A lithospheric footprint of the Tethys orogenic belt beneath the Sichuan-Yunnan block, southeastern Tibetan Plateau

The Sichuan-Yunnan block (SYB), located in the southeastern Tibetan Plateau, is a key area of the eastern Tethys orogenic belt, and its deep structure retains traces of an ancient tectonic history. In this study, the lithospheric structures beneath the SYB have been investigated using S and P receiver functions. An improved S receiver function method for studying the lithosphere-asthenosphere system (LAS) has been used. A thickened and stratified lithosphere in the SYB is indicated, and internal discontinuities within the lithosphere show an eastward tilting trend. By referring to the regional tectonic evolution and the structural characteristics of cratonic lithosphere in other regions around the world, we infer that the stratification and thickening of the lithosphere below the SYB are caused by cratonization in the Tethyan orogenic belt, revealing traces of ancient tectonism. The lateral extension of the Tibetan Plateau has activated the ancient tectonic weak zone around the SYB, resulting in the overall lateral extrusion of the SYB.