Abstract
Numerous physical and mathematical models have simulated highly mature diapirism in which low density material moves upward through more dense material and then spreads out as a layer known as a canopy (Jackson and Talbot, 1989). Until recently such canopies have not been recognized in nature and the distribution of shallow salt beneath the lower continental slope of the northwest Gulf of Mexico has not been known. This study is the first publicly available field confirmation of a very extensive shallow salt canopy in the Gulf of Mexico region. Approximately 6,400 kilometers of 24- and 48-fold common depth point seismic data were interpreted in the region bounded by 94-96° west longitude and 26-27° north latitude. Maps of the seafloor morphology, the structure contour of the top of the allochthonous salt canopy, and the thickness of the suprasalt sediments show that almost the entire lower slope is covered by a shallow canopy. The broad area of little relief on the western side of Alaminos Canyon in underlain by salt and is not salt-free as previously proposed. Both Alaminos and Rio Perdido Canyons are salt-free areas between lobes of the distal front of the salt sheet. The canopy on the west side of the study area is classified as a stock canopy which formed when salt was pushed upward into sediments which have a lower density than salt. Gravitational spreading into low strength sediments formed a canopy in which the stock locations are marked by highs on the top of the salt sheet and/or by bathymetric highs. The salt spread out and downslope from these local highs in a more or less radial fashion and coalesced to form a large stock canopy. The canopy on the east side of the study area is classified as a lobe canopy which formed by downslope spreading from salt stocks; several lobes coalesced into a lobe canopy. Fluid pressure calculations reveal that the salt beneath seafloor uplifts is deeply rooted (7-15 km thick). Exploration strategy would center on the location of deep salt conduits and reservoirs beneath the canopy close to the intersection of the canopy and the deep stocks.
Hardin, Nancy S. (1989). Allochthonous salt sheets in the Alaminos Canyon region, northwest Gulf of Mexico : present configuration and processes of emplacement. Texas A&M University. Texas A&M University. Libraries. Available electronically from
https : / /hdl .handle .net /1969 .1 /DISSERTATIONS -1117124.