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The correlation between theδ~(13)C andδ~(18)O in primary carbonates is affected by several factors such as hydrological balance,total CO_2 concentrations,climatic condition and lake productivity. The influence of these factors on theδ~(13)C-δ~(18)O correlation may be different on different time scales.In this paper,two different-type lakes in southwestern China,Lake Erhai and Lake Chenghai,are selected to investigate the influence of climatic pattern on theδ~(13)C-δ~(18)O correlation and to evaluate the reliability of theδ~(13)C-δ~(18)O covariance as an indicator of hydrological closure.The results show that there exists good correlation between theδ~(13)C andδ~(18)O in Lake Erhai (overflowing open lake) and in Lake Chenghai (closed lake).This suggests that theδ~(13)C-δ~(18)O covariance may be not an effective indicator of hydrological closure for lakes,especially on short time scales.On the one hand,a hydrologically open lake may display covariantδ~(13)C andδ~(18)O as a result of climatic influence.The particular alternate warm-dry and cold-wet climatic pattern in southwestern China may be the principal cause of theδ~(13)C-δ~(18)O covariance in Lake Erhai and Lake Chenghai.On the other hand,a hydrologically closed lake unnecessarily displays covariant trends betweenδ~(13)C andδ~(18)O because of the buffering effect of high CO_2 concentration on theδ~(13)C shift in byper-alkaline lakes.We should be prudent when we use the covariance betweenδ~(13)C andδ~(18)O to judge the hydrological closure of lake.
The correlation between the δ ~ (13) C and δ ~ (18) O in primary carbonates is affected by several factors such as hydrological balance, total CO_2 concentrations, climatic conditions and lake productivity. The influence of these factors on the δ ~ (13) C -δ ~ (18) O correlation may be different on different time scales. In this paper, two different-type lakes in southwestern China, Lake Erhai and Lake Chenghai, are selected to investigate the influence of climatic pattern on the δ ~ (13) C-δ ~ (18) O correlation and to evaluate the reliability of the δ ~ (13) C-δ ~ (18) O covariance as an indicator of hydrological closure. The results show that there exists good correlation between the δ ~ (13) C and δ ~ (18) O in Lake Erhai (overflowing open lake) and in Lake Chenghai (closed lake). This suggests that the δ ~ (13) C-δ ~ (18) O covariance may not an effective indicator of hydrological closure for lakes, especially on short time scales. On the one hand, a hydrologically open lake may display covariant δ ~ (13) C and δ ~ (18) O as a result of climatic influence. The particular alternate warm-dry and cold-wet climatic pattern in southwestern China may be the principal cause of the delta ~ (13) C-δ ~ (18) O covariance in Lake Erhai and Lake Chenghai. On the other hand, a hydrologically closed lake undesirablearily displays covariant trends betweenδ ~ (13) C andδ ~ (18) O because of the buffering effect of high CO_2 concentration on the δ ~ (13) C shift in byper-alkaline lakes. We should be prudent when we use the covariance betweenδ ~ (13) C andδ ~ (18) O to judge the hydrological closure of lake.