Comparing Soil Development in Two Topo-sequences with Different Parent Materials in Part of Karoon 3 Basin, East of Khuzestan Province

Soil evolution is affected by both parent material and topography as the two main factors of soil formation. This study was conducted to compare the effect of marl and calcareous parent materials in different slope positions, including the summit, back-slope, foot- and toe-slopes on soil development using evolutionary indicators along two topo-sequences in the Karoon 3 Basin, east of Khuzestan Province. Accordingly, four soil profiles in each of the two topo-sequences were dug and sampled based on their genetic horizons and properties including Fed, Feo, Fep and the magnetic susceptibility at 0.46, and 4.6 kHz frequencies were measured. The results showed that pedogenic iron (Fed) was higher for both parent materials in all slope positions at subsurface horizons as compared to those at the surface horizons. The results also showed that with increasing soil depth, especially in developed horizons such as Btk, the Fed-Feo index increased. In addition, the Feo/Fed ratio in all slope positions showed a decreasing trend with depth. The results also showed that the lowest χLF value corresponds to the C horizon in all slope positions in both the parent materials. The amount of χLF showed a positive and significant relationship with the clay contents of the soils. Still, no meaningful relationship was observed with the calcium carbonate content of the soils. The higher value of χfd index at the soils developed on the marl parent materials (in all slope positions) compared to those of the calcareous parent materials indicates more weathering in these soils than their corresponding soils in calcareous parent materials.