X-ray fluorescence scannings, diatoms, and dinocyst of ODP Site 189-1172

Eocene sediments drilled at the East Tasman Plateau (ETP) exhibit well-defined cycles, high-resolution magnetic stratigraphy, and environmentally-controlled dinoflagellate and diatom distribution patterns. We derive a cyclostratigraphy from the spectral analysis of high-resolution elemental concentration records (Ca, Fe) for this shallow marine time series spanning the middle to early late Eocene (C16n.2n - C21). Changes in carbonate content, the ratio between Gonyaulacoid and Peridinioid dinocysts, and relative abundance of "oligotrophic" diatoms serve as proxies for a high-resolution climatic and sea-level history with high values representing high sea-level stands and decreased eutrophy of surface waters. Changing ratios between high latitude dinocysts versus cosmopolitan species provide clues on sea surface temperature trends and water mass exchange. Our results show that the relatively shallow-water middle Eocene environments of the ETP are influenced by orbitally-forced climatic cycles superimposed on third order relative sea-level changes. Changes in the dominance of Milankovitch frequency at ~38.6 Ma (late Eocene) is related to an initial deepening-step within the Tasmanian Gateway prior to the major deepening during the middle late Eocene (~35.5 Ma). Decreasing sedimentation rates at 38 Ma and 37.2 Ma reflect winnowing associated with sea-level fall. This episode is followed by renewed transgression. Dinocyst distribution patterns indicate high latitude, probably cool temperate surface water conditions throughout, with the exception of a sudden surge in cosmopolitan species near the base of subchron C18.2r, at ~41 Ma; this event is tentatively correlated to the Middle Eocene Climatic Optimum.

AWI Bathymetric Chart of the Weddell Sea, Antarctica (BCWS)

From data collected by RV Polarstern, and additional echosoundings provided by national hydrographic offices, research institutions and the International Hydrographic Organization (IHO) Digital Bathymetric Data Center, the 1:1,000,000 Bathymetric Chart of the Weddell Sea (AWl BCWS) series has been developed. The heterogeneity of bathymetric data and the lack of observations within ice-covered areas required the incorporation of supplementary geophysical and geographical information. A semi-automatic procedure was developed for terrain modeling and contouring. In coastal regions, adjacent sub-glacial information was included in order to model the bathymetry of the transition zone along the Antarctic ice edge. Six sheets of the AWl BCWS series in the scale of 1:1,000,000 covering the southern Weddell Sea from 66°S to 78°S and from 68°W to 0°E were recently completed and included in the 1997 GEneral Bathymetric Chart of the Oceans (GEBCO) Digital Atlas CD-ROM (http://www.gebco.net). On the basis of these six 1:1,000,000 AWl BCWS sheets, a generalized 1:3,000,000-scale bathymetric chart was compiled for the entire southern Weddell Sea.