Study on the Magnetic Susceptibility of the Xiashu Loess and the Paleoenvironment Changes in the Middle and Lower Changjiang River

ZHANG Jian jun; YANG Da yuan; CHEN Yue you; LI Xu sheng; JIANG Hong jun

The stufy of loess-paleosol sequence reveals the magnetic susceptibility is of indexical significance in identifying loess-paleosol and their progression in the loess section,but also in simulating the changes of paleoenvironment.The magnetic susceptibility is also of indexical significance to Xiashu loess.Therefore,we gathered 595 sample blocks for the study in Zhenjiang Dagang section,which is located in the lower reaches of the Changjiang River. On the basis of systematic testing,we obtain a magnetic susceptibility curve of Dagang section.Compared with the other Xiashu Loess sections in this area,the magnetic suscreptibility curve of Xiashu Loess indicates that the loess-paleosol sequence of Dagang section represented 7 large climatic cycles since the Middle-Pleistocene.It is similar to that disclosed from the other Xiashu sections and the loess-paleosol sequence in north China,reflecting that the middle and lower Changjiang River regions have undergone the same course of the paleoclimate changes in the north China since the Middle-Pleistocene.Comparative study also demonstrates that the extent of the paleoclimate changes is much smaller than that in the loess area in north China.There are frequently minor undulations of climate in both the warm period and the cold period,comparable to the δ¹⁸O stage of deep sea.The study also found the sedimentation rate and the depositional environment of Xiashu Loess varied in different area in the middle and lower Changjiang River region. The study of the magnetic susceptibility curve indicates there were a small quantites of aeolian accumulation in the interglacial warm period. S₁ and S₂ in the magnetic susceptibility curve of Dagang section can be divided into S₁a, S₁b, S₁c and S₂a, S₂b, S₂c respectively. S₁a, S₁b and S₁c of S₁ correspond to 5a,5b and 5c of the δ¹⁸O stage of deep sea,supporting that the climate changes of the middle and lower Changjian River region are largely affected by the ocean. Climate changes of the middle and lower Changjiang River region are quite sensitive to global changes.

Study on the Magnetic Susceptibility of the Xiashu Loess and the Paleoenvironment Changes in the Middle and Lower Changjiang River

1. Department of Geology & Ocean Sciences, Nanjing University, Nanjing 210093;

2. Zhenjiang Prospecting and Magpping Institute Zhenjiang Jiangsu 212000

Received Date: 1998-10-28

Rev Recd Date: 1999-04-02

Publish Date: 2000-03-10

Key words:

Abstract: The stufy of loess-paleosol sequence reveals the magnetic susceptibility is of indexical significance in identifying loess-paleosol and their progression in the loess section,but also in simulating the changes of paleoenvironment.The magnetic susceptibility is also of indexical significance to Xiashu loess.Therefore,we gathered 595 sample blocks for the study in Zhenjiang Dagang section,which is located in the lower reaches of the Changjiang River. On the basis of systematic testing,we obtain a magnetic susceptibility curve of Dagang section.Compared with the other Xiashu Loess sections in this area,the magnetic suscreptibility curve of Xiashu Loess indicates that the loess-paleosol sequence of Dagang section represented 7 large climatic cycles since the Middle-Pleistocene.It is similar to that disclosed from the other Xiashu sections and the loess-paleosol sequence in north China,reflecting that the middle and lower Changjiang River regions have undergone the same course of the paleoclimate changes in the north China since the Middle-Pleistocene.Comparative study also demonstrates that the extent of the paleoclimate changes is much smaller than that in the loess area in north China.There are frequently minor undulations of climate in both the warm period and the cold period,comparable to the δ¹⁸O stage of deep sea.The study also found the sedimentation rate and the depositional environment of Xiashu Loess varied in different area in the middle and lower Changjiang River region. The study of the magnetic susceptibility curve indicates there were a small quantites of aeolian accumulation in the interglacial warm period. S₁ and S₂ in the magnetic susceptibility curve of Dagang section can be divided into S₁a, S₁b, S₁c and S₂a, S₂b, S₂c respectively. S₁a, S₁b and S₁c of S₁ correspond to 5a,5b and 5c of the δ¹⁸O stage of deep sea,supporting that the climate changes of the middle and lower Changjian River region are largely affected by the ocean. Climate changes of the middle and lower Changjiang River region are quite sensitive to global changes.

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Reference (13)

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Study on the Magnetic Susceptibility of the Xiashu Loess and the Paleoenvironment Changes in the Middle and Lower Changjiang River

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