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Differential Translation of Supra-Canopy Minibasin Domains in the Northern Gulf of Mexico Slope


In salt-detached gravity-gliding/spreading systems the detachment geometry is a key control of the degree of downslope mobility of the supra-salt sequence. Here, we use a regional 3D seismic data to examine a salt-stock canopy system in the northern Gulf of Mexico slope, where the base of shallow salt shows regional variations in rugosity. Supra-canopy minibasins subsided vertically and translated downslope above this rugose base of salt. Based on the regional mapping, the study area was divided into two domains according to the topographic characteristics of the base of salt. In the western domain, the base of salt has high relief with abundant large feeders that connect the shallow and deep salt levels. In the eastern domain, the base of salt has less relief, with fewer and narrower feeders. In the western domain, most minibasins have subsided into feeders, in some cases welded against the deep salt level. In the eastern domain instead, the feeders are typically too small for minibasins to sink into. We argue that the different geometries of the base of salt in the two domains conditions the downslope mobility of minibasins above it. No evidence for large-scale translation of minibasins was found in the high-base-salt-relief western domain, whereas large-scale translation of the supra-canopy sequence was recorded in the lower-base-salt-relief eastern domain. Large transport in the eastern domain was indicated by repetition of subsalt stratigraphy in the Poseidon minibasin, and by a ramp syncline basin. These two examples suggest downslope translation in the order of 40 km. We suggest that the differential translation between the two domains was distributed along the salt walls (and their roofs) lying between minibasins. In some cases, the shear was accommodated by the salt structures before there was a roof to record it. Characterizing domains according to base-salt relief in the northern Gulf of Mexico slope was helpful in identifying domains of equivalent supra-canopy minibasins that may share similar subsidence and downslope translation histories.