HOLOCENE EVOLUTION OF VALLEY TRAVERTINES IN THE MEDITERRANEAN SOUTH OF FRANCE

Travertine systems (travertines s.s. and associated deposits) are ecol ogical and geomorphological indicators of the evolution of river envir onments in karstic regions. Their study reveals three main evolutionar y stages. 1) The construction of travertine dams begins as far back as the Preboreal. It appears to be generalized during the Atlantic, than ks to a forest bioclimatic optimum. Behind stromatolite domes, river a nd wetland filling materials accumulate. They sometimes contain fen pe ats dated from 7000 to 3800 years BP. Man's pressure is still weak. 2) Between the late Neolithic-early Chalcolithic (around 4000 BP) and th e beginning of our era, travertine sedimentation either stops or conti nues, according to sites and the fluctuations of human presence, in a slow and degraded form (tufas with travertine sands). Forest cover ope ns under the weight of human pressure. 3) The dismantling of travertin e dams and the downcutting of valleys, both wide (> 10 m)) and rapid ( about one millenium) accelerate during the historic age. Travertine co nstructions and humid ecosystems appear to be attractive to Man. The e mptying of marshy lands and the progressive lowering of the undergroun d waters coincide with the modeling of travertine terraces. Nowadays, stromatolite sedimentation is still occurring, but in a less conspicuo us way in refuge sites. The Holocene history of travertine follows, on the whole, a climatic-anthropic sequence.