Environmental Magnetism of Magnetic Enhancement forSoils Formed on Quaternary Sediments in Yangtze River Valley

LU Sheng gao; YU Jin yan; ZHANG Ming kui; YU Li zhong; ZHANG Wei guo

On the basis of environmental magnetism study on soils formed on Quaternary sediments in Yangtze River valley,the soil magnetic enhancement and its mechanism were discussed.Results showed that soils formed on Quaternary sediments exhibited a distinct ferrimagnetic profile with the magnetic susceptibility enhancement of soil horizons with respect to that of parent materials. It is suggested that formation of pedogenic ferrimagnetic minerals resulted in enhancement of magnetic susceptibility in soils.In addition,the pedogenic ferrimagnetic minerals are mostly superparamagnetic(SP) and stable single domain(SSD)grains.It is found that highly significant relationships between the magnetic susceptibility( χ ) values of the samples and frequency dependent susceptibility ( χ fd ) and between χ values of samples and anhysteretic susceptibility( χ ARM ).It is suggested that χ can be considered an indicator for the environmental fluctuation recorded in soils. Results also suggested that χ fd value of 5% can be regarded as an indicator to reflect the formation of pedogenic SP and SSD ferrimagnetic minerals in the continuous pedogenic development of soils.Thus,magnetic susceptibility can be used to study the Quaternary environmental changes.

1 Zhejiang University,Hangzhou 310029;

2 East China Normal University,Shanghai 200062

Received Date: 1999-01-19

Publish Date: 2000-09-10

Key words:

Abstract: On the basis of environmental magnetism study on soils formed on Quaternary sediments in Yangtze River valley,the soil magnetic enhancement and its mechanism were discussed.Results showed that soils formed on Quaternary sediments exhibited a distinct ferrimagnetic profile with the magnetic susceptibility enhancement of soil horizons with respect to that of parent materials. It is suggested that formation of pedogenic ferrimagnetic minerals resulted in enhancement of magnetic susceptibility in soils.In addition,the pedogenic ferrimagnetic minerals are mostly superparamagnetic(SP) and stable single domain(SSD)grains.It is found that highly significant relationships between the magnetic susceptibility( χ ) values of the samples and frequency dependent susceptibility ( χ fd ) and between χ values of samples and anhysteretic susceptibility( χ ARM ).It is suggested that χ can be considered an indicator for the environmental fluctuation recorded in soils. Results also suggested that χ fd value of 5% can be regarded as an indicator to reflect the formation of pedogenic SP and SSD ferrimagnetic minerals in the continuous pedogenic development of soils.Thus,magnetic susceptibility can be used to study the Quaternary environmental changes.

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Environmental Magnetism of Magnetic Enhancement forSoils Formed on Quaternary Sediments in Yangtze River Valley

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