L'évolution des formes de relief et des formations torrentielles alpines depuis 4 700 BPThe evolution of alpine landforms and torrential formations since 4 700 BP

摘要

Since 4700 BP, alpine torrential catchments record more or less precisely biochmatic evolution and antropization. Subboreal and subatlantic landforms can be juxtaposed, superimposed or inset into early holocene terraces or fans. This is interpreted by the dynamic of the torrent or main rivers. Chronostratigraphic evolution of torrential alluvial deposits shows 5 phasis of active torrentiality (with bed load transport or torrential debris flows deposits). The last one is historical and took place from the middle of the XIIIe to the XIXe centuries. Throught diverses arguments, climatic factors seem to be more important than antropization of catchment witch were discnbed by ancient authors during XIXe century. So, the Little Ice Age appears as a real morphoclimatic crisis, responsible for renewaling sedimentary stocks and increasing in flood frequencies ;