Hyatt Ranch [Member] of Tensleep Formation. A distinctive widespread aeolian unit of the Tensleep Formation on the west flank of the Big Horn Mountains in the Big Horn and Wind River basins, Wyoming, is here named the Hyatt Ranch Member. Consists of white to light-gray and buff, fine- to occasionally coarse-grained, friable to cemented, subrounded, cross-stratified, aeolian sands in the uppermost 30 m of the Tensleep and represents the tops of preserved dunes. Overlies the Medicine Lodge Creek Member (new name) of the Tensleep with angular unconformity. Correlates with the upper member of the Minnelusa Formation. Exhibits distinctive changes in thickness. Age is possibly Early Permian (Wolfcampian).
Type locality: exposures on either side of Hyatt Ranch on Paintrock Creek, in center T. 50 N., R. 89 W., [Hyatt Ranch 7.5-min quadrangle], Big Horn Co., central northern WY.

[Rank term is lowercased by author. Name is listed as a formal unit in US geologic names lexicon (USGS Bull. 1565, p. 138, 1991) and, in accordance with nomenclature guidelines (ASCN, 1961, 1970; NACSN, 1983), the rank term is capitalized. However, it is implied from GNU records (USGS DDS-6; Denver GNULEX, September 10, 1992) that the Hyatt Ranch is informal. No explanation is provided for this change in classification from what is listed in the lexicon (USGS Bull. 1565). Until we are informed otherwise, we will retain the Hyatt Ranch as a formal member of the Tensleep.]

Source: US geologic names lexicon (USGS Bull. 1565, p. 183).