Sulfuric acid speleogenesis in the Majella Massif (Abruzzo, Central Apennines, Italy)

Hypogenic speleogenesis, late stage epigenic overprinting and condensation-corrosion in a complex cave system in relation to landscape evolution (Toirano, Liguria, Italy)

“…Budapest, Léel-Őssy, 2017), and particularly in sulfuric acid (SAS) caves, where degassing of H2S and oxidation is most efficient at or immediately above the water surface (De Waele et al, 2016). Hypogene-SAS caves are reliable indicators of past water table levels and can help in determining base level changes, and especially uplift rates (or related downcutting rates in adjacent valleys) (Piccini et al, 2015;De Waele et al, 2016;D'Angeli et al, 2019).…”

Epigenic vs. hypogenic speleogenesis governed by H2S/CO2 hydrothermal input and Quaternary icefield dynamics (NE French Pyrenees)

“…12d). In such hypogenic conditions, CO 2 and H 2 S degassing and hydration/oxidation is most efficient at or immediately above the water surface (De Waele et al, 2016;D'Angeli et al, 2019), meaning that such caves are reliable indicators of past water table levels and can help in determining base-level changes over time (Piccini et al, 2015;De Waele et al, 2016). Above the water table, various corrosion features and minerals (ceiling channels, ceiling cupolas, aerial convection niches, corrosion furrows and karren, popcorn-like calcite, folia, calcite rafts) confirm that the most significant karstification process was linked to a thermal condensation-corrosion associated to a vadose domain during thermo-mineral water degassing.…”

“…Among hypogenic caves, deep-seated karsts can develop at great depth (e.g. Forti and Sanna, 2010), while shallow caves also formed at former water table levels (De Waele et al, 2016;D'Angeli et al, 2019). Attempts to discriminate between hypogenic and epigenic caves are very recent, and mostly developed during the past two decades (e.g.…”

“…Palmer, 1991): (i) carbonic acid speleogenesis derived from deep-seated CO 2 -rich fluids associated with insitu hydration of CO 2 to H 2 CO 3 (e.g. Piccini, 2000;Ford and Williams, 2007;Sarbu and Lascu 1997;Leél-Őssy, 2017); (ii) Sulfuric Acid Speleogenesis (SAS) linked to the oxidation of deep H 2 S to sulfuric acid H 2 SO 4 (Egemeier, 1981), at or close to the water table (Audra, 2007;Audra et al, 2007a;De Waele et al, 2016;D'Angeli et al, 2019), intensively dissolving carbonate rocks and precipitating significant amounts of gypsum deposits (e.g. Galdenzi and Maruoka, 2003); (iii) "gypsum karsts" in which a meteoric recharge flowing across deep carbonate aquifers is responsible for per ascensum fluid migration into overlying gypsum formations that are dissolved without involving a high content of CO 2 or H 2 S (Klimchouk et al, 2017 and references therein); and (iv) coastal mixing caves or flank margin caves formed by the interaction between fresh-water and salt-water which causes a mixing dissolution process, and also produces organic-trapping horizons enhancing the dissolution through the generation of CO 2 (Mylroie, 1988;Palmer, 1991;Mylroie and Mylroie, 2007;Lopez-Martinez et al, 2020).…”

Speleogenesis of the world's longest cave in hybrid arenites (Krem Puri, Meghalaya, India)

“…Even though arenization in pure quartz sandstone produces exclusively high amounts of quartz sands (Sauro, 2014;Mecchia et al, 2019) that are afterwards removed by piping mechanisms, in the case of Krem Puri hybrid arenites the cave passages show the presence of important residual sediments composed of a mixture of quartz and feldspar grains together with clay minerals (Table 2). It is also important to note that the presence of gypsum crusts on the cave walls probably indicates that sulfide (pyrite) oxidation occurs in places, leading to replacement of calcite by gypsum with the release of carbon dioxide, according to the typical sulfuric acid reaction (Tisato et al, 2012;D'Angeli et al, 2019). This additional weathering process might have taken place in the early phases of speleogenesis, but could still be active today.…”