Using 210Pb Technique to Determine the Closure of Young Stalagmites
用210Pb技术判断年轻石笋封闭性研究

Based on analyzing the 210Pb specific radioactivity of two nearby stalagmites DY-2 and DY-3 in the same cave named Maomaotoudayan cave in Guilin City, the authors obtained the following understanding: (1) although they have grown in the same cave and their distance is about 1.5 meters, the initial 210Pb specific radioactivity of DY-2 is 2 times higher than that of DY-3, and the 210Pb specific radioactivity of DY-2 is 0.7 times higher than that of DY-3 in modern sediments. And the drip monitoring also certified that the deposition rate of DY-3 is faster than that of DY-2 stalagmite, indicating that the 210Pb specific radioactivity could be used as a tool to determine the deposition rate in the same geological background and geographic environment; (2) both of the two stalagmites show fluctuation in the 210Pb specific radioactivity profiles, related to the distribution, size and density of intercrystal porosity, the disturbed DY-3 profile might be attributed to the existence of pores in the stalagmite and the mixture of later 210Pb with the former 210Pb; (3) the problem whether there is an oxygen isotope fractionation in the open system needs further study.