Alternative Models for Salt Sheet Emplacement in the Gulf of Mexico Compared and Tested Against the Data

Frank J. Peel, Christopher J. Travis, Jake R. Hossack

Three end-member models have been proposed for the origins of shallow-level salt sheets within the Gulf of Mexico: the salt glacier model in which allochthonous sheets are emplaced by glacier-like flow of salt over the sea bed; the sill model in which the salt is intruded into the sediment sequence some distance below the sea bed; and a model which calls for in situ deposition of evaporites during the Tertiary. Each model makes testable predictions for the structure and depositional environment and paleogeography.

The glacier model implies that the suprasalt and subsalt sediments were never in connection. Intervals terminating beneath salt are likely to have different thickness and depositional setting from sediments of the same age on top of the salt.

The sill model implies that sediments now immediately above and below salt were initially in connection, so that sediments of equivalent age should have the same thickness and depositional environment. The evolving bathymetric expression of a growing sill should create a particular structural pattern in the supra-salt sediments.

The depositional model rejects an allochthonous origin for the salt sheets, calling instead for Tertiary evaporite deposition. Intervals terminating beneath salt should be of shallow water or continental facies. The model requires evaporite deposition from Oligocene to Pleistocene time.

These predictions can be tested against the available data, and on this basis the sill and depositional models can be conclusively rejected.

AAPG Search and Discovery Article #91020©1995 AAPG Annual Convention, Houston, Texas, May 5-8, 1995