ORIGIN OF TRANSFORM FAULTS IN SOUTH CHINA SEA AND ITS IMPLICATIONS FOR SOUTH CHINA SEA SPREADING

Transform faults are the keys to reveal the evolution of marginal seas. However, the mechanism of their formation remains a puzzle and hotspot in geosciences. Based on high-resolution tectonomorphology, basin geometry, gravity and magnetic anomalies, magnetic lineation pattern, Moho contours, submarine heat flow, and seismic profiles in the Northern South China Sea, together with studies of regional geological settings, plate reconstruction and geodynamic analysis, this paper tries to redefine the spatial distribution pattern of transform faults in the SCS and strike-slip faults in adjacent areas. Our data suggests that transform faults and strike-slip faults are in general in NNE-trending in the SCS. Therefore, a new model of marginal sea spreading is proposed against the previous Cenozoic plate movement models concerning the East Asian Continental Margin and SCS, which believed that the strike of transform faults was NW. The NNE-trending transform faults in the SCS may be the ones inherited from the strike-slip faults at the rifting continental margin. They are actually part of the large-scale NNE-trending dextral strike-slip faults distributed in the continental shelf of the SCS. Therefore, they could be treated as the natural extension of the NNE-trending strike-slip faults in the South China Block. They are not analogous to the positive expansion of the normal mid-ocean ridge, but a kind of oblique spreading. They are not perpendicular to the spreading axis.