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TECTONICS, VOL. 22, NO. 3, 1025, doi:10.1029/2002TC001436, 2003

Frontal belt curvature and oblique ramp development at an obliquely collided irregular margin: Geometry and kinematics of the NW Taiwan fold-thrust belt

Olivier Lacombe

Laboratoire de Tectonique, UMR 7072, Université P. et M. Curie, Paris, France


Frédéric Mouthereau

Laboratoire de Tectonique, UMR 7072, Université P. et M. Curie, Paris, France


Jacques Angelier

Laboratoire de Tectonique, UMR 7072, Université P. et M. Curie, Paris, France


Hao-Tsu Chu

Central Geological Survey, Taipei, Taiwan


Jian-Cheng Lee

Institute of Earth Sciences, Academia Sinica, Taipei, Taiwan


Abstract

Combined structural and tectonic analyses demonstrate that the NW Foothills of the Taiwan collision belt constitute mainly an asymmetric “primary arc” type fold-thrust belt. The arcuate belt developed as a basin-controlled salient in the portion of the foreland basin that was initially thicker, due to the presence of a precollisional depocenter (the Taihsi basin). Additional but limited buttress effects at end points related to interaction with foreland basement highs (Kuanyin and Peikang highs) may have also slightly enhanced curvature. The complex structural pattern results from the interaction between low-angle thrusting related to shallow decollement tectonics and oblique inversion of extensional structures of the margin on the southern edge of the Kuanyin basement high. The tectonic regimes and mechanisms revealed by the pattern of paleostress indicators such as striated outcrop-scale faults are combined with the orientation and geometry of offshore and onshore regional faults in order to accurately define the Quaternary kinematics of the propagating units. The kinematics of this curved range is mainly controlled by distributed transpressional wrenching along the southern edge of the Kuanyin high, leading to the development of a regional-scale oblique ramp, the Kuanyin transfer fault zone, which is conjugate of the NW trending Pakua transfer fault zone north of the Peikang basement high. The divergence between the N120° regional transport direction and the maximum compressive trend that evolved from N120° to N150° (and even to N–S) in the northern part of the arc effectively supports distributed wrench deformation along its northern limb during the Pleistocene. The geometry and kinematics of the western Taiwan Foothills therefore appear to be highly influenced by both the preorogenic structural pattern of the irregularly shaped Chinese passive margin and the obliquity of its Plio-Quaternary collision with the Philippine Sea plate.

Received 8 July 2002; accepted 26 February 2003; published 24 June 2003.

Index Terms: 8102 Tectonophysics: Continental contractional orogenic belts; 8010 Structural Geology: Fractures and faults; 8005 Structural Geology: Folds and folding; 8164 Tectonophysics: Stresses—crust and lithosphere; 9320 Information Related to Geographic Region: Asia.

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Citation: Lacombe, O., F. Mouthereau, J. Angelier, H. Chu, and J. Lee (2003), Frontal belt curvature and oblique ramp development at an obliquely collided irregular margin: Geometry and kinematics of the NW Taiwan fold-thrust belt, Tectonics, 22(3), 1025, doi:10.1029/2002TC001436.