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A geometric and kinematic model for double-edge propagating thrusts involving hangingwall and footwall folding. An example from the Jaca–Pamplona Basin (Southern Pyrenees)



A new geometric and kinematic model is proposed for a particular type of fault-related folding based on the study of a natural example developed in Palaeogene carbonate rocks from the Jaca–Pamplona Basin (Southern Pyrenees). The example consists of a hangingwall anticline related to a reverse fault with variable displacement and a gentle footwall syncline. A detailed structural analysis of the structure and a cross-section, perpendicular to its axis and parallel to the transport direction, reveals that none of the previous published models of fault-related folds is able to simulate its main characteristics and reproduce its geometry. The main features of the new model are: double-edge propagating fault and folding developed in both the hangingwall and the footwall. A MATLAB-based program was created to calculate structural parameters such as shortening, structural relief and fault slip; obtain graphs of different parameters such as shortening versus slip along the fault, shortening versus fault length, and produce sections across forward models showing the different stages of fold growth. The model presented here gives an acceptable geometrical fit to the studied natural structure and provides a reasonable evolutionary history. In addition, the results obtained using the model are similar to those measured on the cross-section. As a final step the subsurface portion of the natural fold was completed following the constraints imposed by the model. Copyright © 2010 John Wiley & Sons, Ltd.