Chapter SN

A SUMMARY OF COAL IN THE COALMONT

FORMATION (TERTIARY),

NORTH PARK BASIN, COLORADO

By S. B. Roberts and G. S. Rossi

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

Contents

Introduction...........................................................................................................................SN-1

Coal Geologic Framework................................................................................................SN-3

Coal Beds and Coal Zones................................................................................................SN-5

McCallum Anticline District.......................................................................................SN-5

Sudduth coal bed......................................................................................................SN-5

Hoyle coal bed..........................................................................................................SN-6

Capron coal zone......................................................................................................SN-6

Winscom coal zone.................................................................................................SN-6

Hill coal bed..............................................................................................................SN-7

Coalmont District...........................................................................................................SN-7

Pole Mountain-Mexican Creek coal zone...........................................................SN-7

Riach coal bed...........................................................................................................SN-8

Coal Production....................................................................................................................SN-8

Coal Quality.......................................................................................................................SN-10

References Cited................................................................................................................SN-12

Figures

SN-1. Map showing North Park Basin and associated coal basins in the Northern

Rocky Mountains and Great Plains region.

SN-2. Generalized geologic map of North Park Basin and vicinity, Colorado.

SN-3. Generalized chart showing Upper Cretaceous (part) and Tertiary stratigraphic

nomenclature, North Park Basin, Colorado.

SN-4. Map showing the location of abandoned underground and surface coal mines,

North Park Basin, Colorado.
SN-iii

Figures—Continued

SN-5. Chart showing stratigraphic nomenclature for Paleocene-Eocene deposits in

the Coalmont Formation, North Park Basin, Colorado.

SN-6. Diagrammatic cross section showing the distribution of alluvial and lacustrine

successions, and the stratigraphic position of coal beds or zones, Coalmont

Formation, North Park Basin, Colorado.
SN-1

INTRODUCTION

North Park Basin is an intermontane structural basin occupying an area of about

2,250 mi2in north-central Colorado (fig. SN-1). The basin is bounded on the east

and west by the Front and Park Ranges, respectively, and on the north by

Independence Mountain (fig. SN-2). The southern margin of the basin is delimited

by volcanic rocks of the Rabbit Ears Range, which separate the North and Middle

Park topographic basins. North Park Basin is the northern end of the larger NorthMiddle Park structural basin (Tweto, 1975; Wellborn, 1977), which formed after

uplift and erosion of the Front and Park Ranges in latest Cretaceous or earliest

Tertiary time (Tweto, 1975; Maughan, 1989). As a result of the erosion, lower

Tertiary rocks in the structural basin unconformably overlie deposits ranging in age

from Late Cretaceous to Precambrian (Tweto, 1975).

Sedimentary rocks in North Park Basin are Permian to Quaternary in age, and the

maximum cumulative thickness of pre-Quaternary units is about 17,000 ft (Hail,

1965); the oldest Tertiary rocks are included in the Paleocene-Eocene Coalmont

Formation (Beekly, 1915; Hail and Leopold, 1960). The Coalmont Formation

unconformably overlies Upper Cretaceous marine deposits of the Pierre Shale

throughout most of the basin. In the central part of North Park Basin, the formation

is unconformably overlain by post-Laramide alluvial strata of the White River

(Oligocene) and North Park (Miocene-Pliocene) Formations (Hail, 1965) (fig. SN3). The Coalmont Formation is composed of conglomerate, sandstone, siltstone,

shale, carbonaceous shale and coal beds. Two of the coal beds (the Sudduth and

Riach coal beds) locally exceed 50 ft in thickness. Because of erosion prior to

deposition of the White River and North Park Formations, the original thickness of

the Coalmont Formation cannot be determined. Tweto (1975) suggested that the
SN-2

preserved thickness of the formation may approach 11,000 ft; Hail (1968) estimated

a possible aggregate thickness of about 12,000 ft .

This report presents a brief summary of the coal geology, coal quality, and

production history of Tertiary coal deposits in the Coalmont Formation in North

Park Basin. Significant coal deposits are present in areas surrounding the small

community of Coalmont in the southwestern part of the basin, and in areas near the

North and South McCallum anticlines, east of the town of Walden (Beekly, 1915)

(fig. SN-4). In the Coalmont area, historic production focused on the Riach coal bed,

although small wagon mines were developed on local, unnamed coal beds (Beekly,

1915). Erdmann (1941) estimated original coal reserves in parts of T. 7 N, Rs. 80

and 81 W., in the Coalmont district to be on the order of 177,450,000 tons. Historic

production in the McCallum anticline district primarily targeted the Sudduth coal bed

and Beekly (1915) estimated that the total Sudduth coal resources in a 60 mi2

 area

adjacent to the south McCallum anticline were on the order of 2,073,600,000 short

tons, with about 1,152,000,000 tons of that total considered as recoverable under

prevailing mining conditions at that time.

Within the framework of the National Coal Resource Assessment (NCRA) project

of the U.S. Geological Survey, Coalmont Formation coal is considered as “low

priority” in terms of its viability as a significant production target in the near future.

This low prioritization is not intended to preclude all possibility of future coal

production within the basin. However, in the context of the NCRA project the

concept of “low priority” suggests a degree of skepticism with regard to any largescale upswing or significant rejuvenation of coal mining in the area during the next

couple of decades.
SN-3

COAL GEOLOGIC FRAMEWORK

Hail (1968) subdivided the Coalmont Formation in southwestern North Park basin

into the following three members (ascending order): the Middle Park Member,

middle member, and upper member (fig. SN-5). The Middle Park Member and the

middle member are Paleocene in age, whereas the upper member is considered to be

Eocene in age (Hail and Leopold, 1960). The Middle Park Member consists of

conglomerate, conglomeratic and arkosic sandstone, sandy claystone, and rare

carbonaceous shale and coal beds; this member is only present in the extreme

southwest area of the basin. The overlying middle member consists primarily of

arkosic and conglomeratic sandstone interbedded with sandy claystone,

carbonaceous shale, and thin coal beds. In much of the area surrounding Coalmont

and to the south, the middle member is in unconformable contact with the

underlying Cretaceous Pierre Shale. In outcrops north of Coalmont and in drill holes

to the east, Hail (1968) recognized three units in the middle member (fig. SN-5): a

lower unit (as much as 1,130 ft thick) composed of interbedded conglomerate,

sandstone, and sandy mudstone beds; a middle unit (about 630 ft thick) of gray to

brownish-gray silty shale; and an upper unit (as thick as 435 ft) of interbedded

conglomerate, conglomeratic sandstone, and olive-green, brown, or gray mudstone

beds. The thickness of these individual units is highly variable throughout the

Coalmont area. The upper member of the Coalmont Formation is characterized by

interbedded sandstone, mudstone, carbonaceous shale, and locally thick coal beds;

conglomerate is rare. The lower part of the upper member primarily consists of

carbonaceous shale that varies in thickness from 775 ft just southwest of Coalmont

to as much as 1,000 ft in exposures along Chedsey Creek, north of Coalmont (Hail,

1968). Overlying the carbonaceous shale is an 800-ft-thick interval of interbedded

micaceous sandstone, shale, carbonaceous shale, and coal; the Riach coal bed, as
SN-4

well as coal included in the Pole Mountain-Mexican Creek coal zone are within this

interval. The uppermost part of the upper member includes beds of arkosic

sandstone, mudstone, and only sparse carbonaceous shale and coal. Hail (1968)

interpreted the contact between the Middle and upper members to be

unconformable.

Using outcrop and subsurface data, Hendricks (1977; 1978) developed a

palynostratigraphic framework for the middle and upper members of the Coalmont

Formation in the Coalmont district. He identified 3 "process-controlled genetic

units" (units 1-3, ascending order; fig. SN-5) in the middle member, which are

essentially correlative to the 3 informal units identified by Hail (1968). An important

aspect of this study was the identification of lower Eocene palynomorphs in the

upper part of the middle member (unit 3), below the Paleocene-Eocene

unconformity proposed by Hail (1968). Based on this evidence, Hendricks (1977)

suggested that the contact between the middle and upper members is best interpreted

as a diastem rather than an unconformity. Additionally, Hendricks (1977) assigned

strata of the middle member below unit 3 to the upper Paleocene.

Stands (1992), in studies of the Coalmont Formation in the McCallum anticline

area, identified palynomorphs of middle Paleocene age in the Sudduth coal bed,

which is within 100-200 ft of the sub-Coalmont unconformity along the flanks of

the south McCallum anticline (Roberts, unpublished data, 1993). He also recognized

upper Paleocene palynomorphs in the Capron coal zone, some 2,000 ft

stratigraphically above the Sudduth coal bed (Beekly, 1915), which established a

relative age equivalency to the middle member deposits in the Coalmont area. Based

on these criteria, Stands (1992) included the Sudduth coal bed, the Capron coal zone,

and all intervening strata in eastern North Park Basin in the middle member of the
SN-5

Coalmont Formation (fig. SN-5). The upper member of the Coalmont Formation

(or its age equivalent) is not present in the McCallum anticline district.

Based on these studies, and the identification of alternating alluvial and lacustrine

successions in the Coalmont Formation (Roberts and Flores, 1996), a generalized

stratigraphic framework for the formation in North Park Basin (fig. SN-6) suggests

that development of peat-forming mires in the McCallum anticline district was

associated with alluvial deposition (river and floodplain environments) that

predominated during the middle Paleocene and early part of the late Paleocene. Peatforming environments in the Coalmont district were closely associated with thick

lake successions that prevailed in North Park Basin in the later Paleocene and the

early Eocene.

COAL BEDS AND COAL ZONES

The discussion that follows is taken primarily from Beekly (1915), and unless

otherwise noted, his report should be considered as the primary source for this

compilation.

MCCALLUM ANTICLINE DISTRICT

Sudduth coal bed

The Sudduth coal bed is present in outcrops along the flanks of the south McCallum

anticline and in some places, has burned naturally to form resistant deposits of

clinker. Along the eastern flank of the south McCallum anticline, coal bed dips are
SN-6

commonly on the order of 60°-70° to the east and locally approach a vertical

orientation. The coal bed ranges from about 25-30 ft thick in areas near the

abandoned Bourg surface mine (fig. SN-4), and increases to more than 50 ft in areas

in and north of the site of the Marr strip mine. At the southern end of the south

McCallum anticline, the Sudduth coal bed thins to less than 20 ft.

Hoyle coal bed

The Hoyle coal bed has only been identified in highwall exposures in the abandoned

Bourg strip mine, and likely is present only in the mine area (Walden coal company,

unpublished field data, 1987). The coal bed is about 18 ft thick, and is about 90-95 ft

stratigraphically above the Sudduth coal bed.

Capron coal zone

The Capron coal zone is about 2,000 ft stratigraphically above the Sudduth coal bed,

and includes two coal beds separated by as much as 300 ft of strata. The upper bed

attains a thickness of 11-12 ft in the abandoned Capron mine. The lower bed

typically comprises a 6-ft-thick interval of thin coal stringers and carbonaceous shale

partings.

Winscom coal zone

Like the Capron coal zone, the Winscom coal zone contains two coal beds separated

by several hundred feet of rock. The coal beds are generally on the order of 5-6 ft

thick, and commonly consist of carbonaceous shale with thin coal interbeds. It is
SN-7

likely that this coal zone is correlative to the Capron coal zone, but discontinuous

exposures hamper an understanding of the exact stratigraphic relation.

Hill coal bed

This coal bed was identified in one abandoned adit on the east side of the Michigan

River in the southwest 1/4 of T. 10 N., R. 79 W. (fig. SN-4). No thickness is

reported and its stratigraphic position is uncertain, although it may be roughly

equivalent (in part) to the Capron and Winscom coal zones.

COALMONT DISTRICT

Pole Mountain-Mexican Creek coal zone

The Pole Mountain-Mexican Creek coal zone is the designation for coal beds that

outcrop in the Pole Mountain and Mexican Creek areas as described by Hail (1968);

we interpret the coal at both localities to be stratigraphically equivalent. The coal zone

is immediately above the uppermost thick succession of lacustrine deposits (fig.

SN-6) in the upper member of the Coalmont Formation on Pole Mountain, and is

below the Riach coal bed, although the exact thickness of the intervening interval is

not well established. Coal beds in this zone are lenticular, and locally contain

abundant carbonaceous shale partings. The coal beds are typically a few ft thick or

less, although some shaley coal beds may attain a thickness of about 9 ft (see, for

example, Hail, 1968).
SN-8

Riach coal bed

This coal bed is prevalent in the vicinity of Coalmont (fig. SN-4), and has been

correlated in drill holes to an area 4-5 miles east and southeast of Coalmont (see, for

example, Madden 1977). The thickness of the coal bed is quite variable, and can

range from less than 5 ft to more than 66 ft in the area of the abandoned Riach mine

at Coalmont. Based on studies of Erdmann (1941), Hail (1968) reports a maximum

Riach coal bed thickness of as much as 80 ft. However, based on correlation of

subsurface data from coal exploratory drill holes (see, for example, Madden, 1977),

the Riach coal bed or its interpreted equivalent more commonly ranges in thickness

from 20-40 ft. Additionally, the coal bed can include abundant carbonaceous shale

partings, although locally the bed consists of clean, hard coal throughout.

Additional, unnamed coal beds are also present within the middle member of the

Coalmont Formation at horizons well below the Riach coal bed and the Pole

Mountain-Mexican Creek coal zone. The thickness of these coal beds generally

ranges from 2 ft or less to as much as 6 ft locally. Most of the thick coal beds in the

Coalmont district are restricted to the upper member of the formation.

COAL PRODUCTION

There is currently no coal mining in North Park Basin, and most of the historic

mines have been completely abandoned and mostly reclaimed. Little or nothing is

published on the amount of coal produced from the numerous small wagon mines

that ranchers and local citizens developed in both the McCallum and Coalmont

districts during the late 1800’s and the early 1900’s. One can probably assume that
SN-9

production totals from these mines were negligible compared to subsequent

commercial ventures, and that most of the coal produced was for local domestic use.

Mining of the Riach coal bed (Coalmont district) began in the late 1800’s in the

Riach mine near Coalmont. By 1915, this mine was operated by the Northern

Colorado Coal Company and approached a capacity of 800 tons per day. The first

commercial mining in this area began in 1909, and continued until the end of World

War II (Hail, 1968). A new surface mine began in 1959, although production ceased

a few years later (Hail, 1968). Erdmann (1941), as reported in Hail (1968),

estimated that total production in the Coalmont district was on the order of

1,438,355 tons as of 1941. At the time of this writing, no additional data on

production in subsequent years could be located.

More recent surface mining of coal in North Park took place in the McCallum

anticline district where, for a period of years in the early 1980’s, as many as three

surface mines (the Bourg, Marr, and Canadian surface mines; fig. SN-4) produced

coal from the Sudduth coal bed along the flanks of the south McCallum anticline.

The Marr mine was the first to open in 1974, followed by the Canadian mine in

1975, and the Bourg mine in 1980 (Kelso and others, 1981). Cumulative production

totals as of 1981 were 3,021,404 tons from the Marr strip mine; 600,567 tons from

the Canadian strip mine; and 48,796 tons from the newly developed Bourg mine

(Kelso and others, 1981). Production totals in years subsequent to 1981 are

somewhat incomplete, but based on data in the Keystone Coal Industry Manual

(years 1982-95), we estimate that additional production was on the order of

1,066,000 tons from the Marr mine and 243,000 tons from the Bourg mine. No

additional production reports for the Canadian mine could be found at the time of

this writing. The Canadian strip mine was listed as inactive by 1985 and the Bourg
SN-10

mine by 1987 (Keystone Coal Industry Manual, 1985, 1987). The Marr mine

ceased mining coal subsequent to 1993, and was fully reclaimed by spring of 1995.

COAL QUALITY

Most of the reported chemical analyses of coal from North Park Basin relate to the

Sudduth and Riach coal beds, which by far were the primary coal beds of

commercial interest. The Sudduth coal bed apparent rank varies from

subbituminous B to subbituminous A, whereas the apparent rank of the Riach coal

bed ranges from subbituminous C to subbituminous B (Hatch and others, 1979).

Proximate analyses (on an as-received basis) of 3 samples of the Sudduth coal bed,

collected from small underground mines by Beekly (1915), indicate moisture

ranging from 16.7 to 20.0 percent, ash yield ranging from 3.59 to 6.29 percent, total

sulfur content varying from 0.16 to 0.59 percent, and heat-of-combustion values

ranging from 9,640 to 10,360 Btu/lb. Chemical analyses (on an as-received basis) of

an isolated sample from the Winscom mine (Winscom coal zone) yielded moisture

of 18.1 percent, an ash yield of 12.13 percent, total sulfur content of 0.08 percent,

and a calorific value of 9,280 Btu/lb.

As-received analyses of five samples from the Sudduth coal bed in the Canadian

strip mine (Colorado Geological Survey, 1981) indicate moisture ranging from 14.5

to 16.1 percent (arithmetic mean of 15.0 percent), ash yield ranging from 3.2 to 19.2

percent (arithmetic mean of 8.4 percent), total sulfur content consistently at 0.2

percent for all samples, and heat-of-combustion values ranging from 8,580 to

10,990 Btu/lb (arithmetic mean of 10,218 Btu/lb). As-received analyses of seven

bench samples of the Sudduth coal bed in the Marr strip mine (Colorado Geological
SN-11

Survey, 1981) show moisture ranging from 11.0 to 14.4 percent (arithmetic mean

of 12.71 percent), ash yield ranging from 2.1 to 10.8 percent (arithmetic mean of 5.9

percent), total sulfur content ranging from 0.2 to 0.3 percent (arithmetic mean of

0.25 percent), and calorific values ranging from 10,040 to 11,280 Btu/lb (arithmetic

mean of 10,755 Btu/lb).

Chemical analyses (on an as-received basis) from 21 samples of the Sudduth coal

bed (Hatch and others, 1979) indicate moisture ranging from 11.0 to 20.7 percent

(arithmetic mean of 15.0 percent), ash yield varying from 2.1 to 19.2 percent

(arithmetic mean of 8.0 percent), total sulfur content ranging from 0.2 to 0.6 percent

(arithmetic mean of 0.3 percent), and heat-of-combustion values ranging from 8,580

to 11,280 Btu/lb (arithmetic mean of 10,135 Btu/lb).

As-received analyses of the Riach coal bed in the Coalmont district, based on 12

samples, indicate moisture ranging from 14.5 to 20.2 percent (arithmetic mean of

17.59 percent), ash yield ranging from 5.1 to 37.0 percent (arithmetic mean of 16.6

percent), total sulfur content varying from 0.3 to 1.4 percent (arithmetic mean of 0.7

percent), and heat-of-combustion values ranging from 6,520 to 9,570 Btu/lb

(arithmetic mean of 8,200 Btu/lb) (Colorado Geological Survey and U.S. Geological

Survey, 1981).
SN-12

REFERENCES CITED

Beekly, A.L., 1915, Geology and coal resources of North Park, Colorado: U.S.

Geological Survey Bulletin 596, 121 p.

Colorado Geological Survey and the U.S. Geological Survey, 1981, Colorado coal

analyses, 1976-1979 [Khalsa, N.S., and Ladwig, L.R., editors]: Colorado

Geological Survey Information Series 10, 364 p.

Erdmann, C.E., 1941, Preliminary report on the geology of the Coalmont district,

Jackson County, Colorado: U.S. Geological Survey Open-File Report, 207 p.

Green, G.N., 1992, The digital geologic map of Colorado in ARC/INFO format:

U.S. Geological Survey Open-File Report 92-0507.

Hail, W.J., Jr., 1965, Geology of northwestern North Park and vicinity, Colorado:

U.S. Geological Survey Bulletin 1188, 133 p.

_____ 1968, Geology of southwestern North Park and vicinity, Colorado: U.S.

Geological Survey Bulletin 1257, 119 p.

Hail, W.J., and Leopold, E.B., 1960, Paleocene and Eocene age of the Coalmont

Formation, North Park, Colorado: U.S. Geological Survey Professional

Paper 400-B, p. 260-261.
SN-13

Hatch, J.R., Madden, D.H., and Affolter, R.H., 1979, Chemical analyses of coal and

coal-associated rock samples from the Coalmont Formation, McCallum and

Coalmont areas, North Park, Jackson County, Colorado: U.S. Geological

Survey Open-File Report 79-1099, 42 p.

Hendricks, M.L., 1977, Stratigraphy of the Coalmont Formation near Coalmont,

Jackson County, Colorado: Golden, Colorado, M.S. thesis, Colorado School

of Mines, 112 p.

_____ 1978, Stratigraphy of the Coalmont Formation near Coalmont, Jackson

County, Colorado, in Hodgson, H.E., ed., Proceedings of the second

symposium on the geology of Rocky Mountain coal--1977: Colorado

Geological Survey, Resource Series 4, p. 35-47.

Jones, D.C., Schultz, J.E., and Murray, D.K., 1978, Coal resources and

development map of Colorado: Colorado Geological Survey, Map series 9,

scale 1:500,000.

Kelso, B.S., Ladwig, L.R., and Sitowitz, L., 1981, Map and directory of permitted

coal mines, 1981: Colorado Geological Survey, Map Series 15, scale

1:500,000.

Keystone Coal Industry Manual (1982-1995); Directory of Mines: McGraw Hill

Mining Publications, New York City, New York.
SN-14

Maughan, E.K., 1989, Hydrocarbon exploration plays in the Colorado Park Basin

Province, in Lorenz, J.C., and Lucas, S.G., eds., Energy Frontiers in the

Rockies: Albuquerque Geological Society, Companion volume for the 1989

meeting of the Rocky Mountain Section of the American Association of

Petroleum Geologists, p. 79-83.

Madden, D.H., 1977, Exploratory drilling in the Coalmont coal field, Jackson

County, Colorado, June-November 1977: U.S. Geological Survey Open-File

Report 77-877, 138 p.

Roberts, S.B., and Flores, R.M., 1996, Facies variations in the Coalmont and

Middle Park Formations, North-Middle Park Basin, Colorado: Factors for

reconstructing Laramide sedimentation history and paleogeography, [abs.]:

Geological Society of America 1996 Annual Meeting, Abstracts with

Programs, p. A-373-A-374.

Rocky Mountain Association of Geologists (RMAG), R.H. Pearl [compiler], 1980,

Colorado stratigraphic nomenclature chart, in Kent, H.C., and Porter, K.W.,

eds., Colorado Geology: Rocky Mountain Association of Geologists, Denver,

Colorado, Plate 1.

Stands, R.E., 1992, Relative ages of major coal beds in the Coalmont Formation

(Paleocene-Eocene), North Park Basin, Jackson County, Colorado: Golden,

Colorado, M.S. thesis, Colorado School of Mines, 91 p.
SN-15

Tweto, Ogden, 1975, Laramide (Late Cretaceous-Early Tertiary) orogeny in the

southern Rocky Mountains: Geological Society of America, Memoir 144, p.

1-44.

Wellborn, R.E., 1977, Structural style in relation to oil and gas exploration in North

Park-Middle Park basin, Colorado, in Veal, H.K., ed., Exploration frontiers

of the central and southern Rockies: Rocky Mountain Association of

Geologists, 1977 Symposium, p. 41-60.
112° 108° 104° 100°

48°

44°

40°

Powder 

River

Basin

Wind River 

Basin

Hanna

Basin

Williston

Basin

Denver

Basin

Greater Green 

River Basin

Raton

Basin

0 50 100 150 miles

Canada

United States

North

Northern Rocky Mountains and

Great Plains region

North Park

Basin

Bull Mountain

Basin

Bighorn

Basin

Figure SN-1. Map showing North Park Basin and associated coal

basins in the Northern Rocky Mountains and Great Plains region.

Montana

Wyoming

Colorado

New

Mexico

North

Dakota

South

Dakota

Nebraska
40° 30'

40° 15'

106° 30'

T. 7 N.

T. 6 N.

T. 5 N.

T. 4 N.

R. 82 W. R. 81 W. 

Coalmont

Quaternary deposits (undifferentiated)

Coalmont Formation (Paleocene-Eocene)

Tertiary sedimentary deposits (undifferentiated

Tertiary volcanic deposits

Cretaceous deposits (undifferentiated)

Cretaceous and Jurassic deposits (undifferenti

E

Tc

Tc

40

Figure SN-2. Generalized geologic m

Green (1992).

A
Pierre

Shale

Coalmont

Formation

White River

Formation

North Park

Formation

Pliocene

and

Miocene

Oligocene

Eocene

Tertiary (part) Cretaceous (part)

Upper Cretaceous

(part)

Erosion or non-deposition

Paleocene

Figure SN-3. Generalized chart (not to scale) showing Upper

Cretaceous (part) and Tertiary stratigraphic nomenclature for

North Park Basin, Colorado. Modified from Rocky Mountain

Association of Geologists (1980).
Grizzly Creek

Little Grizzly Creek

Chedsey Creek

Abandoned underground mine

Abandoned surface mine

40° 30'

40° 15'

106° 30' 

T. 7 N.

T. 6 N.

T. 5 N.

T. 4 N.

R. 82 W. 

Coalmont

R

Coalmont Formation

Tc

Tc

40

BSM, Bourg surface mine

CSM, Canadian surface mine

MSM, Marr surface mine

Figure SN-4. Map showing the locat

Colorado. Locations of coal mines ad
Coalmont Formation

Pierre Shale upper member*

upper member*

middle member*

middle member*

middle member*

Middle Park

Member

Upper Cretaceous

Pierre Shale

Upper Cretaceous

Pierre Shale

Upper Cretaceous

Paleocene Eocene

unit 1 unit 2 unit 3

Paleocene

Paleocene

Eocene

(upper Paleocene)

?

?

upper Paleocene middle Paleocene

upper member (Eocene)

not present

Hail (1968) Hendricks (1977) Stands (1992)undifferentiated

Unconformity

Diastem

lower middle upper

lithostratigraphic units 

Informal lithogenetic units

Diagram not to scale

* Coal-bearing rocks

Informal

gure SN-5. Chart showing stratigraphic nomenclature for Paleocene-Eocene deposits in

 Coalmont Formation, North Park Basin, Colorado. Nomenclature modified from Hail

68), Hendricks (1977), and Stands (1992).
600 Feet

0

6 Miles

Pierre Shale

Lacustrine rocks

Marine and marginal marine rocks Unconformity

middle - upper Paleocene

? 

Paleocene

(part)

(pa

t)

Alluvial rocks

Drill hole

Pole Mountain-Mexican

Creek coal zone

Riach coal bed

Sudduth coal zone

Capron coal zone

Approximate scale

Coalmont Formation

Upper part of the Coalmont Formation

absent because of erosion

Winscom coal zone and

Hill coal bed

Known stratigraphic position

Stratigraphic position uncertain

Figure SN-6. Diagrammatic cross section showing the distribution of alluvial and

lacustrine successions, and the stratigraphic position of major coal beds or zones,

Coalmont Formation, North Park Basin, Colorado. Cross section location shown in

figure SN-2.