Implications of Giant Ooids for the Carbonate Chemistry of Early Triassic Seawater

Xiaowei Li, Elizabeth J. Trower, Daniel J. Lehrmann, Marcello Minzoni, Brian M. Kelley, Ellen K. Schaal, Demir Altiner, Meiyi Yu, Jonathan L. Payne

Research output: Contribution to journalArticlepeer-review

21 Scopus citations


Lower Triassic limestones contain giant ooids (>2 mm) along with other precipitated carbonate textures more typical of Precambrian strata. These features appear to have resulted from changes in seawater chemistry associated with the end-Permian mass extinction, but quantifying the carbonate chemistry of Early Triassic seawater has remained challenging. To constrain seawater carbonate saturation state, dissolved inorganic carbon, alkalinity, and pH, we applied a physicochemical model of ooid formation constrained by new size data on Lower Triassic ooids from south China, finding that the Triassic giant ooids require a higher carbonate saturation state than typifies modern sites of ooid formation. Model calculations indicate that Early Triassic oceans were at least seven times supersaturated with respect to aragonite and calcite. When combined with independent constraints on atmospheric pCO2 and oceanic [Ca2+], these findings require that Early Triassic oceans had more than twice the modern levels of dissolved inorganic carbon and alkalinity and a pH near 7.6.

Original languageEnglish (US)
Pages (from-to)156-161
Number of pages6
Issue number2
StatePublished - Sep 23 2021

All Science Journal Classification (ASJC) codes

  • Geology


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