Soil characterization using patterns of magnetic susceptibility versus effective radium concentration
- 1Équipe de Géomagnétisme, Institut de Physique du Globe de Paris, UMR7154, CNRS-Université Paris Diderot, Sorbonne Paris Cité, 1 rue Jussieu, 75238 Paris cedex 05, France
- 2Équipe de Paléomagnétisme, Institut de Physique du Globe de Paris, UMR7154, CNRS, 1 rue Jussieu, 75238 Paris cedex 05, France
- 3National Seismological Centre, Department of Mines and Geology, Lainchaur, Kathmandu, Nepal
Abstract. Low-field magnetic susceptibility χm and effective radium concentration ECRa, obtained from radon emanation, have been measured in the laboratory with 129 soil samples from Nepal. Samples along horizontal profiles in slope debris or terrace scarps showed rather homogeneous values of both χm and ECRa. One sample set, collected vertically on a lateritic terrace scarp, had homogeneous values of ECRa while χm increased by a factor of 1 to 10 for residual soils and topsoils. However, for a set of samples collected on three imbricated river terraces, values of ECRa, homogeneous over a given terrace, displayed a gradual increase from younger to older terraces. By contrast, χm showed more homogeneous mean values over the three terraces, with a larger dispersion, however, for the younger one. Similarly, Kathmandu sediments exhibited a large increase in ECRa from sand to clay layers, while χm increased moderately. The combination of χm and ECRa, thus, provides a novel tool to characterize quantitatively various soil groups and may be of interest to distinguish modes of alteration or deposition histories.