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Thick vs. Thin-Skinned Formation and Inversion of Salt Walls in SE Iberian Peninsula: Constraints From Paleomagnetic an Inner Diapiric Structural Data


The influence of the motion of a basement fault on an overburden detached above an evaporitic layer is well known, as well as the effect of compression on a thin-skinned overburden with previously existing diapirs. However, practically no studies have dealt with the structure produced by a thin-skinned deformation above a pre-existing basement fault. This gap can be filled in by analyzing the Bicorb-Quesa and NavarRÉs salt walls as they are located above basement faults and between two thin-skinned fold belts, fulfilling the requirements for this kind of study. Understanding the geometry and kinematics of these salt-related structures has taken a step forward mainly from recent accurate geological mapping, structural analysis of the inner diapiric structure, and the acquisition of potential field magnetotelluric and paleomagnetic data. Paleomagnetism is a common technique used to identify and quantify vertical- and inclined-axis rotations. However, it has not been widely applied to salt structures and, when done, it has been mainly used to obtain the layer polarity of diapiric and overburden rocks. Unlike the previous studies, the paleomagnetic study carried out in the Bicorb-Quesa and NavarRÉs salt walls has been designed in order to identify vertical-axis rotations. The obtained results reveal a pre-folding 15-30 degree counter-clockwise rotation in the diapiric rocks and a 20 degree clockwise rotation in one of the salt wall flanks. These rotations, together with the analysis of the salt wall structure, provide a set of constraints in the kinematics of these two salt wall segments. From them, a new kinematic model is established that highlights the role played by the geometric relationships between the propagation direction of cover deformation and the basement faulting in the growth and/or reactivation of salt walls.