Sheep Mountain area

View from Sheep Mountain Table in Badlands National Park. A thin frosting of snow highlights a formation boundary between the Chadron and Brule Formations of the White River Group (of Eocene and Oligocene age, respectively). Sedimentary formations of the White River Group extend across western South Dakota, east of the Black Hills into Nebraska in the Sand Hills region, and correlate with other sedimentary basins in Wyoming.