"Modified from Regional Geologic Map Series, Indiana Geological Survey." Includes insets of "Thickness of unconsolidated materials" and "Distribution of surface tills.", Imprint: [Bloomington, Ind.] : The Survey, 1979., Dimensions: 31 x 22 cm; Scale: 1:1,900,000, Coordinates: W0880500 W0844700 N0414500 N0374600
Tolen, James R. (1979). Map of Indiana showing unconsolidated deposits. Indiana. Geological Survey. https://purl.dlib.indiana.edu/iudl/images/VAC3073/VAC3073-M-00675 (map)