The Fórnia reculée: An international Quaternary geoheritage
|Location||International Geological Congress,oslo 2008|
|Author||Rodrigues, Maria Luisa|
|Holding Date||08 September 2008|
The Fórnia of Alvados reculée is located in the Estremadura Limestone Massif (ELM), the most important limestone karstic unit in Portugal (100km north of Lisbon and 20km from the Atlantic Ocean). The ELM stands out (the maximum altitude is 677m) in the Western Mesocenozoic sedimentary basin just near the contact, by upthrust, with the Tagus Cenozoic sedimentary basin, where the Jurassic limestone block overlaps the detritic terrains.
The Fórnia is the most spectacular reculée of Portugal and have the perfect shape of an inverted cone due to fluvio-karstic processes, assisted by an intense tectonic fragmentation. However, the genesis of its perfect regularized rectilinear slopes is due to frost action and snow melt conditions existing during the latest quaternary cold periods. The geomorphologic heritage preserved in the Fórnia is an important testimony of the complex geomorphologic evolution of the European sectors marginal to the glaciated areas (Portugal only has glaciers in the Estrela and Gerês Mountains).
Indeed, the Fórnia of Alvados is a clear-cut geomorphologic and landscape heritage that must be preserved and classified as a geomorphosite in the frame of the Natural Park of the Serras of Aire and Candeeiros (PNSAC; Rodrigues, 1989, 1996).
To preserve the natural heritage, besides Quaternary deposits (several types and different generations) one should highlight the richness of both its fauna and flora (birds of prey and other protected species, Mediterranean aromatic flora species, and so on) and is particular hydrologic karst features (perennial and seasonal exsurgences, caves, waterfalls and swallow-holes).
These particularities give to the Fórnia an unquestionable scientific value as well as a strong geotouristic interest.