Oxygen and carbon isotopic characteristics of rainwater, drip water and present speleothems in a cave in Guilin area, and their environmental meanings

The studies of the oxgen and carbon isotopes of the rainwater in Guilin area, the drip water and the present carbonate deposit in Panlong cave of Guilin show that: (i) as to the general characteristics of the oxygen isotopes of the rainwater within a year and between years, the delta(18)O values decrease with an increase of air temperature and the rainfall, and the correlation between delta(18)O values and the mean monthly air temperature is much better than that between delta(18)O values and the rainfall, and the delta(18)O values of the rainwater during the summer monsoon are much smaller than those during winter monsoon; (ii) delta(18)O values of the drip water have a quite good correlation with the delta(18)O values of the rainwater in the same period; (iii) when the conditions are appropriate, delta(13)C can be used as an environmental proxy, that is, the smaller delta(13)C Of speleothems is, the larger the proportion of C-3 plants is and the more plentiful the rainfall is. On the contrary, C-4 plants may be prevailing or the environment may be a stony desert caused by climate changes or human activity.