δ~(18)O variation during 54-46 ka recorded by a stalagmite from Northeast Sichuan, Central China and its relationship with summer monsoon evolution

TIMS U-Th dating and high-resolution oxygen isotopic composition measurements were conducted on a stalagmite SI3 collected from Shizi cave, Nuoshuihe, northeastern Sichuan, Central China. The stalagmite SI3 was developed between 54-46 ka. Its δ18O record displays a high similarity with those of stalagmites MSL and MSD from Hulu cave, East China and D4 from Dongge cave, Southwest China, respectively. The trend of the δ18O record of SI3 also parallels with those of ice core GISP2 from polar area and of speleothem in Israel. These suggest that the δ18O record of SI3 is closely related with summer monsoon variation in East Asia. However, some evidences seem to suggest that carbonates in SI3 are more 18O enriched than those deposited under oxygen isotopic equilibrium condition. There was probably kinetic fractionation when SI3 was developed. This may be explained by the locus of SI3 that was collected near the entrance of Shizi cave. The possible mechanism between the δ18O record of SI3 and the variation in East Asian summer monsoon was speculated. It is suggested that in the East Asian summer monsoon domain, the δ18O record of some speleothem deposited even under nonequilibrium condition is still a potential proxy for summer monsoon variation.