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长期以来,川西地区列古六组一直被认为与新元古代冰川晚冰期(Marinoan)地层南沱组相当,从而认为扬子西缘缺失早冰期(Sturtian)沉积,但缺少可靠的年代学证据。针对川西列古六组底部凝灰质杂砾岩锆石LA-ICP-MS U-Pb定年结果表明,~(206)Pb/~(238)U年龄范围为722 Ma~902 Ma,在~725 Ma,~780 Ma,~820 Ma和~850 Ma具有明显的峰值。其中,最年轻一组~(206)Pb/~(238)U年龄加权平均值为724 Ma±12 Ma,代表列古六组底部杂砾岩的最大沉积时间。列古六组沉积序列特征以及华南Sturtian冰期启动年龄分布范围综合分析可知,川西列古六组下段为早冰期沉积,可与长安组对比,而上段则为间冰期沉积,可与富禄组和大塘坡组对比。因此,扬子西缘存在早冰期(Sturtian)和间冰期沉积,不存在晚冰期(Marinoan)沉积。
For a long time, the Leukoo-6 formation in western Sichuan has been considered as equivalent to the Nino Formation in the Marinoan glacier of the Neoproterozoic. Therefore, the western margin of the Yangtze is missing the Sturtian sediments, but lacking reliable chronological evidence. LA-ICP-MS dating of tuffaceous conglomerate rocks in the bottom of the Leukage Formation in western Sichuan Basin shows that the age range of ~ (206) Pb / ~ (238) U is 722 Ma ~ 902 Ma at ~ 725 Ma ~ 780 Ma, ~ 820 Ma and ~ 850 Ma, respectively. Among them, the weighted average age of the youngest 206 Pb / 238 U ages is 724 Ma ± 12 Ma, representing the maximum sedimentary time of the Late Hegaguo Group of bottom conglomerate. Based on the comprehensive analysis of the sedimentary sequences of the Late Palaeo-Liu Formation and the start-up age distribution of the Sturtian glacial period in South China, the lower member of the Liuliu Formation in the western Sichuan Basin was deposited during the early glacial period and can be compared with the Chang’an Formation, while the upper member was deposited during the interglacial period. Datangpo group comparison. Therefore, there is the Sturtian and interglacial deposition in the western margin of the Yangtze, and there is no deposition of Marinoan.