The Baltica-Gondwana suture in central Europe: evidence from K-Ar ages of detrital muscovites and biogeographical data

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Abstract
The Lysogory Unit, the Malopolska Massif and the Upper Silesian Massif in southern Poland are parts of a mosaic of contrasting crustal fragments separating the old Precambrian crust of the East European Platform (EEP) from the Phanerozoic mobile belts of western Europe. The geological histories of these blocks are markedly different. They have been regarded as integral parts of the palaeocontinent of Baltica (that is, the EEP), mostly because of presence of fossils typical for the Baltic realm, although geophysical and geological data and some faunal elements rather suggest linkages to the Peri-Gondwana plates. To provide additional constraints for the plate tectonic affinity of these blocks detrital muscovite grains extracted from Cambrian and Devonian clastic rocks were dated by the K-Ar method. The K-Ar cooling ages show a very complex provenance pattern for clastic material in Cambrian time. Combined with the biogeographical constraints, the new provenance data apparently show that the blocks of Lysogory, Malopolska, and Upper Silesia are in fact crustal fragments derived from the Gondwana margin, not displaced parts of the East European Craton. Thus, the Teisseyre-Tornquist Line (that is, the edge of the EEP) is the Baltica-Gondwana suture in central Europe. The combined data reveal an accretionary scenario in which the Malopolska Block was the first Gondwana-derived microplate that accreted to the margin of Baltica.