HR: 09:30h
AN: T41D-07    [Abstracts]
TI: Structural Variations of an Accretionary Wedge in the Transition Zone from Subduction to Collision Offshore Southern Taiwan
AU: * Liu, C
EM: csliu@ntu.edu.tw
AF: National Taiwan University, P. O. Box 23-13, Taipei, 106, Taiwan
AU: Feng, L
EM: murmurloveyou@yahoo.com.tw
AF: National Taiwan University, P. O. Box 23-13, Taipei, 106, Taiwan
AU: Chuang, H
EM: R92241317@ntu.edu.tw
AF: National Taiwan University, P. O. Box 23-13, Taipei, 106, Taiwan
AU: Chen, L
EM: R92241305@ntu.edu.tw
AF: National Taiwan University, P. O. Box 23-13, Taipei, 106, Taiwan
AB: The area offshore southern Taiwan is the place where the Luzon subduction complex transforms into an incipient arc-continent collision complex near Taiwan. Morphologically, the subduction complex shows a classic trench (Manila Trench) - accretionary wedge (Hengchun Ridge) - forearc basin (North Luzon Trough) - volcanic arc (Luzon Arc) system north of the Luzon Island. The accretionary wedge expanded toward north, the forearc basin was closed north of 21.5N offshore SE Taiwan while the frontal portion of the accretionary wedge encroached on the passive China continental margin off SW Taiwan. A prominent out-of-sequence thrust was developed that divides the accretionary wedge into an upper slope domain and a lower slope domain. Seismic reflection profile data collected in the region provide insights on differentiating morphological and structural characters of the accretionary wedge in this transition zone. The closure of the forearc basin near Taiwan has been attributed to the development of a back thrust system along the rare side of the accretionary wedge. However, strike-slip faulting and block rotation due to oblique arc-continent collision also played significant roles in creating the present morphology off SE Taiwan. At the frontal portion of the accretionary wedge, folds and thrusts are the prominent structural features in the lower slope domain. The distances between the fault-bend-folds increase north of 21.5N, the sediment thickness also increases northward, from about 1000 m thick at 20.5N to about 4000 m thick at 21.5N. The upper slope domain consists of highly deformed accretionary wedge material that was uplifted probably due to under-plating processes. Seismic data also suggest that the activation of the out-of-sequence thrusts migrates westward near SW Taiwan. In the near shore area off SW Taiwan, due to the rapid deposition on top of a thick mud layer, mud diapirs developed. Many of the mud diapirs could be connected to the similar features on land SW Taiwan. The present seismic profiles reveal mostly the upper crustal structures. It is hoped that the deep seismic profiling survey to be conducted in 2008 during the TAIGER active source experiment could provide critical information in constraining the structural evolution from subduction to collision off southern Taiwan.
DE: 3000 MARINE GEOLOGY AND GEOPHYSICS
DE: 3025 Marine seismics (0935, 7294)
DE: 3045 Seafloor morphology, geology, and geophysics
DE: 8038 Regional crustal structure
DE: 8175 Tectonics and landscape evolution
SC: Tectonophysics [T]
MN: 2007 Fall Meeting