Abstract The Ediacaran Period (635–541 Ma) witnessed rapid turnovers of marine organisms that eventually led to the early Cambrian radiation. The Ediacaran Doushantuo Formation (ca. 635–551 Ma) serves as one of the most important and intensively studied stratigraphic units for understanding the co-evolution of life and environment during this critical time interval. To better understand the early-middle Ediacaran climate change, we reconstruct a temporal variation curve of chemical index of alteration (CIA) from a drill core and an outcrop of the Doushantuo Formation, in combination with previously published CIA data from segments of time-equivalent strata. The results show three distinct decreases in CIA values that correlate well with the positive carbon isotope (δ13C) excursion at the low Doushantuo Formation (EP1) and the negative δ13C excursion at the middle (EN2) and upper (EN3) Doushantuo Formation. The decline of CIA in EP1 is consistent with occurrence of glendonites at the same stratigraphic interval that suggests a cooling event. The low CIA values in EN2 and EN3 also suggest relatively colder periods that are consistent with evidence from strontium isotope (87Sr/86Sr) and oxygen isotope (δ18O) data. With existing bio- and chemostratigraphic constraints, the cooling event associated with EN2 might be synchronous with the Gaskiers glaciation. The other two cold periods associated with EP1 and EN3, however, have not been documented from other successions globally, which needs to be tested in future studies.

中文翻译：

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埃迪卡拉纪陡山沱组化学蚀变指数(CIA)变化及其环境影响

摘要 埃迪卡拉纪（635-541 Ma）见证了海洋生物的快速周转，最终导致了早期寒武纪辐射。埃迪卡拉纪陡山沱组（约 635-551 Ma）是了解这一关键时期生命和环境共同演化的最重要和最深入研究的地层单元之一。为了更好地了解埃迪卡拉纪早期中期的气候变化，我们结合先前公布的时间等效段的 CIA 数据，从钻芯和陡山沱组的露头重建了化学蚀变指数 (CIA) 的时间变化曲线。地层。结果显示 CIA 值的三个明显下降与低陡山沱组 (EP1) 的正碳同位素 (δ13C) 偏移和中段 (EN2) 和上段 (EN3) 陡山沱组的碳同位素正偏移 (δ13C) 密切相关。EP1 中 CIA 的下降与在表明冷却事件的同一地层间隔中出现了菱镁矿相一致。EN2 和 EN3 中较低的 CIA 值也表明相对较冷的时期，这与来自锶同位素 (87Sr/86Sr) 和氧同位素 (δ18O) 数据的证据一致。由于现有的生物和化学地层限制，与 EN2 相关的冷却事件可能与加斯基尔冰川同步。然而，与 EP1 和 EN3 相关的另外两个寒冷期尚未从全球其他演替中得到记录，