PALEOECOLOGY OF GASTROPODA IN PLEISTOCENE LAKE SCUPPERNONG, JEFFERSON COUNTY, WISCONSIN: COMPARISON WITH LAKE LAHONTAN, HUMBOLDT COUNTY, NEVADA

An outcrop of lake sediments in Jefferson County, Wisconsin records deposition in the Pleistocene Lake Scuppernong (LS), which formerly existed in southeastern Wisconsin between 15,000 and 12,500 years before present. Gastropod fossils are abundant and diverse and provide data on the pre-industrial human and pre-invasive species conditions of the fauna of midwestern lake ecosystems. Two species, Valvata bicarinata and Helisoma antrosa, are numerical dominants among at least six other molluscan species. Multiple sediment samples between 200-300g were wet sieved, retrieving between 200-500 individuals each. All species were picked, sorted, identified and counted, with the two dominant species measured for biomass calculation. Data produced allow for comparative paleoecologic analysis with gastropod faunas of coeval Lake Lahontan (LL) in Humboldt County Nevada. Preliminary results include: Higher species richness in multiple measures for LS, higher skeletal densities for LS, smaller mean size frequencies for species in LL and concordance of numerical and biomass dominants in both LS and LL.