1. Geologic map of the Round Hill quadrangle, Clarke and Loudoun counties, Virginia, and Jefferson County, West Virginia Yale Public content 1992. 2002-06-01T04:00:00Z. 2012-07-13T18:36:27Z. Geological Survey (U.S.). The Survey ; For sale by Map Distribution. English. Public. Virginia, Clarke County, Loudoun County, West Virginia, and Jefferson County.