Origin and Distribution of Clay Minerals in Calcareous, Gypsiferous, Saline Soils and Sediments of Bakhtegan Lake Bank, Southern Iran

Pedogenesis and clay mineralogy of soils and rock samples were studied in atransect of calcareous, gypsiferous, saline soils and sediments of Bakhtegan lake bank insouthern Iran. The main objectives of study were to determine the occurrence of clay mineralsand factors controlling their distribution pattern and relative abundance in soils and parentmaterials. The soil parent material is highly calcareous in all regions. However, gypsiferous andsaline soils mainly occur near the Bakhtegan Lake with much evaporitic sediments (gypsum andhalite) and where there is a saline and alkaline ground water table. XRD, TEM, SEM and EDXanalyses indicated that chlorite, illite, palygorskite, smectite and interstratified minerals are thedominant clay minerals in both soil and rock samples. The presence of illite, chlorite abundancecould be attributed to the parent rock samples and inherited origin. Interstratified minerals ofchlorite-smectite or illite-smectite are observed in clay fraction of soils situated in plains anddown slope due to further weathering and transportation from upslope to down slope. Studiesindicated the presence of neoformed, transformed and inherited forms of palygorskite in allsoils. Studies have showed that arid soils in southern Iran were affected by post-Tethyansediments and some minerals have evolved from the weathering of these sediments.