Bazhenova, Evgenia (2009) Late Quaternary Glacial/Interglacial Regimes at the East Siberian Sea Continental Margin : Reconstructions Based on a Sedimentary Record from Southern Mendeleev Ridge. (Master thesis), St. Petersburg State University ; University of Bremen, St. Petersburg, Russia ; Bremen, 50 pp.

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Abstract

This study is focused on sediment cores PS72/344-1 (boxcorer) and PS72/344-3 (kastenlot) recovered from the western flank of the Southern Mendeleev Ridge during the ARKXXIII/3 (Arctic-2008) Expedition of RV ‘Polarstern’. The composite core PS 72/344 represents an undisturbed sedimentary sequence with the length of 8 m, scanned onboard for physical properties and then sampled at every 10 cm. In the present research we use various sedimentary proxies such as lithology (sediment colour and ice-rafted debris contents), physical properties (density, magnetic susceptibility, p-wave velocity, shear strength measurements), mineralogy (bulk mineralogical composition), geochemistry (total organic carbon contents, C/N ratio) and biostratigraphy (distribution of planktonic and benthic foraminifers) to reconstruct paleoceonographical conditions in the Siberian part of the Amerasian Basin during the Late Quaternary times. The age model for core PS72/344 is constrained by correlation to the stratigraphy developed for the Mendeleev Ridge (Polyak et al., 2004; Adler et al., 2009). For correlation we mainly used lithology (color cycles, IRD contents) and detrital carbonate (dolomite) contents as well as distribution of forams. According to the proposed tratigraphical
framework, the PS72/344 record comprises marine isotope stages (MIS) 5 to 1.
The PS72/344 proxy record demonstrates that sedimentary environments at the East Siberian Sea continental margin were strongly variable during late Quaternary times. Sedimentation patterns show that based on the proxy data we can suggest that there were three major scenarios of transportation and deposition of terrigenous material derived from the adjacent shelves, generally controlled by the extension of sea-ice cover and iceberg discharge. Using this framework of general paleoenvironmental scenarios in the studied area, we discuss the variable paleoceanographic regimes in the Arctic Ocean related to the history of glaciations in Northern Euarasia and North America during late Quaternary times (MIS 5 to present) using published data on sediment cores from the Arctic Basin. Severe ice conditions in the Arctic Ocean consistent with onsets of land-based glaciations in Northern Eurasia and North America were reconstructed for early and mid MIS 5 (two glacial/interglacial cycles), substage 5a, the MIS 5a/4 transition and MIS 2. Enhanced deposition of ice-rafted debris took place in early MIS 5, during the MIS 5a/5 transition, in MIS 4, late MIS 3. Interglacial periods correspond to MIS 5 (not enough dating points), the transitions MIS 5/5a, MIS 5a/4, MIS 3/2. The proposed age model is still preliminary that limits the paleonvironmental reconstructions and more data should be obtained during further studies.

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