A paleomagnetic cross-section through the Ardenne and the Brabant Massifs (France-Belgium)
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Vols. 1-18 (1924-1944), ISSN 0044-2801
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Abstract
In order to constrain the motions of the allochthonous Ardenne during the Paleozoic, standard paleomagnetic techniques have been applied on acidic and basic sills of the Cambrian Rocroi massif and on Cambrian-to-Visean sedimentary series sampled along the Meuse valley. Ordovician–Silurian volcanics and Devonian–Visean limestones have also been collected in the autochtonous Brabant and Namur basin, in order to get paleomagnetic reference poles. In the Ardenne, two groups of in situ paleomagnetic directions arise. The A components (mean: D = 212°, I = -11°, α95 = 6°, for 10 sites), that are characterized by unblocking temperatures around 330° C, represent Late Variscan (Stephanian–Permian) overprints. The B components (mean: D = 236°, I = 2°, α95 = 11°, for 13 sites) display higher unblocking temperatures, in the range 400°-580° C. They show a large scatter in inclination (–25° < I < 35°) that is not reduced by tectonic correction. The B components are interpreted as post- and partly synfolding overprints of Middle-Late Carboniferous age. In the Brabant, all series display Late Variscan remagnetizations (mean: D = 204°, I = -7°, α95 = 9°, for 5 sites), consistent with the Stephanian- Permian pole of Europe. The existence of Middle-to-Late Variscan B directions in the Armorican Massif, Central Massif, Vosges and Black Forest indicates that in Namurian–Westphalian times the whole investigated Variscan belt, including the Ardenne, was trending N-S. A 45° clockwise rotation relative to the paleomeridian, during the latest Westphalian–Stephanian, has lead the massif to its Permian position.
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References
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