STRUCTURE OF THE LEXINGTON AND KENTUCKY RIVER FAULT SYSTEMS: IMPLICATIONS FOR THE KINEMATICS OF A FORELAND BASIN

Though previous workers have long regarded both the Lexington and Kentucky River Fault Systems as a series of parallel to sub-parallel systems of normal faults, their kinematic histories have been largely debated. Through a combination of field investigations of surficial faulting in Paleozoic strata and proprietary seismic data, a complex history including polyphase faulting involving Paleozoic sediments overlying crystalline basement has been revealed. Surficially, normal faulting is inferred to dominate along the strikes of both systems whereas subsidiary faults trending near perpendicular to the systems are mostly reverse/thrust faults or wrench faults that formed after the Pennsylvanian. Positive flower structures revealed in the seismic reflection data indicate reverse oblique-slip occurred in the past. This reverse oblique-slip motion is indicative of transpressive activity in the region. Furthermore, as this transpressive motion has not been overprinted by the multiple episodes of the Appalachian Orogenesis, it is inferred that transpression occurred during the Pennsylvanian-Permian Allegheny Orogeny. The presence of these highly varied faulting styles present at different stratigraphic levels and geographic proximity to one another indicates that the region evolved through polyphase faulting and under separate yet distinct stress regimes throughout these fault systems' histories.