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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. ...

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Your search for grands causses (Keyword) returned 13 results for the whole karstbase:
Prsentation du Causse Comtal (Aveyron), 1987, Solier, P.
THE " CAUSSE COMTAL " (AVEYRON, FRANCE): GEOLOGY, HYDROGEOLOGY AND INVENTORY OF MAIN CAVES - The " Causse Comtal " (S = 265 km2) forms a sedimentary bridge between the " Causses du Quercy " in the west and the " Grands Causses " in the east. With a middle humid climate (P = 1000 mm/y, T = 9,4 C, Evap. = 450-500 mm/y), this plateau karst presents two aquifer levels in the Lower and Middle Jurassic separated by a marly layer. These formations cover a paleozoic basement (sandstone, argillite from Carboniferous and Permian, crystalline rocks). The hydrogeological basins are controlled by E-W reverse faults due to the N-S pyrenean compression. The main spring is near Salles-la-Source in the western part (average discharge: 840 l/s; flood : 10 m3/s); it drains a 50-55 km2 area. The morphological and speleological evolution is subordinated to an erosion surface from Upper Cretaceous - Tertiary. Often stopped up (blocking), the numerous fossil caves probably date from the end of Cenozoic era. The large subterranean passages (active or semi-actives galleries; ex.: Tindoul de la Vayssire) are plio-quaternary.

Dissolution spcifique la priphrie des Grands Causses franais, 1989, Maurin, Y.
Specific denudation on the periphery of the Great Causses (France) - This paper deals with the results of the specific denudation on the carbonate formations, on the western border of the Great Causses of France: Can de lHospitalet, Can de Tardonenche, le Lempezou, Causse des Bonbons, Valdonnez basin. The results are obtained form the hydrochemical measurements taken form the hydrological cycles of 1982-1983. These results are then compared with those of other local and regional karsts. They show that there is important erosion linked to a well-developed endokarst. This situation contrasts with a deficiency of exokarst phenomena.

Prsentation des principales cavites du Causse de Laissac-Sverac (Aveyron), 1990, Rigal, C.
PRESENTATION OF THE MAIN CAVES OF THE CAUSSE OF LAISSAC-SEVERAC (AVEYRON, FRANCE) - The causse of Laissac-Severac is situated between "Grands Causses" and "Causse of Sauveterre" (Aveyron), in limestones and dolomites of Lias and Middle Jurassic. This speleological area presents two kinds of karst systems: losses and resurgences at the contact of the crystalline massif (Levezou) on the south part (Clos del Pous = 3km), and caves with numerous sumps under the Causse of Severac on the north part (plateau with large depressions (Tantayrou = 3.1km). These caves are post-Miocene because of the dated volcanism; they cut an eogene paleokarst, which is characterised by ferralitic paleosoils (ferruginous sandstone called "Siderolithique") from the alteration of crystalline massif.

Coloration de la grotte-perte du Camp de lUbac (Gorges de la Jonte, Lozre, France), 1994, Andre D. , Vanara N.
Within the framework of a master's degree dissertation on the Jonte basin, in the French department of Lozre, experiments were carried out in the highest sinkhole known of the underground course of this river. The result of the injection of the fluorescent dye into the Puits du Regard stream (Camp de l'Ubac, - 13m) on May 2nd 1990 confirmed that this stream belongs to the subterranean network of the Jonte river. After travelling approximately 9 km, the dye re-emerged 43 hours later in the different resurgences of the Les Douzes spring. The experiment showed that the water travelled at a high speed. 200 m/h. This high speed means that the sinkhole at Le Camp de l'Ubac is near the main drain and that the streams are neither hindered by vast reservoirs nor held by narrow passages.

Quelle est la dimension du massif karstique de la Sainte-Baume ? Elments pour une thorie spatiale et fractale du karst, 2000, Martin, Philippe
The dimension of the surface of Sainte Baume and its neighbourhood is close to 2,2. This value has been obtained the study of 5 contour lines (from 400 to 800 m) and 5 topographic profiles (3 N - S and 2 E - W). 3 methods were used for contour lines: box counting (DB); the information dimension (Di) and surface - perimeter relation (D(P)). Three methods have been used for topo_graphic profiles: the power spectrum (DSPEC); statistics R/S (DR/S) and vario_gramme (DVAR). Average results are: (DB) = 1.20; Di = 1.23; (D(P)) = 1.32; DSPEC = 1.17; DR/S = 1.24; DVAR = 1.23. Thus, the surface of Sainte Baume and its neighbourhood is fractal. It means, theoretically, that Sainte Baume can be characterised by an infi_nite surface in a bounded volume. This first approach focuses on karst surface approach, cave systems approach will be presented in a following paper (in this review). This result raises numerous geomorpho_logic questions. How to calculate a specific erosion? How to think forms in a theoretical frame, which could develo_ped out of the Euclidean geometry conventions? How to think an essential_ly irregular morphology? Elements of answer are brought on a theoretical plan. They constitute the first elements of a karst geometrical theory. Calculation of the specific erosion points out the problem of the size of the surface used. Due to fractal theories, this size is relative to the observation scale used. To be significant, specific erosion calcula_tion needs the use of an efficient scale, in regard of the erosion processes studied. Furthermore, specific erosion expresses only a balance of mass, not a morphoge_nesis. It corresponds to a chronological approach of the karst. Two dynamics can be distinguished in surface morphogenesis. In one hand, increase of the mean slopes is named spatial differentiation, in another hand, decrease of this value is classically called: aplanation or levelling. These 2 dynamics imply the wearing away of spatially various materials. It takes place essentially around thalwegs during the differentiation stage, around the crest during levelling. Thus morphology, space are important factors of the dynamics in the work. Space is not only a support, but an actor in morphogenesis.

Forme et rugosit des surfaces karstiques. Consquences pour une thorie spatiale et fractale de linterface terrestre, 2000, Martin, Philippe
This text proposes a theoretical, hypothetical and speculative approach of the transformation of earth's surfaces. This reflection is based on the notion of otherness. Our approach uses two oppositions: levelled/ roughness and karstic/ non karstic. The dimension of the roughness surfaces is understood between 2 and 3. The dimension of the surfaces of levelling is close to 2. Quantifications showed that massifs are limited by surfaces more or less irregular. In certain cases, the erosion transforms so a surface of levelling into rough surface. In that case initial shape is not preserved. The levellings on the karstic massifs (outliers often) seem better preserved (karstic immunity) than on the other rocks. This conservation would explain a weak value of the fractal dimension of air surfaces of karsts tested always with the same protocol (relation S PD). They were compared with the surfaces of reliefs of basal complex. Three ideas summarise obtained results: [1] The average of fractal dimensions of karsts are smaller than those of the relief of basal complex. [2] The dispersal of the mean values of surface of karst is lower to the dispersal of the mean values of basal complex. [3] Distance between minimal and maximal values for karsts is much bigger than distance between minimal and maximal values for basal complex. To explain the weak roughness of karsts we made three hypotheses: [a] These fragments would correspond to zones still not affected by the erosion (time problem) [b] In such a system some changes on a plan would prevent changes on the another plan (spatial problem) [c] Initial shape is replaced by a similar shape (Platon's Parmnide). The endokarst is described empirically and by analogy with the fractal model of Sierpinski's sponge as a unique surface infinitely folded up in a limited volume. So the growth of the karstic spaces in the endokarst, increases almost until the infinity, the size of the internal surface of the karst. To find a theoretical base at the roughness and at the extreme size of these surfaces, we studied the report between the growth of a volume and the growth of the surface, which limits this volume. Three theoretical models show that if surfaces do not change, volume to be affected by unity of surface grows strongly. Eroded volume depends on the size of the exposed surface. If the eroded volume depends on the size of the exposed surface, then time to erase a mountain could be, in theory, infinite. This is not acceptable because a massif can be erased in about 200 Ma. According to analogies with different morphogenesis (physical, biologic), we make the hypothesis that fractal character, of surfaces of the massifs corresponds to the necessity of increasing, as much as possible, the size of the surface subjected to the erosion so as to decrease the time of destruction of the relief. This is coherent with the idea of a system far from the balance, which tends to join the state of balance as quickly as possible by developing specific morphologies. Distance between the relief and the lower limit of the potential of erosion is then introduced as a factor being able to explain the small roughness of high continental surfaces. The reduction of the volume by erosion is cause (and not consequence) of the decrease of the roughness. The surface can become less rough because volume decreases. The surface of levelling constitutes the final morphology, which is transformed only very slowly. In this perspective the dynamics allows only the fulfillment of spatial rules. In the case of the karst, because of the existence of the subterranean part of the karstic surface and its roughness, it is not useful that air part becomes very rough. Levellings would be preserved by geometrical uselessness to destroy them. They would not correspond to forms in respite as implies him the temporal analysis (hypothesis [a]), but to forms corresponding to a particular balance (hypothesis [b]) who would even be locally transformed (karstic levelling) into the same shape (hypothesis [c]). This theoretical plan supplies with more an explanation on the visible contradiction between the speed of the karstic erosion and the durability of levellings.

Pedogenic and Karstic Features at the Boundaries of Bathonian Depositional Sequences in the Grands Causses Area (Southern France): Stratigraphic Implications, 2000, Charcosset P, Combes Pj, Peybernes B, Ciszak R, Lopez M,
Several exposure surfaces (D1 to D6) underlain by paleosols, paleokarstic surfaces, and subsurface paleokarsts were identified in the Middle to Upper Bathonian Calcaires a Stipites and Dolomies II Formations in southern France. Two kinds of paleosols with different degrees of maturity were recognized: simple ferruginous crusts, capping very irregular bed surfaces, and a rooted horizon. The paleokarstic surfaces are marked by nodular horizons and paleocaves. On the Cevennes shoal, the paleokarsts discontinuities are associated with synsedimentary tectonic processes, which did not extend into the overlying Dolomies II Formation. Subsurface paleokarsts were observed in the Cirque du Bout du Monde (on the Cevennes shoal) within the Calcaires a Stipites Formation, just beneath surface D5. They are characterized by stronger brecciation of the beds. Most of the paleokarstic discontinuities described in this study correspond to the boundaries of four third-order depositional sequences, Bt 1 to Bt 4 (D1 at the base of Bt 1; D2, D3, D4, and D5 capping Bt 1, Bt 2, Bt 3, and Bt 4, respectively; D6 at the top of the Dolomies II Formation). D1, D2, and D3 paleokarsts are geographically limited to the Grands Causses Graben, whereas D4, D5, and D6 are present only on the Cevennes shoal. Geographic trends of paleokarsts confirm the transgressive trend of sequences Bt 3 and Bt 4, and of the overlying Dolomies II Formation towards the shoal. D6 paleokarstic features were also observed within the uppermost part of the Dolomies II Formation in the Horst de Saint-Bresson. The latter transgressive process provides evidence for subaerial exposure of this paleostructure during the latest Bathonian-Callovian interval, induced by tectonic uplifts

Reconstitution morpho_lo_gique du Causse du Larzac (Aveyron, France), rle des formations superficielles dans la morphogense karstique, 2001, Bruxelles, Laurent
The study of post-Jurassic deposits, superficial formations which stay on the plateau or are preserved in caves permits us, together with the morphologies of landscape, to reconstitute the main steps of morphological evolution of this part of the Larzac. In particular, the discovery of numerous witnesses of cretaceous cover, marine and continental, let us know the first morphogenesis of the Grands Causses. After the bauxite episode, coniacian transgression fossilized a differentiated palaeotopography under one hundred meters of sandy limestone. After, the erosion of this deposits and the transit of various alterites, allogene or autochthonous, show further morphological steps. Theses formations can constitute a real cover and contribute to the development of karstic levellings. Residual formations, associated with levels of shelves, regulate lowering of karstic surface between Eocene and Miocene, before the canyon digging and the development of karstic recules. Then, between Miocene and Quaternary, karst declogging changes radically the evolution of the plateau surface and let appear poljes, dolines and underground network. Only some specific areas can keep their cover of alterites and maintain, temporally, an old functioning.

Evolution of river network at the 'Cevennes-Grands Causses' transition: Consequences for the evaluation of uplift, 2001, Camus H,
The Mediterranean catchment of the Cevennes (S. France) presents deep incision of the river network (fig. 1 and 2). Combined geomorphology and analyses of the residual sedimentary formations allows to reconstruct a complex history of river network evolution, including capture of tributaries of the Herault River (fig. 1, 2 and 3). The history of uplift of the upstream drainage area could be estimated from the provenance studies of the fluvial and karstic deposits, however river incision is also controlled sea-level changes and differential erosion, which makes reconstruction more complex. Allochthonous clasts types Analyses of allochtonous deposits on the Grands Causses surface reveals different origin for sediments from the hill top and the Airoles valley (fig. 4b), which was previously unrecognised. Facies 1 is found on the highest points of the Grands Causses surface (well sorted rounded quartz pebbles in red shale matrix) it corresponds to a weathered residual sediments (dismantling of an ancient cover). Facies 2 is found on the slope of the Airoles Valley (fig. 7). It consists of alluvial crystalline poorly sorted clasts with outsized clasts (up to 50cm) of quartz-vein, schists in a matrix of shales and sand (weathered granite). Between the hill tops and the Airoles Valley, karstic network presents a sediment fill with clasts reworked from facies I and facies 2 (fig. 6). Airoles valley model : an example of diachronic formation of drainage network The Airoles dry valley stretches on the Grands Causses from the north (700 m) to the south into the present thalweg line of the Vis canyon (500 m) (fig. 1b & 3). Crystalline deposits witness an ancient catchment in the Cevennes. Presently, the catchment in the crystalline basement is disconnected and captured by the Arre River flowing eastwards (fig. 3 & 4a). The profile of the Airoles abandoned valley connects with the present Vis Canyon, therefore, at the time of capture, incision of the Vis canyon had reached its present altitude (fig. 4a). The geomorphologic evolution of this area took place in three stages (fig. 8). 1) The Grands Causses acted as piedmont for the crystalline highlands of the Massif Central (fig. 8A). A latter karstic evolution (tropical climate) allowed the weathered residual sediments (facies 1) (fig. 8A). 2) Incision of the Vis karstic canyon implies that the Herault incision and terraces (facies 2) (fig, 8B) of the Airoles valley occurred during this stage. 3) The Arre valley head propagates westward by regressive erosion and finaly captured the Airoles river crystalline catchment (fig. 8C). Consequence for the Cevennes uplift and hydrographic network development Although the values of present vertical incision in the Vis canyon and in the Arre valley are similar, but they achieved at different time. In addition, the narrow and deep canyon of the Vis is due to vertical incision from the karstic surface of the Grands Causses, whereas the Arre wide valley results from (a younger) lateral slops retreat from a low Herault base-level. The Vis karstic canyon developed in a similar way to the major karstic canyons of both Mediterranean and Atlantic catchment (i.e. Tarn). This rules out a Messinian Mediterranean desiccation as incision driving mechanism and suggests tectonic uplift of the Cevennes and surrounding areas. The Tam being already incised by 13 My [Ambert, 1990], it implies a Miocene age for the incision. Conclusion The amplitude of the vertical incision cannot therefore be used in a simple way to interpret the uplift history of the basement. Consequently, geomorphologic analysis appears to be a prerequisite to distinguish the part played by each factor, and to select the site of uplift measurement

Inverse modeling of the hydrological and the hydrochemical behavior of hydrosystems: Characterization of karst system functioning, 2001, Pinault J. L. , Plagnes V. , Aquilina L. , Bakalowicz M. ,
Inverse modeling of mass transfer characterizes the dynamic processes affecting the function of karst systems and can be used to identify karst properties. An inverse model is proposed to calculate unit hydrographs as well as impulse response of fluxes from rainfall-runoff or rainfall-flux data, the purpose of which is hydrograph separation. Contrary to what hydrologists have been doing for years, hydrograph separation is carried out by using transfer functions in their entirety, which enables accurate separation of fluxes, as was explained in the companion paper [Pinault et al., this issue]. The unit hydrograph as well as impulse response of fluxes is decomposed into a quick and a slow component, and, consequently, the effective rainfall is decomposed into two parts, one contributing to the quick flow (or flux) and the other contributing to the slow flow generation. This approach is applied to seven French karstic aquifers located on the Larzac plateau in the Grands Causses area (in the south of France). Both hydrodynamical and hydrogeochemical data have been recorded from these springs over several hydrological cycles. For modeling purposes, karst properties can be represented by the impulse responses of flow and flux of dissolved species. The heterogeneity of aquifers is translated to time-modulated flow and transport at the outlet. Monitoring these fluxes enables the evaluation of slow and quick components in the hydrograph. The quick component refers to the 'flush flow' effect and results from fast infiltration in the karst conduit network when connection is established between the infiltration and phreatic zones, inducing an increase in water head. This component reflects flood events where flow behavior is nonlinear and is described by a very short transfer function, which increases and decreases according to water head. The slow component consists of slow and fast infiltration, underground runoff, storage in annex-to-drain systems, and discharge from the saturated zone. These components can be further subdivided by measuring chemical responses at the karst outlet. Using Such natural tracers enables the slow component of the unit hydrograph to be separated into preevent water, i.e., water of the reservoir and event water, i.e., water whose origin can be related to a particular rainfall event. These measurements can be used to determine the rate of water renewal. Since the preevent water hydrograph is produced by stored water when pushed by a rainfall event and the event water hydrograph reflects rainwater transfer, separating the two components can yield insights into the characteristics of karst aquifers, the modes of infiltration, and the mechanisms involved in karstification, as well as the degree of organization of the aquifer

Continental France and Belgium during the early Cretaceous: paleoweatherings and paleolandforms, 2006, Thiry Medard, Quesnel Florence, Yans Johan, Wyns Robert, Vergari Anne, Theveniaut Herve, Simoncoincon Regine, Ricordel Caroline, Moreau Marie Gabrielle, Giot Denis, Dupuis Christian, Bruxelles Laurent, Barbarand
During the early Cretaceous, successive tectonic phases and several sea level falls resulted in the emersion of the main part of western Europe and the development of thick 'lateritic' weathering. This long period of continental evolution ended with the Upper Cretaceous transgressions. During this period, the exposed lands displayed a mosaic of diverse morphologies and weathered landscapes. Bauxites are the most spectacular paleoweathering features, known for long in southern France. Recently, new residual outcrops have been identified, trapped in the karstic depressions of the Grands Causses. Other bauxitic formations, containing gibbsite, have also been recognised, occurring with the Clay-with-Jurassic-cherts in the southeastern border of the Paris Basin. These bauxitic formations overlay Jurassic limestone and are buried beneath Upper Cretaceous marine deposits. The recognition of bauxites up north into the southern Paris Basin significantly widens the extension of the Lower Cretaceous bauxitic paleolandscapes. On the Hercynian basements thick kaolinitic weathering mantles occur. They have been classically ascribed to the Tertiary. The first datings of these in situ paleosoils, by means of paleomagnetism and/or radiogenic isotopes, record especially early Cretaceous ages. This is the case for the 'Siderolithic' formations on the edges of the French Massif Central, but also for the kaolinitic profiles in the Belgian Ardennes. In the Flanders, the Brabant basement is deeply kaolinised beneath the Upper Cretaceous cover. These paleosoils show polygenetic evolutions. The relief of these basement paleolandscapes may have been significant. There where probably high scarps (often of tectonic origin) reaching 200 m in elevation or beyond, as well as wide surfaces with inselbergs, as in the present day landscapes of tropical Africa and South America. On the Jurassic limestone platforms occur diverse kaolinitic and ferruginous weathering products. Around the Paris Basin they show various facies, ranging from kaolinitic saprolites to ferricretes. Due to the lack of sedimentary cover, the age of these ferruginous and kaolinitic weathering products has been debated for long, most often allocated to the Siderolithic sensu lato (Eocene-Oligocene). Recent datings by paleomagnetism have enabled to date them (Borne de Fer in eastern Paris Basin) back also to the early Cretaceous (130 {} 10 Ma). These wide limestone plateaus show karstified paleolandforms, such as vast closed and flat depressions broken by conical buttes, but also deep sinkholes in the higher areas of the plateaus and piedmonts. The depth of the karst hollows may be indicative of the range of relative paleoelevations. Dissolution holes display seldom contemporaneous karst fillings, thus implying that the karstland had not a thick weathering cover or that this cover had been stripped off before or by the late Cretaceous transgression. Nevertheless, some areas, especially above chert-bearing Jurassic limestone or marl, show weathering products trapped in the karst features or as a thick weathering mantle. In the Paris Basin, the Wealden gutter looked like a wide floodplain in which fluvio-deltaic sands and clays were deposited and on which paleosoils developed during times of non-deposition. The edges of the gutter were shaped as piedmonts linked up with the upstream basement areas. The rivers flowing down to the plain deposited lobes of coarse fluvial sands and conglomerates. The intensity of the weathering, the thickness of the profiles and their maturation are directly dependent on the duration of the emersion and the topographic location relative to the gutter. Near the axis of the gutter, where emersion was of limited duration, the paleoweathering features are restricted to rubefaction and argillization of the Lower Cretaceous marine formations. On the other hand, on the borders of the basin and on the Hercynian basement, where emersion was of longer duration, the weathering profiles are thicker and more intensively developed. The inventory of the Lower Cretaceous paleoweathering features shows the complexity of the continental history of this period. Moreover, the preserved weathering products are only a part of this long lasting period, all the aspects relative to erosion phases are still more difficult to prove and to quantify. In this domain, apatite fission tracks thermochronology (AFTT) can be helpful to estimate the order of magnitude of denudation. Residual testimonies and subsequent transgressions may enable to estimate relative elevations, but in return, we presently have no reliable tool to estimate absolute paleoelevations. In the work presented here, the inventory enabled to draw a continental paleogeographic map showing the nature of the weathering mantles and the paleolandscape features, just as paleoenvironments and paleobathymetry presently appear on marine paleogeographic maps. For the future, the challenge is to make progress in dating the paleoweathering profiles and especially in the resolution of these datings, in order to correlate precisely the continental records with the different events which trigger them (eustatism, climate, regional and global geodynamics). The final goal will be to build up a stratigraphic scale of the 'continental geodynamic and climatic events' in parallel with 'sequential stratigraphy' in the marine realm

Formes et formations superficielles de la partie ouest du Causse de Sauveterre (Grands Causses, Aveyron et Lozre), 2007, Bruxelles Laurent , Simoncoinon Rgine, Guendon Jeanlouis, Ambert Paul
MORPHOLOGY AND SUPERFICIAL FORMATIONS OF THE WESTERN PART OF THE CAUSSE DE SAUVETERRE (GRANDS CAUSSES, AVEYRON AND LOZ?RE, FRANCE). In 2002, the Natural Regional Park of Grands Causses has coordinated a hydrogeological study of the western part of the Causse de Sauveterre, the northernmost of the Grands Causses. A multidisciplinary approach (geology, geomorphology, geochemistry and hydrology) was used to delineate the catchment area of the main springs and to estimate the vulnerability of karstic aquifers. The Grands Causses are situated in the southern part of the French Massif Central. The landscape is characterised by huge limestone plateaus cut by deep canyons. The morphologic study of the western part of the Causse de Sauveterre (Causse de Massegros and Causse de S?v?rac), combined with analysis of superficial formations, allows us to identify the main steps of landscape evolution. The discovery of bauxite and of many outcrops of Upper Cretaceous sandstone confirm that the Coniacian ingression invaded some paleo-landscapes developed within a long period of continental evolution which was initiated at the end of the Jurassic. During the Tertiary, many residual formations form covers of the limestone plateaus. We can distinguish alterites developed from different formations of the stratigraphic series (clay with cherts from Bajocian, dolomitic sand from Bathonian and Callovian, sandy clays from Cretaceous deposits) from some allochtonous deposits which can be found in some parts of the Causse de Massegros. These formations are found in association with morphological features (shelves, polj?s, fluvio-karstic valleys, sinkholes) and are more or less responsible of their development. Furthermore, some volcanic rocks cut through or even reused some of them. With the deepening of canyons and the base level drop, horizontal morphologies are preserved only where superficial formations are abundant and thick enough to maintain crypto-corrosion. Elsewhere, karst unplugging removes most of the superficial formations, and the karstic evolution tends to show a vertical development of morphologies and caves. Some springs, which benefit from a favourable lithologic, structural and hydrologic context, are more competitive and expand their catchment area at the expense of the other springs. Many superficial features express this dynamism on the plateau and allow us to determine the most sensible areas for water pollution and the most fragile ones for human activities.

Laltration de type "fantme de roche" : processus, volution et implications pour la karstification, 2011, Quinif Yves, Bruxelles Laurent

Depuis plusieurs années, de nombreux exemples de fantômes de roche ont été reconnus dans les karsts en Belgique, en France et en Italie. Ils correspondent à des poches ou à des couloirs de décalcification emplis d’altérite in situ. Leur genèse relève d’un cas spécial de karstification où, à l’inverse des phénomènes de karstification par enlèvement total, le résidu insoluble ou moins soluble reste en place et forme un squelette qui mime la structure initiale de la roche (fossiles, joints, lits de chailles, etc.). Cette altérite, qui peut également se développer sous une voûte calcaire, forme un vaste réseau interconnecté et calé sur la fracturation. De fait, elle constitue une discontinuité importante au sein des massifs karstiques. Lorsque le niveau de base s’abaisse, l’altérite s’effondre sur elle-même puis elle est érodée par des circulations souterraines qui se mettent en place à son toit. Des réseaux de galeries mais aussi des formes de surface se forment alors rapidement, essentiellement par évidement de l’altérite. Ce phénomène est maintenant reconnu dans le monde entier, affectant tous les types de roches, carbonatées ou non.

For several years, numerous examples of ghost rocks have been recognised in karst areas in Belgium, in France and in Italy. They correspond to decalcified pockets but also to decalcified corridors filled with in-situ alterite. It is a special case of karstification where a non-soluble skeleton remains and preserves the structures of the initial rock (fossils, joints, levels of cherts, etc.). This alterite, which can also be formed under a safe roof, draws a large maze following the tectonic patterns. It constitutes an important discontinuity inside the karstic areas. When the base level drops, the structure of the alterite collapses and a void is formed on his top. Then runoff can use this void and erode the soft alterite. Cave network but also surface features can develop quickly, mainly by the cleaning of the alterite. Now, some examples of this phenomenon have been recognised all around the world and occur in different sorts of rocks, carbonated or not.


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