Benthic foraminiferal assemblages from the eastern South Atlantic Polar Front region

Surface sediment samples taken with a multiple corer from the Polar Front region along two profiles in the eastern South Atlantic sector between 35° and 57°S have been investigated for their benthic foraminiferal content. Live fauna was differentiated from the death assemblage. Based on the dead assemblages, potential fossil assemblages (dead fauna reduced by non-resistant agglutinants) were calculated for comparison with upper Neogene core material. The distribution of the potential fossil assemblages defined by Q-mode principal component analysis mirrors the Recent hydrographic, as well as the trophic situation in the eastern South Atlantic (ocean circulation and productivity). Two Southern Component Bottom Water Faunas reflect the northward flow of Antarctic Bottom Water (AABW) and Lower Circum-Polar Deep Water (LCDW): an assemblage dominated by the arenaceous Multifidella nodulosa below the Calcite Compensation Depth (CCD), and a Nuttallides umbonifer dominated assemblage above the CCD. In the region of highest bio-silicious primary productivity, south of the Polar Front and north of the winter sea-ice limit, these faunas are overprinted by a Southern High-productivity Fauna, dominated by infaunal species such as Pullenia bulloides, Melonis pompilioides and M. zaandamae. North Atlantic Deep Water (NADW) meets the Circum-Polar Deep Water (CDW) at intermediate depth, as reflected in the distribution of the Northern Component Deep Water Fauna, dominated by Epistominella exigua. The high-productivity assemblage overprinting this fauna, the Northern High-productivity Fauna, is dominated by the shallow endobenthic Bulimina aculeata. A Strong Bottom-current Fauna, dominated by Angulogerina angulosa, characterizes areas between 400 and 900 m water depth with sandy sediment, independent from water mass characteristics and food supply.