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土壤具有空间分布广泛、时间分布连续的特点,并且其物理化学性质与气候因素密切相关,因此,可用于古气候重建.以陕西延安两个距离相近、坡度不同的土壤剖面LP和LPM(LP水平,LPM坡度为20°)为研究对象,利用环境磁学方法研究土壤剖面地形(地表坡度)对其磁学性质的影响及对古气候重建的意义.结果表明,LP磁化率平均值和最大值均为LPM两倍,两个剖面磁性矿物类型和粒径分布相似.因此,在应用传统磁学参数磁化率进行古降雨量重建时,同一地点的不同土壤剖面磁化率可能存在很大差异.另外,LP与LPM两剖面因成土作用引起的磁化率增强值与母质的比值分别为2.27和2.04,饱和等温剩磁增强比值分别为1.80和1.86,两剖面比值相差不大.将LP和LPM两个剖面频率磁化率(FD)及非磁滞剩磁(ARM)和“硬”等温剩磁强度(HIRM)进行线性拟合,得到的线性拟合斜率FD/HIRM和ARM/HIRM,包含成土作用生成的亚铁和反铁磁性矿物信息且受母质影响很小,LP和LPM的χFD/HIRM拟合斜率分别为28.7×10 5和28.9×10 5A m 1,ARM/HIRM分别为0.35和0.33.这些结果表明土壤剖面磁化率(或饱和等温剩磁)增强值、FD/HIRM和ARM/HIRM受土壤母质和地形影响较小,在大范围内用来重建古降雨量可能比传统磁学参数(如磁化率)更适合.
The soil has the features of wide spatial distribution and continuous time distribution, and its physicochemical properties are closely related to the climatic factors, so it can be used for paleoclimate reconstruction.The soil profiles of LP and LPM , And LPM gradient of 20 °), the effects of topography (surface slope) of soil profile on the magnetic properties and the significance of palaeoclimate reconstruction were studied by environmental magnetic method.The results showed that the mean and maximum values of LP susceptibility Both are twice as long as LPM, and the distribution of magnetic minerals and particle size are similar in the two sections.Therefore, the magnetic susceptibility of different soil profiles at the same site may vary greatly when the magnetic susceptibility of traditional magnetic parameters is used for paleo-rainfall reconstruction. The ratio of magnetic susceptibility enhancement to parent material in LP and LPM sections was 2.27 and 2.04, respectively, and the ratio of saturation isothermal remanence enhancement was 1.80 and 1.86, respectively, with little difference between the two sections.The LP and LPM The linear fit slopes FD / HIRM and ARM / HIRM were obtained by linear fitting of the frequency-dependent magnetic susceptibility (FD) and the non-hysteresis remanence (ARM) and the “hard” isothermal remanence (HIRM) Soil effect The ferrous and antiferromagnetic mineral information is very little affected by the parent material. The χFD / HIRM fitting slopes of LP and LPM are 28.7 × 10 5 and 28.9 × 10 5A m 1, respectively, and the ARM / HIRM are 0.35 and 0.33, respectively. These results indicate that the enhancement of magnetic susceptibility (or isothermal remanence) of soil profiles, FD / HIRM and ARM / HIRM are less affected by soil parent materials and topography, and the reanalysis of paleo-rainfall over a large area may be more effective than traditional magnetic parameters Such as magnetic susceptibility) is more suitable.