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西北戈壁沙漠-黄土高原区表土磁化率特征及其意义

ISSN号：1001-7410
期刊名称：第四纪研究
时间：2013
页码：360-367
分类：P941.73[天文地球—自然地理学] P318.41[天文地球—固体地球物理学;天文地球—地球物理学]
作者机构：[1]兰州大学西部环境教育部重点实验室,西部环境与气候变化研究院,兰州730000, [2]福建师范大学地理科学学院,福州350007, [3]Department of Environment and Geography, Macquarie University, Sydney NSW 2109, Australia, [4]兰州大学地质科学与矿产资源学院,兰州730000, [5]中国科学院南京地理与湖泊研究所,南京210008
相关基金：国家自然科学基金项目（批准号：41072124,40830105,40721061和41202129）资助
相关项目：甘肃新生代风积与湖积过渡地带地层特征及其变化研究

关键词：干旱半干旱地区, 表土, 磁化率, 降水量, arid and semi-arid regions, topsoil, magnetic susceptibility, precipitation

中文摘要：

黄土高原表土磁化率与降水量呈良好的正相关性，为定量反演这一区域第四纪时期降水量变化提供了理论基础。通过对西北戈壁沙漠一黄土高原表土磁化率研究，表明表土磁化率与降水量的相关性出现在一定的降水范围内。其界限是年平均降水量200—300ram：高于这一界限，表土的磁化率、频率磁化率、百分比频率磁化率与降水量、相对湿度均呈现良好的正相关关系；低于这一界限，磁学参数与气候之间的相关性明显减弱，或者变得不明显。这是因为在该气候条件下．1）风化弱．成土组分贡献小．同时2）风积磁颗粒粒释相．对磁化率影响糖大的缘故．

英文摘要：

The magnetic susceptibility variation of loess-paleosol sequences in Chinese Loess Plateau （CLP） coincides with paleoclimatic changes and hence is widely used for climate reconstruction. Previous studies indicate the existence of a linear relationship between precipitation and magnetic susceptibility of topsoil, which is, however, speculated more complicated. Here we study topsoil（ 170 samples and together with other 61 published）including Gobi and CLP in northwest of China, spanning 96° - 110°E ,33°N to 43°N, with precipitation 50 - 700mm/a. Low field magnetic susceptibility Elf and frequency dependent susceptibility （Xfa and Zfd% ） have been obtained using Bartington MS2. The precipitation,ranging from 1971 -2000,at each sample site is simulated and determined with GIS methods. The correlation between magnetic susceptibility and precipitation presented in this study indicates that： linear relationship between susceptibility and precipitation only occurs to a high precipitation larger than 200mm/a and 300mm/a. Below this threshold,the relationship is unintelligible. This relation boundary likely attributes to different pedogensis degree over this area. Superparamagnetic （SP）particles bearing very high susceptibility form during the strong pedognesis in humid area; while in arid area due to weak pedogenic process,the contribution of SP particles of pedogensis origin is limited.