微体古生物在层序地层划分中的应用——以渤中坳陷为例

THE APPLICATION OF MICROPALEONTOLOGY IN SEQUENCE CLASSIFICATION OF STRATA:AN EXAMPLE OF BOZHONG DEPRESSION

渤中坳陷位于渤海湾盆地中心部位,是渤海湾盆地地质结构、层序地层和沉积环境比较有代表性的地区。该文以渤中坳陷BZ34-1-3井和BZ34-4-4井下第三系明化镇组下段为例,着重分析和讨论了微体古生物的分布规律在层序划分和沉积相判别中具有的重要意义。并对单井进行层序地层划分,结合周缘相关井建立一条连井剖面,进行沉积相判别,从而印证微古生物的指示性。研究表明,在渤中坳陷,微古生物的分布规律可以指示BZ34-1-3井和BZ34-4-4井由下至上为河流相向湖相过渡的沉积环境。

Bozhong depression, located in the central part of Bohai Bay Basin, is a representative for its strata sequences and sedimentary environment. Taking Minghuazhen formation of BZ34-1-3 well and BZ34-4-4 well in Bozhong depression as examples, the paper concentrates on the application of micropaleontology distribution law in the classification of sequences and determination of sedimentary environment. And it also classifies the strata sequence of these two wells, establishes a stratigraphic profile of several wells, and analyzes sedimentary facies and sedimentary environment of the purposeful strata, so as to prove the importance of the micropaleontology indication. It also shows that micropaleontology distribution can demonstrate the sedimentary environment changes from fluvial facies to lacustrine facies with the depth of the wells declining.