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Molecular fossil and paleovegetation records of paleosol S4 and adjacent loess layers in the luochuan loess section, NW China

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Science China Earth Sciences 2008年第3期51卷 321-330页

作者： ZHANG HuCai YANG MingSheng ZHANG WenXiang LEI GuoLiang CHANG FengQin PU Yang FAN HongFang Key Laboratory of Western China’s Environmental Systems Ministry of EducationCollege of Earth and Environment SciencesLanzhou UniversityLanzhou 730000China State Key Laboratory of Lake and Environment Sciences Nanjing Institute of Geography and LimnologyChinese Academy of SciencesNanjing 210008China

Using gas chromatography-mass spectrometry (GC-MS) technique, a series of biomarkers were identi- fied, including n-alkanes, n-alkane-2-ones, isoprenoid etc. from the loess-paleosol samples collected from the S4 and adjacent L5, L4 of the luochuan loess section, Northwestern China. Based on these data, especially n-alkanes and high-resolution magnetic susceptibility and grain size data, the pa- leoenvironment and paleovegetation history during S4 was reconstructed. The CPI (Carbon Predomi- nance Index) and correlation between n-alkanes and magnetic susceptibility and grain size data dem- onstrated that the molecular fossils in paleosol and loess layers can reflect the vegetation condition during the loess-paleosol formation, if the allochthonous organic inputs could be excluded reasonably. The ACL (average chain length) index is correlated well with paleomagnetic susceptibility and grain size variations, displaying their good synchrony with warm and humid climate. However, it relatively lagged behind the paleomagnetic susceptibility and the grain size variations when the climate began to deteriorate. During the formation period of paleosol, the n-alkanes was dominated by C31 homologue, indicating that the primary organic input originated from herbs. Our study also demonstrated that the herbs were more flourish than wood plants in Loess Plateau, especially in the luochuan area during the warm and humid phase, and there was no typical forest vegetation developed in the studied period.

关键词： paleoenvironment Paleosol S4 luochuan loess section biomarker paleovegetation

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High-resolution anisotropy of magnetic susceptibility record in the central Chinese Loess Plateau and its paleoenvironment implications

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Science China Earth Sciences 2012年第3期55卷 488-494页

作者： LIU WeiMing SUN JiMin Key Laboratory of Cenozoic Geology and Environment Institute of Geology and GeophysicsChinese Academy of SciencesBeijing 100029China Key Laboratory of Mountain Hazards and Earth Surface Process Institute of Mountain Hazards and EnvironmentChinese Academy of SciencesChengdu 610041China

We analyze high-resolution anisotropy of magnetic susceptibility (AMS) of the loess-paleosol successions at luochuan, central Chinese Loess Plateau, in order to investigate the AMS characteristics and their climatic implications. Our results indicate a normal sedimentary magnetic fabric for almost of all samples, characterized by minimum susceptibility axes grouped in an almost vertical direction. Magnetic foliation and anisotropy degree show upwards decreasing trend due to decreasing post-depositional compaction. Magnetic lineations show no preferred directions and thus cannot indicate paleowind patterns. AMS parameters at luochuan are controlled by particle size, pedogenesis, and sedimentary compaction. The high peaks of magnetic foliation and anisotropy degree of L2, L3, L6, L9, and L15 correspond to the coarse particle sizes of these loess beds, indicating the grain-size dependence of AMS.

关键词： Chinese loess anisotropy of magnetic susceptibility Quaternary luochuan

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High-resolution anisotropy of magnetic susceptibility record in the central Chinese Loess Plateau and its paleoenvironment implications

High-resolution anisotropy of magnetic susceptibility record...

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中国科学院地质与地球物理研究所2012年度（第12届）学术年会

作者： LIU WeiMing SUN JiMin Key Laboratory of Cenozoic Geology and Environment Institute of Geology and GeophysicsChinese Academy of Sciences Key Laboratory of Mountain Hazards and Earth Surface Process Institute of Mountain Hazards and EnvironmentChinese Academy of Sciences

We analyze high-resolution anisotropy of magnetic susceptibility(AMS) of the loess-paleosol successions at luochuan,central Chinese Loess Plateau,in order to investigate the AMS characteristics and their climatic *** results indicate a normal sedimentary magnetic fabric for almost of all samples,characterized by minimum susceptibility axes grouped in an almost vertical *** foliation and anisotropy degree show upwards decreasing trend due to decreasing post-depositional *** lineations show no preferred directions and thus cannot indicate paleowind patterns. AMS parameters at luochuan are controlled by particle size,pedogenesis,and sedimentary *** high peaks of magnetic foliation and anisotropy degree of L2,L3,L6,L9,and L15 correspond to the coarse particle sizes of these loess beds, indicating the grain-size dependence of AMS.

关键词： Chinese loess anisotropy of magnetic susceptibility Quaternary luochuan

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