Afanasyeva, Victoria (2013) Late Quaternary paleoenvironmental changes in the Arctic Ocean : reconstruction from a sediment core from Mendeleev Ridge. (Master thesis), Saint-Petersburg State University ; University of Hamburg, Saint Petersburg, Russia ; Hamburg, 51 pp.

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Abstract

The Quaternary history of the Arctic Ocean constitutes from alternating glacial, deglacial and interglacial/interstadial periods on the Arctic mainland. A precise knowledge of the past rates and scales of climate change might give an idea about the climate variability and give a possibility to predict future climate changes. The high-resolution records may help to reconstruct the paleoenvironmental conditions and solve some uncertainties in the debate of recent climate change (Stein, 2008 and reference therein).
This study was focused on sediment core PS72/413-3 from the Northern transect across the Mendeleev Ridge. This short sediment core was taken using the giant box corer (GKG) during the Polarstern Expedition ARKXXIII/3 in 2008. Different sedimentary proxies such as geochemistry (total organic carbon, inorganic carbon, carbon to nitrogen ratio), lithology (Stein et al., 2009), micropaleontology (absolute abundances of benthic and planktonic foraminifers, planktonic to benthic foraminifera relation, absolute and relative abundances of C. wuellerstorfi and B. aculeata), grain size composition, tentative X-ray diffraction and colour reflectance measurements were used for the core investigation.
The age model of the core was established by the correlation to the age model developed by Jang et al. (2013) for the adjacent sediment core at site PS72/410. The lithofacies were determined based on Stein et al. (2010b) and colour reflectance measurements. According to established stratigraphic framework the PS72/413-3 comprises marine isotope stages (MIS) 5a to 1.
The proxy results were discussed in terms of depositional environments and paleoenvironmental conditions. The alternation of brown and grey beds down the sediment core was clearly to identify. Brown beds (B1-B3) are supposed to be deposited in the interglacial/interstadial environment with a diminished sea-ice cover and high primary production. The deposition environment of the grey beds (G1-G3) is interpreted as deglacial and/or glacial termination periods with minimum foraminiferal abundances and iceberg-dominated sediment transport. The so called condensed sections were defined based on lithology and proxy correlation with the neighbor-core PS72/410 (Jang et al., 2013) and most likely coincide with glacial environment with a completely packed sea-ice cover. The characteristic for central Arctic Ocean sediments pink-white layers W3 and PW were defined on bases of G1 and B3 beds respectively based on Stein et al. (2010b), inorganic carbon content and X-ray diffraction measurements.
The obtained data were discussed using the published data (Adler et al., 2009; Backman et al., 2004; Darby et al., 2006; Jang et al., 2013; Nørgaard-Pedersen et al., 1998, 2003; Polyak et al., 2004, 2009; Poore et al., 1999; Stein et al., 1994). In general our results are in an agreement with an interpretation of MIS 1, 3, 5a as an interglacial/interstadial and MIS 2 and 4 as glacial periods.
In frame of this study the origin of the inorganic carbon peak within MIS 5a and the paleoecology in terms of foraminiferal abundances were discussed. Based on the proposed age model the sedimentation rates were calculated and they range from 0.1 cm/ky to 2.5 cm/ky during the glacial and interglacial/interstadial periods respectively with an average value of 0.84 cm/ky. That is in agreement with the proposed mean sedimentation rates for the northern Mendeleev Ridge of 0.5-0.9 cm/ky (Stein et al., 2010b).

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