中国西北与华北地区末次冰期黄土气候记录的对比研究

选用末次冰期具有代表性的黄土高原西部区临夏塬堡黄土剖面和华北地区具有代表性的北京西山东斋堂黄土剖面,通过对这两个剖面岩性、质量磁化率、粒度中值的变化幅度、频率、量值和所反映的气候环境状况及产生这种气候状况的原因的对比分析发现:两个剖面均记录了末次冰期可与反映全球冰量变化的SPECMAP曲线对比的MIS2、MIS3和MIS4 3个阶段,尽管其反映的气候状况并不相同。如末次冰期西北和华北地区风力强度基本接近（粒度中值值基本接近）,华北地区气候更为温湿,土壤的成壤强度更高,降水量更大,而西北地区就弱很多。这可能与两个地区地处不同的气候带有关,即西北地区地处温带干旱、半干旱区,华北地区地处暖温带半湿润区,尽管两剖面同处中纬度,但西北地区的塬堡剖面深居内陆,四周多高山,来自海洋的湿润气流很少能够到达,降水量远比同纬度其他地区少的缘故。同时还表明:就磁化率指标和粒度指标而言,磁化率指标对区域气候环境变化的响应更敏感,更能准确记录反映区域的气候环境变化状况。

Comparative Study of Climate Changes Recorded in Loess Strata both in Northwest China and Northern China during the Last Glacial Period

Two loess sections, Yuanbu loess section in Linxia and Dongzaitang loess section in Xishan Mountain of Beijing area, are decided as the representative loess sections in northwest China and northern China. Comparative study is conducted from aspects of strata lithology, mass susceptibility, median particle size change range and frequency and quality, climate condition and its forming causes. These two sections all recorded the MIS2, MIS3 and MIS4 stages which could be compared with SPECMAP curve indicating the changes of global ice volume during the last glacial, thought there were some differences in climate conditions reflected by the records. For example, the wind intensity both in northwest China and northern China was essentially approximate during the last glacial indicated by the same quality of median particle size in the two loess section, but the climate in northern China was warmer and more humid than that in northwest China, consequently had a relatively high level of pedogenic process in northern China. These may be explained by the different climate zones they located. That is, the northern China is located in the warm humid or semi-humid areas of temperate zone but the northwest China is located in the arid or the semi-arid areas of temperate zone;Although the two sections are all located in mid-latitude, the Yuanbu loess section in inland area, where moist air currents from the ocean mostly are stopped by the high mountains and rarely arrive at, so has less precipitation. In addition, it was proved that the susceptibility index is more sensitive to regional climate change than the particle-size index.