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Enviroscan Ukrainian Institute of Speleology and Karstology

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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 corrosion is 1. chemical action of water containing carbonic acid (also humidic, nitric, and other acids) on limestones and dolomites causing partial solution and related chemical changes in the rocks [20]. 2. erosion by solution or chemical action [10]. 3. the act or process of dissolving or wearing away metals [6]. see also accelerated corrosion; alluvial corrosion; corrasion; solution. compare aggressive water. synonyms: (french.) corrosion; (german.) korrosion; (greek.) chemeke thiavroses; (italian.) dissoluzione, corrosione; (russian.) korrozija; (spanish.) corrosion; (turkish.) eritme, yenme, kemirilme; (yugoslavian.) korozija.?

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.
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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 chemistry (Keyword) returned 492 results for the whole karstbase:
Showing 466 to 480 of 492
Water-gas-rock interactions and seasonal control of geochemical environments in the epikarstic zone of the Pennyroyal Plateau, Kentucky, USA, 2013,
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Groves Chris, Polk Jason, Miller Ben, Bolster Carl

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Dragoun J. Ž, á, K K. Vejlupek J. Filippi M. Novotný, J. Dobeš, P.


The Na Javorce Cave is located in the Bohemian Karst, Czech Republic, near the Karlštejn castle, about 25 km SW of Prague. The cave was discovered as a result of extensive exploration including cave digging and widely employed capping of narrow sections. Exploration in the cave has already lasted 20 years. The cave is fitted with several hundred meters of fixed and rope ladders and several small fixed bridges across intra-cave chasms. Access to the remote parts of the cave is difficult because of long narrow crawl passages and deep and narrow vertical sections. The Na Javorce Cave became the deepest cave discovered to date in Bohemia with the discovery of its deepest part containing a lake in 2010. The cave was formed in vertically dipping layers of Lower Devonian limestone; it is 1,723 m long and 129 m deep, of which 9 m is permanently flooded (data as of December 2012). The cave is polygenetic, with several clearly separable evolutionary stages. Cavities discovered to date were mostly formed along the tectonic structures of two main systems. One of these systems is represented by vertical faults of generally N-S strike, which are frequently accompanied by vein hydrothermal calcite with crystal cavities. The second fault system is represented by moderately inclined faults (dip 27 to 45°, dip direction to the W). Smaller tube-like passages of phreatic morphology connect the larger cavities developed along the two above-mentioned systems. The fluid inclusion data obtained for calcite developed along both fault systems in combination with C and O stable isotope studies indicate that the hydrothermal calcite was deposited from moderately saline fluids (0.5 to 8.7 wt. % NaCl equiv.) in the temperature range from 58 to 98 °C. The fluids were NaCl-type basinal fluids, probably derived from the deeper clastic horizons of the Barrandian sedimentary sequence. The age of the hydrothermal processes is unknown; geologically it is delimited by the Permian and Paleogene. The hydrothermal cavities are small compared to cavities formed during the later stages of karstification. The majority of the known cavities were probably formed by corrosion by floodwater derived from an adjacent river. This process was initiated during the Late Oligocene to Early Miocene, as was confirmed by typical assemblage of heavy minerals identical in the surface river sediments and in clastic cave sediments. The morphology of most cavities is phreatic or epiphreatic, with only local development of leveled roof sections (“Laugdecken”). The phreatic evolution of the cave is probably continuing into the present in its deepest permanently flooded part, which exhibits a water level close to that of the adjacent Berounka River. Nevertheless, the chemistry of the cave lake differs from that of the river water. The cave hosts all the usual types of cave decoration (including locally abundant erratics). The most interesting speleothem type is cryogenic cave carbonate, which was formed during freezing of water in relation to the presence of permafrost during the Glacial period. The occurrence of cryogenic cave carbonate here indicates that the permafrost of the Last Glacial period penetrated to a depth of at least 65 m below the surface.

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Frumkin Amos


The city of Jerusalem, Israel, is growing for ~4,000 years on karst terrain. Lacking closed depressions, surface topography seems fluvial, but karst is well demonstrated by speleology and subsurface hydrology. Several caves in the city were truncated by construction works, including an 800 m long river cave (longest limestone river cave in Israel), and a 200 × 140 × 90 m isolated chamber cave (largest chamber cave in Israel). Caves are being discovered at a growing rate, as construction works dig deeper into the subsurface in the crowded city. Some of them are eventually destroyed by the construction works; only presently accessible caves are discussed here. The hydrogeology and hydrochemistry of the Gihon, Jerusalem’s main karst spring, was studied in order to understand its behavior, as well as urbanization effects on karst groundwater resources. High-resolution monitoring of the spring discharge, temperature and electrical conductivity, as well as chemical and bacterial analysis demonstrate a rapid response of the spring to rainfall events and human impact. A complex karst system is inferred, including conduit flow, fissure flow and diffuse flow. Electrical conductivity is high compared to nearby springs located at the town margins, indicating considerable urban pollution in the Gihon area. The previously cited pulsating nature of the spring does not exist today. This phenomenon may have ceased due to additional water sources from urban leakage and irrigation feeding the spring. The urbanization of the recharge area thus affects the spring water dramatically, both chemically and hydrologically.

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Polk J. S. , Vanderhoff S. , Groves C. , Miller B. , Bolster C.


The movement of autogenic recharge through the shallow epikarstic zone in soil-mantled karst aquifers is important in understanding recharge areas and rates, storage, and contaminant transport processes. The groundwater in agricultural karst areas, such as Kentucky’s Pennyroyal Plateau, which is characterized by shallow epikarst and deeper conduits flow, is susceptible to contamination from organic soil amendments and pesticides. To understand the storage and flow of autogenic recharge and its effects on contaminant transport on water flowing to a single epikarst drain in Crump’s Cave on Kentucky’s Mississippian Plateau, we employed several techniques to characterize the nature and hydrogeology of the system. During 2010–2012, water samples and geochemical data were collected every four hours before, during, and between storm events from a waterfall in Crumps Cave to track the transport and residence time of epikarst water and organic soil amendments during variable flow conditions. Geochemical data consisting of pH, specific conductivity, temperature, and discharge were collected continuously at 10-minute intervals, along with rainfall amounts. In addition, stable isotope data from rainfall, soil water, and epikarst water were collected weekly and during storm events to examine storage and recharge behavior of the system. The changes in geochemistry indicate simultaneous storage and transport of meteoric water through epikarst pathways into the cave, with rapid transport of bacteria occurring through the conduits that bypass storage. The isotopic data indicate that recharge is rapidly homogenized in the epikarst, with storage varying throughout the year based on meteorological conditions. Results indicate current best management practices in agricultural karst areas need to be revisited to incorporate areas that do not have surface runoff, but where contaminants are transported by seepage into local aquifers.

Geochemistry and isotope geochemistry of the Monfalcone thermal waters (northern Italy): inference on the deep geothermal reservoir, 2013,
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Petrini R. , Italiano F. , Ponton M. , Slejko F. F. , Aviani U. , Zini L.

Geochemical investigations were carried out to define the origin of the low- to moderate-temperature thermal waters feeding the Monfalcone springs in northern Italy. Chemical data indicate that waters approach the composition of seawater. Mixing processes with cold low-salinity waters are highlighted. The δ18O and δD values are in the range −5.0 to −6.4 ‰, and −33 to −40 ‰, respectively, suggesting the dilution of the saline reservoir by karst-type freshwaters. A surplus of Ca2+ and Sr2+ ions with respect to a conservative mixing is ascribed to diagenetic reactions of the thermal waters with Cretaceous carbonates at depth. The measured Sr isotopic composition (87Sr/86Sr ratio) ranges between 0.70803 and 0.70814; after correction for the surplus Sr, a 87Sr/86Sr ratio indicating Miocene paleo-seawater is obtained. The dissolved gases indicate long-lasting gas–water interactions with a deep-originated gas phase of crustal origin, dominated by CO2 and marked by a water TDIC isotopic composition in the range −5.9 to−8.8 and helium signature with 0.08 < R/Ra < 0.27, which is a typical range for the crust. A possible scenario for the Monfalcone thermal reservoir consists of Miocene marine paleowaters which infiltrated through the karstic voids formed within the prevalently Cretaceous carbonates during the upper Eocene emersion of the platform, and which were entrapped by the progressive burial by terrigenous sediments.

The mineral springs of the Scrajo spa (Sorrento peninsula, Italy): a case of natural seawater intrusion, 2013,
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Corniello A. , Trifuoggi M. , Ruggieri G.

This paper deals with the mineral springs feeding the Scrajo spa in the Sorrento peninsula southeast of Naples, approximately 6 km from Castellammare di Stabia, another spa location. The Scrajo mineral water is sulphureous, salt-bromine-iodic and CO2-rich. The two hydromineral areas fall within the groundwater basin of Mt. Faito formed chiefly by limestones. Due to the high permeability of the limestones, there is considerable rainwater infiltration which recharges a basal fresh groundwater resting on denser seawater. This groundwater body feeds the mineral springs of the Scrajo spa, the springs of Castellammare di Stabia and some submarine springs. All the data gathered for the Scrajo springs led to propose the following mineralisation scheme: (1) The basal fresh groundwater of Mt. Faito (on underlying seawater) receives endogenous contributions of CO2 and H2S which cause a ‘‘natural’’ seawater intrusion within the fresh groundwater; (2) The upwelling of gases would appear to occur via the major faults which bound Sorrento peninsula to the NW; (3) During the year, the chemistry of the springs changes according to different degrees of seawater intrusion: the minimum occurs in June and the maximum in November. The close interaction between the sea and the Scrajo’s mineral waters (but also those of Castellammare di Stabia) highlights their particular vulnerability not only to overextraction of groundwater but also to climate change. Finally, a hypothesis is presented to explain the connection between the mineral waters rich in CO2 and H2S and the concentration of karst phenomena observed in the Scrajo area.

Isotopes of Carbon in a Karst Aquifer of the Cumberland Plateau of Kentucky, USA, 2013,
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Florea Lee J.

In this study, the concentration and isotopic composition of dissolved organic carbon (DOC) and dissolved inorganic carbon (DIC) are measured in the karst groundwater of the Otter Creek watershed of the Cumberland Plateau of Kentucky, USA. Comparisons among these data and with the geochemistry of carbonate and gypsum equilibrium reactions reveal that DOC concentration is inversely related to discharge, multiple reaction pathways provide DIC with isotopic enrichment that may be directly related to mineral saturation, and oxidation of reduced sulfur is possible for dissolution. DOC is derived from C3 vegetation with an average δ13C DOC of ‒27‰. DIC in groundwater is derived from both pedogenic CO2  and HCO3 - from dissolved carbonate. At input sites to the karst aquifers DIC concentrations are expectedly low, less than 1 mmol/L, in waters that are undersaturated with respect to calcite. At the output of these karst aquifers DIC concentrations reach 3 mmol/L in waters that are at or above calcite saturation. Values of δ13C DIC range between ‒6.3 and ‒12.4‰ with CO2 degassing and calcite precipitation at some sites obfuscating a simple relationship between δ13C DIC, discharge, and mineral saturation. In addition, concentrations of DIC in sulfur seeps within the watershed range between 2–7 mmol/L with δ13C DIC values in some samples skewed more toward the anticipated value of carbonate bedrock than would be expected from reactions with carbonic acid alone. This suggests that the oxidation of reduced sulfur from shallow oilfield brines liberates bedrock DIC through reactions with sulfuric acid.

An approach for collection of nearfield groundwater samples in submerged limestone caverns, 2013,
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Mills Aaron L. , Tysall Terrence N. , Herman Janet S.

Walls of submerged caves feeding Florida springs are often lined with a heavy mat of filamentous bacteria, many of which are able to oxidize reduced sulfur in groundwater migrating from the porous bedrock into the cave conduit. To determine changes in water chemistry as water passes through the microbial mat, a simple device made from standard well screen and sealed with a rubber stopper and controllable vents was installed in a hole drilled in the wall of the cave passage. The sampler was sealed in place with marine epoxy. we measured anions in water from the sampler and from the water-filled conduit taken just outside the sampler. Most anions measured viz., Cl, NO3, and PO43−, increased slightly between the matrix and conduit waters. However, traces of sulfide were measured in the water from the rock matrix, but not in the conduit. SO4 2−concentrations in the conduit were about twice that measured in the water from the sampler, about 22 and 11 mg SO42− L−1, respectively, providing further evidence that sulfur oxidation is an important process in the bacterial mats attached to the limestone surfaces in these caves. An additional use of the sampling device is to measure discharge from the local bedrock into the cave conduit.

Hypogene karst: speleogenetic mechanisms and geochemical methods of diagnostics , 2013,
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Dublyansky, Y.

Evidences of hypogenic speleogenesis in Slovenian caves , 2013,
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Otoničar, B.

 In Slovenia, known as the country of classical karst, thinking about caves of predominantly hypogenic origin have been treated almost as a heresy. Although we may agree that only on the basis of cave morphology and wall rock features parts of some “common” caves especially close to allogenic inflow and past epipheratic zones cannot be simply related to some past hypogenic phase of cave development (e. g. Osborne 2008; Knez & Slabe 2009) some caves in Slovenia host too many features diagnostic for hypogenic, hydrothermal or at least ascending water flow that such interpretations shouldn’t be considered.

We will present preliminary studies on caves from different karstic regions of Slovenia where cave morphology, wall rock features, mineralogy, general geological setting of the area and partly hydrogeology and hydrogeochemistry suggest, at least on a level of hypothesis, their partial development with hypogenic processes in a wider sense (sensu Palmer 2011). In each of the discussed karstic regions different phenomena diagnostic for some of the hypogenic processes prevails over the others.

In Jelovica high karstic plateau (Julian pre-Alps) and Raduha Mt. (Kamniško-Savinjske Alpe) many caves are locally decorated with big calcite crystals commonly found also as veins on the karstic surface.

The Vrh Svetih Treh Kraljev in Rovtarsko Hribovje, the Pre-alpine region in the western part of central Slovenia, hosts few caves which channels exhibit ramiform and maze like orientation guided by faults and joints with wall rock features characteristic for dissolution with slowly flowing ascending water. A large part of at least one cave is developed in dedolomite while the biggest cave in the area has no known natural entrance. In addition, three wells in the area discharge “sulphuric” water.

In Slovenia many caves show wall rock features that can also be diagnostic for hypogenic speleogenesis or at least to ascending flow. However, such features are most often found in places where high fluctuation of karstic waters mainly with allogenic river inflow occurs. Perhaps some exceptions could be found in the foothills of Jelovica Plateau where especially in one particular maze or anastomotic cave (Jeralovo brezno) no evidence of substantial allogenic inflow occurs although in the lower parts some smaller channels are partly filled by predominately fine grained sandy stream related allogenic deposits.

For more detail information of the above mentioned karstic regions with potential traces of hypogenic spelogenesis see the guidebook of the excursions.

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

Biospeleogenesis, 2013,
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Microorganisms have shaped the world around us, yet their role in karst processes and speleogenesis remains poorly understood. Biospeleogenesis is the formation of subsurface cavities and caves through the activities of microorganisms, by either respiratory (redox) or metabolic chemistries. In carrying out energy acquisition and the metabolic processes of growth, microorganisms change the local geochemistry of the environment. Such activities can dramatically accelerate speleogenesis and even lead to cave formation in geochemical environments that would otherwise not be conducive to dissolution. The aim of this chapter is to help the reader understand the importance of microbial activity in geochemistry and how such activity can lead to the formation and morphology of caves. The chapter then describes the role that microorganisms are known to have in speleogenesis (carbonic and sulfuric acid biospeleogenesis), hints that such activity may be occurring in newly described cave systems (iron biospeleogenesis), and a potential role in other cave systems (quartzite biospeleogenesis). It is hoped that the reader will gain an understanding of what motivates microorganisms to dramatically change their environment, understand the potential geochemical conditions where such activity could occur, and allow the informed geologist to make predictive statements as to the potential of, and for, biospeleogenesis

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Palmer A. N. , Palmer M. V.

The origin of caves in the Black Hills has long been debated. Their history is long and complex, involving early diagenesis, meteoric karst (now paleokarst), deep burial, tectonic uplift, and, finally, enlargement of previous voids to the caves of today. The final stage is usually the only one recognized and is the topic of this paper. Genetic hypotheses include artesian flow, rising flow (preferably thermal), diffuse infiltration, and mixing of various water sources. The last process best fits the regional setting and water chemistry.  

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Rosaleslagarde L. , Boston P. J.

Conspicuous brackish sulfidic springs have been described at the northern Sierra the Chiapas, Mexico. These springs are produced by a mixture between regional and local groundwater flow paths. The regional groundwater has an average Total Dissolved Ions of 3081 mg/L so it has a brackish composition. This brackish water is saturated with respect to calcite and dolomite but undersaturated with respect to gypsum, anhydrite and halite. The mass balance and the discharge rate are used to quantify the mass and volume of minerals that are dissolved by the brackish spring water following Appelo and Postma (1993). This quantification will allow comparing the various speleogenetic mechanisms in the area. This is considering the composition of the spring water is relatively constant over time, as it is suggested by periodic measurements at the Cueva de Villa Luz springs during the last 10 years.
Sulfur isotopes in the water are consistent with anhydrite dissolution as the main source of the sulfate to the brackish spring water. Thus, the average 6 mol/L of sulfate in the brackish springs are produced by dissolution of 6 mol of anhydrite after subtracting the sulfate that could result from evapotranspiration of rainwater. Each liter of brackish water dissolved an average of 882 mg of anhydrite, which are equivalent to dissolving 0.36 cm3 of this mineral considering a density of 2.981 g/cm3. Additionally, using the average brackish water discharge rate of 144 L/s, an average of 57 g of anhydrite are being dissolved each second per every liter of brackish water. This is a minimal value because some of the sulfate in the water is used by sulfate-reducing bacteria in the subsurface to produce the hydrogen sulfide in the spring water. The anhydrite subject to dissolution is found interbedded in the Cretaceous carbonates, either from the subsurface at 4,000 m below sea level to the carbonate outcrops.
Similarly, we can calculate the volume of halite that is being dissolved by the brackish springs, considering chloride is a conservative element and subtracting the chloride concentration from the rainwater from that of the spring water following Appelo & Postma (1993). The 22 mol/L of chloride in the brackish water can result from dissolution in the subsurface of 22 moles or 1.3 g of halite per liter of brackish water. This mass of halite dissolved is equal to 0.59 cm3 considering a density of 2.168 g/cm3. Alternatively, 118 g of halite are dissolved per second per each liter of brackish water if we use the average discharge rate of 144 L/s.
Even when the brackish springs are oversaturated with respect to calcite and dolomite, their dissolution is still possible due to the common ion-effect of calcium after anhydrite dissolution and by mixing of waters with different compositions. A range of 10 to 80 % of brackish water from the regional aquifers mixes with fresh water from the local aquifer based on their water chemistry. Additionally, sulfuric acid speleogenesis occurs due to the oxidation of hydrogen sulfide to sulfuric acid.
Finally, the increase in the chloride concentration of the fresh water springs with respect to the concentration in rainwater was used to estimate that from the 4000 mm/y of annual precipitation, only 4%, 158 to 182 mm/y, recharge the aquifers. This low percentage is slightly higher than the 3.3% recharge in marls, marly limestone, silts and clays (Sanz et al., 2011), probably because of the relatively small area of carbonate outcrops over the entire region and the lack of recharge in altitudes higher than 1500 m above sea level.
Sulfuric acid is the most obvious speleogenetic mechanism occurring in the caves of the northern Sierra de Chiapas, Mexico due to the high hydrogen sulfide concentration in the spring water. In addition, the location of the springs at a zone of regional and local discharge where waters from different composition converge and mix, and the amount of mixing calculated suggests mixing is also an important speleogenetic mechanism. However, the depth and the time constrains at which these two hypogenic mechanisms occur is still unknown. The relatively low rainwater recharge rate suggests epigenesis is limited. Most likely, the porosity created by dissolution of anhydrite and halite in the subsurface is occluded by the precipitation of calcite. Chemical modeling and petrography will help to elucidate the order of the reactions occurring in the subsurface.

Occurrence of diagenetic alunites within karst cavity infill of the Dammam Formation, Ahmadi, Kuwait: an indicator of hydrocarbon gas seeps, 2014,
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Khalaf F. I. , Abdullah F. A.

Alunite minerals occur as white powdery lumps and laminated coloured deposits within cavity and solution channel infill of the palaeokarst zone of the Upper Eocene Dammam Formation. This formation is exposed in a quarry located on the Al Ahmadi ridge within the Greater Burgan oil field in southern Kuwait. Field occurrences and sedimentary structures of the alunite deposits were described. Collected samples were petrographically described, and their mineralogy and geochemistry were determined using X-ray diffraction and X-ray fluorescence, respectively. Microfabrics were investigated using SEM, revealing that they are primarily composed of fibrous alunogen (hydrous aluminium sulphate) and pseudo-cubical K-alunite (hydrous potassium aluminium sulphate). Their mode of occurrence suggests a hypogenetic origin, where sulphide gases associated with hydrocarbon gases reacted with an Al-rich solution leached from clay minerals and feldspars of the cavity-fill muddy sand sediments. The hydrocarbon gases may have seeped from subsurface petroliferous formations within the Greater Burgan oil field along vertical fractures. This study suggests that these acidic seeps may have played a role in the development of the palaeokarst zone of the Dammam Formation

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