FIRST APPLICATION OF OSL DATING TO TEST THE PERCHED-DUNE MODEL ON MICHIGAN COASTAL DUNES

Coastal sand dunes commonly occur along the Lake Michigan shoreline. Many of these landforms in the northwestern part of Lower Michigan are high-perched dunes that mantle tall (~100m) coastal bluffs. It is believed that high-perched dunes enlarge during high lake levels because waves destabilize bluff faces, such that eolian sand can mobilize from that source. Previous studies rely heavily on radiocarbon dates derived from buried soils to estimate periods of dune growth. However, this may have led to erroneous conclusions due to uncertainties with the method.

This study tests the perched-dune model by using optically stimulated luminescence (OSL) dating, which directly estimates the timing of sand transport, at the Arcadia dune field in Benzie County, MI. At this site approximately 25m of eolian sand overlies about 100m of glacial sediments. Given previous studies elsewhere, we hypothesize that the basal eolian deposits accumulated during the Nipissing high stand (~ 6 ka) of ancestral Lake Michigan. Several distinct eolian units, each separated by paleosols, occur above these basal sands. OSL samples were collected from each of these sand deposits and will directly estimate when they accumulated. Results will be compared with known lake-level fluctuations to test the validity of the perched-dune model.