摘要
In the newly revised Regional Chronostrati-graphic (Geochronologic) Scale of China, the original bipar-tite division of the Neoproterozoic is changed to tripartite division. The three 搒ystem?rank chronostratigraphic units are in ascending order of the Qingbaikou, Nanhua and Sin-ian Systems. This report presents SHRIMP zircon U-Pb dat-ing on volcanic tuffs from the candidate stratotype section of the Nanhua System at the Yangjiaping section that is geo-graphically located in Hupingshan Town, Shimen County, Hunan Province. Tuff from the upper part of the Xieshuihe Formation (equivalent to the Liantuo Formation) in the Lower Nanhua Series yields a zircon U-Pb age of 758 23 Ma, which may provide a constraint on the lower limit of the Gucheng glacial stage in the Nanhua System. Tuff from the Laoshanya Formation of its underlying Qingbaikou System (equivalent to the Banxi Group) gives a zircon U-Pb age of 809 16 Ma. The sampling locality lies 12 m from the upper boundary of the Qingbaikou System. According to the sedi-mentation rate it is estimated that the upper boundary age is about 800 Ma. The present studies also provide a resolution to the long-standing problems concerning stratigraphic cor-relation of the Late Precambrian in South China whether the Liantuo Formation is equivalent to the Banxi Group or not.
In the newly revised Regional Chronostrati-graphic (Geochronologic) Scale of China, the original bipar-tite division of the Neoproterozoic is changed to tripartite division. The three 搒ystem?rank chronostratigraphic units are in ascending order of the Qingbaikou, Nanhua and Sin-ian Systems. This report presents SHRIMP zircon U-Pb dat-ing on volcanic tuffs from the candidate stratotype section of the Nanhua System at the Yangjiaping section that is geo-graphically located in Hupingshan Town, Shimen County, Hunan Province. Tuff from the upper part of the Xieshuihe Formation (equivalent to the Liantuo Formation) in the Lower Nanhua Series yields a zircon U-Pb age of 758 23 Ma, which may provide a constraint on the lower limit of the Gucheng glacial stage in the Nanhua System. Tuff from the Laoshanya Formation of its underlying Qingbaikou System (equivalent to the Banxi Group) gives a zircon U-Pb age of 809 16 Ma. The sampling locality lies 12 m from the upper boundary of the Qingbaikou System. According to the sedi-mentation rate it is estimated that the upper boundary age is about 800 Ma. The present studies also provide a resolution to the long-standing problems concerning stratigraphic cor-relation of the Late Precambrian in South China whether the Liantuo Formation is equivalent to the Banxi Group or not.
基金
jointly supported by the Ministry of Science and Technology of China for fundamental work(Grant No.2001DEA20020-1)
the Natural Science Foundation of China(Grant No.40272015)
China Commission on Stratigraphy(research on the stage establishment for China’s main chronostratigraphy).
