Eustatic sea-level controls on the flushing of a shelf-incising submarine canyon
Eustatic sea-level controls on the flushing of a shelf-incising submarine canyon
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DOI：
10.1130/b31658.1
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发表时间：
2018-01-01
影响因子：
4.9
通讯作者：
Talling, Peter J.
中科院分区：
文献类型：
--
作者：
Allin, Joshua R.;Hunt, James E.;Talling, Peter J.
湍流是雕刻海底峡谷并在地质时间尺度上维持它们的主要过程。维持或“冲刷”海底峡谷的浊流是地球上体积最大的沉积物输送事件之一。长期控制的频率和触发的峡谷冲洗事件是知之甚少，在大多数峡谷系统，由于缺乏长期的沉积记录。在这里，我们分析了一个160米长的大洋钻探计划（ODP）的核心，以确定在过去的180万年在纳扎尔峡谷的峡谷冲洗事件的复发间隔。然后，我们研究了全球海平面在控制这些峡谷冲刷事件的频率和幅度的作用。在过去的180万年里，到达伊比利亚深海平原的冲刷浊流的平均重现期为2770年。先前的研究已经证明全球海平面对峡谷冲刷的重现率没有影响。然而，我们发现，全球海平面在中更新世过渡（1.2-0.9马）的急剧变化与更频繁的峡谷冲洗事件。在中更新世过渡期的高振幅，长周期性的海平面变化的变化可能已经重新动员了大量的陆架沉积物通过陆上风化，并暂时增加了峡谷冲洗浊流的频率和幅度。伊比利亚深海平原的浊积岩复发间隔具有对数正态分布，这与在其他盆地浊积岩记录中观察到的复发间隔的指数分布有根本的不同。在伊比利亚深海平原浊流复发间隔的对数正态分布被证明是由于浊流的变量跑出来的距离，这样的远端记录是不完整的，与可能的影响，从不同的来源或触发机制。沉积体系中不同位置浊流复发间隔的变化形式很重要，因为它最终决定了浊流相关地质灾害的概率。
Turbidity currents are the principal processes responsible for carving submarine canyons and maintaining them over geological time scales. The turbidity currents that maintain or "flush" submarine canyons are some of the most voluminous sediment transport events on Earth. Long-term controls on the frequency and triggers of canyon-flushing events are poorly understood in most canyon systems due to a paucity of long sedimentary records. Here, we analyzed a 160-m-long Ocean Drilling Program (ODP) core to determine the recurrence intervals of canyon-flushing events in the Nazare Canyon over the last 1.8 m.y. We then investigated the role of global eustatic sea level in controlling the frequency and magnitude of these canyon-flushing events. Canyon-flushing turbidity currents that reach the Iberian Abyssal Plain had an average recurrence interval of 2770 yr over the last 1.8 m.y. Previous research has documented no effect of global eustatic sea level on the recurrence rate of canyon flushing. However, we find that sharp changes in global eustatic sea level during the mid-Pleistocene transition (1.2-0.9 Ma) were associated with more frequent canyon-flushing events. The change into high-amplitude, long-periodicity sea-level variability during the mid-Pleistocene transition may have remobilized large volumes of shelf sediment via subaerial weathering, and temporarily increased the frequency and magnitude of canyon-flushing turbidity currents. Turbidite recurrence intervals in the Iberian Abyssal Plain have a lognormal distribution, which is fundamentally different from the exponential distribution of recurrence intervals observed in other basin turbidite records. The log-normal distribution of turbidite recurrence intervals seen in the Iberian Abyssal Plain is demonstrated to result from the variable run-out distance of turbidity currents, such that distal records are less complete, with possible influence from diverse sources or triggering mechanisms. The changing form of turbidite recurrence intervals at different locations down the depositional system is important because it ultimately determines the probability of turbidity current-related geohazards.