Sedimentary patterns in the late Quaternary Southern Ocean

The spatial and temporal distribution of biogenic and lithogenic sediments in the late Quaternary Southern Ocean reflects the zonal character of the Antarctic Circumpolar Current and is basically controlled by glacial dynamics in Antarctica, sea-ice distribution, temperature gradients, wind patterns, and thermohaline ocean circulation. Carbonate patterns in most places reveal a decline in biogenic carbonate preservation during glacial periods, mainly attributed to a reduced influx of North Atlantic Deep Water and increased ocean stratification, which modified deep-water chemistry towards more corrosivity. An important lithological feature of the Southern Ocean is the Circumpolar Opal Belt, which today is situated between the Polar Front and the seasonal sea-ice limit to the south. During the glacial periods the opal belt shifted to the north in response to a wider sea-ice extension that reduced light availability and diatom productivity to the south. Biosiliceous productivity to the north likely was fueled by detrital iron supplied by aeolian dust input and/or hemipelagic processes. Lithogenic fluxes generally increased during the glacial periods. Provenance studies on the origin and dispersal of detrital materials suggest combined effects of low sea-level stands, increased glaciogenic input, and enhanced current transport to have caused elevated detrital fluxes. The relative and absolute contribution of aeolian dust is difficult to decipher and awaits further clarification by integrated provenance studies of both marine sediments and more reference materials from the potential terrestrial source areas. Ice-rafted debris (IRD) represents a minor fraction of lithogenic sediments, but can be used to infer both Antarctic ice-sheet dynamics and the fate of both sea-ice and iceberg survival in the distal Southern Ocean. Future work should be concentrated on a better identification of IRD origin in terms of volcaniclastic influences, the distinction of east and west Antarctic sediment sources, and sea-ice versus iceberg transportation.