More than 300 diapiric structures formed by the intrusion of relatively pure salt are known in Alabama, Mississippi, Louisiana, Arkansas, Texas, Nuevo Leon, Veracruz, Tabasco, and Cuba. In form, the structures are rod-like, domal, anticlinal, and ridge-like. They rise vertically, or nearly so, and increase or decrease with height. Many are capped by residual masses of anhydrite, altered in varied degrees to gypsum, sulfur, and calcite.

Modern theory postulates growth resulting from density differences between the salt and surrounding sediments (1) by upward movement of the salt through the overlying sediments in response to gravitational inequilibrium, or (2) by salt structures remaining at an essentially constant level while the surrounding sediments of sedimentary rocks moved downward around them as deposition progressed. Model studies suggest that variations in overburden and faulting are primary causes of the initiation of salt movement.

The probable source of the salt in Gulf Coast salt domes is the Louann Salt. It may have been as much as 5,000 ft thick and have had an original volume of 200,000 cu mi.

Sediments enclosing salt stocks have varied structural configurations. The strata may be arched, they may be ruptured and pierced by the salt, they may be complexly faulted, or they may be deformed by various combinations of faulting and folding.

All the salt structures in the Gulf of Mexico basin probably are of similar genesis.