碩士 / 國立臺灣大學 / 海洋研究所 / 106 / High energy events, such as tsunami, although occur episodically, are destructive over a wide range of geographic area, and often cause substantial casualties and/or property damages. With the aid of historical records and precise dating, the target tsunami deposits could be correlated over various spatial and temporal scales. This general concept and methodological framework is often challenged under the circumstance where historical records and typical tsunami sediments are fragmentary or absent. As marine sediments bear a variety of geochemical characteristics distinctive from terrestrial ones, geochemical methods would provide additional evidence to constrain the origin of the possible target sediments but have seldom been applied in Taiwan.
In this study, a marine terrace in Fongbin Area was chosen for investigation of geochemical characteristics of sediments that have been previously identified to archive a tsunami event. The terrace is composed of colluvial deposits, within which rounded and poorly sorted gravels with a thickness of 50 cm appear in the upper portion, fade away toward inland, and are interpreted to originate from a tsunami event. Particle size and elemental analyses indicated that the poorly soring tsunami deposits have higher Si and Cr content, which could derive from quartz and Cr-spinel. These two minerals may originate from Paliwan Formation and Suilien Conglomerate and were delivered by a tsunami event. The geochemical difference between tsunami and regular deposits decreases toward inland, but the characteristics still subsists. Apparently, geochemical evidence can give a clue to trace the target layer, even if the grain size and sorting cannot exhibit the feature of tsunami event. It seems that geochemical analyses can provide extra indicators to general features of tsunami deposits, while the difference of sediment source could be fully characterized.
| Identifer | oai:union.ndltd.org:TW/106NTU05279016 |
| Date | January 2018 |
| Creators | Yun-Chun Wang, 王韻淳 |
| Contributors | 王珮玲 |
| Source Sets | National Digital Library of Theses and Dissertations in Taiwan |
| Language | zh-TW |
| Detected Language | English |
| Type | 學位論文 ; thesis |
| Format | 51 |
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