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Short communication : Resolving the discrepancy between U-Pb age estimates for the "Likhall" bed, a key level in the Ordovician timescale

Paul, André Navin ; Lindskog, Anders LU and Schaltegger, Urs (2024) In Geochronology 6(3). p.325-335
Abstract

The "Likhall"bed is a rare case of a single-age zircon population from a carbonate rock, which in this case is contextualised with remarkable biotic and environmental changes and with meteorite bombardment of Earth after an asteroid breakup in space. Published high-precision chemical abrasion isotope dilution thermal ionisation mass spectrometry (CA-ID-TIMS) U-Pb age estimates disagree on the typical precision of <0.1ĝ€¯% for a 206Pb/238U date, which has led to discrepancies in the interpretation of the timing of events and their possible cause-effect relationships. Here we evaluate the relative strengths, weaknesses, and discrepancies in the datasets published so far; propose strategies to overcome them; and present a new U-Pb... (More)

The "Likhall"bed is a rare case of a single-age zircon population from a carbonate rock, which in this case is contextualised with remarkable biotic and environmental changes and with meteorite bombardment of Earth after an asteroid breakup in space. Published high-precision chemical abrasion isotope dilution thermal ionisation mass spectrometry (CA-ID-TIMS) U-Pb age estimates disagree on the typical precision of <0.1ĝ€¯% for a 206Pb/238U date, which has led to discrepancies in the interpretation of the timing of events and their possible cause-effect relationships. Here we evaluate the relative strengths, weaknesses, and discrepancies in the datasets published so far; propose strategies to overcome them; and present a new U-Pb dataset with improved precision and accuracy. Ultimately, we find that domains of residual Pb loss are a significant source of age offset between previously published data, amplified by differences in data evaluation strategies. Our new dataset benefits from an improved chemical abrasion protocol resulting in a more complete mitigation of decay-damage-induced grain portions and points to a weighted mean age estimate of 466.37±0.14/0.18/0.53ĝ€¯Ma for the "Likhall"zircon population. This age is intermediate between previous estimates but outside of analytical uncertainty, and it provides a firm tie point for the Ordovician timescale.

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author
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organization
publishing date
type
Contribution to journal
publication status
published
subject
in
Geochronology
volume
6
issue
3
pages
11 pages
publisher
Copernicus GmbH
external identifiers
  • scopus:85198064572
ISSN
2628-3697
DOI
10.5194/gchron-6-325-2024
language
English
LU publication?
yes
id
73438e01-4804-44d9-8f1e-78e9bd72338a
date added to LUP
2024-09-23 13:03:04
date last changed
2024-09-23 13:04:15
@article{73438e01-4804-44d9-8f1e-78e9bd72338a,
  abstract     = {{<p>The "Likhall"bed is a rare case of a single-age zircon population from a carbonate rock, which in this case is contextualised with remarkable biotic and environmental changes and with meteorite bombardment of Earth after an asteroid breakup in space. Published high-precision chemical abrasion isotope dilution thermal ionisation mass spectrometry (CA-ID-TIMS) U-Pb age estimates disagree on the typical precision of &lt;0.1ĝ€¯% for a 206Pb/238U date, which has led to discrepancies in the interpretation of the timing of events and their possible cause-effect relationships. Here we evaluate the relative strengths, weaknesses, and discrepancies in the datasets published so far; propose strategies to overcome them; and present a new U-Pb dataset with improved precision and accuracy. Ultimately, we find that domains of residual Pb loss are a significant source of age offset between previously published data, amplified by differences in data evaluation strategies. Our new dataset benefits from an improved chemical abrasion protocol resulting in a more complete mitigation of decay-damage-induced grain portions and points to a weighted mean age estimate of 466.37±0.14/0.18/0.53ĝ€¯Ma for the "Likhall"zircon population. This age is intermediate between previous estimates but outside of analytical uncertainty, and it provides a firm tie point for the Ordovician timescale.</p>}},
  author       = {{Paul, André Navin and Lindskog, Anders and Schaltegger, Urs}},
  issn         = {{2628-3697}},
  language     = {{eng}},
  number       = {{3}},
  pages        = {{325--335}},
  publisher    = {{Copernicus GmbH}},
  series       = {{Geochronology}},
  title        = {{Short communication : Resolving the discrepancy between U-Pb age estimates for the "Likhall" bed, a key level in the Ordovician timescale}},
  url          = {{http://dx.doi.org/10.5194/gchron-6-325-2024}},
  doi          = {{10.5194/gchron-6-325-2024}},
  volume       = {{6}},
  year         = {{2024}},
}