南海西南次海盆构造特征及其沉积响应

本文对穿过南海西南次海盆的逾1000 km的多道地震测线CFT剖面进行了地震界面特征的识别和地震层序的划分，分段分析了拆离断层对其减薄陆壳的拆离作用。结合前人研究成果，对南海西南次海盆地壳结构特征开展了分析，并总结了其构造特征。西南次海盆在发生陆缘张裂—海盆扩张、洋壳出现—扩张后稳定沉积这一系列过程中，可划分为4个阶段的沉积响应：A阶段(古新世之前)——前裂谷阶段，表现为地壳在拉张应力下产生小的断层；B阶段（始新世—早渐新世）——陆缘的裂谷阶段，地壳在拉张应力下拉张减薄，A阶段产生的断层出现了旋转，出现了大型掀斜的拆离断层，沉积物为同裂谷沉积，该阶段以产生了破裂不整合结束；C阶段（晚渐新世—早中新世）——海盆扩张阶段，海盆开始扩张，张应力从陆缘转移到了洋盆；D阶段（中中新世以来）——海盆扩张结束以后，以一套稳定沉积为特征。

Tectonic characteristics and sedimentary responses of the southwest Subbasin of the South China Sea

In this paper, the authors analyzed over 1000 kilometers'' multi-channel seismic line (the CFT profile) across the southwestern subbasin of the South China Sea, with identification of seismic interface characteristics and seismic sequence division, and analyzed the detachment effect of detachment faults on the thinning of continental crust in segments. On the basis of the previous research results, an analysis of the crustal structure characteristics of the South China Sea was carried out, and its structural characteristics were summarized. The southwest sub-basin can be divided into four stages of sedimentary response during the series of continental marginal rifting and sea basin spreading and post-expansion: Stage A was the pre-rift stage, showing that the small faults was generated under tensile stress; Stage B was the rifting stage, when the crust of continental margin was thinning in the tensile stress, the fault generated in Stage A was rotated, and the large tilting detachment fault appeared. The sediments were the synrift deposits, and this stage ended with the breakup unconformity; Stage C was the basin expansion stage, during which the sea basin began to expand and the tensile stress shifted from the continental margin to the ocean basin; Stage D was the post-spreading stage, after ending of the basin expansion, the sediments were a set of stable deposits.