Marine geophysical data from the China Basin and geological and geophysical data from the surrounding land areas indicate at least three stages in the tectonic evolution of the China Basin. The first stage was a north-south extension associated with the formation of oceanic crust beneath the China Basin during middle Mesozoic time. The second and third stages of east-west compression are associated with the closing of the China Basin. Closing of the basin during the Tertiary involved the northwestward movement of Borneo toward Asia with underthrusting along the Palawan Trough. Presently Luzon Island is approaching Asia with underthrusting along the Manila Trench. A simple paleogeographic reconstruction for the early Mesozoic Era requires Borneo to have been adjacent to mainland China and Hainan. The opening of the basin can then be explained by a simple rotation of a small plate, which included Borneo and Natuna Islands, away from mainland China about a pole of rotation located at Latitude 13.0°N, Longitude 44.0°E.
|National Science Foundation