5. For 13 million-years (since mid Miocene to now), a heavy erosive process have emptied the basin of Ebre. This process is the main responsible for the current relief of Bages. In the beginning of this period, the former fluvial network that was flowing towards the Ebre’s basin was replaced by the present one as a result of the sinking of the Catalonian massif and the simultaneous rise of the Ebre’s basin.
Differences amongst the resistance of the rocks to be eroded allows the modelling of prominent morphologies like those of Montserrat in places with hard rocks in opposition to the depressed areas with soft materials like in Sant Vicenç de Castellet.
The rivers Llobregat and Cardener are nowadays the outlet towards the Mediterranean sea of the eroded materials. From time to time, episodes of local sedimentation are registered in the Quaternary fluvial terraces (not displayed in the scheme). These Quaternary sediments makes the gravel deposits that are often exploited.
[drawing Oriol Oms]