Effects of inherited structures during lithosphere shearing in the hercynian belt of Brittany (France). In : RST, Strasbourg, SGF, 2004

During Carboniferous times, Central Brittany was affected by dextral strike-slip deformation / associated with the development of the South Armorican Shear Zone. Recent / tomographic studies show that this shearing affected the whole of the lithosphere, with / a quite homogeneous regional-scale deformation. On the other hand, crustal deformations / often combine distributed strains with strains and displacements localised along / faults or shear zones. In Brittany, modelling of the deformation of the crust has been / computed using surface structural features and recently acquired geophysical data. / Results lead to a new kinematic interpretation of several of the structures of the belt, / including the Châteaulin basin, the Plouguenast gneiss dome, or relationships between / strike-slip and thrusting that affected the southern part of the study area. A restoration / model, combined with chronological constraints provided by syn-kinematic intrusions, / further allows us to propose an integrated tectonic history for the area during / Carboniferous times. This study emphasizes the first-order role of pre-existing / crustal-scale faults on the development of the regional structural pattern. These in particular / clearly controlled local basin development or emplacement of syn-kinematic / intrusions. On the other hand, the regional dextral Hercynian shearing controlled the / development and (or) reactivation of the main regional-scale shear zones.