The post-middle Cretaceous sedimentary section in the abyssal Gulf of Mexico (7 to 8 km thick) is divided into seven major depositional sequences. The sequence boundaries represent widespread unconformities which are best observed along the base of the Campeche Bank. These depositional sequences provide a framework for reconstructing the geologic history of the area.

The oldest sequence (middle Cretaceous-early Tertiary) displays strong to weak, discontinuous reflections, interpreted to represent fine-grained pelagites and hemipelagites. The overlying three sequences (early Tertiary-Middle Miocene) are characterized by strong, high-amplitude, continuous to distcontinuous reflections, and probably consist (predominantly) of sandy turbidites, as evidenced from cores recovered from the bottom of Deep Sea Drilling Project hole 90. Seismic facies analysis of these three sequences shows large convex-upward depositional buildups and numerous relict channels, suggesting deposition in large submarine fan complexes. The three youngest sequences consist of fine-grained turbidites and pelagites and display such features as prograding foreset beds deposited in the distal parts of submarine fans, and large-scale, dune-like features with wavelengths of 2 to 4 km. Westward thickening of most of the sequences indicates the source of the detrital sediments was to the west in eastern Mexico.

The southwestern Gulf of Mexico possesses excellent potential for hydrocarbon entrapment, especially in buried stratigraphic features such as the fan channel systems, and also in structural traps along the Mexican Ridges foldbelt.

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