卷 55, 编号 4 (2024)

Within the south of Western Siberia and adjacent territories, 23 types of Land systems (parageneses of genetically homogeneous surfaces/land units) have been identified, belonging to three physiographic zones: flat, foothill and mountain, as well as one type of extrazonal formations. The use of formational analysis has made it possible to identify genetic relationships between large spatially separated geomorphological elements, considering them as formational series. For the first time, a catafluvial geomorphological formation has been identified for the south of Western Siberia, and its place among other geomorphological formations in the region has been shown. A connection has been established between the ancient drainage troughs of Western Siberia, transit erosion valleys and catafluvial events (superfloods).

As a result of recent field studies in the Middle Yenisei Valley, the absence of high terraces of alluvial and periglacial origin, which traditionally formed the basis of the Quaternary stratigraphy of the Minusinsk basins, has been established. Sediments previously attributed to the alluvium of high terraces are super-flood. The article provides lithofacies characteristics of subaerial and megaflood deposits, as well as the features of their relationships in space. Information on paleontological and archaeological objects from stratified locations of the study area, for which geodatabases have been compiled, has been summarized and cartographically visualized. In the North Minusinsk Basin, the analysis of reference sections of the Kurtak region, worked out in detail stratigraphically and published by previous researchers, made it possible to determine the stratigraphic position of megaflood strata based on the occurrence between subaerial packs with paleosols. The geochronometric, paleontological, and geoarchaeological characteristics of the sequence of the studied geological deposits are given. On the basis of systematization of already known materials and generalization of new field data, the presence of deposits of three megaflood strata in the Middle Yenisei Valley was established: Razlog (II₄ rz), Chaninskaya (III₂ chn), Divninskaya (III₄ dv).

A geomorphological study of a key section of the Belaya River valley in the lower reaches is conducted to reconstruct the Holocene history of the development of the valley. The spatial distribution of floodplain generations of different morphology and low terrace levels is analyzed. To clarify the age relationships of various surfaces, a study of the facies structure and composition of deposits of ten pits and seven boreholes on a cross-section profile was carried out, the age of formation of alluvial strata was determined by radiocarbon dating. The structure of the longitudinal profile of the floodplain and the channel, the absence of signs of constrative accumulation of alluvium, suggests the absence of the tectonic influence on the formation of alluvium in the floodplains and low terraces of the Belaya River. However, the control of the development of a number of bands in the lower reaches of the Belaya River by system of lineaments and the associated stability of these landforms determined their representativeness for assessing the rhythm of alluvial sedimentation and the development of fluvial processes in the Holocene. The landscape-climatic changes at the end of the Late Glacial and Holocene caused the alternation of the stages of high and low water level and the stages of development of the Belaya River valley associated with them within the plain part of its basin. Stages of a relatively small river runoff, typical for time intervals 12.9–7.0; 5.6–4.5; 4.1–2.3 and 0.3–0 kyr BP changed by stages of high-water levels and active floodplain sedimentation 7.0–5.6; 4.5–4.1 and 2.3–0.3 kyr BP. The development of fluvial processes and the rhythmicity of the formation of the studied floodplains correlates well with the context of regional temperature and humidity changes during the Late Glacial and Holocene, allowing us to consider the floodplains of the left-bank tributaries of the Angara River as significant paleogeographic archives.

It has been established that two main genetic types of wells are common in the region: karst-gravitational and nival-corrosive. The first ones are widely spread karst sinkholes, the second ones are rare negative landforms formed as a result of nival corrosion caused by snow melt water. The nival-corrosive wells are formed in gypsum of the Kungurian Stage of the Cisuralian Series of the Permian system in conditions of open (bare or Mediterranean) karst. The maximum distribution of such wells was recorded in two areas of karst gypsum outcrop in the watershed areas: Aurgazinsky – on the Pribelsk rolling and wavy plain and Seleuksky – in the western hilly foothills of the Southern Urals. In these areas, wells form karst fields. The density of wells per 1 km² in such fields reaches 5 thousand. This is the highest occurrence of surface karst in the Southern Cis-Ural region. In the rest of the region, nival-corrosive wells are distributed singly and do not form karst fields, but they are also formed in places of karst gypsum outcrops on the surface of watershed spaces. The uniform morphology and morphometry of wells has been recorded everywhere, and their uniform confinedness to certain relief features has been established. With the general conditionally cylindrical shape of the wells, their average diameter is 5 m, and their depth is 10 m. Everywhere wells are formed in the valley-side flattened parts of the watershed spaces that abruptly adjoin steep slopes of river valleys. The determining factor in the formation of wells in different parts of the region are similar geological and geomorphological conditions of their places of distribution – the similar lithotype of karst gypsum outcroped on flat or slightly inclined surfaces of watersheds. The proposed mechanism for the formation of wells, caused by the activity of meteoric (mainly snow) waters, is given.

Article provides the results of palaeoecological reconstruction of vegetation cover changes and climatic conditions at the foot of the Eastern Sayan northwestern macroslope over the past 6600 years. The results are based on radiocarbon AMS dating, pollen, macrofossils, NPP, macrocharcoal and testate amoebae analyses of peat deposits from Bolshoe bog situated on the Yenisei River right bank. It was established that the waterlogging process was initiated by the pyrogenic factor. During the last approximately 6000 cal. a BP dark coniferous forests with a dominant position of Pinus sibirica were common in the foothills. The change in climatic conditions towards decreased moisture availability 4050–3600 cal. a BP contributed to the lower border of dark conifers rise and the strengthening of forest-steppe communities with Betula sect. Albae. This period is characterized by the most dramatic transformations. Less prolonged periods of forest lightening occurred in 3170–3080, 1850–1720, 490–400 and 310–220 cal. a BP, when the taiga and cold deciduous forest biomes were of almost equal importance. The most significant expansion of the dark conifers range began 1600 cal. a BP and reached a maximum 1350–1230 cal. a BP, which can be correlated with Dark Ages Cold Period. Based on the macrocharcoal analysis results six stages of increased fire activity were identified: 6500–6300, 4300–3600 (includes 4 fire episodes, characterized by the shortest fire intervals), 3400–2800, 1800–1550, 1200–1000, and from 150 cal. a BP to present. Based on a multy-proxy analysis, periods of increased moisture were established: 6300–5320, 4700–4200, 3080–2900, 2820–2390, 1720–1230, 400–310 and 130–70 cal. a BP. The decreased moisture was characteristic of the intervals 5320–4960, 4050–3600, 2390–2220, 1000–700 cal. a BP.

This paper proposes a new algorithm that allows performing a high-precision fitting of multi-temporal digital elevation models, which do not have appropriate geographic reference, in order to calculate the difference in elevation over a known time interval. Similar algorithms exist, the proposed algorithm is based on different principles, and therefore it can complement the toolkit for spatial data coregistration. The paper describes the stages of the algorithm operation, which in generalized form includes first the adjustment of the registered model to the reference model in plan, then – in vertical direction. The algorithm was tested on 2 sites and different kinds of data: 1) the 2014 landslide site in the valley of the Geysernaya River in Kamchatka using space imagery and stereo photogrammetry (ArcticDEM), and 2) an erosion monitoring site in the Gitche-Gizhgit catchment in the Greater Caucasus using aerial photography and a structure-from-motion approach (UAV). The proposed algorithm is effectively applicable to data of different origin, detail, spatial coverage. Conditions for its effective application: 1) presence of any significant areas with unchanged relief, 2) presence of a pronounced pattern of topographic dissection (texture of image / digital elevation model). It is shown that the refinement of the geographical reference of the registered elevation model significantly improves estimates of the volumes of denuded and accumulated material, which is especially important in the tasks of dynamic geomorphology. In the given examples, the registration error of digital elevation models decreased from 3–4 to almost 70 times. The volumes of surface changes in the areas of reliably prevailing denudation were corrected both in magnitude (as a rule, downward) and in sign.