碩士 / 國立中央大學 / 應用地質研究所 / 107 / The Taiwan orogenic wedge overrides the northeast rifted continental margin of the South China Sea (SCS) in the offshore area of southwest Taiwan. In this work, I study the temporal and spatial distribution of Quaternary mass transport deposits (MTDs) and sediment waves (SWs) both in the SCS continental slope and its adjacent submarine Taiwan orogenic wedge in order to decipher the origins of MTDs and SWs in both tectonic regimes. Multibeam bathymetry, boreholes and multichannel reflection seismic data were used to characterize the MTDs and SWs. In the rifted continental margin, the Tainan Basin is mainly composed of Neogene and Quaternary sediments underlain by Paleogene synrift infills, especially in the deepwater area. During the rifting phase, many normal faults formed half-graben and graben blocks which were filled in by Paleogene sediments. Miocene sediments are characterized by hemiplegites with packets of turbidites in the deepwater areas. The slope progradational configuration is typical for Pliocene units with submarine channels which became well developed. During the Pleistocene Epoch, Gelasian MTDs, post 1.8 Ma MTDs, and sediment waves, which are separated by stratigrahic horizons of 1.8 Ma and 0.76 Ma, respectively. There are 4 large complexes of MTDs occurred during the Gelasian and 8 MTD sheets are recognized post 1.8 Ma boundary in the lower slope. MTD5 is the largest MTD which covers 4,045 km2, reaching a total volume of ~ 208 km3. Triggers of those MTDs are probably due to high sedimentation rates in the vicinity of the shelf edge, lowering of global sea-level, steepening of the continental slope, and earthquake shaking originated in the incipient arccontinent collision zone. The MTDs were then overlain by widespread SWs since around 0.76 Ma. The modern SWs occur only to the west of the deformation front and are characterized by two fields showing different orientation and geometry. The northern field lies to the north and to the east of the Formosa Canyon, while the southern field lies to the
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south of the Formosa Canyon. Though MTDs occur only in a limited number of slope basins in the accretionary wedge, they seem to occur near the splay fault, with a cumulated thickness up to ~ 500 m. The spatial extent of MTDs in the SCS continental margin is larger than that in the accretionary wedge. This indicates that large-scale and widespread mass movements tend to occur in continental margins, while the mass movements in the accretionary wedge tend to be more localized. The thickest MTDs are found in the accretionary wedge and adjacent to a major fault (i.e., the splay fault), indicating that the mass movements occurring in the accretionary wedge are most likely triggered by earthquake shaking, leading to gigantic thick, albeit localized sediment failures.
| Identifer | oai:union.ndltd.org:TW/107NCU05503018 |
| Date | January 2019 |
| Creators | Thi-Huong Nguyen, 阮氏香 |
| Contributors | Chuen-Fa Ni, Andrew Tien-Shun Lin, 倪春發, 林殿順 |
| Source Sets | National Digital Library of Theses and Dissertations in Taiwan |
| Language | en_US |
| Detected Language | English |
| Type | 學位論文 ; thesis |
| Format | 86 |
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