Five main tectono-stratigraphic terranes are defined for the South China Sea and four main terranes for the Sulu Sea, respectively. The Dangerous Grounds, Reed Bank, Palawan-NW Borneo Trough and Palawan Island represent terranes of continental origin which developed on the proto-China margin by uniform-sense, low-angle, simple shearing within the crust in late Cretaceous to early Paleocene. The leading edge of the southward drifting continental terranes collided with the late Cretaceous to early Eocene subduction complex of the northernmost terrane of the proto-Sulu Sea. Continuous convergence of these terranes, back-arc spreading creating the SE Sulu Sea terrane and the assumed anti-clockwise rotation of Borneo are responsible for the complex collision-compression structures of the Sulu Sea terranes.