Vice Professor XU Bing and his team carry out high-resolution analyses of coupled inorganic and organic carbon isotope on two late Devonian carbonate sequences in south China. The primary aims of this study are to characterize the changes of atmospheric CO₂ level during the F-F transition and address the links between the perturbation of the global carbon cycle and the mass extinction.

The timing of carbon isotope excursions, eustatic change, and conodont evolution across the F-F boundary provides key evidence for identifying the association of carbon cycle with the mass extinction. The onset of conodonts extinction coincides with the sea level fall, while it postdates that of atmospheric CO₂ level decrease. Furthermore, the severest extinction occurs during the interval with the lowest pCO₂ level and sea level. These observations suggest that the environmental changes induced by lowering pCO₂ level, such as temperature decrease and marine regression, might be the important factors for the F-F mass extinction.

Fig.1 Relationships among δ¹³Ccarb, pCO₂ level, conodont evolution, and sea level changes across the F-F boundary in the Dongcun section. (Image by XU)

Xu et al. Carbon isotopic evidence for the associations of decreasing atmospheric CO₂ level with the Frasnian-Famennian mass extinction. Journal of Geophysical Research, 117, G01032, doi:10.1029/2011JG001847 （Download Here）