Coupled δ44/40Ca, δ88/86Sr, and 87Sr/86Sr geochemistry across the end-Permian mass extinction event

Jiuyuan Wang*, Andrew D. Jacobson, Hua Zhang, Jahandar Ramezani, Bradley B. Sageman, Matthew T. Hurtgen, Samuel A. Bowring, Shu Zhong Shen

*Corresponding author for this work

Research output: Contribution to journalArticle

5 Scopus citations

Abstract

We report high-resolution, high-precision δ44/40Ca, δ88/86Sr, and 87Sr/86Sr records spanning the Permian-Triassic boundary (PTB) from the Meishan and Dajiang carbonate successions in south China. The goal of the study was to understand the behavior of Ca and Sr isotopes during a time period in Earth history characterized by severe biological and environmental perturbations, including a major mass extinction, flood basalt volcanism, ocean acidification, and sea level fluctuations. Dajiang displays negative δ44/40Ca and δ88/86Sr excursions and invariant 87Sr/86Sr ratios in the <60 kyr timeframe between the main extinction horizon and the PTB. The Meishan δ44/40Ca and δ88/86Sr records are generally shifted to higher values and display both synchronous and asynchronous trends relative to Dajiang. In addition, 87Sr/86Sr ratios at Meishan are significantly elevated and do not define a clear secular pattern. We reconcile diverse conceptual models for the dataset with the aid of supporting elemental and isotope measurements (e.g., Sr/Ca, δ13C, and δ18O), as well as sequential leaching experiments. The combined body of evidence indicates that Dajiang sediments experienced recrystallization and neomorphism under rock-buffered conditions that preserved primary signals. In contrast, the Meishan records display influences from both primary and secondary processes, including local differences in fractionation, fluid-buffered early marine diagenesis, and late stage diagenetic overprinting. The three isotopic records for Dajiang, and to some extent, the δ44/40Ca and δ88/86Sr records for Meishan, preserve information about the geochemistry of end-Permian seawater. We find that enhanced weathering of shelf carbonates during sea level fall provides the best explanation for rapidly decreasing seawater δ44/40Ca and δ88/86Sr values without affecting 87Sr/86Sr ratios.

Original languageEnglish (US)
Pages (from-to)143-165
Number of pages23
JournalGeochimica et Cosmochimica Acta
Volume262
DOIs
StatePublished - Oct 1 2019

Keywords

  • Calcium isotopes
  • Chemical weathering
  • Diagenesis
  • Radiogenic Sr isotopes
  • Stable Sr isotopes
  • end-Permian

ASJC Scopus subject areas

  • Geochemistry and Petrology

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