The cores recovered by the Deep Sea Drilling Project provide a reservoir of material for paleontologic investigation offering unparalleled opportunities to learn about the global aspects of biostratigraphy, paleobiogeography, paleoecology, paleoclimatology, paleoproductivity, changes in ocean-water chemistry, and diagenetic processes. At the time of inception of the Deep Sea Drilling Project, marine plankton fossil groups were generally poorly known except for planktonic forams. In the last few years, the calcareous nannoplankton have also been used to establish zonations for Jurassic to Holocene strata and a radiolarian zonation of the Cenozoic has been worked out. It is now feasible to evaluate differences in age-equivalent fossil assemblages in the different areas of t e ocean, in different climatic zones, at different depths, and in different sediment types. Biogeographic differences, particularly between the southern ocean and the North Atlantic and North Pacific, have been detected. Distinct climatic zonation of the oceans became well established during the Late Cretaceous and has been subject to periodic intensification during the Cenozoic. The end of the Cretaceous, end of the Eocene, and the Pliocene were times of especially rapid change and evolution. The accumulations of siliceous ooze indicate regions of high productivity. Dissolution of calcareous pelagic fossils is selective, removing some species from the assemblage before others are attacked; this phenomenon offers a method of determining fluctuations of the calcium carbonate compensation epth and a means of investigating diagenetic processes in deep-sea sediments.

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