九州台黄土剖面碳酸盐稳定同位素及其气候意义

The Carbonate Stable Carbon and Oxygen Isotopes of the Jiuzhoutai Loess Profile and Their Climaic Significance

九州台剖面黄土、古土壤稳定同位素进一步的研究揭示:黄土、古土壤中碳酸盐碳、氧同位素的系统变化代表了其形成过程中古气候的历史;当气候条件变得温湿时,碳同位素变小而氧同位素值则变大;而当气候变得干冷时,碳同位素值增加而氧同位素值则相对减小。但在长周期时间尺度上碳、氧同位素的这种变化并不存在绝对的线性对应关系。重建的δ^(13)C及δ^(1(?))O、特别是δ^(13)C曲线表明,在过去1.5Ma尤其是1.3Ma以来,兰州地区气候环境经历了多次温湿——干冷旋回且自约1.Ma以来其变化幅度越来越大。

The further stable isotopic research on loess and paleaosol of the Jiuzhoutai profile has revealed that the systematic variations of the carbonate stable carbon and oxygen .isotopes can be regarded as the recorder of climatic history during loess and paleaosol formation: when the climate condition is warmer and humid, the values of carbon isotope decrease but the values of oxygen isotope increase when the climate condition is colder and dry, the values ofthe carbon isotope decrease but the values of oxygen isotope increase. As far as the long cyclity of the time scale is concerned, there is no linear correspondence between the change of carbon and oxygen isotopes.The carbon and oxygen isotopic curve especially the carbon isotopic curve reconstructed show that during last 1.5 Ma, more clearly and importantly during last 1.3 Ma the climate condition in Lanzhou area has experienced several change from cold-dry to warm-humid changes and the amplitude is becoming bigger.