Antonio Sánchez Navarro

Magnetic and pedological characterisation of a paleosol under aridic conditions in Spain

The systematic use of magnetic techniques for the characterization of soils is still scarce despite its great potential for the identification of pedogenetic processes. The main objective of this study is to analyze the magnetic properties of a soil profile with contrasting horizons and try to relate them to the properties determined through conventional techniques. The horizons of a soil profile located in a tectonic depression in Murcia, Spain are described and their physical, chemical, and mineralogical properties analyzed with conventional techniques. The following magnetic properties are included in the study: the mass-specific magnetic susceptibility, frequency-dependent susceptibility, continuous thermomagnetic curves at low field, isothermal remanent magnetization acquisition and the estimation of magnetic hardness (coercitivity) through the parameter S-200. Detailed description of the soil profile and the results of conventional analyses allowed the identification of a mollic horizon, an argic horizon, and a calcic horizon, as well as a textural discontinuity. Apparently, pedogenic magnetite occurs in the A horizon and is responsible for the magnetization in most cases. The magnetic carriers in the Bt horizons are superparamagnetic particles and they are related to the high percentage of clay. High coercivity minerals (hematite and probably goethite) were detected in different concentrations in all soil horizons. The amount of ferrimagnetic minerals decreases with depth. The magnetic properties allowed a better characterization of the diagnostic horizons. The results and information derived from the analysis of the magnetic properties could not be obtained using conventional soil analysis only.