Geoparque Mundial UNESCO
Geoparque Villuercas > Nº16 – Sierra de la Madrila
The Sierra de la Madrila lies to the north of the town of Cañamero and can easily be reached by car from the Cañamero-Berzocana road. At the roundabout on the pass between the two towns, take the CC-95 towards Navezuelas and after a few metres an old cart track to the right that leads to the top of this sierra.
As well as the places described above, on some quartzite crests of the Sierra de la Madrila we can observe fine examples of Cruziana, trace fossils produced by Trilobites crawling on the sea floor, together with tubular markings of sandworms, which are both from the Ordovician period (some 480 million years ago) of the Palaeozoic era.
In addition, on the eastern hillside very near the peak we can visit an interesting isolated rocky shelter of quarzites known as the Cancho de la Burra to observe numerous schematic cave paintings of reddish and white tones. These paintings were executed by shepherds and hunters from the Chalcolithic period some 3,500 years ago and are very abundant in almost all the caves and shelters of the peaks and hillsides of the valley of the River Ruecas.
On the hillside of the Sierra de la Madrila stands the Interpretation Centre of the Special Bird Protection Area (Zona Especial de Protección de Aves, ZEPA) of Las Villuercas and the Guadarranque Valley; one of its rooms is devoted to the Geopark. Close by can be found the cave known as the Cueva de la Chiquita or Cueva de Álvarez, a sanctuary with schematic cave paintings by Chalcolithic man, and the natural swimming pools of the River Ruecas.
On the crests of the Sierra de la Madrila thick Armorican quartzites can be observed in almost vertical strata, and adjacent to them other less thick quartzites alternating with thin layers of shales that are rich in trace fossils (stratification of the flysch type). The quartzites are formed by the compacting and metamorphism of siliceous sandstones that in turn had been formed by the compacting of sands rich in silica deposited on the beaches of the Ordovician period of the Palaeozoic era. On these strata a further sedimentation of loams and clays gave rise to slates by compacting. Successive alternative series of thin layers of quartzites and shales form the flysch that can be found at the Sierra de la Madrila.
These quartzite rocks belong to the western flank of the extensive Garganta de Santa Lucía–Río Ruecas syncline and are rather fractured. This allows the percolation of rainwater at great depths until it is subsequently drained by means of the free-flowing fountain of La Madrila on the west side of the sierra, which supplied the nearby town of Cañamero with good water from the 1930s to the 1960s.
From the Risco Viejo in this same sierra a magnificent view can be had to the west of the extensive and monotonous peneplain of Precambrian rocks (shales and greywackes), the raised block of Garciaz of the same type, and the granite batholith of the Sierra de San Cristóbal in Logrosán. Towards the east we can also observe the extensive syncline of the River Ruecas with the dam and reservoir of the Cancho del Fresno; and far to the south the sedimentary platforms of the rañas of Cañamero and Logrosán.
