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The texture, structure, ionic and trace element composition of samples of fast (coastal-sea) and lake ice collected in 2014 in the area of Cape Marre-Sale (the North-Western Siberia) were analyzed. The following main types of the ice structure were identified in ice sections: firn ice with randomly oriented small crystals; lake large- and small-crystalline bubble ice; layered fast sea ice with small isometric and vertically elongated crystals. The upper part of the lake ice is formed by recrystallized snow containing marine aerosols and lake water. The coefficient of involvement of the main ions from the solution during the ice formation varies for lake ice from 0.02 to 1.51, for sea ice – from 0.10 to 0.23, and for coastal-marine - from 0.03 to 0.04. The difference in the degree of ion involvement into the lake ice is related to the sources of components entering the process of formation of firn and large ice crystals from lake water. Coastal sea ice has high concentrations of trace elements relative to the clarks of sea waters. The income of trace elements into the coastal sea ice is probably determined by continental runoff. It is established that the mineralization of seasonal ice increases with a decrease in the size of crystals. The dependence of the values of the Europium anomaly on the rate of ice formation was revealed. The Europium anomaly in coastal sea ice is inherited from seawater, and the upper part of lake ice is inherited from precipitation.

Structure of arctic peatlands with massive ice and structure-forming ice were studied in drained lake («khasyrey») of the Pur-Taz interfluves (the north of West Siberia). The period of accumulation of two-meter thickness of the peat was established to be changed from 8413±90 to 897±90 years BP. Composition of the peat deposits is represented by Betula nana, Sphagnum sp., Vaccinium oxycoccos, Eriophorum sp., Equisetum sp. The massive ice is represented by ice wedges with large shoulders and young ice wedges. The central part of the ice wedge is composed by recrystallized crystals of ice veins. Melting zones (elongated crystals of segregated ice and closed-cavity ice) were found in the shoulders of the ice wedge and in the upper part of the young ice wedge. Young ice wedges in the central and lateral parts the main wedge have a similar structure in the cross-section, but they are built by different genetic types of ice: the ice veins or closed-cavity ice with segregated ice. Ice-rich peat contains different types of ice inclusions and subhorizontal ice belts and ice lenses. Ice lenses in the peat can be formed by the segregated ice and/or infiltrated-segregated ice. The hydrochemical composition of the ice wedges, ice lenses, surface water samples and the aqueous extract from peat was analyzed. Hydrochemical analysis did show that polygonal-core ice has basically similar composition with the present-day atmospheric precipitation and surface waters of the polygonal bath; in the area of the shoulder – the composition is intermediate between the ground waters of peat and the central part of the vein. The hydrochemical composition of the ice lenses is similar to the composition of the lake water and peat underlying the active layer. The methane concentrations and its distribution within the ice wedges, peat and lens ice were determined. The closed-cavity ice doesn’t contain methane; the ice wedges with ice veins have minimal methane concentrations; large ice lenses have differentiation of methane concentrations. High concentrations of methane are typical for the frozen peat with inclusions of closed-cavity ice in the uppermost part of permafrost layer; the maximum methane concentration was determined inside the peat with ice lenses. The heterogeneous ices inside the ice wedges, distribution of hydrochemical compounds and methane distribution were conditioned by dynamics of the melting depth during the peatland formation under changing climate of the Holocene in the Arctic.

The syngenetic ice and ice-ground composite veins in khasyrey (alas) and interalas plateaus were studied on the second lake-alluvial terrace located in the North of the Gydan Peninsula near the village of Gyda. On the basis of the radiocarbon dating, the time of formation of deposits containing veins from was established – from 16 640 to 854 BP. The peat deposits are mainly represented by the following species: Carex sp., Eriophorum sp., Betula nana, Equisetum sp., Calamagrostis sp., Vaccinium vitis-idaea, Drepanocladus sp., Empetrum sp., Vaccinium uliginosum, Rubus arcticus, Petasites sp. It is established that the polygonal-veined ice of khasyrey and interalas plateaus, except for vertical-striped «clean» ice, contain areas with vertical wavy streaks of ice-ground. Ice of elementary veins and segregation ice were revealed in the composition of veins according to structural and textural features in polarized light. Elementary ice veins compose «clean» ice sections of veins and segregation ice which are their ice-ground sections. Elementary veins are indicative of the predominance of the process of frost cracking during the formation of polygonal-vein ices. The presence of inclusions of ice-ground in the structure of veins points is evidence of a manifestation of local thermokarst processes under the growth of polygonal-vein ice. Ice-ground veins were formed by repeated thawing of the initial ice veins. The formation of ice-ground veins during syngenetic freezing of sediments of the second lake-alluvial terrace is related to uneven manifestation of thermokarst in different facies situations and and climate changes at the Early Pleistocene and Holocene.