Climatic interpretation of terrestrial malacofaunas of the last interglacial in southeastern France

The sequence of the Ruisseau de lʹAmourette, in the French Alps, covering the isotope stages 5e, 5d, 5c, and part of 5a and 6, was studied for terrestrial mollusks. Correspondence analysis of the mollusk assemblages permits reconstruction of temperature and moisture trends using knowledge of the modern ecology of the recognized species. The classic environmental succession of the last Interglacial–Early Glacial (Würmian) is recognized. The Eemian (Sub-stage 5e) suggests warm and moist conditions. It is followed by the cold Melisey I (Sub-stage 5d) showing moisture variation, from dry in the lower part to moist in the upper part. The mollusk equivalent of St. Germain I and II also indicates warm and moist conditions. The Melisey II stadial (Sub-stage 5b) is missing but may be reflected by the deposition of barren gravel layers. All these environmental oscillations agree with the fluctuations described in the literature. However, Stage 5e indicates a particular trend as the mollusks recorded two well individual cool events which seem to correspond to variations identified in various west-European continental records. However, as no particular cold indicator species were identified, these events cannot be related to strong climatic fluctuations as emphasized in the early studies of the Greenland GRIP ice-core or in North Atlantic and western European records.