Calcium isotopes support spatial redox gradients on the Tethys European margin across the Triassic-Jurassic boundary

Ashley N. Prow-Fleischer*, Zunli Lu, Clara L. Blättler, Tianchen He, Pulkit Singh, Preston Cosslett Kemeny, Jordan P. Todes, Alexandre Pohl, Tripti Bhattacharya, Bas van de Schootbrugge, Paul B. Wignall, Simona Todaro, Jonathan L. Payne

*Corresponding author for this work

Research output: Contribution to journalArticleAcademicpeer-review

Abstract

The end-Triassic mass extinction was among the most severe biotic crises of the Phanerozoic. It has been linked with the global expansion of marine anoxia, and the prolongation of these conditions within epeiric seas has been proposed as a cause for the suppression of biodiversity during the early Jurassic Hettangian Stage. Testing this interpretation is complicated by spatially heterogeneous patterns of local marine redox conditions within the western Tethys European Epicontinental Shelf. In this study, we assess the redox state within this region by focusing on two carbonate successions in Italy, a peritidal platform at Mount Sparagio, Sicily, and an offshore ramp deposit at Val Adrara in the Southern Alps. Based on previously published I/Ca ratios, these locations record distinct local background redox conditions, with Val Adrara showing a notably lower pre-extinction oxygen saturation state than Mount Sparagio. Here, we measure δ13C and δ18O at Mount Sparagio and δ44Ca and trace element ratios at both sites to identify the roles of mineralogical and diagenetic effects on the preservation of primary redox signals. A numerical framework of multiple elemental (Sr, Mg, Mn, I) and isotopic (δ13C, δ18O, δ44Ca, δ238U, and δ34SCAS) ratios was constructed to recognize modes of carbonate diagenesis and source-mixing in the data. While diagenesis is impossible to completely rule out, our state-of-the-art approach provides robust evidence against common forms of diagenetic alteration as the main drivers of the overall paleoredox proxy trends. Where the redox signals are largely preserved, we interpret differences in pre-extinction I/Ca between the two sites to reflect distinct local oxygenation states. Drawing from published Community Earth System Model simulations, we propose that ocean circulation and hydrological regime could have been important drivers of spatial heterogeneity in paleo-redox conditions across the European Epicontinental Shelf.

Original languageEnglish
Article number122530
JournalChemical Geology
Volume673
Early online date5 Dec 2024
DOIs
Publication statusPublished - 5 Feb 2025

Bibliographical note

Publisher Copyright:
© 2024

Keywords

  • Calcium isotope ratios
  • Carbonate-based redox proxies
  • Diagenesis
  • End Triassic mass extinction
  • Geochemical tracers

Fingerprint

Dive into the research topics of 'Calcium isotopes support spatial redox gradients on the Tethys European margin across the Triassic-Jurassic boundary'. Together they form a unique fingerprint.

Cite this