The Tsunamite Problem
The Tsunamite Problem
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DOI：
10.2110/jsr.2006.073
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发表时间：
2006-05
影响因子：
2
通讯作者：
G. Shanmugam
中科院分区：
文献类型：
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作者：
G. Shanmugam
海啸这一术语用于指由与湖泊、沿海、浅海和深海环境中的海啸有关的各种过程（过度冲涌、反冲流、振荡流、混合流、软沉积物变形、滑坡、塌陷、泥石流和浊流）形成的沉积物混合物。海啸表现出巨大的特征变化（例如，正常分级的沙子、漂浮的泥岩碎屑、丘状交叉分层等）。这些沉积特征也可以解释为浊流（浊积岩）、泥石流（碎屑岩）或风暴（风暴岩）的沉积物。然而，当根据海啸及其触发机制（例如地震、火山爆发、山体滑坡和陨石撞击）的历史证据将这些相同的沉积物重新解释为海啸时，沉积特征发挥了被动作用。这种二分法（沉积学与历史）方法允许将同一矿床分类为浊积岩和海啸，模糊了浅海相和深海相之间的区别。该问题的解决方案是仅通过描述性沉积学方法对沉积物进行分类。海啸波可以直接在深海沉积沉积物的想法是不现实的，因为海啸波代表着能量的转移，而它们缺乏沉积物。在海啸和大风暴期间，海底峡谷充当浅水和深水环境之间沉积物运输的物理联系。海啸相关沉积涉及四个渐进步骤：(1) 触发阶段（近海）、(2) 海啸阶段（传入波浪）、(3) 转换阶段（靠近海岸）和 (4) 沉积阶段（流出泥沙流）。在这一过程中，只有在传入的海啸波转变为流出的沉积物流而消亡后，深水沉积才能开始。这些沉积物流的沉积物已经有了确定的名称（例如碎屑岩和浊积岩）。因此，这些矿床的海啸一词已经过时。
The genetic term tsunamite is used for a potpourri of deposits formed from a wide range of processes (overwash surges, backwash flows, oscillatory flows, combined flows, soft-sediment deformation, slides, slumps, debris flows, and turbidity currents) related to tsunamis in lacustrine, coastal, shallow-marine, and deep-marine environments. Tsunamites exhibit enormous variability of features (e.g., normally graded sand, floating mudstone clasts, hummocky cross stratification, etc.). These sedimentary features may also be interpreted as deposits of turbidity currents (turbidites), debris flows (debrites), or storms (tempestites). However, sedimentary features play a passive role when these same deposits are reinterpreted as tsunamites on the basis of historical evidence for tsunamis and their triggering mechanisms (e.g., earthquakes, volcanic explosions, landslides, and meteorite impacts). This bipartite (sedimentological vs. historical) approach, which allows here classification of the same deposit as both turbidite and tsunamite, has blurred the distinction between shallow-marine and deep- marine facies. A solution to this problem is to classify deposits solely by a descriptive sedimentological approach. The notion that tsunami waves can directly deposit sediment in the deep sea is unrealistic because tsunami waves represent transfer of energy and they are sediment starved. During tsunamis and major storms, submarine canyons serve as the physical link between shallow-water and deep-water environments for sediment transport. Tsunami-related deposition involves four progressive steps: (1) triggering stage (offshore), (2) tsunami stage (incoming waves), (3) transformation stage (near the coast), and (4) depositional stage (outgoing sediment flows). In this progression, deep-water deposition can commence only after the demise of incoming tsunami waves due to their transformation into outgoing sediment flows. Deposits of these sediment flows already have established names (e.g., debrite and turbidite). Therefore, the term tsunamite for these deposits is obsolete.