Geology and fossils at the Bufadors de Beví

A day trip with the Grup Mineralògic Català (GMC) to the impressive Bufadors de Beví, a set of labyrinthine cavities located on the border between Osona and Ripollès. The area is part of the deformed South-Pyrenean foreland, situated on the axis of an anticline.

A route under a splendid beech forest led us to the labyrinth of cavities. These are not of karstic origin but are classified as "gravitational" cavities, formed by the breaking and sliding of sandstone packages (hard, rigid rock) over marls (softer, elastic rocks). These sandstones formed the frontal part of a delta, and gravity plays an essential role in their formation.

The communication between these fissures causes the phenomenon of the curious "bufadores" (blowers), maintaining a constant internal temperature (between 13 and 15 ºC) and generating a cool microclimate that allows the survival of plant species normally found further north or at higher altitudes. In this environment, we were able to observe several mushrooms, including a beautiful specimen of Oudemansiella mucida.

In addition to the geology, we noted that the area is an ancient seabed with sediments related to Eocene gypsum. The detected fossil fauna includes a large quantity of foraminifera, bryozoans, echinoids, bivalves, infilled tubes, and even crab claws. We had the opportunity to observe a hard layer called lumachella, interbedded between softer marls, which is almost exclusively formed by foraminifera. These fossils are oriented according to the predominant current direction.

For more information on the area and geology:

• Visita als Bufadors de Beví - Grup Mineralògic Català
• Isabel Benet: Els Bufadors de Beví - Amics del Museu Geològic del Seminari de Barcelona