120万年以来青海东北部极干冷事件探讨

STUDY ON EXTREME DRY-COLD PERIODS IN THE NOTHEAST PART OF QINGHAL PROVINCE SINCE 1.2MaB.P.

对青海东北部湟水各地高阶地上的西宁大墩岭黄土剖面通过多环境指标综合分析，发现其间夹有三层古风成砂，它们反映了自１．２ＭａＢ．Ｐ．以来本区经历的三次极干冷气候事件。根据古地磁测年及１４Ｃ测年推算：最早一次极干冷事件出现在１１１０ＫａＢ．Ｐ．，基本与大姑冰期Ⅰ期相当，可与深海氧同位素３８阶段对应；第二次极干冷事件出现于１４０ＫａＢ．Ｐ．，大致相当于倒数第二次冰期，与深海氧同位素６阶段对应；最未一次极干冷事件，根据１４Ｃ测年结果约出现在２１ＫａＢ．Ｐ．，与未次冰期极盛期相当，可与深海氧同位素２阶段对应。由此可见在青海东北部发生的这三次干冷事件与全球气候变化记录是同步的，但不同的是这三次干冷事件在本区表现最为强烈，呈现一种极干冷的气候状况，具有显著的区域差异性。这与其所处的特殊地理位置有着密不可分的关系。

Abstract The loess profile of Dadunling is located on the higer terrace of Huangshui River in Xining, Notheast Qinghai province. According to the analysis of environmental records of the profile,the three eolian sand layers have been identified which reflect the three extreme dry-cold periods since 1.2MaB.P.. Based on the palaeomagnetic and C 14 dating for the profile. The three eolian sand layers formed in about 21KaB.P.、140KaB.P.、1110KaB.P. separately. Comparison between extreme dry-cold periods and Qxygen isotope curves of the Pacific deep-sea cores,show that the three extreme dry-cold periods is consistent to globe climatic change as a whole, But some regional change of the three extreme dry-cold periods have been found.