This research used samples provided by the Ocean Drilling Program (ODP). ODP is sponsored by the U.S. National Science Foundation (NSF) and participating countries under management of Joint Oceanographic Institutions (JOI), Inc. Funding for this research was provided by the Australian Research Council and ODP Australia Secretariat. The manuscript benefited greatly from two ODP reviewers' comments. The Centre for Electron Microscopy and Microanalysis of Adelaide University provided the electronic scanning facility.