Chapter HS

FERRIS AND HANNA COAL IN THE HANNA AND

CARBON BASINS, WYOMING: A SYNTHESIS

By R.M. Flores,1 V.V. Cavaroc, Jr.,2 and L.R. Bader1

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

1

U.S. Geological Survey

2

North Carolina State University, Raleigh, North Carolina
HS-ii

Contents

Introduction...........................................................................................................................HS-1

History of Coal Mining......................................................................................................HS-4

Geologic Setting...................................................................................................................HS-6

Depositional Setting............................................................................................................HS-9

Coal Geology.....................................................................................................................HS-11

Coal Resources and Coal Quality..................................................................................HS-14

Conclusions........................................................................................................................HS-19

References..........................................................................................................................HS-21

Figures

HS-1. Generalized map of the Hanna and Carbon Basins in south-central

Wyoming showing Paleocene formation boundaries, geologic structures,

mining districts as defined by Glass and Roberts (1979; 1980), and

surrounding mountains and uplifts.

HS-2. Geologic map of the Hanna and Carbon Basins showing areal distribution

of Tertiary, Quaternary, and Holocene rocks (adapted from Green and

Drouillard, 1994).

HS-3. Stratigraphic subdivisions of the Cretaceous Medicine Bow Formation and

Paleocene Ferris and Hanna Formations in the Hanna and Carbon Basins.

Paleocene biostratigraphic zones (P1 through P6) of coal beds in the Ferris

and Hanna Formations in the Hanna Basin are also shown. Ferris coal

bundles are F1 through F4. Hanna coal bundles are H1 through H7.

Stratigraphy and coal bed names were adapted from Dobbin and others

(1929).
HS-iii

HS-4. Normal faults showing displacement of Ferris coal beds in the highwall of

the Medicine Bow coal mines.

HS-5. Basal Ferris sandstone showing large-scale trough crossbeds exposed in the

southwestern part of the Hanna Basin.

HS-6. Pebble fragments in the conglomeratic sandstone at the basal Ferris

Formation exposed in the southwestern part of the Hanna Basin.

HS-7. Laterally extensive basal conglomeratic sandstone of the Hanna Formation

exposed along the central part of the Hanna Basin.

HS-8. Interbedded coal, mudstone, siltstone, and sandstone in the Ferris

Formation. The buff sandstone on the upper right is a lens-shaped, fluvial

channel deposit.

HS-9. Thick coal and carbonaceous shale overlain by tabular crevasse splay

sandstone in the Hanna Formation.

HS-10. Lens-shaped, narrow fluvial channel sandstone (light) bounded by coal,

mudstone, and siltstone in the Hanna Formation.

HS-11. Laterally extensive fluvial channel sandstone (buff) showing pinch out on

the left and bounded by mudstone, siltstone, and coal in the Ferris

Formation.

HS-12. Thick, stacked, multi-erosional sandstone deposited in braided streams of

the basal Hanna Formation.

HS-13. Thin to thick, laterally offset, erosional-based sandstone deposited in

meandering streams of the Hanna Formation.

HS-14. Laterally contemporaneous fluvial channel sandstone flanked by flat-bedded

crevasse splay sandstone, siltstone, and mudstone representing

anastomosed stream deposits of the Ferris Formation.
HS-iv

HS-15. Trough crossbedded fluvial channel sandstone overlain by conglomerate

deposited in alluvial fans of the Hanna Formation exposed along the

northern flank of the Medicine Bow Mountains.

HS-16. Boulder to pebble conglomerate deposited in alluvial fans of the Hanna

Formation exposed along the northern flank of the Medicine Bow

Mountains.

HS-17. Outcrop of the Johnson coal zone in the south Carbon coalfield.

HS-18. Map showing variations in vitrinite reflectance of the Ferris coal in the

western part of the Hanna Basin and the Hanna coal in the eastern part.

Modified from Teerman (1983).
HS-1

INTRODUCTION

Subbituminous and bituminous coal exist in the Paleocene parts of the Ferris and

Hanna Formations in the Hanna and Carbon Basins (Dobbin and others, 1929;

Berryhill and others, 1950; Glass and Roberts, 1979) in south-central Wyoming

(fig. HS-1). These formations are stratigraphically equivalent to the Fort Union

Formation in other Tertiary basins in the Rocky Mountains and northern Great

Plains region. Ferris and Hanna strata make up the surface bedrock over much of

the Hanna and Carbon Basins (fig. HS-2). These strata (fig. HS-3) are conformably

underlain by the Upper Cretaceous part of the Ferris Formation and the Medicine

Bow Formation, conformably overlain by the Eocene part of the Hanna Formation,

and unconformably overlain by Quaternary deposits.

Coal in the Hanna Basin was first discovered by James C. Fremont along the North

Platte River near the mouth of Sage Creek (Dobbin and others, 1929). Coal

occurrences elsewhere along the Overland Trail were reported in Fremont’s

accounts of the "Expedition to Oregon and North California in years 1843-1844."

In 1856, Lt. F.T. Bryan of the U.S. Army Topographic Corps and H. Engelmann, a

geologist, reported the occurrence of coal along the North Platte River and north of

the present town of Elk Mountain (fig. HS-1). In 1865, James Evans, who

surveyed the proposed Union Pacific rail line, reported that coal was found from the

North Platte River eastward to Rock Creek (23 miles east of Elk Mountain), which

is east of the Carbon Basin (Gardner and Flores, 1989). The availability of

significant amounts of coal along the Overland Trail as reported by Fremont and

Evans, dictated the selection of the Union Pacific Railroad route to the West Coast.

In 1868, the earliest geological investigation in the Hanna and Carbon Basins was

made by Hayden (1873). He described the Tertiary formations and reported the
HS-2

presence of coal mines in the Hanna and Carbon Basins along the Union Pacific

Railroad, west of Como Ridge. Here Hayden described "peculiar sands and

sandstones and clays and numerous coal beds" within a 50-mile distance of the rail

line. He also described the structural geology, noting that "rocks incline nearly

southeast, or south and east." Plant fossils of the Tertiary formations were first

examined and described by Lesquereux (1872) for the purpose of dating the rocks.

Veatch (1907) prepared a reconnaissance geologic map of the Hanna and Carbon

Basins and adjacent areas.

Bowen (1918) formally named the coal-bearing Tertiary formations as the Ferris

and Hanna Formations. These formation names were retained, although F.H.

Knowlton, T.W. Stanton, and J.W. Gidley later identified plant, invertebrate, and

vertebrate remains in these rocks as typical "Fort Union" age (Dobbin and others,

1929). The coal beds and resources in the Ferris and Hanna Formations were

investigated in detail by Dobbin and others (1929), who devised a comprehensive

numerical nomenclature for the beds (Nos. 21-89, from bottom to top). Numbers 1-

20 are found in the Cretaceous Medicine Bow Formation, which conformably

underlies the Ferris Formation and outcrops along the flanks of the Hanna and

Carbon Basins. The Medicine Bow coal beds were not studied because they are not

potentially strippable, averaging 5-6 ft thick and dipping greater than 25 degrees (for

example, in the Corral Creek mining district; see fig. HS-1; Glass and Roberts,

1979, 1980). The Hanna Formation was demonstrated by Knight (1961) to be

conformable with the underlying Ferris Formation in the center of the Hanna Basin.

However, the Hanna Formation rests unconformably on older formations along the

basin margin and in the Carbon Basin. The Ferris and Hanna Formations exist over

600 square miles in the Hanna Basin. The Hanna Formation exists over 80 square

miles in the Carbon Basin.
HS-3

This study includes only the Paleocene parts of the Ferris and Hanna Formations in

the Hanna Basin because associated coal beds (for example, Ferris 23, 25, 35, 50,

65, and others; Hanna 77-79, 81; see fig. HS-3) were mined and account for more

than 3 million short tons of the 1998 U.S. total coal production (Resource Data

International, Inc., 1998). The Hanna coal (Johnson-107 coal zone) in the Carbon

Basin is a potentially minable deposit targeted for possible development (U.S.

Bureau of Land Management and U.S. Office of Surface Mining, 1998). These coal

beds and zones are expected to contribute fuel supplies for in-state and out-of-state

electric generating power plants. The intensive exploration and development of the

Ferris and Hanna coal during the early to mid 1900's by the Union Pacific Coal

Company provided a number of data points for this study. Later exploration and

development by other coal companies (for example, Arch Coal Incorporated,

Energy Development Company, Medicine Bow Coal Company, Resource

Exploration and Mining, Inc., Rosebud Coal Sales Company, and Cyprus Amax

Coal Company) provided additional surface and subsurface stratigraphic

information for our coal assessment of the Ferris and Hanna Formations. In

addition, drilling and mapping programs by the U.S. Geological Survey (USGS) in

the 1970's in the Hanna and Carbon Basins contributed stratigraphic information.

Data from a total of 1,960 drill holes from these drilling activities are archived as

digital records at the U.S. Bureau of Land Management in Rawlins, Wyoming, and

in the USGS National Coal Resources Data System in Reston, Virginia (email:

mdcarter@usgs.gov). Most of these data are proprietary.
HS-4

HISTORY OF COAL MINING

Mining of the Ferris and Hanna coal in the Hanna and Carbon Basins began in 1868

near the town of Carbon, Wyoming. The production of the coal in these basins was

intertwined with the establishment of a transcontinental railroad and subsequent

expansion of the Union Pacific Railroad. The railroad benefited from the Pacific

Railroad Act of 1862, which was modified by the Pacific Railroad Act of 1864, that

stated the Union Pacific would be granted ten sections of land (6,400 acres) for

every mile of track laid (Gardner and Flores, 1989). This land was distributed in

alternating sections or "checkerboard" pattern in which the even-numbered sections

were retained by the federal government and the odd-numbered sections were given

to the railroad. (For an example of this checkerboard pattern, see the section on

ownership maps in Chapter HM of this CD-ROM). The Pacific Railroad Act of

1864 liberalized trade and led to doubling the land grant to twenty sections per mile.

The Union Pacific was given the mineral rights to the property received in the land

grant. Thus, the railroad accumulated vast amounts of coal resources, monopolized

the transport of coal from its mines, and produced additional coal from land leased

from the government (Union Pacific Coal Company, 1940). The coal was a source

of fuel for the Union Pacific steam locomotives, for heating fuel, and to fuel

industries in western and midwestern cities.

Seven underground mines were ultimately opened by the Union Pacific Railroad in

the town of Carbon, which produced about 4,680,000 tons of coal from 1868 to

1902 (Dobbin and others, 1929; Union Pacific Coal Company, 1940). Eventually

these mines were abandoned when the main railroad line was shifted farther north to

the present towns of Hanna. Five underground coal mines were opened in the town

of Hanna in 1890 (Dobbin and others, 1929; Gardner and Flores, 1989). The mines
HS-5

were developed in Hanna Formation coal beds. The Hanna beds were sequentially

identified by number according to the order in which the mines were opened. Only

coal mine numbers 2 and 4, which produced about 2,200 tons of coal daily, were

still active through the 1930’s. Increased coal production was enhanced by

mechanization of these underground mines during the 1920's and 1930's.

Underground mine production was increased by transporting coal using electric

locomotives instead of hauling coal using mules and horses and by utilizing modern

coal mining equipment. Initial underground mining was by the room and pillar

method, with longwall mining introduced in the 1980’s. Even though strip mining

was introduced in Wyoming in 1924 (Gardner and Flores, 1989), this method of

mining was not used in the Hanna Basin until the 1960's and 1970's when draglines,

trucks, and shovels were available to mine the steeply-dipping coal beds.

During the recession years in the 1920's and the depression years from 1930 to

1940, mine closures in Wyoming also affected coal mines in the Hanna and Carbon

Basins. During World War II, coal mining was considered to be a critical industry

in the war effort and coal production increased, only to decline again after the war

with the advent of diesel locomotives. The railroads, with their steam locomotives,

had influenced the coal market; however, the "dieselization" of the Union Pacific

Railroad from the 1940's to the mid 1950's led to the closure of a majority of the

mines in the Hanna and Carbon Basins (Union Pacific Coal Company, 1940;

Gardner and Flores, 1989). The Union Pacific began to close their remaining mines

in the Hanna Basin in 1953.

Coal mining again picked up from the 1960's to 1970's as a result of changes in the

state severance tax structure and introduction of modern strip-mining methods.

New power plants were built in-state and out-of-state to (1) satisfy increased
HS-6

demand for electrical power generation in general and (2) to burn low-sulfur coal in

particular. This led to the resurrection of abandoned coal mines and opening of new

ones in the Hanna Basin. The passing of the current severance tax by the Wyoming

State Legislature eventually brought an economic boom to the state (Gardner and

Flores, 1989). The idea behind the tax is to recapture part of the lost value of coal, a

nonrenewable energy source, through excise tax on the mining of a natural resource.

The Wyoming severance tax was levied on the coal industry at a steadily increasing

rate through the 1970's and created a revenue source for the State of Wyoming. In

the late 1970's, 98 percent of the coal production in the Hanna Basin was from strip

mines equipped with modern draglines, truck shovels, and high-capacity haul

trucks. Glass and Roberts (1979) estimated that at least 63.1 million tons of coal

had been strip-mined by 1978.

At present, Arch Coal Incorporated is operating strip mines in the Ferris and Hanna

coalfields. The Cyprus Coal Company operates an underground mine in the Hanna

coalfield. The resources of the Ferris 23, 25, 31, 50, and 65, and Hanna 77-79 and

81 coal beds are assessed by this investigation in the Hanna Basin. In addition, the

resources of the Johnson-107 coal zone is assessed in the Carbon Basin.

GEOLOGICAL SETTING

The Hanna and Carbon Basins are structural and sedimentary basins bounded on the

south by the Medicine Bow uplift, on the north by the Sweetwater arch consisting of

the Granite, Shirley, and Seminoe Mountains, and on the west by the Rawlins uplift

(see fig. HS-1). The Hanna and Carbon Basins are separated by the northeasttrending Saddleback anticline, which was an emergent extension of the Medicine
HS-7

Bow uplift during the early Paleocene (Knight, 1951; Glass and Roberts, 1980;

Flores and Roberts, 1996; Perry and Flores, 1994). The basins are asymmetric

subdivisions of an east-west trending structural trough that formed during the

Laramide deformation. A total of more than 30,000 ft of sedimentary rocks

accumulated on the Precambrian crystalline basement rocks (Dobbin and others,

1929; Knight, 1951). Rapid subsidence of the Hanna Basin is suggested by the

combined thickness of the Ferris and Hanna Formations, which totals about 13,500

ft. Rocks of these formations are steeply dipping (greater than 25 degrees) along the

basin margin and have moderate to low dips (5-15 degrees) in the basin center

(Glass and Roberts, 1980). In addition, Glass and Roberts (1980) indicate that

younger coal-bearing Paleocene rocks steepen to vertical dips.

Both basins were modified by folding and faulting (see fig. HS-1). High-angle,

normal and thrust faults with displacements from a few feet to 0.5 mi or more (fig.

HS-4) are common in the central part and along the flanks of the Hanna Basin

(Glass, 1977; Perry and Flores, 1994). Cross-faults between northwest-trending

faults are also present in the east-central part of the basin. Major faults along the

basin margins developed from Late Cretaceous to early Paleocene time, during the

Laramide deformation (Knight, 1951; Love, 1970). The Hanna Basin is divided into

three synclines with axes almost perpendicular to each other along its northern and

eastern parts (fig. HS-1); it also contains a few folds along the margins of the basin.

In the Carbon Basin, several anticlines are present along the basin margins.

Numerous northeast-trending faults dissect the basin.

The sedimentary infilling of the Hanna and Carbon Basins evidently was controlled

by periodic tectonic movements of the uplifts surrounding the basins (Brooks, 1977;

Ryan, 1977). This interpretation is based on the petrology and mineral composition
HS-8

of the Ferris and Hanna Formations in comparison to rocks of the surrounding

uplifts. Early Paleocene uplift of the ancestral Park Range-Medicine Bow Mountains

shed sediment from the south, which mostly formed the Ferris Formation. A minor

amount of sediment was shed from the inactive Sweetwater arch (Granite, Seminoe,

and Shirley Mountains) during this time. Middle to late Paleocene tectonic

movements of the Sweetwater arch caused shedding of abundant sediment from the

north to form the Hanna Formation. These sediments were transported and

deposited by eastward-flowing braided and meandering rivers. Late Paleocene

tectonic movement of the Rawlins uplift caused closure of the western margin of the

Hanna Basin (Perry and Flores, 1994). The Carbon Basin developed as a

depositional basin only from middle to late Paleocene time, and it was structurally

separated from the Hanna Basin by late Paleocene or Eocene time (Perry and Flores,

1994).

The tectonic settings of the basins and adjacent areas imposed physical differences in

the stratigraphy of the Ferris and Hanna Formations (see fig. HS-3). The lower

1,100 ft of the Ferris Formation consists primarily of conglomeratic sandstone beds

composed of pebble fragments of quartzite, varicolored jasper, rhyolite, and

porphyry (Dobbin and others, 1929). The remaining 5,700 ft of the Ferris

Formation consists of interbedded sandstone, siltstone, mudstone, carbonaceous

shale, and coal. The Hanna Formation consists of interbedded "packages" of thick

conglomeratic to coarse-grained sandstone interbedded with sandstone, siltstone,

mudstone, carbonaceous shale, and coal. The lowermost part of the formation

consists of as much as 1,900 ft of conglomeratic sandstone composed primarily of

pebble fragments derived from the Ferris conglomeratic sandstone together with

granitic fragments. In addition, Hanna sandstone is more arkosic than the Ferris

sandstone (Brooks, 1977; Ryan, 1977).
HS-9

DEPOSITIONAL SETTING

The tectonic imprint on the physical stratigraphy of the Ferris and Hanna

Formations is shown by differences in their depositional environments. Erosional

bases of Ferris and Hanna conglomeratic sandstone beds (figs. HS-5, HS-6, and

HS-7) probably reflect lowering of the base level due to uplifts or basin subsidence.

These events permitted fluvial channels to downcut and form paleovalleys that were

subsequently infilled during succeeding rises in base level. Major events of

downcutting and subsequent infilling of paleovalleys occurred during early Ferris

time and early Hanna time. Braided and meandering streams infilled these

paleovalleys (Cavaroc and others, 1992). Intervening coal-bearing intervals

consisting of sandstone, siltstone, mudstone, and coal (figs. HS-8 and HS-9) reflect

base level rises during which alluvial plains were drained mainly by meandering and

anastomosed rivers (see figs. HS-10 and HS-11; Perry and Flores, 1994). Thus,

cyclic intervals of deposition of conglomeratic sandstone and coal-bearing rocks

represent base-level fall and rise controlled by tectonism and basin subsidence.

Provenance and sediment dispersal studies of the Ferris and Hanna Formations in

the Hanna and Carbon Basins by Ryan (1977) suggested that clastic sediment was

dispersed by three fluvial systems, two entering from the north and one entering

from the south. These dispersal systems were influenced by uplift of the Medicine

Bow Mountains to the south and subsequent uplifts of the Granite Mountains to the

north. Uplift reversals controlled the dynamics of the fluvial systems, changing their

styles from dominantly braided rivers to dominantly meandering and anastomosed

rivers; the latter being overprinted more by changes in basin subsidence than by

uplifts. The evolution of fluvial styles is indicated by the channel sandstone

architecture (figs. HS-12, HS-13, and HS-14). These fluvial systems were probably
HS-10

fed from the mountains through alluvial fans (Hansen, 1986), exemplified by

sandstone and conglomerate deposits (figs. HS-15 and HS-16).

Although coal facies data used to determine whether the Ferris and Hanna coal was

formed in planar (low-lying) or domed (raised) swamps are limited, Pierce (1996)

postulated that the swamps in which Hanna coal formed were low-lying. Based on

the coal petrology and proximate analysis of the Hanna coal, Pierce suggested that

large amounts of gelocollinite and high ash yields indicate accumulation of peat in

low-lying mires or swamps. In addition, Pierce referred to unpublished

palynological data of D.J. Nichols of the USGS that suggested angiosperms

inhabiting the Hanna swamps provided a majority of the gelocollinite precursors. In

contrast, the Ferris coal is composed of lesser amounts of gelocollinite and relatively

more telinite (Pierce, 1996). Ferris coal also is dominated by pollen of woody

taxodiaceous gymnosperms, which may have provided telinite precursors. Ferris

coal probably developed in raised swamps. Thus, differences in swamp vegetation,

as indicated by coal petrography and palynology, may have influenced the

composition of the coal deposited in the Ferris and Hanna Formations.

Cavaroc and others (1992) and Perry and Flores (1994) suggested that basin

subsidence may have controlled the nature of the swamps in the Hanna Basin;

Pierce (1996) reached a similar conclusion. Perry and Flores (1994) indicated that

subsidence may have occurred during the Paleocene in the northern part of the

Hanna Basin at about 1.9 ft per 103 years for decompacted Ferris and Hanna rocks

or 1.4 ft per 103 years uncorrected for compaction. Thus, this rapid rate of

subsidence contributed to over-thickening (13,000 ft) of the Paleocene rocks and

drowning of the basin by floodplain lakes and accompanying swamps. More

importantly, subsidence influenced burial of the swamps by sediments. Thus,
HS-11

sedimentological evidence suggests that the Ferris and Hanna swamps were lowlying because they were prone to floods. It is suggested that the differences in

vegetation between the Ferris and Hanna low-lying swamps and resulting coal

macerals (Pierce, 1996) may be due to adaptability of plants to the tectonic

conditions in the basin and to changing fluvial depositional environments, although

effects of floral evolution cannot be discounted. It is possible that the Hanna

swamps may have been more low-lying than the Ferris swamps, as indicated by

greater degradation of Hanna peat. The similarity in tectonic conditions and

depositional settings for both the Ferris and Hanna coal may explain the similarity in

the thicknesses of assessed coal beds of the Ferris Formation (Ferris 23, 25, 31, 50,

and 65), which range from 5 to 22 ft, and those in the Hanna Formation (Hanna 77-

79 and 81), which range from 5 to 27 ft. Glass and Roberts (1980) indicated that

thicknesses of Ferris coal ranges from 5 to 25 ft and Hanna coal ranges from 5 to 38

ft. In the Carbon Basin, which had a subsidence history similar to that of the Hanna

Basin, the assessed coal beds (Johnson-107 coal zone; fig. HS-17) range from 5 to

25 ft thick.

COAL GEOLOGY

Seventy-seven coal beds are identified by Dobbin and others (1929) and Glass and

Roberts (1980) in the Hanna and Carbon Basins, 47 coal beds are in the Ferris

Formation, and 30 beds are in the Hanna Formation (see fig. HS-3). The interval

containing coal beds in the Ferris Formation ranges from 25 to 400 ft thick, and that

in the Hanna Formation from 30 to 1,100 ft thick (Dobbin and others, 1929). The

thinner coal-bed interval in the Ferris Formation is composed primarily of

interbedded mudstone, siltstone, and sandstone (see fig. HS-3). In contrast, the

thicker coal-bed interval in the Hanna Formation is expanded by thick sandstone and
HS-12

conglomerate beds with minor mudstone and siltstone (see fig. HS-3). Except for

these minor physical characteristics, the Ferris and Hanna Formations contain

similar coal-bearing rocks. The biostratigraphy based on palynology (analysis of

fossil spores and pollen) of the two formations utilizes the zonation of Nichols and

Ott (1978); see also Nichols (1994), Nichols (1996), and Perry and others (1996).

Paleocene Zones P1 through P6 are present in the Hanna Basin (see fig. HS-3; and

Chapter HB in this CD-ROM). The Ferris Formation includes Zones P1 through P2

(lower Paleocene), and the Hanna Formation includes Zones P4 through P6 (middle

and upper Paleocene). Zone P3 was not found; it may be either in the uppermost

Ferris Formation or lowermost Hanna Formation. Palynology also shows that the

lowermost part of the Ferris Formation is in the uppermost Cretaceous and the

uppermost part of the Hanna Formation is in the lower Eocene. The coal

stratigraphy of the Ferris and Hanna Formations in the Hanna Basin may be

simplified by grouping the coal beds into bundles (see fig. HS-3; for example, F1

and H1) interbedded mainly with mudstone and siltstone and generally separated by

intervals of conglomerate, sandstone, siltstone, and mudstone (see fig. HS-3).

Similar coal-bed bundling is observed in the Carbon Basin (see fig. HS-3; for

example, H6-H7). The Ferris coal beds in the middle part of the formation are

vertically stacked. These stacked coal beds may be divided into four bundles of coal

beds, each interbedded with abundant siltstone and mudstone, and subordinate

sandstone, in intervals ranging from 20 to 60 ft thick (see fig. HS-3; F1-F4). The

coal bundles range from 300 to 950 ft thick. The four coal bundles, from bottom to

top, include: (F1) coal bed Nos. 21-24; (F2) bed Nos. 25-29; (F3) bed Nos. 30-50;

and (F4) bed Nos. 51-59 (see fig. HS-3). Coal beds Nos. 60-65 are in intervals of

varying thickness in the uppermost part of the Ferris Formation. The Hanna coal

beds also are grouped in bundles throughout the formation; these coal bundles are

vertically stacked on top of fining-upward intervals consisting of sandstone,
HS-13

siltstone, and mudstone ranging from 200 to 1,050 ft thick (see fig. HS-3; for

example, H1, H2, H3, and H4). Four of the five Hanna coal bundles range from

100 to 800 ft thick, and are interbedded mainly with siltstone and mudstone and

subordinate sandstone. The H5 coal bundle is over 1600 ft thick and is interbedded

with sandstone, siltstone, and mudstone. The five coal bundles, from bottom to top,

include: (H1) bed Nos. 67-69; (H2) bed Nos. 70-72; (H3) bed Nos. 73-76; (H4)

bed Nos. 77-81; and (H5) bed Nos. 82-89 (see fig. HS-3).

The vertical and lateral variations in coal stratigraphy in the Ferris and Hanna

Formations are controlled by the sedimentology and depositional environments of

the rocks interbedded with the coal. In the Ferris Formation, coal beds may split and

merge within short distances (within 0.1 mile; see cross sections in Chapter HF of

this CD-ROM), forming a coal zone. The extent of this zone is controlled by the

areal size and rate of sedimentation of the fluvial depositional systems that formed

the deposits. Thus, a rapid rate of sedimentation in small, lobe-shaped depositional

systems, such as crevasse splays, produced thin intervals of siltstone and mudstone

and subordinate sandstone between coal beds. These sedimentary deposits formed

short-lived swampy platforms on which thin peat deposits accumulated. Frequent

autocyclic (lateral) shifts of these environments influenced the splitting and merging

of the peat deposits; the resulting thick peat formed on these platforms. Stacking of

the peat deposits and sediments related to autocyclic crevasse-floodplain depositional

systems caused bundling or stacking of thin coal beds. The intervening intervals of

sandstone, siltstone, and mudstone represent the fluvial-channel, overbank deposits

of the fluvial systems.

In the Hanna Formation, coal beds split and merge over a few miles, forming a coal

zone. This zone resulted from the rapid rate of sedimentation in wide alluvial plains
HS-14

that were drained by meandering and braided streams and accompanying crevasse

splays. Avulsion and prolonged abandonment of these stream deposits led to the

formation of extensive alluvial platforms on which swamps developed and very

thick peat deposits accumulated. However, rapid successions of avulsion and

abandonment of the fluvial depositional systems along the width of the alluvial plain

led to coal-bed bundling. In addition, the vast expanse of abandoned platforms

contributed to the extensive areal distribution of the peat deposits. This accounts for

the widespread coal deposits of the Hanna Formation.

COAL RESOURCES AND COAL QUALITY

On the basis of strippable coal resources, the Hanna and Carbon Basins were

subdivided into four mining districts by Glass and Roberts (1979; 1980). These

mining districts include, from west to east, the Corral Creek, Seminoe, Hanna, and

Carbon districts, with areas barren of near-surface coal serving to delimit one district

boundary from another (see fig. HS-1). The Corral Creek mining district contains

coal beds of the Cretaceous Medicine Bow Formation. The Seminoe mining district

contains the Ferris coal beds, and the Hanna and Carbon mining districts contain the

Hanna coal beds. Glass and Roberts (1979; 1980) reported that the weighted average

thickness of the Ferris coal beds is 10 ft, based on strippable resources in the

Seminoe mining district. These workers also reported that the weighted average

thickness of the Hanna coal beds is 11-14 ft, based on strippable resources in the

Hanna and Carbon mining districts. The thickening of minable deposits is enhanced

by coalescing of individual coal beds from a coal zone into a single bed.

Dobbin and others (1929) estimated that the Hanna Basin contained 4.2 billion tons

of coal from the surface to a depth of 3,000 ft and about 4 billion tons at greater
HS-15

depths. Berryhill and others (1950) reinvestigated the coal resources of the Hanna

Basin using the data of Dobbin and others (1929) and calculated reliability categories

based on thickness and depths. These investigators reported 3.9 billion tons for coal

found at the surface to a depth of 3,000 ft. In a study instigated by the increasing

demand for near-surface or strippable (0-200 ft depth) coal resources in the Hanna

Basin, the U.S. Bureau of Mines (1971) estimated that 10 million tons of resources

were in eight unnamed coal beds of the Hanna Formation. The U.S. Bureau of

Mines assumed that 80 percent of this volume was recoverable and estimated 8

million tons as a strippable reserve.

Based on resource calculations provided by Berryhill and others (1950), Glass

(1972) estimated about 313 million tons of strippable coal resources existed in the

Hanna Basin for bituminous coals over 42 inches thick and subbituminous coal over

5 ft thick under less than 1,000 ft of overburden. In the Seminoe mining district, the

U.S. Bureau of Land Management (1975) identified 41.21 million tons of strippable

Ferris coal resources within a 9.6 square mile area under 0-200 ft of overburden.

Glass and Roberts (1979) reported about 173 million tons of strippable coal

resources underlie the townships that the U.S. Bureau of Land Management studied.

A series of U.S. Geological Survey Open-File Reports prepared by Texas

Instruments, Inc. (1978a-u), have provided the most detailed estimates for the

Hanna Basin. However, these reports only provided figures for strippable resources

of unleased federal mineral lands. Choate and Lent (1977) estimated coal resources

of steeply dipping coal beds in the Hanna Basin to be about 240 million tons. Their

estimates included beds 5 to 30 ft thick with dips greater than 20 degrees.

Glass and Roberts (1979; 1980) reported comprehensive coal resource estimates in

the Hanna and Carbon Basins. These investigators estimated remaining strippable
HS-16

coal resources of the Ferris and Hanna coal beds and zones as of January 1, 1978, to

be more than 657 million tons. About 299 million tons of this total are under 0-100

ft of overburden, and about 348 million tons are under 100-200 ft of overburden.

Seventy-nine percent of these strippable coal resources are found in the Seminoe and

Hanna mining districts. Prior to January 1, 1979, about 189 million tons of the

strippable coal resources had been mined, and about 80 million tons of this coal

resource were removed or lost by strip mining (Glass and Roberts, 1979; 1980).

Another 110 million tons were removed or lost by underground mining prior to this

date. Resource Data International, Inc. (1998) recorded a total of about 40 million

tons that was produced by seven mines from 1989 to 1997. Thus, not including

production from 1979 to 1989, approximately 218 million tons remain as strippable

coal resources in the Ferris and Hanna coal beds and zones in the Hanna and Carbon

Basins.

Estimates of coal resources of the Ferris, Hanna, and Johnson-107 coal beds and

zones are presented in Chapter HN of this CD-ROM. Estimates of coal resources in

beds thicker than 2.5 ft are: Ferris coal beds and zones—1.75 billion short tons;

Hanna coal beds and zones—4.26 billion short tons; and Johnson-107 coal beds and

zones—2.7 billion short tons; a total for the two basins—8.71 billion short tons (see

Chapter HN). These coal resource estimates are broken down by thickness,

overburden, ownership, and county (see Chapter HN). The methodology of

calculating the resources of these coal beds and zones is discussed in Chapters DB

and HN of this CD-ROM.

The apparent rank of the Ferris and Hanna coal beds varies from subbituminous A

to high-volatile C bituminous. This variation in rank is not related to the age of the

coal because Hanna coal has been reported as high-volatile C bituminous by Glass
HS-17

and Roberts (1979; 1980). These workers reported that the apparent rank of the

Ferris coal is usually subbituminous A. The variations in coal rank between Ferris

and Hanna coal may be explained by the location of the coal samples. That is, the

Ferris coal samples were collected from the Seminoe mining district, or along the

western margin of the Hanna Basin. In contrast, the Hanna coal samples were

collected from the central part of the Hanna Basin and from the Carbon Basin. In

general, the coal rank increases from west to east, ranging from 11,170 Btu/lb for

the Ferris coal on the western part of the Hanna Basin to 11,590 Btu/lb for the

Hanna coal in the east-central part of the Hanna Basin and 12,270 Btu/lb for the

Hanna coal in the Carbon Basin to the east (Glass and Roberts, 1979). Glass and

Roberts (1980) suggested that the spatial variation may be explained by variation in

heat flow, which is higher and longer in duration in the east than in the west.

However, the spatial variation in rank also may be explained by the difference in

depth of burial, because the Hanna coal in the central and deepest part of the basin

was buried deeper than the Ferris coal in the western part or margin of the Hanna

Basin. Vitrinite reflectance of the Ferris coal ranges from 0.48 to 0.53 percent Ro

and of the Hanna coal from 0.45 to 0.54 percent Ro in the Hanna Basin (fig. HS-18;

Teerman, 1983). The vitrinite reflectance of the Hanna coal ranges from 0.51 to

0.54 percent Ro in the Carbon Basin (fig. HS-18; Teerman, 1983). The vitrinite

reflectance of the Ferris and Hanna coal indicates no significant difference from the

west to the east, suggesting that there is no relationship between coal rank and

vitrinite reflectance (McCartney and Teichmuller, 1972).

The ultimate and proximate analyses of coal from the Ferris and Hanna Formations

in the Hanna and Carbon Basins were reported by Lord (1913), Dobbin and others

(1929), U.S. Bureau of Mines (1931; 1971), U.S. Bureau of Land Management

(1975), Glass (1972; 1978), and Texas Instruments, Inc. (1978a; 1978c-h; 1978j-m;
HS-18

1978o-s; 1978u). These analyses were summarized by Glass and Roberts (1979).

The moisture, volatile matter, and fixed-carbon values (arithmetic mean; as-received

basis) for the Ferris coal in the Seminoe mining district are 12.58, 34.30, and 45.19

percent, respectively. The sulfur and ash contents of the coal are 0.49 and 7.93

percent, respectively. In contrast, the moisture, volatile matter, and fixed carbon

values (arithmetic mean; as-received basis) for the Hanna coal in the Hanna mining

district are 12.76, 36.68, and 41.82 percent, respectively, and for the Hanna coal in

the Carbon mining district are 10, 36.71, and 39.55 percent respectively. The sulfur

and ash contents of the Hanna coal are 0.76 and 8.75 percent, respectively, and of

the Hanna coal in the Carbon Basin are 2.72 and 13.74 percent, respectively. Our

coal-quality investigation of the Johnson-107 coal zone indicates the following

arithmetic mean values (on an as-received basis) for the coal not presently being

mined or leased: ash yield—12.48 percent, total sulfur—0.96 percent, and calorific

value—10,090 Btu/lb (see Chapter HQ of this CD-ROM for more detail).

The trace elements of environmental concern in Ferris and Hanna coal, which can

impact coal utilization and reclamation, include arsenic, mercury, selenium, and

uranium. Glass and Roberts (1979) reported that the Ferris coal in the Seminoe

mining district contains 4.6 ppm arsenic, 0.08 ppm mercury, 0.67 ppm selenium,

and 2.4 ppm uranium (n=34-35, arithmetic mean, on a whole coal, as-received

basis). In comparison, the Hanna coal in the Hanna and Carbon mining districts

contains 3.3-25 ppm arsenic, 0.08-0.20 ppm mercury, 0.79-3.2 ppm selenium, and

1.8-3.9 ppm uranium (n=15-19, arithmetic mean, on a whole-coal, as-received

basis). Stricker and others (1998) reported no significant difference in the arithmetic

means for contents of arsenic (4.4 ppm), mercury (0.07 ppm), selenium (0.80

ppm), and uranium (1.9 ppm) (n=14, arithmetic mean, on a whole-coal, as-received

basis) of the Ferris and Hanna coal in the Hanna and Carbon Basins. These workers
HS-19

suggested that the higher sulfur, ash, and trace-element contents (see Chapter HQ of

this CD-ROM for more detail) of the Ferris and Hanna coal beds and zones

compared to other basins in the Rocky Mountains and northern Great Plains region

were controlled by the source rocks in the surrounding uplifts, the intensity of the

tectonic activity in these uplifts, and the low-lying swamps associated with the

fluvial depositional settings.

CONCLUSIONS

The Ferris and Hanna coal beds represent a significant energy resource in the Hanna

and Carbon Basins in south-central Wyoming. The mining history and

development spans about 130 years and continues to support local and national

consumers. The most important use of this high-rank coal resource is fuel for

electric power generating plants. Presently, open-pit mines produce from the Ferris

coal beds and zones, and underground and open-pit mines produce from the Hanna

coal beds and zones. Production from these coal mines supports seven in-state

electric power plants and one degasification plant. Coal production in 1998 from

three mines was more than 3.1 million short tons (Resource Data International, Inc.,

1998).

In order to evaluate subbituminous A to high-volatile C bituminous coal needed for

electric power plants during the next century, assessment of Ferris and Hanna coal

in the Hanna and Carbon Basins in Wyoming concentrated on the compliant coal

beds of the Ferris 23, 25, 31, 50, and 65, Hanna 77-79, 81, as well as the Johnson107 coal beds and zones. Estimates of coal resources in these coal beds and zones of

the Hanna and Carbon Basins total 8.71 billion short tons. These coal deposits are as

much as 30 ft thick and have low sulfur, ash, and trace-element contents. The Ferris
HS-20

and Hanna coal beds and zones contain approximately 218 million tons of

remaining strippable coal resources under less than 200 ft of overburden in the

Hanna and Carbon Basins.

The Ferris coal beds may have been deposited in raised swamps and the Hanna coal

beds in low-lying swamps, all associated with fluvial depositional systems. The

variable vertical and lateral distribution of these coal beds and zones reflect

accumulation in dynamic fluvial settings controlled by basin subsidence and tectonic

uplift of the adjoining ancestral mountains. These fluvial environments and tectonic

conditions also influenced the coal quality (for example, rank, ash, sulfur, and trace

elements) of the Ferris and Hanna coal beds and zones. These coal beds will be a

clean and compliant energy resource during the next few decades.
HS-21

REFERENCES

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resources of Wyoming: U.S. Geological Survey Circular 81, 78 p.

Bowen, C.F., 1918, Stratigraphy of the Hanna Basin, Wyoming: U.S. Geological

Survey Professional Paper 108-L, p. 227-235.

Brooks. K.J., 1977, Petrology and depositional environments of the Hanna

Formation in the Carbon Basin, Carbon County, Wyoming: University of

Wyoming, M.S. thesis, 105 p.

Cavaroc, V.V., Flores, R.M., Nichols, D.J., and Perry, W.J., 1992, Paleocene

tectono-facies relationships between the Hanna, Carbon, and Cooper Lake

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v. 76, p. 1257.

Choate, R., and Lent, J., 1977, Steeply-dipping coal beds suitable for in situ

gasification: a resource assessment: Proceedings of the 3rd Annual

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Energy CONF770652, p. 399-411.

Dobbin, C.E., Bowen, C.F., and Hoots, H.W., 1929, Geology and coal and oil

resources of the Hanna and Carbon basins, Carbon County, Wyoming: U.S.

Geological Survey Bulletin 804, 88 p.

Flores, R.M., and Roberts, S.B., 1996, Drainage-network evolution during

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Geological Society of America, Abstracts with Programs, Denver, Colorado,

p. A372.

Gardner, A.D., and Flores, V.R., 1989, Forgotten Frontier, A History of Wyoming

Coal Mining: Westview Press, Boulder, Colorado, 243 p.
HS-22

Glass, G.B., 1972, Mining in the Hanna coal field: Geological Survey of Wyoming

Miscellaneous Report, 45 p.

_____1977, Wyoming coal deposits, in Murray, D.K., ed., Geology of Rocky

Mountain Coal, Proceedings of the 1976 Symposium: Colorado Geological

Survey Resource Series 1, p. 73-84.

_____1978, Coal analyses and lithologic descriptions of five core holes drilled in the

Carbon Basin of southcentral Wyoming: Geological Survey of Wyoming

Report of Investigations No. 16, 97 p.

Glass, G.B., and Roberts, J.T., 1979, Remaining strippable coal resources and

strippable reserve base of the Hanna coal field in south-central Wyoming:

Geological Survey of Wyoming Report of Investigations No. 17, 166 p.

_____1980, Coal and coal-bearing rocks of the Hanna coal field, Wyoming:

Geological Survey of Wyoming Report of Investigations No. 22, 41 p.

Green, G., and Drouillard, P.M., 1994, Wyoming digital geologic map: U.S.

Geological Survey Open-File Report 94-0425, scale 1:250,000.

Hansen, D.E., 1986, Laramide tectonics and deposition of the Ferris and Hanna

Formations, south-central Wyoming, in Peterson, J.E., ed., Paleotectonics

and Sedimentation in the Rocky Mountain Region, United States: American

Association of Petroleum Geologists Memoir 41, p. 481-496.

Hayden, F.V., 1873, Geologic investigations along the Union Pacific Railroad west

of Como Ridge: U.S. Geological Survey Territory, Second Annual Report,

p. 95-96.

Knight, S.H., 1961, The late Cretaceous-Tertiary history of the northern portion of

the Hanna Basin Carbon County, Wyoming: Wyoming Geological

Association Guidebook, 16th Annual Field Conference, p. 155-164.

Lesquereux, L., 1872, Tertiary flora of North America: U.S. Geological Survey

Territorial Fifth Annual Report, Part 8, p. 306.
HS-23

Lord, N.W., 1913, Analyses of coals in the United States: U.S. Bureau of Mines

Bulletin 22, Part I, Analyses, 321 p.

Love, J.D., 1970, Cenozoic geology of the Granite Mountains area, central

Wyoming: U.S. Geological Survey Professional Paper 495-C, 154 p.

McCartney, J.T., and Teichmuller, 1972, Classification of coals according to degree

of coalification by reflectance of the vitrinite component: Fuel, v. 51, p. 64-

68.

Nichols, D.J., 1994, Palynostratigraphic correlation of Paleocene rocks in the Wind

River, Bighorn, and Powder River Basins, Wyoming, in Flores, R.M.,

Mehring, K.T., Jones, R.W., and Beck, T.L., eds., Organics and the Rockies

Field Guide: Wyoming State Geological Survey, Public Information Circular

No. 33, p. 17-29.

_____1996, Palynological zonation of the Paleocene of the Rocky Mountain

intermontane basins: Geological Society of America, 1996 Annual Meeting,

Abstracts with Programs, v. 28, no. 7, p. 372.

Nichols, D.J., and Ott, H.L., 1978, Biostratigraphy and evolution of the MomipitesCaryapollenites lineage in the early Tertiary in the Wind River Basin,

Wyoming: Palynology, v. 2, p. 93-112.

Perry, W.J., Jr., and Flores, R.M., 1994, Sequential Laramide deformation and deep

gas-prone basins of the Rocky Mountain region, in Dyman, T.S., Rice, D.D.,

and Wescott, W.A., eds., Geologic Controls of Deep Natural Gas Resources

in the U.S.: U.S. Geological Survey Bulletin 2146-E, p. 49-59.

Perry, W.J., Jr., Flores, R.M., and Nichols, D.J., 1996, The role of sequential

Laramide deformation in the northern Rocky Mountains, Montana,

Wyoming, and South Dakota: Geological Society of America, Abstracts

with Programs, Denver, Colorado, p. A371.
HS-24

Pierce, B.S., 1996, Quality and petrographic characteristics of Paleocene coals from

the Hanna Basin, Wyoming, in Stanton, R., ed., Collected Papers from The

Twelfth Annual Meeting of the Society for Organic Petrology: Organic

Geochemistry, v. 24, p. 181-187.

Resource Data International, Inc., 1998, COALdat-Coal database, 1320 Pearl St.,

Suite 300, Boulder, Colorado 80302.

Ryan, J.D., 1977, Late Cretaceous and early Tertiary provenance and sediment

dispersal, Hanna and Carbon Basins, Carbon County, Wyoming: Geological

Survey of Wyoming preliminary Report No. 16, 16 p.

Stricker, G.D., Ellis, M.E., Flores, R.M., and Bader, L.R., 1998, Elements of

environmental concern in the 1990 Clean Air Act Amendments: A

prospective of Fort Union coals in northern Rocky Mountains and Great

Plains region, in Sakkestad, B.A., ed., The Proceedings of the 23rd

International Technical Conference on Coal Utilization and Fuel Systems: p.

967-976.

Teerman, S.C., 1983, A petrographic study of coals from the Hanna coal field,

Wyoming: Southern Illinois University, M.S. thesis, 166 p.

Texas Instruments, Inc., 1978a, Coal resource occurrence and coal development

maps of the Carbon quadrangle, Carbon County, Wyoming: U.S. Geological

Survey Open-File Report 78-044, 29 p.

_____1978b, Coal resource occurrence and coal development maps of the Coal

Bank Basin quadrangle, Carbon County, Wyoming: U.S. Geological Survey

Open-File Report 78-063, 17 p.

_____1978c, Coal resource occurrence and coal development potential maps of the

Como East quadrangle, Carbon County, Wyoming: U.S. Geological Survey

Open-File Report 78-049, 27 p.
HS-25

_____1978d, Coal resource occurrence and coal development maps of the Como

West quadrangle, Carbon County, Wyoming: U.S. Geological Survey OpenFile Report 78-047, 31 p.

_____1978e, Coal resource occurrence and coal development maps of the Dana

quadrangle, Carbon County, Wyoming: U.S. Geological Survey Open-File

Report 78-052, 23 p.

_____1978f, Coal resource occurrence and coal development maps of the Difficulty

quadrangle, Carbon County, Wyoming: U.S. Geological Survey Open-File

Report 78-056, 19 p.

_____1978g, Coal resource occurrence and coal development maps of the Elk

Mountain quadrangle, Carbon County, Wyoming: U.S. Geological Survey

Open-File Report 78-051, 28 p.

_____1978h, Coal resource occurrence and coal development maps of the Elmo

quadrangle, Carbon County, Wyoming: U.S. Geological Survey Open-File

Report 78-045, 227 p.

_____1978i, Coal resource occurrence and coal development maps of the Ferris

Lake quadrangle, Carbon County, Wyoming: U.S. Geological Survey OpenFile Report 78-057, 19 p.

_____1978j, Coal resource occurrence and coal development maps of the Halfway

Hill quadrangle, Carbon County, Wyoming: U.S. Geological Survey OpenFile Report 78-042, 31 p.

_____1978k, Coal resource occurrence and coal development maps of the Hanna

quadrangle, Carbon County, Wyoming: U.S. Geological Survey Open-File

Report 78-054, 26 p.

_____1978l, Coal resource occurrence and coal development maps of the Lone

Haystack Mountain quadrangle, Carbon County, Wyoming: U.S. Geological

Survey Open-File Report 78-062, 19 p.
HS-26

_____1978m, Coal resource occurrence and coal development maps of the Pats

Bottom quadrangle, Carbon County, Wyoming: U.S. Geological Survey

Open-File Report 78-046, 26 p.

_____1978n, Coal resource occurrence and coal development maps of the Schneider

Ridge quadrangle, Carbon County, Wyoming: U.S. Geological Survey

Open-File Report 78-059, 22 p.

_____1978o, Coal resource occurrence and coal development maps of the Seminoe

Dam SE quadrangle, Carbon County, Wyoming: U.S. Geological Survey

Open-File Report 78-048, 28 p.

_____1978p, Coal resource occurrence and coal development maps of the Seminoe

Dam SW quadrangle, Carbon County, Wyoming: U.S. Geological Survey

Open-File Report 78-060, 20 p.

_____1978q, Coal resource occurrence and coal development maps of the TE

Ranch quadrangle, Carbon County, Wyoming: U.S. Geological Survey

Open-File Report 78-055, 29 p.

_____1978r, Coal resource occurrence and coal development maps of the Tenmile

Springs quadrangle, Carbon County, Wyoming: U.S. Geological Survey

Open-File Report 78-050, 22 p.

_____1978s, Coal resource occurrence and coal development maps of the TL Ranch

quadrangle, Carbon County, Wyoming: U.S. Geological Survey Open-File

Report 78-053, 23 p.

_____1978t, Coal resource occurrence and coal development maps of the Walcott

quadrangle, Carbon County, Wyoming: U.S. Geological Survey Open-File

Report 78-058, 21 p.

_____1978u, Coal resource occurrence and coal development maps of the Wild

Horse Mountain quadrangle, Carbon County, Wyoming: U.S. Geological

Survey Open-File Report 78-061, 20 p.
HS-27

Union Pacific Coal Company, 1940, History of the Union Pacific Coal Mines,

1868-1940: The Colonial Press, Omaha, Nebraska, 265 p.

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20241-01, 261 p.

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_____1971, Strippable reserves of bituminous coal and lignite in the United States:

U.S. Bureau of Mines Information Circular IC8531, 148 p.

Veatch, A.C., 1907, Coal in east-central Carbon County, Wyoming: U.S.

Geological Survey Bulletin 316, p. 244-260.

WYOMING

5 0 5 Miles

N

Figure HS2Geologic map of the Hanna and Carbon Basins showing areal distribution of Tertiary

106°45' 106°30' 106°15'

42°00'

41°45'

Faults

Alluvium (Holocene and Quaternary)

Ferris Formation (Paleocene and Cretaceous)

Hanna Formation (Eocene and Paleocene)

Undifferentiated Cretaceous rocks

Saddleback Anticline

Hanna Basin

Carbon

Basin

Seminoe Mountains

Shirley Mountains
Coal

Sandstone

Conglomerate

Biostratigraphic Zones

Mudstone and Siltstone Coal bundles

0

1000

2000

Paleocene

Paleocene

not dated

Hanna Formation

FerrisFormation

Cretaceous

Eocene

P2

P2

F4

F3

P5

H4

H3

H2

H6

Johnson107

H5

F2

F1

P1

P5

P4

H1

P5/

 P6

P2

Numbers of assessed

Ferris coal beds

23-65

Numbers of assessed

Hanna coal beds

77-80

F1, H1

Explanation

Feet

H7

23

25

31

77

81

79

80

78

50

65

Figure HS-3. Stratigraphic subdivisions of the Cretaceous Medicine Bow Formation and Paleocene Ferris and

Hanna Formations in the Hanna and Carbon Basins. Paleocene biostratigraphic zones (P1 through P6) of coal

beds in the Ferris and Hanna Formations in the Hanna Basin are also shown. Ferris coal bundles are F1 through

F4. Hanna coal bundles are H1 through H7. Stratigraphy and coal bed names were adapted from Dobbin and

others (1929).

Medicine Bow

Formation

(Upper Cretaceous)

Ferris Formation

(Upper Cretaceous

and Paleocene) Hanna Formation

(Paleocene and

Eocene)

Carbon

Basin

Hanna

Basin
Figure HS-4. Normal faults showing displacement of Ferris coal beds in the highwall of the Medicine Bow coal mines. 

Photograph by R.M. Flores. 
Figure HS-5. Basal Ferris sandstone showing large-scale trough crossbeds exposed in the southwestern part of the Hanna 

Basin. Photograph by R.M. Flores. 
Figure HS-6. Pebble fragments in the conglomeratic sandstone at the basal Ferris Formation exposed in the 

southwestern part of the Hanna Basin. Photograph by R.M. Flores
Figure HS-7. Laterally extensive basal conglomeratic sandstone of the Hanna Formation exposed along the central 

part of the Hanna Basin. Photograph by R.M. Flores.
Figure HS-8. Interbedded coal, mudstone, siltstone, and sandstone in the Ferris Formation. The buff sandstone on the 

upper right is a lens-shaped, fluvial channel deposit. Photograph by R.M. Flores.
Figure HS-9. Thick coal and carbonaceeous shale overlain by tabular crevasse splay sandstone in the Hanna Formation. 

Photograph by R.M. Flores
Figure HS-10. Lens-shaped, narrow fluvial channel sandstone (light) bounded by coal, mudstone, and siltstone in the 

Hanna Formation. Photograph by R.M. Flores.
Figure HS-11. Laterally extensive fluvial channel sandstone (buff) showing pinch out on the left and bounded by 

mudstone, siltstone, and coal in the Ferris Formation. Photograph by R.M. Flores.
Figure HS-12. Thick, stacked, multi-erosional sandstone deposited in braided streams of the basal Hanna

Formation. Photograph by R.M. Flores.
Figure HS-13. Thin to thick, laterally offset, erosional-based sandstone deposited in meandering streams of the Hanna 

Formation. Photograph by R.M. Flores.
Figure HS-14. Laterally contemporaneous fluvial channel sandstone flanked by flat-bedded crevasse splay 

sandstone, siltstone, and mudstone representing anastomosed stream deposits of the Ferris Formation. Photograph 

by R.M. Flores.
Figure HS-15. Trough crossbedded fluvial channel sandstone overlain by conglomerate deposited in alluvial fans of 

the Hanna Formation exposed along the northern flank of the Medicine Bow Mountains. Photograph by R.M. Flores.
Figure HS-16. Boulder to pebble conglomerate deposited in alluvial fans of the Hanna Formation exposed along the 

northern flank of the Medicine Bow Mountains. Photograph by R.M. Flores.
Figure HS-17. Outcrop of the Johnson coal in the south Carbon coalfield. Photograph by R.M. Flores.
ELK

MOUNTAIN

HANNA

MEDICINE

BOW

HANNA BASIN

CARBON BASIN

T 21 N

T 22 N

T 23 N

T 24 N

T 25 N

R 86 W R 85 W R 84 W R 83 W R 82 W

R 81 W

R 80 W

R 79 W R 78 W R 77 W

C2

C4

C3

4

2

2

1

3

6 5

10 11

12 13

7

8

9

C1

SAD DL

EBA

C

K

HIL

LS

Vitrinite reflectance value

in percent Ro

Wyoming Geological Survey

core hole location

0

0 10 Kilometers

5 10 Miles

WYOMING

Figure HS-18. Map showing variations in vitrinite reflectance of the Ferris coal in the western part

of the Hanna Basin and the Hanna coal in the eastern part. Modified from Teerman (1983).CARBON CO.

ALBANY CO.

N

EXPLANATION

0.45

0.45

0.50

0.55

0.50