重庆石柱地区下奥陶统沉积微相研究

Sedimentary Microfacies in the Lower Ordovician strata in Shizhu,Chongqing

关键词:  碳酸盐岩|沉积微相|下奥陶统|重庆石柱

Key words:  carbonate rock|sedimentary microfacies|Lower Ordovician|Chongqing|Shizhu

摘要:

重庆石柱漆辽乡下奥陶统可划分为13种沉积微相和5种沉积亚相。结合露头沉积学研究得出该时段沉积环境的演化序列为:南津关组和分乡组下部以灰岩为主,夹陆源碎屑透镜体和鲕粒灰岩,属于局限台地亚相;分乡组的中上部以鲕粒滩和泥页岩为主,属于典型的开阔台地亚相;红花园组的底部以生物碎屑灰岩与泥岩互层为主,红花园的中上部为深灰色巨厚层含燧石结核灰岩、砾屑灰岩夹生物碎屑灰岩,分别属于台地边缘浅滩亚相和台地前缘斜坡亚相;大湾组的生物碎屑灰岩与页岩互层属于内陆棚亚相。综合分析表明研究区下奥陶统是一个水体向上变深的沉积旋回。

Abstract:

Thirteen sedimentary microfacies and five sedimentary subfacies have been distinguished for the Lower Ordovician strata in Qiliao,Shizhu,Chongqing.The restricted platform subfacies are recognized in the Lower Ordovician Nanjinguan Formation and the lower part of the Fenxiang Formation,where there occur limestone intercalated with terrigenous clastic lenses and oolitic limestone.The open platform subfacies are arranged into the middle and upper parts of the Fenxiang Formation,in which ooiltic shoal and argillutite are accentuated.The basal part of the Honghuayuan Formation dominated by alternating bioclastic limestone and mudstone is assigned to the platform-margin beach subfacies,whereas the foreslope subfacies occur in the middle and upper parts of the Honghuayuan Formation occupied by thick-bedded dark grey cherty nodular limestone and calcirudite intercalated with bioclastic limestone.The Dawan Formation built up of alternating bioclastic limestone and shale belongs to the inner shelf subfacies.Multidisciplinary analysis indicates that the Lower Ordovician strata in the study area are considered as the deepening-upward depositional cycles from the Lower Ordovician Nanjinguan Formation to the Dawan Formation.