南海中央海盆之东部次海盆后扩张期地层特征与影响因素

海底扩张形成的边缘海盆构造演化可划分为前扩张期、同扩张期与后扩张期等阶段。南海中央海盆巨厚的沉积地层大部分是扩张结束之后形成的，尤以东部次海盆地层厚度为最大。因受到不同因素的影响，在该次海盆不同的区域后扩张期发育的地层特征差别较大。这些现象反映海底扩张结束之后所发育的厚层地层中蕴含了大量南海构造演化的信息，因此深入分析该次海盆后扩张期的地层特征与影响因素是南海构造演化研究中不容忽略的环节。利用若干大洋钻孔年代地层资料，在过井剖面上进行合成地震记录标定、划分层序地层并确定其年代属性，并以此为依据分析讨论了本区的地层特征和相关的影响因素。结果表明，东部次海盆北部持续均衡的基底沉降和充足的陆缘物质形成厚度稳定的地层沉积；东部以微板块向马尼拉海沟俯冲为主要影响因素，使不同年代的地层各具特征；中部和西部岩浆活动是主要的影响因素，形成以火山碎屑物质为主的地层沉积；南部因当时的陆坡沉积环境和浊流活动的影响形成具有沉积物波特征的地层沉积。

Stratigraphic features and controlling factors in the eastern Sub-basin of the Central Basin,South China Sea during the post-spreading period

Driven by sea-floor spreading, the tectonic evolution of a marginal basin could be divided into three stages, namely the pre-spreading, spreading and post-spreading stages. Most of the thick deposits developed in the Central basin of the South China Sea, especially the thickest in the eastern Sub-basin was deposited in the post-spreading stage. Various factors were active in different parts of the eastern Sub-basin, resulting in a great variety of post-spreading stratigraphic features. A great amount of information about the formation and evolution of the South China Sea was preserved in the thick sediments. Therefore, it is important to study the stratigraphic features in the eastern Sub-basin formed during the post-spreading stage. According to the age data from some ODP and IODP drilling holes, the synthetic seismic records passing through the wells were calibrated and then the sequence stratigraphy of the region was established and dated. Upon the basis, we discussed in this paper the characteristics of the strata and related factors. The result shows that deposition of the sediments with stable thickness was mainly caused by stable basement subsidence with substantial terrigenous sediments input from the north, and the micro-plate subducting toward Manila trench was the main influence factor which gave rise to the characters of the strata in different age in the east. The sediments containing certain amount of volcanic debris was deposited in the west and middle part owing to the frequent magmatic activities. And in the south of the basin, turbidite sediment waves occurred due to the control of slope environment.