ABSTRACT

The paleobathymetric configuration of the early Gulf of Mexico is inferred from (1) Cretaceous carbonate shelf margins interpreted from seismic profiles and other stratigraphic data; (2) distribution of Jurassic and Cretaceous platform and basinal facies; and (3) hindcasting of subsidence history in the central basin. Substantial paleogeographic ambiguity results from uncertainty about (1) kinematics and timing of Late Triassic to Jurassic extensional opening of the Gulf basin, which probably involved major strike-slip faulting, (2) the magnitude of subsequent compressive deformation on the western and southern basin margins, and (3) possible accretion of allochthonous terranes.

The initial sub-sea level topographic depression created by crustal extension is manifested by the distribution of Callovian (?) pre-marine salt and Oxfordian basinal marine facies. Late Jurassic sea-floor spreading split the main salt body and created a central deep-water (> 1 km) trough. From the Oxfordian to early Neocomian, ramp-like platform margins generally underwent net retreat, except in the northern Gulf, where major clastic progradation took place.

Carbonate platform margins with sufficient paleorelief for geometric expression on seismic profiles developed early in the Cretaceous. These Cretaceous carbonate margins exhibit a variety of architectural styles, including (1) in the northwestern Gulf, two cycles of progradation (Coahuilan and Comanchean) terminated by drowning events; (2) in the southwestern Gulf, a single cycle of progradation; (3) continuous aggradation along the Florida and Campeche Escarpments. Paleobathymetric relief across Cretaceous carbonate margins ranges from high and steep, to low-relief, to ramplike. The close-of-Comanchean drowning event greatly and permanently reduced the extent of circum-Gulf carbonate platforms and especially rimmed margins.

Locations of Cretaceous carbonate margins were influenced by basement hinge zones and paleohighs developed on attenuated continental crust, by the distribution of salt, and by clastic progradation. Eustacy is commonly invoked to explain behavior and architecture of carbonate margins in the Gulf, but other paleoenvironmental variables such as nutrient abundance are probably important as well.

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