琼东南盆地沉积环境及物源演变特征

运用沉积地球化学、古生态学等手段对琼东南盆地渐新世—中新世沉积环境及沉积物源区特征进行了分析研究,认为渐新世崖三段为淡水滨岸环境,之后海水逐步加深,由海陆过渡环境,演变到崖一段的海湾环境。盆地东部与西部在沉积物源上存在明显差异:在盆地西部的崖城隆起地区,沉积物源区存在较多的基性岩成分,特别是自陵二段开始,基性岩成分所占比例明显增高;盆地东部的松东、宝岛和松南凹陷具有明显混合物源的特性。琼东南盆地存在3套潜在的烃源岩,即始新世湖相烃源岩、渐新世海陆过渡相烃源岩和中新世半深海—深海相烃源岩,松东、宝岛凹陷陵水—三亚期的储层物性要好于松南凹陷。

Evolution of sedimentary environment and provenance in Qiongdongnan Basin in the northern South China Sea

The sedimentary environment and provenance characteristics in the Qiongdongnan Basin during the Oligocene and Miocene periods were analyzed using geochemical and paleoecological methods.The results indicate that,during the early Oligocene,the basin was prevailed by freshwater to littoral environments for the deposition of section 3 of the Yacheng Formation,then altered to sea-land transitional conditions with sea water deepening gradually for section 2,and finally to gulf to outer shelf environments for section 1 of the Yacheng Formation.Apparent differences in the provenance exist between the eastern and the western parts of the basin.While the Yacheng ridge area westward contains mainly sediments of mafic composition,which increases proportionally especially since section 2 of the Lingshui Formation,in the east such as the Songdong,Baodao and Songnan sags are characterized by a mixture of provenance during the late Oligocene.Moreover,the Qiongdongnan Basin comprises three sets of potential hydrocarbon source rocks,namely a lacustrine phase in the Eocene period, a sea-land transition phase in the Oligocene period, and a deep-sea phase in the Miocene period. The late Oligocene to early Miocene Lingshui-Sanya formations in the Songdong and Baodao sags show better reservoir properties than that in the Songnan sag.