Environmental Significance of delta~(18) O Record from Cave Drip Water and Recent Carbonate Deposit at No.15 Branching Cave of Seven Star Cave in Guilin
A prerequisite for the dynamic monitor of modern cave is to provide a reliable basis for the interpretation of a variety or multiple proxies from modern carbonate (CaCO_3) sediment - stalagmites in cave,and to make full use of the multiple proxies from modern carbonate (CaCO_3) sediment in field cave monitoring,and compared to local measuring meteorological data each other and correction,is the key of the accurate and quantitative interpreting multiple climate proxies in stalagmites. The four hydrological years of the meteoric precipitation,cave drips,modern carbonate sediments for 5 sites in No.15 branching cave of Seven Star Cave in Guilin during 2008-2011 were continuously monitored,and the correlation between the delta~(18)O of cave drip and modern carbonate (CaCO_3) and delta~(18)O of the meteoric precipitation were also discussed. The study results have shown that the annual average delta~(18)O value of cave drip and modern carbonate (CaCO_3) is very close to delta~(18)O of the meteoric precipitation and the same change trend,and indicated that the delta~(18)O of cave drip and modern carbonate (CaCO_3) came mainly from delta~(18)O of the meteoric precipitation,that is,it is obviously controlled by delta~(18)O of the meteoric precipitation. In four hydrological years,the year (or annual) change and or many years change trends of delta~(18)O record from the modern secondary chemical carbonate sediments (CaCO_3) and drop water in cave are basically the same and show obvious change characteristics of four peak (low value area of delta~(18)O) and four trough (high value area of delta~(18)O),and has obvious rule of the seasonal change and year change and has the same seasonal characteristics of the meteoric precipitation or heat. The research results shown that delta~(18)O of drip water and modern carbonate (CaCO_3) sediments in cave can record the climate change signal at local or at the top of the cave. So that it has been considered that delta~(18)O of modern carbonate (CaCO_3) sediment in cave is mainly taken as the alternative proxies of the summer monsoon intensity and rainfall amount.