Abstract: The tectonics of the Nansha trough-Northwest Palawan is important for understanding the origin and evolution of the South China Sea (SCS). Based on the analysis of geological and geophysical data in the southern margin of SCS, we suggest that the very thin crust of the Nansha trough may not be the remnant of the Proto South China Sea (PSCS), but may be an abandoned spreading center. As a result of a compressional event after the formation of the SCS, the thrusting structures developed very late on the Nansha trough and were not related to the opening of the SCS. The comparison between the extrusion of the Nansha trough and the Pagasa wedge in Northwest Palawan shows that the time of compressional termination in the east is earlier than in the west in the southern margin of the SCS. The ophiolite in South and Central Palawan was the product of its southern northward thrusting, indicating that the PSCS may subduct from south to north. It is suggested that the Southern Palawan ophiolite may derive from the oceanic crust of Neo-Tethys and the Central Palawan ophiolite may come from the PSCS. The subducted remnants of oceanic crust in different periods were finally overthrusted onto the island arc system. The Palawan ophiolite is the result of a long-term thrusting from south to north, and the time of the final emplacement may be the Middle-Late Miocene.

Key words: Southern margin of South China Sea, Nansha trough thrust structure, Proto South China Sea, Palawan ophiolite