Evidence for the variability of Holocene chemical weathering in a calcareous watershed using coaly particles (Chaillexon basin, Doubs, France)

Matter fluxes result from chemical and mechanical weathering that vary as a function of climate, relief, lithology and human activities. The aim of th is paper is to characterize chemical weathering variations in the past usin g coaly particles found in both the geological substratum and the Holocene lacustrine sediments of a calcareous basin (Chaillexon lake, Doubs, France) . Results point out that chemical weathering was the predominant erosional process in the watershed, which may be due to the calcareous nature of the bedrock. The significant variability of this process relative to mechanical weathering during the Holocene period can be interpreted as a consequence of the development of the vegetal cover induced by climate changes and huma n activity (forest clearing and landuse). Results also suggest that there i s no direct relationship between chemical weathering in the watershed and a utochthonous carbonate precipitation in the lake. (C) Academie des sciences / Elsevier, Paris.