1. Geologic map of the Clay City quadrangle, Powell and Estill Counties, Kentucky [cartographic material] Yale Public content 1967. 2012-01-20T20:50:34Z. 2012-03-05T17:35:08Z. Simmons, George Clarke, 1923-. U.S. Geological Survey. English. Public. Kentucky, Powell County, and Estill County.