贵州草海沉积物碳酸盐碳同位素异常正值的发现及其环境指示意义

摘要

Carbon isotopes(δ13C) of carbonate from sediment core has been measured in Lake Caohai, Guizhou Province, southwest China. The results showed that δ13 C values varied between - 14.25%c and 23.10%o, which was the largest amplitude of carbon isotope variations and the highest positive values discovered so far in lacusrine carbonate sediments. On the basis of combination with oxygen isotope, organic matter and carbonate content proxies, we suggested that the carbon isotope of carbonate from Lake Caohai was controlled by photosynthesis/respiration of aquatic plants, and the input of bacteria to carbon isotope fractionation of organic matter might be responsible for the abnormal positive δI3C values in Lake Caohai. Therefore, much attention should be paid to the carbonate δ13 C in Lake Caohai in the future research.%对贵州草海沉积物柱芯碳酸盐碳同位素组成测定的结果显示,其δ13C值的变化范围为- 14.25‰至23.10‰,变化幅度为37.35％,这是迄今所发现的湖泊沉积物碳酸盐中最大的碳同位素变化幅度,其中的部分同位素值也是迄今发现的最大碳同位素值.综合碳酸盐氧同位素、碳酸盐含量和有机质含量指标,认为草海沉积物碳酸盐碳同位素组成主要反映了湖区水生植物光合/呼吸作用,异常正值可能指示了湖区细菌参与有机质碳同位素分馏过程的特殊环境/气候条件.因此,草海沉积物碳酸盐异常正值在今后的研究中值得进一步关注.