1. Geologic and biostratigraphic map of the Pierre shale in the Canon City-Florence Basin and the Twelvemile Park area, south-central Colorado [cartographic material] Yale Public content 1975. 2013-08-30T18:30:50Z. 2013-09-04T19:53:08Z. Scott, Glenn Robert, 1918-. The Survey. English. Public. Colorado, Fremont County, Custer County, and U.S.