PALAEOZOIC BUILDING OF EUROPE: IDENTITY AND ORIGINS OF CRUSTAL BLOCKS ACCRETED TO BALTICA ALONG THE TRANS-EUROPEAN SUTURE ZONE

A new model for the Palaeozoic sequence and timing of accretion of crustal blocks abutting Baltica along the Trans-European Suture Zone (TESZ) results from multidisciplinary studies of geotransects and borehole data. In south-central Poland, fossil, geochronological and sediment provenance data indicate that the Lysogory, Malopolska and Bruno-Silesian blocks, associated with the Moravian microcontinent, were attached to Baltica by the Late Cambrian in a first accretionary stage. This microcontinent was proximal to both the Uralide margin of Baltica and the Amazonian craton in Gondwana during the early Cambrian. Avalonia, extending from the west to Central England and Belgium, also has links with Amazonia. Apparently similar basement east of the Anglo-Brabant Deformation Zone extends to NW Poland. Borehole fossil and sediment provenance evidence indicates that this basement docked with Baltica, in the second stage of Palaeozoic accretion during the Ashgill, after rifting from Gondwana during the Llanvirn. Despite also originating from near Amazonia, the Moravian microcontinent docked with Baltica while Avalonia was still attached to Gondwana. Beneath the North European Plain and southern North Sea, deep seismic profiles suggest that Avalonian basement overrides thin ?proterozoic sediments overlying Baltican crust for up to 100 km. The third stage of Palaeozoic accretion records the docking of the Armorican Terrane Assemblage (ATA), comprising crustal blocks which migrated across the ocean separately as an archipelago. The main collision with the S margin of Avalonia and Baltica occurred during the Carboniferous, accompanied by N-S compression and dextral transpression in the east, where collision with the west margin of Moravia was particularly oblique. The latter junction, traceable north beneath the Polish Trough as the Moravian Line, is revealed by changes of middle crustal structure and discontinuities of geophysical features recorded in the POLONAISE 1 and TTZ seismic profiles. We thank the European Commission for funding the PACE Network (contract no. ERBFMRXCT97-0136.