This raster is a highly detailed map of geologic materials at the surface (delineations made from maps at 1:24,000 to 1:12,000 scale). The smaller extent maps were merged together by USDA-NRCS to produce the gSSURGO spatial database, covering the entire state of Illinois at a 10m resolution. The gSSURGO map was then interpreted by Iowa State University’s Geospatial Laboratory for Soil Informatics (GLSI) for parent material, which is equivalent to the geologic material to a depth of 2 meters from the surface. Surficial material attributes were extracted from the NRCS official soil series descriptions (OSD), but at times some additional interpretation was needed based on typical soil profile properties and spatial relationships with better-defined soil series. Because of the common relationship between surficial geology and topography, digital elevation models would be complementary to this data set. Draping this surfical geology data set over hillshades derived from fine resolution elevation data works especially well.Download
Miller, B.A. and C.L. Burras. 2015. Comparison of surficial geology maps based on soil survey and in depth geological survey. Soil Horizons 56(1). doi:10.2136/sh14-05-0005.
Soil Survey Staff. 2014. Official Soil Series Descriptions (OSD). United States Department of Agriculture, Natural Resources Conservation Service. https://soilseries.sc.egov.usda.gov/osdname.asp
Soil Survey Staff. 2014. Gridded Soil Survey Geographic (gSSURGO). United States Department of Agriculture, Natural Resources Conservation Service. http://datagateway.nrcs.usda.gov