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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. ...

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That conformal mapping is the transposition and solution of plane flow problems in a complex plane [16].?

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Featured articles from Cave & Karst Science Journals
Chemistry and Karst, White, William B.
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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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Movements of Rhaphidophoridae (Orthoptera) In Caves At Waitomo, New Zealand, 1965, Richards, Aola M.

Cavernicolous Rhaphidophoridae are very active insects, in spite of their immobile appearance on the walls of caves. Movement is continuous to a greater or lesser degree throughout the 24 hour period of each day. Through marking a representative sample of the total adult population of two species of Rhaphidophoridae in limestone caves in New Zealand, it was shown that several different types of movement occurred; that home ranges had no well-defined limits; and that there was no evidence of territorial behaviour. The technique of marking Rhaphidophoridae is discussed in some detail.

A Check on the Radiocarbon Dating of Dessicated Thylacine (Marsupial "Wolf") and Dog Tissue From Thylacine Hole, Nullarbor Region, Western Australia, 1971, Merrilees, D.

A "modern" (180 + or - 76 years B.P.) radiocarbon date (N.S.W. 42) on dessicated rabbit flesh from Thylacine Hole (N63) suggests that dates N.S.W. 28c (4,650 + or - 153 radiocarbon years B.P.) on thylacine flesh and hair and N.S.W. 30 (2,200 + or - 96 radiocarbon years B.P.) on dog (dingo) flesh from the same cave are reliable within limits discussed.

Cave Location by Electrical Resistivity measurements: some misconceptions and the practical limits of detection, 1975, Myers J. O.

Karst Hydrogeology and Geomorphology of the Sierra de El Abra and the Valles-San Luis Potosí Region, México, PhD Thesis, 1977, Fish, Johnnie Edward

The general objective of this work was to develop a basic understanding of the karst hydrology, the nature and origin of the caves, the water chemistry, the surface geomorphology, and relationships among these aspects for a high relief tropical karst region having a thick section of limestone. The Valles-San Luis Potosí region of northeastern México, and in particular, the Sierra de El Abra, was selected for the study. A Cretaceous Platform approximately 200 km wide and 300 km long (N-S) delimits the region of interest. A thick Lower Cretaceous deposit of gypsum and anydrite, and probably surrounded by Lower Cretaceous limestone facies, is overlain by more than 1000 m of the thick-bedded middle Cretaceous El Abra limestone, which has a thick platform-margin reef. The Sierra de El Abra is a greatly elongated range along the eastern margin of the Platform. During the late Cretaceous, the region was covered by thick deposits of impermeable rocks. During the early Tertiary, the area was folded, uplifted, and subjected to erosion. A high relief karst having a wide variety of geomorphic forms controlled by climate and structure has developed. Rainfall in the region varies from 250-2500 mm and is strongly concentrated in the months June-October, when very large rainfalls often occur.
A number of specific investigations were made to meet the general objective given above, with special emphasis on those that provide information concerning the nature of ground-water flow systems in the region. Most of the runoff from the region passes through the karstic subsurface. Large portions of the region have no surface runoff whatsoever. The El Abra Formation is continuous over nearly the whole Platform, and it defines a region of very active ground-water circulation. Discharge from the aquifer occurs at a number of large and many small springs. Two of them, the Coy and the Frío springs group, are among the largest springs in the world with average discharges of approximately 24 m³/sec and 28 m³/sec respectively. Most of the dry season regional discharge is from a few large springs at low elevations along the eastern margin of the Platform. The flow systems give extremely dynamic responses to large precipitation events; floods at springs usually crest roughly one day after the causal rainfall and most springs have discharge variations (0max/0min) of 25-100 times. These facts indicate well-developed conduit flow systems.
The hydrochemical and hydrologic evidence in combination with the hydrogeologic setting demonstrate the existence of regional ground-water flow to several of the large eastern springs. Hydrochemical mixing-model calculations show that the amount of regional flow is at least 12 m³/sec, that it has an approximately constant flux, and that the local flow systems provide the extremely variable component of spring discharge. The chemical and physical properties of the springs are explained in terms of local and regional flow systems.
Local studies carried out in the Sierra de El Abra show that large conduits have developed, and that large fluctuations of the water table occur. The large fossil caves in the range were part of great deep phreatic flow systems which circulated at least 300 m below ancient water tables and which discharged onto ancient coastal plains much higher than the present one. The western margin swallet caves are of the floodwater type. The cave are structurally controlled.
Knowledge gained in this study should provide a basis for planning future research, and in particular for water resource development. The aquifer has great potential for water supply, but little of that potential is presently used.

Limits to common toppling, 1989, Cruden D. M.

Palaeoseismicity from karst sediments: the “Grotta del Cervo” cave case study (Central Italy), 1991, Postpischl D. , Agostini S. , Forti P. , Quinif Y. ,
Karst speleothems can be used for tectonic and palaeoseismic analyses; in particular, stalagmites can be treated as the records of a natural pendulum.Samples of stalagmites from the “Grotta del Cervo” and the “Grotta a Male” caves (Central Italy) have been dated using 14C and U/Th radiometric methods. The present paper shows the limits and validity of such methods for dating strong earthquakes of the past.In particular, radiometric 14C dating shows that the youngest general stalagmitic collapse observed inside the “Grotta del Cervo” cave must be related to the December 1456 earthquake of Central Italy

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

Nouveaux traages sur le massif de la Pierre Saint-Martin (Pyrnes-Atlantiques), 1994, Douat M. , Salomon J. N.
In 1982 and 1992 cavers observed the contamination of the B3 and Couey-Lotge underground rivers emerging at the Issaux springs This contamination was thought to be caused by the PSM water purificatlon station which discharges effluents into a fracture. The ARSIP and the LGPA laboratories were asked by the DDA (Pyrenees-Atlantiques administration) to carry out an hydrogeological study to prove the origin of this contamination and determine the limit of the Issaux catchment in the Guillers area in order to find a new site for a modern water purification station. Three uranine tracings were made (Water purification station - B3 underground river - BG. 106 shaft). The first two tracings emerged at the Issaux springs and the third tracing came out at the Bentia spring (Sainte-Engrace). These tracings confirm the hypothesis on the surficial basin limits between Issaux and Saint Vincent.

Forum: Radon, Caves and Rabbits [A comment on the IRCP dose limits], 1995, Prime David

Agricultural chemicals at the outlet of a shallow carbonate aquifer, 1996, Felton Gk,
A groundwater catchment, located in Woodford and Jessamine Counties in the Inner Bluegrass of Kentucky, was instrumented to develop long-term flow and water quality data. The land uses on this 1 620-ha catchment consist of approximately 59% in grasses consisting of beef farms, horse farms, and a golf course; 16% row crops; 6% orchard; 13% forest; and 6% residential. Water samples were analyzed twice a week for, Ca, Mg, Na, Cl-, HCO3-, SO4=, NO3-, total solids, suspended solids, fecal coliforms, fecal streptococci, and triazines. Flow rate and average ambient temperature were also recorded. No strong linear relationship was developed between chemical concentrations and other parameters. The transient nature of the system was emphasized by one event that drastically deviated from others. Pesticide data were summarized and the ''flushing'' phenomena accredited to karst systems was discussed. The total solids content in the spring was consistent at approximately 2.06 mg/L. Fecal bacteria contamination was well above drinking water limits (fecal coliform and fecal streptococci averages were 1 700 and 4 300 colony-forming-units/100 mL, respectively) and the temporal variation in bacterial contamination was not linked to any other variable

delta N-15 of nitrate derived from explosive sources in a karst aquifer beneath the Ammunition Burning Ground, Crane Naval Surface Warfare Center, Indiana, USA, 1998, Dignazio Fj, Krothe Nc, Baedke Sj, Spalding Rf,
Military institutions involved in the production and demolition of explosives, propellants, and pyrotechnics have the potential to degrade groundwater aquifers through the addition of numerous contaminants including nitrate. A nitrate plume has been identified in a karst aquifer beneath the Ammunition Burning Ground (ABG) at the Crane Naval Surface Warfare Center, Indiana, USA. Wells located in the vicinity of surface impoundments and bum pans used for treatment of explosive materials show the highest concentrations of nitrate ranging from 11.2 to 19.6 mg l(-1) as NO3-. Little is known about the isotopic composition of nitrates originating from these processes. Eight wells within the ABG were sampled and analyzed for nitrogen isotopic composition of nitrate. An enrichment in the delta(15)N (delta(15)N = .9, .0, .1. and .5 parts per thousand) occurred at four wells located near the primary areas of disposal activities within the ABG. Four wells located near the outer limits of the ABG had delta(15)N values significantly lower than those observed in the central area of the ABG (delta(15)N = .0, .1, .6, and .0 parts per thousand). Soil samples and burn-pan ash samples were collected and analyzed for the nitrogen isotopic composition of nitrate. Three soil nitrate samples had low delta(15)N values of -1.7, -1.8. and .2 parts per thousand. The burn-pan ash sample produced nitrate with a delta(15)N value of .9 parts per thousand. The observed enrichment in delta(15)N from samples taken from wells located near the ABG has been postulated to be a result of photodegradation or biochemical modification of RDX and TNT contaminated sludges and volatilization of NH3 in storage lagoons within the ABG. (C) 1998 Elsevier Science B.V. All rights reserved

Facies differentiation and sequence stratigraphy in ancient evaporite basins - An example from the basal Zechstein (Upper Permian of Germany), 1999, Steinhoff I. , Strohmenger C. ,
Due to excellent preservation, the Werra Anhydrite (Al), the upper member of the Upper Permian Zechstein cycle I (Ist cycle, Z1), is readily studied in terms of the distribution of sulfate facies and sequence stratigraphy that can be interpreted from these facies. In this study cores taken from seven wells in the Southern Zechstein Basin were examined for their sedimentary structures and various petrographic features. Facies interpretation and depositional sequences are based on detailed examination of core material. Four main facies environments have been identified: (I) supratidal (II) intertidal (III) shallow subtidal, and (IV) deeper (hypersaline) subtidal. These are further subdivided into 10 subfacies types: (1) karst and (2) sabkha within the supratidal environment (I), (3) algal tidal-flat, (4) tidal flat and (5) beach deposit within the intertidal environment (II), (6) salina, and (7) sulfate arenites within the shallow subtidal enviromnent (III). The (8) slope subfacies type commonly associated with (9) turbidites and the (10) basin subfacies type subdivide the deeper subtidal environment (IV). Vertical stacking patterns of these facies and subfacies types reveal the sequence stratigraphic development of the sulfate cycles in response to sea-level and salinity fluctuations. The lower Werra Anhydrite (belonging to Zechstein Sequence ZS2) is characterized by a transgressive systems tract (IST) overlying the transgressive surface of Zechstein Sequence ZS2 within the Al-underlying upper Zechstein Limestone (Cal). The TST of the AT is several tens of meters thick in platform areas, where it is built up by sulfate arenites and swallow-tail anhydrite-after-gypsum, and thins out to a few meters of thickness toward the condensed basinal section, where laminites ('Linien-Anhydrit') are predominant. Most of the Al succession consists of three relatively thick parasequences belonging to the highstand systems tract (HST) that shows typical prograding sets. Enhanced platform Buildup, including sulfate arenites, salina deposits, intertidal sediments, and sabkha precipitation as well as turbidite shedding off the platforms produced marginal ''sulfate walls' up to 400 m thick as platform to slope portions of the Werra Anhydrite. Seaward, the Al thins to a few tens of meters of laminated sulfate basin muds. Increasingly pronounced Al topography during highstand narrowed the slope subfacies belt parallel to the platform margin This contrasts with the broad but considerably thinner slope deposits of transgressive times with much shallower slopes. The ensuing sea-level lowstand is reflected by a sequence boundary on top of the karstified Al-platform and a lowstand wedge (Zechstein Sequence ZS3) overlying portions of the slope and basinal subfacies of the Al highstand systems tract Beyond the lateral limits of the lowstand wedge, the sequence boundary merges with the transgressive surface of ZS3, shown by the lithologic change from the Al anhydrites to the overlying carbonates of the Stassfurt Carbonates ('Haupt Dolomit' Main Dolomite, Ca2). The Basal Anhydrite (A2), which overlies and seals the carbonate reservoir of the Ca2, can also be subdivided into systems tracts by means of facies analysis. It is, however, much less complex than the Al and is comprised almost exclusively of a transgressive systems tract of Zechstein Sequence ZS4

Structures tectoniques et contraintes de cheminement des eaux dans les aquiferes karstiques du barrois (Lorraine/Champagne, France), 1999, Devos A, Jaillet S, Gamez P,
Between Lorraine and Champagne, in the east of the Paris Basin, covered karst is developed in Portlandien limestone of Barrois in contact with sand and clay of the Perthois Cretaceous. The cuesta landscape is altered by folding tectonics (syncline of Treveray) and faulting tectonics (fault trough of the Marne). These govern the organization of underground flow. In low water period, hydrological methods (smoothed hydrological profiles, water tracing) display disturbances of the Barrois river (Saulx, Marne) and limits of underground watershed ('Rupt-du-Puits' cave system, 21 km long, 13 km). Macro-tectonics influence vertical infiltration (pit). Fault and dip (Macro-tectonics) divide the aquifer into different sections. Hydrological methods with flow studies confirm structural tilting of the area to the west.ResumeEntre Lorraine et Champagne, dans l'est du Bassin parisien, au contact des calcaires portlandiens du Barrois et des sables et argiles cretaces du Perthois, se developpe un karst couvert. Le paysage de cotes est ici perturbe par une tectonique souple (synclinal de Treveray) et cassante (fosse d'effon-drement de la Marne) determinant l'organisation spatiale des ecoulements. En periode d'etiage, les methodes hydrologiques (profils hydrologiques lisses, tracages), permettent de montrer l'influence de cette tectonique d'ondulation et de basculement sur l'ecoulement des rivieres barroises (Saulx, Marne). Fractures et microfractures influencent la zone de transit vertical des eaux du karst (zone des puits) tandis que les failles compartimentent les aquiferes (systeme du Rupt-du-Puits, 21 km de conduits, 13 km2). Les methodes d'etudes hydrologiques, confirment le basculement de la region vers l'ouest deduit des comparaisons de nivellement

Gypsum karst features as evidence of diapiric processes in the Betic Cordillera, Southern Spain, 1999, Calaforra Jm, Pulidobosch A,
In the Triassic evaporite deposits of the Betic Cordillera, halokinesis has played a fundamental role in the morphodynamic evolution of gypsum karst, as evidenced by the morphology and distribution of dolines and poljes, by data obtained from caves, and from the types of water associated with evaporite domes. Distribution patterns of major exokarstic forms display a subcircular array with collapse sinkholes located in the centre of the domes and solution drawdown dolines on the outer limits of the diapiric forms. In addition, the least mineralized waters are situated in association with the caprock gypsum; hypersaline waters, which are also hotter, drain deeper flow systems that flow out at the edges of the halokinetic structures. The morphodynamic and hydrogeological information constitute a valuable tool for the correct interpretation of the tectonic structure of such complex areas. (C) 1999 Elsevier Science B.V. All rights reserved

A conceptual view of carbonate island karst, 1999, Mylroie J. E. , Vacher H. L.
Conceptually, the karst of carbonate islands can be modeled as the result of eogenetic diagenesis, freshwater/ saltwater mixing, and glacioeustasyThe resulting eogenetic karst occurs in small, youthful limestone islands where the evolution of the karst is concurrent with meteoric diagenesis of the host rock, which has never been out of the active circulation of meteoric waterThe rearrangement of the material of high porosity / low permeability sediments into moderate porosity / high permeability rock feeds back to the nature of the diagenetic environment as the flow volume of the lens is reduced by increasing flow efficiencyLimestone islands are a constrained and simple environment, defined as carbonate islands (no noncarbonate rock) and composite islands (mixture of carbonate and non carbonate rock)Simple carbonate islands lack noncarbonate rocks within the active hydrological zone; carbonate-cover islands contain a noncarbonate contact that limits the freshwater lens and deflects vadose flowThe type of island greatly influences the subsequent karst hydrologyIncreasing island size appears to cross a threshold favoring conduit flowThe karst features resulting from these island types, combined with mixing geochemistry and glacioeustasy, differ from those in continental settings and require a unique conceptual approach to modeling

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