image: A white volcanic ash bed (Bed 25) at the Meishan section in Zhejiang Province, China, where the largest mass extinction during the Phanerozoic suddenly began just before this ash bed and lasted no more than 200kyr. This bed is dated as 252.28 ± 0.08 Ma. The Permian-Triassic boundary is in the middle of the overlying limestone bed. This image relates to a paper that appeared in the Nov. 17, 2011, issue of Science Express, published by AAAS. The paper, by Shu-zhong Shen at Nanjing Institute of Geology and Palaeontology in Nanjing, China, and colleagues, was titled, “Calibrating the End-Permian Mass Extinction.” view more
Credit: Image courtesy of Shuzhong Shen