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

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

*望月 伸竜¹、佐藤 雅彦² (1.熊本大学大学院先導機構、2.産業技術総合研究所地質調査総合センター)

キーワード：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.