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首页> 外文期刊>Earth Surface Processes and Landforms: The journal of the British Geomorphological Research Group >Postglacial to Holocene landscape evolution and process rates in steep alpine catchments
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Postglacial to Holocene landscape evolution and process rates in steep alpine catchments

机译：陡峭的高山集水区的全新世景观进化与过程率

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摘要

Climate change and high magnitude mass wasting events pose adverse societal effects and hazards, especially in alpine regions. Quantification of such geomorphic processes and their rates is therefore critical but is often hampered by the lack of appropriate techniques and the various spatiotemporal scales involved in these studies. Here we exploit both in situ cosmogenic beryllium-10 (Be-10) and carbon-14 (C-14) nuclide concentrations for deducing exposure ages and tracing of sediment through small alpine debris flow catchments in central Switzerland. The sediment cascade and modern processes we track from the source areas, through debris flow torrents to their final export out into sink regions with cosmogenic nuclides over an unprecedented five-year time series with seasonal resolution. Data from a seismic survey and a 90 m core revealed a glacially overdeepened basin, filled with glacial and paraglacial sediments. Surface exposure dating of fan boulders and radiocarbon ages constrain the valley fill from the last deglaciation until the Holocene and show that most of the fan existed in early Holocene times already. Current fan processes are controlled by episodic debris flow activity, snow (firn) and rock avalanches. Field investigations, digital elevation models (DEMs) of difference and geomorphic analysis agree with sediment fingerprinting with cosmogenic nuclides, highlighting that the bulk of material exported today at the outlet of the subcatchments derives from the lower fans. Cosmogenic nuclide concentrations steadily decrease from headwater sources to distal fan channels due to the incorporation of material with lower nuclide concentrations. Further downstream the admixture of sediment from catchments with less frequent debris flow activity can dilute the cosmogenic nuclide signals from debris flow dominated catchments but may also reach thresholds where buffering is limited. Consequently, careful assessment of boundary conditions and driving forces is req
机译：气候变化和高幅度大规模浪费事件会产生不利的社会效应和危害，特别是在高山地区。因此，定量这种地貌过程及其速率是至关重要的，但通常由于缺乏适当的技术和这些研究中涉及的各种时空尺度而受到阻碍。在这里，我们利用原位美容铍-10（BE-10）和碳-14（C-14）核素浓度，用于通过瑞士中部的小型高山碎片流量集中推出暴露年龄和沉积物的追踪。我们从源区追踪的沉积物级联和现代流程，通过碎片流动分级与季节性分辨率的前所未有的五年时间序列中的宇宙生成核素流入其最终输出。来自地震测量的数据和90米的核心揭示了一种冰冷的流量盆地，充满了冰川和滑翔伞的沉积物。风扇巨石和无线电碳的表面曝光约会约束山谷从最后的下注到全新世，表明大多数风扇已经存在于早期全新世时间。目前的风扇工艺由情节碎片流动，雪（FIRN）和岩石雪崩控制。差异和地貌分析的数字高度模型（DEMS）与沉积物指纹与富含核素的沉积物，突出显示，当今出口的大部分材料来自较低的风扇。由于掺入具有较低核素浓度的材料，富含核酸核素浓度稳定地从散水源降低到远端风扇通道。进一步下游从缺乏频繁的碎片流动活性的沉积物的混合物可以从碎片流动占主导地层稀释富含核酸核素信号，但也可以达到缓冲受到限制的阈值。因此，请仔细评估边界条件和驱动力

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