Seismic stratigraphy and salt tectonics of the Alaminos Canyon area, Gulf of Mexico.

Abstract

The Alaminos Canyon region is located at the change in the bathymetric trend between the slope and rise. Over 6,435 km of migrated seismic reflection profiles were analyzed to produce two structure and two isopach maps. Maps of the seafloor morphology, salt structure, and suprasalt sediments indicate the majority of the slope is covered by a shallow salt canopy. The salt structure map indicates that the Alaminos Canyon study area represents a transition from a semi-continuous salt sheet in the east to a less continuous salt sheet in the western margin. Salt lobe canopies are located within the eastern and western margins of the study area, while the central region represents a transition zone between the two lobate canopies. The sediment isochron maps show that the salt has played an important role in the sediment deposition and the formation of intraslope basins. The salt sheet interacted with slope sediment deposition by acting as a barrier to downslope sediment transport and by influencing the direction of mass transport. The uplift of the salt has formed topographic lows in which sediment is transported from the shelf beyond the slope. Within the study area, intraslope basins consist of remnants of submarine canyons blocked by diapiric uplift and closed depressions formed by subsidence in response to salt withdrawal. These intraslope basins have trapped thick deposits of sediment, thereby reducing the sediment transport beyond the slope region. Pleistocene sealevel fluctuations appear to be the dominant force in the depostional record. As the lowering of relative sealevel ended, the transport of sandy material decreased and hemipelagic sedimentation increased. Eustatic sealevel fluctuations during the Pleistocene led to cyclic seismic depostional sequences throughout the study area.