3-D deformation pattern analysis and evolution of the Añisclo anticline, southern Pyrenees

Abstract

Understanding the genetic relationships of folding-related deformation structures is of importance for both academic and industrial purposes. We analysed the three-dimensional deformation pattern of the Añisclo anticline, in the southern Pyrenees. The specifically designed statistical method includes sequential steps of statistical and spatial data analysis and classification. Our results indicate that pressure solution cleavage frequency exhibits a spatial distribution that depends on the position within the fold. Conversely, such a dependence does not occur in joints and veins. Consequently, our data suggest that pressure-solution cleavage is the most appropriate deformation structure for unravelling fault-fold kinematics in carbonate multilayer. In particular, we found that the spacing of solution cleavages ( S) is related to the corresponding bed thickness ( H). This supports the use of H/ S value for deformation intensity quantification instead of spacing. In the Añisclo anticline, analysis of H/ S indicates the occurrence of three main deformation panels whose restoration suggests that fold evolution progressed from layer-parallel shortening, to décollement folding, up to thrust breakthrough, and fault-propagation folding. Comparison of H/ S values with finite strain data indicates that line-length was not preserved during fold evolution. This evidence has important implications for the kinematic interpretation of layer-parallel shortening and cross-section balancing.