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See detailEndokarsts and cryptokarsts in Cretaceous coarse and higly porous chalk at the Belgian-Dutch border
Willems, Luc ULg; Rodet, Joël

in Filippi, Michal; Bosák, Pavel (Eds.) Proceedings of the 16th International Congress of Speleology, July 21–28, Brno. Volume 3, p. 499. Czech Speleological Society. Praha. (2013, July 21)

Since 2003, the study of several quarries at the Belgian-Dutch border has made it possible to identify numerous karsts essentially developed in coarse chalk (calcarenites) of the Maastricht Formation ... [more ▼]

Since 2003, the study of several quarries at the Belgian-Dutch border has made it possible to identify numerous karsts essentially developed in coarse chalk (calcarenites) of the Maastricht Formation (Upper Cretaceous). This lithology is highly porous and is often considered unfavorable to karstification. However, caves, solution pipes, sponge networks, roof channel, pockets (alveoli) several meters in diameter developed inside without connection to fractures. These karsts belong to flooded karsts (caves and pockets) or to younger cryptokarsts (input karst type – thousands of solution pipes). When the endokarsts dewater, the high porosity of calcarenites inhibits closed caves from evolving. Tubular solution pipes are produced by the seepage water under fluvial terrace gravels and can exceed 30 m deep under the surface plateau. Sometimes, they encounter caves which are consequently filled and fossilized. By this process, they preserve caves from further collapsing inside a crumbly lithology. [less ▲]

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See detailes grottes de la Serra d’Itaqueri, exemple de karsts dans les grès, Brésil
Willems, Luc ULg; Hardt, Rubens; Rodet, Joël

Conference (2012)

Dans l’état de Sao Paulo, au Brésil, de nombreuses cavités sont trouvées dans des grès continentaux du Jurassique affleurant dans le front de la cuesta d’Itaqueri. Ces grottes se développent ... [more ▼]

Dans l’état de Sao Paulo, au Brésil, de nombreuses cavités sont trouvées dans des grès continentaux du Jurassique affleurant dans le front de la cuesta d’Itaqueri. Ces grottes se développent subhorizontalement dans une lithologie compacte et non carbonatée. Elles peuvent s’enfoncer d’une centaine de mètres à dans le massif. Précédemment, plusieurs auteurs ont donné aux différentes failles parcourant les roches un rôle prépondérant dans la genèse des cavités. Deux hypothèses ont été proposées pour leur formation: une dissolution en profondeur, aux nœuds de fracturation et/ou une évacuation mécanique postérieure des résidus d’altération par des écoulements percolant à travers le massif et résurgeant dans le front de cuesta. Pourtant, plusieurs observations telles que l’absence de circulation d'eau à l’intérieur des grottes ou la dislocation de morphologies anciennes par les différentes fractures contredisent ces deux propositions. Les accidents répertoriés au sein des cavités sont datés de 126 Ma et viennent démanteler plus qu’accompagner le développement des systèmes souterrains préexistants. Ces failles permettent de déterminer une karstification initiale des grès antérieure, vraisemblablement en milieu noyé. [less ▲]

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See detailKarsts des calcarénites de la carrière du Romont (Eben – Belgique)
Willems, Luc ULg; Rodet, Joël

in Bulletin des Chercheurs de la Wallonie (2010), (hors-série n°3), 119-134

Th e quarry of Romont (Eben/Bassenge, near the Belgian-Dutch border) intersects many endo and exokarsts developing essentially in coarse chalk (calcarenites) of the Maastricht Formation (Upper Cretaceous ... [more ▼]

Th e quarry of Romont (Eben/Bassenge, near the Belgian-Dutch border) intersects many endo and exokarsts developing essentially in coarse chalk (calcarenites) of the Maastricht Formation (Upper Cretaceous). It is an appropriate place to study deep and superficial karstification in highly porous rocks. Th e porosity partially inhibits the further development of closed caves (endokarsts) aft er they dewatered. Caves are later fi lled-up by collapsing or when they are cut by solution pipes (exokarsts), and thus partially sealed and preserved in a soft lithology. Th ese solution pipes are generated under river gravels and can go tens of meters deep through calcarenites. [less ▲]

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See detailKarsts dans les gneiss - alvéoles géantes et micro-alvéoles dans la région de Milagres, état de Bahia, Brésil
Rodet, Joël; Willems, Luc ULg; Auler, Augusto

Conference (2009, December 05)

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See detailProblème des karsts en roches silicatées... lacunes d’observation et paradigme du karst
Willems, Luc ULg; Ek, Camille ULg; Rodet, Joël et al

Conference (2009, December 05)

Depuis le développement de la karstologie, la grande majorité des cavités prospectées l'ont été dans les roches carbonatées ou apparentées, réputées fort solubles. Partant de ce principe, les autres ... [more ▼]

Depuis le développement de la karstologie, la grande majorité des cavités prospectées l'ont été dans les roches carbonatées ou apparentées, réputées fort solubles. Partant de ce principe, les autres lithologies n'ont été à ce jour que partiellement investiguées puisque réputées peu ou pas solubles. Pourtant, depuis plusieurs siècles, des grottes et autres formes apparentées sont mentionnées notamment dans des grès, des granites ou les quartzites. Très rapidement, elles ont été catégorisées comme pseudokarst en se basant sur deux principes, le premier, la convergence de forme, le second, les processus physico-chimiques qui présideraient à leur formation seraient différents de ceux rencontrés dans les calcaires. L'évolution des recherches et des techniques de ces vingt dernières années ouvre de nouvelles perspectives sur une réalité karstique commune qui transcenderait les lithologies tant carbonatées que non carbonatées. Peu à peu, elle oblige les chercheurs à se repositionner quant à la notion de karst. [less ▲]

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See detailEXEMPLOS BRASILEIROS DE CARSTE EM ARENITO: CHAPADA DOS GUIMARÃES (MT) E SERRA DE ITAQUERI (SP)
Hardt, Rubens; Rodet, Joël; Dos Anjos Ferreira PintoI, Sergio et al

in Espeleo-Tema - Sociedade Brasileira de Espeleologia (2009), 20(n. 1/2), 7-23

The issue of non-carbonate karst is still controversial in academic circles, there is resistance from classical karst researchers. However, in many studies throughout the world, the karst in non-carbonate ... [more ▼]

The issue of non-carbonate karst is still controversial in academic circles, there is resistance from classical karst researchers. However, in many studies throughout the world, the karst in non-carbonate rocks is a constant. Although their existence is controversial, this is due to the small amount of research conducted in these rocks had not generated a sufficient amount of information that would establish general comparison with the carbonate karst, identifying boundaries and differences. In this article, we attempted to show some of the evolution of the concept through the literature and present two examples of sandstone karst in Brazil. [less ▲]

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See detailAbordagem geomorfológica da bacia do rio Peruaçu e implicações geoarqueológicas
Rodet, Joël; Rodet, Jacqueline; Willems, Luc ULg et al

in Arquivos do Museu de História Natural (2009), 19(1), 75-103

The Rio Peruaçu Basin is the object of a geomorphological redifinition starting from a multi-field approach carried out for over ten years. Based on the works of the Minas Gerais archaeologists and ... [more ▼]

The Rio Peruaçu Basin is the object of a geomorphological redifinition starting from a multi-field approach carried out for over ten years. Based on the works of the Minas Gerais archaeologists and speleologists, this study defines four geomorphological compartments from the springs to the juction with the Sao Francisco river,namely: the zone of the upper valley, the zone of the geological transition, the zone of the karstic canyon and the zone of the alluvial plain. The main stages of the geomorphological evolution of the system were released and make it possible to define the space distribution of the mineral resources potentially usable by the prehistoric groups, and also to work out a typology of the raw material deposits. This approach contributes to the definition of the perception of the space by the first human settlements. [less ▲]

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See detailMorphodynamic incidences of the trepanning of the endokarst by solution pipes. Examples of chalk caves in Western Europe (France and Belgium)
Rodet, Joël; Willems, Luc ULg; Brown, Joël et al

in Contributed Papers Proceedings 15th International Congress of Speleology (2009)

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See detailINCIDENCES MORPHODYNAMIQUES DE LA TREPANATION DE L'ENDOKARST PAR DES RACINES DU MANTEAU D'ALTERATION. EXEMPLES DANS DES GROTTES DE LA CRAIE EN EUROPE OCCIDENTALE (FRANCE ET BELGIQUE).
Rodet, Joël; Willems, Luc ULg; OGIER-HALIM, Sylvie et al

in White, William B (Ed.) Proceedings : 15th International Congress of Speleology, Kerrville, Texas, United States of America, July 19-26, 2009 (2009)

Le débouché de la zone des puits dans les galeries du karst est considéré traditionnellement comme une suite logique de la pénétration des eaux de surface vers les collecteurs souterrains. C'est pourquoi ... [more ▼]

Le débouché de la zone des puits dans les galeries du karst est considéré traditionnellement comme une suite logique de la pénétration des eaux de surface vers les collecteurs souterrains. C'est pourquoi les observations se limitent généralement à de simples descriptions morphologiques. La mise en évidence de deux ensembles dynamiques distincts, l'introduction des eaux superficielles (karst d’introduction) et la collecte/concentration/restitution aux exsurgences des eaux souterraines (karst de restitution), et l’absence de connexion systématique entre karst d'introduction et karst de restitution permettent d’envisager une évolution initialement séparée, voire diachronique, de ces deux ensembles dynamiques. Afin de vérifier cette hypothèse, nous avons étudié l’impact de la trépanation de grottes dans deux réseaux karstiques d’Europe occidentale. Le premier en Normandie (France) se développe dans des craies fines où la porosité de la roche peut atteindre 10 à 15 %. Le second se situe en Basse Meuse liégeoise (Belgique) dans des calcarénites pouvant dépasser 50 % de porosité efficace. La cavité normande, mature et fossile, est largement comblée de sédiments quaternaires (loess). Elle est reconnue sur plus de 600 m, dont un collecteur de 450 m de développement. La trépanation du collecteur fossile et comblé et son fonctionnement séquentiel ont entraîné une ablation de la partie supérieure du comblement et sa substitution par la charge terrigène introduite par les épisodes d'introduction, avec une sédimentation conforme à la dynamique de l'introduction. Mais l'incidence majeure de ces épisodes est la mise en place d'une morphologie spécifique, organisée de l'amont vers l'aval : effet barrage vers l'amont du drain avec une altération profonde de l'encaissant, ouverture d'une rampe de connexion en toit avec le drain, développement d'un chenal de voûte pénétrable, ouverture d'un grand volume vide - réservoir d'équilibre, creusement d'un chenal de voûte plus petit, qui se réduit en aval au fur et à mesure de l'absorption du flux aqueux par le remplissage et les parois du collecteur. La cavité belge, reconnue sur quelques dizaines de mètres de développement, est comblée de sédiments terrigènes, sans qu’aucune liaison karstique ne soit établie avec une quelconque émergence. L'absence de continuité karstique aval interdit le creusement du chenal de voûte, mais on retrouve le comblement terrigène granoclassé, retouché par les épisodes plus récents, et en aval le développement d'une grande chambre réservoir où la porosité élevée des calcarénites encaissantes absorbe l'eau introduite. Ces deux exemples montrent très clairement que la connexion entre l'introduction des eaux et la restitution karstique n'est pas toujours assurée et surtout que le creusement des formes d'introduction peut se réaliser indépendamment du drainage de restitution. Lorsque que ce dernier est trépané alors qu'il n'est plus fonctionnel, il enregistre les effets d'une dynamique d'introduction. La recherche de ces morphologies dans les collecteurs peut alors livrer de sérieuses indications sur l'évolution du système karstique. [less ▲]

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See detailKarsts in sandstones and quartzites of Minas Gerais, Brazil
Willems, Luc ULg; Rodet, Joël; Pouclet, André et al

in Cadernos do Laboratorio Xeolóxico de Laxe (2008), 33

The state of Minas Gerais (Brazil) is characterized by significant karst regions, which develop <br /><br />in both sandstone and quartzite terrains and display complex suites of underground and ... [more ▼]

The state of Minas Gerais (Brazil) is characterized by significant karst regions, which develop <br /><br />in both sandstone and quartzite terrains and display complex suites of underground and surfaceforms. In the Espinhaço Ridge, Central Minas Gerais, several caves of up to a few hundred metres long, occur in the surroundings of the town of Diamantina. Some of these caves, such as Salitre actually consist of swallow-holes. Other horizontal caves are characterized by corrosion forms generated in the phreatic zone. In some places, such as in the Rio Preto area, these phreatic forms are overprinted by ceiling tubes, suggesting a polyphase karst evolution, prior to the draining in the cave. Remains of paths, with circular cross section up to one metre in diameter, can be found through residual tower-like surface landforms widely present in the landscapes. Their dissection is due to a generalised karstification in the area, resulting in closed canyons, megakarrens and kamenitzas. In Southern Minas Gerais, close to the Mantiqueira Ridge, the caves of the Ibitipoca state park can reach more than 2 km in length. These caves are associated with a very large hanging geological syncline. Several of these caves contain active streams, which flow for hundreds of metres before disappearing in sand-choked passages. Keyhole cross sections characterize steeply descending passages in these caves, indicatinga chan ge from slow phreatic flow towards a faster vadose flow responsible for the vertical incision of the passage. Such change is probably related to base level lowering and/or to turn in the direction of the water flow. Several generations of wall-pockets, from a few centimetres to over a metre long, occur into the caves. These features are good indicators of the initial phase of speleogenesis, generating the initial conduits by their coalescence. This mechanism is also responsible for cut-off meanders. In the area, the main river flows along the syncline axis and cuts through a rock barrier, generating a tunnel-like passage. This cave drains, through resurgences in its walls, part of the water that flows in other caves located in the flank of the syncline. [less ▲]

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See detailKarsts des craies et calcarénites de la Montagne Saint-Pierre (Basse Meuse liégeoise)
Willems, Luc ULg; Rodet, Joël; Ek, Camille ULg et al

in Bulletin des Chercheurs de la Wallonie (2007), XLVI

The “Montagne Saint-Pierre” (Sint Pietersberg) is a separate part of the Hesbaye plateau, isolated between the lower valleys of the Geer and the Meuse rivers. It is exploited by a big open-air quarry and ... [more ▼]

The “Montagne Saint-Pierre” (Sint Pietersberg) is a separate part of the Hesbaye plateau, isolated between the lower valleys of the Geer and the Meuse rivers. It is exploited by a big open-air quarry and by numerous underground quarries developing galleries on hundreds of kilometers long. Excavated in Cretaceous chalk and calcarenite, these artificial networks allow an exceptional 3-D observation of karsts inside a very porous and permeable rock, less favourable to a concentrated solution. The most numerous of them are “organ pipes” or “earth pipes”. They are vertical tubular solution pipes that may exceed 60 m in depth. Sponge networks and subhorizontal caves occur, without any visible connection with fracturation. Finally, downwards to at least 20 m below the alluvial plain of the Meuse river, pluridecametric nodes of weathered chalk are found. By their size and rounded morphology, the nodes resemble to the natural caves occurring in the calcarenite and intersected by the underground quarries. All the studied karsts allow us to propose a scenario for the genesis of a polyphase karst system. Independently of surface conditions, caves are generated deeply in the phreatic zone (endokarsts). During the downcutting of theMeuse valley, and related to the fluvial terraces, solution pipes (input karsts) are generated. Due to the valley incision and to the lowering of the aquifer,theses solution pipes progress downward and cut the endokarsts. A concentrated water circulation takes place. In the dewatered upper part of the system, caves cut by solution pipes are rapidly filled by superficial deposits. The high porosity of the calcarenite makes it comparable to a sponge. The rock absorbs quickly the out-flows coming from the surface and causes a rapid deposit of the fine particles transported inside horizontal passages. The sealing of these conduits allows their conservation inside a very crumbly rock. [less ▲]

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See detailPolyphase karst system in Cretaceous chalk and calcarenite of the Belgian-Dutch border
Willems, Luc ULg; Rodet, Joël; Fournier, Matthieu et al

in Zeitschrift für Geomorphologie (2007), 51(3), 361-376

Along the Belgian-Dutch border, underground and surface quarries dug in Cretaceous calcarenite and chalk intersect many karst features as well as deep large nodes of weathered rock. Their observation ... [more ▼]

Along the Belgian-Dutch border, underground and surface quarries dug in Cretaceous calcarenite and chalk intersect many karst features as well as deep large nodes of weathered rock. Their observation allows the reconstruction of the genesis of an original karst system resulting from the merging of initially independent endokarsts and exokarsts. Deep weathering has developed within the Cretaceous formations, creating nodes of weathered chalk and closed cavities. These phenomena are expanded over time and can form interconnected voids. Near the surface, solution pipes are generated under the coarsest deposits of a fluvial terrace capping the Cretaceous formations. These pipes develop vertically and may be related to the progressive lowering of the water table in connection with the incision of the Meuse valley. Some of these phenomena cut up the older endokarsts and organize complex systems of out-flow within the chalk. [less ▲]

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See detailKarsts des craies et calcarénites de la Montagne Saint-Pierre (Basse Meuse liégeoise)
Willems, Luc; Rodet, Joël; Ek, Camille ULg et al

in Bulletin de la Société Royale Belge d'Etudes Géologiques et Archéologiques (2007), XLVI

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See detailPolyphased karst systems in sandstones and quartzites of Minas Gerais, Brazil
Willems, Luc ULg; Rodet, Joël; Pouclet, André et al

in Proceeding 14th UIS Congress, Athens-Kalamos, 23-28 august 2005, Abstract Book : 71. (2005)

The state of Minas Gerais (Brazil) exhibits several major karst areas located in sandstone and quartzite terrains, that display a complex suite of underground and surface karstic forms. In the Espinhaço ... [more ▼]

The state of Minas Gerais (Brazil) exhibits several major karst areas located in sandstone and quartzite terrains, that display a complex suite of underground and surface karstic forms. In the Espinhaço Ridge, central Minas Gerais, several caves, up to a few hundred metres long, occur in the surroundings of the town of Diamantina. Some of these caves, such as Salitre, represent swallow-holes and show dome pits. Other horizontal caves are characterized by corrosion forms generated into the phreatic zone. In some places, such as in the Rio Preto area, these phreatic forms have been overprinted by ceiling tubes, suggesting a polyphase karst evolution, prior to the draining of the cave. Relicts of passages, with circular cross section up to a metre in diametre, can be found amidst the residual tower-like surface landforms, which constitute a typical scenery in the landscape. Their dissection is due to a generalised karstification in the area, resulting in closed canyons, megakarrens and kamenitzas. In southern Minas Gerais, close to the Mantiqueira Ridge, the caves of the state park of Ibitipoca can extent 2 km in length. These caves are associated with a very large hanging geological syncline. Several of these caves contain active streams, that flow for hundreds of metres before disappearing in sand-choked passages. Keyhole cross sections characterize steeply descending passages in these caves, indicating a change from slow phreatic flow towards a faster vadose flow responsible for the vertical incision of the passage. Such change is probably related to base level lowering and/or to turn in the direction of the water flow. Several generations of wall-pockets, from a few centimetres to over a metre long, occur into the caves. These features are good indicators of the initial phase of speleogenesis, generating the initial conduits by their coalescence. This mechanism is also responsible for cut-off meanders. The main river in the area, which flows along the syncline axis, cuts through a rock barrier, generating a tunnel-like passage. This cave drains, through resurgences in its walls, part of the water that flows in other caves located in the flank of the syncline. The non-carbonate karst features observed in the state of Minas Gerais demonstrate the complex organisation of polyphase karst systems due to the linkage of underground and surface forms not previously connected. As in carbonate areas, these systems may play an important hydrological role. [less ▲]

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See detailChalk karsts – Saint-Pierre Mountain – Basse-Meuse (Belgium)
Willems, Luc ULg; Rodet, Joël; Masséi, Nicolas et al

Poster (2004, May)

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See detailKarsts en roches non carbonatées - l'exemple des quartzites et des itabérites de Minas Gerais, Brésil
Willems, Luc ULg; Rodet, Joël; Auler, Augusto et al

in Rodet, Joël (Ed.) Actes des Journées Européennes de l'AFK 2003 (2003)

The state of Minas Gérais, Brazil, contains numerous karsts booth inside carbonated and non carbonated rocks. Différent caves are found in quartzite and Itaberite formations (Banded Iron formation). The ... [more ▼]

The state of Minas Gérais, Brazil, contains numerous karsts booth inside carbonated and non carbonated rocks. Différent caves are found in quartzite and Itaberite formations (Banded Iron formation). The term karst is used in the meaning of "any features of the classical karst morphology (caves, sink-holes, lapies...) where dissolution plays the main genetically action and this in any kind of rocks". In some areas, lapiaz and kamenitza affect wide landscapes (area of Diamantina, Natural Parc of Rio Preto). Several caves are found and some of these are several kilomeetres long (grutta do Bromelias, Natural Parc of Ibitipoca). Inside caves, we found numerous forms like dissolution alveoli, spelothems, .... Many times, the cave sides and solutional forms are covered by crust which solidify a very crumbly quartzite. Différent morphologies show an primary solutional stage of the rocks before a physical erosional stage which destroy the earliest forms (piping, river érosion, collapsing). [less ▲]

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