Burial ages, ghost-rocks and karst network structure. Insights from the Vis canyon (Southern France)
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Date
2020-10-21
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Groupe français de géomorphologie
Abstract
New burial ages by measuring 26 Al / 10 Be isotopic ratios in three cavities near the Vis canyon (south of France, south-eastern limit of Grands-Causses) challenge the classic karstogenesis model. used to explain the structuring of networks. Indeed, the subhorizontal levels of underground galleries are generally used as markers of the position of the regional base level ( ie , river). If the relationship between burial age and height relative to the regional base level expected using the classical model per descensumfor the Scorpions caves (1.2 ± 0.4 Ma, +105 m relative to the base level -rnb-) and Bergougnous (1.2 ± 0.3 Ma, +117 m rnb) is in agreement with the quantification of the average regional incision rate (83 ± 35 m / Ma), it does not explain the age of 0.94 ± 0.07 Ma obtained for the infills of the horizontal levels of the Rocas located much higher in altitude (+317 m rnb). The first two cavities open directly into the gorges, while the third opens onto the plateau less than 4 km from the gorges. To our knowledge, this is the first time that quantitative data support the proposition that the model of regional karstogenesis controlled by the position of the base level is not universal. These dates make it possible to suggest that ghosting plays a primordial role in controlling the location of the sub-horizontal levels. This process internal to the karst relegates the role of the position of the regional base level to that of a simple external triggering of the hollowing out of the alteration products generated by the phantomization. © French group of geomorphology
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Keywords
Aluminium 26, Beryllium 10, Caves, Geomorphology, Morphology, Sediments
Citation
Malcles, O., Vernant, P., Chéry, J., Ritz, J.-F., Cazes, G., & Fink, D. (2020). Burial ages, ghost-rocks and karst network structure. Insights from the Vis canyon (Southern France). Geomorphologie: relief, process, environment, 26(4), 255-264. doi:10.4000/geomorphologie.15043