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首页> 外文期刊>Earth Surface Processes and Landforms: The journal of the British Geomorphological Research Group >Strong slope-aspect control of regolith thickness by bedrock foliation
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Strong slope-aspect control of regolith thickness by bedrock foliation

机译：基岩叶片强大的斜坡方面控制极端厚度

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摘要

The porous near-surface layer of the Earth's crust - the critical zone - constitutes a vital reservoir of water for ecosystems, provides baseflow to streams, guides recharge to deep aquifers, filters contaminants from groundwater, and regulates the long-term evolution of landscapes. Recent work suggests that the controls on regolith thickness include climate, tectonics, lithology, and vegetation. However, the relative paucity of observations of regolith structure and properties at landscape scales means that theoretical models of critical zone structure are incompletely tested. Here we present seismic refraction and electrical resistivity surveys that thoroughly characterize subsurface structure in a small catchment in the Santa Catalina Mountains, Arizona, USA, where slope-aspect effects on regolith structure are expected based on differences in vegetation. Our results show a stark contrast in physical properties and inferred regolith thickness on opposing slopes, but in the opposite sense of that expected from environmental models and observed vegetation patterns. Although vegetation (as expressed by normalized difference vegetation index [NDVI]) is denser on the north-facing slope, regolith on the south-facing slope is four times thicker (as indicated by lower seismic velocities and resistivities). This contrast cannot be explained by variations in topographic stress or conventional hillslope morphology models. Instead, regolith thickness appears to be controlled by metamorphic foliation: regolith is thicker where foliation dips into the topography, and thinner where foliation is nearly parallel to the surface. We hypothesize that, in this catchment, hydraulic conductivity and infiltration capacity control weathering: infiltration is hindered and regolith is thin where foliation is parallel to the surface topography, whereas water infiltrates deeper and regolith is thicker where foliation intersects topography at a substantial angle. These results suggest that bedrock foliation, and perhaps by extension sedimentary layering, can control regolith thickness and must be accounted for in models of critical zone development. (c) 2020 John Wiley & Sons, Ltd.
机译：地壳的多孔近表面层 - 临界区 - 构成生态系统的重要水库，为溪流提供源泉，导游对深含水层的充电，过滤来自地下水的污染物，并规范景观的长期演变。最近的工作表明，对极端厚度的控制包括气候，构造，岩性和植被。然而，在横向尺度上的易氧性结构和特性观察的相对缺乏意味着临界区结构的理论模型是不完全测试的。在这里，我们呈现地震折射和电阻率调查，在美国亚利桑那州圣卡塔琳娜山脉的小集水区中彻底地表征了地下结构，其中基于植被的差异预期了对极孔结构的斜坡方面的影响。我们的结果表明，在物理性质中表现出与相对斜坡上的颗粒状厚度，但在环境模型的相反意义上，观察到的植被模式。虽然植被（如归一化差异植被指数[NDVI]表示）在朝鲜斜坡上更密集，但朝南斜坡上的极升性较厚四倍（如下部地震速度和电阻性所示）。这种对比不能通过地形应力或传统山坡形态模型的变化来解释。相反，极象厚度似乎是由变质叶控制的：卵泡厚度较厚，其中叶片浸入地形，叶片几乎平行于表面。我们假设，在该集水区内，液压导电性和渗透能力控制风化：渗透是受阻的，并且脱脂是薄薄的，其中叶面平行于表面形貌，而水渗透更深，叶片较深，其中叶片以大量的角度相交。这些结果表明，基岩叶，也许通过延伸沉积层，可以控制极象厚度，并且必须占关键区域开发的模型。 （c）2020 John Wiley＆Sons，Ltd。

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