Maximum-limiting ages of Lake Michigan coastal dunes: their correlation with holocene lake level history

Coastal geomorphology along the Great Lakes has long been linked with lake- level history. Some of the most spectacular landforms along the eastern sho re of Lake Michigan are high-relief dunes that mantle take terraces. It has been assumed that these dunes developed during the Nipissing high stand of ancestral Lake Michigan. This hypothesis was tested through stratigraphic analyses and radiocarbon dating of buried soils at four sites between Manis tee and Grand Haven, Michigan. At each site, thick deposits of eolian sand overlie tate-Pleistocene lacust rine sands. Moderately developed Spodosols (Entic Haplorthods) formed in th e uppermost part of the lake sediments are buried by thick dune sand at thr ee sites. At the fourth locality, a similar soil occurs in a very thin (1.3 m) unit of eolian sand buried deep within a dune. These soils indicate lon g-term (similar to 4,000 years) stability of the lake deposits following su baerial exposure. Radiocarbon dating of charcoal in the buried sola indicat es massive dune construction began between 4,900 and 4,500 cal. yr B.P. at the Nordhouse Dunes site, between 4,300 and 3,900 cal. yr B.P. at the Jacks on and Nugent Quarries, and between 3,300 to 2,900 cat. yr B.P. at Rosy Mou nd. Given these ages, it can be concluded that dune building at one site oc curred during the Nipissing high stand but that the other dunes developed l ater Although lake levels generally fell after the Nipissing, it appears th at dune construction may have resulted from small increases in lake level a nd destabilization of lake-terrace bluffs.