Abstract

The Wasatch Plateau of central Utah contains large coal reserves. Rocks in the southern part of the Wasatch Plateau coalfield are early Late Cretaceous (lower Coloradoan) to late Paleocene in age. Major stratigraphic units, from oldest to youngest, are: the Mancos Shale, Mesaverde Group, North Horn Formation, and Flagstaff Limestone. The Mesaverde is divided, in ascending order, into the Star Point Sandstone, Blackhawk Formation, Castlegate Sandstone, and Price River Formation. The Blackhawk is divided into the transitional marine facies, which contains important coal beds, and the fluvial facies.

The Mancos was deposited as offshore, marine claystone and marine shoreface sandstone. Formations of the Mesaverde Group were deposited shoreward of the Mancos Shale and intertongue with it. The Star Point was deposited as littoral marine sandstone and the Blackhawk, Castlegate, and Price River were deposited as restricted marine and continental beds as the sea retreated. Coal beds probably were deposited on the delta-plain facies of actively prograding delta lobes.

The Hiawatha and Upper Hiawatha coal seams of the Blackhawk Formation are thick and extensive. The Hiawatha is about 1.8 m (6 ft) thick whereas the Upper Hiawatha averages 4.2 m (14 ft) thick and is probably minable throughout the study area except south of Convulsion Canyon. The coal is high-volatile C bituminous of noncoking quality. It has low sulfur and low ash content, and contains abundant resin. Mining in the Wasatch Plateau has been continuous since 1875 and over 112 million tons of coal have been produced.

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