EASTERN VARISCAN FOLD BELT - PALEOMAGNETIC EVIDENCE FOR OROCLINAL BENDING

The Rhenohercynian zone of Variscan Europe trends from southern Portug al, around the Ibero-Armorican are, into southern Britain, Belgium, no rthern Germany, and the Moravo-Silesian zone of the east Czech Republi c, Although the geodynamic evolution of the central and western segmen ts of this arcuate belt is now fairly well understood, the scenario fo r 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 fi rst (the A magnetization) is secondary in origin and relates to a rema gnetization of Permian-Carboniferous age. The B magnetization passes t he fold test, is considered Late Devonian in age, and agrees in terms of inclination to previously published paleomagnetic results from coev al rocks of the Hart Mountains and Franconian Forest, central Europe, The declination, however, differs by about 90 degrees. Restoring the M oravo-Silesian zone to its original Devonian orientation as defined by the new paleomagnetic data brings the structural trends of central an d 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 nort hern and eastern flanks of the Bohemian massif occurred sometime betwe en the Late Devonian and Late Carboniferous.