Radiocarbon Dating of Small-sized Foraminifer Samples: Insights into Marine sediment Mixing

Missiaen, L and Wacker, L and Lougheed, B C and Skinner, L. and Hajdas, I and Nouet, J and Pichat, S and Waelbroeck, C (2020) Radiocarbon Dating of Small-sized Foraminifer Samples: Insights into Marine sediment Mixing. Radiocarbon, 62 (2). pp. 313-333. ISSN 0033-8222 DOI

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Radiocarbon (14C) can be used to build absolute chronologies and reconstruct ocean ventilation over the last 40 ka. Sample size requirements have restricted 14C measurements in marine cores with low foraminifer content, impeding 14C-based studies focused on abrupt climate events. Recent developments have demonstrated that small-sized foraminifer samples can now be dated using a gas introduction system at the cost of a small decrease in precision. We explore the potential of gas measurements on benthic and planktonic foraminifers from core SU90-08 (43°03′1″N, 30°02′5″W, 3080 m). Gas measurements are accurate, reproducible within 2σ uncertainty and comparable to graphite measurements. Both techniques yield negative 14C benthic-planktonic (B-P) age-offsets after Heinrich event 1. We argue that negative B-P ages result from bioturbation and changes in foraminifer abundances, with the chance of negative B-P especially increased when the 14C age gradient between the deep and surface waters is decreased. Small-sized 14C measurements seem to capture the variance of the foraminifera age distribution, revealing the active mixing in those archives. Sediment deposition and mixing effects possibly pose a greater obstacle for past 14C-based dating and ocean ventilation reconstructions than the measurement precision itself, particularly in relatively low sedimentation rate settings.

Item Type: Article
Additional Information: © 2020 by the Arizona Board of Regents on behalf of the University of Arizona
Uncontrolled Keywords: 2020AREP; IA76
Subjects: 01 - Climate Change and Earth-Ocean Atmosphere Systems
Divisions: 01 - Climate Change and Earth-Ocean Atmosphere Systems
07 - Gold Open Access
Journal or Publication Title: Radiocarbon
Volume: 62
Page Range: pp. 313-333
Identification Number:
Depositing User: Sarah Humbert
Date Deposited: 14 Dec 2020 19:49
Last Modified: 14 Dec 2020 19:49

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