LOWER MIOCENE COLD-SEEPAGE CARBONATES AND BIOTA ASSOCIATED WITH TURBIDITES OF THE NUMIDIAN FLYSCH (APENNINIC-MAGHREBIAN OROGEN, CENTRAL SICILY)

Stacked units of Lower Miocene quartzarenitic turbidites (Numidian Flysch) contribute to the structural architecture of the Apenninic-Maghrebian orogen in Sicily. A well-exposed section of Numidian turbidites and associated marly hemipelagites crops out at Roccapalumba, central Sicily. This succession contains obvious imprints of deep-submarine cold-fluid seepage under the form of authigenic carbonates and specialized chemosynthetic biota. The chemoherm-complex is a plurimetric-thick, tabular body made up of quartzarenitic turbidites, microbreccias, hemipelagic marls (with abundant holoplanktic and nektic fossils, including foraminifera, thecosomatous pteropods and Aturia), micritic carbonates, and carbonate-cemented arenites containing chemosynthetic sulphur-based assemblages (giant lucinid and Calyptogena bivalves). Numerous veins and cavities characterize sandstones and carbonates, they are filled with laminated and peloidal textures of presumable microbial origin. Stable carbon isotope signature of carbonates is comprised between – 25 and – 17 permil PDB. These d¹³C values suggest that carbon incorporated in limestones derived from both dissolved inorganic carbon in seawater and hydrocarbon-enriched fluids.