The geological story-telling of geopark building stones

Stones used as building materials provide identity to the landscape of towns and cities, especially those of local origin. They are also a direct reference to the regional geology. In line with the main philosophy that defines the UNESCO Global Geoparks network, protection, education and sustainable development, including both their natural and cultural values (https://en.unesco.org/global-geoparks), ornamental and building stones acquire a significant importance, as they are part of the Geoheritage. The results obtained in the characterisation of these lithologies are used for educational and didactic purposes and serve to valorise Geology. This documentation is significantly important for local development activities, especially in the case of rural areas affected by depopulation.

Las Loras Geopark (North Spain) is a territory with a landscape marked by a strong relief (http://geoparquelasloras.es/index.php/las-loras/). There are numerous small rural towns and villages that contain an important built cultural heritage, especially of the Romanesque period, such as the town of Aguilar de Campoo (Palencia, Spain). In the centre of the Geopark is located the Valdelucio Valley (https://www.valledevaldelucio.es/inicio) with an extension of 96.04 km², and a significant depopulation (330 people census in 2020), it is in this region where the need to implement development activities has been established. The geological discourse centred on building stones requires the development of cultural heritage rooted in society, accessible and, especially, appreciated, such as the existing churches. For this reason, the stones of three of them have been studied, the Church of San Pedro in Paúl (pre-Romanesque, the oldest), the church of Santa Leocadia in Quintanas (municipality that houses the town council of the Valley) and the Sanctuary of the Virgen de la Vega in Pedrosa (with important roots in the Valley).

Stones of Jurassic to the Cretaceous ages, mainly sandstones and limestones, have been identified. As they are rocks from the immediate surroundings, the account of their origin is a synthesis of the geological history of the Valley, of its evolution from wetlands, to rivers, alluvial fans, to the establishment of deltas and carbonate marine platforms. In addition, the Quaternary tuffs used allow to explain the recent geomorphological processes. During the research phase, work was organized in cooperation with the local population in workshops, field trips and conferences. The results have been presented with i) geological mappings of the façades representing the different lithologies present in them, ii) a stratigraphic synthetic column of the geological formations, with indication of equivalent hand samples taken in the field, and iii) microscopy images of the hand samples.

In addition to geological story-telling, the collaboration with the population has allowed prioritisation of content and activity concepts. This methodology has introduced the geology of the Valley to them. What is not known is not valued, and these activities help to value the territory from a wider perspective.