A large fluvial geomorphosite: the Seine River downstream Mantes-la-Jolie

International audienceRich in historical and cultural heritages, the stretch of the Seine valley that links Île-de-France to Normandy, between Mantes-la-Jolie and the Eure and Andelle confluence zone, belongs to one of the major sets of entrenched meanders known in the world. The valley presents steep hillsides punctuated by white chalk pinnacles alternating with deep funnels, contributing to the picturesque landscape of the valley segment. The geomorphic history of the Seine valley is inseparable of the Quaternary bioclimatic history, with its alternating glacial-interglacial and stadial-interstadial periods. All along the Pleistocene, periglacial processes interacted with fluvial erosion, leading to the formation, deepening, exaggeration and migration of the large meanders. The resulting, present-day geomorphological landscapes are enriched by many historical landmarks. The most emblematic sites are the medieval castles of La Roche Guyon and Les Andelys (Château-Gaillard) which were built on rocky promontories on the concave sides of two large meanders. The mid-Seine valley is also known as a high place of the impressionism, the founder and master of which, Claude Monet, settled here for the second half of his life and created the wonderful gardens of Giverny on the lower Epte river. He and many other impressionist and post-impressionist painters, sensitive to a certain harmony of the local landforms, represented and immortalized the surrounding landscapes. Therefore, we propose to consider this relatively long valley segment as a “disconnected geomorphosite” (at the geosystem scale) owing to the unique combination of cultural and scientific values offered by its individual geotopes at the geofacies scale