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Oxygen and Hydrogen Isotope Compositions of Lithalsa Frozen Core: A Case Study from the Sentsa Valley, East Sayanстатья Перевод
Дата последнего поиска статьи во внешних источниках: 16 февраля 2016 г.
- Авторы: Vasil’chuk Yu K., Alekseev S.V., Arzhannikov S.G., Alekseeva L.P., Budantseva N.A., Chizhova Ju N., Arzhannikova A.V., Vasil’chuk A.C., Kozyreva E.A., Rybchenko A.A., Svetlakov A.A.
- Журнал: Earth's Cryosphere
- Том: 19
- Номер: 3
- Год издания: 2015
- Издательство: Izdatel'stvo Sibirskogo Otdeleniia RAN
- Местоположение издательства: Russian Federation
- Первая страница: 52
- Последняя страница: 63
- Оригинальные версии: Изотопный состав ледогрунтового ядра минеральных бугров пучения в долине реки Сенца, Восточный Саян
- Аннотация: Mineral permafrost mounds (lithalsas) have been studied in the Sentsa River valley (East Sayan Mountains, western Buryatia). This is the first detailed study of permafrost in the area based on analysis of cryostructures and distribution of stable isotopes in lithalsa intrusive-segregation ice. • Lithalsas often grow in fine-grained permafrost sediments in mountain depressions. They found in Eastern Sayan, Northern and Southern Tibet, the Altai Mountains and Central Ands. Morphological features of lithalsas in different regions of the Earth are similar: their height varies from 5 to 10 m, diameter from tens to hundreds of metres. Cryogenic structure of the ice core is mainly reticulate. • Lithalsas often start to grow during lowering of lake levels. The main source of water for the ice core is pore water from sediments, but some lithalsas partly fed by precipitation or by lake water. The rate of lithalsa growth is rather high – about tens of centimetres per year. Lithalsas 50-100 years old may be more than 5 m high. • As a rule, the range of δ18О values of lithalsa ice is 3-4‰, and δD values – 20‰. More positive isotope values usually mark the level of freezing onset. • Ice-rich sediments studied in the Sentsa River valley are the ice cores of lithalsas. • Vertical and lateral distribution of δ18О and δD values show a step-by-step mechanism of lithalsa growth in Sentsa River valley: at the first stage a large lithalsa formed, at the second stage a small lithalsa formed. • More positive isotope values of large lithalsa ice core (δ18О values vary from –18,4 to –20,3 ‰) than those of small lithalsa (δ18О values vary from –19,7 to –21 ‰) may probably have resulted from gradual release of isotopically more negative water from the central to peripheral part of the massif during freezing of water-saturated fine-grained sediments. • Minor variations of isotope values may suggest intensive recharge of water supply during freezing and lithalsa growth. Therefore, there was no pronounced isotope fractionation during freezing from the central to peripheral part of the massif in spite of constant exclusion of isotopically positive water for ice segregation. • The location of the horizon marked the freezing onset depends on geocryological conditions and may be located at the top, in the middle part, or at the bottom of the ice core.
- Добавил в систему: Буданцева Надежда Аркадьевна
Прикрепленные файлы
| № | Имя | Описание | Имя файла | Размер | Добавлен |
|---|---|---|---|---|---|
| 1. | Vasilchuk_2015_Sentsa_Engl_part_1.pdf | Vasilchuk_2015_Sentsa_Engl_part_1.pdf | 26,3 МБ | 7 марта 2016 [vasilchuk] | |
| 2. | Vasilchuk_2015_Sentsa_Engl_part_2.pdf | Vasilchuk_2015_Sentsa_Engl_part_2.pdf | 25,7 МБ | 7 марта 2016 [vasilchuk] |