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Louann Salt Evolution in the Northeastern Gulf of Mexico From Middle Jurassic to Present


The Northeastern Gulf of Mexico is a proven hydrocarbon province with numerous oil and gas discoveries. The primary success of the northeastern Gulf is linked to the mobilization and remobilization of the Louann Salt, which influenced deepwater depositional systems, formed hydrocarbon traps, and provided migration pathways. The Louann Salt was deposited in the Callovian during the early-rifting stages of the Gulf of Mexico. Subsequent sediment loading resulted in the mobilization of the salt, forming salt ridges, pillows, diapirs, and massifs. While previous research almost exclusively focused on the Neogene salt remobilization and sedimentation in the area, little has been done to understand the deposition and salt evolution of the older stratigraphy. With advances in 3D seismic acquisition and processing, and the recent exploration activity in the deepwater Norphlet Formation, the Mesozoic and Paleogene stratigraphy can be interpreted more reliably, resulting in an improved understanding of the Mesozoic salt evolution in the Gulf of Mexico. The Mesozoic section in the northeastern Gulf shows extensive basin-dipping normal faults, multiple allochthonous salt-wings in the Upper Cretaceous interval, primary salt welds, and large Cretaceous allochthonous salt massifs indicating active salt mobilization period(s) during the Cretaceous. The majority of the Mesozoic faults do not propagate into the Cenozoic section, implying that these faults ceased before the massive influx of Miocene sediment. The lack of Mesozoic fault growth in the Cenozoic, despite the massive influx of Neogene sediment, implies that the overlying strata had welded to the pre-Louann basement. This suggests that majority of the autochthonous Louann Salt had coalesced into discrete allochthonous salt massifs before the Cenozoic. During the remobilization of the salt from the Cretaceous massifs into Neogene diapirs, flower structures formed directly above the allochthonous salt masses caused by changes of the stress regime. Within the Neogene section, large basin-dipping listric faults are common in the northeastern section of the dataset, while detached salt diapirs with associated radial faults and surrounding salt-withdrawn basins are typical in the southwest and central portions. This implies that gravitational loading is the primary deformation force in massif free portions of the Gulf of Mexico, while the Cretaceous salt massifs controls the structural deformation in central and southern portions of the study area.