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ABSTRACT

For the past twenty years, the Red Sea (RS) has been appealed to as a more or less direct analog for the opening and early history of the Gulf of Mexico (GOM). New refraction, gravity/magnetic, and ever-improving seismic reflection data from the GOM, coupled with new field results and interpretations from the area surrounding the RS suggest the direct analog concept may be productively re-evaluated. There is now a general consensus that much of the Jurassic Louann salt was in fact precipitated in an enclosed evaporating basin overlying oceanic crust, although water depths were shelfal rather than bathyal. The apparent discrepancy is explained by rapid subsidence following the Sclater curve: young oceanic crust is isostatically buoyant and easily supports shallow water deposition. The RS follows the same pattern, with the edge of oceanic crust (continent-ocean boundary or COB) coincident with the landward edge of the thick (more than 3-4 km) salt basin. Current models for the COB in the GOM extend oceanic crust far north of the Sigsbee scarp to underlie the entire continental slope offshore Texas and Louisiana. This location solves several long-standing problems, including the “room” problem for the Yucatan block and the gross asymmetry in the widths of transitional crust in earlier models. Although simple shear models may still be appealed to, as in the RS, the scales of the two salt basins are brought much closer together, and the revised COB parallels the lower Cretaceous shelf edge in a much more satisfactory way. Room for interpretation differences still persists in the location of the rotation pole (or poles); both clockwise and counter-clockwise rotations are possible explanations for the revised COB shape, and the different rotation directions produce oceanic ridge and transform patterns at high angles to each other. More research will be needed to resolve these issues, but for the moment the building consensus on the general outlines of the COB is noteworthy and encouraging. A direct comparison of the current RS and the Jurassic GOM at about half its total width establishes the renewed plausibility of the analog concept.

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