SIMS zircon U‐Pb dating from bentonites in the Penglaitan Global Stratotype Section for the Guadalupian–Lopingian boundary (GLB), South China

The Penglaitan section, as the Global Stratotype Section for the Guadalupian–Lopingian boundary (GLB), displays continuous deposition with a complete succession of pelagic conodont zones across the GLB. However, there is no reliable radiometric age from the Penglaitan section itself to constrain the GLB. Here, we report SIMS zircon U-Pb ages from two bentonite layers (Bed 7c) in the Penglaitan Global Stratotype Section near the GLB. The sample PL-62-1 yields a weighted mean 238U/206Pb age of 257.1 ± 2.2 Ma, and the sample PL-62-2 yields a weighted mean 206Pb/238U age of 257.0 ± 4.2 Ma. Therefore, we consider 257.0–257.1 Ma as the age of deposition of Bed 7c (the end of the C. postbitteri postbitteri conodont Zone, ca. 86 cm above the GLB), and, considering the depositional rate of chert, we suggest 258.6 Ma as the age of the GLB. Copyright © 2015 John Wiley & Sons, Ltd.