Catalan Central Depression

It widens towards the west, linking with the Ebro Depression, Catalan: Depressió de l'Ebre, of which it could be considered an eastern extension.

There are eroded river basins limiting these heights wherever the ground is made up of clay or marlstone.

The limits of the Central Depression are different whether considered from the point of view of their origin or their actual relief.

[2] The Central Depression formed in the Tertiary, when a great gulf, that later became a sea, had its boundaries in the Pyrenees and the Catalan-Balearic Massif.

[3] Marine sedimentation formed clay, and other limestone materials, like bluish marl where the sedimentation had been part of a quiet and slow process, as well as conglomerate in the areas of the mouths of ancient rivers coming down from the Pyrenees and the former Catalan-Balearic Massif.