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- The Charente karst basin of the Touvre: alteration of the Jurassic series and speleogenesis by ghost-rock process
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The Charente karst basin of the Touvre: alteration of the Jurassic series and speleogenesis by ghost-rock process
Abstract
The Jurassic limestone of the North-eastern part of the Aquitain Basin (Angoulême, Charente, France) provide evidence of the prominent role of the ghost-rock process from the study of three quarries, drillings and the discovering of a young cave called “La Fuie” (Chasseneuil-sur-Bonnieure). This alteration process explains the genesis of maze caves and also the complexity of the Touvre aquifer which supplies the city of Angoulême. Indeed the large water reserve is situated into the porous rock (slow drainage) constituted by ghost-rocks while a small part is drained by the karst conduits (fast drainage coming from river losses). Moreover, for the first time a speleogenesis by ghost-rock process is demonstrated in a young and active subterranean network in Charente. La Fuie Cave, discovered during road works, was used as subterranean laboratory. Analysis of ascending collapse chimney and the discovery of ghost-rock combined with the study of piezometric level variations, recorded by a Luirograph, allowed to highlight a new way to drain residual deposits by flooding / dewatering of pseudo-galleries from ghost-rocks in cave system. At the same time, the piezometric level variations in the epiphreatic zone are the cause of a partial filling of the galleries.
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About: Gregory DANDURAND
CNRS ADES UMR 5185, University of Bordeaux 3, Maison des Suds, 12, Esplanade des Antilles, 33607 Pessac Cedex, France. E-mail: gregory.dandurand@gmail.com
About: Caroline DUBOIS
University of Mons, 20, Place du Parc, B-7000 Mons, Belgique. E-mail: caroline.dubois@umons.ac.be
About: Richard MAIRE
CNRS ADES UMR 5185, University of Bordeaux 3, Maison des Suds, 12, Esplanade des Antilles, 33607 Pessac Cedex, France. E-mail: rmaire@ades.cnrs.fr
About: Yves QUINIF
University of Mons, 20, Place du Parc, B-7000 Mons, Belgique. E-mail: yves.quinif@umons.ac.be