The English Basin and the Louisville Uplift: Exploration Potential for the Eastern Shelf of the Illinois Basin

By

STARK, JOSHUA T.

Continental Resources of Illinois

Stephen H. Rowley, Carl K. Steffensen, James A. Drahovzal, Louis E. Schultz, Glenn W. Bear, and Steven Bergman

     The English Basin is interpreted as a Meso- and Neoproterozoic-aged depocenter, developed beneath Paleozoic strata in Kentucky and Indiana. The Louisville Uplift defines the eastern basin margin, interpreted as a western vergent foreland-style basement thrust exhibiting 8 km of vertical uplift.

     Seismic data reveals a complex depocenter with a depth to crystalline basement exceeding 6100 m.  Seismic reflectors traced over a large lateral area depict a layered Proterozoic sequence.  Potential field data tied to regional seismic data allows interpretation of basinal geometry.

     A thrust-fault system developed in the lowermost Centralia Group is named the Hoosier Thrust Belt.  Above an angular unconformity truncating Centralia strata, the interpreted volcanic and volcaniclastic sediments of the Wyandot Formation (proposed) are deformed by the 600mya foreland thrust. The Neoproterozoic-aged Marengo Formation is interpreted as foreland basin fill.

     Subsequent tectonism during the Middle Cambrian resulted in rift style sedimentation within the English Basin. Remobilization tectonism is evident during the Taconic, Acadian and Alleghenian Events, and possibly the Jurassic/Triassic break-up of the Pangean supercontinent.

     Significant large-scale structures may provide excellent potential for hydrocarbon exploration. The margins of the Louisville Uplift are expressed in Paleozoic strata by shallow fault systems. The remobilization of the faults controlled the development of hydrocarbon fields along the margins of the basin. Other trap types include far-field thrusting, forced folds, wrench faults, extensional fault blocks, and stratigraphic traps.