Stratigraphy of the Coal-Bearing Blackhawk Formation on North Horn Mountain, Wasatch Plateau, Utah

Abstract

Coal- bearing rocks of the Cretaceous Blackhawk Formation crop out along the eastern margin of the Wasatch Plateau in central Utah. On North Horn Mountain the Blackhawk Formation ranges from 215 to 290 meters in thickness and consists of interbedded sandstone, shale, siltstone, carbonaceous shale, coal, and limestone. The lower half of the formation, which contains the economically important coal beds, was deposited predominantly in a shallow water , wave-modified delta system. The upper half of the unit was deposited in fluvial environments of meandering streams and floodplains. The source for the clastic sediments of the Blackhawk Formation was to the west. Potentially minable coal exists in the Hiawatha and Blind Canyon beds and possibly in the Bear Canyon bed. The thickest beds were measured in the southeastern part of the study area, with 5.3 meters of the Blind Canyon bed found in one measured section. These coals are high quality and have lateral continuity, but the thickness varies and scattered wants and splits are to be found. Coal reserves on North Horn Mountain are large and should become an important source of supply for local and regional markets.