3:30 PM - 3:45 PM
[MIS10-13] Seasonal temperature changes recorded in carbonate clumped isotopes of tufas
Keywords:carbonate, clumped isotopes, tufa, oxygen isotope
Our Δ47-temperature calibration by the synthetic calcites is undistinguishable from many previous studies. A typical inter-measurement error was 0.0078‰ (1σ) estimated by in-house standard, which corresponds to 1.2°C in temperature.
The tufa Δ47 exhibited clear seasonal patterns ranged from 0.695‰ (Dec. 2000) to 0.731‰ (Aug. 2000) in Shimokuraida and from 0.696‰ (Jan. 2000) to 0.733‰ (Oct. 1999) in Shirokawa. These ranges correspond to 10.1–22.5°C and 9.7–22.3°C and these temperature ranges are 0–7°C higher than the actual water temperatures (ranging from 5.6 to 16.0ºC). The temperature offset at both sites became the largest in late summer and early autumn, when the water had high pCO2 and precipitation rate. It is assumed that active CO2 degassing and rapid calcite precipitation caused the temperature offset.
Although absolute temperature calibration of natural samples is in need of improvement, our tufa Δ47 values exhibited clearer seasonal patterns rather than in conventional δ18O thermometry.
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