BECKLEY, LILA M., ARCO Oil and Gas Company, Bakersfield, CA, and WILLIAM E. BEHRENS,* University of Texas at Austin, Austin, TX

ABSTRACT: Seismic Evidence for Timing of Shallow Salt Emplacement on the Continental Slope

The mechanics and timing of salt emplacement are important elements in the evaluation of potential hydrocarbon traps. In a mid-slope study area offshore Texas, several seismic sequences thicken (especially upslope) off several salt structures. Very 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 m.y. and have acted as at least partial dams to downslope sediment transport. Faults over the salt structures commonly terminate within off-salt-expanding sequences 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 fr m it, salt structures are discreet and penetrate to within 200-300 m of the water bottom. The salt surfaces are approximately symmetrically dome shaped in the strike direction (northeast-southwest), and commonly dip basinward (southeast). Downslope and south of the study area, salt appears predominantly as extensive flat surfaces (sheets or canopies?) at about 1 km 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. This or alternative interpretations of the seismic records may be tested with heat flow observations made over two of the diapiric features in t is area.

AAPG Search and Discovery Article #90989©1993 GCAGS and Gulf Coast SEPM 43rd Annual Meeting, Shreveport, Louisiana, October 20-22, 1993.