The South China Sea (SCS) is the largest marginal sea in the East Asian continental margin,and is located in the junction among three palates of the Eurasia,Pacific and Indo Australia plates,which is also under the interaction of the Neo Tethyan and Pacific tectonic domains.It became a geological favorite place that demonstrates the transitional process of two large-scale dynamic systems in the Cenozoic.The oceanic crust of the SCS is roughly rhombus shaped.The SCS consists of three major sub-basins,namely,the eastern,southwestern and northwestern sub basins.The SCS has been called as another ‘Persian Gulf’,because of the rich resources of oil and gas.On the basis of numerous published data of morphology,magnetic strips and transform faults,and combining with important sedimentary facies and unconformities,we try to compare the characteristics of sedimentary sequences,facies and thicknesses and then to analyze the fault systems and patterns in basins.All these regional geological data suggest that the Paleogene sediments in northern basins thinned from west to east,and in the Neogene the sediments thickened from west to east.The northern basins,the Wan'an Basin and the Zhongjiannan Basin in the western SCS developed under the rightstepping dextral strikeslip faulting,which presents a good correlation between faulting and sedimentation,with the activity intensity of the ENE-trending faults stronger in the west than that in the east at the early stage,and then the faulting intensity decreased and vanished from west to east.Thus,we proposed that a dynamic model of the SCS opening is linked to the unified stress field triggered by the NE-trending right stepping dextral strikeslip faulting and the slab pull of the proto-SCS southward subduction to the Borneo Block.In addition,this study also suggests that the NNE trending right-stepping dextral strikeslip faults act as a major fracture zone system during the eastern and northwestern sub basins (EB and NWB) opening under the NNE-SSW directed extension at 34 23 Ma,and the activity intensity of the NNE trending faults migrated eastward and stopped at 32-23 Ma.Then the subduction zone of the proto-SCS rotated from nearly E-Wtrending to NE-trending with an anticlockwise rotation of the Borneo Block and the stopping of the NNE trending strike-slip faulting to the west of the ‘vanished SCS’ since 23 Ma.The southwestern sub-basin (SWB) started its opening under the NW-SE-directed extension due to the slab pull of the proto-SCS and the extension along the trailing edge of the LiyuePalawan Block,and the spreading center of the NNE-SSW trending eastern sub-basin (EB) also changed to be NW-SE-trending coevally.Then the spreading for all the sub-basins stopped synchronously at about 15.5 Ma,just after the closure of the proto-SCS when the Dangerous-LiyuePalawan Block collided with the Borneo Block.%南海作为东亚大陆边缘最大的边缘海,位于太平洋、印澳和欧亚三个板块的夹持之下,处于特提斯构造域和太平洋构造域的联合作用部位,是揭示新生代两大动力学体系交接转换特征的良好场所.南海海盆为菱形洋盆,包括西北次海盆、东部次海盆和西南次海盆,均在古近纪—中中新世形成,同时伴随着南海北部、西部和南部盆地群发育,盆地边缘油气资源丰富,被称为第二个“波斯湾”.本文搜集了前人对南海洋盆深部形态、磁条带、转换断层等成果,以及南海周边盆地群的沉积体系、沉积相、不整合面相关资料,综合对比了南海北部、西部和南部盆地群的沉积序列、沉积相、沉积厚度,厘定了盆地群断裂体系、断裂组合特征,揭示了南海北部、南部盆地群及西部盆地群中的中建南和万安盆地都是在右行右阶走滑拉分背景下形成的.北部盆地群新生代古近系西厚东薄,新近系东厚西薄,NNE NE向断裂体系活动早期西强东弱,而晚期东强西弱,从西向东依次停止.同时指出,南海是在NNE向断裂体系右行右阶走滑拉分和古南海俯冲拖曳的联合作用下打开:于34～32 Ma西北次海盆和东部次海盆受控于NNE向断裂的右行右阶走滑拉分作用,沿着NNE-SSW方向开启;32～23 Ma,NNE向走滑断裂活动自西向东逐步停止;于23 Ma左右,“消失”的南海以西的NNE向走滑断裂完全停止活动,同时由于婆罗洲地块逆时针旋转,古南海的俯冲带走向由近E-W向变为NE向,俯冲板块拖曳力也转变为NW-SE向并且占据主导地位,在拖曳力作用下礼乐 巴拉望地块后缘陆壳伸展,导致西南次海盆打开,东部次海盆的扩张方向由NNE-SSW转变为NW-SE向.于15 Ma,礼乐 巴拉望地块与婆罗洲地块碰撞,南海停止扩张.
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