Paleomagnetism in Extremadura (Central Iberian zone, Spain) Paleozoic rocks: extensive remagnetizations and further constraints on the extent of the Cantabrian orocline

Abstract

Introduction: The winding Variscan belt in Iberia, featuring the Cantabrian orocline (NW Iberia) and the Central Iberian curve, is a foremost expression of the late Carboniferous amalgamation of Pangea, which produced remagnetizations spanning almost the entire globe. Geological settings: Also in Iberia, late Carboniferous remagnetizations are widespread often hindering paleomagnetic interpretations in terms of pre-Pangean geologic history. In contrast, such remagnetizations facilitated the kinematic study of the Cantabrian orocline. Immediately to its south is located the Central Iberian curve whose geometry and kinematics are under debate. Recent studies suggest that this putative structure cannot have formed in the same process as the Cantabrian orocline. Results: Here we present a paleomagnetic and rock magnetic study from Extremadura, a region in the utmost west of the southern limb of the Central Iberian curve. Our new results show two distinct remagnetization events in Paleozoic rocks in Extremadura: (1) Mesozoic or Cenozoic remagnetization occurring in dolomitized limestones and (2) late Carboniferous remagnetization in limestones, characterized by consistent shallow inclinations, but largely scattered declinations indicating a counter clockwise (CCW) vertical axis rotation. Pyrrhotite is documented as magnetic carrier in the limestones which testifies a remagnetization under anchimetamorphic conditions, i.e. during the Variscan orogeny. Interpretation: We interpret the declination scattering as a remagnetization coeval to the vertical axis rotation. The described CCW rotations are those expected for the southern limb of the Cantabrian orocline and are in disagreement with a late Carboniferous secondary origin for the Central Iberian bend, extending the Cantabrian orocline to at least most of the Iberian peninsula.