Variations of biogenic particle flux in the southern Atlantic section of the Subantarctic Zone during the late Quaternary: Evidence from sedimentary and

摘要: Variations of intensity and composition biogenic particle flux at the northern boundary present PolarFrontal Zone in Atlantic sector Southern Ocean are indicators major changes paleoenvironmentalconditions on glacial/interglacial time scales during Late Quaternary. In order to estimate those pastchanges, sediment accumulation patterns two piston cores, one from just north south thepresent day position Subantarctic Front were reconstructed. Using 230Thex method large contributionsof laterally supplied material quantified used correct rates. During lastglacial focussing opal-dominated exceeded original contribution surfacewater above by a maximum factor 8.7. The initial activity ratio 231Paex/230Thex was as tracer forbiogenic indicates that glacial stages 2 4 area high opalproductivity situated location southern core whereas has not beenreached this northward shift last 130 kyr shown pattern focussing-corrected bulkaccumulation If Antarctic Polar remained thehigh opal productivity kyr, results suggest located exactly between thetwo sites 4. A two-box modeling approach involving boundaryscavenging 231Pa applied possible range recordedin sediments. Previous estimates export into SouthernOcean corroborated but model suggests low sensitivity Oceansediments variations residence North Deep Water Ocean.