10Be‐derived assessment of accelerated erosion in a glacially conditioned inner gorge, Entlebuch, Central Alps of Switzerland
10Be‐derived assessment of accelerated erosion in a glacially conditioned inner gorge, Entlebuch, Central Alps of Switzerland
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10Be 对瑞士中部阿尔卑斯山恩特勒布赫冰川条件下的内峡谷加速侵蚀的评估
DOI：
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发表时间：
2012
期刊：
影响因子：
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通讯作者：
P. Kubik
中科院分区：
文献类型：
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作者：
F. Berg;F. Schlunegger;N. Akçar;P. Kubik
内峡谷通常是由于与冰期/间冰期气候变化相关的侵蚀波的传播而形成的。然而，只有少数研究量化了现代对这种冰川条件的侵蚀反应。在这里，我们报告了来自 64 平方公里 Entlen 流域（瑞士阿尔卑斯山）的 10Be 现场数据。该盆地有一条 7 公里长的中央内峡谷，有两条支流深度切入厚厚的冰碛物和基岩 >100 米。在峡谷下游端测得的 10Be 浓度得出流域范围内的侵蚀率为 0.42±±0.04mm yr-1，而内峡谷上游的侵蚀率始终较低，范围为 0.14±0.01mm yr-1 至0.23 ±0.02 mm yr-1。然而，基于 10Be 的沉积物预算计算得出，干流内峡谷的产率约为 1.3mm yr-1。同样，在两个下切支流河段中，侵蚀率分别为~2.0mm yr-1 和~1.9mm yr-1。此外，在峡谷的侵蚀前缘，我们测量了基岩切割率，范围从~2.5 mm yr-1到~3.8 mm yr-1。然而，这些比率太低，无法推断峡谷起始的冰河时代后（15-20ka）。这需要比目前估计高 2 到 6 倍的侵蚀率。然而，末次海冰冰川退缩后，对松散冰碛的下切有利于通过缺口带传播而产生高侵蚀率，而随后的山坡松弛导致侵蚀率逐渐下降。这种侵蚀率下降两到六倍的假设与基于 10Be 的侵蚀率预算并不冲突，因为 10Be 记录的现代侵蚀时间尺度仅涵盖过去的 2-3ka。这些结果表明全新世侵蚀的加速是由于冰川的覆盖而导致的。版权所有 © 2012 约翰·威利父子有限公司
Inner gorges often result from the propagation of erosional waves related to glacial/interglacial climate shifts. However, only few studies have quantified the modern erosional response to this glacial conditioning. Here, we report in situ 10Be data from the 64 km2 Entlen catchment (Swiss Alps). This basin hosts a 7 km long central inner gorge with two tributaries that are >100 m‐deeply incised into thick glacial till and bedrock. The 10Be concentrations measured at the downstream end of the gorge yield a catchment‐wide erosion rate of 0.42 ± 0.04 mm yr‐1, while erosion rates are consistently lower upstream of the inner gorge, ranging from 0.14 ± 0.01 mm yr‐1 to 0.23 ± 0.02 mm yr‐1. However, 10Be‐based sediment budget calculations yield rates of ~1.3 mm yr‐1 for the inner gorge of the trunk stream. Likewise, in the two incised tributary reaches, erosion rates are ~2.0 mm yr‐1 and ~1.9 mm yr‐1. Moreover, at the erosional front of the gorge, we measured bedrock incision rates ranging from ~2.5 mm yr‐1 to ~3.8 mm yr‐1. These rates, however, are too low to infer a post‐glacial age (15–20 ka) for the gorge initiation. This would require erosion rates that are between 2 and 6 times higher than present‐day estimates. However, the downcutting into unconsolidated glacial till favored high erosion rates through knickzone propagation immediately after the retreat of the LGM glaciers, and subsequent hillslope relaxation led to a progressive decrease in erosion rates. This hypothesis of a two‐ to sixfold decrease in erosion rates does not conflict with the 10Be‐based erosion rate budgets, because the modern erosional time scale recorded by 10Be cover the past 2–3 ka only. These results point to the acceleration of Holocene erosion in response to the glacial overprint of the landscape. Copyright © 2012 John Wiley & Sons, Ltd.
瑞士阿尔卑斯山冰川雕刻的上罗讷河谷中宇宙成因核素衍生的扩散和偶发侵蚀率
影响因子：
3.3
作者：
Norton;von Blanckenburg
通讯作者：
von Blanckenburg