North-Central Section (36th) and Southeastern Section (51st), GSA Joint Annual Meeting (April 3–5, 2002)

The northern section of the interlobate zone between the Lake Michigan and Green Bay lobes was produced by large meltwater channels incised into the ice along both lobe margins as ice withdrew. The channels directed meltwater toward the south-southwest, parallel to a central zone where the ice surface was higher and relatively clean. In this debris poor area, large moulin kames directly overlie a streamlined till surface, which is now a low central area. The moulin kames contain gravel, diamicton and laminated silt with dropstones. On either side of this central area, long, linear gravel ridges rise abruptly, bordered by deep kettles. Diamicton and gravel in the moulin kames have a roundness ranging from 0.37 to 0.65 on a 1.0 point scale, with an average of 0.55±0.09 for 7 sites. Other gravel in the interlobate region, particularly on the hummocky edges, have a range of 0.71 to 0.81, with an average of 0.78±0.03 for 13 sites. Imbrication and crossbeds in hummocky sand and gravel indicate that meltwater flowed obliquely towards the debris poor central area, while flow indicators from the hummocky gravel ridges along the edge demonstrate meltwater flowed south-southwest, parallel to the ridges. The well rounded, well sorted gravel suggest that much of the northern Kettle Moraine sediment resulted from large stream systems that drained the Lake Michigan and Green Bay lobes. These subaerial to subglacial channels incised into the ice abutted the central stagnant ice zone, directing meltwater parallel to the interlobate axis, and ultimately producing the high relief hummocky topography along the edge. In the stagnant ice zone that separated the lobes, debris from melt-out of debris in ice collected in cavities, open to the glacier bed, depositing poorly sorted and poorly rounded sediment in the kames with very little fluvial reworking.