CHRONOLOGY OF GLACIAL RETREAT IN THE UPPER PENINSULA OF MICHIGAN FROM KETTLE LAKE CORES

The goal of this study is to interpret the deglaciation of the Laurentide Ice Sheet as it passed from one basin to another—L. Michigan to L. Superior—via the land bridge of the Upper Peninsula of Michigan (UP). To accomplish this goal, a multi-tool (chronology, sedimentology/geomorphology, and geophysics) approach will be used to reconstruct the glacial history of the UP. This paper presents preliminary chronology data extending from L Superior to the Lower Peninsula of MI. 16 kettle lakes were cored and used to establish a minimum age of deglaciation using radiocarbon analysis, loss-on-ignition, and magnetic susceptibility. The lakes in the UP were chosen based on their location in a unique geomorphic area: a chain of kettle lakes that may be a collapse feature. The kettle chain is also surrounded by fan deposits, which indicate a waning stage of deglaciation. It is hypothesized that the deglaciation of the area is almost instantaneous, rather than time-transgressive, due to these kettle lakes and surrounding fans (burial deposits?). In addition, loss-on-ignition and magnetic susceptibility data support rapid deglaciation in the UP.