Redefinition of the Global Stratotype Section and Point (GSSP) and new Standard Auxiliary Boundary Stratotype (SABS) for the base of Wuchiapingian Stage (Lopingian Series, Permian) in South China

The Global Stratotype Section and Point (GSSP) of the base-Wuchiapingian Stage was formally ratified at the Penglaitan section in South China in 2005. However, the riverside GSSP section at Penglaitan and its auxiliary section at Tieqiao have been permanently flooded since 2020. We herein designate an excavated section at Penglaitan as the new GSSP and the Fengshan section as a new Standard Auxiliary Boundary Stratotype (SABS). In addition, we revised the original definition based on a detailed restudy of the conodont succession from the two sections. We define the GSSP of the base-Wuchiapingian by the First Appearance Datum (FAD) of Clarkina postbitteri within the lineage Jinogondolella granti → Clarkina postbitteri → C. dukouensis. It represents a major evolutionary turnover in conodonts from Jinogondolella to Clarkina and marks the end-Guadalupian extinction event. The U-Pb date of 259.51 ± 0.21 Ma from the uppermost part of the Emeishan basalt is adopted for the GLB age. δ13Ccarb chemostratigraphy at the SABS exhibits several excursions between 3‰ and 5‰ across the GLB interval. Carbonate 87Sr/86Sr ratio is 0.707244 at the GLB. Remarkably, the SABS contains six normal and six reverse geomagnetic polarity zones in the uppermost Capitanian and three in the lowest Wuchiapingian.