Evolution of salt structures during burial of salt sheets on the slope, northern Gulf of Mexico

Abstract

Shallow buried, allochthonous salt sheets are the dominant type of salt structure along the lower slope of the northern Gulf of Mexico. Trailing (landward) margins of the sheets are buried during continental margin progradation, while their leading edges advance basinward under thin cover. During burial a series of daughter structures, including stocks, massifs and remnant structures, evolved as the sheet was segmented by extension and differential loading. During extension, fault-bound basins on the upper surface of the sheet initiated the growth of salt rollers. Some rollers matured into stocks and massifs as sediment accumulated rapidly in circular salt withdrawal basins that were localized over the initial fault-bound basins. Lateral extension is a key mechanism in initiating salt structural evolution; however, simple vertical subsidence of sediments is the primary displacement mechanism. Where the salt is completely displaced, a salt weld discontinuity identifies its former stratigraphic position. A variety of structures in the eastern Green Canyon Area have been identified overlying a Neogene salt weld, including remnant salt structures, mature stocks, massifs and sedimentary structures such as turtle structure anticlines.