Some physico-chemical, clay mineralogical and micromorphological characteristics of loess-paleosols sequences indicators of climate change in south of Gorgan

One of the best indicators of the geological and environmental events in the Quaternary is the alternation of loess-paleosol. In this study, for paleoenvironmental identification of buried paleosols in loess sequences, 14 sections located between 36˚ 49′ 6˝ to 36˚ 49′ 20˝ northern latitude and 54˚ 26′ 45˝ to 54˚ 26′ 52˝ eastern longitude in the southern part of Gorgan (Kharazmi town) were studied. The disturbed soil samples for physico-chemical analysis and clay mineralogy and undisturbed samples for prepration of thin sections were collected. The physico-chemical results (calcium carbonate content, particle size distribution, cationexchangable capacity and Feo/Fed) indicated that the soils had experienced several pedogenic periods. The result of mineralogy showed that a high amount of smectite, vermiculite and mixed layer mica-smectite in paleosols compared to loess deposits probably indicates moister regims through interglacial compared to glacial periods. The micromorphological observations revealed many evidences on the occurance of pedogenic processes. One of the most important index of pedogenesis, clay coating and hypocoating around void are presented only in buried paleosols, which is the evidence for moist climate conditions, enough for leaching and translocation of clay. Formation of the studied loess and paleosols, probably took place in glacial and interglacial cycles with different climate condition, respectively.