Named as a tongue (uppermost) in the Blair formation. Named for an isolated remnant of the upper and most prominent sandstone of the golden wall escarpment in sec 6, T16N, R102W, Sweetwater Co, WY in the Greater Green River basin, that was called the "Chimney Rock" by Schultz (1908). Type not specifically designated. Consists of medium-gray fine- to medium-grained sandstone separated by wedge-shaped tongues of sandy shale; sandstones form a conspicuous reddish-brown escarpment named the "golden wall" by Powell (1876). In northern part of the Rock Springs uplift, the sandstones are commonly massive, topographically prominent, and weather yellowish-brown with a notably pitted surface; become progressively less prominent southward, thinning to a knife edge in the shale. Overlies unnamed intermediate off-shore marine facies of Blair formation on Rock Springs uplift; overlies unnamed offshore marine facies of Mancos shale to the southeast. Underlies Rock Springs formation on Rock Springs uplift; underlies Black Butte tongue (new) in vicinity of Ericson's Ranch. Thickness not stated; shown to be about 125 ft thick (including shale in lower part) in measured section 14 (pl. 9A). No diagnostic fossils found. Age is Late Cretaceous.

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

Reassigned as a tongue at the base of the Rock Springs formation on the Rock Springs uplift, Sweetwater Co, WY in Greater Green River basin. Formerly was a tongue at top of Blair formation. Asphalt Ridge and Rim Rock sandstones of Walton (1944) are considered lithologic and time equivalents of the Chimney Rock. Age is Late Cretaceous.

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