8th International Nannoplankton Association Conference


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Kristeen McGonigal, Wuchang Wei, Shipboard Scientific Party:
Tasmanian Seaway: preliminary calcareous nannofossil data from ODP Leg 189

ODP Leg 189 drilled five sites in the Tasmanian region to elucidate the details of the opening of the Tasman Seaway, its influence on the development of the Antarctic Circumpolar Current (ACC), and the subsequent impact on global climate. Sediments recovered contain calcareous nannofossils ranging in age from Maastrichtian to Quaternary. Calcareous nannofossils provide key age-constraint and palaeoceanographic data in marine Neogene sediments, where they are abundant, and also in nearshore Palaeogene sediments, where they are less plentiful.

Standard low-latitude nannofossil zonal schemes (Martini; Okada & Bukry) were used in the Neogene sequences at all Leg 189 sites. Sites 1168 and 1172 recovered complete, detailed Neogene sections that will serve as key reference sites for the Southern Ocean. The Palaeogene nannofossil zonation for the Southern Ocean was successfully applied to the silty claystones/clayey siltstones recovered below the Eocene/Oligocene transition. Eocene through Lower Oligocene sediments recovered at Sites 1168, 1170, 1171 and 1172 yielded calcareous nannofossil assemblages displaying warmer-water characteristics than other Southern Ocean sites of similar palaeolatitude (Sites 512, 513, 699, 703 and 747), reflecting the influence of the 'Proto-Leeuwin' and E Australian currents in this region. Calcareous nannofossils provide crucial palaeoenvironmental and age-control data at all Leg 189 sites, assisting in the formation of a detailed picture of the evolution of the Southern Ocean in the Tasman region.


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 [Division of Micropalaeontology] [Department of Geosciences] [Bremen University]

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