Drainage pattern modifications in the Aude basin (France): tectonic and morphodynamic implications

A study of river capture and palaeodrainage systems in the Aude basin is used to reconstruct the main stages of the palaeogeographical evolution of the region located between the Central Massif and the Pyrenees. Geomorphological and sedimentological (pebble composition, X-ray and heavy-mineral analyses) studies have made it possible to identify and link the different alluvial outcrops from upstream to downstream in the Aude basin. The study of the Castelnaudary terrace and of the high levels of the Aude shows that this river always flowed to the Mediterranean Sea: green hornblende from the Upper Aude did not reach as far as the Naurouze gap. River capture events between the Garonne and the Aude basins were caused by migration of the drainage divide towards the west, with uplift of the Montagne Noire and progressive hollowing-out of the strike depression between the Montagne Noire and the Eocene cuesta. The reconstruction of longitudinal terrace profiles shows the evolution of tectonic deformation since their deposition. The uplift of the Tourouzelle unit and of the Corbières thrust-fold sheet has caused the formation of knick points, the splitting of the middle terrace into two parts and alterations in the course of the Rivers Aude and Cesse.