Geology of the Spruce Run Mountain area, Giles County, Virginia

Abstract

The Spruce Run Mountain area embraces about 45 square miles in the south-central portion of Giles County. It lies wholly within the Appalachian Valley and Ridge Province. The rocks exposed in the Spruce Run Mountain area range in age from Middle Cambrian to Lower Devonian. All the rocks are sedimentary rocks deposited in a marine environment and have an aggregate thickness of approximately 6,500 feet. An important disconformity separates rocks of Lower Ordovician age from those of Middle Ordovician age. The Saltville thrust, a southeast dipping thrust fault, crosses the Spruce Run Mountain area trending northeast. The thrust separates Middle Cambrian dolomite from Ordovician formations on the southeast flank of the Spruce Run Mountain syncline. The Spruce Run Mountain syncline is a northeast trending overturned syncline with a southeast dipping axial surface. The Clover Hollow anticline and the Bane anticline border the northwest flank of the Spruce Run Mountain syncline. The geomorphology and geologic history of the area are briefly discussed.