Feature,genetic model and distribution of calcareous insulating layers in marine strata of western Pearl River Mouth basin in north of South China Sea

中国南海北部珠江口盆地西部海相地层钙质隔层特征、成因及分布

We have systematically investigated the feature, genetic model and distribution of calcareous insulating layers in marine strata of the Ⅰ oil group in member 2 of Zhujiang formation(ZJ2I oil formation), western Pearl River Mouth basin(PRMB) in the north of the South China Sea by using data such as cores, thin sections, X-ray diffraction of whole-rock, and calcite cement carbon and oxygen isotopes. The lithology of the calcareous insulating layers in the study area is mainly composed of the terrigenous clastic bioclastic limestone and a small amount of fine-grained calcareous sandstone. On this basis, two genetic models of calcareous insulating layers are established, including the evaporation seawater genetic model and shallow burial meteoric water genetic model. The calcareous insulating layers of the evaporation seawater genetic model developed in the foreshore subfacies, mainly at the top of the 1-1 strata and 1-3 strata. The calcareous insulating layers of the shallow burial meteoric water genetic model developed in the backshore subfacies, primarily in the 1-2 strata.

综合利用岩心、普通薄片、全岩和黏土矿物X射线衍射、碳氧同位素等资料,对珠江口盆地西部珠江组二段Ⅰ油组海相砂岩地层钙质隔层的岩性和矿物结构特征、成因模式及其分布规律进行系统研究。研究区钙质隔层岩性主要为含陆源碎屑生屑灰岩和少量细粒钙质石英砂岩。在此基础上建立了两种钙质隔层的成因模式:蒸发作用海水成因和浅埋藏淡水成因。蒸发作用海水成因的钙质隔层在前滨亚相发育,主要发育在1-1岩层组和1-3岩层组顶部。浅埋藏淡水成因的钙质隔层在后滨亚相发育,主要发育在1-2岩层组。