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Enviroscan Ukrainian Institute of Speleology and Karstology


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Community news

Speleology in Kazakhstan

Shakalov on 04 Jul, 2018
Hello everyone!   I pleased to invite you to the official site of Central Asian Karstic-Speleological commission ("Kaspeko")   There, we regularly publish reports about our expeditions, articles and reports on speleotopics, lecture course for instructors, photos etc. ...

New publications on hypogene speleogenesis

Klimchouk on 26 Mar, 2012
Dear Colleagues, This is to draw your attention to several recent publications added to KarstBase, relevant to hypogenic karst/speleogenesis: Corrosion of limestone tablets in sulfidic ground-water: measurements and speleogenetic implications Galdenzi,

The deepest terrestrial animal

Klimchouk on 23 Feb, 2012
A recent publication of Spanish researchers describes the biology of Krubera Cave, including the deepest terrestrial animal ever found: Jordana, Rafael; Baquero, Enrique; Reboleira, Sofía and Sendra, Alberto. ...

Caves - landscapes without light

akop on 05 Feb, 2012
Exhibition dedicated to caves is taking place in the Vienna Natural History Museum   The exhibition at the Natural History Museum presents the surprising variety of caves and cave formations such as stalactites and various crystals. ...

Did you know?

That crescentic wall niche is see meander niche.?

Checkout all 2699 terms in the KarstBase Glossary of Karst and Cave Terms


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KarstBase a bibliography database in karst and cave science.

Featured articles from Cave & Karst Science Journals
Chemistry and Karst, White, William B.
See all featured articles
Featured articles from other Geoscience Journals
Karst environment, Culver D.C.
Mushroom Speleothems: Stromatolites That Formed in the Absence of Phototrophs, Bontognali, Tomaso R.R.; D’Angeli Ilenia M.; Tisato, Nicola; Vasconcelos, Crisogono; Bernasconi, Stefano M.; Gonzales, Esteban R. G.; De Waele, Jo
Calculating flux to predict future cave radon concentrations, Rowberry, Matt; Marti, Xavi; Frontera, Carlos; Van De Wiel, Marco; Briestensky, Milos
Microbial mediation of complex subterranean mineral structures, Tirato, Nicola; Torriano, Stefano F.F;, Monteux, Sylvain; Sauro, Francesco; De Waele, Jo; Lavagna, Maria Luisa; D’Angeli, Ilenia Maria; Chailloux, Daniel; Renda, Michel; Eglinton, Timothy I.; Bontognali, Tomaso Renzo Rezio
Evidence of a plate-wide tectonic pressure pulse provided by extensometric monitoring in the Balkan Mountains (Bulgaria), Briestensky, Milos; Rowberry, Matt; Stemberk, Josef; Stefanov, Petar; Vozar, Jozef; Sebela, Stanka; Petro, Lubomir; Bella, Pavel; Gaal, Ludovit; Ormukov, Cholponbek;
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Your search for domain (Keyword) returned 77 results for the whole karstbase:
Showing 61 to 75 of 77
Karst and artificial recharge: Theoretical and practical problems: A preliminary approach to artificial recharge assessment, 2011,
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Daher Walid, Pistre Severin, Kneppers Angeline, Bakalowicz Michel, Najem Wajdi

Managed Aquifer Recharge (MAR) is an emerging sustainable technique that has already generated successful results and is expected to solve many water resource problems, especially in semi-arid and arid zones. It is of great interest for karst aquifers that currently supply 20–25% of the world’s potable water, particularly in Mediterranean countries. However, the high heterogeneity in karst aquifers is too complex to be able to locate and describe them simply via field observations. Hence, as compared to projects in porous media, MAR is still marginal in karst aquifers.
Accordingly, the present work presents a conceptual methodology for Aquifer Rechargeability Assessment in Karst – referred to as ARAK. The methodology was developed noting that artificial recharge in karst aquifers is considered an improbable challenge to solve since karst conduits may drain off recharge water without any significant storage, or recharge water may not be able to infiltrate. The aim of the ARAK method is to determine the ability of a given karst aquifer to be artificially recharged and managed, and the best sites for implementing artificial recharge from the surface. ARAK is based on multi-criteria indexation analysis modeled on karst vulnerability assessment methods. ARAK depends on four independent criteria, i.e. Epikarst, Rock, Infiltration and Karst. After dividing the karst domain into grids, these criteria are indexed using geological and topographic maps refined by field observations. ARAK applies a linear formula that computes the intrinsic rechargeability index based on the indexed map for every criterion, coupled with its attributed weighting rate. This index indicates the aptitude for recharging a given karst aquifer, as determined by studying its probability first on a regional scale for the whole karst aquifer, and then by characterizing the most favorable sites. Subsequently, for the selected sites, a technical and economic feasibility factor is applied, weighted by the difficulties that could occur when trying to undertake a recharge operation at a selected site from the surface. Each site is finally rated by its rechargeability index – the product of two factors, the intrinsic rechargeability and the feasibility index. ARAK was applied to the region of Damour, Lebanon, on the Mediterranean coast where uncontrolled exploitation of public and private wells led to its partial salinization by seawater. A MAR system in Damour region represents an interesting solution to cope with salinization and the insufficiency of the resource


Influence of initial heterogeneities and recharge limitations on the evolution of aperture distributions in carbonate aquifers, 2011,
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Hubinger B. , Birk S.

Karst aquifers evolve where the dissolution of soluble rocks causes the enlargement of discrete pathways along fractures or bedding planes, thus creating highly conductive solution conduits. To identify general interrelations between hydrogeological conditions and the properties of the evolving conduit systems the aperture-size frequency distributions resulting from generic models of conduit evolution are analysed. For this purpose, a process-based numerical model coupling flow and rock dissolution is employed. Initial protoconduits are represented by tubes with log-normally distributed aperture sizes with a mean of 0.5 mm. Apertures are spatially uncorrelated and widen up to the metre range due to dissolution by chemically aggressive waters. Several examples of conduit development are examined focussing on influences of the initial heterogeneity and the available amount of recharge. If the available recharge is sufficiently high the evolving conduits compete for flow and those with large apertures and high hydraulic gradients attract more and more water. As a consequence, the positive feedback between increasing flow and dissolution causes the breakthrough of a conduit pathway connecting the recharge and discharge sides of the modelling domain. Under these competitive flow conditions dynamically stable bimodal aperture distributions are found to evolve, i.e. a certain percentage of tubes continues to be enlarged while the remaining tubes stay small-sized. The percentage of strongly widened tubes is found to be independent of the breakthrough time and decreases with increasing heterogeneity of the initial apertures and decreasing amount of available water. If the competition for flow is suppressed because the availability of water is strongly limited breakthrough of a conduit pathway is inhibited and the conduit pathways widen very slowly. The resulting aperture distributions are found to be unimodal covering some orders of magnitudes in size. Under these suppressed flow conditions the entire range of apertures continues to be enlarged. Hence, the number of tubes reaching aperture sizes in the order of centimetres or decimetres continues to increase with time and in the long term may exceed the number of large-sized tubes evolving under competitive flow conditions. This suggests that conduit development under suppressed flow conditions may significantly enhance the permeability of the formation e.g. in deep-seated carbonate settings.


The significance of turbulent flow representation in single-continuum models, 2011,
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Reimann T. , Rehrl C. , Shoemaker W. B. , Geyer T. , Birk S.

Karst aquifers evolve where the dissolution of soluble rocks causes the enlargement of discrete pathways along fractures or bedding planes, thus creating highly conductive solution conduits. To identify general interrelations between hydrogeological conditions and the properties of the evolving conduit systems the aperture-size frequency distributions resulting from generic models of conduit evolution are analysed. For this purpose, a process-based numerical model coupling flow and rock dissolution is employed. Initial protoconduits are represented by tubes with log-normally distributed aperture sizes with a mean ?0 = 0.5 mm for the logarithm of the diameters. Apertures are spatially uncorrelated and widen up to the metre range due to dissolution by chemically aggressive waters. Several examples of conduit development are examined focussing on influences of the initial heterogeneity and the available amount of recharge. If the available recharge is sufficiently high the evolving conduits compete for flow and those with large apertures and high hydraulic gradients attract more and more water. As a consequence, the positive feedback between increasing flow and dissolution causes the breakthrough of a conduit pathway connecting the recharge and discharge sides of the modelling domain. Under these competitive flow conditions dynamically stable bimodal aperture distributions are found to evolve, i.e. a certain percentage of tubes continues to be enlarged while the remaining tubes stay small-sized. The percentage of strongly widened tubes is found to be independent of the breakthrough time and decreases with increasing heterogeneity of the initial apertures and decreasing amount of available water. If the competition for flow is suppressed because the availability of water is strongly limited breakthrough of a conduit pathway is inhibited and the conduit pathways widen very slowly. The resulting aperture distributions are found to be unimodal covering some orders of magnitudes in size. Under these suppressed flow conditions the entire range of apertures continues to be enlarged. Hence, the number of tubes reaching aperture sizes in the order of centimetres or decimetres continues to increase with time and in the long term may exceed the number of large-sized tubes evolving under competitive flow conditions. This suggests that conduit development under suppressed flow conditions may significantly enhance the permeability of the formation, e.g. in deep-seated carbonate settings.


OBSERVATIONS OF PLIOCENE KARSTS FOSSILIZED BY QUATERNARY EOLIAN SILTS IN THE MATMATA MOUNTAINS (SOUTH-EAST TUNISIA), 2012,
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Sghari, Abdeljalil

The submeridional Dahar chain in southeastern Tunisia is over 200 km long. It is separated from the Mediterranean Sea by the Jeffara plain with some tens of kilometers in width. This landscape continues to the South into Libya, but to the North, the chain ends with the Matmata mountains which form a plateau slightly inclined to the west and some 10 km wide. The eastern scarp shows a mainly calcareous geological stratigraphy from Upper Permian to the Senonian. The Dahar-Matmata structure belongs to the Sahara platform and shows a hiatus during the whole Tertiary, since it was emerged since Upper Cretaceous. The Tunisian Atlas nearby shows a completely different paleogeographic evolution, with a complete Tertiary series and a later Plio-Quaternary structuration. These two paleogeographic domains of Southern Tunisia, the Sahara Atlas and the NE border of the Sahara platform, were influenced by the Messinian crisis (5.9 Ma to 5.3 Ma). This was expressed by the collapse of the Mediterranean Sea level, profoundly modifying the fluvial dynamics with an inversion of the erosional system, from normal erosion to regressive erosion. It results a deepening of canyons in the downstream part and a deepening of the watercourses in the upstream part. The geological structures in the Messinian have been deeply affected by these large eustatic changes, with an incision of cluses in the Atlas and the deposition of a thick clayeysandy series that we could recently link to deltaic systems and Gilbert deltas. The re-establishment of seaways between the Atlantic and the Mediterranean, and the subsequent infill in the Lower Pliocene (Zanclean transgression), with an important inpact in Southern Tunisia, had multiple consequences in that region. The newly adjusted sealevel, together with a more humid climate that was confirmed by faunal and floral extension oof tropical plants in Northern Africa, stimulated an important karstification of the limestone areas. In the Dahar chain, caves, dolines, karstic depressions or karstic dry valleys emerged, the most spectacular ones being found in the Matmata Mountains. The karstic depressions are the forms that represent best this Pliocene karstification that surely was interrupted in an early stage, because localized endokarstic forms had not enough time to develop. So the karstification seems to have been active in Matmata from 5.4 to 4.0 million years, i.e. two times as long than the duration of the Messinian crisis. The interruption of karstification is due to an increase in temperature and dryness, which even gets more intense during the Pliocene, pulverizing the soils. Already at the beginning of the desertification, a calcareous crust forms by rapid cristallization of dirt. It is immediately transported from the karstic zones to the Jeffara plain. This transfer fo dissolved calcite was the origin of the resistant calcitic crust well known in the Jeffara plain. We now identified the same crust in a karstic depression in the Matmata Mountains, opening the way to new geomorphologic and tectonic interpretations, and a review of the eolian silts formerly attributed to the Upper Pleistocene. Later, during Upper Pliocene-Gelasian, we observe a general tectonic uplift of the Dahar chain and the Matmata Mountains as well as the subsidence of the Jeffara plain at the Medenine fault (NW-SE), prolonging the large Gafsa fault towards the East. The karstic paleoforms were thus uplifted more than 500 m, but nevertheless remain open on the Jeffara plain, as seen by large depressions. As a consequence, the karstic depressions of Matmata played the role of traps for eolian silts blown from the Jeffara plain during the extreme desertification in the Upper Pliocene-Gelasian. The morphological reconstruction since the Messinian shows a succession of important events during the Pliocene that profoundly influenced the Quaternary. All indications permit to reject the hypothesis that the Matmata silts came from the West (Eastern Erg).

 


OBSERVATIONS OF PLIOCENE KARSTS FOSSILIZED BY QUATERNARY EOLIAN SILTS IN THE MATMATA MOUNTAINS (SOUTH-EAST TUNISIA), 2012,
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Sghari, Abdeljalil

The submeridional Dahar chain in southeastern Tunisia is over 200 km long. It is separated from the Mediterranean Sea by the Jeffara plain with some tens of kilometers in width. This landscape continues to the South into Libya, but to the North, the chain ends with the Matmata mountains which form a plateau slightly inclined to the west and some 10 km wide. The eastern scarp shows a mainly calcareous geological stratigraphy from Upper Permian to the Senonian. The Dahar-Matmata structure belongs to the Sahara platform and shows a hiatus during the whole Tertiary, since it was emerged since Upper Cretaceous. The Tunisian Atlas nearby shows a completely different paleogeographic evolution, with a complete Tertiary series and a later Plio-Quaternary structuration. These two paleogeographic domains of Southern Tunisia, the Sahara Atlas and the NE border of the Sahara platform, were influenced by the Messinian crisis (5.9 Ma to 5.3 Ma). This was expressed by the collapse of the Mediterranean Sea level, profoundly modifying the fluvial dynamics with an inversion of the erosional system, from normal erosion to regressive erosion. It results a deepening of canyons in the downstream part and a deepening of the watercourses in the upstream part. The geological structures in the Messinian have been deeply affected by these large eustatic changes, with an incision of cluses in the Atlas and the deposition of a thick clayeysandy series that we could recently link to deltaic systems and Gilbert deltas. The re-establishment of seaways between the Atlantic and the Mediterranean, and the subsequent infill in the Lower Pliocene (Zanclean transgression), with an important inpact in Southern Tunisia, had multiple consequences in that region. The newly adjusted sealevel, together with a more humid climate that was confirmed by faunal and floral extension oof tropical plants in Northern Africa, stimulated an important karstification of the limestone areas. In the Dahar chain, caves, dolines, karstic depressions or karstic dry valleys emerged, the most spectacular ones being found in the Matmata Mountains. The karstic depressions are the forms that represent best this Pliocene karstification that surely was interrupted in an early stage, because localized endokarstic forms had not enough time to develop. So the karstification seems to have been active in Matmata from 5.4 to 4.0 million years, i.e. two times as long than the duration of the Messinian crisis. The interruption of karstification is due to an increase in temperature and dryness, which even gets more intense during the Pliocene, pulverizing the soils. Already at the beginning of the desertification, a calcareous crust forms by rapid cristallization of dirt. It is immediately transported from the karstic zones to the Jeffara plain. This transfer fo dissolved calcite was the origin of the resistant calcitic crust well known in the Jeffara plain. We now identified the same crust in a karstic depression in the Matmata Mountains, opening the way to new geomorphologic and tectonic interpretations, and a review of the eolian silts formerly attributed to the Upper Pleistocene. Later, during Upper Pliocene-Gelasian, we observe a general tectonic uplift of the Dahar chain and the Matmata Mountains as well as the subsidence of the Jeffara plain at the Medenine fault (NW-SE), prolonging the large Gafsa fault towards the East. The karstic paleoforms were thus uplifted more than 500 m, but nevertheless remain open on the Jeffara plain, as seen by large depressions. As a consequence, the karstic depressions of Matmata played the role of traps for eolian silts blown from the Jeffara plain during the extreme desertification in the Upper Pliocene-Gelasian. The morphological reconstruction since the Messinian shows a succession of important events during the Pliocene that profoundly influenced the Quaternary. All indications permit to reject the hypothesis that the Matmata silts came from the West (Eastern Erg).


A Sustainability Index for Karst Environments, 2012,
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Van Beynen P. , Brinkmann R. , Van Beynen K.

With growing populations and ever increasing pressure on resources, the need to live sustainably with our environment has increased in significance. When considering such anthropogenic pressures, karst landscapes are as vulnerable, if not more so, than any other environment. Such vulnerability arises from the rapid transit times of percolating water, the poor filtering ability of carbonate bedrock, and the highly specialized biota of subterranean karst. The Karst Sustainability Index (KSI) was created as a standardized metric of sustainable development practices in karst settings. The KSI uses predetermined targets to ascertain the overall sustainability of a karst region. Indicators are designed to incorporate common measures of sustainability for the three domains of social, environmental, and economic resource use. Benchmarking the current state of karst environments allows the comparison of sustainability practices temporally and spatially to highlight areas where remedial policies or actions are needed. This is the first index to incorporate the emerging field of environmental sustainability with karst landscape assessment. To test the applicability of the KSI, a study was undertaken in the Tampa Bay Metropolitan Area, which encompasses four counties that are entirely karst. The TBMA was found to be progressing towards the sustainable management of karst resources, and the KSI provided a robust measure of sustainability.


Geoelectrical Characterization of Sulphate Rocks, 2012,
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Guinea Maysounave, Ander

Gypsum rocks are widely exploited in the world as industrial minerals. The purity of the gypsum rocks (percentage in gypsum mineral –CaSO4•2H2O- in the whole rock) is a critical factor to evaluate the potential exploitability of a gypsum deposit. It is considered than purities higher than 80% in gypsum are required to be economically profitable. Gypsum deposits have been studied with geoelectrical methods; a direct relationship between the electrical resistivity values of the gypsum rocks and its lithological composition has been established, with the presence of lutites being the main controlling factor in the geoelectrical response of the deposit. This phenomenon has been quantified by means of a combination of theoretical calculations, laboratory measurements and field data acquisition. A geoelectrical classification of gypsum rocks defining three types of gypsum rocks has been elaborated. Anhydrite (CaSO4) is frequently found in gypsum quarries and in no-outcropping sulphates. Because of its highest hardness than gypsum it supposes a problem for the extraction of gypsum; the fronts of the quarries in which anhydrite is found are stopped at the moment when it appears. The electrical properties of calcium sulphates have been studied by means of geoelectrical methods. The conductivity of crystals has been tested in laboratory. A direct relationship between the electrical conductivity values of the calcium sulphate rocks and its lithological composition has been established being the lutitic matrix the main controlling factor when it is percolant (connected at long range). When the rock is matrix dominant, the electrical resistivity trend is bond to the Hashin-Shtrikman lower bound for multiphase systems. On the other hand, when the rock is calcium sulphate dominant the trend shows the one of the Hashin-Shtrikman upper bound. A geoelectrical classification for calcium sulphate rocks has been elaborated. With this classification it is possible to differentiate between calcium sulphate rocks with different composition according to their electrical resistivity value. Glauberite (Na2Ca(SO4)2) is nowadays exploited as industrial mineral. Glauberite rocks usually have high lutite content in their composition, together with other evaporictic minerals as gypsum, anhydrite or halite among others. There is no reference to the conductivity of glauberite rocks in the bibliography, but due to their impurity it is expected to observe values as the observed for other sulphates in the matrix domain (less than 55% in purity). Two areas of the Ebro river basin (the Zaragoza and La Rioja sectors) have been studied by means of electrical resistivity tomography profiles, in which glauberite has been found in boreholes. As example of application for the study of sulphate deposits, an electrical resistivity tomography survey has been carried out in the Pira Gypsum member (SE of Catalan margin of the Tertiary Ebro Basin, Spain). Additionally, a continuous coring drill was performed in order to support the study. Electrical imaging has been successfully applied to identify the gypsum deposits interlayered in lutite units. Another resistivity survey has been carried out in an active gypsum quarry in the Gelsa Gypsum unit (Zaragoza, N Spain). During the extraction of the rock, the most important parameters to know are the purity changes in the deposit. Sudden changes in the purity make the processing of the raw material less profitable. The performed profiles have shown different gypsum layers from which the purest layers have been identified. Electrical resistivity tomography lines are useful in prospection of gypsum deposits. However, electrical imaging prospection should be supported by an accurate petrological study of the deposits, in order to properly interpret the resistivity profiles.


La Serreta endokarst (SE Spain): a sustainable value?, 2013,
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Asencio A. D. , Espinosa T.

La Serreta endokarst (SE Spain), which UNESCO declared a World Heritage Site in 1998, was considered a sanctuary with cave art and one of the most important archaeological sites in the Mediterranean region for both the remains it hosts and the spectacular karstic landscape at the site.

To coincide with the 40th anniversary of its discovery, the La Serreta cave-chasm was adapted for public use with the intention of showing visitors the remains, which date back to prehistoric times. The solution included attempts to minimize contact with the valuables in the cave in order to alter the existing remains as little as possible and to make good use of the magnificent interpretative conditions of such a unique place by showing the spectacular views over the Los Almadenes canyon, where the Segura River flowed, which is now a viewpoint over the void.

In order to determine the sustainability of the endokarst, the Karstic Sustainability Index (KSI) was applied as a standard measure of sustainable development practices in karstic environments, which employs indicators for the three domains: use of social, economic and environmental resources. By applying this index, La Serreta endokarst was found to be progressing towards the sustainable management of karst resources.

 
 

Stable isotope (O and C) geochemistry of non-sulfide ZnPb deposits; case study: Chah-Talkh non-sulfide ZnPb deposit (Sirjan, south of Iran), 2013,
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Rezaeian A. , Rasa I. , Amiri A. , Jafari M. R.

The study of oxygen and carbon isotopic ratios has gained importance to determine the origin of ore-bearing fluids, carbon origin, and also to determine the formation temperature of non-sulfide Pb and Zn minerals. In order to determine the origin of fluids and carbon existing in Zn carbonate minerals in Chah-Talkh deposit, initially the amounts of δ18OSMOW and δ13CPDB changes in various zinc minerals in important deposits in Iran and the world were studied, and then by comparing these values in Chah-Talkh deposit with those of other deposits, the origin of fluids responsible for ore forming, carbon, and formation temperature of Chah-Talkh deposit was determined. The range of δ18OSMOW changes in smithsonite mineral in non-sulfide lead and zinc deposits varies from 18.3 to 31.6 ‰, and δ18OSMOW in hydrozincite mineral varies from 7.8 to 27 ‰. Due to the impossibility of smithsonite sampling from Chah-Talkh deposit (due to it being fine-grained and dispersed), hydrozincite minerals which have high isotopic similarities with smithsonite are used for the isotopic analysis of carbon and oxygen. The range of δ18OSMOW changes in hydrozincite mineral of Chah-Talkh deposit varies from 7.8 to 15.15‰, which places in the domain of metamorphic water. The extensiveness of δ18OSMOW changes in Chah- Talkh indicates the role of at least two fluids in the formation of non-sulfide minerals. The obtained formation temperature of non-sulfide minerals (hydrozincite) in Chah- Talkh deposit is 70 to 100 °C, which indicates the role of metamorphic fluids in the formation of deposit. Complete weathering of sulfide minerals to a depth of 134 m confirms the role of rising metamorphic fluids in the formation of non-sulfide minerals. The δ13CPDB values of Chah-Talkh deposit are set in the range of atmospheric CO2 and carbonate rocks, in which the existence of atmospheric CO2 indicates the role of atmospheric fluids, and the existence of carbonate carbon rock indicates of the role of metamorphic fluids in the precipitation of non-sulfide Zn minerals.


Comparison of a karst groundwater model with and without discrete conduit flow, 2013,
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Saller S. P. , Ronayne M. J. , Long A. J.

Karst aquifers exhibit a dual flow system characterized by interacting conduit and matrix domains. This study evaluated the coupled continuum pipe-flow framework for modeling karst groundwater flow in the Madison aquifer of western South Dakota (USA). Coupled conduit and matrix flow was simulated within a regional finite-difference model over a 10-year transient period. An existing equivalent porous medium (EPM) model was modified to include major conduit networks whose locations were constrained by dye-tracing data and environmental tracer analysis. Model calibration data included measured hydraulic heads at observation wells and estimates of discharge at four karst springs. Relative to the EPM model, the match to observation well hydraulic heads was substantially improved with the addition of conduits. The inclusion of conduit flow allowed for a simpler hydraulic conductivity distribution in the matrix continuum. Two of the high-conductivity zones in the EPM model, which were required to indirectly simulate the effects of conduits, were eliminated from the new model. This work demonstrates the utility of the coupled continuum pipe-flow method and illustrates how karst aquifer model parameterization is dependent on the physical processes that are simulated


Karstification as a Predisposing Factor of Seismically Triggered Landslides: Case Study from the Crimean Mountains (Ukraine): Introduction to the Problem, 2013,
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Hradeck J. , Pnek T. , ilhn K. , Smolkov V.

Deep-seated gravitational deformations are significant denudational agents of rock slopes at the margins of karstified plateaus of the Crimean Mountains (CM). The CM evolved during Mesozoic–Cenozoic times as a response to the deformation between the Black Sea domain and East-European platform. The southwestern part of the area is characterized by steep, up to 1000-m-high coastal escarpments consisting of Late Jurassic limestones overlying tuff layers and weak Late Triassic flysch with sporadic small intrusions of Middle Jurassic diorites, gabbros and granites. Steep rock slopes contrast with elevated, highly karstified plateaus situated approximately 500–1300 m a.s.l. The aim of this article is to show long-term evolution of a giant rock slope failure close to the Black Sea coast in the southwestern tip of the CM near Foros Town. The failure evolved in highly anisotropic limestones overlying plastic flysch layers where the main head scarp follows a strike-slip fault. The Foros slope failure is an excellent demonstration of the significance of a preparatory stage in the evolution of large deep-seated slope deformations. Inherited and undisturbed horizontal slickensides on the sub-vertical, inactive fault surface serve as good evidence of significant extensional movement of the surface blocks away from the main headscarp. The studied deformation shows that in a relatively small area tensional (cutting) surfaces can be formed by a great variety of rock discontinuities such as the strike-slip fault, joints and steeply inclined bedding planes. The presence of well-developed, nowadays weathered, speleothems furthermore points to significant karstification that provided additional widening of spaces within rock mass. Gravitational movement destroyed and unroofed several cave systems originally presented at the former edge of a karst plateau. Our findings reveal that large rock slope failures can be added to the factors contributing to the evolution of unroofed caves. Although triggering factors of the activation of individual parts of slope deformations can be determined only hypothetically, lessons learned from widespread landslide activity during and after the 1927 Yalta earthquake and rainfall-driven landslides in the vicinity of Feodosia Town make us consider both seismic loading of slopes and high pore-pressures during heavy winter rainfalls or rapid spring snowmelt to be significant factors. Beside seismic activity, intensive Late Holocene slope processes can be attributed to intensive human activity.

 


Comparison of a karst groundwater model with and without discrete conduit flow, 2013,
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Saller S. P. , Ronayne M. J. , Long A. J.

Karst aquifers exhibit a dual flow system characterized by interacting conduit and matrix domains. This study evaluated the coupled continuum pipe-flow framework for modeling karst groundwater flow in the Madison aquifer of western South Dakota (USA). Coupled conduit and matrix flow was simulated within a regional finite-difference model over a 10-year transient period. An existing equivalent porous medium (EPM) model was modified to include major conduit networks whose locations were constrained by dye-tracing data and environmental tracer analysis. Model calibration data included measured hydraulic heads at observation wells and estimates of discharge at four karst springs. Relative to the EPM model, the match to observation well hydraulic heads was substantially improved with the addition of conduits. The inclusion of conduit flow allowed for a simpler hydraulic conductivity distribution in the matrix continuum. Two of the high-conductivity zones in the EPM model, which were required to indirectly simulate the effects of conduits, were eliminated from the new model. This work demonstrates the utility of the coupled continuum pipe-flow method and illustrates how karst aquifer model parameterization is dependent on the physical processes that are simulated.


GEOPHYSICAL INVESTIGATIONS OF THE EDWARDS-TRINITY AQUIFER SYSTEM AT MULTIPLE SCALES: INTERPRETING AIRBORNE AND DIRECT-CURRENT RESISTIVITY IN KARST, 2013,
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Gary M. O. , Rucker D. F. , Smith B. D. , Smith D. V. , Befus K.

Electrical and electromagnetic geophysical characterization is a proven tool for delineating obscured subterranean karstic features, such as caves, sinkholes, and solution enlarged fissures. Geophysical characterizations allow a wide range of deployment scales; airborne methods can accommodate a regional view on the order of kilometers, and ground-based methods can follow up with focused data on the order of meters. A helicopter frequency domain electro-magnetic (HFDEM) survey and ground-based direct-current electrical resistivity imaging (DC-ERI) geophysical studies at the Camp Bullis Military Training Site (Camp Bullis) in central Texas have been used to characterize permeability properties of the Edwards and Trinity Aquifers in the area. Results of three separate investigations identified zones of high density karst features and characterized specific karstic voids, including caves. In 2003, the USGS completed an HFDEM survey of Camp Bullis and nearby areas to map and image subsurface features related to the groundwater resources. The survey refined locations of mapped and previously unmapped faults and characterized the heterogeneity of the subsurface electrical signature. Karst mapping at Camp Bullis identified over 1500 features, and high density zones of features correspond with areas of high resistivity from the HEM data. DC-ERI surveys at several locations were used to infer and characterize known and hypothesized karst features. Site 8 suggests an inferred fault and 195dissolution feature. Two other sites were surveyed near major caves that directly recharge the Trinity Aquifer (indirectly to Edwards Aquifer) along Cibolo Creek. Integration of multi-scale geophysical datasets could be used to augment aquifer-wide recharge characterization and quantification.


Permeability evolution due to dissolution and precipitation of carbonates using reactive transport modeling in pore networks, 2013,
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A reactive transport model was developed to simulate reaction of carbonates within a pore network for the high-pressure CO2-acidified conditions relevant to geological carbon sequestration. The pore network was based on a synthetic oolithic dolostone. Simulation results produced insights that can inform continuum-scale models regarding reactioninduced changes in permeability and porosity. As expected, permeability increased extensively with dissolution caused by high concentrations of carbonic acid, but neither pH nor calcite saturation state alone was a good predictor of the effects, as may sometimes be the case. Complex temporal evolutions of interstitial brine chemistry and network structure led to the counterintuitive finding that a far-from-equilibrium solution produced less permeability change than a nearer-to-equilibrium solution at the same pH. This was explained by the pH buffering that increased carbonate ion concentration and inhibited further reaction. Simulations of different flow conditions produced a nonunique set of permeability-porosity relationships. Diffusive-dominated systems caused dissolution to be localized near the inlet, leading to substantial porosity change but relatively small permeability change. For the same extent of porosity change caused from advective transport, the domain changed uniformly, leading to a large permeability change. Regarding precipitation, permeability changes happen much slower compared to dissolution-induced changes and small amounts of precipitation, even if located only near the inlet, can lead to large changes in permeability. Exponent values for a power law that relates changes in permeability and porosity ranged from 2 to 10, but a value of 6 held constant when conditions led to uniform changes throughout the domain


MODELING SPELEOGENESIS USING COMPUTATIONAL FLUID DYNAMICS: POTENTIAL APPLICATIONS TO HYPOGENE CAVES, 2014,
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Covington M. , Myre J.

Numerical models of speleogenesis typically simulate flow and dissolution within single fractures or networks of fractures. Such models employ fracture flow and pipe flow equations to determine flow rates and only consider average velocities within each fracture segment. Such approximations make large scale simulations of speleogenesis tractable. However, they do not allow simulation of the formation and evolution of micro- or meso-scale cave passage morphologies. Such morphologies are frequently studied within a field setting and utilized for the interpretation of the speleogenetic processes that formed the cave. One classic example is the formation of scallops in cave streams with turbulent flow. Scallops are used to interpret past flow velocities and directions. However, a recent analysis of the theory of limestone dissolution in turbulent flow conditions suggests a discrepancy between theory and reality concerning the formation of limestone scallops (Covington, in review). Similarly, the only attempt to numerically simulate flute formation in limestone found that the flute forms were not stable (Hammer et al., 2011). Motivated by these puzzles, we are developing a computational fluid dynamics (CFD) framework for the simulation of the evolution of dissolution morphologies.

While this project was initially conceived to better understand dissolution in turbulent flow, the tools being developed are particu­larly well-suited to examine a variety of other questions related to cave morphology on the micro- and meso-scales. There has been significant recent discussion about the interpretation of features that are diagnostic of hypogenic or transverse speleogenesis, such as the morphological suite of rising flow defined by Klimchouk (2007). Other authors have suggested that such forms can be found in a variety of settings where confined flow is not present (Mylroie and Mylroie, 2009; Palmer, 2011). We propose that simulation of such forms using a CFD speleogenesis code will allow a more complete understanding of the connections between process and form, because in such simulations the processes occurring are well-known, well-defined, and also can be adjusted within controlled numeri­cal experiments, where relevant parameters and boundary conditions are systematically varied.

The CFD framework we are developing is based on the Lattice Boltzman method (Chen and Doolen, 1998), which is a popular tech­nique for modeling the mechanics of complex fluids, including fluid mixtures, reactive transport, porous media flow, and complex and evolving domain geometries. With this framework it is straightforward to simulate many of the processes occurring in hypogene settings, including complex fluid flows, dissolution, solute and heat transport, and buoyancy-driven flow. Furthermore, this modeling framework allows these processes to be coupled so that their interactions and feedbacks can be explored. With the suite of capabili­ties provided by this framework, we can begin to numerically simulate the processes occurring in hypogene speleogenesis, including the driving mechanisms and the role of buoyancy-driven flow and its relationship with the morphological suite of rising flow. In the spirit of a workshop, this work is presented as in-progress, in the hopes that it will stimulate discussion on potential applications of the model being developed.


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