The Sedimentary Characteristics And Sequence Stratigraphic Position Of The Miaolingian Series Oolitic Shoal In The Western Suburbs Of Beijing

The Cambrian strata of the Xiaweidian section in the western suburbs of Beijing is exposed completely.The oolitic shoal of Miaolingian Series research for in-depth understanding of Cambrian oolitic shoal and Cambrian of north China sea level change cycle has a very classic representative.Therefore,this study adopted the petrological characteristics and mineralogy characteristics of the Xuzhuang Formation,Zhangxia Formation and Gushan Formation of the Cambrian Miaolingian in the study area,and analysis of the sedimentary characteristics and the sequence stratigraphic location in which it is located.Firstly,based on the collected literature and outcrop data,a detailed classification of the sequence strata of the Cambrian in the Xiaweidian section of the western suburbs of Beijing is carried out.A total of nine tertiary sequences are divided,and then according to the analysis of the microscopic slices.The sedimentary characteristics in the different layers of the Miaolingian Series,namely the Xuzhuang Formation,the Zhangxia Formation and the Gushan Formation,are discussed and compared in detail,and then the sequence stratigraphic location of the sequence is determined and a certain in conclusionIt is generally clear that a set of marine carbonate deposits based on clastic rocks is developed on the Cambrian in the Xiaweidian section of the western suburbs of Beijing.The tidal flat facies in the secondary sea level change cycle transitions to the carbonate platform.The Cambrian in the Xiaweidian section is divided into nine tertiary sequences,.At the top of the tertiary sequence formed by the Xuzhuang Formation,the Zhangxia Formation and the Gushan Formation,a large-scale oolitic shoal is developed.These oolitic are mainly composed of concentric oolite,radiation oolite,single crystal oolite,fake oolite.Although the discovery of these oolitic is found in each strata,due to the different secondary and high-frequency sea level change cycles and different hydrodynamic conditions of these thick oolitic shoales,The same type of oolitic differed in terms of distribution scale,particle size,and at the same time as the development of oolitic shoales,the deep-water biological mounds of the Zhangxia Formation oolitic and the stromatolites of the Gushan Formation were also discovered.There are great differences between both macroscopically and microscopically.Behind the Cambrian microbial carbonate sedimentary diversity,there are some different understandings from the traditional ones: firstly,these oolitic shoales are basically in the forced regressive system domain,of the three-level sea level change cycles in the sequence stratigraphy.This situation does not conform to the standard sequence stratigraphic model.Secondly,in the high-energy environment that forced regressive system domain,a large number of radioactive oolite are also found to have a certain gap with the traditional concept.This study only provides a new research idea and specific examples for a more in-depth study of the oolitic shoal.