The cause of extremely high magnetic susceptibility of the S5S1 paleosol in the central Chinese Loess Plateau

Abstract

The paleosol unit S5S1, which corresponds to Marine Isotope Stage (MIS) 13, is the most prominent paleosol layer in the central Chinese Loess Plateau (CLP). S5S1 has extremely high magnetic susceptibility, but it remains uncertain whether this is related to climate or to time (the duration of pedogenesis) due to the anomalously low loess deposition rate. To address this question, we investigate the iron mineralogical properties of the S5S1 paleosol at the Xifeng loess section located in the central CLP. We compare the results of S5S1 with other paleosol units, yielding additional insights into the CLP climatic changes during MIS-13. The results show that magnetic enhancement of S5S1 paleosol is stronger than that of the other paleosol units, which is mainly governed by pedogenic produce fine-grained ferrimagnetic minerals; the maximum value of the goethite concentration compared with hematite in the S5S1 paleosol unit is markedly higher than those in the other paleosol units. The prolonged period of pedogenesis is not main controlling factor that leads to the magnetic enhancement of S5S1 because the concentration of SD/SP has hardly changed compared with other paleosols as with the increasing of magnetic susceptibility. Changes in the ratio of pedogenic hematite to goethite, as well as in magnetic enhancement, indicate that the S5S1 paleosol developed under extremely humid conditions. This extremely humid climate is a main cause that leads to the extremely high magnetic susceptibility.