Kink-Band and velocity-boundary interference (thesis)
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 two 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. Our first highlighted solution considers an area of overlapping velocity domains as a new domain altogether and solves for the associated velocity vector that conserves area. Using this solution can produce structures analogous to parallel folding interference structures, with minor differences in thickening and thinning. Our second highlighted solution is one that resolves the problem of interference while minimizing the amount of deviation from the parallel folding constraints 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.
Thesis; [FULL-TEXT FREELY AVAILABLE ONLINE]Meredith Rose Townsend is a member of the Class of 2011 of Washington and Lee University.