PALEOHYDROLOGICAL CHANGES IN JURA (FRANCE), AND CLIMATIC OSCILLATIONSAROUND THE NORTH-ATLANTIC FROM ALLEROD TO PREBOREAL

Regional palaeohydrological changes recorded in the Jura lakes, France , have led to a tentative reconstruction of a fine-scale pattern of cl imatic changes from Allerod to the early Holocene. The Younger Dryas ( YD) can be subdivided into three parts: after a first wet phase, this cool period was characterized by increasing dryness; a short rise in l ake level developed during its last part. Moreover, the YD was precede d and followed try two short rises in lake-level, which interrupted th e lake-level lowerings developing during the Allerod and the Preboreal . Climatic oscillations reconstructed in Jura appear to be in phase wi th glacier and tree-limit movements in the Alps, with fluctuations in oxygen-isotope records from the Swiss lakes and the Greenland ice shee t, and with climatic oscillations recorded in the Norwegian Sea. Other correlations between (1) these climatic oscillations, (2) C-14 platea ux recorded in Swiss lake sequences, and (3) fluctuations in the resid ual Delta(14)C, support a correlation between regional palaeohydrologi cal changes defined in Jura and broad-scale climatic oscillations; the y also support the existence of a link between climatic changes in Wes tern and Central Europe and oceanic circulation. Moreover, as working hypothesis, these correlations suggest high-precision timing for the c limatic and environmental changes occurring during the early Holocene.