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Distribution, Amount, and Maturity of Coal Resources in the Sego Coalfield, Grand County, Utah

David E. Tabet, Jeffrey C. Quick, and Brigitte Hucka
Utah Geological Survey, Salt Lake City, UT

Coal resources of the Sego coalfield occur in the Upper Cretaceous Neslen Formation of the Mesaverde Group in the southeastern Uinta Basin of Grand County, Utah. The Neslen consists of a 200- to 520-foot-thick series of paludal to alluvial plain sandstone, mudstone, siltstone, and high-volatile bituminous coal beds. Data from 95 drill holes and 106 outcrop measurements were used to characterize the distribution and amount of resources for seven coal zones in the study area. During Neslen deposition, rapid cycling of sea level did not allow for prolonged subsidence and development of large amounts of accommodation space to provide for the deposition of thick, widespread coals. The resulting coals are therefore patchy in areal extent and generally less than four feet thick. Locally individual beds reach 10 feet thick, generally in the northeastern part of the study area. The total net coal in all the mapped Neslen coal beds has a maximum measured cumulative thickness of 28 feet. The in-ground coal resource in beds greater that 6 feet thick is in excess of 350 million tons.

AAPG Search and Discovery Article #90092©2009 AAPG Rocky Mountain Section, July 9-11, 2008, Denver, Colorado