日本地球惑星科学連合2018年大会

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[JJ] ポスター発表

セッション記号 M (領域外・複数領域) » M-IS ジョイント

[M-IS10] 古気候・古海洋変動

2018年5月23日(水) 13:45 〜 15:15 ポスター会場 (幕張メッセ国際展示場 7ホール)

コンビーナ:岡崎 裕典(九州大学大学院理学研究院地球惑星科学部門)、磯辺 篤彦(九州大学応用力学研究所)、北村 晃寿(静岡大学理学部地球科学教室、共同)、佐野 雅規(早稲田大学人間科学学術院)、長谷川 精(高知大学理工学部)、岡 顕(東京大学大気海洋研究所)、加 三千宣(愛媛大学沿岸環境科学研究センター)

[MIS10-P17] 琉球列島の石筍に記録された完新世の古気候記録

*浅海 竜司1赤嶺 裕二2植村 立2井龍 康文1Shen Chuan-Chou3 (1.東北大学大学院理学研究科、2.琉球大学理学部、3.国立台湾大学)

キーワード:石筍、古気候、酸素同位体組成、炭素同位体組成、完新世、琉球列島

Stalagmites can have continuous deposition of calcium carbonate over long periods of time and well-selected stalagmites are accurately datable with high-precision U-Th dating methods (e.g., Shen et al., 2002). Stable oxygen isotope signatures in stalagmites have been used as a paleoclimate proxy (e.g., McDermott, 2004) because the isotopic values can be controlled by those of the drip water and the cave temperature (e.g., Hendy, 1971). Since 2000, stalagmite-derived oxygen isotope time series have been widely used to reconstruct hydroclimate variations in East Asian monsoon regions during the Quaternary (e.g., Wang et al., 2001).

Here, we present oxygen and carbon isotope time series of 20 stalagmites collected at 5 caves in the Ryukyu Islands, Japan. The Hendy Test performed in this study suggests that the stable isotope profiles along the center of stalagmite growth appear to be primarily of environmental origin with little effects of kinetic fractionation. Since 2009, we have observed cave environments using loggers and collected water samples to establish relationship between oxygen isotope composition of drip waters and stalagmites. We generate a well-dated time series of the oxygen and carbon isotope ratios in stalagmites using a high-precision U-Th dating method to reconstruct hydroclimate changes around the Ryukyus during the Holocene. Coupled with previously published stalagmite records from China (e.g., Wang et al., 2001) and Japan (Shen et al., 2010; Sone et al., 2013; Uemura et al., 2016), our study can allow a better understanding of past spatial climate changes associated with the East Asian Monsoon variability.

Hendy et al. (1971) Geochim. Cosmochim. Acta, 35, 801-824.
McDermott (2004) Quat. Sci. Rev., 23, 901-918.
Shen et al. (2002) Chem. Geol., 185, 165-178.
Shen et al. (2010) Quat. Sci. Rev., 29, 3327-3335.
Sone et al. (2013) Quat. Sci. Rev., 75, 150-160.
Uemura et al. (2016) Geochim. Cosmochim. Acta, 172, 159-176.
Wang et al. (2001) Science, 294, 2345-2348.