Radiogenic lead and neodymium composition of surface sediments from the Arctic Ocean

Dolomite-rich layers of distinct pinkish colour are used as lithostratigraphic markers in the Amerasian Basin of the Arctic Ocean. However, origin of dolomite present in these sediment units has not been investigated in detail. In this study, lead (Pb) and neodymium (Nd) isotope composition of detrital clay-size fraction from different lithofacies was investigated in core PS72/340-5 recovered at the eastern flank of the Mendeleev Ridge. Prior to the geochemical analyses, grain-size distribution in sediments was analyzed in order to minimize the grain-size effect on the provenance signature. For provenance discrimination, results of isotope measurements were compared with marine surface sediment data and values for the circum-Arctic subaerial provinces. Late Quaternary sediment supply variability in core PS72/340-5 was analysed using the mixing model constrained by two tracers: 207Pb/206Pb and eNd. Variations of sediment isotopic composition are inferred to be due to mixing of volcanic and plutonic components. Usage of Pb isotopic ratios alone does not allow distinction between the volcanic and plutonic sources. Results confirm that, in the frame of the existing age model, over the last 200 ka dolomite-rich pink layers at the southern Mendeleev Ridge were deposited during events associated with intensified iceberg transport from North America. In general, however, late Quaternary sedimentation was mostly controlled by terrigenous input from the Chukchi and East Siberian Seas whereas sediment supply from the Laptev Sea area remained less important and relatively constant at the studied location.