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Enviroscan Ukrainian Institute of Speleology and Karstology


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Speleology in Kazakhstan

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

New publications on hypogene speleogenesis

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

The deepest terrestrial animal

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

Caves - landscapes without light

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

Did you know?

That seepage force is the frictional drag of water flowing through voids or interstices in rock causing an increase in the intergranular pressure (i.e. the hydraulic force per unit volume of rock or soil which results from the flow of water and which acts in the direction of flow).?

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


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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;
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Your search for sem (Keyword) returned 472 results for the whole karstbase:
Showing 436 to 450 of 472
Uncommon cave minerals associated to hypogene speleogenesis in Southern France, 2013,
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Audra, Philippe

Five hypogenic-origin caves from Southern France are presented. Investigations using XRD, SEM and Raman spectroscopy, reveal the presence of uncommon cave minerals. Oilloki Cave is a small lead ore mine-cave containing galena, cerussite, and bismuth (present as native element or as sulfide).La Baume Cave is a hydrothermal breccia-pipe, filled with colorful (red, green, white) clays. Some of the clay minerals (clinochlore se-piolite), could originate from hydrothermal weathering of clastic material. The Mala-coste Quarry, harbors a hydrothermal chimney with enlarged vugs lined with calcite spar and filled with iron oxyhydroxides poolfingers (goethite-hematite) and manganese oxides (birnessite, todorokite). Deposition of iron and manganese oxides results of the pH-Eh evolution along the hydrothermal chimney. Pigette Cave is a hydrothermal ver-tical maze with calcite lining and small iron oxyhydroxides and manganese oxides mass-es. The hydrothermal weathering of the walls deposited grains of lithiophorite, barite, and celadonite, which could originate from glauconite. Baume Galinière Cave is a small horizontal maze originating from the oxidation of sulfide masses of pyrite. Beside the common byproducts (gypsum, goethite, sulfur), the six members of the jarosite sub-group are present: jarosite, ammoniojarosite, argentojarosite, hydronium jarosite, natro-jarosite, plumbojarosite, together with fibroferrite. In these caves, three minerals are new cave minerals (bismuth, celadonite, argentojarosite); some others have been men-tioned before only in a few caves worldwide (clinochlore, lithiophorite, ammoniojaro-site, hydronium jarosite, natrojarosite, plumbojarosite, fibroferrite). The mineralogene-sis involves different processes: (i) Deposition in mixing zone from species carried by rising deep flow (barite, galena, bismuth, birnessite, todorokite, lithiophorite); (ii) Hy-drothermal weathering of clay minerals contained in host rock or present as clastic sediments (clinochlore, sepiolite, celadonite); (iii) Oxidation of sulfide masses (goethite, cerussite, jarosite subgroup minerals, fibroferrite).


Marine seismic-reflection data from the southeastern Florida Platform: a case for hypogenic karst, 2013,
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Cunningham, Kevin J.

Recent acquisition of twenty marine seismic-reflection profiles suggests a hypogenic karst origin for the Key Biscayne sinkhole located on the seafloor of Miami Terrace at the southeastern part of Florida Platform. Analysis of the seismic-reflection data strongly suggest the submarine sinkhole was produced by dissolution and collapse of Plio(?)-Pleistocene age carbonate strata. A complex fault system that includes compres-sional reverse faults underlies the sinkhole, providing a physical system for the possible exchange of groundwater with the sinkhole. One seismic profile is suggestive of a mas-ter feeder pipe beneath the sinkhole. The feeder pipe is characterized by seismic-reflection configurations that resemble megabreccia and stratal collapse. The sinkhole is located at a depth of about 365 m below sea level. The record of sea-level change dur-ing the Plio(?)-Pleistocene and amount of subsidence of the Florida Platform during this span of time indicates that the sinkhole has always been submerged at a water depth of about 235 m or more. Thus, the near-surface epigenic karst paradigm can be ruled out. Possible hypogenic models for sinkhole formation include ascending fluids along the fault system, such as, dissolution related to the freshwater/saltwater mixing at a regional groundwater discharge site, or processes related to gases derived from gener-ation of hydrocarbons within deep Mesozoic strata. Hydrocarbon-related karstification provides several possible scenarios: (1) oxidation of deep oil-field derived hydrogen sulfide at or near the seafloor to form sulfuric acid, (2) reduction of Cretaceous or Paleocene anhydrite or both by oil-field methane to form hydrogen sulfide and later oxidation to form sulfuric acid, and (3) carbon-dioxide charged groundwater reacting to form carbonic acid. Further, anerobic microbes could form methane outside of a hy-drocarbon reservoir that ascends through anhydrite to form hydrogen sulfide and later oxidized to sulfuric acid.


Isotopically altered wallrock of the hypogene conduits in the Crimean Piedmont, Ukraine, 2013,
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Klimchouk A. , Dublyansky Y. , Tymokhina E. , Sptl Ch.

The Crimean Piedmont stretches along the tectonic suture separating the fold-and-thrust structure of the Crimean Mountains from the Scythian Plate. It comprises two cuesta-like ridges whose structural slopes are built up of homoclinal limestone beds of the Paleocene- Eocene (the Inner Range), and the Neogene (the Outer Range) ages. Abundant relicts of the hypogene karst have been identified recently in steep cuesta cliffs of the Piedmont. The hypogene cavities formed in confined to semi-confined hydrological conditions due to interaction of the deep-seated waters, ascending along cross-formational fracture conduits, with the strata-bound lateral filtration flow. The ongoing geomorphological dissection of the stratified structure of the Piedmont com-monly follows the pre-formed hypogene conduits, resulting in the development of the pronounced cuesta relief with steep cliffs featuring massive exposure of the hypogene karst conduit paleo-walls with specific morphologies.
Movement of deep-seated fluids through carbonate wallrock may cause isotopic altera-tion of the later. We have studied isotopic composition of C and O along nine cores drilled into the walls of the cliffs decorated with hypogene solutional features, as well as in two hypogene caves. Data from all cores show the presence of a wide isotopic altera-tion halo, whose thickness exceeds the core length (max. 40 cm). In this zone, the rock is slightly depleted in δ18 (ca. 1 -2 ‰) relative to the “pristine”, unchanged values of a given rock unit. In most cores the rock is also depleted in 13 but two cores show high-er 13C values. In addition to this low-gradient alteration, most of the cores also show a narrow (4-50 mm) zone of the high-gradient alteration, across which δ18 and δ13 drop by respectively, 2.0–4.9 ‰ and 0.7–4.5 ‰. At three localities, the walls of the hypogene cavities were coated with phreatic calcite. Isotopic composition of this calcite corresponds to the lowermost values of the altered rock. In one core, the rock in the high-gradient alteration zone is depleted in 18 but enriched in 13. In yet another core the rock is enriched in both 18 and 13. The results corroborate the hypogenic origin of conduits and suggest that the wallrock was exposed to, and interacted with, geo-chemically different waters after the main volume of cavities had been created by disso-lution.


Differences in aquatic microcrustacean assemblages between temporary and perennial springs of an alpine karstic aquifer, 2013,
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Mori N. , Brancelj A.

Microcrustacean (Copepoda, Ostracoda) assemblages were investigated at the interface of the vadose and phreatic zones in the alpine karstic aquifer from the Julian Alps in Slovenia (SE Europe). Two temporary and one perennial karstic outlets were sampled by filtering the water several times over 2 years. Concurrently, benthos from the mouth of a perennial spring and from an adjacent spring brook were collected. Altogether 24 microcrustacean species were recorded. The spatial and temporal variation in drift densities and species composition was high indicating complex groundwater hydrological pathways being dependent on precipitation regime. Non-metric Multidimensional Scaling (NMDS) clearly separated drift samples from temporary springs and other sample groups (drift in perennial spring, spring mouth and spring brook benthos). ANOSIM revealed statistically significant differences between all sample groups (Diacyclops zschokkei, Elaphoidella phreatica and Mixtacandona sp. B contributed over 50 % to the observed differences among sample groups. Three species (Nitocrella sp., Speocyclops infernus, Lessinocamptus pivai), known to be typical epikarst species, were collected only in the drift from one temporary spring (T2). Mao Tau species accumulation curves did not reach asymptote for the drift from temporary springs, but did for the drift from perennial spring, and for the spring mouth and the spring brook benthos. The results on drift composition indicated the variation in the origin of the water discharging at the interface of vadoze and phreatic zones depending greatly on water level conditions, while the drift densities were higher in the water presumably discharging from phreatic zone (perennial spring and temporary springs during low water levels).


Spatial and temporal changes in invertebrate assemblage structure from the entrance to deep-cave zone of a temperate marble cave, 2013,
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Tobin Benjamin W. , Hutchins Benjamin T. , Schwartz Benjamin F.

Seasonality in surface weather results in seasonal temperature and humidity changes in caves. Ecological and physiological differences among trogloxenes, troglophiles, and troglobionts result in species-dependent responses to this variability. To investigate these responses, we conducted five biological inventories in a marble cave in the Sierra Nevada Range, California, USA between May and December 2010. The cave was divided into six quadrats and temperature was continuously logged in each (humidity was logged at the entrance and in the deep cave). With increasing distance from the entrance, temperature changes were increasingly attenuated and lagged relative to surface temperature. Linear regressions were created to determine the relationship between measured environmental variables and diversity for cavernicoles (troglobionts and troglophiles) and trogloxenes cave– wide and in the transition zone. Diversity for cavernicoles and trogloxenes peaked in the entrance and deep cave zones, respectively. Quadrat, date, 2-week antecedent temperature average, 2-week antecedent temperature range, and trogloxene abundance explained 76% of cavernicole diversity variability. Quadrat explained 55% of trogloxene diversity variability. In the transition zone, trogloxene abundance explained 26% of cavernicole variability and 2-week antecedent temperature and 2-week antecedent temperature range explained 40% of trogloxene variability. In the transition zone, trogloxene diversity was inversely related to 2-week antecedent temperature average and 2-week antecedent temperature range, suggesting that species were moving into the transition zone when temperature was most stable. In a CCA of cavernicoles distribution data and environmental variables, 35% of variation in species-specific distributions was attributable to quadrat, and non-significant percentages were explained by date and environmental variables. Differences in assemblage structure among quadrats were largely due to differences between distributions of trogloxenes and cavernicoles, but responses varied among species. Differences are likely due to ecological niche width, physiological constraints, and competition.


NA JAVORCE CAVE A NEW DISCOVERY IN THE BOHEMIAN KARST (CZECH REPUBLIC): UNIQUE EXAMPLE OF RELATIONSHIPS BETWEEN HYDROTHERMAL AND COMMON KARSTIFICATION, 2013,
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Dragoun J. Ž, á, K K. Vejlupek J. Filippi M. Novotný, J. Dobeš, P.

 

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


THE HYPOGENE ORIGIN OF DIANA CAVE (ROMANIA) AND ITS SULFURIC ACID WEATHERING ENVIRONMENT, 2013,
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Onac B. P. Puș, Caș, C. M. Effenberger H. S. Povară, I. Wynn J. G.

 

The Diana Cave in SW Romania develops along a fault line at the contact between Late Jurassic limestones and Early Cretaceous marls. It formed through corrosion of bedrock (limestone and marls) by sulphuric acid-rich steam condensate resulted after oxidation/hydrolysis of H2S escaping from the thermo-mineral water emerging from depth in the cave. The sulfuric acid causes a strong acid sulfate weathering of the bedrock generating a sulfate-dominated secondary cave-mineral assemblage that includes gypsum, anhydrite, bassanite, epsomite, alunite, and halotrichite group minerals. Closely associated with these minerals are two rare sulfate species, namely rapidcreekite and tamarugite that represent new occurrences in limestone caves. Traditional X-ray diffraction and single crystal analyses were used along with scanning electron microscope (SEM), stable isotope, and electron microprobe investigations to fully characterize the primary and secondary speleogenetic by-products of Diana Cave.


Rapidcreekite in the sulfuric acid weathering environment of Diana Cave, Romania, 2013,
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Onac B. P. Effenberger H. S. Wynn J. G. Povară, I.

The Diana Cave in SW Romania develops along a fault line and hosts a spring of hot (Tavg = 51 °C), sulfate-rich, sodium-calcium-chloride bearing water of near-neutral pH. Abundant steam and H2S rises from the thermal water to condensate on the walls and ceiling of the cave. The sulfuric acid produced by H2S oxidation/hydrolysis causes a strong acid-sulfate weathering of the cave bedrock generating a sulfate-dominated mineral assemblage that includes rapidcreekite, Ca2(SO4)(CO3)•4H2O closely associated with gypsum and halotrichite group minerals. Rapidcreekite forms bundles of colorless tabular orthorhombic crystals elongated along [001] and reaching up to 1.5 mm in length. For verifying the hydrogen bond scheme and obtaining crystal-chemical details of the carbonate group a single-crystal structure refinement of rapidcreekite was performed. Its unit-cell parameters are: a = 15.524(2), b = 19.218(3), c = 6.161(1) Å; V = 1838.1(5) Å3, Z = 8, space group Pcnb. Chemi¬cal composition (wt%): CaO 35.65, SO3 24.97, CO2 13.7, H2O 23.9, Na2O 0.291, MgO 0.173, Al2O3 0.07, total 98.75%. The empirical formula, based on 7 non-water O atoms pfu, is: Ca1.98Na0.029Mg0.013 Al0.004(S0.971 O4)(C0.97O3)•4.13H2O. The d34S and d18O values of rapidcreekite and other cave sulfates range from 18 to 19.5‰ CDT and from –9.7 to 7.8‰ SMOW, respectively, indicating that the source of sulfur is a marine evaporite and that during hydration of the minerals it has been an abundant 18O exchange with percolating water but almost no oxygen is derived from O2(aq). This is the first descrip¬tion of rapidcreekite from a cave environment and one of the very few natural occurrences worldwide. We also report on the mineral stability and solubility, parameters considered critical to understand the co-precipitation of carbonates and sulfates, a process that has wide applications in cement industry and scaling prevention.


The hypogene karst of the Crimean Piedmont and its geomorphological role (in Russian), 2013,
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Klimchouk A. B. Tymokhina E. I. Amelichev G. N. Dublyansky Y. V. Spö, Tl C.
The book offers a fundamental new interpretation of the origin of karst in the Crimean Piedmont and explains the role karstification played in the geomorphogenesis of the region. The hypogene origin of karst cavities, their leading role in dismembering the Crimean Piedmont’s homocline and the formation of the characteristic cuesta and rock-remnant relief of the area is demonstrated on the basis of a systematic and comprehensive study, which included modern isotopic and geochemical methods.
The hypogene karst in the area developed in conditions of the confined to semi-confined groundwater flow systems, via interaction between the ascending flow of the deep-seated fracture-karst (conduit) water and the strata-bound, predominantly porous aquifers of the layered formations in the homoclinal northern mega-slope of the Crimean Mountains. The major pre-requisites for hypogene karst development is a position of the area at the flank of the Prichernomorsky artesian basin, and in a geodynamically active suture zone, which separates the fold-thrust structure of the Crimea Mountains and the Scythian plate. Opening of the stratified structure of the Piedmont follows the near-vertical cross-formational fracture-karst channels, resulting in the development of the pronounced cuesta relief with steep cliffs, which feature massive exposure of channels with karst-affected morphology.
Hypogene karstification results in characteristic morphologies, including caves, cliff niches and open chambers, variously sculptured and honeycomb-cellular surfaces of limestone cliffs, wide and shallow couloirs near the rims of cuestas, and rock remnants-“sphinxes”. The carbonate bedrock in the walls of the hypogene cavities revealed isotopic alteration (both O and C) caused by the action of hypogene fluids. The time of formation of cuestas in the Inner Range of the Crimean Mountains, determined on the basis of the U-Th disequilibrium dating of speleothems, turned out to be younger than thought previously. The active development of hypogene karst in the geologically recent past was the main factor responsible for today’s geomorphologic peculiarity of the Crimean Piedmont.
The book will be of interest for karstologists, hydrogeologists, geomorphologists, geologists, and environmental scientists studying karst regions, ore geology and carbonate reservoirs of hydrocarbons. It will also be useful for students of the respective disciplines, and for all those interested in the nature of the Crimean Piedmont.

Analysis of "standard" (Lipica) lemestone tablets and their weathering by carbonate staining and SEM imaging, a case study on the Vis island, Croatia, 2013,
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Krklec Kristina, Marjanac Tihomir, Perica Dražen

This paper focuses on the evolution and patterns of microscale weathering forms and dissolution rates of “standard” (Lipica) limestone tablets. Analysis of carbonate weathering using combination of methods (quantitative analysis by the weight loss of "standard" tablets, and qualitative analysis of the weathered surfaces by stained acetate peels and SEM imaging) showed that dissolution takes place not only at the surface of limestone tablets, but also along voids and cavities in limestone tablets which makes total weathering surface larger than the area of the tablet surface. Dissolution is more pronounced on the micritic calcite surfaces (due to different dissolution kinetics of carbonate minerals), resulting in lowering of the surface (calcite matrix) which causes gradual unburial and removal of authigenic dolomite grains.


Using hydrogeochemical and ecohydrologic responses to understand epikarst process in semi-arid systems, Edwards plateau, Texas, USA, 2013,
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Schwartz Benjamin F. , Schwinning Susanne, Gerrard Brett, Kukowski Kelly R. , Stinson Chasity L. , Dammeyer Heather C.

The epikarst is a permeable boundary between surface and subsurface environments and can be conceptualized as the vadose critical zone of epigenic karst systems which have not developed under insoluble cover. From a hydrologic perspective, this boundary is often thought of as being permeable in one direction only (down), but connectivity between the flow paths of water through the epikarst and the root systems of woody plants means that water moves both up and down across the epikarst. However, the dynamics of these flows are complex and highly dependent on variability in the spatial structure of the epikarst, vegetation characteristics, as well as temporal variability in precipitation and evaporative demand. Here we summarize insights gained from working at several sites on the Edwards Plateau of Central Texas, combining isotopic, hydrogeochemical, and ecophysiological methodologies. 1) Dense woodland vegetation at sites with thin to absent soils (0-30 cm) is in part supported by water uptake from the epikarst. 2) However, tree transpiration typically becomes water-limited in dry summers, suggesting that the plant-available fraction of stored water in the epikarst depletes quickly, even when sustained cave drip rates indicate that water is still present in the epikarst. 3) Flow paths for water that feeds cave drips become rapidly disconnected from the evaporation zone of the epikarst and out of reach for plant roots. 4) Deep infiltration and recharge does not occur in these systems without heavy or continuous precipitation that exceeds some threshold value. Thresholds are strongly correlated with antecedent potential evapotranspiration and rainfall, suggesting control by the moisture status of the epikarst evapotranspiration zone. The epikarst and unsaturated zone in this region can be conceptualized as a variably saturated system with storage in fractures, matrix porosity, and in shallow perched aquifers, most of which is inaccessible to the root systems of trees, although woody vegetation may control recharge thresholds.


The view of Maya cave ritual from the Overlook Rockshelter, Caves Branch River Valley, Central Belize, 2013,
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Wrobel G. D. , Shelton R. , Morton S. , Lynch J. , Andres C.

Archaeological investigations of the Overlook Rockshelter in the Caves Branch River Valley of central Belize offer a unique view of ancient Maya cave ritual through the complete recovery and analysis of all artifacts within the site’s two small activity areas. In general, the assemblage contains many of the same types of objects documented from other nearby caves and rockshelters. However, the nearly 1700 ceramics sherds showed almost no refits, demonstrating that sherds were deposited at the site individually, rather than as complete vessels. The human bone assemblage represents three or four individuals, with the majority of the bones comprising a single individual, and all of these were deposited as incomplete secondary interments. Analogies for this depositional behavior based on archaeological and ethnographic studies suggest that this rockshelter may represent a waypoint within a ritual circuit composed of multiple locations over which fragments of complete items such as ceramic vessels and secondary burials were spread.  

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Fingerprinting water-rock interaction in hypogene speleogenesis: potential and limitations of isotopic depth-profiling, 2014,
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Spötl Ch, Dublyansky Y.

Dissolution processes in karst regions commonly involve (meteoric) water whose stable isotopic (O, H, C) composition is distinctly different from that of the paleowaters from which the host rock (limestone, dolostone) formed. This, in theory, should lead to isotopic alteration of the host rock beyond the active solution surface as the modern karst water is out of isotopic equilibrium with the carbonate rock. No such alteration has been reported, however, in epigenetic karst systems. In contrast, isotopic alteration, commonly referred to as isotopic halos or fronts, are known from various hypogene systems (ore deposits, active hydro­thermal systems, etc.). These empirical observations suggest that stable isotope data may be a diagnostic tool to identify hypogene water-rock interactions particularly in cave systems whose origin is ambiguous.

We have been testing the applicability of this assumption to karst settings by studying the isotopic composition of carbonate host rocks in a variety of caves showing clear-cut hypogene morphologies. Cores drilled into the walls of cave chambers and galleries were stud­ied petrographically and the C and O isotope composition was analyzed along these cores, which typically reached a depth of 0.5 to 1.2 m. We identified three scenarios: (a) no isotopic alteration, (b) a sigmoidal isotope front within a few centimeters of the cave wall, and (c) pervasive isotope alteration throughout the entire core length. Type (a) was found in caves where the rate of cave wall retreat apparently outpaced the rate of isotopic alteration of the wall rock (which is typical, for example, for sulfuric acid speleogenesis). Type (c) was observed in geologically young, porous limestone showing evidence of alteration zones up to 5 m wide. The intermediate type (b) was identified in hypogene karst cavities developed in tight limestone, dolostone and marble.

Our data in conjunction with evidence from speleothems and their geochemical and fluid-inclusion composition suggest that the spa­tial extent of the isotopic alteration front depends on the porosity and permeability, as well as on the saturation state of the water. Wider alteration zones primarily reflect a higher permeability. Shifts are most distinct for oxygen isotopes and less so for carbon, whereby the amplitude depends on a number of variables, including the isotopic composition of unaltered host rock, the isotopic composition of the paleofluid, the temperature, the water/rock ratio, the surface of water-rock contact, the permeability of the rock, and the time available for isotope exchange. If the other parameters can be reasonably constrained, then semi-quantitative temperature estimates of the paleowater can be obtained assuming isotopic equilibrium conditions.

If preserved (scenarios b and c), alteration fronts are a strong evidence of hypogene speleogenesis, and, in conjunction with hypogene precipitates, allow to fingerprint the isotopic and physical parameters of the altering paleofluid. The reverse conclusion is not valid, however; i.e. the lack of evidence of isotopic alteration of the cave wall rock cannot be used to rule out hypogene paleo-water-rock interaction.


BAHAMIAN CAVES AND BLUE HOLES: EXQUISITELY PRESERVED FOSSIL ASSEMBLAGES AND TAPHONOMIC INFLUENCES, 2014,
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Albury N. A. , Mylroie J. E.

In The Bahamas, caves and blue holes provide clues to the geologic and climatic history of archipelago but are now emerging as windows into the ecological and cultural past of islands. Cave environments in The Bahamas alternate cyclically between vadose and phreatic conditions with sea-level change, thereby providing unique but ephemeral fossil capture and preservation conditions.

A diverse assemblage of fossil plants and animals from Sawmill Sink, an inland blue hole on Abaco Island in the northern Bahamas, has revealed a prehistoric terrestrial ecosystem with exquisitely preserved fossil assemblages that result from an unusual depositional setting. The entrance is situated in the pine forest and opens into a flooded collapse chamber that intersects horizontal conduits at depths to 54 meters. The deepest passages are filled with sea water up to an anoxic mixing zone at depths of 14 to 9 meters and into the upper surface fresh-water layer. The collapse chamber is partially filled with a large talus pile that coincides with an anoxic halocline and direct sunlight for much of the day.

During glacioeustatic sea-level lowstands in the late Pleistocene, Sawmill Sink was a dry cave, providing roosting sites for bats and owls. Accumulations of bones deposited in depths of 25 to 30 meters were subsequently preserved by sea-level rise in the Holocene. The owl roost deposits are dominated by birds but also include numerous small vertebrate species that were actively transported by owls to the roost sites.

As sea levels rose in the Holocene, Sawmill Sink became a traditional passive pitfall trap. Significant quantities of surface derived organic material collected on the upper regions of the talus at the halocline where decaying plant material produced a dense layer of peat within an anoxic mixing zone enriched with hydrogen sulfide. Vertebrate species that drowned were entombed in the peat, where conditions inhibited large scavengers, microbial decomposition, and mechanical disarticulation, contributing to the superb preserva­tion of the fossil assemblage in the upper regions of the talus.


HYPOGENE VS EPIGENE CAVES: THE SULFUR AND OXYGEN ISOTOPE FINGERPRINT, 2014,
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Onac, B. P.

The classical epigene speleogenetic model in which CO2 is considered the main source of acidity has been challenged over the last three decades by observations that revealed cave passages unrelated to groundwater drainage routes and surface topography. Most of these passages show unusual morphologies, such are cupolas, floor feeders (i.e., inlets for deep-seated fluids), and huge irregular-shaped rooms that terminate abruptly, and often a rich and diverse mineral association. A hypogenetic speleogenetic pathway was proposed for this group of caves.
The presence of abundant gypsum deposits in caves with one or more of the passage morphologies listed above, have prompted scientists to suggest a new theory (i.e., sulfuric acid speleogenesis, SAS) of cave development. In the hypogenic SAS model, the source of acidity is the sulfuric acid produced by oxidation of H2S (originating from sulfate reduction or petroleum reservoirs) near or at the water table, where it dissolves the limestone bedrock and precipitates extensive gypsum deposits. SAS is now thoroughly documented from numerous caves around the world, with the best examples coming from the Guadalupe Mountains (NM), Frasassi caves (Italy), selected caves in France, Cueva de Villa Luz (Mexico), and Cerna Valley (SW Romania).
To date, discrimination between epigene and hypogene speleogenetic pathways is made using cave morphology criteria, exotic mineral assemblages, and the predominantly negative δ34S values for the cave sulfates. This presentation highlights the role sulfur and oxygen stable isotope analyses have in discriminating between epigene and hypogene caves.
Based on a number of case studies in caves of the Cerna Valley (Romania), we found that relatively S-depleted isotopic composition of cave minerals alone does not provide enough information to clearly distinguish SAS from other complex speleogenetic pathways. In fact, δ34S values of SAS by-products depend not only on the source of the S, but also on the completeness of S redox reactions. Therefore, similar studies to this are needed to precisely diagnose SAS and to provide information on the S cycle in a given karst system.
Integrating cave mineralogy, passage morphology, and geochemical studies may shed light on the interpretation of polygenetic caves, offering clues to processes, mechanisms, and parameters involved in their genesis (sulfate-dominated).


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