Incised River Valleys Research Articles

Microhabitat preferences in the European green lizard (Lacerta viridis): implications for conservation management of isolated populations

The European green lizard (Lacerta viridis) populations in Bohemia, Czech Republic, are isolated by more than 150 km from the northern border of the continuous range of the species. These populations are fragmented and further isolated from each other. In this landscape mosaic, they are tied to specific habitats located in deeply incised river valleys (the so-called river phenomenon) and thus may be viewed as stenotopic. The research site is located on the northern edge of the city of Prague. Since 1998, this site has been the subject of long-term conservation management aimed at strengthening and maintaining the abundance of the local L. viridis population. To formulate recommendations for the management of other isolated L. viridis populations, we performed a spatial analysis of the localities with observed individuals to determine and evaluate the significance of the chosen biotic and abiotic factors for habitat discrimination. We applied principal components and discriminant function analyses and examined the effect of 24 variables on the species’ presence. The results revealed the principal role of the presence of rock debris and hiding places for lizard occurrence. The strongest negative predictors were the presence of tall grass and high vegetation coverage. We discuss the applicability of our findings in both the theory and practice of species conservation and population management.

A diverse Late Pliocene fossil fauna and its paleoenvironment at Māngere, Auckland, New Zealand

ABSTRACT Excavations at Māngere Wastewater Treatment Plant, Auckland, in 2020 provided New Zealand’s richest and most diverse fossil faunas of mid-Pliocene age (Waipipian Stage, 3.7–3.0 million years old). The vast excavated heap of sandy shell was extensively searched and sieved resulting in the recovery of 266 fossil taxa, (particularly rich in Mollusca including 77 Bivalvia, 105 Gastropoda, 32 Foraminifera, 13 Ostracoda, 11 Bryozoa). The fauna includes several undescribed taxa and additional warm-water Pliocene records for New Zealand. The fauna is most similar in composition and age to the fauna obtained from the Otahuhu Brewery well in the late 1940s. The fauna contains a mixture of taxa from many different shallow marine habitats, from intertidal and subtidal rocky shores and intertidal and shallow subtidal soft sediment flats to exposed and semi-exposed subtidal sandy habitats down to depths of 30–40 m. The shelly deposit is inferred to have accumulated in a current swept subtidal channel during one of the mid-Pliocene warm periods when sea level was high and had flooded an incised river valley that flowed from east to west across the Auckland region.

Quantifying the late Quaternary incision rate in the upper Jinsha River with dated fluvial terraces and transient tributary profiles

The region occupied by three parallel rivers on the southeastern edge of the Tibetan Plateau is a zone with dramatically fluctuating topography and a complex tectonic setting. Deeply incised river valleys have become an ideal place for scholars to study the coupling relationships among river erosion, climate change and regional uplift. The fluvial terraces preserved in the upper Jinsha River provide the basis for exploring the history of river erosion. Through field investigation and dating results of terraces, the short-term incision rates of the upper Jinsha River are determined to be 0.18–5.47 mm/yr. In addition, the palaeo-profiles, which were reconstructed using two analytical methods, show that there are two depth intervals for the incision in the Jinsha River, namely, 1200 ± 220 m and 340 ± 250 m. They correspond to two early planation surfaces of the river, and the long-term average incision rates of the upper Jinsha River are estimated to be 0.23–0.34 mm/yr. By analysing the relationship between fluvial terrace formation and climate change, combined with the formation history of the early planation surface, it is recognized that the main force driving incision in the upper reaches of the Jinsha River comes from regional uplift. Climate change causes a continuous alteration between river incision and sediment accumulation, and this transition is also perturbed by mass flow events.

Senorady/Mohelno – ‘Boleniska’: A strategic position within the landscape with palimpsest of prehistoric occupation

The landscapes of the Mohelno settlement microregion are mostly gently undulating, but also dissected by two deeply incised river valleys – the Oslava River valley in the north and the Jihlava River valley in the south. The western boundary is formed by Zelený kopec (491 m above sea level, while the eastern boundary is marked by Biskoupský kopec (397.3 m above sea level) and Vodanský kopec (397.5 m above sea level). This microregion was settled at different intensities during the whole duration of prehistory. The ‘Boleniska’ elevation is located in the central part of the microregion and forms a strategic point – the entire microregion is visible from this elevation. This elevation comprise of an occupational palimpsest with intensive occupation during three different periods: at the beginning of the Upper Paleolithic (probably more than one techno-complex), the Late Neolithic (Lengyel culture) and at the end of the Eneolithic period (Bell Beaker culture). There is a high density of sites in this microregion from all three periods of interest. A similar settlement pattern (similar topography and cultural sequences) is known from other Moravian microregions. A preliminary testing of the site’s spatial distribution and a visibility analysis support the hypothesis indicating Mohelno – ‘Boleniska’ as a central site within the entire microregion only in the Paleolithic. The number of similar palimpsests composed of Paleolithic, Neolithic and Eneolithic sites is low within the entire microregion and the interpretation of this phenomenon must also take into consideration climatic factors, subsistence strategies, and socio-economic conditions in future research.

Сomposition and structure features of the Vikulov productive deposits (Krasnoleninsky arch) and their influence on reservoir properties

Both sedimentological factors and secondary processes of lithogenesis influenced the formation of porosity and permeability properties of the reservoir rocks of the Vikulov suite of the Krasnoleninskoe field. The former includes the conditions of sedimentation of the deposits of the Vikulov suite, which at the initial stages of its formation were controlled by the development of a system of incised river valleys, the stages of filling of which, like their composition, have their own characteristics. Also, various genetic types of deposits were formed here. The formation of the upper part of the Vikulov suite took place in a shallow-marine setting, in conditions of storm and wave shallow water, which affected the thin-layered structure of the VK1-3 reservoir. On the other hand, in the sections of a number of wells, dense interlayers are noted, the formation of which is associated with both sedimentation and superimposed processes in lithogenesis, including the formation of hydrocarbon deposits. Therefore, the prediction of the distribution of productive reservoir rocks is the main task when creating a petrophysical model of the field, and to solve this problem, the methods of lithofacies and staged core analysis are used in the work.

Composite landslide in the dynamic alpine conditions: a case study of Urbas landslide

The alpine environment is characterized by complex geology, high-energy terrain, deeply incised river valleys with high erosional potential, extreme weather conditions and dynamic geomorphic processes. Such settings provide favourable conditions for the formation of composite landslides rather than individual slope mass movement phenomena. As an example, we present the kinematics of the composite landslide Urbas in the North of Slovenia which developed in the complex geological and morphological settings characteristic of the alpine environment. The research combines several monitoring techniques and involves the integration of both surface and subsurface displacements measured in the landslide area. The results indicate that the composite sliding process consists of several simultaneous and interrelated types of movements occurring in different segments of the unstable mass that are governed by different mechanisms of displacements, such as rockfall, sliding and debris flow. The kinematic characteristics of a deep-seated landslide that formed in such conditions vary spatially, but is rather homogenuous vertically, indicating translational type of movement. Spatial kinematic heterogeneity is primarily related to the diverse terrain topography, reflecting in different displacement trends. Based on the revealed kinematic proprieties of the sliding material, the sediment discharge illustrates the sliding material balance which estimates the volume of the retaining material that represents the potential for slope mass movement events of larger scales.

Hydrothermal events in the Linzizong Group: Implications for Paleogene exhumation and paleoaltimetry of the southern Tibetan Plateau

Knowledge of the thermal history of the Linzizong Group (69–47 Ma) within the Gangdese arc is critical for interpreting the geologic evolution and isotope-based paleoaltimetric results of the southern Lhasa terrane of the Tibetan Plateau. Here, we combine results from geochronologic and thermochronologic studies of this group (divided into Dianzhong, Nianbo, and Pana formations upsection) and the structurally overlying Qianggeren granite (∼52 Ma) in the Linzhou basin. Whole rock 40Ar/39Ar ages of volcanic rocks from the stratigraphically lower Dianzhong and Nianbo formations are ∼10 Myr younger than their corresponding zircon U-Pb ages, suggesting a thermal disturbance of the argon system. Zircon (U-Th)/He ages (ZHe, 63 dates) range from 54 to 24 Ma, and apatite (U-Th-Sm)/He ages (AHe, 43 dates) range from 27 to 4 Ma. Inverse modeling of the thermochronologic data from the Qianggeren granite indicates rapid cooling between 42 and 26 Ma, possibly induced by movement of the Gulu-Hamu thrust. Positive correlations between ZHe ages and effective uranium and other geologic observations provide evidence that the Dianzhong and Nianbo formations were heated 300°C at 54–50 Ma, and that the entire Linzizong Group was variably heated to 130–170°C at 42–27 Ma. These findings, together with published geochronologic and thermochronologic data, suggest that abundant 50–45 Ma zircon fission track and ZHe ages from the Gangdese arc likely reflect conductive cooling of the Gangdese arc after a ∼52 Ma magmatic flare-up episode rather than rapid regional exhumation. Areas far from Cenozoic faults and deeply incised river valleys in southern Tibet have experienced only ∼3 km of exhumation since 45 Ma, consistent with the establishment of a low-relief, plateau-like physiography by Eocene time. The (hydro)thermal events are also manifested by widespread calcite recrystallization and δ18O and Δ47 alteration in most carbonates from the Linzizong Group, which must be taken into account in past and future carbonate-based paleoaltimetric studies.

Multi-Proxy Characterisation of the Storegga Tsunami and Its Impact on the Early Holocene Landscapes of the Southern North Sea

Doggerland was a landmass occupying an area currently covered by the North Sea until marine inundation took place during the mid-Holocene, ultimately separating the British landmass from the rest of Europe. The Storegga Event, which triggered a tsunami reflected in sediment deposits in the northern North Sea, northeast coastlines of the British Isles and across the North Atlantic, was a major event during this transgressive phase. The spatial extent of the Storegga tsunami however remains unconfirmed as, to date, no direct evidence for the event has been recovered from the southern North Sea. We present evidence of a tsunami deposit in the southern North Sea at the head of a palaeo-river system that has been identified using seismic survey. The evidence, based on lithostratigraphy, geochemical signatures, macro and microfossils and sedimentary ancient DNA (sedaDNA), supported by optical stimulated luminescence (OSL) and radiocarbon dating, suggests that these deposits were a result of the tsunami. Seismic identification of this stratum and analysis of adjacent cores showed diminished traces of the tsunami which was largely removed by subsequent erosional processes. Our results confirm previous modelling of the impact of the tsunami within this area of the southern North Sea, and also indicate that these effects were temporary, localized, and mitigated by the dense woodland and topography of the area. We conclude that clear physical remnants of the wave in these areas are likely to be restricted to now buried, palaeo-inland basins and incised river valley systems.

Environmental Control on Roman Time Coastal Industrial Settlements at the Confluence of the Atlantic and Mediterranean

Malvarez, G.; Navas, F.; Tello, C., and Hidalgo, R., 2020. Environmental control on Roman time coastal industrial settlements at the confluence of the Atlantic and Mediterranean. In: Malvarez, G. and Navas, F. (eds.), Global Coastal Issues of 2020. Journal of Coastal Research, Special Issue No. 95, pp. 870–874. Coconut Creek (Florida), ISSN 0749-0208.Ancient industries linked to the coast flourished in the rich realms of the temperate latitudes around the Iberian Peninsula from the VIIth century BCE to well after the Vth CE. Central to success during this time was the high productivity of the coastal waters and the value of the products manufactured in the then most important market in western Europe: the Mediterranean countries. It is during Imperial Rome when great romanization standardized the roman world that a network of industries, villae and cities flourished with valuable goods for the Empire even in the distant shores of southern Iberian peninsula (Baetica). Emperors were born in Baetica and olive oil and garum, the precious condiment sauce, generously exported to the heart of Imperial Rome. However, despite the generalized standardization, environmental control at the confluence of the Atlantic and the Mediterranean made that -a short distance apart- two distinct modes of coastal settlements developed. On the Atlantic coast, large scale garum production and fish salting factories generated both industrial settlements -where only workers lived along the installations- and prosperous cities with circa 30.000 inhabitants and municipal status. In the Mediterranean, but only close to the Strait of Gibraltar, a specific type of industry flourished that combined industrial scale but provided enough to establish very wealthy villae maritimae in the Alboran Sea along the current Costa del Sol. The presence of meso tidal conditions in the Atlantic promoted tidal fishing traps and extensive salt extraction, whereas the marked upwelling of the Alboran Sea and incised river valleys serving as natural ports of the estuaries in the Mediterranean approximately 2000 years ago, depicted a very diverse coastal paradigm. This paper revises the environmental control that determined why the different types of settlements occurred and why very distinctive cultures developed in such a short distance.

Reconstruction of atmospheric concentrations of enriched uranium from the former Apollo facility, Apollo, Pennsylvania, USA

The former Apollo facility in western Pennsylvania converted enriched uranium hexafluoride into uranium oxide for shipment to nuclear fuel fabrication plants from 1957 to 1983. Atmospheric releases of uranium from plant operations were estimated from stack sampling and production records. Releases occurred through stacks, rooftop vents, and an incinerator that operated from 1964 to 1969. Roof vents that exhausted workplace air was the major emission source from the plant. Total estimated release of uranium activity (including 234U, 235U, and 238U) to the air was 27.9 GBq. Atmospheric transport modeling was performed using a complex terrain model because the plant was located in an incised river valley. Almost two years of meteorological data were collected from a nearby 10-m tower, along with sounding from a collocated sodar. Light mean wind speed (1.56 m s−1) and predominately stable atmospheric conditions frequently resulted in poor dispersion conditions in the facility environs. Environmental sampling included continuous air monitoring data and depth profiles of uranium in soil that was deposited from airborne releases. Soil measurements exhibited a sharp drop-off in uranium concentrations with distance from the facility, indicating that large non-inhalable particles were emitted to the atmosphere. Large particles (~15–25 μm aerodynamic equivalent diameter) accounted for 17.5% of the total emissions. Soil measurements were used for model calibration and validation, while air measurements were used to evaluate model performance. Air concentrations were generally over-predicted for locations near the facility but showed only a slight positive bias for locations north of the facility. Predicted uranium activity air concentrations from Apollo sources averaged over 34 years were about three times greater than the background gross alpha activity value of 81 μBq m−3 in a ~0.5 km2 region surrounding the Apollo facility. The contribution of Apollo uranium to the gross alpha air concentration would have been negligible several kilometers from the facility.

Late Miocene birth of the Middle Jinsha River revealed by the fluvial incision rate

Abstract The Jinsha River has attracted considerable attention for nearly a century due to the morphology of its drainage basin. To explain the evolution of the Jinsha drainage basin, most researchers have considered that the present-day Jinsha (the upper reach of the Yangtze) was once a tributary of a single, southward-flowing river system called the Paleo-Red River, which drained into the South China Sea and was captured by the Upper Yangtze River, after which the flow direction changed to eastwards. The sudden disappearance, at 5.5 Ma, of the Red River submarine fan, which was fed primarily by the Paleo-Red River system, provides an important chronological constraint on the drainage reorganization and the capture event. However, until now, no geomorphic evidence has been presented to support this hypothesized age. Considering this problem, nine well-preserved terraces (T9 to T1) at Jinjiangjie in the Middle Jinsha River were evaluated in this study. To establish the chronological framework of these terraces, a combined dating approach was employed, incorporating electron spin resonance dating, cosmogenic nuclide (26Al/10Be) burial dating, and optically stimulated luminescence dating. We obtained a complete chronological sequence for terraces T9–T1, with ages of approximately 1.07 (T9), 0.70 (T8), 0.65 (T7), 0.51 (T6), 0.47(T5), 0.44(T4), 0.30 (T3), 0.18 (T2), and 0.047 (T1) Ma, respectively. Constrained by this framework, we calculated an average long-term fluvial incision rate of ~147 mm/ka. The reconstruction of the paleo-topography and paleo-drainage, based on digital elevation model data for the re-filling of the deeply incised river valley, indicates that the present drainage pattern in the Middle Jinsha system was established after the disruption of the paleo-landscape surface at an elevation of ~2000 m above sea level. The age of the present-day Middle Jinsha drainage was determined at approximately 5.5 Ma by extrapolating the average valley incision rate, suggesting that the present-day Jinsha was formed at about this time. Our results agree with the previously estimated timing of the disappearance of the Red River submarine fan.

Natural Conditions and Ecological Potential of Geosystems in the Central Part of the Oka Plateau (Eastern Sayan)

The objective of this study is to make an analysis of the natural characteristics of the mountain territories in Southern Siberia as part of the development of the technique for assessing the ecological potential of geosystems by using the central part of the Oka Plateau as an example. A brief description of the relief and exogenous processes is provided for three geomorphological regions: Okinsko-Sorokskii, Okinsko-Tustukskii and Soroksko-Bel’skii, which are characterized by a predominance of flat-topped interfluves, slopes of moderate steepness and deeply incised river valleys. The main features of the climate and hydrological regime in the study area are emphasized. The first ever bathymetrical survey of Lake Sagan-Nur was made, and its morphometric indicators were calculated. On the basis of the morphology and bottom sediments of the lake basin, the genesis of the lake is treated as glaciotectonic. The chemical composition of the waters and the lake bottom sediments were determined, which may well characterize it as a natural unpolluted reservoir. The natural regionalization scheme for the southeastern part of Eastern Sayan is presented. The large-scale landscape map has been compiled for a portion of the central part of the plateau as well as indicating and the main species of vegetation within its boundaries. The identified features in the natural conditions of the study area (relief, climate, surface waters and landscapes) furnish a means of assessing the ecological potential of geosystems. A combination of the nature- and anthropocentric approaches in assessing the ecological potential of geosystems offers considerable scope for optimal use of natural and human resources of this area which sparsely populated but rich in mineral resources. On the plateau, a detailed study of landscapes and their components is crucial to the assessment of the ecological potential of geosystems, although forecasts of the possible enhancement in the influence of the anthropogenic factor and analysis of the consequences of such an influence on the natural environment are also required.

The Effects of Tropical Cyclone-Generated Deposition on the Sustainability of the Pearl River Marsh, Louisiana: The Importance of the Geologic Framework

Shoreline retreat is a tremendously important issue along the coast of the northern Gulf of Mexico, especially in Louisiana. Although this marine transgression results from a variety of causes, the crucial factor is the difference between marsh surface elevation and rising sea levels. In most cases, the primary cause of a marsh’s inability to keep up with sea level is the lack of input of inorganic material. Although tropical cyclones provide an important source of such sediment, little effort has been made to determine the point of origin of the deposited material. In this study we use sedimentary, geochemical and biogeochemical data to identify the bed of the Pearl River and/or Lake Borgne as the source of a ~5 cm thick clastic layer deposited on the surface of the Pearl River marsh on the Louisiana/Mississippi border. Radiochemical chronologies and sedimentary evidence indicate that this layer was associated with the passage of Hurricane Katrina in 2005. As this material would otherwise have been lost to the system, this deposition indicates a net gain to marsh surface elevation. Accretion rates, determined from 137Cs and 14C profiles and the use of the Katrina layer as a stratigraphic marker, indicate that short-term (~50 years) rates are as much as an order of magnitude higher than the long- term (1000s of years) rates. We suggest that the marsh’s geologic setting in an incised river valley with steep vertical constraints and a large fluvial discharge, promotes rapid accretion rates, with rates accelerating as the sea moves inland, due to extended hydroperiods and the input of clastic material from both the marine and terrestrial sides. These rates are especially large when compared to accretion occurring in the more common open marshes fringing the Gulf that lack fluvial input. The difference is particularly large when related to marsh recovery/regrowth following the deposition of thick hurricane-generated clastic layers. Given the number of similar incised river valleys along the Gulf Coast, we believe that understanding the processes controlling marsh accretion in such environments is essential in evaluating marsh sustainability on a regional basis.

Multiple episodes of fast exhumation since Cretaceous in southeast Tibet, revealed by low-temperature thermochronology

The southeast margin of the Tibetan plateau is characterized by deeply incised river valleys separated by a perched low relief landscape that gently descends from the high Tibetan plateau towards the southeast. When and how this unique landscape formed is debated. The onset of increased river incision is often interpreted as a proxy for the timing of surface uplift. Here, apatite and zircon (U–Th)/He and apatite fission track thermochronometries are employed to map the spatial and temporal pattern of exhumation in the region. Vertical profiles of granitic rocks were collected near Deqin (∼28.5°N) and Weixi (∼27.5°N). The two transects share a similar exhumation history, with two episodes of relatively fast exhumation (∼100–300 m/Myr) in the Cenozoic: during the Paleocene to Eocene (60–40 Ma) and Miocene to present (20–0 Ma), separated by an intervening period of slow exhumation. A pulse of moderate to high exhumation (70–300 m/Myr) during the mid- to late-Cretaceous (120–80 Ma) is also present in the data. However, the rate and total amount of exhumation near Deqin is larger than at Weixi and is especially pronounced in the interval between 20 Ma to present. We interpret this difference as possibly related to differences in erosion rates between the Lancang (Deqin) and the Jinsha (Weixi) rivers. The Paleocene to Eocene episode of fast exhumation is likely in response to early Cenozoic deformation along tectonic boundary structures, related to the transpressional collision of the Indian plate with this region. Pre-Miocene episodes of fast exhumation corroborate recent paleoaltimetric studies, which show that the southeast margin of the Tibetan plateau was elevated prior to the Oligocene.

The evolution (2010–2015) and engineering mitigation of a rockslide-dammed lake (Hunza River, Pakistan); characterisation by analytical remote sensing

The remnants of rockslide dams are widespread in the deeply incised river valleys of the northwest Himalayas and adjacent Pamir Mountains of Central Asia. In January 2010 a major rockslide (estimated volume~55Mm3) dammed the Hunza River (NW Pakistan) and a rockslide-dammed lake (Lake Gojal) immediately began to form. The lake overtopped the rockslide dam 145days later through a spillway excavated in the surface of the debris by Pakistan authorities. Lake Gojal successively reduced in volume in response to spillway widening and deepening in engineering works up to May 2013; on August 28, 2015 (Day 2063 of impoundment) a remnant lake still remains. Using SRTM 3-arc-second digital terrain data and ten high-resolution satellite images from the period March 2010–August 2015, we document the river-damming environment of the Attabad rockslide, track and quantify the development of rockslide-dammed Lake Gojal and calculate lake areas and volumes at various stages of filling, stable overtopping, and partial draining to a final stable configuration. We introduce a method of delimiting lake shorelines by a pixel method which produces a mean elevation surface in the SRTM DEM; this technique results in accurate estimates of shoreline elevation and corresponding lake areas and volumes. We estimate the maximum volume reached by Lake Gojal, 51days after overtopping, to have been approximately 455Mm3. Using this data we also evaluate the mitigation works carried out by Pakistan authorities and find that i) they achieved an initial reduction of about 26% in the maximum possible volume of Lake Gojal that would have been reached without engineering intervention, and ii) as of August 28, 2015, in drawing down the lake by ~40m, they had achieved a 72% reduction in the maximum volume reached by Lake Gojal after overtopping without a catastrophic release taking place. The emplacement of rockslide dams and the behaviour of their impounded lakes are critical hazards to communities and the development of infrastructure, including hydroelectric facilities, in this region of Central Asia. We show that a combination of high-resolution optical satellite imagery and SRTM 3-arc-second digital topography is very effective in producing key first-order data on rockslide-dammed lakes for geomorphic and hydrological analysis as well as the evaluation of engineering mitigation.

Use of numerical methods for identification of hydrodynamic field and hydrogeochemical processes in the Quaternary multi-aquifer system

Abstract The paper presents spatial analysis and numerical methods to describe the hydrodynamic and hydrochemical conditions in a groundwater system. The research was conducted in the northern part of the Białystok High Plane, eastern Poland, within a Quaternary multi-aquifer system. Spatial analysis was used for imaging the quasi-continuous structure of the system based on a discrete set of hydrogeological data. A high-resolution regional flow model was used to identify the groundwater discharge and discharge zones of the individual aquifers. Calculations have shown a marked asymmetry of the flow system. Deeply incised river valleys in the Niemen River basin more strongly affect the groundwater than the discharge zones in the valleys of the Vistula River basin. As a result, the underground watershed in deeper aquifers is clearly shifted westward in relation to the morphological watershed. The hydrodynamic conditions of the system determined by numerical methods were used to identify the points along the groundwater flow-path for the hydrochemical study. It was the basis for the identification of points located along the groundwater flow direction, which were used in the hydrochemical study. Computational schemes of water solution models were calculated for the quasi-equilibrium state of chemical reactions between the solution and the solid and gaseous phases. Presentation of the chemical reactions allowed determining the origin of changes in the concentrations of individual components dissolved in groundwater. It was found that kaolinitization, i.e. chemical weathering of feldspars and plagioclases is the basic process that most affects the groundwater chemistry.

Erosion processes in karst landscapes of the Russian plain northern taiga, based on digital elevation modeling

This paper considers the problems of the potential development of erosion processes in the natural landscapes of northern taiga in the Russian plain. It is considered that in forest ecosystems, erosion processes are slow and are weakly reflected in the terrain. However, the situation changes radically if the vegetation cover integrity is violated, which is inevitable with the modern methods of developing northern territories. Furthermore, global changes in average annual temperatures and the occurrence of karst processes may be the reason behind the development of erosion processes. The authors suggest a method for determining territories with a varying occurrence probability of erosional processes, based on digital elevation modelling. The territory of the Pinezhsky Nature Reserve (Arkhangelsk region) was chosen as the test plot. Direct field studies were previously used to detect exogenous geological processes in this territory. The authors were the first to suggest digital elevation modelling as a method that allows determining the potential danger of erosion in karst landscapes of the northern taiga. The geomorphometric studies resulted in the determination of areas with the greatest and lowest occurrence probability of erosion processes in the Pinezhsky Nature Reserve. It was established that the most significant erosion type was linear erosion, represented by incised river valleys and karst ravines. Sheet erosion is less significant and occurs as sinkholes, local declines, and chasms over the valleys of subterranean rivers.

Morpho-sedimentary characteristics of the Quaternary Matiali fan and associated river terraces, Jalpaiguri, India: Implications for climatic controls

The Matiali fan is a coarse-grained, small alluvial fan in the eastern Himalayan foothills. It co-exists side by side with the large Tista megafan and other Quaternary fluvial deposits, and has been affected by a number of young thrust faults. It is generally believed that tectonics is the main control in the deposition of these proximal fan–terrace systems. In this paper, geomorphologic and sedimentologic study of the Matiali fan and associated river terraces are combined with five OSL dates from these deposits to understand the succession of events and the forcing mechanism that shaped the geomorphology in the study area during late Quaternary time. Two aggradational terraces (T1 and T2; T2>T1) occur within the river valleys incised on the Matiali fan. Three E–W scarps cross the fan surface, and they represent the steeper limb of the asymmetric fault-propagation folds formed over blind thrusts. These folds have deformed the fan (T3) and T2 terrace sediments, but the youngest T1 terrace deposits have remained undeformed. Sedimentological studies indicate continuous gradation from the coarsening-upwards mass-flow megagravel in the proximal part to the traction transported finer sheetflood gravels in the distal part, implying a continuous sedimentation history across the fan, uninterrupted by any evidence of syn-depositional tectonic movement. Poorly consolidated sandy gravels of the terraces indicate deposition through braided fluvial processes during a later period of sediment aggradation that filled up the incised river valleys. Previously published 14C dates indicate that deposition of the Matiali fan started around 34ka coinciding with a period of the intensified Indian summer monsoon of MIS-3. It is suggested that the fan was abandoned and river valleys incised during the LGM between 24 and 18ka when the discharge decreased substantially. Increased rainfall and sediment supply, with their inherent fluctuations, during wetter periods of MIS-2 and MIS-1 since 12ka probably resulted in the aggradation of T2 and T1 as shown by our OSL dates. OSL dates from the top of deformed T2 and base of undeformed T1 indicate that the Chalsa fold formed between ~11 and ~6ka. Succession of geomorphic and deformational events reconstructed from this study and available age data indicate that the Matiali fan and terrace aggradation coincides with periods of increased monsoonal precipitation, whereas tectonic movements along blind thrusts of Chalsa and Matiali took place later, deforming the fan and older terrace deposits. The evidence unequivocally indicates, contrary to the prevalent notion of tectonic control of geomorphic features in the proximal mountain-front setting, that the deposition of the fan–terrace system was primarily controlled by the fluctuation of the Asian summer monsoon rather than Himalayan tectonics.

Near pure surface uplift of the Argentine Frontal Cordillera: insights from (U–Th)/He thermochronometry and geomorphic analysis

Abstract Apatite (U–Th)/He thermochronology from palaeosurface-bounded vertical transects collected in deeply incised river valleys with >2 km of relief, as well as geomorphic analysis, are used to examine the timing of uplift of the Frontal Cordillera and its relation to the evolution of the proximal portions of the Andean foreland between 32° and 34°S latitude. The results of apatite (U–Th)/He (AHe) analyses are complex. However, the data show positive age-elevation trends, with higher elevation samples yielding older AHe ages than samples at lower elevation. Slope breaks occur at c. 25 Ma in both profiles, separating very slow cooling and or residence within a partial retention zone (slope of c. 10 m/Myr) at the highest elevations from a slope of c. 60–100 m/Myr cooling rate at lower elevations. The older AHe ages suggest either (1) minimal burial of the Frontal Cordillera and/or (2) significant pre–middle Miocene local relief. Geomorphic analysis of the adjacent, east-draining Río Mendoza and Río Tunuyán catchments reveals a glacial imprint to the landscape at elevations above 3000 m, including greater channel steepness and lower profile concavities developed during glacial erosion. Detailed analysis of headwall heights provides evidence of ongoing rock uplift along the entire eastern flank of the Frontal Cordillera and in the eastern flank of the Principal Cordillera south of the slab dip transition.

Issues on optimizing the ecological situation and vertical differentiation of landscapes of the forest-steppe zone of the chalk south of Central Russian upland

The southern region of the forest-steppe zone of the Central Russian The upland is the most-developed region for which the natural and economic specificity is predominantly determined by the absolute and relative altitudes of the land. The presence of elevated interfluves (up to 250 m or higher) and deeply incised river valleys (up to 100–150 meters) in this area has created prerequisites for the intrazonal vertical differentiation of landscape. As a result, upland landscape areas have been formed with intrinsic structurally genetic, dynamic, and functional features. In turn, changes in the altitudes of flat landscapes have required nature-reorganizational activity in an effort to optimize the ecological situation of the landscape.