Chapter GN

COAL RESOURCES, GREATER GREEN RIVER BASIN

By M.S. Ellis,1 G.L. Gunther,2 A.M. Ochs,2

J.H. Schuenemeyer,

1

 H.C. Power,

3

 G.D. Stricker,1 and Dorsey Blake1

in U.S. Geological Survey Professional Paper 1625-A

1 U.S. Geological Survey

2 Consultant, U.S. Geological Survey, Denver, Colorado

3

 University of Delaware, Newark, Delaware
GN-ii

Contents

Coal Resources—Deadman Coal Zone, Point of Rocks-Black Butte Coalfield,

Greater Green River Basin, Wyoming...............................................................GN-1

Deadman Coal Zone Resource Estimates—An Overview ...........................GN-1

Deadman Coal Zone Coal Resources...........................................................GN-2

Confidence Limits for Deadman Coal Zone Coal Resources.......................GN-4

References Cited ................................................................................................GN-6

Figures

GN-1 7.5-minute quadrangle maps in the Black Butte area.

GN-2 7.5-minute quadrangle maps in the Jim Bridger area.

GN-3 Federal coal and surface ownership in the Black Butte area.

GN-4 Federal coal and surface ownership in the Jim Bridger area.

GN-5 Deadman net coal isopach map in the Black Butte area.

GN-6 Deadman net coal isopach map in the Jim Bridger area.

GN-7 Deadman overburden isopach map in the Black Butte area.

GN-8 Deadman overburden isopach map in the Jim Bridger area.

GN-9 Mine and resource areas in the Black Butte area.

GN-10 Mine and resource areas in the Jim Bridger area.

Tables

GN-1 Coal resources of the Deadman coal zone in the Point of Rocks-Black

Butte coalfield, Greater Green River Basin reported by overburden, net

coal thickness, and reliability categories
GN-iii

GN-2 Coal resources of the Deadman coal zone in the Point of Rocks-Black

Butte coalfield, Greater Green River Basin reported by Federal coal and

Federal surface ownership in the Jim Bridger and Black Butte study areas

GN-3 Coal resources of the Deadman coal zone in the Point of Rocks-Black

Butte coalfield, Greater Green River Basin reported by 7.5-minute

quadrangle in the Jim Bridger and Black Butte study areas

GN-4 Data used for computation of confidence limits intervals with reliability

categories for Deadman coal resources

GN-5 Estimates of uncertainty with measurement error for the Deadman coal

resources
GN-1

COAL RESOURCES—DEADMAN COAL ZONE, POINT OF

ROCKS-BLACK BUTTE COALFIELD, GREATER GREEN

RIVER BASIN, WYOMING

DEADMAN COAL ZONE RESOURCE ESTIMATES—AN OVERVIEW

• Coal resources are calculated using the specific gravity of the coal calculation

from apparent coal rank, which is the weight of coal per unit volume, net coal

thickness, and areal extent of the coal.

• Resource tables for the Deadman coal zone in the Point of Rocks-Black Butte

coalfield include coal and overburden thickness categories from Wood and

others (1983) that are based on apparent coal rank. Additional categories were

included to provide more detail. Resources are also reported by Federal coal

and surface ownership categories and by 7.5-minute quadrangles in the Black

Butte and Jim Bridger study areas.

• Following USGS published guidelines (Wood and others, 1983), coal resource

estimates are divided into measured, indicated, and inferred categories

according to relative abundance and reliability of data.

• Measured resources are tonnage estimates of coal in the coal zone within a

radius of 0.25 mi of a control point where the net thickness of coal is measured.

• Indicated resources are tonnage estimates of coal that is within a radius of 0.25-

0.75 mi of a control point where the net thickness of the coal is measured.

• Inferred resources are tonnage estimates of coal that is within a radius of 0.75-3

mi of a control point where the net thickness of the coal is measured.
GN-2

• These resource categories assume a high to low degree of geologic certainty. A

statistical method, which measures levels of uncertainty (confidence limits) for

the Deadman resource estimates in the Point of Rocks-Black Butte coalfield, is

also included in this study.

• Resource estimates are reported in millions of short tons with two significant

figures.

DEADMAN COAL ZONE COAL RESOURCES

The Deadman coal zone was investigated in two different study areas; the Jim

Bridger to the north, and the Black Butte to the south. These two areas are referred

to collectively as the Point of Rocks-Black Butte coalfield. The coalfield is along

the east side of the Rock Springs Uplift. The lateral extent (study limit) of the

Deadman coal is defined by the coal outcrop to the west, modified from

unpublished mapping by the Bridger Coal Company, and by a three mile buffer

from our data points (drill holes or measured sections) to the east, south, and north.

The Black Butte and Jim Bridger study areas are divided Interstate Highway 80.

The total study limit for the Deadman coal zone is about 101,000 acres (40,873

hectares) in size.

Deadman coal resources in the Point of Rocks-Black Butte coalfield in the Greater

Green River Basin of Wyoming were calculated using several software packages

and custom programs. Details of the resource calculation methodology are given

in Ellis and others (1999, in press).

To calculate the Deadman coal resources, data were compiled in a StratiFact*

(GRG Corporation, 1996) relational database. The coal zones to be included in the
GN-3

Deadman coal zone, including the Deadman 1 through 5 and the A through C coal

zones, were correlated in the database. Data were initially managed in two

separate datasets, one for the Black Butte area, and the other for the Jim Bridger

area. The data for coal in the Deadman coal zone were downloaded and a custom

program was used to calculate the net coal thickness at each data point (drill hole

or measured section) location.

The net coal thickness and overburden thickness were gridded, and isopach maps

were produced using EarthVision* (Dynamic Graphics, Inc., 1997) software. The

grids were made using an isopach grid option (special handling of 0 values and

terminated data) with grid spacings of 100 x 100 meters.

The spatial parameters for querying coal resources (for example, 7.5-minute

quadrangle map (figs. GN-1 and GN-2) area (U.S. Geological Survey National

Mapping Division unpublished data, undated), Federal coal and surface ownership

(fig GN-3 and GN-4) (Bureau of Land Management, unpublished data, undated),

reliability, net coal thickness (fig. GN-5 and GN-6), and overburden (fig. GN-7

and GN-8) categories) were created on individual layers as ARC/INFO* (ESRI,

1998a) polygon coverages. The coverages were unioned to make one polygon

coverage for each study area, with many attributes for each polygon. The polygons

in the union coverages were edited in ARC/INFO* and ArcView* (ESRI, 1998b).

Coal resources were calculated for each study area using the EarthVision* (EV)

volumetrics tool, which calculates tonnages in each polygon in the union coverage

using the net coal thickness grid, the area of each polygon, and a conversion factor

of 1,770 short tons per acre-ft for subbituminous rank coal (Wood and others,

1983). Data from the EV volumetrics reports and the union coverage polygon

attribute tables for the Jim Bridger and the Black Butte study areas were combined
GN-4

in Excel* (Microsoft, 1997) spreadsheet software. Data for polygons containing

mine areas (figs. GN-9 and GN-10) or in areas of net coal less than 2.5 ft in

thickness were deleted from the data set. Resource tables were created using the

data from the remaining polygons (tables GN-1 through GN-3). The final resource

area (fig. GN-5 and GN-6) (area that met all coal resource criteria) was about

71,000 acres (28,733 hectares) in size.

*Commercial software package

CONFIDENCE LIMITS FOR DEADMAN COAL ZONE COAL

RESOURCES

A confidence interval is a statistic designed to capture uncertainty associated with

a point estimate. In this study we computed 90-percent confidence intervals on the

volume (total resource in millions of short tons) of coal in the Deadman coal zone

in the measured, indicated, and inferred categories.

The three main potential sources of error that might bias the confidence intervals

are preferential sampling, measurement errors, and model fitting. The probabilistic

interpretation of a confidence interval is based upon a random sample, which does

not apply in this situation, because there is preferential sampling in those areas

deemed to be minable. Measurement error can be caused by an error in recording

the coal bed thickness or in the definition of coverage areas. Modeling fitting

variability and bias result from the choice of models and fitting procedures.

Confidence limits for coal resources of the Deadman coal zone in the Point of

Rocks-Black Butte coalfield were calculated by J.H. Schuenemeyer and H.C.

Power. The data set that they used contained net coal measurements from 2,823

locations. This data set only included locations that contained Deadman coal (no 0
GN-5

net coal thickness values) and data that were representative of the entire coal zone

(no terminated holes).

The confidence limits were derived through a complex series of steps. These steps

included investigating coal thickness trends and spatial correlation (neither were

found to be statistically significant). The standard deviation of coal thickness was

obtained directly from the data. Differences in point densities were compensated

for by calculating sample size, called a pseudo n, within each reliability category

and calculating the variability of volume for each of the reliability categories.

Volumes of Deadman coal were then calculated at a 90-percent confidence interval

with measurement error. Some of the parameters used and results of the

confidence interval calculations are shown in tables GN-4 and GN-5. A detailed

description of the methodology used is given in Schuenemeyer and Power (in

press) and in Ellis and others (1999, in press).
GN-6

References Cited

Dynamic Graphics, Inc., 1997, EarthVision, v.4: Dynamic Graphics, Inc., 1015

Atlantic Ave., Alameda, CA 94501.

Ellis, M.S., Gunther, G.L., Flores, R.M., Ochs, A.M., Stricker, G.D., Roberts, S.B.,

Taber, T.T., Bader, L.R., and Schuenemeyer, J.H., 1999, Preliminary report

on coal resources of the Wyodak-Anderson coal zone, Powder River Basin,

Wyoming and Montana: U.S. Geological Survey Open-File Report 98-789A.

Ellis, M.S., Gunther, G.L., Flores, R.M. Stricker, G.D., and Ochs, A.M., in press,

Preliminary report on methodolgy for calculating coal resources of the

Wyodak-Anderson coal zone in the Powder River Basin, Wyoming and

Montana: U.S. Geological Survey Open-File Report 98-789B.

ESRI- Environmental Systems Research Institute, Inc., 1998a, ARC/INFO, v.

7.1.1: Environmental Systems Research Institute, Inc., 380 New York Street,

Redlands, CA 92373, USA.

_____ 1998b, ArcView, v.3.0a: Environmental Systems Research Institute, Inc.,

380 New York Street, Redlands, CA 92373, USA.

GRG Corporation, 1996, StratiFact, relational database software, v. 4.5: GRG

Corporation, 4175 Harlan Street, Wheatridge, CO 80033-5150, USA.

Microsoft, 1997, Excel spreadsheet software, v. Office 97: Microsoft Corporation,

1 Microsoft Way, Redman, WA 98052.
GN-7

Schuenemeyer, J. H. and Power H., in press, Uncertainty estimation for resource

assessment—An application to coal: Mathematical Geology.

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.
Deadman study limit

Greater Green River Basin 

(part)

Faults

0 2 4 6 8

0 2 4 Miles

Kilometers

108 45'

41 37'30''

41 30'

108 37'30''

o

o o

o

Figure GN-1. 7.5-minute quadrangle maps in the Black Butte area of the 

Point of Rocks-Black Butte coalfield.

1 2

3 4

5 6 7

1 Bitter Creek NW

2 Bitter Creek NE

3 Black Buttes

4 Bitter Creek

5 Cooper Ridge NE

6 Sand Butte Rim NW

7 Antelope Flats

 7.5-minute quadrangle maps
Deadman study limit

Greater Green River Basin 

(part)

108 52'30''

41 52'30''

41 45'

108 45'

o

o o

o

108 37'30'' o

41 37'30'' o

0 2 4 Miles

0 2 4 6 8 Kilometers

Faults

Figure GN-2. 7.5-minute quadrangle maps in the Jim Bridger area of the 

Point of Rocks-Black Butte coalfield.

1 Black Rock South

2 Tenmile Rim

3 Twelvemile Well

4 Bitter Creek NW

5 Bitter Creek NE

7.5-minute quadrangle maps

1 2 3

4 5
Figure GN-3. Federal coal and surface ownership in the Black Butte area of 

the Point of Rocks-Black Butte coalfield.

0 2 4 6 8

0 2 4 Miles

Kilometers

Greater Green River Basin (part)

Deadman study limit

108 45'

41 37'30''

41 30'

108 37'30''

o

o o

o

Federal coal= Subsurface Federal 

management of all minerals, 

coal only, or oil, gas, and coal

Federal surface = Federal surface

ownership

Federal coal and surface

Federal coal, but no Federal surface

No Federal coal or surface

Faults
0 2 4 Miles

0 2 4 6 8 Kilometers

Federal coal = Subsurface Federal 

management of all minerals, 

coal only, or oil, gas, and coal

Federal surface = Federal surface

ownership

Figure GN-4. Federal coal and surface ownership in the Jim Bridger area of 

the Point of Rocks-Black Butte coalfield.

108 52'30''

41 52'30''

41 45'

108 45'

o

o o

o

108 37'30'' o

41 37'30'' o

Faults

Greater Green River Basin (part)

Deadman study limit

Federal coal and surface

Federal coal, but no Federal surface

No Federal coal or surface
Faults

0

2.5

5

10

20

30

Net coal 

thickness 

(ft)

Figure GN-5. Deadman net coal isopach map in the Black Butte area of the 

Point of Rocks-Black Butte coalfield.

0 2 4 6 8

0 2 4 Miles

Kilometers

Greater Green 

River Basin (part)

Deadman study 

limit

108 45'

41 37'30''

41 30'

108 37'30''

o

o o

o
Net coal 

thickness 

(ft)

Miles

Kilometers

0

6

2

0 4 8 10

6

2

4

41 52'30"

41 45'

41 37'30"

108 52'30" 108 45' 108 37'30"

0

Figure GN-6. Deadman net coal isopach map in the Jim Bridger area of the 

Point of Rocks-Black Butte coalfield.

2.5

5

10

20

30

Greater Green River Basin (part)

Deadman study limit

Faults

o o o

o

o

o
Greater Green River Basin 

(part)

Deadman study limit

Faults

0

100

200

300

400

500

Overburden 

thickness 

(ft)

Figure GN-7. Deadman overburden isopach map in the Black Butte area of 

the Point of Rocks-Black Butte coalfield.

0 2 4 6 8

0 2 4 Miles

Kilometers

600

700

800

900

1000

1100

108 45' 108 37'30'' o o

41 37' 30''

41 30'

o

o
Overburden 

thickness 

(ft)

0

100

200

300

400

500

Miles

Kilometers

0

6

2

0 4 8 10

6

2

4

41 52'30"

41 45'

41 37'30"

108 52'30" 108 45' 108 37'30"

Figure GN-8. Deadman overburden isopach map in the Jim Bridger area of 

the Point of Rocks-Black Butte coalfield.

Greater Green River Basin (part)

Deadman study limit

Faults

o

o

o

o

o

o
Figure GN-9. Mine and resource areas in the Black Butte area of the Point 

of Rocks-Black Butte coalfield.

0 2 4 6

2 4 Miles

Kilometers

0

108 45'

41 37'30''

41 30'

108 37'30''

o

o o

o

Black Butte mine area

Deadman study limit

Index map showing area

included in resource calculations

(does not include areas of mines,

 or net coal < 2.5 ft thick)

Faults

Resource area

Greater Green River Basin (part)
Figure GN-10. Mine and resource areas in the Jim Bridger area of the Point 

of Rocks-Black Butte coalfield.

108 52'30''

41 52'30''

41 45'

108 45'

o

o o

o

108 37'30'' o

41 37'30'' o

0 2 4 Miles

0 2 4 6 8 Kilometers

Faults

Index map showing area

included in resource calculations

Jim Bridger mine area

Deadman study limit

(does not include areas of mines,

 or net coal < 2.5 ft thick)

Resource area

Greater Green River Basin (part)
Table GN-1. Coal resources of the Deadman coal zone in the Point of Rocks-Black Butte coalfield, Greater Green

River Basin, reported by overburden (figs. GN-7 and GN-8), net coal thickness (figs. GN-5 and GN-6), and

reliability categories. Coal resources are reported in millions of short tons (MST) with two significant figures.

Zeros (0) indicate areas where no resources were calculated. The table does not include coal resources for coal less

than 2.5 ft thick or coal in mine areas (figs. GN-9 and GN-10). Resource numbers will not sum to match totals due

to independent rounding

Overburden Net coal Reliability categories (distance from control point) Total

thickness thickness Measured

(<1/4 mi)

Indicated

(1/4-3/4 mi)

Inferred

(3/4-3 mi)

(MST)

0-100 ft 2.5-5 ft 0.015 0.44 2.8 3.2

5-10 ft 0.36 0.54 0.38 1.3

10-20 ft 5.4 12 58 75

20-30 ft 11 2.3 11 24

30-40 ft 0.39 0.81 0 1.2

0-100 ft total 17 16 72 110

100-200 ft 2.5-5 ft 0 0 1.5 1.5

5-10 ft 0.32 2.4 1.3 4.1

10-20 ft 2.4 1.1 49 52

20-30 ft 25 25 6.2 56

30-40 ft 0.54 0.56 0 1.1

100-200 ft total 28 30 58 120

200-300 ft 2.5-5 ft 0 0 0.18 0.18

5-10 ft 0.29 1.2 3.4 4.9

10-20 ft 2.9 4.2 16 23

20-30 ft 18 75 150 250

30-40 ft 3.1 9.5 0 13

200-300 ft total 25 90 170 290
Overburden Net coal Reliability categories (distance from control point) Total

thickness thickness Measured

(<1/4 mi)

Indicated

(1/4-3/4 mi)

Inferred

(3/4-3 mi)

(MST)

300-400 ft 2.5-5 ft 0 0 0.082 0.082

5-10 ft 0.37 1.5 4.5 6.4

10-20 ft 5.5 13 18 36

20-30 ft 11 93 360 470

30-40 ft 2.5 9.5 0 12

300-400 ft total 20 120 380 520

400-500 ft 5-10 ft 0 0.15 5.6 5.7

10-20 ft 0.3 13 8.4 22

20-30 ft 0.76 32 310 340

30-40 ft 0 3.8 0.66 4.4

400-500 ft total 1.1 49 320 370

500-1,000 ft 5-10 ft 0 0 8.4 8.4

10-20 ft 1.3 6.4 140 140

20-30 ft 0.59 12 850 870

30-40 ft 0 0.37 11 12

500-1,000 ft total 1.8 19 1,000 1,000

1,000-1,500 ft 5-10 ft 0 0 0.024 0.024

10-20 ft 0 0 230 230

20-30 ft 0 0 14 14

1,000-1,500 ft total 0 0 240 240

Grand total (MST) 93 320 2,300 2,700

Table GN-1. Deadman coal resources—continued
Table GN-2. Coal resources of the Deadman coal zone in the Point of Rocks-Black Butte coalfield, Greater Green

River Basin, reported by Federal coal and Federal surface ownership (figs. GN-3 and GN-4) in the Jim Bridger and

Black Butte study areas. The table does not include coal resources for areas containing coal less than 2.5 ft thick, or

coal in mine or lease areas (figs. GN-9 and GN-10). Coal resources are reported in millions of short tons (MST)

with two significant figures. Resource numbers will not sum to match totals due to independent rounding

Study area Federal ownership Total (MST)

Black Butte No Federal coal or surface ownership 440

No Federal coal, but Federal surface ownership 45

Federal coal and surface ownership 480

Black Butte total 960

Jim Bridger No Federal coal or surface ownership 880

No Federal coal, but Federal surface ownership 65

Federal coal and surface ownership 760

Jim Bridger total 1,700

Grand total (MST) 2,700
Table GN-3. Coal resources of the Deadman coal zone in the Point of Rocks-Black Butte coalfield, Greater Green

River Basin, reported by 7.5-minute quadrangle (figs. GN-1 and GN-2) in the Jim Bridger and Black Butte study

areas. Coal resources are reported in millions of short tons (MST) with two significant figures. The table does not

include coal resources for areas containing coal less than 2.5 ft thick or in mine or lease areas (figs. GN-9 and GN10). Resource numbers will not sum to match totals due to independent rounding

Study area 7.5-minute quadrangle Total (MST)

Black Butte ANTELOPE FLATS 2.6

BITTER CREEK 450

BITTER CREEK NE 120

BITTER CREEK NW 25

BLACK BUTTES 94

COOPER RIDGE NE 10

SAND BUTTE RIM NW 250

Black Butte total 960

Jim Bridger BITTER CREEK NE 480

BITTER CREEK NW 210

BLACK ROCK SOUTH 420

TENMILE RIM 570

TWELVEMILE WELL 32

Jim Bridger total 1,700

Grand total (MST) 2,700
Table GN-4. Data used for computation of confidence intervals within reliability categories for Deadman coal

resources in the Point of Rocks-Black Butte coalfield, Greater Green River Basin, Wyoming. Volume refers to the

calculated resource in millions of short tons (MST). NA, not applicable

Parameter Reliability category Entire

Measured Indicated Inferred area

Area (in square meters) 9,717,109 34,140,292 243,970,445 287,827,847

Percent of area 3 12 85 100

Acres (area x 0.0002471) 2,401 8,436 60,286 71,124

SD (standard deviation (in ft) derived directly from the

data)

6.317 6.317 6.317 NA

Acre feet (acres x SD) 15,169 53,294 380,842 NA

Volume standard deviation (MST) 6 35 369 410

Pseudo n 19 7 3 NA

Table GN-5. Estimates of uncertainty (calculated with measurement error) for Deadman coal resources in the Point

of Rocks-Black Butte coalfield, Greater Green River Basin, Wyoming. To show detail, resources calculations are

reported in millions of short tons (MST) with four significant figures

Parameter Reliability category Entire

Measured Indicated Inferred area

Total calculated resource (MST) 92.74 320.5 2,258 2,671

Lower 90% confidence limit (MST) 83.00 264.0 1,651 1,997

Upper 90% confidence limit (MST) 103.0 377.0 2,866 3,346