Preglacial Cavern Systems in Silurian Bedrock in Indiana and Implications for Modeling Groundwater Productivity

Several cave systems are mapped using water well records from the Indiana Department of Natural Resources database. The study encompasses a ten county 10,000 square kilometer area and involves over 20,000 located water well records in East Central Indiana. Due to the variable bedrock topography, the area has essentially equal numbers of glacial and bedrock wells in a range of depths which provide an informative 3-D geometry. This study focuses on the record of possible late Tertiary and Early Quaternary caves and fracture systems recorded on well drilled into the Silurian bedrock. The cave systems are pertinent to the geologic history of drainage across Indiana prior to and during early glacial time and are also pertinent to locating areas of potentially high groundwater productivity. Wells with suggestions of caves, including some that are still open, tend to cluster in areas near the buried Teays and Anderson bedrock valleys. The map pattern of caves suggests cavern systems leading from late Tertiary bedrock plateaus to deeper outlets on the sides of developing bedrock valleys that were subsequently filled during glaciation. Several cave systems are mapped and related to zones of higher groundwater transmissivity (specific capacity) in bedrock and adjacent unconsolidated sediments in the valleys. A Modflow groundwater flow model of a portion of the study area incorporates one of the largest cave systems and examines productivity potential from wells placed in the area of the cave system.