Establishing Paleoclimate Records from Spring Tufa Deposits in the Driftless Area of Wisconsin

Background/Need: Water at two tufa-depositing springs in Grant County, Wisconsin emanates from stratigraphic positions similar to a laterally-extensive perched aquifer that was identified in the eastern Driftless Area and shown to be stable under current climate conditions (Carter et al., 2010). Due to the similarity in hydrogeologic setting, the tufa-depositing springs may be supplied by a similar shallow groundwater flow system. If geochemical records from the tufa deposits correlate with other proxy climate data in the region, this may suggest that tufa deposition, and therefore spring flow from the shallow flow system, has been continuous throughout the Holocene, even during climate regimes that differ from the present. Few domestic wells in the study area are installed at the stratigraphic interval of interest, but the headwaters of streams throughout the Driftless Area are fed by water discharging from the shallow groundwater flow system. Therefore, an understanding of the potential effects of climate change and variability on shallow groundwater levels and flow is important in maintaining aquatic diversity and stream habitat.
Objectives: The objectives of this study are 1) to gain a better understanding of how regional variations in the lithostratigraphy of the Sinnipee Group (Platteville, Decorah, and Galena Formations) affect shallow groundwater flow patterns in the southern Driftless Area of Wisconsin and, specifically, in the vicinity of the tufa-depositing springs and 2) to use the tufa-depositing spring systems to better understand changes in Holocene climate in this region and the effects that climate change had on groundwater levels and flow.