Micromorphological study of the gypsum and calcium carbonate features and clay mineralogy in soils with different parent material in south of Guilan province

Gypsiferous and calcareous soils comprise an important part of soil resources in arid and semiarid areas of south of Guilan province. This study in order to investigation of gypsum and lime in soils of the hilly lands of Aliabad region in Guilan province by soil thin sections was performed. Soil sampling as air-dried undisturbed clods from gypsiferous-salty and calcareous parent material with three replicate at two slope positions (back slope and foot slope) and into surface (0-20 cm) and subsurface (20-40 cm) depths was performed. Results showed that soils with gypsiferous-salty parent material had heavier textural class than the calcareous soils. The results of micromorphology showed that the number of channel and chamber voids and excrements is higher in calcareous soil due to the presence of larger pores and more biological activity. Micromorphological pedofeatures of gypsiferous-salty soils include the forms of gypsum interlocked plates, gypsum lenticular crystals, gypsum pendant, infilling of gypsum as dense complete and incomplete, and loose discontinuous in voids and channel walls and hypo-coating of iron and manganese and in calcareous soils include excrements, halow iron and micritic nodules, rock fragments, gypsum and calcite pendant and different forms of pedogenic calcite as columnar, cluster, needle, micritic and sparitic. The fine fraction in both soils were mainly crystalitic b-fabric and locally stipple speckeld and undifferentiated b-fabric. The micromorphological index for soil evolution index (MISECA) showed that both soils had weak development. Results of clay mineralogy showed that chlorite, illite, vermiculite, smectite and hydroxyl-interlayer minerals were prominent in in both soils. Furthermore, the difference between soils of two parent material was the presence of palygorskite mineral in gypsiferous-salty soil.