The dynamic ocean redox evolution during the late Cambrian SPICE: Evidence from the I/Ca proxy

Ruliang He, Alexandre Pohl, Ashley Prow, Ganqing Jiang, Chin Chai Huan, Matthew R. Saltzman, Zunli Lu

Research output: Contribution to journalArticlepeer-review


The late Cambrian Steptoean positive carbon isotope excursion (SPICE) is a distinct chemostratigraphic feature of the Paleozoic, marked by a 4–5‰ shift in carbonate δ13C that has been recognized across the globe during the Paibian Stage. The SPICE may be related to enhanced burial of organic matter and pyrite during the expansion of marine euxinia, which as a source of O2 also results in a pulse of atmospheric oxygen. However, geochemical proxies have not clearly illustrated how the ocean redox evolved with atmospheric oxygen changes during the SPICE. This study presents new carbonate I/Ca data, a redox proxy for the upper ocean, from three basins. I/Ca values are low at Great Basin and South China from early into the peak of SPICE, indicating generally anoxic conditions in shallow waters. The overall increasing trend in I/Ca through the peak and recovery phase of the SPICE roughly correlates with the previously modeled rise in atmospheric oxygen. Spatially, the Georgina Basin (Mt. Whelan) might have recorded a relatively more oxic upper ocean compared to the Great Basin and South China. Earth system model simulations also demonstrate the importance of paleogeographic and oceanographic settings on local redox conditions, highlighting the redox heterogeneity during the SPICE.

Original languageEnglish (US)
Article number104354
JournalGlobal and Planetary Change
StatePublished - Feb 2024


  • Earth system model
  • I/Ca
  • Late Cambrian
  • Redox condition

ASJC Scopus subject areas

  • Global and Planetary Change
  • Oceanography


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