兰州西津黄土色度指标记录的第四纪气候演化

为了更深入研究黄土高原西部地区第四纪气候演化历史，选取已建立可靠年代的兰州黄河南岸西津黄土钻孔剖面为研究载体，应用CM-700D型分光测色计对等间距取样的417个样品进行实验分析，获得了过去2.2 Ma的兰州地区色度指标记录序列。结合剖面已有其他古气候代用指标，与周边已有记录及全球深海氧同位素记录对比，发现2.2 Ma以来兰州地区气候演化整体呈现阶段性逐渐冷干化趋势，可能反映了全球第四纪气候长期变冷的影响。此外，在1.24 Ma和0.43 Ma左右经历了两次重要气候事件，1.24 Ma事件之后东亚冬季风和夏季风同时发生了增强，与“昆黄运动”起始时间一致，表明该事件可能受到了青藏高原隆升驱动；而0.43 Ma事件则是对全球中布容气候转型事件（MBE）的响应。因而，黄土高原西部地区第四纪气候演化可能受青藏高原隆升和全球变冷的双重调控，二者对不同气候事件的影响不同。

Quaternary climate evolution recorded by loess chromatic proxy in Xijin,Lanzhou

The chronology of Xijin loess section on the southern bank of the Yellow River in Lanzhou Basin was already founded reliably， thus， which was selected as a carrier to deeply study the Quaternary climatic evolution in the western Chinese Loess Plateau. The 417 samples at the same intervals were measured with a Minolta CM-700D spectrochromometer， and the record sequence of chromatic proxy in the Xijin section was obtained since 2.2 Ma ago. The results show that the climate evolution has undergone an overall trend of gradually drying and cooling since 2.2 Ma， with the published records of other paleoclimate proxies， the surrounding area and global stacked deep-sea δ¹⁸O， and which may indicate the impact of the global climate cooling during the Quaternary. Moreover， two significant climatic events were also found at about 1.24 Ma and 0.43 Ma. The winter and summer monsoons were synchronously strengthened after the event at 1.24 Ma， which was consistent with the beginning time of Kun-Huang Movement. This event may be driven by the uplift of the Tibetan Plateau. However， the event at 0.43 Ma in Lanzhou area is sensitively responsible for the global Mid-Brunhes Event （MBE）. It is also shown that Quaternary climate evolution in Lanzhou area may have been regulated by both the uplift of the Tibetan Plateau and global cooling， and both impacts to different climate events may be different.