A. C. Vasil’chuk

Water isotopic-geochemical composition in the Trekhtsvetnoe meromictic lake on the White Sea coast

The isotopic features of Lake Trekhtsvetnoe in the White Sea coast area were studied in 2012–2015 in both winter and summer. Lake Trekhtsvetnoe is a water body, separating from the sea, with constant vertical stratification throughout the observation period. Its isotopic, hydrophysical, and biological characteristics have been studied. By the isotopic profile of lake water body, three zones can be identified in the lake: (1) 0–1 m: mixolimnion zone with δ18O varying from–12 to–11.1‰; (2) 1.0–3.0 m: zone with transitional properties with δ18O varying from–11.1 to–5.5‰; (3) 3.0–7.6 m: monimolimnion zone with highest values of δ18O—from–5.5 to–4.7‰.

Isotopic and palynological compositions of a massive ice in the Mordyyakha River, Central Yamal Peninsula

The investigation objective is to study a new mas� sive ice in the Mordyyakha River valley (the Central Yamal Region), to determine the contents of stable oxygen and hydrogen isotopes in the ice, and to study pollen spectrum remains. These data are used to study the ice formation conditions and to prove that massive ice are heterogeneous and originated from lake waters. The investigated body is similar to those studied in dif� ferent Yamal regions such as Erkutayakha River valley [1], Bovanenkovo field [2], and the lower Yuribei River [3–5].

Local pollen spectra as a new criterion for nonglacial origin of massive ice

985 The stratal ice deposits represent one of the most dangerous cryogenic phenomena, which influences the economic activity in areas with permafrost devel opment. This is particularly true in connection with intense development of Arctic areas, which required extensive studies of stratal ice deposits and their gene sis. Such studies were conducted in the Shpindler Cape area [1], on the southern coast of the Baidar atskaya Estuary [2], near the Marresale [3] and Kha rasavei [4] settlements, in the western Yamal Penin sula, in the Bovanenkovo [5] area, in the Yuribei River valley [6], in the Neito Lake area [7] in the central part of the Yamal Peninsula, and in the Erkutayakh River valley [8]. Genetic interpretation of all these ice deposits is uncertain despite the relatively high degree of knowl edge about them, repeated visits to them, the cryos tratigraphic descriptions, and substantially compre hensive analytical studies [9]. Moreover, the same structural and compositional features are frequently interpreted in different ways [10]. As a whole, all the interpretation variants are limited to the following dilemma: this is either intrastratal or buried glacial ice. The purpose of this work is to demonstrate new possibilities of palynological analysis, primarily using local components of pollen spectra for clarifying the genesis of stratal ice, which allow the ice of buried gla ciers to be discerned from all other types of stratal ice since local pollen and spores cannot accumulate in glaciers of Arctic domes. The long term palynological studies of ground deposit forming ice made it possible to define several characteristic features of their spectra. In short, these characteristic feature may be formulated in the follow ing way: (1) pollen and spores are present in practically all varieties of deposit forming ground ice and their concentration ranges within limits of 50 to 1500 spec imens per 1 kg of ice or in 1 l of thawed water; (2) most stratal ice deposits contain spectra with the composi tion close to that of subfossil tundra pollen spectra with the dominant dwarf birch and Ericaceae pollen and Bryales spores; (3) stratal ice deposits frequently contain pre Quaternary palynomorphs of Cenozoic, Mesozoic, and Paleozoic ages reworked from older sediments; (4) most of the studied stratal ice deposits enclose pollen of aquatic plants such as Potamogeton, Sparganium, Typha as well as Equisetales spores and remains of freshwater diatoms and Chlorophycaceae algae.

Oxygen Isotope and Deuterium Indication of the Origin and 14C Age of the Massive Ice, Bovanenkovo, Central Yamal Peninsula

The conditions and forming time of massive ice were specified (Bovanenkovo gas condensate field, Central Yamal). Here, massive ice lies as stratums, laccoliths, stocks, and lenses. Three thousand boreholes 10–100 m in depth were analyzed. In 260 of them massive ice was broached. The ice foot is situated from 1 to 57 m deep. The maximal thickness of ice broached with boreholes came to 28.5 m; on average, it was about 8 m. The extension of massive ice is sometimes more than 2000 m, and its area is quite often more than 10 km2. According to the radiocarbon method, loams of the third terrace, containing and overlapping ice deposits, were formed from 25 000 to 20 000 years ago or somewhat later. These strongly peat loams containing massive ice formed either in shallow sea conditions or during periodical draining conditions of beaches or low laida, where organic matter appeared due to erosion and deposition and accumulated during draining and overgrowing of drains. In more inclement conditions than at present, loam deposits were frozen immediately, forming massive ice, which occupied the barely water-saturated layers. The oxygen isotope composition (δ18O) of massive ice samples varied from −12.49‰ (here and further, relative to SMOW) to −22.95‰. The deuterium concentration (δD) varied from −91.7 to −177.1‰. Deuterium kurtosis (dexc) varied from 3.4 to 10.6‰. In one seam outcrop, the content of stable isotopes varied significantly. Here, at a depth of 0.2–0.8 m, the δ18O content varied by more than 10‰ (from −12.49 to −22.75), and the δD content, from −91.7 to −171.9‰. Such variations testify about ice extraction upon freezing of water-saturated grounds in a closed system. According to palynological analysis of ice stratums, numerous remains of unicellular green algae and diatoms were revealed. It is possible that this is evidence of the existence of a fresh well, which was a source of water, feeding the layer. Most probably these were near-bottom silt waters of a large lake or desalted bay, which were frozen syngenetically. This accentuates the new type of massive ice, syncriogenic segregative ice, which probably formed 25 000–20 000 yr BP.

A 14C-dating and oxygen-isotope diagram of a Holocene-reformed ice wedge on the Chara River (Transbaikal region)

Climatic conditions in the settlement of Chara in the mid-1960s were as follows: annual mean air temperature ( t a ) –7.8°ë [1] (this is a long-term value, but the annual mean temperature in 1939–1965 differed by more than 3°ë (from –5.8 to –9.1 ° C [2]); average January temperature ( t jan ) –33.7°ë ; average winter temperature ( t w ) − 21.2°ë ; sum of winter temperatures ( Σ t w ) − 4387 deg · day; absolute minimal temperature on the ground surface –57°ë ; average minimum –50°ë ; sum of summer temperatures ( Σ t s ) 1594 deg · day; and average July temperature ( t jul ) 16.4°ë .

Oxygen Isotope Composition of Holocene Ice Wedges of Eastern Chukotka

The isotope-oxygen composition of ice wedges, ground ice, ice of the intrusive-segregated seasonal mound, and segregated ice of Eastern Chukotka near Koolen Lake, the settlement of Lavrentiya on the Chul’kheveem River, the settlement of Lorino, and the city of Anadyr on the Onemen Bay coast was studied. The comparison of isotopic diagrams showed that the variations in δ18O of the Holocene ice wedges of Eastern Chukotka did not exceed 2‰, which indicates the insignificant variability of climatic winter conditions in the late Holocene. The long-term mean-January temperature values varied less than 3°C according to calculations from the equations of interrelation between air temperature and the isotopic composition of the wedges.

New data on variations of stable isotopes in the pingo ice core in the southern part of the Tazovsky Peninsula

The aim of this work is to obtain the vertical isotopic profile of the thick Pestsovoe pingo ice core in the southern part of the Tazovsky Peninsula, to determine the oxygen and hydrogen isotopic composition of the ice, and to reveal its formation conditions. Two trends were identified for the isotopic profile of the pingo ice: an insignificant increase of the δ18O (~1.5‰) and δD (~9‰) values at depths of 12–15 m and a gradual decrease of isotopic values by 3.8 and 23‰ for δ18O and δD, respectively, at a depth of 15–26 m. The formation of the pingo ice core in the semiclosed system resulted in fractionation of the isotopic composition of oxygen and hydrogen by more than 4 and 20‰, respectively.

Isotope composition of a lithalsa in the Sentsa River valley (East Sayan Mountains)

The ice-rich core formation within the core of the lithalsa in the Sentsa River valley (West Buryatia) was studied. The concentrations of stable oxygen and hydrogen isotopes in the ice were determined, the plant residues in the enclosing deposits were aged. It was found that the lacustrine loams enclosing the ice body were accumulated about 4700–7000 years ago. The ice core of the lithalsa was characterized by δD values from 141.9 to–159.8‰, δ18O from–19.52 to–21‰, and dexc within 4.1–17.29‰. Small variations in the isotope composition of the ice–soil material within the lithalsa core point to its formation in an open system with water inflow from outside. The values of δ18O and δD were much closer to those for recent middle-winter and late-autumn atmospheric precipitation, as well as for riverine water, which pointed to a Holocene age of the ice.

δ18O and δD variations in Holocene massive ice in the Sabettayakha river mouth, northern Yamal Peninsula

The conditions of formation of massive ice near the South Tambey gas-condensate field in northern Yamal Peninsula are studied. It is shown that massive ice bodies up to 4.5 m thick occur in the Holocene deposits of the high laida and the first terrace. Therefore, they cannot be the remains of glaciers; they are ground ice formations. All three types of massive ice have quite various isotopic compositions: the values of δD range from–107 to–199.7, and δ18O from–15.7 to–26.48‰. Such a significant differentiation in isotopic composition is a result of cryogenic fractionation in a freezing water-saturated sediment. The most negative isotope values are even lower in this Holocene massive ice than in the Late Pleistocene ice-wedge ice of Yamal Peninsula.