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Abstract: Chronology of fast climatic changes during the last glacial period. The history of the glacial climate is punctuated by events occurring at the scale of a human life. They are characterised by temperature changes of large amplitude, simultaneously in Greenland and the North Atlantic. These events affected not only the surface hydrology, but also the deep circulation of this oceanic basin. A by-product of the obvious correspondence between Dansgaard–Oeschger and Heinrich in the polar ice and marine sediments is to allow, by correlation, the construction of a calendar chronology for the marine records. This chronostratigraphic approach was validated by means of radiocarbon dating of deep-sea sediments raised on the Iberian Margin. Our study also contributes to the international effort of calibration of the radiocarbon time scale by providing significant results in the interval between 33000 and 41000 years calendar BP. To cite this article : É. Bard et al., C. R. Palevol 5 (2006) . [Copyright &y& Elsevier]

An accurate chronometer that covers the past 50,000 years is a fundamental tool for geology and archaeology. Accurate dating is essential to understand crucial time in human evolution. Accurate dating is also of paramount importance in fields such as geophysics, geochemistry, and paleoclimatology. The main chronometer for this time range is radiocarbon (14C), but its use is not free of perils. This is because the atmospheric 14C/12C ratio — the starting point of the radiocarbon clock — varies over time. To obtain accurate dates, these fluctuations must be accounted for with a calibration curve. Fossil trees have been used to produce a high-resolution tree-ring calibration, which has been extended with data from layered sediments and tropical corals.