琼东南盆地构造沉降史及其主控因素

Tectonic subsidence of Qiongdongnan Basin and its main control factors

以28口钻井、3条主干地震剖面最新解释成果资料为依据的构造沉降史恢复结果表明:琼东南盆地新生代存在三期快速沉降过程和一期缓慢沉降过程:第一期为始新世,第二期为渐新世—早中新世,第三期存在时空差异:在盆地西部乐东凹陷为晚中新世以来,在盆地中东部陵水凹陷和松南-宝岛凹陷为上新世以来;缓慢沉降过程亦存在时空差异,盆地西部中中新世沉降缓慢,盆地中东部中—晚中新世沉降缓慢.第一期快速沉降过程受东亚陆缘扩张和红河断裂左旋走滑共同影响,第二期快速沉降受南海海底扩张和红河断裂左旋走滑联合作用,第三期快速沉降主要受红河断裂右旋走滑控制,缓慢沉降过程与南海海底扩张停止以及红河断裂构造活动处于宁静阶段相耦合.

Based on the data from 28 boreholes and the latest data of 3 seismic lines, the estimation of tectonic subsidence shows that Qiongdongnan Basin （QDNB） experienced three episodes of rapid subsiding and one episode of weak subsiding in Cenozoic time. During Eocene and Oligocene to early Miocene time, both western and eastern QDNB underwent two episodes of rapid subsiding with different subsidence rates. There came a weak subsiding period from 16 Ma to 10.5 Ma in western QDNB and from 16 Ma to 5.3 Ma in mid-eastern QDNB. A rapid subsiding event occurred again at 10.5 Ma in the west and at 5.3 Ma in the mid-east areas of QDNB. The first rapid subsiding was a result of the combination of extension of Eastern Asia continental margin and the sinistral strike-slip of Red River Fault （RRF） in Eocene; the second one was related with the seafloor spreading of the South China Sea （SCS） and sinistral strike-slip of RRF in Oligocene to early Miocene; the third one is mainly controlled by the dextral strike-slip of RRF since 10 - 5 Ma; the weak subsiding process was coeval with the weakly strike-slipping period of RRF within mid-late Miocene time and a response to the cease of the seafloor spreading of SCS.