Horizontal Components of Gulf of Mexico Salt Tectonics

Robert O. Brooks

The existence and importance of vertical salt movement and structuring in the Gulf of Mexico are well known and documented by extensive drilling and detailed comprehensive publications. However, on the southern part of the Louisiana and Texas shelf and out onto the slope, the existence of both extensive shale flowage and horizontal components of salt movement is gaining broader acceptance. Several wells have been drilled through considerable thicknesses of salt that, on seismic data, does not appear to be associated with vertical piercements.

These interpreted salt wings or horizontal sills are scattered across a broad area of the southern shelf from Galveston Island through Main Pass and out onto the slope. Rather than being continuous and uniform in appearance, they show considerable variation in structural style. Reviews of high-resolution seismic show seven to eight basic types of horizontal salt bodies with predominance of certain of these styles in specific areas of the shelf-slope. Seismic expressions of top and base of salt in Vermilion-South Marsh Island, for example, are completely different than those seen in West Cameron-Eugene Island.

The concepts of deposition and movement along with the exploration potential of these bodies is being actively pursued and debated. As seismic resolution improves and subsalt well control increases, our understanding will broaden and should ultimately lead to discoveries in unique traps below the salt and possibly associated with the large masses of flowed shale.

AAPG Search and Discovery Article #91022©1989 AAPG Annual Convention, April 23-26, 1989, San Antonio, Texas.