Terrestrial paleoclimate analysis in using tufas developed in temperate-subtropical regions

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In order to reconstruct high-resolution terrestrial paleoclimatology in temperate-subtropical regions, we have focused to freshwater carbonate tufa, analyzed chemistry and isotopes, and observed tufa deposits collected from several localities. Results indicated that 1)laminated texture is formed by temperature-dependent seasonal change in calcite precipitation rate (Kano et al.,2003), and that 2)tufa textures record artificial alterations, such as agricultural water drainage and construction of subsurface dams.Based on the above-mentioned results, climatological analyses have been performed using specimens collected from Niimi, Takahashi (Okayama Prefecture), Kikai (Kagoshima Prefecture), and Miyako (Okinawa Prefecture). We demonstrated that 3)oxygen isotopic ratio is usually correlated with water temperature and records recent trend of the Global Warming. We found that 4)individual rain events were recorded in tufa (Kano et al.,2004). Tufas, such as one collected from Niimi, exhibit 0.1mm-order brown bands, which correspond to peaks of Si- and Al-X-ray strength from analytical results of X-ray micro-analyzer. The bands can be regarded as horizons of high clay contents. 5)The relation between brown bands and rain events was proven by the fact observed during 5-day monitoring of water properties after a rain event at Niimi. Clay contents in water drastically increased up to seven times of the normal level after the rain event. 6)We further performed analysis on a paleo-tufa in Shanxi Province, China, and suggested that the climate in MOI-stage 3 (c.a. 50ka) was more humid than now.Our research revealed many new findings on depositional conditions and origin of annual lamination and analytical procedure, and could successfully proposed a new research theme called as "Tufa-climatology".