岩心观察表明,珠江口盆地文昌凹陷珠海组二段具有交错层理/斜层理含砾砂岩/细砂岩相、正递变层理含砾砂岩相、复合层理砂泥岩相、含泥岩撕裂屑含砾粗砂岩/细砂岩相等11种岩石相类型.从岩石相入手,结合岩电特征、重矿物组合、岩石组成及地震相等分析,识别了珠海组二段扇三角洲、三角洲、潮坪、潟湖等主要沉积相类型,并刻画了其平面展布.文昌凹陷四周的隆起、凸起提供了大量的点物源、线物源,形成了一系列三角洲及扇三角洲,凹陷中心地势平坦,潮坪分布广,潟湖仅在珠三南断裂下降盘出现,分布较局限.

By observing and describing the cores, there are 11 types of lithofacies in Oligocene Zhuhai Member-2 in Wenchang Sag of Pearl River Mouth Basin, including conglomeratic sandstone or fine sandstone with cross-bedding or oblique bedding, conglomeratic sandstone with normally graded bedding, sandstone and mudstone with mixed bedding, conglomeratic coarse sandstone or fine sandstone with torn-apart fragments of mudstone, etc. Four sedimentary facies, including fan delta, delta, tidal flat, and lagoon, are recognized in Zhuhai Member-2 in Wenchang Sag according to the research on the types of lithology and electric curves, the combination of heavy minerals, the composition of rocks, and the seismic facies. It is shown that the uplifts and the bulges around Wenchang Sag provided sediments, and a series of deltas and fan deltas formed. The tidal flats widely develop in the center of the sag with a flat topography, while the lagoons distribute restrictedly in the subsiding center along Zhu Ⅲ South Fault.