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Communication Dans Un Congrès Année : 2022

The paleocaves of Pierre-Saint-Martin/Larra massif (France/Spain). Mapping and diagnostic

Résumé

The Pyrenean Pierre-Saint-Martin/Larra massif presents more than 465 km of surveyed caves. But at the surface of this wellknown karstic mountain area, we can observe "cemeteries" of unroofed and open-air palaeocaves, due to the erosion/dissolution of cretaceous limestones since the Mio-Pliocene. An accurate mapping of these palaeocaves is actually done by remote sensing, in addition to essential field work. Indeed, walls and ground of palaeocaves have not the same micro-topographic characteristics (e.g. roughness) than the surrounding limestone. Those small differences are detected and quantified on the very high-density LIDAR full cover. Moreover, palaeo-speleothems can be detected and localized by the mean of spectral indices analysis, on very high resolution orthophotography and satellite imagery. Some palaeo-galleries have a development of several hundred meters, and show ancient stalagmitic massifs. The first U/Th dating indicate ages older than 400 000 years. An illustration is given by the Lepineux pit, which is extended at the surface by unroofed palaeo-pits, presenting old concretions. Those palaeo-speleothems situated at the surface indicate a pre-ice age, when the entire massif was at a lower elevation, with a forest and a pedologic cover, very favourable to the concretion formation.
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Dates et versions

hal-04040539 , version 1 (22-03-2023)

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  • HAL Id : hal-04040539 , version 1

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Benjamin Lans, Richard Maire, Yves Quinif, Michel Douat. The paleocaves of Pierre-Saint-Martin/Larra massif (France/Spain). Mapping and diagnostic. 18th International Congress of Speleology - Savoie Mont Blanc 2022, Jul 2022, Le Bourget-du-Lac, France. pp.170. ⟨hal-04040539⟩
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