RISSIAN, EEMIAN AND WURMIAN COLEOPTERA ASSEMBLAGES FROM LA-GRANDE-PILE (VOSGES, FRANCE)

The Grande Pile peat-bog sequence is one of the few west European sites that cover the entire time span of the last major climatic cycle (140,000 years). A recent program of coring has provided material for insect analysis. The aim of this palaeoentomological study is to interpret the environmental and climatic evolution from the end of the Rissian glaciation to the Holocene using subfossil Coleoptera. The studied samples yielded 394 taxa of Coleoptera, half of them identified to species level; 19 of which do not belong to the present-day French fauna. The large number of taxa suggests a wide variety of habitats and provides much detailed palaeoecological evidence for the period studied. The lowermost sediments of the sequence, corresponding to the end of the Rissian glaciation, were deposited under very cold conditions in a tundra environment. This is succeeded by a forest period in which two cool interludes of grassland environment occur. Although these periods are decidedly poor in tree-dependent Coleoptera they do not contain any really cold-adapted taxa. They divide the forest phase into three periods. The first one, corresponding to the Eemian Interglacial, shows an early stage in which the beetle fauna is characterized by species dependent on deciduous trees, a later stage in which this fauna is mixed with many conifer-dependent elements, some of which (e.g. Platypus oxyurus) suggest warmer and perhaps wetter climatic condition than today. The two later woodland periods yielded coleopteran assemblages rather similar to those recorded in the second part of the Eemian, i.e. with both deciduous- and conifer-dependent taxa. There is some evidence to suggest that these two periods were slightly cooler than the Eemian proper. Marked climatic deterioration becomes obvious in the upper half of the sedimentary sequence attributed to the last glacial period (Wurm), with the reappearance of tundra beetle assemblages. Sediment and insect evidence suggest that the climate was extremely cold and continental at La Grande Pile at about 30,000 B.P. A comparison of the insect analysis with previous palynological works enables precise correlation between the results provided by these two independent approaches. However, large numbers of running-water Coleoptera in the forest periods, replaced by standing-water Coleoptera in cold periods, raise questions concerning the lacustrine origin of the sedimentation at La Grande Pile.