| 云南白水台现代内生钙华微层的特征及其古气候重建意义 |
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| 关键词:travertine lamina thickness stable carbon and oxygen isotopes dilution rainfall amount effect Southwest China, |
| 基金项目:国家自然科学基金(编号:40572017); 国家社会公益项目(编号:2005DIB3J067) |
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| Thickness and Stable Isotopic Characteristics of Modern Seasonal Climate controlled Sub-annual Travertine Laminas in a Travertine-depositing Stream at Baishuitai, Southwest China: Implications for Paleoclimate Reconstruction |
| A continuous high-resolution monthly record of stable isotopes (δ 13C and δ 18O) in a well laminated freshwater travertine deposited at Baishuitai of Southwest China from May 1998 to November 2001 is presented. The travertine exhibits clear annual bands with coupled brown、white color laminations. Throughout the field investigation, it was found that the thin (1.5～2.2 mm) brown porous lamina was formed in the monsoonal rainy season from April to September, whereas the thick (5～8 mm) dense white lamina was formed in the dry season from October to March. The comparisons of lamina thickness and stable isotope signals in the travertine with the meteorological records allow us to constrain the relevant geochemical processes in the travertine formation under different climate conditions and to relate climate variables to their physico-chemical proxies in the travertine record. Sympathetic variations in lamina thickness, δ 13C and δ 18O along the sampled profile reflect changes in hydrogeochemistry, showing that thin lamina and low δ 13C and δ 18O values occur in warm and rainy seasons. The decreased amount of calcite precipitation and low δ 13C values during the warm and rainy seasons are caused by dilution of overland flow after rainfall. The low δ 18O values are believed to be related to the rainfall amount effect in subtropical monsoonal regions. This process is thought to be markedly subdued whenever the amount of rainfall is lower than a given threshold. Accordingly, distinct minima in lamina thickness, δ 13C and δ 18O are interpreted to reflect events with above-mentioned average rainfall, possibly heavy floods, and vice versa. This study demonstrates the potential of freshwater travertine to provide valuable information on seasonal or even monthly rainfall variations. |
| LIU Zai-fa,LI Chun-hong,YOU Zhen-feng,WAN Nai-rong,SUN Hai-long,LIU Xiang-ling.2006.Thickness and Stable Isotopic Characteristics of Modern Seasonal Climate controlled Sub-annual Travertine Laminas in a Travertine-depositing Stream at Baishuitai, Southwest China: Implications for Paleoclimate Reconstruction[J].Acta Geoscientica Sinica,27(5):479-486. |
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