Geoparque Villuercas-Ibores-Jara

Nº17 – Guadarranque-Gualija Syncline

Geoparque Villuercas > Nº17 – Guadarranque-Gualija Syncline

LOCATION AND ACCESS

The great Guadarranque syncline extends some sixty kilometres within the Geopark, from the Valdecañas reservoir on the Tagus river to the Cijara reservoir on the Guadiana river. The Guadarranque river is the main river that flows into the Guadiana, while the Gualija river flows into the Tagus.

From a geological and structural point of view, it is bounded by the Valdelacasa anticlinorium to the east and the Ibor anticlinorium to the west. It can be reached from several roads that cut across it, the main ones being the CC-202, EX-102 and N-502. Among the main footpaths, the Royal Road from Castile to Guadalupe crosses it from the Arrebatacapas pass, in Navatrasierra, to Hospital del Obispo, and the Camino Natural de las Villuercas from the Peña Amarilla gorge (Alía) to the San Vicente pass.

ATTRACTIONS OF THE VISIT

During the visit, the aim is to observe the megastructure of the synclinal fold and the different nature of the layers that form it. The different rocks are identifiable in the relief, according to their behaviour in the face of differential erosion, as well as their rich fossil content.

The Upper Ordovician quartzites (Cuarcitas de las Majuelas) of the “charco de la garganta de la Trucha ” (pool of the Trout gorge) are transversely fractured, and the displacements of the blocks along the fault plane can be observed in situ. In this gorge we can also observe the “Lorera de La Trucha”, one of the best preserved forests of Portugues laurel, Prunus lusitánica, trees that already existed in the Tertiary period, accompanied by a gallery forest of alder and ash trees. It is also interesting to observe the rupicolous vegetation that accompanies the quartzites.

Further north we come across the winding course of the Gualija river, which flows through the Vadillo cliffs, offering a good spot for birdwatchers. This is an imposing quartzite outcrop that is home to nests of vultures and birds of prey. To end the visit, we can leave via the Arrebatacapas pass towards the plains of “La Jara cacereña” (Valdelacasa de Tajo anticline), or towards Guadalupe along the Hospital del Obispo road.

You can complete your visit in Navatrasierra, where numerous fossils of trilobites and other marine invertebrates from the Ordovician have been found and are on display at the Fossil Interpretation Centre in this town.

GEOLOGICAL INTERPRETATION

Read Geological Interpretation

In a syncline, the oldest materials are located on the flanks and the most modern ones in the core, so that starting from the flanks towards the core we can reconstruct the chronostratigraphic succession. The Guadarranque syncline includes the most complete and continuous series of Palaeozoic materials in the geopark, encompassing the Ordovician and Silurian periods, and where several lithostratigraphic units have been defined.

Following the CC-202 road which runs between the Hospital del Obispo mountain range (southwest flank) and the Altamira mountain range (northeast flank), we find the greatest width of the syncline, some 9.5 km, and, in addition, the most complete stratigraphic series.

The flanks of the syncline are formed by the Armorican Quartzite and include the highest mountain ranges. In the interior, the other two important elongated reliefs are the La Cierva Quartzite (Caradoc Quartzites) and the Las Majuelas Quartzites intercalated between the diamictites of the Gualija Formation (both units are named after the hills “Peña de la Cierva” and “Las Majuelas”, located close to Navatrasierra).

In its core, or central part of the syncline, there are Silurian shales, sandstones and quartzites which are the most modern materials and, being easily eroded, occupy the lower areas where the Guadarranque and Gualija rivers flow.