Folds trending at various angles to the transport direction in the Marcq area, Brabant Massif, Belgium
Abstract
Generally folds in fold belts are expected to trend approximately parallel to the main axis of the fold belt. Indeed, most of the fold hinge lines along the southern rim of the poorly exposed Lower Palaeozoic Brabant Massif reflect the general trend of the massif (transverse folds). However, in some places, folds exist oriented at high angles to the general trend of the massif (longitudinal folds).
New field work in the Marcq area, situated in the southwestern part of the Brabant Massif, reveals the presence of transverse, longitudinal and oblique asymmetric folds. Direct field observations, combined with borehole and geophysical data, indicate the presence of a low-angle high-strain zone, interpreted as a reverse shear zone. The various fold orientations are explained by means of differential movement within this shear zone. All the structural features are considered to be the result of one single progressive deformation.
Although this shear zone is probably of minor regional significance, the kinematic inferences made in the Marcq area may have important implications for the outline of the overall tectonic image of the southwestern part of the Brabant Massif.