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

摘要

Comparisons of red ratings (RR) with Fe_d, Fe_d/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 (Fe_d), 2) ratios of CBD extracted iron to total iron (Fe_d/Fet), 3) clay (< 2 mum), and 4) magnetic susceptibility (x). This suggested that the RR of these loess-paleosol sequences could indicate degreesof loess weathering and pedogenesis and were potential paleo-climatic proxies. The strong correlations of RR to Fe_d 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).