From the site: "Karst regions derived from 1968 geological map of West Virginia.

In 1968 the West Virginia Geological and Economic Survey (WVGES) published a State Geologic Map. The topographic base was compiled from Army Map Service 1:250,000 scale map sheets. In 1998 the WV Division of Environmental Protection (WVDEP) scanned the hardcopy geologic maps at 300 dpi, 8-bit color, and then georeferenced them. Rock unit boundaries were digitized off the images and attributed by WVDEP. The USGS-Water Resources Division later revised the attributes of large water bodies and georeferenced the datum to NAD83. The WV Bureau of Public Health extracted the limestone and dolomite formations from the statewide geologic coverage to create a separate karst GIS coverage."