Caledonian and Hercynian crustal consolidation of Western and Central Europe - A working hypothesis

Abstract

The crystalline basement of Western and Central Europe consists of a mosaic of crustal elements which were consolidated during pre-Grenvillian, the Grenvillian-Dalslandian, Morarian, Cadomian, Caledonian and Hercynian orogenic cycles. Contemporaneous with the Caledonian suturing of the Precambrian Laurentian-Greenland and Fennosarmatian shields a number of Gondwana-derived Cadomian micro-cratons were accreted to the southern margin of Laurasia. Following the Late Caledonian paroxysm, the Devonian and Early Carboniferous evolution of Europe was dominated by continued subduction of the Proto-Tethys plate at an arc-trench system parallelling the southern margin of Laurasia, the accretion of additional Gondwana-derived continental fragments, back-arc rifting, and a sinistral translation of major proportions between the Laurentian-Greenland and the Fennosarmatian sub-plates. The Acadian and Bretonian orogenies were of the Pacific type. The Visean collison of Gondwana with Laurasia marked the onset of the Himalayan-type Variscan orogeny during which collision related compressive stresses overpowered the Devonian-Early Carboniferous back-arc rift systems and caused the development of A-subduction zones. The Central Armorican-Saxothuringian successor basin became folded and destroyed during the latest Visean, whilst the Variscan foredeep became scooped out, in part by basement nappes, during the latest Westphalian. Major crustal shortening during the Variscan diastrophism was accompanied by the anatectic remobilisation of subducted lithosphere and a widespread syn- and late orogenic magmatism. The latest Carboniferous-Early Permian reorientation of the convergence direction between Gondwana and Laurasia induced the development of a complex wrench-fault system transsecting the Variscan fold belt, and extensive post-orogenic volcanism. The hypotheses summarised here require confirmation by further palaeomagnetic and radiometric data.