Stable Carbon Isotope Variations in Cave Percolation Waters and their Implications in Four Caves of Guizhou, China

Monitoring and sampling of main plants, soil CO2, soil water, bedrock, spring water, drip water and its corresponding speleothem were performed at four cave systems of Guizhou, Southwest China, from April 2003 to May 2004, in order to understand stable carbon isotope ratios variations of dissolved inorganic Carbon (DIC) in cave percolation waters (C-13(DIC)) and their implications for paleoclimate. Stable carbon isotopic compositions and ions (Ca, Mg, Sr, SO4, Cl etc.) were measured for all samples. The results indicate that there are significant differences among the C-13(DIC) values from inter-cave, even inter-drip of intra-cave in the four caves. The C-13(DIC) values from the Liangfeng Cave (LFC) is lightest among the four caves, where vegetation type overlying the cave is primary forest dominated by tall trees with lighter average C-13 value (-29.9 parts per thousand). And there are remarkable differences in C-13(DIC) values of different drip waters in the Qixing Cave (QXC) and Jiangjun Cave (JJC), up to 6.9 parts per thousand and 7.8 parts per thousand, respectively. Further analyses show that the C-13(DIC) values in cave drip waters are not only controlled by vegetation biomass overlying the cave, but also hydro-geochemical processes. Therefore, accurate interpreting of C-13 recorded in speleothems cannot be guaranteed if these effects of the above mentioned factors are not taken into consideration.