Upwelling-driven biogenic silica accumulation in the Yangtze Sea, South China during Late Ordovician to Early Silurian time: A possible link with the global climatic transitions

• Published in: Sedimentary geology 2024-03, Vol.461, p.106571, Article 106571
• Main Authors: Zan, Bowen, Mou, Chuanlong, Lash, Gary G., Wang, Qiyu, Wang, Xiuqing, Le Heron, Daniel Paul, Yan, Jiaxin, Zhang, Zhifeng, Hou, Qian, Xia, Yu, Yao, Shengyang
• Format: Article
• Language: English
• Subjects: Biogenic silica; Climate change; Radiolarian; Upwelling
• ISSN: 0037-0738; 1879-0968
• DOI: 10.1016/j.sedgeo.2023.106571

Silica accumulation in the Yangtze Sea during the Ordovician–Silurian (O–S) transition appears to have coincided with global climatic fluctuations, widespread upwelling, and volcanism. There is a need to further evaluate their respective contributions to silica deposition and potential relationships among these factors. The current study selected siliceous deposits in the Wufeng and Longmaxi Formations from four sections spanning the inner to outer Yangtze Sea, South China, to gain a deeper understanding of the climatic and oceanographic evolution associated with silica enrichment. Al/(Al + Fe + Mn) values, the presence of radiolarians, and Si isotope values of samples recovered from the investigated shale successions offer compelling evidence that the silica is largely of biogenic origin with some terrigenous contributions. Further, various productivity and redox proxies suggest that biogenic silica (BSi) accumulated under conditions of enhanced marine productivity and anoxic bottom water conditions. Hg/TOC and Zr/Al2O3 profiles suggest intermittent volcanism during the BSi deposition in the Yangtze Sea. However, the lack of correlation between BSi and Hg/TOC values indicates that volcanic iron fertilization was not responsible for BSi accumulation. Instead, most BSi-rich samples are dominated by low MnEF × CoEF values (