CLIMATIC AND ENVIRONMENTAL VARIATIONS DURING THE LAST INTERGLACIAL RECORDED IN A NORTHERN FRANCE TUFA (CAOURS, SOMME BASIN). COMPARISONS WITH REGIONAL RECORDS

摘要

The geochemical content of calcareous tufa has been recently proven to provide reliable reconstructions of climate variability during Pleistocene interglacials. As one of the best documented, the Last Interglacial (also known as the Eemian in continental area or the MIS 5e in marine records) has been frequently referred to as an analogue for the Holocene. The Caours tufa deposit from northern France provides a long record of the evolution of both climate and environment during the Last Interglacial. Geochemical data in tufa calcite are interpreted to record primarily air temperature (delta O-18), ambient moisture depending on vegetation type and density (enhanced during wetter - warmer - periods; delta C-13) and rainfall amount (Mg/Ca). The combined data identify a warm and wet climatic optimum followed by oscillations of temperature and humidity conditions. These climatic variations recorded through the Caours profile are strongly consistent with the palaeoenvironmental reconstructions from malacological data. Comparison with those derived from a Grande Pile pollen record suggests that tufa may have precipitated at Caours from ca. 126 to ca. 115 ka (i.e. during the MIS 5e) and that the recorded climatic variations could be related to significant events affecting the Northern Atlantic region. Data comparison with the isotopic record from a speleothem (BDinf) from Bourgeois-Delaunay cave, in south-western France, confirms the relative climatic instability recorded during the Last Interglacial at Caours.