HOLOCENE OSL AGE ESTIMATES OF PARABOLIC DUNES ON THE WESTERN SHORE OF LAKE MICHIGAN, DOOR PENINSULA, WI, USA

Whitefish Dunes is an 865-acre state park predominantly covered in forested parabolic sand dunes located on the Door Peninsula along the western shore of Lake Michigan. The dunes occur on portions of a 3.5 sq km wide strand plain found between Lake Michigan and Clark Lake, a small lake inland of the dunes. Most dunes in the study area have ~21 meters of relief, although there is an area of smaller dunes with relief of up to 5 meters. A model of dune formation was developed by observing soil characteristics, Ground Penetrating Radar (GPR) and Optically Stimulated Luminescence (OSL) age estimates. Nine OSL samples were collected from lake sediment (n=2) and dune crests (n=7) and were processed using the single-aliquot regenerative method with 90-180 mm quartz. The lacustrine deposits yielded preliminary ages of 4.6 ka for a beach ridge landward of the dunes and 4.4 ka for lacustrine sediment underlying the dunes. Preliminary OSL ages from the dunes ranged from 1.9 to 7.8 ka, with four of these ages falling between 4.1-5.2 ka. These ages are within or shortly after the Nipissing high lake level phase that occurred from 4.3-6.0 ka. The similarity of the dune and lacustrine ages suggests rapid formation of parabolic dunes from increased sediment supply during Nipissing time. Two younger ages suggest that some dunes may have been formed or were reactivated during the Algoma transgression. These hypotheses will be tested with additional OSL ages. This research was conducted by the Dune Undergraduate Geomorphology and Geochronology (DUGG) project, funded by the National Science Foundation Research Experience for Undergraduates (NSF-REU) program.