Indian Creek Member of the Ste. Genevieve Limestone (Chesterian, Mississippian) in South-central Indiana Report

Abstract

The Middle Mississippian Ste. Genevieve Limestone is a shallow marine to nonmarine carbonate formation in the Illinois Basin. The Ste. Genevieve Limestone is the oldest Chesterian deposit in Indiana, and its predominant oolitic and fossiliferous grainstone packages represent a dynamic shoaling environment. The grainstones of the Ste. Genevieve Limestone are known for their economic significance in the Illinois Basin as sources of oil and gas, industrial minerals, and aquifer potential. With much of the Ste. Genevieve Limestone composed of grain-supported carbonates, the presence of a consistent lime mudstone package ranging from 3 to 41 ft (0.9 to 12.5 m) in thickness should be apparent, yet has historically failed to be recognized for its significance. This laterally correlative lime mudstone package is known as the Indian Creek Limestone Beds, and recent geological mapping in south-central Indiana conducted by the Indiana Geological and Water Survey has recognized the stratigraphic potential of this unit. We provide evidence for the lateral extent, consistent stratigraphic positioning, and diagnostic characteristics of this lime mudstone package to support our elevation of these beds to the Indian Creek Member of the Ste. Genevieve Limestone.