INDIVIDUAL FLOOD EVENTS DETECTED IN THE RECENT SEDIMENTS OF THE PETITLAC-DANNECY, EASTERN FRANCE

A 90-cm long freeze core from the Petit Lac d'Annecy was sampled at I- cm intervals and studied using magnetic measurements, chemical element and pollen analysis. The results reveal four distinctive horizons in each of which the different lines of evidence point to deposition duri ng a single, major flood event. The magnetic evidence shows that the s ediment deposited in each event included a high proportion of surface- soil-derived material and this inference is consistent with the geoche mical and pollen records from these layers. No firm dates can be ascri bed to these inwash events at present, but a tentative chronology deri ved for the core from Pb-210 measurements, varve counting where possib le, and correlation with a nearby, previously dated core, suggest that these hood events date from the late seventeenth to early nineteenth centuries. A tentative correlation is suggested between the single-eve nt deposits and the record of summer/autumn floods during the period.