STRUCTURAL GEOLOGY AND THRUST BELT ARCHITECTURE OF THE WESTERN FOOTHILLS OF TAIWAN

Fernando Rodriguez,

Texas A&M University, Geology and Geophysics Department

College Station, TX, 77840

[email protected]

A structural model of the central and southern Western Foothills Fold and Thrust Belt (WFFTB) was constructed from serial balanced cross sections. The WFFTB is composed of four main thrust sheets with minor splays. On the east, the Tulungwan fault carries a series of low-grade metamorphosed hinterland imbricates. It evolves from a basement-cored fold in the north (~ 24°10' N) where Slate Belt and Foothills rocks are conformable on its western flank. To the south this fault breaks the back limb of the fold and gains displacement. The next thrust to the west includes the Schuantung-Fenghuangchan fault system, interpreted as being underlain by a flat along a Miocene detachment. The next thrust to the west is the Chukou-Lunhou fault system which is characterized by the presence of a wide monocline in the central Foothills related to the Chulungpu fault and two wide synclines in the south, the Yuching and Tinpligling synclines. Modeling of these two structures shows that both have been uplifted with respect to the regional level on a wide and flat feature and that the footwall of the Lunhou fault is a monocline. A geometric solution to this is a low-ramp angle fault-bend-fold with a detachment at ~13 km. The last thrust system toward the west shows a series of structures which are closely associated with the Peikang high implying that the structures are either inversion structures or new thrust faults whose ramps are located in pre-existing normal faults.

AAPG Search and Discovery Article #90060©2006 AAPG Foundation Grants-in-Aid