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Osmium and lithium isotope evidence for weathering feedbacks linked to orbitally paced organic carbon burial and Silurian glaciations

Sproson, Adam D. ; Pogge von Strandmann, Philip A.E. ; Selby, David ; Jarochowska, Emilia ; Frýda, Jiří ; Hladil, Jindřich ; Loydell, David K. ; Slavík, Ladislav ; Calner, Mikael LU orcid and Maier, Georg , et al. (2022) In Earth and Planetary Science Letters 577.
Abstract

The Ordovician (∼487 to 443 Ma) ended with the formation of extensive Southern Hemisphere ice sheets, known as the Hirnantian glaciation, and the second largest mass extinction in Earth History. It was followed by the Silurian (∼443 to 419 Ma), one of the most climatically unstable periods of the Phanerozoic as evidenced by several large scale (>5‰) carbon isotope (δ13C) perturbations associated with further extinction events. Despite several decades of research, the cause of these environmental instabilities remains enigmatic. Here, we provide osmium (187Os/188Os) and lithium (δ7Li) isotope measurements of marine sedimentary rocks that cover four Silurian δ13C excursions. Osmium... (More)

The Ordovician (∼487 to 443 Ma) ended with the formation of extensive Southern Hemisphere ice sheets, known as the Hirnantian glaciation, and the second largest mass extinction in Earth History. It was followed by the Silurian (∼443 to 419 Ma), one of the most climatically unstable periods of the Phanerozoic as evidenced by several large scale (>5‰) carbon isotope (δ13C) perturbations associated with further extinction events. Despite several decades of research, the cause of these environmental instabilities remains enigmatic. Here, we provide osmium (187Os/188Os) and lithium (δ7Li) isotope measurements of marine sedimentary rocks that cover four Silurian δ13C excursions. Osmium and Li isotope records resemble those previously recorded for the Hirnantian glaciation suggesting a similar causal mechanism. When combined with a new dynamic carbon-osmium-lithium biogeochemical model we suggest that astronomical forcing of the marine organic carbon cycle, as opposed to a decline in volcanic arc degassing or the rise of early land plants, resulted in drawdown of atmospheric CO2, triggering continental scale glaciation, intense global cooling and eustatic sea-level lows recognised in the geological record. Lower atmospheric pCO2 and temperatures during the Hirnantian and Silurian glaciations suppressed CO2 removal by silicate weathering, driving 187Os/188Os and δ7Li variability, supporting the existence of climate-regulating feedbacks.

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publication status
published
subject
keywords
eccentricity and precession, Hirnantian glaciation, orbital obliquity, osmium (Os/Os) and lithium (δLi) isotopes, silicate weathering, Silurian palaeoclimate
in
Earth and Planetary Science Letters
volume
577
article number
117260
publisher
Elsevier
external identifiers
  • scopus:85118509507
ISSN
0012-821X
DOI
10.1016/j.epsl.2021.117260
language
English
LU publication?
yes
additional info
Publisher Copyright: © 2021 Elsevier B.V.
id
0436b8a8-8146-4873-b2fb-ced14ab66293
date added to LUP
2021-11-22 10:54:13
date last changed
2023-03-08 02:44:33
@article{0436b8a8-8146-4873-b2fb-ced14ab66293,
  abstract     = {{<p>The Ordovician (∼487 to 443 Ma) ended with the formation of extensive Southern Hemisphere ice sheets, known as the Hirnantian glaciation, and the second largest mass extinction in Earth History. It was followed by the Silurian (∼443 to 419 Ma), one of the most climatically unstable periods of the Phanerozoic as evidenced by several large scale (&gt;5‰) carbon isotope (δ<sup>13</sup>C) perturbations associated with further extinction events. Despite several decades of research, the cause of these environmental instabilities remains enigmatic. Here, we provide osmium (<sup>187</sup>Os/<sup>188</sup>Os) and lithium (δ<sup>7</sup>Li) isotope measurements of marine sedimentary rocks that cover four Silurian δ<sup>13</sup>C excursions. Osmium and Li isotope records resemble those previously recorded for the Hirnantian glaciation suggesting a similar causal mechanism. When combined with a new dynamic carbon-osmium-lithium biogeochemical model we suggest that astronomical forcing of the marine organic carbon cycle, as opposed to a decline in volcanic arc degassing or the rise of early land plants, resulted in drawdown of atmospheric CO<sub>2</sub>, triggering continental scale glaciation, intense global cooling and eustatic sea-level lows recognised in the geological record. Lower atmospheric pCO<sub>2</sub> and temperatures during the Hirnantian and Silurian glaciations suppressed CO<sub>2</sub> removal by silicate weathering, driving <sup>187</sup>Os/<sup>188</sup>Os and δ<sup>7</sup>Li variability, supporting the existence of climate-regulating feedbacks.</p>}},
  author       = {{Sproson, Adam D. and Pogge von Strandmann, Philip A.E. and Selby, David and Jarochowska, Emilia and Frýda, Jiří and Hladil, Jindřich and Loydell, David K. and Slavík, Ladislav and Calner, Mikael and Maier, Georg and Munnecke, Axel and Lenton, Timothy M.}},
  issn         = {{0012-821X}},
  keywords     = {{eccentricity and precession; Hirnantian glaciation; orbital obliquity; osmium (Os/Os) and lithium (δLi) isotopes; silicate weathering; Silurian palaeoclimate}},
  language     = {{eng}},
  month        = {{01}},
  publisher    = {{Elsevier}},
  series       = {{Earth and Planetary Science Letters}},
  title        = {{Osmium and lithium isotope evidence for weathering feedbacks linked to orbitally paced organic carbon burial and Silurian glaciations}},
  url          = {{http://dx.doi.org/10.1016/j.epsl.2021.117260}},
  doi          = {{10.1016/j.epsl.2021.117260}},
  volume       = {{577}},
  year         = {{2022}},
}