The Ediacaran–Cambrian (E-C) transition witnessed dramatic tectonic, climatic, oceanic, and biological co-evolutions at the dawn of the ‘Cambrian explosion’. Although glaciations were reported in some mid-high-latitude continents during this interval, large uncertainties remain concerning timing and extent, as well as their effect on the entire Earth's surface system. We here report magnesium (Mg) isotopic compositions, along with chemical index of alteration (CIA), Al/Ti ratios from a time-dated, nonglacial E-C boundary section on the mid-low-latitude Yangtze Block, South China, to constrain chemical weathering intensity and associated climatic, oceanic and biological co-evolution during this critical interval. Our data demonstrate a rapid and significant negative δ²⁶Mg excursion (from +1.28 to −0.34‰) along with similar CIA and Al/Ti decreases across the E-C boundary, reflecting an apparent attenuation in chemical weathering intensity likely in response to severe climate cooling. This finding further affirms the far-field glaciation reported in the mid-high-latitude continents during the E-C transition. Under this condition, the intense climate cooling could have enhanced oceanic circulation and/or upwelling, and simultaneously caused prominent variations of seawater geochemistry (including alkalinity elevation) and nutrient flux as well as ecological stresses on metazoans. All these could reasonably account for extensive deposition of phosphorites and organic-rich black shales, and faunal turnover (extinction of Ediacaran fauna and appearance of skeletonized small shelly fauna) across this interval. These novel datasets thus shed new insights into the climatic-oceanic-biological interactions and time-specific deposition around the E–C transition at the prelude of the Cambrian explosive bioradiation.

在“寒武纪大爆发”的黎明，埃迪卡拉纪-寒武纪 (EC) 过渡见证了戏剧性的构造、气候、海洋和生物共同进化。尽管在此期间在一些中高纬度大陆报告了冰川作用，但关于时间和范围以及它们对整个地球表面系统的影响仍然存在很大的不确定性。我们在这里报告了镁 (Mg) 同位素组成，以及化学蚀变指数 (CIA)、Al/Ti 比率，来自华南中低纬度扬子地块上一个时间日期的非冰川 EC 边界截面，以限制化学变化。在这个关键时期的风化强度和相关的气候、海洋和生物共同进化。我们的数据显示出快速且显着的负 δ ²⁶Mg 偏移（从 +1.28 到 -0.34‰）以及类似的 CIA 和 Al/Ti 在 EC 边界上下降，反映了化学风化强度的明显衰减，这可能是对严重气候变冷的反应。这一发现进一步证实了 EC 过渡期间中高纬度大陆报告的远场冰川作用。在这种情况下，强烈的气候变冷可能会增强海洋环流和/或上升流，同时引起海水地球化学（包括碱度升高）和养分通量的显着变化以及对后生动物的生态压力。所有这些都可以合理地解释这一区间内磷矿和富含有机物的黑色页岩的广泛沉积以及动物群更新（埃迪卡拉纪动物群的灭绝和骨骼化的小型贝壳动物群的出现）。