New Early Triassic Conodont Data from the Nanpanjiang Basin and Their Im-Plications for Defining the Induan–olenekian Boundary

The Early Triassic was a critical interval for the recovery of life and the rise of the Modern Evolutionary Fauna after the end-Permian mass extinction. Establishing a robust stratigraphic time framework is essential for understanding biological evolution and environmental changes during this period. However, the definition of the Induan–Olenekian Boundary (IOB) is still debated, and a formally defined Global Stratotype Section and Point (GSSP) has not yet been established. Conodonts are widely distributed in marine strata and evolved rapidly, making them an important tool for establishing high-resolution biostratigraphy and constraining the position of the IOB. This study reports new conodont data from two Lower Triassic sections in the Nanpanjiang Basin, Guangxi, South China: Linzhong and Longjiawan sections. Both sections expose the Luolou Formation and encompass the late Induan to the early Olenekian. A total of 131 samples were collected from the two sections, yielding abundant conodont specimens. Ten conodont species were identified and four conodont biozones were established. The first appearance of Novispathodus waageni is widely regarded as an important marker for the base of the Olenekian, while Eurygnathodus costatus, a short-ranging species restricted to the earliest Olenekian, is also considered as a significant indicator of the IOB. In Linzhong section, Novispathodus waageni first occurs in bed LZ-6 and Eurygnathodus costatus in bed LZ-7, suggesting that the IOB may lie between beds LZ-5 and LZ-6. In Longjiawan section, Novispathodus waageni first occurs in bed LJW-52 and Eurygnathodus costatus in bed LJW-53, indicating that the IOB is most likely located between beds LJW-51 and LJW-52. Finally, correlations with ammonoid biostratigraphy, high-precision U-Pb ages from the same sections as well as some nearby sections will be discussed. Collectively, the rich conodont, ammonoid, and high-precision U-Pb age data make the Waili area as an ideal potential GSSP candidate for the IOB.