Basal sandstone of Cloverly Formation named Otter Creek Sandstone Member for exposures in northeast part of sec 7 and northwest part of sec 8, T45N, R87W on Otter Creek, Washakie Co, WY. Can be recognized along southern Big Horn Mountains, Bighorn basin, WY. Is a ledge-forming unit that disconformably overlies Jurassic Morrison Formation. Underlies the mudstone member of Cloverly, a contact that is usually covered by soil or rubble. Is a white to gray, fine- to coarse-grained, cross-bedded, moderately to well-cemented sandstone that is locally yellow, orange, red, or brown, conglomeratic or shaly; 25-92 ft thick on western flank of Bighorn Mountains and 4-40 ft thick on the eastern flank of Bighorns. Is of marine and marginal marine origin. Correlates with lower part of: 1) Kootenai (central MT), 2) Lakota (Black Hills), 3) Lytle (Front Range, CO), 4) Cedar Mountain and Buckhorn (Colorado Plateau), and with Peterson Limestone and Bechler Conglomerate of Gannett Group (southeast ID-southwest WY). Of Early Cretaceous age. Correlation chart.

Source: GNU records (USGS DDS-6; Denver GNULEX).