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一般认为,华南南华系是指板溪群之上、陡山沱组之下的一套地层,其时限大致为720~635Ma。湘西托口地区的南华系原来被划分为江口组和南沱组,由于江口组的停用以及高精度年代学资料的缺乏,加上古沉积环境恢复研究程度较低,严重制约了新一轮南华系区域地层对比与岩相古地理重建。通过对该地区南华系及相关地层的野外地质调查、区域地层对比和碎屑锆石U-Pb同位素测年等研究,认为该区南华系可以被重新划分为滨岸冰融相长安组、障壁岛相富禄组、滨岸冰融相古城组、潮坪相大塘坡组和冰海大陆架相洪江组;其中,长安组和古城组的沉积时代分别晚于732 Ma和705 Ma。结合相关资料研究初步认为,富禄组应同大塘坡组一样属于间冰期沉积;华南南华纪可能至少发生过三次冰川事件,即长安冰期(<732 Ma~?)、古城冰期(<705~670 Ma)和南沱冰期(651~635 Ma)。
It is generally believed that the South China South China System refers to a set of strata below the Doushantuo Formation above the Banxi Group, with a duration of approximately 720-635 Ma. The Nanhua System in the Tuokou area in the western Hunan Province was originally divided into Jiangkou Formation and Nantuo Formation. Due to the discontinuation of the Jiangkou Formation and the lack of high-precision geochronological data, and the relatively low degree of researches on the restoration of paleoenvironments, seriously restricting the new round of Nanhua Regional stratigraphic correlation and facies palaeogeography reconstruction. Based on the field geological survey, regional stratigraphic correlation and detrital zircon U-Pb isotope dating of the South China Stratigraphy and related strata in the area, it is considered that the South China Stratigraphy can be reclassified as the Chang’an Formation of the Coastal Ice-Melting, the Barrier The island phase Fulu Formation, the coastal ice melting ancient city group, the tidal flat Datangpo Formation and the ice-sea continental shelf Hongjiang Formation. Among them, the depositional ages of Chang’an Formation and Gucheng Formation are respectively later than 732 Ma and 705 Ma. Based on the related data, it is preliminarily believed that the Fulu Formation should belong to the interglacial deposition as Datangpo Formation. At least three glaciations may occur in the South China Huayan Period, ie Chang’an Ice Age (<732 Ma ~?), Ancient City Ice Age (<705 ~ 670 Ma) and Nantuo glacier (651 ~ 635 Ma).