References of "Lagrou, David"
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See detailKarst in het krijt van Limburg en ombeving
Lagrou, David; Dusart; Willems, Luc ULg

Poster (2008)

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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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