The origin and development of the Tampa Embayment: implications for the tectonic evolution of the Eastern Gulf of Mexico
Interpreted regional 2D pre-stack depth migrated (PSDM) seismic reflection profiles and restoration of the northern Yucatan and west Florida conjugate rift margins using magnetic anomaly and free-air gravity trends suggest that the Tampa Embayment developed in the Triassic as a NE-SW trending linear graben which, when restored, extended across the Yucatan margin. This graben was later dissected during Early to Middle Jurassic time by the opening of the Eastern Gulf of Mexico (EGoM). A tectonic hinge in the Tampa Embayment and the adjacent Southern Platform is present based on a dip change in the basement reflections that ranges from 6° to 17°. Down-dip faulting caused the basement to rotate beneath the hinge slope. These syn-rift faults were reactivated during Late Jurassic time, and may be the result of continued extension and thinning of the lower crust. An interpreted Moho reflection underlies 6-km-thick eroded continental rift blocks. This suggests that the lower crust may have been highly thinned or completely removed on parts of the rift margin. In Middle Jurassic time, a shallow inland sea was isolated to the EGoM and is represented in the PSDM seismic by a basinward pinchout of salt that overlies tilted rift blocks and syn-rift and pre-salt "sag" deposits. Salt, deposited as this sea evaporated, mobilized down the hinge slope shortly after Smackover deposition through gravity-driven gliding and spreading, resulting in a thickening of the distal tip of the salt wedge. Extension reactivated syn-rift faults during the deposition of the Haynesville Formation and Cotton Valley Group resulting in thick accumulation of these sediments and increased salt mobilization. A transition from a carbonate ramp to a rimmed platform margin during Early Cretaceous time is marked by a large reef near the Florida Escarpment, possibly the along trend Sligo equivalent. It is possible that reef development continued through Cretaceous time basinward of this feature but was subsequently destroyed by erosional backstepping of the Cretaceous carbonate margin. Within the Tampa Embayment, the Cretaceous carbonate margin is ~60 km to the west of the tectonic hinge, indicating a different control on the location of the margin.