The authors would like to thank the officers and crew of the JOIDES Resolution, particularly Captain Ed Onk, who valiantly served at Site 735 through foul and fair weather for three Ocean Drilling Program legs before retiring at the end of Leg 176. His good humor and seamanship contributed enormously to our enterprise. Parker Hackett assisted in preparation and documentation of thin sections for analysis and processed a considerable amount of the data used in this paper. The authors thank S.A. Morse and R. Pedersen for perceptive and often challenging reviews that much improved the manuscript. They are otherwise blameless. Funding for this research was provided by the Woods Hole Oceanographic Institution through the Van Allen Clark Jr. Chair for Excellence in Oceanography, the U.S. Science Support Program, and a grant from the National Science Foundation (NSF-9618442). 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 participating countries under management of Joint Oceanographic Institutions (JOI), Inc.