The evolution of the paleoclimate and the duration of the two glacial periods during the Cryogenian in the Yangtze Block are of great geological significance for understanding “Snowball Earth.” We studied the evolution of the paleoclimate during the Cryogenian, using chemical weathering, and determined the warming time of the interglacial paleoclimate, using zircon U-Pb dating in the Yangtze region. A new laser ablation ICP-MS zircon U-Pb age of 659.9±3.2 Ma is reported from the middle Datangpo Formation. The chemical index of alteration (CIA) for the Cryogenian fine clastic rock samples from a drill core shows that the climate in the provenance area during the Gucheng and Nantuo glacial periods was dry and cold and that the chemical weathering was weak; the average CIA values were 63.3 and 64.2, respectively. In the early stage of the Datangpo period, the climate in the provenance area was still dry and cold, with a CIA average of 60.7, compatible with that in the two glacial periods; in the middle and late stages, the climate was warm and humid, chemical weathering was enhanced, and the average CIA rose to 77.4, compatible with the 76.9 of the Liantuo period before the Cryogenian. The evolution of other chemical weathering (paleoclimate) proxies, such as the chemical index of weathering, the plagioclase index of alteration, and Rb/Sr, is compatible with that of the CIA. The warming time of the interglacial paleoclimate during the Cryogenian in the Yangtze Block was ca. 660 Ma, roughly consistent with the ending time of the Sturtian in Australia and Mongolia, indicating that the lower part of the Datangpo Formation may still represent Sturtian glacial deposits, thus further suggesting the global consistency of the end of the Sturtian.

中文翻译：

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扬子地块低温纪间冰期古气候变暖时间的新锆石U-Pb年龄及其限制

扬子地块低温纪古气候的演变和两次冰期的持续时间对认识“雪球地球”具有重要的地质意义。我们利用化学风化作用研究了低温纪古气候的演变，并利用长江地区的锆石 U-Pb 定年法确定了间冰期古气候变暖的时间。在大塘坡组中部报道了一个新的激光烧蚀ICP-MS锆石U-Pb年龄为659.9±3.2 Ma。岩心低温系细碎屑岩样品的化学蚀变指数(CIA)表明，古城、南沱冰期物源区气候干燥寒冷，化学风化作用较弱；平均 CIA 值分别为 63.3 和 64.2。大塘坡前期，物源区气候依然干燥寒冷，CIA平均值为60.7，与两个冰期一致；中后期气候温暖湿润，化学风化作用增强，平均CIA升至77.4，与低温纪前连陀期的76.9相吻合。其他化学风化（古气候）指标的演变，例如风化的化学指数、蚀变的斜长石指数和 Rb/Sr，与 CIA 的一致。扬子地块低温纪间冰期古气候变暖时间约为 . 660 Ma，大致与澳大利亚和蒙古的Sturtian结束时间一致，