From accretion to collision: Motion and evolution of the Chaochou Fault, southern Taiwan

摘要

The Chaochou Fault (CCF) is an important tectonic boundary of the Taiwan orogenic belt between the metamorphosed Slate Belt to the east and the Western Foothills foreland fold-and-thrust belt to the west. Although the fault is known to be a high-angle oblique sinistral thrust fault in places, both its kinematic history and its current role in the development of the orogen are poorly understood. Field fabric data suggest that hanging wall structural orientations vary along strike, particularly in the on-land extension of the intersection of the Eurasian continent-ocean boundary and the Luzon Arc. Slip lineations also reveal a change in fault motion from dip parallel in the north to a more variable pattern in the south. This correlates somewhat with recent GPS results that indicate that the direction of current horizontal surface motion changes along strike from nearly perpendicular to the fault in the northern to oblique and nearly parallel to the fault in the south. Mountain front sinuosity and the valley floor width/ valley height ratio indicate higher activity and uplift in the north. Geodetic and geomorphic data together indicate that along the northern segment of the CCF the Slate Belt (hanging wall) is currently undergoing rapid uplift related to oblique arc-continent collision between the Eurasian continent and the Luzon Arc. The southern segment of the fault is significantly less active perhaps because (1) the fault is blind or (2) this portion of the fault is south of the point where the Eurasian continental platform intersects the orogenic front.