摘要
南海西部海域构造复杂,主要发育有北东—北东东向、北西向和近南北向3组深大断裂。其中,北西向断裂与板块汇聚、碰撞有关,多具走滑性质;北东—北东东向断裂具有与中国东部裂谷盆地相似的发育特点,呈张扭性质;近南北向断裂可能是南海在扩张活动期间于洋、陆壳过渡部位形成的走滑调节断裂,是洋盆扩张的西部边界。新生代里,南海经历了4次成盆事件与3期扩张活动,盆地经历了古新世—中始新世陆缘断陷、渐新世—早中新世扩展与中中新世以来的热沉降3个演化阶段。陆缘断陷阶段的充填系列主要是北东—北东东向与北西向的河流—冲积扇、湖泊沼泽等陆相沉积及火山岩等;盆地扩展阶段表现为中-小型断陷、断-坳陷逐渐复合与联合为大-中型坳陷,古地理格局逐渐由河流与湖沼陆相环境演变为滨海至浅海相的沉积环境;热沉降阶段的成盆活动逐渐减弱以至停止,地层表现超覆,盆地出现联合迹象。结合以往勘探与油气资源调查成果分析,认为南海西部海域陆架陆坡区发育的大-中型沉积盆地石油地质条件良好,蕴藏着丰富的油气资源,勘探潜力巨大。
The structures in western area of the South China Sea seemed very complicated, and twenties Cenozoic petroliferous basins occurred in the marine area of the South China Sea. There occurred three groups of faults with orientations of NE-NEE, NW and nearly SN respectively. The NW-striking deep faults, related to plate convergence and collision, were strike-slipping ones. The NE-NEE deep faults, similar with the transtensile faults of rift basins in East China, showed a property of transtension. The nearly SN faults, as the west boundary of sea-floor spreading during openning of the South China Sea, made up a transfer belt in the position of transition from oceanic crust to continental crust. The South China Sea experienced four tectonic events and three generations of extension. Correspondingly, the basin evolution could be devided into three periods, namely, the continent marginal fault-depression in Paleocene-Middle Eocene, basin expanding in Oligocene-Early Miocene, and heat depressing since Middle Miocene. The filled successions in the continent marginal fault-depression were mainly continental facies deposits, such as fluvial-alluvial fan, lacustrine and marsch, as well as volcanic rocks controlled by NE-NEE and NW faults. In the period of basin expanding, the mesoscopic and small grabens-depressions combinated and became large-scale depressions, meanwhile, the paleogeographic patterns changed gradually from lacustrine-marsch to littoral and shallow marine. In the period of heat-depressing, the basin developing weakened and stagnated, accompanied with stratigraphic overlap and basins＇ combination. The large- and meso-scale sedimentary basins on continental shelf or slope in the western area of the South China Sea had a favorable condition of petroleum geology. The petroliferous exploration revealed that there was a rich oilgas resource in the Cenozoic strata. The study on Cenozoic lithofacies and palaeogeography framework in western area of the South China Sea had not only a theoretical significance for regional tectonic evolution, but also a practical significance for oil-gas exploration.
出处
《地质科学》
CAS
CSCD
北大核心
2008年第1期133-153,共21页
Chinese Journal of Geology(Scientia Geologica Sinica)
关键词
构造古地理
盆地发育
控盆断裂
油气勘探
南海西部海域
新生代
Tectono-palaeogeography, Basin development, Basin-controlling fractures, Oil-gas exploration, The western South China Sea, Cenozoic
