The most important geographical characteristic
on the Costa Daurada is the Prelittoral Depression located between
the two mountain ranges that border the Mediterranean system.
Crossing the region from north to south, it is the result of a
tectonic trench formed by the folding of an old Hercynian mountain
range. Towards the end of this Tertiary orogenic paroxysm there
were several collapses in the Prelittoral Mountain Range which
gave rise to valleys and bowls of various sizes. The Conca de
Barberā and the Cubeta de Mora are good examples.
The rocks are basically calcareous in the mountain areas with different kinds of Paleozoic outcrops. The Jurassic period is well-represented in the Ports de Besseit mountains. The plains are dominated by Oligocene and Miocene formations and, as with all the edges of the Central Catalan Depression, there are large conglomerate outcrops, such as the Massis de Montsant. The Costa Daurada has 216 km of Mediterranean coastline ending in the south with the Ebro Delta.