serie NOVA TERRA nº 49

43 age, in Sierra Albarrana Unit ( Azor et al., 1991 ). Therefore, a preliminary distinction could be made between the autochthons of the Galicia – Ossa-Morena Zone, and thence the denomination of SW Iberia Autoch- thon is proposed for the domains underlying the Ossa-Morena Complex ( Fig. 2 ). The stratigraphic characteristics of this autochthonous domain are not well known at present, but it likely occupied an outboard posi- tion across the margin of Gondwana compared to the autochthon of the Central Iberian Zone ( Fig. 2 ). The general structure of the Galicia – Ossa-Morena Zone is character- ized by the presence of a large allochthonous sheet, thrust onto different domains of the continental platform of Gondwana ( Fig. 3 ). This alloch- thonous sheet includes the most external domains of the margin of Gondwana. Therefore, the geology of the most internal part of the Iberi- an Massif accounts for a virtual duplication of the Gondwana margin ( Fig. 3 ). The most external domains of this margin were transported during Variscan convergence above other domains of the Gondwana continental platform closer to the mainland, juxtaposing fairly distant regions with different stratigraphic and paleontological features. The stratigraphic and faunal contrast between the Central Iberian Zone and the Obejo-Valsequillo Domain pointed out by Gutiérrez-Marco et al. (2014) highlights these differences. 5. Variscan implications The most important characteristics of the Galicia – Ossa-Morena Zone of the Iberian Massif can be also found in other massifs of the Variscan Orogen. The presence of ophiolitic units and units affected by Variscan high-P metamorphism is described in the Armorican Massif ( Ballèvre et al., 2014 ), the French Massif Central ( Lardeaux et al., 2001 ), the Bohemian Massif ( Kryza and Pin, 2010; Faryad and Kachlík, 2013; Kroner and Romer, 2013 ) and the basement of the Alps, Corsica and Sardinia ( Rossi et al., 2009; Von Raumer et al., 2009, 2015 ). These do- mains can be followed along the orogen and appear in the same geotec- tonic position. They con fi gure an Internal Variscan Zone, limited to the north by the southern margin of Laurussia represented by the Rhenohercynian Zone ( Fig. 4 ). The Internal Variscan Zone includes base- ment exposures that were previously correlated according to their strong Cadomian imprint ( Linnemann et al., 2008; Martínez Catalán, 2011 ). Therefore it represents the external section of the Gondwanan margin, particularly the one showing the most prominent igneous and tectonothermal activity related to the magmatic arc-system developed in the periphery of Gondwana in Ediacaran-Cambrian times. This is also the most strongly deformed section of the Variscan Orogen. This section of the Gondwanan margin was involved in two continental sub- duction systems of Variscan age, and the resulting high-P metamorphic belts can be followed along the orogen ( Arenas et al., 2014b ). The dy- namics of this margin is also characterized by the presence of ophiolitic units with similar ages and probably similar tectonic setting along the Variscan orogen ( Arenas and Sánchez Martínez, 2015 ). The correlations between allochthonous and autochthonous units in Iberia increase the perception of the Variscan Orogen as a markedly lin- ear mountain belt. The Variscan orogeny resulted in a complex suture zone bounded by the southern margin of Laurussia. The duplication of the margin of Gondwana observed in the suture zone exposed in the Iberian Massif has not been described so far in other massifs of the orogen. But the observed analogy between the high-P units and the ophiolites existing throughout the orogen represents a solid argument to search for a similar structural correlation. Acknowledgements Insightful reviews by Antonio Castro and Juan Carlos Gutiérrez- Marco are kindly acknowledged. Financial support has been provided by the Spanish project CGL2012-34618 (Ministerio de Economía y Competitividad). References Abalos, B., Gil Ibarguchi, J.I., Eguiluz, L., 1991. Cadomian subduction, collision and Variscan transpression in the Badajoz-Cordoba Shear Belt, Southwest Spain. Tectonophysics 199, 51 – 72. Abati, J., Castiñeiras, P., Arenas, R., Fernández-Suárez, J., Gómez-Barreiro, J., Wooden, J., 2007. Using SHRIMP zircon dating to unravel tectonothermal events in arc environ- ments. The early Palaeozoic arc of NW Iberia revisited. Terra Nova 19, 432 – 439. Abati, J., Dunning, G.R., Arenas, R., Díaz García, F., González Cuadra, P., Martínez Catalán, J.R., Andonaegui, P., 1999. Early Ordovician orogenic event in Galicia (NW Spain): ev- idence from U – Pb ages in the uppermost unit of the Ordenes complex. Earth Planet. Sci. Lett. 165, 213 – 228. Abati, J., Gerdes, A., Fernández-Suárez, J., Arenas, R., Whitehouse, M.J., Díez Fernández, R., 2010. Magmatism and early-Variscan continental subduction in the Northern 200 km 0 AVALONIAN FORELAND THRUST BELT (RHENOHERCYNIAN ZONE) INTERNAL VARISCAN ZONE WITH OPHIOLITES AND HP ROCKS PARAUTOCHTHON AUTOCHTHON FORELAND THRUST BELT CROPPING OUT / COVERED G O N D W A N A RHEIC SUTURE (REWORKED) VARISCAN STRIKE-SLIP SHEAR ZONES MAIN VARISCAN THRUSTS ALPINE FRONT BOHEMIAN MASSIF RHENISH MASSIF ARMORICAN MASSIF MASSIF CENTRAL IBERIAN MASSIF Fig. 4. Zonation of the Variscan Orogen. 141 R. Arenas et al. / Tectonophysics 681 (2016) 135 – 143