Oxygen isotopic analyses of planktonic foraminifera have provided a picture of many aspects of the evolution of the temperature structure of surface and near-surface oceans during the Miocene. In time slice studies oceanographic conditions have been interpreted from synoptic maps of isotopic data at between 22 and 27 locations in the Atlantic, Pacific and Indian Oceans. Three time slice intervals were examined: 22 Ma (foraminifera! zone N4B) and 16 Ma (N8) in early Miocene time; and 8 Ma (N17) in late Miocene time. In time series studies, the evolution of oceanographic conditions at single localities during an extended period of...