【摘要】 在陕西镇安西口从上石炭统逍遥阶和下杨家河阶到下二叠统上杨家河阶、范家河阶、垭口阶和隆林阶的地层剖面上,区分出10种碳酸盐岩微相类型,即含生物碎屑灰泥灰岩、生物碎屑粒泥灰岩、生物碎屑泥粒灰岩、粒泥灰岩—泥粒灰岩、粗枝藻粒泥灰岩—粗枝藻泥粒灰岩、腕足棘皮粒泥灰岩—腕足棘皮泥粒灰岩、生物碎屑颗粒灰岩、团块颗粒灰岩、核形石颗粒灰岩和含鲕粒团块颗粒灰岩。它们形成于开阔台地和台地边缘浅滩2种沉积环境,开阔台地又进一步分为较浅水的开阔台地浅滩和较深水的开阔台地滩间,台地边缘浅滩内则局部发育藻丘。在此基础上,识别出在晚石炭世逍遥期至早二叠世隆林期研究区发生过12次相对海平面波动,它们构成5次明显的相对海平面升降;最后讨论了三里冲剖面上各阶界线与海平面变化的关系。更多还原

【Abstract】 In the Carboniferous-Permian boundary section at Xikou of Zhen’an County in Shaanxi Province,through the Upper Carboniferous Xiaoyao Stage to Xiayangjiahe Stage and the Lower Permian Shangyangjiahe Stage, Fanjiahe Stage,Yakou Stage and Longlin Stage,10 kinds of carbonate microfacies may be recognized based on the sedimentary grain types, the abundance and diversity of fossils,as well as the textures and structures of limestones.These are bioclastic mudstone,bioclastic wackstone,bioclastic packstone,fusulinids wackstone and packstone,dasyclodaceae wackstone and packstone,brachiopod-echinoderm wackstone and packstone,bioclastic grainstone, peloid grainstone,oncoid grainstone,and oolitic grainstone.From Upper Carboniferous to Lower Permian depositions mentioned above were formed under two types of sedimentary environments,the open carbonate platform and the organic sand at platform edge.The former may be further subdivided into shoal and platform,and the latter into organic sand and bioherm. On the basis of the above analysis,12 high frequency changes of sea level and 5 low frequency ones may be distinguished.The relations between boundaries,including Carboniferous-Permian boundary,Shangyangjiahe-Fanjiahe stage boundary,and Fanjiahe-Yakou stage boundary,and changes of sea level are discussed.更多还原