--> Abstract: Environmental Reconstruction of Middle Blackhawk Formation (Cretaceous) and Its Relation to Coal Resources, Pine Canyon Quadrangle, Carbon County, Utah, by Paul B. Anderson; #90964 (1978).
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Abstract: Environmental Reconstruction of Middle Blackhawk Formation (Cretaceous) and Its Relation to Coal Resources, Pine Canyon Quadrangle, Carbon County, Utah

Previous HitPaulTop B. Anderson

Analysis of drill-hole cores and surface stratigraphic sections from the Pine Canyon quadrangle indicate that the Kenilworth tongue of the Blackhawk Formation is a record of a prograding clastic shoreline. Overlying the marine sequence are restricted marine or brackish-water deposits followed by coastal-plain rocks that contain most of the coal beds.

The marine facies in the Kenilworth tongue consist of offshore, transition, lower-shoreface, upper-shoreface, and foreshore deposits. The overlying restricted marine rocks commonly contain a brackish-water fauna, and wave-formed, linear ripple marks. Beds of the coastal-plain environment indicate several subenvironments, such as fluvial, swamp, and oxidized overbank.

The vertical succession of facies, from marine to restricted marine to coastal plain, indicates a barrier bar (with a muddy mainland beach) or possibly a strand-plain and bay coastal system. An area of local, post-Kenilworth subsidence has been delineated just north of the outcrop by means of detailed drill-hole information. Evidence for subsidence includes thickening of restricted marine facies above the foreshore deposits, thickening of the rock interval between coal beds, and increased amounts of fluvial deposits in the subsided area.

The coal beds in the quadrangle are present in the middle Blackhawk Formation and are divided into five zones, from base to top: the Kenilworth, Gilson, Fish Creek, Rock Canyon, and Sunnyside. The Kenilworth and Fish Creek are too thin (less than 1.3 m) to be minable at present, but the Gilson, Rock Canyon, and Sunnyside are all locally minable. The subsided area corresponds to thinning and splitting of the coal zones and parallels the apparent paleostrandline. Isopach maps of the minable coal beds show that thickness trends of the Gilson and Rock Canyon coal zones are related to local subsidence.

AAPG Search and Discovery Article #90964©1978 AAPG Rocky Mountain Section Meeting, Salt Lake City, Utah