This research used samples and/or data provided by the Ocean Drilling Program (ODP). ODP is sponsored by the U.S. National Science Foundation (NSF) and national agencies including the Centre National de la Recherche Scientifique (CNRS) for France, under management of Joint Oceanographic Institutions (JOI), Inc. This work has been funded by the Centre National de la Recherche Scientifique (France). The author is grateful to Deny Malengros, Julien Paturel, and Philippe Recourt for their assistance and to Jean-François Deconinck and Neville Exon for constructive comments.