Chapter GF

FRAMEWORK GEOLOGY OF FORT UNION COAL IN

THE EASTERN ROCK SPRINGS UPLIFT,

GREATER GREEN RIVER BASIN, WYOMING

By R.M. Flores,1 A.M. Ochs,2 and L.R. Bader1

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

1

U.S. Geological Survey

2

Consultant, U.S. Geological Survey, Denver, Colorado
GF-ii

Contents

Structural Setting..................................................................................................................GF-1

Stratigraphic Setting............................................................................................................GF-1

Depositional Setting............................................................................................................GF-2

Coal Quality..........................................................................................................................GF-2

Stratigraphy and Depositional Environments of Coal-Assessment Units.............GF-2

Stratigraphy.....................................................................................................................GF-2

Depositional Environments.........................................................................................GF-3

Distribution of the Deadman and A-C coal zones in the

Point of Rocks-Black Butte coalfield..............................................................................GF-4

Stratigraphic Framework ...................................................................................................GF-5

Deadman Coal Zone Interpretive Cross Section A–A’........................................GF-6

A-C Coal Zone Interpretive Cross Section B–B’...................................................GF-7

Deadman Coal Zone Interpretive Cross Section C–C’.........................................GF-7

Deadman Coal Zone Interpretive Cross Section D–D’........................................GF-8

Deadman Coal Zone Interpretive Cross Section E–E’.........................................GF-8

Deadman Coal Zone Interpretive Cross Section F–F...........................................GF-9

A–C Coal Zone Interpretive Cross Section G–G’..............................................GF-10

A–C Coal Zone Interpretive Cross Section H–H’..............................................GF-10

A–C Coal Zone Interpretive Cross Section I–I’..................................................GF-10

A–C Coal Zone Interpretive Cross Section J–J’.................................................GF-11

A–C Coal Zone Interpretive Cross Section K–K’..............................................GF-11

References..........................................................................................................................GF-13
GF-iii

Figures

GF-1. Location map showing the Greater Green River Basin.

GF-2. Composite stratigraphic section for the assessment region showing the

studied coal beds and zones with age relationships based on palynology.

GF-3. Composite correlation of Paleocene sections based on palynostratigraphy.

GF-4. Stacked sandstones bounded by silty sandstone, siltstone, and mudstone

above the Deadman coal zone in the Jim Bridger mine.

GF-5. Fining-upward sandstone bounded by silty sandstone, siltstone, and

mudstone above the Deadman coal zone in the Jim Bridger mine.

GF-6. Fining-upward, stacked sandstone thinning from right to the left of the

picture into thin-bedded, silty sandstone, siltstone, and mudstone above the

Deadman coal zone in the Jim Bridger mine.

GF-7. A stack of fining-upward sandstone overlain by silty sandstone, siltstone,

and mudstone above the A-C coal zone in the Black Butte mine.

GF-8. Thick- to thin-bedded sandstone, siltstone, and mudstone above the A-C coal

zone in the Black Butte mine.

GF-9. Index map showing cross section locations in the Point of Rocks-Black

Butte coalfield.

GF-10. Deadman coal zone interpretive cross section A-A’.

GF-11. Peat swamps on abandoned fluvial channel deposits of the Santee River,

South Carolina.

GF-12. A-C coal zone interpretive cross section B-B’.

GF-13. Deadman coal zone interpretive cross section C-C’.

GF-14. Deadman coal zone interpretive cross section D-D’.

GF-15. Crevasse splays, floodplains, lakes, and swamps of the anastomosed

Columbia River in the Province of British Columbia, Canada.
GF-iv

GF-16. Deadman coal zone interpretive cross section E-E’.

GF-17. Deadman coal zone interpretive cross section F-F’.

GF-18. A crevasse splay draining into a floodplain lake and associated swamps of

the Saskatchewan River in the Saskatchewan Province, Canada.

GF-19. A-C coal zone interpretive cross section G-G’.

GF-20. A-C coal zone interpretive cross section H-H’.

GF-21. A-C coal zone interpretive cross section I-I’.

GF-22. A-C coal zone interpretive cross section J-J’.

GF-23. A-C coal zone interpretive cross section K-K’.
GF-1

STRUCTURAL SETTING

• The Greater Green River Basin of southwestern Wyoming consists of the Green

River Basin, Great Divide Basin, and Washakie Basin (fig. GF-1).

• The Green River Basin is separated from the Great Divide and Washakie Basins

by the Rock Springs uplift.

• The Rock Springs uplift is a doubly plunging, north-south trending,

asymmetrical anticline.

• The Fort Union Formation (Paleocene) is present at the surface along the flanks

of the Rock Springs uplift. Associated beds dip 5-15 degrees on the flanks of the

uplift to the subsurface in the center of the basins.

• Fort Union rocks in the Greater Green River Basin are present over a 26,000

square-mile area; they are more than 3,000 ft thick in the subsurface. Fort Union

outcrops are present along the margin of the basin. The Fort Union Formation is

overlain by rocks of the Wasatch Formation (Eocene) in the central part of the basin.

• Assessment coal units in the Fort Union Formation were investigated along the

east flank of the Rock Springs uplift, where there is active mining. The mines

produced about 1 percent of the total 1997 U.S. coal production (Resource Data

International, Inc., 1997).

STRATIGRAPHIC SETTING

• The Fort Union Formation may be divided into lower coal-bearing, middle

sandstone-dominated, and upper coal-bearing parts.

• The middle sandstone-dominated part is as much as 800 ft thick and contains no

coal beds.
GF-2

• Coal beds are as much as 33 ft thick in the lower and upper parts of the Fort

Union Formation.

• Proprietary and non-proprietary data from 4,090 drill holes were used for 

stratigraphic correlation of the coal resource assessment units.

DEPOSITIONAL SETTING

• Depositional environments in the Fort Union Formation are exclusively fluvial

settings (Maywood, 1987; Honey and Hettinger, 1989; Hettinger and Kirschbaum,

1991; Hettinger and others, 1991).

• Coal accumulated in peat swamps on fluvial floodplains and in abandoned fluvial

channels (Maywood, 1987).

COAL QUALITY

• Coal rank is mainly subbituminous B to C (Glass, 1976).

• Coal quality reflects low to intermediate sulfur content and low to high ash

content.

• Concentrations of selected trace-elements of environmental concern are low.

STRATIGRAPHY AND DEPOSITIONAL ENVIRONMENTS

OF COAL-ASSESSMENT UNITS

STRATIGRAPHY

• The Fort Union Formation is composed primarily of sandstone, siltstone, and
GF-3

mudstone and secondarily of limestone, carbonaceous shale, and coal. The

formation contains 60 percent sandstone, 11 percent siltstone, 17 percent mudstone,

9 percent coal, and 3 percent limestone and carbonaceous shale (Maywood, 1987).

• The assessment coal zones include the Deadman coal zone (fig. GF-2) consisting

of the D1, D2, D3, D4, and D5 coal seams in the Jim Bridger mine. The Deadman

coal zone is laterally equivalent to the A, B, and C coal beds or the A-C coal zone in

the Black Butte mine (Maywood, 1987). In this study, these coal zones are

recognized as the Deadman coal zone.

• The Deadman coal zone is in the lower part of the Fort Union Formation.

Biostratigraphic zonation of the formation includes Zones P1-P6 (fig. GF-3).

DEPOSITIONAL ENVIRONMENTS

• Deadman coal accumulated in peat swamps within fluvial environments

(Maywood, 1987). The Deadman coal zone is interbedded with fining-upward,

stacked fluvial-channel sandstone bodies bounded by crevasse-splay and floodplain

mudstone, siltstone, and silty sandstone (fig. GF-4). The fluvial channel sandstone

bodies thin toward their margins and are intercalated with lateral accretion units

composed of siltstone and mudstone typical of deposits in meandering rivers (fig.

GF-5). The margins of the fluvial channel sandstone bodies grade into the crevassesplay deposits, which are locally eroded and infilled by siltstone and silty sandstone

(fig. GF-6).

• Coal beds A-C were also deposited in peat swamps within fluvial environments.

The A-C coal zone is interbedded with fining-upward, erosional-based, fluvial

channel sandstone that grades upward into thick- to thin-bedded silty sandstone,

siltstone and mudstone, which represent overbank deposits (fig. GF-7). The
GF-4

overbank deposits grade laterally (upper right of photo) into erosional-based

sandstone deposits that are laterally offset. This offset pattern of fluvial channel

sandstone beds indicates deposition in meandering rivers. The fluvial channel

sandstone grades laterally into thin- to thick-bedded silty sandstone, siltstone, and

mudstone, which were deposited in floodplain/crevasse-splay environments (fig.

GF-8).

• Fluvial environments developed in an eastward-flowing fluvial system

(Maywood, 1987).

DISTRIBUTION OF THE DEADMAN AND A-C COAL ZONES

IN THE POINT OF ROCKS-BLACK BUTTE COALFIELD

• The Point of Rocks-Black Butte coalfield (fig. GF-9) boundary approximately

follows the outcrop extent of the Fort Union Formation and includes past and

current mines that produced from the Deadman coal zone (Morgenson, 1959;

Maywood, 1987). The coalfield is bounded on the west by the line of contact

between the Lance Formation (Cretaceous) and the Fort Union Formation

(Paleocene). It is bounded on the east by an arbitrary line a few miles from the line

of contact between the Fort Union Formation and Wasatch Formation (Eocene); the

position of that line is based on the distribution of control points.

• The Deadman coal zone in the Jim Bridger mine, which is laterally equivalent to

the A-C coal zone in the Black Butte mine, is in the lower part of the Fort Union

Formation (Madden, 1989; Hettinger and Kirschbaum, 1991).

• These coal zones also occur in the subsurface of Sweetwater County, Wyoming,

in the east-northeast flank of the Rock Springs uplift, and the northern part of

Washakie Basin, and southern part of the Great Divide Basin (Honey and Hettinger,

1989; Hettinger and Kirschbaum, 1991; Hettinger and others, 1991). These authors
GF-5

identified thick, laterally extensive coal beds of the Deadman coal zone in these

basins.

• Surface occurrence of the coal zones is primarily along the east flank of the Rock

Springs uplift (Roehler, 1977; Madden, 1989).

• Minable coal of the Deadman and A-C coal zones is present in the Point of

Rocks-Black Butte coalfield, which includes the Jim Bridger and Black Butte coal

mines (fig. GF-9).

STRATIGRAPHIC FRAMEWORK

• The Deadman and A-C coal zones are interbedded with mudstone, limestone,

carbonaceous shale, siltstone, and sandstone (Maywood, 1987). These clastic rocks

are undifferentiated in our database. However, we utilized Maywood’s interpretation

of the depositional environments.

• Coal seams in the Deadman coal zone are within a 125-ft-thick interval, and beds

of the A-C coal zone are within a 50-ft-thick interval. The thicker interval is

expanded by a sandstone body as much as 40 ft thick interpreted by Maywood

(1987) as a fluvial channel deposit.

• Laterally, the coal beds of these zones merge and split. Coal beds coalesce from

two or more seams to form a single, thick bed. The coal may split into two or more

beds that gradually thin, pinch out, or interfinger with other clastic rocks (Maywood,

1987). Split coal seams may rejoin to form a merged seam and may re-split again

throughout the extent of the coal zones.

• Vertically, the Deadman coal zone may consist of as many as five coal seams, as

a result of splitting, or as few as one coal seam as a result of merging.

• Vertically, the A-C coal zone may consist of as many as three beds, as a result of
GF-6

splitting, or as few as two beds as a result of merging.

• Merged coal seams or beds are interbedded mainly with mudstone and

carbonaceous shale partings.

• Rocks above and below the Deadman coal zone consist of mudstone, siltstone,

and sandstone. These rocks accumulated in channels and floodplains in a fluvial

system.

• The Deadman coal seams accumulated in peat swamps on distal floodplains and

in abandoned fluvial channel deposits (Maywood, 1987).

DEADMAN COAL ZONE INTERPRETIVE CROSS SECTION A-A’

• This greater-than-15.5-mi-long, north (A) to south (A’) cross section (fig. GF10) shows the Deadman coal zone and associated rocks in the Jim Bridger mine.

Datum is the base of the merged seams D1-D3. The cross section was drawn using

data from 51 drill holes, which are not labeled on the cross section.

• Coal beds, 1-26 ft thick, are identified from bottom to top as D1 to D5.

• These coal beds merge and split in a north-south direction.

• Seams D1-D2 merge to form a single seam as much as 13 ft thick.

• Seams D1-D3 merge to form a single seam as much as 16.5 ft thick.

• Seams D1-D4 merge to form a single seam as much as 17 ft thick.

• Seams D1-D5 merge to form a single seam as much as 26 ft thick.

• Splitting of the Deadman seams is prevalent toward the south, and merging is

common toward the north.

• Merging and splitting of coal beds reflects accumulation in peat swamps formed

perpendicular to the eastward flow direction of the fluvial depositional system (fig.

GF-11).
GF-7

A-C COAL ZONE INTERPRETIVE CROSS SECTION B-B’

• This greater-than-17-mi-long, north (B) to south (B’) cross section (fig. GF-12)

shows the A-C coal zone and associated rocks in the Black Butte mine. Datum is the

base of the C coal bed. The cross section was drawn using data from 71 drill holes,

which are not labeled on the cross section.

• Coal beds (from less than 1 to 33 ft thick) of this coal zone are identified, from

bottom to top, as A, B, and C.

• The C coal bed (as much as 33 ft thick) splits northward into the C1 bed (as

much as 24 ft thick) and the C2 bed (as much as 4 ft thick).

• The interval between the A and C coal beds increases in thickness northward.

• Merging and splitting of the coal beds resulted from peat accumulation in

swamps formed perpendicular to the eastward flow direction of the fluvial

depositional system.

DEADMAN COAL ZONE INTERPRETIVE CROSS SECTION C-C’

• This greater-than-2.8-mi-long, west (C) to east (C’) cross section (fig. GF-13)

shows the Deadman coal zone and associated rocks in the northern part of the Jim

Bridger mine. Datum is the base of the merged D1-D4 seams. The cross section

was drawn using data from 12 drill holes, which are not labeled on the cross section.

• The Deadman coal zone includes in the lower part a merged D1-D4 coal seam,

which is as much as 15 ft thick.

• The Deadman coal zone includes in the upper part the D5 coal seam, which is as

much as 7 ft thick.
GF-8

• Merging and splitting are not observed because the coal seams were deposited in

peat swamps parallel to the eastward flow direction of the fluvial depositional

system.

DEADMAN COAL ZONE INTERPRETIVE CROSS SECTION D-D’

• This greater-than-2.6-mi-long, west (D) to east (D’) cross section (fig. GF-14)

shows the Deadman seams and associated rocks in the north-central part of the Jim

Bridger mine. Datum is the base of the merged D1-D3 seam. The cross section

was drawn using data from 15 drill holes, which are not labeled on the cross section.

• The Deadman coal zone includes in the lower part a merged D1-D3 coal seam,

which is as much as 12 ft thick.

• The Deadman coal zone includes in the upper part a merged D4-D5 coal seam,

which is as much as 17 ft thick.

• Splitting of the merged D4-D5 coal seam takes place toward the east. The

splitting may have resulted from crevasse-splay deposition into a peat swamp on the

floodplain (fig GF-15).

• The coal seams were deposited in peat swamps parallel to the eastward flow

direction of the fluvial depositional system.

DEADMAN COAL ZONE INTERPRETIVE CROSS SECTION E-E’

• This 2-mi-long, west (E) to east (E’) cross section (fig. GF-16) shows the

Deadman coal zone and associated rocks in the south-central part of the Jim Bridger

mine. Datum is the base of the merged D1-D2 seams. The cross section was drawn

using data from 13 drill holes, which are not labeled on the cross section.
GF-9

• The Deadman coal zone includes in the lower part a merged D1-D2 coal seam,

which is as much as 12 ft thick.

• The Deadman coal zone includes in the upper part the D4 and D5 coal seams,

which are as much as 7 ft and 5 ft thick, respectively.

• The merged D4-D5 coal seam splits toward the east. This splitting may have

resulted from crevasse-splay deposition into a peat swamp on the floodplain.

• The coal seams were deposited in peat swamps parallel to the eastward flow

direction of the fluvial depositional system.

DEADMAN COAL ZONE INTERPRETIVE CROSS SECTION F-F’

• This 1.8-mi-long, west (F) to east (F’) cross section (fig. GF-17) shows the

Deadman coal zone and associated rocks in the southern part of the Jim Bridger

mine. Datum is the base of the merged D1-D3 seams. The cross section was drawn

using data from 15 drill holes, which are not labeled on the cross section.

• The Deadman coal zone includes in the lower part a merged D1-D3 coal seam,

which is as much as 12 ft thick. This coal seam splits eastward into lower D1-D2

and upper D3 coal seams.

• The Deadman coal zone includes in the upper part the D4 and D5 coal seams,

which are as much as 8 ft and 5 ft thick, respectively.

• The merged D1-D3 coal seam splits toward the east and may have resulted from

crevasse-splay deposition into a peat swamp on the floodplain (fig. GF-18).

• The coal seams were deposited in peat swamps parallel to the eastward flow

direction of the fluvial depositional system.
GF-10

A-C COAL ZONE INTERPRETIVE CROSS SECTION G-G’

• This 0.37-mi-long, west (G) to east (G’) cross section (fig. GF-19) shows the

northern part of the Black Butte mine. Datum is the base of the merged C coal beds.

The cross section was drawn using data from 14 drill holes, which are not labeled

on the cross section.

• The C coal bed, which is the upper bed of the A-C coal zone, is as much as 33 ft

thick. It locally splits into lower and upper beds to the east, and merges into one bed

toward the west.

• Splitting of the coal bed was caused by local incursion of crevasse splays in the

peat swamps associated with the fluvial depositional system.

A-C COAL ZONE INTERPRETIVE CROSS SECTION H-H’

• This 1.09-mi-long, west (H) to east (H’) cross section (fig. GF-20) shows the C

coal bed and associated rocks in the northern part of the Black Butte mine. Datum is

the base of the merged C coal bed. The cross section was drawn using data from 20

drill holes, which are not labeled on the cross section.

• The C coal bed, which is the upper coal bed of the A-C coal zone, is as much as

30 ft thick and is a merged bed.

• The merged C coal bed suggests widespread accumulation of peat in swamps

associated with the fluvial depositional system.

A-C COAL ZONE INTERPRETIVE CROSS SECTION I-I’

• This 1.06-mi-long, west (I) to east (I’) cross section (fig. GF-21) shows the A-C
GF-11

coal zone and associated rocks in the southern part of the Black Butte mine. Datum

is the base of the C coal bed. The cross section was drawn using data from 16 drill

holes, which are not labeled on the cross section.

• The A-C coal zone, which is within a 90-ft-thick interval, consists of coal beds as

much as 10.8 ft thick.

• The uppermost thick coal bed is the C coal.

• Coal beds, which vary in thickness laterally and are found in a gradually

westward-merging interval, suggest accumulation in peat swamps on floodplains

associated with the fluvial depositional system.

A-C COAL ZONE INTERPRETIVE CROSS SECTION J-J’

• This 0.73-mi-long, west (J) to east (J’) cross section (fig. GF-22) shows the A-C

coal zone and associated rocks in the southern part of the Black Butte mine. Datum

is the base of the A coal bed. Coal beds are as much as 10.6 ft thick. The cross

section was drawn using data from 17 drill holes, which are not labeled on the cross

section.

• The lower coal bed is the A coal and the upper coal bed is the C coal.

• The occurrence of coal beds that retain uniform thickness across their west-east

extent suggests accumulation in peat swamps stacked on floodplains associated

with the fluvial depositional system.

A-C COAL ZONE INTERPRETIVE CROSS SECTION K-K’

• This 1.2-mi-long, west (K) to east (K’) cross section (fig. GF-23) shows the AC coal zone and associated rocks in the southern part of the Black Butte mine.
GF-12

Datum is the base of the C coal bed. The cross section was drawn using data from

12 drill holes, which are not labeled on the cross section.

• The A-C coal zone, which is a 33-ft-thick interval, consists of coal beds as much

as 14.3 ft thick. The lower coal bed locally splits, whereas the upper coal bed is

laterally uniform.

• The interval of the A-C coal zone from cross sections I-I’ to K-K’ shows a

merging trend to the south. Southward merging of the A-C coal zone suggests

accumulation in peat swamps on a stable part of the floodplain that was not

repeatedly flooded by sediments.

• Local splitting of the lower coal bed indicates intermittent flooding of sediments

into the peat swamp.
GF-13

REFERENCES

Glass, G.B., 1976, Review of Wyoming coal fields, 1976: Wyoming Geological

Survey, Public Information Circular 4, 91 p.

Hettinger, R.D., Honey, J.G., and Nichols, D.G., 1991, Chart showing correlations

of upper Cretaceous Fox Hills Sandstone and Lance Formation, and lower

Tertiary Fort Union, Wasatch, and Green River Formations, eastern flank of

the Washakie Basin to the southeastern part of the Great Divide Basin,

Wyoming: U.S. Geological Survey Miscellaneous Investigations Series Map

I-2151.

Hettinger, R.D., and Kirschbaum, M.A., 1991, Chart showing correlations of some

Upper Cretaceous and lower Tertiary rocks, from the east flank of the

Washakie Basin to the east flank of the Rock Springs uplift, Wyoming: U.S.

Geological Survey Miscellaneous Investigations Series Map I-2152.

Honey, J.D., and R.D. Hettinger, 1989, Cross sections showing correlations of

upper Cretaceous Fox Hills Sandstone and Lance Formation, and lower

Tertiary Fort Union and Wasatch Formations, southeastern Washakie Basin,

Wyoming, and eastern Sand Wash Basin, Colorado: U.S. Geological Survey

Miscellaneous Investigations Series Map I-1964.

Madden, D.H., 1989, Geological map and measured sections of the Bitter Creek

NW Quadrangle, Sweetwater County, Wyoming: U.S. Geological Survey

Coal Investigations Map C-121.

Maywood, P.S., 1987, Stratigraphic model of the southern portion of the Jim

Bridger coal field, Sweetwater County, Wyoming: Portland, Oregon,

Portland State University, M.S. thesis, 128 p.

Morgensen, P., 1959, Fort Union Formation, east flank of the Rock Springs uplift,
GF-14

Sweetwater County, Wyoming: Laramie, Wyoming, University of

Wyoming, M.A. thesis, 86 p.

Resource Data International, Inc., 1997, COALdat-Coal database, 1320 Pearl St.,

Suite 300, Boulder, Colorado 80302.

Roehler, H.W., 1977, Geologic Map of the Rock Springs uplift and adjacent areas,

Sweetwater County, Wyoming: U.S. Geological Survey Open-File Report

77-242.
Figure GF-1. Location map showing the Greater Green River Basin.

Green River

Basin Rock

Springs

Uplift

Greater Green River Basin

Great Divide

Basin

Washakie

Basin

IDAHO

WYOMING UTAH

COLORADO

10 0 10 20 Miles

N

Sweetwater County
Paleocene

late

(Zones

P5-P6)

middle

(Zones

P3-P4)

early

(Zones

P1-P2)

Wyodak-Anderson

Beulah-Zap 

Hagel 

Harmon

Hansen

Knobloch

Rosebud

Deadman Seams 1-5

}

}

..................Powder River Basin

......................................Williston Basin

...............................................Williston Basin

...............................Powder River Basin

.........................................Williston Basin

....................Greater Green

River Basin

Hanna nos. 77-79, 81

Ferris nos. 23, 

25, 31, 50, & 65 }.................................Hanna Basin

...........................Hanna Basin

Johnson-107 ........................................Carbon Basin

Figure GF-2. Composite stratigraphic section for the assessment region showing

the studied coal beds and zones with age relationships based on palynology.

Assessment units in the Greater Green River Basin are highlighted in red.
500 Meters

Greater

Green River

Basin

Hanna and

Carbon Basins Powder River

Basin

Williston

Basin

Zones: P1 P2 P3

P4 P5 P6

Figure GF-3. Composite correlation of Paleocene sections based on palynostratigraphy. 
Figure GF-4. Stacked sandstone bounded by silty sandstone, siltstone, and mudstone above the Deadman coal zone in the Jim 

Bridger mine. Photograph by R.M. Flores. 
Figure GF-5. Fining-upward sandstone bounded by silty sandstone, siltstone, and mudstone above the Deadman coal zone in the 

Jim Bridger mine. Photograph by R.M. Flores.
Figure GF-6. Fining-upward, stacked sandstone thinning from right to the left of the picture into thin-bedded silty 

sandstone, siltstone, and mudstone above the Deadman coal zone in the Jim Bridger mine. Photograph by R.M. Flores.
Figure GF-7. A stack of fining-upward sandstone overlain by silty sandstone, siltstone, and mudstone above the 

A-C coal zone in the Black Butte mine. Photograph by R.M. Flores. 
Figure GF-8. Thick-to thin-bedded sandstone, siltstone, and mudstone above the A-C coal zone in the Black 

Butte mine. photograph bt R.M. Flores.
Fort Union

Formation

Wasatch

Formation

Cretaceous rocks

(undifferentiated)

D

E

F

G

D'

H H'

E'

I I'

F'

J

K

J'

K'

G'

A'

B

B'

Jim Bridger

mine

Black Butte

mine

Colorado

Wyoming

Greater

Green River

Basin

41°30'

41°45'

GF-9. Index map showing cross

n locations in the Point of Rocks

Butte coalfield. A A'

Point of Rocks-Black Butte coalfield

Cross section with proprietary

drill holes

MAP

AREA
F - F'

15.53 miles

Jim Bridger mine

"Rock"

Clinker

Coal

Part clinker

North

A 

C - C' D - D'

0

100 Feet

D1-D4

D1-D5

D5

D1-D3

D4-D5

D3 D4

D5

D1-D2

E - E'

Figure GF-10. Deadman coal zone interpretive cross section A-A'.

Datum = Base of

 D1-D3 seam

The term "rock" indicates undifferentiated

sandstone, siltstone, mudstone, and limestone.
Figure GF-11. Peat swamps on abandoned fluvial channel deposits of the Santee River, South Carolina. 

Photograph by C. Connor.
17.01 miles

"Rock" Coal

A-C coal zone

A coal bed

C coal bed

B coal bed

North

B

0

100 Feet

G - G'

H - H'

Figure GF-12. A-C coal zone interpretive cross section B-B'.

I - I'

J - J'

Datum = Base of the C coal bed

Black Butte mine

C coal bed

The term "rock" indicates undifferentiated

sandstone, siltstone, mudstone, and limestone.
"Rock" Coal

C C

D1-D4

unnamed

coal beds

D5 Deadman

Jim Bridger mine

}coal zone

}

0

100 Feet

A-A'

Figure GF-13. Deadman coal zone interpretive cross section C-C'.

Datum = Base of

 D1-D4 seam

The term "rock" indicates undifferentiated

sandstone, siltstone, mudstone, and limestone.
"Rock"

Clinker

Coal

Part clinker

2.67 miles

West

D D'

East

D1-D3

D5

D4 Deadman }coal zone

0

100 Feet

Figure GF-14. Deadman coal zone interpretive cross section D-D'. A-A'

Datum = Base of D1-D3 seam Jim Bridger mine

The term "rock" indicates undifferentiated

sandstone, siltstone, mudstone, and limestone.
Figure GF-15. Crevasse splays, floodplains, lakes, and swamps of the anastomosed Columbia River in the Province of 

British Columbia, Canada. Photograph by D. Smith.
2.0 miles

West

E E'

East

D1-D2

D4-D5

D3

Deadman }coal zone

0

100 Feet

"Rock"

Clinker

Coal

Part clinker

A-A'

Figure GF-16. Deadman coal zone interpretive cross section E-E'.

Datum = Base of D1-D2 seam

Jim Bridger mine

The term "rock" indicates undifferentiated

sandstone, siltstone, mudstone, and limestone.
"Rock"

Clinker

Coal

Part clinker

F F'

Deadman }coal zone

0

100 Feet

D1-D2

D1-D3

D3

D4

D5

A-A'

Figure GF-17. Deadman coal zone interpretive cross section F-F'.

Datum = Base of D1-

 D3 seam

Jim Bridger mine

The term "rock" indicates undifferentiated

sandstone, siltstone, mudstone, and limestone.
GF-18. A crevasse splay draining into a floodplain lake and associated swamps of the Saskatchewan River in the 

Saskatchewan Province, Canada. Photograph by N. Smith.
"Rock" Coal

0.37 miles

West

G G'

East

C

coal

beds }

0

00 Feet

B-B'

Figure GF-19. A-C coal zone interpretive cross section G-G'.

Black Butte mine Datum = Base of C coal beds

The term "rock" indicates undifferentiated

sandstone, siltstone, mudstone, and limestone.
"Rock" Coal

H H'

C

coal

bed }

0

0 Feet

B-B'

Figure GF-20. A-C coal zone interpretive cross section H-H'.

Datum = Base of C coal bed Black Butte mine

The term "rock" indicates undifferentiated

sandstone, siltstone, mudstone, and limestone.
"Rock" Coal

1.06 miles

West

I I'

East

A-C

coal }zone

0

00 Feet

? ? ?

B-B'

Figure GF-21. A-C coal zone interpretive cross section I-I'.

Datum = Base of C coal bed

Black Butte mine

coal bed

al bed

The term "rock" indicates undifferentiated

sandstone, siltstone, mudstone, and limestone.
"Rock" Coal

0.73 miles

West

J J'

East

A-C

coal }zone

0

100 Feet

B-B'

Figure GF-22. A-C coal zone interpretive cross section J-J'.

Datum = Base of A coal bed

C coal bed

A coal bed

Black Butte mine

B coal bed

The term "rock" indicates undifferentiated

sandstone, siltstone, mudstone, and limestone.
"Rock" Coal

K K

A-C

coal }zone

0

00 Feet

B-B'

Figure GF-23. A-C coal zone interpretive cross section K-K'.

Datum = Base of C coal bed

oal bed

al bed

al bed

Black Butte mine

The term "rock" indicates undifferentiated

sandstone, siltstone, mudstone, and limestone.