HR: 11:10h
AN: T11F-04    [PDF]
TI: A Multi-Source Assessment of Motion Along the Chaochou Fault, Southern Taiwan
AU: * Hassler, L E
EM: lhassler@geo.tamu.edu
AF: Texas A&M University, Department of Geology and Geophysics, College Station, TX 77843-3115 United States
AU: Wiltschko, D V
EM: wiltschko@geo.tamu.edu
AF: Texas A&M University, Department of Geology and Geophysics, College Station, TX 77843-3115 United States
AB: The Chaochou Fault (CCF) is both an important lithologic boundary and a significant surface feature in the Taiwan orogenic belt. It is the geologic boundary between the Slate Belt Range to the east, and the Western Foothills Range 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. We have divided the CCF and study area into three segments: the Southern area extends from the southern coast up to Tachin, the Middle area from Tachin to Laonung, and the northern section from Laonung to just north of Meishan, into the Yushan National Forrest along the Southern Cross Island highway. Field fabric data suggest that structural orientations vary along strike, particularly in the middle segment, the suspected location of the on-land Eurasian continent-ocean boundary (COB). Foliation/solution cleavage is oriented NE-SW and in the northern and southern segments, but ESE-WNW in the middle segment. Slip lineations also reveal a change in fault motion from dip-parallel in the north to a more scattered pattern in the south. This correlates somewhat with recent GPS results, which indicate that the obliquity of current motion changes along strike. The magnitude of horizontal surface motion vectors, relative to Liudau Island, decreases to the south. Horizontal vectors are directed from relatively NW-SE in the north, to nearly N-S in the southern field area. The magnitude of vertical motion is highest in the northern area and decreases dramatically to the south. Geomorphic data also suggest that fault activity decreases from north to south. Both mountain front sinuosity and basin area increase toward the south. These observations correlate well with published apatite/zircon fission track data that indicate un-reset ages in the south, and reset ages in the northern segment. We suggest that in the northern segment, the Slate Belt is currently undergoing rapid uplift related to oblique arc-continent collision between the Eurasian continent and the Luzon arc. We also suggest that in the southern segment, the CCF is significantly less active because the orogen is not yet involved in direct arc-continent collision.
DE: 8010 Fractures and faults
DE: 8025 Mesoscopic fabrics
DE: 8102 Continental contractional orogenic belts
DE: 8158 Plate motions--present and recent (3040)
DE: 9320 Asia
SC: Tectonophysics [T]
MN: 2003 Fall Meeting