2003 Seattle Annual Meeting (November 2–5, 2003)

Paper No. 13
Presentation Time: 1:30 PM-5:30 PM

A STUDY OF THE HYDROLOGIC CHARACTERISTICS OF THE MAHOMET AQUIFER THROUGH THE USE OF DISSOLVED HELIUM AND HIGH RESOLUTION GEOPHYSICAL PROFILING


CARSTENS, David A.1, VAN DER HOVEN, Stephen J.2, NELSON, Robert S.2 and LARSON, Timothy3, (1)Department of Geography-Geology, Illinois State University, Normal, IL 61790, (2)Department of Geography-Geology, Illinois State Univ, Normal, IL 61790, (3)Illinois State Geol Survey, 615 E. Peabody Drive, Champaign, IL 61820, davidca@hcc.cc.il.us

An ongoing study of the Mahomet Aquifer in Piatt County, IL is being conducted in part to further examine a link that may exist between the surface waters and the buried bedrock valley aquifer. A hydraulic window connection has previously been identified between the Mahomet Sand Member at a depth of 50 to 80 m and the Sangamon River, linking the two. Recharge is thought to occur through the Sangamon River, as indicated by relatively young groundwater ages and low chloride concentrations in the Mahomet Aquifer beneath the Sangamon River. We integrate the use of 4He as a naturally occurring conservative tracer with seismic reflection profiles and Vertical Seismic Profiles provided by the Illinois State Geological Survey. 4He data can allow us to see if younger waters are entering the deeper part of the system, making a stronger case for a recharge point at the Sangamon River. Seismic data provides details of the characteristics of the aquifer system.