Oroclinal arcs of the Variscan Belt: a consequence of transpression during the consolidation of Pangaea

Abstract

Arcuate traces of large structures characterize many mountain chains. The Variscan Belt is not an exception and traces one of the tightest oroclines on Earth, the Ibero-Armorican Arc, as well as more open oroclines in the Eastern Moroccan Meseta, Central Iberia, the French Massif Central and the Bohemian Massif. All the Variscan arcs are considered to be true or secondary oroclines and are late orogenic features, but their timing and mechanisms of deformation differ. Models explaining their origin have been proposed for some individual arcs and are generally controversial. This paper aims to interprete the ensemble of Variscan arcs, highlighting their age relative to previous orogenic features as well as to those associated with arc development. Several mechanisms operated to form the arcs, the most important being ductile transcurrent shearing and rigid–plastic indentation, with shortening parallel to the orogen having a secondary role. These mechanisms acted at different time intervals, their participation or relative importance differs for each arc and they gave rise to distinct associated structures. The development of the arcs is viewed as related to late Variscan dextral transpression provoked by the displacement of Laurussia to the east relative to Gondwana during the Serpukhovian to early Permian.