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 are a, the drip water and the present carbonate deposit in Panlong cave of Guil in 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 dec rease with an increase of air temperature and the rainfall, and the correla tion 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 th an those during winter monsoon; (ii) delta(18)O values of the drip water ha ve 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 spele othems is, the larger the proportion of C-3 plants is and the more plentifu l the rainfall is. On the contrary, C-4 plants may be prevailing or the env ironment may be a stony desert caused by climate changes or human activity.