Journal of

GEOsciences

  (Formerly Journal of the Czech Geological Society)

Original Paper

Krs, Pruner

Palaeomagnetism and palaeogeography of the Variscan formations of the Bohemian Massif, comparison with other European regions

Journal of the Czech Geological Society, volume 40 (1995), issue 1-2, 3 - 46

Palaeomagnetic data published during approximately the last 30 years and derived from rocks from the Triassic to the Devonian periods have been statistically evaluated. The data cover the territories to the north of the Alpine tectonic belt, west of the Ural Mts. and reach up to Great Britain. The aim was to define the palaeotectonic deformations and the palaeogeography of rock complexes of the Hercynian orogene. The data document the consolidation of the European lithospheric plate in the Early Permian as a part of the formation of the Pangea supercontinent. They confirm that, due to continental drift, the European plate moved from the palaeo-equatorial Early Permian position to its present one. Rocks from the Middle to Late Carboniferous age from the western part of the Bohemian Massif, from the Middle to the Late Devonian from the Moravian Zone and rocks from the West-European Hercynides show clear clockwise palaeotectonic rotation deformations. For the West-European Hercynides, these rotation deformations reach very high values (Edel 1987). For the Middle Carboniferous rocks, they represent about 50° and, for the Early Carboniferous, they go up to 120° in a clockwise direction. Such large deformations are related to palaeomeridians of the Early Permian palaeogeographic net of the consolidated European plate. Deformations of comparable magnitude have been found in the Moravian Zone and on the Polish side, in the Holy Cross Mts. Palaeotectonic rotations of similar magnitude were demonstrated in a number of cases in the Alpine tectonic belt. In this paper, we discuss the similarities and differences between the palaeotectonic deformations recognized on rocks affected by the Variscan orogeny to the north of the Alpine belt and with those derived from rocks affected by the Alpine orogeny. Experimental palaeomagnetic data are tested on a model simulating palaeotectonic rotations. Such rotations are regarded as the characteristic sign of tectonic collision zones. A major part of the paper is devoted to the problem of overprint of several Early Variscan and pre-Variscan rock formations in the Bohemian Massif during the Variscan orogeny, which occurred during the Late Carboniferous epoch with possible extension to the Early Permian. The overprint effects were found by magnetomineralogical analyses and by means of the multi-component analysis of remanence applied to Devonian limestones from the Moravian Zone and the Barrandian, to Late Cambrian volcanics and Early Cambrian shales with micro-organic matter of the Barrandian.