COMPARISON OF MITCHELL AND MUSCATATUCK KARST REGIONS IN INDIANA

Indiana contains two karst regions, the Mitchell and Muscatatuck Plateaus. This research will examine reasons for different levels of karstification in these two regions. The Mitchell Plateau (Mississippian) in South-Central Indiana has undergone more extensive karstification, with many more sinkholes and long caves, than the older Muscatatuck Plateau (Ordovician) in Southeastern Indiana. A representative area (∼10km²) from each region has been analyzed to determine sinkhole shape, size, elevation, pattern, and quantity on topo maps and LIDAR . The Mitchell Plateau east of Mitchell, IN contains 70 sinkholes/km², and the Muscatatuck Plateau around Versaille, IN contains 18 sinkholes/km². The average diameter of Mitchell Plateau sinkholes is 115 meters, while the average Muscatatuck Plateau sinkhole is 38 meters in diameter. The Mitchell Plateau sinkholes developed on Blue River Group limestones while the Muscatatuck Plateau sinkholes developed on Maquoketa Group dolomites.

We will test three hypothesis to possibly explain why is karstification of each region so different. This disparity between the two regions is unique because they have similar climate and are separated by less than 50 km. Lithology hypothesis states that the Muscatatuck Plateau developed on dolomites, which are more resistant to karstification and thus have less dense and smaller sinkholes. Glacial burial hypothesis states that Muscatatuck Plateau was glaciated and karst landforms are obscured by glacial till. Glacial erosion hypothesis states that the Muscatatuck Plateau was karstified but glaciers scoured off karst landforms exposing older dolomites and the new cycle of karstification began after glaciation.