碩士 / 國立臺灣大學 / 地質科學研究所 / 91 / The Lichi mélange in the southeastern Coastal Range is composed of intensively sheared scaly argillaceous matrix with variable sizes of exotic ophiolitic, sedimentary and andesitic blocks along with coherent terbidite beds. Different models of formation mechanism and tectonic setting of the Lich mélange have been proposed: sedimentary olistostrom in western forearc basin, subduction complex in the Manila Trench, or collision complex.
Detailed field surveys alone and near the Muken River, from east to west show that sequences progressively change from well-stratified non-sheared coherent turbidites (Takangkou Formation) in the Taiyuan relict forearc basin, to alternations of sheared mélange and non-sheared turbidites of the Takangkou Formation, and finally to the totally completely sheared mélange. We study foraminiferal fossils collected from both sheared and non-sheared parts to see if there is any stratigraphic relationship among these different status of stratification. Preliminary results show:
1. Sheared and non-sheared rock units are both Early Pliocene (N19 or NN14-NN15) in age and were deposited in deep-sea environment (about 1000~1500) with almost identical benthic foraminifers.
2. The matrix of the Lichi mélange was deposited in Early Pliocene age coeval to the middle ~ lower Takangkou Formation in the Taiyuan forearc basin (N19/NN14~15), but obviously older than the upper Takangkou Formation (Pleistocene, N21-22/NN18-19).
3. The sedimentary blocks in the Lichi mélange could be grouped into two types: autochthonous flysch with rich deep-sea foraminifers and those allochthonous ones of white sandstone blocks without foraminifer or with very rare microfossils.
Based on foraminiferal assemblages, we prefer that the Lichi mélange is neither an olistostrome nor a subduction complex, but a faulted and sheared “collision complex” of the forearc sequences equivalent to the Huatung Ridge in the modern initial arc-continent collision zone.
| Identifer | oai:union.ndltd.org:TW/091NTU00138010 |
| Date | January 2003 |
| Creators | CHIEN, CHIH-WEI, 簡至暐 |
| Contributors | , 黃奇瑜, 劉平妹 |
| Source Sets | National Digital Library of Theses and Dissertations in Taiwan |
| Language | zh-TW |
| Detected Language | English |
| Type | 學位論文 ; thesis |
| Format | 110 |
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