台湾位于欧亚大陆板块与菲律宾海洋板块的交会处，地体构造较为活跃．同时，受到古气候冰期与间冰期交互作用的影响，造成海平面上下变动，使得古环境产生变化．本研究利用钻孔岩心做地层分析、环境分析及岩心碳同位素定年等资料，了解台湾西南部地壳的活动性、环境演化与各时期海平面变动的历史．海岸线的变动，除了受到海平面变动的影响，亦受到构造沉降活动的控制．综合地壳升降以及海平面升降的数据，推估全新世6200 a BP、3100 a BP和l800 a BP3个海进时期当时的海岸线位置，分别为现今高程20m、10m及6m的位置，这些海平面的变化导致海岸线的迁移，同时影响着先民聚落遗址的变化．并且，利用前述数据推估得出嘉南平原与浊水溪冲积扇的沉积速率大约在3．9～4．5mm／a之间．%Located in the intersection of Euroasia plate and Philippine sea plate, the tectonic struc- ture of Taiwan is active. For the same time, sea level change around Taiwan has been influenced by paleo-ice age and inter-ice age, producing paleo-environment changes. Especially, sea level change may directly cause coastline migration. By the comparison of stratum analysis, environment analysis and core dating of drilling core samples, the history of sea level change during different periods, the activity of crust in southwestern Taiwan and its paleo-environment evolution can be determined. In ad- dition to impacts from sea level variations, coastline changes will also be affected by tectonic subsid- ence. Through the comprehensive data analysis of crust movement and eustatic movement, the posi- tions of coastline during the three marine ingression periods at the Holocene 6 200 a BP, 3 100 a BP, 1 800 a BP were estimated at the present elevations of 20 m, 10 m and 6 m , respectively. These sea level changes led to the migration of the coastline, affecting the change of ancestors settlement sites. According to study results, we give an estimation of the deposit rate, which is between 3.9 mm/a and 4. 5 mm/a, for Chia-nan Plain and Zhuoshuixi river alluvial fan in southwestern Taiwan.
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