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< 0.3
< 0.3
< 0.4
< 0.2
0.9 +/- 0.6
0.8 +/- 0.2
1.1 +/- 0.30.2 +/- 0.1
0.4 +/- 0.3
0.6 +/- 0.6
3.8 +/- 1.2
1.0 +/- 0.3
0.9 +/- 0.3
1.3 +/- 0.3
0.8 +/- 0.7
0.8 +/- 0.4 1.1 +/- 0.4
1.0 +/- 0.4
1.5 +/- 0.51.0 +/- 0.4
2.2 +/- 0.82.9 +/- 0.9
2.637 +/- 0.166 3.518 +/- 0.1665.067 +/- 0.288
0.013 +/- 0.002
0.117 +/- 0.007
0.019 +/- 0.001
0.024 +/- 0.001
0.652 +/- 0.026
0.287 +/- 0.023
0.155 +/- 0.0090.110 +/- 0.009
0.152 +/- 0.012
0.603 +/- 0.028
0.013 +/- 0.001
0.981 +/- 0.0390.105 +/- 0.005
1.073 +/- 0.086
0.056 +/- 0.004
0.095 +/- 0.029 0.108 +/- 0.005
0.205 +/- 0.009
0.024 +/- 0.010
0.042 +/- 0.002 0.183 +/- 0.008
0.031 +/- 0.006
0.018 +/- 0.004
0.018 +/- 0.012
0.013 +/- 0.010
0.225 +/- 0.028
0.096 +/- 0.004
0.077 +/- 0.017
0.016 +/- 0.0970.012 +/- 0.017
0.239 +/- 0.015
0.270 +/- 0.021
0.127 +/- 0.020
1.113 +/- 0.040
0.237 +/- 0.017
0.227 +/- 0.013
0.326 +/- 0.016
0.217 +/- 0.1270.515 +/- 0.019
0.120 +/- 0.006
0.014 +/- 0.0020.308 +/- 0.025
0.089 +/- 0.013
0.014 +/- 0.005
0.211 +/- 0.012
0.188 +/- 0.0110.191 +/- 0.008
0.114 +/- 0.0050.133 +/- 0.0060.105 +/- 0.005
3.226 +/- 0.2582.840 +/- 0.1612.747 +/- 0.220
z{14-16
z{59
z{20
z{387
z{16
z{18
z{220
z{487
z{59z{14
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§̈¦I-90
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3400
4327
3901
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3392
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3228
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3726
3731
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3269
3970
4396
2706
3583
3743
3948
3490
3365
3121
4245
3270
4807
3304
2941
4407
3764
4301
5155
4541
2502
3310
5204
7723
4011
3757
5175
6064
5307
6049
5370
4991
8255
4586
5130
9358
4002
5717
4835
4886
7414
4636
4672
4262
8305
5303
4470
Devils Tower5110
4892
8318
5645
6090
10534
10828
13167
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626160
5958
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65
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4645
4443
4241
32
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35
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38
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36
3029
28
27
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25
24
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2221
19
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18
1716
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14
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12
11
10
South
Cra
zy
Clea
r Cre
ek
Pow
der
Pow
der
Missouri
Belle
Fou
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Rive
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Keyhole Reservoir
Platte
North Platte RiverPoison Spider Cr
South Fork
Caspe
r
Cr
Fork Casper Cr
Fork
CasperC
r
North
Middle
SouthFork
Wallace
Cr
Powder Rive
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Cottonwood
Cr
IndianCr
Willo
w
Cr
Powder
Buffa
lo
Cr
Fork
Middle
Fork
North
Powder River
Red Fork
Powder River
ForkMiddle
Fork
North
Crazy
Woman
Sout
h Fo
rk
River
Powde
r
Riv
er
SaltCr
SaltCr
Teap
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CrCastle
Cr
Dug
out
Cr Meadow Cr
Cottonwood
Cr
FourmileCr
Pow
der
Fork
River
Pow
der
Riv
er
River
Wom
an
NinemileCr Dry Willow
Cr
PumpkinCr
BeaverCr
Flying E Cr
Dead
Cr
Horse
Barber Cr
Pow
der
Lake DeSmet
Clear Creek
Rock Cr
Tensleep Cr
Now
ood River
Boxeld
er C
r
Piney Cr
Prairie
Dog
Cr
Goose
Cr
Tongue River Reservoir
Tongue River
Cr
Horse
Wild
FortificationCr
Rive
r
Cr
Horse
Cr
Wildcat
Cr
Cottonwood
LittlePowder
R
Little
R
iver
River
Cr
Four Horse Cr
Raven
Cr
Buffalo
Cr
Wind
Cr
Arch
Cr
Inyan Kara
Cabin CrMiller Cr
Little
River
Cr
Thompson
R
North Fork Missouri
Little
RM
issouri
Little
Prairie Cr
Olmstead CrDry
Cr
DuckCr
Spotted
Cr
Horse
Cr
L X Bar
Cr
S A
Cr
Bitter
CrBuffalo
Cr
Badger
Cr
Dutch
Goose
Cr
GooseCr
Big
Cr
Wolf
Tongue R
iver
Rosebud Creek
Ros
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Creek
Rosebud C
reek
Arm
ell’s
Cr
W F
k Ar
mel
l’s C
r
E Fk Armell’s Cr
Yellowstone RiverYellowsto
ne River
Sweeney Cr
Moon CrGraveyard C
r
Sarpy Cr
Big Porcupine Cr
Little Porcupine Cr
Tullock Cr
Tullock Cr
Tong
ue R
iver
Reno Cr
Ow
l Cr
Lodge Grass Cr
Riv
er
Ross Cr
Littl
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orn
River
Little Big
Horn
Otter C
reek
Pum
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Cre
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Pum
pkin
Cre
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Little Pumpkin CrBeaver Cr
Liscom Cr
Foster Cr
Ash Cr
Tongu
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Tongue River
Miz
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Cre
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Mizp
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reek
Sheep Creek
Locate Creek
Powder
River
Powder
River
Ash
Cr
Creek
O’F
allo
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r
Sandstone Cr
Lame Jones Cr
Milk Cr
Spring Cr
Pine Cr
East Fork
Little Beaver C
r
Spring CrDry Cr
Timber Cr
Crow Cr
Cabin Cr
Corral Cr
Box Elder Cr
Powd
er R
iver
Pilgrim Cr
E Fk Little Powder River
Willow Cr
S Cottonwood Cr
Cr
Hay
Cr
Lodgepole
Cr
Black
Cr
ThunderLittle Thunder
Cr
Antelope
Cheyenne River
Cr
Porcupine
Cr
Bates
CrAntelope
CrSand
Cheyenne River
Dry Fork
Cr
Walker
CrBox
Cr
Lightning
Cr
Lightning
CrDry
Cr
Twen
tymile
Cr
Lanc
e
Cr
Caballo
Wild Horse Cr
Mud Spring Four
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Belle
River
Fourche
Belle
Riv
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CrDonkey
Cr
Shaw
nee
Cr
Lost
Cr
LaPre
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Cr
Box
Elde
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Cr
Deer
Cr
Sage
Cr
Sand
RiverNorth
Cr
Cole
CrM
uddy
Soda Lake
O’Fallon
R50E R55E
T9S
T5S
T1S
T1N
T5N
R45ER40ER35E
T9S
T5S
T1S
T1N
T5N
T55N
T50N
T50N
T45N
R70WR75W
T45N
R80WR85W
T40N
T40N
T35N
T35N
T55N
T30N
T55N
T50N
T45N
T40N
R65W
R70WR75WR80WR85W R65W
R70WR75WR80WR85W R65W
T35N
T30N
T30N
R45ER40ER35E
R50E R55E
107°30'0"W
107°0'0"W
107°0'0"W
106°30'0"W
106°30'0"W
106°0'0"W
106°0'0"W
105°30'0"W
105°30'0"W
105°0'0"W
105°0'0"W 104°30'0"W
46°30'0"N
46°0'0"N
46°0'0"N
45°30'0"N
45°30'0"N
45°0'0"N
45°0'0"N
44°30'0"N
44°30'0"N
44°0'0"N
44°0'0"N
43°30'0"N
43°30'0"N
43°0'0"N
43°0'0"N
Block diagram of clinker-dominated landscape (from Heffern and Coates, 1997)
Schematic cross section B–B', Tongue River Valley, near Ashland, MT
(Cross sections from Heffern and others, 2007)
Schematic cross section A–A', Rochelle Hills, east of Wright, WY
Cross section
Ma = millions of years
0
0 5 km
5 mi
0 4 miles2
clinker of Knobloch coal zone
clinker of Anderson coal zone
clinker of other coal beds
0.227+/- 0.013
4921 ft
4593 ft
3937 ft
3281 ft
The Rochelle Hills escarpment capped by the clinker formed by the burning of the Wyodak coalbed, at Keyton Canyon east of Wright, Wyoming.
Ed Heffern below the base of the clinker formed by the burning of the Knobloch coalbed in the Tongue River valley north of Ashland, Montana. Collapsed blocks of reddish baked sandstone overlie the basal ash zone that marks the original base of the coalbed, underneath which is unburned sandstone.
A 25-foot high chimney of hard, welded breccia and paralava formed by the natural burning of the Wyodak coalbed in the Rochelle Hills, Wyoming. Note the person (white oval) standing on the right side of the chimney.
Mark Engle of the U.S. Geological Survey sampling gases coming off a coalbed fire along the banks of the Tongue River north of Sheridan, Wyoming.
View of collapse along burn front of the same active coalbed fire shown in picture to left, north of Sheridan, Wyoming. The reddish color in parts of the collapsed area marks areas where clinker has formed.
10 Miles
10 Kilometers
R70W
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#*#*
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Antelope Mine
North Antelope / Rochelle Mine
Black Thunder Mine
Jacobs Ranch Mine
0.7 +/- 0.3
0.5 +/- 0.30.8 +/- 0.5
0.3 +/- 0.2
A
A'
< 0.5
< 0.6< 0.5
< 0.09
0.7 +/- 0.4
0.5 +/- 0.40.3 +/- 0.3
0.3 +/- 0.2
0.4 +/- 0.2
0.5 +/- 0.30.4 +/- 0.2
0.7 +/- 0.3
0.198 +/- 0.011 0.482 +/- 0.027
0.127 +/- 0.010
0.536 +/- 0.025
0.205 +/- 0.012
0.502 +/- 0.028
0.550 +/- 0.0310.615 +/- 0.035
0.216 +/- 0.012
0.120 +/- 0.008
0.010 +/- 0.001
0.115 +/- 0.008
0.219 +/- 0.009
0.211 +/- 0.012
0.213 +/- 0.012
0.096 +/- 0.0060.249 +/- 0.023
0.007 +/- 0.006
0.016 +/- 0.006
Inset Map 2R70W
T40N
R69W R68W R67W
T41N
T42N
T43N
T39N
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0.648 +/- 0.023
0.352 +/- 0.027
0.301 +/- 0.045
0.396 +/- 0.032
1.009 +/- 0.073
0.202 +/- 0.030
0.924 +/- 0.244
0.578 +/- 0.080
0.498 +/- 0.051
0.802 +/- 0.029
0.565
+/-
0.
019
0.242 +/- 0.0690.130 +/- 0.022
0.562 +/- 0.0340.275 +/- 0.120
0.334 +/- 0.132
0.456 +/- 0.075
Inset Map 1
1 Mile
1 Km
MTWY
R84W R83WR85W
T56N
T57N
T9S
R36E R37E
T9S
T10S
A
A'
B
B'
Forsyth
Miles City
Colstrip
Lame Deer Ashland
Busby
Crow Agency
Broadus
Ekalaka
Hulett
Gillette
Wright
Douglas
Casper
Kaycee
Buffalo
Sheridan
Lodge Grass
Pumpkin Buttes
Rochelle
Hills
Bear LodgeMountains
See Inset Map 1
see Inset Map 2
MontanaWyoming
Custer CountyPowder River County
Fallon CountyCarter County
Big Horn CountyTreasure County
Yellowstone County
Ros
ebud
Cou
nty
Cus
ter C
ount
y
Rosebud County
Pow
der R
iver
Cou
nty
Car
ter C
ount
y
Cam
pbel
l Cou
nty
Cro
ok C
ount
y
She
ridan
Cou
nty
Cam
pbel
l Cou
nty
Sheridan CountyJohnson County
Campbell CountyConverse County
Johnson CountyNatrona County
Was
haki
e C
ount
yJo
hnso
n C
ount
y
Con
vers
e C
ount
yN
iobr
ara
Cou
nty
Weston CountyNiobrara County
Crook CountyWeston County
Big Horn CountyWashakie County
Keyhole Reservoir
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Cloud Peak
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Bighorn Mountains
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A
A'
Rochelle
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0.6 +/- 0.6
z{12
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Laramie Mountains
Jacobs Ranch Mine
Black Thunder Mine
North Antelope/Rochelle Mine
Antelope Mine
Wolf M
ountains
Little
Wolf
Mou
ntains
Bigh
orn
Mou
ntai
ns
Coal CreekMine
Cordero-RojoMine
Caballo MineBelle AyrMine
WyodakMine
Dry Fork Mine
Eagle ButteMine
RawhideMine
BuckskinMine
East DeckerMine
SpringCreekMine
Dave Johnston
Mine
RosebudMine
AbsalokaMine
#I
West DeckerMine
Clinker Distribution and Age in the Powder River Structural Basin
ByEdward L. Heffern, U.S. Bureau of Land Management (Retired)
Peter W. Reiners, University of Arizona, Tucson, AZCatherine A. Riihimaki, Drew University, Madison, NJ
2013
Age of ClinkerHow long ago did coal at a given location burn to form clinker? Clinker can be dated by several means, including uranium-thorium / helium ratios and fission-track counts in zircon grains from within baked sandstone, as well as paleomagnetic dating of magnetite, hematite, and goethite in paralava. These dates, in turn, help us to better understand how the landscape evolved over geologic time as major river systems cut down into the sediment of the Powder River Basin, and the rate at which coalbeds were exposed, burned, and released combustion gases into the atmosphere.
Uranium-Thorium/Helium (ZHe) ages of clinker, in millions of years (Ma)
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0–0.0490.050–0.1490.150–0.2490.250–0.499
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0.500–0.9991.000–1.9992.000 and older
All ZHe analyses are from Reiners and others (2011), Riihimaki and others (2009), and Heffern and others (2007).
Zircon fission-track (ZFT) ages of clinker, in millions of years (Ma)
Paleomagnetic samples of clinker #*
#*
Normal polarity
Reversed polarity
")
")
")
0–0.1490.150–0.2490.250–0.499
")
")
")
0.500–0.9991.000–1.9992.000 and older
All ZFt analyses are from Heffern and others (2007) and Coates and Naeser (1984).
All paleomagnetic analyses are from Jones and others (1984).Normal polarity indicates the coal burned more recently than the Matuyama-Brunhes magnetic reversal at about 0.78 Ma.
The authors thank Stefan Nicolescu, Victor Valencia, and George Gehrels for analytical assistance on dating the ZHe samples; Jason Whiteman, William Reiners, Paul Gore, Zoe Ruge, Camille Jones, Jessica Scheick, and Kaia Davis for field assistance in sample collection; Don Luse for access to the Padlock Ranch; Donald Coates, Charles Naeser, and Roger Colton of the U.S. Geological Survey (retired), for their geological advice and expertise; and Larry Neasloney of the U.S. Bureau of Land Management for Geographic Information System advice.
Layout by Susan Smith, MBMG. Edited by Susan Barth, MBMG.
Base map created in ArcMap for a poster presentation at AAPG Rocky Mountain Section Meeting, Cheyenne, Wyoming June 2011.
No warranty is made by the Bureau of Land Management as to the accuracy, reliability, or completeness of these data for individual use or aggregate use with other data.
Transverse Mercator ProjectionUTM Zone 13N, NAD 1983
Clinker
Clinker outcrops
Clinker is rock that has been baked, sintered, or melted by burning of underlying coalbeds. Clinker forms reddish layers that cap hills and escarpments in the landscape. In the southeast corner of this map (and Inset Map 2), the Rochelle Hills form an east-facing escarpment capped by clinker of the Wyodak coal zone. The coal is being mined just west of its outcrop/burn line. Nearly all of the coal in the map area occurs in formations of Tertiary age. The clinker in the map area results from natural burning in prehistoric times of coalbeds in the Paleocene Fort Union and Eocene Wasatch Formations. Additional clinker may be present in the subsurface beneath younger alluvium, but not exposed at the surface. Clinker is also common in landslides and talus deposits downslope from clinker-capped ridges.
Clinker outcrops shown on this map of the Powder River Basin cover a total of 1,472 sq. mi. (3,812 sq. km.). Of this total, 1,094 sq. mi. (2,833 sq. km.) of clinker are in Montana and 378 sq. mi. (979 sq. km.) are in Wyoming. These clinker outcrops represent the natural burning of tens of billions of tons of coal. Much additional clinker, perhaps an order of magnitude more, has been eroded away and carried downstream into the tributaries of the Missouri River. The record of this eroded clinker is present as clinker cobbles in Quaternary and late Tertiary gravel terraces. Natural coal fires have been a significant source of greenhouse gas emissions in prehistoric times, although the rate of natural burning is much less than the current rate of coal mining.
The clinker outcrops shown were mapped by E.L. Heffern, the lead author, from the following public sources: published geologic maps and digital data files from the U.S. Geological Survey, Montana Bureau of Mines and Geology, and Wyoming State Geological Survey; data interpreted by the author from color and color infrared aerial photography and National Agriculture Imagery Program color and color infrared orthophotos; and data from coal mine permit maps on public file with the State of Wyoming Land Quality Division. The full reference list is available on the Montana Bureau of Mines and Geology website at http://www.mbmg.mtech.edu/.
The Tertiary bedrock of the Fort Union and Wasatch Formations is mostly poorly to moderately consolidated sandstone, siltstone, and shale interfingered with coalbeds. When a subaerially exposed coalbed catches fire, the fire front burns back beneath the sandstone, siltstone, and shale overburden of these sediments. It ‘fires’ the overlying rock in a manner similar to ‘firing’ bricks. The result is the hardened, fractured rock called clinker. Most clinker is red, but some contains shades of yellow, orange, and black. In general, baked sandstone retains its original grain structure. The grains of fine-grained sediments are sintered—heated and welded together to form a coherent mass without melting—resulting in a rock similar to porcelain. A small amount of rock—primarily in fissures that served as chimneys— has been melted to hard black paralava. Virtually all of this clinker is harder than the parent rock. At the base of the clinker lies a thin layer of light tan ash mixed with greenish glass. In addition, clinker is highly fractured and allows much water to drain through rather than run off. The greater hardness, combined with fracture permeability, makes the clinker more resistant to erosion than the unfired bedrock strata above and below. Consequently, regional downwasting leaves the clinker forming the tops of scarps and ridges. See block diagram and cross sections.
Area underlain by Tertiary sediments
Early Quaternary / Late Tertiary gravel terraces (only those in Montana shown)
!
4301#I
Land and Resource Data
Cities and towns
State boundary
County boundary
Major paved highways
Summit elevations in feet above mean sea level
Interstate highways
Rivers and streams
Mined areas through 2010
Coal Mines
The 16 active coal mines in the Powder River Basin—12 in Wyoming and 4 in Montana—include the largest coal mines in North America. These mines produced 462.6 million short tons, 42.2% of total U.S. production, in 2011 (U.S. Energy Information Adminis-tration). Of this total, 426.1 million short tons came from Wyoming and 36.5 million came from Montana. The approximate areas where coal has been mined are shown in dark gray on the map. These areas are based on mine plans and annual reports of coal mine permits on public file with State mine regulatory agencies. Total areas mined through the year 2010 cover about 164 sq. mi. (425 sq. km.). Each mine has a program to quickly extinguish coal fires in mining pits, highwalls, and spoil piles.
The Powder River Basin, with its dry climate, low-rank coalbeds rich in volatile matter, and commonly occurring range fires, provides ideal conditions for coalbed fires. Near-surface and exposed coalbeds above the water table have ignited due to causes as diverse as lightning strikes, wildfires burning trees and bushes rooted in coalbeds, and spontaneous combustion in coal mines and outcrops. The 81 coal fires shown were compiled by the lead author from personal contacts and observations, published maps and articles, U.S. Bureau of Mines fire control project reports, and U.S. Office of Surface Mining, Wyoming Abandoned Mine Land Division, and U.S. Bureau of Land Management records. The recent vast range fires in the northern Powder River Basin during the summer of 2012 may have ignited additional coalbed fires.
Coalbed Fires
42
Active and historical coal fires, identification number indicated. Refer to coal-fire spreadsheet for details, available on the Montana Bureau of Mines and Geology website at http://www.mbmg.mtech.edu/.
$
$$
Mine fires
Spoil fires
Outcrop fires4147
This map prepared in cooperation with the U.S. Bureau of Land Management.
10 0 10 20 30 40 miles
10 0 10 20 30 40 50 kilometers
MONTANA BUREAU OF MINES AND GEOLOGYA Department of Montana Tech of The University of Montana
MBMG Geologic Map 64; Plate 1 of 1Clinker Distribution and Age in the Powder River Structural Basin, 2013
Published by theMontana Bureau of Mines and Geology
MBMG
Maps may be obtained from: Publications Office
Montana Bureau of Mines and Geology1300 West Park Street
Butte, Montana 59701-8997Phone: (406) 496-4167 Fax: (406) 496-4451
http://www.mbmg.mtech.edu