1994. Illinois State Geological Survey. This is a polygon feature class containing driftless areas in Illinois. These areas are analogous to areas of the state where the bedrock surface i...
1994. Illinois State Geological Survey. This feature dataset shows continuous lines representing the lowermost elevations/locations of (buried) bedrock valleys in the state of Illinois. A...
1991. Illinois State Geological Survey. This is an SDE polygon feature class containing named Woodfordian moraines, or Wisconsinan end moraines, of Illinois. Scale is 1:500,000. The prima...