GEOSITE FRAGAS DE DEGOLADOS (PR3)
At this geosite, a succession of Silurian lithologies (Vale da Ursa Formation) is exposed, where the layers are arranged sub-horizontally.
At the base of the sequence, there are massive metasilty-pelitic strata with spheroidal shapes, interbedded with schist layers. Vertically, this succession evolves into a regressive sequence, beginning with alternating schists and quartzites and ending with thick quartzite beds.
The outcrops show numerous discontinuities, both vertical and horizontal, resulting from accumulated stresses within the rock mass. These discontinuities allow rainwater infiltration, promoting the progressive weathering and disaggregation of the rocks—first the schists, and later the finer quartzite layers.
Due to the organization of the sequence, the disaggregation occurs from bottom to top, as the thinner strata are more susceptible to alteration than the thick quartzite beds at the top.
In the early stages, preferential deep drainage pathways develop, gradually widening toward the surface. The quartzitic zones, being more resistant, are not easily disaggregated, leading to the formation of arches beneath which water flows. Over time, these arches collapse when their structural resistance is exceeded, resulting in rapid fall movements.
Landscape shaping continues to this day, with two well-defined water channels visible, wider at depth than at the surface, along with quartzite fragments in their beds resulting from past collapses.
At this site, white sandy beds with micaceous composition can be observed, generally appearing massive and with faint or absent stratification.
Associated with these beds are sedimentary structures such as syn-sedimentary folds, slumps, and water escape structures.
These formations occur at the lower part of a regressive sequence within the Vale da Ursa Formation (Silurian) and are interpreted as resulting from fluidized mass transport associated with rapid glacier melting.
Flora and fauna
Along the Carvoeiro trail, a rare forest of Portuguese cherry laurel (Prunus lusitanica) can be found, a relic species from ancient laurel forests in Europe.
Other plant species such as mock privet, willows, myrtle, purple heather, Lusitanian heather, alder, and cork oak may also be observed. Along the streams, the giant royal fern can be found, reaching heights of 2 to 3 meters under favorable conditions.
In terms of fauna, the Iberian frog, an endemic species of the northwestern Iberian Peninsula, is noteworthy. Birdlife includes the three woodpecker species found in Portugal (green woodpecker, lesser spotted woodpecker, and great spotted woodpecker), as well as the rare black stork and more common species such as the blackcap.
With some luck, mammals such as roe deer and squirrels may be spotted, as well as the solitary blue rock thrush perched on rocky outcrops.
Additional geological context
The region is characterized by diverse geology, highlighting the Aziral folds and the “Balancho ball” sedimentary structures, associated with glacial movements when this region was located near the South Pole.
The Fraga dos Degolados is also noteworthy, having formed under similar paleogeographic conditions, when this region was part of the Southern Hemisphere.
Other points of interest
This geosite also includes a geocaching point of interest, allowing visitors to explore the area in an interactive and engaging way while promoting awareness of its natural heritage.