Paleoenvironmental Changes Recorded by Grain Size of Loess/paleosol Sequence from the Chifeng City, Northeastern China Since the Last Glacial

The accumulation processes of loess in northeastern (NE) China record the varying characteristics of the East Asian Monsoons (EAM) and the evolution of the local environment. In this study, grain size end-member analysis of the Dajiugang (DJG) section deposited since the Last Glacial in Chifeng City, NE China was used to reveal the dynamic depositional characteristics of loess and environmental evolution of NE China. Results showed that the Chifeng loess comprises three grain size end-members (EM), EM1 (7.38 µm), EM2 (49.4 µm) and EM3 (90.00 µm), indicating the three transport dynamics of dust delivered to the region. The EM1 represents atmospheric dust as the background. The EM2, mainly derived from relatively distant-sources deposition, and EM3, material transported over a short distance, correspond to the intensity of southwesterly winds and the East Asian Winter Monsoon (EAWM), respectively. Results of climate reconstruction, combined with other records, showed that the climate was generally cold and dry with a strong EAWM and a weak East Asian summer monsoon (EASM) during the stadial-period [Marine Isotope Stage (MIS) 4 and MIS 2 stage]. The climate was predominantly warm and humid, with weak EAWM and surface winds and strong EASM in interstadial- period (MIS 3 and MIS 1 stage). Comparisons between indicators, e.g., EM3, the LR04 benthic δ18O stack and summer insolation at 65°N suggest that the strong EAWM is induced by increasing the Northern Hemisphere ice volume and reduced summer solar radiation.