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.