Analysis of Geological Structure for Fold-and-Thrust Belt, Centraland Southern Taiwanthe Chelungpu Fault.

• Main Authors: Shiuh-Tsann Huang, 黃旭燦
• Other Authors: Hung, J. H.
• Format: Others
• Language: zh-TW
• Published: 2003
• Online Access: http://ndltd.ncl.edu.tw/handle/05334447219243696059

博士 === 國立中央大學 === 地球物理研究所 === 92 === This study will be focused on the analysis of regional mesoscopic structural framework as well as the analysis of active faults in central and southern Taiwan. Three areas were chosen for structure analysis in order to decipher their geometrical characteristics and sequential developments by an integrated interpretation using seismic , well log, and field-geology data. Three areas include (1) in the vicinity of the Chelungpu Fault in the Taichung area, (2) east margins of the Peikang High, and (3) south of the Peikang High in Tainan and Kaohsiung areas. Several balanced and palinspatic-restored sections are constrained by seismic data. Analysis on drill cores recovered from the 1999 Chi-Chi earthquake rupture (i.e, the Chelungpu Fault) in central Taiwan, shows that the Chelungpu Fault consists of several major shear zones and their mechanical boundaries coincide with the lithological boundaries of stratigraphic sequence. According to the analysis on palinspatic sections using top of Cholan Formation as a datum plane, it shows that there is a displacement along the fault plane of about 13.7 kilometers, at least, for the Chelungpu Fault. At the eastern edge of the Peikang High, geometrical irregularity of the basement high and the discontinuity of the tectonic trend in the north-south direction are the most important factors that control the geological development for each compartment. The Peikang High is plunged both southward and northward to form the Meishan Ridge. The east-west striking Meishan Ridge is bounded by the Tsaoling Fault system to the north and Meishan Fault to the south. The thin skin thrusting was retarded by the ridge 129 and resulted in the emergence of Chiuchungkeng Fault to form a low angle thrust. The Tsoling Fault system is an important inverted fault. This inverted fault shows reverse features in shallow part while in deeper part it remains normal fault features. Data revealed that the southern part of Chelungpu Fault nappe disappears near the Tsoling Fault. The Meishan Fault is also an important inverted fault. The B Fault and the Meishan Fault are composed of one boundary fault in the southern side of Peikang High. The Meishan fault is not directly connected to the B Fault while a relay ramp is verified as a transitional accommodation zone. The Meishan Fault is interpreted to have extended to the Minshung tonship. The Chaiyi graben is determined as a thoroughly inverted graben by the restoration method. The Chaiyi graben is judged to have occurred prior to the deposition of the Nanchuang Formation. On the coastal plain and transitional zone between offshore and land in Kaohsiung and Tainan, the Tsochen Fault is an important NW-SE trending tear fault in southwestern Taiwan. Napalin Anticline and Hsinhua Fault located at the southern side of Tsochen Fault appear as backthrusts and composed as the triangle zone near the Longchuan structure. Nearshore area near Erzenchi is characterized by fault-bend fold in a reverse direction. The foreland deposits of the Gutinkeng Formation is dominated by thick, low density mudstone which is very suitable for the development of triangle zone in the middle and deep part of subsurface. If the deformation front is defined as the appearance of buried frontal low angle thrust or the inverted faults, this study has proved that the position of deformation front has been extended westward some 10-15 kilometers from the junction between foothill and coastal plain, and the zone of front also extended to the offshore of Kaoshung and Tainan areas.