Includes generalized columnar section, 'Sectionized township,' and index of producers of clay and clay products. 'Base modified from U.S. Geological Survey, Base map of Indiana; 1950.' Scale 1:1,000,000. Compiled by Wiliam M. Webb, March 1967.
Ault, Curtis H., Webb, William M. (1968). Locations of clay and shale operations in Indiana. Indiana Geological Survey. https://purl.dlib.indiana.edu/iudl/images/VAC3073/VAC3073-M-00832 (map)