43910-B8
Quaternary Eolian Stratigraphy of the Central Plain of Wisconsin
The purpose of this project is to obtain stratigraphic and chronologic data for Quaternary deposits in Wisconsin’s Central Sand Plain (CSP). During the first year, stratigraphic descriptions, particle-size analysis and optically stimulated luminescence (OSL, or simply “optical”) dating methods were used to investigate eolian dune strata. The age estimates indicate the majority of dune formation occurred between 14-10 ka. These ages 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.
The second year of this project focused on expanding our understanding of other Quaternary strata in the CSP. In addition, an emphasis was placed on involving undergraduates as significantly as possible. That is, an effort was made to let them lead the research. Three students (Jill Thalacker, Elijah Caywood and Bennett Morris) conducted independent research on data collected during the 2007 field season. Collectively, their projects were designed to better understand the relationship between the eolian dunes and adjacent sheet sand, underlying lacustrine strata, and soil development. Jill analyzed several cores collected with Dr Paul Hanson (UN-Lincoln) using stratigraphic descriptions, particle-size analysis and luminescence age analysis. Eli Caywood investigated these strata using ground penetrating radar collected with Dr Dave Hart (UW-Extension Wisconsin Geologic and Natural History Survey) from the crest of a large dune, across the slip-face, and onto the eolian sand sheet. Bennett Morris investigated soils collected with Dr Peter Jacobs (UW-Whitewater) from the crest of a large dune, across the slip-face, and onto the eolian sand sheet using field descriptions, particle-size analysis, and carbon/nitrogen ratios. These three students presented their results at the 2008 National Conference of Undergraduate Research in Salisbury, Maryland.
In addition to Bennett’s work on soils, he was also the recipient of PRF SUMR supplemental funding to investigate the location of large dunes in the CSP. Large dunes, up to 15m high, are limited to a small area (~150 sq km) in the west central portion of the CSP. Proposed reasons for the distribution of thick eolian sand include melting of permafrost, elevation of the basin in relation to ground water, sediment inputs from the Wisconsin River, and sediment particle-size. Particle-size analysis of the large dunes shows that the median grain-size is between 200-300 microns. Therefore, if the distribution of thick eolian sand is controlled by particle-size, areas without dunes should be deficient in those grains. Bennett’s project tested this hypothesis by analyzing ~100 samples across the CSP for particle-size distribution. Based on his analysis, the northern portions of the CSP are to coarse for eolian transportation. However, the southern portion of the CSP has 300 micron grains but dunes are absent or small. These results will be presented at the 2008 Westlakes Divisional Meeting of the Association of American Geographers and the North-Central Sectional Meeting of the Geological Society of America.
In addition to these student projects, several sites were sampled for optical luminescence age analysis. These included sites within eolian sheet sand and glacial Lake Wisconsin strata. These samples were processed over winter break by Nathan Petesch (UW-Platteville undergraduate) at the UN-Lincoln Luminescence Geochronology Laboratory under the guidance of Dr Paul Hanson and Aaron Young. These ages will be presented at the annual meeting of the Geological Society of America and included in future publications. To date, the ACS PRF funding has had a significant impact on collaborative relationships that I continue with faculty at the UW-Extension Wisconsin Geological and Natural History Survey, UW-Whitewater and UN-Lincoln. Additional manuscripts are being drafted to publish the results of these investigations.
