STUDY ON SEDIMENTATION RATE OF MODERN CAVE STALAGMITE CARBONATE (CaCO₃) DEPOSITS AND ITS ENVIRONMENTAL SIGNIFICANCE: A CASE FROM PANLONG CAVE, GUILIN, CHINA

The past environmental information recorded in speleothems has become the focus of short-term and high resolution study of the global changes. Dripping water in cave, as the medium of stalagmite formation, is a proxy responding to rapid change of climatic environment. The changes in composition, drop rate, and amount of the dripping water directly influence the growth rate of stalagmites and to certain extent the environmental information included in it. It is the bridge between the environmental change in the earth's surface and the growth of stalagmites in cave. In this regard, the study of dripping water in cave has become a popular subject for the study of forming mechanism of stalagmites and paleo-climatic reconstruction. Our monitoring of the growth rate of modern carbonate(CaCO₃)-stalagmite during two hydrologic years in the Panlong cave of Guilin has revealed that the main period for modern carbonate(CaCO₃) precipitation is in the summer season from April to October, the monthly average deposits at a single dripping site changes from 0.7 g to 1.5 g, but the highest value could reach 3.086 g at a single dripping site and the daily mean depositional amount is as high as 0.103 g (or 103 mg) in rainy season. The smallest monthly mean depositional amount at a single dripping site occurs in dry season or winter season. It is about 0.3038g, or about 1/10 of the figure in rainy season. There is even no deposition in dry season or winter season in two dripping sites. Data show that the growth rate of carbonate(CaCO₃) has seasonal and Inter-annual changes. The growth rate of modern carbonate(CaCO₃) is closely related with monsoon precipitation in summer season, total biologic activities, change in CO₂ concentrations in air in the cave. Therefore, to monitor the chemical process of modern carbonate(CaCO₃) in cave and its response to environmental changes are critical for the study of global changes.