Coincident negative shifts in sulfur and carbon isotope compositions prior to the end-Permian mass extinction at Shangsi Section of Guangyuan, South China |
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Authors: | Pengwei Li Junhua Huang Min Chen and Xiao Bai |
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Institution: | (1) State Key Laboratory of Geological Processes and Mineral Resources, China University of Geosciences, Wuhan, 430074, China;(2) Key Laboratory of Biogeology and Environmental Geology of Ministry of Education, China University of Geosciences, Wuhan, 430074, China;(3) Faculty of Material Science and Chemistry Engineering, China University of Geosciences, Wuhan, 430074, China |
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Abstract: | Sulfur isotope composition of carbonate-associated sulfate (δ34SCAS) and carbon isotope composition of carbonate (δ13Ccarb) were jointly investigated on the Late Permian rocks at Shangsi Section, Guanyuan, Northeast Sichuan, South China. Both δ34SCAS and δ13Ccarb show gradual decline trends in Late Permian strata, inferring the occurrence of the long-term variation of marine environmental
conditions. Associated with the long-term variation are the two coincident negative shifts in δ34SCAS and δ13Ccarb, with one occurring at the boundary between Middle Permian Maokou Formation and Late Permian Wujiaping Formation and another
at Middle Dalong Formation. Of significance is the second shift which clearly predates the regression and the biotic crisis
at the end of Permian at Shangsi Section, providing evidence that a catastrophic event occurred prior to the biotic crisis.
The frequent volcanisms indicated by the volcanic rocks or fragments, and the upwelling are proposed to cause the second negative
excursion. An abrupt extreme negative δ34SCAS (ca. −20‰) associated with a low relative concentration of CAS and total organic carbon without large change in δ13Ccarb is found at the end of the second shift, which might arise from the short-term oxygenation of bottom waters and sediments
that resulted from the abrupt sea level drop. |
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Keywords: | carbonate-associated sulfate sulfur isotope mass extinction Late Permian South China |
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