Proglacial braided river systems discharge large volumes of meltwater from ice sheets and transport coarse-grained sediments from the glaciated areas to the oceans. Here, we test the hypothesis if high-energy hydrological events can leave distinctive signatures in the sedimentary record of braided river systems. We characterize the morphology and infer a mode of formation of a 25 km long and 1–3 km wide Early Pleistocene incised valley recently imaged in 3-D seismic data in the Hoop area, SW Barents Sea. The fluvial system, named Bjørnelva River Valley, carved 20 m deep channels into Lower Cretaceous bedrock at a glacial paleo-surface and deposited 28 channel bars along a paleo-slope gradient of ~0.64 m km−1. The landform morphologies and position relative to the paleo-surface support that Bjørnelva River Valley was formed in the proglacial domain of the Barents Sea Ice Sheet. Based on valley width and valley depth, we suggest that Bjørnelva River Valley represents a braided river system fed by violent outburst floods from a glacial lake, with estimated outburst discharges of ~160 000 m3 s−1. The morphological configuration of Bjørnelva River Valley can inform geohazard assessments in areas at risk of outburst flooding today and is an analogue for landscapes evolving in areas currently covered by the Greenland and Antarctic ice sheets.

中文翻译：

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使用高分辨率 3-D 地震数据表征冰川古爆发洪水：Bjørnelva River Valley, SW Barents Sea

前冰期辫状河流系统从冰盖中排放大量融水，并将粗粒沉积物从冰川地区输送到海洋。在这里，我们检验了高能水文事件是否可以在辫状河流系统的沉积记录中留下独特特征的假设。我们描述了形态并推断了一个 25 公里长和 1-3 公里宽的早更新世下切谷的形成模式，该谷最近在 SW 巴伦支海 Hoop 地区的 3-D 地震数据中成像。河流系统，名为 Bjørnelva 河谷，在冰川古地表的下白垩统基岩中雕刻了 20 m 深的河道，并沿约 0.64 m km 的古坡度梯度沉积了 28 个河道坝-1. Bjørnelva河谷形成于巴伦支海冰盖的前冰河域的地貌形态和相对于古地表支撑的位置。根据河谷宽度和河谷深度，我们建议 Bjørnelva 河谷代表一个由冰川湖的猛烈爆发洪水喂养的辫状河流系统，估计爆发流量约为 160 000 m3s-1. Bjørnelva 河谷的形态结构可以为当今面临爆发洪水风险的地区的地质灾害评估提供信息，并且是目前格陵兰岛和南极冰盖覆盖地区不断演变的景观的模拟。