Site 3

Abstract

A general description of the deep basin of the Gulf of Mexico is given in the preceding section on Site 2, in the Setting and Purpose, and the reader is referred to that material for a preamble to the following discussion of Site 3.The study of thirty-three cores in 1953 led Ewing, Worzel, Ericson, and Heezen (1955) from a consideration of the nature of the sediments cored, the topography of the Mississippi Cone, and the flat floor of the Sigsbee Deep, to the conclusion that the distribution of sediments in the Gulf of Mexico was profoundly influenced by turbidity currents. These authors also concluded, from seismic refraction measurements, that the crust was oceanic in character.In 1954 a detailed topographic study, supplemented by 124 piston cores taken in the Gulf (Ewing, Ericson, and Heezen, 1958), led to the conclusion that silty sediments-supplied in quantity by the Pleistocene Mississippi River and distributed by a turbidity current process-covered the floor of the Gulf. The situation of the Sigsbee Knolls in an abyssal plain and the character of the sediments cored from them made it probable that

Late Cenozoic cooling favored glacial over tectonic controls on sediment supply to the western Gulf of Mexico

“…WGOM (Ewing et al, 1969;Worzel et al, 1973). In contrast, late Pleistocene sand has a DZ signature like that observed for coeval (ca.…”

“…Miocene strata are prominent across the southern WGOM and indicate average sedimentation rates (a.s.r.) of ~4-6 cm/10 3 yr, largely by sediment-gravity-flow deposition across a broad submarine fan (Ewing et al, 1969;Worzel et al, 1973), where the coarsest turbidites were recovered at Site 91 (Fig. 1C).…”

“…Pleistocene sediment indicates rapid deposition (a.s.r. ~10-20 cm/10 3 yr) of muddy fine-sand turbidites (Ewing et al, 1969;Worzel et al, 1973).…”

“…Sedimentation rates in the WGOM increased significantly at ca. 2 Ma (Ewing et al, 1969;Worzel et al, 1973), and by the end of the mid-Pleistocene transition (ca. 0.7 Ma), debris came almost exclusively from the north via the Mississippi catchment and associated Mississippi and Bryant Fans (Bouma et al, 1986;Tripsanas et al, 2007).…”

“…Deep-water sediment of the WGOM was the first target of R/V Glomar Challenger on Leg 1 of the Deep Sea Drilling Project (DSDP) (Ewing et al, 1969), and again in 1970 on Leg 10 ( Worzel et al, 1973).…”