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A huge flood in the Fraser River valley, British Columbia, near the Pleistocene Termination
Geomorphology ( IF 3.9 ) Pub Date : 2021-02-01 , DOI: 10.1016/j.geomorph.2020.107473
John J. Clague , Nicholas J. Roberts , Brendan Miller , Brian Menounos , Brent Goehring

Abstract Near the Pleistocene Termination, a glacier-dammed lake in central British Columbia suddenly drained to the south along the Fraser River valley. Floodwater travelled 330 km down the valley to Hope, British Columbia, and from there to the west into the Salish Sea near Vancouver. The flood was caused by the failure of an ice dam formed by the terminus of glaciers flowing from the central Coast Mountains across the British Columbia Interior Plateau. The ice dam impounded several hundred cubic kilometres of water to a maximum elevation of about 810 m asl (above sea level); at its maximum, the lake at the ice dam was over 250 m deep. Geomorphic and sedimentary evidence for the flood includes streamlined boulder-strewn bars, gravel dune fields, and terraces sloping up Fraser and lowermost Thompson valleys, opposite the present direction of current river flow. The gravel bars and flood terraces are underlain by sheets of massive to poorly sorted gravel containing large boulders and rip-up clasts of silt and till. Shortly after the flood, a landslide near the northern margin of the former glacier dam impounded water to an elevation of about 550 m asl. This lake emptied due to overflow and incision of the landslide dam. The outburst flood from glacial Lake Fraser and the subsequent draining of the landslide-dammed lake deeply incised the older sediment fill in Fraser Valley and transported much of this sediment into the proto-Salish Sea west of Vancouver, British Columbia and Bellingham, Washington. TCN ages on flood-transported boulders at three localities along the flood path agree with radiocarbon ages on inferred flood layers in ODP cores collected from Saanich Inlet, a fiord on southern Vancouver Island, 80 km south-southwest of Vancouver.

中文翻译:

不列颠哥伦比亚省弗雷泽河谷,更新世末期附近发生大洪水

摘要 在更新世末期附近,不列颠哥伦比亚省中部的一个冰川堰塞湖突然沿着弗雷泽河谷向南排干。洪水沿着山谷行驶 330 公里到达不列颠哥伦比亚省的霍普,然后从那里向西流入温哥华附近的萨利希海。洪水是由从中央海岸山脉流过不列颠哥伦比亚内陆高原的冰川终点形成的冰坝破裂造成的。冰坝蓄积了数百立方公里的水,最高海拔约 810 m asl(海平面以上);最大时,冰坝处的湖水深超过 250 m。洪水的地貌和沉积证据包括流线型的巨石散布的酒吧、砾石沙丘地和向弗雷泽和汤普森谷最下方倾斜的梯田,与当前河流的流动方向相反。砾石栅栏和洪水阶地下面是大块到分选不良的砾石,其中包含大块的巨石和淤泥和碎屑的碎屑。洪水过后不久,前冰川大坝北缘附近发生山体滑坡,蓄水至海拔约 550 m。由于溢流和滑坡大坝的切割,这个湖被清空了。来自冰川弗雷泽湖的洪水爆发和随后的滑坡堰塞湖的排水深深地切割了弗雷泽河谷的旧沉积物填充物,并将大部分沉积物输送到不列颠哥伦比亚省温哥华和华盛顿贝灵厄姆以西的原始萨利希海。
更新日期:2021-02-01
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