臺灣花東海岸海階的地形學研究

Abstract

This paper is the first year report of the research project “A Geomorphological Study of Marine Terrace in Taiwan”. The Huatung coast is along the Pacific coast of Eastern Taiwan, adjacent to the convergent boundary of Eurasia Plate and Philippine Sea Plate, marine terrace is typically developed in this region. Based on air photo interpretation, geomorphometry, field excursion and accurate survey of altitude, the results are summarized as follows: 1. Classified and correlated by the continuity of altitude and extend of the marine terrace surfaces, there are three dominate marine terraces in study area. The flights of marine terraces in the southern part are comparatively more widely distributed than in the north, the lowest one and the newly raised wave-cut platform are well developed throughout the study area. 2. Altitude of terraces in the southern part is obviously more higher, expecially in the upper two steps, showing that there are wave-like uplifted and tilted slightly to the north. Yet the lowest steps together its newly raised wave-cut platform have almost the same height throughout the study area, this implies that recent uplift rates are progressing with equal amount, and in the upper steps, the tectonic movement has the property of accumulation. 3. The displacement of terrace surfaces is observed as a short-wave length warping, upwarping has been taken place with the axes in the vicinity of Chanping, Chengkung and Tulan, the distance between the axes is about 25 to 30 km. 4. The third steps are furnished with multi-levelled terraces, at intervals of 2-5 m in elevation, deduces from the mode of seismic uplifts in the neighborhood, those multi-levelled terraces may originated by the co-seismic uplift. 5. The features of marine terraces are also influenced by geological setting, in the area of more?resistant rocks, marine terraces are very narrow and covered with thin marine boulders, coastal landforms such as wave-cut ben