Small valley bottom deposits in the sandy districts of the Sarthe basin (France): climatic and/or human origin?

The study of the small valley bottom deposits in a sandy district where several recent erosional events have occurred makes it possible to distinguish deposits, which are caused by climatic oscillations from those induced by both climate and human activities. The coarse alluvium with flints, which reached the main valleys prior to the Subboreal, was transported by greater flows than those which resulted from later human-induced flood discharges, where flints were not evacuated from the small valleys. Radiocarbon dates of peat set those deposits in the Iron Age, in the transition from Antiquity to the Medieval period, at the end of the “optimum climatique de lʹan Mil” and during the Little Ice Age. At the present time, human-induced flood discharges reach again the main valleys.