Geoparque Mundial UNESCO
Geoparque Villuercas > Nº18 – El Risco Gordo and Sierra del Pimpollar
The Risco Gordo is the highest spur of the Sierra del Pimpollar (836 m) and rises southeast of the town of Cañamero. Easy vehicle access is provided by a forest track that leaves the Guadalupe road a few metres to the right of the last houses of the town opposite the park. When the threshing floor of Las Escarihuelas is reached this geosite is already visible; we can take the forest track to the summit.
From the Risco Gordo vantage point we can observe the Appalachian relief of the Sierras de las Villuercas, the River Ruecas defile, the Santa Lucía-Río Ruecas syncline, the extensive Precambian peneplain of the Domo Centro-extremeño, and the sedimentary formations of the rañas de Cañamero of Plio-Quaternary age with their characteristic platforms or “plateaus” formed of pebbles of quartzites and clays from the erosion of nearby sierras.
Between the projections of the Armorican quartzites of the Sierra del Pimpollar fine examples of trace fossils can also be found: Cruziana and Skolithos (trails of trilobites and sandworms from the Ordovician).
To the north of the Risco Gordo we can make out the Risco del Castillo and the Risco de las Cuevas, which contain numerous rocky shelters with schematic cave paintings: Los Vencejos, the Cueva de Rosa, the shady side of the Castle, etc. The view also includes the foundations of the Muslim castle of Cañamero where the prince of León, Sancho Fernández, died in 1220.
From a geological point of view the Sierra del Pimpollar is an elevation formed by the differential erosion of “Armorican quartzites” (the rocks that remain after the erosive process as they are harder and more resistant) of the west flank of the great Santa Lucía-Río Ruecas syncline. Here they have been folded to form two structures, which are the narrow Cañamero-Sierra de Berzocana syncline that generates the Sierra del Pimpollar and the Cañamero anticline which can be observed on the nearby Risco de las Cuevas. A reverse fault that extends from Cañamero to Solana de Cabañas delimits and separates this syncline from the rocks of the Upper Precambrian that can be observed on the Trujillo peneplain (the schist-greywacke complex). (See geological map).
Towards the south in the valley of El Cenal it can be seen that the Sierra del Pimpollar disappears below the platforms of the raña plateaus owing to a cross fault, only to reappear to form the Sierra de Valdecaballeros. This cross fault was used by the River Ruecas to change its former course sharply to the west in what must have been a typical fluvial “elbow of capture“.
