Abstract

The South Taiwan Bank Canyon (STBC) is a large canyon on the southwest offshore Taiwan Island, bearing significant implications in fossil energy exploration. In this study, we analyze the morphology and sedimentary structure of the STBC, as well as those in nearby continental margin, using high-resolution swath bathymetry and seismic data. The the STBC is multiple-headed, steep in the upper part as a V-shaped incised trough and gentle in the lower as a U-shaped one; thedirection changes from NW-SE to E-W when it joins the Manila Trench at around 2200 m. The regional tectonic framework shows that the cannon was born in the Neogene under the influence of onshore rivers, followed by rapid thermal subsidence after the mid-Miocene, enhancing the sediment transport with frequent slides, slumps, and other sediment flows, and resulting in an incised slope with multiple gullies and heads. The NW tenso shear faulting triggered by the collision of the Luzon Arc against the Eurasian Plate after mid-Miocene probably pre-determined the position of the canyon and caused heavy down-cutting erosion. Strong magmatism in the underlying oceanic plate segment after the cessation of the South China Sea’s spreading could also play roles in reducing slope stability and generating seamounts that blocked the southeastward flow in the canyon and coerced the direction change into the east.

Key words: South Taiwan Bank Canyon, morphology, tectonic setting, controlling factors.