对我国沿海3个含油盆地－珠江口、北部湾和渤海湾盆地下第三系湖相生油岩中的微体化石群进行比较分析。3个盆地中以渤海湾盆地下第三系湖相化石群最为丰富，数量多，分异度高，而且化石群以地方性属种比例高、咸水类型多，存在“海源陆生生物化石”为特征；北部湾盆地，在涠洲组和流沙港组发现较多的介形类化石及个别腹足类和轮藻化石；而珠江口下经三系湖相地层中，微体化石罕见，只在个别层位发现贝壳碎片。据化石群特征，推测渤海湾盆地早第三纪是封闭型的咸水湖泊，而且部分沉积时期，可能是以Cl^-和Na^ 为主的咸水湖泊；珠江口盆地早第三纪是湖水矿化度低、硬度、pH值也低的淡水湖泊；而北部湾盆地早第三纪可能仍属淡水湖泊，但有一定的矿化度。

Microfossils from Paleogene lacustrine oil source rocks of the Pearl River Mouth Basin, Beibuwan Basin and Bohai Gulf Basin have been studied. The Paleogene lacustrine microfossils of Bohai Gulf Basin are characterized by their high abundances, high diversities, high proportion of local species as well as saline species and the occurrence of talassogenous fauna. In Beibuwan Basin, only ostracods,gastropods and charophytes are discovered in the Weizhou Formation and Liushagang Formation; microfossils are rare in the Paleogene lacustrine sediments and only shell debris were found in some samples. According to the characteristics of microfossils of the three basins, we speculated that the Bohai Gulf Basin was a hydrologically closed lake during Paleogene and in some periods it was a saline lake rich in Na and Cl. The Paleogene lacustrine oil source rocks of Pear River Mouth Basin were deposited in a freshwater lake with lower salinity, hardness and pH. The Paleogene lake of Beibuwan Basin was a freshwater lake too, but with higher salinity.

P618.130.2 Q913.7

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