Quaternary Tephrochronology of the Scotia Sea and Bellingshausen Sea, Antarctica

• Main Author: Moreton, Steven G.
• Format: Thesis
• Language: English
• Published: 1999
• Subjects: GC Oceanography; Bellingshausen Sea; Deception Island; Jane Basin; Scotia Sea; South Shetland Islands; Southern Ocean; Weddell; Antarc*; Antarctica
• Online Access: https://eprints.glos.ac.uk/4865/; https://eprints.glos.ac.uk/4865/1/Moreton%20phd.pdf

The Southern Ocean is a region of the world's ocean which is fundamental to the generation of cold deep ocean water which drives the global thermo-haline circulation. Previous investigations of deep-sea sediment cores south of the Polar Front have been significantly constrained by the lack of a suitable correlation and dating technique. In this study, deep-sea sediment cores from the Bellingshausen, Scotia and Weddell seas have been investigated for the presence of tephra layers. The major oxide and trace element composition of glass shards have been used to correlate tephra isochrones over distances in excess of 600 km. The source volcanoes for individual tephra layers have been identified. Atmospheric transport distances greater than 1500 km for >32 μm shards are reported. One megascopic tephra is identified and correlated across 7 sediment drifts on the continental rise in the Bellingshausen Sea. Its occurrence in a sedimentary unit that has been biostratigraphically dated to δ^18 0 substage 5e identifies it as a key regional marker horizon for that stage. An unusual bimodal megascopic ash layer erupted from Deception Island, South Shetland Islands, has been correlated between 6 sediment cores which form a 600 km NW-SW transect from the central Scotia Sea to Jane Basin. The megascopic ash layer has been ^14C dated at 10,670 years BP. It represents the last significant input of tephra into the Scotia Sea or Jane Basin from that volcano and forms an important early Holocene marker horizon for the region. Five disseminated tephras can be correlated to varying extents across the central Scotia Sea cores. Together with the megascopic tephra they form a tephrostratigraphic framework that will greatly aid palaeoclimatic, palaeoenvironmental and palaeoceanographic investigations in the region.