ARC-CONTINENT COLLISION OROGENY IN OFFSHORE TAIWAN DURING NEOGENE
Ding Weiwei1, Yang Shufeng2, Chen Hanlin2, Cheng Xiaogan2, Wu Nengyou3
1. Key Laboratory of Submarine Geoscience, State Oceanic Administration, Hangzhou 310012; 2. Department of Earth Sciences, Zhejiang University, Hangzhou 310027; 3. Marine Geology Survey of Guangzhou, Ministry of Land and Resources, Guangzhou 510075
The offshore Taiwan arc-continent collisional orogen was situated in the conjunction area of the Eurasian plate, the Philippine Sea plate and the South China Sea, which was created in Neogene. The structural geometry and kinematics of the Taiwan accretion prism were studied using multi-channel seismic profile of no.973 survey. The geological evidence showed that the accretionary prism caused by the collison was consisted of two distincet structural parts: the prisms caused by the arc-continent collision and by the subduction of South China Sea respectively. In the studied area, the two main units were the Gaoping Slope and the Hengchun Ridge. From the Middle Miocene the South China Sea began to subduct beneath the Philippine Sea plate along the Manila Trench, and the Hengchun Ridge came into being. The Philippine Sea plate also moved northwestwards and collided obliquely with the Eurasian continent since 6.5 Ma, the arc-continent collision resulted in the Gaoping Slop west of the Hengchun Ridge, and the both made up the offshore Taiwan accretionary prism. Compared with the onland geology, the offshore Taiwan accectionary prism had a similar and continuous structural characteristics. They had the same tectonic mechanism but varied deformation history, i.e. the collision firstly began in the north part of Taiwan, then propagated southwards, so the north Taiwan Island experienced much longer deformational history.