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The Florida-Bahamas Lineament and Gulf of Mexico Opening: To Move or Not to Move?


Multiple tectonic models have been postulated for the opening of the Gulf of Mexico (GoM). The opening models are constrained using several key elements: the Florida-Bahamas lineament (also known as the Florida-Bahamas Transfer Zone or Florida-Bahamas Fracture Zone), the limits of the Louann and Campeche salt basins, the onshore US and Mexican rift fabric/ fill, the shape of the GoM oceanic crust and Yucatan block and the timing of the Blake Spur Magnetic Anomaly (BSMA). Model variability for the opening generally comes from the interpreted timing of these key elements, with the exception of the Florida-Bahamas lineament. A widely accepted model has the Florida Bahamas lineament acting as a transfer and fracture zone system. A reinterpretation of recent U-Pb data from Florida and the easternmost GoM suggest that the alternate non-fracture zone model may provide a better fit for the Florida-Bahamas lineament and the GoM opening. U-Pb dating of penetrated volcanic rock samples from a well, positioned within the gravity and magnetic anomalies of southern onshore Florida, gives an age of ~180 Ma (Early Jurassic), suggesting continued volcanism between CAMP (Central Atlantic Magmatic Province) and the Middle Jurassic (Callovian) oceanic crust at Atlantic DSDP Site 534. Shelfal GoM and onshore Florida wells contain Palaeozoic basement and sediment ages of accreted Pangaean terrane affinities. Post-CAMP plume volcanism over variably rifted continental crust and Pangaean terranes could account for the anomalous potential fields signatures in southern Florida and Bahamas without requiring the presence of a dominant fracture zone extending from the US Gulf Coast through the Bahamas. Removal of a dominant controlling fracture zone and addition of longer-lived volcanism in the south-eastern GoM, suggests Early to Middle Jurassic reservoir and source rock deposition is likely interbedded and patchy across a longer time span within localized syn-rift basins and embayments. Maturity, timing and fluid quality of any hydrocarbons would also vary across the region, as suggested by current well penetrations. This alternative model for the opening of the GoM highlights the complex nature of passive margin tectonic and depositional systems, which has implications for petroleum exploration in other extensional regions globally.