摘要
In this paper,the Zhaojiachuan section(35°45’N,107°49’E) in Xifeng town is selected for this study.In this study,about 2 240 dry mass samples were taken at 10 cm intervals for organic matter measurements that were quantified by Potassium bichromate-Ferrous ammonium sulfate-heating method.In addition,and magnetic minerals from the paleosol units S1 and S5 together with the loess layers L1 were characterized using transmission electron microscopy(TEM).It is suggested that the magnetic susceptibility of the Late Miocene red clay has same paleoclimatic implication as the Quaternary loess-paleosol sequence,which shows biogeochemical process intensity during aeolian sediment pedogenesis.In addition,the traditional viewpoint is that the Quaternary loess-paleosol sequence form under alternation of cold-dry and warm-wet climate while the red clay results from warm-dry climate which results in the variation of magnetic susceptibility.Thus climate setting should be taken into account for paleoclimatic reconstruction using environmental magnetism.