Sedimentary evolution of the Qiangtang Basin

The Qiangtang Basin is located between the Hoh Xil-Jinsha River suture zone and the Bangong-Nujiang suture zone. Its sedimentary evolution is of great significance for understanding the tectonic evolution of the Paleo-Tethys and Meso-Tethys Oceans. In this study, the authors established the sedimentary evolution mode of the Mesozoic basin (T₃-K₁) based on the sedimentary sequences, lithofacies paleogeography, analysis of sedimentary basin, and the latest research results of chronostratigraphy, and then discussed the relationship between the evolution of the Qiangtang Basin and the closure of the PaleoTethys Ocean as well as the opening of the Meso-Tethys Ocean. The Mesozoic (T₃-K₁) Qiangtang Basin was affected by the diluvial-alluvial facies sedimentary overlap. The sedimentary sequence has undergone an evolution from diluvial-alluvial facies, lacustrine to coastal and shallow-seas facies, which shows a deepening upward transgressive sequence. It can be divided into three typical sedimentary overlap types and five major stages of sedimentary evolution sequence. The Mesozoic Qiangtang Basin is a superimposed basin that evolved from foreland basin into rift basin, then into passive continental marginal basin, and finally into an active continental marginal basin through shrinking and vanishing. The closure of the Early-Middle Triassic foreland basin for the Qiangtang Basin was related to the closure of the Paleo-Tethys Ocean basin. The evolution of Mesozoic (T₃-K₁) Qiangtang Basin was restricted by the rapid opening and closing of the Meso-Tethys Tethys Ocean basin.