南海珠江深水扇系统的沉积构造背景分析

从深水扇系统的观点出发,主要基于对最近所采集的穿越整个白云凹陷的700余公里长电缆深反射(深达14 s)地震资料综合解释,结合南海大洋钻探的成果,对南海珠江深水扇系统沉积的构造背景特征进行了综合分析.研究发现:白云主凹在早中新世-中中新世期间(即大约距今25～10 Ma)是一个因坳陷期盆地基底的持续沉降及其相关断裂活动而形成的南海北部陆缘上的斜坡内盆地;白云主凹这个"斜坡内盆地"有别于世界上其它位于被动大陆边缘背景中(如西非近海、巴西近海、墨西哥湾)的斜坡内盆地;海平面变化、沉积物通量变化、构造活动等地质营力都在斜坡内盆地的构造背景上对南海珠江深水扇系统在不同时期产生了不同程度的重要影响.简言之,斜坡内盆地成就了南海珠江深水扇系统.这为以后进一步全面深入研究南海珠江深水扇系统的形成机制、演化过程、结构特征等有着重要意义.

An analysis of the structural background of the sedimentation of the Zhujiang deep-water fan system in the South China Sea

The turbidite system in the intraslope basin of continental margin is one of the biggest hot spots of deep-water oil and gas exploration and development in recent years.A typical deep-water fan system has been discovered in Pearl River Mouth Basin of the north continental margin of South China Sea.It is the Zhujiang deep-water fan system in South China Sea.It has a giant oil and gas potential.Whether has it the structural background of sedimentation of intraslope basin? An integrated analysis is carried out to the structural background characteristic of sedimentation of the Zhujiang deep-water fan system in South China Sea from the point of view of deep-water fan system,mainly based on the integrated interpretation of 700 km long cables and deep reflection(14 s) seismic data acquired recently(the cable passes through the entire Baiyun sag),and combined with the research results of Ocean Drilling Program in South China Sea(ODP1148 sit).The research shows some results as follows.The Baiyun sag is an intraslope basin on the north continental margin in South China Sea from early Miocene to middle Miocene(i.e.about 25 Ma B.c.~ 10 Ma B.c.).It formed by continuous subsidence of the basin base in the period of depression and the associated tectonic activities.The intraslope basin in Baiyun sag is different from some others on many passive continental margins in the world(for example,West Africa offshore,Brazil offshore,the Gulf of Mexico).Some geological forces,e.g.eustatic change,change of sediment flux,tectonic activity and so on,have important effects on the Zhujiang deep-water fan system in South China Sea in different periods in some degree on the structural background of intraslope basin.In brief,it is the intraslope basin that has favored the formation of the Zhujiang deepwater fan system in South China Sea.This is of great significance for a further comprehensive study on the mechanism of formation,the evolutionary process,the structure characteristic and some others of the Zhujiang deep-water fan system in South China Sea henceforth.