Permafrost and Gas Hydrate Stability Zone of the Glacial Part of the East-Siberian Shelf

Abstract

By using thermal mathematical modeling for the time range of 200,000 years ago, the authors have been studying the role the glaciation, covered the De Long Islands and partly the Anjou Islands at the end of Middle Neopleistocene, played in the formation of permafrost and gas hydrates stability zone. For the modeling purpose, we used actual geological borehole cross-sections from the New Siberia Island. The modeling was conducted at geothermal flux densities of 50, 60, and 75 mW/m2 for glacial and extraglacial conditions. Based on the modeling results, the glaciated area is characterized by permafrost thickness of 150–200 m lower than under extraglacial conditions. The lower boundary of the gas hydrate stability zone in the glacial area at 50–60 mW/m2 is located 300 m higher than the same under extraglacial conditions. At 75 mW/m2 in the area of 20–40 m isobaths, open taliks are formed, and the gas hydrate stability zone was destroyed in the middle of the Holocene. The specified conditions and events were being formed in the course of the historical development of the glacial area with a predominance of the marine conditions peculiar to it from the middle of the Middle Neopleistocene.