HR: 1340h
AN: GP23A-0033    [Abstracts]
TI: Paleomagnetism of the Marble Bar Chert Member, Western Australia: implications for an Apparent Polar Wander Path for Pilbara craton during Archean
AU: * Suganuma, Y
EM: y.suganuma@aist.go.jp
AF: Geological Survey of Japan, AIST, 1-1-1 Central 7, Higashi, Tsukuba, 305-8567 Japan
AU: Hamano, Y
EM: hamano@eps.s.u-tokyo.ac.jp
AF: 2Department of Earth and Planetary Science, University of Tokyo, 7-3-1, Hongo, Bunkyo-ku, Tokyo, 113-0033 Japan
AU: Niitsuma, S
EM: greigite@mail.tains.tohoku.ac.jp
AF: Graduate School of Science, Tohoku University, 6-3, Aoba, Aza, Aramaki, Aoba-ku, Sendai, 980-8578 Japan
AU: Hoashi, M
EM: hoashi@chan.co.jp
AF: Department of Physics, Kagoshima University, 1-21-35, Nunemoto, Kagoshima, 890-0065 Japan
AU: Hisamitsu, T
EM: hisa@jamstec.go.jp
AF: Institute for Frontier Research on Earth Evolution, Japan, 2-15, Natsushima, Yokosuka, 237-0061 Japan
AU: Niitsuma, N
EM: sennit@ipc.shizuoka.ac.jp
AF: Department of Geological Sciences, Shizuoka University, 836, Ohya, Suruga-ku, Shizuoka, 422-8059 Japan
AU: Kodama, K
EM: kdma@ @jimu.kochi-u.ac.jp
AF: Center for Advanced Marine Core Research, Kouchi University, B200, Monobe, Nankoku, 783-8502 Japan
AU: Nedachi, M
EM: nedachi@sci.kagoshima-u.ac.jp
AF: Department of Physics, Kagoshima University, 1-21-35, Nunemoto, Kagoshima, 890-0065 Japan
AB: aleomagnetic study is conducted on the early Archean Marble Bar Chert Member (3454 - 3471 Ma) in Pilbara craton, northwestern Australia, to reconstruct an apparent polar wander path (APWP) for this craton and understand for geodynamic feature during early Archean time. The Archean Biosphere Drilling Project (ABDP) drilled a continuous 270 m long oriented core from the Towers Formation, includes the Marble Bar Chert Member. Stepwise thermal demagnetization (ThD) for 431 discrete specimens, extracted from 158.5 to 182.0 m in depth of the drilled core, revealed two distinct magnetic components (LT and MT). The MT component is divided into two depth groups, which provide the mean paleomagnetic directions of MB1 and MB2. The MB1, MB2, and published paleomagnetic poles of early Archean rocks from the Pilbara craton displays continuous shift of the paleomagnetic poles along the stratigraphic sequence of them. This indicates the MT component preserving the primary magnetization acquired during sedimentation. Based on the result of this study and the other published paleomagnetic poles, the simplest early to late Archean APWP for the Pilbara craton is reconstructed. The fast shift of the paleomagnetic poles was observed between MB1 and MB2, which corresponds to the 4.1° of paleolatitude change and approximately 460 km of latitudinal drift of the Pilbara craton. The estimated speed of the lateral drift is 13.6 -129 cm/y, which is significantly large compared with current plate motion velocities. Plate tectonic process, relating the anomalous active convection of the mantle during Archean time, likely explains the significant fast lateral drift of the Pilbara craton. On the other hand, true polar wander (TPW) also can explain the significant paleolatitude change. Although, an angular velocity of TPW estimated as 1.0° - 9.4°/Myr is extremely lager that reported velocity of the TPW (0.5°/Myr), inertial interchange TPW might explain the fast lateral drift of the Pilbara craton.
DE: 1525 Paleomagnetism applied to tectonics: regional, global
DE: 1527 Paleomagnetism applied to geologic processes
DE: 9623 Archean
SC: Geomagnetism and Paleomagnetism [GP]
MN: Fall Meeting 2005