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文章通过建立更尕海湖泊沉积岩芯软体动物化石属种组合,对比分析了软体动物壳体碳氧同位素的种内、种间变化.结果显示,壳体氧同位素种内变化较小,通常小于0.3‰;相同属不同种的壳体氧同位素种间差异约为0.3‰,但较相同属种的波动幅度大;不同属种的壳体氧同位素的种间差异最大.且波动幅度更大一些.壳体碳同位素的种内和种间差异均较氧同位素大,尤其是碳同位素的种间差异更为显著,可能与软体动物的“生命效应”有关.合理评价软体动物壳体同位素种内和种间变化对于理解软体动物壳体同位素所记录的气候变化具有重要的意义. “,”In this study, the mollusc fossil assemblages of sequential sediments from Genggahai Lake, on the northeastern Qinghai -Tibetan Plateau, were identified. We analysed variations of carbon and oxygen isotopic compositions of mollusc shells. Intraspecific difference of oxygen isotope values of mollusc shells is generally less than 0.3‰. Interspecific diference of - 0. 3‰ for the oxygen isotope values is obvious among different species, occuring at the nearly stone times, but this difference displys wider fluctuations, compared to the intraspecific difference. For the mollusc shells from different genus at the same layer, interspecific difference for the oxygen composition is great, but it is less than 1%o. Intraspecific and interspecific variations of carbon isotope compositions of mollusc shells are lager than those of oxygen isotope compositions. More obvious interspecific variation may be attributed to “vital effects” of individual spieces. Resonable evaluations on the intraspecitlc and interspecific variations of the isotopic values may play an important role in using stable isotopes of molusc shells to reconstruct climatic changes over the past.