The full extent of overlap of the Illinoian upon the Kansan has not been determined. It is certain that a sheet of Kansan drift underlies the Illinoian throughout its extent in southeastern Iowa and in all probability it continues some distance eastward into western Illinois in the section between Rock Island and Quincy.
Proceedings of the Iowa Academy of Sciences
©1897 Iowa Academy of Science, Inc.
"The Weathered Zone (Yarmouth) between the Illinoian and Kansan Till Sheets,"
Proceedings of the Iowa Academy of Science, 5(1), 81-86.
Available at: https://scholarworks.uni.edu/pias/vol5/iss1/15