The South Pass shelf-edge failure complex, which extends from the continental shelf edge to the Mississippi fan, is one of several expressions of late Pleistocene seafloor failure identified off the Mississippi River delta. The headward portion of this feature lies within a 240 km² (93 mi²) study area located 22 km (14 mi) south of South Pass. Water depths within the area range from 50 to 400 m (165 to 1,300 ft). High-resolution sparker and Acousti-pulse seismic data have been correlated with borehole information and radiocarbon dates to document the failure and subsequent infilling of the headward bowl of this massive feature.

Radiocarbon dating of the sediments cut by the failure feature suggest that it was formed 25,000 to 20,000 years ago. The buried failure surface represents the evacuation of a slab of sediments approximately 200 m (660 ft) thick with a volume of 40 km³ (9.5 mi³) from within the study area. Dating of the post-failure sediments indicates that the infilling process was essentially complete by 15,000 y.B.P.

Seismic stratigraphic techniques, and lithologic and geotechnical borehole data were used to subdivide the evacuation and infilling into seven stages. These stages are represented by four surfaces of unconformity and the sediment packages they enclose. Sea level, morphology of the depositional surface, contemporaneous structure, sediment accumulation rate, depositional source, and erosion controlled the duration and development of these stages.

End_of_Article - Last_Page 519------------