Detrital Zircon Fission-Track and U-Pb Dating of the Toukoshan and Cholan Formations in Central Taiwan and its Tectonic Implications

• Main Authors: WU, YI-JU, 吳宜儒
• Other Authors: LEE, YUAN-HSI
• Format: Others
• Language: zh-TW
• Published: 2018
• Online Access: http://ndltd.ncl.edu.tw/handle/4e8m67

碩士 === 國立中正大學 === 地球與環境科學研究所 === 106 === In order to understand the temporal variations of exhumation in Taiwan orogenic belt, we apply detrital low-temperature thermochronology and U-Pb dating to analyze the deposits of the foreland basin in central Taiwan. A total of 9 rock samples were collected in the Toukoshan Formation and the Cholan Formation along the Tsaohu River, the Choushui River and the Bagua Terrace. By combining fission-track technique and U-Pb dating, we are able to investigate the exhumation rate of the Taiwan orogenic belt as well as sedimentary source rocks of the deposits more precisely. Previous study indicate that the depositional age along the Tsaohu River is from 2.6 Ma to 1 Ma. Our result shows that the percentage of annealed zircon is very low prior to 1 Ma in the Tsaohu River, which indicates low exhumation rate. However, between 1 Ma and 0.5 Ma, exhumation rate increases based on the observation of annealed zircon rises to 60%. Furthermore, we also discover that the reset zone in the Hsuehshan Range is ranging from 600-3300 m in altitude resulting in an exhumation rate estimation of at least 2.7-5.4 mm/yr between 1 Ma to 0.5 Ma. In this study, our findings are similar to those studies in the Linkou Terrace (0.78-0.98 Ma). Both areas are dominated by very few annealed zircons at ~1 Ma, which may imply that the northern and the central Hsuehshan Range have comparable exhumation rate. Based on the U-Pb zircon dating we also conclude that the sedimentary source has changed between bottom and top of Cholan Formation.