云南元谋盆地距今210—120ka间干热气候变化重建

DRY-HOT CLIMATE CHANGES FROM 210 TO 120 kaBP BY LACUSTRINE SEDIMENTS IN YUANMOU BASIN,YUNNAN

元谋盆地西侧浪巴铺湖相沉积物(厚27 m)ESR年代测定结果显示,浪巴铺古湖存在于距今216±20 ka至122±10 ka,经历了倒数第二次间冰期末期、倒数第二次冰期以及末次间冰期初期。结合粒度、磁化率和孢粉等数据,重建了元谋地区距今216±20 ka至122±10 ka期间的气候变化历史:距今216～185 ka期间,孢粉平均浓度为全剖面最高,出现了喜高温的苏铁科和栲属植物以及指示湿润环境的莎草科植被,表明这段时期气候相对湿热,对应倒数第二次间冰期晚期;距今185～150 ka期间,孢粉浓度迅速降低,1050 cm深处(距今160 ka)孢粉浓度只有8.67粒/100 g,对应倒数第二次冰期盛冰期;距今150～122 ka期间出现数层砂砾石层,草本植物比例增加,气温回升,降水减少,湖泊面积缩小直至消失,气候干热趋势显著。考虑到浪巴铺古湖沉积物样品平均孢粉浓度只有34.35粒/100g,认为至少在倒数第二次冰期之前,元谋盆地气候的干旱特征已经十分显著,植被稀疏,末次间冰期以来,气候的干热特征已与现代基本相同。

Langbapu Palaeolake is located in the west of Yuanmou Basin. A complete lacustrine sediments stratum （27m-thick） was preserved and the ESR dating was accomplished in this paper. The research results showed that Langbapu Lake existed from 216 ± 20 to 121 ± 10 kaBP, which covered the end of the penultimate interglacial, the penultimate glaciation as well as the beginning of the last interglacial. Based on the analysis of grain size, magnetic susceptibility and pollen, the palaeoelimatie changes during 216 ± 20 and 121 ± 10 kaBP of Yuanmou Basin has been reconstructed. During 216 - 185 kaBP, the mean pollen concentration was the highest and Cyeadaceae and Cyperaceae, as well as Sedge vegetation appeared, which indicated that the climate was relatively hygrothermal. During 185 -150 kaBP, the pollen concentration decreased rapidly. In the 160 kaBP, the pollen concentration was only 8.67 grain/100 g, which was corresponding to the glacial maximum of penultimate glaciation. During 150-122 kaBP, several sandy gravel layers appeared. The proportion of herb increased. The palaeoclimate became warmer but drier, which was very similar to today＇s climate. The Langbapu Lake shrank and disappeared at last. The mean pollen concentration of lake sediments was only 34. 35 grain/100 g, so we thought that dry-hot climate was already significantly before the penultimate interglacial. The characteristics of dry-hot climate were very similar to modern status after the last interglacial.