On the tuning of plateaus in atmospheric and oceanic <sup>14</sup>C records to derive calendar chronologies of deep-sea cores and records of <sup>14</sup>C marine reservoir age changes
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Published:2021-08-16
Issue:4
Volume:17
Page:1701-1725
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ISSN:1814-9332
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Container-title:Climate of the Past
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language:en
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Short-container-title:Clim. Past
Author:
Bard Edouard,Heaton Timothy J.
Abstract
Abstract. We assess the methodology of the so-called 14C plateau tuning (PT) technique used to date marine sediment records and determine 14C marine reservoir ages (MRAs) as recently reviewed by Sarnthein et al. (2020). The main identified problems are linked to the assumption of constant MRA
during 14C age plateaus; the lack of consideration of foraminifera
abundance changes coupled to bioturbation that can create spurious plateaus
in marine sediments; the assumption that plateaus have the same shapes and
durations in atmospheric and oceanic records; the implication that
atmospheric 14C / 12C peaked instantaneously from one plateau to the next; that the 14C plateaus represent 82 % of the total time spent between 14 000 and 29 000 cal yr BP, whereas during the remaining 18 % of
the time, the radiocarbon clock was running almost 5 times faster than the
radioactive decay; that the sparsity, combined with the level of analytical
uncertainties and additional noise, in both atmospheric and marine data do
not currently allow one to reliably or robustly identify plateaus (should
they exist) beyond 15 000 cal yr BP; and that the determination and
identification of plateaus in the deep-sea cores is reliant upon significant
changes in sedimentation rate within those marine sediments which are, a
priori, unknown and are not verified with an independent method. The concerns we raise are supported and strengthened with carbon cycle
box model experiments and statistical simulations of pseudo-atmospheric and
pseudo-marine records, allowing us to question the ability to identify and
tune 14C age plateaus in the context of noisy and sparse data.
Publisher
Copernicus GmbH
Subject
Paleontology,Stratigraphy,Global and Planetary Change
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