--> ABSTRACT: Lithostratigraphy and Petroleum of Stephensport Group (Mississippian) in Indiana, by John B. Droste and Stanley J. Keller; #91023 (1989)

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Lithostratigraphy and Petroleum of Stephensport Group (Mississippian) in Indiana

John B. Droste, Stanley J. Keller

Rocks in the Stephensport Group (Upper Mississippian) of Indiana consist of three limestone formations separating two sandstone-shale formations. Interpretations of maps and cross sections compiled from subsurface data show the interrelationships among these units with respect to sedimentation, stratigraphy, and petroleum accumulation. The Stephensport Group thickens from 150 ft to more than 250 ft westward toward the center of the Illinois basin. General westward thickening is expressed by each of the individual formations except the basal unit, the Beech Creek Limestone, which thins basinward from more than 30 ft thick near its eastern outcrop to 10 ft thick over 90% of the remaining area in Indiana. Sandstones in the Big Clifty are prominent throughout the outcrop area but are characterized in the subsurface by two northeast-southwest-trending sandstone belts. Both belts contain oil fields. Sandstones in the Hardinsburg Formation are randomly distributed except in a north-south-trending belt where net sandstone thickness exceeds 100 ft. Within this thick sandstone belt, the underlying Haney Limestone, normally 40 ft thick, thins and in places is absent. Origin of the thick Hardinsburg belt sandstones is the result of more-or-less contemporaneous scouring and deposition of quartz sand by marine currents in low areas on the sea floor that were produced by locally increased rates of subsidence controlled by basement mechanics. Oil fields in the Hardinsburg lie almost entirely on the east (updip) edge of the thick sandstone belt.

AAPG Search and Discovery Article #91023©1989 AAPG Eastern Section, Sept. 10-13, 1989, Bloomington, Indiana.