MAPPING THE INTERLOBATE ZONE BETWEEN THE LAKE MICHIGAN AND SAGINAW LOBES OF THE LAURENTIDE ICE SHEET: IMPLICATIONS FOR LATE WISCONSIN EPISODE ICE DYNAMICS IN SOUTHWESTERN MICHIGAN, USA

Mapping late Wisconsin Episode landforms and sediments of the southern Laurentide Ice Sheet is critical to understanding and predicting soil and landscape variability, as well as groundwater and aggregate resources. Using LiDAR-derived DEMs and NRCS soils data, we mapped late Wisconsin Episode landforms and sediments in the broad interlobate zone between the Lake Michigan Lobe (LML) and Saginaw Lobe (SL) in southwestern Lower Michigan. Ours may be the first detailed mapping exercise dedicated to this little-studied region, with a goal of to better defining the location and geomorphology of this interlobate. The SL advanced out of Saginaw Bay, forming drumlins, fluted ground moraine, and eskers in Mecosta, Montcalm, Kent, Barry and Ionia Counties. The orientations of these landforms indicate that the SL splayed outward, flowing to the northwest in Mecosta and Montcalm Counties, to the west in Kent County, and to the southwest in Ionia and Barry Counties. Eskers, ice-contact ridges, ice-walled lake plains and kettles indicate areas of down-wasting and stagnation near the SL ice margin. The LML flowed out of the Lake Michigan basin to as far east as Newago, Kent, Allegan, and Barry Counties, where it abutted the SL. LML drumlins and fluted ground moraine indicate that flow was to the northeast in Muskegon and Newago Counties, to the east in Ottawa and Kent Counties, and to the southeast in Allegan, Barry, and Van Buren Counties. Hummocky moraines, kettles, crevasse-fills, and small ice-walled lake plains suggest that ice-stagnation was present in ice-marginal zones during the Valparaiso and Lake Border advances of the LML. A complex network of channels indicate that the majority of the meltwater flowed to the south in the interlobate zone. Till textures in the interlobate zone suggest that the SL advanced over areas of outwash, and that the LML may have advanced over areas previously covered by the SL.