Upper Changhsingian to lower Olenekian conodont successions from the Bozhou section, northern Guizhou Province, southwestern China

Abstract

This study presents an integrated conodont succession from the Bozhou section, northern Guizhou Province, southwestern China. These conodonts were yielded from the Changhsingian Changhsing Formation and the Lower Triassic Yelang and Maocaopu Formations, which were deposited in the transitional setting between the clastic shelf and carbonate platform in the western margin of the Yangtze Platform. A total of 22 conodont species of six genera are identified, and 10 conodont zones are recognized from the top part of Changhsing Formation to the Yelang Formation, namely, the Clarkina changxingensis, C. yini, C. meishanensis, Hindeodus praeparvus, H. parvus, H. postparvus, Neoclarkina discreta, Sweetospathodus kummeli, Neospathodus dieneri, and Eurygnathodus costatus Zones in ascending order. Based on the conodont succession, the ages of Shabaowan, Yulongshan, and Jiujitan members of the Yelang Formation are recognized for the first time and assigned to the early Griesbachian, late Griesbachian, and latest Griesbachian to early Smithian. At this section, the Permian–Triassic boundary (PTB) is placed at the base of Bed 7–2, 10 cm below the top of Changhsing Formation, defined by the first occurrence (FO) of H. parvus. The Induan–Olenekian boundary (IOB) is drawn at the base of Bed 49, the uppermost part of Yelang Formation, based on the FO of Eu. costatus immediately overlying the Ns. dieneri Zone in the absence of Novispathodus waageni. The Bozhou conodont successions can be correlated well with other sections worldwide.