Description: A map showing the relations of the drift sheets of Iowa and northern Illinois. 1, Kansan; 2, Illinoian; 3, Iowan; 4, Early Wisconsin; 5, Late Wisconsin; 6, Driftless area; 7, course of the Mississippi River during the Illinoian glacial epoch.
Source: Isaiah Bowman, Ph. D, Forest Physiography (New York, NY: John Wiley and Sons, 1911) 473
Map Credit: The Private Collection of Roy Winkelman |
|
