Open Access

Geomagnetic paleosecular variation for the past 5 Ma in the Society Islands, French Polynesia

  • Y. Yamamoto1, 3,
  • K. Shimura1,
  • H. Tsunakawa1,
  • T. Kogiso2,
  • K. Uto3,
  • H. G. Barsczus4,
  • H. Oda3,
  • T. Yamazaki3 and
  • E. Kikawa2
Earth, Planets and Space201454:BF03351733

https://doi.org/10.1186/BF03351733

Received: 28 December 2001

Accepted: 21 June 2002

Published: 20 June 2014

Abstract

We report a paleomagnetic secular variation in the Society Islands, French Polynesia for the past 5 Ma. Paleomagnetic measurements were performed on volcanic rocks applying thermal and alternating field demagnetizations and principal-component analysis. As a result, 82 normal, 48 reversed, and 10 intermediate directions were observed after the correction of the site localities for the absolute motion of the Pacific plate. A mean VGP of the combined data set of normal and reversed polarities is located at 87.5°N and 4.0°W (A95 = 2.3°), which is close to the geographic pole. The angular standard deviation (ASD) around the mean VGP resulted in 14.6° (+1.3°, −1.2°). There is no significant inclination anomaly for the time-averaged field. However, if the plate motion is not taken into account, a significant anomaly of −3.4° would be observed at a 95% confidence level. This suggests that correction for the absolute plate motion is needed for the precise paleodirectional analysis of the Pacific region. These features are also supported by an analysis combining the previous data set with our data.

Keywords

Plate MotionNatural Remanent MagnetizationAbsolute MotionSociety IslandLava Sequence