CONTINENTAL MARINE RATIO CHANGES IN SUSPENDED AND SETTLED MATTER ACROSS A MACROTIDAL ESTUARY (THE SEINE ESTUARY, NORTHWESTERN FRANCE)/

Suspended matter movements in the macrotidal Seine estuary (France) ar e mainly controlled by tidal currents. During high river spates, suspe nded matter is carried out of the estuary into the English Channel. A large part of the estuarine suspended matter comes from continental in puts. Throughout the year, suspended matter is trapped in the Turbidit y Maximum Zone and on the estuarine tidal flats. Marine particles whic h are concentrated in the Turbidity Maximum Zone can be transported up stream into fresh water conditions. Physical and chemical measurements , as well as grain size analysis associated with scanning electron mic roscopy techniques, are used to study the characteristics of silty sed iments and suspended matter. In the Turbidity Maximum Zone of the Sein e estuary, particulate tracers, such as diatoms, indicate a continenta l/marine ratio more than 90% in the suspended matter. These results ar e similar with those from radiotracers. Sedimentary analyses on fine d eposits from the estuarine tidal flats show close similarities with su spended matter coming from the Turbidity Maximum Zone. The sedimentolo gical processes of the Seine estuary are compared with those in some o ther estuaries.