SULFURIC ACID CAVES OF ITALY: AN OVERVIEW

The general geodynamic situation of Italy is quite complex. This land has undergone several stages of formation, compressed between the African and the Eurasian continents. The phase of extensional tectonics governed by the rollback of continental terrains (Corsica, Sardinia, Balearic Islands, Kabylies blocks and Calabria) has caused the generation of the Apennine chain crossing the country from NW to SE, forming the backbone of the country's mainland. The structure of this mountain chain, containing many thrusts, horst and graben structures, and deep faults, and the widespread presence of mainly Mesozoic carbonate outcrops, has caused the formation of deep karstic circulation systems. This is testified by the abundance of hydrothermal springs and associated travertine deposits. Furthermore, the presence, at depth, of both hydrocarbon reservoirs and Triassic gypsum deposits, is responsible for the presence of rising waters rich in H2S. Since the late 80s the important cave systems in the Frasassi Canyon and Monte Cucco, with their important gypsum deposits, undoubtedly showed that sulfuric acid played an important role in the creation of voids, similar to what was described for the Guadalupe Mountains in New Mexico. Afterwards many other caves were found to be formed by the sulfuric acid speleogenesis throughout the country, making Italy one of the most important countries in the world for what concerns SAS caves. In the past few years, in a few of these caves detailed studies have been carried out including geomorphology, mineralogy, and geochemistry. Sulfuric acid caves are now known from many regions along the Apennine chain (Tuscany, Umbria, Marche, Latium, Campania, Calabria), but also from Apulia, Sicily, and Sardinia. Here we give a review of the state-of-the-art knowledge on hypogene SAS caves known in Italy, and some ongoing studies in some selected areas.