Abstract

The Perdido fold belt is a frontier petroleum exploration province located in deep waters of the northwestern Gulf of Mexico. The anticlines are northeast-southwest-trending, symmetrical to asymmetrical, with concentric folds usually bounded on both flanks by steep reverse faults. The folds are interpreted as detachment folds cored by autochthonous Middle Jurassic Louann Salt. The fold belt overlies rifted transitional crust characterized by northeast-southwest-trending basement highs and northwest-southeast transverse structures that controlled the original salt thickness and subsequent fold geometry. Upper Jurassic-Eocene strata were folded during the early Oligocene (36-30 Ma), with deformation possibly continuing into the earliest Miocene. Postkinematic sediments gradually buried the folds, with younger strata progressively onlapping the highest structures. Some folds were reactivated during the middle Miocene, and a late phase of broad uplift during the Pliocene-Pleistocene is attributed to loading of the Louann Salt by the advancing Sigsbee salt nappe. The Perdido fold belt marks the basinward margin of a complex, linked system of gravitational spreading above salt. Updip Paleogene sedimentary loading and associated extension were accommodated downdip primarily by salt canopy extrusion. The 5-10% shortening and folding occurred only after canopy feeders were evacuated and closed off. Subsequent loading and deformation were concentrated at higher, allochthonous levels.

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