Seismic Stratigraphic Analyses of the Lower Fangliao Basin Offshore Southwestern Taiwan

• Main Authors: Ya-Ting Chang, 張雅婷
• Other Authors: Char-Shine, Liu
• Format: Others
• Language: zh-TW
• Published: 2012
• Online Access: http://ndltd.ncl.edu.tw/handle/25288564554921352437

碩士 === 國立臺灣大學 === 海洋研究所 === 100 === Taiwan is located at the junction between the Ryukyu and Luzon Arcs in the northwest Pacific, and the region offshore southwestern Taiwan is an incipient collision zone where the accretionary wedge has obliquely impinged on the passive continental margin of the South China Sea. Imbricated fold-and-thrust structures are observed in the lower Kaoping slope domain and mud diapirs, extending in a NNE-SSW direction, emerge through thick orogenic sediments in the upper Kaoping slope domain. Mud diapirs and canyons run across the upper slope domain in NE-SW direction, represent the source of sediments and spatial variation of the intraslope basins distributing in the upper Kaoping slope domain. In this study, we use a 3D seismic and many 2D seismic profiles to reveal the development and sedimentation of the Lower Fangliao Basin, locating in the southern portion of the Fangliao Canyon where it merges into a nearly filled submarine canyon and then join the Kaoping Canyon. We interpreted six depositional units, eight mud diapir structures and one plunge fold in the Lower Fangliao Basin. The unit boundaries have relatively continuous reflections throughout the basin. We propose a 8-stage conceptual model to explain our observation for the evolution of the Lower Fangliao Basin. In this model, Unit A folded during thrust folding (Stage B), and Unit B deposited here during Stage C. The thrust fault was active again and Unit C deposited at the same time (Stage D). The first time occurrence of mass transport deposits (MTDs) were caused by D3 uplifting (Stage E). As the H4 occurrence of erosional surface from eastern Lower Fangliao Basin, channelized sedimentation became dominant and formed Unit E here during Stage F. The D2 and D4 developed simultaneously (Stage G), ceased the channelized sedimentation and induced MTDs to form from D2’s direction. This migrating uplift resulted in shifted depocenters from western to eastern side, and then shifted back to eastern side after D4 developed. Unit E deposited above all units in the end (Stage H).