This map shows the positions of the margin, of the recessional stages and of the substages respectively of the Wisconsin ice sheet in Iowa where these positions have been determined. The outer boundary shown is taken chiefly from the maps of the Iowa Experiment Station and of the U.S. Soil Survey. The margin of the Altamont moraine is taken principally from the maps by the Iowa Geological Survey.
Proceedings of the Iowa Academy of Science
©1924 Iowa Academy of Science, Inc.
Smith, John E.
"A Preliminary Map of the Wisconsin Till in Iowa,"
Proceedings of the Iowa Academy of Science, 31(1), 337-338.
Available at: https://scholarworks.uni.edu/pias/vol31/iss1/103