Révision des données polliniques dans le Pléistocène du Bas-Chablais (Haute-Savoie) : implications chronostratigraphiques et pluralité des glaciations Reconsideration of the pollen data in the Pleistocene of the Bas-Chablais. (Haute-Savoie) : chronostratigraphic implications and plurality of glaciations

摘要

The past studies carried by the French Quaternarists on the Bas-Chablais Pleistocene deposits recognized in the Dranse Valley sections and also by bores and drill cores over the Gavot Plateau - sedimentary faciès, hydrological and hydrochimical contributions, pollen analysis and radiocarbon datings -, allowed to establish a chronology from the Riss to the Late Glacial. A review of palynological records from the «lacustrine complex» of Sionnex dated from the Middle Würm period (isotopic stage 3) by radiocarbon datings allows to set it in the Early Würm (isotopic stage 5d to 5a or transition 5a/ 4). Using this complex as a reference-marker and taking account the whole observations, we propose a new long chronology from the Mindel, following the example of the one established by the Swiss School, but with new correlations between the Dranse Valley deposits and the Plateau Gavot ones. The problem of the glaciations genesis in the french penalpine areas and especially the age of the first large würmian extension of the rhodaman glacier as the «inner moraines» one is discussed.