ABSTRACT

The structural history of the Mississippi Canyon, Atwater Valley, western DeSoto, and western Lloyd Ridge protraction areas in the northeastern deep-water Gulf of Mexico is of a basin influenced by complex salt tectonics that controlled the formation of intraslope minibasins and sediment distribution.

Large volumes of Middle Jurassic autochthonous salt (Louann Salt) were successively mobilized upward into younger sediments, forming three distinctive allochthonous salt layers: at the top Barremian, at the top Cretaceous, and within the Neogene interval. Four types of Neogene allochthonous salt systems are identified based on the geometry of the allochthonous salt bodies and associated faults, folds, and minibasins: (1) basement-controlled, (2) counterregional, (3) roho, and (4) fold-belt–related salt systems. The allochthonous salt systems are defined based on salt-body geometry, salt-stem geometry, associated fault network, and associated stratigraphic geometries. The distribution of the Neogene allochthonous salt systems is controlled by the original autochthonous salt thickness, the basement configuration, and the regional sediment-loading pattern. The basement-controlled Neogene salt systems are present in the eastern and northern part of the study area where little basinward gravitational gliding occurred. The counterregional and roho allochthonous salt systems are associated with the basinward evacuation of salt in response to extensive sediment loading. The fold-belt–related allochthonous salt systems are present in the southern part of the salt province where extensive shortening remobilized salt into and onto contractional structures. The detailed study of those Neogene allochthonous salt systems is used to build conceptual kinematic models for each style of salt system.

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