西藏日喀则末次冰期风成黄土粒度分析及其意义

Analysis of Soil Granularity at Dazhuka Country,Rikeze

通过对西藏日喀则市大竹卡乡风成黄土剖面样品的粒度测试分析,划分出六个气候阶段,显示67.0±7.2kaB.P-10.4±1.6 kaB.P间经历了温暖湿润-干燥多风-温暖干燥-干燥多风-湿干偏湿-温暖湿润环境的变化。该地区的黄土是半干旱-半湿润气候条件下形成的砂黄土,粒度较黄土高原的黄土要粗,表明当时受行星风系及高原隆升的影响,冰期的温度整体较低,雅鲁藏布江中部流域受西南季风的影响减小,规模小的温暖湿润波动不能对气候产生影响。因此,本区地层中的记录信息较黄土高原简单,气候向干冷化发展。

According to the comprehensive analysis of granularity of eolian loess at Dazhuka Country, Tibet, the climate change in this area can be divided into warm and wet climate, dry and windy, warm and dry, dry and windy, mild -dry and slightly wet, warm and wet. Loess in the area is arenaceous loess formed in semiarid - mild - warm climate, and the granularity is bigger than loess plateau. All of those indicate the loess is influenced by planet monsoon and uplifting of Qinghai - Tibet plateau, the ice age temperature is low in total, effect of southwest monsoon become slight in middle of Yarlung Zangbo River. Warm and wet fluctuate in miniature can not affect the climate. The record about stratum is less than loess plateau, the climate is becoming cold -dry .