Tectonic Boundaries of the Eastern Gulf Coast of North America

Abstract

Two Precambrian extensional fault episodes, recorded in mapping from central Arkansas across Mississippi, central Alabama, southern Georgia, and into the Atlantic Ocean affected later Pennsylvanian and Triassic tectonics. This interpretation is from magnetic anomaly data and is supported by seismic, gravity, core, and well-log data. The fault system was first suspected from an anomalous magnetic high, representing a feature that affected tectonism during the Ouachita and the Alleghenian orogenies of the eastern Gulf Coast and southeastern United States. The northernmost upthrown block is considered part of an ancient passive continental margin developed during the late Precambrian. The southern downthrown block is deformed by left-lateral transverse faults active during the Ouachita Orogeny. The Ouachita Orogeny may have deformed terrain farther east than the Black Worrior basin. These transverse fault blocks were buttressed by the footwall of the extensional fault system. These left-lateral faults extending from Florida and Georgia into Alabama, Mississippi, and southern Arkansas.