Geoparque Mundial UNESCO

Nº24 – Valdelacasa Anticline

Geoparque Villuercas > Nº24 – Valdelacasa Anticline

LOCATION AND ACCESS

The Valdelacasa anticlinorium stretches across the provinces of Cáceres, Toledo and Ciudad Real, and is part of the region known as La Jara, located to the east of the orographic massif of Las Villuercas, between the Sierra de Altamira or Sierra de los Puertos and the quartzite reliefs of the Sierra de La Estrella and Sevilleja. Its interpretation is similar to that of the great Ibor megastructure.

It can be accessed from any of the roads that cross it from north to south, such as N-502, or from the town of Puente del Arzobispo, where you can head south along the EX-387 road, as well as from other lesser roads that cross it from east to west, such as CC-20, via the Arrebatacapas pass (which we propose as a viewpoint), or the EX-102, via the San Vicente pass.

ATTRACTIONS OF THE VISIT

During the visit you can appreciate the interesting geomorphological features of the area, such as the large peneplain developed over Ediacaran and granite materials, the rocky outcrops of the Sierra de Altamira, the granite “berrocales” (area with granitic blocks with characteristic weathering), the encasing of the subsidiary fluvial network of the Tagus river in the extensive peneplain that characterises the region of “La Jara” and the residual reliefs of the quartzite mountain ranges that frame it on its eastern edge: Sierra de la Estrella, Sierra Aguda, Sierra de la Nava and Sierra de Sevilleja.

In this area, the sedimentary succession corresponds to the Ediacaran and its transition to the Early Cambrian has been described, with the interesting olistostromes which can be observed next to the Cíjara Formation in the Pedroso stream, to the south of the Pedroso bridge. This area is also the location of the Ediacaran-Cambrian transition, of great palaeontological relevance as it is one of the areas where some of the oldest fossils in the Iberian Peninsula are preserved, constituting one of the best records of “the great Cambrian biotic radiation”, preceded by the appearance in the terminal Ediacaran of the first mineralised metazoans with a calcareous skeleton (Cloudina).

Numerous “verracos”, zoomorphic sculptures from the Iron Age (4th century BC), made by the Vetones cattle-raising people, have been found in the rich pastures of La Jara. In Villar del Pedroso and Valdelacasa, magnificent examples are kept and can be seen in their landscaped squares.

GEOLOGICAL INTERPRETATION

Read Geological Interpretation

The Valdelacasa anticlinorium includes in its core Ediacaran-Lower Cambrian materials belonging, palaeogeographically, to two sectors which represented, at the end of the Ediacaran, the transition between a shallow carbonate platform environment and the deeper environments of the slope to the north, the only area which still included marine environments in the Early Cambrian, and which emerged at the beginning of the Middle Cambrian.

On the southwestern flank of this large megastructure are the carbonate materials of the Ibor Group (Peraleda de San Román area). On the northeastern flank we find the Cíjara Formation, consisting of shales, greywackes (sometimes very sandy) and conglomerates with abundant phosphate clasts. This unit includes numerous sedimentary structures and ichnofossils that indicate transitional environments from the upper part of a slope to a distal platform.

Discordant over these materials are olistostromic formations, which are the result of the collapse of the carbonate platforms of the Ibor Group due to the steep inclination of the slopes, in unstable environments with high seismicity, related to the final phases of the Cadomian Orogeny. The carbonate blocks of the olistostroma of the Pedroso stream, located in the north of the geopark, include specimens of Cloudina.

These materials are followed by an important Lower Cambrian succession that records “the great biotic radiation of the Cambrian”, and includes in areas very close to the Geopark, in the province of Toledo, deposits of the oldest trilobites and archaeocyaths in the Iberian Peninsula. All these sedimentary materials are intruded by granitic materials, which is why it is common to come across berrocales (landscapes with an abundance of stones and granitic boulders) which sometimes leave figures of great scenic and geological value, such as those studied in the “desfiladero de Pedroso” and “berrocal de Peraleda-Cancho Valdecastillo” geosites.

This megastructure is approximately one hundred kilometres long and several kilometres wide and runs in a NW-SE direction. It is bounded to the west by the outcrops of Lower Palaeozoic rocks that make up the Guadarranque syncline, while to the north, east and south its limits are less clear, with outcrops of Palaeozoic rocks alternating with Cenozoic sedimentary materials (rañas).