An analogue modeling approach of progressive arcspreliminary results

Abstract

Progressive arcs, whose curvature is acquired during deformation, have never been studied from an analogue approach. In order to model this type of arcs, an indenter that lengthens and changes its ratio of curvature has been used. We performed three experiments using variable thicknesses of the underlying viscous silicone layer: 0, 0.5 and 1 cm, to test the influence of the brittle or ductile substrate. The resulting fold-and-thrust belts show radial outward thrusting and block rotation with progressive increase of the indenter curvature. The rotations are allowed by conjugated strike-slip systems. As the thickness of the viscous substrate increases: (1) the prevalence of foreland-vergence diminishes, (2) wedges are thinner and wider, (3) normal and strike-slip faults are more frequent and (4) the number of individualized blocks increase and the rotation is higher. Hence, the strain within progressive arcs is partitioned between curved foldand-thrust belts that accommodate arc-perpendicular shortening and arc-perpendicular normal faults. In addition, the conjugated strike-slip systems accommodate the stretching parallel to the arc. This strain partitioning is similar to that observed in the Gibraltar arc.