The Lena River provides important records for understanding the Quaternary history of North-East Siberia. At present, the structure, origin and age of the elements of the Lena River valley remain unresolved. This article presents the results of lithofacies analysis and absolute dating of the Ust-Buotama section exposing the Fourth (Bestyakh) fill Terrace in the middle Lena River valley. Three stratigraphic units have been recognized in the section: lacustrine–alluvial deposits at depth of 120–85 m depth from the surface correlated with the Middle Pleistocene Mavra formation of Central Yakutia; eolian deposits of the Late Pleistocene D’olkuma formation (depth 85–23 m), and eolian deposits of the Holocene wind-blown dunes (from the depth of 23 m to the surface). First quartz and K-feldspar ages have been obtained for the section using luminescence dating. The age relations and standard tests have shown the reliability of the chronology obtained. This chronology suggests that sediments of the Mavra formation were deposited no later than 300 ka, and their stratigraphic position implies a preliminary correlation with the Tobolsk time of the Middle Pleistocene (MIS 11-9). Deposition of the D’olkuma formation took place from late MIS 3 (29–30 ka) to the late MIS 2 (14–15 ka), reflecting the period of eolian activity when sand dunes and sheets were formed. The periods of eolian accumulation alternated with deflation periods at the end of the Late Pleistocene. Short periods of stabilization of the eolian landscape are indicated in the section by poorly developed paleosoils. The uppermost part of the section consists of the Late Holocene dune sediments which accumulation started ~400 years ago during the Little Ice Age. These findings infer that the Bestyakh Terrace is not a fluvial terrace in the classic sense, but rather the remaining part of a complex deflational and depositional plain. Much of the terrace sediments appear to have been formed under subaerial conditions in cold, dry environments of the late Pleistocene.

surface pattern of permafrost area in the Tibetan Plateau, with 15-20 m polygons, resembles the patterned ground of the Arctic periglacial loess plains in northeastern Eurasia and North America. However, unlike the Arctic plains, it consists of semi-stabilized modern sand dunes, up to 2.5-3.0 m high, and U-shaped epigenetic ice wedge casts inherited from an ancient polygonal network on the surface of a 10-12-m terrace of the Yangtze River. The polygonal dunes and the U-shaped sand wedges were studied in the Yangtze headwaters in the vicinity of the high-altitude research station Bei-Lu-Xe. The polygons have desert pavement floors with ventifacts, composed of Late Pleistocene alluvial gravel and debris. The dunes and wedges consist of well sorted quartz-carbonate sand with an average grains size of 2.0-2.2 mm. Ground Penetrating Radar surveys in the area revealed the permafrost table at depths varying from 2 to 4 m below the dunes. The polygonal dunes may have formed by biogenic-aeolian deposition over an ancient system of ice wedges.

We present the first record of Holocene fossil insect assemblages from Central Yakutia. A stratigraphic sequence in the locality within the Vilyuy River valley is a buried oxbow. The late Holocene water body inherited an impervious stratum from the late Pleistocene. The organic layer preserved rich fossil assemblages of macrofossils including insects and other invertebrates, plants, and charcoal. The ancient flora and fauna include species that are common in Yakutia as well as those that are rare and absent in the region. The most abundant finds are leech cocoons and bogbean seeds. The macrofossils of some insects were found along with remains of their host plants. Despite the absence of intensive human land use in the area, traces of fires were recorded. The oxbow represents the environment of a floodplain wetland that developed separately from the ecosystem of the adjacent sand dunes.

Paleocarpological complexes from sections of Central Yakutia including from the aeolian Dyolkuma Formation were established for the first time. The original method of sampling from deposits of deflation lakes is given. The complexes of the Dyolkuma Formation generated in the last thermochron and cryochron of the Late Pleistocene were compared with each other, as well as with complexes of alluvial formations (MIS-3) and the Yedoma Formation (MIS-2) synchronous with them. Southern thermophilic aliens were found in samples from sediments compared with MIS-3. The data obtained made it possible to significantly supplementand define the previously performed paleogeographic reconstructions. Thermoarid steppe formation was determined against the background of the development of forest communities in the last Neo-Pleistocene thermochron in the conditions of intrazonal landscapes,within which the thermal erosion of permafrost was manifested; and the existence of woody vegetation areals in the subsequent cryochron was also noted. The research results can serve as a basis for stratifying similar deposits and performing correlations with other sections of the area.

Продолжение рассказа о комплексной научно-исследовательской российско-датской экспедиции, организованной летом 2021 г. для изучения хронологии четвертичных оледенений Восточной Сибири. В статье описываются ледниковые формы рельефа и отложения, лессово-ледовые образования (едомная свита) с ископаемыми ледяными жилами, курумы, а также рассказывается о специфике работы полевого отряда и о природе Западного Верхоянья.

Приводится аналитический обзор монографии Владимира Романовича Алексеева, посвященной курумам - специфическому типу покровных грубообломочных отложений, наиболее широко распространенных в пределах горной криолитозоны Северной Азии.

The results of long-term studies of a group of aufeis-forming Buluus groundwater sources are given. A stow, which has been formed by the spring, contains the drainage area of the suprapermafrost–intrapermafrost aquifer, which is widespread in the sand deposits of the bestyakhskaya terrace of the Lena River in Central Yakutia. The analysis of observations of 1964–2017 showed stable water chemistry in Buluus spring at the long-term scale. Considerable seasonal variations of water chemistry are typical of low-discharge springs, which start functioning after becoming free of aufeis. The spring water also shows higher concentrations of lithium and fluorine. The possible causes of the different chemistry of spring water are discussed, with special attention paid to the local activity of rock freezing and thawing processes in the aufeis valley. It is shown that groundwater samples are to be taken from all springs in the areas of their group discharge with the aim to assess the effect of natural and technogenic factors on the permafrost–hydrogeochemical conditions.

The areas of dune massif evolution are widely spread in high latitude regions of the northern hemisphere, including Canada, Alaska, Europe and Russia. R.F. Black [1951] points out that Quaternary eolian sediments which consist for the most part of windblown sand and loess cover more than half of the areas of Alaska and Canada. Within the Arctic coastal plain of Alaska alone, the area covered by Late Quaternary dune massifs exceeds 12,000 km2 [Wolfe et al., 2011]. A considerable expansion of the coeval dune massifs into the North Eurasian cryolithozone is observed within the areas of the Polar Urals framing [Astakhov and Svendsen, 2011], the West Siberian plains [Velichko and Timireva, 2005], Transbaikalia and Baikal [Ivanov, 1966; Ufi mtsev et al., 1997; Vyrkin, 2010]. Vast massifs of undulating and cross-bedded quartz loamy sands (sand partcles >90 %) (D’olkuminskaya series) reaching 15–25 m in thickness are known in the Lena, Vilyuy basins and their tributaries; in Central Yakutia, they occupy up to 30 % of some regions [Pavlov, 1981; Kolpakov, 1983; Kut, 2015]. Due to the 250–400 m-thick continuous permafrost with temperatures of –4...–5 °С along peryphery of the area of their distribution, these are characterized by a unique presence of intrapermafrost taliks reaching magnitude of several tens of meters in thickness, whose discharge area represents high-quality drinking water sources [Shepelev, 2011] and favors the formation of thermo-cirques, a product of the suff osional (subsurface erosion) processes and icing. In the lower reaches of the Vilyuy river basin, the most well-known are the year-round Makhatta springs with a fl ow rate of about 760 L/s. Both the age and origin of the D’olkuminskaya series has been a disputable question for over half a century. A number of researchers interpret them as dune covers formed as a result of drastic and rapid desertifi cation during the last Late Pleistocene cryochron [Kolpakov, 1983; Alekseev et al., 1984; Kamaletdinov and Siegert, 1989; Kamaletdinov and Minyuk, 1991; Waters et al., 1999; Galanin et al., 2016; Pavlova et al., 2017]. Others believe them to be of alluvial-lacustrine origin, which is indicative of their deposition in pluvial (moderately wet) environments [Soloviev, 1959; Alekseev, 1961; Ershov, 1989; Bolshiyanov et al., 2016; Spector et al., 2017]. According to the most extraordinary hypotheses, these landforms provide evidence of glacial-hydrogenic catastrophes (fl oods) – severe fl ooding events (surges) associated with bursts of barrier-glacial basins at the turn of the Late Pleistocene and Holocene [Spector et al., 2017]. It is also suggested that cross-bedded loamy sands formed as a result of late Pleistocene marine transgressions [Pomortsev et al., 2017]. The accumulated to date results of absolute age determinations unambiguously indicate to the Late Pleistocene (MIS-2) age of the D’olkuminskaya series [Alekseev et al., 1984; Kamaletdinov and Siegert, 1989; Kamaletdinov and Minyuk, 1991; Waters et al., Kriosfera Zemli, 2018, vol. XXII, No. 6, pp. 3–14 http://www.izdatgeo.ru

On the basis of about 430 analyses, the 18O and D compositions (%o) of atmospheric precipitation, ground ice, surface and inter-permafrost underground waters of cryogenic-aeolian landscapes of Central Yakutia (Eastern Siberia) are discussed. Precipitation compositions here demonstrate a large annual variation (from -6.12 to -45.0 % for δ18O, and from -72.1 to -350.1 % for δD), and they are described by the Local Meteoric Water Line according to the equation δD = 7.81518O - 1.57). In winter and in the process of spring melting, the snow storage is subjected to a significant evaporative fractionation, that is expressed by the equation δD = 6.85518O - 31.9. The heaviest and deuterium-depleted compositions (δ18O = -19.3 %, δD = -160.9, dexc = -6.7 %) are found in the last snow patches in early June. The lightest compositions similar to the present-day winter precipitation (snow) are characteristic of the polygonal wedge ices (PWI) of the Central Yakutia. The most lightweight (from -30 to -34 % for δ18O, and from 240 to 275% for δ D) were established to be typical for the ancient PWI, dated by the first half of the Late Pleistocene (MIS 3-4). Heavier compositions (δ18O = -27.2±1.4, δD = -215.8±8.5, dexc = 1.7±3.1 %) with obvious features of evaporative fractionation correspond to younger PWI (MIS 2-1). The heaviest compositions (δ18O = -12.2±0.7, δD = -99.2±4.7, dexc = -2.0±0.8 %) and high angular coefficients of approximating equations were determined in the investigated cave ices of sublimation origin, that implies the atmospheric origin of them. The current processes of evaporative fractionation are the most intensively reflected in the waters of aeolian lakes (δ18O = -11.8±3.5, δD = -120.2±18.4, dexc = -25.8±10.5 %), and the compositions are described by the regression equation 5D = 5.52 δ18O - 54.12 (R2 = 0.97). The phenomenal objects of the cryogenic-eolian landscapes of the Central Yakutia are high-debit underground sources. Among all other components of the water flows, composition of these sources is the most stable (δ18O = -21.6±0.8, δD = -172.6±5.1, dexc = 0.23±3.0 %). The regression of compositions of the largest underground source Bulus is approximated by the equation 5D = 6.31 δ18O - 36.7 (R2 = 0.78), that is indicative to significant evaporative fractionation and close relation with the aeolian lakes in the alimentation area.

The history of permafrost landscape map compilation is related to the study of ecological problems with permafrost. Permafrost-landscape studies are now widely used in geocryological mapping. Permafrost-landscape classifications and mapping are necessary for studying the trends in development of the natural environment in northern and high-altitude permafrost regions. The cryogenic factor in the permafrost zone plays a leading role in the differentiation of landscapes, so it must be considered during classification construction. In this study, a map's special content was developed using publications about Yakutian nature, archive sources from academic institutes, the interpretation of satellite images, and special field studies. Overlays of 20 types of terrain, identified by geological and geomorphological features, and 36 types of plant groupings, allowed the systematization of permafrost temperature and active layer thickness in 145 landscape units with relatively homogeneous permafrost-landscape conditions in the Sakha (Yakutia) Republic. This map serves as a basis for applied thematic maps related to the assessment and forecast of permafrost changes during climate warming and anthropogenic impacts.

About 550 rock glaciers of different types were identified on the basis of remote sensing and field studies in the Southern Part of the Providenskiy mountain massif (the Chukchi Plateau). The measured occurrence frequency of rock glaciers of about 8 units/km2 is the highest in the North-East Asia. All known morphodynamic types of rock glaciers were found: tongue-shaped cirque-associated, lobate-shaped slope-associated and complex ones. Rock glaciers were found over the entire elevation range starting from the sea level. The slope-associated multi-lobate rock glaciers of abnormal sizes, as well as the ice-ground dams are the most widespread ones and they concentrate in linear zones along the sides of neotectonic grabens and fracture zones. They were distinguished as a particular type of fault-associated rock glaciers. A specific feature of rock glaciers of the Providence massif is the thawed bed that causes water infiltration under the front generations, which is similar to “warm”ˮ glaciers and rock glaciers of Europe and Central Asia, while in the Mountains of Northeast Asia within the continuous permafrost zone rock glaciers have frozen bed, and their temperatures are significantly below zero. The age of active rock glaciers of Povidenskiy massif is not more than 2–2.5 kyr. We attribute their formation to the specific features of the Last Glaciation decay under the conditions of Marine Arctic climate. The increasing role of cryogenic mass movement during the Late Glacial Stage promoted the burial of ice and frozen moraine blocks in the glacial cirques and at valley sides and predetermined their subsequent transformation into rock glaciers.

The data of the comprehensive study of deposits of dune sand massifs—the Makhatta and Kysyl-Syr Tukulans—in the Vilyui River Basin (Central Yakutia) are given. We have revealed the structure and preliminarily reconstructed the evolution of tukulans in the Vilyui River basin and the environmental conditions of the surrounding area in the Late Pleistocene–Holocene period (the chronological period of the formation of tukulans) on the basis of lithological and palynological data and 17 radiocarbon datings. It has been revealed that the tukulans should be assigned to eolian deposits formed on sediments of complicated facial structure. We have distinguished four stages in the vegetation evolution within the last 40000-year period and three chronostratigraphical phases in the development of dune massifs.