Range chart of calcareous nannofossils from ODP Hole 188-1165B (Table 1)

Bio- and magnetostratigraphic age data and nannofossil assemblage analysis from ODP Site 1165 evidence an anomalous warming event of the surface waters in and around Prydz Bay during the Early Pleistocene, approximately 1 Ma. This results from an increase in the abundance of nannofossils at Site 1165, that occurred at 1 Ma. Detailed high-resolution sampling permits a new bio-magnetostratigraphic interpretation for ODP Site 1165. A decrease in delta18O values at Sites 1165 and 1167 also occurs at this time, supporting the presence of warming conditions in the Prydz Bay area. A return to colder surface waters, indicated by the absence or rare occurrence of nannofossils in the upper cores from Site 1165, suggests that more stable glacial conditions existed in the Prydz Bay basin, for the last 900 ka. The biogenic carbonate sequence identified at Site 1167 is similar to the carbonate shales recovered from the Cape Roberts Project 1. Both have been dated at about 1 Ma, supporting the idea that a significant surface waters warming occurred during the Pleistocene. These data and the presence of calcareous nannofossils from locations around the Antarctic continent also suggest that the warming event was not limited to the analysed basin, but it extended around the East Antarctic continent. These new evidence call for a re-evaluation of the notion that the East Antarctic Ice-Sheet has experienced stable conditions similar to today since the late Neogene.