Karst Processes Research Articles

Large non-karst caves of the Altai-Sayan mountain region: morphology and genesis

In the Altai-Sayan mountain region, located in southern Siberia, there are a number of caves developed in rocks in which karst processes are impossible to occur. In East Sayan, these are the Big Oreshnaya and Dudinskaya caves, the total length of which is more than 50 km and 35 km, respectively. Within the Altai Mountains, these are the Altaiskaya and Kek-Tash caves with a total length of 4.7 and 3.2 km, respectively. Mapping of the listed caves revealed that the morphology of their passages and the general structure differ significantly from those of caves in carbonate rocks. The passages have a flattened shape in cross section. Their width is usually meters and tens of meters, vertical extension is tens and hundreds of meters, and lateral extension is hundreds of meters. In general, the pattern of the passages is arranged in a box-like structure, where the pasages fit into a system of disjoint extended subvertical planes with rare short subvertical planes connecting them. The structure of the passages of the studied caves resembles the structure of karst caves, rotated vertically by 90°. The main directions of the passages there are not aligned in subhorizontal planes, but in subvertical ones. The revealed structure corresponds to the geometry of the structural pattern of Late Cenozoic fault systems formed as a result of subhorizontal compression. Signs of abundant argillization (alteration of the initial substance by hydrothermal processes and its replacement by newly formed clay minerals) were found in the studied caves. The formation mechanism of the studied caves is offered: removal of the substrate argillized by hydrothermal processes along the fault zones, by groundwater without significant participation of karst processes.

Geological and Hydrochemical Processes Driving Karst Development in Southeastern Riyadh, Central Saudi Arabia

This study investigates the processes leading to karst development in the southeastern part of Riyadh city extending up to Al Kharj. Numerous solution features such as sinkholes, collapsed dolines, and solution caverns are common in the area. The role of water in the development of the karst features was investigated using an integrated geological and hydrochemical approach. Geological investigations included the petrographic analysis of rock samples collected from zones of intense karstification with special emphasis on mineral dissolution. The study showed that the Sulaiy Formation is commonly fractured, brecciated, foliated, and contains numerous cavities, vugs, and openings. These features have formed by mineral dissolution by circulating groundwater, which has removed anhydrite beds from the underlying Arab–Hith sequence. Karstification likely started from the tectonically weak zones when there was more groundwater recharge. Studies show that during the early to mid-Holocene period, the climate in the Arabian Peninsula was humid, promoting groundwater recharge and subsequent mineral dissolution, though the process of karstification must have started much earlier. Hydrochemical findings reveal that mineral dissolution (halite and calcium sulfate) is the main process affecting groundwater chemistry. The Piper plot revealed two main hydrochemical facies: the (Ca2+ + Mg2+)–(Cl+ SO42−) Type (Type A) and the (Na+ + K+)–(SO42− + Cl) Type (Type B). Most of the samples belong to Type B, typical of groundwater facies affected by dissolution of halite and anhydrite mineral. The absence of the (Ca2+ + Mg2+)–(CO32− + HCO3−) type of groundwater facies indicates a lack of recent groundwater recharge and the removal of carbonate minerals from the system through precipitation, as evidenced by the saturation indices. Plots of the major ionic pairs (cations vs. anions) in groundwater indicate strong halite and gypsum/anhydrite dissolution. Of the three carbonate minerals, calcite has the highest average saturation index followed by aragonite and dolomite. This suggests significant past rock–water interaction leading to carbonate dissolution. Presently, any additional calcium or carbonate ions introduced into the water lead to calcite precipitation. The study indicates that the process of karst development may not be active today. Currently, groundwater chemistry is mainly influenced by rock–water interaction leading to gypsum/anhydrite dissolution, which has resulted in a high concentration of Na+, Ca2+, Cl− and SO42− ions in groundwater. The dissolution of gypsum and halite from the Hith Formation weakens the structural integrity of the overlying Sulaiy Formation, creating large underground cavities. These cavities increase the risk of roof collapse, leading to cover-collapse sinkholes as the roof becomes too thin to support the weight above.

MODERN PROCESSES IN THE BEADED CHANNELS OF STEPPE RIVERS OF THE KHOPER-BUZULUK PLAIN

Beaded-shaped channels (or chain-of-ponds), characterized by alternating lake-like extensions and narrow runs, are widespread on small rivers of the steppe zone of Russia. Extensions of channels - beads (pools or ponds), with a depth of up to 5-6 m, are of great importance for cattle breeding, providing a watering place during the dry periods of the year, when the flow of small rivers stops. However, the mechanisms of their specific channel shape formation are still debatable: it is explained by uneven siltation of channels, formation of whirlpools, groundwater discharge, karst processes or relict thermokarst. The aim of the study was to assess the role of water flow in the formation and support of the beaded shape of river channels. The tasks were to reveal the hydrological regime of the Kardail and Kupava rivers, determine the hydrodynamics of the flow in beads and runs, describe the characteristics of erosion and accumulation processes and the sediment transport, as well as to identify relict elements of the channel and floodplain structure that do not correspond to modern water state. Water flow of the studied rivers shows a long-term decrease in snowmelt flood, as evidenced by the rare flooding of the high-level floodplain, low rates of bank dynamics, and the discrepancy between the size of meanders and the width of the channel. The annual sediment load of the studied beaded rivers is low, estimated at 6,05 t/km2 in 2023. The reason is a low supply of sediments from the catchment area and low rates of erosion of channel bed and banks built of clay and silt. The present-day dynamics of water flow do not help the deepening and expansion of the beads. The flow reaches maximum speed (up to 1-1,3 m/s) in channel runs, while in channel extensions flow speeds drop to 0-0,3 m/s, supporting the sediment accumulation, despite the presence of whirlpools. A significant part of channel extensions is located on sites of former pools of the ancient meandering channel, inherited by the modern watercourse. On the former riffles the channel narrowed and a low-level floodplain was formed. Deep channel extensions were preserved due to the low sediment load and its fine composition, which prevents its rapid settling from the suspension. The results of the study suggest possible contribution of other factors to the formation of original deep pools, including the cryogenic ones.

Characteristics of an Inorganic Carbon Sink Influenced by Agricultural Activities in the Karst Peak Cluster Depression of Southern China (Guancun)

Land use in karst areas affects soil properties, impacting carbon sinks. Accurate estimation of carbon sink flux in karst areas through zoning and classification is crucial for understanding global carbon cycling and climate change. The peak cluster depression is the largest continuous karst landform region in southern China, with the depressions primarily covered by farmland and influenced by agricultural activities. This study focused on the Guancun Underground River Basin, a typical peak cluster depression basin, where sampling and analysis were conducted during the agricultural period of 2021–2022. Using hydrochemical analysis and isotopic methods, the results indicated that: (1) The primary hydrochemical type in the Guancun Underground River Basin is HCO3-Ca, with hydrochemical composition mainly controlled by carbonate rock weathering. (2) The primary sources of Cl−, SO42−, and NO3− are agricultural activities, with agriculture contributing 0.68 mmol/L to dissolved inorganic carbon (DIC), accounting for about 13.86%, as confirmed by ion concentration analysis and isotope verification. (3) The size of the depression area is proportional to the contribution of agricultural activities to DIC, while also being influenced by dilution effects. A comparison was made regarding the contribution of other land use types to DIC. The impact of land use on DIC in karst processes should not be overlooked, and zoning and classification assessments of carbon sink flux under different influencing factors contribute to carbon peaking and carbon neutrality goals.

GEOTOURIST OBJECTS AND ROUTESOF THE SIAN LOWLAND

The geomorphological, geological, and archaeological objects of the Sian Lowlandhave been studied, and their significance as potentially popular geotourist attractions has been substantiated. The Sian Lowlandis located in the northwestern part of the Ukrainian Carpathian Foreland and is a constituent geomorphological element of the Sian-Dniester interfluve. The lowland’s relief is smooth, characterized by the alternation of ridge-like elevations of the Vyshnia‒Vizhomlia, Vizhomlia‒Shklo, Shklo‒Zavadivkainterstreams and shallow trough-shaped river valleys with gently inclined non-terraced slopes and often waterlogged bottoms. The topography of the Vyshniaand Shklo valleys is varied with dunes concentrated in two strips – one stretches along the right side of the Vyshnia river valley through the villages of Malniv, Martyny, Sokolia, ArlamivskaVolia, Khorosnytsia and Zarichchia, and the other one is developed in the Shklo river valley between Krakivets and Yavoriv. The northeastern part of the Sian Lowland has undergone a significant anthropogenic transformation – the Shklo River channel has been regulated, and a complex of anthropogenic landforms and deposits has been formed within the boundaries of the Yavoriv mining district: karst processes and phenomena have been activated. Less large-scale anthropogenic changes have occurred in the lowland’s southern part, which is proposed to be covered by a geotourist route that will run through Rodatychi ‒ SudovaVyshnia ‒ Zarichchia‒Khorosnytsia ‒ ArlamivskaVolia ‒ Sulkivshchyna. The main geotourist attractions here are the following geological, geomorphological and archaeological objects: the preserved valley of glacial meltwater runoff between Rodatychi and SudovaVyshnaya, which is now drained by the Rakivriver, as well as the dunes spread in the valley and the archeological monument KniazhyiMist; eolian, fluvial landforms and deposits, outcrops of fluvioglacial accumulations and archaeological sites developed in the vicinity of the villages of Zarichchiaand Pisky:a complex of eolian and fluvial landforms and deposits, as well as archaeological sites, developed nearKhorosnytsia village; eolian landforms and deposits, an archaeological site near the village of ArlamivskaVolia; glacial accumulations, which were discovered in a quarry located east of the village of Sulkivshchyna (north of Mostyska). These settlements are connected to each other and to Lviv by the M-11 highway (Lviv‒Mostyska‒Shehyni) and/or the Lviv‒Shehynirailway line, which provides convenient access to the proposed geotourist attractions. The developed geotourist route also makes it possible to unite the so far separate Carpathian, Carpathian Foreland and Roztoczegeotourist routes into a single network. Key words: geotourist attractions; Sian Lowland; eolian deposits; dune; terrace; fluvial landform; archaeological site.

LITHOLOGICAL-STRATIGRAPHIC CRITERIA OF KARST ZONING OF THE MIOCENE SULFATE LAYER OF WESTERN UKRAINE

The proposed karst regionalization (zoning) is a novel approach to identifying the unique characteristics of karst processes in specific areas. The sulphate karst of western Ukraine, linked to the Miocene evaporite basin at the junction of the East European Platform and the Pre-Carpathian Foredeep, is a prime example. The previous karst zoning schemes of the East European Plain classified the entire area of sulphate rocks distribution in the west of Ukraine as the Podilsko-Bukovinsky karst Area, with the West Podilsky and Pokutsko-Bukovinsky karst Regions within it. However, with the emergence of numerous detailed stratigraphy works on the evaporite formation of this territory, a new approach to karst zoning in evaporites is necessary. This paper presents a systematic approach to upgrading the mentioned regions to the rank of sub-areas and distinguishing the regions within them based on lithologic-stratigraphic differences. The authors studied six localities as examples. In the first one, the gypsum layer is characterized by the stromatolite, grass-like and sabre-like facies. The last two contain thin carbonate-clay layers, leading to the collapse of large rock blocks inside the Kadubivska Cave. On the second site, the gypsum is composed of stromatolite, coarse-crystalline, and sabre-shaped facies. Only one small Tovtry Cave, which has a hypogene morphology, is known here. The third site has grass-like gypsum facies, and intensive modern karst occurs, with numerous sinkholes, underground rivers, and sinkholes. The influence of facies variability on the development of the mesomorphology of underground galleries is traced here in Pionerka Cave. The fourth area is built of nodular gypsum facies. There are no insoluble layers here, but the facies have many thin mineral films between the grains. Therefore, the entrance parts of the caves are unstable for physical weathering. The fifth section is highlighted as a section of the spread of metasomatic limestone, which replaces sulphate deposits here. They contain a significant cave labyrinth, but whether karstification occurred before or after metasomatization remains unclear. The sixth section is completely composed of stromatolite gypsum facies. It is characterized by stability to collapse due to the monolithic structure of gypsum, which is noticeable in the example of the Cave of Popeliushka (Zolushka) on the border of Ukraine and Moldova. The selected areas are proposed to be considered as examples of karst zoning based on lithologic and stratigraphic features. Key words: karst regionalization; gypsum, limestone; caves, breakdown; relief, landscape.

Temporal insights into karst system evolution: A case study of the unroofed cave above Škocjanske Jame, NW Dinarides

This study presents a comprehensive investigation of the unroofed cave above the active Škocjanske Jame water cave and explains the intricate processes that characterize the karst landscape. Despite extensive knowledge of the karst morphology, the precise development stages and timing of formation remained ambiguous. Through detailed multi-proxy sedimentary analyses, we unveil the sedimentary features documenting relict speleogenetic processes and provide insights into regional tectonic events and climatic changes. The cave was filled with two types of sediments: the upper speleothem section and the lower allogenic clastic section. Based on paleomagnetic characteristic and U/Th data, the fill of the unroofed cave is estimated to be between approximately 5 Ma (probably 5.2 to 4.9 Ma) and >773 ka old. Our results reveal a complex interplay of allogenic and autogenic sediments, suggesting a stable catchment over several million years. The dating results indicate deposition in phreatic regime since at least 5 Ma, with the river flowing through the cave until about 2.6 Ma. Our study emphasizes the importance of tectonically-driven uplift phases in cave speleogenesis rather than the importance of Quaternary climate changes. Furthermore, we define the initial stages of the development of the Škocjanske Jame karst system and estimate the time span of the evolution of solution and collapse dolines. This research underscores the importance of integrating geological, hydrological, and chronological approaches to unravel the history of karst landscapes and their implications for understanding dynamic karst processes. The temporal and spatial reconstruction of the development of the unroofed caves provides an insight into the first stages of the present karst system influenced by the sinking river.

Equifinality and unusual genesis of closed depressions in a mixed carbonate/igneous terrain

Closed depressions such as sinkholes and pits can form through various subsurface processes, leading to similar surface expressions. This study analyzes closed depressions in eastern Galilee, Israel, to evaluate their potential origins. Ten depressions were surveyed, including shallow bowl-like forms and steep-walled pits. The terrain comprises faulted Cretaceous carbonates intruded by Early Pleistocene basalts dated to around 2.25 Ma. The circular morphology of the depressions and lack of ejecta indicate collapse into subsurface voids. Field evidence and geophysical data reveal a complex interplay of tectonic and volcanic factors. Some depressions appear to be structurally controlled by dilational normal faults, while others appear to be associated with volcanic features like dikes. Karst processes in the soluble carbonates likely contributed, most probably by hypogene dissolution related to magmatic fluids which may have enhanced void development. A dike identified within depressions suggests void formation through inflation and deflation of intrusions. Progressive collapse and erosion modified steep pits into shallow bowl-like depressions over time. Our results highlight the equifinality of closed depressions, wherein similar morphologies can arise through multiple subsurface processes. Unraveling this complexity has significance for interpreting pit craters on planetary surfaces using remote sensing.

Identification and Mitigation of Subsidence in Karstic Areas with Sustainable Geotechnical Structures: A Case Study in Gallur (Spain)

In various areas of the Ebro valley in Spain, including the region discussed here, the risk of sinkholes is becoming particularly severe, particularly impacting urban areas and roadways where land subsidence from karstic processes is common. However, knowledge of the area, its geological–geotechnical configuration, and the carrying out of specific research studies are allowing solutions to be tested in an attempt to resolve these situations. A case in point is the examination of settlement issues along a stretch of the access road leading to the city of Gallur from the east (known as Camino Real) in the Zaragoza province, Spain. Numerous surface manifestations of recent subsidence and/or collapse activities have been observed, manifesting as craters and ground undercuts, some several meters in diameter. The prevalence of highly karstifiable materials in the area, evident from the existence of subsidence pockets and collapse dolines, poses significant safety concerns, particularly for traffic and town access, prompting the closure of Camino Real for several years. Local and provincial authorities have embarked on studies to try to recognise this type of situation. Reports aimed at defining karstification processes, conducting geomechanical analyses of subsidence and cavity collapses, and proposing technical measures to mitigate risks have been prepared. Finally, a consolidation solution was proposed based on injections at column-depth of mortar with special characteristics, combined with the replacement and reinforcement of the most superficial soil by means of high-tensile-strength geotextile meshes.

Limited Evidence of Late Quaternary Tectonic Surface Deformation in the Eastern Tennessee Seismic Zone, United States

ABSTRACT The ∼300-km-long eastern Tennessee seismic zone, United States, is the secondmost seismically active region east of the Rocky Mountains. Seismicity generally occurs below the Paleozoic fold-and-thrust belt within the Mesoproterozoic basement, at depths of 5–26 km, and earthquake magnitudes during the instrumental record have been moment magnitude (Mw) ≤4.8. Evidence of surface deformation may not exist or be difficult to detect because of the vegetated and soil-mantled landscape, landslides, locally steep topography, anthropogenic landscape modification, or long, irregular recurrence intervals between surface-rupturing earthquakes. Despite the deep seismicity, analog models indicate that accumulation of strike-slip or oblique-slip displacement at depth could be expected to propagate upward through the Paleozoic section, producing a detectable surficial signal of distributed faulting. To identify potential surface deformation, we interrogated the landscape at different spatial scales. We evaluated morphotectonic and channel metrics, such as channel sinuosity and catchment-scale hypsometry. In addition, we mapped possible fault-related topographic features on 1-m lidar data. Finally, we integrated our observations with available bedrock and Quaternary surficial mapping and subsurface geophysical data. At a regional scale, most morphotectonic and channel metrics have a strong lithologic control. Within smaller regions of similar lithology, we observe changes in landscape metrics like channel sinuosity and catchment-scale hypsometry that spatially correlate with new lineaments identified in this study and previously mapped east–west Cenozoic faults. These faults have apparent left-lateral offsets, are optimally oriented to slip in the current stress field, and match kinematics from the recent focal mechanisms, but do not clearly preserve evidence of late Pleistocene or Holocene tectonic surface deformation. Most newly mapped lineaments might be explained by either tectonic or nontectonic origins, such as fluvial or karst processes. We also reevaluated a previously described paleoseismic site and interpret that the exposure does not record evidence of late Pleistocene faulting but instead is explained by fluvial stratigraphy.

The study of soil organic carbon rate in Gunungsewu Karst Area, Pracimantoro District

Karst landscape has a notable role in carbon cycles. The role isn’t merely through the karstification (solutional) process but also on soil since Soil Organic Carbon (SOC) is the biggest terrestrial organic carbon stock. The purpose of this research was to discover characteristic and calculate organic carbon within rainfed paddy, dry land seasonal crops, shrubland, and homogenic forest in Gunungsewu Karst, Pracimantoro District. The soil sampling method was determined by purposive, then computed through a laboratory test to figure out the soil texture, permeability, bulk density, particle density, porosity, and organic carbon percentage. C-organic assessment refers to the calculation by National Standardization Agency. Permeability is the obvious parameter that was discovered. Soil permeability in the agricultural land uses has a higher value than in non-agriculture land uses. This matter is caused by soil tillage as a human agriculture activity. The result of the SOC assessment is that non-agriculture land use has a higher rate than agriculture land use. SOC within the homogenic forest was the highest rate (30,03 tonnes ha-1), and the dry land seasonal crops was the lowest rate (18,9 tonnes ha-1), whereas the rainfed paddy and shrubland, respectively 21,63 tonnes ha-1 and 23,62 tonnes ha-1. It caused by the litter on the agriculture land use was slightly than the litter that piled up on the non-agriculture land use because the land was tillage and cleaned as an agriculture activity. Research like this should be undertaken in order to gain information about soil or karst roles within carbon cycles as a mitigation to climate change.

The Escarpão Plateau (South of Portugal)—a Study Case of Nested Geosites from the Aspiring Algarvensis Geopark

Located along the southern limit of the Algarvensis aspiring UNESCO Global Geopark (aUGGp), the Escarpão Plateau is a singular geomorphological structure sculpted by fluvial, karst, and tectonic processes. The plateau is deeply scarved by the Quarteira Rivulet, forming a valley that crosses the most complete Upper Jurassic sedimentary sequence of the Eastern Algarve (Southern Portugal). This sequence includes five geological formations representing different depths of carbonate ramp deposition from the Tethys Sea: Peral Formation, Jordana Formation, Cerro da Cabeça Formation, Escarpão Formation, and the upper Limestone Formation with Anchispirocyclina lusitanica (foraminifera), respectively from the oldest formation to the most recent at the top. Throughout the Quaternary Period, the karst processes shaped a landscape of sparse and poor soils, based on which successive generations adapted their subsistence agriculture and way of life. The geomorphology of the plateau and the rivulet valley, the sequence of the carbonated formations, and the diversity of sedimentary and paleontological records can be considered possible sites of diverse geological interest and with different scales that are embedded in each other, forming thus nested sites. To promote and preserve these sites, the Algarvensis aUGGp shaped an 8-km-long interpretative walking path, passing through 11 points of interest, including biosites and geosites. Their interpretative boards highlight not only the different spatial and temporal geological diversity but also its relationship with surrounding cultural and historical heritage. Finally, this work allowed the creation of new products for outreach and public awareness towards an effective geoconservation.

The role of the Serranía del Burro range in the distribution and hydrochemical behavior of water resources in Coahuila, NE Mexico

Highlands form one of the essential links ensuring the good performance of the hydrological cycle on Earth, and significant amounts of good-quality water are concentrated in these areas and distributed to lowlands. These resources are indispensable for arid/semi-arid regions such as NE Mexico, where water is scarce and sometimes lacks good quality. In the state of Coahuila, the Serranía del Burro is one of the most important hydrogeological systems, and at least seven aquifers show some type of relationship with this system or benefit from its recharging. In this paper, data from 50 well and spring samples are presented with the goal of identifying the effect of the range on the chemical composition of the surrounding aquifers and the mechanism of recharging. The results show that in this area, the waters are mostly of the type Ca2+-Mg2+-HCO3-, with minor contributions from more saline and mixed waters. The main processes responsible for the chemistry of the waters are water-rock interactions, mixing and, cationic exchange, in which, the weathering of silicates and, the dissolution of carbonates through karst processes predominates. Recharging is characterized as fresh and deep, due to the influence of karst and tectonic phenomena throughout the geology of the Serranía del Burro and the adjacent areas. Limited shallow meteoric percolation occurs in the NO of the Serranía del Burro due to the presence of conglomerates and caliche sequences, resulting in low permeability. This study highlights the need to take care of good-quality water resources located in the mountains; adequate exploration work must be carried out in these areas, since waters of questionable quality prevail throughout the state, mainly due to natural salinization processes in lowland areas.

HYDRODYNAMIC MODEL OF SOLOTVYN ROCK SALT DEPOSIT

Rock salt development brings risks of harmful impact on water resources, in particular the Tysa River, posing a threat of cross-border spread of saline pollution on the border between Ukraine and Romania (Solotvyn rock salt deposit, Transcarpathia, western Ukraine). The impact of technogenic load (underground mining of rock salt) within the deposit led to deformation of the structure and nature of water exchange, intensification of suffusion and karst processes, ground surface deformations, catastrophic inflows of groundwater into mines, and, as a result, to the cessation of development of this deposit in 2010. However, the suspension of salt mining did not stop the development of the above-mentioned hazardous geological processes caused by both natural and man-made factors. In order to justify measures for prevention pollution of the Tysa River basin, a hydrogeological model of the Solotvyna rock salt deposit and surrounding areas was created, which allowed to predict the direction and flow rate of fresh and saline groundwater. The model was developed using new data on the geological structure and hydrogeological conditions of the study area (groundwater monitoring data). The modernised hydrodynamic model includes five layers (main aquifers and confining layers). As a result of modelling, maps of the velocity vectors and head contours for two aquifers (Quaternary and Tortonian) were obtained. Based on the results of solving a number of inverse problems, the functional correspondence of the model to natural and anthropogenic conditions was proved. According to the preliminary calculations of the actual groundwater filtration velocity and the path lines of the inert pollutant spreading, it was found that the time of its migration from the salt contour to the Tysa River is approximately 2–3 years. The developed groundwater flow model will be used to substantiate the network of hydrological and hydrogeological observation points in order to optimise the monitoring of water pollution processes.

Computer modeling of the interaction of the building underground part with the soil foundation during the karst cavity formation on the example of the administrative and business center construction

In restrained urban conditions of Moscow, the accomplishment of complex urban construction projects is complicated by the choice of construction sites, as well as by lack of methods for computer modeling of the interaction of high-rise and unique buildings and structures with the probable formation of karst cavities in the current regulatory documents. The overall profitability of the project is under the great impact of it, therefore a reliable accounting of karts-suffusion processes is a priority issue in designing buildings and structures, especially if it concerns the unique and high-rise ones. The authors analyze the results of the calculations of the forecast assessment of the impact of a karst cavity probable formation on the subsurface parts of building of the administrative and business center construction in flat and spatial formulation. In spatial formulation different positions of the potential karst cavities are considered; their locations were chosen according to standard procedures and were guided by the results of geological and geophysical research. It has been reviewed the formation of arch over a karst cavity in a 2D and 3D formulation in the condition of different location of the karst cavities in plan and by depth of occurrence. It has been made methodological recommendations for determining the predicted bore of the karst cavity, for taking into account the frame stiffness of the aboveground part of the building, for defining the principles of a karst cavity modeling, as well as for the choice of assessment criteria of stability of cover mass above the potential cavity. The discovered differences in the results of 2D and 3D settings permit to make a conclusion that solving the problem in a flat formulation contributes to the overestimation of karst processes danger and, therefore, to the excess in anti-karst measures included in the project.

3D digital analysis for geo-structural monitoring and virtual documentation of the saint Michael cave in Minervino Murge, Bari (Italy)

The presence of caves and, in general, of subterranean landforms produced by karst processes is among the most typical geological features of the territory of Apulia, southern Italy. Several examples can be counted throughout the region, especially in the Murge area. The need to perform geo-structural analysis aimed at evaluating the stability conditions is especially significant for those caves open to the public. In the Murge area, the cave of Saint Michael at Minervino Murge is among the most famous. Beside the religious and historical interests, the whole cave needed a detailed analysis of the rock mass stability, both for protection of its architectural and archaeological values, and for safeguard of the visitors. At these aims, we performed various digital surveys by means of laser scanners and drones equipped with high-resolution cameras, in order to understand the geological setting of the entire cave and to identify unstable blocks.

Karst of Sterlitamak (BASHKIR) Shikhans and Their Surroundings in Southern Pre-Ural Area

Abstract—Shikhans, or lone mountains, is the local name for island mountains in the flat foothills of the Southern Urals. The shikhans are denudation remnants, sometimes with preserved residuals of Miocene-Pliocene planation surface on their tops, which allows estimating the total time of development of karst processes at least 5 million years. Despite more than 200 years of research on the shikhans, karst and its manifestations have received little attention to date. A map of karst in the shikhan territory was drawn up according to the standard methodology of karstological survey. Widespread and quite rare forms of carbonate karst of the shikhans and sulphate karst of their close vicinities were characterised. It was established that along with widespread and known in temperate latitudes karstic features, very rare corrosion wells are developed in the gypsum of the Kungurian Stage in the study area, forming karst fields with the highest density of karst forms known in the East European Plain. Gypsum caves at various stages of formation, as well as semi-blind karst-erosion gullies not typical for the lowland sulphate karst of the region were recorded. For the carbonate karst of the Shikhans in the limestones of the Sakmarian Stage, the highest location of karst caves in the foothills of the Southern Urals and the oldest (earky Middle Pleistocene) age of their foundation were established. The main peculiarity of distribution of both surface and underground karst-holes is a clearly expressed dependence of forms and frequency of their occurrence on the course of formation of relief elements in the Neogene-Quaternary time. The presence in a small area of two types of karst by composition of karst rocks with very rare karst forms predetermines the high scientific, practical and educational significance of the shikhans and their surroundings.

The impact of subsurface life on ghost-rock karstification processes and cave formation

Karst systems represent an important carbon and freshwater reservoirs. Although karst systems have been studied for many years, a new paradigm has emerged that suggests some of them could be formed by ghost-rock processes (Dubois et al. 2014). Contrarily to the classical total karstification, ghost-rock karstification leaves in place a weathered rock, called the ghost-rock, that can constitute a microbial habitat (Spilde et al. 2005). The first results of a geomicrobiological study of the Sterkfontein’s cave system in South Africa show that these ghost-rocks are mainly composed of iron and manganese oxides mixed with organic matter of putative microbial origin (Pisapia et al. in prep). To further understand the microbial community inhabiting these ghost-rocks, its specificity compared to groundwater, and its functional impact on the karst system of Sterkfontein, a metagenomic analysis from both ghost-rocks and groundwater samples was performed. It was completed by laser microdissection of the microorganisms attached to the mineral particles, followed by whole-genome amplification and transmission electron microscopy to analyze both the nature of the mineral particles and the microorganisms associated with them. The results highlight the differences in community between these two environments (with higher abundance of Actinobacteriota and Acidobacteriota in ghost-rock samples compared to ground water in particular), and suggest a high importance of microbe-minerals interactions in the ghost rocks, through metallophores production and extracellular electron transfer processes between bacteria and metallic ions.

Stressed-deformed state of the system «main pipeline – soil» in the karst sections (on the example of the section of the main gas pipeline «Power of Siberia», «Chayanda – Lensk»)

Currently, modern gas pipeline systems are increasingly demanding in terms of reliability, durability, industrial and environmental safety. Gas pipeline routes are located in poorly established regions where there are no long-term observations of hazardous natural processes. Currently, karst is the most latently occurring and difficult to predict hazardous engineering and geological process. In case of karst process along the pipeline route, additional load may be applied. In this regard, the analysis of the stress-strain state of the trunk gas pipeline-soil system is the most important task for determining the quantitative characteristics of stresses that can cause the development of emergency. The article considers the section currently built, the main gas pipeline "Power of Siberia," "Chayanda - Lensk." Carbonate formations of Cambrian age are widespread within the considered territory, there are manifestations of surface and underground forms of karst. In this regard, it is possible to activate the process during the operation stage, while during the design these geotechnical features may not have caused concerns. In this work, stress-strain analysis was carried out in case of joint deformation of the pipeline and soil under the influence of a possible load - karst dip. Proposals on the use of the obtained results at the operation stage are given.

Challenges of geomorphologic analysis of active tectonics in a slowly deforming karst landscape (W Slovenia and NE Italy)

Remote sensing-based tectonic geomorphology is widely applied to study neotectonic processes. This technique is relatively cheap and easy to apply, and it allows investigating large areas for tectonic activity. Existing literature comprises a variety of indices and techniques, seemingly able to work in almost all tectonic settings. In this paper we study a particularly challenging region in W Slovenia and NE Italy, characterised by slow deformation rates, high precipitation, dense vegetation, and intense modification of the landscape and drainage system due to karst processes. We apply a suite of well-established geomorphic indices including terrain ruggedness, surface roughness, hypsometric integral and analyses of drainage parameters, as well as several less commonly applied analyses, such as the assessment of doline density and doline geometry. The aim was to test the capabilities of the applied techniques at various spatial scales and to extract information about the active tectonics. We begin with broad, regional analyses to detect the morphological imprint of active faults in the landscape. Then, we perform detailed studies of selected sites and single faults. Finally, we analyse a polje located on the trace of an active fault in the highest detail. We then compare the different techniques and different digital elevation models regarding their usefulness for detecting tectonic influences on the karstic landscape. The results show that most of the well-established methods we tested are not suitable to detect even the largest, clearly active faults in the area. The resolution of the used DEMs also has a notable impact on the analyses. We conclude that it is almost impossible to identify active faults solely based on the used techniques. This is mainly due to the low deformation rates and to the intense karstification of the study area that leads to a disconnected surface drainage system. Additional problems arise from the strike-slip mechanism of active faulting. Lithological contrasts and inactive dip-slip faults can lead to false-positive signals of tectonic activity. However, some of our results also show a tectonic signal, indicating neotectonic strike-slip deformation with a notable dip-slip component. Remote sensing studies have demonstrated to be powerful tools for tectonic geomorphology studies, but low tectonic rate karstic landscape conditions as in W Slovenia/NE Italy push even the most trusted methods to their limits and highlight the importance of validation and ground-checks of the results.