ABSTRACT

The mechanics and timing of salt emplacement are important elements in the evaluation of potential hydrocarbon traps. In a mid-slope study area off Texas, several seismic sequences thicken (especially upslope) off several salt structures. Tentative correlations of two boundaries of such sequences with Sangamon and Trim A horizons indicate that the structures have been positive bathymetric elements (thus salt has been intruded) for at least 0.5 ma and have acted as at least partial dams to downslope sediment transport. Faults over the salt structures commonly terminate within sequences which expand off salt, indicating movement of the salt within the respective time intervals and little, if any, lag from the time of forcing sediment loading. Within the study area and upslope from it, salt structures are discreet and penetrate to within 200 - 300 meters of the water bottom. The salt surfaces are approximately symmetrically dome shaped in the strike direction (NE - SW), and often dip basinward (SE). Downslope and southward from the study area, salt appears predominantly as extensive flat surfaces (sheets or canopies?) at about 1 kilometer depth. The studied structures are interpreted to have originated as a wall of salt periodically reactivated by upslope sedimentation. Segmentation of the wall, further flow from depth, and/or salt crest subsidence lead to growth of tongues extending downslope from the original stocks.