In order to understand the geometrical and kinematical compatibility between the autochthonous and the parautochthonous formations in northern Portugal, two small sectors in the vicinity of the main basal thrust have been chosen (Fig. 5). For the selection, three principal criteria have been used:
- they must be representative of the main geodynamical domains where they belong;
- the outcrop conditions must allow a detailed characterization of the Variscan structures;
- there should already exist some relatively well founded geological knowledge of the adjacent regions.
Figure 5. Geological map
Simplified geological map of Murça-Marão area; the quartzitic units are stippled (adapted from 1/1 000 000 Geological Map of Portugal, in press).
The Marão Mountains (near Vila Real) and the Garraia-Santa Comba ones (near Murça) were then selected as representative, respectively, of the Central-Iberian autochthon and the parautochthon. Indeed, not only thick quartzitic layers give rise to very well exposed outcrops, but also several recent structural works allow an easy selection of sectors for detailed studies, not only for Marão (Coke, 2000), but also for Santa Comba (Rodrigues et al., 2003).