Yedoma. Part 2. Annals of geocryological research, especially radiocarbon dating and the stable-isotopes studies in the first decade of the XXI century

Introduction

Edoma studies at the beginning of the XXI century were significantly enriched due to the widespread use of studies of the content of stable oxygen and hydrogen isotopes in vein ice, as well as the use of AMS dating of microinclusions of organic material and CO ₂ in vein ice. These studies were started at the end of the XX century^[1-4], but in the first decade of the XXI century they received a new quantitative impetus. As already mentioned in the previous part^[1], the world's first practically direct determination of the age of edom re-vein ice was performed on the basis of AMS ¹⁴ With the dating of microinclusions of organic matter extracted from the veins of the Seyakhinskaya edoma^[2,3,4]. The ice veins were dated by microinclusions and alkaline extraction from all the organic matter contained in the ice: the re-vein ice, opened at the base of the section, began to form about 21 thousand years ago, and AMS dating from the upper part of the 11 m puff, lying at the base of the section showed that the puff completed its accumulation 14.7 thousand years go back.^[2] For the first time it was possible to confirm the vertical age stratification of re-vein ice - the deeper the vein ice is located, the older the radiocarbon dating in it.

The purpose of this article is to analyze the most notable publications of 2000-2009 devoted to studies of stable isotopes and radiocarbon dating of edom strata in the Russian and North American Arctic.

Arctic Russian Edoma

 Edom of the North of Western Siberia and Taimyr

The village of Seyakha, the eastern coast of the Yamal Peninsula. The studied edom strata was uncovered in the outcrop of the third lagoon-sea terrace on the eastern coast of the Yamal Peninsula at the mouth of theSeyakha (70.157364° s.w., 72.569100° v.d.). The outcrop was studied in detail in 1978-79, 1996 and 2016.^[3]   This was the first study of a typical edom strata in the western part of Siberia.^[5] According to the 1979 collections, a number of radiocarbon dating of peat from the host sediments was obtained,^[5] which showed that 11 m of syngenetically frozen sediments at the base of the section accumulated for approximately 7.5 thousand years, i.e. the accumulation rate was about 1.3 m in 1 thousand years. Repeated sampling in 1996 also confirmed that the rate of precipitation accumulation was determined correctly: in the interval of 29.5–22.8 thousand years, 8.5 m of sediment accumulated, i.e. the rate of accumulation was about 1.2-1.3 m in 1 thousand years, and in the interval of 22.8–11.6 thousand years ago, 11 meters of sediment accumulated – the rate was 1 m in 1 thousand years.^[6-9] The rate of precipitation accumulation and their age were used for indirect dating of ice veins and isotope-oxygen diagrams on them. More accurate age determinations were obtained from the 1996 collections by direct radiocarbon dating of organic matter extracted directly from re-vein ice using the technique of accelerator mass spectrometry.^[2-4] Ice veins are dated by microinclusions and alkaline extraction from all organic matter contained in the ice. For the two upper samples, the alkaline extract turned out to be older. This can most likely be explained by the contamination of the ice veins with ancient fine organic dust. On the contrary, the AMS dating of the alkaline extract and the microorganics in the lower sample are almost identical. Most likely, the natural conditions of the formation of ice veins of the lower stage were less suitable for contamination with older material, since everything was covered with a dense cover of tundra vegetation and peat bogs. Thus, during the formation of the ice of the lower stage, only newly formed organic material could penetrate into the frost-breaking cracks. This explains the identity of the AMS dates for microorganics and for alkaline extraction in the lower sample. Facies conditions probably changed significantly in the second and third stages, when ice veins formed in the conditions of the beach. The organic material that penetrated into the frost-breaking cracks partially came from sandy beaches, from sand with a high concentration of ancient organic matter. This can be confirmed by the high concentration of redeposited pre-Pleistocene pollen and spores in the upper part of the section, both in sediments and in ice veins. Based on the dating data of organic matter from the host sediments, Yu.K. Vasilchuk previously^[9] suggested that the ice veins exposed at the base of the section began to form about 27 thousand years ago. This is most likely a consequence of incomplete consideration of the possibilities of redeposition of ancient organic matter during the accumulation of syncreogenic deposits. The AMS dates showed that the re-vein ice exposed at the base of the section began to form about 21 thousand years ago. Having the data of direct determinations of the age of ice lived from 14 to 21 thousand years, Yu.K. Vasilchuk was able to clarify that some samples were still somewhat more enriched with ancient organic material. Significant conclusions are made: a). AMS-dating shows that for the first time the subhorizontal age stratification of re-vein ice formed by successive penetration of meltwater together with the accumulation of precipitation on the surface has been directly confirmed. The time interval of active formation of ice veins in this section was established both directly and indirectly and turned out to be the same. Ice sampling from ice veins for detailed isotopic oxygen and deuterium determinations was carried out with an interval of 2-3 samples in 1 m. Samples were taken both vertically and horizontally. The values of ?18 ^O in 72 samples vary from -25.0 to -20.4% (the average value of ?18 ^O = -23.31%). Deuterium was analyzed in 10 samples, the value of ?2 H ranges from -189 to -153.3% (the average value of ?2 H = -175.55%). The ratio of ? ² H and ? ¹⁸ O correlates strictly linearly with the line of meteoric waters, which confirms the atmospheric origin of the water - the source of re-vein ice. In modern ice veins, the value of ?18 O varies from -16.6 to ^-18%, and the values of ?2 H are about -130%, i.e. modern veins are isotopically heavier. The values of the average winter paleotemperatures were reconstructed using previously derived simple ratios^[10]. The performed paleoreconstructions showed that the time of formation of the ice veins directly dated by radiocarbon in the east of the Yamal Peninsula (at least 22-14 thousand years ago) was characterized by significantly more severe winters – the average January temperatures were colder than the modern ones by 6-9 °C.

The settlement of Kharasaway, the western coast of the Yamal Peninsula. Yu.K. Vasilchuk^[11] characterized the re-vein ice of the Kharasaway section. Within the Kharasaveysky site, re-vein ice is widespread, occurring both in the Pleistocene deposits of the third terrace and in the Holocene strata of the first terrace, on floodplains of rivers, on the marine laida and in peat bogs. Re-vein ice with a height of more than 5-6 m in the upper part of the section of the third terrace in the area of the village. Kharasaway is shown by N.F.Grigoriev^[12]. M.A.Velikotsky and Yu.V.Mudrov^[13] also describe re-vein ice in the upper part of the loamy strata of the third terrace on the Kharasaway coast of Yamal. The width of the ice veins across the strike (in their upper part, below the layer of seasonal thawing) is about 0.7-0.9 m, the vertical thickness is about 5-6 m.

Marresale Station, west coast of Yamal Peninsula. 4.6-4.7 km south of Marresale station (on the west coast of Yamal, about 150 km from Cape Kharasaway), S.L.Formen and V.N.Gataullin and co-authors^[14] encountered large re-vein ice. The deposits, called by them the Varyakhinsky peat bog, overlap a loamy layer with boulders (called the Kara diamicton), the roof of which is located at an altitude of 2-4 m above sea level. The capacity of this Varyakhinsky peat bog reaches 2 m. It is overlain by a layer of sand (deer sands) with a thickness of about 1 m and a more powerful – up to 3 m – thickness of sand (called Baidaratsky sands). The entire thickness of the reindeer sands and the Varyakhinsky peat bog is penetrated by syngenetic ice veins, the heads of which lie at depths of 5-6 m, and the tails go into the basal layer of fragmented loam, the total height of the veins is more than 4 m. The peat composing the peat bog is well preserved, fibrous; the predominant species is sphagnum, the content of mineral particles does not exceed 20%. Sandy-sandy loam interlayers can be traced at a distance of tens of meters horizontally and can contain up to 20% peat. Fragments of plants from the Varyakhinsky peat bog have been dated by radiocarbon at 33-25 thousand years. Additionally, the IRSL age of polymineral extracts from deposits synchronous to plant residues was determined: Varyakhinsky peat and sandy loam. It is approximately 36-45 thousand years old. Most likely, this Varyakhinsky peat bog was formed in the range of 33 (30)-25 thousand years ago, i.e. in the same time range as the deposits of the third terrace on the Kharasavey coast. During this period, syngenetic re-vein ice grew most actively, as is convincingly evidenced by direct dating of organic material extracted from vein ice - 29,860 ± 720 years (AA-26937).^[14] Most likely, the veins were formed mainly in subaerial conditions of low or high laida (floodplain), but, in any case, not on or under the glacier, i.e. during the formation of veins in this area, the spread of the cover glacier is excluded. It is unlikely that it overlapped this vein array during the accumulation of the overlying Baidaratsky sands, since in this case the vein ice would be significantly deformed. And the Baydaratsky sands were formed already at the very end of the late Pleistocene, judging by a number of radiocarbon dates (from 16.3 to 12.2 thousand years ago)^[14]. Consequently, it is possible to say with a high degree of confidence that there was no cover glaciation in the Marresale area in the period from 33 (30) to 12-10 thousand years ago. This gives reason to believe that the glacier did not spread on the territory of the Kharasaveysky district during this period, but subaerial-subaqual conditions favorable for the development of syngenetic re-vein ice persisted.^[11]

                The western coast of the Yenisei Gulf and the Western Taimyr. I.D. Streletskaya and A.A. Vasiliev^[15] characterized the isotopic composition of the re-vein ice of the Western Taimyr. The cryolithological features of the sections show different conditions for the formation of the ice complex: with the participation of slope, alluvial and Aeolian processes. The values of ?18 About Late ^Pleistocene veins are on average 6% lower than Holocene ones, which suggests extremely harsh climatic conditions of their formation. Ice with a thickness of 10-12 m began to form at the end of the Late Pleistocene and occupied part of the draining shelf. At the same time, the re-vein ice of the second terrace of the river was formed. The Yenisei, whose valley extended far to the north. Syngenetic re-vein ice, opening in the 15-meter coastal cliffs of the second terrace in the area of the Sopochnaya Karga (71°88' s.w., 82°68' v.d.), are characterized by a lighter isotopic composition (the average values of ?18 ^O and ?2 ^H vary in relatively narrow ranges -24.8 – -24.5% and -191.2 – -187.5%, respectively) compared to Holocene re-vein ice. In terms of isotopic parameters, these re-vein ices are close to the Late Pleistocene Sartan re-vein ices studied by A.B. Chizhov and A.Yu.Derevyagin with co-authors in the area of lakes Labaz^[16] and Taimyr^[17].

Syngenetic re-vein ice on the slopes of the watershed levels near the mouth of the Krestyanka River is also characterized by a lighter isotopic composition compared to Holocene veins and is close in content to re-vein ice in the coastal cliffs of the second terrace. The average values of ?18 ^O and ?2 H vary in the ranges from -23.5 to -22.0 and from -179.7 to -167.7, respectively. Within one vein, there are no changes in the isotopic composition of ice both vertically and from the center of the vein to the edges.

Isotopic composition of two syngenetic veins in the section of the ice complex in the area of the village Dixon, according to I.D. Streletskaya and A.A. Vasiliev^[15], differs by almost 7%, whereas within one vein the variations in isotopic composition are insignificant. In the impurity-free milky-white ice of a larger vein, the range of changes in the values of ?18 ^O was 2.5%: from -26.8 to -24.3 % (the values of d _exc vary from 8.4 to 9.7%), there is also a slight relief of the isotopic composition of ice in depth and from the center to the edges, reflecting, according to I.D. Streletskaya and A.A. Vasilyeva^[15], climatic changes in the process of ice formation, the change of cold conditions to warmer ones. On the basis of a simple linear relationship between the average temperature of January and the isotopic composition of oxygen in re-vein ice obtained by Yu.K. Vasilchuk ^{[9, 10]}, the average temperature of January during the formation of the ice complex was determined: January temperatures in the Dixon area (73°31's.w., 80°34' w.d.) dropped to -40 ± 3 °C. This is about 12-15 °C below the average January air temperatures for the entire period of observations since 1917 (according to the Dixon weather station, its value is -25.5 °C). The calculation of the average January air temperature using the same formula showed that for the eastern districts of Taimyr (district m. Saber), winter temperatures 18 thousand years ago were just as severe or slightly lower.^[17]

      In the monograph by D.Y.Bolshiyanov^[18]) it is noted that syngenetic freezing of sediments with cyclic sedimentation of the material carried out by the Upper Taimyr River occurred here several times during 40 thousand years at Cape Sablera. The phases of erosion and accumulation alternated with each other. The analysis of more than 50 radiocarbon dating of lake-alluvial deposits and peat showed that sedimentation occurred with interruptions that marked the lowering of the lake level. With a closer look at the structure of the Cape Sablera strata, D.Yu.Bolshiyanov^[18] noted that the stratum partially consists of inverted blocks of rocks, which introduce disorder into the normal distribution of radiocarbon dating. He attributed this to the fact that the study of the incisions took place along the cleared walls of the baijarakhs, which move down a steep slope, and sometimes even turn over. Currently, fluctuations in the lake level during the year reach 10 m. During the autumn – winter period, most of the lake is free of water and covered with snow or ice lying on the ground. At this time, sediments accumulated during the summer are actively freezing. A rather high rate of summer sedimentation in the western part of the lake is due to the confluence of the Upper Taimyr River and the deposition of organomineral precipitation here. When the lake level falls very low, and the last very low level was noted in 1997, the bottom of the lake is a polygonal surface with frost-breaking cracks in which ice veins are formed. It is this model of sedimentation and formation of powerful syngenetic ice veins that was adopted in the work of D.Y.Bolshiyanov^[18] to explain the formation of the ice complex of rocks of Cape Sablera. The relatively low water standing in the lake basin is witnessed by peat bogs found in the thickness. The whole edom layer is a layering of sandy loam and plant residues brought by the river. "Vegetable puff" is the name of a finely rhythmic layer of layering. Among these deposits, small, up to 20-30 cm, peat interlayers, slightly decomposed moss accumulations containing practically no mineral material (less than 5%) are noticeable. Due to the fact that the slopes of the cape are quite steep, and the blocks of the Baijarakhs are inclined, moss "beards" hang from the steep slopes of the Baijarakhs and create the impression of great power of these moss horizons. They reflect the stages of lowering the level in the existing reservoir, when the surface of the current Cape Sablera came out from under the level of flooding and peat horizons formed on it, consisting almost entirely of moisture-loving mosses. Subsequent accumulation of "puff" above the horizons of peat means that the surface again went below the level of the lake basin. Thus, the time of accumulation of peat horizons is the time of lowering the level of Lake Taimyr and the time of the greatest freezing of accumulated sediments. The permafrost structure of the Cape Sablera sediments, which is characterized by 3 tiers of ice veins, confirms the constructed model of the formation of rocks of the ice complex. One of the most significant features of Lake Taimyr is that it is able, due to the very insignificant height of its location (5 m above sea level), to respond quickly to fluctuations in sea level, with which it is connected by a channel - the Lower Taimyr River.

The main regularities of the course of level fluctuations in the lake Taimyr, according to D.Y.Bolshiyanov^[18] are reduced to the following:

1. The first of the considered time periods is the Karginsky time, when the high level of the lake was due to the Karginsky ingression of the sea. At that time – 40-24 thousand years ago – Lake Taimyr was part of an estuary deeply indented into the land. The backwater of fresh water by the sea was characteristic of the entire peninsula. In particular, the Pyasina River to Lake Pyasino was also an estuary. This is evidenced by the discovery of a deer skeleton under the sediments of a freshwater reservoir in the sources of the Pyasina River. Its radiocarbon age is 41,900 ± 1,380 years (LU-3953). The estuary of Lake Taimyr was connected to the estuary of the Pyasina River along the valleys of the Tareya and Ayatari rivers, the height of the watershed between which even today is less than 25 m. At that time, Lake Pyasino was connected to Lake Taimyr by this water system. It is possible that it was during the Kargin ingression that forms of Baikal and marine hydrofauna got into Lake Taimyr from the Yenisei River. 

2. In the Sartan period (21-17 thousand years AGO), the lake level was also high, despite the fact that the basis of erosion was at a very low position due to a significant regression of the receiving reservoir – the Kara Sea. At that time, the lake was dammed by a glacial dam of a local glacier blocking the valley of the Lower Taimyr River in the area of the tributary of the Shrenk River. Traces of this local passive glaciation are found according to D.Yu.Bolshiyanov^[18] on both sides of the valley of the Lower Taimyr River. And the traces of the underground basin, in addition to the continued accumulation of precipitation in the area of Cape Sablera, are well proven by the presence of paleodelt deposits, which in underwater conditions was formed as a result of water runoff and sediment into the dammed reservoir from the side of the Chernye Yary River. Currently, paleodelta has been found on the left bank of the Lower Taimyr River before the Black Yara River flows into it.^[18] 

3. After 16.8 thousand l.n. the lake level catastrophically fell to levels much lower than the modern bottom of Lake Taimyr. This is confirmed by precipitation from a well drilled in the center of the lake. The catastrophic descent of the dammed reservoir occurred due to the break of the ice dam and caused the deepening of certain parts of the valley of the Lower Taimyr River.^[18]

Edom of the north of Yakutia

       Section Duvanny Yar. Yu.Vasilchuk, together with A.Vasilchuk re-examined the Duvanny Yar section in 1999 (68.616667° s.w., 159.133333° v.d.), based on the results of these field work, new, primarily isotopic and radiocarbon data were obtained ^[19,20], among which AMS dating obtained directly from re-vein ice ^[21-24] are distinguished.  There are two distinct sections of the section: the upper 15-20 m with an insignificant content of organic material suitable for dating and the lower 25-35 m enriched with organic material. Here organic matter is concentrated in the form of 2-3 horizontal lenses and interlayers up to 0.5 m thick. In the lower part of the section, three or four horizons of detached sediments with a significant admixture of allochthonous organic matter are usually revealed. Sediments are highly acidic. In the upper part, the sediments are less torn off, but contain syngenetic re-vein ice. The iciness, taking into account the texture-forming ice, reaches 50%. In the lower part of the section, the ice veins are wide (up to 2-3.5 m wide), the distance between them is 10-15 m, and in the upper part of the section they are narrow (up to 1-1.5 m), the distance between the veins here is reduced to 4-6 m. In the upper part, there are also very narrow (0.5-1 m wide), short (4-5 m high) buried veins overlaid with gray loam. The ice of these veins is gray in color with large air bubbles and vertical layers of gray sandy loam. Large veins often have shoulders at the level of peat horizons. These shoulders vary from pronounced to barely noticeable curves. In the upper part of the incision, the shoulders are located at the same levels as the heads of small ice veins. The binomial structure of the section allows us to talk about two macrocycles of the formation of the Duvannoyarskaya strata (it was previously noted that binomial macrocyclicity is characteristic of other North Yakut sections.^[9] Within these macrocycles, as already mentioned, mesocycles are distinguished, marked by horizons enriched with organic matter, with a thickness of about 1 m, which were formed in subaerial conditions. Sandy loam horizons with a low organic content (3-5 m thick), separated by organic horizons, were formed under subaqual conditions. During the subaerial stages, the rapid growth of ice veins occurred, during the subaqual stages, the growth of veins was suspended. Most likely, the change in the growth rate of re-vein ice was caused not by climate fluctuations, but by a change in subaerial and subaqual regimes. Yu.K. Vasilchuk^[24] proved genetic diversity, i.e. heterogeneity of the edom thickness of the Blown Yar and non-simultaneous formation, i.e., heterochronicity of its various parts not only vertically, but also along the strike, based on the study of the cryogenic structure of the entire massif and comparison of the previously obtained radiocarbon dating results with new (including AMS ¹⁴ C dates obtained using accelerator mass spectrometry) dating of microinclusions of organic matter, alkaline extracts and spore-pollen concentrate extracted directly from syngenetic late Pleistocene re-vein ice. This allowed us to propose a fundamentally new version of the structure, age and conditions of formation of the studied Late Pleistocene polygonal-vein complex.

      New ¹⁴ C-dating of microinclusions of various organic matter from ice veins and critical analysis of more than 80 early radiocarbon dating ^[19-24] allowed for the first time to demonstrate vertical and lateral heterochrony (i.e., the occurrence in different parts of the section at the same height of strata differing in age by 10-20 thousand years, and the location of younger terraced fragments hypsometrically lower than the older domes) and heterogeneity of the Duvan Yar edom massif (i.e., representing a set of thicknesses and lenses of alluvial, lake-alluvial, lake and swamp genesis in a single edom complex). Such a complex heterogeneous and heterochronous structure of large sections along the strike is inherent not only in the Blown Yar, we have encountered similar problems in the study of extended domed massifs: the Seyakhinskaya Edoma on the Gulf of Ob, the outcrop of Edoma on the west coast of O.Aion, an ice cliff on the Main River, etc., which are also most likely heterochronous and genetically heterogeneous in strike. Therefore, it is methodologically incorrect to combine and “superstructure” various fragments of such sections vertically, in cases when they are not opened by a single outcrop and do not actually lie one above the other (unless, of course, detailed dating proves the opposite). The author suggested^[23] that a simpler and relatively homogeneous structure of edom massifs is inherent in less extensive and more surface-aligned massifs (such as the Karetovskaya edoma in the area of the Plakhinsky Yar, the edom part of the Alyoshkin terrace, the Bison section at the mouth of the Lakeevskaya Channel in the lower reaches of the Kolyma, etc.).

Yu.K.Vasilchuk and colleagues^[19,23,24] started developing a strategy for radiocarbon dating of late Pleistocene syngenetic re-vein ice and accurate time-bound distribution diagrams of stable isotopes using AMS dating of microinclusions of organic material extracted directly from ice veins.^[22,23] For AMS dating, small samples of water from ice (weighing up to 40 g, in which the admixture of organic matter was at least 0.5-1 mg), which Yu.To.Vasilchuk selected in the period from 1983 to 1991 in Yakutia and according to which detailed isotope-oxygen diagrams were obtained from four sections - three in the lower reaches of the Kolyma River: Green Cape, Duvan Yar, Plakhinsky Yar and one – Mammoth Mountain on Aldan. The binding of all these sections was initially performed using radiocarbon dating of various organic matter from the host sediments and, as shown by direct dating of organic matter from ice, this was mostly done correctly, but in the latter case, the new results fundamentally changed the idea of the age of Mammoth Mountain veins.

      The section near the village of Zeleny Mys in the lower reaches on the right bank of the Kolyma River (69.293070 ° s.w., 158.192652 ° v.d.) was one of the first isotopically studied in detail.^[9] Powerful re-vein ice permeates the entire 36-meter sandy loam thickness of the section. The time of formation of veins, judging by the dating from scattered roots and from the buried soil horizon near the day surface (13500 ± 160 years), was estimated by Yu.K.Vasilchuk from 45 to 13 thousand years. The three AMS datings obtained directly from the ice^[23] confirmed with absolute accuracy the time of the end of the accumulation of veins – 13 thousand years ago. The other two dates from the ice are slightly older than the comparison with the host sediments suggests, which is obviously the result of the partial introduction of veins of older organic material into the ice. But still, these dates, on the whole, quite fit into the general time range of the formation of the upper part of this housing complex.

The section of the Plakhinsky Yar on the left bank of the Kolyma channel Stadukhinskaya (68.678800 ° s.w., 160.285200 ° v.d.) reveals a relatively small outcrop with a height of about 14 m, composed of heavily sanded sandy loam, with inclusions of plant residues.^[9] The appearance of the ice veins here is markedly different from those described above. The width of the veins in the upper part of the outcrop is 1-1.5 m, they are located at a distance of 3-4 m from each other. Despite the relatively small amount of organic matter (mainly at the base of the section and scattered in the middle part of the thickness), it was possible to date the beginning of the formation of the visible part of the section – about 30-27 thousand years ago, and the completion no later than 15-16 thousand years ago.^{[27, p. 392]} The 17390-year-old ice dating obtained at a depth of 4 m AMS^[23] fully confirmed the correctness of this dating. Special attention was paid to the almost complete correspondence of the isotopic data obtained by Yu.K.Vasilchuk^[9] and later by Japanese researchers led by M.Fukuda^[28] from the middle part of the veins, although the selection and analysis were performed at intervals of 10 years. This indicates the absence of significant gaps in the isotope curve and its good reproducibility.

    The Bison section. Yu.K.Vasilchuk with A.Vasilchuk^[29-32] investigated in 1999 the Bison section (69.366667 ° s.w., 115.566667 ° v.d.), which is located on the right bank of the Kolyma River, downstream of the Duvan Yar, at the mouth of the Lakeevskaya Channel. The section is mainly represented by sandy loam deposits with layers of organic matter in the form of lenses up to 0.5 m thick. Syngenetic ice veins with a vertical thickness of up to 9 m and a width of 2-2.5 m in the upper part are exposed in the circus with a length of 200 m and a height of about 20 m. The ice was gray, with large air bubbles and streaks of gray sandy loam, sometimes there are vertical layers of milky-white ice. To determine the time of formation of ice veins, large samples were selected – weighing up to 30 kg of ice. Seven samples from this section were delivered to the Isotope Center in Groningen. From a thoroughly tested fragment of a vein with a height of 5 m in the root wall, the age of ice veins from 26.4 to 32.6 thousand years was obtained by microorganics.^[29] The alkaline extract contains more ancient organic matter that enters the ice veins, probably through frost-breaking cracks along with the finest dust in winter during strong winds blowing snow and exposing the soil. At the same time, according to the alkaline extraction data, a consistent increase in dates with depth was also obtained: in the same 5-meter fragment, the dates vary from 27.7 to 36.3 thousand years. Thus, it can be stated with a high degree of confidence that the ice opening up the root wall of the outcrop was formed at least from 33 to 26 thousand years. The rate of vertical growth of ice lived here did not exceed 0.8 m in 1 thousand years. Thus, with the help of AMS dating, it was possible to confirm the vertical stratification of ice in veins, i.e. to confirm their syngenetic accumulation, when younger ice, even with wedge–shaped penetration into a previously accumulated vein, turns out to be stratigraphically higher, and the older one is lower. In addition, it was possible to date the ice horizontally and for the first time show that it accumulates not strictly in any one direction, when one would expect a natural change in age horizontally. In this case, a younger wedge would have to lie in the central part of the vein or, conversely, there would be rejuvenation with a steady trend in one direction or another. However, it turned out that frost-breaking cracking and ice buildup of veins can occur quite arbitrarily, and the ice on the side near the axis turned out to be somewhat younger at first, and then a little older. Another important result is that it was possible to study in detail the ice that was continuously formed from 32 to 26 thousand years ago, i.e. during the period, the first half of which was often considered cold (Zyryan) time, and the second – warmer (Karginsky) and even associated with this time a break in the formation of veins and accumulation supposedly more thermophilic peat bogs. However, judging by the dates obtained, the re-vein ice accumulated at this time almost continuously, indicating that such a division into warm and cold interval is incorrect. This was even more convincingly demonstrated by the results of studies of stable isotopes (in total, the concentration of deuterium and heavy oxygen in 183 samples was analyzed here). For this purpose, a detailed sampling of re-vein ice and analysis of stable oxygen and hydrogen isotopes in them was carried out. In terms of the degree of detail, this testing exceeded the one usually performed by almost 10 times: if samples were usually taken after 0.5–1 m, then here the selection was carried out after 0.1 m and more often. This made it possible to obtain an isotopic curve with a resolution of more than 100 years and to confirm with a high degree of detail the stability of the paleoclimatic situation in the period 33-26 thousand years ago. For the ice accumulated during this period and sampled in two vertical profiles, the variations of the values of ?18 ^O ranged from -33.25 to -32.40, and the values of ?2 H varied from -260.5 to -253.2, and taking into account the sampling data on horizontal profiles from veins in the root wall of the outcrop, the values of ?18 ^O vary from -33.32 to -32.02%, and the values of ?2 H from -261.3 to -251.1%.^[29] Only in two samples at the very edge of the lower vein on contact with the host rocks, the values of ?18O = -35.17 and -34.08%, and the values of ?2 H = -266.2 and -260.6%, here and extremely high values of dexc = 15.2 and 12This indicates a different nature of ice in the contact zone. Obviously, mainly segregational ice is widespread here, as evidenced by a significant admixture of soil particles in the near–contact zone of the vein - up to 60%. As can be seen from the consideration of isotopic data, even if we take into account all the re-vein ice exposed by the Bison outcrop, the range of variations in the values of ?18 ^O will be about ²%, and in the root wall it is even smaller – about 1%, and the range of changes in the values of ?2 H is 13.5 and 7%, respectively. Such insignificant variations of stable isotopes indicate a very stable paleotemperature situation of the time of formation of veins opened in this section. So, for the time range from 33 to 26 thousand years ago, temperature variations in the surface air layer (recalculated according to the equations from ^[10]) did not exceed 1 °C (from -32 to -33 °C) for average winter temperatures and 2 °C (from -48 to -50 °C) for average January temperatures, now the components here are -24 and -35 ° C, respectively. The evaporation regime was also very stable in the area where the main inflow of moisture came from in the late Pleistocene. This is evidenced by the stable nature of the dexc values, varying from 4 to 7% for the period 33-26 thousand years ago. These values differ from the dexc values inherent in modern snow – about 10%, which still indicates a different evaporation regime over the ocean in the Late Pleistocene than now, confirming previously obtained data on small dexc values for late Pleistocene glacial ice compared to the Holocene.^[29]

Dating of the spore-pollen concentrate in the Bison section, performed by A.K. Vasilchuk with the participation of Yu.K. Vasilchuk ^[30-32] using AMS, required comparing the dates within each of the studied three ice veins of this section. In the first vein, one AMS dating of pollen concentrate was obtained - 31.4 thousand years. In the immediate vicinity of it, a sample of the total organic matter extracted from the ice of the vein was previously dated also using AMS: by microinclusions and alkaline extraction, 26.4 and 27.7 thousand years, respectively. We can talk about a fairly close coincidence of these two dates and, probably, a high degree of their reliability, while the age of the pollen dated in the neighboring sample is probably somewhat overestimated. This is evidenced by the very high pollen content of cedar elfin – up to 42%, as well as the presence of tree pollen – more than 4%, among which there is a single far-bearing pollen of scots pine and Siberian cedar and the noticeable participation of Siberian planus spores, which reflects their introduction with dust from the surface of almost bare areas of mineral soils in winter. The dating of the pollen concentrate from this sample is most likely not so reliable and is at least 4-5 thousand years old.^[28-30] In the spectra of the three samples of the second vein, the situation is completely different, judging by the composition of the spectra, their autochthonicity is almost beyond doubt. The same follows from the dating of the pollen concentrate, which gave a non-inversion series of dates from 26 to 35 thousand years. The uppermost sample is characterized by a tundra-type palinospectrum. It is especially important here that the youngest radiocarbon date of 26.2 thousand years was obtained from the pollen concentrate, it is even younger than the microinclusions dating by 3 thousand years. Palinospectrums from the third vein reflect a slightly different stage of vegetation development and a different mode of formation of vein ice. In the spectrum from the upper sample from this vein, dated by pollen concentrate at 36.9 thousand years, redeposited pollen grains of QuercussibiricaPan were found. and scraps of coniferous pollen. The content of carbonaceous particles of the pollen dimension is 9.9%, and the content of deliberately redeposited forms is 0.4%, although the signs of redeposition of pollen and spores in the palinospectrum itself are expressed implicitly. Nevertheless, the microorganics dating of 30.5 thousand years, obtained below from the same vein, indicates the age difference of the components of the palinospectrum. Thus, the dating of the pollen concentrate from this sample is unreliable, there are signs of organic decomposition, palynomorphs have different preservation.^[30-32]

 Cape Mammoth Fang. The evolution of periglacial landscapes over the last 60 thousand years was traced by L.Schirrmeister and co-authors^[33] based on the study of the edom strata of Cape Mammoth Fang. This region is also considered to be the westernmost part of Beringia, an ice-free land that was located between the Eurasian and Laurentian ice caps during the Late Pleistocene. Several blocks of sand deposits, sand-peat alternations, edoma - ice complex and peat fillings of thermokarst basins and valleys were presented. The data reflect cold stadial climatic conditions between 60 and 50 thousand years ago, moderate interstadial conditions between 50 and 25 thousand years ago and cold stadial conditions from 25 to 15 thousand years ago, the transition from the Late Pleistocene to the Holocene, including Alleredian warming, is also recorded. Three OSL datings of 56.6 ± 8.3, 31.3 ± 4.6 and 31.8 ± 4.3 thousand years were obtained. If the first date is consistent with the radiocarbon chronology of the formation, then the upper two are much younger. L.Schirrmeister and co-authors^[33] suggested that the radiocarbon estimates are correct, and the age of the two upper OSL dates is underestimated.

           The age of block A from the early to the Middle Hellenic period is also supported by an exorbitant radiocarbon age >44.5 thousand years, which is determined from the roots of grass in the place of occurrence from the transition zone between blocks A and B. It is assumed that block A corresponds to the Zyryan stage. According to the five radiocarbon ages, the peat–sand alternation of Block B was formed about 40-45 thousand years ago. This horizon was formed during the Karginsky stage. The height–age ratio from composite profile 1 shows a relatively large radiocarbon age gap between 40 and 24.6 thousand years ago. The gradual transition to the ice-saturated block C is evident only on one date 31.2 thousand years ago. For both composite profiles in the ice complex (Block C), continuous dates of radiocarbon AMS were found for periods from 26.6 and 15.9 thousand years ago and between 27.2 and 14.5 thousand years ago. They indicate that the Ice Complex was formed in the Sartan time. Radiocarbon dating of bones - 11 radiocarbon dates were obtained: three dates of woolly mammoth bones, six dates of horse bones and two dates of musk ox bones. Radiocarbon dates are between 39 and 17 thousand years.^[33]

     L.Schirrmeister and co-authors^[33] obtained data on the dating of the edom strata of Cape Mammoth Fang on the western coast of the Laptev Sea. According to five radiocarbon dates, the beginning of the formation of this stratum is confidently dated no later than 40-45 thousand years ago, and maybe earlier than 60 thousand years ago. Continuous series of radiocarbon AMS datings were obtained for the period between 27.2 and 14.5 thousand years ago. Radiocarbon dates obtained from the bones of mammoths, horses and musk oxen are between 39 and 17 thousand years ago. A comparative study of stable isotopes and gas composition from two ice veins (Holocene and Late Pleistocene age) was performed at Mammoth Fang Cape^[34]. The Holocene ice vein (IW-26) was sampled in the upper part of the outcrop, at an altitude of 18.6 m above sea level. It (IW-26) reaches 1.6 m in width and about 2.5 m in height. The Late Pleistocene ice vein (IW-28) was sampled at an altitude of 1 m from sea level in sandy sediments.  IW-28 exceeds 3 m in width in its upper part. The Late Pleistocene ice vein is associated with the sand-ice vein (ISW-28), part of which was also selected for research.  The values of ?18 ^O in the Holocene vein vary from -22.6% to -25.8 %, and ?2 H values from -170 % and -191 %, respectively. For the Late Pleistocene ice vein, the value of ?18 ^O varies in the range from -29.4 to 31.9, and the value of ?2 H is between -229 and -247, respectively. In a sand-ice vein, the values of ?18 ^O vary from -29 % to -30.9 %, and the values of ?2 H from -230 % to -246%).^[34]

The total gas content in the studied ice veins is lower than in the ice formed as a result of simple compaction of snow on ice sheets. The total gas content in the Late Pleistocene ice vein (IW-28) is higher than in the sand-ice vein and in the Holocene (ISW-28 and IW-26). For CO2, the total mixing proportions are certainly higher than atmospheric concentrations, the highest values are observed in the Holocene ice vein (IW-26) (on average 62,000 ppm by volume), in the sand-ice vein (ISW-28), lower values of CO2 are noted (on average = 3000 ppm by volume volume), than the Late Pleistocene ice vein (IW-28) (on average 25,000 ppm by volume). On the contrary, the concentration of CH4 in the Holocene ice vein (IW-26) is low (average = 1 ppm by volume) and varies in the same range as the atmospheric concentration, high values of CH4 in the Late Pleistocene ice vein IW-28 (average = 8 ppm by volume) and very high values in the sand-ice vein ISW-28 (average = 55 ppm by volume). Oxygen shows values lower than atmospheric values with values of about 10%)^[34]

An important set of data on the formation of sands and ice complex rocks was obtained by D.Y. Bolshiyanov and co-authors ^[35] when drilling wells on the Laptev Sea shelf near Cape Mammoth Fang (73°42'36.1" s.w., 117°10'01.4" v.d. - coordinates of the extreme offshore well). Marine deposits were recorded in a well with a depth of 58 m according to the marine complex of diatoms, the marine type of salinization of rocks, the remains of marine mollusk shells. Also, signs of marine sediments (fragmented bivalves at the site of occurrence, shell detritus, iloid passages) are also found near the bottom of a well drilled on the shore. These signs definitely indicate basin sedimentation conditions. The gradual transition of marine sediments into freshwater sediments, in which the freezing and formation of the ice complex of rocks took place, is recorded both by lithology and by dating of sediments. Two OSL dates were obtained from the marine part of the section: 111.1±7.5 thousand years (RLQG 1727-026) and 86.2± 5.9 thousand years (RLQG 1728-026). OSL-the age of freshwater deposits of the ice complex from the well turned out to be 59.3±5.8 thousand years (RLQG 1729-026). According to D.Y. Bolshiyanov and co-authors ^[35], there is an indissoluble connection between the rocks of the ice complex and the underlying sands: there are no traces of breaks in sedimentation between them, and besides, dating of those and other deposits show that there are also no chronological breaks. Sands with dates of 111-59 thousand years pass into overlapping sands and sandy loams with a high content of organic sediments (edoma or ice complex) and an age of 60-23 thousand years.^[35]

A.A. Bobrov and co-authors^[36] present the results of rhizopod analysis of permafrost deposits formed in the cryolithozone of northeastern Siberia. Communities of shell amoebas of Late Pleistocene, Holocene and modern habitats of Cape Mammoth Fang (the coast of the Laptev Sea near the Lena River delta) have been studied. The structure of Paleocenosis communities is considered, the diversity of the rhizopod population in deposits of different genesis - fluvial, alluvial, ice complex, alasic and lozhkovye is assessed. According to the species composition of shell amoebas, the late quaternary deposits of the Mammoth Fang, primarily of the Karginsky interstadial, are comparable to the habitats of the forest tundra and the forest-taiga zone. Almost all the tests are presented, with the exception of the inhabiting forest litter and eutrophic swamps of the genus Quadrulella, Sphenoderia, Placocista, Euglypha, Assulina, Trinema, Corythion, Cyphoderia, Pontigulasia, Lesquereusia. In the deposits of Karginsky time (fluvial and alluvial facies and the lower part of the ice complex), the change of ecological groups of testations and indicator species reflect the alternation of water, swamp and soil stages with the dominance of waterlogging processes. In the Sartan period, the degree of xeromorphism of sediment formation increases. There are no obligate hydrobionts in the samples of this period, the hydrological regime is characterized by dry conditions. The alternation of soil mesotrophic conditions and swamp stages is characteristic for the Sartan, as well as for the Kargian time, but to a lesser extent. The main difference in the population of rhizopods of the Kargian and Sartan times is the number of hydrophilic species. Thus, the data of rhizopod analysis once again confirm the existence of the Late Pleistocene (Kargian) interstadial. In the samples of the edom complex of the Bykovsky peninsula by A.A.Bobrov in the Karginsky interstadial (54-30 thousand years ago), the maximum species diversity of testations was also noted. The idea of a colder and drier Sartan time is mainly confirmed by the data of rhizopod analysis. Apparently, the diversity of habitats in the Kargin time and the Sartan time was similar, only the ratio of different types of habitats changed. In the Sartan period, there was a reduction in the number of habitats favorable in terms of humidity and nutrition, especially the areas of wetlands of the landscape decreased.^[36]

 Lena River Delta near the Chekanovsky ridge

Nudity Naked. The section is located on the northern bank of the Olenekskaya Bayou on the island of Ebe-Bazyn near a small village.Naked, in the western part of the delta of theLena (72°52'46" s.w., 123°19'20" v.d.). The section is composed mainly of sands (the first macrocycle), overlain by deposits of the ice complex (the second macrocycle)^[37].

The thickness of the sandy horizon is from 10 to 20 m, it is divided into two main parts with six subhorizons. The lower part (0-6 m above the river's edge) consists of a layering of fine- and medium-grained sand and contains horizons with plant residues and detached sand. The thin layering (1-3 mm) and numerous vertically arranged Equisetum roots probably reflect the accumulation conditions in a shallow reservoir typical of bays. The amount of plant residues decreases with height^[37]. According to IRSL dating, the sands were formed between 57 ± 9 thousand years and 49 ± 22 thousand years. AMS-dating of this horizon (53 + 3,9/-2,6 thousand years ago and > 54 thousand years ago) do not contradict IRSL dates.^[37] The transition to the overlying horizon of the second macrocycle of the ice complex is pronounced. This is primarily expressed in the appearance of small inclusions of peat, larger lenses of peat, and several horizons - mesocycles of buried paleosols that overlap the sandy horizon, as well as in an increase in ice content. At this border, horizons of brownish-gray detached paleosols (0.5-1 m thick) with signs of cryoturbations were encountered in different places at an altitude of 13-15 m above the river's edge. The width of the veins of the ice complex in the upper part reaches 3 m, they penetrate to a depth of several meters into the underlying sands, where their width varies from 0.5 to 0.7 m. The “tails” of ice veins consist of a vertical interlayer of ice strips and sediments 1 cm wide. The ice veins are vertically striped and contain numerous gas bubbles. They have symmetrical shoulders on contact with the host deposits.^[37] This feature, along with the rhythmic distribution of segregation ice (represented by interlayers, lens-like inclusions, ice-cement), according to L. Schirrmeister, reflects the syngenetic growth of ice veins. The radiocarbon age of the deposits of the ice complex from a height of 11 m above the river 's edge was 42,9 + 3,1/-2,2 thousand years old, at an altitude of 21.2 m – 44,2 + 1/-0,9 thousand years, and > 45.6 thousand years.^[37]

Buorkhai section, on Kurungnakh Island. The section is located in the central part of the delta of the river .Lena on the east side of the island .Kurungnah between 72°20'00" s.w., 126°17'16" v.d. and 72°21'02"s.w., 126°19'16" v.d. It also consists of two macrocycles. The deposits of the ice complex cover 15-20 m of the sandy horizon. Large ice veins of the ice complex penetrate into the lower sandy horizon. In the upper part of the sandy horizon, on contact with the deposits of the ice complex, small channel-like pseudomorphoses with a width of about 0.3 m are often found, filled with fine layered organic detritus. This detritus has been dated by radiocarbon >51.7 thousand years. In another part of the section, 2 km east of 3 m, the horizon represented by the interlayer of sand and peat (the thickness of the interlayers is from 1 to 5 cm) is blocked by a horizon of thin-layered sands with a thickness of 10-12 m, which contain branches of shrubs with bark and vertically arranged autochthonous roots. The layering indicates the accumulation of sediments in a shallow river bay. This horizon is comparable to the lower sandy horizon of the Nagy section. According to the IRSL dating, the sandy horizon accumulated between 88 ± 14 and 65 ± 8 thousand years. Within the syngenetically frozen sediments, a sandy loam horizon of paleosols with a thickness of 1 m with traces of significant cryoturbation, involutions and inclusions of peat was noted. Radiocarbon age of peat inclusions 50,1 + 2,8/-2,1 thousand years.^[37]

S. Vetterich and co-authors^[38] emphasized that the stratigraphic configuration of the Late Pleistocene Edom strata on Kurungnakh Island correlates well with regional stratigraphy in northeastern Siberia and with Eurasian analogues (Vistula), as well as with global analogues (MIS 4-1). Between 45 and 32 thousand years ago, paleoecological records indicate the existence of tundra-steppe vegetation in a cold continental climate. After a break in sedimentation at the end of the Late Vistula stage of cooling in the study area, judging by bioindicators, extremely cold-arid conditions prevailed. At the beginning of the Holocene, the tundra steppe completely disappeared due to prolonged waterlogging.^[38]

The section of Sasyr, on O. Dzhangylakh. The combined section of two overlapping fragments was studied by L. Schirmeister and colleagues ^[37] on the left bank of the Aryn Bayou (72°38'40" s.w., 125°30'58" v.d.). The deposits of the ice complex overlap the sandy horizon, which is divided into three parts – three mesocycles. The lower horizon (height from 0 to 3.4 m above the river's edge) consists of fine and medium sand. The isochronously adjusted ²³⁰ Th/U age of the DJI-50L sample, at an altitude of 5.66-5.96 m, sampled in this horizon is 113 ± 14 thousand years.^[37]  The interlayer of sand and peat in the range of 6.4 and 10.3 m above the river 's edge is represented by interlayers from 1 to 7 cm and ice veins from 15 to 25 cm wide . The upper part of the horizon with a thickness of 10.3 to 11.3 m consists of horizontally wavy powdery sand with plant macrostates dated to ¹⁴ C > 51.4 thousand years. The ice complex (at altitudes of 18.5-26.5 m above the river's edge) is composed of ice-saturated, horizontally wavy-layered powdery sands with numerous inclusions of peat and peat lenses. Large ice veins lie here. Radiocarbon dating shows that the lower part is older than 52.7 thousand years.^[37]

The outcrop of Mus-Hai, on the island of Hardang. The section is located in the northeastern part of the island. Hardang Sise, on the left bank of the Aryn Bayou (72°53'15" s.w., 125°11'40" v.d.). Mainly sandy deposits overlain by deposits of the ice complex were uncovered in the section. Plant remains at altitudes of 13.05-13.10 m were dated by radiocarbon at 20.66 ± 0.11 thousand years.^[37]

In the samples of Holocene ice veins, as well as modern ice veins from the Nagym section, a relatively heavy isotopic composition was noted – from -169 to -195 for the values of ?2 H and from -22.7 to -26.0 for the values of ?18 ^O and relatively high dexc values. The veins of the ice complex, from which ice samples were taken, lie in sediments dated from >45 thousand years to about 44 thousand years. These veins are characterized by a lighter (more negative) isotopic composition, varying in the range of -230% for the values of ? ² H and -30% for the values of ? ¹⁸ O, and d _exc of about 5 % for both sections.^[37]

The isotopic composition of the ice veins of the first macrocycle in the alluvial deposits underlying the ice complex varies between -20.5 and -23 for values of ?18 ^O and within – 170 for values of ?2 H. Dexc values are the lowest of all studied ice veins (about 0%). The time of formation of deposits of this horizon is dated by the AMS method to ¹⁴ S and by the IRSL method from 50 to 90 thousand years ago. It is likely that these ice veins were fed from different sources. For example, water could get into frost-breaking cracks during a flood. Therefore, in such veins, the winter signal is less pronounced, the isotopic composition of ice depends more on the isotopic composition of river water, which, moreover, is subject to evaporation. Events of this kind can explain both low dexc values and heavy isotopic oxygen and deuterium composition.

The studied sections of the Lena estuary in the vicinity of the Chekanovsky ridge are, according to Yu.K. Vasilchuk ^[39], heterogeneous formations, and often, for example, Holocene and Late Pleistocene re-vein ice lie at the same height and are quite comparable in their parameters, and cyclicity is clearly distinguished in the section on Kurungnakh Island. In the thickness on the right bank of the Olenek Bayou, the distribution of radiocarbon dates may indicate lateral heterochronicity of the thickness.^[40]

Section of Edoma Mammoth Hayota. Interesting studies were carried out on an outcrop called Mamontova Hayota (Mammoth Mountain), 1.5 km long and 40 m high, located on the east coast of the Bykovsky Peninsula in the Lena River delta.^[41] In 1998-2000, joint studies of Russian and German geocryologists, paleontologists and isotopists were carried out on the Bykovsky Peninsula.^[41] The ice complex is represented by strongly icy sandy loam deposits, in which large ice veins lie up to 40 m in height and about 3-4 m in width.

A series of the first dates for the edom strata in the section of the Mammoth Hayote were obtained by A.G.Fartyshev,^[42] then by the roots of herbs and mammoth bones by S.V.Tomirdiaro and B.I. Chernenky^[43]. They correlate well with each other: the bone dates back to 22 thousand years, the roots of herbs around it are 21.6 thousand years old. The radiocarbon dates of 28.5 and 33 thousand years are obtained below. A series of dates were obtained in the upper part of the outcrop: 21630 ± 240 years (LU-1328), 22070±410 years (LU-1263), 28500±1690 years (LU-1329) and 33040±810 years (LU-1330). In one Mammoth Haiot outcrop, which also characterizes this edom thickness, E.A.Sgrada^[44] obtained a series of even younger dates: from a depth of 20 m – 32200 ±930 years (IM-748), from a depth of 20 m – 19800±500 years (IM-753), from a depth of 17 m – 22000± 1600 years (IM-752), from a depth of 15 m – 20836± 500 years (IM-749), from a depth of 9 m – 15100 ± 750 years (IM-748). 

In the course of the work of the Russian-German team on the section, 70 AMS and 20 new radiocarbon dating obtained by the standard method, from plant residues, were obtained. They were used to chronologically link the ice complex and the overlapping horizon. L.Schirrmeister and co-authors ^[40,41] suggested that these deposits have been continuously accumulating over the past 60 thousand years. The oldest of the dates obtained – 58 400 +4960/-3040 years (KIA-6730). L.Schirrmeister and co-authors^[41,45] identified three stages in the evolution of Mammoth Hayote edoma: lower (0-10 m above sea level), middle (10-25 m) and upper (25-39 m above sea level). The Edom of the average macrocycle (whose age is 50-28 thousand years) it consists of 15 layers of peat fixing macrocycles, while the edom of the lower macrocycle (60-50 thousand years) and the edom of the upper macrocycle (25-12 thousand years) they are characterized by a lower organic content and a more homogeneous composition^[41]. H.Mayer and A.Derevyagin and co-authors ^[46] indicate that the heaviest values of ?18 ^O and ?2 H in the veins of the ice complex reach values of -25 and -190 and are observed at an altitude of 10 m above sea level, in a sample dated 42 thousand years ago. In general, the variations of the values of ?18 ^O and ?2 H in the veins of the Mammoth Hayote edoma are about 11.5 and 100, the values of ?18 ^O vary from -29 to -32, the values of ?2 H from -230 to -250, and average -28.4 and -218, judging by these according to low values, it was relatively cold in winter in the period from 58 to 20 thousand years ago.^[46] 

The results obtained during the study of the ice complex allowed reconstructing the climate of late Pleistocene winters and identifying a period of very cold winters (60-55 thousand years ago), followed by a period of stable cold winters (50-24 thousand years ago). Between 20 and 11 thousand years ago, climate warming was recorded by the rise of the values of ?18 ^O by 5% and ?2 H by 25%. A shift in the values of the deuterium excess by 5% at that time indicates a change in humidity and, possibly, ice cover in the North Atlantic – a source of moisture that provides precipitation on the Bykovsky Peninsula.^[46]

In the works of A.A. Bobrov and co-authors ^[47,48], data on shell amoebas (Protozoa: Testacea) that inhabited various habitats of the Bykovsky Peninsula for the last 53,000 years (Late Pleistocene and Holocene) are presented. Soil conditions about 53,000 years ago were probably quite similar to modern ones. Summer temperatures were relatively favorable for rootlets about 45.3–43 thousand years ago, but much drier about 42 thousand years ago. Drier and colder environmental conditions also occurred about 39.3–35 thousand years ago. Conditions favorable enough for the life of amoebas were about 33,450 years ago. Very cold and dry conditions were observed from 33.4 to 12.2 thousand years ago. At the beginning of the allered about. 12 thousand years ago, climatic conditions changed again to more favorable for amoebas.^[47,48]

S.A.Kuzmina studied insect remains from the Mammoth Hayote section in more than 50 samples. The preservation of insect remains is very good, the remains of beetles predominate. One sample from horizon A sampled at about sea level (radiocarbon age about 60-50 thousand years ago) contained several insect remains. They mainly belong to tundra species, and some to Pleistocene tundra-steppe species.^[41] The percentage of steppe species reaches 50% in some samples in the middle part of the section. Many remains belong to the genus of dung beetlesAphodius (possibly extinct). These beetles disappeared in the Pleistocene along with large mammals. Willow weevils (Lepyrus nordenskjoeldi) and some aquatic and coastal species are also found. Many of the species found here are not currently found in the region. Especially interesting, according to S.A. Kuzmina, is the combination of weevilsStephanocleonus eruditus and Isochnus arcticus. The latter now lives on fr .Wrangel, Chukotka, Taimyr and northern Alaska, but Stephanocleonus eruditus, a true steppe species, lives on relict areas of the steppe in Yakutia (where the average July temperature is 13-15 ° C). S.A.Kuzmina suggests the existence of tundra-steppe landscapes. The climate was more continental with summers warmer than now and cold winters 48-45 thousand years ago.^[41] Higher in the section, insect complexes are distinguished by the absence of thermophilic species. Steppe insects are also found in sediments dated 39-37 thousand years ago, but they play a less important role. Tundra xerophilic insects dominate together with tundra mesophilic species. The presence of typical Arctic tundra species is also noticeable. During this period, mostly dry tundra with some steppe elements existed on the Bykovsky Peninsula. There are several cold-resistant species, for example, the wandering beetle (Tachinus arcticus), it becomes a sodominant in mesotrophic tundras instead of ground beetles (Pterostichus subgenus (subspecies) Cryobius). S.A. Kuzmina suggests that the climate was quite cold. Some thermophilic species (for example, Pterostichus magus and Dytiscus sp.) appear in sediments dated 33 thousand years ago (upper part of horizon B). Usually these species are not found now in tundra regions. Perhaps some warming has been reflected here. In the upper part of the section (horizon B), significant changes in the composition of entomofauna are noticeable. Typical Arctic tundra species (the weevil Isochnus arcticus) and several species of Arctic leaf beetles (Chrysolina subsulcata and Ch. tolli) dominate sediments dated between 24 and 18 thousand years ago. Only tundra mesotrophic and tundra xeromorphic species are found here, and insects of steppe groups are practically absent (it cannot be excluded that the isolated remnants of steppe species encountered have been redeposited). The species diversity is small. These significant changes reflect the harsh climate: very cold summers and dry winters. This climate is probably similar to the modern climate in the north ofWrangel.^[41] In sediments dated 17-14 thousand years ago (the upper part of the horizon B) steppe insect species again dominate. Approximately 14 thousand years ago, the presence of steppe species is the largest by section. During this period, a special type of landscapes appeared, the so-called sedge heaths (a xerophilic type of sedgeCarex argunensis and Politrichum piliferum dominated plant associations) – habitats with pill beetles (Morychus viridis) were widespread. Steppe areas similar to modern relics on the river. Jan and R. Indigirke also existed.^[41]

 More than 1,000 bones were collected by T.V.Kuznetsova during the field seasons from 1998 to 2000. All identified fragments were registered to obtain complete statistics. Most of the bones were found on the banks and bars. However, a large number of bones (195 copies) were taken directly from the Mammoth Hayote outcrop. About 24 bones were found strictly in situ.^[41] The general taxonomic composition of the collection of bones from the Bykovsky Peninsula is typical for all outcrops of the ice complex of Northeastern Siberia. Woolly mammoth, horse, bison, deer, predominate in the collection. All age-related definitions of bone remains were carried out by L.D. Sulerzhitsky. The total number of dated samples is 78. Two in situ bones dated by the standard method from the Mammoth Hayote section correspond to AMS-dating of plant remains from the same level. The age distribution of bone dating from sections of the Bykovsky Peninsula is uneven. The largest number of dates falls on the period 36-26.5 thousand years ago. Another concentration of dating occurred in the period 15-12.5 thousand years ago. There are two periods with several dates: 44.5-36 and 20-14.7 thousand years ago. Such an uneven distribution can be interpreted in two ways. Firstly, it depends on the geological situation, and secondly, on the number of animals in the region. The lower part of the outcrop (from 0 to 14-15 m above sea level) was poorly exposed. Only a few bones were taken from these deposits. This can explain the small number of bones older than 36 thousand years. The uneven distribution of bones may depend on taphonomic conditions, but T.V. Kuznetsova did not find this pattern. From 36 to 12.7 thousand years ago, the uneven distribution of bones reflects the density of animal habitation in this area. The lack of dating of mammoth bones for the period 20-14,7 thousand years ago may mean, if not the complete absence of mammoths here, then perhaps less favorable conditions for the existence of mammoths during this period.^[41] 

 The general conclusion based on the results of the study of sections of the Bykovsky Peninsula may be that continuous data were obtained from the section of the edoma formed in the interval 60-10 thousand years ago for climatic and landscape reconstructions of non-glacial regions of the north-west of Yakutia. The combination of different types of analyses: sedimentological, geocryological, isotopic, geochemical and paleontological allowed us to reconstruct and gain new knowledge about the landscapes that existed in the north of Siberia during the Late Pleistocene and during the transition to the Holocene. Siberian sections of permafrost rocks are an Arctic continental chronicle complementing the marine lake and glacial data. The interpretation of the paleoclimatic archives of permafrost rocks on the coast of the Laptev Sea fits well into the global isotope chronicle of Siberia, which began in the 80s of the 20th century.^{[2,5,7,8, etc.]} 

       D.Y. Bolshiyanov and co-authors^[35] substantiating the connection of edoma formation with level fluctuations indicate that all well-known sections of the ice complex studied in the Lena Delta area consist of two bundles of sediments: lower sands and upper strata of sandy loam with a significant content of plant detritus, called puff. Contrary to popular belief, these are not peat horizons. There are only a few of them in the thickness of the ice complex, the capacity of which does not exceed several tens of centimeters. Vegetable puff is a material enriched to varying degrees with plant residues deposited in the paleobasin, which is characterized by horizontally layered or wavy textures, emphasized or disturbed by freezing processes. In the context of the Nagym, the age of the lower sands, according to IRSL analysis, ranges from 57 to 49 thousand years ^[37], and the age of the deposits of the ice complex ranges from 44 to 45 thousand years or more, according to radiocarbon (AMS) analysis.^[37] Both bundles were deposited at a very close geological time. The underlying sands pass into the overlying thickness of the ice complex without a visible break. The gradual transition of marine sediments into the thickness of the ice complex occurs in the Hedenstroma tract on the island of New Siberia (75°07'10" s.w., 146°38'15" v.d.). EPR is the age of marine clays with Portlandia arctica L. shells. - 47 thousand years (without correction for the uranium content), which indicates the average age of the sediments. OSL-the age of the lower sands in sections of Kurungnakh Island, located near the top of the Lena Delta, is from 88 to 65 thousand years, although samples for determining the age were taken only from the lower half of the sand pack.^[37] The ice complex was formed more than 52,070 years ago.^[37] Marine diatoms of the species have been found in the underlying sands near the water's edge in the Olenek BayouThalassiosira kryophila. Above there are only fragments of freshwater diatoms. In the well-known and studied section of the Mammoth Khayata on the Bykovsky Peninsula, whose sediments were formed 60-5 thousand years ago ^[40,41], gravel interlayers of the beach facies of the reservoir were found among the puff. The most important series of data on the formation of sands and ice complex rocks was obtained by D.Y. Bolshiyanov and co-authors ^[35] when drilling wells on the Laptev Sea shelf near Cape Mamontov Fang (73°42'36.1"s.w., 117°10'01.4" v.d. - coordinates of the extreme offshore well). Marine deposits were recorded in a well with a depth of 58 m according to the marine complex of diatoms, the marine type of salinization of rocks, the remains of shells of marine mollusks. Also, signs of marine sediments (fragmented bivalves at the site of occurrence, shell detritus, iloid passages) are also found near the bottom of a well drilled on the shore. These signs definitely indicate basin sedimentation conditions. The gradual transition of marine sediments into freshwater sediments, in which the freezing and formation of the ice complex of rocks took place, is recorded both by lithology and by dating of sediments. Two OSL dates were obtained from the marine part of the section: 111.1±7.5 thousand years (RLQG 1727-026) and 86.2± 5.9 thousand years (RLQG 1728-026). OSL-the age of freshwater deposits of the ice complex from the well turned out to be 59.3±5.8 thousand years (RLQG 1729-026). According to D.Y. Bolshiyanov and co-authors ^[35], there is an indissoluble connection between the rocks of the ice complex and the underlying sands: there are no traces of breaks in sedimentation between them, and besides, dating of those and other deposits shows that there are also no chronological breaks. Sands with dates of 111-59 thousand years pass into overlapping sands and sandy loams with a high content of organic sediments (edoma or ice complex) and an age of 60-23 thousand years. Only some sections (Mammoth Hayota, Kurungnah) show the Sartan age of the tops of the ice complex rocks. The deposits of the ice complex are distinguished only by the presence of a very large amount of organic material and sandy loam, indicating sedimentation under conditions of significant removal of organic matter from the land. In the valley of the Urasalakh River, the ice complex is composed mainly of sandy deposits. The nature of the sedimentation medium is clearly manifested in almost all the described sections. The texture of sedimentary rocks is horizontally layered, wavy, signs of ripples of unrest are visible in many sections (Nagym sections, Gedenstroma tract, Sardakh Island, Kurungnakh, etc.). Marine features in the rocks of the ice complex, according to D.Y. Bolshiyanov and co-authors ^[35], are difficult to detect because during the formation of the ice complex, the accumulation basin was not marine in terms of water composition. These were practically fresh waters, but they retained a hydraulic connection with the sea. Tidal fluctuations of the level took place in them, there were overflows and surges, age-old fluctuations of the level. It was a basin isolated from the open part of the sea and desalinated as a result of the runoff of the rivers Khatanga, Olenek, Lena, etc.

           A.S.Makarov, V.Yu.Bolshiyanov and M.V.Pavlov^[49] performed rafting on the Urasalakh River for paleogeographic study of the edom between the Olenka and Anabara rivers. In the middle course of the Urasalakh River, in an outcrop with a height of 14 m, sands and sandy loams are layered, the layering is horizontal and wavy with plant detritus, represented by bark and twigs of shrubs. The permafrost texture is massive, ice layers up to 2 cm, inclined ice veins up to 30 cm thick. The radiocarbon age of plant detritus from the horizon from a height of 9 m above the water edge in the river (19 m above sea level) is 32550 ± 750 years ago (LU—5188). Horse vertebrae were found at the foot of the scree, at the river's edge. Edom strata, represented by layered sandy loams with a large number of plant residues and ice veins penetrating them, are rarely opened. They were observed on the eastern slope of Lake Mentikelir Vostochny, on the eastern shore of Lake Tungus-Yunkur, in the "Baijarakh tract" and in the lower reaches of the river. In the "Baijarakhov tract", located 6 km upstream from the mouth, on the right slope of the valley, in the most extreme eastern meander of the river, Edoma is represented by sandy loams with a significant content of plant detritus (the so-called moss "puff"). Edoma is opened from above by half of the visible section (25 m) and is characterized by an ice deposit with an apparent thickness of 3-4 m, formed by fused ice veins, and located below baijarakhs. The lower pack of sediments is horizontally overlapping sands and sandy loams. Ice veins in the Edoma outcrops upstream from the "Baijarakh tract" do not penetrate into the underlying sand deposits, and in the lower reaches, along with a decrease in the absolute and relative height of the lower contact of the edoma, cases of veins entering the underlying sands have been observed. On the seashore, in the area of the delta of the The Urasalakh ledge of the erosion is weakly exposed and is a floating thermodenudation slope with a large number of baijarakhs. Sandy loam here is much more than in Edom, which makes up the coastal plain of the upper and middle reaches of the river. At Cape Mammoth Fang, 20 km east of the mouth of the river. Urasalakh, edom deposits, represented by pulverized sands with plant detritus (moss "puff") and re-vein ice, lie on the underlying thickness without traces of erosion along a clear boundary due to the change in the color of sediments and the content of plant residues. The sands quickly turn into a "puff", but above, among the layering of plant residues and sandy loams, sands of the same composition are often found in layers from 10-20 cm to a meter. This means that the sedimentation situation during the formation of edoma did not differ much from the situation of accumulation of the underlying sands, and the accumulation of the latter was periodically repeated.^[49]

      The work of D.Y.Bolshiyanov and co-authors^[50] provides data on the structure of marine terraces and sediments of the Laptev Sea coast. It is proved that the formation of an ice complex of rocks and underlying sand deposits is inextricably linked with fluctuations in sea level. The research area is the southern coast of the Laptev Sea from the Pronchishchev ridge to the Oygos Yar, the Lena River delta, the Novosibirsk Islands. D.Y. Bolshiyanov and colleagues^[50] concluded that the deposits of the ice complex on the Laptev Sea coast were formed in a shallow and freshwater basin with a significant influx of organic material from rivers in the form of vegetation remnants. This pool had a hydraulic connection to the sea. Fluctuations in the level of the synoptic scale basin (tides, surges, surges) and its secular fluctuations were one of the main factors of syngenetic freezing of deposited basin sediments formed from river sediments. The underlying sands of the ice complex were formed in the marine basin for 111-79 thousand years ago. The sea terrace at the foot of the Angardam Mountains, 138 thousand years old, testifies to the high standing of the sea level during the Kazantsev time. Probably, the deposition of the sands of the island of Arga-Muora-Sise occurred in the same basin. Starting from the middle of the Late Pleistocene, significant sections of the bottom were brought to the surface by tectonic movements, forming a barrier of islands stretching from the Taimyr Peninsula to the Novosibirsk Islands. This is the reason for the poorly preserved signs of marine sediments in the rocks of the ice complex. However, the texture and lithology of sediments, despite the significant influence of cryogenic processes, indicates the accumulation of such a significant complex of sediments in the basin. Due to tectonic movements and eustatic fluctuations in sea level, precipitation accumulation conditions changed. The changing natural conditions on the surrounding land are also attested in the described sediments and relief. Glaciers developed here at the beginning of the Late Pleistocene, which caused an active outflow of their thawed glacial waters into the basin. Rivers have always carried a significant amount of plant residues into the sea, which sometimes accumulated in shallow pools in the form of moss puff - the most characteristic feature of the ice complex rocks. The new data obtained on the geological and geomorphological structure of the Laptev Sea coast and its water area confirmed the point of view previously put forward by Ya.Ya. Gakkel that in the Arctic Ocean in the past there were vast land areas, in particular on the Laptev Sea shelf. The time of existence of this land in the described region is from the middle of the late Pleistocene to the present.^[50]

 Sop-Haya. In 2001 , in the lower reaches of the river . The oldest Paleolithic site in the Arctic Region, about 31 thousand calendar years old, was discovered ^[51] (Pitulko et al., 2004). During the long-term study of the geology and stratigraphy of the vicinity of the site, previously unknown pre-Middle Pleistocene layers were identified at the base of the section of Quaternary sediments and various paleontological materials were found, including the remains of a representative of the Alceini tribe, discussed in this article. The open location of the ancient fauna in accordance with the name of the area was named Sop-Hai. Sop-Khaya is located on the left bank of the river. Yana is 100 km from the coast of the Arctic Ocean. Here, in the coastal cliffs, quaternary deposits of different ages are revealed, composing three above-floodplain terraces. The height of the third terrace reaches 40-45 m, the second – 16-18, the first – 10-12 m. The higher terrace, formed by frozen silt with syngenetic veins of ice 3-4 m wide, rises up to 40 m above the water edge (a.u.v.). Since erosion occurs in the upper part of the terrace, we use the water level as the reference line for all measurements. According to radiocarbon data, the age of this terrace is from 30 to 35 thousand years. The remains of the Pleistocene bone are collected in place in the upper third.

    Edoma is a Snotty Mountain in the lower reaches of the Yana. In 2001 , on the left bank of the The participants of the Russian-American expedition (project "Zhokhov-2000") discovered a unique monument of archeology in the outcrop 195 km from the mouth in the area of Snotlout Mountain – the Paleolithic Yanskaya parking lot.^[51] During the long-term study of the geology and stratigraphy of the vicinity of the site, previously unknown pre-Middle Pleistocene layers were identified at the base of the section of Quaternary sediments and various paleontological materials were found, including the remains of a representative of the Alceini tribe, discussed in this article. The open location of the ancient fauna in accordance with the name of the area was named Sop-Hai. Sop-Khaya is located on the left bank of the river. Yana is 100 km from the coast of the Arctic Ocean. Here, in the coastal cliffs, quaternary deposits of different ages are revealed, composing three above-floodplain terraces. The height of the third terrace reaches 40-45 m, the second – 16-18, the first – 10-12 m. The higher terrace, formed by frozen silt with syngenetic veins of ice 3-4 m wide, rises up to 40 m above the water edge (a.u.v.). Since erosion occurs in the upper part of the terrace, we use the water level as the reference line for all measurements. According to radiocarbon data, the age of this terrace is from 30 to 35 thousand years. The remains of the Pleistocene bone are collected in place in the upper third. The age of the cultural layer according to radiocarbon dating was 28-27.5 thousand years ago^[51,52]. During the subsequent organization of archaeological work, a complex of studies of the enclosing Quaternary deposits was determined in order to restore the natural habitat of Paleolithic man. The history of the formation of Quaternary sediments of the Soplivaya Gora reference section can be traced by biostratigraphic data from the end of the Eopleistocene – the beginning of the Pleistocene. Deposits of this age lie at the base of the section and are represented by a single cycle of alluvial deposits from channel conglomerates to peat bogs of ancient lakes. Reaching 7 m of capacity, they include syncreogenic PPL with a capacity of up to 1.5 m and are one of the most ancient edom complexes known in the Yano-Indigirskaya lowland. Against the background of a gradual facies change up the section from alluvial pebbles and sands of channel alluvium to floodplain and above to Aeolian loess-like siltstones, according to cryolithological signs, nine cycles of sedimentation are distinguished in the thickness, which, according to spore-pollen analysis, are due to climatic changes. By the middle of the Late Pleistocene, as a result of Aeolian sedimentation, a finely divided hilly relief was formed in the studied territory. At the turn of about 40 thousand radiocarbon years ago, there was a restructuring of the sedimentation regime, due to the deep embedding and the beginning of the accumulation of alluvium of the second above-floodplain terrace and genetically related proluvial deposits in depressions between hills. In the thickness of the sediments composing the second above-floodplain terrace, at the level of 7 m from the river's edge, the cultural horizon of the Paleolithic site can be traced, which naturally decreases to the river level in the channel facies. The accumulation of alluvial deposits of the second above-floodplain terrace ends at the turn of the Pleistocene and Holocene with the incision and the beginning of the accumulation of alluvium of the first above-floodplain terrace.^[52]

In the area of the Yansk Paleolithic site, based on the detailed dated sediment strata of the Edom formation II n/a of the terrace R. For example, using species definitions of pollen grains and spores and macrostates of plants by E.Y.Pavlova et al.^[53], a technique for reconstructing scalar climatic indicators based on Grichuk's floristic materials was applied, which includes two independent methods for calculating the main scalar climatic indicators: the method of the range of the complex and the method of summing climatograms. When constructing areal and climatograms, data on modern habitats and ecological characteristics of vascular plants, and climatic indicators of more than 3,000 weather stations were used. For the second half of the Late Pleistocene – the turn of the Holocene, within the time reliably dated to 14C 35-10 thousand years ago, average temperatures of the warmest month, average annual precipitation and their deviations from modern values for the western part of the Yano-Indigir lowland were obtained for different chronological sections. The warmest period with variable humidification conditions corresponding to the Khomus-Yuryakh warming of the Karginsky interstadial was observed between 34-32.5 thousand years ago, when the temperature of the warmest month was 3.5–4 °C higher than the modern one. Between 32.5–29 thousand years ago, there was a relative decrease in the temperature of the warmest month by 0.5–2 ° C. Climatic conditions 28-27 thousand years ago were close to modern. After 26 thousand years ago, there was a deterioration in the climate caused by the onset of cooling and an increase in precipitation, and by 24 thousand l.n. the temperature of the warmest month dropped to -3.5 ° C. The maximum of cooling and aridization occurred 17 thousand years ago – the Muskhain interval corresponding to the Sartan cryochron. At this time, the temperature of the warmest month reaches a negative extreme and is -4.5 ...? 7 ° C. Relative warming and humidification of the climate is noted by 14 thousand years ago, by 12 thousand years ago there is a noticeable warming.^[53]

V.V.Pitulko and colleagues ^[51,54] showed that natural and climatic changes in the Yano-Indigir lowland in the period earlier than 28 thousand years ago, preceding the reliable time of human habitation under 71 ° C.w and 28-23 thousand years ago, characterizing the habitat of Upper Paleolithic man in the final segment of the Karginsky interstadial, are especially important. At this time, warm and dry conditions and tundra landscapes were noted in relation to modern conditions, which is confirmed by the faunal characteristics of the parking lot (mammoth, rhinoceros, bison, horse, musk ox, reindeer, hare, brown bear, wolf, wolverine, arctic fox - definitions by P.A. Nikolsky). The natural conditions of the end of the Kargin time were favorable for human settlement in high latitudes, and then at least the Yano-Indigir lowland was developed. The transition to the conditions of the Sartan cryochron about 23 thousand years ago was quite fast and could lead to a reduction in inhabited territories.^[54]

 Edoma of the Arctic Ocean Islands

      Bol Island. Lyakhovsky. O. Bol. Lyakhovsky is the southernmost of the Novosibirsk Islands, separated from the continent by the Dmitry Laptev Strait. Since 1999, a group of Russian and German researchers has been working on the southernmost islands of the Novosibirsk Archipelago. They studied permafrost deposits discovered on the southern coast of Bolshoy Lyakhovsky Island and their isotopic composition, performed ²³⁰ Th/U dating of frozen peat of Middle Pleistocene age and 14C dating of Late Pleistocene organic matter in Edom.^[55] The studied section is located on the southern coast of Bol Island. Lyakhovsky in the eastern part of the Laptev Sea. In a section with a height of about 35 m, which has both signs of macrocyclicity and clearly manifested mesocyclicity, and no less vividly the microcyclic structure of individual veins ^[39], at least 11 different geocryological horizons can be distinguished. In all horizons, ice veins of various sizes, colors and origin are noted, which lie mainly in ice-saturated sediments with finely dispersed segregational ice.

Bol Island. Lyakhovsky is the southernmost of the Novosibirsk Islands, separated from the continent by the Dmitry Laptev Strait. A powerful outcrop extends from northeast to southwest for about 6 km. It has been studied from both sides of the mouth of the Zimovye river. In the section, which, according to Yu.K. Vasilchuk^[40], has both signs of macrocyclicity and clearly manifested mesocyclicity, and no less vividly the microcyclic structure of individual veins, at least 11 different geocryological horizons can be distinguished. In all horizons, ice veins of various sizes, colors and origin are noted, which lie mainly in ice-saturated sediments with finely dispersed segregational ice. The oldest generation of ice veins of the lower macrocycle, being no more than 0.5 m wide, penetrates into the weathering crust.^[55]

Radiocarbon and uranium-thorium age. According to the section in the area of the Zimovye river on the southern coast of Bol Island. Lyakhovsky obtained very ancient dating of the deposits of the re-vein complex. The buried peat bog at a depth of 39 m, in the thickness of the lowest generation of ice veins, was dated by the uranium-thorium method 200,900 ± 3,400 years.^[55] The obtained uranium-thorium dating data are quite reliable, since the measurement results indicate that the deposits were located in a closed system.  The uranium-thorium age differs significantly from the age determined by the thermoluminescent method (980,000 ± 250,000 years), according to which the same horizon was attributed by A.A.Archangelov to the Jaramillo event and designated as the Olersk formation (hypothetically dated to the late Pliocene – Early Pleistocene).

According to AMS ¹⁴ C dating data, the ice complex on the island of Bol. Lyakhovsky began to form about 50 thousand years ago, as indicated by dating (54.1 ± 3.1 thousand years, 52.9 ± 4.6 thousand years, 51.2 ± 4.7 thousand years, 50.3 ± 2.6 thousand years). The standard 14C dates obtained here earlier by Japanese researchers^[28] show that the ice complex on Bol Island. Lyakhovsky was formed in the interval between > 42.2 thousand years and 28.7 ± 0.4 thousand years and was overlain by Holocene deposits 7.4 ± 0.8 thousand years ago. The ice veins of the oldest horizon have an average isotopic composition of about -32% for the values of ?18 ^O and -250% for the values ^of ?2 H. For the ice veins of the overlying horizon, the extreme values of ?18 ^O are -37.3%, and the magnitude and ?2 H = -290% with the corresponding average values of ?18 O = -35.5% and ^{? 2} H = -280%.^[56] In the ice edom complex, the veins are characterized by the average values of ?18 ^O from -32.5 to -28.5 and the values of ?2 H from -250 to -220.^[55,56] Consequently, winter temperatures during the formation of deposits of the ice complex for the time interval 58-20 thousand years ago are characterized as relatively cold.^[56] Study of ice veins on the island of Bol. Lyakhovsky in the east of the Laptev Sea in northern Siberia, showed the conditions of continuous existence of permafrost rocks over the past 200 thousand years.

 According to AMS 14C dating data, the ice complex on the island of Bol. Lyakhovsky began to form about 50 thousand years ago, as indicated by dating (54.1 ± 3.1 thousand years ago, 52.9 ± 4.6 thousand years ago, 51.2 ± 4.7 thousand years ago, 50.3 ± 2.6 thousand years ago). These dates are in the same range as the dates from horizon B. In an ice vein from the deposits of the ice complex, a small willow leaf (Salix) was dated 35.0 ± 2.1 thousand years ago at an altitude of 15.8 m above sea level. Lemming coprolites found in an ice vein at an altitude of 8.2 m above sea level 49.2 ± 2.1 thousand years ago and at an altitude of 9 m above sea level, 39.7 ± 1.3 thousand years ago were also dated. According to these dates , the age of the ice complex is now determined X .Mayer and A.Y.Derevyagin^[56] in the time interval between 55-28,7 thousand years ago. At the same time, the youngest part of the deposits of the ice complex were unavailable for selection.

     Pollen spectra from the host sediments^[57] demonstrate the predominance of tundra vegetation, which indicates relatively warm summer conditions and with a sufficiently high humidification of the summer season. The combined analysis of palynological and isotope analysis data suggests that at that time the average annual temperatures in the area of Bol. Lyakhovsky Island were quite high.

During the period of the growth of the re-vein ice of the last 50 thousand years, winter temperatures were extremely cold, which follows from the isotopic composition of the re-vein ice of this horizon. The composition of stable isotopes for various generations of ice veins was analyzed on Bol. Lyakhovsky Island to reconstruct the development of paleoclimate. Isotopic composition of ice veins on Bol Island. Lyakhovsky is significantly variable over time, and varies from -37.3% and -19.2% for values of ? ¹⁸ O and from -290% to -150% for values of ? ² H. Within one ice vein, a relatively constant isotopic composition was observed with changes of less than 4 and 30 in the values of ?18 ^O and the magnitude of ?2 H.^[56] For all the ice veins on the island of Bol. Lyakhovsky, including modern ice veins, average values of d _exc vary between 4.5 and 12.^[55]

Based on the study of variations of stable isotopes, three Pleistocene horizons were identified^[56] (although a very light isotopic composition was noted in all horizons): a). The ice veins of the oldest horizon have an average isotopic composition of about -32% for the values of ?18 ^O and -250% for the values of ?2 H; b). For ice veins of horizon B, the extreme values of ?18 ^O are -37.3% and the magnitude of ?2 H = -290% with the corresponding average isotopic composition of the values of ?18 ^O -35.5% and the values of ?2 H -280%; c). The ice veins of the horizon A and B are characterized by a relatively low average deuterium excess dexc from 5 to 7%; d). In the ice complex, the veins are characterized by the average values of ?18 ^O from -32.5 to -28.5 and the values of ?2 H from -250 to -220, and thus are close in values to the veins from the lower part of the horizon A. At the base of the ice complex, the value of the deuterium excess - d _exc varies between 8 and 10.3%. In its upper part, the value of the deuterium excess is about 5%.^[56]

 Winter temperatures during the formation of deposits of the ice complex can be reconstructed as relatively cold for a time interval of 50-28.7 thousand years ago.^[55] The low concentration of pollen with the dominance of pollen of typical tundra plants indicates, according to A.Andreev^[57], the cold climatic conditions of the summer season, wetter than before. We can assume a slight increase in both winter and summer temperatures. Winter temperatures were only slightly warmer, but comparable to the temperatures obtained from the ice veins of horizon A. Due to such a stable isotopic composition, it is possible, according to the conclusion of X.Mayer, consider Horizon A as an older analogue of the ice complex. This is confirmed by the similar structure of precipitation, high iciness (total humidity from 60 to 170%). A similar type of ice veins, the presence of paleosols and ice schliers interrupted by lens-like inclusions and mesh cryotexture. in both horizons.

Bol. Lyakhovsky Island has never had winters warmer than at present, even in the warmest phases of the Holocene optimum, which convincingly confirms the conclusion previously obtained based on the analysis of the isotopic composition of dozens of vein sections formed during the Holocene optimum^[9] about the harsh winters of the Holocene optimum and active (maybe even more more active than now), he lived in the Russian Subarctic. For Holocene ice veins in the deposits of alluvium and thermoerosive valleys, as well as for modern ice veins, the slope of the diagrams ? ¹⁸ O– ? ² H varies about 7.5. Alas ice veins with relatively low slope values of 7.1 may have been influenced by evaporation processes due to the runoff of melt water along the slopes.^[56]

The presence of cryoxerophilic species in palin spectra also indicates cold and dry conditions of the summer season^[56] during the formation of horizon B. This is in good agreement with the morphology of re-vein ice and data on stable isotopes. In horizon B, as well as on contact with the upper part of horizon A and at the base of the ice complex, various ice veins and sub-vertical ice-ground veins were found, demonstrating the heterocyclic development of the complex. A large number of buried and multi-tiered ice veins in the horizon B suggests a rapid accumulation of sediments.

Other explanations for the burial of the heads of re-vein ice may be associated with changes in the thermal or hydrological regime, that is, a decrease in the depth of thawing of the active layer. The high sedimentation rate is indicated by AMS ¹⁴ C dating of organic material- grass roots in situ for about 50 thousand years within 5-8 meters of horizon B. Not only ice veins are associated with high sedimentation rates, but also vertical structures of frost-breaking cracks can also be buried. This leads to the interweaving of ice veins, which was first explained by Ross McKie, so that frost cracking could not occur in the same place. This is one of the possible explanations for the formation of ice–ground veins, which consist of numerous elementary ice veins interspersed with mineral veins. The existing data do not allow us to decide whether the reason for the formation of ice-ground veins is a higher rate of sediment accumulation or a relatively lower amount of winter precipitation. Since ice-ground veins were also found near the lower boundary in a zone with a heavier isotopic composition, according to X.Mayer and A.Y.Derevyagin^[56], it is possible to interpret ice-ground veins as an indicator of the initial stage of the growth of re-vein ice and perhaps this is the beginning of the formation of the Late Pleistocene ice complex on Bolshoy Lyakhovsky Island. This version is confirmed by the occurrence of relatively small ice veins in the lower part of the ice complex. It is well known that the isotopic composition of winter precipitation in Canada formed in the Pacific Ocean is characterized by low values of deuterium excess. Based on this X .Mayer^[56] concludes that the Pacific Ocean is a possible winter source of precipitation for O.Bolshoy Lyakhovsky. It seems to us that this is still a poorly substantiated hypothesis, although to completely deny some participation of Pacific air masses in certain periods of the Pleistocene and Holocene in the addition of O.Bol.Lyakhovsky probably shouldn't. On the Bykovsky Peninsula, a shift towards an increase in the values of the deuterium excess dexc was found in veins dating back about 20 thousand years. This was interpreted as a change in the source of humidity.^[56] If such a change of the main source of winter moisture took place, we can expect a sharp increase in the values of deuterium excess in Holocene ice veins compared to the ice complex. On the island of Bol. Lyakhovsky noted a slight increase in deuterium excess from 5% (in the ice complex) to 7% (in the veins of the Alas).

The study of ice veins on the island of Bol. Lyakhovsky in the east of the Laptev Sea in northern Siberia, shows the conditions of continuous existence of permafrost rocks over the past 200 thousand years. Through the study of stable isotopes, six generations of re-vein ice have been identified, which are used to reconstruct the paleoclimatic situation. These paleoreconstructions are based on a comparison between the stable isotope composition of modern precipitation (snow and rain) with modern ice veins, which have been identified through studies of tritium content. On Bolshoy Lyakhovsky Island, modern ice veins are most likely fed from snow melt water, and, therefore, it is quite reasonable that winter temperatures are derived from the values of the isotopic composition of ice veins.^[9]

Changes in the content of heavy isotopes of oxygen and hydrogen show significant changes in the winter temperature regime on Bolshoy Lyakhovsky Island. The period of cold winter temperatures was determined for the last 200 thousand years. According to radiocarbon data, a break in sedimentation lasting about 100 thousand years has been recorded so far, including the Eem period, followed by a period of extremely cold winters that occurred about 50 thousand years ago, which was characterized by high rates of sediment accumulation, sometimes exceeding the rates of vertical growth of re-vein ice.^[56]

Ice-ground veins appear in the sediments of the last classical Late Pleistocene ice complex. During this time, the winters were very cold. The warming trend was reflected in the isotopic composition of Holocene re-vein ice, compared with Late Pleistocene veins, there was a sharp jump in the content of heavy stable isotopes of oxygen and hydrogen. The highest winter temperatures are noted for modern ice veins on the island of Bol. Lyakhovsky.

According to Yu.K. Vasilchuk^[40] sections of O. Bol. Lyakhovsky are heterogeneous formations, heterocyclicity is confidently distinguished in the development of re-vein ice, and the distribution of radiocarbon dates may indicate lateral heterochronicity of the strata.

 Faddeevsky Island. Pollen analysis, analysis of plant fossils, and radiocarbon analysis of the 1.4-m section of the thermokarst formation on Faddeevsky Island (75°20's.w., 143°50' v.d., height 30 m) allowed A.A. Andreev and co-authors ^[58] to obtain data on the environment during the Late Pleistocene interstadial. Conventional radiocarbon dating (25700 ± 1000, 32780 ± 500, 35200 ± 650 years ago.) and two AMS-dating (29950 ± 660 and 42,990 ± 1280 years) they indicate that the deposits were accumulated during the Karginsky period. Numerous fossil remains of mammoths (Mammuthus primigenius), which were collected in the immediate vicinity of the research site, are dated to 36700-18500 years. Rare bones of bison (Bison priscus) dated to 32200 ± 600 and 33100 ± 320 years. ^[58] 

Continuous clay, sanded and torn sections containing pollen and radiocarbon data from Faddeevsky Island indicate that plant communities existed approximately 32-25 thousand years ago. A.A. Andreev and co-authors ^[58] indicate that there is no evidence that a hypothetical Panarctic ice sheet existed in this area 43-25 thousand years ago. They also found no evidence that it existed on the island during the last ice Age or in the Holocene.

Sand-ice veins on the coast and islands of the Laptev Sea. A.Yu.Derevyagin et al. ^[59] data on the distribution, cryogenic structure and isotopic composition of sand-ice veins in Pleistocene sand deposits (more than 50 thousand years old) on the coast and islands of the Laptev Sea are presented. The thick layers of sand underlie the deposits of the Upper Pleistocene ice complex and contain several tiers of sand-ice veins. The studied sections describe transitions from sand-ice veins to re-vein ice and contact zones of sand-ice veins with overlying re-vein ice of the ice complex. The lightest isotopic composition (average values of ?18 ^O from -34.3 to -36.0 % and values of ?2 H from -258.2 to -280.8 %) is characterized by ancient polygonal vein systems developed in the mid-late quaternary deposits of Bolshoy Lyakhovsky Island. Sand-ice veins in the Upper Pleistocene sands of Cape Mammoth Fang (Anabar–Olenek interfluve) have a heavier isotopic composition (average values of ?18 ^O from -28.5 to -31.7% and values of ?2 H from -222.4 to -245.4%). The isotopic composition of sand-ice veins indicates cold and dry climatic conditions of the period of their formation. A comparative analysis of the isotopic composition of the studied sand-ice veins and re-vein ice shows their similarity. Data on the conditions of formation and isotopic composition of modern sand-ice veins on Bunge Land are also given. Studies conducted by A.Yu.Derevyagin et al.^[59] have shown that permafrost sand deposits widespread in the coastal zone and on the islands of the Laptev Sea contain polygonal vein structures with sand-ice filler - sand-ice veins. The width of the sand-ice veins reaches 4-5 m. The age of the host deposits is more than 50 thousand years. The multi-tiered arrangement of sand-ice veins in sections, frequent transitions within the same polygonal vein system from sand-ice veins to re-vein ice indicate multiple changes in the hydrological regime of a shallow, periodically draining freshwater basin and the facies conditions of sedimentation of sand deposits. The thickness of sands with sand-ice veins, as a rule, is overlain by deposits of the ice complex, whose age in the area of Cape Mammoth Fang is 30-35 thousand years. The transition from the sandy strata to the deposits of the ice complex is accompanied by an increase in the content of dusty particles, organic inclusions, interlayers and lenses of peat, whose age is about 40-46 thousand years. Powerful syngenetic ice veins of the ice complex are embedded in the underlying sandy strata to a depth of 5-6 m, often splitting sand-ice veins. The isotopic composition of sand-ice veins is very close to the isotopic composition of sand-ice veins of the ice complex, which indicates the genetic similarity of their food sources. The characteristics of the isotopic composition of sand-ice veins confirm the existing ideas about dry and cold climatic conditions of the period of their formation. The average winter air temperatures of the period of formation of sand-ice veins in the middle-late Pleistocene, according to the approximate formula of Yu.K. Vasilchuk ^{[9, 10]}, could be lower than the modern ones by 15 °C or more, and the upper Pleistocene – by 10-12 ° C. The modern formation of sand-ice veins in sandy sediments (Bunge Land, Novosibirsk Islands) occurs in conditions of severe (average winter air temperature about -23 ° C) and dry (annual precipitation 130-140 mm) climate. The relatively high values of ?18 ^O and ?2 H are probably related to the processes of isotopic fractionation as a result of intense evaporation.^[59]

                The effect of cryogenesis on clay minerals in edoma by V.N.Konishchev and V.V. Rogov^[60] the effect of cryogenesis on clay minerals in edoma is considered. They have shown that the direction of change of inherited clay minerals, subject to alternating freezing–thawing, is the destruction of all types of their structural groups. V.N.Konishchev and V.V. Rogov^[60] suggested that the revealed differences in mineralogical composition between the syngenetic frozen strata of edom sandy loams and loams and older deposits are explained primarily by the fact that that significant structural changes of clay minerals occur during cryogenic weathering, the group of mixed–layer minerals with a movable lattice present in syngenetic edom strata is the result of cryogenic transformation. The edom contains modified forms of minerals of various structural groups that arose during the cryogenic weathering of the initial association of clay minerals of pre-quaternary sedimentary rocks. Apparently, amorphous compounds characteristic of a fraction with a dimension of less than 1 micron, syngenetic frozen strata, also have a close genetic connection with these formations. The above data should be kept in mind when paleogeographic constructions and conclusions about the genesis of sediments. For example, if we do not take into account the processes of cryogenic changes in clay minerals, we can conclude that the ice-rich loam and sandy loam of the North-East of Russia are exotic in comparison with older strata. This may lead to a conclusion about their Aeolian genesis, although in reality the peculiarity of the mineralogical composition of the clay fraction is explained by cryogenic factors.^[60-63] 

The section of the lake tab of Mammoth Mountain on the left bank of the Aldan (62.978056 ° s.w., 133.952778 ° v.d.) caused the greatest difficulties in dating. Ice veins with a height of more than 5 m in the upper part of the 50-60-meter terrace lie in lake-marsh tabs crowning its section.^[9] Deposits with a thickness of 9-12 m are represented by dark gray lake loam.

Initially, based on a variety of dates on wood from these loams in the range from 35 to 46 thousand years ^[64,65], the accumulation of loams and veins in them was dated to a time older than 30 thousand years. At a depth of 8.0 m (below the sole of brown loams), a date of 44,000 ± 1900 years was obtained (MSU-IOAN-121), at a depth of 3.0 m – 40600 ± 550 years (MSU-IOAN–56), and between them 26.8 thousand years.^[64] There are obvious signs of redeposition of wood material. During the excursion, Pev Troy also took samples for 14C and dated them in the Smithsonian Laboratory ^[65]: from a depth of 1.0 m, the date 415 ± 40 years (SI–1968) was obtained, from a depth of 5.0 m – 42150 ± 3700 years SI–1965), from a depth of 8.0 m – 46700 ± 1500 years (SI–1972). The final dating from a depth of 4.0 m – 4020 ± 150 years – was obtained from the collections of M. S. Ivanov. Two dates from loams from depths of more than 10 m are prohibitive; five dates from the underlying loam sands are also prohibitive. Yu.K.Vasilchuk (according to the 1985 collections) received ^[66] two late Pleistocene dates: on wood fragments at a depth of 2.6 m by – 35000 ± 400 years (GIN-4604), and at a depth of 8.0 m, 38400 ± 500 years (GIN–4603), but from a layer of autochthonous peat lying on the contact of gray and brown loam at a depth of 2 m, a Holocene date of 4800 ± 40 years (GIN–4607) was obtained. The author even believed it was assumed that the age of the veins was rather Holocene, although noticeably isotopically negative values of ?18 ^O (in the main – upper part of the veins averaged -28.5%, whereas on the Aldan floodplain in modern veins the value of ?18 ^O is -26.3 and -25.1%) seriously contradicted this (but at the same time in the tails (several very high values of ?18 ^O up to -16.5% were obtained in lake tabs, which are enriched with continental salts – more than 400 mg/l)^[66]. Direct dating of organic matter from veins by the AMS method^[67]. refuted both points of view. The three dates obtained in the range of 17-19 thousand years ago indicate that the veins are younger than 20, but older than 10 thousand years. Interestingly, one of the first loams at a depth of 5.5 m was obtained a date of 26,800 ± 600 years (MSU-IOAN-44), but it was considered rejuvenated due to poor preservation of wood ^{[64, p. 163]}. In the light of the new dates obtained, it seems to be closer to the true time of the accumulation of loams, although somewhat more ancient, since, most likely, almost all the wood in these loams was re-deposited by streams from older Late Pleistocene sediments. The top-down extension of more conventional microorganics dating has clearly confirmed the presence of vertical stratification of re-vein ice, which, although accumulating in re-emerging frost-breaking cracks, is formed simultaneously with the accumulation of sediments, so from the bottom up its age becomes younger. Measurements on such small samples have shown the wide possibilities of using radiocarbon dating in the study of underground ice, even in cases where the admixture of organic matter in them is very small, i.e. almost every ice deposit, re-vein or formation type, or even schlier segregation ice can be very reliably dated using AMS.

The section of the edom deposits of Mammoth Mountain was studied by S. Popp and co-authors.^[68] Radiocarbon dating of wood residue from sediments slightly above ice sampling yielded a result of 41230 (KI-5183) years. This age is in good agreement with the previously published measurement results on this outcrop, suggesting that the growth of ice veins took place approximately between 46700 ± 1500 ¹⁴ C years ago and 34020 ± 1500 ¹⁴ C years ago^[65]. The values of ?18 ^O are on average equal to -30.5 %, and the value of ?2 H is -237 %, d ^exc is 7.6 %. Variations in the isotopic composition are not large - less than 2 % for ?18O and 16 % for ?2 H.^[68]

The material taken from the re-vein ice on Lake Syrdakh gives an age of 21710 ± 680 ¹⁴ C years. On Lake Ulkakhan Syrdakh, ice dating gives 13110 ± 680 ¹⁴ C years on the lateral boundary of the vein and 3755 ± 30 ¹⁴ C years in the center. The fine-earth material is characterized by non-parallel lenticular cryotextures and a weight iciness of 30%, as well as the presence of paleopedological features.  On Lake Ulakhan Syrdakh, the top of the exposed ice vein is approximately 2.1 m wide and 2.3 m long. However, the vein itself presumably extends down to a depth of 10 m, at least to the thermokarst lake below. At the point near Lake Syrdakh, the exposed vein is approximately 3 m wide and 0.8 m long, but its present stretch is presumably as large as on the previous lake.

The average value of ?18 ^O is -31.3 % and the average value of ?2 H is -246 % on Lake Ulkakhan Syrdakh and on Lake Syrdakh – the average value of ?18 ^O is -30.8 % and the average value of ?2 H is -245 %. These values, as well as their small spread, are very similar to the isotopic data obtained at Mammoth Mountain. But they differ by a lower average value of dexc - -1.8 and 4.5, respectively, while dexc in the veins of Mammoth Mountain is 7.6.^[68]

Edom of Chukotka

  A.N. Kotov^[69] considered the conditions of cryolithogenesis of Chukotka edom rocks in the Late Pleistocene. The most famous remnants of Late Pleistocene rocks of the Chukotka ice complex are located in the valley of the Main River, on the island of Ayon and on the coast of the East Siberian Sea. Similar formations have been discovered and studied on the northern coast of Onemen Bay, on the island of Wrangel, in the valleys of the Anadyr, Amguema and Tanyurer rivers. For the rocks of the Chukotka ice complex formed during the global cooling of the climate at the end of the Late Pleistocene, A.N. Kotov^[69] identified seven cryolithogenesis environments and, in accordance with them, seven cryogenic facies. Probably, this does not exhaust the full set of them, which is due to the insufficient cryolithological study of the territory and the global destruction of icy deposits in the Holocene. For almost each of the cryolithogenesis environments, cryofacial analysis methods were able to quantify such important paleogeocryological characteristics as the power of the STS, the average annual temperature of frozen rocks and the amplitude of temperature fluctuations on the soil surface. A number of the calculated data used were taken from literary sources, which makes the already approximate calculation method sketchy. However, the obtained obviously approximate values of paleotemperature and paleoamplitudes still allow us to identify significant differences in the geocryological conditions of the selected cryolithogenesis environments and the nature of their changes compared with modern parameters. The average annual MMP temperatures were significantly lower than modern ones. The palsoamplitudes of temperature fluctuations on the surface of the accumulation of rocks of the ice complex indicate significantly more continental conditions of that time. For example, the current amplitudes of temperature fluctuations on the soil surface in the hall area. Onemen do not exceed 13 ° C, and at the end of the late Pleistocene they reached 25 °. That is, in the conditions of deep regression of the sea allocated for this period of time, the area turned from coastal to continental. Paleogeocryological constructions are also fully confirmed by reconstructions of mid-winter paleotemperatures performed based on the results of determinations of the isotope-oxygen composition of the PGL

          The performed studies allowed A.N. Kotov^[69] to draw the following main conclusions:

     – the conditions of sedimentation in the cryolithozone determine the nature of freezing and ice formation, but they themselves are directly dependent on geocryological conditions and cryogenic processes. As a result, frozen rock is formed, and not sediment, which takes a long period of time (in the geological sense) to transition into the rock. That is, these are not the conditions of sedimentation in its pure form, but the conditions of cryolithogenesis, and they determine the composition and cryogenic structure of cryolithogenesis products (cryolithogenic rocks);

     – massive, rare and unique facies are distinguished in the structure of the rocks of the ice complex. The situation of cryolithogenesis is captured in the composition and structure of mass facies composing the bulk of cryolithogenic strata. The formation of rare facies is associated with extreme, rarely recurring events (for example, with abnormally large floods) and is due to specific sedimentation conditions. The emergence of unique facies occurred as a result of geological events that are not a consequence of this geological and geomorphological environment (layers of volcanic ash);

     – the leading process in the formation of rocks of the ice complex is a powerful re-vein and segregation ice formation, the volume ice content of deposits exceeds 50-85%. It is the ice component that determines the similar appearance of genetically heterogeneous strata.

Earlier, A.N. Kotov published data on the isotopic composition of edom late Pleistocene re-vein ice at the mouth of the Anadyr River^[70], in the valley of theTanurer ^[71], on Wrangel Island ^[72], etc. 

Pollen and spores in edible re-vein ice

 In 2007, a monograph by A.K. Vasilchuk^[73] was published, based on palynological studies performed on extracts directly extracted from edom re-vein ice, and in 2009 these supplemented materials were defended as a doctoral dissertation^[74]. A.K. Vasilchuk ^[73-77] the problems associated with the reconstruction of landscape and paleotemperature signal in paleopalinospectrums from syngenetic re-vein ice in the cryolithozone of Russia. The palin spectra of the supporting syncreogenic Late Pleistocene and Holocene sections are characterized in detail: the Seyakhinsky polygonal-vein complex, the late Pleistocene syncreogenic strata at the mouth of the Mongatalyangyakh River, polygonal-vein complexes at the mouth of the Gyda River in the north of Western Siberia and Cape Verde, the Duvan Yar and Plakhinsky Yar in the valley of theKolyma. The late Quaternary palinostratigraphy of the cryolithozone of Eurasia and interregional correlation were performed, the connection with global changes in the Earth's climate was traced. The main palynological and geochronological boundaries of the Late Pleistocene and Holocene are considered. The reflection of Heinrich's events on the spore-pollen diagrams of polygonal-vein complexes is shown. To interpret the palynological data of the Arctic and Subarctic, not only the temperatures of the growing season are important, but also the duration of the growing season. Therefore, according to A.K. Vasilchuk^[73,74], the sum of positive temperatures is the most adequate indicator for reconstructions by palinospectrums.

Variations in the sum of positive temperatures for the last 50 thousand years have been reconstructed for the north of Western Siberia and the north of Yakutia a) taking into account the possible redeposition of palynomorphs, including quaternary pollen and spores, b) taking into account the facies variability of edom deposits, c) based on the separation of regional and local components of palinospectres – for this purpose, data on palinospectres of re-vein ice and host sediments, d) by the ratio of the key components of the cryolithozone palinospectres.^[73-77]

A.K. Vasilchuk, studied pollen and spores directly extracting them from vein ice in edom strata ^[73-75] and came to important methodological conclusions concerning the division of pollen spectra into local, regional and long-range components ^[76] and the importance of studying the taphonomy of pollen grains^[77]. According to the conclusions of A.K. Vasilchuk^[76], it is convenient to separate local from regional and long-range components of palinospectres for the analysis of palinospectres formed in the tundra zone. Regional and local components of palinospectres should be used in different ways to assess, identify and reconstruct phytocenoses producing pollen and spores. The long-range and regional components of the spectra cannot be indicators of local tundra phytocenoses, but they can be successfully used to compare the spore-pollen diagrams of sections located at a considerable distance from each other (300-500 km), since the regional pollen rain in the treeless tundra space varies over large areas and synchronously affects the composition of the palinospectres of the sites located at a great distance from each other. The intake of long-range tree pollen in the tundra zone is less susceptible to changes compared to the intake of pollen and spores of local plants, which is associated with fluctuations in productivity. Therefore, the change in the composition of far-bearing pollen indicates the restructuring of plant communities in the territory that is the source of far-bearing components. Local components of palinospectres record the features of local phytocenoses. In addition, they are affected by the redistribution of pollen and spores under the influence of local taphonomic factors. The concentration of tree pollen drops sharply at the border of the forest and tundra. Therefore, tundra palinospectrums can be distinguished on the basis of a sharp drop in the concentration of pollen of tree species during the transition from forest conditions to tundra conditions. A noticeable decrease in the concentration of pollen and spores also occurs during the transition from subarctic tundra to Arctic tundra. In this case, a decrease in the intake of pollen and spores to the surface occurs due to a decrease in the pollen content of shrubs, grasses and shrubs. The supply of far-bearing pollen to the surface in the tundra zone of Eurasia is almost constant, and fluctuations in its content are caused by fluctuations in the pollen productivity of local plants. Far-bearing pollen enters the tundra territory both in the summer-spring and winter seasons. For the Arctic tundra, the arrival of far-bearing pollen on the surface plays a decisive role in the formation of palinospectres. The peculiarities of plant adaptation to the harsh conditions of the tundra directly affect the processes of formation of spore-pollen spectra, especially the local component. Long-term viability of flowers causes uniform dispersion of pollen, and closed flowering contributes to a decrease in pollen productivity of plants and, consequently, a low concentration of pollen in sediments. This is reflected in the pollen productivity of anemophilic plants of the families of sedges, cereals, etc., which play a significant role in the spore-pollen spectra. The amount of pollen of tree species at the northern limit significantly reflects climatic conditions. However, this signal can become noticeable in fossil spectra only when using averaged data over a sufficiently long period (tens to hundreds of years). A regional pollen rain is formed over treeless spaces north of the forest boundary, consisting mainly of long-range components. Analysis of the pollen content of tree species in the subfossile palin spectra of the tundra zone showed that the arrival of pollen on the surface is due to the aerodynamic properties of pollen grains. The distribution of pollen grains of Scots pine is more uniform compared to the distribution of pollen of Siberian cedar and birch tree forms. The concentration of pollen of dwarf birch has a pronounced maximum in the southern shrub tundra.

A.K. Vasilchuk showed ^[77] that the composition of primary palinospectrums changes during the transportation and redistribution of pollen and spores over the Earth's surface and fossilization.^[77] These processes are especially noticeable in the tundra zone. The features of the formation of palynospectres in subaerial and subaqual deposits of the tundra zone are considered, differences in the content of palynomorphs with discontinuous exina disturbances are revealed. The change in the influence of regional and local taphonomic factors on the slope in the Arctic tundra has been traced. The safety of pollen in the deposits of the tundra zone, in snowfields and re-vein ice is considered.^[77]

The southern boundary of the distribution of ancient and modern re-vein ice in Russia

                In 2004, the work of Yu.K. Vasilchuk^[78] was published, in which the southern boundary of the distribution of ancient and modern re-vein ice was considered. The considered southernmost of the currently known locations of veins allow us to significantly clarify the southern boundary of the area of re-vein ice, previously carried out by P.A.Shumsky and B.I.Vtyurin^{[79] [1963]}. It is shown that the border of occurrence of the southernmost locations of re-vein ice in the north of the European part of Russia runs approximately 66°30 - 67° s.w., in Western Siberia it is located at 63°30 - 64°s.w., and east of 90° v.d. in Tuva, Mongolia, China and in the Amur region, the boundary of the distribution of veins reaches 49-52 ° C. The average annual temperatures of permafrost rocks in which re-vein ice is found are about -1, -1.2 ° C, although in principle they can probably be found in frozen rocks close to 0 °C. The current growth of re-vein ice has been noted within the massifs with average annual ground temperatures of about -1.5 -2 °C. When assessing paleogeocryological conditions based on pseudomorphosis findings, it should be taken into account that the gap between the southern boundary of the pseudomorphosis range and the paleocryolithozone boundary reconstructed according to them may be very small and in some cases does not exceed the first hundreds of kilometers. It is shown that cracking can occur at the post-cryogenic stage, at the stage of thawing of the active layer.^[78]

Heterocyclicity, heterochronicity and heterogeneity of edom

                In the monograph published in 2006 ^[40], a new concept of Yu.K. Vasilchuk is presented, considering re-vein ice and permafrost strata containing them as heterocyclic, heterochronous and heterogeneous formations. The materials substantiating the drawing of a new southern boundary of the distribution of modern re-vein ice in Eurasia are presented. A new mechanism of post-cryogenic cracking at the stage of thawing of the active layer is proposed. The chronology and paleogeographic correlation of polygonal-vein structures of the reference sections of the north of the European part of Russia, Western and Central Siberia, the north and central part of Yakutia, Chukotka and Magadan region, Tuva and Transbaikalia, using AMS-radiocarbon dating directly from micro-findings from ice veins, was carried out. A more reliable paleogeographic and paleoclimatic scenario of the development of the paleocryosphere in the polar regions of Russia for the period of the last 50 thousand years has been obtained. Chapter 1 shows the southern boundary of the distribution of modern re-vein ice on the plain and in the middle mountains. In Chapter 2, the author's model of heterocyclic development of edom syngenetic re-vein ice is considered. Chapter 3 is devoted to radiocarbon dating of re-vein ices by organic material in host sediments and direct AMS radiocarbon dating of re-vein ices by microinclusions of organic material from edom veins and by pollen and spore concentrate in re-vein ices. In Chapter 4, the vertical and lateral heterochrony and heterogeneity of the Duvannoyarsky edom massif with syngenetic re-vein ice are considered. Chapter 5 is devoted to the consideration of the radiocarbon age and isotopic characteristics of the reference sections of the north of Russia and North America. Chapter 6 discusses the paragenetic combinations of re-vein ice with segregational and injection-segregational ice in the cores of heave mounds, with intra-soil formation ice, with glacial ice and glacial glacier and iceberg ice. Chapter 7 shows the reflection of the Dansgaard-Eschger events in the isotopic record of syngenetic re-vein ice.^[40]

 Alaska 's Edom

                Fox permafrost tunnel. The most thorough data on edoma in central Alaska were obtained on the basis of studies conducted in the frozen CRREL tunnel near Fairbanks, where only the lower 7 m of the edoma section were exposed. After a thorough review carried out by T. Hamilton and co-authors^[80], the research was continued^[81-83].  The observations of Yu.L. Shura and colleagues^[81] inside the CRREL tunnel showed that layered, lenticular-layered and microlensular cryogenic textures are characteristic of edomous permafrost rocks. Mesh cryogenic textures indicate a local modification of thawing. During the period of growth of syngenetic permafrost rocks along the vein ice, thermokarst erosion may occasionally become active, leading to the development of ravines and tunnels in near-surface sediments. Local cavities resulting from thawing can lead to the formation of thermokarst-cave ice and pseudomorphoses. They can be considered as additional characteristics of syngenetic edoma growth.^[81] Continuing cryostratigraphic studies in the tunnel, the same authors^[82] confirmed that the long-lasting syngenetic growth of permafrost rocks is often accompanied by episodic fluvio-thermal erosion, which acts mainly along vein ice. There may even be re-deposition of sediments, undercutting of the lateral flow and local subsidence of thawed material. As a result, mesh-chaotic and massive cryotextures are formed, reflecting epigenetic freezing in places of localized thermal erosion and redeposition. These secondary or modified deposits are described as pseudomorphoses. They reflect places where ravines and eroded ice veins have been replaced or filled with gravel, sand, silt or various mud-ice complexes. Pseudomorphoses of ice reflect the formation of thermokarst cave ice.^[82]

         T. Katayama and co-authors^[84] took samples of gas preserved in ice veins in the Fox tunnel. The concentration of methane in the vein gas was 0.8 ± 0.006%, which is several orders of magnitude higher than the concentration of methane in the atmosphere. We are sure that our sample of gas in the vein was separated from the atmosphere for thousands of years, since we determined that the concentration of a stable isotope of the value ?13 C was -84.651, which showed that atmospheric air pollution was negligible. The radiocarbon date 24,884 ± 139 years ago (NUTA _2-3477) was determined from methane using AMS at the Nagoya University tandetron accelerator. It is not yet known whether they are active or inactive, but these results indicate that bacteria adapted to the conditions of ice veins have survived for tens of thousands of years.^[84]

        These data were included in the guide to the excursion of the 9th International Conference on Permafrost Studies prepared by M.Kanevsky and co-authors ^[83], which provides a comprehensive cryolithological characteristic of Late Pleistocene syngenetic edomous permafrost rocks studied in the Fox permafrost tunnel. Ice veins are the main type of massive ice that are represented in the CRREL tunnel. The color of the vein ice ranges from gray to dark, which corresponds to the presence of sandy loam particles and organic spots in the ice. The size of the ice vein is difficult to determine. Although the apparent width of the veins varies from 1 to 7 m, their actual width varies between 0.5 and 3 m. It is also important to emphasize, usually, only the middle and lower parts of the veins are visible. Ice veins are also represented in the tunnel, where the veins have a visible width of up to 1.8 m. Here, the head of the vein is limited by stratigraphic contact between the overlying sandy loam and the underlying alluvial gravel. The tunnel provides a good opportunity to see the intersections of several ice veins from the inside: the exposure of ice veins in the ceiling of the tunnel allows you to estimate the height of polygonal-vein ice at 8-12 m.^[83]

Edom Yukon

        E. Kotler and K. Bern^[85] investigated the cryostratigraphy of silty sediments of the Klondike River Valley, the western part of central Yukon. Three bundles, located in the heavily loess sediments of the Previsconsin or Wisconsin age, together make up the retinue of King Solomon. They underlie Holocene organic sediments. The sediment bundles differ in cryostratigraphic features and isotope-oxygen characteristics of the included ice. The description of cryostratigraphic bundles goes from the oldest to the youngest: Last Chance Creek (Last Chance Creek);Quartz Creek (Quartz Creek) pack; Dago Hill pack; and organic pack.

A pack of Chance Creek Fins. Fraser and Byrne^[86] found sandy loams and loams of pre-McConnell age (pre-McConnell more than 40 thousand years ago) only in two sections out of 23 studied by them, and then in the form of an embedded layer, underlain by gravel. They did not find any deposit-forming ice in these deposits. Nevertheless, we see the oldest cryostratigraphic bundle in a continuous, 400 m long outcrop that does not correspond to the river gravel of Last Chance Creek lying on top. Radiocarbon dating of rhizomes collected at the base of the bundle, strictly above the gravel level, and wood residues from the cryoturbated layer showed 45.50 ± 5.80 thousand years (BGS-2019) and 40.06 ± 2.80 thousand years (BGS-2018), respectively. Narrow syngenetic or epigenetic ice veins, up to 4 m thick, extend below the base of the pack and penetrate into the underlying gravel. Two samples were taken in ice veins, the rest from pore ice. The range of values of ?18 ^O for these samples is -28.3 ...-26.3, and, accordingly, the values of ?2 H ranged from -225 ... -209. PackQuartz creek, corresponds to the age of 27.15 ± 0.66 thousand years (BGS-1754), which was determined from peat samples at the base of a loam-sandy loam bundle.^[86] The bundle includes the lower massively stratified layer. Deposits found in a gopher burrow, in a packQuartz Creek, on the border with the pack Dago Hill, were dated 13.91 ± 0.07 thousand years (Beta-111606). The burrow is the youngest in age, a find in this pack, which serves as a relative sign that, recently, the pack has been opened to the daytime surface. The pack is usually located above the gravel, its capacity can reach 17 m. The deposits are compacted layers of loess, from greenish-brown to gray-brown in color. Sometimes 1-10 cm in the lower part of the pack are represented by a pebble-sand layer. Samples of twigs from above and below the extended tephra layer were observed at the base of the bundle in the upper Bonanza Creek, radiocarbon dating, respectively, 23.52 ± 0.21 thousand years (TO-6968) and 22.30 ± 0.19 thousand years (TO-6967). The age inversion of these samples indicates the processing of the material and the youngest according to the present dating is the oldest on this site. Radiocarbon dating of 24.02 ± 0.55 thousand years (BGS-1755) from autochthonous peat buried by tephra in Quartz Creek was obtained in the tephra layer inside this bundle. Where sandy loams of young age are not represented above the pack, ice veins are opened in the upper part. The lower boundary of the pack is the inconsistent contact of thawing, visible where the ice veins are cut by the pack lying aboveLast chance Creek, but not where the pack lies strictly above the river gravel. Nine samples of pore ice were taken from a pack near Quartz Creek to analyze the values of stable isotopes. The range of values of ?18 ^O for these samples is -31.9 ... 29.3, and ?2 H is -257 ... -234, these values are significantly lower than those obtained in other bundles. The Dago Hill pack includes loess deposits overlaid with dark organic material, such as peat, rhizomes, small branches, all this makes the color of the deposits very dark brown almost black. Radiocarbon dating 11.62 ± 0.09 thousand years (TO-6869; 13 450-13 820 calendar years) For this bundle, wood samples were taken from the upper part of the section near the base of Dago Hills, and the dates 10.12 ± 0.38 thousand years (BGS-2016) and 10.18 ± 0.20 thousand years (BGS-2017) were determined for fragments of wood and peat lying over gravel near the boundary of the bundle at Dominion Creek. The ice veins in this pack reach a capacity of 8 m . Twenty-seven samples of pore ice and samples and veins were selected in a pack Dago Hill. The range of values of ?18 ^O for these samples is -28.1 ... -21.2%, and ?2 H is -225% ... -164%. Thirteen were selected with an interval of 50 cm parallel to the border of the packs Quartz Creek – Dago Hill to determine the relative location of sedimentological and cryostratigraphic contacts. The lower seven samples showed variations in the values of ?18 ^O between -32 and -31%, the top three -27 ... -25%. These values represent samples defined for bundles  Quartz Creek and Dago Hill, respectively. The samples from the middle part showed values of ?18 ^O -29.3%, while the upper two samples taken below the organic layer that formed the stratigraphic contact between the Quartz Creek and Dego Hill bundles are characteristic of the values of ?18 ^O in the Dego Hill bundle. 

The Chance Creek Last pack is sediments of pre- and late Wisconsin age, contains preserved re-vein ice inside (? ¹⁸ O ? -28... -26%; ? ² H ?-225... -209%). Overlying Pack Quartz Creek, of late Wisconsin age, is characterized by a predominance of loess rich in organic matter. There is practically no underground ice, although the sediments are highly glaciated. The isotopic composition of the ice of this pack is characteristic of glacial conditions (? ¹⁸ O ?-32...-29‰; ?²H ? –234…–257‰). A sharp change in humidification conditions and temperature to warmer and wetter ones at the end of the glaciation, before the Holocene, was recorded in the strongly hilly colluvial deposits of Dago Hill (? ¹⁸ O ? -28... -21%; ? ² H ? -164...-225%), which began to accumulate 11.62 thousand years ago. Large glacial veins develop from this pack, and, in places that reveal underlying glacial deposits. Even higher values of ?18 ^O and ?2 H are found in the ice of the Holocene organic pack (?18 ^O ? -25... -20%; ?2 H ? -164...-189%). Most of the large ice bodies of King Solomon's retinue are ice veins, but there are also growing underground ice and formation ice, especially in the Dago Hill pack. The deposit-forming ice formed by the intrusion of groundwater into the permafrost occurs in the lower zone of contact with the Quartz Creek pack.^[86]

Studies of cryostratigraphy, age and isotopic composition of the Klodike edom allowed K. Bern and colleagues to formulate the following conclusions^[85,86]:

1). The rich silt loess deposits of the research area can be attributed to the deposits of the King Solomon suite, consisting of three bundles.

2). The lowest bundle  Last chance Creek, consists of silty sandy loams and loams, syngenetic ice veins and cryoturbated organic material, its age is more than 40 thousand years, and the values of ? ¹⁸ O and ? ² H indicate the interstadial conditions preceding the McConnell glaciation.

3). PackQuartz Creek consists of a Late Wisconsin strong loess. The values of ?18 ^O and ?2 H for the ice of this pack indicate conditions of complete glaciation. The deposits of the bundle were deposited during a fairly dry climate, and the growth of veins did not occur.

4). Pack  Dago Hill represents deposits of the period of 3-4 thousand years that underwent the process of colluvium development at the end of the McConnell glaciation. The wide distribution and size of ice veins indicates a greater thickness of snow cover than during complete glaciation, at the same time, isotopic data from underground ice, which are higher in value than in the Quartz Creek pack, also indicate an increase in temperature.

5). The surface pack of organic matter contains underground ice, with values of ?18 ^O characteristic of Holocene deposits. The ice veins of this pack are neither as large in size nor as widespread as in the Dago Hill pack.^[85]

D.Freze and G. Zazula with coauthors ^[87-100] obtained evidence that allows us to date the occurrence of high-ice edom strata with re-vein ice in the Central Yukon at the end of the middle Pleistocene. At least three tiers of ice veins have been discovered at the Dominion Creek site in the southern Klondike, independently dated by two tephra layers.

The first tier of veins, with a capacity of about 10 m, dissects the underlying forest paleosoil with roots and stumps of spruce. Thorn Creek tephra (dated 190 ± 20 thousand years) was found in the paleoactive layer above the veins of the first tier. This tephra layer, in turn, is dissected by the veins of the second generation. The structure of the section indicates that the formation of some veins of the first lower tier occurred simultaneously with the accumulation of Thorn Creek tephra. The Dominion Creek tephra, dating back 170 ± 20 thousand years, is located in the thickness of an underdeveloped steppe enriched – chernozem(?) the paleosoils above the second tier of veins. In this case, this tephra is dissected by the veins of the third tier. A multi-tiered re-vein complex in the valley of Dominion Creek, dated by tephra layers, makes it possible to attribute the occurrence of ice veins to the beginning of the marine isotope stage MIS6, and the formation of forest soils to MIS 7.^[90]

The isotopic composition of the ice veins confirms this version. The ice taken from the re-vein ice is strongly depleted of deuterium isotopes, the values of ?2 H vary from -230 to -233, while the ice from the layer of forest paleosoil with spruce has significantly higher values of ?2 H from -175 to -189, comparable to the values of ?2 H in Holocene veins. These results indicate that the ice in the center of the Yukon has been preserved at least since MIS 7 up to the present.^[90]

 D.Frese and colleagues^[92] studied relict icy soils of the intermittent zone of permafrost rocks of the central Yukon. permafrost rocks here are characterized by an average annual temperature above minus two degrees), their thickness is up to several tens of meters, powerful vertically layered re-vein ice located near the surface has been found near Dominion Creek. The seasonally thawing active layer cut off the tip of the ice wedge, and an active layer formed above this line of disagreement. Volcanic ash called Gold Run tephra was found in such an active layer and laterally for 50 m where it overlaps an ice wedge. The underlying re-vein ice formed earlier than the deposition of tephra. Two independent dating of the ashes were made by two different methods: from 740,000 ± 60,000 years ago. These relic veins overlain by ash represent the oldest ice in North America and are evidence that permafrost rocks were a long-term part of the North American cryosphere. These findings demonstrate that permafrost rocks have existed in the discontinuous zone since at least the Middle Pleistocene. This age includes several cold and warm periods, including the Eem stage, which was even warmer than the present period.^[90]

D. Frese and co-authors ^[88] note that the Dominion Creek gravel sampled at the mouth of Hunter Creek is 5 m above the current valley floor and probably has an age of the mid-Late Pleistocene, which represents a small agradation of the valley after dating the Ross gravel. The radiocarbon age of the wood collected in the gravel column of Dominion Creek has a wide range from >46 thousand years to 6 thousand years. Given the position of modern Dominion and Sulphur creeks at the gravel level of Dominion Creek, it is likely that this bundle covers most of the last few hundred thousand years: 1). Stratigraphy and paleomagnetic chronology of Dominion Creek and its tributaries indicate that the gravel of the White Channel is found on high terraces at an altitude of 20-40 m above the modern valley floor; 2). The Dominion Creek Valley was cut into the bedrock at least 800,000 years ago during or before the deposition of Ross gravel.^[87]

D.Freze and co-authors^[91] have shown that the abundance of Pleistocene fauna of vertebrates and in edom strata make the Klondike a valuable region for solving issues related to the relationship between mammals, Pleistocene vegetation and climate. They analyzed in detail the fossils of Arctic ground squirrels (Spermophilus parryii): nests, seed caches and burrows. On the Klondike, more than 100 sediments were extracted and analyzed in combination with the Ship Creek-To-Dominion Creek tephra (about 80 thousand tons). Years ago) and Dawson's tephra (about 25.3 ¹⁴ C thousand. Years ago), which provides paleoecological records for MIS 4. and early MIS 2, respectively. In the macrostates of plants (seeds, fruits, leaves) from the pile, grasses, land sedge, sage and a wide variety of flowering herbs predominate. Together, these plants formed an open, grass-rich and diverse steppe-tundra community that thrived on well-drained, deeply thawing loess soils of the Klondike during the cold periods of the Pleistocene.      The Klondike gold mines represent an exceptional record of Pleistocene Beringia. The development of a reliable tephrostratigraphic and chronological structure of permafrost deposits facilitated the integration of paleoecological archives of vertebrate remains and paleobotanical, paleosurface and cryostratigraphic observations. This mammoth-steppe environment was characterized by a vegetation rich in cereals and various grasses with more drained loess substrates and deeper active layers, despite summer temperature drops. Taken together, these records confirm the opinion that functional differences between the cryoxeric steppe tundra and the modern boreal environment allow us to explain the existence of a rich pasture fauna in the Pleistocene glacial intervals.^[91]

       Dawson, Klondike, Yukon. D.Frez and coauthors^[90] obtained evidence that allows us to date the occurrence of highly glaciated edom strata with re-vein ice in Central Yukon at the end of the middle Pleistocene.^[90] At the Dominion Creek site on the southern Klondike, at least three tiers of ice veins have been discovered, independently dated by two tephra layers.

The first tier of veins, with a capacity of about 10 m, dissects the underlying forest paleosoil with roots and stumps of spruce. Thorn Creek tephra (dated 190 ± 20 thousand years) was found in the paleoactive layer above the veins of the first tier. This tephra layer, in turn, is dissected by the veins of the second generation. The structure of the section indicates that the formation of some veins of the first lower tier occurred simultaneously with the accumulation of Thorn Creek tephra. The Dominion Creek tephra, dating back 170 ± 20 thousand years, is located in the thickness of an underdeveloped steppe enriched paleosol above the second tier of veins. In this case, this tephra is dissected by the veins of the third tier. A multi-tiered re-vein complex in the valley of Dominion Creek, dated by tephra layers, makes it possible to attribute the occurrence of ice veins to the beginning of the marine isotope stage MIS6, and the formation of forest soils to MIS 7.

The isotopic composition of the ice veins confirms this version. The ice taken from the re-vein ice is strongly depleted of deuterium isotopes, the values of ?2 H vary from -230 to -233, while the ice from the layer of forest paleosoil with spruce has significantly higher values of ?2 H from -175 to -189, comparable to the values of ?2 H in Holocene veins. These results indicate that the ice in the center of the Yukon has been preserved at least since MIS 7 up to the present.^[90]

     On the Klondike, D.Frez and G.Zazula with co-authors^[93] have particularly carefully studied the ash layers, which they call Dawson's tephra, which is the result of one of the largest quaternary eruptions in the eastern part of Beringia, they estimate the volume of emission at 50 km3. Dawson's tephra was discovered by them at more than 20 sites in the Klondike, where it it is usually found as a layer 30-80 cm thick in edom deposits. According to radiocarbon dating of macrostates of plants, its average age is about 25,300 years. Other ash layers are also noted in the Klondike: Old Crow tephra for late MIS 6 (dated 131 ± 11 thousand years), Spike Creek-C tephra (about 90 thousand years) and Spike Creek-K tephra (about 80 thousand years).

According to the conclusion of D.Frez and G.Zazula and co-authors^[93], the edom strata in the Klondike are part of a broader complex of fine-dispersed sediments that cover most of Beringia (which includes the Klondike and Fairbanks regions) and are usually considered by North American researchers to be loess. These deposits reach tens of meters in thickness, they are located on slopes facing north and east and in narrow river valleys along hillsides. Frozen edom strata are characterized by a high content of organic carbon concentrated in buried soils, which, according to Yu.K. Vasilchuk, fix the subaerial stage of cyclic edom development^[40].

P. Sanborn and co-authors ^[100] describe many horizons of paleosols preserved in permafrost edom strata and exposed at two placer gold deposits of the Klondike (Tatlov Camp on the Quartz River and the Christie Mine, 20 km to the southeast, on the left bank of the Dominion River – south of Dawson and the latitudinal flow of the Klondike River). On the Quartz Creek River , they encountered ice veins up to 3 m wide and more than 10 m high . On the left bank of the Dominion Creek River there are narrower veins: veins up to 1-2 m wide. The subaerial conditions for the development of these polygonal soil arrays were apparently dry enough to prevent the accumulation of powerful peat bogs, and the active layer was powerful enough to allow intensive colonization of ground squirrels. The older edom deposits have a vertical sequence of three paleosols with an upward trend towards a decrease in the severity of cryoturbations and less active development of ice veins, which indicates the regional character of progressively more arid conditions during MIS 4 ^[100].

G. Zazula and colleagues^[99] performed paleoecological studies of 48 fossilized nests and caches of Arctic squirrels (Spermophilus parryii) extracted from edom deposits in the Klondike. Radiocarbon dating of AMS and stratigraphy of nests with Dawson tephra (about 25,300 years) indicate that these paleoecological data reflect the onset of glacial conditions of early MIS 2 and the completion of MIS 3 (24,000-29,450 years ago). Fossil nests of Arctic squirrels contain a variety of paleoecological information, including macrofossils of plants, insects, and bones. These nests provide a rare opportunity to explore the relationship between flora and fauna for a particular mammal within the Beringian Pleistocene ecosystem.

Conclusions

The first decade of the XXI century in the study of edoma was marked by the widespread use of AMS radiocarbon dating, performed by insoluble microinclusions and dissolved organic material extracted directly from the re-core ice of Edoma. This allowed us to bring paleogeocryological research to a new level.

1. These studies, together with a detailed study of the content of stable isotopes, were carried out at Lomonosov Moscow State University (Prof. Yu.K. Vasilchuk and A.K. Vasilchuk) on edom sections of Yamal, Kolyma, Central Yakutia together with specialists in AMS dating on accelerator mass spectrometers and conventional radiocarbon dating by Prof. J. van der Plicht (AMS Laboratory of the Isotope Research Center of the University of Groningen), Prof. J.-Ch. Kim (AMS Laboratory of Seoul National University), Prof. H. Jungner (Radiocarbon Laboratory of the University of Helsinki) and L.D. Sulerzhitsky (GIN Moscow). Also, Prof. D. Rank and V. Papesh from Moscow took an active part in the measurements of a large volume of re-vein ice samples.  The University of Vienna and the Vienna firm Arsenal and E.Sonninen from the Stable Isotope Laboratory of the University of Helsinki.

2. Geochronological and isotopic studies of Edoma sections in the west of Taimyr and the right bank of the Yenisei Bay have been initiated (A. K. Vasiliev, E.A.Gusev, I.D. Streletskaya, etc.).

3. During this period, the participants of the Russian-German expedition (A.A. Andreev, A.Yu. Derevyagin, S. Vetterich, Prof. G. Grosse, Prof. H.-V. Hubberten, A.B. Chizhov, L. Shirrmeister, etc.) also began active research of the edom sections of the Anjou Islands (especially in detail the Bolshoy Lyakhovsky), the Lena Delta (peninsula Bykovsky) and the Arctic coast of Western Yakutia with extensive use of radiocarbon and isotope methods.

4. In Chukotka, edom strata were studied by employees of the Chukotka branch of the SVK Research Institute of the Far Eastern Branch of the Russian Academy of Sciences (Kotov A.N. et al.).

5. Researchers from Fairbanks University (M.Z.Kanevsky, Prof. Y.L.Shur, M. Bray and Prof. H. French, who collaborated with them, continued to study the edom strata in the Fox tunnel, as well as the edom strata of central and northern Alaska.

6. Radiocarbon dating and the study of mammoth fauna, as well as stable isotopes, were initiated and intensively developed by Canadian scientists from Carleton University (Prof. K. Bern), the University of Alberta (Prof. D. Frez) and employees of the Yukon Paleontological Program (G. Zazula, etc.) on Yukon edom sections.

7. The study of ancient Paleolithic sites in the edom sections of the lower reaches of the Yana and the Novosibirsk Islands was started in 2001 and intensively continued (V.V.Pitulko, N.P.Pavlova, P. Nikolsky, etc.).