A comprehensive compositional analysis of the alluvium from the river with active gas-hydrothermal manifestations was carried out for the first time. Geysernaya river alluvium is characterized by: poor roundness of boulders and pebbles (grades 1–2), poorly sorted fine-clastic component, abundance of rock fragments and intergrown minerals even in the fine sand fraction. All these indicate the sediment weak disintegration with significant amount of slope material in it, including redeposited by mudflows. The high content of smectite-zeolite and other newly formed (secondary) minerals aggregates (up to 70% of the light fraction 0.1–0.25 mm in size) and altered rock fragments (up to 70–80% in the pebble fraction of alluvium) indicate that a gas-hydrothermal activity significantly impact the bedrock and alluvium weathering within the thermal fields. The material accumulates predominant in the areas of: (1) active delivery of slope material (temporary dams), (2) the longitudinal profile flattening in dammed reservoirs, and (3) mudflow material removal. Formation of two dammed reservoirs over the past 15 years, as well as layers of fine sand found in the low terrace’s sediments, indicate that such short-lived basins form periodically in the Geysernaya river valley. The conditions of the fine sand deposition in sections of a single-branch channel and within dammed reservoirs are differ, which affects the heavy fraction leading minerals ratio. The well-rounded gravel and abundance of coarse sand, and their decrepit appearance indicates that, along with the processing of incoming slope and mudflow material large volumes the Geyzernaya river continues to cut in and erodes the ancient fluvial sediments.

The morphology, structure and composition of sediments at low terraces which occur in the form of non-extended fragments in the Geysernaya River valley have been studied. Coarse, poorly sorted and weakly rounded debris flow material of different age generations are dominated in the sections. Layered sand and gravel deposits that accumulated under dammed reservoir conditions were exposed in some areas. Alluvial deposits are represented by thin layers of pebbles with boulders of better roundness and sorting with sand and gravel filler, underlying and/or overlying debris flow deposits. Some fragments of terrace-like surfaces are characterized by a smaller slope compared to the longitudinal profile of the river: apparently, they represent areas of former debris flow – landslide dams. Sediments of modern debris flows can be traced from 0 up to 50 m and of ancient once from 0.5 to 12 m above the river, which indicates the absence of a direct dependence of the age of sediments from the level of their occurrence. The change in loose material is due to the proximity and activity of thermal manifestations of the Geysernoe thermal field. Gas-hydrothermal processes lead to a significant transformation of the composition and properties of the analyzed sediments – mainly to their cementation, which makes it difficult to determine the time of sediment formation. The structure of the studied sections indicates the repeated occurrence of debris flows along the valley and the formation of temporary dammed reservoirs there as a result of the landslides and debris flow dams. The active supply of material from the slopes and its redeposition by debris flows causes poor rounding and sorting of sediment, and its weak disintegration. Among the rock-forming minerals of the fine sand fraction, magnetite and pyroxenes dominate with the participation of ilmenite. The light fraction is represented mainly by opal-smectite-zeolite aggregates, and to a lesser extent by geyserite. In the mineralogical spectra of sediments accumulated in dammed lake conditions, the set of secondary minerals and aggregates is expanding. In the alluvium units underlying the mudflow material there are signs of redeposition of ancient well-rounded sediments.

The Kamchatka River is the largest river of the Kamchatka Peninsula. The area of the Kamchatka River basin makes it one of the largest that emerged above the subduction zone. The peninsula is located in a temperate maritime climate, which favors intensive fluvial processes, especially for the largest river system of the peninsula. The study of fluvial processes within the Kamchatka River basin is based mainly on the publications of the mid-XX century. Recently dated deposits and remote sensing data permits us to identify the spatial distribution of the factors affecting the Kamchatka River valley topography. For this study, the relative elevation model and the main morphometric characteristics of the Kamchatka River - the stream gradient and the tortuosity ratio – have been calculated. Changes in the morphology of the valley and in the characteristics of its modern channel allow us to distinguish eight segments of the Kamchatka River valley. The contrast topography of the Kamchatka River valley, is caused by a non-uniform submergence of the CKD with rates exceeding those of fluvial processes.

Based on the lithostratigraphic and geomorphological approach, the study of lake level fluctuations in Nero and Seliger over the past 15,000 years was conducted. Common features of level changes were revealed: deep regression at the end of the late glacial period and early Holocene, intensive rise in level in the early-middle Holocene, stabilization (with a slight upward trend) in the late Holocene. Similar features in level changes were revealed in the history of a number of lakes in Germany and Scandinavia. A connection was found between lake level fluctuations and the intensity of fluvial processes in the center of the East European Plain.

In the center of the East European Plain, lake sediments provide the most detailed and high-resolution paleoarchives of the Late Pleistocene and Holocene periods. However, not all lake sediments can be used to reliably reconstruct regional paleoclimate and landscape changes. Factors such as the shape of the lake basin, the type of rocks beneath it, the number and flow of tributaries, and the vegetation present all play a role in determining the rate and composition of sedimentation in lake deposits, creating a unique record of the local environmental conditions. The Sarskoe Bog Basin has promising potential for providing a high-resolution record of the Late Pleistocene period. The core sample collected from the central part of the swamp met all expectations, but during the geophysical study of the geological structure and search for the maximum depth of lake sediments, it was found that the reference well was not in the most appropriate location. The first geophysical surveys conducted in the bog have improved our understanding of the paleorelief of the basin and will allow us to choose a location for the main well that is suitable for our research objectives.

Большие палеорусла – сохранившиеся в рельефе речных пойм древние речные русла, размеры которых значительно превышают размеры современных русел тех же рек. Их параметры и морфология указывают на то, что они формировались при увеличенном речном стоке. Большие палеорусла бассейна Волги могли играть ключевую роль в динамике береговой линии Каспийского моря. Произведено бурение и изучение строения больших палеорусел в разных частях бассейна Волги. Русловую фацию аллювия больших палеорусел подстилают мощные пачки отложений, заполняющих глубокие врезы. Датирование этих отложений показало, что в средневалдайскую эпоху реки были врезаны на значительную глубину, а в её конце и в первую половину поздневалдайского времени в речных долинах происходило заполнение этих врезов. По данным геодезической съёмки установлены отметки высоты кровли современного и поздневалдайского руслового аллювия. Хотя в течение эпохи формирования больших палеорусел реки бассейна должны были испытывать врезание вследствие роста стока воды, часто кровля руслового аллювия больших палеорусел расположена выше кровли современного руслового аллювия, формирующегося при более низком речном стоке. Это объясняется тем, что современные реки унаследовали профили дна долин от поздневалдайских; по окончании эпохи обильного стока лишь у части рек произошла адаптация продольных профилей к уменьшившимся величинам стока. Large paleochannels are ancient river channels preserved in the landscape of river floodplains, the dimensions of which significantly exceed the proportions of modern channels of the same rivers. Their parameters and morphology indicate that they were formed during periods of heightened water runoff. The large paleochannels of the Volga basin may have significant implications for the dynamics of the Caspian shoreline in past. This paper presents results of the drilling, dating, and study of the large paleochannels in different parts within the Volga basin. The channel alluvium of large paleochannels is underlain by thick units of sediments filling deep incisions. Dating of these deposits showed that in the Middle Weichselian time, river valleys were deep-incisioned, and at the end of this epoch and in the first half of the Late Weichselian time, these deep incisions were filled. According to geodetic survey data, the true altitude of modern and ancient alluvium tops was established. Although during the formation of large paleochannels, the rivers of the Volga basin must have incised due to increased runoff, often the top of the channel alluvium of large paleochannels is located above the top of the modern channel alluvium, which formed at the lower runoff volume. This is explained by the fact that modern rivers inherited the grade lines from the late Weichselian ones; at the end of the epoch with high fluvial activity, only a part of the rivers adapted their grade to decreased runoff.

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.

Presented study aims to investigate paleolimnological conditions of Lake Kasplya in northwestern European Russia. An annually-laminated deposits were analyzed with 14C dating, thin section study and varve counting using a semi-automated method. An annual structure is expressed in one or two pairs of layers per year (light – diatomite and calcite, dark – organomineral detritus with pyrite concretions). Differences in the structure of Early Holocene and Middle Holocene varves indicate changing paleolimnological conditions of the water body, while the disappearance of varves around 6.7 thousand years ago suggests the cessation of stable lake stratification. Due to the peculiarities of sediment structure, the obtained varve chronology is older compared to the radiocarbon sedimentation model (3,5 thousand years versus 2,5 thousand years).

The paper discusses new palynological data obtained from the bottom sediments of Lake Chukhlomskoye (Kostroma region). The location of the lake beyond the limits of the Late Valdaian ice sheet made it possible to reconstruct the vegetation changes during the maximum phase of the glaciation and compare them with previously obtained data from sediments of Lake Galichskoye. 25-21 thousand calibrated years BP, the region was occupied by open periglacial steppe with limited participation of birch and spruce open forests in the most protected habitats, with continuous spread of permafrost. Climatic reconstructions based on the modern geographical analogue of the fossil pollen flora indicate that mean annual temperature in the region was about ˗4 °C (7 °C below modern), and annual precipitation was at near-present level.

The paper discusses the structure of the bottom sediments of Lake Chukhlomskoye (Kostroma region, Russia). The results of complex lithological analysis and 14C AMS dating (TOC) of the sediments revealed in two boreholes located in different geomorphological positions of the bottom relief allowed to reconstruct stages and conditions of sedimentation in the lake. Mass accumulation rate (MAR) was calculated. High values of MAR correspond to 25.4–17.5 cal ka BP (up to 0.192 g/cm2 per year), a sharp decrease of MAR corresponds to 17.9–16.7 cal ka BP, and another stage of sediment influx occurred in Younger Dryas. Holocene MAR is low (0.001–0.053 g/cm2 per year).

The results of morphometric analysis based on the SRTM digital elevation model of large enclosed depressions (LEDs) of controversial origin, commonly found on the loess interfluves in the Northern Black Sea region, around the Sea of Azov, at the Western flanks of Caucus Mountains and in the Lower Don basin, are presented in the paper. We have registered 312 LEDs landforms. The morphometric characteristics of landforms vary from 0.4 to 216 km2 for area, from 1 to 21 m for depth, from 0.5 to 13.3 km for width, from 0.7 to 27.5 km for length, from 1 to 4 for elongation coefficient, and from 3.3 to 103.3 m a.s.l for height. The most common depressions have the following parameters: area 24 km2; depth 23 m; width 1.01.5 km; length 2.53.0 km; elongation coefficient 1.21.4; height 1520 m a.s.l. There is a correlation between the area and depth of the depressions. The depressions' shape is mostly elongated, e. g. teardrop-shaped, eggshaped, elliptical, triangular, and rarely round. The sharp ends of the egg-shaped depressions always tend to point to the north, and the blunt ones to the south. We grouped the depressions into seven restricted sites where the differences in size and other morphological features of the LEDs are very small. Within all sites, there is a high consistency of orientation of the long axes of the depressions. The largest depressions around the Sea of Azov and the Western flanks of Caucus Mountains are characterized by longitudinal ridges confined to western side of LEDs. Comparison analysis of sites demonstrated a fan-shaped pattern in changing of the long axes orientation from the NW in the Northern Black Sea region; to the East in the Azov Sea region; to the N in the Western flanks of Caucus Mountains; and the NE in the Central flanks of Caucus Mountains. A radial-centripetal pattern of the erosion network is observed across the territories where LEDs are distributed. Small erosive forms flowing into the center of depressions are represented by very flat and wide gullies and hollows with intermitted channel flow. Such morphological characteristics suggest the relict origin of the erosional forms and, as a result, indicates the pre-Holocene age of the depressions themselves. Morphological and geological data suggests that wind erosion was probably the main factor in the formation of LEDs.

The paleohydrological condition in the Rostov depression (Yaroslavl region) has been the subject of many years of discussions. The ideas about the Holocene fluctuations of the Lake Nero level differ among researchers. We have studied the structure of bottom sediments and bottom topography in the deepest northeastern part of the lake. A bathymetric survey was carried out. Drilling with the selection of undisturbed columns, GPR profiling, radiocarbon dating and a set of lithological analyzes were performed. Stratigraphic unconformities in the structure of bottom sediments indicate a drop in the lake level during the Lateglacial and the early Holocene. The level dropped to 87 m asl, which is 7 m lower than the current water level in the lake. The size of the lake at this stage was reduced several times. From 9 to 6.5 ka BP a transgressive stage was established: the average level of the lake could have risen to 91–94 m asl, which is close to its modern level. From 6.5 to 2.4 ka BP a decrease in the level by 1–3 m below the current one is revealed, followed by a gradual increase in the level. The current level was reached 300–500 years ago. The main factor in the fluctuations in the level of Lake Nero in the Holocene is the change in the height of the runoff threshold, caused by the transformation of the Ustye, Veksa, and Kotorosl river sistems. This transformation was associated both with regional changes in fluvial activity and with the processes of self-development of river channels.

The article discusses the first results of studying the structure of the bottom topography and bottom sediments of Chukhlomskoe Lake (Kostroma Region, Chukhlomsky District). We analyzed the lake bottom topography based on the results of our bathymetric survey and discovered two hollows with maximum depths diverging from the lake’s center towards the city of Chukhloma. The maximum depth inside the hollows (and for the entire lake) reaches 5.4 m, and the average lake depth is 2.2 m. There are two steps seen in the bottom topography; 2.0–2.4 m and 1.5–1.8 m. The bottom sediment structure of Chukhlomskoe Lake was revealed by drilling from the ice with two boreholes (with lengths of 9.45 and 7.45 m, located in the area of background depths and inside the hollow, respectively). Five radiocarbon AMS dates were obtained for the core from the hollow’s bottom. The sedimentary sequences of the pre-Holocene part of both cores show high similarity in structure and depths of the marker horizons identified by a set of lithological analyses. The structure and thickness of Holocene sediments differ significantly. In the area of background depths, the Holocene organo-mineralogenic silt is 3.8 m, and inside the hollow, the thickness of this layer is only 1.45 m. Moreover, hiatuses in sedimentation were documented in the structure of the Holocene sediment inside the hollow. The age of hiatuses, based on the sedimentary model, was estimated as 10.6–5.3 and 4.9–0.06 thousand years ago. A probable mechanism for the origin of hollows is localized erosion caused by wind currents in a highly shallow lake. An additional erosion factor can be the degassing of bottom sediments, which leads to the loosening of the bottom layer of sediments, which makes them susceptible to erosion. The cutoff of sediment erosion inside the hollow coincided in time with the construction of a dam on the Veksa River and a rise in the lake level by 1.0–1.5 m in the 1960s.

The paper presents a reconstruction of geomorphological processes in the Central Kamchatka Depression (CKD) since 30 ka, including the global LGM time. Major geomorphological processes of this period included the evolution of volcanic edifices accompanied by steady tectonic submergence. Glaciers that originated from volcanic edifices were greatly affected by both climatic forcing and the eruptive history of their host volcanoes. The most prominent geomorphological feature of the studied time was a giant paleolake filled the CKD. The reassessed extent and timing of glaciation and volcanism provided the possible lake fill and discharge model due to the evolution of a piedmont glacier originating from the Old Shiveluch Volcano edifice. The lake discharge likely was gradual and started some 19 ka during the cold settings of LGM, and therefore did not have a climatic origin. The most possible trigger of the discharge is the change in ice supply from the highly active Shiveluch Volcano due to large sector collapses. During the Holocene, the ongoing tectonic submergence of the CKD have been preventing the complete drainage of this paleolake. Even now, an enormously wide floodplain of the Kamchatka River hosts a lacustrine system with a total area of water surface comparable to the largest lakes of the peninsula.

The article discusses the first results of studying the structure of the bottom topography and bottom sediments of Chukhlomskoe Lake (Kostroma Region, Chukhlomsky District). We analyzed the lake bottom topography based on the results of our bathymetric survey and discovered two hollows with maximum depths diverging from the lake’s center towards the city of Chukhloma. The maximum depth inside the hollows (and for the entire lake) reaches 5.4 m, and the average lake depth is 2.2 m. There are two steps seen in the bottom topography; 2.0–2.4 m and 1.5–1.8 m. The bottom sediment structure of Chukhlomskoe Lake was revealed by drilling from the ice with two boreholes (with lengths of 9.45 and 7.45 m, located in the area of background depths and inside the hollow, respectively). Five radiocarbon AMS dates were obtained for the core from the hollow’s bottom. The sedimentary sequences of the pre-Holocene part of both cores show high similarity in structure and depths of the marker horizons identified by a set of lithological analyses. The structure and thickness of Holocene sediments differ significantly. In the area of background depths, the Holocene organo-mineralogenic silt is 3.8 m, and inside the hollow, the thickness of this layer is only 1.45 m. Moreover, hiatuses in sedimentation were documented in the structure of the Holocene sediment inside the hollow. The age of hiatuses, based on the sedimentary model, was estimated as 10.6–5.3 and 4.9–0.06 thousand years ago. A probable mechanism for the origin of hollows is localized erosion caused by wind currents in a highly shallow lake. An additional erosion factor can be the degassing of bottom sediments, which leads to the loosening of the bottom layer of sediments, which makes them susceptible to erosion. The cutoff of sediment erosion inside the hollow coincided in time with the construction of a dam on the Veksa River and a rise in the lake level by 1.0–1.5 m in the 1960s.

Abstract. A number of tephrochronologically correlated and dated sedimentary sections provide evidence for the existence of a giant lake filled the Central Kamchatka depression 30-11 thousand years ago. The lake extent bounded by CKD borders is estimated to be ~10 000 km2. This estimate makes this lake comparable in size to the famous Late Pleistocene glacial Lake Missoula.

Loess deposits are widely spread all over Eastern Europe, extending as far south as the Sea of Azov and the northern Black Sea. For many decades these regions have been noted for series of key sections. However, despite prolonged investigations, a lack of absolute dating and detailed lithological data has left many unresolved problems in the correlation of the regional stratigraphic schemes. In this study, integrated studies were undertaken on the loess-paleosol sequence exposed on the northern coast of the Taman Peninsula, separating the Sea of Azov from the Black Sea. The exposure in the coastal scarp near Cape Pekla was sampled in detail for standard lithological and stratigraphic analyses, and for the first time, detailed data on the sediments lithology and petromagnetic properties were obtained, as well as the first optically stimulated luminescence age estimates. The data lead us to conclude that the formation of continental series exposed in the Pekla section started at the beginning of the Middle Pleistocene. There are five well pronounced buried soil complexes (PS 1–5) exposed in the sequence, covering sedimentation from the Middle Pleistocene to the present day. We attribute two lower paleosols (PS 4 and PS 5) to two main warm intervals of the Middle Pleistocene – MIS 9 and MIS 13, and the Kamenka interglacial paleosol, correlated with MIS 7 from other parts of the Azov loess area, is represented in the Pekla section by a sand layer formed at the time of the marine transgression dated to interval 220–280 ka (MIS 7). The upper soil horizons (PS1, PS2 and PS3) developed between 20 and 220 ka. The Pekla section contains a considerable proportion of sand fraction – presumably, due to active eolian processes that developed in immediate vicinities of sources of the material. The paleosol characteristics and the structure of loess horizons in the Pekla subaerial series differ considerably from the well described loess-paleosol series of the Northern Azov Sea coasts. In all probability, this region of the Taman Peninsula belongs to a specific province located south of the North Azov loess-soil province.

Abstract. A comprehensive lithological analysis of bottom sediments from the central part of the Sarskaya depression was carried out. We determined that a shallow lake existed in the Sarskaya depression as least from 22500 to 12400 years ago. The bottom sediments potentially contain traces of global climate change - in particular, a presumable trace of the B lling-Aller d interstadial has been established in sediments formed about 13500 years ago. There are signs of activation of erosion processes during the period from 13100 to 12400 years ago. Since the time the sediment condition stabilized and the water body began to swamp.