Investigation About Belonging Of Badu And Xiajialing Formations In West Qinling Minxian County

The regional structure of West Qingling is complex. Regional stratigraphy are combinations of North and South China plates. The study level of stratigraphy in Minxian county West Qingling is relatively low. Stratigraphic division needs to be further strengthened. Based on the Zhuoping section and the route survey of corresponding formations, we have studied Badu formation of lower Carboniferous and Xiajialing formation of upper Carboniferous. And discussed the belonging of the strata by the analysis of micro body fossils samples and zircon samples in Zhuoping area and corresponding layers. The conclusions and understandings of our work are as follows:1. By the study of sectional measurement Zhuoping in Minxian county formations and regional comparison, we found that there is a difference of Carboniferous stratigraphic characteristics between West Qinling Minxian county and region.2. Micro body fossils conodonts were found in the original Carboniferous strata. Fossils found in Badu formation were identified as Neogondolella srrata,Neog. postsrrata,Neog. asrrata,Sweetognathus inornatus and Hindeodus minutus. Age of strata is Permian Guadalupian Series Wordian to lower part of Capitanian, about 267-263 Ma. According to the exposed situation of the regional strata, it is suitable belong to Shilidun formation. The fessils in original Xiajialing formation show that is more approprite to belong to Longwuhe formation.3. The material sources of Permian strata were analysed. The value of Th/U sample TW02 zircon is more than 0.4, that proved substantially magmatic origin. Zircon, age group 486~383Ma, including 28, about 46% of the total, may be mainly from the North Qinling region, followed Qilian. Ziron, age group 942~624Ma, including 22, about 36% of the total, may be mainly from the yangtze plate and Qinling Mountains orogenic belt. Ziron, including 10, age group 1881~1503Ma and 2566~2470Ma, about 16% of the total, may be from base of ancient North China craton uplift and erosion. Permian clastic material is more affinity with the South China plate, and having diversity, most of the source material for the South China plate and Qinling orogenic belt, followed Qilian plate and North China craton.