Print this pageMegaregional Sequential Structural Restorations of Autochthonous Salt Across the Northern Gulf of Mexico Basin
McBRIDE, BARRY C.
Structural restorations of a megaregional cross section in the northern Gulf of Mexico Basin illustrate that the region has undergone a dynamic, complex history of sedimentation, salt flow, and salt evacuation. Deformation is controlled by gravity and the progradation of Cenozoic sediments over autochthonous and allochthonous Jurassic salt. Major sedimentary depocenters cause autochthonous salt to evacuate by flow primarily basinward as allochthonous salt sheets. These sheets were extruded from the autochthonous salt layer from inclined salt bodies and flowed as salt glaciers near the seafloor. The evacuation of thick salt bodies provides the vertical accommodation space for sediments and unusually thick deposits are generated. As salt evacuation nears completion and the accommodation space it provides diminishes, sedimentation progrades basinward.
Thirteen sequential structural restorations were constructed from the Present to the Late Jurassic. Over 500 km of proprietary seismic and 33 wells, in association with published depth to basement maps, were used to construct the depth section. The restorations incorporated both decompaction and isostatic subsidence (thermal and tectonic). Early stages of the tectonic history of the northern Gulf of Mexico basin was dominated by differential thermal subsidence as a result of Early Jurassic rifling. During the Cenozoic, the structural evolution is dominated by the influx of large clastic depocenters.
A proper understanding of the evolution of allochthonous salt in the northern Gulf of Mexico is essential for determining relationships between salt tectonics, sedimentation, and petroleum accumulations. When integrated with stratigraphic analyses, restorations provide the foundation for evaluating petroleum systems through detailed thermal maturation modeling and petroleum migration analysis.