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《Regional Geology of China》 2005-06
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New advances in the study of “the Nanhuaan System”-with particular reference to the stratigraphic division and correlation of the Nanhuaan System, South China

WANG Jian Chengdu Institute of Geology and Mineral Resources, China Geological Survey, Chengdu 610082, Sichuan,China  
The Neoproterozoic South China rift system is composed of a number of graben-and horst-type subbasins. The strata of the system which onlap unconformably the Sinian orogen and underlie the Nantuoan tillites regionally occur as successions of laterally inextensive wedged-shaped strata. A wealth of new U-Pb isotope age data indicate that the ages of the lower boundary of the wedged-shaped strata (including the Banxi Group and /or its equivalents Gaojian, Furongxi, Danzhou, Xiajiang, Dengshan, Likou and Heshangzhen groups) are all less than or close to 820Ma in age, which represents the onset of the earliest deposition of the Neoproterozoic rift system. It is clear that almost all of the strata(1000-820Ma) corresponding to the Qingbaikouan System in North China are lacking above the Sibaoan orogenic unconformity. This conclusion apparently differs from the existing stratigraphic division schemes for South China. Since the age of 820Ma marks the onset of the most important sedimentary event in South China during the Neoproterozoic and is also close to that of the basal boundary of the Cryogenian System in the tripartite division of the Neoproterozoic in the International Stratigraphic Chart issued under auspices of the International Commission on Stratigraphy, the author suggests that the unconformity between the sedimentary onlapped strata of the Neoproterozoic rift system and the metamorphic series of the Sibaoan orogen be defined as the basal boundary (age ~820 Ma)of the Nanhuaan System.
【Fund】: 国家自然科学基金项目(编号:40472070);; 重点基金项目(编号:40032010-B)联合资助。
【CateGory Index】: P534.3
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