Terranes of different geotectonic settings accreted during Paleozoic time to form a consolidated crust by the end of the Variscan orogenic cycle. An ensimatic island arc, which rested upon back-arc oceanic crust and is now preserved in the Penninic unit of the Tauern window, was active in early Paleozoic time. Accretion of ensialic magmatic arcs and (back-arc?) oceanic crust occurred in Ordovician time to form a composite terrane in the Austroalpine unit. Limited radiometric information from zircon provides evidence for the existence of Precambrian cores. An ocean is inferred to have closed by about the early Carboniferous period, thus forming an important ophiolitic suture. Accretion of oceanic terranes and dispersion of the active continental margin by inferred large-scale wrench faulting accompanied this process.