Biostratigraphie et paléoenvironnements du début du Würm récent d'après les grands mammifères de l'Abri du Flageolet I (Dordogne, France) / Biostratigraphy and paleoenvironments at the onset of the recent Würm as inferred from the large mammals from Le Flageolet (Dordogne, France)

摘要

Biostratigraphy and paleoenvironments at the onset of the recent Würm as inferred from the large mammals from Le Flageolet I (Dordogne, France). The analysis of the large mammals represented in the Aurignacian and Perigordian assemblages of Le Flageolet I was undertaken in part to increase our understanding of the biostratigraphy and paleoenvironments of this part of southwestern France. The work presented here has three goals, the initial aim being to describe the taxa identified from these assemblages. Nine different taxa of carnivores are present, none of which are abundant : only 1.3% of the combined ungulate and carnivore specimens are from carnivores, and over half of these are of foxes ( Vulpes vulpes and Alopex lagopus). The ungulate component of the large mammal fauna is dominated by reindeer and red deer, with smaller numbers of horses and large bovids. Since most of the large bovids could only be identified to the genus level, our analysis emphasizes Rangifer tarandus, Cervus elaphus, and Equus caballus. This analysis allows us to compare the Le Flageolet I assemblages to other early Recent Würm sites, to revisit a series of questions related to the evolution of Cervus elaphus and Equus caballus, and to discern possible environmental causes of both morphological and biometric variability within these three species. The second part of our analysis is dedicated to a biostratigraphic analysis of two additional sites of comparable age, sites which have also provided large mammal assemblages from well-controlled and reasonably homogeneous stratigraphic contexts. This set of assemblages allows us to define eight "biozones" at the beginning of the Recent Würm, each of which appears restricted to a relatively brief period of time. Of these eight, six are represented at Le Flageolet I. The third part of the analysis, directed toward understanding the past climates of this region, is based primarily on the modern climatic correlates of the taxa represented in these "biozones". The period between about 34000 radiocarbon years BP and 26000 BP was marked by contrasting warmer and colder climatic conditions; after 26000 BP, climates increasingly approached those that marked the glacial maximum. Early Würm climates during the time of accumulation of strata XI of Le Flageolet I, K5-7 of La Ferrassie, and 7 of Roc de Combe, on the one hand, and strata IV and V of Le Flageolet I, on the other, were extremely cold. In contrast, markedly temperate climates were in place during the accumulation of strata I to K1-3 at La Ferrassie, and of strata VII of Le Flageolet I and D2 to F of La Ferrassie. These inferred climatic extremes match, and presumably explain, the low taxonomic richness values that mark the ungulate assemblages of Le Flageolet strata XI, VII, V, and IV (cf. Grayson and Delpech 1998), and are supported by the probable presence of both large and small reindeer in these strata. In contrast, Le Flageolet strata IX, VIII, and VI show both greater richness values and contain only large reindeer.