Yedoma. Part 3. Annals of geocryological research, study of radiocarbon age, the stable-isotope composition studies in the 21st century

Vasil'chuk Yurii Kirillovich ORCID: 0000-0001-5847-5568 Doctor of Geology and Mineralogy Professor, Lomonosov Moscow State University, Faculty of Geography, Department of Landscape Geochemistry and Soil Geography 119991, Russia, Moscow, Leninskie Gory str., 1, of. 2009 vasilch_geo@mail.ru Other publications by this author

Introduction

Edoma research, which began in the XIX and XX centuries^[1], actively developed in the second and third decades of the XXI century^[2] and was significantly enriched due to the even wider application of studies of the content of stable isotopes of oxygen and hydrogen in re-vein ice (PGL), as well as, which became almost routine (in any case, rather frequent) application of AMS radiocarbon dating of microinclusions of organic material and CO ₂ inclusions in vein ice. Some of these studies were started earlier, but it was in the second and third decades of the XXI century that they received a new impetus, while some types of high-precision edoma studies were performed for the first time.

The purpose of this article is to analyze the most notable publications of 2010-2023 devoted to radiocarbon dating and studies of stable isotopes in the edom strata of the Russian and North American Arctic.

Arctic Russian Edom

Edom of the north of Western Siberia and Taimyr

Yamal Peninsula

            Seyakha, the Eastern coast of Yamal. The studied edom stratum was uncovered in the outcrop of the third lagoon-marine terrace on the east coast of the Yamal Peninsula at the mouth of the river.Seyakha (70.157364° s.w., 72.569100° v.d.). The outcrop was studied in detail in 1978-79, 1996 and 2016.^[3,4] This was the first study of a typical edomian strata in the western part of Siberia. For the marginal part of the Seyakhinskaya edoma, four new AMS ¹⁴ were obtained with dating from re-vein ice (PGL).^[4] The vein from the middle part was dated from 21 to 25 thousand cal. years ago; the vein from the lower fragment was dated from 28 to 29 thousand cal. years ago – these are the most ancient dates obtained from the veins of the Seyakhinskaya edoma.^[4] It can be noted that in the marginal part of the edom, the dates for the host sediments and veins are quite consistent with each other, they show a non-inversion series of dates from 29 to 21 thousand cal. years ago. Dating from the Baijerach deposits – from 29.5 to 27.6 thousand cal years ago – is comparable to AMS dating by microinclusions of organic matter from the vein at the same depth. It should be clarified that the Baijerakh deposits are not thawed and recycled, they are in a permafrost state, but this block of frozen sediments has sunk (by a maximum of 1.5 m) due to the pulling out of the ice vein. Therefore, the dated horizons of organic matter from this baijerach were primarily located at an altitude of +3.5 to +6.5 m, that is, at the height of the fragment of the vein of the lower tier. In this regard, it can be confidently assumed that the lower tier lived here was formed syngenetically by sediments, about 29-27 thousand cal. years ago.

             A new high-resolution one has been obtained (with a detail step of 80-100 years) isotope-oxygen recording of an ice vein from the marginal part of Edoma. The values of ?18 ^O vary from -25.75 to -23.15. Two isotopic trends were noted: in the range of absolute heights from 12 to 14.2 m, the values of ?18 ^O vary in the range of 1.5 % (between -24.18 and -25.75 %); in the range of heights from 14.2 to 15.8 m, there is a clear tendency for values to increase from bottom to top by 2.6 %, from -25.75 to -23.15 %. For the lower fragment of the vein (opened at a height of +6 m), variations of ?18 ^O values were obtained in almost the same range as in the upper fragment: from -23.41 to -26.74.^[4]

     Previously obtained isotopic oxygen values (?18 ^O) for ice veins in the central part of the Seyakhinskaya edoma^[5] varied between -20.4 and -25 %. Judging by the dating obtained on ¹⁴ With AMS from the lower part of the vein (25.3 thousand cal. years ago), the veins were formed about 25 thousand cal years ago and probably a little earlier, i.e. they are almost synchronous with the vein from the marginal part of edoma, dated from 25 to 21 thousand cal. years ago. The values of the isotopic composition of the ice of these synchronous veins turned out to be quite close, ?18 ^O ranged from -21.4 to -24.8 % in the vein from the central part of edoma and from -23.2 to -25.8 % in the vein from the marginal part.^[6]

        Paleotemperature reconstructions performed using the Vasilchuk equation^[7] show that in the period 26-21 thousand cal years ago, the average January air temperature (T _cf.January) varied between -33 and -39°C. In the period of about 30-29 thousand cal. years ago, T _cf.January ranged from -35 to -40 °C, at the final stage of the development of the edomous stratum of 18-13 thousand cal. years ago, T _cf.January ranged from -33 to -37°C. In general, it can be noted that the values of T _{cf.In January}, during the period of accumulation of the edom layer, they were noticeably lower than the modern values of T _cf.January in the area of the Seedling (averaging -24 °C), while a slight increase in T values was noted_.Jan from an earlier stage to a later one.^[4]

Bovanenkovo, Central Yamal. The re-vein ice in the upper part of the section of the Bovanenkovsky oil and gas condensate field (NGCM) reaches a width of 3-3.5 m, the height of Holocene veins is usually 2-3 m, Late Pleistocene veins – up to 10-12 m.^[8] When comparing the sizes of syngenetic re-vein formations in sediments of all geomorphological levels on the territory of the Bovanenkovsky NGCM, it is noticeable that the largest of them they are concentrated in loamy-sandy loam detached soils, the massifs of which are characterized by maximum macrolidity. Relict syngenetic re-vein formations are confined to Late Quaternary-Early Holocene lagoon-marine, coastal-marine, as well as alluvial, lacustrine-alluvial and lacustrine-marsh sediments. Syngenetic ice veins 10-12 m high have been discovered in sandy and sandy loam sediments of the III terrace in the middle reaches of the Seyakha River in the thickness of alluvial fine sands with peat inclusions. The volume macrolidity of edom deposits in the section of the III marine terrace on Bovanenkovo is 10-30% in loams and sandy loams, 3-10% in sands. According to the composition and structure, among the relict re-vein formations, G.I. Dubikov identified ice veins, ice-ground and mixed.^[9] Ice-ground veins are two-tiered structures: the upper tier - the ground layer - is confined to the seasonally thawed layer and has the features of initially-ground veins; the lower tier is actually an ice vein. According to the observations of many researchers, ice-ground veins are associated exclusively with sandy and sandy loam-sandy sediments. It is important to note that even with a high degree of salinity of the host soils, the re-vein ice within the Bovanenkovsky NGCM is usually characterized by a fresh and ultra-fresh composition. Among the lagoon-marine formations, polygonal-vein ices are often complex in structure. The upper part of them consists of vertically striped ice and horizontally layered ice-ground mass with sandy loam filler. The space between two or three wedge-shaped processes of the lower part of the vein is filled with the same soil mass having a layered slightly wavy cryogenic texture. The layering of the ice ground is almost parallel to the lateral contacts of the vein, and in places it is crumpled into gentle folds. The width of the ice packs can reach 2-3 m. The lateral contacts of the upper 1-1.5-meter part of the vein are complicated by stepped projections, which consist of horizontal layers of ice separated by thin layers of sandy loam. Bundles of such interlayers penetrate the body of the ice vein and the host soil, reaching a length of 2-2.5 m and a thickness of 0.3-0.5 m. The formation of a complex ice body occurred in the first stages epichronically with accumulated sediment and almost simultaneously with the formation of an ice-ground mass. The top of the vein was formed synchronously with the host soils by frontal buildup of layers of segregation ice and ice soil at the base of the active layer. Undeveloped syncreogenic polygonal-vein ice in sections of lagoon-sea terraces lies at depths of at least 3-5 m, and this prevents their further development. Therefore, modern frost-breaking cracking forms a new polygonal system of vein ice, unrelated to the preserved veins located below. Undeveloped syncreogenic polygonal-vein ice in sandy sediments at a depth of 1.5-2.0 m of the second lagoon-sea terrace have a width of up to 2 m on top and a height of at least 6-8 m. When comparing the sizes of syncreogenic polygonal vein formations in Late Pleistocene sediments, it is noticeable that the largest of them are concentrated in loamy sandy loam detached soils with maximum macrolidity. In floodplains of rivers flowing into the Kara Sea, when approaching the mouth, the growing ice veins become smaller in height and width on top. This is due to an increase in the salinity of sediments as they approach the sea. The melt of lagoon-marine polygonal vein ice is characterized by low mineralization (up to 0.2-0.5 g/l), sodium chloride and calcium chloride composition, neutral medium and medium hardness. The qualitative composition and degree of salinity of ice in Holocene floodplain deposits of the deposit's rivers are close. For them, with a noticeable general mineralization, an increase in its values from the sources of rivers to their lower reaches is characteristic. In the same direction, the sodium bicarbonate composition of the ice is replaced by sodium chloride, and the change occurs due to a quantitative increase in the content of chlorine ion. This is due to the penetration of seawater through river valleys deep into the peninsula during high tides and salinization of accumulated sediments and river waters. Vein ice in the Late Pleistocene sediments of marine terraces is characterized by higher total mineralization, constant predominance of chlorine ion and sodium chloride composition. The thickness of the instrative alluvium is formed and freezes during the horizontal movement of the riverbed. In the lower part, it is represented by sandy rusticated facies, which are replaced by fine-grained soils up the section. From above, the channel alluvium is blocked by a low-power cover of floodplain alluvium of fine composition, which accumulates in high water during periodic flooding of the river floodplain. In such facies conditions, polygonal vein ice is formed, and the initial phase of its development begins at the final stages of accumulation and freezing of channel alluvium - in riverbed shoals, riverbed shafts, isolated ples. Epicriogenic lower ends of an ice or ice-ground vein develop here, which, at the stage of accumulation of floodplain alluvium, continues to grow synchronously with the host sediments. The complex shape of the veins makes it possible to judge with confidence the syncreogenic type of their formation. In addition to the icy part, ground and elementary ice veins and larger ice veins consisting of several elementary ones are distinguished in mixed veins. According to textural features, two varieties are distinguished - an ice crater without signs of layering and an ice crater with undisturbed initial layering of precipitation. A non-layered ice crater is genetically the same formation as ice veins. Thin (several millimeters) and short (several centimeters) vertical strips of ice in it are parallel to the lateral planes of the vein. A layered ice sheet is characterized by the fact that the ice sheets, the number of which is much smaller here, are more often parallel to the walls of the vein, sometimes to the primary stratification.^[8]

Vaska's cottages, Central Yamal. In one of the thermal tanks in the area of the Vaskina dacha hospital, near the Bovanenkovsky gas condensate field (70°13'57.632" s.w., 69°0'58.485" v.d.) at an altitude of 28 m above sea level under a layer of loam with a capacity of 1 m. Yu.N. Chizhova^[10], the isotopic composition of syngenetic PL. The values of ?18 ^O and ?2 H of vein ice vary from -21.2 to -26.2 and from -157.5 to -203.1, respectively. The average values are ?18 ^O = -24.8 and ?2 H = -187.6. The values of d _exc are from 6.3 to 17.4 % with an average value of 10.5 %. All the obtained values can be described by the linear regression equation ? ² H = 8 ? ¹⁸ O + 10.5 . At the same time, graphically, the samples of the PLL mostly correspond to the line of meteoric waters. An AMS radiocarbon dating of 13.6 thousand calibrated (cal.) was obtained from a sample selected at the head level of vein No. 1. years (IGAN _AMS-7698) for total organic carbon (TOC - total organic carbon). This allows us to conclude that the age of the tested vein ice is 13 thousand years or older. When using the formula of Yu.K.Vasilchuk^[7] for the average value of the studied by Yu.N.Chizhova PPL ?18 ^O = -24.8 %, the average winter air temperature of the time of vein formation is estimated at -24.8±2 °C, the average January temperature is -37.2±3 °C.^[10]

                P.B.Semenov et al.^[11] studied dissolved organic substances and methane in Late Pleistocene re-vein ice near the Vaskin Dachas station. A discrepancy was revealed between the predicted and measured values of ?2 H-_CH4 in re-vein ice, which, according to the authors of the article^[11] indicates an exogenous source of _CH4 enrichment in re-vein ice. The authors believe that, unlike formation ice, unsuitable conditions for the formation and accumulation of methane are created in re-vein ice. The relatively low values of CH ₄-?13 C (<-80%, PDB) in these samples indicate the insignificant presence of carbonates, which are important for the microbial formation of methane. At the same time, the depletion of _CH4 by deuterium (magnitude ?2H <^-350%), usually attributed to acetoclastic methanogenesis, can also be caused by the absorption of water depleted by 2H as a result of carbonate reduction.^[11]

                The deposits containing the veins are sandy loam with peat lenses. Radiocarbon dating of peat has shown that it was formed during the marine isotope stage (MIS) 3 (30,900 ± 1,300 years ago, 32,200 ± 1,300 years ago; 37,650 ± 1950 years ago).^[11] Taking into account the dating of the vein obtained by Yu.N. Chizhova ^[10], it is possible to designate the range of formation of syngenetic veins in the edom column opened in the area of Vaskina Dacha - from 31 to 13 thousand years.

Edom at the Marre-Sale weather station, West Coast of Yamal. The westernmost key site is located on the Yamal Peninsula, near the Marre-Sale polar station. Two complexes of Quaternary sediments were studied in a coastal outcrop with a height of about 30 m. The upper complex of continental sediments contains syngenetic re-vein ices of different ages. Larger re-vein ices, 2.0–2.5 m wide at the top and 6-7 m long, form a grid with a polygon side of 10-20 m. According to S. Forman et al. ^[12] in the area of art.On the western coast of Yamal, the accumulation of Aeolian and fluvial deposits and the formation of re-vein ice in these deposits occurred between 40 and 11 thousand years ago. A series of dates from 16.4 to 12.2 thousand years ago (from 19.7 to 14.2 thousand cal) has been obtained for icy sandy loams containing large syngenetic re-vein ices. years ago).^[12] The values of ?18 ^O in veins ranged from -24.8 to -23.4 %, the average value of ?18 ^O is -24.2 %. The values of ?2 H in veins ranged from -190.6 to -179.3 %, graphically the values of the ratio ?2 H-?18 ^O of vein ice are located near the global line of meteoric waters.^[12,13,14] According to the conclusions of I.D. Streletskaya and co-authors^[13], the average winter air temperatures at the end of the Pleistocene were 5-7 °C lower than modern ones. Calculation by the equation of Yu.K. Vasilchuk^[7] allowed us to estimate that the average January air temperatures during the formation of veins were about -36 ° C, which is on average 10 ° C lower than modern ones.^[13]

     E.A.Sgrada and colleagues^[15] found that the studied syngenetic vein ice lies in the lacustrine-alluvial thickness, which is 5-15 thousand years old, i.e. the polygonal vein system, which is in paragenesis with laccoliths of the upper deposit, was formed at the end of the Sartan cryochron and the first half of the Holocene. The upper deposit of re-injected ice with layered and massive laccoliths and wedges was formed after the laying and during the development of the polygonal vein system in the early Holocene, their upper parts were eroded and partially removed in the second half of the Holocene^[15]. Fragments of the upper ice deposit differ in the ratio and position of the water injection source in the section. Massive laccoliths and horizontal sections (the first generation of ice) were formed due to water injections during freezing of separated taliks in the sands above the clay barrier, which had infiltration nutrition at an early stage. The occurrence of cracks from below in polygonal blocks and repeated injections of water through them are probably due to the freezing of taliks from above and the unevenness of the freezing front under the polygonal-vein system. Epigenetic ice wedges and layered laccoliths represent the second generation, which was formed later, during freezing of water injections from sandy quicksand located at different depths in clays. In the northern part of the Mare-Sale m., during the formation of layered laccoliths, water was supplied from below to the boundary of frozen clays and sands through vertical cracks and above along annular cracks into polygonal blocks. In the center of M. Marre-Sale, with deep occurrence of quicksand in the clay column above them, annular ruptures appeared in the frozen rocks, through which water injections sometimes captured large xenoliths of clays.

      E.A.Sgrada et al.^[15], it was concluded that polygonal-vein and epigenetic wedge-shaped re-injected ice of the frozen Marre-Sale strata have great morphological similarities, and a set of characteristics, including structural and isotope analyses of ice, should be used to separate them.

  O.L.Opokina and co-authors^[16] obtained radiocarbon analysis data in the Mare-Sale outcrop, which forced them to reconsider the age of formation of formation (more precisely, stocks and laccoliths) and re-vein ice of this section. The formation and growth of polygonal vein ice occurs mainly due to the freezing of thawed snow water in frost-breaking cracks. Meltwater washes away fragments of modern plants from the surface and transfers them to frost-resistant cracks. The authors of the article point out that the organic matter contained in polygonal vein ice mainly indicates the time interval of active frost-breaking cracking of the surface. In syngenetic ice veins, the age of organic matter in ice and host sediments will be close, and the age of plant residues in epigenetic ice veins will be younger than the host rocks. With intensive erosion of rocks, it is possible that redeposited ancient organic matter may enter polygonal vein ice. Injectable ice deposits contain organic matter embedded in the frozen strata through cracks from below, along with pressure waters from freezing water-saturated mainly sandy sediments. In this case, the age of the organic residues from the injection ice will differ from the host strata, and the formation time of the reservoir will be determined by the period of epigenetic freezing. The time of injection ice formation is quite difficult to establish, since lowering the sole of the frozen layer is a long process, and the freezing of deep taliks relative to the upper horizons is delayed in time. In this case, the deposit can be formed in several stages, which correspond to multi-time injections of ice.^[16]   

Over many years of studying the Marre-Sale geocryological section in Western Yamal, researchers have not come to a common understanding of the genesis and age of the sediments and underground ice composing it, and date them in a wide range: Kazantsev time, pre-Kargian - older than 45 thousand years or Sartan.

       Radiocarbon dating obtained by O.L.Opokina and co-authors^[16] showed that the age of the upper part of the section is younger than 35 thousand years. The most ancient Late Pleistocene deposits in the section of Cape Marre-Sale belong to the peatlands of the Karginsky-Sartan horizon. Currently, peatlands with powerful polygonal vein ice are distributed only south of the Yavar-Yakh River. The radiocarbon age of this horizon, obtained by the authors of the article^[16], is younger (23-12 thousand years) compared to previously published data.     

          The upper stratum of the section is represented by sediments, which, according to new radiocarbon definitions, are comparable to the Baidaratsky and deer sands. In the north of the section, they are represented by layered sands, layered-enriched with filamentous roots, in the center — by frequent layering of sandy loams and sands with lenses of autochthonous peat from mosses and subordinate interlayers with filamentous roots. The thickness of the sediments varies from 4 to 7 m, on the high remnants of the III plain it can reach 10 m. The facies variability of rocks laterally, the nature of plant residues and the absence of erosion, according to O.L.Opokina and co-authors ^[16], indicate their accumulation in a lake-swamp environment. At the same time, the filling of lake basins in areas with a submerged clay roof began earlier than in areas with a high position of the clay base. In the northern and central parts of the section, sedimentation began 13-10 thousand years ago and lasted until 6-5 thousand years ago. The presence of syngenetic polygonal vein ice in lake-marsh sediments, as well as stocks and laccoliths complicating the upper ice layer, indicates the freezing of sediments of lake basins and the formation of underground ice during the same period.^[16]    

Gydan Peninsula

         Late Pleistocene re-vein ice was studied at the mouth of the river Yeri-Maretayakh by G.E. Oblogov^[17,18] in the outcrop of a coastal ledge, which consists of thermodenudation surfaces with heights of 10-25 meters and a thermoabrasion cliff descending to a modern beach. ¹⁴ With a dating of 21930±370 years (26.3 thousand cal. years) along the peat horizon at a depth of 7 m can record the early stage of the development of the edom strata, the studied vein fragments are located hypsometrically higher and, most likely, they are younger. Yu.K. Vasilchuk^[19] obtained the dates of the Late Pleistocene peat mineral complex at the mouth of the Mongatalyangyakh River, not far from the section, from 34.8 to 26.3 thousand years. The age of the lower part of the Epa-Maretayakh section probably belongs to MIS 3 (Karginsky horizon). According to the ice of one of the veins in this fragment of edoma, the values of ?18 ^O from -24.6 to -22.6 %, the average value of ?18 ^O -24 % were obtained. The values of ?2H vary from -193.1 to -176.5 and d ^exc do not exceed _6-7. The average temperature of January during vein formation was estimated using the formula of Y.K.Vasilchuk^[7.19] at -36 ± 3 °C.^[13,17,18] The range and average value of the isotopic oxygen composition of Late Pleistocene veins dated from 29 to 12 thousand years ago (stage MIS-2) are close to the isotopic values for synchronous veins of the Seyakhinskaya edoma, which confirms the close winter temperature conditions of the formation of edomous strata in the period between 29 and 13-12 thousand cal. years ago.^[4]

A.V. Kislov and co-authors^[20] showed that, in general, the distribution of predicted temperature and precipitation anomalies is relatively uniform across the territory of the Yamalo-Nenets Autonomous District and, in particular, in the Gydan Peninsula due to the size of the territory and the flat terrain. However, changes in the state of the environment are more complex and mosaic in nature under the influence of factors such as soil properties, the configuration of the coastline and the shape of the relief. Processes directly controlled by air temperature and precipitation will have the greatest response in mountainous areas, such as avalanches and slush. The parameters of environmental change caused by climate change were based on predicted temperature and precipitation data using simple calculation algorithms. The use of complex schemes is considered unproductive due to significant uncertainties related to both the climate forecast and the unreliability of information about the spatial and temporal characteristics of soils. Climate change causes changes in the natural environment of the Arctic, primarily due to the degradation of permafrost, which is sensitive to changes in air temperature and precipitation, which leads to changes in the activity of some exogenous processes. In some cases, the intensity and area of these processes are increasing, for example, the processes of heaving and activation of thermokarst by 2050 due to an increase in soil temperature and the depth of seasonal thawing. In other cases, the processes associated with the transformation of permafrost. Processes for which the dynamics of permafrost is not decisive are much slower. For example, the nature of the thermokarst process is less sensitive to climatic changes, and therefore it is impossible to expect a significant change in thermokarst processes by the middle of the XXI century. Based on the analysis of meteorological data, it was found that by 2050, the activity of thermokarst processes and the risks associated with them will practically not change compared to the current state.^[20]

      Comparison of model and isotopic paleotemperatures of the time of edoma formation. G.V. Surkova and Yu.K. Vasilchuk^[21] performed a comparison of paleotemperature for the period of 18-22 thousand cal. years ago (i.e., for the time designated as the last glacial Maximum - Last Glacial Maximum - LGM) for key areas of the Russian Arctic obtained as a result of paleoclimatic modeling and those reconstructed from isotopic data from homogeneous re-vein ice. A comparison of paleoreconstructions of the deviation of the average air temperature in the cold period (t < 0°C) from the current values based on the results of an ensemble of climatic models (model paleoreconstructions) and the isotopic composition of homogeneous re-vein ices (isotopic paleoreconstructions) at the same points for the LGM period (about 21 thousand years ago). As a result of comparing model and isotopic paleoreconstructions, deviations in the average air temperature during the cold period (average daily t < 0°(C) Very encouraging conclusions have been obtained from current values, suggesting that data validation has generally been successful, even more than expected. Particularly close paleoreconstruction data were obtained for northern and central Yakutia and the Arctic islands, where the temperature difference, performed using modeling data and isotope reconstructions, was 0-1.2 °C. Reconstructions differ the most in the western sector of Siberia – in Western Siberia, deviations from modern average winter temperatures according to model calculations are 7.9 ° C lower than according to isotopic data, and in the mouth of the Lena River according to model paleoreconstructions they are 7.0 °C lower than according to isotopic paleoreconstructions. It is determined that the greatest differences in temperature reconstructions obtained for LGM according to different studies are noted in the north-west of the studied region and are associated with different estimates of the possible area of distribution of ice sheets, in paleoreconstructions of climatic models, the area of glaciation is assumed to be much more extensive than in isotopic ones. It is emphasized that in a number of points (especially in the west and north-west of the Russian Arctic), most models assume that the territory in the Late Pleistocene (18-21 thousand years ago) was covered with ice, but in fact there was probably no glacier during this period.^[21]

Taimyr

I.D. Streletskaya et al. ^{[13, 22]} and G.E. Oblogov ^{[17, 18]} provided geochronological and isotopic data on sections of edom strata on the shore of the Northeastern Bay, P. Dixon, near the mouth of the Krestyanki River and Cape Sopochnaya Karga on the eastern shore of the Yenisei Bay.

        Northeast Bay, P. Dixon. In the area of P. Dixon, two tiers of syngenetic re–vein ice are opened in the coastal cliff. In the Late Pleistocene re-vein ice in the area of P. Dickson, the values of ?18 ^O vary in the range from -24.3 to -26.8, and the values of ?2 H vary from -205 to -184. In Holocene re-vein ice, the values of ?18 ^O are -21.7 to -19.5, and the values of ?2 H range from -161 to -147. Modern ice vein sprouts grow in the area of P. Dickson, which have a heavier isotopic composition – the values of ?18 ^O vary in the range from -17.1 to -16.2, and the values of ?2 H vary from -124 to -118.^[13] The mineralization of PGL increases from 63.5 mg/l in Holocene veins to 360.5 mg/l in Late Pleistocene veins.

         The mouth of the Krestyanka River. Quaternary sediments overlap Permian bedrock on the coastal cliff  The Yenisei Bay is 12-40 m high from Cape Makarevich to the mouth of the Krestyanka River. The ice wedges are about 9 m high and 3-4 m wide at the top and form a polygonal relief. The average values of the isotopic composition vary from -23.5 to -22.0% for oxygen and from -179.7 to -167.7% for deuterium. Within the same wedge, the isotopic composition is quite similar^[13]. The excess of deuterium (d _exc) ranges from 8.2 to 10.2%). G.E. Oblogov^[17,18] obtained a dating of the Quaternary age near Cape Makarevich - 38,000 ± 3,000 years (RLQG 1948-119). A similar age date was obtained by E.A. Gusev from sandy deposits by the IR-OSL method near Cape Shaitansky, which is located 100 km south of Cape Makarevich - 45,800 ± 3,200 years (RLQG 1796-048).^[23] Syngenetic re-vein ice on the considered section of the coastal cliff of the Yenisei Bay was found within the river terrace of the Krestyanka River (at altitudes of 1-2 - 18 m), within the slope and on the watershed surface (with an absolute height of about 40 m). The deposits containing the ice veins are dusty, the number of dusty particles in some parts of the section exceeds 60%. The rocks are strongly glaciated with a total humidity of 76-86%. Near the mouth of the Krestyanka River, pulverized sandy loams include powerful re–vein ice up to 9 m high and 2.4–3.5 m wide veins on top, located 8-10 m apart. The ice in the veins is cloudy with inclusions of small pebbles and pebble framing at the contacts of the veins with the host rocks. In the Late Pleistocene re-vein ice near the mouth of the Krestyanki River, the values of ?18 ^O vary in the range from -23.7 to -22.0, and the values of ?2 H vary from -179.7 to -167.7, respectively.^[13]

           Cape Sopochnaya Karga. Several outcrops of Quaternary sediments containing ice wedges were studied 6 km from Sopochnaya Karga. Layered yellow–gray silty sandy loams and sands with layers of peat with a thickness of 4-10 m are located under the Holocene sediments. The carcass of a woolly mammoth was found at a depth of 6 m in 2012. The dates for it ranged from 42.2 thousand years to 47.3 thousand years. In the north of the central part of the section, under a layer of sandy loam, layers of peat are exposed, the age of which exceeds 42.3 thousand years.^[24] Sandy loams and sands (MIS 3–MIS 2) contain syngenetic re-vein ice about 10 m high and 2-3 m wide in the upper part. The narrow parts of the wedges penetrate into the clay by 0.5–1.0 m, in some parts of the section they continue below sea level. The isotopic composition values range from -26.9 to -21.7% for ?18 ^O and from -204.8 to -164.8% for ?2 H. The excess of deuterium – d _exc is 7.2%.Layered powdery sandy loams and fine sands with a thickness of 4-15 m lie under the Holocene peat, which are also underlain by peat. The peat interlayers on the lower boundary of the sandy loam–sand pack have a radiocarbon age of more than 37,200 years. A reindeer bone was found at the base of the cliff, according to which a radiocarbon age of 13,770 ± 480 years was obtained, the calendar age was 16,690 ± 790 cal. years (LU-6998). Sandy loams and sands contain syngenetic Late Pleistocene re–vein ice with a thickness of 10 m and a width of 2-3 m in the upper parts of the veins. The lower narrow parts of the veins penetrate into clays and formation ice to a depth of 0.5–1.0 m. The values of ?18 ^O of late Pleistocene re-vein ices vary within narrow limits and range from -24.8 to -24.5.^[13] Based on the dependence between the average temperature of January and the values of ?18 ^O in the re-vein ices of Vasilchuk^[7] G.E. Oblogov^[17] determined the average temperature of January during the formation of the re-vein- vein ice. At the beginning of the formation of re-vein ice, the values of ?18 ^O were -23%. Consequently, the January temperature at this time was about -34 °C.

               In his PhD thesis ^[17], G.E. Oblogov provided data on the age and isotopic characteristics of the edom sections of the Kara Sea coast: in the West of Taimyr – Cape Makarevich – the mouth of the Krestyanka River and Cape Sopochnaya Karga, on the Gydan Peninsula – the mouth of the Yerga-Maretayakha River and Cape Paha-Sale, on Sibiryakova Island.

          Sibiryakova Island is located in the northern part of the Yenisei Bay. It is relatively flat, with an average height decreasing from the central part (25-33 m above sea level) to the coastal zone (3-5 m above sea level). Under the peat layer there is a layer of gray obliquely layered sandy loams and sands with plant residues. The lower layer consists of layered iron–rich sands up to 1.2- 2.0 m thick with traces of deformation, inclusions of pebbles, gravel, plants and peat. The sands are dated from 13.3 to 31.4 thousand years old. The sands lie on a dark gray saline silty sandy loam of marine genesis. The deposits were formed during MIS 3, the older date (obtained by the IR–OSL method) is 45.8 thousand years. The values of ?18 ^O in ice wedges range from -22.1 to -16%, the values of ?2 H from -167.5 to -121%.^[13]

                Dixon. The most complete section of Quaternary sediments was studied in the Dixon area, where two tiers of re-vein ice are exposed in the coastal cliff. The Late Pleistocene re-vein ice in this area has a width of 0.4 to 3 m in the upper part and a thickness of more than 5 m. The isotopic composition of re-vein ices shows changes in values from -26.8 to -22.9% for oxygen and from -205 to -175% for deuterium.^[13]

      The edom strata at Cape Sablera on the shore of Lake. Taimyr, located to the east of the Yamal Peninsula, reveals a noticeable similarity in structure and synchronicity of formation time with the Seyakhinskaya edom strata. Almost inversion-free series of dates have been obtained from the sediments of Cape Sabler containing ice veins. One series of dates from 28.5 to 13.5-14 thousand cal. It was obtained by L.D. Sulerzhitsky^[25] years ago for deposits in the depth range of 1-17 m; later, 13 dates from 35.1 to 11.8 thousand cal. Years ago, they were obtained for deposits at depths from 3 to 25 m^[26]. According to the dating, the edom deposits at Cape Sablera were formed between 35 and 13-12 thousand cal. years ago, which is close to the time of the formation of the Seyakhinskaya edoma.

Three tiers of ice veins were uncovered in the Edoma outcrop of Cape Sablera. The values of ?18 ^O in the ice of veins dated from 34.5 to 30.9 thousand cal. years ago, they ranged from -31.5 to -28.3 %; in veins dated between 22 and 14 thousand cal. years ago, the values of ?18 ^O ranged from -29.5 to -24.3 %.^[27] These values are noticeably lower than in the veins of the Seyakhinskaya edoma, which is explained by the more severe winter climatic conditions on the Taimyr Peninsula in the late Pleistocene. However, there is also a general tendency for both sites to increase the values of ?18 ^O at the final stage of vein formation.

     P.Meller and co-authors in two detailed generalizations ^[28,29] examined data from quaternary sedimentary strata studied along the Bolshaya Balakhnya River and the Upper Taimyr-Logata river system in the south of the Taimyr Peninsula. The articles present the composition of the fauna of marine foraminifera and mollusks isolated from samples of bottom sediments. The chronology of sediment accumulation sequences was reconstructed based on three dating methods: radiocarbon dating of organic detritus (from lake/river sediments) and mollusks in marine sediments (a total of 66 radiocarbon dating was obtained in the AMS Radiocarbon Dating Laboratory of the Faculty of Geology of Lund University, Sweden), dating of marine mollusks using electron spin resonance and dating by optically stimulated luminescence (OSL). The dating of the impact of terrestrial cosmogenic nuclides was applied to boulders lying on the tops of moraine ridges. On the R. Logat, data on the edomian thickness with syngenetic re-vein ice are considered. The host deposits contain mammoth tusks and a skull about 43 thousand cal. years old. They also studied the thickness with 2 tiers of re-vein ice on the Bol River. Balakhnya.^[28]

     I.D. Streletskaya et al.22] summed up the research in the north of Western Siberia, according to the study of eight reference sites containing homogenous re-vein and formation ice. The most typical section of Quaternary sediments is represented by a two-layer thickness. The upper part of the section consists of continental sandy and sandy loam deposits accumulated during MIS2–MIS1 (Sartan time and Holocene). Below this section, marine and coastal marine sandy–loamy and clay deposits were formed during MIS3–MIS5 (Kargian and pre-Kargian time). During MIS3, edom deposits accumulated and ice wedges formed. During MIS3–MIS2, rapid cooling, a dry climate and the formation of syngenetic re-vein ice on land and the drained shelf were noted. Based on the isotopic composition of the re-vein ice, the fact established by Yu.K. Vasilchuk^[19] was confirmed that from MIS 4 to the present, western atmospheric transport prevailed in the Russian Western Arctic. There is a pronounced geographical trend in the isotopic composition of ice with high values of ?18 ^O found in the western and the lowest values in the eastern part of the studied region. Based on the isotopic composition of the edom ice veins, the average January air temperature in MIS3–MIS2, calculated by the Vasilchuk equation^[7.19], was 10-15°C lower than the modern one. 

Edom of the north of Yakutia

Batagai failure

       The Batagai basin is a unique active outcrop of permafrost in the north of central Yakutia, having a thickness of more than 70 m and reflecting the evolution of edoma in the most severe climatic conditions of the north-east of Russia. The results of the beginning of an active study of the Batagai basin were published almost simultaneously by J.Merton and co-authors^[30], K.Ashastina and co-authors^[31] and Yu.Vasilchuk and co-authors^[32].

      J.Merton and co-authors^[30] came to a number of preliminary conclusions about the thickness of permafrost Batagaika rocks. They believe that Aeolian sand, which probably originates from the neighboring floodplain, accumulated gradually on the hilly territory for many thousands of years, its thickness is several tens of meters. Permafrost rocks developed syngenetically during the formation of sandy deposits with the parallel formation of numerous syngenetic ice veins in them. As a result, two ice complexes were formed. During the decrease in sand accumulation, several horizons of paleosols developed. The remains of wood from the upper woody lens are approximately related to interstadial conditions during MIS 3 (57-29 thousand years ago), in turn, the lower woody lens indicates interglacial conditions during MIS 5 (130-71 thousand years ago). Sand deposits and paleosols between the forest layers accumulated during MIS 4 (71-57 thousand years ago) or possibly before MIS 5.^[30,33]

      K.Ashastina and co-authors^[31] obtained OSL dating, which indicates that the outcrop reveals the cryolithogenic strata at least since the middle of the Pleistocene. For Radiocarbon Mass Spectrometry (AMS)  The plant residues that have been identified were used. No aquatic plant species were found in the samples. Thus, the influence of freshwater on the formation of sediments is excluded. Samples of permafrost deposits from the lower part of the section were selected for OSL (optically stimulated luminescent dating). K.Ashastina and co-authors^[31] identified five separate sedimentological layers representing different phases of accumulation: the Holocene cover layer; the Late Pleistocene edom ice complex; an organic horizon formed during the last interglacial period; layered deposits without visible ice veins; and another ice complex, probably older than the last interglacial. The identified five cryolithological units characterize individual phases in the history of the climate of inner Yakutia: the presence of a Middle Pleistocene ice complex indicates cold climatic conditions during the accumulation of a layer of the lower ice complex. K.Ashastina and co-authors^[31] suggested that interglacial climatic conditions existed during the accumulation of an organically saturated layer. But there were no plant remains or mollusks found in it, indicating an aquatic or swamp environment. On the contrary, the plant macrostates reflected the open forest vegetation existing in dry conditions during the last interglacial period. The Late Pleistocene edom ice complex (MIS 4-MIS 2), composing the Edom ice complex, indicates the presence of severe cold climatic conditions when ground temperatures could be 8-10 °C lower than now. General conclusion: The edom ice complex of the Batagai outcrop can be attributed to the medium-mountain type of edom ice complex, remote from rivers and sea coasts.^[31]

At the time of the study^[32] in 2017, the Batagai outcrop was a sheer wall up to 75 m high. From the surface to a depth of 75 m, highly acidic sediments are deposited. In the westernmost part of the outcrop, the edom stratum is divided into two layers: the upper one with a thickness of 30-45 m and the lower one with a thickness of about 30 m. The upper layer accommodates narrow ice veins, no more than 1.5-2 m wide. The heads of ice veins lie at a depth of 3-4 m (in some places they lie almost at the surface). The ice of the ice veins is clearly vertically layered, saturated with sandy loam particles, up to 1-2 cm wide. The polygons separating the veins are small – they rarely exceed 4-5 m in width, and, as a rule, they are 1.5-3 m (but in the western part of the outcrop the polygons are larger – up to 10 m). In the western sector of the outcrop in the upper part of the edom strata, a facies feather-like contact with the lake or taberal strata (practically without ice), in the form of a horizontal wedge about 150-200 m long, is embedded into the edom strata and overlaps it from above, and the edom strata underlies from below (to a depth of 65-75 m). In this lower part, the ice veins are yellowish-gray obliquely layered, with practically no soil inclusions, whereas in the rest they are predominantly gray in color. The edom strata in the lowest part of the section are underlain by a horizontally layered loam layer, which may represent ancient taberal deposits. The thickness contains more than 20 horizontal layers, more often layered at the bottom, a pronounced horizontal dark layer in the middle part, layering is less common here, frequent layering is observed in the roof of this horizontally layered thickness due to a higher organic content. In the re-vein ice at the base of the edom thickness, fluctuations in the values of ?18 ^O are 2.6 %, in a very negative range (from -37.2 to -34.51%), and variations in the values of ?2 H reached 23 % (from -290.8 to -267.8%).^[32] These are, in fact, the lowest isotopic characteristics obtained for the edomian strata of Siberia. In the younger re-vein ice exposed in the uppermost part of the Batagai edoma, the variations in the values of ?18 ^O are only about 1% (from -34.83 to -33.8%), and the change in the values of ?2 H was 17% (from -272.6 to -255.6%). The paleotemperatures reconstructed according to the variations ?18 ^O in re-vein ice: the average winter temperature is from -34 to -36 °C, the average January temperature is from -51 to -55 °C, these are the lowest winter temperatures obtained by Yu.K.Vasilchuk[1 9, p. 26] for the Late Pleistocene cryochron in the territory of the Russian cryolithozone: in The Kulara, Zeleny Cape and Duvan Yar reconstructed the average January paleotemperature of -48 °C, and in the section of the Plakhinsky Yar -49 °C^[19]. Perhaps only in the lower part of the Itkillik section in Alaska, low isotopic values comparable to those of Batagai were recorded – there is also a ?18 ^O slightly lower than -35%. On the maps of the distribution of January paleotemperature in the north of the Eurasian cryolithozone, compiled for the late Pleistocene by Yu.K. Vasilchuk in 1992 ^{[13, p. 261]}, Batagai is located inside the isoline of -48 ° C on the paleoreconstruction map for the period 30-25 thousand years ago and inside the isoline of -44 ° C on the map for the period 22-14 thousand years. The materials on the isotopic composition of the Batagaika re-vein ice and the paleotemperature reconstructed from them in January – below -51 °C^[32] fully confirmed the reliability of these maps.

               Yu.Vasilchuk and his co-authors^[32] came to the following conclusions:

A. The re-vein ice at depths of 5-10 m, 68-70 m and 65-73 m is fresh and has a bicarbonate-calcium composition, Mg prevails at a depth of 21 m and in textured ice at depths of 30-60 m, which may indicate excellent conditions for the formation of these ice bodies, the ratio of chlorides and sulfates indicates the continental nature of ice formation.

B. In general, compared with glacial ice, the chemical composition of the considered re-vein ice of the Batagai section is homogeneous, that is, the distribution of elements within each vein is slightly contrasting.

B. Re-vein ices at a depth of 65-73 m are characterized by the lowest content of most chemical elements, they may have been formed in conditions when winter precipitation was less mineralized, which may indicate a low level of dust content in winter precipitation, and probably low Aeolian activity during the formation of veins. These veins are also the closest in chemical composition to the water of the Batagaika river. The re-vein ices at a depth of 5-10 and at a depth of 68-70 m are more mineralized, which may indicate a relatively higher dust content in winter precipitation during their formation.^[32]

The re-vein ice exposed at a depth of 68-70 m and at a depth of 5-10 m formed in a very close temperature range: the average winter air temperature was close to -34, -35 °C, and the average January air temperature was -51, -53 °C, as evidenced by isotopic values: on average ?18 ^O, -34.4 and -34.36%, and ?2H -265.0% and -266.3%. In slightly more severe conditions, re-vein ice formed at a depth of 65-73 m: the average winter air temperature was close to -36 °C, and the average January paleotemperature was -54, -55 °C – in this vein, the average value of ?18 ^O was -35.69%, and the average value of ?2 H was -276.0%.^[32]

To. Ashastina, in her dissertation^[34] and in a generalizing article with co–authors^[35], based on the analysis of the remains of fossil organisms, including plant macrofossils, charcoal, pollen and invertebrates preserved in syngenetic sediments of the Batagai strata, reconstructed the Pleistocene paleocene vegetation of the stages MIS6-MIS2: To describe the history of vegetation, starting from the penultimate cold stage of MIS 6, 41 plant complexes were identified. Meadow steppes, similar to the modern communities of Festucetalia lenensis, formed the main vegetation during the Zaal and Vislin cold stages. Cryophilic species characteristic of tundra vegetation associationsCarici rupestris-Kobresietea bellardii turned out to be unexpectedly small in number for deposits of the Vislin cold stage. In the last interglacial period, the main vegetation in this area was sparsely wooded, resembling modern larch taiga. The abundance of charcoal indicates forest fires during the last interglacial. Zoogenic disturbances of the local vegetation were indicated by the presence of ruderal plants, especially abundant Urtica dioica, which suggests that this area was an interglacial refugium for large herbivores. The preservation of plants and invertebrates characteristic of meadow steppe vegetation in inner Yakutia throughout the Late Quaternary period indicates, according to K.Ashastina^[34], climatic continuity and demonstrate the suitability of this region as a refuge for other organisms of the Pleistocene mammoth steppe, including iconic large herbivores.

Yu.K. Vasilchuk and his collaborators carried out detailed cryolithological-isotope and geochronological studies of the Batagai section for 6 years, as a result of which, for the first time, high-resolution isotope-oxygen and deuterium diagrams in re-vein ice were obtained in the Batagai edome.^[32,36-44] AMS ¹⁴ C dating of microinclusions of organics in the re-vein ice of the upper and lower tiers, ^{[37,38,42-44]} isotopic composition of carbon and polyarenes in the pedogenic material of ice veins,^[39-41] vertical and horizontal distribution of micro- and macronutrients in ice veins,^[32,39] and precision comparison were performed isotopic data on two closely located adjacent ice veins.^[44]

       Yu.K. Vasilchuk and co-authors^[36] constructed high-resolution isotope-oxygen and deuterium diagrams for the re-vein ice of the Batagai edoma, compiled according to data from the carefully selected PLL No. 3 and PLL No.2. Isotope-oxygen diagrams made it possible to reconstruct the course of average January air temperatures and arrange them in chronological order on the diagrams.^[36]

      Yu.K. Vasilchuk and J.Y. Vasilchuk presented a series of the first AMS dating of microinclusions of organic matter in the upper tier of the Batagai edoma PLL No. 3.^[37] Seven new ¹⁴ C dates were obtained, all of them finite and distributed in the range from 22,760 to 29,910 radiocarbon years (or from 27.1 to 33.8 thousand cal years). There are small inversions in the distribution of dates: older dates are located above younger ones, which can be explained by two reasons. Firstly, by the fact that the selection was not carried out in the frontal section of the vein and, in addition, the autopsy was such that the intersection of two perpendicular veins was also uncovered in the outcrop as a single ice body. Secondly, the presence of redeposited organic matter is natural for frozen strata and re-vein ice. Thirdly, the depth of penetration of frost-breaking cracks during the formation of the Batagai edoma was extremely large (as indirectly evidenced by the significant vertical dimensions of the edoma and the veins located in it) and apparently varied from year to year, which led to different depths of penetration of cracks and organic material along them. These circumstances may have led to the dating of 27.4 (about 31 thousand cal. years) and 24.4 thousand years (about 28 thousand caliber. years) turned out to be higher than two dates of 22 thousand years (about 27 thousand cal. years). Taking into account these limitations, the time of formation of PPL No. 3 is dated to the period from 25 to 34 thousand cal. years ago.^[37]

Yu.K. Vasilchuk and co–authors^[38] dated microinclusions of organic material represented by organic dust: settled soil and biogenic aerosols, organic dust-like particles - pollen and spores, polycyclic aromatic hydrocarbons, etc., from powerful Pleistocene syngenetic re-vein ices opening in the lower part of the outcrop of the Bata Gaya edoma using an accelerator mass spectrometry to solve the problem of determining the time of the beginning of the accumulation of the food column. The powerful Pleistocene syngenetic re-vein ices dated by the authors: PLL No. 5, PLL No. 6 and PLL No. 7, opening in the lower part of the outcrop of the Batagai edoma, were formed 38-47 thousand years ago, or approximately 42-49 thousand calibers. years ago.^[38]

In two articles summarizing the data of radiocarbon dating in the upper and lower parts of the Batagai edoma, Yu.K. Vasilchuk and co-authors ^[42,43] examined the data of dating microinclusions of organic material in 13 samples from the upper and lower tiers of powerful Pleistocene syngenetic re-vein ices exposed in the Batagai edoma outcrop using accelerator mass spectrometry (AMS), as well as the results of detailed isotopic determinations of the values of ?18 ^O and ?2 H in ³ syngenetic vein ices (PLL No. 3, PLL No. 5 and PLL No. 7): 39, 53 and 79 samples, respectively. New interesting conclusions have been obtained:

A. The re-vein ice of the Batagai edoma was formed during the MIS-3 period, from 48 to 43 thousand cal. years ago (lower tier) and during the MIS-2 period, from 37 to 24 thousand cal. years ago (upper tier).

B. Ice veins formed duringMIS-3 are located at different absolute altitudes: one at an altitude of 239-227 m above sea level, the second at an altitude of 274-266 m above sea level, while very close radiocarbon dating was obtained from them, which is a good indicator of the slope genesis of the deposits of the Batagai Edoma.

B. The range of isotopic values in the re-lived ices of both tiers is quite narrow: in the ice veins formed during the MIS-3 period, the variations of the values of ?18 ^O were 3% (from -35.36 to -32.36%), the values of ?2 H were 38% (from -276.0 to -238.1%); in In the ice veins formed during the MIS-2 ^period, the variations in the values of ?18 O ^{did not exceed} 2.5% (from -34.83 to -32.47%), the values of ?2H -17% (from -272.60 to -255.60%).

According to isotopic data, the average January air temperature of the Late Pleistocene was calculated for the Batagai section and for a number of reference sections in the north-west of Yakutia. It is shown that the lowest average January air temperature (during this period was in the Batagaika region (-51, -53°C), whereas in areas located 500-600 km north of where ice veins also actively grew during the stages of MIS-3 and MIS-2 (Kular, Cape Mammoth Fang, Kurungnah-Sise and Buor-Khaya Islands) The average January air temperature was 5-7 °C higher and was about -44....-48°C. This is explained by the existence of the Yakut anticyclone in the late Pleistocene in winter, it was also pronounced, as it is now.^[42,43]

Yu.K. Vasilchuk and co-authors ^[44] performed for the first time a diagnostic comparison of isotopic data from parallel ice veins from a single section. The main task of this work is to compare the results of isotope analysis obtained from parallel and synchronous re–vein ice exposed in a single outcrop in the upper part of the Batagai edoma and analyze their precision, i.e., the measure of proximity of independent results of isotope studies of two veins, their similarities and differences. This may allow for more objective calculation of both average and extremely low paleotemperatures based on isotopic data. In the mouth part of the thermoerosion ravine opening into the southeastern part of the Batagai crater, detailed isotope testing of two extended ice veins was performed: PZHL-17 - and PZHL-20 in parallel to a depth of 13.1 m, below - only along the PZHL-17 vein - to a depth of 22.1 m. Ice veins PZHL-17 and PZHL-20 They are located parallel to each other at a distance of 5 to 10 m and dissect the edom thickness to a depth of more than 20 m. According to unidentified organic microstates in the ice of PZHL-17 using AMS, 4 radiocarbon dating was obtained: from sandy loam with organic inclusions directly above the vein at a depth of 1.30 m, a Holocene date of 10510 cal. years was obtained, at a depth of 3.3 m, a date of 26140 cal. years was obtained from the axial part of the ice vein, at a depth of 12.3 m (due to a change in the angle of opening of the ice vein, the sample was taken 0.5 m to the left of the axis of the vein), its ¹⁴ With age was 29100 cal. years, at a depth of 21.1 m in the lower part of the PL, the sample was taken from the axial part, its ¹⁴ With age was 42220 cal. years. The new AMS radiocarbon dating obtained allows us to conclude with a high degree of probability that the examined powerful syngenetic re-vein ice, opening in the upper 20-meter part of the outcrop of the Batagai edoma, began to accumulate no later than 42 thousand cal. years ago, and completed the formation of about 11.7 thousand cal. years ago. Thus, ice veins in the upper Batagai ice complex in the central part of the outcrop have accumulated over the course of 30 thousand years.^[44]

              The vertical records in the veins of PZHL-17 and PZHL-20 are divided into 4 fragments in depth: a) 1.3-1.7 m; b) 1.9-7.1 m; c) 7.3-11.5 m; d) 11.7-13.1 m, and in the more powerful vein of PZHL-17, an additional fragment e) 13.3-22.1 m . In the range a – 1.3-1.7 m – the values of ?18 ^O and ?2 H change almost synchronously in both veins, but the isotopic values differ significantly, the average values for PL-17: values of ?18 ^O = -31.21, values of ?2 H = -237.03, for PL-20: ?18 ^O = -33.37%, ?2 H = -251.0%. In the b interval (1.9-7.1 m)  – the values of ?18 ^O and ?2 H change almost synchronously in both veins. The average values for PL-17 are: ?18 ^O = -33.82%, ?2 H = -250.83%, for PL-20 the value of ?18 ^O = -33.74%, the value of ?2 H = -260.10%. In the range b (7.3-11.5 m), the opposite distribution of isotopic values is observed, while the values of ?18 ^O and ?2 H are usually lower in PLL-20 compared to PLL-17. The average isotopic values in PL-17: ?18 ^O = -33.70%, ?2 H= -259.28%, the average isotopic values in PL-20: ?18 ^O = -34.49% ?2 H = -265.94 %. In the range of g (11.7-13.1 m), extremely low values of ?18 ^O are observed for PLL-17 -36.07%, while for PLL-20 the values of ?18 ^O and ?2 H are close to the cross-sectional averages: the average values of isotopic values in PLL-¹⁷ ?18 O = -35.36% ?2 H = – 275.86%, the average isotopic values of PPL-20 ?18 ^O = -34.40?2 H = – 268.49%. In the interval d in the PL-17 (13.3-22.1 m), the average value of ?18 ^O = -35.12, ?2 H = -272.79, extremely low values were noted for the considered data set ?18 ^O = -36.16, ?2 H = – 282.10. According to the results of the research, the following conclusions were obtained:

A. The studied large fragment of the Batagai edoma was formed from 45 to 23 caliber thousand years ago. In a single almost vertical outcrop of edoma, more than 5 syngenetic ice veins are revealed with a length of more than 20 m and a width in the upper part of 2.3-2.5 m. The veins are located at a distance of 2-3 m from each other.

B. A comparison of detailed isotope records of two neighboring syngenetic ice veins PZHL-17 and PZHL-20, selected in detail vertically (after 0.2 m), was performed. Testing was also carried out in 5 horizontal profiles. The vertical records in the veins of PZHL-17 and PZHL-20 are divided into 4 fragments in depth: a) 1.3-1.7 m; b) 1.9-7.1 m; c) 7.3-11.5 m; c) 11.7-13.1 m, in the more powerful vein of PZHL-17, an additional fragment e) 13.3-22.1 m.^[44]

V. Fragments (a and b) at the same depths, the isotopic records of which coincide or are very close, were isolated in the studied veins PZHL-17 and PZHL-20. Fragments of veins (fragments b and d) were also found, where at the same depths the isotopic records of which differ in values of ?18 ^O by 1.5%, and in values of ?2 H by more than 10%.^[44]

Significant differences in the isotope signal from neighboring ice veins at the same depths have been revealed, most likely the differences are due to the belonging of these veins to different polygonal systems: PLL-17 to the polygonal system of primary generation, PLL-20 to the polygonal system of the second generation located inside the primary polygonal network. This led to a rarer cracking of the secondary polygonal network, which occurred only in the most severe winters.^[44]

The isotopic characterization of neighboring parallel ice veins makes it possible to expand the range of paleotemperature reconstructions and obtain information on both average and extreme temperatures of the winter period for a particular period of time during which veins were formed. 

    Y. K. Vasilchuk and co-authors published a number of articles devoted to the consideration of the distribution of trace elements^[39] and the isotopic composition of carbon and polyarenes in the pedogenic material of the ice veins of the Batagai edoma^[39,40], as well as, for comparison, variations in the PAH content and the ratio of carbon and nitrogen content in soils in the Batagaika area^[41]. The isotopic composition of carbon lipids in the organic material included in the ice veins of the Batagai edoma corresponds to the composition of plants with the type of photosynthesis C ₃, that is, it has a pedogenic origin. As the depth of the ice vein increases and the age of inclusions increases, the carbon isotope composition of soil lipids shows a tendency to lighten. The high PAH content in the ice veins of the Batagai edoma (up to 430 ng/g, an average of 170 ng/g) may indicate that this material was formed from substances rich in organic matter (humus or blocked soil horizons).^[40] Compared with the data of the work performed for Arctic soils, the amount of PAHs in the pedogenic material of the studied ice veins is somewhat increased. The PAH association contains naphthalene and phenanthrene homologues as the dominant components. Combinations of the obtained parameters (organic carbon content from 1.2 to 3.2%, ?13 values from -26.2 to -31.1%, predominance of phenanthrene and naphthalene homologues in PAHs) in the pedogenic material of the Batagai edoma ice veins are, apparently, the result of a combination of the following processes: a) the introduction of PAHs with substances rich in organic matter (material of humus horizons of ancient soils, etc.); b) the introduction of certain amounts of heavy hydrocarbons (in particular, benz (a)pyrene) with material formed as a result of natural fires; c) selective decomposition of lipid components followed by isotopic relief of the total lipid fraction in the process soil formation (until the sediment enters the ice veins). The content of polyarenes and the composition of the PAH association in the ice veins of the Batagai edoma may reflect the change of landscapes in this area.^[40]

    The specified height of the Batagai outcrop ranges from 50 to 92 m, with a length and width of more than 1 km. From the surface to a depth of about 75 m, a vertical wall of highly acidic sediments is exposed. The Batagai section was divided into several main stratigraphic units^[33,45] in accordance with the results of dating by ¹⁴ C, OSL, IRSL, ³⁶ Cl/Cl: Upper sand (age from 15,090 to 42,390 years); upper ice complex (age from 27,160 to 52,210 years); lower sand (age >123,200 years (OSL)) and the lower ice complex (about 650 thousand years ago). Between the upper ice complex and the lower sand there are lenses of wood residues with a thickness of up to 3 m.

       J. Merton and co-authors^[45] performed age studies of almost all formations of the Batagai section using different methods. All available chronostratigraphic data on the Batagai outcrop, given in ^[45], are summarized from: [30-32, [36-38, 42-43], etc.].

     According to the luminescent dating data, the ages of the four studied re-vein complexes are in the correct stratigraphic order, that is, without age inversions. The re-vein ice from the upper ice complex is 10 ± 19 thousand years older than the re-vein ice from the upper sand. The re-vein ice from the lower ice complex is 573 ± 42 thousand years older than the re-vein ice from the upper ice complex^[45]. Six OSL datings were obtained from quartz and K–feldspar fractions. The lower re-vein complex, sampled at a depth of 49.5 m, gave the age of quartz OSL 244 ± 16 thousand years. The upper re-vein complex, selected at a height of 5 m above its base, gave quartz OSL age 57.5 ± 5.8 thousand years and K–feldspar age 90.5 ± 6.2 thousand years. The upper sand block, sampled at depths of 11, 2.3 and 2.1 m below the earth's surface, gave the age of OSL 40.0 ± 3.9 thousand years, 41.0 ± 3.9 thousand years and 27.1 ± 2.1 thousand years according to quartz.

Radiocarbon dating of the Batagai mega-ravine can only be used for the upper part of the section, exorbitant radiocarbon dates have been obtained in the lower part of the section. Based on all available radiocarbon dating, but excluding those that are considered redeposited by different authors, it was found that the upper sands layer has a finite age from 15.09 to 42.39 thousand cal. years. The age of the upper ice complex ranges from 27.16 to 52.21 thousand cal. years.

¹⁴. Dating of different types of organic matter has proved to be useful to varying degrees for determining the age of ice complexes in Batagai. Dated organic samples (n = 40) from the upper ice complex, the upper sand block and the cover layer include the remains of plant macrofossils (fragments of wood, branches, leaves, stems, roots in situ, charcoal), squirrel droppings, insect remains and unidentified microinclusions in re-vein ice. The calibrated age varies from 0.39 thousand cal.  years ago, up to 51.92 thousand cal. years ago, and many dates are not final. The interpretation of the final ¹⁴ C dates reveals a number of problems. First, some materials, especially fragments of wood, are likely to have been recycled – for example, as a result of erosion, and therefore give the maximum age of sediment deposition. Therefore, it is necessary to compare ^{the 14} C age with the age obtained by other methods, only from the material selected in situ. The depth measurements obtained from different parts of the large and topographically variable relief of the mega-ravine had to be well compared, since this introduces a significant error in determining the exact stratigraphic position of the samples. This error is aggravated by the slope of the layers downhill, variable thickness and complex geometry of stratigraphic units, as well as local disturbances in the distribution of re-vein ice and the mineral component of the edoma. Nevertheless, age estimates allow us to generally assume that the cover layer is of Holocene age, the upper sand began to form somewhere within the 3rd marine isotope stage (MIS) 58-28 thousand years ago and its formation continued during the MIS 2 period 28-11.7 thousand years ago, and the upper ice complex it developed during MIS 3, but the time of the beginning of its formation is unknown, since the oldest dating is beyond ^{the 14th} century dating (older than 40-50 thousand years).

J. Merton and co-authors^[45] consider plant material that can be identified taxonomically and is in ^situ to be the best material for 14 C dating. If the material is not available in situ, it is better to date fragile organic remains, which are unlikely to have survived significant processing and probably represent paleoecological conditions and, consequently, the local environment.

      Since the ³⁶ Cl/Cl method provides relative dates relative to a reference point with a known age, other available age information must be used for these age definitions to limit the age of the reference ice core. J. Merton and co-authors^[45] decided not to choose the youngest and uppermost re-vein ice from the upper sand as a reference standard for re-vein ice, because it is located only 2 m below the modern surface and its isotopic composition is quite close to the composition of Holocene re-vein ice nearby^[45]. Therefore, it cannot be excluded that this ice is epigenetic Holocene, that is, it was formed much later than the time of deposition of its host sediments of age from MIS 3 to MIS 2. Instead, J. Merton and co-authors^[45] chose re-vein ice from the upper ice complex as a reference for ³⁶ Cl/Cl results. Based on the available ¹⁴ C dating for this re-vein ice (calibrated average age of 29 thousand years) and the host sediments (> 50 thousand years), the period 40 ± 10 thousand years ago was chosen as the base age for ³⁶ Cl/Cl to calculate the age of re-vein ice. It seems that the choice of the reference age was not sufficiently justified, since in order to choose a reference point, it is necessary to analyze all the available consistent dating according to the PLL from the same stratigraphic layer.

The age of re-vein ice from older layers is 51 ± 30 thousand years for re-vein ice from the upper ice complex and 624 ± 51 thousand years for re-vein ice B17–IW1 from the lower ice complex. It is noteworthy that the large range of uncertainty for the ³⁶ Cl/Cl age covers the estimate of the OSL age from the upper ice complex, but slightly younger than the pIRIR age. ³⁶ Cl/Cl age of the re-core ice B17–IW1 from the lower ice complex is clearly older than the age of the OSL from the lower ice complex, but falls into the The uncertainty range of both ages is pIRIR. Due to the long half-life of ³⁶ Cl (434 thousand years), the method is much better applicable to ancient ices (Middle Pleistocene) than to younger ones (Late Pleistocene). The results obtained by the ³⁶ Cl/Cl method should not be used as the only source of information, but as additional evidence in combination with other dating results.

The synthesis of the dating of four dating methods performed by J. Merton and co-authors^[45] made it possible to estimate the probable age of the lower ice complex, the upper edom complex and the upper sand. The lower ice complex gives two pirirs of age 658 ± 74 thousand years and 693 ± 97 thousand years from sand, they are indistinguishable not only from each other, but also from a single age of ³⁶ Cl/Cl in 624 ± 51 thousand years from the ice wedge B17–IW1. This consistency makes it possible to assume that the lower ice complex developed during the Early Middle Pleistocene or earlier, and it can be tentatively assumed that the age of the lower ice complex is about 650 thousand years (MIS 16) or older.^[45].

The Upper Edom ice complex demonstrates agreement between the ages obtained by three of the four dating methods. Sixteen final ¹⁴ C dates from more than 50 to 27 thousand years[36-38,42-43] and seven exorbitant ¹⁴ C dates from various sites inside the edomian strata, one reduced age of ³⁶ Cl/Cl equal to 51 ± 30 thousand years, and one OSL age of 67.6 ± 9.9 thousand years indicate the development of the upper ice complex during the 3rd stage of MIS, which may have stopped at the beginning of the 2nd stage of MIS.

The dating of the upper sands demonstrates the agreement between the ages obtained by the two dating methods. Eight final ¹⁴ C dates from more than 42 to 15 cal. thousand years and two exorbitant ¹⁴ C age dates are quite close to the three OSL dates of 40.0 ± 3.9 thousand years, 41.0 ± 3.9 thousand years and 27.1 ± 2.1 thousand years. These OSL dates are affected by feldspar contamination of quartz, but removal of this contaminant suggests that any age shift at these depths will be statistically insignificant. Agreement is enhanced for organic samples that were clearly in situ (e.g. roots) or included thin organic material (e.g. brittle leaves of Empetrum nigrum) that were unlikely to survive significant processing. This sample gives three final ¹⁴ C ages from rhizomes in situ of more than 27 and 22 thousand years from a depth of about 1 m below the earth's surface and one date of more than 41 cal. thousand years from a depth of 18.5 m. In addition, dating of about 42 thousand years was obtained from a depth of about 11 m, although the sample is considered less reliable than rhizomes (since it is a heterogeneous complex consisting of leaves of twigs and remnants of sedges - Cyperaceae). The three dates obtained by the pIRIR method are 61.0 ± 3.7 thousand years, 50.9 ± 3.5 thousand years and 45.5 ± 2.9 thousand years. slightly older than the ¹⁴ C and OSL dates, which can be explained by residual doses in K–feldspar. In general, J. Merton and co-authors^[33,45] concluded that the upper sand block accumulated during MIS3 and MIS2, although further dating is necessary to confirm this and determine the time of the beginning of sedimentation.

The dating results suggest that the lower ice complex formed during or before the 16th MIS (about 677-622 thousand years ago), i.e. the period coinciding with the maximum glaciation in the Northern Hemisphere. J. Merton and co-authors^[45] claim that, judging by the dating of more than 650 thousand years, the Batagai section uncovered the oldest known permafrost in Western Beringia and the second oldest in the Northern Hemisphere. The ancient permafrost in Batagai belongs to the early-Middle Pleistocene, which began about 774 thousand years ago, during MIS 19. The ancient permafrost strata in Batagai indicate that the highly glaciated permafrost strata experienced repeated episodes of climate warming, and even exceptionally warm and humid conditions during the "superglacial" - 420 thousand years ago, warmer than the modern climate, as well as the last interglacial (MIS 5e) and the warm summer period of the Holocene optimum. It is obvious that the lower ice complex, buried under more than 50 meters of permafrost deposits, was resistant to natural climate and environmental changes during numerous glacial-interglacial cycles, but it is vulnerable to anthropogenic disturbances and local thermokarst activity. Based on this study, J. Merton and co-authors^[45] made four important conclusions. First, the good agreement of age estimates between two independent dating methods (pIRIR dating of K–feldspar from sand and ³⁶ Cl/Cl dating of ice) provides a reasonable degree of confidence in dating ancient permafrost preserved since the last interglacial. Secondly, the ³⁶ Cl/Cl method is a good way to date ancient re-vein ice. This method is more suitable for dating older underground ices and their host sediments (Middle Pleistocene) than younger sediments (Late Pleistocene). Thirdly, if the pIRIR and ³⁶ Cl/Cl dating are correct, then the ancient permafrost strata within the lower ice complex in the Batagai mega-ravine have been preserved since the beginning of the Middle Pleistocene (about 650 thousand years ago or earlier) and represent the oldest permafrost strata known in western Beringia and the second (after the ice veins on the Klondike dated by the track method - more than 700 thousand years) by age, a fragment of dated permafrost in the Northern Hemisphere. Fourth, the ancient permafrost strata in Batagai were resistant to numerous episodes of climate warming and environmental change, but vulnerable to local disturbances as a result of anthropogenic and thermokarst activity.

Future studies on the dating of permafrost deposits and ice in the Batagai mega ravine are necessary both to confirm the previously obtained results and to shed light on the discrepancy between the results of dating the lower ice complex and the lower sand, as well as the lower sand and the woody layer.^[45]

       J. Merton and T.Opel and colleagues^[46] showed that the Batagai mega-ravine is exceptional in two respects. Firstly, it provides unique access to very ancient permafrost and has great potential for reconstructing paleoecological conditions and studying past interactions of climate and permafrost, starting from the Middle Pleistocene.

Secondly, it demonstrates the high sensitivity of permafrost rocks rich in ice to sudden thawing as a result of terrain disturbance.

The Batagai mega ravine is the largest known outcrop of permafrost in the world. The outcrop reveals a sequence of deposits of permafrost rocks of the Pleistocene, which record the interaction of colluvial, Aeolian and periglacial processes on the hillside, which has been sporadically overgrown with forest over the past 650 thousand years or more, in response to climate variability. Numerous bones, teeth, and occasional carcasses of Pleistocene and Holocene mammals have been extracted from permafrost rocks. Megaovrag has been developing for several decades in three stages: 1) ravine formation, 2) thawing and 3) mega-landslides. A comparison of the Batagai mega-ravine with megaproves in northwestern Canada (Peel Plateau) reveals a number of similarities and differences in terms of their geomorphology, permafrost deposits and Quaternary history.^[46]

      L.Jongejens and co-authors^[47] took samples of five stratigraphic units and analyzed lipid biomarkers (alkanes, fatty acids and alcohols). The analysis of biomarkers indicated that the organic matter in the edom was better preserved and of higher quality than other suites. Thus, edom deposits have a higher potential for decomposition of organic matter, although they make up only 25% of the total pool of organic matter in the Batagai section. The rapid decomposition of easily degradable organic matter can potentially lead to significant greenhouse gas emissions. This study revealed similar biogeochemical signs of cold periods: the lower ice complex (marine isotope stage (MIS 16 and earlier), the lower sand complex (somewhere between MIS 16–MIS 6) and the upper ice complex (MIS 4–MIS 2). The organic matter in these units is terrestrial in nature, and microbial activity was probably limited. The distribution of n-alkanes and fatty acids, on the contrary, differed for the interglacial thicknesses: the woody layer (MIS 5) separating the lower sand pack and the upper ice complex, and the Holocene cover (MIS 1) on top of the glacial complex. The woody layer, marking some degradation of frozen rocks, contained markers of terrestrial origin (sterols) and high microbial decomposition (iso- and anti-fatty acids). In the Holocene cover, biomarkers indicated wet sedimentation conditions; branched and cyclic alkanes, probably of microbial origin, were identified here^[47]. Holocene layers are characterized by higher decomposition of organic matter. These data show that there were no significant changes in the vegetation of the predominant meadow steppe during the cold periods: during MIS 16, between MIS 16 and MIS 6 and MIS 4–MIS 2. The woody layer (MIS 5), both of the eroded and accumulated material, showed a high content of organic matter of higher plants and strong microbial decomposition.  For relatively warmer periods, the inventory of biomolecules indicates a higher microbial transformation of organic matter and, consequently, a decrease in the quality of organic matter. On the contrary, in colder periods, biomolecules assume a variable, but generally higher quality of organic matter compared to warmer periods. The analysis of biomarkers of ancient permafrost deposits contributes to a better understanding of how organic matter is incorporated and preserved in permafrost deposits.^[47]

      Oygos Yar

T.Opel and his colleagues, as part of a joint Russian-German expedition, examined the famous outcrop of Oygos Yar, on the shore of the Dmitry Laptev Strait^[48]. Typically, the sediments in the section are represented by gray-brown desalinated sandy loams and loams with peat inclusions that originate from buried cryogenic soils, and fragments of branches, plant roots and small, scattered plant detritus. Syngenetic re-vein ice has a vertical length of more than 20 m and a width of more than 3-4 m. According to radiocarbon dating, the Edom ice complex was formed approximately 49.4 to 36.3 thousand years ago. In the ice veins of the edom complex, the average values of ?18 ^O = -30.8 %, and the values of ?2 H = -240.2 %, the average value of d _exc = 5.9%, the equation for the regression line ?2 H =8.3318 ^O+15.92. The values of ?18 ^O of pore and segregation ice showed a huge variation and vary between -34.5 and -18.5, and the values of ?2 H vary from -253.9 to -150.5. According to T.Opel et al.^[48], the edom complex began to form in the area of the Oygos Yar at least 50 thousand years ago, confirming the early conclusions of G.F. Gravis, T.N. Kaplina and A.V. Lozhkin, S.V. Tomirdiaro et al. The huge variation in the values of ?18 ^O and ?2 H of pore and segregation ice inside the edom ice complex reflects mainly secondary fractionation processes rather than climatic conditions^[48]. For climatic interpretation, T.Opel proposed an experimental classification of the average values of ?18 ^O for re-vein ice (a similar classification was proposed in 1987 by Yu.K. Vasilchuk for the veins of the Duvan Yar) with six classes (extremely cold: from -38 to -35%; very cold: from -35 to -32%; cold: from -32 up to -29%; moderate from -29 to -26%; warm: -26 to -23%; very warm: -23 to -20%)^[48]. The average values of ?18 ^O and ?2 H -31 and -240in the edom veins confirm the cold winter temperatures during the formation of the re-vein ice, but reflect slightly warmer temperatures than in the preceding Yukaghir and Bychchygian times. The variability in the values of ?18 ^O and ?2 H with altitude in edom reflects the change in winter temperatures from very low (cold) to moderate.^[48]

      Sobo-Sise Island in the Lena Delta

S. Wetterich and co-authors^[49,50] investigated cryostratigraphy and isotopic composition in 511 samples of edible re-vein ice on the island of Sobo-Sis in the Lena Delta. Three sediment profiles were selected in close proximity to each other to cover the entire section of permafrost rocks with a resolution of 0.5 m. Overlaps during sampling were applied to account for the possible influence of relief on the development of polygonal vein complexes during the development of permafrost rocks. The first profile covers the uppermost part of the outcrop between 24.2 and 15.5 meters, dating from 2,440 to 27,540 cal. years. The second profile, the adjacent outcrop of the landfill, was selected between 18.8 and 10.2 m, dating from 25,680 to 40,840 cal. years. The third - lowest profile was selected approximately 120 m to the east between 13.4 and 0.8 m. It is dated from 41,420 to more than 50,000 cal. years. The compiled sequence is not continuous and reflects three time intervals that are associated with erosion breaks. One break is obvious between about 36 and 29 thousand cal. years ago, the second break was between 20 and 17 thousand calories. years ago, and the third break was approximately between 15 and 7 thousand calories. years ago.^[49]

Age inversions are observed in permafrost rocks as a result of the manifestation of cryogenic processes such as cryoturbation, thermal erosion. A clear evidence of the manifestation of thermal erosion is the incision Itself, where one of the samples is 15,294 ± 67 years old (18,570 cal. years), while the entire profile dates from 25,680 to 40,840 cal. years.^[49] It is likely that the date is 18,570 cal. years, rather a consequence of the re-deposition in the thawed state of sediments that were re-deposited and represent a mixture of Holocene organic matter with older organic material. To confirm this assumption, additional plant material was selected from the same sample (the total material was dated according to the bulk sample of 18,570 cal. years ago), and this plant material has been dated to 40,840 cal. years ago.^[49]

Three profiles of the re-vein ice of block A. Seven ¹⁴ C dates from the profile range in the time range from 48,660 to 36,970 cal. years ago. One specimen with an exorbitant age >48,500 years ago was also found here. The re-vein ice has been dated to 43,270 and 30,930 cal. years. Organic material extracted directly from the recycled ice yielded ¹⁴ with an age of 49,610 cal. years ago. The re-vein ice of block B was dated with two dates – 25,350 and 23,470 cal. years ago. The host sediments at an altitude of 18 to 20 meters above the river level showed an age range from 23,170 to 21,940 cal. years ago, which is generally consistent with the estimated time of formation of re-vein ice^[49]. In the ice vein of block A, the average values of ?18 ^O = -29.7%, ?2 H = -232% and d _exc = 5.2 %. The re-vein ice shows identical average values: ?18 ^O = -29.7% and ?2 H = ^-231%, but higher values of d _exc, which are 7.2 The eastern part of the profile is characterized by lower values of ?18 ^O (by 4%), ?2 H (by 40%) and d _exc (by 4%) compared to the main part of the profile, which is assigned to block C. The average values are: ?18 ^O = -29.6%, ?2 H = -230% and d _exc = 6.8%, they are close to the corresponding values of the other two profiles of the re-core ice of block A.^[49]

Depleted average isotopic values were obtained in the re-core ice of block A: ?18 ^O = -29.9% (range from -31.4% to -26.9%) and ?2 H = -232% b (range from -244% to -213%). They are mainly located below the global meteor water line (GLMW) and show low values of d _exc between 5.2 and 7.4% compared to blocks B and C. The slope of the ratio lines in the diagrams ? ² H–? ¹⁸ O for ice veins from block A varies from 7.2 to 8.3. The isotopic composition of re-vein ice differs in the western part of the profile by higher average isotopic values: ? ¹⁸ O = -28.8±0.5% v, ? ² H = -225±5% and d _exc 5,8±0,9 %. The slope of the ratio lines in the diagrams ? ² H–? ¹⁸ O is 9.4. It can be assumed that the isotopic composition of all re-vein ices carries reliable paleoclimatic information for the winter season and is not significantly changed by secondary fractionation processes. The data on stable isotopes of ice veins generally fit well into the regional picture of the central coast of the Laptev Sea and the Lena Delta, as well as into the large-scale picture presented by T.Opel, and reflect the cold and stable winter climatic conditions during the Late Pleistocene cryochron. Ice veins of Block A (MIS 3) (average ?18 ^O = -29.7 %; average ?2 H = -231.8 %) are slightly less isotopically depleted compared to the Bykovsky Peninsula (average ?18 ^O = -30.8 %; average ?2 H = -242.8 %) in the east and Kurungnakh Island-Cise (average value ?18 ^O = -31.6 %; average value ?2 H = -247.6 %) in the west. On the contrary, the values of d _exc are slightly higher in Themselves (average value of d _exc: 5.7 %) compared to Bykovsky (average value of d _exc: 3.7 %) and Kurungnakh Sisa (average value of d _exc: 5.3 %). For the re-vein ices of MIS ², the picture is similar, with slightly less isotopically depleted values for Itself (the average value of ?18 ^O is about -28.8 %; the value of ?2 H = -224.6 %) and slightly higher values of d _exc 7.4%) compared with Bykovsky (the average values of ?18 ^O = -30.6 , the value of ?2 H = -239.5 %; d ^exc = 5.1 %. Since the sampled re-vein ices probably reflect different time slices of MIS 3 and MIS ₂ and, therefore, small differences should not be spatially interpreted in terms of winter temperature differences. The isotopic composition of the ice veins Itself does not reveal significant differences between the ice veins of blocks A and B dated to MIS 3 and MIS 2. This may indicate that the globally cold last glacial maximum during MIS 2 is not reflected in the winter climatic data of the ice veins Themselves.^[49]

                 Kular

Yu.K. Vasilchuk and A.K. Vasilchuk investigated syngenetic re-vein ice and the age of the slope edoma in the foothills of the Kular ridge ((70.6431° S., 134.3550° V.D.)^[51] and their isotopic composition.^[52] In a detailed fragment studied on the gentle slope of the southern exposure of the valley of the stream. Burguat, 0.5 km west of the mouth of the Emis creek, the thickness of the PLL is located in the form of an inclined (slope 4-5 ^o) slope with a length of more than 1 km. The absolute marks of the sole of the edom range from 95 m near the stream to 110-120 m in the upper part of the slope, and the roofs range from 105 to 140 m. In the section, there are both powerful syngenetic PLL, penetrating the entire thickness, and multi-tiered PLL. The heads of multi-tiered veins lie at different depths: 0-1 m, 4-5 m, 8.5-10 m, 15-17 m. In total, there are three or four tiers of PPL. The width of the veins reaches 3 m, the ice is brownish-gray with an admixture of peat and sandy loam. The distance between the PL is 13-15 m. There is a difference between veins directed along and across the slope. The PLL located along the slope are symmetrical, lie subvertically, reach a width of 3-3.5 m. The PLL located perpendicular to the fall of the slope are usually asymmetric, much narrower, their width in the upper part is 1.5-2 m, the occurrence is inclined up to subhorizontal.^[51]

      Dating of wood and peat in the lowest peat lens at a depth of 17.8-18.0 m outside the radiocarbon method, but at a depth of 17.6 m, almost there the trunk of a larch was dated in the range of 47244-42769 cal. years.^[51] Only the lower part of the Edoma section, which contains a large amount of diverse organic material, has been reliably dated. The dates for wood, bone material and pure peat do not contradict each other. According to the dating results, the beginning of the accumulation of edom deposits in the section studied by the authors refers to a period of about 47 (50) thousand cal. years. Obviously, vein No. 1 was formed approximately in the range of 47-45 thousand cal. years ago. Wood at a depth of 17.6 m has an age of about 47 thousand cal. years, and peat at a depth of 11.2 m has an age of about 37 thousand cal. years, i.e., the growth of edom deposits occurred at a rate of about 0.7 m per 1 thousand years. We have assumed this rate of vertical growth of the pancreas and the host sediments to be constant for the Kulara edoma. The upper 11 m of the host sediments, therefore, accumulated for at least 10-17 thousand years. Judging by the fact that vein No. 2 began to form during the completion of peat accumulation, the period of its formation can be attributed approximately to the interval of 37-25 thousand cal. years ago. Consequently, edom deposits began to form no later than 50 (47) thousand cal. years ago, the accumulation was completed no earlier than 25 (22) thousand cal. years ago. After the formation of the sandy loam pack, about 47 thousand cal. years ago, intensive peat accumulation began, which caused the active growth of re-vein ice of the lower tier, synchronous to the lower peat horizon and epigenetic in relation to the underlying sandy loams.^[51] The primary lake most likely originated as a floodplain. An increase in the erosion base of 42-40 thousand cal. years ago, it led to the resumption of accumulation of lake-alluvial sandy loams, which preserved the lower tier of re-vein ice. The veins did not grow, despite the harsh geocryological conditions of the sandy loam formation period. About 37 thousand calories. years ago, the basis of erosion decreased again, which led to the accumulation of a thick layer of peat, and the active growth of re-vein ice resumed. The thickness of this peatland exceeds 2 m, late Pleistocene autochthonous peatlands of such capacity in the north of the cryolithozone are unknown. There is a combination of favorable factors that caused the accumulation of peat. Obviously, this is a peripheral part of the lake-marsh tab. The cracking process probably occurred quite often and led to deep penetration of cracks, their greater opening, which ensured the formation of veins of the middle tier to a depth of more than 6-8 m. The tails of many newly formed veins of the middle tier reached the surface of the buried veins of the lower tier, which contributed to the formation of a single ice wedge. Some of the new veins did not reach the buried ones, as indicated by the different heights of their tails. A similar process was repeated again about 33-27 thousand cal. years ago, when sandy loams accumulated, and about 27 thousand cal. years ago, the intensive growth of veins in width began. The largest veins formed during this period were also introduced and merged with the previously formed housing complex, while smaller ones or located somewhat to the side formed independently.^[51]

       The values of ?18 ^O of the re-vein ice of the slope edoma of the Kular ridge range from -32.6 to -30%^[52], in texture-forming segregation ice in the edoma thickness, the values of ?18 ^O range from -35.6 to -22.1%, in segregation ice lenses – from -24.4 to -21.5%. For two periods of the Late Pleistocene: 47-42 thousand cal. years ago and 37-32 thousand calories. years ago, the values of ?18 ^O _w (in the area of the Kular ridge) were -31 and -32.5%, respectively. The average January temperature in the area of the Kular ridge is 47-42 thousand kcal. years ago it was 1-3.8 °C higher than 37-32 thousand cal. years ago, it was -46 and -49 °C, respectively. The lowest average January temperature (about 10 °C lower than the modern one) in the area of the Kular ridge dates back to the period 37-32 thousand years ago.^[52]

      D.Y.Bolshiyanov and co-authors^[53] provide evidence that Edoma, as well as all other geomorphological levels of the delta and coastal terraces in the Lena River delta, were formed under conditions of periodic secular fluctuations in sea level at the end of the Late Pleistocene and Holocene. They obtained new data by studying the chemical composition of the sediments of the first terrace of the delta, the underlying sediments; from the waters of thermokarst lakes formed on the remnants of Edoma. A well with a depth of 65 m was drilled in the sediments of Samoilovsky Island in April 2018. The upper 24 meters of the core consist of interlaying sandy loams, sands and vegetable detritus. The layering is horizontal, sometimes like a Christmas tree. Similar deposits are uncovered by the river in the surface part of Samoilovsky Island and are called puff pastry by the authors. Below, the amount of organic material decreases, it lies in the form of lenses of plant detritus, gravel and pebbles of wood. The first pebbles were found at a depth of 26-27 m, where they are represented by sedimentary rocks. From a depth of 41-42 meters, well-rounded pebbles consist of igneous rocks (dolerite) and its amount increases towards the bottom of the well. The nature of the penetrations indicates that the pebbles are layered with sand and sandy loam. Small boulders have also been drilled. The last noticeable lens of plant detritus was raised from a depth of 49.5 m. A gravel grain of carnelian agate was taken from a depth of 57.5 m. In the lower part, among the prevailing horizontal stratification of sediments, there are often inclined layers, most likely obliquely layered bundles. Sand samples for determining the age of IR-SL methods were taken from depths of 36.6-36.8 and 64.85-65.0 m. The age of the deposits uncovered by the well is Holocene in other sections and wells, at least up to a depth of 30-31 m, where stratigraphic disagreement is observed. The analysis of trace elements was carried out using quantitative X-ray fluorescence analysis. Increased concentrations of sulfur, bromine, chlorine and minimal strontium-to-aluminum ratios in sediments at depths 2-5, 23-24, and 49-50 m indicate that during the formation of these sediments, the influence of marine waters extended at least to the top of the Lena River delta. According to the authors, the mechanisms of sedimentation during the formation of edoma at the end of the Late Pleistocene and during sedimentation in the Holocene in the Lena River delta are of the same type. In both cases, thick layers of organomineral sediments were formed with intense fluctuations in sea level. Edoma deposits differ from Holocene ones only by a large amount of underground ice formed in harsh climatic conditions. In both cases, the accumulation of organo-mineral mass occurred in estuarine bays closed from the sea, but with the direct influence of both sea support and periodic penetration of seawater into the estuary area of the river for tens^[1] hundreds of kilometers from the modern edge of the delta.^[53]

G. Schwamborn and co-authors^[54] investigated late Quaternary sedimentation in the Beenchim-Salatinsky crater located west of the Olenek River in northern Yakutia. A number of Holocene and 4 Late Pleistocene dates were obtained in pits and wells of shallow drilling (up to 1.85 m): 46.5, 43.1, 31.3 and 28.2 thousand years in total organic matter and coal. Relict re-vein ice has been uncovered in one of the wells located near the shore. The values of ?18 ^O in it range from -26.7 to -26.2, the value of ?2 H varies from -203.5 to -200.3, and the values of d _exc from 9 to 11.^[54]

      N.V. Torgovkin and co-authors^[55] examined the isotopic composition of the underground ice of the Momo-Selennyakh depression and the Aby lowland in 5 outcrops of edoma uncovered in the valley of the Indigirka River in a section extending about 1000 km from the village. Ust-Nera to the village of Belaya Gora. Here p. The Indigirka crosses the Chersky Ridge, the Momo-Selennyakh depression, the Momsky Ridge and enters the Aby lowland. The first outcrop is located on the left bank of the Indigirka River, above the mouth of the Tirekhtyakh River, in the southern part of the Momo-Selennyakh depression. The outcrop is a washout of a basement terrace up to 41 m high and 2.5 km long, at the base of which sloping siltstones and sandstones are exposed. Above, up to about a height of 34 m, they are overlain by alluvial deposits, represented by pebbles with sand and gravel aggregate, above there are deposits of an ice complex with a capacity of 5-6 m, represented by sandy loams and loams, in the lower with inclusions of crushed stone, pebbles and gravel. Syngenetic re-vein ice with a visible thickness of up to 6-7 m and a width of up to 3 m. The second outcrop is located on the left bank of the Indigirka River, on the northern edge of the Momo-Selennyakh depression. The apparent thickness of the ice complex is 10-12 m, the width of the veins reaches 3 m. In the marginal part of the thermocircle, thermoerosive cave ice with a thickness of about 1 m was found. Syngenetic PLL vertically striped, enclosing deposits are represented by bluish-gray loams with detached inclusions and plant detritus. The third outcrop is located on the right bank of the Indigirka River near the village. The Cross is a Major. The ice complex is opened in thermocells, its apparent thickness is 1-1.5 m, the host deposits are represented by gray loam with inclusions of wood residues. Edomous re-vein ices penetrate with their lower ends into the underlying lake sediments, represented by glued loams with inclusions of woody residues covered with vivianite. The width of the re-vein ice is up to 1 m. The fourth outcrop is a small thermal tank with a rear wall height of 6-7 m on the right bank of the Selennyakh River. The re-vein ice has a visible vertical length of 5-6 m, the host soils are represented by brown-gray loam.^[55] The fifth outcrop is in the Malykhchyn tract, located on the right bank of the Indigirka River, 45 km below the village of Belaya Gora. The length of the outcrop is about 2 km, the height is 35 m relative to the level of the Indigirka River, it has a two-tiered structure. The lower level from the edge to 13 m is composed of brown-gray loams with syngenetic re-vein ice with a width of more than 3 m. Epigenetic re-vein ice, ice-ground veins with a wavy parallel structure and thermoerosive cave ice embedded in syngenetic re-vein ice were also found here. Late Pleistocene syngenetic re–vein ices have a very light isotopic composition: the values of ?18 ^O vary from -37.6 to -30.1, and the values of ?2 H vary from -293.9 to -231.4. The values of d _exc range from -10.9...9.9%. The ice of the first outcrop located above the mouth of the Tirekhtyakh River, in the southern part of the Momo–Selennyakh depression, has the lightest isotopic composition.^[55] In the joint ?2 H-?18 ^O diagram, the second part of the studied vein samples is located below the GLMV line, which indicates the predominance of the evaporation process. In Holocene re–vein ice, the values of ?18 ^O vary from -31.5 to -25.5, and the values of ?2 H vary from -245.4 to -195.7. The values for d _exc are 6.3...10.9. For most of the Holocene re–vein ices, the values of d _exc are in the region of 8%, which indicates their relatively equilibrium conditions of vein formation. Ice–ground veins also have a very light isotopic composition: the values of ?18 ^O are on average -35.7 ± 0.8%, the values of ?2 H are -273.5 ± 10.4%, d _exc is 12.3±6.3%.^[55]

                 I.A. Platonov and co-authors ^[56] described the structure and conditions of the edoma occurrence in the valley of the middle course of the Indigirka River. The southernmost outcrop of Edoma studied by the authors is located in the Momo-Selennyakh depression above the village of Sobolokh on the northern slopes of the Chemalginsky ridge at latitude 66°05’ on the left bank of the Indigirka River before the confluence of the Tirekhtyakh River. The surface height here is 41 m above the water level in the river, the thickness of the edom is only 5-6 m. Edoma deposits are represented by sandy loams, brown and brownish-gray, with inclusions of weakly and medium-rolled detrital material up to 5 cm in size, rarely up to 10 cm. The width of the ice veins is about 3 m, the size of the polygons is about 10 m. It is underlain by a thick layer of gray gravel-pebble deposits with a sandy filler. The next outcrop of Edoma was studied on the left bank of the Indigirka River above the village. Kubergan. An upstream thermocircle with a width of 95 m was examined, in which the apparent thickness of the edom was 11.7 m. Edoma is underlain by alluvial gravel-pebble deposits lying on bedrock. The sediments of edoma are represented by a dark greenish-gray loam. Ice veins are up to 3 m wide, sometimes more, and the distance between them is about 12-13 m. The northernmost outcrop of Edoma studied by the authors is located 45 km downstream from the village of Belaya Gora and is located within the limits of the Malykhchyn outcrop. The incision was opened only in the lower part to a height of about 14 m and in the upper part, near the watershed surface. The sediments are represented by sandy loam grayish-brown. The ice content of edoma in the upper part of the outcrop is higher than in the lower part.^[56]

      A.V.Bartova^[57] explored edoma in three areas of the Kolyma lowland – on the coast of the East Siberian Sea and on the Maly and Bolshoy Anyui rivers. On the coast of the East Siberian Sea, the main emphasis was placed on studying the sediments underlying the edom. Near the coast in the eastern part of the site, on the Nekkeivey River, edoma overlaps the Neogene weathering crust – bluish-green clays with rounded "constrictions" compacting towards the center (to the rubble of greenish-gray sandstones, the destruction of which probably formed this weathering crust). In the cliffs on the shore of the East Siberian Sea, gravel and pebbles, considered alluvium of different ages - from Q _I to Q _III, lie under the loams of the edom strata; their alluvial genesis was accepted "... due to the absence of finds of marine fauna ...". According to the observations of A.V. Bartova^[57], the gravel-pebble layer is much more widespread along the coast, it was observed in routes almost throughout their entire length. These deposits are represented by horizontally and obliquely layered gravel and pebbles, of good and medium thickness, with interlayers and lenses of sand, with inclusions of tree trunks up to 10 cm in diameter. Thickness of the thickness is more than 12 m. By the nature of the stratification, these deposits can be attributed to both alluvial and coastal-marine. Edoma in sections on the coast is dense, frozen, brownish-gray sandy loams and loams, with unclear or thin lenticular layering, with lenses and interlayers of peat, dusty sands, an abundance of vegetable detritus, grains of vivianite and bright blue mineralization in contact with organic residues. In one of the sections, an accumulation of horizontally lying woody remains was found – trunks and branches, including white birch. On p . A layer of sandy gravel beds with a thickness of up to 0.25 m and lenses of fine sand were observed in sandy loams and loams. The finds of a mammoth vertebra, jaw and tusks with bright blue mineralization (vivianite) on the surfaces are confined to the gravel layer. Ice veins were often observed at the tops of coastal cliffs in sandy loams and loams; at the contact of sandy loams and loams and ice wedges, "tightening" of sandy loams and loams upward. In the outcrops in the lower reaches of the Kolyma, on the Maly and Bolshoy Anyui rivers, the lower parts of both new and well-known supporting outcrops of the Edom strata (Molotkovsky stone, Krasoe, Stanchikovsky Yar) were studied mainly. A similar structure was observed in all sections: two levels of sandy loam and loam and a peat horizon separating them. The upper sandy loams and loams are torn off, their horizontal layering is emphasized by interlayers and lenses of peat with a thickness from the first millimeters to the first centimeters, with inclusions of plant (woody) residues. Thickness of the thickness is more than 10 m. The peat horizon is represented by layered peat with remnants of herbaceous and woody vegetation. In some sections along the strike, the peat layer is replaced by detached sandy loams and loams or by layering siltstones and peat, with a concentration of woody vegetation residues at this level. The thickness is up to 2 m. The lower sandy loams and loams are gray, bluish on a fresh cut, with a thin (first millimeters) lenticular layering due to the alternation of lighter and darker layers (lighter correspond to larger, sometimes sandy loams and loams, darker to smaller ones), with inclusions of peat lenses, with scattered the layer contains plant residues (mainly stems of herbaceous plants), with bright blue grains of vivianite and the same mineralization in contact with organic inclusions. The thickness of the layer is more than 20 m. This stratum is attributed to alluvial or lacustrine-alluvial deposits of the Middle Pleistocene. The finds of freshwater mollusks are confined to the peat horizon and the upper part of the lower loams. The size of the shells is from 1 to 5 mm, rarely larger. In the scree at the water's edge, the bones of terrestrial vertebrates are often found. In all the observed sections, re-vein ice is exposed, in most cases they are confined to the "upper" sandy loams and loams. The apparent "height" of the re-core ice is 4.5-5 m. At the contact of sandy loams and loams and ice wedges, there is often a "tightening" of sandy loams and loams upwards. On the Maly Anyui River, pseudomorphoses were observed in the "lower" sandy loams and loams over re-vein ice. Based on the observations made (granulometric composition, layering, finds of vegetation and fauna, grains of vivianite, the presence of lenses and peat interlayers), A.V. Bartova^[57] made preliminary conclusions: - the lower sandy loams and loams of the supporting sections were formed in conditions of a calm freshwater shallow basin (lake-alluvial), the upper ones – even shallower, swampy (closer to lake-marsh); - sandy loams and loams described in sections on the coast of the East Siberian Sea are similar to the lower loamy strata, but their structure is larger the participation of the alluvial factor (the presence of interlayers of sandy gravel beds with a large amount of crushed stone and poorly rounded pebbles); - during the accumulation of "upper" sandy loams and loams separating sandy loams and loams of the peat horizon and sandy loams and loams of the coast of the East Siberian Sea, woody vegetation grew, including white birch;A.V. Bartova^[57] expresses doubt whether it is worth using the general name "edom strata" or showing these deposits, where possible, separately as lake-marsh and lake-alluvial.

The lower reaches of the Kolyma

The lower course of the Kolyma River is one of the key areas for the study of Edoma. Radiocarbon and isotope studies of the Kolyma edom strata, which had been carried out for 30-40 years during this period, received a new impetus, mainly due to more detailed isotope work and the use of dating using AMS. Some progress has also been made in developing a strategy for selecting the most reliable dates for radiocarbon dating of syncryogenic strata^[58,59,60], mainly the marine or fluvial nature of most of the syncryogenic strata (marine, alluvial, lacustrine), very good preservation of organic material in permafrost sediments, repeated reburial of organic remains from older strata to younger ones are taken into account. The modern redeposition of organic material under conditions of subaqueous syncreogenic sedimentation, as well as the possible redeposition of organic material under conditions of subaerial-subaqueous syncreogenic sedimentation, is considered. Based on the conducted revision of the dating by Yu.K. Vasilchuk and A.K. Vasilchuk^[58,59,60], a number of new provisions have been formulated that can be used to develop a strategy for adequate radiocarbon dating of syncreogenic strata:

• The redeposition of organic matter in the cryolithozone is a common phenomenon; in syncreogenic deposits, allochthonous organic material is much more common than autochthonous;
• Obviously older samples should be carefully rejected (and among them, first of all, those with exorbitant dates, which are usually redeposited in polygonal vein complexes).
• The closest to the true time of sedimentation and syncreogenic freezing will always be the youngest dating from the entire series of dates obtained from one horizon or another.
• Syngenetic re-vein ice is the best medium for the accumulation of synchronous ice formation of microparticles of organic matter, and, practically, an ideal medium for long-term conservation of organic material. This provides an opportunity for adequate radiocarbon dating of veins.
• Based on the revision of two edom arrays containing about 100 ^14s of dates, it is shown that the formation of the uncovered part of the re-vein complex of the Duvan Yar began about 35-37 thousand years ago and ended about 13-10 thousand years ago, and the formation of the edom strata of the Mammoth Hyota began about 55 (or later) thousand years ago and ended about 10.8 thousands of years ago.
•  The youngest ¹⁴ From the dating in the edomian strata naturally increase in depth, which serves as proof that they more adequately date syncreogenic edomian strata.
•  When dating syncreogenic strata using AMS, it is necessary to select synchronous material for age definitions very precisely. Samples with a carbon mass of less than 0.05 mg may give an inaccurate dating result.^[58-60]

 D.V.Mikhalev and V.I.Nikolaev and colleagues ^[61,62] published two papers on the reconstruction of conditions for the formation of underground ice, mainly native, of the Kolyma Lowland in the Late Pleistocene based on the results of isotope studies. Isotopic studies of permafrost rocks on the supporting sections of the Kolyma lowland (Duvanny and Plakhinsky Yar in the valley of the Kolyma River, Krasivoe, Molotkovsky Stone and Stanchikovsky Yar in the lower reaches of the Maly Anyui River) were carried out, which made it possible to perform their climatostratigraphic dismemberment. It is shown that the simultaneous use of isotopic methods (?18 ^O and ?2 H) is useful in studying the genesis of different types of underground ice. The studied PPLS were formed from water of atmospheric genesis. Texture-forming ice with a massive cryotexture, apparently, is a product of frosty desiccation of the soil (isotopic fractionation in a "closed system"). In the formation of texture-forming ices of all types in cold epochs, the role of mass transfer processes (freezing?) It increased sharply compared to the warm periods of the Pleistocene. Isotopic data allowed us to estimate the range of variations in average January temperatures in the study area in the Late Pleistocene – Holocene from -32, -34 °C to -46,-48 °C.^[61] Later, the authors clarified that the range of variations in the average January temperature in the Late Pleistocene–Holocene ranged from -30...-48 °C in the Lower Kolyma and up to -32...-45 °C in the valley of the Maly Anyui River.^[62]

V.I. Solomatin in the textbook^[63] summarized the isotope data obtained by him together with D.V.Mikhalev and M.A. Konyakhin. In Chapter 10, written jointly with M.A.Konyakhin, V.I. Solomatin considered various features of the isotope-oxygen composition of re-vein ice. They considered the isotope-oxygen composition of modern vein ice of alluvial, lake-marsh and coastal-marine sediments. V.I.Solomatin and M.A.Konyakhin ^[63] considered the processes of fractionation of oxygen isotopes during freezing of water in a frost-breaking crack, changes in the primary isotopic composition of vein ice under the influence of the processes of diffusion, sublimation and condensation of ice and the preservation of isotopic-oxygen information in ancient vein ice. For the isotopic study of edom strata, the sections written by V.I.Solomatin and M.A.Konyakhin^[63] on dating and reconstruction of winter paleotemperatures of air from the isotopy of ancient ice veins and re-vein ice of the reference sections of the Kolyma lowland are important. 

V.I.Solomatin and M.A.Konyakhin examined^[63] whether thawed snow water is sufficient to completely fill frost-breaking cracks. They compared the physical volume of frost-breaking cracks with the volume of water accumulated in the snow in their "catchment area". The coastal lowlands of Yakutia are characterized by the formation of frost-breaking cracks with a depth of 3-5 m with a maximum width on the sole of the STS (during the period of filling cracks with water) up to 1 cm. For convenience, it is assumed that the crack has a rectangular shape in the cross section and its width at the base is the same as on the sole of the STS. Then a frost-breaking crack with a length of 10 m, a depth of 5 m and a width of 1 cm will have a volume of no more than 0.5 ^m3 (most likely, it will be 30-50% smaller, since the real crack is wedged down). The thickness of the snow cover in the coastal lowlands of Yakutia reaches 30-35 cm by the end of the winter period. The average density of snow on the high floodplain of the Kolyma in the area of the village. Nizhnekolymsk at the end of January 1980 was 0.19 g/^cm3. If we use these data and assume that the height of the snow cover on the coastal shoal, low and mature floodplain at the end of the winter period is at least 30 cm, it turns out that 0.06 ^m3 of water is accumulated on an area of 1 ^m2. It follows from this that in order to fill a frost-breaking crack with a length of 10 m, a depth of 5 m and a width of 1 cm, the catchment area should be less than 9 ^m2. This corresponds to a 0.45 m wide strip of soil on both sides of the crack. It is obvious that in real conditions the catchment area of frost–breaking cracks is much larger (since the development of polygonal roller microrelief is not typical for low levels), and therefore the volume of melted snow water significantly exceeds the volume of frost-breaking cracks.^[63] The values of the isotopic composition of modern PLL mature and high floodplains of the Kolyma, as well as modern vein sprouts on the edom, which indicates the significant role of thawed snow water in their formation. The isotopic composition of floodplain sprouts is somewhat heavier than the composition of edoma sprouts and in its values approaches the isotopic composition of the high-water water of the Kolyma River, which may indicate the participation of the latter in its formation. However, there is no contradiction here, since flood waters consist of 90% of snowmelt water and only 10% of river water. Consequently, even that part of the frost-breaking cracks that is filled with high-water river water is essentially filled with melted snow water.^[63]

Yu. K. and A. K. Vasilchuk published a series of articles devoted to a detailed examination of the age and isotopic composition of edom sections in the lower reaches of the Kolyma: Plakhinsky Yar^[64], Bison^[65], Cape Verde^[66], and their correlation ^[67].

According to the results of studying the isotopic composition of the edoma of the Plakhinsky Yar in the outcrop of the Karetovskaya edoma, located near the winter quarters of the Plakhino on the shore of the Stadukhinskaya channel of the Kolyma River, winter paleotemperatures of the air in the lower reaches of the Kolyma were reconstructed 30-12 thousand years ago.^[64] It is shown that Late Pleistocene two-tiered narrow re-vein ices with polygon sizes no more than 3-5 m are developed in the outcrop of the Plakhinsky Yar. The beginning of the accumulation of edomous strata dates back to 32 thousand cal. years ago, the beginning of the formation of the uncovered lower part of the veins was a period of 30-25 thousand cal. years ago, and the completion of the accumulation of edomous strata is dated no later than 12 thousand cal. years ago. Significantly negative isotopic compositionPPL in the supporting sections of the edom strata of the lower reaches of the river. Kolyma makes it possible to attribute the entire period from 30 to 12 thousand years ago to a single Late Pleistocene cryochron. Data on the isotopic composition of veins in the supporting sections of the edom strata of the Plakhinsky Yar, the Golden Cape, the Duvan Yar, the Beautiful, and the Barchik allow us to conclude that winters were significantly more severe than modern winters that prevailed here at the end of the Late Pleistocene cryochron. The lowest average January air temperature (14-17 °C lower than the modern one) in the lower reaches of the Kolyma was obtained by the authors for the period from 30 to 28 thousand cal. years ago, which corresponds to a sharp decrease in temperature in the global mass – the third Heinrich event.^[64] 

      A.K.Vasilchuk and co-authors^[65] presented the results of a combined ¹⁴ C analysis of pollen and microinclusions of organic matter for dating the ice veins of Edoma Bison, located slightly downstream of the Blown Ridge, and came to a number of important conclusions:

a. The application of the AMS ^14C method to the dating of pollen concentrate and spores makes it possible to assess the degree of autochthonous pollen spectrum and ensures its binding to the absolute time scale;

b. Dated palinospectrums, in addition to a good chronological reference, have reliable information about paleolandscapes;
B. Signs of different age of the components of the palynospectrum of re-vein ice are the presence of pre-Pleistocene palynomorphs, different degrees of preservation of pollen grains and spores;
d. A high content of coal particles may affect the result of AMS ¹⁴ From the dating of pollen concentrate and spores if the coal particles differ in age from pollen and spores;
D. AMS ¹⁴ C dating confirmed the vertical stratification of ice in veins, so their syngenetic accumulation is proved, 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;
e. Horizontal dating of re-vein ice proved for the first time that it does not accumulate strictly in any one direction;
g. The ice, which was continuously formed from 32 to 26 thousand years ago, has been studied in detail. Judging by the dates obtained, the re-vein ice accumulated almost continuously at this time.^[65]

      Reconstruction of the average January paleotemperature of 48-15 thousand cal. A few years ago, according to the isotope-oxygen composition of the edoma of Cape Verde, located on the right bank of the Kolyma River, Yu.K. was performed.Vasilchuk and A.K. Vasilchuk^[66] on the basis of repeated detailed study of the isotope-oxygen composition of the PL and generalization of all radiocarbon data on the section. The cyclical structure of the Cape Verde edoma strata and the cyclic change in the conditions of the formation of PPL were confirmed, subaqual and subaerial stages of accumulation of edom deposits and PPL were identified. It is shown that late Pleistocene three- and two-tiered wide re-vein ice and buried narrow ice veins are developed in the edomous thickness of Cape Verde in the lower reaches, fixing individual stages of the formation of the edom complex. The calendar age of the Cape Verde edoma has been established: the beginning of the accumulation of the edoma strata dates back to 48 thousand cal. years ago, the completion was 15 thousand cal. years ago. In the section of the Green Cape, three cycles in the dynamics of the isotopic composition of re-vein ice are identified, dated: 46-41, 37-32 and approximately 24-22 thousand cal. years ago. The data of comparison with the isotopic composition of veins in the supporting sections of the edom strata of the Plakhinsky Yar, Duvan Yar, Stanchikov Yar, Chersky and others allow us to conclude that winters were significantly more severe than modern winters that prevailed in the lower reaches of the Kolyma at the end of the Late Pleistocene cryochron. The lowest average January air temperature (15 °C below the modern one) in the lower reaches of the Kolyma was obtained by the authors for the period from 37 to 25 thousand cal. years ago, which corresponds to a decrease in temperature on a global scale.^[66]

The fundamental work of an international team of authors, led by J.Merton's monograph article was published in the journal Permafrost and Periglacial Processes in 2015.^[67] J. Merton and co-authors^[67] obtained about 50 new radiocarbon dates in addition to almost 100 previously published dates^[58,60,68]

It is noted that the composition of the organic fraction in the sediments of the Duvan Yar is dominated by semi-decomposed small plant material with small particles of roots. Larger tree roots and fragments of wood are rare. Two organic layers with a thickness of 0.15–0.20 m, at an altitude of 11.7 and 30.2 m above the river level, were noted. Syngenetic ice veins with a total height of at least 34 m and more, a width of several meters penetrate into the edoma and contain a small amount of scattered sandy loams and loams.^[67] The age model of edoma deposition in DuvannoeYare is based on 47 definitions of ¹⁴ C from the consolidated section and supplemented by three OSL dates for quartz grains. The age range for the Edoma deposit is based on dates from 19,000 ± 300 cal years at a depth of 36.7 m to about 50,000 cal years at an altitude of 4.3 m above river level. The article considers alternative mechanisms of sediment formation: Aeolian genesis and polygenetic lacustrine-alluvial and slope genesis.^[67]

A detailed examination of the Edom strata in the lower reaches of the Kolyma resulted in isotopic and paleotemperature correlations of Late Pleistocene reference sections of the Kolyma lowland^[69]. For a period of 47-42 thousand cal.  years ago, the lowest temperature in January was recorded for the area of Duvan Yar -48 °C. As follows from the results of the testing of PPL in the Cape Verde edom in this section of the Kolyma Valley, the average January temperature did not rise above -45 ° C. Later in the range of 37-32 thousand cal. years ago, in the Cape Verde area, the average January temperature dropped to -49 °C. In the range of 30-25 thousand cal. thousand years ago, the average January temperature in the area of Cape Verde was -45 °C, and in the area of Plakhinsky Yar it decreased to -51 °C. In the period of 24-22 thousand cal.  years ago, the average January temperature in the Kolyma valley did not change compared to the previous interval: in the area of Cape Verde -45 °C and in the area of Duvan Yar -48 °C. 20-18 thousand cal. years ago, in the Kolyma valley, the lowest average January temperatures were noted for the area of Plakhinsky Yar -48 ° C, in the area of Duvan Yar slightly above -46 ° C, and in the area of Cape Verde -47 ° C, i.e. these are not the lowest temperatures. In the period of 16-12 thousand cal. years ago, the average January temperature in the Kolyma Valley remained low in the Cape Verde region (-45°C) and in the area of Duvan Yar and Plakhinsky Yar (-46 ° C). Isotopic data show that the average Barbarian temperatures in the coldest epochs were 12-15°C lower than modern ones and ranged from -48 to -51°C, and in more moderate periods from -40 to -45°C.^[69]

        Yu.K.Vasilchuk and co-authors^[70] studied the distribution of stable oxygen and hydrogen isotopes in a well-known section of the edom deposits of the Stanchikov Yar on the Maly Anyui River. The results of the observation of the cyclicity of the edoma of the Stanchikov Yar by other authors are presented: G.S.Konstantinova, T.P. Kuznetsova, T.N.Kaplina and O.V. Lakhtina, D.V. Mikhalev, S.V. Gubin and O.G. Zanina. Most authors describe from 3 to 4 cryocyclites in the Stanchikov Yar section, with which several tiers of buried veins and several horizons of buried soils and peat bogs are associated. Yu.K.Vasilchuk and co-authors ^[70] recorded at least three tiers of cryocyclites represented by veins composed of gray (less often yellowish-gray) vertically layered ice. In the ice vein of the lower tier, the values of ?18 ^O along the horizontal axis vary in the range of about 1.7% – from -31.06 to -32.74 %. The highest values of ?18 ^O (from -31.06 to -31.62%) were obtained in the marginal parts of the vein, the lowest (from -32.11 to -32.74 %) – in the central part of the vein. In the ice vein of the middle tier, the highest values of ?18 ^O were also obtained in the marginal parts of the vein (-31.62 and -31.76 %), in the central part of the vein and along the vertical axis, the values of ?18 ^O varied between -32 and -33 %. The obtained values of the isotope-oxygen composition of the vein ice correlate with the data of D.V.Mikhalev and V.I.Nikolaev with co-authors ^[61,62] on ice veins of the lower fragment of the Stanchikov Yar outcrop, according to which they obtained the lowest values of ?18 ^O from -30.1 to -32.1. Taking into account radiocarbon dating of the lower horizon of buried soils, obtained by S.V.Gubin and O.G.Zanina, it can be assumed that the age of the ice veins of the lower tier studied by us is more than 30-34 thousand years, and the middle tier is close to 25-29 thousand years. For quantitative paleotemperature estimation of isotopic variations, the ratio obtained by Yu.K. Vasilchuk was used.^[7] In the period from about 25 to 40 thousand years ago, judging by the consistently low values of the isotope-oxygen composition, geocryological conditions were quite harsh, the average winter air temperatures were -31, -33 °C, and the average January temperatures could reach -46, -47 °C.^[70]

        Y.K.Vasilchuk and N.A. Budantseva^[71] studied the distribution of stable oxygen and hydrogen isotopes in a new section of edom and sediments located on the outskirts of the village of Chersky (68.7511° S., 161.3331° V.D.). On the outskirts of the village. Chersky, 300 m below the pier on the right bank of the Kolyma River, an edom tab embedded in pre-Pleistocene rocks has been uncovered. The sediments are represented by a heavy dark gray sandy loam with a low organic content. The height of the outcrop is 20-25 m. Ice veins have been opened at a depth of 1-1.5 m. They are relatively narrow, with a width of no more than 1 m in the frontal section. The values of ?18 ^O in the ice of the Late Pleistocene ice vein turned out to be quite low and ranged from -31.45 to -32.26, while a noticeable decrease in the values of ?18 ^O from bottom to top in the tested vein fragment. Applying the dependencies from ^[7], it can be concluded that in the area of the village At the end of the Pleistocene, the average winter air temperature varied in the range from -31.5 to -32.5 °C, the average air temperature of the coldest winter month (January or February) varied from -47 to -49 °C.^[71]

      V.N. Konishchev^[72] considered the possibilities of studying the genesis of loess edom strata using mineralogical analysis. Earlier, he proposed additional lithological criteria (the coefficient of cryogenic contrast and the coefficient of heavy fraction), which make it possible to distinguish the genetic nature of the granulometric composition of loess deposits, i.e. to find out what products they are — cryogenic weathering or Aeolian sedimentation. The wide application of these criteria to the study of the genetic nature of loess-like non-carbonate rocks of the modern cryolithozone (cover loams of the north of the European part of Russia, Western Siberia, edom strata of Eastern Siberia), where signs of Pleistocene periglacial zones have been preserved almost completely, allowed V.N. Konishchev^[72] to talk about the cryogenic nature of the mineral matter of these deposits. Earlier, V.N. Konishchev ^[72] experimentally showed that under the influence of repeated cyclic freezing-thawing in various rocks — both monolithic (granites, sandstones, etc.) and dispersed (sands, sandy loams, loams) — particles of the loess fraction accumulate due to the destruction of larger ones (quartz, feldspar, etc.) particles and aggregations of clay-sized particles. These conclusions were confirmed by the experimental results presented in the works of A.V. Minervin. He also studied the cryogenic stability of monomineral and monofractive samples, but the number of freeze-thaw cycles was 1000 and the experiment lasted more than 3 years. But the result was the same, but expressed more clearly: quartz is crushed to smaller particles (up to 0.05–0.01 mm) than feldspar (microcline) (up to 0.1–0.5 mm).^[72]

        In D.G. Shmelev's dissertation^[73], carried out under the supervision of V.V.Rogov, two mechanisms of cryogenic destruction of mineral matter were identified. In the sediments of the active layer of the Antarctic oases, weathering is associated with temperature gradient stresses in rock fragments, which leads to the appearance of direct cracks and the accumulation of sharp-angled particles with coarse chips. In the north-east of Yakutia, weathering is realized due to the cryohydration mechanism of destruction of particles by ice in cracks and cavities of gas-liquid inclusions, which leads to the accumulation of predominantly destroyed cryogenic aggregates and particles with cavities. D.G. Shmelev ^[73] believes that the most favorable conditions for cryogenesis processes developed at the boundary of the Late Pleistocene and Holocene, what follows from his cryolithological analysis of the edom deposits of Mammoth Hyota on the Bykovsky Peninsula, Cape Chukochy and Duvan Yar on the Kolyma lowland. He showed the cyclicity of cryogenic processing of mineral matter from quaternary deposits in the north-east of Yakutia. It manifests itself in the fact that during the formation of rocks, periods of different cryogenesis intensity alternate, due to changes in the conditions of accumulation and freezing of rocks of different scales, such as climate and sea level changes, descent and filling of thermokarst and dammed lakes, interannual variations in the depth of the seasonal melt layer (STS). D.G. Shmelev ^[73] on the basis of year-round measurements, the features of the temperature and humidity regime of the STS of loose sediments of the north-east of Yakutia and Antarctic oases were revealed and connections between the mechanisms of cryogenic weathering and the parameters of the active layer were established;The cryogenic contrast coefficient was determined for the deposits of the oases of Antarctica and the Kolyma Edoma and morphological differences of clastic particles due to different cryogenic weathering mechanism were revealed. The existing ideas about the development of cryogenesis in the Pleistocene-Holocene time in the north-east of Yakutia have been expanded on the basis of new sections for which the values of the cryogenic contrast coefficient have not been calculated before; the synchronous cyclicity of cryogenic weathering processes has been revealed, which does not depend on the genesis of Pleistocene-Holocene deposits of the Northern and Southern Polar regions.^[73]

The Edom of Central Yakutia

Vilyu River Valley

Y.K. Vasilchuk and colleagues^[74] examined the radiocarbon age and stable isotopes of oxygen and hydrogen in the Late Pleistocene re-vein ice on the Vilyu River. The main task of this work is to establish the time of accumulation of Pleistocene Syngenetic re–vein ice that broke up in the upper part of the Vilyui Edoma outcrop and reconstruct the Middle Janvarian paleotemperature during this period. The age of recycled ice was determined by microinclusions of organic material represented by organic dust - settled soil and biogenic aerosols, organic dust particles from a sample of recycled ice dated using accelerator mass spectrometry (AMS). The studied ice vein is located in the upper part of the section of the edom strata, uncovered in the valley of the Vilyu River, near the village. Kysyl Cheese. Its width in the upper part exceeds 1.5 m, a fragment about 2 m high has been uncovered. To assess the degree of reliability of radiocarbon dating and determination of the composition of the “pollen rain”, A.K. Vasilchuk conducted a study of pollen, spores and other organic inclusions in a dated ice sample, as well as in samples containing a sufficient number of organic inclusions. The isotopic composition of ice (oxygen and hydrogen) has been determined for the reconstruction of the Middle January paleotemperature. The radiocarbon age of the ice vein fragment tested in detail for isotope analysis was determined using AMS dating of microinclusions of organic material in a sample from a depth of 2.88 m 18,460 ± 50 years (IGAN _AMS - 9564), or 22,380 cal. years. In the spore-pollen spectra of 5 samples of the Virian re-vein ice, the presence of Betula sect pollen was mainly recorded. Apterocaryon and Alnus alnobetula, a single three-pronged underdeveloped pollen attributed to Varia, as well as pollen from Artemisia and Chenopodiaceae, was noted. The spore-pollen spectra obtained directly from the re-vein ice reflect the composition of the regional pollen “rain” brought by the wind and, possibly, partially by spring waters. The presence of immature pollen, obviously, indicates that the pollen passed into a permafrost state quite quickly. This most likely indicates a very short growing season, during which the grass pollen practically did not have time to mature, the plants were covered with snow. Among the spores, spores of Selaginella sibirica and sporadically Bryales spores are noted in a small number. All components of the palinospectrums are ecologically compatible, the pre-quaternary palinomorphs are not fixed. In the dated sample, only Betula sect pollen is present in the fraction of the pollen concentrate. Apterocaryon and Alnus alnobetula, no coal particles, no additional Stocene palynomorphs were found. There were no signs of redeposition in the fraction of 56-2 microns. This suggests that the complex of organic compounds consists mainly of organic residues synchronous to the formation of a vein. Consequently, the carbon dating obtained from organic microinclusions of AMS radio is reliable and reflects the accumulation of recycled ice. The palinospectrums obtained in the Vilyui PLL revealed similarities with palinospectrums in the section of the Plakhinsky Yar, dated 14-12 thousand cal.  years and 21-20 thousand calories.  years old ^[74]. Variations of stable isotopes of oxygen and deuterium in the re-vein ices of the Vilyui edoma are insignificant: the value of ?18 ^O varies by 1.4% – from -29.4% to -28% (on average -28.9%), and ?2H ^by 14.4% – from -228.4% to -214% (on average -221.4%). The value of d _exc varies by 11.7% – from 5.2 to 16.9% (on average 9.7%). On the Vilyui floodplain, at the mouth of the river.The value of ?18 O ^{in the} temporary growth of the vein is -25.7%. The approximate values of the average January air temperature for the Vilyui Valley calculated according to the Vasilchuk equation^[7] are 22-23 thousand cal. The years per butt varied from -44 to -42°C (±3°C). The same temperature was in other nearby areas during this period, judging by the close average values of the isotopic composition of synchronous fragments of Mammoth Mountain veins in the valley of the Aldan River and the PLL in the valley of the Tumara River.^[74]

In 2021-2022, M.Pavlova and V.Lytkin^[75] conducted studies of various types of underground ice in six key areas within the Central Yakut plain - the valley of the Vilyu River in the lower reaches, the valley of the Buotama River, the vicinity of the village. Upper Bestyakh, the valley of the Linde River and the Western Verkhoyany ? the valley of the Undyulyung and Dyanyshka rivers. In the upper part of the 65-meter basement-accumulative terrace of the Vilyui River in the lower reaches, a loamy-sandy loam sediment layer, including PLL, with a thickness of up to 2-3 m and a penetration depth of up to 6-8 m was uncovered. The age of the deposits belongs to the Sartan period of the Upper Pleistocene (radiocarbon dating is 23630 ± 550 years). The isotopic composition of the PFL on the Vilyui River varies: ? ¹⁸ O from -30.04 to -28.58, ? ² H from -231.86 to -221.83, d _exc from 6.32 to 8.45.^[75]

       Sections of Mammoth Mountain and Syrdakh, in Central Yakutia

The analysis of the methane gas composition, its isotope-carbon composition, the composition of stable isotopes of water and microbiological composition in the edoms of Central Yakutia: the outcrops of Mammoth Mountain and Lake. Syrdakh, and obtained during drilling in the Neger tract.^[76] It was found that the methane carbon composition of the ice complex of Central Yakutia is characterized by a higher content of heavy isotope (values of ?13 C from -49.3 to -64.5 %) than the ice complex of the Northeast (values of ?13 C from -64 to -99%), which is probably due to the mixing of thermogenic methane (possibly from coal seams of Neogene or Cretaceous sediments that migrated through the frozen strata) with biogenic methane, which was produced simultaneously with the formation of sediments. Data on the composition of microbial communities for outcrops of the ice complex of Central Yakutia were obtained and it was shown that on the basis of these data it is possible to identify deposits of different ages and freezing conditions. The similarity of the microbial composition of re-vein ice and host deposits in frozen syngenetic deposits of the ice complex has been established, while significant differences were noted in epigenetic type deposits.^[76]

     Sections of Churapcha, Syrdakh and Chuya

Y.-V. Yang and co-authors ^[77] studied the ratio of a mixture of carbon dioxide (CO ₂), methane (CH ₄) and nitrous oxide (N ₂ O) in three homogeneous re-vein ice near the village. Churapcha, Syrdakh and Chuya, located in the central part of Yakutia. The ratios of the gas mixture in the studied vein ice range from 0.0 to 13.8% _CO2, 1.3–91.2 million^–1 CH ₄ and 0.0–141.4 million^–1 N ₂ O. In particular, all three ice veins demonstrate that ice veins enriched with CH ₄ were depleted by the ratio of the N 2 O mixture, and vice versa, the composition of N ₂-O ₂-Ar indicates that the studied ice veins were most likely formed due to dry snow or frost, and not freezing of thawed snow water, and biological metabolism with active oxygen consumption took place. Most of the observed ratios of the components of the gas mixture cannot be explained without the participation of microbial metabolism. The inhibitory effect of nitrate denitrification products (including N ₂ O) may be an important factor regulating the ratio of the CH 4 mixture between ice veins.^[77] Greenhouse gases trapped in the ice veins of Chuya contain information about the biogeochemistry of ground ice in central Yakutia since the Late Pleistocene cryochron. The ratio N ₂/Ar and bubbles indicate that the vein was formed as a result of "compaction of dry snow". Microbiological respiration could expend O2 _{and contribute to the accumulation of CO 2} (~ 10%). The 13 C isotope content for CO ₂ corresponds to the biological origin (-27.8 %). The concentration of _CH4 was increased to 7-130 ppm compared to atmospheric levels during LGM (~ 0.4 ppm). The concentration of _N2o ice veins was measured, which turned out to be in a wide range from half the atmospheric level for the Ice Age (200 ppb) to significantly higher than the atmospheric concentration level (5000 ppm). The elevated level of _N2o is probably also of biological origin. The negative correlation between _N2O and CH4 can be explained by the inhibitory effect of _N2o on methanogenic bacteria.

H. Park and colleagues^[78] analyzed the gas mixing ratios in air bubbles, in the vein ice of two ice complexes of the Batagai sinkhole, formed in the Middle and Late Pleistocene. Previous studies suggest the age of these deposits as MIS 4-2 and at least MIS 16 for the upper and lower ice complexes, respectively. Concentrations of CO ₂ were 1.9–10.3%, N ₂ O 0.1–8 ppm and CH ₄ 30-170 ppm for the lower ice complex, and for the upper Late Pleistocene ice edom complex: CO ₂ 0.03–8.89%, N ₂ O 0.3–70 ppm and CH ₄ 5-170 ppm. Greenhouse gas mixture ratios above atmospheric levels indicate active microbial activity. This is confirmed by the values of ?(O ₂/Ar), which range from -89.01 to -67.43% and from -98.07 to -47.06% for the lower and upper ice complexes, respectively. Severely underestimated ?(O2/Ar) values may indicate strong oxidation reactions due to microbial activity and/or non-biological oxidation reactions. Although there is no significant correlation between CO ₂ and CH ₄, the abiotic formation of CH ₄ may be insignificant, since it is unlikely that it will occur under conditions of constant freezing. Interestingly, CH ₄ and N ₂ O show a weak negative correlation in both ice complexes, which can be explained by the inhibitory effect of nitrogen compounds on methanogenesis. The values of ?(N ₂/Ar) range from -8.06 to 33.86% for the lower ice complex and from -5.49 to 30.64% for the upper ice complex. Since nitrogen is more soluble in water than argon, this may indicate that re-vein ices could have formed without significant contribution from snowmelt, but mainly as a result of compaction of dry snow, which is also confirmed by the spherical shape of gas bubbles inside the re-vein ices. In addition, the penetration coefficient of argon in ice is higher than that of nitrogen. Thus, the high values of ?(N ₂/Ar) (>10%) are due to the diffusion of argon through ice.^[78]

K.Kim and coauthors^[79] investigated greenhouse gases in ice veins near the village. Chuya (61°44' s.w., 130°25' v.d.), which is located near Yakutsk in Central Yakutia. The ratio N ₂/Ar in air bubbles indicates, according to K.Kim and co-authors^[79] point out that the vein was formed as a result of "compaction of dry snow". Microbiological respiration could expend O2 _{and contribute to the accumulation of CO 2} (~ 10%). The isotope content ^{of 13} C for CO ₂ corresponds to the biological origin (?13 C = -27.8 %). The concentration of CH4 was increased to 7-130 ppm compared to atmospheric levels during LGM (~ 0.4 ppm). The concentration of N2o ice veins was measured, which turned out to be in a wide range from half the atmospheric level for the Late Pleistocene (200 ppb) to significantly higher than the atmospheric concentration level (5000 ppm). The elevated level of _N2o is probably also of biological origin. The negative correlation between _N2O and CH4 can be explained by the inhibitory effect of _N2o on methanogenic bacteria.^[79]

       Korean researchers, in collaboration with Russian geocryologists, assessed the effect of thawing conditions during sample processing on the chemical properties of re-vein ice in Eastern Siberia^[80] and showed (in samples of re-vein ice taken in Chui, Eastern Siberia) that paleoinformation can be inadvertently changed during thawing of vein ice samples. They investigated four different modes of thawing of vein ice with different temperatures (4 and 23 °C) and exposure to oxygen (oxygen and oxygen-free). Samples of ice veins thawing at 4°C in oxygen-free conditions, while biological activity and oxidation were minimized, were selected as standard thawing conditions, with which the effects of temperature and oxygen were compared. The results showed that temperature and oxygen exposure have little effect on the physicochemical characteristics of solid particles. However, the chemical characteristics of the solution (for example, pH, electrical conductivity, alkalinity and concentration of basic cations and trace elements) at 4 °C under oxygen conditions changed significantly compared to those measured under standard oxygen-free thawing conditions. This study showed that the thawing conditions of re-vein ice samples can affect their chemical properties and thus geochemical information for the reconstruction of paleoclimate and/or paleomedium.^[80]

       M. Ulrich and co-authors^[81] investigated the isotopic composition of textural ices of edom deposits within the boundaries of Alas Yukechi in Central Yakutia. In general, the values of ?18 ^O decrease from the bottom (amounting to about -26 % at a depth of 12.5 m below lake level) to -29.5% at a depth of 13.17 m, and then increase to -25.3% at a depth of 19.3 m. The value of ?2 H in this depth range also initially decreases from about -195 to -230%, and then it increases to -184 %. The values of d _exc in the edoma core showed a similar course and lie between 5.1 and 22.6. According to M. Ulrich^[81], the geochemical composition of the atmospheric deposits indicates that during the Late Pleistocene and Holocene thawing associated with the formation of the Alasna basin and lakes, the isotope-geochemical properties of the deposits changed very slightly. This was indirectly confirmed by the discovery, together with researchers from the French University of Aix-Marseille in the core of Alas Yukechi, of the oldest known virus, pandoravirus, the oldest ever revived. It is dated to about 48.5 thousand years.^[82]

J.M. Alempik and co-authors ^[82] presented the characteristics of 13 new viruses isolated from edom deposits and mammoth remains in them of Duvan Yar, Yukechi, Maly Lyakhovsky Island, Paleolithic site on the river. Yane and for comparison, they cited viruses from modern permafrost rocks on the Lena River and from the Kamchatka cryogenic soil. These viruses belong to five different species of soil amoebae of the genusAcanthamoeba spp. Interestingly, the genomes of viruses (Pandoravirus, Cedravirus, Megavirus and Pacmanvirus) previously found in permafrost rocks, in addition to a new strain of pitovirus. It is likely that these unknown viruses may be released during thawing of the food strata. It is still unclear how long these viruses can remain contagious after exposure to external conditions.^[82] A year earlier, S. Rigu and co-authors^[83] noted that giant viruses are widespread in the aquatic environment and have important ecological significance due to reprogramming the metabolism of their hosts. Less is known about giant viruses from soils, although two of them belonging to two different viral families were reactivated from 30,000-year-old permafrost samples. This indicates the unexplored diversity of the eukaryotic virusNucleocytoviricota in this environment. With the help of metagenomics of permafrost, a unique model of diversity and high heterogeneity in the number of giant viruses, amounting to up to 12% of the total coverage of sequences in one sample, was discovered. The Pithoviridae and Orpheoviridae, similar to viruses, have made the most important contributions. A complete 1.6 Mb ring genome, similar to Pithoviridae, was also collected from a 42,000-year-old permafrost sample. Virus sequences from long-term frozen rocks have revealed a huge reservoir of genes with unknown functions. Phylogenetic reconstructions have revealed the possibility of gene transfer not only between cells and viruses, but also between viruses from different families.^[83]

V. V. Spector et al.^[84] investigated the thickness of dispersed permafrost quaternary sediments with a thickness of about 100 m, opened by a well in the central part of the Leno-Amginsky plain. According to lithogenetic and cryolithological features, six bundles were identified in the section: I - seasonal freezing-thawing (int. 0-1.1 m); II - cover loams (1.1-2.65 m); III - ice complex (2.65-26.15 m); IV - lake (26.15-63.45 m); V - lacustrine-alluvial (63.45-78.9 m); VI - alluvial (78.9-94.5 m) deposits. The two upper bundles (I and II) belong to cryogenic eluvium. The pack of the III - ice complex is characterized by low density, high indicators of weight humidity, organic matter content and mineralization, the presence of re-vein ice and a variety of cryotextures. The upper part of pack III (2.65–17.63 m), corresponding to the Sartan horizon, includes three horizons of re-vein ice: PLL 1 (int. 2.65–4.6 m), PLL 2 (5.85–6.72 m) and PLL 3 (11.88–13.95 m). Individual fragments of the PLL were found at depths of 10.77, 15.5 and 17.55 m. The indicators of total mineralization (mg/l) and pH in the PL horizons were, respectively: 51, 7.21 (PL 1, int. 3.3–3.6 m), 127, 7.56 (PL 2, int. 6.25–6.36 m) and 49.3, 7.34 (PL 3, int. 12.87–12.95 m). There is a decrease in the degree of mineralization of ice in comparison with the aqueous extracts of the host sediments and the preservation of the redox potential at the same level. The upper horizon (PLL 1) is characterized by a weakly differentiated isotopic composition with relatively low values of ?18 ^O (from -28.54 to -28.24 %) and ?2 H (from -217.5 to -220.6 %). The revealed features of the isotopic characteristics of the horizon indicate the origin of ice due to snow moisture. The average horizon (PLL 2) is characterized by a higher content and a differentiated distribution of values: ?18 ^O from -24.87 to -25.06 and ?2 H from -188 to -186.2. It is likely that the PLCs of this horizon were formed with the insignificant participation of rain moisture. The lower horizon (PLL 3) is characterized by the lightest and most differentiated composition by section: values ?18 ^O -29.5 to -30.77 and values ?2 H from -243.2 to -199.4. The ice of this horizon was formed from sharply continental moisture and, probably, with some rainwater. The ice of the near-contact zone of the PLL differs from the ice of the middle parts in a higher and differentiated content: the values of ?18 ^O from -30.47 to -24.87 and the value of ?2 H from -224.1 to -187.9. This phenomenon may be associated with the fractionation of pore moisture of rocks adjacent to the vein during its migration to the freezing front of the lateral contact of the ice vein. For the middle parts of the PL, the values of d _exc = 5-10 %, which is close to the values of atmospheric (meteoric) waters. The contact zones are characterized by an increase in _dex to 10-20 %. The isotopic composition data make it possible to estimate using the equations of Yu.K. Vasilchuk^[7] the average January (t _i) and average winter (t _nw) air temperatures during the formation of the PL. The features of the structure and composition of sediments indicate the absence of diagenetic transformations of sediments. The composition of stable isotopes of re-vein ices indicates their origin, mainly due to snow moisture. Packs IV-VI are characterized by undisturbed layering, the absence of ice slots, the ubiquitous presence of a massive cryogenic texture, higher density, low mineralization and organic matter content. The listed features of packs IV-VI indicate deeper transformations of precipitation corresponding to the end of the initial stage of diagenesis. According to the degree of diagenetic transformations of precipitation preceding freezing, pack III is classified as syncreogenic, and packs IV-VI - as epicryogenic deposits. Changes in the regime of accumulation and freezing of precipitation on the Leno-Amga plain are associated with climatic fluctuations and glaciations. The freezing of the main volume of the epicriogenic strata occurred in the Karginian-Sartan period of the Late Pleistocene.^[84]

Chukotka

Yu.K.Vasilchuk and A.K.Vasilchuk (2017-2019) published articles ^[85,86] summarizing the isotope and radiocarbon studies of the supporting cryolithological sections of the island of Ayon and the valley of the Main River. 

Iona Island

      In the work on Ayon Island^[85], the features of the cryolithological structure of the Late Pleistocene and Holocene re-vein ices of Ayon Island are considered: data on the analysis of their isotope-oxygen composition, radiocarbon dating and hydrochemical characteristics are analyzed, compared with data for adjacent areas and changes in paleogeocryological and paleoclimatic conditions in the north of Chukotka in the Late Pleistocene and Holocene are estimated. Based on the data obtained by interpolation, the lower fragment of the section, including the lowest fourth tier of re-vein ice, is assumed to be in the range of 30-26 thousand years ago. In the veins of this tier, the values of ?18 ^O range from -34.0 to -30.3, the average value of ?18 ^O is -31.15. The distribution of ?18 ^{O values} is contrasting, the beginning of accumulation of vein ice of this tier is probably associated with a very cold period, since the lowest content of heavy oxygen isotopes is noted here (?18 ^O=-34%). The section fragment, which includes the most powerful veins of the third tier, was presumably formed 26-20 thousand years ago. The lowest values of ?18 ^O (-33%) are marked at +13 m. The average value of ?18 ^O in the veins of this tier is -31.6%. The time of formation of the second-tier re-vein ice is presumably dated to the period 15-20 thousand years ago. The fluctuations in the isotopic oxygen composition are 3 % (?18 ^O from -32 to -29%). The distribution is contrasting, but in general the content of heavy oxygen isotopes is higher than in the first and second tiers, the average value of ?18 ^O in the veins of this tier is -30.5%. The veins of the upper (first) tier are characterized by a relatively high content of heavy isotopes of oxygen, the average value of ?18 ^O in this fragment is -29.3%.^[85]

       The features of isotopic characteristics and paleotemperature conditions of Aion Island and adjacent areas of Northern Chukotka during the last 45 thousand years include: a). There is an almost complete coincidence of trends in the distribution of isotopic characteristics of the post-Pleistocene re-vein ice on the island. Aion and in the lower reaches of the Kolyma River; b). according to the isotopic characteristics of the re-vein ice, the winter air temperature reached the lowest values 21-18 and 29-28 thousand years ago – there was a sharper shift towards less negative values of winter air temperature during the transition from the Late Pleistocene to the Holocene compared with the Nizhnekolymsky regions, which is associated with the influence of sea level changes and the transition the territories of the island of Ayon from the continental state to the island state.^[85]

Main River Valley

The features of the structure and composition of Late Pleistocene re-vein ice in the Main River valley, near the city of Anadyr and in the adjacent areas of southern Chukotka are considered, their isotopic composition and radiocarbon age are investigated.^[86] Late Pleistocene multilayered re-vein structures and syngenetic ice veins are common in the Main River valley, which have been studied in detail in the outcrops of the Ice Formation and the Ust-Algansky Cliff. The markedly isotope-negative composition of the repeated vein ice in the supporting sections of the Southern Chukotka ice strata made it possible to attribute the entire period from 38 to 12 thousand years ago to a single Late Pleistocene cryochron.^[86] Data on the isotopic composition of veins in the supporting sections of the edom strata in the valley of the Main River, near the city of Anadyr and in other areas of southern Chukotka allowed us to conclude that winters were significantly more severe than modern ones, prevailing here at the end of the Late Pleistocene cryochron.^[86]

The values of ?18 ^O in the powerful syngenetic ice veins of the edom thickness of the Ice Cliff range from -28.6 to -26.2%, whereas in modern and Late Holocene veins they range from -20.4 to -20.0%. The isotopic composition of the ice from the bottom up becomes lighter, while three tiers are distinguished on the isotope diagram. The values of ?18 ^O in textural ices from edom deposits containing veins vary from -23.9 to -19.6%. It is also somewhat lighter than in the textural ice of the Holocene Alas (?18 ^O to -16.2%).

According to Vasilchuk's equations^[7], winter air temperatures of the Late Pleistocene 38-12 thousand years ago were calculated for a number of sections in the south of Chukotka. The lowest temperatures were observed for the periods 24-22 and 20-18 thousand years ago – the January temperature dropped in the Main River valley to -43 and -44 °C at current values of -27 °C, and on the coast nearAnadyr to -32 °C at current values of -21 °C. The lowest average winter air temperature (8-11 °C below the current one) both in the central and coastal regions of Southern Chukotka, it was obtained for the period from 24 to 18 thousand years ago.^[86]

The bottom layer of the Ice Cliff has been repeatedly dated in series ¹⁴ With dates, with almost no inversions.^[86-88] Previously, A.N. Kotov, A.V. Ryabchun and A.V.Lozhkin obtained a range from 42 to 19.5 thousand years. The youngest radiocarbon dating was obtained by S.Kuzmina^[87] at +27.4 m 15810 ± 75 thousand years (OxA-14930). Below, at 26.3, the date 19850 ± 80 thousand years (OxA-15668) ^[87] was obtained, which practically coincides with the dating of 19500 ± 500 thousand years (MAG-815). The calibrated age of the Ice Cliff deposits is from 46667-41351 to 19439-18800 cal. years.^[87] Dating of the edom deposits of the Ice Cliff at different times also demonstrated that, despite the rather monotonous appearance of the edom strata, horizons with a high content of organic matter reflect the stages of stable surface position and formation of soil horizons.^[86] Therefore, it can be assumed that these horizons correspond to the subaerial phase of the formation of the polygonal-vein complex. In total, about 7 groups of radiocarbon dating of organic interlayers corresponding to subaerial phases, which lasted about 1-3 thousand years, can be distinguished.: 18,8-21, 23-24, 25-26, 28-31, 34-35, 40-43, thousand cal. years ago. The intervals between subaerial phases decreased with the accumulation of sediments, which indicates a decrease in the rate of accumulation of sediments of the subaqual phase of the ice complex. Therefore, the massive re-vein ice of the upper tier, accumulated 23-28 thousand years ago, was formed under conditions of slow sedimentation with frequent and average changes in the rhythms of re-vein ice sedimentation. Data on diatoms obtained from edoma by A.A.Svitoch indicate periodic flooding of the previously shallow lake. The re-vein ice of the middle tier, according to the available series of dating, accumulated 30-38 thousand calibers. years ago, under conditions of an average sedimentation rate, with an average and rare change in sedimentation rhythms. According to the data of diatom analysis, during the formation of re-vein ice of the middle tier, conditions for deep and cold-water reservoirs (subaqual phases of the formation of a re-vein complex) occurred at least three times. The re-vein ice of the lower tier was formed earlier than 43 thousand cal. years. According to the data of diatom analysis, diatom species typical of shallow swampy reservoirs predominate here. Thus, the edom of the Ice Cliff is heterocyclitic, in the process of its formation, the sedimentation rate and the frequency of changing sedimentation rhythms changed. The lake pack accumulated almost simultaneously with the edoma in the range of 39-15 thousand years ago. The lower fragment of the lake sands dates approximately from the period 39-34 thousand years ago. The peat sample from the base of the lake pack was dated 34900 ± 500 (MAG-395). A complex of diatoms was found in the lower part of the lake pack, represented by 40% boreal and 30% arctoboreal species. Data on diatoms indicate the accumulation of precipitation in a shallow swampy reservoir. About the dating of the end of the period of accumulation of lake sands, special mention should be made, since at an altitude of 30-35 meters from the edge and, accordingly, at a depth of about 5-7 meters from the roof, in the thickness of the sands along the branches of A.N.Kotov, a radiocarbon date of 14000 ± 200 years (MAG-1026) was obtained. Here, according to the mammoth tusk lying in the thickness, the date 15100 ± 70 years was obtained (GIN-5370).^[86] The detailed radiocarbon dating of the Late Pleistocene deposits of the Ice Cliff^[88] fully confirmed the reliability of the radiocarbon definitions obtained by A. N. Kotov and A.V. Lozhkin, also demonstrating that the age of the Ice Cliff edoma discovered in the 80s of the XX and at the beginning of the XXI century is from 40 to 20 thousand years. It was also investigated^[88] whether this vegetation favored the development of megafauna. Analyzing samples (47-20 thousand years ago) from edom deposits on the Main River, in the south of Chukotka, using plant plastids and 16S of mammalian mitochondrial DNA, E. Willerslev and colleagues^[88] found that the average proportion of various grasses was higher in samples from which herbivorous megafauna DNA was obtained (for example, woolly mammoth, woolly rhinoceros, horse, deer and moose) than in samples that do not have such DNA.

The Ust-Algansky section is located on the left bank of the Main River 6 km below the mouth of the Algan River, i.e. 7 km above the Ice Cliff. The Ust-Algan strata is similar in composition to the lake sediments of the Ice Cliff. It is mainly fine sand, yellowish-gray and gray, horizontally layered. In the depth range of 20-23 m (at an altitude of 37-40 m from the river's edge), 49-53 m (at an altitude of 7-11 m above the river's edge) and 55.3–55.7 m (at an altitude of 4.7–4.3 m above the river's edge)  frequent interlayers of allochthonous peat with a thickness of 0.5 to 2 cm were noted^[86]. The two lower detached layers contain a large number of shrub branches, occasionally tree trunks. In the section, the authors noted seven tiers of narrow re-vein ice, their width rarely exceeds 1 m, height is 7-8 m, the distance between the veins is from 3 to 4 m. Apparently, in the initial period of the formation of the Ust-Algan strata, riverbed processes actively participated in its formation, which led to the accumulation of powerful lenses and interlayers of allochthonous material. Inversions of radiocarbon dates also indicate an allochthonous origin. At a height of 5 m above the edge, according to well-preserved branches and wood, the authors obtained a date of 32,700 ± 1,800 years (GIN–5367), and at a height of 7 m - an older date of 42,400 ± 2,100 years (GIN-5366). Earlier, A.N. Kotov and V.K. Ryabchun obtained the date 43 thousand years ago at the base of the branch section, and above it – more than 57 thousand years ago. The chronological inversion is caused by the introduction of organic matter from older strata eroded upstream of the river. A younger dating can be taken as the lower limit of the accumulation of strata, then, taking into account the high thickness of the strata, it must be recognized that sedimentation occurred very quickly at certain stages here. This view is also confirmed by the data of isotopic oxygen determinations from re-vein ice, which, as well as in the lake strata of the Ice Cliff, lie in tiers. In the veins of the lower tier at an altitude of 4-6 m above the river level, the values of ?18 ^O ranged from -24.9 to -23.4 %, and in the veins of the second tier from below at an altitude of 8-10 m above the river's edge, they vary from -27.8 to -27.1 %, which obviously testifies to the predominant feeding of the veins of the second tier from below with melted snow water Whereas the presence of river or lake (ancient) water is noticeable in the inhabitants of the lower tier. However, the more significant values of ?18 ^O in veins can also be explained by the influence of milder winters 32-30 thousand years ago.^[86,89]

  Yu.K. Vasilchuk and A.K. Vasilchuk considered ^[89] the types of cyclicity of edom strata in the Main River valley:

but. The hierarchy of the main types of cyclicity observed in the studied syncreogenic strata has been clarified;

b. The duration of micro-, meso- and macrocycles in the formation of the edom strata of the Main Valley is established: a cyclitic polygonal-vein complex in the section of the lake thickness of the Ice cliff, a heterocyclitic polygonal-vein complex in the section of the edom thickness of the Ice cliff, a heterocyclitic polygonal-vein complex in the section of the Ust-Algansky cliff;

It is shown that microcycles in the section of a heterocyclite polygonal-vein complex in the bottom layer of an Ice cliff were formed as a result of changes in the depth of the active layer and accumulation of thin sediment over several years. Their vertical scale varies from centimeters to tens of centimeters, and their formation time ranges from one to hundreds of years;

It has been established that mesocycles in the section of the cyclitic polygonal-vein complex in the lake column of the Ice Cliff and in the section of the heterocyclitic polygonal-vein complex of the Ust-Algansky cliff are the result of changes in the level of the Main River, on the flooded floodplain and in the ancient lakes on which these strata were formed. The vertical scale of the isolated mesocycles is several meters, and their formation period ranges from several hundred to several thousand years;

D. 7 mesocryocyclites were isolated in the edom strata of the Ice and Ust-Algan cliffs, which were formed at intervals of about 2-3 thousand years: 15-16, 20-21, 23-25, 27-28, 30-32, 33-34, 38-40 thousands of years ago.^[89]

Edom islands of the Arctic Ocean

              Bolshoy Lyakhovsky Island

Studies by S. Vetterich and co-authors ^[95] have shown that radiocarbon dating of a horse bone (metacarpal, MC III) found in situ under the dated horizon shows an age of about 29.4 thousand years. Both subprofiles are dated from plant remains (from 22.3 to 25.7 thousand years and from 23.9 to 24.4 thousand years) and belong to the Sartan stadium. The total age of the outcrop deposits varies from 22.3 to 25.7 thousand years. A very similar composition was found in two ice veins of the outcrop, the isotopic composition with narrow variations from -38 to -36% for ?18 ^O and from -295 to -280% for ?2 H. The deuterium excess reaches an average of 7.1and 6.7% for the first and second veins, respectively.^[95] According to the conclusion of S. Vetterich and co-authors ^[95], the ice veins of Bolshoy Lyakhovsky Island show extremely cold winter temperatures of Sartan time (average ?18 ^O about -37 and ?2 H about -290%), which strongly contrasts with data from ice veins of the more western regions of the Laptev Sea (?18 ^O between -31 and -26%, ?2 H is the average between -245 and 197%). The spatial distribution of the onset of the glacial maximum is reflected in the data from the ice veins, which differ between the data from the island of Bol. Lyakhovsky and other (more western) regions due to various sources of moisture.

       S. Vetterich and co-authors ^[96] studied an outcrop located on the southern coast of Bolshoy Lyakhovsky Island, west of the mouth of the Zimovye River, with a height of about 25 m, in which edom deposits are exposed from above. The chronology of these deposits is based on 20 radiocarbon dates of organic material (of which 14 are final), in general, a bottom-up decrease in age from about 53 to 29 thousand years was revealed. Isotopic data in a narrow range were obtained from 25 samples of a syngenetic ice vein with a height of 16 m: the values of ?18 ^O vary from -31.9 to -30.3% (on average -31%), the values of ?2 H range from -251 to -238% (on average -243%), indicating relatively stable, cold winter conditions of ice formation He lived. The values of d _exc vary from 3.9 to 7.8 % (on average 5.4 %). The ratio ? ² H–? ¹⁸ O has a slope of 8.9, which is slightly higher than for the Late Pleistocene cryochron. S. Vetterich and co-authors ^[96] indicate that during the Molotkov interstadial, continuous edoma formation took place on Bolshoy Lyakhovsky Island. The development of the polygonal tundra has formed nine cryogenic horizons that reflect the local development of the landscape, i.e. the dynamics of polygons during the last ice Age. In general, stable landscape conditions are recorded on Bolshoy Lyakhovsky Island, changes in accumulation conditions were noted at the end of MIS3 during the transition to MIS2. Between approximately 48 and 38 thousand years ago, a climatic optimum of MIS3 is assumed in the sediments on Bolshoy Lyakhovsky Island.^[96]

S. Vetterich and co-authors ^[97] investigated the Bychchygyi formation ice complex, which is located on the southern coast of Bolshoy Lyakhovsky Island east of the mouth of the Zimovye River and is also exposed in the Oygos Yar outcrop west of the mouth of the Kondratiev River. The ice complex of the Bychchygyi formation either lies under the Edoma or under Holocene sediments. ²³⁰ Th/U dating of peat horizons of the Bychchygyi formation complex 126+16/-13 thousand years and 117+19/-14 thousand years (lower peat horizon) and 98 ± 5 thousand years and 89 ± 5 thousand years (upper peat horizon) confirm the formation of this complex during the stages of MIS5e-5b. The ice complex of the Bychchygyi formation includes syngenetic re-vein ice, 2-4 m wide, up to 10 m high with pronounced "shoulders".^[97] The total capacity of the complex is 6-8 m. The average values of ?18 ^O syngenetic ice veins are -33.0%, and the value of ?2 H is -257.2%, and d _exc is 7%. Minima and maxima vary slightly ?18 ^O from -33.6 to -32.6, ?2H values vary from -260.4 and -253.7, and d ^exc from ₆ to 8. The slope of the regression line ? ² H–? ¹⁸ O is 6.9.^[97]Palynological data of the Bychchygyi formation complex (MIS5) They are comparable to the records of the Edoma complex (MIS3-2). For all the studied periods, steppe vegetation is characteristic, and the palin spectra of the period MIS5 correspond to a drier and colder summer season than in the interstadial period MIS3 and very similar conditions during MIS2. The winter conditions of MIS5, judging by the stable isotopes of the re-vein ice, were also colder than in MIS3, but warmer than in MIS2.^[97]

S. Vetterich and co-authors ^[98] performed cryostratigraphic and isotopic studies of syngenetic re-vein ice of Bolshoy Lyakhovsky Island, which formed approximately the last 200 thousand years. Four different generations of ice complexes of age MIS 7, MIS 5, MIS 3 and MIS 2 have been studied. 357 samples from seven re-vein ices were analyzed. The time of formation of the MIS 3 re-vein complex of the Bolshoy Lyakhovsky edoma has been established by numerous radiocarbon dating of frozen sediments. Two vertical sections with a thickness of 15 m reveal a continuously forming edoma dating from between >50 and 32.7 thousand years ago and between >50 and 33.4 thousand years ago. The previously established radiocarbon age of the re-vein ice of the Bolshoy Lyakhovsky edoma ranges from 51.7 to 39.5 thousand years ago. The recently obtained dates from woody inclusions in the older part of the L6 re-vein ice fit into this range (43.3 thousand years in L6-A and 43.9 thousand years in L6-B).^[98] On the slope of the Zimovye River valley, previously published radiocarbon dates and new dating on reindeer bones confirm the formation of the re-housing complex of Edoma MIS 2 from about 30 to 26 thousand years ago. New dates from the re-vein ice of Edoma MIS 2 show an age of 27.5 thousand years (L14–13), 25.9 and 24 thousand years (both L14–07). Thus, the general formation of the MIS 2 re-housing complex covers a period from 30 to 24 thousand years. In the MIS 2 Edome on Bolshoy Lyakhovsky Island, three reindeer bones sampled at an altitude of 7 m above sea level were dated in the range from 26.2 to 26 thousand years, while the dates of organic matter from the L14-07 re–vein ice at the same altitude are slightly younger – 25.9 thousand years and 24 thousand years. Ice lived from edoma aged MIS 3 and MIS 2. Bolshoy Lyakhovsky Island has a different isotopic composition. The average values of ?18 ^O of MIS 3 re-core ice vary from -32.0 ± 0.3 to -28.7 ± 0.9. The older ice of the MIS 2 re-vein ice shows average values of ?18 ^O between -34.7 ± 0.4 and -34.1 ± 0.2, while the average values of ?18 ^O in the ice of the Late Glacial maximum vary between -37.4 ± 0.4 and -37.0 ± 0.2. Ice veins from edoma with an age of MIS 3 show lower average values of ?18 ^O of re-core ice R9 with an age of 51.7 thousand years (-30.1 ± 0.4%) and re-core ice L6-A with an age of 43.3 thousand years (values of ?18 ^O -32.0 ± 0.3%) compared to re-core ice TZ-2-4 with an age of 39.5 thousand years (values ?18 ^O–28.7 ± 0.9%). Isotope exchange processes after the formation of re-vein ices probably smoothed out the initial isotopic composition to some extent, although distinct differences are still visible. The average value of d _exc in re-vein ice MIS 3 ranges from 6.8 to 9.3, and the slope in linear regression ? ² H– ? ¹⁸ O varies from 7.2 to 8.3. In the profile of re-vein ice L6, a smooth and directional transition from ice MIS 3 L6-A is obvious (values ? ¹⁸ O from -32.0 ± 0.3%) to more depleted isotopic values of L6-C (values of ?18 ^O from -34.7 ± 0.4%). Taking into account the overlapping age ranges for the L6-A (42.5-44.1 thousand years old) and L6–B (42.6-44.8 thousand years old) re–vein ices, a hypothesis was put forward about a change in the prevailing directions of frost-breaking cracking, possibly due to a change in the polygonal pattern and, consequently, the predominance of lateral growth of the re-vein ice L6. The age of the L6-B re-vein ice is most likely derived from re-deposited and re-deposited organic material and excluded from interpretation. Earlier it was reported about uneven growth, which differs from the model of re-vein ice increment from the center, and, as the researchers believe, explains the directional isotopic trend from L6-A to L6-C presumably by the lateral direction of growth. The growth of younger ice on the side (L6-C) is also confirmed by field observations. The L6-C re-vein ice is very close in isotopic composition to the composition of L14-13 re-vein ice (27.5 thousand years; ?18 ^O -34.1 ± 0.2%, d _exc 5.9 ± 0.4%, although the average value of d _exc in L6-C re-vein ice (7.2 ± 0.9%) a little higher. Both ice veins, L14-13 and L6-C, were selected in similar stratigraphic and morphological positions west and east of the mouth of the Zimovye River, respectively. Given the very similar isotopic composition, the researchers suggested that the formation time of both L14-13 and L6–C re–core ices at the beginning of MIS 2 reflects the trend of winter cooling. The re-vein ice formed in the LGM was found in fragments of the L14-07 section (dated 25.9 and 24 thousand years old), as well as L7-07-1. These isotopic records characterize the LGM winter conditions with the most depleted mean values of ?18 ^O to -37.4 ± 0.4% and an average value of d _exc from 6.1 to 7.3%.^[98] S. Vetterich and co-authors ^[98] are convinced that directly dated re-vein ices are the only convincing archives of the winter climate for the Late Pleistocene in Beringia. However, the winter climate variability between interstadial MIS 3 and stadial MIS 2, including the last glacial maximum, has not yet been well provided with radiocarbon data and measurements of stable isotopes in re-vein ice. On Bolshoy Lyakhovsky Island, the interstadial variability of the winter season MIS 3 is characterized by average values of ?18 ^O between -32 and -29% (dated 51.7–39.5 thousand years), followed by an early cooling of MIS 2, reflected by average values of ?18 ^O from -35 to -34% (dated 27.5 thousand years) and a later cooling corresponding to LGM with average values ?18 ^O = -37% (dated 25.9–24 thousand years). However, further west in the Central Coastal area of the Laptev Sea, this minimum winter temperature is not observed.^[98]

      The last glacial maximum (LGM), according to English-speaking researchers, covers from 26.5 to 19 thousand years ago, this is the time of the marine isotope stage (MIS) 2. For non-glacial areas, this period can also be called the final phase of the Late Pleistocene cryochron.^[19]  

Studies carried out by S. Wetterich and co-authors ^[99] on the southern coast of the island.Bolshoy Lyakhovsky, the southernmost island of the Novosibirsk Archipelago in the Dmitry Laptev Strait, has confirmed that the indirectly dated ice wedges are the only convincing archives of the winter climate for the Late Pleistocene in Beringia. 

On the slope of the Zimovye River valley, previously published radiocarbon dates^[95] and new data on reindeer bones confirm the time of edoma formation in MIS 2 from 30 to 26 thousand years ago. New dates have been obtained from ice veins: 27.5, 25.9 and 24 thousand years. On Bolshoy Lyakhovsky Island, the interstadial winter climate variability MIS 3 is reflected by the average values of ?18 ^O between -32 and -29% (dated 51.7- 39.5 thousand years), followed by the early cooling of MIS 2, reflected by the average values of ?18 ^O from -35 to -34% (dated 27.5 thousand years) and the Late Pleistocene cryochron with values of ?18 ^O -37% in ?18 O (dated 25.9^–24 thousand years). The increased continentality in the studied region was caused by the minimum sea level during the LGM. Together with the configuration of ice sheets in the northern hemisphere and the stable sea ice cover of the Arctic Ocean, a stronger Siberian maximum is likely in winter and, consequently, a stronger winter cold snap. The isotopic record of the ice vein on Bolshoy Lyakhovsky Island of LGM time, according to S. Vetterich, reflects the coldest winter conditions in Northern Siberia during global minima of atmospheric _CO2 and sea level.^[99]

       A.Pismenyuk and co-authors^[100] investigated the isotope-geochemical features of the underground ice of the Faddeevsky Peninsula. The Late Pleistocene Edom ice complex lies on clays. To the east of Cape Nerpichy, in the upper part of a 12-meter cliff at a distance of 5 m, two veins of ice are exposed, the tested vein has a width of about 3-4 m and a visible vertical length of about 5 m. The host deposits are represented by peat and organically rich (with _org - 4.7%) powdery loams with layered cryotexture. For a similar section in the area of the Khastyr River in the east of the Faddeevsky Island, dates in the range of 25.7–43 thousand years were obtained. To the west of Cape Sanga-Balagan, the quaternary section is represented by a series of vein ice of different ages. At the lowest absolute levels (0.5–3 m above sea level), relatively small narrow veins of ice are exposed (up to 1.5 m wide and 2 m vertically), and the ends of some of them are below the beach level. To the east, with an increase in the height of the coastal cliff, edom deposits are exposed. It is difficult to estimate the size of the veins, since the ice opens in the longitudinal section, forming a single ice "wall". A narrow (0.4 m wide) epigenetic ice vein penetrates into the Late Pleistocene Edom ice complex to a depth of 2 m. Between the outcrops of Paleogene-Neogene bedrock, a 9-meter coastal cliff exposes stratified underground ice, transparent, coarse-grained, with mineral inclusions unevenly distributed in the ice body. The host clays are saline (the salinity of clays is 0.5%), Na, Mg and Cl ions predominate in the composition of water solutions. According to the position of the values in the diagram ? ² H-? ¹⁸, vein ice, formation ice and lenticular ice formed three groups. The isotopic values of various re-vein ices correlate well with the global line of meteoric waters, which confirms their atmospheric origin and indicates equilibrium isotopic fractionation during the formation of atmospheric moisture and vein ices. In addition, two groups of re-vein ice can be distinguished: with values of ?18 ^O > -29 and with values of ?18 ^O from -22.5 to -24. For this region, A.Pismenyuk and co-authors^[100] isolated vein ice formed in different periods of the Holocene and Late Pleistocene. Late Pleistocene edomial re-vein ices are characterized by an almost uniform distribution of ?18 O values from -31 to -29.3%, as well as a small spread ^of ?2 H values from -240.6 to -226.5% and d _exc from 7.2 to 8.8%. Holocene veins reflect a great variability of isotopic values. For one of the Holocene veins, the highest isotopic values were recorded in a sample taken from the "tail": The value of ?18 ^O = -21.7% and the value of ?2 H is -163.4%, while for most samples the value of ?18 ^O was close to -25%, and the value of ?2 H is approximately -129%, the values of d _exc are up to 13 %. The isotopic record for another Holocene vein indicates the same features, but with slightly higher ? values: the average value of ?18 ^O was -22.5%, and the average value ^of ?2 H was -170.3%. The values of d _exc are close to 10 %. The most modern re-vein ice had an average value of -24.0% for ?18 ^O and -182.3% for ?2 H. The values of d _exc ranged from 7 to 11%.

      The Late Pleistocene re-vein ices of the Kotelny and Faddeevsky islands record a wide range of ?18 O values from -31 to -25, reflecting the great variability of winter air temperatures at this time. A slight difference in stable isotope data between the re-vein ice formed in MIS-3 and MIS-2 is due to the absence of a record of the last glacial maximum. The data on the Bolshoy Lyakhovsky re-vein ice^[33] represent the most isotopically low values (?18 ^O = -37%) in the isotope records of veins formed during MIS-2. The average value of ?18 ^O for Holocene re-vein ices at the Boiler House is about -23%, and the variations of ?18 ^O do not exceed 2%^[92]. The data obtained by A.Pismenyuk and co-authors^[100] on the magnitude of ?18 ^O for re-vein ice from the eastern shore of the Faddeevsky Peninsula are generally consistent with previously published data; however, some distinctive features have been identified. The values of ?18 ^O for re-vein ice were close to -30% and showed no significant variations compared to Holocene wedges, where the changes in the values of ?18 ^O even within one vein reached 4%. The observed variations in the values of ?18 ^O may be associated with temperature fluctuations during the growth of the vein or with the mixing of waters entering the vein. For example, heavier isotope values (?18 ^O = -22%) in the "tail" of re-vein ice may be associated with the possible inflow of seawater and sea levels close to modern values at the early stages of vein growth. The Holocene veins of Faddeevsky have a heavier isotopic composition by an average of 6 % compared to the Late Pleistocene; however, the obtained average values are slightly higher than those recorded on Kotelny Island ^[91,92], which can be explained by the more severe climatic conditions of the East Siberian coast. Holocene PLCs differ from Late Pleistocene ones not only by higher values of ?18 ^O, but also by the highest average value of d _exc 11-13. Usually, changes in the values of d _exc were interpreted as changes in moisture sources or individual local processes as fractionation of snow cover. Previous studies have interpreted these variations as the marked participation of early winter snow in the composition of veins fed by meltwater, the increased influence of the Atlantic, as well as the long-range transfer of air masses to the Holocene snow cover. Temperature estimates made according to the equation of Yu.K.Vasilchuk^[7] for the studied coast showed that the average temperature for MIS 3 in January dropped to -45 ± 3 °C, and in the Holocene it was about -35 ± 3 °C. Higher winter temperatures were reconstructed for the Holocene formation of re-vein ice, temperature fluctuations were more pronounced than during MIS 3; the average temperature in January ranged from -38 to -31 °C. Thus, in the warmest periods of the Holocene, the January temperature was comparable to the modern value of -31 °C.^[100]

    F.A. Romanenko and co-authors ^[101] analyzed changes in the isotopic composition of the edom re-vein ice of the coast of the East Siberian Sea on the coastal plains of Faddeevsky Island (Novosibirsk Islands), Lopatka Peninsula in the northwestern part of the Indigirka Delta, the right bank of the Lower Kolyma from Ambarchik to Cape Bolshoy Baranov, the Apapelkhinsky lowland and east of Cape Shelagsky to the mouth of the Kuyvivey river. F.A. Romanenko especially notes the adjacency of high-acidic sediments of the Kolyma lowland to the rocks (clay shales, sandstones and siltstones of the Upper Triassic) of the low mountains of the Verkhoyano-Chukchi folded region, broken through by large (up to 30 km in diameter) Cretaceous granite intrusions. In rock massifs, the edom layer is fixed to a height of 100 m or more above sea level, and on the adjacent basement plains it lowers the roof of the rock foundation.

On Faddeevsky Island, on the right side of the Hastyr river valley, in the upper part of the ledge of the erosion-thermokarst plain, at an absolute height of about 8 m, bluish-dark brown loams with interlayers of ice ground, ice veins up to 4-5 m wide and numerous lenses and peat interlayers are revealed. These deposits, ubiquitous in the area, close the Quaternary section. A series of radiocarbon dating in the range 25 700-43 000 years ago was obtained from peat by scintillation method, as well as from sedge seeds and pieces of wood by AMS method. The formation of edom deposits here took place during the Kargian period. An inversion of dates obtained by different methods has been revealed, which is probably caused by the fact that the loam-peat layer was formed under conditions of significant waterlogging, as evidenced by its high ice saturation.

The minimum values of ?18 ^O in the homogeneous re-vein ice in the valley of the Khastyr River are -31.1%.^[101]. On the shore of Lake. Mogotoevo (Lopatka peninsula) remains up to 2-3 m high, towering among a flat low-lying swampy marine terrace are composed of dark brown loams of an ice complex with lenses of dark gray peat. Layered and reticulated cryogenic textures predominate, formed by ice layers of 2-3 mm. Numerous ice veins with a width of up to 3-4 m in the upper part are found here. The minimum values of ?18 ^O in the homogeneous re-vein ice on the Shoulder are -32.4% (in the sprouts of modern veins here, the values of ?18 ^O vary from -19.9 to -23.2%). On the right bank of the lower reaches of the Kolyma River from Ambarchik to Cape Bolshoy Baranov, the sediments of the ice complex in the context of a series of inclined and subhorizontal surfaces up to 90-100 m high overlap the rocky basement. They are represented by loess-like dark gray and dark brown loams with abundant inclusions throughout the thickness of vegetable detritus and peat lenses with a thickness of 15 cm and a width of up to 10 cm. Ice veins up to 4 m wide and with a visible vertical thickness of up to 10 m dissect the entire thickness of loose sediments. The ice complex lowers the roof and its capacity decreases with distance from the sea. On the northern slope of Kamenka Mountain, it can be traced to a height of about 100 m. In small areas (for example, east of Cape Letyatkin), edom deposits are underlain by pebbles and coarse-grained quartz-feldspar sands with pebbles. The ice veins dissecting the gray loam enriched with crushed stone at the eastern foot of Kamenka Mountain differ significantly from others. Here, in a cliff with a height of up to 35 m, polygonal vein ice with a width of 3-4 m and a thickness of up to 2.5 m, containing a large amount of crushed stone of local rocks, are opened in a series of thermocircles. At the base of this section, up to a height of 9-11 m above the cut, there are Triassic shales overlain by a 1.5–2 m thick gravelly weathering crust, on which the ice edom complex lies. The presence of crushed stone in the ice indicates that local deposits, mainly of slope origin, participated in the formation of the ice complex. The minimum values of ?18 ^O in the homogeneous re-vein ice near the Ambarchik polar station are -31.6%.^[101]

To the south of the Shelagh granite massif is the Apapelkha lowland, a flat plain up to 60 m high, gently inclined to the sea, made of brown loam with a massive cryogenic texture, peat interlayers, scattered plant detritus and crushed stone of Triassic shales, especially in the parts adjacent to the mountains. The systems of baijerakhs up to 3 m high here are confined mainly to the slopes of erosive forms and catchment depressions. The Baijerakhs are separated by hollows, in the bottoms of which ice veins with a "light" isotopic composition are opened below the seasonally shallow layer, the minimum values of ?18 ^O in the homogeneous re-vein ice of the Apapelkha lowland are -35.3%. On the coast, in the area of the Valkarkai polar station, there is a flat surface 3-5 m high, composed mainly of loamy sediments with crushed stone and broken up by an orthogonal network of polygonal-vein ice. The surface is covered with a layer of peat up to 1.5 m thick, which is 7-4.8 thousand radiocarbon years old. Below, grayish-brown and bluish-gray loams are revealed, mainly with a massive cryogenic texture and numerous lenses and layers of peat, saturated with plant detritus. The thickness is dissected by ice veins up to 2 m wide, there are layers of ice ground and single ice slots and lenses up to 1.5 cm thick. The minimum values of ?18 ^O in the Late Pleistocene re-vein ice near the Valkarai polar station are -30.7%. The authors conclude that the isotopic composition of edomous polygonal vein ice varies slightly from west to east and from north to south, remaining in the range from -27 to -32% and only occasionally dropping to -36%. The dependence of the isotopic composition of the veins on the absolute height, distance from the ocean and the geomorphological position of the section (vertex surface, slope, thermodenudation remnant, etc.) was not revealed.^[101]

       Two articles by L. Schirrmeister and co-authors ^[102,103] should be mentioned, which, although they do not contain new isotopic or radiocarbon data, are very important for the study of edoma, since they are devoted to the granulometric composition of the edoma of Siberia and Alaska^[102] and the consideration of associations of heavy and light minerals of edoma The North-East of Siberia.^[103]

The Edom of North America

                H.French and S.Millar ^[104], analyzing permafrost strata in North America at the time of the last glacial maximum, came to the conclusion that, compared with studies in Europe and Russia, in North America, studies of relict permafrost strata are in their infancy. Based on a thorough analysis of modern literature, H.French and S. Millar have compiled 3 maps of the maximum distribution of permafrost strata in North America: 1. A map showing the distribution of permafrost strata (including mountainous areas) during the Late Glacial maximum in North America. The map is based on the maps of T. Peve; 2. A map showing the territories not covered by a glacier at the time of the late glacial maximum. 3. A map showing the approximate distribution of the Laurentian ice sheet about 10,000 years ago and during the last glacial maximum.

 EdomAlaska

      Itkillik River. M.Kanevsky, Yu.L. Shur and others^[105] investigated a 33 m high outcrop located along the lower reaches of the Itkillik River in the north of Alaska. They divided the studied thickness into 7 cryostratigraphic parts: (1) an active layer and a transition layer with a thickness from 0.5 to 1.0 m; (2) an intermediate layer from 0.5-1 to 1.5 m deep; (3) an edoma of silt with "thin" ice veins at a depth of 1.5 to 13-14 m; a silty edoma with powerful ice veins at a depth of 13-14 to 27-28 M. The ice veins in this layer are relatively wide at the top (up to 3-4 m), and their width gradually decreased with depth. In the lower part of the layer (at depths from 6-7 to 13-14 m), the width of the ice veins rarely exceeded 1-2 m. The ice veins had a well-developed vertical stratification formed by silt particles that were brought into the frost-breaking cracks by water during the formation of ice veins. The ice was yellowish-gray in color, due to inclusions of silt and dissolved organic substances. The distance between the ice veins is from 7 to 10 m.; (5) buried peat layer from 27-28 to 29-31 m deep; (6) buried intermediate layer at a depth of 29-31 to 30-32 m; (7) silt with small buried ice veins at a depth of 30-31 to 32.7 m. The entire thickness was formed in the range from more than 48 to 5 thousand years ago. The 3rd and 4th edoma bundles were formed in the range from 48.0 to 14.3 thousand years ago.^[105]

L.Lapointe, together with M.Z.Kanevsky, Yu.L. Shur and other colleagues^[106] reconstructed some paleoecological characteristics in the context of Itkillik, reflecting climatic and ecological changes after the turn of 35 thousand years ago. They showed that during this period, pollen from the sedge and cereal families dominated the palin spectra. The high content of sediment pollen corresponds to a noticeably higher iciness of sediments and an increased content of organic carbon. The predominance of pollen from cereals and grasses, according to the authors, corresponds to the arid and cold conditions of the summer season. About 30 thousand years ago, the conditions of the summer season became more favorable for vegetation cover.^[106] In the same work, the isotopic characteristics of re-vein ices are given. The average value of ?18 ^O in the lower 7th layer is -33.6 %. The average value of ?18 ^O in the overlying 6th layer is -28.7 %. The average value of ?18 ^O in the 5th layer at a depth of 20.9 to 13.3 m is -30.9 %. The average value of ?18 ^O in the 5thThe m layer at a depth of 13.3 to 3.3 m is equal to -33.0 %. The average value of ?18 ^O in modern veins here is -25 %.^[106]

        Yu.K. Vasilchuk ^[107] examined the edom strata of Alaska and Klondike with well-marked signs of cyclicity: on the Chatanika River, on the Itkillik River, Fox permafrost tunnel, in the Colville River valley, etc. In the structure of the Itkillik polygonal-vein complex (description of the M.Z. outcropKanevsky, Yu.L. Shura et al.^[105]), they ^[107] distinguish at least 4 mesocyclite tiers – three represented by Late Pleistocene veins: the lower one is small buried veins formed under a buried peat bog, probably older than 48 thousand years, the second and third represented by a height of up to 30 m, at the bottom these are powerful - wide veins, 15-20 m high, narrower at the top, penetrating into the lower ones, about 13-15 m high, aged from 40-45 to 13-14 thousand years, and the fourth – upper Holocene with an age of more than 8.6-5.3 thousand years.^[107]

                The Volt Creek tunnel on the Chatanika River. In a 15-meter outcrop on the banks of the Chatanika River, 2 km downstream from the Elliott Highway Bridge over the Chatanika River, 40 km north of Fairbanks in the northwest, i.e. in ^[108], the outcrop of deposits of the Goldstream formation containing powerful syngenetic ice veins and sedimentary formations is described Reddy Bullian with low-power veins of ice. A layer of volcanic ash with a thickness of 1 to 10 mm is marked in the sediments. The radiocarbon date of 14,760 ± 850 years (GX-0250) was obtained from a gopher mink 4 m below the ash layer. The date 14 510 ± 450 years (W-2703) was obtained from gopher coprolites from silt 1 m above the ash layer. Thus, the ashes are dated to about 14 thousand years old. and the ice veins in the sediments of the Goldstream formation date back to the very end of the Late Pleistocene.

L. Schirrmeister and co-authors ^[109] studied a 36-meter thick frozen rock in the valley of Volt Creek (valley of the Chatanika River, 10 km north of Fairbanks), located in the zone of intermittent permafrost. The thickness of the frozen layer here reaches 120 m, the average annual temperature of the rocks in the tunnel is -0.7 ° C. The lower block of rocks is represented by a 9-meter layer of gravel and sand with peat lenses, the age of the lower layer is presumably late Sangamon (MIS 5a, judging by the OSL date of 93.1 thousand years). The overlying block is represented by a 10-meter fluvial thickness of alternating layers of gravel, loess-like silt and sand, penetrated by ice veins. The method of optically stimulated luminescence (54.4 and 59.4 thousand years old, at the same time, a fragment of wood at a depth of 19.6 m was dated to ¹⁴ With age 49,5 +2.2/-1.7 thousand years) confirms the Early Wisconsin (MIS 4) age of this strata. Typically, the edom strata are located at a depth of 2 to 17 m and are mainly represented by silty sandy loam. Frequent large ice veins (their apparent width in the upper part is up to 3 m), consisting of many thin vertically oriented ice veins, are visible on both walls of the tunnel. Most of the radiocarbon dating falls in the range between 52.4 and 42.17 thousand years. Three younger ¹⁴ From the date were obtained from ice vein samples from a depth of 12 m (34,4 +4,4/-2,8 thousand years), from soil samples from a depth of 2.7 m (25.3 ± 0.24 thousand years) and from the upper layer of ash at a depth of 2 m (20.7 ± 0.12 thousand years). Shell amoebas were found in twelve samples, mainly from peat lenses in both lower blocks, and in organic matter- and peat-rich sandy loam silt lenses of edoma. The amoeba community includes 32 taxa (species and subspecies) that belong to soil-biotic, calcifilic, hydrophilic, and sphagnobiotic ecological groups. Stable isotopes were determined in 25 ice veins (145 samples). A weak tendency of transition from higher isotopic values from a depth of 21 m (average value of ?18 ^O: -20.5%, average value of ?2 ^{H: -163.8%; d exc: 0.5%) to lower ones from a depth of 2} m (average value of ?18 ^O is -29.2 %; average value of ?2 H is equal to -229.8%; d _exc 4.0%). In Holocene veins sampled at the entrance to the tunnel, the average value of ?18 ^O is -21.9 %, the average value of ?2 H is -171.8 %; d _exc: 3.2 %). The lightest isotopic composition in ice veins (as well as in segregated ice) indicates the coldest winter conditions at the time of edoma formation. Consequently, the data on the upper part of the edom block C belong to the Late Wisconsin epoch. AMS ¹⁴ C dating shows that the accumulation of silty sandy loam in Edom and the growth of ice veins occurred in the vicinity of the valley of Volt Creek, at least from 50 - 40 thousand years ago (MIS 3) to 25 thousand years ago (MIS 2). It is noteworthy that in the valley of Volt Creek, loess accumulation continued at least until 25 thousand years ago, while in the Fox tunnel there was a break between 30 and 14 thousand years ago.^[109]

               Fox permafrost tunnel. Significant results of new research in the tunnel were published in articles by T.Douglas and co-authors ^[110] and M.Lachnet and colleagues.^[111] The only previously obtained^[112] radiocarbon dating of dispersed methane in ice veins selected by M.Lachnet for repeated study was 24,884 ± 139 radiocarbon years (29,770 ± 230 calendar years), which is significantly younger than the previously estimated age of the lower silt layer. This dating led M.Lachnet to the question of the time relations of the horizons of various sediments in the tunnel and how they relate to the paleoclimatic interpretation of MIS 2 and MIS for ice veins and host sediments. Ice samples were taken by M.Lachnet in a part of the vein saturated with air bubbles, about 1 m long and 0.2 m thick. The age of the wood material in the silt inclusions of the left part of the vein (about 0.6 meters below its upper boundary) is dated to the age of 40800 ± 410 calendar years, which can be taken as the maximum age of the vein. The wood material enclosed in deformed and recomposed silts 70 cm above the thawing zone was dated to an age of 34,750 ± 290 calendar years. The fact that these deposits lie above the thawing zone (and the thermokarst lake) indicates that the wood material in them cannot be used to determine the minimum age of the vein growth period, it must be older. Ten fragments of organic material included in the ice vein range in age from 28260 ± 180 to 37040 ± 410 calendar (or calibrated) years. However, these dates are significantly scattered and do not correspond to the stratigraphy of the ice layers. The spread excludes the creation of an age-distance model for an ice vein. These ages are similar and slightly younger than those obtained in the host sediments, indicating a possible common origin of the material. The sources may be surface or underground organic substances entering the crack in the spring. In addition, carbon particles could be brought in by meltwater or by filtering water through the active layer in the spring. The active layer may include carbon from modern vegetation and soil, as well as old sediments below the soil horizon. Three dates of CO ₂ and DOC (dissolved organic carbon) turned out to be significantly younger than the others within the vein, with a maximum age difference of 11170 years. Based on the conclusion of Yu. and A. Vasilchukov ^[59,60] that ice can "pollute" organic material whose age is equal to or older than the age of ice, M. Lachnet determined the maximum age limit: the youngest measured age will be closest to the true age of ice if a crack develops far from the center of the vein. Given the long-term preservation of carbon in permafrost rocks, even the youngest CO ₂ and DOC may have been contaminated with "old" carbon. Since the carbon particles in this study showed a significant age variation, M. Lachnet interpreted the age of the ice in the vein according to the minimum dating. The values of ?13 C by POC were approximately -27% V _PDB, which is typical for sedges and other vegetation of type C ₃ in Alaska (for example, grasses, shrubs)^[111]. According to CO ₂, four dates were obtained in a large vein: 25935 ± 2537, 22187 ± 2634, 24575 ± 2340 and 39,835 ± 7830 cal. years. After analyzing these data, M.Lachnet and colleagues came to the conclusion that this vein was formed in the period from 23 to 29 cal. thousand years ago.^[111]

              M.Lachnet et al.,^[111] following the principle of choosing the youngest dating as reliable, formulated by Yu. and A. Vasilchuk ^[59,60] concluded: one of the ice veins was dated 31140±140 cal. years and 214700±200 cal. years according to CO ₂ and DOC, respectively, and the sedge enclosed in this vein is dated to 26430 ± 280 cal. years. The youngest age is 21.5 thousand cal. The age of the DOC is probably the closest to the age of the ice, but since it may contain old carbon, the age of the ice is probably even younger.^[111]

         K.E. Griffin^[113] in her master's thesis, conducted under the supervision of M. Lachnet, considered some features of the Pleistocene climate of Alaska based on the analysis of stable isotopes of the ice wedge in the Fox tunnel aged from 28.3 to 37 cal. thousand years. In the ice vein, higher isotopic values are noted along the edges of the ice vein (?18 ^O = -22.0 %) and the lowest values of ?18 ^O in its center are -27.9 %, the difference is 5.95 %. The calibrated age of the organic material contained in the ice veins varies significantly. Organic material collected from 19.5 - 20.5 cm gives a calibrated age of 34.727 ± 142 years; from 29.5-30.5 cm, age 36.991 ± 350 years; 35718 ± 246 years from a depth of 39.5-40.5 cm, and age 28.275 ± 182 years from a depth of 50.5 to 52.0 cm. The center of the ice wedge is visually estimated at 61.3 cm. The sediments from this site show a date of 32643 ± 369 years, which is about 4820 years older than the sediments 10 cm to the left of the sample. Branches found in frozen sediments to the left of the ice wedge indicate that the calibrated age is 40,837 ± 374 years, which is older than any dates obtained inside the vein. The wood from the sediments above the ice wedge gave a calibrated age of 34.765 ± 199 years, which is older than some of the sediments found within the wedge.^[113] K.E. Griffin attributes the formation of a separate vein studied by her to the cooling corresponding to the 3rd Heinrich event. And K.E. Griffin^[113] estimates the difference in the values of ?18 ^O at 5.95 °C.

        E. Slot ^[114] in her dissertation, conducted under the supervision of M. Lachnet, considered the paleodynamics of the climate of Alaska based on the study of stable isotopes in the Fox Tunnel. In ice vein samples dated 32030 ± 400 and 35690 ± 450, the ?18 ^O variations ranged from -20.4 to -21.2%, in ice vein samples dated 17910 ± 210, the ?18 ^O variations ranged from -26.2 to -28.9%, in ice vein samples dated 34970 ± 460, the ?18 ^O variations ranged from -21.8 up to -26.8%, in ice vein samples dated 28,870 ± 270, the ?18 ^O variations ranged from -22.0 to -27.9%, for comparison, in modern snow in Denali National Park, the ?18 ^O value is -22.3 ± 3.5%. E. Slot^[114] concluded that Central Alaska experienced at least five cold events and at least one warmer event. Large ice veins from the lower silt block in the tunnel formed between 25.9 and 21.5 kcal. thousand years ago or during the 2nd Heinrich event. A warmer event with partial thawing of the upper part of the veins probably occurred between 21.5 and 17.9 cal. thousand years ago. Another cold event probably occurred between 17.9 and 12.9 cal. thousand years ago.^[114]

Extensive new isotope studies of edom deposits were performed by M.Kanevsky and co–authors^[115] in the CRREL tunnel, which was originally built in the early 1960s in Fox, Alaska by employees of the US Army Cold Regions Research and Engineering Laboratory (CRREL) to test methods of mining, tunneling and construction on permafrost. New tunnel penetrations were carried out by CRREL in five stages: in 2011, 2013, 2018, 2020 and 2021. The length of the main tunnel of the new tunnel is approximately 110 m from the portal, and its average width and height are approximately 4.25 m. The sections (C1, C2 and C3) connect the old (T1) and new (T2) tunnels. Samples of various types of underground ice were taken from the new CRREL tunnel and adjacent wells and analyzed at the Alaska Stable Isotope Center at the University of Alaska Fairbanks (UAF) and CRREL. For age analysis, the AMS method analyzed the remains of terrestrial plants, such as wood or herbaceous plants (usually cereal stems, leaves or roots). The tunnel revealed sections of frozen rocks typical of the highly acidic syngenetic permafrost rocks of Edoma and the presence of a large amount of almost undecomposed organic matter, including small roots, throughout the thickness of edoma. The ice veins exposed in the tunnel had a distinct vertical layering due to the admixture of particles of mineral soil and organic matter. The isotopic composition of the re-vein ice exposed by the new CRREL tunnel ranges from -28.7% to -20.4% for ?18 O (average value -24.9 ± 1.9%, n = 184), and in Holocene ice veins, the average value of ?18 ^O = -24.0 ± 1.3%, n = 16).^[115] The isotopic composition of the segregation ice slots ranges from -23.4 to -21.0 % according to the values of ?18 O (the average value is -21.7 ± 0.7%). These relatively high values (compared to vein ice) can be explained by a different water source: if for vein ice it is mainly meltwater, then ice sluices are formed from groundwater of the active layer, which is mainly a mixture of meltwater and rainwater.

A total of 54 dates of ¹⁴ C allowed the age to be determined in the new CRREL tunnel and wells drilled from the surface and in wells drilled from the bottom of the tunnel. According to these dates, the Edom sections date from about 31,000 to 38,500 years ago (all dates are given in calibrated years). A number of dates have been obtained from wood that is suspended in ice (presumably thermokarst-cave ice). These dates range from 32,500 to 35,000 years, although one sample gave an age of almost 43,500 years.^[115] The dates obtained from the well that was drilled at the bottom of the tunnel showed a range from 36,300 to 36,800 years ago. The oldest date (42,300 years) was obtained from a well at a depth of 18.2 m from the surface near the boundary between clay (silt) and gravel. The results showed that there was no systematic error associated with wood material compared to non-wood material. In some cases, the wood was older, in others, the grassy material was older. The age difference between these materials ranges from 2000 to 300 years. The radiocarbon dates obtained from the new tunnel are consistent with previously obtained dates from the old tunnel. Radiocarbon dating in other parts of inner Alaska has shown a similar age of edoma. In the area of the permafrost tunnel of Volt Creek, the accumulation of edoma and the growth of ice veins occurred from 40,000 to 50,000 years ago to 25,000 years ago, forming an edoma thickness of about 15 m^[109]. Radiocarbon dates from 22,600 to 43,100 years ago were obtained in the 9-Mile Hill study area for edom with a thickness of ~ 25-30 m. For the Klondike region, the edomian stratum has been dated from 24,000 to 31,000 and from 24,000 to 29,500 years ¹⁴ C, respectively.

A comparison of the cryostratigraphy of the old and new parts of the CRREL tunnel demonstrated significant differences. The edom in the old tunnel was severely destroyed or modified by erosion and thermokarst phenomena, and almost all the ice veins in the main tunnel of the old tunnel were cut off by thermal erosion. Erosion formations and thermokarst-cave ice bodies are also found in recently opened sections of the tunnel, but edoma has been preserved much better here. Another significant difference between the cryostratigraphy of the new sections of the CRREL tunnel and the old ones is the absence of gravel Holocene deposits, which were described near the portal of the old tunnel.

New studies in the CRREL tunnel have not confirmed the existence of two Pleistocene finely dispersed strata separated by a continuous thawed layer, as previously described. The processes of edoma formation and thermal erosion occurred simultaneously, and cryostratigraphic inconsistencies are associated with local thermokarst and thermal erosion processes.^[115]

From 2005 to 2008, in the near-surface part of the permafrost rocks of the coast of the Beaufort Sea in Alaska, ^[116] underground ice was studied in 65 sites located between Cape Barrow and the Canadian border.  According to the descriptions of M.Kanevsky and coauthors^[116] on a 20-kilometer stretch of the coast of Camden Bay, strongly glaciated Pleistocene edom strata are found here. Large ice veins, more than 48 thousand years old, have been observed in these places.^{[116, p. 64]} Polygons typical of edom complexes on the Earth's surface were not observed. At a distance of approximately 1.8 km from the coast, thawing landslides and numerous baijaraks typical of Edoma are clearly visible on satellite images. The size of the polygons in this area varied from 6 to 10 m; the width of the ice veins varied from 1 to 4 m. The values of volumetric ice content, including re-vein ice, pore ice and segregation ice, were up to 89%.^[116] M.Kanevsky and co-authors ^[117] showed that the plains of Innoko and Koyukuk, located in the interior of Alaska, were developed as a result of the formation of basins of large lakes. They identified ^[117] nine stages of lake plains formation, including four stages of edoma degradation and five stages of subsequent agradation and degradation of permafrost.

S. Ewing, Y.L.Shur, M. Kanevsky, and others^[118] performed dating of the underground ice of Central Alaska using uranium isotopes. A series of dates has been obtained in sections between the Yukon and Tanana rivers up to 200-230 thousand years old.

      Seward Peninsula. Despite the fact that for the first time vein ice in the Seward peninsula edom was described by O.E. von Kotzebue and J.F.G. von Eschscholz in 1816, so far the study of Seward Peninsula edom has made little progress. Data have been obtained on the widespread occurrence of highly glaciated strata with powerful cyclically constructed ice vein systems within the peninsula. Good photos of two-tiered ice veins with a thickness of more than 5 m were published by B.Higman and E. McKittrick ^{[107, p. 97]}. In the northern part of the Seward Peninsula, in the Devil Mountain lake basin, Y.L.Shur, M. Kanevsky and M. Georgenson,^[119] having drilled 21 wells in the lake basin and on the surface of Edoma, describe the edoma thickness with powerful ice veins reaching vertically at least 36 m, the edoma sites are characterized by a total volume of ice from 70 to 90% (moreover, ice veins were preserved in the ice column under the lake, although it was quite extensive - more than 120 m in diameter).^[119] Earlier, similar work was carried out on the shores of Kotzebue Bay^[120], and later on the lakes Cloudy, Yeager and Maar in Devil Mountain, and on Lake. Mama Rhonda is on the coast of the Chukchi Sea ^[121,122], but in them little attention was paid to the study of the edom strata.

               Baldwin Peninsula. The appendix to the article^[123] contains 3 photos.Schrauss, who recorded the coastal cliff of Edoma with a capacity of 16 m. With the help of a hand drill, 25 samples of edom deposits were taken at five different sampling points. 15 AMS radiocarbon dates have been obtained, of which 9 are Late Pleistocene - but unfortunately only 3 are final: 46361 cal. years from a depth of 3.4 m, 44747 cal. years from a depth of 11.2 m and 19551 cal. years - from a depth of 16 m. Radiocarbon dating is inversely arranged, there is no tendency for age to increase with depth. Biomarkers were studied in the study: the ratio of C/N varies from 4.4 to 14.0 (average value 10.1), the concentration of n-alkanes ranges from 0.5 to 1.8 mg/g per _organ (average: 1.0 mg/g per _organ).

Edom Yukon

      T.Porter and T.Opel^[124] note that, compared with the Russian Arctic, there have been fewer studies of stable isotopes of relict underground ice as indicators of paleoclimate in the western part of the North American Arctic, although this region has a long history of research. Data on stable isotopes in the ground ice have been used for other purposes, such as determining the age and genetic classification of the ground ice. Over the past 10-15 years, several relevant studies have been conducted that have contributed to progress in the study of the Arctic paleoclimate, mainly on the Arctic coast of Yukon–Alaska and in the continental Yukon and Alaska.

Quartz Creek, Klondike. T.Porter and co-authors ^[125] on the Quartz Creek River described powerful multi-tiered re-core systems (although this tiering is implicit in most cases). In veins formed 31.9-30.2 cal. thousand years ago, the values of ?18 ^O were -29.3%, and the values of ?2 H were -227.3%.

For the Klondike region in central Yukon, T.Porter et al.^[125] reported values of ?18 ^O re-vein ice of -29.3 % for the end of the MIS 3 stage (~ 31.9–30.2 cal. thousand years ago) and -24.5 % for the Late Holocene (~ 0-500 years ago), respectively. Based on an average difference of 4.8 % between the values of ?18 ^O of re-vein ice MIS 3 and the Late Holocene (5.5 % after standardization for ?18 ^O of _seawater) and the estimated ?18 ^O _{precipitation}-?T ratio of 0.41 °C ^{? 1}, they calculated that the winter season during MIS 3 in the Klondike was ~ 13 ± 3 °C colder than the modern one. The decrease in temperature according to the results of isotopic studies of PLL in the central part of Alaska during the last glacial maximum (26.5 - 20 thousand years ago) is estimated by T.Porter et al.^[125] ~ 17 ± 3 ° C. The pore ice from the host deposits of the Klondike, which, as T.Porter believes, reflects the composition of annual precipitation, has average values ?18 ^O = -28.0 and -22.7 for MIS 3 and MIS 1, respectively. T. Porter et al.^[125] calculated that the average annual temperatures during MIS 3 were lower by ~ 15 ± 3 °C compared to the Holocene, which corresponds to the value of the decrease in winter temperature during MIS 3 obtained by analyzing re-vein ice. However, the authors cautioned that paleotemperature estimates based on isotopic values obtained from studying pore ice containing a mixture of meteoric waters of all seasons are inevitably more uncertain, since the isotopic composition of pore ice is largely determined by sensitivity to changes in precipitation seasonality than re-vein ice with a more narrowly limited seasonality.^[125]

But. Reyes and co-authors ^[126] conducted cryostratigraphic observations at four sites in the north of Yukon and nearby outcrops on the Old Crow River, Palisades on the Yukon River in Alaska and outcrops of placer deposits in Thistle Creek in the west-central part of Yukon, which give an idea of the reaction of permafrost rocks to regional warming during the last interglacial. The chronology is based on the dating of the Old Crow tephra, an important regional stratigraphic marker that belongs to MIS 6. The Old Crow tephra overlaps several relict ice veins in Palisades and Thistle Creek, indicating that the permafrost rocks in these areas did not completely thaw during the last interglacial, even during the warmest periods the last Interglacial and Early Holocene thermal maximum, as indicated by the arctic ice veins preserved under the late Old Crow tephra of age MIS 6 in Palisades and Thistle Creek. This finding, as well as the discovery by D. Frez of relict ice veins in Dominion Creek, whose age exceeds 700 thousand years ago, shows that in the zone of intermittent distribution, permafrost rocks have been preserved, at least locally, even during several long (multi-thousand-year) periods of existence of a climate warmer than the modern one. Pseudomorphoses of ice veins in stratigraphic association with Old Crow tephra in Thistle Creek, Chidgis Bluff and Old Crow Flats, as well as in other places in eastern Beringia, indicate the degradation of shallow permafrost rocks during the last interglacial, when some ice veins in these areas melted. Wood-saturated accumulations of organic silt, which cut or overlap Old Crow tephra and are of an indeterminate age of ¹⁴ C, are widespread in Thistle Creek, Chigis Bluff, Palisades and many other places in eastern Beringia. Although they are usually called "forest beds" of the last interglacial, in situ paleosols with stumps and roots are rarely exposed, most of the woody deposits are probably the result of catastrophic melting, accompanied by massive movement of material or processing of woody detritus in thermokarst reservoirs or basins. Field data from the Palisades, together with preserved pre-glacial ice wedges in Thistle Creek, Dominion Creek and Palisades, suggest that the depth of soil thawing during the last interglacial was on the order of the first meters, and not 10 meters or more.^[126]

      But. Reyes and co-authors^[127] report that in most previous studies of recent interglacial deposits in eastern Beringia, a minimum age of 14 C for wood or humic acids was obtained, complementing the maximum age determined by old crow tephra: Chijis Bluff, Birch Creek, Holitna Lowland (Holitna River, left tributary of Kuskokwim), Noatak River. In the Fairbanks area, the minimum age of the last interglacial deposits was also based on the presence of ash, which is younger than Old Crow tephra and older than 56 thousand years. The data obtained at Palisade are a useful reminder that minimum age estimates should be considered more reliable, even when the mass of stratigraphy, tephrochronology and paleoecological indicators seems more convincing due to the possibility of processing and redeposition of older organic material into younger sediments.^[127] 

      M. Fritz and co-authors ^[128-130] studied Late Pleistocene stratified and re-vein ice on Herschel Island. Ice veins often exhibit rather low values of ?18 ^O – from -26.5 to -30.7%, the average is -29.1%, the values of ?2H vary from -213 to -245%, the average is -232%, and d exc from 1.7 to -2.8%, the average is 0.1%.^[130]Such values of ?18 ^O-26% in Late Pleistocene ice veins, as M. Fritz and co-authors write ^[130], indicate a decrease in winter temperature during the formation of snow cover. Although the winter temperature increased from 16 kcal. thousand years ago, nevertheless, temperatures lower than now persisted in eastern Beringia up to 13 thousand kcal. years ago. The re-vein ice and fossil insect complexes of northern Alaska record a large-scale cooling of winter and summer temperatures in the time range from 12.8 to 11.5 thousand cal. years ago, which accounts for the cooling of the early Dryas. Similar low values of ?18 ^O, usually below -26 to -32, were found in the Late Pleistocene re-vein ice of Herschel Island, Taktoyaktak Peninsula, central Yukon, and Cape Barrow, Alaska.^[128-130] 

      But.Montet and co-authors ^[131] studied permafrost rocks, pollen samples, fossil insects, Arctic ground squirrels and the isotopic composition of pore ice in the Lucky Ledi sediments on the Klondike and found that the habitat was characterized by xerotic, steppe-tundra vegetation and deep seasonal thawing. The remains of thermophilic insects were found, which may indicate that soil temperatures during the growing season were comparable to modern ones. The collapse of the mammoth steppe ecosystem in this area of the Yukon began about 13,480 years ago. During this period, paleosoils actively developed, and the dominance of shrubby tundra was noted. The expansion of the shrub tundra in the Lucky Ledi area coincided with abrupt changes in climatic conditions, as evidenced by measurements of ?18 ^O pore ice in permafrost rocks. During the transition from the Pleistocene to the Holocene, the zotopic ratios also become more positive: the values of ?18 ^O increase from -29.1 to -21.2, and the values of ?2 H from -220.3 to -167.7.^[131]

A.V. Pitulko and E.Y.Pavlova^[132] continued archaeological research on a high-ice edom with powerful re-vein ice in the lower reaches of the Yana River. Detailed schemes of the spatial distribution of re-vein ice are presented. The results of long-term (since 2003) field observations and the results of radiocarbon dating are summarized (about 50 ^14s of dating are given). The taphonomic features that can modify archaeological data are considered. It is emphasized that secondary redeposition as a result of thermokarst processes leads to the transfer of material, both archaeological and geochronological, to a lower position than the initial hypsometric location. It is shown that partial thawing of frozen primary sediments can distort the stratigraphic sequence of sediments, which is reflected in the formation of pseudomorphoses along ice veins. Fragments of the edom strata in the lower reaches of the Yana are dated at different time intervals: 21.0-18.5 thousand years, 29.6-26.4 thousand years, 31.2-21.5 thousand years, 24.8 11.9 thousand years, 27.3-18.1 thousand years. Dating in the range of 28-27 thousand years prevails.^[132]

      An international team of authors^[133] compiled a circumpolar map of the distribution of edom strata, which was completed in a timely manner, but I would like to note that some areas are not reflected on the map, first of all  Eastern and Central Yamal and Chukotka, where Edoma has been described for more than 40 years,[3-6,14-17,19,85,87] this is an absolute omission of the authors of the map.

        Yu.K. Vasilchuk and A.K. Vasilchuk,^[134,135] having studied the edom strata containing coarse-grained material, came to a number of important conclusions for understanding the genesis of edoma:

(1). Syncryogenic strata with ice veins, including sediments, with layers of gravel and pebbles, or even completely saturated with crushed stone and gravel, are not an abnormal, but a common cryolithological phenomenon.

(2). Syncreogenic Late Pleistocene strata, saturated with coarse-grained material, are common not only in the harshest northern regions of the cryolithozoic of Russia. Powerful syngenetic veins in strata saturated with coarse-grained material are also found in southern regions, such as the valleys of tributaries of the Olekma, Biryusa, and Uda rivers in the Eastern Sayan, i.e. south of 56-54 ° C.

(3). Edom strata saturated with coarse-grained material in the state of Alaska and in the Yukon territory are exposed during the construction of highways (for example, along the Dalton Highway) and during the development of gold mines in the Klondike region.

(4). On the Kamchatka Peninsula, PLCs are found even in large-scale clastic volcanic rocks.

(5). The relatively rare occurrence of edom masses composed of sands or strata with an abundance of coarse-grained material is associated with a high degree of fluidity of such material. After thawing in the outcrops and in the presence of low connectivity, coarse-dispersed deposits quickly collapse and cover the exposed ice. Powerful PGLS are often found in the overburden walls of surface deposits of gold mining pits. Thus, it is possible to assume the widespread presence of powerful syngenetic ice veins in the Late Pleistocene massifs covered with talus.

(6). The presence of coarse sand, gravel and pebbles in the water strata in river valleys usually indicates the dominant role of alluvial riverbed processes in their formation.

(7). The presence of crushed stone and gravel in the edom strata on the slopes indicates the dominant role of slope processes and their formation below the outcrops of rock ridges.

(8). The role of Aeolian processes in the formation of edoma is often overestimated, because, for example, in sections of Late Pleistocene tuculans, powerful PGLS are usually not found. At the same time, the Aeolian transfer of material on the surface of polygonal masses of river and lake floodplains, marine laids, and the lower parts of slopes is one of the noticeable factors of sediment accumulation, which should be taken into account in research.

     Yu.L. Shur and colleagues ^[136] reviewed the history of the study of edoma for 150 years from the beginning of the XIX century to the 80s of the XX century. For more than 150 years, there were disputes about its origin. The erroneous opinions of prominent and influential scientists prevailed over the idea proposed at the end of the XIX century by Dr. Alexander von Bunge and delayed the solution of the problem of the origin of edoma for more than 50 years. History shows that just a hypothesis without verification methods has a very low probability of being fruitful. The authors believe that when there is an encounter with new and unusual phenomena, both outstanding scientists and young researchers have an equal chance to offer a valuable idea. Although the authors point out that after the mystery of the origin of edoma has been solved as a whole and it is clear that edoma is a syngenetic permafrost permeated with formed ice veins ^[136], it still seems to us that there is still a lot to be done in this direction and isotopic and radiocarbon studies should play almost the leading role the role in solving the problem of the genesis of edoma.

      A not very successful tradition has been established among some researchers: the study of the isotopic characteristics of re-vein ices, including edom ones, should be completed by generalizing the isotope data itself. But isotope data is not the goal of paleogeocryological research, it is rather a very good, even wonderful, tool, but not the goal. The aim in the study of syngenetic re-vein ice is the paleotemperature interpretation of isotopic data, and in the study of intracranial formation, segregation ice, ice cores of heave mounds, the purpose of isotopic studies is to identify the genesis of ice, establish the isotopic composition of the source water, determine the main and additional sources of nutrition, etc. Moreover, an inexplicable tradition has been established - even in the title of the article to include paleoclimatic reconstruction,^{[31,33,48,99,106,127]} and the reconstruction of paleotemperature itself, at the same time, should not be carried out, limiting itself to comparing isotopic data with each other. Perhaps the reason for this is the difficulty of paleotemperature interpretation of isotope data in glaciers, especially mountain ones, where strong wind transport and transformation of the isotopic composition of snow during solidification, self-diffusion, and large-scale plastic displacements of glacial masses really make paleotemperature interpretation difficult and sometimes impossible. But this in no way applies to isotopic data in syngenetic vein ice, which remain unchanged and are, at least in Eurasia, one of the best proxy data for paleotemperature reconstructions among all paleoobjects. Authors who use Yu's equations in their paleotemperature calculations.There are quite a lot of Vasilchuk^[7]: A.K.Vasilchuk^[137], N.A. Budantseva, A.A. Vasiliev, A.Y. Derevyagin^[27], A.N. Kotov, E.Y. Pavlova^[90], A.A. Pisisyuk^[100], V.V. Spector^[84], I.D. Streletskaya^[22], G.V. Surkova^[21], Y.V.Tikhonravova, N.V.Torgovkin^[84], M.Y.Cherbunina^[76], Yu.N.Chizhova^[10]. Paleotemperature calculations based on isotopic data were performed by K.Bern, K.E. Griffin^[113], M.A. Konyakhin, E. Kotler, H. Mayer, D.V. Mikhalev^[62], V.I. Nikolaev^[61], G.E. Oblogov^[18], E. Slot^[114], T.Porter.^[130], K.Holland. I would like to emphasize once again that isotopic data is not an end in itself, so the next step is paleotemperature reconstruction, which is necessary and logically justified. It is another matter with what accuracy it can be performed, this is a debatable issue and it is unlikely that it will ever be fully resolved. But let us recall F.'s aphorism.Bacon: "Truth nevertheless arises more from error than from obscurity," quoted by T. Kuhn in his book "The Structure of Scientific Revolutions."

Yu.K. Vasilchuk and A.K.Vasilchuk^{[138, 139]} summarized the interim results of paleoclimatic reconstructions in Northern Eurasia for edom strata dated 30-12 thousand years ago, which are as follows:

(1) Syngenetic ice veins were actively formed in the ice strata in the Arctic regions during the entire period 30-12 thousand years ago.

(2) The period of intensive growth of a particular ice vein massif in a particular region could differ from the neighboring region and even from the neighboring massif, and it lasted, as a rule, no more than 10-15 thousand years, then growth could either stop altogether or temporarily stop due to a change in the watering regime, and then resume again, but already within the framework of another sedimentation cycle.

(3) Isotope diagrams for syngenetic ice veins linked in time were constructed, and then the average values of ?18 ^O for time periods with increments of 2-4 thousand years were calculated, dating from the time intervals 30-28, 24-22, 20-18, 16-12 thousand years ago.

(4) Schematic maps of the distribution of ?18 ^O values in syngenetic ice veins dating from the time intervals 30-28, 24-22, 20-18, 16-12 thousand years ago have been constructed.

(3). Paleoreconstruction of the average January temperatures was performed, based on the values of ?18 ^O in syngenetic ice veins, for time intervals of 30-28, 24-22, 20-18, 16-12 thousand years, and schematic maps of the distribution of winter paleotemperatures for these time intervals for the entire territory of Siberia were constructed.

(4) Trends in the distribution of ?18 ^O in ice veins formed during the entire period 30-12 thousand years ago are similar to modern ones, i.e. the values of ?18 ^O became more negative in Late Pleistocene veins when moving from west to east by about 8-10 %, averaging: in Western Siberia -23, -25% (in in modern veins -17, -19%), in Northern Yakutia -31 to -33% (in modern veins -25, -27%); With further progress to the east, they increased from -28, -31 % in Northern Chukotka (in modern veins -22, -27%) and the central regions of the Magadan region, to -25 to -28 % in Eastern Chukotka (in modern veins -16, -20%).

(5) The average January temperatures over the Russian Arctic were ^about 8-12 °C lower than modern ones. In areas with variable climatic conditions, such as Chukotka, the average temperature range in January was up to 17-18 °C less than in our time.

(6) The Eurasian cryolithozone during the entire period 30-12 thousand years ago was similar to the modern cryolithozone of the Yakut sector.

(7) Trends in the distribution of ?18 ^O values in syngenetic ice veins in Siberia 30-12 thousand years ago indicate that the transportation of air masses of transport throughout the Subarctic zone of Siberia was similar to modern air transport. The influence of Atlantic air masses was dominant over the territory of northern Siberia, prevailing from the Yamal Peninsula to the northeastern part of Yakutia, but this influence may have been weaker then at present, due to the more frequent advection of cold and dry Arctic air. It is also likely that the influence of the air masses of the Pacific Ocean was insignificant in the eastern part of North Asia. Apparently, the continental anticyclonic regime dominated the areas of the Pacific coast, especially in winter.

These paleoclimatic reconstructions,^[138,139] supplemented by studies of older edom strata^{[37,38,42,43,52,64,66,68]} did not reveal any significant changes in the distribution of permafrost strata at different stages within the period 30-12 thousand years ago in northern Siberia. Uniform trends in the values of ?18 ^O in the re-vein ice in the vast territory of the north of Siberia indicate a uniform atmospheric circulation at that time. This, in turn, serves as clear evidence of the absence of powerful glacial covers on the plains of Siberia, the presence of which could significantly affect not only the distribution of ?18 ^O values in syngenetic ice veins, but also the very fact of the development of powerful ice veins, which of course do not form under the glacial cover.   

Conclusions

1. Edoma research in the second and third decades of the XXI century was significantly enriched due to the even wider use of high-precision measurements of the content of stable oxygen and hydrogen isotopes in re-vein ice, as well as the use of AMS radiocarbon dating of microinclusions of organic material and CO 2 inclusions in vein ice.

2. A notable event of this period was the comprehensive study of the Edoma of the Batagai section, the largest cryolithological object on Earth, and possibly one of the most ancient, the underlying Edoma strata in this section have been dated to more than 600 thousand years.

3. In-depth studies of biomarkers, DNA, PAHs, gas components, etc., which began during this period and are rapidly developing, are promising for studying the nature and conditions of the formation of edomic strata.

4. Isotopic data is not an end in itself for edoma research, paleotemperature reconstruction using them is necessary and logically justified. Improving research in order to increase the accuracy of paleotemperature reconstructions is one of the pressing problems of studying edoma.