Abstract: Polygonal tundra histosols are among the most widespread soils of the Central Yamal Peninsula (around Bovanenkovo) together with Gleysols and Cryosols. The authors study the trench crossing the peat polygons on the surface of the third terrace near Bovanenkovo village. The authors study the transformation of sub-types of histosols from oligotrophic to eutrophic histic horizons. It is impossible to properly describe the soils of those flat-topped polygonal landscapes, according to the current classification of Russian soils, due to the small variety of organic horizons and strict criteria for their differentiation. The authors assigned Sphagnum horizon to the horizon T, and the underlying layer of eutrophic peat – to the TE horizon. Thus the authors classify such type of soil as eutrophic peat despite the presence of oligotrophic peat components. The age of peat was ascertained using the scintillation radiocarbon methodic. Carbon dioxide emission was measured by a portable gas-analyzer. The content of oxygen, carbon and nitrogen in the peat was measured as well as the composition of carbon stable isotopes . The considered Histosols are aged 2,5 thousand years. At the top of the polygonal mound in the profile the authors trace an increase in sulfur (apparently associated with the darker colored peat layer) and nitrogen content and a decrease in the carbon content. At the same time local maximum of the carbon isotope composition was observed. The carbon content varies in general from 45 to 28%. The carbon isotope composition is from –25.5 to –28 ‰, which is close to the values in organic horizons of soils in the Arctic regions.