Structure and stratigraphy of late quaternary deposits on the outer Louisiana Shelf

Abstract

Regional investigation of late Quaternary deposits on the outer Louisiana shelf indicated two principle structural provinces: (1) a western province between West Cameron and Ship Shoal Areas which is highly faulted and structurally controlled by salt tectonics; and (2) an eastern province occupying South Timbalier and Grand Isle Areas which is greatly influenced by the effects of tectonics and sedimentation associated with the Old Mississippi Canyon complex. Vertical forces due to a mobile salt layer at depth, continual basin subsidence, and the incompetence of the overlying sedimentary strata dominate the western structural province where the main locus of deposition was located during Pleistocene time. Growth faults, post-depositional faults, salt dome faults (Radial and peripheral), grabens, horsts, and collapse faults are found in the western province; movement along several of these faults is occurring at the present. In the eastern province little deformation is apparent in the late Quaternary section where thick accumulations of recent sediments are deposited. Thick regional sands are widely distributed across the outer Louisiana shelf. These sands represent fluvial-deltaic sediments that were initially deposited in a series of coalescing deltas during low stands of sea level. As sea level rose these sands were subsequently transported to the north and laterally spread across large areas. Transgressive bars formed during intermittent halts in sea level rises..