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Geochronology Advances in geochronological science
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Discussion papers
https://doi.org/10.5194/gchron-2019-5
© Author(s) 2019. This work is distributed under
the Creative Commons Attribution 4.0 License.
https://doi.org/10.5194/gchron-2019-5
© Author(s) 2019. This work is distributed under
the Creative Commons Attribution 4.0 License.

Submitted as: research article 16 Jul 2019

Submitted as: research article | 16 Jul 2019

Review status
This discussion paper is a preprint. A revision of the manuscript is under review for the journal Geochronology (GChron).

Amino acid racemization in Quaternary foraminifera from the Yermak Plateau

Gabriel West1, Darrell S. Kaufman2, Francesco Muschitiello3, Matthias Forwick4, Jens Matthiessen5, Jutta Wollenburg5, and Matt O'Regan1 Gabriel West et al.
  • 1Department of Geological Sciences, Stockholm University, 10691Stockholm, Sweden
  • 2School of Earth and Sustainability, Northern Arizona University, Flagstaff, AZ 86011,USA
  • 3Department of Geography, University of Cambridge, Cambridge, CB2 3EN, UK
  • 4Department of Geosciences, UiT The Arctic University of Norway, 9037 Tromsø, Norway
  • 5Alfred-Wegener Institute for Polar and Marine Research, 27570 Bremerhaven, Germany

Abstract. Amino acid racemization (AAR) geochronology is a powerful tool for dating Quaternary marine sediments across the globe, yet its application to Arctic Ocean sediments has been limited. Anomalous rates of AAR in foraminifera from the central Arctic were reported in previously published studies, indicating that either the rate of racemization is higher in this area, or inaccurate age models were used to constrain the sediment ages. This study investigates racemization rates in foraminifera from three well-dated sediment cores taken from the Yermak Plateau during the 2015 TRANSSIZ Expedition on RV Polarstern. D and L isomers of the amino acids, aspartic acid (Asp) and glutamic acid (Glu), were separated in samples of the planktic foraminifera, Neogloboquadrina pachyderm and the benthic species, Cassidulina neoteretis to quantify the extent of racemization. In total, 241 subsamples were analysed, extending back to Marine Isotope Stage (MIS) 7. Two previously published power functions, which relate the extent of racemization of Asp and Glu in foraminifera to sample age are revisited, and a comparison is made between the ages predicted by these calibrated age equations and independent geochronological constraints available for the cores. Our analyses reveal an excellent match between ages predicted by a global compilation of racemization rates for N. pachyderma, and confirm that a proposed Arctic-specific calibration curve is not applicable at the Yermak Plateau. These results generally support the rates of AAR determined for other cold bottom water sites, and further highlight the anomalous nature of the purportedly high rate of racemization indicated by previous analyses of central Arctic sediments.

Gabriel West et al.
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Gabriel West et al.
Gabriel West et al.
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We report amino acid racemization analyses of foraminifera from well-dated sediment cores from the Yermak Plateau, Arctic Ocean. Sample ages are compared with model predictions, revealing that the rates of racemization generally conform to a global compilation of racemization rates at deep-sea sites. These results highlight the need for further studies to test and explain the origin of the purportedly high rate of racemization indicated by previous analyses of central Arctic sediments.
We report amino acid racemization analyses of foraminifera from well-dated sediment cores from...
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