The Upper Miocene Sedimentation and Salt Tectonics of the East Central Gulf of Mexico Basin

Xinxia Wu¹ and William E. Galloway^2
1 ConocoPhillips China Inc, Beijing, China
² The University of Texas at Austin, Austin, TX

The Upper Miocene genetic sequence records extensive continental margin offlap. Rapid sediment influx from the Tennessee and Mississippi Rivers constructed large fluvial-dominated, wave-modified Tennessee and Mississippi fluvial/deltaic systems that persistently dominated the entire Upper Miocene deposition. The Tennessee fluvial and deltaic system was primarily responsible for margin progradation beneath the modern SE Louisiana coastal plain. Thickest sediments consistently accumulated in the Tennessee and Mississippi shelf-margin deltas, where four major depocenters are recognized. Sediments were dispersed downdip by gravity mass transport processes to form the thick continental slope apron, intraslope fan and abyssal fan systems of the deep Gulf. Shelf margin and slope sediment accumulation was controlled by salt-generated topography and subsidence.

In the east central Gulf, sediment loading onto the mobile salt substrate induced major structural deformation in the form of extensional faulting, salt stock emplacement, folding and thrusting. The location of sediment depocenters was a dominant control on the location of structural activity. At the same time, Upper Miocene sediment accumulation was profoundly influenced by salt structures that controlled both the patterns and locations of sediment accumulation. Salt-controlled bathymetric relief provided accommodation for the deposition of reservoir sands in shelf-margin and slope minibasins of the central Gulf of Mexico. Sediment distribution was strongly complicated by various salt-related structures and compartmentalized by the spectacular intraslope ridges. Five major genetic structural provinces are identified, based on structural style, age, paleogeographic location, association with major sediment accumulation sites, and application of the concept of linked systems.