Preprints
https://doi.org/10.5194/gchron-2022-25
https://doi.org/10.5194/gchron-2022-25
 
18 Oct 2022
18 Oct 2022
Status: this preprint is currently under review for the journal GChron.

Amino acid racemization in Neogloboquadrina pachyderma and Cibicidoides wuellerstorfi from the Arctic Ocean and its implications for age models

Gabriel West1,2, Darrell S. Kaufman3, Martin Jakobsson1,2, and Matt O'Regan1,2 Gabriel West et al.
  • 1Department of Geological Sciences, Stockholm University, Stockholm, 10691, Sweden
  • 2Bolin Centre for Climate Research, Stockholm University, Stockholm, 10691, Sweden
  • 3School of Earth and Sustainability, Northern Arizona University, Flagstaff, AZ 86011, USA

Abstract. We report the results of amino acid racemization (AAR) analyses of aspartic and glutamic acids in the planktic foraminifera, Neogloboquadrina pachyderma, and the benthic species, Cibicidoides wuellerstorfi, collected from sediment cores from the Arctic Ocean. The cores were retrieved at various deep-sea sites of the Arctic, which cover a large geographical area; from the Greenland and Iceland seas to the Alpha and Lomonosov Ridges in the central Arctic Ocean. Age models for the investigated sediments were developed by multiple dating techniques, including oxygen isotope stratigraphy, magnetostratigraphy, bio-, litho-, and cyclostratigraphy. The extent of racemization (D/L values) was determined on 95 samples (1028 subsamples) and shows a progressive increase downcore for both foraminifera species. Differences in the rates of racemization between the species were established by analysing specimens of both species from the same stratigraphic levels (n = 21). Aspartic acid and glutamic acid racemize on average 16±2 % and 23±3 % faster, respectively, in C. wuellerstorfi than in N. pachyderma. D/L values typically increase with sample age, with a trend that follows a simple power function. Scatter around least square regression fits are larger for samples from the central Arctic Ocean than for those from the Nordic Seas. Calibrating the rate of racemization in C. wuellerstorfi using independently dated samples from the Greenland and Iceland seas for the past 400 ka enables estimation of sample ages from the central Arctic Ocean, where bottom water temperatures are similar. The resulting ages are older than expected when considering the existing age models for the central Arctic Ocean cores. These results confirm that the differences are not due to taxonomic effects and further warrant a critical evaluation of existing Arctic Ocean age models and the environmental factors that may influence racemisation rates in central Arctic Ocean sediments.

Gabriel West et al.

Status: final response (author comments only)

Comment types: AC – author | RC – referee | CC – community | EC – editor | CEC – chief editor | : Report abuse
  • RC1: 'Comment on gchron-2022-25', Anonymous Referee #1, 08 Nov 2022
  • RC2: 'Comment on gchron-2022-25', Colin V. Murray-Wallace, 10 Nov 2022
  • RC3: 'Comment on gchron-2022-25', Anonymous Referee #3, 25 Nov 2022

Gabriel West et al.

Gabriel West et al.

Viewed

Total article views: 270 (including HTML, PDF, and XML)
HTML PDF XML Total Supplement BibTeX EndNote
211 50 9 270 25 1 2
  • HTML: 211
  • PDF: 50
  • XML: 9
  • Total: 270
  • Supplement: 25
  • BibTeX: 1
  • EndNote: 2
Views and downloads (calculated since 18 Oct 2022)
Cumulative views and downloads (calculated since 18 Oct 2022)

Viewed (geographical distribution)

Total article views: 261 (including HTML, PDF, and XML) Thereof 261 with geography defined and 0 with unknown origin.
Country # Views %
  • 1
1
 
 
 
 
Latest update: 03 Dec 2022
Download
Short summary
We report aspartic and glutamic acid racemization analyses on Neogloboquadrina pachyderma and Cibicidoides wuellerstorfi from the Arctic Ocean (AO). The rates of racemization in the species are compared. Calibrating the rate of racemization in C. wuellerstorfi for the past 400 ka allows the estimation of sample ages from the central AO. Estimated ages are older than existing age assignments (as previously observed for N. pachyderma), confirming that differences are not due to taxonomic effects.