Core-derived historical records of suspended sediment origin in a mesoscale mountainous catchment: the River Bléone, French Alps
Core-derived historical records of suspended sediment origin in a mesoscale mountainous catchment: the River Bléone, French Alps
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中尺度山区流域悬浮沉积物起源的岩芯历史记录：法国阿尔卑斯山布莱昂河
DOI：
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发表时间：
2012
影响因子：
3.6
通讯作者：
P. Bonté
中科院分区：
文献类型：
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作者：
O. Navratil;O. Evrard;M. Esteves;S. Ayrault;I. Lefèvre;C. Legoût;J. Reyss;N. Gratiot;J. Némery;N. Mathys;Alain Poirel;P. Bonté
研究目的定量研究山区悬浮泥沙通量和动力学特征，确定侵蚀严重地区泥沙来源，对水资源管理具有重要意义。这一贡献的目的是概括2007-2009年期间在中尺度阿尔卑斯流域获得的悬浮泥沙指纹以前的结果（布莱奥内河; 905平方公里），并评估整个世纪后半叶沉积物来源的变化。在流域出口冲积漫滩收集的沉积物岩心上进行。这种技术相结合的水文沉积时间序列重建悬浮沉积物沉积在这个位置在过去的50 years.Results and discussionInterpretation沉积的历史水文数据库的基础上证实了137 Cs和210 Pbxs活动测量获得的核心测年。黑色泥灰岩和（泥灰岩）石灰岩来源提供了整个序列的沉积物的主要部分（分别为40%和22%）。然而，我们也发现了发生大洪水的证据，这些洪水携带了大量来自第四纪沉积物和砾岩的沉积物（分别为25%和16%）。整个序列中沉积物来源的变异性可能反映了集水区内降雨的空间变异性，而降雨的空间变异性又反映了其来源。然而，相对均匀的沉积物组成在整个序列证实，核心衍生的信息是代表广泛的floodevents.ConclusionsThese结果是一致的，在以前的研究中获得的。它们还概述了需要考虑到细粒沉积物的整个粒度范围，以便全面了解高度侵蚀集水区内的沉积物来源和转移情况。这项研究还强调，必须利用档案数据来验证在短期现代监测方案期间进行的沉积物指纹研究的结果，并将沉积物来源的指纹研究扩展到更长的时间尺度，包括大规模和广泛的洪水。
PurposeQuantifying suspended sediment fluxes and dynamics across mountains, and identifying the origin of sediment in severely eroded areas, are of primary importance for the management of water resources. This contribution aims to generalise previous results from suspended sediment fingerprinting obtained during 2007–2009 in a mesoscale Alpine catchment (the Bléone River; 905 km2) in France, and to assess variability in sediment sources throughout the second half of the twentieth century.Materials and methodsSediment fingerprinting, based on elemental geochemistry and radionuclide measurements, was conducted on a sediment core collected in an alluvial floodplain at the basin outlet. This technique was combined with hydro-sedimentary time-series to reconstruct the origin of suspended sediment deposited at this location over the last 50 years.Results and discussionInterpretation of sedimentation based on historical hydrological databases corroborates core dating obtained with 137Cs and 210Pbxs activity measurements. Black marls and (marly) limestone sources provided the main fraction of sediment throughout the sequence (40 and 22 %, respectively). However, we also found evidence for the occurrence of major floods carrying large quantities of sediment originating from Quaternary deposits and conglomerates (25 and 16 %, respectively). The variability of sediment sources throughout the sequence may reflect the spatial variability of rainfall within the catchment, which in turn reflects its origin. However, the relatively homogeneous sediment composition throughout the sequence confirms that core-derived information is representative of widespread flood events.ConclusionsThese results are consistent with those obtained in previous studies. They also outline the need to take into account the entire grain size range of fine sediment in order to provide an overall picture of sediment sources and transfers within highly erosive catchments. This study also emphasizes the importance of using archival data to validate the results of sediment fingerprinting studies conducted during short contemporary monitoring programmes, and to extend fingerprinting of sediment sources over longer time-scales which include large and widespread floods.