Subsidence history of the Alabama promontory in response to Late Paleozoic Appalachian-Ouachita thrusting

The Alabama promontory of North American continental crust was framed during late Precambrian-Cambrian rifting by the northeast-striking Blue Ridge rift and the northwest-striking alabama-Oklahoma transform fault. A passive margin persisted along the western side of the promontory from Cambrian to Mississippian time, but the eastern side was affected by the Taconic and Acadian orogenies. Prior to initiation of Ouachita and Appalachian (Alleghanian) thrusting, the outline of the rifted margin of continental crust on the Alabama promontory remained intact; and the late paleozoic thrust belt conformed to the shape of the promontory, defining northwest-striking Ouachita thrust faults along the southwest side of the promontory, north-striking Appalachian (Georgia-Tennessee) thrust faults on the east, and northeast-striking Appalachian (Alabama) thrust faults across the corner of the promontory. Subsidence profiles perpendicular to each of the strike domains of the thrust belt have been constructed by calculating total subsidence from decompacted thickness of the synorogenic sedimentary deposits. The profile perpendicular to the Ouachita thrust belt shows increasing subsidence rates through time and toward the thrust front, indicating the classic signature of an orogenic foreland basin. The profile perpendicular to the Georgia-Tennessee Appalachian thrust belt similarly shows increasing subsidence rates through time and toward the orogenic hinterland.more » These quantitative results support the conclusion that Black Warrior basin subsidence is tectonically rather than sedimentologically driven, and the timing of subsidence events reported here has implications for regional tectonic models.« less