The fluctuations of the forest/tundra boundary are among the most significant indicators of climate change in the Arctic. The most reliable information regarding the historical position of this boundary is obtained through spatial-temporal analysis of wood remains collected from permafrost deposits. We conducted extensive research in the tundra zone of northwestern Chukotka, aiming to establish a comprehensive collection of fossil wood samples; to identify these samples to the genus/species levels; and to date samples through radiocarbon dating (over 60 dates) and uranium-thorium methods.Our findings demonstrate that trees extended into the present tundra zone in the Rauchua-Chaun Lowland at least twice during the Last Interglacial and the Holocene. During the Last Interglacial (MIS-5), larch forests (taiga) interspersed with birch were prevalent in what is now tundra. In the early Holocene (11,000-8700 cal BP), riparian forests featuring willow, & scy;hosenia, and poplar, along with tree birch, thrived in river valleys

Tianzuo hydrothermal field (THF) in the eastern Southwest Indian Ridge (SWIR) is reported as an inactive ultramafic-hosted system and fragments of massive and altered sulphides were recovered from the hydrothermal field at (27 degrees 57 ' S, 63 degrees 32 ' E). The sulphide formation happened in the THF in two phases, at both high-temperature and low to medium temperature environment. The mineral assemblages in massive sulphides suggest the contribution of high-temperature hydrothermal fluid in the ore formation process. The presence of covellite and Fe-oxy-hydroxides in the altered sulphides indicates a low to medium-temperature environment and subseafloor alteration of fluid by seawater mixing. Elevated TREE contents with no significant Eu anomaly in both massive and altered sulphides further supports the subseafloor hydrothermal fluid mixed with seawater. Elevated Pd and Rh concentrations, along with their positive correlation with Cu, suggest Pd and Rh fractionation during the seawater-hydrothermal fluid mixing. 230Th/U dating results of massive hydrothermal sulphide samples give the age of 24 kyr (+2.4) and 15.6 kyr (+0.8), and an incomplete sampling demonstrates a possible minimum age of the vent field.

The chronology of the Mikulino Interglacial and its individual phases has been the subject of discussion. The goal of this study is to evaluate the time limits of the main stages of the Mikulino Interglacial on the Russian Plain according to 230Th/U dating and paleobotanical studies of lake and peat sediments from the known sections located in Tver Province on the Bolshaya Dubenka River, Malaya Kosha River, Granichnaya River, and Sizhina River (Kileshino-2 section). An improved geochronological approach has been applied to identify the layers that are suitable for the 230Th/U isochronous approximation. Together with palynological and carpological studies, this made it possible to date the layers corresponding to relatively narrow time intervals in the development of plant formations at the different stages of the Last Interglacial. New paleobotanical studies of buried lake and peat sediments from the sections located on the Bolshaya Dubenka River, Malaya Kosha River, and Granichnaya River allowed us to reconstruct the vegetation development of the Mikulino Interglacial in the interval of pollen zones M1–M7, i.e., more pollen zones have been analyzed and in greater detail than in the 1960s–1970s. A chronological scheme of the main stages of the development of vegetation in the Mikulino Interglacial is proposed based on the results of 230Th/U dating and paleobotanical studies of the deposits from the sections in Tver Province together with previously published data obtained for the Nizhnyaya Boyarshchina section in Smolensk Province. The beginning of the Mikulino Interglacial is recorded at about 130–126 ka. Its first phase, corresponding to the M2 zone, ended about 118 ka. The preoptimal stages of vegetation development (zones M3 and M4) fit into the time interval of about 118–112 ka, while the climatic optimum of the Interglacial (zones M5 and M6) began about 112 ka and ended about 100 ka. Thus, the duration of the Mikulino Interglacial was likely to be at least 25 000 years.

The chronology of the Mikulino Interglacial and its individual phases have been the subject of discussion. The goal of this study was to evaluate the time limits of the main stages of the Mikulino Interglacial on the Russian Plain according to ²³⁰Th/U dating and paleobotanical studies of lake and peat sediments from the known sections located within the Tver region on the Bolshaya Dubenka River, Malaya Kosha River, Granichnaya River, and Sizhina River (“Kileshino-2” section). An improved geochronological approach has been applied to identify layers suitable for the ²³⁰Th/U isochronous approximation. In combination with pollen and carpological studies of the deposits, this made it possible to date units corresponding to relatively narrow time intervals in the development of plant formations at different stages of the Last Interglacial. New paleobotanical studies of buried lake and peat sediments from the sections located on the Bolshaya Dubenka River, Malaya Kosha River, and Granichnaya River allowed us to restore the vegetation development during the Mikulino Interglacial in the interval of pollen zones M1–M7, i.e., more pollen zones have been analyzed and in greater detail than in 1960–1970. A chronological scheme of the main stages of vegetation development in the Mikulino Interglacial is proposed based on the results of ²³⁰Th/U dating and paleobotanical studies of organic-rich deposits from the Tver region sections in combination with previously published data obtained for the “Nizhnyaya Boyarshchina” section from the Smolensk region. The Mikulino Interglacial had begun about 130–126 kyr ago. Its first phase, corresponding to the M2 zone, ended ca. 118 kyr ago. The pre-optimal stages of vegetation development (M3 and M4 zones) fit into the time range of ca. 118–112 kyr ago. The climatic optimum of the interglacial (M5 and M6 zones) began ca. 112 kyr ago and ended ca. 100 kyr ago. The duration of the Mikulino Interglacial was probably at least 25 thousand years.

Large paleochannels with sizes far greater than the modern ones are widespread on the floodplains and low terraces of rivers in the Volga basin. These are indicators of higher values of river runoff in the end of the latest glacial epoch. The assessment of the time interval of the epoch of abundant runoff requires the determination of the age of large paleochannels. With this in view, drilling of large paleochannels has been carried out all over the Volga basin. Radiocarbon dating of the channel alluvium was carried out. The majority of dates lied within the time interval 14.5–17.0 thousand years ago, which suggests the conclusion that the epoch of abundant river flow approximately coincides in time with the early Khvalynian transgression of the Caspian Sea.

— The results of 230 Th/U dating of massive sulfides and metalliferous sediments (288 and 245 analyses, respectively) of hydrothermal sites in the northern equatorial area of the Mid-Atlantic Ridge (MAR) from 12° to 20° N are presented. The maximum and average ages of sulfides are 223 ± 38.2 and 80.5 ka, respectively. The comparison of ages of massive sulfides from various MAR hydrothermal sites showed asynchronous stages of hydrothermal activity along the ridge axis indicating the features of tectonic activity and magmatism, which control the hydrothermal activity within each region. The glaciation periods, which record the activation and low- and high-temperature hydrothermal activity, are an exception. A direct positive correlation between the age of a hydrothermal site and its distance from the axial ridge zone is typical of mafic-related hydrothermal sites in contrast to ultramafic-related hydrothermal sites, which is related to the different scenarios of the formation of these two types of sulfide mineralization within slow-spreading ridges. The ages of sulfides and sediments have been jointly analyzed based on the example of the Pobeda and Semenov hydrothermal sites. The interpretation of data on sediments indicates the continuous character of hydrothermal activity, which is partly supported by the age of sulfides.

Speleothems are unique archives of information on climate, geomagnetism, and environmental conditions of the past, and have been successfully used for paleoclimatic and paleomagnetic studies in the last two decades. The uniqueness of these geological objects lies in the peculiarities of their formation and preservation of a wide range of geochemical, geological and geophysical proxies, and, most importantly, in the ability to obtain time series of the corresponding characteristics in an unprecedentedly accurate resolution using isotope-geochronological dating methods and incremental chronology. This paper presents the first results of dating the Vor speleothem from the Vorontsovskaya Cave (Krasnodar region), which preserved a record of the geomagnetic excursion, obtained by 230Th/U α-spectrometry, 14C dating, and incremental chronology. Such studies have been carried out in Russia for the first time. Despite the limitations of using the methods of isotope geochronology, it was possible to obtain an upper limit on the age of the excursion, which probably occurred no earlier than 5500–6000 years ago. By the method of incremental chronology, the duration of the main phase of the excursion Vor – 871 ± 16 years – was determined with great accuracy.

Comprehensive study of sections of mares in the Bolshaya Ussurka River basin has allowed highlighting climate changes over the past 2900 years. Reconstructions are based on the data of botanical, diatom, and palynological analyses and radiocarbon dating. The moisture content changed most significantly. Periods of prolonged droughts, which coincided with the weakening of the summer monsoon, were established. A long dry period continued from about 2900 up to 1360 yr BP. Dry conditions did not exclude floods caused by heavy rain caused by the passage of typhoons or deep cyclones. The Medieval Warm Period and Little Ice Age were humid and characterized by increased cyclogenesis. There were short-term fluctuations in humidity: droughts about 530–460 yr BP ago, then conditions became more humid about 400 yr BP and especially about 330–260 yr BP ago. The age ranges of periods with different flood activity and paleo-fires were determined. Events were correlated with data on regional and global events. A different response of mountain and bog landscapes to short-period climatic changes has been established. The role of the Korean pine in forest vegetation changed significantly; its distribution is controlled by changes in the hydroclimatic conditions. The optimum environments for the development of Korean pine forests were 780–530 yr BP ago. The role of Korean pine decreased during dry phases and after fires. The most variable vegetation of the mares was during the Little Ice Age. Modern anthropogenic changes in landscapes are also recorded in the sections. The scale of floods has significantly increased under human impact.

Studies of peat stratigraphy in the upper reaches of the Milogradovka River made it possible to restore changes in humidity as a source of moisture in the middle Sikhote-Alin over the last 3400 years. High-resolution reconstructions were based on the data from biostratigraphic analyses (botanical and diatom); the ash content of peat was also studied. Radiocarbon dating of the events was performed using an age-depth model. In the upper part of the section, the B-Tm cryptotephra of the Baitoushan caldera-forming volcano was found, which was identified by the volcanic glass chemical composition. Prolonged rains are assumed to cause a massive landslide with the formation of a dam and a shallow reservoir turning the river valley into a swamp. Bioindicators of changes in humidity in the river valley and the occurrence of floods were identified. Events were correlated with the data for the main watershed of the Sikhote-Alin, mountainous plateaus, lakes on the slopes of the ancient Solontsovsky volcano and the eastern Primorye coast. The peat section in the valley is shown to record in more detail the hydrological changes associated with the nature of cyclogenesis. A relationship was revealed between paleoevents and anomalies of large-scale atmospheric circulation. Long dry phases occurred during global cooling and were accompanied by aridization in East Asia, caused by a decrease in the intensity of the East Asian summer monsoon. Studies show that floods occurred in the summer to autumn season even in dry phases. The phases of flooding were associated with the activation of the summer monsoon, as well as more intense cyclogenesis. The most complex climate rhythm was established for the last 1340 years.

—The rarely visited islands of the Kara Sea in its Pritaymyr zone have been studied during a geological survey on the scale 1:1,000,000. The Quaternary deposits of the islands are represented by the Middle Neopleistocene to Holocene marine, lacustrine-marsh, alluvial and slope sediments. New radiocarbon and uranium-thorium dating has been obtained for the Quaternary sediments, using organic remains (wood, peat, mollusk shells). For the first time, dating on sandy sediments was obtained for the islands, using the method of infrared optically stimulated luminescence (IR-OSL). The sediments of marine terraces are of the greatest distribution on the islands; these sediments can be correlated with the Karginsky (MIS 3) horizon, lacustrine-marsh sediments and deposits of the cover complex, containing flora remains, mainly the Holocene.

Temporal evolution of hydrothermal processes used to be reconstructed based on chemistry and chronology of the sediments around vent fields. However particle-by-particle deposition of metalliferous sediments proximal to sulfide mounds is usually superimposed by mass-wasted events. Quantitative assessment of the relative amount of slumped sulfide debris and plume fallout matter in metalliferous sediments has been done for similar to 83 kyr on Pobeda hydrothermal site at the 17 degrees 08' N, Mid Atlantic Ridge. Three sediment cores have been investigated for uranium series isotopes and rare earth elements (REE). Their distribution patterns with an enrichment in heavy REE, a weak positive Eu, and negative Ce anomalies give evidence to the contribution of slumped sulfides from nearby edifices. The Th-230-U radiochronology dataset for distal and proximal metalliferous sediments and sulfide deposits from different Atlantic and Pacific hydrothermal sites allowed for the distinction between sediments containing oxidized sulfide debris and those derived predominantly from plume fallout oxyhydroxide particles in terms of Th-230/Fe vs. U/Fe ratios. The calculated amount of plume particulates and the sedimentation rate for each core allowed accurate temporal reconstruction of the hydrothermal activity within the Pobeda site through a novel approach.

This article presents new data from geochronological study the lake-bog organic-rich layer from of the “Ilya Prorok” sequence (Upper Volga Basin, Tver Region) that is a one of the reference sections located on the Russian Plain. Ideas concerning the age and climatic conditions of these organic-mineral deposits formation changed significantly over the long history of their study. As a result, the viewpoint about the belonging of this layer to the Likhvin time began to prevail. However, it is still unclear with which marine isotope-oxygen stage (MIS) the Likhvin interglacial can be compared. According to the paleobotanical study of the lake-bog from the Ilya Prorok section, it was confirmed that the lower part of the lake-bog layer can be attributed to the warm phases of the Likhvin interglacial, while its upper half was deposited during the transition to cooling after the interglacial period. For the first time, the radioisotope age of the buried lake-bog deposits of the reference section “Ilya Prorok” have obtained. According to the data of direct 230Th/U dating, the formation of the sequence probably began no earlier than ~ 326–260 Kyr ago. The 230Th/U age of the buried peat bog from its upper half, according to the results of applying the isochronous approximation, can be correlated with the interval ~256–225 Kyr ago. According to these data, the Likhvin deposits were formed no earlier than MIS-9.

We received a unique material on the natural environment development for the last 12 400 cal. yr. BP in the central part of Iturup Island. The high-resolution paleoreconstructions were based on multi-proxy study of the paleolake sediments found on the plateau (height 400–420 m) located northwest of the Baransky Volcano. For the first time, a record of paleogeographic events was obtained for the Late Glacial and the early Holocene. The age model is based on 9 radiocarbon dates. Diatom analysis allowed us to distinguish 11 stages of lake-swamp evolution. The paleolake reached its maximum depth at ~9 890–7 900 cal. yr. BP and became extinct at 1 400 cal. yr. BP. The stages of vegetation development and the factors determining the change of landscapes have been restored. The Younger Dryas cooling recorded in Iturup was characterized by humidity changes. The role of forest vegetation abruptly increased at the Pleistocene-Holocene boundary of ~11 470 cal. yr. BP) under warmer climatic conditions. Distribution of shrub pine as an indicator of stable snow cover was analyzed. Dark-coniferous forests existed in the mountainous part of the island since the Late Glacial and were most widely developed in the early Holocene. The onset of birch forest expansion at 6 200 cal. yr. BP was associated with the intensification of volcanic activity and frequent ash falls. A number of cold events were identified, whose manifestations were enhanced by the weakening of the Soya warm current. The intensive transfer of allochthonous pollen from the southern Kuril Islands and the Japanese Islands at 3 540 cal. yr. BP is a sign of cyclogenesis intensification in the Kuril Islands. Manifestations of the Holocene climatic rhythms in the landscape development of the Iturup mountainous part, as well as the influence of warm and cold currents and other regional factors, were analyzed.

In 1996-1999, with our participation, a number of sections of the bog sediments in Northwestern Russia were studied to develop a chronology of the stages in the vegetation and climate evolution during the Holocene. However, the resulting chronology failed to take into account the error in determining the radiocarbon age arising due to the changes in the concentration of atmospheric radiocarbon. To allow for this error and make the chronology more precise and reliable, here we used C. Bronk Ramsey's model based on comparing the radiocarbon chronology of the surveyed section with the calibration curve chronology. Thanks to this model, we were able to calculate the calibrated (modeled) age span of the entire series of radiocarbon dates that had been previously obtained by us for samples taken from the thickest (6.4-6.7 m) sediment layers of the raised bogs Nikolsko-Lyutinskoe, Shirinsky Mokh, and Sambal'skoe in Northwestern Russia. The deviations of the average annual temperature from its present value (Delta T, degrees C), which had been represented in our earlier works as a graph, were converted into digital values and employed to define the modeled age that is most approximate to the calendar one and the corresponding values of Delta T for all the dated samples. The Delta T values were reconstructed for a period of 200-11000 cal yr. The modeled age of the cooling and warming stages was compared with the age of the stages of low and high solar activity established by counting the number of sunspots and by determining the concentration of cosmogenic isotopes (C-14 in tree rings of known age and Be-10 in polar glaciers). It was revealed that, within the error in the measured values of age and Delta T, the short-term changes in the average annual temperature occurred simultaneously at three sites of the bog sediments under consideration. The identified changes in the average annual temperature turned out to be synchronous with similar temperature changes in the Northern Hemisphere over the last 1000 years, as well as with the chronologies developed from the GISP 2 polar ice cores and the mountain glacier advances. In general, the comparison of the modeled age of the cooling stages with the corresponding grand minima of solar activity demonstrates the synchronicity of the periods of cooling and low solar activity during the Holocene. It was concluded that short-term climate change depends mainly on variations in solar activity, which is important for predicting and modeling climate shifts.

The paper presents the results of studies of authigenic carbonates sampled in the near-surface sediments of the gas-hydrate-bearing CHAOS structure located on the western slope of the Deryugin Basin in the Sea of Okhotsk. Carbonates were at different stages of formation, the most common morphological forms of which were concretions. Microscopic studies have shown that the concretions are formed by pelitomorphic carbonate cementing the terrigenous clay-clastic matrix and organic detritus. According to X-ray phase analysis, the dominant mineral composing nodules is cryptocrystalline high-Mg calcite (14.2-16.9 mol% Mg). Based on the geochemical modeling the intervals of the sediments with favorable conditions for the formation of basic carbonate minerals (aragonite, calcite, and dolomite) were identified. Almost over the entire area of the structure, the formation of carbonates occurs at more than 1m and up to 5m sub-bottom depths. In the central part of the structure (station LV31-27GC) the formation of carbonates is also possible in the upper part of the sedimentary section - from 0 to 1,5 m. On the basis of balance calculations of the δ13C isotopes content in nodules, the contribution of the main carbon sources involved in their formation was estimated. These sources turned out to be organic matter and microbial methane in a ratio of 67.5: 32.5. It was found that the conversion of carbon dioxide into bicarbonate ion occurs under conditions of early diagenesis due to the interaction of the fluid with aluminosilicates. Calculations of the isotopic composition of pore waters (the main source of oxygen in carbonates) and paleotemperatures indicate crystallization of carbonates at low (close to 0 ° C) temperatures. Based on 230Th/U-dating of carbonates, the age of the studied unloading source was determined as ~ 3.5 thousand years. It was found that the CHAOS structure is one of the “youngest” on the northeastern slope of the Sakhalin Island.

In this paper, the authors report results of a detailed technological and typological analysis of the Epipalaeolithic assemblages from three stratified sites in the North Caucasus that were excavated in recent years at a modern scientific level with application of sediment water screening, which allowed to obtain numerous microlithic artefacts. The lithic analysis of the assemblages indicates a gradual development in the knapping technology, which resulted in the first application of the pressure flaking technique in the final Epipalaeolithic, and innovations in the tool set, particularly in the assortment of geometric microliths. The authors consider the stone industry transformations at the edge of Pleistocene and Holocene in the context of cultural continuity during the final Epipalaeolithic and up to the beginning of the Holocene in the region.

Despite considerable progress in understanding Late Pleistocene and Holocene palaeoenvironmental changes worldwide, there are still very few such data for the Far East, and Kuril islands, in particular. Here, the sea level rise during the Late Glacial-Holocene transition was accompanied by a loss of the land connectivity culminating into the development of isolated islands. The ecosystems evolution and importance of isolation for vegetation dynamics on islands are still insufficiently understood. We investigated a unique natural record of environmental change since 14 ka has been recently discovered in lake-mire complex on Kunashir Island. The sediments include 12 tephra layers from Kunashir and Hokkaido volcanoes. The lake level was highest during warmer and humid climate of the Allerod. Diatom assemblages indicated the higher lake level between 12 730-12 160 cal yr BP. The first half of Younger Dryas was characterized by heavy snowfalls. Cooling attributed to the Younger Dryas in the Southern Kurils was less distinct than on the continent. The pollen assemblages recorded changes in vegetation on the land bridge. At the end of the Pleistocene large areas were occupied by birch forests and shrub pine. The broadleaf species first appeared at the end of Allerod. Starting from the Pleistocene-Holocene transition and during the early Holocene, the role of conifers sharply increased. In the middle Holocene the proportion of broadleaf trees in forests increased. Coniferous forests became abundant during the Little Ice Age. Short-tern climatic fluctuations correlate well with regional pattern, particularly with fluctuations of the moisture supply.