Access to Portinho da Arrábida from:

- Setúbal (± 10 km) - N10-4 and the road to Outão hospital / beaches, always following the road by the sea.

Portinho da Arrábida beach has many visitors in Summer, so do not go there when weather is good, because it will be difficult to park. The site is on the East side of the beach and the access is only on foot.

GPS: 38.4808333, -8.9747222

Arrábida is exceptional for the diversity of geological processes that are registered there for the understanding and knowledge of fundamental stages of Earth history, namely in the testimony in continuous succession of the 4 rifting phases which led to Laurasia fragmentation and the North Atlantic formation. It is the only mountain range on the Atlantic facade that witnesses the westward spread of the progressive closure of the Tethys Sea and consequent formation of the Mediterranean Sea due to the collision between Africa and Eurasia plates since the Upper Cretaceous.

The unconformity that allows to date the formation of Arrábida mountain range (Burdigalian, Miocene - 17.6 million years ago) can be seen along the main road (Setúbal - Portinho da Arrábida), where it has an 90º angle and shows an enormous deformation contrast between the units before and after the mountain elevation. Angular unconformity occurs between the Miocene (with subhorizontal layers) and the Jurassic (with subvertical carbonate layers).

Portinho da Arrábida unconformity is a testimony of the 1^st phase of tectonic inversion of the western margin of Iberia and is the best place to see the several phases of the raise of Arrábida mountain range, showing a very high elevation rate (similar to the Himalayan one) for a small relief. There, you can see several sedimentary rocks, some containing fossils of sea-urchin, oyster’s shells and marks of organisms that pierce the rocks.

Discordance or unconformity – substantial break or gap in the geologic record where a unit is overlain by another that is not in stratigraphic succession.

Angular unconformity – occurs when layers of sediments has been tilted, truncated by erosion, and a younger set of sediments was deposited on this erosion surface.

Tethys sea or ocean –ocean existing during the Mesozoic Era (251 to 65.5 million years ago), between the Laurasia and Gondwana continents before the existence of the Indian and Atlantic oceans. It divided the Pangaea into two super large continents known as Laurasia and Gondwana. 100 million years ago, the Iberian Peninsula was an island separated from the European continent and surrounded by the Tetis Sea.About 50 million years ago, when the plates moved towards each other, this sea was closed down, being reduced to the Mediterranean, Aral, Caspian and Black seas. Tethys was a Greek goddess (titan) daughter of Uranus and Gaia, origin of the freshwater springs and woman of Oceanus, mother of the deities connected to the sea and rivers.