Les rythmes d'évolution morphologique des vallées françaises au Tardiglaciaire et à l'Holocène. Rapport de synthèse. Discussions (The rythms of the evolution of the french valleys during the Tardiglacial period and the Holocene)

摘要

Abstract. - A synthesis of recent studies dealing with the sedimentary fills of french valleys stresses the occurrence of three main phases. During the Tardiglacial period, the processes of river load generation and transport in braided rivers were intense and widespread. The first part of the Holocene was caracterized by the stabilisation of slopes, by the reworking of sediments inherited from the previous period and by the importance of organic sedimentation in floodplains. From the Subboreal and the Subatlantic onward, the valley bottoms experience a succession of crisis, precisely during the Early Iron Age and the Little Ice Age ; they may be described by dowmstream progradation of gravel outwash in the forelands, by river bed aggradation and by braided patterns.