Late Quaternary fluctuations of biogenic component fluxes on the continental slope of the Ross Sea, Antarctica

A sediment core, collected from the western part of the continental slope o f the Ross Sea at 2380 m water depth, records events of the last two climat ic cycles (250 kyr). A Th-230(ex)-based chronology was obtained and boundar ies of the isotope stages were set assuming that biological productivity wa s enhanced during periods of less ice cover. Then, Th-230(ex)0, organic car bon, biogenic silica and biogenic Pa distributions were compared to the gla cial-interglacial stage boundaries and corresponding ages of the delta(18)O record of Martinson et al. [Martinson, D.G., Pisias, N.G., Hays, J.D., Imb rie, J., Moore, T.C., Jr., Shackleton, N.J, 1987. Age dating and the orbita l theory of the ice ages: development of a high-resolution 0 to 300,000-yea r chronostratigraphy. Quaternary Research, 27: 1-29]. Sediment accumulation rates ranged between 1.2 cm kyr(-1) in the isotope stage 6 and 3.8 cm kyr( -1) during the Holocene. Variations in the concentrations and fluxes of org anic carbon, biogenic Pa biogenic silica and Mn gave information on palaeoc limate changes. Processes of sediment redistribution in the Ross Sea margin were enlightened from a comparison of the measured and expected fluxes of Th-230(ex). Calculation of the focusing-corrected accumulation rates of bio genic Ba enabled us to evaluate the export palaeoproductivity. Corrected ac cumulation rates of biogenic components and calculated palaeoproductivities were low, compared to the Antarctic Polar Front in the Atlantic sector, th roughout the last two climatic cycles. Glacial-interglacial changes of sea ice cover and ventilation of the Ross Sea were probably major causes of var iations in biogenic particle flux and distribution of redox-sensitive eleme nts within the sediment column.