新疆伊犁晚全新世风成沙—古土壤序列磁化率特征及气候变化

Late Holocene Climate Change Revealed by the Magnetic Susceptibility of Paleoaeolian Sand-Paleosol Sedimentary Sequence in Yili Valley of Xinjiang

选择新疆伊犁河谷塔克尔莫乎尔沙漠古风成沙—古土壤沉积剖面为研究对象,通过73块样品的磁化率及其与TOC、CaCO3、Fe2O3和粒度组成的相关分析,并以OSL测年为时间标尺,讨论剖面沉积的磁化率变化机制及其古气候意义。结果表明:剖面低频磁化率(χlf)与16～250μm百分含量为正相关,即低频磁化率χlf变化主要受粗组分含量变化的影响。其中,古风成沙χlf值多高于古土壤,这与我国季风区沙漠沉积的磁化率变化特征相反。根据剖面磁化率及各种环境指标综合分析,研究区3.7 kaBP以来的气候变化可划分为5个阶段:3.71～3.06 kaBP凉湿、3.06～2.78 kaBP冷干、2.78～2.10 kaBP凉湿、2.10～0.50 kaBP冷湿、0.50～0.00 kaBP温干。晚全新世气候变化与周边地区古气候记录有较好的一致性,并与同期北大西洋表层海温变化事件呈现很好的遥相关,总体上表现为相对暖干、凉湿的典型西风气候变化模式。

By studying on correlation between magnetic susceptibility,TOC, CaCO3, Fe203and grainsize component of 73 samples from the paleosand-paleosol sedimentary section of Xinjiang Takermohuer desert, according to OSL date ,we discussed mechanism of magnetic susceptibility change and paleoclimate significance. The results were that ： The corre- lation betweenxlfand percent content of 16 ~ 250 p,m component was positive, coarse component percent content affect- ed the change of X1f. In the section, Xlf of paleosand is higher than Xlf of paleosol, this characteristic is opposite to mag- netic susceptibility of monsoon desert sediment in China. According to magnetic susceptibility and other paleoclimate indexes of section sediment, we divided 5 paleoclimate stages of study area from 3.71 ka BP： 3.71 - 3.06 kaBP, the climate was cool and wet,from 3.06 kaBP to 2.78 kaBP was cold and dry,2.78 ~2.10 kaBP was cool wet,2.10 -0. 50 kaBP was cold and wet,0.50 kaBP to now was warm and dry. Climate change of research area is simliar to the oth- er regiones during late holocene, and it was related to the temperature change events of surface sea-water in north Alantic Ocean. The climate change was typical westerly climate model,warm-dry or cool-wet.