Japan Geoscience Union Meeting 2019

Presentation information

[J] Oral

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

[S-EM18] Geomagnetism, paleomagnetism and rock magnetism

Sun. May 26, 2019 9:00 AM - 10:30 AM A08 (TOKYO BAY MAKUHARI HALL)

convener:Hisayoshi Shimizu(Earthquake Research Institute, University of Tokyo), Masahiko Sato(Department of Earth and Planetary Science, The University of Tokyo), Chairperson:Masahiko Sato(Department of Earth and Planetary Science, University of Tokyo), Akira Baba(山梨県富士山科学研究所)

9:30 AM - 9:45 AM

[SEM18-03] Reconstruction of full-vector archaeomagnetic reference curve in East Asia from 200 CE to 1100 CE

*Yu Kitahara1, Daiki Nishiyama2, Masao Ohno1, Yuhji Yamamoto3, Tadahiro Hatakeyama4 (1.Faculty of Social and Cultural Studies, Kyushu University, 2.Faculty of Science, Kochi University, 3.Center for Advanced Marine Core Research, Kochi University, 4.Information Processing Center, Okayama University of Science)

Keywords:Archaeointensity, Reference curve, East Asia, Tsunakawa-Shaw method, Old kiln

Paleomagnetic information reconstructed from archaeological materials is used to estimate the archaeological age of excavated relics, in addition to revealing the geomagnetic secular variation and core dynamics. The direction and intensity of the Earth’s magnetic field (archaeodirection and archaeointensity) have been estimated using different methods, many of which have been proposed over the past decades. Among them a new experimental technique for archaeointensity estimate is the Tsunakawa-Shaw method.

This study carried out the reconstruction of the archaeointensity using the Tsunakawa-Shaw method for a large number of samples of baked clay belonging to different ages from archaeological relics in Osaka Prefecture mainly, and constructs a dataset and the reference curve of archaeointensity in Japan (East Asia).

As the result, we estimated archaeointensities from 98 specimens belonging to 39 relics. We screened these data, compiled them for each pottery sequence, and finally obtained 10 mean intensity values of the pottery sequence level. All of the mean intensity values satisfy the selection criteria, which indicates that they have sufficient reliability. It is notable that these newly estimated archaeointensity values are lower than those in previous studies in Japan. On the other hand, new archaeointensity values show a harmonic trend in the archaeointensity data set obtained by the IZZI-Thellier method reported recently in Korea. We combined the dataset of Japan newly obtained in this study and the dataset in Korea, and drew an interpolation curve to construct an archaeointensity reference curve covering from around 200 CE to around 1100 CE in East Asia. This reference curve includes events of decrease and increase of archaeointensity occurred at around 600 CE and around 950 CE. The trends of rapid decrease and increase in intensity are a characteristic pattern of the intensity variation found for the first time in this study.