| dc.description.abstract | Taiwan, locted at the boundary between the Philippine Sea plate and Eurasian plate, is a product of arc-continental collision. Because this collision takes place in an oblique direction to the convergent boundery, the orogenic belt of Taiwan has been propagating southward. As a newly emerged accretionary prism at the southern tip of Taiwan orogen, the Hengchun peninsula exhibits the youngest, least deformed and most complete accretionary prism in Taiwan.
The main body of the Hengchun peninsula is composed of the Middle-Late Miocene turbidite sequences. Few backthrusts being left apart, most faults and folds of the Hengchun peninsula are western-verging. The N-S trending structural pattern of the peninsula suggests that most of the deformation resulted from an E-W directed compressional tectonic regime during the period of tectonic uplift. However, in the western part of the peninsula, the West Hengchun Hill, mainly composed of the Quaternary coral reef, is gentlely tilted to the east but without any compressional structures. The origin and the uplift mechanism of the West Hengchun Hill is thus still a debate.
From previous study, they think that the West Hengchun Hill is the eastern limb of an uplifted anticline. From our geomorphologic analysis, the topography in northern West Hengchun Hill shows a linear scarp feature but half-dome topography in southern part. The topographic difference in these northern and southern West Hengchun Hill might indicate the different uplift mechanism. Also from our field investigation, Maanshan Formation usually crops out with cold seep carbonates in southern West Hengchun Hill. The presence of cold-seep carbonates and the dorm-shaped topography reveal mud diapiric features in Maanshan. According to the the evidences mentioned before, we believe the uplifted mechanisms are different in the northern and southern West Hengchun Hill, the anticline uplifted the northern West Hengchun Hill and a series of mud diapiric structure triggerd the uplift of southern offshore part. Some previous seismic profiles show reflectional signals of coral reef can be found in the western offshore of the West Hengchun Hill. We also interpret these as the western limb of the the West Hengchun Hill anticline, that slide down to the west along a NW trending normal fault during the uplifting period.
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