北京下苇甸地区张夏组沉积环境及沉积模式

Study on Sedimentary Environment and Patterns of the Cambrian Zhangxia Formation at Xiaweidian,Beijing

北京下苇甸张夏组作为华北寒武系的标准剖面之一,一直以来是广大地质学者研究的重点。通过野外观察、实测,并结合室内薄片鉴定、XRD测试等技术,对北京西山下苇甸张夏组的岩性特征进行了详细的分析,结合其特征,对张夏组沉积相做了细致划分。通过研究,该区张夏组主要发育碎屑岩浅海相及碳酸盐岩台地相沉积,其中碎屑岩浅海主要发育过渡亚相及页岩局限浅海亚相;台地相主要发育局限台地、滩、潮坪亚相。通过岩性特征观察及剖面相组合,首次对研究区的滩进行了划分,将滩分为高能滩及间歇高能滩。总体上,张夏组表现为一个典型的离岸缓坡碳酸盐岩台地沉积模式,由下向上水体加深,陆源碎屑沉积逐渐往后迁移,被碳酸盐岩沉积所取代,台地成熟。

The Xiaweidian outcrop in the Western Hills of Beijing is one of the typical outcrops of the Cambrian system in North China.It has always been a focus of study for geological scientists.This paper describes a detailed analysis of the sedimentary deposits of the Cambrian Zhangxia based on previous research,involving field observation and measurement combined with indoor wafer identification,XRD tests,and other technologies.Through research,the main face of the Zhangxia deposit was determined to be detrital bathyal shallow marine facies and platform facies.The subfacies and shale were limited in shallow seas;the main development of the platform was limited to platform,beach,and tidal flat subfacies,and the beach was divided into high-energy beach and intermittent high-energy beach.The Zhangxia Formation is an offshore,gently sloping carbonate platform,consisting of many M-level cycles which gradually become shallow as one moves upward.In general,the water from the bottom grows deeper,and the carbonate platform gradually becomes stable.