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首页> 外文期刊>Earth Surface Processes and Landforms: The journal of the British Geomorphological Research Group >Tailings fans and valley-spur cutoffs created by hydraulic mining
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Tailings fans and valley-spur cutoffs created by hydraulic mining

机译：水工采矿造成的尾矿扇和谷刺截断

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Sand and gravel tailings from nineteenth century open-pit hydraulic gold mines formed large alluvial fans at tributary confluences in the northwestern Sierra Nevada, California. In the Bear River watershed, several of these fans were so large that they blocked main channels for decades. Some channels not only aggraded deeply, but also moved laterally and cut across the inner bends of valley spurs. Now locked in bedrock channels, these valley-spur cutoffs impose local controls on geomorphic, hydraulic, and sedimentary processes. One cutoff has incised 25 m into bedrock over the past century (25 cm a~(-1)) with rapid initial incision rates of up to 50 cm a~(-1) (1884-1890). Recognition of spur cutoffs in the geological record may help to identify large landslides and provide an analogue for a type of natural earthfill dam spillway not prone to catastrophic failures. Tailing fans, valley-spur cutoffs, and the sediment they trap are described from contemporary accounts and recent field conditions in the Bear River watershed. These anthropogenic changes represent a major shift in the watershed from supply-limited to transport-limited sediment budgets and a change in geomorphic processes away from long-term drainage evolution dominated by ingrown meanders. The large volumes of mining sediment stored in these landforms will be slowly released over the next millennium and could be significant to contemporary ecological and public health issues due to recent findings of high mercury loadings associated with hydraulic mines.
机译：十九世纪露天水力金矿的砂石残渣在加利福尼亚内华达州西北部的支流汇合处形成了大型冲积扇。在熊河流域，这些风扇中的几个风扇是如此之大，以至于数十年来阻塞了主要通道。一些沟渠不仅深陷，而且还横向移动并切穿了谷刺的内弯。现在被锁定在基岩河道中，这些谷底支流对地貌，水力和沉积过程施加了局部控制。在过去的一个世纪中，一个边界已在基岩中切入25 m（25 cm a〜（-1）），初始切入速度很快，最高可达50 cm a〜（-1）（1884-1890）。在地质记录中识别出支流截止点可能有助于识别大型滑坡，并为不易发生灾难性故障的天然填土大坝溢洪道提供类似物。尾矿迷，河谷支流截留物以及它们捕获的沉积物是根据当代记述和熊河流域的近期田间条件进行描述的。这些人为变化代表流域从供应受限的沉积物预算到运输受限的沉积物预算的重大转变，以及地貌过程的变化，远离了由向内生长的河曲为主的长期排水演变。存储在这些地貌中的大量采矿沉积物将在下一个千年缓慢释放，由于最近发现的与水力矿有关的高汞含量，可能对当代生态和公共卫生问题具有重大意义。

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