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RESEARCH PRODUCT

Biogeography of the Pleistocene pleniglacial malacofaunas in Europe. Stratigraphic and climatic implications

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Abstract As determined by Lozek, malacological associations are significant of a particular vegetal environment. In Quaternary sequences, different types of associations are recognized which can be assimilated to the present types of malacofaunas. There are associations of grass group, of forest group and of the ecotone of these two biogeographical entities. On the European scale, in Pleistocene sequences, the interglacial faunas indicate similarly the same differences as today, being of stratigraphic interest. On the contrary, pleniglacial faunas, which are mainly preserved in the loess belt, seemed not interesting for stratigraphy since they indicate more generalized and more homogeneous conditions. Moreover they are composed of few species which, for the most part, had their distribution area destroyed by the ice-cap advance. Yet, the global analysis of pleniglacial biome faunas, by ecological biogeographical approach, provides a particular stratigraphic element which allows to determine stratigraphic entities: provinces or domains in accordance with sedimentary interpretations. So, for Quaternary pleniglacial faunas, the biozone concept is efficiently supplied by ecostratigraphy. Consequently to a review of European localities, it appears that the distribution of pleniglacial malacofaunas is mainly controlled by precipitations. So the variations which are recorded in some privileged deposits, as i.e. Achenheim sequence in Alsace (France), indicate variations through time of eastern limit of oceanic facies and western limit of continental facies of the climate.