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oa The Role of Salt in Cenozoic Gravity Spreading of the Northwestern Gulf of Mexico Basin
- Publisher: European Association of Geoscientists & Engineers
- Source: Conference Proceedings, 5th International Congress of the Brazilian Geophysical Society, Nov 1997, cp-299-00014
Abstract
The northwestern Gulf of Mexico Basin is a Mesozoic-Cenozoic passive margin initiated during Late Triassic to Early Jurassic continental rifting. Widespread deposition of the early postrift Louann Salt occurred during the Callovian (late Middle Jurassic) and was immediately followed by oceanic spreading during the Oxfordian (early Late Jurassic). Subsequent thermal subsidence led to a Late Jurassic through Cretaceous transition from shallow- to deep-water carbonates to chalks, marls, and shales in what is presently the offshore portion of the basin. The Cenozoic was dominated by the influx of large volumes of clastics and the progradation of associated deltas. Although some salt-related deformation occurred early in the history of the passive margin, the bulk of tectonic activity was triggered by the Cenozoic clastic deposition. The asymmetric sedimentary load and associated bathymetric relief of the shelf margin set up a gravitational instability that was accommodated by gravity spreading above the salt layer. Updip sedimentation and accompanying extension was balanced downdip by extrusion of allochthonous salt sheets and by contractional folding at the basin ward pinchout of the autochthonous Louann Salt. In tum, the allochthonous sheets also accommodated the gravity spreading as they were loaded and evacuated. In this paper, we examine allochthonous salt systems and deep-water fold belts in detail, speculate on the role of rifted basement geometry in controlling the type and distribution of salt tectonics, and comment on various aspects of petroleum exploration in these provinces.