Magnetic measurement characterisation of red earth profile in eastern China and its environmental implications

Environmental magnetism parameters, including magnetic susceptibility (χ), anhysteretic remanent magnetization (ARM), saturation isothermal remanent magnetization (SIRM), Frequency dependent susceptibility (χ(fd)), magnetization parameters (F (+ xmT)) and demagnetization parameters (F (- xmT)), have been measured on a red earth profile from eastern China. The variation curves of ferrimagnetic mineral concentration, mineralogy assemblages and grain size of red earth profile with depth before and after iron oxides were removed by dithionite-citrate system buffered with sodium bicarbonate (DCB) were illustrated. On the basis of the magnetic properties of red earth, three distinctive stratigraphic horizons have been identified. The spherulitic magnetic particles were separated by magnetic separation method, indicating that the contribution of magnetism in red earth is maghemite, hematite and goethite. Results suggested that enhancement of magnetism and shift in magnetic domain and mineralogy assemblage are correlated with pedogenic environments. Frequency dependent susceptibility and the fraction of magnetic susceptibility that is removed by DCB treatment are attributed to the pedogenic ferrimagnetic component, suggesting that they are index of soil development degree. Thus, magnetism of red earth, an easily measured soil attribute, can be used to evaluate the environmental change of Quaternary in southern China.