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Speleology in Kazakhstan

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

New publications on hypogene speleogenesis

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

The deepest terrestrial animal

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

Caves - landscapes without light

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

Did you know?

That bed, upper confining is impermeable bed overlying an aquifer [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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Your search for parameters (Keyword) returned 351 results for the whole karstbase:
Showing 16 to 30 of 351
Le Vercors : un massif de la moyenne montagne alpine, 1984, Delannoy, J. J.
THE VERCORS: A MASSIF OF MIDDLE ALPINE MOUNTAIN - The Vercors is a forested massif of middle mountain, in the French Northern Prealps. The characteristic of the Vercors massif is the thick and massif urgonian limestones, which underlines a folded structure. The Vercors quickly hold the attention of speleologists, who had put forward the density and diversity of karstic aspects since the beginning of the century. Landforms display glacial karstic landscapes more or less damaged in terms of bio-climatic levels of mounts and depressions landscapes and of deep water gaps, which main flows of the massif are flowing in. The notion of the morphoclimatic heritage applies to the underground karst for which glacial quaternary episodes have been determinant in the large systems genesis (gouffre Berger - Scialet de la Fromagre, Antre des Damns, Combe de Fer...). The study of underground deposits allows to bring up-to-date various period of karst development; a preglacial stage (e.g. upper levels of Cuves de Sassenage, Gournier, Coufin-Chevaline...). The study of the current dynamic shows that the Vercors as an important karstic ablation, between 120 to 170mm/ky. The karstic dynamic exerts mainly on the superficial slab of the massif (from 80 to 50% of the whole ablation). The Vercors can be considered as the best example of calcareous massif in temperate middle mountains, thanks to the combination of various favourable parameters: pure karst rocks, morpho-climatic episodes not constraining, and a high karstic dynamic.

Le rle des hritages quaternaires dans les karsts alpins : le cas des Alpes du Sud, 1984, Julian, M.
THE PART OF THE QUATERNARY INHERITED FEATURES IN THE ALPINE KARSTS: THE EXAMPLE OF THE SOUTHERN ALPS - The periglacial past-processes influenced karst landforms. 1) the paleoclimatical change (Wrm) related to the present climatical parameters; 2) the impact of periglacial processes on the superficial karst; 3) the internal evolution of the karst during the cold phases.

Les massifs karstiques des Alpes occidentales, trame structurale et bioclimatique, 1984, Nicod, J.
THE KARSTIC MASSIFS OF WESTERN ALPS: structural and bioclimatic framework - The structural conditions determine several types of karst units: the northern Prealps (thrusts), the southern Jura (folded or tabular), the southern Prealps (faulted and folded plateaus), the complex land of Low Provence, and the high karsts of Inner Alps. The bioclimatic framework explains the altitudinal sequence of current processes. The value of the runoff, the part of the snow, and the biochemical parameters (vegetation, CO2), have particularly holded the attention. The specific dissolution reaches its maximum in the wooded mountain karsts. Heritages also determine the landforms (glacial, periglacial, terra-rossa).

Le massif du Parmelan, Haute-Savoie, relations fractura-tion-karstification, 1985, Masson, M.
THE MASSIF OF PARMELAN, HAUTE-SAVOIE, FRANCE: RELATIONS BETWEEN FRACTURATION AND KARSTIFICATION - The massif of Parmelan (Haute-Savoie), encloses a well-karstified and highly organised perched aquifer. Its simple geological structure and easy-speleological penetration (more than 45km are known) have allowed a statistical study of the fracturation and karstification parameters at different scales. This study shows that the karst has developed on the most frequent fracturation directions (study of the cumulated lengths), whereas its directional distribution in frequency is relatively homogeneous; the most used fractures are the tension faults, linked with the folding of the massif.

Cave to Surface Communications, 1985, Allum, Ron

The reasons for needing a cave to surface communication system are many, including safety, search and rescue, surveying, science, exploration and commentary. Ideally a unit should be lightweight, portable, robust, easy to operate, have adequate range and be able to communicate speech intelligibly in both directions. The unit described here was designed specifically for use on the 1983 Cocklebiddy Cave expedition. When considering design parameters for a communication system there are many limitations, but in a cave as large as Cocklebiddy these can be less of a restriction. The unit as used does not meet all of the above criteria as an ideal system for all caves, but it worked well in Cocklebiddy Cave, conveying our speech intelligibly with tolerable noise and interference levels.


Apports des datations U/Th dans la karstogense de la Grande Moucherolle-Rochers de la Balme (Vercors), 1986, Delannoy J. J. , Holliger Ph.
234 U - 230 Th DATING OF SPELEOTHEMS AND KARSTOGENESIS OF THE "GRANDE MOUCHEROLLE-ROCHERS DE LA BALME" (VERCORS) - In this article, is presented a first geomorphological and speleological synthesis of the subalpine karst of the Grande Moucherolle (2285 m) - Rochers de Ia Balme. This area of Vercors (Alps), which has 8 caves deeper than 300m (Antre des Damns -720m; Clos de La Fure -580m...) is surely the most promising sector from a speleological point of view. Through the study of the glacio-karstic landforms and the distri-bution of the great caves, it seems that there is a real relation between these two parameters. In order to evaluate the contribution of quaternary glaciations in the genesis of caves, isotopic dating (234U-230Th) have been performed on underground carbonated deposits. After a presentation of the chronometric method 234U-230Th, the results are analysed according to their speleological environment. A paleogeographic reconstitution through the middle and recent Quaternary is proposed for the geosystem of the Grande Moucherolle - Rochers de la Balme.

Thermal aspects of the East Midlands aquifer system, 1987, Wilson N. P. , Luheshi M. N. ,
A case study of a heat flow anomaly in the E Midlands of England is reported. The anomaly has been suggested to be an effect of water movement at depth within the E Midlands basin, with recharge to the Lower Carboniferous limestones in their outcrop, eastward movement and ascent of water up a steep faulted anticline at Eakring where the heat flow measurements were made. Numerical modelling of heat and fluid flow has been undertaken for a section running from the Peak District through Eakring to the coast. The results indicate that, although an anomaly is expected for reasonable values of hydrological parameters, its magnitude is less than that observed. The geological structure at Eakring is such that three-dimensional flow is likely to be important, and this could easily account for the discrepancy between the modelling results and the observations. The regional water flow regime has other effects on heat flow, notably the depression of heat flow above the Sherwood Sandstone aquifer

Use of Electronic Data-Logging Equipment to Monitor Hydrologic Parameters in a Humid Cave Environment in Wind Cave National Park, South Dakota, 1989, Greene, Earl A.

RECOGNITION OF MICROCLIMATE ZONES THROUGH RADON MAPPING, LECHUGUILLA CAVE, CARLSBAD-CAVERNS-NATIONAL-PARK, NEW-MEXICO, 1991, Cunningham Ki, Larock Ej,
Radon concentrations range from < 185 to 3,515 Bq m-3 throughout Lechuguilla Cave, Carlsbad Caverns National Park, New Mexico. Concentrations in the entrance passages and areas immediately adjacent to these passages are controlled by outside air temperature and barometric pressure, similar to other Type 2 caves. Most of the cave is developed in three geographic branches beneath the entrance passages; these areas maintain Rn levels independent of surface effects, an indication that Rn levels in deep, complex caves or mines cannot be simply estimated by outside atmospheric parameters. These deeper, more isolated areas are subject to convective ventilation driven by temperature differences along the 477-m vertical extent of the cave. Radon concentrations are used to delineate six microclimate zones (air circulation cells) throughout the cave in conjunction with observed airflow data. Suspected surface connections contribute fresh air to remote cave areas demonstrated by anomalous Rn lows surrounded by higher values, the presence of mammalian skeletal remains, CO2 concentrations and temperatures lower than the cave mean, and associated surficial karst features

FLOW PARAMETERS IN A SHALLOW CONDUIT-FLOW CARBONATE AQUIFER, INNER BLUEGRASS KARST REGION, KENTUCKY, USA, 1991, Thrailkill J. , Sullivan S. B. , Gouzie D. R. ,
In the carbonate aquifers which underlie most karst terrains, groundwater flow is through a dendritic system of solution conduits. In such aquifers, termed shallow conduit-flow aquifers. the methods used to mode) granular and fracture aquifers are not generally applicable. Investigations were conducted in the Inner Bluegrass Karst Region of central Kentucky with the objective of developing methods of modeling shallow conduit-flow aquifers as well as obtaining quantitative information on a specific portion of the aquifer to assist in its management for water supply purposes. In the Inner Bluegrass Karst Region, groundwater basins are developed. in each of which there is an integrated system of solution conduits which conducts recharge to a major spring. One of the largest of these groundwater basins feeds Royal Spring, which serves as the principal water supply for the town of Georgetown. The basin extends over 15 km to the southeast and most of its flow is furnished by underground diversions of Cane Run, a surface stream with headwaters near the center of the City of Lexington. The principal objectives of the field investigation were to determine discharges at the spring and travel times to the spring from discrete recharge points within the basin, termed swallets. The spring is ungaged. and an attempt was made to obtain a continuous discharge record by the dilution of dye introduced at a swallet. Comparison of the dye-dilution discharge record with stage discharges at the spring revealed substantial discrepancies which are believed to be caused by as much as five-sixths of the low-flow discharge from the upper portion of the basin bypassing the spring. The dye-dilution method, therefore, provided significant insights into the geometry of the conduit system of the groundwater basin although it proved unsatisfactory as a method of determining discharges at the spring. Analysis of the travel times and stage discharges provided information on the conduit geometry by modeling the flow as open-channel flow in a rectangular channel. Flow in the system is rapid, ranging from 140 to 590 m h-1. Although the flow rate increases with discharge, the relationship is not simple owing to substantial increases in conduit cross-sectional area at higher discharges. Flow is turbulent and subcritical under all conditions. The most surprising result was the very low depth of flow calculated; less than 17 cm at even the highest discharge. Although this must be considered an 'equivalent' depth, it is believed to indicate that active flow in shallow conduit-flow aquifers is generally in a thin zone just beneath the water table

APPLICATION OF MICROBIAL TRACERS IN GROUNDWATER STUDIES, 1991, Hotzl H. , Kass W. , Reichert B. ,
In situ tracing experiments have proved to be reliable tools to get direct information on subsurface flow direction and flow parameters. Beside dyes, salts, radioisotopes and drift bodies, microbes can be used as tracers. In several comparative experiments carried out in porous and karst aquifers by the International Association of Tracer Hydrology (ATH) the microbial markers (bacteria and bacteriophages) have shown promising results. They are especially suitable to explain and model the subsurface transport of microorganisms

Morphometric analysis of dolines, 1992, Bondesan Aldino, Meneghel Mirco, Sauro Ugo
The doline is the most specific surface form of karst landscapes, which enables one to distinguish them from "normal" erosion landscapes shaped by surface water. From a morphodynamic point of view the doline constitutes an elementary hydrographic unit, comparable to a simple basin, which, with its system of slopes, conveys water to the absorbing points at the bottom into an underground network. The morphometric study of these karst landforms enables a quantitative analysis of karst environment. Comparisons of the various parameters may give unexpected results and lead to new hypotheses about the evolution and the dynamism of the karst "geo-ecosystem". All the main morphometric parameters of the dolines are listed and explained and a preliminary discussion about some methods of spatial analysis is developed. It is intended to give methodological suggestions about data sources, systems of measurement, and to stimulate some reflection on the choices of possible processing of morphometric variables and on the significance of statistical analysis applied to different parameters. After a brief review of some morphometric and spatial analyses made in the past by different authors, three different examples are presented, relative to karst areas of the Venetian Prealps (Cansiglio-Cavallo, Montello) and of the Carso di Trieste. From these few examples one can understand how to confront this complex subject and what kind of results the analysis of morphometric parameters may give. In interpreting the results it is evident that one must not forget the geological, geomorphological, pedological, vegetational and climatic context of the karst area.

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

GROUNDWATER GEOCHEMISTRY OF THE CARBONATE KARST AQUIFER, SOUTH-CENTRAL KENTUCKY, USA, 1993, Hess J. W. , White W. B. ,
Analyses of 441 water samples from 15 sample sites, mainly springs and sinking creeks in the southcentral Kentucky karst, were used to determine hardness, P(CO2), and state of saturation with respect to calcite and dolomite. Most of the waters are undersaturated with respect to calcite and more undersaturated with respect to dolomite, in agreement with recent kinetic models. Time series data revealed chemical fluctuations on both weekly and seasonal time scales. Much of the short-term variation and some of the seasonal variation in the hardness and saturation index parameters can be accounted for by dilution effects from storm and seasonal runoff. Seasonal cycles in CO2 partial pressure arise from a dependence of soil CO2 on temperature and the growing season. Waters from different locations in the aquifer system are chemically distinct and fit into the concept of a hydrochemical facies

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

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