Stretching lineation and transport direction in the Ibero-Armorican arc during the siluro-devonian collision |
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| Authors: | Jean-Pierre Burg Pascal Bale Jean-Pierre Brun Jacques Girardeau |
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| Institution: | 1. Centre Géologique et Géophysique (CNRS), USTL Place Bataillon, 34060 Montpellier Cedex, France.;2. Centre Armoricain de I’Etude Structurale des Socles (CNRS), Université de Rennes, 35042 Rennes Cedex, France;3. UA 1093 (CNRS), UER Sciences Physiques de la Terre, IPGP et Universite Paris VII, 75251 Paris Cedex 05, France |
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| Abstract: | AbstractLarge structures, lineations, foliations and sense of shear criteria are examined on the scale of the whole Ibero-Armorican Arc. Four sections (Galicia, Brittany-Vendée, Limousin and Eastern Massif Central) exemplify the major thrust sheets observed around the Arc. Stretching lineations are contemporaneous with the siluro-devonian metamorphism and are either transverse, oblique or parallel to the collision zone. A kinematic analysis shows that these lineations have resulted from a dominanüy transverse shear deformation which was followed by, or combined with, a longitudinal shear direction. On the scale of the entire Arc, this variation in the shear direction is interpreted as resulting from an early head on thrusting relative movement evolving to large scale movements parallel to the plate boundaries. Experiments with sand-silicone models support a model which generates the Arc by interaction between a transform sinistral direction, and a converning zone at a high angle to the transform direction. |
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| Keywords: | Variscan Belt Stretching lineation Transport direction Collision Thrusts Orogenic arcs Experimental models |
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