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Oxygen isotope-based evidence for stepwise climate cooling aligns with the tripartite division of the Ordovician

Zhang, Zhutong ; Wu, Rongchang ; Lehnert, Oliver ; Calner, Mikael LU orcid ; Rasmussen, Christian M.Ø. ; Tang, Guo Qiang and Li, Xian Hua (2026) In Global and Planetary Change 257.
Abstract

The Ordovician Period includes two major macroevolutionary events: the Great Ordovician Biodiversification Event (GOBE) and the Late Ordovician Mass Extinction (LOME), alongside a fundamental climate transition from a greenhouse to an icehouse state. Although both biological events occurred during relatively short-term global cooling conditions, their starkly contrasting biotic responses remain poorly understood. Here, we present high-resolution conodont apatite δ18O records from Sweden combined with global data to reconstruct a stepwise seawater temperature decline from ∼43.7 °C in the Floian to ∼25.1 °C by the late Katian. Three discrete periods of global cooling occurred at 471.2–469 Ma (CE1), 460.2–456.1 Ma (CE2), and... (More)

The Ordovician Period includes two major macroevolutionary events: the Great Ordovician Biodiversification Event (GOBE) and the Late Ordovician Mass Extinction (LOME), alongside a fundamental climate transition from a greenhouse to an icehouse state. Although both biological events occurred during relatively short-term global cooling conditions, their starkly contrasting biotic responses remain poorly understood. Here, we present high-resolution conodont apatite δ18O records from Sweden combined with global data to reconstruct a stepwise seawater temperature decline from ∼43.7 °C in the Floian to ∼25.1 °C by the late Katian. Three discrete periods of global cooling occurred at 471.2–469 Ma (CE1), 460.2–456.1 Ma (CE2), and 443–442.4 Ma (CE3), with rates of 5–6 °C/Myr, 2–3 °C/Myr, and > 15 °C/Myr. Hence, the three steps coincide with the tri-partite Ordovician series boundaries. CE1 aligns with the initiation of the GOBE, while CE3 coincides with the LOME. This indicates that cooling regulated both the GOBE and the LOME, framing possible end-member states of organismal homeostasis. During CE1, the transition from warm to temperate conditions occurred at a relatively moderate cooling rate, reaching an optimal window for promoting biodiversity growth. In contrast, during CE3, the shift from temperate to cold conditions involved a more rapid cooling rate, exceeding organismal thresholds and negatively impacting biodiversity. These three cooling episodes coincide with a decline in seawater 87Sr/86Sr suggesting enhanced weathering and CO2 drawdown, further reinforced by the expansion of marine algae and land vegetation.

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author
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organization
publishing date
type
Contribution to journal
publication status
published
subject
keywords
Baltica, Climate change, Conodont apatite, Metazoan homeostatic optimum, Ordovician biodiversity change, SIMS
in
Global and Planetary Change
volume
257
article number
105246
publisher
Elsevier
external identifiers
  • scopus:105024897590
ISSN
0921-8181
DOI
10.1016/j.gloplacha.2025.105246
language
English
LU publication?
yes
id
f299a8c3-0902-45bb-bfe3-05cd145ca775
date added to LUP
2026-03-09 14:40:34
date last changed
2026-03-10 10:21:20
@article{f299a8c3-0902-45bb-bfe3-05cd145ca775,
  abstract     = {{<p>The Ordovician Period includes two major macroevolutionary events: the Great Ordovician Biodiversification Event (GOBE) and the Late Ordovician Mass Extinction (LOME), alongside a fundamental climate transition from a greenhouse to an icehouse state. Although both biological events occurred during relatively short-term global cooling conditions, their starkly contrasting biotic responses remain poorly understood. Here, we present high-resolution conodont apatite δ<sup>18</sup>O records from Sweden combined with global data to reconstruct a stepwise seawater temperature decline from ∼43.7 °C in the Floian to ∼25.1 °C by the late Katian. Three discrete periods of global cooling occurred at 471.2–469 Ma (CE1), 460.2–456.1 Ma (CE2), and 443–442.4 Ma (CE3), with rates of 5–6 °C/Myr, 2–3 °C/Myr, and &gt; 15 °C/Myr. Hence, the three steps coincide with the tri-partite Ordovician series boundaries. CE1 aligns with the initiation of the GOBE, while CE3 coincides with the LOME. This indicates that cooling regulated both the GOBE and the LOME, framing possible end-member states of organismal homeostasis. During CE1, the transition from warm to temperate conditions occurred at a relatively moderate cooling rate, reaching an optimal window for promoting biodiversity growth. In contrast, during CE3, the shift from temperate to cold conditions involved a more rapid cooling rate, exceeding organismal thresholds and negatively impacting biodiversity. These three cooling episodes coincide with a decline in seawater <sup>87</sup>Sr/<sup>86</sup>Sr suggesting enhanced weathering and CO<sub>2</sub> drawdown, further reinforced by the expansion of marine algae and land vegetation.</p>}},
  author       = {{Zhang, Zhutong and Wu, Rongchang and Lehnert, Oliver and Calner, Mikael and Rasmussen, Christian M.Ø. and Tang, Guo Qiang and Li, Xian Hua}},
  issn         = {{0921-8181}},
  keywords     = {{Baltica; Climate change; Conodont apatite; Metazoan homeostatic optimum; Ordovician biodiversity change; SIMS}},
  language     = {{eng}},
  publisher    = {{Elsevier}},
  series       = {{Global and Planetary Change}},
  title        = {{Oxygen isotope-based evidence for stepwise climate cooling aligns with the tripartite division of the Ordovician}},
  url          = {{http://dx.doi.org/10.1016/j.gloplacha.2025.105246}},
  doi          = {{10.1016/j.gloplacha.2025.105246}},
  volume       = {{257}},
  year         = {{2026}},
}