Hypogenic caves of Syracuse area, Sicily (Italy): geomorphological evidence of CO₂ degassing, freshsalt water mixing, and late condensaAon corrosion

Cave morphologies clearly indicate a hypogenic phase, with aggressive ascending flows creaKng the typical Morphologic Suites of Rising Flow (MSRF). The bubble trails and acid notches are formed by carbonic degassing and subsequent acidificaKon in more or less closed aerated environments at the water table. CO₂ probably derived from both the bedrock and the oxidaKon of surface-derived organic carbon at the density boundaries of the freshwater lens. We propose a mixed Flank Margin Cave and hypogenic speleogenesis model, where dissoluKon was concentrated in areas of greater CO₂ concentraKon, producing phreaKc maze paRerns recording past sea-level posiKons. We suggest that aggressiveness of the rising fluids could have partly originated at a shallow depth, in the mixing zone between fresh and salt water.