Formation du canyon de l'Ardèche en analogie avec l'endokarst de sa plateforme urgonienne périphérique durant le Néogène (Ardèche - France) ; Formation du canyon de l'Ardèche en analogie avec l'endokarst de sa plateforme urgonienne périphérique durant le Néogène (Ardèche - France): Comparaison avec les vallées du Rhône et de la Cèze.

This paper follows the publications entitled "Paleogeography of the Ardèche canyon from the Lower Cretaceous to the Oligocene" ( Jolivet et al , 2022) and "Karstic evolution of the Saint-Remèze anticline during the Paleogene (Ardèche - France)" ( Jolivet et al , 2023). This third and final article discusses the incision progress of the Ardèche canyon during the Neogene all along the evolution of the Miocene Rhodano-Provençal basin (BRPM) and of the Bruguière ria belonging to the Cèze basin. A large drainage network with NW-SE axis has been installing from the finished Eocene high-levelled surface to settle the paleo-Ardèche between the Cèze-Ardèche interfluvium and the Saint-Remèze plateau. Its bed must have spread out in wide valleys dug into sandstone to sandy formations dating from past Upper Cretaceous to Middle Eocene times. At the beginning of the Miocene, under constraints of extensive Oligocene followed by compressive Alpine tectonics, the Ardèche river sees its course incised in stages into the Barrémo-Aptian limestones in relation to the eustatic and climatic periods of the Neogene. In parallel, the speleogenesis, which developed in the limestone plateaus located on either side of its canyon, has made it possible to create a kind of “endokarstic analogue” preserving varied and evolving morphologies developed during the Neogene. The concept of this analogue is taken up and distributed throughout the different sections of this article. In situ observations, exploration and surveying work in caves carried out since many years by speleologists (Bulletins CDS 07, 1966 à 2023), made it possible to draw up a more or less rigorous synopsis where one can find the altitude of the main caves. Throughout this framework, this study attempts a chronological alignment in relation to the evolutions of the incision of the Rhône, Cèze and Ardèche canyons. The paleocovers deposited from the Upper Cretaceous, the Paleogene generated characteristic fillings such as neoformed sandstones, and authigenic clays in particular, ...