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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. ...

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Calculating flux to predict future cave radon concentrations, Rowberry, Matt; Marti, Xavi; Frontera, Carlos; Van De Wiel, Marco; Briestensky, Milos
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Your search for dedolomitization (Keyword) returned 14 results for the whole karstbase:
Karstification without carbonic acid; bedrock dissolution by gypsum-driven dedolomitization, 1994, Bischoff Jl, Julia R, Shanks Wc, Rosenbauer Rj,
Aggressive karstification can take place where dolomite and gypsum are in contact with the same aquifer. Gypsum dissolution drives the precipitation of calcite, thus consuming carbonate ions released by dolomite. Lake Banyoles, in northeastern Spain, is a karst lake supplied by sublacustrine springs, and karstic collapse is occurring in the immediate vicinity of the lake. Lake water is dominated by Mg-Ca and SO 4 -HCO 3 , and is supersaturated with calcite that is actively accumulating in lake sediments. Water chemistry, sulfur isotope composition, local stratigraphy, and mass-balance modeling suggest that the primary karst-forming process at Lake Banyoles is dedolomitization of basement rocks driven by gypsum dissolution. Karstification takes place along the subsurface contact between the gypsiferous Beuda Formation and the dolomitic Perafita Formation. This process is here recognized for the first time to cause karstification on a large scale; this is significant because it proceeds without the addition of soil-generated carbonic acid. Gypsum-driven dedolomitization may be responsible for other karstic systems heretofore attributed to soil-generated carbonic acid

KARSTIFICATION WITHOUT CARBONIC-ACID - BEDROCK DISSOLUTION BY GYPSUM-DRIVEN DEDOLOMITIZATION, 1994, Bischoff Jl, Julia R, Shanks Wc, Rosenbauer Rj,
Aggressive karstification can take place where dolomite and gypsum are in contact with the same aquifer. Gypsum dissolution drives the precipitation of calcite, thus consuming carbonate ions released by dolomite. Lake Banyoles, in northeastern Spain, is a karst lake supplied by sublacustrine springs, and karstic collapse is occurring in the immediate vicinity of the lake. Lake water is dominated by Mg-Ca and SO4-HCO3, and is supersaturated with calcite that is actively accumulating in lake sediments. Water chemistry, sulfur isotope composition, local stratigrapy, and mass-balance modeling suggest that the primary karst-forming process at Lake Banyoles is dedolomitization of basement rocks driven by gypsum dissolution. Karstification takes place along the subsurface contact between the gypsiferous Beuda Formation and the dolomitic Perafita Formation. This process is here recognized for the first time to cause karstification on a large scale; this is significant because it proceeds without the addition of soil-generated carbonic acid. Gypsum-driven dedolomitization may be responsible for other karstic systems heretofore attributed to soil-generated carbonic acid

Origin of some atypical speleothems ('stalagmitic pipes') and the role of concomitant dedolomitization in their formation, 1995, Rodriguezfernandez Jose, Martinpenela Antonio J. ,

Dedolomitization as a mechanism for karst generation in permian Blane formation, southwestern Oklahoma, USA., 1997, Raines M. A. , Dewers T. A.

Dedolomitization as a driving mechanism for karst generation in Permian Blaine formation, southwestern Oklahoma, USA, 1997, Raines M. A. , Dewers T. A. ,
Cyclic deposits of Permian shales, dolomites, and halite and gypsum-bearing strata in the Blaine Formation of Southwestern Oklahoma contain abundant karst features. The present study shows that an important mechanism of karst development in these sequences is dedolomitization, wherein gypsum and dolomite in close spatial proximity dissolve and supersaturate groundwaters with respect to calcite. The net loss of mass accompanying this process (dolomite and gypsum dissolution minus calcite precipitation) can be manifest in secondary porosity development while the coupled nature of this set of reactions results in the retention of undersaturated conditions of groundwater with respect to gypsum. The continued disequilibrium generates karst voids in gypsum-bearing aquifers, a mineral-water system that would otherwise rapidly equilibrate. Geochemical modeling (using the code PHRQPITZ, Plummer et al 1988) of groundwater chemical data from Southwestern Oklahoma from the 1950's up to the present suggests that dedolomitization has occurred throughout this time period in evaporite sequences in Southwestern Oklahoma. Reports from groundwater well logs in the region of vein calcite suggest secondary precipitation, an observation in accord with dedolomite formation In terms of the amounts of void space produced by dissolution, dedolomitization can dominate gypsum dissolution alone, especially in periods of quiescent aquifer recharge when gypsum-water systems would have otherwise equilibrated and karst development ceased. Mass balance modeling plus molar volume considerations show that for every cubic cm of original rock (dolomite plus gypsum), there is 0.54 cm(3) of calcite and 0.47 cm(3) of void space produced Only slightly more pore space results if the dedolomitization reaction proceeds by psuedomorphic replacement of dolomite by calcite than in a reaction mechanism based on conservation of bicarbonate

Geologic controls on porosity development in the Maynardville limestone, Oak Ridge, Tennessee, 1997, Goldstrand P. M. , Shevenell L. A. ,
Understanding the geologic controls of porosity development and their relationship to the karst aquifer system in the Cambrian Maynardville Limestone is important in determining possible contaminant transport pathways and provides essential data for hydrologic models within the Oak Ridge Reservation of east Tennessee. In the Maynardville Limestone, several important factors control porosity development: (1) lithologic controls on secondary microporosity and mesoporosity are related to dissolution of evaporite minerals and dedolomitization in supratidal facies; (2) depth below the ground surface controls the formation of karst features because the most active portion of the groundwater system is at shallow depths, and karst features are rare below approximate to 35 m; and (3) structural controls are related to solution enlargement of fractures and faults

Contribution to knowledge of gypsum karstology, PhD thesis, 1998, Calaforra Chordi, J. M.

The objective of this study was not to establish a definitive judgement regarding a topic for which very little previous information was available, but rather to open new routes for research into karst by means of a particularized analysis of some of the factors involved in the speleogenesis of gypsiferous materials. The main obstacle to the attainment of this goal has been the scientific community's lack of interest in karst in gypsum, particularly in our country, until the nineteen eighties. To overcome this neglect it was decided, in my opinion quite correctly, to extend the bounds of the study as far as possible, so that the information obtained from the contrast found between the most important worldwide zones of karst in gypsum could be applied to the gypsiferous karst in our country, and in particular, to the most significant, the karst in gypsum of Sorbas.
This is the justification for the numerous references in the text to the gypsiferous karst and cavities in gypsum that are most relevant in Spain (Sorbas, Gobantes, Vallada, Archidona, Estremera, Baena, the Ebro Basin, Estella, Beuda, Borreda, etc.) and also to the best-known gypsiferous karsts worldwide (Podolia, Secchia, Venna del Gesso Romagnolo, Sicily and New Mexico). By means of these comparisons, the initial lack of information has been overcome.
The study is based on three central tenets, which are interrelated and make up the first three chapters of this report. The first consideration was to attempt to characterize the particular typology of gypsiferous karst from the geological (both stratigraphic and structural) point of view. This chapter also provides an introduction to each of the gypsiferous karsts examined. The second chapter is dedicated to the geomorphology of gypsiferous karst, under both superficial and subterranean aspects. It is important to note that the study of a gypsiferous karst from the speleological point of view is something that may seem somewhat unusual; however, this is one of the points of principle of this paper, the attempt to recover the true meaning of a word that has historically been unfairly condemned by a large part of the Spanish scientific community. Thirdly, a detailed study has been made of the hydrochemistry of the most important gypsiferous karsts in our region, together with the presentation of a specific analytical methodology for the treatment of the hydrochemical data applicable to the gypsiferous karst.
Geological characterization of gypsum karst
In the characterization of karst in gypsum, the intention was to cover virtually all the possibilities from the stratigraphic and structural standpoints. Thus, there is a description of widely varying gypsiferous karsts, made up of Triassic to Miocene materials, some with a complex tectonic configuration and others hardly affected by folding. The gypsiferous karsts described, and their most significant geological characteristics, are as follows:
Karst in gypsum at Sorbas (Almeria): composed of Miocene gypsiferous levels with the essential characteristic of very continuous marly interstrata between the layers of gypsum, which decisively affect the speleogenesis of the area. The gypsum layers have an average thickness of about 10 m and, together with the fracturing in the zone, determine the development of the gypsiferous cavities. These are mainly selenitic gypsum - occasionally with a crystal size of over 2 m - and their texture also has a geomorphologic and hydrogeologic influence. This area is little affected by folding and so the tectonic influence of speleogenesis is reduced to the configuration of the fracturing.
The Triassic of Antequera (Malaga): this is, fundamentally, the gypsiferous outcrop at Gobantes-Meliones, originating in the Triassic and located within the well-known "Trias" of Antequera. It is made up of very chaotic gypsiferous materials containing a large quantity of heterometric blocks of varied composition; the formation may be defined as a Miocene olitostromic gypsiferous breccia that is affected by important diapiric phenomena. The presence of hypersoluble salts at depth is significant in the modification of the hydrochemical characteristics of the water and in the speleogenetic development of the karst.
The Triassic of Vallada (Valencia): Triassic materials outcrop in the Vallada area; these mainly correspond to the K5 and K4 formations of the Valencia Group, massive gypsum and gypsiferous clays. The influence of dolomitic intercalations in the sequence is crucial to the speleogenesis of the area and this, together with intense tectonic activity, has led to the development in this sector of the deepest gypsiferous cavity in the world: the "Tunel dels Sumidors". As in the above case, the presence of hypersoluble salts at depth and the varied lithology influence the variations in the hydrodynamics and hydrochemistry of the gypsiferous aquifer.
Other Spanish gypsum karsts: this heading covers a group of gypsiferous areas and cavities of significant interest from the speleogenetic standpoint. They include the area of Estremera (Madrid), with Miocene gypsiferous clays and massive gypsum arranged along a large horizontal layer; this has produced the development of the only gypsiferous cavity in Spain with maze configuration, the Pedro Fernandez cave. The study of this cave has important hydrogeological implications with respect to speleogenesis in gypsum in phreatic conditions. The Baena (Cordoba) sector, in terms of its lithology, is comparable to the "Trias de Antequera". Here, the cavities developed in gypsiferous conglomerates, following structural discontinuities have enabled contact between carbonate and gypsiferous levels, and so we may speak of a mixed karstification: a karst in calcareous rocks and gypsum. The karst of Archidona (Malaga) is similar to that of the Gobantes-Meliones group and is significant because of the geomorphologic evolution of the karst, which is related to the diapiric ascent of the area and the formation of karstic ravines. The karst in the Miocene and Oligocene gypsum of the Ebro Basin (Zaragoza), has been taken as a characteristic example of a gypsiferous karst developed under an alluvial cover, with the corresponding geomorphological implications in the evolution of the surface landforms. In the gypsiferous area of Borreda (Barcelona), the presence of anhydritic levels in the sequence might have influenced the speleogenesis of its cavities. The cavity of La Mosquera, in Beuda (Girona), developed in massive Paleogene gypsum. This is the only Spanish example of a phreatic gypsiferous cavity developed in saccaroid gypsum, which is related to the particular subterranean morphology discovered. Finally, this group includes other Spanish gypsiferous outcrops visited during the preparation of this report, the references to which may be found in the relevant chapters.
Karst in gypsum in Europe and America: In order to complete the study of karst in gypsum, and with the idea of using all the available data on the karstology of gypsiferous materials for comparative studies of data for our country, a complementary activity was to define the most significant geological characteristics of the most important gypsiferous karsts in the world. An outstanding example is the gypsiferous karst at Podolia (Ukraine), developed in microcrystalline Miocene gypsum which has undergone block tectonics related to the collapse of the Precarpatic foredeep. This gypsum provides interesting data on speleogenesis in gypsiferous materials, as its evolution is related to the confining of the only gypsiferous stratum (of 10 to 20 m depth) producing interconnected labyrinthine galleries of over 100 km in length. Another well-known karst in gypsum is the one located at "Venna del Gesso Romagnolo" (Italy), in the Bologna region, with a lithology that is very similar to that which developed at Sorbas, but with the difference that it underwent more intense tectonics with folding and fracturing of the Tertiary sediments of the Po basin. In the same Italian province, in "L'alta Val di Sec-chia", there are outcrops of karstified Triassic materials which correspond to the formation of Burano, composed of gypsum and anhydrite with hypersoluble salts at depth and very notable diapiric phenomena. The study of this area has been used for a comparative analysis - geomorphology and hydrogeochemistry - with the Spanish gypsiferous karsts developed in Triassic levels. The third Italian gypsiferous karst to be considered is the one developed in Sicily, which has extensive Messinian outcrops of microcrystalline and selenitic gypsum as well as a great variety of lithologic types within the gypsiferous sequence, which we term the "gessoso solfifera" sequence. This gypsiferous karst is especially interesting from the geomorphologic standpoint due to the great quantity and variety of present superficial karstic forms. This has also served as a guide for the study of Spanish gypsiferous karsts. Finally, considering the relation between climatology and the development of karstic forms, we have also studied the karst in gypsum in New Mexico, where there is an extensive outcrop of Permian gypsum, both micro and macrocrystalline, situated on a large platform almost unaffected by deformation, and where the conditions of aridity are very similar to those found in the gypsiferous karst of Sorbas.
Geomorphological characterization of gypsum karst
From the geomorphological standpoint, the intention is to give an overview of the great variety of karstic forms developed in gypsum, traditionally considered less important than those developed in carbonate areas. This report shows this is not the case.
The theory of Convergence of Forms has been shown to be an efficient tool for the study of the morphology of karst in gypsum. Here, its principles have been used to provide genetic explanations for various gypsiferous forms derived from carbonate studies, and for the reverse case. In fact, studying a karst in gypsum is like having available a geomorphological laboratory where not only are the processes faster but they are also applicable to the karstology of carbonate rocks.
A large number of minor karstic forms (Karren) have been identified. The most important factors conditioning their formation are the texture of the rock, climatology and the presence of overlying deposits. The first, particularly, is largely responsible for determining the abundance of certain forms with respect to others. Thus, Rillenkarren, Trittkarren and small "kamenitzas" are more frequently found in microcrystalline and sandstone gypsum (for example, karst in gypsum in Sicily (Italy) and Va-llada (Valencia, Spain). Others seem to be more exclusive to selenitic gypsum, such as exfoliation microkarren, or are closely related to the climatology of the area (Spitzkarren develops from the alteration of gypsum in semiarid conditions). Others are related either to the presence of developed soil cover (Rundkarren, using Convergence of Forms), or to their specific situation (candelas and Wallkarren around dolines and sinkholes) or to the microtexture of the gypsum and the orientation of the 010 and 111 crystalline planes and twinning planes for the development of nanokarren.
The tumuli are the most peculiar forms of the Sorbas karst in gypsum, though they have also been identified in other gypsiferous karsts (Bolonia, New Mexico, Vallada, etc.). These are subcircular domes of the most superficial layer of the gypsum. Their formation has been related to processes of precipitation-solution and of capillary movement through the gypsiferous matrix. Their extensive development is largely determined by the climatology of the area and by the structural organization. It is therefore clear that the best examples are found in the karst of Sorbas due to the abrupt changes in temperature and humidity that occur in a semiarid climate, and because of the horizontality of the gypsiferous sequence.
Karst in gypsum and its larger exokarstic forms, apart from being climatically determined, also depend on the structural state and lithological determinants of the area. Thus, it is possible to differentiate between gypsiferous karsts where the lithology, together with erosive breakup, is more important (Sorbas and New Mexico) and others where confining hydraulic conditions persist (Estremera and Podolia). In other cases, tectonics has played a significant modelling role, and there is a clear possibility of an inversion of the relief (Bolonia or Sicily) or of the effect of diapiric processes (Secchia, Vallada, Antequera). The typological diversity of the dolines is obviously also related to these premisses. Another example is the relation existing between carbonate precipitation and gypsum solution, as evidenced in contrasting examples (Bolonia versus Sorbas).
Subterranean karstic forms have been examined from a double perspective: the morphology of the passages and the mineralization within the cavities. With respect to the former, a noteworthy example is the interstratification karst of Sorbas, where subterranean channels have developed during two well-differentiated phases, the phreatic and the vadose. The first was responsible for the formation of the small proto-galleries, currently relicts that are observable as false dome channels in the bottom of the gypsiferous strata. The second, with an erosive character, enabled the breakup of the marly interstrata and the formation of the large galleries found today. Other aspects considered include the speleogenetic influence of the presence of calcareous intercalations in the gypsiferous sequence (Vallada karst), gypsiferous agglomerates (Baena karst), anhydrite (Rotgers karst), suffusion processes (Sorbas karst) and the importance of condensation.
Spelothemes in gypsiferous cavities have been approached with special concern for gypsiferous speleothemes, in particular those which, due to their genetic peculiarity or to the lack of previous knowledge about them, are most significant. Among these are gypsum balls, with phenomena of solution, detritic filling, capillarity and evaporation; gypsum hole stalagmites, where the precipitation-solution of the gypsum controlling the formation of the central orifice is related to the previous deposit of carbonate speleothemes; gypsum trays that mark the levels of maximum evaporation; gypsum dust, determined by abrupt changes in temperature and humidity in areas near the exterior of gypsiferous cavities. All of these are characteristic of, and practically exclusive to, gypsiferous karsts in semiarid ztenes such as Sorbas and New Mexico.
Karst in gypsum has been morphologically classified with reference to the previously-mentioned criteria: the presence and typology of epigean karstic forms, both macro and microform; the typology of hypogean karstic forms (passages) and the type of speleothemes within the cavities (gypsiferous or carbonate). All these variables are clearly influenced by climatology, and so a study of the geomorphology of gypsiferous karst is seen to be an efficient tool for the analysis of the paleoclimatology of an area.
Hydrogeochemical characterization of gypsum karst
The hydrogeochemical characterization of karst in gypsum was approached in two stages. The first one was intended to establish themodels to be applied to the hydrochemistry approach, while the second provided various examples of hydrochemical studies carried out in gypsiferous karsts.
The theoretical framework which has been shown to be most accurate with respect to the formulation of chemical equilibria in water related to gypsiferous karst is the Virial Theory and the Pitzer equations.
For this study, we used a simplification of these equations as far as the second virial coefficient by means of a simple, polynomial variation to obtain the equilibrium state of the water with respect to the gypsum, for an ionic strength value greater than 0.1 m and temperatures of between 0.5 and 40 "C. This was the case of the gypsiferous karsts found to be related to hypersaline water at depth (Vallada, Gobantes-Meliones, Poiano). In the remaining situations, where the ionic strength was below 0.1 m, only the theory of ionic matching was used.
The hydrochemical study of the gypsiferous karst of Gobantes-Meliones (Malaga) led to the hypothesis of the possible influence of hypersaline water on karstification in gypsum. Using theoretical examples of the mixing of water derived both from hypersaline water and from water related only to the gypsiferous karst, it was shown that above a percentage content of 0.1:0.9 of saline and sulphated water, the mixture is subsaturated with respect to gypsum and other minerals. On reaching percentages greater than 0.5:0.5, values of oversaturation are again found. This could mean that the contact between sulphated and hypersaline water is a karstification zone in gypsum at depth.
In the gypsiferous karst at Salinas-Fuente Camacho (Granada), a study has been made of the hydrochemical influence of dolomitic levels in the sequence by means of the analysis of the hydrochemical routes between hydraulically-connected points. The generic case of mass transfer in this gypsiferous aquifer implies a precipitation of calcite which is in-congruent with dolomitic solution, proving that the process of dedolomitization in gypsiferous aquifers with an abundance of dolomitic rocks can be an effective process. In situations of high salinity, with contributions of hypersaline water, the process may be inverted, such as occurs in coastal carbonate aquifers influenced by the fresh-saltwater interface.
The gypsiferous aquifer of Sorbas-Tabernas (Almeria) provides the best case of karstification in gypsum in Spain; the hydrochemical study carried out has been used as an example of karstification in gypsum completely uninfluenced by sodium-chloride facies. It is shown, from the hydrochemical similarities between the different sectors, that the uniformity of the flow from the system main spring (Los Molinos) responds to the delayed hydraulic input through the overlying post-evaporitic materials and to the pelitic intercalations of the gypsiferous sequence. The aquifer is partially semiconfined, a situation which is comparable to the onset of the karstification stage, while the area of the Sorbas karst, strictly speaking, bears no hydriaulic relation to the rest of the system, behaving like a free aquifer intrinsically related to the epikarstic zone. This fact is demonstrated by the hydrochemical differences between the main spring and those related to gypsiferous cavities.
Apart from the general study of the Sorbas-Tabemas aquifer, a study was also made of the hydrochemical-time variations within cavities, and in particular within the Cueva del Agua, where it is possible to observe particular processes affecting karstification in gypsum, such as the precipitation of carbonates on the floor of the cavity which produce, in that area, a greater solution of gypsum (the phenomenon of hyperkarstification). Furthermore, the temporal evolution of the chemistry of the cavity, along 800 m of subterranean flow through its interior, shows the existence of inertial sectors where the variations were less abrupt. Only in the case of particular sectors, related to sporadic hydriaulic contributions or to the proximity to points of access., was a notable seasonal influence detected.
A similar hydrochemical study was carried out in the karst of Vallada (Valencia), along the cavity of the Tunel dels Sumidors. The chemistry here was compared with that of the springs of Brolladors (whose water rapidly infiltrates into the cavity) and Saraella (a saline resurgence of the whole system). Unexpected increases in the ionic content of certain salts (sulphates and chlorides) were detected during periods of increased flow; these were interpreted as the effect of the recharging of the Saraella spring arising from the immediate contribution of rapidly circulating sulfated water coming from the cavity and the subsequent mobilization of interstitial water with an ionic content higher than the characteristic level of the spring.
We present as a hypothesis the idea that, in addition to the hydrogeochemical processes described that can affect the evolution of a gypsiferous karst, the processes of sulphate reduction also influence karstification in gypsum, at least during the earliest stages. Some examples such as the presence of gypsum with abundant organic matter reprecipitated into phreatic channels (Sorbas) or veins of sulphur related to gypsiferous karsts (Podolia, Sicily) lend support to this idea.
Studies of the solution-erosion of gypsum have been performed by physical methods (tablets and M.E.M.) showing that the solution-erosion of gypsum within cavities is minimal (0.03 mm/ year) compared to that existing in the exterior (0.3 mm/year). The speleogenetic effect of condensation within the cavities has also been shown, with solution-erosion rates of 0.005 mm/year to be like the equivalent surface lowering. These data correspond to the karst in gypsum at Sorbas, where, additionally, a study about the time variation of the solution-erosion was carried out. It was found that the process is not continuous but clearly sporadic. During periods of torrential rain, the solution-erosion ranges from a weight loss of 400 mg/cm2/year on the surface of the karst to 75 mg/cm2/year inside the caves, while during the rest of the year the weight loss was barely 1 mg/cm2/year. The physical methods were compared with the results obtained from chemical methods, and it was found that, in general, higher values were obtained with the former (10-20% higher when weighted for the rainfall during the measuring periods). Thus it is reasonable to consider that the erosive process is more marked than was at first assumed.
In total, three cavity tracing experiments were carried out, all with fluoresceine, two of them in Cueva del Agua in Sorbas (during periods of high and low water levels) and the other in Tunel dels Sumidors in Vallada. At the first site, the comparison of the two tracing tests reveals a differential hydrodynamic behaviour of the cavity for the two contrasting situations; periods of high water input and periods of low rainfall. This behaviour is characteristic of well developed karstic aquifers, where the hydrodynamic effect of the circulation of water through small channels or, in this case, through the gypsiferous matrix and interbedded marly layers, seems to be more important under conditions of low hydraulic input than when rainfall is abundant. The two situations tested seem to confirm that the Cueva del Agua system, an epikarstic aquifer, which is representative of karstification in gypsum, has scarce retentive power and so large volumes of precipitation are totally discharged via the spring within a few days. However, the explanation of the small but continuous flow from the base of the cavity requires the inclusion of other factors in the interpretation. In this case, the flow seems to be fairly independent of rainfall and attributable to other processes, in addition to the previously described ones, such as the retentive power of the gypsiferous matrix and the marly interstrata. These might include the high degree of condensation measured over long periods, both on the surface of the karst in gypsum and within the cavities. In the case of the Tunel dels Sumidors, a highly irregular response was found, despite the fact that the coefficient of dispersivity was found to be 0.4. This value is similar to that obtained for the karst in gypsum at Sorbas in response to low water conditions, and so, here too, one might assume the influence of greater than expected flow-retaining processes, between the entry and exit points. Doubtless the karstic system of the Tunel dels Sumidors is more complex than was initially expected and in fact, the irregularity reflected by the fluoresceine concentration curve over time implies the existence of other factors to explain the diversity of the relative maxima obtained. Firstly, the presence of numerous Triassic clay intercalations might delay the flow, in addition to retaining a certain quantity of fluoresceine by ionic exchange. There is also a possibility that the flow is dispersed through a network of small conduits and pores, due to the permeability of the gypsiferous matrix. Finally, we cannot discount the possible existence of a deep-level input which, in this case, would be responsible for the variation in the flow and the chemical composition. This set of suppositions, as a whole, would explain the fact that the response of the spring to tracing is so irregular, even though we cannot achieve a definition of the qualitative influence of each one on the hydrodynamics of the system.
In order to verify some of the above hypotheses, particularly those referring to the process of condensation within cavities, an experiment was designed, consisting of a microtracing test at some points where condensation had been detected within the Cueva del Agua at Sorbas. The test produced a range of condensation flow speed values of 0.2 to 30 cm/hour and shows that, in those sections where the presence of condensation flow is visually apparent, there is a rapid dispersion of the colourant. However, it also shows that at points where there is no apparent condensation the process also occurs, but at a lower rate of efficiency. The importance of condensation within cavities has two aspects; firstly, speleogenetic, with the development of solution forms (cupolas) and deposit forms (capillarity boxwork); and secondly, hydrogeological, as this is the reason why certain processes (strong changes in temperature and humidity, multiple routes of airflow exchange with the exterior) may in themselves constitute a hydraulic contribution, of slight importance, but sufficient to explain a large part of the base flow (0.2 - 0.8 L/s) of a whole cavity system such as the Cueva del Agua in semiarid conditions.
With the intention of completing the analyses carried out in various karsts in gypsum, instruments were installed in the Cueva del Agua at Sorbas to measure, by continuous registration, some important physico-chemical parameters that might provide additional data on the hydro-geologic behaviour of this gypsiferous karst, especially at the level of the epikarstic zone. The parameters of temperature and water conductivity were considered most important, due to their singular behaviour patterns. During the experiment there were two periods of rainfall that modified the chemistry of the cavity, one of 30 mm in two days and another of 200 mm (almost the annual total) in four days. In the second case, which was much more extreme, a very significant increase in water temperature (up to 7 °C during the initial period of high water flow) was detected, while conductivity fell. But suddenly, when the minimum conductivity was reached, the temperature dropped sharply by 6-7 °C to return to the base temperature of the cavity. Subsequently, the temperature again stabilized at about 7 °C above the data recorded during the dry period. This behaviour pattern was not detected when the rainfall was slight. The explanation for this dual behaviour observed is fundamentally based on the quantity of rainfall and on the differences between the exterior air temperature, the temperature of interstitial water and the temperature recorded in the spring during high water flow. When water temperature in the cavity during high water flow is higher than the base temperature recorded in the period immediately before, it means that the interstitial water does not mobilize. However, when at any time the two temperatures coincide, one might suppose that there might have existed a process of mobilization of the water previously resident in the rock, by a piston effect, but in the unsaturated zone. On the other hand, the temporal variations of these parameters during the months following periods of high rainfall have enabled us to detect the existence of distinct periods during the return to normal cavity conditions. By carefully examining the decrease curve of water temperature inside the cavity while conductivity regained its maximum stable value, two periods may be differentiated. The first may be termed the "inertial influence period", when the rainfall occurring removes all signs of natural variation in the cavity. Thus, the daily external influences are not clearly detectable and the curve is downward-sloping and asymptotic with no significant oscillations. In the second period, which ends with the total stabilization of the parameter at the level of the initial conditions, the asymptotic descent is seen to be affected by daily temperature variations. This is termed the "inertial recovery period", during which external variations start to have an effect on the interior of the cavity such that there is a progressive increase in the amplitude of the daily variation in water temperature, air temperature and relative humidity. This behaviour pattern of variation of these parameters during periods of high rainfall, might be extended to all karstic systems, varying only in magnitude and temporal extent.


Dedolomitization and other early diagenetic processes in Miocene lacustrine deposits, Ebro Basin (Spain), 1999, Arenas C, Zarza Ama, Pardo G,
A variety of meteoric diagenetic features reveal the development of a syngenetic karst on lacustrine deposits of the Ebro Basin. Diagenetic processes that operated on lacustrine laminated and stromatolitic carbonates include the following. (1) A first syndepositional stage with processes such as dolomitization, desiccation and related breccia formation and sulphate precipitation, either as lenticular gypsum crystals or nodules. This stage took place under progressive evaporation due to lake level fall, when the previous carbonate deposits became exposed as a supra-littoral fringe surrounding saline mud flats of adjacent sulphate depositional environments. (2) A second early diagenetic stage in which processes such as sulphate dissolution and collapse brecciation, dedolomitization, calcite spar cementation and silicification occurred as a result of meteoric water input that caused a progressive rise in lake level. Light isotopic compositions (delta(13)C and delta(18)O) of diagenetic calcites, versus heavier compositions in primary laminated and stromatolitic limestones, confirm a meteoric influence. The syngenetic karst is best developed at the boundary between two allostratigraphic units and coincided with one of the extensive stages of sulphate deposition at the end of the Early Miocene. The karst facies occurred in an area that was a low-relief barrier that separated two sites of sulphate deposition during low lake levels, This indicates that the karat development was controlled by topographic changes within the basin and record a shift from arid to wetter climatic conditions, as suggested by the overlying freshwater carbonate deposits. The presence of diagenetic features such as those described in the central Ebro Basin affecting saline lacustrine carbonates is relevant because they can be used as indicators of subaerial exposure periods in terrestrial environments and they also reveal important palaeogeographic and palaeoclimatic events of basinal extent.

Geostatistical and geochemical analysis of surface water leakage into groundwater on a regional scale: a case study in the Liulin karst system, northwestern China, 2001, Wang Y. , Ma T. , Luo Z. ,
The Liulin karst system is typical of hydrogeological systems in northern China, with a group of springs as the dominant way of regional groundwater discharge. Surface water leakage into groundwater has been observed in six sections of the rivers in the study area. To extract hydrogeological information from hydrochemical data, 29 water samples were collected from the system. On a trilinear diagram, most of the groundwater samples are clustered around the surface waters, indicating the effect of leakage on their chemistry. R-mode factor analysis was made on seven variables (Na, Ca, Mg, SO4, Cl, HCO3, and NO3) of the samples and three principal factors were obtained: the F-1 factor is composed of Ca, Mg and SO4, the F-2 of HCO3 and NO3, and the F-3 of Na and Cl. These factors are then used as regionalized variables in ordinary Kriging for unbiased estimates of the spatial variations of their scores. Considering regional hydrogeological conditions, the hydrogeological implications of the spatial distribution of the factor scores as related to the effects of the surface leakage are discussed. To evaluate the geochemical processes, the geochemical modeling code NETPATH was employed. The modeling results: show that mixing commonly occurs in the system and dolomite dissolution is more important than calcite dissolution. Dedolomitization (calcite precipitation and dolomite dissolution driven by anhydrite dissolution) is locally important, in the western flank of the system where the surface water leakage has the least effect.

The hydrogeochemistry of the karst aquifer system of the northern Yucatan Peninsula, Mexico, 2002, Perry E. , Velazquezoliman G. , Marin L. ,
Based on groundwater geochemistry, stratigraphy, and surficial and tectonic characteristics, the northern Yucatan Peninsula, Mexico, a possible analog for ancient carbonate platforms, is divided into six hydrogeochemical/physiographic regions: (1) Chicxulub Sedimentary Basin, a Tertiary basin within the Chicxulub impact crater; (2) Cenote Ring, a semicircular region of sinkholes; (3) Pockmarked Terrain, a region of mature karst; (4) Ticul fault zone; (5) Holbox Fracture Zone-Xel-Ha Zone; and (6) Evaporite Region. Regional characteristics result from tectonics, rock type, and patterns of sedimentation, erosion, and rainfall. The Cenote Ring, characterized by high groundwater flow, outlines the Chicxulub Basin. Most groundwater approaches saturation in calcite and dolomite but is undersaturated in gypsum. Important groundwater parameters are: SO4/Cl ratios related to seawater mixing and sulfate dissolution; Sr correlation with SO4, and saturation of Lake Chichancanab water with celestite. indicating celestite as a major source of Sr; high Sr in deep water of cenotes, indicating deep circulation and contact of groundwater with evaporite; and correlation of Ca, Mg, and SO4, probably related to gypsum dissolution and dedolomitization. Based on geochemistry we propose: (1) a fault between Lake Chichancanab and Cenote Azul; (2) deep seaward movement of groundwater near Cenote Azul; and (3) contribution of evaporite dissolution to karst development in the Pockmarked Terrain. Chemical erosion by mixing-zone dissolution is important in formation of Estuario Celestun and other estuaries, but is perhaps inhibited at Lake Bacalar where groundwater dissolves gypsum, is high in Ca, low in CO3, and does not become undersaturated in calcite when mixed with seawater

Quaternary dedolomitization along fracture systems in a Late Triassic dolomitized platform (western Southern Alps, Italy), 2004, Ronchi P. , Jadoul F. , Savino R. ,
The studied area belongs to a south vergent thrust and fold belt of the Southern Alps of central Lombardy where the norian Dolomia Principale crops out. This up to 2 km thick carbonate platform succession has been massively dolomitized from early to shallow burial diagenesis. Dark grey bedded dolostones (basal Dolomia Principale), outcropping along the both lower slopes of Iseo Lake (lower Camonica Valley), show a complex network of dedolomitized white-grey areas. The calcareous lenses show an irregular, elongated (up to few ineters large) shape; they are usually located along fault-fracture systems and extending along the strata bedding. Two main fabrics have been recognized: the fabric A is formed by a reticulate of small fractures filled by calcite and surrounded by fine grained calcitized halos, the fabric B is associated to more intense fracturation process that locally gave rise to breccia fabric; moreover a ochre-reddish internal sediment is locally present in small cavities or as a breccia matrix, a huge speleothem-like cementation is associated to these dedolomitized fabric. This study was aimed to reconstruct the dedolomitization process and to propose a relevant genetic model. The petrographic analyses, integrated using cathodoluminescence and electron scanning microscope allowed to find out that dedolomitization process is composed of a first phase of dolomite dissolution along permeable path ways, both at the macro and at the micro scale, followed by calcite precipitation in the pore spaces. The negative delta(13)O and delta(13)C values of the calcite cements and the calcitic fraction of the dedolomitized fabrics suggest precipitation in presence of meteoric water derived fluids. Radiometric absolute age determination (U-230/Th-234) indicates that calcite cements precipitated in the last 100000 years: age during which the area was subject to several advances and retreats of glacial tongues. The field mapping, analytical data and the geomorphology of the areas where the dedolomitized patches are more frequent, in correspondence of a narrow passage of the lower Camonica valley, allowed us to infer that the dedolomitization developed during glacial-interglacial phases particularly active in the region during the Pleistocene. In particular we propose that the fracturation and the first phase of dedolomitization (fabric A) occurred during the glacial period, while extensive calcite precipitation and brecciation (fabric B) formed during the interglacial periods, dominated by a warm climate during which extensive soil cover and karst processes developed

Tectonic-hydrothermal brecciation associated with calcite precipitation and permeability destruction in Mississippian carbonate reservoirs, Montana and Wyoming , 2006, Katz D. A. , Eberli G. P. , Swart P. K. , Smith Jr. L. B.

The Mississippian Madison Formation contains abundant fracture zones and breccias that are hydrothermal in origin based on their morphology, distribution, and geochemical signature. The hydrothermal activity is related to crustal shortening during the Laramide orogeny. Brecciation is accompanied by dedolomitization, late-stage calcite precipitation, and porosity occlusion, especially in outcrop dolomites. The tectonic-hydrothermal late-stage calcite reduces permeability in outcrops and, potentially, high-quality subsurface reservoir rocks of the subsurface Madison Formation, Bighorn Basin. The reduction of permeability and porosity is increased along the margins of the Bighorn Basin but not predictable at outcrop scale. The destruction of porosity and permeability by hydrothermal activity in the Madison Formation is unique in comparison to studies that document enhanced porosity and permeability and invoke hydrothermal dolomitization models. Hydrothermal breccias from the Owl Creek thrust sheet are classified into four categories based on fracture density, calcite volume, and clast orientation. Shattered breccias dominate the leading edge of the tip of the Owl Creek thrust sheet in the eastern Owl Creek Mountains, where tectonic deformation is greatest, whereas fracture, mosaic, and chaotic breccias occur throughout the Bighorn Basin. The breccias are healed by calcite cements with d18O values ranging between _26.5 and _15.1xPeedee belemnite (PDB), indicating that the cements were derived from isotopically depleted fluids with elevated temperatures. In the chaotic and mosaic breccia types, large rotated and angular clasts of the host rock float in the matrix of coarse and nonzoned late-stage calcite. This appearance, combined with similar d18O values across even large calcite veins, indicates that the calcite precipitated rapidly after brecciation. Values for d13C(_5–12xPDB) from the frontal part of the Owl Creek thrust sheet indicate equilibrium between methane and CO2-bearing fluids at about 180jC. Fluid inclusions from the eastern basin margin show that these cements are in equilibrium with fluids having minimum temperatures between 120 and 140jC and formed from relatively low-salinity fluids, less than 5 wt.% NaCl. Strontium isotope ratios of these hydrothermal fluids are more radiogenic than proposed values for Mississippian seawater, suggesting that the fluids mixed with felsic-rich basement before migrating vertically into the Madison Formation. We envisage that the tectonic-hydrothermal late-stage calcitecemented breccias and fractures originated from undersaturated meteoric ground waters that migrated into the burial environment while dissolving and incorporating Ca2+ and CO3 2_ and radiogenic Sr from the dissolution of the surrounding carbonates and the felsic basement, respectively. In the burial environment, these fluids were heated and mixed with hypersaline brines from deeply buried parts of the basement. Expulsion of these fluids along basementrooted thrust faults into the overlying strata, including the Madison Formation, occurred most likely during shortening episodes of the Laramide orogeny by earthquake-induced rupturing of the host rock. The fluids were injected forcefully and in an explosive manner into the Madison Formation, causing brecciation and fracturing of the host rock, whereas the subsequent and sudden decrease in the partial pressure of CO2 caused the rapid precipitation of calcite cements. The explosive nature of hydrothermal fluid migration ultimately produces heterogeneities in reservoir-quality carbonates. In general, flow units in the Madison Formation are related to sequence boundaries, which create vertical subdivisions in the porous dolomite. The late-stage calcite cement surrounds hydrothermal breccia clasts and invades the dolomite, reducing porosity and permeability of the reservoir-quality rock. As a consequence, horizontal flow barriers and compartments are established that are locally unpredictable in their location and extent and regionally predictable along the margins of the Bighorn Basin. 


Fluid migration and porosity evolution in the Buda Hills, Hungary – selected examples from Triassic and Paleogene carbonate rocks/Dissertation submitted to the Ph.D. program for Geology and Geophysics at the Ph.D. School of Earth Sciences, Eötvös Lor, 2011, Poros, Zsófia

Porosity evolution of carbonates in the Buda Hills was the subject of this research. The aim was to provide an analogue for carbonate reservoirs that underwent multiphase diagenesis. Two major porosity types were recognized: 1) micro-porosity of powdered Triassic dolomites 2) cavernous and fracture porosity represented by the famous hypogenic cave system, hosted by Triassic and Paleogene carbonates. Powderization of dolomite is a general phenomenon in the Buda Hills, where its areal extent is exceptionally large compared to similar occurrences elsewhere in the world. Geochemistry and mineralogy of the dolomite remained constant throughout the disintegration. Powderization is absent at places where the Triassic dolomites are partially calcitized as a result of karst related dedolomitization. Since powderization was controlled by surface related processes and no geochemical changes were associated with it, disintegration of dolomite is interpreted as the result of sub-recent physical weathering, supposedly related to frost action.

Hypogenic caves are found along older calcite-barite-fluorite-sulphide veins, pointing to the fact that young cave-forming fluids migrated along the same fractures as the older mineralizing fluids did. Predominantly NNW–SSE strike of fractures concludes a latest Early Miocene maximum age for the fracture-filling minerals. Vein-calcite contains coeval primary, HC-bearing- and aqueous inclusions indicating that also HCs have migrated together with the mineralizing fluids. The coexistence of aqueous and HC inclusions permitted to establish the entrapment temperature (80°C) and pressure (85 bar) of the fluid and thus also the thickness of sediments, having been eroded since latest Early Miocene times, was calculated (800 m). Low salinity of the fluids (<1.7 NaCl eq. wt%) implies that HC-bearing fluids were diluted by regional karst water. Fluid inclusion studies also revealed that aggressive gases (e.g. CO2, H2S) were associated with HCs and that these gases may have played a role in dissolution of the carbonates. Based on the location of the paleo- and recent HC indications, identical migration pathways were reconstructed for both systems. It was proved that HC-bearing fluids have migrated northwestward from the basin east to the Buda Hills from the Miocene on. Due to the uplift related intensification of groundwater circulation, the proportion of hydrothermal fluids has diminished in favour of cold meteoric fluids. Establishment of the actual porosity of the Buda Karst initiated in Miocene times and earlier diagenetic history of the carbonates affected only the powderization of dolomite, and it had no direct effect on the localization of hypogenic caves.


Karstification of Dolomitic Hills at south of Coimbra (western-central Portugal) - Depositional facies and stratigraphic controls of the (palaeo)karst affecting the Coimbra Group (Lower Jurassic), 2014, Dimuccio, Luca Antonio

An evolutionary model is proposed to explain the spatio-temporal distribution of karstification affecting the Lower Jurassic shallow-marine carbonate succession (Coimbra Group) of the Lusitanian Basin, cropping out in the Coimbra-Penela region (western-central Portugal), in a specific morphostructural setting (Dolomitic Hills). Indeed, in the Coimbra Group, despite the local lateral and vertical distributions of dolomitic character and the presence of few thick sandy-argillaceous/shale and marly interbeds, some (meso)karstification was identified, including several microkarstification features. All types of karst forms are commonly filled by autochthonous and/or allochthonous post-Jurassic siliciclastics, implying a palaeokarstic nature.

The main aim of this work is to infer the interplay between depositional facies, diagenesis, syn- and postdepositional discontinuities and the spatio-temporal distribution of palaeokarst. Here, the palaeokarst concept is not limited to the definition of a landform and/or possibly to an associated deposit (both resulting from one or more processes/mechanisms), but is considered as part of the local and regional geological record.

Detailed field information from 21 stratigraphic sections (among several dozens of other observations) and from structural-geology and geomorphological surveys, was mapped and recorded on graphic logs showing the lithological succession, including sedimentological, palaeontological and structural data. Facies determination was based on field observations of textures and sedimentary structures and laboratory petrographic analysis of thin-sections. The karst and palaeokarst forms (both superficial and underground) were classified and judged on the basis of present-day geographic location, morphology, associated discontinuities, stratigraphic position and degree of burial by post-Jurassic siliciclastics that allowed to distinguish a exposed karst (denuded or completely exhumed) than a palaeokarst (covered or partially buried).

A formal lithostratigrafic framework was proposed for the local ca. 110-m-thick combined successions of Coimbra Group, ranging in age from the early Sinemurian to the early Pliensbachian and recorded in two distinct subunits: the Coimbra formation, essentially dolomitic; and the overlying S. Miguel formation, essentially dolomitic-limestone and marly-limestone.

The 15 identified facies were subsequently grouped into 4 genetically related facies associations indicative of sedimentation within supra/intertidal, shallow partially restricted subtidal-lagoonal, shoal and more open-marine (sub)environments - in the context of depositional systems of a tidal flat and a very shallow, inner part of a low-gradient, carbonate ramp. In some cases, thick bedded breccia bodies (tempestites/sismites) are associated to synsedimentary deformation structures (slumps, sliding to the W to NW), showing the important activity of N–S and NNE–SSW faults, during the Sinemurian. All these deposits are arranged into metre-scale, mostly shallowing-upward cycles, in some cases truncated by subaerial exposure events. However, no evidence of mature pedogenetic alteration, or the development of distinct soil horizons, was observed. These facts reflect very short-term subaerial exposure intervals (intermittent/ephemeral), in a semiarid palaeoclimatic setting but with an increase in the humidity conditions during the eogenetic stage of the Coimbra Group, which may have promoted the development of micropalaeokarstic dissolution (eogenetic karst).

Two types of dolomitization are recognized: one (a) syndepositional (or early diagenetic), massive-stratiform, of “penesaline type”, possibly resulting from refluxing brines (shallow-subtidal), with a primary dolomite related to the evaporation of seawater, under semiarid conditions (supra/intertidal) and the concurrent action of microbial activity; another (b) later, localized, common during diagenesis (sometimes with dedolomitization), particularly where fluids followed discontinuities such as joints, faults, bedding planes and, in some cases, pre-existing palaeokarstic features.

The very specific stratigraphic position of the (palaeo)karst features is understood as a consequence of high facies/microfacies heterogeneities and contrasts in porosity (both depositional and its early diagenetic modifications), providing efficient hydraulic circulation through the development of meso- and macropermeability contributed by syn- and postdepositional discontinuities such as bedding planes, joints and faults. These hydraulic connections significantly influenced and controlled the earliest karst-forming processes (inception), as well as the degree of subsequent karstification during the mesogenetic/telogenetic stages of the Coimbra Group. Multiple and complex karstification (polyphase and polygenic) were recognized, including 8 main phases, to local scale, integrated in 4 periods, to regional scale: Jurassic, Lower Cretaceous, pre-Pliocene and Pliocene-Quaternary. Each phase of karstification comprise a specific type of (palaeo)karst (eogenetic, subjacent, denuded, mantled-buried and exhumed).

Finally, geological, geomorphological and hydrogeological characteristics allowed to describe the local aquifer. The elaborated map of intrinsic vulnerability shows a karst/fissured and partially buried aquifer (palaeokarst) with high to very high susceptibility to the contamination.


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