Effects of chemical and mineralogical properties of marls on different erosion types in the south of Guilan province

Marls in arid climates، are high erodeable regions that produce sediments. Erosional processes in marls are too active، especially in marl hillslopes، because of low amount of permeability and lack of vegetation cover. However، different erosional forms، particularly، badland erosion is one of the distinctive properties in marly lands. This research was conducted to study chemical and mineralogical properties effect on soil erosion froms in southern Guilan province. After field surveying، Soil samples taken from different erosional forms including sheet، rill، gully، badland and their parent materials. 12 samples from surface layer of each erosional form (48 samples، totally) selected. Then، chemical parameters such as، Electrical Conductivity، exchangeable and soluble cations، organic carbon، calcium carbonate، gypsum، Cation Exchangeable Capacity، and anions، were determined. 8 samples from marly soils and 2 samples from parent material prepared for X-Ray tests، too. Means of chemical parameters in different erosional forms compared with Duncan test. Statistical analysis showed that amounts of Electrical Conductivity and sodium ions had significant difference between all forms of erosion. While، other parameters، have no significant difference between all erosional forms. On the other hand، these parameters haven’t important role on erosion form and severness. Furthermore، XRD patterns of the clay fraction from surface layers showed smectitic presence in gullies and badlands. Whereas، there weren’t any expansible minerals in rill and sheet erosion. With respect to statistical results and X-Ray tests، this fact concluded sodium ions and smectitic clay minerals are the most important factors that control severness and form of erosion.