萨拉乌苏河流域全新世风成砂-湖沼相沉积物磁学性质  

Magnetic properties of Holocene aeolian sand and lacustrine sediments from the Salawusu River Basin

作　　者：吕珂欣 赵爽[1] 张文昌 夏敦胜[2] Lü Kexin;Zhao Shuang;Zhang Wenchang;Xia Dunsheng(Key Laboratory of Terrestrial Ecological Remediation in Jining City/School of Geography and Tourism,Qufu Normal University,Rizhao 276826,Shandong,China;Key Laboratory of Western China's Environmental Systems(Ministry of Education),Lanzhou University,Lanzhou 730000,China)

机构地区：[1]曲阜师范大学、济宁市地表生态修复重点实验室/地理与旅游学院,山东日照276826 [2]兰州大学西部环境教育部重点实验室,甘肃兰州730000

出　　处：《中国沙漠》2024年第1期75-85,共11页Journal of Desert Research

基　　金：国家自然科学基金项目(41907380)。

摘　　要：磁化率是古环境研究常用的代用指标,不同沉积环境中沉积物的磁化率增强机制不同,系统的磁学性质研究对磁化率参数的古环境意义解读尤为重要。选取萨拉乌苏河流域滴哨沟湾全新世风成砂-湖沼相沉积剖面为研究对象,通过系统的环境磁学参数研究,明确不同沉积相的磁学性质,并探讨其变化机制。结果表明:风成砂和湖沼相沉积物的磁学性质存在显著差异。风成砂中的磁性矿物以亚铁磁性磁铁矿和磁赤铁矿为主,矫顽力较低,磁性矿物的含量较高,且磁粒径较粗,以多畴和假单畴为主;湖沼相沉积物中除亚铁磁性和反铁磁性矿物以外,可能还含有磁性较弱的铁的硫化物,矫顽力较高,磁性矿物的含量较低,且磁粒径较细,以稳定单畴为主。风成砂的磁化率受成土作用影响小,主要受“风尘输入模式”的影响,风尘输入的粗粒磁铁矿和磁赤铁矿对磁化率的贡献大;湖沼相的磁性特征则受湖泊的还原环境的影响,还原作用导致强磁性的铁的氧化物发生溶解并向弱磁性的铁的硫化物转化,进而磁性矿物粒径减小,磁化率降低,矫顽力增加。Magnetic susceptibility is a commonly used proxy for paleoenvironmental research.However,the magnetic enhancement mechanism of sediments from different sedimentary environments is different,so the sys-tematic magnetic study is particularly important for the interpretation of the paleoenvironmental significance of magnetic susceptibility.In this study,we selected the Holocene aeolian sand and lacustrine sedimentation section of Dishaogouwan from the Salawusu River Basin to clarify the magnetic properties of different sedimentary fa-cies and explore their variation mechanisms through systematic study of environmental magnetic parameters.The results show that the magnetic properties of aeolian sand and lacustrine sediments are significantly different.The magnetic minerals in aeolian sand are mainly ferrimagnetic magnetite and maghemite,with lower coercivity,higher magnetic minerals concentration,and coarser magnetic grain size,mainly multi-domains and pseudo-sin-gle domains.In addition to ferromagnetic and antiferromagnetic minerals,lacustrine sediments may also contain weakly magnetic iron sulfides,with higher coercivity,lower concentration of magnetic minerals,and finer mag-netic grain size,mainly coarse stable single domains.Magnetic susceptibility of aeolian sand are less influenced by pedogenesis and are mainly influenced by the“dust input mode”,with the dominant contribution of coarsegrained magnetite and maghemite to the magnetic susceptibility.The magnetic characteristics of the lacustrine sediments are influenced by the reducing environment of the lake,where the strongly magnetic iron oxides under-go dissolution and conversion to the weakly magnetic iron sulfides,resulting in a decrease in the magnetic grain size,a decrease in the magnetic mineral concentration and an increase in the coercivity.

关 键 词：风成砂 湖沼相沉积物 磁学性质 萨拉乌苏河流域 

分 类 号：P539.3[天文地球—古生物学与地层学]