Description: Total Clay Thickness (Shapefile), 2000 - Shows total thickness of clay, as derived from logs of water wells. Because clay layers can constitute capping and confining units for aquifers, such layers are potentially of hydrologic significance. The layer is derived from the iLITH Water-Well Database of the Indiana Geological Survey, which allows users to interact with a portion of the Water-Well Record Database of the Indiana Department of Natural Resources. iLITH differs from the IDNR database in that lithologic descriptions and drilling contractor names have been standardized and locational information for a subset of water-well logs has been verified. This shapefile presents the same data as shown in a grid named 'CLAY_ILITH_IN.'