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

Regional DEMs of southwestern Michigan provide a new and important tool for interpretations of glacial landscapes. The principle benefit of regional DEMs is the ability to examine large areas without a loss of detail caused by the large contour interval inherent in regional topographic maps. Hillshade DEMs are most useful for interpretations of glacial landforms, although variation in sun direction and angle is essential to obtain optimal images for terrains formed by glacial lobes with different directions of movement. In the study area these include the southwesterly moving Saginaw lobe and the east-southeasterly moving Lake Michigan lobe. Among the features that appear in spectacular detail for the Saginaw lobe is the separation of a drumlinized terrain south of the Kalamazoo River from a terrain composed of tunnel valleys and eskers north of the River. In the Lake Michigan lobe terrain, a narrow band of isolated drumlinized uplands is clearly continuous on the image. The continuity of the tracts had not been recognized prior to viewing the image. The broad, deeply intrenched Kalamazoo Valley can be traced on the image to a series of anastomosing convergent tunnel valleys, supporting a new interpretation as the track of a subglacial outburst (Kozlowski et al., 2001). Traditionally mapped moraines are not all clearly visible on the image. The Sturgis moraine of the Saginaw lobe is clearly demarked by its position at the downglacier margin of the drumlinized region, and by the presence of large glaciofluvial fans. However, the Tekonsha and Kalamazoo moraines of the Saginaw Lobe are not easily recognized. Although the Kalamazoo and Lake Border Moraines of the lake Michigan lobe stand out as distinct ridges of ice marginal origin, the appearance of the Valparaiso moraine is consistent with its recent (Kehew et al., 2001) interpretations as a group of upland tracts of multiple origins. Thus the DEMs call into question some long held interpretations that have appeared on all state maps since the early 20th century. In the Midwest, regional DEMs allow the visualization of the terrain of large portions of one or more lobes of the Laurentide Ice Sheet. As such, they constitute an invaluable complement alone, or when combined with other geologic data sets to aid small scale mapping of glaciated regions in the Midwest.