In this master's thesis, we investigated the mineralogical, geochemical, and pedological characteristics of soils in the Brkini Flysch Basin to compare the properties of soils developed on sandstone and siltstone. Soil samples were collected at three sites along a northwest-to-southeast transect, with a total of 15 samples taken from various soil horizons and the parent material.
We conducted standard pedological analyses, examined thin sections of rock samples under a transmitted polarized light microscope, and determined the mineral composition using X-ray powder diffraction (XRD). The chemical composition, including major oxides, trace elements, and rare earth elements (REEs) in both rock and soil samples, was analyzed using inductively coupled plasma emission spectroscopy (ICP-ES) and inductively coupled plasma mass spectrometry (ICP-MS).
The study revealed that Dystric Cambisols (WRB) or Inceptisols (USDA) have developed on sandstone, while Dystric Leptosols (WRB) or Entisols (USDA) are present on siltstone. All soils are moderate to heavy in texture, with variable particle size distribution. In all profiles, SiO₂ is the dominant oxide, followed by Al₂O₃ and Fe₂O₃. The primary minerals identified in all three profiles include quartz, plagioclase, muscovite/illite, and chlorite-group minerals.
Kruskal-Wallis variance analysis revealed significant differences in fine silt content, pH, Ca²⁺, Mg²⁺, and Na⁺ concentrations, as well as in the sum and saturation of base cations. The profiles also varied in their concentrations of Al₂O₃, Fe₂O₃, MgO, CaO, K₂O, MnO, and trace elements such as Ba, Cu, Ga, Ni, Rb, Zn, Zr, V, Sc, and Hf, along with most REEs. Compared to sandstone-derived soils, siltstone and its associated soils exhibited higher concentrations of all major oxides except for SiO₂ and Na₂O, as well as higher levels of trace elements and REEs, except for Cr, Zr, and Pb. Additionally, differences were observed in the intensity of XRD diffraction peaks and the relative proportions of mineral phases.
A Mann-Whitney U test comparing sandstone-derived soils confirmed pedological differences in the same parameters as those identified in the broader three-profile comparison. Notably, CaO and MnO concentrations were statistically distinct in sandstone-derived soils.
Comparisons with soils developed on similar lithological substrates of differing origins and ages indicate that, despite comparable parent materials, substantial variability exists in soil properties.
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