| 摘要: |
| 伊犁盆地位于亚洲中纬度内陆，其特殊的构造和地理位置，使得该区具有特殊的气候
环境。分布在盆地内的黄土记录了该区气候环境的变化过程，但是由于受到区域气候、海拔及
近地物源的影响，使得磁化率在该区的表现和环境意义与黄土高原黄土中的会有差异。为了较
准确的应用磁化率指标表征气候环境意义，就必须理解磁化率变化所受到的制约因素。本文通
过伊犁盆地近地表采取的38 个黄土样品（相当于黄土高原马兰黄土顶层），应用粒度，磁化率，
元素分析的方法，结合地形和气候因素，初步探讨了近地表黄土的磁性特征、地域分异和受控
因素，指出了磁化率在伊犁古环境研究中需考虑的问题。结果表明，近地表黄土样品的磁化率
与<2 μm 的粘粒含量、Fe2O3 含量成负相关，与>63 μm 的粗粒级含量呈正相关关系；样品的频
率磁化率与<2 μm 含量、Fe2O3 含量呈正相关；成壤作用形成的超顺磁颗粒对磁化率的贡献有限，
粗颗粒组分对磁化率贡献较大。近地表黄土磁化率与降水、海拔高度、局地物源等多种因子有关，
在黄土古气候解译中需要综合考虑这些因子对磁化率变化的可能影响。 |
| 关键词: 黄土 磁化率 影响因素 伊犁盆地 |
| DOI：10.7515/JEE201402011 |
| CSTR：32259.14.JEE201402011 |
| 分类号:P318；P532 |
基金项目:国家自然科学基金项目(41172166)；国家重点基础研究发展规划项目(2013CB955904)；中国科学院科技创新“交叉与合作团队”项目
|
| 英文基金项目: |
|
| Magnetic susceptibility characteristics of near-surface loess in the Ili basin, Xinjiang |
|
ZENG Meng-xiu1,2, SONG You-gui1
|
|
1. State Key Laboratory of Loess and Quaternary Geology, Institute of Earth and Environment, Chinese Academy of Sciences,
Xi'an 710075, China; 2. School of Geographic and Oceanographic Sciences, Nanjing University, Nanjing 210093, China
|
| Abstract: |
| Located in the middle latitude of Central Asian, the Ili Basin has specific geology, geomorphic
and geography characters, the moisture and warm water flow from the Atlantic Ocean, Caspian Sea,
Balkhash Lake get into the region, thus the climate is very special in the Xinjiang. Because of the
influence of the climate condition, the altitude and the nearby materials, there have some environment
significance differences of the loess between the Ili Basin and the CLP. Loess magnetic susceptibility
(MS) in the Chinese Loess Plateau is usually regarded as an index of East Asian Summer Monsoon
intensity; however, the paleoclimatic significance of loess MS value in Central Arid Asia is still unclear.
In order to break through the barriers in the application of the MS in the paleoclimate research, we must
understand the constraints of the MS. Here the authors report the results of MS, sedimentology and
geochemistry of 38 near-surface loess samples from different geomorphological-climatic units of the Ili
Basin, Xinjiang, Central Asia, and discuss the possible effect factors of loess MS value, and point out a
few remarks about the application of MS in the paleoenvironment research in the Ili basin. The results
show that the MS of the near-surface loess samples are negatively correlated to clay fractions (<2 μm)
and Fe2O3 content, but positively correlated to coarse fractions (>63 μm). Superparamagnetic particlesproduced by pedogensis and fine fractions have limited contribution to loess MS value and coarse
fractions play important role on the enhancement of MS. There is a high degree of complexity of nearsurface
loess susceptibility vary with temperature and precipitation in Ili basin. The loess in the Ili basin
is near its dust source, the wind moving distance is shorter, resulting to the higher proportion of coarse
grain particles, which causes that the susceptibility is positively correlated to coarse fractions. There is
a weak negative correlation between MS and altitude, a weak positive correlation between frequencydependent
susceptibility and altitude. The possible effector factors of loess MS such as the ratio of the
distal aeolian dust and regional sources, climatic conditions and altitude should be considered in the
paleoenvironmental interpretation. |
| Key words: loess magnetic susceptibility, affecting factors Ili Basin |
