HYDROSTRATIGRAPHIC CHARACTERIZATION OF THE PATOKA AND SHELBURN AQUIFER SYSTEMS IN SOUTHWESTERN INDIANA

The Inglefield sandstone member of the Pennsylvanian Patoka Formation and the Shelburn Formation are the primary aquifers for domestic water supply in southwestern Indiana. The objectives of this study were to generate conceptual models of the regional hydrostratigraphy, and to produce potentiometric maps of these aquifer horizons. The study used water levels, ground elevations, and stratigraphic data from logs of wells drilled over a forty-year period in Southwestern Vanderburgh County, Indiana to construct cross-sections and potentiometric maps. Map locations, well depths, and analyses of basal stratigraphy identified the specific aquifer horizon for each well. Water levels measured in wells that were screened in the Patoka Formation during the ten wettest and ten driest years of the forty-year period were used to construct potentiometric maps. These maps suggest a local recharge zone that parallels the Ohio River valley, and is nearly coincident with areas of recent and rapid commercial development. Potentiometric maps need to be constructed using current and synchronous water-level data to verify recharge and discharge zones. Constructed cross-sections identified high-angle normal faults beneath the research area, as indicated by offsets in the West Franklin Limestone; the West Franklin Limestone separates the Patoka and Shelburn aquifers. In addition to potential hydrostratigraphic implications of these faults, their identification may have bearing on seismic studies of the Wabash Valley Seismic Zone. This study has provided a working conceptual model to further design investigations of the stratigraphic, hydrogeologic, and water-quality characteristics of the Patoka and Shelburn aquifer horizons in and around Evansville, IN.