Two deep marine oxygenation events during the Permian-Triassic boundary interval in South China: relationship with ocean circulation and marine primary productivity

Ge, Yuzhu; Bond, David P.G.

Abstract

Marine redox conditions through the Permian-Triassic (P-T) boundary interval have been intensively studied in South China with different redox proxies and from different sections. However, the resultant interpretations are inconsistent and sometimes even controversial, thereby impeding an overall understanding of global environmental changes and of causes for the P-T mass extinction events. This study summarizes and reevaluates these previous studies. The apparent inconsistent interpretations in some of these previous studies may be partly because some redox proxies (e.g., pyrite framboid size distribution, iron speciation, biomarkers, U isotopes) are also influenced by early marine diagenesis and local ocean upwelling patterns; therefore they do not always reflect redox conditions in the overlying water column. Based on multiple redox proxies from P-T sections in different paleo-depth settings in South China, it is proposed that there were two deep marine oxygenation events during the P-T boundary interval. The first oxygenation event occurred immediately before and during the end-Permian mass extinction horizon; and the second event occurred during the H. parvus conodont zone of earliest Triassic following the P-T boundary. The first oxygenation event affected lower slope and basinal marine settings, whereas upper slope settings experienced an oxygen depletion. This first oxygenation event was also recorded in deep-marine settings of other localities in the Paleotethys and the Panthalassic Ocean and this may have been caused by a global enhancement of ocean circulation related to a general climate cooling associated with volcanic SO2 release from the Siberian Traps. The second oxygenation event affected only the upper slope marine settings in South China and is not yet recorded in the Panthalassic Ocean. The cause for the second event is suggested to have been driven by a reduction in marine primary productivity caused by shifting local patterns of ocean upwelling and nutrient cycling over the relatively restricted South China area. Conclusively, the complex P-T marine redox histories recorded at different paleo-depths in South China were driven by the combination of paleogeography, major climate changes, ocean circulation and marine productivity.

Citation

Ge, Y., & Bond, D. P. (2022). Two deep marine oxygenation events during the Permian-Triassic boundary interval in South China: relationship with ocean circulation and marine primary productivity. Earth-Science Reviews, 234, Article 104220. https://doi.org/10.1016/j.earscirev.2022.104220

• Journal Article Type: Review
• Acceptance Date: Oct 10, 2022
• Online Publication Date: Oct 14, 2022
• Publication Date: Nov 1, 2022
• Deposit Date: Oct 11, 2022
• Publicly Available Date: Oct 15, 2023
• Journal: Earth-Science Reviews
• Print ISSN: 0012-8252
• Publisher: Elsevier
• Peer Reviewed: Peer Reviewed
• Volume: 234
• Article Number: 104220
• DOI: https://doi.org/10.1016/j.earscirev.2022.104220
• Keywords: Permian-Triassic; South China; Oxygenation events; Ocean circulation; Marine productivity
• Public URL: https://hull-repository.worktribe.com/output/4094072