南华北盆地青白口系—侏罗系层序界面时空分布特征研究

Characteristics and Temporal and Spatial Distributions of Sequence Boundary of Qingbaikou-Jurassic in South Huabei Basin

以位于秦岭—大别造山带之北、华北陆块南部、地跨华北陆块稳定块体、陆块南部边缘变形带的南华北盆地为研究对象,通过对研究区42条不同时代的野外剖面详细观测,运用层序地层学理论,把南华北盆地作为一个整体系统,对青白口系—侏罗系层序界面特征及时空分布规律进行了系统分析,共识别出了8种类型层序界面的物质表现形式,分别是不整合面、渣状层、古喀斯特作用面、冲刷侵蚀面、超覆面、岩性岩相转换面、最大海泛面、最大湖泛面。并重点讨论了各类型界面的时空分布特征。结果表明:在时间演化上,从早到晚由海相—海陆过渡相—陆相,层序界面经历了海相沉积不整合、古喀斯特作用面、渣状层到陆相不整合面、冲刷侵蚀面等;在空间上,同一层序界面在不同相带表现形式不同,同一种类型的界面可在不同相带出现,但不同相带表现特征有一定差异性。

Qingbaikou-Jurassic of south Huabei Basin located in the north of Qinling-Dabie orogenic belt or the south of North China Block,and acrossed the stable North China Block and the deformation belt of southern block margin.42 field geologic sections of different eras were observed;based on the theory of sequence stratigraphy,south Huabei Basin was taken as a whole,characteristics and temporal and spatial distributions of sequence boundary of Qingbaikou-Jurassic were discussed.8 types of sequence boundary identified were unconformity surface,paleosoil,action surface of ancient karst,washing erosion surface,onlap surface,transition surface of rock character and facies,maximum marine flooding surface,maximum lacustrine flooding surface.Finally,Distribution characteristics of different boundaries were discussed in time and space.The results showed that the boundary in time from begin to end appeared marine facies,sea-land transition facies,continental facies,respectively,and the sequence boundary experienced marine deposition unconformity surface,action surface of ancient karst,paleosoil to the continental unconformity surface,washing erosion surface,etc;in space,the same sequence boundary could occur in different facies and have different forms,but there were some differences of the characteristics among the facies.