Modelling flanking structures using deformable high axial ratio ellipses: Insights into finite geometries

Flanking structures develop locally around material inhomogeneities. The evolution of these structures is investigated here by modelling peturbations around a deformable ellipse using a 2D analytical solution. Non-unique instantaneous and finite geometries are predicted, and it is shown that in terms of slip and curvature, complex histories are possible under simple shear, whereas under pure shear instantaneous geometries map directly into finite state geometries. Single flanking structures are of limited use in kinematic analysis but can help constrain the kinematics when interpreted in conjunction with other structural features. Flanking structures exhibiting a range of CE (cross-cutting element) orientations have more potential as kinematic indicators. Flanking structures serve as an excellent example of the role that material homogeneity can play in locally producing complex structures in a relatively simple bulk flow field.