| Paleoclimate and Environment Evolution |
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| Paleoenvironmental Significance of Magnetic Susceptibility and Grain Size of Lake Sediments from Gaxun Nur, Inner Mongolia, China |
| WANG Jun-lan1, LI Hui1, DENG Wei2, GUO Xiao-yan1, LI Shuang1, ZHANG Jia-wu1 |
1.MOE Key Laboratory of Western China’s Environmental Systems/Research School of Arid Environment & Climate Change, Lanzhou University, Lanzhou 730000, China;
2.Gansu Institute of Geological Survey, Lanzhou 730000, China |
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Abstract Grain size and magnetic susceptibility information of lake sediments have been widely used in palaeoenvironment and paleoclimate research. However, the relationship between these two parameters is different due to different types, sources, and particle sizes of magnetic minerals in different regions. In order to identify the environmental change information and the magnetic mineral sources and their occurrence states in lake sediments from arid regions in northwest China, we analyzed the magnetic susceptibility and grain size of the lake sediments along a section in Gaxun Nur, Inner Mongolia, in combination with rock magnetic information. Results show that the magnetic susceptibility of the bottom and the top of the section is positively correlated to the content of coarse sand; the magnetic susceptibility in the middle part of the section is positively correlated to the content of fine sand. The main magnetic minerals down the middle part of the section are ferrimagnetic minerals with small amount of paramagnetic materials (maghemite+magnetite). The main magnetic minerals in the upper part of the section are paramagnetic materials with some ferrimagnetic minerals (magnetite+maghemite). Three stages of environmental change could be identified from the section of Gaxun Nur: the flood plain (200~105 cm), shallow lake (105~36 cm) and near-shore environment (36~0 cm). Fractions of <4 μm and 4~64 μm mainly reflect the changes of water dynamics, which is determined by the detritus compositions and hydrodynamic conditions. The >64 μm coarse sand components in the flood plain period may have been transported by wind. Coarser grain size and higher magnetic susceptibility in the flood plain and the near-shore periods indicate decreased lake level with increased hydrodynamics and more magnetic mineral flow into the lake with sand components. Finer grain size and lower magnetic susceptibility during the shallow lake period suggest relatively higher lake level with lowered hydrodynamics and less magnetic mineral flow into the lake with coarser components.
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Received: 23 October 2011
Published: 20 May 2012
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Cite this article:
WANG Jun-lan, LI Hui, DENG Wei, GUO Xiao-yan, LI Shuang, ZHANG Jia-wu. Paleoenvironmental Significance of Magnetic Susceptibility and Grain Size of Lake Sediments from Gaxun Nur, Inner Mongolia, China. JOURNAL OF DESERT RESEARCH, 2012, 32(3): 661-668.
URL:
http://www.desert.ac.cn/EN/ OR http://www.desert.ac.cn/EN/Y2012/V32/I3/661
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2012, Vol. 32 
