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首页> 外文期刊>Earth Surface Processes and Landforms: The journal of the British Geomorphological Research Group >Exploring geochemical controls on weathering and erosion of convex hillslopes: beyond the empirical regolith production function
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Exploring geochemical controls on weathering and erosion of convex hillslopes: beyond the empirical regolith production function

机译：探索地球化学对凸型山坡的风化和侵蚀的控制作用：超出经验性的重石生产功能

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摘要

Landscape curvature evolves in response to physical, chemical, and biological influences that cannot yet be quantified in models. Nonetheless, the simplest models predict the existence of equilibrium hillslope profiles. Here, we develop a model describing steady-state regolith production caused by mineral dissolution on hillslopes which have attained an equilibrium parabolic profile. When the hillslope lowers at a constant rate, the rate of chemical weathering is highest at the ridgetop where curvature is highest and the ridge develops the thickest regolith. This result derives from inclusion of all the terms in the mathematical definition of curvature. Including these terms shows that the curvature of a parabolic hillslope profile varies with distance from the ridge. The hillslope model (meter-scale) is similar to models of weathering rind formation (centimeter-scale) where curvature-driven solute transport causes development of the thickest rinds at highly curved clast corners. At the clast scale, models fit observations. Here, we similarly explore model predictions of the effect of curvature at the hillslope scale. The hillslope model shows that when erosion rates are small and vertical porefluid infiltration is moderate, the hill weathers at both ridge and valley in the erosive transport-limited regime. For this regime, the reacting mineral is weathered away before it reaches the land surface: in other words, the model predicts completely developed element-depth profiles at both ridge and valley. In contrast, when the erosion rate increases or porefluid velocity decreases, denudation occurs in the weathering-limited regime. In this regime, the reacting mineral does not weather away before it reaches the land surface and simulations predict incompletely developed profiles at both ridge and valley. These predictions are broadly consistent with observations of completely developed element-depth profiles along hillslopes denuding under erosive transport-limitation but incompletely developed profiles along hillslopes denuding under weathering limitation in some field settings.
机译：景观曲率是根据尚未在模型中量化的物理，化学和生物影响而演变的。但是，最简单的模型可以预测平衡山坡轮廓的存在。在这里，我们开发了一个模型，该模型描述了由于达到平衡抛物线轮廓的山坡上的矿物溶解而引起的稳态碎屑生成。当山坡以恒定速率下降时，化学风化率在曲率最高的山脊处最高，并且山脊发育出最厚的块石。该结果源自将所有术语包括在曲率的数学定义中。包括这些术语表明，抛物线型山坡轮廓的曲率随距山脊的距离而变化。山坡模型（米级）与风化果皮形成模型（厘米级）相似，在这种模型中，曲率驱动的溶质运移导致高度弯曲的岩屑拐角处最厚的果皮发育。在最大尺度上，模型适合观察。在这里，我们类似地探索在坡度尺度上曲率影响的模型预测。山坡模型显示，当侵蚀速率较小且垂直孔隙流体渗透程度适中时，在侵蚀性运输受限状态下，山脊在山脊和谷地均受天气影响。在这种情况下，反应的矿物在到达陆地表面之前就被风化了;换句话说，该模型可以预测在山脊和山谷完全发育的元素深度剖面。相反，当侵蚀速率增加或孔隙流体速度降低时，在受风化限制的条件下发生剥蚀。在这种情况下，发生反应的矿物不会到达地表之前就风化，并且模拟预测在山脊和谷地的剖面发育不完全。这些预测与在侵蚀性运输限制下沿山坡剥蚀的完全发育的元素深度剖面的观察结果基本一致，但在某些田地环境下，在风化限制下沿剥蚀的山坡的不完整发育剖面的观察结果基本一致。

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