1. Geologic map of the Seneca quadrangle, Montgomery County, Maryland, and Fairfax and Loudoun counties, Virginia Yale Public content 1999. 2002-06-01T04:00:00Z. 2022-12-08T02:20:31Z. Geological Survey (U.S.). The Survey ; Information Services [distributor]. English. Public. Maryland, Montgomery County, Virginia, Fairfax County, and Loudoun County.