碩士 / 國立成功大學 / 地球科學系碩博士班 / 101 / In the frontal part of a fold-and-thrust belt of in-sequence and ongoing development, all fault-related structures represent the initial features of the following structural evolution. Due to the Penglai orogeny from the Pliocene to Pleistocene, two sets of fault system developed separately as a series of NW-SE fold-thrust belts and E-W high-angle reversed faults, which were extensional normal faults in early stage and finally reactivated by late compression. In this study, we choose three areas including Tiehchanshan structure, Yunghoshan-Chinshui structure and Hukou fault structure in offshore Hsinchu ,and use the following concepts to investigate the evolution of fault structure: 1. In-sequence development of thrust-related folding; 2. The interaction between high-angle thrusts, which are reactivated by compression, and in-sequence development of thrusts during late period; 3. The reversion of normal fault during late orogeny results in the inversion structures. We use a grid of seismic profile and well bore data to interpret subsurface structural geometry, and integrate trishear modeling to analyze the structural evolution, and build a three-dimensional structural model.
The Tiehchanshan structure, located at the front part of outer foothills belt of Northwestern Taiwan, is comprised of two antithetic thrusts as fault-propagation folds. The two anticlines gradually become symmetric toward transfer structure zone, which has a gentle and broad anticline deformed by a westward slipping low-angle thrust and an eastward slipping thrust-wedge. Based on trishear modeling, the P/S ratio increases toward the transfer structure zone. The variations of P/S ratio are especially obvious during folding stage. As the dip of fault plane moderates, the influence of apical angle of trishear zone becomes weaker on fold geometry.
The Yunghoshan-Chinshui structure is located at the outer foothills belt. The Luchukeng fault is characterized by flat-ramp-flat structural geometry in the Yunghoshan structure, but transformed into a high-angle thrust in the Chinshui structure. The shallow and asymmetric Yunghoshan anticline resulted from Luchukeng thrusting in early period. In contrast, the deeper Yunghoshan anticline and Chinshui anticline, both featured by more symmetric and gentle limbs, were caused by basal-detachment fault in late stage. Being obstructed by Lungkang fault and high-angle Luchukeng faults, which might be the lateral ramp during the basal-detachment faulting, the deeper Yunghoshan anticline and Chinshui anticline formed the two isolated structural high areas. The trishear modeling shows that the P/S ratio of main folding stage is similar to the result of the Tiehchanshan structure.
In the offshore Hsinchu, the main structural forms caused by the orogeny during late Pliestocene are oblique-inversion structures and transcurrent fauts. The E-W striking transcurrent faults of Hukou fault system in the eastern part change to NE-SW striking westward. And these transcurrent faults accompanied with symmetric fold geometries are high-angle reverse faults which resulted from normal faults, whose arrangement is en echelon and reactivated by late compression. For the western part of Hukou fault system, the tight fold was formed by the structure inversion when the E-W striking normal fault and the NE-SW striking normal fault were connecting.
On the whole, three types of structural transfer zone can be identified as follows: 1. The structural features of transfer zone are controlled by the arrangements and connected relationship of early normal faults; 2. The continuity of fold geometry is influenced by dips of fault plane, in the meantime, when folds were cut by high-angle transcurrent fault, the fold structures would be formed isolatedly during late compression; 3. The lateral variation of fault plane formed by lately thrust represents the complex fault-related fold structure. Besides, the variation of P/S ratio along strike also reflects the complex fault-related fold structure.
| Identifer | oai:union.ndltd.org:TW/101NCKU5135136 |
| Date | January 2013 |
| Creators | Ching-YunHsieh, 謝青雲 |
| Contributors | Kenn-Ming Yang, 楊耿明 |
| Source Sets | National Digital Library of Theses and Dissertations in Taiwan |
| Language | zh-TW |
| Detected Language | English |
| Type | 學位論文 ; thesis |
| Format | 97 |
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