Publication Date:
2009-12-22
Description:
The final pulse of the Variscan Orogeny in the northern Bohemian Massif (Saxo-Thuringian Zone) is related to the closure of the Rheic Ocean, which resulted in subduction-related D1-deformation followed by dextral strike-slip activity (D2-deformation, the Elbe Zone). Taken together, these deformation events reflect the amalgamation of Pangaea in central Europe. Lateral extrusion of high-grade metamorphosed rocks from an allochthonous domain (Saxonian Granulitgebirge) and the top-NW-directed transport of these domains (Erzgebirge nappe complex, Saxonian Granulitgebirge) are responsible for these dextral strike-slip movements. Geochronological data presented herein, together with published data, allow the timing of the final pulse of the Variscan Orogeny and related plutonic, volcano-sedimentary and tectonic processes. Marine sedimentation lasted at least until the Tournaisian (357 Ma). Onset of Variscan strike-slip along the Elbe Zone is assumed to be coeval with the beginning of the top-NW-directed lateral extrusion of the Saxonian Granulitgebirge at 342 Ma (D2-deformation). The sigmoidal shape of the Meissen Massif indicates that strike-slip activity was coexistent with intrusion of the pluton at c. 334 Ma into the schist belt of the Elbe Zone. In contrast, the intrusion of the Markersbach Granite provides a minimum age of c. 327 Ma for the termination of D2 strike-slip activity, because this undeformed pluton cross-cuts all strike-slip related tectonic structures. Geochronological data of an ash bed from the Permo-Carboniferous Dohlen Basin show clearly that post-orogenic sedimentation of Variscan molasse in that area was already active at 305 Ma. This pull-apart basin is a local example of regional Permo-Carboniferous extension within Pangaea. The uplift and denudation of the Variscan basement in the Saxo-Thuringian Zone occurred between c. 327-305 Ma.
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