Reconstruction of late Quaternary sedimentary environments at the southern Mendeleev Ridge (Arctic Ocean)

Ruediger.Stein [ at ]


The late Pleistocene history of the Arctic comprised cyclical changes in the extension of land-based ice sheets and sea-ice cover that affected sedimentary environments in the Arctic Ocean. This PhD thesis focuses on sediment records from the Mendeleev Ridge spanning the last 200 ka. Over this time period, variable sedimentation patterns were described and possible implications for reconstruction of glacial/interglacial paleoenvironments were provided. One of the main goals of this study was to identify mineralogical and inorganic-geochemical tracers in marine sediments that could be used for discrimination of sediment provenance and consequently for reconstruction of sediment pathways. In Chapter 5 possibility of provenance discrimination based on bulk mineral composition of surface sediments is discussed. This study compares the results from two software packages, RockJock and QUAX, for quantification of mineral assemblages from the X-Ray diffraction (XRD) data. Comparison with published overviews on the mineral composition of Arctic Ocean surface sediments demonstrates that in provenance studies bulk mineral composition of sediments should be used along with other indicators for source areas. In Chapter 6 stratigraphy for 4 cores recovered along a transect at ca. 77°36’N across the Mendeleev Ridge during the ARK-XXIII/3 Expedition of RV “Polarstern” was revised using paleomagnetic parameters (inclination and paleointensity) supported by AMS 14C datings and micropaleontological evidences. Changes of sedimentary settings from the Mendeleev Ridge towards the East Siberian Sea margin were documented for the last 200 ka. As evidenced by grain-size and mineralogical data, there were several events of intensified sediment discharge at the Mendeleev Ridge possibly linked to paleoenvironmental changes in North America and Eurasia. Chapter 7 describes provenance investigations using the isotopic composition of radiogenic lead (Pb) and neodymium (Nd) of detrital fraction in core PS72/340-5 at the eastern flank of the Mendeleev Ridge. Obtained results were compared with marine surface sediment data and values for the circum-Arctic subaerial provinces. Late Quaternary sediment supply variability was analyzed using the mixing model constrained by two tracers: 207Pb/206Pb and #Nd. Our results confirm that 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. On the whole, 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.

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Bazhenova, E. (2012): Reconstruction of late Quaternary sedimentary environments at the southern Mendeleev Ridge (Arctic Ocean) , PhD thesis, University of Bremen.

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