IMPACT OF THE NIPISSING AND ALGOMA HIGH LAKE PHASES FROM OSL DATING OF BAYMOUTH BARRIER SYSTEMS IN THE DOOR PENINSULA, WISCONSIN

This study focuses on the geomorphology and geochronology of three baymouth barrier systems at Clark, Europe and Kangaroo Lakes in the Door Peninsula of Wisconsin. The Lake Michigan shoreline in the peninsula contains abundant evidence for fluctuations in lake level as evidenced by strandplains and beach ridges that lie up to ~ 7 m above the present shoreline. Our study was conducted on three baymouth barriers that contain beach ridges that were buried by varying depths of eolian sand in the form of sandsheets, as well as parabolic and transverse dunes with relief of up to 21 m. The purpose of this study was to document when the barriers were deposited and when the subsequent eolian activity occurred. Our chronology for barrier emplacement and dune development is based on 65 OSL samples which were collected from lacustrine sediment within the barrier fills (n = 17) and the overlying eolian sand (n = 48). Sediment samples were collected using bucket augers or a vibracoring device at depths ranging from 0.5 to 4.1 m below the ground surface. Our OSL ages show that baymouth barriers in each of our study sites were constructed between ~ 5.9 to 3.9 ka, and most of our ages correspond closely to the Nipissing high lake level phase. Both geomorphic and geochronological evidence from the Kangaroo Lake site shows portions of this barrier were re-occupied after the Nipissing phase. Our OSL ages from lacustrine sediment taken from within the barrier suggest this occurred at 3.3 to 2.5 ka, correspondingly closely with the Algoma high lake level phase. The majority of our eolian ages fall into two primary groups that overlap with or are slightly younger than the ages acquired from the barriers. OSL ages from dune crests and sand sheets suggest that dune formation most likely ceased between 4.5-3.7 (n = 20 OSL ages) and again around 2.5-1.8 (n = 11 ages) ka. Both geomorphic and geochronological evidence suggests that dune development was rapid, and that dunes were primarily active during recessional phases of Lake Michigan when sand supply was elevated. This project was carried out in large part through the efforts of undergraduate researchers and was funded through the National Science Foundation’s Research Experience for Undergraduates (REU) program.