- Fort Union Formation
The Fort Union Formation is a
geologic unit containing sandstones, shales, and coal beds inWyoming ,Montana , and parts of adjacent states. In thePowder River Basin , it contains important economic deposits ofcoal ,uranium , andcoalbed methane . [ [http://www.searchanddiscovery.net/documents/2005/ashley/index.htm "Wyodak Coal, Tongue River Member of the Fort Union Formation, Powder River Basin, Wyoming: "No-Coal Zones" and Their Effects on Coalbed Methane Production", by Mark Ashley, 2005] ]The Fort Union is mostly of
Paleocene age and represents a time of extensive swamps as well as fluvial andlacustrine conditions. The rocks are more sandy in southwestern Wyoming and more coal-bearing in northeast Wyoming and southeast Montana, reflecting a general change from rivers and lakes in the west to swamps in the east, but all three environments were present at various times in most locations. ["Eocene and Paleocene rocks of the southern and central basins", by Robert E. McDonald, "in" Geologic Atlas of the Rocky Mountain Region, Rocky Mountain Association of Geologists, Denver, CO, 1972: p. 248]Coal in the Fort Union in the Powder River Basin occurs mainly in the Tongue River Member, where as many as 32 coal seams total more than 300 feet in thickness. [ [http://www.searchanddiscovery.net/documents/2005/ashley/index.htm "Wyodak Coal, Tongue River Member of the Fort Union Formation, Powder River Basin, Wyoming: "No-Coal Zones" and Their Effects on Coalbed Methane Production", by Mark Ashley, 2005] ] One such bed, the Wyodak Coal near
Gillette, Wyoming , is as much as 110 feet thick. Most of the coals in the Fort Union Formation are rankedsubbituminous . ["Cretaceous and Tertiary coals of the Rocky Mountains and Great Plains regions", by R.M. Flores and T.A. Cross, 1991, "in" Economic Geology, U.S., Geological Society of America, Decade of North American Geology Series, vol. P-2, p. 547-571.]ee also
Uranium mining in Wyoming References
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