Strippable Lignite 

Deposits, Slope and 

Bowman Counties 

North Dakota

GEOLOGICAL SURVEY BULLETIN 1015-E

Strippable Lignite 

Deposits, Slope and 

Bowman Counties 

North Dakota

By ROY C. KEPFERLE and WILLIAM C. CULBERTSON

A CONTRIBUTION TO ECONOMIC GEOLOGY 

GEOLOGICAL SURVEY BULLETIN 1015-E

A description of two deposits 

that contain 1,370 million short 

tons of strippable lignite

UNITED STATES GOVERNMENT PRINTING OFFICE, WASHINGTON : 1955
V , ^«

t ;

, f V . 

UNITED STATES DEPARTMENT OF THE INTERIOR 

Douglas McKay, Secretary

GEOLOGICAL SURVEY 

W. E. Wrather, Director

For sale by the Superintendent of Documents, U. S. Government Printing Office 

Washington 25, D. C. - Price $1 (paper cover)
CONTENTS

Page

Abstract________________________________________ 123

Introduction __ ______________________________ .______.. 124

Previous geologic work________________________________ ______ 127"

Acknowledgments-___________________________ _________ 12§

Geography. ______________ __________________ _______ 128

Surf a ce features _______________________________________________ 129

Drainage and water supply____..________________________________ 131

Climate--__________.._________________..-______ 131

Settlement and land use_________________________________________ 131

Transportation.- _______________________________________________ 132

Electric Power._____"_________..______________________________ 132

Land ownership_______________________________________________ 133

Stratigraphy______ ________________________________________________ 133

Fort Union formation_________..________________________________ 134

Ludlow member___________________________________________ 134

Tongue River member. ___ _________________________________ 134

Sentinel Butte shale member..______________________________ 135

White River formation.________________________________________ 136

Terrace deposits and Recent alluvium..__________________________ 137

Structure____________________.____________----__-_----__ 137

Lignite____________________________________.____------_- 137

Physical and chemical characteristics.__________________________ 137

Leonardite__ _ _________________________________________________ 140

Clinker and its relation to lignite________________________________ 140

Principal lignite beds__________________________________________ 142

History of mining.____________________________________________ 144

Utilization___________________.______________________________ 146

Scope and method of investigation__._________________________________ 147

Criteria for selection of strippable deposits________________________ 147

Preliminary investigation._______________________________________ 150

Detailed investigation._________________________________________ 150

Determination of thickness of the lignite_____-___-______---_- 151

Plotting of outcrop and overburden lines_____________________ 152

Estimation of strippable reserves,___________________________ 152

Estimation of stripping ratio,________________-__-----__----_ 153

Deposits of strippable lignite______________________________________ 153

Bowman deposit_____________________________________________ 153

Northern part___________________________________________ 154

Topography and land use________________-_-_--__------- 154

Harmon lignite bed____________________________________ 155

Overburden and floor rock______________________________ 155

Reserves and stripping ratio_________________-_-_----___ 156
IV CONTENTS

Deposits of strippable lignite Continued 

Bowman deposit Continued

North-central part_________________________ ___ 156

Topography and land use__________________________ 157

Harmon lignite bed______________ _____________ 157

Overburden and floor rock_____________________________ 158

Reserves and stripping ratio____________________________ 159

South-central part________________________________________ 159

Topography and land use____________________________ 159

Harmon lignite bed_________________________________ 160

Overburden and floor rock____________________ 161

 - Reserves and stripping ratio____________________________ 162

 '* Southern part___________________________________ 162

'' Topography and land use_________________________ 162

Harmon lignite bed__________________________________ 163

Overburden and floor rock_____________________________ 164

Reserves and stripping ratio.___________________________ 165

Scranton deposit.___________________________________________ 165

Topography and land use_________________________________ 166

Harmon lignite bed_______________________________________ 166

Overburden'and floor rock_________________________________ 168

Reserves and stripping ratio______________________________ 168

Possible deposits of strippable lignite_________________________ 169

Deposit 1___________________________________ 169

Deposit 2______________________________________ 172

Deposit 3______________________________________ 174

Deposit 4______________________________________ 176

Literature cited.__________________________________________________ 178

Index.___________________________________________ 181

ILLUSTRATIONS

[Plates 14-20 in pocket]

Page

PLATE 12. A, Clinker formed around vent for hot gases; B, Slumped surface and fissures caused by burning of Harmon bed_______ 141

13. Loading lignite at the Peerless mine______________________ 146

14. Generalized columnar sections, showing stratigraphic position 

and suggested correlation of main lignite beds.

15. Map of northern and north-central parts of Bowman strippable deposit.

16. Map of southern and south-central parts of Bowman strip- 

: pable deposit.

17. Sections of Harmon lignite bed in northern and north-central 

, *. parts of Bowman strippable deposit.

18. Sections of Harmon lignite bed in southern and south-central 

parts of Bowman strippable deposit.

19. Map of Scranton strippable deposit.

20. Sections of Harmon lignite bed in Scranton strippable deposit.
CONTENTS V

Page 

FIGURE 18. Index map of the Fort Union-Powder River coal region,

showing location of area described in this report.-._______ 124

19. Index map of Slope and Bowman Counties, N. Dak., showing

deposits of lignite described in this report______________ 125

20. Map of the east half of section 24, T. 132 N., R. 102 W., 

Bowman County, N. Dak., showing location of prospect 

holes___________________.______________ 163

21. Sketch map of possible strippable deposit 1 ________________ 170

22. Sections of Harmon lignite bed in and near possible strippable

deposit !_______________________-._________.._..____ 171

23. Sketch map of possible strippable deposit 2________________ 172

24. Sections of Harmon lignite bed in and near possible strippable

deposit 2________________________________________ 173

25. Sketch map of possible strippable deposit 3___-____--___-__ 174

26. Sections of T Cross lignite bed in and near possible strippable

deposit 3__-____-__--_-________-____-__-..-__----_---_ 175

27. Sketch map of possible strippable deposit 4___.______________ 176

28. Sections of Hansen lignite bed in and near possible strippable

deposit 4_________._______________________________ 177

TABLES

TABLE 1. Thickness, strip ratio, extent, and indicated remaining reserves

in the Bowman and Scranton deposits.__--_________-_- 126

2. Monthly and annual runoff of three rivers____.____________ 130

3. Analyses of lignite from Slope and Bowman Counties, N. Dak._ 139

4. Lignite produced in Slope and Bowman Counties, N. Dak.,

1925-52. ____._.____...._________-..___-_.-_---. 145

A CONTRIBUTION TO ECONOMIC GEOLOGY

STRIPPABLE LIGNITE DEPOSITS, SLOPE AND BOWMAN 

COUNTIES, NORTH DAKOTA

By ROT C. KEPFERLE and WILLIAM C. CULBERTSON

ABSTRACT

Slope and Bowman Counties, N. Dak., include an area of about 2,450 square 

miles in the southeastern part of the Fort Union coal region of North Dakota, 

South Dakota, and Montana. In anticipation of a future increase in the demand 

for the low-rank coal of this region as a fuel for electric power plants and as a 

raw material for various chemical synthesizing processes, Slope and Bowman 

Counties were investigated for deposits of lignite that could be mined by large 

scale strip mining methods. All the lignite beds of economic importance in this 

area are in the Fort Union formation, particularly in the Tongue River member. 

The beds are nearly horizontal, dipping about 25 to 50 feet per mile north and 

northeast from the Cedar Creek anticline in the southwest corner of the area. 

The rocks overlying the lignite beds are generally incompetent and consist mainly 

of massive friable sandstone, shale, clay, and a few thin beds of fresh water 

limestone. At least 9 lignite beds in the Fort Union formation are known to 

attain a thickness of 5 feet, and the thickest and most extensive of these, the 

Harmon bed, attains a thickness of about 40 feet. Two large deposits in the 

Harmon bed, the Bowman deposit lying north of Bowman, N. Dak., and the 

Scranton deposit lying east of Scranton, N. Dak., are particularly well suited to 

mining by large scale strip mining methods. Two other deposits in the Harmon 

bed and one deposit in the Hansen and one in the T Cross bed are possibly suited 

to large scale strip mining.

The coal in the Bowman and Scranton deposits is a woody-textured darkbrown lignite, containing some impurities of pyrite and gypsum, but generally 

free of partings. On the "as received" basis the heating value is about 6,300 

Btu, slightly less than the average for North Dakota lignites. The ash and 

sulfur content are fairly low and the moisture content is high. On exposure to 

air, the lignite loses moisture rapidly and slacks readily into small pieces. It 

is well suited to the manufacture of synthetic liquid fuels, ammonia, dyes and' 

other chemicals.

Both the Bowman and the Scranton deposits lie beneath less than 120 feet of 

overburden. The reserves in the two deposits, in a bed averaging 24 feet thick,

123
124 CONTRIBUTIONS TO ECONOMIC GEOLOGY

CANADA

1. Central Rosebud Counties, Mont Bull. 995-1

2. Southern Custer and northern Powder River Counties, Mont Bull. 995-£

3. Southern Richland and northern Dawson Counties, Mont Bull. 995 H

4. Wibauxarea, Mont, and N. Dak. Bull. 995-6

5. Slope and Bowman Counties, N. Dak. This report

FIGURE 18. Index map of the Fort Union-Powder River coal region, showing location of 

area described in this report, and the areas in eastern Montana in which deposits of / 

etrippable coal have been described in bulletins of the U. S. Geological Survey.

total about 1,370 million short tons of lignite, of which about 590 million tons 

are under less than 60 feet of overburden and can be recovered at a stripping 

ratio of about 1.7 to 1. The Bowman deposit contains 80 percent of all reserves. 

About 75 percent of the reserves under less than 60 feet of overburden are within 

half a mile of any point at which information about the thickness of the lignite 

was obtained, and all the reserves are in the indicated category of the reliability 

classification of coal reserves.

INTRODUCTION {

As part of the program of the United States Department of the 

Interior for the integrated development of the Missouri River basin,
STRIPPABLE LIGNITE, SLOPE AND BOWMAN COUNTIES, N. DAK. 125

BILLINGS CO

EXPLANATION

 R. 107 W.I a R. 106 W. R. 105 W. R. 104 W. R. 103 W. R. 102 W. R. 101 W. R. 100 W, R.99W.

104° SOUTH DAKOTA

FIGURE 19. Index map of Slope and Bowman Counties, N. Dak., showing location of 

deposits of lignite described in this report.

the United States Geological Survey is reinvestigating some of the 

coal-bearing areas of the Fort Union coal region (fig. 18) to find 

deposits of coal that are particularly well suited to recovery by largescale strip-mining methods. This report describes in detail 2 deposits 

of strippable lignite in Slope and Bowman Counties, N. Dak., that 

contain a total of about 1,370 million short tons of lignite under less 

than 120 feet of overburden (table 1). It also outlines 4 other deposits 

that are potentially suited to strip mining and that contain additional 

reserves totaling about 600 million short tons (fig. 19). Slope and 

Bowman Counties lie in the southwestern corner of North Dakota and 

comprise an area of about 2,450 square miles. Other reports on strippable coal in the Fort Union coal region described areas in eastern 

Montana (Brown and others, 1954; Culbertson, 1954; Kepferle, 1954; 

and May, 1954).

319129 55-
126 CONTRIBUTIONS TO ECONOMIC GEOLOGY

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STRIPPABLE LIGNITE, SLOPE AND BOWMAN COUNTIES, N. DAK. 127

Strip-mining methods are particularly advantageous in mining coal 

in the Fort Union coal region, for this region contains many thick, 

continuous, and nearly horizontal beds of lignite at shallow depths, 

and the overburden is soft and easily removed. The trend in this 

region, as in the nation, has been towards the recovery of coal by 

strip mining rather than by underground mining. In the 25-year 

period from 1926 to 1951, for example, the production of lignite from 

strip mines in North Dakota increased from 37 percent of the national 

total to 92 percent (Tryon and others, 1926, p. 488; Young and others, 

1952, p. 20). Since 1946 all mining in Slope and Bowman Counties 

has been by strip-mining methods. The primary reason for this trend 

is that less manpower and more machinery are used in strip mining 

than in underground mining, and it is correspondingly less expensive. 

In 1951, the North Dakota coal was produced at the rate of 23.30 tons 

per man day by strip mining as compared with 7.57 tons per man day 

for underground mining (Young and others, 1952, p. 67); in Montana 

the difference is even more striking, for coal was produced at the rate 

of 89.93 tons per man day for strip mines as compared with 6.83 tons 

per man day for underground mines. Another advantage of strip 

mining is its better recovery of coal. Because of the necessity for leaving large amounts of coal in roofs and pillars, only about 50 percent 

of a bed is usually recovered by underground mining (Averitt and 

Berryhill, 1950, p. 8), whereas in strip mining as much as 95 percent 

is recovered (W. V. Styles, 1951, superintendent of Foley Bros., Inc., 

mining company, at Colstrip, Mont., oral communication). Because 

of the conspicuous advantages of strip mining, future large-scale coal 

mining in this area probably will be by strip-mining methods.

PREVIOUS GEOLOGIC WORK

Although the occurrence of lignite along the Little Missouri River 

was mentioned in the literature as early as 1896 (Darton, 1896, p. 603- 

694), it was not until 1911 that a detailed investigation was made in 

this area. In 1911-12 the U. S. Geological Survey investigated that 

part of Slope and Bowman Counties west of and including R. 102 W. 

as part of the Marmarth lignite field and published a map of the lignite beds at the scale of 1:126,720 (Hares, 1928). The North Dakota 

Geological Survey studied the lignite deposits of western North 

Dakota intermittently during the early 1900's, and in 1925 published 

a summary report that contained a section describing the lignite deposits of Slope and Bowman Counties (Leonard, 1925, p. 58-77). In 

preparing the present report the writers have drawn freely from these 

reports.
128 CONTRIBUTIONS TO ECONOMIC GEOLOGY

ACKNOWLEDGMENTS

Important information about the depth and thickness of the lignite 

beds was generously given by the following companies and individuals: 

Magnolia Petroleum Co. and the Shell Oil Co., who provided the logs 

of seismograph shotholes; Mr. T. Harris of the H and H Drilling Co., 

and Mr. W. Wagner, who furnished the logs of water wells that had 

been drilled in the area; Mr. B. Meggers, operator and co-owner of 

the Meggers Bros, mine, north of Rhame; Mr. T. Carignan, superintendent of the Knife River Coal Co.'s Peerless mine near Gascoyne; 

Gustav Helm of Helms Bros. Inc., the company that maintains the 

stripping operation at the Peerless mine; and W. M. Edmunds of 

Grand Forks; all permitted the use of drill-hole data in their possession. The staff of the area office of the U. S. Soil Conservation 

Service kindly allowed the use of their office facilities and aerial 

photographs. The hospitality and information given by the Harold 

Brooks family, the Roen brothers, and other farmers and ranchers in 

the area greatly aided the investigation. Robert L. McMurtrie, Alexander C. Burr, Alfred F. Traverse, and other members of the staff of 

the U. S. Bureau of Mines Lignite Research Laboratory at Grand 

Forks, N. Dak., freely furnished much valuable information about 

the composition and utilization of lignite.

The field work forming the basis of this report was done during 

the summer and fall of 1952 with the assistance of W. T. Arnesen.

GEOGRAPHY

SURFACE FEATURES

The area covered by this report is in the unglaciated Missouri 

Plateau section of the Great Plains physiographic province. The 

topography reflects the position of the area, for the western half 

has the dissected uplands of the western part of the Missouri Plateau 

and the eastern half has the nearly featureless plains of the eastern 

part of the plateau.

The conspicuous surface feature of the western part of the area 

is the valley of the Little Missouri River. The Little Missouri River 

flows northward through the area in a meandering channel that is 

from 100 to 200 feet below the old, nearly level surface of the adjacent 

countryside (Hares, 1928, p. 8). Many tributaries have dissected the 

adjacent rocks into a zone of badlands that extend several miles back 

from the river. The character of the badlands depends largely upon 

the kind of rocks in which they are cut. In western Bowman County, 

where the rocks are predominantly soft clayey sediments, the badlands 

consist of many low rounded hills and deep, vertical-sided gullies. In
STRIPPABLE LIGNITE, SLOPE AND BOWMAN COUNTIES, N. DAK. 129

northwestern Slope County, where the sediments contain many hard 

strata, erosion has produced steep cliffs, pinnacles, narrow serrate 

ridges, and other weirdly shaped features that have made the badlands 

of the Little Missouri River the primary scenic attraction of North 

Dakota. In the eastern two-thirds of Slope and Bowman Counties, 

the surface ,is predominantly level to rolling, although somewhat hilly 

in the upper part of the Deep Creek drainage basin.

The most conspicuous surface features in this part of the area are 

the many buttes that project as much as 500 feet above the adjacent 

countryside; their tops are capped by layers of resistant rock, including clinker, ortho-quartzite, and sandstone. H T Butte, the largest 

and highest, is capped by a bed of massive sandstone. Its level top, 

3,468 feet above sea level, is the highest po,int in North Dakota and 

dominates the central part of Slope County.

The total relief of the area, measured from the Little Missouri River 

in T. 136 N., R. 102 W., to the top of H T Butte, is about 1,070 feet, 

Throughout most of the area, however, the relief seldom exceeds 400 

feet.

DRAINAGE AND WATER SUPPLY

The drainage of Slope and Bowman Counties is divided almost 

equally between the northward-flowing Little Missouri River, on 

the west, and the eastward-flowing Cannonball and Grand Rivers, on 

the east. All three are perennial streams and tributaries of the Missouri River. Runoff .reaches these rivers from many creeks, which 

usually are dry except during heavy rains and during the spring 

thaw. Springs furnish a small but steady flow to parts of the larger 

creeks throughout the year. The area is well drained by these creeks; 

in fact, rain and melt water drain away so rapidly that many farmers 

have built small earthen dams in the creek beds to retain the water for 

the use of the livestock, and to check erosion. Several large dams that 

back up perennial lakes about half a square mile in area have been 

built to aid wildlife.

Immediate supplies of water in this area probably are not adequate 

for thermal electric power plants, synthetic liquid fuels plants or 

other potential industrial consumers of large amounts of lignite. The 

sandstone and lignite beds of the Fort Union formation furnish sufficient ground water for the needs of the farmers and ranchers in the 

area, but most of the towns are supplied from deep wells reaching the 

Fox Hills sandstone. All ground water, however, is so highly mineralized that it must be treated before being used in boilers. In a 

few places "black" water is obtained from shallow wells, the dark 

color presumably resulting from the flow of ground water through 

weathered lignite. The nearest large, reliable supplies of water are
TABLE 2. Monthly ana annual runoff in acre-feet of three rivers a

[Adapted from U. S. Geological Survey Water-Supply Pa

Water year

1939-40 

1940-41 

1941-42 

1942-43 

1943-44......................

1944-45...... .......-.....

1945-46- -- --_-

1946-47 

1947-48 . . _ ..

1948-49 

Little Missouri River at Marmarth, N. Dak.

Monthly

Maximum i

29, 600 

159, 500 

58, 570 

119, 200 

300, 700 

140, 900 

81, 670 

170, 100 

92,090 

217, 200

Minimum 8

0 

0 

12 

719 

0 

60 

309 

877 

379 

0

Mean

11, 000 

23,200 

16, 590 

26, 300 

54,780 

16,600 

14, 500 

41,100 

18,800 

26,200

Annual

131, 900 

278, 900 

199, 060 

315, 500 

657, 370 

199, 000 

173, 900 

493, 700 

225, 300 

314, 100

Missouri River at Mobridge, 

Monthly

Maximum *

1, 750, 000 

2, 474, 000 

3, 305, 000 

4, 405, 000 

4, 799, 000 

2, 521, 000 

2, 122, 000 

3, 785, 000 

3, 882, 000 

3, 371, 000

Minimum 4

207, 900 

325, 300 

336, 400 

320, 300 

705, 100 

707, 800 

419, 300 

480,200 

548, 800 

505, 200

Mean

802, 000 

986, 000 

1, 220, 000 

1, 848, 000 

1, 816, 000 

1, 403, 000 

1, 151, 000 

1, 833, 000 

1, 906, 000 

1, 616, 000

1 Maximum monthly runoff usually occurs in March, but in some years as late as in July.

* Minimum monthly runoff usually occurs in January, but discharge in fall months is also low.

3 Maximum monthly runoff usually occurs in June.

4 Minimum monthly runoff usually occurs in December, January, or February.
STRIPPABLE LIGNITE, SLOPE AND BOWMAN COUNTIES, N. DAK. 131

the Missouri River at Mobridge, S. Dak., and the Yellowstone River 

at Fallon, Mont. Mobridge is about 170 miles east of Bowman, 

N. Dak., and Fallon is about 115 miles west. During the period 1939- 

49 the Missouri Eiver at Mobridge had an average annual runoff of 

about 17,500,000 acre-feet (table 2), while the Yellowstone Eiver at 

Miles City, Mont. the gaging station nearest Fallon had an average 

annual runoff of 8,767,000 acre-feet. The only large source of water 

within the area is the Little Missouri Eiver. During the 10-year 

period from 1939 to 1949 the annual runoff averaged about 300,000 

acre-feet, but runoff is so variable from year to year and during the 

year that the river would have to be dammed to assure a continuous 

supply.

CLIMATE

The climate of Slope and Bowman Counties is semiarid. The average annual precipitation is about 15 inches; 70 percent falls as rain 

from April to September, and the rest as snow during the other 

months. The precipitation is variable, however, and drouths are 

sometimes severe. Summer is a relatively pleasant time of year in 

this area, for, although the daytime temperatures sometimes exceed 

100° F., the humidity is low and the nights are usually cool. Winter 

is a time of extreme cold. Although the winter is milder in this area 

than that of the rest of North Dakota January temperatures average 14° F. compared to a State average of 7° F. temperatures of 

 30° F. and lower are often recorded. Heavy snows are uncommon, 

but each year one or two blizzards violent storms combining high 

winds, snow, and low temperatures can be expected to stall traffic 

and endanger the lives of any who venture out in them. The growing season is short; killing frosts can be expected as late in the spring 

as the middle of May, and as early in the fall as the middle of 

September.

SETTLEMENT AND LAND USE

According to the 1950 census, the combined population of Slope and 

Bowman Counties is 6,316. Bowman, the county seat of Bowman 

County, is the largest of the incorporated towns, having a population 

of 1,382. The other incorporated towns are Marmarth (469), Scranton (360), Bhame (340), Amidon (82), and Gascoyne (76). With 

the exception of Amidon, the county seat of Slope County, these towns 

are all located on the main line of the Chicago, Milwaukee, St. Paul, 

and Pacific Railroad, and on XI. S. Highway 12. The townspeople 

constitute only 43 percent of the population; the others live on farms 

and ranches and are settled mostly throughout the central and eastern 

parts of the area; the western part is very sparsely settled. Exclusive of the towns, the population density is l1/^ persons per square 

mile.
132 CONTRIBUTIONS TO ECONOMIC GEOLOGY

In the early days of settlement the land was used only for raising 

cattle, horses, and sheep, and the grass proved to be well suited to this 

purpose. With the coming of the railroad in 1907, however, large 

numbers of homesteaders moved in and started to raise wheat and 

other crops on most of the arable land. Eventually most of the farms 

reverted to grassland. In 1940, only about 25 percent of the land 

was cultivated. The subsequent high crop prices, however, again 

focussed interest on the raising of grain. Cultivated acreage was 

increased until at present (1952) about 60 percent of the central and 

eastern part of the area is devoted to the raising of grain, principally 

wheat. In the western part of the area mostly badlands livestock 

raising is still the principal industry.

TRANSPORTATION

The only railroad within Slope and Bowman Counties is the main 

line of the Chicago, Milwaukee, St. Paul, and Pacific Railroad. This 

line connects the area with Mobridge and Aberdeen, S. Dak., on the 

east, and with Miles City, Mont., by way of Terry, Mont., on the west.

The two main roads are U. S. Highways 12- and 85. U. S. 12 is an 

all-weather paved road that crosses the area from east to west, paralleling the railroad. U. S. Highway 85 is paved only from the northern border of Slope County to Amidon, elsewhere it is gravelled. 

U. S. 85 extends south from Belfield, N. Dak., passes through Amidon 

and Bowman, and continues on to the Black Hills. North Dakota 

State Route 21, which is paved in part, leads east from U. S. 85 to 

New England, N. Dak. On the west side of the Little Missouri, the 

only north-south road of any consequence is gravelled North Dakota 

State Route 16, which connects with U. S. 10 to the north at Beach, 

N. Dak. With the exception of these roads the ease of travel within 

the area depends largely on the topography. The badlands area of 

the Little Missouri River, which comprises the western quarter of 

Bowman County and the northwestern half of Slope County, contains 

only a few scattered roads, usually of poor quality. The uplands 

area, on the other hand, which makes up the rest of Slope and Bowman Counties, contains roads on nearly every section line. Some of 

these roads are clinker or gravel surfaced, although most are merely 

graded or unimproved. Travel by car is possible almost anywhere on 

the uplands area in dry weather; in wet weather only the surfaced 

roads are passable.

ELECTRIC POWER

Electric power for this area is furnished by means of a line extending from Mobridge, S. Dak., roughly paralleling U. S. Highway 12 

through Hettinger, Gascoyne, Bowman, and Marmarth, N. Dak., to 

Baker, Mont. This line is a 44,000 volt transmission line between
STRIPPABLE LIGNITE, SLOPE AND BOWMAN COUNTIES, N. DAK. 133

Hetttinger and Baker. Power is furnished by steam electric plants 

operated by the Montana-Dakota Utilities Co. at Mobridge, S. Dak., 

and Bismarck, N. Dak. A connection with a line from Fort Peck, 

Mont., is made by a line extending from Baker to Glendive, Mont. 

Future plans include a connection of this network with the power 

supplied by the Garrison Dam project in N. Dak. Eural domestic 

consumers of power in Slope and Bowman Counties are supplied by 

local electric cooperatives, which in turn are furnished by the Montana-Dakota Utilities Co. line.

LAND OWNEBSHIP

All the land in Slope and Bowman Counties originally belonged to 

the Federal Government. Sections 16 and 36 of every township in the 

State of North Dakota were set aside as school lands, and practically 

all the rest of the land passed into private ownership. Much of the 

school land has since been sold to private interests. In the late 1930's 

the Federal Government commenced buying submarginal farm land 

for soil conservation purposes, and now owns about 160,000 acres, 

nearly all in Slope County. The surface rights of nearly all the land 

overlying the strippable deposits are now in private hands.

Before 1950 the coal rights in this area belonged to individual 

farmers, to coal mining companies, and, in small part, the Federal 

Government. Since the discovery of oil in commercial amounts in 

North Dakota in 1951, however, there has been much selling and leasing 

of mineral rights. Some of the leases specify only oil and gas rights, 

but many of them include coal rights as well.

STRATIGRAPHY

The rocks that crop out in Slope and Bowman Counties, N. Dak., 

comprise the Pierre shale, the Fox Hills sandstone, and the Hell Creek 

formation of Late Cretaceous age; the Fort Union formation of 

Paleocene age; the White River formation (imdifferentiated) of 

Oligocene age; and terrace deposits and alluvium of Pleistocene and 

Rec'ent age (Benson, 1952). The Pierre shale is a dark-gray or tan 

marine shale; the uppermost 400 feet is exposed in the extreme western 

part of Bowman County along the crest of the Cedar Creek anticline. 

The Fox Hills sandstone rests conformably on the Pierre shale and is 

exposed along the flanks of the anticline in western Bowman County, 

and southwestern Slope County. The Fox Hills sandstone consists of 

40 to 85 feet of light-brown concretionary, marine sandstone, which 

grades upward into a light-gray sandstone, 15 to 45 feet thick, that is 

equivalent to the Colgate member of the Fox Hills sandstone of eastern 

Montana (W. E. Benson, U. S. Geological Survey, written communication, 1954). The Hell Creek formation, the uppermost Upper Cre319129 55 3
134 CONTRIBUTIONS TO ECONOMIC GEOLOGY

taceous formation in this area, is nonmarine in origin and unconformably overlies the Fox Hills formation. It consists of about 575 

feet of alternating dark-gray and brown sandstones, shales, bentonitic 

clay, and in the lower 200 feet thin, impure lignite beds. The Hell 

Creek formation crops out in a narrow strip along the Little Missouri 

River in the western part of Bowman and the southwestern part of 

Slope Counties, and forms the badlands in that area.

FORT UNION FORMATION

Rocks of the Fort Union formation crop out over nearly four-fifths 

of the area of Slope and Bowman Counties. The Fort Union formation in this area is comprised of the Ludlow, Tongue River, and Sentinel Butte members, and has a total thickness of about 1,200 feet.

LTTDLOW MEMBER

The Ludlow member of the Fort Union formation consists of dark 

shale, slightly indurated sandstone, and many thin lignite beds. It 

overlies the Hell Creek formation conformably and is distinguished 

from the upper part of the Hell Creek by the absence of fossils of the 

dinosaur Triceratops, by the presence of a Tertiary flora, and by the 

presence of lignite beds. The base of the Ludlow member is marked 

in many places by the Cannonball lignite bed, the lowest persistent 

lignite bed in the area, about 60 feet stratigraphically below the T 

Cross bed. The outcrop of the Ludlow is a sinuous band about 10 miles 

wide and extends from southern Golden Valley County southward 

through northwestern Slope County to southern Bowman County and 

thence eastward to Adams County. This band of outcrop i§ generally 

characterized by low, rolling hills, though buttes are formed locally 

where a resistant bed of the overlying Tongue River member has 

prevented the erosion of the softer Ludlow member. The base of the 

Ludlow coincides with the western limit of commercial lignite shown 

on the index map (fig. 19). The Ludlow is equivalent to the Tullock 

and Lebo shale members of the Fort Union formation in eastern 

Montana, and to the Cannonball formation with which it interfingers 

to the east in Adams, Grant, and Sioux Counties, N. Dak. One finger 

of the Cannonball formation crops out along the Grand River and its 

tributaries in the southeastern corner of Bowman County and two 

tongues of Cannonball are exposed along the Little Missouri River 

near Yule. The total thickness of the Ludlow member in Bowman 

County is about 250 feet.

TONGUE RIVER MEMBER

The Tongue River member in Slope and Bowman Counties comprises 400 to 600 feet of light gray clay and shale, which generally
STRIPPABLE LIGNITE, SLOPE AND BOWMAN COUNTIES, N. DAK. 135

weathers to yellow or buff; gray to buff sandy shale and siltstone; fineto medium-grained massive to crossbedded calcareous sandstone; thick 

persistent lignite beds; and a few thin fresh-water limestone lenses. 

Locally, a massive buff conglomeratic channel sandstone forms the 

base of the Tongue River member, but this apparently only marks a 

local unconformity at the top of the underlying Ludlow member. 

It is difficult to distinguish between clay and shale in the sediments of 

the Tongue River member inasmuch as the two are gradational. The 

shale is generally as incompetent as the clay, and the property of 

fissibility in the shale is obscure.

Where adjacent to the lignite beds, the clays and shales commonly 

contain well formed crystals of gypsum. Nodules of an iron sulfide, 

probably marcasite, are also common, as are small limonite concretions, some of which may result from the oxidation of the marcasite 

nodules. Impressions of leaves and other plant remains are numerous 

in the sediments of the Tongue River member. At several localities, 

of which the best known is atop the Twin Buttes a mile north of 

Bowman, casts of plant stems are preserved in a hard flaggy quartzite 

(Hares, 1928, p. 34-36). Fossils of several invertebrates and plants 

have been collected from this member in Slope and Bowman Counties 

(Hares, 1928, p. 37-39). Numerous fossils of fresh-water mollusks 

were found in a small knoll about 30 feet above the inferred outcrop 

of the Harmon lignite bed along the section line in the SE^SW1/^ 

sec. 34, T. 132 K, R. 101W.

The Tongue River member can be distinguished from the overlying 

Sentinel Butte shale member and the underlying Ludlow member by 

a lighter color, a greater percentage of sandy sediments and lignite 

beds, and by scattered red clinker beds formed by the baking of the 

rocks during the burning of the underlying lignite beds.

SENTINEL, BTJTTE SHALE MEMBER

The Sentinel Butte shale member of the Fort Union formation 

comf onnably overlies and is gradational with the Tongue River member (Brown, 1948, p. 1265-1274). It consists mainly of dark sandy 

shale and clayey sandstone that contains many concretions and darkbrown ferruginous nodules. It also contains a few lignite beds, which 

locally attain minable thickness. It is as much as 350 feet thick in 

Slope County, where it is exposed around the base of H T Butte and 

the uplands to the east. In Slope County the contact between the 

Sentinel Butte shale member and the underlying Tongue River member is placed at the base of the H T Butte lignite bed the highest 

persistent lignite bed in the area. The Sentinel Butte shale is the 

uppermost member of the Fort Union formation and is overlain unconformably by a massive sandstone of the White River formation.
136 CONTRIBUTIONS TO ECONOMIC GEOLOGY

Fossil bones were found by the writers in the Sentinel Butte shale 

about 15 feet below the contact with the White River formation in 

the SE14SE14 sec. 15, T. 134 N., R. 101 W., Slope County, N. Dak. 

These bones tentatively have been identified as remains of a freshwater reptile, Champsosaurus, by J. R. Macdonald, curator of vertebrate paleontology at the museum of the South Dakota School of 

Mines and Technology (oral communication, 1954).

WHITE RIVER FORMATION

The White River formation is of Oligocene age, and consists mainly 

of white calcareous sandstones and shales, bentonite, and a few bentonitic clays (Clarke, 1948, p. 8-10, and Leonard, 1922, p. 218-222). The 

sandstone is locally conglomeratic and contains pebbles from 2 to 

3 inches in diameter. These sediments total about 300 feet in thickness 

south of Amidon in the Chalky Buttes and in White Butte where they 

are best exposed. Remnants of White River sediments also lie atop 

Medicine Pole Hills in Bowman County and East and West Rainy 

Buttes in Slope County.

As described by Hares (1928, p. 40-41), the White River formation 

includes a basal massive, resistant, medium-grained unfossiliferous 

sandstone composed of quartz grains cemented by calcium carbonate 

and including small amounts of muscovite. This sandstone is 60 to 

80 feet thick on H T Butte and presumably is the same sandstone that 

caps the Rainy Buttes about 20 miles northeast of H T Butte. The 

sandstone weathers to yellow brown and the exposed surface is locally 

pockmarked by differential erosion. Hares (1928, p. 41) classed this 

sandstone as Oligocene (?) because of the

«* * * striking contrast of its lithology with that of the underlying rocks; because of a probable erosional unconformity at its base suggested by marked 

local irregularities of thickness of the Sentinel Butte shale; and because of the 

apparent conformability of the sandstone with the normal White River Oligocene deposits that overlie it in White Butte, 6 miles southeast of H T Butte, and 

also in Sentinel Butte, in T. 139 N., R. 104 W. Fragments of white calcareous 

rock resembling normal White River material are present on the top of Bullion 

Butte, which is capped by the massive sandstone under discussion."

According to W. E. Benson (written communication, 1954), this 

same bed on Medicine Pole Hills in Bowman County and on West 

Rainy Butte in Slope County contains a fauna representative of the 

lower White River formation and is Chadron in age. On an eastern 

outlier of the Chalky Buttes in the NE^SW^ sec. 31, T. 134 N., R. 

100 W., a fauna of late Oligocene age was collected in 1953 by J. R. 

Gill and R. C. Kepferle, and identified by Jean Hough of the Paleontology and Stratigraphy Branch. The beds containing the fauna 

correlate with the Brule formation in South Dakota and Nebraska.
STRIPPABLE LIGNITE, SLOPE AND BOWMAN COUNTIES, N. DAK. 137 

TERRACE DEPOSITS AND RECENT ALLUVIUM

Gravel deposits lie in terrace remnants along the uplands bordering 

the Little Missouri River and its larger tributaries, such as Deep 

Creek and Sand Creek, and also along some of the eastward-flowing 

streams of the area. Some of the higher terrace remnants may be of 

Tertiary age, but most are of Quaternary age. These terraces are 

composed of pebbles of igneous rocks and clinker. They also contain 

a few bones, which probably were derived from the reworking of 

sediments of the White Kiver formation. The deposits attain a 

thickness of at least 20 feet.

Alluvium of Recent age is present along the valleys of most of the 

creeks and rivers in the area, attaining a thickness of at least 20 feet 

in the flood plain of the Little Missouri River. This alluvium consists mainly of fine silt, clay, and sand, and locally contains gravel.

STRUCTURE

Slope and Bowman Counties lie on the southwestern flank of the 

Williston structural basin and are crossed in the extreme west by the 

Cedar Creek anticline, also called the Glendive anticline and the 

Baker-Glendive anticline, which extends N. 30° W. from near the 

northwestern corner of South Dakota to Glendive, Mont. Petroleum 

is being produced from the Montana part of this anticline; in the 

North Dakota part, wells have produced gas in western Bowman 

County, but as yet no oil has been found. The Cedar Creek anticline 

is asymmetrical. On the west flank the strata dip southwestward 

from 5° to 20°, and on the east flank, dip generally northeastward at 

about 3°. Eastward from the anticline, the strata are more nearly 

horizontal, and within the lignite-bearing area of Slope and Bowman 

Counties the regional dip is from 25 to 50 feet per mile northeastward 

and northward. Minor undulations of the strata cause local changes 

in the regional dip.

Although aerial photographs show what appears to be a fault scar 

on the west end of H T Butte in sees. 23 and 26, T. 134 N., R. 102 W., 

this evidence could not be corroborated during a cursory field examination of the locality, and no indication of faulting was found elsewhere in the area.

LIGNITE

PHYSICAL AND CHEMICAL CHARACTERISTICS

Fresh lignite in Slope and Bowman Counties is dark brown and has 

a brownish streak. A large part of it has a pronounced woody texture, and is exceedingly tough and resilient. When mined the lignite 

tends to break into irregular elongate or slablike pieces parallel to the
138 CONTRIBUTIONS TO ECONOMIC GEOLOGY

bedding. Examination of the cross section of a bed at a fresh exposure shows that the lignite consists of alternating elongate, roughly 

parallel lenses of previtrain and attrital lignite with a few thin layers 

of black fusain. The previtrain, or woody textured, lenses usually 

range from a fraction of an inch to about 6 inches in thickness and 

are a few inches to several feet long. The lignite in places contains 

impurities: pyrite as fracture fillings or as desseminated masses 

(known as "sulfur balls"); gypsum as fracture fillings; clay in 

layers; and, rarely, silicified wood.

When the lignite is exposed to air, it loses moisture rapidly, cracks, 

and gradually breaks into small fragments. This characteristic of 

lignite, which is called slacking, is a disadvantage for those users who 

prefer lump lignite, but does not necessarily affect its industrial utility 

for those who use finely ground and pea-sized lignite.

Another important characteristic of lignite is the tendency to ignite 

spontaneously when stored in loose piles for long periods. Under 

these conditions, the heat generated by the oxidation of the small particles accumulates until the lignite becomes so hot that it starts smouldering, and it may eventually break into flame. The present practice 

of tfie railroads in North Dakota is to ship the lignite in open cars, for 

the lignite practically never catches fire during the few weeks that it 

is in the car. Lignite will not ignite spontaneously unless a good supply of oxygen is available. When lignite is to be stored for many 

months or years, the best method is to grind it into small sizes, and 

then place it in a pile layer by layer, compacting each layer as it is laid 

down. Other methods of storing lignite are to store it under water, 

in open pits, or in piles covered by road tar.

Analyses of 10 samples of the lignite in Slope and Bowman Counties 

are given in Table 3. Of these, nos. 10218, 10217, A45696, A45697, 

A45698, and D73701 are analyses of samples of the Harmon lignite 

bed taken from mines in the 2 strippable deposits described in this 

report. These 6 analyses show that the Harmon lignite in the deposits 

has an average heating value of about 6,300 Btu and an average moisture content of 42 percent, both on the "as received" basis the as received basis being the equivalent of freshly mined lignite. This heating value is slightly less than the average of North Dakota lignites, 

and the moisture content is somewhat greater. The ash and sulfur 

content of the lignite is fairly low. The ash is of medium fusibility, 

for all the samples tested softened in the from 2200° F to 2600° F 

temperature range. Lignite is more reactive chemically than the 

higher rank coals and is well suited to the various processes for producing synthetic liquid fuels and other chemicals.
TABLE 3. Analyses of lignite from Slope and Bowman Co

[By U. S. Bureau of Mines except where noted] 

Type of sample: DC, core sample from drill hole; M, sample from mine face; T, sample from tipple; Condition of samp

Sample 

no. and 

date of 

analysis

D-68871 

(1951)

14857 

(1912) 

1 10218 

(1934) 

1 10306 

(1934)

A-45696 

(1928)

1 10217 

(1934)

(1946)

A-45697 

(1928)

A-45698 

(1928)

D-73701 

(1951)

Name and location of mine or 

prospect

Drill hole in NEHNW14 sec. 2, T. 

130 N., R. 104 W., Bowman Co.

Durkin prospect, SWJ^sec. 34, T. 

130 N., R. 103 W., Bowman Co. 

Hallenbeckmine, sec. 1, T. 133 N., 

K. 102 W., Slope Co. 

Langer mine, sec. 12, T. 135 N., 

R. 101 W., Slope Co.

Halleck mine, SE}£ sec. 15, T. 132 

N., R. 102 W., Bowman Co.

Bowman mine, sec. 14, T. 132 N., 

R. 102 W., Bowman Co. 

Twin Buttes mine, sec. 2, T. 131 

N., R. 102 W., Bowman Co.

Scranton Mine, SW}4 sec. 24, T. 

131 N., R.100 W., Bowman Co.

Buffalo Creek mine, S WJi sec. 25, 

T. 131 N., R. 100 W., Bowman 

Co. 

Peerless mine, sec. 34, T. 131 N., 

R. 99 W., Bowman Co.

Name and stratigraphic 

position of lignite bed

Harmon(?) bed, Tongue 

River member.

T Cross bed, Ludlow member. 

Harmonbed; Tongue River 

member. 

Unnamed bed (possibly 

H T Butte bed), Sentinel 

Butte shale member. 

Harmon bed, Tongue River 

member.

. _ do _ ..

.....do. _ - . .

Harmon bed (upper bench), 

Tongue River member.

Harmon bed (lower bench), 

Tongue River member.

 ..do..- ...............

Type of 

sample

} DC

} M 

M 

M

| M 

M

} T

} M 

} M

} *

Condition of 

sample

f A 

B

1 o

( A 

1 B

A

A

f A 

1 B 1 c

A

/ A 

1 B

f A 

B

1 c

f A 

1 B I c

( A B 

I o

Proximate analy

Moisture

41.0

43.6

42.5 

44.4

41.1

43.0 

48.3

41.2

39.2

43.1

Volatile 

matter

26.2 

44.4 

53.8 

23.2 

41.2

27.2 

25.2

25.6 

43.5 

48.2 

27.3

46.5 

24.8 

42.2 

47.9 

24.2 

39.8 

45.8 

24.5 

43.0 

49.1

Fixed 

carbo

22.

38.

46.

27.

47.

24.

23.

27.

46.

51.

25.

43.

26.

45.

52.

28.

47.

54.

25.

44.

50.

1 Circular 8, University of North Dakota College of Engineering, 1934.
140 CONTRIBUTIONS TO ECONOMIC GEOLOGY

LEONAKDITE

Leonardite is a colloidal material that can be extracted from weathered lignite by alkaline solutions. It is used in making wood stain and 

dye, and, having the property of swelling and forming a gel, as a 

stabilizing agent in well-drilling fluid. Weathered lignite has been 

mined intermittently since 1942 from pits at locations 62, 64, and 70 

(pi. 16) and at the Peerless mine (location 93, pi. 19) and used for 

the extraction of this material.

Leonardite was named and described by Dove (1926, p. 33). It is 

a waxlike, black or brown, shiny, vitreous material formed by the 

oxidation of lignite, particularly the previtrain layers. Lavine (1939, 

p. 157) also attributes leonardite to humus materials of lignite that 

are changed by progressive oxidation to an alkali soluble form.

In the localities from which leonardite is mined, the lignite has 

been weathered under thin overburden, possibly by means of water 

percolating downward from the surface. At none of these localities 

was the leonardite seen in the form described by Dove, probably because it is disseminated throughout the lignite. Leonardite can be 

concentrated by solution and redeposition, and the waxlike, shiny, 

vitreous material described by Dove is probably leonardite that.has 

been formed in this manner. At present, not enough is known about 

the environment under which it is formed to enable the ready location 

of minable quantities by means of surface exploration. The most 

likely localities are in the areas marked on the deposit maps as "Harmon lignite inferred to be weathered or partly weathered."

CLINKER AND ITS RELATION TO LIGNITE

The term clinker includes all the several types of rock that have 

been changed from their original composition, texture, or appearance 

by the heat of gases given off by the subsurface burning of coal beds. 

In Slope and Bowman Counties the clinker locally called "scoria" 

generally in the form of reddish fissile shale, is notably more indurated 

than the unaltered shale of the Fort Union formation. Locally, the 

original clay, sandstone, or shale of the overburden has been completely fused to form a brittle, resistant rock that now is exposed in 

huge, irregular masses (pi. 12-^4) along the former outcrops of a 

few of the thicker lignite beds.

Some of the more brittle pieces of clinker were fashioned into 

knives, arrowheads and other implements by Indians who once 

roamed this region. The present use of clinker is all-weather-road 

surfacing in areas in which gravel is not readily available.

Although most of the burning of the lignite beds appears to have 

occurred many years ago some of it as early as Pleistocene time 
GEOLOGICAL SURVEY BULLETIN 1015 PLATE 12

A. MASS OF CLINKER FORMED AROUND A VENT FOR HOT GASES GIVEN OFF DURING BURNING

OF HARMON LIGNITE BED

Less resistant clinker has been removed by erosion. View northeast in the SWi/4 sec. 18, T. 133 N., R. 101 W.,

Slope County.

J?. SLUMPED SURFACE AND FISSURES CAUSED BY BURNING OF THE HARMON LIGNITE BED 

View west in the southwest corner of sec. 12, T. 136 N., R. 101 W., Slope County.

141

319129 55 4
142 CONTRIBUTIONS TO ECONOMIC GEOLOGY

a f ow of the beds have been burning since the area was settled. In sec. 

12, T. 136 N., R. 102 W., the Harmon lignite bed is still burning, 

much as it was when visited by Hares in 1912 (1928, p. 50-51). (See 

pi. 12-5). The burning bed has received much publicity as a tourist 

attraction, and no attempt has been made to extinguish the fire. The 

cause of the fire is not known.

PRINCIPAL LIGNITE BEDS

The lignite beds that contain strippable or possible strippable deposits described in this report are the T Cross bed of the Ludlow 

member, the Hansen and Harmon beds of the Tongue Eiver member, 

all in the Fort Union formation. Six other beds in this area are known 

to attain a maximum thickness of at least 5 feet. Two, the H T Butte 

bed of the Sentinel Butte shale member and an unnamed bed possibly 

correlative with the Garner Creek bed of the Tongue Eiver member, 

exceed 10 feet in thickness. The H T Butte bed crops out on the 

slopes of H T Butte and two smaller buttes to the east, as well as along 

the foot of the western slope of the Chalky Buttes, and the other bed 

crops out in the hills in Tps. 132 and 133 N., R. 101 W. (See pp. 161, 

165," and 166.) The stratigraphic relation of these beds within the 

Fort Union formation is shown by generalized columnar sections in 

plate 14. These sections were compiled from information contained in 

published reports of the lignite fields in and near the investigated area, 

from logs of prospect holes, and from logs of seismograph shotholes 

and water wells drilled in the area. The lignite beds discussed below 

were named by Hares and their outcrops are shown on his map of the 

Marmarth lignite field (1928, pi. 14), except for some of the outcrops 

of the Harmon lignite bed east of the Marmarth lignite field, which are 

shown in plates 16 and 19 of this report.

T Cross lignite bed. The T Cross lignite bed is one of the most 

extensive lignite beds in Slope and Bowman Counties. It crops out 

mainly east of the Little Missouri River and lies from 40 to 100 feet 

above the base of the Ludlow member. The T Cross bed has been 

correlated with the Giannonatti bed (Winchester and others, 1916, p. 

73) of South Dakota and has been traced from T. 20 N., R. 8 E., in 

South Dakota through Bowman and Slope Counties, N. Dak., to 

Montana (Hares, 1928, p. 47). Possible strippable deposit 3 is 

mapped in this bed where the thickness of the bed reaches 24 feet and 

probably averages 15 feet. The bed is notably irregular from place 

to place, however, generally ranging from 3 to 9 feet in thickness and 

locally containing too many partings to be of commercial use. The 

only analysis of lignite from this bed was made of a sample taken from 

the Durkin prospect, now abandoned, in the SW1^ sec. 34, T. 130 N.,
STRIPPABLE LIGNITE, SLOPE AND BOWMAN COUNTIES, N. DAK. 143

R. 103 W., Bowman County, N. Dak. (See analysis 14857, table 3.) 

No lignite is now mined commercially from the T Cross bed.

Hansen lignite bed. The Hansen lignite bed crops out along both 

sides of the uplands between Deep Creek and the Little Missouri River 

in Tps. 133 to 136 N., Rs. 103 and 104 W., and along the eastern side of 

Deep Creek in Tps. 132 to 136 N., R. 102 W. It also underlies a few of 

the high, isolated hills in Bowman County. The Hansen bed lies from 

45 to 90 feet stratigraphically above the base of the Tongue River 

member and is from 5 to 60 feet below the Harmon bed. The bed is 

fairly persistent over a wide area. It ranges in thickness from 2.5 to 

13.7 feet at measured exposures, but commonly is from 3 to 7 feet 

thick. Possible strippable deposit 4 is in the Hansen lignite in T. 133 

N., Rs. 102 and 103 W. (fig. 28), where logs of water wells and seismograph shotholes indicate that the bed averages 15 feet in thickness over 

an area of about 12 square miles and reaches a maximum of 25 feet 

in thickness. No lignite is now mined in commercial quantities from 

the Hansen bed, although it is still mined from small open pits by some 

ranchers to satisfy their requirements. No analyses of samples of 

lignite from the Hansen bed are available. According to Mr. B. 

Meggers, a mine operator, local residents prefer lignite from the Hansen bed to that of the other beds in the area because of its excellent 

burning properties.

Harmon lignite bed. The Harmon lignite bed is the thickest bed in 

Slope and Bowman Counties and is one of the thickest and most extensive lignite beds in North Dakota. It lies from 100 to 140 feet above 

the base of the Tongue River member and crops out mainly along the 

uplands bordering the Little Missouri River, Deep Creek, and Sand 

Creek. Clinker on slopes and hilltops in western Slope and Bowman 

Counties at the stratigraphic horizon of the Harmon bed indicate that 

the bed once occupied a much greater area than it does now. The Harmon bed extends northward into Billings and Golden Valley Counties, 

N. Dak., where it correlates with bed A of the Sentinel Butte lignite 

field (Leonard and Smith, 1909, p. 24-25), and thence westward into 

Wibaux, Richland, and Dawson Counties, Mont., where it correlates 

with bed G of the Sidney lignite field (Stebinger, 1912, p. 288). In 

the vicinity of Bowman the Harmon bed has been known as the Bowman bed (Leonard, 1925, p. 62-67), and in the vicinity of Scranton 

it has been called the Scranton bed (Leonard, 1925, p. 59-62, and 

Brant, 1953, p. 46). Hares (1928, p. 94) states that he traced the Harmon bed from outcrops in T. 132 N., R. 102 W. to the vicinity of Scranton with a fair degree of certainty. The investigations of the writers 

indicate that Hares' correlation was probably correct. In the vicinity 

of Scranton the Harmon bed is present in two benches, that locally
144 ' CONTRIBUTIONS TO ECONOMIC GEOLOGY

coalesce to one bed. The lower bench may be considered a separate 

bed, possibly the Haynes bed, in Adams County to the east.

The Harmon bed in Slope and Bowman Counties ranges from 

3 to 37 feet in thickness where measured by the writers and averages 

more than 20 feet in thickness over an area of at least 50 square miles. 

It generally is free of partings. Analyses of samples from the bed are 

presented in table 3. Within the 2 strippable deposits described in this 

report the bed contains a total of 1,370 million short tons, with an additional 310 million tons in 4 possible strippable deposits. Thus, a 

total of 1,680 million tons, or nearly 10 percent of the estimated remaining reserves of the Harmon lignite bed in Slope and Bowman 

Counties (Brant, 1953), are in the strippable or possible strippable 

deposits described in this report.

HISTOBY OF MINING

Commercial mining in Slope and Bowman Counties did not begin 

until after the railroad was built in 1907. Although there were always 

a few mines operating at other localities, Scranton, from the first, was 

the center of mining in the area, because of the thick lignite underlying the town and because it was on the main line of the railroad. 

The Scranton mines provided fuel for the many homesteaders who 

came into the area, and after 1910 increasingly larger amounts of lignite were shipped out. The peak year for production of lignite was 

1927, when 60,346 tons were produced in Bowman County from 4 

mines (table 4), 3 in the vicinity of Scranton 2 underground mines 

and 1 strip mine. Lignite from the mines furnished fuel for a large 

power plant; a briqueting plant was operating at full capacity; and 

a specially designed rotary drying plant was being planned. The depression of the 1930's, however, ended the mining prosperity of the 

area, and the large mines began to cease operations. Locally, farmers 

opened up smaller mines to supply neighboring families, but the 

production of lignite continued to decrease to reach a low of 5,121 

tons for Bowman County in 1945. Production continued low until 

1950, when the Knife River Coal Co. took over the Gascoyne mine 

(in sec. 34, T. 131 K, R. 99 W.), renamed it the Peerless mine, and 

began shipping the lignite to thermal power plants in South Dakota 

and Minnesota. In 1952 the total production of lignite in Slope and 

Bowman Counties was 144,873 tons, of which 99 percent came from 

the Peerless mine.
STRIPPABLE LIGNITE, SLOPE AND BOWMAN COUNTIES, N. DAK. 145

TABLE 4. Lignite produced in Slope and Bowman Counties, N. DaJc., from 1925

through 1952

[From annual reports of the North Dakota State Coal Mine Inspection Department]

Year

1925 __ -

1926 

1927---. _ --

1928 

1929 

1930 

1931- _ - ___ _

1932 

1933 

1934 

1935 

1936 

1937 -

1QQQ

1939 

Bowman 

County

Production 

(short 

tons)

41, 144

55, 286 

60, 346 

45,411 

39, 876

28, 589 

21, 035 

19, 240 

19, 943 

16, 983

15,202 

9,513 

11,376

8,275 

7,024

Number 

of 

mines

5 

4 

4 

5 

5

4 

6 

6 

6 

9

4

7 

5 

5 

5

Slope County

Production 

(short 

tons)

45 

880 

405 

384 

450

378 

20 

65 

219 

209

790 

700 

2,704 

3,054 

2,114

Number 

of 

mines

1 

4 

1 

1 

2

1 

1 

1 

1 

1

4 

3 

6 

11 

4

Year

1940 

1941 __ . . . .

1942 _

1943 . _ 

1944 _ 

1945 __ 

1946 ___ - _ 

1947 

1948 

1949. 

1950 

1951 

1952 

Total.....

Bowman 

County

Production 

(short 

tons)

8,766 

9,214 

10,497 

11, 620 

10, 500

5,121 

6,366 

7,384 

5,186 

5,379

11, 326

84, 689 

144, 188

719, 479

Number 

of 

mines

4 

4 

5 

2 

2

1 

2 

3 

3 

2

2 

2 

2

Slope County

Production 

(short 

tons)

2,293 

2,182 

1,790 

2,192 

966

500 

132

560

225

340 

400 

685

24, 682

Number 

of 

mines

5 

3 

8 

4 

3

2 

2 

2 

1 

1

1 

1 

1

Although Slope County contains about 3 times as much lignite as 

Bowman County 20,091 million tons as compared with 7,021 million 

tons, according to an estimate by Brant (1953) the production of 

lignite from Slope County has always been small, never exceeding 

more than a few thousand tons a year. The reason is clear: the main 

routes of transportation pass through Bowman County, consequently 

the Slope County mines could not compete with the Bowman County 

mines except for local trade.

The mining methods in Slope and Bowman Counties have changed 

radically. In the early days practically all the lignite was produced 

from underground mines. As better earth-moving equipment was 

developed, however, strip mining became more popular, and gradually supplanted underground mining. Since 1946 all mining has been 

by strip-mining methods.

In 1952 only one mine was operating in Slope County the Gress 

mine in sec. 24, T. 136 N., R. 102 W. This mine operates only during 

the fall and winter and supplies lignite to the nearby farmers. Of 

the 2 mines operating .in Bowman County in 1952, the Lamb mine (in 

sec. 25, T. 132 N., E. 105 W.), also has a small production and operates seasonally. The other mine, the Peerless, operates throughout 

the year. At the Peerless mine the overburden is loosened by light 

blasting, and a bulldozer scrapes it from the surface. The lignite is 

loaded into 10-ton trucks by a small diesel-powered shovel (pi. 13) and 

is hauled three-fourths of a mile to the tipple, where it is crushed,' 

screened, and loaded into open railroad cars for shipment.
146 CONTRIBUTIONS TO ECONOMIC GEOLOGY

GEOLOGICAL SURVEY BULLETIN 1015 PLATE 13

LOADING LIGNITE FROM THE LOWER BENCH OF THE HARMON BED AT THE PEERLESS MINE

View northeast in sec. 34, T. 131 N., R. 99 W., Bowman County, N. Dak. The weathered upper bench is

about 7 feet thick and is separated from the main bench of the Harmon bed by about 15 feet of clay.

UTILIZATION

In 1952 about 20 percent of the North Dakota lignite production of 

3 million tons was used for domestic purposes, about 65 percent, for the 

generation of electric power, and the rest, for industries, such as sugar 

refineries (A. Burr, oral communication, 1953). The briqueting of 

lignite increases the heating value and does away with the tendency to 

slack and to ignite spontaneously when stored, but lignite briquets 

have not been able to compete with oil and gas in the domestic market, 

and the industrial user finds it more economical to use lignite as 

mined. At present the largest use of lignite is in the generation of 

electric power; lignite from this area is being shipped to South Dakota and Minnesota for that purpose. The out-of-state market is 

limited, however, because of transportation costs, and competition 

from the higher rank coal from the midwestern fields. Industries 

coming into this area, however, would find that lignite is a cheap and 

abundant fuel.

An increase in competition from petroleum and natural gas in this 

region may be expected in the near future as a result of the newly 

discovered oil fields in western North Dakota and eastern Montana,
STRIPPABLE LIGNITE, SLOPE AND BOWMAN COUNTIES, N. DAK. 147

and the completion, late in 1954, of a natural gas plant and three 

petroleum refineries, as well as pipelines transporting crude petroleum 

and petroleum products.

The most promising use of lignite in the future, in addition to its 

use as an industrial fuel, is as a raw material in the production of 

synthetic liquid fuels and chemicals. Lignite is well suited to the 

production of synthetic liquid fuels, and the tremendous reserves of 

lignite in this region provide a valuable resource, should the supply 

of liquid fuel from other sources run short. Production of other types 

of chemicals, however, show more promise for the immediate future. 

Two processes that appear to be well suited for the extraction of 

chemicals from lignite are gas synthesis and carbonization. The gas 

synthesis process, in which lignite is burned in the presence of steam, 

produces hydrogen and carbon monoxide. These gases can be used 

locally to make other chemical products, of which ammonia, for the 

manufacture of nitrate fertilizers and explosives, has the greatest 

present potential market. The carbonization process, in which lignite 

is heated in the absence of air, produces aromatic chemicals and tars. 

These products are used in the manufacture of a variety of other 

materials, including plastics, synthetic fibers, and sulfa drugs. In 

addition, the solid residue, or char, can be used as fuel. This process 

is being developed at the present time at Rockdale, Tex., where the 

Aluminum Co. of America will carbonize lignite to produce a char to 

be used in generating electricity and will sell the other products to the 

chemical industry.

SCOPE AND METHOD OF INVESTIGATION

The purpose of this investigation was to find large deposits of 

lignite that could be developed economically by strip-mining methods 

and to collect sufficient data on the thickness and depth of these lignite 

deposits so that the reserves of lignite under specified thicknesses of 

overburden could be calculated. The first step in accomplishing this 

purpose was to adopt uniform criteria for selection of deposits that 

can be considered economically strippable. These criteria may not 

conform to those of some strip-mine operations, because operating 

costs and market conditions differ from place to place. They are 

based, however, upon stripping practices of the coal industry of 

Montana and North Dakota during 1951, with allowance for future 

advances in strip-mining methods.

CRITERIA FOR SELECTION OF STRIPPABLE DEPOSITS

Of the many factors that affect the value of a deposit of strippable 

coal, those judged to be within the scope of this investigation were:
148 CONTRIBUTIONS TO ECONOMIC GEOLOGY

thickness of the lignite bed, thickness of the overburden, location, 

reserves, weathering of the lignite bed, partings in the lignite bed, 

and shape of the deposit. The criteria discussed below are similar to 

those used in other strip coal investigations of the U. S. Geological 

Survey (Brown and others, 1954; Culbertson, 1954; May, 1954; 

Kepferle, 1954). A few of the criteria have been modified to allow 

for special conditions in Slope and Bowman Counties.

Thickness of lignite. The minimum thickness of lignite that can 

be strip mined economically depends on local conditions. In most 

parts of North Dakota a bed thickness of 5 feet is generally considered to be the minimum. In Slope and Bowman Counties, however, so much of the reserves are in beds more than 10 feet thick 

nearly two-thirds of the total reserves according to a recent estimate 

(Brant, 1953, p. 45) that it is unlikely that any beds less than 10 feet 

thick would be strip mined on a large scale in the forseeable future. 

Consequently, a bed thickness of 10 feet was adopted as the minimum 

for strippable deposits in this investigation. The term "bed thickness" as used in this report refers to the thickness of lignite only and 

does not include the thickness of partings.

Thickness of overburden. In conformity with earlier investigations 

of deposits of strippable coal, an overburden thickness of 120 feet was 

considered to be the maximum for a strippable deposit in Slope and 

Bowman Counties. Each deposit was subdivided into three categories 

according to thickness of overburden less than 60 feet, 60 to 90 feet, 

and 90 to 120 feet to accommodate the various types of stripping 

equipment now in use or that may be in use in the near future, and to 

accommodate the various thicknesses of lignite beds that are found 

in a large deposit. For greatest economy the power shovel or drag 

line should be able to remove all the overburden by casting it directly 

on the spoil pile without rehandling. The capacity of most equipment 

now in use for this type of operation is from 50 to 60 feet of overburden, and this is considered to be a rough maximum for ordinary 

bed thicknesses. If more than 60 feet thick the overburden becomes 

increasingly difficult to remove, and the extra expense of rehandling 

usually is not justified unless the lignite bed is exceptionally thick. 

The strip mine at Colstrip, Mont., for example, which mines a 25-foot 

bed of subbituminous coal, regularly strips 80 feet sometimes 90 feet 

of overburden, and on one occasion stripped 145 feet of overburden to 

remove a small hill (Coal Age, March 1949, p. 98-102). It is doubtful, however, if more than 120 feet of overburden will be stripped as a 

regular practice in the near future, even in the Slope and Bowman 

County area where the beds range from 10 to 40 feet in thickness.

A stripping ratio, or ratio of the thickness of overburden to the 

thickness of the coal bed, is often used by strip miners to express the
STRIPPABLE LIGNITE, SLOPE AND BOWMAN COUNTIES, N. DAK. 149

maximum thickness of overburden that can be stripped economically 

from a coal bed of a given thickness. In North Dakota a strip ratio 

of 10 to 1 is sometimes mentioned as the maximum for a profitable 

operation, but this ratio probably applies only to beds less than about 8 

feet thick. Where the bed thickness exceeds 8 feet, the rapidly increasing cost of removing the overburden of necessity decreases the maximum acceptable strip ratio. In this area, where the beds are as much 

as 40 feet thick, a single maximum stripping ratio could not be applied 

to the entire area. Consequently a stripping ratio was not used in 

selecting deposits in this investigation.

By way of comparison, it may be mentioned that in 1952 North 

Dakota strip mines stripped an average of 38.2 feet of overburden 

from lignite beds that averaged 9.4 feet thick, which is a strip ratio of 

about 4.1 to 1 (Young and Anderson, 1952, p. 13). In the two 

deposits described in this report the strip ratio is about 2.Y to 1 for 

beds that average about 24 feet thick.

Location. For low cost development a strippable deposit should be 

as near as possible to the market or point of utilization, or at least be 

near a good means of transportation to these points. In Slope and 

Bowman Counties the main line of the Chicago, Milwaukee, St. Paul, 

and Pacific Railroad was considered to be the only feasible way at 

present to transport a large amount of lignite to its ultimate point of 

use. Thus, nearness to the railroad was an important consideration 

in selecting a deposit of strippable lignite for detailed investigation.

Reserves. Because of the abundance of strippable lignite in western North Dakota, only the larger deposits were considered in the 

present investigation. A reserve of at least 10 million tons of lignite 

should be available under less than 60 feet of overburden to make it 

profitable to move heavy stripping equipment into an area, by presentday stripping practices.

Weathering of the lignite ~bed. In North Dakota strip mines, 

weathered lignite generally is discarded because the weathering 

process causes the lignite to break down into small flakes and particles 

that are difficult to handle as fuel, and that have a reduced heat 

content because of oxidation. Consequently, a lignite bed in this 

area was considered suitable for stripping only if it was unweathered 

or if not more than the top 20 percent to 25 percent of the bed was 

affected by weathering.

Partings in the lignite bed. Partings of clay or other mineral 

matter, if not removed, decrease the value of a lignite bed by increasing its ash content. As the cleaning of lignite is extremely difficult 

and correspondingly expensive, lignite beds that are free of partings 

are much preferred. In this investigation, only those lignite beds 

were considered strippable which were free of partings or in which

319129 55 5
150 CONTRIBUTIONS TO ECONOMIC GEOLOGY

the partings are so few or thin that the ash content is not increased 

significantly thereby, or in which the partings are so thick that they 

can readily be removed in a normal stripping operation.

Shape of deposit. A strippable deposit should be relatively wide 

in proportion to its length in order to allow flexibility in planning 

the stripping operation and to minimize the waste along the outcrop 

caused by weathering of the lignite. Most deposits that are narrow 

and sinuous can not be stripped as advantageously as can the wider 

deposits, because of the high cost of the initial cut in relation to the 

subsequent cuts, and because of the smaller number of subsequent 

cuts available in a long narrow deposit.

PRELIMINARY INVESTIGATION

The preliminary investigation began with a study of the published 

reports on the lignite in Slope and Bowman Counties for the purpose of locating areas underlain by thick lignite and eliminating from 

further investigation those that were definitely unsuitable for strippable deposits. This study showed, for example, that the eastern 

and north-central parts of the area contains the thickest lignite beds 

and that the far western part contains no lignite beds of commercial 

thickness (fig. 19). For some parts of Slope and Bowman Counties, 

however, little or no information on the lignite appears in published 

reports, so an extended reconnaissance of the area was made to gather 

the considerable amount of information that was available locally. 

The main sources of this information were water-well drillers, 

farmers whose water wells reached the lignite beds, mine owners, and 

geophysical companies that were drilling seismograph shotholes 

throughout the area. Reports from these sources, together with the 

published data, indicated that several areas contain thick lignite under 

thin overburden. Of these areas, that north of Bowman and that east 

of Scranton were chosen for detailed investigation.

DETAILED INVESTIGATION

The detailed investigation of the specific areas consisted of determining the thickness of the lignite, and locating and plotting on aerial 

photographs the lignite bed outcrop and the three lines outlining 

thickness of overburden. These lines bound the three subdivisions 

of the strippable deposit: lignite under less than 60 feet of overburden, under 60 to 90 feet of overburden, and under 90 to 120 feet 

of overburden. These data were then transferred from the photographs to a base map made from General Land Office plats. Isopach 

lines were drawn for the strippable lignite from the thickness information available, and, finally, the reserves of lignite and the approximate stripping ratio were calculated.
STRIPPABLE LIGNITE, SLOPE AND BOWMAN COUNTIES, N. DAK. 151 

DETERMINATION OF THICKNESS OP THE LIGNITE

The writers added to the data obtained in the preliminary investigation by logging some of the holes that were being drilled by shothole 

drillers and by drilling additional holes with a power auger mounted 

on a pickup truck. An effort was made to place the power-auger holes 

so that the results therefrom would complement less reliable data on 

thickness, and so that no part of the strippable deposit would be more 

than a mile from a point of thickness information.

Of the several kinds of information about the thickness, the detailed 

measurement of an exposure of the bed is the most accurate. Only a 

few measurements of exposures are used in this report, however, for 

the complete thickness of a strippable bed is rarely exposed in this 

area. Much of the information about thickness of the lignite was 

obtained by some type of drilling. Because of the toughness of the 

lignite as compared with the usual soft clays, shales, and sandstones 

in this area, the lignite beds are readily noted in drilling operations, 

even by those drillers who ordinarily would not be interested in lignite. The precision of the various drilling methods does not differ 

significantly, but the reliability of the reports depends chiefly upon 

the interest of the driller in recording the thickness of the lignite 

bed. In two types of drilling, the auger holes and prospect drilling 

by coal-mining companies, the primary object is to measure the thickness of the lignite bed. In the other two types, water-well drilling 

and seismograph-shothole drilling, lignite thickness is only of minor 

interest. Accordingly, measurements of thickness from water wells 

or seismograph shotholes were used only where they were verified 

by measurements from a power-auger hole nearby, or where they were 

logged by a driller who, to the writers' knowledge kept a reliable log. 

This kind of information was used also in a few places where there 

was no other reliable information for the immediate vicinity, but 

where the thickness and depth reported for the lignite bed conformed 

closely to the thickness and depth inferred for that point from 

nearby measurements.

The precision of the four types of drilling is inferred to be as 

follows: In most power-auger holes, the thickness of the bed could be 

determined to within 1 or 2 feet and the thickness of clay partings 

to within a few inches. Partings less than 2 inches thick, however, 

may not have been recognized. The prospect holes of the coal mining companies, though drilled with different equipment, probably 

measured the lignite with similar precision. Water-well drillers probably recorded the true thickness within an accuracy of about 2 feet, but 

may not have recorded partings of less than a foot or two. Seismograph shothole drillers probably measured the lignite with the 

least accuracy, because of the speed of their drilling operations, On
152 CONTRIBUTIONS TO ECONOMIC GEOLOGY

the average, the bed thickness reported from shotholes are probably 

accurate to within about 3 feet, although partings may not have 

been recognized or recorded if they were less than 1 or 2 feet thick. 

Inasmuch as the Harmon lignite bed was found to be free from 

partings at most localities investigated by the writers, the fact that 

thin partings were not recorded by water well and seismograph-shothole drillers probably does not affect the value of their logs significantly.

After all thickness data were gathered and evaluated, the average 

thicknesses were calculated, and an isopach, or thickness, map was 

made of the strippable lignite deposits.

PLOTTING OF OUTCROP AND OVERBURDEN LINES

The line of outcrop of the strippable lignite was first located in 

the field, and then plotted on aerial photographs printed at a scale 

of 1:20,000. The line of outcrop of the other lignite beds shown on 

the Bowman deposit map were either located by reconnaissance methods in the field, or were taken directly from the map of the Marmarth 

lignite field (Hares, 1928, pi. 14), modified in part by the use of aerial 

photographs.

Next, the 60-foot, 90-foot, and 120-foot overburden lines (imaginary 

lines on the ground, every point of which is the same height above 

the bed of strippable lignite) were added to the photographs. These 

lines were located by reconnaissance methods, in which differences 

of elevation were found by use of the surveying altimeter and hand 

level, and horizontal distances by measurements from aerial photographs. The altimeter traverses were based on true elevation taken 

from U. S. Coast and Geodetic Survey benchmarks, or from seismograph shotholes at which the elevation had been determined by geophysical crews using plane table and alidade.

Because the points at which information was obtained are scattered 

and because of the reconnaissance method of mapping, the overburden 

lines are, of necessity, somewhat generalized. Before any mining 

operations are started, therefore, the deposit should be mapped and 

drilled in detail sufficient to permit accurate calculation of the total 

yardage of overburden and tonnage of lignite.

ESTIMATION OF STRIPPABLE RESERVES

After the field mapping was completed, the lines on the aerial photographs were transferred to a map base drawn from General Land 

Office plats. On this map the acreage underlain by strippable lignite, 

excluding any area in which the lignite bed had been mined out or is 

inferred to be weathered, was measured with a planimeter. The acreage was then multiplied by the average thickness of the lignite bed to 

obtain the volume of lignite in acre-feet, the volume in turn was mul-
STRIPPABLE LIGNITE, SLOPE AND BOWMAN COUNTIES, N. DAK. 153

tiplied by 1,750 tons per acre-foot, the average density of lignite in 

North Dakota and eastern Montana (Brant, 1953, p. 4), to get the remaining reserves in short tons.

The reserves in each deposit are tabulated in table 1 according to the 

three categories: less than 60 feet, 60 to 90 feet, and 90 to 120 feet of 

overburden. The reserves that would actually be recovered from these 

deposits are somewhat less than the amount shown, for some coal is 

always lost in the mining process. Because of the high efficiency of 

strip mining, however, the amount lost by this method usually is comparatively small. The large strip mine at Colstrip, Mont., for example, recovers nearly 95 percent of the coal in a bed 25 feet thick (Styles, 

1951, oral communication).

The reliability of the reserve figures in table 1 can be inferred from 

the spacing of the points at which data on thickness was obtained and 

from the persistence of the lignite bed. They are so spaced that about 

90 percent of the total reserves are within one mile and about 75 percent of the reserves under less than 60 feet of overburden are within 

half a mile of such a point. As the Harmon lignite bed is one of the 

most persistent beds in the United States (Hares, 1928, p. 49), and all 

the reserves are within 1% miles of such a point, the reserve figures in 

table 1 are considered reliable enough to fall within the indicated 

category of the reliability classification of lignite reserves of North 

Dakota (Brant, 1953, p. 8).

ESTIMATION OF STRIPPING RATIO

A stripping ratio is the ratio between the thickness of the overburden 

on a lignite bed to the thickness of the bed itself. Strip ratios are 

widely used in the coal mining industry to evaluate deposits of coal and 

for that reason an attempt was made to calculate the stripping ratios 

for the two deposits described in this report. An accurate determination of stripping ratio was not possible because of the lack of precise 

information on the variation of the thickness of overburden. It was 

possible, however, to obtain an approximate stripping ratio for each 

deposit or deposit subdivision by taking a weighted average of overburden thicknesses in each of the three categories of thickness of overburden, as estimated from the writers' knowledge of the topography of 

the area, and comparing it with the average thickness of lignite as previously determined. These strip ratios, which are presented in table 

1, are average ratios, however, and cannot be applied to small parts 

of the deposits with assured accuracy.

DEPOSITS OF STRIPPABLE LIGNITE

BOWMAN DEPOSIT

The Bowman deposit the larger of the two deposits of strippable 

lignite described in this report has an areal extent of nearly 40
154 CONTRIBUTIONS TO ECONOMIC GEOLOGY

square miles, and contains indicated reserves of 1,099 million short 

tons of strippable lignite in one continuous bed. (See table 1 and pis. 

15 and 16.) It lies in Tps. 132 to 135 N., Rs. 101 and 102 W., Slope and 

Bowman Counties, N. Dak. Bowman, the county seat and largest 

town in Bowman County, is about 4 miles south of the deposit and is 

served by the main line of the Chicago, Milwaukee, St. Paul and Pacific Railroad and by U. S. Highways 12 and 85. Amidon, the county 

seat of Slope County, lies about 2 miles east of the northern part of the 

deposit. The deposit is accessible by means of gravel-surfaced, graded 

U. S. Highway 85, which crosses the deposit between Bowman and 

Amidon, and by the many graded county roads that serve the areas on 

either side of the highway.

A 44,000 volt power transmission line that roughly parallels U. S. 

Highway 12 is the nearest source of electric power. The nearest 

accessible water supply is the Little Missouri River at Marmarth, 31 

road miles west of Bowman. Water in quantities sufficient to supply 

the needs of large-scale industry is available from the Missouri River 

at Mobridge, S. Dak., 170 miles southeast of Bowman, and from the 

Yellowstone River at Fallon, Mont., about 115 miles northwest of 

Bowman by way of the railroad.

Because it is large, the Bowman deposit will be discussed in four 

parts in the following order: northern part, which includes all the 

deposit within T. 135 N., Rs. 101 and 102 W.; north-central part, which 

includes all the deposit within T. 134 N., Rs. 101 and 102 W.; southcentral part, which includes all the deposit within T. 133 N., Rs. 101 

and 102 W.; and southern part, which includes all the deposit within 

T. 132 N., Rs. 101 and 102 W.

NORTHERN PART

The northern part of the Bowman deposit (pi. 15) is in sees. 13, 25, 

and 36, T. 135 N., R. 102 W., and sees. 17 to 21 and 28 to 34, T. 135 N., 

R. 101 W., Slope County, N. Dak.

TOPOGRAPHY AND LAND USE

The northern part of the Bowman deposit is drained by Sand Creek, 

which lies to the west. This creek flows in a well-defined channel that 

meanders along a fairly flat, alluvial-filled valley bottom from oneeighth to one-fourth of a mile wide. The sides of the valley rise 

abruptly for 20 to 60 feet and form typical breaks against the generally 

smooth slopes back from the valley. These smooth slopes are modified 

by the U-shaped valley of Hay Creek a major tributary and the 

V-shaped valleys of the minor tributaries, and by the rounded ridges 

that extend from the high divide to the east. Gravel-capped terraces 

.are conspicuous north of Hay Creek and east of Sand Creek to the
STRIPPABLE LIGNITE, SLOPE AND BOWMAN COUNTIES, N. DAK. 155

south. The maximum relief within the mapped area is about 250 

feet.

Most of the gently sloping land is farmed. The steep slopes of the 

uplands and the flat creek bottoms are covered with grass, which is cut 

for hay or used as pasture. Some low brush and a few trees border 

Sand Creek.

HARMON LIGNITE BED

The Harmon lignite bed ranges in thickness from 12 to 40 feet in the 

northern part of the Bowman deposit and probably averages 25.8 

feet; it is thickest in the southwestern corner of T. 135 N., R. 101 W. 

(See map, pi. 15). The information about the bed was derived from 

8 seismograph shotholes, 4 power-auger holes, 1 water well, and 2 

exposures (graphic sections nos. 1 through 15, pi. 17). Of the seismograph shotholes, those at locations 11 and 14 were logged by one of 

the writers. These observations show that the Harmon bed consists 

of clean lignite, except for a clay parting 2 to 3 feet thick that lies 

3 to 5 feet below the top of the bed at locations 10, 11, 12, and 13. 

This same parting is visible where the top 5 or 6 feet of the bed is 

exposed along the bank of Sand Creek about half a mile south of 

location 13. The two exposures at locations 10 and 12 were measured 

by Hares (1928, pi. 13). When visited by the writers only the upper 

bench and the upper part of the lower bench were visible, the rest 

having been covered by slump since the bed was last mined. The base 

of the Harmon bed is exposed just north of the reservoir in sec. 31, 

T. 135 N., R. 101 W. Elsewhere in the mapped area the former outcrops of the Harmon bed is marked mainly by clinker produced by 

the burning of the bed.

Water was found near the base of the Harmon bed in the hole 

drilled at location 4, and water in standing pools along Sand Creek 

in sec. 31, T. 135 N., E. 101 W., probably comes from the Harmon 

bed.

The Harmon bed dips northward about 40 feet per mile in the 

northernmost part of the deposit, and, as the bed is above the main 

drainage channels, draining water from strip pits would not be very 

difficult in this area. Southward, however, pumping probably would 

be necessary to rid the strip pits of water because the direction of 

dip changes from northward to east-northeastward, which is almost 

directly opposed to the general land drainage.

OVERBURDEN AND FLOOR ROCK

The lowest 30 feet of overburden of the Harmon lignite bed in the 

northern part of the Bowman deposit is predominantly clay. At location 12, this clay contains abundant leaf imprints. Above the clay,
156 CONTRIBUTIONS TO ECONOMIC GEOLOGY

the overburden is mainly a light-yellow massive to crossbedded fineto medium-grained sandstone that is composed chiefly of quartz 

grains cemented loosely with calcium carbonate. Locally this sandstone is cemented more firmly forming a resistant calcareous sandstone. Much of it is water bearing, particularly in the valley of Hay 

Creek. Small iron sulfide concretions that alter to limonite on exposure are fairly common throughout the sandy sediments. The 

sandstone may be interbedded with thin beds of clay and lignite.

In sec. 19, T. 135 N., R. 101 W., a lignite bed crops out about 30 feet 

above the Harmon bed. This bed is reported to be 5 feet thick at a 

depth of 80 feet in a seismograph shothole drilled half a mile east 

of location 4, and is 8 feet thick at a depth of 110 feet in a similar 

hole a mile east of location 11. Clinker of another bed about 60 feet 

above the Harmon bed is present at location 1, and bloom from this 

bed is visible at various points along the contour line marking 60 

feet of overburden in sec. 13, T. 135 N., E. 102 W., and in adjacent 

sec. 18 of the township to the east. Gravel deposits attain a thickness of 15 feet where they cap the terraces on the east side of Sand 

Creek.

The Harmon bed is underlain by clay in the northern part of the 

Bowman deposit.

RESERVES AND STRIPPING RATIO

The northern part of the Bowman deposit contains reserves of 183 

million tons, of which 70 million tons, or about 38 percent, are beneath less than 60 feet of overburden, and about 72 percent are beneath less than 90 feet of overburden. (See table 1.) The stripping 

ratio averages 2.7 feet of overburden to each foot of coal, although it 

is probably as much as 8 to 1 near the contour line bounding 120 feet 

of overburden in the extreme north, where the Harmon bed thins 

to less than 15 feet in thickness.

The Harmon bed contains additional reserves of lignite in the 

area to the north of the Bowman deposit, but the available time was 

insufficient to allow the drilling and mapping necessary to determine 

the average thickness of the bed and the location of the overburden 

lines. These reserves, however, are farther from existing transportation facilities.

NORTH-CENTRAL PART

The north-central part of the Bowman deposit lies in sees. 1, 2, 12, 

13, 14, 22, 23, 25, 26, 27, 35, and 36, T. 134 N., E. 102 W., and sees. 

4 to 9, 16, 17, 18, 30, 31, and 32, T. 134 N., E. 101 W., Slope County, 

N. Dak. (pi. 15).
STRIPPABLE LIGNITE, SLOPE AND BOWMAN COUNTIES, N. DAK. 157 

TOPOGRAPHY AND LAND USE

The most prominent feature in the area, H T Butte, locally called 

Black Butte, lies in sees. 19 and 30, T. 134 N., R. 101 W., and sees. 23, 

24, and 25, T. 134 N., K. 102 W., and rises about 500 feet above the 

surrounding countryside. The divide between Sand Creek and Deep 

Creek extends northward from the west end of H T Butte and southeastward from the east end of the butte along a rolling grass-covered 

upland. Sand Creek on the east side of the divide receives most of 

the drainage from the deposit north of the butte. Sand Creek is a 

perennial stream in the township to the north, but flows only intermittently in this area of the deposit. The channel of Sand Creek is 

made up of well-sorted quartz sand derived from the erosion of the 

rocks of White Eiver age that are exposed in White Butte just east 

of the mapped area. Sand Creek flows in a flat flood plain as much 

as a third of a mile wide, but its tributaries occupy V-shaped valleys. 

The relief of these valleys is as little as 30 feet near their confluence 

with the main creek valley but increases greatly as the valleys encroach upon the slopes of H T Butte and its associated uplands.

Flat-topped ridges capped by remnants of terrace gravel extend 

northward from H T Butte in sees. 8,17, and 18, T. 134 N., K. 101 W. 

Similar, though less dissected, terraces border the uplands of White 

Butte just east of the mapped area and extend northwestward into 

sees. 4, 5, 6, 9, and 16 of the same township. On the deposit map (pi. 

15) the rough outline and lineation of these terraces are indicated by 

the contour line for 120 feet of overburden.

West and south of H T Butte the deposit is drained by Deep Creek, 

which flows northward to the Little Missouri Kiver. From H T 

Butte a gently sloping surface extends for about a mile to the west 

and about a mile and a half to the south. This surface is broken 

only by a few terracelike ridges and, to the south, by a westwardtrending, intermittent stream that has incised a channel to a depth 

of about 30 feet. Most of the area is grass-covered pasture land, although some of the rolling land north of H T Butte is farmed. A few 

trees and shrubs grow along the creek bottoms as well as on the rough 

slopes of H T Butte.

HARMON LIGNITE BED

The Harmon lignite bed in the north-central part of the Bowman 

deposit ranges from 15 to 40 feet in thickness, and averages 28.3 feet. 

The thickness data in this part of the deposit were derived from 10 

prospect holes drilled with a power auger and from 11 seismograph 

shotholes, of which those at locations 18, 23, 25, 28, 30, and 33 were 

logged by the writers (Graphic sections nos. 16 through 36, pi. 17).
158 CONTRIBUTIONS TO ECONOMIC GEOLOGY

The strippable lignite seems to be the thickest along the channel of 

Sand Creek in the three northern tiers of sections in T. 134 N., 

R. 102 W.; the thinnest part of the strippable bed is along the outcrop. 

Because of uncertainty as to the thickness of lignite penetrated at 

location 16, the bed is considered to constitute a thickness of not less 

than 21 feet of clean lignite nor more than 31 feet of lignite containing 

a few thin partings near the base. A seismograph shothole logged by 

the writers at location 25 gave similarly inconclusive results within the 

thickness range of from 32 to 42 feet. The graphic sections (pi. 17) 

show no partings at locations 16 and 25, and the average thickness 

shown by these sections, 26 and 37 feet, respectively, are the thicknesses 

used in calculating the reserves in the immediate vicinity of the holes. 

At location 33 the bed was penetrated for 13 feet without reaching the 

bottom, and at location 34 the top part of the bed was eroded, apparently before or during the deposition of the thin gravel deposit that 

overlies it. Clay partings ranging from 2 inches to 2 feet in thickness 

lie from 2 to 4 feet below the top of the Harmon bed at locations 19, 

21, and 31. The Harmon lignite has been mined at an opencut at location 27 near the west end of H T Butte and has been reached by wells 

in the west half of sees. 23 and 26, T. 134 N., R. 102 W. The top of the 

bed is exposed in the channel of Sand Creek just south of the-township line in sec. 6, T. 134 N., R. 101 W.

At location 18, in a seismograph shothole logged by the writers, 

clinker totaling 15 feet in thickness immediately overlies 22 feet of 

lignite. As clinker is not exposed at the surface around this hole, 

the extent to which the Harmon lignite has burned in this area is not 

known. The unburned lignite beneath should be of good quality, and 

therefore is included in the strippable reserves. Unburned lignite beneath clinker indicates that oxygen was not available to the lower part 

of the bed at the time of burning possibly because the lower part was 

saturated with water.

The bed dips northeastward from 20 to 40 feet a mile throughout 

most of T. 134 N., Rs. 101 and 102 W., increasing to about 60 feet a mile 

just south of H T Butte. At location 25, a structural anomaly in the 

lignite bed is indicated by a somewhat lower altitude for the top of 

the bed than is suggested by the regional dip that persists in the surrounding locations. The lignite bed is higher than the drainage level 

throughout most of the north-central part of the deposit, except east 

of Sand Creek and south of H T Butte.

OVERBURDEN AND FLOOR ROCK

South of H T Butte the overburden on the Harmon bed in the northcentral part of the Bowman deposit is predominantly clay for as much 

as 90 feet above the lignite, but becomes more sandy above this dis-
STRIPPABLE LIGNITE, SLOPE AND BOWMAN COUNTIES, N. DAK. 159

tance. North and east of H T B'utte the overburden is clayey only 

within 20 to 30 feet above the Harmon bed and is predominantly sandy 

above 30 feet. A lignite bed not more than 2 feet thick was found 

about 35 feet above the Harmon bed at location 33. A lignite bed 5 

feet thick was logged at about 60 feet above the Harmon bed in the 

hole drilled at location 28. No trace of either of these beds was 

found at the surface. Gravel deposits 5 to 15 feet thick cap the ridgelike terrace remnants that extend northward into the deposit in sees. 

17 and 18, T. 134 1ST., R. 101 W. Gravel deposits also underlie the 

surface of the terraces that border the east side of Sand Creek and 

the south side of H T Butte. A few of the ridges that rise to slightly 

more than 120 feet above the general land surface impart a sinuous 

outline to the deposit. Inasmuch as these ridges are extremely narrow, they probably would be removed rather than bypassed by any 

stripping operation that was removing as much as 120 feet of overburden.

The rock beneath the Harmon bed is clay in this part of the deposit, 

except at location 30, where sand was found.

RESERVES AND STRIPPING RATIO

The remaining reserves of strippable lignite in the north-central 

part of the Bowman deposit total 299 million tons, of which 107 million tons, or 35 percent, lie beneath less than 60 feet of overburden, 

and 63 percent lies beneath less than 90 feet of overburden. (See 

table 1.) The average stripping ratio for this part of the Bowman 

deposit is less than that for any other part of the deposit. It averages 

2.4 to 1 throughout and ranges from an average of 1.5 to 1 in the category of less than 60 feet of overburden, to 2.4 to 1 in the category 

of 90-120 feet of overburden.

SOUTH-CENTRAL PART

The south-central part of the Bowman deposit lies in sees. 1,12,13,, 

24, and 25, T. 133 1ST., R. 102 W., and sees. 4 to 11, and 14 to 33, T. 133 N.r 

R. 101 W., Slope County, N. Dak. (pi. 16).

TOPOGRAPHY AND LAND USE

In this area, the high divide between southeastward-flowing Cedar 

Creek on the east and northward-flowing Deep Creek on the west borders the eastern edge of the strippable deposit. This divide follows 

the tops of rolling hills that are about 200 feet high in the north to as 

low as 60 feet in the central part, and rise to more than 150 feet above 

the surrounding countryside in the south. These hills are generally 

grass covered near their tops but are farmed along the more gentle 

slopes near their bases. Three roughly parallel ridges extend north-
160 CONTRIBUTIONS TO ECONOMIC GEOLOGY

westward into the deposit from this main divide. One, in the southern third of T. 133 N., E. 101 W., is about 2 miles long and has a 

maximum relief of about 100 feet; another, near the center of the same 

township, is about 5 miles long and has a maximum relief of about 

150 feet; the third, near the northern boundary of the township, is 

about 2 miles long and extends westward from a small butte on the 

line between sees. 4 and 5. Three major tributaries to Deep Creek 

receive most of the drainage of the township. The northernmost 

of these is the largest and drains most of the north half of the area, 

flowing westward into Stewart Lake and thence into Deep Creek, 

Stewart Lake is the only perennial lake in the area; it is supplied not 

only from runoff but also by many springs, some issuing from the 

Harmon lignite bed. The valley in which Stewart Lake lies is as 

much as a mile wide and is fairly mature. Gravel-covered terrace 

remnants rise to about 75 feet above the present stream bottom on the 

north side of the valley, and the stream channel is entrenched 10 to 

20 feet below the level of the main valley floor.

This valley is unusual among those of the deposit area in that it 

broadens headward, due mainly to the low relief of the Cedar CreekDeep Creek divide to the east. This headward broadening combined 

with a flattening of the already low dip of the strippable lignite provides a large area in which the Harmon lignite lies beneath more than 

 60 and less than 120 feet of overburden. The two main Deep Creek 

tributaries that drain the southern half of the south-central part of 

the deposit are fairly short. The flat valley bottom of the more 

northern of these two tributaries is at least half a mile wide, whereas, 

the other is much narrower. Except in the immediate vicinity of the 

farmsteads, the area is practically treeless. Approximately half of 

the area is farmed, the rest is grass covered.

HAEMON LIGNITE BED

The Harmon lignite bed in the south-central part of the Bowman 

deposit thickens from east to west from 16 to 37 feet (pi. 16). The 

average thickness of the bed is 22.5 feet. The sources of thickness 

information are 12 holes drilled with a power auger, reports from 2 

water wells, and 13 seismograph shotholes, of which those at locations 

47, 50, 54, and 61 were logged by the writers (graphic sections, nos. 

37 through 63, pi. 18). One of the writers was also present when the 

well at location 39 was drilled. A third well, about two-thirds of a 

mile east of location 39, entered lignite presumed to be the Harmon 

bed at a depth of 72 feet, but did not transect the complete thickness 

of the bed. Other wells in the area are reported to have reached the 

Harmon bed, but have been drilled so long ago that the present resident of the farmstead has no recollection of the depth or thickness of 

the bed.
STRIPPABLE LIGNITE, SLOPE AND BOWMAN COUNTIES, N. DAK. 161

The thickest lens of the Harmon lignite bed in this area centers 

around location 58, where 37 feet of lignite was penetrated in drilling, 

A clay parting 6 inches thick was found 21/£ feet below the top of the 

bed at location 37, and a similar parting was found 5 feet below the 

top of the bed at location 41. A bed that appears to be an upper 

bench of the Harmon lignite bed is 3 feet thick at location 50 and is 

separated from the lower bench of 18 feet of lignite by a parting of 

shale and clay 14 feet thick. A seismograph shothole about one mile 

east of location 55 reached a bed of lignite 4 feet thick that may be 

the upper bench of the Harmon bed. This hole, however, passed 

through 21 feet of sediments below this bench without reaching any 

other lignite. Two miles east of location 55 a seismograph shothole 

passed through 3 feet of lignite, 5 feet of clay, and 8 feet of lignite. 

The 16 feet of lignite and clay was assumed to be the Harmon bed. 

The top of the Harmon bed seems to have been eroded at location 38.

The Harmon bed has been mined from several small openings, that 

most recently operated being at location 62 where the National Aluminate Co. has mined weathered lignite for use in making dye. Other 

openings are the Hallenbeck mine in the SE1/^ sec. 1, T. 133 N., E. 

102 W., where the bottom part of the bed was being mined by the local 

ranchers as recently as 1940, and in the NW% sec. 19, T. 133 N., K. 

101 W., where Hares (1928, p. 89) reported that 5y2 feet of lignite 

was exposed, but that the bottom part of the bed was covered by water. 

An analysis of a sample of lignite from the Hallenbeck mine is given 

in table 3.

OVERBURDEN AND FLOOR ROCK

Gray to yellow clay and shale constitute most of the overburden 

within 50 feet of the top of the Harmon bed in the south-central part 

of the Bowman deposit. Above 50 feet, the overburden is .increasingly 

sandy and contains at least three thin lignite beds. Two of these thin, 

beds have burned along parts of their outcrops and can be traced by 

the resulting clinker. Clinker from a bed about 90 feet above the 

Harmon bed crops out along the ridge just south of Stewart Lake 

and is also conspicuous just east of the section corner to the east. 

Clinker from this bed and from a bed 30 to 45 feet higher crop out in 

several places along the upland slopes of the high ridges in the area 

and indicate that these beds are fairly persistent. A third bed, 50 to 60 

feet above the Harmon lignite bed, has burned to form clinker along 

the slopes of the ridge about half a mile east of location 51. Clinker at 

this same stratigraphic position was also found in a seismograph shothole drilled at location 61. This same bed is 2, 10, 11, and 9 feet 

thick where it was reached in holes drilled respectively at location 43, 

one mile west of location 43, location 56, and 2 miles east of location 

61. Silicified tree stumps and other silicified wood in association with
162 CONTRIBUTIONS TO ECONOMIC GEOLOGY

a discontinuous quartzitic layer are scattered along the top of the 

ridge in the SE% of sec. 33, T. 133 K, E. 101 W.5 at about 180 feet 

above the Harmon bed.

The rock beneath the Harmon bed is mainly clay, although holes 

drilled at locations 43,47,54,61, and 63 entered shale, and holes drilled 

at locations 50 and 59 entered sandstone just under the lignite.

RESERVES AND STRIPPING EATIO

The remaining reserve of strippable lignite in the south-central part 

of the Bowman deposit total 389 million tons, of which 152 million 

tons, or 39 percent, lie beneath less than 60 feet of overburden, and 72 

percent lie beneath less than 90 feet of overburden (table 1). The 

stripping ratio for this part of the deposit is greater than that for 

any other part. It averages 3.1 to 1 in all 3 categories of thickness of 

overburden and ranges from an average of 1.7 to 1 in the category of 

less than 60 feet of overburden to an average of 4.9 to 1 in the category 

of 90-120 feet of overburden. The south-central part of the deposit 

in the west overlaps an area in which lignite from the underlying 

Hansen bed could be obtained by removing an additional 40 to 60 feet 

of sandstone, shale, and clay which lie beneath the Harmon bed. The 

Hansen bed ,in this area is more than 10 feet thick and contains possible strippable reserves totalling about 200 million tons (fig. 27).

SOUTHERN PART

The southern part of the Bowman deposit (pi. 16) lies in sees. 1, 2, 

11 to 16, and 22 to 25, T. 132 N., E. 102 W., and sees. 7,18 to 21, 27 to 

30, and 32 to 34, T. 132 N., E. 101 W., Bowman County, N. Dak.

TOPOGRAPHY AND LAND USE

The drainage divide between the Little Missouri Eiver and the 

Missouri Eiver passes southward along the range line common to 

Es. 101 and 102 W., in T. 132 N. Deep Creek drains the land west of 

the divide. Cedar Creek and Buffalo Creek drain the land east of the 

divide, their drainage basins being separated by a ridge that extends 

eastward from the S% sec. 19, T. 132 N., E. 101 W. Most of the hills 

are low, fairly rounded, and slightly elongated in a northwesterly 

direction. The gentle low slopes are farmed, but the steeper, high 

slopes are left in grass. The western part of the mapped area has a 

fairly low relief except where hummocks and ridges capped with 

clinker have resisted the levelling effects of erosion.

Twin Buttes form a conspicuous landmark just south of the mapped 

area in sees. 35 and 36, T. 132 N., E. 102 W., and adjoining sees. 1 and
STRIPPABLE LIGNITE, SLOPE AND BOWMAN COUNTIES, N. DAK. 163

2 of the township to the south. These buttes rise to about 150 feet 

above the Harmon lignite bed and are capped by a slabby layer of 

quartzite.

HARMON LIGNITE BED

The Harmon lignite bed in and near the southern part of the Bowman deposit ranges in thickness from a reported 38 feet at location 67, 

to 5 feet at location 78. Information about the thickness of the Har-

*s

jliAbandoned

.0

KK. ^

Hole LOG * 

A. 31 feet of sand, 1 foot of soft coal, 6 feet of blue

clay, 33 feet of hard coal, 2 feet below coal. 

B. 18 feet of clay, 6 feet of slack, 26 feet of hard

coal, 3 feet below coal. (Location unknown). 

C. 23 feet of clay, 2 feet of slack, 29 feet of hard

coal, 2 feet below coal. 

D. 21 feet of clay, 2 feet of red clay and sand, 4 feet

of slack, 15 feet of hard coal, 5 feet below coal. 

E. 35 feet of clay, 1 foot of slack, 4 feet of hard

coal, 6 feet below coal. 

F. 38 feet of clay, 3 feet of scoria, 6 feet of clay,

no coal. 

G, 30 feet of clay, 2 feet of slack, 31 feet of hard

coal, 2 feet below coal. 

H. 48 feet of clay, 1 foot of slack, 33 feet of hard

coal, 3 feet below coal. 

I. 18 feet of clay, 6 feet of slack, 21 feet of hard

coal, 3 feet below coal.

J. 34 feet of clay, 8 feet of scoria, 8 feet of clay. 

K. 31 feet of clay, 9 feet of slack, 4 feet of mixed

hard coal, 3 feet below coal. 

K K. 20 feet of clay, 10 feet of slack, 18 feet of hard

coal, 2 feet below coal. 

L. 16 feet of clay, 4 feet of slack, 23 feet of hard

coal, 3 feet below coal. 

M. 14 feet of clay, 3 feet of slack, 1 foot of clay,

33 feet of hard coal, 4 feet below coal. 

N. 20 feet of clay, 7 feet of slack, 21 feet of hard

coal, 3 feet below coal. 

O. 16 feet of clay, 18 feet of slack, 9 feet of hard

coal, 2 feet below coal.

P. 18 feet of clay, 9 feet of slack, 18 feet of hard 

|J> coal, 2 feet below coal.

;j Q. 18 feet of clay, 10 feet of sand, 4 feet of clay 

5 6 feet of scoria, 4 feet mixed. 

"> R. 20 feet clay, 10 feet slack, 8 feet of hard coal, 

^ 2 feet below coal.

32 S. 4 feet of clay, 35 feet of sand, 17 feet of clay, 

i 2 feet of slack, 32 feet of hard coal, 2 feet 

§ below coal. 

I

: The last item indicates depth drilled after passing

2000 Feet through last coal bed. Lithology not recorded.

FIGURE 20. Map of the east half of sec. 24, T. 132 N., R. 102 W., Bowman County, N. Dak., 

showing location of prospect holes drilled in 1925 by the Bowman Holding Co.

mon bed in this area is derived from 9 power-auger holes, 2 well 

reports, 1 report from an abandoned mine, and 3 prospect holes drilled 

by the Bowman Holding Co. (graphic sections nos. 64 through 78, 

pi. 18). In 1925 this company drilled 20 prospect holes which are 

shown in figure 20, but only the three shown at locations 69, 71, and 73 

on plate 16 were found in the field. The logs that are presented with
164 CONTRIBUTIONS TO ECONOMIC GEOLOGY

the map indicate that the Harmon bed penetrated by the prospect 

holes has a much greater range in thickness within the SE*4 sec. 24r 

than is shown by the isopach lines on plate 16. This may be explained 

in part by the fact that normal local variations in thickness are not 

shown by the isopach lines, and in part by the indication that the 

lignite at locations D, E, K, and K, may be eroded. The logs (fig. 20) 

also show that many of the holes were drilled where the Harmon 

bed has weathered under a fairly thin overburden. Holes at locations 

F, J, and Q (fig. 20) penetrated only clinker ("scoria") indicating 

that the Harmon bed has been burned beneath some of the area.

The thickness or isopach map of the Bowman deposit (pi. 16) shows 

that the thickest lignite lies in the west of the southern part. East of 

sees. 27 and 34, T. 133 N., K. 101 W., the lignite becomes too thin 

to be considered economically strippable. At the Halleck mine (location 67, pi. 16) the lignite is reported by Leonard (1925, p. 64) a& 

being from 30 to 38 feet thick. Other reports that the lignite in this 

mine is 60 feet thick are not considered valid, because holes drilled 

near the mine at locations 66 and 68 show that the bed is 31 feet and 

27 feet thick, respectively, at these locations. The writers were unable to confirm a report that a 35-foot thickness of the Harmon bed 

was entered at a depth of about 55 feet by a well drilled in the NE 

corner of the Sy2 sec. 19, T. 132 N., E. 101 W. The lignite at location 

72 appears to be eroded at the top. At all but two locations the Harmon bed is free from partings: at location 76 a clay parting 1 foot 

thick, lies 1 foot below the top of the bed; and just outside the strippable area at location 78 the top 1 foot of the lignite bed is separated 

from the lower 4 feet by a parting of sand and clay 10 feet thick* 

South of location 78 an additional prospect was drilled that showed 

the bottom bench had thinned to less than 2 feet thick. A report from 

the well at location 75 indicates that the Harmon bed there is only 

9 feet thick. Analyses of samples from the Halleck mine (location 

67) and the Bowman mine (near location 68) are presented in table 3.

Because the outcrop of the Harmon lignite bed is only slightlyabove the main stream valleys, and because the strata dip northeastward from 25 to 50 feet per mile, pumping would be necessary to drainthe pits of water, unless special care is taken to lay out the pits parallel 

to the strike of the lignite bed.

OVERBURDEN AND FLOOR BOCK

The overburden of the Harmon lignite bed in the southern part of 

the Bowman deposit appears to be mainly light gray to yellow shale 

and clay, with sand in increasing amounts in the overburden more
STRIPPABLE LIGNITE, SLOPE AND BOWMAN COUNTIES, N. DAK. 165

than 50 feet above the lignite. Two fairly persistent lignite beds were 

found at 80 to 90 feet and at 120 to 135 feet above the Harmon bed. 

The higher of the two is more conspicuous, and its outcrop trace is 

marked by clinker in sees. 18 and 19, T. 132 N., K. 101 W. These beds 

are exposed in several road cuts along U. S. Highway 85. The lower 

of the two beds was mined at one time from an exposed bank about 

half a mile east of location 75, where it was reported to be 5 or 6 feet 

thick. One of these beds is reported to attain a thickness of 15 feet 

in the Ny2 sec. 27, T. 132 N., K. 101 W.

An abundance of mollusks were found within a layer of sand on top 

of a small knoll along the south line of sec. 34, T. 132 N., K. 101 W., 

about 30 feet above the inferred base of the Harmon lignite bed.

Clay constitutes the floor rock of the Harmon bed in the southern 

part of the Bowman deposit.

RESERVES AND STRIPPING RATIO

The remaining reserves in the southern part of the Bowman deposit 

total about 228 million tons. Fifty-five percent of this amount, 126 

million tons, lies beneath less than 60 feet of overburden. This percentage of reserves in the category of less than 60-f eet of overburden 

is greater than for any other part of the Bowman deposit. (See table 

1.) The average stripping ratio for this part of the deposit is 2.7 

to 1, and ranges from 1.6 to 1 in the category of less than 60 feet of 

overburden to 4.3 to 1 in the category of 90-120 feet of overburden.

SCBANTON DEPOSIT

The Scranton deposit (pi. 19) is the smaller of the two strippable 

lignite deposits described in this report. It contains reserves of 

273 million short tons of lignite (table 1) and underlies about 10.4 

square miles in sees. 13, 14, 23, 24, and 25, T. 131 N., K. 100 W., sees. 

18 to 23, 25 to 30, and 32 to 36, T. 131 N., K. 99 W., and sees. 1 and 2, 

T. 130 N., R. 99 W., Bowman County, N. Dak.

The main line of the Chicago, Milwaukee, St. Paul and Pacific 

Kailroad and paved U. S. Highway 12 parallel the deposit on the 

south, and pass through the small towns of Scranton and Gascoyne. 

In addition to sidings at these two towns, the railroad also has a 

siding at the tipple of the Peerless mine about 1% miles east of 

Oascoyne, as most of the lignite from this mine is shipped by rail to 

markets in the eastern part of North and South Dakota and southern 

Minnesota. By rail, the deposit is 150 miles west of the Missouri
166 CONTRIBUTIONS TO ECONOMIC GEOLOGY

River at Mobridge, S. Dak., is 45 miles east of the Little Missouri 

River at Marmarth, N. Dak., and is about 127 miles southeast of 

the Yellowstone River at Fallon, Mont.

TOPOGRAPHY AND LAND USE

The entire runoff of the area of the Scranton deposit is received 

by Buffalo Creek, which parallels the deposit on the south and is 

a southeastward-flowing intermittent tributary to the Grand River. 

The deposit lies along the southern slopes of the uplands which parallel the deposit to the north and form the divide between Buffalo 

Creek and Cedar Creek. A southwestward trending ridge extends 

into the northwestern part of the area from this high divide, and 

in the SW}4 sec. 13 is surmounted by Scranton Butte, which rises 

about 160 feet above the strippable lignite bed. For the 

most part, however, the land surface over the deposit is gently 

rolling. The valley bottom of Buffalo Creek is fairly flat and is generally about half a mile wide. From this bottom, the surface rises 

fairly steeply for 20 to 40 feet on either side, then flattens out to form 

a low rolling bench that extends as much as three miles back from the 

bottom and is modified only by low ridges and the slightly entrenched 

channels of southeastward-flowing intermittent tributaries to Buffalo 

Creek. Northwest of Gascoyne one of these tributaries has been 

dammed, forming a perennial reservoir fed in part by springs and in 

part by runoff. The uplands are fairly rounded. At their highest 

point within the mapped area they rise about 185 feet above the 

strippable lignite bed. The maximum relief in the mapped area is 

about 250 feet. Most of the land underlain by the Scranton deposit 

is farmed, the rest is grass covered and devoid of trees or shrubs.

HARMON LIGNITE BED

Thickness data obtained from 1 seismograph-shothole drill report, 

7 power-auger holes, 3 exposures, and 16 prospect reports of the Knife 

River Mining Co., indicate that the strippable lignite in the Scranton 

deposit ranges from 10 to 32 feet in thickness (graphic sections 79 

through 105, pi. 20). Throughout most of the deposit area, the Harmon bed occurs in two benches, which in the central part of the deposit 

at location 90 converge to form 31 feet of solid lignite. The upper 

bench of the Harmon bed ranges from 4 to 20 feet in thickness and 

contains clay partings from 6 inches to 2 feet thick at locations 80, 81, 

and 86. Only the upper bench was penetrated at locations 79, 80, 81,
STRIPPABLE LIGNITE, SLOPE AND BOWMAN COUNTIES, N. DAK. 167

84, 85, 86, 99,103,104, and 105. The lower bench ranges in thickness 

from 7 to 23 feet and contains a parting V/2 feet thick at location 

93, and 8% feet thick at location 97. Only the lower bench was penetrated at locations 98 and 101. The upper bench and part of the lower 

bench are exposed at location 100 and both benches were penetrated at 

locations 82, 83, 87 to 97, and 102 (pi. 19).

In the western half of the deposit, only the upper bench is considered strippable, partly because the thickness of the parting between 

the two benches exceeds 5 feet, and partly because insufficient thickness 

information precludes making reliable estimates of the extent and 

thickness of the lower bench. In the central part of the deposit, 

where the two benches converge or are separated by a parting less than 

5 feet thick, both benches are considered strippable. In the eastern 

part of the deposit, where the parting increases to more than 5 feet 

thick, only the thick lower bench or, at location 97, the upper part of 

the lower bench is considered strippable. The thin upper bench is 

excluded in the eastern part of the deposit because of its nearness to 

the surface and the resulting extent to which it is weathered back from 

the outcrop precludes making an estimate of the minable reserves it 

contains without additional prospecting and mapping. Additional 

unweathered reserves from the upper bench probably could be recovered by any operation strip mining the lower bench of the Harmon 

lignite bed. The isopach lines on plate 19 indicate only the thickness 

of the strippable lignite as described above.

Westward from Scrantoii the upper bench of the Harmon bed thins, 

and is only 4% feet thick at an abandoned opening near the NE corner 

of sec. 17, T. 131 N., K. 100 W. Lack of thickness information northeast of Scranton precludes extending the deposit northward beyond 

the limits indicated on the map (pi. 19). Further prospecting may 

disclose additional reserves of thick lignite beneath the valley of the 

creek to the north. The Harmon bed is partly exposed at locations 81, 

83, 84, and 100, as well as at the opencuts of the abandoned mines in 

and near Scrantoii. In addition, the top of the bed is visible at several 

openings along the east margin of the reservoir northwest of Gascoyne, 

and in several of the road cute of both the railroad and the highway 

between the Adams County line and Scranton. These exposures all 

show some weathering; the only fresh exposure of the bed was at the 

Peerless mine (location 93), where a detailed megascopic examination 

was made of the upper part of the lower bench. In this examination, 

one-third of the measured section consisted of identifiable previtrain
168 CONTRIBUTIONS TO ECONOMIC GEOLOGY

in lenses more than one-fourth of an inch thick. The rest was predominantly attrital with a few disseminated flecks of pyrite and some 

thin veinlets of fusain. Clinker formed by burning of the Harmon 

bed is conspicuous along the highway and railroad.

Water is found near the base of the lignite bed at almost every 

point of information. Because the bed dips northeast 20 to 25 feet per 

mile and the land surface slopes in the opposite direction, the accumulated water probably could be drained from the pits only by 

pumping.

Three samples of the Harmon bed in the Scranton deposit have been 

.analyzed by the U. S. Bureau of Mines (table 3). One of these samples 

was taken from the Peerless mine; another was taken from the nowabandoned strip mine southeast of Scranton; and the third was taken 

from the now-abandoned underground mine near location 83.

OVERBURDEN AND FLOOR ROCK

The rocks overlying the Scranton deposit consist of poorly indurated sandstone, shale, and a few isolated lenses of fresh-water limestone. At the Peerless mine, clay predominates in the overburden for 

.about 30 feet above the Harmon bed. Above 30 feet the sediments 

become increasingly sandy. Minor constituents in the overburden are 

small iron sulfide concretions, which on exposure weather to limonite; 

gypsum crystals, which are particularly large and abundant just above 

the lignite bed at location 84; petrified tree stumps as large as 3 feet 

in diameter, which are scattered over the surface in the S% sec. 27, 

north of the Peerless mine; and lenses of dense, gray fresh-water limestone, which are 3 to 5 feet thick, and 15 to 20 feet in diameter, and 

contain carbonized plant stems and leaves. Several of these limestone 

lenses are interbedded with clay in the 20-foot section between the top 

bench and the main bench of the Harmon bed at the Peerless mine. 

A conglomerate competed of quartz sand and well-rounded pebbles of 

igneous rocks imbedded in a limy matrix tops Scranton Butte. This 

conglomerate is about 6 feet thick, slabby, and probably a remnant of 

a terrace formed during the erosion of White Kiver sediments, remains 

of which surmount the uplands of east-central Slope County to the 

north.

The floor rock at every point of information consists of clay.

RESERVES AND STRIPPING RATIO

The remaining reserves of strippable lignite in the Scranton deposit 

total 273 million tons, or about one-fifth of the total remaining reserves in the Bowman and Scranton deposits. (See table 1.) Of the 

;total reserves in the Scranton deposit, 140 million tons, or 51 percent,
STRIPPABLE LIGNITE, SLOPE AND BOWMAN COUNTIES, N. DAK. 169

is in the category of less than 60 feet of overburden. The stripping 

ratio in this category of reserves averages 1.9 to 1. The average 

stripping ratio for the Scranton deposit is 2.6 to 1.

POSSIBLE DEPOSITS OF STRIPPABLE LIGNITE

At least four other deposits in Slope and Bowman Counties possibly 

contain large reserves of strippable lignite. Four deposits arbitrarily numbered 1, 2, 3, and 4 and described below were located by 

means of data from seismograph shothole logs, water-well logs, or by 

reports of thick lignite by Hares (1928). Either because of insufficient field time, or because the deposits are too far from transportation to be of commercial importance at the present, the writers made 

no attempt to verify the indicated thickness of the lignite bed or to 

map thickness-of-overburden lines in detail. The reliability of the 

data, for the most part, are unknown and they are considered to be no 

more than a fair indication of the true thickness of the bed. However, the data may be of value to anyone making further investigations in this area. Therefore a map of each deposit was made (figs. 

21, 23, 25, and 27), and on each map is shown the probable line of 

outcrop of the strippable bed (modified after Hares, 1928, pi. 14), 

and the probable location of the 120-feet-of-overburden line, as well 

as the location of all available thickness information. These maps 

are merely sketch maps and do not show the outcrops of clinker or of 

other lignite beds in the area.

Reports of thick coal in other parts of the area for which no geologic maps have been published indicate that there may be other 

deposits of lignite which may be strippable. The following information is given as an aid to future investigation: (1) Seven seismograph 

shotholes drilled a mile apart along the east line of sees. 19, 30, and 31, 

and the south line of sees. 32 to 36, T. 134 K, K. 100 W., indicate that 

a lignite bed under from 29 to 120 feet of overburden ranges from 

7 to 27 feet in thickness; (2) in the four sections adjoining the township corner common to Tps. 133 and 134 1ST., Rs. 98 and 99 W., seismograph-shothole logs indicate that a lignite bed ranges from 10 to 20 

feet in thickness and lies beneath overburden from 20 to 85 feet thick; 

and (3) at the SW corner of sec. 15, T. 133 X., R. 99 W., a lignite bed 

that appears to be the same bed as that mentioned in (2) above is 

reported to attain a thickness of 30 feet below a depth of 4 feet, in a 

seismograph shothole.

DEPOSIT 1

Possible strippable deposit 1 occupies about 7y2 square miles in sees. 

17, 20,21, and 28 to 33, T. 136 K, R. 102 W., and sees. 5 to 9, 16,17, 20, 

21, and 22, T. 135 K, R. 102 W., Slope County, N. Dak. (fig. 21).
170 CONTRIBUTIONS TO ECONOMIC GEOLOGY

The northern tip of the deposit is just half a mile south of the Great 

Bend in the Little Missouri Kiver; the southern tip lies 8 miles west 

of the village of Amidon, reached by a graded, gravel-surfaced county 

road. The deposit underlies the northern part of the uplands which 

form the north-trending divide between Sand Creek and Deep Creek. 

These uplands generally present a smooth and fairly rolling surface, 

except along their margins where the slopes are steep and dissected.

R.103W. R. 102 W.

EXPLANATION

Outcrop of Harmon lignite bed, 

dashed where approximates 

(after Hares, 1928, pi. M)

Isopach lines showing thickness 

or Harmon lignite bed in feet

122 126^

Exposure Seismograph shothole 

or water well

Points where Hansen lignite bed 

was measured. Numbers refer 

to graphic sections on fig. 22

FIGURE 21. Sketch map of possible strippable deposit in 1 in Harmon lignite bed, Slope

County, N. Dak.

A few pines and cedars grow on these dissected slopes. Most of the 

land in the southern part of the deposit is farmed; the northern part 

of the deposit is mainly grass-covered pasture land.

In addition to three exposures, thickness information was provided 

by logs of 11 seismograph shotholes, of which those at locations 117 

and 125 were logged by the writers. These data (graphic sections 

nos. 114^-127, fig. 22) indicate that the Harmon bed ranges from 10
STRIPPABLE LIGNITE, SLOPE AND BOWMAN COUNTIES, N. DAK. 171

114 115

h

116 117 118

Ft in i^ 

1 2

2

8

4

U9

h

120 121

iFt in. 

4 3

14 10 120 125

122

h

123 124 125 126 127

EXPLANATION

Lignite Clay Shale

Depth figures give interval between surface 

of ground and top of lignite

Locations of sections are shown on fig. 21

Letters refer to source of lignite thickness information

h-Hares, C.J., 1928, pi. 10,

measured exposure 

s-seismograph shothole log

FIGURE 22. Sections of Harmon lignite bed in and near possible strippable deposit 1,

Slope County, N. Dak.

to 35 feet in thickness and probably averages at least 20 feet thick. 

Thus, the deposit is inferred to contain possible strippable reserves of 

about 170 million tons of lignite.
172 CONTRIBUTIONS TO ECONOMIC GEOLOGY

The overburden consists mainly of clay, shale, and soft sandstone. 

The thickness of the overburden is greatest in sec. 29, T. 136 N., 

R. 102 W., where the summit of a hill is about 150 feet above the lignite 

bed. The average thickness of the overburden in the northern part of 

the deposit is probably about TO feet. In the central part of the deposit the thickness of the overburden does not exceed 80 feet, and probably averages about 60 feet. At the extreme southern tip of the deposit, in the NE% sec. 21, T. 135 N., R. 102 W., the summit of a hill is 

about 130 feet above the lignite, but elsewhere the thickness of the overR. 104 W. R. 103 W.

EXPLANATION

Outcrop of Harmon lignite bed, 

dashed where approximate 

(after Hares, 1928, pi. 14)

Harmon lignite bed less than 10 

feet thick; no data on thickness 

of overburden

Exposure Seismograph shothole 

or water well

Points where Harmon lignite bed 

was measured. Numbers refer 

to graphic section in fig. 24

FIGURE 23. Sketch may of possible strippable deposit 2 in Harmon lignite bed, Slop&

County, N. Dak.

burden probably averages about 40 feet. The lignite bed dips northward and northeastward from 20 to 40 feet per mile. The bed lies 

entirely above the main drainage channels of the area.

DEPOSIT 2

Possible strippable deposit 2 (fig. 23) occupies about 8y2 square 

miles in sees. 5 to 9,16 to 21, and 29 to 32, T. 134 N., R. 103 W.; sees. 1, 

2,24, and 25, T. 134 N., K. 104 W.; sees. 31 and 32, T. 135 N., R. 103 W.; 

and sees. 35 and 36, T. 135 N., K. 104 W., Slope County, N. Dak. The 

deposit underlies part of the uplands which form the north-trending 

divide between Deep Creek on the east and the Little Missouri River
STRIPPABLE LIGNITE, SLOPE AND BOWMAN COUNTIES, N. DAK. 173

011 the west. The village of Rhame lies south of the deposit and is accessible by means of gravel-surfaced county roads. Marmarth, on the 

Little Missouri River, is 16 road-miles to the southwest. Only about 

one-fifth of the land is under cultivation, the rest being treeless, grasscovered pasture. This area was once farmed extensively, but as most 

of the land is submarginal, the Federal Government has purchased 

it and reseeded it with grass.

Four exposures measured by Hares (1928) and one seismographshothole log indicate that the Harmon bed in the northern part of

130 131 133 134

EXPLANATION

Lignite Shale Soil

Depth figures give interval between surface 

of ground and top of lignite

Locations of sections are shown on fig. 23 

Letters refers to source of thickness information 

h-Hares, C. J., 1928, pis. 12 and 13,

measured exposure 

s-seismograph.shot holelog 

w-water well-log

FIGURE 24. Sections of Harmon lignite bed in and near possible strippable deposit 2,

Slope County, N. Dak.

the. deposit ranges from 5 feet 7 inches to 12 feet 11 inches in thickness, 

and a seismograph shothole and a water-well log indicate that the bed 

in the southern part of the deposit may thicken to 35 feet (fig. 24). 

If an average thickness of 15 feet is assumed, the reserves of lignite 

under less than 120 feet of overburden are about 140 million tons. 

The Harmon bed in this area dips northeastward at about 20 feet 

per mile. Because the lignite lies well above the main drainage channels of the area, water may be disposed of easily.
174 CONTRIBUTIONS TO ECONOMIC GEOLOGY

The overburden consists mainly of soft sandstone, shale, and clay. 

The terraces that border the eastern margin of the deposit are capped 

by gravel. Except where modified by stream valleys, the land rises 

fairly steeply along the margin of the deposit; hence, the overburden 

throughout the deposit probably averages about 75 feet in thickness.

DEPOSIT 3

Possible strippable deposit 3 comprises about 9 square miles in 

sees. 16, 17, 20, 21, 22, 23, and 26 to 36, T. 133 N., K. 104 W., Slope 

County, and partial sees. 4 and 6, T. 132 N., K. 104 W., and partial 

sections 1 and 2, and sections 11 and 12, T. 132 N., E. 105 W., Bowman

EXPLANATION

Outcrop of T Cross lignite bed, 

dashed where approximate 

(after Hares, 1928, pi. 14)

T Cross lignite bed less than 10 

feet thick; overburden less than 

120 feet thick

Exposure

Points where T Cross lignite bed 

was measured. Numbers refer 

to graphic sections in fig. 26

Abandoned lignite mine

FIGURE 25. Sketch map of possible strippable deposit 3 in the T Cross lignite bed, Slope 

and Bowman Counties, N. Dak.

County, N. Dak. (fig. 25). The deposit is in the T Cross lignite bed 

of the Ludlow member, and occupies the headward part of the valley 

formed by westward-flowing Bacon Creek, an intermittent tributary 

of the Little Missouri Eiver. The land surface in the western part of 

the deposit is gently rolling and much of it is farmed. The surface in 

the eastern part of the deposit is characterized by steep slopes and is 

used mainly as pasture for livestock. Marmarth is 12.5 miles west 

from the deposit by way of the graded county road to the north, and is 

11.3 miles to the west by way of the county road and paved U. S. Highway 12 to the south. Ives, a siding on the railroad, lies less than a 

miles south of the deposit, and the Little Missouri lies about 5 miles 

to the west.
STRIPPABLE LIGNITE, SLOPE AND BOWMAN COUNTIES, N. DAK. 175

The only thickness data available for the T Cross lignite bed in and 

near the deposit are exposures measured by Hares (1928). These 

measurements show that the bed ranges in thickness from 4 to 24 feet, 

and at location 106 contains many shale partings (fig. 26). The 

lignite bed is assumed to average 15 feet in thickness throughout the 

deposit. Thus, the deposit is inferred to contain about 150 million 

short tons of lignite beneath less than 120 feet of overburden. Because of the lack of thickness information throughout the deposit, and 

because of the indicated variations in the thickness and quality of the 

T Cross bed along the outcrop, extensive drilling would be necessary 

to determine more precisely the amount of reserves within the deposit.

106 107 108 109 110 111 112 113

I Ft in 

2

2

1 6

1

2 6

6

Lignite Shale

locations of sections are shown on fig. 25 

Source of thickness information - 

Hares, C. 1,1928, pi. 13,measured exposure

FIGURE 26. Sections of T Cross lignite bed in and near possible strippable deposit 3, Slope 

and Bowman Counties, N. Dak.

A sample of lignite taken from the T Cross bed at the Durkin prospect 

has been analyzed by the U. S. Bureau of Mines (table 3).

The overburden consists mainly of shale and sandy shale with some 

sandstone. Gravel-capped terraces cover a wide area near the outcrop 

of the T Cross bed in the vicinity of the abandoned T Cross mine, and 

the Ives lignite bed lies 50 feet stratigraphically above the T Cross 

bed. The dip in this area is greater than in the eastern part of the 

county, owing to the proximity of the Cedar Creek anticline. Local 

dips of 5° and 3° to the northeast are reported by Hares (1928, p. 87) 

in the SEi/4 sec. 26, T. 133 N., E. 104 W., but the general dip within 

the area is about 45 feet per mile to the northeast.
176 CONTRIBUTIONS TO ECONOMIC GEOLOGY

DEPOSIT 4

Possible strippable deposit 4 comprises about 12 square miles in 

sees. 17 to 21,28,29, 30,32, and 33, T. 133 K, R. 101W., and sees. 10 to 

16 and 21 to 27, T. 133 N., R. 102 W., Slope County, N. Dak. (fig. 27). 

The deposit is in the Hansen lignite bed of the Tongue River member 

and underlies the low, rolling uplands of the upper tributaries of Deep 

Creek. Most of the land is farmed; the rest is grass covered and is 

used as pasture for livestock. The town of Bowman is about 8 miles

BOWMAN CO 

2 Mites

EXPLANATION

Overburden less than 

120 feet thick

Overburden more than 

120 feet thick

Hansen lignite bed less than 

10 feet thick; overburden 

'less than 120feet thick

Outcrop of Hansen lignite bed 

(modified after Hares, 1928 

plate 14) dashed where 

approximate

Exposure Seismograph shothole

or water well

Points where Hansen lignite bed 

was measured. Numbers refer 

to graphic sections on fig. 28

FIGURE 27. Sketch may of possible strippable deposit 4 in Hansen lignite bed, Slope

County, N. Dak.

south of the deposit and readily accessible by means of any of the 

three graded county roads which cross the area or by the all-weather, 

gravel-surfaced U. S. Highway 85, which passes along the eastern 

margin of the deposit.

The Hansen lignite bed in and near the deposit, as measured at the 

outcrop by Hares (1928), ranges from 6 feet 8 inches to 10 feet 7 inches 

in thickness, and at locations 145 and 146 contains a 2-inch parting of 

shale 2 feet above the base of the bed. Additional thickness data are
STRIPPABLE LIGNITE, SLOPE AND BOWMAN COUNTIES, N. DAK. 177

furnished by 3 water wells and 11 seismograph shotholes, of which 

those at locations 138,139, and 152 were logged by the writers (fig. 28).

I

137 138 139 140 141 142 143

Clay Shale

Depth figures give interval between surface 

of ground and top of lignite

Locations of sections are shown on fig. 27 

Letters refer to source of lignite thickness information 

s- seismograph shot-hole log 

w - water well report 

h - Hares, C, J., 1928, pis, 12 and 13, 

measured exposure

FIGUEH 28. Sections of Hansen lignite bed in and near possible strippable deposit 4,

Slope County, N. Dak.

These additional measurements indicate that the bed attains a maximum of 25 feet in thickness at location 147 the greatest known thickness of the Hansen bed in Slope and Bowman Counties. Within the 

deposit the Hansen bed probably averages 15 feet in thickness. In this
178 CONTRIBUTIONS TO ECONOMIC GEOLOGY

average are included the thickness of the top 2 of the 3 benches of 

lignite that are reported in the log from a water well drilled at location 

144. The 3 benches at location 144 and the unusual thickness of lignite 

at location 147 indicate that the Hansen bed may coalesce with the 

underlying H bed in this- area. The indicated reserves within the 

deposit total about 200 million short tons of lignite. No allowance 

is made for weathered lignite in these reserves, although as much as 

10 percent of the reserves may be weathered along the outcrop where 

the overburden is thin.

The overburden consists mainly of poorly indurated calcareous sandstone, clayey shale, and clay. The Harmon lignite bed and clinker 

from the burned Harmon bed lie from 40 to 60 feet above the Hansen 

bed and are mapped in detail as part of the Bowman deposit (pi. 16) 

The contour line outlining 60 feet of overburden in the Bowman 

deposit approximates the 120 feet-of-overburden contour of deposit 4.

LITERATURE CITED

American Society for Testing Materials, 1939, Standard specifications for classification of coals by rank (A. S. T. M. designation: D 388-380) : 1939 Book

of A. S. T. M. Standards, pt. 3, p. 1-6. 

Averitt, Paul, and Berryhill, L. R., 1950, Coal resources of the United States:

U. S. Geol. Survey Circ. 94. 

Benson, W. E., 1949, The Golden Valley formation of North Dakota (Abs.) :

Geol. Soc. America Bull., v. 60, no. 12, pt. 2, p. 1873-1874. 

 1952, Geologic Map of North Dakota southwest of the Missouri River:

U. S. Geol. Survey prelim, map. 

Benson, W. E., and Laird, W. M., 1947, Eocene in North Dakota (Abs.) : Geol.

Soc. America Bull., v. 58, no. 12, p. 1166-1167. 

Brant, R. A., 1953, Lignite resources of North Dakota: U. S. Geol. Survey Circ.

226. 

Brown, Andrew, and others, 1954, Strippable coal in Ouster and Powder River

Counties, Mont.: U. S. Geol. Survey Bull. 995-E. 

Brown, R. W., 1948, Correlation of Sentinel Butte shale in western North Dakota:

Am. Assoc. Petroleum Geologists Bull., vol. 32, no. 7, p. 1265-1274. 

Clarke, F. F., 1948, Southwestern North Dakota clay deposits, Stark, Slope, and

Billings Counties, N. Dak.: U. S. Bureau of Mines Rept. Inv. 4219. 

Coal Age, 1949, Rosebud stripping: v. 54, p. 98-102, March. 

Culbertson, W. 0., 1954, Three deposits of strippable lignite west of Tellowstone

River, Montana: U. S. Geol. Survey Bull. 995-H. 

Darton, N. H., 1896, Preliminary report on artesian waters of a portion of the

Dakotas: U. S. Geol. Survey 17th Ann. Rept., p. 603-694. 

Dove, L. P., 1926, Dakalite: m Leonard, A. G., Gauger, A. W. Budge, W. E., and

Dove, L. P., Geology and Natural Resources of North Dakota: N. Dak. Univ.

Dept. Bull., v. 11, Bull. no. 9, p. 33-37. 

Federal Emergency Relief Administration, Project S-F2-56, 1934, Analyses of

lignite samples from two hundred forty-five mines under lignite survey and

investigations North Dakota Univ. Coll. Engineering, Div. Mines and Min.

Experiments Circ. 8.
STRIPPABLE LIGNITE, SLOPE AND BOWMAN COUNTIES, N. DAK. 179

Hares, C. J., 1928, Geology and lignite resources of the Marmarth field, southwestern North Dakota: U. S. Geol. Survey Bull. 775. 

Kepferle, R. C., 1954, Selected deposits of strippable coal in central Rosebud

County, Mont.: U. S. Geol. Survey Bull. 995-1. 

Lavine, Irvin, 1939, Lignite: Department of Chemical Engineering, N. Dak. Univ.

(mimeographed reproduction). 

Leonard, A. G., 1922, The White River formation of North Dakota: N. Dak. Univ.

Quart. Jour., v. 12, no. 3, p. 218-228. 

 1925, Lignite deposits in Bowman and Slope Counties, in Leonard, A. G.,

Babcock, E. J., and Dove, L. P., The lignite deposits of North Dakota:

N. Dak. Geol. Survey Bull. 4, p. 58-77. 

Leonard, A. G., and Smith, C. D., 1909, The Sentinel Butte lignite field of North

Dakota and Montana: U. S. Geol. Survey Bull. 341, p. 15-35. 

May, P. R., 1954, Strippable lignite deposits, Wibaux area, Mont, and N. Dak.:

U. S. Geol. Survey Bull. 995-G. 

Stebinger, Eugene, 1912, The Sidney lignite field, Dawson County, Mont.: U. S.

Geol. Survey Bull. 471, p. 284-292. 

Tryon, F. G., Kiessling, O. E., and Mann, L., 1926, Coal: U. S. Bur. Mines, Min.

Res. U. S, pt 2, p 419-585. 

United States Bur. Mines 1948, Analyses of Michigan, North Dakota, South

Dakota, and Texas coals: Tech. Paper 700, p. 42-58, 69-90. 

United States Geol. Survey, 1942-1952, Surface water supply of the United States,

pt. 6, Missouri River basin: Water-Supply Papers 896, 926, 956, 976, 1006,

1036,1056,1086,1116,1146. 

Winchester, D. E., Hares, C. J., Lloyd, E. R., and Parks, E. M., 1916, The lignite

field of northwestern South Dakota: U. S. Geol. Survey Bull. 627. 

Young, W. H., and Anderson, R. L., 1952, Thickness of bituminous coal and

lignite seams at all mines and thickness of overburden at strip mines in

the United States in 1950: U. S. Bur. Mines Information Circ. 7642, p. 13. 

Young, W. H., Anderson, R. L., and Hall, E. M., 1952, Bituminous coal and

lignite in 1951: U. S. Bur. Mines Mineral Market Rept. No. 2102.

INDEX

Page 

Abstract.- 123-124

Acknowledgments_______..___-_ 128 

Agricultural activities. See Land use. 

Alluvium-- 137

Analyses of lignite-.-.--__ 138,139 

Attrain. - 138,168

Badlands. . 128-129,132,134

Baker-Qlendive anticline. See Cedar Creek anticline. 

Bed A of Sentinel Butte field...... __. 143

Bed G of Sidney lignite field- 143

in Hansen lignite bed-__________ 178

Benches, in Harmon lignite bed_-__.__ 143-144,

155,164,166-167

Benson, W. E., cited 133,136

Black Butte. See H T Butte.

Bowman deposit, dip---_.________. 155,158

drainage, northern part--_________- 155

southern part_____________ 164

floor rock, north-central part--____._. 159

northern part ______-.___. 156

south-central part--.______.__ 162

southern part____ - __ _ - _. __ 165

Harmon lignite bed, north-central part- 157-158

northern part____.___.-____ 155

south-central part-.-________ 160-161

southern part ____________ 163-164

land use, north-central part________ 157

northern part -___________. 155

south-central part..._______... 160

southern part ____. __ ____ __ 162

location, north-central part.-______., 156

northern part____________. 154

south-central part--.________ 159 

southern part.---_____-_____ 162 

overburden, north-central part_.__.- 158-159 

northern part ._______-. 155-156 

south-central part---___.._..____ 161

southern part--_____._____ 164-165

reserves, north-central part._____._ 126,159

northern part_____....._____ 126,156

south-central part----________ 126,162

southern part__....______ 126,165

stripping ratio, north-central part--._ 126,159 

northern part..--..._______.. 126,156 

south-central part,-_________ 126,162 

southern part ------_______ 126,165

topography, north-central part--.____ 157 

northern part------________.... 154

south-central part_.--__.____ 159-160

southern part _______.__.. 162-163

Bowman lignite bed. See Harmon lignite bed.

Bowman mine, analysis.---___..____ 139

Buffalo Creek..---....-----------.----..-.... 166

Buffalo Creek mine, analysis..._..__._. 139 

Burning lignite beds__-_. .____.. 140-142 

Burr, A. C., cited____...._.. .-........ 146

Page 

Cannonball formation.-_------_ . 134

Cannonball lignite bed.--__________ 134 

Cedar Creek.- 159,160,162,166 

Cedar Creek anticline.. -----_._ 133,137,175

Chalky Buttes 136,142

Chemicals from lignite....__.______ 146-147

Climate... - . 131

Clinker...... 135,137,140,143,155,156,

158,161,164,168,169,178 

Coal rights--...... - - 133

Criteria for selection of strippable deposits,

location-. .----__..._._ 149

partings--._... ____..... 149-150

reserves. _ . -. 149 

shape._______...__-.._. 150 

thickness of lignite. _...._... . 148

thickness of o verburden.. ________ 148-149 

weathering of bed..._..__---------- 149

Data, collection--.____..._______ 151 

Deep Creek--..--.-._ 137,157,159,160,162,170,172 

Dip of the beds. See Structure. 

Durkin prospect__________.______ 175

Earlier geologic investigations-.________ 127

Faulting--- 137

Field work 128,152

Floor rock . 156,159,162,165,168 

Fort Union formation......_..... . 133,134-136

Fossfls... - _--------- 134,135,136,161,165,168

Fox Hills sandstone-.---------- -----.. 129,133

Fusain _ 138,168

Future uses of lignite___. _________ 138,147

Gascoyne mine. See Peerless mine. 

Giannonatti lignite bed .____ ..__ 142 

Glendive anticline. See Cedar Creek anticline.

Gravel. _... 135,137,154,156,157,159,168,169,174,175 

Gress mine.___ ._----______-_ 145 

Ground water-.. . 129,155,156,158,161,168 

Gypsum..-...... . 135,138

Halleck mine_-____..______-

Hallenbeck mine..___- _______- 

Hansen lignite bed 142,143,162,

Hares, C. J., geologic investigations cited... 

Harmon lignite bed...-___-____-.-. 

139, 142, 143-144, 155, 157-158, 

163-164, 166-168, 170-173, 178. 

Haynes lignite bed-.._-..--.______.. 

Hells Creek formation.--...-...-...--_... 

H lignite bed...._________..______.

H T Butte--. . -129,135,137,142,157, 

H T Butte lignite bed._-------------- 135,

139,164 

139,161 

176-178 

136,143

- 135, 

160-161,

-. 144 

133-134

- 178 

158,159 

139,142

Investigation, detailed. ...________ 150-153

181
182 INDEX

Page

Investigation Continued

preliminary________________ 150 

purpose...._.._....._________ 147

Ives lignite bed________________ 176

Lamb mine_. ________________ 146 

Land use... 132,156,157,160,162,166,170,173,174,176 

Langermlne, analysis..___________ 139 

Leonardite________.___________ 140 

Lignite, analyses..------__________ 138-139

physical characteristics_________ 137-138 

storage methods._____________ 138 

use... ........................... 128-129,137

Limestone.....__..___.__.____ 135,168

Little Missouri River. ..........,__________ 127,

128-129,131,137,156,170,172,174 

Lndlow member, Fort Union formation ___ 134

Macdonald, J. R., cited__._..._ __ 136

Marmarth lignite field...__._.__....__ 142

Measurements, accuracy..._.._____ 151-162

how obtained._______________ 161

Meggers, B., cited_______________ 143

Mining of lignite, for commercial markets.... 146

for local use- .._____....._ 143,144,145

historical sketch______________ 144

Oil and natural gas, effect on use of lignite.. 146-147 

Orthoquartzite..______..__..... 124,135,162

Other deposits. See possible deposits. 

Outcrops......... ........... 142,143,152,167,176

Overburden, average thickness _______ 149,178

mapping method._____,______ 152

removal.._________________ 105

Ownership of land____ __________ 133

Partings in lignite.................. 142,149-150,151

152,155,158,161,164,166-167,174,176 

Peerless mine....... 139,140,144,145,146,165,167,168

Pierre shale...._____________.___ 133

Population.--.--.- -_...._.-..._.-...- 131

Possible deposits..- . . 125,142,143,169,178 

land use.. . . 170,173,174,176 

lignite in.... 171-172,173,175,176-178

location, deposit 1..___________ 169,170 

deposit 2.. _ 172,173 

deposits... . 174

deposit 4... ... .. 176 

reserves...... ............... 171,173,175,178

topography.... ..._ _... 170,174

Power-auger drill holes, discussion______ 151 

Power supplies.._._.____....... 132-133,154

Previtrain . . 138,140,167,168 

Production of lignite in area. ________ 144,145 

Prospecting drill holes, discussion... 151,152,163-164

Pyrite and marcasite.

Page

135,138,156,168

Reserves..-_________________ 125,

126,149,156,162,165,168,171,173,175,178

calculation of______________ 162,153

Sand Creek .............. 137,154,155,157,158,170

Scranton Butte..... . ......._. .. 166,168

floor rock_________________ 168

Scranton deposit, drainage__________ 166

Harmon bed in.......... __ .. 166-168

land use..____._._..___.___ 166 

location--.. . 165,166 

overburden________________ 168 

reserves...________..._______ 168 

stripping ratio_______________ 16& 

topography...... __ ___ . 166

transportation_______________ 165 

Scranton lignite bed. See Harmon lignite bed. 

Scranton mine, analysis...._.___.___ 139

Seismograph shotholes, discussion______ 151 

Sentinel Butte shale member Fort Union formation.......... .... 135-136,142

Stratigraphy... ....................... 133-137

Strip-mining methods.. _________ 145,148,150

advantages________________ 127

Stripping ratio ....._.__~_._...... 126,

148-149,153,154,156,159,162,165,16* 

Structure 137,155,158,164,168,172,173,17& 

Styles, W. V., cited..... . 127,15*

Surface-water supplies.___________ 129-131

T Cross lignite bed . 134,139,142-143,174,175-17& 

T Cross mine......____..-....-_ . 139,175

Terraces ... 137,154,156,157,159,160,174,175 

Thickness, lignite...._____._______ 126,^

142,143,144,148,155,157,161,164,166,169,170, 

171,173,175,176-177

overburden_______ .... MSMO, 155,156,158-159,161,164-165,168,172,174 

categories _.. 148 

Tongue River member, Fort Union formation. 134-

135,14i

Topography of the area...__ ... 128-129,154 

Transportation 132,145,149,154,165,173,174,176 

Twin Buttes-. . - 162-163

Unnamed lignite beds. 139,156,165,169

Water-bearing lignite. 155,158,181,168- 

Water supply.... ..... 129-131,154,156

Water-well drill holes, discussion.. 151 

Weathered lignite.. ....... 129,140,161,164,167,178

White Butte.--. - -- 136,157

White River formation.... 133,136,137,157

I. 5. GOVERNMENT PRINTING OFFICEl I(II>