SOURCES AND SINKS OF SEDIMENT TO THE AMAZON MARGIN - THE AMAPA COAST

Modern and Holocene muddy strata were studied along the shoreline adja cent to the Amazon river mouth using sedimentological, radiochemical, physical, and seismic methods. The present paper is a synthesis of the results, collected during the AmasSeds project, that is used to outli ne a regional shoreline sediment budget. Erosion of relict Amazon muds in southern Amapa supplies 10(6) tons yr(-1) to the Amazon advective mud stream. Local rivers are sediment-poor (total suspended discharge similar to 1 x 10(6) tons yr(-1)), but form depositional sandflats on the shoreface downdrift of the river mouths. Mudflat accumulation in n orthern Amapa sequesters 10(6)-10(7) tons yr(-1) by tidal-flat aggrada tion, alongshore mudcape accretion, and sediment trapping by mangroves . The processes temporarily store 1.5 x 10(8) tons of Amazon mud in Ja nuary-June.