Conodont calcium isotopic evidence for multiple shelf acidification events during the Early Triassic

Haijun Song, Huyue Song, Jinnan Tong, Gwyneth W. Gordon, Paul B. Wignall, Li Tian, Wang Zheng, Thomas J. Algeo, Lei Liang, Ruoyu Bai, Kui Wu, Ariel D. Anbar

Research output: Contribution to journalArticlepeer-review

21 Scopus citations


The marine calcium (Ca) cycle is controlled by rates of continental weathering, seawater pH, and carbonate deposition on the seafloor and is linked to atmospheric CO2, climate change, and marine biotic evolution. Here, we provide the first continuous seawater Ca isotope profile from conodont apatite in South China for the latest Permian to early Middle Triassic, revealing major fluctuations in the Early Triassic calcium cycle. Three episodes of decreasing conodont δ44/40Ca (by 0.16–0.23‰) occurred around the Permian-Triassic, Smithian-Spathian, and Olenekian-Anisian boundaries. The first episode, coincident with a negative excursion of carbonate carbon isotopes, global warming, oceanic anoxia, enhanced weathering, and sea-level fall, was likely caused by a combination of volcanic CO2 release, ocean acidification, a reduced skeletal carbonate sink, and enhanced weathering of shelf carbonates. The latter two episodes, coincident with positive excursions of carbon isotopes, global cooling, and oceanic anoxia, possibly resulted from upwelling-driven shelf acidification and reduced skeletal carbonate burial. All three events were associated with marine biotic diversity losses, demonstrating a link between the calcium cycle and mass extinctions.

Original languageEnglish (US)
Article number120038
JournalChemical Geology
StatePublished - Feb 20 2021


  • Ca isotope
  • Mass extinction
  • Permian-Triassic
  • Seawater chemistry
  • Smithian-Spathian
  • Upwelling

ASJC Scopus subject areas

  • Geology
  • Geochemistry and Petrology


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