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Large perturbations of the carbon and sulfur cycle associated with the Late Ordovician mass extinction in South China

¹ Canada Research Chairs Program in Biogeochemistry, University of Quebec at Montreal, Montreal, QC H3C 3P8, Canada
² State Key Laboratory of Palaeobiology and Stratigraphy, Nanjing Institute of Geology and Palaeontology, Chinese Academy of Sciences, Nanjing 21008, China

Correspondence: *E-mail: shen.yanan{at}uqam.ca.

High-resolution ¹³C data of organic carbon from a continuous section of the Late Ordovician–Early Silurian reveal two positive ¹³C excursions that are associated with the mass extinction in South China. The first stratigraphic ³⁴S measurements on pyrite tied to well-established biostratigraphy indicate a large perturbation of the sulfur cycle, consistent with major sea-level changes related to the glaciation. The elevated ³⁴S values of pyrites and a large, short-lived negative ³⁴S excursion of ~20 associated with the decay of the glaciation suggest deep-water anoxia during the Hirnantian Stage, in contrast to the conventional view that the global oceans were oxygenated. We suggest that deep-water anoxia may have contributed to the Late Ordovician mass extinction in South China and possibly elsewhere.