(a/b) AF demagnetization of IRM given at 300 mT for different loess/palaeosol samples. (c/d) Gradients of the demagnetization curves. The higher coercivity component (maximum 40–58 mT) is present in all samples (even in the strongly developed palaeosol S1) and represents the detrital population D, assumed to be uniform across the Chinese Loess Plateau (Evans & Heller 1994). With increasing humidity the loess is affected by weathering and a new low coercivity population P of (bio)chemical grains is formed. The contribution of each component is given in Table 1. The dashed line in (d) represents the continuation of the spectrum of palaeosol S7.