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Encyclopedia of geology, five volume set, volume 1 5 (encyclopedia of geology series) ( PDFDrive ) 718

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82 EUROPE/Variscan Orogeny Figure Plate kinematic evolution of the Variscan belt in Iberia: 1, mantle; 2, continental crust; 3, oceanic crust; 4, volcanic island arc; 5, Early Palaeozoic sediments; 6, Carboniferous foreland sediments CCSZ, Coimbra Cordoba Shear Zone the situation in the central European section, there appears to be only one Armorican microcontinent (instead of Saxo-Thuringia and Bohemia) Nappes and sutures of the Ibero-Armorican domain are characterized by oceanic lithospheric rocks and early (420–370 Ma) ultrahigh-pressure, high-pressure and medium-pressure metamorphism The most external parts of the belt comprise low-grade to nonmetamorphic Carboniferous marine to paralic basins, which were deformed between 320 Ma and 290 Ma The structures and tectonothermal histories of the Iberian and French sections of the Variscan IberoArmorican arc are described below (Figures and 7) The Iberian section (Figures and 7A) combines a southern segment from the South Portuguese Zone to the Central Iberian Zone and a northern segment based upon observations in north-western Spain (Figure 1) The northern segment originated from the closure of the Galicia-Brittany–Massif Central–Moldanubian ocean Westward-directed subduction (in present-day coordinates) under an Armorican terrane affected first oceanic and then continental rocks between about 400 Ma and 300 Ma Collision produced an eastward-facing accretionary wedge, in which deformation migrated from west to east The lower autochthonous part consists of Early Palaeozoic shallow-water sediments deposited on the margin of Gondwana The upper allochthonous part includes, from bottom to top, rocks of a passive margin thinned during the Ordovician, ophiolitic rocks (400–480 Ma) of arc or oceanic mantle, representing the remnants of the Galicia-Brittany– Massif Central ocean, and an uppermost ultranappe, which may represent the extended eastern margin of Armorica The southern segment of the Iberian section shows an opposite orogenic polarity, with south-west-facing folds and thrust sheets Four main units are separated

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