Frost Mounds in the Sentsa River Valley, the Oka Plateau, East Sayan MTS

Alekseev, S. V.; Alekseeva, L. P.; Vasil'chuk, Yurij K; Козырева, Е. А.; Svetlakov, А. А.; Rybchenko, A. A.

doi:10.17513/use.35836

Cited by 3 publications

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“…In the ice‐rich core of Lithalsa A, there is a strong change of chemical composition and sulfate and ammonium composition between the lower and upper parts (Alexeev et al ., ). Icy sediments in the lower part of Lithalsa A resulted from freezing of more mineralized lake water, enriched with NH 4+ and SO 4 2− .…”

Section: Discussionmentioning

confidence: 99%

Lithalsas in the Sentsa River Valley, Eastern Sayan Mountains, Southern Russia

Vasil'chuk

Alexeev

Arzhannikov

et al. 2015

Permafrost & Periglacial

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Perennial frost mounds identified as lithalsas occur in the Sentsa River valley of the Eastern Sayan Mountains, Russia. We report the first detailed study of permafrost in this region, based on analysis of the cryostructure and distribution of stable isotopes of oxygen and hydrogen, and ion concentrations from the ice‐rich cores of two lithalsas 3–7 m high. Their main cryostructures are reticulate and lenticular, with visible ice contents exceeding 50–60%. The vertical and lateral distribution of δ18О and δD values show a step‐by‐step mechanism of lithalsa growth: in the first stage a large lithalsa formed, and in the second stage a small lithalsa formed. The more negative isotope values of ice in the large lithalsa ice probably resulted from gradual release of isotopically depleted water from the central to peripheral part of the massif during ice segregation in water‐saturated fine‐grained lake sediments. Minor variations of isotope values suggest intensive recharge of lake‐fen and meteoric water supply during freezing and lithalsa growth. Copyright © 2015 John Wiley & Sons, Ltd.

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Section: Discussionmentioning

confidence: 99%

Lithalsas in the Sentsa River Valley, Eastern Sayan Mountains, Southern Russia

Vasil'chuk

Alexeev

Arzhannikov

et al. 2015

Permafrost & Periglacial

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“…Extensive studies of natural ecosystems in the cryolithozone in terms of their current state and modern dynamics under conditions of climate change started in the early 2000s. The studies were conducted in the areas of both continuous and discontinuous permafrost in the Alaska Peninsula and in the Northern Eurasia (including its European part, Western Siberia, and Eastern Siberia) [16][17][18][19][20][21][22][23][24][25][26]. A wide range of recent studies have convinced the noticeable and relatively rapid transformations of permafrost mire landforms, leading to dramatic decrease in an areal extent of frozen plateau peatlands and heaving mounds (palsas), as observed in the Northern Eurasia [1, 3,7,8,16,27] and in the northern part of North America [28].…”

Section: Introductionmentioning

confidence: 99%

Pilot Studies of the Unique Highland Palsa Mire in Western Sayan (Tuva Republic, Russian Federation)

et al. 2021

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In contrast to the well-studied West Siberian sector of frozen bogs in the Russian Arctic, the frozen mound bogs (so-called “palsas”) on the highlands of Southern Siberia have not yet been studied, but they are suspected to be even more sensitive to ongoing climate change. This article provides the pilot study on palsa mire Kara-Sug in the highland areas of Western Sayan mountain system, Tuva Republic. The study focuses on the current state of palsa mire and surrounding landscapes, providing wide range of ecological characteristics while describing ongoing transformations of natural landscapes under a changing climate. The study used a variety of field and laboratory methods: the integrated landscape-ecological approach, the study of peat deposits, geobotanical analysis, and modern analysis of the chemical composition of water, peat, and soils. The study shows that highland palsa mires are distinguished by their compactness and high variety of cryogenic landforms leading to high floristic and ecosystem diversity compared with lowland palsa mires. This information brings new insights and contributes to a better understanding of extrazonal highland palsa mires, which remain a “white spot” in the global environmental sciences.

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Geochemistry of ice in frost mounds in the valley of the River Sentsa (Oka plateau, East Sayan)

Alekseev

Alekseeva

2018

Lëd i sneg

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Te authors examined the chemical composition of underground ice sampled from the frost mounds located in the loose (unconsolidated) sediments of the Sentsa River valley (Oka plateau, Eastern Sayan) with the purpose of reconstruction the formation history of these cryogenic creations. Numerous frost mounds of various sizes are mainly composed of alternating icy loams, sandy loams, and lenses of pure ice. Samples of underground ice taken in the outcrops of the river ledges and cores from wells together with samples of river and lake waters were analyzed by traditional hydrochemical techniques (methods) in the center "Geodynamics and geochronology" (Institute of the Earth's Crust of the Siberian branch of RAS, Irkutsk). It was found that the chemical composition of pure ice melts from lenses and layers of the frost mounds is hydrocarbonate calcium (HCO3 Ca, SO4-HCO3 Ca and NH4-HCO3 Ca) with mineralization of 6.5 – 15.6 mg/L, pH = 5.6÷6.1. Mineralization of melts of texture-forming ice, taken from icy ground (i.e. with fractions of enclosing loams) was much higher – from 50 to 792.5 mg/L. River and lake water is ultra-fresh with 99–132 mg/L salinity, and according to geochemical type it is hydrocarbonate calcium (HCO3 Ca). Te specifc features of chemical composition of the underground ice (high content of ammonium salts and sulfates) depend on a water-rock interaction, the presence of organic matter in the loose (unconsolidated) sediments and a repeated volcanic activity in the late Pleistocene–Holocene. Te frost mounds are confned to a lacustrine sediments area in the backwater zone that was formed by the Late Pleistocene terminal moraine. Teir formation in the Holocene took place as a result of segregational ice formation during freezing of water-saturated lake sediments, and, presumably, repeated injections of underground waters of the under-channel and ﬂoodplain aquifers hydraulically connected with river waters. Tus, the genesis of the studied frost mounds is probably a mixed segregation-injection process.

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Frost Mounds in the Sentsa River Valley, the Oka Plateau, East Sayan MTS

Cited by 3 publications

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Lithalsas in the Sentsa River Valley, Eastern Sayan Mountains, Southern Russia

Lithalsas in the Sentsa River Valley, Eastern Sayan Mountains, Southern Russia

Pilot Studies of the Unique Highland Palsa Mire in Western Sayan (Tuva Republic, Russian Federation)

Geochemistry of ice in frost mounds in the valley of the River Sentsa (Oka plateau, East Sayan)

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