Large-scale post-9Ma block rotation and westward extrusion of the Gibraltar Arc Systema Tortonian reconstruction

Abstract

We propose a reconstruction for 9 Ma (Late Tortonian) of the Gibraltar Arc System (GAS) based on the dating of the folds and thrusts associated with the main shortening event in the external wedge, their structural pattern and the relationships of this pattern with vertical-axis block rotations evidenced by previous paleomagnetic data (Neogene remagnetization). These relationships permit us to identify homogeneous domains in terms of relationships between timing of deformation events and rotations. These latter took place from 9 Ma to Present and can be as high as 52º. Our reconstruction shows that from 9 Ma onwards, these rotations together with plate convergence produced the tightening of the GAS and modified drastically its geometry. Since the orientation and position of pre-9 Ma kinematic indicator or structural element is also modified, our reconstruction should be used as starting point for any pre-Late Tortonian model of the GAS.