Characterizing and Study of Clay Minerals in a Loess- Paleosol Sequence, (Case Study: Neka Area)

Loess–paleosol sequence is a valuable information source related to previous climate of the environment. Studying clay minerals is a suitable index for evaluation of climate change in previous conditions. The aim of this study was to study the evolutionary and mineralogical indices according to Infrared Spectrum Transformation and analyzing X-ray Diffraction in a loess–paleosol sequence in Neka region, Mazandaran Province. For this purpose, a transect was selected and were conducted. Disturbed and undisturbed soil samples from 13 identified horizons and layers were selected for physical, chemical and mineralogical analysis. Results showed that studied soil experienced four soil formation stages. Mineralogy results showed that in paleosol, presence of weathered minerals like smectite, vermiculite and mixed minerals including smectite-ilite represent moister and weathering-favorable conditions during interglacial period. Presence of primary clays and without evolution as loess covers represents glacial arid and cold conditions. Results of investigations indicated that at initial stages of soil weathering and development, it is possible to releasing non-crystalline (active) iron from soil minerals being more than crystalline (pedogenic) iron and cause increasing Feo/Fed ratio, while by increasing soil age and degree of evolution, pedogenic iron increases and reduces the ratio. Mineralogy using infrared spectroscopy confirmed presence of kaolinite in old horizons.