Palaeomagnetic data from the Precordillera fold and thrust belt constraining Neogene foreland evolution of the Pampean flat-slab segment (Central Andes, Argentina)

Available and new palaeomagnetic data reveal transpressional deformation in the Argentine Precordillera fold and thrust belt contemporaneous with Juan Fernández ridge subduction. Localized changes in the orientation of palaeomagnetic directions indicate a vertical axis rotation pattern linked to local, oblique brittle-ductile shear zones that overprint the regional structure. The nearly homogeneous clockwise block rotation pattern from Western-Central Precordillera shows localized rotation nulls along NNW-trending left-lateral oblique belts, revealing that overprinting anticlockwise tectonic rotations could have balanced previous clockwise rotations. Conversely, clockwise rotations in Eastern Precordillera are only localized in the vicinity of these NNW-trending structures, and are controlled by rigid block rotations linked to basement involved deformation. These results combined with available regional palaeomagnetic data in the forearc would indicate a regional bending of the upper plate margin between 27º S and 33º S that seems to be related to the subduction of the Juan Fernández aseismic ridge.