| Summary: | 碩士 === 國立中正大學 === 地震研究所 === 102 === We employed a geodynamic program modified from Gerya to explore the tectonic evolution in Taiwan Hengchun Peninsula. According to the geological records, it is likely that an ancient South China Sea was closed during the formation of the Hengchun Peninsula and the Kenting mélange. Based on this hypothesis, we set up a numerical model to test how it may evolve. Our simulation results show that the Hengchun Peninsula may most likely result from eastward subduction of the Eurasian continental crust along the Longitudinal Valley rather than arc-continent collision. While the Eurasia continental crust was colliding with the Philippine Sea Plate, the compression force scraped off part of the continental crust and created a new mountain. Subsequently, the ocean basin also went below the Philippine Sea plate, and similar mechanism resulted in piling up the sediments in the oceanic basin and some debris form oceanic crust and mantle, which formed the Kenting Mélange. Our optimal model implies that the crustal strain softening is essential to reproduce the tectonic structures observed by seismic tomography. When strain softening was taking into account, a shear zone would gradually develop along the base of the upper continental crust, which allowed the plate boundary to transfer from the Longitudinal Valley to the Manila Trench. As a result, the orogeny in the Hengchun Peninsula has been slowing down ever since.
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