Spreading direction in the central South China Sea

Recent work^1,2 indicates that the South China Sea is an `Atlantictype' marginal basin of late Tertiary age. Magnetic anomalies in the eastern part of the sea are consistent with seafloor spreading directed approximately north-south^1,2. We present here a new morphostructural study based on coupled seabeam mapping and single-channel seismic reflection profiling, which reveals dominant normal fault scarps, striking N50° E between 113 and 119° E longitude near the axis of this basin. Such a structural fabric implies a NW-SE spreading direction, at least in the 150-200-km-wide axial region of the South China Sea, and places new constraints on geodynamic models for the formation of this basin in the tectonic and palaeogeographic framework of South-East Asia and the South-West Pacific.