• 责任者：Ye Wei (Geography Process Laboratory ; Zhejiang Normal University ; Jinhua 321004 ; China) ; Zhu Lidong
• 刊名：Quaternary Sciences
• 出版年：2013
• 卷期：33(5)
• 关键词：红色土 ; Red soil ; 黄土 ; loess ; 环境磁学 ; environmental magnetism ; 江西 ; Jiangxi Province ; 浙江 ; Zhejiang Province ; 江苏 ; Jiangsu Province
• 页码：p.911-926
• 图表：10 illus., 2 tables, 70 refs.
• 分类号：1400
• issnNo：ISSN1001-7410
• isbnNo：CN11-2708/P

     The Quaternary red earth and Xiasu loess that derived from aeolian dusts is widespread in the present subtropical area of China.Like the loess-paleosol sequences in the north of China,the red earth and Xiasu loess provides detailed records of Quaternary environmental and climatic change.Variations in the magnetic susceptibility of Chinese loess have been used to indicate pedogenetic intensity and the past climate change across the Chinese Loess Plateau.According to pedogenetic enhancement model,the magnetic enhancement of paleosols in the Chinese Loess Plateau is mostly attributed to the formation of pedogenetic superparamagnetic particles（SP）,which resulted from strengthened East Asia summer monsoon activity.However,the relationship between climate and magnetic properties of eolian deposits is uncertain in the south of China.In this study,we have investigated two red earth sections（JL and PJ）at Lushan（29°42＇2.04＂N,116°01＇42.1＂E） and Pujiang（29°27＇06＂N,119°56＇14.9＂E）,and a section（XG-3）of the Xiasu loess（32°08＇45.5＂N,118°50＇51.6＂E） at Xingang,China.All the sections are situated in a modern subtropical climate region with a thickness of 2.75m（PJ section）,18.5m（JL section）and 9.0m（XG-3 section）respectively.Three stratigraphic units are included in these sequences：Xiashu Loess,vermiculated red earth and yellow brown earth.Magnetic low field susceptibility（X）was measured with a Bartington MS2 meter at frequencies of 470 Hz（Xlf） and 4700 Hz（Xhf）.Two parameters of frequency-dependent magnetic susceptibility Xfd（Xlf-Xhf） and Xfd% （（Xlf-Xhf）/Xlf×100% ）were calculated from these measurements.Anhysteresis remnant magnetization（ARM）,isothermal remnant magnetization（IRM）and saturation isothermal remnant magnetization（SIRM）were also measured.High-temperature magnetic susceptibility measurements were made using a KLY -3 Kappabridge.The results suggest：（1）JL and PJ red earth profile are made of two different units,yellow brown earth and vermiculated red earth,which differ in susceptibility due to the different concentration,composition and domain of magnetic minerals.On the whole,yellow brown earth shows high susceptibility,high concentration of ferromagnetic minerals and dominance of fine-grained magnetite and maghemite.Semi-quantitative estimation indicates that SP component of yellow brown earth variations from 50% to 75%, and that of paleosols is larger than 75% .Vermiculated red earth is characterized by the low susceptibility,low magnetic content,and coarse grain size of magnetic minerals compared with yellow brown earth.The magnetic minerals in the vermiculated red earth are dominated by hematite.（2）Xiashu loess exhibits high X,Xfd,SIRM and XARM,positive linear relationship（r2=0.87）between X and Xfd,and much lower XARM/SIRM in loess units than in paleosol units,which suggests the presence of MD grains as well as SP and SD grains.Fine-grained ferrimagnetics contribute significantly to susceptibility.（3）Combining magnetic parameters with other physical and chemical proxies,it is suggested that the environment in which yellow brown earth and Xiashu loess deposited and developed was similar to modern subtropical environment.Relatively high CIA and Rb/Sr,low Ba,and low ratio of silt to clay imply more intensive chemical weathering in yellow brown earth than in Xiashu loess,indicating climatic latitude effect.（4） The widespread vermiculated red earth in subtropical areas demonstrates similar magnetic properties,grain size distribution and geochemical features,revealing that the zonal differentiation of the environment in which vermiculated red earth developed was not significant as that at present.High content of hematite and total iron,coarse magnetic grain size and high 87Sr/86Sr in vermiculated red earth suggest the material source of vermiculated red earth is not identical with that of yellow brown earth.Further work is needed to provide more evidence for this speculation.