HR: 1340h
AN: T13A-1354    [Abstracts]
TI: Preliminary Summary Of Current Fault Zones In The Hole-A Of TCDP
AU: * Yeh, E
EM: yeh@jamstec.go.jp
AF: Program for deep sea research, Institute for research on earth evolution (IFREE), Japan Agency for Marine-Earth Science and Technology (JAMSTEC), 2-15 Natsushima-cho, Yokosuka, 237-0061 Japan
AU: Sone, H
EM: hirokisone@kueps.kyoto-u.ac.jp
AF: Dept. of Geology and Mineralogy, Kyoto University, Kitashirakawa Oiwakecho, Sakyo-ku, Kyoto, 606-8502 Japan
AU: Nakaya, T
EM: taichin@cc.kochi-u.ac.jp
AF: Dept. of Natural Environmental Science, Kochi University, 2-5-1 Akebono-cho, Kochi, 780-8520 Japan
AU: Ian, K
EM: nanigaaida@hotmail.com
AF: Dept. of Earth Sciences, National Central University, No.300, Jhongda Rd, Jhongli, 320 Taiwan
AU: Song, S
EM: srsong@ntu.edu.tw
AF: Dept. Geosciences, National Taiwan University, No. 245 Choushan Rd., Taipei, 106 Taiwan
AU: Hung, J
EM: jhung@earth.ncu.edu.tw
AF: Dept. of Earth Sciences, National Central University, No.300, Jhongda Rd, Jhongli, 320 Taiwan
AB: Hole-A of Taiwan Chelungpu Drilling Project (TCDP) has drilled through four thick fault zones at the depth of 1111m, 1153m, 1222m and 1241m, respectively. Here we will note preliminary observations of the structures, lithology, bedding dip, and fault architecture for these fault zones. Four structure groups with different senses of shear are identified from the Hole-A of TCDP. The dip direction and dip of bedding between 500-1300m is 105/20-40. For the structures, thrust fault of 355-035/20-60 is very commonly observed. The FZA1111 and FZA1153 are belonged to the thrust-fault group. Strike-slip faults with normal shear are also frequently observed. Sinistral fault is orientated as 075-105/30-80, and calcite-filling is common as calcite-steps on these fault planes. The FZA1222 is belonged to the sinistral fault with normal shear. The attitude of dextral fault is 275-305/30-80. Backthrust of 215-155/30-70 is limited to FZA1241 and few locations of hanging walls of FZA1111 and FZA1153. Normal faults of 355-035/5-10 with distinct slickenside are observed below FZA1222. Lithology between 500-1300m is mainly sandstone, siltstone or their combinations of alternation or interbeds and different degrees of bioturbation. However, the four fault zones are within the siltstone-dominant region. For FZA1111 and FZA1153, the grain size of hanging wall is finer than that of foot wall. The feature of lithology is opposite in the FZA1222, i.e. the grain size of hanging wall is coarser. For FZA1241, the lithology of hanging wall and foot wall are the same. The distribution of bedding dip is influenced by the fault zones. This variation of bedding dip with depth is related with the distribution of the FAZ1111, FZA1153 and FZA1241. Bedding dip gradually changes from 30 to 20 when approaching the FZA1111. Then it quickly became steeper around 35 again after we pass through the fault zone. The same kind of variation of bedding dip was observed in the FZA1152 as well. This variation of the bedding dip could be explained by the drag effect of thrusting. However, the disturbance of bedding dip around FZA1241 is different. There is no distinct change of bedding dip when approaching the fault zone but the dip becomes sub-vertical within the fault zone. The architectures of the FZA1111 and FZA1153 show some characteristic patterns. From top to bottom, the architectural patterns change from fractured zone to intensely fractured zone, breccia zone, gouge zone, black material (carboneous?), and at last, thin layer of breccia zone or fractured zone. Therefore, the damaged zone is thicker above the fault core than below, and thus, the lower boundary is appears sharper compared to the broad upper boundary. Another notable feature of the fault zones is that there usually is a thin layer of coal-like black material at the bottom part of the fault core. The architecture of the FZA1222 is opposite to the shallower fault zones. That is, the gouge and coal-like material is at the top and breccia zone and fractured zone are at the bottom of the fault zone.
DE: 8010 Fractures and faults
DE: 8025 Mesoscopic fabrics
DE: 8107 Continental neotectonics
DE: 8123 Dynamics, seismotectonics
SC: Tectonophysics [T]
MN: 2004 AGU Fall Meeting