The effect of the rheological column on the structural style in progressive arcsductile and brittle-ductile analogue models

Zusammenfassung

Analogue models have been performed to simulate a progressive arc indenting in a parallelepiped composed only of silicone and of silicone and a layer of sand of progressively increasing thickness. The experiments permit to study the ductile deformation within the silicone and the influence of the sand thickness on the development of structures. To do so, we used an indenter that diminished its curvature ratio while its protrusion degree increased with progressive deformation. In all models, strain was partitioned between arc-perpendicular shortening and arc-parallel stretching. In silicone models, the deformation was homogeneous, while even when a very thin sand layer was sieved on top, heterogeneous deformation was observed, and folds, thrusts, strike-slip and normal faults formed. With increasing sand layer thickness, folds wavelength increases and blocks capped by sand individualize and rotate clockwise and counterclockwise in the left and right arc limbs, respectively. With progressive deformation, some of these structures evidence a change in the kinematic regime because of rotations around a vertical axis.