Abstract This paper traces the touristic trajectories of three spectacular gorges located in the Alpine foreland and the southern Jura: the gorges of the upper Rhône (Ain/Haute-Savoie), the Sierroz (Savoie) and the Fier (Haute-Savoie). All three are located within a distance of 50 km from each other. The upper Rhône gorge, already famous at the end of the eighteenth century, was drowned under the floodwaters of the Génissiat dam in 1948; only a significant iconography remains of two centuries of (geo)tourism. The Sierroz gorge, close to the spa resort of Aix-les-Bains, became famous after the dramatic and tragic death in 1810 of a young noblewoman. Following that event many tourists staying on the shore of the lake Bourget visited the gorge until 1970 when it was closed to the public. Since then, the gorge has gradually become a touristic wasteland. The Fier gorge near Annecy became a tourist attraction in 1869 with the opening of the nearby railway station of Lovagny; since then, visitors have been attracted to it in increasing numbers. The history of these three gorges illustrates how tourism and heritage are in constant interaction; however, the development of the one will not always ensure the protection of the other. Today, geoheritage assessment is based upon criteria that are as objective as is possible. The intrinsic geological and geomorphological characteristics are the initial geoheritage values, to which can be added the cultural value elements. Associated with the development of geotourism and geoparks, this new approach should ensure a better and sustainable use of these sites in the long term.

Detrital geochronological analyses, combined with information on river sediment load, are widely employed to constrain erosion patterns in orogenic belts. Major assumptions in most detrital studies are that detrital samples are fully representative of eroding bedrock, and variation in original mineral concentration, often referred to as fertility, is negligible. Nevertheless, hydraulic sorting effects during transport may strongly affect sediment composition, and mineral fertility strongly depends on bedrock lithology. In this detrital geochronology study, we illustrate how hydraulic sorting effects can be properly evaluated, and how mineral fertility in bedrock can be determined from detrital samples, in order to infer reliable erosion patterns on short-term time scales. Fission-track, bulk-petrography, and geochemical analyses were carried out on modern sands of Rivers Dora Baltea and Arc in the Western Alps. These rivers drain in opposite directions two major fault-bounded blocks (Eastern and Western Blocks) that have undergone contrasting exhumation paths since the Miocene. Samples were collected from different sites along the river trunk, in order to investigate how the detrital signal evolves when detritus from different sub-basins is progressively added to the system. In the Dora Baltea catchment, petrographic data indicate that 29% of the total river load was derived from the Western Block, whereas the Eastern Block contributes the remaining 71%. Petrographic signatures in the modern Arc sands are more homogeneous, thus preventing a precise discrimination of the sources. Apatite fission-track data from the Dora Baltea River show that the Western Block yields 43% of the total apatite load, and the Eastern Block the remaining 57%. In the Arc catchment, apatite contribution is 29% from the Eastern Block, 14% from the Houiller-Subbriançonnais units, and 57% from the Belledonne-Dauphinois units. We assessed apatite fertility in source rocks by measuring apatite content in processed sediments, after checking for anomalous hydraulic concentrations by geochemical analyses. Apatite flux from each sub-basin was converted into a specific sediment yield to infer the short-term erosion pattern in the drainage. The annual sediment load measured along the trunk was then partitioned between sub-basins, in order to calculate erosion rates during the late- to post-glacial time interval. Results document focused erosion in the External Massifs, at rates of 0.4–0.5 mm/a, irrespective of their position inside the drainage, and a westward migration of erosional foci through time along the Western Alps transect.