GEOLOGICAL CONTROLS ON HYDROLOGIC PATHWAYS IN THE GREAT SAVANNAH CAVE SYSTEM, LEWISBURG, WEST VIRGINIA, USA

Each cave is unique from structural or hydrological perspectives, which often complicates the prediction of subsurface flow routes needed for planning the economic development of karst landscapes and responding to groundwater contamination. This is true of the Great Savannah Cave System (GSCS) in southeastern West Virginia since the growing city of Lewisburg is expanding northward over the 50-mile-long cave system. The GSCS is the sixth-longest cave in the United States and pollution is affecting the cave in many still poorly defined ways. We report findings of a geological and hydrological study of critical passages in GSCS as these findings relate to subsurface flow paths and prediction of unknown pathways. McClung Cave is in Greenbrier County in which the primary lithology is a Mississippian-age formation containing limestone and minor shales with negligible amounts of sandstone. Karst features of the GSCS formed along the contact zone between the Greenbrier and an underlying shale where streams sink upon encountering the limestones. Dip- and strike-oriented flow routes are analyzed using structural contouring, structural mapping, and passage morphologies. Vadose infeeders are generally oriented downdip, but with significant variability and hard to predict meandering due to geological features too small to be resolved in general geological mapping. Strike-oriented collector passages receive vadose streams from updip but are epiphreatic with infrequent filling during low recurrence interval floods. However, geological structures are only one control on the GSCS, and we present analyses of the host bedrock, including the results of thin section studies designed to understand stratigraphic perching and selective cave development in certain lithologies. Initially, passages followed bedding planes’ dip directions. We use the information gained to make predictions about flow routes and master conduits that have yet to be observed. These findings are relevant to land use impacts on the karst due to the expansion of Lewisburg northward.