Stable isotope record and depositional environments in the Antarctic Polar Front of Drake Passage, Western Antarctica

Abstract

A high-resolution study including oxygen and carbon stable isotopes as well as planktonic foraminifera, carbonate, ice-rafted debris (IRD) contents, were performed on one core sediment (DP00-02) taken from the seamount top near Antarctic Polar Front (APF) in the Drake Passage, Western Antarctica. Based on the oxygen stable isotope records measured on Neogloboquadrina pachyderma (sin.), this sediment core is interpreted to represent a stratigraphic record back to the lower isotope stage 5 (-129 kyr). Isotope stages 5, 4 and 1 show a high abundance of carbonate and planktonic foraminifer with relatively low IRD content. In contrast, isotope stages 3 and 2 are characterized by low abundance of carbonate with remarkably high IRD content. This is probably attributed by a local/regional influence due to front structural changes, related to the fluctuation of APF, i.e., the south and northward migration of polar water mass. The glacial-interglacial shifts in δ 18 O values of N. pachyderma (sin.) may reach up to 1 to 1.2‰ indicating that, global ice volume changes have affected the isotope records. However, the isotope stage 3, generally interpreted as the less warmer period in the global record than Holocene and stage 5, corresponds to much lighter values compared to the global climate curve. This may be resulted from change in the salinity rather than change in the global ice volume or the temperature.