Twisting without breaking
The area situated at southeast of “Pedras Parideiras” has particular interest because it is highly bent. The “bends” are deformations on the rocks, where it is possible to observe the bending of surfaces originally flat. Actually, the rocks of this geosite were formed for more than 500 million years in the deep basins of an old sea, where alternate layers of sediments were horizontally deposited and which, by diagenesis and metamorphism, originated the schist and metagraywacke rocks. In this region, it also occurs several veins of quartz, whose bright color and high resistance to weathering facilitates the perception of the bends. The compression movements felt about 350 million years ago have caused an increase of the pressure and temperature, making the rocks more ductile, and thus forming bends of different amplitude.
The relevance of this geosite is even bigger due to the fact that the bends and foliations present in these materials underline a multiphase orogenic evolution. The last generation of bends was assigned to the third phase of the Variscan deformation, although one of the outcrops has a bend assigned to the second phase. The bends of the third phase have a NW-SE axial plan with steep slopes, usually higher than 65° to SW and NE. The axis of the bends tilts between 10º and 20º systematically to SE.
The Castanheira bends field is drained by the Castanheira stream, a tributary of the Caima river. This water line serves as the shelter for several species, like the bryophytes (primarily the Sphagnum species) and vascular plants, like the cervum (Nardus stricta). In the rocky areas, there is the Sedum brevifolium or the late crocus Iberian endemism (Crocus serotinus). The birds of prey, like the montagu’s harrier (Circus pygargus), the common kestrel (Falco tinnunculus) or the Eurasian sparrowhawk (Accipiter nisus) fly over this place.