ABSTRACT: Geologic folds are not comprised of a single flexed layer but of a heterogeneous stack of rock strata. If layer interfaces slip upon flexure, the frictional contact between layers dictates that the fold deform inelastically. This is numerically modeled using the boundary element method. The model is loaded in flexure and then unloaded in to explore both elastic and inelastic deformation of the fold. The curvature maxima are larger for frictionally slipping than for bonded interfaces and occur limbward of the crest and trough of the fold. The inelastically deformed fold has straight limbs and concentrated hinges after unloading.
The presence of bedding plane faults within a flexure may play an important role in the localization of fractures. Fractures are likely to be associated spatially with regions of greater curvature and with large slip gradients on bedding plane faults.
