Magnetic susceptibility as a pedogenic proxy for grouping of geochemical transects in landscapes

Magnetic susceptibility (χ lf) is a sensitive, fast, and accurate technique to detect soil pedogenic processes and features, and can improve understanding of soil-forming factors. The aim of this study was to determine catenary groupings of geochemical segments by identifying the relationship between magnetic susceptibility and the soil-forming factors within and along the landscape. Soil physical and chemical properties, as well as soil mineralogy were evaluated in twenty-two topsoil samples from three different landscapes in southern Brazil. The bulk χ lf and frequency-dependent susceptibility (χ fd) were also measured, represented by i) air-dried fine earth (< n μm, χ lf ADFE) ii) after dithionite-citrate-bicarbonate treatment (χ lf CBD), and iii) the parent material (χ lf ROCK). Geochemical segments were grouped using multivariate analysis. Our results indicate that soil parent material and climate, are first order factors for the pedogenic enhancement of magnetic minerals. Magnetic susceptibility of air-dried fine earth (χ lf ADFE) is widely variable, from 11.00 to 2.075 × 10 −8 m 3 kg −1. χ lf was higher in soils developed on basalt, and much lower for soils developed on sandstone. χ lf ADFE also reveals a strong positive linear correlation with χ lf CBD (r = 0.96) and a moderate positive linear correlation with “free” and total Fe content (r = 0.49 and 0.69, respectively). The χ fd (< 2%) indicates samples in which either non-SP grains dominate the assemblage or where the SP fraction is