Geologica Belgica

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Timothy N. Debacker, Manuel SINTUBIN & Philippe ROBION

On the use of magnetic techniques for stratigraphic purposes: examples from the Lower Palaeozoic Anglo-Brabant Deformation Belt (Belgium)

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Mots-clés : magnetic susceptibility., AMS, composite fabric, ferromagnetic mineralogy, magnetic fabric

Abstract

Within the Lower Palaeozoic Anglo-Brabant Deformation Belt, magnetic susceptibility on its own does not allow for a straightforward distinction between different lithostratigraphic units, except for the high-susceptibility levels of the Lower Cambrian Tubize Formation. Moreover, the variation in magnetic susceptibility within individual lithostratigraphic units is often larger than that between different units, but at the same time, this internal variation in susceptibility may show no clear relationship to features obvious in outcrop or hand specimens. Hence, the applicability of magnetic susceptibility for stratigraphic purposes in the Anglo-Brabant Deformation Belt is low. Better results are obtained using the temperature-dependent variation in terms of percentage of magnetic susceptibility within the “room temperature interval”. Also the anisotropy of magnetic susceptibility allows for a better distinction between different lithostratigraphic units than does magnetic susceptibility. The best results are obtained by a comparison of thermal demagnetisation curves of magnetic remanence, used for determining ferromagnetic mineralogy. This method even allows distinguishing lithostratigraphic units in which ferromagnetic carriers do not contribute to overall magnetic susceptibility and its anisotropy. Ideally, each magnetic technique should be used for stratigraphic purposes only in combination with other magnetic techniques. Moreover, knowledge about the magnetic carriers (s.l.) facilitates this use of magnetic techniques and strongly improves the accuracy of the interpretations.

To cite this article

Timothy N. Debacker, Manuel SINTUBIN & Philippe ROBION, «On the use of magnetic techniques for stratigraphic purposes: examples from the Lower Palaeozoic Anglo-Brabant Deformation Belt (Belgium)», Geologica Belgica [En ligne], number 4 - Magnetic susceptibility, correlations and Palaeozoic environments, volume 13 (2010), 333-350 URL : http://popups.ulg.ac.be/1374-8505/index.php?id=3166.

About: Timothy N. Debacker

Vakgroep Geologie & Bodemkunde, Universiteit Gent, Krijgslaan 281, S8, 9000 Gent, Belgium

About: Manuel SINTUBIN

Geodynamics & Geofluids Research Group, Katholieke Universiteit Leuven, Celestijnenlaan 200E, 3001 Leuven, Belgium

About: Philippe ROBION

Université de Cergy-Pontoise, Département des Sciences de la Terre et de l’Environnement, 5 mail Gay Lussac, Neuville sur Oise, 95031 Cergy Cédex, France