https://scholars.lib.ntu.edu.tw/handle/123456789/571654
標題: | Tropical cyclone deposits in the Pliocene Taiwan Strait: Processes, examples, and conceptual model | 作者: | Dashtgard S.E L?wemark L Vaucher R Pan Y.-Y Pilarczyk J.E Castelltort S. LUDVIG LOWEMARK |
關鍵字: | Hurricanes; Parallel flow; Scour; Sedimentary rocks; Storms; Tropics; Conceptual model; Cross stratifications; Current redistribution; Foreland basin; High probability; Oscillatory structure; Sedimentological data; Tropical cyclone; Deposits; conceptual framework; modeling; mudstone; Pliocene; sedimentology; shallow water; tropical cyclone; Taiwan Strait | 公開日期: | 2020 | 卷: | 405 | 來源出版物: | Sedimentary Geology | 摘要: | The characteristics of tropical cyclone (TC) deposits are highly variable, and in the shallow waters of straits their character has not been established. Multiple coarse-grained beds in lower Pliocene strata in the Western Foreland Basin of Taiwan are interpreted as TC deposits, and the sedimentology of these beds reflects evolving TC processes and storm stages. By comparing sedimentological data from these beds with previous research on TCs, and with analysis of TCs that cross Taiwan from east to west, a conceptual model is built for understanding deposition in the Taiwan Strait during tropical cyclones. Taiwan is impacted by more than three TCs per year, including more than two super-typhoons every 10 years. These storms can deliver immense volumes of rain over very short time periods and are associated with intense winds. During TCs, and in shallow water in the Taiwan Strait (10–35 m water depth), hyperpycnal discharge, strong bottom currents, and oscillatory wave motion all impact deposition. These processes are manifested in the resulting deposits, and we propose that the best sedimentological criteria for recognizing TC deposits, include: 1) a basal scour surface; 2) an absence of within-bed bioturbation; 3) trough cross-stratification that preserves multi-directional, mainly shore-parallel flow with a 180° change in flow direction; 4) preservation of oscillatory structures towards the top of the bed; and, 5) organic lamina and clasts throughout the bed. Mudstone intercalated with trough cross-stratification is also a useful indicator of TC deposition as it probably reflects wave- and current-redistribution of sediment delivered to the strait through hyperpycnal and hypopycnal discharge from rivers. Contemporaneous mud deposition within TC beds is manifested as mudstone drapes on foresets and toesets, and discontinuous mudstone beds between trough cross-stratified sandstone beds. While not all TC beds exhibit all sedimentological characteristics, we hypothesize that high-probability TC beds should show three or more of them. ? 2020 Elsevier B.V. |
URI: | https://www.scopus.com/inward/record.uri?eid=2-s2.0-85085240505&doi=10.1016%2fj.sedgeo.2020.105687&partnerID=40&md5=d6999bb77886fa9a8ccc4603b20e563a https://scholars.lib.ntu.edu.tw/handle/123456789/571654 |
ISSN: | 370738 | DOI: | 10.1016/j.sedgeo.2020.105687 |
顯示於: | 地質科學系 |
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