Carbon Conglomerate

Geossítio 28 Carbon Conglomerate

As a result of the break-up of the Variscan mountain range…

A closer look at the rocks that outcrop at this geosite allows us to identify various fragments of pebbles (clasts) of a more or less rounded shape held together by cement. The clasts are made up of older rocks that we see in nearby areas, such as schists, grauvaques and quartzites, which are evidence of the disintegration and erosion of the slopes of the Douro Carboniferous Basin during the Carboniferous period, around 300 million years ago.

Este geossítio faz parte do itinerário C: Paiva, the surprising valley.
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Informação Geológica

The Carbónico Conglomerate is a clast-supported conglomerate, made up of elements from older neighboring rocks, such as schist and grauvaques from the Dúrico-Beirão Supergroup and also quartzites possibly from the Santa Justa and Sobrido formations.

The origin of this conglomerate dates back to the upper Paleozoic, when the continents that existed on Earth collided, leading to the formation of the supercontinent Pangea and a process of mountain formation known as the Variscan Orogeny. This process of folding and uplift of the Varisca chain is thought to have led to the formation of intramountainous lake basins, which were filled in by the breakdown of their slopes, giving rise to the Douro Carboniferous Basin, which is the most extensive outcrop of continental Carboniferous in Portugal, stretching from S. Pedro Fins (E of Porto) to the Douro. It stretches from S. Pedro Fins (E of Oporto) to Janarde (E of Arouca), along a narrow strip about 50 kilometers long and rarely more than 500 meters wide.

The orientation of the rocks in the basin is approximately N130º+10ºE, almost always sloping towards the NE quadrant and varying between 45 and 90 degrees.