Reconstruction of paleo-ocean redox environment during the Late Permian Wuchiapingian， Upper Yangtze

Key words: 
• Late Permian /
• Ce anomaly /
• Ocean anoxia /
• Biological recovery /
• Upper Yangtze

Abstract: [Objective] After the End-Guadalupian extinction, the global biodiversity gradually recovered in the Late Permian. However, the specific relationship between biological recovery during this period and paleo-ocean redox condition remains unclear. [Method] To further determine the evolution characteristics of the redox condition of shallow waters in the Late Permian, the Wujiaping Formation in the Shangsi section of the northern margin of the Yangtze Block with high-resolution time frame constraints was selected as the research object. Detailed sedimentological and geochemical studies have been employed to reconstruct the marine redox environment of the Wujiaping Formation in the Late Permian.[Results] The results indicate that: (1) Based on the systematic changes of carbon isotope and cerium anomaly indicators, the entire geochemical profiles can be divided into three stages: Stage I exhibits a relatively positive carbon isotope shift, and the seawater tends towards an oxic environment; stage II shows a rapidly negative carbon isotope shift, and the ocean transitions to an anoxic environment; in stage III, the carbon isotopes are generally stable, and the anoxic conditions wane. (2) The global carbon cycle fluctuations during the Wuchiapingian can be observed evidently in various regions worldwide, and the carbon isotope compositions transform from a positive shift in the early period to a negative bias in the mid-period. (3) In the early Wuchiapingian, the gradual recovery of marine biota in the photic zone led to increased primary productivity and photosynthesis. During this time, the cool climate facilitated current circulation and atmosphere-ocean oxygen exchange, leading to an overall oxic environment; With the subsequent warming climate and the demise of the Late Paleozoic Ice Age, the weakening of ocean ventilation and the rise of sea level jointly drove the significant expansion of the oxygen minimum zone, transforming the ocean into an anoxic environment. [Conclusion] This study aimed to reconstruct the redox evolution process of the shallow marine environment during the Late Permian Wuchiapingian. Combining relevant environmental indicators, further explores the carbon cycle fluctuations, redox condition, and their deep connections with biological evolution during this period.