The relation of two well-known ancient carbonate deposits to hydrocarbon seepage was confirmed by this study. Archaea are found to be associated with the formation of Oxfordian seep carbonates from Beauvoisin and with a Miocene limestone from Marmorito ("tube-worm limestone"). Carbonates formed due to a mediation by archaea exhibit extremely positive or extremely negative d 13 C carbonate values, respectively. Highly positive values (c15‰) reflect the use of 13 C-enriched CO 2 produced by methanogenesis. Low d 13 C values of the Marmorito carbonates (-30‰) indicate the oxidation of seepagederived hydrocarbons. Likewise, the d 13
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.