HR: 1340h
AN: T53A-1416    [Abstracts]
TI: Tectonic Evolution of the Southern tip of the Parece Vela Basin
AU: * Okino, K
EM: okino@ori.u-tokyo.ac.jp
AF: Ocean Research Institute, University of Tokyo, 1-15-1 Minamidai, Nakano-ku, Tokyo, 164-8639 Japan
AU: Ohara, Y
EM: ohara@jodc.go.jp
AF: Hydrographic and Oceanographic Department of Japan, 5-3-1 Tsukiji, Chuo-ku, Tokyo, 104-0045 Japan
AU: Fujiwara, T
EM: toshi@jamstec.go.jp
AF: Japan Agency for Marine-Earth Science and Technology, 2-15 Natsushima, Yokosuka, 237-0061 Japan
AU: Lee, S
EM: smlee@snu.ac.kr
AF: Seoul National University, Sillim-dong, Gwanak-gu, Seoul, 151-747 Korea, Republic of
AU: Nakamura, Y
EM: saru@ori.u-tokyo.ac.jp
AF: Ocean Research Institute, University of Tokyo, 1-15-1 Minamidai, Nakano-ku, Tokyo, 164-8639 Japan
AU: Wu, S
EM: swu@ms.qdio.ac.cn
AF: Institute of Oceanology, China Academy of Science, 7 Nanhai Road, Qindao, 266071 China
AB: The southern tip of the Parece Vela Basin was mapped using state-of-the-art instruments for the first time. The basin is known as an extinct backarc basin behind the Mariana arc-trench system and has developed from ~26 to 12 Ma. The backarc spreading consists of two stages: early east-west spreading and later NE-SW spreading accompanied by several oceanic core complexes. The remnant spreading center, the Parece Vela Rift, seems to connect the Yap Trench at its southern end (~12°N) and is not traceable in the southern tip of the basin (9~11°N) west of the Yap Trench. The evolution of the area seems to be linked to the collision of the Caroline Ridge to the Yap Trench, however no systematic mapping had been done before and the tectonics of the area remained enigmatic. New mapping/seismic reflection/dredging results reveal the complex structure of the area, which cannot be seen in northern part of the basin. Relatively continuous N-S fabrics are found in the northern part of the studied area and these fabrics develops within a V-shaped triangle zone. The short NW-SE abyssal hills offset by the NE-SW fracture zones are recognized in the very narrow area just east of the V-shaped area of N-S fabrics. These fabrics indicate the southward propagation of the N-S trending ridge and following NE-SW opening as same as seen in the northern part of the basin, although the eastern wing of the basin was lost. The western part of the area is completely different from the other part of the basin. The most prominent morphology is en echelon, curved deeps near the Kyushu-Palau Ridge. Two deeps are crescent-shaped and curve towards northward. The northern deep is ~6100 m and the abyssal hills seem approximately perpendicular to the deep. The southwestern extension of the northern deep is a narrow curved rift trending 030° and the rift develops within a topographic high. The southern deep is characterized with voluminous dome, which consists of branched topographic highs. The morphological pattern with curved deeps is very much like those of the Pito Deep in the Easter Microplate and of the Endeavor Deep in the Juan Fernandez Microplate. It is likely that the rotational deformation associated with continuous rift propagation and with some finite broad transform zone is related to the origin of the deeps. The area may be the remnant old lithosphere created before the Parece Vela Basin formation and indicate the robust magmatism in the past.
DE: 3001 Back-arc basin processes
DE: 3025 Marine seismics (0935, 7294)
DE: 3045 Seafloor morphology, geology, and geophysics
SC: Tectonophysics [T]
MN: Fall Meeting 2005