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O promontório da Nazaré (Centro Oeste de Portugal) e o ensino de campo das Ciências da Terra num contexto turístico de fama global
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The promontory of Nazaré and its characteristic steep silhouette, with an incisive and rough outline emerging through the sandy beach landscapes of the west central coast of Portugal, has become world-wide known for the tourist circuits, due to the proximity of outstanding hydrodynamic conditions for radical sport practices. Achieved over the last decade, this reputation also contributed greatly to an increased interest about this exceptional geoform and the singular sites and landscapes associated with it, of recognized importance for the practice of natural and historical tourism. Along with the formalization of the Nazaré promontory as a geosite, currently underway through research projects about the Cretaceous of Portugal, the geological diversity and unusual features of this outcrop become particularly useful for educational interventions based on practical activities easily adapted to themes of the curricular programs approved for the basic and secondary school levels. Although limited by the terrain relief, the accessibility to stop points within the study area allows multiple practical activities at various scales, mainly of geomorphological, stratigraphical, paleontological and structural nature, with access through the south side of the promontory, near the “Sítio” viewpoint and along the cliff slopes of the Northern Beach. The stratigraphic succession exposed on both flanks of the promontory has been known since the early studies of Paul Choffat on the Cenomanian and Turonian (1894 to 1902) and, since then, has been the object of several researches and thesis, mostly from the 1970’s onwards. These stages are recorded by two units of the post-rift succession of the western continental margin of Iberia, suggesting a paleogeographical evolution in which alluvial systems with essentially coarse sedimentation and rich in vegetal remains (Figueira da Foz Formation) are followed by the progressive installation of lagoon systems and a Tethyan carbonate platform with parareefal facies with rudists. One of the remarkable aspects of this succession consists of an extensive intracretaceous endokarst, overlain by a coarse siliciclastic unit of Campanian age ("Conglomerates and Clays of Sítio da Nazaré” Fm.). This scenery is complemented by the occurrence of weathered basaltic dykes, posterior to the development of the carbonate platform. The field-trip should be mostly emphasized for the implementation of non-formal strategies to this context, being structured through phased methodologies such as Orion. This is already a common practice in other areas of geological and educational relevance located in the Portuguese territory, including Figueira da Foz and Cabo Mondego, São Pedro de Moel and Peniche. For this purpose, there is also suitable bibliographical and logistic support, as well as a local museum and numerous websites that allow previous research activities for the students, in a pre-field-trip context. The upper levels of the fluvio-deltaic unit can be observed with exceptional conditions at the southern end of the beach, including a variety of lithologies and sedimentary structures that enable both paper-and-pencil and field activities, among them photographic records and the collection of samples for later treatment in the classroom. Many fallen blocks of fossiliferous limestone can also be observed, allowing the identification and sampling of fossils, but also a focus on the importance of slope movements and erosional features. At the “Sítio” viewpoint the observation and interpretation of a landscape where several exceptional geoforms can be revealed, such as the Berlengas archipelago (structuration of the Variscan basement and the Lusitanian Basin), the typhonic valley of Caldas da Rainha (flanks of the anticline structure and sub-ophitic basic intrusion of S. Bartolomeu dome), the promontory and the submarine canyon of Nazaré. It is also from this point that the geology and the historical background are combined in a mystic of secular myths, such as that of the inconsolable D. Rodrigo and the legend of D. Fuas Roupinho, whose horse halted in front of the infernal precipice would have molded its hooves on the local marine limestones of Late Cenomanian age. On the way from the S. Miguel Arcanjo fortress to the Northern Beach, there are privileged conditions for a detailed observation of the thick conglomerates and reddish claystones of Campanian age, contemporary of a compressive and uplift phase that affected the region. Near the end of the outcrop, the “Forno d'Orca” can be visited and interpreted as an extensive erosional structure with circular contour, which was formed by marine abrasion after the collapse of a cavity opened in limestone and sandstone beds of early Turonian age. There are also weathered basaltic dykes and several complex collapse structures from the intrakarst that can be recorded, as well as abundant fossils, including rudists and actaeonelids, both typical groups of Cretaceous molluscs.
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Ensino Contexto turístico Nazaré (Portugal) SDG 14 - Life Below Water