Paper No. 19
Presentation Time: 9:00 AM-6:00 PM
GEOMORPHOLOGY AND OSL DATING OF LAKE MICHIGAN'S NIPISSING SHORELINE FEATURES, EUROPE LAKE, DOOR PENINSULA, WISCONSIN
HOBBS, Daniel, Geology, Middlebury College, McCardell Bicentennial Hall, 276 Bicentennial Way, Middlebury, VT 05753, NEUMANN, Christian, Environmental Studies, Gettysburg College, Campus Box 393, 300 North Washington St, Gettysburg, PA 17325,
O'BRIEN, Maura, Geology, Oberlin College, 135 West Lorain Street, OCMR 1997, Oberlin, OH 44074, TARGOS, Courtney, Department of Geosciences, Indiana University Northwest, 3400 Broadway, Marram Hall, Room 243, Gary, IN 46408, RAWLING III, J. Elmo, Geography/Geology, University of Wisconsin Platteville, 1 University Plaza, Platteville, WI 53818, HANSON, Paul R., Conservation and Survey Division, School of Natural Resources, Univ. of Nebraska, 102 Nebraska Hall, Lincoln, NE 68588-0517 and HART, David J., Wisconsin Geological and Natural History Survey, University of Wisconsin-Extension, 3817 Mineral Point Rd, Madison, WI 53705, mobrien@oberlin.edu
Shoreline features of Lake Michigan’s Nipissing phase (~4.5-5.5ka) in Wisconsin are poorly understood. This study focuses on the development and stabilization of Holocene eolian sand at Newport State Park, located on the northern tip of Door Peninsula, Wisconsin. The site falls within a region of low isostatic rebound, minimizing the potential error in estimating the elevation of late Holocene shorelines. Within the site, five distinct ridges capped with eolian sand separate Lake Michigan from inland Europe Lake. The ridges range from approximately 1.5 to 3 meters in relief, with the largest ridge located furthest from Lake Michigan.
Site stratigraphy was determined with ground-penetrating radar (GPR) and particle-size analysis (PSA). OSL ages of eolian sand were used to establish the age range of stabilization and its relationship to the Nipissing lake level. Samples were collected for OSL dating from five sites and for PSA from eighteen sites. Optical ages range from 4.2 to 6.1 ka, which are within the Nipissing time period. Four of these ages are located on the largest ridge. All but one of the sites sampled for PSA included a distinct sediment change from very fine sand to significantly coarser sand. This change is also supported by GPR imaging on the larger ridge, which shows a reflector at 4 meters below the surface.
A previous study on the geochemistry of sediment cores from Europe Lake suggests that it may have been an embayment of Lake Michigan through the Algoma phase. However, based on our ages and LiDAR data, as well as lake level estimates from previous studies, we suggest that Europe Lake and Lake Michigan were separated following the Nipissing. Therefore, the age for the initial isolation of Europe Lake occurred prior to the Algoma phase of Lake Michigan. 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.
