Biostratigraphic correlation and paleoceanographic interpretation of Pleistocene calcareous nannofossils from the subtropical front to the Antarctic divergence

The study of calcareous nannofossil distributions in three cores from the subtropical front to the Antarctic Divergence (IMAGES MD 97-2114, Subtropical Front; PNRA Anta 95-157, Polar Front; ODP 188-1165. Antarctic Divergence) provides a way to check the reproducibility from low to high latitudes of the mose recent calcareous nannoplankton biostratigraphic schemes (Raffi et al. 2006) and to verify the geographic calcareous nannofossil distribution during the Quaternary climate phases. The cores cover different sedimentary records and have various degrees of preservation. Four bioevents are recorded in all studied successions. From older to younger, these are: the re-entry of Medium Gephyrocapsa, the Highest Occurrence (HO) of Reticulofenestra asanoi the Pseudoemiliania lacunosa HO, and the Lowest Occurrence (LO) of Emiliania huxley. This study interprets the calcareous nannofossil distributions in the cores in paleoceanographic terms, evaluating the Anatarctic ice-sheet evolution and testifying to the climate relationships between the different geographic areas. During the Early Pleistocene (Jaramillo subchron), while the calcareous nannofossils experienced their maximal abundance in the subtropical region, they are also found near the Antarctic Divergence. From this interval upwards at the Antarctic Divergence, the calcareous nannofossils decrease in relation to more stable glacial conditions of Antarctica. The climate evolution of the Antarctic continent influences the entire Southern Ocean and has led to a sporaidc occurrence of calcareous nannofossils near the polar front (PNRA Anta 95-157) and to a slight decrease in their abudance in the subtropical region (MD 97-2114).