Stratigraphie et structure de Trás-os-Montes oriental (Portugal)

Rocks in the eastern part of the province of Trás-os-Montes, N. Portugal belong to five units: 1: a complex of pre-Ordovician schists and greywackes; 2: Ordovician and Silurian sediments; 3: a low-grade metamorphic scries of Silurian age; 4: two complexes of probably Precambrian, predominantly meso- to catazonal rocks (amphibolites, eclogites, basic and ultrabasic igneous rocks, augengneisses and micaschists) : the units of Morais-Bragança; 5: igneous rocks (intrusive hercynian granites, small gabbro massifs and dykes of dolerite and granite-prophyry). The stratigraphy of the (meta)sedimentary series is described. Three hercynian tectonic phases affected the region, a first giving rise to axial plane cleavage of varying dip and strike, a second phase causing crenulation cleavage and E-W folds (mainly seen in areas with subhorizontal S1) and a third phase flexuring the axes of earlier folds. Some aspects of a structural interpretation of the geology of the area are discussed.