Japan Geoscience Union Meeting 2015

Presentation information


Symbol U (Union) » Union

[U-06] Evolution of New Seamless Science: From Space, Sun to the Earth Surface

Sun. May 24, 2015 6:15 PM - 7:30 PM Convention Hall (2F)

Convener:*Yutaka Matsumi(Solar-Terrestrial Environment Laboratory, Nagoya University), Kanya Kusano(Solar-Terrestrial Environment Laboratory, Nagoya University), Joji Ishizaka(Hydrospheric Atmospheric Research Center, Nagoya University), Kazuhisa Tsuboki(Hydrospheric Atmospheric Research Center, Nagoya University), Masaki Enami(Center for Chronological Research, Nagoya University)

6:15 PM - 7:30 PM

[U06-P07] Seasonal variation of dead carbon fraction in dripwater in the Ryugashi Cave, Shizuoka Prefecture, Japan

*Masayo MINAMI1, Tomomi KATO2, Keiji HORIKAWA3, Toshio NAKAMURA1 (1.Center for Chronological Research, Nagoya University, 2.Graduate School of Environmental Studies, Nagoya University, 3.Department of Environmental Biology and Chemistry, Toyama University)

Keywords:dripwater, stalagmite, radiocarbon

Stalagmite is a cave deposit precipitated from dripwater. Dripwater contains some dead carbon derived from carbonate-dissolved CO2 through interaction with cave bedrock limestone, which will make the 14C ages of the stalagmite older, and so a correction of the dead carbon fraction (DCF) is needed for 14C dating of stalagmites. In this study, we investigated seasonal variation in 14C in dripwater in the Ryugashi Cave, Shizuoka Prefecture, to examine the DCF stability in a stalagmite. The results show that 14C concentration in dripwater was different depending on the site in the Ryugashi Cave, and that the 14C showed similar seasonal variations at all sites: lower in fall and winter, while higher in spring and summer, though the extent of the seasonal variations was different by site. The 14C concentration in dripwater tended to be higher (DCF tends to be lower) in dripwater with lower drip rate, indicating that the 14C in dripwater was correlated with the drip rate, and also correlated with rainfall amount around the Ryugashi Cave.
A growing stalagmite collected from a site in the Ryugashi Cave showed a roughly constant DCF (around 12%) compared with the 14C with the IntCal13 calibration curve, though the DCF was slightly fluctuated in detail. The results indicate that high-resolution 14C measurement can be performed on stalagmites in the Ryugashi Cave, and further that the DCF fluctuation observed for stalagmites could give information on change of paleo-rainfall amount. Based on the scenario that the increase in rainfall amount brings the increase in drip rate of dripwater, followed by the increase in soil-derived carbon fraction in dripwater, further followed by the 14C increase (DCF decrease) in dripwater, the reconstruction of precipitation could be performed using DCF variation in a stalagmite.