1. Geologic cross section C-C' through the Appalachian basin from Erie County, north-central Ohio, to the Valley and Ridge Province, Bedford County, south-central Pennsylvania Author/Creator: Ryder, Robert T. Publication/Creation: Denver, Colo. : For sale by U.S. Geological Survey, Information Services Resource Type: Map Access & Availability: Loading
2. Stratigraphic framework of Cambrian and Ordovician rocks in the Appalachian Basin from Sequatchie County, Tennessee, through eastern Kentucky, to Mingo County, West Virginia Author/Creator: Ryder, Robert T. Publication/Creation: [Reston, Va.] : U.S. Dept. of the Interior, U.S. Geological Survey ; Denver, Colo. : For sale by U.S. Geological Survey, Information Services, 2008 Resource Type: Map Access & Availability: Loading