This research used samples and data 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 and partial graduate stipend for E. Blanche Sunderland was provided by JOI grant number F001240. We also thank Kitty L. Milliken (University of Texas at Austin, Department of Geological Sciences) and Scott Stookey (CoreLab, Houston, Texas) for providing valuable assistance and advice on SEM analysis and interpretation. In addition, we thank Mike B. Underwood for providing advance copies of lithology and grain size data for comparison with our results. Kevin M. Brown and one anonymous reviewer provided very helpful comments that inspired a careful reconsideration of our interpretations, leading to a much improved manuscript.