Stepped Counter-Regional Salt Systems: Evolution and Controls on Sediment Distribution, Eastern Louisiana Shelf, Northern Gulf of Mexico

Bruce Trudgill
Colorado School of Mines, Golden, CO

Analysis of two large volumes of 3D seismic data, along with structural restorations has allowed the reconstruction of complex, composite stepped counter-regional salt systems in the West Delta protraction area of the northern Gulf of Mexico. Based on these reconstructions, salt evolution involved the following stages: (1) sea-floor extrusion of isolated salt tongues; (2) amalgamation of the salt tongues to form complex salt-tongue canopies; (3) counter-regional evacuation of the salt-tongue canopies into a series of salt walls; (4) evacuation of the salt walls to form counter-regional salt welds and isolated salt domes. At each of these stages in salt evolution, new minibasins developed in response to salt evacuation, and these minibasins subsequently became sites of enhanced sediment deposition.

The three-dimensional counter-regional evacuation of the mapped salt systems illustrates the value and limitations of published end-member models for allochthonous salt. The reconstructed evolution also yields important insights into the complex interactions between salt deformation and sediment distribution patterns. The evolving salt systems significantly affected sediment transport pathways, trap geometries and possibly late stage petroleum migration across evacuating salt welds.

The results of this study should prove beneficial to those exploring in similar areas or those investigating salt evolution and salt-sediment interaction. The detailed analysis of these composite salt systems and their surrounding minibasins illustrates many of the factors that combine to determine salt system geometry and evolution and its impact on sediment dispersal and deposition.

AAPG Search and Discovery Article #90039©2005 AAPG Calgary, Alberta, June 16-19, 2005