Geologica Belgica

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Lorraine DEWAIDE, Jean-Marc BAELE, Pauline COLLON-DROUAILLET, Yves QUINIF, Gaëtan ROCHEZ, Sara VANDYCKE & Vincent HALLET

Karstification in dolomitized Waulsortian mudmounds (Belgium)

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Annexes

Mots-clés : dedolomite, Calcite cementation, Waulsort Formation, karstogenesis, dolomite dissolution, calcite replacement, cavity, dissolution porosity.

Abstract

The Waulsortian mudmounds consist of massive limestones that developed from late Tournaisian to early Visean. Secondary dolomitization has locally affected these mudmounds conducting to the coexistence of dolostone and limestone patches. Numerous karst cavities are preferentially developed in dolomitic intervals and are geometrically related to one or several fracture directions. These cavities, called the “dolostone cavity type” can be partially filled with coarse calcite and are usually bounded to the host dolostone by a calcitic transition zone which has roughly a lenticular shape. Petrographic observations, especially under cathodoluminescence, show the following sequence starting from the micro-cavities/micro-fractures network in the transition zone: 1) calcite cement in cavities, 2) dedolomite fabric, 3) host dolomite. The observed microscopic features, as well as morphological data, lead to the development of a conceptual genetic model of karst formation at macro- and microscale. In this model, first a strong dissolution of the host dolostone occurred from the fracture network thereby creating karst cavities (at macroscale) and important pervasive porosity (at microscale). Dissolution was then followed by dedolomitization in one or two-steps of the already corroded dolospar. Afterwards cementation of the residual porosity and precipitation of coarse calcite in the karst cavities occur.  Even if the geological conditions under which these processes took place are not fully unraveled yet, a model that could fit with the data is presented. A discussion about the paleo-environment and paleo-hydrological conditions is settled and we also propose that the development of karst in the dolomitized mudmounds is favored by the coexistence of dolostone and limestone patches given their initial difference in porosity and competence.  

To cite this article

Lorraine DEWAIDE, Jean-Marc BAELE, Pauline COLLON-DROUAILLET, Yves QUINIF, Gaëtan ROCHEZ, Sara VANDYCKE & Vincent HALLET, «Karstification in dolomitized Waulsortian mudmounds (Belgium)», Geologica Belgica [En ligne], volume 17 (2014), 43-51 URL : http://popups.ulg.ac.be/1374-8505/index.php?id=4354.

About: Lorraine DEWAIDE

Université de Namur, Département de Géologie, Faculté des Sciences, 5000 Namur, Belgique.

About: Jean-Marc BAELE

Université de Mons, Géologie Fondamentale et Appliquée, Faculté Polytechnique de Mons, 7000 Mons, Belgique.

About: Pauline COLLON-DROUAILLET

Université de Lorraine, CNRS, CREGU, Georessources Laboratory, ENSG, 54518 Vandoeuvre-Lès-Nancy Cedex, France.

About: Yves QUINIF

Université de Mons, Géologie Fondamentale et Appliquée, Faculté Polytechnique de Mons, 7000 Mons, Belgique.

About: Gaëtan ROCHEZ

Université de Namur, Département de Géologie, Faculté des Sciences, 5000 Namur, Belgique.

About: Sara VANDYCKE

Université de Mons, Génie Minier, Faculté Polytechnique de Mons, 7000 Mons, Belgique.

About: Vincent HALLET

Université de Namur, Département de Géologie, Faculté des Sciences, 5000 Namur, Belgique.