Holocene and modern sediments in the Seine Estuary (France): a synthesis

This synthesis of numerous studies on the Holocene and modern sediments in the macrotidal setting of the Seine estuary demonstrates their overall evolution. In common with a number of estuaries, the lower Seine was an incised valley during the Weichselian glacio-eustatic sea-level fall, and infilling occurred during the subsequent lowstand, the Holocene sea-level rise and the late Holocene stillstand. in the upper estuary, above the basal gravel bed, fluvial freshwater deposits filled the valley. Next, fine sand and silts invaded the, estuary upstream to Rouen; the sequence ends in loam, resulting from an increase in the supply of sediment to the fluvial system. In the upper estuary, anthropogenic deepening of the modern channel results in erosion of the Holocene sediments; the only bedforms are thin and narrow sand sheets and some rare megaripples. In the lower estuary, above the Weichselian basal gravel, the Holocene wedge records the change from a transgressed fluvial setting (i.e. gravel beds) to an open estuarine environment (i.e. tidal delta). The modern Seine estuary has been progressively infilled by marine sands and silts. Now silts and clays supplied during high river flows accumulate at the outlet, and offshore sands and gravel of the eastern Bay of the Seine are temporarily covered with veneers of mud. These freshly deposited muds (i.e. mud patches) are periodically partly reworked by waves and strong tidal currents, but silting of the inner shelf is noticeable. Copyright (C) 2003 John Wiley Sons, Ltd.