AN INTEGRATED STUDY OF UPPER TRIASSIC CONODONT AND RADIOLARIAN BIOSTRATIGRAPHY IN THE TETHYAN REALM

The Late Triassic is a crucial period in Earth's geological history, marked by the initial break-up of the Pangaea supercontinent, significant global climatic fluctuations, and episodes of faunal turnovers/extinctions. These significant events are intricately interrelated, making the Late Triassic a time interval of profound environmental and biotic transformation. Within this context, the conodonts and radiolarians have proven invaluable for the Upper Triassic stratigraphic division, comparison, and paleo-environmental reconstruction, owing to their rapid evolution, wide geographic distribution, and distinctive morphological features. For the Upper Triassic radiolarian, which zonal schemes have been primarily established in North America, Japan, Far East Russia, and Europe. However, the radiolarian zones in Europe are discontinuous, with certain zones being omitted and replaced by those from other regions. For the Upper Triassic conodont, two recognized conodont zonal schemes are established in the western Tethys and North America, respectively. In contrast, the conodonts from the eastern Tethys region have been reported only sporadically. Therefore, further research and refinement of the Upper Triassic conodont and radiolarian biostratigraphy is urgently necessary. This study aims to advance our understanding of Upper Triassic conodont and radiolarian biostratigraphy within the Tethyan realm by examining four research sections from distinct regions. In the western Tethys, the upper Carnian to lower Norian radiolarian biostratigraphy is revised at the Pizzo Mondello section, the Norian GSSP. In the eastern Tethys, the conodont biostratigraphy of the lower to middle Norian is thoroughly documented at the Sanhedong section within the Simao terrane. Similarly, the middle to upper Norian conodont and radiolarian biostratigraphy have been comprehensively investigated at the Hongyan-B section in the Baoshan terrane. Additionally, in the Tethys Himalaya, the discovery of conodonts is significant for stratigraphic dating, and conodont assemblages in the strata from the base to the top of the Jiesheng section indicate an age of upper Carnian to lower Norian. Furthermore, Upper Triassic to Lower Jurassic conodonts from the Katsuyama section in the Inuyama area, Japan, are reported. Based on the conodont biostratigraphy, two globally correlatable negative carbon-isotope excursions (CIE1 and CIE2) have been identified in the Sanhedong section.