Influence of décollement friction on anisotropy of magnetic susceptibility in a fold-and-thrust belt model

Abstract Anisotropy of magnetic susceptibility can provide insights into strain distribution in models simulating fold-and-thrust belts. Models with layers of sand and magnetite mixture shortened above adjacent decollements with high and low friction, are used to study the effect of decollement friction on the magnetic fabric. Above high-friction decollement, an imbricate stack produced a ‘tectonic’ fabric with magnetic foliation parallel to thrusts. In contrast, above the low-friction decollement deformation propagated farther into the foreland, and deformation intensity is gradual from the foreland to the hinterland by defining a transition zone in between. In this zone, magnetic lineation rotated parallel to the deformation front, whereas in the hinterland the principal axes do not show a preferred orientation due to different deformation mechanisms between “thrust-affected” and “penetrative-strain affected” area. Above both decollement types, the principal axes of susceptibility developed tighter clustering with depth. Along the boundary between the two decollements, a deflection zone formed where rotation of surface markers and magnetic fabric reflect the transition between structures formed above the different decollements. Through quantifying magnetic fabric, this study reemphasises the clear link between decollement friction, strain distribution and magnitude in fold-and-thrust belts.