(Appendix) Oxygen and carbon isotopes in bulk sediments at DSDP Leg 74 Holes

Carbon and oxygen isotope measurements were made in bulk sediments from the five sites drilled on Leg 74, covering much of the Cenozoic.
These stable carbon isotope analyses document a lightening across the Cretaceous/Tertiary boundary (already documented by other workers), with a minimum about 0.2 Ma after the boundary; a trend to very heavy values in the late Paleocene; a lightening near the Paleocene/Eocene boundary to a second minimum early in the early Eocene; more positive values in the remainder of the Eocene with a minor peak immediately below the Eocene/Oligocene boundary, at which there is a lightening trend; a moderately positive peak in the middle Miocene, and a lightening toward the present, where the isotopically lightest values in the Cenozoic are to be found. The carbon isotope variations observed are largely a function of changes in the 13C content of oceanic dissolved inorganic carbon that resulted from alterations in the global carbon budget. Slight differences among sediments of the same age at different sites probably result from diagenetic changes, but do not obscure the major pattern, which has considerable potential value for stratigraphic correlation.