First Records of Moscovian (Late Carboniferous) Conodonts from Rejuechaka, Nyima County, Tibet, and Its Implications

Late Paleozoic strata in the Northern Qiangtang Basin are regionally well developed, preserving relatively stable and continuous sedimentary records. However, biostratigraphic research in this region remains limited, particularly regarding correlation with Tethyan standard conodont biozonation. This deficiency has hindered high-resolution stratigraphic subdivision and regional correlation of the Late Paleozoic strata in the Northern Qiangtang Basin. In this study, conodont specimens collected from the Walongshan Formation at the Changshehu 5th section, Rejuechaka, Nyima County, Tibet, were systematically studied. Based on the overall morphological characteristics of the well-preserved P1 elements, all these P1 elements are assigned to the genusIdiognathodus, and only a single species, Idiognathodus aff. anteparallelus, is recognized. This species is indicative of the early Moscovian, suggesting that the corresponding strata of the Walongshan Formation in the Rejuechaka area of the Northern Qiangtang Basin can be assigned to the Moscovian Stage of the Late Carboniferous. Combined with previously reported fossil assemblages, including fusulinids and corals, the fossil assemblage in the study area shows strong affinity with that of the South China Block. This provides newly important constraints on the age and palaeogeographic position of the Rejuechaka area within the Northern Qiangtang Basin during the Late Carboniferous.