北京大学学报（自然科学版） ›› 2026, Vol. 62 ›› Issue (4): 819-837.DOI: 10.13209/j.0479-8023.2026.043

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蒙古西部巴彦峡谷埃迪卡拉系–寒武系界线地层地球化学特征及其对寒武纪生命大爆发前海水氧化还原状态的指示意义

郑澳男1, 刘建波1,2,†, 江﨑洋一3, 足立奈津子3, Altanshagaid Gundsambuu4, Batkhuyag Enkhbaatard4, Dorj Dorjnamjaa4
  

  1. 1. 北京大学地球与空间科学学院, 北京 100871 2. 北京大学地球与空间科学学院, 造山带与地壳演化教育部重点实验室, 北京 100871 3. 日本大阪公立大学理学部地球学系, 大阪 558-8585 4. 蒙古科学院古生物与地质研究所, 乌兰巴托 15160
  • 收稿日期:2025-04-23 修回日期:2025-05-26 出版日期:2026-07-20 发布日期:2026-07-20
  • 基金资助:
    国家重点研发计划(2022YFF0800204)资助

Geochemical Characteristics of the Ediacaran-Cambrian Boundary Strata in Bayan Gorge, Western Mongolia: Implications for Paleoeceanic Redox Prior to the Cambrian Explosion

ZHENG Aonan1, LIU Jianbo1,2,†, Ezaki Yoichi3, Adachi Natsuko3, Altanshagaid Gundsambuu4, Batkhuyag Enkhbaatard4, Dorj Dorjnamjaa4
  

  1. 1. School of Earth and Space Sciences, Peking University, Beijing 100871 2. The Key Laboratory of Orogenic Belts and Crustal Evolution (MOE), School of Earth and Space Sciences, Peking University, Beijing 100871 3. Department of Earth Sciences, Faculty of Science, Osaka Metropolitan University, Osaka 558-8585 4. Institute of Paleontology and Geology, Mongolian Academy of Sciences, Ulaanbaatar 15160
  • Received:2025-04-23 Revised:2025-05-26 Online:2026-07-20 Published:2026-07-20

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摘要：

选取蒙古巴彦峡谷埃迪卡拉系–寒武系界线(E-C界线)剖面为研究对象, 系统地采集埃迪卡拉系顶部至寒武系底部的碳酸盐岩样品, 开展稀土元素(REE)、主量元素、微量元素和无机碳氧同位素等多指标地球化学分析, 评估 REE 的原始海水信号保存程度, 重建研究区古海水氧化还原状态的演化过程。结果显示, 寒武纪幸运阶早期, 研究区发生一期短暂的海洋氧化事件, 随后进入氧化还原频繁波动阶段。氧化还原指标(Ce/Ce*)SN在BACE(basal Cambrian carbon isotope excursion)事件后显著下降(最小值为 0.57), 指示海水发生快速氧化, 之后该值逐渐上升(最大值接近 1.0), 指示海水逐步还原。Th/U比值与Ce异常的变化趋势高度一致, 进一步印证海水氧化还原状态的快速响应与阶段性变化。研究结果首次提供蒙古西部地区埃迪卡拉系–寒武系界线附近高分辨率的古海水氧化还原记录, 揭示研究区海洋氧化过程的区域时序特征, 可为寒武纪生命大爆发的海洋环境背景研究提供新的地球化学证据。

关键词: 埃迪卡拉系–寒武系界线(E-C界线), 稀土元素(REE), 铈异常, Th/U比值, 氧化还原演化, 寒武纪生命大爆发

Abstract:

We conducted high-resolution geochemical analyses on carbonate rocks from the Ediacaran-Cambrian (E-C) boundary strata at the Bayan Gorge section, western Mongolia. The dataset includes rare earth elements (REE), major and trace elements, inorganic carbon and oxygen isotopes. Evaluating the preservation of primary REE signals against diagenetic alteration and detrital input, we reconstructed the temporal evolution of local seawater redox conditions. The results reveal a transient but significant oxygenation event during the early Fortunian Stage of the Cambrian, followed by pronounced redox fluctuations. The redox proxy (Ce/Ce*)SN decreased markedly following the BACE (Basal Cambrian Carbon Isotope Excursion) event, reaching a minimum value of 0.57, indicative of rapid seawater oxidation. Subsequently, (Ce/Ce*)SN values gradually increased to near 1.0, reflecting a return to more reducing conditions. The Th/U ratio exhibits a synchronous trend with Ce anomalies, further supporting a scenario of rapid redox oscillations and phased changes in seawater redox state. This study provides the first high-resolution redox record across the E-C boundary from western Mongolia, filling a critical geographic gap in global redox reconstructions. This study offers new geochemical evidence for understanding the environmental dynamics that preceded the Cambrian Explosion.

Key words: Ediacaran-Cambrian (E-C) boundary, rare earth elements (REE), Ce anomaly, Th/U ratio, redox evolution, Cambrian Explosion

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