Reference : Karsts in silicated and non carbonated rocks
Scientific congresses and symposiums : Unpublished conference/Abstract
Physical, chemical, mathematical & earth Sciences : Earth sciences & physical geography
Karsts in silicated and non carbonated rocks
Willems, Luc mailto [Université de Liège - ULiège > Département de géologie > Pétrologie sédimentaire >]
International Symposium "Karst Research, Challenges for the XXIst century" Brussels, 30 September 2011 & Rochefort, 01 October 2011
du 30 septembre au 1 octobre 2013
Sophie Verheyden, Belgian Science Policy Office - Vrije Universiteit Brussel
Rudy Swennen, Katholieke Universiteit Leuven
Jacques Schittekat, Tractebel Engineering & KU Leuven
Yves Quinif, Université de Mons
Alain Rorive, Université de Mons
Michiel Dusar, Geological Survey of Belgium, RBINS
Camille Ek, Université de Liège
Luc Willems, Université de Liège
Eric Groessens, Geological Survey of Belgium
Christophe Frippiat, IAH Belgium
Charles Bernard, Scientific Commission of "Union Belge de Spéléologie"
Roger Vandenvinne, Scientific Commission of "Union Belge de Spéléologie"
Bruxelles - Rochefort
[en] karsts ; silicated rocks
[en] Karsts in silicated and non carbonated rocks refer to morphologies similar to those found in limestones (caves, lapies, polje…) as being equally generated by predominantly dissolution processes. Their discovery in allegedly not very soluble rocks raises the question of existing water resources in lithologies which are rarely considered from this point of view.
A rough inventory of this kind of karsts shows that they essentially develop in sandstones and quartzites. Other silicated lithologies such as granites or gneisses seem to contain only a few examples. Karsts in silicated and non carbonated rocks are found at all latitudes, though mainly in the warm and temperate climate zones of the world. Nevertheless, these conclusions may result from the lack of systematic prospecting in numerous regions of the world. Typically, most studied cavities are located in Paleozoic to Proterozoic rocks. Underground networks can stretch for several kilometers.
Two types of cavities can be identified. The first one is characterized by cave entrances located in a cliff or in a raised hillside. These subhorizontal cavities end blind within the rock massif. No trace of fracturing authorizing mechanical erosion by flows, which would explain their genesis, was ever recorded.
The second type of cavities is characterized by the presence of an underground stream which disappears in a siphon or in some impenetrable passages. In some cases, an important granular disintegration of the surrounding rock produces quantities of sand which seal large pre-existent voids. The latter were formed in different physico-chemical conditions than those present in the open air environment.
An initial deep karstification is possible despite the surface environment. Secondary morphologies on the cave walls (alveoli, pillars of dissolution, passages with “key hole” section, ceiling bells …) enable us to partially reconstitute the genesis of these caves. It would start in a phreatic environment with the development of spots of dissolution along deep water circulations. Initially, independent cavities grow and interconnect to form embryonal karst networks. The incision of valleys and the weathering processes progressing from the surface can intersect these. Physical erosion then becomes more prominent than chemical erosion. The pre-existent forms, depending on their organization, can either be dismantled or contribute to the evolution of a complex karst network.
A comprehensive study of karsts in silicated and non carbonated rocks is an opportunity to a better understanding of generally inaccessible deep karstification, including in the carbonated rocks. Moreover, the presence of these karsts and sometimes of underground rivers in regions hit by chronic droughts represents a potential of water resources disregarded today.
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