Parent rock derived soils and Mineralogy in forests of Amlash (Guilan province)

In order to identify the minerals in bedrocks of shale, tuff, basalt and soils derived from these rocks, three soil profiles were dug in footslope position in three forest lands of Guilan province. Based on results, pyroxene, biotite, feldspar and smectitic clay minerals were dominant in shale. Higher amount of smectite has resulted in decrease in soil drainage and illuvial clays as well as increase in stress cutan. In tuff, Na-plagioclase exists in higher amount. However there was lower smectite in soils derived from tuff due to acidic pH, so higher illuvial clay were observed in substratum. In basalt, weathering process was prominent, because there were higher amount of Ca-plagioclase and mafic minerals such as pyroxene and olivine, hence higher amount of clay mineral production especially smectite was provided. Well-permeability in surface soils of basalt was an important factor for remarkable illuvial clay accumulation in sub-surface soils.