Dying in the Sun: direct evidence for elevated UV-B radiation at the end-Permian mass extinction

Liu, F.; Peng, H.; Marshall, J.E.A.; Lomax, B.H.; Bomfleur, B.; Kent, M.S.; Fraser, W.T.; Jardine, P.E.

Abstract

Land plants can adjust the concentration of protective ultraviolet B (UV-B)–absorbing compounds (UACs) in the outer wall of their reproductive propagules in response to ambient UV-B flux. To infer changes in UV-B radiation flux at Earth’s surface during the end-Permian mass extinction, we analyze UAC abundances in ca. 800 pollen grains from an independently dated Permian-Triassic boundary section in Tibet. Our data reveal an excursion in UACs that coincide with a spike in mercury concentration and a negative carbon-isotope excursion in the latest Permian deposits, suggesting a close temporal link between large-scale volcanic eruptions, global carbon and mercury cycle perturbations, and ozone layer disruption. Because enhanced UV-B radiation can exacerbate the environmental deterioration induced by massive magmatism, ozone depletion is considered a compelling eco- logical driver for the terrestrial mass extinction.