The basin contains more than 6,000,000 cu mi of predominantly Mesozoic and Cenozoic sediments. Deep-water sediments overlying an oceanic crust occupy its central part.

Late Paleozoic orogenies influence the basin shape: the "buried" Llanoria structural belt along the northern margin, the Chiapas-Guatemalan structural belt along the southern margin, and a "connecting" structural belt (now "buried") along the western margin. This last margin was more strongly established by Nevadan (Jurassic) and Laramide (early Tertiary) orogenies. A complex system of transcurrent faulting, created as the Gulf basin (and Mexico) drifted westward (leaving the Caribbean "Pacific tongue" behind), marks the southeastern margin.

Great thicknesses of Jurassic salt occur in major depressions within the basin. Much of this salt apparently was deposited rather abruptly in deep water. During salt deposition, the African continent probably marked the eastern margin of the Gulf basin. The Nevadan orogeny restricted normal gulf circulation from the Pacific, creating conditions favorable for salt sedimentation.

Post-salt sediments came from two major provenances: Mesozoic from the Appalachians and Cenozoic from the Rocky Mountains.

The history of the Gulf basin supports modern concepts of continental drift. The Gulf "salt basin" appears to be related genetically to a series of "salt basins" which formed from north to south as continents began to drift apart along the Mid-Atlantic "swell." Progressive decrease in age from late Paleozoic at the north to Early Cretaceous at the south suggests the supercontinent began rifting apart first at the northern end. The sedimentary and structural records indicate that drift was spasmodic rather than continuous.

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