Ages of Pleistocene marine terraces in the south coast of Japan using in situ cosmogenic 10Be and 26Al

Prof. Yusuke Yokoyama1, Dr  Atsunori Nakamura2, Mr Gen  Nagano1, Prof. Hideaki Maemoku3, Dr Yosuke Miyairi1, Prof. Hiroyuki Matsuzaki4

1Atmosphere And Ocean Research Institute, The University Of Tokyo, Kashiwa, Japan, 2Geological Survey of Japan, National Institute of Advanced Industrial Science and Technology , Tsukuba, Japan, 3Hosei University, Chiyoda-ku, Japan, 4MALT, The University of Tokyo, Bunkyo-ku, Japan

Marine terraces are formed with the changes in the relative sea level (RSL) that is affected by combined effects of the eustatic sea level (ESL) and the tectonic movements (e.g. uplift, subsidence and isostatic effect). Therefore, determining the ages and the elevations of the marine terraces allows us to reconstruct the ESL and/or the tectonic history (eg., Tam and Yokoyama, 2021).
The southern coast of the Shikoku Island and the Kii Peninsula are located along the Nankai Trough where the Philippine Sea Plate is subducting under the Eurasian plate. There exist relatively well-preserved marine terraces along the coast with the elevation ranges between ca. 50 –100 m. The terraces are regarded as the suitable counterparts to reconstruct uplift history of the south coast of Japan due to this unique tectonic setting. However, the ages of these terraces have been inferred partially using tephrochronology. In this study, we attempted to determine the age of the marine terraces employing terrestrial in-situ cosmogenic radionuclides (TCN), 10Be and 26Al. This is the first age estimation of the marine terraces in Japan using TCN, allowing us to determine the uplift rates and the seismic history of the region.

References
Tam, E., and Yokoyama, Y. (2021) A review of MIS5e Sea-level proxies around Japan, Earth System Science Data, 13, 1477-1497.
Yokoyama, Y., and Purcell, A. (2021) On the geophysical processes impacting palaeo-sea-level observations. Geoscience Letters, 8, 13.


Biography:

Yusuke Yokoyama have been studying the Earth surface environment including Atmosphere, Ocean, Cryosphere and Biosphere using geocemical and geophysical techniques.

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Date

Nov 08 - 19 2021