卷 54, 编号 3 (2023)

The study of the geomorphological and sedimentary systems forming at mouth of large rivers flowing into the inland seas and lakes of the arid zone shows that they have passed a long evolutionary path of development, repeatedly accumulating and reworking alluvial deposits depending on the position of the receiving reservoir level. Following the level fluctuations, the rivers moved their deltas, Pleistocene relics of which are found in the range of absolute marks from +50 to –20 m on the shores of the Caspian Sea, from +50 to 110 m of the Aral Sea and from +370 to 400 m of Lake Balkhash. The Aral-Caspian arid zone is distinguished by following natural factors affecting the processes of delta formation: aridity of the climate, formation of river flow in the upper reaches and lack of inflow in the lower reaches, increased water turbidity and a huge runoff of suspended sediments, as well as significant influence of human economic activity associated with intensive irrigation. The most common morphogenetic type of river deltas on the coasts of intracontinental reservoirs of the arid zone are huge alluvial outflow cones in the form of extension deltas and “dry internal deltas” in the form of alluvial outflow cones. The delta arms and the lower reaches of the rivers of the arid zone are characterized by a high intensity of channel deformations due to weak resistance to erosion of fine-grained valley alluvial-proluvial deposits, high flow velocities and high saturation of the flow with suspended sediments. The oversaturation of the river flow with sediments usually leads to shallowing of the riverbed in high water and its gradual increase over the surrounding terrain. An increase in the bottom elevation and fast delta progradation provoke frequent breakthroughs of the riverbed shafts, a change in the direction of the flow of delta arms, the creation of new branching nodes and the formation of regional jointed deltas of the breakthrough type (delta blades) on the periphery of the old delta (subdelta according to American terminology). Partially superimposed or superimposed deltas can also form inside delta systems after the breakthroughs of channel shafts (or enclosing dams). The poor preservation of ancient deltas is noted due to intensive economic development and high dynamics of the coast and the hydrographic network of river deltas in conditions of huge runoff of suspended sediments and significant variability of the level of the receiving reservoir.

We studied the debris flow relief of the Malaya Paipudyna basin, the Polar Ural Mountains. Based on the analysis of remote sensing data and field surveys, we established that 14 debris flow basins are located on the territory. We found traces of five slushflow occurrence in the streams in the spring of 2021. Typical landforms for different morphodynamic zones of debris flow basins were identified. The initiation zones of debris flows are mainly represented by catchment funnels on the slopes of the Bolshoi and Maliy PaIpudynskii ranges. The transit zones V-shaped bottom incisions alternate with box- and trough-shaped transverse profile. Within the debris flow fans, two generations of accumulative debris flow relief are clearly distinguished. Young accumulation zones are represented by pebble-boulder ridges up to 0.5 m high, localized directly in the near-channel areas of debris flow fans. Usually, they are either devoid of soil and vegetation cover, or are overgrown only by herbs. Ancient debris flow fans are triangular in shaped with convex transverse profile, consisting of a system of ridges and hollows, and overgrown with shrubs. The area of young accumulation zones for each debris flow basin is no more than 0.03 km², the area of ancient accumulation zones is 0.4 km². Debris flow fans are superimposed on the bottom of the trough valley of Malaya Paipudyna, which is mainly the surface of glacial accumulation. Probably, the formation of these fans began after the degradation of the last extensive glaciation of the territory. We calculated the morphometric features of the debris flow basins.

The Middle Volga region is an area of layer-tiered and stepped uplands, in which the upper plateau is the most ancient surviving (among the known) element of the relief of this region of the East European Plain. The plateau is located within the highest interfluves at the prevailing elevations of 280–380 m, representing the upper level of the relief. Most researchers support the denudation (pediplanation) nature of its origin. The age of formation of the plateau surface is still a matter of debate. In this paper, based on literature sources, the author’s ideas about the development of the Neogene valleys of the paleo-Volga and its tributaries, an analysis of changes in the geomorphological, paleoclimatic and paleolandscape conditions of the Middle Volga region and neighboring regions was presented. It is concluded that the most optimal time for the pediplanation of the region’s relief and, consequently, the formation of the surface of the upper plateau was the time period between the time boundary of the Middle and Late Miocene (Sarmatian?) and the middle of the Maeotis (Late Miocene), which was distinguished by relative tectonic stability and general increase of climate aridization.

Baer knolls (BK) are elongated ridges often close to the sub-latitudinal orientation sometimes spatially isometric that are widespread in the entire Northern Caspian Region up to 0 m a.s.l. (the upper limit of the Late Khvalynian sea transgression). The goal of this study was to establish the genesis of BK based on interpretation of textural and lithologic characteristics of sediments and dating the material composing these landforms. Research has led to the following conclusions that BK have been formed during the transition of Late Khvalynian and Early Holocene time. Sediments of BK consists of three lithofacies (LF1, LF2, LF3). Chocolate clay (CC) and Volga alluvium were significant sources of material for knolls formation. Nonetheless, for lithofacies 1, it was also sandy material lying below the CC. The BK material cannot be attributed to the aeolian genesis because of its lithological, faunal and geochemical characteristics. The knolls formed in brackish subaquatic conditions of the lagoon floor, where a low-energy currents occurred due to the descent of Late Khvalynian basin waters through the Manych Strait. Thus, BK are analogues of river bedforms appearing as the result of turbulent flow, like ripples and river dunes, where, in concordance with the accumulation of sandy material and detritus of redeposited shells, clay particles were deposited under the mixing of the brackish water of the lagoon and the fresh water of the rivers flowing into it.

A continuous record of paleogeographic events in south-eastern Primorye has been reconstructed based on the deposits of Gniloe Lake. The lake is located on the northern coast of Nakhodka Bay. Starting from 3240 cal. BP. 5 warming periods were identified: 3240–2500, 1865–1653, 1330–838, 733–624 cal. BP and from the second half of the 17th century to the present; 4 periods of cooling: 2500–1865, 1653–1330, 838–733 and 624–322 cal. BP; 6 wet periods: 3240–2500, 1865–1653, 1479–1330, 1056–838, 733–624 cal. BP and last 280 years; 5 dry periods: 2500–1865, 1653–1479, 1330–1056, 838–733 and 624–210 cal. BP. According to palynological analysis, the expansion of Pinus koraiensis and dark coniferous species occurred during the second phase of the Mid-Subatlantic cooling of 1479–1330 cal. BP. In the last 150 years, the most significant changes have been associated with the anthropogenic transformation of landscapes as a result of urbanization. The area of forests and their species composition have decreased. At present, shrubs have occupied areas of the deforested oak forests. Based on the results of diatom analysis, 7 stages of the development of Gniloe Lake were identified. There was a shallow semi-open lagoon at a sea level 1–1.5 m higher than the present day about 3240 cal. BP. Cooling and decrease in humidity about 2500 cal. BP led to the formation of a slightly saline semi-enclosed lagoon. Shallowing of the lagoon about 2000 cal. BP was due to a decrease in sea level. Finally, the lagoon separated from the sea about 1450 cal. BP. The transformation of the lagoon into a fresh lake occurred around 1080 cal. BP. During the period of cooling 840–733 cal. BP the shallowing of the lake began, which continued in the Little Ice Age. The increase of the lake level associated with moderate warming and an increase in humidity began at 210 cal. BP. Traces of three catastrophic events were recorded in the sediments of Gniloe Lake – a high-intensity storm about 3000 cal. BP and 2 tsunamis around 2000 and 1560 cal. BP.

Coast landslide processes take a special place in the study and monitoring of processes in permafrost under the climate change, however, not much attention has been paid to the morphology and quantitative characteristics of the landslides. The aim of the work is to reveal quantitative relationships between the abrasion slopes and a landslide process for coasts within the cryolithozone, mainly in contact with the adjacent interfluves. The research is based on the interpretation of high-resolution space imagery at five costal sites of the Kanin and Yamal peninsulas. The study was focused on the morphological features of the upper part of the landslides at the border with the adjacent interfluve. This border is a combination of arc elements. Besides, there are arcuate residual sections of the interfluve surface, corresponding to different stages of landslide process, in some places on the slope. Analysis of the coastline from images gave us such characteristics of landslides as the length of the arcs forming the boundary, the length of the chords of the arcs, the arrows of the arcs, the average radii of curvature, the central angles of the arc, the angles of orientation of the chords with respect to the vector of the general strike of the corresponding section of the coastline. Some of these characteristics were obtained by direct measurement from satellite images, the others by calculation. The analysis included 30 samples with a volume of 103–183 elements. Statistical processing using Pearson’s goodness-of-fit test showed that in the vast majority of the sites, the distributions of the landslide upper boundary arc sizes, chords, arc arrows, and curvature radii, as well as central angles, correspond to a lognormal one. The chord orientations with respect to the strike of the site are normally distributed. The values of the distribution parameters of the studied quantitative characteristics of the landslide morphological features differ and depend on the physical-geographical and engineering-geocryological conditions of specific areas.

There are problems with the co-registration of digital terrain models which were created by drones to obtain useful data for a numerical hydrological or erosional modeling. The different surveys can be produced at different time of a day, in various seasons or even years, making it difficult spatially reference the data. Many co-registration algorithms usually perform the statistical fitting of point clouds or raster models. Such approach violates the hydrological correctness of the final data, it makes artifacts appearing, such as various escarps and visible joints. The search for the contour of “zero error” on the raster of elevations difference is the bases of presented algorithm. This contour is used for the stitching of original elevation models together. As criteria for the quality assessment of the final elevation models are used: 1) the statistical distributions of slope gradient, i.e. parameter that affects the results of modeling the water and sediment flows, slope stability, etc., 2) the constancy of the microcatchments geometric structure. The algorithm was tested on three sites located in plain, low-mountain and mid-mountain zones. In all examples, the high efficiency of the method was shown. At the same time, the technique was constructed for keeping the significant features of terrain morphology in data. The average slope does not deviate by more than 1° in comparison with the original data. The Spearman rank correlation of the slope varies in different cases at 0.9–0.99 (with an average value of 0.96). The coefficients of geometric similarity of microcatchment patterns on the final models in all cases show even larger values (1.09) than on the original data without any correction (0.98) in the areas their overlap.