Geology

Maciço of Morais

The territory of Geopark Terras de Cavaleiros has a geological patrimony of national and international relevance. Where it’s rocks tell a stories with millions of years.

The geology of this region takes us back 540 million years, when the Varisco Cicle was initiated. This cycle was initiated by the dismemberment of a super-continent and the opening of an ocean. This ocean was called Rheic, and was accumulating sediments from the erosion of the continents on its margins. However because all of the oceans are ephemeral, they tend to close up when they arrive at their expansion limit. The cycle ended with the collision of all of the existent continents, forming the big mountain range Varisca, edified between the Devonian-carboniferous (380-280 Ma).This new mountain range covers the testimonies of the continents involved in the process, as well as the ocean that was surrounding them. With the collision of all of the continents 250 million years ago. It was formed to new continent Pangea, that later began to separate to give place to the continents as we know them today.

In the Maciço of Morais it is possible to find the testimonies (materialized by the rocks) of this collision between continents and the consequent formation of the mountain range Varisca, a rarity on planet earth.

Image 2- position of the main continents 425 milion years ago. (adapted from Meyer-Berthaud et al., 1997)

Image 3 - simplified geological map of the Geopark Terras of Macedo de Cavaleiros. The lower allochthonous represents a fragment of the margin of the Gondwana continent; the medium allochthonous or Opholytic represents a complete fragment of the oceanic crust of the ancient ocean Galizia Trás-os Montes, an inferior ramification of the Rheic Ocean; the upper allochthonous corresponding to the continental crust of the ancient continent Armorica.

The Land

The rift of Vilariça, which develops between Bragança, Vilariça and Manteigas, corresponds to a big tectonic accident, with an extension of 250KM. This rift, although of low seismic activity, was responsible for the earthquake that destroyed the village of Moncorvo in 1858. associated with the movement of the rift occurred the lifting of blocks (a model of the push-up kind) like the mountain chain of Bornes (1199 m) and the mountain chain of Nogueira (1320m) and at the same time the decreasing of others, like the Santa Combinha, Macedo de Cavaleiros or Vilariça depressions.

The mount of Morais appears like a flattened relief, about 750 m of altitude, and represents part of the Fundamental Surface of the North Meseta. (Surface resulting from the destruction of the Varisca mountain chain).

Figure 4 - Overview of the mountain range of Bornes.

Drainage to the interior of the Iberian

The poorly consolidated sediments that occasionally cover the ancient rocky substratum are evidence of a drainage system predating the current drainage system into the Iberian Peninsula that would later be captured by the Douro River and would then drain into the Ocean Atlantic. This ancient river system is represented by ancient excavated valleys, which were filled by different types of sediments that result from the tectonic and climatic conditions of the Neogene.

Image 5 - Panoramic view of Cabeço Berrão on the River Sabor.

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