New biostratigraphic data and U–Pb geochronology for the Middle Permian to Triassic Succession of the South Qiangtang Block, Xizang

The general lack of Middle Permian to Lower Triassic deposits associated with the South Qiangtang Block (SQB) has restricted biostratigraphic correlation of the SQB with the Lhasa Block (LSB) and the North Qiangtang Block (NQB). In this study, we document for the first time a continuous Middle Permian to Lower Triassic succession and an Upper Triassic Norian–Rhaetian succession in the Samenxiong area of the west SQB using biostratigraphy and detrital zircon U–Pb geochronology. Identified fusuline zones include the Middle Permian Parafusulina–Neoschwagerina Assemblage Zone and the Late Permian Codonofusiella Zone. Conodont zones include the Middle Permian Mesogondolella Fauna, the Early Triassic Hadrodontina Zone and Eurygnathodus cf. costatus–Neospathodus pakistanensis Assemblage Zone, and the Late Triassic Mockina bidentata Zone. U–Pb age data confirms the viability of the proposed Rhaetian to Lower Jurassic Samenxiong Formation. Our biostratigraphic and geochronologic data permit re-evaluation of the originally described Longge, Jipuria, and Riganpeico formations. The fact that the Middle Permian to Lower Triassic and the Norian–Rhaetian successions of the SQB can be correlated with deposits of the LSB and NQB demonstrates their close palaeogeographic relationship during Middle Permian to Late Triassic time.