Named as a member of Pierre shale for exposures along Mitten Prong, T56N, R68W, Crook Co, WY in Powder River basin. Consists of blue-black fissile shale with a few iron-stained calcareous concretions. Marine fossils. Forms a prominent scarp. Thickness 150-200 ft. Type section not given. Overlies Gammon ferruginous member (new); underlies an unnamed member. Exposed on the west side of the Black Hills, northeastern WY and southeastern MT, in Powder River and Williston basins. Samples of Upper Cretaceous mudstone, shale, and marl, including a sample probably from the member, are compared for their mineralogy, chemical composition, grain size, density, porosity, fissility, and bedding laminations. Late Cretaceous in age.

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

Is a member in middle part of Pierre Shale at Red Bird, Niobrara Co, WY in the Powder River basin. Overlies Sharon Springs Member of Pierre. Underlies Red Bird Silty Member of Pierre. Of BACULITES PERPLEXUS to BACULITES ASPERIFORMIS (descending order) (late Campanian, Late Cretaceous) age. [B. PERPLEXUS to B. ASPERIFORMIS now considered middle Campanian age (Obradovich, 199_). Note: Believe this remark refers to Obradovich, J.D., 1993, A Cretaceous time scale, IN Caldwell, W.G.E., and Kauffman, E.G., eds., Evolution of the Western Interior basin: Geological Association of Canada, Special Paper 39, p. 379-396.(nrs, 5/29/98)] Correlation chart. Correlates with the 1) upper part of Steele Shale in the Powder River and Laramie basins, 2) Wallace Creek Tongue and Fales Sandstone Member of the Mesaverde Formation in the Wind River basin, 3) upper part of the Haystack Mountain Formation in the Hanna basin, and 4) lower part of the Ericson Sandstone on the Rock Springs uplift.

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

Nomenclature applied to divisions of the Pierre Shale in exposures at Francis Ranch, secs 7-10 and 15-16, T14N, R69W and in subsurface in Apache Corp. 1 Polo Ranch, sec 14, T14N, R68W, Laramie Co, WY, Denver basin modified. Term: 1) Gammon Ferruginous Member replaces use of lower transition zone; 2) Mitten Black Shale Member replaces use of rusty zone; 3) Hygiene replaces use of the subsurface Sussex; 4) Rocky Ridge, Larimer, and Richard Sandstone Members replace use of the subsurface Parkman. Terry Sandstone Member of Pierre in the Fort Collins, CO area is equivalent to the subsurface Sussex and is not present at Francis Ranch or in the Apache Corp. well. Use of Shannon, Sussex, and Parkman is discontinued in the Denver basin because the sandstones of the Denver basin are not time-equivalents or time-transgressive facies of the Shannon, Sussex, or Parkman of the Powder River basin. As modified, divisions of Pierre are (ascending): Gammon, Sharon Springs, Mitten, Hygiene Members, unnamed interval, Rocky Ridge Sandstone Member, unnamed interval, Larimer Sandstone Member, unnamed interval, Richard Sandstone Member, unnamed interval, units A, B, C, unnamed interval. Pierre overlies Niobrara Formation and underlies Fox Hills Sandstone. Of Campanian age. Measured section; nomenclature chart.

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