Revised conodont zonation and conodont evolution across the Permian-Triassic boundary at the Shangsi section, Guangyuan, Sichuan, South China

摘要

Large conodont samples (20 kg at most) have been collected from the uppermost Permian and the lowermost Triassic (beds 26-33) at Shangsi, northern Sichuan. These have enabled us to establish parallel hindeodid and gondolellid conodont zones through the section similar to previously recognized in the Meishan section. In ascending order, three newly established gondolellid zones at the Shangsi section are: Neogondolella yini Zone (bed 26), Neogondolella meishanensis Zone (beds 27a-27c), Neogondolella taylorae Zone (beds 28a-29 d). Also in ascending order, four revised or newly established hindeodid zones are: Hindeodus changxingensis Zone (beds 28a-29b) Hindeodus parvus Zone (beds 29c-30a), lsarcicella lobata Zone (beds 30b-31a), Isarcicella isarcica Zone (bed 31b and above). According to the new data, the first occurrence of H. parvus is about 2 m lower than the previously reported horizon. On the basis of both hindeodid and gondolellid taxa, the PTB is placed 22 cm above the base of bed 28a. This conodont zonation of the Shangsi section will help improve correlations of global Permian-Triassic boundary sections.