Genesis, Micromorphology and Clay Mineralogy of Soils Located on Different Geomorphic Surfaces in Jiroft Area

Geomorphology and soil genesis and its development are closely related. Besides, soil-landscape studies provide a better understanding of soil forming processes. The objectives of the present research include soil genesis studies, micromorphology and clay mineralogy of soils related to geomorphic surfaces in Jiroft area. Soil temperature and moisture regimes of the area are hyperthermic and aridic respectively. Alluvial fan, mantled pediment, intermediate surfaces, alluvial plain, and lowland landforms were identified. Each landform was divided into different surfaces due to geomorphic stability. One representative pedon was studied and sampled on each geomorphic surface. Routine physicochemical, clay mineralogy, and micromorphology analysis were performed on soil samples. The results showed that electrical conductivity, pH, and SAR contents increased from mantled pediments toward lowland positions. Besides, fine soil textures were found in downward positions. Chlorite, illite, palygorskite, smectite, and kaolinite clay minerals were found. Moving down toward alluvial plain, palygorskite stability decreased due to high water table, that is why smectite is the dominant clay mineral in alluvial plain. Source of palygorskite in mantled pediment, intermediate surfaces, and alluvial plain is inherited, pedogenic, and detrital respectively. Clay coating and infillings in Btn and Btk horizons of stable and unstable surfaces were investigated during thin section observations. Besides, calcite coating and infilling were found in Btk horizon at stable geomorphic surfaces. Results of the present research show that difference in soil characteristics is highly affected by geomorphology.