Open Access

Paleomagnetism and fission-track ages of Oki-Dogo Island in Southwest Japan

  • Takeshi Kojima1Email author,
  • Makoto Okada1,
  • Hiroto Ohira2,
  • Katsuyasu Tokieda2,
  • Hiroaki Komuro2 and
  • Kazuo Amano1
Earth, Planets and Space201453:BF03352361

DOI: 10.1186/BF03352361

Received: 21 March 2000

Accepted: 30 September 2000

Published: 6 June 2014

Abstract

Zircon fission-track (F.T.) ages and paleomagnetic directions were measured on the Neogene series of the Oki-Dogo Island. The results of F.T. dating on the the Tokibariyama Formation show ages of 23.7 ± 1.3 and 20.0 ± 2.3 Ma, indicating the early Early Miocene. Paleomagnetic measurements of the Tokibariyama, Kori Formations (24–17 Ma) and the Oki Trachyte-Rhyolite (6.8 Ma) were done to reveal the movement of Oki-Dogo Island during the Japan Sea opening. The Tokibariyama and Kori Formations show an average declination of 39.9°. The Oki Trachyte-Rhyolite has the same average geomagnetic direction as the present day value. These results show that a clockwise rotation of 40° ± 15° of the Oki-Dogo Island occurred between 17 and 6.8 Ma which is similar to the main land of southwest Japan.