Est-ce que les spéléothèmes refaçonnés sont des indicateurs d'anciennes remontées du niveau de base. Quelques critères pour distinguer les traces d'une remise en charge des impacts de la biocorrosion.

Classical speleothems (stalactites, stalagmites, pillars and flowstones) form in the vadose parts of karst cavities. Their presence therefore represents the total or partial, sometimes temporary, dewatering of associated parts of the karstic network. Conversely, the hydrogeological reuse of an old gallery, for example in connection with the rise of the base level, limits or even stops the development of these concretions. When cavities are flooded, corrosion of the speleothem surface or mechanical erosion (abrasion by sand, pebbles impacts) can alter their morphology. Many highly altered concretions, recognized in fossil networks across the world, have been interpreted as indicators of previous base level rises. The resultant hydrodynamic interpretations sometimes require the development of complex supporting geodynamic hypotheses. But it appears that in many cases speleothems are instead affected by biocorrosion linked to the ancient presence of bat colonies. Guano fermentation and convection of acidic gases combined to deeply reshape nearby calcite deposits – meaning that these altered speleothems were never submerged after their formation. We will present some examples of this process and some criteria that allow us to distinguish submerged concretions from those that were affected by biocorrosion