Salt ridges and domes underlie much of the present Louisiana slope. The bathymetric expression of underlying salt could be either a mound or a flattening of the normal rate of descent down the slope. The "mounded" salt features form barriers to the gravity-driven sediments from the shelf break. Much industrial research has been done in the search for reservoir sands about such an obstruction. Clues to depositional patterns about salt features may be obtained from studies in the deep ocean about seamounts located in pathways of ocean-bottom-following currents. Parallel-bedded sediments form foredrifts on the upcurrent side of a seamount. These foredrift sediments were deposited where the prevailing ocean bottom currents were locally decelerated by the obstructing seamount. In waters overlying the obstruction, a Taylor column of dead water or a slow cyclonic eddy provides tranquil oceanographic conditions, permitting a greater fallout of sediments. Moats are found on the sides of the obstruction and are the result of erosion or non-deposition owing to acceleration of deflected waters. Leedrifts are found on the downcurrent side of the obstruction. Current gyres result from deceleration of accelerated currents along the obstruction's flanks, and a complex sedimentation pattern results. Flow over the obstruction's top is determined by size and shape of the obstruction relative to size and velocity of the bottom-following current. A turbulent wave will be set up which may have sufficient amplitude to influence sedimentation on the downcurrent side. There are a preciable differences between the sedimentation patterns about a dome and a ridge.

If ocean bottoms currents equal gravity-driven terrigenous sediment movement and seamounts equal salt domes and ridges, then the result of deep ocean surveys are directly applicable to sedimentation on slopes with underlying salt basement. The salt-related sedimentation pattern of the present slope should be applicable to similar paleoenvironments.

End_of_Article - Last_Page 1215------------