Paleo-export production and terrigenous sedimentation in the Southern Ocean
As a result of the opening of important seaways (Tasmanian Seaway and Drake Passage) and the subsequent formation of the Antarctic Circumpolar Current during the Cenozoic, the Southern Ocean became an important feature of the climate system in terms of ocean circulation and carbon dioxide exchange between the surface ocean and the atmosphere. Therefore, it is vital that we understand the Southern Ocean's role in either forcing or amplifying climate changes of the Cenozoic, either through physical processes such as changes in ocean circulation and sea-ice extent or through changes in the biological carbon pump, particularly export production.
The purpose of this research is to evaluate changes in export production and terrigenous provenance in the Southern Ocean near the Eocene-Oligocene boundary and on glacial/interglacial time scales using major and minor element bulk sediment geochemical proxies. The major findings of this research suggest (1) down core P/Ti ratios match records of reactive P concentrations, suggesting that the two different P-based proxies are comparable in the Southern Ocean; (2) AIM ratios and Ba concentrations suggest the Drake Passage was open or opening at 32.8 Ma; (3) elemental ratios of P and Ba across the Eocene-Oligocene boundary suggest an interval of elevated export production, which supports previous observation based on microfossils assemblages that primary productivity was higher during this time interval; (4) export production across the entire southeastern Atlantic Ocean was maximum during some glacial terminations, which is contrary to other finding suggesting that productivity increased north of the Antarctic Polar Front (APF) during glacial intervals and increased south of the APF during interglacial intervals; and (5) comparisons of the timing between records of export production and atmospheric CO2 from ice cores, suggest that Southern Ocean productivity was not responsible for glacial CO2 drawdown.