中文摘要：

根据高分辨率重、磁测网数据的分析,结合多波束海底地貌的构造解释,南海海盆新生代经历了两期不同动力特征的海底扩张,25 Ma的沉积-构造事件是其重要分界.早期扩张从约33.5 Ma开始至25 Ma停止,在东部海盆南、北两侧和西北海盆形成了具有近E-W向或NEE向磁条带的老洋壳,是近NNW-SSE向扩张的产物；晚期扩张从25 Ma开始至16.5 Ma结束,在东部海盆中央区和西南海盆形成了具有NE向磁条带的新洋壳,是NW-SE向扩张的产物.南海海盆分区特点明显,南北分区,东西分段.从南到北可进一步分为3个亚区,南、北亚区由早期扩张产生,而晚期扩张的中央亚区从东到西又可进一步分为6个洋段,中间均由NNW或NW向断裂分割,是扩张中脊分段性的表现.南海晚期扩张具有渐进式扩张的特点,虽然它们均于磁条带异常C5c停止扩张,但开始扩张的时间从东部的C6c（23.5Ma）,到中部的C6b（22.8 Ma）,一直变新到西部的C5e（18.5Ma）.东部海盆与西南海盆之间的NNW向断裂是分割两海盆的边界断裂,不仅切割了磁条带异常,控制了两海盆不同的地球物理场特征,而且还使扩张中脊左行平移约95km,造成扩张中心和磁条带不连续.南海海盆扩张期间,其东部没有菲律宾群岛封闭,当时是一个面向大洋的港湾,与亚丁湾洋盆可以对比,是洋中脊向大陆边缘入侵的产物.

英文摘要：

Based on investigations of the new high resolution gravity and magnetic data, combined with swath bathymetry, the Cenozoic evolution model of the South China Sea is revisied. Two major sea-floor spreading stages were revealed with different dynamic mechanisms, separated by a remarkable tectonic-sedimentary event near 25 Ma. Sea-floor spreading started firstly in the East and Northwest Sub-basins from -33.5 Ma to 25 Ma, and formed the original oceanic crust with E-W or NEE-oriented magnetic anomalies in the northern and southern side of the East Sub-basin nowadays and whole Northwest Sub-basin. Since 25 Ma the sea-floor spreading continued with different direction until 16. 5 Ma. The later NW-SE-oriented spreading made the NE oriented magnetic anomalies in the central East Sub-basin and Southwest Sub-basin. Different tectonic areas developed during these two spreading episodes in the oceanic basin. The whole oceanic basin could be divided into three subregions from north to south. The northern and southern subregions are related to the first episodic sea-floor spreading, while the central one was formed during the later sea-floor spreading. And the central subregion could be separated into six segments further bounded with NW-NNW-oriented transform faults. Evidence from magnetic anomalies showed that the sea-floor spreading in the later episode began in the east segments with C6c anomaly （23.5 Ma）, and continued with C6b （22.8 Ma） in the middle segments and with C5e （18.5 Ma） in the west. We indicated that between 25 Ma and 16.5 Ma, the central part of the East Sub-basin and Southwest Sub-basin experienced rifting propagation from east to west, and the spreading direction changed in each segment. A NNW-trending transform fault separated the East and So directions, but a collision of the L uthwest Sub-basins. It not only cuts the magnetic anomalies with different lso makes a near uzon arc with and ly E 95 uras km sinistral offset of the spreading ridge. Before the ia Plate, the South China Sea was a gul