A Smooth Negative Shift of Organic-Carbon Isotope Ratios at an End-Permian Mass Extinction Horizon in Central Pelagic Panthalassa

摘要

The most significant mass extinction of the Phanerozoic occurred at the end of the Permian. Evidence of global oceanic anoxia during this event has been reported by previous investigators (e.g., Isozaki, 1997; Wignall and Twitchett, 1996). Increasing volumes of euxinic water at the end of the Permian are suggested by an increase in sulfur isotope ratios (δ34S) of sulfates (Newton et al., 2004; Kaiho et al., 2002). Previous works suggested that end-Permian euxinic water reached the photic zone on the strength of pronounced blooms of anaerobic green sulphur bacteria (Cao et al., 2009; Riccardi et al., 2007; Grice et al., 2005). Increased cyanobacterial biomass is suggested in the photic zone of the eastern Paleotethys immediately after the mass extinction (Xie et al., 2007, 2005). However, the global extent of such algal and bacterial increases is uncertain.