The Santa Lucía-Río Ruecas syncline is part of the great synclinorium of Las Villuercas; it is located on its western edge and borders on the Trujillo-Cáceres peneplain. It extends for several tens of kilometres from Cabañas del Castillo to the Sierra del Pimpollar and Puerto Llano in Cañamero, and does not exceed three kilometres in width.
The village of Cabañas del Castillo is an excellent vantage point for the observation of this syncline and the Appalachian relief of the district. In order to climb to the ruins of Cabañas Castle, we leave the village in the direction of the cemetery on a path leading south-east towards a hillock that separates the peaks of El Castillo and Peña Buitrera. From here if we continue to climb northwards on the same path we will come to the remains of this fortress of Muslim origin.
Geomorphologically the Santa Lucia syncline is an example of inverted relief of the Appalachian type, constituting a “hanging syncline” specifically in the area of the Collado del Brazo (the watershed between the basins of the Tajo and the Guadiana). In other words, it is a topographical elevation regarding the anticlinal structures that flank it and which have suffered more from the effects of erosion. This syncline retains Palaeozoic materials (quartzites, sandstones, and shales) with a complete sedimentary sequence from the Ordovician and Silurian eras in which quartzites alternate with shales and sandstones.
As its outcrops form the projections of the peaks, the most visible rocks are Armorican quartzites. The latter have suffered considerable tectonic movements so that although they are very competent hard rocks, they have been heavily folded and fractured. The main fracture system has a NE-SW orientation and distorts the strata of the synclinal structures, as well as favouring the separation of the individual crags that make up the line of peaks.
As well as the impressive geology afforded by the vertical outcropping of Armorican quartzites on which the Arabian castle of Cabañas stands, the visitor can also observe the Appalachian relief with the crest lines of the sierras, and in the surrounding area fine examples of deformation structures (folds and faults) and geomorphologic structures such as defiles, cliffs, pedreras, and the extensive Trujillo-Cáceres peneplain to the west.
Trace fossils can be found in this area such as trails of the crawling of trilobites (Cruziana) or others in the form of vertical galleries of simple tubes known as Skolithos, which are attributed to highly mobile soft-bodied animals (marine worms).
This geosite is also very interesting for watching the birds that nest on these crags (Peña Buitrera), together with roe and red deer, ocellated lizards, butterflies, and other arthropods. The visitor can also enjoy the oak woodlands on the shady side and old cork oaks on the sunny side.
The rocky shelters and caves of the Ruecas Valley, the Collado del Brazo, and the Garganta de Santa Lucía contain the best collections of schematic rock paintings in the Geopark.
Castillo de Cabañas Castle and Santa Lucía syncline (background).
The Santa Lucía syncline retains the materials deposited up to the Silurian period.
The adjacent River Almonte anticline, which was originally higher after the Hercynian movement, lost a considerable part of its core material to erosion and forms a deeper valley today.
In the inverted relief we can find raised or “hanging” synclines that retain the various strata of materials deposited throughout geological history, while the core of the anticlines has been totally “emptied” of these materials to form deep valleys today.