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Re-Os geochronology for the Cambrian SPICE event : Insights into euxinia and enhanced continental weathering from radiogenic isotopes

Rooney, Alan D. ; Millikin, Alexie E.G. and Ahlberg, Per LU (2022) In Geology 50(6). p.716-720
Abstract

The late Cambrian Steptoean positive carbon isotope excursion (SPICE) represents a major perturbation to the global carbon cycle and was associated with trilobite extinctions and expansion of anoxic and/or euxinic water masses during episodes of eustatic sea-level change. We present a new Re-Os age together with Os and Nd isotope stratigraphy and major and trace-element data from the Alum Shale Formation (Scania, Sweden). The Re-Os age of 494.6 ± 2.9 Ma is from the interval of peak δ13Corg values, providing the first radiometric age constraint for this Cambrian carbon isotope excursion, interpreted as a possible pre-Mesozoic ocean anoxia event, and the timing of biomere-level extinctions. The Os isotope... (More)

The late Cambrian Steptoean positive carbon isotope excursion (SPICE) represents a major perturbation to the global carbon cycle and was associated with trilobite extinctions and expansion of anoxic and/or euxinic water masses during episodes of eustatic sea-level change. We present a new Re-Os age together with Os and Nd isotope stratigraphy and major and trace-element data from the Alum Shale Formation (Scania, Sweden). The Re-Os age of 494.6 ± 2.9 Ma is from the interval of peak δ13Corg values, providing the first radiometric age constraint for this Cambrian carbon isotope excursion, interpreted as a possible pre-Mesozoic ocean anoxia event, and the timing of biomere-level extinctions. The Os isotope chemostratigraphic profile can be explained by an increase in terrigenous weathering prior to the SPICE, potentially driven by sea-level fall, and in agreement with enhanced nutrient supply, primary productivity, and organic matter burial as the driver of the SPICE event. Post-SPICE, the Os isotopes become increasingly unradiogenic; however, invariant εNd(t) values argue against a change in provenance and instead support a decrease in the continental weathering flux, possibly related to eustatic sea-level rise.

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author
; and
organization
publishing date
type
Contribution to journal
publication status
published
subject
in
Geology
volume
50
issue
6
pages
716 - 720
publisher
Geological Society of America
external identifiers
  • scopus:85131078402
ISSN
0091-7613
DOI
10.1130/G49833.1
language
English
LU publication?
yes
additional info
Funding Information: We thank S. Anseeuw and D. Skarzynski for laboratory and field assistance. This manuscript was greatly improved after constructive criticism from Ben Gill, David van Acken, Jim Schiffbauer, and an anonymous reviewer. Publisher Copyright: © 2022. Geological Society of America. For permission to copy, contact editing@geosociety.org.
id
9945dd6d-7b4c-44a5-9c47-50cf9c7981cd
date added to LUP
2022-12-30 12:57:49
date last changed
2023-03-21 16:39:18
@article{9945dd6d-7b4c-44a5-9c47-50cf9c7981cd,
  abstract     = {{<p>The late Cambrian Steptoean positive carbon isotope excursion (SPICE) represents a major perturbation to the global carbon cycle and was associated with trilobite extinctions and expansion of anoxic and/or euxinic water masses during episodes of eustatic sea-level change. We present a new Re-Os age together with Os and Nd isotope stratigraphy and major and trace-element data from the Alum Shale Formation (Scania, Sweden). The Re-Os age of 494.6 ± 2.9 Ma is from the interval of peak δ<sup>13</sup>C<sub>org </sub>values, providing the first radiometric age constraint for this Cambrian carbon isotope excursion, interpreted as a possible pre-Mesozoic ocean anoxia event, and the timing of biomere-level extinctions. The Os isotope chemostratigraphic profile can be explained by an increase in terrigenous weathering prior to the SPICE, potentially driven by sea-level fall, and in agreement with enhanced nutrient supply, primary productivity, and organic matter burial as the driver of the SPICE event. Post-SPICE, the Os isotopes become increasingly unradiogenic; however, invariant εNd<sub>(t)</sub> values argue against a change in provenance and instead support a decrease in the continental weathering flux, possibly related to eustatic sea-level rise.</p>}},
  author       = {{Rooney, Alan D. and Millikin, Alexie E.G. and Ahlberg, Per}},
  issn         = {{0091-7613}},
  language     = {{eng}},
  number       = {{6}},
  pages        = {{716--720}},
  publisher    = {{Geological Society of America}},
  series       = {{Geology}},
  title        = {{Re-Os geochronology for the Cambrian SPICE event : Insights into euxinia and enhanced continental weathering from radiogenic isotopes}},
  url          = {{http://dx.doi.org/10.1130/G49833.1}},
  doi          = {{10.1130/G49833.1}},
  volume       = {{50}},
  year         = {{2022}},
}