SURFICIAL GEOLOGIC MAPPING OF THE BRONSON QUADRANGLES IN SOUTHWEST MICHIGAN AND THE LEGACY OF THE EDMAP PROGRAM UNDER DR. ALAN KEHEW

During the summer of 2017, the Bronson North and Bronson South 7.5-Minute Quadrangles in Southwest Michigan were mapped as part of an USGS EDMAP program project. Mapping was conducted in conjunction with the Michigan Geological Survey. Hand-auger borings, grain size analysis tests, passive seismic depth-to-bedrock measurements, and ground penetrating radar transects were collected for this study of the Quaternary geology of these quadrangles. A bedrock cuesta of Mississippian Coldwater Shale was discovered shallowly buried in the northern portion of the quadrangles through passive seismic surveys. Proximal drumlins to the cuesta have notably different shapes and geometries than more distal ones, effects attributed to the unique basal lithology. Much of the field area to the south of this cuesta-influenced region, is predominantly composed of coarse-grained outwash, which exhibit hummocky topography and remnants of braided stream channels. Surficial sediments in this region were deposited by meltwater streams derived from the retreat of the Huron-Erie and Saginaw Lobes of the Laurentide Ice Sheet during final retreat approximately 19,000 cal yr. The mapping of the Bronson Quadrangles was a part of the last EDMAP project under the advisement of Dr. Alan Kehew at Western Michigan University. Al was an advocate for the EDMAP program and traditional geologic mapping eventually being the Principal Investigator on nine separate projects. These nine students had the privilege to conduct mapping projects using funds provided by the EDMAP grant to further the knowledge of the Pleistocene in Southwest Michigan and Great Lakes Region. Dr. Kehew’s insight into geomorphology, hydrogeology and hydrogeochemistry was vital in teaching mapping and understanding the glacial dynamics of the Great Lakes Region. Many of Dr. Kehew’s protégés have gone on to continue mapping after graduating and unfolding more of the Pleistocene in the Great Lakes Region due to his insight and advisement.