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Mid-Ludfordian uranium isotope records distinguish the role of expansive marine anoxia in global carbon cycle dynamics during the late Silurian Lau/Kozlowskii bioevent

del Rey, Álvaro ; Frýda, Jiří ; Calner, Mikael LU orcid ; Frýdová, Barbora ; Zhang, Feifei ; Wang, Changle ; Planavsky, Noah and Dahl, Tais W. (2023) In Global and Planetary Change 229.
Abstract

The late Silurian Lau/Kozlowskii bioevent marks a time interval with substantial loss in marine biodiversity linked to the largest positive carbon isotope excursion (Mid-Ludfordian CIE; MLCIE) recorded in the Phanerozoic (δ13Ccarb peaks at +8–10‰). The positive δ13C excursion and the extinctions have been linked to increased marine productivity (ocean eutrophication), leading to increased organic carbon burial, and expansion of marine anoxia in shallow continental seas. To explore this idea, we reconstruct the contemporaneous global extent of marine anoxia using uranium (U) isotopes from Ludfordian marine carbonates sampled from two widely spaced paleogeographic locations. Our δ238U results... (More)

The late Silurian Lau/Kozlowskii bioevent marks a time interval with substantial loss in marine biodiversity linked to the largest positive carbon isotope excursion (Mid-Ludfordian CIE; MLCIE) recorded in the Phanerozoic (δ13Ccarb peaks at +8–10‰). The positive δ13C excursion and the extinctions have been linked to increased marine productivity (ocean eutrophication), leading to increased organic carbon burial, and expansion of marine anoxia in shallow continental seas. To explore this idea, we reconstruct the contemporaneous global extent of marine anoxia using uranium (U) isotopes from Ludfordian marine carbonates sampled from two widely spaced paleogeographic locations. Our δ238U results demonstrate that the overall MLCIE was not coupled to expanding marine anoxia and a presumed associated increased marine primary productivity. Instead, a time interval of widespread global anoxia occurred only before and during the onset of the MLCIE (up to end of P. siluricus conodont zone; ca. δ13C ∼ 2.6‰), which is when the extinctions took place. Strong climatic variability at this time suggests anoxia and climate change led to the extinctions of the Lau/Kozlowskii bioevent. The major part of the rise to the peak (δ13C ∼ 10‰) and falling limb of the MLCIE was not coupled with corresponding changes in δ238U values. Thus, increased marine primary productivity and marine anoxia may have caused the initial carbon cycle disturbance and the extinctions but was not a main driver for the continued growth and exceptional magnitude of the MLCIE.

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author
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organization
publishing date
type
Contribution to journal
publication status
published
subject
keywords
Late Silurian, Lau/Kozlowskii bioevent, Marine carbonates, Ocean anoxia, U isotopes, Uranium cycle
in
Global and Planetary Change
volume
229
article number
104248
publisher
Elsevier
external identifiers
  • scopus:85172150229
ISSN
0921-8181
DOI
10.1016/j.gloplacha.2023.104248
language
English
LU publication?
yes
id
9122d219-f094-4ff5-8de6-bc9c7f3a96f3
date added to LUP
2023-12-06 09:04:23
date last changed
2023-12-06 09:04:31
@article{9122d219-f094-4ff5-8de6-bc9c7f3a96f3,
  abstract     = {{<p>The late Silurian Lau/Kozlowskii bioevent marks a time interval with substantial loss in marine biodiversity linked to the largest positive carbon isotope excursion (Mid-Ludfordian CIE; MLCIE) recorded in the Phanerozoic (δ<sup>13</sup>C<sub>carb</sub> peaks at +8–10‰). The positive δ<sup>13</sup>C excursion and the extinctions have been linked to increased marine productivity (ocean eutrophication), leading to increased organic carbon burial, and expansion of marine anoxia in shallow continental seas. To explore this idea, we reconstruct the contemporaneous global extent of marine anoxia using uranium (U) isotopes from Ludfordian marine carbonates sampled from two widely spaced paleogeographic locations. Our δ<sup>238</sup>U results demonstrate that the overall MLCIE was not coupled to expanding marine anoxia and a presumed associated increased marine primary productivity. Instead, a time interval of widespread global anoxia occurred only before and during the onset of the MLCIE (up to end of P. siluricus conodont zone; ca. δ<sup>13</sup>C ∼ 2.6‰), which is when the extinctions took place. Strong climatic variability at this time suggests anoxia and climate change led to the extinctions of the Lau/Kozlowskii bioevent. The major part of the rise to the peak (δ<sup>13</sup>C ∼ 10‰) and falling limb of the MLCIE was not coupled with corresponding changes in δ<sup>238</sup>U values. Thus, increased marine primary productivity and marine anoxia may have caused the initial carbon cycle disturbance and the extinctions but was not a main driver for the continued growth and exceptional magnitude of the MLCIE.</p>}},
  author       = {{del Rey, Álvaro and Frýda, Jiří and Calner, Mikael and Frýdová, Barbora and Zhang, Feifei and Wang, Changle and Planavsky, Noah and Dahl, Tais W.}},
  issn         = {{0921-8181}},
  keywords     = {{Late Silurian; Lau/Kozlowskii bioevent; Marine carbonates; Ocean anoxia; U isotopes; Uranium cycle}},
  language     = {{eng}},
  publisher    = {{Elsevier}},
  series       = {{Global and Planetary Change}},
  title        = {{Mid-Ludfordian uranium isotope records distinguish the role of expansive marine anoxia in global carbon cycle dynamics during the late Silurian Lau/Kozlowskii bioevent}},
  url          = {{http://dx.doi.org/10.1016/j.gloplacha.2023.104248}},
  doi          = {{10.1016/j.gloplacha.2023.104248}},
  volume       = {{229}},
  year         = {{2023}},
}