Structural analysis of the adjacent Acadian and Variscan fold belts in Belgium and northern France from geophysical and geological evidence

Two Palaeozoic fold belts are juxtaposed in Belgium and northern France. Th e northern belt of the Brabant Massif, traditionally considered a part of t he European Caledonides, was folded during the Acadian orogeny in the early Devonian. Although it is largely concealed, gravity and magnetic maps give a general picture of the existing structures. A curved gravity trend is in terpreted as an are-shaped succession of granitic batholiths. Structures no rth and south of this are are completely different. The northern subdomain, containing magnetic lower Cambrian metasediments, shows multiple thrust fa ults towards the south over the granites, whereas the southern subdomain, w ithout magnetic rocks, is moulded around the granitic core. The southern Va riscan belt is characterized in general by thrusting with a north, NW and N E vergence. During the Variscan orogeny the Brabant Massif acted as an obst acle to the general transport of the Ardennes Massif to the N-NW. The obliq ue convergence with the Brabant Massif caused differential displacement tow ards the northwest, the western areas having travelled farther, as seen fro m a pattern of WNW-oriented strike-slip faults. (C) 1999 Elsevier Science B .V. All rights reserved.