Unfolding the arc: The use of pre-orogenic constraints to assess the evolution of the Variscan belt in Western Europe

We present a pre-orogenic, early Paleozoic, palinspastic reconstruction of the northern Gondwana margin that was subsequently involved in the Late Paleozoic Variscan orogeny in central and Western Europe. Our reconstruction is based on two pre-orogenic data sets, the age and distribution of Cambrian-Ordovician magmatism and the detrital zircon age signature of late Neoproterozoic-early Paleozoic clastic rocks. We obtain this reconstruction by unfolding the Ibero-Armorican arc and by restoring the movement of the large-scale dextral strike-slip faults that transect the different tectono-stratigraphic units. Our results favour an irregular shape for this part of the northern Gondwana margin with a N-S central segment linking two E-W oriented segments. The proposed reconstruction and the structural restoration of the main features of Variscan deformation is in accordance with some aspects of previously proposed structural models, such as the curved geometry of the Gondwanan margin required by the indentor model for continental collision, the role played by the large strike slip faults in dispersing formerly juxtaposed units, and the regional-scale oroclinal folding of part of this margin during late Carboniferous-Early Permian times. The combined use of the pre-orogenic geological constraints and palinspastic restoration is a useful approach that may provide a foundation for continual refinement of reconstructions as more data become available.