中晚全新世科尔沁沙地沉积物化学特征及其气候变化

Chemical Characteristics of Sediments in Horqin Desert and Climatic Change during the Middle and Late Holocene

科尔沁沙地位于我国沙漠—黄土边界带和北方农牧交错带,深受东亚季风的影响,对全球气候变化反应非常敏感,是研究全球气候变化的理想区域。TL剖面磁化率、粒度和地球化学元素氧化物及其比值变化分析表明:中晚全新世研究区气候极不稳定,可以大致划分为:①6.0～4.2 ka BP,气候暖湿,夏季风逐渐增强,并占据主导,冬季风较弱,与全新世大暖期对应,但存在百年尺度的气候波动,其中:6.0～5.6 ka BP,5.5～5.4 ka BP,4.9～4.7 ka BP,4.5～4.2 ka BP气候暖湿;5.6～5.5 ka BP,5.4～4.9 ka BP,4.7～4.5 ka BP气候相对冷干。②4.2～1.3 ka BP,气候相对暖湿,与上一阶段相比夏季风有所减弱,其间也存在次一级波动,4.2～3.63 ka BP,3.57～3.4 ka BP气候相对干冷;3.63～3.57 ka BP,3.4～1.3 ka BP,气候相对暖湿。③1.3～0.65 ka BP以来,气候波动频繁,后期有向暖湿发展的趋势。这些气候变化与区域和全球变化具有良好的对应关系,反映该区气候变化与全球气候变化具有高度一致性。

The Horqin desert,intensely influenced by East Asian monsoon,is located in the desert-loess boundary belt and agricultural and animal husbandry interlaced zone in North China.The geographic setting suggests that the Horqin desert is very sensitive to the global climatic change,so it is an ideal zone for studying the response of global climatic change.Analysis on magnetic susceptibility,grain size and oxides and ratios of chemical elements from TL profile during the middle and late Holocene indicates that the regional climate is very unstable,which is classified into the following phases： ① From 6.0 ka BP to 4.2 ka BP,the summer monsoonal strength is continuously increased and dominated this region,the warm and humid climate is corresponding to the Holocene thermal maximum period,but exists climatic fluctuation on centennial scale,accompanying with weaker winter monsoon.During this period,the climate is warm and humid in 6.0-5.6 ka BP,5.5-5.4 ka BP,4.9-4.7 ka BP,4.5-4.2 ka BP while it is relatively cold and dry in 5.6-5.5 ka BP,5.4-4.9 ka BP,4.7-4.5 ka BP.② From 4.2 ka BP to 1.3 ka BP,compared with the former phase,the regional climate becomes relatively warm and humid but have smaller fluctuations,accompanying with the declined summer monsoonal strength.The climate is dominated by cold and dry in 4.2-3.63 ka BP,3.57-3.4 ka BP while it is relatively warm and humid in 3.63-3.57 ka BP,3.4-1.3 ka BP.③ From 1.3 ka BP to 0.65 ka BP,the regional climate is frequently fluctuated and tends to warm and humid in the later stage.These climatic changes in Horqin desert are very coincident with the regional and global climatic change,reflecting the obvious consistency between them.