Paper No. 5
Presentation Time: 2:45 PM
LATE HOLOCENE SHORELINE DEVELOPMENT AND EOLIAN ACTIVITY IN THREE BAYS OF THE DOOR PENINSULA, WISCONSIN, USA
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, rawlingj@uwplatt.edu
The geomorphology of Wisconsin’s Door Peninsula is unusual for the western shoreline of Lake Michigan because it contains a series of bedrock-controlled headlands and bays. Several of the bays currently contain lakes that were isolated from Lake Michigan by strand-plains that have elevations ranging from the modern Lake Michigan shoreline (~177 m) up to the Nipissing highstand (~184 m), which dates to around 5 ka. The strand-plains are covered with beach ridges capped by varying thicknesses of eolian sand and parabolic dunes. For this project we chose three of these strand-plains for detailed study, each with a unique shoreline configuration and eolian geomorphology. Clark Lake’s strand-plain (the southernmost site) is ~0.75 km wide with small parabolic dunes ranging from 3-7m and large parabolic dunes ranging from 18-24 m in relief. At this site, 18 OSL ages taken from dune crests span the late Holocene from ~7 to 1 ka, with an apparent peak in activity around 4.2 ka.
At Kangaroo Lake, the strand-plain is ~0.8 km wide with 0.35 km separating a large Nipissing beach ridge/parabolic dune complex from lower relief dunes that are found at ~ 180 m, near shorelines of the Algoma phase of Lake Michigan. Here, the strand-plain has fewer distinct parabolic dunes, and those present have relief similar to the highest dunes at Clark Lake. The strand-plain at Europe Lake is ~0.3 km wide and covered by a large Nipissing beach ridge with smaller beach ridges towards Lake Michigan. There are no distinct dune forms at this site. Eleven preliminary OSL ages of eolian sand at these latter two sites cluster around the Nipissing lake phase, with little or no apparent reactivation in the late Holocene. In general the higher influx of sand during the Nipissing lake level in the southern portion of our study area resulted in more well-developed parabolic dunes and more periods of late-Holocene eolian activity. This variability is likely due to both shoreline configuration and local littoral factors, given that these sites are found within ~45 km of each other. This research is part of the Dune Undergraduate Geomorphology and Geochronology (DUGG) Project, a NSF-Research Experience for Undergraduates site.
