Grabens overlying diapirs have previously been ascribed to intrusion, withdrawal, or dissolution of salt. We propose, however, that many grabens or half grabens above diapirs form by regional thin-skinned extension of a brittle overburden.

The Plio-Pleistocene hydrocarbon fairway of offshore western Louisiana is restricted to the outer continental shelf and upper continental slope where a thick wedge of nearshore and deep-marine sediments was deposited.