琉球嶼的海階及珊瑚定年研究

Abstract

The Liu-chiu Y? is a raised coral reef island, located southwest offshore 14 km from Tung-kang, Pintung Hsien. Two structural depression lines striking NE-SW and E-W separate the island into four blocks. The Liu-Chiu Y? Limestone overlays the Liu-Chiu Y? Mudstone with a uncon-formity relationship. Three steps of marine terraces can be recognized: Pleistonce I, Pleistonce II and Holocene terrace. Based on coral reef dating, elevation of samples and sea level curve, the average uplift rate of west coast is estimated about 2 mm/yr during the period from 34 ka to 10 ka YBP whereas 0.4 mm/yr in east coast since Holocene. The uplift and deformation of marine terraces are influenced both by the tectonic stress coming southweast and downwarping near Kao-Ping Drowned Valley.