Chenoweth, CheriHerzog, B. L. (Beverly L.)J.B. SieveringK.L. WarnerStiff, Barbara J.Topography of the bedrock surface in Illinois. Bedrock topography is shown as 50-foot (15-meter) contours of bedrock elevation above mean sea level (msl). Several major bedrock valleys are found across the state. Attributes include contour values. ISGS, 1994.Shapefilehttps://clearinghouse.isgs.illinois.edu/data/geology/bedrock-topographyengIllinois Geospatial Data ClearinghousePublicBuried Bedrock Surface [Illinois]DatasetsIllinois1994