Further examples of archaeal-derived hydrocarbons in mid-Cretaceous oceanic anoxic event (OAE) 1b sediments

Biomarker and total organic carbon (TOC) analyses were carried out on laminated black shales and massive marls from the Goguel level (OAE1a) and the Paquier and Kilian levels (OAE1b) of the Vocontian Basin of southeast France. TOC content was high (ca. 3–8%) throughout the Goguel, the Paquier and Kilian levels. Archaeal-derived hydrocarbons such as 2,6,15,19-tetramethylicosane (TMI) and 2,6,10,15,19-pentamethylicosane (PMI) were present in the OAE1b sediments, as reported previously [Kuypers, M.M.M., Blokker, P., Erbacher, J., Kinkel, H., Pancost, R.D., Schouten, S., Sinninghe Damsté, J.S., 2001. Massive expansion of marine archaea during a mid-Cretaceous oceanic anoxic event. Science 293, 92–94]. However, we did not detect these archaeal biomarkers in the Goguel level, confirming that the prevalence of archaea producing TMI and PMI was restricted to OAE1b.