论文部分内容阅读
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.
Nansha sea area is an important part of our country’s territory, rich in oil and gas resources, but there are also many scientific problems.In order to systematically analyze and contrast the structural characteristics and sedimentary history of each basin, combined with the existing seismic section data, , Zengmu, Beikang, Nanwei West and Li Le Basin, the sedimentary sequences were compared and classified.The results show that, except for the Zengmu Basin, the sedimentary strata in the Nansha Sea Area can basically be divided according to the faults There are three tectonic strata in the four tectonic periods, ie, the Lower Cretaceous (Mesozoic), unconformity surface and discontinuous unconformity, and the Mesozoic strata, And the western Mesozoic strata are thick and thicker than the inner part of the depression in the uplift, which belongs to the pre-fault sequence. The middle Tazhong and Wan’an basin are T40 in the middle tectonic layer and T60 is the top boundary in the other several basins, while the lower part is the fault Deposition sequence, the upper part is fault-order sequence, the fault-sequence is presumed to be deposition during drift period, and the upper one after T40 (or T32) is depression period. According to the situation of formation tilt, erosion and folds The basin in the Nansha block developed before and after the Middle Miocene (T40) A significant compressive uplift and fold deformation event occurred. The deformation event was particularly evident in the Beikang-Nanwei West basin. The formation beneath the T40 interface showed lenticular thickening along with the development of new fractures (T40-T32) strata have the top thin-wing thickness of the depositional characteristics of the deposition, presumably with the Nansha block and borneo land-continent collision contact after preliminary conjugate comparison that the Zengmu and Orioles The Songhua Basin is relatively similar. The sedimentary structure and evolution history of the Beikang-Nanweixi Basin are similar to those of the Qiongdongnan Basin. According to the conjugate comparison of the South China Sea Basin, before the expansion of the South China Sea Basin, Conjunction with the Central-South uplift, which is consistent with the explanation for the unconformity of the T60 within the Ritual Basin.