Carbon and sulfur isotopic fluctuations associated with the end-Guadalupian mass extinction in South China |
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| Institution: | 1. Key Laboratory of Tectonics and Petroleum Resources of Ministry of Education, China University of Geosciences, Wuhan 430074, China;2. Institute of Geology and Geophysics, Chinese Academy of Sciences, Beijing 100029, China;3. Key Laboratory of Geospace Environment and Geodesy of Ministry of Education, Wuhan University, Wuhan 430079, China;1. State Key Laboratory of Coal Resources and Safe Mining, China University of Mining and Technology, China;2. College of Geoscience and Surveying Engineering, China University of Mining and Technology (Beijing), Beijing, 100083, China;3. School of Biological, Earth and Environmental Sciences, University of New South Wales, Sydney 2052, Australia;1. Institute of Geology and Paleontology, Graduate School of Science, Tohoku University, Sendai 980-8578, Japan;2. Department of Geoscience, University of Calgary, Calgary, Alberta T2N 1N4, Canada;1. Centre for Earth Evolution and Dynamics (CEED), University of Oslo, Oslo, Norway;2. DougalEARTH ltd., Solihull, UK;3. Visiting Fellow, Earth, Environmental and Biological Sciences, Queensland University of Technology, Brisbane, Queensland, Australia;4. Department of Geography, Earth and Environmental Sciences (GEES), University of Hull, Hull HU6 7RX, UK;5. School of Earth and Environment, University of Leeds, Leeds LS2 9JT, UK;6. Key Laboratory of Geobiology and Environmental Geology, China University of Geosciences, Wuhan 430074, PR China;7. Humboldt post-doc fellow, GeoZentrum Nordbayern, University of Erlangen-Nuremberg, Schlossgarten 5, 91054 Erlangen, Germany;8. NGU Geodynamics, Trondheim, Norway;9. School of Geosciences, University of Witwatersrand, Johannesburg, South Africa;1. State Key Laboratory of Paleobiology and Stratigraphy, Nanjing Institute of Geology and Palaeontology, Center for Excellence in Life and Paleoenvironment, Chinese Academy of Sciences, Nanjing 210008, China;2. State Key Laboratory of Isotope Geochemistry, Guangzhou Institute of Geochemistry, Chinese Academy of Sciences, Guangzhou 510640, China;3. Department of Earth, Atmospheric and Planetary Sciences, Massachusetts Institute of Technology, Cambridge, MA 02142, USA |
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| Abstract: | Concentrations of total organic matter (TOC), carbon isotopic compositions of carbonate and organic matter (δ13Ccarb, δ13Corg), and sulfur isotopic compositions of carbonate associated sulfate (δ34Ssulfate) across the Guadalupian–Lopingian (G–L) boundary were analyzed from identical samples of Tieqiao section, Laibin, Guangxi province, South China. The δ13Ccarb values show a positive excursion from ? 0.45‰ to the peak of 3.80‰ in the Laibin limestone member of the Maokou Formation, followed by a drastic drop to ? 2.60‰ in the lowest Heshan formation, then returned to about 1.58‰. Similar to the trends of the δ13Ccarb values, Δ13Ccarb–org values also show a positive excursion followed by a sharp negative shift. The onset of a major negative carbon isotope excursion postdates the end Guadalupian extinction that indicates subsequent severe disturbance of the ocean–atmosphere carbon cycle. The first biostratigraphic δ34Ssulfate values during the G–L transition exhibit a remarkable fluctuation: a dramatic negative shift followed by a rapid positive shift, ranging from 36.88‰ to ? 37.41‰. These sulfate isotopic records suggest that the ocean during the G–L transition was strongly stratified, forming an unstable chemocline separating oxic shallow water from anoxic/euxinic deep water. Chemocline excursions, together with subsequent rapid transgression and oceanic anoxia, were likely responsible for the massive diversity decline of the G–L biotic crisis. |
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