CoachA fault-bend fold is a fold of the hanging wall of a thrust produced as it slides over a bend of the fault, a ramp between two flats. A fault-propagation fold grows above the tip of a thrust that is still propagating upward: the shortening that the fault no longer carries is taken up by folding in front of its tip, which gives a steep or overturned forelimb. A detachment fold grows above a flat with no ramp: the shortening is taken up by folding and by a weak layer, salt or shale, that flows into its core.
