HR: 14:25h
AN: PP32C-04    [PDF]
TI: Productivity Patterns at the Eocene-Oligocene Transition: Beginning of the High Productivity Area in the Southern Ocean
AU: * Schumacher, S
EM: stefanie.schumacher@museum.hu-berlin.de
AF: Museum of Natural History Berlin, Institute for Paleontology, Invalidenstrasse 43, Berlin, 10115 Germany
AU: Lazarus, D
EM: david.lazarus@rz.hu-berlin.de
AF: Museum of Natural History Berlin, Institute for Paleontology, Invalidenstrasse 43, Berlin, 10115 Germany
AB: At the end of Eocene extensive plate tectonic events affected a reorganisation of the southern world's oceans. The opening of the Tasman and Drake passages enabled a first establishment of an initial Antarctic Circumpolar Current (ACC) with a frontal system. Cooling and glaciation of the Antarctic was reflected in an enhanced latitudinal temperature and density gradient, and a stronger mixing of the high latitude vertical water column. The beginning of the ACC enhanced an austral upwelling system. Serveral DSDP/ODP sites of the Southern Ocean and the lower latitudes have been investigated to recover long term productivity patterns from the middle Eocene to the late Oligocene. A multi-proxy approach including biological, sedimentological and geochemical proxies is chosen. The aim of the study is a reconstruction of the productivity in southern high latitudes in comparison to lower latitudes. Changes in paleoproductivity at the Eocene-Oligocene transition took mainly place in the southern high latitudes. Here we note a change to higher paleoproductivity starting in the latest Eocene or at the Eocene-Oligocene transition. In the Weddell Sea the benthic foraminifera fauna indicate an increase in seasonality. In equatorial oceans, we have no indications for a shift to higher paleoproductivity at the Eocene-Oligocene transition. On the contrary a few sites show a shift to lower productivity at or after the transition. Sites between 40 and 50 degrees paleolatitudes near Australia and New Zealand show changes to higher paleoproductivity, but changes at the northern site are not highly significant. Changes in paleoproductivity were forced by the reconstruction of ocean circulation. The stronger mixing of the water column, the beginning upwelling and the enhanced bottom water production effected an increase of southern high latitude productivity. Oceanographic changes in lower latitudes were less dramatic. Surface water temperatures were nearly constant while the bottom waters cooled. Vertical stability of the water column increased and therefore changes in paleoproductivity were either negligible, or negative. The boundary between the areas may be at 30-40 degrees S.
DE: 3030 Micropaleontology
DE: 4863 Sedimentation
DE: 9310 Antarctica
DE: 9604 Cenozoic
SC: Paleoceanography and Paleoclimatology [PP]
MN: 2003 Fall Meeting