珠江口盆地白云凹陷珠海组浅海三角洲沉积特征

利用白云凹陷北坡钻井资料、地球物理资料以及ODP相关资料进行的井震分析、地层对比和地震地层学解释表明,珠海组顶、底界面T6(距今23.8Ma)和T7(距今32.0Ma)为两次南海大规模构造运动形成的大型不整合界面,是沉积—构造—气候条件的转换面。珠海组沉积时期(渐新世晚期)白云凹陷为浅海陆架环境,发育一套几乎覆盖白云凹陷全区的大型浅水陆架三角洲砂泥互层沉积,与距今23.8Ma以来的半深水-深水的偏泥细粒沉积明显不同。同时,珠海组沉积时期古陆架坡折带自北向南迁移,穿越白云凹陷至南部隆起带附近,强烈推进的三角洲沉积表现出明显海退的相对海平面变化响应。白云凹陷珠海组存在优良的浅水三角洲储盖组合条件,这对白云深水区的油气勘探具有重要意义。

Characteristics of continental delta deposits in Zhuhai Formation of Baiyun Depression in Pearl River Mouth Basin

The drilling data,geophysical data in the north part of Baiyun Depression and ODP files were used to well-seismic analysis,strata correlation and seismic stratigraphic interpretation.The results showed that Baiyun Depression was in the continental shelf in the late Oligocene from 32.0 Ma to 23.8 Ma before present.The large-scale shallow-water continental delta sandstone and mudstone interbedding deposits of Zhuhai Formation were developed around Baiyun Depression,which is different from half-deep or deep water fine deposit since 23.8 Ma.At the same time,the upper surface(at 23.8Ma) and lower surface(at 32.0Ma) of Zhuhai Formation are two large unconformities created by two times of large-scale structural movement in the South China Sea and the transferring interfaces of sedimentary-tectonic-climate conditions.During deposition period of Zhuhai Formation,the continental-shelf slope break migrated from north to south till to the southern uplift belt in the Pearl River Mouth Basin,and the large progradational delta depositional systems was clesely correlative with the extensive regression of relative sea level changes in the late Oligocene.Zhuhai Formation in Baiyun Depression has good shallow marine delta reservoir-seal combination conditions,which is significant for petroleum exploration in deepwater area of Baiyun Depression.