Description: The object of the present study is to introduce a means of comparing the Vostok and marine chronologies. Our strategy has been to use the delta18O of atmospheric O2 (denoted delta18Oatm) from the Vostok ice core as a proxy for the delta18O of seawater (denoted delta18Osw). Our underlying premise in using delta18Oatm as a proxy for delta18Osw is that past variations in delta18Osw (an indicator of continental ice volume) have been transmitted to the atmospheric O2 reservoir by photosynthesizing organisms in the surface waters of the world's oceans. We compare our record of delta18Oatm to the delta18Osw record which has been developed from studies of the isotopic composition of biogenic calcite (delta18Oforam) in deep-sea cores. We have tied our delta18Oatm record from Vostok to the SPECMAP timescale throughout the last 135 kyr by correlating delta18Oatm with a delta18Osw record from V19-30. Results of the correlation indicate that 77% of the variance is shared between these two records. We observed differences between the delta18Oatm and the delta18Osw records during the coldest periods, which indicate that there have been subtle changes in the factors which regulate delta18Oatm other than delta18Osw. Our use of delta18Oatm as a proxy for delta18Osw must therefore be considered tentative, especially during these periods. By correlating delta18Oatm with delta18Osw, we provide a common temporal framework for comparing phase relationships between atmospheric records (from ice cores) and oceanographic records constructed from deep-sea cores. Our correlated age-depth relation for the Vostok core should not be considered an absolute Vostok timescale. We consider it to be the preferred timescale for comparing Vostok climate records with marine climate records which have been placed on the SPECMAP timescale. We have examined the fidelity of this common temporal framework by comparing sea surface temperature (SST) records from sediment cores with an Antarctic temperature record from the Vostok ice core. We have demonstrated that when the southern ocean SST and Antarctic temperature records are compared on this common temporal framework, they show a high degree of similarity. We interpret this result as supporting our use of the common temporal framework for comparing other climate records from the Vostok ice core with any climate record that has been correlated into the SPECMAP chronology.

Description: Because of a close relationship between detrital flux variations and magnetic susceptibility (MS) flux (MS cm**3 of bulk sediment multiplied by the linear sedimentation rate) variations in the southeast Indian basin of the southern ocean, MS flux profiles have been used to examine the spatial and temporal detrital flux changes in this basin during the last climatic cycle. Results indicate a general increase in detrital material input during the coldest periods, suggesting a widespread phenomenon, at least on the basin scale. Mineralogical data, geochemical data, and 87Sr/86Sr isotopic ratios have been used to determine the origin and transport mechanisms responsible for increased detrital flux during glacial periods. Mineralogical and geochemical data show that these glacial 'highs' are due to increases in both Kerguelen-Crozet volcanic and Antarctic detrital inputs. The 87Sr/86Sr isotopic composition of the 〉45-µm fraction indicates that the Kerguelen-Crozet province contributes to at least 50% of the coarse particule input to the west. This contribution decreases eastward to reach less than 10%. These tracers clearly indicate that the Crozet-Kerguelen province was a major source region of detrital in the western part of the basin during glacial times. In contrast, material of Antarctic origin is well represented in the whole basin (fine and coarse fractions). Because of the minor amount of coarse particles in the sediments, volcanic particles from Kerguelen and crustal particles from Antarctica have most probably been transported by the Antarctic bottom water current and/or the Circumpolar deepwater current during glacial periods as is the case today. Nevertheless, the presence of coarse particles even in low amount suggests also a transport by ice rafting (sea-ice and icebergs), originated from both Kerguelen and Antarctic sources. However, the relative importance of both hydrographic and ice-rafting modes of transport cannot be identified accurately with our data. During low sea level stands (glacial maximum periods), increasing instability and erosion of the continental platform and shallow plateaus could have resulted in a more efficient transfer of crustal and volcano-detrital material to the Southeast Indian basin. At the same time, extension of the grounded ice shelves over the continental margins and increase in the erosion rate of the Antarctic ice sheet could have induced a greater input of ice rafted detritus (IRD) to southern ocean basins. Enhancement of the circumpolar deepwater current strength might have also carried a more important flux of detrital material from Kerguelen. However, an increase in the bottom water flow is not necessarily required.