GLACIAL/INTERGLACIAL CHANGES IN SEDIMENT PROVENANCE IN THE CENTRAL ARCTIC OCEAN: MINERALOGY, TRACE ELEMENT AND ISOTOPE ND AND PB SIGNATURE OF DETRITAL FRACTION

Mineralogy (XRD), geochemistry (ICP-MS) and Nd and Pb isotope (MC-ICP-MS) signatures of sediments from Central Arctic were analysed to trace detrital particle provenance. Changes in relative contribution of the different source-areas were used to reconstruct paleoceanographical changes over the last 300 kyr. Cores HLY0503-12TC and 12MC were collected at 1585 m on Mendeleev Ridge during HOTRAX cruise (Darby et al., 2005). Stratigraphy was constrained by ²³⁰Th (Not and Hillaire-Marcel, 2010) and ²¹⁰Pb profiles. The upper 70 cm of core 12TC covers MIS 1 to 11; the upper 50 cm of core 12MC represent MIS 1 to 7. Bulk mineralogy depicts pronounced changes in the relative contribution of calcite and dolomite in regard with quartz and feldspars. Temporal changes in Nd and Pb isotopic composition confirm that sediment supply is controlled glacial/interglacial variability. Pb mixing calculation evidences contribution from Mackenzie and Lena river areas. All intergacial-deglacial samples are shifted towards the Mackenzie end-member. Such source is consistent with their carbonate-rich lithology, detrital carbonates and especially dolomite being originated mainly from this area and from Canadian channels. During glacial stages, both mineralogy and radiogenic signatures evidence less contribution from the Mackenzie area. Nd mixing reports contribution from a third volcanic source. A compilation of trace element content of regional geological sources suggests that the most probable candidate is the Okhotsh-Chutoka province (Eastern border of Siberian platform). Our mineralogical and geochemical data confirm that the sediment provenances in Central Arctic remain close to the Present conditions during the earlier interglacials. Glacial stage 4 and 6 are characterised by the lowest supplies from the American margin (< 20%), suggesting reduced particle supplies by the Beaufort Gyre to the Mendeleeiv Ridge.