Bonaire's boulder fields revisited: evidence for Holocene tsunami impact on the Leeward Antilles
Bonaire's boulder fields revisited: evidence for Holocene tsunami impact on the Leeward Antilles
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DOI：
10.1016/j.quascirev.2011.12.011
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发表时间：
2012-10-26
影响因子：
4
通讯作者：
May, Simon Matthias
中科院分区：
文献类型：
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作者：
Engel, Max;May, Simon Matthias
沿岸巨砾和岩块是世界各地沿着岩石海岸线的突出沉积特征。在大多数情况下，它们的沉积归因于高能量的波浪事件（海啸，强烈的风暴）。即使海啸波预计有更高的运输能力相比，风暴波，高达100吨的巨型已被观察到后一种波形的横向移动。因此，从巨石记录中推断某些极端波浪事件（海啸、强烈风暴）仍然是古事件研究中的一个主要挑战;关于它们的区别的辩论正在进行中。在加勒比海南部博内尔岛（背风安的列斯群岛）的东海岸，许多石灰岩块和巨石（高达c。130 t）分布在3-6 m a.s.l.（高于平均海平面）古礁台地。许多作者对巨石区形成所涉及的运输过程存在分歧。在本文中，国家的最先进的建模方法的沿海漂砾夹带和运输，以提供新的和更可靠的数据来支持/挑战海啸沉积的工作假设。为了提高漂砾运输模型的可靠性，通过新的DGPS测量漂砾尺寸和考虑到礁岩漂砾的异质性计算堆积密度，提供了更切合实际的输入参数。现有的流体动力学方程进行了修改，以允许不规则的形状和真实的尺寸的巨石。结果表明，（i）巨石的重量和尺寸，因此（ii）计算的波能和波高被高估在大多数以前的研究，其中计算的巨石体积的基础上的主轴乘法。这项研究的结果和波高观察到在最近的强烈热带气旋似乎排除了风暴产生的波错位的最大的块。然而，大多数粗碎屑沉积物可能是由周期性的飓风涌浪产生的。结果强调了更现实的现场数据的意义，在模拟巨石运输波。(C)2011爱思唯尔有限公司保留所有权利。
Supralittoral boulders and blocks are prominent sedimentary features along rocky shorelines worldwide. In most cases, their deposition is attributed to high-energy wave events (tsunamis, severe storms). Even though tsunami waves are expected to have higher transport capacities compared to storm waves, megaclasts of up to 100 t were observed to have been moved laterally by the latter waveform. The deduction of certain extreme wave events (tsunamis, severe storms) from the boulder record thus remains a major challenge in palaeo-event research; the debate on their differentiation is ongoing. At the eastern coast of Bonaire (Leeward Antilles) in the southern Caribbean, numerous limestone blocks and boulders (up to c. 130 t) are distributed on top of a 3-6 m a.s.l. (above mean sea level) palaeo-reef platform. Disagreement exists among a number of authors concerning the transport processes involved in the formation of the boulder fields. In this paper, state-of-the-art modelling approaches of coastal boulder entrainment and transport were applied in order to provide new and more reliable data to support/challenge the working hypothesis of tsunami deposition. To improve the reliability of the boulder transport model, more realistic input parameters were provided by new DGPS measurements of the boulder dimensions and the calculation of bulk densities by taking into account the heterogeneity of the reef-rock boulders. Existing hydrodynamic equations were modified to allow for the irregular shape and real dimensions of the boulders. The results indicate that (i) boulder weight and dimension, and thus (ii) calculated wave energy and wave heights were overestimated in most of the previous studies, where calculations of boulder volume were based on multiplication of the main axes. The results of this study and wave heights observed during recent severe tropical cyclones seem to rule out storm-generated waves for the dislocation of the largest blocks. However, the majority of coarse-clast deposits may have been generated by periodic hurricane swells. The results underline the significance of more realistic field data in modelling boulder transports by waves. (C) 2011 Elsevier Ltd. All rights reserved.