UNITED STATES DEPARTMENT OF THE INTERIOR 

GEOLOGICAL SURVEY

Text to accompany: 

Open-File Report 79-777 

1979

COAL RESOURCE OCCURRENCE AND

COAL DEVELOPMENT POTENTIAL MAPS OF THE

SPRING CREEK RANCH QUADRANGLE,

BIG HORN COUNTY, MONTANA

[Report includes 13 plates]

By 

Colorado School of Mines Research Institute

This report has not been edited for 

conformity with U.S. Geological Survey 

editorial standards or stratigraphic 

nomenclature.
CONTENTS

Page

Introduction------------------------------------------ - ----------- i

Purpose--------------------------- ----------------------------- 1

Location---------------------------- ------- __________________ i

Accessibility----------------------- --------------------------- 1

Physiography----- -------- ____________________________________ 2

Climate---------------------------------------------------------- 2

Land Status 3

General geology---------------------------- ---------_--------------- 3

Previous work---- -- --------_--_----------------_-_----------- 3

Stratigraphy-- - --------------------- ____ _________________ 3

Structure--------------------------------------------- --------- 4

Coal geology------- ------- ______________________________ ________ 4

Wall coal bed---- ------------------- ______ _________________ 5

Local coal bed ----- ___________________ _ __________________ 5

Canyon coal bed--------------------------- --------------------- 6

Dietz 2 and 3 coal beds------- - ----------- _______ ________ 7

Anderson (Dietz 1) clinker bed---------- ---- ----------------- g

Coal resources------------- ----------------------------------------- g

Coal development potential------ --------------- ___________________ n

Development potential for surface-mining methods----------------- 12

Development potential for underground mining and in-situ

gasification----------------- ----------------------------- 14

References------------------------------------------------------------ 17

ILLUSTRATIONS

[Plates are in pocket]

Plates 1-12. Coal resource occurrence maps:

1. Coal data map.

2. Boundary and coal data map

3. Coal data sheet.
Illustrations--Continued

Page

4. Isopach and structure contour map of the 

combined Dietz 2 and Dietz 3 coal beds.

5. Overburden isopach and mining-ratio map of 

the combined Dietz 2 and Dietz 3 coal beds.

6. Areal distribution and tonnage map of identified resources of the combined Dietz 2 and 

Dietz 3 coal beds.

7. Isopach and structure contour map of the 

Canyon coal bed.

8. Overburden isopach and mining-ratio map of 

the Canyon coal bed.

9. Areal distribution and tonnage map of identified and hypothetical resources of the 

Canyon coal bed.

10. Isopach and structure contour map of the Wall 

coal bed.

11. Overburden isopach and mining-ratio map of 

the Wall coal bed.

12. Areal distribution and tonnage map of identified resources of the Wall coal bed.

Plate 13. Coal development potential map for surface-mining 

methods.

TABLES

Table 1. Surface-minable coal resource tonnage (in short tons) by

development-potential category for Federal coal lands---- 15

Table 2. Underground-minable coal resource tonnage (in short tons) by

development-potential category for Federal coal lands- - 16

11
	Conversion table 

To convert Multiply by __________To obtain_________

feet 0.3048 meters (m)

miles 1.609 kilometers (km)

acres 0.40469 hectares (ha)

tons (short) 0.9072 metric tons (t)

short tons/acre-ft 7.36 metric tons/hectare-meter (t/ha-m)

Btu/lb 2.326 kilojoules/kilogram (kJ/kg)

111
INTRODUCTION 

Purpose

This text is for use in conjunction with the Coal Resource Occurrence 

(CRO) and Coal Development Potential (CDP) maps of the Spring Creek Ranch quadrangle, Big Horn County, Montana, (13 plates; U.S. Geological Survey Open-File 

Report 79-777). This set of maps was compiled to support the land-use planning 

work of the Bureau of Land Management in response to the Federal Coal Leasing 

Amendments Act of 1976 and to provide a systematic inventory of coal resources on 

Federal coal lands in Known Recoverable Coal Resource Areas (KRCRAs) in the western United States. The inventory includes only those beds of subbituminous coal 

that are 5 feet (1.5 m) or more thick and under less than 3,000 feet (914 m) of 

overburden and those beds of lignite that are 5 feet (1.5 m) or more thick and 

under less than 1,000 feet (305 m) of overburden.

Location

The Spring Creek Ranch 7 1/2-minute quadrangle is in eastern Big Horn 

County, Montana, about 34 miles (54.7 km) southeast of Hardin, Montana, a town in 

the valley of the Bighorn River near the confluence of the Bighorn River and the 

Little Bighorn River. Hardin is on U.S. Highway 212, U.S. Interstate Highway 

90, and on the Chicago, Burlington, and Quincy Railroad.

Accessibility

The Spring Creek Ranch quadrangle is accessible from Hardin, Montana, by 

going first southward on U.S. Interstate Highway 90 and then eastward on U.S. 

Highway 212 for a total of about 39 miles (62.8 km) to the Rosebud Creek Road, 

thence southward on the Rosebud Creek Road about 15 miles (24.1 km), thence westward on an unimproved local road about 2 miles (3.2 km) to the eastern border of 

the quadrangle. The nearest mainline railroad is the Chicago, Burlington, and 

Quincy Railroad, which is about 12 miles (19.3 km) west of the quadrangle at
Lodge Grass, Montana. A branch of the railroad serves the Decker coal mine, 

which is about 16 miles (25.8 km) southeast of the quadrangle.

Physiography

The Spring Creek Ranch quadrangle is near the western edge of the Missouri 

Plateau Division of the Great Plains physiographic province where the nearly flatlying strata of the plateau start to be upturned near the mountains. The quadrangle is on the eastern slope of the Wolf (Rosebud) Mountains which crest 1 to 3 

miles (0.9 to 2.7 km) west of the quadrangle. The land surface is dissected and 

drained by four eastward-flowing tributaries of Rosebud Creek which flows northward about 0.5 to 1.5 miles (0.8 to 2.4 km) east of the quadrangle. The stream 

valleys have narrow flood plains from which the parallel interstream divides rise 

steeply about 500 feet (152 m) to rounded crests. The crests are devoid of trees 

which are generally limited to north-facing slopes in the northern part of the 

quadrangle.

The highest elevation, about 5,000 feet (1,524 m) is on an interstream 

divide in the southwestern part of the quadrangle. The lowest elevation, 3,800 

feet (1,158 m), is close to the northeastern corner of the quadrangle. Topographic relief is about 1,200 feet (366 m).

Climate

The climate of Big Horn County is characterized by pronounced variations in 

seasonal precipitation and temperature. Annual precipitation in the region varies from less than 12 inches (30 cm) to about 16 inches (41 cm). The heaviest 

precipitation is from April to August. The largest average monthly precipitation 

is during June. Temperatures in eastern Montana range from as low as -50°F 

(-46°C) to as high as 110°F (43°C). The highest temperatures occur in July and 

the lowest in January; the mean annual temperature is about 45°F (7°C) (Matson 

and Blumer, 1973, p. 6).
Land status

The Boundary and Coal Data Map (pi. 2) shows the land ownership status within the Spring Creek Ranch quadrangle. All of the quadrangle except the eastern 

row of sections is within the Crow Indian Reservation. The two northeastern-most 

sections are within the Northern Cheyenne Indian Reservation. Federal coal lands 

are only found outside of the Indian Reservations. All of the land outside of 

the Indian Reservations is within the Northern Powder River Basin Known Recoverable Coal Resource Area (KRCRA). There were no outstanding Federal coal leases 

or prospecting permits recorded as of 1977.

GENERAL GEOLOGY 

Previous work

Baker (1929, pi. 28) mapped that part of the Spring Creek Ranch quadrangle 

south and east of the Northern Cheyenne and Crow Indian Reservations as part of 

the northern extension of the Sheridan coal field. Matson and Blumer (1973, pis. 

5-A, 5B, and 5C) remapped the coal beds in the same area.

Traces of coal outcrops shown by previous workers on planimetric maps that 

lack topographic control have been modified to fit the modern topographic map of 

the quadrangle.

Stratigraphy

A generalized columnar section of the coal-bearing rocks is shown on the 

Coal Data Sheet (pi. 3) of the CRO maps. The exposed bedrock units belong to the 

upper part of the Tongue River Member, the uppermost member of the Fort Union 

Formation (Paleocene).

The Tongue River Member is made up mainly of yellow sandstone, sandy shale, 

carbonaceous shale, and coal. Much coal has burned along outcrops, baking the 

overlying sandstone and shale and forming thick, reddish-colored clinker beds. 

The uppermost part of the Tongue River Member has been removed by erosion. The
uneroded lower part of the member is estimated to be as much as 1,500 feet (457 

m) thick, but its exact thickness cannot be determined.

Coal and other rocks comprising the Tongue River Member were deposited in a 

continental environment at elevations of perhaps a few tens of feet (a few 

meters) above sea level in a vast area of shifting rivers, flood plains, sloughs, 

swamps, and lakes that occupied the area of the Northern Great Plains in Paleocene (early Tertiary) time.

Representative samples of the sedimentary rocks overlying and interbedded 

with minable coal beds in the eastern and northern Powder River Basin have been 

analyzed for their content of trace elements by the U.S. Geological Survey, and 

the results have been summarized by the U.S. Department of Agriculture and others 

(1974) and by Swanson (in Mapel and others, 1977 r pt. A, p. 42-44). The rocks 

contain no greater amounts of trace elements of environmental concern than do 

similar rocks found throughout other parts of the western United States.

Structure

The Spring Creek Ranch quadrangle is in the western part of the Powder River 

structural basin. The coal beds and other strata in general dip eastward or 

southeastward at an angle of less than 2 degrees. In places this dip is modified 

by minor, low-relief folds and by faults as shown by the structure contour maps 

(pis. 4, 7, and 10). Some of the nonconformity in structure may be due to differential compaction and to irregularities in deposition of the coals and other 

beds as a result of their continental origin.

COAL GEOLOGY

The coal beds in the Spring Creek Ranch quadrangle are shown in outcrop on 

the Coal Data Map (pi. 1) and in section on the Coal Data Sheet (pi. 3). All of 

the mapped coal beds occur in the upper part of the Tongue River Member of the 

Fort Union Formation. No commercial coals are found below the Tongue River Member.

4
The lowermost recognized coal bed is the Wall coal bed. The Wall coal bed is 

overlain successively by a noncoal interval of 13 feet (4m), a local coal bed, a 

noncoal interval of about 175 to 200 feet (53 to 61 m), the Canyon coal bed, a 

noncoal interval of about 200 feet (61 m), the Dietz 2 and 3 coal beds, a noncoal 

interval of about 200 feet (61 m) , and the Anderson (Dietz 1) clinker bed.

The trace element content of coals in this quadrangle has not been determined; however, coals in the Northern Great Plains, including those in the Fort 

Union Formation in Montana, have been found to contain, in general, appreciably 

lesser amounts of most elements of environmental concern than coals in other 

areas of the United States (Hatch and Swanson, 1977, p. 147).

Wall coal bed

The Wall coal bed was named by Baker (1929, p. 37), probably from exposures 

of the coal along Wall Creek, a tributary of the Tongue River, about 19 miles 

(30.6 km) east of the Spring Creek Ranch quadrangle in the Birney quadrangle. 

This coal bed crops out only in the northeastern part of the quadrangle where it 

was mapped by Baker (1929, pi. 8) and by Matson and Blumer (1973, pi. 5-A). The 

coal is generally burned near the surface and there are no measurements of coal 

at the surface. The isopach and structure contour map of the Wall coal bed (pi. 

10) was constructed by using the data in adjacent quadrangles. This map shows 

that the Wall coal bed ranges from about 5 to 50 feet (1.5 to 15 m) in thickness 

and dips southeastward at a low angle where it is not affected by minor, lowrelief folding. Overburden on the Wall coal bed (pi. 11) ranges from zero at the 

outcrops to about 650 feet (198 m) in thickness. There are no known publicly 

available chemical analyses of the Wall coal in or close to the Spring Creek 

Ranch quadrangle. However, it is assumed that the Wall coal is similar to other 

closely associated coals in the quadrangle and is subbituminous C in rank.
Local coal bed

A local coal bed of limited areal extent, 5 feet (1.5 m) thick, occurs 18 

feet (5.5 m) above the Wall coal bed in sec. 19, T. 6 S., R. 39 E. (Matson and 

Blumer, pi. 5A). Economic coal resources have not been assigned to this local 

coal bed.

Canyon coal bed

The Canyon coal bed was first described by Baker (1929, p. 36) from exposures in the northern extension of the Sheridan coal field, although a type 

locality was not given. In the Spring Creek Ranch quadrangle, the Canyon coal 

bed occurs about 185 to 210 feet (56 to 64 m) above the Wall coal bed. A clinker bed formed by the burning of this coal crops out on the lower slopes of the 

hills. Because the coal is generally burned, there is only one measurement of 

its thickness in the quadrangle. The isopach and structure contour map of the 

Canyon coal bed (pi. 7) is based to a considerable extent on measurements in 

adjacent quadrangles. This map shows that the Canyon coal bed ranges in thickness from less than 5 feet (1.5 m) to possibly as much as 30 feet (9 m) in thickness and dips eastward or southeastward at a gentle angle where it is not affected by minor, low-relief folding. Overburden on the Canyon coal bed (pi. 8) 

ranges from about 50 to 400 feet (15 to 122 m) in thickness. There is no known, 

publicly available chemical analysis of the Canyon coal in the Spring Creek Ranch 

quadrangle. However, a chemical analysis of this coal in coal test hole SH-36, 

sec. 16, T. 6 S., R. 39 E., about 1.7 miles (2.7 km) east of this quadrangle in 

the Kirby quadrangle (Matson and Blumer, 1973, p. 34) shows ash 3.243 percent, 

sulfur 0.026 percent, and heating value 9,113 Btu per pound (21,197 kJ/kg) on an 

as-received basis. This heating value converts to about 9,418 Btu per pound 

(21,906 kJ/kg) on a moist, mineral-matter-free basis, indicating that the Canyon 

coal at this location is subbituminous C in rank. Because of the proximity of
this location to the Spring Creek Ranch quadrangle, it is assumed that the Canyon 

coal in this quadrangle is similar and is subbituminous C in rank.

Dietz 2 and 3 coal beds

The Dietz 1,2, and 3 coal beds were first described by Taff (1909, p. 139- 

140) from exposures in the Sheridan coal field, Wyoming. The coal bed which Baker (1929, pi. 28) mapped as the Anderson coal bed in the Spring Creek Ranch quadrangle was remapped by Matson and Blumer (1973, pi. 5B) as the Dietz coal beds 

(upper or combined benches). Matson and Blumer (1973, pi. 5A) mapped a higher 

bed near the south border of the quadrangle as the Anderson coal bed. Faults, 

unsuspected by Baker, were revealed by coal test holes drilled to support the 

field mapping of Matson and Blumer. These authors (1973, p. 31) state, "Extensive field work and interpretations were required on the Kirby area because of 

the structural complexity. Drilling was begun during the 1969 field season, and 

additional holes were drilled during the 1970 field season. In midwinter 1972- 

73, more holes were drilled to verify some of the interpretations and to assist 

in final preparation of the maps." The compiled maps accompanying this report 

follow the interpretations of Matson and Blumer (1973, pis. 5A and 5B). We believe that the two combined Dietz benches mapped by Matson and Blumer are equivalent to the Dietz 2 and 3 of Taff, and that the overlying Anderson coal bed includes the Dietz 1 of Taff.

In the Spring Creek Ranch quadrangle, the Dietz 2 and 3 coal beds occur 

about 200 feet (61 m) above the Canyon coal bed. The Dietz coal has been extensively burned, and unburned coal is believed to occur only in the southern part 

of the quadrangle (pi. 1). The isopach and structure contour map of the Dietz 2 

and 3 coal beds (pi. 4), based principally on measurements in adjacent quadrangles, shows that this coal ranges from about 35 to 40 feet (10.7 to 12.2 m) in 

thickness and dips southwest at a very gentle angle. Overburden on the Dietz 2
and 3 coal beds (pi. 5) ranges from about 60 to 250 feet (18 to 76 m) in thickness .

There is no known, publicly available chemical analysis of the Dietz 2 and 

3 coal beds in the Spring Creek Ranch quadrangle. However, a chemical analysis 

of this coal from a depth of 89 to 99 feet (27 to 30 m) in coal test hole SH-35, 

sec. 14, T. 6 S., R. 39 E., about 3.25 miles (5.2 km) east of the Spring Creek 

Ranch quadrangle in the Kirby quadrangle (Matson and Blumer, 1973, p. 34) shows 

ash 6.684 percent, sulfur 0.000 percent, and heating value 8,383 Btu per pound 

(19,499 kJ/kg) on an as-received basis. This heating value converts to about 

8,983 Btu per pound (20,894 kJ/kg) on a moist, mineral-matter-free basis, indicating that the coal at this location is subbituminous C in rank. Because of the 

proximity of this location to the Spring Creek Ranch quadrangle, it is assumed 

that the Dietz 2 and 3 coal in this quadrangle is similar and is also subbituminous C in rank.

Anderson (Dietz 1) clinker bed

The reddish-colored clinker bed which caps a small ridge near the southern 

border of the quadrangle has been formed by burning of the Anderson (Dietz 1) 

coal bed. There is no unburned Anderson (Dietz 1) coal in this quadrangle, and 

consequently economic coal resources have not been assigned to this coal bed.

COAL RESOURCES

Data from all publicly available drill holes and from surface mapping by 

others (see list of references) were used to construct outcrop, isopach, and 

structure contour maps of the coal beds in this quadrangle.

A coal resource classification system has been established by the U.S. Bureau of Mines and the U.S. Geological Survey in U.S. Geological Survey Bulletin 

1450-B (1976). Coal resource is the estimated gross quantity of coal in the 

ground that is now economically extractable or that may become so. Resources are
classified as either Identified or Undiscovered. Identified Resources are specific bodies of coal whose location, rank, quality, and quantity are known from 

geologic evidence supported by specific measurements. Undiscovered Resources are 

bodies of coal which are surmised to exist on the basis of broad geologic knowledge and theory.

Identified Resources are further subdivided into three categories of reliability of occurrence, namely Measured, Indicated, and Inferred, according to 

their distance from a known point of coal-bed measurement. Measured coal is coal 

located within 0.25 mile (0.4 km) of a measurement point, Indicated coal extends 

0.5 mile (0.8 km) beyond Measured coal to a distance of 0.75 mile (1.2 km) from 

the measurement point, and Inferred coal extends 2.25 miles (3.6 km) beyond Indicated coal to a distance of 3 miles (4.8 km) from the measurement point.

Undiscovered Resources are classified as either Hypothetical or Speculative. 

Hypothetical Resources are those undiscovered coal resources in beds that may 

reasonably be expected to exist in known coal fields under known geologic conditions. In general, Hypothetical Resources are located in broad areas of coal 

fields where the coal bed has not been observed and the evidence of coal's existence is from distant outcrops, drill holes, or wells that are more than 3 miles 

(4.8 km) away. Hypothetical Resources are located beyond the outer boundary of 

the Inferred part of Identified Resources in areas where the assumption of continuity of the coal bed is supported only by extrapolation of geologic evidence. 

Speculative Resources are undiscovered resources that may occur in favorable 

areas where no discoveries have been made. Speculative Resources have not been 

estimated in this report.

For purposes of this report, Hypothetical Resources of subbit luminous coal 

are in coal beds which are 5 feet (1.5 m) or more thick, under less than 3,000 

feet (914 m) of overburden, but occur 3 miles (4.8 km) or more from a coal-bed 

measurement.

9
Reserve Base coal is that economically minable part of Identified Resources 

from which Reserves are calculated. In this report, Reserve Base coal is the 

gross amount of Identified Resources that occurs in beds 5 feet (1.5 m) or more 

thick and under less than 3,000 feet (914 m) of overburden for subbituminous 

coal.

Reserve Base coal may be either surface-minable coal or underground-minable 

coal. In this report, surface-minable Reserve Base coal is subbituminous coal 

that is under less than 500 feet (152 m) of overburden (stripping limit). In 

this report, underground-minable Reserve Base coal is subbituminous coal that is 

under more than 500 feet (152 m), but less than 3,000 feet (914 m) of overburden.

Reserves are the recoverable part of Reserve Base coal. In this area, 85 

percent of the surface-minable Reserve Base coal is considered to be recoverable 

(a recovery factor of 85 percent). Thus, these Reserves amount to 85 percent of 

the surface-minable Reserve Base coal. For economic reasons coal is not presently being mined by underground methods in the Northern Powder River Basin. Therefore, the underground-mining recovery factor is unknown and Reserves have not 

been calculated for the underground-minable Reserve Base coal.

Tonnages of coal resources were estimated using coal-bed thicknesses obtained from the coal isopach map for each coal bed (see list of illustrations). The 

coal resources, in short tons, for each isopached coal bed are the product of the 

acreage of coal (measured by planimeter), the average thickness in feet of the 

coal bed, and a conversion factor of 1,770 short tons of subbituminous coal per 

acre-foot (13,018 metric tons per hectare-meter). Tonnages of coal in Reserve 

Base, Reserves, and Hypothetical categories, rounded to the nearest one-hundredth 

of a million short tons for each coal bed, are shown on the Areal Distribution 

and Tonnage maps (see list of illustrations).

10
As shown by table 1, the total tonnage of federally owned, surface-minable 

Reserve Base coal in this quadrangle is estimated to be 230.72 million short tons 

(209.31 million t). The total tonnage of federally owned, surface-minable Hypothetical coal is estimated to be 0.74 million short tons (0.67 million t). As 

shown by table 2, the total federally owned, underground-minable Reserve Base 

coal is estimated to be 11.60 million short tons (10.52 million t). There is no 

federally owned, underground-minable Hypothetical coal. The total tonnage of 

surface- and underground-minable Reserve Base coal is 242.32 million short tons 

(219.83 million t), and the total of surface- and underground-minable Hypothetical coal is 0.74 million short tons (0.67 million t).

About 3 percent of the surface-minable Reserve Base tonnage is classed as 

Measured, 42 percent as Indicated, and 55 percent as Inferred. All of the underground-minable Reserve Base tonnage is Inferred.

The total tonnages per section for both Reserve Base and Hypothetical coal, 

including both surface- and underground-minable coal are shown in the northwest 

corner of the Federal coal lands in each section on plate 2. All numbers on 

plate 2 are rounded to the nearest one-hundredth of a million short tons.

COAL DEVELOPMENT POTENTIAL

There is a potential for surface-mining in the Northern Powder River Basin 

in areas where subbituminous coal beds 5 feet (1.5 m) or more thick are overlain 

by less than 500 feet (152 m) of overburden, or where lignite beds of the same 

thickness are overlain by 200 feet (61 m) or less of overburden. Areas having a 

potential for surface mining were assigned a high, moderate, or low development 

potential based on their mining-ratios (cubic yards of overburden per short ton 

of recoverable coal).

The formula used to calculate mining-ratio values for subbituminous 

coal is:

11
= o where MR = mining ratio

c t = thickness of overburden, in feet

t = thickness of coal, in feet 

rf = recovery factor = 0.85 in this area 

cf = conversion factor = 0.911 cu. yds./ 

short ton for subbituminous coal

The mining-ratio values are used to rate the degree of potential that areas 

within the stripping limit have for surface-mining development. Areas having 

mining-ratio values of 0 to 10, 10 to 15, and greater than 15 are considered to 

have high, moderate, and low development potential, respectively. This grouping 

of mining-ratio values was provided by the U.S. Geological Survey and is based on 

economic and technological criteria. Mining-ratio contours and the strippinglimit overburden isopach, which serve as boundaries for the development-potential 

areas, are shown on the overburden isopach and mining-ratio contour plates. 

Estimated tonnages of surface-minable Reserve Base and Hypothetical coal 

resources in each development-potential category (high, moderate, and low) are 

shown in table 1.

Estimated tonnages of underground-minable coal resources are shown in table 

2. Because coal is not presently being mined by underground mining in the Northern Powder River Basin for economic reasons, for purposes of this report all of 

the underground-minable coal resources are considered to have low development 

potential.

Development potential for surface-mining methods

The Coal Development Potential (CDP) map included in this series of maps 

pertains only to surface mining. It depicts the highest coal development-potential category which occurs within each smallest legal subdivision of 

land (normally about 40 acres or 16.2 ha). For example, if such a 40-acre

12
(16.2-ha) tract of land contains areas of high, moderate, and low development 

potential, the entire tract is assigned to the high development-potential category for CDP mapping purposes. Alternatively, if such a 40-acre (16.2-ha) tract 

of land contains areas of moderate, low, and no development potential, the entire 

tract is assigned to the moderate development-potential category for CDP mapping 

purposes. For practical reasons, the development-potential categories of areas 

of coal smaller than 1 acre (0.4 ha) have been disregarded in assigning a development potential to the entire 40-acre (16.2-ha) tract.

In areas of moderate to high topographic relief, the area of moderate-development potential for surface mining of a coal bed (area having mining-ratio values of 10 to 15) is often restricted to a narrow band between the high and low 

development-potential areas. In fact, because of the 40-acre (16.2-ha) minimum 

size of coal development-potential tracts, the narrow band of moderate development-potential area often does not appear on the CDP map because it falls within 

the 40-acre (16.2-ha) tracts that also include areas of high development potential. The Coal Development Potential (CDP) map then shows areas of low development potential abutting against areas of high development potential.

The coal development potential that the Federal coal lands have for surfacemining methods is shown on the Coal Development Potential map (pi. 13). Most of 

the Federal coal lands have a high development potential for surface mining. 

Scattered tracts have a moderate or low development potential, and only one small 

tract has no development potential.

The Wall coal bed (pi. 11) has a high development potential over a considerable part of the Federal lands extending from the boundary of the coal to the 

10 mining-ratio contour or to the arbitrarily assigned stripping limit at the 

500-foot overburden isopach.

13
The Canyon coal bed (pi. 8) has limited areas of high development potential 

on the hill slopes extending from the boundary of the coal to the 10 mining-ratio 

contour. The Canyon bed also has narrow bands of moderate development potential 

between the 10 and 15 mining-ratio contours, and wider areas of low development 

potential extending above the 15 mining-ratio contour to the crests of the hills.

The Dietz 2 and 3 coal beds have a limited area of high development potential in the southeastern part of the quadrangle. This area extends from the 

boundary of the unburned coal to the crests of the hills.

About 87 percent of the Federal coal lands in the quadrangle have a high 

development potential for surface mining, 6 percent have a moderate development 

potential, and about 1 percent have a low development potential.

Development potential for underground 

mining and in-situ gasification

Subbituminous coal beds 5 feet (1.5 m) or more in thickness lying more than 

500 feet (152 m) but less than 3,000 feet (914 m) below the surface are considered to have development potential for underground mining. Estimates of the tonnage of underground-minable coal are listed in table 2 by development-potential 

category for each coal bed. Coal is not currently being mined by underground 

methods in the Northern Powder River Basin because of poor economics. Therefore, 

the coal development potential for underground mining of these resources for purposes of this report is rated as low, and a Coal Development Potential map for 

underground mining was not made.

In-situ gasification of coal on a commercial scale has not been done in the 

United States. Therefore, the development potential for in-situ gasification of 

coal found below the surface-mining limit in this area is rated as low, and a 

Coal Development Potential map for in-situ gasification of coal was not made.

14
Table 1.--Surface-minable coal resource tonnage (in short tons) by development-pot

for Federal coal lands in the Spring Creek Ranch quadrangle, Big Horn Co

[Development potentials are based on mining ratios (cubic yards of overburden/

recoverable coal). To convert short tons to metric tons, multiply by 0

Coal bed

High development

potential 

(0-10 mining ratio)

Moderate development

potential 

(10-15 mining ratio)

Low develo

potent

(>15 mining 

Reserve Base tonnage

Dietz 2 and Dietz 3

Canyon

Wall

Total

Hypothetical Resource tonnage

Canyon

Total

15,970,000

6,630,000

87,440,000

110,040,000

740,000

740,000

0

5,590,000

67,990,000

73,580,000

0

0

0

9,970,

37,130,

47,100,

0

0

Grand Total 110,780,000 73,580,000 47,100,
Table 2.--Underground-minable coal resource tonnage (in short tons) by development

for Federal lands in the Spring Creek Ranch quadrangle, Big Horn C

[To convert short tons to metric tons, multiply by 0.9072]

Coal bed

Reserve Base tonnage 

Wall

Hypothetical Resource tonnage

Total

High Development 

potential

0

0 

0

0

Moderate development 

potential

0

0 

0

0

Low dev

pote

11,

11,

Grand Total 0 0 11,
REFERENCES

Baker, A. A., 1929, The northward extension of the Sheridan coal field, Big Horn 

and Rosebud Counties, Montana: U.S. Geological Survey Bulletin 806-B, 

p. 15-67.

Hatch, J. R. , and Swanson, V. E., 1977, Trace elements in Rocky Mountain coals, 

in Proceedings of the 1976 symposium, Geology of Rocky Mountain coal, 

1977: Colorado Geological Survey, Resource Series 1, p. 143-163.

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