The Roccapalumba Miocene seep system (Sicily): Integrated Geobiology and Mars analogue potential

Backgroud: Neogene hydrocarbon-related carbonate deposits are common in the Apennines and in Sicily. They are traditionally named “Calcare a Lucina” (Lucina limestone), and mainly consist of isolated carbonate masses embedded in Neogene deep-water siliciclastic deposits. Results: In this presentation, we will describe the geological and sedimentological context, the paleobiological and geochemical well preserved seep-related diagnostic features of an exceptionally large Lower Miocene Lucina limestone that crops out near to the town of Roccapalumba, western Sicily. The sedimentary units cropping out nearby Roccapalumba are organized in several stratigraphic-structural units resulting from the deformation of sedimentary sequences. These sedimentary sequences were deposited in different paleogeographic domains, and covered in uncorformity by late-orogenic Numidian Flysh. The Roccapalumba Lucina limestones are part of the Numidian Flysh that shows a very complex geological contest because of the regional thrust that affected the Roccapalumba area The Roccapalumba carbonate deposit mostly consists of foraminiferal-bearing authigenic micrite with a detrital siliciclastic component and abundant macro-invertebrate assemblage including densely packed lucinid-like shells. Methane-induced microbial fabrics and textures, and specific carbon stable isotope will be also discussed. The complex network of veins and cavities and related biosedimentological features (e.g., peloidal and spheroidal cements, biominerals, biofilm remain) suggest that these veins were probably acting as fluid migration or escape structures. Mars Analogue: These carbonate bodies might represent analogues - in terms of basic processes - of some potential fluid expulsion features recognized in correspondence of the high albedo layered deposits of Arabia Terra on Mars. We describe similarities and differences in terms of morphologies and sedimentary textures and we discuss possible analogies in term of depositional processes and controls on the deposition. The composition of Martian bodies generally consist of either monohydrated or polyhydrated sulphates but the presence of carbonates has been locally suggested. Still the detrital texture and the network of veins suggest analogies among the depositional processes controlling Roccapalumba and Arabia Terra deposits.