海域区古近系含煤地层基准面旋回识别与对比:以琼东南盆地为例

研究了琼东南盆地古近系含煤地层的沉积体系。研究区主要发育冲积扇/扇三角洲-海底扇体系、滨浅湖-中深湖-浊积扇体系、辫状河-辫状河三角洲-水下扇体系、潮坪-泻湖体系、滨浅海-浊积扇体系等沉积体系,其中辫状河-辫状河三角洲-水下扇体系、潮坪-泻湖体系聚煤作用较强。运用高分辨率层序地层学理论与技术方法,进行了中、短期基准面识别与对比。短期基准面对比界面主要类型是冲刷现象及其上覆的滞留沉积物、土壤化沉积与泥炭化事件沉积组合、微相岩相类型或相组合在垂向剖面上转换、测井曲线突变界面等。琼东南盆地古近系的地层中,由不同成因特征的边界所界定的短期基准面旋回主要有向上"变深"的非对称型短周期旋回层序(A型层序)、向上变浅的非对称型短周期旋回层序(B型层序)和向上变深再变浅的对称型短周期旋回层序(C型层序)。

Identification and Correlation of Base-level Cycles of Coal-bearing Strata in Paleogene System of China Seas: Taking the Case of Qiongdongnan Basin as an Example

This paper researched coal-bearing strata depositional systems of Paleogene System in Qiongdongnan basin.The main depositional systems in the study area are alluvial fan(fan delta)-abyssal fan system,shore marine and middle-deep lake and turbidite fan system,braided stream-braided channel delta-subsea apron system,tide flat-lagoon system,offshore-epeiric sea-turbidite fan system,etc.Among the above depositional systems,the braided stream-braided channel delta-subsea apron system and tide flat-lagoon system have undergone great coal-forming actions.With high resolution sequence stratigraphy theory and technology,the middle-and short-term basal levels were identified.The main boundary types of short-term basal level are erosion and the overlying lag sediments,soil sediments and peatification event sediments,microfacies and lithofacies types or facies group changes in vertical,abrupt interfaces in well logging curves,etc.In the Paleogene strata of Qiongdongnan basin,the short-term basal level cycle types,controlled by different genetic feature boundaries,are deepening-upward asymmetric short-term basal level cycle(type A),shallowing-upward asymmetric short-term basal level cycle(type B) and symmetric short-term basal level cycle(type C).