Contact: Dave Harris
Abstract from The Bulletin, Houston Geological Society, February 2000, p. 27; also available at the Houston Geological Society Web site
STARK, T. Joshua, Tulsa, OK; Stephen H. ROWLEY, Emet Consulting, Plano, TX; Carl K. STEFFENSEN, Steven BERGMAN, Vastar Resources Inc., Houston, TX; James A. DRAHOVZAL, Kentucky Geological Survey, Lexington, KY; Glenn W. BEAR, Exxon Production Corp., Houston, TX; and Louis SCHULTZ, Williams Gas Pipeline Texas Gas, Owensboro, KY
The English Basin is interpreted as a Meso-, Neoproterozoic, and Cambrian depocenter, forming a portion of the East Continent Rift Complex in areas of Kentucky and Indiana. Both proprietary and published seismic sections show a complex structural depocenter with a depth to crystalline basement exceeding 6,100 m. Two boreholes penetrate the Proterozoic sequence of the depocenter and have strata similar in lithology to both the Precambrian Middle Run Formation (Centralia Group) described in Ohio and Kentucky and low-density clastic sediments of the overlying Marengo Formation.
A newly discovered thrust-fault system in the lowermost Mesoproterozoic Centralia Group is referred to as the Hoosier Thrust Belt and corresponds to the positions of overlying Paleozoic fault systems, pinnacle reefs, and shallow petroleum production. Above a major angular unconformity truncating Centralia strata, the newly described clastic sediments of the Marengo Formation are locally deposited within the English Basin.
The eastern basin margin is defined by the Louisville Uplift, a 600-million-year-old foreland-style basement thrust with approximately 8 kilometers of uplift. Paleozoic strata at the margins of the uplift are cut by a series of shallow fault systems, currently being developed for fractured shale reservoirs of Devonian age.
Extending north of the bounding feature is the Mt. Carmel Uplift. Features interpreted on seismic data are flanking Proterozoic basins, forced folds, and complex faulting associated with gas storage fields and Ordovician oil production. Petroleum fields along the margins of the basin appear to be associated with remobilization of bounding fault systems that have controlled the structural and stratigraphic development of the area.
Potential field data tied to regional seismic reconnaissance of the basin illustrate the lateral geometry of the basin and underlying thrust belt system. Epicenters of earthquakes recorded in the area may be localized along detachment structures within the Precambrian thrust belt, relating contemporary seismicity to the current east–west horizontal maximum principal compressive stress along the Hoosier Thrust Belt.