The Structural and Sedimentary Characteristics of the Formosa Ridge Offshore Southwestern Taiwan
Date Issued
2008
Date
2008
Author(s)
Liao, Yi-Hsiang
Abstract
The Formosa Ridge is located in the passive South China Sea continental margin, to the west of the deformation front offshore southwestern Taiwan. The structural character is mainly extensional horst-and-graben structure. On the continental slope region, there are numerous submarine canyons and slope ridges formed by submarine erosion mechanism. The seismic data show clear BSR（Bottom Simulating Reflector）distributed widely in the study area. High concentrations of methane are also revealed from the core samples collected at the crest of the Formosa Ridge. It indicates that there are venting activities of methane gases in the area. From seafloor photographic images, bacterial mats and carbonate mounds were observed. Massive chemosynthetic colonies have also been observed from the video clips taken by the ROV Hyper Dolphin. Therefore, we consider that the Formosa Ridge has an active cold seep site which is worth further studying.he data we used include a deep seismic reflection profile EW9509-45, the MCS719 and MCS754 multichannel seismic reflection data collected for the gas hydrate investigation, and the high-resolution single channel seismic reflection data of the JAMSTEC R/V Natsushima cruise NT07-05. The Formosa Ridge is located east of the Tainan basin. There is a large growth fault dipping toward SE, and this fault may provide a convenient path for the deeper gases flow up to the shallow reservoir. Gas vents could be identified on the high resolution seismic profile. This suggests possible fluid paths. This thesis summarizes some characters of the Formosa Ridge and proposes a simple model trying to explain the fluid circulation at the observed cold seep site. In the Formosa Ridge, sediment waves or polygonal faulting system could be the major factors controlling the fluid migrating upward from BSR to the seafloor.
Subjects
Formosa Ridge
gas hydrate
Bottom Simulating Reflector (BSR)
SDGs
Type
thesis
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