The eastern termination of the Variscides: terrane correlation and kinematic evolution
Published:January 01, 2000
Wolfgang Franke, Andrzej Żelaźniewicz, 2000. "The eastern termination of the Variscides: terrane correlation and kinematic evolution", Orogenic Processes: Quantification and Modelling in the Variscan Belt, Wolfgang Franke, Volker Haak, Onno Oncken, David Tanner
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Analysis of tectonostratigraphic units in the West Sudetes reveals the same geological events as in the areas west of the Elbe Fault Zone: a late Proterozoic (Cadomian) orogenic event, Cambro-Ordovician to Devonian rift–drift, and late Devonian to early Carboniferous subduction–collision. There is no conclusive evidence of an Ordovician orogenic event. Tectonic units in the Sudetes are shown to be related to terranes defined in western parts of the Bohemian Massif. The Lausitz–Izera Block, the Orlica–Śnieżnik Unit and the Staré Město Belt represent easterly continuations of the Saxo-Thuringian Terrane. The Rudawy Janowickie Unit and the Sudetic Ophiolite contain fragments of the Saxo-Thuringian Ocean. The protoliths of the Görlitz–Kaczawa Unit, the South Karkonosze Unit, the Góry Sowie and the Klodzko Units either belong to the Bohemian Terrane or else were welded onto it during mid–late Devonian metamorphism and deformation. Relicts of the Saxo-Thuringian Foreland Basin are marked by flysch with olistoliths in the Görlitz– Kaczawa Unit and in the Bardo Basin. The spatial array of terranes in and around the Bohemian Massif reveals a disrupted orocline, dissected by dextral transpression along the Moldanubian Thrust. This orocline was formed when central parts of the Variscan belt were accommodated in an embayment of the southern margin of the Old Red Continent.
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Orogenic Processes: Quantification and Modelling in the Variscan Belt
Research into the orogenic processes that shaped the continental crust of Europe has a long-standing tradition. Why the need to quantify and model? It is not just satisfactory to identify subduction zones, accretionary prisms, island arcs, extensional collapse and other standard items of the geodynamic menu. Such interpretations need to be quantified: extent and composition of subducted crust, angle and speed of subduction, amount and composition olmelts produced, heat sources for metamorphism. All such interpretations have to conform to first principles, and also to stand the test of quantitative balancing – a concept first developed for the conservation of length or volume in tectonic cross sections. Also in other fields, the correlation of causes and effects and the internal consistency of dynamic models requires a numerical approach.
The present volume combines review articles with reports on recent progress in an attempt to address these aims. There is a foldout map of the region, which locates the main areas of outcrop and tectono-stratigraphic units, and a reassesment of the Palaeozoic time scale permits correlation of tectonic, metamorphic and magmatic events with the sedimentary record of the upper crust.