Rounding hinges to fault-bend folding: geometric and kinematic implications

Fault-bend folding is a common folding mechanism in thrust and fold belts worldwide. The widely used kink-band geometric model of fault-bend folding necessitates complex ramp segmentations to reproduce the rounded shape of many natural thrust related anticlines. Curvilinear hinge sectors provide a geometric and kinematic alternative solution to kink bands for modelling curved-hinge folds. We developed an analytical solution for modelling fault-bend folding using circular hinge sectors. The velocity field of this kinematic solution is different from that associated with the classical, kink-style model. Our solution predicts the development of curvilinear anticlines above staircase fault geometries, the occurrence of limb rotation and, consequently, the development of rotational syngrowth wedges on both the forelimb and the crest. Conversely to the kink-style kinematics, curvilinear hinge sectors imply a dependence of deformation intensity from the fold shape and stratigraphic position of the folded layer. Application to natural thrust-related anticlines validates the effectiveness of curvilinear fault-bend folding.