Abstract

A revised North and South American Plate join removes some of the unsatisfactory aspects of earlier reconstructions of Pangaea, and better explains late Paleozoic history and the initiation of continental rifting and breakup. The Gulf of Mexico evolved as spreading gave rise to a trailing margin on North America that became the depositional site for prograded sedimentary infill of Triassic to Recent age. As newly created Gulf and Caribbean crust converged with an advancing South American Plate, the margin of northwest South America became an accretionary volcanic arc-trench, plutonic complex.

Gulf Coast strata reveal the influence of several variables on sediment thickness and facies distribution. In addition, they exhibit the tensional effects of continental rupture, which established the depositional surface for the sedimentary sequence. Upper Triassic red beds are confined to rift grabens. These are overlain by Jurassic red beds and evaporites. The evaporites formed as brine-mixing and evaporitic processes operated in the restricted circulation of a young, narrow seaway similar to the Red Sea. Upper Jurassic and Cretaceous strata, dominantly shelf carbonates, represent transgressive, open marine deposits of the trailing and subsiding plate margin. A thick, prograding Cenozoic clastic wedge reflects a hinterland source area rejuvenated in Laramide time. A reorientation of plate motion resulted with the shift of the Gulf-Caribbean spreading ridge to the South Atlantic following separation of South America from Africa. The Caribbean crust, thickened by flood basalts and no longer able to subduct, became the consuming plate beneath which Atlantic Ocean crust subducted to complete formation of the Antillean volcanic arc.