KINK-BAND AND VELOCITY-BOUNDARY INTERFERENCE

The established techniques for constructing and restoring balanced cross sections using flexural slip work well for modeling simple faults and folds, but these methods show weaknesses when applied to more complicated structures, particularly imbricates and multi-bend fault-bend folds in which kink-band interference occurs. For such cases, conservation of layer thickness and line length with no-loose-line are more challenging. Parallel folding interference structures in which one kink band is sheared and the other is fragmented are one solution that honors these constraints. While this geometric solution is mathematically plausible and in some places geologically plausible, it appears that many structures formed where we know kink bands are interfering actually show much simpler geometries. We suggest that more general velocity-based solutions are an appropriate method for handling these cases, allowing one to perform kinematic forward and inverse modeling to predict geometries that better match observed geologic structures. A similar problem exists in velocity-based solutions however when velocity boundaries converge. Here we present five potential kinematic solutions and elaborate on one in particular which we have solved in detail and incorporated into a current forward modeling program for fault-bend folding. In some of the solutions, we experiment with relaxing certain constraints, and our highlighted solution is one that resolves the problem of interference while minimizing the amount of deviation from the parallel folding constraint by conserving area and maintaining the no-loose-line criterion. When put in action, this model appears to create structures that are geologically reasonable, demonstrating its applicability to structural interpretation.