Detrital zircon records variable expressions of Paleoproterozoic (2.2 - 2.4 Ga) glaciation between Sclavia and Superia supercratons

Evidence of glaciation is recognized in Earth’s history from 2.9 Ga to the present, providing important information regarding the climatic, sedimentary, and tectonic evolution of our planet. Glaciers are highly effective agents of erosion that generate and transport large amounts of sediments for 100ʹs of kilometres. Therefore, detrital zircon geochronology of glaciogenic sedimentary rocks can elucidate the provenance and evolution of the sedimentary record through time. In this study, we investigate the Paleoproterozoic Glaciation Event which is hypothesized to be the oldest global glaciation in Earth’s history (2.4 to 2.2 Ga). We identify distinct sedimentary provenance patterns between the Archaean supercratons Sclavia and Superia, which, comprised most of the extant Archean crust. The detrital zircon of Sclavia exhibit increasing dissimilarity through time whereas the detrital zircon ages of Superia show consistent age peaks through time. Coupled with the absence of glacial deposits and predominance of marine sedimentary successions within Sclavia, the detrital zircon provenance likely indicates limited subaerial exposure of continental crust in Sclavia with glaciers narrow mountain belts producing no diamictites. This model resolves previous issues related to hypotheses proposing high-obliquity low latitude glaciation of Superia as the only explanation available.

地球历史中距今29亿年（Ga）至现代均有冰川作用（glaciation）的证据，这些记录为揭示地球的气候、沉积与构造演化提供了关键信息。冰川是极具效率的侵蚀营力，可生成并搬运巨量沉积物至数百公里之外。因此，对冰川成因沉积岩开展碎屑锆石年代学（detrital zircon geochronology）研究，可阐明沉积记录随时间推移的物源与演化历程。本研究聚焦于被认为是地球历史上最古老全球性冰川事件的古元古代冰川事件（距今24亿至22亿年）。本研究明确了构成现今绝大多数太古宙地壳的两个太古宙超级克拉通——斯克拉维亚（Sclavia）与苏佩里亚（Superia）之间存在显著不同的沉积物源特征。斯克拉维亚的碎屑锆石年龄组成随时间推移差异逐渐增大，而苏佩里亚的碎屑锆石年龄则始终呈现稳定的年龄峰值。结合斯克拉维亚区域缺失冰川沉积、且以海相沉积序列为主的特征，碎屑锆石物源分析结果表明，斯克拉维亚的大陆地壳陆上暴露程度有限，仅存在狭窄的山地冰川带，未能形成杂砾岩（diamictites）。该模型解决了此前仅以高转轴倾角低纬度冰川作用解释苏佩里亚冰川事件时存在的相关问题。