The sedimentological and geotechnical characteristics of the lower continental slope and rise of the Mississippi Fan fold belt

Abstract

The study is based on geological and geotechnical laboratory testing data of 70 three inch diameter piston cores. Concentration is along the Sigsbee Escarpment in a grid area between 90⁰ and 91⁰W and 26.7⁰ and 27.3⁰N. Water depth ranges from 1,200 meters below sea level to 2,500 meters below sea level. All data were used to characterize the seafloor processes that deposited these sediments. The Sigsbee Escarpment represents a complex topographic and geologic feature involving faults, slumps and steep slopes. Most of the study area is covered by hemipelagic Holocene sediments in 0.05 to 2.9 m thickness, greatest thickness being in bathymetric lows indicating that Holocene sediments are eroded at the bathymetric highs and transported down the slope. The underlying Pleistocene sediments are mostly laminated clays in the southwestern part of the study area, indicating no mass wasting. Hemipelagic sedimentation in quiet sea bottom environment was dominant throughout the accumulation of the unit. Several generations of slumps have occurred in the northeastern part of the Sigsbee Escarpment during the Pleistocene showing that this part of the study area is an area where active mass wasting and down slope processes dominate.