Electron-microprobe analyses of glass shards from volcanic ash in Pliocene and Pleistocene deep-sea sediments in the Gulf of Aden and the Somali Basin demonstrate that most of the tephra layers correlate with tephra layers known on land in the Turkana Basin of northern Kenya and southern Ethiopia. Previous correlations are reviewed, and new correlations proposed. Together these data provide correlations between the deep-sea cores, and to the land-based sections at eight levels ranging in age from about 4 to 0.7 Ma. Specifically, we correlate the Moiti Tuff (???4.1 Ma) with a tephra layer at 188.6 m depth in DSDP hole 231 and with a tephra layer at 150 m depth in DSDP hole 241, the Wargolo Tuff with a tephra layer at 179.7 m in DSDP Hole 231 and with a tephra layer at 155.3 m depth in DSDP Hole 232, the Lomogol Tuff (defined here) with a tephra layer at 165 m in DSDP Hole 232A, the Lokochot Tuff with a tephra layer at 140.1 m depth in DSDP Hole 232, the Tulu Bor Tuff with a tephra layer at 160.8 m depth in DSDP Hole 231, the Kokiselei Tuff with a tephra layer at 120 m depth in DSDP Hole 231 and with a tephra layer at 90.3 m depth in DSDP Hole 232, the Silbo Tuff (0.74 Ma) with a tephra layer at 35.5 m depth in DSDP Hole 231 and possibly with a tephra layer at 10.9 m depth in DSDP Hole 241. We also present analyses of other tephra from the deep sea cores for which correlative units on land are not yet known. The correlated tephra layers provide eight chronostratigraphic horizons that make it possible to temporally correlate paleoecological and paleoclimatic data between the terrestrial and deep-sea sites. Such correlations may make it possible to interpret faunal evolution in the Lake Turkana basin and other sites in East Africa within a broader regional or global paleoclimatic context. ?? 1992.