| 研究実績の概要 |
The 14C dating of tufa samples from Laguna Hedionda suggests that the age of this deposit is 10,036 to 9,642 cal yrs BP. Stable isotope analysis of tufa from Uyuni overlap with previous studies of tufa from the same area (δ18O +0.73 ± 0.05 to －2.59 ± 0.05‰ and δ13C +4.78 ± 0.02 to +2.94 ± 0.02‰) that formed during the last major lake phases. Analysis of tufa from the Lipez Lakes are internally consistent and, after secondary carbonate values are removed, illustrate a difference between the capping tufa found around Laguna Hedionda and Chiar Khota (δ18O +2.55 to －0.12‰ and δ13C +6.23 to +1.29‰) and the beach tufa found around Laguna Honda and Ramaditas (δ18O +2.93 to +1.29‰ and δ13C +5.23 to +1.60‰). For this study the capping tufa is the most appropriate to examine in more detail as it is less likely to have been contaminated by groundwater.
The data show a general signal of aridity across all tufa samples, as well as high-resolution evidence for annual or seasonal variations in rapidly formed laminated tufa. Combined with the age data from these deposits it can be suggested that the formation of these tufa, as well as Lipez Lakes above present day depths, is associated with the wet phase in the northern Chile basins to the south rather than the large lakes on the central and northern Altiplano to the north. Further work needs to be carried out in the remote regions on the Altiplano to find further high-resolution climate proxies to better understand regional climate systems.
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