Illinois Quaternary Deposits.

Lineback, J.A. 1979. Quaternary Deposits of Illinois. (a 1: 500000 map). Illinois State Geological Survey, Champaign, Illinois. SEE ALSO https://www.isgs.uiuc.edu/isgsroot/isgshome/fra3.htm

Image courtesy of Illinois Department of Natural Resources & the Illinois State Geological Survey.