Japan Geoscience Union Meeting 2016

Presentation information

International Session (Oral)

Symbol S (Solid Earth Sciences) » S-EM Earth's Electromagnetism

[S-EM05] Full vector geomagnetic and paleomagnetic secular variation: direction, intensity and dynamo simulations

Sun. May 22, 2016 10:45 AM - 12:15 PM 105 (1F)

Convener:*Hidetoshi Shibuya(Department of Earth and Environmental Sciences, Graduate School of Science and Technology, Kumamoto University), Yuhji Yamamoto(Center for Advanced Marine Core Research, Kochi University), Greig Paterson(Institute of Geology and Geophysics Chinese Academy of Sciences), Maxwell Brown(GFZ German Research Centre for Geosciences), Chair:Hidetoshi Shibuya(Department of Earth and Environmental Sciences, Graduate School of Science and Technology, Kumamoto University), Toshiya Kanamatsu(Japan Agency for Marine-Earth Science and Technology)

11:55 AM - 12:10 PM

[SEM05-10] Paleointensity study on lava flows of Fuji Volcano and implications for the atmospheric 14C variation for the last 30 kyr

*Nobutatsu Mochizuki1, Masahiko Sato2 (1.Priority Organization for Innovation and Excellence, Kumamoto University, 2.Geological Survey of Japan, AIST)

Keywords:paleointensity, 14C, Fuji Volcano

The atmospheric 14C production rate is considered to be controlled by the solar activity and geomagnetic field intensity. The 14C variation of timescale of the order of 10-100 years is mainly caused by the solar activity, while the 14C variation of longer timescales is probably related to the geomagnetic field intensity change. We can recognize a decreasing trend in the atmospheric 14C for the last 30 kyr and an increasing trend in paleointensity data in the database for the same period. However, a quantitative evaluation on the relationship between the geomagnetic dipole moment and the atmospheric 14C has been difficult, because the paleointensity database shows a very large scatter. The present study attempts to obtain reliable paleointensities from 14C dated lava flows and then discuss the relationship between absolute paleointensity and the atmospheric 14C. We sampled seven lava flows of 4-30 ka 14C ages of Fuji and Aso Volcanoes in Japan. These ages were reported from the charred material in/below the lava flows or organic sediment below the lava flows in previous studies. Sixty-three samples were subjected to the LTD-DHT Shaw paleointensty experiment (Tsunakawa-Shaw experiment), and forty-six of them passed the selection criteria. These paleointensity data and the 14C data reported for the same lava flows give a constraint on the relationship between virtual axial dipole moment and the atmospheric 14C.