MONTANA BUREAU OF MINES AND GEOLOGY MBMG Geologic Map 64; Plate 1 of 1 A Department of Montana Tech of The University of Montana Clinker Distribution and Age in the Powder River Structural Basin, 2013 107°30'0"W 107°0'0"W 106°30'0"W 106°0'0"W 105°30'0"W 105°0'0"W 104°30'0"W 46°30'0"N Clinker Distribution and Age in the Powder O’Fallon Sandstone Cr Little Porcupine Cr 59 z{ I-94 ¨¦§ 3310I# Locate Creek Powder River Structural Basin z{12 Miles City ! z{12 By I# 2502I# 3269 Edward L. Heffern, U.S. Bureau of Land Management (Retired) 3121I# 2941I# Big Porcupine Cr Custer County Pine Cr Rosebud County Tongue River Peter W. Reiners, University of Arizona, Tucson, AZ River Creek Yellowstone River Catherine A. Riihimaki, Drew University, Madison, NJ I# 2623 Yellowstone River 2013 Moon Cr Sheep Creek ¨¦§I-94 ! Graveyard Cr Sarpy Cr Forsyth Land and Resource Data Rosebud Creek $ 80 Powder Sweeney Cr Lame Jones Cr ! Cities and towns Major paved highways $ 79 T5N 2706 I# State boundary Interstate highways Yellowstone Armell’s Cr County Milk Cr County boundary Rivers and streams T5N Spring Cr Tullock Cr Fallon County I# 4301 Summit elevations in feet above mean sea level River Carter County z{59 Area underlain by Tertiary sediments Ash Cr East Fork E Fk Armell’s Cr I#3270 Early Quaternary / Late Tertiary gravel terraces (only those in Montana shown) 2.747 +/- 0.220 2.840 +/- 0.161 Ash Cr I#3400 &-&-") 3.226 +/- 0.258 2.637 +/- 0.166 &- 3.518 +/- 0.166 Mizpah Creek 5.067 +/- 0.288 Coalbed Fires 46°0'0"N 3.8 +/- 1.2 Tongue River O’Fallon Cr Active and historical coal fires, identification number indicated. Refer to coal-fire spreadsheet for details, available on the Foster Cr 46°0'0"N Montana Bureau of Mines and Geology website at http://www.mbmg.mtech.edu/. 39 z{ Pumpkin Creek W Fk Armell’s Cr $ 42 Mine fires $ 47 Spoil fires I#3392 Treasure County $ 41 Outcrop fires Big Horn County I# Liscom Cr 3726 Little Beaver Cr The Powder River Basin, with its dry climate, low-rank coalbeds rich in volatile matter, and commonly occurring range fires, $ 8 ! I# ! provides ideal conditions for coalbed fires. Near-surface and exposed coalbeds above the water table have ignited due to causes 4462 Colstrip Ekalaka as diverse as lightning strikes, wildfires burning trees and bushes rooted in coalbeds, and spontaneous combustion in coal mines ") 2.2 +/- 0.8 I#") and outcrops. The 81 coal fires shown were compiled by the lead author from personal contacts and observations, published 2.9 +/- 0.9 4807 Tullock Cr Rosebud 3228 Spring Cr maps and articles, U.S. Bureau of Mines fire control project reports, and U.S. Office of Surface Mining, Wyoming Abandoned T1N $ 9 I# Dry Cr Mine I#3948 Mine Land Division, and U.S. Bureau of Land Management records. The recent vast range fires in the northern Powder River $ 11 I#3764 T1N Basin during the summer of 2012 may have ignited additional coalbed fires. Absaloka $ $ 10 $ 12 Custer County Mine 64 Beaver Cr Rosebud Creek 0.603 +/- 0.028 Powder River County &- Powder River Coal Mines T1S I# 2944 Mined areas through 2010 Little Pumpkin Cr T1S ") &- 0.120 +/- 0.006 Timber Cr < 0.4 &- 0.515 +/- 0.019 &- $ 3583I# 0.217 +/- 0.127 The 16 active coal mines in the Powder River Basin—12 in Wyoming and 4 in Montana—include the largest coal mines in North Rosebud County 13 $ 73 America. These mines produced 462.6 million short tons, 42.2% of total U.S. production, in 2011 (U.S. Energy Information Adminis- 1.1 +/- 0.3 ") $ 71 15 &- 0.326 +/- 0.016 Little Wolf Mountains &- 1.073 +/- 0.086 ") 0.2 +/- 0.1 $ tration). Of this total, 426.1 million short tons came from Wyoming and 36.5 million came from Montana. The approximate areas Little 14 $ B' I# &- 0.652 +/- 0.026 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 4541 0.981 +/- 0.039 &-&- 0.110 +/- 0.009 17 0.105 +/- 0.005 &-") 0.8 +/- 0.2 ") 0.6 +/- 0.6 0.155 +/- 0.009 mine permits on public file with State mine regulatory agencies. Total areas mined through the year 2010 cover about 164 sq. mi. $ &- # Crow Cr 16 $ B I ! 4327 (425 sq. km.). Each mine has a program to quickly extinguish coal fires in mining pits, highwalls, and spoil piles. ! Crow Agency 18 Pumpkin Creek Lame Deer $ ") 1.0 +/- 0.3 Ashland 4407 ") I# $ 0.4 +/- 0.3 ! &- 0.287 +/- 0.023 Cabin Cr Big 19 &- 0.227 +/- 0.013 &- 0.152 +/- 0.012 Clinker Creek &- 0.308 +/- 0.025 212 &- 0.014 +/- 0.002 z{ Mizpah Creek I#4396 20 &- 0.089 +/- 0.013 Clinker outcrops Busby! *# $&- 0.056 +/- 0.004 212 ") Powder River County Horn Reno Cr z{ 0.9 +/- 0.3 Carter County * 45°30'0"N # Clinker is rock that has been baked, sintered, or melted by burning of underlying coalbeds. Clinker forms reddish layers that cap hills Pilgrim Cr and escarpments in the landscape. In the southeast corner of this map (and Inset Map 2), the Rochelle Hills form an east-facing ") 1.3 +/- 0.3 Otter Creek * # Corral Cr 45°30'0"N 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 1.0 +/- 0.4 ") 21 $ Rosebud 22 * # $ ") I#4161 coal in the map area occurs in formations of Tertiary age. The clinker in the map area results from natural burning in prehistoric times * 1.5 +/- 0.5 # ¨¦§I-90 ") &- 1.0 +/- 0.4 0.014 +/- 0.005 3304I# of coalbeds in the Paleocene Fort Union and Eocene Wasatch Formations. Additional clinker may be present in the subsurface River < 0.2 ") &- beneath younger alluvium, but not exposed at the surface. Clinker is also common in landslides and talus deposits downslope from 0.237 +/- 0.017 ! clinker-capped ridges. $ Broadus 23 T5S 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. I#3648 T5S 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 R35E Box Elder Cr R40E ") 0.8 +/- 0.4 ") 1.1 +/- 0.4 natural burning of tens of billions of tons of coal. Much additional clinker, perhaps an order of magnitude more, has been eroded ") R45E R55E away and carried downstream into the tributaries of the Missouri River. The record of this eroded clinker is present as clinker cobbles Lodge Grass 0.8 +/- 0.7 Tongue River R50E in Quaternary and late Tertiary gravel terraces. Natural coal fires have been a significant source of greenhouse gas emissions in ! # River I4348 3440I# E Fk Little Powder River prehistoric times, although the rate of natural burning is much less than the current rate of coal mining. I# I#4774 5155 &- 1.113 +/- 0.040 I#3365 The clinker outcrops shown were mapped by E.L. Heffern, the lead author, from the following public sources: published geologic maps Wolf Mountains and digital data files from the U.S. Geological Survey, Montana Bureau of Mines and Geology, and Wyoming State Geological Survey; Lodge Grass Cr I# z{59 3901 data interpreted by the author from color and color infrared aerial photography and National Agriculture Imagery Program color and River # Owl Cr 4301I 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/. I# &- 0.127 +/- 0.020 # S Cottonwood Cr 3743 I 4245 The Tertiary bedrock of the Fort Union and Wasatch Formations is mostly poorly to moderately consolidated sandstone, siltstone, Horn z{212 and shale interfingered with coalbeds. When a subaerially exposed coalbed catches fire, the fire front burns back beneath the &- 0.270 +/- 0.021 sandstone, siltstone, and shale overburden of these sediments. It ‘fires’ the overlying rock in a manner similar to ‘firing’ bricks. The Big 72 result is the hardened, fractured rock called clinker. Most clinker is red, but some contains shades of yellow, orange, and black. In $ I#3490 Spring &- general, baked sandstone retains its original grain structure. The grains of fine-grained sediments are sintered—heated and welded Ross Cr 0.239 +/- 0.015 24 Creek $ together to form a coherent mass without melting—resulting in a rock similar to porcelain. A small amount of rock—primarily in Little Willow Cr fissures that served as chimneys— has been melted to hard black paralava. Virtually all of this clinker is harder than the parent rock. Mine Tongue River Reservoir Powder 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 I#4450 $81 much water to drain through rather than run off. The greater hardness, combined with fracture permeability, makes the clinker more West Decker &- 0.013 +/- 0.001 58 63 5444I# resistant to erosion than the unfired bedrock strata above and below. Consequently, regional downwasting leaves the clinker forming $ $ 59 $ 3731 T9S Mine $ I# 62 the tops of scarps and ridges.