Fill, flush or shuffle: How is sediment carried through submarine channels to build lobes?
Fill, flush or shuffle: How is sediment carried through submarine channels to build lobes?
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填充、冲洗或洗牌：沉积物如何通过海底通道形成波瓣？
DOI：
10.1016/j.epsl.2022.117481
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发表时间：
2022
影响因子：
5.3
通讯作者：
Heijnen M
中科院分区：
文献类型：
--
作者：
Heijnen M
海底通道是陆源物质（包括有机碳、污染物和营养物）进入深海的主要通道。穿越这些系统的水流（浊流）可能对海底基础设施（如电缆和管道）造成危害。在这里，我们使用一种新的组合重复海底调查和浊流监测沿着一个50公里长的海底通道在布特湾，不列颠哥伦比亚省，并从主要补给河流流量测量。这些源到汇的观测提供了最详细的信息，但浊流的大小，频率，距离的关系，和海底通道波瓣系统内的沉积物输运的时空格局。这项分析提供了新的见解质量再分布，和粒子在海底通道中的停留时间，以及粒子最终被埋在哪里，以及如何在沉积物中记录。我们观察到逐步沉积物运输的渠道，浊流变得越来越不频繁的距离。大多数水流消散并存款在系统的近端（< 11 km）部分，而较长的流出水流则带走这些沉积物，将其沿着河道进一步向下游“移动”。这种洗牌主要通过断点的上游迁移发生，这可以在10-100年的时间尺度内产生沉积物绕过沿着通道。罕见的大型事件冲洗通道，并最终将沉积物输送到叶上。这些刷新事件可能会在没有明显触发器的情况下发生，因此可能是内部生成的。然后，我们提出了有史以来第一次沉积物预算分析的整个海底通道系统，这表明，河流输入和叶加积可以近似平衡超过十年的时间尺度。最后，我们讨论了海底地质灾害和颗粒埋藏的沉积物洗牌的影响。
Submarine channels are the primary conduits for land-derived material, including organic carbon, pollutants, and nutrients, into the deep-sea. The flows (turbidity currents) that traverse these systems can pose hazards to seafloor infrastructure such as cables and pipelines. Here we use a novel combination of repeat seafloor surveys and turbidity current monitoring along a 50 km-long submarine channel in Bute Inlet, British Columbia, and discharge measurements from the main feeding river. These source-to-sink observations provide the most detailed information yet on magnitude-frequency-distance relationships for turbidity currents, and the spatial-temporal patterns of sediment transport within a submarine channel-lobe system. This analysis provides new insights into mass redistribution, and particle residence times in submarine channels, as well as where particles are eventually buried and how that is recorded in the deposits. We observe stepwise sediment transport down the channel, with turbidity currents becoming progressively less frequent with distance. Most flows dissipate and deposit within the proximal (< 11 km) part of the system, whilst longer run-out flows then pick up this sediment, ‘shuffling’ it further downstream along the channel. This shuffling occurs mainly through upstream migration of knickpoints, which can generate sediment bypass along the channel over timescales of 10–100 yrs. Infrequent large events flush the channel and ultimately transport sediment onto the lobe. These flushing events can occur without obvious triggers, and thus might be internally generated. We then present the first ever sediment budget analysis of an entire submarine channel system, which shows that the river input and lobe aggradation can approximately balance over decadal timescales. We conclude by discussing the implication of this sediment shuffling for seafloor geohazards and particle burial.
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