USING OSL DATING TO CONSTRAIN THE DEVELOPMENT OF LATE HOLOCENE BAYMOUTH BARRIERS AND SUBSEQUENT DUNE FORMATION IN DOOR PENINSULA, WISCONSIN, USA

This study focuses on the dune and lacustrine sediments in two baymouth barrier systems found along Lake Michigan’s western shoreline. We used optically stimulated luminescence (OSL) dating to constrain when littoral sediments were deposited and the overlying dunes were activated at two baymouth barriers near Kangaroo and Clark Lakes. Sediments for particle size analysis and OSL dating were sampled using bucket augers and a vibracoring device. Particle size analysis and mineralogical observations indicate that the lacustrine sediment found in the two baymouth barriers range from 179-184 meters above mean sea level (mamsl). These deposits lie several meters above Lake Michigan, which historically fluctuated around ~ 177 mamsl, but within range of the Nipissing transgression that reached elevations of ~ 184 mamsl in the region. Our elevation data and 10 OSL ages that range from 5.8 to 4.0 ka suggest that the lacustrine sediments within the barrier were deposited during the Nipissing, which dates to ~ 5.5 to 4.5 ka in the Lake Michigan basin. The dunes found on these barriers correspond closely to the Nipissing and Algoma lake level highstands. Dunes at the Clark Lake site include small parabolics with 3-7 m of relief and large complex parabolic dunes that are 18-24 m in relief. At the Kangaroo Lake site two dune ridges are separated by ~0.4 km, where the ridge close to Lake Michigan has dunes with ~ 6 meters of relief and the ridge close to Kangaroo Lake has dunes with 15-24 meters of relief. At Clark Lake 21 OSL ages taken from dune crests span the late Holocene from ~7 to 1 ka, with an apparent peak in activity around 4.2 ka. The larger dunes at Kangaroo Lake have OSL ages between ~5.5 and 3.0 ka, with most corresponding to the regression of Lake Michigan after the Nipissing high. The ages of the smaller dunes at the Kangaroo Lake site range from 2.8 to 2.2 ka, corresponding roughly with the Algoma lake level high that dates to ~ 2.5 ka. Our findings show that the formation of the baymouth barriers and the subsequent activation of the dunes on these barriers occurred rapidly and within error of the OSL age estimates. This research is part of the Dune Undergraduate Geomorphology and Geochronology (DUGG) Project, a NSF-Research Experience for Undergraduates site.