syncline in which the coalbearing rocks have been broken by many faults and have 

been intruded by swarms of dikes and sills. Near the thick 

igneous intrusions the coals have been metamorphosed to 

semianthracite and anthracite. 

The coal-bearing strata are in the Mesaverde 

Formation. The major beds are as much as 6 ft in thickness 

and have yielded considerable tonnages of anthracite and 

bituminous coals. Some of the bituminous lenses are of 

medium coking coal. Anthracite is restricted to the parts of 

the White Ash seam that are near the intrusive rocks and to 

a thinner, unnamed seam immediately overlying the 

intrusive body. 

As much as 45,000 tons of anthracite was mined 

annually from the Cerrillos field during the period 1888 to 

1957 and was supplied to users throughout the central and 

western parts of the nation. Read and others (1950) 

estimated resources of 4 7.5 million tons of bituminous coal 

and 5.7 million tons of anthracite. Analyses of 82 samples 

as-received gave the following averages: 

Proximate analyses 

(82 samples; data in 

percent, except Btu/lb) 

Moisture ...... . 

Ash .......... . 

Volatile matter . 

Fixed Carbon .. 

Btu/lb: 

3.15±2.13 

10.26±4.60 

21.77±12.88 

65.90±14.37 

As received ... 12,913±1,018 

Mineral matter 

free .. .. .. .. . 14,503±864 

CARTHAGE FIELD 

Ultimate analyses 

(13 samples; 

data in percent) 

Carbon . . . . . . . . 77 .69±4.98 

Hydrogen. . . . . . 3.85±1.29 

Nitrogen . . . . . . . 1.25±0.11 

Oxygen. . . . . . . . 7 .69±2.55 

Sulfur . . . . . . . . . 0.97±0.52 

The Carthage coalfield lies in central New Mexico on 

the northwest edge of Jornada del Muerto, an extensive 

syncline-graben of that semiarid region. U.S. Highway 380 

cuts across the northern edge of the field. The area is 8 miles 

east of San Antonio, which is served by the Atchison, 

Topeka, and Santa Fe Railway and by Interstate Highway 

25. 

Two coal seams, ranging from 4 to 7 ft in thickness, 

occur in the Crevasse Canyon Formation. Only the lower 

coal, the Carthage seam, has been mined; it is excellent 

coking coal of high-volatile C bituminous rank. 

This small field occupies about 10 mi2 and is cut into 

a mosaic of small fault blocks, making mining difficult and 

expensive. U.S. Army troops stationed at nearby Fort Craig 

opened mining in this field in 1861, the earliest "largescale" mining in New Mexico. In the late 1800's and early 

1900's, the Carthage field supplied coking coal to many 

smelters in southwestern New Mexico and northern 

Mexico, but between 1950 and 1975 only a single small 

underground mine operated intermittently to provide coal 

for local heating (Kottlowski and others, 1984 ). 

Most of the easily mined coal has been removed; 

remaining reserves may be as much as 30 million tons. The 

averages of 11 analyses on an as-received basis follow: 

Proximate analyses 

(11 samples; data in 

percent, except Btu/lb) 

Moisture ...... . 

Ash .......... . 

Volatile matter . 

Fixed carbon ... 

Btu/lb: 

3.36±1.30 

11.55±3.01 

36.55±2.64 

48.68±3.08 

As received . . . 12,508±560 

Mineral matter 

free ......... 14,405±533 

HAGAN FIELD 

Ultimate analyses 

(4 samples; 

data in percent) 

Carbon ........ 69.38±3.52 

Hydrogen. . . . . . 5.25±0.21 

Nitrogen . . . . . . . 1.28±0.11 

Oxygen ........ 12.50±3.66 

Sulfur......... 0.83±0.15 

The Hagan field lies in north-central New Mexico in 

a dissected valley drained by Tongue Arroyo northeast of 

the Sandia Mountains and southwest of Ortiz Mountain. 

The coal seams are 3-5ft thick, occur in the Mesaverde Group, are of high-volatile C bituminous rank, and are 

cut by numerous faults. Several small underground mines 

operated near Hagan in the early 1900's and again from 

1927 to 1939 (Kelley and Northrop, 1975). The field's 

remoteness and difficulties of mining caused by the 

complex geologic structure closed the mining operations. 

Read and others (1950) estimated resources of 17.3 million 

tons for this field (then called the Una del Gato field). The 

averages of 10 analyses on an as-received basis follow: 

Proximate analyses 

(1 0 samples; data in 

percent, except Btu/lb) 

Moisture . . . . . . . 1 0.56±2.14 

Ash .. . .. .. .. .. 8.26±2.42 

Volatile matter. 38.00±3.90 

Fixed carbon... 43.20±3.09 

Btu/lb: 

As received ... 10,508±1,477 

Mineral matter 

free ......... 11,625±1,653 

Ultimate analyses 

(4 samples; 

data in percent) 

Carbon ........ 62.30±4.76 

Hydrogen . . . . . . 5.01±1.06 

Nitrogen . . . . . . . 1.26±0.04 

Oxygen ........ 19.00±4.06 

Sulfur . . . . . . . . . 0.66±0.13 

New Mexico's Small Coalfields 75 
TIJERAS FIELD 

The Tijeras field is amid the rolling eastern foothills 

of the Sandia Mountains in north-central New Mexico. The 

coal-bearing rocks are in the Mesaverde Group and occur in 

a small down-dropped fault block, the Tijeras graben. The 

strata are folded into two synclines and an intervening 

anticline, and they dip steeply (Kelley and Northrop, 1975). 

Several thin beds of bituminous rank coal crop out, but only 

a few tons have been mined for minor local use. Read and 

others (1950) estimated resources of 1.6 million tons. The 

averages of three as-received analyses follow (proximate 

analyses; results in percent, except Btu/lb ): 

Moisture .................. . 

Ash ...................... . 

Volatile matter ............ . 

Fixed carbon .............. . 

Btu/lb: 

4.20±3.82 

15.83±10.81 

34.93±2.76 

45.03±7.11 

As received . . . . . . . . . . . . .. . 11, 104± 1 ,997 

Mineral matter free ........ 13,631±2,424 

JORNADA DEL MUERTO FIELD 

Five to twenty miles east and northeast of the 

Carthage field, Mesaverde Group coal-bearing rocks 

underlie the northwest edge of Jomada del Muerto. 

Windblown sand conceals much of the bedrock, the area is 

remote, and there has been no appreciable mining. The few 

known outcrops of coal have maximum thickness of only 3 

ft (Tabet, 1979a). However, drilling might delineate 

additional reserves, as the Cretaceous strata extend for at 

least 10 miles in a north-south direction. Analyses of three 

coal samples as received show an average composition 

similar to that of the Carthage field coals (proximate 

analyses; results in percent, except Btu/lb ): 

Moisture .................. . 

Ash ...................... . 

Volatile matter ............ . 

Fixed carbon .............. . 

Sulfur .................... . 

Btu/lb: 

2.3±.0.64 

16.3±5.80 

38.2±3.01 

43.1±4.71 

2.3±0.64 

As received ............... 11,410±1,353 

Mineral matter free ........ 13,897±700 

ENGLE FIELD 

The geologic setting of the Engle field is similar to 

that of the Jomada del Muerto field, although the Engle field 

is about 50 miles farther south. It lies on the west edge of the 

Jomada del Muerto syncline on the alluvial fans east of the 

Caballo Mountains. Prospect pits have opened thin lenses of 

76 Coalfields of New Mexico: Geology and Resources 

coal, and drill holes have penetrated several coal beds in the 

Mesaverde Group, but the apparent maximum thickness of 

coal seams is 4 ft. Information from drilling indicates 32 

million tons of deep coal (Tabet, 1979b) having an average 

as-received composition as follows (proximate analyses; 

results in percent, except Btu/lb ): 

Moisture .................. . 

Ash ...................... . 

Volatile matter ............ . 

Fixed carbon .............. . 

Sulfur .................... . 

Btu/lb: 

6.5±5.50 

20.0±0.15 

18.9±6.41 

54.7±12.30 

0.5±0.12 

As received............... 9,745±2,080 

Mineral matter free ........ 12,429±2,637 

REFERENCES CITED 

Anderson, O.J., 1981, Geologic map of the Cantaralo Spring 

quadrangle, Cibola County, New Mexico: New Mexico 

Bureau of Mines and Mineral Resources Open-File 

Report 142. 

__ 1982, Geology and coal resources of the Venadito Camp 

quadrangle, Cibola County, New Mexico: New Mexico 

Bureau of Mines and Mineral Resources Open-File 

Report 163. 

Arkell, B.W., 1983, Geology and coal resources of the Cub 

Mountain area, Sierra Blanca coal field, New Mexico: 

Socorro, N. Mex., New Mexico Institute of Mining and 

Technology, M.S. thesis, 104 p. 

Bodine, M.W., Jr., 1956, Geology of Capitan coal field, Lincoln 

County, New Mexico: New Mexico Bureau of Mines and 

Mineral Resources Circular 35, 19 p. 

Campbell, F.W., 1981, Geology and coal resources of Cerro Prieto 

and The Dyke quadrangles: New Mexico Bureau of Mines 

and Mineral Resources Open-File Report 144, 44 p. 

__ 1984, Geology and coal resources of the Cerro Prieto and 

The Dyke quadrangles: New Mexico Bureau of Mines and 

Mineral Resources, New Mexico Geology, v. 6, no. 1, 

p. 6--10. 

Campbell, F.W., and Roybal, G.H., 1984, Geology and coal 

resources of the Fence Lake 1 :50,000 quadrangle: New 

Mexico Bureau of Mines and Mineral Resources Open-File 

Report 207, 37 p. 

Hook, S.C., Molenaar, C.M., and Cobban, W.A., 1983, Stratigraphy and revision of nomenclature of Upper Cenomanian to 

Turonian (Upper Cretaceous) rocks of west-central New 

Mexico: New Mexico Bureau of Mines and Mineral 

Resources Circular 185, p. 7-28. 

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

Mountains and vicinity, New Mexico: New Mexico Bureau 

of Mines and Mineral Resources Memoir 29, 136 p. 

Kottlowski, F.E., Campbell, F.W., Roybal, G.H., and Hatton, K.S., 

1984, New Mexico, in 1984 Keystone coal industry manual: 

New York, McGraw-Hill, p. 558-567. 

Landis, E.R., and Dane, C.H., 1969, The Tierra Amarilla coal 

field, Rio Arriba County, New Mexico: New Mexico 

Bureau of Mines and Mineral Resources Circular 100, 11 p. 
Landis, E.R., McLellan, M.W., McKay, E.J., Carter, M.D., and 

Medlin, A.L., 1984, Geologic map of the Fence Lake SW 

quadrangle, Cibola and Catron Counties, New Mexico: U.S. 

Geological Survey Miscellaneous Field Studies Map 

MF-1750, scale 1:24,000. 

McLellan, M.W., Biewick, L.R., and Landis, E.R., 1984, 

Stratigraphic framework, structure, and general geology of 

the Salt Lake coal field, Cibola and Catron Counties, New 

Mexico: U.S. Geological Survey Miscellaneous Field 

Studies Map MF-1689, scale 1:24,000. 

McLellan, M.W., Haschke, L.R., and Robinson, L.N., 1982, 

Geologic map of the Rincon Hondo quadrangle, Cibola 

County, New Mexico: U.S. Geological Survey 

Miscellaneous Field Studies Map MF-1506, scale 1:24,000. 

McLellan, Marguerite, Haschke, Laura, Robinson, Laura, Carter, 

M.D., and Medlin, Antoinette, 1983a, Middle Turonian and 

younger Cretaceous rocks, northern Salt Lake coal field, 

Cibola and Catron Counties, New Mexico, in Hook, S.C., 

compiler, Contributions to mid-Cretaceous paleontology 

and stratigraphy of New Mexico-part II: New Mexico 

Bureau of Mines and Mineral Resources Circular 185, 

p. 41-47. 

McLellan, M.W., Haschke, L.R., Robinson, L.N., and Landis, 

E.R., 1983b, Geologic map of the Moreno Hill quadrangle, 

Cibola and Catron Counties, New Mexico: U.S. Geological 

Survey Miscellaneous Field Studies Map MF-1509, scale 

1:24,000. 

McLellan,, M.W., Robinson, L.N., and Haschke, L.R., 1983, 

Geologic map of the Fence Lake quadrangle, Cibola 

County, New Mexico: U.S. Geological Survey 

Miscellaneous Field Studies Map MF-1533, scale 1:24,000. 

McLellan, M.W .... Robinson, L.N., Haschke, Laura, Carter, M.D., 

and Medlin, A.L., 1982, Fence Lake Formation (Tertiary), 

west-central New Mexico: New Mexico Geology, v. 4, no. 

4, p. 53-55. 

Molenaar, C.M., 1974, Correlation of the Gallup Sandstone and 

associated formations, Upper Cretaceous, eastern San Juan 

and Acoma basins, New Mexico: New Mexico Geological 

Society Guidebook, 25th Field Conference, p. 251-258. 

-trU$ GOVERNMENT PRINTING OFFICE: 1991-573-049/46011 

Osburn, J.C., 1982, Geology and coal resources of three 

quadrangles in the central Datil Mountains coal field, 

Socorro County, New Mexico: New Mexico Bureau of 

Mines and Mineral Resources Open-File Report 164, 82 p., 

6 pl. 

___ 1983, Coal resources of Socorro County, New Mexico, in 

Chapin, C.E., ed., Socorro region II: New Mexico 

Geological Society Guidebook, 34th Field Conference, 

1983, p. 223-226. 

___ 1984, Geology of Pueblo Viejo Mesa quadrangle, Socorro 

and Cibola Counties, New Mexico: New Mexico Bureau of 

Mines and Mineral Resources Geologic Map 55, scale 

1:24,000. 

Read, C.B., Duffner, R., Wood, G.H., Jr., and Zapp, A.D., 1950, 

Coal resources of New Mexico: U.S. Geological Survey 

Circular 89, 24 p. 

Roybal, G.H., 1982, Geology and coal resources of Tejana Mesa 

quadrangle: New Mexico Bureau of Mines and Mineral 

Resources Open-File Report 178, 38 p. 

Roybal, G.H., and Campbell, F.W., 1981, Stratigraphic sequence 

in drilling data from Fence Lake area, New Mexico: New 

Mexico Bureau of Mines and Mineral Resources Open-File 

Report 145, 59 p. 

Shomaker, J.W., Beaumont, E. C., and Kottlowski, F.E., eds., 1971, 

Strippable low-sulfur coal resources of the San Juan basin in 

New Mexico and Colorado: New Mexico Bureau of Mines 

and Mineral Resources Memoir 25, 189 p. 

Tabet, D.E., 1979a, Geology of Jornada del Muerto coal field, 

Socorro County, New Mexico: New Mexico Bureau of 

Mines and Mineral Resources Circular 168, 19 p. 

__ 1979b, Summary of the geology of the Engle coal field: 

New Mexico Bureau of Mines and Mineral Resources 

Open-File Report 115, 9 p. 

Tabet, D.E., and Frost, S.J., 1978, Coal fields and mines of New 

Mexico: New Mexico Bureau of Mines and Mineral 

Resources Resource Map 10. 

Winchester, D.E., 1921, Geology of Alamosa Creek valley, 

Socorro County, New Mexico: U.S. Geological Survey 

Bulletin 716-A, 15 p. 

New Mexico's Small Coalfields 77 

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is 1:24,000 and regional studies are at 1:250,000 scale or smaller. 

Catalogs 

Permanent catalogs, as well as some others, giving comprehensive listings of U.S. Geological Survey publications are available under 

the conditions indicated below from the U.S. Geological Survey, Books 

and Open-File Reports Section, Federal Center, Box 25425, Denver, 

CO 80225. (See latest Price and Availability List) 

"Publications ofthe Geological Survey, 1879-1961" may be purchased by mail and over the counter in paperbaek book form and as a 

set of microfiche. 

"Publications of the Geological Survey, 1962- 1970" may be purchased by mail and over the counter in paperback book form and as a 

set of microfiche. 

"Publications ofthe U.S. Geological Survey, 1971-1981" may be 

purchased by mail and over the counter in paperback book form (two 

volumes, publications listing and index) and as a set of microfiche. 

Supplements for 1982,1983, 1984, 1985,1986, and for subsequent 

years since the last permanent catalog may be purchased by mail and 

over the counter in paperback book form. 

State catalogs, "List of U.S. Geological Survey Geologic and 

Water-Supply Reports and Maps For (State)," may be purchased by mail 

and over the counter in paperback booklet form only 

"Price and Availability List of U.S. Geological Survey Publications," issued amually, is available free of charge in paperback booklet form only. 

Selectedcopiesofamonthlycatalog"NewPublicationsoftheU.S. 

Geological Survey" available free of charge by mail or may be obtained 

over the counter in paperback booklet form only. Those wishing a free 

subscription to the monthly catalog "New Publications of the U.S. 

Geological Survey" should write to the U.S. Geological Survey, 582 

National Center, Reston, VA 22092. 

Note.--Prices of Government publications listed in older catalogs, 

amouncements, and publications may be incorrect Therefore, the 

prices charged may differ from the prices in catalogs, announcements, 

and publications.