INTERACTIONS OF THE SAGINAW AND LAKE MICHIGAN GLACIAL LOBES - THE KALAMAZOO COUNTY MAPPING PROJECT

Alan Kehew detailed the significant role tunnel valleys play in Michigan’s glacial landscape. Northeast-southwest trending tunnel valleys associated with the Saginaw Lobe cut across Kalamazoo County, as well as less developed, northwest-southeast trending tunnel valleys associated with the Lake Michigan Lobe. These two tunnel valley systems influenced the direction of their respective ice movements and dictated development of their associated depositional patterns and post-glacial fluvial networks.

Northeast-southwest trending drumlins are also observed. They were formed by Saginaw ice originally extending farther to the southwest; however, these southwest drumlins are now mostly gone. Computer-generated topographic flooding-surfaces indicate that mass movements associated with any remaining drumlins all occur at approximately the same water level. Thereby, a closely linked origin for all these mass failures is suggested.

Glacial channels, kettle lakes, and pitted/hummocky terrain features are observed in north-east Kalamazoo County. They formed along a Saginaw ice margin that is also the beginning of an outwash fan that buries two major northeast-southwest trending Saginaw Lobe tunnel valleys. This fan occupies the terrain north of the Kalamazoo River and extends west to the City of Kalamazoo. Landforms covering central and western Kalamazoo County are the result of Lake Michigan ice forming the Kalamazoo moraine and its eastward-extending outwash apron.

One of Alan Kehew’s Ph.D. students, Andrew Kozlowski, proposed that the early Kalamazoo River cut through the Kalamazoo Moraine by flowing to the east, not to the west, as it currently flows. This temporary eastward flow was interpreted to be the result of catastrophic drainage of a proglacial lake to the west. Much of south-central Kalamazoo County, originally deposited as part of the: (1) Saginaw Lobe drumlin field, and (2) overlying Lake Michigan Lobe-Kalamazoo moraine outwash fan, has been highly reworked, or even removed, as a result of this catastrophic flooding. The insightful interpretation of Kozlowski and Kehew is supported by this recent, LiDAR-enhanced, mapping project.