Integrated Stratigraphy and Chronologic Significance of the Upper Triassic Tela Section, Tethyan Himalaya, Southern Tibet

The Norian–Rhaetian interval of the Late Triassic was a critical time of biotic turnover, carbon-cycle perturbation, and environmental instability, yet its chronostratigraphic framework remains poorly constrained. In China, progress has been particularly limited because continuous marine Norian–Rhaetian successions suitable for high-resolution integrated stratigraphy are rare. The Tela section in the Tethyan Himalaya of southern Tibet provides an important opportunity to improve this framework. The Tela section is composed mainly of limestone, marly limestone, and thin mudstone interbeds deposited in a shallow-marine setting on the northern margin of the Indian continent during the Late Triassic. Our recent work shows that the section preserves a relatively continuous upper Norian to latest Rhaetian succession and yields abundant conodonts, radiolarians, carbon isotope records, and zircon-bearing volcaniclastic horizons. Four conodont biozones have been recognized: the Mockina bidentata Zone, the Parvigondolella andrusovi–Misikella hernsteini Zone, the Misikella posthernsteini Zone, and the Misikella ultima Zone. The occurrence of Misikella ultima, together with the radiolarian Globolaxtorum tozeri, supports a latest Rhaetian age for the upper part of the section. Zircon U-Pb ages from volcaniclastic limestone beds in the lower part of the studied interval are 217.0 ± 1.4 Ma, 214.5 ± 1.9 Ma, and 214.4 ± 1.4 Ma. These ages are consistent with the conodont biostratigraphic framework and suggest that the zircons closely approximate depositional age. Carbon isotope stratigraphy reveals four negative excursions, including three in the late Norian and one strong excursion in the upper part of the section that can be correlated with the Initial-CIE associated with the end-Triassic crisis. These results demonstrate that the Tela section is one of the most promising marine Upper Triassic sections for integrating biostratigraphy, geochronology, and chemostratigraphy, and provides important new constraints on the Norian–Rhaetian interval in China.