Formation and evolution of soils formed on Quaternary sediments in some parts of Urmia Plain

Quaternary sediments have occupied most of the agricultural and natural resources of urmia region. Recognition of physicochemical and mineralogical properties of these soils is essential to optimum and stable use of these lands. In this study, eight soils profiles excavated on Quaternary sediments of Urmia region were investigated. The results showed that little thickness and evolution of studied soil was possibly due to the sequential soil erosion and sedimentation processes.Consecutive erosion-deposition processes at different periods led to the formation of calcic horizons and sedimentary layers in lower depths indicating climatic fluctuation, along with dissolution and translocation of carbonate in wetter periods as well as its deposition and accumulation in drier periodsClay mineralogical results revealed smectite, kaolinite, illite, chlorite and vermiculite as dominant clay minerals in the study area. Illite, cholorite and kaolinite mainly considered as inheritance fromthe parent materials while pedogenic formation explain the presence of vermiculite. Moreover, smectites was found to have three origins of inheritance, neoformation and transformation and its abundance was increased with depth. The origin of smectite in the buried horizons was attributed to the illite transformation. According to the heavy moisture demand on illite weathering, the occurrence of this process can be associated with more humid condition during the past climate. So the achieved results of present study can be a clue to recognize the climatic changes in the study area.