Goethite Concentration Variations in the Red Clay Sequence on the Chinese Loess Plateau

The Goethite is a common magnetic mineral in soils and is important for understanding past climatic and environmental change. Although goethite concentration records are available for the Quaternary loess-paleosol sequences from the Chinese Loess Plateau (CLP), no goethite concentration record is available for the underlying Red Clay sequence. Here, we generate a record of goethite concentration from the Chaona section on the CLP and investigate the relationship between goethite and ferrimagnetic mineral concentration and climate parameters on the Red Clay sequence deposited from 6 to 2.7 Ma. We found that increasing goethite concentration generally corresponds to decreasing magnetic susceptibility for the Red Clay sequence, with the exception of an anomalous section from 4.3 to 3.7 Ma where both records show increasing trends. Precipitation seasonality could explain this opposite variation pattern between magnetic susceptibility and goethite concentration in the Red Clay sequence. From 3.6 to 2.7 Ma, goethite concentration has a decreasing trend while magnetic susceptibility increased, which we interpret as more seasonally distributed precipitation associated with intensification of the East Asian summer monsoon (EASM). Similar pattern was observed from 0.65 to 0 Ma from the Lingtai section. Taken together, the goethite record reveals that the EASM experienced two stages of rapid intensification with apparent seasonally distributed precipitation since 6 Ma.