Japan Geoscience Union Meeting 2025

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S (Solid Earth Sciences ) » S-CG Complex & General

[S-CG57] Hybrid Geochronology from Date to Age

Tue. May 27, 2025 1:45 PM - 3:15 PM 201A (International Conference Hall, Makuhari Messe)

convener:Sota Niki(Division for Chronological Research, Institute for Space-Earth Environmental Research, Nagoya University), Ito Kengo(The University of Tokyo), Shuhei Sakata(Earthquake Research Institute, The University of Tokyo ), Hideki Iwano(Geochemical Research Center, The University of Tokyo), Chairperson:Ito Kengo(The University of Tokyo), Shuhei Sakata(Earthquake Research Institute, The University of Tokyo)

2:00 PM - 2:15 PM

[SCG57-08] Age estimation by paleomagnetic field intensity: from submarine volcanoes to archeological artifacts

*Yutaka Yoshimura1 (1.National Institute of Polar Research)

Keywords:paleomagnetic field intensity age estimation, submarine volcanoes, archeological artifacts, non-dipole field

It is known that the direction and intensity of the geomagnetic field vary over a time scale of thousands to tens of thousands of years, called geomagnetic secular variations. Generally, the geomagnetic field is assumed to be a dipole field, but the secular variation is due to a non-dipole field. The secular variations have regional patterns. A standard curve of direction and intensity is constructed using ancient geomagnetic records (paleomagnetic records) with age data from each region. Using the standard curve as a time marker for that period, it is possible to estimate the eruption age of volcanic rocks with unknown age and the making age of fired archeological artifacts (Pottery, roof tiles, etc.). This is the paleomagnetic age estimation. For submarine volcanic rocks formed more recently than 10 kyr, it is generally difficult to determine their absolute age. This is because radiocarbon dating of carbides is possible for land-based volcanoes, but it is impossible for submarine volcanoes. Also, in some cases, only fragments of fired archeological artifacts are excavated. When the archeological artifacts are not with carbides, it is impossible to conduct radiocarbon dating. Besides, detailed chronology based on the shape of pottery is difficult for fragments of archeological artifacts. Furthermore, sampling with orientation is difficult for these materials. Age estimation by paleomagnetic field intensity is attracting attention as a method that complements age estimation and needs no orientation, which is difficult by conventional methods. In this presentation, I focus on age estimation using paleomagnetic field intensity and introduce examples of estimating the ages of central ocean ridge basalts, Izu submarine volcanoes, and the ages of fired archeological artifacts in Japan and overseas.