The loess in the Qinling Mountains and its records of Palaeoenvironmental changes

The Fengzhou loess section is very typical in the Qinling Mountains. The se ction, which is about 82 m thick and underlain by Neogene red clays, consis ts of 33 layers of loess and 33 layers of palaeosol. It covers the Brunhes normal polarity zone and Matuyama reversed polarity zone, and the B / M bou ndary is located in the middle part of loess layer 8 (L-8). The loess of th e Matuyama reversed polarity zone records the Jaramillo, Olduvai and Reunio n normal polarity subchrons. The boundary between the Matuyama reversed pol arity zone and Gauss normal polarity zone (M / Ga) appears on the lithologi cal boundary between loess and Neogene red clays. Loess accumulation in the Fengzhou section started before 2.48 Ma B.P. Based on the stratigraphical structure, the material composition and magnetic susceptibility curve of th e Fengzhou loess section, the palaeoclimatic changes during the last 2.48 M a ih the Qinling Mountains are subdivided into 66 cold-dry and warm-humid s tages, equivalent to 33 climatic cycles. The above climatic fluctuations ag ree very well with those of the oxygen isotopic records from deep-sea depos its.