HR: 1340h
AN: PP13C-1420    [Abstracts]
TI: Paleoenvironmental records since 1300 years AD from the calcite stalagmite in the Yongcheon Cave, Jeju Island, Korea
AU: * Woo, K
EM: wooks@kangwon.ac.kr
AF: Kanwon National University, Department of Geology, Kangwon National University, Korea, Chuncheon, 200-701, Korea, Republic of
AU: Jo, K
EM: gcwater@cavequest.net
AF: Kanwon National University, Department of Geology, Kangwon National University, Korea, Chuncheon, 200-701, Korea, Republic of
AU: Li, H
EM: hli@usc.edu
AF: National Cheng Kung University, Department of Earth Sciences, National Cheng Kung University, Taiwan, Tainan, 701, ROC, Taiwan
AU: Luo, S
EM: sluo@usc.edu
AF: National Cheng Kung University, Department of Earth Sciences, National Cheng Kung University, Taiwan, Tainan, 701, ROC, Taiwan
AU: Wan, N
EM: l4893103@ccmail.ncku.edu.tw
AF: National Cheng Kung University, Department of Earth Sciences, National Cheng Kung University, Taiwan, Tainan, 701, ROC, Taiwan
AU: Tsai, Y
EM: l4694404@ccmail.ncku.edu.tw
AF: National Cheng Kung University, Department of Earth Sciences, National Cheng Kung University, Taiwan, Tainan, 701, ROC, Taiwan
AB: Yongcheon Cave is located on Jeju Island, the southernmost part of Korea. It is a typical lava tube cave that formed between 0.2~0.4 Ma ago, and includes numerous carbonate speleothems. A 11cm-long stalagmite (YC-1) was collected from its growth position in 2005. The ²¹⁰Pb dating results show that the top 0.9cm of YC-1 is less than 100 years old with the constant growth rate of 0.033mm/yr. ²³⁰Th/²³⁴U and ¹⁴C dating results show that the stalagmite is about 1,600 years old. Textural and stable isotopic analyses were carried out to infer the paleoclimatic variation during its growth. We have analyzed oxygen and carbon isotopes for 200 samples from the 2.5cm-long, uppermost part with a sampling interval of 0.125mm and for 100 samples from the lower 2.5cm-long part with a sampling interval of 0.250mm. δ¹⁸O and δ¹³C values range from -8.1‰ to -5.8‰ and from -8.1‰ to -1.5‰ (PDB), respectively. Both isotope values show the decreasing trends past 60 years due to global warming (depletion of δ¹⁸O= 1.2‰ and δ¹³C=4‰). Carbon isotopic compositions are more enriched in SGL (zone of Spaced Growth Laminae; δ¹³C=ca -2.5‰, PDB) than DGL (Zone of Dense Growth Laminae; δ¹³C=ca -7.5‰). This indicates that the overlying carbonates played relatively more significant role to supply carbon for SGL than DGL. Also more depleted carbon isotopic values in DGL should reflect more influence by organic carbon from overlying soil layers. Carbon isotopic variation also clearly shows the period of the Little Ice Age and coincides with the instrumental records of Northern Hemisphere temperature variation during the last 700 years. This preliminary result implies that the carbon isotopic signals have been affected by groundwater residence time which was related to the intensity of regional precipitation and buffering with overlying carbonates. Further analysis of this stalagmite may promise a great potential for the reconstruction of climate and environmental changes during the last 1,600 years.
DE: 4958 Speleothems
SC: Paleoceanography and Paleoclimatology [PP]
MN: 2007 Fall Meeting