Lake-level fluctuations at Lake Bourget (eastern France) around 4500-3500?cal. a BP and their palaeoclimatic and archaeological implications
Résumé
On the basis of sedimentological analysis of two cores taken at Chatillon, Lake Le Bourget (northern French Pre-Alps), and well dated by radiocarbon dates in addition to tree ring dates obtained from an archaeological layer, this paper presents a high-resolution lake-level record for the period 45003500?cal. a BP. The collected data provide evidence of a complex palaeohydrological (climatic) oscillation spanning the ca. 43003850?cal. BP time interval, with major lake-level maxima at ca. 4200 and 40503850?cal. a BP separated by a lowering episode around 4100?cal. a BP. The lake-level highstands observed at Chatillon between 4300 and 3850?cal. BP appear to be synchronous with (i) a major flooding period recorded in deep cores from the large lakes Le Bourget and Bodensee, and (ii) glacier advance and tree line decline in the Alps. Such wetter and cooler climatic conditions in west-central Europe around 4000?cal. a BP may have been a nonlinear response to decrease and seasonal changes in insolation. They may also provide a possible explanation for the general abandonment of prehistoric lake dwellings north of the Alps between 4360 and 3750?cal. a BP