The Saxothuringian “Wrench-and-Thrust Zone” – the connecting link between the Peri-Gondwana shelf and the Variscan orogen.

The Saxothuringian Zone of the Central European Variscides preserves the sedimentary record of the post-Cadomian shelf and an Early Carboniferous synorogenic basin. Thus, this area reflects the transition from a passive continental margin setting to an active plate boundary zone. Particularly the record of the so called “Wrench-and-Thrust Zone” (WTZ) can be regarded as the connecting link between the Peri-Gondwana shelf and the Variscan orogen. The WTZ separates the complex metamorphic stack of the Erzgebirge-Fichtelgebirge Zone to the SE and the Paleozoic lithologies of the Schwarzburg Antiform to the NW. Compared with the adjacent Schwarzburg area, the WTZ differs in two essential points: i) It contains the record of a Late Devonian phase of bimodal magmatism, and ii) it experienced Early Carboniferous stacking that was partially related to a greenschist facies metamorphic overprint. Based on detailed studies such as structural mapping and 3D-modeling we propose the tectono-sedimentary evolution of the WTZ as follows. Late Devonian strike-slip faulting dissected the inner shelf of the W-African promontory of the Gondwana plate, culminating in localized and short-lived magmatism. Continued sedimentation on the segmented shelf is indicated by facies variations and prevailed until the onset of synorogenic sedimentation in the Tournaisean. Due to ongoing Gondwana – Laurussia plate convergence, first collisional tectonics, (D1) occurred in the Middle Viséan and led to SW-directed nappe stacking and the juxtaposition of low grade and non-metamorphic lithologies. The evolved synorogenic basin has been overfilled c. 10 Myrs after the D1 deformation. Late orogenic (N)NW-(S)SE-directed transpression finally overprinted the entire area.