We use observations from the 1985 R.V. Charcot Nanhai Cruise to document NW-SE spreading in the 150-200 km wide region of the South China Sea (SCS), along the 1000 km long axial ridge. The data include Seabeam and single channel seismic profiles, completed by magnetic and gravity anomalies. Two detailed surveyed boxes were performed on both sides of the ridge to illustrate the structural fabric. A fine scale structural survey of the flank of a seamount with a side-scan sonar is also presented, as well as dredges and cores results.