Community news

Speleology in Kazakhstan

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

New publications on hypogene speleogenesis

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

The deepest terrestrial animal

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

Caves - landscapes without light

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

Did you know?

That divide is 1. a line connecting the highest topographic elevations or ground-water crests that separate one drainage basin from another [16]. 2. a ridge in the water table or potentiometric surface from which the ground water represented by that surface moves away in both directions. water in other aquifers above or below, and even in the lower part of the same aquifer, may have a potentiometric surface lacking the ridge, and so may flow past the divide. see also ground-water divide; water-table divide. synonyms: ground-water divide; groundwater ridge; water-table divide. 3. (a) the line of separation, or the ridge, summit, or narrow tract of high ground, marking the boundary between two adjacent drainage basins or dividing the surface waters that flow naturally in one direction from those that flow in the opposite direction; the line forming the rim of or enclosing a drainage basin; a line across which no water flows. 3. (b) a tract of relatively high ground between two streams; a line that follows the summit of an interfluve [1]. see also drainage divide.?

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

What is Karstbase?

Search KARSTBASE:

keyword
author

Browse Speleogenesis Issues:

KarstBase a bibliography database in karst and cave science.

Featured articles from Cave & Karst Science Journals
Chemistry and Karst, White, William B.
See all featured articles
Featured articles from other Geoscience Journals
Karst environment, Culver D.C.
Mushroom Speleothems: Stromatolites That Formed in the Absence of Phototrophs, Bontognali, Tomaso R.R.; D’Angeli Ilenia M.; Tisato, Nicola; Vasconcelos, Crisogono; Bernasconi, Stefano M.; Gonzales, Esteban R. G.; De Waele, Jo
Calculating flux to predict future cave radon concentrations, Rowberry, Matt; Marti, Xavi; Frontera, Carlos; Van De Wiel, Marco; Briestensky, Milos
Microbial mediation of complex subterranean mineral structures, Tirato, Nicola; Torriano, Stefano F.F;, Monteux, Sylvain; Sauro, Francesco; De Waele, Jo; Lavagna, Maria Luisa; D’Angeli, Ilenia Maria; Chailloux, Daniel; Renda, Michel; Eglinton, Timothy I.; Bontognali, Tomaso Renzo Rezio
Evidence of a plate-wide tectonic pressure pulse provided by extensometric monitoring in the Balkan Mountains (Bulgaria), Briestensky, Milos; Rowberry, Matt; Stemberk, Josef; Stefanov, Petar; Vozar, Jozef; Sebela, Stanka; Petro, Lubomir; Bella, Pavel; Gaal, Ludovit; Ormukov, Cholponbek;
See all featured articles from other geoscience journals

Search in KarstBase

Your search for stalactite (Keyword) returned 103 results for the whole karstbase:
Showing 76 to 90 of 103
The role of the epikarst in karst and cave hydrogeology: a review., 2008, Williams, P. W.

The epikarst (also known as the subcutaneous zone) comprises highly weathered carbonate bedrock immediately beneath the surface or beneath the soil (when present) or exposed at the surface. Porosity and permeability are higher near the surface than at depth, consequently after recharge percolating rainwater is detained near the base of the epikarst, the detention ponding producing an epikarstic aquifer. Such an aquifer is found only where the uppermost part of the vadose zone is very weathered compared to the bedrock at depth. Sometimes this contrast in porosity and permeability does not occur either because the epikarst has been scraped off by glacial scour or because high porosity exists throughout the bedrock. In some conditions porosity may even diminish near the surface because of case-hardening. The epikarst is best developed in pure, crystalline limestones or marble where it is typically about 10 m thick. It then contains a suspended aquifer that is under-drained and sustains the distal tributaries of cave streams and small perennial flows emerging on hillsides (epikarstic springs). Slow leakage paths from the epikarst maintain seepage to many stalactites throughout the year. A distinction should be recognized between the location (and form) of the epikarst and the function of the epikarst, because the near surface zone in carbonate rocks does not always contain a suspended aquifer


Hydrogeochemical processes as environmental indicators in drip water: Study of the Cueva del Agua (Southern Spain), 2008, Fernandezcortes A. , Calaforra J. M. , Snchezmartos F.

Karst caves exhibit a wide range of hydrological and hydrochemical responses to infiltration events, due to their physical heterogeneity space and dynamic variability over time, and due to non-Gaussian inputs (rain) and outputs (discharge). This paper reviews different approaches of studying seepage water in caves, in order to understand the infiltration regimen in the non-saturated zone of karst areas. As an illustration, we describe a four-year study of the active carbonate-water system the Cueva del Agua (Granada, southern Spain) that automatically logs the discharge from a stalactite. The results indicate that: (1) the drip water regime is not seasonal, but is linked instead to slow infiltration. Sudden changes in drip water regime occur due to infiltration along preferential flow paths and the draining of water of supersaturated water from reserves in the microfissure and pore system; (2) the drip rate is not linear over time. When dripping is constant, barometric oscillation of the air is the principal factor causing a chaotic a drip flow regime. Over a short period of two to three days, a mean variation in air pressure inside the cave of 10 (±3.7) mbar causes a oscillation the drip rate of 0.5 (±0.2) mm/h. The increase air translates into an the relative thickness of the gaseous phase of the drip water at the cost of the aqueous phase, so leading to a reduction the drip rate from the stalactite.


Palaeoclimate Research in Villars Cave (Dordogne, SW-France), 2008, Genty, D.

Villars Cave is a typical shallow cave from South-West France (45.44°N; 0.78°E; 175 m asl) that has provided several speleothem palaeoclimatic records such as the millennial scale variability of the Last Glacial period and the Last Deglaciation. Monitoring the Villars cave environment over a 13-year period has helped in the understanding of the stable isotopic speleothem content and in the hydrology. For example, it was demonstrated that most of the calcite CaCO3 carbon comes from the soil CO2, which explains the sensitivity of the δ13C to any vegetation and climatic changes. Drip rate monitoring, carried out under four stalactites from the lower and upper galleries, has shown a well marked seasonality of the seepage water with high flow rates during winter and spring. A time delay of about two months is observed between the water excess (estimated from outside meteorological stations) and the drip rate in the cave. A great heterogeneity in the flow rate amplitude variations and in the annual quantity of water between two nearby stalactites is observed, confirming the complexity of the micro-fissure network system in the unsaturated zone. At a daily scale, the air pressure and drip rates are anti-correlated probably because of pressure stress on the fissure network. Cave air CO2 concentration follows soil CO2 production and is correlated with its δ13C content. Since the beginning of the monitoring, the cave air temperature, in both lower and upper galleries, displays a warming trend of ~+0.4°C±0.1/10yrs. This might be the consequence of the outside temperature increase that reaches the Villars Cave galleries through thermal wave conduction. Chemistry monitoring over a few years has shown that the seepage water of the lower gallery stations is significantly more concentrated in trace and minor elements (i.e. Sr, Mg, Ba, U) than the upper stations, probably due to the 10-20 m depth difference between these galleries, which implies a different seepage pathway and different water/rock interaction durations. There is also, in the elemental concentration (i.e. [Ca]), a seasonal signal which causes variation in the speleothem growth rates. Modern calcite deposit experiments conducted for several years have permitted the calculation of vertical growth rates, which are extremely high in Villars (i.e. 1.0 to 1.75 mm/yr). Pollen filter experiments in the cave have demonstrated that most of the pollen grain found in the cave comes from the air and not from the water. The specificity of the Villars Cave records is that the climatic variations were well recorded in the calcite δ13C whereas the δ18O is usually used in such studies. Overall, these results are helpful for the interpretation of speleothem records for palaeoclimatic reconstructions, but more work is needed, especially numerical modelling of the temperature, chemistry and hydrology.


Neuforschungen in der Gassel-Tropfsteinhhle (1618/3) bei Ebensee, 2008, Kuffner, D.
The Gassel-Tropfsteinhhle was discovered in 1918 and established as a show cave during the following years. The exploration history can be divided into three phases, whereby the latest one has started at the end of 2006 and involved the most significant discoveries ever made. The discovery of the Nord-Territorium (North-Territory) increased the length of the cave from 1307 m to 2716 m. The new cave parts host a great variety of speleothems, in particular stalactites and stalagmites, which surpass previously known formations in both abundance and size.

Formation of seasonal ice bodies and associated cryogenic carbonates in Caverne de lOurs, Que bec, Canada: Kinetic isotope effects and pseudo-biogenic crystal structures, 2009, Lacelle D. , Lauriol B. , And Clark I. D.
This study examines the kinetics of formation of seasonal cave ice formations (stalagmites, stalactites, hoar, curtain, and floor ice) and the associated cryogenic calcite powders in Caverne de lOurs (QC, Canada), a shallow, thermally-responsive cave. The seasonal ice formations, which either formed by the: (1) freezing of dripping water (ice stalagmite and stalactite); (2) freezing of stagnant or slow moving water (floor ice and curtain ice) and; (3) condensation of water vapor (hoar ice), all (except floor ice) showed kinetic isotope effects associated with the rapid freezing of calcium bicarbonate water. This was made evident in the dD, d18 O and d (deuterium excess) compositions of the formed ice where they plot along a kinetic freezing line. The cryogenic calcite powders, which are found on the surface of the seasonal ice formations, also show kinetic isotope effects. Their d13 C and d18 O values are among the highest measured in cold-climate carbonates and are caused by the rapid rate of freezing, which results in strong C-O disequilibrium between the water, dissolved C species in the water, and precipitating calcite. Although the cryogenic calcite precipitated as powders, diverse crystal habits were observed under scanning electron microscope, which included rhombs, aggregated rhombs, spheres, needles, and aggregated structures. The rhomb crystal habits were observed in samples stored and observed at room temperature, whereas the sphere and needle structures were observed in the samples kept and observed under cryogenic conditions. Considering that the formation of cryogenic calcite is purely abiotic (freezing of calcium bicarbonate water), the presence of spherical structures, commonly associated with biotic processes, might represent vaterite, a polymorph of calcite stable only at low temperatures. It is therefore suggested that care should be taken before suggesting biological origin to calcite precipitates based solely on crystal habits because they might represent pseudo-biogenic structures formed through abiotic processes.

The genesis of cave rings explained using empirical and experimental data, 2009, Nozzoli F. , Bevilacqua S. , And Cavallari L.
A cave ring is a faint speleothem consisting in a thin circle on the floor symmetrically surrounding a water drop impact point. Two different mechanisms seem to be responsible for cave ring formation: the drop splash at the floor, for the splash rings, and the ejection of a secondary droplet during the fall, for the fall down rings. A systematic investigation of 67 speleothem rings discovered in five different caves in central Italy was conducted. The data show compatibility with a common nature for all the observed rings. For the observed rings, the hypothesis of a falling secondary droplet origin is confirmed and the hypothesis of a primary drop splash is rejected. The trajectory of a secondary droplet has been measured, and the collected data suggest that the secondary droplets originate from a primary drop breakup at a distance y0 5 142.7 6 7.2 cm from the stalactite tip. Assuming this spontaneous breakup hypothesis, the velocities ratio b 5 uy/ux 5 25.5 6 1.6 at the breakup time was measured. Finally, the collected ring data (5-cm- to 50-cm-diameter range) exhibit a negative curva- ture trajectory. The large departure from a gravity dominant parabolic trajectory suggests other forces, such as air friction or lift force, are at work on the small secondary droplets.

Unique iron-manganese colonies of microorganisms in Zoloushka Cave (Ukraine-Moldova), 2009, Andreychouk V. N. , Klimchouk A. , Boston P. , Galuskin E.

During open-pit quarrying and related lowering of groundwater level in the gypsum karst aquifer (since 1950), large cave Zoloushka became accessible for direct exploration, in which considerable geochemical transformations of environment occurred, accompanied by the formation of specific deposits, as well as by burst of microbial activity. Among microorganisms, some of the most active were various iron bacteria. Microbial activity has resulted in precipitation of black and red biochemical formations – microbialites (coatings, crusts, films, stalactites, stalagmites, etc.), which cover walls and floors of cave passages. Most interesting among the microbialites are iron-rich colonial formations of various shapes (stalagmite-like, tube-like, coral-like, etc.) formed by yet unidentified fungi-like microorganisms which likely are new to science. In this paper, we characterize occurrence and morphology of the colonial aggregates, morphology and chemical composition of microorganisms  and develop working hypotheses of their identification.


Spatial distribution of soda straws growth rates of the Coufin Cave (Vercors, France), 2010, Perrette Y. And Jaillet S.
The Choranche Cave system (Vercors, France) is an excellent locality for measuring the growth rates of large numbers soda straws. This is especially the case for the Coufin Cave, as enlargement of the cave entrance in 1875 led to a change in stalactite color from brown to white, thus providing a reliable chronomarker. The date of this brown-to-white calcite transition has been confirmed by lamina counting. We measured and georeferenced the growth-lengths of 306 soda straws in a 1m2 area of the roof of the Coufin Cave entrance chamber. Because of the very slow and sometimes inexistent water feeding of those stalactites, hydrochemistry analysis were not achieved and drop rate effect on growth were neglected; this study is based on a geomorphological and geostatistical work. By measuring a large number of soda straws in a very small area for which most of the parameters affecting stalactite growth could be considered uniform, and because flow rates are very slow (frequencies are always superior to 1 drop per half hour), we could ascribe differences in growth rates to variations in the global increase of water flow through the unsaturated matrix. Statistical and geostatistical analyses of the measurements showed that this set of similarly shaped stalactites actually consisted of three Gaussian populations with different mean growth rates: fast growth rate (FGR- mean of 0.92 mm.y-1), medium growth rate (MGR- mean of 0.47 mm.y-1) and low growth rate (LGR- 0.09 mm.y-1). Plotting the lengths and spatial distribution of the 20 longest FGR soda straws revealed that there is a rough pattern to the water flow through the cave roof. Even if no direction is statisticaly different from others, the observed directional pattern is consistent with local and regional tectonic observations. Plots of the spatial distribution of the soda straws show that FGR soda straws follow lines of regional geological stress, whereas MGR and LGR soda straws are more dispersed.

Polyphase speleogenesis in Lick Creek Cave, Little Belt Mountains, Montana, USA, 2010, Carriere K. L. , Machel H. G. , Hopkins J. C.

Lick Creek Cave in northern Montana (USA) is hosted in limestones of the Lower Carboniferous Madison Group near Tiger Butte, an Eocene quartz–syenite porphyry intrusive dome. The cave is located within the zone of contact metamorphism of the dome, which crops out 300 m from the cave entrance. The cave consists of two genetically distinct cave systems separated by a fracture zone: (1) a 80 50 m dome-shaped cavern in breccias of a Carboniferous paleocave, and (2) anastomosing conduits 2–10 m across, parallel to the bedding of the Madison Group and extending 100 m up dip to the present cave entrance. The conduits are further subdivided into a tectonised and a maze zone and are variably decorated in several combinations by phreatic isopachous calcite spar cements, with crystals up to several cm long, and with vadose speleothems, including stalactite–stalagmite pairs, flowstone, corallite (cave popcorn), and moonmilk. Our database is comprised of field survey, thin section, XRD, and SEM observations along with 118 ?18O/?13C analyses and 27 87Sr/86Sr measurements from samples of county rock and speleothems. The limestone matrix samples with the heaviest ?18O/?13C ratios are interpreted as the least recrystallised proxy to Tournaisian seawater. Stable isotope data from other Carboniferous limestones, including paleocave breccias, follow a regional meteoric pathway established elsewhere in the Madison for the Late Carboniferous transition from greenhouse to icehouse conditions. Isopachous calcite spar cements from the conduit zone are interpreted as the result of late-stage, Eocene hydrothermal fluid circulation. Stalactite–stalagmite pairs, flowstone, corallite, and moonmilk carry a signature similar to modern or Quaternary high-alpine meteoric water. Previous workers have determined separate hydrothermal and meteoric ?18O/?13C stable isotope fields for speleothems in caves in Carboniferous limestones from the Black Hills, South Dakota. We re-define the stable isotope ranges for meteoric and magmatic–hydrothermal calcites based on a comparison of stable isotope data from the Little Belt Mountains with those from the Black Hills. We further propose that the hydrothermal calcite end-member ?18O composition is around ?20‰ PDB, represented by the lowest oxygen isotope values from all data sets, with a corresponding ?13C of about ?7‰ PDB. Sr-isotope data from speleothems, Carboniferous limestone wall rocks, and from the igneous intrusion itself support the interpretation of an Eocene hydrothermal speleogenic event. The integration of petrographic and geochemical data shows that Lick Creek Cave is the result of polyphase speleogenesis in three major episodes: (1) Middle to Late Carboniferous, (2) Eocene, and (3) (sub-)Recent to Recent. The Carboniferous and (sub-)Recent to Recent speleogenesis appear epigenic, i.e., driven by surface-derived waters, whereas the Eocene event was hypogenic, i.e., driven by ascending hydrothermal waters. Each of the three major speleogenic events probably consisted of two or more distinct “phases”, but our database does not permit these phases to be resolved with certainty.


Spatial distribution of soda straws growth rates of the Coufin Cave (Vercors, France), 2010, Perrette Y. , Jaillet S.

The Choranche Cave system (Vercors, France) is an excellent locality for measuring the growth rates of large numbers soda straws. This is especially the case for the Coufin Cave, as enlargement of the cave entrance in 1875 led to a change in stalactite color from brown to white, thus providing a reliable chronomarker. The date of this brown-to-white calcite transition has been confirmed by lamina counting. We measured and georeferenced the growth-lengths of 306 soda straws in a 1m2 area of the roof of the Coufin Cave entrance chamber. Because of the very slow and sometimes inexistent water feeding of those stalactites, hydrochemistry analysis were not achieved and drop rate effect on growth were neglected; this study is based on a geomorphological and geostatistical work. By measuring a large number of soda straws in a very small area for which most of the parameters affecting stalactite growth could be considered uniform, and because flow rates are very slow (frequencies are always superior to 1 drop per half hour), we could ascribe differences in growth rates to variations in the global increase of water flow through the unsaturated matrix. Statistical and geostatistical analyses of the measurements showed that this set of similarly shaped stalactites actually consisted of three Gaussian populations with different mean growth rates: fast growth rate (FGR- mean of 0.92 mm.y-1), medium growth rate (MGR- mean of 0.47 mm.y-1) and low growth rate (LGR- 0.09 mm.y-1). Plotting the lengths and spatial distribution of the 20 longest FGR soda straws revealed that there is a rough pattern to the water flow through the cave roof. Even if no direction is statisticaly different from others, the observed directional pattern is consistent with local and regional tectonic observations. Plots of the spatial distribution of the soda straws show that FGR soda straws follow lines of regional geological stress, whereas MGR and LGR soda straws are more dispersed.


New peculiar cave ceiling forms from Carlsbad Caverns (New Mexico, USA): The zenithal ceiling tube-holes, 2011, Calaforra Josemaria, De Waele Jo

During a trip to the Hall of the White Giant, Carlsbad Caverns (NM, USA) cigar-shaped vertically upward developing holes were observed on the ceiling at different heights of the passages. They have a circular cross-section with diameters of 1 to some centimetres and taper out towards their upper end. Their walls are smooth and their bottom edges are sharp, while their length can reach several decimetres. Sometimes gypsum can be found inside. They often occur randomly distributed in groups and their development is not necessarily controlled by fractures or other bedrock structures.

We name these peculiar karren-like cave microforms “zenithal ceiling tube-holes” because of their origin by H2S environment corrosion processes and their vertical (zenithal) upward growth in ceilings. A comparison is made between zenithal ceiling tube-holes and other karstic or non karstic similar forms such as bell holes, oxidation vents, snailholes, Korrosionskolke (mixture-solution hollows) or pockets, röhrenkarren, light-oriented photokarren, borings of (often marine) organisms and negative stalactites.

Zenithal ceiling tube-holes are created by the corrosive effect of sulphuric acid. H2S(g) dissolves in water giving rise to widespread sulphuric acid corrosion. When H2S bubbles are trapped underneath overhanging surfaces or ceilings and water level rises steadily the corrosive effect is concentrated vertically upwards, drilling vertical holes that can also completely pass overhanging rock ledges.


Minerals of the Okhotnichiya Cave (Baikal Region, Irkutsky Region) , 2011, Bazarova E. P. , Gutareva O. S. , Kononov A. M. , Ushchapovskaya Z. F. , Nartova N. V. , Osintsev A. V.

Ice, calcite, aragonite, monohydrocalcite, gypsum and ikaite speleothems were found in the Okhotnichiya cave. The aragonite occurs as layers in calcite stalactites and speleothemic crusts. Monohydrocalcite and gypsum occurs as crusts on the top of the calcite corallites. Gypsum crystallictites and antholites were found in the cave. Criomineral formations are represented by ikaite. Coarse-grained criogenic cave carbonates occur as accumulations of non-cemented ikaite crystal aggregates on the surface of limestone-dolomite boulders.


Geomorphology and genesis of the remarkable Araras Ridge tufa deposit, Western Brazil, 2011, Corrê, A Daniel, Auler Augusto S. , Wang Xianfeng, Edwards R. Lawrence, Cheng Hai

The Araras Ridge tufa extends for over 30 km along a c. 100 m high fault scarp, probably representing one of the most extensive tufa deposits in South America. The deposit comprises massive crystalline calcite occurring both as in situ tufa deposited along the vertical face of the scarp or as extensive debris deposits resulting from erosional disaggregation of the scarp. Although minor active tufa precipitation can be observed in streams, the deposit is not active at present, except for volumetrically limited reprecipitation of calcite as subaerial stalactites or surface flowstone. 230Th dating confirms that the bulk of the deposit is considerably old, basal ages being beyond the dating limit of the method (> 600 ka B.P.) and most ages being older than 250 ka B.P. Field and remote sensing observations demonstrate that the upper limit of the deposit parallels the fault scarp, being associated with the contact between the upper dolomitic and the lower limestone members of the Araras Formation. Carbonate beds are arranged in a regional scale synclinal structure that allows water infiltration and storage at the top of the more impure limestone, favouring discharge at the ascending limb of the syncline, close to the scarp. Genesis of the deposit thus probably involved a series of palaeo perched springs aligned along the top of the scarp. Current climatic and geomorphic conditions are not conductive to major tufa development, suggesting a distinct palaeoenvironment during former depositional phases.


Alunite formation within silica stalactites from the Sydney Region, South-eastern Australia, 2011, Wray, R. A. L. .

This paper presents X-ray diffraction and SEM evidence for the formation of alunite, and possibly small quantities of natroalunite, within opal-A stalactites formed on quartz sandstone near Sydney in south-eastern, Australia. Alunite has been reported as a speleogenetic mineral from sediments within a number of caves around the world, but this is believed to be the first report of speleothemic alunite in opaline silica speleothems. Individual alunite crystals have not been visually identified, but SEM X-ray element mapping suggests the alunite has formed amongst kaolinite clay. Sedimentary alunite and natroalunite formation is usually associated with the reaction of sulphuric acid on illite, smectite and kaolinite clay materials. In this location groundwater sulphate levels are not high, but evaporative concentration of stalactite drip-water containing small amounts of sulphuric acid generated by oxidization of pyrite might lower the pH to a level sufficiently acidic for conversion of kaolinite or illite to alunite. The ferrolysis of hydrous Fe2+-oxides, or the biochemical activities of bacteria or other micro-organisms, also provide conceivable pathways for the generation of pH sufficiently low to contribute to alunite formation. The occurrence of alunite in these silica stalactites, whilst unusual, is consistent with the normal silica stalactite-forming process in this region, and in accord with observations of the authigenic formation of alunite and groundwater opal in weathering profiles elsewhere.


Secondary halite deposits in the Iranian salt karst: general description and origin, 2011, Filippi Michal, Bruthans Jiř, , Palatinus Luk, Zare Mohammad, Asadi Naser

This paper summaries 12 years of documentation of secondary halite deposits in the Iranian salt karst.
A variety of secondary halite deposits was distinguished and classified into several groups, on the basis of the site and mechanism of their origin. Deposits formed: i) via crystallization in/on streams and pools, ii) from dripping, splashing and aerosol water, iii) from evaporation of seepage and capillary water, and iv) other types of deposits. The following examples of halite forms were distinguished in each of the above mentioned group: i) euhedral crystals, floating rafts (raft cones), thin brine surface crusts and films; ii) straw stalactites, macrocrystalline skeletal and hyaline deposits, aerosol deposits; iii) microcrystalline forms (crusts, stalactites and stalagmites, helictites); iv) macrocrystalline helictites, halite bottom fibres and spiders, crystals in fluvial sediments, euhedral halite crystals in rock salt, combined or transient forms and biologically induced deposits. The occurrence of particular forms depends strongly on the environment, especially on the type of brine occurrence (pool, drip, splashing brine, microscopic capillary brine, etc.), flow rate and its variation, atmospheric humidity, evaporation rate and, in some cases, on the air flow direction. Combined or transitional secondary deposits can be observed if the conditions changed during the deposition. Euhedral halite crystals originate solely below the brine surface of supersaturated streams and lakes. Macrocrystalline skeletal deposits occur at places with rich irregular dripping and splashing (i.e., waterfalls, places with strong dripping from the cave ceilings, etc.). Microcrystalline (fine grained) deposits are generated by evaporation of capillary brine at places where brine is not present in a macroscopically visible form. Straw stalactites form at places where dripping is concentrated in small spots and is frequent sufficient to assure that the tip of the stalactite will not be overgrown by halite precipitates. If the tip is blocked by halite precipitates, the brine remaining in the straw will seep through the walls and helictites start to grow in some places.
Macrocrystalline skeletal deposits and straw stalactites usually grow after a major rain event when dripping is strong, while microcrystalline speleothems are formed continuously during much longer periods and ultimately (usually) overgrow the other types of speleothems during dry periods. The rate of secondary halite deposition is much faster compared to the carbonate karst. Some forms increase more than 0.5 m during the first year after a strong rain event; however, the age of speleothems is difficult to estimate, as they are often combinations of segments of various ages and growth periods alternate with long intervals of inactivity.
Described forms may be considered in many cases as the analogues of forms found in the carbonate karst. As they are created in a short time period the conditions of their origin are often still visible or can be reconstructed. The described halite forms can thus be used for verification of the origin of various carbonate forms. Some of the described forms bear clear evidence of the paleo-water surface level (transition of the skeletal form to halite crystals and vice versa). Other kinds of deposits are potential indicators of the microclimate under which they developed (humidity close to the deliquescence relative humidity).


Results 76 to 90 of 103
You probably didn't submit anything to search for