High-resolution diatom stratigraphy of Quaternary sediments from the Scotia Sea

Upper Quaternary pelagic and hemipelagic sediments from the Scotia Sea and South Scotia Ridge range from diatom ooze to diatom-bearing mud. Diatom content increases northwards, and at most sites diatom-rich and diatom-poor sediments alternate downcore on a scale of metres. A local stratigraphy is based on relative abundance of six prominent diatom taxa:Eucampia antarctica, Rhizosolenia spp.,Thalassiosira spp.,Chaetoceros spores,Nitzschia kerguelensis and otherNitzschia species and one silicoflagellate species (Distephanus speculum). These stratigraphic units defined using diatoms are correlated with radiolarian abundance stratigraphy (Cycladophora davisiana) and with palaeomagnetic stratigraphy. Information from modern environments (phytoplankton and sediment trap studies) indicates that changes in diatom species composition are related to N-S movement of the winter ice edge and of the Antarctic Convergence.