Sediment gravity transport on the Weddell Sea continental margin
Anderson, John B.
Master of Arts
Understanding sediment gravity transport and continental slope processes has become increasingly important, especially with the current emphasis upon oil and gas exploration in the deep marine environment. Core x-radiography and textural and mineralogic analysis of sediment samples from Weddell Sea piston cores has enabled identification of several mechanisms of sediment mass transport which significantly influence sedimentation on the continental slope, abyssal plain, and continental shelf. End member processes such as debris flows and turbidity currents are found to occur throughout the eastern Weddell Sea, between °W and 45°W; however textural and visual evidence also substantiates the presence of sediment gravity flow processes which are transitional between end-member mechanisms. Downslope transition in sediment character between slump, debris flow, and turbidite deposits is related to a corresponding transition in the mechanics of grain support and transport. Because most material transported to the marine environment in the Weddell Sea is of poorly sorted glacial origin, analysis of the competence of the marine transport agents is augmented. Textural and mineralogic sorting within the turbidity current mechanism, for example, is found to be extremely efficient. Generation of well sorted quartz-rich sands from poorly sorted lithic source material occurs over relatively short distances, and proves to be a mechanism by which potentially large amounts of quartz sands are produced in the Weddell Sea. The intimate association of these sands with glacial sediments offers an alternative explanation for the quartzite/diamictite associations in ancient sequences which have been cited as evidence against a glacial origin for these deposits.