Eastern Variscan fold belt: Paleomagnetic evidence for oroclinal bending

The Rhenohercynian zone of Variscan Europe trends from southern Portugal, around the Ibero-Armorican arc, into southern Britain, Belgium, northern Germany, and the Moravo-Silesian zone of the east Czech Republic. Although the geodynamic evolution of the central and western segments of this arcuate belt is now fairly well understood, the scenario for the more easterly parts remains enigmatic. A paleomagnetic study of Upper Devonian rocks from the Moravo-Silesian zone has been undertaken. Two ancient directions of magnetization have been identified. The first (the A magnetization) is secondary in origin and relates to a remagnetization of Permian-Carboniferous age. The B magnetization passes the fold test, is considered Late Devonian in age, and agrees in terms of inclination to previously published paleomagnetic results from coeval rocks of the Harz Mountains and Franconian Forest, central Europe. The declination, however, differs by about 90°. Restoring the Moravo-Silesian zone to its original Devonian orientation as defined by the new paleomagnetic data brings the structural trends of central and eastern Europe into agreement. Because they were previously part of the same tectonostratigraphic unit, as suggested by the stratigraphic record, this implies that rotational oroclinal bending around the northern and eastern flanks of the Bohemian massif occurred sometime between the Late Devonian and Late Carboniferous.