Parametric unfolding of flexural folds using palaeomagnetic vectors

Abstract

AbstractProviding that a primary and reliable record of the magnetic field and its reference in a deformed area exists, the incorporation of palaeomagnetic constraints in restoration methods reduces uncertainty of rotation because such constraints can be applied both before and after deformation. In this paper, we utilize palaeomagnetic data to improve an unfolding algorithm based on the parameterization of the surface using isometric constraints. This method is more robust than others based on piecewise restoration of a triangulated surface, which are dependent on the meshing and, especially, on the pin-element. A disadvantage of this approach is that parametric restoration is sensitive to the initial solution, which hampers results for complex non-coaxial or non-cylindrical structures. We show that the use of palaeomagnetism as the initial gradient of one of the parameters improves the results of the method. We use analogue models to test the method because the expected restoration result can be stated, since the initial surface is known. We study the restoration sensitivity to surface meshing and the initial palaeomagnetic orientation. All in all, the use of palaeomagnetic vectors in the studied analogue models achieves the best restoration results. The implementation of palaeomagnetic vectors is crucial to obtain reliable 3D restorations of complex structures.