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Speleothems show an array of shapes. Flowstones are commonly tabular sheet-like deposits, which cover cave floors and walls. They can procure detailed information about past hydrogeological conditions through their morphology, geochemical composition and stratigraphic properties, which in turn are related to the climate conditions at the surface. This is possible if the climate and environmental factors controlling the formation of these deposits are well understood. In Bossea Cave (north-east Italy), we have investigated highly symmetrical wavy flowstones that have never been described in detail before. These deposits show a cyclical repetition of sloped and sub-vertical layers, with knickpoints migrating downslope. This paper investigates the origin of these peculiar carbonate deposits, using: i) terrestrial laser scanning surveys; ii) petrographic observations; iii) oxygen and carbon stable isotope analyses; iv) hydrochemical monitoring data of feeding waters. According to these analyses, we have generated a genetic model that demonstrates: 1) laminar flow of CaCO3–rich water prevails during the deposition of the flowstone; in accordance, the final flowstone architecture does not appear to be influenced by random irregularities of the underlying bedrock substrate. 2) The peculiar morphology is inherited by ripples occurring in the flowing water films during carbonate deposition, which trigger the precipitation of regularly spaced CaCO3 deposits along the bedrock slopes. Because of these ripple-induced initial deposits, calcite then deposits as sloped and sub-vertical layers, giving rise to a wavy-like morphology. 3) Wavy calcite layers are only deposited after heavy rainfall events occurred within two to four consecutive rainy days (10 to 20 mm/hour during rainfall peaks; average rates between 3.5 and 7.0 mm/hour); in contrast, calcite deposition cannot occur during low rainfall events (less than 5 mm/hour during rainfall peaks, average rates around 0.8 mm/hour). We therefore propose that the studied wavy flowstones are hydroclimatic indicators, testifying the occurrence of flashy type recharge related to heavy rainfall events. Similar deposits could record these same hydro-climatic conditions in other karst areas. In recent decades, storms have caused more frequent flooding in highly populated Mediterranean areas, especially in Italy. Wavy flowstones may offer a new archive to gain a better understanding of the long-term dynamics of intense precipitation events and, thus, help to improve future climate scenarios.

The aesthetic value of a wild and/or tourist cave is well known everywhere. Anyway, presently only few people are aware that caves are the most important natural laboratories, in which it is possible to complete studies and researches that, in some cases, would be impossible in any other place. The caves are normally characterized by low energy and by the absence, or at least scarcity, of perturbing factors characterizing the external environments. Therefore, natural cavities may be regarded as perfect accumulation traps, preserving all the materials falling inside them. In the last half century the importance of cave deposits grew enormously in the field of paleoenvironmental and paleoclimatological studies, often allowing to reconstruct the chronology of the events a given environment underwent. From this point of view speleothems are by far the most important cave deposits, because their layered structure is always chronologically ordered and several techniques allow for an easy absolute dating of even a single event. Moreover, all these events may sometimes be restricted to a single year interval (or even less) on the basis of the speleothem growth layers. The speleothem’s layered structure makes reasonable to consider each of them a “stone book”, where each growing layer corresponds to a “page” of a multidisciplinary encyclopaedia. We are still unable to extract most of the information recorded by them. But in the near future, when we will be able to read all the pages of these “stone books”, their scientific importance will grow exponentially.

A totally new corrosion form has been recently observed inside the Natuturingam cave (better known as Puerto Princesa Underground River) in Palawan (Philippines): the guano holes. They consist of perfectly rounded holes, 4–5 cm wide and up to 10–15 cm deep, developing over a flat limestone surfaces covered by a thin layer of fresh guano. In the same cave larger guano-related corrosion forms have also been encountered, but are not presented in detail here (guano pots). A 3D photogrammetric survey has been carried out on a series of guano-holes to make some morphometric measurements. Their development is controlled by the peculiar Palawan climate, which is characterized by short but heavy rainfalls followed by rather long dry periods. During rainfalls each water drip drills a perfectly rounded hole into the fresh guano reaching the limestone surface which is then corroded by the acids produced by guano digestion. The corrosion process on the exposed limestone surface continues during the whole subsequent dry period and causes the deepening of the initial depression with respect to the surrounding area. At the end of the dry period the drilled holes are partially refilled by fresh guano, and the process restarts at the beginning of a new rainstorm. Subsequent cycles of wet and dry periods cause a progressive deepening of each hole. When two or more drops and their splashing areas interfere, their holes coalesce thus giving rise to relatively larger and complex forms. Finally, during the dry periods, capillary rise and evaporation of the solution trapped within the hole may cause the deposition of small aggregates of different minerals (mainly hydroxylapatite, with minor quantities of calcite). During the next rainstorm, sometimes dripping may not be able to wash away all these minerals, so that they progressively accumulate inside thehole developing a layered speleothem.

The area around Ragusa in Sicily is well known for the exploration of petroleum deposits hosted in Mesozoic carbonate rocks. These reservoirs are overlain by less permeable rocks, whereas the surface geology is characterized by outcrops of Oligo-Miocene carbonate units hosting important aquifers. Some of the karst springs of the area are used as drinking water supplies, and therefore these vulnerable aquifers should be monitored and protected adequately. In the early afternoon (14:00) of 27 May until the late evening (19:30) of 28 May 2011, during the construction of an exploitation borehole (Tresauro 2), more than 1000 m3 of drilling fluids were lost in an unknown karst void. Two days later, from 06:30 on 30 May, water flowing from Paradiso Spring, lying some 13.7 km SW of the borehole and 378 m lower, normally used as a domestic water supply, was so intensely coloured that it was unfit for drinking. Bulk chemical analyses carried out on the water have shown a composition that is very similar to that of the drilling fluids lost at the Tresauro borehole, confirming a hydrological connection. Estimations indicate that the first signs of the drilling fluids took about 59 h to flow from their injection point to the spring, corresponding to a mean velocity of ∼230 m/h. That Paradiso Spring is recharged by a well-developed underground drainage system is also confirmed by the marked flow rate changes measured at the spring, ranging from a base flow of around 10–15 l/s to flood peaks of 2–3 m3/s. Reflecting the source and nature of the initial contamination, the pollution lasted for just a few days, and the water returned to acceptable drinking-water standards relatively quickly. However, pollution related to heavy-mineral fines continues to be registered during flooding of the spring, when the aqueducts are normally shut down because of the high turbidity values. This pollution event offers an instructive example of how hydrocarbon exploitation in intensely karstified areas, where natural springs provide domestic water supplies, should be controlled effectively to prevent such disasters occurring. This pollution incident is also a useful example of how such “accidental” tracer tests can identify rapid karstic flowpaths over long distances.

15 páginas.- 5 figuras.- 85 referencias.- The following are available online at http://www.mdpi.com/2079-6412/10/11/1134/s1 .- This article belongs to the Special Issue Biofilms on Cultural Heritage, The Galapagos Islands (Ecuador) have a unique ecosystem on Earth due to their outstanding biodiversity and geological features. This also extends to their subterranean heritage, such as volcanic caves, with plenty of secondary mineral deposits, including coralloid-type speleothems and moonmilk deposits. In this study, the bacterial communities associated with speleothems from two lava tubes of Santa Cruz Island were investigated. Field emission scanning electron microscopy (FESEM) was carried out for the morphological characterization and detection of microbial features associated with moonmilk and coralloid speleothems from Bellavista and Royal Palm Caves. Microbial cells, especially filamentous bacteria in close association with extracellular polymeric substances (EPS), were abundant in both types of speleothems. Furthermore, reticulated filaments and Actinobacteria-like cells were observed by FESEM. The analysis of 16S rDNA revealed the presence of different bacterial phylotypes, many of them associated with the carbon, nitrogen, iron and sulfur cycles, and some others with pollutants. This study gives insights into subsurface microbial diversity of the Galapagos Islands and further shows the interest of the conservation of these subterranean geoheritage sites used as show caves, This research was funded by the Ecuadorian Ministry of Environment (Project PC-65-14 National Park Galapagos), by the Spanish project MINECO CGL2016-75590-P with European Regional Development Fund and the Portuguese Foundation for Science and Technology (Fundação para a Ciência e a Tecnologia-FCT) under the project UID/Multi/04449/2019 for HERCULES/UE. AMGS was supported by a FPU fellowship of the Spanish Ministry of Education, Culture and Sport (AP2010-2052). AZM was supported by a Marie Curie Intra-European Fellowship of the European Commission’s 7th Framework Programme (PIEF-GA-2012-328689-DECAVE) and a CEECIND/01147/2017 contract from FCT. MLC was supported by a CEECIND/00349/2017 contract from FCT. FG was financially supported by the “HIPATIA” research program of the University of Almeria.

Three-dimensional X-ray micro-computed tomography permits to investigate the internal structure of objects at a high resolution without altering its original form. It also facilitates the rendering and visualization of a virtual replica, which can be subjected to rigorous and complex analyses. In the present study, micro-computed tomography was used to investigate a unique and fragile speleothem (cave formation) named a “Hairy Stalagmite”. Non-destructive analyses have revealed the calcareous internal structure of this speleothem, which consists of hollow, interconnected tubes. Rendered two-dimensional cross-sections also clearly revealed the outline of a once dense root nest that formed part of the speleothem’s biogenic origin. The internal structure was further visualized using an image sequence of two-dimensional cross-sections to create a video that “brings the speleothem to life”, also illustrating its complexity and variability. Statistical analyses revealed structural variability in void fraction, which is likely related to changing environmental conditions. In addition, the micro-computed tomography data were used as input for additive manufacturing (three-dimensional printing) in order to produce an enlarged replica of the Hairy Stalagmite sample, which made physical inspection possible. This combined approach represents the first of its kind and provides much benefit for future studies.

Gypsum beds host the majority of the caves in the north-eastern flank of the Apennines, in the Emilia Romagna region (Italy). More than six hundred of these caves have been surveyed, including the longest known epigenic gypsum cave systems in the world (Spipola-Acquafredda, ~11 km). Although this area has been intensively studied from a geological point of view, the age of the caves has never been investigated in detail. The rapid dissolution of gypsum and uplift history of the area have led to the long-held view that speleogenesis commenced only during the last 130 000 years. Epigenic caves only form when the surface drainage system efficiently conveys water into the underground. In the study area, this was achieved after the dismantling of most of the impervious sediments covering the gypsum and the development of protovalleys and sinkholes. The time necessary for these processes can by constrained by understanding when caves were first formed. The minimum age of karst voids can be indirectly estimated by dating the infilling sediments. U–Th dating of carbonate speleothems growing in gypsum caves has been applied to 20 samples from 14 different caves from the Spipola-Acquafredda, Monte Tondo-Re Tiberio, Stella-Rio Basino, Monte Mauro, and Castelnuovo systems. The results show that: (i) caves have been forming since at least ~600 kyr ago; (ii) the peak of speleogenesis was reached during relatively cold climate stages, when rivers formed terraces at the surface and aggradation caused paragenesis in the stable cave levels; (iii) ~200 000 years were necessary for the dismantling of most of the sediments covering the karstifiable gypsum and the development of a surface mature drainage network. Besides providing a significant contribution to the understanding of evaporite karst evolution in the Apennines, this study refines our knowledge on the timescale of geomorphological processes in a region affected by rapid uplifting. Copyright © 2016 John Wiley & Sons, Ltd.

Over the past 15 years several expeditions by French, American and especially Italian cavers have unveiled over 50 caves in the Cordillera de la Sal (Atacama Desert, Northern Chile). Many of these caves contain a variety of speleothems and minerals, some of which have rarely been observed within karst systems. Most of the secondary deposits in these caves are composed of halite, but also other halide, carbonate, sulphate, nitrate, phosphate, and silicate minerals have been found. Among the sixteen cave mineral species recognized, atacamite, darapskite, blödite, leonite, anhydrite, and especially antarcticite are worth mentioning. In one of the samples an unknown Ca-Sr-bearing chloride mineral has also been discovered, but it has not been possible to carry out detailed mineralogical analyses. These often-rare minerals have formed in this region due to the very extreme hyperarid and salt-rich environment. This research reports the mineralogical results and proposes the genetical mechanisms leading to the formation of antarcticite, powdery anhydrite, and the paragenesis of the halite-darapskite-blödite. This study also shows that Atacama caves may be excellent analogues to study weathering processes and subsurface secondary minerals in hyperarid and hypersaline environments on Mars.

Geomorphological studies have been carried out in rapidly evolving salt caves related to small watersheds in the San Pedro de Atacama area, Chile. Radiocarbon ages of bones and wood from cave deposits, combined with the presence of large salt caves, geomorphological and sedimentological observations, and the results of micrometer measurements outside and in some of the caves, suggest a period of speleogenesis in the Cordillera de la Sal during the onset of the Holocene, during which the large halite cave systems developed, followed by an early Holocene hyperarid period. Most smaller caves (i.e. Lechuza del Campanario) most probably formed at the start of the wetter mid-Holocene period (5–4.4 ka), when precipitation was never intense enough to entrain large amounts of sediments, but enough to trigger cave development. A diamicton in Lechuza del Campanario Cave radiocarbon dated at ca. 4.4 ka shows that at least one high intensity rainfall event occurred in this recharge basin during the mid-Holocene wet interval. A wet period with lower intensity rainfall events followed between 4.0 and 2.5 ka, causing the 4.4 kyrs old diamicton in Lechuza del Campanario Cave to be entrenched, and the alluvial fan at the downstream end of Palacio del Sal Cave to be covered with windborne sediments dated by OSL at around 3.6 ka. At ca. 2 ka there was a high-intensity rainfall event documented by the age of a twig stuck in the ceiling of the Palacio del Sal Cave, followed by a period with lower intensity rain events until ca. 1.3 ka, when another intense flood produced a mudflow that deposited a second diamicton in Lechuza del Campanario Cave. From then on clustering of radiocarbon ages for wood and bone recovered from caves indicates increased rainfall intensity in the period ca. 0.9–0.5 ka, followed by no registered events until a minor flood at ca. 0.13 ka. The four-centuries long wetter time interval (0.9–0.5 ka), corresponding to the Medieval Climate Anomaly, has been an archeologically important period in the Atacama Desert (Tiwanaku culture). The observations and a detailed review of paleoclimate literature from this key area have allowed the development of a landscape evolution model related to changing climate conditions during the Late Holocene.

Fascinating and fragile environments as are the underground estuaries, need to be studied, understood and protected for present and future generations. Even if wide and abundant bibliography related to tides and their behaviour with respect to the external estuaries is available, none dealed with the estuary caves and the related hydrogeology. This paper aims to partially fill this gap presenting a preliminary study done at the Puerto Princesa Underground River (PPUR), in the Palawan Island (Philippines). The data was collected during the last expedition (November 2016) organised by La Venta, in which some of the authors took part. During the survey, the cave has been instrumented with in continuous diver data-logger devices (CTD) recording temperature (T), electrical conductivity (EC) and water level fluctuations. Longitudinal and vertical water hydrogeological profiles of the cave were realised with the aim of understanding the dynamics of the waters during different hydrogeological regimes in combination with salt water intrusion. In addition, a bathymetric profile was done to better identify the point where to realise the vertical logs. A significant rainstorm occurred during the expedition, lasting for approximately 12 hours resulting in 80 mm of rain, and its effects gave the researchers the opportunity to analyse the hydrodynamics of the flowing waters during a flood. In normal flow conditions, the longitudinal logs highlighted the presence of freshwater inlets and the vertical logs testified to a clear stratification of the waters (freshwaters at the surface and brackish waters at the bottom). During floods, the EC and T data showed evidence of a fast substitution of the resident waters. Key words: anchialine caves, sea water intrusion, hydrodynamics, karst springs, PPUR, Philippines. Ucinek mocnega naliva na hidrodinamiko podzemske reke Puerto princese (Palawan, Filipini) Ocarljivo in obcutljivo okolje, kot so podzemni estuariji, je treba preucevati, razumeti in zascititi za sedanje in prihodnje generacije. Cetudi imamo na voljo siroko in bogato bibliografijo o plimovanju in delovanju plimovanja v zunanjih estuarijih, nobeno delo ne obravnava estuarskih jam in s tem povezane hidrogeologije. Namen tega clanka je delno zapolniti to vrzel in predstaviti predhodno studijo na podzemni reki Puerto Princesa (PPUR) na otoku Palawan (Filipini). Podatki so bili zbrani med zadnjo ekspedicijo (novembra 2016), ki jo je organizirala La Venta, v kateri so sodelovali tudi nekateri avtorji. V raziskavi je bila jama opremljena z zveznimi merilci (CTD) temperature (T), elektricne prevodnosti (EC) in nihanja nivojev vode. Vzdolžni in navpicni hidrogeoloski vodni profili jame so bili izmerjeni, da bi razumeli dinamiko voda med razlicnimi hidrogeoloskimi nivoji in med vdori morske vode. Poleg tega je bil opravljen tudi batimetricni profil, da bi lažje dolocili, kje izvesti navpicne meritve. Med ekspedicijo se je zgodil mocan naliv, ki je trajal približno 12 ur, padlo je 80 mm dežja, njegov ucinek pa je raziskovalcem omogocil analizo hidrodinamike tekocih voda med poplavo. V obicajnih vodostajih so vzdolžne meritve pokazale na dotoke sveže vode, vertikalne meritve pa so pokazale jasno stratifikacijo lastnosti vode (sveža voda na povrsini in brakicna voda na dnu). Med poplavami so podatki EC in T potrdili hitro zamenjavo vode. Kljucne besede: anhialine jame, vdor morske vode, hidrodinamika, kraski izviri, PPUR, Filipini.

Ngamiland in northwestern Botswana hosts the Gcwihaba Caves which present unique subterranean environments and host speleothems never before recorded. Cave atmospheric conditions can be extreme with temperatures as high as 28°C and relative humidity nearing 99.9%. Within Dimapo and Diviner’s Caves peculiar root speleothems that we named ‘Hairy Stalagmites’ were found. These stalagmites are closely associated with the roots of Namaqua fig (Ficus cordata) trees that enter the cave environment in search of water. Pieces of broken stalagmites were sampled from Dimapo Cave for further investigations. Stereo and electron microscopy revealed that the Hairy Stalagmites consist of multiple intertwined tubes created when thin films of CaCO3 are deposited around fine lateral roots. The importance of the roots is substantiated with evidence of calcified epidermal cells, apical meristems and epidermal imprints. The development of these stalagmites starts when roots accumulate on the cave floor in the vicinity of a water drip and a root nest is created to capture the water. From this point the roots grow upwards (positive hydrotropism) allowing the development of the calcite structure, and as CO2 diffusion and evaporation occurs, CaCO3 is deposited. The environmental conditions necessary for the growth of Hairy Stalagmites, as well their developmental mechanism, are discussed and illustrated.

The caves of Naica (Chihuahua, Mexico) have been known since the beginning of the nineteenth century, when they were intersected by mines. They became world famous in 2000 when the mining activities intersected three small caves, which hosted gigantic gypsum crystals. Their genesis and evolution is strictly related to rising thermal fluids induced by Tertiary intrusive magmatic activity, giving rise to polysulfide deposits. Speleogenesis began about 1.5 Myr BP, induced by rising thermal water. This process lasted for a relatively short time. Later evolutionary stages varied from cave to cave, reflecting alternately deep-seated phreatic, epiphreatic, and vadose environments. Deposition of the giant gypsum crystals began ~400–350 Kyr BP, when the water temperature dropped below 58 °C. Their growth suddenly ceased in 1985, when mine dewatering dried up the caves. Besides the giant gypsum crystals, Naica caves contain a wide variety of other cave minerals (over 40), ten of which are new for the cavern environment. In addition, they include fossil pollen trapped in the gypsum lattice, which allow reconstruction of the external climate of 350 Kyr BP, and microorganisms new to science, which were preserved in the fluid inclusions of the gypsum crystals for tens or even hundreds of thousands of years. In 2015, mining intercepted a major thermal water source, which flooded the mine, and the Cueva de los Cristales and other caves at −290 m were flooded by more than 160 m of hot water.

In Sardinia, no active hypogenic caves have yet been discovered or described. Although there are a few thermal springs, mostly correlated to Quaternary volcanic activity, none of these thermal waters have interacted with carbonate rocks. Nevertheless, in the SW of the Island many metal ore deposits hosted in Cambrian limestones have been exploited over the last two centuries, allowing the discovery of so-called mine caves, some of which are clearly of hypogenic origin. These caves formed by thermal waters in a phreatic setting and are now located far above the water table and are no longer active, apart from some recent dripstone formation. The mine tunnels in Mount San Giovanni, near Iglesias and Gonnesa towns, have cut most of these caves: among them the well-known Santa Barbara cave, covered with barite crystals, Santa Barbara 2 cave, with its unique oxidation vents, and Crovassa Ricchi in Argento. Other hypogenic caves have been discovered in the mines of Campo Pisano and Monteponi (Iglesias), Mount Onixeddu (Gonnesa), and especially Masua (Iglesias). A very special case of hypogenic cave is the Corona ’e Sa Craba quartzite system, known for its barite crystals and rich in many mineral species. This chapter summarizes these known inactive hydrothermal and sulfuric acid caves.

none 16 si Although outcropping rarely in Italy, evaporite (gypsum and anhydrite) karst has been described in detail since the early 20th century. Gypsum caves are now known from almost all Italian regions, but are mainly localised along the northern border of the Apennine chain (Emilia Romagna and Marche), Calabria, and Sicily, where the major outcrops occur. Recently, important caves have also been discovered in the underground gypsum mines in Piedmont. During the late 80s and 90s several multidisciplinary studies were carried out in many gypsum areas, resulting in a comprehensive overview, promoting further research in these special karst regions. More recent and detailed studies focused on the gypsum areas of Emilia-Romagna and Sicily. Sinkholes related to Permian-Triassic gypsum have been studied in Friuli Venezia Giulia. This article reviews the state of the art regarding different aspects of evaporite karst in Italy focusing on the main new results. open De Waele, J.; Piccini, L.; Columbu, A.; Madonia, G.; Vattano, M.; Calligaris, C.; D’Angeli, I.M.; Parise, M.; Chiesi, M.; Sivelli, M.; Vigna, B.; Zini, L.; Chiarini, V.; Sauro, F.; Drysdale, R.; Forti, P. De Waele, J.; Piccini, L.; Columbu, A.; Madonia, G.; Vattano, M.; Calligaris, C.; D’Angeli, I.M.; Parise, M.; Chiesi, M.; Sivelli, M.; Vigna, B.; Zini, L.; Chiarini, V.; Sauro, F.; Drysdale, R.; Forti, P.

Speleothems are usually composed of thin layers of calcite (or aragonite). However, cemented detrital materials interlayered between laminae of speleothemic carbonate have been also observed in many caves. Flowstones comprising discontinuous carbonate layers form due to flowing water films, while flood events introduce fluviokarstic sediments in caves that, on occasion, are recorded as clayey layers inside flowstones and stalagmites. This record provides a potential means of understanding the frequency of palaeofloods using cave records. In this work, we investigate the origin of this type of detrital deposit in El Soplao Cave (Northern Spain). The age of the lowest aragonite layer of a flowstone reveals that the earliest flood period occurred before 500 ka, though most of the flowstone formed between 422 +69/-43 ka and 400 +66/-42 ka. This suggests that the cave was periodically affected by palaeoflood events that introduced detrital sediments from the surface as a result of occasional extreme rainfall events, especially at around 400 ka. The mineralogical data enable an evolutionary model for this flowstone to be generated based on the alternation of flood events with laminar flows and carbonate layers precipitation that can be extrapolated to other caves in which detrital sediments inside speleothems have been found. Copyright © 2014 John Wiley & Sons, Ltd.

The karst of Sorbas (SE Spain) is one of the most important gypsum areas worldwide. Its underground karst network comprises over 100 km of cave passages. Rounded smooth forms, condensation cupola and pendant-like features appear on the ceiling of the shallower passages as a result of gypsum dissolution by condensation water. Meanwhile, gypsum speleothems formed by capillarity, evaporation and aerosol deposition such as coralloids, gypsum crusts and rims are frequently observed closer to the passage floors. The role of condensation–dissolution mechanisms in the evolution of geomorphological features observed in the upper cave levels has been studied by means of long-term micro-erosion meter (MEM) measurements, direct collection and analysis of condensation waters, and micrometeorological monitoring. Monitoring of erosion at different heights on gypsum walls of the Cueva del Agua reveals that the gypsum surface retreated up to 0.033 mm yr− 1 in MEM stations located in the higher parts of the cave walls. The surface retreat was negligible at the lowest sites, suggesting higher dissolution rates close to the cave ceiling, where warmer and moister air flows. Monitoring of microclimatic parameters and direct measurements of condensation water were performed in the Covadura Cave system in order to estimate seasonal patterns of condensation. Direct measurements of condensation water dripping from a metal plate placed in the central part of the El Bosque Gallery of Covadura Cave indicate that condensation takes place mainly between July and November in coincidence with rainless periods. The estimated gypsum surface lowering due to this condensation water is 0.0026 mm yr− 1. Microclimatic monitoring in the same area shows differences in air temperature and humidity of the lower parts of the galleries (colder and drier) with respect to the cave ceiling (warmer and wetter). This thermal sedimentation controls the intensity of the condensation–evaporation mechanisms at different heights in the cave.

The “espada” speleothems of Cueva de las Espadas (Naica Mine, Chihuahua, Mexico) comprise a high-purity selenite core overlain by successive deposits of calcite, gypsum and aragonite. Gypsum precipitated under water from a hydrothermal solution (~ 58°C) when the water table was above the cave level ca. 57 ka, during the last glaciation, and some intervals during deglaciation and the Holocene. Aragonite was deposited at lower temperatures (~ 26°C) in a perched lake occupying the cave bottom, when the water table dropped below the cave level during brief dry intervals during deglaciation and the early Holocene. The isotopic composition of gypsum water of crystallization shows that the deglaciation–Holocene aquifer water was enriched in deuterium by 12.8–8.7‰ relative to water from the last glaciation. This is attributed to an increased relative moisture contribution from the Gulf of Mexico during deglaciation and the Holocene compared to the last glaciation. This indicates that drier conditions occurred in the Naica area during the Holocene than around 57 ka. Furthermore, trace element analyses of gypsum served to deduce the circulation regime of the Naica aquifer during the past 60,000 yr, and also suggest that higher aquifer recharge occurred during the last glaciation.

The present work deals with the results of long-term micro-erosion measurements in the most important gypsum cave of Spain, the Cueva del Agua (Sorbas, Almeria, SE Spain). Nineteen MEM stations were positioned in 1992 in a wide range of morphological and environmental settings (gypsum floors and walls, carbonate speleothems, dry conduits and vadose passages) inside and outside the cave, on gypsum and carbonate bedrocks and exposed to variable degree of humidity, different air flow and hydrodynamic conditions. Four different sets of stations have been investigated: (1) the main cave entrance (Las Vinicas spring); (2) the main river passage; (3) the abandoned Laboratory tunnel; and (4) the external gypsum surface. Data over a period of about 18 years are available. The average lowering rates vary from 0.014 to 0.016 mm yr− 1 near the main entrance and in the Laboratory tunnel, to 0.022 mm − 1 on gypsum floors and 0.028 mm yr− 1 on carbonate flowstones. The denudation data from the external gypsum stations are quite regular with a rate of 0.170 mm yr− 1. The observations allowed the collecting of important information concerning the feeding of the karst aquifer not only by infiltrating rainwater, but under present climate conditions also by water condensation of moist air flow. This contribution to the overall karst processes in the Cueva del Agua basin represents over 20% of the total chemical dissolution of the karst area and more than 50% of the speleogenetically removed gypsum in the cave system, thus representing all but a secondary role in speleogenesis. Condensation–corrosion is most active along the medium walls, being slower at the roof and almost absent close to the floor. This creates typical corrosion morphologies such as cupola, while gypsum flowers develop where evaporation dominates. This approach also shows quantitatively the morphological implications of condensation–corrosion processes in gypsum karst systems in arid zones, responsible for an average surface lowering of 0.047 mm yr− 1, while mechanical erosion produces a lowering of 0.123 mm yr− 1.

The study area of Tang sorkh Aquifer is located on the northern flank of the Derak anticline, a part of the Zagros Mountain Range, in the central-south of Iran. The study area is limited to undifferentiated non-salt Gachsaran Formation (NSGF), mainly composed of alternative layers of marl and marlstone, and gypsum. This paper is focused on the hydrogeological and hydrochemistry characteristics of the NSGF. A detailed geological cross section, perpendicular to the strike of the GF was prepared by detailed field surveying. The thickness of GF is 1,268 m, with 82 alternative units of marl, marlstone, gypsum, sandstone and limestone. The sub-aquifers are limited to four limestone, five gypsum, and one gypsum-halite units. The waters of these sub-aquifers emerge as springs or seepage into the Tang sorkh River (TR). The average discharge of springs emerging from limestone and gypsum units ranges between 0.3–8.4 and 0.5–0.75 l s−1, respectively. The source for sub-aquifers is mainly recharge from precipitation or river water. Marly layers disconnect the hydraulic connection between the sub-aquifers, directing the general flow parallel to the strikes. The lack of sinkholes and caves in the gypsum units is due to the small thickness of sub-aquifers, and consequently, low amounts of recharge water. The springs are classified into four groups based on their lithology, electrical conductivity, type of water, and trend of ion-concentration. The type of water in most of the springs is calcium-sulfate. The electrical conductivity is the main parameter to differentiate the hydrochemistry of the groups. The hydrochemistry of springs depends on the recharge from the TR, and the lithology of sub-aquifers and their adjacent units.

The Karun River is one of the most important waterways in Iran and the quality level of its waters is very important for all the communities living around it. The salinity of river waters increases and the water quality decreases while it passes through the four km long valley consist of Gachsaran geological formation (mainly gypsum and halit), in the Ambal ridge area. This ridge is located some 5 km upstream of the Gotvand dam (under construction), which in the future will be inundated. In this section of the river, water chemistry suddenly evolves from Ca-HCO3 type with TDS of ~0.4 g/l to Na(Ca)-Cl(SO4) type with TDS of ~1.5 g/l, possibly due to mixing, carbonates precipitation and dolomitization. These variations suggest that saline water mixed with the river water extensively in the Ambal ridge area. Two hypotheses are suggested for the origin of the saline waters: first, in situ dissolution of halite and gypsum units of exposed Gachsaran Formation of the nearby area could produce saline ground-water flow into the river, and second, the intrusion of Karun River water itself through fractures of evaporite layers at location, where it first comes in contact with the Ambal area and in consequence, dissolution of halite and gypsum by the water, which discharge into the river via a number of exposed and underwater springs in the ridge. Calculations indicate that the average annual saline water seepage required for the change of the chemical composition is ~0.24% of the total river flow rate. Water balance calculations suggest that the required catchment area for the saline ground-water flow should be >300 km2, much larger than the Ambal area itself. However, this excess area almost is exist in a closed by plain, the impermeable marl layers in the Gachsaran Formation restraint the flow of groundwater and suggest that the first hypothesis is less likely.