新疆伊犁盆地黄土古气候记录与Heinrich事件对比分析

Climatic record in the loess-paleosol sediment in the Ili basin and comparative analysis with the Heinrich events

伊犁盆地作为中国黄土高原与欧洲黄土区的过渡区域,其第四纪古气候研究对于揭示全球气候驱动及耦合机制具有重要的意义.通过对伊犁盆地塔勒德晚更新世黄土-古土壤剖面粒度、低频磁化率及地球化学元素分析,探讨了西风区黄土-古土壤序列中古气候指标变化特征及记录的全球气候突变事件.结果表明:古土壤层中粒径<10μm颗粒物含量明显高于黄土层,与之相反的是古土壤层中的低频磁化率、Zr/Rb值和元素Ti含量均小于黄土层,且元素Ti含量与Zr/Rb间具有较高的相关性.黄土-古土壤剖面中古气候代用指标清晰的记录了6次Heinrich(H)事件及Younger Drays(YD)事件,但YD事件、H1、H2、H5和H6事件变幅较H3和H4事件显著,古气候指标与格陵兰冰芯δ18O、季风区李家塬粒度和洛川、西峰及环县Zr/Rb值均具有较好的一致性,所记录的气候事件较李家塬、洛川、西峰更为显著.结合已有研究说明,Heinrich和D-O旋回等气候事件是由西风区向季风区传递的,MIS3阶段温度的升高和常年受西风的影响是造成塔勒德气候环境变化特征的主要控制因素.

The loess-paleosol deposited in the Central Asian is a sensitive indicator for studying the evolution of the Quaternary paleoclimate in the westerly regions,providing additional insight into the Quaternary climate history and its relationship with global climatic changes. Based on the analysis of grain size,lowfrequency magnetic susceptibility and geochemical elements of the Talede loess-paleosol sequences,the characteristics of environmental proxies and the records of global abrupt climatic events were discussed in this paper. The results showthat the values of environmental proxies in paleosol are significantly higher than those in loess of section; particles of grain size( < 10 μm) in paleosol are more than those in loess. However,in paleosol lowfrequency magnetic susceptibility,Zr / Rb and Ti are less than those in loess,and the content of Ti has a rather high correlation with Zr / Rb. The Heinrich( H) events and Younger Drays( YD) event have been clearly recorded in the proxies of Talede deposition. However,the changing amplitudes of H1,H2,H5,H6 and YD were much more significant than those of H3 and H4. Meanwhile,the climatic records of Talede section are in accord well with the δ18O of Greenland ice core,the grain size of Lijiayuan and the Zr / Rb of the Loess Plateau( LP). But the abrupt climatic events( e. g. Heinrich and YD events) in the record of Talede section are clearer than those in Lijiayuan and LP sections. The increasting temperature during MIS3 and the influenced by westerly are the key factors to affect the climatic and environmental characteristics in the study regions all the year round; the signal of Heinrich events are possibly passed from the westerly regions to Asian monsoon regions.