| Geomorphological and palaeoenvironmental research on Holocene sedimentation in the Mue valley provides evidence for fluvial system changes related to climate and human activities in Normandy, a poorly studied area of the Paris basin. The 24 km long valley bottom has been investigated through a systematic survey. It shows an original longitudinal sedimentary pattern in relation with valley morphology and local geological controls. Minerogenic, tufaceous and peaty deposits provide opportunities for multi-proxy analyses and radiocarbon dating control. The filling begins around 9 500 14C BP with silt deposition in a meandering system. The Boreal and the Lower Atlantic periods (8 500-6 000 14C BP) are mainly characterized by unlithified calcareous tufa. Locally, these deposits are very thick (7 to 13 m) and form barrages across the valley bottom. During the Upper Atlantic period (6 000-4 700 14C BP), the valley has experienced a decrease in calcareous sedimentation and the development of organic deposits. At the beginning of the Subboreal (4 700-3 500 14C BP), peat deposits expanded, especially behind the tufa barrages. The valley bottom was characterized by large marshy areas whereas the regional vegetation was progressively modified by human activities. At the end of the Subboreal (3 300-3 000 14C BP) the infilling of the valley by calcareous silt was caused by an increase of river activity related to climatic and land use changes. From the Iron Age and Gallo-Roman periods (2 800-1 700 14C BP), the valley bottom is filled by silty overbank deposits related to an increase of soil erosion. Hence, river appears as a continuum. The alluvial record of the Mue valley reflects a broad regional pattern of environmental changes but presents particular features, which highlight the need of longitudinal studies to take into account spatial and temporal discontinuities of Holocene hydro-sedimentary systems, even in small order valleys. |
Export this paper
