ИСТИНА

Presented and discussed the new data of methane quantity, isotopic values 13C and D in methane, and water stable isotopes of two climatically contrasted Holocene and Pleistocene syngenetic ice wedges (SIW) and two types of intrasedimental ground ice near Marre-Sale polar station, West Yamal, Russia. The first type of intrasedimental ground ice is large massive tabular ice bodies (MI) more than 25 m thick. The second type of intrasedimental ground ice is icy sediments (IS) not more than 2-3 m thick contained excess ice and have a volumetric ice content in the 60 to 100% range. The extraction of gases accomplished following the dry extraction technique, a large sample of ice (∼100 g) is crushed in a stainless steel cylinder to release the gases. Methane values in gas bubbles of SIW show close the range in Holocene Pleistocene ice (not more 0.8pm). Methane entrapped in MI and IS show the high content (till 23pm). The round gas bubbles are unevenly distributed in the MI. Relative concentration of methane in ice is adjustable within 0.2 to 23.4pm. A lot of round 1-3mm diameter bubbles are distributed evenly in IS, and relative concentration of methane in ice varies between 4.6-17.1pm. Such a distribution of bubbles suggests syngenetic for IS and sediments, and epigenetic for MI freezing conditions. One approach that has been used with success to determine the origin of methane is the analysis of the δ13C and D value of CH4 gases. Our data of isotopic measurements of the 13C -70,5pm, and D -326pm in methane are typical for gas formed with the participation of vital functions of bacteria. It is difficult to select potential sources bubbles trapped gas in intrasedimental ground ice. This heterogeneous medium, rich in organic matter, might have favored the anaerobic microenvironmental conditions necessary to explain the maximum methane content levels. Marshy coasts near shallow seas may have contributed to such conditions. The content of marsh gas in intrasedimental ground ice excludes their glacial origin. Found that the isotopic values 13C in methane are close to the values of the carbon isotopes of methane horizons at depths of 46-52 and 114-120 m in the Bovanenkovo gas field, West Yamal, and characterized of same isotope volume -70,4 -76,8pm. Source of methane in intrasedimental ground ice could not be methane hydrates, because methane hydrates have a specific deuterium isotopic signature of about -190pm, versus about -290pm for mean of other sources. It is assumed that the methane originally located within the intrasedimental ground ice and late ice thawed, and voids were filled up gas. This study detailed gas content and composition, and water and gas isotope analyses of ground ice sheds more light on the conditions of ground ice growth under changing environmental conditions.