Processi paleocarsici e geositi: il caso del “libeccio antico” nel distretto marmifero di Custonaci, Sicilia nord-occidentale

Abstract The Upper Triassic strata that crops out along the northern slope of Monte Sparagio, in the Custonaci “marble” district in northwestern Sicily, show an extensive development of dissolution cavities with a very variable shape and dimensions. Several different types of dissolution morphologies can be differentiated from microkarst to giant caverns. The cavities are filled up by polychrome silts or calcite cements or, in the larger caverns, by collapse breccias. The matrix between the collapse breccias is a polychrome silt that gives rise to an attractive ornamental stone, quarried in the past with the name of “Libeccio Antico”. The diagenetic processes that have controlled the formation of this complex dissolution network were sea-level oscillations, either of low-amplitude and high-frequence, or major, tectonically enhanced, sea-level fall. The cut surfaces of several old quarries of an ornamental stone known as “Libeccio Antico” offer the possibility to observe the high-diverse dissolution features and their relationships with the peritidal host carbonates. In particular some quarries in Contrada Cocuccio allow to observe at a glance either the fossiliferous host rock or the multiscale dissolution features and are worth to be preserved as a multiple geosite.