The present data set is based on samples provided by the Ocean Drilling Program (ODP). ODP is sponsored by the U.S. National Science Foundation and participating countries under the management of Joint Oceanographic Institutions. We thank Michael Howell for constructive comments for the final version of this paper. Isotope measurements have been accomplished in the Alfred Wegener Institute isotope laboratory under the helpful guidance of A. Mackensen. We are grateful to Ute Bock and Ruth Cordelair for technical support. This research was also supported by the Deutsche Forschungsgesellschaft (DFG grant Ge516/6).