Heavy minerals in the 2011 Tohoku-oki tsunami deposits-insights into sediment sources and hydrodynamics
Heavy minerals in the 2011 Tohoku-oki tsunami deposits-insights into sediment sources and hydrodynamics
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DOI：
10.1016/j.sedgeo.2012.07.015
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发表时间：
2012-12-30
影响因子：
2.8
通讯作者：
Sugawara, Daisuke
中科院分区：
文献类型：
--
作者：
Jagodzinski, Robert;Sternal, Beata;Sugawara, Daisuke
2011年的东北海啸在日本仙台沿海平原内陆4公里处留下了沙子和泥沙。分析了海啸沉积、海啸前土壤和海滩沉积物的粒度、重矿物含量和组合，以测试重矿物分析在识别海啸沉积和解释相关沉积过程中的适用性。重矿物平均占海啸沉积物的35%，粒度为0.125-0.25毫米。最常见的是斜方辉石、单斜辉石、角闪石、柠檬石和不透明矿物。海啸沉积物、海滩和海啸前土壤和沉积物中的重矿物浓度和组合相似，因此不能简单地根据其重矿物来确定海啸沉积物。沉积物来源分析表明，海岸线1.5公里以内的海啸沉积物主要来自海滩、沙丘和当地土壤的侵蚀，而更远的内陆(>；1.5公里)的沉积物主要来自当地的土壤侵蚀。没有发现任何证据表明近海沉积物有重大贡献。详细的分析表明，海啸沉积的最下部大多来自当地，而上部的沉淀物来源多种多样。与2004年物联网沉积物中以前对重矿物的研究相比较，证实了海啸沉积物中的重矿物大多与来源有关，可作为研究海啸沉积物的有用辅助工具。然而，解释必须始终放在当地的地质背景下，并与其他“海啸替代物”相印证。(C)2012爱思唯尔B.V.保留所有权利。
The 2011 Tohoku-oki tsunami left sand and mud deposits more than 4 km inland on the coastal plain of Sendai, Japan. The tsunami deposits, pre-tsunami soils and beach sediments were analysed for grain size, and heavy mineral content and assemblages to test the applicability of heavy mineral analyses in the identification of tsunami deposits and interpretation of associated sedimentation processes. Heavy minerals comprised on average 35% of the tsunami deposit in the 0.125-0.25 mm grain size fraction. The most common were orthopyroxenes, clinopyroxenes, amphiboles, limonites and opaque minerals. Heavy mineral concentrations and assemblages were similar in the tsunami deposits, beach and pre-tsunami soils and sediments and thus tsunami deposits could not simply be identified based on their heavy minerals. Sediment provenance analysis revealed that tsunami deposits left within 1.5 km of the shoreline were mostly eroded from the beach, dune and local soils, while deposits farther inland (> 1.5 km) were mostly derived from local soil erosion. No evidence was found for a significant contribution of offshore sediments. Detailed analyses revealed that the lowermost portion of tsunami deposits was mostly of local origin, while the sediment source of the upper portion was variable. A comparison with a previous study of heavy minerals in 2004 IOT deposits confirms that heavy minerals in tsunami deposits are mostly source-dependent and may represent a useful supplementary tool in studies of tsunami deposits. However, the interpretation must always be placed in the local geological context and corroborated with other "tsunami proxies". (c) 2012 Elsevier B.V. All rights reserved.