The Hirnantian glaciation, which was the first in the Phanerozoic to occur with elevated CO₂ levels, caused severe mass extinctions and disrupted biogeochemical cycling in the latest Ordovician. Previous research that aimed at exploring the triggers and consequences (both abiotic and biotic) of this glacial event have largely been based on condensed or incomplete sections. However, there is much debate over the detailed glacio-eustatic processes, and especially over the possible existence and characterization of multiple glacial cycles. Herein we conduct high-resolution geochemical analyses (via XRF core scanning and ICP-OES/MS) and a sedimentological study of three continuous upper Katian – lower Rhuddanian drill cores (Well Huangge-1, Well Shuanghe-1 and Well Yiwan-1), which represent a combination of nearshore and offshore facies in South China. The geochemical and sedimentological evidences reveal for the first time three glacio-eustatic cycles encompassed within a major sea level cycle through the upper Katian and Hirnantian. Each glacio-eustatic cycle comprises a combination of regressive and transgressive systems tracts, with the third one denoting the largest sea level fall and the glacial maximum. This pattern of sea level changes can be correlated with both the glacial sedimentary records and geochemical signals in North Gondwana, Laurentia and Baltica. These glacio-eustatic changes likely led to perturbations in regional marine nutrient cycling and formed a redox landscape that is depicted herein as somewhat different from previous models. We also present the glacio-eustatic effects at a basin scale, and a refined constraint for the tempo of polar ice sheet advances and retreats. It also calls for a re-evaluation of the mechanisms whereby a multi-cycle glaciation led to the Hirnantian biotic crisis, a relationship that may be much more complicated than the simplified cause-and-effect relationship proposed before.

Hirnantian 冰川作用，这是显生宙中第一次发生 CO ₂升高的冰川作用水平，导致了最近奥陶纪的严重大规模灭绝和生物地球化学循环中断。先前旨在探索这一冰川事件的触发因素和后果（非生物和生物）的研究主要基于浓缩或不完整的部分。然而，关于详细的冰川-浮沉过程，尤其是多个冰川循环的可能存在和特征存在很多争论。在此，我们进行了高分辨率地球化学分析（通过 XRF 岩心扫描和 ICP-OES/MS）和三个连续的上卡蒂安 - 下罗丹阶钻芯（黄阁 1 井、双河 1 井和伊万 1 井）的沉积学研究，代表了华南近岸相和近岸相的组合。地球化学和沉积学证据首次揭示了三个冰川 - 静海循环，它们包含在一个主要的海平面循环中，通过上卡蒂安和赫南蒂安。每个冰川 - 静水循环包括回归和海侵系统域的组合，第三个表示最大的海平面下降和冰川最大值。这种海平面变化模式可以与北冈瓦纳、劳伦特和波罗的海的冰川沉积记录和地球化学信号相关。这些冰川 - eustatic 变化可能导致区域海洋养分循环的扰动并形成氧化还原景观，此处描述的与以前的模型有些不同。我们还展示了盆地尺度的冰川 - eustatic 效应，以及对极地冰盖前进和后退节奏的精细约束。