青海湖冰后期以来古气候波动模式的研究

本文根据青海湖QH-16A近代沉积物岩芯中介形虫壳体的δ¹⁸O、δ¹³C、Mg/Ca和Sr/Ca值分析,讨论了青海湖区12,000年以来的气候特征。利用氧、碳同位素的相关性和相对温度、盐度变化曲线建立了青海湖区冰后期以来的气候波动模式,划分出5个气候期和23个气候阶。通过与布列特-谢尔南德冰后期气候方案对比,证实该气候波动模式具有世界性。

ON THE MODEL OF POST-GLACIAL PALAEOCLIMATIC FLUCTUATION IN QINGHAI LAKE REGION

The climatic change becomes one of the scientific interests in the world today. For predicting the climatic development in furture, people tend to study the evolution of climate in the past.Studies on oxygen and carbon isotopes in lacustrine sediments are used as an effective means to illustrate the changing of temperature, hydrology and evaporation characteristics etc. On the basis of the cores from drilling hole QH-16A （5.22m in length）collected in 1985, the present paper aims at reconstructing the climatic shift of the Qinghai Lake area during the postglacial period. Pure phospheric acid is used for carbonate sample preparation: 3MeCO₃+2H₃PO₄（?）Me₃（PO₄）₂+3CO₂+3H₂O According to assay conditions in our laboratory,the analytical results are accurete and reliable.Under the confidence level of 2o,the confidence limit of values determined is less than 0.09‰(δ¹⁸O)and 0.06‰(δ¹³C).The ostracods used in the analysis of δ¹⁸O and δ¹³C are Eucypris inflata （Sars）and Limnocythere dubiose （Daday）. Their principal chemical and mineral compositions are calcium carbonate and calcite, respectively. On the basis of δ¹⁸O and δ¹³C values of the ostracod shells from QH-16A core, the climatic fluctuation model in Qinghai Lake region during past 12,000 years is obtained. Since the late glacial, the climatic shifting in the region are divided into five climatic periods with twenty-three stages. The five climatic periods are: QH-Ⅰ（12,000-10,200aB.P.）: cold and dry. QH-Ⅱ（10,200-5,000aB.P. ）: warm. QH-Ⅱ-a（10,200-7,530aB.P.）: warm and dry. QH-Ⅱ-b（7,530—5,000aB. P. ）: warm and wet. QH-Ⅲ（5,000—3,130aB.P.）: cool and wet. QH-Ⅳ（3,130—2,010aB.P.）: mild and dry. QH-Ⅴ（2,010—Present）: cold and dry. 12,000—7,500 aB.P., the lake water is shallow with high salinity, after about 7,500 aB.P., it became deeper gradually and the salinity levels decreased. At about 3,400 aB.P., the lake water reached the maximum depth. Afterwards, the lake was slowly getting shallow, but still belonged to the deep lake stage.