Magnetic susceptibility of soils along a lithotoposequence in southeast Iran

• Diamagnetic material reduced soil magnetic susceptibility.
• Soil χlf were influenced by parent material, relief and soil forming processes.
• The χlf was affected by soil formation processes, where parent material was similar.
• Soil χlf values decreased with increasing soil development.

Magnetic susceptibility (χ) is a simple and quick technique to determine soil properties and to describe soil forming processes. Knowledge about factors affecting χ data helps better interpretation. Magnetic susceptibility of soils along a lithotoposequence was studied in this research in order to investigate the effects of soil forming factors (parent material and relief) and processes on the χ content and its vertical distribution. The study area is a transect from Jiroft to Kahnooj area, south Kerman Province, Iran. Rock pediment, mantled pediment, inselberg, alluvial fan, alluvial plain, and flood plain landforms with igneous parent materials (gabbro, diorite, and granite) were selected in the area. Thirteen representative pedons on different geomorphic positions were studied. Low frequency χ (χlf) values ranged from 193.1 × 10− 8 m3 kg− 1 to 2704.2 × 10− 8 m3 kg− 1 in studied soils and decreased with increasing diamagnetic material contents. Mean χlf values in soils formed on gabbro, diorite, and granite parent rock were > 1700 × 10− 8 m3 kg− 1, 515.22 × 10− 8 m3 kg− 1, and 352.53 × 10− 8 m3 kg− 1, respectively. Frequency dependent χ of soils (in the range of 0.06 to 1.05%) showed that coarse multi domain grains inherited from igneous parent material were the main source of χlf in the area under study. Both increasing and decreasing trends of χlf with depth were observed. Decreasing trend of χlf with depth was due to illuviation of diamagnetic material into subsurface layers. On the other hand, increasing χlf with depth was attributed to the primary ferrimagnetic material inherited from igneous parent material. Alluvial plain (320.44 × 10− 8 m3 kg− 1) and mantled pediment (328.50 × 10− 8 m3 kg− 1) showed low values of χlf due to high amounts of soluble salts, anhydrite, and calcium carbonate investigated in these geomorphic positions. A positive significant relationship (R2 = 0.018; r = 0.27, P < 0.05) between χlf and Feo/Fed activity ratio was found. Soil χlf decreased with development and relative dating of soils. Results of the study showed that soil χlf values were highly affected by parent material, relief, and soil development.