哺乳动物化石牙齿釉质的碳、氧同位素组成与古气候重建方面的研究进展

哺乳动物化石牙齿釉质能有效地抵抗成岩作用的影响，并保存原始的碳、氧稳定同位素组成信息。通过对食草类哺乳动物化石牙齿釉质同位素组成的分析可以重建这些动物生存时代的古气候。釉质碳酸盐的碳同位素组成响应于取食植物的碳同位素组成，藉此可以恢复陆地生态系统中C3和C4植物的分布比例，这个比例主要受控于大气的CO2水平、气压和光照等因素，与不同的纬度带和气候带有关；釉质磷酸盐的氧同位素组成响应于饮用水的氧同位素组成，饮用水来源于大气降水，其氧同位素组成响应于温度变化，所以釉质的氧同位素组成与气温之间有显著的线性相关，藉此可以计算地史时期的年平均温度、绘制气候的冷暖变化曲线。

PALEOCLIMATIC RECONSTRUCTION USING CARBON AND OXYGEN ISOTOPES OF TOOTH ENAMEL FROM MAMMALIAN FOSSILS

The tooth enaml of mammalian fossil is able to be efficientiy resistant todiagenesis and retains the original carbon and oxygen isotopic composition. On thebasis of the analyses to the isotopc composition of herbivorous mammalian toothenamel, the paleoclimares when these mammals. lived can be reconstructed. The carbonisotopic composition of structural carbonare in tooth enaml responds to that of dietaryplants. According to thes principle, the proportions of C3 and C4 plants in thetermstrial ecosystem can be estimated, which were contrlled mainly by CO2atmospheric levels, moisture stress and irradiance as well as related to differentlatitudinal or climatic zones. The oxygen isotopic composition of biogenic phosphatein tooth enamel responds tD that of ingested water from precipitation whose oxygenisotopic composition responds to temperature vallations. As a result there is anoutstanding cormlation between oxygen isotopic composition of tooth enaml andtemperature. In the light of ths pattem, the annual average temperature in thegeological periods can be calculated and the climatic variation curve of cold and warmin the geological periods can be made.