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43910-B8
Quaternary Eolian Stratigraphy of the Central Plain of Wisconsin
Wind-blown sand has been recognized in the Central Sand Plain (CSP) of Wisconsin for several decades, yet the timing of eolian activity remains obscure. The purpose of this project is to obtain stratigraphic and chronological data for the largest dunes in the eastern CSP, which consists of two major components: the broad sandy outwash plain flanking the western margin of the Green Bay Lobe, and the extensive sandy lake plain of glacial Lake Wisconsin. Both of these have been modified to some extent by eolian processes. We used optically stimulated luminescence (OSL, or simply “optical”) dating methods to constrain the timing of dune development in the CSP. These age estimates not only constrain eolian activity but are also minimum age estimates of the drainage of glacial Lake Wisconsin and the abandonment of meltwater streams flanking the Green Bay Lobe of the Laurentide Ice Sheet.
Eleven sites in the large dunes were selected for obtaining particle-size analysis and 24 optical samples. At Site 10, a split-spoon coring apparatus was used to collect sediment, and a ground-penetrating radar survey was conducted to better understand the local stratigraphy. Sites were located on what we interpreted to be stable dune crests with A-Bw soils. The majority of the optical ages indicate that dunes in Wisconsin's CSP were active from ~14–10 ka. More recent activation in the early or middle Holocene was limited, if present at all, to the deposition of < 1 m of sand on dune crests. Soils have increasing amounts of silt near their surface, which is likely the result of eolian additions during the Holocene. It is likely that dunes in central Wisconsin formed because of an influx of sand from either the Wisconsin River outwash plains or the melting of permafrost. Future work will aim to address the cause of dune formation in central Wisconsin.
This ACS PRF funding has had a significant impact on my career. Data collected from the first year resulted in two presentations at the North-Central Geological Society of America (NC-GSA) meetings. A manuscript with results of the first year's work is in review with the journal Geomorphology. Collaborative relationships with Wisconsin Geological and Natural History Survey (WGNHS) faculty include ground penetrating radar with Dr David Hart, analysis of glacial Lake Oshkosh sediments with Dr Tom Hooyer and analysis of glacial Lake Wisconsin sediments with Dr John Attig. I was recently appointed Research Associate with the WGNHS because of these projects that were made possible by the PRF funding. In addition, supplemental funding through the ACS PRF SRF program supported Dr Peter Jacobs and two of his students to study soil development on the dunes. Dune stability is followed by soil formation and many models of rates of weathering and soil development are poorly constrained because we lack precise estimates of the age of landscape stabilization. This is especially true in quartz-rich eolian sands of the humid Midcontinent, where typically no direct age control was available prior to this study. Combining age estimates of landforms with measures of soil development is useful for constructing calibrated age estimates in similar strata and sediments, thus allowing this research to be extended to similar sandy strata in the Midcontinent.
Finally, nine students including four women, one Native American and two veterans of the current conflicts in Afghanistan and Iraq, have benefitted from the first year of this PRF project. Their involvement ranges from hourly lab work to significant field and lab analysis on their own projects. David Burney helped with field work during the 2006 summer field season, prepared OSL samples for analysis at the UNL Luminescence Geochronology Laboratory, and conducted an independent project analyzing outlying eolian sand in the nearby Sandhills Wildlife Area, a Wisconsin DNR managed preserve. David's research was presented at the NC GSA meeting and he is currently applying for graduate school. Three students (Jill Thalacker, Bennett Morris and Elijah Caywood) conducted independent research during the 2007 field season. Their results are pending and will be presented at the 2008 National Conference of Undergraduate Research.
