Abstract The weathering mechanisms that cause fragmentation of particles in the transition from bedrock to saprolite and regolith are little known. Yet, their quantification is an important missing link in the development of critical zones. To provide observational underpinning of mechanistic inference, we sampled and analysed the vertically changing particle size distribution in weathering profiles of varying lithology: quartzite, schist, gneiss and shale. The samples were studied for mineral composition by X-ray powder diffraction (XRD) and assessed whether these were consistent with the field identification. Then, simulations from twelve theoretical particle fragmentation models were confronted to the vertical particle size distribution measured. The models simulate different particle-size implications of physical and chemical weathering, but do not include surface effects on particle size distribution such as armouring. The results demonstrate that the lithology is an important determinant of the rock fragmentation mechanism. Furthermore, it is shown that the rock fragmentation models used here are a useful tool to identify geomorphological processes as soil redistribution or amouring. Further research will need to generate more data on weathering sequences in different environments.

中文翻译：

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风化指纹：不同岩性下沿风化层序的粒度分布变化

摘要 在基岩向腐泥土和风化层转变过程中导致颗粒破碎的风化机制鲜为人知。然而，它们的量化是关键区域发展中一个重要的缺失环节。为了提供机械推断的观测基础，我们采样并分析了不同岩性风化剖面中垂直变化的粒度分布：石英岩、片岩、片麻岩和页岩。通过 X 射线粉末衍射 (XRD) 研究样品的矿物组成，并评估这些是否与现场鉴定一致。然后，将来自十二个理论颗粒破碎模型的模拟与测量的垂直粒度分布进行对比。这些模型模拟了物理和化学风化对不同粒度的影响，但不包括对粒度分布的表面影响，例如铠装。结果表明，岩性是岩石破碎机制的重要决定因素。此外，结果表明，这里使用的岩石破碎模型是一种有用的工具，可以识别土壤重新分布或侵蚀等地貌过程。进一步的研究将需要生成更多关于不同环境中风化序列的数据。