Miocene ostracodes of cold seep settings from northern Apennines (Italy)

The Miocene Termina Formation of the northern Apennines (Italy) contains thin marly limestone or marly sandstone bodies rich in macrofauna mainly consisting of large lucinid clams. Modern representatives of this fauna occur in cold seep settings where they house chemosymbiotic bacteria. Moreover, these rocks record a delta 13C-depletion confirming their origin influenced by a cold seep. The Miocene sections of Sasso delle Streghe and Sarsetta (near Modena) represent classic examples of cold seeps. These sections consist of marls and marly sandstones, respectively, with lucinids (Sasso delle Streghe) or bioclastic sands with lucinids (Sarsetta); both sections are capped by the Sandstones of Montebaranzone. They yield ostracodes that are mainly represented by deep-water filter-feeder species (Platycopa, i.e. Cytherella sp.) and numerous deposit-feeders (Podocopa: i.e. Neonesidea and Krithe), together with species frequently occurring in shallow water environments. These assemblages are able to colonize disaerobic environments such as cold seeps. Although some authors consider the filter-feeders as dominant taxa in disaerobic settings, our data do not provide evidence of significant differences in the ostracode assemblage composition between the deposits originated in seafloors with or without seepage influence. However, the number of specimens is greater in seafloors devoid of seepage influence.