Holocene evolution of a wetland in the Lower Seine Valley, Marais Vernier, France

Estuaries like that of the Seine River in NW Europe developed in incised fluvial valleys after the last glacial maximum. Since the 1940s, several authors have studied the largest wetland of the Seine estuary, the Marais Vernier, to understand depositional environments during Holocene infilling. We reinterpret previous research based on new and published data (for example fill thickness and material source) to (1) describe facies and depositional environments; (2) reconstruct palaeoenvironmental evolution; (3) show the influence of local and global forcing on depositional environments. Before 7000-6000 cal. BC, terrestrial material was deposited because of catchment erosion related to changes in climate. Just before 7000-6000 cal. BC, estuarine material began to be deposited in low-lying areas in response to sea-level rise, while terrestrial material still settled at higher elevations. After this, but before 5850-5710 cal. BC, estuarine material areas began to accumulate at both high and low elevations. This marked a general flooding of the Marais Vernier, synchronous with that at the Seine estuary mouth. Soon after, peat accumulated over a wide area as a response to a local change in accommodation and a worldwide drop in sea level. A tidal channel developed to the west of the Marais Vernier, providing minerogenic material. After 1130-900 cal. BC, human influence becomes increasingly clear in the record. This record of regional change during the Holocene can serve as a reference for further studies in the area.