**The origin of tablet boudinage: Results from experiments using power–law rock analogs**. J. Zulauf , G. Zulauf, R. Kraus, G. Gutiérrez-Alonso, F. Zanella. 2011, Tectonophysics, 510, 327-336. **DESCARGAR-DOWNLOAD**

** RESUMEN-ABSTRACT**

We used non-linear viscous plasticine as rock analogue to simulate boudinage of rocks undergoing dislocation creep and brittle fracture. A competent plasticine layer, oriented perpendicular to the main shortening direction, *Z,* underwent bulk pure flattening with equal layer-parallel extension in all directions inside a weaker plasticine matrix. The viscosity ratio between layer and matrix was set at 5 and the stress exponent of layer and matrix was 7. The samples were deformed at a strain rate, *ė*, of 5 * 10^{-5} s^{-1} up to a maximum finite strain, *e _{Z}*, of -40%. Computer tomographic analyses of the deformed samples revealed that boudinage results from a first phase of viscous necking succeeded by extension fracture along the previously formed pinches. As the boudins display a polygonal shape in plan-view, they are referred to as ‘tablet boudins’ (in contrast to the rectangular chocolate-tablet boudins). The ratio between long and short axis,

*R*, is ranging from 1.2 to 2.6 in plan-views. The polygonal, non-isometric shape of the tablet boudins is explained by the strong interaction of concentric and radial tensile fractures. With increasing layer thickness,

*H*, the mean diameter of the boudins,

_{i}*W*, increases, while the number of boudins,

_{a}*N*, decreases. The relation between layer thickness and number of boudins can be described by the equation:

*N*= A * exp(-

*H*/ B) + C, where A = 229 ±12, B = 0.89 ±0.04, and C = -0.2 ±1.0. Progressive finite strain results in a higher number and a smaller mean diameter of the boudins. The thickness of the boudins,

_{i}*H*, is almost the same like the initial layer thickness,

_{f}*H*, while the aspect ratio (

_{i}*W*=

_{d}*W*/

_{a}*H*) decreases with layer thickness and finite strain. The mean

_{f}*W*values obtained from all runs are ranging from ca. 4 to ca. 11. This range is higher than the values published so far for cylindrical and non-cylindrical boudins in the literature.

_{d}