EFFECTS OF LONG-TERM CLIMATE CHANGES AND GEOCHEMICAL PROCESSES ON MERCURY ACCUMULATION ON SOUTH AMERICAN AND AFRICAN MARGINS DURING THE LAST GLACIAL/INTERGLACIAL CYCLE

Marine sediments from the Western and Eastern South Atlantic continental margins are used to reconstruct mercury (Hg) accumulation over the last glacial/interglacial cycle. Sediment core GL-1248, collected from the continental slope off northeastern Brazil, and sediment core ODP1077, retrieved from the Congo deep-sea fan area, both dated to the last 128 ka and 130 ka respectively. Mercury concentrations in GL-1248 ranged between 14.95 and 69.43ng/g, and varied with periodicities of 56 ka and 900 yr suggesting the presence of glacial-interglacial changes and millennial-scale variability respectively. Parallel trends of Hg and XRF-Fe plots suggest that following atmospheric Hg deposition onto the continent, Hg is incorporated with iron (Fe) minerals before transportation and eventual immobilization at the NE Brazil continental slope. Mercury concentrations in ODP1077 varied significantly, having concentrations between 23.12 ng/g and 256 ng/g, and its plot exhibits an anti-phase pattern with the Fe/Ca ratio ...