EOLIAN SAND CYCLES IN TRAPPED EMBAYMENTS OF LAKE MICHIGAN RECORD CLIMATE FLUCTUATIONS

Silver Lake, Hamlin Lake and Stony Lake, along the western coastline of Michigan, are separated from Lake Michigan by a barrier/dune complex. Numerous vibracores from the lakes reveal variations in weight percent sand within the lacustrine and paludal sediment from ~8500 calendar years BP to present. Based on sorting and grain size analysis, the sand in the sediment appears to be eolian in origin. It is suggested that the eolian sand is deposited on the lake ice via niveo-eolian transport, which has been empirically observed. When the lake ice melts, the sand is introduced into the sediment. Plots of weight percent sand vs. calendar years BP, display in-phase relationships with the Lake Michigan relative lake level curve, derived from dated beach ridges of known elevation. High peaks in the sand record correspond to high water levels of Lake Michigan since the Nipissing II phase. Both show evidence of a quasi-periodic cycle of ~160 years, however the benefit of the sand record is the ability to document the cyclicity ~3800 years before the Nipissing II phase. It does not appear that fluctuating water levels of Lake Michigan are directly driving the variations in the sand record, but rather, both are driven by the same climate fluctuations. Therefore, it is suggested that the eolian sand record within the lacustrine and paludal sediment of Silver Lake can be used as a climate proxy.