Collaborative Research- Laterally Extensive Breccias in the Mesoproterozoic Atar Group, Mauritania: Tsunami Deposition resulting from a Marine Extraterrestrial Impact?

海啸是具有长波长、长周期和高速度的海洋波，最常见的是由海底断层运动、山体滑坡、火山爆发或外星物体对海洋的影响造成的水柱灾难性位移。当海啸波越过大陆边缘时，深海中波浪传播过程中保存的能量转化为波高，并通过与沉积物基底的摩擦而逐渐消散。虽然在大陆架的广大地区都可能发生底质移动，但海啸最具破坏性的影响发生在海浪淹没沿海地区的过程中，沿海地区遭受严重的侵蚀和沉积物的搬运，然后沉积在内陆地区，海啸的反冲可能导致更多的侵蚀和沉积物向海洋的搬运。尽管海啸沉积物频繁重现，并具有潜在的非凡沉积作用，但我们对海啸沉积物的了解主要限于全新世和更年轻的沉积物。虽然更古老的地质沉积物已被归因于海啸波，直到最近才有详细的分析波的行为和相关的沉积沉积允许一个更系统的汇编沉积签名，可以归因于过程中的海啸波列的通道。在这样一个框架内，详细分析古代海啸沉积物可能允许区分特定的海啸过程。最大的沉积物（即巨型海啸沉积物），如果在地层厚度、地层变异性和横向范围方面保存良好，甚至可以提供足够的数据来区分潜在的海啸源mechanism.Carbonate地层在元古宙Atar组，毛里塔尼亚，包含一个4至6米厚的角砾岩间隔，已被归因于地震液化。横跨西非克拉通的1000公里以上的沉积物横向范围很广，而且存在具有明显角砾岩内冲刷的混合层、可变碎屑级配和双向叠瓦状构造的迹象，这表明沉积物是通过一系列巨大的波浪（例如海啸波列）形成的。此外，相重建表明米级的巨石运输到150公里，横跨浅的三角洲海道，这表明一个非常巨大的海啸源。该项目是田纳西州诺克斯维尔大学和俄亥俄州大学之间的一项合作，将对这些沉积物进行详细的沉积学、岩相学和地球化学分析，以描述海啸过程的沉积学影响，探索浅地震波海道中的海啸行为和能量消耗，并验证波浪能量来源于海洋外星撞击的假设。该项目旨在推进发现，同时促进教学，培训，通过将两位研究员的沉积学和行星专业知识联系起来，并让研究生和本科生参与国际合作和科学探究过程，进行学习。两位调查人员都有很长的公共宣传历史。田纳西大学将支持当地的一名中学教师构建一系列物理包含的动手练习（和相关的网络材料），探索海啸和外星影响作为塑造我们世界的地质现象。这些演习将提供给一些地区学校，资金也将支持本科生和研究生？学生大使？访问多达10所当地中学，与学生和教师一起实施这些练习，从而加强田纳西州东部的中学科学教育。

Tsunamis are oceanic waves with long wavelengths, long periods, and high velocities, and are most commonly caused by catastrophic displacement of the water column by submarine fault movements, landslides, volcanic eruptions, or the marine impact of extraterrestrial bodies. Energy conserved during wave propagation in the deep ocean is translated to wave height as tsunami waves cross the continental margins, and is gradually dissipated through friction with the sediment substrate. Although mobilization of the substrate can occur over wide areas of the continental shelf, the most devastating effects of tsunami occur during wave inundation of coastal zones, which experience significant erosion and transport of sediment that is then deposited en masse in inland zones, and during tsunami back-surge, which can result in additional erosion and seaward transport of sedimentary materials. Despite their frequent recurrence and their potentially extraordinary sedimentologic effect, our understanding of tsunami deposits is largely restricted to Holocene and younger deposits. Although more ancient geologic deposits have been attributed to tsunami waves, only recently has the detailed analysis of wave behavior and related sedimentary deposition permitted a more systematic compilation of sedimentary signatures that can be ascribed to processes acting during passage of a tsunami wave-train. Within such a framework, detailed analysis of ancient tsunami deposits potentially allow differentiation of specific tsunami processes. The largest deposits (i.e. mega-tsunami deposits), if well preserved in terms of their stratigraphic thickness, stratigraphic variability, and lateral extent, may even provide sufficient data to differentiate among potential tsunamigenic source mechanisms.Carbonate strata within the Proterozoic Atar Group, Mauritania, contain a 4 to 6 meter-thick breccia interval that has been attributed previously to seismic liquefaction. The wide lateral extent of deposits over a thousand kilometers across the West African craton, as well the presence of amalgamated beds with distinct intrabreccia scours, variable clast grading, and indication of bi-directional imbrication, suggests formation via passage of a series of anomalously large waves (e.g. a tsunami wave-train). Furthermore, facies reconstruction indicates transport of meter-scale boulders up to 150 km across a shallow cratonal seaway, suggesting a tsunamigenic source of extraordinary magnitude. This project, a collaboration between the University of Tennessee Knoxville and Ohio University, will carry out a detailed sedimentologic, petrographic, and geochemical analysis of these deposits to characterize the sedimentological effect of tsunami processes, to explore tsunami behavior and energy depletion in a shallow epicratonic seaway, and test the hypothesis that the wave energy originated from a marine extraterrestrial impact.This project aims to advance discovery while promoting teaching, training, and learning by linking sedimentologic and planetary expertise of the two Investigators and involving both graduate and undergraduate students in international collaboration and the process of scientific inquiry. Both investigators have a long history of public outreach. The University of Tennessee will support a local middle school teacher to construct a series of physically contained, hand-on exercises (and associated web materials) that explore tsunamis and extraterrestrial impacts as geologic phenomena that shape our world. These exercises will be provided to a number of regional schools, and funding will also support undergraduate and graduate ?student ambassadors? to visit up to ten local middle schools to work with students and teachers inimplementing these exercises, thereby enhancing secondary science education in eastern Tennessee.