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Article Dans Une Revue Geology Année : 2020

Ocean acidification during the early Toarcian extinction event: Evidence from boron isotopes in brachiopods

Tamás Müller
  • Fonction : Auteur
Hana Jurikova
  • Fonction : Auteur
Marcus Gutjahr
  • Fonction : Auteur
Adam Tomašových
  • Fonction : Auteur
Jan Schlögl
  • Fonction : Auteur
Volker Liebetrau
  • Fonction : Auteur
Luís Duarte
  • Fonction : Auteur
Rastislav Milovský
  • Fonction : Auteur
Guillaume Suan
  • Fonction : Auteur
Bernard Pittet
  • Fonction : Auteur
Anton Eisenhauer
  • Fonction : Auteur

Résumé

Abstract The loss of carbonate production during the Toarcian Oceanic Anoxic Event (T-OAE, ca. 183 Ma) is hypothesized to have been at least partly triggered by ocean acidification linked to magmatism from the Karoo-Ferrar large igneous province (southern Africa and Antarctica). However, the dynamics of acidification have never been directly quantified across the T-OAE. Here, we present the first record of temporal evolution of seawater pH spanning the late Pliensbachian and early Toarcian from the Lusitanian Basin (Portugal) reconstructed on the basis of boron isotopic composition (δ11B) of brachiopod shells. δ11B declines by ∼1‰ across the Pliensbachian-Toarcian boundary (Pl-To) and attains the lowest values (∼12.5‰) just prior to and within the T-OAE, followed by fluctuations and a moderately increasing trend afterwards. The decline in δ11B coincides with decreasing bulk CaCO3 content, in parallel with the two-phase decline in carbonate production observed at global scales and with changes in pCO2 derived from stomatal indices. Seawater pH had declined significantly already prior to the T-OAE, probably due to the repeated emissions of volcanogenic CO2. During the earliest phase of the T-OAE, pH increased for a short period, likely due to intensified continental weathering and organic carbon burial, resulting in atmospheric CO2 drawdown. Subsequently, pH dropped again, reaching the minimum in the middle of the T-OAE. The early Toarcian marine extinction and carbonate collapse were thus driven, in part, by ocean acidification, similar to other Phanerozoic events caused by major CO2 emissions and warming.

Dates et versions

hal-03860153 , version 1 (18-11-2022)

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Citer

Tamás Müller, Hana Jurikova, Marcus Gutjahr, Adam Tomašových, Jan Schlögl, et al.. Ocean acidification during the early Toarcian extinction event: Evidence from boron isotopes in brachiopods. Geology, 2020, 48 (12), pp.1184-1188. ⟨10.1130/G47781.1⟩. ⟨hal-03860153⟩
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