Text to accompany:

Open-File Report 79-1116

1979

COAL RESOURCE OCCURRENCE MAPS AND 

COAL DEVELOPMENT POTENTIAL MAPS OF THE

FLORA VISTA QUADRANGLE,

SAN JUAN COUNTY, NEW MEXICO

[Report includes 8 plates]

by 

Dames & Moore

This report has not been edited 

for conformity with U.S. Geological Survey editorial standards or 

stratigraphic nomenclature.
CONTENTS

Page

Introduction 1

Purpose 1

Location 1

Accessibility 2

Physiography 2

Climate 2

Land status 3

General geology 3

Previous work 3

Geologic history 3

Stratigraphy 5

Structure 7

Coal geology 7

Fruitland 1 coal bed 8

Chemical analyses of the Fruitland 1 coal bed 10

Coal resources 10

Coal development potential 12

Development potential for surface mining methods 12 

Development potential for subsurface mining methods 12

References 15
CONTENTS

PLATES

Page

Coal resource occurrence maps: 

Plate 1. Coal data map

2. Boundary and coal data map

3. Coal data sheet

4. Isopach map of the Fruitland 1 coal bed

5. Structure contour map of the Fruitland 1 coal bed

6. Isopach map of overburden of the Fruitland 1 coal 

bed

7. Areal distribution and identified resources of the 

Fruitland 1 coal bed

Coal development potential maps:

8. Subsurface mining methods

TABLES

Table 1. Analyses of coal samples from the Fruitland Formation 9

2. Coal resource data for underground mining methods 13 

for Federal coal lands (in short tons) in the 

Flora Vista quadrangle, San Juan County, 

New Mexico

ii
FLORA VISTA 7 1/2-MINUTE QUADRANGLE

INTRODUCTION

Purpose

This text is to be used in conjunction with the Coal Resource 

Occurrence (CRO) Maps and the Coal Development Potential (CDP) Map of the 

Flora Vista quadrangle, San Juan County, New Mexico. These maps were 

compiled to provide a systematic coal resource inventory of Federal coal 

lands in Known Recoverable Coal Resource Areas (KRCRA's) of the western 

United States. The work was performed under contract with the Conservation 

Division of the U.S. Geological Survey (Contract No. 14-08-0001-17172).

The resource information gathered in this program is in response to 

the Federal Coal Leasing Amendments Act of 1976 and is a part of the U.S. 

Geological Survey's coal program. The information provides basic data on 

coal resources for land-use planning purposes by the Bureau of Land Management, state and local governments, and the public.

Location

The Flora Vista 7 1/2-minute quadrangle is located in north-central 

San Juan County, New Mexico. The area is approximately 8 miles (13 km) 

northeast of Farmington. Aztec, New Mexico, is located on the east-central 

border of the quadrangle.

-I-
Accessibility

The Flora Vista quadrangle is accessible by New Mexico State Route 

550 which passes northeast-southwest through the area. Light-duty roads 

which extend across State Route 550 provide access to other parts of the 

quadrangle. The Atchison, Topeka, and Santa Fe Railroad operates a route 

which is 96 miles (154 km) to the southwest at Gallup, New Mexico, and 

extends southeast and southwest.

Physiography

This quadrangle is in the northwestern portion of the Central Basin 

area (Kelley, 1950) of the structural depression known as the San Juan 

Basin. Elevations range from 5,448 ft (1,661 m) in the Animas River Valley 

in the west to 6,282 ft (1,915 m) in the northwest. The Animas River flows 

northeast-southwest through the quadrangle and is surrounded by low hills 

which are dissected by numerous arroyos. The Beeline Reservoir is north 

of the Animas River in the western part of the area.

Climate

The climate of the San Juan Basin is arid to semi-arid. Annual 

precipitation is usually less than about 10 inches (25 cm) with slight variations across the basin due to elevational differences. Rainfall is rare 

in the early summer and winter; most precipitation is received in July and

-2-
August as intense afternoon thundershowers. Annual temperatures range from 

below 0°F (-18°C) to over 100° (38°C) in the basin. Snowfall may occur from 

November to April.

Land Status

The quadrangle is in the northern part of the San Juan Basin Known 

Recoverable Coal Resource Area. The Federal Government owns the coal rights 

for approximately 68 percent of the KRCRA land within the quadrangle as shown 

on Plate 2 of the Coal Resource Occurrence Maps. No Federal coal leases 

occur in the quadrangle.

GENERAL GEOLOGY 

Previous Work

Reeside (1924) mapped the surficial geology of the area as part of 

a study of the Upper Cretaceous and Tertiary formations of the San Juan 

Basin. More recently, Fassett and Hinds (1971) made subsurface interpretations of Fruitland Formation coal occurrences in the quadrangle area as 

part of a larger San Juan Basin coal study.

Geologic History

The San Juan Basin, an area of classic transgressive and regressive 

sedimentation, provided the ideal environment for formation of coals during

-3-
Late Cretaceous time. At that time a shallow epeiric sea, which trended 

northwest-southeast, was northeast of the basin. The sea transgressed southwesterly into the basin area and regressed northeasterly numerous times; 

consequently, sediments from varying environments were deposited across the 

basin. Noncarbonaceous terrestrial deposition predominated during Paleocene 

and Eocene time.

The first depositional evidence of the final retreat of the Late 

Cretaceous sea is the nearshore regressive Pictured Cliffs Sandstone. 

Southwest (shoreward) of the beach deposits, swamps, which were dissected by 

streams, accumulated organic matter which later became coals of the Fruitland 

Formation. Deposition of organic material was influenced by the strandline 

as shown by both the continuity of the coal beds parallel to the northsouth strandline in this quadrangle and their discontinuity perpendicular to 

it to the east. The less continuous Fruitland coals appear to be noncorrelative, but are stratigraphically equivalent in terms of their relative 

position within the Fruitland Formation.

The brackish-water swamp environment of the Fruitland moved farther 

to the northeast as the regression continued in that direction. Terrestrial 

freshwater sediments covered the quadrangle as indicated by the lacustrine, 

channel, and floodplain deposits of the Kirtland Shale. This sequence of 

events is evidenced by both an upward decrease in occurrence and thickness of 

Fruitland coals and a gradational change to noncarbonaceous deposits of the 

Kirtland. Continuous deposition during Late Cretaceous time ended with the 

Kirtland. The sea then retreated beyond the limits of the quadrangle area, 

and modern basin structure began to develop. An erosional unconformity 

developed in a relatively short time as part of the Cretaceous Kirtland Shale 

was removed.

 A 
Terrestrial deposition resumed in the Paleocene as represented by 

the Ojo Alamo Sandstone and the overlying Nacimiento Formation. Alluvial 

plain and floodplain deposits of the Ojo Alamo were followed by the thick, 

lithologically varied deposits of the Nacimiento during continuous nonmarine 

deposition. The Nacimiento was later exposed to erosion.

The Eocene San Jose Formation was subsequently deposited over the 

Nacimiento erosional surface, reflecting various nonmarine environments 

which developed across the basin. Deposition and structural deformation of 

the basin then ceased, and the warped strata of the San Juan Basin have been 

exposed to the present time. A significant amount of erosion has occurred, 

as indicated by the removal of the San Jose Formation and the upper part of 

the Nacimiento Formation from the area.

Stratigraphy

The formations studied in this quadrangle range from Late 

Cretaceous to Paleocene in age. They are, in order from oldest to youngest: 

Pictured Cliffs Sandstone, Fruitland Formation, Kirtland Shale, Ojo Alamo 

Sandstone, and Nacimiento Formation. A composite columnar section on CRO 

Plate 3 illustrates the stratigraphic relationships of these formations and 

is accompanied by lithologic descriptions of the individual formations.

The Pictured Cliffs Sandstone averages 120 ft (37 m) thick in the 

area. Because the unit is persistent throughout most of the San Juan Basin 

and easily recognized on geophysical logs, the top was picked as the datum 

(CRO Plate 3) for Fruitland coal correlations. The formation consists of a 

light gray to tan, friable, kaolinitic, slightly glauconitic sandstone, and
interbedded gray siltstone with sandy stringers near the base of the unit. 

Intertonguing with the overlying Fruitland Formation occurs throughout the 

entire basin and, consequently, minor Fruitland coal beds commonly are 

present in the upper portion of the Pictured Cliffs.

The major coal-bearing unit in the quadrangle, the Fruitland 

Formation, conformably overlies the Pictured Cliffs Sandstone. Wide variations in reported thickness of the Fruitland are common due to an indistinct 

upper contact with the Kirtland Shale, but the average is about 350 ft 

(107 m) in this quadrangle. Many authors have utilized various criteria 

to establish the upper contact, but, in general, for this study the uppermost 

coal was chosen (after Fassett and Hinds, 1971). The formation consists 

primarily of gray, carbonaceous shale with plant fossils and siderite 

nodules, interbedded light gray, calcareous sandstone with interstitial 

kaolinite, and lenticular coal beds.

The Upper Cretaceous Kirtland Shale conformably overlies the 

Fruitland Formation and averages 1,060 ft (323 m) thick in this area. It is 

predominantly freshwater, gray-green to brown siltstone with sandy stringers 

and plant fossils, interbedded buff, slightly calcareous sandstone, and 

interbedded gray shale. The formation has previously been divided into 

several members by various authors; however, for the purposes of this report 

it was not necessary to distinguish between the individual members.

The Paleocene Ojo Alamo Sandstone, which unconformably overlies 

the Kirtland Shale, is a light gray, locally conglomeratic sandstone with 

interstitial kaolinite, and interbedded gray shale near the base of the 

formation. It averages 110 ft (34 m) in thickness and is exposed in the 

southwestern corner of the area in the Animas River Valley.

-6-
The Paleocene Nacimiento Formation is exposed across most of the 

quadrangle. It consists of gray to gray-green shale, interbedded gray to 

green siltstone and claystone, and interbedded white to tan sandstone.

Structure

The Flora Vista quadrangle is in the Central Basin area (Kelley, 

1950) of the major structural depression known as the San Juan Basin. The 

axis of the basin is in the east-central part of the quadrangle area and 

trends eastward in an arcuate pattern across the northern portion of the 

Central Basin area (Baltz, 1967). Reeside (1924) stated that the rocks in 

this area are "nearly horizontal".

COAL GEOLOGY

Four coal beds (Fruitland 1, Fruitland 2, Fruitland 3, Fruitland 4) 

and a coal zone (Fruitland) are identified in the subsurface of this quadrangle (CRO Plate 1). The Fruitland 1 (Fr 1) coal bed is defined by the 

authors as the lowermost coal of the Fruitland Formation; it is generally 

directly above the Pictured Cliffs Sandstone. However, occasionally there is 

a local (L) coal bed. Above the Fruitland 1 (when present) is the Fruitland 

2 (Fr 2) coal bed; the two are separated by a rock interval averaging 8 ft 

(2.4 m); above the Fruitland 2 is the Fruitland 3 (Fr 3) coal bed; they are 

separated by a rock interval of 41 to 62 ft (12.5-18.9 m); stratigraphically 

above the Fruitland 3 is the Fruitland 4 (Fr 4) coal bed (these two coal beds 

are not present together in any drill hole within this quadrangle). Although

-7-
these coal beds have been correlated as consistent horizons, they may actually be several different coal beds that are lithostratigraphically equivalent 

but not laterally continuous. Since the Fruitland 2, 3, and 4 coal beds are 

less than reserve base thickness (5 ft [1.5 m]), derivative maps were not 

constructed.

The remaining coals of the Fruitland Formation are grouped together 

as the Fruitland coal zone (Fr zone). These coals are generally noncorrelative, discontinuous, and less than reserve base thickness (5 ft [1.5m]). 

Therefore, derivative maps were not constructed.

Fruitland Formation coals in the northwest part of the San Juan 

Basin are considered high volatile A to high volatile B bituminous in rank. 

The rank has been determined on a moist, mineral-matter-free basis with 

calorific values averaging 14,258 Btu's per pound (33,164 kj/kg) (Amer. Soc. 

for Testing and Materials, 1977). The coal is hard, brittle, and black with 

a bright luster. The coal readily slakes with exposure to weather; however, 

it stocks fairly well when protected. The "as received" analyses indicate 

moisture content varying from 1.8 to 5.7 percent, ash content averaging 

13.7 percent, sulfur content less than one percent, and heating values on 

the order of 12,131 Btu's per pound (28,217 kj/kg). Analyses of several 

Fruitland coals are given in Table 1 (Bauer and Reeside, 1921; Dane, 1936; 

Fassett and Hinds, 1971).

Fruitland 1 Coal Bed

As shown by the structure contour map (CRO Plate 5), the Fruitland 

1 coal bed dips less than 1° in a northeasterly direction. As a result of

-8-
TABLE 1

Analyses of coal samples from the Fruitland Formation 

(Form of analysis: A, as received; B, moisture free; C, moisture a

U.S. 

Bureau 

Mine* 

Lab No.

H-12704

H-24567

H-7225

H-3028

H-13060

H-3030

H-8360

H-4052

H-13062

H-15140

H- 16 308

H-19399

Location

Well or Other Source Section T.N. R.U.

Redfern I Herd SVk 10 28 11

Red fern & Herd No. 5

Sunray Mid-continent NW*t 18 28 12

Callegoi No. 122

Pan American NWk 16 28 13

Holder No. 7

International Oil NWk 9 29 11

Fogelson No. 1-9

Tidewater Slk 12 29 11

N.M.-Fed. No. 12-E

Tennet.ee Oil & Cat NW>t 10 29 12

Cornell C«« Unit A

No. 1

Aitec Oil t Caa SW>t 20 29 13

Uagood No. 21-C

Aitec Oil i Caa SEH 34 29 13

Uagood No. 13-C

Artec Oil i Cat NE»t 7 30 11

Ruby Jonet No. 1

Southweat Production K&t 22 30 12

Sullivan No. 1

R&C Drilling N\*t 18 30 13

Lunt No. 62

M

Com pa a Exploration NEk 31 30 13

Fedaral No. 1-3 1A

Approx. Dapth 

Interval of 

Sample (ft.)

1,490-1,500

1,305-1,315

1,705-1,715

1,905-1,910

2,065-2,070

1,740-1,750

1,125-1,140

1,635-1,640

2,020-2,030

1,713-1,742

1,425-1,440

1,070-1,080

Proximate, percent

Form of 

Analyaia

A

B

C

A

B

C

A

B

C

A

B

C

A

B

C

A

B

C

A

B

C

A

B

C

A

B

C

A

B

C

A

B

C

A

B

C

Moiature

2.1

 

 

3.0

 

 

4.1

 

_. 

1.8

 

 ~ 

2.1

 

 

2.1

 

 ~

5.6

 

 

3.5

 

. 

1.4

 

 

2.2

 

 

2.8

 

 

5.7

 

 

Volatile 

matter

39.8

40.7

47.9

38.9

40.1

46.8

39.4

41.1

47.9

39.9

40.6

47.6

38.7

39.5

44.7

40.0

40.9

47.2

39.0

41.3

48.5

39.6

41.0

47.8

37.2

37.7

45.7

38.8

39.7

46.1

40.4

41.6

47.5

38.8

41.2

47.4

Fixed 

Carbon

43.4

44.3

52.1

44.4

45.8

53.2

42.8

44.6

52.1

43.9

44.8

52.4

47.9

48.9

55.3

44.8

45.7

52.8

41.3

43.8

51. 5

43.2

44.8

52.2

44.1

44.8

54.3

45.3

48.3

53.9

44.7

45.9

52.5

43.0

45.5

52.6

Aah Su

14.7

15.0

 

13.7

14.1

 ' "" 

13.7

14.3

 

14.4

14.6

 

11.3

11.6

 

13.1

13.4

- 

14.1

14.9

. 

13.7

14.2

 

17.3

17.5

 

13.7

14.0

 

12.1

12.5

 

12.5

13.3

 

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

To convert Btu'a/lb to kj/kg, multiply Btu'e/lb by 2.326. 

To convert feet to metera, multiply feat by 0.3048.
topography and dip, the overburden (CRO Plate 6) varies in thickness from 

less than 1,500 ft (457 m) in the southwest in the Animas River Valley to 

more than 2,400 ft (732 m) at the northern edge of the quadrangle. The 

isopach map (CRO Plate 4) shows the coal bed is more than 15 ft (4.6 m) thick 

in several areas in the quadrangle and thins in all directions. It is absent 

in the extreme northwest corner and in a portion in the east-central part of 

the quadrangle.

Chemical Analyses of the Fruitland 1 Coal Bed - Analyses of several 

coals of the Fruitland Formation from this quadrangle and the surrounding 

area are given in Table 1 (Fassett and Hinds, 1971).

COAL RESOURCES

Coal resource data from oil and gas wells and pertinent publications were utilized in the construction of isopach and structure contour maps 

for this quadrangle. All of the coals studied in the Flora Vista quadrangle 

are more than 1,190 ft (363 m) below the ground surface and, thus, have no 

outcrop or surface development potential.

The U.S. Geological Survey designated the Fruitland 1 coal bed 

for the determination of coal resources in this quadrangle. Coals of the 

Fruitland 2, Fruitland 3, and Fruitland 4 beds and the Fruitland zone were 

not evaluated because the thickness of the coal beds is generally less than 

the reserve base thickness (5 ft [1.5 m]). In addition, the Fruitland zone 

coals are irregular, noncorrelative, and limited in areal extent.

For Reserve Base and Reserve calculations, the Fruitland 1 coal bed 

was areally divided into measured, indicated, and inferred resource catego-

-10-
ries (CRO Plate 7) according to criteria established in U.S. Geological 

Survey Bulletin 1450-B. Data for calculation of Reserve Base and Reserves 

for each category were obtained from the coal isopach (CRO Plate 4) and areal 

distribution maps (CRO Plate 7). The surface area of the isopached Fruitland 

1 bed was measured by planimeter, for each category, in acres, then multiplied by the average isopached thickness of the coal bed and 1,800 short tons 

of coal per acre-foot (13,239 tons/hectare-meter), the conversion factor for 

bituminous coal. This yields the Reserve Base coal, in short tons, for the 

Fruitland 1 coal bed.

In order to calculate Reserves, a recovery factor of 50 percent was 

applied to the Reserve Base tonnages for underground coal. However, in areas 

of underground coal exceeding 12 ft (3.7 m) in thickness, the Reserves (mineable coal) were calculated on the basis of a maximum coal bed thickness of 

12 ft (3.7 m), which represents the maximum economically mineable thickness 

for a single coal bed in this area by current underground mining technology.

Reserve Base and Reserve values for measured, indicated, and 

inferred categories of coal for the Fruitland 1 coal bed are shown on CRO 

Plate 7, and are rounded to the nearest hundredth of a million short tons. 

The total coal Reserve Base, by section, is shown on CRO Plate 2 and totals 

approximately 503 million short tons (456 million metric tons).

The coal development potential for the Fruitland 1 bed is calculated in a manner similar to the Reserve Base, from planimetered measurements, in acres, for areas of high, moderate, and low potential for subsurface mining methods. The Flora Vista quadrangle has development potential 

for subsurface mining methods only (CDP Plate 8).

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COAL DEVELOPMENT POTENTIAL

Coal beds of 5 ft (1.5 m) or more in thickness which are overlain 

by 200 to 3,000 ft (61-914 m) of overburden are considered to have potential 

for underground mining, and are designated as having high, moderate, or low 

development potential according to the overburden thickness: 200 to 1,000 ft 

(61-305 m), high; 1,000 to 2,000 ft (306-610 m), moderate; and 2,000 to 3,000 

ft (610-914 m), low. Table 2 summarizes the coal development potential, in 

short tons, for underground coal of the Fruitland 1 coal bed.

Development Potential for Surface Mining Methods

All coals studied in the Flora Vista quadrangle occur more than 

1,190 ft (363 m) below the ground surface and, thus, they have no coal development potential for surface mining methods.

Development Potential for Subsurface Mining Methods

The underground coal of the Fruitland 1 coal bed has moderate 

development potential in the west-central and southern half of the quadrangle 

(CDP Plate 8) where the coal bed thickness varies from 5 to 18 ft (1.5-5.5 m) 

(CRO Plate 4), and the overburden thickness increases from approximately 

1,600 ft (488 m) in the southwest to 2,000 ft (610 m) across the center of 

the quadrangle (CRO Plate 6). Low development potential occurs in the southwest and northern half of the quadrangle where the Fruitland 1 coal bed has 

overburden thickness increasing from 2,000 ft (610 m) in the center of the

-12-
TABLE 2

COAL RESOURCE DATA FOR UNDERGROUND MINING METHODS FOR FEDERAL COAL 

(in short tons) IN THE FLORA VISTA QUADRANGLE,

SAN JUAN COUNTY, NEW MEXICO

(To convert short tons to metric tons, multiply by 0.9072)

High Moderate Low 

Coal Bed____Development Potential Development Potential Development Pot

Fruitland 1 ____________202,210,000_________300,310,000_

£ TOTAL 202,210,000 300,310,000 
area to more than 2,400 ft (732 m) in the north. The coal bed thickness 

ranges from 5 to 19 ft (1.5-5.8 m) in this area. The Fruitland 1 coal bed 

has unknown development potential in the northwest and south-central areas 

where it is less than the reserve base thickness of 5 ft (1.5 m). A small 

area in the extreme northwest corner of the quadrangle has no Fruitland 1 

coal and, thus, has no development potential.

-14-
REFERENCES

American Soc. for Testing and Materials, 1977, Gaseous fuels; coal and 

coke; atmospheric analysis, in Annual book of ASTM standards, part 26: 

p. 214-218.

Baltz, E.H., Jr., 1967, Stratigraphy and regional tectonic implications of 

part of Upper Cretaceous and Tertiary rocks, east-central San Juan 

Basin, New Mexico: U.S. Geol. Survey Prof. Paper 552, p. 12.

Bauer, C.M., and Reeside, J.B., Jr., 1921, Coal in the middle and eastern 

parts of San Juan County, New Mexico: U.S. Geol. Survey Bull. 716-G, 

p. 177-178.

Dane, C.H., 1936, The La Ventana - Chacra Mesa coal field, pt. 3 of Geology 

and fuel resources of the southern part of the San Juan Basin, New 

Mexico: U.S. Geol. Survey Bull. 860-C, p. 137-138, [1937].

El Paso Natural Gas Co., Well log library, Farmington, New Mexico.

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. Geol. Survey Prof. Paper 676, 76 p.

Kelley, V.C., 1950, Regional structure of the San Juan Basin in New Mexico 

Geol. Soc. Guidebook of the San Juan Basin, New Mexico and Colorado, 

1st Field Conf., p. 102.

Reeside, J.B., Jr., 1924, Upper Cretaceous and Tertiary formations of the 

western part of the San Juan Basin of Colorado and New Mexico: U.S. 

Geol. Survey Prof. Paper 134, p. 1-70.

U.S. Bureau of Mines and U.S. Geological Survey, 1976, Coal resource classification system of the U.S. Bureau of Mines and U.S. Geological Survey: 

U.S. Geol. Survey Bull. 1450-B, 7 p.

U.S. Department of the Interior, 1940, Fulcher Basin-Kutz Canyon areas, San 

Juan County, New Mexico: U.S. Geol. Survey Oil and Gas Operations Map 

Roswell 60, revised 1972, 1:31,680.

____, 1950, Map of portion of San Juan County, New Mexico, and La Plata 

County, Colorado: U.S. Geol. Survey Oil and Gas Operations Map Roswell 

91, revised 1972, 1:31,680.

____, 1950, Map of portion of San Juan County, New Mexico, and La Plata 

County, Colorado: U.S. Geol. Survey Oil and Gas Operations Map Roswell 

90, revised 1973, 1:31,680.

-15-