Paleomagnetism of the Cantabria-Asturias Arc: Kinematics of arc formation and implications for final collisional adjustments within the Pangea supercontinent

The Cantabria-Asturias Arc (CAA) of SW Europe is a highly curved Variscan belt that formed along the ancient plate boundary between Gondwana and Laurussia during the assembly of Pangea. To construct a viable kinematic and tectonic model for CAA formation, a paleomagnetic, rock magnetic, scanning electron microscopy (SEM) and structural study of two Devonian carbonate formations was undertaken to distinguish the discrete stages of deformation that the are experienced. The combination of these approaches provides a method for dating the complex deformation history experienced by the CAA and sheds new light on the mechanism of orogen-related remagnetizations and, and particularly, arc formation.; The Devonian carbonates acquired three late Paleozoic remagnetizations during the Variscan orogeny of northern Spain. Rock magnetic data and SEM analyses reveal that the three late Paleozoic remagnetizations are chemical remanent magnetizations, likely facilitated by the presence of fluids. The fluids, whether externally or internally derived, were activated as a response to orogeny based on the acquisition of remagnetizations subsequent to local Variscan deformation phases. The protracted deformation history increased fluid mobility as a product of tectonic thickening, tectonically induced permeability, and/or gravity-driven flow.; The paleomagnetic and structural data show that the CAA experienced true (∼100%) oroclinal bending of an originally linear belt in a two-stage tectonic history. This history represents two regional compression phases: (1) east-west compression in the Late Carboniferous and (2) north-south compression in the Permian (both in present-day coordinates). The later compression phase reflects the northward movement of Gondwana and its final collision with Laurussia. The new paleomagnetic data and this tectonic scenario argue against previously proposed syn-thrusting rotation, wrenching and indentor models for the formation of the CAA, because rotation occurred after the folding and thrusting that imparted the north-south structural grain of the belt. On a larger scale, this scenario does not support a 3500 km dextral megashear proposed by some previous paleomagnetic reconstructions of the Pangea supercontinent.