CLEAVAGE/FOLD RELATIONSHIP IN THE SILURIAN OF THE MÉHAIGNE-BURDINALE AREA, SOUTHEASTERN BRABANT MASSIF, BELGIUM
Ghent University, Department of Geology and Pedology, Krijgslaan 281, S8, B-9000 Gent
Abstract
ABSTRACT. New structural observations show that the Méhaigne-Burdinale area, situated along the southeastern rim of the Brabant Massif, below the Silurian-Devonian angular unconformity, does contain sub-horizontal to gently plunging, upright to steeply inclined folds characterised by convergent cleavage fans. As such, the Méhaigne-Burdinale area is analogous to the Silurian of the southern Orneau valley and the southern Sennette valley. In addition, like in the latter two areas, also the folds in the Méhaigne-Burdinale area are of an en-echelon periclinal nature, situated within a large-scale host synform. A periclinal nature is also proposed for the host synform. Although many folds show a small-angle clockwise cleavage transection, the sense and amount of cleavage transection are to a large extent influenced by the en-echelon periclinal nature of the folds.
There is no evidence for a ductile Variscan imprint, nor for a poly-phase deformation. Like in the other Silurian outcrop areas, the convergent cleavage fans formed prior to the Silurian-Devonian unconformity. Although the convergent cleavage fans might be explained by a continued fold amplification after cleavage development during a single progressive deformation, the question why these fans occupy such a specific position along the southern rim of the Brabant Massif remains unresolved.