Kansu （KS） profile is located in the east of Yili basin, western Xinjiang, where typical loess sediments are distributed. The magnetic parameters （such as IRM, SIRM SOFT, and M） and grain size in the KS profile we...Kansu （KS） profile is located in the east of Yili basin, western Xinjiang, where typical loess sediments are distributed. The magnetic parameters （such as IRM, SIRM SOFT, and M） and grain size in the KS profile were analyzed in the study. The results showed that the magnetic property of KS loess is dominated by ferrimagnetic minerals, such as magnetite and maghemite. Antiferromagnetic and superparamagnetic minerals also exist in the profile, but had less impact on magnetic susceptibility. Compared with the typical loess sediments of the central Loess Plateau in China, the strata of Kansu profile contained more magnetic minerals and hard magnetic minerals. The analysis of grain size for magnetic minerals indicated that the properties of loess and paleosol were respectively dominated by PSD/MD and coarse SSD magnetite. The research found that the contents of magnetic minerals in loess and paleosol sequences in Kansu profile were similar, but the proportion of fine grained magnetite and soft magnetic minerals were varying, which implies a positive relationship between the value of magnetic susceptibility and intensity of pedogenesis.展开更多
The distribution, optically stimulated luminescence dating and granulometric properties suggest that the loess on the northern flank of Tian Shan should be divided into two types. One which is like mantle and is named...The distribution, optically stimulated luminescence dating and granulometric properties suggest that the loess on the northern flank of Tian Shan should be divided into two types. One which is like mantle and is named type A, is located on the windward slopes and dated to about 54.5±5.73 Ka. The other, called type B, lies flatly on the terraces of the rivers or low hills and penetrated 30.8±2.05 Ka ago. Here we study the origin and the age of two types of loess, and a model of loess formation is proposed. The dust was entrained from the Gobi Desert located to the north of Tian Shan by the monsoon from Mongolia, obstructed by the high mountains and deposited on the windward slopes of the mountains. The rivers and flows then transported the aeolian loess to low terraces and piedmont alluvial plains.展开更多
对天山北麓黄土年代的认识还存在一定分歧。文章在对天山北麓河流阶地进行划分的基础上,通过分析黄土分布与地貌单元(河流阶地与冲积扇)的依附关系,同时结合黄土-古土壤序列分析与ESR测年,初步确定天山北麓地貌面上覆盖的最老黄土年代为...对天山北麓黄土年代的认识还存在一定分歧。文章在对天山北麓河流阶地进行划分的基础上,通过分析黄土分布与地貌单元(河流阶地与冲积扇)的依附关系,同时结合黄土-古土壤序列分析与ESR测年,初步确定天山北麓地貌面上覆盖的最老黄土年代为0.54 Ma B.P.,这为分析黄土所赋含的环境信息提供时间标尺。展开更多
基金funded by the National 973 Project (2009CB421308)the Natural Science Foundation of China (40871080 and 90502008)
文摘Kansu （KS） profile is located in the east of Yili basin, western Xinjiang, where typical loess sediments are distributed. The magnetic parameters （such as IRM, SIRM SOFT, and M） and grain size in the KS profile were analyzed in the study. The results showed that the magnetic property of KS loess is dominated by ferrimagnetic minerals, such as magnetite and maghemite. Antiferromagnetic and superparamagnetic minerals also exist in the profile, but had less impact on magnetic susceptibility. Compared with the typical loess sediments of the central Loess Plateau in China, the strata of Kansu profile contained more magnetic minerals and hard magnetic minerals. The analysis of grain size for magnetic minerals indicated that the properties of loess and paleosol were respectively dominated by PSD/MD and coarse SSD magnetite. The research found that the contents of magnetic minerals in loess and paleosol sequences in Kansu profile were similar, but the proportion of fine grained magnetite and soft magnetic minerals were varying, which implies a positive relationship between the value of magnetic susceptibility and intensity of pedogenesis.
基金sponsored by the National Key Basic Research Program of China(2007CB411305) to Z.J.Guo
文摘The distribution, optically stimulated luminescence dating and granulometric properties suggest that the loess on the northern flank of Tian Shan should be divided into two types. One which is like mantle and is named type A, is located on the windward slopes and dated to about 54.5±5.73 Ka. The other, called type B, lies flatly on the terraces of the rivers or low hills and penetrated 30.8±2.05 Ka ago. Here we study the origin and the age of two types of loess, and a model of loess formation is proposed. The dust was entrained from the Gobi Desert located to the north of Tian Shan by the monsoon from Mongolia, obstructed by the high mountains and deposited on the windward slopes of the mountains. The rivers and flows then transported the aeolian loess to low terraces and piedmont alluvial plains.
基金Nature Science Foundation of China(40972230,40772116,40871018)National Basic Research Program of China(2010CB833406)Chinese polar scientific strategic studies fund of State Oceanic Administration(20070226)
