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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. ...

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. ...

Speleology in Kazakhstan

Shakalov on 11 Jul, 2012
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 wash load is the incoming load of suspended sediment passing through a river network without deposition [16].?

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Karst environment, Culver D.C.
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Your search for thickness (Keyword) returned 170 results for the whole karstbase:
Showing 1 to 15 of 170
Anomalous behaviour of specific electrical conductivity at a karst spring induced by variable catchment boundaries: the case of the Podstenjšek spring, Slovenia, , Ravbar, N. , Engelhardt, I. , Goldscheider, N.

Anomalous behaviour of specific electrical conductivity (SEC) was observed at a karst spring in Slovenia during 26 high-flow events in an 18-month monitoring period. A conceptual model explaining this anomalous SEC variability is presented and reproduced by numerical modelling, and the practical relevance for source protection zoning is discussed. After storm rainfall, discharge increases rapidly, which is typical for karst springs. SEC displays a first maximum during the rising limb of the spring hydrograph, followed by a minimum indicating the arrival of freshly infiltrated water, often confirmed by increased levels of total organic carbon (TOC). The anomalous behaviour starts after this SEC minimum, when SEC rises again and remains elevated during the entire high-flow period, typically 20–40 µS/cm above the baseflow value. This is explained by variable catchment boundaries: When the water level in the aquifer rises, the catchment expands, incorporating zones of groundwater with higher SEC, caused by higher unsaturated zone thickness and subtle lithologic changes. This conceptual model has been checked by numerical investigations. A generalized finite-difference model including high-conductivity cells representing the conduit network (“discrete-continuum approach”) was set up to simulate the observed behaviour of the karst system. The model reproduces the shifting groundwater divide and the nearly simultaneous increase of discharge and SEC during high-flow periods. The observed behaviour is relevant for groundwater source protection zoning, which requires reliable delineation of catchment areas. Anomalous behaviour of SEC can point to variable catchment boundaries that can be checked by tracer tests during different hydrologic conditions.


Hydrogeology of the Great Nubian Sandstone basin, Egypt, 1982, Shata A. A. ,
In Egypt, the strata of major hydrogeological interest are composed of a sandstone complex ranging from Cambrian to Upper Cretaceous in age. This sandstone complex, commonly known as the Nubian Sandstone, has a thickness varying from less than 500 m to more than 3000 m and rests directly on Precambrian basement. This simple picture is complicated by a number of major structural fault and fold axes which traverse the region in a north-easterly direction. The sandstones reach their max-imum development in the Ain Dalla basin, a downthrown structural block SW of Bahariya oasis. Basement features exercise a dominant control on the structural and sedimentological form of the sandstone complex. In spite of the structural complications, the Nubian sand-stone, underlying an extensive area of Egypt, probably con-stitutes a single hydrogeological system to the W of the Gulf of Suez. To the E, on the Sinai peninsula, a second system may exist with some connection to the main western system in the N. The main western system, which extends into Libya and Sudan, comprises a multi-layered artesian basin where huge groundwater storage reserves were accumulated, principally during the pluvials of the Quaternary. The carbonate rocks overlying the Nubian Sandstone complex display karst features locally and are recharged by upwards leakage from the underlying major aquifer. Large-scale development of the Nubian Sandstone aquifer in Egypt has been under consideration since 1960. Latest proposals for the New Valley development project involve exploitation at the annual rate of 156.2 x l06m3 at El-Kharga, 509.2 at

Geophysical mapping techniques in environmental planning, 1987, Culshaw Mg, Jackson Pd, Mccann Dm,
Geophysical information can be used to identify geological features, some of which may be a problem during the planning, design or construction of a new development. The location of magnetic dykes, the investigation of buried channels, or of landslips, the determination of the thickness of drift deposits or the identification of natural or man-made cavities are all problems which can be studied by geophysical surveying methods on both a regional or local scale. The information obtained can then be incorporated into factual or interpreted engineering geological maps for use by planners or engineers. In this paper, the contribution that geophysical surveying methods can make at the planning, design, construction and monitoring stages of a development is examined and illustrated with a number of case histories

COMPARISON OF THE C-14 ACTIVITY OF GROUNDWATER AND RECENT TUFA FROM KARST AREAS IN YUGOSLAVIA AND CZECHOSLOVAKIA, 1989, Horvatincic N. , Srdoc D. , Silar J. , Tvrdikova H. ,
C-14 activity of dissolved inorganic carbon (DIC) in water and in recent tufa samples in several karst areas of Yugoslavia and Czechoslovakia was measured. Groundwater from 11 karst springs were measured for their isotopic content (C-14, H-3, C-13), chemical composition (HCO3, Ca2, Mg2) and physico-chemical properties (temperature, pH). Seasonal variations of the C-14 activity of DIC in two karst springs in Plitvice Lakes area, Yugoslavia, were measured systematically from 1979-1987. C-14 activity of recent tufa samples from several locations downstream were also measured. The activity of DIC in karst spring water in both countries ranged from 63-87 pMC, which is attributed to differences in geologic structure of the recharge area, topsoil thickness and composition. Grouping of C-14 activities of DIC ca (824)% is evident. Tritium activity at all the springs indicated short mean residence time (1-10 yr). Concentration of HCO3, Ca2 and Mg2 in spring water varied with geomorphology. C-14 activity of streamwater and recent tufa increased downstream from karst springs due to the exchange between atmospheric CO2 and DIC

Approche gomorphologique des karsts du gypse de la Vanoise (la zone alpine et glaciaire du vallon du Fruit-Gbroulaz,Alpes), 1991, Chardon, M.
GYPSUM KARSTIC LANDFORMS IN VANOISE: the alpine and glacial valley of Vallon du Fruit-Gbroulaz (Alps, France) - In the inner part of the northern french Alps, the higher regions of the Vanoise offer outcrops of Triassic gypsum of which the surface and thickness vary. In the vallon du Fruit, the Gbroulaz glacier partially covers a long strip of gypsum, which reaches its highest point at the Roc de la Soufrire (2940 m). Rivers and springs in the vallon du Fruit are fed both by sub-aerial glacial outflows and by karstic underground flows, which are pro-glacial and sub-glacial. A very low chemical dissolution exists under the glacier and along the fast pro-glacial underground and sub-aerial flows, whereas the rate of karstic denudation is high in the margin of the glacier where it reaches 1500 mm/ky at around 2500m (1 ky = 1000 years). The formation and evolution of the dolines is rapid and occurs through underground sucking and dissolution once the area is deglaciated, thanks to underground active flows fed by the glacier and snow melting. Gypsum domes are uplifted under the effects of neotectonic movements and postglacial decompression brings about considerable superficial fissuring because of the elasticity of the rock. Over 10,000 years, the morphogenesis of these domes in the humid and cold climatic conditions of these high alpine mountains has transformed them into perforated ladle and domes. Small outcrops are changed into monoliths or gypsum inselberg. A model of the geomorphologic post-glacial evolution of these domes, over some 20,000 years, is proposed.

Le karst de Vaucluse (Haute Provence), 1991, Mudry J. , Puig J. M.
The catchment area of the Fontaine de Vaucluse system is more than 1100km2 wide, with an average altitude of 870m. The thickness of the Lower Cretaceous limestone (1500m) gives the system a very thick (800m) unsaturated zone. Karstification is highly developed (four shafts are more than 500m deep) as well as on the valley (pit of 300m depth inside the spring). The bottom of the shafts of the Plateau does not reach the saturated zone of the karst, as their flows are the chemical content of the seepage water. The maximum hydraulic gradient from the Plateau to the spring is low, only 0.3%. Dye tracings permit the assignment of the Ventoux-Lure rang (including its calcareous northern slope with a southward dipping) and the Vaucluse Plateau in the catchment area. The water balance computed by altitude belts shows that the rainfall strongly increases with altitude: 120mm at 200m, 1380mm over 1800m. The dynamic of the system, studied by discharge and physical and chemical content, shows of a well karstified media, that reacts with slight inertia upon the rainy periods, and that is made up of important reserves, particularly within the unsaturated zone, that supply long decline and depletion episodes.

WATER-BUDGET, FUNCTIONING AND PROTECTION OF THE FONTAINE-DE-VAUCLUSE KARST SYSTEM (SOUTHEASTERN FRANCE), 1992, Blavoux B, Mudry J, Puig Jm,
The karst aquifer of the well-known Fontaine de Vaucluse has been recently studied, results have been got about delimitation of the system and its working. Geological data (lithology and structure) have allowed to delimit an 1115 Km2 intake area including Ventoux-Lure north facing range (1,909-1,826 m) and the Plateau which is prolonging it southwards (Fig. 1 and 2). The average altitude of the whole area, obtained by balancing elevation belt surfaces, is about 870 m. This elevation squares with results of tracing tests (Fig. 3), environmental physical, chemical and isotopic tracings, that allow to value a 850 m average altitude for the intake area (Fig. 4). The moisture balance has been computed from an altitude belts climatic model, using local rain an temperature gradients (Fig. 5 and Table II), because the weather network is not representative. So, rainfalls rise of about 55 mm per 100 m elevation and temperature decreases of about 0.5-degrees-C per 100 m. The consequence of these two antagonist phenomena is the quasi constant value of actual evapotranspiration on each altitude belt. With the Fig. 7 organigram, curves of effective rainfalls and infiltration coefficient versus elevation can be plotted (Fig. 6). This computation shows that 3/4 of the total and the whole of dry season effective rainfalls are provided by the part of the intake area situated above the average altitude: on the lowest belt, effective rainfalls are only 120 mm per year and increase to 1380 mm on the upper section (Fig. 8 and Table 1). The weighted effective rainfalls are about 570 mm per year for the whole intake area. Hydrodynamical and physico-chemical studies show, despite its large size, the weak inertia of the system, so proves its good karstification, that confirms for the whole system the pin-point speleological observations. The discharge of the spring, which average value is 21 m3.s-1 (only 18 for the last ten years), can exceed 100 m3.s-1 and the minimum has never been lower than 3.7 m3.s-1 (Fig. 9). When it rains on the intake area, the increase of the discharge is very sudden in a rainy period : one to four days. This short delay is due to seepage through epikarst and unsaturated zone. During dry periods, the spring reaction is deadened, due to storage in the unsaturated zone. The silica content distribution was plotted during several hydrokinematical phases (Fig. 10). It shows: an almost unimodal distribution for the 8 km2 fissured limestone aquifer of Groseau; a multimodal one for the 1115 km2 karst aquifer of Fontaine de Vaucluse. This proves that karstification is more important than size in the response of the system. Weak summer rainfalls do not influence the discharge, nevertheless they influence chemistry of the spring water, and so interrupts the water depletion phasis. Then, the decrease of discharge can continue after the end of the chemical depletion phasis, water which is overflowing after summer rainfalls (in a dry period) is influenced hy the chemistry of seepage water : on the graph of a principal components analysis, done on chemical variables. an hysteresis phenomenon can be seen (Fig. 11). A discriminant analysis (Fig. 12) confirms that these autumn waters, with high ratio seepage tracers, are not reserve waters from the saturated zone. The ratio of reserve water in the total discharge, is preponderant: 3/4 and 2/3 respectively of the yearly runoff volumes for 1981 and 1982 (Fig. 13), but an important part of these reserves can be stored in the unsaturated zone. This storage capacity can be valued by different means: transposing to Vaucluse (1115 km2) the volume measured on another karst system in the Pyrenees (13 km2); it gives about 100 million m2; using setting parameters of Bezes model (1976) on the same aquifer: it gives 113 million m3; using depletion curves, that show, for instance during the 1989 summer and autumn dry period, a 80 million m3 volume. In all cases, we get a value of about one hundred million m3 for the storage capacity of the unsaturated zone. With a 20 m range of fluctuation for the water table and with a 10(-2) specific yield, on a 500 to 1,000 km2 saturated zone, the zone of fluctuation can release about 10 to 20 million m3. Then, the volume of water stored in the whole saturated zone, with a 300 m minimum thickness (depth of the waterlogged pit of the Fontaine), a 500 km2 minimum surface and a 10(-3) specific yield, is about 150 million m3, including 27 million m3 stored in the channels. So, the unsaturated zone represents a significant part of the whole storage capacity and most of the yearly renewable reserves. Paradoxically, the biggest french spring is not tapped at all; as its intake area is neither a regional nor a national park, no general protection covers it : because of its good karstification, the vulnerability of the system is important. Good quality of water is attributable to the low population and human activities density on the intake area (4 inh.km-2). A great part of the intake area is uncultivated (large forest and ''garrigues'' areas). Due to the lack of surface water and scantness of soils, agriculture is not intensive (lavender, thyme, sage and bulk wheat fields. meadowlands). On the mountainous zone, roads are salted in winter and snowmelt water can reach a significantly high chloride ratio than in a natural climatic functioning (for instance 25 mg.l-1 in Font d'Angiou where the ratio would have been 3 mg.l-1). As tourism is developing both on the mountain and on the plateau, the management of the highest intake area must be carefully held: its part is preponderant in the feeding of the system

PALUSTRINE CARBONATES AND THE FLORIDA EVERGLADES - TOWARDS AN EXPOSURE INDEX FOR THE FRESH-WATER ENVIRONMENT, 1992, Platt N. H. , Wright V. P. ,
Palustrine carbonates are shallow fresh-water deposits showing evidence of subaqueous deposition and subaerial exposure. These facies are common in the geological record. The intensity of modification is highly variable depending on the climate and the length of emergence. Palustrine limestones have previously been interpreted as marginal lacustrine deposits from fluctuating, low-salinity carbonate lakes, but several problems remain with existing facies models: 1) palustrine carbonates possess a lacustrine biota but commonly display fabrics similar to those of calcretes and peritidal carbonates; 2) the co-occurrence of calcrete horizons and karst-like cavities is somewhat unusual and appears to indicate contemporaneous carbonate precipitation and dissolution in the vadose zone; 3) the dominance of gray colors indicates water-saturation, apparently inconsistent with the evidence for strong desiccation overprint; 4) profundal lake deposits are generally absent from palustrine sequences, and sublittoral facies commonly make up only a small proportion of total thicknesses; 5) no good modem analogue has been identified for the palustrine environment. Analogy with the Florida Everglades suggests a re-interpretation of palustrine limestones, not as pedogenically modified lake margin facies but as the deposits of extensive, very shallow carbonate marshes. The distribution of environments in the Everglades is determined by the local hydrology, reflecting the control of seasonal water-level fluctuations and topography. Climate and topography were the main controls on deposition of ancient palustrine carbonates. As in peritidal sequences, aggradational cycles are capped by a range of lithologies (evaporites, desiccation and microkarst breccias, calcretes, lignite or coal horizons etc.), permitting interpretation of the climate. Careful analysis of lateral facies variations may permit reconstruction of subtle topography. Consideration of the Florida Everglades as a modem analogue for the palustrine environment has suggested the development of an exposure index for fresh-water carbonates

HALITE SALTERN IN THE CANNING BASIN, WESTERN-AUSTRALIA - A SEDIMENTOLOGICAL ANALYSIS OF DRILL CORE FROM THE ORDOVICIAN-SILURIAN MALLOWA SALT, 1992, Cathro Dl, Warren Jk, Williams Ge,
The Late Ordovician-Early Silurian Mallowa Salt of the Carribuddy Group, Canning Basin, north-west Australia, is the largest halite deposit known in Australia, attaining thicknesses of 800 m or more within an area of approximately 200 000 km2. Study of 675 m of drill core from BHP-Utah Minerals' Brooke No. 1 well in the Willara Sub-basin indicates that the Mallowa Salt accumulated within a saltern (dominantly subaqueous evaporite water body) that was subject to recurrent freshening, desiccation and exposure. Textures and bromine signatures imply a shallow water to ephemeral hypersaline environment typified by increasing salinity and shallowing into evaporitic mudflat conditions toward the top of halite-mudstone cycles (Type 2) and the less common dolomite/anhydrite-halite-mudstone cycles (Type 1). The borate mineral priceite occurs in the capping mudstones of some cycles, reinforcing the idea of an increasing continental influence toward the top of mudstone-capped halite cycles. The rock salt in both Type 1 and Type 2 cycles typically comprises a mosaic of large, randomly orientated, interlocking halite crystals that formed during early diagenesis. It only partially preserves a primary sedimentary fabric of vertically elongate crystals, some with remnant aligned chevrons. Intraformational hiati, halite karst tubes and solution pits attest to episodic dissolution. Stacked Type 2 cycles dominate; occasional major recharges of less saline, perhaps marine, waters in the same area produced Type 1 cycles. The envisaged saltern conditions were comparable in many ways to those prevailing during the deposition of halite cycles of the Permian Salado Formation in New Mexico and the Permian San Andres Formation of the Palo Duro Basin area in Texas. However, in the Canning Basin the cycles are characterized by a much lower proportion of anhydrite, implying perhaps a greater degree of continental restriction to the basin. The moderately high level of bromine in the Mallowa Salt (156.5 43.5 ppm Br for primary halite, 146.1 54.7 ppm Br for secondary halite) accords with evolved continental brines, although highly evaporative minerals such as polyhalite and magnesite are absent. The bromine levels suggest little or no dissolution/reprecipitation of primary halite and yet, paradoxically, there is little preservation of the primary depositional fabric. The preservation of early halite cements and replacement textures supports the idea of an early shutdown of brine flow paths, probably at burial depths of no more than a few metres, and the resultant preservation of primary bromine values in the secondary halite

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

Alpine karsts. Genesis of large subterranean networks. Examples : the Tennengebirge (Austria) - the Ile de Crémieu, the Chartreuse and the Vercors (France), PhD Thesis, 1993, Audra, Philippe

This work, based on the study of several underground alpine networks, aims to propose some milestone in the history of these karstic regions.

The first part of the work is made up of three regional studies.

The Tennengebirge mountains are a massif of the limestone High Alps in the region of Salzburg in Austria. A cone karst close to the base level developed in the Neogene. Streams from the Alps fed the karst, resulting in the huge horizontal networks of which the Eisriesenwelt provides evidence. During the successive phases of upthrust, the levels of karstification, whether on the surface or deeper down, settled into a tier pattern, thus descending in stages from the base level. From the Pliocene era onwards, thanks to an increase in potential, alpine shafts replace the horizontal networks. The formation of these shafts is more pronounced during glaciation. The study of the Cosa Nostra - Bergerhöhle system developing 30 km of conduits on a gradient reaching almost 1 500 m provides a fairly full view of the karstification of this massif. It includes the horizontal levels developed in the Miocene and the Plio-Pleistocene, joined together by vertical sections. The most noteworthy features of the Tennengebirge, as in the neighboring massifs, lie first and foremost in the extreme thickness of the limestone which has recorded and immunized the differents steps of karstification. Secondly, the size of the networks can be, for the most part, accounted for by the contribution of allogenous waters from the streams of the Neogene and the glaciers of the Pleistocene. Generally sudden and unexpected, these flows of water engendered heavy loads (up to 600 m), simultaneously flooding several levels. To a lesser extent, the situation is similar today.

The Ile de Cremieu is a low limestone plateau on the western edge of the Jura. Due to its location in the foothills, the lobes of the Rhône glacier have covered it up, obliterating the surface karst. However, widespread evidence of anteglacial morphologies remains : paleokarst, cone karst, polygenic surface. Because of glacial plugging, access to the underground karst is limited. The main cavity is the cave of La Balme. Its initial development dates back to an early period. The morphological study has permitted the identification of several phases which go back to the Pleistocene and which are related to the Rhône glacier. The latter brought about modifications in the base level by supplying its merging waters as well as moraine material. These variations in the base level shaped the drainage structure. The underground glacial polishes are one of the noteworthy aspects recorded.

The massives of the Moucherotte and dent de Crolles belong to the northern French Prealps. They conceal large networks, respectively the Vallier cave and the Dent de Crolles. They were formed in the early Pliocene after the final orogenic phase and are in the form of horizontal conduits. The upthrust, which brought about the embanking of the Isère valley, left them in a perched position by taking away the basin which fed them. They were later, however, able to take advantage of waters from the Isère glacier during a part of the Pleistocene. The Vallier cave contains particularly glacio-karstic sediments of the lower Pleistocene, representing unique evidence of glaciation during this period. The vertical networks were put in place at the end of the Pliocene with the increase in karstification potential ; they underwent changes in the Pleistocene due to the effect of autochton and allogenous glaciers.

The second part of the work deals in general with the various forms and processes of karstification, sometimes going beyond the Alps. The study of cave deposits is a privileged tool in the understanding and reconstruction not only of the history of the networks but also the regional environment. The dating of speleothems by the U / Th method has very ofen given an age of over 350 000 years. The age of the networks is confirmed by the use of paleomagnetism which has yielded evidence of speleothems and glacio-karstic sediments anterior to 780 000 years. Anisotropic measurements of magnetic susceptibility have been used to distinguish the putting into place of glacio-karstic deposits by decantation.

Measurements of calcite rates lead to a typology of sediments based on their nature and carbonate content (rehandled weathered rocks, fluvial sands, carbonated varves, decantation clays). Granulometry confirms this differenciation by supplying precise details of transport and sedimentation modes : suspension and abrupt precipitation of clay, suspension and slow decantation of carbonated varves, suspension and rolling together with a variable sorting of sand and gravel. Mineralogical analyses oppose two types of detrital deposits. On the one hand, the rehandling of antequaternary weathered rocks extracted by the karst as a result of scouring during environmental destabilization and on the other hand, sediments characteristic of the ice age of the Pleistocene. The latter are not highly developed and their arrival in the karst is always later. Examination of heavy minerals, the morphoscopy of quartz grains and study of micromorphologies on thin blades provide precise details of conditions of evolution. The use of these methods of investigation allows for an accurate definition of the features of the evolution of the differents types of fillings, particularly speleothems, rehandled weathered rocks as well as carbonated varves. This wealth and complexity are emphasized by a detailed study of the sedimentary sequences of the Vallier cave and of the Bergerhöhle.
Speleogenesis is approached last of all in the light of above study. Emphasis is placed on the major part played by corrosion in the temporarily phreatic zone and on its many consequences (multi-level concept, simultaneous evolution of levels, origin of deep waterlogged karsts…).
Varia tions in the base level have induced karstification in contexts in which the potential was weak. These were followed by periods of increased potential to which were added the effects of glaciation. Perched horizontal levels belong to the first stages which ended in the early Pliocene, whereas alpine shafts developed in the second context. The role of structure and the parameters governing the shape of conduits (pits, meanders, canyons) are also dealt with. The different parts of the karst are borne in mind when dealing with the strength of karstic erosion during the ice age. It notably appears that it is weak on the crests and more or less non-existent in the deep parts of the karst which are liable to flooding. Finally, a preliminary analysis of an observation of neotectonic traces is presented.


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

Synsedimentary collapse of portions of the lower Blomidon Formation (Late Triassic), Fundy rift basin, Nova Scotia, 1995, Ackermann Rv, Schlische Pw, Olsen Pe,
A chaotic mudstone unit within the lower Blomidon Formation (Late Triassic) has been traced for 35 km in the Mesozoic Fundy rift basin of Nova Scotia. This unit is characterized by highly disrupted bedding that is commonly cut by small (<0.5 m) domino-style synsedimentary normal faults, downward movement of material, geopetal structures, variable thickness, and an irregular, partially faulted contact with the overlying unit. The chaotic unit is locally overlain by a fluvial sandstone, which is overlain conformably by mudstone. Although the thickness of the sandstone is highly variable, the overlying mudstone unit exhibits only gentle regional dip. The sandstone unit exhibits numerous soft-sediment deformation features, including dewatering structures, convoluted bedding, kink bands, and convergent fault fans. The frequency and intensity of these features increase dramatically above low points at the base of the sandstone unit. These stratigraphic relations suggest buried interstratal karst, the subsurface dissolution of evaporites bounded by insoluble sediments. We infer that the chaotic unit was formed by subsidence and collapse resulting from the dissolution of an evaporite bed or evaporite-rich unit by groundwater, producing dewatering and synsedimentary deformation structures in the overlying sandstone unit, which infilled surface depressions resulting from collapse. In coeval Moroccan rift basins, facies similar to the Blomidon Formation are associated with halite and gypsum beds. The regional extent of the chaotic unit indicates a marked period of desiccation of a playa lake of the appropriate water chemistry. The sedimentary features described here may be useful for inferring the former existence of evaporites or evaporite-rich units in predominantly elastic terrestrial environments

Paleoalpine karstification - The longest paleokarst period in the Western Carpathians (Slovakia), 1995, Cincura J, Kohler E,
The considerable areal extent and great thicknesses of Middle/Upper Triassic carbonate complexes influenced favourably the formation of karst during subaerial periods. The lower boundary of the Paleoalpine karst period is age-determined by the gradual emergence of the basement - during the Upper Cretaceous in the Central Western Carpathians and even earlier in the Inner Carpathians. The upper boundary can be dated by marine transgression The start of the transgression is not synchronous and it varies in a broad range from Upper Cretaceous to Upper Eocene and maybe even up to Oligocene/Miocene. The typical products of the period include typical karst bauxites filling karst cavities, ferri crusts, red clays, collapse and crackle breccias with speleothems, freshwater limestones or polymict conglomerates

Breakdown development in cover beds, and landscape features induced by intrastratal gypsum karst., 1996, Andrejchuk Vjacheslav, Klimchouk Alexander
Intrastratal karst is by far the predominant gypsum karst type. Its development may begin in deep-seated settings within rocks already buried by younger strata, and it proceeds increasingly rapidly as uplift brings gypsum sequences into progressively shallower positions. Such development commonly occurs under confined (artesian) hydrogeological conditions, that subsequently change to open conditions (phreatic-water table-vadose). The general evolutionary line of intrastratal karst is typified by progressive emergence of a sequence into a shallower position, activation of groundwater circulation and development of cave systems within karst units, commencement of gravitational breakdown and its upward propagation through overlying beds, and development of a karst landscape. These processes and phenomena progress through the directed evolution of karst types as follows: deep-seated intrastratal karst (1K) to subjacent 1K to entrenched 1K to denuded karst. One of the main characteristics of intrastratal karst is that it induces gravitational breakdown in cover beds. With the aid of processes other then simple breakdown, such effects may propagate upwards and may, or may not, reach the surface, depending upon the thickness and structure of the overburden. A karst landscape evolves when such features reach the surface. This paper considers the conditions and mechanisms of such development.

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