Jurassic Reconstruction of the Gulf of Mexico Basin

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Abstract
The Jurassic evolution of the Gulf of Mexico Basin is related intimately to the break-up of the late Paleozoic supercontinent Pangea and to the early evolution of the Atlantic/proto-Caribbean system. A new two-stage model presented here is constrained by a refined oceanic crust definition in the Gulf of Mexico and by the known kinematic framework of the large continental blocks (North America plate, Afro-South America plate). Oceanic crust definition in the Gulf of Mexico was obtained by combining the results of independent geophysical data sets, including: (a) refraction data, (b) magnetic data, (c) multichannel seismic data in the eastern Gulf of Mexico area, and (d) gravity data. Reconstruction of the basin was completed using the Plates 2.0 plate reconstruction software to visualize the movement of the Afro-South America plate and the Yucatan, Florida-Bahamas microplates during the Mesozoic break-up. During the Late Triassic(?) to late Middle Jurassic syn-rift stage, the relatively stable Yucatan block translated southeastward (present coordinates) along a major transform zone in eastern Mexico. This motion accommodated a large amount of extension in the area of the future northern Gulf. At the same time the Florida-Bahamas block extended also in a southeast direction to form a series of basins and arches along the present-day west Florida shelf. Contrary to many published Gulf of Mexico evolution schemes, this model does not require major strike-slip faulting between Yucatan and Florida, although left-lateral displacement along a major shear zone in the eastern Gulf (the Bahamas Fracture Zone and its northwestward extension) is postulated. Rock evidence from the rim of the basin indicates that throughout the rifting phase the basin was emergent and was an area of erosion with localized continental sedimentation and volcanism. A rotation pole for the Yucatan block in the southeastern Gulf of Mexico (23.18° N, 84.24° W) is proposed for the late Middle Jurassic (Callovian) to earliest Cretaceous (Berriasian) drifting stage. Around this pole the Yucatan block rotated about 42° counterclockwise out from the northern Gulf to accommodate the newly formed oceanic crust in the basin. Reconstruction of the Louann and Campeche salt provinces shows that some of the original salt may have been deposited in an already partially opened oceanic basin in Callovian to early Oxfordian time. The drifting stage marked the cessation of continental margin volcanism, major transgression, and basinwide marine sedimentation. Seismic data provide clear evidence that in the southeastern Gulf of Mexico, between the relatively stable Yucatan and Florida blocks, a Late Jurassic NW-trending continental rift separates the oceanic domains of the Gulf of Mexico and the Caribbean. The kinematic framework for the Gulf of Mexico opening implies that major rifting in the southeastern Gulf of Mexico occurred contemporaneously with Late Jurassic oceanic crust formation in the Gulf of Mexico, as the Yucatan block rotated counterclockwise relative to the Florida-Bahamas region. Decreasing amounts of extensional deformation towards the rotation pole is well supported by the seismic data, providing evidence for a southward-propagating rift model for this area. Rifting in the southeastern Gulf ceased by late Berriasian time, providing the only constraint for the completion of oceanic crust formation in the Gulf of Mexico.