Tectono-stratigraphic terranes and detachment faulting of the South China Sea and Sulu Sea

Geoscientific data acquired from the South China Sea and Sulu Sea areas by BGR since 1977 are compiled and interpreted as comprehensive data sets, together with available information of commercial wells and drillsites of the Ocean Drilling Program (ODP). Generalized stratigraphy and lithology are discussed and correlated with the interpreted seismic profiles. On the basis of the stratigraphic and structural analysis 5 main tectono-stratigraphic terranes are defined for the South China Sea and 4 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. This rift was abandoned and a new westward propagating rift system developed north of the Dangerous Grounds-Reed Bank area from the middle Eocene to the Oligocene/Early Miocene together with seafloor spreading in the South China Sea Basin. 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-are spreading creating the SE Sulu Sea terrane and the assumed anti-clockwise rotation of Borneo are responsible fdr the complex collision-compression structures of the Sulu Sea terranes, including the formation of splinters of oceanic crust. Major right-lateral wrench systems are NNW-SSE running, up to 500 km long and cut across most of the identified terranes. Wrenching presumably ceased 12 to 16 Myr ago.