SIMULTANEOUS MOUNTAIN BUILDING IN TAIWAN OROGENIC BELT

Most researches consider the Taiwan Orogeny to be the result of an oblique arc-continental collision between the Philippine Sea Plate and Eurasia Plate. According to kinematic modeling, the mountains started to build from the north and progressively propagated southward at a rate of 60-90 km/my. Because of the oblique nature of the collision, the influence of the collision on mountain building resulted in the southern Central Range experiencing orogenic processes more recently than in the north. We use zircon fission track to identify the initial stage of the exhumation which show the oldest total reset ages are similar ca. 4-5 Ma from north to south of the highest mountain in Hsuehshan Rang that indicates the mountain building is Simultaneous. The oldest reset ages of the apatite fission track ages show ca. 3 Ma in southernmost and northernmost of the fold and thrust belt that also indicates the mountain building is simultaneous.

We considered the mountain building mechanism of Taiwan orogeny result from collision between crust of Philippine Sea plate and continental margin of the Eurasia plate rather than arc-continental collision. The N-S extension of the South China Sea associated with N-S trending transform fault that results in that the Eurasia continental margin is near N-S trending. The boundary of the Philippine Sea plate is near the N-S trending. The ca. N-S trending Philippine Sea plate collided with ca. N-S trending continental margin that result in the timing of the mountain building is near the same 5 Ma rather than southward propagation. The southern central range progressively decreases the elevation to the southward that result from the decreasing the thickness of the continental crust.