Quantitative measurements on the paleo-weathering intensity of the loess-soil sequences and implication on paleomonsoon  

作　　者：郝青振 郭正堂 

出　　处：《Science China Earth Sciences》2001年第6期566-576,共11页中国科学（地球科学英文版）

基　　金：the National Natural Science Foundation of China (Grant Nos. 49725206, 4897176) and the Key Project of the Chinese Academy of Sciences (KZCX2-108).

摘　　要：The loess-soil sequences in northern China provide a near continuous record of Quaternary paleoclimate. The pedogenetic intensity of the sequences is closely linked with the variations of the East Asian summer monsoon. In this study, 2181 samples from the Changwu and Xifeng loess sections are analyzed and two high-resolution paleo-weathering timeseries of the last 1.2 Ma are generated, using the ratio of CBD extractable free Fe2O3 (FeD) versus the total iron (FeT). This new index is compared with micromorphological features, low-frequency magnetic susceptibility, frequency-dependent magnetic susceptibility, and the Rb/Sr ratio[5,6]. The results suggest that the FeD/FeT ratio is able to better reflect the degree of soil development. Since the chemical weather-ing of loess in the Loess Plateau region mainly depends upon the summer precipitation and tem-perature under modern climate condition, which are closely associated with strength of summer monsoon, and the chemical weathering intensity of loess primarily reflects the variations of the summer monsoon circulation.The loess-soil sequences in northern China provide a near continuous record of Quaternary paleoclimate. The pedogenetic intensity of the sequences is closely linked with the variations of the East Asian summer monsoon. In this study, 2181 samples from the Changwu and Xifeng loess sections are analyzed and two high-resolution paleo-weathering timeseries of the last 1.2 Ma are generated, using the ratio of CBD extractable free Fe2O3 (FeD) versus the total iron (FeT). This new index is compared with micromorphological features, low-frequency magnetic susceptibility, frequency-dependent magnetic susceptibility, and the Rb/Sr ratio[5,6]. The results suggest that the FeD/FeT ratio is able to better reflect the degree of soil development. Since the chemical weathering of loess in the Loess Plateau region mainly depends upon the summer precipitation and temperature under modern climate condition, which are closely associated with strength of summer monsoon, and the chemical weathering intensity of loess primarily reflects the variations of the summer monsoon circulation.

关 键 词：LOESS Paleo-Weathering Intensity East Asian Summer Monsoon Fed/Fet Ratio magnetic susceptibility 

分 类 号：X144[环境科学与工程—环境科学]