Fold interference from simultaneous shortening in different directions: the Cape Fold Belt syntaxis

Abstract The Cape Fold Belt syntaxis displays antitaxial bends on either side of a well-developed intermediate fold trend. Folds of the NW-trending and E-trending branches merge relatively smoothly with the NE-trending syntaxial folds. The general pattern of fold coalescence, arcuations and the presence of many smaller folds of divergent trends show strong similarities with patterns generated in experimental models simulating the shortening of a multilayer simultaneously in two perpendicular directions and at unlike magnitudes. Interference between structures formed in response to different shortening directions led to a distinct regional variation of fold trends in the Witteberg Group of the Ceres arc. The special fold overprinting relationships at fold intersections in this area are interpreted in terms of bulk constrictional deformation. The structure of the syntaxis is probably the combined effect of the superpositioning of two roughly coeval, non-coaxial fold belts upon a much larger nonrotational arc, initially formed by the molding of the orogen around the irregular shape of the craton.