伊朗黄土高原表土磁性特征与古气候指示意义  

MAGNETIC CHARACTERISTICS OF SURFACE SAMPLES FROM NE IRAN,AND ITS PALEOENVIRONMENTAL IMPLICATIONS

作　　者：魏海涛[1] 陈发虎[1,2] WEI Haitao;CHEN Fahu(Key Laboratory of Western China's Environmental Systems,Ministry of Education,College of Earth and Environmental Sciences,Lanzhou University,Lanzhou 730000,Gansu;Key Laboratory of Alpine Ecology(LAE),Institute of Tibetan Plateau Research,Chinese Academy of Sciences,Beijing 100101)

机构地区：[1]兰州大学资源环境学院,西部环境教育部重点实验室,甘肃兰州730000 [2]中国科学院青藏高原研究所高寒生态重点实验室,北京100101

出　　处：《第四纪研究》2022年第1期261-271,共11页Quaternary Sciences

基　　金：国家自然科学基金项目(批准号:41402145);国家重点研究发展计划项目(批准号:2018YFA0606401);科技部第二次青藏高原综合考察研究项目(批准号:2019QZKK0602)共同资助。

摘　　要：全球变化研究中的现代过程研究越来越成为定量重建工作的先决前提,而由于如黄土等气候记录载体沉积分布的全球性与沉积环境的多样性,更需要就具体的研究区进行有针对性的现代过程工作以最大程度地保证重建工作的可靠性。西起地中海、东至帕米尔的广大区域是丝路文明演化的关键地区,其过去气候变化也是了解北半球中纬度气候演化与机制的重要拼图。本研究即采集位于该区之里海东南缘的伊朗黄土沉积区域的现代表土,并联系气候要素考察其磁性特征的空间变化。结果显示主要分布于冬春季节的年均降水其变化控制了亚铁磁性矿物的空间分异,包括次生超细颗粒含量变化与磁赤铁矿化程度,典型的磁学参数如百分频率磁化率值的变化可以定量记录年均降水值的变化。结合相关关系函数,可以为该区过去降水变化的定量重建提供准备并为进一步理解区域气候系统演化与机制提供支持。As globally distributed loess deposits distinctively from site to site,numerous researches have been conducted to empirically correlate modern climatic factors with the variations in magnetic parameters of topsoil and underlying loess at typical loess sites,in order to discover the correlations between magnetic properties and climatic factors by identifying the transferation and transformation of ferrimagnetic carriers for reliable quantitative paleo-reconstruction.In this work,systematic magnetic analysis has been performed aiming to obtain functionalized paleoclimatic proxies,on surface samples collected from the so-called Iranian Loess Plateau region in northeast of Iran,southeast of the Caspian Sea,which is climatically characterized by Mediterranean climate with hot,dry summers and mild,wet winters. What’s more,regional annual average temperature is almost spatially unchanging,while the annual average precipitation increases gradually from 200 mm up to more than 800 mm southeastwards,providing an excellent natural site for modern processes research,and 20 topsoil samples were collected.According to hysteresis measurement,apparent hysteresis phenomenon and loop-closing at magnetic field of ca.350 m T indicate the magnetic dominance of ferrimagnetism,such as magnetite and/or maghemite. Regional χl f values of surface samples vary between 28. 40 × 10-8~ 56. 05 × 10-8 m3/kg,with average value of 37. 22 × 10-8 m3/kg,which is significantly lower than that of surface samples from Chinese Loess Plateau. As to frequencydependent magnetic susceptibility χf d%,which is between 0. 44% ~ 5. 43%,the average value is 2. 82%,is lower than that of surface samples from Chinese Loess Plateau,both of which imply roughly low concentration of magnetic carriers, especially for ferrimagnetic assemblages, and possible less weathering and pedogenic processes.Granulometric state of magnetic assemblages are estimated via Day plot showing that data set falls in PSD region,similar to data of typical loess samples from central and

关 键 词：伊朗黄土高原 丝绸之路核心区 百分频率磁化率 定量重建 表土现代过程 地中海气候 

分 类 号：P318[天文地球—固体地球物理学] P467[天文地球—地球物理学]