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Origin and Development of the Apalachicola Basin

Abstract

Paleomagnetic data suggests that the Apalachicola Basin formed during Late Triassic time as a NE-SW trending graben. The basin is one of a series of topographic highs and lows in the Eastern Gulf of Mexico (EGoM) with the Pensacola Arch to the north and the Middle Ground Arch to the south. Previous studies suggest the basin may be bounded by strike-slip faults trending NW-SE on its east and west sides. Interpretation of multiple 2D seismic reflection lines along with well data from within the Apalachicola basin reveal no evidence for strike-slip faults. The basin's multistage tectonic history is characterized by Late Triassic oblique shear extension accommodated by normal faults followed by stratigraphic thinning updip and reactivated normal faults during Middle Jurassic time. An abrupt change in the dip of basement reflectors east of the Florida Escarpment identifies a tectonic hinge zone marking the boundary between attenuated and unattenuated continental crust. In the Apalachicola Basin, this tectonic hinge zone demarcates the maximum limit of crustal extension during rifting and indicates that attenuated crust covers a much larger area than previously predicted. The Pensacola Arch and Middle Ground Arch controlled the depositional pathways of sediment shed into the basin. The extent and origin of the Middle Jurassic Norphlet petroleum play is controlled by the location and composition of these topographic highs. Incised basement geometries indicate depositional pathways of the Norphlet Formation from these highs into the basin. A kinematic restoration will determine regional tectonic, stratigraphic and structural evolution. The adjacent Tampa Embayment serves as an analog for the Apalachicola Basin/ Desoto Canyon Salt Basin. Previous work in the Tampa Embayment indicates that it is also a NE-SW trending graben, not bounded by regional transform faults. The Tampa Embayment has a “steer's” head geometry along strike due to differential crustal and mantle stretching during rifting. The Apalachicola Basin shares a common origin with the Tampa Embayment including a steer's head basinal geometry, sediment deposition from surrounding arches and a prominent tectonic hinge zone east of the Florida Escarpment.