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首页> 外文期刊>Earth Surface Processes and Landforms: The journal of the British Geomorphological Research Group >Improved discrimination of subglacial and periglacial erosion using Be-10 concentration measurements in subglacial and supraglacial sediment load of the Bossons glacier (Mont Blanc massif, France)
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Improved discrimination of subglacial and periglacial erosion using Be-10 concentration measurements in subglacial and supraglacial sediment load of the Bossons glacier (Mont Blanc massif, France)

机译：使用Be-10浓度测量法对Bossons冰川（法国勃朗峰地块）的冰川下和冰川下沉积物负荷，改进了对冰川下和冰川周围侵蚀的区分

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Deciphering the complex interplays between climate, uplift and erosion is not straightforward and estimating present-day erosion rates can provide useful insights. Glaciers are thought to be powerful erosional agents, but most published glacial' erosion rates combine periglacial, subglacial and proglacial erosion processes. Within a glaciated catchment, sediments found in subglacial streams originate either from glacial erosion of substratum or from the rock walls above the glacier that contribute to the supraglacial load. Terrestrial cosmogenic nuclides (TCN) are produced by interactions between cosmic ray particles and element targets at the surface of the Earth, but their concentration becomes negligible under 15 m of ice. Measuring TCN concentrations in quartz sand sampled in subglacial streams and in supraglacial channels is statistically compliant with stochastic processes (e.g. rockfalls) and may be used to discriminate subglacial and periglacial erosion. Results for two subglacial streams of the Bossons glacier (Mont Blanc massif, France) show that the proportion of sediments originating from glacially eroded bedrock is not constant: it varies from 50% to 90% (n = 6). The difference between the two streams is probably linked to the presence or absence of supraglacial channels and sinkholes, which are common features of alpine glaciers. Therefore, most of the published mean catchment glacial erosion rates should not be directly interpreted as subglacial erosion rates. In the case of catchments with efficient periglacial erosion and particularly rockfalls, the proportion of sediments in the subglacial stream originating from the supraglacial load could be considerable and the subglacial erosion rate overestimated. Here, we estimate warm-based subglacial and periglacial erosion rates to be of the same order of magnitude: 0.39 +/- 0.33 and 0.29 +/- 0.17 mm a(-1), respectively. Copyright (c) 2015John Wiley & Sons, Ltd.
机译：了解气候，隆升和侵蚀之间的复杂相互作用并不是一件容易的事，估计当前的侵蚀速率可以提供有用的见解。人们认为冰川是强大的侵蚀剂，但大多数已发表的冰川侵蚀率综合了冰川期，冰川下和冰川期侵蚀过程。在冰川集水区中，冰川下流中发现的沉积物要么来自基底的冰川侵蚀，要么来自冰川上方的岩壁，这些岩壁有助于冰川作用。宇宙射线核素（TCN）是由宇宙射线粒子与地球表面的元素目标之间的相互作用产生的，但在15 m的冰层下其浓度可忽略不计。测量冰川下河流和冰川上河道中石英砂中TCN的浓度在统计上符合随机过程（例如落石），可用于区分冰川下和冰川下的侵蚀。 Bossons冰川（法国勃朗峰地块）的两个冰河下流的结果表明，源自冰川侵蚀基岩的沉积物比例不是恒定的：从50％到90％不等（n = 6）。两条河流之间的差异可能与冰川上河道和下沉孔的存在与否有关，这是高山冰川的共同特征。因此，大多数已公布的平均集水区冰川侵蚀率不应直接解释为冰川下侵蚀率。对于集水带有效的冰川侵蚀，特别是落石流域，冰川下的水流中沉积物所占比例可能很大，而冰川下的侵蚀率被高估了。在这里，我们估计基于温暖的冰川下和冰川周围的侵蚀速率处于相同的数量级：分别为0.39 +/- 0.33和0.29 +/- 0.17 mm a（-1）。版权所有（c）2015 John Wiley＆Sons，Ltd.

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