GEOMORPHOLOGY OF PARABOLIC DUNES ALONG THE WESTERN SHORE OF LAKE MICHIGAN, DOOR PENINSULA, WI, USA: INSIGHTS TAKEN FROM GROUND PENETRATNG RADAR, LIDAR AND PARTICLE SIZE ANALYSIS

We conducted a detailed study of the geomorphology of dunes on the northwestern shore of Lake Michigan at Whitefish Dunes State Park, Door County, WI. The dunes are superimposed on an 800m wide strand plain that separates Lake Michigan from Clark Lake. All of the dunes are parabolic with the largest (18-24 m relief) found adjacent to Lake Michigan. Further inland, there are smaller (3-7 m relief) dunes and closest to Clark Lake are a series of beach ridges, with most having approximately one meter of relief. This surficial description was based on three-meter LiDAR data, aerial photographs and field observations. Azimuth measurements on dune slip face orientations suggest the dunes formed from a paleowind direction from the south-south west. Ground penetrating radar (GPR) lines were taken following a visual observation of the surrounding topography of the dunes and the results indicated linear reflectors at varying depths. On the low dunes closer to Clark Lake, there was a pronounced reflective layer at approximately seven meters below the dune surface. A similar reflector was seen in other GPR lines located in the large dunes found closer to Lake Michigan. Sediment sampling along the GPR lines indicate that some of these reflectors are buried lake sediments, as indicated by gravels, at approximately 179-181 meters elevation. In addition, samples collected along the beach to dune transition demonstrate that the percent coarse sand in dune sediment is ~2.7% and beach sediment is ~18%. This research was made possible by the 2010 Dune Undergraduate Geomorphology and Geochronology project, a National Science Foundation Research Experience for Undergraduates.