Radiocarbon Dating of Small-sized Foraminifer Samples: Insights into Marine sediment Mixing - Université Claude Bernard Lyon 1 Accéder directement au contenu
Article Dans Une Revue Radiocarbon Année : 2020

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

Résumé

Radiocarbon (14 C) can be used to build absolute chronologies and reconstruct ocean ventilation over the last 40 ka. Sample size requirements have restricted 14 C measurements in marine cores with low foraminifer content, impeding 14 C-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 0 1 00 N, 30°02 0 5 00 W, 3080 m). Gas measurements are accurate, reproducible within 2σ uncertainty and comparable to graphite measurements. Both techniques yield negative 14 C 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 14 C age gradient between the deep and surface waters is decreased. Small-sized 14 C 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 14 C-based dating and ocean ventilation reconstructions than the measurement precision itself, particularly in relatively low sedimentation rate settings.
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Dates et versions

hal-02884300 , version 1 (30-10-2020)

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Lise Missiaen, Lukas Wacker, Bryan C. Lougheed, Luke C. Skinner, Irka Hajdas, et al.. Radiocarbon Dating of Small-sized Foraminifer Samples: Insights into Marine sediment Mixing. Radiocarbon, 2020, 62 (2), pp.313-333. ⟨10.1017/RDC.2020.13⟩. ⟨hal-02884300⟩
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