A chemical index of weathering without effect of wind sorting: Fe/Mg ratios in the acid-insoluble phases of loess deposits

Chemical analysis of acid-insoluble fractions in loess and paleosols shows that concentrations of Fe and Mg were under control of wind sorting and pos t-depositional weathering-pedogenesis. The former caused Fe and Mg concentr ated in the finer grain-size fractions, displaying synchronous variations, while the latter made Fe and Mg separated, leading to Fe retained in the we athered section and Mg leached out. Therefore, Fe/Mg ratios in the acid ins oluble fraction of loess and paleosols can eliminate the effect of wind sor ting and serve as an excellent proxy record on intensity of weathering-pedo genesis. Based on calculation, leaching percentage of Mg in the paleosol S1 from the Luochuan, Xifeng and Huanxian sections is 15%, 11% and 2%, respec tively, and on average 9% for the paleosols S-2-S-14 from the Luochuan sect ion, with the highest value amounting to 22% in S5-1, suggesting the strong est weathering-pedogenesis.