Stable isotope imprint of hypogene speleogenesis: Lessons from Austrian caves

Hypogene speleogenesis involves the formation of solution-enlarged permeability structures driven by ascending water acquiring its acidity from deep-seated sources. This process occurs in a wide range geological settings and different lithologies. Although hypogene has received increasing attention last two decades, identification former activity caves remains challenging, unless unambiguous morphological, mineralogical and/or hydrogeological evidence is available. Here, we document that geochemical analyses (mainly stable oxygen carbon isotopes) cave wall rock samples may fill this methodological gap provide useful tool to identify karstification through fingerprinting water-rock interaction. Stable isotope profiles comprehensive set cores eight Austria both limestone dolomite were investigated. Alteration halos typically few centimeters characterized up 12‰ 15‰ depletion ?13C ?18O, respectively, identified calcite marble caves. Besides isotopic alteration, bleaching staining was observed due oxidizing conditions paleowater. No change carved dolomite, which be attributed low Ca/Mg ratios paleowater aggressive fluids leading fast retreat. On other hand, dedolomitization some rocks implying presence paleowaters with elevated ratios. Similarly dolomitic caves, no alteration front formed sulfuric acid speleogenesis. A likely explanation high rate retreat outpacing exchange rock. Our study also shows interaction during epigene does not lead halos. approach offers powerful test origin additional insights into temperature provenance source(s) dissolved inorganic carbon.