A late-glacial - Holocene fossil insect succession from Vallée des Merveilles, French Alps, and its paleoecological implications

Abstract

We studied the composition of assemblages of fossil insects from the Quaternary in the high- altitude Lac Long Inférieur located at 2090 m a.s.1 in the "Vallée des Merveilles" (southern French Alps). The insect assemblages extracted from the lake sedimentary sequence were divided into five faunal units, which enable us to reconstruct the evolution of paleoenvironments from the Würmian ice retreat to the present. Our results indicate that the periglacial desert was replaced by steppic environments, followed by the rise of the treeline and the establishment of a mature conifer forest, which ended in the final collapse of the forest cover Human action was clearly responsible for this last event, but in contrast to other alpine sites, agropastoral activities around the lake itself were not clearly indicated by insect data. Comparisons between insect and pollen data for the same sedimentary sequence agreed in most cases, but these two approaches have a complementary value when they are applied on the same site.