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黄土/古土壤序列和红粘土均已被证明是风积成因,然而红粘土研究的程度远低于黄土/古土壤序列,比如强发育红粘土获得比较低磁化率值的原因并没有得到清楚解释,红粘土磁化率代用指标问题和红粘土搬运路径等问题还存在较大的争议,红粘土记录古气候意义研究也相对薄弱,因此加强对红粘土的研究,有助于对古气候的理解。佳县位于黄土高原与毛乌素沙漠交接地区,季风区与非季风区过渡地带。对佳县厚60m的红粘土样品进行系统磁学参数测量分析发现,佳县红粘土以软磁性矿物(磁铁矿、磁赤铁矿)为主,同时含有一定量硬磁性矿物(赤铁矿、针铁矿,主要是赤铁矿);强发育古土壤层含有较多软磁性矿物,弱发育古土壤层含有较多硬磁性矿物;磁颗粒粒径基本在0.2μm以下,χ>64×10~(-8)m~3/kg时,磁颗粒粒径小于0.1μm。剖面底部磁学参数变化存在异常,原因可能是:赤铁矿含量增加,超顺磁(SP)亚铁磁性颗粒含量急剧减少,单畴(SD)颗粒相对含量增加。该异常原因解释符合前人提出的成壤路径:水铁矿→SP磁赤铁矿→SD磁赤铁矿→SD赤铁矿。
Both loess / paleosol sequence and red clay have been proven to be aeolian causations, however, the degree of red clay study is much lower than that of loess / palaeosol sequences, as evidenced by the fact that the reason for obtaining lower magnetic susceptibility values for strongly developed red clays is not clearly explained There are still some controversial issues such as the index of substitution of magnetic susceptibility of red clay and the transportation path of red clay. The research on the significance of paleoclimate recorded by red clay is relatively weak. Therefore, it is helpful to understand the paleoclimate. Jiaxian County is located in the Loess Plateau and the Mu Us desert junction area, monsoon and non-monsoon transition zone. The results show that the red clay in Jiaxian is mainly composed of soft magnetic minerals (magnetite and maghemite) and a certain amount of hard magnetic minerals (hematite , Goethite, mainly hematite); the strong developed paleosol layer contains more soft magnetic minerals and the weakly developed paleosol layer contains more hard magnetic minerals; the particle size of magnetic particles is below 0.2μm, χ> 64 × 10 ~ (-8) m ~ 3 / kg, the magnetic particle size is less than 0.1μm. The variation of the magnetic parameters at the bottom of the section is abnormal. The reason may be that the content of hematite increases sharply, the content of superparamagnetic (SP) ferrous magnetic particles decreases sharply, and the relative content of single domain (SD) particles increases. The explanation of this anomaly is in line with the previously proposed pathways into the soil: water iron ore → SP maghemite → SD maghemite → SD hematite.