Amino acid racemization in Quaternary foraminifera from theYermak Plateau, Arctic Ocean

Gabriel West1, Darrell S. Kaufman2, Francesco Muschitiello3, Matthias Forwick4, Jens Matthiessen5,Jutta Wollenburg5, and Matt O’Regan1

1Department of Geological Sciences, Stockholm University, 10691 Stockholm, 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

Amino acid racemization (AAR) geochronol-ogy is a powerful tool for dating Quaternary marine sedi-ments across the globe, yet its application to Arctic Oceansediments has been limited. Anomalous rates of AAR inforaminifera from the central Arctic were reported in pre-viously published studies, indicating that either the rate ofracemization is higher in this area, or inaccurate age modelswere used to constrain the sediment ages. This study inves-tigates racemization rates in foraminifera from three well-dated sediment cores taken from the Yermak Plateau duringthe 2015 TRANSSIZ (TRansitions in the Arctic SeasonalSea Ice Zone) expedition on RV Polarstern. D and L iso-mers of the amino acids aspartic acid (Asp) and glutamic acid(Glu) were separated in samples of the planktic foraminifer Neogloboquadrina pachyderma and the benthic species Cas-sidulina neoteretis to quantify the extent of racemization. Intotal, 241 subsamples were analysed, extending back to ma-rine oxygen isotope stage (MIS) 7. Two previously publishedpower functions, which relate the extent of racemization ofAsp and Glu in foraminifera to sample age are revisited, anda comparison is made between the ages predicted by thesecalibrated age equations and independent geochronologicalconstraints available for the cores. Our analyses reveal an ex-cellent match between ages predicted by a global compilationof racemization rates for N. pachyderma and confirm that aproposed Arctic-specific calibration curve is not applicable atthe Yermak Plateau. These results generally support the ratesof AAR determined for other cold bottom water sites and fur-ther highlight the anomalous nature of the purportedly highrate of racemization indicated by previous analyses of centralArctic sediments.

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