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首页> 外文期刊>Earth Surface Processes and Landforms: The journal of the British Geomorphological Research Group >Proglacial sediment trapping in recently formed Silt Lake, Upper Lillooet Valley, Coast Mountains, British Columbia
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Proglacial sediment trapping in recently formed Silt Lake, Upper Lillooet Valley, Coast Mountains, British Columbia

机译：在不列颠哥伦比亚省海岸山脉上Lillooet谷，新近形成的淤泥湖中沉积了冰川沉积物

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The sedimentology of proglacial Silt Lake was assessed by lake sediment coring and monitoring of lacustrine processes during a late-summer period of high glacier melt to characterize sediment delivery from the heavily glacierized catchment and investigate the sediment trapping dynamics of this upland lake. A complete varve chronology was established for a distal basin of the lake which was exposed by Lillooet Glacier retreat between 1947 and 1962. The varve record showed decreasing sedimentation rates in the basin while the glacier retreated, and as the lake became free of ice contact in the early 1970s. Although recession has continued over recent decades, and glacier proximity to the lake has, therefore, continued decreasing, lacustrine sedimentation rates are now accelerating due to changing basin morphometry caused by delta progradation. Over shorter time scales, lake sedimentation patterns respond to changing runoff conditions, including late-summer glacier melt intensity, intra-annual flooding events, diurnal runoff fluctuations, and within-lake turbidity currents. Turbidity currents included quasi-regular flows during high diurnal discharges and an episodic flushing of temporarily stored sediment from the sandur or delta at a time of low stage. Suspended sediment yield to Silt Lake is estimated to exceed 103 Mg km"2 a"1, a magnitude that surpasses previous local and regional yield estimates for the glacierized headwaters of the Lillooet River valley. Since Silt Lake currently traps a significant prooportion of that upland sediment supply, and the trapping efficiency of the basin has been variable at decadal time scales, the formation and continued development of Lilt Lake has likely had a significant influence on downstream sediment delivery. Lacustrine sediment-based proxies of long-term hydroclimatic variability being developed in glacially distal settings should include provisions for dynamic sediment trapping effects in upstream water bodies that often form in the active proglacial environment.
机译：在盛夏的冰川融化后期，通过湖泊沉积物取芯和湖相过程监测，评估了冰河淤泥湖的沉积学，以表征从高度冰川化的集水区输送的沉积物，并研究了该陆上湖泊的沉积物捕集动力学。在1947年至1962年之间，Lillooet冰川撤退暴露了该湖的远端盆地，建立了完整的年代学年表。该瓦尔维记录显示，冰川退缩时该盆地的沉积率下降，并且随着湖泊在2000年不再与冰接触， 1970年代初期。尽管近几十年来经济衰退一直在继续，冰川与湖泊之间的距离也因此持续减少，但由于三角洲积水引起的盆地形态变化，湖相沉积速率现在正在加速。在较短的时间尺度上，湖泊的沉积模式对径流条件的变化做出了响应，包括夏末冰川融化强度，年内洪水事件，日径流波动和湖内浊流。浊流包括日间高流量时的准规则流动，以及在低水位时从sandur或三角洲临时冲走临时存储的沉积物。淤泥湖的悬浮泥沙产量估计超过103 Mg km“ 2 a” 1，超过了先前对Lillooet河谷冰川化的上游水域的当地和区域产量的估计。由于淤泥湖目前捕获了大量的陆地沉积物，并且流域的捕获效率在十年时间尺度上是可变的，因此，淤泥湖的形成和持续发展可能对下游沉积物的输送产生重大影响。在冰川末梢地区正在开发的基于湖泊水沉积物的长期水文气候变化的代理应包括对活跃水环境中经常形成的上游水体动态沉积物捕集作用的规定。

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