In 1968, when the Deep Sea Drilling Project started, our biostratigraphy was held together almost totally by a single thread--the foraminiferal zonations. In carbonate-rich sediments, these zonations provided an average age resolution of about 6 m.y. in the Cretaceous and about 1.5 m.y. in the Cenozoic. The study of calcareous nannofossils was rapidly advancing at this time and soon "challenged" the Foraminifera for high stratigraphic resolution. Perhaps the biggest impact on biostratigraphy of the material recovered by DSDP has been the development of stratigraphic zonation for the siliceous microfossils. Radiolarian stratigraphy, in particular, has grown from a rough grouping of species with which one could distinguish epochs to a detailed zonation with an average age r solution of about 2 m.y. With this rapid growth in both the number of microfossil groups used in marine stratigraphy and in the degree of stratigraphic resolution, the question arises as to the ultimate resolution that is achievable. Recent work on the upper Tertiary and Quaternary provides a guide to what might be accomplished. The use of many biostratigraphic datums increases the average age resolution to as little as a few hundred thousand years, and the coupling with magnetic and isotopic stratigraphic zonation provides a check on global synchroneity. Development of stratigraphic zonation aided by the determination of fluctuations in abundance of faunal and floral assemblages offers the promise of increasing resolution another order of magnitude; studies of how faunal distribution pa terns change with time indicate where such refined techniques may be useful and where they may be misleading.

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