MWH Global

Enviroscan Ukrainian Institute of Speleology and Karstology

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 water resources is the total supply of surface, ground, and reclaimed water that can be used [16].?

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 layers (Keyword) returned 184 results for the whole karstbase:
Showing 16 to 30 of 184
Le massif de la Chartreuse, Alpes franaises du Nord : paysages karstiques et organisation des rseaux souterrains, 1990, Lismonde B. , Delannoy J. J.
The massif of Chartreuse: karsts features and underground systems (Alps, France) - The Chartreuse massif is the smallest of the subalpine massifs, but it contains the most important underground systems of French Alps. The massif of Chartreuse is characterised by parallel folds directed N020. The eastern plateau spreads out urgonian limestone (perched syncline); it contains the two largest cave systems: "Alpe-Alpette" (54 km) and "Dent de Crolles" (54 km). To the W, the limestone layers are uplifted by the orogenic strains and thereby, the caves are very deep: "rseau Ded" (- 780m), "puits Francis" (- 723m), "gouffre de Gnieux" (- 675m). Two transverse rivers make the hydrologic drainage: the "Guiers Vif" and the "Guiers Mort", which cut up the region into small hydrological basins. The greatest of them is "Guiers Vif" basin, with an area of 9.2 km2.

MINERALOGICAL AND SEDIMENTOLOGICAL INVESTIGATIONS OF A KARST FILLING IN THE COTENCHER CAVE (NEUCHATEL, JURA MOUNTAINS, SWITZERLAND), 1991, Adatte T, Rentzel P, Kubler B,
Mineralogical and sedimentological investigations were carried out on a karst filling located in the Cotencher cave (Neuchatel, Jura mountains, Switzerland). Radiometric and archeological dating give evidence for a rather incomplete record of the climatic history of the last glacial period. The major hiatus is situated in the younger Wurmian Pleniglacial age. Following the mineralogical and sedimentological results, it is possible to divide this profile in three parts. Late glacial and holocene sediments are characterized by fine morainic material, redeposited due to karst activity. The middle part (C-14: > 40 Ky BP), directly located below this hiatus shows a typical mineralogical association with the appearance of kaolinite and the persistance of the amphibole. This association is thought to be of eolian origin, older than the one described on the Jura mountains actual soils. This eolian sediment component was deposited after the early Wurmian Pleniglacial period. on the soils in the vicinity of the cave, and resedimented into the cave during the Wurmian Interpleniglacial. The lower part of the sediment column is characterized by a mineralogical association of kaolinite, mixed-layers and mica. Especially high amounts of kaolinite, possibly derived from old, probably Eemian mature soils give evidence for relatively warm climate with strong seasonal variations

SMALL-SCALE RETROSPECTIVE GROUND-WATER MONITORING STUDY FOR SIMAZINE IN DIFFERENT HYDROGEOLOGICAL SETTINGS, 1991, Roux P. H. , Hall R. L. , Ross R. H. ,
A ground water monitoring study was conducted for the triazine herbicide simazine at 11 sites in the United States. The study used carefully selected, small-scale sites (average size: about 33 acres) with documented product use and sensitive hydrogeological settings. The sites selected were Tulare County, California (two sites); Fresno County, California; Sussex County, Delaware; Hardee and Palm Beach counties, Florida; Winnebago County, Illinois; Jackson County, Indiana; Van Buren and Berrien counties, Michigan; and Jefferson County, West Virginia. These sites satisfied the following criteria: a history of simazine use, including the year prior to the start of the study; permeable soil and vadose zone; shallow depth to water; no restrictive soil layers above the water table; and gentle slopes not exceeding 2 percent. A variety of crop types, climates, and irrigation practices were included. Monitoring well clusters (shallow and deep) were installed at each site except in California and West Virginia, where only shallow wells were installed. Simazine was monitored at these sites at quarterly intervals for a two-year period during 1986-1988. The results of the study showed that out of 153 samples analyzed, 45 samples showed simazine detections. A substantial majority of the detections (32 out of 45) occurred in Tulare, Fresno, and Jefferson counties. The detections in these areas were attributed to mechanisms other than leaching, such as drainage wells, karst areas, surface water recharge, or point source problems. An additional 11 detections in Van Buren County were apparently due to an unknown upgradient source. Only one detection (in Palm Beach County, Florida) near the screening level of 0.1 ppb was attributed to possible leaching. The results of this investigation support the hypothesis that simazine does not leach significantly under field use conditions

Les mouvements tectoniques rcents dans les grottes du Monte Campo dei Fiori (Lombardie, Italie), 1992, Bini A. , Quinif Y. , Sules O. , Uggeri A.
Recent tectonic movements have been studied in the caves of Monte Campo dei Fiori in Lombardy (Italy). These develop in limestones and dolomites ranging from the Lower Trias to the Lower Lias. In the Frassino cave, movements can be observed along the layers (shifts in galleries) as well as speleothems that have been broken and displaced. U/Th datings of speleothems indicate ages of more 350.000 years. Karstification therefore preceded neotectonic movements. On the whole, observations point out an increasing folding of the syncline of the Varese Lake, together with an uplift of the neighbouring anticlines.

DISSOLUTION OF ARAGONITE-STRONTIANITE SOLID-SOLUTIONS IN NONSTOICHIOMETRIC SR(HCO3)2-CA(HCO3)2-CO2-H2O SOLUTIONS, 1992, Plummer L. N. , Busenberg E. , Glynn P. D. , Blum A. E. ,
Synthetic strontianite-aragonite solid-solution minerals were dissolved in CO2-saturated nonstoichiometric solutions of Sr(HCO3)2 and Ca(HCO3)2 at 25-degrees-C. The results show that none of the dissolution reactions reach thermodynamic equilibrium. Congruent dissolution in Ca(HCO3)2 solutions either attains or closely approaches stoichiometric saturation with respect to the dissolving solid. In Sr(HCO3)2 solutions the reactions usually become incongruent, precipitating a Sr-rich phase before reaching stoichiometric saturation. Dissolution of mechanical mixtures of solids approaches stoichiometric saturation with respect to the least stable solid in the mixture. Surface uptake from subsaturated bulk solutions was observed in the initial minutes of dissolution. This surficial phase is 0-10 atomic layers thick in Sr(HCO3)2 solutions and 0-4 layers thick in Ca(HCO3)2 solutions, and subsequently dissolves and/or recrystallizes, usually within 6 min of reaction. The initial transient surface precipitation (recrystallization) process is followed by congruent dissolution of the original solid which proceeds to stoichiometric saturation, or until the precipitation of a more stable Sr-rich solid. The compositions of secondary precipitates do not correspond to thermodynamic equilibrium or stoichiometric saturation states. X-ray photoelectron spectroscopy (XPS) measurements indicate the formation of solid solutions on surfaces of aragonite and strontianite single crystals immersed in Sr(HCO3)2 and Ca(HCO3)2 solutions, respectively. In Sr(HCO3)2 solutions, the XPS signal from the outer approximately 60 angstrom on aragonite indicates a composition of 16 mol% SrCO3 after only 2 min of contact, and 14-18 mol% SrCO3 after 3 weeks of contact. The strontianite surface averages approximately 22 mol% CaCO3 after 2 min of contact with Ca(HCO3)2 solution, and is 34-39 mol% CaCO3 after 3 weeks of contact. XPS analysis suggests the surface composition is zoned with somewhat greater enrichment in the outer approximately 25 angstrom (as much as 26 mol% SrCO3 on aragonite and 44 mol% CaCO3 on strontianite). The results indicate rapid formation of a solid-solution surface phase from subsaturated aqueous solutions. The surface phase continually adjusts in composition in response to changes in composition of the bulk fluid as net dissolution proceeds. Dissolution rates of the endmembers are greatly reduced in nonstoichiometric solutions relative to dissolution rates observed in stoichiometric solutions. All solids dissolve more slowly in solutions spiked with the least soluble component ((Sr(HCO3)2) than in solutions spiked with the more soluble component (Ca(HCO3)2), an effect that becomes increasingly significant as stoichiometric saturation is approached. It is proposed that the formation of a nonstoichiometric surface reactive zone significantly decreases dissolution rates

DISLOCATION OF THE EVAPORITIC FORMATIONS UNDER TECTONIC AND DISSOLUTION CONTROLS - THE MODEL OF THE DINANTIAN EVAPORITES FROM VARISCAN AREA (NORTHERN FRANCE AND BELGIUM), 1993, Rouchy J. M. , Groessens E. , Laumondais A. ,
Within the Franco-Belgian segment of the Hercynian orogen, two thick Dinantian anhydritic formations are known, respectively in the Saint-Ghislain (765 m) and Epinoy 1 (904 m) wells. Nevertheless, occurrences of widespread extended breccias and of numerous pseudomorphs of gypsum/anhydrite in stratigraphically equivalent carbonate deposits (boreholes and outcrops), suggest a larger extent of the evaporitic conditions (fig. 1, 2). The present distribution of evaporites is controlled by palaeogeographical differentiation and post-depositional parameters such as tectonics and dissolution. These latter have dissected the deposits formerly present in all the structural units. By using depositional, diagenetic and deformational characters of these formations, the article provides a model for the reconstruction of a dislocated evaporitic basin. This segment of the Hercynian chain is schematically composed of two main units (fig. 1, 3) : (1) the autochthonous or parautochthonous deposits of the Namur synclinorium, (2) the Dinant nappe thrusted northward over the synclinorium of Namur. The major thrust surface is underlined by a complex fault bundle (faille du Midi) seismically recognized over more than 100 km. A complex system of thrust slices occurs at the Hercynian front. Except for local Cretaceous deposits, most of the studied area has been submitted to a long period of denudation since the Permian. Sedimentary, faunistic and geochemical data argue for a marine origin of the brines which have generated the evaporites interbedded with marine limestones. Sedimentary structures. - The thick evaporitic formations are composed of calcium-sulfates without any clear evidence of the former presence of more soluble salts (with the exception of a possible carbonate-sulfate breccia in the upper part of the Saint-Ghislain formation). As in all the deeply buried evaporitic formations, the anhydrite is the main sulfate component which displays all the usual facies : pseudomorphs after gypsum (fig. 4A, B), nodular and mosaic (fig. 4C), laminated. The gypsum was probably an important component during the depositional phase despite the predominant nodular pattern of the anhydrite. Early diagenetic nodular anhydrite may have grown during temporary emersion of the carbonates (sabkha environments), but this mechanism cannot explain the formation of the whole anhydrite. So, most of the anhydrite structures result from burial-controlled gypsum --> anhydrite conversion and from mechanical deformations. Moreover, a complex set of diagenetic processes leads to various authigenic minerals (celestite, fluorite, albite, native sulfur, quartz and fibrous silica) and to multistaged carbonate <> sulfate replacements (calcite and dolomite after sulfate, replacive anhydrite as idiomorphic poeciloblasts, veinlets, domino-like or stairstep monocrystals...). These mineral transformations observed ill boreholes and in outcrops have diversely been controlled during the complex evolution of the series as : depositional and diagenetic pore-fluid composition, pressure and temperature changes with burial, bacterial and thermochemical sulfate reduction, deep circulations favored by mechanical brecciation, mechanical stresses, role of groundwater during exhumation of the series. Deformational structures. - A great variety of deformational structures as rotational elongation, stretching, lamination, isoclinal microfolding, augen-like and mylonitic structures are generated by compressive tectonic stresses (fig. 4D to J). The similarities between tectonic-generated structures and sedimentary (lamination) or diagenetic (pseudo-nodules) features could lead lo misinterpretations. The calcareous interbeds have undergone brittle deformation the style and the importance of which depend of their relative thickness. Stretching, boudins, microfolds and augen structures F, H. I) affect the thin layers while thicker beds may be broken as large fractured blocks dragged within flown anhydrite leading to a mylonitic-like structure (fig, 4G). In such an inhomogeneous formation made of interlayered ductile (anhydrite) and brittle (carbonate) beds, the style and the intensity of the deformation vary with respect to the relative thickness of each of these components. Such deformational features of anhydrite may have an ubiquitous significance and can result either from compressive constraints or geostatic movements (halokinesis). Nevertheless, some data evidence a relation with regional tangential stresses: (1) increase of the deformation toward the bottom of the Saint-Ghislain Formation which is marked by a deep karst suggesting the presence of a mechanical discontinuity used as a drain for dissolving solutions (fig. 3, 4); (2) structural setting (reversed series, internal slidings) of the Epinoy 1 formation under the Midi thrust. However, tectonic stresses also induce flowing deformations which have contributed to cause their present discontinuity. It can be assumed that the evaporites played an active role for the buckling of the regional structure as detachment or gliding layers and more specifically for the genesis of duplex structures. Breccia genesis. - Great breccia horizons are widely distributed in outcrops as well as in the subsurface throughout the greater part of the Dinant and Namur units (fig. 2). The wide distribution of pseudomorphosed sulfates in outcrops and the stratigraphical correlation between breccia and Saint-Ghislain evaporitic masses (fig. 2) suggest that some breccia (although not all) have been originated from collapse after evaporites solution. Although some breccia may result from synsedimentary dissolution, studied occurrences show that most of dissolution processes started after the Hercynian deformation and, in some cases, were active until recently : elements made of lithified and fractured limestones (Llandelies quarries) (fig. 5A), preservation of pseudomorphs of late replacive anhydrite (Yves-Gomezee) (fig. 5B, C), deep karst associated with breccia (Douvrain, Saint Ghislain, Ghlin boreholes) (fig. 3, 4, 5D)). Locally, the final brecciation may have been favored by a mechanical fragmentation which controlled water circulations (fig. 5E). As postulated by De Magnee et al. [19861, the dissolution started mostly after the Permian denudation and continued until now in relation with deep circulations and surface weathering (fig. 6). So, the above-mentioned occurrences of the breccia are logically explained by collapse after dissolution of calcium-sulfates interbeds of significant thickness (the presence of salt is not yet demonstrated), but other Visean breccia may have a different origin (fig. 5F). So, these data prove the extension of thick evaporitic beds in all the structural units including the Dinant nappe, before dissolution and deformation. Implications. - Distribution of Visean evaporites in northern France and Belgium is inherited from a complicated paleogeographic, tectonic and post-tectonic history which has strongly modified their former facies, thicknesses and limits (fig. IA, 6). Diversified environments of deposition controlled by both a palaeogeographical differentiation and water level fluctuations led to the deposition of subaqueous (gypsum) or interstitial (gypsum, anhydrite) crystallization. Nevertheless, most of the anhydrite structures can be interpreted as resulting from burial conversion of gypsum to anhydrite rather than a generalized early diagenesis in sabkha-like conditions. Deformation of anhydrite caused by Hercynian tangential stresses and subsequent flow mechanisms, have completed the destruction of depositional and diagenetic features. The tectonic deformations allow us to consider the role of the evaporites in the Hercynian deformations. The evaporites supplied detachment and gliding planes as suggested for the base of the Saint-Ghislain Formation and demonstrated by the structural setting of Epinoy 1 evaporites in reverse position and in a multi-system of thrust-slices below the Midi overthrust (fig. 7). So, although the area in which evaporation and precipitation took place cannot be exactly delineated in geographic extent, all the data evidence that the isolated thick anhydritic deposits represent relics of more widespread evaporites extending more or less throughout the different structural units of this Hercynian segment (fig. 1B). Their present discontinuity results from the combination of a depositional differentiation, mechanical deformations and/or dissolution

GEOMORPHOLOGY AND HYDROLOGY OF UPPER SINKING COVE, CUMBERLAND PLATEAU, TENNESSEE, 1993, Davis Jd, Brook Ga,
Upper Sinking Cove, dissecting the eastern escarpment of the Cumberland Plateau, is characterized by a multiple aquifer, predominantly vadose hydrologic system with minor surface components. There is a central trunk channel along the axis of the cove and a network of independent tributaries. Aquitards within the limestones, particularly Hartselle Formation shales, have influenced both cave and surface landform development by perching ground waters and slowing the vertical growth of closed depressions. Long-term solutional denudation in the portion of the cove underlain by limestones (40 per cent) is an estimated 56 mm per 1000 years, suggesting that karst development began 15-16 million years ago. Despite lower soil CO2 and spring water hardness, 61 per cent of annual denudation occurs in the six winter months when 76 per cent of yearly runoff occurs. Landform development in Upper Sinking Cove appears to have begun as stream erosion carved a valley first in the sandstone caprock of the escarpment and later in the underlying Pennington Formation limestones containing numerous shale layers which promoted surface stream flow. Eventually stream erosion exposed the massive Bangor limestones which allowed deep ground water flow. Surface streams were pirated underground with the eventual formation of the chain of three closed depressions which constitute Upper Sinking Cove

THE CATCHMENT-AREA OF THE SV-IVAN-KARST SPRING IN ISTRIA (CROATIA), 1993, Bonacci O, Magdalenic A,
This paper discusses the results of a geological, hydrogeological, and hydrological analysis of the catchment boundaries and area of the Sv. Ivan karst spring. The underground watershed has been determined by geological and hydrogeological methods. The control used was the hydrologic water budget analysis appropriate for karst basins with limited data (Turc, 1954). The Sv. Ivan spring includes one main spring and several intermittent springs. The water in the main spring penetrates the flysch layers which limit the spring's discharge; therefore, the discharge of the main spring is fairly uniform. The ratio between minimum and maximum yearly discharges ranges from 1:3.3 to 1:12.8. Only a part of the water flows through the main spring while the other springs in the zone are overflows. The catchment area of Sv. Ivan spring zone is defined as 65 km2

HOLOCENE MARINE CEMENT COATINGS ON BEACH-ROCKS OF THE ABU-DHABI COASTLINE (UAE) - ANALOGS FOR CEMENT FABRICS IN ANCIENT LIMESTONES, 1994, Kendall C. G. S. , Sadd J. L. , Alsharhan A. ,
Marine carbonate cements, which are superficially like travertines from meteoric caves, are coating and binding some intertidal sedimentary rock surfaces occurring in coastal Abu Dhabi, the United Arab Emirates, (UAE). Near Jebel Dhana these surficial cements can be up to 3 cm thick and envelope beach rock surfaces and fossils. They are also present both as thin coats and a fracture-fill cement in the intertidal hard grounds associated with the Khor Al Bazam algal flats. The thickness, microscopic characteristics, and morphology of the marine cement coatings from Jebel Dhana indicates incremental deposition of aragonite in conjunction with traces of sulfate minerals. Most of these cement coatings are micritic, but the layers which encrust the hard grounds from the algae flat of the Khor al Bazam have a more radial and fibrous micro-structure and are composed solely of aragonite. The stable isotopic composition of coatings from Jebel Dhana (delta(18)O = .35, delta(13)C = .00) falls within the compositional range for modem marine non skeletal aragonite and suggests that the marine travertine-like cements precipitate from the agitated slightly hypersaline Arabian Gulf sea water during repeated cycles of exposure, evaporation and immersion. Similar cement coatings and microfabrics are present in the tepee structured and brecciated sediments of the Guadalupe Mountains (Permian) and the Italian Alps (Triassic), in Holocene algal head cements from the Great Salt Lace, and in similar Tertiary algal heads in the Green River Formation of the western US. The petrographic similarity of these ancient ''flow stone'' like cements with Recent hypersaline marine cement coatings suggests that high rates of carbonate cementation and hypersaline conditions contribute to tepee formation and cavity fill

RELATION OF MINERALIZATION TO WALL-ROCK ALTERATION AND BRECCIATION, MASCOT JEFFERSON-CITY MISSISSIPPI-VALLEY-TYPE DISTRICT, TENNESSEE, 1994, Haynes F. M. , Keslr S. E. ,
This study was undertaken to assess the relation of Mississippi Valley-type mineralization to wall-rock alteration and brecciation in the Mascot-Jefferson City district, the largest part of the East Tennessee Mississippi Valley-type ore field. The main question of interest was whether the Mississippi Valley-type-forming brines created or greatly enlarged the breccia system that hosts the ore or whether the breccia system was a preexisting paleoaquifer that simply controlled movement of the mineralizing brines. A secondary, and closely related, question was whether brine-wall rock interaction deposited Mississippi Valley-type ore. The breccia system that hosts the East Tennessee ore field began as karst breccias which formed in the upper part of the Late Cambrian-Early Ordovician Knox Group during Middle Ordovician emergence. Brecciation, which was most common at the paleosurface and in a limestone-rich zone about 200 m below the surface, took place when limestone solution caused collapse of primary dolostone layers. Mississippi Valley-type mineralization, consisting of sphalerite and sparry dolomite, fills interstices in the breccias that formed in the limestone-rich part of the Knox Group. Ore is associated with ''recrystalline dolomite'' that replaced limestone and there is an inverse correlation between the original limestone and sphalerite abundance suggesting that the ore-forming fluids reacted strongly with limestone wall rock, possibly dissolving it where alteration was most intense. The assessment of a relation between alteration and Mississippi Valley-type mineralization was based on 3,533 surface drill holes covering the 110-km2 Mascot-Jefferson City district, each of which provided stratigraphic data and quantified estimates of mineralization intensity and alteration intensity. These data show clearly that as much as 50 percent of the limestone in the mineralized breccia section was lost over enormous areas that extend far beyond significant mineralization. The intensity of this effect clearly decreases downdip (toward the east), away from the probable source of meteoric karst-forming waters. These relations, combined with isotopic analyses and reaction path calculations, suggest that breccia formation and limestone dissolution took place during the original karst breccia formation. In contrast, later Mississippi Valley-type mineralization was associated with replacement of limestone by recrystalline dolomite. The main effect of dolomitization on the chemistry of the Mississippi Valley-type brines, an increase in their Ca/Mg ratio, would not cause sulfide precipitation. Thus, it appears unlikely that Mississippi Valley-type-forming brines created much of their ore-hosting breccias or that water-rock interaction was a major cause of Mississippi Valley-type ore deposition

Environmental controls on the petrology of a late Holocene speleothem from Botswana with annual layers of aragonite and calcite, 1994, Railsback L. Bruce, Brook George A. , Chen Jian, Kalin Robert, Fleisher Christopher J. ,

THE ORIGIN OF RAUHWACKES (CORNIEULES) BY THE KARSTIFICATION OF GYPSUM, 1995, Schaad W. ,
Rauhwackes (cornieules or cargneules) are breccias with a caicareous matrix and mainly dolomitic components that weather to form cavernous rocks. They are very often associated with tectonic contacts, e.g. detachment horizons. The origin of rauhwackes is still controversial, but has been attributed to the weathering and alteration of dolomite-bearing evaporites, the tectonisation of dolomites or other processes. New data based on field investigations show that the karstification of evaporites leads to the formation of rauhwackes. Two end member evaporitic protoliths can be distinguished: dolomite-bearing gypsum and gypsum-bearing dolomite. The karstification of the different protoliths leads to the formation of structurally distinct rauhwackes. Dolomite-bearing gypsum is associated with unstructured, often polymictic rauhwackes which reflect the shape of the karst cavities and which are interpreted as karst sediments. Gypsum-bearing dolomite occurs with stratiformal rauhwackes with fitting dolomite fragments that are arranged in layers. These rauhwackes can be regarded as collapse breccias. All investigated rauhwackes seem to have been formed after the alpine deformations and are probably of Quaternary age. In certain cases, the karstification of the evaporites and the formation of rauhwackes may have been favoured by fluvial or fluvioglacial processes at the surface. Therefore, these rauhwackes have nothing to do with alpine tectonics. Rather, it was the evaporitic protoliths of the rauhwackes that acted as detachment horizons and incompetent layers during folding

OCCURRENCE OF HYPOGENIC CAVES IN A KARST REGION - EXAMPLES FROM CENTRAL ITALY, 1995, Galdenzi S, Menichetti M,
The caves of the Umbria and Marche regions in central Italy are made up of three-dimensional maze systems that display different general morphologies due to the various geological and structural contexts. At the same time, the internal morphologies of the passages, galleries, and shafts present some similarity, with solutional galleries characterized by cupolas and blind pits, anastamotic passages, roof pendants, and phreatic passages situated at different levels. Some of these caves are still active, as is the case for Frassassi Gorge, Parrano Gorge, and Acquasanta Terme, with galleries that reach the phreatic zone, where there is a rising of highly mineralized water, rich in hydrosulfydric acid, and with erosion of limestone walls and the formation of gypsum. Elsewhere there are fossil caves, such as Monte Cucco and Pozzi della Piana, where large speleothems of gypsum are present 500 m or more above the regional water table. In all of these important karst systems it is possible to recognize basal input points through fracture and intergranular porosity networks at the base of the oxidizing zone in the core of the anticline, where mineralized water rises up from the Triassic evaporitic layers in small hydrogeological circuits. Different underground morphologies can derive from the presence of a water table related to an external stream or from the confined setting of the carbonate rocks, underlying low permeable sedimentary cover, where artesian conditions can occur

Contribution to geomorphological and hydrogeological study of karst in Mediterranean environment: the Aït Abdi plateau (central limestone High Atlas, Maroc),PhD thesis, 1995, Perritaz, L.

The Ait Abdi karstic plateau is located in the heart of the calcareous High Atlas (32°N/6°W). With an area of 160 km2, it is situated between 2,200 and 3,000 meters above sea level, i.e. 800 meters above the nearest valleys and canyons. It consists of a large series of massive Bajocian limestones which form a large brachysyncline, the axial plane of which dips gently to the NE. These limestones overlie a thick series of Toarcian-Aalenian detritic sediments forming the regional aquiclude and the top of the half captive Middle Liasic aquifer. The plateau is limited both in the N and S by strong changes in dip to the vertical of the sedimentary layers (ejective thrusted anticlines), and in the W and E by deep canyons created by major rivers. Therefore the plateau is a totally isolated calcareous compartment, from both a morphologic and a hydrogeologic point of view.
The climate of this region is Mediterranean with an altitude modification: maximum rainfall occurs in winter and in spring, snow cover is not durable but sometimes important, storms are common for dry season in summer. The precipitations comprise only 500 to 700 mm/year (subhumide zone) and the effective evapotranspiration is approximately 400 mm/year, including the losses due to sublimation. The snow coefficient is 60 %. This means that the recharge of the aquifer, occurring almost entirely during snow melting, is limited, but the large bare surfaces of the plateau with typical well developed karst forms (dolines, poljes, dry valleys, holes) improve the infiltration rate (40%). The specific discharge is only 8.1 L/s/km2.
The morphologic peculiarity of this nival karst consist of a succession of small parallel and asymmetric dry valleys forming some "waves". For that reason, the French geomorphologist Couvreur termed these climate controlled features "karst en vagues". The role of wind and snow in the genesis of these forms is predominant. The most of time structure controlled plateau's poljes are quasi inactive today. All kinds of high mountain karren landforms are present on the plateau and prove the great role of snow role in the microforms genesis.
An ancient speleological network with vertical shafts occluded lower down suggest of ancient more humid climatic conditions. U-Th dating indicates ages between 3,200 and 220,000 years, or outside the range of the method (more than 400,000 years). The lateral flow is conducted by an interstrata network, inactive and dry in the upper part, or active and phreatic at the base, near the regional aquiclude, attesting three karstification phases.
The water discharges as typically karstic hillfoot springs, most of the time oversaturated and forming tufas. Large doleritic vertical dykes cut the plateau and form major drainpipes. The physical-chemical and chemical signature of these spring waters is quite different of the signature of other springs of this area, which discharge whether from small local Toarcian-Aalenian aquifers or from the huge semi confined karstic Middle Liasic aquifer. The plateau springs hydrodynamic response is characteristic for an elevated karstic aquifer with rapid flow. The aquifer geometry does not allow important reserves, but the mean discharge from all perennial springs (about 1 m3/s) is a precious resource for the population of this far area of the Atlas Mountains.


High-resolution temporal record of Holocene ground-water chemistry; tracing links between climate and hydrology, 1996, Banner Jl, Musgrove M, Asmerom Y, Edwards Rl, Hoff Ja,
Strontium isotope analysis of precisely dated calcite growth layers in Holocene speleothems from Barbados, West Indies, reveals high-resolution temporal variations in ground-water composition and may provide a new approach to documenting the links between climate variability and fluctuations in the hydrologic cycle such as recharge rates and flow paths. The speleothems grew in a cave that developed in a fresh-water aquifer in uplifted Pleistocene reef limestones. Three periods of ground-water Sr isotope evolution are observed: 87 Sr/ 86 Sr values decreased from 6 to 4 ka, increased from 4 to 1 ka, and decreased again after 1 ka. The Sr isotope oscillations appear to record periodic variations in the relative Sr fluxes to ground water from exchangeable soil sites vs. carbonate mineral reactions, as reflected in 87 Sr/ 86 Sr values of modern Barbados ground waters. A hydrologic model that explains changes in ground-water flow routes in karst aquifers as a function of amount of rainfall recharge can account for the speleothem Sr isotope record. Independent Holocene climate records that indicate a major period of aridity at around 1.3-1.1 ka in the American tropics correspond with periodic variations in rainfall on Barbados that are predicted by this hydrologic model

Results 16 to 30 of 184
You probably didn't submit anything to search for