Previous studies show that the CaCO content is normally

Previous studies show that Dequalinium the CaCO3 content is normally between 10 and 15% in the loess layers and less than 1–2% in the palaeosols (Liu, 1985, An et al., 1985 and Wen and Diao, 1995). In the Shuangzhu and Hejiacun profiles the CaCO3 content is very low (less than 1%) in the Bts horizon and the cracked loess horizons (Fig. 6). It is as high as 58% in the horizon of carbonate nodules, and decreases to 10–15% in the unaltered loess layers under the weathered loess layer (Fig. 6). This proves that strong leaching took place in the Bts, Cs, and Cl horizons. The S4 in the loess profile was taken to be a palaeosol rather than a pedocomplex and could be attributed to fact luteal phase the Cs and Cl horizons in which CaCO3 was depleted were neglected. On the basis of analysis of 38 samples, the Fe2O3 and Al2O3 contents in S4 are 4.8–6.9% and 13.1–15.3% respectively and decrease from the upper to the lower part of the profile, with the highest content occurring in the Bts horizon (Fig. 6), which indicates that accumulation of Fe2O3 and Al2O3 and a moist climate occurred at that time. Fe2O3 and Al2O3 content obviously decrease beneath the CaCO3 nodule horizon, showing that weathering and leaching did not affect the loess layer beneath the CaCO3 nodule horizon.