Clay Minerals in Response to the Mid-Pliocene Global Warmth in Polar Regions (ODP, Site 911, Yermak Plateau, Arctic Ocean and Site 1165, Prydz Bay, Antarctica)

The Mid-Pliocene global warmth (MPGW), a period when the global average temperatures were significantly warmer than the present, was possibly caused by higher CO2 levels than today and significantly stronger ocean thermohaline circulation due to drastic climatic changes in the Southern Ocean. In the Northern Hemisphere, MPGW could have been one decisive trigger for the intensification of glaciation at 2.7 Ma. Some recent studies in the East Antarctica have shown that the East Antarctic Ice Sheet (EAIS) may have varied from a polythermal, dynamic condition to a predominantly cold stable state as recently as the Pliocene period, including MPGW. This presentation may illuminate the Mid-Pliocene climate conditions of the Arctic Ocean and the dynamics of the EAIS based on a clay mineral study. Research of this kind, integrated with other proxies, can provide some indication of how the Earth may respond to the future global warming The Ocean Drilling Program (ODP) Site 911 was drilled on the Yermak Plateau, Arctic Ocean to a depth of 505.8 meters below the seafloor (mbsf). It contained sediments from the Pliocene to Pleistocene ages. ODP Site 1165 was drilled on the Wild Drift on the Continental Rise off Prydz Bay, East Antarctica, to a total depth of 999.1 mbsf. Of special interest is the sediment column between 0 and 50 mbsf, which consists of a well-preserved section of Pliocene- to Pleistocene-age sediments. The Pliocene sediments at Site 911 have higher smectite content and lower kaolinite and chlorite contents compared to the Pleistocene samples. This may indicate more active sea-ice conditions for smectite transportation from the Kara and Laptev Seas during the Pliocene compared to the Pleistocene sea-ice transportation conditions. The Mid-Pliocene sediments at Site 1165 show increasing smectite contents and decreasing illite contents and suggest that the EAIS at that time may have been more dynamic than that during the Plio-Pleistocene transition, to which the results were compared.