中文摘要：

为确定南海西部的中—西沙地块是否存在前新生代地层与构造,对研究区内多道反射地震剖面资料进行了地层-构造解释,并结合围区钻井、拖网等岩石地层资料,在研究区北部发现了前新生代地层-构造变形形迹。运用回剥法、去断层恢复法和地质反序法对前新生代地层的构造变形进行了古恢复。结果表明,研究区的地层可划分为上、中、下三套构造层,其中属于前新生界的下构造层可见褶皱、逆冲等挤压构造样式,前新生代末期,其构造形态表现为一系列连续的宽缓褶皱,结合断层逆冲推覆方向可判断其主要挤压应力来自于东南方向,并推测该挤压作用与古南海的扩张有关。

英文摘要：

Multi-channel seismic data are interpreted with the support of drilling and trawling samples from surrounding areas to identify Pre-Cenozoic strata in the middle-west block of the western South China Sea.Results suggest that the Pre-Cenozoic strata do occur in the north of the study area.Upon this fact,the tectonic deformation of the Pre-Cenozoic strata is reconstructed using the back-stripping method,the faultrecovery method and the antitone structural analysis method.The strata can be divided into upper,middle and lower structural layers in the study area.Compressive structures,such as folds and thrusts,are found in the lower structure layer.By the end of Pre-Cenozoic,the region was suffered from continuous gently folding.Combined with the fault thrust direction,it is concluded that the main compressive stress came from the southeast direction,which may be related to evolution of the paleo-South China Sea.