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Czarna Cave represents phreatic cave with multiple loops. No cave level developed at the water table was detected. The cave was later modified by invasion vadose waters and breakdown processes. The phreatic paleoflow directions were analysed from the asymmetry of scallops. The paleoflow was directed from the east to the west, that is in a direction of Kościeliska Valley. Therefore, this valley represented the main discharge zone of the region during the formation of Czarna Cave.
Aix-les-Bains (Savoie, France) owes its name and reputation to the thermal springs that occur along the eastern shore of Lake Bourget, France largest natural lake. Although the city waters have been exploited since Antiquity, scientific investigations into the nature and characteristics of the hydrothermal karst from which they emerge did not begin until the early 19th century. The present article traces the history of these investigations and summarizes the results of more than two centuries of scientific research. Today, the only visible signs of karstification related to hydrothermal flows are to be found in the discharge zone in the Urgonian limestone anticline that rises above the city centre. These features are: – the Grotte des Serpents, which houses the Alun Spring, the system main natural discharge, – the Chevalley Aven, a blind chimney that was accidentally uncovered in 1996, – other hydrothermal springs that are too small to enter, including the Soufre Spring. Although scientific investigation of the thermal springs at Aix-les-Bains began in the early 19th century, it was not until the 1920s that scientists started examining the relationship between karstification and the state of the aquifer. E.A.Martel was the first researcher to describe the Aix-les-Bains site as an active hydrothermal karst, in a pioneering study published in 1935. Sixty years later, the discovery of the Chevalley Aven during building work on a new hydrotherapy center gave fresh impetus to research into the karstification of the Aix-les-Bains thermo-mineral aquifer. Recent studies have also investigated the deep aquifer below the karst, using data provided by boreholes. The Urgonian limestone karst at Aix-les-Bains is the site of mixing between thermal waters rising through the anticline and meteoric waters percolating from the surface. Meteoric infiltration is sufficiently high for the hydrological behavior of the thermal springs to be identical to that of exsurgences in gravity-fed, cold-water transmissive karsts. The Chevalley Aven is a shaft that descends 30 meters below the surface, thereby providing access to the ground-water at depth. Monitoring of the water quality in the aven has shown that the Legionella contamination of the springs was due to high concentrations of the bacteria in upstream passages in the karst. In 2006, dye-tracing tests confirmed the existence of a hydraulic connection between the Chevalley Aven and the Alun and Soufre Springs, the fact there is a single ascending hydrothermal conduit, which lies between the Chevalley Aven and the Alun Spring. In addition to providing a valuable source of information about the functioning of the thermo-mineral aquifer, the cavities at Aix-les-Bains are of great karstological interest, especially for the study of hypogene speleogenetic processes. The circulation of warm (40oC), sulfur-rich waters and vapours through the system has led to the development of conduits with specific morphologies and the precipitation of characteristic deposits. These features include: – “beaded” chimneys and galleries formed by the linking of spheres produced by condensation-corrosion. Diffuse karstification along bedding planes around the main conduit; – deposition of non-carbonate minerals (gypsum, native sulfur); – formation of biothems and biofilms on walls subject to condensation. The Grotte des Serpents is a horizontal cavity that formed at the upper limit of the water table. The Chevalley Aven is a hypogene chimney that was sculpted under vadose conditions by the release of sulfuric acid-rich vapours above the thermal water table. As well as a surface coating of microbial mats and the presence of bacterial flakes in the thermal water, the vadose parts of the Aix-les-Bains hydrothermal karst contain a characteristic microfauna and flora. These microorganisms are thought to play an active role in hypogene karstification processes.
The Buda Thermal Karst (Budapest, Hungary) developed in the regional discharge zone of a carbonate rock aquifer system. High radioactivity of the spring waters has already been reported in 1912, but there has been no detailed study and no consistent explanation for its origin. In this area mixing of cold and hot karst waters was hitherto assigned to be responsible for cave formation. However, the dissimilarity of the discharging waters within Budapest (in the North: Rozsadomb; in the South: Gellert Hill), may suggest also different cave forming processes. The application of radionuclides as natural tracers represents a novel approach to investigate these questions. For this study, we used uranium, radium and radon to identify mixing of fluids in the Buda Thermal Karst system and to infer the temperature and chemical composition of the end members. Chloride as a conservative component allowed the mixing ratios for the sampled waters to be calculated. Their fluid compositions were modeled and through the comparison of modeled and measured values, the end members were validated. As the result of this study, it was possible to characterize the mixing end members for the Rozsadomb area, whereas for the Gellert Hill discharge zone, mixing components could not be identified with the aid of radionuclides. Therefore, it is suggested that different processes are responsible for cave formation in these areas. In the Rozsadomb area, structurally-controlled mixing is the dominant cave forming process, whereas in the Gellert Hill area, due to the lack of mixing members, other processes have to be found, which are responsible for the formation of the caves, such as retrograde calcite solubility and/or geogenic acids, such as H2S. The application of radionuclides thus further supported the differences between the two study areas. This study identified moreover the source of elevated radon content of the waters in the Gellert Hill area in form of iron-hydroxide precipitates that accumulate in the spring caves. These precipitates are highly efficient in adsorbing radium, which generates radon by alpha decay, and hence act as local radon source for the waters. In this study we showed that uranium, radium and radon naturally occurring in groundwater can be used to characterize fluids of different flow systems in regional discharge areas owing to the contrasting geochemical behaviors of these elements
This paper presents an approach for solving the problem of exploitation of freshwater in the coastal karst aquifer during summer dry periods in the conditions of potential salt water intrusion. The approach is presented on the example of spring zone Novljanska Zrnovnica, situated in the northern part of Croatian Adriatic coastal region. The spring zone is used for water supply (about 250 l/s) of an important tourist area of Crikvenica and Novi Vinodolski. After unsuccessful attempts of physical separation of freshwater system from the sea influence, by construction of grout curtain, hydrogeological studies have focused on the possibility of groundwater capturing in the hinterland of discharge zone, outside of the zone of periodical salinity. The final research results with the exploitation well in the spring hinterland can serve as a model for research and exploitation of drinking water in natural conditions of unstable freshwater-saltwater interface in similar natural conditions.
This paper presents an approach for solving the problem of exploitation of freshwater in the coastal karst aquifer during summer dry periods in the conditions of potential salt water intrusion. The approach is presented on the example of spring zone Novljanska Žrnovnica, situated in the northern part of Croatian Adriatic coastal region. The spring zone is used for water supply (about 250 l/s) of an important tourist area of Crikvenica and Novi Vinodolski. After unsuccessful attempts of physical separation of freshwater system from the sea influence, by construction of grout curtain, hydrogeological studies have focused on the possibility of groundwater capturing in the hinterland of discharge zone, outside of the zone of periodical salinity. The final research results with the exploitation well in the spring hinterland can serve as a model for research and exploitation of drinking water in natural conditions of unstable freshwater-saltwater interface in similar natural conditions.
Uplifted unconfined and adjoining confined continental carbonate aquifers contain thermal water with marginal thermal springs as decisive discharge features connected to tectonic contact between the unconfined and confined part of the system. These areas are characterised by positive thermal anomaly, particular mineral precipitates and phre-atophyte vegetation. These systems are important not only as sources of thermal water but the confined parts of the system can serve as hydrocarbon reservoirs, moreover Mississippi Valley Type (MVT) ore deposits can also be connected to such environ-ments. Hypogenic speleogenesis can be active at such marginal discharge zones of groundwater due to the direct corrosive effect of deep originated fluids. These different processes are known from the literature however their relationships have not been revealed comprehensively. The application of regional groundwater flow system theory and evaluation can give a chance to understand the common origin of these different processes, which is moving groundwater. The Buda Thermal Karst offers an exception-al natural laboratory where groundwater flow systems and their effect on rock matrix and the environment can be examined and proved directly. Moreover as new discharge phenomenon a karst corrosive biofilm was recognized here. The presentation displays the most important conclusions which can be generalized for areas with similar hydro-geological settings. The research is supported by the NK 101356 OTKA research grant