Investigation of Formation and Development of Gypsiferous Soils of Jiroft and Anbarabad Regions, South of Kerman Province

For better management of gypsiferous soils, it is essential to have knowledge about distribution and its various characteristics. The objectives of the present research included soil genesis studies, classification, micromorphology and clay mineralogy of gypsiferous soils in Jiroft and Anbarabad regions, located in the south of Kerman Province. For this purpose, seven representative pedons were selected, described and sampled. Routine physicochemical, micromorphological and clay mineralogy analysis were performed on the soil samples. Finally, the soils were classified according to two systems: Soil Taxonomy (2014) and WRB (2015). The origin of gypsum in the soils of the studied area was gypsum marl formations at altitudes. Soils of the region were classified using Soil Taxonomy system in two suborders of gypsids and salids, and classified according to the WRB in three soil reference groups of Gypsisol, Solonchak and Slonetz. Coating and lenticular gypsum crystals and clay coating were observed in the thin sections of the studied soils. Lenticular gypsum crystals were observed in fine-textured soils. The clay coatings observed in the natric and argillic horizons were due to the role of sodium dispersion and paleoclimate, respectively. Illite, chlorite, smectite, kaolinite, sepiolite and palygorskite clay minerals were found in the soils of the regions. The presence of gypsum in the soil and evaporitic formations in the area caused the formation of palygorskite and sepiolite minerals in the soil. An inverse relationship was found between the amount of palygorskite and sepiolite with the amount of smectite, so that due to more weathering in the more humid paleoclimate and with reducing the amount of gypsum, the amount of smectite increased and that of palygorskite and sepiolite minerals decreased.