Clay mineral distribution in surface sediments of the South Atlantic: sources, transport, and relation to oceanography

• Published in: Marine Geology
• Main Authors: Petschick, Rainer, Kuhn, Gerhard, Gingele, Franz
• Format: Article in Journal/Newspaper
• Language: unknown
• Published: 1996
• Subjects: Antarctic; Antarctic Ocean; Antarctic Peninsula; Bouvet; Bouvet Island; East Antarctica; Ronne Ice Shelf; The Antarctic; Antarc*; Antarctica; Filchner Ronne Ice Shelf; Filchner-Ronne Ice Shelf; Ice Shelf
• Online Access: https://epic.awi.de/id/eprint/2393/; https://epic.awi.de/id/eprint/2393/1/petschick-etal_1996.pdf; https://hdl.handle.net/10013/epic.12981; https://hdl.handle.net/10013/epic.12981.d001

Surface samples, mostly from abyssal sediments of the South Atlantic, from parts of the equatorial Atlantic, and of the Antarctic Ocean, were investigated for clay content and clay mineral composition. Maps of relative clay mineral content were compiled, which improve previous maps by showing more details, especially at high latitudes. Large-scale relations regarding the origin and transport paths of detrital clay are revealed. High smectite concentrations are observed in abyssal regions, primarily derived from southernmost South America and from minor sources in Southwest Africa. Near submarine volcanoes of the Antarctic Ocean (South Sandwich, Bouvet Island) smectite contents exhibit distinct maxima, which is ascribed to the weathering of altered basalts and volcanic glasses. The illite distribution can be subdivided into five major zones including two maxima revealing both South African and Antarctic sources. A particularly high amount of Mg- and Fe-rich illites are observed close to East Antarctica. They are derived from biotite-bearing crystalline rocks and transported to the west by the East Antarctic Coastal Current. Chiorite and well-crystallized dioctaedral illite are typical minerals enriched within the Subantarctic and Polarfrontal-Zone but of minor importance off East Antarctica. Kaolinite dominates the clay mineral assemblage at low latitudes, where the continental source rocks (West Africa, Brazil) are mainly affected by intensive chemical weathering. Surprisingly, a slight increase of kaolinite is observed in the Enderby Basin and near the Filchner-Ronne Ice shelf. The investigated area can be subdivided into ten, large-scale clay facies zones with characteristic possible source regions and transport paths. Clay mineral assemblages of the largest part of the South Atlantic, especially of the western basins are dominated by chlorite and illite derived from the Antarctic Peninsula and southernmost South America and supported by advection within the Circumantarctic Deep Water flow. In contrast, the ...