Denudation Processes Research Articles

Геоморфометрический анализ рельефа Приольхонья

The use of geomorphometric analysis to obtain relevant data and their interpretation in geomorphological and geographical studies is becoming more widespread in recent times. In this study, such an analysis is used for the Priolkhonsky plateau (Western Baikal region), whose territory has recently been subjected to intense recreational impact. Under such conditions, it becomes relevant to determine the erosion-accumulative potential of the territory, its subsequent regionalization, as well as the possibility of using the obtained results in landscape-recreational zoning. The surface curvature maps were made using a digital elevation model based on ALOS data with a resolution of 30 m. Using geoinformation analysis, slope steepness, horizontal, vertical, and general curvature maps were obtained, and statistical coefficients of these indicators for the study area were determined. A geomorphological interpretation of the areas spatial distribution with different values of curvature was carried out. The analysis of the territory geomorphometric parameters showed that denudation processes prevail within the study area. It was also determined that the territory under favorable climatic conditions could have a significant potential for the development of erosion-accumulative processes. Areas of accumulation associated with the development of linear erosion forms, gullies along unpaved roads, were identified. Areas with the maximum values of curvature in the summit level of the relief have a high potential for the development of landslide processes. In the middle level of relief with positive values of the total curvature, prevail low-intensity processes (downwash, creeping).

БЕРЕГА СЕВЕРО-ЗАПАДНОЙ ЧАСТИ ЧЕРНОМОРСКОГО ПОБЕРЕЖЬЯ КАВКАЗА В НАЧАЛЕ XXI ВЕКА

The Black Sea coast of the Caucasus has the most valuable economic resources, primarily recreational. In addition, coastal geosystems are a key element of the region's natural biodiversity. This paper provides an overview of the current state of abrasion and accumulative shores of the Black Sea between c. Panagia and r. Tuapse. Materials of long-term monitoring observations, satellite imagery, the results of mathematical modeling, literary and archival sources are used. The most important natural processes that determine the development of the coasts are considered and the analysis of their dynamics due to climate changes and increasing anthropogenic load is performed. It is shown that the significant differences between individual sections of the north-western part of the Caucasus Black Sea coast in terms of natural features and the degree of their economic development are determined by a variety of natural and socio-economic factors. Abrasion coasts with high cliffs, where denudation processes are the main source of solid material to the coastal zone, predominate. The general deficit of beach-forming sediments is a characteristic feature, as a result of which there is no single alongshore sediment flux. Small lithodynamic systems bounded by capes are characteristic of the coast under consideration. The movement of sediments has the character of reverse migrations and the beach is formed in the concavities of the coast. The only large accumulative form is the Anapa bay-bar, in the formation of which the alluvium of the Kuban River played an important role. Predominance of erosion processes over accumulative ones is the geomorphological feature of the Caucasus Black Sea coasts, therefore the main problems of environmental management are the protection of the coast from storm waves and shortage of beaches. Creation of complexes of artificial beaches with beach-retaining structures, that simultaneously perform coastal protection and recreational functions, is the most promising solution to these problems in the 21st century. It is noted that the conditions of the considered coastal section are favorable for the use of local coastal protection.

Elemental composition of biogenic sediments reveals palaeoclimatic changes during the Late Weichselian in a Central European river valley: A statistical approach

Five sections of sediment from mire infillings located in different part of the catchment small river valley in central Europe were studied by lithological and geochemical analysis in order to examine the response of aquatic ecosystems to the environment changes during Late Weischselian (LW). Differentiation of geochemical composition and grain-size properties in biogenic deposits is being considered as a result of change hydroclimatic conditions and geology structure in individual parts of the catchment. The principal component analysis (PCA) and clustered by hierarchical method (HCA) were chosen to create the lithogeochemical facies and their chronostratigraphy variability. Biogenic sediments of the studied river mires, regardless of the location in a given reach of the valley, are represents mainly by mineral or organic-mineral lithogeochemial facies with increased of lithophilic elements (Na, K and Mg). Similar chemical composition of gyttja and peat sediments in almost all periods of LW, indicate the strongly mechanical denudation processes in the Grabia River valley. The major process, conditioning the development of the mires (in it type and rate sedimentation), was the variable terrigenous material input which are related to its variable dynamic of floods. The higher than expected chemical denudation probably a result of specific groundwater flow direction and dissolving vari-grained sands and silts, which build plains in the central part of the study catchment. The number and thickness of individual lithogeochemical facies are caused by differences in the potential volume of the hydrologically active zone and geological conditions of the emerge or disappear permafrost.

Differential Phanerozoic evolution of cratonic and non-cratonic lithosphere from a thermochronological perspective: São Francisco Craton and marginal orogens (Brazil)

The São Francisco Craton (SFC) and its marginal Araçuaí and Brasília orogens exhibit a significant diversity in their lithospheric architecture. These orogens were shaped during the Neoproterozoic–Cambrian amalgamation of West Gondwana. The rigid cratonic lithosphere of the SFC and the relatively weak lithosphere of the Araçuaí Orogen were disrupted during the Cretaceous opening of the South Atlantic Ocean, whereas the Brasília Orogen remained in the continental hinterland. In earlier research, the thermal effects of the Phanerozoic reactivations in the shallow crust of the Araçuaí Orogen have been revealed by low-temperature thermochronology, mainly by apatite fission track (AFT) analysis. However, analyses from the continental interior are scarce. Here we present new AFT data from forty-three samples from the Brasília Orogen, the SFC and the Araçuaí Orogen, far from the passive margin of the Atlantic coast (~150 to 800 km). Three main periods of basement exhumation were identified: (i) Paleozoic, recorded both by samples from the SFC and Brasília Orogen; (ii) Early Cretaceous to Cenomanian, recorded by samples from the Araçuaí Orogen; and (iii) Late Cretaceous to Paleocene, inferred in samples from all domains. We compare the differential exhumation pattern of the different geotectonic provinces with their lithospheric strengths. We suggest that the SFC likely concentrated the Meso-Cenozoic reactivations in narrow weak zones while the Araçuaí Orogen displayed a far-reaching Meso-Cenozoic deformation. The Brasília Orogen seems to be an example of a stronger orogenic lithosphere, inhibiting reworking, confirmed by our new AFT data. Understanding the role of the lithosphere rigidity may be decisive to comprehend the processes of differential denudation and the tectonic–morphological evolution over Phanerozoic events.

New Method for Automated Quantification of Vertical Spatio-Temporal Changes within Gully Cross-Sections Based on Very-High-Resolution Models

Gully erosion is one of the most prominent natural denudation processes of the Mediterranean. It causes significant soil degradation and sediment yield. Most traditional field methods for measurement of erosion-induced spatio-temporal changes are time and labor consuming, while their accuracy and precision are highly influenced by various factors. The main research question of this study was how the measurement approach of traditional field sampling methods can be automated and upgraded, while satisfying the required measurement accuracy. The VERTICAL method was developed as a fully automated raster-based method for detection and quantification of vertical spatio-temporal changes within a large number of gully cross-sections (GCs). The developed method was tested on the example of gully Santiš, located at Pag Island, Croatia. Repeat unmanned aerial vehicle (UAV) photogrammetry was used, as a cost-effective and practical method for the creation of very-high-resolution (VHR) digital surface models (DSMs) of the chosen gully site. A repeat aerophotogrammetric system (RAPS) was successfully assembled and integrated into one functional operating system. RAPS was successfully applied for derivation of interval (the two-year research period) DSMs (1.9 cm/pix) of gully Santiš with the accuracy of ±5 cm. VERTICAL generated and measured 2379 GCs, along the 110 m long thalweg of gully Santiš, within which 749 052 height points were sampled in total. VERTICAL proved to be a fast and reliable method for automated detection and calculation of spatio-temporal changes in a large number of GCs, which solved some significant shortcomings of traditional field methods. The versatility and adaptability of VERTICAL allow its application for other, similar scientific purposes, where multitemporal accurate measurement of spatio-temporal changes in GCs is required (e.g., river material dynamics, ice mass dynamics, tufa sedimentation and erosion).

Eroding Cascadia—Sediment and solute transport and landscape denudation in western Oregon and northwestern California

AbstractRiverine measurements of sediment and solute transport give empirical basin-scale estimates of bed-load, suspended-sediment, and silicate-solute fluxes for 100,000 km2 of northwestern California and western Oregon. This spatially explicit sediment budget shows the multifaceted control of geology and physiography on the rates and processes of fluvial denudation. Bed-load transport is greatest for steep basins, particularly in areas underlain by the accreted Klamath terrane. Bed-load flux commonly decreases downstream as clasts convert to suspended load by breakage and attrition, particularly for softer rock types. Suspended load correlates strongly with lithology, basin slope, precipitation, and wildfire disturbance. It is highest in steep regions of soft rocks, and our estimates suggest that much of the suspended load is derived from bed-load comminution. Dissolution, measured by basin-scale silicate-solute yield, constitutes a third of regional landscape denudation. Solute yield correlates with precipitation and is proportionally greatest in low-gradient and wet basins and for high parts of the Cascade Range, where undissected Quaternary volcanic rocks soak in 2–3 m of annual precipitation. Combined, these estimates provide basin-scale erosion rates ranging from ∼50 t · km−2 · yr−1 (approximately equivalent to 0.02 mm · yr−1) for low-gradient basins such as the Willamette River to ~500 t · km−2 · yr−1 (∼0.2 mm · yr−1) for steep coastal drainages. The denudation rates determined here from modern measurements are less than those estimated by longer-term geologic assessments, suggesting episodic disturbances such as fire, flood, seismic shaking, and climate change significantly add to long-term landscape denudation.

Mesozoic uplift exhumation history of East Kunlun

位于中央造山带西段的东昆仑造山带因多期次造山和复杂演化历史而备受关注，约束其中生代隆升剥露历史，对于理解青藏高原大规模隆升在东昆仑地区的扩展及影响颇具意义。东昆仑造山带内中生代侏罗系-白垩系地层缺失严重，体现中生代以来强烈的隆升剥露过程，也是该区热演化的研究难点。本文通过对东昆仑造山带样品的磷灰石、锆石裂变径迹分析和热演化史研究，并结合东昆仑及周缘地区现有低温热年代学研究，识别出东昆仑造山带所经历的五次隆升冷却事件，即201~193Ma（早侏罗世）、172~152Ma（中-晚侏罗世）、120~98Ma（早白垩世末-早白垩世初）、98~20Ma（晚白垩世-中新世）及20~0Ma（中新世至今）。所获5个年龄组响应东昆仑地区所经历的构造热事件，其中201~193Ma年龄组响应南部羌塘地块与昆仑地块的碰撞事件；172~152Ma年龄组为中-晚侏罗世古特提斯洋闭合后，造山后伸展的构造事件的记录；120~98Ma热事件吻合拉萨地块和羌塘地块碰撞事件；98~20Ma年龄组为东昆仑地区长期缓慢剥蚀去顶过程的印证；20~0Ma的快速隆升剥露事件则为东昆仑周缘断裂系活化相伴，多期隆升剥蚀事件均得到地层不整合及沉积记录等研究成果的证实。区内剥蚀起始时间从由南到北逐渐变老，体现东昆仑地区隆升剥蚀的不均一性。;As the western part of the Central Orogenic Belt, the East Kunlun Orogenic Belt draws great attention in the geological community because of its multi-phase orogenesis and complex evolutionary history. Constraining its Mesozoic uplift denudation history has important implications for understanding the expansion and impact of large-scale uplift of the Tibetan Plateau in the East Kunlun region. The absence of the Mesozoic Jurassic-Cretaceous stratigraphy in the East Kunlun Orogenic Belt reflects the intensive uplift and denudation process since the Mesozoic, which is also a difficult research problem in the thermal evolution of the area. In this paper, through the analysis of apatite, zircon fission tracks and thermal evolutionary history of samples within the East Kunlun, we identify five uplift cooling events, i.e. 201~193Ma (Early Jurassic), 172~152Ma (Middle-Late Jurassic), 120~98Ma (Late Early Cretaceous-Early Cretaceous), 98~20Ma (Late Cretaceous-Miocene), and 20~0Ma (Miocene to present). The five age groups obtained respond to the tectonothermal events experienced in the East Kunlun region. The 201~193Ma age group responds to the collision between the Qiangtang Block and the Kunlun Block in the south; the 172~152Ma age group is the record of the tectonic event of post-formation extension after the closure of the Middle-Late Jurassic Paleo-Tethys Ocean; the 120~98Ma thermal event coincides with the collision between the Lhasa Block and the Qiangtang Block; the 98~20Ma age group is the record of the long-term slow denudation process. The rapid uplift and denudation events from 20 to 0Ma are due to the activation of the fault system. The onset of denudation in the area is gradually older from south to north, reflecting the heterogeneity of uplift denudation in the East Kunlun region.

ОЦЕНКА БАЛАНСА НАНОСОВ РЕК ОБЬ И ЕНИСЕЙ

This paper presents results of comparative analysis of the sediment budgets of the Ob’ and the Yenisei, base on universal erosion equations, RUSLE using 250 m resolution DEM GMTED 2010. Cumulative volumes of sediments accumulated in the stream catchments were estimated calculating the difference between erosion and sediments runoff of the studied basins. Thus, the difference between total erosion (watershed erosion + bank erosion) is (1250 MT/year + 35 MT/year) for the Ob and (315 MT/year + 21.9 MT/year) for the Yenisei. Sediment runoff in the mouths of both rivers estimated based on MSU data is 63.5 MT/year for the Ob and 32.5 MT/year for the Yenisei; Sediment runoff in the mouths estimated based on Roshydromet data is 16 MT/year for the Ob and 2.4 MT/year for the Yenisei. Sediment runoff was used to calculate the total deposition of matter in the catchment area during the transport of sediments from sources to sinks, for the Ob total deposition is 1270 MT/year, for the Yenisei is 335 MT/year. For the unregulated part of the Ob’ catchment, the accumulation was 56.5 MT/year, and for the unregulated part of the Yenisei catchment was 43 MT/year. The coefficient of reduction of sediment runoff (1/SDR) downstream, based on new samplings of sediment runoff in 2018–2019 in the mouths of both, Ob and Yenisei, was 2.3, and for the entire catchment area 20 and 30 respectively. Volume of sediments moved by denudation processes in the basin ends up being redeposited within the same fluvial systems. Thus, under the current hydro-meteorological regime, the large drainage basins in Russia and elsewhere are major depositional systems.

Полевые исследования на территории Булунского района (Республика Саха (Якутия)) в 2021 году

The study of the problem of the initial development and subsequent settlement by ancient human populations of extreme natural zones is difficult to study, but, in the case of discovering archaeological and paleontological locations, it is a very informative source. The first discoveries of traces of the presence of an ancient man in the Bulunsky district date back to the beginning of the 19th century, and they continued sporadically throughout the entire 20th century, and especially intensified at the beginning of the 21st century. The discovered locations are represented by both mass material and single finds. In 2021, field studies were carried out in Neelov Bay on the side of the Bykovsky peninsula and the Kozhevin-Vollosovich interfluve in the north of the Kotelny Island of the Anju archipelago of the New Siberian Islands. These areas represent the arctic tundra with active thermal denudation processes, which contribute to the discovery of paleontological remains of mammoth fauna, and often lead to the regular seasonal destruction of paleontological and archaeological sites. New archaeological and paleontological material found on the southeastern coast of Neelov Bay demonstrates the intensity of the development of the most ancient populations of people in the Arctic zone of Eastern Siberia. The result was the discovery of new Pleistocene fauna complexes, as well as the verification of the previously discovered Taba-Yuryakh location. The obtained osteological material belongs to the Late Pleistocene mammoth complex. On some of the bones, traces of human influence were found, presumably hunting or cutting, which indicates the active development of the ancient population of the Arctic zone of Yakutia in the Paleolithic. The obtained data will make it possible to significantly correct the existing ideas of the chronology and sequence of development of the Paleolithic industries and paleoecological settings of this region at a later stage of the Quaternary age.

Morphological Changes Detection of a Large Earthflow Using Archived Images, LiDAR-Derived DTM, and UAV-Based Remote Sensing

In mountainous landscapes, where strongly deformed pelitic sediments outcrop, earthflows can dominate denudation processes and landscape evolution. This paper investigated geological and geomorphological features and space-time evolution over a 65-year time span (1954–2019) of a large earthflow, representative of wide sectors of the Apennine chain of southern Italy. The landslide, with a maximum length of 1.85 × 103 m, affects an area of 4.21 × 105 m2 and exhibits two source zones: a narrow and elongated transport zone and a lobate accumulation zone. Spatial and temporal morphological changes of the earthflow were assessed, comparing multi-source and multi-temporal data (aerial photographs, Google Earth satellite images, Light Detection and Ranging (LiDAR) and Unmanned Aerial Vehicles (UAV) system data). Geomorphic changes, quantified using Digital Terrain Models (DTMs) of differences, highlighted an extensive lowering of the topographic surface in the source area and a significant uplift at the landslide toe. Moreover, the multi-temporal analysis showed a high increase of landslide surface (more than 66%) during the last 65 years. The volumetric analyses showed that different sectors of the earthflow were active at different times, with different rates of topographic change. Overall, the used approach highlighted the great potentiality of the integration of multi-source and multi-temporal data for the diachronic reconstruction of morphological landslide evolution.

Unraveling multiple tectonic events and source areas in the intracratonic Bauru Basin through combined zircon geo and thermochronological studies

The application of Fission-Track Thermochronology (FTT), and U-Pb and Lu-Hf isotope analyses on the same zircon grains revealed the provenance and thermal/tectonic events related to the build-up and evolution of the Bauru Basin filling in Minas Gerais, Brazil. The U-Pb on detrital zircon reveals that the potential source areas were dominated by Brasiliano outcrops and subordinately, Paleoproterozoic, Mesoproterozoic, and Carboniferous sources. Positive εHf(t) signatures can characterize the Goiás magmatic Arc and older adjacent terranes as the most probable region that supplied the Bauru Basin. The FTT data display five main age peaks at 569, 337, 235, 132, and 83 Ma. They record the exhumation and denudation processes of Brasiliano and Gondwanide orogens and later, the Serra Geral magmatism of the South American Platform. A younger subordinate age (100–80 Ma) is recorded, and it may be associated with intense alkaline magmatism that occurred during the initial stages of basin deposition.

The unsteady post-rift stage of the South American passive margin based on the tectono-sedimentary evolution of the onshore Paraíba Basin, NE Brazil

The post-rift tectono-sedimentary history of passive margins has been an issue of increased interest after the perception of their unsteady nature during the Neogene and Quaternary. The evolution of the eastern South America margin might be benefited from investigations of the sedimentary record in a number of marginal basins. The Paraíba Basin is of particular interest to discuss the post-rift evolution of the South American passive margin, because it represents the last bridge with the African plate. This work aims to analyze the post-rift sedimentary record of the onshore Paraíba Basin as a contribution to discuss the neotectonic history of the South American passive margin. Surface and subsurface data were integrated from outcrops, deep stratigraphic profiles, airborne geophysical maps and remote sensing products. The depositional and denudational processes in this basin were a result of tectonic subsidence and uplifting. Tectonics after the main rifting phase are indicated by abundant structures, including normal, reverse, and strike–slip faults, as well as folds that affected the Neogene and Late Pleistocene sedimentary deposits. The ductile and brittle deformation resulted mainly from multiple reactivations of E–W, NE–SW and NW–SE trending basement shear zones. The deformation mechanism included distension and compression under a strike–slip regime. Tectonic reactivations even during the late Pleistocene support an unsteady South Atlantic passive continental margin throughout the post–rifting stage.

The International Association of Geomorphologists (IAG) Working Group on Denudation and Environmental Changes in Different Morphoclimatic Zones (DENUCHANGE): Scientific need, research objective, key activities and products

Denudation, including both chemical and mechanical processes, is of high relevance for Earth surface and landscape development and the transfer of solutes and sediments from headwater systems through main stem of drainage basin systems to the world oceans. The better understanding of possible effects of ongoing and accelerated environmental changes on present-day denudation requires systematic and quantitative studies on the actual drivers of denudational processes in differentiated landscape controls. Only if we have an improved knowledge of drivers, mechanisms and rates of contemporary denudational processes across a range of different selected climatic environments, possible effects of global environmental changes on denudation can be better assessed. However, a systematic geomorphologic comparison of present-day denudation rates in different defined climatic zones combined with a coordinated analysis and compilation of the respective key controls of denudation that is presently occurring in clearly defined drainage basin systems in the different selected morphoclimatic settings is still largely missing. The International Association of Geomorphologists (IAG) Working Group on Denudation and Environmental Changes in Different Morphoclimatic Zones (DENUCHANGE) is since 2017 helping to close this still existing knowledge gap and contributes to a better understanding of the possible effects of global environmental changes on contemporary Earth surface systems.

Quantification of Erosion and Uplift in a Rising Orogen—A Large-Scale Perspective (Late Tortonian to Present): The Case of the Gibraltar Arc, Betic Cordillera, Southern Spain

The present study deals with the morphometric quantification of erosion and illustrates the uplift component triggered by denudation (isostasy) in the growth and evolution of a rising orogeny by the application of Airy isostasy concepts. The Gibraltar Arc, located in the Western–Central sector of the Betic Cordillera, developed an exceptional geological scenario during the Messinian Salinity Crisis since the thin emerged fringe of the uprising Cordillera disconnected the Atlantic and Mediterranean basins, generating a relevant misbalance and asymmetry in the fluvial erosion between the two slopes of the emergent orogeny. Our analysis was applied to 50 individual drainage basins (spatial isostatic units) in the Western–Central Betic Cordillera, allowing us to obtain individual and bulk estimates for these isostatic parameters. GIS-based numerical estimations were obtained using LiDAR Digital Elevation Models (DEMs) provided by the Spanish Geographical Institute and reconstructed pre-incision surface models obtained from proxy paleo-elevation data, estimated from stratigraphic and geomorphological littoral to shallow marine markers. The obtained values for geophysical relief, denudation plates, erosion/uplift rates and computed accumulated uplift (245–407 ±20 m) are higher for the ancient Mediterranean slope of the orogen. On the contrary, the Atlantic slope presents an accumulated uplift of only 138–236 ±20 m, indicating the strong control of the ancient Messinian Atlantic–Mediterranean water divide. The temporal study of erosion indicates that most of the difference in uplift in the Mediterranean slope was achieved during or soon after the Messinian Salinity Crisis, resulting in mean uplift rates of 0.21 mm/y, but practically null (0.01 mm/y) for the Atlantic slope. The comparison of the geophysical relief models with proxy paleo-elevation data allowed us to assess the current state of the denudation process in the range. The results indicate that, towards the west of the range denudation compensated elevation, and is actively back-feeding isostatic rebound. Therefore, the contribution of external processes to mountain range elevation through isostasy is quantitatively estimated using elevation data. In this case, a relevant part of the surface uplift (50-55%) is undertaken by the orogen. Ultimately, the Messinian Salinity Crisis-related isostatic response to differential denudation may be behind the quaternary westward tilting of Iberia, causing more than 70% of the Peninsula to drain towards the Atlantic.

Effects of Land Cover Changes on Sediment and Nutrient Balance in the Catchment with Cascade-Dammed Waters

It is commonly believed that changes in the use of the catchment area have a direct impact on the quality of the water environment. Rivers with dams and reservoirs are characterized by a disturbed outflow of sediments and nutrients from the catchment area. The research was based on indicating the variation in time and space of loads of selected parameters of the water quality of the Brda River (Northern Poland) against the land cover changes based on the CORINE Land Cover (CLC) data for the 1990–2018 period. In the lower part of the Brda catchment area, there are three hydropower dams with reservoirs in the form of a cascade, whose work clearly affects the hydrological regime of the river. The analysis of the dependence of the dynamics of water quality changes on the usage of CLC was based on indicators such as sediments (suspended sediment load) and nutrients (total phosphorus load and total nitrogen load). The use of hydrological data on the Brda discharge above and below the reservoirs made it possible to calculate sediment and nutrient trapping efficiency. Linking the CLC data with the indices responsible for the mechanical denudation of the catchment area made it possible to show the strength of changes taking place in the catchment area. The results of the research do not indicate any direct correlation between land cover changes and the dynamics of the denudation process and matter transport in the Brda catchment area. As our research shows, the strong influence on the hydrological regime of the catchment points out the necessity to search for still other research methods supporting the decision-making cycle in the field of water management in the face of climate change.

Applied gamma-ray spectrometry for evaluating tropical soil processes and attributes

Geophysical methods, such as gamma-ray spectrometry, have great potential to enhance knowledge of the pedosphere (pedogenesis, pedogeochemistry and pedogeomorphology), helping to predict tropical soil attributes. We applied proximal gamma-ray spectrometry to evaluate tropical landscape dynamics, pedogenesis and spatial distribution of radionuclides and selected soil attributes. This study was carried out in southeast Brazil, where 79 soil samples (0–20 cm) along transects were collected to perform physical-chemical analysis coupled with collection of surface gamma-ray spectrometric data, allowing the detection of the radionuclides uranium (U238), thorium (Th232), and potassium (K40). Additionally, we analyzed soils in four toposequences, with varying lithology, relief, and hydrology. The radionuclide concentrations in soils showed a direct relationship with the parent material composition, either rocks or sediments. Weathering degree and the geochemical behavior of each radionuclide determines its permanence or removal in soils. Denudation processes along the toposequences also influence the distribution of radionuclides. On one hand, the radionuclide contents of mature, weathered soils are closely associated with advanced pedogenesis, with a higher clay contents and argic horizon formation, whereas in younger, less weathered soils the parent material exerts a greater influence than pedogenesis. Uranium decreased with altitude, and showed greater mobility compared with thorium. Thorium presented a higher correlation with clay content, and the opposite with sand content. Potassium detection increased with soil cation exchange capacity (CEC) and clay content. Gamma-spectrometry detected significant variations in some segments along the toposequences, undetectable by conventional soil survey techniques. This may indicate changes from one soil class to another or the continuity of a particular soil class, demonstrating the potential of this tool in digital soil mapping, pedogeochemical, pedogeomorphological and pedogenesis processes studies.

Shallow erosion on grassland slopes in the European Alps – Geomorphological classification, spatio-temporal analysis, and understanding snow and vegetation impacts

Erosion with the subsequent loss of soil and soil fertility is one of the urgent environmental problems worldwide. On grassland slopes from the montane to the alpine elevation zones of the European Alps, shallow erosion is a widespread and regionally increasing phenomenon. This group of mechanical denudation processes includes shallow landslides and nival abrasion (i.e., by snow gliding and avalanches), which are displacing patches of vegetation, soil and unconsolidated material. The resulting bare ground areas as well as the dislocated material are susceptible to further transport by water, snow, or wind. Our review summarizes the current knowledge on the main geomorphological processes for Alpine grassland erosion, namely shallow landslides and abrasion by snow movements as well as combinations of both processes. We shortly discuss the basic and variable controlling factors and further present a comprehensive approach for identifying and classifying shallow erosion phenomena and processes. In this context, the possibilities, limitations, and challenges for identification, classification and analysis of these processes by remote sensing are discussed in detail. Furthermore, the article focuses particularly on the role of snow-related processes, the relationship of erosion and vegetation, and the re-stabilization of affected areas by plants. Finally, we outline the discussion on the impact of land-use and climate change on these shallow erosion processes and identify the main research gaps that should be bridged in order to both better understand and deal with these erosion types on Alpine slopes.

A Multi Criteria Approach for Morpho-tectonic Evaluation of Sai River Basin in Uttar Pradesh

Abstract The study integrates the morphometric analysis, lineament evaluation and fluvial geomorphology to investigate the morphotectonic setup of Sai basin. The Sai river basin forms an integral part of the central Ganga plain where the gentle slope is significantly controlled by intra-basinal tectonic activity. The fluvial setup of the Sai basin which comprises of vast old flood plains now is displayed as an entrenched river with straight channel symmetry with multiple sinuous bends. The structural control and geomorphic asymmetry can be well established by using multi criteria approach of morphometric parameters and lineament analysis. The morphometric analysis of the basin shows that the Sai river comprises of 5th order stream basin with high elongation ratio and high bifurcation ratio suggesting structural and tectonic controls. The form factor, drainage density, and length of overland flow shows low permeability with low infiltration rate indicating sheet erosion as a major denudational process. The lineament analysis from the stream pattern analysis indicates structural control for drainages while geomorphology corresponds to the landscape of the basin. The lineaments analysis shows a major NW-SE trend in concordance to present foreland basin. Thus, the study confirms that the Sai basin has conclusive evidences of morpho-tectonic control in the central Ganga plain indicating the role of the tectonics in basin evoluation.

The role of frost cracking in local denudation of steep Alpine rockwalls over millennia (Eiger, Switzerland)

Abstract. Denudation of steep rockwalls is driven by rock fall processes of various sizes and magnitudes. Rockwalls are sensitive to temperature changes mainly because thermo-cryogenic processes weaken bedrock through fracturing, which can precondition the occurrence of rock fall. However, it is still unclear how the fracturing of rock together with cryogenic processes impacts the denudation processes operating on steep rockwalls. In this study, we link data on long-term rockwall denudation rates at the Eiger (Central Swiss Alps) with the local bedrock fabric and the reconstructed temperature conditions at these sites, which depend on the insolation pattern. We then estimate the probability of bedrock for failure through the employment of a theoretical frost cracking model. The results show that the denudation rates are low in the upper part of the NW rockwall, but they are high both in the lower part of the NW rockwall and on the SE face, despite similar bedrock fabric conditions. The frost cracking model predicts a large difference in cracking intensity from ice segregation where the inferred efficiency is low in the upper part of the NW rockwall but relatively large on the lower section of the NW wall and on the SE rock face of the Eiger. We explain this pattern by the differences in insolation and temperature conditions at these sites. Throughout the last millennium, temperatures in bedrock have been very similar to the present. These data thus suggest the occurrence of large contrasts in microclimate between the NW and SE walls of the Eiger, conditioned by differences in insolation. We use these contrasts to explain the relatively low denudation rates in the upper part of the NW rockwall and the rapid denudation in the SW face and in the lower part of the NW rock face where frost cracking is more efficient.

Изменение поглотительной способности почв по элементам рельефа балочных водосборов ЦЧР

Работа посвящена изучению особенностей состава почвенного поглощающего комплекса (ППК) по элементам рельефа балочного водосбора. Целью работы является выявление зависимости ППК от степени развития и характера водной эрозии и аккумуляции. Для достижения поставленной цели был решен ряд задач: проведение площадной почвенно-эрозионной съемки балочного водосбора; определение физико-химических и физических свойств почв по ГОСТированным и общепринятым методикам; сравнительный анализ поглотительных свойств почв по элементам рельефа балочного водосбора. Высокая степень эродированности территории определяет актуальность исследования поглотительных свойств почв, подверженных смыву и намыву. Объектом исследования являются почвы водосборной площади балки «Лог Репный». Согласно почвенно-эрозионному районированию Воронежской области объект исследования расположен в Семилукско-Нижнедевицком районе. Наблюдалось обеднение всего профиля почв водораздельных склонов и берега балки илистой фракцией за счет влияния эрозии почв и денудации. На днище балки было зафиксировано обогащение верхней части почвенного профиля илистой фракцией под влиянием аккумуляции почвенного материала, смываемого с вышележащих склонов. Поглотительная способность почв различных элементов рельефа водосборной площади балки «Лог Репный» может быть охарактеризована с помощью величины суммы поглощенных оснований. Наибольшая сумма поглощенных оснований наблюдалась на водораздельном плато (15.73 ммоль/100 г почвы). На берегу балки в условиях влияния процесса денудации зафиксировано уменьшение суммы поглощенных оснований в 2.5 раза. На днище балки в зоне преимущественной аккумуляции смываемого со склонов почвенного материала сумма поглощенных оснований была ниже, чем на водоразделе в 1.4 раза. Это связано с различным содержанием илистой фракции в этих почвах. Так, в почвах водоразделов илистая фракция составляла 24.8%, на берегу балки ее содержание было в 2.5 раза ниже, а на днище балки вновь возрастало до 22.4 %. Установлена зависимость суммы поглощенных оснований почв от перераспределения илистой фракции под влиянием эрозии и аккумуляции почв.