Pollen Distribution in Marine Surface Sediments From South-east Pacific and Paleoclimate Changes During the Last 20kyr From Core MD 07 3088 (46°S) off Patagonia

The Chilean Patagonia corresponds to the only mid to high latitude continental climate in the Southern Hemisphere and therefore represents one of the key-areas to understand the past and future climate variability. The “Pachiderme” cruise (MD 159), within the framework of IMAGES program (International MArine Global changES), gave the opportunity to collect a set core by the French R/V Marion Dufresne off Chilean coast from 40°S to 55°S as well in open ocean as in Fjords (Kissel and the shipboard Scientific party, 2007). The pollen analysis of 32 core top samples illustrates the relationships between pollen/spore distribution in marine sediments and (1) their carrying mechanisms and (2) the vegetation source. The pollen and spore concentration pattern shows two distinct gradients: (a) from the North to the South, which is mainly controlled by the influence of westerly winds and, the vegetation changes from the North to the South; (b) from the fjords to the open sea, which is significantly controlled by the correlative influence of the fluvial discharges, the precipitation, the westerly winds and, reinforced by the distance from the coast. Although the pollen contribution in marine recent surface sediments off Chilean Patagonia may be considered as local in fjord areas and as more regional in open sea areas, it remains everywhere widely linked to the local vegetation expanded on nearby continental area (Montade et al., submitted). Thus, the pollen spectra reflect the natural vegetation that marks the reliability of pollen analysis in marine sediment in order to reconstruct present-day and past vegetation of southern Patagonia. We present here the preliminary pollen record of the oceanic core MD 07 3088 (46°04’S; 76°05’W) near Taitao peninsula. Results show that the vegetation changes are linked to climate variations during the Holocene and the Last Glacial Maximum. These changes will be directly compared with oceanic records (oxygen isotope and foraminifera assemblages) obtained on the same core.