青海湖介壳与无机碳酸盐氧同位素组成差异的环境意义

Environmental Significance of Oxygen Isotopic Composition Disparity between Co-existing Ostracod and Inorganic Precipitated Carbonate Minerals:Evidence from Qinghai Lake

青海湖Q14B沉积物柱芯560—415cm（约14．0—10．5kaB．P．）段，介壳δ^18O高于无机碳酸盐δ^18O可能反映了此时青海湖表层水温高于底层水温；介壳δ^18O与无机碳酸盐δ^18O之间的较小差值可能揭示了此时青海湖水位很浅，气候干冷；介壳δ^18O变幅大于无机碳酸盐δ^18O变幅，则可能源于此时青海湖水位大幅度波动导致的底层水温变幅超过表层，以及无机碳酸盐δ^18O测自全碳酸盐所致。在利用湖泊碳酸盐δ^18O进行气候及环境变化研究时，有必要分别测试不同种属介形虫及不同无机碳酸盐矿物的同住素值。

At the 560- 415 cm section of sediment core Q14B in Qinghai lake, δ^18O of ostracod being heavier than of inorganic carbonate, indicates the higher temperature of lake surface water than of lake bottom water. The minor difference between ostracod δ^18O and inorganic carbonate δ^18O reflects the situation of shallow lake water induced by the cold and dry climate. The changing range of ostracod δ^18O is in excess of that of inorganic carbonate δ^18O,which possibly proves that the changing range of bottom water temperature exceeds that of surface water. When lacustrine carbonate δ^18O is used to study the climatic and/or environmental evolution,it is of importance to test the single carbonate mineral δ^18O.