Geomorphology and Ground Penetrating Radar Stratigraphy at Three Nipissing Baymouth Barrier Systems in the Door Peninsula, Wisconsin, USA

This study focuses on the geomorphology and ground penetrating radar (GPR) stratigraphy of three baymouth barrier systems at Clark Lake, Kangaroo Lake, and Europe Lake in the Door Peninsula of Wisconsin. These sites are located within ~45 km of each other and have similar late Holocene histories. However, each consists of different geomorphic features including parabolic dunes, baymouth bars, and beach ridges on the barrier platform. Also, their modern beaches are different and transition into large dunes or beach ridges. The purpose of this study was to analyze the underlying stratigraphy of typical landscapes within the barriers to identify stratigraphic structures and GPR signatures. Fourteen GPR profiles were collected with 500 and 120 MHz antennae and penetrations of ~7 to 15 meters were achieved. Profiles were collected in five landscapes including: modern beaches (n=2), Nipissing age simple parabolic dunes (n=2), Nipissing, Algoma, and younger age superimposed parabolic dunes (n=7), a Nipissing age baymouth bar with an inlet (n=1), and the barrier platform (n=2). This GPR stratigraphy was verified by bucket augering at ~150 sites, vibracoring at eight sites, and particle-size analysis by laser diffraction (n= ~950). Most GPR profiles have clear reflectors marking the elevation of the water table and the transition from eolian to littoral deposits. Eolian strata include high angle oblique-tangential reflectors dipping away from Lake Michigan, and complex scour and fill reflectors occur even in simple parabolic dunes. Buried portions of superimposed parabolic dunes are recognizable in the GPR surveys. Littoral strata are commonly oriented horizontally with hummocky reflectors, contain some high angle oblique-tangential reflectors dipping toward Lake Michigan, and contain contorted reflectors likely caused by cobbles. This research is part of the Dune Undergraduate Geomorphology and Geochronology (DUGG) Project, an NSF-Research Experience for Undergraduates site.