Sediment Pathways of the Northwest Green Canyon Area, Offshore Louisiana

Abstract

ABSTRACT Physiography of the upper slope in the northwest Green Canyon area is strongly influenced by the occurrence of shallow salt features. During sea level lowstands, sediments are transported from the shelf through feeder channels in pathways between bathymetric highs controlled by salt tectonics. Five seismic sequences have been mapped in the northwest Green Canyon area. Each sequence is bounded by condensed sections, which commonly display high-amplitude, continuous reflections overlain by thin highstand/transgressive systems tracts with typically high- to moderately-high amplitude, continuous reflections on seismic profiles. Comparatively thick lowstand systems tracts overlie highstand/transgressive tracts. The hummocky-to-chaotic lowstand systems tracts in this area consist almost entirely of mass-transport complexes. These features develop from slumping and mass-wasting along the shelf-slope break and the over-steepened margins along the sediment pathways. The oldest mapped horizon corresponds to the highest occurrence of Trimosina 'A' (0.65 Ma, Shaffer, 1990). Time-thickness maps of five lowstand sequences were used to map sediment pathways. A strong correlation exists between present-day bathymetry and positions of Late Pleistocene to Recent sediment pathways.