<P> Geologists and other Earth scientists agree in general that the present Gulf of Mexico basin originated in Late Triassic time as the result of rifting within Pangea . The rifting was associated with zones of weakness within Pangea, including sutures where the Laurentia, South American, and African plates collided to create it . First, there was a Late Triassic - Early Jurassic phase of rifting during which rift valleys formed and filled with continental red beds . Second, as rifting progressed through Early and Middle Jurassic time, continental crust was stretched and thinned . This thinning created a broad zone of thick transitional crust, which displays modest and uneven thinning with block faulting, and a broad zone of uniformly thinned transitional crust, which is half the typical thickness, 35 kilometers, of normal continental crust . It was at this time that tectonics first created a connection to the Pacific Ocean across central Mexico and later eastward to the Atlantic Ocean . This flooded the subsiding basin created by rifting and crustal thinning to create the Gulf of Mexico . While the Gulf of Mexico was a restricted basin, the subsiding transitional crust was blanketed by the widespread deposition of Louann Salt and associated anhydrite evaporites . Initially, during the Late Jurassic, continued rifting widened the Gulf of Mexico and progressed to the point that sea - floor spreading and formation of oceanic crust occurred . At this point, sufficient circulation with the Atlantic Ocean was established that the deposition of Louann Salt ceased . </P> <P> During the Late Jurassic through Early Cretaceous, the basin occupied by the Gulf of Mexico experienced a period of cooling and subsidence of the crust underlying it . The subsidence was the result of a combination of crustal stretching, cooling, and loading . Initially, the combination of crustal stretching and cooling caused about 5--7 km of tectonic subsidence of the central thin transitional and oceanic crust . Because subsidence occurred faster than sediment could fill it, the Gulf of Mexico expanded and deepened . </P> <P> Later, loading of the crust within the Gulf of Mexico and adjacent coastal plain by the accumulation of kilometers of sediments during the rest of the Mesozoic and all of the Cenozoic further depressed the underlying crust to its current position about 10--20 km below sea level . Particularly during the Cenozoic, thick clastic wedges built out the continental shelf along the northwestern and northern margins of the Gulf of Mexico . </P> <P> To the east, the stable Florida platform was not covered by the sea until the latest Jurassic or the beginning of Cretaceous time . The Yucatán platform was emergent until the mid-Cretaceous . After both platforms were submerged, the formation of carbonates and evaporites has characterized the geologic history of these two stable areas . Most of the basin was rimmed during the Early Cretaceous by carbonate platforms, and its western flank was involved during the latest Cretaceous and early Paleogene periods in a compressive deformation episode, the Laramide Orogeny, which created the Sierra Madre Oriental of eastern Mexico . </P>

Map of gulf of mexico and atlantic ocean