The sierra madre oriental orocline. paleomagnetism of the nazas system in north-central méxico

Curved mountain belts are spectacular natural features, which contain crucial 3D information about the tectonic evolution of orogenic systems. The Mesozoic units exposed at the Cordilleran Mexican Fold and Thrust belt in NE Mexico show a striking curvature that has not been explained nor included in the existent tectonic models of the region. We have investigated with paleomagnetism and rock magnetism the kinematic history of that curvature, which is observed in the rocks of the Jurassic Nazas igneous province and its overlying red beds. Our results show a complex history of remagnetizations that occurred during the Late Jurassic and Cretaceous, as well as clockwise and counterclockwise vertical axis rotations of up to 50˚ respectively in each limb of the curvature. Although our data cannot provide precise timing for such rotations yet, our results confirm that the Mexican Fold and Thrust Belt underwent post-Late Jurassic orocline bending or bucking in NE Mexico.