The picture shows the angular discordance between Upper Carboniferous Slates, deposited about 310 million years ago in the former Rheic Ocean, and Upper Triassic coarse red Sandstones which were formed during Upper Triassic, about 220 million years ago. The site is near Querença (Loulé, Algarve).
You can see a flat line between the slates and the sandstone, which corresponds to the angular discordance.
In this line there is a time gap of about 90 million years, during which the material of the slates was deposited at the bottom of the former Rheic Ocean, then the continents of Laurussia, Armorica and Gondwana collided, closing the Rheic Ocean and building up the super-continent of Pangea. Because of the collision, the huge Variscan mountain chain rose up, which was eroded still during the time gap. Finally, red sandstones were deposited on the eroded surface of Pangea, with a sharp angle to the older slates.
