Structural Controls of the Taitung Canyon in the Huatung Basin East of Taiwan

Abstract

The Taitung Canyon originates at the southern end of the Longitudinal Valley. It runs southward along the axis of the Taitung Trough. The canyon turns eastward into the Huatung Basin, after crossing the Luzon arc between the volcanic islands of Lanyu and Lutao. It then flows northeastward for about 170 km and merges with the Hualien Canyon near the Ryukyu Trench, thus forming the largest canyon in the Huatung Basin. High resolution bathymetric data, and several multi-channel seismic profiles are used to describe the structural fabric in the vicinity of the Taitung Canyon and the factors controlling its path within the Huatung Basin. Crossing the eastern slope of the Lanyu-Lutao volcanic ridge, the head of the Taitung Canyon is fan shaped and its entrenchment rapidly increases downslope. Throughout the canyon's upper and central portions, the channel depth ranges from 300 to 500 m with respect to the surrounding seafloor. The canyon's levees are generally asymmetric and turbidite overbank deposits are observed. Then, a basement high, trending parallel to the Gagua Ridge, forces the path of the Taitung Canyon to turn 90° toward the northwest. As the canyon reaches the Ryukyu Trench, the width of the main channel has decreased from 14 km near the Luzon are, to less than 200 m at the outer-slope of the Ryukyu Trench. The importance of structural controls, such as basement highs and faulting, on the canyon's development are examined. Thus, the existence of a strike-slip fault system, affecting the oceanic basement in the Huatung Basin, and its role in controlling the path of the canyon are discussed.