CHARACTERISTICS OF CONODONTS AND SEDIMENTARY ENVIRONMENT OF UPPER NORIAN NANSHUBA AND DASHUITANG FORMATIONS IN BAOSHAN,YUNNAN PROVINCE
Article
Figures
Metrics
Preview PDF
Reference
Related
Cited by
Materials
Abstract:
Norian marine deposits are developed in Baoshan block, Yunnan Province. So far, few studies on palaeochronology have been carried out. In this study, the Norian sections at Dabaozi and Hongyan in Baoshan are measured and sampled. Conodont fossils were obtained from the limestone in middle Nanshuba Formation and the top part of Dashuitang Formation, These conodonts identified as Mockina bidentata, Mockina englandi and Mockina aff. englandi, are with the age of Sevatian 1 Subage, late Norian. Based on the analysis of thin sections, it is found that the limestones of Nanshuba and Dashuitang formations contain a large number of radiolarians, and debris with different degrees of roundness in clastic rocks can also be seen. In view of the slump structures seen in outcrops and the microscopic features of sedimentary rocks, it is deduced that Nanshuba Formation was deposited in a mixed shelf environment at Dabaozi area, controlled by the tectonic setting of an island arc(or microplate) in the Norian Tethys Ocean.
