Earth Planets Space, Vol. 59 (No. 7), pp. 879-885, 2007
K. Uto1, Y. Yamamoto2, M. Sudo3, S. Uchiumi1, O. Ishizuka1, T. Kogiso4, and H. Tsunakawa5
1Geological Survey of Japan, AIST, Tsukuba, Ibaraki 305-8567, Japan
2Geomagnetism Laboratory, University of Liverpool, Oliver Lodge Laboratories, Oxford Street, Liverpool, L69 7ZE, United Kingdom
3Institute of Earth Sciences, University of Potsdam, Karl-Liebknechtstrasse 24, Haus 25, 14476 Golm, Germany
4Institute for Research on Earth Evolution (IFREE), JAMSTEC, Kanagawa 237-0061, Japan
5Department of Earth and Planetary Sciences, Tokyo Institute of Technology, Tokyo 152-8551, Japan
(Received October 2, 2006; Revised January 29, 2007; Accepted January 29, 2007; Online published July 20, 2007)
We report 52 new K-Ar age determinations of volcanic rocks from the Society Islands in French Polynesia. The newly obtained ages range from 0.51 to 4.61 Ma, which are consistent with previously reported ones. The magnetostratigraphy based on 45 data sets combining K-Ar ages and paleomagnetic polarity agrees with the geomagnetic polarity time scale at the 2σ level, except for a few age data. Assuming the absolute motion of the Pacific plate, paleopositions of the dated rocks are estimated from the K-Ar ages, showing a narrow distribution in the western part of the easternmost volcano of the active hotspot region. This suggests that a hotspot of a few tens of kilometers in diameter might have been fixed nearly at the eastern margin of the presently active region in the Society archipelago and that the volcanism of each island might have persisted for about 1 myr.
Key words: K-Ar ages, Society Islands, magnetostratigraphy, hotspot, paleoposition.