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首页> 外文期刊>Earth Surface Processes and Landforms: The journal of the British Geomorphological Research Group >Episodic bedrock erosion by gully-head migration, Colorado High Plains, USA
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Episodic bedrock erosion by gully-head migration, Colorado High Plains, USA

机译：美国科罗拉多高平原因沟壑状迁移而引起的偶发性基岩侵蚀

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This study explores the frequency of bedrock exposure in a soil-mantled low-relief (i.e. non-mountainous) landscape. In the High Plains of eastern Colorado, gully headcuts are among the few erosional features that will incise through the soil mantle to expose bedrock. We measured the last time of bedrock exposure using optically stimulated luminescence dating of alluvial sediment overlying bedrock in gully headcuts. Our dating suggests that headcuts in adjacent gullies expose bedrock asynchronously, and therefore, the headcuts are unlikely to have been triggered by a base-level drop in the trunk stream. This finding supports the hypothesis that headcuts can develop locally in gullies as a result of focused scour in locations where hydraulic stress during a flash flood is sufficiently high, and/or ground cover is sufficiently weak, to generate a scour hole that undermines vegetation. Alluvium dating also reveals that gullies have been a persistent part of this landscape since the early Holocene. Copyright (C) 2016 John Wiley & Sons, Ltd.
机译：这项研究探讨了土壤覆盖的低浮雕（即非山地）景观中基岩暴露的频率。在科罗拉多州东部的高平原，沟壑状的割口是少数几个侵蚀性特征之一，这些侵蚀性特征会切穿土壤地幔以露出基岩。我们使用沟渠切口上方基岩上冲积沉积物的光激发发光测年法测量了基岩暴露的最后时间。我们的测年表明，相邻沟渠中的挖口异步地暴露了基岩，因此，这些挖口不太可能是由干流中的基准面下降触发的。这一发现支持了这样的假设，即在暴洪期间水力压力足够高和/或地表覆盖物足够弱，从而产生冲刷破坏植被的冲刷孔的位置，由于集中冲刷，沟渠可能会在沟壑中局部发展。冲积年代还表明，自全新世以来，沟壑一直是该景观的持久部分。版权所有（C）2016 John Wiley＆Sons，Ltd.

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