@article{62bf9bdf3070456ba35a8b3a563f9c78,
title = "Comparison of Ediacaran platform and slope δ238U records in South China: Implications for global-ocean oxygenation and the origin of the Shuram Excursion",
abstract = "The Ediacaran Shuram negative carbon isotope excursion (SE) records major paleoceanographic changes during the late Neoproterozoic, possibly linked to a global oceanic oxygenation event, yet its cause(s) remain uncertain. Earlier studies of the upper Ediacaran Doushantuo Formation in South China based on local redox proxies have documented strong spatial redox heterogeneity along shelf-to-basin transects, but variations of δ238U (a global redox proxy) have not yet been examined in deep-water SE carbonates. In this study, we examined δ238U variations through the SE in the upper slope Siduping section. Similar to platform SE sections, Siduping exhibits a shift toward higher δ238U values correlative with the peak of the SE (i.e., maximum negative δ13Ccarb), confirming inferences of global ocean oxygenation during the SE. This raises an apparent paradox, because a global negative carbon isotope excursion implies net oxidant consumption, requiring an ocean-based oxygenation mechanism. We hypothesize that an increase in the efficiency of phosphorus burial due to a plankton-driven shift from dominantly dissolved organic matter (DOM) cycling to greater particulate organic matter (POM) export depleted the ocean of nutrient phosphorus. By producing a steep redox gradient close to the sediment-water interface, we suggest that ocean oxygenation also triggered a globally simultaneous diagenetic event in which isotopically light δ13Ccarb was precipitated in authigenic carbonate minerals. This scenario can account for δ238U differences between shallow-water and deep-water carbonates, which reflect precipitation of relatively larger amounts of authigenic carbonate minerals in shallow-water settings, generating both a larger negative δ13Ccarb shift and a larger early diagenetic δ238U offset.",
keywords = "CIE, Carbon isotopes, Doushantuo, Neoproterozoic, Ocean redox, Uranium isotopes",
author = "Mengchun Cao and Daines, {Stuart J.} and Lenton, {Timothy M.} and Huan Cui and Algeo, {Thomas J.} and Dahl, {Tais W.} and Wei Shi and Chen, {Zhong Qiang} and Ariel Anbar and Zhou, {Yao Qi}",
note = "Funding Information: We thank Dr. Chao Li from the China University of Geosciences (Wuhan) for helpful discussion that improved the manuscript. We thank Jeremy Owens, Karen Johannesson, and Jeffrey Catalano for editorial oversight. M.C. acknowledges financial support from National Natural Science Foundation of China (No. 41772190) and Fundamental Research Funds for the Central Universities (No. 18CX06026A). T.W.D. acknowledges support from the Danish Council for Independent Research (DFF - 7014-00295) and the Carlsberg Foundation (grant number CF16-0876). T.M.L. acknowledges support from the Natural Environment Research Council (NE/P013651 and NE/N018508/1). H.C. acknowledges the open research grant from the State Key Laboratory of Palaeobiology and Stratigraphy, Nanjing Institute of Geology and Palaeontology, Chinese Academy of Sciences. Funding Information: We thank Dr. Chao Li from the China University of Geosciences (Wuhan) for helpful discussion that improved the manuscript. We thank Jeremy Owens, Karen Johannesson, and Jeffrey Catalano for editorial oversight. M.C. acknowledges financial support from National Natural Science Foundation of China (No. 41772190 ) and Fundamental Research Funds for the Central Universities (No. 18CX06026A ). T.W.D. acknowledges support from the Danish Council for Independent Research ( DFF - 7014-00295 ) and the Carlsberg Foundation (grant number CF16-0876 ). T.M.L. acknowledges support from the Natural Environment Research Council ( NE/P013651 and NE/N018508/1 ). H.C. acknowledges the open research grant from the State Key Laboratory of Palaeobiology and Stratigraphy, Nanjing Institute of Geology and Palaeontology, Chinese Academy of Sciences. Publisher Copyright: {\textcopyright} 2020",
year = "2020",
month = oct,
day = "15",
doi = "10.1016/j.gca.2020.04.035",
language = "English (US)",
volume = "287",
pages = "111--124",
journal = "Geochimica et Cosmochimica Acta",
issn = "0016-7037",
publisher = "Elsevier Ltd",
}