Variabilité et origine des apports détritiques dans le secteur indien de l'océan Austral au cours des derniers 30 000 ans

The surface water circulation variability in the southeastern Indian Sector has been investigated using micropalaeontological and isotopic analysis in a deep-sea core located near the Subantarctic Front. The frequency and intensity of iceberg and meltwater discharges have been studied by counting detrital grains >45 mu m, by determining their mineralogical composition, and by measuring delta(18)O in the planktonic foraminifera Neogloboquadrina pachyderma sinistral. The variability of hydrologic fronts was determined by estimating the sea surface temperatures (SST) using the Imbrie and Kipp foraminifera transfer function. Four iceberg discharge events were determined between 24 and 12 ka C-14 BP during the last glacial stage. Distinct but low magnitude increases in lithic grain concentrations probably indicate little-modified surface hydrology. There is no evidence of significant variation in delta(18)O isotopic anomalies. A comparison of southern iceberg discharges with North Atlantic Heinrich events shows that these events occur more or less synchronously but depict differences in the dynamics of deposition.