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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 subcutaneous flow is lateral and vertical flow that occurs within the epikarst zone under saturated conditions. lateral flow distances can exceed hundreds of meters and several meters per day while vertical within discrete percolation drains (subcutaneous drains) may allow flow rates in excess of several hundred meters per hour. see also epikarst zone; subcutaneous drain; subcutaneous zone; transition zone.?

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Featured articles from Cave & Karst Science Journals
Chemistry and Karst, White, William B.
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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 hypogenic cave (Keyword) returned 68 results for the whole karstbase:
Showing 46 to 60 of 68
Boxwork and ferromanganese coatings in hypogenic caves: An example from Sima de la Higuera Cave (Murcia, SE Spain), 2012, Gazquez Fernando, Calaforra Josemaria, Rull Fernando

This paper examines the greyish-blue deposits that were recently discovered in the lower levels of the Sima de la Higuera Cave (Murcia, SE Spain) which occur as patinas over the walls and ceilings, as well as coating boxwork formations. Their mineralogy was determined using XRD and micro-Raman spectroscopy, while EDX microanalysis was used to determine their elemental composition. The mineralogical analyses revealed the presence of Mn oxides (todorokite and pyrolusite) and Fe with a low degree of crystallinity, whereas EDX microprobe showed elevated concentrations of Mn (38.2 wt.%), Fe (15.2 wt.%) and Pb (8.1 wt.%). The ferromanganese oxyhydroxides occur as botryoidal aggregates overlying blades of calcite that have a visibly sugary texture. The speleogenetic model proposed describes (1) an initial phase of precipitation of hydrothermal calcite veins (of hypogenic origin) within the fissures of the host rock under phreatic conditions and (2) a subsequent vadose phase involving preferential corrosion of the carbonate host rock caused by lowering of the pH resulting from CO2 diffusion in condensed water and oxidation of Fe and Mn under aerobic conditions, probably mediated by microorganisms. It is this later phase that gave rise to the boxwork. The boxwork of the Sima de la Higuera Cave is a singular example of a formation that is generated by dissolution–corrosion of the rock due to acidification caused by oxidation of iron and manganese.


Hypogene Speleogenesis, 2013, Klimchouk, A. B.

Recognition of the wide occurrence, significance, and specific characteristics of hypogene speleogenesis during last twodecades signifies a major paradigm shift in karst science, previously overwhelmingly dominated by epigene concepts and models. Hypogene karst is one of the fundamental categories of karst, at least of equal importance with more familiar epigenic karst. Hypogene and epigenic karst systems are regularly associated with different types, patterns, and segments off low systems, which are characterized by distinct hydrokinetic, chemical, and thermal conditions. Hypogene speleogenesis is the formation of solution-enlarged permeability structures by water that recharges thecavernous zone from below, independent of recharge from the overlying or immediately adjacent surface. It develops mainly in leaky confined conditions, although it may continue through unconfined ones. Hydraulic communication along cross-formational flow paths, across lithological boundaries, different porosity systems, and flow regimes allows deeper ground waters in regional or intermediate flow systems to interact with shallower and more local systems, permittinga variety of dissolution mechanisms to operate. A specific hydrogeologic mechanism acting in hypogenic transverse speleogenesis (restricted input/output) suppresses the positive flow-dissolution feedback and speleogenetic competition seen in the epigenic development. Hypogenic caves occur in different soluble rocks in a wide range of geological and tectonic settings, basinal throughorogenic. Overall patterns of cave systems are strongly guided by the spatial distribution of the initial (prespeleogenetic) permeability features and hydrostratigraphic barriers and interfaces within the soluble and adjacent units, by the mode of water input to, and output from, cave-forming zones and by the overall recharge–discharge configuration in the multiple aquifer system. Because of their transverse nature, hypogene caves have a clustered distribution in plan view, althoughinitial clusters may merge laterally across considerable areas. Hypogene caves display remarkable similarity in their pattern sand mesomorphology, strongly suggesting that the type of flow system is the primary control. The rapidly evolving understanding of hypogene speleogenesis has broad implications for many applied fields such asprospecting and characterization of hydrocarbon reservoirs, groundwater management, geological engineering, and mineral resources industries


Speleogenesis of an exhumed hydrothermal sulphuric acid karst in Cambrian carbonates (Mount San Giovanni, Sardinia), 2013, Dewaele Jo, Forti Paolo, Naseddu Angelo

In the past few years the systematic study of caves intercepted by mine workings in southwest Sardinia has permitted us to observe morphologies due to rare speleogenetic and minerogenetic processes related to ancient hydrothermal activity. These relic morphologies are slowly being overprinted by recent speleogenetic processes that tend to obscure the hypogene origin of these caves. A combined geomorphological and mineralogical investigation has permitted a fairly detailed reconstruction of the various phases of evolution of these caves. Cave formation had already started in Cambrian times, but culminated in the Carboniferous, when most of the large voids still accessible today were formed. A key role in carbonate dissolution was played by sulphuric acid formed by the oxidation of the polymetallic ores present in the rocks since the Cambrian. During the Quaternary a variety of minerals formed inside the caves: calcite and aragonite, that yielded sequences of palaeo-environmental interest, and also barite, phosgenite, hydrozincite, hemimorphite and many others. These minerals are in part due to a phreatic thermal hypogenic cave forming phase, and in part to later epigene overprinting in an oxidizing environment rich in polymetallic ores. Massive gypsum deposits, elsewhere typical of this kind of caves, are entirely absent due to dissolution during both the phreatic cave formation and the later epigenic stage


Hypogenic origin of Provalata Cave, Republic of Macedonia: a distinct case of successive thermal carbonic and sulfuric acid speleogenesis, 2013, Temovski Marjan, Audra Philippe, Mihevc Andrej, Spangenberg Jorge E. , Polyak Victor, Mcintosh William, Bigot Jeanyves.

Provalata Cave (Republic of Macedonia) is a small but remarkable hypogenic cave, developed in Cambrian marbles by successive thermal carbonic and sulfuric acid speleogenesis. The cave has a thick partly corroded calcite crust, abundant gypsum deposits, with cupolas, ceiling and wall channels, feeders and replacement pockets as some of the most characteristic morphological features. Distribution of morphology and deposits suggest a hypogenic origin in two distinct speleogenetic phases: the first by thermal CO2 rich waters, the second by sulfuric acid dissolution, which were separated by complete infilling of cave passages with pyroclastic-derived clays. In the first phase of speleogenesis, cave passages were formed by dissolution along fractures due to cooling of rising carbonated thermal waters. These phreatic morphologies were later covered with a thick calcite crust deposited in a shallow phreatic environment. In Early Pleistocene the cave was completely filled with clays due to deposition of pyroclastic rocks in a lacustrine environment in the nearby Mariovo Basin. Mariovo Lake sediments were later incised by the Buturica River, which cut down into Cambrian marbles, creating its superimposed valley. Incision lowered the water table and allowed removal of the clay deposits in Provalata Cave. The second phase of speleogenesis started after introduction of H2S associated with rising thermal waters. Oxidation produced sulfuric acid, which rapidly dissolved first calcite crust, then marble host rock. Condensation-corrosion by sulfuric vapors replaced carbonate rock with gypsum producing replacement pockets as well as second generation of pockets and cupolas. The contact of sulfuric acid with the clay deposits formed alunite, jarosite, and natroalunite. 40Ar/39Ar dating gave maximum ages of 1.6 Ma (alunite) and 1.46 Ma (jarosite) for this last stage of speleogenesis, thus making it the second 40Ar/39Ar dating of a sulfuric cave in Europe (after Kraushöhle in Austria), and the first dated cave in the Republic of Macedonia.


Hypogene speleogenesis in Italy, 2013, Menichetti, M.

Through more than one century of speleological research in Italy, many hypogenic limestone caves have been explored, mapped and studied. These caves are characterized by a variety of patterns and morphological sizes including three-dimensional maze sys-tems and deep shafts, with both active endogenic CO2 and H2S vents.
An integrate approach taking in account geological, hydrological and geochemical set-tings permit to recognize the main hypogenic speleogenetic process. The H2S oxidation to sulfuric acid, by oxygen-rich groundwaters as well as in the atmosphere is actually the main active hypogenic cave-forming processes. Both phreatic and vadose corrosion reactions involve chemotropic microbial activity, with sulfur-redox bacterial communi-ties that generate sulfuric acid as metabolic product. The bedrock corrosion produce sulfate ions in the phreatic zone and gypsum replacement in the limestone walls of the vadose sectors of the caves. The caves are characterized by both fossil and active pas-sages in which water rich in H2S as well as endogenic CO2 plays a determinant role in speleogenesis. Although sulfuric acid-related speleogenesis typically produces gypsum deposits, in caves where the karstification processes are driven by subterranean CO2 sources, voids and speleothems are the only final products.
In Italy all the end-members of the karst processes can be found, from solution caves to outcrop of carbonate travertine. The hypogenic caves are concentrated for largest and both fossils and active systems in the Tuscany, Umbria, Marche and Latium regions (Menichetti, 2009). These consist of few tens of kilometers of solutional passages with galleries and shafts, which are characterized by large rooms, cupola and blind pits, anas-tomotic passages, bubble trails roof pendants, knife edges, and phreatic passages. Ac-tive smaller karst systems are known in Southern Italy in Apulia, Campania and Sicily, related to the geothermal anomaly associated with CO2 and H2S vents.


Hypogene speleogenesis in Italy, 2013, Menichetti, Marco

HYPOGENE SULFURIC ACID SPELEOGENESIS AND RARE SULFATE MINERALS (FIBROFERRITE, JAROSITE SUBGROUP) BAUME GALINIERE CAVE (ALPES-DE-HAUTE-PROVENCE, FRANCE), 2013, Audra P. Gá, Zquez F. Rull F. Bigot J. Y. Camus H.

 

The oxidation of sulfide sources (H2S gas, pyrite, hydrocarbons) produces sulfuric acid that strongly reacts with bedrock, causing limestone dissolution and complex interactions with other minerals. This type of cave development, known as sulfuric acid speleogenesis, is a subcategory of hypogenic speleogenesis, where aggressive water rises from depth. It also produces uncommon minerals, mainly sulfates. Baume Galinière is located in Southern France, in the Vaucluse spring watershed. This small maze cave displays characteristic features such as corrosion notches, calcite dikes and iron crusts, and sulfate minerals. Thirteen minerals were identified, including elemental sulfur, calcite, quartz, pyrite, goethite, gypsum, fibroferrite, plus all of the six members of the jarosite subgroup (jarosite, argentojarosite, ammoniojarosite, hydroniumjarosite, natrojarosite, plumbojarosite). The Baume Galinière deposits are the first documented cave occurrence of argentojarosite and the second known occurrence of plumbojarosite, hydronium jarosite, ammoniojarosite, and fibroferrite. Together with other hypogenic caves in the Vaucluse watershed, Baume Galinière Cave owes its origin in buried conditions to deep water rising along major faults, mixing with meteoric water at the contact of the karst aquifer and overlying impervious cover, and causing pyrite deposition. Sulfuric acid speleogenesis occurred later after base level drop, when the cave arrived in shallow phreatic then in vadose zone, with oxidation of pyrites involving sulfidic gases. Attenuated oxidation is still occurring through condensation of incoming air from outside. Baume Galinière Cave records the position of the paleo-cover and documents its retreat in relationship to valley incision caused by uplift and tilting of the Vaucluse block during Neogene.


HYPOGENE SPELEOGENESIS AND SPELEOTHEMS OF SIMA DE LA HIGUERA CAVE (MURCIA, SOUTH-EASTERN SPAIN), 2013, Gá, Zquez Fernando Calaforra José, Marí, A

 

Sima de la Higuera Cave (Pliego, south-eastern Spain) has been recently adapted for speleological use. Nevertheless, knowledge of the hypogenic origin of this cavity is still quite limited. The peculiar genetic mechanisms could provide added value if the cave is exploited for speleotourism. By studying geomorphological features and speleothem characteristics, it has been possible to deduce the predominant speleogenetic mechanism (whether hypogenic or epigenic) that controlled the evolution of this cave. The hypogenic mechanism that gave rise to this cavity was associated with upflow of CO2-rich hydrothermal fluid from depth, and was unconnected to meteoric water seepage. In this paper we describe some of the geomorphological evidence and unusual speleothems in Sima de la Higuera Cave. Large scallops are found on the upper level (-74 m); these are related to the mechanism of hypogenic speleogenesis and generally indicate the direction of ascending flow. There are also corrosion crusts made of micritic calcite. In addition, bubble trails related to bubbles of rising CO2 have been identified. Centimetric calcite spar speleothems frequently fill fractures in the host rock. Other typical hypogenic speleothems occur in this cave, including calcite raft cones, folia, cave clouds, tower coral and calcite raft deposits, all suggesting the influence of thermal water during the cave’s formation. Furthermore, the first reported occurrence of calcite raft double-tower cones has been described in this cave; their origin is linked to water table oscillations in Paradise Chamber (-82 m). At the deepest level (-110 m), Mn-Fe oxyhydroxides occur as a black coating totally covering the cave walls, usually over subaerial “boxwork” formations. The wide variety of speleothems unconnected to meteoric water seepage make Sima de la Higuera Cave one of the most unusual hypogenic caves in Spain.


Speleogenesis of an exhumed hydrothermal sulphuric acid karst in Cambrian carbonates (Mount San Giovanni, Sardinia), 2013, De Waele Jo, Forti P. , Naseddu A.

n the past few years the systematic study of caves intercepted by mine workings in southwest Sardinia has permitted us to observe morphologies due to rare speleogenetic and minerogenetic processes related to ancient hydrothermal activity. These relic morphologies are slowly being overprinted by recent speleogenetic processes that tend to obscure the hypogene origin of these caves. A combined geomorphological and mineralogical investigation has permitted a fairly detailed reconstruction of the various phases of evolution of these caves. Cave formation had already started in Cambrian times, but culminated in the Carboniferous, when most of the large voids still accessible today were formed. A key role in carbonate dissolution was played by sulphuric acid formed by the oxidation of the polymetallic ores present in the rocks since the Cambrian. During the Quaternary a variety of minerals formed inside the caves: calcite and aragonite, that yielded sequences of palaeo-environmental interest, and also barite, phosgenite, hydrozincite, hemimorphite and many others. These minerals are in part due to a phreatic thermal hypogenic cave forming phase, and in part to later epigene overprinting in an oxidizing environment rich in polymetallic ores. Massive gypsum deposits, elsewhere typical of this kind of caves, are entirely absent due to dissolution during both the phreatic cave formation and the later epigenic stage.


HYPOGENIC CAVES OF SICILY (SOUTHERN ITALY), 2013, Vattano M. Audra P. Benvenuto F. Bigot J. Y. Waele J. D. Galli E. Madonia G. Nobé, Court J. C.

 

First results of a study on hypogenic caves in Sicily are presented. Inactive water-table sulphuric acid caves and 3D maze caves linked to rising of thermal waters rich in H2S were recognized. Cave patterns are guided by structural planes, medium and small scale morphological features are due mainly to condensation-corrosion processes. Calcite and gypsum represent the most common cave minerals. Different types of phosphates linked to the presence of large bat guano deposits were analyzed.


HYPOGENIC SPELEOGENESIS WITH FERRUGINOUS ORE. THE PIEI MINE-CAVE (LAGNES, VAUCLUSE, FRANCE) SPELEOGENESI IPOGENICA IN UN GIACIMENTO DI FERRO. LA GROTTA MINIERA DI PIEI (LAGNES, VAUCLUSE, FRANCIA), 2013, Audra Philippe, Bigot Jeanyves, Camus Hubert, Gauchon Christophe, Wienin Michel

The Piei mine-cave (Lagnes, Vaucluse, France) locates at the contact of the Vaucluse Mounts and the Carpentras basin, close to the Fontaine de Vaucluse spring. It develops in Cretaceous limestone (Urgonian facies), close to a main regional lineament, the Salon-Cavaillon fault. The cave was mined in the XIXth Century, giving access to passages previously filled with diverse neogene sands and massive iron crusts. The exploitation mainly followed the natural passages. The origin of the cave is related to hypogenic flow rising from deep fissures or hydraulic breccias, with ferruginous deposition at the contact or on top of the neogene sands filling. Microbial activity was present during the cave activity, associated to the ferruginous deposits. This cave probably corresponds to the Neogene period, when the Vaucluse plateau was uplifted. The Piei mine-cave record the position of the corresponding base level and thus the progressive tilting of the massive, together with a range of similar caves located around the western edge of the Vaucluse Plateau


THE SAN PAOLO MINE TUNNEL AT SA DUCHESSA (DOMUSNOVAS, SW SARDINIA): TEN INTERCEPTED NATURAL CAVES AND FIRST DATA ON THE COMPOSITION OF SOME SPELEOTHEMS , 2013, Simone Argiolas, Caddeo Guglielmo Angelo, Casu Lucilla, Muntoni Alberto, Papinuto Silvestro

Since many years cavers from different caving teams are carrying out a systematic study on the caves of Sulcis-Iglesiente, including geomorphological studies. Over thirty natural caves have been explored, surveyed and registered in the past few years, and over half of these have been made accessible by mine galleries. Among these are worth to be mentioned the “Tre Sorelle” of Domusnovas: these are three mine caves intercepted by the San Paolo mine tunnel. This tunnel, whose collapsed entrance has been reopened after a long digging campaign, has been explored and surveyed for around 700 meters. A total of 10 natural caves, mostly developed along fractures, have been explored and mapped, with developments ranging between 10 and 250 meters and depths from 15 to over 160 meters. Only two of these caves were previously known in the Regional Cave Register. In most of the caves, speleothems consist mainly of flowstones, some of which are clear or usually white, others are dark-brown or tending to black. Some samples of the first and the second flowstone types were collected respectively from the “Sesta Sorella” and “Seconda Sorella” Caves. The powders of these samples were analysed by an X-ray diffractometer. The first type consists of thicker layers of white and fibrous aragonite, which sometimes alternate with thinner layers of grey columnar calcite. In some samples, however, calcite interlayers were absent and just aragonite was found. The second type is composed of alternating layers of darkbrown hemimorphite. Some additional analyses were performed on these samples by Laser Ablation ICP-MS to determine the concentration of minor and trace elements in the different layers and mineralogical phases. The most abundant minor elements in calcite layers are Mg and Zn. Magnesium is about constant (~ 2000 ppm) on different spots and remains under the average Mg content of the cave calcite in this region, whereas Zn ranges from 103 to 104 ppm and is well above the Zn average in calcite of caves in the world. Barium concentration is about 80 ppm and more abundant than Pb (20 ppm) and Sr (10 ppm). Barium is also the main minor element in aragonite, where it can reach almost 2000 ppm. The Zn concentration is very high even in aragonite and is comparable to that of Sr (400-500 ppm), overcoming considerably the Pb concentration (20 ppm). In hemimorphite, the most abundant minor elements are Al and Fe (about 104 ppm). However, it was not quantified how much of these are in the hemimorphite lattice or come from some impurities. Actually, we notice that concentration of Fe and Al in the black layers of hemimorphite is an order of magnitude greater than in the brown ones. In addition, the black layers show an abrupt increase of Mn concentration, which overcomes Fe and Al. The evolution of these flowstones is most probably related to the circulation of fluids connected to the oxidation of sulphides, specially sphalerite.


Naica caves: perhaps the most important mine caves of the world, 2013, Badino Giovanni, Forti Paolo

In 2005 La Venta Esplorazioni Geografiche together with C/Producciones of Mexico City and Peñoles Society started with the “Projecto Naica” a complex multidisciplinary project to explore, document and study all the relevant aspects of Naica caves. The project lasted about five years. Thanks to the “Projecto Naica” it is now clear that the Naica caves are presently the most important mine caves of the world, not only from the aesthetic point of view but also from the scientific one. But these cave will be likely destroyed in a short span of time and therefore La Venta Esplorazioni Geografiche is now working hard to try to preserve for future generations not only the memory and the records (already achieved with the “Projecto Naica”), but also a significant part of this incredible underground world.


PRELIMINARY CONSIDERATIONS ON HYPOGENE MORPHOLOGY IN TOCA DA BOA VISTA E TOCA DA BARRIGUDA CAVES, NORTHEASTERN BRAZIL, 2014, Borges S. , Casarin C. , Menezes C. , Srivastava N. , Silva R. , Bezerra F. , Auler A.

The Toca da Boa Vista and Barriguda caves are located in Northeastern Brazil. They occur in the Neoproterozoic carbonates (limestones and dolomites) of the Salitre Formation, located at Irecê Basin. This set of rocks occurs within the São Francisco Craton, a region that was not affected by the Brasiliano-Pan-African orogeny (Pedreira et al., 1987). The caves occur at a dis­tance of approximately 300 m apart and there is a possibility of a link between them, but so far this has not been proven. Toca da Boa Vista has about 108 km of mapped passages and is therefore the largest cave in South America. Toca da Barriguda is smaller and has about 32 km of mapped galleries.

The architecture of the Toca da Boa Vista and Barriguda caves present both a 2D network and spongework type (Auler, 2009). The control of the conduits is related to faults, fractures and axial planes of antiforms. The general configuration of the caves seems to follow the Pacuí riverbed that has its channel located about 1km southeast. The origin of these hypogenic caves was first postulated by Auler & Smart (2004), who described some hypogenic features and reported a acid source (H2S) coming from existing pyrite in carbonates to explain the corrosion and dissolution of carbonate rocks. Klimchouk (2009) wrote about the need to investigate deeper this issue. He drew attention to the apparent feeders presence coming from the lower aquifer as well as to the importance of determi­nation of the source of acidity, since the amount of pyrite present doesn’t seem to be significant for the origin and development of the caves by hypogenic speleogenesis.

Although the origin and development of the caves are still under discussion, abundant hypogenic forms are present. Feeders, rising wall channels, half ceiling tubes, half wall tubes, ceiling cupolas, convection cupolas and wall niches are the major forms found. The linear geometry of caves suggests that they have a structural control. In addition, cavities generated at Toca da Boa Vista and Barriguda caves seem to follow the same stratigraphic level, as well as existing permeable structures such as fractures, faults and axial planes of antiforms. The process of ascending flow through these structures has resulted in the opening of the cavities by hypogenic dissolution as well as the collapse of blocks caused by the lack of sustainability of the layers generated by the voids left by the dis­solution. Outlets that would flow to levels above were not found. The origin and evolution of the cave system, however, needs further investigation.


Sulphuric acid speleogenesis and landscape evolution: Montecchio cave, Albegna river valley (Southern Tuscany, Italy), 2014, Piccini L. : Dewaele J. , Galli E. , Polyak V. J. , Bernasconi S. M. , Asmerom Y.

Montecchio cave (Grosseto province, Tuscany, Italy) opens at 320 m asl, in a small outcrop of Jurassic limestone (Calcare Massiccio Fm.), close to the Albegna river. This area is characterised by the presence of several thermal springs and the outcropping of travertine deposits at different altitudes. The Montecchio cave, with passage length development of over 1700 m, is characterised by the presence of several sub-horizontal passages and many medium- and small-scale morphologies indicative of sulphuric acid speleogenesis (SAS). The thermal aquifer is intercepted at a depth of about 100 m below the entrance: the water temperature exceeds 30 °C and sulphate content is over 1300mg l−1. The cave hosts large gypsumdeposits from40 to 100mbelowthe entrance that are by-products of the reaction between sulphuric acid and the carbonate host rock. The lower part of the cave hosts over 1 m thick calcite cave raft deposits, which are evidence of long-standing, probably thermal, water in an evaporative environment related to significant air currents. Sulphur isotopes of gypsumhave negative δ34S values (from−28.3 to−24.2‰), typical of SAS. Calcite cave rafts and speleogenetic gypsumboth yield young U/Th ages varying from68.5 ka to 2 ka BP, indicating a rapid phase of dewatering followed by gypsumprecipitation in aerate environment. This fastwater table lowering is related to a rapid incision of the nearby Albegna river, andwas followed by a 20–30mfluctuation of the thermalwater table, as recorded in the calcite raft deposits and gypsum crusts.


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