9:15 AM - 9:30 AM
[MIS19-18] Terrestrial paleoclimate since 80 ka recorded in stable and clumped isotopes of two stalagmites obtained from the Pacific side of the Japanese islands
Keywords:clumped isotope, speleothem paleoclimatelogy
Two analyzed stalagmites (KA01 and 03) were obtained from Taiki town, Mie prefecture, Japan. 32 U-Th age points determined at National Taiwan University reveal that KA01 was dated from ca. 14 ka to ca. 1 ka and KA03 (Mori et al., 2018) was from ca. 80 ka to ca. 20 ka as well as the Holocene. δ18O changes of KA01 and KA03 show similar trends with the cave records in south Chinese (e.g. Hulu cave), but the amplitude of the δ18O changes was reduced in half.
Results of our Δ47 values require reconsideration of the previous interpretation for the Chinese stalagmite δ18O, dominant control by δ18O of meteoric water. A reconstructed temperature at the top of KA01 is consistent with modern temperature at the cave. The whole trend of reconstructed temperature combined with δ18O of modern rainfall indicates that δ18O changes of KA01 are mainly controlled by temperature changes instead of rainfall δ18O. Δ47 of KA03 yields higher temperature during cool periods of Heinrich events (HE), which apparently contradicts with previous studies. Before and after HEs, the carbon isotopic value increases by 0.5–1 ‰, indicating degassing of 13C-depleted CO2 from dripwater and carbonate precipitation in the conduit of the host rock because of reduced water supply. Drying during HEs could have made the surface of the stalagmite dry and resulted in apparent contradictory temperature. This study verifies that δ18O change should be used together with Δ47 for robust interpretation of the stalagmite records.