Methane seepages recorded in benthic foraminifera from Miocene seep carbonates, Northern Apennines (Italy)

Benthic foraminifera from seep carbonates and from enclosing non-seep marls presentwithin Miocene formations in the Northern Apennines (Italy) were investigated as proxies ofmethane seepage in the marine environment. Negative δ13C values of benthic foraminiferafrom these seeps indicate unambiguously the local influence of CO2 produced by microbialanaerobic methane oxidation on the benthic ecosystem. Calcareous species living withinmethane seeps display δ13C values ranging from -9.04 to -25.74 ‰ PDB, whereas in thecoeval surrounding marls the same species display δ13C values from -1.54 to 0.62 ‰ PDB.Different species analysed (Cibicidoides kullenbergi, C. pachyderma, Siphonina rethiculata,Planulina wuellestorfi, Bolivina miocenica, Brizalina dilatata, Vulvulina pennatula, andACCEPTED MANUSCRIPTACCEPTED MANUSCRIPTACCEPTED MANUSCRIPT2Cibicides praecinctus) in different seep carbonates indicate that benthic foraminifera,independently of the taxa and of microhabitat preferences, have more negative δ13C valuesthan those found in the enclosing marls. Therefore each species represents a potential proxyfor past seafloor methane emissions. In addition to the calcareous species, the agglutinatedspecies Vulvulina pennatula displays -27.5 ‰ PDB in seep carbonates against -2.69 ‰ PDBin the enclosing marls. This suggests that the species utilized strongly 13C depleted carbonateparticles from authigenic carbonate precipitation during the mineralization of their tests.