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Cemetery of Ancient beaches of Alcantilado de Montedor

Evolution of coastal platforms and climate cycles

The Cemetery of Ancient beaches of Alcantilado de Montedor Local Natural Monument is the most diversified in terms of preserved geomorphic interests, in particular residual, tectonic and coastal interests. Fluvial, aeolis, periglacial and geocultural interests were also identified.

The Montedor’s hill constitutes an interval of the coastal platform, geologically explained by the west magma extravasating from Bouça de Frade's main plutonite body, in direction of the current ocean.

The Rheic’s rock erosion, which surrounded the magmatic chambers (plutonites), and the uprising processes, that the territory suff­ered since the end of the Mesozoic era (Alpine orogeny), revealed to the surface the Palaeozoic origins of this territory. The heat transfer and the space that plutonites won over Rheic’s rocks, as well the geometry of the Palaeozoic super continents collision (oblique and diachronic collision) might be interpreted as geological aspects of great interest and beauty, like the thrust fault, the folding or the mineralogical assembly, that today we can contemplate, for example, in Montedor.

Therefore, these are the materials and structures of Palaeozoic heritage, that interacting with external geodynamic processes (coastal and climatic ones), control the quaternary geology and geomorphology. In this context and in a large scale analysis, the existence of outcropping granitic coastal platforms, allows us to know the altimetry of 5 ancient beach’s levels (coastal platforms) preserved above the actual (<1.8 meters): Platform I (18 m), Platform II (13 m), Platform III (8 m), Platform IV (4.5-5.5 m) and Platform V (2.0-3.5 m). Some of these platforms still preserve some ancient biological activity remains such as urchin’s alveoli (ichnofossils) and other records of the beach dynamics, in the form of notches and fossilized dune fields.


Bibliography

Carvalhido, Ricardo (2012). O Litoral Norte de Portugal (Minho-Neiva): evolução paleoambiental quaternária e proposta de conservação do património geomorfológico. Tese de Doutoramento. Universidade do Minho. 562 p.

The Cemetery of Ancient beaches of Alcantilado de Montedor Local Natural Monument is the most diversified in terms of preserved geomorphic interests, in particular residual, tectonic and coastal interests. Fluvial, aeolis, periglacial and geocultural interests were also identified.

The Montedor’s hill constitutes an interval of the coastal platform, geologically explained by the west magma extravasating from Bouça de Frade's main plutonite body, in direction of the current ocean.

The Rheic’s rock erosion, which surrounded the magmatic chambers (plutonites), and the uprising processes, that the territory suff­ered since the end of the Mesozoic era (Alpine orogeny), revealed to the surface the Palaeozoic origins of this territory. The heat transfer and the space that plutonites won over Rheic’s rocks, as well the geometry of the Palaeozoic super continents collision (oblique and diachronic collision) might be interpreted as geological aspects of great interest and beauty, like the thrust fault, the folding or the mineralogical assembly, that today we can contemplate, for example, in Montedor.

Therefore, these are the materials and structures of Palaeozoic heritage, that interacting with external geodynamic processes (coastal and climatic ones), control the quaternary geology and geomorphology. In this context and in a large scale analysis, the existence of outcropping granitic coastal platforms, allows us to know the altimetry of 5 ancient beach’s levels (coastal platforms) preserved above the actual (<1.8 meters): Platform I (18 m), Platform II (13 m), Platform III (8 m), Platform IV (4.5-5.5 m) and Platform V (2.0-3.5 m). Some of these platforms still preserve some ancient biological activity remains such as urchin’s alveoli (ichnofossils) and other records of the beach dynamics, in the form of notches and fossilized dune fields.


Bibliography

Carvalhido, Ricardo (2012). O Litoral Norte de Portugal (Minho-Neiva): evolução paleoambiental quaternária e proposta de conservação do património geomorfológico. Tese de Doutoramento. Universidade do Minho. 562 p.

Technical details

Location

The Natural Monument of Alcantilado de Montedor has approximately 55ha, bounded to the north by the Forte do Paçô and to the south by the Praia da Câmboa do Marinheiro.

Coordinates

Lat: 41.7456112

Long: -8.878909

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Technical details

Cemetery of Ancient beaches of Alcantilado de Montedor

The combination of the erosion of the Rheic rocks, which surrounded the consolidated magmatic chambers (plutonites), with the survey processes that the territory has been subjected to since the end of the Mesozoic era (alpine orogeny), revealed the Paleozoic depths of this territory to the surface. The effects of heating and space conquest of plutonites on the rocks of the Rheic, and the collision geometry of the Paleozoic supercontinents (oblique and diachronic collision - phases of varicose deformation - D1, D2 and D3) can be interpreted in geological aspects of great interest and beauty, such as carriages, folds or mineralogical paragenesis, which today we can contemplate, for example, in Montedor.

It is therefore the materials and structures of the Paleozoic heritage that control quaternary geology and geomorphology, through interaction with external geodynamic processes such as coastal processes or those resulting from climatic evolution.

In this context and in a large scale analysis, the existence of platforms molded in exhumed granite, allows us to know the altimetric position of 5 levels of old beaches (coastal platforms) preserved above the current beach (<1.8 m): Platform I (~ 18 m), Platform II (~ 13 m), Platform III (~ 8 m), Platform IV (4.5-5.5 m) and Platform V (2.0-3.5 m) (values ​​nmm ).

Some of these platforms still retain remains of biological activity, such as sea urchin alveoli (ichnofossils) and other signs of beach dynamics, such as notches or fossilized dune fields. In other locations, where the Viana do Castelo massif is placed on the margin and allows the coastal platform to develop, the coastal platforms remain hidden under the muddy sand sediments that give it a flattened shape.

This monument is also special for us to understand how the slopes evolve and are dismantled, a process registered in residual geoforms such as tafoni, pans and exutories, grooves, pseudo-stratification, peduncles, wavy floors and exfoliation.

References and scientific articles

  1. Carvalhido, R. (2016). O livro da Pedra - monumentos naturais Locais de Viana do Castelo.
  2. Carvalhido, R. (2012). O Litoral Norte de Portugal (Minho-Neiva): evolução paleoambiental quaternária e proposta de conservação do património geomorfológico. Tese de Doutoramento. Universidade do Minho. 564p.

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