The Alpine mediterranean highlands : geosystems under long-lasting natural and anthropogenic pressures (Millefonds catchment, southern alps, France )

Mediterranean mountains are very sensitive geosystems to erosion processes. These environments combine three steep gradients: topographic, ecologic and climatic. They are extremely vulnerable to both anthropogenic and climate-driven global changes. We propose a multiproxy approach from sediments sequence of Petit Lake (2200m, Millefonts catchment, Mercantour massif, France). We combine sedimentological, geochemical and palaeoecological analyses in order to resolve conjointly each compartment of this high elevation geosystem: vegetation dynamics, lacustrine productivity variability, modalities and rhythms of erosion processes. The 5 millennia drastic collapse of the geosystem is the result of intense precipitations on slopes already affected by human activities (e.g. pastoralism, ore smelting). Natural and Human agencies are necessary both the causes of landscape disturbance of this environment.