Red Ratings for Loess-Paleosol Sequences on China’s Loess Plateau and Their Paleo-Climatic Implications

Comparisons of red ratings (RR) with Fed, Fed/Fet, clay content, and magnetic susceptibility (X) of two loess-paleosol sequences at Luochuan and Lingtai on China's Loess Plateau were conducted to study the possible relationship between RR and pedogenic degrees of the two loess-paleosol sequences, and to discuss whether the RR could become new paleo-climatic indicators. Results showed that the RR of the two loess-paleosol sequences had positive, highly significant (P ＜ 0.01)correlations with: 1) citrate-bicarbonate-dithionite (CBD) extracted iron (Fed), 2) ratios of CBD extracted iron to total iron (Fed/Fet), 3) clay (＜ 2 μm), and 4) magnetic susceptibility (X). This suggested that the RR of these loess-paleosol sequences could indicate degrees of loess weathering and pedogenesis and were potential paleo-climatic proxies. The strong correlations of RR to Fed and X also implied that during pedogenic processes, pedogenic hematite in loess and paleosols were closely related to the amount of total secondary iron oxides and pedogenic ferrimagnetic minerals (predominantly maghemite).

Comparisons of red ratings (RR) with Fe_d, Fe_d/Fet, clay content, andmagnetic susceptibility (x) of two loess-paleosol sequences at Luochuan and Lingtai on China's LoessPlateau were conducted to study the possible relationship between RR and pedogenic degrees of thetwo loess-paleosol sequences, and to discuss whether the RR could become new paleo-climaticindicators. Results showed that the RR of the two loess-paleosol sequences had positive, highlysignificant (P < 0.01) correlations with: 1) citrate-bicarbonate-dithionite (CBD) extracted iron(Fe_d), 2) ratios of CBD extracted iron to total iron (Fe_d/Fet), 3) clay (< 2 mum), and 4) magneticsusceptibility (x). This suggested that the RR of these loess-paleosol sequences could indicatedegreesof loess weathering and pedogenesis and were potential paleo-climatic proxies. The strongcorrelations of RR to Fe_d and x also implied that during pedogenic processes, pedogenic hematite inloess and paleosols were closely related to the amount of total secondary iron oxides and pedogenicferrimagnetic minerals (predominantly maghemite).