Low Resolution Examination of Cool-water Carbonate Foraminifera around Tasmania during the Pleistocene

Benthic foraminifera from nine sediment samples recovered during Ocean Drilling Program (ODP) Leg 189: The Tasman Gateway were examined to determine how changing Southern Ocean conditions affect benthic foraminiferal populations. All samples come from Site 1168 situated 70km from the coast of Tasmania on the western continental slope (2463 m below the surface) and are spaced at roughly 150,000 years apart. Identifications of benthic foraminifera were done with a dissecting microscope and several reference books. Foraminifera were correlated with environmental proxy data obtained from Brughmans (2003) (total organic carbon, carbonate, siliciclastics, coarse fractions, chlorin, barium, aluminum, iron, and titanium) and The Scientific Shipboard Party (2001) (density, magnetic susceptibility, and lightness). The data demonstrates that benthic foraminifera responded to large-scale changes in the ocean surface waters caused by the movement of the subtropical convergence during glacial and interglacial periods. Genera such as Uvigerina, Cibicidoides, Cibicides, and Notoralia tend to be more successful during glacial periods when there is greater abundance of wind-blown terrigenous metals delivered to the ocean; whereas genera Pyrgo and species Epistominella elegans and Hansenisca soldanii seem to thrive under interglacial conditions when there is higher productivity in the surface waters. This research also adds to the growing knowledge base of cool-water carbonate environments and provides further evidence of a mid-Pleistocene extinction event affecting the genus Siphondosaria and others