ABSTRACT

Deformed and faulted sediments coupled with mobile salt and overpressurized shale at depth make it difficult to deduce the pre-deformation history of much of the Texas-Louisiana shelf and slope. A small window exists, however, between the present-day mouth of the Mississippi river and the area in the western Visoca Knoll OCS area underlain by the Lower Cretaceous shelf edge. The northern part of this area and the adjacent Lower Cretaceous shelf are relatively undeformed and seismic quality is good.

A very low rate of deposition during Late Cretaceous and Lower Miocene times resulted in sediment starvation in the area. Water depths and conditions of deposition during this interval favored deposition and preservation of hydrocarbons and the sediments may have source rock potential.

The development of a depocenter in southeastern Louisiana during the Middle Miocene resulted in deposition of prodelta shales and distal turbidite sands above the starved section. Sediments of a Late Miocene depocenter centered just west of the present-day mouth of the Mississippi river prograded into the area. These filled the basin southwest of the shelf edge and overflowed onto the region underlain by the Lower Cretaceous shelf. The Late Miocene sediments consist of five 3rd-order sequences. Stacked deltaic sands within the highstand systems tracts make attractive exploration targets. Stacked segments of the sequences deposited in progressively shallower water can be pieced together to form a nearly complete composite generalized sequence.

Much if not all of the slope and rise of the northeastern Gulf of Mexico basin also appears to have experienced sediment starvation during between the Late Cretaceous and early Neogene. If this is true, the history of the report area provides unique insight into the depositional history of a large portion of the Late Cretaceous-Paleogene Texas-Louisiana paleoslope and rise.