Changes

The Lower-Upper Cretaceous, Albian-Cenomanian-aged Mowry Shale in the Powder River Basin of northeastern Wyoming and southeastern Montana (Figures 1 and 2) is a siliceous, organic-rich, dark-gray to black marine mudstone interbedded with bentonite, sandstone, and silt. (Nixon, 1973; Burtner and Warner, 1984; Davis et al., 1989). Radiolaria tests, Fish scales, fish teeth, fish bones, fecal pellets, inoceramus debris, and ammonites are found in the bedding planes and silt-laminae of the Mowry Shale throughout Wyoming (Davis, 1970; Anderson and Kowallis, 2005). Calcareous cone-in-cone concretions are seen in core and outcrop (Hollon, 2014). Numerous bentonite beds up to 3 ft thick in the Mowry Shale allow for the precise recognition of time equivalent strata over vast areas (Nixon, 1973). In outcrop, the Mowry Shale has a distinct profile and weathers to a dark to light gray, is hard, and often has large jointing sets. The Mowry Shale is ranges in thickness from 150 to 250 ft and is a significant source rock for the Cretaceous reservoirs in the Powder River Basin.

The Lower-Upper Cretaceous, Albian-Cenomanian-aged Mowry Shale in the Powder River Basin of northeastern Wyoming and southeastern Montana (Figures 1 and 2) is a siliceous, organic-rich, dark-gray to black marine [[mudstone]] interbedded with bentonite, sandstone, and silt. (Nixon, 1973; Burtner and Warner, 1984; Davis et al., 1989). Radiolaria tests, Fish scales, fish teeth, fish bones, fecal pellets, inoceramus debris, and ammonites are found in the bedding planes and silt-laminae of the Mowry Shale throughout Wyoming (Davis, 1970; Anderson and Kowallis, 2005). Calcareous cone-in-cone concretions are seen in core and outcrop (Hollon, 2014). Numerous bentonite beds up to 3 ft thick in the Mowry Shale allow for the precise recognition of time equivalent strata over vast areas (Nixon, 1973). In outcrop, the Mowry Shale has a distinct profile and weathers to a dark to light gray, is hard, and often has large jointing sets. The Mowry Shale is ranges in thickness from 150 to 250 ft and is a significant source rock for the Cretaceous reservoirs in the Powder River Basin.