The Cirque de Navacelles: A Major Geomorphosite in the Grands Causses Karstic Region

Abstract

The Cirque de Navacelles is a perfect, incised meander that sits at the base of the deep Vis river gorge; this gorge slices through the southernmost of the Grands Causses (limestone plateaus), the Causse du Larzac, south of the metamorphic and granitic Cévennes Mountains. Two panoramic viewpoints, opposite one another on either side of the basin, provide a magnificent view 300 m above this highly scenic location. Over time, this major geomorphosite has acquired a certain degree of scientific and touristic notoriety, but the understanding of its formation was until recently rather incomplete. The Cirque de Navacelles is in fact a unique example of an incised meander because it is much more complex than a simple bend in a watercourse. Its shape is typical of other fully formed meanders, but the way it formed is unique. Karstic contributions in the form of Holocene travertines lifted the thalweg and led to an eventual overflow. As time passed, changes in the landscape continued, with erosion creating a 10-m-high waterfall at the end of the meander. What is interesting about this site is that three different types of formations are interconnected at a single place, the gorge, the meander, and the waterfall, with each one corresponding to a different phase in the chronology of the site’s history. Analysis of the creation of the gorges has also allowed researchers to include the gorges of the Tarn river in their studies and to show the impact on the karstic formations of the bordering plateaus.