The Perdido fold belt, northwestern deep Gulf of Mexico, Part 1: Structural geometry, evolution and regional implications

The Perdido fold belt is a frontier petroleum exploration province located in deep waters of the northwestern Gulf of Mexico. The anticlines are north east-southwest-trending, symmetrical to asymmetrical, with concentric folds usually bounded on both flanks by steep reverse faults. The folds are inte rpreted as detachment-folds cored by autochthonous Middle Jurassic Louann S alt, The fold belt overlies rifted transitional crust characterized by nort heast-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, Postki nematic sediments gradually buried the folds, with younger strata progressi vely onlapping the highest structures. Some folds were reactivated during t he middle Miocene, and a late phase of broad uplift during the Pliocene-Ple istocene is attributed to loading of the Louann Salt by the advancing Sigsb ee salt nappe. The Perdido fold belt marks the basinward margin of a complex, linked syste m of gravitational spreading above salt, Updig Paleogene sedimentary loadin g and associated extension were accommodated downdip primarily by salt cano py extrusion. The 5-10% shortening and folding occurred only after canopy f eeders were evacuated and closed off. Subsequent loading and deformation we re concentrated at higher, allochthonous levels.