Carbon-Isotope Excursions Recorded in the Cambrian System, South China: Implications for Mass Extinctions and Sea-Level Fluctuations

• Published in: Journal of earth science (Wuhan, China) Vol. 29; no. 3; pp. 479 - 491
• Main Authors: Zuo, Jingxun, Peng, Shanchi, Qi, Yuping, Zhu, Xuejian, Bagnoli, Gabriella, Fang, Huaibin
• Format: Journal Article
• Language: English
• Published: Wuhan China University of Geosciences 01.06.2018; Springer Nature B.V; Henan Institute of Geological Survey, Zhengzhou 450001, China%State Key Laboratory of Palaeobiology and Stratigraphy, Nanjing Institute of Geology and Paleontology, Chinese Academy of Sciences, Nanjing 210008, China%Department of Earth Sciences, University of Pisa, Via S. Maria, 53, Pisa 56126, Italy
• Subjects: Biogeosciences; Cambrian; Carbon; Carbonates; Deep water; Deepwater drilling; Earth and Environmental Science; Earth Sciences; Eustatic changes; Fossils; Geochemistry; Geology; Geotechnical Engineering & Applied Earth Sciences; Isotopes; Marine invertebrates; Mass; Mass extinctions; Paleontology; Sea level; Variation; China; carbon-isotope excursion; Cambrian; mass extinction; South China; sea-level change
• ISSN: 1674-487X; 1867-111X
• DOI: 10.1007/s12583-017-0963-x

Cambrian carbonates with abundant fossils of agnostoid trilobites deposited on the southern slope (Jiangnan slope belt) of the Yangtze Platform and in the Jiangnan deepwater basin are well exposed in the Wangcun Section of western Hunan, South China, and in the Duibian A Section of western Zhejiang, southeastern China, respectively. To better understand the response of carbon-isotope excursions to depositional environment changes, mass extinctions and eustatic events, we collected 530 carbonate samples in fresh roadcut exposures of the two measured sections for analysis of carbon and oxygen isotopic compositions. Data of δ 13 C from the Wangcun Section, western Hunan, South China, demonstrate that the Cambrian carbon-isotope profile includes three remarkable positive excursions CPE wc -1, 2, 3 in the Upper Series 2, in the Lower and in the Middle Furongian Series. Three distinctive negative excursions CNE wc -1, 2, 3 were separately tested in the Lower Terreneuvian Series, Lower Series 3 and in the Upper Furongian Series. Similarly, in the corresponding horizons in the Duibian A Section, Zhejiang Province, southeastern China, three positive excursions CPE db -1, 2, 3 and three negative excursions CNE db -1, 2, 3 also have been discovered. We interpret these significant carbon-isotope excursions as being associated with enhanced biogenic productivity, mass extinctions and eustatic events.