This feature dataset shows the distribution and extent of the bedrock geologic units within the State of Illinois, as depicted on the map Bedrock Geology of Illinois (2005) by D. Kolata (compiler), published by the Illinois State Geologic Survey. The component feature classes show geologic units (polygons) and faults (lines.) The nominal scale of the published hardcopy map is 1:500,000. In some areas data of greater scale were generalized and incorporated.
