【摘要】 南沙海区是我国领土的重要部分,富含油气资源,但也存在很多的科学问题.为了系统分析和对比各盆地的结构特征和沉积历史,结合已有的地震剖面资料,对南沙海区的万安、曾母、北康、南薇西和礼乐盆地几个代表性盆地,开展了沉积层序的划分对比.结果发现,除曾母盆地以外,南沙海区的沉积地层基本上可以根据张裂不整合面(Tg)、解体不整合面和断拗不整合面分为3个构造层4个构造期.其中,下构造层为中生代地层,分布范围不连续,东区的礼乐盆地要比中区和西区中生代地层厚,隆起下比凹陷内部厚,属于断陷前层序;中构造层在曾母和万安盆地以T40为顶界,其他几个盆地都以T60为顶界面,下部为断陷层序,上部为断拗层序,断拗层序推测为漂移期沉积;T40(或T32)之后的上构造层为拗陷期.根据地层的翘倾、削蚀和褶皱的情况来看,南沙地块内盆地在中中新世(T40)前后发生了一期明显的受压抬升和褶皱变形事件,这一变形事件在北康-南薇西盆地表现尤为明显,T40界面之下地层表现出明显的透镜状增厚,且伴随着新断裂的发育,中新世(T40-T32)地层具有顶薄翼厚的披覆沉积特点,推测其与南沙地块和婆罗洲的陆陆碰撞接触有关.经过初步的共轭对比认为,曾母盆地与莺歌海盆地比较相似,北康-南薇西盆地的沉积结构和演化历史与琼东南盆地有很多相似;根据南海海盆的共轭对比可知,礼乐盆地在南海海盆扩张前,大致以西南次海盆与中沙隆起共轭,这与礼乐盆地内解体不整合面为T60的解释一致.更多还原

【Abstract】 Nansha region is an important part of our country,with great potential for hydrocarbon resources and scientific researches.In order to analyze and compare the basins’ structure as well as the sedimentary history systematically,we interprete most of the seismic profiles we have to carry out the stratigraphic correlation between Wan’an,Zengmu(Great Sarawak),Beikang,Nanweixi and Liyue basin.It is found that the stratigraphy are divided into three tectonic periods and four stages,divided by rifting unconformity(Tg),breakup unconformity(T60 or T40),and rifting-depressing unconformity(T40 or T32).The lower tectonic periods are composed of Mesozoic strata,distributed discontinuously,thicker in the Liyue basin and beneath uplift.It’s the pre-kinematic sequence.The middle tectonic period is separated into rifting stage in the lower part and rifting-depressing stage in the upper part by T40 in Wan’an and Zengmu basin,and by T60 in Beikang,Nanweixi and Liyue basin.The sedimentation in the rifting-depressing stage may be caused by the drift of the Nansha block.The sequence after T40(or T32) belongs to depressing stage.According to the rotation,erosion and fold structure,there is a collision event around Middle Miocene(T40),which is especially obvious in Beikang-Nanweixi basin.Besides the folding wave on the surface,the lens-shaped Early Miocene sequence accompanied with newly formed shear faults between T60 and T40 showed a compressive moment around T40,furthermore the Middle Miocene sequence(T40-T32) appear draping with thin top and thick wing.We suppose that the Nansha block collided with Borneo at this time.Relative to the northern continental margin,Zengmu seems much similar with Yinggehai basin,Beikang-Nanweixi basin seems to be conjugate with Qiongdongnan and Zhongjiannan.Liyue basin should be conjugate with Zhongsha uplift by SW sub sea basin.This conjugate pattern is consistent with the phenomena that T60 is the breakup unconformity.更多还原