珠江口盆地西江南洼古近系构造演化与沉积特征

摘要

西江南洼是珠江口盆地珠一坳陷西部一个相对独立的洼陷,其在古近纪始新世是一个断陷湖盆,断陷的形成与演化受到区域应力场的控制,随着区域应力场由NE-SW向拉伸向NNW-SSE向拉伸的转变,断陷的形成表现为由初始断陷期、强烈断陷期、弱断陷期到断陷萎缩期的一个完整演化序列,以及断陷中心由北至南逐渐迁移的过程.沉积作用受构造活动的控制,在主成湖期断陷作用最强的北部地区发育了西江南洼最主要的中深湖一深湖相优质烃源岩和交互沉积的近岸水下扇沉积,它们构成了该区古近系最有潜力的勘探组合.%As a relatively separated sag in the western Zhu Ⅰ depression,Pearl River Mouth basin,South Xijiang sag was an Eocene rifted lake,and its formation and evolution was controlled by the regional stress field.When the regional stress changed from NE-SW to NNW-SSE extension,an entire evolution sequence,from initial rifting,strong rifting,weak rifting to rift shrinkage,was exhibited in the sag,with the rifting center gradually migrating from the north to the south.Owing to the sedimentation controlled by the tectonic activities,the most important part of good-quality source rocks in South Xijiang sag and some interbedded nearshore-subaqueous fans have developed in the northern area with the strongest rifting during the main lake-formation episode,and may make up the most favourable exploration plays in Paleogene here.