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Location: 67 km S from Gillette, Wyoming, United States
5669 Highway 450P.O. Box 406WrightWyoming, United States82732
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On January 14, 2025, CONSOL Energy and Arch Resources closed an all-stock merger of equals. Arch survived as a wholly owned subsidiary, and CONSOL was renamed Core Natural Resources, Inc., which began trading as “CNR” on January 15, 2025.
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The Black Thunder reserve area is a relatively flat lying sedimentary deposit of Paleocene Age. Black Thunder is actively mining a single coal seam, the Wyodak, that can be comprised of several splits, the Upper and Main splits of the Wyodak Seam.The Powder River Coal Basin of northeastern Wyoming lies entirely within the boundaries of the Powder River structural and topographic basin. Coal-bearing strata range in age from Upper Cretaceous in the Mesa Verde Formation to Eocene in the Wasatch Formation. The Powder River Coal Basin covers parts of Campbell, Converse, Crook, Natrona, Niobrara, Johnson, and Weston Counties and is the largest coal basin in Wyoming.Regionally, the most economical coal seams are contained in the Paleocene Fort Union Formation and the Eocene Wasatch Formation. Individual seams range to greater than 100 feet in thickness. The basin is a broad asymmetric syncline bounded on the west by the Big Horn Mountains, on the east by the Black Hills, and to the south by the Casper Core, Laramie Mountains, and the Hartville Uplift. The basin continues north into Montana where the Miles City Core separates it from the Williston Basin.The axis of the syncline is slightly west of the center of the basin. Flanking dips are gentle on the eastern limb (two to three degrees) but dip more steeply on the western limb. Faulting occurs in many localities, especially around the basin edge and is in association with folding. Vertical displacements can be several hundred feet. Faulting is more common on the western limb of the syncline than on the eastern limb.The lower Eocene Wasatch Formation consists of interbedded, lenticular clays, silty clays, sandy clays, thin, discontinuous coals, mudstones, and dirty sandstones. Correlation of individual strata is difficult due to the discontinuous and lens-like nature of the units which is inherent in fluvial deposition, e.g., channel sand deposits.The Upper Paleocene Fort Union Formation underlies the Wasatch Formation. The Fort Union Formation consists of noncarbonaceous to highly-carbonaceous clays, mudstones, sandstones, and coal. The top of the Fort Union Formation is designated as the top of the Wyodak Seam. The Wyodak Seam is the main coal seam, and it lies atop lensoidal clay, silt, and sand beds. The seam base is variable due to changes in the environment of deposition, from the non-coal forming environment of the sands, clays, and silts, to the fringes of the coal forming, swampy conditions in which the Wyodak Seam was deposited.Clinker (locally known as scoria), a baked or fused rock, is present along the coal outcrop on the eastern edge of Black Thunder’s permit area. This fused material was formed by prehistoric burning of the Main Wyodak coal seam. Both the Wasatch and the Fort Union formations have been affected by this prehistoric burning and have contributed to the volume of baked material present.The mudstone is a uniformly textured material composed of 40 to 80 percent clay, and generally 5 to 40 percent silt; the remainder being sand. It is generally medium to dark gray with occasional brown and tan oxidized zones. The mudstone is basically soft to medium stiff with some extremely stiff waxy mudstone throughout much of the area. The mudstone contains some carbonaceous material and thin coal partings.Sandstone is a major lithologic component of the overburden in the mine area.The economically mineable coal in Campbell County occurs within the Tongue River Member of the Fort Union Formation. The Wyodak coal seam occurs at the top of the Fort Union Formation and is overlain by the Wasatch Formation. The coal is low sulfur, low ash, and is subbituminous C in rank. Surface mineable coal deposits occur along the north-northwesterly striking subcrop of the Wyodak coal seam. The coal seam subcrops on the eastern edge of the lease and dips approximately two to three degrees to the west, with some slight rolling. This seam contains multiple benches or plys of coal of variable thickness, although in some local areas, it becomes one seam that reaches a thickness in excess of 100 feet. Across the permit area, the Wyodak Seam ranges in thickness from 10 feet to 100 feet, averaging approximately 70 feet.
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