Abstract: Regional Distribution of Salt and Basin Architecture in the Northwestern Gulf of Mexico

William R. Bryant

The physiography of the continental slope in the northwestern Gulf of Mexico is controlled primarily by the emplacement and subsequent remobilization of allochthonous salt. Regional overthrusts (i.e. salt wedges) and shallow intrusions (i.e. salt tongues and tabular bulbs) represent fundamentally different styles for the emplacement of allochthonous salt. Elevated portions of the slope with comparatively smooth bathymetry are typically underlain by shallow salt (300 to 500 m below the seafloor) with a smooth, flat top. Prominent seafloor escarpments correspond to allochthonous salt fronts. Locally, the highest points of the seafloor often correspond to sediment piles (1000 to 2000 m in thickness) floating buoyantly within allochthonous salt. Thicker sedimentary sections g nerally represent sedimentary basins. Sedimentary basins are of interdomal, interlobal and supralobal types based on their spatial relationship with surrounding shallow salt structures. Supralobal basins occurring "above allochthonous salt lobes" are most common across the lower slope. Interlobal basins occurring "between allochthonous salt lobes" exist over the entire slope. Interdomal basins occurring "between isolated salt domes and massifs" are present across the shelf and upper slope. The basin types often appear to be related along an evolutionary continuum. Suture zones occur where neighboring allochthonous salt structures converge. They are generally overlain by narrow troughs in the seafloor (forming narrow synforms upon burial). Directly overlying sediments are generally deform d. Coherent energy reflecting from within the salt along suture zones is believed to be indicative of incorporated sediments within the zone of convergence.

AAPG Search and Discovery Article #90950©1996 AAPG GCAGS 46th Annual Meeting, San Antonio, Texas