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Permafrost evolution in Western Yamal region during Late Quaternary Period inferred from the analysis of ground ice compositionтезисы доклада
- Авторы: Gleb Oblogov, Irina Streletskaya, Alexander Vasiliev, Georgii Artyukov
- Сборник: Book of Abstracts of EUCOP4 – 4th European Conference on Permafrost, 18-21 June 2014 - Évora, Portugal
- Тезисы
- Год издания: 2014
- Место издания: Evora, Portugal
- Первая страница: 299
- Последняя страница: 299
- Аннотация: Polygonal ice wedges and massive ground ice bodies are characteristic features of Western Yamal and are often found within the same geological section. Two-layered syngenetic ice wedges were formed during two cold periods separated by the Holocene Thermal Optimum. Radiocarbon dating showed the lower layer was formed during the Last Glacial Maximum (MIS 2) about 20-11 ka BP. The upper layer formed after the Holocene Thermal Optimum about 4-3 ka PB (MIS 1). The oxygen stable isotope content (δO18) of the Pleistocene wedges is on average 6 ‰ lighter than the Holocene one. Paleotemperature reconstruction based on stable isotope content showed that average winter temperature of the Holocene was 5-6⁰C below present during wedge formation, and end of the Late Pleistocene was 18-20⁰C colder than present. Massive ground ice bodies are presented by two types. One type is lenticular bodies up to 1.5 m thick found in sandy-loam and sandy sediments of Pleistocene age (MIS3). Homogeneous distribution of stable isotopes of oxygen and hydrogen which line up close to the Global Meteoric Water Line and deuterium excess close to 10‰ indicate that the water has predominantly atmospheric origin. Significant concentration of methane of bacterial genesis (up to 26 ml / kg) found in air inclusions within the ice precludes its glacial origin. Rather water-saturated sediments were syngenetically frozen in the coastal marine environment. Second type of ice is thick (more than 30 m) and found in clay deposits of marine origin. Stable isotope content of ice indicates that water was exposed to fractionation before freezing. Presence of mineral inclusions of marcasite (FeS2) and high content of sulfate ions in the ice indicate the hydrogen sulfide contamination of water before freezing. Such conditions are characteristic of the freezing of shallow sea water. New results of the chemical, isotopic, and gas composition of ground ice allow to reconstruct the genesis, age and formation conditions of ground ice at the Western Yamal in Late Pleistocene-Holocene.
- Добавил в систему: Стрелецкая Ирина Дмитриевна