LACUSTRINE CARBONATE CHEMICAL SEDIMENTATION AND CLIMATIC-ENVIRONMENTAL EVOLUTION --A CASE STUDY OF QINGHAI LAKE AND DAIHAI LAKE
Wang Yunfei(Nanjing Institute oj Geography and Limnology, Academia Sinica, 210008)
Temperature and precipitation are clima ic factors which control the water balance of inland lakes in semi-arid to semi-humid areas to the extent that they may definitely cause fluctuation in lake capacity, water mineraliza ion and carbonate sedimentation. Thus analysis of carbonate sediments in geological sections may give useful information on past climatic and environmental evolutionary trends. According to the pattern of fluctuation of carbonate sediments in Qinghai and Daihai lakes, the climate changes over the past 500 a in Qinghai Lake suggest that during the little ice age the climate was cold and humid, during the temperature increasing period, warm and dry, resulting in a 100 a meta-cyclicity. Dry and cold ice age, warm and humid interglacial periods have been the mjor climatic features in Daihai Lake since the Late Pleistocene. Drastic climatic changes took place during the transition from glacial to interglacial period. The water balance of lakes in the marginal monsoon areas suggested that they were sensitive to climatic changes.