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南海在新生代期间发生多次裂解和离散,在南海南部陆缘地层中留下了多次构造运动的痕迹.选取南沙海域内覆盖曾母、北康、南薇西、万安盆地的24个模拟井位,分别进行构造沉降速率的计算,并分析了自中生代末期以来的4次重要构造运动对南沙海域盆地的形成和构造演化的控制作用.结果显示,南沙海域构造沉降分为3幕:第一幕为40.5～30.0Ma,在西卫运动的影响下,南沙海域盆地进入断陷阶段,发生大规模的沉降作用,构造沉降速率最大达到了160m/Ma;第二幕为30.0～10.2Ma,随着南海的张开,区内盆地相继发生热沉降作用,进入拗陷期,由于古南海与婆罗洲的碰撞,区内盆地地层发生整体抬升,构造沉降速率达到最小值20～50m/Ma;第三幕为10.2～0Ma,晚中新世由于南沙运动影响,研究区内盆地发生了一次大规模的快速沉降作用,随着南沙地区一起进入区域沉降阶段.
During the Cenozoic, the South China Sea has repeatedly cracked and dispersed during the Cenozoic era, leaving many traces of tectonic movement in the continental margin of the southern South China Sea. Twenty-four of the Nansha sea areas covering Zengmu, Beikang, Nanwei West and Wan’an basins were selected We simulated the well location and calculated the sedimentation rate separately and analyzed the control of formation and tectonic evolution of the Nansha Sea basin since four important tectonic movements since the end of the Mesozoic.The results show that the structural subsidence of the Nansha Sea is divided into three stages: The first act is 40.5 ~ 30.0Ma. Under the influence of Xijian movement, the basin of Nansha Basin entered the fault depression stage with large-scale subsidence and the maximum rate of structural subsidence reached 160m / Ma and 30.0 ~ 10.2Ma With the expansion of the South China Sea, thermal basins have successively occurred in the basin. During the depression period, due to the collision between the ancient South China Sea and Borneo, the basin strata in the area experienced a total uplift and the rate of structural subsidence reached the minimum value of 20-50 m / Ma ; The third act is from 10.2 to 0 Ma. Due to the influence of the Nansha movement during the late Miocene, a large-scale rapid subsidence occurred in the basins within the study area, and entered into the regional subsidence stage together with the Nansha region.