Bedform genesis in bedrock substrates: Insights into formative processes from a new experimental approach and the importance of suspension-dominated abrasion
Bedform genesis in bedrock substrates: Insights into formative processes from a new experimental approach and the importance of suspension-dominated abrasion
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基岩基质中的床形成因：通过新的实验方法深入了解形成过程以及悬浮主导磨损的重要性
DOI：
10.1016/j.geomorph.2015.12.008
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发表时间：
2016
期刊：
影响因子：
3.9
通讯作者：
Yin D
中科院分区：
文献类型：
--
作者：
Yin D
基岩河道在自然环境中很常见，基岩河道侵蚀决定了许多河流流域的剥蚀速度。然而，与大量关于冲积基床形成的研究相比，关于基岩基床成因的研究相对较少。基岩河道内雕塑形态的现场分析明显受到此类环境中床形发育速度缓慢的限制。此外，只进行了有限数量的水槽规模的实验，试图模拟基岩河道中雕刻的河床的成因。这项研究表明，通过分析粘土强度来优化粘土层，可以开发出类似于基岩河道河床的特征--即使是在比一些自然例子小一个数量级的规模上。采用硬粘土、中粘土和软粘土作为底质，进行了三组含沙悬浮试验。在所有实验床上开发了一套侵蚀床(包括凹坑、凹槽和沟槽)。所有观察到的侵蚀特征都与在天然基岩河流中观察到的明显相当。在我们的实验中发现，在流速、河床坡度和水流深度基本不变的情况下，床面剪切强度是不同类型模拟基岩床面成因的一个重要因素。重要的是，在没有悬浮泥沙的情况下进行的一系列实验中，流体流动不会导致粘土层中床面的侵蚀和发育。因此，这项工作表明，在我们的实验中，在没有推移质磨损的情况下，悬浮泥沙的磨损是形成这些模拟基岩底形所需的关键过程；其他过程，如采摘、空化和溶解将被忽略。
Bedrock channels are common in the natural environment, and bedrock channel erosion sets the pace of denudation in many river catchments. However, in comparison to the large number of studies concerning the formation of alluvial bedforms, relatively few investigations have concerned bedrock bedform genesis. Field-based analysis of sculptured forms within bedrock channels has been restricted notably by the slow rate of bedform development in such environments. Furthermore, only a limited number of flume-scale experiments have been conducted that attempt to simulate the genesis of sculpted bedforms in bedrock channels. This study demonstrates that optimisation of clay beds through analysis of clay strength enables the development of features analogous to bedrock river channel bedforms — even at a scale that is orders of magnitude smaller than some natural examples. Three sets of suspended sediment-laden experiments were carried out using hard, medium, and soft clay bed substrates. A suite of erosive bedforms (including potholes, flutes, and furrows) developed on all experimental beds. All observed erosional features have clear equivalents to those observed in natural bedrock rivers. Bed shear strength was found to be a significant factor for the genesis of different types of simulated bedrock bedforms in our experiments with other factors, such as flow velocity, bed slope, and flow depth held approximately constant. Importantly, in a subset of experiments performed with an absence of suspended sediment, fluid flow did not result in the erosion and development of bedforms in the clay bed. Hence, this work illustrates that abrasion by suspended sediments is the key process required for the formation of these simulated bedrock bedforms in our experiments, in the absence of bedload abrasion; other processes such as plucking, cavitation, and dissolution will have been negligible.
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DOI：
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发表时间：
1963
期刊：
Transactions of the Edinburgh Geological Society
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